^ ^»ii? i Digitized by the Internet Archive in 2007 with funding from Microsoft Corporation http://www.archive.org/details/anatdescsurgiOOgrayrich *4? TO SIR BENJAMIN COLLINS BRODIE, BART,.F.R.S, D.C.L, SERJEANT-SURGEON TO THE QUEEN, CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE, fflfis Mark is $*tattb t IN ADMIRATION OF HIS GREAT TALENTS, IN REMEMBRANCE OF MANY ACTS OF KINDNESS SHOWN TO THE AUTHOR, FROM AN EARLY PERIOD OF HIS PROFESSIONAL CAREER. BQS&k (in) AMERICAN PUBLISHERS' NOTICE. The present edition, like the last American reprint, has been passed through the press under the supervision of Dr. Richard J. Dunglison, who has carefully corrected whatever errors had escaped the attention of the author, and has made such changes in the typographical arrangement as seemed calculated to render the volume more convenient for consulta- tion and reference. February, 1862. ( iv ) PREFACE. In preparing a Second Edition of my " Descriptive and Surgical Anatomy," I trust that I have corrected any inaccuracies contained in the previous one ; every page has been carefully revised ; much addi- tional matter has been added to the text; and several new Illustrations, executed with great care and fidelity by Dr. Westmacott, have been inserted. December, 1860. (v) viii PREFACE. The Veins are described as in ordinary anatomical works; and illustrated by a series of engravings, showing those in each region. The veins of the spine are described and illustrated from the well-known work of Breschet. The Lymphatics are described, and figured in a series of illustrations copied from the elaborate work of Mascagni. Tlie Nervous System and Organs of Sense. A concise and accurate description of this important part of anatomy has been given, illustrated by sixty-six engravings, showing the spinal cord and its membranes ; the anatomy of the brain, in a series of sectional views; the origin, course, and distribution of the cranial, spinal, and sympathetic nerves; and the anatomy of the organs of sense. The Viscera. A detailed description of this essential part of anatomy has been given, illustrated by fifty-five large, accurately-lettered engravings. Regional Anatomy. The anatomy of the perineum, of the ischio-rectal region, and of femoral and inguinal hernia, is described at the end of the work; the region of the neck, the axilla, the bend of the elbow, Scarpa's triangle, and the popliteal space, in the section on the arteries; the laryngo-tracheal region, with the anatomy of the trachea and larynx. The regions are illustrated by many engravings. Microscopical Anatomy. A brief account of the microscopical anatomy of some of the tissues, and of the various organs, has also been introduced. The Author gratefully acknowledges the great services he has derived in the execution of this work, from the assistance of his friend, Dr. H. V. Carter, late Demonstrator of Anatomy at St. George's Hospital. All the drawings from which the engravings were made, were executed by him. In the majority of cases, they have been copied from, or corrected by, recent dissections made jointly by the Author and Dr. Carter. The Author has also to thank his friend, Mr. T. Holmes, for the able assistance afforded him in correcting the proof-sheets in their passage through the press. The engravings have been executed by Messrs. Butterworth and Heath ; and the Author cannot omit thfanking these gentlemen for the great care and fidelity displayed in their execution. Wilton-Street, Belgrave-Squark. August, 1858. CONTENTS. Osteology. Structure and Physical Properties of Bone .... Chemical Composition of Bone Form of Bones Surfaces of Bones Microscopic Structure Vessels of Bone Periosteum Marrow . Development of Bone Growth of Bone Number of Bones The Spine. General Characters of a Yertebra . Characters of the Cervical Vertebrae Peculiar Cervical Vertebra; Atlas Axis Vertebra Prominens Characters of the Dorsal Vertebrae Peculiar Dorsal Vertebrae Characters of the Lumbar Vertebrae Structure and Development of the Verte- brae Atlas . Axis . Seventh Cervical Lumbar Vertebrae Progress of Ossification in the Spine Sacral and Coccygeal Vertebrae Sacrum Coccyx Of the Spine in general . The Skull. Division of Bones of Bones of the Cranium Occipital Bone . Parietal Bones . Frontal Bone . Temporal Bones Sphenoid Bone Sphenoidal Spongy Bones Ethmoid Bone . Development of the Cranium The Fontanelles "Wormian Bones Congenital Fissures and Gaps Bones of the Face . Nasal Bones Superior Maxillary Bone . Lachrymal Bones Malar Bones Palate Bones 33 33 34 35 36 37 :is 38 38 •Id 40 40 41 42 42 43 44 44 45 47 47 49 49 49 49 49 50 50 54 55 57 57 57 Gl 83 (17 72 7(1 77 79 79 80 80 so Bl 83 86 87 88 PAOB Inferior Turbinated Bones . . 91 Vomer .... 92 Inferior Maxillary Bone . 92 Changes produced by age 95 Sutures of the Skull 97 Vertex of the Skull 98 Base of the Skull, Internal Surface . 100 Anterior Fossae . 100 Middle Fossae . 100 Posterior Fossae . . 101 Base of Skull, External Surface . 102 Lateral Kegion of the Skull 105 Temporal Fossae . 105 Zygomatic Fossae . 106 Spheno-maxillary Fossae . . 106 Anterior Begion of Skull . 106 Orbits 108 Nasal Fossae .... . 109 Os Hyoides .... 111 The Thorax. The Sternum . . . . . 112 Development of the Sternum . 114 The Ribs .... . 116 Peculiar Ribs . - 118 Costal Cartilages . 120 The Upper Extremity. The Clavicle 121 Development of the Clavicle 123 The Scapula 123 Development of the Scapula The Humerus . 127 129 Development of the Humerus 133 The Forearm . 133 The Ulna 133 The Radius 138 The Hand 140 The Carpus 140 Bones of Upper Row 141 Bones of Lower Row 143 The Metacarpus 146 Peculiar Metacarpal Bones 146 Phalanges 147 Development of the Hand 148 The Lower Extremity. Os Innominatum 149 149 Pubes 153 Development of the Os Innominatum 154 The Pelvis 155 Boundaries of Pelvis .... 155 ( ix) CONTENTS. Position of Pelvis Axes of Pelvis ..... Differences between the Male and Female Pelvis The Femur Development of the Femur The Leg Patella ....... Tibia Development of Tibia .... Fibula Development of Fibula .... The Foot PAGE 157 Tarsus .... 157 Oalcaneum or Os Calcis . Cuboid .... 158 Astragalus 158 Scaphoid .... 163 Internal Cuneiform . 163 Middle Cuneiform . 164 External Cuneiform 165 j Metatarsal Bones 168 j Peculiar Metatarsal Bones 168 j Phalanges 170 Development of the Foot 170 i Sesamoid Bones PAGE 170 170 173 173 175 175 176 176 177 177 178 178 179 The Articulations. General Anatomy of the Joints . . 181 Cartilage 181 Fibro-cartilage 183 Ligament 183 Synovial Membrane .... 183 Synovia . . . . . . 184 Forms of Articulation .... 184 Synarthrosis 184 Amphiarthrosis 185 Diarthrosis 185 Movements of Joints .... 187 Gliding Movement .... 187 Angular Movement .... 187 Circumduction 187 Potation 187 Articulations of the Trunk. Articulations of the Vertebral Column . 188 Atlas with the Axis . 191 Spine with Cranium 194 Temporo-maxillary Articulation . . 195 Articulation of the Ribs with the Verte- brae 197 Articulations of the Cartilages of the Ribs with the Sternum . . . 200 Ligaments of the Sternum . . . 202 Articulations of the Pelvis with the Spine 203 Inter-pubic 205 Articulations of the Upper Extremity. Sterno-clavicular 207 Scapuloclavicular 208 Ligaments of the Scapula . . . 210 Shoulder-joint 210 Elbow-joint 211 Radio-ulnar Articulation .... 213 Wrist-joint 216 Articulations of the Carpus . . .217 Carpo-metacarpal Articulations . . 218 Metacarpo-phalangeal Articulations . 220 Articulation of the Phalanges . . . 220 Articulations of the Lower Extremity. Hip-joint 221 Knee-joint 223 Articulation between the Tibia and Fibula 226 Ankle-joint 228 Articulations of the Tarsus . . . 229 Tarso-metatarsal Articulations . .233 Articulations of the Metatarsus . . 233 Metatarso-phalangeal Articulations . 233 Articulation of the Phalanges . . . 234 Muscles and Fascia3. General Anatomy of Muscle . Tendons . Aponeuroses . Fasciae . Muscles and Fasciae op the Head and Face. Subdivision into Groups .... Epicranial Region. 235 237 237 237 238 Dissection Occipito-frontalis .... . 239 . 240 Auricular Region. Dissection Attollens Aurem .... Attrahens Aurem .... Retrahens Aurem .... Actions . 241 . 241 . 242 . 242 . 242 Palpebral Region. Dissection Orbicularis Palpebrarum . . 242 . 242 Corrugator Supercilii Tensor Tarsi . Actions . Orbital Region. Dissection Levator Palpebrae Superioris . Rectus Superior, Inferior, Internal and External Superior Oblique Inferior Oblique Actions Surgical Anatomy Nasal Region. Pyramidalis Nasi Levator Labii Superioris Alaeque Nasi Dilator Naris . Compressor Naris Narium Minor Depressor Ahe Nasi Actions . 243 243 243 243 243 244 245 245 245 245 246 2-1 G 246 246 246 246 246 CONTENTS. XI Superior Maxillary Region. Levator Labii Snperioris Levator Anguli Oris Zygomatici Actions . Inferior Maxillary Region. Dissection Levator Labii Inferioris . Depressor Labii Inferioris Depressor Anguli Oris . Intermaxillary Region. Dissection Orbicularis Oris Buccinator Eisorius . Actions . Temporo- Maxillary Region. Masseter Temporal Fascia .... Dissection of Temporal Muscle Temporal Pterygo-Maxillary Region. Dissection Internal Pterygoid .... External Pterygoid .... Actions Muscles and Fasciae of the Neck. Subdivision into Groups .... Superficial Cervical Region. Dissection Superficial Cervical Fascia Platysma Myoides .... Deep Cervical Fascia Sterno-cleido-mastoid Boundaries of the Triangles of the Neck Surgical Anatomy .... Actions Infra-hyoid Region. Dissection .... Sterno-hyoid .... Sterno-thyroid .... Thyro-hyoid, Omo-hyoid . Actions PAC1E 247 247 247 247 247 247 248 248 248 248 249 249 249 249 250 250 251 251 251 252 252 252 253 253 253 254 254 255 256 256 256 256 257 258 258 Supra-hyoid Region. Dissection Digastric Stylo-hyoid, Mylo-hyoid, Genio-hyoid Actions Lingual Region. Dissection .... Genio-hyo-glossus, Hyo-glossus Stylo-glossus, Lingualis . Palato-glossus .... Actions Pharyngeal Region. Dissection Inferior Constrictor Middle Constrictor, Superior Constrictor Stylo-pharyngeus Actions 258 259 259 260 260 260 261 262 262 262 262 263 263 264 Palatal Region. Dissection .... Levator Palati Tensor Palatfi, Azygos Uvulae . Palato-glossus, Palato-pharyugeus Actions, Surgical Anatomy Anterior Vertebral Region. Bectus Capitis Anticus Major Pectus Capitis Anticus Minor Bectus Lateralis .... Longus Colli Lateral Vertebral Region. Scalenus Anticus, Scalenus Medius Scalenus Posticus .... Actions Muscles and Fascle of the Trunk. Subdivision into Groups .... Muscles of the Back. Subdivision into Layers .... First Layer. Dissection Trapezius Ligamentum Nuchae Latissimus Dorsi Second Layer, Dissection Levator Anguli Scapulae Bhomboideus Minor Bhomboideus Major Actions . Third Layer. Dissection Serratus Posticus Superior Serratus Posticus Inferior Vertebral Aponeurosis . Splenius Capitis and Splenius Colli Actions . Fourth Layer, Dissection Erector Spinae . Sacyo-lumbalis . Musculus Accessorius ad Sacro-lumbalem Cervicalis Ascendens Longissimus Dorsi . Transversalis Colli . Trachelo-mastoid Spinalis Dorsi, Spinalis Cervicis Complexus Biventer Cervicis Fifth Layer. Dissection Semispinalis Dorsi, Semispinalis Colli Multifidus Spinae .... Botatores Spinae .... Supra-spinales Inter-spinales Extensor Coccygis, Inter-transversales Bectus Posticus Major . Bectus Posticus Minor . Obliquus Superior .... Obliquus Inferior .... Actions PAdK 264 265 265 265 266 266 267 267 267 268 268 268 269 269 269 269 270 270 272 272 272 273 273 273 273 274 274 274 274 278 276 276 276 276 276 277 277 277 277 277 278 278 278 278 279 279 279 279 279 280 280 280 Xll CONTENTS. Muscles of the Abdomen. Dissection Obliquus Externus Obliquus Interims Transversalis . Lumbar Fascia Rectus Abdominis Pyramidalis, Quadratus Lumborum Linea Alba, Lineae Semilunares Linear Transversa? . Actions PAGE 281 281 283 284 285 286 287 287 287 287 Muscles and Fasciae of the Thorax. Intercostal Fasciae ...... 288 External Intercostals .... 288 Internal Intercostals .... 288 Infra-costales, Triangularis Sterni . . 289 Levatores Costarum .... 289 Actions 289 Diaphragm Actions Diaphragmatic Region. Muscles and Fascia of the Upper Extremity. Subdivision into Groups .... Dissection of Pectoral Region and Axilla Fasciae of the Thorax .... Anterior Thoracic Region Pectoralis Major Costo-coracoid Membrane Pectoralis Minor Subclavius Actions . Lateral Thoracic Region. Serratus Magnus .... Actions Deltoid Action Acromial Region. Anterior Scapular Region. Subscapular Aponeurosis Subscapularis Actions Posterior Scapular Region Supra-spinous Aponeurosis Supra-spinatus Infra-spinous Aponeurosis Infra-spinatus . Teres Minor Teres Major Actions .... Anterior Humeral Region. Deep Fascia of Arm < oraco-brachialis, Biceps Brachialis Anticus .... Actions 289 292 293 293 294 294 296 296 296 297 298 298 299 299 299 •299 300 300 300 300 300 301 301 302 302 303 304 304 Posterior Humeral Region. Triceps . . . . . . 304 Subanconeus 304 Actions 304 Muscles of Forearm. PAOK Deep Fascia of Forearm . . . 305 Anterior Brachial Region, Superficial Layer. Pronator Radii Teres .... 306 . 306 . 307 . 307 . 307 Flexor Carpi Radialis Palmaris Longus Flexor Carpi Ulnaris Flexor Digitorum Sublimis Anterior Brachial Region, Deep Layer. Flexor Profundus Digitorum . . . 308 . 309 . 309 . 310 Flexor Longus Poinds Pronator Quadratus Actions . Radial Region. Dissection Supinator Longus Extensor Carpi Radialis Longior Extensor Carpi Radialis Brevior 310 310 310 311 Posterior Brachial Region, Superficial Layer. Extensor Communis Digitorum . . 312 Extensor Minimi Digiti .... 312 Extensor Carpi Ulnaris .... 312 Anconeus 312 Posterior Brachial Region, Deep Layer. Supinator Brevis ..... 313 Extensor Ossis Metacarpi Pollicis . . 313 Extensor Primi Internodii Pollicis . . 313 Extensor Secundi Internodii Pollicis . 313 Extensor Indicis .... . 314 . 314 Muscles and Fasciae of the Ham I. Dissection . 315 Anterior Annular Ligament . 315 Posterior Annular Ligament . . 315 Palmar Fascia .... . 316 Muscles of the Hand. Radial Group . 316 Ulnar Group . 318 . 319 Middle Palmar Group . 319 . 320 Surgical Anatomy of the Muscles q, f the Upper Extremity. Fractures of the Clavicle . 320 Acromion Process . 321 Coracoid Process . . 321 Humerus . 321 Ulna . . 322 Olecranon . 322 Radius . . 323 Muscles and Fascia of the Low ER Extremity. Subdivision into Groups . . 324 Iliac Region. Dissection . 325 Iliac Fascia . 325 Psoas Magnus, Psoas Parvus . . 326 . 326 . 327 CONTENTS. Xlll Anterior Femoral Region. PAGE 327 Fasciae of the Thigh .... 327 Superficial Fascia 327 Deep Fascia, Fascia Lata 328 Saphenous Opening 329 Iliac and Pubic Portions of Fascia Lata . 329 Tensor Vaginas Femoris, Sartorius . 329 Quadriceps Extensor Cruris . 330 Rectus Femoris, Vastus Externus . 330 Vastus Internus and Crureus . 331 331 331 Internal Femoral Region. 332 332 332 Adductor Longus 333 Adductor Brevis, Adductor Magnus 333 334 Gluteal Region. 334 Gluteus Maximus 334 Gluteus Medius 335 Gluteus Minimus 336 Pyriformis ...... 336 Obturator Internus, Gemelli . 337 Quadratus Femoris, Obturator Externus 337 338 Posterior Femoral Region. 339 Biceps, Semitendinosus .... 339 Semimembranosus 340 340 Surgical Anatomy of Hamstring Tendons 340 Muscles and Fascia} of Leg. Dissection of Front of Leg 340 Fascia of the Leg 340 Muscles of the Leg 341 Anterior Tibio-fibular Region. Tibialis Anticus 341 Extensor Proprius Pollicis 342 Extensor Longus Digitorum . 342 Peroneus Tertius 342 342 Posterior Tibio-fibular Region, Superficial Layer. PAGE Dissection 343 Gastrocnemius 343 Soleus, Tendo Achillis, Plantaris . . 344 Actions 344 Posterior Tibio-fibular Region, Deep Layer. Deep Fascia of Leg 345 Popliteus 345 Flexor Longus Pollicis .... 346 Flexor Longus Digitorum, Tibialis Pos- ticus 346 Actions 347 Fibular Region. Peroneus Longus 347 Peroneus Brevis 348 Actions 348 Surgical Anatomy of Tendons around Ankle 348 Muscles and Fascial of Foot. Anterior Annular Ligament . . . 348 Internal Annular Ligament . . . 349 External Annular Ligament . . . 349 Plantar .Fascia 349 Muscles of the Foot, Dorsal Region. Extensor Brevis Digitorum . . . 350 Plantar Region. Subdivision into Groups . Subdivision into Layers . First Layer . Second Layer Third Layer . Interossei 350 350 350 352 353 354 Surgical Anatomy of the Muscles of the Lower Extremity. Fracture of the Femur .... 353 the Patella . . . .356 the Tibia . . . .356 the Fibula, with Displace- ment of the Tibia . .357 The Arteries. General Anatomy. Subdivision into Pulmonary and Systemic Distribution of — Where found . Mode of Division — Anastomoses Structure of Arteries Sheath — Vasa Vasorum . Capillaries .... Aorta. Arch of Aorta Dissection Ascending Part of Arch . Transverse Part of Arch . Descending Part of Arch Peculiarities Surgical Anatomy . Branches .... Peculiarities of Branches 358 358 358 359 360 360 361 362 363 364 364 364 365 365 Coronary Arteries. Peculiarities 366 Arteria Innominata. Relations 366 Peculiarities 366 Surgical Anatomy 367 Common Carotid Arteries. Course and Relations .... 367 Peculiarities 370 Surgical Anatomy 370 External Carotid Artery. Relations 371 Surgical Anatomy 372 Branches 372 XIV CONTENTS. Superior Thyroid Artery. Course and Relations Surgical Anatomy . Lingual Artery. Course and Relations Branches .... Surgical Anatomy . Facial Artery, Course and Relations Branches .... Peculiarities Surgical Anatomy . Occipital Artery. Course and Relations Branches . PAOE 372 372 373 373 374 374 375 376 376 Posterior Auricular Artery. 376 377 Branches 377 Ascending Pharyngeal Artery. Branches . Thyroid Axis . Supra-scapular Artery Transversalis Colli . Internal Mammary . Superior Intercostal . Deep Cervical Artery Surgical Anatomy of the Axilla Axillary Artery. First Portion .... Second Portion Third Portion .... Peculiarities, Surgical Anatomy Branches . 378 378 378 379 Temporal Artery. Course and Relations Branches Surgical Anatomy . Internal Maxillary Artery. Course and Relations . 379 Peculiarities ...... 379 Branches from First Portion . '. ' 379 Second Portion . . 381 Third Portion . . .381 Surgical Anatomy of the Triangles of the Neck. Anterior Triangular Space. Inferior Carotid Triangle . . . 333 Superior Carotid Triangle . ." .' 383 Submaxillary Triangle . . '. [ 383 Posterior Triangular Space. Occipital Triangle . . . 334 Subclavian Triangle . . 334 Internal Carotid Artery. Cervical Portion Petrous Portion Cavernous Portion . Cerebral Portion Peculiarities, Surgical Anatomy Branches Ophthalmic Artery . . " Cerebral Branches of Internal Carotid '. Arteries of the Upper Extremity. Brachial Artery. Relations Bend of the Elbow . Peculiarities of Brachial Artery Surgical Anatomy . Branches Radial Artery. Relations Deep Palmar Arch . Peculiarities, Surgical Anatomy Branches Ulnar Artery. Relations ..... Superficial Palmar Arch . Peculiarities of Ulnar Artery . Surgical Anatomy . Branches Descending Aorta Thoracic Aorta. Relations Surgical Anatomy . Branches . 386 386 386 386 386 387 387 390 Subclavian Arteries. First Part of Right Subclavian Artery First Part of Left Subclavian Alter Second Part of Subclavian Artery Third Part of Subclavian Artery Peculiarities Surgical Anatomy . Branches . Vertebral Artery Basilar Artery . Circle of Willis . 391 392 393 393 393 394 395 396 397 397 Abdominal Aorta. Relations Surgical Anatomy . Branches Cceliac Axis, Gastric Artery Hepatic Artery Splenic Artery . Superior Mesenteric Artery Inferior Mesenteric Artery Supra-renal Arteries Renal Arteries . Spermatic Arteries Phrenic Arteries Lumbar Arteries Middle Sacral Artery Common Iliac Arteries Course and Relations Peculiarities, Surgical Anatomy Internal Iliac Artery. Course and Relations Peculiarities, Surgical Anatomy Branches Vesical Arteries Hemorrhoidal Arteries Uterine and Vaginal Arteries Obturator Artery PAOK 398 398 398 399 400 400 401 402 403 403 404 404 405 407 407 408 409 410 410 411 412 413 414 414 414 415 416 417 417 417 419 420 420 421 422 423 423 425 426 426 427 427 427 428 429 429 430 431 4:52 432 4:12 4:2 4i.2 CONTENTS. xv Internal Pudic Artery Sciatic Artery Gluteal, Ilio-lumbar, and Lateral Sacral Arteries . External Iliac Artery. Course and Relations . Surgical Anatomy Branches Epigastric Artery . Circumflex Iliac Artery . Femoral Artery. Course and Relations . Scarpa's Triangle Peculiarities Surgical Anatomy Branches Profunda Artery Popliteal Artery. Popliteal Space Course and Relations . Peculiarities, Surgical Anatomy Branches PAOE 433 435 436 437 437 437 437 438 438 438 440 440 441 442 443 444 445 445 Anterior Tibial Artery. Course and Relations Peculiarities, Surgical Anatomy Branches Dorsalis Pedis Artery. Course and Relations Peculiarities, Surgical Anatomy Branches Posterior Tibial Artery. Course and Relations Peculiarities, Surgical Anatomy Branches Peroneal Artery. Course and Relations Peculiarities .... Plantar Arteries. Internal Plantar External Plantar Pulmonary Artery. Right and Left Pulmonary PAOB 446 447 448 449 449 449 450 450 451 451 452 452 452 454 The Veins. General Anatomy. Subdivision into Pulmonary, Systemic, and Portal 455 Anastomoses of Yeins .... 455 Superficial Veins, Deep Yeins or Venae Comites 455 Sinuses, their Structure .... 455 Structure of Veins 456 Valves of Veins 457 Vessels and Nerves of Veins . . . 457 Veins of the Head and Neck. Facial Vein 458 Temporal Vein 459 Internal Maxillary Vein .... 459 Temporo-maxillary Vein .... 459 Posterior Auricular Vein, Occipital Vein 459 Veins of the Neck. External Jugular Vein .... 460 Posterior External Jugular Vein . . 460 Anterior Jugular Vein .... 460 Internal Jugular Vein .... 460 Lingual, Pharyngeal, and Thyroid Veins 461 Vertebral Veins 461 Veins of the Diploe 461 Cerebral Veins. Superficial Cerebral Veins . . . 462 Deep Cerebral Veins .... 463 Cerebellar Veins . . . . . 463 Sinuses of the Dura Mater. Superior Longitudinal Sinus . . . 463 Inferior Longitudinal, Straight, Lateral, and Occipital Sinuses .... 464 Cavernous Sinuses 465 Circular Sinus 465 Inferior Petrosal, and Transverse Sinuses 466 Superior Petrosal Sinus .... 466 Veins of the Upper Extremitt. Superficial Veins Deep Veins Axillary Vein . Subclavian Vein Innominate Veins Peculiarities of . Internal Mammary Vein . Inferior Thyroid Veins Superior Intercostal Veins Superior Vena Cava Azygos Veins . Spinal Veins . Veins of the Lower Extremity Internal Saphenous Vein . External Saphenous Vein Popliteal Vein . Femoral Vein . External Iliac Vein Internal Iliac Vein Common Iliac Vein Inferior Vena Cava Peculiarities Lumbar and Spermatic Veins . Ovarian, Renal, Supra-renal Veins Phrenic Veins .... Hepatic Veins .... Portal System of Veins. Inferior and Superior Mesenteric Veins Splenic and Gastric Veins Portal Vein Cardiac Veins. Coronary Sinus .... Pulmonary Veins. Distribution of .... 466 466 468 468 468 469 469 469 470 470 470 471 473 473 474 474 474 474 475 475 476 476 476 476 477 477 477 477 479 479 CONTENTS. The Lymphatics. General Anatomy. PAGE Structure of, 481 Subdivision into Deep and Superficial . 481 Coats of Lymphatics .... 481 Valves of Lymphatics .... 482 Lymphatic or Conglobate Glands . . 482 Structure of Lymphatic Glands . . 482 Thoracic Duct 483 Right Lymphatic Duct .... 484 Lymphatics of Head, Face, and Neck. Superficial Lymphatic Glands of Head . 484 Lymphatics of Head . . 484 of the Face . 484 Deep Lymphatics of the Face . . 484 of the Cranium . . 485 Lymphatic Glands of the Neck . . 485 Superficial Cervical Glands . . . 486 Deep Cervical Glands .... 486 Superficial and Deep Cervical Lym- phatics 486 Lymphatics of the Upper Extremity. Superficial Lymphatic Glands . Deep Lymphatic Glands .... Axillary Glands Superficial Lymphatics of Upper Ex- tremity ....... Deep Lymphatics of Upper Extremity . Lymphatics of the Lower Extremity. Superficial Inguinal Glands Deep Lymphatic Glands . Anterior Tibial Gland Deep Popliteal Glands Deep Inguinal Glands Gluteal and Ischiatic Glands . Superficial Lymphatics of Lower Ex- tremity .... Internal Group . External Group Deep Lymphatics of Lower Extremity . Lymphatics of Pelvis and Abdomen. Deep Lymphatic Glands of Pelvis . External Iliac Glands Internal Iliac Glands 487 487 487 488 488 488 488 489 489 489 489 489 489 489 490 490 490 Sacral Glands PAGE 490 Lumbar Glands .... 490 Lymphatics of Pelvis and Abdomen 490 Superficial Lymphatics of Wall of Ab- domen 490 of Gluteal Region 490 of Scrotum and Perineum . 490 of Penis .... 490 of Labia, Nymphse, and Clitoris 491 Deep Lymphatics of Pelvis and Ab- domen 491 Lymphatics of Bladder .... 492 of Rectum .... 492 of Uterus .... 492 of Testicle .... 492 of Kidney .... 492 of Liver .... 492 Lymphatic Glands of Stomach 492 Lymphatics of Stomach .... 492 Lymphatic Glands of Spleen . 493 Lymphatics of Spleen .... 493 Lymphatic System of the Intestines. Lymphatic Glands of Small Intestine (Mesenteric Glands) .... 493 Lymphatic Glands of Large Intestine 493 Lymphatics of Small Intestine (Lacteals) 493 of Large Intestine 493 Lymphatics of Thorax. Deep Lymphatic Glands of Thorax 493 Intercostal Glands .... 493 Internal Mammary Glands 493 Anterior Mediastinal Glands . 493 Posterior Mediastinal Glands . 493 Superficial Lymphatics on Front of Thorax . . . 494 Deep Lymphatics of Thorax . 494 Intercostal Lymphatics .... 494 Internal Mammary Lymphatics 494 Lymphatics of Diaphragm 494 Bronchial Glands 494 Lymphatics of Lung .... 494 Cardiac Lymphatics .... 494 Thymic Lymphatics .... 494 Thyroid Lymphatics .... 494 Lymphatics of (Esophagus 494 Nervous System. General Anatomy. Subdivision into Cerebro-spinal Axis, Ganglia, and Nerves .... Constituent Elements of Nervous System Fibrous Nervous Substance . ... Vesicular Nervous Substance . Chemical Composition .... Microscopic Structure of Tubular Fibres of Gelatinous Fibres of Vesicular Nervous Substance Where found. Ganglia. Structure 495 495 495 495 495 496 496 496 497 Nerves. Subdivision into Cerebro-spinal and Sym- pathetic . . ... 497 General Anatomy of the Nerves . . 498 TJie Spinal Cord and its Membranes. Dissection 500 Membranes of the Cord .... 500 Dura Mater 500 Arachnoid 501 Pia Mater 502 Lisramcntum Denticulatum . . 502 SpinafCord . .... 502 CONTENTS. xvn PAflE Fissures of Cord .... 503 Columns of Cord .... 503 Structure of Cord .... 504 Mode of Arrangement of Gray and White Matter . . . .504 "White Matter of Cord. Structure . 504 Gray Substance of Cord. Struc- ture 505 The Central Canal . . . .506 The Brain and its Membranes. Membranes of the Brain .... 507 Dura Mater. Structure .... . 507 Arteries, Veins, Nerves . . 507 Glanduhe Pacchioni . 507 Processes of the Dura Mater . . 508 Falx Cerebri . . 508 Tentorium Cerebelli . 508 Falx Cerebelli -. 508 Arachnoid Membrant Subarachnoid Space . *509 Cerebro-spinal Fluid . 509 Pia Mater. The Brain. Subdivision into Cerebrum, Cerebellum, Pons Varolii, Medulla Oblongata 510 Weight of Brain .... 510 Medulla Oblongata. Anterior Pyramids .... 511 Lateral Tract, and Olivary Body . 511 Restiform Bodies .... 511 Posterior Pyramids .... 511 Posterior Surface of Medulla Oblongata 512 Structure of Medulla Oblongata 512 of Anterior Pyramid 512 of Lateral Tract. 512 of Olivary Body 512 of Restiform Body . 513 Septum of Medulla Oblongata . 513 Gray Matter of Medulla Oblongata . 513 Pons Varolii. Structure . 514 Transverse Fibres .... 514 Longitudinal Fibres .... 514 Septum 515 Cerebrum. Upper Surface of Cerebrum . 515 Convolutions and Sulci . 515 Base of the Brain ..... 517 General Arrangement of the Parts com- posing the Cerebrum . 520 Interior of the Cerebrum . 520 Corpus Callosum 521 Lateral Ventricles 522 Boundaries of, and Parts forming the Lateral Ventricles 523 Septum Lucidum 525 Fornix 525 Velum Interpositum . 526 Thalami Optici .... 526 Third Ventricle 2 527 Anterior, Middle, and Posterior Commis- sures Gray Matter of Third Ventricle Pineal Gland . Corpora Quatlrigemina Valve of Vieussens . Corpora Geniculata . Structure of Cerebrum 1. Diverging or Peduncular Fibres 2. Transverse Commissural Fibres 3. Longitudinal Commissural Fibres Cerebellum. Its Position, Size, Weight, etc. Cerebellum, Upper Surface Under Surface Lobes of the Cerebellum . Fourth Ventricle Boundaries of Ventricle . Lining Membrane. Choroid Plexus Gray Matter of Cerebellum Structure of the Cerebellum Its Lamina; Corpus Dentatum Peduncles of Cerebellum . Cranial Nerves. Subdivision into Groups . Nerves of Special Sense . of Common Sensation of Motion Mixed Nerves . Olfactory Nerve Optic Nerve . Tracts . Commissure . Auditory Nerve Third Nerve Fourth Nerve . Sixth Nerve Relations of the Orbital Nerves in the Cavernous Sinus in the Sphenoidal Fissure . in the Orbit Facial Nerve .... Branches of Ninth or Hypoglossal Nerve . Fifth Nerve .... Casserian Ganglion . Ophthalmic Nerve . Lachrymal, Frontal, and Nasal Branches Superior Maxillary Nerve Inferior Maxillary Nerve . Auriculotemporal, Gustatory, and In- ferior Dental Branches . . . 550, Ophthalmic Ganglion Sphenopalatine Ganglion Otic Ganglion . Submaxillary Ganglion Eighth Pair Glosso-pharyngeal Pneumogastric . Spinal Accessory Spinal Nerves. Roots of the Spinal Nerves Origin of Anterior Roots . of Posterior Roots Ganglia of the Spinal Nerves . 561 56L 561 562 XY1U CONTENTS. Anterior Branches of the Spinal Nerves . 562 Posterior Branches of the Spinal Nerves 562 Cervical Nerves. Roots of the Cervical Nerves . . . 562 Anterior Branches of the Cervical Nerves 563 Cervical Plexus. Superficial Branches #>f the Cervical Plexus 564 Deep Branches of the Cervical Plexus . 565 Posterior Branches of the Cervical Nerves 565 Brachial Plexus. Branches above the Clavicle. Posterior Thoracic, Supra-scapular 567, 568 Branches below the Clavicle. Anterior Thoracic, and Subscapular Nerves 568, 569 Circumflex, and Musculo - cutaneous Nerves 569 Internal, and Lesser Internal Cutaneous Nerves 570 Median Nerve 571 Ulnar Nerve 573 Musculo-spiral Nerve .... 574 Radial Nerve 575 Posterior Interosseous Nerve . . 575 Dorsal Nerves. Roots of the Dorsal Nerves . . . 576 Intercostal Nerves 576 Upper Intercostal Nerves . . . 576 Intercosto-humeral Nerves . . . 577 Lower Intercostal Nerves . . . 577 Peculiar Dorsal Nerves .... 577 First Dorsal Nerve .... 577 Last Dorsal Nerve .... 577 Lumbar Nerves. Roots of Lumbar Nerves .... 578 Posterior Branches of Lumbar Nerves . 578 Anterior Branches of Lumbar Nerves . 578 Lumbar Plexus. Branches of Lumbar Plexus . . . 578 Uio-hypogastric Nerve .... 578 Ilio-inguinal, and Genito-crural Nerves . 580 External Cutaneous, and Obturator Nerves 580 Accessory Obturator Nerve . . . 582 Anterior Crural Nerve .... 582 Branches of 582 Middle Cutaneous 583 Internal Cutaneous, Long Saphenous . 583 Muscular and Articular Branches . 584 Sacral and Coccygeal Nerves. Roots of origin of 584 Posterior Sacral Nerves .... 584 Anterior Sacral Nerves . Posterior Branch of Coccygeal Nerve Anterior Branch of Coccygeal Nerve Sacral Plexus. Superior Gluteal Nerve . Pudic and Small Sciatic Nerves Great Sciatic Nerve .... Internal Popliteal Nerve . Posterior Tibial Nerve Plantar Nerves .... External Popliteal or Peroneal Nerve Anterior Tibial Nerve Musculo-cutaneous Nerve Sympathetic Nerve. Subdivision of Branches of the Ganglia, scription of . General De- PAOB 585 585 585 586 586 588 588 589 589 590 590 591 592 592 Cephalic Portion of Sympathetic Ganglia of Cervical Portion of the Sympathetic. Superior Cervical Ganglion Middle Cervical Ganglion Inferior Cervical Ganglion Carotid and Cavernous Plexuses Cardiac Nerves. Superior, Middle, and Inferior Cardiac Nerves Deep Cardie Plexus .... Superficial Cardiac Plexus Anterior and Posterior Coronary Plexus Thoracic Part of the Sympathetic. Great Splanchnic Nerve . . . Lesser Splanchnic Nerve Smallest Splanchnic Nerve Epigastric or Solar Plexus Semilunar Ganglia .... Phrenic, Supra-renal, and Renal Plexuses Spermatic, Cceliac, and Gastric Plexuses Hepatic, Splenic, and Superior Mesen- teric Plexuses . . . . Aortic, and Inferior Mesenteric Plexuses 594 594 595 595 595 596 596 597 597 597 598 598 598 598 598 599 599 599 Lumbar Portion of Sympathetic. 600 Branches of Pelvic Portion of Sympathetic Hypogastric Plexus Inferior Hypogastric or Pelvic Plexus Inferior Hemorrhoidal Plexus Vesical Plexus Prostatic Plexus .... Vaginal Plexus ..... Uterine Nerves .... 600 600 600 600 601 601 601 601 601 CONTENTS. xix Organs of Sense. Skin Derma or true Skin . Corium Papillary Layer Epidermis or Cuticle Vessels and Nerves of the Skin Appendages of the Skin. Nails Hairs Sebaceous md Sudoriferous Glands Tongue. Papillae of, and their Structure Follicles, and Mucous Glands of Fibrous Septum of . Muscular Fibres of . Arteries and Nerves of . Nose. Cartilages of . Muscles of ... . Skin, Mucous Membrane . Arteries, Veins, and Nerves . Nasal Fossa?. Mucous Membrane of ... Peculiarities of, in Superior, Middle, and Inferior Meatuses Arteries, Veins, and Nerves of Nasal Fossae Eye. Situation, Form of . Tunics of Sclerotic and its Structure Cornea and its Structure . Choroid and its Structure Ciliary Processes .... Iris Membrana Pupillaris, Ciliary Ligament Ciliary Muscle Retina Structure of Retina Jacob's Membrane Granular Layer Nervous Layer .... Radiating Fibres of the Retina Arteria Centralis Retina; Structure of Retina, at Yellow Spot Humors of the Eye. Aqueous Humor Anterior Chamber . Posterior Chamber . Vitreous Body .... Crystalline Lens and its Capsule Changes produced in the Lens by Age 615 PAGE 602 603 603 604 605 605 606 607 609 610 610 610 611 612 612 612 613 613 613 614 614 615 616 616 617 618 619 620 620 620 621 621 621 621 622 622 622 622 622 622 623 623 624 Suspensory Ligament of Lens . . 624 Canal of Petit 684 Vessels of the Globe of the Eye . . 024 Nerves of Eyeball .625 Appendages of the Eye Eyebrows . . . . . . &25 Eyelids 625 Structure of the Eyelids . . . .625 Tarsal Cartilages 625 Meibomian Glands 626 Eyelashes . .... 626 Conjunctiva 626 Caruncula Lacrymalis .... 627 Lachrymal Apparatus. Lachrymal Gland 628 Canals 628 Sac 628 Nasal Duct 628 Ear. Pinna or Auricle 628 Structure of Auricle .... 628 Ligaments of the Pinna .... 629 Muscles of the Pinna .... 630 Arteries, Veins, and Nerves of the Pinna 631 Auditory Canal 631 Middle Ear or Tympanum. Openings in Cavity of ... 632 Walls of 632, 633, 634 Eustachian Tube 634 Membrana Tympani .... 634 Structure of 634 Ossicles of the Tympanum . . . 634 Ligaments of the Ossicula . . . 635 Muscles of the Tympanum . . . 636 Mucous Membrane of Tympanum . . 636 Arteries, Veins, and Nerves of Tym- panum 636, 637 Internal Ear or Labyrinth. Vestibule Semicircular Canals Superior Semicircular Canal Posterior Semicircular Canal . External Semicircular Canal Cochlea Central Axis or Modiolus Spiral Canal .... Lamina Spiralis .... Scala Tympani, Scala Vestibuli Membranous Labyrinth . Utricle and Saccule Membranous Semicircular Canals Structure of the (Membranous) Labyrinth Vessels of the Labyrinth Auditory Nerve, Vestibular Nerve, Coch lear Nerve 637 638 638 638 638 639 639 639 640 640 640 641 641 641 641 642 CONTENTS. VISCERA. Organs of Digestion and their Appendages. Alimentary Canal Its Subdivisions The Mouth The Lips . The Cheeks The Gums Teeth. General Characters of Permanent Teeth .... Incisors, Canine, Bicuspid, Molars . Temporary or Milk Teeth Structure of the Teeth Ivory or Dentine, Chemical Composition Enamel, Cortical Substance Development of the Teeth of the Permanent Teeth . Growth of the Teeth Eruption of the Teeth Palate. Hard Palate Soft Palate Uvula, Pillars of the Soft Palate Mucous Membrane, Aponeurosis, and Muscles of Soft Palate Tonsils. Arteries, Veins, and Nerves of Tonsils . Salivary Glands. Parotid Gland. Steno's Duct . . . Vessels and Nerves of Parotid Gland Submaxillary Gland. Wharton's Duct * Vessels and Nerves of Submaxillary Gland Sublingual Gland. Vessels and Nerves of ... Structure of Salivary Glands . Structure of Pharynx. (Esophagus. PAGE 643 643 643 643 644 644 645 646 646 647 648 648 649 649 649 651 651 652 652 652 653 653 654 655 655 655 655 655 656 Kelations, Surgical Anatomy, and Struc- ture of Abdomen. Boundaries Apertures of . Regions . 657 658 659 659 Peritoneum. Reflections traced . Foramen of Winslow 660 661 Lesser Omentum .... PAGE . 662 Great Omentum . 662 Gastro-splenic Omentum . . 662 Mesentery . 662 Mesocaecum, Mesocolon . . 663 Stomach. 663 Splenic end, Pyloric end . . 663 Cardiac and Pyloric Orifices . . 663 Greater and Lesser Curvatures . 683 664 Ligaments of . . 664 Alterations in Position . 664 Pylorus . 665 Structure of Stomach . 665 Serous and Muscular Coats . 666 Mucous Membrane . . 666 Gastric Follicles . 666 Vessels and Nerves of Stomach . 667 Small Intestines. Duodenum .... . 667 Ascending portion . 667 Descending portion . . 667 Transverse portion . . 667 Vessels and Nerves of Duodenum . 668 . 668 , 668 Structure of Small Intestines . . 668 Serous, Muscular, and Cellular Coats . 668 Mucous Membrane . . 668 Epithelium and Valvuke Conniventes . 668 Villi — their Structure . 669 Simple Follicles, Duodenal Glands . 669 Solitary Glands . 969 Aggregate Glands . . 670 Large Intestine. . 670 Appendix Vermiformis Caeci . 671 Ileo-caecal Valve . 671 , 672 Ascending . 672 Transverse . 672 Descending . 672 Sigmoid Flexure . 672 672 Upper portion . . 673 Middle portion . . 673 Lower portion . . 673 Structure of Large Intestine . . 673 Serous and Muscular Coats . 673 Cellular and Mucous Coats . 674 Epithelium, Simple Follicles . . 674 Solitary Glands . 675 Liver. Size, Weight, Position of . 675 Its Surfaces and Borders . 675 Changes of Position . 675 CONTENTS. xxi PAGE Ligaments of the Liver .... 675 Longitudinal, Lateral. Coronary . 676 Round Ligament .... 676 Fissures of the Liver .... 676 Longitudinal 67G Fissure of Ductus Yenosus, Portal Fis- sure 677 Fissures for Gall-bladder and Vena Cava 677 Lobes of the Liver 677 Eight, Left .... 677, G78 Lobus Quadratus, L. Spigelii, L. Cauda- tus 678 Vessels of Liver 678 Lymphatics, Nerves .... 678 Structure of Liver 678 Serous Coat 678 Fibrous Coat 679 Lobules 679 Hepatic Cells 679 Biliary Ducts, Portal Vein . . .680 Hepatic Artery, Hepatic Veins . . 680 Gall-bladder. Structure 681 Biliary Ducts 681 Hepatic Ducts 681 Cystic, and Common Choledoch Ducts 682 Structure of Biliary Ducts . . 682 Pancreas. Dissection 682 Relations 683 Duct 683 Structure, Vessels, and Nerves . 684 Spleen. Relations . . . . . . .684 Size and Weight . . . . .684 Structure of Serous and Fibrous Coats . 685 Proper Substance 685 Malpighian Corpuscles .... 686 Splenic Artery and its distribution . . 687 Capillaries of Spleen .... 688 Veins of Spleen 688 Lymphatics and Nerves . . . 689 Thorax. PAllE Boundaries of 689 Superior Opening, Base .... 689 Parts passing through Upper Opening . 689 Pericardium. Structure 689 Fibrous Layer, Serous Layer . . . 680 Heart. Position, Size 691 Subdivision into Four Cavities . . 691 Circulation of Blood in Adult . . . 691 Auriculo-ventricular, and Ventricular Grooves 691 Right Auricle. Openings 693 Valves 693 Relics of Foetal Structure . . .693 Musculi Pectinati 693 Right Ventricle. Openings 694 Tricuspid Valve 694 Semilunar Valves 695 Chorda? Tendineae and Columnae Carnea; . 695 Left Auricle. Sinus and Appendix . . . . 695 Openings, Musculi Pectinati . . . 696 Left Ventricle. Openings 697 Mitral and Semilunar Valves . . . 697 Endocardium 697 Structure of Heart. Fibrous Rings 697 Muscular Structure 698 of Auricles .... 698 of Ventricles . . . .698 Vessels and Nerves of Heart . . . 699 Peculiarities in Vascular System of Foetus 699 Foramen Ovale, Eustachian Valve . . 699 Ductus Arteriosus 699 Umbilical or Hypogastric Arteries . .699 Fcetal Circulation 700 Changes in Vascular System at Birth . 702 Organs of Yoice and Eespiration. Tlie Larynx. Cartilages of the Larynx Thyroid Cartilage Cricoid and Arytenoid Cartilages Cartilages of Santorini andWrisberg Epiglottis. Its Structure Ligaments of the Larynx Ligaments connecting the Thyroid Carti lage with the Os Hyoides Ligaments connecting the Thyroid Carti lage with the Cricoid ... Ligaments connecting the Arytenoid Car- tilages to the Cricoid . Ligaments of the Epiglottis . Upper Aperture of the Larynx Cavity of the Larynx Glottis False Vocal Cords .... 703 703 704 705 705 705 705 706 706 706 706 707 707 707 True Vocal Cords .... 708 Ventricle of Larynx, Sacculus Laryngis 708 Muscles of Larynx ..... 708 Crico-thyroid .... 708 Crico-arytaenoideus posticus 708 lateralis 709 Thyro-arytaenoideus . 709 Muscles of the Epiglottis . 709 Thyro-epiglottideus . 710 Arytaeno-epiglottideus, superior 710 inferior 710 Actions of Muscles of Larynx 710 Mucous Membrane of Larynx . 710 Glands, Vessels and Nerves of 711 Trachea. Relations 712 Bronchi 712 xxu CONTENTS. PAOK Struciure of Trachea .... 712 Surgical Anatomy of Laryngotracheal Eegion . 713 The Pleura. Eeflections 715 Vessels and Nerves . . . .716 Mediastinum. Anterior Mediastinum .... 716 Middle Mediastinum .... 716 Posterior Mediastinum . . . .716 The Lungs. Surfaces, Lobes 717 Eoot of Lung 719 Weight, Color, and Properties of Sub- stance of Lung 719 Structure of Lung 719 Serous Coat, and Subserous AreolarTissue 719 PABB Parenchyma and Lobules of Lung . . 719 Bronchi, Arrangement of in Substance of Lung 719 Structure of Smaller Bronchial Tubes . 720 The Air-cells 720 Pulmonary Artery 720 Pulmonary Capillaries and Veins . . 720 Bronchial Arteries and Veins . . . 720 Lymphatics and Nerves of Lung . . 721 Thyroid Gland. Structure 721 Vessels and Nerves .... 721 Chemical Composition .... 722 Tliymus Gland. Structure 722 Vessels and Nerves .... 723 Chemical Composition .... 723 The Urinary Organs. Kidneys. Eelations Dimensions, Weight Cortical Substance . Medullary Substance Minute Structure Malpighian Bodies . Ureter, Pelvis, Infundibula Eenal Artery, Eenal Veins Lymphatics and Nerves . Ureters. Situation, Course, Eelations Structure Supra-renal Capsules. Eelations 724 724 724 725 725 726 726 726 727 727 727 727 Structure Vessels and Nerves Pelvis. Boundaries and Contents Bladder. Shape, Position, Eelations Subdivisions Ligaments Structure . Interior of Bladder Vessels and Nerves Male Urethra. Membranous Portion Spongy Portion Structure . 728 728 728 729 730 730 731 731 732 733 733 733 Male Generative Organs. Prostate Gland .... 735 Structure 735 Vessels and Nerves . 736 Cowper's Glands . . 736 Prostatic Secretion .... 736 Penis. Eoot 736 Glans Penis 736 Body ....... 736 Corpora Cavernosa .... 737 Structure 737 Corpus Spongiosum 737 The Bulb 737 Structure of Corpus Spongiosum 738 Erectile Tissue .... 738 Arteries of the Penis 738 Lymphatics of the Penis . 738 Nerves of the Penis 738 • The Testes. Form and Situation 739 Size and Weight .... 739 Scrotum 739 Other Coverings of the Testis . 739 Proper Coverings of the Testis 739 Tunica Vaginalis 740 Tunica Albuginea 740 Mediastinum Testis . 740 Tunica Vasculosa 740 Structure of the Testis 741 Lobules of the Testis 741 Number, Size, Shape, Position 741 Structure of the Lobuli Testis 741 Tubuli Seminiferi .... . 741 Arrangement in Lobuli . 741 in Mediastinum Testis 741 in Epididymis 741 Vasculum Aberrans 741 Vas Deferens, Course, Eelations 742 Structure 742 Vessels and Nerves of the Coverings o F the Testis 742 Spermatic Cord. Its Composition .... 742 Eelations of in Inguinal Canal 742 Arteries of the Cord 742 Veins of the Cord .... 743 Lymphatics and Nerves of the Cord 743 CONTENTS. xxin Vesicvlce Seminales. Form and Size Relations . Structure . PAOE 743 744 744 Ejaculatory Ducts . Structure of The Semen Descent of the Testes Gubernaculum Testis PAOK 744 744 744 744 745 Female Organs of Generation. Mons Veneris, Labia Majora . Labia Minora, Clitoris, Meatus Urinarius Hymen, Glands of Bartholine . Bladder . . . . • Urethra Rectum ....... Vagina. Relations Structure Uterus. Situation, Form, Dimensions Fundus, Body and Cervix Ligaments Cavity of the Uterus Structure .... Vessels and Nerves . Its Form, Size, and Situation in the Foetus at Puberty 746 747 747 748 748 749 749 749 750 750 750 750 751 751 752 752 752 during and after Menstruation 752 after Parturition 752 in Old Age 752 Appendages oftlie Uterus. Fallopian Tubes .... 752 Structure . 752 Ovaries . 752 Structure . 753 Graafian Vesicles 753 Ovum 754 Discharge of the Ovum 754 Corpus Luteum 754 Ligament of the Ovary 755 Round Ligaments . 755 Vessels and Nerves of Appendages 755 Mammary Glands. Structure of Mamma . 756 Vessels and Nerves . 757 Surgical Anatomy of Inguinal Hernia. Dissection 758 Inguinal Hernia. Superficial Fascia Superficial Vessels and Nerves 758 758 Varieties of . 764 Deep Layer of Superficial Fascia 758 Oblique Inguinal Hernia. Aponeurosis of External Oblique 759 External Abdominal Ring 760 Course and Coverings of . ... 764 Pillars of the Ring . 760 Seat of Stricture .... 764 Intercolumnar Fibres 760 Scrotal Hernia .... 765 Fascia 760 Bubonocele 765 Poupart's Ligament 760 Congenital Hernia .... 765 Gimbernat's Ligament 761 Infantile Hernia 765 Internal Oblique Muscle 761 Triangular Ligament Cremaster 761 761 Direct Inguinal Hernia. Trans versalis Muscle 762 Course and Coverings of the Hernia 765 Spermatic Canal Fascia Transversalis 762 Seat of Stricture .... 765 # 763 Incomplete Direct Hernia 766 Internal Abdominal Ring 763 Comparative Frequency of Oblique ant Subserous Areolar Tissue 763 Direct Hernia .... 76G Epigastric Artery . 764 Diagnosis of Oblique and Direct Hernia 766 Peritoneum 764 Surgical Anatomy of Femoral Hernia. Dissection 766 Superficial Fascia .... 766 Cutaneous Vessels .... 766 Internal Saphenous Vein ' . Superficial Inguinal Glands 767 767 Cutaneous Nerves .... 767 Deep Layer of Superficial Fascia . 768 Cribriform Fascia .... 768 Fascia Lata 768 Iliac Portion .... 768 Pubic Portion .... 769 Saphenous Opening .... 769 Crural Arch Gimbernat's Ligament Crural Sheath . Deep Crural Arch . Crural Canal . Femoral or Crural Ring Position of Parts around the Ring Septum Crurale Descent of Femoral Hernia Coverings of Femoral Hernia . Varieties of Femoral Hernia . Seat of Stricture 769, 769 770 770 771 771 771 771 772 773 773 773 774 XXIV CONTENTS. Surgical Anatomy of Perineum and Ischio-rectal Region. Ischio-rectal Region. Dissection Boundaries of . Superficial Fascia External Sphincter Internal Sphincter Ischio-rectal Fossa Position of Parts contained in Perineum. Boundaries, and Extent . Superficial Layer of Superficial Fascia Deep Layer of Superficial Fascia . Course taken by the Urine in Rupture of the Urethra .... Muscles of the Perineum (Male) Accelerator Urina? . Erector Penis Transversus Perinei Superficial Perineal Vessels and Nerves Transversus Periaei Artery Muscles of the Perineum (Female) Sphincter Vaginae .... Erector Clitoridis .... PAGE 775 775 775 776 77G 776 776 777 777 777 778 778 778 77'.) 779 780 780 780 780 780 Transversus Perinei Compressor Urethra; Levator Ani Deep Perineal Fascia Anterior Layer Posterior Layer Parts between the two Layers Compressor Urethra; Cowper's Glands Pudic Vessels and Nerves Artery of the Bulb . Levator Ani Relations, Actions . Coccygeus, Relations, Actions Position of Viscera at Outlet of Pelvis Parts concerned in the Operation of Lithotomy Parts divided in the Operation Parts to be avoided in the Operation Abnormal Course of Arteries in the Perineum Pelvic Fascia . Obturator Fascia Recto-vesical Fascia 780 780 780 781 781 781 781 781 781 781' 781 781 782 782 782 783 784 784 785 785 786 786 Surgical Anatomy of Muscles of the Extremities 320 —354 a " Talipes .... * . 348 " Arteries " Triangles of the Neck . 364—450 . 382 u " Axilla .... 401 u " Bend of Elbow 407 u " Scarpa's Triangle . 438 u 11 " Popliteal Space " (Esophagus • 443 657 « " Laryngotracheal Region 713 • ( " Inguinal Hernia 7G2 u (( " Femoral Hernia •" Perineum " Prostate Gland • \ 766 775 782 - " Base of Bladder , 783 LIST OF ILLUSTRATIONS. 4S* The Illustrations, when copied from any other work, have the author's name affixed ; when no such acknow- ledgment is made, the drawing is to be considered original. Those marked with * are new in this edition. FIG 1. 2. 3. 4. 5. 6. 7. 8 14, 15. 16. 17 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. Osteology. A Cervical Vertebra Atlas .... Axis .... *Seventh Cervical Vertebra A Dorsal Vertebra Peculiar Dorsal Vertebrae A Lumbar Vertebra to 13. Development of the Vertebrae Sacrum, anterior surface * Vertical Section of the Sacrum Sacrum, posterior surface to 19. Development of Sacrum . Coccyx, anterior and posterior surfaces Lateral View of Spine . Occipital Bone, outer surface Occipital Bone, inner surface Occipital Bone, development of Parietal Bone, external surface Parietal Bone, internal surface Frontal Bone, outer surface Frontal Bone, inner surface *Frontal Bone at Birth . Temporal Bone, outer surface Temporal Bone, inner surface Temporal Bone, petrous portion Temporal Bone, development of Sphenoid Bone, superior surface Sphenoid Bone, anterior surface Sphenoid Bone, posterior surface Plan of the Development of Sphenoid Ethmoid Bone, outer surface Perpendicular Plate of Ethmoid *Ethmoid Bone, inner surface of right lateral mass *Skull at Birth, showing the anterior and posterior Fontanelles *Lateral Fontanelles Nasal Bone, outer surface Nasal Bone, inner surface Superior Maxillary Bone, outer surface Superior Maxillary Bone, inner surface Development of Superior Maxillary Bone Lachrymal Bone, outer surface . Malar Bone, outer surface Malar Bone, inner surface Palate Bone, internal view Quain Quain Quain Quain Quain ( xxv ) XXVI LIST OF ILLUSTRATIONS. FIG. 52. Palate Bone, posterior view 53. Inferior Turbinated Bone, inner surface 54. Inferior Turbinated Bone, outer surface 55. Vomer ..... 56. Inferior Maxillary Bone, outer surface . 57. Inferior Maxillary Bone, inner surface . 58. *Side-view of the Lower Jaw, at Birth 59. *Side-view of the Lower Jaw, at Puberty 60. *Side-view of the Lower Jaw, in the Adult 61. *Side-view of the Lower Jaw, in Old Age 62. Base of Skull, inner surface 63. Base of Skull, outer surface 64. *Side-view of the Skull . 65. Anterior Region of Skull 66. Nasal Fossae, roof, floor, and wall 67. Nasal Fossae, inner wall or septum 68. Hyoid Bone, anterior surface 69. Sternum and Costal Cartilages, anterior surface 70. Sternum, posterior surface 71 to 74. Development of Sternum 75. A Rib . 76. Vertebral Extremity of a Rib . 77 to 81. Peculiar Ribs 82. Clavicle, anterior surface 83. Clavicle, inferior surface 84. Scapula, anterior surface or venter 85. Scapula, posterior surface or dorsum 86. Plan of the Development of the Scapula 87. Humerus, anterior view . 88. Humerus, posterior surface 89. Plan of the Development of the Humerus 90. Bones of the Forearm, anterior surface 91. Bones of the Forearm, posterior surface 92. Plan of the Development of the Ulna . 93. Plan of the Development of the Radius 94. Bones of the Hand, dorsal surface 95. Bones of the Hand, palmar surface 96. Plan of the Development of the Hand . 97. Os innominatum, external surface 98. Os Innominatum, internal surface 99. Plan of the Development of the Os Innominatum 100. *Male Pelvis (adult) .... 101. *Female Pelvis (adult) . . 102. *Vertical Section of the Pelvis, with lines indicating the Axes of the 103. Right Femur, anterior surface . 104. Right Femur, posterior surface . 105. *Diagram showing the Structure of the Neck of the Femur 106. Plan of the Development of the Femur 107. Right Patella, anterior surface . 108. Right Patella, posterior surface 109. Tibia and Fibula, anterior surface 110. Tibia and Fibula, posterior surface 111. Plan of the Development of the Tibia 112. Plan of the Development of the Fibula 113. Bones of the Foot, dorsal surface 114. Bones of the Foot, plantar surface 115. Plan of the Development of the Foot Pelvis Ward LIST OF ILLUSTRATIONS. XXTll Articulations. FIO. 116. Vertical Section of Two Vertebra; and their Ligaments, front view 117. Occipito-atloid and Atlo-axoid Ligaments, front view . 118. Occipito-atloid and Atlo-axoid Ligaments, posterior view 119. Articulation between Odontoid Process and Atlas 120. Occipito-axoid and Atlo-axoid Ligaments 121. Temporo-maxillary Articulation, external view 122. Temporo-maxillary Articulation, internal view 123. Temporo-maxillary Articulation, vertical section 124. Costo-vertebral and Costo-transverse Articulations, anterior view 125. Costo-transverse Articulation ..... 126. Costo-sternal, Costo-xiphoid, and Intercostal Articulations, anterior 127. Articulations of Pelvis and Hip, anterior view 128. Articulations of Pelvis and Hip, posterior view 129. Vertical Section of the Symphysis Pubis 130. Sterno-clavicular Articulation ..... 131. Shoulder-Joint, Scapuloclavicular Articulation, and proper Ligament 132. Elbow-Joint, showing anterior and internal Lateral Ligaments 133. Elbow-Joint, showing posterior and external Lateral Ligaments 134. Ligaments of "Wrist and Hand, anterior view . 135. Ligaments of Wrist and Hand, posterior view . 136. Vertical Section of Wrist, showing the Synovial Membranes 137. Articulations of the Phalanges 138. Hip-Joint, laid open 139. Knee-Joint, anterior view 140. Knee-Joint, posterior view 141. Knee-Joint, showing internal Ligaments 142. Head of Tibia, with semilunar Cartilages, &c, seen from above 143. Ankle-Joint, Tarsal and Tarso-metatarsal Articulations, internal view 144. Ankle-Joint, Tarsal and Tarso-metatarsal Articulations, external view 145. Ligaments of Plantar surface of the Foot . 146. Svnovial Membranes of the Tarsus and Metatarsus Muscles and Fascise. 147. Plan of Dissection of the Head, Face, and Neck 148. Muscles of the Head, Face, and Neck . 149. Muscles of the right Orbit 150. Relative position and attachment of the Muscles of the left Eyeball 151. Temporal Muscle .... 152. Pterygoid Muscles . . . 153. Muscles of the Neck, and Boundaries of the Triangles 154. Muscles of the Neck, anterior view 155. Muscles of the Tongue, left side 156. Muscles of the Pharynx, external view . 157. Muscles of the Soft Palate 158. The Prevertebral Muscles .... 159. Plan of Dissection of the Muscles of the Back . 160. Muscles of tjie Back — first, second, and part of the third layers 161. Muscles of the back — deep layers 162. Plan of Dissection of Abdomen 163. External Oblique Muscle 164. Internal Oblique Muscle 165. Transversalis, Rectus, and Pyramidalis Muscles 166. Transverse Section of Abdomen in Lumbar Region 167. Diaphragm, under surface 168. Dissection of Upper Extremity . view Arnold Arnold s of Scapula Arnold do. Arnold uam Quain XXV111 LIST OF ILLUSTRATIONS. Fia. 169. Muscles of the Chest and Front of the Arm, superficial view 170. Muscles of the Chest and Front of the Arm, with the boundaries of the Axilla 171. Muscles on the Dorsum of the Scapula and the Triceps 172. Front of the Forearm, superficial muscles 173. Front of the Forearm, deep muscles 174. Posterior surface of Forearm, superficial muscles 175. Posterior surface of Forearm, deep muscles 176. *Transverse section through the Wrist, showing Posterior Annular Canals for the passage of the Extensor Tendons 177. Muscles of the Hand, palmar surface . 178. Dorsal Interossei of Hand 179. Palmar Interossei of Hand 180. Fracture of the Middle of the Clavicle . 181. Fracture of the Surgical Neck of the Humerus 182. Fracture of the Humerus above the Condyles . 183. Fracture of the Olecranon 184. Fracture of shaft of the Radius . 185. Fracture of the lower end of the Radius 186. Plan of Dissection of Lower Extremity, front view 187. Muscles of the Iliac and Anterior Femoral Eegions 188. Muscles of the Internal Femoral Region 189. Plan of Dissection of Lower Extremity, posterior view 190. Muscles of the Hip and Thigh . 191. Muscles of the Front of the Leg 192. Muscles of the back of the Leg, superficial layer 193. Muscles of the back of the Leg, deep layer 194. Muscles of the sole of the Foot, first layer 195. Muscles of the sole of the Foot, second layer . 196. Muscles of the sole of the foot, third layer 197. Dorsal Interossei of Foot 198. Plantar Interossei of Foot 199. Fracture of the neck of the Femur within the Capsular Ligament 200. Fracture of the Femur below the Trochanters . 201. Fracture of the Femur above the Condyles 202. Fracture of the Patella .... 203. Oblique fracture of the shaft of the Tibia 204. Fracture of the Fibula, with displacement of the Tibia Arteries. 205. Arch of the Aorta and its branches 206. Plan of the branches of the Arch of the Aorta 207. Surgical Anatomy of the. Arteries of the Neck 208. Plan of the branches of the External Carotid . 209. Arteries of the Face and Scalp . 210. The Internal Maxillary Artery, and its branches 211. Plan of the branches of the Internal Maxillary Artery 212. Internal Carotid and Vertebral Arteries 213. Ophthalmic Artery and its branches 214. Arteries of the base of the Brain 215. Plan of the branches of the Right Subclavian Artery 216. Scapular and Circumflex Arteries 217. Axillary Artery, and its branches 218. Surgical Anatomy of the Brachial Artery " . 219. Surgical Anatomy of the Radial and Ulnar Arteries 220. Ulnar and Radial Arteries, deep view . 221. Arteries of the back of the Forearm and Hand 222. Abdominal Aorta and its branches PAGE 295 he Axilla 297 301 306 • 309 . 311 311 Ligament, and 315 . 317 . 319 . . 320 Hind 321 do. 321 do. 322 do. 322 do. 323 do. 324 327 328 Q uain 332 335 336 341 343 345 351 352 353 354 354 Hind 355 do. 355 do. 356 do. 356 do. 356 do. 357 362 362 369 369 374 380 380 385 387 389 395 399 401 406 410 413 415 41,9 LIST OF ILLUSTRATIONS. . XXIX FIG. 223. C celiac Axis and its branches, the Liver having been raised, and the Lesser Omen- tum removed ........ 224. Cceliac Axis and its branches, the Stomach having been raised, and the Transverse Mesocolon removed ..... 225. Superior Mesenteric Artery and its branches . 226. Inferior Mesenteric Artery and its branches 227. Arteries of the Pelvis ..... 228. 229. Variations in Origin and Course of Obturator Artery 230. Arteries of the Gluteal and Posterior Femoral Regions 231. Surgical Anatomy of the Femoral Artery 232. Popliteal, Posterior Tibial, and Peroneal Arteries 233. Surgical Anatomy of the Anterior Tibial and Dorsalis Pedis Arteries 234. Plantar Arteries, superficial view 235. Plantar Arteries, deep view .... Yeins. 236. Veins of the Head and Neck ........ 237. Veins of the Diploe, as displayed by the removal of the outer table of the Skull Breschet 238. Vertical Section of the Skull, showing the Sinuses of the Dura Mater 239. Sinuses at the Base of the Skull ..... 240. Superficial Veins of the Upper Extremity .... 241. Vena? Cavae and Azygos Veins, with their Formative Branches 242. Transverse Section of a Dorsal Vertebra, showing the Spinal Veins Breschet 243. Vertical Section of two Dorsal Vertebra?, showing the Spinal Veins 244. Internal or long Saphenous Vein and its Branches 245. External or short Saphenous Vein . . . 246. Portal Vein and its Branches ..... 421 422 424 426 429 433 435 439 446 448 453 453 458 462 464 465 466 469 472 472 473 474 478 Lymphatics. 247. Thoracic and Right Lymphatic Ducts .... 248. Superficial Lymphatics and Glands of the Head, Face, and Neck 249. Deep Lymphatics and Glands of the Neck and Thorax 250. Superficial Lymphatics and Glands of the Upper Extremity . 251. Superficial Lymphatics and Glands of the Lower Extremity . 252. Deep Lymphatic Vessels and Glands of the Abdomen and Pelvis Nervous System. 253. Spinal Cord and its Membranes .... 254. Transverse Section of the Spinal Cord and its Membranes 255. Spinal Cord, side view. Plan of the Fissures and Columns . 256. Transverse Sections of the Cord ... . 257. *Transverse Section of the Gray Substance of the Spinal Cord, i near the middle of the Dorsal Region . . . j 258. *Transverse Section of the Gray Substance of the Spinal Cord, -i through the middle of the Lumbar Enlargement . . j 259. *Longitudinal Section of the White and Gray Substance of the i Spinal Cord, through the middle of the Lumbar Enlargement j 260. Medulla Oblongata and Pons Varolii, anterior surface 261. Posterior Surface of Medulla Oblongata 262. Transverse Section of Medulla Oblongata 263. Columns of the Medulla Oblongata, and their Connection with the l Cerebrum and Cerebellum .....) 264. Upper Surface of the Brain, the Pia Mater having been removed 265. Base of the Brak ...... 266. Section of the Brain, made on a level with the Corpus Callosum Mascagni do. do. do. do. Arnold Quain Arnold do. do. Arnold Altered from Arnold 483 485 486 487 489 491 501 501 503 504 J. L. Clarke 505 505 506 511 512 512 513 516 518 521 XXX LIST OF ILLUSTRATIONS. 267. Lateral Ventricles of the Brain ....... 522 268. Fornix, Velum Interpositum, and Middle or Descending Cornu of the Lateral Ventricle 524 269. Third and Fourth Ventricles ........ 527 270. Upper Surface of the Cerebellum ...... 530 271. Under Surface of the Cerebellum . . . . - . . 531 272. Vertical Section of the Cerebellum ..... Arnold 533 Cranial Nerves. 273. Optic Nerves and Optic Tracts .... 274. Course of the Fibres in the Optic Commissure 275. Nerves of the Orbit, seen from above .... 276. Nerves of the Orbit and Ophthalmic Ganglion, side view 277. Course and Connections of the Facial Nerve in the Temporal Bone 278. Nerves of the Scalp, Face, and Side of the Neck 279. Hypoglossal Nerve, Cervical Plexus, and their Branches . . 280. Distribution of the Second and Third Divisions of the Fifth Nerve i and Submaxillary Ganglion .... J 281. Spheno-Palatine Ganglion and its Branches 282. Otic Ganglion and its Branches .... 283. Origin of the Eighth Pair, their Ganglia and Communications 284. Course and Distribution of the Eighth Pair of Nerves Bowman After Arnold After Arnold After Bidder After Arnold Bendz 536 537 538 539 540 542 544 ■After Arnold 549 553 554 555 556 Spinal Nerves. 285. Plan of the Brachial Plexus .... 286. Cutaneous Nerves of Upper Extremity, anterior view 287. Cutaneous Nerves of Upper Extremity, posterior view 288. Nerves of the Upper Extremity, front view 289. Supra-scapular, Circumflex, and Musculo-spiral Nerves 290. Lumbar Plexus and its Branches 291. Cutaneous Nerves of Lower Extremity, front view • 292. Nerves of the Lower Extremity, front view 293. Cutaneous Nerves of Lower Extremity, posterior view 294. Nerves of the Lower Extremity, posterior view 295. Plantar Nerves ...... 296. Sympathetic Nerve ..... . 567 . 569 . 570 . 572 . 574 Altered from Quain 579 . 581 . 581 . 587 . 587 . 589 . 593 Organs of Sense. 297. Sectional View of the Skin, magnified ....... 298. Upper Surface of the Tongue ........ 299. Three kinds of Papillae of the Tongue, magnified . . Bowman 300. Cartilages of the Nose ....... Arnold 301. Bones and Cartilages of Septum of Nose, right side . . . do. 302. Nerves of Septum of Nose, right side ..... do. 303. Vertical Section of the Eyeball, enlarged . . ... 304. Choroid and Iris, enlarged ..... Altered from Zinn 305. Veins of the Choroid, enlarged ...... Arnold 306. Arteries of the Choroid and Iris, enlarged . . . .do. 307. Arteria Centralis Betinae, Yellow Spot, etc., the anterior half of the Eyeball being removed, enlarged .....•••• 308. Crystalline Lens, hardened and divided, enlarged . . . Arnold 309. Meibomian Glands, etc., seen from the Inner Surface of the Eyelids . do. 310. Lachrymal Apparatus, right side ....... 311. Pinna or Auricle, outer surface ........ 312. Muscles of the Pinna ....... Arnold 602 608 608 611 612 614 615 617 618 619 621 624 626 627 629 630 LIST OP ILLUSTRATIONS XXXI Scarpa PAGE 631 . 633 Arnold 635 Scemmerrmg 638 Arnold 639 Breschet 641 313. Front View of the Organ of Hearing, right side 314. View of Inner Wall of Tympanum, enlarged 315. Small Bones of the Ear, seen from the outside, enlarged 316. Osseous Labyrinth, laid open, enlarged 317. Cochlea laid open, enlarged .... 318. Membranous Labyrinth detached, enlarged Organs of Digestion and their Appendages. 319. Sectional View of the Nose, Mouth, Pharynx, etc. . 320. Permanent Teeth, external view 321. Temporary or Milk Teeth, external view 322. Vertical Section of a Molar Tooth 323. Vertical Section of a Bicuspid Tooth, magnified . . After Retzius 324 to 329. Development of Teeth ..... Goodsir 330. Salivary Glands ...... 331. The Regions of the Abdomen and their contents 332. Reflections of the Peritoneum, as seen in a Vertical Section of •» Altered from the Abdomen ..... } Quain 333. Mucous Membrane of the Stomach and Duodenum, with the Bile Ducts 334. Muscular Coat of the Stomach ....... 335. Minute Anatomy of Mucous Membrane of Stomach . . Dr. Sprott Boyd 336. Two Villi, magnified ........ 337. Patch of Peyer's Glands, from the lower part of the Ileum 338. A portion of Peyer's Glands, magnified . . . . Boehm 339. Caecum and Colon laid open, to show the Ilio-caecal Valve 340. Minute Structure of Large Intestine ..... Boehm 341. Liver, upper surface ........ 342. Liver, under surface ........ 343. Longitudinal section of an Hepatic Vein .... Kieman 344. Longitudinal section of a small Portal Vein and Canal . . • do. 345. Transverse section of a small Portal Canal and its vessels . . do. 346. Pancreas and its Relations ........ 347. Transverse section of the Spleen, showing the Tubercular Tissue, and the Splenic Vein and its branches ........ 348. Malpighian Corpuscles, and their Relation with the Splenic Artery and its branches 349. One of the Splenic Corpuscles, showing its Relations with flic Bloodvessels . 350. Transverse section of the Human Spleen, showing the distribution of the Splenic Artery and its branches ........ 644 645 647 648 648 650 054 658 660 664 665 666 669 670 670 671 674 676 677 679 679 680 683 685 686 687 688 Organs of Circulation. 351. *Front view of the Thorax, showing the relation of the Thoracic Viscera to the walls of the Chest .......... 690 352. Right Auricle and Ventricle laid open, the anterior walls of both being removed . 692 353. Left Auricle and Ventricle laid open, the anterior walls of both being removed . 696 354. Plan of the Fcetal Circulation ........ 700 , Organs of Voice and Eespiration. 355. Side view of the Thyroid and Cricoid Cartilages 356. Cartilages of the Larynx, posterior view .... 357. *Larynx and adjacent parts, seen from above .... 358. *Vertical section of the Larynx and upper part of the Trachea 359. Muscles of Larynx, side view, right Ala of Thyroid Cartilage removed 360. Interior of the Larynx, seen from above, enlarged 361. Front view of Cartilages of Larynx, the Trachea and Bronchi Willis 703 704 706 707 709 709 711 xxxn LIST OF ILLUSTRATIONS. 362. *Transverse section of the Trachea, just above its Bifurcation, with a bird's-eye view of the interior ........ 363. Surgical Anatomy of the Laryngotracheal Region .... 364. Transverse section of the Thorax, showing the relative position of the Yiscera, and the reflections of the Pleura ...... 365. *Front view of the Thorax, showing the relation of the Thoracic Viscera to the walls of the Chest . . . . . . 366. Front view of the Heart and Lungs ...... 712 714 715 717 718 The Urinary and Generative Organs. 367. Vertical section of the Kidney .... 368. Plan to show the minute structure of the Kidney . . . Bowman 369. Vertical section of Bladder, Penis, and Urethra • . 370. Bladder and Urethra laid open, seen from above 371. Testis in situ, the Tunica Vaginalis having been laid open 372. Vertical section of the Testicle, to show the arrangement of the ducts 373. Base of the Bladder, with the Vasa Deferentia and Vesiculae Seminales Haller 374. Vulva and External Female Organs of Generation ..... 375. Section of Female Pelvis, showing position of Viscera .... 376. Uterus and its Appendages, anterior view .... Wilson 377. *Section of the Ovary of a Virgin, showing the Stroma and Graafian Vesicles 378. *Section of the Graafian Vesicle .... After Van Baer 379. *Ovum of the Sow ...... After Barry 380. Inguinal Hernia, Superficial Dissection ..... 381. Inguinal Hernia, showing the Internal Oblique, C remaster, and Spermatic Canal 382. Inguinal Hernia, showing the Transversalis Muscle, the Transversalis Fascia, and the Internal Abdominal Ring .... 383. Femoral Hernia, Superficial Dissection 384. Femoral Hernia, showing Fascia Lata, and Saphenous Opening 385. Femoral Hernia, Iliac Portion of Fascia Lata removed, and Sheath of Femoral Vessels and Femoral Canal exposed 386. Hernia ; the Relations of the Femoral and Internal Abdominal Rings, seen from within the Abdomen, right side ...... 387. 388. Variations in Origin and Course of Obturator Artery 389. Plan of Dissection of Perineum and Ischio-rectal Region 390. Perineum; the Integument and Superficial Layer of Superficial Fascia reflected 391. The Superficial Muscles and Vessels of the Perineum . . 392. Deep Perineal Fascia ; on the Left Side the Anterior Layer has been removed 393. A view of the Position of the Viscera at the Outlet of the Pelvis 394. A transverse section of the Pelvis, showing the Pelvic Fascia . After Wilson 395. Side view of the Pelvic Viscera of the Male Subject, showing the Pelvic and Perineal Fasciae .......... 725 725 729 732 740 741 743 746 748 753 753 753 754 759 761 763 767 768 770 772 772 776 778 779 780 783 784 785 ANATOMY, DESCRIPTIVE AND SURGICAL. Osteology. In the construction of the human body, it would appear essential, in the first place, to provide some dense and solid texture capable of forming a framework for the support and attachment of the softer parts of the frame, and of forming cavities for the protection of the more important vital organs; and such a structure we find provided in the various bones, which form what is called the Skeleton (oxexxu>, to dry tip). Structure and Physical Properties of Bone. Bone is one of the hardest structures of the animal body ; it possesses also a certain degree of toughness and elasticity. Its color, in a fresh state, is of a pinkish-white externally, and deep red within. On examining a section of any bone, it is seen to be composed of two kinds of tissue, one of which is dense and compact in texture, like ivory; the other consisting of slender fibres and lamellae, which join to form a reticular structure; this, from its resemblance to lattice-work, is called cancellated. The compact tissue is always placed on the exterior of a bone; the cancellous tissue is always internal. The relative quantity of these two kinds of tissue varies in different bones, and in different parts of the same bone, as strength or lightness is requisite. Close examination of the compact tissue shows it to be extremely porous, so that the difference in structure between it and the cancellous tissue depends merely upon the different amount of solid matter, and the size and number of the spaces in each; in the compact tissue the cavities being small, and the solid matter between them abundant, whilst in the cancellous tissue the spaces are large, and the solid matter diminished in quantity. Chemical Analysis. Bone consists of an organic or animal, and an inorganic or earthy material, intimately combined together: the animal matter giving to bone its elasticity and toughness, the earthy part its hardness and solidity. The animal constituent may be separated from the earthy by steeping bone in a dilute solution of nitric or muriatic acid : by this process the earthy constituents are gradually dissolved out, leaving a tough semi-transparent substance, which retains, in every respect, the original form of the bone. This is often called cartilage, but differs from it in being softer, more flexible, and, when boiled under a high pressure, it is almost entirely resolved into gelatine. Cartilage does, however, form the animal basis of bone in certain parts of the skeleton. Thus, according to Tomes and De Morgan, it occurs in the petrous part of the temporal bone; and, according to Dr. Sharpey, on the articular ends of adult bones, lying underneath the natural cartilage of the joint. The earthy constituent may be obtained by subjecting a bone to strong heat in an open fire with free access of air. By these means the animal matter is entirely consumed, the earthy part remaining as a white brittle substance still preserving the original shape of the bone. Both constituents present the singular property of remaining unaltered in chemical composition after a lapse of centuries. 3 34 OSTEOLOGY. The organic constituent of bone forms about one-third, or 33.3 per cent.; the inorganic matter, two-thirds, or 66.7 per cent. : as is seen in the subjoined analysis by Berzelius: — Organic Matter, Gelatine and Bloodvessels . 33.30 1 Phosphate of Lime . . 51.04 Inorganic Carbonate of Lime . . 11.30 or Fluoride of Calcium . 2.00 Earthy Matter, Phosphate of Magnesia . 1.16 V Soda and Chloride of Sodium . . 1.20 100.00 Some chemists add to this about one per cent, of fat. The relative proportions of the two constituents of bone are found to differ in different hones of the skeleton, as shown by Dr. Owen Eees. Thus, the bones of the head, and the long bones of the extremities, contain more earthy matter than those of the trunk; and those of the upper extremity somewhat more than the corresponding bones of the lower extremity. The humerus contains more earthy matter than the bones of the forearm ; and the femur more than the tibia and fibula. The vertebras, ribs, and clavicle contain nearly the same proportion of earthy matter. The metacarpal and metatarsal bones contain about the same proportion as those of the trunk. Much difference exists in the analyses given by chemists as to the proportion between the two constituents of bone at different periods of life. According to Schreger, and others, there is considerable increase in the earthy constituents of the bones with advancing years. Dr. Eees states that this is especially marked in the long bones, and the bones of the head, which, in the foetus, do not contain the excess of earthy matter found in those of the adult. But the bones of the trunk in the foetus, according to this analyst, contain as much earthy matter as those of the adult. On the other hand, the analyses of Stark and Yon Bibra show that the proportions of animal and earthy matter are almost precisely the same at different periods of life. According to the analyses of Yon Bibra, Yalentin, and Dr. Kees, the compact substance contains more earthy matter than the cancellous. The comparative analysis of the same bones in both sexes shows no essential difference between them. There are facts of some practical interest, bearing upon the difference which seems to exist in the amount of the two constituents of bone at different periods of life. Thus, in the child, where the animal matter predominates, it is not uncommon to find, after an injury to the bones, that they become bent or only partially broken, from the large amount of flexible animal matter which they contain. Again, also in aged people, where the bones contain a large proportion of earthy matter, the animal matter at the same time being deficient in quantity and quality, the bones are more brittle, their elasticity is destroyed, and, hence, fracture takes place more readily. Some of the diseases, also, to which bones are liable, mainly depend on the disproportion between the two constituents of bone. Thus, in the disease called rickets, so common in the children of scrofulous parents, the bones become bent and curved, either from the superincumbent weight of the body, or under the action of certain muscles. This depends upon some deficiency of the nutritive system, by which bone becomes minus its normal proportion of earthy matter, whilst the animal matter is of unhealthy quality. In the vertebra of a rickety subject, Dr. Bostock found in 100 parts 79.75 animal, and 20.25 earthy matter. Form of Bones. The various mechanical purposes for which bones are employed in the animal economy require them to be of very different forms. All the scien- tific principles of Architecture and Dynamics are more or less exemplified in the construction of this part of the human body. The power of the arch in resisting ^ GENERAL ANATOMY OF BONE. 35 superincumbent pressure is well exhibited in various parts of the skeleton, such as the human foot, and more especially in the vaulted roof of the cranium. Bones are divisible into four classes : Long, Short, Flat, and Irregular. The Long Bones are found chiefly in the limbs, where they form a system of levers, which have to sustain the weight of the trunk, and to confer extensive powers of locomotion. A long bone consists of a lengthened cylinder or shaft, and two extremities. The shaft is a hollow cylinder, the walls consisting of dense compact tissue of great thickness in the middle, and becoming thinner towards the extremities ; the spongy tissue is scanty, and the bone is hollowed out in its interior to form the medullary canal. The extremities are generally somewhat expanded for greater convenience of mutual connection, for the purposes of articulation, and to afford a broad surface for muscular attachment. Here the bone is made up of spongy tissue with only a thin coating of compact substance. The long bones are, the clavicle, humerus, radius, ulna, femur, tibia, fibula, metacarpal and metatarsal bones, and the phalanges. Short Bones. Where a part is intended for strength and compactness, and the motion at the same time slight and limited, it is divided into a number of small pieces united together by ligaments, and the separate bones are short and com- pressed, such as the bones of the carpus and tarsus. These bones, in their struc- ture, are spongy throughout, excepting at their surface, where there is a thin crust of compact substance. Flat Bones. Where the principal requirement is either extensive protection, or the provision of broad surfaces for muscular attachment, we find the osseous struc- ture remarkable for its slight thickness, becoming expanded into broad flat plates, as is seen in the bones of the skull and shoulder-blade. These bones are composed of two thin layers of compact tissue, inclosing between them a variable quantity of cancellous tissue. In the cranial bones, these layers of compact tissue are familiarly known as the tables of the skull ; the outer one is thick and tough, the inner one thinner, denser, and more brittle, and hence termed the vitreous table. The intervening cancellous tissue is called the diploe. The flat bones are, the occipital, parietal, frontal, nasal, lachrymal, vomer, scapulee, ossa innominata, sternum, and ribs. The Irregular or Mixed bones are such as, from their peculiar form, cannot be grouped under either of the preceding heads. Their structure is similar to that of other bones, consisting of a layer of compact tissue externally, and of spongy cancellous tissue within. The irregular bones are, the vertebrse, sacrum, coccyx, temporal, sphenoid, ethmoid, superior maxillary, inferior maxillary, palate, inferior turbinated, and hyoid. Surfaces of Bones. If the surface of any bone is examined, certain eminences and depressions are seen, to which descriptive anatomists have given the following names. A prominent process projecting from the surface of a bone, which it has never been separate from, or movable upon, is termed an apophysis (from drtoyveis, an excrescence) ; but if such process is developed as a separate piece from the rest of the bone to which it is afterwards joined, it is termed an epiphysis (from hnlyvais, an accretion). These eminences and depressions are of two kinds: articular and non-articular. Well-marked examples of articular eminences are found in the heads of the humerus and femur; and of articular depressions, in the glenoid cavity of the scapula, and the acetabulum. Non-articular eminences are designated according to their form. Thus, a broad, rough, uneven elevation is called a tuberosity; a small, rough prominence, a tubercle; a sharp, slender, pointed eminence, a spine; a narrow, rough elevation, running some way along the surface, a ridge, or line. The non-articular depressions are also of very variable form, and are described as fossre, grooves, furrows, fissures, notches, etc. These non-articular eminences and depressions serve to increase the extent of surface for the attachment of liga 3G OSTEOLOGY. inents and muscles, and are usually well marked in proportion to the muscularity of the subject. Microscojjcc Structure. If a thin transverse section from the shaft of a long bone be examined with a power of about 20 diameters, a number of aper- tures, surrounded by a series of concentric rings, are observed, with small, dark spots grouped around them, also in a concentric manner. The apertures are sections of the Haversian canals (so called after their discoverer, Clopton Havers); the concentric rings are sections of the lamellae, which are developed around the Haversian canals ; the dark spots are small cavities in the substance of the bone, called lacunse. The Haversian canals are channelled out of the compact substance for the pur- pose of conveying bloodvessels for its nutrition. They vary in size from the 2 ^ to the tj^'ott °f an mcn m diameter, the average size being about z \-$. They are generally round or oval, sometimes angular. Those nearest to the outer sur- face, where the bone is most compact, are very small ; but, towards the medullary canal, they gradually acquire a larger size, and open into it, or into the cells of tlm cancellous tissue. The Haversian canals are lined by a delicate membrane con- tinuous with the periosteum ; the smallest canals contain a single capillary vessel ; those larger in size contain a network of vessels: whilst the largest contain blood- vessels and marrow. If a thin longitudinal section of the shaft of a long bone be examined, the Haversian canals will be found to run in the long axis of the bone, and parallel with each other, communicating freely by transverse or oblique canals, so as to form, for the most part, rectangular meshes. Some of these canals open on the outer surface, to admit bloodvessels from the periosteum ; others communi- cate with the medullary canal, receiving bloodvessels from the interior of this part. By this means, the Haversian canals establish a free communication between the bloodvessels of the periosteum, and those of the medullary membrane. If a higher power is now applied to the same transverse section, each Haversian canal appears surrounded by a series of concentric rings, varying in number from eight to fifteen ; these rings are termed the lamellve, and their appearance is pro- duced by transverse sections of concentric layers of bone that have been developed around the Haversian canal, the last formed layer being deposited on that surface next to the bloodvessel. This concentric arrangement is not complete around all the canals; for here and there one set of lamellae may be seen ending between two adjacent ones. Besides the lamellae surrounding the Haversian canals, some are disposed parallel with the outer and inner surfaces of the bone ; these are termed circumferential lamellae, and may be considered as concentric with the medullary canal. Others, again, penetrate between the Haversian systems ; these are termed interstitial lamellae. Each Haversian canal, together with its concentric lamellae of bone, lacunae, etc., is called an Haversian system, the bloodvessel contained in the central canal being the source of nutrition to the lamellae which surround it. Nearly the whole of the compact tissue is made up of these Haversian systems, each one being, to a certain extent, independent of the rest. In a longitudinal section, the lamellae are seen running in lines parallel with the Haversian canal which they surround, except when the section passes transversely or obliquely across a canal, in which case an appearance is seen, somewhat similar to that observed in a transverse section. This lamellated structure may be easily demon- strated on a piece of bone softened in dilute acid, when the lamellae may be peeled from the surface of the bone in a longitudinal direction. According to Dr. Sharpey, the lamella3, in structure, consist of fine transparent fibres decussating each other, so as to form a delicate network, the fibres apparently coalescing at their point of junction. The lamellae are perforated, in certain situations, by bundles of fibres which penetrate them in a more or less oblique direction, serving to securely approximate the several plates. The lamellae are also perforated by numerous minute apertures placed at regular distances apart, which are, probably, transverse sections of the canaliculi. In this fibrous basis of the lamellae, the inorganic elements of bone are intimately united. GENERAL ANATOMY OF BONE. 37 A transverse section of compact bone sometimes exhibits certain vacuities or spaces, termed, by Messrs. Tomes and De Morgan, Haversian spaces. These spaces are found at al\ periods of life, but especially in young and growing bones. They are characterized by an irregular or jagged outline, and are apparently produced by the absorption of parts of several Haversian systems, which have been, to a greater or less extent, removed in order to form them. These spaces may exist in various conditions: in some, the process of absorption is evidently going on; in others, the spaces are lined by newly-formed lamellae which fill up the peripheral portion of the space; in others, the lamellas fill in the whole of the space, leaving a Haversian canal in the centre. It would thus appear, that portions of the Haversian systems are, from time to time, removed by absorption, and a new system of lamellae re-formed in place of those previously existing. Sometimes, these spaces may be seen filled in, at one part, by the deposition of lamellas; while, at another part, they are extending themselves by absorption. We have already said, that the dark spots seen in and between the lamellae, arranged in concentric circles around the Haversian canals, are the lacunse. They are minute cavities existing in the osseous substance, having numerous fine ^ tubes called canaliculi issuing from all parts of their circumference. In fresh bones, each lacuna contains a delicate cell, with pellucid contents, and a single nucleus ; and from the cell numerous fine processes are given off, which fill the canaliculi. These are the bone cells, discovered by Virchow. The lacunae are oval flattened spaces, lying parallel to the direction of the lamellae. The canaliculi issuing from them are extremely minute, their diameter ranging from T1 kw to 5 noun °f aT1 inch. They communicate freely with the canaliculi of adjoining lacunae, some opening into the Haversian canals, or in the cancelli of the spongy substance, and some upon the free surface of the bone. By this communication between the lacunae and canaliculi traversing the entire substance of the bone, the plasma of the blood is carried into every part. Vessels of Bone. The bloodvessels of bone are very numerous. Those of the compact tissue are derived from a close and dense network of vessels, which ramify in a fibrous membrane termed the periosteum, which covers the surface of the bone in nearly every part. From this membrane, vessels pass through the minute orifices in the compact tissue, running through the canals which traverse its substance. The cancellous tissue is supplied in a similar way, but by a less numerous set of larger vessels, which, perforating the outer compact tissue, are distributed to the cavities of the spongy portion of the bone. In the long bones, numerous apertures may be seen at the ends near the articular surfaces, some of which give passage to the arteries referred to; but the greater number, and these are the largest of them, are for the veins of the cancellous tissue which run separately from the arteries. The medullary canal in the shafts of the long bones is supplied by one large artery, — or sometimes more, — which enters the bone at the nutritious foramen (situated, in most cases, near the centre of the shaft), and perforates obliquely the compact substance. This vessel, usually accompanied by one or two veins, sends branches upwards and downwards, to supply the medullary membrane, which lines the central cavity and the adjoining canals. The ramifications of this vessel anastomose with the arteries both of the cancellous and compact tissues. In most of the flat, and in many of the short spongy bones, one or more large apertures are observed, which transmit, to the centre of the bone, vessels which correspond to the medullary arteries and veins. The veins emerge from the long bones in three places (Kolliker). 1. By a large vein which accompanies the nutrient artery; 2. by numerous large and small veins at the articular extremities; 3. by many small veins which arise in the compact substance. In the flat cranial bones, the veins are large, very numerous, and run in tortuous canals in the diploic tissue, the sides of which are constructed of a thin lamella of bone, perforated here and there for the passage of branches from the adjacent cancelli. The veins thus inclosed and supported by the osseous structure, 38 OSTEOLOGY. have exceedingly thin coats; and when the bony structure is divided, thej remain patulous, and do not contract in the canals in which they are. contained. Hence the constant occurrence of purulent absorption after amputation, in those cases where the stump becomes inflamed, and the cancellous tissue is infiltrated and bathed in pus. Lymphatic vessels have been traced, by Cruikshank, into the substance of bone, but Kolliker doubts their existence. Nerves are distributed freely to the perios- teum, and accompany the nutritious arteries into the interior of the bone. They are said, by Kolliker, to be most numerous in the articular extremities of the long bones, in the vertebrae, and the larger flat bones. Periosteum. The bones are covered by a tough fibrous membrane, the periosteum, which adheres to their surface in nearly every part, excepting at their cartilaginous extremities, and where strong tendons are attached. ,It is highly vascular; and, from it, numerous vessels pass into minute orifices which cover the entire surface of the bone. It consists of two layers closely united together; the outer one formed chiefly of connective tissue, and occasionally a few fat-cells ; the inner one, of elastic fibres of the finer kind, which form dense elastic membranous networks, superimposed in several layers (Kolliker). In young bones, this membrane is thick, very vascular, intimately connected at either end of the bone with the epiphysal cartilage ; but less closely connected with the shaft, from which it is separated by a layer of soft blastema, in which ossification proceeds on the exterior of the young bone. Later in life, the periosteum is thinner, less vascular, and more closely connected with the adjacent bone, this adhesion growing stronger as age advances. The periosteum serves as a nidus for the ramification of the vessels previous to their distribution in the bone ; hence the liability of bone to exfolia- tion or necrosis, when, from injury, it is denuded of this membrane. Marrow. The medullary canal of adult long bones, the cavities of the cancellous tissue, and the larger Haversian canals, are filled with a substance called marrow, and lined by a highly vascular areolar tissue, the medullary membrane, or internal periosteum. It is by means of the vessels which ramify through this membrane, that the nourishment of the medulla and contiguous osseous tissue is effected. The marrow differs in composition at different periods of life, and in different bones. In young bones, it is a transparent reddish fluid, of tenacious consistence, free from fat; and contains numerous minute roundish polynucleated cells. In the shafts of adult long bones, the marrow is of a yellow color, and contains, in 100 parts, 96.0 fat, 1.0 areolar tissue and vessels, and 3.0 of fluid with extractive matters ; whilst, in the flat and short bones, in the articular ends of the long bones, in the bodies of the vertebras, the base of the cranium, and in the sternum and ribs, it is of a red color, and contains, in 100 parts, 75.0 water, and 25.0 solid matter, consisting of albumen, fibrin, extractive matter, salts, and a mere trace of fat. It consists of fat-cells with a large quantity of fluid, containing numerous polynucleated cells, similar to those found in foetal marrow. Development of Bone. From the peculiar uses to which bone is applied in forming a hard skeleton or framework for the softer materials of the body, and in inclosing and protecting some of the more important vital organs, we find its development takes place at a very early period. Hence, the parts that appear soonest in the embryo are the vertebral column and the skull, the great central column, to which the other parts of the skeleton are appended. At an early period of embryonic life, the parts destined to become bone consist of a congeries of cells, connected together by an amorphous blastema which constitutes the simplest form of cartilage. This temporary cartilage, as it is termed, is an exact miniature of the bone which, in due course, is to take its place ; and as the process of ossification is slow, and not completed until adult life, it increases in bulk by an interstitial development of new cells. The next step in this process is the ossification of the intercellular substance, and of the cells composing the cartilage. Ossification commences in the interior of the cartilage at certain points, called points or centres of ossification, from which it extends into the surrounding substance. This mode GENERAL ANATOMY OF BONE. 39 of ossification is called intra-cartilaginous, to distinguish it from that which takes {)lace in a membranous tissue, quite different in its nature from cartilage. The atter mode of ossification is called intra-membranous. Examples of it are seen, according to Kolliker, in the upper half of the expanded portion of the occipital bone ; the parietal and frontal bones ; the squamous portion and tympanic ring of the temporal bone ; the internal lamella of the pterygoid process of the sphenoid ; the cornua sphenoidalia ; in all the bones of the face, excepting the inferior turbi- nated ; and, according to Brack, in the clavicle. The period of ossification is different in different bones. The order of succes- sion may be thus arranged (Kolliker) : — In the second month, first, in the clavicle, and lower jaw (fifth to seventh week); then, in the vertebrae, humerus, femur, the ribs, and the cartilaginous portion of the occipital bone. At the end of the second, and commencement of the third month, the frontal bone, the scapula, the bones of the forearm and leg, and upper jaw, make their appearance. In the third month, the remaining cranial bones, with few exceptions, begin to ossify, the metatarsus, the metacarpus, and the phalanges. In the fourth month, the iliac bones, and the ossicula auditus. In the fourth or fifth month, the ethmoid, sternum, pubis, and ischium. From the sixth to the seventh month, the calcaneum, and astragalus. In the eighth month, the hyoid bone. At birth, the epiphyses of all cylindrical bones, occasionally with the exception of those of the femur and tibia ; all the bones of the carpus ; the five smaller ones of the tarsus ; the patella ; sesamoid bones ; and the last pieces of the coccyx, are still unossified. From the time of birth to the fourth year, osseous nuclei make their appearance also in these parts. At twelve years, in the pisiform bone. The number of ossific centres is different in different bones. In most of the short bones, ossification commences by a single point in the centre, and proceeds towards the circumference. In the long bones, there is a central point of ossification for the shaft or diaphysis ; and one or more for each extremity, the epiphyses. That for the shaft is the first to appear ; those for the extremities appear later. For a long period after birth, a thin layer of unossified cartilage remains between the diaphysis and epiphyses, until their growth is finally completed, their junction taking place either at the period of puberty, or towards the end of the period of growth. The union of the epiphyses with the shaft takes place in the inverse order to that in which their ossification began ; for, although ossification commences latest in those epiphyses towards which the nutritious artery in the several bones is directed, they become joined to the diaphyses sooner than the epiphyses at the opposite extremity, with the exception of the fibula, the lower end of which commences to ossify at an earlier period than the upper end, but, nevertheless, is joined to the shaft earliest. The order in which the epiphyses become united to the shaft appears to be regulated by the direction of the nutritious artery of the bone. Thus the arteries of the bones of the arm and forearm are directed towards the elbow, and the epiphyses of the bones forming this joint become united to the shaft before those at the opposite extremity. In the lower extremities, on the contrary, the nutritious arteries pass in a direction from the knee; that is upwards in the femur, downwards in the tibia and fibula ; and in them it is observed, that the upper epiphysis of the femur, and the lower epiphyses of the tibia and fibula, become first united to the shaft. Where there is only one epiphysis, the medullary artery is directed towards that end of the bone where there is no additional centre : as, towards the acromial end in the clavicle ; towards the distal end of the metacarpal bone of the thumb and great toe; and towards the proximal end of the other metacarpal and metatarsal bones. A knowledge of the exact periods when the epiphyses become joined to the tJ^sI. 40 OSTEOLOGY. shaft aids the surgeon in the diagnosis of many of the injuries to which the joints are liable ; for it not unfrequently happens that, on the application of severe force to a joint, the epiphyses become separated from the shaft, and such injuries may be mistaken for fracture. Growth of Bone. Increase in the length of a bone is provided for by the deve- lopment of new bone in the cartilage at either end of the shaft (diaphysis); and in the thickness, by the deposition of soft ossifying blastema in successive layers upon the inner surface of the periosteum. The entire skeleton in an adult consists of 204 distinct bones. These are — Vertebral column (sacrum and coccyx included) 26 Cranium ........ 8 Ossicula auditus ...... 6 Face 14 Os hyoides, sternum, and ribs .... 26 Upper extremities ...... 64 Lower extremities 60 204 In this enumeration, the patellae and other sesamoid bones, as well as the Wormian bones, are excluded, as are also the teeth, which differ from bone both in structure, development, and mode of growth. THE SPINE. The Spine is a flexuous column, formed of a series of bones called Vertebrse. The Vertebrae are thirty-three in number, exclusive of those which form the skull, and have received the names cervical, dorsal lumbar, sacral, and coccygeal, according to the position which they occupy ; seven being found in the cervical region, twelve in the dorsal, five in the lumbar, five in the sacral, and four in the coccygeal. This number is sometimes found increased by an additional segment in one region, or the number may be diminished in one region, the deficiency being supplied by an additional segment in another. These observations do not apply to the cervical portion of the spine, the number of segments forming which is seldom increased or diminished. The Vertebrae in the three uppermost regions of the spine are separate segments throughout the whole of life ; but those found in the sacral and coccygeal regions are, in the adult, firmly united, so as to form two bones — five entering into the formation of the upper bone or sacrum, and four into the terminal bone of the spine or coccyx. General Characters of a Vertebra. Each vertebra consists of two essential parts, an anterior solid segment or body, and a posterior segment, the arch. The arch is formed of two pedicles and two laminae, supporting seven processes ; viz., four articular, two transverse, and one spinous process. The Bodies of the vertebrae are piled one upon the other, forming a strong pillar, for the support of the cranium and trunk; the arches forming behind these a hollow cylinder for the protection of the spinal cord. The different segments are connected together by means of the articular processes, and the transverse and spinous processes serve as levers for the attachment of muscles which move the different parts of the spine. Lastly, between each pair of vertebrae apertures exist through which the spinal nerves pass from the cord. Each of these con- stituent parts must now be separately examined. / CHARACTERS O^ THE CERVICAL VERTEBRJE. 41 The Body is the largest and most solid part of a vertebra. Above and below, it is slightly concave, presenting a rim around its circumference ; and its surfaces are rough, for the attachment of the intervertebral fibro-cartilages. In front it is convex from side to side, concave from above downwards. Behind, flat from above down- wards and slightly concave from side to side. Its anterior surface is perforated by a few small apertures, for the passage of nutrient vessels ; whilst on the posterior surface is a single irregular-shaped aperture, or occasionally several large apertures, for the exit of veins from the body of the vertebra, the vense basis vertebrse. The Pedicles project backwards, one on each side, from the upper part of the body of the vertebra, at the line of junction of its posterior and lateral surfaces. The concavities above and below the pedicles are the intervertebral notches ; they are four in number, two on each side, the inferior ones being generally the deeper. When the vertebrae are articulated, the notches of each contiguous pair of bones form the intervertebral foramina, which communicate with the spinal canal and transmit the spinal nerves. The Laminse are two broad plates of bone, which complete the vertebral arch behind, inclosing a foramen which serves for the protection of the spinal cord ; they are connected to the body by means of the pedicles. Their upper and lower borders are rough, for the attachment of the ligamenta subjlava. The Articular Processes, four in number, two on each side, spring from the junction of the pedicles with the laminae. The two superior project upwards, their articular surfaces being directed more or less backwards, the two inferior project downwards, their articular surfaces looking more or less forwards. The Spinous Process projects backwards from the junction of the two laminae, and serves for the attachment of muscles. The Transverse Processes, two in number, project one at each side from the point where the articular processes join the pedicle. They also serve for the attachment of muscles. Characters of the Cervical Vertebrae. The Body (fig. 1) is smaller than in any other region of the spine, and broader from side to side than from before backwards. The anterior and posterior surfaces are flattened and of equal depth ; the former is placed on a lower level than the Fig. 1. — A Cervical Vertebra. Anterior Talercle of Trans.Troc foramen fm- Vertebral Art TostencrTulcrch of Trans . P roc, Transverse Process. ^Superior Articular Prores*. -Life riorArtlcala r Srccest. latter, and its inferior border is prolonged downwards so as to overlap the upper and fore part of the vertebra below. Its upper surface is concave transversely, and presents a projecting lip on each side ; its lower surface being convex from side to side, concave from before backwards, and presenting laterally a shallow concavity, which receives the corresponding projecting lip of the adjacent verte- bra. The pedicles are directed obliquely outwards, and the superior intervertebral 42 OSTEOLOGY. notches are deeper, but narrower, than the inferior. The laminse are narrow, long, thinner above than below, and overlap each other; inclosing the spinal foramen, which is very large, and of a triangular form. The spinous processes are short, bifid at the extremity, to afford greater extent of surface for the attach- ment of muscles, the two divisions being often of unequal size. They increase in length from the fourth to the seventh. The transverse processes are short, directed downwards, outwards, and forwards, are bifid at their extremity, and marked by a groove along their upper surface, which runs downwards and out- wards from the superior intervertebral notch, and serves for the transmission of one of the cervical nerves. The transverse processes are pierced at their base by a foramen, for the transmission of the vertebral artery, vein, and plexus of nerves. Each process is formed by two roots ; the anterior root arises from the side of the body, and corresponds to the ribs ; the posterior root springs from the junction of the pedicle with the lamina, and corresponds with the transverse processes in the dorsal region. It is by the junction of these two processes, that the vertebral foramen is formed. The extremities of each of these roots form the anterior and posterior tubercles of the transverse processes. The articular processes are oblique: the superior are of an oval form, flattened, and directed upwards and backwards; the inferior downwards and forwards. The peculiar vertebrae in the cervical region are the first or Atlas; the second or Axis; and the seventh or Vertebra prorninens. The great modifications in the form of the atlas and axis are- to admit of the nodding and rotatory movements of the head. The Atlas (fig. 2) is so named from supporting the globe of the head. The chief Fig. 2. — 1st Cervical Vertebra or Atlas. Tubercle- Trans. Prooc Toramen for Vertebral Art?. Groove fcr Verz>e£. Art ? ajid'l.'-' Cerv.Nerva Spin. Proc, peculiarities of this bone are, that it has neither body nor spinous process. The body is detached from the rest of the bone, and forms the odontoid process of the second vertebra, the parts corresponding to the pedicles pass in front and join to form the anterior arch. The atlas consists of an anterior arch, a posterior arch, and two lateral masses. The anterior arch forms about one-fifth of the bone ; its anterior surface is convex, and presents about its centre a tubercle, for the attachment of the Longus colli muscle ; posteriorly it is concave, and marked by a smooth oval or circular facet, for articulation with the odontoid process of the axis. The posterior arch forms about two-fifths of the circumference of the bone ; it terminates behind in a tubercle, which is the rudiment of a spinous process, and gives origin to the Eectus capitis posticus minor. The diminutive size of this process prevents any interference in the movements between it and the cranium. The posterior part of the arch presents above a rounded edge ; whilst in front, immediately behind each superior articular process, is a groove, sometimes converted into a foramen by a delicate bony spiculum which arches CERVICAL VERTEBRAE. 43 backwards from the posterior extremity of the superior articular process. These grooves represent the superior intervertebral notches, and are peculiar from being situated behind the articular processes, instead of before them, as in the other vertebne. Thej serve for the transmission of the vertebral artery, which, ascending through the foramen in the transverse process, winds round the lateral mass in a direction backwards and inwards. They also transmit the sub-occipital nerves. On the under surface of the posterior arch, in the same situation, are two other grooves, placed behind the lateral masses, and representing the inferior interver- tebral notches of other vertebrae ; they are much less marked than the superior. The lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head ; they present two articulating processes above, and two below. The two superior are of large size, oval, concave, and approach towards one another in front, but diverge behind ; they are directed upwards, inwards, and a little backwards, forming a kind of cup for the condyles of the occipital bone, and are admirably adapted to the nodding movements of the head. Not unfrequentl} 7 ' they are partially subdivided by a more or less deep indentation which encroaches upon each lateral margin ; the inferior articular processes are circular in form, flattened, or slightly concave, and directed downwards, inwards, and a little backwards, articulating with the axis, and permitting the rotatory movements. Just below the inner margin of each superior articular surface, is a small tubercle, for the attachment of a ligament which, stretching across the ring of the atlas, divides it into two unequal parts ; the anterior or smaller segment receiving the odontoid process of the axis, the posterior allowing the transmission of the spinal cord and its membranes. This part of the spinal canal is of con- siderable size, to afford space for the spinal cord ; and hence lateral displacement of the atlas may occur without compression of the spinal cord. (This ligament and the odontoid process are marked in figure 2 in dotted outline.) The trans- verse processes are of large size, for the attachment of special muscles which assist in rotating the head — long, not bifid, perforated at their base by a canal for the vertebral artery, which is directed from below, upwards and backwards. The Axis (fig. 3) is so named from forming the pivot upon which the head Fig. 3. — 2d Cervical Vertebra or Axis. Odontoid JPros , Rovgh Surf, for CAee'A Lig^- Artic.Swrf.fer Trant.Ligt • Spin. Free. J Artie. Surf.foT Atlas A— Body Trant.Proe. Infer. A. rtic. Pro*. rotates. The most distinctive character of this bone is the strong prominent process, tooth-like in form (hence the name odontoid), which rises perpendi- cularly from the upper part of the body. The body is of a triangular form ; deeper in front than behind, and prolonged downwards anteriorly so as to overlap the upper and fore part of the adjacent vertebra. It presents in front a median longitudinal ridge, separating two lateral depressions for the attachment of the Longi colli muscles. The odontoid process presents two articulating surfaces: 44 OSTEOLOGY. one in front of an oval form, for articulation with the atlas ; another behind, for the transverse ligament; the latter frequently encroaches on the sides of the process ; the apex is pointed. Below the apex this process is somewhat enlarged, and presents on either side a rough impression for the attachment of the odontoid or check ligaments, which connect it to the occipital bone ; the base of the process, where attached to the body, is constricted, so as to prevent displacement from the transverse ligament, which binds it in this situation to the anterior arch of the atlas. Sometimes, however, this process does become displaced, especially in children, where the ligaments are more relaxed ; instant death is the result. The pedicles are broad and strong, especially their anterior extremities which coalesce with the sides of the body and the root of the odontoid process. The laminae are thick and strong, and the spinal foramen very large. The superior articular surfaces are round, slightly convex, directed upwards and outwards, and are peculiar in being supported on the body, pedicles, and transverse processes. The inferior articular surfaces, have the same direction as those of the other cervical vertebras. The superior intervertebral notches are very shallow, and lie behind the articular processes ; the inferior in front of them, as in the other cervical vertebras. The transverse processes are very small, not bifid, and perforated by the vertebral foramen, which is directed obliquely upwards and outwards. The spinous process is of large size, very strong, deeply channelled on its under surface, and presents a bifid tubercular extremity for the attachment of muscles, which serve to rotate the head upon the spine. Seventh Cervical (fig. 4). The most distinctive character of this vertebra is the existence of a very long, and prominent spinous pro- cess; hence the name Vertebra prominens. This process is thick, nearly horizontal in direction, not bifurcated, and has attached to it the ligamentum nuchas. The transverse process is usually of large size, especially its posterior root, its upper surface has usually a shallow groove, and seldom pre- sents more than a trace of bifur- cation at its extremity. The ver- tebral foramen is sometimes as large as in the other cervical ver- tebrae, usually smaller, on one or both sides, and sometimes want- On the left side, it occasion - Pig. 4. -7th Cervical Vertebra or Vertebra Prominens. Bcdy. msr. Spinous .Prscj/S ally gives passage to the vertebral artery; more frequently the ver- tebral vein traverses it on both sides ; but the usual arrangement is for both artery and vein to pass through the foramen in the transverse process of the sixth cervical. Characters of the Dorsal Vertebrae. The bodies of the dorsal vertebrae (fig. 5) resemble those in the cervical and lumbar regions at the respective ends of this portion of the spine ; but in the middle of the dorsal region their form is very characteristic, being heart-shaped, and broader in the antero-posterior than in the lateral direction. They are thicker behind than in front, flat above and below, convex and prominent in front, deeply concave behind, slightly constricted in front and at the sides, and marked on- each side, near the root of the pedicle, by two demi-facets, one DORSAL YERTEBRJE. 45 above, the other below. These are covered with cartilage in the recent state; and, when articulated with the adjoining vertebrae, form oval surfaces for the reception of the heads of the corresponding ribs. The pedicles are directed backwards, and the inferior intervertebral notches are of large size, and deeper than in any other region of the spine. The laminse are broad and thick, and the spinal foramen small, and of a circular form. The articular processes are flat, nearly vertical in direction, and project from the upper and lower part of the pedicles, the superior being directed backwards and a little outwards and upwards, the inferior forwards and a little inwards and downwards. The transverse pro- cesses arise from the same parts of the arch as the posterior roots of the trans- verse processes in the neck ; they are thick, strong, and of great length, directed obliquely backwards and outwards, presenting a clubbed extremity, lipped on its anterior part by a small concave surface, for articulation with the tubercle of a rib. Besides the articular facet for the rib, two indistinct tubercles may be seen rising from the extremity of the transverse processes, one' near the upper, the other near the lower border. In many they are comparatively of small size, and serve only for the attachment of muscles. But in some animals, they attain con- siderable magnitude either for the purpose of more closely connecting the seg- ments of this portion of the spine, or for muscular and ligamentous attachment. The spinous processes are long, triangular in form, directed obliquely downwards, and terminate by a tubercular margin. They overlap one another from the fifth, to the eighth, but are less oblique in direction above and below. Fig. 5. — A Do i sal Vertebra. Superior Artie. 1'rocest jffil Facet fr Tulercle ofJZii Demi facet for head cf Eil Demi facet furliea.d, of Jill lW Infer. Artie. Froc. The peculiar dorsal vertebrae are the first, ninth, tenth, eleventh, and twelfth (fig. 6). The First Dorsal Vertebra presents, on each side of the body, a single entire articular facet for the head of the first rib, and a half facet for the upper half of the second. The upper surface of the body is like that of a cervical vertebra, being broad transversely, concave, and lipped on each side. The articular sur- faces are oblique, and the spinous process thick, long, and almost horizontal. The Ninth Dorsal has no demi-facet below. In some subjects, the ninth has two demi-facets on each side ; then the tenth has a demi-facet at the upper part, none below. The Tenth Dorsal has an entire articular facet on each side above ; no demi facet below. 46 OSTEOLOGY. In the Eleventh Dorsal, the body approaches in its form and size to the lumbar vertebras.! The articular facets for the heads of the ribs, one on each side, are of large size, and placed chiefly on the pedicles, which are thicker and stronger in this and the next vertebra, than in any other part of the dorsal region. The transverse processes are very short, tubercular at their extremities, and have no articular facets for the tubercles of the ribs. The spinous process is short, nearly horizontal in direction, and presents a slight tendency to bifurcation at its extremity. Fig. 6. — Peculiar Dorsal Vertebrae. An. entire faeet ov4 A Demi facet lelow — A Demi facet aiove — On* entire farev n entire facet Vo facet on Trans.Pror. •/tts n/ dime/it a r/r n entire facet No facet tin.Tra ?is jir. Infer.Artic. Proe convene and turned outward The Twelfth Dorsal has the same general characters as the eleventh ; but may be distinguished from it by the inferior articular processes being convex and turned outwards, like those of the lumbar vertebra? ; by the general form of the body, lamime, and spinous process, approaching to that of the lumbar vertebrae; and by the transverse processes being shorter, and the tubercles at their extremi- ties more marked. LUMBAR VERTEBRA. 4T Characters of the Lumbar Vertebra. The Lumbar Vertebrae (fig. 7) are the largest segments of the vertebral column. The body is large, broader from side to side than from before backwards, and about equal in depth in front and behind, flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides, presenting prominent margins which afford a broad basis for the support of the superincum- bent weight. The pedicles are very strong, directed backwards from the upper Fig. 7. — A Lumbar Vertebra. Super. Artec. Proc. part of the bodies; consequently the inferior intervertebral notches are of large size. The laminse are short, but broad and strong ; and the • foramen triangular, larger than in the dorsal, smaller than in the cervical region. The superior articular processes are concave, and look almost directly inwards; the inferior, convex, look outwards and a little forwards ; the former are separated by a much wider interval than the latter, embracing the lower articulating processes of the vertebra above. The transverse processes are long, slender, directed transversely outwards in the upper three lumbar vertebras, slanting a little upwards in the lower two. By some anatomists they are considered homologous with the ribs. Of the two tuber- cles noticed in connection with the transverse processes in the dorsal region, the superior ones become connected in this region with the back part of the superior articular processes, the inferior ones with the posterior part of the base of the transverse processes. Although in man they are comparatively small, in some animals they attain considerable size, and serve to lock the vertebrae more closely together. The spinous processes are thick and broad, somewhat quadrilateral, horizontal in direction, thicker below than above, and terminate by a rough uneven border. The Fifth Lumbar vertebra is characterized by having the body much thicker in front than behind, which accounts for the prominence of the sacro-vertebral articulation, by the smaller size of its spinous process, by the wide interval between the inferior articulating processes, and by the greater size and thickness of its transverse processes. Structure and Development of the Vertebrae. The structure of a vertebra differs in different parts. The body is composed of light spongy cancellous tissue, having a thin coating of compact tissue on its external surface perforated by numerous orifices, some of large size, for the passage 48 OSTEOLOGY. of vessels, its interior being traversed by one or two large canals for the reception of veins, which converge towards a single large irregular aperture or several small ones at the posterior part of the body Fig. 8. — Development of a Vertebra. By o primary eertfret plY t for Body (i$ zivcA) J for each Lamina (6*- uteJj Pijf. 9. J}y 4 Secnn.dt.vr u Centres 1 for each Traiin.Proo. ft v » 2 tomttimes / J for Spin.proc (I6y r*j Fitf. 10. 1 far upper su rfat of body 1for u it dor »urfae*\ of body II Fie. 11.— Atlas. 12.— Axis. f for anter. area (1''y r ) / for eeuth ) lj . ; . .» — , J , I before Om-tn lateral, mats) J Fig. 13. — Lumbar Vertebra. 2 additional ce-nt ret Zfor odontoid proe f6r*> mo J //or ear A lateral mass I ^ mo.) \3? for tubercles on Sup. of each bone. The arch and processes projecting from it have, on the con- trary, an exceedingly thick covering of compact tissue. Development. Each vertebra is form- ed of three primary cartilaginous por- tions (fig. 8); one for each lamina and its processes, and one for the body. Ossification commences in the laminae about the sixth week of foetal life, in the situation where the transverse pro- cesses afterwards project, the ossific granules shooting backwards to the spine, forwards to the body, and out- wards into the transverse and articular processes. Ossification in the body makes its appearance in the middle of the cartilage about the eighth week. At birth, these three pieces are per- fectly separate. During the first year, the laminae become united behind, by a portion of cartilage in which the spinous process is ultimately formed, and thus the arch is completed. About the third year, the body is joined to the arch on each side, in such a man- ner that the body is formed from the three original centres of ossification, the amount contributed by the pedicles increasing in extent from below up- wards. Thus the bodies of the sacral vertebrae are formed almost entirely from the central nuclei, the bodies of the lumbar segments are formed late- rally and behind by the pedicles. In the dorsal region the pedicles advance as far forwards as the articular depres- sions for the heads of the ribs, forming these cavities of reception ; and in the neck the whole of the lateral portions of the bodies are formed by the ad- vance of the pedicles. Before puberty, no other changes occur excepting a gradual increase in the growth of these primary centres, the upper and under surface of the bodies, and the ends of the transverse and spinous processes, being tipped with cartilage, in which ossific granules are not as yet depo- sited. At sixteen years (fig. 9), four secondary centres appear, one for the tip of each transverse process, and two (sometimes united into one) for the end of the spinous process. At twenty- DEVELOPMENT OF THE VERTEBRAE. 49 one years (fig. 10), a thin circular plate of bone is formed in the thin layer of carti- lage situated on the upper and under surface of the body, the former being the thicker of the two. All these become joined ; and the bone is completely formed about the thirtieth year of life. Exceptions to this mode of development occur in the first, second, and seventh cervical, and in the vertebrae of the lumbar region. The Atlas (fig. 11) is developed by two primary centres, and by one or more epiphyses. The two primary centres consist of the two lateral of neural masses, ossification of which commences before birth, near the articular processes, and extending backwards, they are separated from one another behind, at birth, by a narrow interval filled in with cartilage. Between the second and third years, they unite either directly or through the medium of an epiphysal centre, developed in the cartilage near their point of junction. The anterior arch, at birth, is alto- gether cartilaginous, and this portion of the atlas is completed by the gradual extension forwards and ultimate junction of the two neural processes. Occasion- ally a separate nucleus is developed in the anterior arch, which, extending laterally, joins the neural processes in front of the pedicles ; or, there are two nuclei deve- loped in the anterior arch, one on either side of the median line; they join to form a single mass, which is afterwards united to the lateral portions in front of the articulating processes. The Axis (fig. 12) is developed by six centres. The body and arch of this bone are formed in the same manner as the corresponding parts in the other vertebras : one centre for the lower part of the body, and one for each lamina. The odontoid process, which is really the centrum or body of the axis, consists originally of an extension upwards of the cartilaginous mass, in which the lower part of the body is formed. At about the sixth month of foetal life, two osseous nuclei make their appearance in the base of this process : they are placed laterally, and join before birth to form a conical-shaped bilobed mass, deeply cleft above; the interval between the cleft and the summit of the process is formed by a wedge-shaped piece of cartilage ; the base of the process being separated from the body by a cartilaginous interval, which gradually becomes ossified, sometimes by a separate epiphysal nucleus. Finally, as Mr. Humphry has lately demonstrated, the apex of the odontoid process has a separate nucleus. The Seventh Cervical. The anterior or costal part of the transverse process of the seventh, cervical is developed from a separate osseous centre at about the sixth month of fcetal life, and joins the body and posterior division of the trans- verse process between the fifth and sixth years. Sometimes this process continues as a separate piece, and becoming lengthened outwards constitutes what is known as a cervical rib. The Lumbar Vertebrse (fig. 13) have two additional centres (besides those peculiar to the vertebras generally), for the tubercles, which project from the back part of the superior articular processes. The transverse process of the first lumbar is sometimes developed as a separate piece, which may remain permanently uncon- nected with the remaining portion of the bone ; thus forming a lumbar rib, a peculiarity which is sometimes, though rarely, met with. Progress of Ossification in the Spine generally. Ossification of the laminas of the vertebras commences at the upper part of the spine, and proceeds gradually downwards; heDce the frequent occurrence of spina bifida in the lower part of the spinal column. Ossification of the bodies, on the other hand, commences a little below the centre of the spinal column, about the ninth or tenth dorsal vertebra, and extends both upwards and downwards. Although, however, the ossific nuclei make their first appearance in the lower dorsal vertebras, the lumbar and first sacral are those in which these nuclei are largest at birth. Attachment of Muscles. To the Atlas are attached the Longus colli, Rectus anticus minor, Rectus lateralis, Rectus posticus minor, Obliquus superior and inferior, Splenitis colli, Levator anguli scapulas, Interspinous, and Intertransverse. To the Axis are attached the Longus colli, Obliquus inferior, Rectus posticus 4 50 OSTEOLOGY. major, Semispinals colli, Multifidus spinas, Levator anguli scapulas, Splenius colli, Transversalis colli, Scalenus posticus, Intertransversales, Interspinales. To the remaining Vertebras generally are attached, anteriorly, the Rectus anticus major, Longus colli, Scalenus anticus and posticus, Psoas magnus, Psoas parvus, Quadratus lumborum, Diaphragm, Obliquus internus and Transversalis, — poste- riorly, the Trapezius, Latissimus dorsi, Levator anguli scapulas, Rhomboideus major and minor, Serratus posticus superior and inferior, Splenius, Sacro-lumbalis, Longissimus dorsi, Spinalis dorsi, Cervicalis ascendens, Transversalis colli, Trachelo-mastoid, Complexus, Serni-spinalis dorsi and colli, Multifidus spinas, Interspinales, Supraspinales, Intertransversales, Levatores costarum. Saceal and Coccygeal Vertebrae. The Sacral and Coccygeal Vertebras consist, at an early period of life, of nine separate pieces, which are united in the adult, so as to form two bones, five entering into the formation of the sacrum, four of the coccyx. The Sacrum (fig. 14), so called from its having been offered in sacrifice, and hence considered sacred, is a large triangular bone, situated at the lower part of Fig. 14. — Sacrum: Anterior Surface. Promontory the vertebral column, and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two ossa innominata; its upper part, or base, articulating with the last lumbar vertebra, its apex with the coccyx. The sacrum is curved upon itself, and placed very obliquely, its upper extremity projecting forwards, forming, with the last lumbar vertebra, a very prominent angle, called the promontory or sacro-vertebral angle, whilst its central part is directed backwards, so as to give increased capacity to the pelvic cavity. It SACRUM. 51 Fig. 15. — Vertical Section of the Sacrum. presents for examination an anterior and posterior surface, two lateral surfaces, a base, an apex, and a central canal. Tlie Anterior Surface is concave from above downwards, and slightly so from side to side. In the middle are seen four transverse ridges, indicating the original division of the bone into five separate pieces. The portions of bone intervening between the ridges correspond to the bodies of the vertebrae. The body of the first segment is of large size, and in form resembles that of a lumbar vertebra; the succeeding ones diminish in size from above downwards, are flattened from before backwards, and curved so as to accom- modate themselves to the form of the sacrum, being concave in front, convex behind. At each end of the ridges, above mentioned, are seen the anterior sacral foramina, analogous to the intervertebral foramina, four in number on each side, somewhat rounded in form, diminishing in size from above downwards, and di- rected outwards and forwards; they transmit the anterior branches of the sacral nerves. External to these fora- mina is the lateral mass, consisting, at an early period of life, of separate seg- ments, which correspond to the anterior transverse processes ; these become blend- ed, in the adult, with the bodies, with each other, and with the posterior trans- verse processes. Each lateral mass is traversed by four broad shallow grooves, which lodge the anterior sacral nerves as they pass outwards, the grooves being separated by prominent ridges of bone, which give attachment to the slips of the Pyriformis muscle. If a vertical section is made through the centre of the bone (fig. 15), the bodies are seen to be united at their circumfe- rence by bone, a wide interval being left centrally, which, in the recent state, is filled by intervertebral substance. In some bones, this union is more complete between the lower segments than between the upper ones. The Posterior Surface (fig. 16) is convex, and much narrower than the anterior. In the middle line, are three or four tubercles, which represent the rudimentary spinous processes of the sacral vertebrae. Of these tubercles, the first is usually prominent, and perfectly distinct from the rest ; the second and third are either separate, or united into a tubercular ridge, which diminishes in size from above downwards; the fourth usually, and the fifth always, remaining undeveloped. Ex- ternal to the spinous processes on each side are the laminse, broad and well marked in the three first pieces; sometimes the fourth, and generally the fifth, being un- developed ; in this situation the lower end of the sacral canal is exposed. External to the laminae is a linear series of indistinct tubercles representing the articular processes; the upper pair are large, well developed, and correspond in shape and direction to the superior articulating processes of a lumbar vertebra; the second and third are small ; the fourth and fifth (usually blended together) are situated on each side of the sacral canal : they are called the sacral cornua, and articulate with the cornua of the coccyx. External to the articular processes are the four 52 OSTEOLOGY. posterior sacral foramina ; they are smaller in size, and less regular in form than the anterior, and transmit the posterior branches of the sacral nerves. On the outer side of the posterior sacral foramina is a series of tubercles, the rudimentary Fig. 16. — Sacrum: Posterior Surface. posterior transverse processes of the sacral vertebra?. The first pair of transverse tubercles are of large size, very distinct, and correspond with each superior angle of the bone ; the second, small in size, enter into the formation of the sacro-iliac articulation ; the third give attachment to the oblique sacro-iliac ligaments ; and the fourth and fifth to the great sacro-ischiatic ligaments. The interspace between the spinous and transverse processes on the back of the sacrum, presents a wide shallow concavity, called the sacral groove; it is continuous above with the vertebral groove, and lodges the origin of the Erector spina?. The Lateral surface, broad above, becomes narrowed into a thin edge below. Its upper half presents in front a broad ear-shaped surface for articulation with the ilium. This is called the auricular or ear-shaped surface, and in the fresh state is coated with cartilage. It is bounded posteriorly by deep and uneven impressions, for the attachment of the posterior sacro-iliac ligaments. The lower half is thin and sharp, and gives attachment to the greater and lesser sacro-ischiatic ligaments, and to some fibres of the Gluteus maximus; below, it presents a deep notch, which is converted into a foramen by articulation with the transverse process of the upper piece of the coccyx, and transmits the anterior branch of the fifth sacral nerve. The Base of the sacrum, which is broad and expanded, is directed upwards and forwards. In the middle is seen an oval articular surface, which corresponds with the under surface of the body of the last lumbar vertebra, bounded behind by the large triangular orifice of the sacral canal. This orifice is formed behind by the spinous process and laminae of the first sacral vertebra, whilst projecting from DEVELOPMENT OF SACRUM. 53 Fig. 17. — Development of Sacrum. Formed ly union, of £ Verteb ra. 2 characteristic points. 2 Additional centres far the first 3 pieces * at birth it on each side are the superior articular processes; they are oval, concave, directed backwards and inwards, like the superior articular processes of a lumbar vertebra; in front of each articular process is an intervertebral notch, which forms the lower half of the last intervertebral foramen. Lastly, on each side of the articular surface is a broad and flat triangular surface of bone, which extends outwards, and is continuous on each side with the iliac fossa. The Apex, directed downwards and forwards, presents a small oval concave surface for articulation with the coccyx. The Sacral Canal runs throughout the greater part of the bone ; it is large and triangular in form above, small and flattened from before backwards below. In this situation its posterior wall is incomplete, from the non-development of the lamina? and spinous processes. It lodges the sacral nerves, and is perforated by the anterior and posterior sacral foramina, through which these pass out. Structure. It consists of much loose spongy tissue within, invested exter- nally by a thin layer of compact tissue. Differences in the Sacrum of the Male and Female. The sacrum in the female is usually wider than in the male; and it is much less curved, the upper half of the bone being nearly straight, the lower half presenting the greatest amount of curvature. The bone is also directed more obliquely backwards; which increases the size of the pelvic cavity, and forms a more pro- minent sacro-vertebral angle. In the male, the curvature is more evenly dis- tributed over the whole length of the bone, and is altogether greater than in the female. Peculiarities of the Sacrum. This bone, in some cases, consists of six pieces; occasionally the number is reduced to four. Sometimes the bodies of the first and second segments are not joined, or the laminae and spinous processes have not coalesced. Occa- sionally, the upper pair of transverse tubercles are not joined to the rest of the bone on one or both sides; and, lastly, the sacral canal may be open for nearly the lower half of the bone, in consequence of the imperfect develop- ment of the laminae and spinous pro- cesses. The sacrum, also, varies con- siderably with respect to its degree of curvature. From the examination of a large number of skeletons, it would appear, that, in one set of cases, the anterior surface of this bone was nearly straight, the curvature, which was very slight, affecting only its lower end. In another set of cases, the bone was curved throughout its whole length, but especially towards its middle. In Fig. 18. at 4J y'rs Fig. 19. . nr tJl at 2o r-. y. 54 OSTEOLOGY. a third set, the degree of curvature was less marked, and affected especially the lower third of the bone. Development (fig. 17). The sacrum, formed by the union of five vertebra?, has thirty-five centres of ossification. The bodies of the sacral vertebra? have each three ossific centres ; one for the central part, and one for the epiphysal plates on its upper and under surface. The laminse of the sacral vertebra? are each developed by two centres ; these meet behind to form the arch, and subsequently join the body. The lateral masses have six additional centres, two for each of the first three vertebra?. These centres make their appearance above and to the outer side of the anterior sacral foramina (fig. 17), and are developed into separate segments, which correspond with the anterior transverse processes (fig. 18); they are subse- quently blended with each other, and with the bodies and the posterior transverse processes, to form the lateral mass. Lastly, each lateral surface of the sacrum is developed by two epiphysal plates (fig. 19); one for the articular surface, and one for the remaining part of the thin lateral edge of the bone. Period of Development. At about the eighth or ninth week of foetal life, ossifi- cation of the central part of the bodies of the first three vertebra? commences ; and, at a somewhat later period, that of the last two. Between the sixth and eighth months, ossification of the lamina? takes place : and, at about the same period, the characteristic osseous tubercles for the three first sacral vertebra? make their appearance. The lamina? join to form the arch, and are united to the bodies, first, in the lowest vertebra?. This occurs about the second year, the uppermost segment appearing as a single piece about the fifth or sixth year. About the six- teenth year, the epiphyses for the upper and under surfaces of the bodies are formed : and, between the eighteenth and twentieth years, those for each lateral surface of the sacrum make their appearance. At about this period, the last two segments are joined to one another; and this pro- cess gradually extending upwards, all the pieces become united, and the bone completely formed from the twenty-fifth to the thirtieth year of life. Articulations. With four bones; the last lumbar vertebra, coccyx, and the two ossa innominata. Attachment of Muscles. The Pyriformis and Coccygeus on either side ; behind, the Gluteus maxi- mus, and Erector spina?. The Coccyx. The Coccyx (x6xxv%, cuckoo), so called from resem- bling a cuckoo's beak (fig. 20), is usually formed of four small segments of bone, the most rudi- mentary parts of the vertebral column. In each of the first three segments may be traced a rudi- mentary body, articular and transverse processes; the last 'piece (sometimes the third) being merely a rudimentary nodule of bone, without distinct processes. All the segments are destitute of lami- na? and spinous processes; and, consequently, of spinal canal, and intervertebral foramina. The first segment is the largest, resembles the loAvermost sacral vertebra, and often exists as a separate piece ; the last three, diminishing in size from above down- wards, are usually blended together so as to form a single bone. The gradual diminution in the size of the pieces gives this bone a triangular form, articulating by its base with the end of the Fig. 20.— Coccyx. Cornva jlnterior Surfars JPotterior S-u-rfca THE SPINE. 55 sacrum. It presents for examination an anterior and posterior surface, two borders, a base, and an apex. The anterior surface is slightly concave, and marked with three transverse grooves, indicating the points of junction of the different pieces. It has attached to it the anterior sacro-coecygeal ligament, ( the Levator ani muscle, and supports the lower end of the rectum. The posterior surface is convex, marked by transverse grooves similar to those on the anterior surface; and presents on each side a linear row of tubercles, the rudimentary articular processes of the coccygeal vertebra. Of these, the superior pair are very large ; and are called the cornua of the coccyx; they project upwards, and articulate with the cornua of the sacrum, the junction between these two bones completing the fifth sacral foramen for the transmission of the posterior branch of the fifth sacral nerve. The lateral borders are thin, and present a series of small eminences, which re- present the transverse processes of the coccygeal vertebrae. Of these, the first on each side is of large size, flattened from before backwards ; and often ascends to join the lower part of the thin lateral edge of the sacrum, thus completing the fifth sacral foramen : the others diminish in size from above downwards, and are often wanting. The borders of the coccyx are narrow, and give attachment on each side to the sacro-sciatic ligaments and Coccygeus muscle. The base presents an oval surface for articulation with the sacrum. The apex is rounded, and has attached to it the tendon of the external Sphincter muscle. It is occasionally bifid, and sometimes deflected to one or other side. Development. The coccyx is developed by four centres, one for each piece. Occasionally, one of the first three pieces of this bone is developed by two centres, placed side by side. The ossific nuclei make their appearance in the following order: in the first segment, at birth; in the second piece, at from five to ten years; in the third, from ten to fifteen years ; in the fourth, from fifteen to twenty years. As age advances, these various segments become united in the following order : the first two pieces join; then the third and fourth; and, lastly, the bone is com- pleted by the union of the second and third. At a late period of life, especially in females, the coccyx becomes joined to the end of the sacrum. Articulation. With the sacrum. Attachment of Muscles. On either side, the Coccygeus; behind, the Gluteus maxim us ; at its apex, the Sphincter ani ; and in front, the Levator ani. Of the Spine in general. The spinal column, formed by the junction of the vertebras, is situated in the median line, at the posterior part of the trunk : its average length is about two feet two or three inches; the lumbar region contributing seven parts of that length, the dorsal eleven, and the cervical five. Viewed in front, it presents two pyramids joined together at their bases, the upper one being formed by all the vertebrae from the second cervical to the last lumbar ; the lower one by the sacrum, and coccyx. Viewed somewhat more closely, the uppermost pyramid is seen to be formed of three smaller pyramids. Of these, the most superior one consists of the six lower cervical vertebrae; its apex being formed by the axis or second cervical ; its base, by the first dorsal. The second pyramid, which is inverted, is formed by the four upper dorsal vertebrae, the base being at the first dorsal, the smaller end at the fourth. The third pyramid com- mences at the fourth dorsal, and gradually increases in size to the fifth lumbar. Viewed laterally (fig. 21), the spinal column presents several curves, which correspond to the different regions of the column, and are called cervical, dorsal, lumbar, and pelvic. The cervical curve commences at the apex of the odontoid process, and terminates at the middle of the second dorsal vertebra ; it is convex in front, but the least marked of all the curves. The dorsal curvature, which is concave forwards, commences at the middle of the second, and terminates at the middle of the twelfth dorsal. Its most prominent point behind corresponds to the body of the seventh or eighth vertebra. The lumbar curve commences at the middle of the last dorsal, and terminates at the sacro-.vertebral angle. It is convex 56 OSTEOLOGY. Fig. 21. — Lateral View of Spine. lsl Cervical orAtlat. 6-\ IV Dorsal. %A /? 1? Lumbar.^r^, u- ^mm anteriorly; the convexity of the lower three vertebrae being much greater than that of the upper ones. The 'pelvic curve commences at the sacro- vertebral articula- tion, and terminates at the point of the coccyx. It is concave posteriorly. These curves are partly due to the shape of the bodies of the vertebrae, and partly to the intervertebral substances, as will be ex- plained in the Articulations of the Spine. The spine has also a slight lateral curvature, the convexity of which is di- rected toward the right side. This is most probably produced, as Bichat first explained, from the effect of muscular action; most persons using the right arm in preference to the left, especially in making long-continued efforts, when the body is curved to the right side. In support of this explanation, it has been found, by Beclard, that in one or two in- dividuals who were left-handed, the lateral curvature was directed to the left side. The spinal column presents for exami- nation an anterior, a posterior, and two lateral surfaces; a base, summit, and ver- tebral canal. The anterior surface presents the bodies of the vertebrae separated in the recent state by the intervertebral disks. The bodies are broad in the cervical region, narrow in the upper part of the dorsal, and broadest in the lumbar region. The whole of this surface is convex transversely, concave from above downwards in the dorsal region, and convex in the same direction in the cervical and lumbar regions. The posterior surface presents in the median line the spinous processes. These are short, horizontal, with bifid extremi- ties in the cervical region. In the dorsal region, they are directed obliquely above, assume almost a vertical direction in the middle, and are horizontal, like the spines of the lumbar vertebras, below. They are separated by considerable intervals in the loins, by narrower intervals in the neck, and are closely approximated in the middle of the dorsal region. Oc- casionally one of these processes deviates a little from the median line, a fact to be remembered, as irregularities of this sort are attendant on fractures or dis- placements of the spine. On either side of the spinous processes, extending the whole length of the column, is the vertebral groove, formed by the laminaa in the cer- THE SKULL. 5T vical and lumbar regions, where it is shallow, and by the laminrc and transverse processes in the dorsal region, where it is deep and broad. In the recent state, these grooves lodge the deep muscles of the back. External to the vertebral grooves are the articular processes, and still more externally the transverse pro- cesses. In the dorsal region, the latter processes stand backwards, on a place con- siderably posterior to the same processes in the cervical and lumbar regions. In the cervical region, the transverse processes are placed in front of the articular processes, and between the intervertebral foramina. In the lumbar, they are placed also in front of the articular process, but behind the intervertebral foramina. In the dorsal region, they are posterior both to the articular processes and foramina. The lateral surfaces are separated from the posterior by the articular processes in the cervical and lumbar regions, and by the transverse processes in the dorsal. These surfaces present in front the sides of the bodies of the vertebras, marked in the dorsal region by the facets for articulation with the heads of the ribs. More posteriorly are the intervertebral foramina, formed by the juxtaposition of the inter- vertebral notches, oval in shape, smallest in the cervical and upper part of the dorsal regions, and gradually increasing in size to the last lumbar. They are situated between the transverse processes in the neck, and in front of them in the back and loins, and transmit the spinal nerves. The base of the vertebral column is formed by the under surface of the body of the fifth lumbar vertebra; and the summit by the upper surface of the atlas. The vertebral canal follows the different curves of the spine ; it is largest in those regions in which the spine enjoys the greatest freedom of movement, as in the neck and loins, where it is wide and triangular ; and narrow and rounded in the back, where motion is more limited. THE SKULL. The Skull, or superior expansion of the vertebral column, is composed of four vertebras, the elementary parts of which are specially modified in form and size, and almost immovably connected, for the reception of the brain, and special organs of the senses. These vertebras are the occipital, parietal, frontal, and nasal. Descriptive anatomists, however, divide the skull into two parts, the Cranium and the Face. The Cranium (xponos, a helmet) is composed of eight bones: viz., the occipital, two parietal, frontal, two temporal, sphenoid, and ethmoid. The face is composed of fourteen bones: viz., the two nasal, two superior maxillary, two lachry- mal, two malar, two palate, two inferior turbinated, vomer, inferior maxillary. The ossicula auditus, the teeth, and Wormian bones, are not included in this enumeration. Occipital. Two Parietal. Cranium, 8 bones. ) zJ on ~" , Two Temporal. Sphenoid. Ethmoid. Skull, 22 bones. ( / Two Nasal. Face, 14 bones. Two Superior Maxillary. Two Lachrymal. Two Malar. Two Palate. Two Inferior Turbinated. Vomer. Inferior Maxillary. BONES OF THE CRANIUM. The Occipital Bone. The Occipital Bone (fig. 22) is situated at the back part and base of the cranium, is trapezoid in form, curved upon itself, and presents for examination two sur- faces, four borders, and four angles. 58 OSTEOLOGY. The External Surface is convex. Midway between the summit of the bone and the posterior margin of the foramen magnum is a prominent tubercle, the external occipital protuberance, for the attachment of the Ligamentum nuchas; and descending from it, as far as the foramen, a vertical ridge, the external occipital crest. This tubercle and crest vary in prominence in different skulls. Passing outwards from the occipital protuberance on each side are two semicircular ridges, the superior curved lines ; and running parallel with these from the middle of the crest, are the two inferior curved lines. The surface of the bone above the supe- rior curved lines is smooth on each side, and in the recent state is covered by the Occipito-frontalis muscle, whilst the ridges, as well as the surface of the bone between them, serve for the attachment of numerous muscles. The superior 22.— Occipital Bone. Outer Surface. t>f Hiarynx curved line gives attachment internally to the Trapezius, externally to the Occi- pito-frontalis, and Sterno-cleido-mastoid, to the extent shown in the figure. The depressions between the curved lines to the Complexus internally, the Splenius capitis and Obliquus superior externally. The inferior curved line, and the depressions below it, afford insertion to the Rectus capitis posticus, major and minor. The foramen magnum is a large oval aperture, its long diameter extending from before backwards. It transmits the spinal cord and its membranes, the spinal accessory nerves, and the vertebral arteries. Its back part is wide for the transmission of the cord, and the corresponding margin rough for the attachment of the dura mater inclosing it ; the forepart is narrower, being encroached upon by the condyles ; it has projecting towards it from below the odontoid process, and its margins are smooth and bevelled internally to support the medulla oblongata. On each side of the foramen magnum are the condyles for articulation with the atlas; they are convex, oblong or reniform in shape, and directed down- wards and outwards; they converge in front, and encroach slightly upon the anterior segment of the foramen. On the inner border of each condvle is a rough OCCIPITAL BONE. 59 tubercle for the attachment of the ligaments (check) which connect this bone with the odontoid process of the axis ; whilst external to them is a rough tubercular prominence, the transverse or jugular process (the representative of the trans- verse process of a vertebra), channelled in front by a deep notch, which forms part of the jugular foramen. The under surface of this process affords attach- ment to the Rectus capitis lateralis ; its upper or cerebral surface presents a deep groove, which lodges part of the lateral sinus, whilst its prominent extremity is marked by a quadrilateral rough surface, covered with cartilage in the fresh state, and articulating with a similar surface on the petrous portion of the temporal bone. On the outer side of each condyle, near its forepart, is a foramen, the anterior condyloid ; it is directed downwards, outwards, and forwards, and trans- mits the hypoglossal nerve. This foramen is sometimes double. Behind each condyle is a fossa,' perforated at the bottom by a foramen, the posterior condyloid, for the transmission of a vein to the lateral sinus. In front of the foramen magnum is a strong quadrilateral plate of bone, the basilar process, wider behind than in front ; its under surface, which is rough, presenting in the median line a tubercular ridge, the pharyngeal spine, for the attachment of the tendinous raphe and Superior constrictor of the pharynx ; and on each side of it are rough depressions for the attachment of the Rectus capitis anticus major, and Rectus capitis minor. Fig. 23. — Occipital Bone : Inner Surface. Su/ieri'or Angle • ''Of, Inferior Ant/lp V« The Internal or Cerebral Surface (fig. 23) is deeply concave. The posterior 1 This fossa presents many variations in size. It is usually shallow, and the foramen small ; occasionally wanting, on one, or both sides. Sometimes both fossa and foramen are large, but confined to one side only ; more rarely, the fossa and foramen are very large on both sides. 60 OSTEOLOGY. or occipital part is divided by a crucial ridge into four fossae. The two superior, the smaller, receive the posterior lobes of the cerebrum, and present slight emi- nences and depressions corresponding to their convolutions. The two inferior, which receive the lateral lobes of the cerebellum, are larger than the former, and comparatively smooth ; both are marked by slight grooves for the lodgment of arteries. At the point of meeting of the four divisions of the crucial ridge is an eminence, the internal occipital protuberance. It nearly corresponds to that on the outer surface, and is perforated by one or more large vascular foramina. From this eminence, the superior division of the crucial ridge runs upwards to the superior angle of the bone ; it presents occasionally a deep groove for the superior longitudinal sinus, the margins of which give attachment to the falx cerebri. The inferior division, the internal occipital crest, runs to the posterior margin of the foramen magnum, on the edge of which it becomes gradually lost: this ridge, which is bifurcated below, serves for the attachment of the falx cere- belli. The transverse grooves pass outwards to the lateral angles; they are deeply channelled, for the lodgment of the lateral sinuses, their prominent margins affording attachment to the tentorium cerebelli. 1 At the point of meeting of these grooves is a depression, the " Torcular Herophili,"* placed a little to one or the other side of the internal occipital protuberance. More anteriorly is the foramen magnum, and on each side of it, but nearer its anterior than its posterior part, the internal openings of the anterior condyloid foramina ; the internal openings of the posterior condyloid foramina being a little external and posterior to them, protected by a small arch of bone. In front of the foramen magnum is the basilar process, presenting a shallow depression, the basilar groove, which slopes from behind, upwards and forwards, and supports the medulla oblongata ; and on each side of the basilar process is a narrow channel, which, when united with a similar channel on the petrous portion of the temporal bone, forms a groove, which lodges the inferior petrosal sinus. Angles. The superior angle is received into the interval between the posterior superior angles of the two parietal bones ; it corresponds with that part of the skull in the foetus which is called the posterior fontanelle. The inferior angle is represented by the square-shaped surface of the basilar process. At an early period of life, a layer of cartilage separates this part of the bone from the sphenoid ; but in the adult, the union between them is osseous. The lateral angles correspond to the outer ends of the transverse grooves, and are received into the interval between the posterior inferior angles of the parietal and the mastoid portion of the temporal. Borders. The superior extends on each side from the superior to the lateral angle, is deeply serrated for articulation with the parietal bone, and forms by this union the lambdoid suture. The inferior border extends from the lateral to the inferior angle ; its upper half is rough, and articulates with the mastoid por- tion of the temporal, forming the masto-occipital suture : the inferior half articu- lates with the petrous portion of the temporal, forming the petro-occipital suture : these two portions are separated from one another by the jugular process. In front of this process is a deep notch, which, with a similar one on the petrous portion of the temporal, forms the foramen lacerum posterius. This notch is occasionally subdivided into two parts by a small process of bone, and presents an aperture at its upper part, the internal opening of the posterior condyloid foramen. Structure. The occipital bone consists of two compact laminae, called the outer and inner tables, having between them the diploic tissue ; this bone is especially ' Usually one of the transverse grooves is deeper and broader than the other ; this seems in nearly equal proportion on the two sides; occasionally both grooves are of equal depth and breadth, or both equally indistinct. The broader of the two transverse grooves is nearly always continuous with the vertical groove for the superior longitudinal sinus, and occupies the corre- sponding side of the median line. 2 The columns of blood coming in different directions were supposed to be pressed together at this point. OCCIPITAL BONE. 61 JJt/ 4- centres at lirfJL the 1, pit res *cj>a rale thick, at the ridges, protuberances, condyles, and anterior part of the basilar process; whilst at the bottom of the fossae, especially the inferior, it is thin, semi- transparent, and destitute of diploe. Development (fig. 24). The occipital bone has four centres of development ; one for the posterior or occi- pital part, Which is formed in F'S- 24. -Development of Occipital Boue. membrane ; one for the basilar portion; and one for each condyloid portion, which are formed in cartilage. The centre for the occipi- tal portion appears about the tenth week of foetal life ; and consists, according to Blandin and Cruveilhier, of a small oblong plate which appears in the situation of the occi- pital protuberance. 1 The condyloid portions then ossify, and lastly the basilar portion. At birth, the bone consists of four parts, separate from one another, the occipital portion being fissured in the direction above indicated. At about the fourth year, the occipital and the two condyloid pieces join; and about the sixth year the bone consists of a single piece. At a later period between the eighteenth and twenty-fifth years, the occipital and sphenoid become united, forming a single bone. Articulations. With six bones ; two parietal, two temporal, sphenoid, and atlas. Attachment of Muscles. To the superior curved line are attached the Occipito- frontalis, Trapezius, and Sterno-cleido-mastoid. To the space between the curved lines, the Complexus, Splenius capitis, and Obliquus superior; to the inferior curved line, and the space between it and the foramen magnum, the Kectus posticus major and minor ; to the transverse process, the Rectus lateralis ; and to the basilar process, the Recti antici majores and minores, and Superior Constrictor of the pharynx. / for occipital portion I for each condyloid portion or otLthlar portion The Parietal Boxes. The Parietal Bones {paries, a wall) form by their union the sides and roof of the skull ; each bone is of an irregular quadrilateral form, and presents for ex- amination two surfaces, four borders and four angles. Surfaces. The external surface (fig. 25) is convex, smooth, and marked about its centre by an eminence, called the parietal eminence, which indicates the point where ossification commenced. Crossing the centre of the bone in an arched direction is a curved ridge, the temporal ridge, for the attachment of the temporal fascia. Above this ridge, the surface of the bone is rough and porous, and covered by the aponeurosis of the Occipito-frontalis.; below it the bone is smooth, forms part of the temporal fossa, and affords attachment to the Temporal muscle. At the back part of the superior border, close to the sagittal suture, is a small foramen, the parietal foramen, which transmits a vein to the superior longitudinal sinus. Its existence is not constant, and its size varies considerably. The internal surface (fig. 26), concave, presents eminences and depressions for lodging the convolutions of the cerebrum, and numerous furrows for the ramifica- tions of the meningeal arteries ; the latter run upwards and backwards from the 1 BGclard considers this segment to have four centres of ossification, arranged in pairs, two above, and two below the curved lines, and Meckel describes eight, four of which correspond in situation with those above described : of the other four, two are placed in juxta-position, at the upper angle of the bone, and the remaining two, one at each side, in the lateral angles. 62 OSTEOLOGY. anterior inferior angle, and from the central and posterior part of the lower border of the bone. Along the upper margin is part of a shallow groove, which, when joined to the opposite parietal, forms a channel for the superior longitudinal sinus, the elevated edges of which afford attachment to the falx cerebri. Near the groove are seen several depressions; they lodge the Pacchionian bodies. The internal opening of the parietal foramen is also seen when that aperture exists. Fig. 25. — Left Parietal Bone : External Surface. • ..T(tt,cs f Roirf ef /yose Horizontal Portion; external Surface. This portion of the bone consists of two thin plates, which form the vault of the orbits, separated from one another by the ethmoidal notch. Each orbital vault consists of a smooth, concave, triangular plate of bone, marked at its anterior and external part, immediately beneath the external angular process, by a shallow depression, the lachrymal fossa, for lodging the lachrymal gland; and at its anterior and internal part, by a depression, some- times a small tubercle, for the attachment of the fibrous pulley of the Superior oblique muscle. The ethmoidal notch separates the two orbital plates: it is quadrilateral, and filled up, when the bones are united, by the cribriform plate of the ethmoid. The margins of this notch present several half-cells, which, when united with corresponding half-cells on the upper surface of the ethmoid, complete the ethmoidal cells : two grooves are also seen crossing these edges transversely ; 5 66 OSTEOLOGY. they are converted into canals by articulation with the ethmoid, and are called the anterior and posterior ethmoidal canals; they open on the inner wall of the orbit. The anterior one transmits the nasal nerve and anterior ethmoidal vessels; the posterior one, the posterior ethmoidal vessels. In front of the ethmoidal notch is the nasal spine, a sharp-pointed eminence which projects downwards and forwards, and articulates in front with the crest of the nasal bones ; behind, it is marked by two grooves, separated by a vertical ridge : the ridge articulates with the perpendicular lamella of the ethmoid, the grooves form part of the roof of the nasal fossa?. On either side of the base of the nasal spine are the openings of the frontal sinuses. These are two irregular cavities, which extend upwards and outwards, a variable distance, between the two tables of the skull, and are separated from one another by a thin bony septum. They give rise to the prominences above the root of the nose, called the nasal eminences and superciliary ridges. In the child they are generally absent, and they become gradually developed as age advances. These cavities vary in size in different persons, are larger in men than in women, and are frequently of unequal size on the two sides, the left being commonly the larger. Occasionally they are subdivided by incomplete bony laminae. They are lined by mucous membrane ; and communicate with the nose by the infundibulum, and occasionally with each other by apertures in the septum. The Internal Surface of the horizontal portion presents the convex upper surfaces of the orbital plates, separated from each other in the middle line by the ethmoidal notch, and marked by eminences, and depressions for the convolutions of the anterior lobes of the brain. Borders. The border of the vertical portion is thick, strongly serrated, bevelled at the expense of the internal table above, where it rests upon the parietal, at the expense of the external table at each side, where it receives the lateral pressure of those bones: this border is continued below, into a triangular rough surface, which articulates with the great wing of the sphenoid. The border of the horizontal portion is thin, serrated, and articulates with the lesser wing of the sphenoid. Structure. The vertical portion, and external angular processes, are very thick, consisting of diploic tissue contained between two compact laminae. The hori- zontal portion is thin, translucent, and composed entirely of compact tissue ; hence the facility with which instruments can penetrate the cranium through this part of the orbit. Development (fig. 29). The frontal bone is formed in membrane, being developed by tico centres, one for each lateral half, which make their appearance, at an early period of foetal life, in the situ- ation of the orbital arches. From this point, ossification extends, in a radiating manner, upwards into the forehead, and backwards over the orbit. At birth, it consists of two pieces, which afterwards become united along the middle line, by a suture which runs from the vertex to the root of the nose. This suture be- comes obliterated within a few years after birth ; but it occasionally remains through- out life. Articulations. With twelve bones : two parietal, sphenoid, ethmoid, two nasal, two superior maxillary, two lachrymal, and two malar. Attachment of Muscles. To three pairs: the Corrugator supercilii, Orbicularis palpebrarum, and Temporal. Fig. 29.— Frontal Bone at Birth. Developed by two lateral Halves. TEMPORAL BONE. GT The Temporal Bones. The Temporal Bones are so called because they occupy that part of the head on which the hair first begins to turn gray, thus indicating the age. They are situated at the side and base of the skull, and present for examination a squamous, mastoid, and petrous portion. The Squamous Portion {squama, a scale), the most anterior and superior part of the bone (fig. 30), is scale-like in form, thin and translucent in texture. Its outer surface is smooth, convex, and grooved at its back part for the deep temporal arteries ; it affords attachment to the Temporal muscle, and forms part of the temporal fossa. At its back part may be seen a curved ridge, part of the tem- poral ridge ; it serves for the attachment of the temporal fascia, limits the origin of the Temporal muscle, and marks the boundary between the squamous and mastoid portions of the bone. Projecting from the lower part of the squamous Fig. 30. — Left Temporal Bone. Outer Surface. teiZfot portion is a long arched outgrowth of bone, the zygomatic process. It is at first directed outwards, its two surfaces looking upwards and downwards ; it then appears as if twisted upon itself, and takes a direction forwards, its surfaces now looking inwards and outwards. The superior border of this process is long, thin, and sharp, and serves for the attachment of the temporal fascia. The inferior, short, thick, and arched, has attached to it some fibres of the Masseter muscle. Its outer surface is convex and subcutaneous ; its inner is concave, and also affords attachment to the Masseter. The extremity, broad, and deeply serrated, articulates with the malar bone. This process is connected to the temporal bone by three divisions, called the roots of the zygomatic process, an anterior, middle, and posterior. The anterior, which is short, but broad and strong, runs transversely inwards into a rounded eminence, the eminentia articularis. This eminence forms the front boundary of the glenoid fossa, and in the recent state is covered with cartilage. The middle root forms the outer margin of the glenoid cavity ; running obliquely 68 OSTEOLOGY. inwards it terminates at the commencement of a well-marked fissure, the Glaserian fissure ; whilst the posterior root, which is strongly marked, runs from the upper border of the zygoma, in an arched direction, upwards and backwards, forming the posterior part of the temporal ridge. At the junction of the anterior root with the zygoma is a projection, called the tubercle, for the attachment of the external lateral ligament of the lower jaw ; and between the anterior and middle roots is an oval depression, forming part of the glenoid fossa (y*.^, a shallow pit), for the reception of the condyle of the lower jaw. This fossa is bounded, in front, by the eminentia articularis ; behind, by the vaginal process ; and, externally, by the auditory process, and middle root of the zygoma ; and is divided into two parts by a narrow slit, the Glaserian fissure : the anterior part, formed by the squamous portion of the bone, is smooth, and covered in the recent state with cartilage, and articulates with the condyle of the lower jaw. This part of the glenoid fossa is separated from the auditory process, by a small tubercle, the post- glenoid process, Fig. 31. — Left Temporal Bone. Inner Surface. ■parietal Aqticduetux Veshhuli. jDepTCXsivii far DuTCr-vuitrr Meatus Atiduonas i ttternus "'Ln^ejor Superior B rn fim r mfar Ca,n*l • Jliatus FaLlopii Opcmnyfor Smaller Petrosal Mrt-c Dcnrfsuan for Cassertan gaiujhcm BriUlf passed thrcuyh Carotid Ctuud the representative of a prominent tubercle which, in some of the mammalia, descends behind the condyle of the jaw, and prevents it being displaced backwards during mastication (Humphry). The posterior part of the glenoid fossa is formed chiefly by the vaginal process of the petrous portion, and lodges part of the parotid gland. The Glaserian fissure, which leads into the tympanum, lodges the pro- cessus gracilis of the malleus, and transmits the Laxator tympani muscle and the anterior tympanic artery. The chorda tympani nerve passes through a separate canal parallel to the Glaserian fissure (canal of Huguier), on the outer side of the Eustachian tube, in the retiring angle between the squamous and petrous portions of the temporal bone. The internal surface of the squamous portion (fig. 31) is concave, presents numerous eminences and depressions for the convolutions of the cerebrum, and two well-marked grooves for branches of the middle meningeal artery. Borders. The superior border is thin, bevelled at the expense of the internal surface, so as to overlap the lower border of the parietal bone, forming the TEMPORAL BONE. 09 squamous suture. The anterior inferior border is thick, serrated, and hovelled alternately at the expense of the inner and outer surfaces, for articulation with the great wing of the sphenoid. The Mastoid Portion (paatos, a nipple or teat) is situated at the posterior part of the bone ; its outer surface is rough, and perforated by numerous foramina. One of these, of large size, situated at the posterior border of the bone, is termed the mastoid foramen; it transmits a vein to the lateral sinus and a small artery. The position and size of this foramen arc very variable, being sometimes situated in the occipital bone, or in the suture between the temporal and the occipital. The mastoid portion is continued below into a conical projection, the mastoid pro- cess, the size and form of which vary somewhat in different individuals. This process serves for the attachment of the Sterno-mastoid, Splenius capitis, and Trachelo-mastoid muscles. On the inner side of the mastoid process is a deep groove, the digastric fossa, for the attachment of the Digastric nmscle; and running parallel with it, but more internal, the occipital groove, which lodges the occipital artery. The internal surface of the mastoid portion presents a deeply curved groove, which lodges part of the lateral sinus ; and into it may be seen opening the mastoid foramen. A section of the mastoid process shows it to be hollowed out into a number of cellular spaces, communicating with each other, called the mastoid cells ; they open by a single or double orifice into the back of the tym- panum ; are lined by a prolongation of its lining membrane ; and, probably, form some secondary part of the organ of hearing. The mastoid cells, like the other sinuses of the cranium, are not developed until after puberty ; hence the promi- nence of this process in the adult. Borders. The superior border of the mastoid portion is broad and rough, its serrated edge sloping outwards, for articulation with the posterior inferior angle of the parietal bone. The posterior border, also uneven and serrated, articulates with the inferior border of the occipital bone between its lateral angle and jugular process. The Petrous Portion («irpo?, a rock), so named from its extreme density and hardness, is a pyramidal process of bone, wedged in at the base of the skull between the sphenoid and occipital bones. Its direction from without is forwards, inwards, and a little downwards. It presents for examination a base, an apex, three sur- faces, and three borders ; and contains, in its interior, the essential parts of the organ of hearing. The base is applied against the internal surface of the squamous and mastoid portions, its upper half being concealed ; but its lower half is exposed by their divergence, which brings into view the oval expanded orifice of a canal leading into the tympanum, the meatus auditorius externus. This canal is situated between the mastoid process and the posterior and middle roots of the zygoma ; its upper margin is smooth and rounded, but the greater part of its circumference is surrounded by a curved plate of bone, the auditory process, the free margin of which is thick and rough for the attachment of the cartilage of the external ear. The apex of the petrous portion, rough and uneven, is received into the angular interval between the spinous process of the sphenoid, and the basilar process of the occipital; it presents the anterior orifice of the carotid canal, and forms the posterior and external boundary of the foramen lacerum medium. The anterior surface of the petrous portion (fig. 31) forms the posterior boundary of the middle fossa of the skull. This surface is continuous with the squamous portion, to which it is united by a suture, the temporal Suture, the remains of which are distinct at a late period of life. This surface presents six points for examination. 1. An eminence near the centre which indicates the situation of the superior semicircular canal. 2. On the outer side of this eminence is a depression, indicating the position of the tympanum, the layer of bone which separates the tympanum from the cranial cavity being extremely thin. 3. A shallow groove, sometimes double, leading backwards to an oblique opening, the hiatus Fallopii, for the passage of the petrosal branch of the Vidian nerve. 4. A smaller opening, occasionally seen external to the latter for the passage of the 10 OSTEOLOGY. smaller petrosal nerve. 5. Near the apex of the bone is seen the termination of the carotid canal, the wall of which in this situation is deficient in front. 6. Above this canal is a shallow depression for the reception of the Casserian ganglion. The posterior surface forms the front boundary of the posterior fossa of the skull, and is continuous with the inner surface of the mastoid portion of the bone. It presents three points for examination. 1. About its centre is a large orifice, the meatus auditorius internus. This aperture varies considerably in size ; its margins are smooth and rounded; and it leads into a short canal, about four lines in length, which runs directly outwards. The end of the canal is closed by a vertical plate, divided by a horizontal crest into two unequal portions. It trans- mits the auditory and facial nerves, and auditory artery. 2. Behind the meatus auditorius is a small slit, almost hidden by a thin plate of bone, leading to a canal, the aquoeductus vestibuli ; it transmits a small artery and vein, and lodges a process of the dura mater. 3. In the interval between these two openings, but Fig. 32. — Petrous Portion. Inferior Surface. fon&MluiUufimn tab* and Te^ar^mpani^,^^ Levator palati Rough Quadrilateral, Su-rfa+e °J»™y of carrtd camd Canal/or Jaeohon, nerve ^uMacrus Corhleic Canal far Arnold'* nerve- Jugular fossa Vagcnal _pracer jwrt. m To,r. JVfc r °*ii u and the serrated for- articulation with the vertical part of the sphenoidal turbinated bone. The internal or ethmoidal surface is directed inwards, up- wards and forwards, and articu- lates with the lateral mass of the ethmoid bone. In some cases, the cellular cavity above-men- tioned opens on this surface of the bone; it then communicates with the posterior ethmoidal cells. More rarely it opens on both surfaces, and then commu- nicates with the posterior eth- moidal cells, and the sphenoidal sinus. The non-articular or free surfaces are the superior or or- bital, directed upwards and out- wards, of triangular form, concave, smooth, articulating with tne superior maxillary bone, and forming the back part of the floor of the orbit. The external or zygomatic surface, directed out- wards, backwards and downwards, is of an oblong form, smooth, and forms part of the zygomatic fossa. This surface is separated from the orbit by a smooth rounded border, which enters into the formation of the spheno-maxillary fissure. The Sphenoidal Process of the palate bone is a thin compressed plate, much smaller than the orbital, and directed upwards and inwards. It presents three surfaces and two borders. The superior surface, the smallest of the three, arti- culates with the horizontal part of the sphenoidal turbinated bone ; it presents a groove which contributes to the formation of the pterygo-palatine canal. The internal surface is concave, and forms part of the outer wall of the nasal fossa. The external surface is divided into an articular, and a non-articular portion ; the former is rough for articulation with the inner surface of the pterygoid process of the sphenoid; the latter is smooth, and forms part of the zygomatic fossa. The anterior border forms the posterior boundary of the spheno-palatine foramen. The posterior border, serrated at the expense of the outer table, articulates with the inner surface of the pterygoid process. The orbital and sphenoidal processes are separated from one another by a deep notch, which is converted into a foramen, the spheno-palatine, by articulation with the sphenoidal turbinated bone. Sometimes the two processes are united above, and form between them a complete foramen, or the notch is crossed by one or more spicula of bone, so as to form two or more foramina. In the articulated skull, this foramen opens into the back part of the outer wall of the superior meatus, and transmits the spheno-palatine vessels and nerves. Development. From a single centre, which makes its appearance at the angle of junction of the two plates of the bone. From this point ossification spreads, in- wards, to the horizontal plate ; downwards, into the tuberosity ; and upwards, into the vertical plate. In the foetus, the horizontal plate is much longer than the vertical ; and even after it is fully ossified, the whole bone is remarkable for its shortness. Articulations. "With seven bones: the sphenoid, ethmoid, superior maxillary, inferior turbinated, vomer, opposite palate, and sphenoidal turbinated. INFERIOR TURBINATED BONE. 9J Attachment of Muscles. The Tensor palati, Azygos uvulae, Internal and External pterygoid. The Inferior Turbinated Bones. The Inferior Turbinated Bones are situated one on each side of the outer wall of the nasal fossse. Each bone consists of a layer of thin spongy bone, curled upon itself like a scroll, hence its name "turbinated;" and extends horizontally across the outer wall of the nasal fossa, immediately below the orifice of the antrum. Each bone presents two surfaces, two borders, and two extremities. The internal surface (fig. 53) is convex, perforated by numerous apertures, and traversed by longitudinal grooves Fig. 53. — Right Inferior Turbinated Bone. Surface. Inner Fig. 54. — Right Inferior Turbinated Bone. Outer Surface. and canals for the lodgment of arte- ries and veins. In the recent state it is covered by the lining membrane of the nose. The external surface is con- cave (fig. 54), and forms part of the inferior meatus. Its upper border is thin, irregular, and connected to vari- ous bones along the outer wall of the nose. . It may be divided into three portions; of these, the anterior arti- culates with the inferior turbinated crest of the superior maxillary bone; the posterior with the inferior turbinated crest of the palate bone ; the middle portion of the superior border presents three well-marked processes, which vary much in their size and form. Of these the anterior and smallest is situated at the junction of the anterior fourth with the posterior three-fourths of the bone; it is small and pointed, and is called the lachry- mal process, for it articulates with the ante- rior inferior angle of the lachrymal bone, and by its margins with the groove on the back of the nasal process of the supe- rior maxillary, and thus assists in forming the lachrymal canal. At the junction of the two middle fourths of the bone, but en- croaching on the latter, a broad thin plate, the ethmoidal process, ascends to join the unciform process of the ethmoid ; from the lower border of this process, a thin lamina of bone curves downwards and outwards, hooking over the lower edge of the orifice of the antrum, which it narrows below ; it is called the maxillary pro- cess, and fixes the bone firmly on to the outer wall of the nasal fossa. The infe- rior border is free, thick and cellular in structure, more especially in the centre of the bone. Both extremities are more or less narrow and pointed. If the bone is held so that its outer concave surface is directed backwards (i. e., towards the holder), and its superior border, from which the lachrymal and ethmoidal pro- cesses project, upwards, the lachrymal process will be directed to the side to which the bone belongs. Development. By a single centre which makes its appearance about the middle of foetal life. Articulations. "With four bones: one of the cranium, the ethmoid; and three of the face, the superior maxillary, lachrymal and palate. No muscles are attached to this bone. 92 OSTEOLOGY. •"^A. Sup -M«* &. ^ The Vomer. The Vomer is a single bone, situated vertically at the back part of the nasal fossae, forming part of the septum of the nose. It is thin, somewhat like a ploughshare in form ; but it varies in different individuals, being frequently bent to one or the other side; it Fig. 55.— Vomer. presents for examination two surfaces and four borders. The lateral surfaces are smooth, marked with small furrows for the lodgment of bloodvessels, and by a groove on each side, sometimes a canal, the naso- palatine, which runs obliquely downwards and forwards to the intermaxillary suture be- tween the two anterior palatine canals; it transmits the naso- palatine nerve. The superior border, the thickest, presents a deep groove, bounded on each side by a horizontal pro- jecting ala of bone ; the groove receives the rostrum of the sphenoid, whilst the alas are overlapped and retained by laminae (the vaginal processes) which project from the under surface of the body of the sphenoid at the base of the pterygoid processes. At the front of the groove a fissure is left for the transmission of bloodvessels to the substance of the bone. The inferior border, the longest, is broad and uneven in front, where it articulates with the two superior maxillary bones ; thin and sharp behind where it joins with the palate bones. The upper half of the anterior border usually consists of two laminae of bone, between which is received the perpendicular plate of the ethmoid, the lower half consisting of a single rough edge, also occa- sionally channelled, which is united to the triangular cartilage of the nose. The posterior border is free, concave, and separates the nasal fossae behind. It is thick and bifid above, thin below. Development. The vomer at an early period consists of two laminae separated by a very considerable interval, and inclosing between them a plate of cartilage which is prolonged forwards to form the remainder of the septum. Ossification commences in it at about the same period as in the vertebrae, the coalescence of the laminae taking place from behind forwards, but is not complete until after puberty. Articulations. With six bones: two of the cranium, the sphenoid and ethmoid; and four of the face, the two superior maxillary and the two palate bones ; and with the cartilage of the septum. The vomer has no muscles attached to it. The Inferior Maxillary Bone. The Inferior Maxillary Bone, the largest and strongest bone of the face, serves for the reception of the inferior teeth. It consists of a curved horizontal portion, the body, and of two perpendicular portions, the rami, which join the former nearly at right angles behind. The Horizontal portion or body (fig. 56), is convex in its general outline, and curved somewhat like a horseshoe. It presents for examination two surfaces and two borders. The external surface is convex from side to side, concave from above downwards. In the median line is a vertical ridge, the symphysis ; it extends from the upper to the lower border of the bone, and indicates the point of junction of the two pieces of which the bone is composed at an early period of life. The lower part of the ridge terminates in a prominent triangular eminence, the mental process. On either side of the symphysis, just below the roots of the o INFERIOR MAXILLARY BONE. 93 incisor teeth, is a depression, the incisive fossa, for the attachment of the Levator menti ; and, still more externally, a foramen, the mental foramen, for the passage of the mental nerve and artery. This foramen is placed just below the root of the second bicuspid tooth. Running outwards from the base of the mental process on each side, is a well-marked ridge, the external oblique line. This ridge is at first nearly horizontal, but afterwards inclines upwards and backwards, and is continuous with the anterior border of the ramus ; it affords attachment to the Depressor labii inferioris and Depressor anguli oris; below these the Platysma myoides is inserted. The external oblique line, and the internal oblique or mylo-hyoidean line, to be hereafter described, divide the body of the bone into a superior or alveolar, and an inferior or basilar portion. Fig. 56. — Inferior Maxillary Bone. Outer Surface. Side View. ,<<<*> Men ial /iroeesa The internal surface (fig. 57) is concave from side to side, convex from above downwards. In the middle line is an indistinct linear depression, corresponding to the symphysis externally; on either side of this depression, just below its centre, are four prominent tubercles, placed in pairs, two above and two below ; they are called the genial tubercles, and afford attachment, the upper pair to the Genio-hyoglossi muscles, the lower pair to the Genio-hyoidei muscles. Sometimes the tubercles on each side are blended into one, or they all unite into an irregular eminence of bone, or nothing but an irregularity may be seen on the surface of the bone at this part. On either side of the genial tubercles is an oval depression, the sublingual fossa, for lodging the sublingual gland ; and beneath the fossa a rough depression on each side, which gives attachment to the anterior belly of the Digastric muscle. At the back part of the sublingual fossa, the internal oblique or mylo-hyoidean line commences ; it is at first faintly marked, but becomes more distinct as it passes upwards and outwards, and is especially prominent opposite the last two molar teeth ; it divides the lateral surface of the bone into two por- tions, and affords attachment throughout its whole extent to the Mylo-hyoid muscle, the Superior constrictor being attached above its posterior extremity, nearer the alveolar margin. The portion of bone above this ridge is smooth, and covered by the mucous membrane of the mouth ; whilst that below it presents an oblong depression, the submaxillary fossa, wider behind than in front, for the lodgment of the submaxillary gland. The superior or alveolar border is wider, and its margins thicker, behind than in front. It is hollowed into numerous cavities, for the reception of the teeth; these are sixteen in number, and vary in depth and size according to the teeth which they contain. The inferior border is rounded, longer than the superior, and thicker in front than behind ; it presents 94 OSTEOLOGY. a shallow groove, just where the body joins the ramus, over which the facial artery turns. The Perpendicular Portions or Rami are of a quadrilateral form. Each presents for examination two surfaces, four borders, and two processes. The external surface is flat, marked with ridges, and gives attachment throughout nearly the whole of its extent to the Masseter muscle. The internal surface pre- sents about its centre the oblique aperture of the inferior dental canal, for the passage of the inferior dental vessels and nerve. The margin of this opening is irregular ; it presents in front a prominent ridge, surmounted by a sharp spine, which gives attachment to the internal lateral ligament of the lower jaw ; and at its lower and back part a notch leading to a groove, the mylo-hyoidean, which runs obliquely downwards to the back part of the submaxillary fossa, and lodges the mylo-hyoid vessels and nerve ; behind the groove is a rough surface, for the insertion of the Internal pterygoid muscle. The inferior dental canal descends obliquely downwards and forwards in the substance of the ramus, and then hori- zontally forwards in the body ; it is here placed under the alveoli, with which it communicates by small openings. On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals, which run Fig. 57. — Inferior Maxillary Bone. Inner Surface. Side View. >^^ CENIO-HYO-CLOSSUS CEN10-HY0IDCU5 Mylo-hyoid Ridge Bod forward, to be lost in the cancellous tissue of the bone beneath the incisor teeth. This canal, in the posterior two-thirds of the bone, runs nearest the internal sur- face of the jaw ; and in the anterior third, nearer its external surface. Its walls are composed of compact tissue at either extremity, cancellous in the centre. It contains the inferior dental vessels and nerve, from which branches are distributed to the teeth through small apertures at the bases of the alveoli. The upper border of the ramus is thin, and presents two processes, separated by a deep concavitv, the sigmoid notch. Of these processes, the anterior is the coronoid, the posterior the condyloid. The Coronoid Process is a thin, flattened, triangular eminence of bone, which varies in shape and size in different subjects, and serves essentially for the attach- ment of the Temporal muscle. Its external surface is smooth, and affords attachment to the Masseter and Temporal muscles. Its internal surface gives attachment to the Temporal muscle, and presents the commencement of a longi- tudinal ridge, which is continued to the posterior part of the alveolar process. On the outer side of this ridge is a deep groove, continued below on the outer side of INFERIOR MAXILLARY BONE. 9S the alveolar process ; this ridge and part of the groove afford attachment, above, to the Temporal ; below, to the Buccinator muscle. The Condyloid Process, shorter but thicker than the coronoid, consists of two portions : the condyle, and the constricted portion which supports the condyle, the neck. The condyle is of an oblong form, its long axis being transverse, and set obliquely on the neck in such a manner that its outer end is a little more forward and a little higher than its inner. It is convex from before backwards, and from side to side, the articular surface extending further on the posterior than on the anterior surface. The neck of the condyle is flattened from before backwards, and strengthened by ridges which descend from the fore part and sides of the condyle. Its lateral margins are narrow, and present externally a tubercle for the external lateral ligament. Its posterior surface is convex; its anterior is hollowed out on its inner side by a depression, the pterygoid fossa, for the attach- ment of the External pterygoid muscle. The lower border of the ramus is thick, straight, and continuous with the body of the bone. At its junction with the posterior border is the angle of the jaw, which is either inverted or everted, and marked by rough oblique ridges on each side for the attachment of the Masseter externally, and the Internal pterygoid internally; and, between them, is the attachment of the stylo-maxillary ligament. The anterior border is thin above, thicker below, and continuous with the external oblique line. The posterior border is thick, smooth, rounded, and covered by the parotid gland. The Sigmoid Notch, separating the two processes, is a deep semilunar depression, crossed by the masseteric artery and nerve. Development. This bone is formed at such an early period of life, before, indeed, any other bone, excepting the clavicle, that it has been found impossible at present to determine its earliest condition. It appears probable, however, that it is devel- oped by two centres, one for each lateral half, the two segments meeting at the symphysis, where they become united. Additional centres have also been described for the coronoid process, the condyle, the angle, and the thin plate of bone which forms the inner side of the alveolus. Changes produced in the Lower Jaw by Age. The changes which the Lower Jaw undergoes after birth, relate — 1. To the alterations effected in the body of the bone by the first and second dentitions, the loss of the teeth in the aged, and the subsequent absorption of the alveoli ; 2. To the size and situation of the dental canal ; and, 3. To the angle at which the ramus joins with the body. At birth (fig. 58), the bone consists of two lateral halves, united by fibro-cartilaginous tissue, in which one or two osseous nuclei are generally found. The body is a mere shell of bone, con- taining the sockets of the two incisor, the canine, and the first molar teeth, imperfectly partitioned from one another. The dental canal is of large size, and runs near the lower border of the bone, the mental foramen opening beneath the socket of the first molar. The angle is obtuse, from the jaws not being as yet separated by the eruption of the teeth. After birth (fig. 59), the two segments of the bone become joined at the symphysis, from below upwards, in the first year ; but a trace of separation may be visible in the beginning of the second year, near the alveolar margin. The body becomes elongated in its whole length, but more espe- cially behind the mental foramen, to provide space for the three additional teeth developed in this part. The depth of the body becomes greater, owing to increased growth of the alveolar part, to afford room for the fangs of the teeth, and by thickening of the snbdental portion which enables the jaw to withstand the powerful action of the masticatory muscles ; but the alveolar portion is the deeper of the two, and, consequently, the chief part of the body lies above the oblique line. The dental canal, after the second dentition, is situated just above the level of the mylo-hyoid ridge ; and the mental foramen occupies the position usual to it in the adult. The angle becomes less obtuse, owing to the separation of the jaws by the teeth. In the adult (fig. 60), the alveolar and basilar portions of the body are usually of equal depth. The mental foramen opens midway between the upper and lower border of the bone, and the dental canal runs nearly parallel with the mylo-hyoid line. The ramus is almost vertical in direction, and joins the body nearly at right angles. In old age (fig. 61), the bone becomes greatly reduced in size; for, with the loss of the teeth, the alveolar process is absorbed, and the basilar part of the bone alone remains ; consequently, the chief part of the bone is beloiv the oblique line. The dental canal, with the mental foramen opening from it, is close to the alveolar border. The rami are oblique in direction, and the angle obtuse. 8£ OSTEOLOGY. Side "View of the Lower Jaw at different Periods of Life. Fig. 58.— At Birth. Fig. 59.— At Puberty. Fig. 60.— In the Adult. Fig. 61.— In Old Age. SUTURES OF THE SKULL. 97 Articulations. With the glenoid fossae of the two temporal bones. Attachment of Muscles. By its external surface, commencing at the symphysis and proceeding backwards : Levator menti, Depressor labii inferioris, Depressor anguli oris, Platysma myoides, Buccinator, Masseter. By its internal surface, com- mencing at the same point; Genio-hyo-glossus, Genio-hyoideus, Mylo-hyoideus, Digastricus, Superior constrictor, Temporal, Internal pterygoid, External pterygoid. THE SUTURES. The bones of the cranium and face are connected to each other by means of sutures. The dentations by which they are joined are confined to the external table, the edges of the internal table lying merely in apposition with the contiguous bone. The Cranial Sutures may be divided into three sets: 1. Those at the ver- tex of the skull. 2. Those at the side of the skull. 3. Those at the base. The sutures at the vertex of the skull are three, the sagittal, coronal, and lamb- doid. The Sagittal Suture (interparietal) is formed by the junction of the two parietal bones, and extends from the middle of the frontal bone, backwards to the superior angle of the occipital. In childhood, and occasionally in the adult, when the two halves of the frontal bone are not united, it is continued forwards to the root of the nose. This suture sometimes presents, near its posterior extremity, the parietal foramen on each side ; and in front, where it joins the coronal suture, a space is occasionally left, which incloses a large Wormian bone. The Coronal Suture (fronto-parietaT) extends transversely across the vertex of the skull, and connects the frontal with the parietal bones. It commences at the extremity of the great wing of the sphenoid on one side, and terminates at the same point on the opposite side. The dentations of this suture are more marked at the sides than at the summit, and are so constructed that the frontal rests on the parietal above, whilst laterally the frontal supports the parietal. The Lambdoid Suture (occipitoparietal), so called from its resemblance to the Greek letter a, connects the occipital with the parietal bones. It commences on each side at the mastoid portion of the temporal bone, and inclines upwards to the end of the sagittal suture. The dentations of this suture are very deep and dis- tinct, and are often interrupted by several small Wormian bones. The sutures at the side of the skull are also three in number: the spheno-parietal, squamo-parietal, and masto-parietal. They are subdivisions of a single suture, formed between the lower border of the parietal, and the temporal and sphenoid bones, and which extends from the lower end of the lambdoid suture behind, to the lower end of the coronal suture in front. The Spheno-parietal is very short ; it is formed by the tip of the great wing of the sphenoid, which overlaps the anterior inferior angle of the parietal bone. The Squamo-parietal, or squamous suture, is arched. It is formed by the squamous portion of the temporal bone overlapping the middle division of the lower border of the parietal. The Masto-parietal is a short suture, deeply dentated, formed by the posterior inferior angle of the parietal, and the superior border of the mastoid portion of the temporal. The sutures of the base of the skull are, the basilar in the centre, and, on each side, the petro-occipital and masto-occipital, the petro-sphenoidal and the squamo- sphenoidal. The Basilar Suture is formed by the junction of the basilar surface of the occipital bone with the posterior surface of the body of the sphenoid. At an early period of life, a thin plate of cartilage exists between these bones; but in the adult they become inseparably united. Between the outer extremity of the basilar suture, and the termination of the lambdoid, an irregular suture exists which is subdivided into two portions. The inner portion, formed by the union of the petrous part of the temporal with the occipital bone, is termed the petro-occipital. The outer 7 98 OSTEOLOGY. portion, formed by the junction of the mastoid part of the temporal with the occi- pital, is called the masto-occipital. Between the bones forming the petro-occipital suture, a thin plate of cartilage exists ; in the masto-occipital is occasionally found the opening of the mastoid foramen. Between the outer extremity'of the basilar suture and the spheno-parietal an irregular suture may be seen, formed by the union of the sphenoid with the temporal bone. The inner and smaller portion of this suture is termed the petro-sphenoidal ; it is formed between the petrous portion of the temporal and the great wing of the sphenoid : the outer portion, of greater length, and arched, is formed between the squamous portion of the temporal and the great wing of the sphenoid : it is called the squamo-sphenoidal. The cranial bones are connected with those of the face, and the facial bones with each other, by numerous sutures, which, though distinctly marked, have received no special names. The only remaining suture deserving especial consideration is the transverse. This extends across the upper part of the face, and is formed by the junction of the frontal with the facial bones ; it extends from the external angular process of one side, to the same point on the opposite side, and connects the frontal with the malar, the sphenoid, the ethmoid, the lachrymal, the superior maxillary, and the nasal bones on each side. The sutures remain separate for a considerable period after the complete forma- tion of the skull. It is probable, that they serve the purpose of permitting the growth of the bones at their margins ; while their peculiar formation, and the interposition of the sutural ligament between the bones forming them, prevents the dispersion of blows or jars received upon the skull. Mr. Humphry remarks, "that, as a general rule, the sutures are first obliterated at the parts in which the ossification of the skull was last completed, viz., in the neighborhood of the fontanelles ; and the cranial bones seem in this respect to observe a similar law to that which regulates the union of the epiphyses to the shafts of the long bones." The Skull. The Skull, formed by the union of the several cranial and facial bones already described, when considered as a whole, is divisible into five regions ; a superior region or vertex, an inferior region or base, two lateral regions, and an anterior region, the face. Veetex of the Skull. The Superior Region or Vertex presents two surfaces, an external, and an internal. The External Surface is bounded, in front, by the nasal eminences, and super- ciliary ridges ; behind, by the occipital protuberance and superior curved -lines of the occipital bone ; laterally, by an imaginary line extending from the outer end of the superior curved line, along the temporal ridge, to the external angular process of the frontal. This surface includes the vertical portion of the frontal, the greater part of the parietal, and the superior third of the occipital bone ; it is smooth, convex, of an elongated oval form, crossed transversely by the coronal suture, and from before backwards by the sagittal, which terminates behind in the lambdoid. From before backwards may be seen the frontal eminences and remains of the suture connecting the two lateral halves of the frontal bone ; on each side of the sagittal suture are the parietal foramen and parietal eminence, and still more pos- teriorly the smooth convex surface of the occipital bone. The Internal Surface is concave, presenting eminences and depressions for the convolutions of the cerebrum, and numerous furrows for the lodgment of branches of the meningeal arteries. Along the middle line of this surface is a longitudinal groove, narrow in front, where it terminates in the frontal crest : broader behind ; it lodges the superior longitudinal sinus, and its margins afford attachment to the falx cerebri. On either side of it are several depressions for the Pacchionian bodies, and at its back part, the internal openings of the parietal foramina. This surface is crossed, in front, by the coronal suture ; from before backwards, by the sagittal ; behind, by the lambdoid. BASE OP THE SKULL. 99 Base of the Skull. The Inferior Region or Base of the skull presents two surfaces, an internal or cerebral, and an external or basilar. Fig. 62.— Base of the Skull. Inner or Cerebral Surface. Groove for Super. "Lmoititd. Sinus Qroovtt for Avter. Meiiiiitjfal A Foramen t'otruiti Crista GtiMi Slit for Vttml nervtk. Qrooi't Jnr Tfvtxnlj nerve. Anterior Ethmoidal For. Orifioee far Olfactory verve Posterior Etlimaidal Fort .Ethmoidal Spine - Olfactory Croats Optic Foravun Optic Oroovt- Olivary pre, Anterior Clinoid proa Middle Clinoid proc Foste rio r Clinoid proa Groove for 6'$ nerve Tor" laeerum medium. Orifice of Carotid, Canal Depression for Casserian Ganglion Meatus Auditor. Tntemris Slit for Vara -Ma Wr Sup. Petrosal groove For. laeerum poster itu Anterior Condyloid For Aqueduct. Veetibuli Posterior Condyloid For. Mastoid Foe Lost. Meningeal Grooves. 100 OSTEOLOGY. The Internal or Cerebral Surface (fig. 62) presents three fossae on each side, called the anterior, middle and posterior fossae of the cranium. The Anterior Fossa is formed by the orbital plate of the frontal, the cribriform plate of the ethmoid, the ethmoidal process and lesser wing of the sphenoid. It is the most elevated of the three fossae, convex externally where it corresponds to the roof of the orbit, concave in the median line in the situation of the cribriform plate of the ethmoid. It is traversed by three sutures, the ethmoido-frontal, ethmo-sphenoidal, and fronto-sphenoidal ; and lodges the anterior lobe of the cere- brum. It presents, in the median line, from before backwards, the commencement of the groove for the superior longitudinal sinus, and crest for the attachment of the falx cerebri; the foramen caecum, this aperture being formed by the frontal and crista galli of the ethmoid, and, if pervious, transmitting a small vein from the nose to the superior longitudinal sinus. Behind the foramen caecum is the crista galli, the posterior margin of which affords attachment to the falx cerebri. On either side of the crista galli is the olfactory groove, which supports the bulb of the olfactory nerve, perforated by three rows of orifices which give passage to its filaments; and in front by a slit-like opening, which transmits the nasal branch of the ophthalmic nerve. On the outer side of each olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina; the former, situated about the middle of its outer margin, transmits the nasal nerve, which runs in a groove along its surface to the slit-like opening above mentioned; whilst the latter, the posterior ethmoidal foramen, opens at the back part of the margin under cover of a projecting lamina of the sphenoid ; it transmits the posterior ethmoidal artery and vein to the posterior ethmoidal cells. Further back in the middle line is the ethmoidal spine, bounded behind by an elevated ridge, sepa- rating a longitudinal groove on each side which supports the olfactory nerve. The anterior fossa presents laterally eminences and depressions for the convolu- tions of the brain, and grooves for the lodgment of the anterior meningeal arteries. The Middle Fossa, somewhat deeper than the preceding, is narrow in the middle, and becomes wider as it expands laterally. It is bounded in front by the posterior margin of the lesser wing of the sphenoid, the anterior clinoid process, and the anterior margin of the optic groove; behind, by the petrous portion of the tem- poral, and basilar suture; externally, by the squamous portion of the temporal, and anterior inferior angle of the parietal bone ; and is separated from its fellow by the sella Turcica. It is traversed by four sutures, the squamous, sphenoparietal, spheno-temporal, and petro-sphenoidal. In the middle line, from before backwards, is the optic groove, which supports the optic commissure, terminating on each side in the optic foramen, for the passage of the optic nerve and ophthalmic artery ; behind the optic groove is the olivary process, and laterally the anterior clinoid processes, which afford attachment to the folds of the dura mater, which form the cavernous sinuses. Separating the middle fossae is the sella Turcica, a deep depression, which lodges the pituitary gland, bounded in front by a small eminence on either side, the middle clinoid process, and behind by a broad square plate of bone, surmounted at each superior angle by a tubercle, the posterior clinoid process; beneath the latter process is a groove, for the lodgment of the sixth nerve. On each side of the sella Turcica is the cavernous groove; it is broad, shallow, and curved somewhat like the Italic letter/: it commences behind at the foramen lacerum medium, and terminates on the inner side of the anterior clinoid process. This groove lodges the cavernous sinus, the internal carotid artery, and the orbital nerves. The sides of the middle fossa are of considerable depth; they present eminences and depres- sions for the middle lobes of the brain, and grooves for lodging the branches of the middle meningeal artery ; the latter commence on the outer side of the fora- men spinosum, and consist of two large branches, an anterior and a posterior ; the former passing upwards and forwards to the anterior inferior angle of the parietal bone, the latter passing upwards and backwards. The following foramina may also be seen from before backwards. Most anteriorly is the foramen lacerum BASE OF THE SKULL. 101 anterius, or sphenoidal fissure, formed above by the lesser wing of the sphenoid ; below, by the greater wing ; internally, by the body of the sphenoid ; and com- pleted externally by the orbital plate of the frontal bone. It transmits the third, fourth, the three branches of the ophthalmic division of the fifth, the sixth nerve, and the ophthalmic vein. Behind the inner extremity of the sphenoidal fissure is the foramen rotundum, for the passage of the second division of the fifth or superior maxillary nerve ; still more posteriorly is seen a small orifice, the foramen Vesalii; this opening is situated between the foramen rotundum and foramen ovale, a little internal to both ; it varies in size in different individuals, and transmits a small vein. It opens below in the pterygoid fossa, just at the outer side of the scaphoid depression. Behind and external to the latter opening is the foramen ovale, which transmits the third division of the fifth or inferior maxillary nerve, the small meningeal artery, and the small petrosal nerve. On the outer side of the foramen ovale is the foramen spinosum, for the passage of the middle meningeal artery ; and on the inner side of the foramen ovale, the foramen lacerum medium. The lower part of this aperture is filled up with cartilage in the recent state. On the anterior surface of the petrous portion of the temporal bone is seen, from without inwards, the eminence caused by the projection of the superior semicircular canal, and the groove leading to the hiatus Fallopii, for the transmission of the petrosal branch of the Vidian nerve; beneath it, the smaller groove, for the passage of the smaller petrosal nerve ; and near the apex of the bone, the depression for the Casserian ganglion, and the orifice of the carotid canal, for the passage of the internal carotid artery and carotid plexus of nerves. The Posterior Fossa, deeply concave, is the largest of the three, and situated on a lower level than either of the preceding. It is formed by the occipital, the petrous and mastoid portions of the temporal, and the posterior inferior angle of the parietal bone ; is crossed by three sutures, the petro-occipital, masto-occipital, and masto-parietal ; and lodges the cerebellum, pons Varolii, and medulla oblon- gata. It is separated from the middle fossa in the median line by the basilar suture, and on each side by the superior border of the petrous portion of the temporal bone. This serves for the attachment of the tentorium cerebelli, is grooved externally for the superior petrosal sinus, and at its inner extremity pre- sents a notch, upon which rests the fifth nerve. Its circumference is bounded posteriorly by the grooves for the lateral sinuses. In the centre of this fossa is the foramen magnum, bounded on either side by a rough tubercle, which gives attachment to the odontoid ligaments; and a little above these are seen the internal openings of the anterior condyloid foramina. In front of the foramen magnum is the basilar process, grooved for the support of the medulla oblongata and pons Varolii, and articulating on each side with the petrous portion of the tem- poral bone, forming the petro-occipital suture, the anterior half of which is grooved for the inferior petrosal sinus, the posterior half being encroached upon by the foramen lacerum posterius or jugular foramen. This foramen is partially subdi- vided into two parts ; the posterior and larger division transmits the internal jugu- lar vein, the anterior the eighth pair of nerves. Above the jugular foramen is the internal auditory foramen, for the auditory and facial nerves and auditory artery; behind and external to this is the slit-like opening leading into the aquaeductus vestibuli; whilst between the two latter, and near the superior border of the petrous portion, is a small triangular depression, which lodges a process of the dura mater, and occasionally transmits a small vein into the substance of the bone. Behind the foramen magnum are the inferior occipital fossae, which lodge the lateral lobes of the cerebellum, separated from one another by the internal occipital crest, which serves for the attachment of the falx cerebelli, and lodges the occipital sinuses. These fossae are surmounted, above, by the deep transverse grooves for the lodgment of the lateral sinuses. These channels, in their passage outwards, groove the occipital bone, the posterior inferior angle of the parietal, the mastoid portion of the temporal, and the occipital just behind the jugular foramen, at the back part of which they terminate. Where this sinus grooves the mastoid 102 OSTEOLOGY. part of the temporal bone, the orifice of the mastoid foramen may be seen ; and, just previous to its termination, it has opening into it the posterior condyloid foramen. The External Surface of the base of the skull (fig. 63) is extremely irregular. It is bounded in front by the incisor teeth in the upper jaws ; behind, by the superior curved lines of the occipital bone ; and laterally, by the alveolar arch, the lower border of the malar bone, the zygoma, and an imaginary line, extending from the zygoma to the mastoid process and extremity of the superior curved line of the occiput. It is formed by the palate processes of the two superior maxillary and palate bones, the vomer, the pterygoid, under surface of the great wing, spinous process and part of the body of the sphenoid, the under surface of the squamous, mastoid, and petrous ' portions of the temporal, and occipital bones. The anterior part of the base of the skull is raised above the level of the rest of this surface (when the skull is turned over for the purpose of examination), surrounded by the alveolar process, which is thicker behind than in front, and excavated by sixteen depressions for lodging the teeth of the upper jaw ; they vary in depth and size according to the teeth they contain. Immediately behind the incisor teeth is the anterior palatine fossa. At the bottom of this fossa may usually be seen four apertures, two placed laterally, which open above, one in the floor of each nostril, and transmit the anterior palatine vessels, and two in the median line of the intermaxillary suture, one in front of the other, the most anterior one transmitting the left, and the posterior one (the larger) the right naso-palatine nerve. These two latter canals are sometimes wanting, or they may join to form a single one, or one of them may open into one of the lateral canals above referred to. The palatine vault is concave, uneven, perforated by numerous foramina, marked by depressions for the palatal glands, and crossed by a crucial suture, which indicates the point of junction of the four bones of which it is com- posed. One or two small foramina, seen in the alveolar margin behind the incisor teeth, occasionally seen in the adult, almost constant in young subjects, are called the incisive foramina ; they transmit nerves and vessels to the incisor teeth. At each posterior angle of the bard palate is the posterior palatine foramen, for the trans- mission of the posterior palatine vessels and anterior palatine nerve, and running forwards and inwards from it a groove, which lodges the same vessels and nerve. Behind the posterior palatine foramen is the tuberosity of the palate bone, per- forated by one or more accessory posterior palatine canals, and marked by the commencement of a ridge, which runs transversely inwards, and serves for the attachment of the tendinous expansion of the Tensor palati. muscle. Projecting backwards from the centre of the posterior border of the hard palate is the pos- terior nasal spine, for the attachment of the Azygos uvulae. Behind and above the hard palate is the posterior aperture of the nares, divided into two parts by the vomer, bounded above by the body of the sphenoid, below by the horizontal plate of the palate bone, and laterally by the pterygoid processes of the sphenoid. Each aperture measures about an inch in the vertical, and half an inch in the transverse direction. At the base of the vomer may be seen the expanded aloe of this bone, receiving between them the rostrum of the sphenoid. Near the lateral margins of the vomer, at the root of the pterygoid processes, are the pterygo-palatine canals. The pterygoid process, which bounds the posterior nares on each side, presents near its base the pterygoid or Vidian canal, for the Vidian nerve and artery. Each process consists of two plates, which bifurcate at the extremity to receive the tuberosity of the palate bone, and are separated behind by the pterygoid fossa, which lodges the Internal pterygoid muscle. The internal plate is long and narrow, presenting on the outer side of its base the scaphoid fossa, for the origin of the Tensor palati muscle, and at its extremity the hamular process, around which the tendon of this muscle turns. The external pterygoid plate is broad, forms the inner boundary of the zygomatic fossa, and affords attachment to the External pterygoid muscle. BASE OF THE SKULL. 103 Behind the nasal fossa) in the middle line is the basilar surface of the occipital bone, presenting in its centre the pharyngeal spine for the attachment of the Fig. 63.— Base of the Skull. External Surface. Ant. pala/tim fossa 'mnsmits left Naso-palat. n. Transmit* Aer Dor»al Vr/rtcbra. Ridtjt f.rr Title r-artictdar L!yt~ facet for body of loutr Dorsal Viert' far traiuv. vroc. of lomti The neck is that flattened portion of the rib which extends outwards from the head ; it is about an inch long and rests upon the transverse process of the lower of the two vertebrae with which the head articulates. Its anterior surface is flat and smooth, its posterior rough, for the attachment of the middle costo-transverse ligament, and perforated by numerous foramina, the direction of which is less constant than those found on the inner surface of the shaft. Of its two borders, the superior presents a rough crest for the attachment of the anterior costo- transverse ligament ; its inferior border is rounded. On the posterior surface of the neck, just where it joins the shaft, and nearer the lower than the upper border, is an eminence — the tuberosity ; it consists of an articular and a non-articular portion. The articular portion, the most internal and inferior of the two, presents a small oval surface, for articulation with the extremity of the transverse process of the lower of the two vertebrae to which the head is connected. The non-arti- cular portion is a rough elevation, which affords attachment to the posterior costo- transverse ligament. The tubercle is much more prominent in the upper than in the lower ribs. The shaft is thin and flat, so as to present two surfaces, an external and an internal; and two borders, a superior and an inferior. The external surface is convex, smooth, and marked, at its back part, a little in front of the tuberosity, by a prominent line, directed obliquely from above, downwards and outwards ; this gives attachment to a tendon of the Sacro-lumbalis muscle, and is called the angle. At this point, the rib is bent in two directions. If the rib is laid upon its lower border, it will be seen, that the anterior portion of the shaft, as far as the angle, rests upon this margin, while the vertebral end of the bone, beyond the angle, is bent inwards, and at the same time tilted upwards. The interval between the angle and the tuberosity increases gradually from the second to the tenth rib. The portion of bone between these two parts is rounded, rough, and irregular, and serves for the attachment of the Longissimus dorsi. The portion of bone between the angle and sternal extremity is also slightly twisted upon its own axis, the external surface looking downwards behind the angle, a little upwards in front of it. This surface presents, towards its sternal extremity, an oblique line, the anterior angle. The internal surface is concave, smooth, directed a little upwards 118 OSTEOLOGY. behind the angle ; a little downwards in front of it. This surface is marked by a ridge ay Inch, commences at the lower extremity of the head; it is strongly marked as far as the inner side of the angle, and gradually becomes lost at the junction of the anterior with the middle third of the bone. The interval between it and the inferior border is deeply grooved, to lodge the intercostal vessels and nerve. At the back part of the bone, this groove belongs to the inferior border ; but just in front of the angle, where it is deepest and broadest, it corresponds to the internal surface. The superior edge of the groove is rounded ; it serves for the attachment of the Internal intercostal muscle. The inferior edge corresponds to the lower margin of the rib, and gives attachment to the External intercostal. Within the groove are seen the orifices of numerous small foramina, which traverse the wall •of the shaft obliquely from before backwards. The superior border, thick and rounded, is marked by an external and an internal lip, more distinct behind than in front ; they serve for the attachment of the External and Internal intercostal muscles. The inferior border, thin and sharp, has attached the External intercostal muscle. The anterior or sternal extremity is flattened, and presents a porous, oval, concave depression, into which the costal cartilage is received. Structure. The ribs consist of cancellous tissue, inclosed in a thin compact layer. Development. Each rib, with the exception of the last two, is developed by three centres, one for the shaft, one for the head, and one for the tubercle. The last two have only two centres, that for the tubercle being wanting. Ossification commences in the body of the ribs at a very early period, before its appearance in the vertebras. The epiphysis of the head, which is of a slightly angular shape, and that for the tubercle, of a lenticular form, make their appearance between the sixteenth and twentieth years, and are not united to the rest of the bone until about the twenty-fifth year. Attachment of Muscles. The Intercostals, Scalenus anticus, Scalenus medius, Scalenus posticus, Pectoralis minor, Serratus magnus, Obliquus externus, Trans- versalis, Quaclratus lumborum, Diaphragm, Latissimus dorsi, Serratus posticus superior, Serratus posticus inferior, Sacro-lumbalis, Musculus accessorius ad sacro- lumbalem, Longissimus dorsi, Cervicalis ascendens, Levatores costarum. Peculiar Eibs. The ribs which require especial consideration are five in number, viz., the first, second, tenth, eleventh, and twelfth. The first rib (fig. 77) is one of the shortest and the most curved of all the ribs ; it is broad, flat, and placed horizontally at the upper part of the thorax, its surfaces looking upwards and downwards, and its borders inwards .and outwards. The head is of small size, rounded, and presents only a single articular facet for arti- culation with the body of the first dorsal vertebra. The neck is narrow and rounded. The tuberosity, thick and prominent, rests on the outer border. There is no angle, and the shaft is not twisted on its axis. The upper surface of the shaft is marked by two shallow depressions, separated from one another by a ridge, which becomes more prominent towards the internal border, where it terminates in a tubercle; this tubercle and ridge serve for the attachment of the Scalenus anticus muscle, the groove in front of it transmitting the subclavian vein ; that behind it, the subclavian artery. Between the groove for the subclavian artery and the tuberosity, is a depression for the attachment of the Scalenus medius muscle. The under surface is smooth, and destitute of the groove observed on the other ribs. The outer border is convex, thick, and rounded. The inner, concave, thin, and sharp, and marked about its centre by the tubercle before mentioned. The anterior extremity is larger and thicker than in any of the other ribs. The second rib (fig. 78) is much longer than the first, but bears a very consider- able resemblance to it in the direction of its curvature. The non-articular portion of the tuberosity is occasionally only slightly marked. The angle is slight, and situated close to the tuberosity, and the shaft is not twisted, so that both ends RIBS. 119 touch any plane surface upon which it may be laid. The shaft is not horizontal, like that of the first rib ; its outer surface, which is convex, looking upwards and a little outwards. It presents, near the middle, a rough eminence for the attach- ment of part of the first, and the second serration of the Serratus magnus. The inner surface, smooth and concave, is directed downwards and a little inwards; it presents a short groove towards its posterior part. The tenth rib (fig. 79) has only a single articular facet on its head. Peculiar Ribs. Fig. 77. , Fig. 78 ^t dost to tube/roti iluwf K^ S Fig. 79. SinqU urtir.ula/r facet - Fig. 80. Single artie. fwmt — Fig. 81. iSingU turtle. fa,c The eleventh and twelfth ribs (figs. 80 and 81) have each a single articular facet on the head, which is of rather large size ; they have no neck or tuberosity . and are pointed at the extremity. The eleventh has a slight angle and a shallow groove on the lower border. The twelfth has neither, and is much shorter than the eleventh. 120 OSTEOLOGY. The Costal Caetilages. The Costal Cartilages (fig. 69) are white elastic structures, which serve to pro- long the ribs forward to the front of the chest, and contribute very materially to the elasticity of this cavity. The first seven are connected with the sternum, the next three with the lower border of the cartilage of the preceding rib. The cartilages of the last two ribs, which have pointed extremities, float freely in the walls of the abdomen. Like the ribs, the costal cartilages vary in their length, breadth, and direction. They increase in length from the first to the seventh, then gradually diminish to the last. They diminish in breadth, as well as the intervals between them, from the first to the last. They are broad at their attachment to the ribs, and taper towards their sternal extremities, excepting the first two, which are of the same breadth throughout, and the sixth, seventh, and eighth, which are enlarged where their margins are in contact. In direction they also vary ; the first descends a little, the second is horizontal, the third ascends slightly, whilst all the rest follow the course of the ribs for a short extent, and then ascend to the sternum or preceding cartilage. Each costal cartilage presents two surfaces, two borders, and two extremities. The anterior surface is convex, and looks forwards and upwards ; that of the first gives attachment to the costo-clavicular ligament ; that of the first, second, third, fourth, fifth, and sixth, at their sternal ends, to the Pectoralis major. The others are covered, and give partial attachment to some of the great flat muscles of the abdomen. The posterior surface is concave, and directed backwards and downwards, the six or seven inferior ones affording attachment to the Transversalis and Diaphragm muscles. Of the two borders, the superior is concave, the inferior convex ; they afford attachment to the Inter- costal muscles, the upper border of the sixth giving attachment to the Pectoralis major muscle. The contiguous borders of the sixth, seventh, and eighth, and sometimes the ninth and tenth costal cartilages, present smooth oblong surfaces at the points where they articulate. Of the two extremities, the outer one is con- tinuous with the osseous tissue of the rib to which it belongs. The inner extremity of the first is continuous with the sternum ; the six succeeding ones have rounded extremities, which are received into shallow concavities on the lateral margins of the sternum. The inner extremities of the eighth, ninth, and tenth costal carti- lages are pointed, and lie in contact with the cartilage above. Those of the eleventh and twelfth are free, and pointed. The costal cartilages are most elastic in youth, those of the false ribs being more so than the true. In old age, they become of a deep yellow color. Under certain diseased conditions, they are prone to ossify. Mr. Humphry's observa- tions on this subject have led him to regard the ossification of the costal cartilages as a sign of disease rather than of age. " The ossification takes place in the first cartilage sooner than in the others ; and in men more frequently, and at an earlier period of life, than in women." Attachment of Muscles. The Subclavius, Sterno-thyroid, Pectoralis major, Internal oblique, Transversalis, Pectus, Diaphragm, Triangularis sterni, Internal and External intercostals. OF TEE EXTEEMITIES. The Extremities or limbs are those long-jointed appendages of the body, which are connected to the trunk by one end, being free in the rest of their extent. They are four in number : an upper or thoracic pair, connected with the thorax through the intervention of the shoulder, and subservient mainly to tact and pre- hension ; and a lower pair, connected with the pelvis, intended for support and locomotion. Both pairs of limbs are constructed after one common type, so that they present numerous analogies ; while, at the same time, certain differences are observed in each, dependent on the peculiar offices they severally perform. CLAVICLE. 121 OF THE UPPER EXTREMITY. The upper extremity consists of the arm, the forearm, and the hand. Its con- tinuity with the trunk is established by means of the shoulder, which is homo- logous with the innominate or haunch bone in the lower limb. OF THE SHOULDER. The shoulder is placed upon the upper part and side of the chest, connecting the upper extremity to the trunk ; it consists of two bones, the clavicle, and the scapula. The Clavicle. The Clavicle (clavis, a key) or collar-bone forms the anterior portion of the shoulder. It is a long bone, curved somewhat like the Italic letter/, and placed nearly horizontally at the upper and anterior part of the thorax, immediately above the first rib. It articulates internally with the upper border of the sternum, and with the acromion process of the scapula by its outer extremity ; serving to sustain the upper extremity in the various positions which it assumes, whilst, at the same time, it allows it great latitude of motion. The horizontal plane of the clavicle is nearly straight ; but in the vertical plane it presents a double curvature, the convexity being, in front, at the sternal end; and, behind, at the scapular end. Its outer third is flattened from above downwards, and extends, in the natural position of the bone, from the coracoid process to the acromion. Its inner two- thirds are of a cylindrical form, and extend from the sternum to the coracoid process of the scapula. External or Flattened Portion. The outer third is flattened from above down- wards, so as to present two surfaces, an upper, and a lower ; and two borders, an anterior, and a posterior. The upper surface is flattened, rough, marked in front, for the attachment of the Deltoid ; behind, for the Trapezius ; between these two impressions, externally, a small portion of the bone is subcutaneous. The under surface is flattened. At its posterior border, at the junction of the prismatic with the flattened portion, is a rough eminence, the conoid tubercle ; this, in the natural position of the bone, surmounts the coracoid process of the scapula, and gives attachment to the conoid ligament. From this tubercle, an oblique line, occasionally a depression, passes forwards and outwards to near the outer end of the anterior border ; it is called the oblique line, and affords attachment to the trapezoid ligament. The anterior border'is concave, thin, and rough; it limits the attachment of the Deltoid, and occasionally presents, near 'the centre, a tubercle, the deltoid tubercle, which is sometimes distinct in the living subject. The posterior border is convex, rough, broader than the anterior, and gives attachment to the Trapezius. Internal or Cylindrical Portion. The cylindrical portion forms the inner two- thirds of the bone. It is curved, so as to be convex in front, concave behind, and is marked by three borders separating three surfaces. The anterior border is continuous with the anterior margin of the flat portion. At its commencement it is smooth, and corresponds to the unoccupied interval between the attachment of the Pectoralis major and Deltoid muscles ; about the centre of the clavicle it divides to inclose an elliptical space for the attachment of the clavicular portion of the Pectoralis major. This space extends inwards as far as the anterior margin of the sternal extremity. The superior border is continuous with the posterior margin of the flat portion, and separates the anterior from the posterior surface. At its commencement it is smooth and rounded, becomes rough towards the inner third for the attachment of the Sterno-cleido-mastoid muscle, and terminates at the upper angle of the eternal extremity. 122 OSTEOLOGY. The .posterior or subclavian border separates the posterior from the inferior surface, and extends from the conoid tubercle to the rhomboid depression. It forms the posterior boundary of the groove for the Subclavius muscle, and gives attachment to the fascia which incloses it. The anterior surface is included between the superior and anterior borders. It is directed forwards and a little upwards at the sternal end, outwards and still more upwards at the acromial extremity, where it becomes continuous with the upper surface of the flat portion. Externally, it is smooth, convex, nearly sub- cutaneous, being covered only by the Platysma ; but, corresponding to the inner half of the bone, it is divided by a more or less prominent line into two parts : an anterior portion, elliptical in form, rough, and slightly convex, for the attachment of the Pectoralis major; and an upper part, which is rough behind, for the attachment of the Sterno-cleido-mastoid. Between the two muscular impressions is a small subcutaneous interval. Fi«r. 82. — Left Clavicle. Anterior Surface. StcTTitilJSxrt^ Acromial HxtJ/ Fig. 83. — Left Clavicle. Inferior Surface. The posterior or cervical surface is smooth, flat, directed vertically, and looks backwards towards the root of the neck. It is limited, above, by the superior border; below, by the subclavian border; internally, by the margin of the sternal extremity; externally, it is continuous with the posterior border of the flat portion. It is concave from within outwards, and is in relation, by its lower part, with the suprascapular vessels. It gives attachment, near the sternal extremity, to part of the Sterno-hyoid muscle ; and presents, at or near the middle, a foramen, directed obliqiiely outwards, which transmits the chief nutrient artery of the bone. Some- times, there are two foramina on the posterior surface ; or one on the posterior, the other on the inferior surface. The inferior or subclavian surface is bounded, in front, by the anterior border ; behind, by the subclavian border. It is narrow internally, but gradually increases in width externally, and is continuous with the under surface of the flat portion. Commencing at the sternal extremity may be seen a small facet for articulation with the cartilage of the first rib. This is continuous with the articular surface at the sternal end of the bone. External to this is a broad rough impression, the rhomboid, rather more than an inch in length, for the attachment of the costo- clavicular or rhomboid ligament. The remaining part of this surface is occupied by a longitudinal groove, the subclavian groove, broad and smooth externally, SCAPULA. 123 narrow and more uneven internally; it gives attachment to the Subclavius muscle, ami, by its anterior margin, to the strong aponeurosis which incloses it. Not untivquently this groove is subdivided into two parts, by a longitudinal line, which gives attachment to the intermuscular septum of the Subclavius muscle. The internal or sternal end of the clavicle is triangular in form, directed inwards, and a little downwards and forwards ; and presents an articular facet, concave from before backwards, convex from above downwards, which articulates with the sternum through the intervention of an interarticular fibro-cartilage ; the circumference of the articular surface is rough, for the attachment of numerous ligaments. This surface is continuous with the costal facet on the inner end of the inferior or subclavian surface, which articulates with the cartilage of the first rib. The outer or acromial extremity, directed outwards and forwards, presents a small, flattened, oval facet, directed obliquely downwards and inwards, for articu- lation with the acromion process of the scapula. The direction of this surface serves to explain the greater frequency of dislocation of this bone upon, and not beneath, the acromion process. The circumference of the articular facet is rough, especially above, for the attachment of the acromio-clavicular ligaments. Peculiarities of the Bone in the Sexes and in Individuals. In the female, the cla- vicle is generally less curved, smoother, and more slender than in the male. In those persons who perform considerable manual labor, which brings into constant action the muscles connected with this bone, it requires considerable bulk, becomes shorter, and more curved, its ridges for muscular attachment become prominently marked, and its sternal end of a prismatic or quadrangular form. The right clavicle is generally heavier, thicker, and rougher, and ofte*n shorter, than the left. Structure. The shaft, as well as the extremities, consists of cancellous tissue, invested in a compact layer much thicker in the centre than at either end. The clavicle is highly elastic, by reason of its curves. From the experiments of Mr. "Ward, it has been shown that it possesses sufficient longitudinal elastic force to raise its own weight nearly two feet on a level surface ; and sufficient transverse elastic force, opposite the centre of its anterior convexity, to raise its own weight about a foot. This extent of elastic power must serve to moderate very consi- derably the effect of concussions received upon the point of the shoulder. Development. By two centres : one for the shaft, and one for the sternal extremity. The centre for the shaft appears very early, before any other bone ; the centre for the sternal end makes its appearance about the eighteenth or twentieth year, and unites with the rest of the bone a few years after. Articulations. With the sternum, scapula, and cartilage of the first rib. Attachment of Muscles. The Sterno-cleido-mastoid, Trapezius, Pectoralis major, Deltoid, Subclavius, and Sterno-hyoid. The Scapula. The Scapula forms the back part of the shoulder. It is a large flat bone, tri- angular in shape, situated at the posterior aspect and side of the thorax, between the first and eighth ribs, its posterior border or base being about an inch from, and nearly parallel with, the spinous processes of the vertebras. It presents for examination two surfaces, three borders, and three angles. The anterior surface or venter (fig. 84) presents a broad concavity, the sub- scapular fossa. It is marked, in the posterior two-thirds, by several oblique ridges, which pass from behind obliquely forwards and upwards, the anterior third being smooth. The oblique ridges, above-mentioned, give attachment to the tendinous intersections; and the surfaces between them, to the fleshy fibres of the Subscapu- lars muscle. The anterior third of the fossa, which is smooth, is covered by, but does not afford attachment to, the fibres of this muscle. This surface is sepa- rated from the posterior border by a smooth triangular margin at the superior and inferior angles, and in the interval between these, by a narrow edge which is 124 OSTEOLOGY. often deficient. This inargin.il surface affords attachment throughout its entire extent to the Serratus magnus muscle. The subscapular fossa presents a trans- verse depression at its upper part, called the subscapular angle; it is in this situa- tion that the fossa is deepest ; and consequently the thickest part of the Sub- scapularis muscle lies in a line parallel with the glenoid cavity, and must conse- quently operate most effectively on the humerus which is contained in it. The posterior surface or dorsum (fig. 85) is arched from above downwards, alternately convex and concave from side to side. It is subdivided unequally Fig. 84. — Left Scapula. Anterior Surface or Venter. into two parts by the spine ; that portion above the spine is caned the supra- spinous fossa, and that below it, the infra-spinous fossa. The supraspinous fossa, the smaller of the two, is concave, smooth, and broader at the vertebral than at the humeral extremity. It affords attachment by its inner two-thirds to the Supra-spinatus muscle. The infra-spinous fossa is much larger than the preceding : towards its ver- tebral margin a shallow concavity is seen at its upper part ; its centre presents a SCAPULA. 125 prominent convexity, -whilst towards the axillary border is a deep groove, which runs from the upper towards the lower part. The inner three-fourths of this surface afford attachment to the Infra-spinatus muscle ; the outer fourth is only covered by it, without giving origin to its fibres. This surface is separated from the axillary border by an elevated ridge, which runs from the lower part of the glenoid cavity, downwards and backwards to the posterior border, about an inch «<»** Fig. 85. — Left Scapula. Posterior Surface or Dorsum. Cora co j Qf above the inferior angle. This ridge serves for the attachment of a strong apon- eurosis, which separates the Infra-spinatus from the two Teres muscles. The surface of bone between this line and the axillary border is narrow for the upper two-thirds of its extent, and traversed near its centre by a groove for the passage of the dorsalis scapuhe vessels; it affords attachment to the Teres minor. Its lower third presents a broader, somewhat triangular surface, which gives origin to the Teres major, and over which glides the Latissimus dorsi ; sometimes the latter muscle takes its origin by a few fibres from this part. The broad and narrow 126 - OSTEOLOGY. portions of bone above alluded to are separated by an oblique line, which runs from the axillary border, downwards and backwards ; to it is attached the aponeu- rosis separating the two Teres muscles from each other. The Spine is a prominent plate of bone, which crosses obliquely the inner four-fifths of the dorsum of the scapula at its upper part, and separates the supra-spinous from the infra-spin ous fossa : it commences at the vertebral border by a smooth triangular surface, over which the Trapezius glides, separated by a bursa ; and, gradually becoming more elevated as it passes forwards, terminates in the acromion process which overhangs the shoulder-joint. The spine is triangular and flattened from above downwards, its apex corresponding to the posterior border ; its base, which is directed outwards, to the neck of the scapula. It presents two surfaces and three borders. Its superior surface is concave, assists in forming the supra-spinous fossa, and affords attachment to part of the Supra-spinatus muscle. Its inferior surface forms part of the infra-spinous fossa, gives origin to part of the lnfra-spinatus muscle, and presents near its centre the orifice of a nutritious canal. Of the three borders, the anterior is attached to the dorsum of the bone ; the posterior, or crest of the spine, is broad, and presents two lips, and an intervening rough interval. To the superior lip is attached the Trapezius, to the extent shown in the figure. A very rough prominence is generally seen occupying that portion of the spine which receives the insertion of the middle and inferior fibres of this muscle. To the inferior lip, throughout its whole length, is attached the Deltoid. The interval between the lips is also partly covered by the fibres of these muscles. The external border, the shortest of the three, is slightly concave, its edges thick and round, continuous above with the under surface of the acromion process ; below, with the neck of the scapula. The narrow portion of bone external to this border serves to connect the supra-spinous and infra-spinous fossae. The Acromion process, so called from forming the summit of the shoulder (axpov, a summit ; t3,aos, the shoulder), is a large, and somewhat triangular process, flattened from behind forwards, directed at first a little outwards, and then curving forwards and upwards, so as to overhang the glenoid cavity. Its upper surface directed upwards, backwards and outwards, is convex, rough, and gives attachment to some fibres of the Deltoid. Its under surface is smooth and concave. Its outer border, which is thick and irregular, affords attachment to the Deltoid muscle. Its inner margin, shorter than the outer, is concave, gives attachment to a portion of the Trapezius muscle, and presents about its centre a small oval surface, for articulation with the scapular end of the clavicle. Its apex, which corresponds to the point of meeting of these two borders in front, is thin, and has attached to it the coraco-acromial ligament. ,Of the three borders or costaa of the scapula, the superior is the shortest and thinnest ; it is concave, terminating at its inner extremity at the superior angle, at its outer extremity at the coracoid process. At its outer part is a deep semicircular notch, the supra-scapular, formed partly by the base of the coracoid process. This notch is converted into a foramen by the transverse ligament, and serves for the passage of the supra-scapular nerve. The adjacent margin of the superior border affords attachment to the Omo-hyoid muscle. The external or axillary border is the thickest of the three. It commences above at the lower margin of the glenoid cavity, and inclines obliquely downwards and backwards to the inferior angle. Immediately below the glenoid cavity is a rough depression about an inch in length, which affords attachment to the long head of the Triceps muscle ; to this succeeds a longitudinal groove, which extends as far as its lower third, and affords origin to part of the Subscapularis muscle. The inferior third of this border, which is thin and sharp, serves for the attachment of a few fibres of the Teres major behind, and of the Subscapularis in front. The internal or vertebral border, also named the base, is the longest of the three, and extends from the superior to the inferior angle of the bone. It is arched, intermediate in thickness between the superior and the external borders, and that portion of it above the spine is bent considerably outwards, so as to form an obtuse angle with SCAPULA. 127 the lower part. The vertebral border presents an anterior lip, a posterior lip, and an intermediate space. The anterior lip affords attachment to the Serratus mag- mis ; the posterior lip, to the Supra-spinatus above the spine, the Infra-spinatus below ; the interval between the two lips, to the Levator anguli scapulas above the triangular surface at the commencement of the spine ; the Ehomboideus minor, to the edge of that surface; the Ehomboideus major being attached by means of a fibrous arch, connected above to the lower part of the triangular surface at the base of the spine, and below to the lower part of the posterior border. Of the three angles, the superior, formed by the junction of the superior and internal borders, is thin, smooth, rounded, somewhat inclined outwards, and gives attachment to a few fibres of the Levator anguli scapulas muscle. The inferior angle, thick and rough, is formed by the union of the vertebral and axillary borders, its outer surface affording attachment to the Teres major, and occasionally a few fibres of the Latissimus dorsi. The anterior angle is the thickest part of the bone, and forms what is called the head of the scapula. The head presents a shallow, pyriform, articular surface, the glenoid cavity (y^vrj, a superficial cavity; nSo?, like); its longest diameter is from above downwards, and its direction outwards and forwards. It is broader below than above ; at its apex is attached the long tendon of the Biceps muscle. It is covered with cartilage in the recent state; and its margins, slightly raised, give attachment to a fibro- cartilaginous structure, the glenoid ligament, by which its cavity is deepened. The neck of the scapula is the slightly depressed surface which surrounds the head ; it is more distinct on the posterior than on the anterior surface, and below than above. In the latter situation it has, arising from it, a thick prominence, the coracoid process. The Coracoid process, so called from its fancied resemblance to a crow's beak (xopat, a crow ; «8os, resemblance), is a thick curved process of bone, which arises by a broad base from the upper part of the neck of the scapula ; it ascends at first upwards and inwards ; then, becoming smaller, it changes its direction and passes forwards and outwards. The ascending portion, flattened from before backwards, presents in front a smooth concave surface, over which passes the Subscapularis muscle. The horizontal portion is flattened from above downwards ; its upper surface is convex and irregular ; its under surface is smooth ; its anterior border is rough, and gives attachment to the Pectoralis minor ; its posterior border is also rough for the coraco-acromial ligament, while the apex is embraced by the con- joined tendon of origin of the short head of the Biceps and Coraco-brachialis muscles. At the inner side of the root of the coracoid process is a rough depres- sion for the attachment of the conoid ligament, and, running from it obliquely forwards and outwards on the upper surface of the horizontal portion, an elevated ridge for the attachment of the trapezoid ligament. Structure. In the head, processes, and all the thickened parts of the bone, it is cellular in structure, of a dense compact tissue in the rest of its extent. The centre and upper part of the dorsum, but especially the former, is usually so thin as to be semi-transparent ; occasionally the bone is found wanting in this situation, and the adjacent muscles come into contact. Development (fig. 86). By seven centres ; one for the body, two for the coracoid process, two for the acromion, one for the posterior border, and one for the inferior angle. Ossification of the body of the scapula commences about the second month of fcetal life, by the formation of an irregular quadrilateral plate of bone, imme- diately behind the glenoid cavity. This plate extends itself so as to form the chief part of the bone, the spine growing up from its posterior surface about the third month. At birth the chief part of the scapula is osseous, the coracoid and acromion processes, the posterior border, and inferior angle, being cartilaginous. About the first year after birth, ossification takes place in the middle of the coracoid process ; which usually becomes joined with the rest of the bone at the time when the other centres make their appearance. Between the fifteenth und 128 OSTEOLOGY. seventeenth years, ossification of the remaining centres takes place in quick suc- cession, and in the following order : first, near the base of the acromion, and in the upper part of the coracoid process, the latter appearing in the form of a broad scale ; secondly, in the inferior angle and contiguous part of the posterior border ; thirdly, near the extremity of the acromion; fourthly, in the posterior border. The acromion process, besides being formed of two separate nuclei, has its base formed by an extension into it of the centre of ossification which belongs to the spine, the extent of which varies in- different cases. The two separate nuclei unite, and then join with the extension carried in from the spine. These various epiphyses become joined to the bone between the ages of twenty-two and twenty- five years. Sometimes failure of union between the acromion process and spine occurs, the junction being effected by fibrous tissue, or by an imperfect articulation; Fig. 86. — Plan of the Development of the Scapula. By Seven Centres. 2 for f c Kferio* in some cases of supposed fracture of .the acromion with ligamentous union, it is probable the detached segment was never united to the rest of the bone. Articulations. With the humerus and clavicle. Attachment of Muscles. To the anterior surface, the Subscapularis ; posterior surface, Supra- spinatus, Infra-spinatus ; spine, Trapezius, Deltoid; superior border, Omo-hyoid ; vertebral border, Serratus magnus, Levator anguli scapulas, Ehom- boideus minor and major ; axillary border, Triceps, Teres minor, Teres major ; glenoid cavity, long head of the Biceps ; coracoid process, short head of Biceps, Coraco-brach'ialis, Pectoralis minor ; and to the inferior angle, occasionally a few fibres of the Latissimus dorsi. HUMERUS. 12? The Humerus. The Humerus (fig. 87) is the longest and largest bone of the upper extremity ; it presents for examination a shaft and two extremities. The Upper Extremity is the largest part of the bone ; it presents a rounded head, a constriction around the base of the head, the neck, and two other emi- nences, the greater and ]esser tuberosities. The head, nearly hemispherical in form, is directed upwards, inwards, and a little backwards ; its surface is smooth, coated with cartilage in the recent state, and articulates with the glenoid cavity of the scapula. The circumference of its articular surface is slightly constricted, and is termed the anatomical neck, in contradistinction to the constriction which exists below the tuberosities, and is called the surgical neck, from its often being the seat of fracture. It should be remembered, however, that fracture of the anatomical neck does sometimes, though rarely, occur. The anatomical neck is obliquely directed, forming an obtuse angle with the shaft. It is more distinctly marked in the lower half of its circumference than in the upper half, where it presents a narrow groove, separating the head from the tuberosities. Its circumference affords attachment to the capsular ligament, and is perforated by numerous vascular foramina. The greater tuberosity is situated on the outer side of the head and lesser tuberosity. Its upper surface is rounded and marked by three flat facets, separated by two slight ridges ; the most anterior facet gives attachment to the tendon of the Supra-spinatus ; the middle one, to the Infra-spinatus ; the posterior one, to the Teres minor. The outer surface of the great tuberosity is convex, rough, and continuous with the outer side of the shaft. The lesser tuberosity is more prominent, although smaller than the greater ; it is situated in front of the head, and is directed inwards and forwards. Its summit presents a prominent facet for the insertion of the tendon of the Subscapularis muscle. The tuberosities are separated from one another by a deep groove, the bicipital groove, so called from its lodging the long tendon of the Biceps muscle. It commences above between the two tuberosities, passes obliquely downwards and a little inwards, and terminates at the junction of the upper with the middle third of the bone. It is deep and narrow at its commencement, and becomes shallow and a little broader as it descends. In the recent state it is covered with a thin layer of cartilage, lined by a prolongation of the synovial membrane of the shoulder-joint, and receives part of the tendon of insertion of the Latissimus dorsi about its centre. The Shaft of the humerus is almost cylindrical in the upper half of its extent ; prismatic and flattened below, it presents three borders and three surfaces for examination. The anterior border runs from the front of the great tuberosity above, to the coronoid depression below, separating the internal from the external surface. Its upper part is very prominent and rough; forms the outer lip of the bicipital groove, and serves for the attachment of the tendon of the Pectoralis major. About its centre is seen the rough deltoid impression ; below, it is smooth and rounded, affording attachment to the Brachialis anticus. The external border runs from the back part of the greater tuberosity to the external condyle, and separates the external from the posterior surface. It is rounded and indistinctly marked in its upper half, serving for the attachment of the external head of the Triceps muscle ; its centre is traversed by a broad but shallow oblique depression, the musculo-spiral groove.; its lower part is marked by a prominent rough margin, a little curved from behind forwards, which presents an anterior lip for the attachment of the Supinator longus, above the Extensor carpi radialis longior below; a posterior lip for the Triceps, and an interstice for the attachment of the external intermuscular aponeurosis. L30 OSTEOLOGY. Fig. 87. — Left Humerus. Anterior View. Surgical Neck Common Origin WFjA rLEXOft CARPI RADIALI8 WT^m fAi.MAR18 LONCUS * FLEXOR nr.lTORUM SUBLIMIS ,, UHH ULNARI* fflfTroch 8UPINATOB RADII lONCUf EXTEN30R OARPI RADIALI3 LQNCIQB .t> Comrn-on Amm of y .V EXTENSOR. CARP. BAD. SREV j& „ DICITOHUM COMMUNIS ., MINIMI DICITI „ CARPI UlNARIS iUPikUTQR SREVIS HUMERUS. 131 The internal border extends from the lesser tuberosity to the internal condyle. Its upper third is marked by a prominent ridge, forming the inner lip of the bicipital groove, and gives attachment from above downwards to the tendons of the Latissimus dorsi, Teres major, and part of the origin of the inner head of the Triceps. About its centre is a rough ridge for the attachment of the Coraco- brachialis, and just below this is seen the entrance of the nutritious canal directed downwards. Sometimes there is a second canal higher up, which takes a similar direction. Its inferior third is raised into a slight ridge, which becomes very prominent below; it presents an anterior lip for the attachment of the Brachialis anticus, a posterior lip for the internal head of the Triceps, and an intermediate space for the internal intermuscular aponeurosis. The external surface is directed outwards above, where it is smooth, rounded, and covered by the Deltoid muscle ; forwards below, where it is slightly concave from above downwards, and gives origin to part of the Brachialis anticus muscle. About the middle of this surface, is seen a rough triangular impression for the insertion of the Deltoid muscle, and below it the musculo-spiral groove, directed obliquely from behind, forwards and downwards ; it transmits the musculo-spiral nerve and superior profunda artery. The internal surface, less extensive than the external, is directed forwards above, forwards and inwards below ; at its upper part it is narrow, and forms the bicipital groove. The middle part of this surface is slightly rough for the attachment of the Coraco-brachialis ; its lower part is smooth, concave, and gives attachment to the Brachialis anticus muscle. 1 The "posterior surface (fig. 88) appears somewhat twisted, so that its upper part is directed a little inwards, its lower part backwards, and a little outwards. Nearly the whole of this surface is covered by the external and internal heads of the Triceps, the former being attached to its upper and outer part, the latter to its inner and back part, their origin being separated by the musculo-spiral groove. The Lower Extremity is flattened from before backwards, and curved slightly forwards : it terminates below in a broad articular surface, which is divided into two parts by a slight ridge. On either side of the articular surface are the ex- ternal and internal condyles. The articular surface extends a little lower than the condyles, and is curved slightly forwards, so as to occupy the more anterior part of the bone ; its greatest breadth is in the transverse diameter, and it is obliquely directed, so that its inner extremity occupies a lower level than the outer. The outer portion of the articular surface presents a smooth rounded eminence, which has received the name of the lesser or radial head of the humerus ; it articulates with the cup-shaped depression on the head of the radius, is limited to the front and lower part of the bone, not extending as far back as the other portion of the articular surface. On the inner side of this eminence is a shallow groove, in which is received the inner margin of the head of the radius. The inner or trochlear portion of the articular surface presents a deep depression between two well-marked borders. This surface is convex from before back- wards, concave from side to side, and occupies the anterior lower and posterior parts of the bone. The external border, less prominent than the internal, corresponds 1 A small hook-shaped process of bone, varying from T ' ff to $ of an inch in length, is not unfrequently found projecting from the inner surface of the shaft of the humerus two inches above the internal condyle. It is curved downwards, forwards, and inwards, and its pointed extremity is connected to the internal border just above the inner condyle, by a ligament or fibrous band; completing an arch, through which the median nerve and brachial artery pass, when these structures deviate from their usual course. Sometimes the nerve alone is transmitted through it, or the nerve may be accompanied by the ulnar interosseous artery, in cases of high division of the brachial. A well-marked groove is usually found behind the process, in which the nerve and artery are lodged. This space is analogous to the supra-condyloid foramen in many animals, and probably serves in them to protect the nerve and artery from compression during the contraction of the muscles in this region. A detailed account of this process is given by Dr. Struthers, in his " Anatomical and Physiological Observations," p. 202. 132 OSTEOLOGY. Fie;. 88. — Left Humerus. Posterior Surface. 1 9 e f* [Jrochi to tlie interval between the radius and ulna. The internal border is thicker, more prominent, and consequently of greater length than the external. The grooved portion of the articular surface fits accurately within the greater sigmoid ca- vity of the ulna ; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is directed obliquely from behind forwards, and from without in- wards. Above the back part of the trochlear surface, is a deep triangular de- pression, the olecranon depression in which is received the summit of the olecranon process in extension of the forearm. Above the front part of the trochlear surface, is seen a small depression, the coronoid de- pression ; it receives the coronoid process of the ulna during flexion of the fore- arm. These fossae are separated from one another by a thin transparent laminae of bone, which is sometimes perforated; their margins afford attachment to the anterior and posterior ligaments of the elbow -joint, and they are lined in the recent state by the synovial membrane of this articula- tion. Above the front part of the radial tuberosity, is seen a slight depression which receives the anterior border of the head of the radius when the forearm is strongly flexed. The external condyle is a small tubercular eminence, less pro- minent than the internal, curved a little forwards, and giving attachment to the external lateral ligament of the elbow- joint, and to a tendon common to the origin of some of the extensor and supi- nator muscles. The internal condyle, larger and more prominent than the ex- ternal, is directed a little backwards, and gives attachment to the internal lateral ligament, and to a tendon common to the origin of some of the flexor muscles of the forearm. These eminences are di- rectly continuous above with the external and internal borders. The greater pro- minence of the inner one renders it more liable to fracture. Structure. The extremities consist of cancellous tissue, covered with a thin compact layer ; the shaft is composed of a cylinder of compact tissue, thicker at the centre than at the extremities, and hollowed out by a large medullary canal, which extends along its whole length. Development, By seven centres (fig. 89): one for the shaft, one for the head, HUMERUS. 133 Fig. 89. — Plan of the Development of the Humerus. By 7 Centres. Epiphyses ef Head fcj A* Tuberosities blrml at\<*j S.Uranil unite \ *>i'L& SAaft at 2U 4*y '. J one for the greater tuberosity, one for the radial portion of the articular surface, one for the trochlear portion, and one for each condyle. The centre for the shaft appears very early, soon after ossification has commenced in the clavicle, and soon extends towards the extremities. At birth, it is ossified nearly in its whole length, the extremities remaining cartilaginous. Between the first and second years, ossification commences in the head of the bone, and between the second and third years the centre for the tuberosities makes its appearance usually by a single ossific point, but sometimes, according to Beclard, by one for each tube- rosity, that for the lesser being small, and not appearing until after the fourth year. By the fifth year, the centres for the head and tuberosities have enlarged and become joined, so as to form a single large epiphysis. The lower end of the humerus is devel- oped in the following manner : At the end of the second year, ossification commences in the radial portion of the articular sur- face, and from this point extends inwards, so as to form the chief part of the articular end of the bone, the centre for the inner part of the articular surface not appearing until about the age of twelve. Ossification commences in the internal condyle about the fifth year, and in the external one not until between the thirteenth or fourteenth year. About the sixteenth or seventeenth year, the outer condyle and both portions of the articulating surface, having already joined, unite with the shaft ; at eighteen years, the inner condyle becomes joined, whilst the upper epiphysis, although the first formed, is not united until about the twentieth year. Articulations. "With the glenoid cavity of the scapula, and with the ulna and radius. Attachment of Muscles. To the greater tuberosity, the Supra-spinatus, Infraspina- tus, and Teres minor ; to the lesser tube- rosity, the Subscapularis ; to the anterior bicipital ridge, the Pectoralis major; to the posterior bicipital ridge and groove, the Latissimus dorsi and Teres major ; to the shaft, the Deltoid, Coraco-brachialis, Bra- chialis anticus, external and internal heads of the Triceps ; to the internal condyle, the Pronator radii teres, and common tendon of the Flexor carpi radialis, Palmaris longus, Flexor digitorum sublimis, and Flexor carpi ulnaris ; to the external condyloid ridge, the Supinator longus, and Extensor carpi radialis longior ; to the external condyle, the common tendon of the Extensor carpi radialis brevior, Extensor communis digitorum, Extensor minimi digiti, and Extensor carpi ulnaris, the Anconeus, and Supinator brevis. TTnites with. Shaftat 18* '*' )A THE FOREARM. The Forearm is that portion of the upper extremity, situated between the elbow and wrist. It is composed of two bones, the Ulna, and the Radius. The Ulna. The Ulna (figs. 90 and 91), so called from its forming the elbow {iumfo is a long bone, prismatic in form, placed at the inner 6ide of the forearm, parallel with the 134 OSTEOLOGY. Fig. 90. — Bones of the Left Forearm. Anterior Surface. ULNA i * T <* ME „,-,/■'« RADIUS fJXKOR DICITORUM SUBLIMIS PRONATOR RAOII. TERES accairicrn/iZ origi tf FLEXOR IONCUS POLL1CIS RadiuZ Oriain FLEXOR DICITORUM SUBLIMIS Styloid Process ^ SUPINATOR LONCU» Grooix for ext. ossis METACARPI FOLLIC/5 GrceivfinEKT. PR1MI ERNOOII POLLICIS /Styloid J.'rJcess ULNA. 135 radius, being the largest and longest of the two. Its upper extremity, of great thickness and strength, forms a large part of the articulation of the elbow-joint ; it diminishes in size from above downwards, its lower extremity being very small, and excluded from the wrist-joint by the interposition of an interarticular fibro-cartilage. It is divisible into a shaft, and two extremities. The Upper Extremity, the strongest part of the bone, presents for examination two large curved processes, the Olecranon process, and the Coronoid process ; and two concave articular cavities, the greater and lesser Sigmoid cavities. The Olecranon Process (dvov, head) is a large, thick, curved eminence, situated at the upper and back part of the ulna. It rises somewhat higher than the coronoid, is curved forwards at the summit so as to present a pro- minent tip, its base being contracted where it joins the shaft. This is the narrowest part of the upper end of the ulna, and, consequently, the most usual seat of fracture. Its posterior surface, directed backwards, is of a triangular form, smooth, subcutaneous, and covered by a bursa. Its upper surface, directed upwards, is of a quadrilateral form, marked behind by a rough impression for the attachment of the Triceps muscle ; and, in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, covered with cartilage in the recent state, and forms the upper and back part of the great sigmoid cavity. The lateral borders present a continuation of the same groove that was seen on the margin of the superior surface ; they serve for the attachment of ligaments, viz., the back part of the interior lateral ligament internally ; the posterior liga- ment externally. The olecranon process, in its structure as well as in its position and use, resembles the Patella in the lower limb ; and, like it, sometimes exists as a separate piece, not united to the rest of the bone. 1 The Coronoid Process (xopAvt], a crow's beak; n'So$, form) is a rough triangular eminence of bone which projects horizontally forwards from the upper and front part of the ulna, forming the lower part of the great sigmoid cavity. Its base is continuous with the shaft, and of considerable strength, so much so, that fracture of it is an accident of rare occurrence. Its apex is pointed, slightly curved upwards, and received into the coronoid depression of the humerus in flexion of the forearm. Its upper surface is smooth, concave, and forms the lower part of the great sigmoid cavity. The under surface is concave, and marked internally by a rough impression for the insertion of the Brachialis anticus. At the junction of this surface with the shaft is a rough eminence, the tubercle of the ulna, for the attachment of the oblique ligament. Its outer surface presents a narrow, oblong, articular depression, the lesser sigmoid cavity. The inner surface, by its prominent free margin, serves for the attachment of part of the internal lateral ligament. At the front part of this surface is a small rounded eminence for the attachment of one head of the Flexor digitorum sublimis. Behind the eminence, a depression for part of the origin of the Flexor profundus digitorum ; and, descending from the eminence, a ridge, which gives attachment to one head of the Pronator radii teres. The Greater Sigmoid Cavity (olyna, fJSoj, form), so called from its resemblance to the Greek letter x, is a semilunar depression of large size, situated between the olecranon and coronoid processes, and serving for .articulation with the trochlear surface of the humerus. About the middle of either lateral border of this cavity is a notch which contracts it somewhat, and serves to indicate the junction of the two processes of which it is formed. The cavity is concave from above downwards, and divided into two lateral parts by a smooth elevated ridge, which runs from the summit of the olecranon to the tip of the coronoid process. Of these two portions, the internal is the largest ; it is slightly concave transversely, the external portion being nearly plane from side to side. 1 Professor Owen regards the olecranon to be homologous not with the patella, but with an extension of the upper end of the fibula above the knee-joint, which is met with in the Ornitho- rynchus, Echidna, and some other animals. (Owen, " On the Nature of Limbs.") 136 OSTEOLOGY. The Lesser Sigmoid Cavity is a narrow, oblong, articular depression, placed on the outer side of the coronoid process, and serving for articulation with the head of the radius. It is concave from before backwards ; and its extremities, which are prominent, serve for the attachment of the orbicular ligament. The Shaft is prismatic in form at its upper part, and curved from behind for- wards, and from within outwards, so as to be convex behind and externally ; its central part is quite straight ; its lower part rounded, smooth, and bent a little outwards ; it tapers gradually from above downwards, and presents for examina- tion three borders, and three surfaces. The anterior border commences above at the prominent inner angle of the coro- noid process, and terminates below in front of the styloid process. It is well marked above, smooth and rounded in the middle of its extent, and affords attachment to the Flexor profundus digitorum : sharp and prominent in its lower fourth for the attachment of the Pronator quadratus. It separates the anterior from the internal surface. The posterior border commences above at the apex of the triangular surface at the back part of the olecranon, and terminates below at the back part of the styloid process ; it is well marked in the upper three-fourths, and gives attachment to an aponeurosis common to the Flexor carpi ulnaris, the Extensor carpi ulnaris, and the Flexor profundus digitorum muscles ; its lower fourth is smooth and rounded. This border separates the internal from the posterior surface. The external border commences above by two lines, which converge one from each extremity of the lesser sigmoid cavity, inclosing between them a triangular space for the attachment of part of the Supinator brevis, and terminates below at the middle of the head of the ulna. Its two middle fourths are very prominent, and serve for the attachment of the interosseous membrane ; its lower fourth is smooth and rounded. This border separates the anterior from the posterior surface. The anterior surface, much broader above than below, is concave in the upper three-fourths of its extent, and affords attachment to the Flexor profundus digi- torum; its lower fourth, also concave, to the Pronator quadratus. The lower fourth is separated from the remaining portion of the bone by a prominent ridge, directed obliquely from above downwards and inwards ; this ridge marks the extent of attachment of the Pronator above. At the junction of the upper with the middle third of the bone, is the nutritious canal, directed obliquely upwards and inwards. The posterior surface, directed backwards and outwards, is broad and concave above, somewhat narrower and convex in the middle of its course, narrow, smooth, and rounded below. It presents above, an oblique ridge, which runs from the posterior extremity of the lesser sigmoid cavity, downwards to the posterior border ; the triangular surface above this ridge receives the insertion of the An- coneus muscle, whilst the ridge itself affords attachment to the Supinator brevis. The surface of bone below this is subdivided by a longitudinal ridge into two parts ; the internal part is smooth, concave, and gives origin to, occasionally is merely covered by, the Extensor carpi ulnaris. The external portion, wider and rougher, gives attachment from above downwards to part of the Supinator brevis, the Extensor ossis metacarpi pollicis, the Extensor secundi internodii pollicis, and the Extensor indicis muscles. The internal surface is broad and concave above, narrow and convex below. It gives attachment by its upper three-fourths to the Flexor profundus digitorum muscle ; its lower fourth is subcutaneous. The Lower Extremity of the ulna is of small size, and excluded from the articu- lation of the wrist-joint. It presents for examination two eminences ; the outer and larger is a rounded articular eminence, termed the head of the ulna. The inner, narrower and more projecting, is a non- articular eminence, the styloid process. The head presents an articular facet, part of which, of an oval form, is directed downwards, and plays on the surface of the triangular fibro-cartilage, which separates this bone from the wrist-joint ; the remaining portion, directed ULNA. 137 Fig. 91. — Bones of the Left Forearm. Posterior Surface. ULNA RADIUS for £XT. CARFI RAD.LONC. EXT. CARD RAD.BKEVIOR EXT. StCUNDI INTERNOOII POLLIC1* LfXOR TJiaiTOnUM SUSLIMIS firr CXT. CARPI ULNAR. [' EXT. INDICII ft/'ri tvr. DICITORUM COMMUNIS [ »~T. MINIMI DIGIT! 138 OSTEOLOGY, Fi 92. — Plan of the Development of the Ulna. By 3 Centres. Olec ran&n Agpca rs at 10^^-f^^^JointS'Jiafc ac /(>.'? y* outwards, is narrow, convex, and received into the sigmoid cavity of the radius. The styloid process projects from the inner and back part of the bone, and descends a little lower than the head, terminating in a rounded summit, which affords attachment to the internal lateral ligament of the wrist. The head is separated from the styloid process by a depression for the attachment of the triangular interarticular fibro-cartilage ; and behind, by a shallow groove for the passage of the tendon of the Extensor carpi ulnaris. Structure. Similar to that of the other long bones. Development. By three centres: one for the shaft, one for the inferior extremity, and one for the olecranon (fig. 92). Ossification commences near the middle of the shaft about the fifth week, and soon extends through the greater part of the bone. At birth, the ends are cartilaginous. About the fourth year, a separate osseous nucleus appears in the middle of the head, which soon extends into the styloid pro- cess. About the tenth year, ossific matter appears in the olecranon near its extremity, the chief part of this process being formed from an extension of the shaft of the bone into it. At about the sixteenth year, the upper epiphysis becomes joined, and at about the twentieth year the lower one. Articulations. With the humerus and radius. Attachment of Muscles. To the olecra- non : the Triceps, Anconeus, and one head of the Flexor carpi ulnaris. To the coro- noid process; the Brachialis anticus, Pro- nator radii teres, Flexor sublimis digito- rum, and Flexor profundus digitorum. To the shaft: the Flexor profundus digitorum, Pronator quadratus, Flexor carpi ulnaris, Extensor carpi ulnaris, Anconeus, Supi- nator brevis, Extensor ossis metacarpi pollicis, Extensor secundi internodii polli- cis, and Extensor indicis. Appear? at 4 3f# {j3fS-J»itU Slmft at ZOtl ■;* °^Har «**' The Eadius. The Radius, so called from its fancied resemblance to the spoke of a wheel, is situated on the outer side of the forearm, lying parallel with the ulna, which exceeds it in length and size. Its upper end is small, and forms only a small part of the elbow-joint; but its lower end is large, and forms the chief part of the wrist. It is one of the long bones, having a prismatic form, slightly curved longitudinally, and presenting for examination a shaft and two extremities. The Upper Extremity presents a head, neck, and tuberosity. The' head is of a cylindrical form, depressed on its upper surface into a shallow cup, which articulates with the radial or lesser head of the humerus in flexion of the .joint. Around the circumference of the head is a smooth articular surface, coated with cartilage in the recent state, broad internally where it rotates within the lesser sigmoid cavity of the ulna, narrow in the rest of its circumference, to play in the orbicular ligament. The head is supported on a round, smooth, and constricted portion of bone, called the neck, which presents, behind, a slight ridge, for the attachment of part of the Supinator brevis. Beneath the neck, at the inner and front aspect of the bone, is a rough eminence, the tuberosity. Its surface is divided into two parts by a vertical line ; a posterior rough portion, for the RADIUS. 139 insertion of the tendon of the Biceps muscle, and an anterior smooth portion, on which a bursa is interposed between the tendon and the bone. The Shaft of the bone is prismoid in form, narrower above than below, and slightly curved, so as to be convex outwards. It presents three surfaces, separated by three borders. The anterior border extends from the lower part of the tifberosity above, to the anterior part of the base of the styloid process below. It separates the anterior from the external surface. Its upper third is very prominent ; and, from its oblique direction, downwards and outwards, has received the name of the oblique line of the radius. It gives attachment, externally, to the Supinator brevis; internally, to the Flexor longus pollicis, and between these to the Flexor digito- rum sublimis. The middle third of the anterior border is indistinct and rounded. Its lower fourth is sharp, prominent, affords attachment to the Pronator quadra- tus, and terminates in a small tubercle, into which is inserted the tendon of the Supinator longus. The posterior border commences above, at the back part of the neck of the radius, and terminates below, at the posterior part of the base of the styloid pro- cess ; it separates the posterior from the external surface. It is indistinct above and below, but well marked in the middle third of the bone. The internal or interosseous border commences above, at the back part of the tuberosity, where it is rounded and indistinct, becomes sharp and prominent as it descends, and at its lower part bifurcates into two ridges, which descend to the anterior and posterior margins of the sigmoid cavity. This border separates the anterior from the posterior surface, and has the interosseous membrane attached to it throughout the greater part of its extent. The anterior surface is narrow and concave for its upper two-thirds, and gives attachment to the Flexor longus pollicis muscle ; below, it is broad and flat, and gives attachment to the Pronator quadratus. At the junction of the upper and middle thirds of this surface is the nutritious foramen, which is directed obliquely upwards. The posterior surface is rounded, convex, and smooth in the upper third of its extent, and covered by the Supinator brevis muscle. Its middle third is broad, slightly concave, and gives attachment to the Extensor ossis metacarpi pollicis above, the Extensor primi internodii pollicis below. Its lower third is broad, convex, and covered by the tendons of the muscles which subsequently run in the grooves on the lower end of the bone. The external surface is rounded and convex throughout its entire extent. Its upper third gives attachment to the Supinator brevis muscle. About its centre is seen a rough ridge, for the insertion of the Pronator radii teres muscle. Its lower part is narrow, and covered by the tendons of the Extensor ossis metacarpi pollicis and Extensor primi internodii pollicis muscles. The Lower extremity of the radius is large, of quadrilateral form, and provided with two articular surfaces, one at the extremity for articulation with the carpus, and one at the inner side of the bone for articulation with the ulna. The carpal articular surface is of triangular form, concave, smooth, and divided by a slight antero-posterior ridge into two parts. Of these, the external is large, of a trian- gular form, and articulates with the scaphoid bone; the inner, smaller and quadrilateral, articulates with the semilunar. The articular surface for the ulna is called the sigmoid cavity of the radius; it is narrow, concave, smooth, and articulates with the head of the ulna. The circumference of this end of the bone presents three surfaces, an anterior, external, and posterior. The anterior surface, rough and irregular, affords attachment to the anterior ligament of the wrist-joint. The external surface is prolonged obliquely down- wards into a strong conical projection, the styloid process, which gives attachment by its base to the tendon of the Supinator longus, and by its apex to the external lateral ligament of the wrist-joint. The outer surface of this process is marked by two grooves, which run obliquely downwards and forwards, and are separated 140 OSTEOLOGY. Fig. 93. — Plan of the Development of the Radius. By 3 Centres. Aj>Dta.rs at Jt*y-- JTeatf )- : lfruttll it-ith Shaft aba puberty from one another by an elevated ridge. The most anterior one gives passage to the tendon of the Extensor ossis metacarpi pollicis, the posterior one to the tendon of the Extensor primi internodii pollicis. The posterior surface is convex, affords attachment to the posterior ligament of the wrist, and is marked by three grooves. The most external is broad, but shallow, and subdivided into two by a slightly elevated ridge. The external groove transmits the tendon of the Extensor carpi radialis longior, the inner one the tendon of the Extensor carpi radialis brevior, Near the centre of the bone is a deep, but narrow, groove, directed obliquely from above downwards and outwards; it transmits the tendon of the Extensor secundi internodii pollicis. Internally is a broad groove, for the passage of the tendons of the Extensor communis digitorum, and Extensor indicis ; the tendon of the Extensor minimi digiti passing through the groove at its point of articulation with the ulna. Structure. Similar to that of the other long bones. Development (fig. 93). By three centres: one for the shaft, and one for each extremity. That for the shaft makes its appearance near the centre of the bone, soon after the development of the humerus commences. At birth, the shaft is ossified ; but the ends of the bone are cartilaginous. About the end of the second year, ossification commences in the lower epiphysis; and about the fifth year, in the upper one. At the age of puberty, the up- per epiphysis becomes joined to the shaft; the lower epiphysis becoming united about the twentieth year. Articulations. With four bones; the humerus, ulna, scaphoid, and semi- lunar. Attachment of Muscles. To the tu- berosity, the Biceps ; to the oblique ridge, the Supinator brevis, Flexor digitorum sublimis, and Flexor longus pollicis ; to the shaft — its anterior sur- face, the Flexor longus pollicis and Pronator quadratus ; its posterior sur- face, the Extensor ossis metacarpi pollicis, and Extensor primi internodii pollicis; its outer surface, the Pro- nator radii teres; and to the styloid process, the Supinator longus. feaw Appears at Zv^-yH \ "Unites with. SAa ft al.t . f cxtrcmi THE HAND. The Hand is subdivided into three segments, the Carpus or wrist, the Meta- carpus or palm, and the Phalanges or fingers. Carpus. The bones of the Carpus, eight in number, are arranged in -two rows. Those of the upper row, enumerated from the radial to the ulnar side, are the scaphoid, semilunar, cuneiform, and pisiform ; those of the lower row, enumerated in the same order, are the trapezium, trapezoid, magnum, and unciform. Common Characters of the Carpal Bones. Each bone (excepting the pisiform) presents six surfaces. Of these, the ante- rior or palmar, and the posterior or dorsal, are rough, for ligamentous attachment, CARPUS. 141 the dorsal surface being generally the broadest of the two. The superior and inferior are articular, the superior generally convex, the inferior concave ; and the internal and external are also articular when in contact with contiguous bones, otherwise rough and tubercular. Their structure in all is similar, con- sisting within of cancellous tissue inclosed in a layer of compact bone. Each bone is also developed from a single centre of ossification. Bones of the Upper Row. (Figs. 94 and 95.) The Scaphoid is the largest bone of the first row. It has received its name from its fancied resemblance to a boat, being broad at one end, and narrowed like a prow at the opposite. It is situated at the upper and outer part of the carpus, its direction being from above downwards, outwards, and forwards. Its superior surface is convex, smooth, of triangular shape, and articulates with the lower end of the radius. Its inferior surface, directed downwards, outwards, and backwards, is smooth, convex, and triangular, and divided by a slight ridge into two parts, the external of which articulates with the trapezium, the inner with the trapezoid. Its posterior or dorsal surface presents a narrow, rough groove, which runs the entire breadth of the bone, and serves for the attachment of ligaments. The anterior or palmar surface is concave above, and elevated at its lower and outer part into a prominent rounded tubercle, which projects forwards from the front of the carpus, and gives attachment to the anterior annular ligament of the wrist. The external surface is rough and narrow, and gives attachment to the external lateral ligament of the wrist. The internal surface presents two articular facets : of these the superior or smaller one is flattened, of semilunar form, and articulates with the semilunar bone; the inferior or larger is concave, forming, with the semilunar bone, a concavity for the head of the os magnum. To ascertain to which hand this bone belongs, hold the convex radial articular surface upwards, and the dorsal surface backwards ; the prominent tubercle will be directed to the side to which the bone belongs. Articulations. With five bones ; the radius above, trapezium and trapezoid below, os magnum and semilunar internally. The Semilunar bone may be distinguished by its deep concavity and crescentic outline. It is situated in the centre of the upper range of the carpus, between the scaphoid and cuneiform. Its superior surface, convex, smooth, and quadrilateral in form, articulates with the radius. Its inferior surface is deeply concave, and of greater extent from before backwards, than transversely ; it articulates with the head of the os magnum, and by a long narrow facet, separated by a ridge from the general surface, with the unciform bone. Its anterior or palmar and posterior or dorsal surfaces are rough, for the attachment of ligaments, the former being the broader, and of somewhat rounded form. The external surface presents a narrow, flattened, semilunar facet, for articulation with the scaphoid. The internal surface is marked by a smooth, quadrilateral facet, for articulation with the cuneiform. To ascertain to which hand this bone belongs, hold it with the dorsal surface upwards, and the convex articular surface backwards ; the quadrilateral articular facet will then point to the side to which the bone belongs. Articulations. With five bones : the radius above, os magnum and unciform below, scaphoid and cuneiform on either side. The Cuneiform (VOs Pyramidal) may be distinguished by its pyramidal shape, and from having an oval-shaped, isolated facet, for articulation with the pisiform bone. It is situated at the upper and inner side of the carpus. The superior surface presents an internal, rough, non-articular portion; and an external or articular portion, which is convex, smooth, and separated from the lower end of the ulna by the interarticular fibro-cartilage of the wrist. The inferior surface, directed outwards, is concave, sinuously curved, and smooth, for articulation with the unciform. Its posterior or dorsal surface is rough, for the attachment of liga- ments. Its anterior or palmar surface presents, at its inner side, an oval-shaped 142 OSTEOLOGY. facet, for articulation with the pisiform ; and. is rough externally, for ligamentous attachment. Its external surface, the base of the pyramid, is marked by a flat, quadrilateral, smooth facet, for articulation with the semilunar. The internal surface, the summit of the pyramid, is pointed and roughened, for the attachment of the internal lateral ligament of the wrist. Fig. 94. — Bones of the Left Hand. Dorsal Surface. ""■"""•iDM l,s snviog Metacarpus ,XT - MUM, mT ERMoo„ Phalange* 1U Row Z^Row T r?M0Ufi CARPUS. 143 To ascertain to which hand this bone belongs, hold it so that the base is directed backwards, and the articular facet for the pisiform bone upwards ; the concave articular facet will point to the side to which the bone belongs. Articulations. With three bones: the semilunar externally, the pisiform in front, the unciform below, and with the triangular interarticular fibro-cartilage which separates it from the lower end of the ulna. The Pisiform bone may be known by its small size, and from its presenting a single articular facet. It is situated at the anterior and inner side of the carpus, is nearly circular in form, and presents on its posterior surface a smooth, oval facet, for articulation with the cuneiform bone. This facet approaches the supe- rior, but not the inferior, border of the bone! Its anterior or palmar surface is rounded and rough, and gives attachment to the anterior annular ligament. The outer and inner surfaces are also rough, the former being convex, the latter usually concave. To ascertain to which hand it belongs, hold the bone with its posterior or artic- ular facet downwards, and the non-articular portion of the same surface back- wards ; the inner concave surface will then point to the side to which the bone belongs. Articulations. With one bone, the cuneiform. Attachment of Muscles. To two : the Flexor carpi ulnaris, and Abductor minimi digiti ; and to the anterior annular ligament. Bones of the Lower Row. (Figs. 94 and 95.) The Trapezium is of very irregular form. It may be distinguished by a deep groove, for the tendon of the Flexor carpi radialis muscle. It is situated at the external and inferior part of the carpus, between the scaphoid and first meta- carpal bone. The superior surface, concave and smooth, is directed upwards and inwards, and articulates with the scaphoid. Its inferior surface, directed down- wards and outwards, is oval, concave from side to side, convex from before back- wards, so as to form a saddle-shaped surface, for articulation with the base of the first metacarpal bone. The anterior or palmar surface is narrow and rough. At its upper part is a deep groove, running from above obliquely downwards and inwards; it transmits the tendon of the Flexor carpi radialis, and is bounded externally by a prominent ridge, the oblique ridge of the trapezium. This sur- face gives attachment to the Abductor pollicis, Flexor ossis metacarpi, and Flexor brevis pollicis muscles; and the anterior annular ligament. The posterior or dorsal surface is rough, and the external surface also broad and rough, for the attachment of ligaments. The internal surface presents two articular facets ; the upper one, large and concave, articulates with the trapezoid; the lower one, narrow and flattened, with the base of the second metacarpal bone. To ascertain to which hand it belongs, hold the bone with the grooved palmar surface upwards, and the external, broad, non-articular surface backwards; the saddle-shaped surface will then be directed to the side to which the bone belongs. Articulations. With four bones : the scaphoid above, the trapezoid and second metacarpal bones internally, the first metacarpal below. Attachment of Muscles. Abductor pollicis, Flexor ossis metacarpi, part of the Flexor brevis pollicis, and the anterior annular ligament. The Trapezoid is the smallest bone in the second row. It may be known by its wedge-shaped form ; its broad end occupying the dorsal, its narrow end the palmar surface of the hand. Its superior surface, quadrilateral in form, smooth and slightly concave, articulates with the scaphoid. The inferior surface articu- lates with the upper end of the second metacarpal bone ; it is convex from side to side, concave from before backwards, and subdivided, by an elevated ridge, into two unequal lateral facets. The posterior or dorsal, and anterior or palmar surfaces are rough, for the attachment of ligaments ; the former being the larger of the two. The external surface, convex and smooth, articulates with the 144 OSTEOLOGY. trapezium. The internal surface is concave and smooth below, for articulation with the os magnum ; rough above, for the attachment of an interosseous ligament. Fig. 95. — Bones of the Left Hand. Palmar Surface. Ccorjms FLEXOR. CARPi ULNARIS FLEXOR BREVtS MINIMI DICIT fLEXOR OSSIS METACARPI MINIMI DICITl h"'' ...» MrfMcar/iiLS D p „ofU" ou8 CARPUS. 145 To ascertain to which side this bone belongs, let the broad dorsal surface be held upwards, and its inferior concavo-convex surface forwards; the internal concave surface will then point to the side to which the bone belongs. Articulations. With four bones : the scaphoid above, second metacarpal bone below, trapezium externally, os magnum internally. Attachment of Muscks. Part of the Flexor brevis pollicis. The Os Magnum is the largest bone of the carpus, and occupies the centre of the wrist. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and semilunar bones ; a constricted portion or neck; and, below, the body. Its superior surface is rounded, smooth, and articulates with the semilunar. Its inferior surface is divided by two ridges into three facets, for articulation with the second, third, and fourth metacarpal bones ; that for the third, the middle facet, being the largest of the three. The posterior or dorsal surface is broad and rough ; and the anterior or palmar, narrow, rounded, but also rough, for the attachment of ligaments. The external surface articulates with the trapezoid by a small facet at its anterior inferior angle, behind which is a rough depression for the attachment of an interosseous ligament. Above this is a deep and rough groove, which forms part of the neck, and serves for the attachment of ligaments, bounded superiorly by a smooth, convex surface, for articulation with the scaphoid. The internal surface articulates with the unciform by a smooth, concave, oblong facet, which occupies its posterior and superior parts ; rough in front, for the attachment of an interosseous ligament. To ascertain to which hand this bone belongs, the rounded head should be held upwards, and the broad dorsal surface forwards ; the internal concave articular surface will point to its appropriate side. Articulations. With seven bones : the scaphoid and semilunar above ; the second, third, and fourth metacarpal below ; the trapezoid on the radial side ; and the unciform on the ulnar side. Attachment of Muscles. Part of the Flexor brevis pollicis. The Unciform bone may be readily distinguished by its wedge-shaped form, and the hook-like process that projects from its palmar surface. It is situated at the inner and lower angle of the carpus, with its base downwards, resting on the two inner metacarpal bones, and its apex directed upwards and outwards. Its superior surface, the apex of the wedge, is narrow, convex, smooth, and articulates with the semilunar. Its inferior surface articulates with the fourth and fifth meta- carpal bones, the concave surface for each being separated by a ridge, which runs from before backwards. The posterior or dorsal surface is triangular and rough, for ligamentous attachment. The anterior or palmar surface presents, at its lower and inner side, a curved, hook-like process of bone, the unciform process, directed from the palmar surface forwards and outwards. It gives attachment, by its apex, to the annular ligament ; by its inner surface, to the Flexor brevis minimi digiti, and the Flexor ossis metacarpi minimi digiti ; and is grooved on its outer side, for the passage of the Flexor tendons into the palm of the hand. This is one of the four eminences on the front of the carpus, to which the anterior annular ligament is attached ; the others being the pisiform internally, the oblique ridge of the trapezium, and the tuberosity of the scaphoid externally. The internal surface articulates with the cuneiform by an oblong surface, cut obliquely from above downwards and inwards. Its external surface articulates with the os mag- num by its upper and posterior part, the remaining portion being rough, for the attachment of ligaments. To ascertain to which hand it belongs, hold the apex of the bone upward^ and the broad dorsal surface backwards ; the concavity of the unciform process will be directed to the side to which the bone belongs. Articulations. With five bones : the semilunar above, the fourth and fifth meta- carpal below, the cuneiform internally, the os magnum externally. Attachment of Muscles. To two : the Flexor brevis minimi digiti, and the Flexor ossis metacarpi minimi digiti ; and to the anterior annular ligament. 10 146 OSTEOLOGY. The Metacaepus. The Metacarpal bones are five in number : they are long cylindrical bones, presenting for examination a shaft, and two extremities. Common Chaeactees of the Metacaepal Bones. The shaft is prismoid in form, and curved longitudinally, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces : two lateral, and one posterior. The lateral surfaces are concave, for the attach- ment of the Interossei muscles, and separated from one another by a prominent line. The posterior or dorsal surface is triangular, smooth, and flattened below, and covered, in the recent state, by the tendons of the extensor muscles. In its upper half, it is divided by a ridge into two narrow lateral depressions, for the attachment of the Dorsal interossei muscles. This ridge bifurcates a little above the centre of the bone, and its branches run to the small tubercle on each side of the digital extremity. The carpal extremity or base is of a cuboidal form, and broader behind thnn in front: it articulates, above, with the carpus; and,' on each side, with the adjoining metacarpal bones ; its dorsal and palmar surfaces being rough, for the attachment of tendons and ligaments. The digital extremity or head presents an oblong surface, flattened at each side, for articulation with the first phalanx; it is broader and extends farther forwards in front than behind ; and is longer in the antero-posterior than in the transverse diameter. On either side of the head is a deep depression, surmounted by a tubercle, for the attachment of the lateral ligament of the metacarpophalan- geal joint. The posterior surface, broad and flat, supports the Extensor tendons ; and the anterior surface presents a median groove, bounded on each side by a tubercle, for the passage of the Flexor tendons. Peculiae Metacaepal Bones. The metacarpal bone of the thumb is shorter and wider than the rest, diverges to a greater degree from the carpus, and its palmar surface is directed inwards towards the palm. The shaft is flattened and broad on its dorsal aspect, and does not present the bifurcated ridge peculiar to the other metacarpal bones ; concave from before backwards on its palmar surface. The carpal extremity or base presents a concavo-convex surface, for articulation with the trapezium, and has no lateral facets. The digital extremity is less convex than that of the other metacarpal bones, broader from side to side than from before backwards, and terminates anteri- orly in a small articular eminence on each side, over which play two sesamoid bones. The metacarpal bone of the index finger is the longest, and its base the largest of the other four. Its carpal extremity is prolonged upwards and inwards ; and its dorsal and palmar surfaces are rough, for the attachment of tendons and ligaments. It presents four articular facets: one at the end of the bone, which has an angular depression, for articulation with the trapezoid ; on the radial side, a flat quadri- lateral facet, for articulation with the trapezium ; its ulnar side being prolonged upwards and inwards, to articulate, above, with the os magnum ; internally, with the third metacarpal bone. The metacarpal bone of the middle finger is a little smaller than the preceding ; it presents a pyramidal eminence on the radial side of its base (dorsal aspect), which extends upwards behind the os magnum. The carpal articular facet is concave be- hind, flat and horizontal in front, and corresponds to the os magnum. On the radial side is a smooth concave facet, for articulation with the second metacarpal bone ; and on the ulnar side two small oval facets, for articulation with the f jurth metacarpal. The metacarpal bone of the ring finger is shorter and smaller than the pre- ceding, and its base small and quadrilateral, its carpal surface presenting two facets, for articulation with the unciform and os magnum. On the radial side are two oval facets, for articulation with the third metacarpal bone ; and on the ulnar side a single concave facet, for the fifth metacarpal. METACARPUS AND PHALANGES. 147 The metacarpal bone of the little finger may be distinguished by the concavo- convex form of its carpal surface, for articulation with the unciform, and from having only one lateral articular facet, which corresponds with the fourth meta- carpal bone. On its ulnar side, is a prominent tubercle for the insertion of the tendon of the Extensor carpi ulnaris. The dorsal surface of the shaft is marked by an oblique ridge, which extends from near the ulnar side of the upper extremity, to the radial side of the lower. The outer division of this surface serves for the attachment of the fourth Dorsal interosseous muscle ; the inner division is smooth, and covered by the Extensor tendons of the little finger. Articulations. The first, with the trapezium ; the second, with the trapezium, trapezoides, os magnum, and third metacarpal bones ; the third, with the os mag- num, and second and fourth metacarpal bones ; the fourth, with the os magnum, unciform, and third and fifth metacarpal bones ; and the fifth, with the unciform and fourth metacarpal. Attachment of Muscles. To the metacarpal bone of the thumb, three : the Flexor ossis metacarpi pollicis, Extensor ossis metacarpi pollicis, and first Dorsal inter- osseous. To the second metacarpal bone, five : the Flexor carpi radialis, Extensor carpi radialis longior, first and second Dorsal interosseous, and first Palmar inter- osseous. To the third, five : the Extensor carpi radialis brevior, Flexor brevis pollicis, Adductor pollicis, and second and third Dorsal interosseous. To the fourth, three : the third and fourth Dorsal interosseous and second Palmar. To the fifth, four : the Extensor carpi ulnaris, Flexor carpi ulnaris, Flexor ossis metacarpi minimi digiti, and third Dorsal interosseous. Phalanges. The Phalanges are the bones of the fingers ; they are fourteen in number, three for each finger and two for the thumb. They are long bones, and present for examination a shaft, and two extremities. The shaft tapers from above down- wards, is convex posteriorly, concave in front from above downwards, flat from side to side, and marked laterally by rough ridges, which give attachment to the fibrous sheaths of the Flexor tendons. The metacarpal extremity or base, in the first row, presents an oval concave articular surface, broader from side to side, than from before backwards ; and the same extremity in the other two rows, a double concavity separated by a longitudinal median ridge, extending from before backwards. The digital extremities are smaller than the others, and terminate, in the first and second row, in two small lateral condyles, separated by a slight groove, the articular surface being prolonged farther forwards on the palmar than on the dorsal surface, especially in the first row. The Ungual phalanges are convex on their dorsal, flat on their palmar surfaces; they are recognized by their small size, and from their ungual extremity presenting, on its palmar aspect, a roughened elevated surface of a horseshoe form, which serves to support the sensitive pulp of the finger. Articulations. The first row with the metacarpal bones, and the second row of phalanges ; the second row, with the first and third ; the third, with the second row. Attachment of Muscles. To the base of the first phalanx of the thumb, four muscles : the Extensor primi internodii pollicis, Flexor brevis pollicis, Abductor pollicis, Adductor pollicis. To the second phalanx, two : the Flexor longus pollicis, and the Extensor secundi internodii. To the base of the first phalanx of the index finger, the first Dorsal and the first Palmar interosseous; to that of the middle finger, the second and third Dorsal interosseous; to the ring finger, the fourth Dorsal and the second Palmar interosseous ; and to that of the little finger, the third Palmar interosseous, the Flexor brevis minimi digiti, and Abductor minimi digiti. To the second phalanges, the Flexor sublimis digitorum, Extensor com- munis digitorum ; and, in addition, the Extensor indicis, to the index finger ; the Extensor minimi digiti, to the little finger. To the third phalanges, the. Flexor profundus digitorum and Extensor communis digitorum. 148 OSTEOLOGY. Development of the Hand. The Carpal hones are each developed by a single centre; at birth they are all cartilaginous. Ossification proceeds in the following order (fig. 96): in the os magnum and unciform an ossific point appears during the first year, the former preceding the latter ; in the cuneiform, at the third year ; in the trapezium and semilunar, at the fifth year, the former preceding the latter ; in the scaphoid, at the sixth year ; in the trapezoid, during the eighth year ; and in the pisiform, about the twelfth year. Fig. 96. — Plan of the Development of the Hand. Carpus 1 cent re jo reach bone Ml cartilaginous at lirtJt Metacarpus 2 Centres for euch bone ■Ifor Shaft i for Digital Extremity except 1-4 Phalanges 2 Centres for each lone t for Shaft 1 for Metacarpal L'xt*. ap/i.fr-O'f'yr untie f8-Z0^'y^ The Metacarpal bones are each developed by two centres : one for the shaft, and one for the digital extremity, for the four inner metacarpal bones ; one for the shaft and one for the base, for the metacarpal bone of the thumb, which, in this respect, resembles the phalanges. Ossification commences in the centre of the shaft about the sixth week, and gradually proceeds to either end of the bone ; about the third year the digital extremities of the four inner metacarpal bones and the base of the first metacarpal, commence to ossify, and they unite about the twentieth year. The Phalanges are each developed by two centres : one for the shaft and one for the base. Ossification commences in the shaft, in all three rows, at about the sixth week, and gradually involves the whole of the bone excepting the upper extremity. Ossification of the base commences in the first row between the third and fourth years, and a year later in those of the second and third row. The two centres become united, in each row, between the eighteenth and twentieth years. OS INNOMINATUM. 149 OF THE LOWER EXTREMITY. The Lower Extremity consists of three segments, the thigh, leg, snadfoot, which correspond to the arm, forearm, and hand in the upper extremity. It is connected to the trunk through the os innominatum or haunch, which is homologous with the shoulder. The Os Innominatum. The Os Innominatum or nameless bone, so called from bearing no resemblance to any known object, is a large irregular-shaped bone, which, with its fellow of the opposite side, forms the sides and anterior wall of the pelvic cavity. In young subjects it consists of three separate parts, which meet and form the large cup-like cavity, situated near the middle of the outer side of the bone; and, although in the adult these have become united, it is usual to describe the bone as divisible into three portions, the ilium, the ischium, and the pubes. The ilium, so called from its supporting the flank (ilia), is the superior broad and expanded portion which runs upwards from the upper and back part of the acetabulum, and forms the prominence of the hip. The ischium (lax^, the hip) is the inferior and strongest portion of the bone ; it proceeds downwards from the acetabulum, expands into a large tuberosity, and then, curving upwards, forms with the descending ramus of the pubes a large aperture, the obturator foramen. The pubes is that portion which runs horizontally inwards from the inner side of the acetabulum for about two inches, then makes a sudden bend, and descends to the same extent ; it forms the front of the pelvis, supports the external organs of generation, and has received its name from being covered with hair. The Ilium presents for examination two surfaces, an external and an internal, a crest, and two borders, an anterior and a posterior. External Surface or Dorsum of the Ilium (fig. 97). The back part of this sur- face is directed backwards, downwards, and outwards ; its front part forwards, downwards and outwards. It is smooth, convex in front, deeply concave behind; bounded above by the crest, below by the upper border of the acetabulum ; in front and behind, by the anterior and posterior borders. This surface is crossed in an arched direction by three semicircular lines, the superior, middle, and inferior curved lines. The superior curved line, the shortest of the three, com- mences at the crest, about two inches in front of its posterior extremity ; it is at first distinctly marked, but as it passes downwards and outwards to the upper part of the great sacro-sciatic notch, where it terminates, it becomes less marked, and is often altogether lost. The rough surface included between this line and the crest, affords attachment to part of the Gluteus maximus above, a few fibres of the Pyriformis below. The middle curved line, the longest of the three, com- mences at the crest, about an inch behind its anterior extremity, and, taking a curved direction downwards and backwards, terminates at the upper part of the great sacro-sciatic notch. The space between the middle and superior curved lines, and the crest, is concave, and affords attachment to the Gluteus medius muscle. Near the central part of this line may often be observed the orifice of a nutritious foramen. The inferior curved line, the least distinct of the three, com- mences in front at the upper part of the anterior inferior spinous process, and taking a curved direction backwards and downwards, terminates at the anterior part of the great sacro-sciatic notch. The surface of bone included between the middle and inferior curved lines is concave from above downwards, convex from before backwards, and affords attachment to the Gluteus minimus muscle. Beneath the inferior curved line, and corresponding to the upper part of the acetabulum, is a smooth eminence, sometimes a depression, to which is attached the reflected tendon of the Rectus femoris muscle. The Internal Surface (fig. 98) of the ilium is bounded above by the crest, below by a prominent line, the linea ilio-pectinea, and before and behind by the 150 OSTEOLOGY. anterior and posterior borders. It presents anteriorly a large smooth concave surface called the internal iliac fossa or venter of the ilium ; it lodges the Iliacus muscle, and presents at its lower part the orifice of a nutritious canal. Behind the iliac fossa is a rough surface, divided into two portions, a superior and an Fig. 97. — Right Os Innominatum. External Surface. Anfrriom prruir Iho-pirtttua I Lin* for GimbtT nat't Lie T. CEMELL.U3 SUPERIOR fifint. of Sick, CEREU.US IN TEH 10 Spine of Fulirs for Fat/parti lic anient .ArujlitfPubts cctus abuomimi* ctumioams inferior. The inferior or auricular portion, so called from its resemblance to the external ear, is coated with cartilage in the recent state, and articulates with a similar shaped surface on the side of the sacrum. The superior portion is con- cave and rough for the attachment of the posterior sacro-iliac ligaments. The crest of the ilium is convex in its general outline and sinuously curved, being bent inwards anteriorly, outwards posteriorly. It is longer in the female than in the male, very thick behind, and thinner at the centre than at the extremities. It terminates at either end in a prominent eminence, the anterior superior, and posterior superior spinous process. The surface of the crest is OS INNOMINATUM. 151 broad, and divided into an external lip, an internal lip, and an intermediate space.' To the external lip is attached the Tensor vaginae femoris, Obliquus externus abdominis, and Latissimus dorsi, and by its whole length the fascia lata ; to the interspace between the lips, the Internal oblique ; to the internal lip, the Trans versalis, Quadratus lumborum, and Erector spinas. Fig. 98. — Right Os Innominatum. Internal Surface. ■ MIMUBt'OUIUIA The anterior border of the ilium is concave. It presents two projections separated by a notch. Of these, the uppermost, situated at the junction of the crest and anterior border, is called the anterior superior spinous process of the ilium, the outer border of which gives attachment to the fascia lata, and the origin of the Tensor vaginas femoris ; its inner border, to the Iliacus internus ; whilst its extremity affords attachment to Poupart's ligament, and the origin of the Sartorius. Beneath this eminence is a notch which gives attachment to the Sartorius muscle, and across which passes the external cutaneous nerve. Below the notch is the anterior inferior spinous process, which terminates in the upper lip of the aceta- bulum ; it gives attachment to the straight tendon of the Kectus femoris muscle. 152 OSTEOLOGY. On the inner side of the anterior inferior spinous process is a broad shallow groove, over which passes the Iliacus muscle. The posterior border of the ilium, shorter than the anterior, also presents two projections separated by a notch, the posterior superior, and the posterior inferior spinous processes. The former corresponds with that portion of the posterior surface of the ilium which serves for the attachment of the sacro-iliac ligaments ; the- latter, to the auricular portion which articulates with the sacrum. Below the posterior inferior spinous process is a deep notch, the great sacro-sciatic. The Ischium forms the lower and back part of the os innominatum. It is divisible into a thick and solid portion, the body ; and a thin ascending part, the ramus. The body, somewhat triangular in form, presents three surfaces, external, internal, and posterior. The external surface corresponds to that portion of the acetabulum formed by the ischium; it is smooth and concave above, and forms a little more than two-fifths of that cavity ; its outer margin is bounded by a pro- minent rim or lip, to which the cotyloid fibro- cartilage is attached. Below the acetabulum, between it and the tuberosity, is a deep groove, along which the tendon of the Obturator externus muscle runs, as it passes outwards to be inserted into the digital fossa of the femur. The internal surface is smooth, concave, and forms the lateral boundary of the true pelvic cavity ; it is broad above, and separated from the venter of the ilium by the linea ilio-pectinea ; narrow below ; its posterior border is encroached upon a little below its centre, by the spine of the ischium, above and below which are the greater and lesser sacro-sciatic notches ; in front it presents a sharp margin, which forms the outer boundary of the obturator foramen. This surface is perforated by two or three large vascular foramina, and affords attachment to part of the Obturator internus muscle. The posterior surface is quadrilateral in form, broad and smooth above, narrow below where it becomes continuous with the tuberosity ; it is limited, in front, by the margin of the ace- tabulum ; behind, by the front part of the great sacro-sciatic notch. This surface supports the Pyriformis, the two Gemelli, and the Obturator internus muscles, in their passage outwards to the great trochanter. The body of the ischium presents three borders, posterior, inferior, and internal. The posterior border presents, a little below the centre, a thin and pointed triangular eminence, the spine of the ischium, more or less elongated in different subjects. Its external surface gives attachment to the Gemellus superior ; its internal surface, to the Coccygeus and Levator ani ; whilst to the pointed extremity is connected the lesser sacro-sciatic ligament. Above the spine is a notch of large size, the great sacro-sciatic, con- verted into a foramen by the lesser sacro-sciatic ligament ; it transmits the Pyri- formis muscle, the gluteal vessels and nerve passing out of the pelvis above this muscle ; the sciatic, and internal pudic vessels and nerve, and a small nerve to the Obturator internus muscle below it. Below the spine is a smaller notch, the lesser sacro-sciatic ; it is smooth, coated with cartilage in the recent state, the surface of which presents numerous markings corresponding to the subdivisions of the tendon of the Obturator internus which winds over it. It is converted into a foramen by the sacro-sciatic ligaments, and transmits the tendon of the Obturator internus, the nerve which supplies this muscle, and the pudic vessels and nerve. The inferior border is thick and broad ; at its point of junction with the posterior, is a large rough eminence upon which the body rests in sitting ; it is called the tube- rosity of the ischium. The internal border is thin, and forms the outer circum- ference of the obturator foramen. The tuberosity, situated at the junction of the posterior and inferior borders, presents for examination an external lip, an internal lip, and an intermediate space. The external lip gives attachment to the Quadratus femoris, and part of the Ad- ductor magnus muscles. The inner lip is bounded by a sharp ridge for the attach- ment of a falciform prolongation of the great sacro-sciatic ligament ; presents a groove on the inner side of this for the lodgment of the internal pudic vessels and nerve ; and, more anteriorly, has attached the Transversus perinei, Erector penis, and Compressor urethra muscles. The intermediate surface presents four OS INNOMINATUM. 153 distinct impressions. Two of these, seen at the front part of the tuberosity, are rough, elongated, and separated from each other by a prominent ridge ; the outer one gives attachment to the Adductor magnus, the inner one to the great sacro- sciatic ligament. Two, situated at the back part, are smooth, larger in size, and separated by an oblique ridge; from the upper and outer arises the Semi-mem- branosus ; from the lower and inner, the Biceps and Semi-tendinosus. The upper- most part of the tuberosity gives attachment to the Gemellus inferior. The ramus is the thin flattened part of the ischium, which ascends from the tuberosity upwards and inwards, and joins the ramus of the pubes, their point of junction being indicated in the adult by a rough eminence. Its outer surface is rough for the attachment of the Obturator externus muscle. Its inner surface forms part of the anterior wall of the pelvis. Its inner border is thick, rough, slightly everted, forms part of the outlet of the pelvis, and serves for the attach- ment of the crus penis. Its outer border is thin and sharp, and forms part of the inner margin of the obturator foramen. The Pubes forms the anterior part of the os innominatum ; it is divisible into a horizontal ramus or body, and a perpendicular ramus. The body or horizontal ramus presents for examination two extremities, an outer and an inner, and four surfaces. The outer extremity, the thickest part of the bone, forms one-fifth of the cavity of the acetabulum ; it presents, above, a rough emi- nence, the ilio-pectineal, which serves to indicate the point of junction of the ilium and pubes. The inner extremity is the symphysis ; it is oval, covered by eight or nine transverse ridges, or a series of nipple-like processes arranged in rows, separated by grooves ; they serve for the attachment of the interarticular fibro-cartilage, placed between it and the opposite bone. The upper surface, triangular in form, wider externally than internally, is bounded behind by a sharp ridge, the pectineal line, or linea ilio-pectinea, which, running outwards, marks the brim of the true pelvis. The surface of bone in front of the pubic portion of the linea iliq-pectinea serves for the attachment of the Pectineus muscle. This ridge terminates internally at a tubercle, which projects forwards, and is called the spine of the pubes. The portion of bone included between the spine and inner extre- mity of the pubes is called the crest ; it serves for the attachment of the Rectus, Pyramidalis, and conjoined tendon of the Internal oblique and Transversalis. The point of junction of the crest with the symphysis is called the angle of the p>ubes. The inferior surface presents, externally, a broad and deep oblique groove, for the passage of the obturator vessels and nerve ; and, internally, a sharp margin, which forms part of the circumference of the obturator foramen. Its external surface, flat and compressed, serves for the attachment of muscles. Its internal surface, convex from above downwards, concave from side to side, is smooth and forms part of the anterior wall of the pelvis. The descending ramus of the pubes passes outwards and downwards, becoming thinner and narrower as it descends, and joins with the ramus of the ischium. Its external surface is rough, for the attachment of muscles. Its inner surface is smooth. Its inner border is thick, rough, and everted, especially in females. In the male, it serves for the attachment of the crus penis. Its outer border forms part of the circumference of the obturator foramen. The cotyloid cavity, or acetabulum, is a deep, cup-shaped, hemispherical depres- sion, formed, internally, by the pubes; above, by the ilium; behind and below, by the ischium ; a little less than two-fifths being formed by the ilium, a little more than two-fifths by the ischium, and the remaining fifth by the pubes. It is bounded by a prominent uneven rim, which is thick and strong above, and serves for the attachment of a fibro-cartilaginous structure, which contracts its orifice, and deepens the surface for articulation. It presents on its inner side a deep notch, the cotyloid notch, which transmits the nutrient vessels into the interior of the joint, and is continuous with a circular depression at the bottom of the cavity; this depression is perforated by numerous apertures, lodges a mass of fat, and its margins serve for the attachment of the ligamentum teres. The notch is con- 154 OSTEOLOGY. verted, in the natural state, into a foramen by a dense ligamentous band which passes across it. Through this foramen, the nutrient vessels and nerves enter the joint. The obturator or thyroid foramen is a large aperture, situated between the ischium and pubes. In the male it is large, of an oval form, its longest diameter being obliquely from above downwards ; in the female, smaller, and more trian- gular. It is bounded by a thin uneven margin, to which a strong membrane is attached; and presents, at its upper and outer part, a deep groove, which runs from the pelvis obliquely forwards, inwards, and downwards. This groove is converted into a foramen by the obturator membrane, and transmits the obturator vessels and nerve. Structure. This bone consists of much cancellous tissue, especially where it is thick, inclosed between two layers of dense compact tissue. In the thinner parts of the bone, as at the bottom of the acetabulum, and centre of the iliac fossa, it is usually semi-transparent, and composed entirely of compact tissue. Development (fig. 99). By eight centres ; three primary — one for the ilium, ote Fig. 99. — Plan of the Development of the Os Innominatum. •n * ft . I & -Primary (/IvuaniJJic/tiun^tc Pu/hcs j i 5.Stconda,TTt The 3 l*rimevry centre* finite fArouyA ~YShetfi€VRiron«is JJr/irttmlon. for UO.MtMTUH tcd: ''/•iVwuliJ 160 OSTEOLOGY. behind, the Obturator interim s and Gemelli in front. The inferior border corre- sponds to the point of junction of the base of the trochanter with the outer surface of the shaft ; it is rough, prominent, slightly curved, and gives attachment to the upper part of the Vastus externus muscle. The anterior border is prominent, somewhat irregular, as well as the surface of bone immediately below it ; it affords attachment by its outer part to the Gluteus minimus. The posterior border is very prominent, and appears as a free rounded edge, which forms the back part of the digital fossa. The Lesser Trochanter is a conical eminence, which varies in size in different subjects; it projects from the lower and back part of the base of the neck. Its base is triangular, and connected with the adjacent parts of the bone by three well-marked borders : of these, the superior is continuous with the lower border of the neck ; the posterior, with the posterior intertrochanteric line ; and the inferior, with the middle bifurcation of the linea aspera. Its summit, which is directed inwards and backwards, is rough, and gives insertion to the tendon of the Psoas magnus. The Iliacus is inserted into the shaft below the lesser trochanter, between the Vastus internus in front, and the Pectineus behind. A well-marked promi- nence, of variable size, which projects from the upper and front part of the neck, at its junction with the great trochanter, is called the tubercle of the femur ; it is the point of meeting of three muscles, the Gluteus minimus externally, the Vastus externus below, and the tendon of the Obturator internus and Gemelli above. Eunning obliquely downwards and inwards from the turbercle, is the spiral line of the femur, or anterior intertrochanteric line ; it winds round the inner side of the shaft, below the lesser trochanter, and terminates in the linea aspera, about two inches below this eminence. Its upper half is rough, and affords attachment to the capsular ligament of the hip -joint; its lower half is less prominent, and gives attachment to the upper part of the Vastus internus. The posterior intertro- chanteric line is very prominent, and runs from the summit of the great trochanter downwards and inwards to the upper and back part of the lesser trochanter. Its upper half forms the posterior border of the great trochanter. A well-marked eminence commences about the middle of the posterior intertrochanteric line, and passes vertically downwards for about two inches along the back part of the shaft ; it is called the linea quadrati, and gives attachment to the Quadratus femoris, and a few fibres of the Adductor magnus muscles. The Shaft, almost perfectly cylindrical in form, is a little broader above than in the centre, and somewhat flattened from before backwards below. It is slightly arched, so as to be convex in front ; concave behind, where it is strengthened by a prominent longitudinal ridge, the linea aspera. It presents for examination three borders separating three surfaces. Of the three borders, one, the linea aspera, is posterior ; the other two are placed laterally. The linea aspera (fig. 104) is a prominent longitudinal ridge or crest, presenting on the middle third of the bone an external lip, an internal lip, and a rough inter- mediate space. A little above the centre of the shaft, this crest divides into three lines : the most external one becomes very rough, and is continued almost vertically upwards to the base of the great trochanter : the middle one, the least distinct, is continued to the base of the trochanter minor ; and the internal one is lost above in the spiral line of the femur. Below, the linea aspera divides into two bifur- cations, which inclose between them a triangular space, the popliteal space, upon which rests the popliteal artery. Of these two bifurcations, the outer branch is the most prominent, and descends to the summit of the outer condyle. The inner branch is less marked, presents a broad and shallow groove for the passage of the femoral artery, and terminates at a small tubercle at the summit of the internal condyle. To the inner lip of the linea aspera, its whole length, is attached the Vastus internus ; and to the whole length of the outer lip, the Vastus externus. The Adductor magnus is also attached to the whole length of the linea aspera, being connected with the outer lip above, and the inner lip below. Between the Vastus FEMUR. 161 externus and the Adductor magnus are attached two muscles, viz., the Gluteus maximus above, and the short head of the Biceps below. Between the Adductor magnus and the Vastus internus, four muscles are attached: the Iliacus and Pectineus above, the latter to the middle division of the upper bifurcation ; below these, the Adductor brevis and Adductor longus. The linea aspera is perforated a little below its centre by the nutritious canal, which ip directed obliquely from below upwards. The two lateral borders of the femur are only very slightly marked, the outer one extending from the anterior inferior angle of the great trochanter to the an- terior extremity of the external condyle ; the inner one passes from the spiral line, at a point opposite the trochanter minor, to the anterior extremity of the internal condyle. The internal border marks this limit of attachment of the Crureus muscle internally. The anterior surface includes that por- tion of the shaft which is situated between the two lateral borders. It is smooth, convex, broader above and below than in the centre, slightly twisted, so that its upper part is directed forwards and a little outwards, its lower part forwards and a little inwards. The upper three-fourths of this surface serve for the attachment of the Crureus ; the lower fourth is separated from this muscle by the intervention of the synovial membrane of the knee-joint, and affords attachment to the Subcrureus to a small extent. The external surface includes the portion of bone between the external border and the outer lip of the linea aspera ; it is continuous, above, with the outer surface of the great trochanter; below, with the outer surface of the ex- ternal condyle : to its upper three-fourths is attached the outer portion of the Cru- reus muscle. The internal surf ace includes the portion of bone between the internal border and the inner lip of the linea as- pera; it is continuous, above, with the lower border of the neck; below, with the inner side of the internal condyle : it is covered by the Vastus internus muscle. The Lower Extremity, larger than the upper, is of a cuboid form, flattened from before backwards, and divided by an interval presenting a smooth depression in front, and a notch of considerable size 11 Fig. 104. — Right Femur. Posterior Surface. . OBTURATOR EXTERNU* 5! ff w :.W Q I-: Hi i . trtoavt for trtulj* POPL.U.i >•< .V 1 . ^ J* 162 OSTEOLOGY. behind, into two large eminences, the condyles (x6vhvxo i} a knuckle). The interval is called the intercondyloid notch. The external condyle is the most prominent anteriorly, and is the broadest both in the antero-posterior and transverse diameters. The internal condyle is the narrowest, longest, and most prominent internally. This difference in the length of the two condyles is only observed when the bone is perpendicular, and depends upon the obliquity of the thigh-bones, in conse- quence of their separation above at the articulation with the pelvis. If the femur is held obliquely, the surfaces of the two condyles will be seen to be nearly hori- zontal. The two condyles are directly continuous in front, and form a smooth trochlear surface, the external border of which is more prominent, and ascends higher than the internal one. This surface articulates with the patella. It pre- sents a median groove, which extends downwards and backwards to the inter- condyloid notch ; and two lateral convexities, of which the external is the broader, more prominent, and prolonged farther upwards upon the front of the outer condyle. The intercondyloid notch lodges the crucial ligaments ; it is bounded laterally by the opposed surfaces of the two condyles, and in front by the lower end of the shaft. Outer Condyle. The outer surface of the external condyle presents, a little behind its centre, an eminence, the outer tuberosity ; it is less prominent than the inner tuberosity, and gives attachment to the external lateral ligament of the knee. Immediately beneath it is a groove which commences at a depression a little behind the centre of the lower border of this surface : the depression is for the tendon of origin of the Popliteus muscle ; the groove in which this tendon is contained is smooth, covered with cartilage in the recent state, and runs upwards and back- wards to the posterior extremity of the condyle. The inner surface of the outer condyle forms one of the lateral boundaries of the intercondyloid notch, and gives attachment, by its posterior part, to the anterior crucial ligament. The inferior surface is convex, smooth, and broader than that of the internal condyle. The posterior extremity is convex and smooth : just above the articular surface is a depression, for the tendon of the outer head of the Gastrocnemius. Inner Condyle. The inner surface of the inner condyle presents a convex eminence, the inner tuberosity, rough for the attachment of the internal lateral ligament. Above this tuberosity, at the termination of the inner bifurcation of the linea aspera, is a tubercle, for the insertion of the tendon of the Adductor magnus ; and behind and beneath the tubercle a depression, for the tendon of the inner head of the Gastrocnemius. The outer side of the inner condyle forms one of the lateral boundaries of the intercondyloid notch, and gives attachment, by its anterior part, to the posterior crucial ligament. Its inferior or articular surface is convex, and presents a less extensive surface than the external condyle. Structure. The shaft of the femur is a cylinder of compact tissue hollowed by a large medullary canal. The cylin- der is of great thickness and density in the middle third of the shaft, w r here the bone is narrowest, and the medullary canal well formed ; but above and below this, the cylinder gradually becomes thinner, owing to a separation of the layers of the bone into cancelli, which project into the medullary canal, and finally obliterate it, so that the upper and lower ends of the shaft, and the articular extremities more especially, consist of cancellated tissue invested by a thin compact layer. The arrangement of the cancelli in the ends of the femur is remarkable. In the Fig. 105. — Diagram showing the Structure of the Neck of the Femur. (Ward.) FEMUR. 133 Fig. 106. — Plan of the Development of the Femur. By 5 Centres. Appears at U$y? JVfSiuftMut m *y?(£ Appears at vnd «f>y? Jci/isS/iaft aiout tS.'y 1 Ajipt(trs13-U* yr- Joins Shaft aiout 1 8*^ y T upper end (fig. 105), they run in parallel columns a a from the summit of the head to the thick under wall of the neck, while a series of transverse fibres b b decus- sates the parallel columns, and connects them to the thin upper wall of the neck. Another series of plates c c springs from the whole interior of the cylinder above the lesser trochanter ; passing upwards, they converge to form a series of arches beneath the upper wall of the neck, near its junction with the great trochanter. This structure is admirably adapted to sustain, with the greatest mechanical advantage, concussion or weight transmitted from above, and serves an important office in strengthening a part especially liable to fracture. In the lower end, the cancelli spring on all sides from the inner surface of the cylinder, and descend in a perpendicular direction to the articular surface, the cancelli being strongest, and having a more decided perpendicular course, above the condyles. Articulations. With three bones : the os innominatum, tibia, and patella. Development (fig. 106). The femur is developed by jive centres ; one for the shaft, one for each ex- tremity, and one for each trochanter. Of all the long bones, it is the first to show traces of ossification: this first commences in the shaft, at about the fifth week of foetal life, the centres of ossification in the epiphyses appearing in the follow- ing order: First, in the lower end of the bone, at the ninth month of foetal life; from this the condyles and tuberosities are formed ; in the head, at the end of the first year after birth ; in the great trochanter, during the fourth year ; and in the lesser trochanter, between the thir- teenth and fourteenth. The order in which the epiphyses are joined to the shaft, is the direct reverse of their appearance ; their junction does not commence until after puberty, the lesser trochanter being first joined, then the greater, then the head, and, lastly, the inferior extremity, the first in which ossi- fication commenced, which is not united until the twentieth year. Attachment of Muscles. To the great trochanter: the Gluteus medius, Gluteus minimus, Pyriformis, Obturator internus, Obturator externus, Gemellus superior, Gemellus inferior, and Quadratus femoris. To the lesser trochanter : the Psoas magnus, and the Iliacus below it. To the shaft : its posterior surface ; the Vastus externus, Gluteus maximus, short head of the Biceps, Vastus internus, Adductor magnus, Pectineus, Adductor brevis, and Adductor longus ; to its anterior surface; the Crureus, and Subcrureus. To the condyles: the Gastrocnemius, Plantaris, and Popliteus. , 4 i'PVt trs-atQ' Joins SJiaflatZO'tf- **• ExtrertW THE LEG. The Leg consists of three bones : the Patella, a larg* front of the knee ; the Tibia, and Fibula. sesamoid bone, placed in 1G4 OSTEOLOGY. Fig. 107.— Right Patella. Anterior Surface. The Patella. (Figs. 107 and 108.) The Patella is a small, flat, triangular bone, situated at the anterior part of the knee-joint. It resembles the sesamoid bones, from being developed in the tendon of the Quadriceps extensor, and in its structure, being composed throughout of dense cancellous tissue; but it is generally regarded as analogous to the olecranon process of the ulna, which occasionally exists as a separate piece, connected to the shaft of the bone by a continuation of the tendon of the Triceps muscle. 1 It serves to protect the front of the joint, and increases the leverage of the Common extensor by making it act at a greater angle. It presents an anterior and posterior surface, three borders, a base, and an apex. The anterior surface is convex, perforated by small apertures, for the passage of nutrient vessels, and marked by numerous rough longitudinal striae. This surface is covered, in the recent state, by an expansion from the tendon of the Quadriceps extensor, separated from the integument by a bursa, and gives attachment below to the liga- mentum patellae. The posterior surface presents a smooth, oval-shaped, articular surface, covered with cartilage in the recent state, and divided into two facets by a vertical ridge, which descends from the superior towards the inferior angle of the bone. The ridge corresponds to the groove on the trochlear surface of the femur, and the two facets to the articular surfaces of the two condyles ; the outer facet, for articulation with the outer condyle, being the broader and deeper, serves to indicate the leg to which the bone belongs. Below the articular surface is a rough, convex, non-articular depression, the lower half of which gives attachment to the ligamentum patellar ; the upper half being separated from the head of the tibia by adipose tissue. Its superior and lateral borders give attachment to the tendon of the Quadriceps extensor; the superior border, to that portion of the tendon which is derived from the Eectus and Crureus muscles; and the lateral borders, to the portion derived from the external and internal Vasti muscles. The base or superior border is thick, directed upwards, and cut obliquely at the expense of its outer surface; it receives the attachment, as already mentioned, of part of the Quadriceps extensor tendon. The apex is pointed, and gives attachment to the ligamentum patellae. Structure. It consists of dense cancellous tissue, covered by a thin compact lamina. Development. By a single centre, which makes its appearance, according to Beclard, about the third year. In two instances, I have seen this bone cartilaginous throughout, at a much later period (six years). More rarely, the bone is developed by two centres, placed side by side. Articulations. With the two condyles of the femur. Attachment of Muscles. The Eectus, Crureus, Vastus internus, and Vastus externus. These muscles, joined at their insertion, constitute the Quadriceps ex- tensor cruris. Fig. 108.— Right Patella. Posterior Surface. 1 Professor Owen states, that, "in certain bats, there is a development of a sesamoid bone in the biceps brachii, which is the true homotype of the patella in the leg," regarding the olecranon to be homologous, not with the patella, but with an extension of the upper end of the fibula above the knee-joint, which is met with in some animals. ('■ On the Nature of Limbs," pp. 19, 24.) TIBIA. 1C5 The Tibia. The Tibia (so named from its resemblance to a flute or pipe) is situated at the front and inner side of the leg, and, excepting the femur, is the longest and largest bone in the skeleton. It is pris- moid in form, expanded above, where it enters into formation with the knee-joint, more slightly enlarged below. In the male, its direction is vertical, and parallel with the bone of the opposite side ; but in the female it has a slight oblique direction downwards and outwards, to compensate for the oblique direction of the femur itiwards. It presents for exami- nation a shaft and two extremi- ties. The Upper Extremity or head is large and expanded on each side into two lateral eminences, the tuberosities. Superiorly, the tuberosities present two smooth concave surfaces, which articulate with the condyles of the femur; the internal articular surface is longer than the ex- ternal, oval from before back- wards, to articulate with the internal condyle; the external one being broader, flatter, and more circular, to articulate with the external condyle. Between the two articular surfaces, and nearer the posterior than the anterior aspect of the bone, is an eminence, the spinous process of the tibia, surmounted by a pro* minent tubercle on each side, which give attachment to the extremities of the semilunar fibro-cartilages ; and in front and behind the spinous process, a rough depression for the attach- ment of the anterior and poste- rior crucial ligaments and the semilunar cartilages. Anteriorly the tuberosities are continuous with one another, presenting a large and somewhat flattened triangular surface, broad above, and perforated by large vascular foramina; narrow below, where it terminates in a prominent Fig. 109. — Bones of the Right Leg. Anterior Surface. H « a. tg StyTeiif merer* fIBUU Jnttrn^l Mali4clul Internal NnUtatut 1G6 OSTEOLOGY. oblong elevation of large size, the tubercle of the tibia ; the lower half of this tubercle is rough, for the attachment of the ligamentum patellae ; the upper half is a smooth facet corresponding, in the recent state, with a bursa which separates the ligament from the bone. Posteriorly, the tuberosities are separated from each other by a shallow depression, the popliteal notch, which gives attach- ment to the posterior crucial ligament. The posterior surface of the inner tuberosity presents a deep transverse groove, for the insertion of the tendon of the Semi-membranosus ; and the posterior surface of the outer one, a flat articular facet, nearly circular in form, directed downwards, backwards, and outwards, for articulation with the fibula. The lateral surfaces are convex and rough; the internal one, the most prominent, gives attachment to the internal lateral ligament. The Shaft of the tibia is of a triangular prismoid form, broad above, gradually decreasing in size to the commencement of its lower fourth, its most slender part, where fracture most frequently occurs, and then enlarging again towards its lower extremity. It -presents for examination three surfaces and three borders. The anterior border, the most prominent of the three, is called the crest of the tibia, or, in popular language, the shin ; it commences above at the tubercle, and terminates below at the anterior margin of the inner malleolus. This border is very prominent in the upper two-thirds of its extent, smooth and rounded below. It presents a very flexuous course, being curved outwards above, and inwards below ; it gives attachment to the deep fascia of the leg. The internal border is smooth and rounded above and below, but more promi- nent in the centre ; it commences at the back part of the inner tuberosity, and terminates at the posterior border of the internal malleolus ; its upper third gives attachment to the internal lateral ligament of the knee, and to some fibres of the Popliteus muscle ; its middle third, to some fibres of the Soleus and Flexor longus digitorum muscles. The external border is thin and prominent, especially its central part, and gives attachment to the interosseous membrane ; it commences above in front of the fibular articular facet, and bifurcates below, to form the boundaries of a triangular rough surface, for the attachment of the interosseous ligament, connecting the tibia and fibula. The internal surface 'is smooth, convex, and broader above than below; its upper third, directed forwards and inwards, is covered by the aponeurosis derived from the tendon of the Sartorius, and by the tendons of the Gracilis and Semi- tendinosus, all of which are inserted nearly as far forwards as the anterior border ; in the rest of its extent it is subcutaneous. The external surface is narrower than the internal; its upper two-thirds present a shallow groove for the attachment of the Tibialis anticus muscle ; its lower third is smooth, convex, curves gradually forwards to the anterior part of the bone, and is covered from within outwards by the tendons of the following muscles : Tibialis anticus, Extensor proprius pollicis, Extensor longus digitorum, Peroneus tertius. The 'posterior surface (fig. 110) presents at its upper part a prominent ridge, the oblique line of the tibia, which extends from the back part of the articular facet for the fibula, obliquely downwards, to the internal border, at the junction of its upper and middle thirds. It marks the limit for the insertion of the Popliteus muscle, and serves for the attachment of the popliteal fascia, and part of the Soleus, Flexor longus digitorum, and Tibialis posticus muscles ; the triangular concave surface, above, and to the inner side of, this line, gives attachment to the Popliteus muscle. The middle third of the posterior surface is divided by a vertical ridge into two lateral halves ; the ridge is well marked at its commence- ment at the oblique line, but becomes gradually indistinct below ; the inner and broadest half gives attachment to the Flexor longus digitorum, the outer and narrowest, to part of the Tibialis posticus. The remaining part of the bone is covered by the Tibialis posticus, Flexor longus digitorum and Flexor longus TIBIA. 167 pollicis muscles. Immediately below the oblique line is the medullary foramen, which is di- rected obliquely downwards. The Lower Extremity, much smaller than the upper, is some- what quadrilateral in form, and prolonged downwards on its in- ner side, into a strong process, the internal malleolus. The inferior surface of the bone presents a quadrilateral smooth surface, for articulation with the astragalus ; narrow internally, where it becomes continuous with the articular surface of the inner malleolus, broader externally, and traversed from before back- wards by a slight elevation, se- parating two lateral depressions. The anterior surface is smooth and rounded above, and covered by the tendons of the Extensor muscles of the toes; its lower margin presents a rough trans- verse depression, for the attach- ment of the anterior ligament of the ankle-joint. The posterior surface presents a superficial groove directed obliquely down- wards and inwards, continuous with a similar groove on the pos- terior extremity of the astragalus ; it serves for the passage of the tendon of the Flexor longus polli- cis. The external surface presents a triangular rough depression, the lower part of which, in some bones, is smooth, and covered with cartilage in the recent state, and articulates with the fibula; the remaining part is rough for the attachment of the inferior interosseous ligament, which connects it with the fibula. This surface is bounded by two prominent ridges, continuous above with the interosseous ridge ; they afford attachment to the anterior and posterior tibio-fibular ligaments. The internal surface is prolonged downwards to form a strong py- ramidal-shaped process, flattened from without inwards, the inner malleolus; its inner surface is convex and subcutaneous. Its Fig. 110. — Bones of the Eight Leg. Posterior Surface. ■tfloidji rticesa 168 OSTEOLOGY. Fig. 111.— Plau of the Development of the Tibia. By 3 Centres. Upper extremity Apj>»t{ rx part of the Flexor accessorius muscle. This surface presents an eminence of 'urne, the lesser process, which projects horizontally inwards from its upper and 1 re part. This process is concave above, and supports the anterior articular surface of the astragalus ; below, it is convex, and grooved for the tendon of the Flexor longus pollicis. Its free margin is rough, for the attachment of ligaments. The anterior surface, of a somewhat triangular form, is smooth, concavo-convex, and articulates with the cuboid. It is surmounted, on its outer side, by a rough prominence, which forms an important guide to the surgeon in the performance of Chopart's operation. The posterior surface is rough, prominent, convex, and wider below than above. Its lower part is rough, for the attachment of the tendo Achillis ; its upper part smooth, coated with cartilage, and corresponds to a bursa which separates this tendon from the bone. Articulations. With two bones : the astragalus and cuboid. Attachment of Muscles. Part of the Tibialis posticus, the tendo Achillis, Plan- taris, Abductor pollicis, Abductor minimi digiti, Flexor brevis digitorum, Flexor accessorius, and Extensor brevis digitorum. tarsus. m The Cuboid. The Cuboid bone is placed on the outer side of the foot, in front of the os calcis, and behind the fourth and fifth metatarsal bones. It is of a pyramidal shape, its base being directed upwards and inwards, its apex downwards and outwards. It may be distinguished from the other tarsal bones, by the existence of a deep groove on its under surface, for the tendon of the Peroneus longus muscle. It presents for examination six surfaces ; three articular, and three non-articular : the non-articular surfaces are the superior, inferior, and external. The superior or dorsal surface, directed upwards and outwards, is rough, for the attachment of numerous ligaments. The inferior or plantar surface presents in front a deep groove, w r hich runs obliquely from without, forwards and inwards ; it lodges the tendon of the Peroneus longus, and is bounded behind by a promi- nent ridge, terminating externally in an eminence, the tuberosity of the cuboid, the surface of which presents a convex facet, for articulation with the sesamoid bone of the tendon contained in the groove. The ridge and surface of bone behind it are rough, for the attachment of the long and short plantar ligaments. The external surface, the smallest and narrowest of the three, presents a deep notch, formed by the commencement of the peroneal groove. The articular surfaces are the posterior, anterior, and internal. The posterior surface is smooth, triangular, concavo-convex, for articulation with the anterior surface of the os calcis. The anterior, of smaller size, but also irregularly trian- gular, is divided by a vertical ridge into two facets ; the inner facet, quadrilateral in form, articulates with the fourth metatarsal bone; the outer one, larger and more triangular, articulates with the fifth metatarsal. The internal surface is broad, rough, irregularly quadrilateral, presenting at its middle and upper part a small oval facet, for articulation with the external cuneiform bone ; and behind tliis. occasionally, a smaller facet, for articulation with the scaphoid ; it is rough in the rest of its extent, for the attachment of strong interosseous ligaments. To ascertain to which foot it belongs, hold the bone so that its under surface, marked by the peroneal groove, looks downwards, and the large concavo-convex articular surface backwards, towards the holder ; the narrow non-articular surface, marked by the commencement of the peroneal groove, will point to the side to wiiich the bone belongs. Articulations. With four bones : the os calcis, external cuneiform, and the fourth and fifth metatarsal bones; occasionally with the scaphoid. Attachment of Muscles. Part of the Flexor brevis pollicis. The Asteagalus. The Astragalus (fig. 113), next to the os calcis, is the largest of the tarsal bones. It occupies the middle and upper part of the tarsus, supporting the tibia above, articulating with the malleoli on either side, resting below upon the os calcis, and joined in front to the scaphoid. This bone may easily be recognized by its large rounded head, the broad articular facet on its upper convex surface, and by the two articular facets separated by a deep groove on its under concave surface. It presents six surfaces for examination. The superior surface presents, behind, a broad smooth trochlear surface, for articulation with the tibia ; it is broader in front than behind, convex from before backwards, slightly concave from side to side. In front of the trochlea is the upper surface of the neck of the astragalus, rough for the attachment of liga- ments. The inferior surface presents two articular facets separated by a deep groove. The groove runs obliquely forwards and outwards, becoming gradually broader and deeper in front : it corresponds with a similar groove upon the upper surface of the os calcis, and forms, when articulated with that bone, a canal, filled up in the recent state by the calcaneo-astragaloid interosseous ligament. Of the two articular facets, the posterior is the larger, of an oblong form, and deeply concave from side to side : the anterior, although nearly of equal length,, is. nar- OSTEOLOGY. Fig. 114.— Bones of the Right Foot. Plantar Surface. LEXOR BREVI* POUICIC Taltrcle of ScajJuid TIBIALIS AMICUS FLEXOR L0NCU8 DIClTORUM TARSUS. 175 rower, of an elongated oval form, convex longitudinally, and often subdivided into two by an elevated ridge : of these the posterior one articulates with the lesser process of the os calcis ; the anterior one, with the upper surface of the calcaneo- scaphoid ligament. The internal surface presents at its upper part a pear-shaped articular facet for the inner malleolus, continuous above with the trochlear surface ; below the articular surface is a rough depression, for the attachment of the deep portion of the internal lateral ligament. The external surface presents a large triangular facet, concave from above downwards, for articulation with the external malleolus ; it is continuous above with the trochlear surface, and in front of it is a rough depression for the attachment of the anterior fasciculus of the external lateral ligament. The anterior surface, convex and rounded, forms the head of the astragalus ; it is smooth, of an oval form, and directed obliquely- inwards and downwards ; it is continuous below with that part of the anterior facet on the under surface which rests upon the calcaneo-scaphoid ligament. The head is sur- rounded by a constricted portion, the neck of the, astragalus. The posterior sur- face is narrow, and traversed by a groove, which runs obliquely downwards and inwards, and transmits the tendon of the Flexor longus pollicis. To ascertain to which foot it belongs, hold the bone with the broad articular surface upwards, and the rounded head forwards ; the lateral triangular articular surface for the external malleolus will then point to the side to which the bone belongs. Articulations. With four bones : tibia, fibula, os calcis, and scaphoid. The Scaphoid. The Scaphoid or Navicular bone, so called from its fancied resemblance to a boat, is situated at the inner side of the tarsus, between the astragalus behind and the three cuneiform bones in front. This bone may be distinguished by its boat- like form, being concave behind, convex and subdivided into three facets in front. The anterior surface, of an oblong form, is convex from side to side, and sub- divided by two ridges into three facets, for articulation with the three cuneiform bones. The posterior surface is oval, concave, broader externally than internally, and articulates with the rounded head of the astragalus. The superior surface is convex from side to side, and rough for the attachment of ligaments; the inferior, somewhat concave, irregular, and also rough for the attachment of ligaments. The internal surface presents a rounded tubercular eminence, the tuberosity of the scaphoid, which gives attachment to part of the tendon of the Tibialis posticus. The external surface is broad, rough, and irregular, for the attachment of ligamentous fibres, and occasionally presents a small facet for articulation with the cuboid bone. To ascertain to which foot it belongs, hold the bone with the concave articular surface backwards, and the broad dorsal surface upwards ; the broad external surface will point to the side to which the bone belongs. Articulations. With four bones : astragalus and three cuneiform ; occasionally also with the cuboid. Attachment of Muscles. Part of the Tibialis posticus. The Cuneiform Bones. The Cuneiform Bones have received their name from their wedge-like shape. They form with the cuboid the most anterior row of. the tarsus, being placed between the scaphoid behind, the three innermost metatarsal bones in front, and the cuboid externally. They are called the first, second, and third, counting from the inner to the outer side of the foot, and, from their position, internal, middle, and external. The Internal Cuneiform. The Internal Cuneiform is the largest of the three. It is situated at the inner side of the foot, between the scaphoid behind and the base of the first metatarsal 176 OSTEOLOGY. in front. It may be distinguished by its large size, as compared with the other two, and from its more irregular wedge-like form. It presents for examination six surfaces. The internal surface is subcutaneous, and forms part of the inner border of the foot. It is broad, quadrilateral, and presents at its anterior inferior angle a smooth oval facet, over which the tendon of the Tibialis anticus muscle glides ; rough in the rest of its extent, for the attachment of ligaments. The external surface is concave, presenting, along its superior and posterior borders, a narrow surface for articulation with the middle cuneiform behind, and second metatarsal bone in front ; in the rest of its extent, it is rough for the attachment of ligaments, and prominent below, where it forms part of the tuberosity. The anterior surface, reniform in shape, articulates with the metatarsal bone of the great toe. The posterior surface is triangular, concave, and articulates with the innermost and largest of the three facets on the anterior surface of the scaphoid. The inferior or plantar surface is rough, and presents a prominent tuberosity, at its back part for the attachment of part of the tendon of the Tibialis posticus. It also gives attachment in front to part of the tendon of the Tibialis anticus. The superior surface is the narrow pointed end of the wedge, which is directed upwards and outwards ; it is rough for the attachment of ligaments. To ascertain to which side it belongs, hold the bone so that its superior narrow edge looks upwards, and the long articular surface forwards ; the external surface marked by its vertical and horizontal articular facets will point to the side to which it belongs. Articulations. With four bones: scaphoid, middle cuneiform, and first and second metatarsal bones. Attachment of Muscles. The Tibialis anticus and Tibialis posticus. The Middle Cuneifokm. The Middle Cuneiform, the smallest of the three, is of very regular wedge- like form ; the broad extremity being placed upwards, the narrow end downwards. It is situated between the other two bones of the same name, and corresponds to the scaphoid behind, and the second metatarsal in front. The anterior surface, triangular in form, and narrower than the posterior, arti- culates with the base of the second metatarsal bone. The posterior surface, also triangular, articulates with the scaphoid. The internal surface presents an articular facet, running along the superior and posterior borders, for articulation with the internal cuneiform, and is rough below for the attachment of ligaments. The external surface presents posteriorly a smooth facet for articulation with the external cuneiform bone. The superior surface forms the base of the wedge ; it is quadrilateral, broader behind than in front, and rough for the attachment of ligaments. The inferior surface, pointed and tubercular, is also rough for liga- mentous attachment. To ascertain to which foot the bone belongs, hold its superior or dorsal surface upwards, the broadest edge being towards the holder, and the smooth facet, limited to the posterior border, will point to the side to which it belongs. Articulations. With four bones : scaphoid, internal and external cuneiform, and second metatarsal bone. The External Cuneiform. The External Cuneiform, intermediate in size between the two preceding, is of a very regular wedge-like form, the broad extremity being placed upwards, the narrow end downwards. It occupies the centre of the front row of the tarsus between the middle cuneiform internally, the cuboid externally, the scaphoid behind, and the third metatarsal in front. It has six surfaces for examination. The anterior surface, triangular in form, articulates with the third metatarsal bone. The posterior surface articulates with the most external facet of the scaphoid, and is rough below for the attachment of ligamentous fibres. The internal surface METATARSAL BONES. ITT presents two articular facets separated by a rough depression ; the anterior one, situated at the superior angle of the bone, articulates with the outer side of the base of the second metatarsal bone ; the posterior one skirts the posterior border, and articulates with the middle cuneiform ; the rough depression between the two gives attachment to an interosseous ligament. The external surface also presents two articular facets, separated by a rough non-articular surface. The anterior facet, situated at the superior angle of the bone, is small, and articulates with the inner side of the base of the fourth metatarsal ; the posterior, and larger one, articulates with the cuboid ; the rough non-articular surface serves for the attachment of an interosseous ligament. The three facets for articulation with the three metatarsal bones are continuous with one another, and covered by a prolongation of the same cartilage ; the facets for articulation with the middle cuneiform and scaphoid are also continuous, but that for articulation with the cuboid is usually separate. The superior or dorsal surface, of an oblong form, is rough for the attachment of liga- ments. The inferior or plantar surface is an obtuse rounded margin, and serves for the attachment of part of the tendon of the Tibialis posticus, part of the Flexor brevis pollicis, and ligaments. To ascertain to which side it belongs, hold the bone with the broad dorsal surface upwards, the prolonged edge backwards ; the separate articular facet for the cuboid will point to the proper side. Articulations. With six bones : the scaphoid, middle cuneiform, cuboid, and second, third, and fourth metatarsal bones. Attachment of Muscles. Part of Tibialis posticus, and Flexor brevis pollicis. The Metatarsal Bones. The Metatarsal bones are five in number ; they are long bones, and subdivided into a shaft, and two extremities. The Shaft is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is slightly curved longitudinally, so as to be concave below, slightly convex above. The Posterior Extremity or Base is wedge-shaped, articulating by its terminal surface with the tarsal bones, and by its lateral surfaces with the contiguous bones ; its dorsal and plantar surfaces being rough, for the attachment of ligaments. The Anterior Extremity or Head presents a terminal rounded articular surface, oblong from above downwards, and extending further backwards below than above. Its sides are flattened, and present a depression, surmounted by a tubercle, for ligamentous attachment. Its under surface is grooved in the middle line, for the passage of the Flexor tendon, and marked on each side by an articular eminence continuous with the terminal articular surface. Peculiar Metatarsal Bones. The First is remarkable for its great size, but is the shortest of all the meta- tarsal bones. The shaft is strong, and of well-marked prismoid form. The posterior extremity presents no lateral articular facets ; its terminal articular surface is of large size, of semilunar form, and its circumference grooved for the tarso- metatarsal ligaments ; its inferior angle presents a rough oval prominence, for the insertion of the tendon of the Peroneus longus. The head is of large size ; on its plantar surface are two grooved facets, over which glide sesamoid bones, the facets being separated by a smooth elevated ridge. The Second is the longest and largest of the remaining metatarsal bones ; being prolonged backwards, into the recess formed between the three cuneiform bones. Its tarsal extremity is broad above, narrow and rough below. It presents four articular surfaces: one behind, of a triangular form, for articulation with the middle cuneiform ; one at the upper part of its internal lateral surface, for articu- lation with the internal cuneiform; and two on its external lateral surface, a superior and an inferior, separated by a rough depression. Each of the latter articular surfaces is divided by a vertical ridge into two parts ; the anterior seg- 12 178 OSTEOLOGY. merit of each facet articulates with the third metatarsal; the two posterior sometimes continuous with the external cuneiform. The Third articulates behind, by means of a triangular smooth surface, with the external cuneiform ; on its inner side by two facets, with the second metatarsal ; and on its outer side, by a single facet, with the fourth metatarsal. The latter facet is of circular form, and situated at the upper angle of the base. The Fourth is smaller in size than the preceding ; its tarsal extremity presents a. terminal quadrilateral surface, for articulation with the cuboid; a smooth facet on the inner side, divided by a ridge into an anterior portion for articulation with the third metatarsal, and a posterior portion for articulation with the external cunei- form ; on the outer side a single facet, for articulation with the fifth metatarsal. The Fifth is recognized by the tubercular eminence on the outer side of its base ; it articulates behind, by a triangular surface cut obliquely from without inwards, with the cuboid ; and internally, with the fourth metatarsal. Articulations. Each bone articulates with the tarsal bones by one extremity, and by the other with the first row of phalanges. The number of tarsal bones with which each metatarsal articulates is one for the first, three for the second, one for the third, two for the fourth, and one for the fifth. Attachment of Muscles. To the first metatarsal bone, three : part of the Tibialis anticus, Peroneus longus, and First dorsal interosseous. To the second, three : the Adductor pollicis, and First and Second dorsal interosseous. To the third, four : the Adductor pollicis, Second and Third dorsal interosseous, and First plantar. To the fourth, four : the Adductor pollicis, Third and Fourth dorsal, and Second plantar interosseous. To the fifth, five : the Peroneus brevis, Peroneus tertius, Flexor brevis minimi digiti, Fourth dorsal, interosseous and Third plantar inter- osseous. Phalanges. The Phalanges of the foot, both in number and general arrangement, resemble those in the hand ; there being two in the great toe, and three in each of the other toes. The phalanges of the first row resemble closely those of the hand. The shaft is compressed from side to side, convex above, concave below. The posterior extremity is concave ; and the anterior extremity presents a trochlear surface, for articulation with the second phalanges. The phalanges of the second row are remarkably small and short, but rather broader than those of the first row. The ungual phalanges, in form, resemble those of the fingers ; but they are smaller, flattened from above downwards, presenting a broad base for articulation with the second row, and an expanded extremity for the support of the nail and end of the toe. Articulations. The first row, with the metatarsal bones, and second phalanges ; the second of the great toe, with the first phalanx, and of the other toes, with the first and third phalanges ; the third, with the second row. Attachment of Muscles. To the first phalanges : Great toe ; innermost tendon of " Extensor brevis digitorum, Abductor pollicis, Adductor pollicis, Flexor brevis pollicis, Transversus pedis. Second toe ; First and Second dorsal interosseous. Third toe; Third dorsal and First plantar interosseous. Fourth toe; Fourth dorsal and Second plantar interosseous. Fifth toe ; Flexor brevis minimi digiti, Adductor minimi digiti, and Third plantar interosseous. — Second phalanges: Great toe ; Extensor longus pollicis, Flexor longus pollicis. Other toes ; Flexor brevis digitorum, one slip from the Extensor brevis digitorum, and Extensor longus digitorum. — Third phalanges ; two slips from the common tendon of the Extensor longus and Extensor brevis digitorum, and the Flexor longus digitorum. Development of the Foot. (Fig. 115.) The Tarsal bones are each developed by a single centre, excepting the os calcis, which has an epiphysis for its posterior extremity. The centres make their SESAMOID BONES. H9 appearance in the following order : in the os calcis, at the sixth month of fcetal life ; in the astragalus, about the seventh month ; in the cuboid, at the ninth month , external cuneiform, during the first year ; internal cuneiform, in the third year ; middle cuneiform, in the fourth year. The epiphysis for the posterior tuberosity of the os calcis appears at the tenth year, and unites with the rest of the bone soon after puberty. Fig. 115. — Plan of the Development of the Foot. ' s is Ml ■Jpp.f /O* ■•/.? unites after p-ulerty Tarsus f Centre for e&eJi ione tacept Os Calcts Metatarsus 2 Centres fir each ions 1 for Shaft 1 for Digital Extremity except 1.& cent Jippcars 6t? yf \ UiiiU/8-Z0# y.: - App. 7&mi Fhalanges iCentresfor each bo7i0 tforSliaft f fin Metatarsal Ext J TfniU 18-20 jf.rf App'3? d y. App.&& yx-ggr') Unite /J-tSy-'l Agp- Z-J^-inA—J f£^3 Unite IT -18 y^^^ftj App. 2- A. mo: AyfiJ>$ y? Unite 11-18 y.7 App J* »*-IJ>t. The Metatarsal bones are each developed by two centres: one for the shaft, and one for the digital extremity, in the four outer metatarsal; one for the shaft, and one for the base, in the metatarsal bone of the great toe. Ossification commences in the centre of the shaft about the seventh week, and extends towards either extremity, and in the digital epiphyses about the third year ; they become joined between the eighteenth and twentieth years. The Phalanges are developed by two centres for each bone : one for the shaft, and one for the metatarsal extremity. Sesamoid Bones. These are small rounded masses, cartilaginous in early life, osseous in the adult, which are developed in those tendons which exert a certain amount of pressure upon the parts over which they glide. It is said that they are more commonly found in the male than in the female, and in persons of an active muscular habit 180 OSTEOLOGY. than in those that are weak and debilitated. They are invested throughout their whole surface by the fibrous tissue of the tendon in which they are found, excepting upon that side which lies in contact with the part over which they play, where they present a free articular facet. They may be divided into two kinds ; those which glide over the articular surfaces of joints, and those which play over the cartilaginous facets found on the surfaces of certain bones. The sesamoid bones of the joints are, in the lower extremity, the patella, which is developed in the tendon of the Quadriceps extensor ; two small sesamoid bones, found opposite the metatarso-phalangeal joint of the great toe in each foot, in the tendons of the Flexor brevis pollicis, and occasionally one in the metatarso- phalangeal joint of the second toe, the little toe, and, still more rarely, in the third and fourth toes. In the upper extremity, there are two on the palmar surface of the metacarpo- phalangeal joint in the thumb, developed in the tendons of the Flexor brevis pollicis. Occasionally, one or two opposite the metacarpo-phalangeal articulations of the fore and little fingers, and, still more rarely, one opposite the same joints of the third and fourth fingers. Those found in tendons which glide over certain bones occupy the following situations. One in the tendon of the Peroneus longus, where it glides through the groove in the cuboid bone. One appears late in life in the tendon of the Tibialis anticus, opposite the smooth facet on the internal cuneiform bone. One in the tendon of the Tibialis posticus, opposite the inner side of the astragalus. One in the outer head of the Gastrocnemius, behind the outer condyle of the femur; and one in the Psoas and Iliacus, where they glide over the body of the pubes. Occasionally in the tendon of the Biceps, opposite the tuberosity of the radius ; in the tendon of the Gluteus maximus, as it passes over the great trochanter; and in the tendons which wind round the inner and outer malleoli. The author has to acknowledge valuable aid derived from the perusal of the works of Cloquet, Cruveilhier, Bourgery, and Boyer, especially of the latter. Reference has also been made to the following: "Outlines of Human Osteology," by F. O. Ward. "A Treatise on the Human Skeleton, and Observations on the Limbs of Vertebrate Animals," by G. M. Humphry. Holden's "Human Osteology." Henle's "Handbuch der Systematischen Anatomie des Menschen. Erster Band. Erste Abtheilung. Knochenlehre." " Osteological Memoirs (The Clavicle)," by Stru- thers. "On the Archetype and Homologies of the Vertebrate Skeleton," and "On the Nature of Limbs," by Owen. — Todd and Bowman's "Physiological Anatomy," and Kolliker's "Manual of Human Microscopic Anatomy," contain the most complete account of the structure and development of bone. — The development of the bones is minutely described in "Quain's Ana- tomy," edited by Sharpey and Ellis. On the chemical analysis of bone, refer to "Lehmann's Physiological Chemistry," translated by Day, vol. iii. p. 12. "Simon's Chemistry," translated by Day, vol. ii. p. 396. A paper by Dr. Stark, "On the Chemical Constitution of the Bones of the Yerteb rated Animals" (Edinburgh Medical and Surgical Journal, vol. liii. p. 308) ; and Dr. Owen Rees's paper in the 21st vol. of the Medico-chirurgical Transactions. The Articulations. The various bones of which the Skeleton consists are connected together at different parts of their surfaces, and such connection is designated by the name of Joint or Articulation. If the joint is immovable, as between the cranial and most of the facial bones, the adjacent margins are applied in almost close contact, a thin layer of fibrous membrane, the sutural ligament, and, at the base of the skull, in certain situations, a thin layer of cartilage, being interposed. "Where slight movement is required, combined with great strength, the osseous surfaces are united by tough and elastic fibro-cartilages, as in the joints of the spine, the sacro-iliac, and interpubic articulations; but in the movable joints, the bones forming the articulation are generally expanded for greater convenience of mutual connection, covered by an elastic structure, called cartilage, held together by strong bands or capsules, of fibrous tissue, called ligament, and lined by a membrane, the synovial membrane, which secretes a fluid that lubricates the various parts of which the joint is formed, so that the structures which enter into the formation of a joint are bone, cartilage, fibro-cartilage, ligament, and synovial membrane. Bone constitutes the fundamental element of all the joints. In the long bones, the extremities are the parts which form the articulations ; they are generally somewhat enlarged, consisting of spongy cancellous tissue, with a thin coating of compact substance. In the flat bones, the articulations usually take place at the edges ; and, in the short bones, by various parts of their surface. The layer of compact bone which forms the articular surface, and to which the cartilage is attached, is called the articular lamella. It is of a white color, extremely dense, and varies in thickness. Its structure differs from ordinary bone-tissue in this respect, that it contains no Haversian canals, and its lacunas are much larger than in ordinary bone, and have no canaliculi. The vessels of the cancellous tissue, as they approach the articular lamella, turn back in loops, andkdo not perforate it; this la}''er is consequently more dense, and firmer than ordinary bone, and is evidently designed to form a steady and unyielding support for the articular cartilage. Cartilage is firm, opaque, of a pearly-white or bluish-white color, in some varieties yellow, highly elastic, readily yielding to pressure, and recovering its shape when the force is removed, flexible, and possessed of considerable cohesive power. In man, that form of cartilage which constitutes the original framework of the body, and which in time becomes ossified throughout the greater part of its extent, is called temporary cartilage. But there is another form of cartilage em- ployed in the construction of the body that is not prone to ossify, viz., permanent cartilage. This is found — 1. In the joints, covering the ends of the bones (articular cartilage) : 2. Forming a considerable part of the solid framework of the chest (costal cartilages) : 3. Arranged in the form of plates or lamellas, of greater or less thickness, which enter into the formation of the external ear, the nose, the eyelids, the Eustachian tube, the larynx, and the windpipe (reticular cartilage). They serve to maintain the shape of canals or passages, or to form tubes that require to be kept permanently open without the expenditure of vital force. Structure. Cartilage consists either of a parenchyma of nucleated cells, or the cells are imbedded in an intercellular substance or matrix. The cells or cartilage corpuscles are contained in hollow cavities or lacunae in thp intercellular substance, which appear to be lined by a firm, clear, or yellowish layer, the cartilage capsule. Under the influence of certain rea»erns, the 181 182 ARTICULATIONS. cartilage cell shrinks up, and is separated from its capsule by a well-marked interval. The car- tilage cells are usually round or oblong, sometimes flattened or fusiform. Each contains a nucleus, furnished occasionally with one or two nucleoli. The nuclei vary from 25 , ( 5n to ^'j,, of an inch; they sometimes contain fat globules, or appear converted into fat. The intercellular substance is either homogeneous, or finely granular, or fibrous. In temporary cartilage, the intercellular substance is not abundant ; but the cartilage cells are numerous, and situated at nearly equal distances apart. The cells vary in shape and size, the majority being round or oval, and their nuclei are minutely granular. When ossification commences in it, the cells become arranged in clusters or rows, the ends of which are directed towards the ossifying part. In articular cartilage, the intercellular substance is more abundant than in the former variety; it appears dim, like ground glass, and has a finely granular or homogeneous aspect. The cells are oval or roundish, from j^ViT to 9 Hjy of an inch, the nuclei small and commonly vesicular, and parent cells are frequently seen inclosing two or more younger cells. On the surface of the cartilage the cells are numerous, and disposed in isolated groups of two, three, or four, the groups being flattened, and lie with their planes parallel to the surface. In the interior, and nearer the bone, they are less numerous, and assume more or less of a linear direction, pointing towards the surface. This arrangement appears to be connected with a corresponding peculiarity of structure in the matrix, and serves to explain the disposition which this form of cartilage has to break in a direction perpendicular to the surface, the broken surface being to the eye striated in the same direction. In the costal cartilages, the intercellular substance is very abundant, finely mottled, and, in certain situations, presents a distinctly fibrous structure, the fibres being fine and parallel. This is most evident in advanced age. The cells, which are collected into groups, are larger than in any other cartilages of the body, being from ^ to T £ 5 of an inch in diameter. Many contain two or more clear transparent nuclei, and some contain oil globules. Near the exterior of the cartilage the cells are flattened, and lie parallel with the surface ; in the interior, the cells have a linear arrangement, the separate rows being turned in all directions. The ensiform cartilage of the sternum, the cartilages of the nose, and the cartilages of the larynx and windpipe (excepting the epiglottis and cornicula laryngis) resemble the costal carti- lages in their microscopic characters. Reticular cartilage. The epiglottis, the cornicula laryngis, the cuneiform cartilages, the carti- lage of the ear, of the eyelid, and of the Eustachian tube, are included in a separate class under the name of " reticular," " yellow," or " spongy" cartilages. They are yellow, of a spongy texture throughout, more flexible than ordinary cartilage, and not prone to ossify. This variety of cartilage consists of an intercellular substance, composed of minute opaque fibres, which inter- sect each other in all directions, and are so arranged as to inclose numerous small oval spaces, in which the cartilage corpuscles are deposited. Articular cartilage forms a thin incrustation upon the articular surfaces of bones, and is admirably adapted, by its elastic property, to break the force of con- cussions, and, by^ts smoothness, to afford perfect ease and freedom of movement between the bones. Where it covers the rounded ends of bones, upon which the greatest pressure is received, it is thick at the centre, and becomes gradually thinner towards the circumference : an opposite arrangement exists where it lines the corresponding cavities. On the articular surfaces of the short bones, as the carpus and tarsus, the cartilage is disposed in a layer of uniform thickness through- out. The attached surface of articular cartilage is closely adapted, by a rough, uneven surface, to the articular lamella ; the free surface is smooth, polished, and partially covered by a perichondrium, prolonged from the periosteum, a short dis- tance over the cartilage ; in the foetus, an extremely thin prolongation of synovial membrane may be traced over the surface of the cartilage, according to Mr. Toynbee, but, at a later period of life, this cannot be demonstrated. Articular cartilage in the adult does not contain bloodvessels; its nutrition being derived from the vessels of the synovial membrane which skirt the circumference of the cartilage, and from those -of the adjacent bone, which are, however, separated from direct contact with the cartilage by means of the articular lamella. Mr. Toynbee has shown, that the minute vessels of the cancellous tissue, as they approach the articular lamella, dilate, and, forming arches, return into the substance of the bone. The vessels of the synovial membrane also advance forwards upon the circum- ference of the cartilage for a very short distance, and then return in loops ; they are only found on the parts not subjected to pressure. In the foetus, the vessels are said, by Toynbee, to advance for some distance upon the surface of the cartilage, beneath the synovial membrane ; but Kolliker, from more recent examination, STRUCTURE OF JOINTS. 183 doubts this. Lymphatic vessels and nerves have not, as yet, been traced in its substance. Fibro-cartilage is also employed, in the construction of the joints, contributing to their strength and elasticity. It consists of a mixture of white fibrous and cartilaginous tissues in various proportions ; it is to the first of these two consti- tuents that its flexibility and toughness is chiefly owing, and to the latter its elasticity. The fibro-cartilages admit of arrangement into four groups, inter- articular, connecting, circumferential, and stratiform. The interarticular fibro-cartilages or menisci are flattened fibro-cartilaginous plates, of a round, oval, or sickle-like form, interposed between the articular car- tilages of certain joints. They are free on both surfaces, thinner toward their centre than at their circumference, and held, in position by their extremities being connected to the surrounding ligaments. The synovial membrane of the joint is prolonged over them a short distance from their attached margin. They are found in the temporo-maxillary, sterno-clavicular, acromio-clavicular, wrist and knee-joints. These cartilages are usually found in those joints most exposed to violent concussions, and. subject to frequent movement. Their use is, to maintain the apposition of the opposed surfaces in their various motions ; to increase the depth of the articular surface, and. give ease to the gliding movement ; to mode- rate the effects of great pressure, and deaden the intensity of the shocks to which they may be submitted. The connecting fibro-cartilages are interposed between the bony surfaces of those joints which admit of only slight mobility, as between the bodies of the vertebrae, and the symphysis of the pubes ; they exist in the form of disks, intimately adhe- rent to the opposed surfaces, being composed of concentric rings of fibrous tissue, with cartilaginous laminae interposed, the former tissue predominating towards the circumference, the latter towards the centre. The circumferential fibro-cartilages consist of a rim of fibro-cartilage, which surrounds the margin of some of the articular cavities, as the cotyloid cavity of the hip, and the glenoid cavity of the shoulder ; they serve to deepen the articular surface and protect the edges of the bone. The stratiform fibro-cartilages are those which form a thin layer in the osseous grooves, through which the tendons of certain muscles glide. Ligaments are found in nearly all the movable articulations ; they consist of bands of various forms, serving to connect together the articular extremities of bones, and composed mainly of bundles of white fibrous tissue placed parallel with, or closely interlaced with, one another, and presenting a white, shining, silvery aspect. Ligament is pliant and flexible, so as to allow of the most perfect freedom of movement, but strong, tough, and inextensile, so as not readily to yield under the most severely applied force ; it is, consequently, admirably adapted to serve as the connecting medium between the bones. Some ligaments consist entirely of yellow elastic tissue, as the ligamenta subflava, which connect together the adjacent arches of the vertebrae, and the ligamentum nuchae. - * Synovial Membrane is a thin, delicate membrane, arranged in the form of a short wide tube, attached by its open ends to the margins of the articular ex- tremities of the bones, and covering the inner surface of the various ligaments which connect the articulating surfaces. It resembles the serous membranes in structure, but differs from them in the nature of its secretion, which is thick, viscid, and glairy, like the white of egg, and hence termed synovia. The synovial membranes found in the body admit of subdivision into three kinds, articular, bursal, and vaginal. The articular synovial membranes are found in all the freely movable joints. In the foetus, this membrane is said, by Toynbee, to be continued over the surface of the cartilages ; but in the adult it is wanting, excepting at their circumference, upon which it encroaches for a short distance : it then invests the inner surface of the capsular or other ligaments inclosing the joint, and is reflected over the surface of any tendons passing through its cavity, as the tendon of tha Popliteus 184 ARTICULATIONS. in the knee, and the tendon of the Biceps in the shoulder. In most of the joints, the synovial membrane is thrown into folds, which project into the cavity. Some of these folds contain large masses of fat. These are especially distinct in the hip and the knee. Others are flattened folds, subdivided at their margins into fringe-like processes, the vessels of which have a convoluted arrangement. The latter generally project from the synovial membrane near the margin of the cartilage, and lie flat upon its surface. They consist of connective tissue, covered with epithelium, and contain fat cells in variable quantity, and, more rarely, isolated cartilage cells. They are found in most of the bursal and vaginal, as well as in the articular synovial membranes, and were described, by Clopton Havers, as mucilaginous glands, and as the source of the synovial secretion. Under certain diseased conditions, similar processes are found covering the entire surface of the synovial membrane, forming a mass of pedunculated nbro-fatty growths, which project into the joint. The bursse are found interposed between surfaces which move upon each other, producing friction, as in the gliding of a tendon, or of the integument over pro- jecting bony surfaces. ' "They admit of subdivision into two kinds, the bursse mucosse and the synovial bursse. The former are large, simple, or irregular cavities in the subcutaneous areolar tissue, inclosing a clear viscid fluid. They are found in various situations, as between the integument and front of the patella, over the olecranon, the malleoli, and other prominent parts. The synovial bursse are found interposed between muscles or tendons as they play over projecting bony surfaces, as between the Glutei muscles and surface of the great trochanter. They consist of a thin wall of connective tissue, partially covered by epithelium, and contain a viscid fluid. Where one of these exists in the neighborhood of a joint, it usually communicates with its cavity, as is generally the case with the bursa between the tendon of the Psoas and Iliacus, and the capsular ligament of the hip, or the one interposed between the under surface of the Subscapularis and the neck of the scapula. The vaginal synovial membranes or synovial sheaths serve to facilitate the gliding of tendons in the osseo-fibrous canals through which they pass. The membrane is here arranged in the form of a sheath, one layer of which adheres to the wall of the canal, and the other is reflected upon the outer surface of the con- tained tendon ; the space between the two free surfaces of the membrane being partially filled with synovia. These sheaths are chiefly found surrounding the tendons of the Flexor and Extensor muscles of the fingers and toes, as they pass through the osseo-fibrous canals in the hand or foot. Synovia is a transparent, yellowish- white, or slightly reddish fluid, viscid like the white of egg, having an alkaline reaction, and slightly saline taste. It consists, according to Frerichs, in the ox, of 94.85 water, 0.56 mucus and epithelium, 0.07 fat, 3.51 albumen and extractive matter, and 0.99 salts. The Articulations are divided into three classes: Synarthrosis, or immovable joints; Amphiarthrosis, or mixed joints; and Diarthrosis, or movable joints. 1. Synarthrosis. Immovable Articulations. Synarthroses (avv, with, apflpoi/, a joint) or Immovable Joints include all those articulations in which the surfaces of the bones are in almost direct contact, not separated by an intervening synovial cavity, and immovably connected with each other, as between the bones of the cranium and face, excepting the lower jaw. The varieties of synarthrosis are three in number ; Sutura, Schindylesis, and Gomphosis. Sutura (a seam). Where the articulating surfaces are connected by a series of processes and indentations interlocked together, it is termed sutura vera ; of which there are three varieties, sutura dentata, sutura serrata and sutura limbosa. The surfaces of the bones are not in direct contact, being separated by a layer of mem- brane continuous externally with the pericranium, internally with the dura mater. SUBDIVISION INTO THREE CLASSES. 185 The sutura dentata {dens, a tooth) is so called from the tooth-like form of the projecting articular processes, as in the suture between the parietal bones. In the sutura serrata (serra, a saw), the edges of the two bones forming the articula- tion are serrated like the teeth of a fine saw, as between the two portions of the frontal bone. In the sutura limbosa {limbus, a selvage), besides the dentated pro- cesses, there is a certain degree of bevelling of the articular surfaces, so that the bones overlap one another, as in the suture between the parietal and frontal bones. Where the articulation is formed by roughened surfaces placed in apposition with one another, it is termed the false suture, sutura nolha, of which there are two kinds, the sutura squamosa (squama, a scale), formed by the overlapping of two contiguous bones by broad bevelled margins, as in the temporo-parietal or squa- mous suture ; and the sutura harmonia (dpuv, to adapt), where there is simple apposition of two contiguous rough bony surfaces, as in the articulation between the two superior maxillary bones, or of the horizontal plates of the palate. Schindylesis (o^cvgvx^atj, a fissure) is that form of articulation in which a thin plate of bone is received into a cleft or fissure formed by the separation of two laminae of another, as in the articulation of the rostrum of the sphenoid, and perpendicular plate of the ethmoid with the vomer, or in the reception of the latter in the fissure between the superior maxillary and palate bones. Gomphosis (y6(it, on all sides, apepov, a joint) or Mixed Articulation. In this form of articulation, the contiguous osseous surfaces are connected together by broad flattened disks of fibro-cartilage, which adhere to the ends of both bones, as in the articulation between the bodies of the vertebrae, and first two pieces of the sternum ; or the articulating surfaces are covered with fibro-cartilage, partially lined by synovial membrane, and connected together by external ligaments, as in the sacro-iliac and pubic symphyses; both these forms being capable of limited motion in every direction. The former resemble the synarthrodial joints in the continuity of their surfaces, and absence of synovial sac ; the latter, the diarthro- dial. These joints occasionally become obliterated in old age : this is frequently the case in the interpubic articulation, and occasionally in the intervertebral and sacro-iliac. 3. Diarthrosis. Movable Articulations. Diarthrosis (Sta, through, apOpov, a joint). This form of articulation includes the greater number of the joints in the body, mobility being their distinguishing character. They are formed by the approximation of two contiguous bony sur- faces, covered with cartilage, connected by ligaments, and lined by synovial membrane. The varieties of joints in this class have been determined by the kind of motion permitted in each, and are four in number: Arthrodia, Enarthrosis, Ginglymus, Diarthrosis Rotatorius. Arthrodia is that form of joint which admits of a gliding movement ; it is formed by the approximation of plane surfaces, or one slightly concave, the other slightly convex ; the amount of motion between them being limited by the liga- ments, or osseous processes, surrounding the articulation, as in the articular processes of the vertebras, temporo-maxillary, sterno-clavicular, and acromioclavi- cular, inferior radio-ulnar, carpal, carpo-metacarpal, superior tibio-fibular, tarsal, and tarso- metatarsal articulations. Enarthrosis is that form of joint which is capable of motion in all directions. It is formed by the reception of a globular head into a deep cup-like cavity (hence the name ball and socket), the parts being kept in apposition by a capsular liga- ment strengthened by accessory ligamentous bands. Examples of this form of articulation are found in the hip and shoulder. 186 ARTICULATIONS. Ginglymus or Hinge-joint (y 177X1^6$, a hinge). In this form of joint, the articular surfaces are moulded to each other in such a manner as to permit motion only in two directions, forwards and backwards, the extent of motion at the same time being considerable. The articular surfaces are connected together bj strong lateral ligaments, which form their chief bond of union. The most perfect forms of ginglymi are the elbow and ankle ; the knee is less perfect, as it allows a slight degree of rotation in certain positions of the limb : there are also the metatarso- phalangeal and phalangeal joints in the lower extremity, and the metacarpo-pha- langeal and phalangeal joints in the upper extremity, Diarthrosis rotatorius or Lateral Ginglymus. Where the movement is limited to rotation, the joint is formed by a pivot-like process turning within a ring, or the ring on the pivot, the ring being formed partly of bone, partly of ligament. In the articulation of the odontoid process of the axis with the atlas, the ring is formed in front by the anterior arch of the atlas; behind, by the transverse liga- ment : here the ring rotates round the odontoid process. In the superior radio • ulnar articulation, the ring is formed partly by the lesser sigmoid cavity of the ulna ; in the rest of its extent, by the orbicular ligament : here the head of the radius rotates within the ring. Subjoined, in a tabular form, are the names, distinctive characters, and examples of the different kinds of articulations. Synarthrosis or Im movable Joint. Sur- faces separated by fibrous membrane, no intervening synovial cavity, and immova- bly connected with each other. Example : bones of the cranium and face, except lower jaw. S. Dentata, having tooth-like processes. Interparietal su • ture. S. Serrata, having Sutura vera ^serrated edges, like '(true), articulation /the teeth of a saw. by indented bor-( Interfrontal su- ders. \ture. I S. Limbosa, having /bevelled margins, I and dentated pro- Sutura. Arti- \ I cesses, culation by pro- J \ Fronto-parietal su- cesses and i ndent- / ture. ations interlocked together. S. Squamosa, form- ed by thin bevelled margins overlapping each other. Sutura notha \ Temporo - parietal (false), articulation /suture. \by rough surfaces. \ S. Harmonia, form- ed by the apposition of contiguous rough surfaces. Intermaxillary su- ture. Schindylesis. Articulation formed by the reception of a thin plate of bone into a fissure of another. Rostrum of sphenoid with vomer. Gomphosis. An articulation formed by the insertion of a conical process into a socket. Tooth in socket. SUBDIVISION INTO THREE CLASSES. 187 / 1. Surfaces connected by nbro-cartilage, not separated by ( synovial membrane, and having limited motion. Bodies of a 1 mpliiarthrosis, ) vertebras. Mixed Articulation.) 2. Surfaces covered by nbro-cartilage; lined by a partial ( synovial membrane. Sacro-iliac and pubic symphyses. Arthrodia. Gliding joint ; articulation by plane surfaces, which glide upon each other. As in sterno- clavicular and acromio-clavicular articulations. Enarthrosis. Ball-and-socket joint ; capable of motion in lall directions. Articulation by a globular head received into Diarthrosis, ' a cup-like cavity. As in hip and shoulder -joints. Movable Joint. / Oinglymus. Hinge joint ; motion limited to two directions, forwards and backwards. Articular surfaces fitted together /so as to permit of movement in one plane. As in the elbow, ankle, andjaiee. Diarthrosis' rotatorius. Articulation by a pivot process turning within a ring, or ring around a pivot. As in supe- Vrior radio-ulnar articulation, and atlo-axoid joint. The Kinds of Movement admitted in Joints. The movements admissible in joints may be divided into four kinds, gliding, angular movement, circumduction, and rotation. Gliding movement is the most simple kind of motion that can take place in a joint, one surface gliding over another. It is common to all movable joints ; but in some, as in the articulations of the carpus and tarsus, is the only motion per- mitted. This movement is not confiried to plane surfaces, but may exist between any two contiguous surfaces, of whatever form, limited by the ligaments which inclose the articulation. Angular movement occurs only between the long bones, and may take place in four directions, forwards or backwards, constituting flexion and extension, or inwards and outwards, which constitutes abduction and adduction. Flexion and extension are confined to the strictly ginglymoid or hinge-joints. Abduction and adduction, combined with flexion and extension, are met with only in the most movable joints ; as in the hip, shoulder, and metacarpal joint of the thumb, and partially in the wrist and ankle. s Circumduction is that limited degree of motion which takes place between the head of a bone and its articular cavity, whilst the extremity and sides of a limb are made to circumscribe a conical space, the base of which corresponds with the inferior extremity of the limb, the apex with the articular cavity ; and is best seen in the shoulder and hip-joints. Botation is the movement of a bone upon its own axis, the bone retaining the same relative situation with respect to the adjacent parts : as in the articulation between the atlas and axis, where the odontoid process serves as a pivot around which the atlas turns ; or in the rotation of the radius upon the humerus, and also in the hip and shoulder. The articulations may be arranged into those of the trunk, those of the upper extremity, and those of the lower extremity. 1 188 ARTICULATIONS. ARTICULATIONS OF THE TRUNK. These may be divided into the following groups, viz : — I. Of the vertebral column. V. Of the ribs with the vertebras. II. Of the atlas with the axis. VI. Of the cartilages of the ribs with III. Of the spine with the cranium. the sternum, and with each other 1. Of the atlas with the occipital bone. VII. Of the sternum. 2. Of the axis with the occipital bone. VIII. Of the pelvis with the spine. IV. Of the lower jaw. IX. Of the pelvis. I. ARTICULATIONS OF THE VERTEBRAL COLUMN. The different segments of the spine are connected together by ligaments, which admit of the same arrangement as the vertebrae. They may be divided into five sets. 1. Those connecting the bodies of the vertebras. 2. Those connecting the laminae. 3. Those connecting the articular processes. 4. The ligaments con- necting the spinous processes. 5. Those of the transverse processes. The articulation of the bodies of the vertebras with each other forms a series of amphiarthrodial joints ; whilst those between the articular processes form a series of arthrodial joints. 1. The Ligaments of the Bodies. Anterior Common Ligament. Posterior Common Ligament. Intervertebral Substance. The Anterior Common Ligament (fig. 116) is a broad and strong band of liga- mentous fibres, which extends along the front surface of the bodies of the vertebras, from the axis to the sacrum. It is broader below than above, and thicker in the dorsal than in the cervical or lumbar regions ; it is also somewhat thicker opposite the front of the body of each vertebra, than opposite the intervertebral substance. It is attached, above, to the body of the axis by a pointed process, which is con- nected with the tendon of origin of the Longus colli muscle ; and extends down as far as the upper bone of the sacrum. It consists of dense longitudinal fibres, which are intimately adherent to the intervertebral substance and prominent margins of the vertebras, but less closely with the middle of the bodies. In the latter situation the fibres are exceedingly thick, and serve to fill up the concavities on their front surface, and to make the anterior surface of the spine more even, This ligament is composed of several layers of fibres, which vary in length, but are closely interlaced with each other. The most superficial or longest fibres extend between four or five vertebras. A second subjacent set extend between two or three vertebras; whilst a third set, the shortest and deepest, extend from one vertebra to the next. At the sides of the bodies, this ligament consists of a few short fibres, which pass from one vertebra to the next, separated from the median portion by large oval apertures, for the passage of vessels. The Posterior Common Ligament is situated within the spinal canal, and extends along the posterior surface of the bodies of the vertebras, from the body of the axis above, where it is continuous with the occipito-axoid ligament., to the sacrum below. It is broader at the upper than at the lower part of the spine, and thicker in the dorsal than in the cervical or lumbar regions. In the situation of the intervertebral substance and contiguous margins of the vertebras, where the ligament is more intimately adherent, it is broad, and presents a series of dentations with intervening concave margins ; but it is narrow and thick over the centre of the bodies, from which it is separated by the venae basis vertebrae. This ligament is composed of smooth, shining, longitudinal fibres, denser and more com- pact than those of the anterior ligament, and composed of a superficial layer OF THE SPINE. 189 occupying the interval between three or four vertebrae, and of a deeper layer, which extends between one vertebra and the next adjacent to it. It is separated from the dura mater of the spinal cord by some loose filamentous tissue, very liable to serous infiltration. The Intervertebral Substance (fig. 116) is a lenticular disk of fibro-cartilage, interposed between the adjacent surfaces of the bodies of the vertebrae, from the axis to the sacrum, forming the chief bond of connection between these bones. These disks vary in shape, size, and thickness, in different parts of the spine. In shape, they accurately correspond with the surfaces of the bodies between which they are placed, being oval in the cervical and lumbar regions, circular in the dorsal. Their size is greatest in the lumbar region. In thinness, they vary not only in the different regions of the spine, but in different parts of the same region : thus, they are uniformly thick in the lumbar region ; thickest, in front, in the cervical and lumbar regions which are convex forwards ; and behind, to a slight extent in the dorsal region. They thus contribute, in a great measure, to the curvatures Fig. 116. — Vertical Section of two Vertebrae and their Ligaments, from the Lumbar Region. ANTERIOR POSTERIOR. COMMON COMMON lltf. IICT of the spine in the neck and loins ; whilst the concavity of the dorsal region is chiefly due to the shape of the bodies of the vertebrae. The intervertebral disks form about one-fourth of the spinal column, exclusive of the first two vertebrae ; they are not equally distributed, however, between the various bones ; the dorsal portion of the spine having, in proportion to its length, a much smaller quantity than in the cervical and lumbar regions, which necessarily gives to the latter parts greater pliancy and freedom of movement. The intervertebral disks are adherent, by their surfaces, to the adjacent parts of the bodies of the vertebrae ; and by their circumference are closely connected in front to the anterior, and behind to the posterior, common ligament ; whilst, in the dorsal region, they are connected laterally to the heads of those ribs which articulate with two vertebrae, by means of the interarticular ligament. They, consequently, form part of the articular cavities in which the heads of these bones are received. The intervertebral substance is composed, at its circumference, of laminae of fibrous tissue and fibro-cartilage ; and, at its centre, of a soft, elastic, pulpy matter. The laminae are arranged concentrically one within the other, with their edges 190 ARTICULATIONS. turned towards the corresponding surfaces of the vertebrae, and consist of alternate plates of fibrous tissue and fibro- cartilage. These plates are not quite vertical in their direction, those near the circumference being curved outwards and closely approximated, whilst those nearest the centre curve in the opposite direction, and are somewhat more widely separated. The fibres of which each plate is composed are directed, for the most part, obliquely from above downwards ; the fibres of an adjacent plate have an exactly opposite arrangement, varying in their direction in every layer ; whilst in some few they are horizontal. This laminar arrangement belongs to about the outer half of each disk, the central part being occupied by a soft, pulpy, highly elastic substance, of a yellowish color, which rises up con- siderably above the surrounding level, when the disk is divided horizontally. This substance presents no concentric arrangement, and consists of white fibrous tissue, having interspersed cells of variable shape and size. The pulpy matter, which is especially well developed in the lumbar region, is separated from imme- diate contact with the vertebrae, by the interposition of thin plates of cartilage. 2. Ligaments connecting the Laminae. Ligamenta Subflava. The Ligamenta Subflava are interposed between the laminaa of the vertebrae, from the axis to the sacrum. They are most distinct when seen from the interior of the spinal canal ; when viewed from the outer surface, they appear short, being overlapped by the laminae. Each ligament consists of two lateral portions, which commence on each side at the root of either articular process, and pass backwards to the point where the laminae converge to form the spinous process, where their margins are thickest, and separated by a slight interval, filled up with areolar tissue. These ligaments consist of yellow elastic tissue, the fibres of which, almost perpendicular in direction, are attached to the anterior surface of the margin of the lamina above, and to the posterior surface, as well as to the margin, of the lamina below. In the cervical region, they are thin in texture, but very broad and long ; they become thicker in the dorsal region, and in the lumbar acquire very consi- derable thickness. Their highly elastic property serves to preserve the upright posture, and to counteract the efforts of the flexor muscles of the spine. These ligaments do not exist between the occiput and atlas, or between the atlas and axis, 3. Ligaments connecting the Articular Process. Capsular. The Capsular Ligaments are thin and loose ligamentous sacs, attached to the contiguous margins of the articulating processes of each vertebra, through the greater part of their circumference, and completed internally by the ligamenta subflava. They are longer and more loose in the cervical than in the dorsal or lumbar regions. The capsular ligaments are lined on their inner surface by synovial membrane. 4. Ligaments connecting the Spinous Processes. Inter-spinous. Supra-spinous. The Inter-spinous Ligaments, thin and membranous, are interposed between the spinous processes in the dorsal and lumbar regions. Each ligament extends from the root to near the summit of each spinous process, and connects together their adjacent margins. They are narrow and elongated in the dorsal region, broader, quadrilateral in form, and thicker in the lumbar region. The Supraspinous Ligament is a strong fibrous cord, which connects together the apices of the spinous processes from the seventh cervical to the spine of the sacrum. It is thicker and broader in the lumbar than in the dorsal region, and intimately blended, in both situations, with the neighboring aponeuroses. The OF THE ATLAS WITH THE AXIS. 191 most superficial fibres of this ligament connect three or four vertebras; those deeper seated pass between two or three vertebras ; whilst the deepest connect the contiguous extremities of neighboring vertebras. 5. Ligaments connecting the Transverse Processes. Inter-transverse. The Inter-transverse Ligaments consist of a few thin scattered fibres, interposed between the transverse processes. They are generally wanting in the cervical region; in the dorsal, they are rounded cords; in the lumbar region, thin and membranous. Actions. The movements permitted in the spinal column are, Flexion, Exten- sion, Lateral movement, Circumduction, and Eotation. In Flexion or movement of the spine forwards, the anterior common ligament is relaxed, and the intervertebral substances are compressed in front; the posterior common ligament, the ligamenta subflava, and the inter-spinous and supra-spinous ligaments are stretched, as well as the posterior fibres of the intervertebral disks. The interspaces between the laminae are widened, and the inferior articular pro- cesses glide upwards, upon the articular processes of the vertebras below. Flexion is the most extensive of all the movements of the spine. In Extension or movement of the spine backwards, an exactly opposite dispo- sition of the parts takes place. This movement is not extensive, being limited by the anterior common ligament, and by the approximation of the spinous processes. Flexion and extension are most free in the lower part of the lumbar, and in the cervical regions ; extension in the latter region being greater than flexion, the reverse of which exists in the lumbar region. These movements are least free in the middle and upper part of the back. In Lateral Movement, the sides of the intervertebral disks are compressed, the extent of motion being limited by the resistance offered by the surrounding liga- ments, and by the approximation of the transverse processes. This movement may take place in any part of the spine, but is most free in the neck and loins. Circumduction is very limited, and is produced merely by a succession of the preceding movements. Rotation is produced by the twisting of the intervertebral substances; this, although only slight between any two vertebras, produces great extent of move- ment, when it takes place in the whole length of the spine, the front of the column being turned to one or the other side. This movement takes place only to a slight extent in the neck, but is more free in the lower part of the dorsal and lumbar regions. It is thus seen, that the cervical region enjoys the greatest extent of each variety of movement, flexion and extension being very free ; lateral movement and rota- tion, although less extensive than the former, being greater than in any other region. In the dorsal region, especially at its upper part, the movements are most limited ; flexion, extension, and lateral motion taking place only to a slight extent. In the lumbar region, all the movements are very free. II. ARTICULATION OF THE ATLAS WITH THE AXIS. The articulation of the anterior arch of the atlas with the odontoid process forms a lateral ginglymoid joint, whilst that between the articulating processes of the two bones forms a double arthrodia. The ligaments of this articulation are the Two Anterior Atlo-axoid. Transverse. Posterior Atlo-axoid. Two Capsular. Of the Two Anterior Atlo-axoid Ligaments (fig. 117), the most superficial is a rounded cord, situated in the middle iine ; attached, above, to the tubercle on the anterior arch of the atlas ; below, to the base of the odontoid process and body of the axis. The deeper ligament is a membranous layer, attached, above, to the 192 ARTICULATIONS. lower border of the anterior arch of the atlas ; below, to the base of the odontoid process, and body of the axis. These ligaments are in relation, in front, with the .Recti antici majores. Fig. 117. — Occipito-atloid and Atlo-axoid Ligaments. Anterior View. 10 J CAPSULAR LICT It J SYNOVIAL M EMORANS AXOIO f CAPSULAR LICT 6c SYNOVIAL MEMO RAN 6 Fig. 118. — Occipito-atloid and Atlo-axoid Ligaments. Posterior View. Arch forjiaasagi ofVeTuLraZAra &, 1t? Ct-rvical i The Posterior Atlo-axoid Ligament (fig. 118) is a broad and thin membranous Layer, attached, above, to the lower border of the posterior arch of the atlas ; OF THE SPINE WITH THE CRANIUM. 193 below, to the upper edge of the lamina of the axis. This ligament supplies the place of the ligamenta subflava, and is in relation, behind, with the Inferior oblique muscles. The Transverse Ligament (figs. 119 and 120) is a thick and strong ligamentous band, which arches across the ring of the atlas, and serves to retain the odontoid process in firm connection with its anterior arch. This ligament is flattened from before backwards, broader and thicker in the middle than at either extremity, and firmly attached on each side of the atlas to a small tubercle on the inner surface of each of its lateral masses. As it crosses the odontoid process, a small fasciculus is derived from its upper and lower borders ; the former passing upwards, to be inserted into the basilar process of the occipital bone ; the latter downwards, to Fig. 119. — Articulation between Odontoid Process and Atlas. be attached to the root of the odontoid process : hence, this ligament has received the name of cruciform. The transverse ligament divides the ring of the atlas into two unequal parts : of these, the posterior and larger serves for the transmission of the coed and its membranes ; the anterior and smaller serving to retain the odontoid process in its position. The lower border of the space between the atlas and transverse ligament being smaller than the upper, on account of the transverse ligament embracing firmly the narrow neck of the odontoid process, this process is retained in firm connection with the atlas when all the other ligaments have been divided. The Capsular Ligaments are two thin and loose capsules, connecting the articu- lar surfaces of the atlas and axis, the fibres being strongest on the anterior and external part of the articulation. There are four Synovial Membranes in this articulation. One lining the inner surface of each of the capsular ligaments ; one between the anterior surface of the odontoid process and anterior arch of the atlas ; and one between the posterior surface of the odontoid process and the transverse ligament. The latter often communicates with those between the condyles of the occipital bone and the articular surfaces of the atlas. Actions. This joint is capable of great mobility, and allows the rotation of the atlas, and, with it, of the cranium upon the axis, the extent of rotation being limited by the odontoid ligaments. III. ARTICULATION OF THE SPINE WITH THE CRANIUM. The ligaments connecting the spine with the cranium may be divided into two sets : 1. Those connecting the occipital bone with the atlas ; 2. Those connecting the occipital bone with the axis. 13 194 ARTICULATIONS. 1. Articulation of the Atlas with the Occipital Bone. This articulation is a double arthrodia. Its ligaments are the Two Anterior Occipito-atloid. Posterior Occipito-atloid. Two Lateral Occipito-atloid. Two Capsular. Of the Two Anterior Ligaments (fig. 117), the most superficial is a strong narrow, rounded cord, attached, above, to the basilar process of the occiput; below, to the tubercle on the anterior arch of the atlas : the deeper ligament is a broad and thin membranous layer, which passes between the anterior margin of the foramen magnum above, and the whole length of the upper border of the anterior arch of the atlas below. This ligament is in relation, in front, with the Recti antici minores ; behind, with the odontoid ligaments. The Posterior Occipito-atloid Ligament (fig. 118) is a very broad but thin mem- branous lamina, intimately blended with the dura mater. It is connected, above, to the posterior margin of the foramen magnum; below, to the upper border of the posterior arch of the atlas. This ligament is incomplete at each side, and forms, with the superior intervertebral notch, an opening for the passage of the vertebral artery and suboccipital nerve. It is in relation, behind, with the Recti postici minores and Obliqui superiores; in front, with the dura mater of the spinal canal, to which it is intimately adherent. Fig. 120. — Occipito-axoid and Atlo-axoid Ligaments. Posterior View. He Vertical fierfitn &/OOONTCID LIC:? OCCIXTOI CAPSULAR LICT A atlOiD j Synovial membrane ATLO-f CAPSULAR LICT s, MOID [Synovia I membrane The Lateral Ligaments are strong fibrous bands, directed obliquely upwards and inwards, attached, above, to the jugular process of the occipital bone; below, to the base of the transverse process of the atlas. The Capsular Ligaments surround the condyles of the occipital bone, and con- dect them with the articular surfaces of the atlas ; they consist of thin and loose capsules, which inclose the synovial membrane of the articulation. The synovial membranes between the occipital bone and atlas communicate occasionally with TEMPORO-MAXILLARY. 195 that between the posterior surface of the odontoid process and transverse liga- ment. Actions. The movements permitted in this joint are flexion and extension, which give rise to the ordinary forward or backward nodding of the head, besides slight lateral motion to one or the other side. When either of these actions is carried beyond a slight extent, the whole of the cervical portion of the spine assists in its production. 2. Articulation of the Axis with the Occipital Bone. Occipito-axoid. Three Odontoid. To expose these ligaments, the spinal canal should, be laid open by removing the posterior arch of the atlas, the laminae and spinous process of the axis, and that portion of the occipital bone behind the foramen magnum, as seen in fig. 120. The Occipito-axoid Ligament (Apparatus ligamentosus colli) is situated at the upper part of the front surface of the spinal canal. It is a broad and strong ligamentous band, which covers the odontoid process and its ligaments, and appears to be a prolongation upwards of the posterior common ligament of the spine. It is attached, below, to the posterior surface of the body of the axis, and becoming expanded as it ascends, is inserted into the basilar groove of the occipital bone, in front of the foramen magnum. Relations. By its anterior surface, it is intimately connected with the transverse ligament ; by its posterior surface with the dura mater. By dividing this ligament transversely across, and turning its ends aside, the transverse and odontoid liga- ments are exposed. The Odontoid or Check Ligaments are strong rounded fibrous cords, which arise one on either side of the apex of the odontoid process, and passing obliquely upwards and outwards, are inserted into the rough depressions on the inner side of the condyles of the occipital bone. In the triangular interval left between these ligaments and the margin of the foramen magnum, a third strong ligamentous band (ligamentum suspensorium) may be seen, which passes almost perpendicularly from the apex of the odontoid process to the anterior margin of the foramen, being intimately blended with the anterior occipito-atloid ligament, and upper fasciculus of the transverse ligament of the atlas. Actions. The odontoid ligaments serve to limit the extent to which rotation of the cranium may be carried ; hence they have received the name of check ligaments. IY. TEMPORO-MAXILLARY" ARTICULATION. This articulation is a double arthrodia. The parts entering into its formation are, on each side, the anterior part of the glenoid cavity of the temporal bone and the eminentia articularis above; with the condyle of the lower jaw below. The ligaments are the following: — External Lateral. Stylo-maxillary. Internal Lateral. Capsular. Interarticular Fibro-cartilage. The External Lateral Ligament (fig. 121) is a short, thin, and narrow fasciculus, attached above to the outer surface of the zygoma and to the rough tubercle on its lower border ; below, to the outer surface and posterior border of the neck of the lower jaw. This ligament is broader above than below; its fibres are placed parallel with one another, and directed obliquely downwards and back- wards. Externally, it is covered by the parotid gland and by the integument. Internally, it is in relation with the interarticular fibro-cartilage and the synovial membranes. 196 ARTICULATIONS. The Internal Lateral Ligament (fig. 122) is a long, thin, and loose "band, attached above to the spinous process of the sphenoid bone, and, becoming broader as it descends, is inserted into the inner margin of the dental foramen. Its outer Fig. 121. — Temporo-maxillary Articulation. External View. si surface is in relation above with the External pterygoid muscle; lower down it is separated from the neck of the condyle by the internal maxillary artery; and still more inferiorly the in- Fig. 122. — Temporo-maxillary Articulation. Internal View. ferior dental vessels and nerve separate it from the ramus of the jaw. Internally it is in rela- tion with the Internal pterygoid. The Stylo-maxillary Ligament is a thin apo- neurotic cord, which ex- tends from near the apex ' of the styloid process of the temporal bone, to the angle and posterior border of the ramus of the lower jaw, between the Masseter and In- ternal pterygoid mus- cles. This ligament separates the parotid from the submaxillary gland, and has attached to its inner side, part of the fibres of origin of the Stylo-glossus muscle. Although usually classed among the ligaments of the law, it can only be considered as an accessory in the articulation. TEMP ORO-M AXILLARY. 197 Articulation. The Capsular Ligament consists of a thin and loose ligamentous capsule, attached above to the circumference of the glenoid cavity and the articular surface immediately in front; below, to the neck of the condyle of the lower jaw. It consists of a few, thin scattered fibres, and can hardly be considered as a distinct ligament ; it is thickest at the back part of the articulation. The Interarticular fibro-cartilage (fig. 123) is a thin plate of an oval form, placed horizontally between the condyle of the jaw and the glenoid cavity. Its upper surface is concave from before backwards, and a little convex transversely, to accommodate itself to the form of the glenoid cavity. Its under sur- s * ction of Temporo-m face, where it is in contact with the condyle, is concave. Its circumfer- ence is- connected externally to the external lateral ligament, internally to the capsular ligament ; and in front ^^ ' KSPf^^ / to the tendon of the External ptery- ^ goid muscle. It is thicker at its cir- cumference, especially behind, than at its centre, where it is sometimes perforated. The fibres of which it is composed have a concentric ar- rangement, more apparent at the cir- cumference than at the centre. Its surfaces are smooth, and divide the joint into two cavities, each of which is furnished with a separate synovial membrane. When the fibro-cartilage is perforated, the synovial membranes are continuous with one another. The Synovial Membranes, two in number, are placed one above, and the other below, the fibro-cartilage. The upper one, the larger and looser of the two, is con- tinued from the margin of the cartilage covering the glenoid cavity and eminentia articularis, over the upper surface of the fibro-cartilage. The lower one is inter- posed between the under surface of the fibro-cartilage and the condyle of the jaw, being prolonged downwards a little further behind than in front. The Nerves of this joint are derived from the auriculo-temporal, and masseteric branches of the inferior maxillary. Actions. The movements permitted in this articulation are very extensive. Thus, the jaw may be depressed or elevated, or it may be carried forwards or backwards, or from side to side. It is by the alternation of these movements performed in succession, that a kind of rotatory movement of the lower jaw upon the upper takes place, which materially assists in the mastication of the food. If the movement of depression is carried only to a slight extent, the condyles remain in the glenoid cavities, their anterior part descending only to a slight extent ; but if depression is considerable, the condyles glide from the glenoid fossae on to the eminentia articularis, carrying with them the interarticular fibro-cartilages. When this movement is carried to too great an extent, as, for instance, during a convulsive yawn, dislocation of the condyle into the zygomatic fossa occurs; the interarticular cartilage being carried forwards, and the capsular ligament rup- tured. When the jaw is elevated, the condyles and fibro-cartilages are carried backwards into their original position. When the jaw is carried forwards or backwards, a horizontal gliding movement of the fibro-cartilages and condyles upon the glenoid cavities takes place in the antero-posterior direction j whilst in the movement from side to side, this occurs in the lateral direction. Y. ARTICULATION OF THE RIBS WITH THE VERTEBRAE. The articulation of the ribs with the vertebral column may be divided into two sets. 1. Those which connect the heads of the ribs with the bodies of the verte- 198 ARTICULATIONS. Fig. 124. — Costovertebral and Costo-transverse Articulations. Anterior View. brae ; 2. Those which connect the neck and tubercle of the ribs with the trans- verse processes. 1. Akticulation between the Heads of the Ribs and the Bodies OF THE VeKTEBB^!. These constitute a series of angular ginglymoid joints, formed by the articula- tion of the heads of the ribs with the cavities on the contiguous margins of the bodies of the dorsal vertebrae, connected together by the following ligaments : — Anterior Costo- vertebral or Stellate. Capsular. Interarticular. The Anterior Costo-vertebral or Stellate Ligament (fig. 124) connects the anterior part of the head of each rib, with the sides of the bodies of the vertebrae, and the intervening in- tervertebral disk. It con- sists of three flat bundles of ligamentous fibres, which radiate from the anterior part of the head of the rib. The superior fasciculus passes up- wards to be connected with the body of the vertebra above ; the in- ferior one descends to the body of the vertebra below; and the middle one, the smallest and least distinct, passes ho- rizontally inwards to be attached to the interver- tebral substance. delations. In front, with the thoracic ganglia of the sympathetic, the pleura, and, on the right side, with the vena azygos major ; behind, with the interarticular ligament and synovial membranes. In the first rib, which articulates with a single vertebra only, this ligament does not present a distinct division into three fasciculi ; its superior fibres, however, pass to be attached to the body of the last cervical vertebra, as well as to the body of the vertebra with which the rib articulates. In the eleventh and twelfth ribs, which also articulate with a single vertebra, the same division does not exist ; but the upper fibres of the ligament, in each case, are connected with the vertebra above, as well as to that with which the ribs articulate. The Capsular Ligament is a thin and loose ligamentous bag, which surrounds the joint between the head of the rib and the articular cavity formed by the junc- tion of the vertebrae. It is very thin, firmly connected with the anterior ligament, and most distinct at the upper and lower parts of the articulation. The Interarticular Ligament is situated in the interior of the joint. It consists of a short band of fibres, flattened from above downwards, attached by one extremity to the sharp crest on the head of the rib, and by the other to the intervertebral disk. It divides the joint into two cavities, which have no communication with one another, and are each lined by a separate synovial membrane. In the first. Xju.tr SytiovtaZ COSTO- TRANSVERSE. 199 eleventh, and twelfth ribs, the interarticular ligament does not exist; consequently, there is but one synovial membrane. Actions. The movements permitted in these articulations are limited to eleva- tion, depression, and slightly forwards and backwards. This movement varies, however, very much in its extent in different ribs. The first rib is almost entirely immovable, excepting in deep inspiration. The movement of the second rib is also not very extensive. In the other ribs, their mobility increases successively to the last two, which are very movable. The ribs are generally more movable in the female than in the male. 2. Articulation between the Neck and Tubercle of the Ribs with the Transverse Processes. The ligaments connecting these parts, are : — Anterior Costo-transverse. Middle Costo-transverse (Interosseous). Posterior Costo-transverse. Capsular. The Anterior Costo-transverse Ligament (fig. 125) is a broad and strong band of fibres, attached, below, to the sharp crest on the upper border of the neck of each rib, and passing obliquely upwards and outwards, to the lower border of the Fig. 125. — Costo-transverse Articulation. Seen from above. ANTERIO* COSTO-TRANSVERSE LI C MIDDLE COSTO-TRANSVERSE or, INTEROSSEOUS SYNOVIAL CAVITY POSTERIOR COSTO-TRANSVERSE CAPSULAR MEMBRANC transverse process immediately above. It is broader below than above, broader and thinner between the lower ribs than between the upper, and more distinct in front than behind. This ligament is in relation, in front, with the intercostal vessels and nerves; behind, with the Longissimus dorsi. Its internal border completes an aperture formed between it and the articular processes, through which pass the posterior branches of the intercostal vessels and nerves. Its ex- ternal border is continuous with a thin aponeurosis, which covers the External intercostal muscle. The first and last ribs have no anterior costo-transverse ligament. The Middle Costo-transverse or Interosseous Ligament consists of short, but strong, fibres, which pass between the rough surface on the posterior part of the 200 ARTICULATIONS. neck of each rib, and the anterior surface of the adjacent transverse process. In order fully to expose this ligament, a horizontal section should be made across the transverse process and corresponding part of the rib ; or the rib may be forcibly separated from the transverse process, and its fibres torn asunder. In the eleventh and twelfth ribs, this ligament is quite rudimentary. The Posterior Costo-transverse Ligament is a short, but thick and strong fasci- culus, which passes obliquely from the summit of the transverse process to the rough non-articular portion of the tubercle of the rib. This ligament is shorter and more oblique in the upper than in the lower ribs. Those corresponding to the superior ribs ascend, and those of the inferior ones slightly descend. In the eleventh and twelfth ribs, this ligament is wanting. The articular portions of the tubercle of the rib, and adjacent transverse pro- cess, form an arthrodial joint, provided with a thin capsular ligament attached to the circumference of the articulating surfaces, and inclosing a small synovial membrane. In the eleventh and twelfth ribs, this articulation is wanting. Actions. The movement permitted in these joints is limited to a slight gliding motion of the articular surfaces one upon the other. VI. ARTICULATION OF THE CARTILAGES OF THE RIBS WITH THE STERNUM. The articulations of the cartilages of the true ribs with the sternum are arthro- dial joints. The ligaments connecting them are : — Anterior Costo-sternal. Posterior Costo-sternal. Capsular. The Anterior Costo-sternal Ligament (fig. 126) is a broad and thin membranous band that radiates from the inner extremity of the cartilages of the true ribs, to the anterior surface of the sternum. It is composed of fasciculi, which pass in different directions. The superior fasciculi ascend obliquely, the inferior pass obliquely downwards, and the middle fasciculi horizontally. The superficial fibres of this ligament are the longest ; they intermingle with the fibres of the ligaments above and below them, with those of the opposite side, and with the tendinous fibres of origin of the Pectoralis major ; forming a thick fibrous membrane, which covers the surface of the sternum. This is more distinct at the lower than at the upper part. The Posterior Costo-sternal Ligament* less thick and distinct than the anterior, is composed of fibres which radiate from the posterior surface of the sternal end of the cartilages of the true ribs, to the posterior surface of the sternum, becom- ing blended with the periosteum. The Capsular Ligament surrounds the joints formed between the cartilages of the true ribs and the sternum. It is very thin, intimately blended with the anterior and posterior ligaments, and strengthened at the upper and lower part of the articulation by a few fibres, which pass from the cartilage to the side of the sternum. These ligaments protect the synovial membranes. Synovial Membranes. The cartilage of the first rib is directly continuous with the sternum, the synovial membrane being absent. The cartilage of the second rib is connected with the sternum by means of an interarticular ligament, attached by one extremity to the cartilage of the second rib, and by the other extremity to the cartilage which unites the first and second pieces of the sternum. This articulation is provided with two synovial membranes. That of the third rib has also two synovial membranes; and that of the fourth, fifth, sixth, and seventh, each a single synovial membrane. Thus there are eight synovial cavities in the articulations between the costal cartilages of the true ribs and the sternum. They COSTO-STERNAL AND INTERCOSTAL. 201 may be demonstrated by removing a thin section from the anterior surface of the sternum and cartilages, as seen in fig. 126. After middle life, the articular surfaces lose their polish, become roughened, and the synovial membranes appear to be wanting. In old age, the articulations do not exist, the cartilages of most of the ribs becoming firmly united to the sternum. The cartilage of the seventh Fig. 126. — Costo^sternal, Costo-xiphoid, and Intercostal Articulations. Anterior View. The eynovidl cavities expoted by a vcrUcal section, {f the Sternum k Cxrtuageff continuous with SttmuMr 1 NTCR-ARTICU IAR 1 1 C ! two iSynovva,LmemoraneS Single Synovial Membrane rib, and occasionally also that of the sixth, is connected to the anterior surface of the ensiform appendix, by a band of ligamentous fibres, which varies in length and breadth in different subjects. It is called the costo-xiphoid ligament. Actions. The movements which are permitted in the costo-sternal articulations are limited to elevation and depression ; and these only to a slight extent ; 202 ARTICULATIONS. Articulation of the Cartilages of the Ribs with each other. The cartilages of the sixth, seventh, and eighth ribs articulate, by their lower borders, with the corresponding margin of the adjoining cartilages, by means of a small, smooth, oblong-shaped facet. Each articulation is inclosed in a thin capsular ligament, lined by synovial membrane, and strengthened externally and internally by ligamentous fibres (intercostal ligaments), which pass from one cartilage to the other. Sometimes the cartilage of the fifth rib, more rarely that of the ninth, articulates, by its lower border, with the adjoining cartilage by a small oval facet; more frequently they are connected together by a few ligamentous fibres. Occasionally, the articular surfaces above mentioned are found wanting. Articulation of the Ribs with their Cartilages. The outer extremity of each costal cartilage is received into a depression in the sternal end of the ribs, and held together by the periosteum. Fig. 127. — Articulations of Pelvis and Hip. Anterior View. Jihirim-r of eomnumieukon Jiurstt of PSOAS Ml. ILIACLJ VII. LIGAMENTS OF THE STERNUM. The first and second pieces of the Sternum are united by a layer of cartilage which rarely ossifies, except at an advanced period of life. These two segments are connected by an anterior and posterior ligament. The anterior sternal ligament consists of a layer of fibres, having a longitudinal direction; it blends with the fibres of the anterior costo-sternal ligaments on both sides, and with the aponeurosis of origin of the Pectoralis major. This ligament is rough, irregular, and much thicker at the lower than at the upper part of the bone. SACRO-ILIAC. 203 The posterior sternal ligament is disposed in a somewhat similar manner on ths posterior surface of the articulation. VIII. ARTICULATIONS OF THE PELVIS WITH THE SPINE. The ligaments connecting the last lumbar vertebra with the sacrum are similar to those which connect the segments of the spine with each other, viz. : 1. The continuation downwards of the anterior and posterior common ligaments. 2. The intervertebral substance connecting the flattened oval surfaces of the two bones, thus forming an amphiarthrodial joint. 3. Ligamenta subflava, connecting the arch of the last lumbar vertebra with the posterior border of the sacral canal. 4. Capsular ligaments connecting the articulating processes and forming a double arthrodia. 5. Inter-spinous and supra-spinous ligaments. The two proper ligaments connecting the pelvis with the spine are the lumbo- sacral and lumbo-iliac. The Lumbosacral Ligament (fig. 127) is a short, thick, triangular fasciculus, connected above to the lower and front part of the transverse process of the last lumbar vertebra, and, passing obliquely outwards, is attached below to the lateral Fig. 128. — Articulations of Pelvis and Hip. Posterior View. surface of the base of the sacrum, becoming blended with the anterior sacro-iliac ligament. This ligament is in relation in front with the Psoas muscle. The Lumbo-iliac Ligament (fig. 127) passes horizontally outwards from the apex of the transverse process of the last lumbar vertebra, to that portion of the crest of the ilium immediately in front of the sacro-iliac articulation. It is of a triangular form, thick and narrow internally, broad and thinner externally. It is in relation, in front, with the Psoas muscle ; behind, with the muscles occupying the vertebral groove ; above, with the Quadratus lumborum. 204 ARTICULATIONS. IX. ARTICULATIONS OF THE PELVIS. The Ligaments connecting the bones of the pelvis with each other may be divided into four groups. 1. Those connecting the sacrum and ilium. 2. Those passing between the sacrum and ischium. 3. Those connecting the sacrum and coccyx. 4. Those between the two pubic bones. 1. Articulation of the Sacrum and Ilium. The sacro-iliac articulation is an amphiarthrodial joint, formed between the lateral surfaces of the sacrum and ilium. The anterior or auricular portion of each articular surface is covered with a thin plate of cartilage, thicker on the sacrum than on the ilium. The surfaces of these cartilages in the adult are rough and irregular, and separated from one another by a soft yellow pulpy substance. At an early period of life, occasionally in the adult, and in the female during pregnancy, they are smooth and lined by a delicate synovial membrane. The ligaments connecting these surfaces are the anterior and posterior sacro-iliac. The Anterior Sacro-iliac Ligament consists of numerous thin ligamentous bands, which connect the anterior surfaces of the sacrum and ilium. The Posterior Sacro-iliac (fig. 128) is a strong interosseous ligament, situated in the deep depression between the sacrum and ilium behind, and forming the chief bond of connection between these bones. It consists of numerous strong fasciculi, which pass between the bones in various directions. Three of these are of large size ; the two superior, nearly horizontal in direction, arise from the first and second transverse tubercles on the posterior surface of the sacrum, and are inserted into the rough uneven surface at the posterior part of the inner surface of the ilium. The third fasciculus, oblique in direction, is attached by one ex- tremity to the third or fourth transverse tubercle on the posterior surface of the sacrum, and by the other to the posterior superior spine of the ilium ; it is some- times called the oblique sacro-iliac ligament. 2. Articulation of the Sacrum and Ischium. The Great or Posterior Sacro-sciatic . The Lesser or Anterior Sacro-sciatic. The Great or Posterior Sacro-sciatic Ligament is situated at the lower and back part of the pelvis. It is thin, flat, and triangular in form, narrower in the middle than at the extremities, attached by its broad base to the posterior inferior spine of the ilium, to the third and fourth transverse tubercles on the sacrum, and to the lower part of the lateral margin of that bone and the coccyx; passing obliquely downwards, outwards, and forwards, it becomes narrow and thick, and, at its insertion into the inner margin of the tuberosity of the ischium, it increases in breadth, and is prolonged forwards along the inner margin of the ramus forming the falciform ligament. The free concave edge of this ligament has attached to it the obturator fascia, with which it forms a kind of groove, protecting the internal pudic vessels and nerve. One of its surfaces is turned towards the perineum, the other towards the Obturator internus muscle. The posterior surface of this ligament gives origin, by its whole extent, to fibres of the Gluteus maximus. Its anterior surface is united to the lesser sacro-sciatic ligament. Its superior border forms the lower boundary of the lesser sacro-sciatic foramen. Its lower border forms part of the boundary of the perineum. This ligament is pierced by the coccygeal branch of the sciatic artery. The Lesser or Anterior Sacro-sciatic Ligament, much shorter and smaller than the preceding, is thin, triangular in form, attached by its apex to the spine of the ischium, and internally, by its broad base, to the lateral margin of the sacrum and coccyx, anterior to the attachment of the great sacro-sciatic ligament, with which its fibres are intermingled. SACRO-COCCYGEAL. 205 It is in relation, anteriorly, with the Coccygeus muscle ; posteriorly, it is covered by the posterior ligament, and crossed by the pudic vessels and nerve. Its supe- rior border forms the lower boundary of the great sacro-sciatic foramen ; its infe- rior border, part of the lesser sacro-sciatic foramen. These two ligaments convert the sacro-sciatic notches into foramina. The superior or great sacro-sciatic foramen is bounded, in front and above, by the pos- terior border of the os innominatum ; behind, by the great sacro-sciatic ligament ; and below, by the lesser ligament. It is partially filled up, in the recent state, by the Pyriformis muscle. Above this muscle, the gluteal vessels and nerve emerge from the pelvis ; and below it, the ischiatic vessels and nerves, the internal pudic vessels and nerve, and the nerve to the Obturator internus. The inferior or lesser sacro-sciatic foramen is bounded, in front, by the tuber ischii ; above, by the spine and lesser ligament; behind, by the greater ligament. It transmits the tendon of the Obturator internus muscle, its nerve, and the pudic vessels and nerve. 3. Articulation of the Sacrum and Coccyx. This articulation is an amphiarthrodial joint, formed between the oval surface on the summit of the sacrum, and the base of the coccyx. It is analogous to the joints between the bodies of the vertebrae, and is connected by similar ligaments. They are the — Anterior Sacro-coccygeal. Posterior Sacro-coccygeal. Interarticular Fibro-cartilage. The Anterior Sacro-coccygeal Ligament consists of a few irregular fibres, which descend from the anterior surface of the sacrum to the front of the coccyx, becom- ing blended with" the periosteum. The Posterior Sacro-coccygeal Ligament is a flat band of ligamentous fibres, of a pearly tint, which arises from the margin of the lower orifice of the sacral canal, and descends to be inserted into the posterior surface of the coccyx. This liga- ment completes the lower and back part of the sacral canal. Its superficial fibres are much longer than the deep-seated ; the latter extend from the apex of the sacrum to the upper cornua of the coccyx. This ligament is in relation in front with the arachnoid membrane of the sacral canal, a portion of the sacrum, and almost the whole of the posterior surface of the coccyx ; behind with the Gluteus maximus. An Interarticular Fibro-cartilage is interposed between the contiguous surfaces of the sacrum and coccyx ; it differs from that interposed between the bodies of the vertebrae, in being thinner, and its central part more firm in texture. It is somewhat thicker in front and behind, than at the sides. Occasionally a synovial membrane is found where the coccyx is freely movable, which is more especially the case during pregnancy. The different segments of the coccyx are connected together by an extension downwards of the anterior and posterior sacro-coccygeal ligaments, a thin annular disk of fibro-cartilage being interposed between each of the bones. In the adult male all the pieces become ossified ; but in the female, this does not commonly occur until a later period of life. The separate segments of the coccyx are first united, and at a more advanced age the joint between the sacrum and the coccyx. Actions. The movements which take place between the sacrum and coccyx, and between the different pieces of the latter bone, are slightly forwards and back- wards ; they are very limited. Their mobility increases during pregnancy. 4. Articulation of the Pubes. The articulation between the pubic bones is an amphiarthrodial joint, formed 206 ARTICULATIONS. by the junction of the two oval surfaces which has received the name of the symphysis. The ligaments of this articulation are the — Anterior Pubic. Posterior Pubic. Superior Pubic. Subpubic. Interarticular Fibro-cartilage. The Anterior Pubic Ligament consists of several superimposed layers, which pass across the front of the articulation. The superficial fibres pass obliquely from one bone to the other, decussating and forming an interlacement with the fibres of the aponeurosis of the External oblique muscle. The deep fibres pass transversely across the symphysis, and are blended with the interarticular fibro- cartilage. The Posterior Pubic Ligament consists of a few thin, scattered fibres, which unite the two pubic bones posteriorly. The Superior Pubic Ligament is a band of fibres, which connects together the two pubic bones superiorly. The Subpubic Ligament is a thick, triangular arch of ligamentous fibres, con- necting together the two pubic bones below, and forming the upper boundary of the pubic arch. Above, it is blended with the interarticular fibro-cartilage; laterally, with the rami of the pubes. Its fibres are of a yellowish color, closely connected, and have an arched direction. Fig. 129. — Vertical Section of the Symphysis Pubis. Made near its Posterior Surface. Two Flhro-Cartilaginoiis plates In.twmejlia.te elaeUc tissue Synovial cavity at upper &■ haek part The Interarticular Fibro-cartilage consists of two oval-shaped plates, one cover- ing the surface of each symphysis pubis. They vary in thickness in different subjects, and project somewhat beyond the level of the bones, especially behind. The outer surface of each plate is firmly connected to the bone by a series of nipple-like processes, which accurately fit within corresponding depressions on the osseous surface. Their opposed surfaces are connected, in the greater part of their extent, by an intermediate fibrous elastic tissue ; and by their circumference to the various ligaments surrounding the joint. An interspace is left between the plates at the upper and back part of the articulation, where the fibrous tissue is deficient, and the surface of the fibro-cartilage is lined by epithelium. The space is found at all periods of life, both in the male and female ; but it is larger in the latter, especially during pregnancy, and after parturition. It is most frequently limited to the upper and back part of the joint ; but it occasionally reaches to the front, and may extend the entire length of the cartilages. This structure may be easily demonstrated, by making a vertical section of the symphysis pubis near its pos- terior surface. STERNO-CLAVICULAR. 207 The Obturator Ligament is a dense membranous layer, consisting of fibres which interlace in various directions. It is attached to the circumference of the obtu- rator foramen, which it closes completely, except at its upper and outer part, where a small oval canal is left for the passage of the obturator vessels and nerve. It is in relation, in front, with the Obturator externus ; behind, with the Obtura- tor internus ; both of which muscles are in part attached to it. ARTICULATIONS OF THE UPPER EXTREMITY. The articulations of the Upper Extremity may be arranged into the following groups: — 1. Sterno-clavicular articulation. 2. Scapuloclavicular articulation. 3. Ligaments of the Scapula. 4. Shoulder-joint. 5. Elbow-joint. 6. Radio- ulnar articulation. 7. Wrist-joint. 8. Articulations of the Carpal bones. 9. Carpo-metacarpal articulations. 10. Metacarpo-phalangeal articulations. 1L Articulations of the Phalanges. Fig. 130. — Sterno-clavicular Articulation. Anterior View. 1. Sterno-clavicular Articulation. The Sterno-clavicular is an arthrodial joint. The parts entering into its forma- tion are the sternal end of the clavicle, the upper and lateral part of the first piece of the sternum, and the cartilage of the first rib. The articular surface of the clavicle is much longer than that of the sternum, and invested with a layer of cartilage, 1 which is considerably thicker than that on the latter bone. The ligaments of this joint are the Anterior Sterno-clavicular. Interclavicular. Posterior Sterno-clavicular. Costo-clavicular or rhomboid. Interarticular Fibro-Cartilage. The Anterior Sterno-clavicular Ligament is a broad band of ligamentous fibres, which covers the anterior surface of the articulation, being attached, above, to the upper and front part of the inner extremity of the clavicle ; and, passing obliquely downwards and inwards, is attached, below, to the front and upper part of the first piece of the sternum. This ligament is covered in front by the sternal por- 1 According to Bruch, the sternal end of the clavicle is covered by a tissue which is more fibrous than cartilaginous in structure. 208 ARTICULATIONS. tion of the Sterno-cleido-mastoid and the integument; behind, it is in relation with the interarticular fibro-cartilage and the two synovial membranes. The Posterior Sternoclavicular Ligament is a broad band of fibres, which covers the posterior surface of the articulation, being attached, above, to the posterior part of the inner extremity of the clavicle ; and, passing obliquely downwards and inwards, is connected, below, to the posterior and upper part of the sternum. It is in relation, in front, with the interarticular fibro-cartilage and synovial mem- branes ; behind, with the Sterno-hyoid and Sterno-thyroid muscles. The Interclavicular Ligament is a flattened ligamentous band, which varies considerably in form and size in different individuals ; it passes from the upper part of the inner extremity of one clavicle to the other, and is closely attached to the upper margin of the sternum. It is in relation, in front, with the integument ; behind with the Sterno-thyroid muscles. The Costo-clavicular or rhomboid Ligament is a short, flat, and strong band of ligamentous fibres of a rhomboid form, attached, below, to the upper and inner part of the cartilage of the first rib ; and, ascending obliquely backwards and out- wards, is attached, above, to the rhomboid depression on the under surface of the clavicle. It is in relation, in front, with the tendon of origin of the Subclavius ; behind, with the subclavian vein. The Interarticular Fibro-cartilage is a flat and nearly circular disk, interposed between the articulating surfaces of the sternum and clavicle. It is attached, above, to the upper and posterior border of the clavicle ; below, to the cartilage of the first rib, at its junction with the sternum ; and by its circumference to the anterior and posterior sterno-clavicular ligaments. It is thicker at the circum- ference, especially its upper and back part, than at its centre, or below. It divides the joint into two cavities, each of which is furnished with a separate synovial membrane ; when the fibro-cartilage is perforated, which not unfrequently occurs, the synovial membranes communicate. Of the two Synovial Membranes found in this articulation, one is reflected from the sternal end of the clavicle, over the adjacent surface of the fibro-cartilage, and cartilage of the first rib ; the other is placed between the articular surface of the sternum and adjacent surface of the fibro-cartilage. The latter is the more loose of the two ; they seldom contain much synovia. Actions. This articulation is the centre of the movements of the shoulder, and admits of motion in nearly every direction, upwards, downwards, backwards, forwards, as well as circumduction ; the sternal end of the clavicle and the inter- articular cartilage gliding on the articular surface of the sternum. 2. Scapuloclavicular Articulation". The Scapuloclavicular is an arthrodial joint, formed between the outer ex- tremity of the clavicle, and the upper edge of the acromion process of the scapula. Its ligaments are the Superior Acromio-clavicular. Inferior Acromio-clavicular. n t . i I Trapezoid. (Joraco-clavicular < n r ., ( Conoid. Interarticular Fibro-cartilage. The Superior Acromio-clavicular Ligament is a broad band of fibres, of a quad- rilateral form, which covers the superior part of the articulation, extending between the upper part of the outer end of the clavicle, and the adjoining part of the acromion. It is composed of parallel fibres, which interlace with the aponeurosis of the Trapezius and Deltoid muscles ; below, it is in contact with the interarticular fibro-cartilage and synovial membranes. The Inferior Acromio-clavicular Ligament, somewhat thinner than the preceding, covers the under part of the articulation, and is attached to the adjoining surfaces SCAPULOCLAVICULAR. 209 of the two bones. It is in relation, above, with the interarticular fibro-cartilage (when it exists) and the synovial membranes; below, with the tendon of the Supra-spinatus. These two ligaments are continuous with each other in front and behind, and form a complete capsule around the joint. The Coraco -clavicular Ligament serves to connect the clavicle with the coracoid process of the scapula. It consists of two fasciculi, called the trapezoid and conoid ligaments. The Trapezoid ligament, the anterior and external lasciculus, is a broad, thin, quadrilateral-shaped band of fibres, placed obliquely between the coracoid process aud the clavicle. It is attached, below, to the upper surface of the coracoid Fig. 131.- -The Lett Shoulder-joint, Scapuloclavicular Articulations, and Proper Ligaments of Scapula- process ; above, to the oblique line on the under surface of the clavicle. Its anterior border is free ; its posterior border is joined with the conoid ligament, the two forming by their junction a projecting angle. The Conoid ligament, the posterior and internal fasciculus, is a dense band of fibres, conical in form, the base being turned upwards, the summit downwards. It is attached by its apex to a rough depression at the base of the coracoid process, internal to the preceding ; above, by its expanded base, to the conoid tubercle on the under surface of the clavicle, and into a line proceeding internally from it for half an inch. These ligaments are in relation, in front, with the Subclavius; behind, with the Trapezius : they serve to limit rotation of the scapula forwards and backwards. The Interarticular Fibro-cartilage is most frequently absent in this articulation. When it exists, it generally only partially separates the articular surfaces, and 14 210 ARTICULATIONS. occupies the upper part of the articulation. More rarely, it completely separates the joint into two cavities. There are two Synovial Membranes where a complete interarticular cartilage exists ; more frequently, there is only one synovial membrane. Actions. The movements of this articulation are of two kinds, x. A gliding motion of the articular end of the clavicle on the acromion. 2. Rotation of the scapula forwards and backwards upon the clavicle, the extent of this rotation being limited by the two portions of the coraco-clavicular ligament. 3. Proper Ligaments of the Scapula. The proper ligaments of the scapula are, the Coraco-acromial. Transverse. The Coraco-acromial Ligament is a broad, thin, flat band, of a triangular shape, extended transversely above the upper part of the shoulder-joint, between the coracoid and acromion processes. It is attached, by its apex, to the summit of the acromion just in front of the articular surface for the clavicle ; and by its broad base, to the whole length of the outer border of the coracoid process. Its posterior fibres are directed obliquely backwards and outwards, its anterior fibres trans- versely. This ligament completes the vault formed by the coracoid and acromion processes for the protection of the head of the humerus. It is in relation, above, with the clavicle and under surface of the Deltoid ; below, with the tendon of the Supra-spinatus muscle, a bursa being interposed. Its anterior border is continuous with a dense cellular lamina that passes beneath the Deltoid upon the tendons of the Supra-spinati and Infra-spinati muscles. The Transverse or Coracoid Ligament converts the suprascapular notch into a foramen. It is a thin and flat fasciculus, narrower at the middle than at the extremities, attached, by one end, to the base of the coracoid process, and by the other, to the inner extremity of the scapular notch. The suprascapular nerve passes through the foramen ; its accompanying vessels above it. 4. Shoulder-joint. The Shoulder is an enarthrodial or ball-and-socket joint. The bones entering into its formation are the large globular head of the humerus, which is received into the shallow glenoid cavity of the scapula, an arrangement which permits of very considerable movement, whilst the joint itself is protected against displace- ment by the strong ligaments and tendons which surround it, and above by an arched vault, formed by the under surface of the coracoid and acromion processes, and the coraco-acromial ligament. The articular surfaces are covered by a layer of cartilage : that on the head of the humerus is thicker at the centre than at the circumference, the reverse being observed in the glenoid cavity. Its liga- ments are the Capsular. Coraco-humeral. Glenoid. The Capsular Ligament completely encircles the articulation ; being attached, above, to the circumference of the glenoid cavity beyond the glenoid ligament ; below, to the anatomical neck of the humerus, approaching nearer to the articular cartilage above, than in the rest of its extent. It is thicker above than below, remarkably loose and lax, and much larger and longer than is necessary to keep the bones in contact, allowing them to be separated from each other more than an inch, an evident provision for that extreme freedom of movement which is peculiar to this articulation. Its external surface is strengthened, above, by the Supra- spinatus ; above and internally, by the coraco-humeral ligament ; below, by the long head of the Triceps ; externally, by the tendons of the Infra-spinatus and ELBOW-JOINT. 211 Teres minor ; and internally, by the tendon of the Subscapularis. The capsular ligament usually presents three openings ; one at its inner side, below the coracoid process, partially filled up by the tendon of the Subscapularis ; it establishes a communication between the synovial membrane of the joint and a bursa beneath the tendon of that muscle ; a second, not constant, at its outer part, where a com- munication sometimes exists between the joint and a bursal sac belonging to the Infra-spinatus muscle. The third is seen in the lower border of the ligament, between the two tuberosities, for the passage of the tendon of the Biceps muscle. The Coraco-humeral or Accessory Ligament is a broad band which strengthens the upper and inner part of the capsular ligament. It arises from the outer border of the coracoid process, and descends obliquely downwards and outwards to the front of the great tuberosity of the humerus, being blended with the tendon of the Supra-spinatus muscle. This ligament is intimately united to the capsular in the greater part of its extent. The Glenoid Ligament is a firm fibrous band attached round the margin of the glenoid cavity. It is triangular on section, the thickest portion being fixed to the circumference of the cavity, the free edge being thin and sharp. It is con- tinuous above with the long tendon of the Biceps muscle, which bifurcates at the upper part of the cavity into two fasciculi, which encircle its margin, and unite at its lower part. This ligament deepens the cavity for articulation, and protects the edges of the bone. It is lined by the synovial membrane. The Synovial Membrane lines the margin of the glenoid cavity and the fibro- cartilaginous rim surrounding it ; it is then reflected over the internal surface of the capsular ligament, covers the lower part and sides of the neck of the humerus, and is continued a short distance over the cartilage covering the head of this bone. The long tendon of the Biceps muscle which passes through the joint is inclosed in a tubular sheath of synovial membrane, which is reflected upon it at the point where it perforates the capsule, and is continued around it as far as the summit of the glenoid cavity. The tendon of the Biceps is thus enabled to traverse the articu- lation, but is not contained in the interior of the synovial cavity. The synovial membrane communicates with a large bursal sac beneath the tendon of the Sub- scapularis, by an opening at the inner side of the capsular ligament; it also occasionally communicates with another bursal sac, beneath the tendon of the Infra-spinatus, through an orifice at its outer part. A third bursal sac, which does not communicate with the joint, is placed between the under surface of the deltoid and the outer surface of the capsule. The Muscles in relation with the joint are, above, the Supra-spinatus ; below, the long head of the Triceps ; internally, the Subscapularis ; externally, the Infra- spinatus, and Teres minor; within, the long tendon of the Biceps. The Deltoid is placed most externally, and covers the articulation on its outer side, and in front and behind. The Arteries supplying the joint are articular branches of the anterior and posterior circumflex, and suprascapular. The Nerves are derived from the circumflex and suprascapular. Actions. The shoulder-joint is capable of movement in almost any direction, forwards, backwards, abduction, adduction, circumduction, and rotation. 5. Elbow-joint. The Elbow is a ginglymoid or hinge joint. The bones entering into its forma- tion are the trochlear surface of the humerus, which is received in the greater sigmoid cavity of the ulna, and admits of the movements peculiar to this joint, those of flexion and extension, whilst the cup-shaped depression of the head of the radius articulates with the radial tuberosity of the humerus, its circumference with the lesser sigmoid cavity of the ulna, allowing of the movement of rotation of the radius on the ulna, the chief action of the superior radio-ulnar articulation. 212 ARTICULATIONS. The articular surfaces are covered with a thin layer of cartilage, and connected together by the following ligaments : — Anterior Ligament. Internal Lateral. Posterior Ligament. External Lateral. The Anterior Ligament (fig. 132) is a broad and thin fibrous layer, which covers the anterior surface of the joint Fig. 132.— Left Elbow-Joint, showing Ante- rior and Internal Lateral Ligaments. It is attached to the front of the humerus immediately above the coronoid fossa; below, to the anterior surface of the coronoid process of the ulna and orbicu- lar ligament, being continuous on each side with the lateral ligaments. Its super- ficial or oblique fibres pass from the inner condyle of the humerus outwards to the orbicular ligament. The middle fibres, vertical in direction, pass from the upper part of the coronoid depression, and become blended with the preceding. A third, or transverse set, intersect these at right angles. This ligament is in relation, in front, with the Brachialis anticus; behind, with the synovial membrane. The Posterior Ligament is a thin and loose membranous fold, attached, above, to the lower end of the humerus, imme- diately above the olecranon depression ; below, to the margin of the olecranon. The superficial or transverse fibres pass between the adjacent margins of the ole- cranon fossa. The deeper portion consists of vertical fibres, which pass from the upper part of the olecranon fossa to the margin of the olecranon. This ligament is in relation, behind, with the tendon of the Triceps and Anconeus ; in front, with the synovial membrane. The Internal Lateral Ligament is a thick triangular band of ligamentous fibres, consisting of two distinct portions, an anterior and posterior. The anterior portion, directed obliquely forwards, is attached, above, by its apex, to the front part of the internal condyle of the humerus ; and, below, by its broad base, to the inner margin of the coronoid process. The posterior portion, also of triangular form, is attached, above, by its apex, to the lower and back part of the internal condyle ; below, to the inner margin of the olecranon. This ligament is in rela- tion, internally, with the Triceps and Flexor carpi ulnaris muscles, and the ulnar nerve. The External Lateral Ligament (fig. 133) is a short and narrow fibrous fasci- culus, less distinct than the internal, attached, above, to the external condyle of the humerus ; below, to the orbicular ligament, some of its most posterior fibres passing over that ligament, to be inserted into the outer margin of the ulna. This ligament is intimately blended with the tendon of origin of the Supinator brevjs muscle. The Synovial Membrane is very extensive. It covers the margin of the arti- cular surface of the humerus, and lines the coronoid and olecranon depressions on that bone; from these points, it is reflected over the anterior, posterior, and lateral RADIO-ULNAR. 213 ligaments, and forms a pouch between Fig. 133.-Left Elbow-Joint showing Tosterior ,o , ' • -i -i xi • i. i and External Lateral Ligaments. the lesser sigmoid cavity, the internal surface of the annular ligament, and the circumference of the head of the radius. The Muscles in relation with the joint are, in front, the Brachialis anticus; behind, the Triceps and Anconeus; ex- ternally, the Supinator brevis, and the common tendon of origin of the Extensor muscles; internally, the common tendon of origin of the Flexor muscles, the Plexor carpi ulnaris, and ulnar nerve. The Arteries supplying the joint are de- rived from the communicating branches between the superior profunda, inferior profunda, and anastomotic branches of the brachial, with the anterior, posterior and interosseous recurrent branches of the ulnar, and the recurrent branch of the radial. These vessels form a complete chain of inosculation around the joint. The Nerves are derived from the ulnar, as it passes between the internal condyle and the olecranon ; and a few filaments from the musculo-cutaneous. Actions. The elbow is one of the most perfect hinge-joints in the body ; its move- ments are, consequently, limited to flexion and extension, the exact apposition of the articular surfaces preventing the least lateral motion. 6. Radioulnar Articulations. The articulation of the radius with the ulna is effected by ligaments, which connect together both extremities as well as the shafts of these bones. They may, consequently, be subdivided into three sets : 1, the superior radio-ulnar ; 2, the middle radio-ulnar ; and 3, the inferior radio-ulnar articulations. 1. Superior Radio-ulnar Articulation. This articulation is a lateral ginglymoid joint. The bones entering into its for- mation are the inner side of the circumference of the head of the radius, which rotates within the lesser sigmoid cavity of the ulna. These surfaces are covered with cartilage, and invested with a duplicature of synovial membrane, continuous with that which lines the elbow-joint. Its only ligament is The Annular or Orbicular. The Orbicular Ligament (fig. 133) is a strong flat band of ligamentous fibres, which surrounds the head of the radius, and retains it in firm connection with the lesser sigmoid cavity of the ulna. It forms about three-fourths of a fibrous ring attached by each end to the extremities of the sigmoid cavity, and is broader at the upper part of its circumference than below, by which means the head of the radius is more securely held in its position. Its outer surface is strengthened by the ex- ternal lateral ligament of the elbow, and affords partial origin to the Supinator brevis muscle. Its inner surface is smooth, and lined by synovial membrane. Actions. The movement which takes place in this articulation is limited to rotation of the head of the radius within the orbicular ligament, and upon the 214 ARTICULATIONS. lesser sigmoid cavity of the ulna ; rotation forwards being called pronation ; rota- tion backward, supination. 2. Middle Radioulnar Articulation. The interval between the shafts of the radius and ulna is occupied by two liga- ments. Oblique. Interosseous. The Oblique or Round Ligament (fig. 132) is a small round fibrous cord, which extends obliquely downwards and outwards, from the tubercle of the ulna at the base of the coronoid process, to the radius a little below the bicipital tuberosity. Its fibres run in the opposite direction to those of the interosseous ligament ; and it appears to be placed as a substitute for it in the upper part of the interosseous interval. This ligament is sometimes wanting. The Interosseous Membrane is a broad and thin plane of aponeurotic fibres, descending obliquely downwards and inwards, from the interosseous ridge on the radius to that on the ulna. It is deficient above, commencing about an inch be- neath the tubercle of the radius ; is broader in.the middle than at either extremity ; and presents an oval aperture just above its lower margin for the passage of the anterior interosseous vessels to the back of the forearm. This ligament serves to connect the bones, and to increase the extent of surface for the attachment of the deep muscles. Between its upper border and the oblique ligament an interval exists, through which the posterior interosseous vessels pass. Two or three fibrous bands are occasionally found on the posterior surface of this membrane, which descend obliquely from the ulna towards the radius, and which have consequently a direction contrary to that of the other fibres. It is in relation, in front, by its upper three-fourths (radial margin) with the Flexor longus pollicis (ulnar margin), with the Flexor profundus digitorum, lying upon the interval between which are the anterior interosseous vessels and nerve, by its lower fourth with the Pronator quadratus ; behind, with the Supinator brevis, Extensor ossis metacarpi pollicis, Extensor primi internodii pollicis, Extensor secundi internodii pollicis, Extensor indicis ; and, near the wrist, with the anterior interosseous artery and posterior interosseous nerve. 3. Inferior Radio-ulnar Articulation. This is a lateral ginglymoid joint, formed by the head of the ulna being received into the sigmoid cavity at the inner side of the lower end of the radius. The articular surfaces are covered by a thin layer of cartilage, and connected together by the following ligaments. Anterior radio-ulnar. Posterior radio-ulnar. Triangular Interarticular Fibro-cartilage. The Anterior Radio-ulnar Ligament (fig. 134) is a narrow band of fibres, ex- tending from the anterior margin of the sigmoid cavity of the radius to the anterior surface of the head of the ulna. The Posterior Radio-ulnar Ligament (fig. 135) extends between similar points on the posterior surface of the articulation. The Triangular Fibro-cartilage (fig. 136) is placed transversely beneath the head of the ulna, binding the lower end of this bone and the radius firmly together. Its circumference is thicker than its centre, which is thin and occasionally per- forated. It is attached by its apex to a depression which- separates the styloid process of the ulna from the head of that bone; and, by its base, which is thin, to the prominent edge of the radius, which separates the sigmoid cavity from the carpal articulating surface. Its margins are united to the ligaments of the wrist-joint. Its upper surface, smooth and concave, is contiguous with the head of the ulna ; its tinder surface, also concave and smooth, with the cuneiform bone. Both surfaces are lined by a synovial membrane : the upper surface, by one peculiar RADIO-TTLNAR. 215 to the radioulnar articulation ; the under surface, by the synovial membrane of the wrist. Fig. 134. — Ligaments of "Wrist and Hand. Anterior View. NFERIOR RADIO-ULNAR ARTICJ WRIST-JOINT CARPAL ARTICf? CARPO-METACARPAL ARTIC •« The Synovial Membrane of this articulation has been called, from its extreme looseness, the membrana sacciformis ; it covers the margin of the articular surface of the head of the ulna and where reflected from this bone on to the radius forms Fig. 135. — Ligaments of Wrist and Hand. Posterior View. Inferior Hadio -ulnar Artie ~Wrl*t- Joint Carpal Artio 7 ^ Carpo-M^etaearpal /SpS; ArtieV* a very loose cul-de-sac ; from the radius, it is continued over the upper surface of the fibro-cartilage. The quantity of synovia which it contains is usually 216 ARTICULATIONS. considerable. When the fibro-cartilage is perforated, the synovial membrane is continuous with that which lines the wrist. Actions. The movement which occurs in the inferior radio-ulnar articulation is just the reverse of that which takes place between the two bones above ; it is limited to rotation of the radius round the head of the ulna ; rotation forwards being termed pronation, rotation backwards supination. In pronation, the sigmoid cavity glides forward on the articular edge of the ulna ; in supination, it rolls in the opposite direction, the extent of these movements being limited by the anterior and posterior ligaments. 7. Wrist-joint. The Wrist presents most of the characters of an enarthrodial joint. The parts entering into its formation are, the lower end of the radius, and under surface of the triangular interarticular fibro-cartilage, above ; and the scaphoid, semilunar, and cuneiform bones below. The articular surfaces of the radius and interarticular fibro-cartilage form a transversely elliptical concave surface. The radius is sub- divided into two parts by a line extending from before backwards ; and these, together with the interarticular cartilage, form three facets, one for each carpal bone. The three carpal bones are connected together, and form a convex surface, which is received into the concavity above mentioned. All the bony surfaces of the articulation are covered with cartilage, and connected together by the follow- ing ligaments. External Lateral. Anterior. Internal Lateral. Posterior. The External Lateral Ligament extends from the summit of the styloid process of the radius to the outer side of the scaphoid, some of its fibres being prolonged to the trapezium and annular ligament. The Internal Lateral Ligament is a rounded cord, attached, above, to the ex- tremity of the styloid process of the ulna ; below, it divides into two fasciculi, which are attached, one to the inner side of the cuneiform bone, the other to the pisiform bone and annular ligament. The Anterior Ligament is a broad membranous band, consisting of three fasci- culi, attached, above, to the anterior margin of the lower end of the radius, its styloid process, and the ulna; its fibres pass downwards and inwards, to be inserted into the palmar surface of the scaphoid, semilunar, and cuneiform bones. This ligament is perforated by numerous apertures for the passage of vessels, and is in relation, in front, with the tendons of the Flexor profundus digitorum and Flexor longus pollicis ; behind, with the synovial membrane of the wrist-joint. The Posterior Ligament, less thick and strong than the anterior, is attached, .above, to the posterior border of the lower end of the radius ; its fibres descend obliquely downwards and inwards to be attached to the dorsal surface of the scaphoid, semilunar, and cuneiform bones, its fibres being continuous with those of the dorsal carpal ligaments. This ligament is in relation, behind, with the extensor tendons of the fingers ; in front, with the synovial membrane of the wrist. The Synovial Membrane lines the under surface of the triangular interarticular fibro-cartilage above ; and is reflected on the inner surface of the ligaments above mentioned. Relations. The wrist-joint is covered in front by the flexor, and behind by the extensor tendons ; it is also in relation with the radial and ulnar arteries. The Arteries supplying the joint are the anterior and posterior carpal branches of the radial and ulnar, the anterior and posterior interosseous, and some ascend- ing branches from the deep palmar arch. The Nerves are derived from the ulnar. Actions. The movements permitted in this joint are flexion, extension, abduc- OF THE CARPUS. 217 tion, adduction, and circumduction. ' It is totally incapable of rotation, one of the characteristic movements in true enarthrodial joints. 8. Articulations of the Carpus. These articulations may be subdivided into three sets : — 1. The articulation of the first row of carpal bones. 2. The articulation of the second row of carpal bones. 3. The articulation of the two rows with each other. 1. Articulation of the First Row of Carpal Bones. These are arthrodial joints. The articular surfaces are covered with cartilage and connected together by the following ligaments : — Two Dorsal. Two Palmar. Two Interosseous. The Dorsal Ligaments, two in number, are placed transversely behind the bones of the first row ; they connect the scaphoid and semilunar, and the semilunar and cuneiform. The Palmar Ligaments, also two in number, connect the scaphoid and semi- lunar, and the semilunar and cuneiform bones ; they are less strong than the dorsal, and placed very deep under the anterior ligament of the wrist. The Interosseous Ligaments (fig. 135) are two narrow bundles of fibrous tissue, connecting the semilunar bone, on one side with the scaphoid, on the other with the cuneiform. They close the upper part of the interspaces between the scaphoid, semilunar, and cuneiform bones, their upper surfaces being smooth, and lined by the synovial membrane of the wrist-joint. The articulation of the pisiform with the cuneiform is provided with a separate synovial membrane, protected by a thin capsular ligament. There are also two strong fibrous fasciculi, which connect this bone to the unciform, and base of the fifth metacarpal bone. 2. Articulation of the Second Row of Carpal Bones. These are arthrodial joints, the articular surfaces are covered with cartilage, and connected by the following ligaments : — Three Dorsal. Three Palmar. Two Interosseous. The three Dorsal Ligaments extend transversely from one bone to another on the dorsal surface, connecting the trapezium with the trapezoid, the trapezoid with the os magnum, and the os magnum with the unciform. The three Palmar Ligaments have a similar arrangement on the palmar surface.- The two Interosseous Ligaments, much thicker than those of the first row, are placed one on each side of the os magnum, connecting it with the trapezoid exter- nally, and the unciform internally. The former is less distinct than the latter. 3. Articulation of the Two Rows of Carpal Bones with each other. The articulation between the two rows of the carpus consists of an enarthrodial joint in the middle, formed by the reception of the os magnum into a cavity formed by the scaphoid and semilunar bones, and of an arthrodial joint on each side, the outer one formed by the articulation of the scaphoid with the trapezium and trapezoid, the internal one by the articulation of the cuneiform and unciform. The articular surfaces are covered by a thin layer of cartilage, and connected by the following ligaments : — Anterior or Palmar. External Lateral. Posterior or Dorsal. Internal Lateral. 218 ARTICULATIONS. The Anterior or Palmar Ligaments consist of short fibres, which pass obliquely between the bones of the first and second row on the palmar surface. The Posterior or Dorsal Ligaments have a similar arrangement on the dorsal surface of the carpus. The Lateral Ligaments are very short ; they are placed, one on the radial, the other on the ulnar side of the carpus ; the former, the stronger and more distinct, connecting the scaphoid and trapezium bones, the latter the cuneiform and unci- form : they are continuous with the lateral ligaments of the wrist-joint. There are two Synovial Membranes found in the articulation of the carpal bones with each other. The first of these, the more extensive, lines the under surface of the scaphoid, semilunar, and cuneiform bones, sending upwards two prolongations between their contiguous surfaces; it is then reflected over the bones of the second row, and sends down three prolongations between them, which line their contiguous surfaces, and invest the carpal extremities of the four outer metacarpal bones. The second is the synovial membrane between the pisiform and cuneiform bones. Actions. The partial movement which takes place between the bones of each row is very inconsiderable ; the movement between the two rows is more marked, but limited chiefly to flexion and extension. 9. Carpo-metacarpal Articulations. Articulation of the Metacarpal Bone of the Thumb with the Trapezium. This is an enarthrodial joint. Its ligaments are a capsular and synovial mem- brane. The capsular ligament is a thick but loose capsule, which passes from the circumference of the upper extremity of the metacarpal bone, to the rough edge bounding the articular surface of the trapezium ; it is thickest externally and behind, and lined by a separate synovial membrane. Articulation of the Metacarpal Bones of the Fingers with the Carpus. The joints formed between the carpus and four inner metacarpal bones are connected together by dorsal, palmar, and interosseous ligaments. The Dorsal Ligaments, the strongest and most distinct, connect the carpal and metacarpal bones on their dorsal surface. The second metacarpal bone receives two fasciculi, one from the trapezium, the other from the trapezoid ; the third metacarpal receives one from the os magnum ; the fourth two, one from the os magnum, and one from the unciform ; the fifth receives a single fasciculus from the unciform bone. The Palmar Ligaments have a somewhat similar arrangement on the palmar surface, with the exception of the third metacarpal, which has three ligaments, an external one from the trapezium, situated above the sheath of the tendon of the Flexor carpi radialis ; a middle one, from the os magnum ; and an internal one, from the unciform. The Interosseous Ligaments consist of short thick fibres, which are limited to one part of the carpo-metacarpal articulation ; they connect the contiguous inferior angles of the os magnum and unciform, with the adjacent surfaces of the third and fourth metacarpal bones. The Synovial Membrane is a continuation of that between the two rows of carpal bones. Occasionally, the articulation of the unciform with the fourth and fifth metacarpal bones has a separate synovial membrane. The Synovial Membranes of the wrist (fig. 136) are thus seen to be five in number. The first, the membrana sacciformis, lining the lower end of the ulna, the sigmoid cavity of the radius, and upper surface of the triangular interarticular fibro-cartilage. The second lines the lower end of the radius and interarticular fibro-cartilage above, and the scaphoid, semilunar, and cuneiform bones below. The third, the most extensive, covers the contiguous surfaces of the two rows of carpal CARPO-MET A CARPAL. 219 bones, and, passing between the bones of the second range, lines the carpal extre- mities of the four inner metacarpal bones. The fourth lines the adjacent surfaces of the trapezium and metacarpal bone of the thumb. And the fifth the adjacent surfaces of the cuneiform and pisiform bones. Actions. The movement permitted in the carpo-metacarpal articulations is limited to a slight gliding of the articular surfaces upon each other, the extent of which varies in the different joints. Thus the articulation of the metacarpal bone of the thumb with the trapezium is most movable, then the fifth metacarpal, and then the fourth. The second and third are almost immovable. In the articulation of the metacarpal bone of the thumb with the trapezium, the movements permitted are flexion, extension, adduction, abduction, and circumduction. Fig. 136. -Vertical Section through the Articulations at the Wrist, showing the five Synovial Membranes. Articulations of the Metacarpal Bones with each other. The carpal extremities of the metacarpal bones articulate with one another at each side by small surfaces covered with cartilage, and connected together by dorsal, palmar, and interosseous ligaments. The Dorsal and Palmar Ligaments pass transversely from one bone to another on the dorsal and palmar surfaces. The Interosseous Ligaments pass between their contiguous surfaces, just beneath their lateral articular facets. The Synovial Membrane lining the lateral facets is a reflection from that between the two rows of carpal bones. The digital extremities of the metacarpal bones are connected together by a narrow fibrous band, the transverse ligament, which passes transversely across their under surfaces, and is blended with the ligaments of the metacarpophalan- geal articulations. Its anterior surface presents four grooves for the passage of the flexor tendons. , Its posterior surface blends with the ligaments of the meta- carpophalangeal articulation. 220 ARTICULATIONS. LATERAL LICAMENT Metacurpo -jihala. n/jeal Artie*! 10. Metacarpophalangeal Articulations (fig. 137). These articulations are of the ginglymoid kind, formed by the reception of the rounded head of the metacarpal bone, into a superficial cavity in the extremity of the first phalanx. They are connected by the following ligaments : — Anterior. Two Lateral. The Anterior Ligaments are thick, dense, and fibro-cartilaginous in texture. Each is placed on the palmar Fig. l37.-Articulations of the Phalanges. surface of the joint, in the interval between the lateral ligaments, to which they are connected ; they are loosely united to the metacarpal bone, but very firmly to the base of the first phalanges. Their palmar surface is intimately blended with the transverse ligament, each ligament form- ing with it a groove for the passage of the flexor tendons, the sheath surrounding which is connected to it at each side. By their internal surface, they form part of the articular surface for the head of the metacarpal bone, and are lined by a synovial membrane. The Lateral Ligaments are strong rounded cords, placed one on each side of the joint, each being attached by one extremity to the tubercle on the side of the head of the metacarpal bone, and by the other to the contiguous ex- tremity of the phalanx. The Posterior Ligament is supplied by the extensor ten- don placed over the back of each joint. Actions. The movements which occur in these joints are flexion, extension, adduc- tion, abduction, and circumduction ; the lateral movements are very limited. 11. Articulations of the Phalanges (fig. 137). These are ginglymoid joints, connected by the following ligaments : — Anterior. Two Lateral. The arrangement of these ligaments is similar to those in the metacarpo-pha- langeal articulations; the extensor tendon supplies the place of a posterior ligament. Actions. The only movements permitted in the phalangeal joints are flexion and extension ; these movements are more extensive between the first and second phalanges than between the second and third. The movement of flexion is very extensive, but extension is limited by the anterior and lateral ligaments. FJi&lantfeal Artie Vf HIP-JOINT. 221 ARTICULATIONS OP THE LOWER EXTREMITY. The articulations of the Lower Extremity comprise the following groups. 1. The hip-joint. 2. The knee-joint. 3. The articulations between the tibia and fibula. 4. The ankle-joint. 5. The articulations of the tarsus. 6. The tarso- metatarsal articulations. 7. The metatarso-phalangeal articulations. 8. The articulation of the phalanges. 1. Hip-joint (fig. 138). This articulation is an enarthrodial or ball-and-socket joint, formed' by the reception of the head of the femur into the cup-shaped cavity of the acetabulum. The articulating surfaces are covered with cartilage, that on the head of the femur being thicker at the centre than at the circumference, and covering the entire surface with the exception of a depression just below its centre for the ligamen- tum teres ; that covering the acetabulum is much thinner at the centre than at the circumference, being deficient in the situation of the circular depression at the bottom of this cavity. The ligaments of the joint are the Capsular. Teres. Ilio-femoral. Cotyloid. Transverse. Fig. 138. — Left Hip-joint laid open. The Capsular Ligament is a strong, dense, ligamentous capsule, embracing the margin of the acetabulum above, and surrounding the neck of the femur below. Its upper circumference is attached to the acetabulum two or three lines external to the cotyloid ligament ; but, opposite the notch where the margin of this cavity is deficient, it is connected with the transverse ligament, and by a few fibres to the edge of the obturator foramen. Its lower circumference surrounds the neck of the femur, being attached, in front, to the spiral or anterior inter-trochanteric line ; above, to the base of the neck ; behind, to the middle of the neck of the bone, about half an inch from the posterior inter-trochanteric line. It is much thicker 222 • ARTICULATIONS. at the upper and fore part of the joint where the greatest amount of resistance is required, than below where it is thin, loose, and longer than in any other situation. Its external surface is rough, covered by numerous muscles, and separated in front from the Psoas and Iliacus by a synovial bursa, which not unfrequently commu- nicates by a circular aperture with the cavity of the joint. It differs from the capsular ligament of the shoulder, in being much less loose and lax, and in not being perforated for the passage of a tendon. The llio-femoral Ligament (fig. 127) is an accessory band of fibres, extending obliquely across the front of the joint: it is intimately connected with the capsular ligament, and serves to strengthen it in this situation. It is attached, above, to the anterior inferior spine of the ilium ; below, to the anterior intertrochanteric line. The Ligamentum Teres is a triangular band of fibres, implanted, by its apex, into the depression a little behind and below the centre of the head of the femur; and by its broad base, which consists of two bundles of fibres, into the margins of the notch at the bottom of the acetabulum, becoming blended with the transverse ligament. It is formed of a bundle of fibres, the thickness and strength of which are very variable, surrounded by a tubular sheath of synovial membrane. Some- times, the synovial fold only exists, or the ligament may be altogether absent. The use of the round ligament is to check rotation outwards, when combined with flexion : it thus assists in preventing dislocation of the head of the femur forwards and outwards, an accident likely to occur from the necessary mechanism of the joint, if not provided against by this ligament and the thick anterior part of the capsule. 1 The Cotyloid Ligament is a fibro -cartilaginous rim attached to the margin of the acetabulum, the cavity of which it deepens ; at the same time it protects the edges of the bone, and fills up the inequalities on its surface. It is prisnioid in form, its base being attached to the margin of the acetabulum, its opposite edge being free and sharp ; whilst its two surfaces are invested by synovial membrane, the external one being in contact with the capsular ligament, the internal one being inclined inwards so as to narrow the acetabulum and embrace the cartila- ginous surface of the head of the femur. It is much thicker above and behind than below and in front, and consists of close compact fibres, which arise from different points of the circumference of the acetabulum, and interlace with each other at very acute angles. The Transverse Ligament is a strong flattened band of fibres, which crosses the notch at the lower part of the acetabulum, and converts it into a foramen. It is continuous at each side with the cotyloid ligament. An interval is left beneath the ligament for the passage of nutrient vessels to the joint. The Synovial Membrane is very extensive. Commencing at the margin of the cartilaginous surface of the head of the femur, it covers all that portion of the neck which is contained within the joint ; from this point it is reflected on the internal surface of the capsular ligament, covers both surfaces of the cotyloid ligament, and the mass of fat contained in the fossa at the bottom of this cavity, and is prolonged in the form of a tubular sheath around the ligamentum teres, as far as the head of the femur. The Muscles in relation with the joint are, in front, the Psoas and Iliacus, sepa- rated from the capsular ligament by a synovial bursa ; above, the short head of the Rectus and Gluteus minimus, the latter being closely adherent to it ; internally, the Obturator externus and Pectineus ; behind, the Pyriformis, Gemellus superior, Obturator internus, Gemellus inferior, Obturator externus, and Quadratus femoris. The Arteries supplying it are derived from the obturator, sciatic, internal cir- cumflex, and gluteal. The Nerves are articular branches from the sacral plexus, great sciatic, obtu- rator, and accessory obturator nerves. Actions. The movements of the hip, like all enarthrodial joints, are very exten- sive; they are, flexion, extension, adduction, abduction, circumduction, and rotation. 1 See an interesting paper, "On the Use of the Round Ligament of the Hip-joint," by Dr. J. Struthers. Edinburgh Medical Journal, 1858. 223 are, the condyles of the femur above, the head of the tibia below, and the patella in front. The articular surfaces are covered with cartilage, and connected toge- ther by ligaments, some of which are placed on the exterior of the joint, whilst others occupy its interior. KNEE-JOINT. 2. Knee-joint. External Ligaments. Anterior or Ligamentum Pa- tellae. Posterior or Ligamentum Posticum Winslowii. Internal Lateral. Two External Lateral. Capsular. Internal Ligaments. Anterior or External Crucial. Posterior or Internal Crucial. Two Semilunar Fibro-cartilages. Transverse. Coronary. Ligamentum mucosum. Ligamenta alaria. The Anterior Ligament cr Ligamentum Patellse (fig. 139) is that portion of the common tendon of the extensor muscles of the thigh which is continued from Fig. 139.— Right Knee-joint. Anterior "View. Fig. 140.— Right Knee-joint. Posterior View. the patella to the tubercle of the tibia, supplying the place of an anterior ligament, It is a strong, flat, ligamentous band, about three inches in length, attached, above, to the apex of the patella and the rough depression on its posterior surface ; below, to the lower part of the tuberosity of the tibia ; its superficial fibres being continu- ous across the front of the patella with those of the tendon of the Quadriceps ex- tensor. Two synovial bursas are connected with this ligament and the patella ; one is interposed between the patella and the skin covering its anterior surface ; the 224 ARTICULATIONS. other, of small size, between the ligamentum patellae and the upper part of the tuberosity of the tibia. The posterior surface of this ligament is separated above from the knee-joint by a large mass of adipose tissue ; its lateral margins are con- tinuous with the aponeuroses derived from the Vasti muscles. The Posterior Ligament or Ligamentum, Posticum Winslowii (fig. 140) is a broad, flat, fibrous band, which covers over the whole of the back part of the joint. It consists of two lateral portions, formed chiefly of vertical fibres, which arise above from the condyles of the femur, and are connected below with the back part of the head of the tibia, being closely united with the tendons of the Gastrocnemius, Plantaris, and Popliteus muscles ; the central portion is formed of fasciculi ob- liquely directed and separated from one another by apertures for the passage of vessels. The strongest of these fasciculi is derived from the tendon of the Semi- membranosus ; it passes from the back part of the inner tuberosity of the tibia, obliquely upwards and outwards, to the back part of the outer condyle of the femur. The posterior ligament forms part of the floor of the popliteal space, and upon it rests the popliteal artery. The Internal Lateral Ligament is a broad, flat, membranous band, thicker behind than in front, and situated nearer to the back than the front of the joint. It is attached, above, to the inner tuberosity of the femur ; below, to the inner tuberosity and inner surface of the shaft of the tibia, to the extent of about two inches. It is crossed, at its lower part, by the aponeurosis of the Sartorius, and the tendons of the Gracilis and Semi-tendinosus muscles, a synovial bursa being interposed. Its deep surface covers the anterior portion of the tendon of the Semi-membra- nosus, the synovial membrane of the joint, and the inferior internal articular artery ; it is intimately adherent to the internal semilunar fibro-cartilage. The Long External Lateral Ligament is a strong, rounded, fibrous cord, situated nearer to the back than the front of the joint. It is attached, above, to the outer condyle of the femur ; below, to the outer part of the head of the fibula. Its outer surface is covered by the tendon of the Biceps, which divides into two parts, separated by the ligament, at its insertion. It has, passing beneath it, the tendon of the Popliteus muscle, and the inferior external articular vessels and nerve. The Short External Lateral Ligament is an accessory bundle of fibres, placed behind and parallel with the preceding ; attached, above, to the lower part of the outer condyle of the femur ; below, to the summit of the styloid process of the fibula. This ligament is intimately connected with the capsular ligament, and has, passing beneath it, the tendon of the Popliteus muscle. The Capsular Ligament consists of an exceedingly thin, but strong, fibrous membrane, which fills in the intervals left by the preceding ligaments. It is attached to the femur immediately above its articular surface ;' below, to the upper border and sides of the patella, the margins of the head of the tibia and inter- articular cartilages, and is continuous behind with the posterior ligament. This membrane is strengthened by fibrous expansions, derived from the fascia lata, from the Vasti and Crureus muscles, and from the Biceps, Sartorius, and tendon of the Sami-membranosus. The Crucial are two interosseous ligaments of considerable strength, situated' in the interior of the joint, nearer its posterior than its anterior part. They are called crucial, because they cross each other, somewhat like the lines of the letter X ; and have received the names anterior and posterior, from the position of their attachment to the tibia. The Anterior or External Crucial Ligament (fig. 141), smaller than the poste- rior, is attached to the inner side of the depression in front of the spine of the tibia, being blended with the anterior extremity of the external semilunar fibro- cartilage, and passing obliquely upwards, backwards, and outwards, is inserted into the inner and back part of the outer condyle of the femur. The Posterior or Internal Crucial Ligament is Larger in size, but less oblique v.\ its direction than the anterior. It is attached to the back part of the depres- KNEE-JOINT. 225 Fig. 141. — Right Knee-joint. Showing Internal Ligaments. sion behind the spine of the tibia, and to the posterior extremity of the external semilunar fibro-cartilage ; passing upwards, forwards, and inwards, it is inserted into the outer and fore part of the inner condyle of the femur. As it crosses the anterior crucial ligament, a fasciculus is given off from it, which blends with its posterior part. It is in relation, in front, with the anterior crucial ligament; behind, with the ligamentum posticum Winslowii. The Semilunar Fibro-cartilages (fig. 142) are two crescentic lamellae attached to the margins of the head of the tibia, serving to deepen its surface for articula- tion with the condyles of the femur. The circumference of each cartilage is thick and convex ; the inner free border, thin and concave. Their upper surfaces are concave, and in relation with the condyles of the femur; their lower surfaces are flat, and rest upon the head of the tibia. Each cartilage covers nearly the outer two-thirds of the corresponding articular surface of the tibia, the inner third being uncovered ; both surfaces are smooth, and invested by synovial membrane. The Internal Semilunar Fibro-cartilage is nearly semicircular in form, a little elongated from before backwards, and broader behind than in front ; its convex border is united to the internal lateral ligament, and to the head of the tibia, by means of the coronary ligaments^ its anterior extremity, thin and pointed, is firmly implanted into a depression in front of the inner articular surface of the tibia; its posterior extremity to the depression behind the spine, between the attach- ment of the external cartilage and posterior crucial ligament. The External Semilunar Fibro-cartilage forms nearly an entire circle, covering a larger portion of the articular surface than the internal one. It is grooved on its outer side, for the tendon of the Pop- liteus muscle. Its circumference is held in connection with the head of the tibia, by means of the coronary ligaments; and its two extremities are firmly im- planted in the depressions in front and behind the spine of the tibia. These ex- tremities, at their insertion, are interposed between the attachments of the internal cartilage. The external semilunar fibro- cartilage gives off from its anterior bor- der a fasciculus, which forms the trans- verse ligament. By its anterior extremity, it is continuous with the anterior crucial ligament. Its posterior extremity divides into three slips ; two of these pass upwards and forwards, and are inserted into the outer side of the inner condyle, one in front, the other behind the posterior crucial ligament ; the third fasciculus is inserted into the back part of the anterior crucial ligament. The Transverse Ligament is a band of fibres, which passes transversely be- 15 Fig. 142.— Head of Tibia, with Semilnnai Cartilages, etc. Seen from above. Right Side. 226 ARTICULATIONS. tween the anterior convex margin of the external semilunar cartilage, to the anterior extremity of the internal cartilage ; its thickness varies considerably in different subjects. The Coronary Ligaments consist of numerous short fibrous bands, which con- nect the convex border of the semilunar cartilages with the circumference of the head of the tibia, and with the other ligaments surrounding the joint. The Synovial Membrane of the knee-joint is the largest and most extensive in the body. Commencing at the upper border of the patella, it forms a large cul- de-sac beneath the Extensor tendon of the thigh : this is sometimes replaced by a synovial bursa interposed between the tendon and the front of the femur, which in some subjects communicates with the synovial membrane of the knee-joint, by an orifice of variable size. On each side of the patella, the synovial membrane extends beneath the aponeurosis of the Vasti muscles, and more especially beneath that of the Vastus internus ; and, beneath the patella, it is separated from the anterior ligament by a considerable quantity of -adipose tissue. In this situation, it sends off a triangular-shaped prolongation, containing a few ligamentous fibres, which extends from the anterior part of the joint below the patella, to the front of the intercondyloid notch. This fold has been termed the ligamentum mucosum. The ligamenta alaria consist of two fringe-like folds, which extend from the sides of the ligamentum mucosum, upwards and outwards, to the sides of the patella. The synovial membrane invests the semilunar fibro-cartilages, and on the back part of the external one forms a cul-de-sac between the groove on its surface and the tendon of the Popliteus ; it is continued to the articular surface of the tibia, surrounds the crucial ligaments, and the inner surface of the ligaments which inclose the joint ; lastly, it approaches the condyles of the femur, and from them is continued on to the lower part of the front of the shaft. The pouch of synovial membrane between the Extensor tendon and front of the femur is supported, during the movements of the knee, by a small muscle, the Subcrureus, which is inserted into it. The Arteries supplying the joint are derived from the anastomotic branch of the femoral, articular branches of the pqrjliteal, and recurrent branch of the anterior tibial. The Nerves are derived from the obturator, anterior crural, and external and internal popliteal. Actions. The chief movements of this joint are flexion aud extension ; but it is also capable of performing some slight rotatory movement. During flexion, the articular surfaces of the tibia, covered by their interarticular cartilages, glide backwards upon the condyles of the femur, the lateral, posterior, and crucial liga- ments are relaxed, the ligamentum patella? is put upon the stretch, the patella filling up the vacuity in front of the joint between the femur and tibia. In extension, the tibia and interarticular cartilages glide forwards upon the femur; all the ligaments are stretched, with the exception of the ligamentum patellae, which is relaxed, and admits of considerable lateral movement. The movement of rotation is permitted when the knee is semi-flexed, rotation outwards being most extensive. 3. Articulation between the Tibia and Fibula. The articulations between the tibia and fibula are effected by ligaments which connect both extremities, as well as the shaft of these bones. They may, con- sequently, be subdivided into three sets. 1. The Superior Tibio-fibular articula- tion. 2. The Middle Tibio-fibular articulation. 3. The Inferior Tibio-fibular articulation. 1. Superioe Tibio-fibular Articulation. This articulation is an arthrodial joint. The contiguous surfaces of the bode." TIBIO-FIBULAR. 227 present two flat oval surfaces covered with, cartilage, and connected together by the following ligaments. Anterior Superior Tibio-fibular. Posterior Superior Tibio-fibular. The Anterior Superior Ligament (fig. 141) consists of two or three broad and flat bands, which pass obliquely upwards and inwards, from the head of the fibula to the outer tuberosity of the tibia. The Posterior Superior Ligament is a single thick and broad band, which passes from the back part of the head of the fibula to the back part of the outer tuberosity of the tibia. It is covered in by the tendon of the Popliteus muscle. A Synovial Membrane lines this articulation. It is occasionally continuous with that of the knee-joint at its upper and back part. 2. Middle Tibio-fibular Articulation". An interosseous membrane extends between the contiguous margins of the tibia and fibula, and separates the muscles on the front from those on the back of the leg. It consists of a thin aponeurotic lamina composed of oblique fibres, which pass between the interosseous ridges on the two bones. It is broader above than below, and presents at its upper part a large oval aperture for the passage of the anterior tibial artery forwards to the anterior aspect of the leg ; and at its lower part, an opening for the passage of the anterior peroneal vessels. It is continuous below with the inferior interosseous ligament ; and is perforated in numerous parts for the passage of small vessels. It is in relation in front with the Tibialis anticus, Extensor longus digitorum, Extensor proprius pollicis, Peroneus tertius, and the anterior tibial vessels and nerve ; behind, with the Tibialis posticus and Flexor longus pollicis. 3. Inferior Tibio-fibular Articulation. This articulation is formed by the rough convex surface at the inner side of the lower end of the fibula, being connected with a similar rough surface on the outer side of the tibia. Below, to the extent of about two lines, these surfaces are smooth and covered with cartilage, which is continuous with that of the ankle- joint. Its ligaments are — Inferior Interosseous. Posterior Inferior Tibio-fibular. Anterior Inferior Tibio-fibular. Transverse. The Inferior Interosseous Ligament consists of numerous short, strong fibrous bands, which pass between the contiguous rough surfaces of the tibia and fibula, constituting the chief bond of union between these bones. It is continuous, above, with the interosseous membrane. The Anterior Inferior Ligament (fig. 144) is a flat triangular band of fibres, broader below than above, which extends obliquely downwards and outwards between the adjacent margins of the tibia and fibula on the front aspect of the articulation. It is in relation, in front, with the Peroneus tertius, the aponeurosis of the leg, and the integument ; behind, with the inferior interosseous ligament, and lies in contact with the cartilage covering the astragalus. The Posterior Inferior Ligament, smaller than the preceding, is disposed in a similar manner on the posterior surface of the articulation. The Transverse Ligament is a long narrow band of ligamentous fibres, con- tinuous with the preceding, passing transversely across the back of the joint, from the external malleolus to the tibia, a short distance from its malleolar process. This ligament projects below the margins of the bones, and forms part of the articulating surface for the astragalus. The Synovial Membrane lining the articular surfaces is derived from that of the ankle-joint. 228 ARTICULATIONS. Actions. The movement permitted in these articulations is limited to a very slight gliding of the articular surfaces one upon another. 4. Ankle-joint. ^ The Ankle is a ginglymoid or hinge-joint. The bones entering into its forma- tion are the lower extremity of the tibia and its malleolus, and the malleolus of the fibula, above, which, united, form an arch, in which is received the upper convex surface of the astragalus and its two lateral facets. These surfaces are covered with cartilage, and connected together by the following ligaments : — Anterior. Internal Lateral. External Lateral. The Anterior Ligament (fig. 143) is a broad, thin, membranous layer, attached above, to the margin of the articular surface of the tibia ; below, to the margin of Fig. 143. — Ankle-joint : Tarsal and Tarso-metatarsal Articulations. Internal View. Right bide. T»S30- MCTATAR ANTIC ?! TARSAL ARTI C the astragalus, in front of its articular surface. It is in relation, in front, with the Extensor tendons of the toes, the tendons of the Tibialis anticus and Peroneus tertius, and the anterior tibial vessels and nerve ; behind, it lies in contact with the synovial membrane. The Internal Lateral or Deltoid Ligament consists of two layers, superficial and deep. The superficial layer is a strong, flat, triangular band, attached, above, to the apex and anterior and posterior borders of the inner malleolus. The most anterior fibres pass forwards to be inserted into the scaphoid ; the middle descend almost perpendicularly to be inserted into the os calcis ; and the posterior fibres pass backwards and outwards to be attached to the inner side of the astragalus. The deep layer consists of a short, thick, and strong fasciculus which passes from the apex of the malleolus to the inner surface of the astragalus, below the articular surface. This ligament is covered in by the tendons of the Tibialis posticus and Flexor longus digitorum muscles. The External Lateral Ligament (fig. 144) consists of three fasciculi, taking different directions, and separated by distinct intervals. ANKLE-JOINT. 229 The anterior fasciculus, the shortest of the three, passes from the anterior margin of the summit of the external malleolus, downwards and forwards, to the astra- galus, in front of its external articular facet. The posterior fasciculus, the most deeply seated, passes from the depression at the inner and back part of the external malleolus to the astragalus, behind its external malleolar facet. Its fibres are almost horizontal in direction. The middle fasciculus, the longest of the three, is a narrow rounded cord, pass- ing from the apex of the external malleolus downwards and slightly backwards to the middle of the outer side of the os calcis. It is covered by the tendons of the Peroneus longus and brevis. There is no posterior ligament, its place being supplied by the transverse ligament of the tibia and fibula. The Synovial Membrane invests the inner surface of the ligaments, and sends a duplicature upwards between the lower extremities of the tibia and fibula for a short distance. Fig. 144. — Ankle-joint : Tarsal and Tarso- metatarsal Articulations. External View. Right Side. NFERIOR TlBlO-FlBULAf* ARTIES ANKLE-JOINT TARSAL ARTIC"? TARSO-METATARSAL ARTIC55 Relations. The tendons, vessels, and nerves in connection with the joint are, in front, from within outwards, the Tibialis anticus, Extensor proprius pollicis, anterior tibial vessels, anterior tibial nerve, Extensor communis digitorum, and Peroneus tertius ; behind, from within outwards, Tibialis posticus, Flexor longus digitorum, posterior tibial vessels, posterior tibial nerve, Flexor longus pollicis, and, in the groove behind the external malleolus, the tendons of the Peroneus longus and Peroneus brevis. The Arteries supplying the joint are derived from the malleolar branches of the anterior tibial and peroneal. The Nerves are derived from the anterior tibial. Actions. The movements of the joint are limited to flexion and extension. There is no lateral motion. 5. Articulations of the Tarsus. These articulations may be subdivided into three sets : 1. The articulation of the first row of tarsal bones. 2. The articulation of the second row of tarsal bones. 3. The articulations of the two rows with each other. 230 ARTICULATIONS. 1. Articulation of the First Eow of Tarsal Bones. The articulation between the astragalus and os calcis is an arthrodial joint connected together by three ligaments : — External Calcaneo-astragaloid. Posterior Calcaneo-astragaloid. Interosseous. The External Calcaneo-astragaloid Ligament (fig. 144) is a short, strong fasci- culus, passing from the outer surface of the astragalus, immediately beneath its external malleolar facet, to the outer edge of the os calcis. It is placed in front of the middle fasciculus of the external lateral ligament of the ankle-joint, with the fibres of which it is parallel. The Posterior Calcaneo-astragaloid Ligament (fig. 143) connects the posterior extremity of the astragalus with the upper contiguous surface of the os calcis ; it is a short narrow band, the fibres of which are directed obliquely backwards and inwards. The Interosseous Ligament forms the chief bond of union between these bones. It consists of numerous vertical and oblique fibres, attached, by one extremity, to the groove between the articulating surfaces of the astragalus; by the other, to a corresponding depression on the upper surface of the os calcis. It is very thick and strong, being at least an inch in breadth from side to side, and serves to unite the os calcis and astragalus solidly together. The Synovial Membranes (fig. 146) are two in number ; one for the posterior calcaneo-astragaloid articulation; a second for the anterior calcaneo-astragaloid joint. The latter synovial membrane is continued forwards between the contigu- ous surfaces of the astragalus and scaphoid bones. 2. Articulations of the Second Row of Tarsal Bones. The articulations between the scaphoid, cuboid, and three cuneiform are effected by the following ligaments : — Dorsal. Plantar. Interosseous. The Dorsal Ligaments are small bands of parallel fibres, which pass from each bone to the neighboring bones with which it articulates. The Plantar Ligaments have the same arrangement on the plantar surface. The Interosseous Ligaments are four in number. They consist of strong trans- verse fibres, which pass between the rough non-articular surfaces of adjoining bones. There is one between the sides of 'the scaphoid and cuboid ; a second between the internal and middle cuneiform bones ; a third between the middle and external cuneiform ; and a fourth between the external cuneiform and cuboid. The scaphoid and cuboid, when in contact, present each a small articulating facet, covered with cartilage, and lined either by a separate synovial membrane, or by an offset from the common tarsal synovial membrane. 3. Articulations of the Two Rows of the Tarsus with each other. These articulations may be conveniently divided into three sets. ] . The arti- culation of the os calcis' with the cuboid. 2. The os calcis with the scaphoid. 3. The astragalus with the scaphoid. 1. The ligaments connecting the os calcis with the cuboid are four in number : — j. , j Superior Calcaneo-cuboid. .Dorsal. -j j nterna ] Calcaneo-cuboid or Interosseous. •p, j Long Calcaneo-cuboid. riantar. < ghort Calcaneo-cuboid. OF THE TARSUS. 23J The Superior Calcaneo-cuboid Ligament (fig. 144) is a thin and narrow fasci- culus, which passes between the contiguous surfaces of the os calcis and cuboid, on the dorsal surface of the joint. The Internal Calcaneo-cuboid or Interosseous Ligament (fig. 144) is a short, but thick and strong, band *of fibres, arising from the os calcis, in the deep groove which intervenes between it and the astragalus; being closely blended, at its ori- gin, with the superior calcaneo-scaphoid ligament. It is inserted into the inner side of the cuboid bone. This ligament forms one of the chief bonds of union between the first and second row of the tarsus. The Long Calcaneo-cuboid (fig. 145), F%- 145. -Ligaments of Plantar Surface of the the most superficial of the two plantar ligaments, is the longest of all the liga- ments of the tarsus, being attached to the under surface of the os calcis, from near the tuberosities, as far forwards as the anterior tubercle ; its fibres pass forwards to be attached to the ridge on the under surface of the cuboid bone, the more su- perficial fibres being continued onwards to the bases of the second, third, and fourth metatarsal bones. This ligament crosses the groove on the under surface of the cuboid bone, converting it into a canal for the passage of the tendon of the Peroneus longus. The Short Calcaneo-cuboid Ligament lies nearer to the bones than the preceding, from which it is separated by a little areo- lar adipose tissue. It is exceedingly broad, about an inch in length, and ex- tends from the tubercle and the depression in front of it on the fore part of the under surface of the os calcis, to the inferior sur- face of the cuboid bone behind the peroneal groove. A synovial membrane is found in this articulation. 2. The ligaments connecting the os calcis with the scaphoid, are two in num- ber: — Superior Calcaneo-scaphoid. Inferior Calcaneo-scaphoid. The Superior Calcaneo-scaphoid (fig. 144) arises, as already mentioned, with the internal calcaneo-cuboid, in the deep groove between the astragalus and os calcis ; it passes forward from the inner side of the anterior extremity of the os calcis to the outer side of the scaphoid bone. These two ligaments resemble the letter Y, being blended together behind, but separated in front. The Inferior Calcaneo-scaphoid (fig. 145) is by far the largest and strongest of the two ligaments of this articulation ; it is a broad and thick band of ligamentous fibres, which passes forwards and inwards from the anterior and inner extremity of the os calcis, to the under surface of the scaphoid bone. This ligament not only serves to connect the os calcis and scaphoid, but supports the head of the astragalus, forming part of the articular cavity in which it is received. Its upper surface is lined by the synovial membrane continued from the anterior calcaneo- astragaloid articulation. Its under surface is in contact with the tendon of the Tibialis posticus muscle. 232 ARTICULATIONS. 3. The articulation between the astragalus and scaphoid is an enarthrodial joint ; the rounded head of the astragalus being received into the concavity formed by the posterior surface of the scaphoid, the anterior articulating surface of the calcaneum, and the upper surface of the calcaneo-scaphoid ligament, which fills up the triangular interval between these bones. The only •ligament of this joint is the superior astragalo-scaphoid, a broad band of ligamentous fibres, which passes obliquely forwards from the neck of the astragalus, to the superior surface of the scaphoid bone. It is thin and weak in texture, and covered by the Extensor tendons. The inferior calcaneo-scaphoid supplies the place of an inferior liga- ment. The Synovial Membrane which lines the joint is continued forwards from the anterior calcaneo-astragaloid articulation. This articulation permits of consider- able mobility ; but its feebleness is such as to occasionally allow of dislocation of the astragalus. The Synovial Membranes (fig. 146) found in the articulations of the tarsus are four in number : one for the posterior calcaneo-astragaloid articulation ; a second for the anterior calcaneo-astragaloid and astragalo-scaphoid articulations ; a third Fig. 146. -Oblique Section of the Articulations of the Tarsus and Metatarsus. Showing the Six Synovial Membranes. for the calcaneo-cuboid articulation; and a fourth for the articulations between the scaphoid and the three cuneiform, the three cuneiform with each other, the external cuneiform with the cuboid, and the middle and external cuneiform with the bases of the second and third metatarsal bones. The prolongation which lines the metatarsal bones passes forwards between the external and middle cuneiform bones. A small synovial membrane is sometimes found between the contiguous surfaces of the scaphoid and cuboid bones. Actions. The movements permitted between the bones of the first row, the astragalus and os calcis, are limited to a gliding upon each other from before backwards, and from side to side. The gliding movement which takes place between the bones of the second row is very slight, the articulation between the scaphoid and cuneiform bones being more movable than those of the cuneiform with each other and with the cuboid. The movement which takes place between the two rows is more extensive, and consists in a sort of rotation, by means of which the sole of the foot may be slightly flexed, and extended, or carried inwards and outwards. TARSO-METATARSAL. 233 6. Takso-metatarsal Articulations. These are arthrodial joints. The bones entering into their formation are the internal, middle, external cuneiform, and cuboid, which articulate with the meta- tarsal bones of the five toes. The metatarsal bone of the great toe articulates with the internal cuneiform ; that of the second is deeply wedged in between the in- ternal and external cuneiform, resting against the middle cuneiform, and being the most strongly articulated of all the metatarsal bones ; the third metatarsal articu- lates with the extremity of the external cuneiform ; the fourth with the cuboid and external cuneiform ; and the fifth with the cuboid. The articular surfaces are covered with cartilage, lined by synovial membrane, and connected together by the following ligaments : — Dorsal. Plantar. Interosseous. The Dorsal Ligaments consist of strong, flat, fibrous bands, which connect the tarsal with the metatarsal bones. The first metatarsal is connected to the internal cuneiform by a single broad, thin, fibrous band; the second has three dorsal ligaments, one from each cuneiform bone ; the third has one from the external cuneiform ; and the fourth and fifth have one each from the cuboid. The Plantar Ligaments consist of longitudinal and oblique fibrous bands con- necting the tarsal and metatarsal bones, but disposed with less regularity than on the dorsal surface. Those for the first and second metatarsal are the most strongly marked ; the second and third receive strong fibrous bands, which pass obliquely across from the internal cuneiform ; the plantar ligaments of the fourth and fifth consist of a few scanty fibres derived from the cuboid. The Interosseous Ligaments are three in number : internal, middle, and external. The internal one passes from the outer extremity of the internal cuneiform, to the adjacent angle of the second metatarsal. The middle one, less strong than the preceding, connects the external cuneiform with the adjacent angle of the second metatarsal. The external interosseous ligament connects the outer angle of the external cuneiform with the adjacent side of the third metatarsal. The Synovial Membranes of these articulations are three in number : one for the metatarsal bone of the great toe, with the internal cuneiform ; one for the second and third metatarsal bones, with the middle and external cuneiform, which is continuous with the great tarsal synovial membrane ; and one for the fourth and fifth metatarsal bones with the cuboid. The synovial membranes of the tarsus and metatarsus are thus seen to be six in number (fig. 146). i Articulations of the Metatarsal Bones with each other. The bases of the metatarsal bones, except the first, are connected together by dorsal, plantar, and interosseous ligaments. The dorsal and plantar ligaments pass from one metatarsal bone to another. The interosseous ligaments lie deeply between the rough non-articular portions of their lateral surfaces. The articular surfaces are covered with cartilage, and provided with synovial membrane, con- tinued forwards from the tarso-metatarsal joints. The digital extremities of the metatarsal bones are united by the transverse metatarsal ligament. It connects the great toe with the rest of the metatarsal bones ; in this respect it differs from the transverse ligament in the hand. Actions. The movement permitted in the tarsal ends of the metatarsal bones is limited to a slight gliding of the articular surfaces upon one another ; considerable motion, however, takes place in their digital extremities. Metatarsophalangeal Articulations. The heads of the metatarsal bones are connected with the concave articular surfaces of the first phalanges by the following ligaments : — Anterior or Plantar. Two Lateral. 234 ARTICULATIONS. They are arranged precisely similar to the corresponding parts in the hand. The expansion of the Extensor tendon supplies the place of a posterior ligament. Actions. The movements permitted in the metatarso-phalangeal articulations are flexion, extension, abduction, and adduction. Akticulation of the Phalanges. The ligaments of these articulations are similar to those found in the hand ; each pair of phalanges being connected by an anterior or plantar and two lateral ligaments, and their articular surfaces lined by synovial membrane. Their actions are also similar. For further information on this subject, the Student is referred to Cruveilhier's "Anatomie Descriptive ;" to Mr. Humphry's able work on the " Human Skeleton, including the Joints ;" and to Arnold's " Tabulae Anatomicse," Fascic. 4. Pars 2, " Icones articulorum et ligamentorum.'' On the textures composing the Joints refer to Todd and Bowman's " Physiological Anatomy," and Kblliker's " Manual of Human Microscopic Anatomy." The Muscles and Fasciae. The Muscles are the active organs of locomotion. They are formed of bundles of reddish fibres, consisting chemically of fibrine, and endowed with the pro- perty of contractility. Two kinds of muscular tissue are found in the animal body, viz., that of voluntary or animal life, and that of involuntary or organic life. The muscles of animal life {striped muscles) are capable of being either exerted or controlled by the efforts of the will. They are composed of bundles of fibres inclosed in a delicate web of areolar tissue. Each bundle consists of numerous smaller ones, inclosed in a similar fibro-areolar covering, and these again of primi- tive fasciculi. The primitive fasciculi consist of a number of filaments, inclosed in a tubular sheath of transparent, elastic, and apparently homogeneous membrane, named by Bowman the " Sarcolemma." The primitive fasciculi are cylindriform or prismatic. Their breadth varies in man from 5 ^ to 5 ^ of an inch, the average of the ma- jority being about ^11 ; their length is not always in proportion to the length of the muscle, but depends on the arrangement of the tendons. This form of muscular fibre is especially characterized by being apparently marked with very fine, dark, parallel lines or strise, which pass transversely round them, in curved or wavy parallel lines, from t ^^tt to j^^s °f an mcn apart. Other striae pass longitu- dinally over the tubes, indicating the direction of the primitive fibrils of which the primitive fasciculus is composed. They are less distinct than the former. The primitive fibrils constitute the proper contractile tissue of the muscle. Each fibril is cylindriform, somewhat flattened, about th^tttf oi> an i nc h m thick- ness, and marked by transverse strise placed at the same distance from each other as the striae on the surface of the fasciculus. Each fibril apparently consists of a single row of minute particles, named " sarcous elements" by Bowman, connected together like a string of beads. Closer examination, however, shows that the elementary particles are little masses of pellucid substance, having a rectangular outline, and appearing dark in the centre. These appearances would favor the suggestion that the elementary particles of which the fibrils are composed are possibly nucleated cells, cohering in a linear series, the transverse marks between them corresponding to their line of junction. Kolliker, however, considers "the sarcous elements as artificial products, occasioned by the breaking up of the fibrils at the parts where they are thinner." This form of muscular fibre composes the whole of the voluntary muscles, all the muscles of the ear, those of the larynx, pharynx, tongue, and upper half of the oesophagus, the heart, and the walls of the large veins at the point where they open into it. The muscles of organic life (unstriped muscles) consist of flattened bands, or of elongated, spindle-shaped fibres, flattened, of a pale color, from j^^ to 3^77 of an inch broad, homogeneous in texture, having a finely mottled aspect, which sometimes appears granular, the granules being occasionally arranged in a linear series, so as to present a striated appearance. Each fibre contains a cylindrical 1 The Muscles and Fasciae are described conjointly, in order that the student may consider the arrangement of the latter in his dissection of the former. It is rare for the student of anatomy in this country to have the opportunity of dissecting the fasciae separately ; and it is for this reason, as well as from the close connection that exists between the muscles and their investing aponeuroses, that they are considered together. Some general observations are first made on the anatomy of the muscles and fasciae, the special description being given in connection with the different regions. 235 236 MUSCLES AND FASCIAE. rod-shaped nucleus, which sometimes appears as a narrow, continuous, dark streak The fibres are united into bundles, which are connected together by areolar tissue and elastic fibres. This form of muscular tissue occurs either scattered" in the areolar tissue, or exists in the form of a muscular membrane, the bundles being arranged parallel, or forming a close interlacement, crossing each other at various angles. The muscular fibre of organic life is found in the alimentary canal, form- ing the muscular coat of the digestive tube from the middle of the oesophagus to the internal sphincter of the anus ; in the posterior wall of the trachea, and in the bronchi; in the ducts of the submaxillary glands; in the gall-bladder and common bile duct ; in the calyces and pelvis of the kidney ; in the ureters and bladder ; and, scantily, in the urethra. In the female it is met with in the vagina, the uterus, Fallopian tubes, and broad ligaments ; in the male, in the scrotum, the epi- didymis, the vas deferens, vesiculoe seminales, the prostate ; and in the cavernous bodies, in both sexes. It is found also in the coats of all arteries, in most veins, and lymphatic vessels ; in the iris and ciliary muscle, and in the skin. Bloodvessels are distributed in considerable abundance to the muscular tissue. In the voluntary muscles the capillaries, which are of extremely minute size, form narrow, oblong meshes, which run in the direction of the fibres. The lymphatic vessels in muscles are few in number, and appear to exist only in the largest muscles. The nerves of voluntary muscles are of large size. The larger branches pass between the fasciculi, and, subdividing, unite to form primary plexuses ; from these, finer bundles, or, single nerve tubes, pass between the mus- cular fibres, and, forming loops, return to the plexus. Each muscle is invested externally by a thin cellular layer, forming what is called its sheath, which not only covers its outer surface, but penetrates into its interior in the intervals between the fasciculi, surrounding these, and serving as a bond of connection between them. The muscles are connected with the bones, cartilages, ligaments and skin, either directly or through the intervention of fibrous structures, called tendons or apo- neuroses. Where a muscle is attached to bone or cartilage, the fibres terminate in blunt extremities upon the periosteum or perichondrium, and do not come into direct relation with the osseous or cartilaginous tissue. Where muscles are con- nected with the skin, they either lie as a flattened layer beneath it, or are con- nected with its areolar tissue by larger or smaller bundles of fibres, as in the muscles of the face. The muscles vary considerably in their form. In the limbs, they are of con- siderable length, especially the more superficial ones, the deep ones being generally broad ; they surround the bones, and form an important protection to the various joints. In the trunk, they are broad, flattened, and expanded, forming the parietes of the cavities which they inclose ; hence the reason of the terms, long, broad, short, etc., used in the description of a muscle. There is considerable variation in the arrangement of the fibres of certain muscles, to the tendons to which they are attached. In some, the fibres are arranged longitudinally, and terminate at either end in a narrow tendon. If the fibres converge, like the plumes of a pen, to one side of a tendon, which runs the entire length of a muscle, it is said, to be penniform, as the Peronei ; or, if they converge to both sides of a tendon, they are called bipenniform, as the Rectus femoris ; if they converge from a broad surface to a narrow tendinous point, they are then said to be radiated, as the Temporal and Glutei muscles. Their size presents considerable variation ; the Gastrocnemius forms the chief bulk of the back of the leg, and the fibres of the Sartorius are nearly two feet in length, whilst the Stapedius, a small muscle of the internal ear, weighs about a grain, and its fibres are not mpre than two lines in length. Tn each case, how- ever, they are admirably adapted to execute the various movements they are required to perform. The names applied to the various muscles have been derived : 1, from their situa- tion, as the Tibialis, Radialis, Ulnaris, Peroneus ; 2, from their direction, as the GENERAL ANATOMY. 23T Rectus abdominis, Obliquus capitis, Transversalis ; 3, from their uses, as Flexors, Extensors, Abductors, etc. ; 4, from their shape, as the Deltoid, Trapezius, Rhom- boideus ; 5, from the number of their divisions, as the Biceps from having two heads, the Triceps from having three heads ; 6, from their points of attachment, as the Sterno-cleido-mastoid, Sterno-hyoid, Sterno-thyroid. In the description of a muscle, the term origin is meant to imply its more fixed or central attachment; and the term insertion, the movable point upon which the force of the muscle is directed : this holds true, however, for only a very small number of muscles, such as those of the face, which are attached by one extremity to the bone, and by the other to the movable integument ; in the greater number, the muscle can be made to act from either extremity. In the dissection of the muscles, the student should pay especial attention to the exact origin, insertion, and actions of each, and its more important relations with surrounding parts. An accurate knowledge of the points of attachment of the muscles is of great importance in the determination of their action. By a knowledge of the action of the muscles, the surgeon is able at once to explain the causes of displacement in the various forms of fracture, or the causes which produce distortion in various forms of deformities, and, consequently, to adopt appropriate treatment in each case. The relations, also, of some of the muscles, especially those in immediate apposition with the larger bloodvessels, and the surface- markings they produce, should be especially remembered, as they form most useful guides to the surgeon in the application of a ligature to these vessels. Tendons are white, glistening, fibrous cords, varying in length and thickness, sometimes round, sometimes flattened, of considerable strength, and only slightl v elastic. They consist almost entirely of white fibrous tissue, the fibrils of which have an undulating course parallel with each other, and firmly united together. They are very sparingly supplied with bloodvessels, the smaller tendons pre- senting in their interior not a trace of them. Nerves also are not present in the smaller tendons ; but the larger ones, as the tendo A chillis, receive nerves which accompany the nutrient vessels. The tendons consist principally of a substance which yields gelatine. Aponeuroses are fibrous membranes, of a pearly- white color, iridescent, glisten- ing, and similar in structure to the tendons. They are destitute of nerves, and the thicker ones are only sparingly supplied with bloodvessels. The tendons and aponeuroses are connected, on the one hand, with the muscles ; and, on the other hand, with the movable structures, as the bones, cartilages, ligaments, fibrous membranes (the sclerotic, for instance), and the synovial mem- branes, the subcrureus and subanconeus for example. Where the muscular fibres are continuous in a direct line, with those of the tendon or aponeurosis, the two are directly continuous, the muscular fibre being distinguishable from that of the tendon only by its striation. But where the muscular fibre joins the tendon or aponeurosis at an oblique angle, the former terminates, according to Kolliker, in rounded extremities, which are received into corresponding depressions on the surface of the latter, the connective tissue between the fibres being continuous with that of the tendon. The latter mode of attachment occurs in all the penni- form and semi-penniform muscles, and in those muscles the tendons of which commence in a membranous form, as the Gastrocnemius and Soleus. The Fasciae {fascia, a bandage) are fibro-areolar or aponeurotic laminae, of variable thickness and strength, found in all regions of the body, investing the softer and more delicate organs. The fasciae have been subdivided, from the structure which they present, into two groups, fibro-areolar or superficial fasciae, and aponeurotic or deep fasciae. The fibro-areolar fascia is found immediately beneath the integument over almost the entire surface of the body, and is generally known as the superficial fascia. It connects the skin with the deep or aponeurotic fascia, and consists of fibro-areolar tissue, containing in its meshes pellicles of fat in varying quantity. In the eyelids and scrotum, where adipose tissue is rarely deposited, this tissue is 238 MUSCLES AND FASCIJE. very liable to serous infiltration. The superficial fascia varies in thickness in different parts of the body : in the groin it is so thick as to be capable of being subdivided into several laminae, but in the palm of the hand it is of extreme thinness, and intimately adherent to the integument. The superficial fascia is capable of separation into two or more layers, between which are found the superficial vessels and nerves, and superficial lymphatic glands ; as the superficial epigastric vessels in the abdominal region, the radial and ulnar veins in the fore- arm, the saphenous veins in the leg and thigh, and, in certain situations, cutaneous muscles, as the Platysma myoides in the neck, Orbicularis palpebrarum around the eyelids. It is most distinct at the lower part of the abdomen* the scrotum, perineum, and in the extremities ; is very thin in those regions where muscular fibres are inserted into the integument, as on the side of the neck, the face, and around the margin of the anus, and almost entirely wanting in the palms of the hands and soles of the feet, where the integument is adherent to the subjacent aponeurosis. The superficial fascia connects the skin to the subjacent parts, serves as a soft nidus for the passage of vessels and nerves to the integument, and retains the warmth of the body, from the adipose tissue contained in its areolae being a bad conductor of caloric. The aponeurotic or deep fascia is a dense, inelastic and unyielding fibrous membrane, forming sheaths for the muscles, and affording them broad surfaces for attachment ; it consists of shining tendinous fibres, placed parallel with one another, and connected together by other fibres disposed in a reticular manner. It is usually exposed on the removal of the superficial fascia, forming a strong invest- ment, which not only binds down collectively the muscles in each region, but gives a separate sheath to each, as well as to the vessels and nerves. The fasciae are thick in unprotected situations, as on the outer side of a limb, and thinner on the inner side. Aponeurotic fasciae are divided into two classes, aponeuroses of insertion, and aponeuroses of investment. The aponeuroses of insertion serve for the insertion of muscles. Some of these are formed by the expansion of a tendon into an aponeurosis, as, for instance, the tendon of the Sartorius ; others do not originate in tendons, as the aponeuroses of the abdominal muscles. The aponeuroses of investment form a sheath for the entire limb, as well as for each individual muscle. Many aponeuroses, however, serve both for investment and insertion. Thus, the aponeurosis given off from the tendon of the Biceps brachialis near its insertion is continuous with, and partly forms, the investing fascia of the forearm, and gives origin to the muscles in this region. The deep fasciae assist the muscles in their action, by the degree of tension and pressure they make upon their surface ; and, in certain situations, this is increased and regulated by muscular action, as, for instance, by the Tensor vaginae femoris and Gluteus maximus in the thigh, by the Biceps in the leg, and Palmaris longus in the hand. In the limbs, the fasciae not only invest the entire limb, but give off septa, which separate the various muscles, and are attached beneath to the periosteum ; these prolongations of fasciae are usually spoken of as intermuscular septa. The Muscles and Fasciae may be arranged, according to the general division of the body, into, 1. Those of the head, face, and neck. 2. Those of the trunk. 3. Those of the upper extremity. 4. Those of the lower extremity. MUSCLES AND FASCIAE OF THE HEAD AND FACE. The Muscles of the Head and Face consist of ten groups, arranged according to the region in which they are situated. 1. Epicranial Eegion. 6. Superior maxillary Begion. 2. Auricular Begion. 7. Inferior maxillary Begion. 8. Palpebral Begion. 8. Intermaxillary Begion. 4. Orbital Begion. 9. Temporo-maxillary Begion. 5. Nasal Begion. 10. Pterygo-maxillary Begion. OCCIPITO-FRONTALIS. 239 The muscles contained in each of these 1. Epicranial Region. Occipito-frontalis. 2. Auricular Region. Attolens aurem. Attrahens aurem. Retrahens aurem. 3. Palpebral Region. Orbicularis palpebrarum. Corrugator supercilii. Tensor tarsi. Levator palpebrae. 4. Orbital Region. Levator palpebrse. Rectus superior. Rectus inferior. Rectus internus. • ■ Rectus externus. Obliquus superior. Obliquus inferior. 5. Nasal Region. Pyramidalis nasi. Levator labii superioris alaaque nasi. Dilator naris posterior. groups are the following: — Dilator naris anterior. Compressor naris. Compressor narium minor. Depressor alae nasi. 6. Superior Maxillary Region. Levator labii superioris. Levator anguli oris. Zygomaticus major. Zygomaticus minor. 7. Inferior Maxillary Region. Levator labii inferioris. Depressor labii inferioris. Depressor anguli oris. 8. Intermaxillary Region. Buccinator. Risorius. Orbicularis oris. ' 9. Temporo-maxillary Region. Masseter. Temporal. 10. Ptery go-maxillary Region. Pterygoideus externus. Pterygoideus internus. 1. Epicranial Region — Occipito-Frontalis. Dissection (fig. 147). The head being shaved, and a block placed beneath the back of the neck, make a vertical incision through the skin from before backwards, commencing at the root of the nose in front, and terminating behind at the occipital protuberance ; make a second incision in a horizontal direction along the forehead and round the side of the head, from the anterior to the Fig. 147. — Dissection of the Head, Face, and Neck. -/ Dissection of scalp 2.3.qf AURICULAR REC1CW 4-.5.G.cf FACE %.8. the mucous membrane, and muscles of the lower lip ; and anastomoses with the inferior labial, and mental branch of the inferior dental artery. The superior coronary is larger, and more tortuous in its course than the pre- ceding. It follows the same course along the edge of the upper lip, lying between the mucous membrane and the Orbicularis, and anastomoses with the artery of the opposite side. It supplies the textures of the upper lip, and gives off in its course two or three vessels which ascend to the nose. One, named the artery of the septum, ramifies on the septum of the nares as far as the point of the nose ; another supplies the ala of the nose. The lateralis nasi is derived from the facial, as that vessel is ascending along the side of the nose ; it supplies the ala and dorsum of the nose, anastomosing with its fellow, the nasal branch of the ophthalmic, the artery of the septum, and the infra-orbital. The angular artery is the termination of the trunk of the facial ; it ascends to the inner angle of the orbit, accompanied by a large vein, the angular ; it dis- tributes some branches on the cheek which anastomose with the infra-orbital, and, after supplying the lachrymal sac, and Orbicularis muscle, terminates by anas- tomosing with the nasal branch of the ophthalmic artery. The anastomoses of the facial artery are very numerous, not only with the vessel of the opposite side, but with other vessels from different sources ; viz., with the sublingual branch of the lingual, with the mental branch of the inferior dental as it emerges from the dental foramen, with the ascending pharyngeal and pos- terior palatine, and with the ophthalmic, a branch of the internal carotid ; it also inosculates with the transverse facial, and with the infra-orbital. Peculiarities. The facial artery not unfrequently arises by a common trunk with the lingual. This vessel also is subject to some variations in its size, and in the extent to which it supplies the face. It occasionally terminates as the submental, and not unfrequently supplies the face only as high as the angle of the mouth or nose. The deficiency is then supplied by enlargement of one of the neighboring arteries. Surgical Anatomy. The passage of the facial artery over the body of the jaw would appear to afford a favorable position for the application of pressure in cases of hemorrhage from the lips, the result either of an accidental wound, or from an operation; but its application is useless, on account of the free communication of this vessel with its fellow, and with numerous branches from different sources. In a wound involving the lip, it is better to seize the part between the fingers, and evert it, when the bleeding vessel may be at once secured with a tenaculum. In order to prevent hemorrhage in cases of excision, or in the removal of diseased growths from the part, the lip should be compressed on each side between the finger and thumb, whilst the surgeon excises the diseased part. In order to stop hemorrhage where the lip has been divided in an operation, it is necessary, in uniting the edges of the wound, to pass the sutures through the cut edges, almost as deep as its mucous surface; by these means, not only are the cut surfaces more neatly adapted to each other, but the possibility of hemorrhage is prevented by including in the suture the divided artery. If the suture is. on the contrary, passed through merely the cutane- ous portion of the wound, hemorrhage occurs into the cavity of the mouth. The student should, lastly, observe the relation of the angular artery to the lachrymal sac, and it will be seen that, aa the vessel passes up along the inner margin of the orbit, it ascends on its nasal side. In operat- ing for fistula lacrymalis, the sac should always be opened on its outer side, in order that this vessel may be avoided. The Occipital Artery arises from the posterior part of the external carotid, opposite the facial, near the lower margin of the Digastric muscle. At its origin, it is covered by the posterior belly of the Digastric and Stylo-hyoid muscles, and part of the parotid gland, the hypoglossal nerve winding around it from behind forwards ; higher up, it passes across the internal carotid artery, the internal jugular vein, and the pneumogastric and spinal accessory nerves; it then ascends to the interval between the transverse process of the atlas and the mastoid process of the temporal bone, passes horizontally backwards, grooving the surface of the latter bone, OCCIPITAL— POSTERIOR AURICULAR— PHARYNGEAL. 377 being covered by the Sternomastoid, Splenius, Digastric, and Trackelo-mastoid muscles, resting upon the Complexus, Superior oblique, and Rectus posticus major muscles ; it then ascends vertically upwards, piercing the cranial attachment of the Trapezius, and passes in a tortuous course over the occiput, as high as the vertex, where it divides into numerous branches. The branches given off from this vessel are the Muscular. Inferior meningeal. Auricular. Arteria princeps cervicis. The muscular branches supply the Digastric, Stylo-hyoid, Sterno-mastoid, Splenius, and Trachelo-mastoid muscles. The branch distributed to the Sterno- mastoid is of large size. The auricular branch supplies the back part of the concha. The meningeal branch ascends with the internal jugular vein, and enters the skull through the foramen lacerum posterius, to supply the dura mater in the posterior fossa. The arteria princeps cervicis (fig. 212) is a large branch which descends along the back part of the neck, and divides into a superficial and deep branch. The former runs beneath the Splenius, giving off branches which perforate that muscle to supply the Trapezius, anastomosing with the superficial cervical artery ; the latter passes beneath the Complexus, between it and the Semi-spinalis colli, and anastomoses with the vertebral, and deep cervical branch of the superior intercostal. The anastomosis between these vessels serves mainly to establish the collateral circulation after ligature of the carotid or subclavian artery. The cranial branches of the occipital artery are distributed upon the occiput; they are very tortuous, and lie between the integument and Occipito-frontalis, anastomosing with the artery of the opposite side, the posterior auricular, and temporal arteries. They supply the back part of the Occipito-frontalis muscle, the integument, pericranium, and one or two branches occasionally pass through the parietal or mastoid foramina, to supply the dura mater. The Posterior Auricular Artery (fig. 209) is a small vessel, which arises from the external carotid, above the Digastric and Stylo-hyoid muscles, opposite the apex of the styloid process. It ascends, under cover of the parotid gland, to the groove between the cartilage of the ear and the mastoid process, immediately above which it divides into two branches, an anterior, which passes forwards to anastomose with the posterior division of the temporal ; and a posterior, which communicates with the occipital. Just before arriving at the mastoid process, this artery is crossed by the portio dura, and has beneath it the spinal accessory nerve. Besides several small branches to the Digastric, Stylo-hyoid, and Sterno-mas- toid muscles, and to the parotid gland, this vessel gives off two branches, the Stylo-mastoid. Auricular. The stylo-mastoid branch enters the stylo-mastoid foramen, and supplies the tympanum, mastoid cells, and semicircular canals. In the young subject, a branch from this vessel forms, with the tympanic branch from the internal maxil- lary, a vascular circle, which surrounds the auditory meatus, and from which delicate vessels ramify on the membrana tympani. The auricular branch is distributed to the back part of the cartilage of the ear, upon which it minutely ramifies, some branches curving round its margin, others perforating the fibro-cartilage, to supply its anterior surface. The Ascending- Pharyngeal Artery (fig. 212), the smallest branch of the external carotid, is a long slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and Stylo-pharyngeus muscle. It arises from the back part of the external carotid, near the commencement of that vessel, and passes up to the under surface of the base of the skull, ascending the neck between the internal carotid and the side of the pharynx, and lying on the 378 ARTERIES. Rectus capitis an ticus major. Its branches maybe subdivided into three sets: 1. Those directed outwards to supply muscles and nerves. 2. Those directed inwards to the pharynx. 3. Meningeal branches. The external branches are numerous small vessels, which supply the Recti antici muscles, the sympathetic, hypoglossal and pneumogastric nerves, and the lymphatic glands of the neck, anastomosing with the ascending cervical artery. The pharyngeal branches are three or four in number. Two of these descend to supply the middle and inferior Constrictors and the Stylo-pharyngeus, ramifying in their substance and in the mucous membrane lining them. The largest of the pharyngeal branches passes inwards, running upon the Superior constrictor, and sends ramifications to the soft palate, Eustachian tube, and tonsil, which take the place of the ascending palatine branch of the facial artery, when that vessel is of small size. The meningeal branches consist of several small vessels, which pass through foramina in the base of the skull, to supply the dura mater. One, the posterior meningeal, enters the cranium through the foramen lacerum posterius with the internal jugular vein. A second passes through the foramen lacerum basis cranii ; and occasionally a third through the anterior condyloid foramen. They are all distributed to the dura mater. The Temporal Artery (fig. 209), the smaller of the two terminal branches of the external carotid, appears, from its direction, to be the continuation of that vessel. It commences in the substance of the parotid gland, in the interspace between the neck of the condyle of the lower jaw and the external meatus ; cross- ing over the root of the zygoma, immediately beneath the integument, it divides about two inches above the zygomatic arch into two branches, an anterior and a posterior. The anterior temporal inclines forwards over the forehead, supplying the muscles, integument, and pericranium in this region, and anastomoses with the supra-orbital and frontal arteries, its branches being directed from before back- wards. The posterior temporal, larger than the anterior, curves upwards and back- wards along the side of the head, lying above the temporal fascia, and inosculates with its fellow of the opposite side, and with the posterior auricular and occipital arteries. The temporal artery, as it crosses the zygoma, is covered by the Attrahens aurem muscle, and by a dense fascia given off from the parotid gland ; it is also usually crossed by one or two veins, and accompanied by branches of the facial and temporo-auricular nerves. Besides some twigs to the parotid gland, the articulation of the jaw, and the Masseter muscle, its branches are the Transverse facial. Middle temporal. Anterior auricular. The transverse facial is given off from the temporal before that vessel quits the parotid gland ; running forwards through its substance, it passes transversely across the face, between Stenon's duct and the lower border of the zygoma, and divides on the side of the face into numerous branches, which supply the parotid gland, the Masseter muscle, and the integument, anastomosing with the facial and infra-orbital arteries. This vessel rests on the Masseter, and is accompanied by one or two branches of the facial nerve. The middle tempioral artery arises immediately above the zygomatic arch, and, perforating the temporal fascia, supplies the Temporal muscle, anastomosing with the deep temporal branches of the internal maxillary. It occasionally gives off an orbital branch, which runs along the upper border of the zygoma, between the two layers of the temporal fascia, to the outer angle of the orbit ; it supplies the Orbicularis, and anastomoses with the lachrymal and palpebral branches of the ophthalmic artery. INTERNAL MAXILLARY. 379 The anterior auricular branches are distributed to the anterior portion of the pinna, the lobule, and part of the external meatus, anastomosing with branches of the posterior auricular. Surgical Anatomy. It occasionally happens that the surgeon is called upon to perform the operation of arteriotomy upon this vessel in cases of inflammation of the eye or brain. Under these circumstances, the anterior branch is the one usually selected. If the student will con- sider the relations of the trunk of this vessel as it crosses the zygomatic arch, with the surround- ing structures, he will observe that it is covered by a thick and dense fascia, crossed by one or ' two veins, and accompanied by branches of the facial and temporo-auricular nerves. Bleeding should not be performed in this situation, as much difficulty may arise from the dense fascia covering this vessel preventing a free flow of blood, and considerable pressure is requisite after- wards to repress it. Again, a varicose aneurism may be formed by the accidental opening of one of the veins covering it; or severe neuralgic pain may arise from the operation implicating one of the nervous filaments which accompany the artery. The anterior branch is, on the contrary, subcutaneous, is a large vessel, and as readily com- pressed as any other portion of the artery ; it should consequently always be selected for the operation. The Internal Maxillary, the larger of the two terminal branches of the external carotid, passes inwards, at right angles from that vessel, to the inner side of the neck of the condyle of the lower jaw, to supply the deep structures of the face. At its origin, it is imbedded in the substance of the parotid gland, being on a level with the lower extremity of the lobe of the ear. In the first part of its course (maxillary portion), the artery passes horizon- tally forwards and inwards, between the ramus of the jaw and the internal late- ral ligament. The artery here lies parallel with the auriculo-temporal nerve ; it crosses the inferior dental nerve, and lies beneath the narrow portion of the Ex- ternal pterygoid muscle. In the second part of its course (pterygoid portion), it ascends obliquely for- wards and upwards upon the outer surface of the External pterygoid muscle, being covered by the ramus of the lower jaw, and lower part of the Temporal muscle. In the third part of its course (spheno-maxillary portion), it approaches the superior maxillary bone, and enters the spheno-maxillary fossa, in the interval between the processes of origin of the External pterygoid, where it lies in rela- tion with Meckel's ganglion, and gives off its terminal branches. Peculiarities. Occasionally, this artery passes between the two Pterygoid muscles. The ves- sel in this case passes forwards to the interval between the processes of origin of the External pterygoid, in order to reach the maxillary bone. Sometimes the vessel escapes from beneath the External pterygoid by perforating the middle of this muscle. The branches of this vessel may be divided into three groups, corresponding with its three divisions. 1. Branches from the Maxillary Portion. Tympanic. Small meningeal. Middle meningeal. Inferior dental. The tympanic branch passes upwards behind the articulation of the lower jmv, enters the tympanum through the fissura Glaseri, supplies the Laxator tympani, and ramifies upon the membrana tympani, anastomosing with the stylo-mastoid and Vidian arteries. The middle meningeal is the largest of the branches which supply the dura mater. It arises from, the internal maxillary between the internal lateral ligament and the neck of the jaw, and ascends vertically upwards to the foramen spinosum in the spinous process of the sphenoid bone. On entering the cranium, it divides into two branches, an anterior and a posterior. The anterior branch, the larger, crosses the great ala of the sphenoid, and reaches the groove, or canal, in the anterior inferior angle of the parietal bone ; it then divides into branches which 380 ARTERIES. spread out between the dura mater and internal surface of the cranium, some passing upwards over the parietal bone as far as the vertex, and others backwards to the occipital bone. The posterior branch crosses the squamous portion of the temporal, and on the inner surface of the parietal bone divides into branches which supply the posterior part of the dura mater and cranium. The branches of this vessel are distributed to the dura mater, but chiefly to the bones; they anastomose Fig. 210. — The Internal Maxillary Artery, and its Branches. tPttryqe 'Palatini f I & . 211. Elan cf the franc hes [^tZ^naFaMin. \SplunPalat\itt with the arteries of the opposite side, and with the anterior and posterior menin- geal. The middle meningeal, on entering the cranium, gives off the following colla- teral branches: 1. Numerous small vessels to the ganglion of the fifth nerve, and to the dura mater in this situation. 2. A branch to the facial nerve, which enters the hiatus Fallopii, supplies the facial nerve, and anastomoses with the stylo- mastoid branch of the posterior auricular artery. 3. Orbital branches, which pass through the sphenoidal fissure, or through separate canals in the great wing of the sphenoid, to anastomose with the lachrymal or other branches of the oph- thalmic artery. 4. Temporal branches, which pass through foramina in the great wing of the sphenoid, and anastomose in the temporal fossa with the deep temporal arteries. The small meningeal is sometimes derived from the preceding. It enters the skull through the foramen ovale, and supplies the Casserian ganglion and dura INTERNAL MAXILLARY. 381 mater. Before entering the cranium, it gives off a branch to the nasal fossa and soft palate. The inferior dental descends with the dental nerve, to the foramen on the inner side of the ramus of the jaw. It runs along the dental canal in the substance of the bone, accompanied by the nerve, and opposite the bicuspid tooth divides into two branches, incisor and mental ; the former is continued forwards beneath the incisor teeth as far as the symphysis, where it anastomoses with the artery of the opposite side ; the mental branch escapes with the nerve at the mental foramen, supplies the structures composing the chin, and anastomoses with the submental, inferior labial, and inferior coronary arteries. As the dental artery enters the foramen, it gives off a mylo-hyoid branch, which runs in the mylo-hyoid groove, and ramifies on the under surface of the Mylo-hyoid muscle. The dental and incisor arteries, during their course through the substance of the bone, give off a few twigs which are lost in the diploe, and a series of branches which corre- spond in number to the roots of the teeth ; these enter the minute apertures at the extremities of the fangs, and ascend to supply the pulp of the teeth. 2. Branches of the Second or Pterygoid Portion. Deep temporal. Masseteric. Pterygoid. Buccal. These branches are distributed, as their names imply, to the muscles in the maxillary region. The deep temporal branches, two in number, anterior and posterior, each occupy that part of the temporal fossa indicated by its name. Ascending between the Temporal muscle and pericranium, they supply that muscle, and anastomose with the other temporal arteries ; the anterior branch communicating with the lach- rymal through small branches which perforate the malar bone. The pterygoid branches, irregular in their number and origin, supply the Ptery- goid muscles. The masseteric is a small branch which passes outwards above the sigmoid notch of the lower jaw, to the deep surface of the Masseter. It supplies that muscle, and anastomoses with the masseteric branches of the facial and transverse facial arteries. The buccal is a small branch which runs obliquely forwards between the Internal pterygoid and the ramus of the jaw, to the outer surface of the Buccinator, to which it is distributed, anastomosing with branches of the facial artery. 3. Branches of the Third or Spheno-maxillary Portion. Alveolar. Vidian. Infra-orbital. Ptery go-palatine. Posterior or Descending palatine. Nasal or Spheno-palatine. The alveolar is given off from the internal maxillary by a common branch with the infra-orbital, and just as the trunk of the vessel is passing into the spheno- maxillary fossa. Descending upon the tuberosity of the superior maxillary bone, it divides into numerous branches ; one, the superior dental, larger than the rest, supplies the molar and biscuspid teeth, its branches entering the foramina in the alveolar process ; some branches pierce the bone to supply the lining of the antrum, and others are continued forwards on the alveolar process to supply the gums. The infra-orbital appears, from its direction, to be the continuation of the trunk of the internal maxillary. It arises from that vessel by a common trunk with the preceding branch, and runs along the infra-orbital canal with the superior maxillary nerve, emerging upon the face at the infra-orbital foramen, beneath the Levator labii superioris. Whilst contained in the canal, it gives off' branches which ascend into the orbit, and supply the Inferior rectus, and Inferior oblique 382 SURGICAL ANATOMY. muscles, and the lachrymal gland. Other branches descend through canals hi tha bone, to supply the mucous membrane of the antrum, and the front teeth of the upper jaw. On the face, it supplies the lachrymal sac, and inner angle of the orbit, anastomosing with the facial artery and nasal branch of the ophthalmic; and other branches descend beneath the elevator of the upper lip, and anastomose with the transverse facial and buccal branches. The four remaining branches arise from that portion of the internal maxillary which is contained in the spheno-maxillary fossa. The descending palatine passes down along the posterior palatine canal with the posterior palatine branches of Meckel's ganglion, and, emerging from the posterior palatine foramen, runs forwards in a groove on the inner side of the alveolar border of the hard palate, to be distributed to the gums, the mucous membrane of the hard palate, and palatine glands. Whilst it is contained in the palatine canal, it gives off branches, which descend in the accessory palatine canals to supply the soft palate, anastomosing with the ascending palatine artery ; and ante- riorly it terminates in a small vessel, which ascends in the anterior palatine canal, and anastomoses with the artery of the septum, a branch of the spheno-palatine. The Vidian branch passes backwards along the Vidian canal with the Vidian nerve. It is distributed to the upper part of the pharynx and Eustachian tube, sending a small branch into the tympanum. The pterygopalatine is also a very small branch, which passes backwards through the pterygopalatine canal with the pharyngeal nerve, and is distributed to the upper part of the pharynx and Eustachian tube. The nasal or spheno-palatine passes through the spheno-palatine foramen into the cavity of the nose, at the back part of the superior meatus, and divides into two branches ; one internal, the artery of the septum, passes obliquely downwards and forwards along the septum nasi, supplies the mucous membrane, and anasto- moses in front with the ascending branch of the descending palatine. The external branches, two or three in number, supply the mucous membrane cover- ing the lateral wall of the nares, the antrum, and the ethmoid and sphenoid cells. Surgical Anatomy of the Triangles of the Neck. The student having considered the relative anatomy of the large arteries of the neck and their branches, and the relations they bear to the veins and nerves, should now examine these structures collectively, as they present themselves in certain regions of the neck, in each of which important operations are being con- stantly performed. For this purpose, the Sterno-mastoid, or any other muscles that have been divided in the dissection of these vessels, should be replaced in their normal posi- tion ; the head should be supported by placing a block at the back of the neck, and the face turned to the side opposite to that which is being examined. The side of the neck presents a somewhat quadrilateral outline, limited, above by the lower border of the body of the jaw, and an imaginary line extending from the angle of the jaw to the mastoid process; below, by the prominent upper border of the clavicle ; in front, by the median line of the neck ; behind, by the anterior margin of the Trapezius muscle. This space is subdivided into two large triangles by the Sterno-mastoid muscle, which passes obliquely across the neck, from the sternum and clavicle, below, to the mastoid process, above. The trian- gular space in front of this muscle is called the anterior triangle; and that behind it, the posterior triangle. Anterior Triangular Space. The anterior triangle is limited, in front, by a line extending from the chin to the sternum; behind, by the anterior margin of the Sterno-mastoid; its base, directed upwards, is formed by the lower border of the body of the jaw, and a line OF THE TRIANGLES OF THE NECK. 383 extending from the angle of the jaw to the mastoid process ; its apex is formed below by the sternum. This space is covered by the integument, superficial fascia, Platysma, deep fascia, crossed by branches of the facial and superficial cer- vical nerves, and subdivided into three smaller triangles by the Digastric muscle, above, and the anterior belly of the Omo-hyoid, below. These are named, from below upwards, the inferior carotid triangle, the superior carotid triangle, and the submaxillary triangle. The Inferior Carotid Triangle, is limited, in front, by the median line of the neck ; behind, by the anterior margin of the Sterno-mastoid ; above, by the anterior belly of the Omo-hyoid ; and it is covered by the integument, superficial fascia, Platysma, and deep fascia ; ramifying between which is seen the descending branch of the superficial cervical nerve. Beneath these superficial structures are the Sterno-hyoid and Sterno-thyroid muscles, which, together with the anterior margin of the Sterno-mastoid, conceal the lower part of the common carotid artery. This vessel is inclosed within its sheath, together with the internal jugular vein, and pneumogastric nerve; the vein lying on the outer side of the artery on the right side of the neck, but overlapping it, or passing directly across it on the left side ; the nerve lying between the artery and vein, on a plane posterior to both. In front of the sheath are a few filaments descending from the loop of communi- cation between the descendens and communicans noni ; behind the sheath are seen the inferior thyroid artery, the recurrent laryngeal and sympathetic nerves ; and on its inner side, the trachea, the thyroid gland, much more prominent in the female than in the male, and the lower part of the larynx. In the upper part of this space, the common carotid artery may be tied below the Omo-hyoid muscle. The Superior Carotid Triangle is bounded, behind, by the Sterno-mastoid; below, by the anterior belly of the Omo-hyoid ; and above, by the posterior belly of the Digastric muscle. Its floor is formed by parts of the Thyro-hyoid, Hyo- glossus, and the inferior and middle Constrictor muscles of the pharynx ; and it is covered by the integument, superficial fascia, Platysma, and deep fascia; rami- fying between which are branches of the facial and superficial cervical nerves. This space contains the upper part of the common carotid artery, which bifurcates opposite the upper border of the thyroid cartilage into the external and internal carotid. These vessels are concealed from view by the anterior margin of the Sterno-mastoid muscle, which overlaps them. The external and internal carotids lie side by side, the external being the most anterior of the two. The following branches of the external carotid are also met with in this space : the superior thyroid, which runs forwards and downwards ; the lingual, which passes directly forwards ; the facial, forwards and upwards ; the occipital is directed backwards ; and the ascending pharyngeal runs directly upwards on the inner side of the in- ternal carotid. The veins met with are: — the internal jugular, which lies on the outer side of the common and internal carotid vessels ; and veins corresponding to the above-mentioned branches of the external carotid, viz., the superior thyroid, the lingual, facial, ascending pharyngeal, and sometimes the occipital; all of which accompany their corresponding arteries, and terminate in the internal jugular. In front of the sheath of the common carotid is the descendens noni, the hypo- glossal, from which it is derived, crossing both carotids above, curving round the occipital artery at its origin. Within the sheath, between the artery and vein, and behind both, is the pneumogastric nerve ; behind the sheath, the sympathetic. On the outer side of the vessels, the spinal accessory nerve runs for a short distance before it pierces the Sterno-mastoid muscle ; and on the inner side of the internal carotid, just below the hyoid bone, may be seen the superior laryngeal nerve ; and still more inferiorly, the external laryngeal nerve. The upper part of the larynx and the pharynx are also found in the front part of this space. The Submaxillary Triangle corresponds to that part of the neck immediately beneath the body of the jaw. It is bounded, above, by the lower border of the body of the jaw, the parotid gland, and mastoid process ; behind by the posterior belly of the Digastric and Stylo-hyoid muscles : in front, by the middle line of 384 SURGICAL ANATOMY. the neck. The floor of this space is formed by the anterior belly of the Digastric, the Mylo-hyoid, and Hyo-glossus muscles, and it is covered by the integument, superficial fascia, Platysma, and deep fascia ; ramifying between which are branches of the facial and. ascending filaments of the superficial cervical nerve. This space contains, in front, the submaxillary gland, imbedded in the surface of which is the facial artery and vein, and its glandular branches ; beneath this gland, on the sur- face of the Mylo-hyoid muscle, are the submental artery, and the mylo-hyoid artery and nerve. The back part of this space is separated from the front part by the stylo-maxillary ligament ; it contains the external carotid artery, ascending deeply in the substance of the parotid gland; this vessel here lies in front of, and super- ficial to, the internal carotid, being crossed by the facial nerve, and gives off in its course the posterior auricular, temporal, and internal maxillary branches ; more deeply are the internal carotid, the internal jugular vein, and the pneumogastric nerve, separated from the external carotid by the Stylo-glossus and Stylo-pharyn- geus muscles, and the glosso-pharyngeal nerve. Posteeior Triangular Space. The posterior triangular space is bounded, in front, by the Sterno-mastoid muscle ; behind, by the anterior margin of the Trapezius ; its base corresponds to the upper border of the clavicle, its apex to the occiput. This space is crossed, about an inch above the clavicle, by the posterior belly of the Omo-hyoid, which divides it unequally into two triangles, an upper or occipital, and a lower or subclavian. The Occipital, the larger of the two posterior triangles, is bounded, in front, by the Sterno-mastoid ; behind, by the Trapezius ; below, by the Omo-hyoid. Its floor is formed from above downwards by the Splenius, Levator anguli scapulas, and the middle and posterior Scaleni muscles. It is covered by the integument, the Platysma below, the superficial and deep fasciae, and crossed, above, by the ascending branches of the cervical plexus : the spinal accessory nerve is directed obliquely across the space from the Sterno-mastoid, which it pierces, to the under surface of the Trapezius; below, it is crossed by the descending branches of the same plexus, and the transversalis colli artery and vein. A chain of lymphatic glands is also found running along the posterior border of the Sterno-mastoid, from the mastoid process to the root of the neck. The Subclavian, the smaller of the two posterior triangles, is bounded, above, by the posterior belly of the Omo-hyoid ; below, by the clavicle ; its base, directed forwards, being formed by the Sterno-mastoid. The size of this space varies according to the extent of attachment of the clavicular portion of the Sterno- mastoid and Trapezius muscles, and also according to the height at which the Omo-hyoid crosses the neck above the clavicle. The height also of this space varies much, according to the position of the arm, being much diminished on raising the limb, on account of the ascent of the clavicle, and increased on drawing the arm downwards, when this bone is consequently depressed. This space is covered by the integument, superficial and deep fascioa ; and crossed by the descending branches of the cervical plexus. Just above the level of the clavicle, the third portion of the subclavian artery curves outwards and downwards from the outer margin of the Scalenus anticus, across the first rib, to the axilla. Sometimes, this vessel rises as high as an inch and a-half above the clavicle, or to any point intermediate between this and its usual level. Occasionally, it passes in front of the Scalenus anticus, or pierces the fibres of this muscle. The subclavian vein lies beneath the clavicle, and is usually not seen in this space ; but it occasionally rises as high up as the artery, and has even been seen to pass with that vessel behind the Scalenus anticus. The brachial plexus of nerves lies above the artery, and in close -contact with it. Passing transversely across the clavicular margin of the space, are the suprascapular vessels ; and traversing its upper angle in the same direction, the transverse cervical vessels. The external jugular vein descends INTERNAL CAROTID. 385 vertically downwards behind the posterior border of the Sterno-mastoid, to terminate in the Subclavian; it receives the transverse cervical and suprascapular veins, which occasionally form a plexus in front of the artery, and a small vein which crosses the clavicle from the cephalic. The small nerve to the Subclavius also crosses this space about its centre. Internal Carotid Artery. The Internal Carotid Artery commences at the bifurcation of the common carotid, opposite the upper border of the thyroid cartilage, and ascends perpen- dicularly upwards, in front of the transverse processes of the three upper cervical vertebrae, to the carotid foramen in the petrous portion of the temporal bone. Fig. 212. — The Internal Carotid and Vertebral Arteries. Right Side. 386 ARTERIES. After ascending in it for a short distance, it passes forwards and inwards through the carotid canal, and, ascending a little by the side of the sella Turcica, curves upwards by the anterior clinoid process, where it pierces the dura mater, and divides into its terminal branches. This vessel supplies the anterior part of the brain, the eye, and its appendages. Its size, in the adult, is equal to that of the external carotid. In the child, it is larger than that vessel. It is remarkable for the number of curvatures that it presents in different parts of its course. In its cervical portion it occasionally pre- sents one or two flexures near the base of the skull, whilst through the rest of its extent it describes a double curvature, which resembles the italic letter / placed horizontally S>. These curvatures most probably diminish the velocity of the current of blood, by increasing the extent of surface over which it moves, and adding to the amount of impediment produced from friction. In considering the course and relations of this vessel, it may be conveniently divided into four por- tions, a cervical, petrous, cavernous, and cerebral. Cervical Portion. This portion of the internal carotid at its commencement is very superficial, being contained in the superior carotid triangle, on the same level as, but behind, the external carotid, overlapped by the Sterno-mastoid, and covered by the Platysma, deep fascia, and integument ; it then passes beneath the parotid gland, being crossed by the hypoglossal nerve, the Digastric and Stylo-hyoid muscles, and the external carotid and occipital arteries. Higher up, it is separated from the external carotid by the Stylo-glossus and Stylo-pharyngeus muscles, the glossopharyngeal nerve, and pharyngeal branch of the vagus. It is in relation, behind, with the Rectus anticus major, the superior cervical ganglion of the sympathetic, and superior laryngeal nerve ; externally, with the internal jugular vein, and pneumogastric nerve ; internally, with the pharynx, tonsil, and ascend- ing pharyngeal artery. Petrous Portion. When the internal carotid artery enters the canal in the petrous portion of the temporal bone, it first ascends a short distance, then curves forwards and inwards, and again ascends as it leaves the canal to enter the cavity of the skull. In this canal, the artery lies at first anterior to the tympanum, from which it is separated by a thin bony lamella, which is cribriform in the young subject, and often absorbed in old age. It is separated from the bony wall of the carotid canal by a prolongation of dura mater, and is surrounded by fila- ments of the carotid plexus. Cavernous Portion. The internal carotid artery, in this part of its course, at first ascends to the posterior clinoid process, then passes forwards by the side of the body of the sphenoid bone, being situated on the inner wall of the cavernous sinus, in relation, externally, with the sixth nerve, and covered by the lining membrane of the sinus. The third, fourth, and ophthalmic nerves are placed on the outer wall of the sinus, being separated from its cavity by the lining membrane. Cerebral Portion. On the inner side of the anterior clinoid process the internal carotid curves upwards, perforates the dura mater bounding the sinus, and is received into a sheath of the arachnoid. This portion of the artery is on the outer side of the optic nerve ; it lies at the inner extremity of the fissure of Sylvius, having the third nerve externally. Peculiarities. The length of the internal carotid varies according to the length of the neck, and also according to the point of bifurcation of the common carotid. Its origin sometimes takes place from the arch of the aorta; in such rare instances, this vessel was placed nearer the middle line of the neck than the external carotid, as far upwards as the larynx, when the latter vessel crossed the internal carotid. The course of the vessel, instead of being straight, may be very tortuous. A few instances are recorded in which this vessel was altogether absent : in one of these the common carotid ascended the neck, and gave off the usual branches of the external carotid, the craninl portion of the vessel being replaced by two branches of the internal maxil- lary, which entered the skull through the foramen rotundum and foramen ovale, and joined to form a single vessel. Surgical Anatomy. The cervical part of the internal carotid is sometimes wounded by a stab or gunshot wound in the neck, or even occasionally by a stab from within the mouth, as when OPHTHALMIC. 387 a person receives a thrust from the end of a parasol, or falls down with a tobacco-pipe in his mouth. In such cases a ligature should be applied to the common carotid. Its relation with the tonsil should be especially remembered, as instances have occurred in which the artery has been wounded, during the operation of scarifying the tonsil, and fatal hemorrhage has super- vened. The branches given off from the internal carotid are : — From the Petrous Portion From the Cavernous Portion From the Cerebral Portion Tympanic. ( Arteria receptaculi. < Anterior meningeal. ( Ophthalmic, f Anterior cerebral. J Middle cerebral. I Posterior communicating. (_ Anterior choroid. The cervical portion of the internal carotid gives off no branches. The tympanic is a small branch which enters the cavity of the tympanum, through a minute foramen in the carotid canal, and anastomoses with the tympanic branch of the internal maxillary, and stylo-mastoid arteries. The arterise receptaculi are numerous small vessels, derived from the internal carotid in the cavernous sinus ; they supply the pituitary body, the Casserian gan- glion, and the walls of the cavernous and inferior petrosal sinuses. One of these branches, distributed to the dura mater, is called the anterior meningeal; it anas- tomoses with the middle meningeal. The Ophthalmic Artery arises from the internal carotid, just as that vessel is emerging from the cavernous sinus, on the inner side of the anterior clinoid Fig. 213. — The Ophthalmic Artery and its Brandies, the Roof of the Orbit having been removed. Katal PaJfthral Itvntal AnUrior X3i<™>Xo.1- Ftuttritr JSSibo. Oplukalmio Tntemat Carotid process, and enters the orbit through the optic foramen, below, and on the outer side of, the optic nerve. It then crosses above, and to the inner side of, this nerve, to the inner wall of the orbit, and passing horizontally forwards, beneath 388 ARTERIES. the lower border of the Superior oblique muscle, passes to the inner angle of the eye, where it divides into two terminal branches, the frontal and nasal. Branches. The branches of this vessel may be divided into an orbital group, which are distributed to the orbit and surrounding parts ; and an ocular group, which supply the muscles and globe of the eye. Orbital Group. Ocular Group. Lachrymal. . Muscular. Supra-orbital. Anterior ciliary. Posterior ethmoidal. Short ciliary. Anterior ethmoidal. Long ciliary. Palpebral. Arteria centralis retinae. Frontal. Nasal. The lachrymal is the first, and one of the largest branches, derived from the ophthalmic, arising close to the optic foramen, and not unfr^quently from that vessel before entering the orbit. It accompanies the lachrymal nerve along the upper border of the External rectus muscle, and is distributed to the lachrymal gland. Its terminal branches, escaping from the gland, are distributed to the upper eyelid and conjunctiva, anastomosing with the palpebral arteries. The lachrymal artery gives off one or two malar branches, one of which passes through a foramen in the malar bone to reach the temporal fossa, and anastomoses with the deep temporal arteries; the other appears on the cheek, and anasto- moses with the transverse facial. A branch is also sent backwards, through the sphenoidal fissure, to the dura mater, which anastomoses with a branch of the middle meningeal artery. Peculiarities. The lachrymal artery is sometimes derived from one of the anterior branches of the middle meningeal artery. The supra-orbital artery, the largest branch of the ophthalmic, arises from that vessel above the optic nerve. Ascending so as to rise above all the muscles of the orbit, it passes forwards, with the frontal nerve, between the periosteum and Levator palpebrae ; and, passing through the supra-orbital foramen, divides into a superficial and deep branch, which supply the muscles and integument of the forehead and pericranium, anastomosing with the temporal, angular branch of the facial, and the artery of the opposite side. This artery in the orbit supplies the Superior rectus and the Levator palpebral sends a branch inwards, across the pulley of the Superior oblique muscle, to supply the parts at the inner canthus, and at the supra-orbital foramen frequently transmits a branch to the diploe. The ethmoidal branches are two in number, posterior and anterior. The former, which is the smaller, passes through the posterior ethmoidal foramen, supplies the posterior ethmoidal cells, and, entering the cranium, gives off a meningeal branch, which supplies the adjacent dura mater, and nasal branches, which descend into the nose through apertures in the cribriform plate, anasto- mosing with branches of the spheno-palatine. The anterior ethmoidal artery accompanies the nasal nerve through the anterior ethmoidal foramen, supplies the anterior ethmoidal cells, and frontal sinuses, and, entering the cranium, divides into a meningeal branch, which supplies the adjacent dura mater, and a nasal branch which descends into the nose, through an aperture in the cribriform plate. The palpebral arteries, two in number, superior and inferior, arise from the ophthalmic, opposite the pulley of the Superior oblique muscle ; they encircle the eyelids near their free margin, forming a superior and an inferior arch, which lie between the Orbicularis muscle and tarsal cartilages; the superior palpebral inosculating at the outer angle of the orbit with the orbital branch of the temporal artery; the inferior palpebral anastomosing with the orbital branch of the infra-orbital artery, at the inner side of the lid. From this anastomosis, a branch OPIITHALMIC. 389 passes to the nasal duet, ramifying, in its mucous membrane, as far as the inferior meatus. Fig. 214.— The Arteries of the Base of the Brain. The Right Half of the Cerebellum and Pons have been removed. The fron tal artery, one of the terminal branches of the ophthalmic, passes from the orbit at its inner angle, and, ascending on the forehead, supplies the muscles, integument, and pericranium, anastomosing with the supra-orbital artery. The nasal artery, the other terminal branch of the ophthalmic, emerges from the orbit above the tendo oculi, and, after giving a branch to the lachrymal sac, 390 ARTERIES. divides into two, one of which anastomoses with the angular artery ; the other branch, the dorsalis nasi, runs along the dorsum of the nose, supplies its entire surface, and anastomoses with the artery of the opposite side. The ciliary arteries are divisible into three groups, the short, long, and anterior. The short ciliary . arteries, from twelve to fifteen in number, arise from the ophthalmic, or some of its branches ; they surround the optic nerve as they pass forwards to the posterior part of the eyeball, pierce the sclerotic coat around the entrance of this nerve, and supply the choroid coat and ciliary processes. The long ciliary arteries, two in number, also pierce the posterior part of the sclerotic, and run forwards, along each side of the eyeball, between the sclerotic and choroid, to the ciliary ligament, where they divide into two branches ; these form an arterial circle around the circumference of the iris, from which numerous radiating branches pass forwards, in its substance, to its free margin, where they form a second arterial circle around its pupillary margin. The anterior ciliary arteries are derived from the muscular branches; they pierce the sclerotic a short distance from the cornea, and terminate in the great arterial circle of the iris. The arteria centralis retinse is one of the smallest branches of the ophthalmic artery. It arises near the optic foramen, pierces the optic nerve obliquely, and runs forwards, in the centre of its substance, to the retina, in which its branches are distributed as far forwards as the ciliary processes. In the human foetus, a small vessel passes forwards, through the vitreous humor, to the posterior surface of the capsule of the lens. The muscular branches, two in number, superior and inferior, supply the muscles of the eyeball. The superior, the smaller, often wanting, supplies the Levator palpebrse, Superior rectus, and Superior oblique. The inferior, more constant in its existence, passes forwards, between the optic nerve and Inferior rectus, and is distributed to the External and Inferior recti, and Inferior oblique. This vessel gives off most of the anterior ciliary arteries. The Cerebral Branches of the internal carotid are, the anterior cerebral, the middle cerebral, the posterior communicating, and the anterior choroid. The anterior cerebral arises from the internal carotid, at the inner extremity of the fissure of Sylvius. It passes forwards in the great longitudinal fissure between the two anterior lobes of the brain, being connected, soon after its origin, with the vessel of the opposite side by a short anastomosing trunk, about two lines in length, the anterior communicating. The two anterior cerebral arteries, lying side by side, curve round the anterior border of the corpus callosum, and run along its upper surface to its posterior part, where they terminate by anastomosing with the posterior cerebral arteries. They supply the olfactory and optic nerves, the under surface of the anterior lobes, the third ventricle, the anterior perforated space, the corpus callosum, and the inner surface of the hemispheres. The anterior communicating artery is a short branch, about two lines in length, but of moderate size, connecting together the two anterior cerebral arteries across the longitudinal fissure. Sometimes this vessel is wanting, the two arteries joining together to form a single trunk, which afterwards subdivides ; or the' vessel may be wholly or partially subdivided into two ; frequently, it is longer and smaller than usual. The middle cerebral artery, the largest branch of the internal carotid, passes obliquely outwards along the fissure of Sylvius, within which it divides into three branches : an anterior, which supplies the pia mater, investing the surface of the anterior lobe ; a posterior, which supplies the middle lobe ; and a median branch, which supplies the small lobe at the outer extremity of the Sylvian fissure. Near its origin, this vessel gives off numerous small branches, which enter the substantia perforata, to be distributed to the corpus striatum. The 2 losier " l ' or communicating artery arises from the back part of the internal carotid, runs directly backwards, and anastomoses with the posterior cerebral, a SUBCLAVIAN. 391 branch of the basilar. This artery varies considerably in size, being sometimes small, and occasionally so large that the posterior cerebral may be considered as arising from the internal carotid rather than from the basilar. It is frequently larger on one side than on the other. The anterior choroid is a small but constant branch which arises from the back part of the internal carotid, near the posterior communicating artery. Passing backwards and outwards, it enters the descending horn of the lateral ventricle, beneath the edge of the middle lobe of the brain. It is distributed to the hippo- campus major, corpus flmbriatum, and choroid plexus. ARTERIES OF THE UPPER EXTREMITY. The artery which supplies the upper extremity, continues as a single trunk from its commencement, as far as the elbow ; but different portions of it have received different names, according to the region through which it passes. Thus, that part of the vessel which extends from its origin, as far as the outer border of the first rib, ds termed the subclavian ; beyond this point to the lower border of the axilla, it is termed the axillary ; and from the lower margin of the axillary space to the bend of the elbow, it is termed the brachial ; here, the single trunk terminates by dividing into two branches, the radial and ulnar, an arrangement precisely similar to what occurs in the lower limb. Subclavian Aeteries. The Subclavian Artery on the right side arises from the arteria innominata, opposite the right sterno-clavicular articulation ; on the left side, it arises from the arch of the aorta. It follows, therefore, that these two vessels must, in the first part of their course, differ in their length, their direction, and in their relation with neighboring parts. In order to facilitate the description of these vessels, more especially in a sur- gical point of view, each subclavian artery has been divided into three parts. The first portion, on the right side, ascends obliquely outwards, from the origin of the vessel to the inner border of the Scalenus anticus. On the left side, it ascends perpendicularly to the inner border of that muscle. The second part passes out- wards, behind the Scalenus anticus; and the third part passes from the outer margin of that muscle, beneath the clavicle, to the lower border of the first rib, where it becomes the axillary artery. The first portions of these two vessels differ so much in their course, and in their relation with neighboring parts, that they will be described separately. The second and third parts are precisely alike on both sides. First Part of the Right Subclavian Artery (figs. 205 and 207). It arises from the arteria innominata, opposite the right sterno-clavicular arti- culation, passes upwards and outwards across the root of the neck, and terminates at the inner margin of the Scalenus anticus muscle. In this part of its course, it ascends a little above the clavicle, the extent to which it does so varying in different cases. It is covered, in front, by the integument, • superficial fascia, Platysma, deep fascia, the clavicular origin of the Sterno-mastoid, the Sterno-hyoid and Sterno- thyroid muscles, and another layer of the deep fascia. It is crossed by the internal jugular and vertebral' veins, and by the pneumogastric, the cardiac branches of the sympathetic, and phrenic nerves. Beneath, the artery is invested by the pleura, and behind, it is separated by a cellular interval from the Longus colli, the transverse process of the seventh cervical vertebra, and the sympathetic; the recurrent laryngeal nerve winding around the lower and back part of this vessel. The subclavian vein lies below the subclavian artery, immediately behind the clavicle. 392 ARTERIES. Plan of Relations of First Portion of Right Subclavian Artery. In front. Integument and superficial fascia. Platysma and deep fascia. Clavicular origin of Sterno-mastoid. Sterno-hyoid and Sterno-thyroid. Internal jugular and vertebral veins. Pneumogastric, cardiac, and phrenic nerves. Beneath. Pleura. Behind. Recurrent laryngeal nerve. Sympathetic. Longus colli. , Transverse process of seventh cervical vertebra. First Part of the Left Subclavian Artery (fig. 205). It arises from the end of the transverse portion of the arch of the aorta, oppo- site the second dorsal vertebra, and ascends to the inner margin of the first rib, behind the insertion of the Scalenus anticus muscle. This vessel is, therefore, longer than the right, situated more deeply in the cavity of the chest, and directed almost vertically upwards, instead of arching outwards like the vessel of the opposite side. It is in relation, in front, with the pleura, the left lung, the pneumogastric, phrenic, and cardiac nerves, which lie parallel with it, the left carotid artery, left internal jugular and innominate veins, and is covered by the Sterno-thyroid, Sterno-hyoid, and Sterno-mastoid muscles ; behind, with the oesophagus, thoracic duct, inferior cervical ganglion of the sympathetic, Longus colli, and vertebral column. To its inner side, are the oesophagus, trachea, and thoracic duct ; to its outer side, the pleura. Plan of Relations of First Portion of Left Subclavian Artery. In front. Pleura and left lung. Pneumogastric, cardiac, and phrenic nerves. Left carotid artery. Left internal jugular and innominate veins. Sterno-thyroid, Sterno-hyoid, and Sterno-mastoid muscles. Inner side. / \ Outer side. (Esophagus. / _ t L , eft . \ Pleura. I rachea. Thoracic duct. Behind. (Esophagus and thoracic duct. Inferior cervical ganglion of sympathetic. Longus colli and vertebral column. The relations of the second and third portions of the subclavian arteries are precisely similar on both sides. The Second Portion of the Subclavian Artery lies between the two Scaleni muscles ; it is very short, and forms the highest part of the arch described by that vessel. SUBCLAVIAN. 393 Relations. It is covered, in front, by the integument, Platysma, Sterno- mastoid, cervical fascia, and by the phrenic nerve, which is separated from the artery by the Scalenus anticus muscle. Behind, it is in relation with the Middle scalenus. Above, with the brachial plexus of nerves. Below, with the pleura. The sub- clavian vein lies below and in front of the artery, separated from it by the Scalenus anticus. „ Plan of Eelations of Second Portion of Subclavian Artery. In front. Platysma. Stern o-mastoid. Cervical fascia. Scalenus anticus. Phrenic nerve. Subclavian Vein. Above. Brachial plexus. Beloio. Pleura. Behind. Middle scalenus. The Third Portion of the Subclavian Artery passes downwards and outwards from the outer margin of the Scalenus anticus to the lower border of the first rib, where it becomes the axillary artery. This portion of the vessel is the most superficial, and is contained in a triangular space, the base of which is formed in front by the Anterior scalenus, and the two sides by the Omo-hyoid above and the clavicle below. Relations. It is covered, in front, by the integument, the superficial fascia, the Platysma, deep fascia ; and by the clavicle, the Subclavius muscle, and the supra- scapular artery and vein; the clavicular descending branches of the cervical plexus and the nerve to the Subclavius pass vertically downwards in front of the artery. The external jugular vein crosses it at its inner side, and receives the suprascapular and transverse cervical veins, which occasionally form a plexus in front of it. The subclavian vein is below the artery, lying close behind the clavicle. Behind, it lies on the Middle scalenus muscle. Above it, and to its outer side, are the brachial plexus and Omo-hyoid muscle. Below, it rests on the outer surface of the first rib. Plan of Eelations of Third Portion of Subclavian Artery. In front. Integument, fasciae, and Platysma. The external jugular, suprascapular, and transverse cervical veins. Descending branches of cervical plexus. Subclavius muscle, suprascapular artery, and clavicle. Above. Brachial plexus. Omo-hyoid. Below. First rib. Behind. Scalenus medius. Peculiarities. The subclavian arteries vary in their origin, their course, and in the height to which they rise in the neck. The origin of the right subclavian from the innominate takes place, in some cases, above the sterno-clavicular articulation; more frequently in the cavity of the thorax, below that joint. Or 394 ARTERIES. the artery may arise as a separate trunk from the arch of the aorta ; in such cases it may be either the first, second, third, or even the last branch derived from that vessel: in the majority of cases, it is the first or last, rarely the second or third. When it is the first branch, it occupies the ordinary position of the innominate artery; when the second or third, it gains its usual position by passing behind the right carotid ; and when the last branch, it arises from the left extremity of the arch, at its upper or back part, and passes obliquely towards the right side, behind the oesophagus and right carotid, sometimes between the oesophagus and trachea, to the upper border of the first rib, where it follows its ordinary course. In very rare instances, this vessel arises from the thoracic aorta, as low down as the fourth dorsal vertebra. Occasionally it perforates the Anterior scalenus ; more rarely it passes in front of this muscle : sometimes the subclavian vein passes with the artery behind the Scalenus. The artery sometimes ascends as high as an inch and a half above the clavicle, or to any intermediate point between this and the upper border of this bone, the right subclavian usually ascending higher than the left. The left subclavian is occasionally joined at its origin with the left carotid. Surgical Anatomy. The relations of the subclavian arteries of the two sides having been examined, the student should direct his attention to consider the best position in which compres- sion of the vessel may be effected, or in what situation a ligature may be best applied in cases of aneurism or wounds. Compression of the subclavian artery is required in cases of operations about the shoulder, in the axilla, or at the upper part of the arm ; and the student will observe that there is only one situation in which it can be effectually applied, viz., where the artery passes across the outer surface of the first rib. In order to compress the vessel in this situation, the shoulder should be depressed, and the surgeon, grasping the side of the neck, may press with his thumb in the hollow behind the clavicle downwards against the rib ; if from any cause the shoulder cannot be suffi- ciently depressed, pressure may be made from before backwards, so as to compress the artery against the Middle scalenus and transverse process of the seventh cervical vertebra. Ligature of the subclavian artery may be required in cases of wounds of the axillary artery, or in aneurism of that vessel ; and the third part of the artery is consequently that which is most favorable for such an operation, on account of its being comparatively superficial, and most re- mote from the origin of the large branches. In those cases where the clavicle is not displaced, this operation may be performed with comparative facility ; but where the clavicle is elevated from the presence of a large aneurismal tumor in the axilla, the artery is placed at a great depth from the surface, which materially increases the difficulty of the operation. Under these circum- stances, it becomes a matter of importance to consider the height to which this vessel reaches above the bone. In ordinary cases, its arch is about half an inch above the clavicle, occasionally as high as an inch and a half, and sometimes so low as to be on a level with its upper border. If displacement of the clavicle occurs, these variations will necessarily make the operation more or less difficult, according as the vessel is more or less accessible. The chief points in the operation of tying the third portion of the subclavian artery are as fol- lows : The patient being placed on a table in the horizontal position, and the shoulder depressed as much as possible, the integument should be drawn downwards upon the clavicle and an inci- sion made through it upon that bone from the anterior border of the Trapezius to the posterior border of the Sterno-mastoid, to which may be added a short vertical incision meeting the centre of the preceding; the Platysma and cervical fascia should be divided upon a director, and if the interval between the Trapezius and Sterno-mastoid muscles be insufficient for the performance of the operation, a portion of one or both -may be divided. The external jugular vein will now be seen towards the inner side of the wound ; this and the suprascapular and transverse cervical veins which terminate in it should be held aside, and if divided both ends should be included in a ligature : the suprascapular artery should be avoided, and the Omo-hyoid muscle must now be looked for, and held aside if necessary. In the space beneath this muscle, careful search must be made for the vessel ; the deep fascia having been divided with the finger-nail or silver scalpel, the outer margin of the Scalenus muscle must be felt for, and the finger being guided by it to the first rib, the pulsation of the subclavian artery will be felt as it passes over its surface. The aneurism needle may then be passed around the vessel from before backwards, by which means the vein will be avoided, care being taken not to include a branch of the brachial plexus instead of the artery in the ligature. If the clavicle is so raised by the tumor that the application of the liga- ture cannot be effected in this situation, the artery may be tied above the first rib, or even behind the Scalenus muscle : the difficulties of the operation in such a case will be materially increased, on account of the greater depth of the artery, and alteration of the surrounding parts. The second division of the subclavian artery, from being that portion which rises highest in the neck, has been considered favorable for the application of the ligature, where it is diffi- cult to apply it in the third part of its course. There are, however, many objections to the operation in this situation. It is necessary to divide the Scalenus anticus muscle, upon which lies the phrenic nerve, and at the inner side of which is situated the internal jugular vein; a wound of either of these structures might lead to the most dangerous consequences. Again, the artery is in contact, below, with the pleura, which must also be avoided ; and, lastly, the prox- imity of so many of its larger branches arising internal to this point, must be a still further SUBCLAVIAN. 395 objection to the operation. If, however, it has been determined upon to perform the operation in this situation, it should be remembered that it occasionally happens, that the artery passes in front of the Scalenus anticus, or through the fibres of that muscle ; or that the vein sometimes passes with the artery behind the Scalenus anticus. In those cases of aneurism of the axillary or subclavian artery which encroach upon the outer portion of the Scalenus muscle to such an extent that a ligature cannot be applied in that situa- tion, it may be deemed advisable, as a last resource, to tie the first portion of the subclavian artery. On the left side, this operation is quite impracticable ; the great depth of the artery from the surface, its intimate relation with the pleura, and its close proximity with so many im- portant veins and nerves, present a series of difficulties which it is impossible to overcome. On the right side, the operation is practicable, and has been performed, though not with success. The main objection to the operation in this situation is the smallness of the interval which usu- ally exists between the commencement of the vessel, and the origin of the nearest branch. This operation may be performed in the following manner. The patient being placed on a table in the horizontal position, with the neck extended, an incision should be made parallel with the inner part of the clavicle, and a second along the inner border of the Sterno-mastoid. meet- ing it at right angles. The sternal attachment of the Sterno-mastoid may now be divided on a director, and turned outwards ; a few small arteries and veins, and occasionally the anterior jugular, must be avoided, and the Sterno-hyoid and Sterno-thyroid muscles divided in the same manner as the preceding muscle. After tearing through the deep fascia with the finger-nail, the internal jugular vein will be seen crossing the artery ; this should be pressed aside, and the artery secured by passing the needle from below upwards, by which the pleura is more effectually avoided. The exact position of the vagus nerve, the recurrent laryngeal, the phrenic and sympathetic nerves, should be remembered, and the ligature should be applied near the origin of the vertebral, in order to afford as much room as possible for the formation of a coagulum between the ligature and the origin of the vessel. It should be remembered, that the right subclavian artery is occa- sionally deeply placed in the first part of its course, when it arises from the left side of the aortic arch, and passes in such cases behind the oesophagus, or between it and the trachea. Collateral Circulation. After ligation of the third part of the subclavian artery, the collate- ral circulation is mainly established by three sets of vessels, as was described in a case of axillary aneurism, in which Mr, Aston Key had tied the subclavian artery on the outer edge of the Scalenus muscle, twelve years previously. 1 " 1. A posterior set, consisting of the suprascapular and posterior scapular branches of the subclavian, which anastomosed with the infrascapular from the axillary. " 2. An internal set, produced by the connection of the internal mammary on the one hand, with the short and long thoracic arteries, and the infrascapular, on the other. "3. A middle or axillary set, which consisted of a number of small vessels derived from branches of the subclavian, above ; and passing through the axilla, to terminate either in the main trunk, or some of the branches of the axillary, below. This last set presented most con- spicuously the peculiar character of newly-formed, or, rather, dilated arteries," being excessively tortuous, and forming a complete plexus. "The chief agent in the restoration of the axillary artery below the tumor, was the infra- scapular artery, which communicated most freely with the internal mammary, suprascapular, and posterior scapular branches of the subclavian, from all of which it received so great an influx of blood as to dilate it to three times its natural size." Branches of the Subclavian Artery. These are four in number. Three arising from the first portion of the vessel, the vertebra], the internal mammary, and the thyroid axis ; and one from the second portion, the superior intercostal. The vertebral arises from the upper and back part of the first portion of the arterj^ ; the thyroid axis from the front, and the in- ternal mammary from the under part of this vessel. The superior intercostal is given off from the upper and back part of the second portion of the artery. On the left side, the second portion usually gives off no branch, the superior inter- Fig. 215. — Plan of the Branches of the Subclavian Artery. Right 1 Guy's Hospital Reports, vol. i. 1836. 396 'ARTERIES. costal arising at the inner side of the Scalenus anticus. On both sides of the body, the first three branches arise close together at the inner margin of the Scalenus anticus ; in the majority of cases, a free interval of half an inch to an inch exist- ing between the commencement of the artery and the origin of the nearest branch ; in a smaller number of cases, an interval of more than an inch existed, never exceeding an inch and three-quarters. In a very few instances, the interval was less than half an inch. The Vertebral Artery (fig. 212) is generally the first and largest branch of the subclavian ; it arises from the upper and back part of the first portion of the vessel, and, passing upwards, enters the foramen in the transverse process of the sixth cervical vertebra, and ascends through the foramina in the transverse processes of all the vertebra? above this. Above the upper border of the axis, it inclines out- wards and upwards to the foramen in the transverse process of the atlas, through which it passes ; it then winds backwards behind its articular process, runs in a deep groove on the surface of the posterior arch of this bone, and, piercing the posterior occipito-atloid ligament and dura mater, enters the skull through the foramen magnum. It then passes in front of the medulla oblongata, and unites w r ith the vessel of the opposite side at the lower border of the pons Varolii, to form the basilar artery. At its origin, it is situated behind the internal jugular vein, and inferior thyroid artery ; and, near the spine, lies between the Longus colli and Scalenus anticus muscles, having the thoracic duct in front of it on the left side. Within the foramina formed by the transverse processes of the vertebrae, it is accompanied by a plexus of nerves from the sympathetic, and lies between the vertebral vein, which is in front, and the cervical nerves, which issue from the intervertebral foramina behind it. Whilst winding round the articular process of the atlas, it is contained in a triangular space formed by the Rectus posticus minor, the Superior and Inferior oblique muscles ; and it is covered by the Rectus posticus major and Complexus. Within the skull, as it winds round the medulla oblongata, it is placed between the hypoglossal and anterior root of the suboccipital nerves. Branches. These may be divided into two sets, those given off in the neck, and those within the cranium. Cervical Branches. Cranial Branches. Lateral spinal. Posterior meningeal. Muscular. Anterior spinal. Posterior spinal. Inferior cerebellar. The lateral spinal branches enter the spinal canal through the intervertebral foramina, each dividing into two branches. Of these, one passes along the roots of the nerves, to supply the spinal cord and its membranes, anastomosing with the other spinal arteries ; the other is distributed to the posterior surface of the bodies of the vertebrae. Musctdar branches are given off to the deep muscles of the neck, where the vertebral artery curves round the articular process of the atlas. They anastomose with the occipital and deep cervical arteries. The posterior meningeal are one or two small branches given off from the ver- tebral opposite the foramen magnum. They ramify between the bone and dura mater in the cerebellar fossa?, and supply the falx cerebelli. The anterior spinal is a small branch, larger than the posterior spinal, which arises near the termination of the vertebral, and unites with its fellow of the opposite side in front of the medulla oblongata. The single trunk thus formed descends a short distance on the front of the spinal cord, and joins with a succession of small branches which enter the spinal canal through some of the intervertebral foramina ; these branches are derived from the vertebral and ascend- ing cervical, in the neck ; fronTthe intercostal, in the dorsal region ; and from the VERTEBRAL. 397 xumbar, iliolumbar, and lateral sacral arteries in the lower part of the spine. They unite, by means of ascending and descending branches, to form a single anterior median artery, which extends as far as the lower part of the spinal cord. This vessel is placed beneath the pia mater along the anterior median fissure ; it supplies that membrane and the substance of the cord, and sends oft' branches at its lower part, to be distributed to the cauda equina. The posterior spinal arises from the vertebral, at the side of the medulla ob- longata; passing backwards to the posterior aspect of the spinal cord, it descends on either side, lying behind the posterior roots of the spinal nerves ; and is re- inforced by a succession of small branches, which enter the spinal canal through the intervertebral foramina, and by which it is continued to the lower part of the cord, and to the cauda equina. Branches from these vessels form a free anastomosis round the posterior roots of the spinal nerves, and communicate, by means of very tortuous transverse branches, with the vessel of the opposite side. At its com- mencement, it gives off an ascending branch, which terminates on the side of the fourth ventricle. The inferior cerebellar artery, the largest branch of the vertebral, winds back- wards round the upper part of the medulla oblongata, passing between the origin of the spinal accessory and pneumogastric nerves, over the restiform body, to the under surface of the cerebellum, where it divides into two branches ; an internal one, which is continued backwards to the notch between the two hemispheres of the cerebellum ; and an external one, which supplies the under surface of the cerebellum, as far as its outer border, where it anastomoses with the superior cerebellar. Branches from this artery supply the choroid plexus of the fourth ventricle. The Basilar artery, so named from its position at the base of the skull, is a single trunk, formed by the junction of the two vertebral arteries ; it extends from the posterior to the anterior border of the pons Varolii, where it divides into two terminal branches, the posterior cerebral arteries. Its branches are, on each side, the following: — Transverse. Superior cerebellar. Anterior cerebellar. Posterior cerebral. The transverse branches supply the pons Varolii and adjacent parts of the brain ; one accompanies the auditory nerve into the internal auditory meatus : and another, of larger size, passes along the crus cerebelli, to be distributed to the anterior border of the under surface of the cerebellum. It is called the anterior (inferior) cerebellar artery. The superior cerebellar arteries arise near the termination of the basilar. They wind round the crus cerebri, close to the fourth nerve, and, arriving at the upper surface of the cerebellum, divide into branches which supply the pia mater, covering its surface, anastomosing with the inferior cerebellar. It gives several branches to the pineal gland, and also to the velum interpositum. The posterior cerebral arteries, the two terminal branches of the basilar, are larger than the preceding, from which they are separated near their origin by the third nerves. Winding round the crus cerebri, they pass to the under surface of the posterior lobes of the cerebrum, which they supply, anastomosing with the anterior and middle cerebral arteries. Near their origin, they give oft* numerous branches, which enter the posterior perforated spot, and receive the posterior communicating arteries from the internal carotid. They also give off a branch, the posterior choroid, which supplies the velum interpositum and choroid plexus, entering the interior of the brain, beneath the posterior border of the corpus callosum. Circle of Willis. The remarkable anastomosis which exists between the branches of the internal carotid and vertebral arteries at the base of the brain, constitutes the circle of "Willis. It is formed, in front, by the anterior cerebral and anterior communicating arteries ; on each side, by the trunk of the internal carotid, and the 398 ARTERIES. posterior communicating ; behind, by the posterior cerebral, and point of the basilar It is by this anastomosis that the cerebral circulation is equalized, and provision made for effectually carrying it on if one or more of the branches are obliterated. The parts of the brain included within this arterial circle are, the lamina cinerea, the commissure of the optic nerves, the infundibulum, the tuber cinereum, the corpora albicantia, and the pars perforata postica. The Thyroid Axis is a short, thick trunk, which arises from the fore part of the first portion of the subclavian artery, close to the inner side of the Scalenus anticus muscle, and divides, almost immediately after its origin, into three branches, the inferior thyroid, suprascapular, and transversalis colli. The Inferior Thyroid Artery passes upwards, in a serpentine course, behind the sheath of the common carotid vessel and sympathetic nerve (the middle cervical ganglion resting upon it), and is distributed to the under surface of the thyroid gland, anastomosing with the superior thyroid, and with the correspond- ing artery of the opposite side. Its branches are the Laryngeal. (Esophageal. Tracheal. Ascending cervical. The laryngeal branch ascends upon the trachea to the back part of the larynx, and supplies the muscles and the mucous membrane of this part. The tracheal branches are distributed upon the trachea, anastomosing below with the bronchial arteries. The esophageal branches are distributed to the oesophagus. The ascending cervical is a small branch which arises from the inferior thyroid, just where that vessel is passing behind the common carotid artery, and runs up the neck in the interval between the Scalenus anticus and Rectus anticus major. It gives branches to the muscles of the neck, which communicate with those sent out from the vertebral, and sends one or two through the intervertebral foramina, along the cervical nerves, to supply the bodies of the vertebrae, the spinal cord, and its membranes. The Suprascapular Artery, smaller than the transversalis colli, passes obliquely from within outwards, across the root of the neck. It at first lies on the lower part of the Scalenus anticus, being covered by the Sterno-mastoid ; it then crosses the subclavian artery, and runs outwards behind and parallel with the clavicle and Subclavius muscle, and beneath the posterior belly of the Omo- hyoid, to the superior border of the scapula, where it passes over the transverse ligament of the scapula to the supra-spinous fossa. In this situation it lies close to the bone, and ramifies between it and the Supra-spinatus muscle to which it is, mainly distributed, giving off a communicating branch, which crosses the neck of the scapula, to reach the infra-spinous fossa, where it anastomoses with the dorsal branch of the subscapular artery. Besides distributing branches to the Sterno- mastoid, and neighboring muscles, it gives off" a supra-acromial branch, which, piercing the Trapezius muscle, supplies the cutaneous surface of the acromion, anastomosing with the acromial thoracic artery. As the artery passes across the suprascapular notch, a branch descends into the subscapular fossa, ramifies beneath that muscle, and anastomoses with the posterior and subscapular arteries. It also supplies the shoulder-joint. The Transversalis Colli passes transversely outwards, across the upper part 01' the subclavian triangle, to the anterior margin of the Trapezius muscle, beneath which it divides into two branches, the superficial cervical, and the posterior scapular. In its passage across the neck, it crosses in front of the Scaleni muscles and the brachial plexus, between the divisions of which it sometimes passes, and is covered by the Platysma, Sterno-mastoid, Omo-hyoid, and Trapezius muscles. The superficial cervical ascends beneath the anterior margin of the Trapezius, distributing branches to it, and to the neighboring muscles and glands in the neck. INTERNAL MAMMARY. 399 The posterior scapular, the continuation of the transversalis colli, passes beneath the Levator anguli scapulas to the superior angle of the scapula, and descends along the posterior border of that bone as far as the inferior angle, where it anas- tomoses with the subscapular branch of the axillary. In its course it is covered Fig. 216. — The Scapular and Circumflex Arteries. Better it r Srafia/ar ial Brarrb by the Rhomboid muscles, supplying these, the Latissimus dorsi and Trapezius, and anastomosing with the suprascapular and subscapular arteries, and with the posterior branches of some of the intercostal arteries. Peculiarities. The superficial cervical frequently arises as a separate branch from the thyroid axis ; and the posterior scapular from the third, more rarely from the second, part of the sub- clavian. The Internal Mammary arises from the under surface of the first portion of the subclavian artery, opposite the thyroid axis. It descends behind the clavicle, to the inner surface of the anterior wall of the chest, resting upon the costal cartilages, a short distance from the margin of the sternum ; and, at the interval between the sixth and seventh cartilages, divides into two branches, the musculo- phrenic, and superior epigastric. At its origin, it is covered by the internal jugular and subclavian veins, and crossed by the phrenic nerve. In the upper part of the thorax, it lies upon the costal cartilages, and Internal intercostal muscles in front, covered by the pleura behind. At the lower part of the thorax, the Triangularis sterni separates this vessel from the pleura. It is accompanied by two veins, which join at the upper part of the thorax into a single trunk. The branches of the internal mammary are the Comes nervi phrenici or Superior phrenic. Mediastinal. Pericardiac. Sternal. Anterior intercostal. Perforating. Musculo-phrenic. Superior epigastric. The comes nervi phrenici or superior phrenic is a long slender branch, which accompanies the phrenic nerve, between the pleura and pericardium, to the Dia- phragm, to which it is distributed ; anastomosing with the other phrenic arteries from the internal mammary, and abdominal aorta. 400 ARTERIES. The mediastinal branches are small vessels, which are distributed to the areolar tissue in the anterior mediastinum, and the remains of the thymus gland. The pericardiac branches supply the upper part, of the pericardium, the lower part receiving branches from the musculo-phrenic artery. Some sternal branches are distributed to the Triangularis sterni, and both surfaces of the sternum. The anterior intercostal arteries supply the five or six upper intercostal spaces. The branch corresponding to each space passes outwards, and soon divides into two, which run along the opposite borders of the ribs, and inosculate with the intercostal arteries from the aorta. They are at first situated between the pleura and the Internal intercostal muscles, and then between the two layers of these muscles. They supply the Intercostal and Pectoral muscles, and the mammary gland. The anterior or perforating arteries correspond to the five or six upper inter- costal spaces. They arise from the internal mammary, pass forwards through the intercostal spaces, and, curving outwards, supply the Pectoralis major, and the integument. Those which correspond to the first three spaces are distributed to the mammary gland. In females, during lactation, these branches are of large size. The musculo-phrenic artery is directed obliquely downwards and outwards, behind the cartilages of the false ribs, perforating the Diaphragm at the eighth or .ninth rib, and terminating, considerably reduced in size, opposite the last intercostal space. It gives off anterior intercostal arteries to each of the intercostal spaces across which it passes ; they diminish in size as the spaces decrease in length, and are distributed in a manner precisely similar to the anterior intercostals from the internal mammary. It also gives branches backwards to the Diaphragm, and downwards to the abdominal muscles. The superior epigastric continues in the original direction of the internal mam- mary, descends behind the Rectus muscle, and, perforating its sheath, divides into branches which supply the Rectus, anastomosing with the epigastric artery from the external iliac. Some vessels perforate the sheath of the Rectus, and supply the muscles of the abdomen and the integument, and a small branch, which passes inwards upon the side of the ensiform appendix, anastomoses in front of that cartilage with the artery of the opposite side. The Superior Intercostal arises from the upper and back part of the sub- clavian artery, beneath the anterior scalenus on the right side, and to the inner side of the muscle on the left side. Passing backwards, it gives off the deep cervical branch, and then descends behind the pleura in front of the necks of the first two ribs, and inosculates with the first aortic intercostal. In the first intercostal space, it gives off a branch which is distributed in a similar manner with the aortic intercostals. The branch for the second intercostal space usually joins with one from the first aortic intercostal. Each intercostal gives off a branch to the posterior spinal muscles, and a small one, which passes through the corresponding inter- vertebral foramen to the spinal cord and its membranes. The deep cervical branch [profunda cervicis) arises, in most cases, from the superior intercostal, and is analogous to the posterior branch of an aortic intercostal artery. Passing backwards, between the transverse process of the seventh cervical vertebra and the first rib, it ascends the back part of the neck, between the Complexus and Semi-spinalis colli muscles, as high as the axis, supplying these and adjacent muscles, and anastomosing with the arteria princeps cervicis of the occipital, and with branches which pass outwards from the vertebral. OF THE AXILLA. 401 Surgical Anatomy of the Axilla. The Axilla is a conical space, situated between the upper and lateral parts of the chest, and inner side of the arm. Boundaries. Its apex, which is directed upwards towards the root of the neck, corresponds to the interval between the first rib internally, the superior border of the scapula externally, and the clavicle and Subclavius muscle in front. The base, directed downwards, is formed by the integument, and a thick layer of fascia, extending between the lower border of the Pectoralis major in front, and the lower border of the Latissimus dorsi behind ; it is broad internally, at the chest, but narrow and pointed externally, at the arm. Its anterior boundary is formed by the Pectoralis major and Pectoralis minor muscles, the former covering the whole of Fig. 217. — The Axillary Artery and its Branches. the anterior wall of the axilla, the latter covering only its central part. Its posterior boundary, which extends somewhat lower than the anterior, is formed by the Sub- scapulars above, the Teres major and Latissimus dorsi below. On the inner side are the first four ribs and their corresponding Intercostal muscles, and part of the Serratus magnus. On the outer side, where the anterior and posterior boundaries converge, the space is narrow, and bounded by the humerus, the Coraco-brachialis and Biceps muscles. ^ Contents. This space contains the axillary vessels, and brachial plexus of nerve? with their branches, some branches of the intercostal nerves, and a large number of lymphatic glands ; all connected together by a quantity of fat and loose areolar tissue. 26 402 ARTERIES. Tlieir Position. The axillary artery and vein, with the brachial plexus of nerves, extend obliquely along the outer boundary of the axillary space, from its apex to its base, and are placed much nearer the anterior than the posterior wall, the vein lying to the inner or thoracic side of the artery, and altogether concealing it. At the fore part of the axillary space, in contact with the Pectoral muscles, are the thoracic branches of the axillary artery, and, along the anterior margin of the axilla, the long thoracic artery extends to the side of the chest. At the back part, in contact with the lower margin of the Subscapularis muscle, are the sub- scapular vessels and nerves ; winding around the lower border of this muscle, are the dorsalis scapulee artery and veins ; and towards the outer extremity of the muscle, the posterior circumflex vessels and nerve are seen curving backwards to the shoulder. Along the inner or thoracic side, no vessel of any importance exists, its upper part being crossed by a few small branches from the superior thoracic artery. There are some important nerves, however, in this situation ; the posterior thoracic or external respiratory nerve, descending on the surface of the Serratus magnus, to which it is distributed ; and perforating the upper and anterior part of this wall, are the intercosto-humeral nerves, which pass across the axilla to the inner side of the arm. The cavity of the axilla is filled by a quantity of loose areolar tissue, a large number of small arteries and veins, all of which are, however, of inconsiderable size, and numerous lymphatic glands ; these are from ten to twelve in number, and situated chiefly on the thoracic side, and lower and back part of this space. The student should attentively consider the relation of the vessels and nerves in the several parts of the axilla ; for it not unfrequently happens, that the sur- geon is called upon to extirpate diseased glands, or to remove a tumor from this situation. In performing such an operation, it will be necessary to proceed with much caution in the direction of the outer wall and apex of the space, as here the axillary vessels will be in danger of being wounded. Towards the posterior wall, it will be necessary to avoid the subscapular, dorsalis scapulae, and posterior circumflex vessels, and, along the anterior wall, the thoracic branches. It is only along the inner or thoracic wall,' and in the centre of the axillary cavity, that there are no vessels of any importance; a most fortunate circumstance, for it is in this situation more especially that tumors requiring removal are most fre- quently situated. The Axillary Artery. The axillary artery, the continuation of the subclavian, commences at the lower border of the first rib, and terminates at the lower border of the tendons of the Latissimus dorsi and Teres major muscles, when it becomes the brachial. Its direction varies with the position of the limb ; when the arm lies by the side of the chest, the vessel forms a gentle curve, the convexity being upwards and out- wards ; when it is directed at right angles with the trunk, the vessel is nearly straight ; and if elevated still higher, it describes a curve, the concavity of which is directed upwards. At its commencement the artery is very deeply situated, but near its termination is superficial, being covered only by the skin and fascia. The description of the relations of this vessel may be facilitated by its division into three portions ; the first portion being that above the Pectoralis minor, the second portion beneath, and the third, below, that muscle. The first portion of the axillary artery is in relation, in front, with the clavicular portion of the Pectoralis major, the costo-coracoid membrane, and the cephalic vein ; behind, with the first intercostal space, the corresponding Intercostal muscle, the first serration of the Serratus magnus, and the posterior thoracic nerve; on its outer side with the brachial plexus, from which it is separated by a little cellular interval; on its inner or thoracic side, with the axillary vein. AXILLARY. 403 Relations of First Portion of the Axillary Artery. In front. Pectoralis major. Costo-coracoid membrane. Cephalic vein. Order side. I Axillary \ Inner side. Brachial plexus. I HrBtportton. J Axillary vein. Behind. First intercostal space, and Intercostal muscle. First serration of Serratus magnus. Posterior thoracic nerve. The second portion of the axillary artery lies beneath the Pectoralis minor. It is covered, in front, by the Pectoralis major and Pectoralis minor muscles; behind^ it is separated from the Subscapulars by a cellular interval ; on the inner side, it is in contact with the axillary vein. The brachial plexus of nerves surrounds the artery, and separates it from direct contact with the vein and adjacent muscles. Relations of Second Portion of the Axillary Artery. In front. Pectoralis major and Pectoralis minor. Outer side. I %$£? \ Inner side. Brachial plexus. Isecoiid portion.) Axillary vein. Behind. Subscapularis. The third portion of the axillary artery lies below the Pectoralis minor. It is in relation, in front, with the lower border of the Pectoralis major above, being covered only by the integument and fascia below ; behind, with the lower part of the Subscapularis, and the tendons of the Latissimus dorsi and Teres major ; on its outer side, with the Coraco-brachialis ; on its inner or thoracic side, with the axillary vein. The brachial plexus of nerves bears the following relation to the artery in this part of its course ; on the outer side are the median nerve, and the musculo-cutaneous for a short distance ; on the inner side, the ulnar, the internal, and lesser internal cutaneous nerves ; and behind, the musculo-spiral and circumflex, the latter extending only to the lower border of the Subscapularis muscle. Relations of Third Portion of the Axillary Artery. In front. Integument and fascia. Pectoralis major. Outer side. f \ Inner side. Coraco-brachialis. | briery 7 j Ulnar nerve. Median nerve. \ Third portion./ Internal cutaneous nerr 33. Musculo-cutaneous nerve. \ / Axillary vein. Behind. Subscapularis. Tendons of Latissimus dorsi and Teres major. Musculo-spiral, and circumflex nerves. 404 ARTERIES. Peculiarities. The axillary artery, in about one case out of every ten, gives off a large branch, which forms either one of the arteries of the forearm, or a large muscular trunk. In the first set of cases, this artery is most frequently the radial (1 in 33), sometimes the ulnar (1 in 72), and, very rarely, the interosseous (1 in 506). In the second set of cases, the trunk gave origin to the subscapular, circumflex, and profunda arteries of the arm. Sometimes only one of the circumflex, or one of the profunda arteries, arose from the trunk. In these cases, the brachial plexus surrounded the trunk of the branches, and not the main vessel. Surgical Anatomy. The student having carefully examined the relations of the axillary artery in its various parts, should now consider in what situation compression of this vessel may be most easily effected, and the best position for the application of a ligature to it when necessary. Compression of this vessel is required in the removal of tumors, or in amputation of the upper part of the arm ; and the only situation in which this can be effectually made, is in the lower part of its course ; on compressing it in this situation from within outwards upon the humerus, the circulation may be effectually suspended. The application of a ligature to the axillary artery may be required in cases of aneurism of the upper part of the brachial ; and there are only two situations in which it may be secured, viz., in the upper, or in the lower part of its course ; for the axillary artery at its central part is «o deeply seated, and, at the same time, so closely surrounded with large nervous trunks, that the application of a ligature to it in this situation would be almost impracticable. In the lower part of its course, the operation is more simple, and may be performed in the following manner : The patient being placed on a bed, and the arm separated from the side, with the hand supinated, the head of the humerus is felt for, and an incision made through the integu- ment over it, about two inches in length, a little nearer to the anterior than the posterior fold of the axilla. After carefully dissecting through the areolar tissue and fascia, the median nerve and axillary vein are exposed ; the former having been displaced to the outer, and the latter to the inner side of the arm, the elbow being at the same time bent, so as to relax these structures, and facilitate their separation, the ligature may be passed round the artery from the ulnar to the radial side. This portion of the artery is occasionally crossed by a muscular slip derived from the Latissimus dorsi, which may mislead the surgeon during an operation. It may easily be recognized by the transverse direction of its fibres (see p. 272). The upper portion of the axillary artery may be tied, in cases of aneurism encroaching so far upwards that a ligature cannot be applied in the lower part of its course. Notwithstanding that this operation has been performed in some few cases, and with success, its performance is attended with much difficulty and danger. The student will remark, that in this situation it would be necessary to divide a thick muscle, and, after separating the costo-coracoid mem- brane, the artery would be exposed at the bottom of a more or less deep space, with the cepha- lic and axillary veins in such relation with it as must render the application of a ligature to this part of the vessel particularly hazardous. Under such circumstances, it is an easier, and, at the same time, more advisable operation, to tie the subclavian artery in the third part of its course. In a case of wound of this vessel the general practice of cutting down upon it, and tying it above and below the wounded point, should be adopted in all cases. The branches of 1 the axillary artery are From 1st Part. J Superior thoracic. ( Acromial thoracic. From 2d Part. J Thoracica longa. ( Thoracica alaris. I Subscapular. From 3d Part. < Anterior circumflex. ( Posterior circumflex. The superior thoracic is a small artery, which arises from the axillary, or by a common trunk with the acromial thoracic. Running forwards and inwards along the upper border of the Pectoralis minor, it passes between it and the Pectoralis major to the side of the chest. It supplies these muscles, and the parietes of the thorax, anastomosing with the internal mammary and intercostal arteries. The acromial thoracic is a short trunk, which arises from the fore part of the axillary artery. Projecting forwards to the upper border of the Pectoralis minor, it divides into three sets of branches, thoracic, acromial, and descending. The thoracic branches, two or three in number, are distributed to the Serratus magnus and Pectoral muscles, anastomosing with the intercostal branches of the internal AXILLARY— BRACHIAL. 405 mammary. The acromial branches are directed outwards towards the acromion, supplying the Deltoid muscle, and anastomosing, on the surface of the acromion, with the suprascapular and posterior circumflex arteries. The descending branch passes in the interspace between the Pectoralis major and Deltoid, accompanying the cephalic vein, and supplying both muscles. The thoracica longa passes downwards and inwards along the lower border of the Pectoralis minor to the side of the chest, supplying the Serratus magnus, the Pectoral muscles, and mammary gland, and sending branches across the axilla to the axillary glands and Subscapularis, which anastomose with the internal mam- mary and intercostal arteries. The thoracica alaris is a small branch, which supplies the glands and areolar tissue of the axilla. Its place is frequently supplied by branches from some of the other thoracic arteries. The subscapular, the largest branch of the axillary artery, arises opposite the lower border of the Subscapularis muscle, and passes downwards and backwards along its lower margin to the inferior angle of the scapula, where it anastomoses with the posterior scapular, a branch of the subclavian. It distributes branches to the Subscapularis, Serratus magnus, Teres major, and Latissimus dorsi muscles, and gives off, about an inch and a-half from its origin, a large branch, the dorsalis scapulae. This vessel curves round the inferior border of the scapula, leaving the axilla in the interspace between the Teres minor above, the Teres major below, and the long head of the Triceps in front ; and divides into three branches, a sub- scapular, which enters the subscapular fossa beneath the Subscapularis which it supplies, anastomosing with the subscapular and suprascapular arteries ; an infra- spinous branch (dorsalis scapulas), which turns round the axillary border of the scapula, between the Teres minor and the bone, enters the infra-spinous fossa, supplies the Infra-spinatus muscle, and anastomoses with the suprascapular and posterior scapular arteries ; and a median branch, which is continued along the axillary border of the scapula, between the Teres major and minor, and, at the dorsal surface of the inferior angle of the bone, anastomoses with the supra- scapular. The circumflex arteries wind round the neck of the humerus. The posterior circumflex, the larger of the two, arises from the back part of the axillary, opposite the lower border of the Subscapularis muscle, and, passing backwards with the circumflex veins and nerve, through the quadrangular space bounded by the Teres major and Teres minor, the scapular head of the Triceps and the humerus, winds round the neck of that bone, is distributed to the Deltoid muscle and shoulder-joint, anastomosing with the anterior circumflex, suprascapular, and acromial thoracic arteries. The anterior circumflex, considerably smaller than the preceding, arises just below that vessel, from the outer side of the axillary artery. It passes horizontally outwards, beneath the Coraco-brachialis and short head of the Biceps, lying upon the fore part of the neck of the humerus, and, on reaching the bicipital groove, gives off an ascending branch, which passes upwards along it, to supply the head of the bone and the shoulder-joint. The trunk of the vessel is then continued •outwards beneath the Deltoid which it supplies, and anastomoses with the posterior circumflex and acromial thoracic arteries. Brachial Artery (fig. 218). The brachial artery commences at the lower margin of the tendon of the Teres major, and, passing down the inner and anterior aspect of the arm, terminates about half an inch below the bend of the elbow, where it divides into the radial and ulnar arteries. The direction of this vessel is marked by a line drawn from the outer side of the axillary space between the folds of the axilla, to a point midway between the 406 ARTERIES. Fig. 218.— The Surgical Jtirrv* Anatomy of the Brachial Artery, condyles of the humerus, which corresponds to the depression along the inner border of the Coraco- brachial! s and Biceps muscles. In the upper part of its course, this vessel lies internal to the humerus ; but below, it is in front of that bone. Relations. This artery is super- ficial throughout its entire extent, being covered, in front, by the in- tegument, the superficial and deep fasciae ; the bicipital fascia separates it opposite the elbow from the me- dian basilic vein ; the median nerve crosses it at its centre ; and the basilic vein lies in the line of the artery, but separated from it by the fascia, in the lower half of its course. Behind, it is separated from the inner side of the humerus above, by the long and inner heads of the Triceps, the musculo- spiral nerve and superior profunda artery inter- vening ; and from the front of the bone below, by the insertion of the Coraco-brachialis and the Brachialis anticus muscles. By its outer side, it is in relation with the commence- ment of the median nerve, and the Coraco-brachialis and Biceps muscles, which slightly overlap the artery. By its inner side, with the internal cutaneous and ulnar nerves, its upper half; the median nerve, its lower half. It is accompanied by two veins, the venae comites; they lie in close contact with the artery, being connected together at intervals by short transverse communicating branches. Aniaatomo ticct Plan of the Kelations of the Brachial Artery. In front. Integument and fascia?. Bicipital fascia, median basilic vein. Median nerve. Outer side. Median nerve. Coraco-brachialis. Biceps. Inner side. Internal cutaneous. Ulnar and median nervea. Behind. Triceps. Musculo-spiral nerve. Superior profunda artery. Coraco-brachialis. Brachialis anticus. BRACHIAL. 407 Bexd of the Elbow. At the bend of the elbow, the brachial artery sinks deeply into a triangular interval, the base of which is directed upwards towards the humerus, and the sides of which are bounded, externally, by the Supinator longus ; internally, by the Pronator radii teres ; its floor is formed by the Brachialis anticus and Supinator brevis. This space contains the brachial artery, with its accompanying veins ; the radial and ulnar arteries; the median and musculo-spiral nerves; and the tendon of the Biceps. The brachial artery occupies the middle line of this space, and divides opposite the coronoid process of the ulna into the radial and ulnar arteries ; it is covered, in front, by the integument, the superficial fascia, and the median basilic vein, the vein being separated from direct contact with the artery by the bicipital fascia. Behind, it lies on the Brachialis anticus, which separates it from the elbow-joint. The median nerve lies on the inner side of the artery, but is separated from it below by an interval of half an inch. The tendon of the Biceps lies to the outer side of the space, and the musculo-spiral nerve still more externally, lying upon the Supinator brevis, and partly concealed by the Supinator longus. Peculiarities of the Artery as regards its Course. The brachial artery, accompanied by the median nerve, may leave the inner border of the Biceps, and descend towards the inner condyle of the humerus, where it usually curves round a prominence of bone, to which it is connected by a fibrous band ; it then inclines outwards, beneath or through the substance of the Pronator teres muscle, to the bend of the elbow. This variation bears considerable analogy with the normal condition of the artery in some of the carnivora (see p. 131). Peculiarities as regards its Division. Occasionally, the artery is divided for a short distance at its upper part into two trunks, which are united above and below. A similar peculiarity occurs in the main vessel of the lower limb. The point of bifurcation may be above or below th» usual point, the former condition being by far the most frequent. Out of 481 examinations recorded by Mr. Quain, some made on the right, and some on the left side of the body, in 386 the artery bifurcated in its normal position. In one case only was the place of division lower than usual, being two or three inches below the elbow-joint. In 90 cases out of 481, or about 1 in 5£, there were two arteries instead of one in some part, or in the whole of the arm. There appears, however, to be no correspondence between the arteries of the two arms, with respect to their irregular division; for in 61 bodies it occurred on one side only in 43 ; on both sides, in different positions, in 13 ; on both sides, in the same position, in 5. The point of bifurcation takes place at different parts of the arm, being most frequent in the upper part, less so in the lower part, and least so in the middle, the most usual point for the application of a ligature ; under any of these circumstances, two large arteries would be found in the arm instead of one. The most frequent (in three out of four) of these peculiarities is the high division of the radial. It often arises from the inner side of the brachial, and runs parallel with the main trunk to the elbow, where it crosses it, lying beneath the fascia ; or it may perfo- rate the fascia, and pass over the artery, immediately beneath the integument. The ulnar sometimes arises from the brachial high up, and then occasionally leaves that vessel at the lower part of the arm, and descends towards the inner condyle. In the forearm, it gene- rally lies beneath the deep fascia, superficial to the Flexor muscles ; occasionally between the integument and deep fascia, and very rarely beneath the Flexor muscles. The interosseous artery sometimes arises from the upper part of the brachial or axillary : as it descends the arm, it lies behind the main trunk, and at the bend of the elbow regains its usual position. In some cases of high division of the radial, the remaining trunk (ulnar interosseous) occasion- ally passes, together with the median nerve, along the inner margin of the arm to the inner con- dyle, and then passing from within outwards, beneath or through the Pronator teres, regains its usual position at the end of the elbow. Occasionally, the two arteries representing the brachial are connected at the bend of the elbow by a short transverse branch, and are even sometimes reunited. Sometimes, long slender vessels, vasa aberrantia, connect the brachial or axillary arteries with one of the arteries of the forearm, or a branch from them. These vessels usually join the radial. 408 ARTERIES. Varieties in 3Iuscular Relations} The brachial artery is occasionally concealed, in some part of its course, by muscular or tendinous slips derived from various sources. In the upper third of the arm, the brachial vessels and median nerve have been seen concealed to the extent of three inches by a muscular layer of considerable thickness, derived from the Coraco-brachialis, which passed round to the inner side of the vessel, and joined the internal head of the Triceps. In the lower half of the arm it is occasionally concealed by a broad thin head to the Biceps muscle (see p. 303). A narrow fleshy slip from the Biceps has been seen to cross the artery, concealing it for an inch and a half, its tendon ending in the aponeurosis covering the Pronator teres. A muscular and tendinous slip has been seen to arise from the external bicipital ridge by a long tendon, cross obliquely behind the long tendon of the Biceps, end in a fleshy belly, which appears on the inner side of the arm between the Biceps and Coraco-brachialis. passes down along the inner edge of the former, and crosses the artery very obliquely, so as to lie in front of it for three inches, and, finally, end in a narrow flattened tendon, which is inserted into the aponeurosis over the Pronator teres. A tendinous slip, arising from the deep part of the tendon of the Pectoralis major, has been seen to cross the artery obliquely at or below the Coraco-brachialis, and join the intermuscular septum above the inner condyle. The Brachialis anticus not unfrequently projects at the outer side of the artery, occasionally overlaps it, sending inwards, across the artery, an aponeurosis which binds the vessel down upon the Brachialis anticus. Sometimes a fleshy slip from the muscle covers the vessel, in one case, to the extent of three inches. In some cases of high origin of the Pronator radii teres, an aponeurosis extends from it to join the Brachialis anticus external to the artery; a kind of arch being thus formed, under which the principal artery and median nerve pass, so as to be concealed for half an inch above the transverse level of the condyle. Surgical Anatomy. Compression of the brachial artery is required in cases of amputation of the arm or forearm, in resection of the elbow-joint, and the removal of tumors ; and it will be observed, that it may be effected in almost any part of its course ; if pressure is made in the upper part of the limb it should be directed from within outwards, and if in the lower part from before backwards, as the artery lies on the inner side of the humerus above, and in front of it below. The most favorable situation is either above or below the insertion of the Coraco-brachialis. The application of a ligature to the brachial artery may be required in cases of wounds of the vessel, or in wounds of the palmar arch, where compression of the radial and ulnar arteries fails to arrest the hemorrhage. It is also necessary in cases of aneurism of the brachial, the radial, ulnar, or interosseous arteries; and it may be secured in any part of its course. The chief guides in determining its position are the surface-markings produced by the inner margin of the Coraco- brachialis and Biceps, the known course of the vessel, and its pulsation, which should be care- fully felt for before any operation is performed, as the vessel occasionally deviates from its usual position in the arm. In whatever situation the operation is performed, great care is necessary on account of the extreme thinness of the parts covering the artery, and the intimate connection which the vessel has throughout its whole course with important nerves and veins. Sometimes a thin layer of muscular fibre is met with concealing the artery; if such is the case, it must be divided across, in order to expose the vessel. In the upper third . Sympathetic nerve. Inferior vena cava. / \ Left semilunar ganglion. Vena azygos. r Thoracic duct. Right semilunar ganglion. Behind. Left lumbar veins. Receptaculum chyli. Thoracic duct. Vertebral column. Surgical Anatomy. Aneurisms of the abdominal aorta near the cceliac axis communicate in nearly equal proportion with the anterior and posterior parts of this vessel. "When an aneurismal sac is connected with the back part of the abdominal aorta, it usually produces absorption of the bodies of the vertebra;, and forms a pulsating tumor, that presents itself in the left hypochondriac or epigastric regions, accompanied by symptoms of disturbance of the alimentary canal. Pain is invariably present, and is usually of two kinds, a fixed and constant pain in the back, caused by the tumor pressing on or displacing the branches of the solar plexus and splanchnic nerves, and a sharp lancinating pain, radiating along those branches of the lumbar nerves pressed on by the tumor; hence the pain in the loins, the testes, the hypo- gastrium, and in the lower lfmb. usually of the left side. This form of aneurism usually bursts into the peritoneal cavity, or behind the peritoneum, in the left hypochondriac region ; or it may form a large aneurismal sac, extending down as low as Poupart's ligament ; hemorrhage in these cases being generally very extensive, but slowly produced, and never rapidly fatal. When aij aneurismal sac is connected with the front of the aorta, near the cceliac axis, it forms a pulsating tumor in the left hypochondriac or epigastric regions, usually attended with symptoms of disturbance of the alimentary canal, as sickness, dyspepsia, or constipation, and accompanied- by pain, which is constant but nearly always fixed in the loins, epigastrium, or some part of the abdomen ; the radiating pain being rare, as the lumbar nerves are seldom implicated. This form of aneurism may Lyurst into the peritoneal cavity, or behind the peritoneum, between the layers of the mesentery, or, more rarely, into the duodenum ; it rarely extends backwards so as to affect the spine. Branches of the Abdominal Aorta. Phrenic. I Gastric. Cceliac axis. I Hepatic. ( Splenic. Superior mesenteric. Supra-renal. Renal. Spermatic. Inferior mesenteric. Lumbar. Sacra media. The branches of the abdominal aorta may be divided into two sets : 1. Those supplying the viscera. 2. Those distributed to the walls of the abdomen. Visceral Branches. [ Gastric. Cceliac axis. -! Hepatic. ( Splenic. Superior mesenteric. Inferior mesenteric. Supra-renal. Renal. Spermatic. Parietal Branches. Phrenic. Lumbar. Sacra media. CCELIAC AXIS. 421 Qeliac Axis * To expose this artery, raise the liver, draw down the stomach, and then tear through the layers of the lesser omentum. The Coeliac Axis is a short thick trunk, about half an inch in length, arising from the aorta, opposite the margin of the Diaphragm, and, passing nearly hori- zontally forwards (in the erect posture), divides into three large branches, the gastric, hepatic, and splenic, occasionally giving off one of the phrenic arteries. Relations. It is covered by the lesser omentum. On the right side, it is in relation with the right semilunar ganglion, and the lobus Spigelii. On the left side, with the right semilunar ganglion and cardiac end of the stomach. Below, it rests upon the upper border of the pancreas. Fig. 223.- -The Coeliac Axis and its Branches, the Liver having been raised, and the Lesser Omentum removed. The 5a.stric Artery (Coronaria ventriculi), the smallest of the three brandies of the coeliac axis, passes upwards and to the left side, to the cardiac orifice of the stomach, distributing branches to the oesophagus, which anastomose with the aortic oesophageal arteries ; others supply the cardiac end of the stomach, inoscu- lating with branches of the splenic artery ; it then passes from left to right, along the lesser curvature of the stomach to the pylorus, lying in its course between the layers of the lesser omentum, and giving branches to both surfaces of the organ ; at its termination it anastomoses with the pyloric branch of the hepatic. The Hepatic Artery in the adult is intermediate in size between the gastric and splenic ; in the foetus, it is the largest of the three branches of the coeliac 422 ARTERIES. axis. It passes upwards to the right side, between the layers of the lesser omentum, and in front of the foramen of Winslow, to the transverse fissure of the liver, where it divides into two branches (right and left), which supply the cor- responding lobes of that organ, accompanying the ramifications of the vena portse and hepatic duct. The hepatic artery, in its course along the right border of the lesser omentum, is in relation with the ductus communis choledochus and portal vein, the former lying to the right of the artery, and the vena portae behind. Its branches are the Pyloric. Gastro-d uodenalis Cystic. Qastro-epiploica dextra. Pancreatico-duodenalis. Fip 224. — The Cceliac Axis and its Blanches, the Stomach having been raised, and the Transverse Meso-colon removed. Grtnt K The "pyloric branch arises from the hepatic, above the pylorus, descends to the pyloric end of the stomach, and passes from right to left along its lesser curvature, supplying it with branches, and inosculating with the gastric artery. The gastro-duodenalis is a short but large branch, which descends behind the duodenum, near the pylorus, and divides at the lower border of the stomach into two branches, the gastro-epiploica dextra and the pancreatico-duodenalis. Previous to its division, it gives off two or three small inferior pyloric branches to the pyloric end of the stomach and pancreas. The gastro-ejriploica dextra runs from right to left along the greater curvature SUPERIOR MESENTERIC- 423 of the stomach, between the layers of the great omentum, anastomosing about the middle of the lower border of this organ with the gastro-epiploica sinistra from the splenic artery. This vessel gives off numerous branches, some of which ascend to supply both surfaces of the stomach, whilst others descend to supply the great omentum. The pancreatico-duodenalis descends along the contiguous margins of the duode- num and pancreas. It supplies both these organs, and anastomoses with the inferior pancreatico-duodenal branch of the superior mesenteric artery. In ulceration of the duodenum, which frequently occurs in connection with severe burns, this artery is often involved, and death may occur from hemorrhage into the intestinal canal. The cystic artery, usually a branch of the right hepatic, passes upwards and forwards along the neck of the gall-bladder, and divides into two branches, one of which ramifies on its free surface, the other between it and the substance of the liver. The Splenic Artery, in the adult, is the largest of the three branches of the cceliac axis, and is remarkable for the extreme tortuosity of its course. It passes horizontally to the left side behind the upper border of the pancreas, accompanied by the splenic vein, which lies below it ; and, on arriving near the spleen, divides into branches, some of which enter the hilus of that organ to be distributed to its structure, whilst others are distributed to the great end of the stomach. The branches of this vessel are the Pancreaticae parvae. Gastric (Yasa brevia). Pancreatica magna. Gastro-epiploica sinistra. The pancreaticse are numerous small branches derived from the splenic as it runs behind the upper border of the pancreas, supplying its middle and left parts. One of these, larger than the rest, is given off from the splenic near the left extremity of the pancreas ; it runs from left to right near the posterior surface of the gland, following the course of the pancreatic duct, and is called the pancreatica magna. These vessels anastomose with the pancreatic branches of the pancreatico- duodenal arteries. The gastric (vasa brevia) consist of from five to seven small branches, which arise either from the termination of the splenic artery, or from its terminal branches ; and passing from left to right, between the layers of the gastro-splenic omentum, are distributed to the great curvature of the stomach ; anastomosing with branches of the gastric and gastro-epiploica sinistra arteries. The gastro-epiploica sinistra, the largest branch of the splenic, runs from left to right along the great curvature of the stomach, between the layers of the great omentum, and anastomoses with the gastro-epiploica dextra. In its course, it distributes several branches to the stomach, which ascend upon both surfaces; others descend to supply the omentum. Superior Mesenteric Artery. In order to expose this vessel, raise the great omentum and transverse colon, draw down the small intestines, and, if the peritoneum is divided where the transverse meso-colon and mesentery join, this artery will be exposed just as it issues beneath the lower border of the pancreas. The Superior Mesenteric Artery (fig. 225) supplies the whole length of the small intestine, except the first part of the duodenum ; it also supplies the caecum, ascending and transverse colon. It is a vessel of large size, arising from the fore part of the aorta, about a quarter of an inch below the cceliac axis ; being covered, at its origin, by the splenic vein and pancreas. It passes forwards, between the pancreas and transverse portion of the duodenum, crosses in front of this portion of the intestine, and descends between the layers of the mesentery to the right iliac fossa, where it terminates considerably diminished in size. In its course it forms an arch, the convexity being directed forwards and downwards to the left side, the concavity backwards and upwards to the right. It is accompanied by 424 ARTERIES. the superior mesenteric vein, and is surrounded by the superior mesenteric plexus of nerves. Its branches are the Inferior pancreatico-duodenal. Ileo-colic. Vasa intestini tenuis. . Colica dextra. Colica media. The inferior pancreatico-duodenal is given off from the superior mesenteric below the pancreas, and is distributed to the head of the pancreas, and the trans- verse and descending portions of the duodenum ; anastomosing with the pancrea- tico-duodenal artery. Fig. 225.— The Superior Mesenteric Artery and its Branches. The vasa intestini tenuis arise from the convex side of the superior mesenteric artery. They are usually from twelve to fifteen in number, and are distributed to the jejunum and ileum. They run parallel with one another between the layers of the mesentery ; each vessel dividing into two branches, which unite with a similar branch on each side, forming a series of arches, the convexities of which are directed towards the intestine. From this first set of arches branches arise, which again unite with similar branches from either side, and thus a second series of arches is formed; and from -these latter, a third, and even a fourth or fifth series of arches is constituted, diminishing in size the nearer they approach the intes- tine. From the terminal arches numerous small straight vessels arise which encircle the intestine, upon which they are minutely distributed, ramifying between its coats. INFERIOR MESENTERIC. 425 The ileo-colic artery is the lowest branch given off from the concavity of the superior mesenteric artery. It descends between the layers of the mesentery to the right iliac fossa, where it divides into two branches. Of these the inferior one inosculates with the lowest branches of the vasa intestini tenuis, from the convexity of which branches proceed to supply the termination of the ileum, the ccecum and appendix cceci, and the ileo-ccecal and ileo-colic valves. The superior division inosculates with the colica dextra, and supplies the commencement of the colon. The colica dextra arises from about the middle of the concavity of the superior mesenteric artery, and, passing beneath the peritoneum to the middle of the ascend- ing colon, divides into two branches ; a descending branch, which inosculates with the ileo-colic, and an ascending branch which anastomoses with the colica media. These branches form arches, from the convexity of which vessels are distributed to the ascending colon. The branches of this vessel are covered with peritoneum only on their anterior aspect. The colica media arises from the upper part of the concavity of the superior mesenteric, and, passing forwards between the layers of the transverse mesocolon, divides into two branches ; the one on the right side inosculating with the colica dextra, that on the left side with the colica sinistra, a branch of the inferior mesenteric. From the arches formed by their inosculation, branches are dis- tributed to the transverse colon. The branches of this vessel lie between two layers of peritoneum. Inferior Mesenteric Artery. In order to expose this vessel, draw the small intestines and mesentery over to the right side of the abdomen, raise the transverse colon towards the thorax, and divide the peritoneum cover- ing the left side of the aorta. The Inferior Mesenteric Artery (fig. 226) supplies the descending and sig- moid flexure of the colon, and greater part of the rectum. It is smaller than the superior mesenteric, and arises from the left side of the aorta, between one and two inches above its division into the common iliacs. It passes downwards to the left iliac fossa, and then descends, between the layers of the mesorectum, into the pelvis, under the name of the superior hemorrhoidal artery. It lies at first in close relation with the left side of the aorta, and then passes in front of the left common iliac artery. Its branches are the Colica sinistra. Sigmoid. Superior hemorrhoidal. The colica sinistra passes behind the peritoneum, in front of the left kidney, to reach the descending colon, and divides into two branches ; an ascending branch, which inosculates with the colica media, and a descending branch, which anasto- moses with the sigmoid artery. From the arches formed by these inosculations, branches are distributed to the descending colon. The sigmoid artery runs obliquely downwards across the Psoas muscle to the sigmoid flexure of the colon, and divides into branches which supply that part of the intestine ; anastomosing above, with the colica sinistra, and, below, with the superior hemorrhoidal artery. This vessel is sometimes replaced by three or four small branches. The superior hemorrhoidal artery, the continuation of the inferior mesen- teric, descends into the pelvis between the layers of the mesorectum, crossing, in its course, the ureter, and left common iliac vessels. Opposite the middle of the sacrum it divides into two branches, which descend one on each side of the rectum, where they divide into several small branches, which are distributed between the mucous and muscular coats of that tube, to near its lower end ; anas- tomosing with each other, with the middle hemorrhoidal arteries, branches of the internal iliac, and with the inferior hemorrhoidal, branches of the internal pudic. The student should especially remark, that the trunk of the vessel descends 426 ARTERIES. along the hack part of the rectum as far as the middle of the sacrum before it divides ; this is about a finger's length or four inches from the anus. In disease Fig. 226. — The Inferior Mesenteric Artery and its Branches. Midd.lt Jluviarrko. Inferior KsmorrhoiJul of this tube, the rectum should never be divided beyond this point in that direc- tion, for fear of involving the artery. SUPRA-RENAL ARTERIES. The Supra-renal Arteries are two small vessels which arise, one on each side of the aorta, opposite the superior mesenteric artery. They pass obliquely upwards and outwards, to the under surface of the supra-renal capsules, to which they are distributed, anastomosing with capsular branches from the phrenic and renal arteries. In the adult these arteries are of small size ; in the foetus they are as large as the renal arteries. Renal Arteries. The Renal Arteries are two large trunks, which arise from the sides of the aorta, immediately below the superior mesenteric artery. Each is directed out- wards, so as to form nearly a right angle with the aorta. The right one longer than the left, on account of the position of the aorta, passes behind the inferior vena cava. The left is somewhat higher than the right. Previously to entering the kidney, each artery divides into four or five branches, which are distributed to its substance. At the hilum, these branches lie between the renal vein and PHRENIC AND LUMBAR. 427 ureter, the vein being usually in front, the ureter behind. Each vessel gives off some small branches to the supra-renal capsules, the ureter, and to the surround- ing cellular membrane and muscles. Spermatic Arteries. The Spermatic Arteries are distributed to the testes in the male, and to the ovaria in the female. They are two slender vessels, of considerable length, which arise from the front of the aorta, a little below the renal arteries. Each artery passes obliquely outwards and downwards, behind the peritoneum, cross- ing the ureter, and resting on the Psoas muscle, the right spermatic lying in front of the inferior vena cava, the left behind the sigmoid flexure of the colon. On reaching the margin of the pelvis, each vessel passes in front of the corresponding external iliac artery, and takes a different course in the two sexes. In the male, it is directed outwards, to the internal abdominal ring, and accompanies the other constituents of the spermatic cord along the spermatic canal to the testis, where it becomes tortuous, and divides into several branches, two or three of which accompany the vas deferens, and supply the epididymis, anastomosing with the artery of the vas deferens ; others pierce the back part of the tunica albuginea, and supply the substance of the testis. At an early period of foetal life, when the testes lie by the side of the spine, below the kidneys, the spermatic arteries are short ; but as these organs descend from the abdomen into the scrotum, they become gradually lengthened. In the female, the spermatic arteries (ovarian) are shorter than in the male, and do not pass out of the abdominal cavity. On arriving at the margins of the pelvis, each artery passes inwards, between the two laminae of the broad ligament of the uterus, to be distributed to the ovary. One or two small branches supply the Fallopian tube ; another passes on to the side of the uterus, and anastomoses with the uterine arteries. Other offsets are continued along the round ligament, through the inguinal canal, to the integument of the labium and groin. Phrenic Arteries. The Phrenic Arteries are two small vessels, which present much variety in their origin. They may arise separately from the front of the aorta, immediately below the coeliac axis, or by a common trunk, which may spring either from the aorta, or from the coeliac axis. Sometimes one is derived from the aorta, and the other from one of the renal arteries. In only one out of thirty -six cases, did these arteries arise as two separate vessels from the aorta. They diverge from one another across the crura of the Diaphragm, and then pass obliquely upwards and outwards upon its under surface. The left phrenic passes behind the oesophagus, and runs forwards on the left side of the oesophageal opening. The right phrenic passes behind the liver and inferior vena cava, and ascends along the right side of the aperture for transmitting that vein. Near the back part of the central tendon, each vessel divides into two branches. The internal branch runs forwards to the front of the thorax, supplying the Diaphragm, and anastomosing with its fellow of the opposite side, and with the musculo-phrenic, a branch of the internal mammary. The external branch passes towards the side of the thorax, and in- osculates with the intercostal arteries. The internal branch of the right phrenic gives off a few vessels to the inferior vena cava; and the left one some branches to the oesophagus. Each vessel also sends capsular branches to the supra-renal capsule of its own side. The spleen on the left side, and the liver on the right, also receive a few branches from these vessels. Lumbar Arteries. The Lumbar Arteries are analogous to the intercostal. They are usually four in number on each side, and arise from the back part of the aorta, nearly at right angles with that vessel. They pass outwards and backwards, around the sides of 428 ARTERIES. the body of the corresponding lumbar vertebra, behind the sympathetic nerve and the Psoas muscle ; those on the right side being covered by the inferior vena cava, and the two upper ones on each side by the crura of the Diaphragm. In the interval between the transverse processes of the vertebrae, each artery divides into a dorsal and an abdominal branch. The dorsal branch gives off) immediately after its origin, a spinal branch, which enters the spinal canal; it then continues its course backwards, between the transverse processes, and is distributed to the muscles and integument of the back, anastomosing with its fellow, and with the posterior branches of the inter- costal arteries. The spinal branch, besides supplying offsets which run along the nerves to the dura mater and cauda equina, anastomosing with the other spinal arteries, divides into two branches, one of which ascends on the posterior surface of the body of the vertebra above, and the other descends on the posterior surface of the body of the vertebra below, both vessels anastomosing with similar branches from neigh- boring spinal arteries. The inosculations of these vessels on each side, throughout the whole length of the spine, form a series of arterial arches behind the bodies of the vertebras, which are connected with each other, and with a median longi- tudinal vessel, extending along the middle of the posterior surface of the bodies of the vertebrae, by transverse branches. From these vessels offsets are distributed to the periosteum and bones. The abdominal branches pass outwards, behind the Quadratus lumborum, the lowest branch occasionally in front of that muscle, and, being continued between the abdominal muscles, anastomose with branches of the epigastric and internal mammary in front, the intercostals above, and those of the ilio-lumbar and circum- flex iliac, below. Middle Saceal Arteey. The Middle Sacral Artery is a small vessel, about the size of a crow-quill, which arises from the back part of the aorta, just at its bifurcation. It descends upon the last lumbar vertebra, and along the middle line of the front of the sacrum, to the upper part of the coccyx, where it terminates by anastomosing with the lateral sacral arteries. From it, branches arise which run through the mesorectum, to supply the posterior surface of the rectum. Other branches are given off on each side, which anastomose with the lateral sacral arteries, and send off small offsets which enter the anterior sacral foramina. Common Iliac Arteeies. The abdominal aorta divides into the two common iliac arteries. The bifurcation usually takes place on the left side of the body of the fourth lumbar vertebra. This point corresponds to the left side of the umbilicus, and is on a level with a line drawn from the highest point of one iliac crest to the other. The common iliac arteries are about two inches in length; diverging from the termination of the aorta, they pass downwards and outwards to the margin of the pelvis, and divide opposite the intervertebral substance, between the last lumbar vertebra and the sacrum, into two branches, the external and internal iliac arteries; the former supplying the lower extremity ; the latter, the viscera and parietes of the pelvis. The right common iliac is somewhat larger than the left, and passes more ob- liquely across the body of the last lumbar vertebra. It is covered by the peri- toneum, the ileum, the branches of the sympathetic nerve ; and crossed, at its point of division, by the ureter. Behind, it is separated from the last lumbar vertebra, by the two common iliac veins. On its outer side, it is in relation with the inferior vena cava, and right common iliac vein, above ; and the Psoas magnus muscle, below. The left common iliac is in relation, in front, with the peritoneum, branches of the sympathetic nerve, the rectum and superior hemorrhoidal artery ; and crossed, ::t its point of bifurcation, by the ureter. The left common iliac vein lies partly COMMON ILIAC. 429 on the inner side, and partly beneath the artery; on its outer side, it is in relation with the Psoas magnus. Branches. The common iliac arteries give off small branches to the peritoneum, Psoae muscles, ureters, and to the surrounding cellular membrane, and occasionally give origin to the ilio-lumbar, or renal arteries. Peculiarities. Its point of origin varies according to the bifurcation of the aorta. In three- fourths of a large number of cases, the aorta bifurcated either upon the fourth lumbar vertebra, or upon the intervertebral disk between it and the fifth ; one case in nine being below, and one in eleven above this point. In ten out of every thirteen cases, the vessel bifurcated within half an inch above or below the level of the crest of the ilium ; more frequently below than above. The point of division is subject to great variety. In two-thirds of a large number of cases, it was between the last lumbar vertebra and the upper border of the sacrum ; in one case in eight being above, and in one in six below that point. The left common iliac artery divides lower down more frequently than the right. The relative length, also, of the two common iliac arteries varies. The right common iliac was longest in sixty-three cases ; the left, in fifty-two ; whilst they were both equal in fifty-three. The length of the arteries varied in five-sevenths of the cases examined, from an inch and a half to three inches ; in about half of the remaining cases, the artery was longer ; and in the other half, shorter ; the minimum length being less than half an inch, the maximum four and a half inches. In one instance, the right common iliac was found wanting, the external and internal iliacs arising directly from the aorta. Fig. 227. — Arteries of the Felvis. Surgical Anatomy. The application of a ligature to the common iliac artery may be required on account of aneurism or hemorrhage, implicating the external or internal iliacs, or on account 430 ARTERIES. of secondary hemorrhage after amputation of the thigh high up. It has been seen, that the origin of this vessel corresponds to the left side of the umbilicus on a level with a line drawn from the highest point of one iliac crest to the opposite one, and its course to a line extending from the left side of the umbilicus downwards towards the middle of Poupart's ligament The line of incision required in the first steps of an operation for securing this vessel, would materially depend upon the nature of the disease. If the surgeon select the iliac region, a curved incision, about five inches in length, may be made, commencing on the left side of the umbilicus, carried outwards towards the anterior superior iliac spine, and then along the upper border of Poupart's ligament, as far as its middle. But if the aneurismal tumor should extend high up in the abdo- men, along the external iliac, it is better to select the side of the abdomen, approaching the artery from above, by making an incision from four to five inches in length, from about two inches above and to the left of the umbilicus, carried outwards in a curved direction towards the lumbar region, and terminating a little below the anterior superior iliac spine. The abdominal muscles (in either case) having been cautiously divided in succession, the transversalis fascia must be carefully cut through, and the peritoneum, together with the ureter, separated from the artery, and pushed aside : the sacro-iliac articulation must then be felt for, and upon it the vessel will be felt pulsat- ing, and may be fully exposed in close connection with its accompanying vein. On the right side, both common iliac veins, as well as the inferior vena cava, are in close connection with the artery, and must be carefully avoided. On the left side, the vein usually lies on the inner side, and behind the artery ; but it occasionally happens, that the two common iliac veins are joined on the left instead of the right side, which would add much to the difficulty of an operation in such a case. If the common iliac artery is so short that danger is to be apprehended from secondary hemorrhage if a ligature is applied to it, it would be preferable, in such a case, to tie both the external and internal iliacs near their origin. This operation has been performed in 17 cases, 9 of which were cured, and 8 died. Collateral Circulation. The principal agents in carrying on the collateral circulation after the application of a ligature to the common iliac, are, the anastomoses of the hemorrhoidal branches of the internal iliac with the superior hemorrhoidal from the inferior mesenteric ; and by the anastomoses of the uterine and ovarian arteries, and of the vesical arteries of opposite sides; of the lateral sacral with the middle sacral artery; of the epigastric with the internal mammary, inferior intercostal and lumbar arteries ; of the ilio-lumbar with the last lumbar artery ; of the obturator artery, by means of its pubic branch, with the vessel of the opposite side, and with the internal epigastric ; and of the gluteal with the posterior branches of the sacral arteries. Internal Iliac Artery. The Internal Iliac Artery supplies the walls and viscera of the pelvis, the gene- rative organs, and inner side of the thigh. It is a short, thick vessel, smaller than the external iliac, and about an inch and a-half in length, which arises at the point of bifurcation of the common iliac ; and, passing downwards to the upper margin of the great sacro-sciatic foramen, divides into two large trunks, an anterior and posterior ; a partially obliterated cord, the hypogastric artery, extending from the extremity of the vessel forwards to the bladder. Relations. In front, with the ureter, which separates it from the peritoneum. Behind, with the internal iliac vein, the lumbo-sacral nerve, and Pyriformis muscle. By its outer side, near its origin, with the Psoas magnus muscle. Plan of the Relations of the Internal Iliac Artery. In front. Peritoneum, Ureter. Outer side. Psoas magnus. Behind. Internal iliac vein. Lumbo-sacral nerve. Pyriformis muscle. In the foetus, the internal iliac artery (hypogastric) is twice as large as the external iliac, and appears the continuation of the common iliac. Passing forwards INTERNAL ILIAC. 431 to the bladder, it ascends along the side of that viscus to its summit, to which it gives branches ; it then passes upwards along the back part of the anterior wall of the abdomen to the umbilicus, converging towards its fellow of the opposite side. Having passed through the umbilical opening, the two arteries twine round the umbilical vein, forming with it the umbilical cord ; and, ultimately, ramify in the placenta. That portion of the vessel placed within the abdomen is called the hypogastric artery ; and that external to that cavity, the umbilical artery. At birth, when the placental circulation ceases, that portion of the hypogastric artery which extends from the umbilicus to the summit of the bladder, contracts, and ultimately dwindles to a solid fibrous cord; the portion of the same vessel extending from the summit of the bladder to within an inch and a half of its origin, is not totally impervious, though it becomes considerably reduced in size, and serves to convey blood to the bladder, under the name of the superior vesical artery. Peculiarities, as regards its length. In two-thirds of a large number of cases, the length of the internal iliac varied between an inch and an inch and a half; in the remaining third, it was more frequently longer than shorter, the maximum length being three inches, the minimum half an inch. The lengths of the common and internal iliac arteries bear an inverse proportion to each other, the internal iliac artery being long when the common iliac is short, and vice versa. As regards its place of division. The place of division of the internal iliac va/ies between the upper margin of the sacrum, and the upper border of the sacro-sciatic foramen. The arteries of the two sides in a series of cases often differed in length, but neither seemed constantly to exceed the other. Surgical Anatomy. The application of a ligature to the internal iliac artery may be required in cases of aneurism or hemorrhage affecting one of its branches. This vessel may be secured by making an incision through the abdominal parietes in the iliac region, in a direction and to an extent similar to that for securing the common iliac ; the transversalis fascia having been cau- tiously divided, and the peritoneum pushed inwards from the iliac fossa towards the pelvis, the finger may feel the pulsation of the external iliac at the bottom of the wound ; and, by tracing this vessel upwards, the internal iliac is arrived at, opposite the sacro-iliac articulation. It should be remembered that the vein lies behind, and on the right side, a little external to the artery, and in close contact with it ; the ureter and peritoneum, which lie in front, must also be avoided. The degree of facility in applying a ligature to this vessel will mainly depend upon its length. It has been seen that, in the great majority of. the cases examined, the artery was short, varying from an inch to an inch and a half; in these cases, the artery is deeply seated in the pelvis; when, on the contrary, the vessel is longer, it is found partly above that cavity. If the artery is very short, which occasionally happens, it would be preferable to apply a ligature to the common iliac, or upon the external and internal iliacs at their origin. This operation has been performed in seven cases, four of which recovered, and three died. Collateral Circulation. In Mr. Owen's dissection of a case in which the internal iliac artery hid been tied by Stevens ten years before death, for aneurism of the sciatic artery, the internal iliac was found impervious for about an inch above the point where the ligature had been applied; but the obliteration did not extend to the origin of the external iliac, as the ilio-lumbar artery arose just above this point. Below the point of obliteration, the artery resumed its natural diameter, and continued so for half an inch ; the obturator, lateral sacral, and gluteal, arising in succession from the latter portion. The obturator artery was entirely obliterated. The lateral sacral artery was as large as a crow's quill, and had a very free anastomosis with the artery of the opposite side, and with the middle sacral artery. The sciatic artery was entirely obliterated as far as its point of connection with the aneurismal tumor ; but, on the distal side of the sac, it was continued down along the back of the thigh nearly as large in size as the femoral, being pervious about an inch below the sac by receiving an anastomosing vessel from the superior profunda. 1 In addition to the above, the circulation in the parts supplied by the internal iliac would be carried on by the anastomoses of the uterine and ovarian arteries ; of the opposite vesical arteries ; of the hemorrhoidal branches of the internal iliac with those from the inferior mesenteric ; of the obturator artery, by means of its pubic branch, with the vessel of the opposite side, and with the epigastric and internal circumflex ; by the anastomoses of the circumflex, and perforating branches of the femoral, with the sciatic ; of the gluteal with the posterior branches of the sacral arteries ; of the ilio-lumbar with the last lumbar ; of the lateral sacral with the middle sacral ; and by the anastomoses of the circumflex iliac with the ilio-lumbar and gluteal. 1 Medico-Chirurgical Transactions, vol. xvi. 432 ARTERIES. Branches of the Internal Iliac. From the Anterior Trunk. From the Posterior Trunk. Superior vesical. Gluteal. Middle vesical. Ilio-lumbar. Inferior vesical. Lateral sacral. Middle hemorrhoidal. T r 7 ( Uterine. In female. { T7 - • 1 J [ Vaginal. Obturator. Internal pudic. Sciatic. The superior vesical is that part of the foetal hypogastric artery, which remains pervious after birth. It extends to the side of the bladder, distributing numerous branches to the body and fundus of this organ. From one of these, a slender vessel is derived, which accompanies the vas deferens in its course to the testis, where it anastomoses with the spermatic artery. This is the artery of the vas deferens. Other branches supply the ureter. The middle vesical, usually a branch of the superior, is distributed to the base of the bladder, and under surface of the vesiculoe seminales. The inferior vesical arises from the anterior division of the internal iliac, in common with the middle hemorrhoidal, and is distributed to the base of the bladder, the prostate gland, and vesiculae seminales. Those branches distributed to the prostate communicate with the corresponding vessel of the opposite side. The middle hemorrhoidal artery usually arises together with the preceding vessel. It supplies the rectum, anastomosing with the other hemorrhoidal arteries. The uterine artery passes downwards from the anterior trunk of the internal iliac to the neck of the uterus. Ascending, in a tortuous course, on the side of this viscus, between the laj^ers of the broad ligament, it distributes branches to its substance, anastomosing, near its termination, with a branch from the ovarian artery. Branches from this vessel are also distributed to the bladder and ureter. The vaginal artery is analogous to the inferior vesical in the male ; it descends upon the vagina, supplying its mucous membrane, and sending branches to the neck of the bladder, and contiguous part of the rectum. The Obturator Artery usually arises from the anterior trunk of the internal iliac, frequently from the posterior. It passes forwards below the brim of the pelvis, to the canal in the upper border of the obturator foramen, and, escaping from the pelvic cavity through this aperture, divides into an internal and an external branch. In the pelvic cavity, this vessel lies upon the pelvic fascia, beneath the peritoneum, and a little below the obturator nerve; and, whilst passing through the obturator foramen, is contained in an oblique canal, formed by the horizontal branch of the pubes, above; and the arched border of the obturator membrane, below. Branches. Within the pelvis, the obturator artery gives off an iliac branch to the iliac fossa, which supplies the bone and the Iliacus muscle, and anastomoses with the ilio-lumbar artery ; a vesical branch, which runs backwards to supply the bladder; and & pubic branch, which is given off from the vessel just before it leaves the pelvic cavity. This branch ascends upon the back of the pubes, com- municating with offsets from the epigastric artery, and with the corresponding vessel of the opposite side. This branch is placed on the inner side of the femoral ring. External to the pelvis, the obturator artery divides into an external and an internal branch, which are deeply situated beneath the Obturator externus muscle ; skirting the circumference of the obturator foramen, they anastomose at the lower part of this aperture with each other, and with branches of the internal circumflex artery. OBTURATOR— INTERNAL PUDIC. 433 The internal branch curves inwards along the inner margin of the obturator foramen, distributing branches to the Obturator muscles, Pectineus, Adductors, and Gracilis, and anastomoses with the external branch, and with the internal circumflex artery. The external branch curves round the outer margin of the foramen, to the space between the Gemellus inferior and Quadratus femoris, where it anastomoses with the sciatic artery. It supplies the Obturator muscles, anastomoses, as it passes backwards, with the internal circumflex, and sends a branch to the hip-joint through the cotyloid notch, which ramifies on the round ligament as far as the head of the femur. Peculiarities. In two out of every three cases the obturator arises from the internal iliae. In one case in three and a half cases, from the epigastric ; and in about one in seventy-two cases by two roots from both vessels. It arises in about the same proportion from the external iliac artery. The origin of the obturator from the epigastric is not commonly found on both sides of the same body. , . , When the obturator artery arises at the front of the pelvis from the epigastric, it descends almost vertically downwards to the upper part of the obturator foramen. The artery in this course usually descends in contact with the external iliac vein, and lies on the outer side of the femoral ring (fig. 228) ; in such cases it would not be endangered in the operation for femoral hernia. Occasionally, however, it curves inwards along the free margin of Gimbernat's ligament (fig. 229), and under such circumstances would almost completely encircle the neck of a hernial sac' (supposing a hernia to exist in such a case), and would be in great danger of being wounded if an operation was performed. Variations in Origin and Course of Obturator Artery. Fig. 228. Fig. 229. The Internal Pudic is the smaller of the two terminal branches of the anterior trunk of the internal iliac, and supplies the external organs of generation. It passes downwards and outwards to the lower border of the great sacro-sciatic foramen, and emerges from the pelvis between the Pyriformis and Coccygeus muscles ; it then crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro-sciatic foramen. The artery now crosses the Obturator internus muscle, to the ramus of the ischium, being covered by the obturator fascia, and situated about an inch and a half from the margin of the tuberosity ; it then ascends for- wards and upwards along the ramus of the ischium, pierces the posterior layer of the deep perineal fascia, and runs forwards along the inner margin of the ramus of the pubes ; finally, it perforates the anterior layer of the deep perineal fascia, and divides into its two terminal branches, the dorsal artery of the penis and the artery of the corpus cavernosum. Relations. In the first part of its course, within the pelvis, it lies in front of the Pyriformis muscle and sacral plexus of nerves, and on the outer side of the rectum (on the left side). As it crosses the spine of the ischium, it is covered by the Gluteus maximus, and great sacro-sciatic ligament ; and when it enters the pelvis, it lies on the outer side of the ischio-rectal fossa, upon the surface of the Obtura- tor internus muscle, contained in a fibrous canal formed by the obturator fascia and the falciform process of the great sacro-sciatic ligament. It is accompanied by the pudic veins, and the internal pudic nerve. Peculiarities. The internal pudic is sometimes smaller than usual, or fails to give off one oi two of its usual branches; in such cases, the deficiency is supplied by branches derived from an additional vessel, the accessory pudic, which generally arises from the pudic artery before its exit 28 434 ARTERIES. from the great sacro-sciatic foramen, and passes forwards near the base of the bladder, on the upper part of the prostate gland, to the perineum, where it gives off those branches usually derived from the pudic artery. The deficiency most frequently met with, is that in which the internal pudic ends as the artery of the bulb ; the artery of the corpus cavernosum and arteria dorsalis penis being derived from the accessory pudic. Or the pudic may terminate as the super- ficial perineal, the artery of the bulb being derived, with the other two branches, from the acces- sory vessel. The relation of the accessory pudic to the prostate gland and urethra, is of the greatest interest in a surgical point of view, as this vessel is in danger of being wounded in the lateral operation of lithotomy. Branches. Within the pelvis, the internal pudic gives off several small branches, which supply the muscles, sacral nerves, and viscera in this cavity. In the peri- neum the following branches are given off. Inferior or external hemorrhoidal. Artery of the bulb. Superficial perineal. Artery of the corpus cavernosum. Transverse perineal. Dorsal artery of the penis. The external hemorrhoidal are two or three small arteries, which arise from the internal pudic as it passes above the tuberosity of the ischium. Crossing the ischio-rectal fossa, they are distributed to the muscles and integument of the anal region. The superficial perineal artery supplies the scrotum, and muscles and integu- ment of the perineum. It arises from the internal pudic, in front of the preceding branches, and piercing the lower border of the deep perineal fascia, runs across the Transversus perinei, and through the triangular space between the Accelerator urinas and Erector penis, both of which it supplies, and is finally distributed to the skin of the scrotum and dartos. In its passage through the perineum it lies beneath the superficial perineal fascia. The transverse perineal is a small branch which arises either from the internal pudic, or from the superficial perineal artery as it crosses the Transversus perinei muscle. Piercing the lower border of the deep perineal fascia, it runs trans- versely inwards along the cutaneous surface of the Transversus perinei muscle, which it supplies, as well as the structures between the anus and bulb of the urethra. The artery of the bulb is a large but very short vessel, arising from the internal pudic between the two layers of the deep perineal fascia, and passing nearly transversely inwards, pierces the bulb of the urethra, in which it ramifies. It gives off a small branch which* descends to supply Cowper's gland. This artery is of considerable importance in a surgical point of view, as it is in danger of being wounded in the lateral operation of lithotomy, an accident usually attended with severe and alarming hemorrhage. This vessel is sometimes very small, occasionally wanting, or even double. It sometimes arises from the internal pudic earlier than usual, and crosses the perineum to reach the back part of the bulb. In such a case the vessel could hardly fail to be wounded in the performance of the lateral operation for lithotomy. If, on the contrary, it should arise from an accessory pudic, it lies more forward than usual, and is out of daDger in the operation. The artery of the corpus cavernosum, one of the terminal branches of the inter- nal pudic, arises from that vessel while it is situated between the crus penis and the ramus of the pubes ; piercing the crus penis obliquely, it runs forwards in the corpus cavernosum by the side of the septum pectiniforme, to which its branches are distributed. The dorsal artery of the penis ascends between the crus and pubic symphysis, and, piercing the suspensory ligament, runs forward on the dorsum of the penis to the glans, where it divides into two branches, which supply the glans and prepuce. On the dorsum of the penis, it lies immediately beneath the integument, parallel with the dorsal vein and corresponding artery of the opposite side. It supplies the integument and fibrous sheath of the corpus cavernosum. SCIATIC. 435 Iuttrnai CircumjiMC The internal pudic artery in the female is smaller than in the male. Its origin and course are similar, and there is considerable analogy in the distribution of its branches. The superficial artery supplies the labia pudendi ; the artery of the bulb supplies the erectile tissue of the bulb of the vagina, whilst the two terminal branches supply the clitoris ; the artery of the corpus cavernosum, the cavernous body of the clitoris; and the arteria dorsalis clitori- Fi S- 230.-The Arteries of the Gluteal and Posterior Femoral dis, the dorsum of that organ. The Sciatic Artery (fig. 230), the larger of the two terminal branches of the anterior trunk of the internal iliac, is distributed to the muscles on the back of the pelvis. It passes down to the lower part of the great sacro-sciatic fora- men, behind the internal pudic, resting on the sacral plexus of nerves and Pyri- formis muscle, and escapes from the pelvis between the Pyriformis and Coccy- geus. It then descends in the interval between the trochanter major and tu- berosity of the ischium, accompanied by the sciatic nerves, and covered by the Gluteus maximus, and di- vides into branches, which supply the deep muscles at the back of the hip. Within the pelvis, it dis- tributes branches to the Pyriformis, Coccygeus, and Levator ani muscles ; some hemorrhoidal branches, which supply the rectum, and occasionally take the place of the middle hemor- rhoidal artery; and vesical branches to the base and neck of the bladder, vesi- culae seminales, and pros- tate gland. External to the pelvis, it gives off the coccy- geal, inferior gluteal, comes nervi ischiadici, muscular, and articular branches. The coccygeal branch runs inwards, pierces the great sacro-sciatic ligament, and supplies the Gluteus maximus, the integument, and other structures on the back of the coccyx. The inferior gluteal branches, three or four in number, supply the Gluteus maximus muscle. The comes nervi ischiadici is a long slender vessel, which accompanies the great Super Untcrnal Art^ula Terferntiny Inferior Titrating moruiia* JJusruIam External Jlrtlcular 436 ARTERIES. sciatic nerve for a short distance ; it then penetrates it, and runs in its substance to the lower part of the thigh. The muscular branches supply the muscles on the back part of the hip, anas- tomosing with the gluteal, internal and external circumflex, and superior per- forating arteries. Some articular branches are distributed to the capsule of the hip-joint. The Gluteal Artery is the largest branch of the internal iliac, and appears to he the continuation of the posterior division of that vessel. It is a short thick trunk, which passes out of the pelvis above the upper border of the Pyriformis muscle, and immediately divides into a superficial and deep branch. Within the pelvis, it gives off a few muscular branches to the Iliacus, Pyriformis, and Obtu- rator internus, and just previous to quitting that cavity a nutritious artery, which enters the ilium. The superficial branch passes beneath the Gluteus maximus, and divides into numerous branches, some of which supply this muscle, whilst others perforate its tendinous origin, and supply the integument covering the posterior surface of the sacrum, anastomosing with the posterior branches of the sacral arteries. _ The deep branch runs between the Gluteus medius and Gluteus minimus, and sub- divides into two. Of these, the superior division, continuing the original course of the vessel, passes along the upper border of the Gluteus minimus to the anterior superior spine of the ilium, anastomosing with the circumflex iliac and ascending branches of the external circumflex artery. The inferior division crosses the Gluteus minimus obliquely to the trochanter major, distributing branches to the Glutei muscles, and inosculates with the external circumflex artery. Some branches pierce the Gluteus minimus to supply the hip-joint. The llio-lumbar Artery ascends beneath the Psoas muscle and external iliac vessels, to the upper part of the iliac fossa, where it divides into a lumbar and an iliac branch. The lumbar branch supplies the Psoas and Quadratus lumborum muscles, anas- tomosing with the last lumbar artery, and sends a small spinal branch through the intervertebral foramen, between the last lumbar vertebra and the sacrum, into the spinal canal, to supply the spinal cord and its membranes. The iliac branch descends to supply the Iliacus internus, some offsets running between the muscle and the bone, one of which enters an oblique canal to supply the diploe, whilst others run along the crest of the ilium, distributing branches to the Gluteal and abdominal muscles, and anastomosing in their course with the gluteal, circumflex iliac, external circumflex, and epigastric arteries. The Lateral Sacral Arteries are usually two in number on each side, superior and inferior. The superior, which is of large size, passes inwards, and, after anastomosing with branches from the middle sacral, enters the first or second sacral foramen, is dis- tributed to the contents of the sacral canal, and, escaping by the corresponding posterior sacral foramen, supplies the skin and muscles on the dorsum of the sacrum. The inferior branch passes obliquely across the front of the Pyriformis muscle and sacral nerves to the inner side of the anterior sacral foramina, descends on the front of the sacrum, and anastomoses over the coccyx with the sacra media and opposite lateral sacral arteries. In its course, it gives off branches, which enter the anterior sacral foramina ; these, after supplying the bones and membranes of the interior of the spinal canal, escape by the posterior sacral foramina, and are distributed to the muscles and skin on the dorsal surface of the sacrum. External Iliac Artery. The External Iliac Artery is the chief vessel which supplies the lower limb. It is larger in the adult than the internal iliac, and passes obliquely downwards and outwards along the inner border of the Psoas muscle, from the bifurcation of the common iliac to the femoral arch, where it enters the thigh, and becomes the EXTERNAL ILIAC. 43t femoral artery. The course of this vessel would be indicated by a line drawn from the left side of the umbilicus to a point midway between the anterior supe- rior spinous process of the ilium and the symphysis pubis. Relations. In front, with the peritoneum, sub-peritoneal areolar tissue, the intestines, and a thin layer of fascia, derived from the iliac fascia, which surrounds the artery and vein. At its origin it is occasionally crossed by the ureter. The spermatic vessels descend for some distance upon it near its termination, and it is crossed in this situation by a branch of the genito-crural nerve and the circumflex iliac vein ; the vas deferens curves down along its inner side. Behind, it is in rela- tion with the external iliac vein, which, at the femoral arch, lies at its inner side ; on the left side the vein is altogether internal to the artery. Externally, it rests against the Psoas muscle, from which it is separated by the iliac fascia. The artery rests upon this muscle near Poupart's ligament. Numerous lymphatic vessels and glands are found lying on the front and inner side of the vessel. Plan of the Eelations of the External Artery. In front. Peritoneum, intestines, and iliac fascia. Near f Spermatic vessels. Poupart's j Genito-crural nerve. Ligament, "j Circumflex iliac vein. I Lymphatic vessels and glands. Outer side. / \ Inner side. Psoas magnus. ( External j External iliac vein and vas deferens Iliac fascia. I Ihac - / at femoral arch. Behind. External iliac vein. Surgical Anatomy. The application of a ligature to the external iliac maybe required in cases of aneurism of the femoral artery, or in cases of secondary hemorrhage, after the latter vessel has been tied for popliteal aneurism. This vessel may be secured in any part of its course, excepting near its upper end, on account of the circulation through the internal iliac, and near its lower end, on account of the origin of the epigastric and circumflex iliac vessels. One of the chief points in the performance of the operation is to secure the vessel without injury to the peritoneum. The patient having been placed in the recumbent position, an incision should be made, commencing about an inch above and to the inner side of the anterior superior spinous process of the ilium, and running downwards and outwards to the outer end of Poupart's liga- ment, and parallel with its outer half, to a little above its middle. The abdominal muscles and transversalis fascia having been cautiously divided, the peritoneum should be separated from the iliac fossa and pushed towards the pelvis ; and on introducing the finger to the bottom of the wound the artery may be felt pulsating along the inner border of the Psoas muscle. The external iliac vein is situated along the inner side of the artery, and must be cautiously separated from it by the finger-nail, or handle of the knife, and the aneurism needle should be introduced on the inner side, between the artery and vein. Collateral Circulation. The principal anastomoses in carrying on the collateral circulation, after the application of a ligature to the external iliac, are, the ilio-lumbar with the circumflex iliac ; the gluteal with the external circumflex ; the obturator with the internal circumflex ; the sciatic with the profunda artery; the internal pudic with the external pudic, and with the internal circumflex. When the obturator arises from the epigastric, it is supplied with blood by branches, either from the internal iliac, the lateral sacral, or from the internal pudic. The epigastric receives its supply from the internal mammary and inferior intercostal arteries, and from the internal iliac, hy the anastomoses of its branches with the obturator. Branches. Besides several small branches to the Psoas muscle and the neigh- boring lymphatic glands, the external iliac gives off two branches of considerable size : — Epigastric. Circumflex iliac. The epigastric artery arises from the external iliac, a few lines above Poupart's ligament. It at first descends to reach this ligament, and then ascends obliquely upwards and inwards between the peritoneum and transversalis fascia, to the 438 ARTERIES. margin of the sheath of the Rectus muscle. Having perforated the sheath near its lower third, it ascends vertically upwards behind the Rectus, to which it is distributed, dividing into numerous branches, which anastomose above the umbi- licus with the terminal branches of the internal mammary and inferior intercostal arteries. It is accompanied by two veins, which usually unite into a single trunk before their termination in the external iliac vein. As this artery ascends from Poupart's ligament to the Rectus, it lies behind the inguinal canal, to the inner side of the internal abdominal ring, and immediately above the femoral ring, the vas deferens in the male and the round ligament in the female crossing behind the artery in descending into the pelvis. Branches. The branches of this vessel are the cremasteric, which accompanies the spermatic cord, and supplies the Cremaster muscle, anastomosing with the spermatic artery ; a pubic branch, which runs across Poupart's ligament, and then descends behind the pubes to the inner side of the femoral ring, and anastomoses •with offsets from the obturator artery; muscular branches, some of which are distributed to the abdominal muscles and peritoneum, anastomosing with the lumbar and circumflex iliac arteries ; others perforate the tendon of the External oblique and supply the integument, anastomosing with branches of the external epigastric. Peculiarities. The origin of the epigastric may take place from any part of the external iliac between Poupart's ligament and two inches and a half above it ; or it may arise below this ligament, from the femoral, or from the deep femoral. Union with Branches. It frequently arises from the external iliac by a common trunk with the obturator. Sometimes the epigastric arises from the obturator, the latter vessel being fur- nished by the internal iliac, or the epigastric may be formed of two branches, one derived from the external iliac, the other from the internal iliac. The circumflex iliac artery arises from the outer side of the external iliac, nearly opposite the epigastric artery. It ascends obliquely outwards behind Poupart's ligament, and runs along the inner surface of the crest of the ilium to about its middle, where it pierces the Transversalis and runs backwards between this muscle and the Internal oblique, to anastomose with the ilio-lumbar and gluteal arteries. Opposite the anterior superior spine of the ilium, it gives off a large branch, which ascends between the Internal oblique and Transversalis muscles, supplying them and anastomosing with the lumbar and epigastric arteries. The circumflex iliac artery is accompanied by two veins, which, uniting into a single trunk, cross the external iliac artery just above Poupart's ligament, and enter the external iliac vein. Femoral Artery. The Femoral Artery is the continuation of the external iliac. It commences immediately beneath Poupart's ligament, midway between the anterior superior spine of the ilium and the symphysis pubis, and, passing down the fore part and inner side of the thigh, terminates at the opening in the Adductor magnus, at the junction of the middle with the lower third of the thigh, where it becomes the popliteal artery. A line drawn from a point midway between the anterior supe- rior spine of the ilium and the symphysis pubis to the inner side of the inner condyle of the femur, will be nearly parallel with the course of the artery. This vessel, at the upper part of the thigh, lies a little internal to the head of the femur ; in the lower part of its course, on the inner side of the shaft of this bone ; and between these two points, the vessel is separated from the bone by a consi- derable interval. In the upper third of the thigh the femoral artery is very superficial, being covered by the integument, inguinal glands, and by the superficial and deep fasciae, and is contained in a triangular space, called " Scarpa's triangle." Scarpa's triangle corresponds to the depression seen immediately below the fold of the groin. It is a triangular space, the apex of which is directed downwards, and the sides of which are formed externally by the Sartorius, internally by the FEMORAL. 439 Adductor longus, and the base, by Poupart's ligament. The floor of this space is formed from without inwards by the Iliacus, Psoas, Pectineus, Adductor longus, and a small part of the Adductor brevis muscles; and it is divided into two nearly equal parts by the femoral vessels, which extend from the middle of its base to its apex ; the artery giving off in this Fig. 231. — Surgical Anatomy of the Femoral Artery, situation its cutaneous and profunda branches, the vein receiving the deep femoral and internal saphenous veins. In this space, the femoral artery rests on the inner margin of the Psoas muscle, which separates it from the capsular ligament of the hip-joint. The artery in this situation is crossed in front by the crural branch of the genito-crural nerve, and behind by the branch to the Pectineus from the anterior crural. The femoral vein lies at its inner side, between the margins of the Pectineus and Psoas muscles. The anterior crural - nerve lies about half an inch to the outer side of the femoral artery, deeply imbedded between the Iliacus and Psoas muscles; and on the Iliacus muscle, internal to the anterior superior spi- nous process of the ilium, is the external cutaneous nerve. The femoral artery and vein are inclosed in a strong fibrous sheath, form- ed by fibrous and cellular tissue, and by a process of fascia sent inwards from the fascia lata ; the vessels are separated, however, from one another by thin fibrous partitions. In the middle third of the thigh, the femoral artery is more deeply seated, being covered by the integument, the superficial and deep fascise, and the Sartorius, and is contained in an aponeurotic canal, formed by a dense fibrous band, which extends transversely from the Vastus internus to the tendons of the Adductor longus and Adductor magnus muscles. In this part of its course it lies in a depression, bounded externally by the Vastus internus, internally by the Adductor longus and Adductor magnus. The femoral vein lies Zettg Saphenous Kern* Ajiaetomcti en JUJucna Super. External Art-infa Jnfir. Eztrrnal Arlio Anter. Tibial —■AmultomoHrt*- XVxern Sup*'.J*C*r*alArU**lut .LUmnuil Artie f- 440 ARTERIES. on the outer side of the artery, in close apposition with it, and, still more ex. ternally, is the internal or long saphenous nerve. Relations. From above downwards, the femoral artery rests upon the Psoas muscle, which separates it from the margin of the pelvis and capsular ligament of the hip; it is next separated from the Pectineus by the profunda vessels and femoral vein ; it then lies upon the Adductor longus ; and lastly, upon the tendon of the Adductor magnus, the femoral vein being interposed. To its inner side, it is in relation, above, with the femoral vein, and, lower down, with the Ad- ductor longus and Sartorius. To its outer side, the Vastus internus separates it from the femur, in the lower part of its course. The femoral vein, at Poupart's ligament, lies close to the inner side of the artery, separated from it by a thin fibrous partition, but, as it descends, gets behind it, and then to its outer side. The internal saphenous nerve is situated on the outer side of the artery, in the middle third of the thigh, beneath the aponeurotic covering, but not within the sheath of the vessels. Small cutaneous nerves cross the front of the sheath. Peculiarities. Double femoral reunited. Four cases are at present recorded, in which the femoral artery divided into two trunks below the origin of the profunda, and became reunited near the opening in the Adductor magnus, so as to form a single popliteal artery. One of them occurred in a patient operated upon for popliteal aneurism. Change of Position. A similar number of cases have been recorded, in which the femoral artery was situated at the back of the thigh, the vessel being continuous above with the internal iliac, escaping from the pelvis through the great sacro-sciatic foramen, and accompanying the great sciatic nerve to the popliteal space, where its division occurred in the usual manner. Position of the Vein. The femoral vein is occasionally placed along the inner side of the artery, throughout the entire extent of Scarpa's triangle ; or it may be slit, so that a large vein is placed on each side of the artery for a greater or less extent. Origin of the Profunda. This vessel occasionally arises from the inner side, and more rarely, from the back of the common trunk ; but the more important peculiarity, in a surgical point of view, is that which relates to the height at which the vessel arises from the femoral. In three- foui'ths of a large number of cases, it arose between one and two inches below Poupart's liga- ment ; in a few cases, the distance was less than an inch ; more rarely, opposite the ligament ; and in one case, above Poupart's ligament, from the external iliac. Occasionally, the distance between the origin of the vessel and Poupart's ligament exceeds two inches, and in one case it was found to be as much as four inches. Surgical Anatomy. Compression of the femoral artery, which is constantly requisite in am- putations or other operations on the lower limb, is most effectually made immediately below Poupart's ligament. In this situation, the artery is very superficial, and is merely separated from the margin of the acetabulum and front of the head of the femur, by the Psoas muscle ; so that the surgeon, by means of his thumb, or any other resisting body may effectually control the circulation through it. This vessel may also be compressed in the middle third of the thigh, by placing a compress over the artery, beneath the tourniquet, and directing the pressure from within outwards, so as to compress the vessel on the inner side of the shaft of the femur. The application of a ligature to the femoral artery may be required in cases of wound or aneurism of the arteries of the leg, of the popliteal or femoral ; and the vessel may be exposed and tied in any part of its course. The great depth of this vessel in the lower part of its course, its close connection with important structures, and the density of its sheath, render the operation in this situation one of much greater difficulty than the application of a ligature at its upper part, where it is more superficial. Ligation of the femoral artery, within two inches of its origin, is usually considered very unsafe, on account of the connection of large branches with it, the epigastric and circumflex iliac arising just above its origin ; the profunda, from one to two inches below; occasionally, also, one of the circumflex arteries arises from the vessel in the interspace between these. The profunda some- times arises higher than the point above-mentioned, and rarely between two or three inches (in one case four) below Pouparfs ligament. It would appear, then, that the most favorable situa- tion for the application of a ligature to this vessel is between four and five inches from its point of origin. In order to expose the artery in this situation, an incision, between two and three inches long, should be made in the course of the vessel, the patient lying in the recumbent posi- tion, with the limb slightly flexed and abducted. A large vein is frequently met with, passing in the course of the artery to join the saphena ; this must be avoided, and the fascia lata having BRANCHES OF THE FEMORAL. 441 been cautiously divided, and the Sartorius exposed, this muscle must be drawn outwards, in order to fully expose the sheath of the vessels. The finger being introduced into the wound, and the pulsation of the artery felt, the sheath should be divided over it to a sufficient extent to allow of the introduction of the ligature, but no further; otherwise the nutrition of the coats of the vessel may be interfered with, or muscular branches which arise from the vessel at irregular intervals may be divided. In this part of the operation, a small nerve which crosses the sheath should be avoided. The aneurism needle must be carefully introduced and kept close to the artery, to avoid the femoral vein, which lies behind the vessel in this part of its course. To expose the artery in the middle of the thigh, an incision should be made through the integu- ment, between three and four inches in length, over the inner margin of the Sartorius, taking care to avoid the internal saphenous vein, the situation of which may be previously known by com- pressing it higher up in the thigh. The fascia lata having been divided, and the Sartorius muscle exposed, it should be drawn outwards, when the strong fascia which is stretched across from the Adductors to the Vastus internus, will be exposed, and must be freely divided ; the sheath of the vessels is now seen, and must be opened, and the artery secured by passing the aneurism needle between the vein and artery, in the direction from within outwards. The femoral vein in this situation lies on the outer side of the artery, the long saphenous nerve on its anterior and outer side. It has been seen that the femoral artery occasionally divides into two trunks, below the origin of the profunda. If, in the operation for tying the femoral, two vessels are met with, the surgeon should alternately compress each, in order to ascertain which vessel is connected with the aneu- rismal tumor, or with the bleeding from the wound, and that one only tied which controls it. If, however, it is necessary to compress both vessels before the circulation in the tumor is controlled, both should be tied, as it would be probable that they had become reunited, as is mentioned above. Collateral Circulation. The principal agents in carrying on the collateral circulation after ligature of the femoral artery are, according to .Sir A. Cooper, as follows :' — " The arteria profunda formed the new channel for the blood." " The first artery sent off passed down close to the back of the thigh bone, and entered the two superior articular branches of the popliteal artery." " The second new large vessel arising from the profunda at the same part with the former, passed down by the inner side of the Biceps muscle, to an artery of the popliteal which was dis- tributed to the Gastrocnemius muscle; whilst a third artery dividing into several branches passed down with the sciatic nerve behind the knee-joint, and some of its branches united themselves with the inferior articular arteries of the popliteal, with some recurrent branches of those arteries, with arteries passing to the Gastrocnemii, and, lastly, with the origin of the anterior and posterior tibial arteries." " It appears then that it is those branches of the profunda which accompany the sciatic nerve, that are the principal supporters of the new circulation." Branches. The branches of the femoral artery are the Superficial epigastric. Superficial circumflex iliac. Superficial external pudic. Deep external pudic. {External circumflex. Internal circumflex. Three perforating. Muscular. Anastomotica magna. The superficial epigastric arises from the femoral, about half an inch below Poupart's ligament, and, passing through the saphenous opening in the fascia lata, ascends on to the abdomen, in the superficial fascia covering the External oblique muscle, nearly as high as the umbilicus. It distributes branches to the inguinal glands, the superficial fascia and integument, anastomosing with branches of the deep epigastric and internal mammary arteries. The superficial circumflex iliac, the smallest of the cutaneous branches, arises close to the preceding, and, piercing the fascia lata, runs outwards, parallel with Poupart's ligament, as far as the crest of the ilium, dividing into branches which supply the integument of the groin, the superficial fascia, and inguinal glands- anastomosing with the circumflex iliac, and with the gluteal and external circum flex arteries. 1 Medico-Chirurgical Transactions, vol. ii. 1811. 442 ARTERIES. The superficial external pudic (superior) arises from the inner side of the femoral artery, close to the preceding vessels, and, after piercing the fascia lata at the saphenous opening, passes inwards, across the spermatic cord, to be distributed to the integument on the lower part of the abdomen, and of the penis and scrotum in the male, and to the labia in the female, anastomosing with branches of the internal pudic. The deep external pudic (inferior), more deeply seated than the preceding, passes inwards on the Pectineus muscle, covered by the fascia lata, which it pierces opposite the ramus of the pubes, its branches being distributed, in the male, to the integument of the scrotum and perinaeum, and in the female to the labium, anastomosing with branches of the superficial perineal artery. The Peofunda Femoris or Deep Femoral Artery nearly equals the size of the superficial femoral. It arises from the outer and back part of the femoral artery, from one to two inches below Poupart's ligament. It at first lies on the outer side of the superficial femoral, and then passes beneath it and the femoral vein to the inner side of the femur, and terminates at the lower third of the thigh in a small branch, which pierces the Adductor magnus, to be distributed to the Flexor muscles, on the back of the thigh, anastomosing with branches of the popliteal and inferior perforating arteries. Relations. Behind, it lies first upon the Iliacus, and then on the Adductor brevis and Adductor magnus muscles. In front, it is separated from the femoral artery, above, by the femoral and profunda veins, and below by the Adductor longus. On its outer side, the insertion of the Yastus internus separates it from the femur. Plan of the Relations of the Profunda Artery. In front. Femoral and profunda veins. Adductor longus. Outer side. Vastus internus. Behind. Iliacus. Adductor brevis. Adductor magnus. The External Circumflex Artery supplies the muscles on the front of the thigh. It arises from the outer side of the profunda, passes horizontally outwards, between the divisions of the anterior crural nerve, and beneath the Sartorius and Rectus muscles, and divides into three sets of branches, ascending, transverse, and descending. The ascending tranches pass upwards, beneath the Tensor vaginas femoris muscle, to the outer side of the hip, anastomosing with the terminal branches of the gluteal and circumflex iliac arteries. The descending branches, three or four in number, pass downwards, beneath the Rectus, upon the Vasti muscles, to which they are distributed, one or two passing beneath the Vastus externus as far as the knee, anastomosing with the superior articular branches of the popliteal artery. The transverse branches, the smallest and least numerous, pass outwards over the Crureus, pierce the Vastus externus, and wind round the femur to its back part, just below the great trochanter, anastomosing at the back of the thigh with the internal circumflex, sciatic, and superior perforating arteries. The Internal Circumflex Artery, smaller than the external, arises from the inner and back part of the profunda, and winds round the inner side of the femur, POPLITEAL SPACE. 443 between the Pectineus and Psoas muscles. On reaching the tendon of the Obtu- rator externus, it divides into two branches ; one, ascending, is distributed to the Adductor muscles, the Gracilis, and Obturator externus, anastomosing with the obturator artery, the other descending, which passes beneath the Adductor brevis, to supply it and the great Adductor ; the continuation of the vessel passing back- wards, between the Quadratus femoris and upper border of the Adductor magnus, anastomosing with the sciatic, external circumflex, and superior perforating arte- ries. Opposite the hip-joint, this branch gives off an articular vessel, which enters the joint beneath the transverse ligament ; and, after supplying the adipose tissue, passes along the round ligament to the head of the bone. The Perforating Arteries (fig. 230), usually three in number, are so called from their perforating the tendons of the Adductor brevis and Adductor magnus muscles to reach the back of the thigh. The first is given off above the A dductor brevis, the second in front of that muscle, and the third immediately below it. The first or superior perforating artery passes backwards between the Pectineus and Adductor brevis (sometimes perforates the latter) ; it then pierces the Adduc- tor magnus close to the linea aspera, and divides into branches which supply both Adductors, the Biceps, and Gluteus maximus muscle ; anastomosing with the sciatic, internal circumflex, and middle perforating arteries. The second or middle perforating artery, larger than the first, pierces the tendons of the Adductor brevis and Adductor magnus muscles, divides into ascending and descending branches, which supply the Flexor muscles of the thigh, anasto- mosing with the superior and inferior perforantes. The nutrient artery of the femur is usually given off from this branch. The third or inferior perforating artery is given off below the Adductor brevis ; it pierces the Adductor magnus, and divides into branches which supply the Flexor muscles of the thigh, anastomosing with the perforating arteries, above, and with the terminal branches of the profunda, below. Muscular Branches are given off from the superficial femoral throughout its entire course. They vary from two to seven in number, and supply chiefly the Sartorius and Vastus internus. The Anastomotica Magna arises from the femoral artery just before it passes through the tendinous opening in the Adductor magnus muscle, and divides into a superficial and deep branch. The superficial branch accompanies the long saphenous nerve, beneath the Sartorius, and, piercing the fascia lata, is distributed to the integument. The deep branch descends in the substance of the Vastus internus, lying in front of the tendon of the Adductor magnus, to the inner side of the knee, where it anastomoses with the superior internal articular artery and recurrent branch of the anterior tibial. A branch from this vessel crosses outwards above the articular surface of the femur, forming an anastomotic arch with the superior external arti- cular artery, and supplies branches to the knee-joint. The Popliteal Space. Dissection. A vertical incision about eight inches in length should be made along the back part of the knee-joint, connected above and below by a transverse incision passing from the inner to the outer side of the limb. The flaps of integument included between these incisions should be reflected in the direction shown in tig. 189. On removing the integument, the superficial fascia is exposed, and ramifying in it along the middle line are found some filaments of the small sciatic nerve, and, towards the inner part, some offsets from the internal cutaneous nerve. The superficial fascia having been removed, the fascia lata is brought into view. In this region it is strong and dense, being strengthened by transverse fibres, and firmly attached to the tendons on the inner and outer sides of the space. It is perforated below by the external saphenous vein. This fascia having been reflected back in the same direction as the integument, the small sciatic nerve and external 444 ARTERIES. saphenous vein are seen immediately beneath it, in the middle line. If the loose adipose tissue is now removed, the boundaries and contents of the space may be examined. Boundaries. The popliteal space, or the ham, occupies the lower third of the thigh and the upper fifth of the leg ; extending from the aperture in the Adductor magnus to the lower border of the Popliteus muscle. It is a lozenge-shaped space, being widest at the back part of the knee-joint, and deepest above the arti- cular end of the femur. It is bounded, externally, above the joint, by the Biceps, and below the articulation, by the Plantaris and external head of the Gastroc- nemius ; internally, above the joint, by the Semi-membranosus, Semi-ten- dinosus, Gracilis, and Sartorius; below the joint, by the inner head of the Gastrocnemius. Above, it is limited by the apposition of the inner and outer hamstring muscles: below by the junction of the two heads of the Gastrocnemius. The floor is formed by the lower part of the posterior surface of the shaft of the femur, the posterior ligament of the knee-joint, the upper end of the tibia, and the fascia covering the Popliteus muscle, and the space is covered in by the fascia lata. Contents. It contains the popliteal vessels and their branches, together with the termination of the external saphenous vein, the internal and external popliteal nerves and their branches, the small sciatic nerve, the articular branch from the obturator nerve, a few small lymphatic glands, and a considerable quantity of loose adipose tissue. Position of contained parts. The internal popliteal nerve descends in the middle line of the space, lying superficial, and a little external to the vein and artery. The external popliteal nerve descends on the outer side of the space, lying close to the tendon of the Biceps muscle. More deeply at the bottom of the space are the popliteal vessels, the vein lying superficial and a little external to the artery, to which it is closely united by dense areolar tissue ; sometimes the vein is placed on the inner instead of the outer side of the artery ; or the vein may be double, the artery then lying between them, the two veins being usually connected by short transverse branches. More deeply, and close to the surface of the bone, is the popliteal artery, and passing off from it at right angles are its articular branches. The articular branch from the obturator nerve descends upon the popliteal artery to supply the knee ; and occasionally there is found deep in the space an articular filament from the great sciatic nerve. The popliteal lymphatic glands, four or five in number, are found surrounaing the artery ; one usually lies superficial to the vessel, another is situated between it and the bone, and the rest are placed on either side of it. In health, these glands are small ; but when enlarged and indu- rated from inflammation, the pulsation communicated to them from the popliteal artery makes them resemble so closely an aneurismal tumor, that it requires a very careful examination to discriminate between them. Popliteal Artery. The Popliteal Artery commences at the termination of the femoral, at the opening in the Adductor magnus, and, passing obliquely downwards and outwards behind the knee-joint to the lower border of the Popliteus muscle, divides into the anterior and posterior tibial arteries. Through this extent the artery lies in the popliteal space. In its course downwards from the aperture in the Adductor magnus to the lower border of the Popliteus muscle, the Popliteal artery (fig. 232) rests first on the inner, and then on the posterior surface of the femur ; in the middle of its course, on the posterior ligament of the knee-joint ; and below, on the fascia covering the Popliteus muscle. Superficially, it is covered, above, by the Semi-membra- nosus ; in the middle of its course, by a quantity of fat, which separates it from the deep fascia and integument ; and below, it is overlapped by the Gastrocnemius, Plantaris and Soleus muscles, the popliteal vein, and the internal popliteal nerve. POPLITEAL. 445 The popliteal vein,, which is intimately attached to the artery, lies superficial and external to it, until near its termination, when it crosses it and lies to its inner side. The popliteal nerve is still more superficial and external, crossing, however,' the artery below the joint, and lying on its inner side. Laterally, it is bounded by the muscles which form the boundaries of the popliteal space. /' culiarttiea in point of division. Occasionally the popliteal artery divides prematurely into its terminal branches ; this division occurs most frequently opposite the knee-joint. Unusual branches. This artery sometimes divides into the anterior tibia2 and peroneal, the posterior tibial being wanting, or very small. In a single case, this artery divided into three branches, the anterior and posterior tibial, and peroneal. Surgical Anatomy. Ligation of the popliteal artery is required in cases of wound of that vessel, but for aneurism of the posterior tibial it is preferable to tie the superficial femoral. The popliteal may be tied in the upper or lower part of its course ; but in the middle of the space the operation is attended with considerable difficulty, from the great depth of the artery, and from the extreme degree of tension of its lateral boundaries. In order to expose the vessel in the upper part of its course, the patient should be placed in the prone position, with the limb extended. An incision about three inches in length should then be made through the integument, along the posterior. margin of the Semi-membranosus, and, the fascia lata having been divided, this muscle must be drawn inwards, when the pulsation of the Vessel will be detected with the finger; the nerve lies on the outer or fibular side of the artery, the vein, superficial and also to its outer side ; having cautiously separated it from the artery, the aneurism needle should be passed around the latter vessel from without inwards. To expose the vessel in the lower part of its course, where the artery lies between the two heads of the Gastrocnemius, the patient should be placed in the same position as in the preceding operation. An incision should then be made through the integument in the middle line, com- mencing opposite the bend of the knee-joint, care being taken to avoid the external saphenous vein and nerve. After dividing the deep fascia and separating some dense cellular membrane, the artery, vein, and nerve will be exposed, descending between the two heads of the Gastrocnemius. Some muscular branches of the popliteal should, if possible, be avoided, or, if divided, tied immedi- ately. The leg being now flexed, in order the more effectually to separate the two heads of the Gastrocnemius, the nerve should be drawn inwards and the vein outwards. &ad the aneurism needle passed between the artery and vein from without inwards. The branches of the popliteal artery are the Muscular \ T JP . ' , ( Interior or Sural. Cutaneous. Superior external articular. Superior internal articular. Azygos articular. Inferior external articular. Inferior internal articular. The superior muscular branches, two or three in number, arise from the upper part of the popliteal artery, and are distributed to the Vastus externus and Flexor muscles of the thigh; anastomosing with the inferior perforating, and terminal branches of the profunda. The inferior muscular or sural are two large branches, which are distributed to the two heads of the Gastrocnemius and Plantaris muscles. They arise from the popliteal artery opposite the knee-joint. Cutaneous branches descend on each side and in the middle of the limb, between the Gastrocnemius and integument ; they arise separately from the popliteal artery, or from some of its branches, and supply the integument of the calf. The superior articular arteries, two in number, arise one on either side of the popliteal, and wind round the femur immediately above its condyles to the front of the knee-joint. The internal branch passes beneath the tendon of the Adductor magnus, and divides into two, one of which supplies the Vastus internus, inosculating with the aua.stomotica magna and inferior internal articular ; the other ramifies close to the 446 ARTERIES. 232.— The Popliteal, Posterior Tibial, and Peroneal Arteries. *'•■ surface of the femur, supplying it and the knee-joint, and anastomosing with the superior external articular artery. The external branch passes above the outer condyle, beneath the tendon of the Biceps, and divides into a superficial and Fig. 232.— The Popliteal, Posterior Tibial, deep branch : the superficial branch sup- plies the Vastus externus, and anastomoses with the descending branch of the exter- nal circumflex artery ; the deep branch supplies the lower part of the femur and knee-joint, and forms an anastomotic arch across the bone with the anastomotica magna artery. The azygos articular is a small branch, arising from the popliteal artery opposite the bend of the knee-joint. It pierces the posterior ligament, and supplies the ligaments and synovial membrane in the interior of the articulation. The inferior articular arteries, two in number, arise from the popliteal, beneath the Gastrocnemius, and wind round the head of the tibia, below the joint. The internal one passes below the inner tuberosity, beneath the internal lateral ligament, at the anterior border of which it ascends to the front and inner side of the joint, to supply the head of the tibia and the articulation of the knee. The external one passes outwards above the head of the fibula, to the front of the knee-joint, lying in its course beneath the outer head of the Gastrocnemius, the external lateral ligament, and the tendon of the Biceps muscle, and divides into tfM J^Lhicus I branches, which anastomose with the \{:'J artery of the opposite side, the superior articular, and the recurrent branch of the anterior tibial. Anterior Tibial Arteey. The Anterior Tibial Artery commences -Anterior Peroneal at the bifurcation of the popliteal, at the lower border of the Popliteus muscle, passes forwards between the two heads of the Tibialis posticus, and through the aperture left between the bones at the upper part of the interosseous membrane, to the deep part of the front of the leg; it then descends on the anterior surface of the interosseous ligament, and of the tibia, to the front of the ankle-joint, where it lies more superficially, and becomes the dorsalis pedis. A line drawn from the inner side of the head of the fibula to midway between the two malleoli, will be parallel with the course of the artery. ANTERIOR TIBIAL. 447 Relations. In the upper tworthirds of its extent, it rests upon the interosseous ligament, to which it is connected by delicate fibrous arches thrown across it. In the lower third, upon the front of the tibia, and the anterior ligament of the ankle-joint. In the upper third of its course, it lies between the Tibialis anticus and Extensor longus digitorum; in the middle third, between the Tibialis anticus and Extensor proprius pollicis. In the lower third, it is crossed by the tendon of the Extensor proprius pollicis, and lies between it and the innermost tendon of the Extensor longus digitorum. It is covered, in the upper two-thirds of its course, by the muscles which lie on either side of it, and by the deep fascia ; in the lower third, by the integument, annular ligament, and fascia. The anterior -tibial artery is accompanied by two veins (venae comites), which lie one on either side of the artery ; the anterior tibial nerve lies at first to its outer side, and about the middle of the leg is placed superficial to it ; at the lower part of the artery, the nerve is on the outer side. Plan of the Kelations of the Anterior Tibial Artery. In front. Integument, superficial and deep fasciae. Tibialis anticus. Extensor longus digitorum. Extensor proprius pollicis. Anterior tibial nerve. Inner side. • f \ Outer side. Tibialis anticus. / . \ Anterior tibial nerve. Extensor proprius pollicis. ( Vibiai° r ) Extensor longus digitorum. Extensor proprius pollicis. Behind. Interosseous membrane. Tibia. Anterior ligament of ankle-joint. Peculiarities in Size. This vessel may be diminished in size, or it may be deficient to a greater or less extent, or it may be entirely wanting, its place being supplied by perforating branches from the posterior tibial, or by the anterior division of the peroneal artery. Course. This artery occasionally deviates in its course towards the fibular side of the leg, regaining its usual position beneath the annular ligament at the front of the ankle. In two instances, this vessel has approached the surface in the middle of the leg, from this point onwards being covered merely by the integument and fascia. Surgical Anatomy. The anterior tibial artery may be tied in the upper or lower part of the leg. In the upper part, the operation is attended with great difficulty, on account of the depth of the vessel from the surface. An incision, about four inches in length, should be made through the integument, midway between the spine of the tibia and the outer margin of the fibula, the fascia and intermuscular septum between the Tibialis anticus and Extensor communis digitorum being divided to the same extent. The foot must be flexed to relax these muscles, which must be separated from each other by the finger. The artery is then exposed, deeply seated, lying upon the interosseous membrane, the nerve lying externally, and one of the venae comites on either side ; these must be separated from the artery before the aneurism needle is passed round it. . To tie this vessel in the lower third of the leg above the ankle-joint, an incision about three inches in length should be made through the integument between the tendons of the Tibialis anticus and Extensor proprius pollicis muscles, the deep fascia being divided to the same extent; the tendon on either side should be held aside, when the vessel will be seen lying upon the tibia, with the nerve superficial to it, and one of the venae comites on either side. In order to secure this vessel over the instep, an incision should be made on the fibular side of the tendon of the Extensor proprius pollicis, between it and the innermost tendon of the long Extensor ; the deep fascia having been divided, the artery will be exposed, the nerve lying either superficial to it, or to its outer side. 448* ARTERIES. The branches of the anterior tibial Fit 233. — Snrgical Anatomy of the Anterior Tibial and Dorsalis Pedis Arteries. CnurauicaZl xrtery are the Recurrent tibial. Muscular. Internal malleolar. External malleolar. The recurrent branch arises from the anterior tibial, as soon as that vessel has passed through the interosseous space ; it ascends in the Tibialis anticus muscle, and ramifies on the front and sides of the knee-joint, anastomosing with the articular branches of the popliteal. The 'muscular branches are numerous ; they are distributed to the muscles which lie on either side of the vessel, some piercing the deep fascia to supply the integument, others passing through the interosseous membrane, and anastomosing with branches of the posterior tibial and peroneal arteries. The malleolar arteries supply the ankle- joint. The internal arises about two inches above the articulation, passes beneath the tendon of the Tibialis anticus to the inner ankle, upon which it ramifies, anastomos- ing with branches of the posterior tibial and internal plantar arteries. The external passes beneath the ten- dons of the Extensor longus digitorum and Extensor proprius pollicis, and sup- plies the outer ankle, anastomosing with the anterior peroneal artery, and with ascending branches from the tarsea branch of the dorsalis pedis. Doesalis Pedis Artery. The Dorsalis Pedis, the continuation of the anterior tibial, passes forwards from the bend of the ankle along the tibial side of the foot to the back part of the first interosseous space, where it divides into two branches, the dorsalis hallucis and communicating. Relations. This vessel, in its course for- wards, rests upon the astragalus, scaphoid, and internal cuneiform bones, and the ligaments connecting them, being covered by the integument and fascia, and crossed near its termination by the innermost tendon of the Extensor brevis digitorum. On its tibial side is the tendon of the Extensor proprius pollicis ; on its fibular side, the innermost tendon of the Extensor longus digitorum. It is accompanied by two veins, and by the anterior tibial nerve, which lies on its outer side. DORSALIS PEDIS. 449 Plan of the Kelations of the Dorsalis Pedis Artery. In front. Integument and fascia. Innermost tendon of Extensor brevis digitorum. Tibial side. / \ Fibular side. Extensor proprius pollicis. ( 1klLIMa31a \ Extensor longus digitorum Anterior tibial nerve. Behind. Astragalus. Scaphoid. Internal cuneiform. Their ligaments. Peculiarities in Size. The dorsal artery of the foot may be larger than usual, to compensate for a deficient plantar artery; or it may be deficient in its terminal branches to the toes, which are then derived from the internal plantar ; or its place may be supplied altogether by a large anterior peroneal artery. Position. This artery frequently curves outwards, lying external to the line between the middle of the ankle and the back part of the first interosseous space. Surgical Anatomy. This artery may be tied, by making an incision through the integument, between two and three inches in length, on the fibular side of the tendon of the Extensor pro- prius pollicis, in the interval between it and the inner border of the short Extensor muscle. The incision should not extend further forwards than the back part of the first interosseous space, as the artery divides in this situation. The deep fascia being divided to the same extent, the artery will be exposed, the nerve lying upon its outer side. Branches. The branches of the dorsalis pedis are the Tarsea. . Interossese. Metatarsea. Dorsalis hallucis. Communicating. The tarsea artery arises from the dorsalis pedis, as that vessel crosses the sca- phoid bone ; it passes in an arched direction outwards, lying upon the tarsal bones, and covered by the Extensor brevis digitorum ; it supplies that muscle and the articulations of the tarsus, and anastomoses with branches from the metatarsea, external malleolar, peroneal, and external plantar arteries. The metatarsea arises a little anterior to the preceding ; it passes outwards to the outer part of the foot, over the bases of the metatarsal bones, beneath the tendons of the short Extensor, its direction being influenced by its point of origin ; and it anastomoses with the tarsea and external plantar arteries. This vessel gives off three branches, the interossese, which pass forwards upon the three outer Dorsal interossei muscles, and, in the clefts between the toes, divide into two dorsal collateral branches for the adjoining toes. At the back part of each interosseous space these vessels receive the posterior perforating branches from the plantar arch ; and at the fore part of each interosseous space, they are joined by the anterior perforating branches from the digital arteries. The outer- most interosseous artery gives off a branch which supplies the outer side of the little toe. The dorsalis halhicis runs forwards along the outer border of the first meta- tarsal bone, and, at the cleft between the first and second toes, divides into two branches, one of which passes inwards, beneath the tendon of the Flexor longus pollicis, and is distributed to the inner border of the great toe ; the other branch bifurcating to supply the adjoining sides of the great and second toes. The communicating artery dips down into the sole of the foot, between the two heads of the first Dorsal interosseous muscle, and inosculates with the termination 29 450 ARTERIES. of the external plantar artery, to complete the plantar arch. It here gives off two digital branches ; one runs along the inner side of the great toe, on its plantar surface, the other passes forwards along the first metatarsal space, and bifurcates for the supply of the adjacent sides of the great and second toes. Posterior Tibial Artery. The Posterior Tibial is an artery of large size, which extends obliquely down- wards from the lower border of the Popliteus muscle, along the tibial side of the leg, to the fossa between the inner ankle and the heel, where it divides beneath the origin of the Abductor pollicis, into the internal and external plantar arteries. At its origin it lies opposite the interval between the tibia and fibula; as it descends, it approaches the inner side of the leg, lying behind the tibia, and, in the lower part of its course, is situated midway between the inner malleolus and the tuberosity of the os calcis. Relations. It lies successively upon the Tibialis posticus, the Flexor longus digitorum, and, below, upon the tibia and back part of the ankle-joint. It is covered by the intermuscular fascia, which separates it above from the Gastroc- nemius and Soleus muscles. In the lower third, where it is more superficial, it is covered only by the integument and fascia, and runs parallel with the inner border of the tendo Achillis. It is accompanied by two veins, and by the posterior tibial nerve, which lies at first to the inner side of the artery, but soon crosses it, and is. in the greater part of its course, on its outer side. Plan" of the Relations of the Posterior Tibial Artery. In front. Tibialis posticus. Flexor longus digiterum. Tibia. Ankle-joint. Inner side. f \ Outer side. Posterior tibial nerve, / Posterior \ Posterior tibial nerve, upper third. I Tibial. I lower two-thirds. Behind. Gastrocnemius. Soleus. Deep fascia and integument. Behind the Inner Ankle, the tendons and bloodvessels are arranged in the following order, from within outwards : First, the tendons of the Tibialis posticus and Flexor longus digitorum, lying in the same groove, behind the inner mal- leolus, the former being the most internal. External to these is the posterior tibial artery, having a vein on either side ; and, still more externally, the posterior tibial nerve. About half an inch nearer the heel is the tendon of the Flexor longus pollicis. Peculiarities in Size. The posterior tibial is not unfrequently smaller than usual, or absent, its place being compensated for by a large peroneal artery, which passes inwards at the lower end of the tibia, and either joins the small tibial artery, or continues alone to the sole of the foot. Surgical Anatomy. The application of a ligature to the posterior tibial may be required in cases of wound of the sole of the foot, attended with great hemorrhage, when the vessel should be tied at the inner ankle. In cases of wound of the posterior tibial, it will be necessary to enlarge the opening so as to expose the vessel at the wounded point (excepting where the vessel is injured by a punctured wound from the front of the leg). In cases of aneurism from injury of the artery PERONEAL. 451 low down, the vessel should be tied in the middle of the leg. But in aneurism of the posterior tibial high up, it would be better to tie the femoral artery. To tie the posterior tibial artery at the ankle, a semilunar incision should be made through the integument, about two inches and a half in length, midway between the heel and inner ankle, but a little nearer the latter. The subcutaneous cellular membrane having been divided, a strong and dense fascia, the internal annular ligament, is exposed. This ligament is continuous above with the deep fascia of the leg, covers the vessels and nerves, and is intimately adherent to the sheaths of the tendons. This having been cautiously divided upon a director, the sheath of the vessels is exposed, and, being opened, the artery is seen with one of the venae comites on each side. The aneurism needle should be passed round the vessel from the heel towards the ankle, in order to avoid the posterior tibial nerve, care being at the same time taken not to include the venae comites. The vessel may also be tied in the lower third of the leg, by making an incision about three inches in length, parallel with the inner margin of the tendo Achillis. The internal saphenous vein being carefully avoided, the two layers of fascia must be divided upon a director, when the artery is exposed along the inner margin of the Flexor longus digitorum, with one of its venae comites on either side, and the nerve lying external to it. To tie the posterior tibial in the middle of the leg, is a very difficult operation, on account of the great depth of the vessel from the surface, and from its being covered in by the Gastrocne- mius a"d Soleus muscles. The patient being placed in the recumbent position, the injured limb should rest on its outer side, the knee being partially bent, and the foot extended, so as to relax the muscles of the calf. An incision about four inches in length should then be made through the integument, along the inner margin of the tibia; taking care to avoid the internal saphenous vein. The deep fascia having been divided, the margin of the Gastrocnemius is exposed, and must be drawn aside, and the tibial attachment of the Soleus divided, a director being previously passed beneath it. The artery may now be felt pulsating beneath the deep fascia, about an inch from the margin of the tibia. The fascia having been divided, and the limb placed in such a position as to relax the muscles of the calf as much as possible, the veins should be separated from the artery, and the aneurism needle passed round the vessel from without inwards, so as to avoid wounding the posterior tibial nerve. The branches of the posterior tibial artery are the Peroneal. Nutritious. Muscular. Communicating. Internal calcanean. The Peroneal Artery lies, deeply seated, along the back part of the fibular side of the leg. It arises from the posterior tibial, about an inch below the lower border of the Popliteus muscle, passes obliquely outwards to the fibula, and then descends along the inner border of this bone to the lower third of the leg, where it gives off the anterior peroneal. It then passes across the articulation, between the tibia and fibula, to the outer side of the os calcis, supplying the neighboring muscles and back of the ankle, and anastomosing with the external malleolar, tarsal, and external plantar arteries. Relations. This vessel rests at first upon the Tibialis posticus, and, in the greater part of its course, in the fibres of the Flexor longus pollicis, in a groove between the interosseous ligament and the bone. It is covered, in the upper part of its course, by the Soleus and deep fascia : below, by the Flexor longus pollicis. Plan of the Relations of the Peroneal Artery. In front. Tibialis posticus. Flexor longus pollicis. Outer side. Fibula. Behind. Soleus. Deep fascia. Flexor longus pollicis. 452 ARTERIES. Peculiarities in Origin. The Peroneal artery may arise three inches below the Popliteus, or from the posterior tibial high up, or even from the popliteal. Its Size is more frequently increased than diminished, either reinforcing the posterior tibial by its junction with it, or by altogether taking the place of the posterior tibial, in the lower part of the leg and foot, the latter vessel only existing as a short muscular branch. In those rare cases, where the peroneal artery is smaller than usual, a branch from the posterior tibial supplies its place, and a branch from the anterior tibial compensates for the diminished anterior peroneal artery. In one case, the peroneal artery has been found entirely wanting. The anterior peroneal is sometimes enlarged, and takes the place of the dorsal artery of the foot. The peroneal artery, in its course, gives off branches to the Soleus, Tibialis posticus, Flexor longus pollicis, and Peronei muscles, and a nutrient branch to the fibula. The anterior peroneal pierces the interosseous membrane, about two inches above the outer malleolus, to reach the fore part of the leg, and, passing down beneath the Peroneus tertius to the outer ankle, ramifies on the front and outer side of the tarsus, anastomosing with the external malleolar and tarsal arteries. The nutritious artery of the tibia arises from the posterior tibial near its origin, and, after supplying a few muscular branches, enters the nutritious canal of that bone, which it traverses obliquely from above downwards. This is the largest nutrient artery of bone in the body. The muscular branches are distributed to the Soleus and deep muscles along the back of the leg. The communicating branch to the peroneal runs transversely across the back of the tibia, about two inches above its lower end, passing beneath the Flexor longus pollicis. The internal calcanean consists of several large branches, which arise from the posterior tibial just before its division ; they are distributed to the fat and integument behind the tendo Achillis and about the heel, and to the muscles on the inner side of the sole, anastomosing with the peroneal and internal malleolar arteries. Plantae Aeteeies. The Internal Plantar Artery, much smaller than the external, passes forwards along the inner side of the foot. It is at first situated above the Abductor pollicis, and then between it and the Flexor brevis digitorum, both of which it supplies. At the base of the first metatarsal bone, where it has become much diminished in size, it passes along the inner border of the great toe, inosculating with its digital branches. The External Plantar Artery, much larger than the internal, passes obliquely outwards and forwards to the base of the fifth metatarsal bone. It then turns obliquely inwards to the interval between the bases of the first and second meta- tarsal bones, where it inosculates with the communicating branch from the dorsalis pedis artery, thus completing the plantar arch. As this artery passes outwards it is at first placed between the os calcis and Abductor pollicis, and then between the Flexor brevis digitorum and Flexor accessorius ; and as it passes forwards to the base of the little toe, it lies more superficially between the Flexor brevis digitorum and Abductor minimi digiti, covered by the deep fascia and integument. The remaining portion of the vessel is deeply situated : it extends from the base of the metatarsal bone of the little toe to the back part of the first interosseous space, and forms the plantar arch ; it is convex forwards, lies upon the Interossei muscles, opposite the tarsal ends of the metatarsal bones, and is covered by the Adductor pollicis, the Flexor tendons of the toes, and the Lumbricales. Branches. The plantar arch, besides distributing numerous branches to the muscles, integument, and fascia3 in the sole, gives off the following branches : — Posterior perforating. Digital — Anterior perforating. The Posterior Perforating are three small branches, which ascend through the back part of the three outer interosseous spaces, between the heads of the Dorsal PLANTAR— PULMONARY. 453 interossei muscles, and anastomose with the interosseous branches from the meta- tarsal artery. The Digital Branches are four in number, and supply the three outer toes and half the second toe. The first passes outwards from the outer side of the plantar arch, and is distributed to the outer side of the little toe, passing in its course beneath the Abductor and short Flexor muscles. The second, third, and fourth run for- wards along the metatarsal spaces, and, on arriving at the clefts between the toes, divide into collateral branches, which supply the adjacent sides of the three outer toes and the outer side of the second. At the bifurcation of the toes, each digital artery sends upwards, through the fore part of the corresponding metatarsal space, a small branch, which inosculates with the interosseous branches of the metatarsal artery. These are the anterior perforating branches. Fig. 234.— The Plantar Arteries. Superficial View. Fig. 235.— The Plantar Arteries. Deep View. Cemmanicattnj Branch of QOASAli* PUIS From the arrangement ' already described of the distribution of the vessels to the toes, it will be seen that both sides of the three outer toes, and the outer side of the second toe, are supplied by branches from the plantar arch ; both sides of the great toe, and the inner side of the second, being supplied by the dorsal artery of the foot. Pulmonary Artery. The Pulmonary Artery conveys the venous blood from the right side of the heart to the lungs. It is a short wide vessel, about two inches in length, arising from the left side of the base of the right ventricle, in front of the ascending aorta. It ascends obliquely upwards, backwards, and to the left side, as far as the under surface of the arch of the aorta, where it divides into two branches of nearly equal size, the right and left pulmonary arteries. Relations. The greater part of this vessel is contained, together with the ascending part of the arch of the aorta, in the pericardium, being inclosed with it in a tube of serous membrane, continued upwards from the base of the heart, 454 ARTERIES. and has attached to it, above, the fibrous layer of this membrane. Behind, it rests at first upon the ascending aorta, and higher up in front of the left auricle. On either side of its origin are the appendix of the corresponding auricle, and a coronary artery ; and higher up it passes to the left side of the ascending aorta. A little to the left of its point of bifurcation, it is connected to the under surface of the arch of the aorta by a short fibrous cord, the remains of a vessel peculiar to foetal life, the ductus arteriosus. The right pulmonary artery, longer and larger than the left, runs horizontally outwards, behind the ascending aorta and superior vena cava, to the root of the right lung, where it divides into two branches, of which the lower, the larger, supplies the lower lobe ; the upper giving a branch to the middle lobe. The left pulmonary artery, shorter and somewhat smaller than the right, passes horizontally in front of the descending aorta and left bronchus to the root of the left lung, where it divides into two branches for the two lobes. The author has to acknowledge valuable aid derived from the following works : Harrison's " Sur- gical Anatomy of the Arteries of the Human Body," Dublin, 1824. — Richard Quain's ''Ana- tomy of the Arteries of the Human Body," London, 1844. — Sibson's " Medical Anatomy," and the other works on General and Microscopic Anatomy before referred to. Of the Veins. The Veins are the vessels which serve to return the blood from the capillaries of the different parts of the body to the heart. They consist of two distinct sets of vessels, the pulmonary and systemic. The Pulmonary Veins, unlike other vessels of this kind, contain arterial blood, which they return from the lungs to the left auricle of the heart. The Systemic Veins return the venous blood from the body generally to the right auricle of the heart. The Portal Vein, an appendage to the systemic venous system, is confined to the abdominal cavity, returning the venous blood from the viscera of digestion, and carrying it to the liver by a single trunk of large size, the vena portae. From this organ, the same blood is conveyed to the inferior vena cava by means of the hepatic veins. The veins, like the arteries, are found in nearly every tissue of the body ; they commence by minute plexuses, which communicate with the capillaries, the branches from which, uniting together, constitute trunks, which increase in size as they pass towards the heart, from the termination of larger branches in them. The veins are larger and altogether more numerous than the arteries ; hence, the entire capacity of the venous system is much greater than the arterial, the pul- monary veins excepted, which do not exceed in capacity the pulmonary arteries. From the combined area of the smaller venous branches being greater than the main trunks, it results, that the venous system represents a cone, the summit of which corresponds to the heart ; its base, to the circumference of the body. In form, the veins are not perfectly cylindrical, like the arteries, their walls being collapsed when empty, and the uniformity of their surface being interrupted at intervals by slight contractions, which indicate the existence of valves in their interior. They usually retain, however, the same calibre as long as they receive no neighboring branches. The veins communicate very freely with one another, especially in certain regions of the body ; and this communication exists between the larger trunks as well as between the smaller branches. Thus in the cavity of the cranium, and between the veins of the neck, where obstruction of the cerebral venous system would be attended with imminent danger, we find that the sinuses and larger veins have large and very frequent anastomoses. The same free communication exists between the veins throughout the whole extent of the spinal canal, and between the veins composing the various venous plexuses in the abdomen and pelvis, as the spermatic, uterine, vesical, prostatic, etc. The veins are subdivided into three sets ; superficial, deep, and sinuses. The Superficial or Cutaneous Veins are found between the layers of superficial fascia, immediately beneath the integument; they return the blood from these structures, and communicate with the deep veins by perforating the deep fascia. The Deep Vein's accompany the arteries, and are usually inclosed in the same sheath with those vessels. In the smaller arteries, as the radial, ulnar, brachial, tibial, peroneal, they exist generally in pairs, one lying on each side of the vessel, and are called vense comites. The larger arteries, as the axillary, subclavian, popliteal and femoral, have usually only one accompanying vein. In certain organs of the body, however, the deep veins do not accompany the arteries ; for instance, the veins in the skull and spinal canal, the hepatic veins in the liver, and the larger veins returning blood from the osseous tissue. Sinuses are venous channels, which, in their structure and mode of distribution, differ altogether from the veins. They exist, for example, in the interior of the skull, and are formed by a subdivision of the layers of the dura mater ; their outer coat 455 456 VEINS. consisting of fibrous tissue, their inner of a serous membrane continuous with the serous membrane of the veins. Veins have thinner walls than the arteries, which is due to the small amount of elastic and muscular tissues which they contain. The superficial veins usually have thicker coats than the deep veins, and the veins of the lower limbs are thicker than those of the upper. Veins are composed of three coats ; internal, middle, and external. The internal coat is similar in structure to that of the arteries. In the smallest veins, it consists of epithelium and nucleated connective tissue, arranged so as to form an outer and an inner layer ; the latter, which is the thinnest, representing the middle coat. As these vessels approach the capillaries, the epithelium and outer layer of connective tissue become gradually lost. On the contrary, in those of rather larger size, there is superadded a layer of muscular fibre-cells, a circu- lar fibrous coat, with areolar elastic tissue beneath the epithelium, and in the muscular and external coats. In medium-sized veins, the internal coat consists of epithelium supported on one or more striped nucleated lamellae, external to which is a layer of elastic fibrous tissue. In the veins of the gravid uterus, and in the long saphenous and popliteal veins, muscular tissue is one of the component parts of the inner coat. In the largest veins, as the inferior vena cava, the trunks of the hepatic, and in the innominate veins, the internal coat has a structure similar to that already mentioned ; but is somewhat thicker, owing to the increase in the number of the striped lamellae, and the greater thickness of the elastic fibrous coat. The middle coat is thin, and differs in structure from the middle coat of arteries in containing a smaller amount of elastic and muscular tissues, and more con- nective tissue. In the smallest veins, as already mentioned, it consists merely of a thin layer of nucleated connective tissue, the fibres of which run in a longitu- dinal direction ; to which is added, in those of rather larger size, a layer of mus- cular tissue, the cells of which are disposed transversely. In medium-sized veins, such as the cutaneous and deep veins of the limbs, as far as the brachial and pop- liteal, and the visceral veins, the middle coat is of a reddish-yellow color, remark- able for its great thickness, being more developed than the same coat in the large veins. It consists of a thick inner layer of connective tissue with elastic fibres, having intermixed in some veins a transverse layer of muscular fibres ; and an outer layer consisting of longitudinal elastic lamellae, varying from five to ten in number, alternating with layers of transverse muscular fibres and connective tissue, which resembles somewhat in structure the middle coat of large arteries. In the large veins, as in the commencement of the vena portas, in the upper part of the abdominal portion of the inferior vena cava, and in the large hepatic trunks within the liver, the middle coat is thick, and its structure similar to that of the middle coat in medium-sized veins ; but its muscular tissue is scanty, and the longitudinal elastic networks less distinctly lamellated. The muscular tissue of this coat is best marked in the splenic and portal veins, it is absent in certain parts of the vena cava below the liver, and wanting in the subclavian vein and terminal parts of the two cavae. The external coat is usually the thickest, increasing in thickness with the size of the vessel ; it is similar in structure to the external coat of arteries, but its chief peculiarity is that in some veins it contains a longitudinal network of mus- cular fibres. In the smallest veins, it consists of a thick layer of nucleated con- nective tissue. In medium-sized veins, it is much thicker than the middle^ coat, and consists of elastic and connective tissues, the fibres of which are longitudinally arranged. In the largest veins, this coat is from two to five times thicker than the middle coat, and contains a large number of longitudinal muscular fibres. This is most distinct in the hepatic part of the inferior vena cava, and at the termination of this vein in the heart ; in the trunks of the hepatic veins ; in all the large trunks of the vena portae ; in the splenic, superior mesenteric, external iliac, renal, and azygos veins. Where the middle coat is absent, this_ muscular layer extends as far as the inner coat. In the renal and portal veins, it extends GENERAL ANATOMY. 457 through the whole thickness of the outer coat ; but in the other veins mentioned, a layer of connective and elastic tissues is found external to the muscular fibres. All the large veins which open into the heart are covered for a short distance by a layer of muscular tissue continued on to them from the heart. Muscular tissue is wanting in the veins : 1. Of the maternal part of the placenta. 2. In most of the cerebral veins and sinuses of the dura mater. 3. In the veins of the retina. 4. In the veins of the cancellous tissue of bones. 5. In the venous spaces of the corpora cavernosa. The veins of the above-mentioned parts have an internal epithelial lining, supported on one orj the Removal of the Outer Table of the Skull. vein, by an aperture at the supra-orbital notch ; the anterior temporal, which is confined chiefly to the frontal bone, and opens into one of the deep temporal veins, after escaping by an aperture in the great wing of the sphenoid ; the posterior temporal, which is confined to the parietal bone, and terminates in the lateral sinus by an aperture at the posterior inferior angle of the parietal bone ; and the occipital, which is confined to the occipital bone, and opens either into the occipital vein, or the occipital sinus. Cerebral Veins. The Cerebral Veins are remarkable for the extreme thinness of their coats, from the muscular tissue in them being wanting, and for the absence of valves. They may be divided into two sets, the superficial, which are placed on the surface, and the deep veins, which occupy the interior of the organ. The Superficial Cerebral Veins ramify upon the surface of the brain, being lodged in the sulci, between the convolutions, a few running across the convolu- tions. They receive branches from the substance of the brain, and terminate in the sinuses. They are named from the position they occupy, superior, inferior, internal, and external. The Superior Cerebral Veins, seven or eight in number on each side, pass forwards and inwards towards the great longitudinal fissure, where they receive the internal cerebral veins, which return the blood from the convolutions of the flat surface of the corresponding hemisphere ; passing obliquely forwards, they become invested with a tubular sheath of the arachnoid membrane, and open into CEREBRAL. 4G3 the superior longitudinal sinus, in the opposite direction to the course of the blood. The Inferior Anterior Cerebral Veins commence on the under surface of the anterior lobes of the brain, and terminate in the cavernous sinuses. The Inferior Lateral Cerebral Veins commence on the lateral parts of the hemispheres and at the base of the brain : they unite to form from three to five veins, which open into the lateral sinus from before backwards. The Inferior Median Cerebral Veins, which are very large, commence at the fore part of the under surface of the cerebrum, and from the convolutions of the posterior lobe, and terminate in the straight sinus behind the venae Galeni. The Deep Cerebral or Ventricular Veins (venae Galeni) are two in number, one from the right ventricle, the other from the left. They are each formed by two veins, the vena corporis striati and the choroid vein. They pass back- wards, parallel with one another, inclosed within the velum interpositum, and pass out of the brain at the great transverse fissure, between the under surface of the corpus callosum and the tubercula quadrigemina, and enter the straight sinus. The vena corporis striati commences in the groove between the corpus striatum and thalamus opticus, receives numerous veins from both of these parts, and unites behind the anterior pillar of the fornix with the choroid vein, to form one of the venae Galeni. The choroid vein runs along the whole length of the outer border of the choroid plexus, receiving veins from the hippocampus major, the fornix and corpus callosum, and unites; at the anterior extremity of the choroid plexus, with the vein of the corpus striatum. The Cerebellar Veins occupy the surface of the cerebellum, and are disposed in three sets, superior, inferior, and lateral. The superior pass forwards and inwards, across the superior vermiform process, and terminate in the straight sinus ; some open into the venae Galeni. The inferior cerebellar veins, of large size, run transversely outwards, and terminate by two or three trunks in the lateral sinuses. The lateral anterior cerebellar veins terminate in the superior petrosal sinuses. Sinuses of the Dura Mater. The sinuses of the dura mater are venous channels, analogous to the veins, their outer coat being formed by the dura mater ; their inner, by a continuation of the serous membrane of the veins. They are twelve in number, and are divided into two sets: — 1. Those situated at the upper and back part of the skull. 2. The sinuses at the base of the skull. 1. The sinuses of the upper and back part are the Superior longitudinal. Straight sinus. Inferior longitudinal. Lateral sinuses. Occipital sinuses. The Superior Longitudinal Sinus occupies the attached margin of the falx cerebri. Commencing at the crista Galli, it runs from before backwards, groov- ing the inner surface of the frontal, the adjacent margins of the two parietal and the superior division of the crucial ridge of the occipital bone, and terminates by dividing into the two lateral sinuses. This sinus is triangular in form, narrow in front, and gradually increasing in size as it passes backwards. On examining its inner surface, it presents the internal openings of the cerebral veins : these vessels are, for the most part, directed from behind forwards, and chiefly open at the back part of the sinus, their orifices being concealed by fibrous areolae; numerous fibrous bands, chordse Willisii, are also seen, which extend transversely across its inferior angle ; and lastly, some small, white, projecting bodies, the glandulae Pacchioni. This sinus receives the superior cerebral veins. 464 VEINS. numerous veins from the diploe and dura mater, and, at the posterior extremity of the sagittal suture, the parietal veins from the pericranium. The point where the superior longitudinal and lateral sinuses are continuous is called the confluence of the sinuses or the torcular Herophili. It presents a con- siderable dilatation, of very irregular form, and is the point of meeting of six sinuses, the superior longitudinal, the two lateral, the two occipital, and the straight. The Inferior Longitudinal Sinus, more correctly described as the inferior longitudinal vein, is contained in the posterior part of the free margin of the falx cerebri. It is of a circular form, increases in size as it passes backwards, and terminates in the straight sinus. It receives several veins from the falx cerebri, and occasionally a few from the flat surface of the hemispheres. The Straight Sinus is situated at the line of junction of the falx cerebri with the tentorium. It is triangular in form, increases in size as it proceeds back- wards, and runs obliquely downwards and backwards from the termination of the inferior longitudinal sinus to the torcular Herophili. Besides the inferior lon- gitudinal sinus, it receives the venae Galeni, the inferior median cerebral veins, and the superior cerebellar. A few transverse bands cross its interior. Fig. 238. — Vertical Section of the Skull, showing the Sinuses of the Dura Mater. Toreular_ Herophili The Lateral Sinuses are of large size, and situated in the attached margin of the tentorium cerebelli. They commence at the torcular Herophili, and, passing horizontally outwards to the base of the petrous portion of the temporal bone, curve downwards and inwards on each side to reach the jugular foramen, where they terminate in the internal jugular vein. Each sinus rests, in its course, upon the inner surface of the occipital bone, the posterior inferior angle of the parietal, the mastoid portion of the temporal, and on the occipital again just before its termi- nation. These sinuses are of unequal size, the right being the larger, and they increase in size as they proceed from behind forwards. The horizontal portion is of a triangular form, the curved portion semi -cylindrical ; their inner surface is smooth, and not crossed by the fibrous bands found in the other sinuses. These sinuses receive blood from the superior longitudinal, the straight, and the occipital sinuses ; and in front they communicate with the superior and inferior petrosal. They communicate with the veins of the pericranium by means of the mastoid and posterior condyloid veins, and they receive the inferior cerebral and inferior cerebellar veins, and some from the diploe. The Occipital are the smallest of the cranial sinuses. They are usually two in ruimber, and situated in the attached margin of the falx cerebelli. They commence SINUSES OF THE DURA MATER. 46( by several small veins around the posterior margin of the foramen magnum, which communicate with the posterior spinal veins, and terminate by separate openings (sometimes by a single aperture) in the torcular Herophili. 2. The sinuses at the base of the skull are the Cavernous. Circular. Transverse. Inferior petrosal. Superior petrosal. The Cavernous Sinuses are named from their presenting a reticulated structure. They are two in number, of large size, and placed one on each side of the sella Turcica, extending from the sphenoidal fissure to the apex of the petrous portion Fig. 239.— The Sinuses at the Base of the Skull. of the temporal bone : they receive anteriorly the ophthalmic vein through the sphenoidal fissure, communicate behind with the petrosal sinuses, and with each other by the circular and transverse sinuses. On the inner wall of each sinus is found the internal carotid artery, accompanied by filaments of the carotid plexus and by the sixth nerve ; and on its outer wall, the third, fourth, and ophthalmic nerves. These parts are separated from the blood flowing along the sinus by the lining membrane, which is continuous with the inner coat of the veins. The cavity of the sinus, which is larger behind than in front, is intersected by filaments of fibrous tissue and small vessels. The cavernous sinuses receive the inferior anterior cerebral veins; they communicate with the lateral sinuses by means of the superior and inferior petrosal, and with the facial vein through the ophthalmic. The ophthalmic is a large vein, which connects the frontal vein at the inner angle of the orbit with the cavernous sinus ; it pursues the same course as the ophthalmic artery, and receives branches corresponding to those derived from that vessel. Forming a short single trunk, it passes through the inner extremity of the sphenoidal fissure, and terminates in the cavernous sinus. The Circular Sinus completely surrounds the pituitary body, and communicates on each side with the cavernous sinuses. Its posterior half is larger than the 30 466 VEINS, Fig. 240.— The Superficial Veins of the Upper Extremity. anterior ; and in old age it is more capacious than at an early period of life. It receives veins from the pituitary body, and from the adjacent bone and dura mater. The Inferior Petrosal Sinus is situated in the groove formed by the junction of the inferior border of the petrous portion of the temporal with the basilar process of the occipital. It commences in front at the termination of the cavernous sinus, and opens behind into the jugular foramen, forming with the lateral sinus the commencement of the internal jugular vein. These sinuses are semi-cylindrical in form. The Transverse Sinus is placed trans- versely across the fore part of the basilar process of the occipital bone, serving to connect the two inferior petrosal and cavern- ous sinuses. A second is occasionally found opposite the foramen magnum. The Superior Petrosal Sinus is situated along the upper border of the petrous por- tion of the temporal bone, in the front part of the attached margin of the tentorium. It is small and narrow, and connects together the cavernous and lateral sinuses at each side. It receives a cerebral vein (inferior lateral cerebral) from the under part of the middle lobe, and a cerebellar vein (anterior lateral cerebellar) from the anterior border of the cerebellum. IZeitanCejjXaJt'c, External , CulaMCoutNi rwt Veins of the Upper Extremity and Thorax. The veins of the upper extremity are divided into two sets: 1. The superficial veins. 2. The deep veins. The Superficial Veins are placed imme- diately beneath the integument between the two layers of superficial fascia ; they com- mence in the hand chiefly on its dorsal aspect, where they form a more or less com- plete arch. The Deep Veins accompany the arteries, and constitute the venas comites of those vessels. Both sets of vessels are provided with valves, which are more numerous in the deep than in the superficial. 1. The Superficial Veins of the Upper Extremity are the Anterior ulnar. Posterior ulnar. Basilic. Eaclial. The Anterior Ulnar Cephalic. Median. Median basilic. Median cephalic. Vein commences on the anterior surface of the wrist and ulnar side of the hand, and ascends along the • OF THE UPPER EXTREMITY. 467 inner side of the forearm to the bend of the elbow, where it joins with the posterior ulnar vein to form the basilic. It communicates with branches of the median vein in front, and with the posterior ulnar behind. The Posterior Ulnar Vein commences on the posterior surface of the ulnar side of the hand, and from the vein of the little finger (vena salvatella), situated over the fourth metacarpal space. It ascends on the posterior surface of the ulnar side of the forearm, and just below the elbow unites with the anterior ulnar vein to form the basilic. The Basilic is a vein of considerable size, formed by the coalescence of the anterior and posterior ulnar veins ; ascending along the inner side of the elbow, it receives the median basilic vein, and, passing upwards along the inner side of the arm, pierces the deep fascia, and ascends in the course of the brachial artery, ter- minating either in one of the venae comites of that vessel, or in the axillary vein. The Radial Vein commences from the dorsal surface of the thumb, index finger, and radial side of the hand, by branches which communicate with the vena salva- tella. They form by their union a large vessel, which ascends along the radial side of the forearm, receiving numerous branches from both its surfaces. At the bend of the elbow it receives the median cephalic, when it becomes the cephalic vein. The Cephalic Vein ascends along the outer border of the Biceps muscle, to the upper third of the arm ; it then passes in the interval between the Pectoralis major and Deltoid muscles, accompanied by the descending branch of the thoracica acro- mialis artery, and terminates in the axillary vein just below the clavicle. This vein is occasionally connected with the external jugular or subclavian, by a branch which passes from it upwards in front of the clavicle. The Median Vein collects the blood from the superficial structures in the palmar surface of the hand and middle line of the forearm, communicating with the anterior ulnar and radial veins. At the bend of the elbow, it receives a branch of communication from the deep veins, accompanying the brachial artery, and divides into two branches, -the median cephalic and median basilic, which diverge from each other as they ascend. The Median Cephalic, the smaller of the two, passes outwards in the groove between the Supinator longus and Biceps muscles, and joins with the cephalic vein. The branches of the external cutaneous nerve pass behind this vessel. The Median Basilic vein passes obliquely inwards, in the groove between the Biceps and Pronator radii teres, and joins with the basilic. This vein passes in front of the brachial artery, from which it is separated by a fibrous expansion, given off from the tendon of the Biceps to the fascia covering the Flexor muscles of the forearm. Filaments of the internal cutaneous nerve pass in front of as well as behind this vessel. 2. The Deep Veins of the Upper Extremity follow the course of the arteries, forming their vena3 comites. They are generally two in number, one lying on each side of the corresponding artery, and they are connected at intervals by short transverse branches. There are two digital veins, accompanying each artery along the sides of the fingers ; these, uniting at their base, pass along the interosseous spaces in the palm, and terminate in the two superficial palmar veins. Branches from these vessels on the radial side of the hand accompany the superficialis vola3, and on the ulnar side terminate in the deep ulnar veins. The deep ulnar veins, as they pass in front of the wrist, communicate with the interosseous and superficial veins, and unite at the elbow with the deep radial veins, to form the vense comites of the brachial artery. The Interosseous Veins accompany the anterior and posterior interosseous arteries. The anterior interosseous veins commence in front of the wrist, where they communicate with the deep radial and ulnar veins ; at the upper part of the forearm they receive the posterior interosseous veins, and terminate in the venoa comites of the ulnar artery. 4G8 VEINS. The Deep Palmar Veins accompany the deep palmar arch, being formed bv branches which accompany the ramifications of this vessel. They communicate with the superficial palmar veins at the inner side of the hand ; and, on the outer side, terminate in the venaa comites of the radial artery. At the wrist, they receive a dorsal and a palmar branch from the thumb, and unite with the deep radial veins. Accompanying the radial artery, these vessels terminate in the vense comites of the brachial artery. The Brachial Veins are placed one on each side of the brachial artery, receiving branches corresponding with those given off from this vessel ; at the lower margin of the axilla they unite with the basilic to form the axillary vein. The deep veins have numerous anastomoses, not only with each other, but also with }he superficial veins. The Axillary Yein is of large size and formed by the continuation upwards of the basilic vein. It commences at the lower part of the axillary space, and increasing in size as it ascends, by receiving branches corresponding with those of the axillary artery, terminates immediately beneath the clavicle at the outer mar- gin of the first rib, and becomes the subclavian vein. This vessel is covered in front by the Pectoral muscles and costo-coracoid membrane, and lies on the thoracic side of the axillary artery. Opposite the Subscapularis, it is joined by a large vein, formed by the junction of the vense comites of the brachial ; and near its termination it receives the cephalic vein. This vein is provided with a pair of valves opposite the lower border of the Subscapularis muscle ; valves are also found, at the termination of the cephalic and subscapular veins. The Subclavian Yein, the continuation of the axillary, extends from the outer margin of the first rib to the inner end of the sterno-clavicular articulation, where it unites with the internal jugular, to form the vena innominata. It is in relation, in front, with the clavicle and Subclavius muscle ; behind, with the subclavian artery, from which it is separated internally by the Scalenus anticus and phrenic nerve. Below, it rests in a depression on the first rib and upon the pleura. Above, it is covered by the cervical fascia and integument. The subclavian vein occasionally rises in the neck to a level with the third part of the subclavian artery, and, in two instances, has been seen passing with the latter behind the Scalenus anticus. This vessel is provided with valves about an inch from its termination in the innominate, just external to the entrance of the external jugular vein. Branches. It receives the external and anterior jugular veins and a small branch from the cephalic, outside the Scalenus; and on the inner side of this muscle, the internal jugular veins. The YENiE Innominate (fig. 241) are two large trunks, placed one on each side of the root of the neck, and formed by the union of the internal jugular and subclavian veins of the corresponding side. The Bight Vena Innominata is a short vessel, about an inch and a half in length, which commences at the inner end of the clavicle, and, passing almost vertically downwards, joins with the left vena innominata just below the cartilage of the first rib, to form the superior vena cava. It lies superficial and external to the arteria innominata ; on its right side the pleura is interposed between it and the apex of the lung. This vein, at its angle of junction with the subclavian, receives the right vertebral vein, and right lymphatic duct ; and, lower down, the right internal mammary, right inferior thyroid, and right superior intercostal veins. The Left Vena Innominata, about three inches in length, and larger than the right, passes obliquely from right to left across the upper and front part of the chest, to unite with its fellow of the opposite side, forming the superior vena cava. It is in relation, in front, with the sternal end of the left clavicle, the left sterno- clavicular articulation, and with the first piece of the sternum, from which it is separated by the Sterno-hyoid and Sterno-thyroid. muscles, the thymus gland or its remains, and some loose areolar tissue. Behind, it lies across the roots of the INNOMINATE. 469 three large arteries arising from the arch of the aorta. This vessel is joined "by the left vertebral, left inferior thyroid, left internal mammary, and the left supe- rior intercostal veins, and occasionally some thymic and pericardiac veins. Fi s- 241 -- T J 1 I e 7 e " ffi Ca ™ a " d Az P° 9 Veins ' " , " ... with their Formative Branches. There are no valves in the '„ A T / \\3.~-^AnUrior Jugular* venas mnominatoe. Peculiarities. Sometimes the innominate veins open se- parately into the right auri- cle ; in such cases the right vein takes the ordinary course of the superior vena cava, but the left vein, after communi- cating by a small branch with the right one, passes in front of the root of the left lung, and, turning to the back of the heart, receives the cardiac veins, and terminates in the back of the right auricle. This occasional condition of the veins in the adult is a regular one in the foetus at an early period, and the two ves- sels are persistent in birds and some mammalia. The subsequent changes which take place in these vessels are the following : The communi- cating branch between the two trunks enlarges and forms the future left innominate vein ; the remaining part of the left trunk is obliterated as far as the heart, where it remains pervious, and forms the coro- nary sinus ; a remnant of the obliterated vessel is seen in adult life as a fibrous band passing along the back of the left auricle and in front of the root of the left lung, called, by Mr. Marshall, the vestigial fold of the pericardium. The internal mammary veins, two in number to each artery, follow the course of that vessel, and receive branches corre- sponding with those de- rived from it. The two veins unite into a single trunk, which terminates in the innominate vein. The inferior thyroid veins, two, frequently three or four in number, arise in the venous plexus, on the thyroid body, commu- nicating with the middle and superior thyroid veins. The left one descends in Superior Thyroid WLJJlt 'vntal Jugular 4T0 VEINS. front of the trachea, behind the Sterno-thyroid muscles, communicating with ita fellow by transverse branches, and terminates in the left vena innominata. The right one, which is placed a little to the right of the median line, opens into the right vena innominata, just at its junction with the superior cava. These veins receive tracheal and inferior laryngeal branches, and are provided with valves at their termination in the innominate veins. The Superior Intercostal Veins return the blood from the upper intercostal spaces. The rigid superior intercostal, much smaller than the left, closely corresponds with the superior intercostal artery, receiving the blood from the first, or first and second intercostal spaces, and terminates in the right vena innominata. Some- times it passes down, and opens into the vena azygos major. The left superior intercostal is always larger than the right, but varies in size in different subjects, being small when the left upper azygos vein is large, and vice versa. It is usually formed by branches from the two or three upper intercostal spaces, and, passing across the arch of the aorta, terminates in the left vena inno- minata. The left bronchial vein opens into it. The Superior Vena Cava receives the blood which is conveyed to the heart from the whole of the upper half of the body. It is a short trunk, varying from two inches and a half to three inches in length, formed by the junction of the two venae innominatae. It commences immediately below the cartilage of the first rib on the right side, and, descending vertically downwards, enters the peri- cardium about an inch and a half above the heart, and terminates in the upper part of the right auricle. In its course, it describes a slight curve, the convexity of which is turned to the right side. Relations. In front, with the thoracic fascia, which separates it from the thymus gland, and from the sternum ; behind, with the root of the right lung. On its right side, with the phrenic nerve and the pleura of the right side ; on its left side, with the ascending part of the aorta. The portion contained within the pericardium is covered by the serous layer of that membrane, in its anterior three-fourths. It receives the vena azygos major, just before it enters the peri- cardium, and several small veins from the pericardium and parts in the medias- tinum. The superior vena cava has no valves. The Azygos Veins connect together the superior and inferior venae cavae, supplying the place of these vessels in that part of the trunk in which they are deficient, on account of their connection with the heart. The larger, the right azygos vein, commences opposite the first or second lumbar vertebra, by receiving a branch from the right lumbar veins ; sometimes by a branch from the renal vein, or from the inferior vena cava. It enters the thorax through the aortic opening in the Diaphragm, and passes along the right side of the vertebral column to the third dorsal vertebra, where it arches forward, over the root of the right lung, and terminates in the superior vena cava, just before that vessel enters the pericardium. Whilst passing through the aortic opening of the Diaphragm, it lies with the thoracic duct on the right side of the aorta ; and in the thorax, it lies upon the intercostal arteries, on the right side of the aorta and thoracic duct, covered by the pleura. Branches. It receives nine or ten lower intercostal veins of the right side, the vena azygos minor, several oesophageal, mediastinal, and vertebral veins ; near its termination, the right bronchial vein ; and it is occasionally connected with the right superior intercostal vein. A few imperfect valves are found in this vein ; but its branches are provided with complete valves. The intercostal veins on the left side, below the two or three upper intercostal spaces, usually form two trunks, named the left lower, and the left upper, azygos veins. The left lower or smaller azygos vein commences in the lumbar region, by a branch from one of the lumbar veins, or from the left renal. It passes into the thorax, through the left crus of the Diaphragm, and, ascending on the left side of AZYGOS— SPINAL. 471 the spine, as high as the sixth or seventh vertebra, passes across the column, behind the aorta and thoracic duct, to terminate in the right azygos vein. It Teceives the four or five lower intercostal veins of the left side, and some oesopha- geal and mediastinal veins. The left upper azygos vein varies according to the size of the left superior intercostal. It receives veins from the intercostal spaces between the left superior intercostal vein, and highest branch of the left lower azygos. They are usually two or three in number, and join to form a trunk which ends in the right azygos vein, or in the left lower azygos. When this vein is small, or altogether wanting, the left superior intercostal vein will extend as low as the fifth or sixth intercostal space. The bronchial veins return the blood from the substance of the lungs ; that of the right side opens into the vena azygos major, near its termination ; that of the left side, in the left superior intercostal vein. The Spinal Veins. The numerous venous plexuses placed upon and within the spine may be arranged into four sets : — 1. Those placed on the exterior of the spinal column (dorsi-spinal veins). 2. Those situated in the interior of the spinal canal, between the vertebrae and the theca vertebralis {meningo-rachidian veins). 3. The veins of the bodies of the vertebrae {vense basis vertebrarum). 4. The veins of the spinal cord {medulli- spinal veins). 1. The Dorsi-spinal Veins commence by small branches, which receive their blood from the integument of the back of the spine, and from the muscles in the vertebral grooves. They form a complicated network, which surrounds the spinous processes, laminae, and the transverse and articular processes of all the vertebrae. At the bases of the transverse processes, they communicate, by means of ascending and descending branches, with the veins surrounding the contiguous vertebrae, and they join with the veins in the spinal canal by branches which per- forate the ligamenta subflava; in the intervals between the arches of the vertebrae, they terminate in the vertebral veins in the neck, in the intercostal veins in the thorax, in the lumbar and sacral veins in the loins and pelvis. 2. The veins contained in the spinal canal are situated between the theca vertebralis and the vertebrae. They consist of two longitudinal plexuses, one of which runs along the posterior surface of the bodies of the vertebrae, throughout the entire length of the spinal canal {anterior longitudinal spinal veins), receiving the veins belonging to the bodies of the vertebrae (venae basis verte- brarum). The other plexus {posterior longitudinal spinal veins) is placed on the inner or anterior surface of the laminae of the vertebrae, and extends also along the entire length of the spinal canal. The Anterior Longitudinal Spinal Veins consist of two large, tortuous venous canals, which extend along the whole length of the vertebral column, from the foramen magnum to the base of the coccyx, being placed one on each side of the posterior surface of the bodies of the vertebrae, external to the posterior common ligament. These veins communicate together opposite each vertebra, by transverse trunks, which pass beneath the ligament, and receive the large venae basis verte- brarum, from the interior of the body of each vertebra. The anterior longitudinal spinal veins are least developed in the cervical and sacral regions. They are not of uniform size throughout, being alternately enlarged and constricted. At the intervertebral foramina, they communicate with the dorsi-spinal veins, and with the vertebral veins in the neck, with the intercostal veins in the dorsal region, and with the lumbar and sacral veins in the corresponding regions. The Posterior Longitudinal Spinal Veins, smaller than the anterior, are situated one on either side, between the inner surface of the laminae and the theca verte- bralis. They communicate, like the anterior, opposite each vertebra, by transverse 472 VEINS. trunks ; and with the anterior longitudinal veins, by lateral transverse branches which pass from behind forwards. These veins, at the intervertebral foramina, join with the dorsi-spinal veins. Fig. 242. — Transverse Section of a Dorsal Vertebra, showing the Spinal Veins. 3. The Veins of the Bodies of the Vertebrse (venae basis vertebrarum) emerge from the foramina on their posterior surface, and join the transverse trunk connecting the anterior longitudinal spinal veins. They are contained in large, tortuous channels, in the substance of the bones, similar in every respect to those found in the diploe of the cranial bones. These canals lie parallel to the upper and lower surface of the bones, arise from the entire circumference of the vertebra, communicate with veins which enter through the foramina, on the anterior surface of the bodies, and converge to the principal canal, which is sometimes double towards its posterior part. They become greatly developed in advanced age. Fig. 243. — Vertical Section of two Dorsal Vertebrje, showing the Spinal Veins. . 4. The Veins of the Spinal Cord (medulli-spinal) consist of a minute tortuous venous plexus, which covers the entire surface of the cord, being situated between the pia mater and arachnoid. These vessels emerge chiefly from the posterior median furrow, and are largest in the lumbar region. Near the base of the skull they unite, and form two or three small trunks, which communicate with the ver- tebral veins, and then terminate in the inferior cerebellar veins, or in the petrosal sinuses. Each of the spinal nerves is accompanied by a branch as far as the in- tervertebral foramina, where they join the other veins from the spinal canal. There are no valves in the spinal veins. OF THE LOWER EXTREMITY. IVi VEINS OF THE LOWER EXTREMITY. Fig. 244.— The Internal or Long Saphenous Vein and its Branches. \ -r\4 The veins of the lower extremity are subdivided, like those of the upper, into two sets, superficial and deep ; the superficial veins being placed beneath the integu- ment, between the two layers of superficial fascia, the deep veins accompanying the arteries, and form- ing the vena? comites of those vessels. Both sets of veins are provided with valves, which are more nu- merous in the deep than in the superficial set. These valves are also more numerous in the lower than in the upper limbs. The Superficial Veins of the lower extremity are the internal or long saphenous, and the external or short saphenous. The internal saphenous vein (fig. 244) com- mences from a minute plexus, which covers the dorsum and inner side of the foot; it ascends in front of the inner ankle, and along the inner side of the leg, behind the inner margin of the tibia, accompanied by the internal saphenous nerve. At the knee, it passes backwards behind the inner condyle of the femur, ascends along the inside of the thigh, and, passing through the saphenous opening in the fascia lata, terminates in the femoral vein, an inch and a half below Poupart's ligament. This vein receives in its course cutaneous branches from the leg and thigh, and, at the saphenous open- ing, the superficial epigastric, superficial circumflex iliac, and external pudic veins. The veins from the inner and back part of the thigh frequently unite to form a large vessel, which enters the . main trunk near the saphenous opening, and sometimes those on the outer side of the thigh join to form a large branch ; so that occasionally three large veins are seen converging from different parts of the thigh towards the saphenous opening. The internal saphenous vein communicates in the foot with the internal plantar vein ; in the leg, with the posterior tibial veins, by branches which perforate the tibial origin of the Soleus muscle, and also with the ante- rior tibial veins ; at the knee, with the articular veins ; in the thigh, with the femoral vein by one or more branches. The valves in this vein vary from two to six in number ; they are more numerous in the thigh than in the leg. The external or short saphenous vein is formed by branches which collect the blood from the dorsum and outer side of the foot ; it ascends behind the outer ankle, and along the outer border of the tendo Achillis, across which it passes at an acute angle to reach the middle line of the posterior aspect of the leg. Ascending directly upwards, it perforates the deep fascia in the lower part of the popliteal space, and terminates in the popliteal vein, between the heads of the Gastrocnemius muscle. It is accompanied by the external saphenous nerve. m 474 VEINS. Fig. 245. -External or Short Saphe- nous Vein. It receives numerous large branches from the back part of the leg, and communicatee with the deep veins on the dorsum of the foot, and behind the outer malleolus. This vein has only two valves, one of which is always found near its termination in the popliteal vein. The Deep Veins of the lower extremity accom- pany the arteries and their branches, and are called the vense comites of those vessels. The external and internal plantar veins unite to form the posterior tibial. They accompany the posterior tibial artery, and are joined by the pero- neal veins. The anterior tibial veins are formed by a continua- tion upwards of the venae dorsales pedis. They perforate the interosseous membrane at the upper part of the leg, and form, by their junction with the posterior tibial, the popliteal vein. The valves in the deep veins are very nume- rous. The Popliteal Vein" is formed by the junction of the venae comites of the anterior and posterior tibial vessels; it ascends through the popliteal space to the tendinous aperture in the Adductor magnus, where it becomes the femoral vein. In the lower part of its course, it is placed internal to the artery; between the heads of the Gastrocnemius, it is superficial to that vessel ; but above the knee- joint, it is close to its outer side. It receives the sural veins from the Gastrocnemius muscle, the articular veins, and the external saphenous. The valves in this vein are usually four in number. The Femoral Yein accompanies the femoral artery through the upper two-thirds of the thigh. In the lower part of its course, it lies external to the artery ; higher up, it is behind it ; and beneath Poupart's ligament, it lies to its inner side, and on the same plane as that vessel. It receives numerous muscular branches; the profunda femoris joins it about an inch and a half below Poupart's ligament, and near its termination the internal saphenous vein. The valves in this vein are four or five in number. The External Iliac Vein commences at the termination of the femoral, be- neath the crural arch, and, passing upwards along the brim of the pelvis, terminates opposite the sacro-iliac symphysis, by uniting with the internal iliac to form the common iliac vein. On the right side, it lies at first along the inner side of the external iliac artery, but, as it passes upwards, gradually inclines behind it. On the left side, it lies altogether on the inner side of the artery. It receives, imme- diately above Poupart's ligament, the epigastric and circumflex iliac veins. It has no valves. The Internal Iliac Vein is formed by the venae comites of the branches of the internal iliac artery, the umbilical arteries excepted. It receives the blood from the exterior of the pelvis by the gluteal, sciatic, internal pudic, and obturator veins ; and from the organs in the cavity of the pelvis by the hemorrhoidal and vesico-prostatic plexuses in the male, and the uterine and vaginal plexuses in the female. The vessels forming these plexuses are remarkable for their large size, their frequent anastomoses, and the number of valves which they contain. The internal iliac vein lies at first on the inner side and then behind the internal iliac ILIAC— INFERIOR VENA CAVA. 475 artery, and terminates opposite the sacro-iliac articulation, by uniting with the external iliac, to form the common iliac vein. This vessel has no valves. The hemorrhoidal plexus surrounds the lower end of the rectum, being formed by the superior hemorrhoidal veins, branches of the inferior mesenteric, and the middle and inferior hemorrhoidal, which terminate in the internal iliac. The portal and general venous systems have a free communication by means of the branches composing this plexus. The vesico-prostatic plexus surrounds the neck and base of the bladder and prostate gland. It communicates with the hemorrhoidal plexus behind, and receives the dorsal vein of the penis, which enters the pelvis beneath the sub- pubic ligament. This plexus is supported upon the sides of the bladder by a reflection of the pelvic fascia. The veins composing it are very liable to become varicose, and often contain hard earthy concretions, called phlebolites. The dorsal vein of the penis is a vessel of large size, which returns the blood from the body of this organ. At first it consists of two branches, which are con- tained in the groove on the dorsum of the penis, and receives veins from the glans, the corpus spongiosum, and numerous superficial veins ; these unite near the root of the penis into a single trunk, which pierces the triangular ligament beneath the pubic arch, and divides into two branches, which enter the prostatic plexus. The vaginal plexus surrounds the mucous membrane of the vagina, being espe- cially developed at the orifice of this canal ; it communicates with the vesical plexus in front, and with the hemorrhoidal plexus behind. The uterine plexus is situated along the sides and superior angles of the uterus, receiving large venous canals (the uterine sinuses) from its substance. The veins composing this plexus anastomose frequently with each other and with the ovarian veins. They are not tortuous like the arteries. Each Common Iliac Vein is formed by the union of the external and internal iliac veins in front of the sacro-vertebral articulation ; passing obliquely upwards towards the right side, they terminate upon the intervertebral substance between the fourth and fifth lumbar vertebrae, where they unite at an acute angle to form the inferior vena cava. The right common iliac is shorter than the left, nearly vertical in its direction, and ascends behind and then to the outer side of its corresponding artery. The left common iliac, longer and more oblique in its course, is at first situated at the inner side of the corresponding artery, and then behind the right common iliac. Each common iliac receives the ilio-lumbar, and some- times the lateral sacral veins. The left one receives, in addition, the middle sacral vein. No valves are found in these veins. The middle sacral vein accompanies its corresponding artery along the front of the sacrum, and terminates in the left common iliac vein; occasionally in the commencement of the inferior vena cava. Peculiarities. The left common iliac vein, instead of joining with the right one in its usual position, occasionally ascends on the left side of the aorta as high as the kidney, where, after receiving the left renal vein, it crosses over the aorta, and then joins with the right vein to form the vena cava. In these cases, the two common iliacs are connected by a small communicating branch at the spot where they are usually united. The Inferior Vena Cava returns to the heart the blood from all the parts below the Diaphragm. It is formed by the junction of the two common iliac veins on the right side of the intervertebral substance, between the fourth and fifth lumbar vertebras. It passes upwards along the front of the spine, on the right side of the aorta, and, having reached the under surface of the liver, is contained in a groove in its posterior border. It then perforates the tendinous centre of the Diaphragm, enters the pericardium, where it is covered by its serous layer, and terminates in the lower and back part of the right auricle. At its termination in the auricle, it is provided with a valve, the Eustachian, which is of large size during fcetal life. Relations. In front, from below upwards, with the mesentery, transverse por- 476 VEINS. tion of the duodenum, the pancreas, portal vein, and the posterior border of th? liver, which partly and occasionally completely surrounds it ; behind, it rests upon the vertebral column, the right crus of the Diaphragm, the right renal and lumbar arteries ; on the left side, it is in relation with the aorta. It receives in its course the following branches : — Lumbar. Supra-renal. Eight spermatic. Phrenic. Renal. Hepatic. Peculiarities of Position. This vessel is sometimes placed on the left side of the aorta, as high as the left renal vein, after receiving which it crosses over to its usual position on the right side ; or it may be placed altogether on the left side of the aorta, as far upwards as its termination in the heart : in such cases, the abdominal and thoracic viscera, together with the great vessels, are all transposed. Peculiarities of Termination. Occasionally the inferior vena cava joins the right azygos vein, which is then of large size. In such cases, the superior cava receives the whole of the blood from the body before transmitting it to the right auricle, the blood from the hepatic veins excepted, these vessels terminating directly in the right auricle. The lumbar veins, three or four in number on each side, collect the blood by dorsal branches from the muscles and integument of the loins, and by abdominal branches from the walls of the abdomen, where they communicate with the epigastric veins. At the spine, they receive branches from the spinal plexuses, and they pass forwards round the sides of the bodies of the vertebras beneath the Psoas magnus, and terminate at the back part of the inferior cava. The left lumbar veins are longer than the right, and pass behind the aorta. The lumbar veins commu- nicate with each other by branches which pass in front of the transverse processes. Occasionally two or more of these veins unite to form a single trunk, the ascending lumbar, which serves to connect the common iliac, ilio-lumbar, lumbar, and azygos veins of the corresponding side of the body. The spermatic veins emerge from the back of the testis, and receive branches from the epididymis ; they form a branched and convoluted plexus, called the spermatic plexus or plexus pampiniformis, below the abdominal ring. The vessels composing this plexus are very numerous, and ascend along the cord in front of the vas deferens ; having entered the abdomen, they coalesce to form two branches, which ascend on the Psoas muscle, behind the peritoneum, lying one on each side of the spermatic artery, and unite to form a single vessel, which opens on the right side in the inferior vena cava, piercing this vessel obliquely; on the left side in the left renal vein, terminating at right angles with this vein. The spermatic veins are provided with valves. The left spermatic vein passes behind the sigmoid flexure of the colon ; this circumstance, as well as the indirect communication of • the vessel with the inferior vena cava, may serve to explain the more frequent occurrence of varicocele on the left side. The ovarian veins are analogous to the spermatic in the male ; they form a plexus near the ovary, and in the broad ligament and Fallopian tube, communi- cating with the uterine plexus. They terminate as in the male. Valves are occasionally found in these veins. These vessels, like the uterine veins, become much enlarged during pregnancy. The renal veins are of large size, and placed in front of the divisions of the renal arteries. The left is longer than the right, and passes in front of the aorta, just below the origin of the superior mesenteric arter}'-. It receives the left spermatic and left inferior phrenic veins. It usually opens into the vena cava, a little higher than the right. The supra-renal vein terminates, on the right side, in the vena cava ; on the left side, in the left renal or phrenic vein. The phrenic veins follow the course of the phrenic arteries. The two superior, of small size, accompany the corresponding nerve and artery; the right te rminatin g PORTAL SYSTEM. 47T opposite the junction of the two venae innominate, the left in the left superior intercostal or left internal mammary. The two inferior phrenic veins follow the course of the inferior phrenic arteries, and terminate, the right in the inferior vena cava, the left in the left renal vein. The hepatic veins commence in the substance of the liver, in the capillary ter- minations of the vena portae ; these branches, gradually uniting, form three large veins, which converge towards the posterior border of the liver, and open into the inferior vena cava, whilst that vessel is situated in the groove at the back part of this organ. Of these three veins, one from the right and another from the left lobes open obliquely into the vena cava; that from the middle of the organ and lobus Spigelii having a straight course. The hepatic veins run singly, and are in direct contact with the hepatic tissue. They are destitute of valves. PORTAL SYSTEM OF VEINS. The portal venous system is composed of four large veins, which collect the venous blood from the viscera of digestion. The trunk formed by their union, the vena portae, enters the liver, ramifies throughout its substance, and its branches, again emerging from that organ as the hepatic veins, terminate in the inferior vena cava. The branches of this vein are in all cases single, and destitute of valves. The veins forming the portal system are the Inferior mesenteric. Splenic. Superior mesenteric. Gastric. The inferior mesenteric vein returns the blood from the rectum, sigmoid flexure, and descending colon, corresponding with the ramifications of the branches of the inferior mesenteric artery. Ascending beneath the peritoneum in the lumbar region, it passes behind the transverse portion of the duodenum and pancreas, and terminates in the splenic vein. Its hemorrhoidal branches inosculate with those of the internal iliac, and thus establish a communication between the portal and the general venous system. The superior mesenteric vein returns the blood from the small intestines, and from the caecum and ascending and transverse portions of the colon, correspond- ing with the distribution of the branches of the superior mesenteric artery. The large trunk formed by the union of these branches ascends along the right side and in front of the corresponding artery, passes in front of the transverse portion of the duodenum, and unites behind the upper border of the pancreas with the splenic vein, to form the vena portae. The splenic vein commences by five or six large branches, which return the blood from the substance of the spleen. These uniting form a single vessel, which passes from left to right behind the upper border of the pancreas, and terminates at its greater end by uniting at a right angle with the superior mesenteric to form the vena portae. The splenic vein is of large size, and not tortuous like the artery. It receives the vasa brevia from the left extremity of the stomach, the left gastro-epiploic vein, pancreatic branches from the pancreas, the pancreatico- duodenal vein, and the inferior mesenteric vein. The gastric is a vein of small size, which accompanies the gastric artery from left to right along the lesser curvature of the stomach, and terminates in the vena portae. The Portal Vein is formed by the junction of the superior mesenteric and splenic veins, their union taking place in front of the vena cava, and behind the upper border of the great end of the pancreas. Passing upwards through the right border of the lesser omentum to the under surface of the liver, it enters the transverse fissure, where it is somewhat enlarged, forming the sinus of the portal vein, and divides into two branches, which accompany the ramifications of the 41S VEINS. hepatic artery and hepatic duct throughout its substance. Of these two branches the right is the larger but the shorter of the two. The portal vein is about four inches in length, and, whilst contained in the lesser omentum, lies behind and between the hepatic duct and artery, the former being to the right, the latter to the left. These structures are accompanied by filaments of the hepatic plexus and numerous lymphatics, surrounded by a quantity of loose areolar tissue, the Fig. 246.— Portal Vein aud its Branches. capsule of Glisson, and placed between the layers of the lesser omentum. The vena portae receives the gastric and cystic veins ; the latter vein sometimes ter- minates in the right branch of the vena porta?. Within the liver, the portal vein receives the blood from the branches of the hepatic artery. CARDIAC— PULMONARY. 479 CARDIAC VEINS. The veins which return the blood from the substance of the heart are the Great cardiac vein. Anterior cardiac veins. Posterior cardiac vein. Venae Thebesii. The Great Cardiac Vein is a vessel of considerable size, which commences at the apex of the heart, and ascends along the anterior interventricular groove to the base of the ventricles. It then curves to the -left side, around the auriculo- ventricular groove, between the left auricle and ventricle, to the back part of the heart, and opens into the coronary sinus, its aperture being guarded by two valves. It receives the posterior cardiac vein, and the left cardiac veins from the left auricle and ventricle, one of which, ascending along the left margin of the ventricle, is of large size. The branches joining it are provided with valves. The Posterior Cardiac Vein commences, by small branches, at the apex of the heart, communicating with those of the preceding. It ascends along the posterior interventricular groove to the base of the heart, and terminates in the coronary sinus, its orifice being guarded by a valve. It receives the veins from the posterior surface of both ventricles. The Anterior Cardiac Veins are three or four small branches, which collect the blood from the anterior surface of the right ventricle. One of these, the vein of Galen, larger than the rest, runs along the right border of the heart. They open separately into the lower part of the right auricle. The Vense Thebesii are numerous minute veins, which return the blood directly from the muscular substance, without entering the venous current. They open, by minute orifices, foramina Thebesii, on the inner surface of the right auricle. The Coronary Sinus is that portion of the great cardiac vein which is situated in the posterior part of the left auriculo-ventricular groove. It is about an inch in length, presents a considerable dilatation, and is covered by the muscular fibres of the left auricle. It receives the great cardiac vein, the posterior cardiac vein, and an oblique vein from the back part of the left auricle, the remnant of the obliterated left innominate trunk of the foetus, described by Mr. Marshall. The coronary sinus terminates in the right auricle, between the inferior vena cava and the auriculo-ventricular aperture, its orifice being guarded by a semilunar fold of the lining membrane of the heart, the coronary valve. All the branches joining this vessel, excepting the oblique vein above mentioned, are provided with valves. THE PULMONARY VEINS. The Pulmonary Veins return the arterial blood from the lungs to the left auricle of the heart. They are four in number, two for each lung. The pul- monary differ from other veins in several respects: — 1. They carry arterial instead of venous blood. 2. They are destitute of valves. 3. They are only slightly larger than the arteries they accompany. 4. They accompany those vessels singly. They commence in a capillary network, upon the parietes of the bronchial cells, where they are continuous with the ramifications of the pulmonary artery, and, uniting together, form a single trunk for each lobule. These branches, successively uniting, form a single trunk for each lobe, three for the right, and two for the left, lung. The vein of the middle lobe of the right lung unites with that from the upper lobe, in most cases, forming two trunks on each side, which open 480 VEINS. separately into the left auricle. Occasionally they remain separate ; there are then three veins on the right side. Not unfrequently, the two left pulmonary veins terminate by a common opening. Within the lung, the branches of the pulmonary artery are in front, the veins behind, and the bronchi between the two. At the root of the lung, the veins are in front, the artery in the middle, and the bronchus behind. Within the pericardium, their anterior surface is invested by the serous layer of this membrane, the right pulmonary veins pass behind the right auricle and ascending aorta, the left pass in front of the thoracic aorta, with the left pul- monary artery. Of the Lymphatics. The Lymphatics have derived their name from the appearance of the fluid contained in their interior (lympha, water). They are also called absorbents, from the property they possess of absorbing certain materials for the replenishing of the blood, and conveying them into the circulation. The lymphatic system includes not only the lymphatic vessels and the glands through which they pass, but also the lacteal or chyliferous vessels. The lacteals are the lymphatic vessels of the small intestine, and differ in no respect from the lymphatics generally, excepting that they contain a milk-white fluid, the chyle, during the process of digestion, and convey it into the blood through the thoracic duct. The lymphatics are exceedingly delicate vessels, the coats of which are so transparent that, the fluid they contain is readily seen through them. They retain a nearly uniform size, being interrupted at intervals by constrictions, which give to them a knotted or beaded appearance. These constrictions correspond to the presence of valves in their interior. Lymphatics are found in nearly every texture and organ of the body, with the exception of the substance of the brain and spinal cord, the eyeball, cartilage, tendon, membranes of the ovum, the placenta, and umbilical cord, the nails, cuticle, and hair. Their existence in the substance of bone is doubtful. The lymphatics are arranged into a superficial and deep set. The superficial lymphatics, on the surface of the body, are placed immediately beneath the integu- ment, accompanying the superficial veins ; they join the deep lymphatics in certain situations by perforating the deep fascia. In the interior of the body, they lie in the submucous areolar tissue, throughout the whole length of the gastro-pulmonary and genito- urinary tracts ; or in the subserous areolar tissue, beneath the serous membrane covering the various organs in the cranial, thoracic, and abdominal cavities. These vessels probably arise in the form of a dense plexiform network interspersed among the proper elements and bloodvessels of the several tissues; the vessels composing which, as well as the meshes between them, are much larger than those of the capillary plexus. From these networks small vessels emerge, which pass, either to a neighboring gland, or to join some larger lymphatic trunk. The deep lymphatics, fewer in number, and larger than the superficial, accompany the deep bloodvessels. Their mode of origin is not known; it is, however, probably similar to that of the superficial vessels. The lymphatics of any part or organ exceed, in number, the veins; but in size, they are much smaller. Their anastomoses also, especially of the large trunks, are more frequent, and are effected by vessels equal in diameter to those which they connect, the continuous trunks retaining the same diameter. The lymphatic vessels, like arteries and veins, are composed of three coats. The internal is an epithelial and elastic coat ; it is thin, transparent, slightly elastic, and ruptures sooner than the other coats. It is composed of a layer of elongated epithelial cells, supported on a simple network of elastic fibres. The middle coat is composed of smooth muscular and fine elastic fibres disposed in a transverse direction. The external or areolo-fibrous coat consists of filaments of areolar tissue, intermixed with smooth muscular fibres, longitudinally or obliquely disposed. It forms a protective covering to the other coats, and serves to connect the vessel with the neighboring structures. 31 481 482 LYMPHATICS. The lymphatics are supplied by nutrient vessels, which are distributed to their outer and middle coats ; but no nerves have at present been traced into them. The lymphatics are very generally provided with valves, which assist materially in effecting the circulation of the fluid they contain. They are formed of a thin layer of fibrous tissue, lined on both surfaces with scaly epithelium. Their form is semilunar ; they are attached by their convex edge to the sides of the vessel, the concave edge being free, and directed in the course of the contained current. Usually, two such valves, of equal size, are found placed opposite one another ; but occasionally exceptions occur, especially at or near the anastomoses of lymphatic vessels. Thus one valve may be of very rudimentary size, the other increased in proportion. In other cases, the semilunar flaps have been found directed trans- versely across the vessel, instead of obliquely, so as to impede the circulation in both directions, but not to completely arrest it in either ; or the semilunar flaps, taking the same direction, have been united on one side, so that they formed, by their union, a transverse septum, having a partial transverse slit ; and sometimes the flap was constituted of a circular fold, attached to the entire circumference of the vessel, and having in its centre a circular or elliptical aperture, the arrange- ments of the flaps being similar to those composing the ileo-ceecal valve. The valves in the lymphatic vessels are placed at much shorter intervals than in the veins. They are most numerous near the lymphatic glands, and they are found more frequently in the lymphatics of the neck and upper extremity, than in the lower. The wall of the lymphatics, immediately above the point of attachment of each segment of a valve, is expanded into a pouch or sinus, which gives to these vessels, when distended, the knotted or beaded appearance which they present. Valves are wanting in the vessels composing the plexiform network in which the lymphatics originate. There is no satisfactory evidence to prove that any natural communication exists between the lymphatics of glandular organs and their ducts, or between the lymphatics and the capillary vessels. The lymphatic or absorbent glands, named also conglobate glands, are small solid glandular bodies, situated in the course of the lymphatic and lacteal vessels. They are found in the neck and on the external parts of the head ; in the upper extremity, in the axilla and front of the elbow ; in the lower extremity, in the groin and popliteal space. In the abdomen, they are found in large numbers in the mesentery, and along the side of the aorta, vena cava, and iliac vessels ; and in the thorax, in the anterior and posterior mediastina. They are somewhat flattened, and of a round or oval form. In size, they vary from a hempseed to an almond, and their color, on section, is of a pinkish-gray tint, excepting the bronchial glands which in the adult are mottled with black. Each gland has a layer of cellular tissue investing it, forming a capsule, from which prolongations dip into its substance forming partitions. The lymphatic and lacteal vessels pass through these bodies in their passage to the thoracic and lymphatic ducts. A lymphatic or lacteal, previous to its entering a gland, divides into several small branches, which are named afferent vessels. As they enter, their external coat becomes continuous with the capsule of the gland, and the vessels, much thinned, and consisting only of their internal coat and epithelium, pass into the gland, where, subdividing, they pursue a tortuous course ; and finally anastomosing form a plexus. The vessels composing this plexus unite to form two or more efferent vessels, which on emerging from the gland are again invested with their external coat. Within the lymphatic vessels, as supposed by Kolliker, Goodsir, and others, or lying between them, grouped in cells, like the acini of secreting glands, is a large number of minute dotted corpuscles. They are spheroidal or disk-shaped pellucid particles, about -g^Vtr of an inch in diameter, having two or three minute dark particles in their interior. It is probable that they play an important part in the more complete elaboration of the lymph or chyle traversing the glands. Capillary vessels are abundantly distributed on the walls of the lymphatics in the glands. THORACIC DUCT. 483 Thoracic Duct. The Thoracic Duct (fig. 247) conveys the great mass of the lymph and chyle into the blood. It is the common trunk of all the lymphatic vessels of the body, excepting those of the right Side of the head, neck, and &S- 247.-The Thoracic and Right Lymphatic Ducts. thorax, and right upper ex- tremity, the right lung, right side of the heart, and the convex surface of the liver. It varies from eighteen to twenty inches in length in the adult, and extends from the second lumbar vertebra to the root of the neck. It commences in the abdomen by a triangular dilatation, the receptaculum chyli (reservoir or cistern of Pecquet), which is situated upon the front of the body of the second lumbar vertebra, to the right side of and behind the aorta, by the side of the right crus of the Diaphragm. It ascends into the thorax through the aortic opening in the Diaphragm, and is placed in the posterior mediastinum in front of the vertebral column, lying be- tween the aorta and vena azygos. Opposite the fourth dorsal vertebra it inclines to- wards the left side and ascends behind the arch of the aorta, on the left side of the oeso- phagus, and behind the first portion of the left subclavian artery, to the upper orifice of the thorax. Opposite the upper border of the seventh cervical vertebra it curves downwards above the sub- clavian artery, and in front of the Scalenus muscle, so as to form an arch ; and ter- minates near the angle of junction of the left internal jugular and subclavian veins. The thoracic duct, at its com- mencement, is about equal in size to the diameter of a goose- quill, diminishes considerably in its calibre in the middle of the thorax, and is again dilated just before its termination. It is generally flexuous in its course, and constricted at intervals so as to present a varicose 484 LYMPHATICS. appearance. The thoracic duct not unfrequently divides in the middle of its course into two branches of unequal size which soon reunite, or into several branches which form a plexiform interlacement. It occasionally bifurcates, at its upper part, into two branches, the left one terminating in the usual manner, the right one opening into the right subclavian vein, in connection with the right lymphatic duct. The thoracic duct has numerous halves throughout its whole course, but they are more numerous in the upper than in the lower part ; at its termination it is provided with a pair of valves, the free borders of which are turned towards the vein, so as to prevent the regurgitation of venous blood into the duct. Branches. The thoracic duct at its commencement receives four or five large trunks from the abdominal lymphatic glands, and also the trunk of the lacteal vessels. Within the thorax, it is joined by the lymphatic vessels from the left half of the wall of the thoracic cavity, the lymphatics from the sternal and intercostal glands, those of the left lung, left side of the heart, trachea, and oeso- phagus ; and, just before its termination, receives the lymphatics of the left side of the head and neck, and left upper extremity. Structure. The thoracic duct is composed of three coats, which differ in some respects from those of the lymphatic vessels. The internal coat consists of a layer of epithelium, resting upon some striped lamellae, and an elastic fibrous coat, the fibres of which run in a longitudinal direction. The middle coat consists of a layer of connective tissue, beneath which are several laminae of muscular tissue, the fibres of which are disposed transversely, and intermixed with fine elastic fibres. The external coat is composed of areolar tissue, with elastic fibres and isolated fasciculi of muscular fibres. The Right Lymphatic Duct is a short trunk, about an inch in length, and a line or a line and a half in diameter, which receives the lymph from the right side of the head and neck, the right upper extremity, the right side of the thorax, the right lung and right side of the heart, and from the convex surface of the liver, and terminates at the angle of union of the right subclavian and right internal jugular veins. Its orifice is guarded by two semilunar valves, which prevent the entrance of blood from the veins. Lymphatics of the Head, Face, and Neck. The Superficial Lymphatic Glands of the Head (fig. 248) are of small size, few in number, and confined to its posterior region. They are the occipital, placed at the back of the head along the attachment of the Occipito-frontalis ; and the posterior auricular, near the upper end of the Sterno-mastoid. These glands become considerably enlarged in cutaneous affections and other diseases of the scalp. In the face, the superficial lymphatic glands are more numerous : they are the parotid, some of which are superficial and others deeply placed in its substance ; the zygomatic, situated under the zygoma ; the buccal, on the surface of the Buccinator muscle ; and the submaxillary, the largest, beneath the body of the lower jaw. The superficial lymphatics of the head are divided into an anterior and a posterior set, which follow the course of the temporal and occipital vessels. The temporal set accompany the temporal artery in front of the ear, to the parotid lymphatic glands, from which they proceed to the lymphatic glands of the neck. The occipital set follow the course of the occipital artery, descend to the occipital and posterior auricular lymphatic glands, and from thence join the cervical glands. The superficial lymphatics of the face are more numerous than those of the head. They commence over its entire surface, those from the frontal region accom- panying the frontal vessels; they then pass obliquely across the face, accompanying the facial vein, pass through the buccal glands on the surface of the Buccinator muscle, and join the submaxillary lymphatic glands. The latter receive the OF THE HEAD, FACE, AND NECK. 485 lymphatic vessels from the lips, and are often found enlarged in cases cf malignant disease of these parts. The deep lymphatics of the face are derived from the pituitary membrane of the nose, the mucous membrane of the mouth and pharynx, and the contents of the temporal aud orbital fossae; they accompany the branches of the internal maxillary artery, and terminate in the deep parotid and cervical lymphatic glands. The deep lymphatics of the cranium consist of two sets, the meningeal and cere- bral. The meningeal lymphatics accompany the meningeal vessels, escape through foramina at the base of the skull, and join the deep cervical lymphatic glands. Fig. 248. — The Superficial Lymphatics and Glands of the Head, Face and Neck. The cerebral tymphatics are described by Fohmann as being situated between the arachnoid and pia mater, as well as in the choroid plexuses of the lateral ven. tricles ; they accompany the trunks of the carotid and vertebral arteries, and pro- bably pass through foramina at the base of the skull, to terminate in the deep cervical glands. They have not at present been demonstrated in the dura mater, or in the substance of the brain. The Lymphatic Glands of the Neck are divided into two sets, superficial and deep. The superficial cervical glands are placed in the course of the external jugular vein, between the Platysma and Sterno-mastoid. They are most numerous at the root of the neck, in the triangular interval between the clavicle, the Sterno- 486 LYMPHATICS mastoid, and the Trapezius, where they are continuous with the axillary glands. A few small glands are also found on the front and sides of the larynx. The deep cervical glands (fig. 249) are numerous and of large size ; they form an uninterrupted chain along the sheath of the carotid artery and internal jugular vein, lying by the side of the pharynx, oesophagus, and trachea, and extending from the base of the skull to the thorax, where they communicate with the lym- phatic glands in this cavity. Fig. 249. — The Deep Lymphatics and Glands of the Neck and Thorax. The superficial and deep cervical lymphatics are a continuation of those already described on the cranium and face. After traversing the glands in those regions, they pass through the chain of glands which lie along the sheath of the carotid vessels, being joined by the lymphatics from the pharynx, oesophagus, larynx., trachea, and thyroid gland. At the lower part of the neck, after receiving some lymphatics from the thorax, they unite into a single trunk, which termi- nates on the left side, in the thoracic duct ; on the right side, in the right lym- phatic duct. Lymphatics of the Upper Extremity. The Lymphatic Glands of the upper extremity (fig. 250) may be subdivided into two sets, superficial and deep. OF THE UPPER EXTREMITY. 481 The superficial lymphatic glands are few, and. of small size. There are occa- sionally two or three in front of the elbow, and one or two above the internal condyle of the humerus, near the basilic vein. The deep lymphatic glands are also few in number. In the forearm a few small ones are occasionally found in the course of the radial and ulnar vessels ; and in the arm, there is a chain of small glands along the inner side of the brachial artery. Fig. 250. — The Superficial Lymphatics and Glands of the Upper Extremity. The axillary glands are of large size, and usually ten or twelve in number. A chain of these glands surrounds the axillary vessels, imbedded in a quantity of loose areolar tissue ; they receive the lymphatic vessels from the arm ; others are dispersed in the areolar tissue of the axilla : the remainder are arranged in two series, a small chain running along the lower border of the Pectoralis major, as far as the mammary gland, receiving the lymphatics from the front of the chest and mamma ; others are placed along the lower margin of the posterior wall of 488 LYMPHATICS. the axilla, which receive the lymphatics from the integument of the back. Two or three subclavian lymphatic glands are placed immediately beneath the clavicle; it is through these that the axillary and deep cervical glands communicate with each other. One is figured by Mascagni near the umbilicus. In malignant diseases, tumors, or other affections implicating the upper part of the back and shoulder^ the front of the chest and mamma, the upper part of the front and side of the abdomen, or the hand, forearm, and arm, the axillary glands are usually found enlarged. The superficial lymphatics of the upper extremity arise from the skin of the hand, and run along the sides of the fingers chiefly on the dorsal surface of the hand ; they then pass up the forearm, and subdivide into two sets, which take the course of the subcutaneous veins. Those from the inner border of the hand accom- pany the ulnar veins along the inner side of the forearm to the bend of the elbow, where they join with some lymphatics from the outer side of the forearm ; they then follow the course of the basilic vein, communicate with the glands immediately above the elbow, and terminate in the axillary glands, joining with the deep lymphatics. The superficial lymphatics from the outer and back part of the hand accompany the radial veins to the bend of the elbow, being less numerous than the preceding. Here the greater number join the basilic group ; the rest ascend with the cephalic vein on the outer side of the arm, some crossing obliquely the upper part of the Biceps to terminate in the axillary glands, whilst one or two accompany the cephalic vein in the cellular interval between the Pectoralis major and Deltoid, and enter the subclavian lymphatic glands. The deep lymphatics of the upper extremity accompany the deep bloodvessels. In the forearm, they consist of three sets, corresponding with the radial, ulnar, and interosseous arteries ; they pass through the glands occasionally found in the course of these vessels, and communicate at intervals with the superficial lymphatics. In their ascent upwards, some of them pass through the glands which lie upon the brachial artery ; they then enter the axillary and subclavian glands, and at the root of the neck terminate, on the left side in the thoracic duct, and on the right side in the right lymphatic duct. Lymphatics of the Lower Extremity. The Lymphatic Glands of the lower extremity may be subdivided into two sets, superficial and deep. The superficial lymphatic glands are confined to the inguinal region. The superficial inguinal glands, placed immediately beneath the integument, are of large size, and vary from eight to ten in number. They are divisible into two groups ; an upper, disposed irregularly along Poupart's ligament, receiving the lymphatic vessels from the integument of the scrotum, penis, parietes of the abdomen, perineum, and gluteal regions ; and an inferior group, which surrounds the saphenous opening in the fascia lata, a few being sometimes continued along the saphenous vein to a variable extent. The latter receive the superficial lymphatic vessels from the lower extremity. These glands frequently become enlarged in diseases implicating the parts from which their efferent lymphatics originate. Thus, in malignant or syphilitic affections of the prepuce and penis, the labia majora in the female, in cancer scroti, in abscess in the perineum, or in any other disease affecting the integument and superficial structures in these parts, or the sub-umbilical part of the abdomen or gluteal region, the upper chain of glands is almost invariably enlarged, the lower chain being implicated in diseases affecting the lower limb. The deep lymphatic glands are the anterior tibial, popliteal, deep inguinal, gluteal, and ischiatic. The anterior tibial gland is not constant in its existence. It is generally found by the side of the anterior tibial artery, upon the interosseous membrane at the upper part of the leg. Occasionally, two glands are found in this situation. OF THE LOWER EXTREMITY. 489 The deep popliteal glands, four or five in number, are of small size; they sur- round the popliteal vessels, imbedded in the cellular tissue and fat of the popliteal space. The deep inguinal glands are placed beneath the deep fascia around the femoral artery and vein. They are of small size, and communicate with the superficial inguinal glands through the saphenous opening. The gluteal and ischiatic glands are placed, the former above, the latter below, the Pyriformis muscle, resting on their corresponding vessels as they pass through the great sacro -sciatic foramen. The Lymphatics of the lower extremity, like the veins, may be divided into two sets, superficial and deep. The superficial lymphatics are placed between the integument and superficial fascia, and are divisible into two groups, an internal group, which follow the course of the internal saphenous vein; and an external group, which accompany the external saphenous. The internal group, the largest, com- mence on the inner side and dorsum of the foot ; they pass, some in front of, and some behind, the inner ankle, ascend the leg with the internal saphenous vein, pass with it behind the inner condyle of the femur, and accompany it to the groin, where they terminate in the group of in- guinal glands which surround the saphe- nous opening. Some of the efferent vessels from these glands pierce the cribriform fascia and sheath of the femoral vessels, and terminate in a lymphatic gland contained in the femoral canal, thus establishing a communication between the lymphatics of the lower extremity and those of the trunk ; others pierce the fascia lata, and join the deep inguinal glands. The external group arise from the outer side of the foot, ascend in front of the leg, and, just below the knee, cross the tibia from without inwards, to join the lym- phatics on the inner side of the thigh. Others commence on the outer side of the foot, pass behind the outer malleolus, and accompany the external saphenous vein along the back of the leg, where they enter the popliteal glands. The deep lymphatics of the lower ex- tremity are few in number, and accompany Fig. 251. — The Superficial Lymphatics and Glands of the Lower Extremity. Superficia 490 LYMPHATICS. the deep bloodvessels. In the leg, they consist of three sets, the anterior tibial, peroneal, and posterior tibial, which accompany the corresponding vessels, being two or three in number to each ; they ascend with the bloodvessels, and enter the lymphatic glands in the popliteal space. The efferent vessels from these glands accompany the femoral vein, and join the deep inguinal glands ; from these, the vessels pass beneath Poupart's ligament, and communicate with the chain of glands surrounding the external iliac vessels. The deep lymphatics of the gluteal and ischiatic regions follow the course of the bloodvessels, and join the gluteal and ischiatic glands at the great sacro-sciatic foramen. Lymphatics of the Pelvis and Abdomen. The Deep Lymphatic Glands in the Pelvis are, the external iliac, the internal iliac, and the sacral. Those of the abdomen are the lumbar glands. The external iliac glands form an uninterrupted chain round the external iliac vessels, three being placed round the commencement of the vessel just behind the crural arch. They communicate below with the femoral lymphatics, and above with the lumbar glands. The internal iliac glands surround the internal iliac vessels ; they receive the lymphatics corresponding to the branches of the internal iliac artery, and com- municate with the lumbar glands. The sacral glands occupy the sides of the anterior surface of the sacrum, some being situated in the mesorectal fold. These and the internal iliac glands become greatly enlarged in malignant disease of the bladder, rectum, or uterus. The lumbar glands are very numerous ; they are situated on the front of the lumbar vertebras, surrounding the common iliac vessels, the aorta, and vena cava ; they receive the lymphatic vessels from the lower extremities and pelvis, as well as from the testes and some of the abdominal viscera. The efferent vessels from these glands unite into a few large trunks, which, with the lacteals, form the com- mencement of the thoracic duct. In some cases of malignant disease, these glands become enormously enlarged, completely surrounding the aorta and vena cava, and occasionally greatly contracting the calibre of these vessels. In all cases of malignant disease of the testis, and in malignant disease of the lower limb, before any operation is attempted, careful examination of the abdomen should be made, in order to ascertain if any enlargement exists ; and if any should be detected, all operative measures are fruitless. The lymphatics of the pelvis and abdomen may be divided into two sets, superficial and deep. The superficial lymphatics of the walls of the abdomen and pelvis follow the course of the superficial bloodvessels. Those derived from the integument of the lower part of the abdomen below the umbilicus follow the course of the superficial epigastric vessels, and converge to the superior group of the superficial inguinal glands ; the deep set accompany the deep epigastric vessels, and communicate with the external iliac glands. The superficial lymphatics from the sides and lumbar part of the abdominal wall wind round the crest of the ilium, accompanying the super- ficial circumflex iliac vessels, to join the superior group of the superficial inguinal glands; the greater number, however, accompany the ilio-lumbar and lumbar vessels backwards, to join the lumbar glands. The superficial lymphatics of the gluteal region turn horizontally round the outer side of the nates, and join the superficial inguinal glands. The superficial lymphatics of the scrotum and perinseum follow the course of the external pudic vessels, and terminate in the superficial inguinal glands. The superficial lymphatics of the penis occupy the sides and dorsum of the organ, the latter receiving the lymphatics from the skin covering the glans penis; they all converge to the upper chain of the superficial inguinal glands. The deep lymphatic vessels of the penis follow the course of the internal pudic vessels, and join the internal iliac glands. OF THE PELVIS AND ABDOMEN 491 In the female, the lymphatic vessels of the mucous membrane of the labia, nymphae, and clitoris, terminate in the upper chain of the inguinal lymphatic glands. The deep lymphatics of the pelvis and abdomen take the course of the principal bloodvessels. Those of the parietes of the pelvis, which accompany the gluteal, ischiatic, and obturator vessels, follow the course of the internal iliac artery, and ultimately join the lumbar lymphatics. Fig. 252. — The Deep Lymphatic Vessels and Glands of the Abdomen and Pelvis. Sxttrnal Ilia* daul* Clanrti Sacral G//z>/ch Internal \lliae Glands Deej} Lymphati.es of Pe M 3 The efferent vessels from the inguinal glands enter the pelvis beneath Poupart's ligament, where they lie in close relation with the femoral vein ; they then pass through the chain of glands surrounding the external iliac vessels, and finally terminate in the lumbar glands. They receive the deep epigastric, circumflex iliac, and ilio-lumbar lymphatics. 492 LYMPHATICS. The lymphatics of the Madder arise from the entire surface of the organ ; the greater number run beneath the peritoneum on its posterior surface, and, after passing through the lymphatic glands in this situation, join with the lymphatics from the prostate and vesicular seminales, and enter the internal iliac glands. The lymphatics of the rectum are of large size ; after passing through some small glands that lie upon its outer wall and in the mesorectum, they pass to the sacral or lumbar glands. The lymphatics of the uterus consist of two sets, superficial and deep; the former being placed beneath the peritoneum, the latter in the substance of the organ. The lymphatics of the cervix uteri, together with those from the vagina, enter the internal iliac and sacral glands ; those from the body and fundus of the uterus pass outwards in the broad ligaments, and, being joined by the lymphatics from the ovaries, broad ligaments, and Fallopian tubes, ascend with the ovarian vessels to open into the lumbar glands. In the unimpregnated uterus, they are small ; but during gestation they become very greatly enlarged. The lymphatics of the testicle consist of two sets, superficial and deep; the former commence on the surface of the tunica vaginalis, the latter in the epidi- dymis and body of the testis. They form several large trunks, which ascend with the spermatic cord, and, accompanying the spermatic vessels into the abdomen, open into the lumbar glands ; hence the enlargement of these glands in malignant disease of the testis. The lymphatics of the kidney arise on the surface, and also in the interior of the organ; they join at the hilus, and, after receiving the lymphatic vessels from the ureter and supra-renal capsule, open into the lumbar glands. The lymphatics of the liver are divisible into two sets, superficial and deep. The former arise in the sub-peritoneal areolar tissue over the entire surface of the organ. Those on the convex surface may be divided into four groups : — 1. Those which pass from behind forwards, consisting of three or four branches, which ascend in the longitudinal ligament, and unite to form a single trunk, which passes up between the fibres of the Diaphragm, behind the ensiform cartilage, to enter the anterior mediastinal glands, and finally ascends to the root of the neck, to terminate in the right lymphatic duct. 2. Another group, which also incline from behind forwards, are reflected over the anterior margin of the liver to its under surface, and from thence pass along the longitudinal fissure to the glands in the gastro-hepatic omentum. 3. A third group incline outwards to the right lateral ligament, and, uniting into one or two large trunks, pierce the Diaphragm, and run along its upper surface to enter the anterior mediastinal glands; or, instead of entering the thorax, turn inwards across the crus of the Diaphragm, and open into the commencement of the thoracic duct. 4. The fourth group incline outwards from the surface of the left lobe of the liver to the left lateral ligament, pierce the Diaphragm, and, passing forwards, terminate in the glands in the anterior mediastinum. The superficial lymphatics on the under surface of the liver are divided into three sets: — 1. Those on the right side of the gall-bladder enter the lumbar glands. 2. Those surrounding the gall-bladder form a remarkable plexus, which accompanies the hepatic vessels, and open into the glands in the gastro-hepatic omentum. 3. Those on the left of the gall-bladder pass to the oesophageal glands, and to those placed along the lesser curvature of the stomach. The deep lymphatics accompany the branches of the portal vein and the hepatic artery and duct through the substance of the liver ; passing out at the transverse fissure, they enter the lymphatic glands along the lesser curvature of the stomach and behind the pancreas, or join with one of the lacteal vessels previous to its termination in the thoracic duct. The lymphatic glands of the stomach are of small size ; they are placed along the lesser and greater curvatures, some within the gastro-splenic omentum, whilst others surround its cardiac and pyloric orifices. The lymphatics of the stomach consist of two sets, superficial and deep ; the OF THE INTESTINES AND THORAX. 493 former originating in the subserous, and the latter in the submucous coat. They follow the course of the bloodvessels, and may consequently be arranged into three groups. The first group accompany the coronary vessels along the lesser curvature, receiving branches from both surfaces of the organ, and pass to the glands around the pylorus. The second group pass from the great end of the stomach, accompany the vasa brevia, and enter the splenic lymphatic glands. The third group run along the greater curvature with the right gastro-epiploic vessels, and terminate at the root of the mesentery in one of the principal lacteal vessels. The lymphatic glands of the spleen occupy the hilus. Its lymphatic vessels consist of two sets, superficial and deep ; the former are placed beneath its peritoneal covering, the latter in the substance of the organ : they accompany the blood- vessels, passing through a series of small glands, and, after receiving the lymphatics from the pancreas, ultimately pass into the thoracic duct. The Lymphatic System of the Intestines. The lymphatic glands of the small intestine are placed between the layers of the mesentery, occupying the meshes formed by the superior mesenteric vessels, and hence called mesenteric glands. They vary in number from a hundred to a hundred and fifty ; and in size, from that of a pea to that of a small almond. These glands are most numerous, and largest, superiorly near the duodenum, and inferiorly opposite the termination of the ileum in the colon. The latter group become greatly enlarged and infiltrated with deposit in cases of fever accompanied with ulceration of the intestines. The lymphatic glands of the large intestine are much less numerous than the mesenteric glands ; they are situated along the vascular arches formed by the arteries previous to their distribution, and even sometimes upon the intestine itself. They are fewest in number along the transverse colon, where they form an unin- terrupted chain with the mesenteric glands. The lymphatics of the small intestine are called lacteals, from the milk-white fluid they usually contain ; they consist of two sets, superficial and deep ; the former lie beneath the peritoneal coat, taking a longitudinal course along the outer side of the intestine ; the latter occupy the submucous tissue, and course transversely round the intestine, accompanied by the branches of the mesenteric vessels: they pass between the layers of the mesentery, enter the mesenteric glands, and finally unite to form two or three large trunks, which terminate in the thoracic duct. The lymphatics of the large intestine consist of two sets: those of the caecum, ascending and transverse colon, which, after passing through their proper glands, enter the mesenteric glands ; and those of the descending colon and rectum, which pass to the lumbar glands. The Lymphatics of the Thorax. The deep lymphatic glands of the thorax are the intercostal, internal mammary, anterior mediastinal, and posterior mediastinal. The intercostal glands are small, irregular in number, and situated on each side of the spine, near the costo-vertebral articulations, some being placed between the two planes of intercostal muscles. The internal mammary glands are placed at the anterior extremity of each intercostal space, by the side of the internal mammary vessels. The anterior mediastinal glands are placed in the loose areolar tissue of the anterior mediastinum, some lying upon the Diaphragm in front of the pericardium, and others round the great vessels at the base of the heart. The posterior mediastinal glands are situated in the areolar tissue in the posterior mediastinum, forming a continuous chain by the side of the aorta and oesophagus; 494 LYMPHATICS. they communicate on each side with the intercostal, below with the lumbar glands, and above with the deep cervical. The superficial lymphatics of the front of the thorax run across the great Pectoral muscle, and those on the back part of this cavity lie upon the Trapezius and Latissimus dorsi; they all converge to the axillary glands. The lymphatics from the mamma run along the lower border of the Pectoralis major, through a chain of small lymphatic glands, and communicate with the axillary glands. The deep lymphatics of the thorax are the intercostal, internal mammary, and diaphragmatic. The intercostal lymphatics follow the course of the intercostal vessels, receiving lymphatics from the Intercostal muscles and pleura ; they pass backwards to the spine, and unite with lymphatics from the back part of the" thorax -and spinal canal. After traversing the intercostal glands, they incline down the spine, and terminate • in the thoracic duct. The internal mammary lymphatics follow the course of the internal mammary vessels ; they commence in the muscles of the abdomen above the umbilicus, communicating with the epigastric lymphatics, ascend between the fibres of the Diaphragm at its attachment to the ensiform appendix, and in their course behind the costal cartilages are joined by the intercostal lymphatics, terminating on the right side in the right lymphatic duct, on the left side in the thoracic duct. The lymphatics of the Diaphragm follow the course of their corresponding vessels, and terminate, some in front in the anterior mediastinal and internal mammary glands, some behind in the intercostal and hepatic lymphatics. The bronchial glands are situated round the bifurcation of the trachea and roots of the lungs. They are ten or twelve in number, the largest being placed opposite the bifurcation of the trachea, the smallest round the bronchi and their primary divisions for some little distance within the substance of the lungs. In infancy, they present the same appearance as lymphatic glands in other situations; in the adult they assume a brownish tinge, and in old age a deep black color. Occasionally they become sufficiently enlarged to compress and narrow the canal of the bronchi ; and they are often the seat of tubercle or deposits of phosphate of lime. The lymphatics of the lung consist of two sets, superficial and deep : the former are placed beneath the pleura, forming a minute plexus, which covers the outer surface of the lung; the latter accompany the bloodvessels, and run along the bronchi : they both terminate at the root of the lungs in the bronchial glands. The efferent vessels from these glands, two or three in number, ascend upon the trachea to the root of the neck, traverse the tracheal and oesophageal glands, and terminate on the left side in the thoracic duct, and on the right side in the right lymphatic duct. The cardiac lymphatics consist of two sets, superficial and deep ; the former arise in the subserous areolar tissue of the surface, and the latter beneath the internal lining membrane of the heart ; they follow the course of the coronary vessels. Those of the right side unite into a trunk at the root of the aorta, which, ascending across the arch of that vessel, passes backwards to the trachea, upon which it ascends, to terminate at the root of the neck in the right lymphatic duct; those of the left side unite into a single vessel at the base of the heart, which passing along the pulmonary artery, and traversing some glands at the root of the aorta, ascends on the trachea to terminate in the thoracic duct. The thymic lymphatics arise from the spinal surface of the thymus gland, and terminate on each side in the internal jugular veins. The thyroid lymphatics arise from either lateral lobe of the thyroid gland ; they converge to form a short trunk, which terminates on the right side in the right lymphatic duct, on the left side in the thoracic duct. The lymphatics of the oesophagus form a plexus round that tube, traverse the glands in the posterior mediastinum, and, after communicating with the pulmonary lymphatic vessels near the roots of the lungs, terminate in the thoracic duct. Nervous System. The Nervous System consists of a series of connected central organs, called collectively, the cerebrospinal centre or axis, of the ganglia, and of the nerves. The cerebrospinal portion of the nervous system includes the brain and spinal cord, with the nerves connected with them, and the ganglia seated upon these nerves. It was distinguished, by Bichat, as the nervous system of animal life. It includes those nervous organs in and through which the several functions of the mind are more immediately connected ; the nerves of the senses, and those relating to volition and common sensation, are connected with it, as well as those concerned in many nervous actions, with which the mind has no connection. The ganglionic or sympathetic system consists of a double chain of ganglia connected by nervous cords, situate along the spinal column; and from which nerves with ganglia developed upon them proceed to the viscera in the thoracic, abdominal and pelvic cavities. It was distinguished, by Bichat, as the nervous system of organic life. This system is less immediately connected with the mind, appearing to be more closely concerned than the cerebro-spinal system with the processes of organic life. The several organs of the nervous system are composed of two different substances, which differ from each other in density, color, in their minute struc- ture, and in their chemical composition. They are called the vesicular nervous matter and the fibrous nervous matter. The former is often called the gray or cineritious substance ; and the latter, the white or medullary. The fibrous nervous matter is most extensively diffused throughout the body. It forms a large portion of the nervous centres, either alone, or mixed with vesicular matter ; and is the principal constituent of the nerves which connect them with the various tissues and organs. The vesicular nervous matter is usually known by its soft consistence, and dark reddish-gray color ; it is generally collected into masses intermingled with the fibrous structure, in various parts of the brain and spinal cord, and in the several ganglia. Chemical Composition. The following analysis by Lassaighe represents the relative proportion of the different constituents composing the gray and white matter of the brain : — Gray. White Water .... . 85.2 . 73.0 Albuminous matter . . 7.5 . 9.9 Colorless fat . 1.0 . 13.9 Red fat ... . . 3.7 0.9 Osmazome and lactates . 1.4 1.0 Phosphates . 1.2 1.3 100.0 100.0 It appears from this analysis that the cerebral substance consists of albumen, dissolved in water, combined with fatty matters and salts. The fatty matters, according to Fremy, consist of cerebric acid, which is most abundant, cholesterin, oleophosphoric acid, and olein, margarin, and traces of their acids. The same analyst states, that the fat contained in the brain is confined almost exclusively to the white substance, and that its color becomes lost when the fatty matters are removed. According to Vauquelin, the cord contains a larger proportion of fat 495 496 NERVOUS SYSTEM. than tlie brain ; and, according to L'Heritier, the nerves contain more albumen and more soft fat than the brain. Microscopic Structure. The fibrous nervous matter consists of two different kinds of nerve fibres, which are distinguished as the tubular fibre and the gela- tinous fibre. In most nerves these two kinds are intermingled; the tubular fibres being more numerous in the nerves of the cerebro-spinal system, the gela- tinous predominating in the nerves of the sympathetic system. • The tubular fibres appear to consist of tubules of simple membrane, homogeneous in structure, and analogous to the sarcolemma of striped muscle. Within is the proper nerve substance, composed apparently of two different materials ; the central part, which occupies the axis of the nerve tube, is a transparent material, termed the axis cylinder ; while the outer portion, which forms a tube within the tubular membrane, inclosing the axis-cylinder, is usually opaque and dimly granular, as if from a kind of coagulation, and is generally known as the white substance of Schwann. The peculiar white appearance of the cerebro-spinal nerves is principally due to the large amount of the white substance of Schwann which they contain. It is probable that the essential element of the nerve tube is the axis cylinder, the tubular membrane and white substance of Schwann affording me- chanical protection to this substance, insulating it from the constituent parts of the neighboring fibres. In a perfectly fresh state, the nerve tubes present the appearance of simple membranous tubes, perfectly cylindrical, and containing a transparent and ap- parently homogeneous material ; but shortly after death, when pressed or separated by coarse manipulation, they undergo changes which render it probable that their contents are composed of the two materials above mentioned, for the fine outline of the previously cylindrical tube is exchanged for a dark double contour, the outer line being formed by the tubular sheath, the inner by the white substance of Schwann, at the same time the granular material collects into small masses which distend the tubular membrane at irregular intervals, while the intermediate spaces collapse, giving the fibres a varicose or beaded appearance. In the brain, spinal cord, and nerves of special sense, the tubes are very apt to exhibit this change, owing to extreme thinness of the tubular membrane and to a diminished con- sistence of the contained nervous matter. The contents of the nerve tubes are extremely soft, for when subjected to slight pressure they readily pass from one part of the canal to another, and often cause a bulging at the side of the tube. The contents, also, readily escape on pressure from the extremities of the tube, assuming the appearance and form of globules, consisting of a transparent central part, surrounded by a layer of the white substance of Schwann, marked by its double contour. The nerve fibres vary in size ; they are largest within the trunk and branches of the nerves, measuring from tj^Vtt to 35VTT of an inch. They become gradually smaller as they approach the brain and spinal cord, and usually also in the tissues in which they are distributed. In the gray matter of the brain and spinal cord, they seldom measure more than TT j^t to y^^u of an inch. The gelatinous fibres constitute the main part of the trunk and branches of the sympathetic nerve, and are intermingled in various proportions in the cerebro-spinal nerves. When collected together in great numbers, they exhibit a yellowish-gray color. They are flattened, soft, and homogeneous in appearance, containing nuclei, of a round or oval form, arranged at nearly equal distances, and frequently presenting nucleoli. They vary in diameter, from ^^ to -^^ of an inch, and resemble much the fibres of unstriped muscle. They differ from the tubular fibres in their smaller size, being only one-half or one-third their size, in the absence of the double contour, their apparently uniform structure, and their yellowish-gray color. It appears probable that these nerves are composed ex- clusively of the substance which corresponds with the axis cylinder of the tubular nerves, and differs from them in not possessing the tubular membrane, and white substance of Schwann. GENERAL ANATOMY. 491 The vesicular nervous substance is distinguished by its dark reddish-gray color, and soft consistence. It is found in the brain, spinal cord, and various ganglia, intermingled with the fibrous nervous substance, but is never found in the nerves. It is composed, as its name implies, of vesicles or corpuscles, commonly called nerve or ganglion corpuscles, containing nuclei and nucleoli ; the vesicles being imbedded either in a finely granular substance, as in the brain, or in a capsule of nucleated cells, as in the ganglia. Each vesicle consists of an exceed- ingly delicate membranous wall, inclosing a finely granular material, part of which is occasionally of a coarser kind, and of a reddish or yellowish-brown color. The nucleus is vesicular, much smaller than the vesicle, and adherent t< > some part of its interior. The nucleolus, which is inclosed within the nucleus, is vesicular in form, of minute size, and peculiarly clear and brilliant. The nerve corpuscles vary in shape and size; some are small, spherical, or ovoidal, with an uninterrupted outline ; these forms being most numerous in the ganglia of the sympathetic. Others, called caudate or stellate nerve corpuscles, are characterized by their larger size, and from having one or more tail-like processes issuing from them, which occasionally divide and subdivide into numerous branches. These processes are very delicate, apparently tubular, and contain a similar granular material to that found within the corpuscle. Some of the processes terminate in fine transparent fibres, which become lost among the other elements of the nervous tissue; others may be traced until, after losing their granular appearance, they become continuous with an ordinary nerve fibre. The Ganglia may be regarded as separate and independent nervous centres, of smaller size and less complex structure than the brain, connected with each other, with the cerebro-spinal axis, and with the nerves in various situations. They are found on the posterior root of each of the spinal nerves ; on the posterior or sensory root of the fifth cranial nerve; on the facial nerve; on the glosso- pharyngeal and pneumogastric nerves ; in a connected series along each side of the vertebral column, forming the trunk of the sympathetic ; on the branches of that nerve in the head, neck, thorax, and abdomen ; or at the point of junction of branches of that nerve with the cerebro-spinal nerves. On section, they an; seen to consist of a reddish-gray substance, traversed by numerous white nerve fibres : they vary considerably in form and size, the largest being those found in the cavity of the abdomen; the smallest, the microscopic ganglia, which exist in considerable numbers upon the nerves distributed to the different viscera. The ganglia are invested by a smooth and firm closely-adhering membranous envelope, consisting of dense areolar tissue and continuous with the neurilemma of the nerves. It sends numerous processes into the interior of the ganglia, which support the bloodvessels supplying its substance. In structure, all ganglia are essentially similar, consisting of the same structural elements as the other nervous centres, viz., a collection of vesicular nervous matter, traversed by tubular and gelatinous nerve fibres. The vesicular nervous matter consists of nerve cells or ganglion -globules,, most of which appear free, and of a round or oval form, being more especially seated near the surface of the ganglion ; others have caudate processes, and give origin to nerve fibres. In the ganglia, the nerve cells are usually inclosed in a capsule of granular corpuscles and fibres. The tubular nerve fibres run through the ganglion, some being collected into bundles ; others, separating from each other, take a circuitous course among the nerve cells before leaving the ganglia. The Nerves are round or flattened cords, communicating, on the one hand, with the cerebro-spinal centre or the ganglia, and, by the other, distributed to the various textures of the body, forming the medium of communication between the two. The nerves are subdivided into two great classes, the cerebro-spinal, which proceed from the cerebro-spinal axis, and the sympathetic or ganglionic nerves, which proceed from the ganglia of the sympathetic ; the cerebro-spinal are the nerves of animal life, being distributed to the organs of the senses, the skin, and 32 498 NERVOUS SYSTEM. to the active organs of locomotion, the muscles. The sympathetic or ganglionic nerves are distributed chiefly to the viscera and bloodvessels, and are termed the nerves of organic life. The Cerebrospinal nerves consist of numerous nerve fibres, collected together and inclosed in a membranous sheath. A small bundle of primitive fibres, inclosed in a tubular sheath, is called a funiculus: if the nerve is of small size, it may consist only of a single funiculus, but, if large, the funiculi are collected together into larger bundles or fasciculi; and are bound together in a common membranous investment, termed the sheath. In structure, the common sheath investing the whole nerve, as well as the septa given off from it, which separate the fasciculi, consist of areolar tissue, composed of white and yellow elastic fibres, the latter existing in greatest abundance. The tubular sheath of the funiculi, the neurilemma, consists of a fine, smooth, transparent membrane, which may be easity separated, in the form of a tube, from the fibres it incloses; in structure, it is, for the most part, a simple and homogeneous transparent film, occasionally composed of numerous minute reticular fibres. The cerebro-spinal nerves consist almost exclusively of the tubular nerve fibres, the gelatinous fibres existing in very small proportion. The bloodvessels supplying a nerve terminate in a minute capillary plexus, the vessels composing which run, for the most part, parallel with the funiculi ; they are connected together by short transverse vessels, forming narrow oblong meshes, similar to the capillary system of muscle. The nerve fibres, as far as is at present known, do not coalesce, but pursue an uninterrupted course from the centre to the periphery. In dissecting a nerve, however, into its component funiculi, it may be seen that they do not pursue a perfectly insulated course, but occasionally join at a very acute angle with other funiculi proceeding in the same direction ; from these, again, branches are given off, which join again in like manner with other funiculi. It must be remembered, however, that in these communications the nerve fibres do not coalesce, but merely pass into the sheath of the adjacent, nerve, become intermixed with the nerve fibres, and again pass on to become blended with the nerve fibres in some adjoining fasciculus. Nerves, in their course, subdivide into branches, and these frequently commu- nicate with branches of a neighboring nerve. In the subdivision of a nerve, the filaments of which it is composed are continued from the trunk into the branches, and at their junction with the branches of neighboring nerves the filaments pass to become intermixed with those of the other nerve in their further progress ; in no instance, however, do the separate nerve fibres inosculate. The communications which take place between two or more nerves form what is called a plexus. Sometimes a plexus is formed by the primary branches of the trunks of the nerves, as the cervical, brachial, lumbar, and sacral plexuses, and occasionally by the terminal fasciculi, as in the plexuses formed at the periphery of the body. In the formation of a plexus, the component nerves divide, then join, and again subdivide in such a complex manner that the individual fasciculi become interlaced most intricately ; so that each branch leaving a plexus may contain filaments from each of the primary nervous trunks which form it. In the formation also of the smaller plexuses at the periphery of the body, there is a free interchange of the fasciculi and primitive fibrils. In each case, however, the individual filaments remain separate and distinct, and do not inosculate with each other. It is probable, that, through this interchange of fibres, the different branches passing off from a plexus have a more extensive connection with the spinal cord than if each of them had proceeded to be distributed without such connection with other nerves. Consequently, the parts supplied by these nerves have more ex- tended relations with the nervous centres ; by this means, also, groups of muscles may be associated for combined action. The termination of nerve fibres signifies their mode of distribution and con- GENERAL ANATOMY. 499 nection in the nerve centres, and in the different organs and tissues they supply ; the former are called their central, the latter their peripheral terminations. As to the mode in which the nerve fibres are disposed in the nervous centres, it is probable that many originate from nerve corpuscles, in the manner before men- tioned; others probably form simple loops. As to the more exact mode of connection of the nerve fibres with the nerve corpuscles, it appears that more commonly as the fibre approaches the vesicle, the white substance of Schwann gradually disappears, and the tubular membrane expands, so as to envelope the corpuscle ; the sheath, contracting at the opposite side of the corpuscle, is again continuous with the tubular sheath of the nerve fibre, a prolongation from the granular substance of the corpuscle extending for some distance along each, part of the nerve tube, and taking the place of the usual elements of the nerve fibre. "Whether this relation of nerve fibres to ganglion-corpuscles is common to all kinds of nerve fibre's, has yet to be determined. In the peripheral distribution of the nerves, small bundles of nerve fibres com- monly form delicate plexuses ; these, dividing, give off the primitive fibres, which are disposed of in various ways in different tissues. — 1. Occasionally the elemen- tary fibres are disposed in hops, as has been found in the internal ear, in the papiike of the tongue and of the skin, in the tooth pulp, and in striped muscular tissue ; each fibre, after issuing from a branch in a terminal plexus, runs over or through the substance of the tissue, and, turning back, joins the same or a neigh- boring branch, in which it probably passes back to a nervous centre. 2. Some- times each ultimate nerve fibre divides into several branches, which spread out in the substance of the tissue, as is seen in the retina, in the muscular tissue of the frog and lower vertebrata. 3. Sometimes the ultimate nerve fibres form minute plexuses, as in certain serous membranes, viz., the peritoneum, and in the pia mater of the brain and cord. 4. Not uncommonly the nerve fibres terminate by free ends, as is seen in the Pacinian corpuscles, and in some of the papiike of the skin. 5. Occasionally, the nerve fibres are brought into direct connection with nerve- corpuscles, as in the retina and in the lamina spiralis of the internal ear. Some nerve fibres have no peripheral termination. Gerber has shown, that nerve fibres occasionally form loops, by their j unction with a neighboring fibre in the same fasciculus, and return to the cerebro-spinal centre without having any peripheral termination. These he considers to be sentient nerves, appropriated exclusively to the nerve itself, the nervi nervorum, upon which the sensibility of the nerve depends, and quite exclusive of the sensation produced by an impression made at the peripheral end of the nerve. These fibres bear some analogy to those met with in the back part of the optic commissure, where a set of fibres passes from one optic tract across the commissure to the opposite tract, having no com- munication with the optic nerve ; also in the communications formed between the cervical nerves and spinal accessory and descendens noni, the nerve fibres forming an arch connected by each extremity with the cerebro-spinal centre, and having no peripheral termination. Again, some nerve fibres would appear to have no central connection with the cerebro-spinal centre, as those forming the most anterior part of the optic con> missure. These inter-retinal fibres, as they are called, commence in the retina, pass along the optic nerve, and across the commissure to the optic nerve and retina of the opposite side. The point of connection of a nerve with the brain or spinal cord is called, for convenience of description, its origin or root. If the fasciculi of which the nerve is composed should all arise at or near one point, or along one tract, the root is called single. If, on the contrary, the fasciculi divide into two separate bundles, which are connected at two different points with any part of the cerebro-spinal centre, such nerve is said to have a double origin, or to arise by two roots, each of which may have a separate function, as in the spinal nerves. The point where the separate fasciculi of a nerve are connected to the surface of the cerebro-spinai 500 NERVOUS SYSTEM. centre, is called the apparent origin of a nerve ; the term, real or deep origin, being given to that part of the centre from which a nerve actually springs. The Sympjathetic nerve consists of tubular and gelatinous fibres, intermixed with a varying proportion of filamentous areolar tissue, and inclosed in a sheath formed of fibro-areolar tissue. The tubular fibres are, for the most part, smaller than those composing the cerebro-spinal nerves; their double contour is less distinct, and, according to Eemak, they present nuclei similar to those found in the gelatinous nerve fibres. Those branches of the sympathetic which present a well-marked gray color are composed more especially of gelatinous nerve fibres, intermixed with few tubular fibres ; whilst those of a white color contain more of the tubular fibres, and few gelatinous. Occasionally the gray and white cords run together in a single nerve, without any intermixture, as in the branches of communication between the sympathetic ganglia and the spinal nerves, or in the communicating cords between the ganglia. The nerve fibres both of the cerebro-spinal and sympathetic system convey impressions of a twofold kind. The sensitive nerves, called also centripetal or afferent nerves, transmit impressions made upon their peripheral extremities to the nervous centres, and in this way the mind, through the medium of the brain, becomes conscious of external objects. The motor nerves, called also centrifugal or efferent nerves, transmit impressions from the nervous centres to the parts to which the nerves are distributed, these impressions either exciting muscular con- tractions, or influencing the processes of nutrition, growth, and secretion. The Cerebro-spinal Centre consists of two parts, the spinal cord and the ence- phalon : the latter may be subdivided into the cerebrum, the cerebellum, the pons Varolii, and the medulla oblongata. THE' SPINAL COED AND ITS MEMBRANES. Dissection. To dissect the cord and its membranes, it will be necessary to lay open the whole length of the spinal canal. For this purpose the muscles must be separated from the vertebral grooves, so as to expose the spinous processes and laminae of the vertebrae ; and the hitter must be sawn through on each side, close to the roots of the transverse processes, from the third or fourth cervical vertebra, above, to the sacrum below. The vertebral arches haviDg been dis- placed, by means of a chisel, and the separate fragments removed, the dura mater will be exposed, covered by a plexus of veins and a quantity of loose areolar tissue, often infiltrated with a serous fluid. The arches of the upper vertebrae are best divided by means of a strong pair of forceps. Membeanes of the Cord. The membranes which envelop the spinal cord are three in number. The most external is the dura mater, a strong fibrous membrane, which forms a loose sheath around the cord. The most internal is the pia mater, a cellulo- vascular membrane, which closely invests the entire surface of the cord. Between the two, is the arachnoid membrane, an intermediate serous sac, which envelopes the cord, and is then reflected on the inner surface of the dura mater. The Dura Mater of the cord, continuous with that which invests the brain, is a loose sheath which surrounds it, being separated from the bony walls of the spinal canal by a quantity of loose areolar adipose tissue, and a plexus of veins. It is attached to the circumference of the foramen magnum, and to the posterior common ligament, throughout the whole length of the spinal canal, by fibrous tissue ; and extends, below, as far as the top of the sacrum ; but, beyond this point, it is impervious, being continued, in the form of a slender cord, to the back of the coccyx, where it blends with the periosteum. This sheath is much larger tnan is necessary for its contents, and its size is greater in the cervical and lumbar regions, than in the dorsal. Its inner surface is smooth, and covered by a layer of polygonal cells ; and on each side may be seen the double openings which trans- mit the two roots of the corresponding spinal nerve, the fibrous layer of the dura /J~U* C^* a variable length become superficial. The longitudinal fibres are more superficial, run nearly parallel with each other, and form the greater portion of the white columns. The gray substance of the cord con- sists of, 1. Nerve fibres of variable, but smaller, average diameter than those of the columns. 2. Nerve cells of various shapes and sizes, with from two to eight processes. 3. Bloodvessels and con- nective tissue. Each lateral half of the gray sub- stance is divided into an anterior and posterior horn, and the tractus inter- medio lateralis, or lateral part of the gray substance between the anterior aud posterior cornua. The posterior horn consists of two parts, the caput cornu, or expanded ex- tremity of the horn (fig. 257), round which is the lighter space or lamina, the gelatinous substance; and the cervix cornu, or remaining narrow portion of the horn, as far forwards as the central canal. The gelatinous substance contains along its border a series of large nerve cells ; but more internally consists of a stratum of small cells traversed by transverse, oblique, and longitudinal fibres (figs. 258 and 259). Fig. 258. — Transverse Section of the gray substance of the spinal cord through the middle of the lumbar enlargement. On the left side the groups of large cells are seen ; on the right side the course of the fibres without the cells. Magnified 13 diameters. i.fc.ftr&SV'f Nearly the whole inner half of the cervix is occupied by a remarkable and important column of nerve cells, called the posterior vesicular column (fig. 257), which varies in size and appearance in different regions of the cord, and is intimatelv connected with the posterior roots of the nerves. 506 NERVOUS SYSTEM. Fig. 259.— Longitudinal Section of the white and gray substance of the spinal cord, through the middle of the lambar enlargement. Mag. 14 diam. Within and along the outer border of the cervix are several thick bundles of longitudinal fibres, represented in the adjoining figure by the dark spots ; other bundles of the same kind may be seen in the gray substance along the line of junction of the caput with the cervix cornu (fig. 258). The anterior horn of the gray substance in the cervical and lumbar swellings, where it gives origin to the nerves of the extremities, is much larger than in any other region, and contains several distinct groups of large and variously shaped cells. This is well shown on comparing the above figures. The tractus intermedia lateralis (fig. 257) extends from the upper part of the lumbar to the lower part of the cervical enlargement, and consists of variously shaped cells, which are smaller than those of the anterior cornu. In the neck above the cervical en- largement, a similar tract reappears, and is traversed by the lower part of the spinal accessory nerve. Origin of the Spinal Nerves. The posterior roots are larger than the anterior; but their component filaments are finer and more delicate. They are all attached immediately to the posterior columns only, and decussate with each other in all directions through the columns; but some of them pass through the gray substance into both the lateral and anterior columns. Within the gray substance, they run lon- gitudinally upwards and downwards ; transversely through the posterior commissure to the opposite side ; and into the anterior cornu of their own side (figs. 258 and 259). The anterior roots are attached exclusively to the anterior columns, or rather to the anterior part of ihe antero-lateral columns ; for there is no antero-lateral fissure dividing the anterior from the lateral column. Within the gray substance, the fibrils cross each other, and diverge in all directions like the expanded hairs of abrush (figs. 258 and 259), some of them running more or less longitudinally upwards and downwards ; and others decussating with those of the opposite side through the anterior commissure in front of the cen- tral canal. All the fibres of both roots of the nerves proceed through the white columns into the gray substance, with, perhaps, the exception of some which appear to run longitudinally in the posterior columns ; but whether these latter fibres of the posterior roots ulti- mately enter the gray substance of the cord after a very oblique course, or whether they proceed upwards to the brain, is uncertain.' 6e(at Salsl'ctnce Grey Substance Mt T Boots The Central Canal. In the foetus, until after the sixth month, a canal, continuous with the general ventricular cavity of the brain, extends throughout the entire length of the spinal cord, formed by the closing-in of a previously open groove. In the adult, this canal can only be seen at the upper part of the cord, extending from the point of the calamus scriptorius, in the floor of the fourth ventricle, for about half an inch down the centre of the cord, where it terminates in a cul-de- sac ; the remnant of the canal being just visible in a section of the cord, as a small, pale spot, corresponding to the centre of the gray commissure, its cavity being lined with a layer of cylindrical ciliated epithelium. In some cases, this canal remains pervious throughout the whole length of the cord. 1 The above description, and accompanying illustrations, kindly furnished me by my friend, Mr. Lockhart Clarke, embodies a condensed account of his laborious and extensive observations on the structure of the spinal cord. For further information on this subject, vide Phil. Traus. iS51— 1853, Part iii. ; 1858, Part i. ; 1859, Part i. DURA MATER. 50? THE BRAIN AND ITS MEMBRANES. Dissection. To examine the brain with its membranes, the skull-cap should first be removed. This may be effected by sawing through the external table, commencing, in front, about an inch above the margin of the orbit, and extending, behind, to a level with the occipital protuberance. The internal table must then be broken through with the chisel and hammer, to prevent injury to the investing membranes or brain, and, after having been loosened, it should be forcibly detached, when the dura mater will be exposed. The adhesion between the bone and the dura mater is very intimate, and much more so in the young subject than in the adult. The membranes of the brain are, the dura mater, arachnoid membrane, and pia mater. Dura Matee. The dura mater is a thick and dense inelastic fibrous membrane, which lines the interior of the skull. Its outer surface is rough and fibrillated, and adheres closely to the inner surface of the bones, forming their internal periosteum, this adhesion being more intimate opposite the sutures and at the base of the skull ; at the margin of the foramen magnum it becomes continuous with the dura mater lining the spinal canal. Its inner surface is smooth and epitheliated, being lined by the parietal layer of the arachnoid. The dura mater is, therefore, a fibro-serous membrane, composed of an external fibrous lamella, and an internal serous layer. It sends numerous processes inwards, into the cavity of the skull, for the support and protection of the different parts of the brain ; it is also pro- longed to the outer surface of the skull, through the various foramina which exist at its base, where it is continuous with the pericranium; and its fibrous layer forms sheaths for the nerves which pass through these apertures. At the base of the skull, it sends a fibrous prolongation into the foramen caecum ; it lines the olfactory groove, and sends a series of tubular prolongations round the filament; of the olfactory nerves as they pass through the cribriform foramina ; a prolonga- tion is also continued through the sphenoidal fissure into the orbit, and another is continued into the same cavity through the optic foramen, forming a sheath for the optic nerve, which is continued as far as the eyeball. In certain situations in the skull already mentioned, the fibrous layers of this membrane subdivide, to form sinuses for the passage of venous blood. Upon the upper surface of the dura mater, in the situation of the longitudinal sinus, may be seen numerous small whitish bodies, the gland ul® Pacchioni. Structure. The dura mater consists of white fibrous and elastic tissues, arranged in flattened laminae, which intersect one another in every direction. , Its arteries are very numerous, but are chiefly distributed to the bones. Those found in the anterior fossa are the anterior meningeal, from the anterior and posterior ethmoidal, and internal carotid. In the middle fossa are the middle and small meningeal, from the internal maxillary, and a third branch from the ascending pharyngeal, which enters the skull through the foramen lacerum basis cranii. In the posterior fossa, are the posterior meningeal branch of the occipital, which enters the skull through the jugular foramen; the posterior meningeal, from the vertebral ; and occasionally meningeal branches from the ascending pharyn- geal, which enter the skull, one at the jugular foramen, the other at the anterior condyloid foramen. The veins, which return the blood from the dura mater, and partly from the bones, anastomose with the diploic veins. These vessels terminate in the various sinuses, with the exception of two which accompany the middle meningeal artery; these pass from the skull at the foramen spinosum. The nerves of the dura mater are, the recurrent branch of the fourth, and fila- ments from the Casserian ganglion, the ophthalmic nerve, and sympathetic. The so-called glandulae Pacchioni are numerous small whitish granulations, usually collected into clusters of variable size, which are found in the following situations : 1. Upon the outer surface of the dura mater, in the vicinity of the 508 NERVOUS SYSTEM. superior longitudinal sinus, being received into little depressions on the inner surface of the calvarium. 2. On the inner surface of the dura mater. 3. In the superior longitudinal sinus. 4. On the pia mater near the margin of the hemispheres. These bodies are not glandular in structure, but consist of a fibro-cellular matrix originally developed from the pia mater ; by their growth, they produce absorption or separation of the fibres of the dura mater; in a similar manner they make their way into the superior longitudinal sinus, where they are covered by the lining membrane. The cerebral layer of the arachnoid in the situation of these growths is usually thickened and opaque, and adherent to the parietal portion. These bodies are not found in infancy, and very rarely until the third year. They are usually found after the seventh year ; and from this period they increase in number as age advances. Occasionally they are wanting. Processes of the Dura Mater. The processes of the dura mater, sent inwards into the cavity of the skull, are three in number, the falx cerebri, the tentorium cerebelli, and the falx cerebelli. The falx cerebri, so named from its sickle-like form, is a strong arched process of the dura mater, which descends vertically in the longitudinal fissure between the two hemispheres of the brain. It is narrow in front, where it is attached to the crista galli process of the ethmoid bone ; and broad behind, where it is connected with the upper surface of the tentorium. Its upper margin is convex, and attached to the inner surface of the skull as far back as the internal occipital protuberance. In this situation, it is broad, and contains the superior longitudinal sinus. Its lower margin is free, concave, and presents a sharp curved edge which contains the inferior longitudinal sinus. The tentorium cerebelli, so named from its tent-like form, is an arched lamina of dura mater, elevated in the middle, and inclining downwards towards its cir- cumference. It covers the upper surface of the cerebellum, supporting the posterior lobes of the brain, and preventing their pressure upon it. It is attached, behind, by its convex border, to the transverse ridges upon the inner surface of the occi- pital bone, and there incloses the lateral sinuses ; in front, to the superior margin of the petrous portion of the temporal bone, inclosing the superior petrosal sinuses, and from the apex of this bone, on each side, is continued to the anterior and posterior clinoid processes. Along the middle line of its upper surface, the pos- terior border of the falx cerebri is attached, the straight sinus being placed at their point of junction. Its anterior border is free and concave, and presents a large oval opening for the transmission of the crura cerebri. The falx cerebelli is a small triangular process of dura mater, received into the indentation between the two lateral lobes of the cerebellum behind. Its base is attached, above, to the under and back part of the tentorium ; its posterior margin, to the lower division of the vertical crest on the inner surface of the occipital bone. As it descends, it sometimes divides into two smaller folds, which are lost on the sides of the foramen magnum. Arachnoid Membrane. The arachnoid (apa^, f ZSoj, like a spider's web), so named from its extreme thinness, is the serous membrane which, envelops the brain, and is then reflected on the inner surface of the dura mater. Like other serous membranes, it is a shut sac, and consists of a parietal and a visceral layer. The parietal layer covers the inner surface of the dura mater, 1 and gives this membrane the smooth and polished surface which it presents ; it is also reflected over those processes which separate the hemispheres of the brain and cerebellum. 1 Kolliker denies this ; and states, that the inner surface of the dura mater is covered with pavement epithelium, but has no other investment which can be regarded as a parietal layer of the arachnoid. PIA MATER. 509 The visceral layer invests the brain more loosely, being separated from direct contact with the cerebral substance by the pia mater, and a quantity of loose areolar tissue, the sub-arachnoidean. On the upper surface of the cerebrum, the arachnoid is thin and transparent, and may be easily demonstrated by injecting a stream of air beneath it by means of a blowpipe ; it passes over the convolutions without dipping down into the sulci between them. At the base of the brain, the arachnoid is thicker, and slightly opaque towards the central part ; it covers the anterior lobes, is extended across between the two middle lobes, so as to leave a considerable interval between it and the brain, the anterior sub-arachnoidean spiace; it is closely adherent to the pons and under surface of the cerebellum ; but between the hemi- spheres of the cerebellum and the medulla oblongata, another considerable interval is left between it and the brain, called the posterior sub-arachnoidean space. These two spaces communicate together across the crura cerebri. The arachnoid mem- brane surrounds the nerves which arise from the brain, and incloses them in loose sheaths as far as their point of exit from the skull, where it becomes continuous with the parietal layer. The sub-arachnoid space is the interval between the arachnoid and pia mater : this space is narrow on the surface of the hemispheres ; but at the base of the brain, a wide interval is left between the two middle lobes, and behind, between the hemispheres of the cerebellum and the medulla oblongata. This space is the seat of an abundant serous secretion, the cerebro-spinal fluid, which fills up the interval between the arachnoid and pia mater. The sub-arachnoid space usually communicates with the general ventricular cavity of the brain, by means of an opening in the inferior boundary of the fourth ventricle. The sac of the arachnoid also contains serous fluid ; this is, however, small in quantity compared with the cerebro-spinal fluid. Structure. The arachnoid consists of bundles of white fibrous and elastic tissues intimately blended together. Its outer surface is covered with a layer of scaly epithelium. It is destitute of vessels, and the existence of nerves in it has not been satisfactorily demonstrated. The cerebro-spinal fluid fills up the sub-arachnoid space, keeping the opposed surfaces of the arachnoid membrane in contact. It is a clear, limpid fluid, having a saltish taste, and a slightly alkaline reaction. According to Lassaigne, it con- sists of 98.5 parts of water, the remaining 1.5 per cent, being solid matters, animal and saline. It varies in quantity, being most abundant in old persons, and is quickly reproduced. Its chief use is probably to afford mechanical protection to the nervous centres, and to prevent the effects of concussions communicated from without. Pia Mater. The Pia Mater is a vascular membrane, and derives its blood from the internal carotid and vertebral arteries. It consists of a minute plexus of bloodvessels, held together by an extremely fine areolar tissue. It invests the entire surface of the brain, dipping down between the convolutions and laminae, and is prolonged iuto the interior, forming the velum interpositum and choroid plexuses of the fourth ventricle. Upon the surface of the hemispheres, where it covers the gray matter of the convolutions, it is very vascular, and gives off from its inner surface a multitude of minute vessels, which extend perpendicularly for some distance into the cerebral substance. At the base of the brain, in the situation of the substantia perforata and locus perforatus, a number of long straight vessels are given off, which pass through the white matter to reach the gray substance in the interior. On the cerebellum, the membrane is more delicate, and the vessels from its inner surface are shorter. Upon the crura cerebri and pons Varolii, its characters are altogether changed; it here presents a dense fibrous structure, marked only by slight traces of vascularity. According to Fohmann and Arnold, this membrane contains numerous lym- phatic vessels. Its nerves are derived from the sympathetic, and also from the 510 NERVOUS SYSTEM. third, sixth, seventh, eighth, and spinal accessory. They accompany the branches of the arteries. The Brain. The brain {encephalon) is that portion of the cerebro-spinal axis that is con- tained in the cranial cavity. It is divided into fonr principal parts, viz : the cerebrum, the cerebellum, the pons Varolii, and medulla oblongata. The cerebrum forms the largest portion of the encephalic mass, and occupies a considerable part of the cavity of the cranium, resting in the anterior and middle fossas of the base of the skull, and separated posteriorly from the cerebellum by the tentorium cerebelli. About the middle of its under surface, is a narrow con- stricted portion, part of which, the crura cerebri, is continued onwards into the pons Varolii below, and through it to the medulla oblongata and spinal cord ; whilst another portion, the crura cerebelli, passes down into the cerebellum. The cerebellum (little brain or after-brain) is situated in the inferior occipital fossse, being separated from the under surface of the posterior lobes of the cere- brum by the tentorium cerebelli. It is connected to the rest of the encephalic mass by means of connecting bands, called crura; of these, two ascend to the cerebrum, two descend to the medulla oblongata, and two blend together in front, forming the pons Varolii. Therms Varolii is that portion of the encephalic mass which rests upon the upper part of the basilar process. It constitutes the bond of union of the various segments above-named, receiving, above, the crura from the cerebrum ; at the sides, the crura from the cerebellum; and being connected, below, with the medulla oblongata. The medulla oblongata extends from the lower border of the pons Varolii to the upper part of the spinal cord. It lies beneath the cerebellum, resting on the lower part of the basilar groove of the occipital bone. Weight of the encephalon. The average weight of the brain, in the adult male, is 49 \ oz., or a little more than 3 lbs. avoirdupois; that of the female, 44 oz.; the average difference between the two being from 5 to 6 oz. The prevailing weight of the brain, in the male, ranges between 46 oz. and 53 oz. ; and in the female, between 41 oz. and 47 oz. In the male, the maximum weight out of 278 cases was 65 oz., and the minimum weight 34 oz. The maximum weight of the adult female brain, out of 191 cases, was 56 oz., and the minimum weight 31 oz. It appears that the weight of the brain increases rapidly up to the seventh year, more slowly to the period between sixteen and twenty, and still more slowly to that between thirty and forty, when it reaches its maximum. Beyond this period, as age advances and the mental faculties decline, the brain diminishes slowly in weight, about an ounce for each subsequent decennial period. These results apply alike to both sexes. The size of the brain appears to bear a general relation to the intellectual capacity of the individual. Cuvier's brain weighed rather more than 64 oz., that of the late Dr. Abercrombie 63 oz., and that of Dupuytren 62 J oz. On the other hand, the brain of an idiot seldom weighs more than 23 oz. The human brain is heavier than that of all the lower animals excepting the elephant and whale. The brain of the former weighs from 8 lbs. to 10 lbs.; and that of the whale, in a specimen seventy-five feet long, weighed rather more than 5 lbs. Medulla Oblongata. The medulla oblongata is the upper enlarged part of the spinal cord, and extends Crom the upper border of the atlas to the lower border of the pons Varolii. It is directed obliquely downwards and backwards, its anterior surface resting on the basilar groove of the occipital bone, its posterior surface being received into the fossa between the hemispheres of the cerebellum, forming the floor of the fourth MEDULLA OBLONGATA. 511 ventricle. It is pyramidal in form, its broad, extremity directed upwards, its lower end being narrow at its point of connection with the cord. It measures an inch and a quarter in length, three-quarters of an inch in breadth at its widest part, and half an inch in thickness. Its surface is marked, in the median line, in front and behind, by an anterior and posterior median fissure, which are con- tinuous with those of the spinal cord. The anterior fissure contains a fold of pia mater, and terminates just below the pons in a cul-de-sac, the foramen ca?cum. The posterior is a deep but narrow fissure, continued upwards along the floor of the fourth ventricle, where it is finally lost. These two fissures divide the medulla into two symmetrical halves, each lateral half being subdivided by minor grooves into four columns, which, from before backwards, are named, the anterior pyramid, lateral tract and olivary body, the restiform body, and the posterior pyramid. The anterior pyramids or corpora pyramidalia are two pyramidal-shaped bundles of white matter, placed one on either side of the anterior median fissure, and separated from the olivary body, Which is external to them, by a slight Fi S- 260.— Medulla Oblongata and Pods Varolii. j • A , ,1 i i i n?i Anterior Surtace. depression. At the lower border ot the pons they are somewhat constricted; they then become enlarged, and taper slightly as they descend, being con- tinuous below with the anterior co- lumns of the cord. On separating the pyramids below, it will be observed that the innermost fibres of the two form from four to five bundles on each side, which decussate with one another ; this decussation, however, is not formed entirely of fibres from the pyramids, but mainly from the deep portion of the lateral columns of the cord which pass forwards to the surface between the diverging anterior columns. The outermost fibres do not decussate ; they are derived from the anterior columns of the cord, and are continued directly upwards through the pons Varolii. Lateral tract and olivary body. The lateral tract is continuous with the lateral column of the cord. Below, it is broad, and includes that part of the medulla between the anterior pyramid and restiform body ; but, above, it is pushed a little backwards, and narrowed by the projection forwards of the olivary body. The olivary bodies are two prominent, oval masses, situated behind the anterior pyramids, from which they are separated by slight grooves. They equal, in breadth, the anterior pyramids, are a little broader above than below, and are about half an inch in length, being separated, above, from the pons "Varolii, by a slight depression. Numerous white fibres, fibrse arciformes, are seen winding round the lower end of each body ; sometimes crossing their surface. The restiform bodies are the largest columns of the medulla, and continuous, below, with the posterior columns of the cord. They are two rounded, cord-like eminences, placed between the lateral tracts, in front, and the posterior pyramids, behind; from both of which they are separated by slight grooves. As they ascend, they diverge from each other, assist in forming the lateral boundaries of the fourth ventricle, and then enter the corresponding hemisphere of the cere- bellum, forming its inferior peduncle, from which it is probable that some fibres are continued from them into the cerebrum. The posterior pyramids or fasciculi graciles are two narrow, white cords, placed one on each side of the posterior median fissure, and separated from the restiform 512 NERVOUS SYSTEM. Fig. 2G1. — Posterior Surface of Medulla Oblongata. bodies by a narrow groove. They consist entirely of white fibres, and are con tinuous with the posterior median columns of the spinal cord. These bodies lie at first in close contact. Opposite the apex of the fourth ventricle, they form an enlargement, the processus clavatus, and then, diverging, are lost in the correspond- ing restiform body. The upper part of the posterior pyramids forms the lateral boundaries of the calamus scriptorius. The posterior surface of the medulla oblongata forms part of the floor of the fourth ventricle. It is of a triangular form, bounded on each side by the di- verging posterior pyramids, and is that part of the ventricle which, from its resemblance to the point of a pen, is called the calamus scriptorius. The di- vergence of the posterior pyramids and the restiform bodies opens to view the gray matter of the medulla, which is con- tinuous, below, with the gray commissure of the cord. In the middle line is seen a longitudinal furrow, continuous with the posterior median fissure of the cord, ter- minating, below, at the point of the ven- tricle, in a cul-de-sac, the ventricle of Arantius, which descends into the medulla for a slight extent. It is the remains of a canal, which, in the foetus, extends throughout the entire length of the cord. Structure. The columns of the cord are directly continuous with those of the medulla oblongata, below; but, higher up, both the white and gray constituents are re-arranged before they are continued upwards to the cerebrum and cere- bellum. The anterior pyramid is composed of fibres derived from the anterior column of the cord of its own side, and from the lateral column of the opposite half of the cord, and is continued upwards into the cerebrum and cerebellum. The cerebellar fibres form a superficial and deep layer, which pass beneath the olive to the restiform body, and spread out into the structure of the cerebellum. A deeper fasciculus incloses the olivary body, and, receiving fibres from it, enters the pons as the olivary fasciculus or Fir. 2b2. — Transverse Section of Medulla .en . t , ,i i • r. o n-\ n Oblongata. fillet; but the cbiei mass 01 fibres trom the pyramid, the cerebral fibres, enter the pons in their passage upwards to the cerebrum. The anterior pyramids contain no gray matter. The lateral tract is continuous, be- low, with the lateral column of the cord. Its fibres pass in three different direc- tions. The most external join the restiform body, and pass to the cerebellum. The internal, more numerous, pass forwards, pushing aside the fibres of the anterior column, and form part of the opposite anterior pyramid. The middle fibres ascend, beneath the olivary body, to the cerebrum, passing along the back of the pons, and form, together with fibres from the restiform body, the fasciculi teretes, in the floor of the fourth ventricle. Olivary hody. If a transverse section is made through either olivary body, it will be found to consist of a small ganglionic mass, deeply imbedded in the medulla, Tntcrior Tietare- Fasciculi Terete! JUstrjvrm ~Bo3tf Olivary Body A ntrriar Pyramid. STRUCTURE OF THE MEDULLA OBLONGATA. 513 partly appearing on the surface as a smooth, olive-shaped eminence (fig. 262). It consists, externally, of white substance ; and, internally, of a gray nucleus, the corpus dentatum. The gray matter is arranged in the form of a hollow capsule, open at its upper and inner part, and presenting a zig-zag or dentated outline. White fibres pass into or from the interior of this body, by the aperture in the posterior part of the capsule. They join with those fibres of the anterior column which ascend on the outer side, and beneath the olive, to form the olivary fasci- culus, which ascends to the cerebrum. Fig. 2G3. — The Columns of the Medulla Oblongata, and their Connection with the Cerebrum and Cerebellum. Medulla Oblongata The restiform body is formed chiefly of fibres from the posterior column of the cord ; but it receives some from the lateral column, and a fasciculus from the anterior, and is continued, upwards, to the cerebrum and cerebellum. On entering the pons, it divides into two fasciculi, above the point of the fourth ventricle. The most external one enters the cerebellum ; the inner one joins the posterior pyramid, is continued up along the fourth ventricle, and, joining the fasciculi teretes, passes up to the cerebrum. Septum of the medulla oblongata. Above the decussation of the anterior pyramids, numerous white fibres extend, from behind forwards, in the median line, forming a septum, which subdivides the medulla into two lateral halves. Some of these fibres emerge at the anterior median fissure and form a band which curves round the lower border of the olivary body, or passes transversely across it, and round the sides of the medulla, forming the arc/form fibres of Rolando. Others appear in the floor of the fourth ventricle, issuing from the posterior median fissure, and form the white striae in that situation. Gray matter of the medulla oblongata. The gray matter of the medulla is a continuation of that contained in the interior of the spinal cord, besides a series of special deposits or nuclei. In the lower part of the medulla, the gray matter is arranged as in the cord, but, at the upper part, it becomes more abundant, and is disposed with less apparent regularity, becoming blended with all the white fibres, except the anterior pyramids. The part corresponding to the transverse gray commissure of the cord is exposed to view in the floor of the medulla oblongata, by the 514 NERVOUS SYSTEM. divergence of the restiform bodies, and posterior pyramids, becoming blended with the ascending fibres of the lateral column, and thus forming the fasciculi teretes. The lateral crescentic portions, but especially the posterior horns, become enlarged, blend with the fibres of the restiform bodies, and form the tuberculo cinereo of Rolando. Special deposits of gray matter are found both in the anterior and posterior parts of the medulla; in the former situation, forming the corpus dentatum within the olivary body, and, in the latter, a series of special masses, or nuclei, connected with the roots of origin of the spinal accessory, vagus, glosso-pharyn- geal, and hypoglossal nerves. It thus appears that the closest analogy in structure, and also probably in general endowments, exists between the medulla oblongata and the spinal cord. The larger size and peculiar form of the medulla depending on the enlargement, divergence, and decussation of the various columns ; and also from the addition of special deposits of gray matter in the olivary bodies and other parts, evidently in adaptation to the more extended range of function which this part of the cerebro-spinal axis possesses. PONS VAROLII. The pons Varolii (mesocephale, Chaussier) is the bond of union of the various segments of the encephalon, connecting the cerebrum above, the medulla oblongata below, and the cerebellum behind. It is situated above the medulla oblongata, below the crura cerebri, and between the hemispheres of the cerebellum. Its under surface presents a broad transverse band of white fibres, which arches like a bridge across the upper part of the medulla, extending between the two hemispheres of the cerebellum. This surface projects considerably beyond the level of these parts, is of a quadrangular form, rests upon the basilar groove of the occipital bone, and is limited before and behind by very prominent margins. It presents along the middle line a longitudinal groove, wider in front than behind, which lodges the basilar artery ; numerous transverse striae are also observed on each side, which indicate the course of its superficial fibres. Its upper surface forms part of the floor of the fourth ventricle, and at each side it becomes contracted into a thick rounded cord, the crus cerebelli, which enters the substance of the cerebellum, constituting its middle peduncle. • Structure. The pons Varolii consists of alternate layers of transverse and longi- tudinal fibres intermixed with gray matter (fig. 263). The transverse fibres connect together the two lateral hemispheres of the cerebellum, and constitute its great transverse commissure. They consist of a superficial and a deep layer. The superficial layer passes uninterruptedly across the surface of the pons, forming a uniform layer, consisting of fibres derived from the crus cerebelli on each side, which meet in the median line. The deep layer of transverse fibres decussates with the longitudinal fibres continued up from the medulla, and contains much gray matter between its fibres. The longitudinal fibres are continued up through the pons. 1. From the anterior pyramidal body. 2. From the olivary body. 3. From the lateral and posterior columns of the cord, receiving special fibres from the gray matter of the pons itself. 1. The fibres from the anterior pyramid ascend through the pons, imbedded between two layers of transverse fibres, being subdivided in their course into smaller bundles ; at the upper border of the pons they enter the crus cerebri, forming its fasciculated portion. 2. The olivary fasciculus divides in the pons into two bundles, one of which ascends to the corpora quadrigemina ; the other is continued to the cerebrum with the fibres of the lateral column. 3. The fibres from the lateral and posterior columns of the cord, with a bundle from the olivary fasciculus, are intermixed with much gray matter, and appear in CEREBRUM. 515 the floor of the fourth ventricle as the fasciculi teretes; they ascend to the deep or cerebral part of the crus cerebri. Foville considers that a few fibres from each of the longitudinal tracts of the medulla turn forwards, and are continuous with the transverse fibres of the pons. Septum. The pons is subdivided into two lateral halves by a median septum, which extends through its posterior half. The septum consists of antero-posterior and transverse fibres. The former are derived from the floor of the fourth ven- tricle and from the transverse fibres of the pons, which bend backwards before passing across to the opposite side. The latter are derived from the floor of the fourth ventricle ; they pierce the longitudinal fibres, and are then continued across from one to the other side of the medulla, piercing the antero-posterior fibres. The two halves of the pons, in front, are connected together by transverse com- missural fibres. CEREBRUM. Upper Surface. The Cerebrum, in man, constitutes the largest portion of the encephalon. Its upper surface is of an ovoidal form, broader behind than in front, convex in its general outline, and divided into two lateral halves or hemispheres, right and left, by the great longitudinal fissure. This fissure extends throughout the entire length of the cerebrum in the middle line, reaching down to the base of the brain in front and behind, but interrupted in the middle by a broad transverse commissure of white matter, the corpus callosum, which connects the two hemi- spheres together. This fissure lodges the falx cerebri, and indicates the original development of the brain by two lateral halves. Each hemisphere presents an outer surface, which is convex, to correspond with the vault of the cranium ; an inner surface, flattened, and in contact with the opposite hemisphere, the two inner surfaces forming the sides of the longitudinal fissure ; and an under surface or base, of more irregular form, which rests, in front, on the anterior and middle fossae at the base of the skull, and, behind, upon the tentorium. Convolutions. If the pia mater is removed with the forceps, the entire surface of each hemisphere will present a number of convoluted eminences, the convolu- tions, separated from each other by depressions {sulci) of various depths. The outer surface of each convolution, as well as the sides and bottom of the sulci between them, are composed of gray matter, which is here called the cortical sub- stance. The interior of each convolution is composed of white matter, and white fibres also blend with the gray matter at the sides and bottom of the sulci. By this arrangement the convolutions are admirably adapted to increase the amount of gray matter without occupying much additional space, and also afford a greater extent of surface, for the fibres to terminate in it. On closer examination, how- ever, the gray matter of the cortical substance is found subdivided into four layers, two of which are composed of gray and two of white substance. The most external is an outer white stratum, not equally thick over all parts of the brain, being most marked on the convolutions in the longitudinal fissure and on the under part of the brain, especially on the middle lobe, near the descending horn of the lateral ventricle. Beneath the latter is a thick reddish gray lamina, and then another thin white stratum ; lastly, a thin stratum of gray matter, which lies in close contact with the white fibres of the hemispheres ; consequently white and gray laminae alternate with one another in the gray matter of the convolu- tions. In certain convolutions, however, the cortical substance consists of no less than six layers, three gray and three white, an additional white stratum dividing the most superficial gray one into two ; this is especially marked in those convo- lutions which are situated near the corpus callosum. A perfect resemblance between the convolutions does not exist in all brains, 516 NERVOUS SYSTEM. nor are they symmetrical on the two sides of the same brain. Occasionally the free borders or the sides of a deep convolution present a fissured or notched appearance. The sulci are generally an inch in depth, but they vary in different brains, and in different parts of the same brain, being usually deepest on the outer convex surface of the hemispheres ; the deepest is situated on the inner surface of the hemisphere, on a level with the corpus callosum, and corresponds to the projection in the posterior horn of the lateral ventricle, the hippocampus minor. The number and extent of the convolutions, as well as their depth, appear to bear a close relation to the intellectual power of the individual, as is shown in their increasing complexity of arrangement as we ascend from the lowest mam- malia up to man. Thus they are absent in some of the lower orders of mammalia, and they increase in number and extent through the higher orders. In man they present the most complex arrangement. Again, in the child at birth before the Fig. 264. — Upper Surface of the Brain, the Pia Mater having been removed. Great Xonyi'lua'ixcl Fissurs intellectual faculties are exercised, the convolutions have a very simple arrange- ment, presenting few undulations ; and the sulci between them are less deep than in the adult. In old age, when the mental faculties have diminished in activity, the convolutions become much less prominently marked. Those convolutions which are the largest and most constantly present are the convolution of the corpus callosum, the convolution of the longitudinal fissure, the supra-orbital convolution, and the convolutions of the outer surface of the hemisphere. BASE OF THE BRAIN. 517 The convolution of the corpus calhsum {gyrus fornicatus) is always well marked. It lies parallel with the upper surface of the corpus callosura, com- mencing on the under surface of the brain in front of the anterior perforated space ; it winds round the curved border of the corpus callosum, and passes along its upper surface as far as its posterior extremity, where it is connected with the convolutions of the posterior lobe ; it then curves downwards and forwards, embracing the cerebral peduncle, passes into the middle lobe, forming the hippocampus major, and terminates just behind the point from whence it arose. The supra-orbital convolution on the under surface of the anterior lobe is well marked. The convolution of the longitudinal fissure bounds the margin of the fissure on the upper surface of the hemisphere. It commences on the under surface of the brain, at the anterior perforated space, passes forwards along the inner margin of the anterior lobe, being here divided by a deep sulcus, in which the olfactory nerve is received ; it then curves over the anterior and upper surface of the hemi- sphere, along the margin of the longitudinal fissure, to its posterior extremity, where it curves forwards along the under surface of the hemisphere as far as the middle lobe. The convolutions on the outer convex surface of the hemisphere, the general direction of which is more or less oblique, are the largest and the most complicated convolutions of the brain, frequently becoming branched like the letter Yin their course upwards and backwards towards the longitudinal fissure : these convolutions attain their greatest development in man, and are especially characteristic of the human brain. They are seldom symmetrical on the two sides. Under Surface or Base. The under surface of each hemisphere presents a subdivision, as already mentioned, into three lobes, named, from their position, anterior, middle, and posterior. The anterior lobe, of a triangular form, with its apex backwards, is somewhat concave, and rests upon the convex surface of the roof of the orbit, being separated from the middle lobe by the fissure of Sylvius. The middle lobe, which is more prominent, is received into the middle fossa of the base of the skull. The posterior lobe rests upon the tentorium, its extent forwards being limited by the anterior margin of the cerebellum. The various objects exposed to view on the under surface of the cerebrum in the middle line are here arranged in the order in which they are met with from before backwards. Longitudinal fissure. Tuber cinereum. Corpus callosum and its peduncles. Infundibulum. Lamina cinerea. Pituitary body. Olfactory nerve. Corpora albicantia. Fissure of Sylvius. Posterior perforated space. Anterior perforated space. Crura cerebri. Optic commissure. The longitudinal fissure partially separates the two hemispheres from one another ; it divides the two anterior lobes in front, and, on raising the cerebellum and pons, it will be seen completely separating the two posterior lobes, the inter- mediate portion of the fissure being arrested by the great transverse band of white matter, the corpus callosum. Of these two portions of the longitudinal fissure, that which separates the posterior lobes is the longest. In the fissure between the two anterior lobes the anterior cerebral arteries may be seen ascending to the corpus callosum ; and at the back part of this portion of the fissure, the anterior curved portion of the corpus callosum descends to the base of the brain. 518 NERVOUS SYSTEM. The corpus callosum terminates at the base of the brain by a concave margin, which is connected with the tuber cinereum through the intervention of a thin layer of gray substance, the lamina cinerea. This may be exposed by gently raising and drawing back the optic commissure. A broad white band may be observed on each side, passing from the under surface of the corpus callosum backwards and outwards, to the commencement of the fissure of Sylvius ; these bands are called the peduncles of the corpus callosum. Laterally, the corpus callosum extends into the anterior lobe. « The lamina cinerea is a thin layer of gray substance, extending backwards from the termination of the corpus callosum above the optic commissure to the tuber cinereum ; it is continuous on either side with the gray matter of the anterior perforated space, and forms the anterior part of the inferior boundary of the third ventricle. Fig. 265.— Base of the Brain. M The olfactory nerve, with its bulb, is seen on either side of the longitudinal fissure, upon the under surface of each anterior lobe. The fissure of Sylvius separates the anterior and middle lobes, and lodges the middle cerebral artery. At its entrance is seen a point of medullary substance, corresponding to a subjacent band of white fibres, connecting the anterior and middle lobes, and called the fasciculus unciformis ; on following this fissure out- wards, it divides into two branches, which inclose a triangular-shaped prominent cluster of isolated convolutions, the island of Reil. These convolutions, from being covered in by the sides of the fissure, are called the gyri operti. BASE OF THE BRAIN. 519 The anterior perforated space is situated at the inner side of the fissure of Sylvius. It is of a triangular shape, bounded in front by the convolution of the anterior lobe and roots of the olfactory nerve ; behind, by the optic tract ; externally, by the middle lobe and commencement of the fissure of Sylvius ; internally, it is continuous with the lamina cinerea, and crossed by the peduncle of the corpus callosum. It is of a grayish color, and corresponds to the under surface of the corpus striatum, a large mass of gray matter, situated in the interior of the brain ; it has received its name from being perforated by numerous minute apertures for the transmission of small straight vessels into the substance of the corpus striatum. The optic commissure is situated in the middle line, immediately behind the lamina cinerea. It is the point of junction between the two optic nerves. Immediately behind the diverging optic tracts, and between them and the peduncles of the cerebrum [crura cerebri) is a lozenge-shaped interval, the inter- peduncular space, in which are found the following parts, arranged in the following order from before backwards : the tuber cinereum, infundibulum, pituitary body, corpora albicantia, and the posterior perforated space. The tuber cinereum is an eminence of gray substance, situated between the optic tracts and the corpora albicantia ; it is connected with the surrounding parts of the cerebrum, forms part of the floor of the third ventricle, and is continuous with the gray substance in that cavity. From the middle of its under surface, a conical tubular process of gray matter, about two lines in length, is continued downwards and forwards to be attached to the posterior lobe of the pituitary body ; this is the infundibulum. Its canal, funnel-shaped in form, communicates with the third ventricle. : , The pituitary body is a small, reddish-gray, vascular mass, weighing from five to ten grains, and of an oval form, situated in the sella Turcica, in connection with which it is retained by the dura mater which forms the inner wall of the cavernous sinus. It is very vascular, and consists of two lobes, separated from one another by a fibrous lamina. Of these, the anterior is the larger, of an oblong form, and somewhat concave behind, where it receives the posterior lobe, which is round. The anterior lobe consists externally of firm yellowish-gray substance, and inter- nally of a soft pulpy substance of a yellowish-white color. The posterior lobe is darker than the anterior. In the foetus it is larger proportionally than in the adult, and contains a cavity which communicates through the infundibulum with the third ventricle. In the adult it is firmer and more solid, and seldom "contains any cavity. Its structure, especially the anterior lobe, is similar to that of the ductless glands. The corpora albicantia are two small round white masses, each about the size of a pea, placed side by side immediately behind the tuber cinereum. They are formed by the anterior crura of the fornix, hence called the bulbs of the fornix, which, after descending to the base of the brain, are folded upon themselves, before passing upwards to the thalami optici. They are composed externally of white substance, and internally of gray matter ; the gray matter of the two being connected by a transverse commissure of the same material. At an early period of foetal life they are blended together into one large mass, but become separated about the seventh month*. The posterior perforated space or pons Tarini corresponds to a whitish-gray substance, placed between the corpora albicantia in front, the pons Varolii behind, and the crura cerebri on either side. It forms the back part of the floor of the third ventricle, and is perforated by numerous small orifices for the passage of bloodvessels to the thalami optici. The crura cerebri or peduncles of the cerebrum are two thick cylindrical bundles of white matter, which emerge from the anterior border of the pons, and diverge as they pass forwards and outwards to enter the under part of either hemisphere. Each crus is about three-quarters of an inch in length, and somewhat broader in front than behind. They are marked upon their surface with longitudinal stria?, and each is crossed, just before entering the hemisphere, by a flattened white band. 520 NERYOUS SYSTEM. the optic tract, which is adherent by its upper border to the peduncle. In its interior is contained a mass of dark-gray matter, called the locus niger. The third nerves may be seen emerging from the inner side of either crus ; and the fourth nerve winding around its outer side from above. Each crus consists of a superficial and deep layer of longitudinal white fibres, continued upwards from the pons, separated by a mass of gray matter, the locus niger. The superficial longitudinal fibres are continued upwards, from the anterior pyramids to the cerebrum. They consist of coarse fasciculi, which form the free part of the crus, and have received the name of the fasciculated portion of the peduncle or crus. The deep layer of longitudinal fibres is continued upwards, to the cerebrum, from the lateral and posterior columns of the medulla, and from the olivary fasci- culus, these fibres consisting of some derived from the same, and others from the opposite lateral tract of the medulla. More deeply, is a layer of finer fibres, mixed with gray matter, derived from the cerebellum, blended with the former. The cerebral surface of the crus cerebri is formed of these fibres, and is named the tegumentum. The locus niger is a mass of gray matter, situated between the superficial and deep layer of fibres above described. It is placed nearer the inner than the outer side of this body. The posterior lobes of the cerebrum are concealed from view by the upper surface of the cerebellum, and pons Yarolii. When these parts are removed, the two hemispheres are seen to be separated by the great longitudinal fissure, this fissure being arrested, in front, by the posterior rounded border of the corpus callosum. Geneeal Aeeangement of the Paets composing the Ceeebeum. As the peduncles of the cerebrum enter the hemispheres, they diverge from one another, so as to leave an interval between them, the interpeduncular space. As they ascend, the component fibres of each pass through two large masses of gray matter, the ganglia of the brain, called the thalaini optici and corpora striata, which project as rounded eminences from the upper and inner side of each peduncle. The hemispheres are connected together, above these masses, by the great transverse commissure, the corpus callosum, and the interval left between its under surface, the upper surface of the ganglia, and the parts closing the interpeduncular space, forms the general ventricular cavity. The upper part of this cavity is subdivided into two by a vertical septum, the septum luciclum : and thus the two lateral ventricles are formed. The lower part of this cavity forms the third ventricle, which communicates with the lateral ventricles, above, and with the fourth ventricle, behind. The fifth ventricle is the interval left between the two layers composing the septum lucidum. ' Inteeioe of the Ceeebeum. If the upper part of either hemisphere is removed with a scalpel, about half an inch above the level of the corpus callosum, its internal white matter will be exposed. It is an oval-shaped centre, of white substance, surrounded on all sides by a narrow, convoluted margin of gray matter which presents an equal thickness in nearly every part. This white central mass has been called the centrum ovale minus. Its surface is studded with numerous minute red dots, the puncta vasculosa, produced by the escape of blood from divided bloodvessels. In inflammation, or great congestion of the brain, these are very numerous, and of a dark color. If the remaining portion of one hemisphere is slightly separated from the other, a broad band of white substance will be observed connecting them, at the bottom of the longitudinal fissure : this is the corpus callosum. The margins of the CORPUS CALLOSUM. 521 hemispheres, which overlap this portion of the brain, are called the labia cerebri. Each labium is part of the convolution of the corpus callosum (gyrus fornicatus), already described ; and the space between it and the upper surface of the corpus callosum has been termed the ventricle of the corpus callosum. The hemispheres should now be sliced off; to a level with the corpus callosum, when the white substance of that structure will be seen connecting together both hemispheres. The large expanse of medullary matter now exposed, surrounded by the convoluted margin of gray substance, is called the centrum ovale majus of Vieussens. The corpus callosum is a thick stratum of transverse fibres, exposed at the bottom of the longitudinal fissure. It connects the two hemispheres of the brain, forming their great transverse commissure ; and forms the roof of a space in the Fig. 266.— Section of the Brain. Made on a level with the Corpus Callosum. interior of each hemisphere, the lateral ventricle. It is about four inches in length, extending to within an inch and a half of the anterior, and to within two inches and a half of the posterior, part of the brain. It is somewhat broader behind than in front, and is thicker at either end than in its central part, being thickest behind. It presents a somewhat arched form, from before backwards, terminating anteriorly in a rounded border, which curves downwards and back- wards, between the anterior Jobes to the base of the brain. In its course, it forms a distinct bend, named the knee or genu, and the reflected portion, named the beak or rostrum, becoming gradually narrower, is attached to the anterior cerebral lobe, and is connected, through the lamina cinerea, with the optic commissure. The reflected portion of th,e corpus callosum gives off, near its termination, two 522 NERVOUS SYSTEM. bundles of white substance, which, diverging from one another, pass backwards, across the anterior perforated space, to the entrance of the fissure of Sylvius. They are called the peduncles of the corpus callosum. Posteriorly, the corpus callosum forms a thick, rounded fold, which is free for a little distance, as it curves forwards, and is then continuous with the fornix. On its upper surface, its fibrous structure is very apparent to the naked eye, being collected into coarse, transverse bundles. Along the middle line, is a linear depression, the raphe, bounded laterally by two or more slightly elevated longitudinal bands, called the striae longitudinales or nerves of Lancisi ; and, still more externally, other longitudinal stria? are seen, beneath the convolutions, which rest on the corpus callosum. These are the strioe longitudinales laterales. The under surface of the corpus callosum Fig. 267.— The Lateral Ventricles of the Brain. is continuous behind with the fornix, being separated from it in front by the septum lucidum, which forms a vertical partition between the two ventricles. On either side, the fibres of the corpus callosum penetrate into the substance of the hemispheres, and connect together the anterior, middle, and part of the posterior lobes. It is the large number of fibres derived from the anterior and posterior lobes, which explains the great thickness of the two extremities of this commissure. An incision should now be made through the corpus callosum, on either side of the raphe, when two large irregular cavities will be exposed, which extend throughout the entire length of each hemisphere. These are the lateral ventricles. The lateral ventricles are serous cavities, formed by the upper part of the general ventricular space in the interior of the brain. They are lined by a thin diaphanous lining membrane, covered with ciliated epithelium, and moistened by a LATERAL VENTRICLES. 523 serous fluid, which is sometimes, even in health, secreted in considerable quantity. These cavities are two in number, one in each hemisphere, and they are separated from each other by a vertical septum, the septum lucidum. Each lateral ventricle consists of a central cavity or body, and three smaller cavities or cornua, which extend from it in different directions. The anterior cornu curves forwards and outwards, into the substance of the anterior lobe. The posterior cornu, called the digital cavity, curves backwards into the posterior lobe. The middle cornu descends into the middle lobe. The central cavity or body of the lateral ventricle is triangular in form. It is bounded, above, by the under surface of the corpus callosum, which forms the roof of the cavity. Internally, is a vertical partition, the septum lucidum, which separates it from the opposite ventricle, and connects the under surface of the corpus callosum with the fornix. Its floor is formed by the following parts, enumerated in their order of position, from before backwards, the corpus striatum, taenia semicircularis, thalamus opticus, choroid plexus, corpus fimbriatum, and fornix. The anterior cornu is triangular in form, passing outwards into the anterior lobe, and curving round the anterior extremity of the corpus striatum. It is bounded, above and in front, by the corpus callosum; behind, by the corpus striatum. The posterior cornu or digital cavity curves backwards into the substance of the posterior lobe, its direction being backwards and outwards, and then inwards. On its floor is seen a longitudinal eminence, which corresponds with a deep sulcus between two convolutions ; this is called the hippocampus minor. Between the middle and posterior horns, a smooth eminence is observed, which varies consi- derably in size in different subjects. It is called the eminentia collateralis. The corpus striatum has received its name from the striated appearance which its section presents, from white fibres diverging through its substance. The intra- ventricular portion is a large pear-shaped mass, of a gray color externally ; its broad extremity is directed forwards, into the forepart of the body, and anterior cornu of the lateral ventricle ; its narrow end is directed outwards and backwards, being separated from its fellow by the thalami optici ; it is covered by the serous lining of the cavity, and crossed by some veins of considerable size. The extra- ventricular portion is imbedded in the white substance of the hemisphere. The tsenia semicircularis is a narrow, whitish, semitransparent band of medul- lary substance, situated in the depression between the corpus striatum and thala- mus opticus. Anteriorly, it descends in connection with the anterior pillar of the fornix ; behind, it is continued into the descending horn of the ventricle, where it becomes lost. Its surface, especially at its forepart, is transparent, and dense in structure, and was called by Tarinus the horny band. It consists of longitu- dinal white fibres, the deepest of which run between the corpus striatum and thalamus opticus. Beneath it is a large vein, the vena corporis striati, which receives numerous smaller veins from the surface of the corpus striatum, and thalamus opticus, and terminates in the venae Galeni. The choroid plexus is a highly vascular, fringe-like membrane, occupying the margin of the fold of pia mater (velum interpositum), in the interior of the brain. It extends, in a curved direction, across the floor of the lateral ventricle. In front, where it is small and tapering, it communicates with the choroid plexus of the opposite side, through a large oval aperture, the foramen of Monro. Posteriorly, it descends into the middle horn of the lateral ventricle, where it joins with the pia mater through the transverse fissure. In structure, it consists of minute and highly vascular villous processes, the villi being covered by a single layer of epithelium, composed of large round corpuscles, containing, besides a central nucleus, a bright yellow spot. The arteries of the choroid plexus enter the ven- tricle, at the descending cornu, and, after ramifying through its substance, send branches into the substance of the brain. The veins of the choroid plexus ter- minate in the venae Galeni. 524 NERVOUS SYSTEM. The corpus fimbriatum, called also the tsenia hippocampi, is a narrow, white, tape-like band, situated immediately behind the choroid plexus. It is the lateral edge of the posterior pillar of the fornix, and is attached along the inner border of the hippocampus major as it descends into the middle horn of the lateral ventricle. It may be traced as far as the pes hippocampi. The thalami optici and fornix will be described when more completely exposed, in a later stage of the dissection of the brain. The middle cornu should now be exposed, throughout its entire extent, by introducing the little finger gently into it, and cutting through the hemisphere, between it and the surface, in the direction of the cavity. The middle or descending cornu, the largest of the three, traverses the middle lobe of the brain, forming in its course a remarkable curve round the back of the' Fig. 268. — The Fornix, Velum Interpositum, and Middle or Descending Cornu of the Lateral Ventricle. optic thalamus. It passes, at first, backwards, outwards, and downwards, and then curves around the crus cerebri, forwards and inwards, nearly to the point of the middle lobe, close to the fissure of Sylvius. Its upper boundary is formed by the medullary substance of the middle lobe, and the under surface of the thalamus opticus. Its lower boundary presents for examination the following parts : The hippocampus major, pes hippocampi, pes accessorius, corpus fimbria- tum, choroid plexus, fascia dentata, transverse fissure. The hippocampus major or cornu ammonis, so called from its resemblance to a ram's horn, is a white eminence, of a curved elongate form, extending along the LATERAL VENTRICLE — MIDDLE CORNU. 525 entire length of the floor of the middle horn of the lateral ventricle. At its lower extremity it becomes enlarged, and presents a number of rounded elevations with intervening depressions, which, from presenting some resemblance to the claw of an animal, is called the pes hippocampi. If a transverse section is made through the hippocampus major, it will be seen that this eminence is the inner surface of the convolution of the corpus callosum, doubled upon itself like a horn, the white convex portion projecting into the cavity of the ventricle ; the gray portion being on the surface of the cerebrum, the edge of which, slightly indented, forms the fascia dentata. The white matter of the hippocampus major is continuous through the corpus fimbriatum, with the fornix and corpus callosum. The pes accessor ius or eminentia collateralis has been already mentioned, as a white eminence, varying in size, placed between the hippocampus major and minor, at the junction of the posterior with the descending cornu. Like the hippo- campi, it is formed of white matter corresponding to one of the sulci, between two convolutions protruding into the cavity of the ventricle. The corpus fimbriatum is a continuation of the posterior pillar of the fornix, prolonged, as already mentioned, from the central cavity of the lateral ventricle. Fascia dentata. On separating the inner border of the corpus fimbriatum from the choroid plexus, and raising the edge of the former, a serrated band of gray substance, the edge of the gray substance of the middle lobe, will be seen beneath it; this is the fascia dentata. Correctly speaking, it is placed external to the cavity of the descending cornu. The transverse fissure is seen on separating the corpus fimbriatum from the thal- amus opticus. It is situated beneath the fornix, extending from the middle line behind, downwards on either side, to the end of the descending cornu, being bounded on one side by the fornix and the hemisphere, and on the other by the thalamus opticus. Through this fissure the pia mater passes from the exterior of the brain into the ventricles, to form the choroid plexuses. Where the pia mater projects into the lateral ventricle, beneath the edge of the fornix, it is covered by a prolongation of the lining membrane, which excludes it from the cavity. The septum lucidum forms the internal boundary of the lateral ventricle. It is a thin, semi-transparent septum, attached, above, to the under surface of the corpus callosum ; below, to the anterior part of the fornix ; and, in front of this, to the prolonged portion of the corpus callosum. It is triangular in form, broad in front, and narrow behind, its surfaces looking towards the cavities of the ven- tricles. The septum consists of two laminae, separated by a narrow interval, the fifth ventricle. Each lamina consists of an internal layer of white substance, covered by the lining membrane of the fifth ventricle ; and an outer layer of gray matter, covered by the lining membrane of the lateral ventricle. The cavity of the ventricle is lined by a serous membrane, covered with epithelium, and contains fluid. In the foetus, and in some animals, this cavity communicates, below, with the third ventricle, but in the adult, it forms a separate cavity. In cases of serous effusion into the ventricles, the septum is often found softened and partially broken down. The fifth ventricle may be exposed by cutting through the septum and attached portion of the corpus callosum, with the scissors ; after examining which, the corpus callosum should be cut across, towards its anterior part, and the two portions carefully dissected, the one forwards, the other backwards, when the fornix will be exposed. The fornix is a longitudinal lamella, of fibrous matter, situated beneath the corpus callosum, with which it is continuous behind, but separated from it in front by the septum lucidum. It may be described as consisting of two symmetrical halves, one for either hemisphere. These two portions are joined together in the middle line, where they form the body, but are separated from one another in front and behind ; in front, forming the anterior crura, and behind, the posterior crura. 526 NERVOUS SYSTEM. The body of the fornix is triangular in form ; narrow in front, broad behind. Its upper surface is connected, in the median line, to the septum lucidum in front, and the corpus callosum behind. Its under surface rests upon the velum interpo- situm, which separates it from the third ventricle, and the inner portion of the optic thalami. Its lateral edges form, on each side, part of the floor of the lateral ventricles, and are in contact with the choroid plexuses. The anterior crura arch downwards towards the base of the brain, separated from each other by a narrow interval. They are composed of white fibres, which descend through a quantity of gray matter in the lateral walls of the third ven- tricle, and are placed immediately behind the anterior commissure. At the base of the brain, the white fibres of each crus form a sudden curve upon themselves, spread out and form the outer part of., the corresponding corpus albicans, from which point they may be traced upwards into the substance of the corresponding thalamus opticus. The anterior crura of the fornix are connected in their course with the optic commissure, the white fibres covering the optic thalamus, the peduncle of the pineal gland, and the superficial fibres of the taenia semicircu- laris. The posterior crura, at their commencement, are intimately connected by their upper surfaces with the corpus callosum ; diverging from one another, they pass downwards into the descending horn of the lateral ventricle, being continuous with the concave border of the hippocampus major. The lateral thin edges of the posterior crura have received the name corpus fimbriatum, already described. On the under surface of the fornix, towards its posterior part, between the diverg- ing posterior crura, may be seen some transverse lines, and others longitudinal or oblique. This appearance has been termed the lyra, from the fancied resemblance it bears to the strings of a harp. Between the anterior pillars of the fornix and the anterior extremities of the thalami optici, an oval aperture is seen on each side, the foramen of Monro. The two openings descend towards the middle line, and, joining together, lead into the upper part of the third ventricle. These openings communicate with the lateral ventricles on each side, and below with the third ventricle. Divide the fornix across anteriorly, and reflect the two portions, the one forwards, the other backwards, when the velum interpositum will be exposed. The velum interpositum is a vascular membrane, reflected from the pia mater into the interior of the brain through the transverse fissure, passing beneath the posterior rounded border of the corpus callosum and fornix, and above the corpora quadrigemina, pineal gland, and optic thalami. It is of a triangular form, and separates the under surface of the body of the fornix from the cavity of the third ventricle. Its posterior border forms an almost complete investment for the pineal gland. Its anterior extremity, or apex, is bifid ; each bifurcation being continued into the corresponding lateral ventricle, behind the anterior crura of the fornix, forming the anterior extremity of the choroid plexus. On its under surface are two vascular fringes, which diverge from each other behind, and project into the cavity of the third ventricle. These are the choroid plexuses of the third ventricle. To its lateral margins are connected the choroid plexuses of the lateral ventricles. The arteries of the velum interpositum enter from behind, beneath the corpus callosum. Its veins, the venee Galeni, two in number, run along its under sur- face ; they are formed by the venee corporis striati, and the venaa plexus choroidis ; the ven&e Galeni unite posteriorly into a single trunk, which terminates in the straight sinus. The velum interpositum should now be removed. This must be effected carefully, especially at its posterior part, where it invests the pineal gland ; the thalami optici will then be exposed with the cavity of the third ventricle between them (fig. 269). The thalami optici are two large oblong masses, placed between the diverging portions of the corpora striata ; they are of a white color, superficially ; internally, THIRD VENTRICLE. 52T they are composed of white fibres intermixed with gray matter. Each thalamus rests upon its corresponding crus cerebri, which it embraces. Externally, it is bounded by the corpus striatum, and taania semicircularis ; and is continuous with the hemisphere. Internally, it forms the lateral boundary of the third ventricle ; and running along its upper border is seen the peduncle of the pineal gland. Its upper surface is free, being pa#ly seen in the lateral ventricle ; it is partly covered by the fornix, and marked in front by an eminence, the anterior tubercle. Its under surface forms the roof of the descending cornu of the lateral ventricle ; into it the crus cerebri passes. Its posterior and inferior part, which projects into the descending horn of the lateral ventricle, presents two small round eminences, the internal and external geniculate bodies. Its anterior extremity, which is narrow, forms the posterior boundary of the foramen of Monro. Fig. 269.— The Third and Fourth Ventricles. The third ventricle is the narrow oblong fissure placed between the thalami optici, and extending to the base of the brain. It is bounded, above, by the under surface of the velum interpositum, from which are suspended the choroid plexuses of the third ventricle ; and, laterally, by two white tracts, one on either side, the peduncles of the pineal gland. Its floor, somewhat oblique in its direction, is formed, from before backwards, by the parts which close the interpeduncular space, viz., the iamma cinerea, the tuber cinereum and infundibulum, the corpora albicantia, and the locus perforatus ; its sides, by the optic thalami ; in front, by the anterior 528 NERVOUS SYSTEM. crura of the fornix, and part of the anterior commissure ; behind, by the posterior commissure, and the iter e tertio ad quartum venlriculum. The cavity of the third ventricle is crossed by three commissures, named, from their position, anterior, middle, and posterior. The anterior commissure is a rounded cord of white fibres, placed in front of the anterior crura of the fornix. It perforates the corpus striatum on either side, and spreads out into the substance of the hemispheres, over the roof of the descending horn of each lateral ventricle. The middle or soft commissure consists almost entirely of gray matter. It connects together the thalami optici. and is continuous with the gray matter lining the anterior part of the third ventricle. The posterior commissure, smaller than the anterior, is a flattened white band of fibres, connecting together the two thalami optici posteriorly. It bounds the third ventricle posteriorly, and is placed in front of and beneath the pineal gland, above the opening leading to the fourth ventricle. The third ventricle has four openings connected with it. In front are two oval apertures, one on either side, the foramina of Monro, through which the third communicates with the lateral ventricles. Behind, is a third opening leading into the fourth ventricle by a canal, the aqueduct of Sylvius or iter e tertio ad quartum ventriculum. The fourth, situated in the anterior part of the floor of the ventricle, is a deep pit, which leads downwards to the funnel-shaped cavity of the infundi- bulum, the iter ad infundibulum. The lining membrane of the lateral ventricles is continued through the foramina of Monro into the third ventricle, and extends along the iter a tertio into the fourth ventricle ; at the bottom of the iter ad infundibulum, it ends in a cul- de-sac. Gray matter of the third ventricle. A layer of gray matter covers the greater part of the surface of the third ventricle. In the floor of this cavity it exists in great abundance, and is prolonged upwards on the sides of the thalami, extending across the cavity as the soft commissure ; below, it enters into the corpora albi- cantia, and surrounds in part the anterior pillars of the fornix. Behind the third ventricle, and in front of the cerebellum, are the corpora quadrigemina ; and resting upon these, the pineal gland. The jmieal gland, so named from its peculiar shape (pinus, the fruit of the fir), called also the conarium, is a small reddish-gray body, conical in form, placed immediately behind the posterior commissure, and between the nates, upon which it rests. It is retained in its position by a duplicature of pia mater, derived from the under surface of the velum interpositum, which almost completely invests it. The pineal gland is about four lines in length, and from two to three in width at its base, and is said to be larger in the child than in the adult, and in the female than in the male. Its base is connected with the cerebrum by some transverse commissural fibres, derived from the posterior commissure ; and by four slender peduncles, formed of medullary fibres. Of these, the two superior pass forwards upon the upper and inner margin of the optic thalami to the anterior crura of the fornix, with which they become blended. The inferior peduncles pass vertically downwards from the base of the pineal gland, along the back part of the inner surface of the thalami, and are only seen on a vertical section through the gland. The pineal gland is very vascular, and consists chiefly of gray matter, with a few medullary fibres. In its base is a small cavity, said by some to communicate with that of the third ventricle. It contains a transparent viscid fluid, and occasionally a quantity of sabulous matter, named acervulus cerebri, composed of phosphate and carbonate of lime, phosphate of magnesia and ammonia, with a little animal matter. These concretions are almost constant in their existence, and are found at all periods of life. When this body is solid, the sabulous matter is found upon its surface, and occasionally upon its peduncles. On the removal of the pineal gland and adjacent portion of pia mater, the corpora quadri- gemina are exposed. CORPORA QUADRIGEMINA — VALVE OF VIEUSSENS. 529 The corpora or iubercula quadrigemina — the optic lobes — are four rounded emi- nences placed in pairs, two in front and two behind, separated from another by a crucial depression. They are situated immediately behind the third ventricle and posterior commissure, beneath the posterior border of the corpus callosum, and above the iter e tertio ad quartum ventriculum. The anterior pair, the nates, are the larger, oblong from before backwards, and of a gray color. The posterior pair, the testes, are hemispherical in form, and lighter in color than the preceding. They are connected on each side with the thalamus opticus, and commencement of the optic tracts, by means of two white prominent bands, termed brachia. Those connecting the nates with the thalamus {brachia anteriora) are the larger, and pass obliquely outwards. Those connecting the testes with the thalamus are called the brachia posteriora. Both pairs, in the adult, are quite solid, being composed of white matter externally, and gray matter within. These bodies are larger in the lower, animals than in man. In fishes, reptiles, and birds, they are only two in number, are called the optic lobes, from their connection with the optic nerves, and are hollow in their interior ; but in mammalia, they are four in number, as in man, and quite solid. In the human foetus, they are developed at a very early period, and form a large proportion of the cerebral mass ; at first, they are only two in number, as in the lower mammalia, and hollow in their interior. These bodies, from below, receive white fibres from the olivary fasciculus or fillet; they are also connected with the cerebellum, by means of a large white cord on each side, the processus ad testes or superior peduncles of the cerebellum, which pass up to the thalami from the tubercula quadrigemina. The valve of Vieussens is a thin translucent lamina of medullary substance, stretched between the two processus e cerebello ad testes ; it covers in the canal leading from the third to the fourth ventricle, forming part of the roof of the latter cavity. It is narrow in front, where it is connected with the testes ; and broader behind, at its connection with the vermiform process of the cerebellum. A slight elevated ridge, the frenulum, descends upon the upper part of the valve from the corpora quadrigemina, and on either side of it may be seen the fibres of origin of the fourth nerve. Its lower half is covered by a thin transversely grooved lobule of gray matter prolonged from the anterior border of the cerebellum ; this is called the linguetta laminosa. The corpora geniculata are two small, flattened, oblong masses, placed on the outer side of the corpora quadrigemina, and on the under and back part of each optic thalamus, and named, from their position, corpus geniculatum externum and corpus geniculatum internum. They are placed one on the outer and one on the inner side of each optic tract. In this situation, the optic tract may be seen dividing into two bands, one of which is connected with the external geniculate body and nates, the other being connected with the internal geniculate body and testis. Structure of the cerebrum. The white matter of each hemisphere consists of three kinds of fibres. 1. Diverging or peduncular fibres, which connect the hemisphere with the cord and medulla oblongata. 2. Transverse commissural fibres which connect together the two hemispheres. 3. Longitudinal commissural fibres, which connect distant parts of the same hemisphere. The diverging or peduncular fibres consist of a main body, and of certain accessory fibres. The main body of fibres originates in the columns of the cord and medulla oblongata, and enters the cerebrum through the crus cerebri, where they are arranged in two bundles, separated by the locus niger. Those fibres which form the inferior or fasciculated portion of the crus are derived from the anterior pyramid, and, ascending, pass mainly through the centre of the striated body ; those on the opposite surface of the crus, which form the tegmentum, are derived from the posterior pyramid and fasciculi teretes ; ascending, they pass, some through the under part of the thalamus, and others through both thalamus and corpus striatum, decussating in these bodies with each other, and with the fibres of the corpus callosum. The optic thalami also receive accessory fibres from the jwocessus ad testes, the olivary fasciculus, the corpora quadrigemina, and corpora geniculata 34 530 NERVOUS SYSTEM. Some of the diverging fibres end in the cerebral ganglia, whilst others pass through and receive additional fibres from them, and, as they emerge, radiate into the anterior, middle, and posterior lobes of the hemisphere, decussating again with the fibres of the corpus cailosum, before passing to the convolutions. The transverse commissural fibres connect together the two hemispheres across the middle line. They are formed by the corpus cailosum, and the anterior and posterior commissures. The longitudinal commissural fibres connect together distant parts of the same hemisphere, the fibres being disposed in a longitudinal direction. They form the fornix, the taenia semicircularis, and peduncles of the pineal gland, the stria? longitudinales, the fibres of the gyrus fornicatus, and the fasciculus uncinatus. CEREBELLUM. The Cerebellum or little brain is that portion of the encephalon which is con- tained in the inferior occipital fossee. It is situated beneath the posterior lobes of the cerebrum, from which it is separated by the tentorium. Its average weight in the male is 5 oz. 4 drs. It attains its maximum weight between the twenty-fifth and fortieth years ; its increase in weight after the fourteenth year being relatively greater in the female than in the male. The proportion between the cerebellum and cerebrum is, in the male, as 1 to 8$ ; and, in the female, as 1 to 8 J. In the infant, it is proportionally much smaller than in the adult, the relation between them being, according to Chaussier, between 1 to 13 and 1 to 26 ; by Cruveilhier it was found to be 1 to 20. In form, the cerebellum is oblong, flattened from above downwards, its greatest diameter being from side to side. It measures from three and a half to four inches transversely, from two to two and a half inches from before backwards, being about two inches thick in the centre, and about six lines at its circumference, the thinnest part. It consists of gray and white matter : the former, darker than that of the cerebrum, occupies the surface ; the latter, the interior. The surface of the cerebellum is not convoluted like the cerebrutr^but traversed by numerous curved furrows or sulci, which vary in depth at different parts, and correspond to the intervals between the laminae of which its exterior is composed. Its upper surface (fig. 270) is somewhat elevated in the median line, and de- Upper Surface of the Cerebellum. [tressed towards its circumference; it consists of two lateral hemispheres, connected together by an elevated median portion or lobe, the superior vermiform process. CEREBELLUM. 531 The median lobe is the fundamental part, and in some animals, as fishes and reptiles, the only part which exists ; the hemispheres being additions, and attaining their maximum in man. The hemispheres are separated, in front, by a deep notch, the incisura cerebelli anterior, which encircles the corpora quadrigemina behind ; they are also separated by a similar notch behind, the incisura cerebelli posterior, in which is received the upper part of the falx cerebelli. The superior vermiform process (upper part of the median lobe of the cerebellum), extends from the notch on the anterior to that on the posterior border. It is divided into three lobes : the lobulus centralis, a small lobe, situated in the incisura anterior ; the monticulus cere- belli, the central projecting part of the process; and the commissura simplex, a small lobe near the incisura posterior. The under surface of the cerebellum (fig. 271) is subdivided into two lateral hemispheres by a depression, the valley, which extends from before backwards in the middle line. The lateral hemispheres are lodged in the inferior occipital fossae ; the median depression, or valley, receives the back part of the medulla oblongata, is broader in the centre than at either extremity, and has, projecting from its floor, part of the median lobe of the cerebellum, called the inferior vermiform process. The parts entering into the composition of this body are, from behind forwards, the Fig. 271. — Under Surface of che Cerebellum. commissura brevis, situated in the incisura posterior ; in front of this, a laminated conical projection, the pyramid; more anterior, is a larger eminence, the uvula, placed between the two rounded lobes which occupy the sides of the valley, the amygdalae, and connected with them by a commissure of gray matter, indented on the surface, called the furrowed band. In front of the uvula is the nodule; it is the anterior pointed termination of the inferior vermiform process, and projects into the cavity of the fourth ventricle; it has been named by Malacarne the laminated tubercle. On each side of the nodule is a thin layer of white substance, attached externally to the flocculus, and internally to the nodule, and to a corre- sponding part on the opposite side ; they form together the posterior medullary velum or commissure of the flocculus. It is usually covered in and concealed by the amygdalae, and cannot be seen until these are drawn aside. This band is of a semilunar form on each side, its anterior margin being free and concave, its posterior being attached just in front of the furrowed band. Between it and the nodulus and uvula behind, is a deep fossa, called the swallow's nest {nidus hirun- dinis). Lobes of the cerebellum. Each hemisphere is divided into an upper and a lower portion by the great horizontal fissure, which commences in front at the pons, and passes horizontally round the free margin of either hemisphere, backwards to the middle line. From this primary fissure numerous secondary fissures proceed, which separate the cerebellum into lobes. 532 NERVOUS SYSTEM. Upon the upper surface of either hemisphere there are two lobes, separated from each other by a fissure. These are the anterior or square lobe, which extends as far back as the posterior edge of the vermiform process, and the posterior or semilunar lobe, which passes from the termination of the preceding to the great horizontal fissure. Upon the under surface of either hemisphere there are five lobes, separated by sulci ; these may be described from before backwards. The flocculus or sub-pedun- cular lobe is a prominent tuft, situated behind and below the middle peduncle of the cerebellum ; its surface is composed of gray matter, subdivided into a few small laminae ; it is sometimes called the pneumo gastric lobule, from being situated be- hind the pneumogastric nerve. The amygdala or tonsil is situated on either side of the great median fissure or valley, and projects into the fourth ventricle. The digastric lobe is situated on the outside of the tonsil, being connected in part with the pyramid. Behind the digastric is the slender lobe, which is connected with the back part of the pyramid and the commissura brevis ; and more posteriorly is the inferior posterior lobe, which also joins the commissura brevis in the valley. Fourth Ventricle. The fourth ventricle or ventricle of the cerebellum is the space between the pos- terior surface of the medulla oblongata and pons in front, and the cerebellum behind. It is lozenge-shaped, being contracted above and below, and broadest across its central part. It is bounded laterally by the processus e cerebello ad testes above, and by the diverging posterior pyramids and restiform bodies below. The roof is arched; it is formed by the valve of Vieussens and the under surface of the cerebellum, which presents in this situation four small eminences or lobules, two occupying the median line, the nodulus and uvula, the remaining two, the amygdalae, being placed on either side of the uvula The anterior boundary or floor is formed by the posterior surface of the medulla oblongata and pons. In the median line is seen the posterior median fissure ; it becomes gradually obliterated above, and terminates below in the point of the calamus scriptorius, formed by the convergence of the posterior pyramids. At this point is the orifice of a short canal terminating in a cul-de-sac, the remains of the canal which extends in fcetal life through the centre of the cord: On each side of the median fissure are two slightly convex longitudinal eminences, the fasciculi teretes ; they extend the entire length of the floor, being indistinct below, and of a grayish color, but well marked and whitish above. Each eminence consists of fibres derived from the lateral tract and restiform body, which ascend to the cere- brum. Opposite the crus cerebelli, on the outer side of the fasciculi teretes, is a small eminence of dark gray substance, which presents a bluish tint through the thin stratum covering it ; this is called the locus cceruleus; and a thin streak of the same color continued up from this on either side of the fasciculi teretes, as far as the top of the ventricle, is called the taenia violacea. The lower part of the floor of the ventricle is crossed by several white transverse lines, linese transversa ; they emerge from the posterior median fissure ; some enter the crus cerebelli, others enter the roots of origin of the auditory nerve, whilst some pass upwards and outwards on the floor of the ventricle. The lining membrane of the fourth ventricle is continuous with that of the third, through the aqueduct of Sylvius, and its cavity communicates below with the sub-arachnoid space of the brain and cord through an aperture in the layer of pia mater, extending between the cerebellum and medulla oblongata. Laterally, this membrane is reflected outwards a short distance between the cerebellum and medulla. The choroid plexuses of the fourth ventricle are two in number ; they are delicate vascular fringes, which project into the ventricle on each side, passing from the point of the inferior vermiform process to the outer margin of the resti- form bodies. STRUCTURE OF CEREBELLUM. 533 The gray matter in the floor of the ventricle consists of a tolerably thick stratum, continuous below with the gray commissure of the cord, and extending up as high as the aqueduct of Sylvius, besides some special deposits connected with the roots of origin of certain nerves. In the upper half of the ventricle is a projection situated over the nucleus, from which the sixth and facial nerves take a common origin. In the lower half are three eminences on each side for the roots of origin of the eighth and ninth nerves. Structure. If a vertical section is made through either hemisphere of the cere- bellum, midway between its centre and the superior Fig. 272.— Vertical Section of the Cerebellum, vermiform process ; it will be found to consist of a central stem of white mat- ter, which contains in its interior a dentate body. From the surface of each hemisphere, a series of plates of medullary matter are detached, which, co- vered with gray matter, form the laminae ; and from its anterior part arise three large processes or pedun- cles, superior, middle, and inferior, by which it is con- nected with the rest of the encephalon. The laminae are about ten or twelve in number, including those on both surfaces of the cerebellum, those in front being detached at a right angle, and those behind at an acute angle ; as each lamina proceeds outwards, other secondary laminae are detached from it, and, from these, tertiary laminae. The arrangement thus described gives to the cut surface of the organ a foliated appearance, to which the name arbor vitse has been given. Each lamina consists of white matter, covered externally by a layer of gray substance. The white matter of each lamina is derived partly from the central stem ; in addition to which white fibres pass from one lamina to another. The gray matter resembles somewhat the cortical substance of the convolutions. It consists of two layers, the external one, soft and of a grayish color, the internal one, firmer and of a rust color. The corpus dentatum. or ganglion of the cerebellum is situated a little to the inner side of the centre of the stem of white matter. It consists of an open bag or capsule of gray matter, the section of which presents a gray dentated outline, being open at its anterior part. It is surrounded by white fibres ; white fibres are also contained in its interior, which issue from it to join the superior peduncles. The peduncles of the cerebellum, superior, middle, and inferior, serve to connect it with the rest of the encephalon. The superior peduncles (processus e cerebello ad testes) connect the cerebellum with the cerebrum ; they pass forwards and upwards to the testes, beneath which they ascend to the crura cerebri and optic thalami, forming part of the diverging cere- bral fibres ; each peduncle forms part of the lateral boundary of the fourth ventricle, and is connected with its fellow of the opposite side by the valve of Vieussens. The peduncles are continuous behind with the folia of the inferior vermiform process, and with the white fibres in the interior of the corpus den- tatum. Beneath the corpora quadrigemina. the innermost fibres of each peduncle decussate with each other, so that some fibres from the right half of the cerebellum are continued to the left half of the cerebrum. 534 NERVOUS SYSTEM. The inferior peduncles (processus admedullam) connect the cerebellum with the medulla oblongata. They pass downwards to the back part of the medulla, and form part of the restiform bodies. Above, the fibres of each process are con- nected chiefly with the laminae, on the upper surface of the cerebellum; and below, they are connected with all three tracts of one half of the medulla, and, through these, with the corresponding half of the cord, excepting the posterior median columns. The middle peduncles (processiLS ad pontem), the largest of the three, connect together the two hemispheres of the cerebellum, forming their great transverse commissure. They consist of a mass of curved fibres, which arise in the lateral parts of the cerebellum, and pass across to the same points on the opposite side. They form the transverse fibres of the pons Yarolii. On the General Anatomy of the Nerves and Nervous Centres, the student may consult the works of Kblliker, and Todd and Bowman, before alluded to ; and the Articles " Nerve and Nerv- ous Centres," in the Cyclop, of Anat. and Physiol. — For further information on the Descriptive Anatomy of the Nervous Centres, consult: — Cruveilhier's " Anatomie Descriptive ;" Todd's " Descriptive Anatomy of the Brain, Spinal Cord, and Ganglions ;" Herbert Mayo's " Plates of the Brain and Spinal Cord;" and Arnold's " Tabulae Anatomical. Fascic. i. Icones Cerebri et Medullar Spinalis." Cranial Nerves. The Cranial Nerves, nine in number on each side, include those nerves which arise from some part of the cerebro-spinal centre, and are transmitted through foramina in the base of the cranium. They have been named numerically, according to the order in which they pass out of this cavity. Their names are also derived from the part to which each is distributed, or from the special function appropriated to each. Taken in their order, from before backwards, they are as follows : — 1st. Olfactory. ,_ , ( Facial or Portio dura. 2d. Optic. ' \ Auditory or Portio mollis. 3d. Motor oculi. I Glosso-pharyngeal. 4th. Pathetic. 8th. < Pneumogastric or Par vagum. 5th. Trifacial or Trigemini. ( Spinal accessory. 6th. Abducens. 9th. Hypoglossal. If, however, the 7th pair be considered as two, and the 8th pair as three distinct nerves, then their number will be increased to twelve, which is the arrangement adopted by Sommering. The cranial nerves may be subdivided into four groups, according to the peculiar function possessed by each, viz., nerves of special sense; nerves of common sensation ; nerves of motion ; and mixed nerves. These groups may be thus arranged : — 1. Nerves of Special Sense. 2. Nerves of Motion. Olfactory. Motor oculi - Optic Pathetic. Auditorv Part of third division of fifth (de- Part of giosso-pharyngeal (described scr ^ under the fifth nerve, under the eighth pair, p. 555). P' 5 °)* ' Lingual branch of the fifth (described Abducens. under the fifth nerve, p. 550). facial. Hypoglossal. 4. Mixed Nerves. 3. Nerves of Common Sensation. Pneumogastric _ (described under the eighth pair, p. 557). Fifth (greater portion). Spinal acce ssory (described under Part oi glosso-pharyngeal. the eighth pair, p. 560). All the cranial nerves are connected to some part of the surface of the brain. This is termed their superficial or apparent origin. But their fibres may, in all cases, be traced deeply into the substance of the organ. This would form their deep or real origin. 1. Nerves o» Special Sense. Olfactory Nerve. The First or Olfactory Nerve, the special nerve of the sense of smell, may be regarded as a portion of the cerebral substance, pushed forwards in direct relation with the organ to which it is distributed. It arises by three roots. The external or long root is a narrow white medullary band, which passes outwards across the fissure of Sylvius, into the substance of the middle lobe of the cerebrum. Its deep origin may be traced to the corpus striatum 1 , the superficial fibres of the optic thalamus 2 , the anterior commissure 3 , and the convolutions of the island of Eeil. 1 Vicussens, Winslow, Monro, Mayo. a Valentin. « Cruveilhier. 535 536 CRANIAL NERVES. The middle or gray root arises from a papilla of gray matter, the caruncula mammillaris, imbedded in the anterior lobe. This root is prolonged into the nerve from the adjacent part of the brain, and contains white fibres in its interior, which are connected with the corpus striatum. The internal or short root is composed of white fibres, which arise from the inner and back part of the anterior lobe, being connected, according to Foville, with the longitudinal fibres of the gyrus fornicatus. These three roots unite, and form a flat band, narrower in the middle than at either extremity, and its section of a somewhat prismoid form. It is soft in texture, and contains a considerable amount of gray matter in its substance. As it passes forwards, it is contained in a deep sulcus, between two convolutions, lying on the under surface of the anterior lobe, on either side of the longitudinal fissure, and is retained in position by the arachnoid membrane which covers it. On reaching the cribriform plate of the ethmoid bone, it expands into an oblong mass of grayish- white substance, the olfactory bulb. From the under part of this bulb are given off numerous filaments, about twenty in number, which pass through the cribriform foramina, and are distributed to the mucous membrane of the nose. Each filament is surrounded by a tubular prolongation from the dura mater and pia mater; the former being lost on the periosteum lining the nose ; the latter, in the neurilemma of the nerve. The filaments, as they enter the nares, are divisible into three groups : an inner group, larger than those on the outer Avail, spread out over the upper third of the septum ; a middle set, confined to the roof of the nose ; and an outer set, which are distributed over the superior and middle turbinated bones, and the surface of the ethmoid in front of them. As the filaments descend, they unite in a plexiform network, and become gradually lost in the lining membrane. Their mode of termination is unknown. The olfactory differs in structure from other nerves, in containing gray matter in its interior, and being soft and pulpy in structure. Its filaments are deficient in the white substance of Schwann, are not divisible into fibrillae, and resemble the gelatinous fibres in being nucleated, and of a finely-granular texture. Fig. 273.— The Optic Nerves and Optic Tracts. Optic Nerve. The Second or Optic Nerve, the special nerve of the sense of sight, is distributed exclusively to the eyeball. The nerves of opposite sides are connected together at the commissure ; and from the back of the commissure, they may be traced to the brain, under the name of the optic tracts. The optic tract, at its connection with the brain, divides into two bands which are continued into the optic thalami, the corpora geniculata, and the corpora quadrigemina. The fibres of origin from the thalamus may be traced partly from its surface, and partly from its interior. From this origin, the tract winds obliquely across the under surface of the crus cerebri, in the form of a flattened band, destitute of neurilemma, and is attached to the crus by its anterior margin. It now assumes a cylindrical form, and, as it passes forwards, is connected with the tuber cinereum, and lamina cinerea, from both of which it receives fibres. According to Foville, it is also connected with the taenia semi- circularis, and the anterior termination of the gyrus fornicatus. It finally joins with the nerve of the opposite side, to form the optic commissure. OPTIC — AUDITORY — MOTOR OCULI. 537 The commissure, somewhat quadrilateral in form, rests upon the olivary process of the sphenoid bone, being bounded, in front, by .the lamina cinerea; behind, by the tuber cinereum ; on either side, by the anterior perforated space. Within the commissure, the optic nerves of the two sides undergo a partial decussation. The fibres which form the inner margin of each tract, are continued across from one to the other side of the ^f^^SJLS^ brain, and have no connection with the optic nerves. These may be regarded as commissural fibres (inter- cerebral) between the thalami of opposite sides. Some fibres are continued across the anterior border of the chiasma, and connect the optic nerves of the two sides, having no relation with the optic tracts. "^ •/w"'*— *• They may be regarded as commissural fibres between the two retinas (inter-retinal fibres). The outer fibres of each tract are continued into the optic nerve of the same side. The central fibres of each tract are continued into the optic nerve of the opposite side, decussating in the commissure with similar fibres of the opposite tract. 1 The optic nerves arise from the fore part of the commissure, and, diverging from one another, become rounded in form, firm in texture, and are inclosed in a sheath derived from the arachnoid. As each nerve passes through the corresponding optic foramen, it receives a sheath from the dura mater ; and as it enters the,orbit, this sheath subdivides into two layers, one of which becomes continuous with the periosteum of the orbit ; the other forms a sheath for the nerve, and surrounds it as far as the sclerotic. The nerve passes through the cavity of the orbit, pierces the sclerotic and choroid coats at the back part of the eyeball, a little to the nasal side of its centre, and expands into the retina. A small artery, the arteria cen- tralis retinas, perforates the optic nerve a little behind the globe, and runs along its interior in a tubular canal of fibrous tissue. It supplies the inner surface of the retina, and is accompanied by corresponding veins. Auditory Nerve. The Auditory Nerve, the portio mollis of the seventh pair, is the special nerve of the sense of hearing, being distributed exclusively to the internal ear. The portio dura of the seventh pair, the facial nerve, is the motor nerve of the muscles of the face. It will be described with the motor cranial nerves. The auditory nerve arises from numerous white striae, the lineae transversae, which emerge from the posterior median fissure in the anterior wall, or floor, of the fourth ventricle. It is also connected with the gray matter of the medulla, which corresponds to the locus caeruleus. According to Foville, the roots of this nerve are connected, on the under surface of the middle peduncle, with the gray substance of the cerebellum, with the flocculus, and with the gray matter at the borders of the calamus scriptorius. The nerve winds round the restiform body, from which it receives fibres, and passes forwards across the posterior border of the eras cerebelli, in company with the facial nerve, from which it is partially separated by a small artery. It then enters the meatus auditorius, in company with the facial nerve, and, at the bottom of the meatus, divides into two branches, cochlear and vestibular, which are distributed, the former to the cochlea, the latter to the vestibule and semicircular canals. The auditory nerve is very soft in texture (hence the name portio mollis), destitute of neurilemma, and, within the meatus, receives one or two filaments from the facial. 2. The Motor Cranial Nerves. Third or Motor Oculi Nerve. The Third or Motor Oculi Nerve supplies all the muscles of the eyeball, except the Superior oblique and External rectus ; it also sends motor filaments to the iris. 1 A specimen of congenital absence of the optic commissure is to be found in the Museum of the Westminster Hospital. 538 CRANIAL NERVES. £ j la.TroelileqgX. It is a rather large nerve, of rounded form and firm texture, having its apparent origin from the inner surface of the crus cerebri, immediately in front of the pons Varolii. The deep origin may be traced into the substance of the crus, where some of its fibres are connected with the locus niger ; others run downwards, among the longitudinal fibres of the pons, whilst others ascend, to be connected with the tubercula quadrigemina and valve of Vieussens. According to Stilling, the fibres of the nerve pierce the peduncle and locus niger, and arise from a gray nucleus in the floor of the aqueduct of Sylvius. On emerging from the brain, it is invested in a sheath of pia mater, and inclosed in a prolongation from the arachnoid. It then pierces the dura mater on the outer side of the anterior clinoid process, where its serous covering is reflected from it, and passes along the outer wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic. It then divides into two branches, which enter the orbit through the sphenoidal fissure, between the two Fig. 275.— Nerves of the Orbit. Seen from above. heads of the External rec- tus muscle. On passing through the fissure, the nerve is placed below the fourth, and the frontal and lachrymal branches of the ophthalmic nerve. The superior division, the smaller, passes inwards across the optic nerve, and supplies the Superior rectus and Levator palpebral. The inferior division, the larger, divides into three branches. One passes beneath the optic nerve to the Internal rectus ; another to the Inferior rectus ; and the third, the largest of the three, passes forwards, be- tween the Inferior and Ex- ternal recti, to the Inferior oblique. From the latter, a short, thick branch is given off to the lower part of the lenticular ganglion, forming its inferior root, as well as two filaments to the Inferior rectus. All these branches enter the muscles on their ocular surface. (Hi 'current Filamrni I U Aura-JIattr Fourth Nerve. The Fourth or Trochlear nerve, the smallest of the cranial nerves, supplies the Superior oblique muscle. It arises from the upper part of the valve of Vieussens, immediately behind the testis, and divides, beneath the corpora quadri- gemina, into two fasciculi ; the anterior one arising from a nucleus of gray matter, close to the middle line of the floor of the Sylvian aqueduct ; the posterior one from a gray nucleus, at the upper part of the floor of the fourth ventricle, close to the origin of the fifth nerve. The two nerves are connected together, at their FOURTH— SIXTH. 539 origin, by a transverse band of white fibres, which crosses the surface of the velum. The nerve winds round the outer side of the crus cerebri, immediately above the pons Varolii, pierces the dura mater in the free border of the tentorium cerebelli, near the posterior clinoid process, above the oval opening for the fifth nerve, and passes forwards through the outer wall of the cavernous sinus, below the third ; but, as it enters the orbit, through the sphenoidal fissure, it becomes the highest of all the nerves. In the orbit, it passes inwards, above the origin of the Levator palpebrae, and finally enters the orbital surface of the Superior oblique muscle. In the outer wall of the cavernous sinus, this nerve receives some filaments from the carotid plexus of the sympathetic. It is not unfrequently blended with the ophthalmic division of the fifth ; and occasionally gives off' a branch to assist in the formation of the lachrymal nerve. It also gives off a recurrent branch, which passes backwards between the layers of the tentorium, dividing into two or three filaments, which may be traced as far back as the wall of the lateral sinus. Fig. 276. — Nerves of the Orbit and Ophthalmic Ganglion. Side view. Internal Cavatid As. h Carotid Plaits. Hot/)* Hoot Sixth or Abducens Nerve. The Sixth or Abducens Nerve supplies the External rectus muscle. Its apparent origin is by several filaments from the constricted part of the corpu3 pyramidale, close to the pons, or from the lower border of the pons itself. The deep origin of this nerve has been traced by Mayo, between the fasciculi of the corpus pyramidale, to the posterior part of the medulla, where Stilling has shown its connection with a gray nucleus in the floor of the fourth ventricle. The nerve pierces the dura mater, immediately below the posterior clinoid pro- cess, lying in a groove by the side of the body of the sphenoid bone. It passes forwards through the cavernous sinus, lying on the outer side of the internal carotid artery, where it is joined by several filaments from the carotid plexus, by one from Meckel's ganglion (Bock), and another from the ophthalmic nerve. It enters the orbit through the sphenoidal fissure, and lies above the ophthalmic vein, from which it is separated by a lamina of dura rnater. It then passes between the two heads of the External rectus, and is distributed to that muscle on its ocular surface. Relations of the Orbital Nerves. The above-mentioned nerves, as well as the ophthalmic division of the fifth, as they pass to the orbit, bear a certain relation to each other in the cavernous 540 CRANIAL NERVES. sinus, at the sphenoidal fissure, and in the cavity of the orbit, which will be now described. In the cavernous sinus, the third, fourth, and ophthalmic division of the fifth. are placed in the dura mater, forming the outer wall of the sinus in numerical order, both from above downwards, and from within outwards. The sixth nerve lies at the outer side of the internal carotid artery. As these nerves pass forwards to the sphenoidal fissure, the third and fifth nerves become divided ; and the sixth approaches the rest ; so that their relative position becomes considerably changed. In the sphenoidal fissure, the fourth, and the frontal and lachrymal divisions of the ophthalmic, lie upon the same plane, the former being most internal, the latter external ; and they enter the cavity of the orbit above the muscles. The remaining nerves enter the orbit between the two heads of the External rectus. The superior division of the third is the highest ; beneath this, the nasal branch of the fifth ; then the inferior division of the third ; and the sixth lowest of all. In the orbit, the fourth, and the frontal and lachrymal divisions of the ophthalmic, lie on the same plane immediately beneath the periosteum, the fourth nerve being internal and resting on the Superior oblique, the frontal resting on the Levator palpebral, and the lachrymal on the External rectus. Next in order comes the superior division of the third nerve lying immediately beneath the Superior rectus, and then the nasal division of the fifth crossing the optic nerve from the outer to the inner side of this cavity. Beneath these is found the optic nerve, surrounded in front by the ciliary nerves, and having the lenticular ganglion on its outer side, between it and the External rectus. Below the optic is the inferior division of the third, and the sixth, which lies on the outer side of the cavity. Facial Nerve. The Facial Nerve, the portio dura of the seventh pair, is the motor nerve of all the muscles of the face, the Platysma and Buccinator. It supplies also the muscles of the external ear, the posterior belly of the Digastric and the Stylo-hyoid. Through the chorda tympani it supplies the Lingualis ; by its tympanic branch, the Stapedius and Laxator tympani; through the otic ganglion, the Tensor tympani ; and through the connection of its trunk with the Vidian nerve, by the petrosal nerves, it probably supplies the Levator palati and Azygos uvulas. It arises from the lateral tract of the medulla oblongata, in the groove between the olivary and restiform bodies. Its deep origin may be traced to the floor of the fourth ventricle, where it is connected with the same nucleus as the sixth nerve. This nerve is situated a little nearer to the middle line than the portio mollis, close to the lower border of the pons Varolii, from which some of its fibres are derived. Connected with this nerve, and lying between it and the portio mollis, is a small fasciculus, the portio inter duram et mollem of Wrisberg. This accessory portion arises from the lateral column of the cord. The nerve passes forwards and outwards upon the crus cerebelli, and enters the internal auditory meatus with Fig. 277.— The Course and Connections of the Facial the auditory nerve. Within Nerve in the Temporal Bone. the meatus> the faeial nerve tttv^ Jf. . T> lies first to the inner side of ***** Mr—i l^L^^r^^^^Sli^ tne auditory, and then in a *«y'^Z^%f^SB|^OirmA groove upon this nerve, and is intumescnu* Ca "^-"'-'^^^^^\T»'i connected to it by one or two juj.r f '-««Kl8f^^R'l At tllc bottom of the mea- • ■ {Audit™, ^^ijJwjm J.j tus, it enters the aquasductus ^^ Fallopii, and follows the ser- pentine course of that canal through the petrous portion of the temporal bone, from its commencement at the internal meatus to its termina- tion at the stylo-mastoid foramen. It is at first directed outwards towards the FACIAL. 541 hiatus Fallopii, where it forms a reddish gangliform swelling (intumescentia gangliformis), and is joined by several nerves ; bending suddenly backwards, it runs in the internal wall of the tympanum, above the fenestra ovalis, and at the back of this cavity passes vertically downwards to the stylo-mastoid foramen. On emerging from this aperture, it runs forwards in the substance of the parotid gland, crosses the external carotid artery, and divides behind the ramus of the lower jaw into two primary branches, temporo-facial and cervico-facial, from which numerous offsets are distributed over the side of the head, face, and upper part of the neck, supplying the superficial muscles in these regions. The communications of the facial nerve may be thus arranged : — In the internal auditory meatus In the aquaeductus Fallopii At its exit from the stylo-mastoid foramen . On the face With the auditory nerve. With Meckel's ganglion by the large petrosal nerve. With the otic ganglion by the small petrosal nerve. With the sympathetic on the middle me- ningeal by the external petrosal nerve. With the pneumogastric. " glossopharyngeal. " carotid plexus. " auricularis magnus. " auriculotemporal. With the three divisions of the fifth. In the internal auditory meatus, some minute filaments pass between the facial and auditory nerves. Opposite the hiatus Fallopii, the gangliform enlargement on the facial nerve communicates, by means of the large petrosal nerve, with Meckel's ganglion, forming its motor root ; by a filament from the small petrosal with the otic ganglion ; and by the external petrosal, with the sympathetic filaments accom- panying the middle meningeal artery (Bidder). From the gangliform enlarge- ment, according to Arnold, a twig is sent back to the auditory nerve. At its exit from the stylo-mastoid foramen, it sends a twig to the pneumogastric, another to the glossopharyngeal nerve, and communicates with the carotid plexus of the sympathetic, with the great auricular branch of the cervical plexus, with the auriculo-temporal branch of the inferior maxillary nerve in the parotid gland, and on the face with the terminal branches of the three divisions of the fifth. Branches of Distribution. Within aquaeductus Fallopii At exit from stylo-mastoid foramen On the face Tympanic. Chorda tympani. Posterior auricular. Digastric. Stylo-hyoid. ( Temporal. Temporo-facial < Malar. ( Infra-orbital. ( Buccal. ■! Supra-maxillary. ( Infra-maxillary. Cervico-facial The Tympanic branch arises from the nerve opposite the pyramid; it is a small filament, which supplies the Stapedius and Laxator tympani muscles. 542 CRANIAL NERVES. The Chorda tympani is given off from the facial as it passes vertically down- wards at the back of the tympanum, about a quarter of an inch before its exit from the stylo-mastoid foramen. It ascends from below upwards in a distinct canal, parallel with the aquaeductus Fallopii, and enters the cavity of the tym- panum through an opening between the base of the pyramid and the attachment of the membrana tympani, and becomes invested with mucous membrane. It passes forwards through the cavity of the tympanum, between the handle of the malleus and vertical ramus of the incus, to its anterior inferior angle, and emerges from ' that cavity through a foramen (the canal of Huguier) at the inner side of Fig. 278.— The Nerves of the Scalp, Face, and Side of the Neck. Terminations >f Supra - trochlear tf Infra -trochlea* cf Nasal the Glaserian fissure. It then descends between the two Pterygoid muscles, and meets the gustatory nerve at an acute angle, after communicating with which, it accompanies it to the submaxillary gland ; it then joins the submaxillary ganglion, and terminates in the Lingualis muscle. The Posterior auricular nerve arises close to the stylo-mastoid foramen, and passes upwards- in front of the mastoid process, where it is joined by a filament FACIAL. 543 from the auricular branch of the pneumogastric, and communicates with the deep branch of the auricularis magnus ; as it ascends between the meatus and mastoid process it divides into two branches. The auricular branch supplies the Retra- hens aurem, and the integument at the back part of the auricle. The occipital branch, the larger, passes backwards along the superior curved line of the occi- pital bone, and supplies the occipital portion of the Occipito-frontalis and the integument. The Stylo-hyoid is a long slender branch, which passes inwards, entering the Stylo-hyoid muscle about its middle ; it communicates with the sympathetic fila- ments on the external carotid artery. The Digastric branch usually arises by a common trunk with the preceding ; it divides into several filaments, which supply the posterior belly of the Digastric ; one of these perforates that muscle to join the glosso-pharyngeal nerve. The Temporo-facial, the larger of the two terminal branches, passes upwards and forwards through the parotid gland, crosses the neck of the condyle of the jaw, being connected in this situation with the auriculo-temporal branch of the inferior maxillary nerve, and divides into branches, which are distributed over the temple and upper part of the face ; these may be divided into three sets, temporal, malar, and infra-orbital. The temporal branches cross the zygoma to the temporal region, supplying the Attrahens aurem and the integument, and join with the temporal branch of the superior maxillary, and with the auriculo-temporal branch of the inferior maxillary. The more anterior branches supply the frontal portion of the Occipito- frontalis, and the Orbicularis palpebrarum muscle, joining with the supra-orbital branch of the ophthalmic. The malar brandies pass across the malar bone to the outer angle of the orbit, where they supply the Orbicularis and Corrugator supercilii muscles, joining with filaments from the lachrymal and supra-orbital nerves ; others supply the lower eyelid, joining with filaments of the malar branches of the superior maxillary nerve. The infra-orbital, of larger size than the rest, pass horizontally forwards to be distributed between the lower margin of the orbit and the mouth. The superficial branches run beneath the skin and above the superficial muscles of the face, which they supply, being distributed to the integument and hair follicles ; some supply the lower eyelid and Pyramidalis nasi, joining, at the inner angle of the orbit, with the infra-trochlear and nasal branches of the ophthalmic. The deep branches pass beneath the Levator labii superioris, supply it and the Levator anguli oris, and form a plexus (infra-orbital) by joining with the infra-orbital branch of the superior maxillary nerve. The Cervico-facial division of the facial nerve passes obliquely downwards and forwards through the parotid gland, where it is joined by branches from the great auricular nerve ; opposite the angle of the lower jaw it divides into branches, which are distributed on the lower half of the face and upper part of the neck. These may be divided into three sets : buccal, supra-maxillary, and infra-maxillary. The buccal branches cross the Masseter muscle, join the infra-orbital branches of the temporo-facial division of the nerve, and with filaments of the buccal branch of the inferior maxillary nerve. They supply the Buccinator and Orbi- cularis oris. The supra-maxillary branches pass forwards beneath the Platysma and De- pressor anguli oris, supplying the muscles and the integument of the lip and chin, anastomosing with the mental branch of the inferior dental nerve. The infra-maxillary branches run forward beneath the Platysma, and form a series of arches across the side of the neck over the supra-hyoid region. One of these branches descends vertically to join with the superficial cervical nerve from the cervical plexus ; others supply the Platysma and Levator labii inferioris. 544 CRANIAL NERVES. Ninth or Hypoglossal Nerve. The Ninth or Hypoglossal Nerve is the motor nerve of the tongue. It arises by several filaments, from ten to fifteen in number, from the groove between the pyramidal and olivary bodies, in a continuous line with the anterior roots of the spinal nerves. According to Stilling, these roots may be traced to a gray nucleus in the floor of the medulla oblongata, between the posterior median furrow and the nuclei of the glossopharyngeal and vagus nerves. The filaments of this nerve are collected into two bundles, which perforate the dura mater separately, opposite the anterior condyloid foramen, and unite together after their passage through it. The nerve descends almost vertically to a point corresponding with Fig. 279. — Hypoglossal Nerve, Cervical Plexus, and their Branches. the arTgle of the jaw. It is at first deeply seated beneath the internal carotid and internal jugular vein, and intimately connected with the pneumogastric nerve ; it then passes forwards between the vein and artery, and, descending the neck, becomes superficial below the Digastric muscle. The nerve then loops round the occipital artery, and crosses the external carotid below the tendon of the Digastric muscle. It passes beneath the Mylo-hyoid muscle, lying between it and the Hyoglossus, and is connected at the anterior border of the latter muscle with the gustatory nerve ; it is then continued forwards into the Genio-hyo-glossus muscle as far as the tip of the tongue, distributing branches to its substance. NINTH OR HYPOGLOSSAL NERVE. 545 Branches of this nerve communicate with the Pneumogastric. First and second cervical nerves. Sympathetic. Gustatory. The communication with the pneumogastric takes place close to the exit of the nerve from the skull, numerous filaments passing between the hypoglossal and second ganglion of the pneumogastric, or both being united so as to form one mass. *The communication with the sympathetic takes place opposite the atlas, by branches derived from the superior cervical ganglion, and in the same situation it is joined by a filament with the loop connecting the first two cervical nerves. The communication with the gustatory takes place near the anterior border of the Hyo-glossus muscle by numerous filaments, which ascend upon it. The branches of distribution are the Descendens noni. Thyro-hyoid. Muscular. The Descendens noni is a long slender branch, which quits the hypoglossal where it turns round the occipital artery. It descends obliquely across the sheath of the carotid vessels, and joins just below the middle of the neck, to form a loop with the communicating branches from the second and third cervical nerves. From the convexity of this loop, branches pass forwards to supply the Sterno-hyoid, Sterno-thyroid, and both bellies of the Omo-hyoid. According to Arnold, another filament descends in front of the vessels into the chest, which joins the cardiac and phrenic nerves. The descendens noni is occasionally contained in the sheath of the carotid vessels, being sometimes placed over and sometimes beneath the internal jugular vein. The Thyro-hyoid is a small branch, arising from the hypoglossal near the pos- terior border of the Hyo-glossus ; it passes obliquely across the great cornu of the hyoid bone, and supplies the Thyro-hyoid muscle. The Muscular branches are distributed to the Stylo-glossus, Hyo-glossus, Genio-hyoid, and Genio-hyo-glossus muscles. At the under surface of the tongue, numerous slender branches pass upwards into the substance of the organ. 3. Nerves of Common Sensation. Fifth Nerve. The Fifth Nerve [trifacial, trigeminus) is the largest cranial nerve, and resem- bles a spinal nerve, in its origin by two roots, and in the existence of a ganglion on its posterior root. The functions of this nerve are various. It is a nerve of special sense, of common sensation, and of motion. It is the great sensitive nerve of the head and face, the motor nerve of the muscles of mastication (except the Buccinator), and its lingual branch is one of the nerves of the special sense of taste. It arises by two roots, a posterior larger or sensory, and an anterior smaller or motor root. Its superficial origin is from the side of the pons Varolii, a little nearer to its upper than its lower border. The smaller root consists of three or four bundles ; in the larger, the bundles are more numerous, varying in number from seventy to a hundred ; the two roots are separated from one another by a few of the transverse fibres of the pons. The deep origin of the larger or sensory root may be traced between the transverse fibres of the pons Varolii to the lateral tract of the medulla oblongata, immediately behind the olivary body. According to some anatomists, it is connected with the gray nucleus at the back part of the medulla, between the fasciculi teretes and restiform columns. By others, it is said to be continuous with the fasciculi teretes and lateral column of the cord ; and, according to Foville, some of its fibres are connected with the transverse fibres of the pons ; whilst others enter the cerebellum, spreading out on the sur- face of its middle peduncle. The motor root has been traced by Bell and Retzius to be connected with the pyramidal body. The two roots of the nerve pass for- wards through an oval opening in the dura mater, at the apex of the petrous 35 54G CRANIAL NERVES. portion of the temporal bone ; here the fibres of the larger root enter a large semilunar ganglion (Casserian), while the smaller root passes beneath the ganglion without having any connection with it, and joins outside the cranium with one of the trunks derived from it. The Casserian or Semilunar Ganglion is lodged in a depression near the apex of the petrous portion of the temporal bone. It is of a somewhat crescentic form, with its convexity turned forwards. Its upper surface is intimately adhe- rent to the dura mater. Branches. This ganglion receives, on its inner side, filaments from the carotid plexus of the sympathetic ; and from it some minute branches are given off to the ten- torium cerebelli, and the dura mater, in the middle fossa of the cranium. From its anterior border, which is directed forwards and outwards, three large branches proceed ; the ophthalmic, superior maxillary, and inferior maxillary. The two first divisions of this nerve consist exclusively of fibres derived from the larger root and ganglion, and are solely nerves of common sensation. The third or inferior maxillary is composed of fibres from both roots. This, therefore, strictly speaking, is the only portion of the fifth nerve which can be said to resemble a spinal nerve. Branches of the Fifth Nerve. (1.) Ophthalmic Nerve. The Ophthalmic, the first division of the fifth, is a sensory nerve. It supplies the eyeball, the lachrymal gland, the mucous lining of the eye and nose, and the integument and muscles of the eyebrow and forehead (fig. 275). It is the smallest of the three divisions of the fifth, arising from the upper part of the Casserian ganglion. It is a short, flattened band, about an inch in length, which passes for- wards along the outer wall of the cavernous sinus, below the other nerves, and just before entering the orbit, through the sphenoidal fissure, divides into three branches, frontal, lachrymal, and nasal. The ophthalmic nerve is joined by fila- ments from the cavernous plexus of the sympathetic, and gives off recurrent filaments which pass between the layers of the tentorium, with a branch from the fourth nerve. Its branches are the Lachrymal. Frontal. Nasal. The Lachrymal is the smallest of the three branches of the ophthalmic. Not un frequently it arises by two filaments, one from the ophthalmic, the other from the fourth, and this, Swan considers, as the usual condition. It passes forwards in a separate tube of dura mater, and enters the orbit through the narrowest part of the sphenoidal fissure. In this cavity, it runs along the upper border of the External rectus muscle, with the lachrymal artery, and is connected with the orbital branch of the superior maxillary nerve. Within the lachrymal gland it gives off several filaments, which supply it and the conjunctiva. Finally it pierces the palpebral ligament, and terminates in the integument of the upper eyelid, joining with filaments of the facial nerve. The Frontal is the largest division of the ophthalmic, and may be regarded, both from its size and direction, as the continuation of this nerve. It enters the orbit above the muscles, through the highest and broadest part of the sphenoidal fissure, and runs forwards along the middle line, between the Levator palpebral and the periosteum. Midway between the apex and base of this cavity, it divides into two branches, supra-trochlear and supra-orbital. The supra-trochlear branch, the smaller of the two, passes inwards, above the pulley of the Superior oblique muscle, and gives off a descending filament, which joins with the infra-trochlear branch of the nasal nerve. It then escapes from the orbit between the pulley of the Superior oblique and the supra-orbital foramen, curves up on to the forehead close to the bone, and ascends behind the Corru gator supercilii and Occipito-frontalis muscles, to both of which it is distributed finally, it is lost in the integument of the forehead. SUPERIOR MAXILLARY NERVE. 547 The supra-orbital branch passes forwards through the supra-orbital foramen, and gives oftj in this situation, palpebral filaments to the upper eyelid. It then ascends upon the forehead, and terminates in muscular, cutaneous, and pericranial branches. The muscular branches supply the Corrugator supercilii, Occipito- frontalis, and Orbicularis palpebrarum, joining in the substance of the latter muscle with the facial nerve. The cutaneous branches, two in number, an inner and an outer, supply the integument of the cranium as far back as the occiput. They are at first situated beneath the Occipito-frontalis, the inner branch per- forating the frontal portion of the muscle, the outer branch its tendinous aponeu- rosis. The pericranial branches are distributed to the pericranium over the frontal and parietal bones. They are derived from the cutaneous branches whilst beneath the muscle. The Nasal nerve is intermediate in size between the frontal and lachrymal, and more deeply placed than the other branches of the ophthalmic. It enters the orbit between the two heads of the External rectus, passes obliquely inwards across the optic nerve beneath the Levator palpebras and Superior rectus muscles, to the inner wall of this cavity, where it enters the anterior ethmoidal foramen, immediately below the Superior oblique. It then enters the cavity of the cranium, traverses a shallow groove on the front of the cribriform plate of the ethmoid bone, and passes down, through the slit by the side of the crista galli, into the nose, where it divides into two branches, an internal and an external. The internal branch supplies the mucous membrane near the fore part of the septum of the nose. The external branch descends in a groove on the inner surface of the nasal bone, and supplies a few filaments to the mucous membrane covering the fore part of the outer wall of the nares as far as the inferior spongy bone ; it then leaves the cavity of the nose, between the lower border of the nasal bone and the upper lateral cartilage of the nose, and, passing down beneath the Com- pressor naris, supplies the integument of the ala and tip of the nose, joining with the facial nerve. The branches of the nasal nerve are the ganglionic, ciliary, and infra- trochlear. The ganglionic is a long, slender branch, about half an inch in length, which usually arises from the nasal, between the two heads of the External rectus. It passes forwards on the outer side of the optic nerve, and enters the superior and posterior angle of the ciliary ganglion, forming its superior or long root. It is sometimes joined by a filament from the cavernous plexus of the sympathetic, or from the superior division of the third nerve. The long ciliary nerves, two or three in number, are given off from the nasal as it crosses the optic nerve. They join the short ciliary nerves from the ciliary ganglion, pierce the posterior part of the sclerotic, and, running forwards between it and the choroid, are distributed to the Ciliary muscle and iris. The infra- trochlear branch is given off just as the nasal nerve passes through the anterior ethmoidal foramen. It runs forwards along the upper border of the Internal rectus, and is joined, beneath the pulley of the Superior oblique, by a filament from the supra-trochlear nerve. It then passes to the inner angle of the eye, and supplies the Orbicularis palpebrarum, the integument of the eyelids and side of the nose, the conjunctiva, lachrymal sac, and caruncula lacrymalis. (2.) Superior Maxillary Nerve (fig. 280). The Superior Maxillary, the second division of the fifth, is a sensory nerve. It is intermediate, both in position and size, between the ophthalmic and inferior maxillary. It commences at the middle of the Casserian ganglion as a flattened plexiform band, and passes forwards through the foramen rotundum, where it be- comes more cylindrical in form, and firmer in texture. It then crosses the spheno- maxillary fossa, traverses the infra-orbital canal in the floor of the orbit, and ap- pears upon the face at the infra-orbital foramen. At its termination, the nerve 548 CRANIAL NERVES. lies beneath the Levator labii superioris muscle, and divides into a leash of branches, which spread out upon the side of the nose, the lower eyelid, and upper lip, joining with filaments of the facial nerve. The branches of this nerve may be divided into three groups : 1. Those given off in the spheno-maxillary fossa. 2. Those in the infra-orbital canal. 3. Those on the face. I Orbital. Spheno-maxillary fossa •< Spheno-palatine. ( Posterior dental. Infra-orbital canal On the face . . Anterior dental. {Palpebral. Nasal. , Labial. The Orbital branch arises in the spheno-maxillary fossa, enters the orbit by the spheno-maxillary fissure, and divides at the back of that cavity into two branches, temporal and malar. Fig. 280. — Distribution of the Second and Third Divisions of the Fifth Nerve and Submaxillary Ganglion. The temporal branch runs in a groove along the outer wall of the orbit (in the malar bone), receives a branch of communication from the lachrymal, and, passing through a foramen in the malar bone, enters the temporal fossa. It ascends between the bone and substance of the Temporal muscle, pierces this muscle and the temporal fascia about an inch above the zygoma, and is distributed to the integument covering the temple and side of the forehead, communicating with the facial and auriculotemporal branch of the inferior maxillary nerve. The malar branch passes along the external inferior angle of the orbit, emerges INFERIOR MAXILLARY NERVE. 549 upon the face through a foramen in the malar bone, and, perforating the Orbi- cularis palpebrarum muscle on the prominence of the cheek, joins with the facial. The Spheno-palatine branches, two in number, descend to the spheno-palatine ganglion. The Posterior dental branches arise from the trunk of the nerve just as it is about to enter the infra-orbital canal; they are two in number, posterior and anterior. The posterior branch passes from behind forwards in the substance of the supe- rior maxillary bone, and joins opposite the canine fossa with the anterior dental. Numerous filaments are given off from the lower border of this nerve, which form a minute plexus in the outer wall of the superior maxillary bone, immediately above the alveolus. From this plexus, filaments are distributed to the pulps of the molar and bicuspid teeth, the lining membrane of the antrum, and correspond- ing portion of the gums. The anterior branch is distributed to the gums and Buccinator muscle. The Anterior dental, of large size, is given off from the superior maxillary nerve just before its exit from the infra-orbital foramen ; it enters a special canal in the anterior wall of the antrum, and anastomoses with the posterior dental. From this nerve some filaments are distributed to the incisor, canine, and first bicuspid teeth ; others are lost upon the lining membrane covering the fore part of the inferior meatus. The Palpebral branches pass upwards beneath the Orbicularis palpebrarum. They supply this muscle, the integument, and conjunctiva of the lower eyelid, joining at the outer angle of the orbit with the facial nerve and malar branch of the orbital. The Nasal branches pass inwards ; they supply the muscles and integument of the side of the nose, and join with the nasal branch of the ophthalmic. The Labial branches, the largest and most numerous, descend beneath the Leva- tor labii superioris, and are distributed to the integument and muscles of the upper lip, the mucous membrane of the mouth, and labial glands. All these branches are joined, immediately beneath the orbit, by filaments from the facial nerve, forming an intricate plexus, the infra-orbital. (3.) Inferior Maxillary Nerve. The Inferior Maxillary Nerve distributes branches to the teeth and gums of the lower jaw, the integument of the temple and external ear, the lower part of the face and lower lip, and the muscles of mastication : it also supplies the tongue with one of its special nerves of the sense of taste. It is the largest of the three divisions of the fifth, and consists of two portions, the larger or sensory root, proceeding from the inferior angle of the Casserian ganglion; and the smaller or motor root, which passes beneath the ganglion, and unites with the inferior maxillary nerve, just after its exit through the foramen ovale. Immediately beneath the base of the skull, this nerve divides into two trunks, anterior and posterior. The Anterior and smaller division, which receives nearly the whole of the motor root, divides into five branches, which supply the muscles of mastication. They are the masseteric, deep temporal, buccal, and pterygoid. The masseteric branch passes outwards, above the External pterygoid muscle, in front of the temporo-maxillary articulation, and crosses the sigmoid notch, with the masseteric artery, to the Masseter muscle, in which it ramifies nearly as far as its anterior border. It occasionally gives a branch to the Temporal muscle, and a filament to the articulation of the jaw. The deep temporal branches, two in number, anterior and posterior, supply the deep surface of the temporal muscle. The posterior branch, of small size, is "aced at the back of the temporal fossa. It is sometimes joined with the 550 CRANIAL NERVES. masseteric branch. The anterior branch is reflected upwards, at the pterygoid ridge of the sphenoid, to the front of the temporal fossa. It is occasionally joined with the buccal nerve. The buccal branch pierces the External pterygoid, and passes downwards beneath the inner surface of the coronoid process of the lower jaw or through the fibres of the Temporal muscle, to reach the surface of the Buccinator, upon which it divides into a superior and an inferior branch. It gives a branch to the External pterygoid during its passage through this muscle, and a few ascending filaments to the Temporal muscle, one of which occasionally joins with the anterior branch of the deep temporal nerve. The upper branch supplies the integument and upper part of the Buccinator muscle, joining with the facial nerve round the facial vein. The lower branch passes forwards to the angle of the mouth ; supplies the integu- ment and Buccinator muscle, as well as the mucous membrane lining its inner surface, joining with the facial nerve. The pterygoid branches are two in number, one for each Pterygoid muscle. The branch to the Internal pterygoid is long and slender, and passes inwards to enter the deep surface of the muscle. This nerve is intimately connected at its origin with the otic ganglion. The branch to the External pterygoid is most frequently derived from the buccal, but it may be given off separately from the anterior trunk of the nerve. The Posterior and larger division of the inferior maxillary nerve also receives a few filaments from the motor root. It divides into three branches, auriculo- temporal, gustatory, and inferior dental. The Auriculo-tempoeal Nerve generally arises by two roots, between which passes the middle meningeal artery. It passes backwards beneath the External pterygoid muscle to the inner side of the articulation of the lower jaw. It then turns upwards with the temporal artery, between the external ear and condyle of the jaw, under cover of the parotid gland, and, escaping from beneath this struc- ture, divides into two temporal branches. The posterior temporal, the smaller of the two, supplies the Attrahens aurem muscle, and is distributed to the upper part of the pinna and the neighboring integument. The anterior temporal accompanies the temporal artery to the vertex of the skull, and supplies the integument of the temporal region, communicating with the facial nerve. The auriculo-temporal nerve has branches of communication with the facial and otic ganglion. Those joining the facial nerve, usually two in number, pass forwards behind the neck of the condyle of the jaw, and join this nerve at the posterior border of the Masseter muscle. They form one of the principal branches of communication between the facial and the fifth nerve. The filaments of com- munication with the otic ganglion are derived from the commencement of the auriculo-temporal nerve. The auricular branches are two in number, inferior and superior. The inferior auricular arises behind the articulation of the jaw, and is distributed to the ear below the external meatus ; other filaments twine round the internal maxillary artery, and communicate with the sympathetic. The superior auricular arises in front of the internal ear, and supplies the integument covering the tragus and pinna. Branches to the meatus auditorius, two in number, arise from the point of com- munication between the temporo-auricular and facial nerves, and are distributed to the meatus. The branch to the temporo-maxillary articulation is usually derived from the auriculo-temporal nerve. The parotid branches supply the parotid gland. The Gustatory or Lingual Nerve (fig. 280), one of the special nerves of the sense of taste, supplies the papillas and mucous membrane of the tongue. It is deeply placed throughout the whole of its course. It lies at first beneath the External pterygoid muscle, together with the inferior dental nerve, being placed to the inner side of the latter nerve, and is occasionally joined to it by a branch GAXGLIA OF THE FIFTH NERVE. 551 which crosses the internal maxillary artery. The chorda tympani also Joins it at an acute angle in this situation. The nerve then passes between the Internal pterygoid muscle and the inner side of the ramus of the jaw, and crosses obliquely to the side of the tongue over the Superior constrictor muscle of the pharynx, and between the Stylo-glossus muscle and deep part of the submaxillary gland ; the nerve lastly runs across Wharton's duct, and along the side of the tongue to its apex, being covered by the mucous membrane of the mouth. Its branches of communication are with the submaxillary ganglion and hypo- glossal nerve. The branches to the submaxillary ganglion are two or three in number ; those connected with the hypoglossal nerve form a plexus at the anterior margin of the Hyo-glossus muscle. Its branches of distribution are few in number. They supply the mucous mem- brane of the mouth, the gums, the sublingual gland, the conical and fungiform papillae and mucous membrane of the tongue, the terminal filaments anastomosing at the tip of this organ with the hypoglossal nerve. The Inferior Dental is the largest of the three branches of the inferior maxillary nerve. It passes downwards with the inferior dental artery, at first beneath the External pterygoid muscle, and then between the internal lateral ligament and the ramus of the jaw to the dental foramen. It then passes forwards in the dental canal in the inferior maxillary bone, lying beneath the teeth, as far as the mental foramen, where it divides into two terminal branches, incisor and mental. The incisor branch is continued onwards within the bone to the middle line, and supplies the canine and incisor teeth. The mental branch emerges from the bone at the mental foramen, and divides beneath the Depressor anguli oris into an external branch, which supplies this muscle, the Orbicularis oris, and the integument, communicating with the facial nerve ; and an inner branch, which ascends to the lower lip beneath the Quadratus menti and supplies this muscle and the mucous membrane and integument of the lip, communicating with the facial nerve. ' The branches of the inferior dental are the mylo-hyoid and dental. The Mylo-hyoid is divided from the inferior dental just as that nerve is about to enter the dental foramen. It descends in a groove on the inner surface of the ramus of the jaw, in which it is retained by a process of fibrous membrane. It supplies the cutaneous surface of the Mylo-hyoid muscle, and the anterior belly of the Digastric, occasionally sending one or two filaments to the submaxillary gland. The Dental branches supply the molar and bicuspid teeth. They correspond in number to the fangs of those teeth ; each nerve entering the orifice at the point of the fang, and supplying the pulp of the tooth. Two small ganglia are connected with the inferior maxillary nerve : the otic, with the trunk of the nerve ; and the submaxillary, with its lingual branch, the gustatory. Ganglia connected with the Fifth Nerve. Connected with the three divisions of the fifth nerve are four small ganglia, which form the whole of the cephalic portion of the sympathetic. With the first division is connected the ophthalmic ganglion ; with the second division, the spheno- palatine or Meckel's ganglion ; and with the third, the otic and submaxillary ganglia. These ganglia receive sensitive filaments from the fifth, and motor and sympathetic filaments from various sources ; these filaments are called the roots of the ganglia. The ganglia are also connected with each other, and with the cervical portion of the sympathetic. (1.) Ophthalmic or Ciliary Ganglion. The Ophthalmic, Lenticular or Ciliary Ganglion (fig. 276) is a small, quadrangular, flattened ganglion, of a reddish-gray color, and about the size of a 552 CRANIAL NERVES. pin's head, situated at the back part of the orbit between the optic nerve and the External rectus muscle, generally lying on the outer side of the ophthalmic artery. It is inclosed in a quantity of loose fat, which makes its dissection somewhat difficult. Its branches of communication, or its roots, are three, all of which enter its posterior border. One, the long root, is derived from the nasal branch of the ophthalmic, and joins its superior angle. Another branch, the short root, is a short thick nerve, occasionally divided into two parts ; it is derived from that branch of the third nerve which supplies the Inferior oblique muscle, and is connected with the inferior angle of the ganglion. A third branch, the sympathetic root, is a slender filament from the cavernous plexus of the sympathetic. This is occasion- ally blended with the long root, and sometimes passes to the ganglion separately. According to Tiedemann, this ganglion receives a filament of communication from the spheno-palatine ganglion. Its branches of distribution are the short ciliary nerves. These consist of from ten to twelve delicate filaments, which arise from the fore part of the ganglion in two bundles, connected with its superior and inferior angles ; the upper bundle consisting of four filaments, and the lower of six or seven. They run forwards with the ciliary arteries in a wavy course, one set above and the other below the optic nerve, pierce the sclerotic at the back part of the globe, pass forwards in delicate grooves on its inner surface, and are distributed to the Ciliary muscle and iris. A small filament is described by Tiedemann, penetrating the optic nerve with the arteria centralis retinas. (2.) Spheno-palatine Ganglion. The Spheno-palatine Ganglion or Meckel's Ganglion (fig. 281), the largest of the cranial ganglia, is deeply placed in the spheno-maxillary fossa, close to the spheno-palatine foramen. It is triangular or heart-shaped in form, of a reddish- gray color, and placed mainly behind the palatine branches of the superior maxil- lary nerve, at the point where the sympathetic root joins the ganglion^ It conse- quently does not involve those nerves which pass to the palate and nose. Like other ganglia, it possesses a motor, a sensory, and a sympathetic root. Its motor root is derived from the facial, through the Vidian ; its sensory root from the fifth ; and its sympathetic root from the carotid plexus, through the Vidian. Its branches are divisible into four groups ; ascending, which pass to the orbit ; descending, to the palate ; internal, to the nose ; and posterior branches to the pharynx. The Ascending branches are two or three delicate filaments, which enter the orbit by the spheno-maxillary fissure, and supply the periosteum. Arnold describes and delineates these branches as descending to the optic nerve ; one, to the sixth nerve (Bock) ; and one, to the ophthalmic ganglion (Tiedemann). The Descending or Palatine branches are distributed to the roof of the mouth, the soft palate, tonsil, and lining membrane of the nose. They are almost a direct continuation of the spheno-palatine branches of the superior maxillary nerve, and are three in number, anterior, middle, and posterior. The anterior or large palatine nerve descends through the posterior palatine canal, emerges upon the hard palate, at the posterior palatine foramen, and passes forwards through a groove in the hard palate, nearly as far as the incisor teeth. It supplies the gums, the mucoUs membrane and glands of the hard palate, and com- municates in front with the termination of the naso-palatine nerve. While in the posterior palatine canal, it gives off inferior nasal branches, which enter the nose through openings in the palate-bone,, and ramify over the middle meatus, and the middle and inferior spongy bones; and, at its exit from the canal, a palatine branch is distributed to both surfaces of the soft palate. The middle or external palatine nerve, descends in the same canal as the pre- ceding, to the posterior palatine foramen, distributing branches to the uvula, tonsil, and soft palate. It is occasionally wanting. SPHENO-PALATINE GANGLION. 553 The posterior or small palatine nerve descends with a small artery through the small posterior palatine canal, emerging by a separate opening behind the posterior palatine foramen. It supplies the Levator palati and Azygos uvulae muscles, the soft palate, tonsil, and uvula. The Internal branches are distributed to the septum, and outer wall of the nasal fossae. They are the superior nasal (anterior), and the naso-palatine. The superior nasal branches (anterior), four or five in number, enter the back part of the nasal fossa by the spheno-palatine foramen. They supply the mucous membrane, covering the superior and middle spongy bones, and that lining the posterior ethmoidal cells, a few being prolonged to the upper and back part of the septum. The naso-palatine nerve (Cotunnius) enters the nasal fossa with the other nasal nerves, and passes inwards across the roof of the nose, below the orifice of the sphenoidal sinus, to reach the septum ; it then runs obliquely downwards and forwards along the lower part of the septum, to the anterior palatine foramen, lying between the periosteum and mucous membrane. It descends to the roof of the mouth by a distinct canal, which opens below in the anterior palatine fossa ; the right nerve, also in a separate canal, being posterior to the left one. In the mouth, they become united, and supply the mucous membrane behind the incisor teeth, joining with the anterior palatine nerve. It occasionally furnishes a few small filaments to the mucous membrane of the septum. 281. — The Spheno-palatine Ganglion and its Branches. Term* ular nerve enters the axillary border of the Sub^laris, «* «*£££»« »SS& fif* UpP " and terminates in the Teres major, lhe latter muscle is sometimes supplied by a separate branch. The long subscapular, the largest of the three, descends along the lower border of the Subscapularis to the Latissimus dorsi, through which it may be traced as far as its lower border. The Circumflex Nerve supplies some of the muscles, and the integument of the shoulder, and the shoulder -joint. It arises from the posterior cord of the brachial plexus, in common with the musculo- spiral nerve. It passes down behind the axillary artery, and in front of the Subsca- pularis; and, at the lower border of this muscle, passes backwards, and divides into two branches. The upper branch winds round the neck of the humerus, beneath the Deltoid, with the posterior circumflex vessels, as far as the anterior border of the muscle, supply- ing it, and giving off cutaneous branches, which pierce it to ramify in the integument covering its lower part. The lower branch, at its origin, dis- tributes filaments to the .Teres minor and back part of the Deltoid muscles. Upon the filament to the former muscle, a gangliform enlargement usually exists. The nerve then pierces the deep fascia, and supplies the integument over the lower two-thirds of the posterior surface of the Deltoid, as well as that covering the long head of the Triceps. The circumflex nerve, before its divi- sion, gives off an articular filament, which enters the shoulder-joint below the Subsca- pularis. The Musculo-cutaneous Nerve {exter- nal cutaneous, perforans Casserii) supplies some of the muscles of the arm, and the integument of the forearm. It arises from the outer cord of the brachial plexus, opposite the lower border of the Pectoralis minor. It then perforates the Coraco-brachialis muscle, and passes obliquely between the Biceps and Brachialis anticus, to the outer side of the arm, a little above the elbow, where it perforates the deep fascia and becomes cutaneous. This nerve, in its course through the arm, supplies the Coraco-brachialis, Biceps, and Brachialis anticus muscles, besides some filaments to the elbow-joint and humerus. 570 SPINAL NERVES. Fit 287. — Cutaneous Nerves of Right Upper Extremity. Posterior View. _ The cutaneous portion of the nerve passes behind the median cephalic vein, and divides, opposite the elbow -joint, into an anterior and a posterior branch. The anterior branch descends along the radial border of the forearm to the wrist. It is here placed in front of the radial artery, and, piercing the deep fascia, accompanies that vessel to the back of the wrist. It communicates with a branch from the radial nerve, and dis- tributes filaments to the integument of- the ball of the thumb. The posterior branch is given off about the middle of the forearm, and passes downwards, along the back part of its radial side, to the wrist. It supplies the integument of the lower third of the forearm, communicating with the radial nerve, and the external cutaneous branch of the musculo-spiral. The Internal Cutaneous Nerve is one of the smallest branches of the brachial plexus. It arises from the inner cord, in common with the ulnar and internal head of the median, and, at its commence- ment, is placed on the inner side of the brachial artery. It passes down the inner side of the arm, pierces the deep fascia with the basilic vein, about the middle of the limb, and, becoming cutaneous, di- vides into two branches. This nerve gives off, near the axilla, a cutaneous filament, which pierces the fascia, and supplies the integument cover- ing the Biceps muscle, nearly as far as the elbow. This filament lies a little ex- ternal to the common trunk from which it arises. The anterior branch, the larger of the two, passes in front of, occasionally be- hind, the median basilic vein. It then descends on the anterior surface of the ulnar side of the forearm, distributing filaments to the integument as far as the wrist, and communicating with a cuta- neous branch of the ulnar nerve. The posterior branch passes obliquely downwards on the inner side of the basilic vein, winds over the internal condyle of the humerus to the back of the forearm, and descends, on the posterior surface of its ulnar side, to a little below the middle, distributing filaments to the integument. It anastomoses above the elbow with the lesser internal cutaneous, and above the wrist with the dorsal branch of the ulnar nerve (Swan). The Lesser Internal Cutaneous Nerve (nerve of Wrisberg) is distributed to the integument on the inner side of the arm. It is the smallest of the branches of the brachial plexus, and usually arises from the inner cord, with the internal cutaneous MEDIAN. 5TI and ulnar nerves. It passes through the axillary space, at first lying beneath, and then on the inner side of, the axillary vein, and communicates with the intercosto- humeral nerve. It then descends along the inner side of the brachial artery, to the middle of the arm, where it pierces the deep fascia, and is distributed to the integument of the back part of the lower third of the arm, extending as far as the elbow, where some filaments are lost in the integument in front of the inner con- dyle, and others over the olecranon. It communicates with the inner branch of the internal cutaneous nerve. In some cases, the nerve of Wrisberg and intercosto-humeral are connected by two or three filaments, which form a plexus at the back part of the axilla. In other cases, the intercosto-humeral is of large size, and takes the place of the nerve of Wrisberg, receiving merely a filament of communication from the brachial plexus, which represents this nerve. In other cases, this filament is wanting, the place of the nerve of Wrisberg being supplied entirely from the intercosto-humeral. The Mediax Nerve (fig. 288) has received its name from the course it takes along the middle line of the arm and forearm to the hand, lying between the ulnar and musculo-spiral and radial nerves. It arises by two roots, one from the outer, and one from the inner cord of the brachial plexus ; these embrace the lower part of the axillary artery, uniting either in front or on the outer side of that vessel. As it descends through the arm, it lies at first on the outer side of the brachial artery, crosses that vessel in the middle of its course, usually in front, but occa- sionally behind it, and lies on its inner side to the bend of the elbow, where it is placed beneath the bicipital fascia, and is separated from the elbow-joint by the Brachialis anticus. In the forearm, it passes between the two heads of the Pronator radii teres, and descends beneath the Flexor sublimis, to within two inches above the annular ligament, where it becomes more superficial, lying between the Flexor sublimis and Flexor carpi radialis, covered by the integument and fascia. It then passes beneath the annular ligament into the hand. Branches. No branches are given off from the median nerve in the arm. In the forearm, its branches are the muscular, anterior interosseous, and palmar cutaneous. The muscular branches supply all the superficial muscles on the front of the forearm, except the Flexor carpi ulnaris. These branches are derived from the nerve near the elbow. The branch furnished to the Pronator radii teres often arises above the joint. The anterior interosseous supplies the deep muscles on the front of the fore- arm. It accompanies the anterior interosseous artery along the interosseous membrane, in the interval between the Flexor longus pollicis and Flexor pro- fundus digitorum rnuscles, both of which it supplies, and terminates below in the Pronator quadratus. The palmar cutaneous branch arises from the median nerve at the lower part of the forearm. It pierces the fascia above the annular ligament, and divides into two branches; the outer one supplies the skin over the ball of the thumb, and communicates with the external cutaneous nerve ; the inner one supplies the inte- gument of the palm of the hand, anastomosing with the cutaneous branch of the ulnar. Both nerves cross the annular ligament previous to their distribution. In the palm of the hand, the median nerve is covered by the integument and palmar fascia, and rests upon the tendons of the Flexor muscles. In this situation it becomes enlarged, somewhat flattened, of a reddish color, and divides into two branches. Of these, the external one supplies a muscular branch to some of the muscles of the thumb, and digital branches to the thumb and index-finger; the internal branch supplying digital branches to the middle finger and part of the index and ring fingers. The branch to the muscles of the thumb is a short nerve, which subdivides to supply the Abductor, Opponens, and outer head of the Flexor brevis pollicis muscles ; the remaining muscles of this group being supplied by the ulnar nerve. 572 SPINAL NERVES. Pig. 288.— Nerves of the Left Upper Extremity. Front View. External 'Anterior T7u>raete Tntemat ULNAR. 573 The digital branches are five in number. The first and second pass along the borders of the thumb, the most external one communicating with branches of the radial nerve. The third passes along the radial side of the index-finger, and supplies the first Lumbrical muscle. The fourth subdivides to supply the adjacent sides of the index and middle fingers, and sends a branch to the second Lumbrical muscle. The fifth supplies the adjacent sides of the middle and ring fingers, and communicates with a branch from the ulnar nerve. Each digital nerve, opposite the base of the first phalanx, gives off a dorsal branch, which joins the dorsal digital nerve, and runs along the side of the dorsum of the finger, ending in the integument over the last phalanx. At the end of the finger, the digital nerve divides into a palmar and a dorsal branch ; the former supplies the extremity of the finger, and the latter ramifies round and beneath the nail. The digital nerves, as they run along the fingers, are placed superficial to the digital arteries. The Ulnar Nerve is placed along the inner or ulnar side of the upper limb, and is distributed to the muscles and integument of the forearm and hand. It is smaller than the median, behind which it is placed, diverging from it in its course down the arm. It arises from the inner cord of the brachial plexus, in common with the inner head of the median and the internal cutaneous nerves. At its commencement, it lies at the inner side of the axillary artery, and holds the same relation with the brachial artery to the middle of the arm. From this point, it runs obliquely across the internal head of the Triceps, pierces the internal intermuscular septum, and descends to the groove between the internal condyle and olecranon, accompanied by the inferior profunda artery. At the elbow, it rests upon the back of the inner condyle, and passes into the forearm between the two heads of the Flexor carpi ulnaris. In the forearm, it descends in a perfectly straight course along its ulnar side, lying upon the Flexor profundus digitorum, its upper half being covered by the Flexor carpi ulnaris, its lower half lying on the outer side of this muscle, covered by the integument and fascia. The ulnar artery, in the upper part of its course, is separated from the ulnar nerve by a considerable interval : but in the rest of its extent, the nerve lies to its inner side. At the wrist, the ulnar nerve crosses the annular ligament on the outer side of the pisiform bone, a little behind the ulnar artery, and immediately beyond this bone divides into two branches, superficial and deep palmar. The branches of the ulnar nerve are : — ' Articular (elbow). -Musculir In the forearm A Cutaneous. In hand 1 Superficial palmar, j Dorsal branch. 1 Deep palmar. [ Articular (wrist). The articular branches distributed to the elbow-joint consist of several small filaments. They arise from the nerve as it lies in the groove between the inner condyle and olecranon. The muscular branches are two in number; one supplying the Flexor carpi ulnaris ; the other, the inner half of the Flexor profundus digitorum. They arise from the trunk of the nerve near the elbow. The cutaneous branch arises from the ulnar nerve about the middle of the fore- arm, and divides into a superficial and deep branch. The superficial branch (frequently absent) pierces the deep fascia near the wrist, and is distributed to the integument, communicating with a branch of the internal cutaneous nerve. The deep branch lies on the ulnar artery, which it accompanies to the hand, some filaments entwining round the vessel, which end in the integument of the palm, communicating with branches of the median nerve. The dorsal cutaneous branch arises about two inches above the wrist ; it passes backwards beneath the Flexor carpi ulnaris, perforates the deep fascia, and, running 574 SPINAL NERYES. Fig. 289. — The Suprascapular, Circumflex, and Musculo-spiral Nerves. Supra-Seetyuli Circumflex along the ulnar side of the wrist and hand, supplies the inner side of the little finger, and the adjoining sides of the little and ring fingers ; it also sends a com- municating filament to that branch of the radial nerve which supplies the adjoining sides of the middle and ring fingers. The articular filaments to the wrist are also supplied by the ulnar nerve. The superficial palmar branch supplies the Palmaris brevis, and the integument on the inner side of the hand, and terminates in two digital branches, which are distributed, one to the ulnar side of the little finger, the other to the adjoining sides of the little and ring fingers, the latter com- municating with a branch from the median. The deep palmar branch passes between the Abduc- tor and Flexor brevis minimi digiti muscles, and follows the course of the deep palmar arch beneath the flexor tendons. At its origin, it supplies the muscles of the little finger. As it crosses the deep part of the hand it sends two branches to each interos- seous space, one for the Dorsal and one for the Palmar interosseous mus- cle, the branches to the second and third Palmar interossei supplying fila- ments to the two inner Lumbrical muscles. At its termination between the thumb and index-finger, it supplies the Adductor pol- licis and the inner head of the Flexor brevis pollicis. The Musculo-spikal Nerve (fig. 289), the largest branch of the brachial plexus, supplies the mus- cles of the back part of the arm and forearm, and the integument of the same parts, as well as that of the hand. It arises from the posterior cord of the brachial plexus by a com- mon trunk with the cir- cumflex nerve. At its commencement, it is placed behind the axillary and upper part of the brachial arteries, passing down in front of the tendons of the Latissimus dorsi and Teres major. It winds round MUSCULO-SPIRAL. 515 the "humerus in the spiral groove with the superior profunda artery and vein, passing from the inner to the outer side of the bone, beneath the Triceps muscle. At the outer side of the arm, it descends between the Brachialis anticus and Supinator longus to the front of the external condyle, where it divides into the radial and posterior interosseous nerves. The branches of the musculo-spiral nerve are : — Muscular. Radial. Cutaneous. Posterior interosseous. The muscular branches supply the Triceps, Anconeus, Supinator longus, Extensor carpi radialis longior, and Brachialis anticus. These branches are derived from the nerve, at the inner side, back part, and outer side of the arm. The internal muscular branches supply the inner and middle heads of the Triceps muscle. That to the inner head of the Triceps is a long, slender filament, which lies close to the ulnar nerve, as far as the lower third of the arm. The posterior muscular branch, of large size, arises from the nerve in the groove between the Triceps and the humerus. It divides into branches which supply the outer head of the Triceps and Anconeus muscles. The branch for the latter muscle is a long, slender filament, which descends in the substance of the Triceps to the Anconeus. The external muscular branches supply the Supinator longus, Extensor carpi radialis longior, and Brachialis anticus. The cutaneous branches are three in number, one internal and two external. The internal cutaneous branch arises in the axillary space, with the inner muscular branch. It is of small size, and passes across the axilla to the inner side of the arm, supplying the integument on its posterior aspect nearly as far as the olecranon. The two external cutaneous branches perforate the outer head of the Triceps, at its attachment to the humerus. The upper and smaller one follows the course of the cephalic vein to the front of the elbow, supplying the integument of the lower half of the upper arm on its anterior aspect. The lower branch pierces the deep fascia below the insertion of the Deltoid, and passes down along the outer side of the arm and elbow, and along the back part of the radial side of the forearm to the wrist, supplying the integument in its course, and joining, near its termination, with a branch of the external cutaneous nerve. The radial nerve passes along the front of the radial side of the forearm, to the commencement of its lower third. It lies at first a little to the outer side of the radial artery, concealed beneath the Supinator longus. In the middle third of the forearm, it lies beneath the same muscle, in close relation with the outer side of the artery. It quits the artery about three inches above the wrist, passes beneath the tendon of the Supinator longus, and, piercing the deep fascia at the outer border of the forearm, divides into two branches. The external branch, the smaller of the two, supplies the integument of the radial side, and ball of the thumb, joining with the posterior branch of the external cutaneous nerve. The internal branch communicates, above the wrist, with a branch from the external cutaneous, and, on the back of the hand, forms an arch with the dorsal branch of the ulnar nerve. It then divides into four digital nerves, which are distributed as follows : — The first supplies the ulnar side of the thumb ; the second, the radial side of the index finger ; the third, the adjoining sides of the index and middle fingers; and the fourth, the adjacent borders of the middle and ring fingers. The latter nerve communicates with a filament from the dorsal branch of the ulnar nerve. The posterior interosseous nerve pierces the Supinator brevis, winds to the back of the forearm, in the substance of this muscle, and, emerging from its lower border, 5 ?6 SPINAL NERVES. passes down between the superficial and deep layer of muscles, to the middle of the forearm. Considerably diminished in size, it descends on the interosseous membrane, beneath the Extensor secundi internodii pollicis, to the back of the carpus, where it presents a gangliform enlargement, from which filaments are distributed to the ligaments and articulations of the carpus. It supplies all the muscles of the radial and posterior brachial regions, excepting the Anconeus, Supinator longus, and Extensor carpi radialis longior. Dorsal Nerves. The Dorsal Nerves are twelve in number on each side. The first appears between the first and second dorsal vertebrae, and the last between the last dorsal and first lumbar. The roots of origin of the dorsal nerves are few in number, of small size, and vary but slightly from the second to the last. Both roots are very slender ; the posterior ones exceeding in thickness those of the anterior only in a slight degree. These roots gradually increase in length from above downwards, and remain in contact with the spinal cord for a distance equal to the height of, at least, two vertebrae, in the lower part of the dorsal region. They then join in the inter- vertebral foramen, and, at their exit, divide into two branches, a posterior or dorsal, and an anterior or intercostal branch. The first and last dorsal nerves are exceptions to these characters. The posterior branches of the dorsal nerves, which are smaller than the intercostal, pass backwards between the transverse processes, and divide into external and internal branches. The external branches increase in size from above downwards. They pass through the Longissimus dorsi, corresponding to the cellular interval between it and the Sacro-lumbalis, supplying these muscles, as well as those by which they are continued upwards to the head, and the Levatores costarum ; the five or six lower ones giving off cutaneous filaments. The internal branches of the six upper nerves pass inwards to the interval between the Multifidus spinas and Semi-spinalis dorsi muscles, which they supply; then, piercing the origin of the Khomboidei and Trapezius, become cutaneous by the side of the spinous processes. The internal branches of the six lower nerves are distributed to the Multifidus spinas, without giving off any cutaneous filaments. The cutaneous branches of the dorsal nerves are twelve in number, the six upper being derived from the internal branches, and the six lower from the ex- ternal branches. The former pierce the Rhomboid and Trapezius muscles, close to the spinous processes, and ramify in the integument. They are frequently 'furnished with gangliform enlargements. The six lower cutaneous branches pierce the Serratus posticus inferior, and Latissimus dorsi, in a line with the angles of the ribs. Intercostal Nerves. The Intercostal Nerves (anterior branches of the dorsal nerves) are twelve in number on each side. They are distributed to the parietes of the thorax and abdomen, separately from c;ich other, without being joined in a plexus, in which respect they differ from all the other spinal nerves. Each nerve is connected with the adjoining ganglia of the sympathetic by one or two filaments. The intercostal nerves may be divided into two sets, from the difference they present in their dis- tribution. The six upper, with the exception of the first, are limited in their distribution to the parietes of the chest. The six lower supply the parietes of the chest and abdomen. The Upper Intercostal Nerves pass forwards in the intercostal spaces with the intercostal vessels, lying below the veins and artery. At the back of the chest, INTERCOSTAL. 5T7 they lie between the pleura and the External intercostal muscle, but are soon placed between the two planes of Intercostal muscles as far as the costal car- tilages, where they lie between the pleura and the Internal intercostal muscles. Near the sternum, they cross the internal mammary artery, and Triangularis sterni, pierce the Internal intercostal and Pectoralis major muscles, and supply the integument of the mamma and front of the chest, forming the anterior cutaneous nerves of the thorax ; that from the second nerve becoming joined with the cla- vicular nerve. Branches, Numerous slender muscular filaments supply the Intercostal and Triangularis sterni muscles. Some of these branches, at the front of the chest, cross the costal cartilages from one to another intercostal space. Lateral cutaneous nerves. These are derived from the intercostal nerves, midway between the vertebrae and sternum, pierce the External intercostal and Serratus magnus muscles, and divide into two branches, anterior and posterior. The anterior branches are reflected forwards to the side and forepart of the chest, supplying the integument of the chest and mamma, and the upper digitations of the External oblique. The posterior branches are reflected backwards, to supply the integument over the scapula and Latissimus dorsi. The first intercostal nerve has no lateral cutaneous branch. The lateral cutaneous branch of the second intercostal nerve is of large size, and named, from its origin and distribution, the intercosto- humeral nerve. It pierces the External intercostal muscle, crosses the axilla to the inner side of the arm, and joins with a filament from the nerve of Wrisberg. It then pierces the fascia, and supplies the skin of the upper half of the inner and back part of the arm, communicating with the internal cutaneous branch of the musculo-spiral nerve. The size of this nerve is in inverse proportion to the size of the other cutaneous nerves, especially the nerve of Wrisberg. A second intercosto-humeral nerve is frequently given off from the third intercostal. It supplies filaments to the arm-pit and inner side of the arm. The Lower Intercostal Nerves (excepting the last) have the same arrangement as the upper ones as far as the anterior extremities of the intercostal spaces, where they pass behind the costal cartilages, and between the Internal oblique and Trans- versalis muscles, to the sheath of the Rectus, which they perforate. They supply the Rectus muscle, and terminate in branches which become subcutaneous near the linea alba (anterior cutaneous nerves of the abdomen), supplying the integument in front of the abdomen, being directed outwards to the lateral cutaneous nerves. The lower intercostal nerves supply the Intercostal and abdominal muscles, and, about the middle of their course, give off lateral cutaneous branches, which pierce the External intercostal and External oblique muscles, and are distributed to the integument of the abdomen, the anterior branches passing nearly as far forwards as the margin of the Rectus ; the posterior branches passing to supply the skin over the Latissimus dorsi, where they join the dorsal cutaneous nerves. Peculiar Dorsal Nerves. First dorsal nerve. Its roots of origin are similar to those of a cervical nerve. Its posterior or dorsal branch resembles, in its mode of distribution, the dorsal branches of the cervical nerves. Its anterior branch enters almost wholly into the formation of the brachial plexus, giving off, before it leaves the thorax, a small intercostal branch, which runs along the first intercostal space, and terminates on the front of the chest, by forming the first anterior cutaneous nerve of the thorax. The first intercostal nerve gives off no lateral cutaneous branch. The last dorsal is larger than the other dorsal nerves. Its anterior branch runs along the lower border of the last rib in front of the Quadratus lumborum, perforates the aponeurosis of the Transversalis, and passes forwards between it and the Internal oblique, to be distributed in the same manner as the preceding 37 578 SPINAL NERYES. nerves. It communicates with the iliohypogastric branch of the lumbar plexus, and is occasionally connected with the first lumbar nerve by a slender branch, the dorsi-lumbar nerve, which descends in the substance of the Quadratus lum- borum. The lateral cutaneous branch of the last dorsal is remarkable for its large size ; it perforates the Internal and External oblique muscles, passes downwards over the crest of the ilium, and is distributed to the integument of the front of the hip, some of its filaments extending as low down as the trochanter major. Lumbar Nerves. The Lumbar nerves are five in number on each side ; the first appears between the first and second lumbar vertebras, and the last between the last lumbar and the base of the sacrum. The roots of the lumbar nerves are the largest, and their filaments the most numerous, of all the spinal nerves, and they are closely aggregated together upon the lower end of the cord. The anterior roots are smaller ; but there is not the same disproportion between them and the posterior roots as in the cervical nerves. The roots of these nerves have a vertical direction, and are of considerable length, more especially the lower ones, as the spinal cord does not extend beyond the first lumbar vertebra. The roots become joined in the intervertebral foramina, and, at their exit, divide into two branches, anterior and posterior. The posterior branches of the lumbar nerves diminish in size from above down- wards ; they pass backwards between the transverse processes, and divide into external and internal branches. The external branches supply the Erector spinas and Inter-transverse muscles. From the three upper branches cutaneous nerves are derived, which pierce the Sacro-lumbalis and Latissimus dorsi muscles, and descend over the back part of the crest of the ilium, to be distributed to the integument of the gluteal region, some of the filaments passing as far as the trochanter major. The internal branches, the smaller, pass inwards close to the articular processes of the vertebrae, and supply the Multifidus spinas and Inter-spinales muscles. The anterior branches of the lumbar nerves increase in size from above down- wards. At their origin, they communicate with the lumbar ganglia of the sym- pathetic by long slender filaments, which accompany the lumbar arteries round the sides of the bodies of the vertebrae, beneath the Psoas muscle. The nerves pass obliquely outwards behind the Psoas magnus, or between its fasciculi, distributing filaments to it and the Quadratus lumborum. The anterior branches of the four upper nerves are connected together in this situation by anastomotic loops, and form the lumbar plexus. The anterior branch of the fifth lumbar, joined with a branch from the fourth, descends across the base of the sacrum to join the anterior branch of the first sacral nerve, and assist in the formation of the sacral plexus. The cord resulting from the union of these two nerves is called the lumbosacral nerve. Lumbar Plexus. The Lumbar plexus is formed by the loops of communication between the ante- rior branches of the four upper lumbar nerves. The plexus is narrow above, and occasionally connected with the last dorsal by a slender branch, the dorsi-lumbar nerve ; it is broad below, where it is joined to the sacral plexus by the lumbo-sacral. It is situated in the substance of the Psoas muscle, near its posterior part, in front of the transverse processes of the lumbar vertebrae. The mode in which the plexus is formed is the following : — The first lumbar nerve gives off the ilio-hypogastric and ilio-inguinal nerves, and a communicating branch to the second. The second gives off the external cutaneous and genito- crural, and a communicating branch to the third nerve. The third nerve gives a descending filament to the fourth, and divides into two branches, which assist in LUMBAR PLEXUS. 579 forming the anterior crural and obturator nerves. The fourth nerve completes the formation of the anterior crural, and the obturator, furnishes part of the accessory obturator, and gives off a communicating branch to the fifth lumbar. The branches of the lumbar plexus are the Ilio-hypogastric. Ilio-inguinal. Genito-crural. External cutaneous. Obturator. Accessory obturator. Anterior crural. These branches may be divided into two groups, according to their mode of distribution. One group, including the ilio-hypogastric, ilio-inguinal, and part of the genito-crural nerves, supplies the lower part of the parietes of the abdomen ; the other group, which includes the remaining nerves, supplies the forepart of the thigh and inner side of the leg. Fig. 290. — The Lumbar Plexus and its Branches. The Ilio-hypogastric nerve (superior muscuh-cutaneous) arises from the first lumbar nerve. It pierces the outer border of the Psoas muscle at its upper part, and crosses obliquely in front of the Quadratus lumborum to the crest of the ilium. It then perforates the Transversalis muscle at its back part, and divides between it and the Internal oblique into two branches, iliac and hypogastric. 580 SPINAL NERVES. The iliac hranch pierces the Internal and External oblique muscles imme- diately above the crest of the ilium, and is distributed to the integument of the gluteal region, behind the lateral cutaneous branch of the last dorsal nerve (fig. 293). The size of this nerve bears an inverse proportion to that of the cutaneous branch of the last dorsal nerve. The hypogastric branch continues onwards between the Internal oblique and Transversalis muscles. It first pierces the Internal oblique, and near the middle line perforates the External oblique above the external abdominal ring, and is distributed to the integument covering the hypogastric region. The Ilioinguinal nerve (inferior musculo-cutaneous), smaller than the pre- ceding, arises with it from the first lumbar nerve. It pierces the outer border of the Psoas just below the ilio-hypogastric, and, passing obliquely across the Quad- ratus lumborum and Iliacus muscles, perforates the Transversalis, near the fore- part of the crest of the ilium, and communicates with the ilio-hypogastric nerve between that muscle and the Internal oblique. The nerve then pierces the Internal oblique, distributing filaments to it, and, accompanying the spermatic cord, escapes at the external abdominal ring, and is distributed to the integument of the scrotum and upper and inner part of the thigh in the male and to the labium in the female. The size of this nerve is in inverse proportion to that of the ilio- hypogastric. Occasionally it is very small, and ends by joining it ; in such cases, a branch from the ilio-hypogastric takes the place of that nerve, or the nerve may be altogether absent. The Genito-crueal Nerve arises from the second lumbar, and by a few fibres from the cord of communication between it and the first. It passes obliquely through the substance of the Psoas, descends on its surface to near Poupart's ligament, and divides into a genital and a crural branch. The genital hranch descends on the .external iliac artery, sending a few fila- ments round that vessel; it then pierces the fascia transversalis, and, passing through the internal abdominal ring, descends along the back part of the sper- matic cord to the scrotum, and supplies, in the male, the Cremaster muscle. In the female, it accompanies the round ligament, and is lost upon it. The crural hranch passes along the inner margin of the Psoas muscle, beneath Poupart's ligament, into the thigh, where it pierces the fascia lata, and is distri- buted to the integument of the upper and anterior aspect of the thigh, communi- cating with the middle cutaneous nerve. A few filaments from this nerve may be traced on to the femoral artery ; they are derived from the nerve as it passes beneath Poupart's ligament. The External Cutaneous Nerve arises from the second lumbar, or from the loop between it and the third. It perforates the outer border of the Psoas muscle about its middle, and crosses the Iliacus muscle obliquely, to the notch imme- diately beneath the anterior superior spine of the ilium, where it passes beneath Poupart's ligament into the thigh, and divides into two branches of nearly equal size. The anterior hranch descends in an aponeurotic canal formed in the fascia lata, becomes superficial about four inches below Poupart's ligament, and divides into branches, which are distributed to the integument along the anterior and outer part of the thigh, as far down as the knee. This nerve occasionally com- municates with the long saphenous nerve. The posterior hranch pierces the fascia lata, and subdivides into branches which pass across the outer and posterior surface of the thigh, supplying the integument in this region as far as the middle of the thigh. The Obturator Nerve supplies the Obturator externus and Adductor muscles of the thigh, the articulations of the hip and knee, and occasionally the integu- ment of the thigh and leg. It arises by two branches ; one from the third, the other from the fourth lumbar nerve. It descends through the inner fibres of the Psoas muscle, and emerges from its inner border near the brim of the pelvis ; it then runs along the lateral wall of the pelvis, above the obturator vessels, to the CUTANEOUS NERYBS OF LOWER EXTREMITY. 581 Fig. 291. — Cutaneous Nerves of Lower Extremity. Front View. Fig. 292.— Nerves of the Lower Extremity. Front View. 1 •*./?9i SYMPATHETIC NERVE. Cephalic Portion of the Sympathetic. The cephalic portion of the sympathetic consists of four ganglia. 1. The oph- thalmic ganglion. 2. The spheno-palatine or Meckel's ganglion. 3. The otic or Arnold's ganglion. 4. The submaxillary ganglion. These have been already described in connection with each of the three divi- sions of the fifth nerve. Cervical Portion of the Sympathetic. • The cervical portion of the sympathetic consists of three ganglia on each side, which are distinguished according to their position, as the superior, middle, and inferior cervical. The Superior Cervical Ganglion, the largest of the three, is placed opposite the second and third cervical vertebrae, and sometimes as low as the fourth or fifth. It is of a reddish-gray color, and usually fusiform in shape ; sometimes broad, and occasionally constricted at intervals, so as to give rise to the opinion, that it con- sists of the coalescence of several smaller ganglia. It is in relation, in front, with the sheath of the internal carotid artery, and internal jugular vein ; behind, it lies on the Eectus capitis anticus major muscle. Its branches may be divided into superior, inferior, external, internal, and anterior. The Superior branch appears to be a direct continuation of the ganglion. It is soft in texture, and of a reddish color. It ascends by the side of the internal carotid artery, and, entering the carotid canal in the temporal bone, divides into two branches, which lie, one on the outer side, and the other on the inner side, of that vessel. The outer branch, the larger of the two, distributes filaments to the internal caro- tid artery, and forms the Carotid Plexus (described on page 595). The inner branch also distributes filaments to the internal carotid, and, continu- ing onwards, forms the Cavernous Plexus (described on page 595). The Inferior or Descending branch of the superior cervical ganglion communi- cates with the middle cervical ganglion. The External branches are numerous, and communicate with the cranial nerves, and with the four upper spinal nerves. Sometimes, the branch of the fourth spinal nerve may come from the cord connecting the upper and middle cervical ganglia. The branches of communication with the cranial nerves consist of delicate filaments, which pass from the superior cervical ganglion to the ganglion of the trunk of the pneumogastric, and to the ninth nerve. A separate filament from the cervical ganglion subdivides and joins the petrosal ganglion of the glosso-pharyngeal, and the ganglion of the root of the pneumogastric in the jugular foramen. The Internal branches are three in number: pharyngeal, laryngeal, and the superior cardiac nerve. The pharyngeal branches pass inwards to the side of the pharynx, where they join with branches from the pneumogastric, glosso-pharyn- geal, and external laryngeal nerves, and assist in forming the pharyngeal plexus. The laryngeal branches unite with the superior laryngeal nerve and its branches. The superior cardiac nerve will be described in connection with the other cardiac nerves. The Anterior branches ramify upon the external carotid artery and its branches, forming round each a delicate plexus, on the nerves composing which small ganglia are occasionally found. These ganglia have been named, according to their position, intercarotid (one placed at the angle of bifurcation of the common carotid), lingual, temporal, and pharyngeal. The plexuses accompanying some of these arteries have important communications with other nerves. That sur- rounding the external carotid is connected with the digastric branch of the facial; that surrounding the facial communicates with the submaxillary ganglion by one or two filaments ; and that accompanying the middle meningeal artery sends CERVICAL GANGLIA. 595 offsets which pass to the otic ganglion and to the intumescentia gangliformis of the facial nerve. The Middle Cervical Ganglion (thyroid ganglion) is the smallest of the three cervical ganglia, and is occasionally altogether wanting. It is placed opposite the fifth cervical vertebra, usually upon, or close to, the inferior thyroid artery; hence the name " thyroid ganglion," assigned to it by Haller. Its superior branches ascend to communicate with the superior cervical ganglion. Its inferior branches descend to communicate with the inferior cervical ganglion. Its external branches pass outwards to join the fifth and sixth spinal nerve?. These branches are not constantly found. Its internal brandies are the thyroid and the middle cardiac nerve. The thyroid branches are small filaments, which accompany the inferior thyroid artery to the thyroid gland ; they communicate, on the artery, with the superior cardiac nerve, and, in the gland, with branches from the recurrent and external laryngeal nerves. The middle cardiac nerve is described with the other cardiac nerves. The Inferior Cervical Ganglion is situated between the base of the trans- verse process of the last cervical vertebra and the neck of the first rib, on the inner side of the superior intercostal artery. Its form is irregular ; it is larger in size than the preceding, and frequently joined with the first thoracic ganglion. Its superior branches communicate with the middle cervical ganglion. Its inferior branches descend, some in front of, others behind, the subclavian arterv, to join the first thoracic ganglion. The most important of these branches constitutes the inferior cardiac nerve, to be presently described. The external branches consist of several filaments, some of which communicate with the seventh and eighth spinal nerves; others accompany the vertebral artery along the vertebral canal, forming a plexus round this vessel, supplying it with filaments, and communicating with the cervical spinal nerves as high as the fourth. Carotid and Cavernous Plexuses. The Carotid Plexus is situated on the outer side of the internal carotid. Fila ments from this plexus occasionally form a small gangliform swelling on the under surface of the artery, which is called the carotid ganglion. The carotid plexus communicates with the Casserian ganglion, with the sixth nerve, and spheno- palatine ganglion, and distributes filaments to the wall of the carotid artery, and to the dura mater (Valentin). The communicating branches with the sixth nerve consist of one or two fila- ments, which join that nerve as it lies upon the outer side of the internal carotid. Other filaments are also connected with the Casserian ganglion. The communica- tion with the spheno-palatine ganglion is effected by the carotid portion of the Vidian nerve, which passes forwards, through the cartilaginous substance filling in the foramen lacerum medium, along the pterygoid canal, to the spheno-palatine ganglion. In this canal it joins the petrosal branch of the Vidian. The Cavernous Plexus is situated below, and to the inner side of, that part of the internal carotid, which is placed by the side of the sella Turcica, in the cavernous sinus, and is formed chiefly by the internal division of the ascending branch from the superior cervical ganglion. It communicates with the third, fourth, fifth, and sixth nerves, and with the ophthalmic ganglion, and distributes filaments to the wall of the internal carotid. The branch of communication with the third nerve joins it at its point of division ; the branch to the fourth nerve joins it as it lies on the outer wall of the cavernous sinus ; other filaments are connected with the under surface of the trunk of the ophthalmic nerve ; and a second filament of communication joins the sixth nerve. The filament of connection with the ophthalmic ganglion arises from the ante- 596 SYMPATHETIC NERVE. rior part of the cavernous plexus ; it accompanies the nasal nerve, or continues forwards as a separate branch. The terminal filaments from the carotid and cavernous plexuses are prolonged along the internal carotid, forming plexuses which entwine round the cerebral and ophthalmic arteries ; along the former vessel they may be traced on to the pia mater ; along the latter, into the orbit, where they accompany each of the subdivisions of the vessel, a separate plexus passing with the arteria centralis retinas into the interior of the eyeball. Cardiac Nerves. The cardiac nerves are three in number on each side ; — superior, middle, and inferior, one being derived from each of the cervical ganglia. The Superior Cardiac nerve (nervus superficialis cordis) arises by two or more branches from the superior cervical ganglion, and occasionally receives a filament from the cord of communication between the first and second cervical ganglia. It runs down the neck behind the common carotid artery, lying upon the Longus colli muscle, and crosses in front of the inferior thyroid artery, and the recurrent laryngeal nerve. The right superior cardiac nerve, at the root of the neck, passes either in front of or behind the subclavian artery, and along the arteria innominata, to the back part of the arch of the aorta, to the deep cardiac plexus. This nerve, in its course, is connected with other branches of the sympathetic ; about the middle of the neck it receives filaments from the external laryngeal nerve ; lower down, one or two twigs from the pneumogastric, and, as it enters the thorax, it joins with the recurrent laryngeal. Filaments from this nerve accompany the inferior thyroid artery to the thyroid gland. The left superior cardiac nerve runs by the side of the left carotid artery, and in front of the arch of the aorta, to the superficial cardiac plexus; it occasionally passes behind this vessel, and terminates in the deep cardiac ..plexus. The Middle Cardiac nerve (nervus cardiacus magnus), the largest of the three, arises from the middle cervical ganglion, or from the interganglionic cord between the middle and inferior ganglia. On the right side, it descends behind the common carotid artery ; and, at the root of the neck, passes either in front of or behind the subclavian artery ; it then descends on the trachea, receives a few filaments from the recurrent laryngeal nerve, and joins the deep cardiac plexus. In the neck, it communicates with the superior cardiac and recurrent laryngeal nerves. On the left side, the middle cardiac nerve enters the chest between the left carotid and subclavian arteries, and joins the left side of the deep cardiac plexus. The Inferior Cardiac nerve (nervus cardiacus minor) arises from the inferior cervical or first thoracic ganglion. It passes down behind the subclavian artery, and along the front of the trachea, to join the deep cardiac plexus. It communi- cates freely behind the subclavian artery with the recurrent laryngeal and middle cardiac nerves. Cardiac and Coronary Plexuses. The Great or Deep Cardiac Plexus {p>lexus magnus profundus — Scarpa) is situated in front of the trachea at its bifurcation, above the point of division of the pulmonary artery, and behind the arch of the aorta. It is formed by the cardiac nerves derived from the cervical ganglia of the sympathetic, and the cardiac branches of the recurrent laryngeal and pneumogastric. The only cardiac nerves which do not enter into the formation of this plexus are the left superior cardiac nerve, and the left inferior cardiac branch from the pneumogastric. The branches derived from the great cardiac plexus form the posterior coronary plexus, and part of the anterior coronary plexus ; whilst a few filaments proceed to the pul- monary plexuses, and to the auricles of the heart. The branches from the right side of this plexus pass some in front of, and othera THORACIC GANGLIA. 597 behind, the right pulmonary artery ; the former, the more numerous, transmit a few filaments to the anterior pulmonary plexus, and are continued along the trunk of the pulmonary artery, to form part of the anterior coronary plexus ; those behind the pulmonary artery distribute a few filaments to the right auricle, and form part of the posterior coronary plexus. The branches from the left side of the cardiac plexus distribute a few filaments to the left auricle of the heart and the anterior pulmonary plexus, and then pass on to form the greater part of the posterior coronary plexus, a few branches passing to the superficial cardiac plexus. The Superficial {anterior) Cardiac plexus lies beneath the arch of the aorta, in front of the right pulmonary artery. It is formed by the left superior cardiac nerve, the left (and occasionally the right) inferior cardiac branches of the pneu- mogastric, and by filaments from the deep cardiac plexus. A small ganglion (cardiac ganglion of Wrisberg) is occasionally found connected with these nerves at their point of junction. This ganglion, when present, is situated immediately beneath the arch of the aorta, on the right side of the ductus arteriosus. The superficial cardiac plexus forms the chief part of the anterior coronary plexus, and several filaments pass along the pulmonary artery to the left anterior pulmonary plexus. The Posterior Coronary plexus is formed chiefly by filaments from the left side of the deep cardiac plexus, and by a few from the right side. It surrounds the branches of the coronary artery at the back of the heart, and its filaments are distributed with those vessels to the muscular substance of the ventricles. The Anterior Coronary plexus is prolonged chiefly from the superficial cardiac plexus, but receives filaments from the deep cardiac plexus. Passing forwards between the aorta and pulmonary artery, it accompanies the right coronary artery on the anterior surface of the heart. Valentin has described nervous filaments ramifying under the endocardium; and Bemak has found, in several mammalia, numerous small ganglia on the cardiac nerves, both on the surface of the heart and in its muscular substance. The elaborate dissections lately completed by Dr. Robert Lee have demonstrated with- out any doubt the existence of a dense mesh of nerves distributed both to the surface, and in the substance of the heart, having numerous ganglia developed upon them. Thoeacic Part of the Sympathetic. The thoracic portion of the sympathetic consists of a series of ganglia, which usually correspond in number to that of the vertebrae ; but, from the occasional coalescence of two, their number is uncertain. These ganglia are placed on each side of the spine, resting against the heads of the ribs, and covered by the pleura costalis: the last two are, however, anterior to the rest, being placed on the side of the bodies of the vertebras. The ganglia are small in size, and of a grayish color. The first, larger than the rest, is of an elongated form, and usually blended with the last cervical. They are connected together by cord-like pro- longations from their substance. The external branches from each ganglion, usually two in number, communicate with each of the dorsal spinal nerves. The internal branches from the six upper ganglia are very small, and distribute filaments to the thoracic aorta and its branches, besides small branches to the bodies of the vertebras and their ligaments. Branches from the third and fourth ganglia form part of the posterior pulmonary plexus. The internal branches from the six lower ganglia are large and white in color ; they distribute filaments to the aorta, and unite to form the three splanchnic nerves. These are named, the great, the lesser, and the smallest or renal splanchnic. The Great Splanchnic nerve is of a white color, firm in texture, and bears a marked contrast to the ganglionic nerves. It is formed by branches from the thoracic ganglia between the sixth and tenth, receiving filaments (according to 598 SYMPATHETIC NERYE. Mr. Beck) from all the thoracic ganglia above the sixth. These roots unite to form a large round cord of considerable size. It descends obliquely inwards in front of the bodies of the vertebras along the posterior mediastinum, perforates the crus of the Diaphragm, and terminates in the semilunar ganglion, distributing filaments to the renal plexus and supra-renal gland. The Lesser Splanchnic nerve is formed by filaments from the tenth and eleventh ganglia, and from the cord between them. It pierces the Diaphragm with the preceding nerve, and joins the coeliac plexus. It communicates in the chest with the great splanchnic nerve, and occasionally sends filaments to the renal plexus. The Smallest or Renal Splanchnic nerve arises from the last ganglion, and, piercing the Diaphragm, terminates in the renal plexus and lower part of the coeliac plexus. It occasionally communicates with the preceding nerve. A striking analogy appears to exist between the splanchnic and the cardiac nerves. The cardiac nerves are three in number; they arise from the three cervical ganglia, and are distributed to a large and important organ in the thoracic cavity. The splanchnic nerves, also three in number, are connected probably with all the dorsal ganglia, and are distributed to important organs in the abdominal cavity. The Epigastric or Solar plexus supplies all the viscera in the abdominal cavity. It consists of a dense network of nerves and ganglia, situated behind the stomach and in front of the aorta and crura of the Diaphragm. It surrounds the coeliac axis and root of the superior mesenteric artery, extending downwards as low as the pancreas, and outwards to the supra-renal capsules. This plexus, and the ganglia connected with it, receive the great splanchnic nerve of both sides, part of the lesser splanchnic nerves, and the termination of the right pneumogastric. It distributes filaments, which accompany, under the name of plexuses, all the branches from the front of the abdominal aorta. The semilunar ganglia of the solar plexus, two in number, one on each side, are the largest ganglia in the body. They are large irregular gangliform masses, formed by the aggregation of smaller ganglia, having interspaces between them. They are situated by the side of the coeliac axis and superior mesenteric artery, close to the supra-renal glands, the one on the right side lying beneath the vena cava; the upper part of each ganglion is joined by the greater and lesser splanchnic nerves, and to the inner side of each the branches of the solar plexus are connected. From the solar plexus are derived the following : — Phrenic or diaphragmatic plexus. Supra-renal plexus. Coeliac plexus. Eenal plexus. Gastric plexus. Superior mesenteric plexus. Hepatic plexus. Spermatic plexus. Splenic plexus. Inferior mesenteric plexus. The phrenic plexus accompanies the phrenic artery to the Diaphragm, which it supplies, some filaments passing to the supra-renal gland. It arises from the upper part of the semilunar ganglion, and is larger on the right than on the left side. In connection with this plexus, on the right side, at its point of junction with the phrenic nerve, is a small ganglion (ganglion diaphragmaticum). This ganglion is placed on the under surface of the Diaphragm, near the supra-renal gland. Its branches are distributed to the vena cava, supra-renal gland, and the hepatic plexus. The ganglion is absent on the left side. The supra-renal plexus is formed by branches from the solar plexus, from the semilunar ganglion, and from the splanchnic and phrenic nerves, a ganglion being formed at the point of junction of the latter nerve. It supplies the supra-renal gland. The branches of this plexus are remarkable for their large size, in com- parison with the size of the organ they supply. The renal plexus is formed by filaments from the solar plexus, the oiater part SOLAR PLEXUS— SEMILUNAR GANGLIA. 599 of the semilunar ganglion, and the aortic plexus. It is also joined by filaments from the lesser and smallest splanchnic nerves. The nerves from these sources, fifteen or twenty in number, have numerous ganglia developed upon them. They accompany the branches of the renal artery into the kidney ; some filaments on the right side being distributed to the vena cava, and others to the spermatic plexus, on both sides. The spermatic plexus is derived from the renal plexus, receiving branches from the aortic plexus. It accompanies the spermatic vessels to the testes. In the female, the ovarian plexus is distributed to the ovaries and fundus of the uterus. The coeliac plexus, of large size, is a direct continuation from the solar plexus : it surrounds the coeliac axis, and subdivides into the gastric, hepatic, and splenic plexuses. It receives branches from one or more of the splanchnic nerves, and, on the left side a filament from the pneumogastric. The gastric plexus accompanies the gastric artery along the lesser curvature of the stomach, and joins with branches from the left pneumogastric nerve. It is distributed to the stomach. The hepatic plexus, the largest offset from the cceliac plexus, receives filaments from the left pneumogastric and right phrenic nerves. It accompanies the hepatic artery, ramifying in the substance of the liver upon its branches and upon those of the vena portse. Branches from this plexus accompany all the divisions of the hepatic artery. Thus there is a pyloric plexus accompanying the pyloric branch of the hepatic, which joins with the gastric plexus, and pneumogastric nerves. There is also a gastro-duodenal plexus, which subdivides into the pancreatico-duodenal plexus, which accompanies the pancreatico-duodenal artery, to supply the pancreas and duodenum, joining with branches from the mesenteric plexus; and a gastro- epiploic plexus, which accompanies the right gastro-epiploic arter3 r along the greater curvature of the stomach, and anastomoses with branches from the splenic plexus. A cystic plexus, which supplies the gall-bladder, also arises from the hepatic plexus, near the liver. The splenic plexus is formed by branches from the right and left semilunar ganglia, and from the right pneumogastric nerve. It accompanies the splenic artery and its branches to the substance of the spleen, giving oft) in its course, filaments to the pancreas (pancreatic plexus), and the left gastro- epiploic plexus, which accompanies the gastro-epiploica sinistra artery along the convex border of the stomach. The superior mesenteric plexus is a continuation of the lower part of the great solar plexus, receiving a branch from the junction of the right pneumogastric nerve with the cceliac plexus. It surrounds the superior mesenteric artery, which it accompanies into the mesentery, and divides into a number of secondary plex- uses, which are distributed to all the parts supplied by the artery, viz., pan- creatic branches to the pancreas ; intestinal branches, which supply the whole of the small intestine ; and ileo- colic, right colic, and middle colic branches, which supply the corresponding parts of the great intestine. The nerves composing this plexus are white in color, and firm in texture, and have numerous ganglia developed upon them near their origin. The aortic plexus is formed by branches derived, on each side, from the semi- lunar ganglia and renal plexuses, receiving filaments from some of the lumbar ganglia. It is situated upon the sides and front of the aorta, between the origins of the superior and inferior mesenteric arteries. From this plexus arise the in- ferior mesenteric, part of the spermatic, and the hypogastric plexuses ; and it dis- tributes filaments to the inferior cava. The inferior mesenteric plexus is derived chiefly from the left side of the aortic plexus. It surrounds the inferior mesenteric artery, and divides into a number of secondary plexuses, which are distributed to all the parts supplied by the artery, viz., the left colic and sigmoid plexuses, which supply the descending and sigmoid 600 SYMPATHETIC NERYE. flexure of the colon ; and the superior hemorrhoidal plexus, which supplies the upper part of the rectum, and joins in the pelvis with branches from the left hypogastric plexus. The Lumbar Portion of the Sympathetic. The lumbar portion of the sympathetic is situated in 'front of the vertebral column, along the inner margin of the Psoas muscle. It consists usually of four ganglia, connected together by interganglionic cords. The ganglia aie of small size, of a grayish color, hordeiform in shape, and placed much nearer the median line than the thoracic ganglia. The superior and inferior branches of the lumbar ganglia serve as communicat- ing branches between the chain of ganglia in this region. They are usually single, and of a white color. The external branches communicate with the lumbar spinal nerves. Prom the situation of the lumbar ganglia, these branches are longer than in the other regions. They are usually two in number for each ganglion, and accompany the lumbar arteries around the sides of the bodies of the vertebrae, passing beneath the fibrous arches from which the fibres of the Psoas muscle partly arise. The internal branches pass inwards, in front of the aorta, and form the lumbar aortic plexus (already described). Other branches descend in front of the com- mon iliac arteries, and join, over the promontory of the sacrum, to form the hypogastric plexus. Numerous delicate filaments are also distributed to the bodies of the vertebras and the ligaments connecting them. Pelvic Portion of the Sympathetic. The pelvic portion of the sympathetic is situated in front of the sacrum, along the inner side of the anterior sacral foramina. It consists of four or five small ganglia on each side, connected together by interganglionic cords. Below, they converge and unite on the front of the coccyx, by means of a small ganglion (ganglion impar). The superior and inferior branches are the cords of communication between the ganglia above and below. The external branches, exceedingly short, communicate with the sacral nerves. They are two in number to each ganglion. The coccygeal nerve communicates either with the last sacral or the coccygeal ganglion. The internal branches communicate, on the front of the sacrum, with the corresponding branches from the opposite side ; some, from the first two ganglia, pass to join the pelvic plexus, and others form a plexus, which accompanies the middle sacral artery. The hypogastric plexus supplies the viscera of the pelvic cavity. It is situated in front of the promontory of the sacrum, between the two common iliac arteries, and is formed by the union of numerous filaments, which descend on each side from the aortic plexus, from the lumbar ganglia, and from the first two sacral ganglia. This plexus contains no ganglia, and bifurcates, below, into two lateral portions, which form the inferior hypogastric or pelvic plexuses. Inferior Hypogastric or Pelvic Plexus. The inferior hypogastric or pelvic plexus is situated at the side of the rectum and bladder in the male, and at the side of the rectum, vagina, and bladder, in the female. It is formed by a continuation of the hypogastric plexus, by branches from the second, third, and fourth sacral nerves, and by a few filaments from the sacral ganglia. At the point of junction of these nerves, small ganglia are found. From this plexus numerous branches are distributed to all the viscera of the pelvis. They accompany the branches of the internal iliac artery. PELVIC PLEXUS. 601 The inferior hemorrhoidal plexus arises from the back part of the pelvic plexus. It supplies the rectum, joining with branches of the superior hemorrhoidal plexus. The vesical plexus arises from the fore part of the pelvic plexus. The nerves composing it are numerous, and contain a large proportion of spinal nerve fibres. They accompany the vesical arteries, and are distributed to the side and base of the bladder. Numerous filaments also pass to the vesiculas seminales, and vas deferens ; those accompanying the vas deferens join, on the spermatic cord, with branches from the spermatic plexus. The prostatic plexus is continued from the lower part of the pelvic plexus. The nerves composing it are of large size. They are distributed to the prostate gland, vesicula3 seminales, and erectile structure of the penis. The nerves sup- plying the erectile structure of the penis consist of two sets, the small and large cavernous nerves. They are slender filaments, which arise from the fore part of the prostatic plexus; and, after joining with branches from the internal pudic nerve, pass forwards beneath the pubic arch. The small cavernous nerves perforate the fibrous covering of the penis near its root. The large cavernous nerve passes forwards along the dorsum of the penis, joins with the dorsal branch of the pudic nerve, and is distributed to the corpus caver - nosum and corpus spongiosum. The vaginal plexus arises from the lower part of the pelvic plexus. It is lost on the walls of the vagina, being distributed to the erectile tissue at its anterior part, and to the mucous membrane. The nerves composing this plexus contain, like the vesical, a large proportion of spinal nerve fibres. The uterine nerves arise from the lower part of the hypogastric plexus, above the point where the branches from the sacral nerves join the pelvic plexus. They accompany the uterine arteries to the side of the organ between the layers of the broad ligament, and are distributed to the cervix and lower part of the body of the uterus, penetrating its substance. Other filaments pass separately to the body of the uterus and Fallopian tube. Branches from the hypogastric plexus accompany the uterine arteries into the substance of the uterus. Upon these filaments ganglionic enlargements are found. 1 1 Much difference of opinion still exists as to whether the uterine nerves enlarge during preg- nancy. Dr. Robert Lee states, as the result of a series of elaborate investigations, that the nerves and ganglia supplying the uterus become greatly enlarged during gestation, thus confirm- ing the observations previously made by William Hunter, and Tiedemann. Dr. Snow Beck, on the other hand, asserts that the nerves do not alter in size during pregnancy. For a detailed account of this subject, the reader should refer to "The Anatomy of the Nerves of the Uterus," by Robert Lee, M. D., 1841; to two papers by the same author in the Phil. Trans., for 1842 ; and to Dr. Snow Beck's paper, "On the Nerves of the Uterus," in the Phil. Trans., for 1846. Organs of the Senses. The Organs of the Senses are the instruments by which the mind is brought into relation with external objects. These organs are five in number, viz., the organs of touch, of smell, of taste, of hearing, and of sight. The Skin. The skin is the principal seat of the sense of touch, and may be regarded as a covering for the protection of the deeper tissues ; it is also an important excretory and absorbing organ. It consists of two layers, the derma or cutis vera, and the epidermis or cuticle. On the surface of the former layer are the sensitive Fig. 297.— A Sectional View of the Skin (magnified). 1/u.trUat Artery papillae j and within, or imbedded beneath it, are the sweat-glands, hair-follicles, and sebaceous glands. The derma or true skin is tough, flexible, and highly elastic, being admirably adapted to defend the internal parts from violence. It consists of fibro-areolar tissue, intermixed with numerous bloodvessels, lymphatics, and nerves. The fibro-areolar tissue forms the framework of the cutis ; it is composed of firm 602 THE SKIN. 603 interlacing bundles of white fibrous tissue, intermixed with a much smaller pro- portion of yellow elastic fibres, the amount of which varies in different parts. The fibro-areolar tissue is more abundant in the deeper layers of the cutis, where it is dense and firm, the meshes being large, and gradually becoming blended with the subcutaneous areolar tissue ; towards the surface, the fibres become finer and more closely interlaced, the most superficial layer being covered with numerous small, conical, vascular eminences, the papilla?. From these differences in the structure of the cutis at different parts, it is usual to describe it as consisting of two layers ; the deep layer or corium, and the superficial or papillary layer. The corium consists of strong interlacing fibrous bands, composed chiefly of the white variety of fibrous tissue ; but containing, also, some fibres of the yellow elastic tissue, which vary in amount in different parts. Towards the attached surface, the fasciculi are large and coarse ; and the areola? left by their interlacing large and occupied by adipose tissue and the sweat-glands. This element of the skin becomes gradually blended with the subcutaneous areolar tissue. Towards the free surface, the fasciculi are much finer, and they have a closer interlacing, the most superficial layers consisting of a transparent, homogeneous matrix with imbedded nuclei. The corium varies in thickness, from a quarter of a line to a line and a half, in different parts of the body. Thus, it is thicker in the more exposed regions, as the palm of the hand and sole of the foot ; on the posterior aspect of the body, than the front ; and on the outer side of the limbs than the inner. In the eye- lids, scrotum, and penis, it is exceedingly thin and delicate. The skin generally is thicker in the male than in the female. The areolae are occupied by adipose tissue, hair follicles, and the sudatory and sebaceous glands; they are the channel by which the vessels and nerves are distributed to the more superficial strata of the corium, and to the papillary layer. Plain muscular fibres are found in the superficial layers of the corium, where- ever hairs are found ; and in the subcutaneous areolar tissue of the scrotum, penis, perineum, and areolae of the nipple. In the latter situations, the fibres are arranged in bands, closely reticulated and disposed in superimposed lamina?. The papillary layer is situated upon the free surface of the corium ; it consists of numerous small, highly sensitive, and vascular eminences, the papillae, which' rise perpendicularly from its surface, and form the essential element of the organ of touch. The papillae are conical-shaped eminences, having a round or blunted extremity, occasionally divided into two or more parts, and connected by their base with the free surface of the corium. Their average length is about T ^th of an inch, and they measure at their base about 35 ^th of an inch in diameter. On the general surface of the body, more especially in those parts which are endowed with slight sensibility, they are few in number, short, exceedingly minute, and irregularly scattered over the surface ; but in other situations, as upon the palmar surface of the hands and fingers, upon the plantar surface of the feet and toes, and around the nipple, they are long, of large size, closely aggregated together, and arranged in parallel curved lines, 'forming the elevated ridges seen on the free surface of the epidermis. In these ridges, the larger papillae are arranged in a double row, with smaller papillae between them ; and these rows are subdivided into small square-shaped masses by short transverse furrows regularly disposed, in the centre of each of which is the minute orifice of the duct of a sweat-gland. No papillae exist in the grooves between the ridges. In structure the papillae resemble the superficial layer of the cutis; consisting of a homogeneous tissue, faintly fibrillated, and containing a few fine elastic fibres. The smaller papilla? contain a single capillary loop ; but in the larger the vessels are convoluted to a greater or less degree ; each papilla also contains one or more nerve fibres* but the mode in which these terminate is uncertain. In those parts in which the sense of touch is highly developed, as in the lips and palm of the hand, the nerve fibres appear to have some intimate connection with an oval-shaped body, 604 ORGANS OF THE SENSES. not unlike a Pacinian corpuscle, which occupies the principal part of the interior of each papilla, named "tactile corpuscle." The nature of these bodies is obscure. Wagner described them as oval-shaped bodies, made up of superimposed saccular laminae, presenting some resemblance to a miniature fir cone, and regarded them as directly concerned in the sense of touch. Kolliker considers that the central part of the papillae generally consists of a more homogeneous connective tissue than the outer part, surrounded by a sort of sheath of elastic fibres, and believes that these corpuscles are merely a variety of this structure. The nerve fibres, accord- ing to this observer, run up in a waving course to the corpuscle, not penetrating it, but forming two or three coils round it, and finally join together in loops. These bodies are not found in all the papillae ; but from their existence in those parts in which the skin is highly sensitive, it is probable that they are specially concerned in the sense of touch, but their absence from the papillae of other tactile parts shows that they are not essential to this sense. No lymphatics have as yet been discovered in the papillae. The epidermis, cuticle, or scarf-skin, is an epithelial structure, accurately moulded on the papillary layer of the derma. It forms a defensive covering to. the surface of the true skin, and limits the evaporation of watery vapor from its free surface. It varies in thickness in different parts. Where it is exposed to pressure and the influence of the atmosphere, as upon the palms of the hands and soles of the feet, it is thick, hard, and horny in texture ; whilst that which lies in contact with the rest of the body is soft and cellular in structure. The deeper and softest layers have been called the rete mucosum, the term rete being applied, from the deepest layers presenting, when isolated, numerous depressions, or complete apertures, which have been occupied by the projecting papillae. The free surface of the epidermis is marked by a network of linear furrows of variable size, marking out the surface into a number of spaces of polygonal or lozenge-shaped form. Some of these furrows are large, as opposite the flexures of the joints, and correspond to the folds in the derma produced by their move- ments. In other situations, as upon the back of the hand, they are exceedingly fine, and intersect one another at various angles ; upon the palmar surface of the hand and fingers, and upon the sole, these lines are very distinct, and have a curvilinear arrangement, and depend upon the large size and peculiar arrangement of the papillae upon which the epidermis is placed. The deep surface of the epidermis is accurately moulded upon the papillary layer of the derma, each papilla being invested by its epidermic sheath ; so that when this layer is removed by maceration, it presents a number of pits or depressions corresponding to the elevations of the papillae, as well as the furrows left in the intervals between them. Fine tubular prolongations from this layer are continued into the ducts of the sudatory and sebaceous glands. In structure, the epidermis consists of flattened cells, agglutinated together, and having a laminated arrangement. In the deeper layers the cells are large, rounded or columnar, and filled with soft opaque contents. In the superficial layers the cells are flattened, transparent, dry, and firm, and their contents converted into a kind of horny matter. The difference in the structure of these layers is dependent upon the mode of growth of the epidermis. As the external layers desquamate, from their being constantly subjected to attri- tion, they are reproduced from beneath, successive layers gradually approaching towards the free surface, which, in their turn, die and are cast off. These cells are developed in the liquor, sanguinis, which is poured out on the free surface of the derma ; they contain nuclei, and form a thin stratum of closely- aggregated nucleated cells, which cover the entire extent of the papillary layer. The deepest layer of cells, according to Kolliker, are of a columnar form, and are arranged perpendicularly to the free surface of the derma, forming either a single or a double, or even triple, layer ; the laminae succeeding these are composed of cells of a more rounded form, the contents of which are soft, opaque, granular, and soluble in acetic acid. As these cells successively approach the surface by the development of fresh layers from beneath, they assume a flattened shape from the APPENDAGES OF THE SKIN. 605 evaporation of their fluid contents, and finally form a transparent, dry, mem- branous scale, lose their nuclei, and apparently become changed in their chemical composition, as they are unaffected now by acetic acid. The black color of the skin in the negro, and the tawny color among some of the white races, is due to the presence of pigment in the cells of the cuticle. This pigment is more especially distinct in the cells of the deeper layer or rote mucosum, and is similar to that found in the choroid. As the cells approach the surface and desiccate, the color becomes partially lost. The arteries which supply the skin divide into numerous branches in the sub- cutaneous tissue ; they then pass through the areola? of the corium, and divide into a dense capillary plexus, which supplies the sudatory and sebaceous glands and the hair follicles, terminating in the superficial layers of the corium, by form- ing a capillary network, from which numerous fine branches ascend to the papilla?. The lymphatic vessels are arranged in a minute plexiform network in the superficial layers of the corium, where they become interwoven with the capillary and nervous plexuses ; they are especially abundant in the scrotum and round the nipple. The nerves which supply the skin ascend with the vessels through the areola? of the deep layers of the corium to the more superficial layers, where they form a minute plexiform mesh. From this plexus, the primitive nerve fibres pass to be distributed to the papilla?. The nerves are most numerous in those parts which are provided with the greatest sensibility. Appendages of the Skin. The appendages of the skin are, the nails, the hairs, the sudoriferous and sebaceous glands, and their ducts. The nails and hairs are peculiar modifications of the epidermis, consisting essentially of the same cellular structure as that membrane. The Nails are flattened elastic structures of a horny texture, placed upon the dorsal surface of the terminal phalanges of the fingers and toes. Each nail is convex on its outer surface, concave within, and is implanted by a portion called the root into a groove of the skin; the exposed portion is called the body, and the anterior extremity, the free edge. The nail has a very firm adhesion to the cutis, being accurately moulded upon its surface, as the epidermis is in other parts. The part of the cutis beneath the body and root of the nail is called the matrix, from its being the part from which the nail is produced. Corresponding to the body of the nail, the matrix is thick, and covered with large highly vascular papilla?, arranged in longitudinal rows, the color of which is seen through the transparent tissue. Behind this, near the root of the nail, the papilla? are small, less vascular, and have no regular arrangement ; hence the portion of the nail corresponding to this part is of a whiter color, and called lunula from its form. The cuticle, as it passes forwards on the dorsal surface of the finger, is attached to the surface of the nail, a little in advance of its root ; at the extremity of the finger, it is connected with the under surface of the nail, a little behind its free edge. The cuticle and horny structure of the nail, both epidermic structures, are thus seen to be directly continuous with each other. The nails, in structure, consist of cells having a laminated arrangement, and these are almost essentially similar to those composing the epidermis. The deepest layer of cells which lie in contact with the papilla? at the root and under surface of the nail, are of elongated form, arranged perpendicularly to the surface, and provided with nuclei ; those which succeed these are of a rounded or polygonal form, the more superficial ones becoming broad, thin, and flattened, and so closely compacted together as to make the limits of each cell very indistinct. It is by the successive growth of new cells at the root and under surface of the body of the nail, that it advances forwards, and maintains a due thickness, whilst, at the same time, the growth of the nail in the proper direction is secured. As these cells in their turn become displaced by the growth of new cells, they assume 606 . ORGANS OF THE SENSES. a flattened form, lose their nuclei, and finally become closely compacted together into a firm, dense, horny texture. In chemical composition, the nails resemble the epidermis. According to Mulder, they contain a somewhat larger proportion of carbon and sulphur. Hairs are peculiar modifications of the epidermis, and consist essentially of the same structure as that membrane. They are found on nearly every part of the surface of the body, excepting the pa*lms of the hands and soles of the feet, and vary much in length, thickness, and color in different parts of the body, and in the different races of mankind. In some parts they are so short as not to project beyond the follicle containing them ; in other parts, as upon the scalp, they are of considerable Jength ; along the margin of the eyelids and upon the face, they are remarkable for their thickness. A hair consists of a root, the part implanted in the skin ; the shaft, the portion projecting from its surface ; and the point. They generally present a cylindrical or more or less flattened form, and a reniform out- line upon a transverse section. The root of the hair presents a bulbous enlargement at its extremity ; it is whiter in color, and softer in texture, than the stem, and is lodged in a follicular involution of the epidermis, called the hair-follicle. When the hair is of con- siderable length, the follicle extends into the subcutaneous cellular tissue. The hair-follicle is bulbous at its deep extremity, like the hair which it contains, and has opening into it, near its free extremity, the orifices of the ducts of one or more sebaceous glands. In structure, the hair-follicle consists of two coats : an outer or dermic, and an inner or cuticular. The outer coat is formed mainly of areolar tissue; it is continuous with the corium, is highly vascular, and supplied by numerous minute nervous filaments. The inner or cuticular lining is continuous with the epidermis, and, at the bottom of the hair-follicle, with the root of the hair ; this cuticular lining resembles the epidermis in the peculiar rounded form and soft character of those cells which lie in contact with the outer coat of the hair-follicle, and the thin, dry, and scaly character of those which lie near the surface of the hair, to which they are closely adherent. "When the hair is plucked from its follicle, this cuticular lining most commonly adheres to it, and forms what is called the root-sheath. At the bottom of each hair-follicle is a small conical-shaped vascular eminence or papilla, similar in every respect to those found upon the surface of the skin; it is continuous with the dermic layer of the follicle, is highly vascular, and probably supplied with nervous fibrils : this is the part through which material is supplied for the production and constant growth of the hair. The root of the hair rests upon this conical-shaped eminence, and is continuous with the cuticular lining of the follicle at this part. It consists of nucleated cells, similar in every respect to those which in other situations form the epidermis. These cells gradually enlarge as they are pushed upwards into the soft bulb, and some of them contain pigment granules, which exist either in separate cells, or the granules are separate, but aggregated round the nucleus ; it is these granules which give rise to the color of the hair. It occasionally happens that these pigment granules completely fill the cells in the centre of the bulb, which gives rise to the dark tract of pigment often found, of greater or less length, in the axis of the hair. The shaft of the hair consists of a central part or medulla ; surrounding this is the fibrous part of the hair, covered externally by the cortex. The medulla occupies the centre of the shaft, and ceases towards the point of the hair. It is usually wanting in the fine hairs covering the surface of the body, and commonly in those of the head. It is more opaque and deeper colored than the fibrous part, and consists of cells containing pigment or fat-granules. The fibrous portion of the hair constitutes the chief part of the stem ; its cells are elongated, and unite to form flattened fusiform fibres. These also contain pigment granules, which assume a linear arrangement. The cells which form the cortex of the hair consist of a single layer which surrounds those about to form the fibrous layer ; they arc converted into thin flat scales, having an imbricated arrangement. APPENDAGES OF THE SKIN. 607 The Sebaceous Glands are small, sacculated, glandular organs, lodged in the substance of the corium or sub-dermoid tissue. They are found in most parts of the skin, but are most abundant in the scalp and face ; they are also very numerous around the apertures of the anus, nose, mouth, and external ear ; but are wanting in the palms of the hands, and the soles of the feet. Each gland consists of a single duct, more or less capacious, which terminates in a lobulated pouch-like extremity. The basement membrane forming the wall of the sac, as well as the duct, is lined by epithelium, which is filled with particles of sebaceous matter ; and this becoming detached into the cavity of the sac, as its growth is renewed, constitutes the secretion. The number of sacculi connected with each duct vary from two to five, or even twenty, in number. The orifices of the ducts open most frequently into the hair-follicles, but occasionally upon the general surface. On the' nose and face, the glands are of large size, distinctly lobulated, and often become much enlarged from the accumulation of pent-up secretion. The largest sebaceous glands are those found in the eyelid, the Meibomian glands. The Sudoriferous or Sweat-glands are the organs by which a large portion of the aqueous and gaseous materials are excreted by the skin. They are found in almost every part of the skin, and are situated in small pits in the deep parts of the corium, or in the subcutaneous areolar tissue, surrounded by a quantity of adipose tissue. They are small, lobular, reddish bodies, consisting of one or more convoluted tubuli, from which the efferent duct proceeds upwards through the corium and cuticle, and opens upon the surface by a slightly enlarged orifice. The efferent duct, as it passes through the corium, pursues, for a short distance, a spiral course, becoming straight in the more superficial part of this layer, and opens on the surface of the cuticle by an oblique valve-like aperture. In the parts where the epidermis is thin, the ducts are finer and almost straight in their course ; but where the epidermis is thicker, they assume again a spiral arrange- ment, the separate windings of the tube being as close and as regular as those of a common screw. The spiral course of these ducts is especially distinct in the thick cuticle of the palm of the hand and sole of the foot. The size of these glands varies. They are especially large in those regions where the amount of perspira- tion is great, as in the axillae, where they form a thin mammillated layer of a reddish color, which corresponds exactly to the situation of the hair in this region ; they are large, also, in the groin. Their number varies : they are most numerous on the palm of the hand, and present, according to Krause, 2,800 orifices on a square inch of the integument, and a rather less number on the sole of the foot. In both of these situations, the orifices of the ducts are exceedingly regular, and correspond to the small transverse grooves which intersect the ridges of papillae. In other situations they are more irregularly scattered, but in nearly equal numbers over parts including the same extent of surface. In the neck and back they are least numerous, their number amounting to 417 on the square inch (Krause). Their total number is estimated by the same writer at 2,381,248 ; and supposing the aperture of each gland to represent a surface of ? ' 5 of a line in diameter, he calculates that the whole of these glands would present an evaporat- ing surface of about eight square inches. Each gland consists of a single tube intricately convoluted, at one end termi- nating by a blind extremity ; at the other end opening upon the surface of the skin. In the larger glands, this single duct usually divides and subdivides dichotomously ; the smaller ducts ultimately terminating in short caecal pouches, rarely anastomosing. The wall of the duct is thick ; the width of the canal rarely exceeding one-third of its diameter. The tube, both in the gland and where it forms the excretory duct, consists of two layers : an outer, formed by fine areolar tissue ; and an epithelium lining its interior. The external or fibro-cellular coat is thin, continuous with the superficial layer of the corium, and extends only as high as the surface of the true skin. The epithelial lining is much thicker, con- tinuous with the epidermis, and alone forms the spiral portion of the tube. When the cuticle is carefully removed from the surface of the cutis, these convoluted G08 ORGANS OF THE SENSES. tubes of epidermis may be drawn out, and form nipple-shaped projections on its under surface. According to Kolliker, a layer of non-striated muscular fibres, arranged longitudinally, is found between the areolar and epithelial coats of the ducts of the larger sweat-glands, as in the axilla, root of the penis, on the labia majora, and around the anus. The contents of the smaller sweat-glands are quite fluid ; but in the larger glands, the contents are semi-fluid and opaque, and contain a number of colored granules, and cells which appear analogous to epithelial cells. The Tongue. The tongue is the organ of the special sense of taste. It is situated in the floor of the mouth, in the interval between the two lateral portions of the body of Fig. 298. — Upper Surface of the Tongue. Tiliform -4 ]i e * FIC.299. The 3 hinds ef PAPILLA magnified ha tulle* CtrrinnTitFTrtt* the lower jaw. Its base or root is directed backwards, and connected with the os hyoides by numerous muscles, to the epiglottis by three folds of mucous mem- brane, which form the glosso-epiglottic ligaments, and to the soft palate and pharynx by means of the anterior and posterior pillars of the fauces. Its apex THE TONGUE. 609 or tip, thin and narrow, is directed forwards against the inner surface of the lower incisor teeth. The under surface of the tongue is connected with the lower jaw by the Genio-hyo-glossi muscles; from its sides, the mucous mem- brane is reflected to the inner surface of the gums ; and, in front, a distinct fold of that membrane, the fraenum linguae, is formed beneath its under surface. The tip of the tongue, part of its under surface, its sides, and dorsum, are free. The dorsum of the tongue is convex, marked along the middle line by a raphe, which divides it into two symmetrical halves ; and this raphe terminates behind, about half an inch from the base of the organ, a little in front of a deep mucous follicle, the foramen csecum. The anterior two-thirds of this surface are rough, and covered with papillae ; the posterior third is more smooth, and covered by the projecting orifices of numerous muciparous glands. The mucous membrane invests the entire extent of the free surface of the tongue. On the under surface of the organ it is thin and smooth, and may be traced on either side of the fraenum, through the ducts of the submaxillary glands ; and between the sides of the tongue and the lower jaw, through the ducts of the sublingual glands. On being traced over the borders of the organ, it gradually assumes its papillary character. The mucous membrane of the tongue consists of structures analogous to those of the skin, namely, a cutis or corium, supporting numerous papillse, and covered, as well as the papillae, with epithelium. The cutis is tough, but thinner and less dense than in most parts of the skin, and is composed of similar tissue. It contains the ramifications of the numerous vessels and nerves from which the papillae are supplied, and affords insertion to all the intrinsic muscular fibres of the organ. The papillae of the tongue are thickly distributed over the whole of its upper surface, giving to it its characteristic roughness. They are more prominent than those of the skin, which is chiefly due to their not being concealed under the epithelium, but from their standing out prominently from the surface like the villi of the intestine. The principal varieties are the papillae maximae (circumvallatae), papillae mediae (fungiformes), and papillae minimae (conicae and filiformes). The papillse maximse (circumvallatae) are of large size, and vary from eight to ten in number. They are situated at the back part of the dorsum of the tongue, near its base, forming a row on each side, which, running backwards and inwards, meet in the middle line, like the two lines of the letter A inverted. Each papilla consists of a central flattened projection of mucous membrane, circular in form, from 2 'jj to ^ of an inch wide, attached to the bottom of a cup-shaped depression of the mucous membrane ; the exposed part being covered with numerous small papillae. The cup-shaped, depression forms a kind of fossa round the papilla, having a circular margin of about the same elevation, covered with smaller papillae. The fissure corresponding to the papilla, where the two lines of the circum vallate papillae meet, is so large and deep, that the name foramen csecum has been applied to it. In the smaller papillae, the fissure exists only on one side. The papillse medise (fungiformes), more numerous than the preceding, are scattered irregularly and sparingly over the dorsum of the tongue, but are found chiefly at its sides and apex. They are easily recognized, among the other papillae, by their large size, rounded eminences, and deep red color. They are narrow at their attachment to the tongue, but broad and rounded at their free extremities, and covered with secondary papillae. Their epithelium investment is very thin. The papillse minimse (conicae et filiformes) cover the anterior two-thirds of the dorsum of the tongue. They are very minute, more or less conical or filiform in shape, and arranged in lines corresponding in direction with the two rows of the papillae circumvallatae, excepting at the apex of the organ, where their direction is transverse. The filiform papillae are of a whitish tint, owing to the thickness and density of their epithelium; they are covered with numerous secondary papillae, are firmer and more elastic than the papillae of mucous, membrane generally, and often inclose minute hairs. 39 610 ORGANS OF THE SENSES. Simple papillse, similar to those of the skin, are dispersed very unequally among the compound forms, and exist sparingly on the surface of the tongue behind the circumvallate variety, buried under a layer of epithelium. Structure of the papillse. The papillae, in structure, apparently resemble those of the cutis, consisting of a cone-shaped projection of homogeneous tissue, covered with a thick layer of squamous epithelium, and contain one or more capillary loops, amongst which nerves are distributed in great abundance. If the epithelium is removed it will be found that they are not simple processes like the papillae of the skin, for, according to Todd and Bowman, the surface of each is studded with minute conical processes of the mucous membrane, which form secondary papillae. In the papillae circumvallatae, the nerves are numerous and of large size ; in the papillae fungiformes they are also numerous, and terminate in a plexiform network, from which brush-like branches proceed; in the papillae flliformes, their mode of termination is uncertain. Besides the papillae, the mucous membrane of the tongue is provided with numerous follicles and glands. The follicles are found scattered over its entire surface, but are especially numerous between the papillae circumvallatae and the epiglottis. The mucous glands (lingual), similar in structure to the labial and buccal, are found chiefly beneath the mucous membrane of the posterior third of the dorsum of the tongue. There is a small group of these glands beneath the tip of the tongue, a few along the borders of the organ, and some in front of the circum- vallate papillae projecting into the muscular substance. Their ducts open either upon the surface, or into the depressions round the large papillae. The epithelium is of the scaly variety like that of the epidermis. It covers the free surface of the tongue, as may be easily demonstrated by maceration, or boiling, when it can be detached entire, but it is much thinner than in the skin, the inter- vals between the large papillae not being filled up by it, but each papilla has a separate investment from root to summit. The deepest cells may sometimes be detached as a separate layer, corresponding to the rete mucosum, but these never contain coloring matter. The tongue consists of two symmetrical halves, separated from each other, in the middle line, by a fibrous septum. Each half is composed of muscular fibres arranged in various directions, containing much interposed fat, and supplied by vessels and nerves ; the entire organ is invested by mucous membrane, and a submucous fibrous stratum. The latter membrane invests the greater part of the surface of the tongue, and into it the muscular fibres are inserted that pass to the surface. It is thicker behind than in front, and is continuous with the sheaths of the muscles attached to it. The fibrous septum consists of a vertical layer of fibrous tissue, extending throughout the entire length of the middle line of the tongue, from the base to the apex. It is thicker behind than in front, and occasionally contains a small fibro-cartilage, about a quarter of an inch in length. It is well displayed by making a vertical section through the organ. Another strong fibrous lamina, termed the hyo-glossal membrane, connects the under surface of the base of the tongue to the body of the hyoid bone. This membrane receives, in front, some of the fibres of the Genio-hyo-glossi. Each half of the tongue consists of extrinsic aud intrinsic muscles. The former have been already described ; they are the Hyo-glossus, Genio-hyo-glossus, Stylo- glossus, Palato-glossus, and part of the Superior constrictor. The intrinsic mus- cles are the Superior longitudinal, Inferior longitudinal, and Transverse. The superior longitudinal fibres {lingualis superficialis) form a superficial stratum of oblique and longitudinal fibres on the upper surface of the organ, beneath the mucous membrane, and extend from the apex backwards to the hyoid bone, the individual fibres being attached in their course to the submucous and glandular structures. The inferior longitudinal fibres are formed by the Lingualis muscle, already described (p. 261). THE NOSE. 611 The transverse fibres are placed between the two preceding layers ; they are intermixed with a considerable quantity of adipose substance, and form the chief part of the substance of the organ. They are attached internally to the median fibrous septum ; and, passing outwards, the posterior ones taking an arched course, are inserted into the dorsum and margins of the organ, intersecting the other muscular fibres. The arteries of the tongue are supplied from the lingual, the facial, and ascending pharyngeal. The nerves of the tongue are three in number in each half; the gustatory branch of the fifth, which is distributed to the papilla? at the fore part and sides of the tongue ; the lingual branch of the glosso-pharyngeal, which is distributed to the mucous membrane at the base and side of the tongue, and to the papilla) circumvallatse ; and the hypoglossal nerve, which is distributed to the muscular substance of the tongue. The two former are nerves of common sensation and of taste ; the latter is the motor nerve of the tongue. The Nose. The Nose is the special organ of the sense of smell ; by means of the peculiar properties of its nerves, it protects the lungs from the inhalation of deleterious gases, and assists the organ of taste in discriminating the properties of food. The organ of smell consists of two parts, one external, the nose ,- the other internal, the nasal fossae. The nose is the more anterior and prominent part of the organ of smell. It is of a triangular form, directed vertically downwards, and projects from the centre of the face, immediately above the upper lip. Its summit or root is connected directly with the forehead. Its inferior part, the base of the nose, presents two elliptical orifices, the nostrils, separated from each other by an antero-posterior septum, the columna. The margins of these orifices are provided with a number Figs. 299, 300.— Cartilages of the Nose. Seen from I el our JfM St J*- Vic us otL-crLalwal C, 'esauiola C of stiff hairs or vibrissse which arrest the passage of foreign substances carried with the current of air intended for respiration. The lateral surfaces of the nose form, by their union, the dorsum, the direction of which varies considerably in different individuals. The dorsum terminates below in a rounded eminence, the lobe of the nose. 612 ORGANS OF THE SENSES. Fig. 301. -Bones and Cartilages of Septum of Nose. Right Side. The nose is composed of a framework of bones and cartilages, the latter being slightly acted upon by certain muscles. It is covered externally by the integument^ internally by mucous membrane, and supplied with vessels and nerves. The bony framework occupies the upper part of the organ ; it consists of the nasal bones, and the nasal processes of the superior maxillary. The cartilaginous framework consists of five pieces, the two upper and the two lower lateral cartilages, and the cartilage of the septum. The upper lateral cartilages are situated below the free margin of the nasal bones ; each cartilage is flattened, and triangular in shape. Its anterior margin is thicker than the posterior, and connected with the fibro-cartilage of the septum. Its posterior margin is attached to the nasal process of the superior maxillary and nasal bones. Its inferior margin is connected by fibrous tissue with the lower lateral cartilage ; one surface is turned outwards, the other inwards towards the nasal cavity. The lower lateral cartilages are two thin, flexible plates, situated immediately below the preceding, and curved in such a manner as to form the inner and outer walls of each orifice of the nostril. The por- tion which forms the inner wall, thicker than the rest, is loosely connected with the same part of the opposite cartilage, and forms a small part of the columna. Its outer extremity, free, rounded, and projecting, forms, with the thickened integument and sub- jacent tissue, the lobe of the nose. The part which forms the outer wall is curved to correspond with the ala of the nose; it is oval and flattened, narrow behind, where it is connected with the nasal process of the superior maxilla by a tough fibrous membrane, in which are found three or four small cartilaginous plates, cartilagines minores or sesamoid cartilages. Above, it is connected to the upper lateral cartilage and front part of the cartilage of the septum ; below, it is separated from the margin of the nostril by dense cellular tissue ; and in front, it forms, with its fellow, the prominence of the tip of the nose. The cartilage of the septum is somewhat triangular in form, thicker at its mar- gins than at its centre, and completes the separation between the nasal fossoe in front. Its anterior margin, thickest above, is connected from above downwards with the nasal bones, the front part of the two upper lateral cartilages, and the inner portion of the two lower lateral cartilages. Its posterior margin is con- nected with the perpendicular lamella of the ethmoid ; its inferior margin with the vomer and palate processes of the superior maxillary bones. These various cartilages are connected to each other, and to the bones, by a tough fibrous membrane, the perichondrium, which allows the utmost facility of movement between them. The muscles of the nose are situated immediately beneath the integument ; they* are (on each side) the Pyramidalis nasi, the Levator labii superioris alasque nasi, the Dilator naris anterior, and Dilator naris posterior, the Compressor naris, the Compressor narium minor, and the Depressor alee nasi (see p. 246). The integument covering the dorsum and sides of the nose is thin, and loosely connected with the subjacent parts; but where it forms the tip or lobe and the NASAL FOSSAE. 613 alae of the nose, it is thicker, and more firmly adherent. It is furnished with a large number of sebaceous follicles, the orifices of which are usually very distinct. The mucous membrcme lining the interior of the nose is continuous with the skin externally, and with that which lines the nasal fossa} within. The arteries of the nose are the lateralis nasi from the facial, and the nasal artery of the septum from the superior coronary, which supplies the alae and septum; the sides and dorsum being supplied from the nasal branch of the ophthalmic and infra-orbital. The veins of the nose terminate in the facial and ophthalmic. The nerves of the nose are branches from the facial, infra-orbital, and infra- trochlear, and a filament from the nasal branch of the ophthalmic. Nasal Fossjs. The Nasal Fossae are two irregular cavities, situated in the middle of the face, and extending from before backwards. They open in front by the two anterior nares, and terminate behind in the pharynx, by the posterior nares. The boundaries of these cavities, and the openings which are connected with them, as they exist in the skeleton, have been already described (p. 109). The mucous membrane lining the nasal fossae is called pituitary, from the nature of its secretion, or Schneiderian from Schneider, the first anatomist who showed that the secretion proceeded from the mucous membrane, and not, as was formerly imagined, from the brain. It is intimately adherent to the periosteum or perichondrium over which it lies. It is continuous externally with the skin, through the anterior nares, and with the mucous membrane of the pharynx, through the posterior nares. From the nasal fossae its continuity may be traced with the conjunctiva, through the nasal duct and lachrymal canals; with the lining membrane of the tympanum and mastoid cells, through the Eustachian tube; and with the frontal, ethmoidal, and sphenoidal sinuses, and the antrum maxillare, through the several openings in the meatuses. The mucous membrane is thickest, and most vascular, over the turbinated bones. It is also thick over the septum ; but, in the intervals between the spongy bones, and on the floor of the nasal fossae, it is very thin. Where it lines the various sinuses and the antrum maxillare, it is thin and pale. The surface of the membrane is covered with a layer of tessellated epithelium, at the upper part of the nasal fossae, corresponding with the distribution of the olfactory nerve, but ciliated throughout the rest of its extent, excepting near the aperture of the nares. This membrane is also provided with a nearly continuous layer of branched mucous glands, the ducts of which open upon its surface. They are most nume- rous at the middle and back parts of the nasal fossae, and largest at the lower and back part of the septum. Owing to the great thickness of this membrane, the nasal fossae are much narrower, and the turbinated bones, especially the lower ones, appear larger, and more prominent, than in the skeleton. From the same circumstance, also, the various apertures communicating with the meatuses are either narrowed or completely closed. In the superior meatus, the aperture of communication with the posterior ethmoidal cells is considerably diminished in size, and the spheno-palatine foramen completely covered in. In the middle meatus, the opening of the infundibulum is partially hidden by a projecting fold of mucous membrane, and the orifice of the antrum is contracted to a small circular aperture, much narrower than in the skeleton. In the inferior meatus, the orifice of the nasal duct is partially hidden by either a single or double valvular mucous fold, and the anterior palatine canal either complete^ closed in, or a tubular cul-de-sac of mucous membrane is continued a short distance into it. 614 ORGANS OF THE SENSES. In the roof, the opening leading to the sphenoidal sinus is narrowed, and the apertures in the cribriform plate of the ethmoid completely closed in. The arteries of the nasal fossse are the anterior and posterior ethmoidal, from the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof of the nose ; the spheno-palatine, from the internal maxillary, which supplies the mucous membrane covering the spongy bones, the meatuses, and septum ; and the alveolar branch of the internal maxillary, which supplies the lining membrane of the antrum. The ramifications of these vessels form a close, plexiform network, beneath and in the substance of the mucous membrane. The veins of the nasal fossse form a close network beneath the mucous mem- brane. They pass, some with the veins accompanying the spheno-palatine artery, through the spheno-palatine foramen ; and others, through the alveolar branch, join the facial vein; some accompany the ethmoidal arteries, and terminate in the ophthalmic vein ; and, lastly, a few communicate with the veins in the interior of the skull, through the foramina in the cribriform plate of the ethmoid bone. The nerves are the olfactory, Fig. 303.— Nerves of Septum of Nose. Right Sid,e. fa Q nasa l branch of the ophthal- mic, filaments from the anterior dental branch of the superior maxillary, the Vidian, naso-pala- tine, descending anterior palatine, and spheno-palatine branches of Meckel's ganglion. The olfactory, the special nerve of the sense of smell, is distri- buted over the upper third of the septum, and over the surface of the superior and middle spongy bones. The nasal branch of the oph- thalmic distributes filaments to the upper and anterior part of the septum, and outer wall of the nasal fossae. Filaments from the anterior dental branch of the superior maxillary supply the inferior meatus and inferior turbinated bone. The Vidian nerve supplies the upper and back part of the septum, and superior spongy bone ; and the upper anterior nasal branches from the spheno-palatine ganglion, have a similar distribution. The nasopalatine nerve supplies the middle of the septum. The larger or anterior palatine nerve supplies the middle and lower spongy bones. The Eye. The eyeball is contained in the cavity of the orbit. In this situation it is securely protected from injury, whilst its position is such as to insure the most extensive range of sight. It is acted upon by numerous muscles, by which it is capable of being directed to any part, is supplied by vessels and nerves, and is additionally protected in front by several appendages, such as the eyebrow, eyelids, etc. The eyeball is spherical in form, having the segment of a smaller and more prominent sphere engrafted upon its anterior part. It is from this circumstance, that the antero-posterior diameter of the eyeball, which measures about an inch, exceeds the transverse diameter by about a line. The segment of the larger sphere, which forms a"bout five-sixths of the globe, is opaque, and formed by the sclerotic, the tunic of protection to the eyeball ; the smaller sphere, which forms the remaining sixth, is transparent, and formed by the cornea. The axes of the THE EYE, 615 eyeballs are nearly parallel, and do not correspond to the axes of the orbits, which are directed outwards. The optic nerves follow the direction of the axes of the orbits, and enter the eyeball a little to their inner or nasal side. The eyeball is composed of several investing tunics, and of fluid and solid refracting media, called humors. The tunics are three in number : — 1. Sclerotic and Cornea. 2. Choroid, Iris, and Ciliary Processes. 3. Eetina. The refracting media or humors are also three : — Aqueous. Crystalline (lens) and Capsule. Yitreous. The sclerotic and cornea form the most external tunic of the eyeball ; they are essentially fibrous in structure, the sclerotic being opaque, and forming the pos- terior five-sixths of the globe ; the cornea, which forms the remaining sixth, being transparent. Tunics of the Eye. scleeotic and cornea. The Sclerotic (axxfaoc, hard) has received its name from its extreme density and hardness ; it is a firm, unyielding, fibrous membrane, serving to maintain the peculiar form of the globe (fig. 303). It is much thicker behind than in front. Fig. 303.— A Vertical Section of the Eyeball. (Enlarged.) Sclerotic _ Choroid • Retina ■ Tendon of rectus Hyaloid Mrmbrane Ciliary Muscle £= Ligament Circular Sinua anal of Petit Its external surface is of a white color, quite smooth, except at the points where the Recti and Obliqui muscles are inserted into it, and covered, for part of its extent, by the conjunctival membrane ; hence the whiteness and brilliancy of the front of the eyeball. Its inner surface is stained of a brown color, marked by grooves, in which are lodged the ciliary nerves, and connected by an exceedingly fine cellular tissue {lamina fused) with the outer surface of the choroid. Behind, it is pierced by the optic nerve a little to its inner or nasal side, and is continuous with its fibrous sheath, which is derived from the dura mater. At the point where the optic nerve passes through the sclerotic, this membrane forms a thin cribriform 616 ORGANS OF THE SENSES. lamina {lamina cribrosa); the minute orifices in this part serve for the trans- mission of the nervous filaments, and the fibrous septa dividing them from one another are continuous with the membranous processes which separate the bundles of nerve fibres. One of these openings, larger than the rest, occupies the centre of this lamellae ; it is called the porus opticus, and transmits the arteria centralis retinas to the interior of the eyeball. Around the cribriform lamella are numerous smaller apertures for the transmission of the ciliary vessels and nerves. In front, this membrane is continuous with the cornea by direct continuity of tissue ; but the opaque sclerotic overlaps it rather more on its outer than upon its inner surface. Structure. The sclerotic is formed of white fibrous tissue intermixed with the elastic fibres, and fusiform nucleated cells. These are aggregated into bundles, which are arranged chiefly in a longitudinal direction. It yields gelatin on boiling. Its vessels are not numerous, the capillaries being of small size, uniting at long and wide intervals. The existence of nerves in it is doubtful. The Cornea is the projecting transparent part of the external tunic of the eye- ball, and forms the anterior sixth of the globe. Its form is not quite circular, being a little broader in the transverse than in the vertical direction, in conse- quence of the sclerotic overlapping the margin above and below. It is concavo- convex, and projects forwards from the sclerotic in the. same manner that a watch- glass does from its case. Its degree of curvature varies in different individuals, and in the same individual at different periods of life, being more prominent in youth than in advanced life, when it becomes flattened. This difference in the greater or smaller convexity of the cornea influences considerably the refractive power of the eye, and is the chief cause of the long or short sight peculiar to different individuals. It is dense and of uniform thickness throughout, its pos- terior surface is perfectly circular in outline, and exceeds the anterior surface slightly in extent, from the latter being overlapped by the sclerotic. Structure. The cornea consists of five layers : a thick central fibrous structure, the cornea proper ; in front of this the anterior elastic lamina, covered by the con- junctiva ; behind, the posterior elastic lamina, covered by the lining membrane of the anterior chamber of the eyeball. The proper substance of the cornea is fibrous, tough, unyielding, perfectly transparent, and continuous with the sclerotic, with which it is in structure identical. The anastomosing fusiform cells of which it is composed are arranged in superimposed flattened laminae, at least sixty in number, all of which have the same direction, the contiguous laminae becoming united at frequent intervals. If the relative position of the component parts of this tissue is in any way altered, either by pressure or by an increase of its natural tension, it immediately presents an opaque milky appearance. The interstices between the laminae are tubular, and usually contain a small amount of transparent fluid. The anterior and posterior elastic laminse, which cover the proper structure of the cornea behind and in front, present an analogous structure. They consist of a hard, elastic, and perfectly transparent homogeneous membrane, of extreme thinness, which is not rendered opaque by either water, alcohol, or acids. This membrane is intimately connected by means of a fine cellular web to the proper substance of the cornea both in front and behind. Its most remarkable property is its extreme elasticity, and the tendency which it presents to curl up, or roll upon itself, with the attached surface innermost, when separated from the proper substance of the cornea. Its use appears to be, as suggested by Dr. Jacob, "to preserve the requisite permanent correct curvature of the flaccid cornea proper." The conjunctival epithelium, which covers the front of the anterior elastic lamina, consists of two or three layers of transparent nucleated cells, the deepest being of an oblong form and placed perpendicular to the surface, the superficial ones more flattened. The epithelial lining of the aqueous chamber covers the posterior surface of the CORNEA— CHOROID. 617 posterior elastic lamina. It consists of a single layer of polygonal transparent nucleated cells, similar to those found lining other serous cavities. Arteries and Nerves. The cornea is a non-vascular structure, the capillary vessels terminating in loops at its circumference. Lymphatic vessels have not as yet been demonstrated in it. The nerves are numerous, twenty or thirty in number : they are derived from the ciliary nerves, and enter the laminated sub- stance of the cornea. They ramify throughout its substance in a delicate net- work. Dissection. In order to separate the sclerotic and cornea, so as to expose the second tunic, the eyeball should be immersed in water contained in a small vessel. A fold of the sclerotic near its anterior part having been pinched up, an operation not easily performed from the ex- treme tension of the membrane, it should be divided with a pair of blunt-pointed scissors. As soon as the choroid is exposed, the end of a blowpipe should be introduced into the orifice, and a stream of air forced into it, so as to separate the slight cellular connection between the sclerotic and choroid. The sclerotic should now be divided around its entire circumference, and may be removed in separate portions. The front segment being then drawn forwards, the handle of the scalpel should be pressed gently against it at its connection with the iris, and, these being sepa- rated, a quantity of perfectly transparent fluid will escape ; this is the aqueous humor. In the course of the dissection, the ciliary nerves may be seen lying in the loose cellular tissue between the choroid and sclerotic, or contained in delicate grooves on the inner surface of the latter membrane. Fig. 304.— The Choroid and Iris. (Enlarged.) Choroid, Iris, and Ciliary Processes. The second tunic is formed by the choroid behind ; the iris and ciliary pro- cesses in front ; and by the ciliary ligament, and Ciliary muscle, at the point of junction of the sclerotic and cornea. The Choroid is the vascular and pigmentary tunic of the eyeball, investing the posterior five-sixths of the globe, and extending as far forwards as the cornea ; the Ciliary Processes being appendages of the choroid developed from its inner surface in front. The Iris is the circular-shaped muscular septum, which hangs vertically behind the cornea, presenting in its centre a large circular aperture, the pupil. The ciliary ligament and Ciliary muscle form the white ring observed at the point where the choroid and iris join with each other, and with the sclerotic and cornea. 618 ORGANS OF THE SENSES. The Choroid is a thin, highly vascular membrane, of a dark brown or chocolate color, which invests the posterior five-sixths of the central part of the globe. It is pierced behind by the optic nerve, and terminates in front at the ciliary ligament, where it bends inwards, and forms on its inner surface a series of folds or plaitings, the ciliary processes. It is thicker behind than in front. Externally, it is con- nected by a fine cellular web (membrana fused) with the inner surface of the sclerotic. Its inner surface is smooth, and lies in contact with the retina. The choroid is composed of three layers, external, middle, and internal. Fig. 305.— The Veins of the Choroid. (Enlarged.) The external layer consists of the larger branches of the short ciliary arteries, which run forwards between the veins before they bend downwards to terminate on the inner surface. This coat consists, however, principally of veins, which are disposed in curves ; hence their name, vense vorticosse. They converge to four or five equidistant trunks, which pierce the sclerotic midway between the margin of the cornea and the entrance of the optic nerve. Interspersed between the vessels, are lodged dark star-shaped pigment cells, the fibrous offsets from which, communicating with similar branches from neighboring cells, form a delicate network, which, towards the inner surface of the choroid, loses its pigmentary character. The middle layer consists of an exceedingly fine capillary plexus, formed by the short ciliary vessels, and is known as the tunica Ruyschiana. The network is close, and finer at the hinder part of the choroid than in front. About half an inch behind the cornea, its meshes become larger, and are continuous with those of the ciliary processes. The internal or pigmentary layer is a delicate membrane, consisting of a single layer of hexagonal nucleated cells, loaded with pigment granules, and applied to each other, so as to resemble a tessellated pavement. Each cell contains a nucleus, and is filled with grains of pigment, which are in greater abundance at the circumference of the cell. In perfect albinos this epithelium contains no pigment, and none is present in the star-shaped cells found in the other layers of the choroid. The ciliary processes should be next examined ; they may be exposed, either by detaching the iris from its connection with the ciliary ligament, or by making a transverse section of the globe, and examining them from behind. The Ciliary processes are formed by the plaiting or folding inwards of the middle and internal layers of the choroid, at its anterior margin, and are received CHOROID— IRIS. 619 between corresponding foldings of the suspensory ligament of the lens, thus establishing a communication between the choroid and inner tunic of the eye. They are arranged in a circle, behind the iris, round the margin of the lens. They vary in number between sixty and eighty, lie side by side, and may be divided into large and small ; the latter, consisting of about one-third of the entire number, are situated in the spaces between the former, but without regular alter- nation. The larger processes are each about one-tenth of an inch in length, and Fig. 306. — The Arteries of the Choroid and Iris. The Sclerotic has been mostly removed. (Enlarged.) Jl nterior Ciliary At Short Ciliary &i nterior CiliarijA^ hemispherical in shape, their periphery being attached to the ciliary ligament, and continuous with the middle and inner layers of the choroid ; the opposite margin is free, and rests upon the circumference of the lens. Their anterior surface is turned towards the back of the iris, with the circumference of which it is con- tinuous. The posterior surface is closely connected with the suspensory ligament of the lens. Structure. The ciliary processes are similar in structure to the choroid ; the vessels are larger, having chiefly a longitudinal direction. Externally they are covered with several layers of pigment cells; the component cells are small, rounded, and full of pigment granules. The Iris {iris, a rainbow) has received its name from the varied color it pre- sents in different individuals. It is a thin circular-shaped, contractile curtain, suspended in the aqueous humor behind the cornea, and in front of the lens, being perforated at the nasal side of its centre by a circular aperture, the pupil, for the transmission of light. By its circumference it is intimately connected with the choroid; externally to this is the ciliary ligament, by which it is con- nected to the sclerotic and cornea; its inner edge forms the margin of the pupil; its surfaces are flattened, and look forwards and backwards, the anterior surface towards the cornea, the posterior towards the ciliary processes and lens. The anterior surface is variously colored in different individuals, and marked by lines which converge towards the pupil. The posterior surface is of a deep purple tint, from being covered by dark pigment; it is hence named uvea, from its resemblance in color to a ripe grape. Structure. The iris is composed of a fibrous stroma, muscular fibres, and pig- ment cells. The fibrous stroma consists of fine, delicate bundles of fibrous tissue, which have a circular direction at the circumference; but the chief mass radiate towards the pupil. They form, by their interlacement, a delicate mesh, in which the pig- ment cells, vessels, and nerves are contained. G20 ORGANS OF THE SENSES. The muscular fibre is involuntary, and consists of circular and radiating fibres. The circular fibres (sphincter of the pupil) surround the margin of the pupil on the posterior surface of the iris, like a sphincter, forming a narrow band, about one-thirtieth of an inch in width ; those near the free margin being closely aggre- gated ; those more external are separated somewhat, and form less complete circles. The radiating fibres (dilator of the pupil) converge from the circumference towards the centre, and blend with the circular fibres near the margin of the pupil. The circular fibres contract the pupil, the radiating fibres dilate it. The pigment cells are found in the stroma of the iris, and also as a distinct layer on its anterior and posterior surfaces. In the stroma, the cells are ramified, and contain yellow or brown pigment, according to the color of the eye. On the front of the iris, there is a single layer of oval or rounded cells, with branching offsets. On the back of the iris, there are several layers of small, round cells, filled with dark pigment. *This layer is continuous with the pigmentary covering of the ciliary processes. The arteries of the iris are derived from the long and anterior ciliary, and from the vessels of the ciliary processes. Membrana pupillaris. In the foetus, the pupil is closed by a delicate, transparent vascular membrane, the membrana pupillaris, which divides the space in which the iris is suspended into two distinct chambers. This membrane contains numerous minute vessels continued from the margin of the iris to those on the front part of the capsule of the lens. These vessels have a looped arrangement, converging towards each other without anastomosing. Between the seventh and eighth month, this membrane begins to disappear, by its gradual absorption from the centre towards the circumference, and at birth only a few fragments remain. Sometimes it remains permanent, and produces blindness. The Ciliary ligament is a narrow ring of circular fibres, about one-fortieth of an inch thick, and of a whitish color, which serves to connect the external and middle tunics of the eye. It is placed round the circumference of the iris, at its point of connection with the external layer of the choroid, the cornea, and sclerotic. Its component fibres are delicate, and resemble those of elastic tissue. At its point of connection with the sclerotic a minute canal is situated between the two, called the sinus circular is iridis. The Ciliary muscle (Bowman) consists of unstriped fibres ; it forms a grayish, semi-transparent, circular band, about one-eighth of an inch broad, on the outer surface of the forepart of the choroid. It is thickest in front, and gradually becomes thinner behind. Its fibres are soft, of a yellowish- white color, longitu- dinal in direction, and arise at the point of junction of the cornea and sclerotic. Passing backwards, they are attached to the choroid, in front of the retina, and correspond by their inner surface to the plicated part of the former membrane. Mr. Bowman supposes that this muscle is so placed as to advance the lens, by exercising compression on the vitreous body, and by drawing the ciliary processes towards the line of junction of the sclerotic and cornea, and by this means to adjust the eye to the vision of near objects. The Retina. The Retina may be exposed by carefully removing the choroid from its external surface. It is a delicate nervous membrane, upon the surface of which the images of external objects are received. Its outer surface is in contact with the pigmentary layer of the choroid ; its inner surface, with the vitreous body. Behind, it is con- tinuous with the optic nerve ; it gradually diminishes in thickness from behind forwards ; and, in front, extends nearly as far forwards as the ciliary ligament, where it terminates by a jagged margin, the ora serrata. It is soft, and semi- transparent, in the fresh state ; but soon becomes clouded, opaque, and of a pinkish tint. Exactly in the centre of the posterior part of the retina, and at a point corresponding to the axis of the eye, in which the sense of vision is most perfect, is a round, elevated, yellowish spot, called, after its discoverer, limbus luteus, RETINA. G21 yellow spot, of SG'mmering ; having a central depression at its summit, the fovea centralis. The retina in the situation of the fovea centralis is exceedingly thin, so' much so, that the dark color of the choroid is distinctly seen through it ; so that it presents more the appearance of a foramen, and hence the name " foramen of Sommering" at first given to it. It exists only in man, the quadrumana, and some saurian reptiles. Its use is unknown. About T V of an inch to the inner side of the yellow spot is the point of entrance of the optic nerve ; the arteria centralis retinse piercing its centre. This is the only part of the surface of the retina from which the power of vision is absent. Fig, 307. — The Arteria Centralis Retinse, Yellow Spot, etc., the Anterior Half of the Eyeball being removed. (Enlarged.) Sclerotic Choroid ■Retina Structure. The retina is composed of three layers, together with bloodvessels : — External or columnar layer (Jacob's membrane). Middle or granular layer. Internal or nervous layer. The bloodvessels do not form a distinct layer ; they ramify in the substance of the internal layer. The external or JacoVs membrane is exceedingly thin, and can be detached from the external surface of the retina by the handle of the scalpel, in the form of a flocculent film. It is thicker behind than in front, and consists of rod-like bodies of two kinds : — 1. Columnar rods, solid, nearly of uniform size, and arranged per- pendicularly to the surface. 2. Bulbous particles or cones, which are interspersed at regular intervals among the former ; these are conical or flask-shaped, their broad ends resting upon the granular layer, the narrow-pointed extremity being turned towards the choroid ; they are not solid, like the columnar rods, but consist of an external membrane with fluid contents. By their deep ends, both kinds are joined to the fibres of Miiller. The middle or granular layer forms about one-third of the entire thickness of the retina. It consists of two laminae of rounded or oval nuclear particles, separated from each other by an intermediate layer, which is transparent, finely fibrillated, and contains no bloodvessels. The outermost layer is the thickest, and its con- stituent particles are globular. The innermost layer is the thinnest ; its component particles are flattened, looking like pieces of money seen edgeways ; hence it has been called by Bowman, the nummular layer. The internal or nervous layer is a thin semi-transparent membrane, consisting of an expansion of the terminal fibres of the optic nerve and nerve cells. The nerve fibres are collected into bundles, which radiate from the point at which the trunk of the optic nerve terminates. As they proceed in a tolerably straight G22 ORGANS OF THE SENSES. course towards the anterior margin of the retina the bundles interlace, forming a delicate net, with flattened elongated meshes. The nerve fibres which form this layer differ from the fibres of the optic nerve in this respect ; they lose their dark outline, and their tendency to become varicose, and consist only of the central part or axis of the nerve tubes. The mode of termination of the nerve fibres is unknown. According to some observers, they terminate in loops ; according to others, in free extremities. Recent observers have stated, that some of the nerve fibres are continuous with the caudate prolongations of the nerve cells external to the fibrous layer. The nerve cells are placed on both sides of the fibrous layer, but chiefly upon its inner surface, and imbedded within the meshes formed by the interlacing nerve fibres ; they are round or pear-shaped transparent cells, nucleated, with granular contents, furnished with caudate prolongations, some of which join the fibres of the optic nerve, whilst others are directed externally towards the granular layer. It is probable that these cells are identical with the ganglion cor- puscles of vesicular nervous substance. An extremely thin and delicate structureless membrane lines the inner surface of the retina, and separates it from the vitreous body ; it is called the membrane limitans. The radiating fibres of the retina, described by Heinrich Miiller, consist of extremely fine fibrillated threads, which are connected externally with each of the rods of the columnar layer, of which they appear to be direct continuations ; and, passing through the entire substance of the retina, are united to the outer surface of the membrana limitans. In their course through the retina, they become con- nected with the nuclear particles of the granular layer, and give off branching processes opposite its innermost lamina ; as they approach the fibrous expansion of the optic nerve, they are collected into bundles, which pass through the areolae* between its fibres, and are finally attached to the inner surface of the membrana limitans, where each fibre terminates in a triangular enlargement. The arteria centralis retinse and its accompanying vein pierce the optic nerve, and enter the globe of the eye through the porus opticus. It immediately divides into four or five branches, which at first run between the hyaloid membrane and the nervous layer ; but they soon enter the latter membrane, and form a close capillary network in its substance. At the ora serrata they terminate in a single vessel, which bounds the terminal margin of the retina. The structure of the retina at the yellow spot presents some modifications. Jacob's membrane is thinner, and of its constituents only the cones are present ; but they are small, and more closely aggregated than in any other part. The granular layer is absent over the fovea centralis. Of the two elements of the nervous layer, the nerve fibres extend only to the circumference of the spot ; but the nerve cells cover its entire surface. The radiating fibres are found at the cir- cumference, and here only extend to the inner strata of the granular layer. Of the capillary vessels, the larger branches pass round the spot, but the smaller capil- laries meander through it. The color of the spot appears to imbue all the layers except Jacob's membrane ; it is of a rich yellow, deepest towards the centre, and does not appear to consist of pigment cells, but resembles more a straining of the constituent parts. humoes of the eye. Aqueous Humoe. The Aqueous Humor completely fills the anterior and posterior chambers of the eyeball. It is small in quantity, scarcely exceeding, according to Petit, four or five grains in weight, has an alkaline reaction, in composition is little more than water, less than one-fiftieth of its weight being solid matter, chiefly chloride of sodium. The anterior chamber is the space bounded in front by the cornea ; behind, by the front of the iris and ciliary ligament. The posterior chamber, smaller than the anterior, is bounded in front by the VITREOUS BODY— CRYSTALLINE LENS. 623 iris; behind, by the capsule of the lens and its suspensory ligament, and the ciliary processes. In the adult, these two chambers communicate through the pupil ; but in the foetus before the seventh month, when the pupil is closed by the membrana pupil- laris, the two chambers are quite separate. It has been generally supposed that the two chambers are lined by a distinct membrane, the secreting membrane of the aqueous humor, analogous in struc- ture to that of a serous sac. An epithelial covering can, however, only be found on the posterior surface of the cornea. That the two chambers do, however, secrete this fluid separately, is shown from its being found in both spaces before the removal of the membrana pupillaris. It is probable that the parts concerned in the secretion of the fluid are the posterior surface of the cornea, both surfaces of the iris, and the ciliary processes. Vitreous Body. The Vitreous Body forms about four-fifths of the entire globe. It fills the concavity of the retina, and is hollowed in front for the reception of the lens and its capsule. It is perfectly transparent, of the consistence of thin jelly, and consists of an albuminous fluid inclosed in a delicate, transparent membrane, the hyaloid. This membrane invests the outer surface of the vitreous body ; it is intimately connected in front with the suspensory ligament of the lens ; and is continued into the back part of the capsule of the lens. It has been supposed by Hannover, that from its inner surface numerous thin lamellae are prolonged inwards in a radiating manner, forming spaces in which the fluid is contained. In the adult, these lamellae cannot be detected even after careful microscopic examination ; but in the foetus a peculiar fibrous texture pervades the mass, the fibres joining at numerous points, and presenting minute nuclear granules at their point of junction. The fluid from the vitreous body resembles nearly pure water; it contains, however, some salts, and a little albumen. In the foetus, the centre of the vitreous humor presents a tubular canal, through which a minute artery passes along the vitreous body to the capsule of the lens. In the adult, no vessels penetrate its substance; so that its nutrition must be carried on by the vessels of the retina and ciliary processes, situated upon its exterior. Crystalline Lens and its Capsule. The Crystalline Lens, inclosed in its capsule, is situated immediately behind the pupil, in front of the vitreous body, and surrounded by the ciliary processes, which slightly overlap its margin. The capsule of the lens is a transparent, highly elastic, and brittle membrane, which closely surrounds the lens. It rests, behind, in a depression in front of the vitreous body : in front, it forms part of the posterior chamber of the eye ; and it is retained in its position chiefly by the suspensory ligament of the lens. The capsule is much thicker in front than behind, structureless in texture ; and when ruptured, the edges roll up with the outer surface innermost, like the elastic laminae of the cornea. The lens is connected to the inner surface of the capsule by a single layer of transparent, polygonal, nucleated cells. These, after death, absorb moisture from the fluids of the eye ; and, breaking down, form the liquor Morgagni. In the foetus, a small branch from the arteria centralis retinae runs forwards, as already mentioned, through the vitreous humor to the posterior part of the cap- sule of the lens, where its branches radiate and form a plexiform network, which covers its surface, and are continuous round the margin of the capsule, with the vessels of the pupillary membrane, and with those of the iris. In the adult, no vessels enter its substance. The lens is a transparent, double convex body, the convexity being greater on the posterior than on the anterior surface. It measures about a third of an inch in the transverse diameter, and about one-fourth in the antero-posterior. It 624 ORGANS OP THE SENSES. consists of concentric layers, of which the external, in the fresh state, are soft and easily detached ; those beneath are firmer, the central ones forming a hardened nucleus. These laminae are best demonstrated by Fig. 308.— The Crystalline Lens, boiling, or immersion in alcohol. The same reagents hardened ai^d divided. demonstrate that the lens consists of three triangular n arge .) segments, the sharp edges of which are directed towards the centre, the bases towards the circumference. The laminae consist of minute parallel fibres, which are united to each other by means of wavy margins, the convexities upon one fibre fitting accurately into the concavities of the adjoining fibre. The changes produced in the lens by age are the fol- lowing : — In the foetus, its form is nearly spherical, its color of a slightly reddish tint, not perfectly transparent, and so soft as to readily break down on the slightest pressure. In the adult, the posterior surface is more convex than the anterior, it is color- less, transparent, and firm in texture. In old age, it becomes flattened on both surfaces, slightly opaque, of an amber tint, and increases in density. The suspensory ligament of the lens is a thin, transparent, membranous struc- ture, placed between the vitreous body and the ciliary processes of the choroid : it connects the anterior margin of the retina with the anterior surface of the lens, near its circumference. It assists in retaining the lens in its position. Its outer surface presents a number of folds or plaitings, in which the corresponding folds of the ciliary processes are received. These plaitings are arranged round the lens in a radiating form, and are stained by the pigment of the ciliary processes. The suspensory ligament consists of two layers, which commence behind, at the ora serrata. The external, a tough, milky, granular membrane, covers the inner surface of the ciliary processes, and extends as far forwards as their anterior free extremities. The inner layer, an elastic transparent, fibro-membranous structure, extends as far forwards as the anterior surface of the capsule of the lens, near its circumference. That portion of this membrane which intervenes between the ciliary processes and the capsule of the lens, forms part of the boun- dary of the posterior chamber of the eye. The posterior surface of this layer is turned towards the hyaloid membrane, being separated from it at the circum- ference of the lens by a space called the canal of Petit. The canal of Petit is about one-tenth of an inch wide. It is bounded in front by the suspensory ligament ; behind, by the hyaloid membrane, its base being formed by the capsule of the lens. When inflated with air, it is sacculated at intervals, owing to the foldings on its anterior surface. Bloodvessels and Nerves of the Eye. The Vessels of the globe of the eye are the short, long, and anterior ciliary arteries, and the arteria centralis retinas. The short ciliary arteries pierce the back part of the sclerotic, round the entrance of the optic nerve, and divide into branches which run parallel with the axis of the eyeball : they are distributed to the middle layer of the choroid, and ciliary processes. The long ciliary arteries, two in number, pierce the back part of the sclerotic, and run forward, between this membrane and the choroid, to the Ciliary muscle, where they each divide into an upper and lower branch; these anastomose, and form a vascular circle round the outer circumference of the iris ; from this circle branches are given off which unite, near the margin of the pupil, in a smaller vascular circle. These branches, in their course, supj)ly the muscular structure. APPENDAGES OF THE EYE. . 625 The anterior ciliary arteries, five or six in number, are branches of the muscular and lachrymal branches of the ophthalmic. They pierce the eyeball, at the anterior part of the sclerotic, immediately behind the margin of the cornea, and are distributed to the ciliary processes, some branches joining the greater vascular circle of the iris. The arteria centralis retinse has been already described. The veins, usually four in number, are formed mainly by branches from the surface of the choroid. They perforate the sclerotic, midway between the cornea and the optic nerve, and end in the ophthalmic vein. The nerves of the eyeball are the optic, the long ciliary nerves from the nasal branch of the ophthalmic, and the short ciliary nerves from the ciliary ganglion. Appendages of the Eye. The appendages of the eye {tutamina oculi) include the eyebrows, the eyelids, the conjunctiva, and the lachrymal apparatus, viz., the lachrymal gland, the lachrymal sac, and the nasal duct. The eyebrows {supercilia) are two arched eminences of integument, which surmount the upper circumference of the orbit on each side, and support numerous short, thick hairs, directed obliquely on the surface. In structure, they consist of thickened integument, connected beneath with the Orbicularis palpebrarum, Corrugator supercilii, and Occipito-frontalis muscles. These muscles serve, by their action on this part, to control to a certain extent the amount of light admitted into the eye. The eyelids (palpebrse) are two thin, movable folds, placed in front of the eye, protecting it from injury by their closure. The upper lid is the larger, the more movable of the two, and supplied by a separate elevator muscle, the Levator palpebrse superioris. When the eyelids are opened, an elliptical space {fissura palpebrarun%) is left between their margins, the angles of which correspond to the junction of the upper and lower lids, and are called canthi. The outer canthus is more acute than the inner, and the lids here lie in close contact with the globe ; but the inner canthus is prolonged for a short distance inwards, towards the nose, and the two lids are separated by a triangular space, the lacus lacrymalis. At the commencement of the lacus lacrymalis, on the margin of each eyelid, is a small conical elevation, the lachrymal papilla, or tubercle, the apex of which is pierced by a small orifice, the vunctum lacrymale, the commencement of the lachrymal canal. Structure of the eyelids. The eyelids are composed of the following structures, taken in their order from without inwards : — Integument, areolar tissue, fibres of the Orbicularis muscle, tarsal cartilage, fibrous membrane, Meibomian glands, and conjunctiva. The upper lid has, in. addition, the aponeurosis of the Levator palpebrse. The integument is extremely thin, and continuous at the margin of the lids with the conjunctiva. The subcutaneous areolar tissue is very lax and delicate, seldom contains any fat, and is extremely liable to serous infiltration. The fibres of the orbicularis muscle, where they cover the palpebrae, are thin, pale in color, and possess an involuntary action. The tarsal cartilages are two thin elongated plates of fibro-cartilage, about an inch in length. They are placed one in each lid, contributing to their form and support. The superior, the larger, is of a semilunar form, about one-third of an inch in breadth at the centre, and becoming gradually narrowed at each extremity. Into the fore part of this cartilage the aponeurosis of the Levator palpebrse is attached. The inferior tarsal cartilage, the smaller, is thinner, and of an elliptical form. 40 626 ORGANS OF THE SENSES. The free or ciliary margin of the cartilages is thick, and presents a j^erfectlj straight edge. The attached or orbital margin is connected to the circumference of the orbit by the fibrous membrane of the lids. The outer angle of each cartilage is attached to the malar bone by the external palpebral or tarsal ligament. The inner angles of the two cartilages terminate at the commencement of the lacus lacrymalis, being fixed to the margins of the orbit by the tendo oculi. The fibrous membrane of the lids, or tarsal ligament is a layer of fibrous membrane, beneath the Orbicularis, attached, externally, to the margin of the orbit, and internally to the orbital margin of the lids. It is thick and dense at the outer part of the orbit, but becomes thinner as it approaches the cartilages. This membrane serves to support the eyelids, and retains the tarsal cartilages in their position. The Meibomian glands (fig. 309) are situated upon the inner surface of the eyelids, between the tarsal cartilages and conjunctiva, and" may be distinctly seen through the mucous membrane on everting the eyelids, presenting the appearance of parallel strings of pearls. They are about thirty in number in the upper cartikge, FiL 309. — The Meibomian Glands, etc., seen from the Inner Surface of the Eyelids. JboNb Xar/iri/iiial. and somewhat fewer in the lower. They are imbedded in grooves in the inner surface of the cartilages, and correspond in length with the breadth of each cartilage ; they are, consequently, longer in the upper than in the lower eyelid. Their ducts open on the free margin of the lids by minute foramina, which correspond in number to the follicles. These glands are a variety of the cutaneous sebaceous glands, each consisting of a single straight tube or follicle, having a ccecal termination, into which open a number of small secondary follicles. The tubes consist of basement membrane, covered by a layer of scaly epithelium ; the cells are charged with sebaceous matter, which constitutes the secretion. The peculiar parallel arrangement of these glands side by side forms a smooth layer, admirably adapted to .the surface of the globe, over which they constantly glide. The use of their secretion is to prevent adhesion of the lids. The eyelashes (cilia) are attached to the free edges of the eyelids ; they are short, thick, curved hairs, arranged in a double or triple row at the margin of the lids; those of the upper lid, more numerous and longer than the lower, curve upwards; those of the lower lid curve downwards, by which means they do not interlace in closing the lids. The conjunctiva is the mucous membrane of the eye. It lines the inner surface LACHRYMAL APPARATUS. 627 of the eyelids, and is reflected over the fore part of the sclerotic and cornea. In each of these situations, its structure presents some peculiarities. The palpebral portion of the conjunctiva is thick, opaque, highly vascular, and covered with numerous papilke, which, in the disease called granular lids, become greatly hypertrophied. At the margin of the lids, it becomes continuous with the lining membrane of the ducts of the Meibomian glands, and, through the lachrymal canals, with the lining membrane of the lachrymal sac and nasal duct. At the outer angle of the upper lid, it may be traced along the lachrymal ducts into the lachrymal gland ; and at the inner angle of the eye, it forms a semilunar fold, the plica semilunaris. The folds formed by the reflection of the conjunctiva from the lids on to the eye are called the superior and inferior palpebral folds, the former being the deeper of the two. Upon the sclerotic, the conjunctiva is loosely connected to the globe; it becomes thinner, loses its papillary structure, is transparent, and only slightly vascular in health. Upon the cornea, the con- junctiva is extremely thin and closely adherent, and no vessels can be traced into it in the adult in a healthy state. In the foetus, fine capillary loops extend, for some little distance forwards, into this membrane ; but in the adult they pass only to the circumference of the cornea. The caruncula lacrymalis is a small, reddish, conical-shaped body, situated at the inner canthus of the eye, and filling up the small triangular space in this situation, the lacus lacrymalis. It consists of a cluster of follicles similar in structure to the Meibomian, covered with mucous membrane, and is the source of the whitish secretion which constantly collects at the inner angle of the eye. A few slender hairs are attached to its surface. On the outer side of the caruncula is a slight semilunar fold of mucous membrane, the concavity of which is directed towards the cornea; it is called the plica semilunaris. Between its two layers is found a thin plate of cartilage. This structure is considered to be the rudiment of the third eyelid in birds, the membrana nictitans. Lachrymal Apparatus (fig. 310). The lachrymal apparatus consists of the lachrymal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the eye, Fig. 310. — The Lachrymal Apparatus. Right Side. This fluid is carried away by the lachrymal canals into the lachrymal sac, ana along the nasal duct into the cavity of the nose. G28 ORGANS OF THE SENSES. The lachrymal gland is lodged in a depression at the outer angle of the orbit, on the inner side of the external angular process of the frontal bone. It is of an oval form, about the size and shape of an almond. Its upper convex surface is in contact with the periosteum of the orbit, to which it is connected by a few fibrous bands. Its under concave surface rests upon the convexity of the eyeball, aud upon the Superior and External recti muscles. Its vessels and nerves enter its posterior border, whilst its anterior margin is closely adherent to the back part of the upper eyelid, and is covered, on its inner surface, by a reflection of the conjunctiva. This margin is separated from the rest of the gland by a slight depression, hence it is sometimes described as a separate lobe, called the palpe- bral portion of the gland. In structure and general appearance, it resembles the salivary glands. Its ducts, about seven in number, run obliquely beneath the mucous membrane for a short distance, and, separating from each other, open by a series of minute orifices on the upper and outer half of the conjunctiva, near its reflection on to the globe. These orifices are arranged in a row, so as to disperse the secretion over the surface of the membrane. The lachrymal canals commence at the minute orifices, puncta lacrymalia, seen on the margin of the lids, at the outer extremity of the lacus lacrymalis. They commence on the summit of a slightly elevated papilla, the papilla lacry- malis, and lead into minute canals, the canaliculi, which proceed inwards to terminate in the lachrymal sac. The superior canal, the smaller and longer of the two, at first ascends, and then bends at an acute angle, and passes inwards and downwards to the lachrymal sac. The inferior canal at first descends, and then, abruptly changing its course, passes almost horizontally inwards. They are dense and elastic in structure, and somewhat dilated at their angle. The lachrymal sac is the upper dilated extremity of the nasal duct, and is lodged in a deep groove formed by the lachrymal bone and nasal process of the superior maxillary. It is oval in form, its upper extremity being closed in and rounded, whilst below it is continued into the nasal duct. It is covered by the Tensor tarsi muscle and by a fibrous expansion derived from the tendo oculi, which is attached to the ridge on the lachrymal bone. In structure, it consists of a fibrous elastic coat, lined internally by mucous membrane ; the latter is continuous, through the canaliculi, with the mucous lining of the conjunctiva, and through the nasal duct with the pituitary membrane of the nose. The nasal duct is a membranous canal, about three quarters of an inch in length, which extends from the lower part of the lachrymal sac to the inferior meatus of the nose, where it terminates by a somewhat expanded orifice, provided with an imperfect valve formed by the mucous membrane. It is contained in an osseous canal, formed by the superior maxillary, the lachrymal, and the inferior turbinated bones, is narrower in the middle than at each extremity, and takes a direction downwards, backwards, and a little outwards. It is lined by mucous membrane, which is continuous below with the pituitary lining of the nose. In the canaliculi, this membrane is provided with scaly epithelium; but in the lachrymal sac and nasal duct, the epithelium is ciliated as in the nose. The Ear. The Organ of Hearing consists of three parts ; the external ear, the middle ear or tympanum, and the internal ear or labyrinth. External Ear. The External Ear consists of an expanded portion named the pinna or auricle, and the auditory canal or meatus. The former serves to collect the vibrations of the air constituting sound, and the latter conducts those vibrations to the tym- panum. The pinna or auricle (fig. 311) consists of a layer of cartilage, covered by integument, and connected to the commencement of the auditory canal ; it is of an TIIE EAR. G29 Fig. 311. — The Pinna or Auricle. Outer Surface. ovoid form, its surface uneven, with its larger end directed upwards. Its outer surface is irregularly concave, directed slightly forwards, and presents numerous eminences and depressions, which result from the foldings of its fibro-cartilaginous element. To each of these names have been assigned. Thus, the external pro- minent rim of the auricle is called the helix. Another curved prominence, parallel with, and in front of, the helix, is called the anti- helix ; this bifurcates above into two parts, so as to inclose a triangular depression, the fossa of the antihelix. The narrow curved depression between the helix and antihelix is called the /055a of the helix {fossa innomi- rtata seu scaphoidea). The antihelix de- scribes a circuit round a deep, capacious cavity, the concha, which is partially divided into two parts by the commencement of the helix. In front of the concha, and project- ing backwards over the meatus, is a small pointed eminence, the tragus; so called from its being generally covered, on its under surface, with a tuft of hair, resembling a goat's beard. Opposite the tragus, and sepa- rated from it by a deep notch (incisura intertragica), is a small tubercle, the anti- tragus. Below this is the lobule, composed of tough areolar and adipose tissues, wanting the firmness and elasticity of the rest of the pinna. Structure of the pinna. The pinna is composed of a thin plate of yellow cartilage, covered with integument, and connected to the surrounding parts by ligaments, and a few muscular fibres. The integument is thin, closely adherent to the cartilage, and furnished with sebaceous glands, which are most numerous in the concha and scaphoid fossa. The cartilage of the pinna consists of one single piece ; it gives form to this part of the ear, and upon its surface are found all the eminences and depressions above described. It does not enter into the construction of all parts of the auricle, and presents several intervals or fissures in its substance, which partially separate the different parts. Thus, it does not form a constituent part of the lobule ; it is deficient, also, between the tragus and beginning of the helix, the notch between them being filled up by dense fibrous tissue. The fissures in the cartilage are the fissure of the helix, a short, vertical slit, situated at the fore part of the pinna, immediately behind a small conical projection of cartilage, opposite the first curve of the helix {process of the helix) ; another fissure, the fissure of the tragus, is seen upon the anterior surface of the tragus. The antihelix is divided below, by a deep fissure, into two parts ; one part terminates by a pointed, tail-like extremity {processus caudatus) ; the other is continuous with the antitragus. The cartilage of the pinna is very pliable, elastic, of a yellowish color, and similar in structure to the cartilages of the ala3 nasi. The ligaments of the pinna consist of two sets: — 1. Those connecting it to the side of the head. 2. Those connecting the various parts of its cartilage together. The former, the most important, are two in number, anterior and posterior. The anterior ligament extends from the process of the helix to the root of the zygoma. The posterior ligament passes from the posterior surface of the concha to the outer surface of the mastoid process of the temporal bone. A few fibres connect the tragus to the root of the zygoma. Those connecting the various parts of the cartilage together are also two in 630 ORGANS OF THE SENSES. number. Of these, one is a strong fibrous band, stretching across from the tragus to the commencement of the helix, completing the meatus in front, and partly encircling the boundary of the concha ; the other extends between the concha and the processus caudatus. The muscles of the pinna (fig. 312), like the ligaments, also consist of two sets : — 1. Those which connect it with the side of the head, moving the pinna as a whole, Fig. 312.— The Muscles of the Pinna. viz., the Attollens aurem, Attrahens aurem, and Retrahens aurem (p. 241). 2. The proper muscles of the pinna, which extend from one part of the auricle to another. These are the Helicis major. Antitragicus. Helicis minor. Transversus auriculae. Tragicus. Obliquus auris. The Helicis major is a narrow, vertical band of muscular fibres, situated upon the anterior margin of the helix. It arises, below, from the tubercle of the helix, and is inserted into the anterior border of the helix, just where it is about to curve backwards. It is pretty constant in its existence. The Helicis minor is an oblique fasciculus, firmly attached to that part of the helix which commences from the bottom of the concha. The Tragicus is a short, flattened band of muscular fibres, situated upon the outer surface of the tragus, the direction of its fibres being vertical. The Antitragicus arises from the outer part of the antitragus ; its fibres are inserted into the processus caudatus oftheanti helix. This muscle is usually very distinct. The Transversus auriculae is placed on the cranial surface of the pinna. It consists of radiating fibres, partly tendinous and partly muscular, extending from the convexity of the concha to the prominence corresponding with the groove of the helix. AUDITORY CANAL. 631 The Obliquus auris (Todd) consists of a few fibres extending from the upper and back part of the concha to the convexity immediately above it. The arteries of the pinna are the posterior auricular, from the external carotid ; the anterior auricular, from the temporal ; and. an auricular branch from the occi- pital artery. The veins accompany the corresponding arteries. The nerves are the auricularis magnus, from the cervical plexus ; the posterior auricular, from the facial ; the auricular branch of the pneumogastric ; and the auriculo-temporal branch of the inferior maxillary nerve. The Auditory Canal, meatus auditorius externus (fig. 313), extends from the bottom of the concha to the membrana tympani. It is about an inch and. a quarter in length, its direction obliquely forwards and inwards, and it is slightly Fig. 313. — A Front View of the Organ of Hearing. Right Side. Incus \ Ma. 1 leas \\ S tap i3 ^^^tSimi-ehvalar Ca^ia.1' \'t»ft>:,* if .Cochlt^ curved upon itself, so as to be higher in the middle than at either extremity. It forms an oval cylindrical canal, narrowest at the middle, somewhat flattened from before backwards, the greatest diameter being in the vertical direction at the ex- ternal orifice ; but, in the transverse direction, at the tympanic end. The membrana tympani, which occupies the termination of the meatus, is obliquely directed, in consequence of the floor of this canal being longer than the roof, and the anterior wall longer than the posterior. The auditory canal is formed partly by cartilage and membrane, and partly by bone. The cartilaginous portion is about half an inch in length, being rather less than half the canal ; it is formed by the cartilage of the concha and tragus, being pro- longed inwards to the circumference of the auditory process, to which it is firmly attached. This tube is deficient at its upper and back part, its place being supplied by fibrous membrane. This part of the canal is rendered extremely movable, by two or three deep fissures (incisure Santorini), which extend through the cartilage in a vertical direction. The osseous portion is about three-quarters of an inch in length, and narrower than the cartilaginous portion. It is directed inwards and a little forwards, forming a slight curve in its course, the convexity of which is upwards and backwards. Its inner end, which communicates with the cavity of the tympanum, is smaller than the outer, and sloped, the anterior wall projecting beyond the posterior about two lines ; it is marked, excepting at its upper part, by a narrow groove for the insertion of the membrana tympani. Its outer end is dilated, and rough in the greater part of its circumference for the attachment of the cartilage of the pinna. Its vertical transverse section is oval, the greatest diameter being from above C32 ORGANS OF THE SENSES. downwards. The front and lower parts of this canal are formed by a curved plate of bone, which, in the foetus, exists as a separate ring (tympanic bone), incomplete at its upper part. The skin lining the meatus is very thin, closely adherent to the cartilaginous and osseous portions of the tube, and covers the surface of the membrana tympani, forming its outer layer. After maceration, the thin pouch of epidermis, when withdrawn, preserves the form of the meatus. The skin near the orifice is fur- nished with hairs and sebaceous glands. In the thick subcutaneous tissue of the cartilaginous part of the meatus are numerous ceruminous glands, which secrete the ear wax, the ducts of which open on the surface of the skin. The arteries supplying the meatus are branches from the posterior auricular, internal maxillary, and temporal. The nerves are chiefly derived from the temporo-auricular branch of the inferior maxillary nerve. i Middle Ear or Tympanum. The middle ear or tympanum is an irregular cavity, compressed from without inwards, and situated within the petrous bone. It is placed above the jugular fossa, the carotid canal lying in front, the mastoid cells behind, the meatus audito- rius externally, and the labyrinth within. It is filled with air, and communicates with the pharynx by the Eustachian tube. The tympanum is traversed by a chain of movable bones, which connect the membrana tympani with the laby- rinth, and serve to convey the vibrations communicated to the membrana tympani across the cavity of the tympanum to the internal ear. The cavity of the tympanum measures about five lines from before backwards, three lines in the vertical direction, and between two and three in the transverse, being a little broader behind and above than below and in front. It is bounded externally by the membrana tympani and meatus ; internally, by the outer surface of the internal ear; behind, by the mastoid cells; and, in front, by the Eustachian tube and canal for the Tensor tympani. Its roof and floor are formed by thin osseous laminae, which connect the squamous and petrous portions of the temporal bone. The roof is broad, flattened, and formed of a thin plate of bone, which separates the cranial and tympanic cavities. The floor is narrow, and corresponds to the jugular fossa, which lies beneath. The outer wall is formed by the membrana tympani, a small portion of bone being seen above and below this membrane. It presents three small apertures, the iter chordae posterius, the Glaserian fissure, and the iter chordae anterius. The aperture of the iter chordee posterius is behind the aperture for the membrana tympani, close to its margin, at a level with its centre ; it leads into a minute canal, which descends in front of the aquaeductus Fallopii, and terminates in this canal near the stylo-mastoid foramen. Through it the chorda tympani nerve enters the tympanum. The Glaserian fissure opens just above and in front of the orifice of the mem- brana tympani; in this situation it is a mere slit, about a line in length. It gives passage to the long process of the malleus, the Laxator tympani muscle, and some tympanic vessels. The aperture of the iter chordae anterius is seen just above the preceding fissure ; it leads into a canal (canal of Huguier), which runs parallel with the Glaserian fissure. Through it the chorda tympani nerve leaves the tympanum. The internal wall of the tympanum is vertical in direction, and looks directly outwards. It presents for examination the following parts : — Fenestra ovalis. Eidge of the Aquaeductus Fallopii. Fenestra rotunda. Pyramid. Promontory. . Opening for the Stapedius. THE TYMPANUM. 633 The fenestra ovalis is a reniform opening, leading from the tympanum into the vestibule ; its long diameter is directed horizontally, and its convex border upwards. The opening in the recent state is closed by the lining membrane common to both cavities, and is occupied by the base of the stapes. This mem- brane is placed opposite the membrana tympani, and is connected with it by the ossicula auditus. The fenestra rotunda is an oval aperture, placed at the bottom of a funnel- shaped depression, leading into the cochlea. It is placed below and rather behind Fig. 314. — View of Inner Wall of Tympanum. (Enlarged.) Chorda Tjjn^a the fenestra ovalis, from which it is separated by a rounded elevation, the pro- montory ; it is closed in the recent state by a membrane {membrana tympani secundaria, Scarpa). This membrane is concave towards the tympanum, convex towards the cochlea. It consists of three layers; the external or mucous, derived from the mucous lining of the tympanum ; the internal or serous, from the lining membrane of the cochlea ; and an intermediate or fibrous layer. The promontory is a rounded hollow prominence, formed by the projection outwards of the first turn of the cochlea ; it is placed between the fenestras, and furrowed on its surface by three small grooves, which lodge branches of the tympanic plexus. The rounded eminence of the aquseductm Fallopii is placed between the fenestra ovalis and roof of the tympanum ; it is the prominence of the bony canal in which the portio dura is contained. It traverses the inner wall of the tympanum above the fenestra ovalis, and, behind that opening, curves nearly vertically downwards along the posterior wall. The pyramid is a conical eminence, situated immediately behind the fenestra ovalis, and in front of the vertical portion of the eminence above-described ; it is hollow in the interior, and contains the Stapedius muscle; its summit projects forwards towards the vestibular fenestra, and presents a small aperture, which transmits the tendon of the muscle. The cavity in the pyramid is prolonged into a minute canal, which communicates with the aquaeductus Fallopii. The posterior wall of the tympanum is wider above than below, and presents for examination the Openings of the Mastoid Cells. These consist of one large irregular aperture, and several smaller openings, situated at the upper part of the posterior wall ; they lead into canals, which com- municate with large irregular cavities contained in 'the interior of the mastoid 634 ORGANS OF THE SENSES. process. These cavities vary considerably in number, size, and form ; they are lined by mucous membrane, continuous with that covering the cavity of the tympanum. The anterior wall of the tympanum is wider above than below ; it corresponds with the carotid canal, from which it is separated by a thin plate of bone ; it presents for examination the Canal for the Tensor tympani. Orifice of the Eustachian Tube. Processus Cochleariformis. The orifice of the canal for the Tensor tympani, and the orifice of the Eustachian tube, are situated at the upper part of the interior wall, being separated from each other by a thin, delicate horizontal plate of bone, the processus cochleari- formis. These canals run from the tympanum forward, inward, and a little downward, to the retiring angle between the squamous and petrous portions of the temporal bone. The canal for the Tensor tympani is the superior and the smaller of the two : it is rounded and lies beneath the upper surface of the petrous bone, close to the hiatus Fallopii. The tympanic end of this canal forms a conical eminence, which is prolonged backwards into the cavity of the tympanum, and is perforated at its summit by an aperture, which transmits the tendon of the muscle contained in it. This eminence is sometimes called the anterior pyramid. The canal contains the Tensor tympani muscle. The Eustachian tube is the channel through which the tympanum communicates with the pharynx. Its length is from an inch and a half to two inches, and its direction downwards, forwards, and inwards. It is formed partly of bone, partly of cartilage and fibrous tissue. The osseous portion is about half an inch in length. It commences in the lower part of the anterior wall of the tympanum, below the processus cochleariformis, and, gradually narrowing, terminates in an oval dilated opening, at the angle of junction of the petrous and squamous portions, its extremity presenting a jagged margin, which serves for the attachment of the cartilaginous portion. The cartilaginous portion, about an inch in length, is formed of a triangular plate of cartilage, curled upon itself, an interval being left below, between the non-approximated margins of the cartilage, which is completed by fibrous tissue. Its canal is narrow behind, wide, expanded, and somewhat trumpet-shaped in front, terminating by an oval orifice, placed at the upper part and side of the pharynx, behind the back part of the inferior meatus. Through this canal the mucous membrane of the pharynx is continuous with, that which lines the tympanum. The membrana tympani separates the cavity of the tympanum from the bottom of the external meatus. It is a thin semi-transparent membrane, nearly oval in form, somewhat broader above than below, and directed very obliquely down- wards and inwards. Its circumference is contained in a groove at the inner end of the meatus, which skirts the circumference of this part excepting above. The handle of the malleus descends vertically between the inner and middle layers of this membrane as far down as its centre, where it is firmly attached, drawing the membrane inwards, so that its outer surface is concave, its inner convex. Structure. This membrane is composed of three layers, an external or cuticular, a middle or fibrous, and an internal or mucous. The cuticular lining is derived from the integument lining the meatus. The fibrous layer consists of fibrous and elastic tissues ; some of the fibres radiate from near the centre to the circumfer- ence ; others are arranged, in the form of a dense circular ring, round the attached margin of the membrane. The mucous lining is derived from the mucous lining of the tympanum. The vessels pass to the membrana tympani along the handle of the malleus, and are distributed between its layers. Ossicles of the Tympanum. The tympanum is traversed by a chain of movable bones, three in number, the malleus, incus, and stapes. The former is OSSICLES OF THE TYMPANUM. 635 attached to the membrana tympani, the latter to the fenestra ovalis, the incus being placed between the two, to both of which it is connected by delicate articulations. The Malleus, so named from its fancied resemblance to a hammer, consists of a head, neck, handle or manubrium, and two processes, viz., the processus gracilis and the processus brevis. The head is the large upper extremity of the bone ; it is oval in shape, and articulates posteriorly with the incus, being free in the rest of its extent. The neck is the narrow contracted part just beneath the head ; and below this is a prominence, to which the various processes are attached. The manubrium is a vertical portion of bone, which is connected by its outer margin with the membrana tympani. It decreases in size towards its extremity, where it is curved slightly forwards, and flattened from within outwards. The processus gracilis is a long and very delicate process, which passes from the eminence below the neck forwards and outwards to the Glaserian fissure, to which it is connected by bone and ligamentous fibres. It gives attachment to the Laxator tympani. The processus brevis is a slight conical projection, which springs from the root of the manubrium, and lies in contact with the membrana tympani. Its summit gives attachment to the Tensor tympani. The Incus has received its name from its resemblance to an anvil, but it does not look unlike a bicuspid tooth, with two roots, which differ in length, and are widely separated from each other. It consists of a Fi «- ™^Z Sld^l"?ed T' "~ body and two processes. The body is somewhat quadrilateral, but compressed laterally. Its summit is deeply concave, and articulates with the malleus ; in the fresh state, it is covered with cartilage and lined with synovial membrane. The two processes diverge from one another nearly at right angles. The sltort process, somewhat conical in shape, projects nearly horizontally back- wards, and is attached to the margin of the opening leading into the mastoid cells by ligamentous fibres. The long process, longer and more slender than the preceding, descends nearly vertically behind the handle of the malleus, and, bending inwards, terminates in a rounded globular projection, the os orbiculare, tipped with cartilage, and articu- lating with the head of the stapes. In the foetus the os orbiculare exists as a separate bone, but becomes united to the long process of the incus in the adult. The Stapes, so called from its close resemblance to a stirrup, consists of a head, neck, two branches, and a base. The head presents a depression, tipped with cartilage, which articulates with the os orbiculare. The neck, the constricted part of the bone below the head, receives the insertion of the Stapedius muscle. The two branches or crura diverge from the neck, and are connected at their extremities by a flattened, oval-shaped plate (the base), which forms the foot of the stirrup, and is fixed to the margin of the fenestra ovalis by ligamentous fibres. Ligaments of the Ossicula. These small bones are connected with each other, and with the tympanum, by ligaments, and moved by small muscles. The articular surfaces of the malleus and incus, the orbicular process of the incus and the head of the stapes, are covered with cartilage, connected together by delicate capsular ligaments, and lined by synovial membrane. The ligaments connecting the ossicula with the walls of the tympanum are three in number, one for each bone. «36 ORGANS OF THE SENSES. The suspensory ligament of the malleus is a delicate, round bundle of fibres, which, descends perpendicularly from the roof of the tympanum to the head of the malleus. The posterior ligament of the incus is a short, thick, ligamentous band, which connects the extremity of the short process of the incus to the posterior wall of the tympanum, near the margin of the opening of the mastoid cells. The annular ligament of the stapes connects the circumference of the base of this bone to the margin of the fenestra ovalis. A suspensory ligament of the incus has been described by Arnold, descending from the roof of the tympanum to the upper part of the incus, near its articulation with the malleus. The Muscles of the tympanum are three : — Tensor tympani. Laxator tympani. Stapedius. The Tensor tympani, the largest, is contained in a bony canal, above the osseous portion of the Eustachian tube, from which it is separated by the processus cochleariformis. It arises from the under surface of the petrous bone, from the cartilaginous portion of the Eustachian tube, and from the osseous canal in which it is contained. Passing backwards, it terminates in a slender tendon, which is reflected outwards over the processus cochleariformis, and is inserted into the handle of the malleus, near its root. It is supplied by a branch from the otic ganglion. The Laxator tympani major (Sommering) arises from the spinous process of the sphenoid bone, and from the cartilaginous portion of the Eustachian tube; passing backwards through the Glaserian fissure, it is inserted into the neck of the malleus, just above the processus gracilis. It is supplied by the tympanic branch of the facial. The Laxator tympani minor (Sommering) arises from the upper and back part of the external meatus, passing forwards and inwards between the middle and inner layers of the membrana tympani; it is inserted into the handle of the malleus, and processus brevis. This is considered as a ligament by some anatomists. The Stapedius arises from the sides of a conical cavity hollowed out of the interior of the pyramid ; its tendon emerges from the orifice at its apex, and, passing forwards, is inserted into the neck of the stapes. Its surface is aponeurotic, its interior fleshy, and its tendon occasionally contains a slender bony spine, which is constant in some mammalia. It is supplied by a filament from the facial nerve. Actions. The Tensor tympani draws the membrana tj^mpani inwards, and thus heightens its tension. The Laxator tympani draws the malleus outwards, and thus the tympanic membrane, especially at its fore part, is relaxed. The Stapedius depresses the back part of the base of the stapes, and raises its fore part. It probably compresses the contents of the vestibule. The Mucous Membrane of the tympanum is thin, vascular, and continuous with the mucous membrane of the pharynx, through the Eustachian tube. It invests the ossicula, and the muscles and nerves contained in the tympanic cavity, forms the internal layer of the membrana tympani, covers the foramen rotundum, and is reflected into the mastoid cells, which it lines throughout. In the tympanum and mastoid cells, this membrane is pale, thin, slightly vascular, and covered with ciliated epithelium. In the osseous portion of the Eustachian tube, the membrane is thin; but in the cartilaginous portion it is very thick, highly vascular, covered with laminar ciliated epithelium, and provided with numerous mucous glands. The Arteries supplying the tympanum are five in number, viz., the tympanic branch of the internal maxillary, which supplies the membran/i tympani ; the stylo-mastoid branch of the posterior auricular, which supplies the back part of the tympanum and mastoid cells ; the smaller branches being the petrosal branch INTERNAL EAR. 637 of the middle meningeal, and branches from the ascending pharyngeal and internal carotid. The Veins of the tympanum terminate in the middle meningeal and pharyngeal veins, and, through these, in the internal jugular. The Nerves of the tympanum may be divided into : — 1. Those supplying the mus- cles. 2. Those distributed to the lining membrane. 3. Branches communicating with other nerves. Nerves to muscles. The Tensor tympani is supplied by a branch from the otic ganglion ; the Laxator tympani and the Stapedius, by a filament from the facial (Sommering). The nerves distributed to the lining membrane are derived from the tympanic plexus. Communications between the following nerves take place in the tympanum ; the tympanic branch, from the petrous ganglion of the glossopharyngeal ; a filament from the carotid plexus ; a branch which joins the great superficial petrosal nerve from the Vidian ; and a branch to the otic ganglion (small superficial petrosal nerve). The tympanic branch of the glossopharyngeal (Jacobson's nerve) enters the tym- panum by an aperture in its floor, close to the inner wall, and ascends on to the promontory. It distributes filaments to the lining membrane of the tympanum, and divides into three branches, which are contained in grooves on the promontory, and serve to connect this with other nerves. One branch runs in a groove, for- wards and downwards, to an aperture situated at the junction of the anterior and inner walls, just above the floor, and enters the carotid canal, to communicate with the carotid plexus of the sympathetic. The second branch is contained in a groove which runs vertically upwards to an aperture on the inner wall of the tympanum, just beneath the anterior pyramid, and in front of the fenestra ovalis. The canal leading from this opens into the hiatus Fallopii, where the nerve contained in it joins the great petrosal nerve. The third branch ascends towards the anterior surface of the petrous bone ; it then passes through a small aperture in the sphenoid and temporal bones to the exterior of the skull, and joins the otic ganglion. As this nerve passes by the gangliform enlargement of the facial, it has a connecting filament with it. The chorda tympani quits the facial near the stylo-mastoid foramen, enters the tympanum at the base of the pyramid, and arches forwards across its cavity, between the handle of the malleus and long process of the incus, to an opening internal to the Glaserian fissure. It is invested by a reflection of the lining mem- brane of the tympanum. Internal Ear or Labyrinth. The internal ear is the essential part of the acoustic organ, receiving the ulti- mate distribution of the auditory nerve. It is called the labyrinth, from the com- plexity of its communications, and consists of three parts, the vestibule, semi- circular canals, and cochlea. It consists of a series of cavities, channelled out of the substance of the petrous bone, communicating externally with the cavity of the tympanum, through the fenestra ovalis and fenestra rotunda ; and internally, with the meatus auditorius internus, which contains the auditory nerve. Within the osseous labyrinth is contained the membranous labyrinth, upon which the ramifi- cations of the auditory nerve are distributed. The Vestibule is the common central cavity of communication between the parts of the internal ear. It is situated on the inner side of the tympanum, behind the cochlea, and in front of the semicircular canals. It is somewhat ovoidal in shape from before backwards, flattened from side to side, and measures about one-fifth of an inch from before backwards, as well as from above downwards, being narrower from without inwards. On its outer or tympanic wall is the fenestra ovalis, closed, in the recent state, by the base of the stapes, and its annular ligament. C38 ORGANS OF THE SENSES. On its inner wall, at its fore part, is a small circular depression, fovea hemisplie- rica; it is perforated, at its anterior and inferior part (macula cribrosa), by seve- ral minute holes for the passage of filaments of the auditory nerve ; and behind it is a vertical ridge, the pyramidal eminence. At the hinder part of the inner wall is the orifice of the aquseductus vestibuli, which extends to the posterior sur- face of the petrous portion of the temporal bone. It transmits a small vein, and, Fig. 316. — The Osseous Labyrinth laid open. (Enlarged.) Opcrrim, Jlm*f/e passed t/troit, I'am m . rotund. Opening of according to some, contains a tubular prolongation of the lining membrane of the vestibule, which ends in a cul-de-sac, between the layers of the dura mater within the cranial cavity. On the upper wall or roof is a transversely-oval depression, fovea semi-elliptica, separated from the fovea hemispherica by the pyramidal eminence, already mentioned. Behind, the semicircular canals open into the vestibule by five orifices. In front is a large oval opening which communicates with the scala vestibuli of the cochlea by a single orifice, apertura scalse vestibuli cochleae. The Semicircular canals are three bony canals, situated above and behind the vestibule. They are of unequal length, compressed from side to side, and describe the greater part of a circle. They measure about one-twentieth of an inch in diameter, and each presents a dilatation at one end, called the ampulla, which measures more than twice the diameter of the tube. These canals open into the vestibule by five orifices, one of the apertures being common to two of the canals. The superior semicircular canal is vertical in direction, its arch forming a round projection on the anterior surface of the petrous bone. It forms about two- thirds of a circle. Its outer extremity, which is ampullated, commences by a distinct orifice in the upper part of the vestibule ; the opposite end of the canal, which is not dilated, joins with the corresponding part of the posterior canal, and opens by a common orifice with it in the back part of the vestibule. The posterior semicircular canal, also vertical in direction, is directed back- wards to the posterior surface of the petrous bone ; it is the longest of the three, its ampullated end commencing at the lower and back part of the vestibule, its opposite end joining the common canal already mentioned. The external or horizontal canal is the shortest of the three, its arch being COCHLEA. G39 directed outwards and backwards. Its ampullated end corresponds to the upper and outer angle of the vestibule, just above the fenestra ovalis ; its opposite end opens by a distinct orifice at the upper and back part of the vestibule. The Cochlea bears some resemblance to a common snail-shell ; it forms the anterior part of the labyrinth, is conical in form, and placed almost horizontally in front of the vestibule ; its apex is directed forwards and outwards towards the upper and front part of the inner wall of the tympanum ; its base corresponds with the anterior depression at the bottom of the internal auditory meatus ; and is perforated by numerous apertures, for the passage of the cochlear branch of the auditory nerve. It measures about a quarter of an inch in length, and its breadth towards the base is about the same. It consists of a conical-shaped central axis, the modiolus or columella; of a canal wound spirally round the axis for two turns and a half, from the base to the apex ; and of a delicate lamina {lamina- spiralis) contained within the canal, which follows its windings, and subdivides it into two. The central axis or modiolus is conical in form, and extends from the base to the apex of the cochlea. Its base is broad, corresponds with the first turn of tho cochlea, and is perforated by numerous orifices, which transmit filaments of the cochlear branch of the auditory nerve ; the axis diminishes rapidly in size in the second coil, and terminates within the last half-coil or cupola, in an expanded, delicate, bony lamella, which resembles the half of a funnel, divided longitudinally, and called the infundibulum • the broad part of this funnel is directed towards the summit of the cochlea, and blends with the last half-turn of the spiral canal of the cochlea, the cupola. The outer surface of the modiolus is formed of the wall of the spiral canal, and is dense in structure ; but its centre is channelled, as far as the last half-coil, by numerous branching canals, which transmit nervous filaments in regular succession into the canal of the cochlea, or upon the surface of the lamina spiralis. One of these, larger than the rest, occupies the centre of the modiolus, and is named the tubulus centralis modioli; it extends from the base to the extremity of the modiolus, and transmits a small nerve and artery (arteria centralis modioli). The spiral canal (fig. 317) takes two turns and a half round the modiolus. It is about an inch and a half in length, measured along its outer wall ; and diminishes Fig. 317.— The Cochlea laid open. (Enlarged.) gradually in size from the base to the summit, where it terminates in a cul-de- sac, the cupola, which forms the apex of the cochlea. The commencement of this canal is about the tenth of an inch in diameter; it diverges from the modiolus towards the tympanum and vestibule, and presents three openings. One, the fenestra rotunda, communicates with the tympanum; in the recent state, this aperture is closed by a membrane, the membrana tympani secundaria. Another aperture, of an oval form, enters the vestibule. The third is the aperture of the 640 ORGANS OF THE SENSES. aquseductus cochlese, which leads to a minute funnel-shaped canal, which opens on the basilar surface of the petrous bone, and transmits a small vein. The interior of the spiral canal is divided into two passages {scalse) bj a thin, osseous, and membranous lamina, which winds spirally round the modiolus. This is the lamina spiralis, the essential part of the cochlea upon which the nerve tubules are distributed. The osseous part of the spiral lamina -extends about half way across the diameter of the spiral canal ; it is called the osseous zone. It commences in the vestibule between the tympanic and vestibular opening of the cochlea, and gradually becoming narrower in its course, terminates in a projecting hook, the hamular process, just where the expansion of the infundibulum com- mences. The lamina spiralis consists of two thin lamellae of bone, between which are numerous canals for the passage of nervous filaments, which open chiefly on the lower or tympanic surface. At the point where the osseous lamina is attached to the modiolus, and following its windings, is a small canal, called by Rosenthal, the canalis spiralis modioli. In the recent state, the osseous zone is continued to the opposite wall of the canal by a membranous and muscular layer (membranous zone), so as to form a complete partition in the tube of the cochlea. Two passages or scalce are thus formed, by a division of the canal of the cochlea into two. One, the scala tympani, is closed below by the membrane of the fenestra rotunda; the other, the scala vestvbuU, communicates, by an oval aperture, with the vestibule. Near the termination of the scala vestibuli, close by the fenestra rotunda, is the orifice of the aquosductus cochleae. The scalae communicate, at the apex of the cochlea, by an opening common to both, the helicotrema, which exists in consequence of the deficiency of the lamina spiralis in the last half-coil of the canal. In structure, the membranous zone is a transparent glassy lamina, presenting near its centre a number of minute transverse lines, which radiate outwards, ana give it a fibrous appearance; and at its circumference, where it is connected with the outer wall of the spiral canal, it is composed of a semi-transparent structure, the Cochlearis muscle (Todd and Bowman), connective tissue (Kolliker). The vestibular surface of the osseous portion of the lamina spiralis is covered, for about the outer fifth of its surface, with a thin layer, resembling cartilage in texture. It is described as the denticulate lamina (Todd and Bowman), from its presenting a series of wedge-shaped teeth which form its free margin, and which project into the vestibular scalar. The inner surface of the osseous labyrinth is lined by an exceedingly thin fibro-serous membrane, analogous to a periosteum, from its close adhesion to the inner surface of these cavities, and performing the office of a serous membrane by its free surface. It lines the vestibule, and from this cavity is continued into the semicircular canals and the scala vestibuli of the cochlea, and through the heli- cotrema into the scala tympani. Two delicate tubular processes are prolonged along the aqueducts of the vestibule and cochlea, to the inner surface of the dura mater. This membrane is continued across the fenestra ovalis and fenestra rotunda, and consequently has no communication with the lining membrane of the tympa- num. Its attached surface is rough and fibrous, and closely adherent to the bone ; its free surface is smooth and pale, covered with a layer of epithelium, and secretes a thin, limpid fluid, the aqua labyrinthi, perilymph (Blainville), or liquor Cotunnii. In the vestibule and semicircular canals, it separates the osseous from the mem- branous labyrinth; but in the cochlea it lines the two surfaces of the bony lamina spiralis, and, being continued from its free margin across the canal to its outer wall, forms the lamina spiralis membranacea, serving to complete the separation between the two scalce. The Membranous Labyrinth. The Membranous Labyrinth (fig. 318) is a closed membranous sac, containing d aid ; upon the wall of the sac, the ramifications of the auditory nerve are distributed. MEMBRANOUS LABYRINTH. 641 It has the same general form as the vestibule and semicircular canals, in which it is inclosed ; but is considerably smaller, and separated from their lining membrane by the perilymph. The vestibular 'portion consists of two sacs, the utricle and the saccule. The utricle is the larger of the two, of an oblong form, compressed laterally, and occupies the upper and back part of the vestibule, lying in contact with the Fig. 318. — The Membranous Labyrinth detached. (Enlarged.) Ofoliths ixn iArcupA. tht ira JK to Cochlea fovea semi-elliptica. Numerous filaments of the auditory nerve are distributed on the wall of 1 this sac ; and its cavity communicates, behind, with the membranous semicircular canals by five orifices. The saccule is the smaller of the two vestibular sacs; it is globular in form, lies in the fovea hemispherica, near the opening of the vestibular scala of the cochlea, and receives numerous nervous filaments, which enter from the bottom of the depression in which it is contained. Its cavity is apparently distinct from that of the utricle. The membranous semicircular canals are about one-third the diameter of the osseous canals, but in number, shape, and general form they are precisely similar ; they are hollow, and open by five orifices into the utricle, one being common to two canals. Their ampullae are thicker than the rest of the tubes, and nearly fill the cavities in which they are contained. The membranous labyrinth is held in its position by the numerous nervous fila- ments distributed to the utricle, the saccule, and to the ampulla of each canal. These nerves enter the vestibule through the minute apertures on its inner wall. Structure. The wall of the membranous labyrinth is semi-transparent, and con- sists of three layers. The outer layer is a loose and flocculent tissue, containing bloodvessels and numerous pigment-cells, analogous to those in the choroid. The middle layer, thicker and more transparent, bears some resemblance to the hyaloid membrane, but it presents in parts marks of longitudinal fibrillation and elongated nuclei on the addition of acetic acid. The inner layer is formed of polygonal nucleated epithelial cells, which secrete the endolymph. 41 642 ORGANS OF THE SENSES. The endolyrnph {liquor Scarpa) is a limpid serous fluid, which fills the mem- branous labyrinth ; in composition, it closely resembles the perilymph. The otoliths are two small rounded bodies, consisting of a mass of minute crystalline grains of carbonate of lime, held together in a mesh of delicate fibrous tissue, and contained in the wall of the utricle and saccule, opposite the distribu- tion of the nerves. A calcareous material is also, according to Bowman, sparingly scattered in the cells lining the ampulla of each semicircular canal. The Arteries of the labyrinth are the internal auditory from the basilar or superior cerebellar, the stylo-mastoid from the posterior auricular, and, occasion- ally, branches from the occipital. The internal auditory divides at the bottom of the internal meatus into two branches, cochlear and vestibular. The cochlear branch subdivides into from twelve to fourteen twigs, which traverse the canals in the modiolus, and are distributed, in the form of a capillary network, in the substance of the lamina spiralis. The vestibular branches accompany the nerves, and are distributed, in the form of a minute capillary network, in the substance of the membranous labyrinth. The Veins of the vestibule and semicircular canals accompany the arteries, and, receiving those of the cochlea at the base of the modiolus, terminate in the superior petrosal sinus. The Auditory nerve, the special nerve of the sense of hearing, divides, at the bottom of the internal auditory meatus, into two branches, the cochlear and vesti- bular. The trunk of the nerve, as well as the branches, contains numerous ganglion cells with caudate prolongations. The Vestibular nerve, the most posterior of the two, divides into three branches, superior, middle, and inferior. The superior vestibular branch, the largest, divides into numerous filaments, which pass through minute openings at the upper and back part of the cul-de-sac at the bottom of the meatus, and, entering the vestibule, are distributed to the utricle, and to the ampulla of the external and superior semicircular canals. The middle vestibular branch consists of numerous filaments, which enter the vestibule by a smaller cluster of foramina, placed below those above mentioned, and which correspond to the bottom of the fovea hemispherica ; they are dis- tributed to the saccule. The inferior and smallest branch passes backwards in a canal behind the foramina for the nerves of the saccule, and is distributed to the ampulla of the posterior semicircular canal. The nervous filaments enter the ampullary enlargement at a deep depression seen on their external surface, and a corresponding elevation is seen within, the nerve fibres ending in loops, and in free extremities. In the utricle and saccule, the nerve fibres spread out, some blending with the calcareous matter, others radiat- ing on the inner surface of the wall of each cavity, becoming blended with a layer of nucleated cells, and terminating in a thin fibrous film. The Cochlear nerve divides into numerous filaments at the base of the modiolus, which ascend along its canals, and then, bending outwards at right angles, pass between the plates of the bony lamina spiralis, close to its tympanic surface. Between the plates of the spiral lamina, the nerves form a plexus, which contains ganglion cells ; and from the margin of the osseous zone, branches from this plexus are distributed to the membranous part of the septum, where they are arranged in small, conical-shaped bundles, parallel with one another. The filaments which supply the apical portion of the lamina spiralis are conducted to this part through the tubulus centralis modioli. Organs of Digestion. The Apparatus for the digestion of the food consists of the alimentary canal, and of certain accessory organs. The alimentary canal is a musculo-membranous tube, about thirty feet in length, extending from the mouth to the anus, and lined throughout its entire extent by mucous membrane. It has received different names in the various parts of its course : at its commencement, which comprises the mouth, we find every provision for the mechanical division of the Food (mastication), and for its admixture with a peculiar fluid secreted by the salivary glands (insalivation) ; beyond this are the pharynx and the oesophagus (the organs of deglutition), which convey the food into the stomach, that part of the alimentary canal in which the principal chemi- cal changes occur ; in that organ the reduction and solution of the food take place ; by its admixture with the bile and pancreatic fluid, in the small intestines, the nutritive principles of the food (the chyle) are separated from that portion which passes into the large intestine, and which is expelled from the system. Mouth. Pharynx. (Esophagus. Stomach. Teeth. Alimentary Canal. Small intestine Large intestine Accessory Organs. {Parotid. Submaxillary. Sublingual. Duodenum. Jejunum. Ileum. Caecum. Colon. Eectum. Liver. Pancreas. Spleen. The Mouth (fig. 319) is placed at the commencement of the alimentary canal; it is a nearly oval-shaped cavity, in which the mastication of the food takes place. It is bounded, in front, by the lips ; laterally, by the cheeks and alveolar process of the upper and lower jaw ; above, by the hard palate and teeth of the upper jaw ; below, by the tongue, the mucous membrane stretched between the under surface of this organ and the inner surface of the jaws, and by the teeth of the lower jaw; behind, by the soft palate and fauces. The mucous membrane lining the mouth is continuous with the integument at the free margin of the lips, and with the mucous lining of the fauces behind ; it is of a pink rose tinge during life, and very thick where it covers the hard parts bounding this cavity. The Lips are two fleshy folds, which surround the orifice of the mouth, formed externally of integument, internally of mucous membrane, between which are found the Orbicularis oris muscle, the coronary vessels, some nerves, areolar tissue, fat, and numerous small labial glands. The inner surface of each lip is connected in the middle line to the gum of the corresponding jaw by a fold of mucous mem- brane, the frsenum labii superioris and frsenum ktbii inferioris, the former being the larger of the two. The labial glands are situated between the mucous membrane and the Orbicularis 646 644 ORGANS OF DIGESTION. oris, round the orifice of the mouth. They are rounded in form, about the size of a small pea, their ducts opening by small orifices upon the mucous membrane. In structure, they resemble the other salivary glands. The Cheeks form the sides of the face, and are continuous in front with the lips. They are composed, externally, of integument ; internally, of mucous mem- brane ; and, between the two, of a muscular stratum, besides a large quantity of fat, areolar tissue, vessels, nerves, and buccal glands. The mucous membrane lining the cheek is reflected above and below upon the gums, and is continuous behind with the lining membrane of the soft palate. Opposite the second molar tooth of the upper jaw is a papilla, the summit of Fig. 319. — Sectional View of the Nose, Mouth, Pharynx, etc. K) fie nitty of A'atai duct Bristle pa**ed through i's duct which presents the minute aperture of the duct of the parotid gland. The prin- cipal muscle of the cheek is the Buccinator; but numerous others enter into its formation, viz., the Zygomatic!, Masseter, and the Platysma myoides. The buccal glands are placed between the mucous membrane and Buccinator muscle : they are similar in structure to, but smaller than, the labial glands. Two or three, of larger size than the rest, are placed between the Masseter and Buccinator muscles; their ducts open into the mouth, opposite the last molar tooth. They are called molar glands. The Gums are composed of a dense fibrous tissue, closely connected to the periosteum of the alveolar processes, and surrounding the necks of the teeth. THE TEETH. 645 They are covered by smooth and vascular mucous membrane, which is remarkable for its limited sensibility. Around the necks of the teeth, this membrane presents numerous fine papillae; and from this point it is reflected into the alveolus, where it is continuous with the periosteal membrane lining that cavity. The Teeth. The human subject is provided with two sets of teeth, which make their ap- pearance at different periods of life. The first set appear in childhood, and are called the temporary, deciduous, or milk teeth. The second set, which also appear at an early period, continue until old age, and are named permanent. The temporary teeth are twenty in number ; four incisors, two canine, and four molars, in each jaw. The permanent teeth are thirty- two in number ; four incisors (two central and two lateral), two canine, four bicuspids, and six molars, in each jaw. General characters. Each tooth consists of three portions; the crown or body, Fig. 320.— The Permanent Teeth. External View. Jfolarf Wiiclom t„nh. Uj>2>er Juw Bicuspid* Canine TiusitoT* FU71J Keck JLotver Jaw which projects above the gum ; the root or fang, entirely concealed within the alveolus ; and the neck, the constricted portion between the other two. The roots of the teeth are firmly implanted within the alveoli : these depressions are lined with periosteum, which is reflected on to the tooth at the point of the fang, and covers it as far as the neck. At the margin of the alveolus, the peri- osteum becomes continuous with the fibrous structure of the gums. G46 ORGANS OF DIGESTION. Permanent Teeth. The Incisors or cutting teeth are so named from their presenting a sharp, cut- ting edge, adapted for cutting the food. They are eight in number, and form the four front teeth in each jaw. The crown is directed vertically, is wedge-like in form, being bevelled at the expense of its posterior surface, so as to terminate in a sharp, horizontal cutting edge, which, before being subject to attrition, presents three small prominent points. It is convex, smooth, and highly polished in front ; slightly concave be- hind, where it is frequently marked by slight longitudinal furrows. The neck is constricted. The fang is long, single, conical, transversely flattened, thicker before than behind, and slightly grooved on each side in the longitudinal direction. The incisors of the upper jaw are altogether larger and stronger than those of the lower jaw. They are directed obliquely downwards and forwards. The two central ones are larger than the two lateral, and their free edges sharp and chisel-like, being bevelled at the expense of their posterior edge ; the root is more rounded. The incisors of the lower jaw are smaller than the upper; the two central ones are smaller than the two lateral, and are the smallest of all the incisor teeth. The Canine Teeth (cuspidati) are four in number, two in the upper, and two in the lower jaw; one being placed behind each lateral incisor. They are larger and stronger than the incisors, especially the root, which sinks deeply into the jaw, and causes a well-marked prominence upon its surface. The crown is large and conical, very convex in front, a little hollowed and un- even posteriorly, and tapering to a blunted point or cusp which rises above the level fcf the other teeth. The root is single, but longer and thicker than that of the incisors, conical in form, compressed laterally, and marked by a slight groove on each side. The upper canine teeth (vulgarly called eye-teeth) are larger and longer than the two lower, and situated a little behind them. The lower canine teeth are placed in front of the upper, so that their summits correspond to the interval between the upper canine teeth and the neighboring incisor. The Bicuspid Teeth (small or false molars) are eight in number, four in each jaw, two being placed immediately behind each of the canine teeth. They are smaller and shorter than the canine. The crown is compressed from without inwards, and surmounted by two pyra- midal eminences or cusps separated by a groove ; hence their name, bicuspidate. The outer of these cusps is larger and more prominent than the inner. The neck is oval. The root is generally single, compressed, and presents a tendency to become double, as seen from the deep groove on each side. The apex is generally bifid. The upper bicusjnds are larger, and present a greater tendency to the division of their roots than the lower; this is especially marked in the second upper bicuspid. The Molar Teeth {multicuspidati, true or large molars) are the largest of the permanent set, and are adapted, from the great breadth of their crowns, for grind- ing and pounding the food. They are twelve in number, six in each jaw, three being placed behind each of the posterior bicuspids. The crown is nearly cubical in form, rounded on each of its lateral surfaces, flattened in front and behind ; the upper surface being surmounted by four or five tubercles or cusps (four in the upper, five in the lower molars) separated from each other by a crucial depression; hence their name, multicuspidati. THE TEETH. G4V The neck is distinct, large, and rounded. The root is subdivided into from two to five fangs, each of which presents an aperture at its summit. The first molar tooth is the largest and broadest of all; its crown has usually five cusps, three outer and two inner. In the upper jaw, the root consists of three fangs, widely separated from one another, two being external, the other internal. The latter is the largest and the longest, slightly grooved, and some- times bifid. In the lower jaw, the root consists of two fangs, one being placed in front, the other behind ; they are both compressed from before backwards, and grooved on their contiguous faces, indicating a tendency to division. The second molar is a little smaller than the first. The crown has four cusps in the upper, and five in the lower jaw. The root has three fangs in the upper jaw, and two in the lower, the characters of which are similar to the preceding tooth. The third molar tooth is called the wisdom tooth (dens sapientise), from its late appearance through the gum. It is smaller than the others, and its axis is directed inwards. The crown is small and rounded, and furnished with three tubercles. The root is generally single, short, conical, slightly curved, and grooved so as to present traces of a subdivision into three fangs in the upper, and two in the lower jaw. Temporary Teeth. The temporary or milk teeth are smaller, but resemble in form those of the permanent set. The hinder of the two temporary molars is the largest of all the Fig. 321.— The Temporary or Milk Teeth. External View. Zjoiver J u w Canine Inciters milk teeth, and is succeeded by the second permanent bicuspid. The first upper molar has only three cusps, two external, one internal ; the second upper molar has four cusps. The first lower molar has four cusps ; the second lower molar has five. The fangs of the temporary molar teeth are smaller, and more diverging than those of the permanent set ; but, in other respects, bear a strong resemblance to them. 648 ORGANS OF DIGESTION". Fig. 322.— Vertical Section of a Molar Tooth. T-Cr Neck -J^a Fig. 323.— Vertical Section of a Bicuspid Tooth. Magnified. Structure of the Teeth. Structure. On making a vertical section of a tooth (fig. 322), a hollow cavity will be found in the interior. This cavity is situated at the base of the crown, and is continuous with a canal which traverses the centre of each fang, and opens by a minute orifice at its extremity. The shape of the cavity corresponds somewhat with that of the tooth : it forms what is called the pulp cavity, and con- tains a soft, highly vascular, and sensitive substance, the dental pulp. The pulp is richly supplied with vessels and nerves, which enter the cavity through the small aperture at the point of each fang. The solid portion of the tooth consists of three distinct structures, viz., ivory (tooth-bone or dentine), which forms the larger portion of the tooth ; enamel, which covers the exposed part or crown ; and the cortical substance or cement (crusta petrosa), which is disposed as a thin layer on the surface of the fang. The Ivory or dentine (fig. 323) forms the principal mass of a tooth ; in its central part is the cavity inclosing the pulp. It is a modification of the osseous tisue, from which it differs, however, in structure and chemical composition. On examination with the microscope, it is seen to consist of a number of minute wavy and branching tubes, having distinct parietes. They are called the dental tubuli, and are imbedded in a dense homogeneous sub- stance, the intertubular tissue. The dental tubuli are placed parallel with one ano- ther, and open at their inner ends into the pulp cavity. They pursue a wavy and undulating course towards the periphery. The direction of these tubes varies; they are vertical in the upper portion of the crown, oblique in the neck and upper part of the root, and towards the lower part of the root they are inclined downwards. The tubuli, at their commencement, are about 75^71 °f an mcn i n diameter; in their course they divide and subdivide dichotomously, so as to give to the cut surface of the dentine a striated appearance. From the sides of the tubes, especially in the fang, ramifications of extreme minuteness are given off, which join together in loops in the inter- tubular substance, or terminate in small dilatations, from which branches are given off. Near the periphery of the dentine, the finer ramifications of the tubuli ter- minate in a somewhat similar manner. In the fang, these ramifications occasionally pass into the crusta petrosa. The dental tubuli have comparatively thick walls, and contain, according to Mr. Tomes, slender cylindrical prolongations of the pulp-tissue. The intertubular substance is translucent, finely granular, and contains the chief part of the earthy matter of the dentine. After the earthy matter has been removed, by steeping a tooth in weak acid, the animal basis remaining is described by Henle as consisting of bundles of pale, granular, flattened fibres, running parallel with the tubes ; but by Mr. Nasmyth as consisting of a mass of brick- shaped cells surrounding the tubules. By Czermak and Mr. Salter it is supposed to consist of laminae which run parallel with the pulp cavity, across the direction of the tubes. Chemical Composition. According to Berzelius and Bibra, dentine consists of 28 parts of animal, and 72 of earthy matter. The animal matter is resolvable by Fang DEVELOPMENT OF THE TEETH. 049 boiling into gelatin. The earthy matter consists of phosphate of lime, carbonate of lime, a trace of fluoride of calcium, and phosphate of magnesia, and other salts. The Enamel is the hardest and most compact part of a tooth, and forms a thin crust over the exposed part of the crown, as far as the commencement of the fang. It is thickest on the grinding surface of the crown, until worn away by attrition, and becomes thinner towards the neck. It consists of a congeries of minute hexa- gonal rods. They lie parallel with one another, resting by one extremity upon the dentine, which presents a number of minute depressions for their reception ; the outer extremity forming the free surface of the crown. These fibres are directed vertically on the summit of the crown, horizontally at the sides ; they are about the -gs^-ir of an inch in diameter, and pursue a more or less w r avy course, which gives to the cut surface of the enamel a series of concentric lines. Numerous minute interstices intervene between the enamel-fibres near their dentinal surface, a provision calculated to allow of the permeation of fluids from the dentinal tubuli into the substance of the enamel. The enamel-rods consist of solid hexagonal or four-sided prisms, connected by their surfaces and ends, and filled with calcareous matter. If the latter is removed, by weak acid, from newly-formed or growing enamel, it will be found to present a network of delicate prismatic cells of animal matter. Chemical Composition. According to Bibra, enamel consists of 96.5 per cent. of earthy matter, and 3.5 per cent, of animal matter. The earthy matter consists of phosphate of lime, with traces of fluoride of calcium, carbonate of lime, phos- phate of magnesia and other salts. The Cortical Substance or cement (crusta petrosa) is disposed as a thin layer on the roots of the teeth, from the termination of the enamel, as far as the apex of the fang, where it is usually very thick. In structure and chemical com- position, it resembles bone. It contains, sparingly, the lacunae and canaliculi which characterize true bone ; those lacunas placed near the surface have the canaliculi radiating from the side of the lacunae towards the periodontal membrane ; and those more deeply placed, join with the adjacent dental tubuli. In the thicker portions of the crusta petrosa, the lamellae and Haversian canals peculiar to bone are also found. As age advances, the cementum increases in thickness, and gives rise to those bony growths or exostoses, so common in the teeth of the aged ; the pulp cavity becomes also partially filled up by a hard substance, intermediate in structure between dentine and bone (osieo-dcntine, Owen ; secondary dentine, Tomes). It appears to be formed by a slow conversion of the dental pulp, which shrinks, or even disappears. Development of the Teeth (figs. 324 to 329). According to the observations of Arnold and Groodsir, the teeth are developed from the mucous membrane covering the edges of the maxillary arches. About the sixth week of foetal life (fig. 324), the mucous membrane covering the edge of the upper jaw, presents a semicircular depression or groove ; this is the primitive dental groove (Goodsir), from the floor of which the germs of the ten deciduous or milk-teeth are developed. The germ of each tooth is formed by a conical elevation or papilla of mucous membrane (fig. 325), which constitutes the rudimen- tary pulp of a milk-tooth. The germs of the milk-teeth make their appearance in the following order : at the seventh week, the germ of the first deciduous molar of the upper jaw appears ; at the eighth week, that for the canine tooth is deve- loped ; the two incisor papillae appear about the ninth week (the central preceding the lateral) ; lastly, the second molar papilla is seen at the tenth week, behind the anterior molar. The teeth of the lower jaw appear rather later, the first molar papilla being only just visible at the seventh week; and the tenth papilla not being developed before the eleventh week. This completes the first or papillary stage of their development. 650 ORGANS OF DIGESTION. Development of Teeth. Flo. 224. Frimifive .Dental Groove* * r I c . 325. TaJiilla.in-Gtr-m. ofMXf^tootb He. 327. fie. 328. r I C . 329. Srlc/dian ofMM.'totrth £*finusitnt IcuUt The dental groove now becomes contracted, its margins thickened and prominent, and the groove is converted into follicles for the re- ception of the papillae, by the growth of mem- branous septa, which pass across the groove between its borders (fig. 326). The follicles by this means become the alveoli, lined by periosteum, from the bottom of which a process of the mucous membrane of the gum rises, which is the germ of the future tooth. The follicle for the first molar is complete about the tenth week ; the canine follows next, succeeded by the follicles for the incisors, which are com- pleted about the eleventh or twelfth week ; and, lastly, the follicle of the posterior deciduous molar is completed about the fourteenth week. These changes constitute the second or follicu- lar stage. About the thirteenth week, the papilla? begin to grow rapidly, project from the follicles, and assume a form corresponding with that of the future teeth ; the follicles soon become deeper, and from their margins small membranous processes or opercula are developed, which, meeting, unite and form a lid to the now closed cavity (fig. 327). These processes correspond in shape to the form of the crown of the tooth, and in number to the tubercles on its surface. The follicles of the incisor teeth have two opercula, the canine three, and the molars four or five each. The follicles are thus con- verted into dental sacs, and the contained papillae become pulps. The lips of the dental groove gradually advance over the follicles from behind forwards, and, uniting, gradually ob- literate it. This completes the third or saccular stage, which takes place about the end of the fifteenth week. The deep portion of the primitive dental groove is now closed-in; but the more super- ficial portion, near the surface of the gum, still remains open ; it is called, by Mr. Goodsir, the secondary dental groove; from it are developed the ten anterior permanent teeth. About the fourteenth week, certain lunated depressions are formed, one behind each of the sacs of the rudimentary milk-teeth. They are ten in number in each jaw, and are formed successively from before backwards; they are the rudimentary follicles of the four permanent incisors, the two canine, and the four bicuspids. As the secondary dental groove closes in, these follicles become closed cavities of reserve (fig. 327). The cavities soon elongate, and recede from the surface into the substance of the gum, behind the sacs of the deciduous teeth, and a papilla projects from the bottom of DEVELOPMENT OF THE TEETH. 651 each, which is the germ of the permanent tooth ; at the same time, one or more operculse are developed from the sides of the cavity ; and these, uniting, divide it into two portions ; the lower portion containing the papilla of the permanent tooth, the upper narrower portion becoming gradually contracted in the same way that the primitive dental groove was obliterated over the sacs of the deciduous teeth (fig. 328). The six posterior permanent teeth in each jaw, three on each side, arise from successive extensions backwards of the back part of the primitive dental groove. During the fourth month, that portion of the dental groove which lies behind the last temporary molar follicle remains open, and from it is developed the papilla, the rudiment of the first permanent molar. The follicle in which it is contained becomes closed by its operculum, and the upper part of the now- formed sac elongates backwards to form a cavity of reserve, in which the papilla of the second permanent molar appears at the seventh month after birth. After a considerable interval, during which the sacs of the first and second permanent molars have considerably increased in size, the remainder of the cavity of reserve presents for the last time a series of changes similar to the preceding, and gives rise to the sac and papilla of the wisdom-tooth, which appears at the sixth year. Growth of the Teeth. As soon as the dental sacs are formed by the closing-in of the follicles, they gradually enlarge, as well as their contained papillae. Each sac consists of two layers ; an internal, highly vascular layer, lined by epithelium ; and an external or areolo-fibrous membrane, analogous to the corium of the mucous membrane. The dental pulps soon become moulded to the form of the future teeth, and are adherent by their bases to the bottom of the dental sacs ; in the case of the molars, the base of the pulp is divided into two or more portions, which form the future fangs. During the fourth or fifth month of fcetal life, a thin lamina or cap of dentine is formed on the most prominent point of the pulp of all the milk-teeth. In the incisor and canine teeth, this newly-formed lamina has the form of a hollow cone ; in the molar teeth, as many separate laminas are found as there are eminences upon its crown. These lamina) grow at the expense of the pulp-substance, increasing in breadth by a growth round their margins, and in thickness by a similar forma- tion in its substance ; the separate cones (if a molar tooth) ultimately coalesce, and the crown is completely formed. The pulp now becomes constricted, so as to form the cervix ; and the remaining portion becomes narrow and elongated, to form the fang. The growth of dentine takes place from the surface towards the interior, until nothing but the small cavitas pulpse remains in the centre of the tooth, com- municating by the aperture left at the point of each fang, with the dental vessels and nerves. As soon as the formation of the dentine has commenced, there is developed from the inner wall of the dental sac, a soft pulpy mass, the enamel organ, which is intimately united to the surface of the dental pulp, or its cap of dentine. It consists of a mesh of fibres, elastic and spongy, containing within its reticulations fluid albumen; and at the point of junction of each fibre, a transparent nucleus is visible. The surface towards the dentinal pulp is covered by a layer of elongated nucleated cells, the enamel membrane. The deposition of the enamel takes place on the outer surface of the cap of dentine. The cementum appears to be formed, at a later period of life, by the periodontal membrane, extending from the margin of the enamel downwards. Eruption. When the calcification of the different tissues of the tooth is suffi- ciently advanced to enable it to bear the pressure to which it will be afterwards subjected, its eruption takes place, the tooth making its way through the gum. The gum is absorbed by the pressure of the crown of the tooth against it, which is itself pressed up by the increasing size of the fang (fig. 329). Concurrent with this, the septa between the dental sacs, at first fibrous in structure, soon ossify, and G52 * ORGANS OF DIGESTION. constitute the alveoli ; these firmly embrace the necks of the teeth, and afford them a solid basis of support. The eruption of the temporary teeth commences at the seventh month, and is complete about the end of the second year, those of the lower jaw preceding the upper. The periods for the eruption of the temporary set are : — 7th month, central incisors. 14th to 20th month, canine. 7th to 10th month, lateral incisors. 18th to 36th month, posterior molars. 12th to 14th month, anterior molars. Calcification of the permanent teeth commences a little before birth, and pro- ceeds in the following order in the upper jaw, in the lower jaw appearing a little earlier : — First molar, five or six months ; the central incisor a little later ; lateral incisors and canine, about the eighth or ninth month ; the bicuspids at the second year ; second molar,- five or six years ; wisdom-tooth, about twelve years. Previous to the permanent teeth penetrating the gum, the bony partitions separating their sacs from the deciduous teeth are absorbed, the fangs of the temporary teeth disappear, and the permanent teeth become placed under the loose crowns of the deciduous teeth ; the latter finally become detached, when the permanent teeth take their place in the mouth. The eruption of the permanent teeth takes place at the following periods, the teeth of the lower jaw preceding those of the upper by a short interval : — 6| years, first molars. 10th year, second bicuspid. 7th year, two middle incisors. 11th to 12th year, canine. 8th year, two lateral incisors. 12th to 13th year, second molars. 9th year, first bicuspid. 17th to 21st year, wisdom-teeth. The Palate. The Palate forms the roof of the mouth ; it consists of two portions, the hard palate in front, the soft palate behind. The hard palate is bounded in front and at the sides by the alveolar arches and gums ; behind, it is continuous with the soft palate. It is covered by a dense structure, formed by the periosteum and mucous membrane of the mouth, which are intimately adherent. Along the middle line is a linear ridge or raphe, which terminates anteriorly in a small papilla, corresponding with the inferior opening of the anterior palatine fossa. This papilla receives filaments from the naso- palatine and anterior palatine nerves. On either side and in front of the raphe, the mucous membrane is thick, pale in color, and corrugated ; behind, it is thin, smooth, and of a deeper color ; it is covered with squamous epithelium, and fur- nished with numerous glands (palatal glands), which lie between the mucous membrane and the surface of the bone. The soft palate or Velum pendulum palati is a movable fold, suspended from the posterior border of the hard palate, forming an incomplete septum between the mouth and pharynx. It consists of a fold of mucous membrane, inclosing mus- cular fibres, an aponeurosis, vessels, nerves, and mucous glands. "When occupy- ing its usual position (a relaxed pendent state), its anterior surface is concave, continuous with the roof of the mouth, and marked by a median ridge or raphe, which indicates its original separation into two lateral halves. Its posterior surface is convex, and continuous with the mucous membrane covering the floor of the posterior nares. Its upper border is attached to the posterior margin of the hard palate, and its sides are blended with the pharynx. Its lower border is free. Hanging from the middle of its lower border is a small conical-shaped pendu- lous process, the uvula; and arching outwards and downwards from the base of PALATE — SALIVARY GLANDS. 653 the uvula on each side, are two curved folds of mucous membrane, containing muscular fibres, called the arches or pillars of the soft palate. The anterior pillar runs downwards and forwards to the side of the base of the tongue, and is formed by the projection of the Palato-glossus muscle, covered by mucous membrane. The posterior filter* are more closely approximated and larger than the anterior; they run downwards and backwards to the sides of the pharynx, and are formed by the projection of the Palato-pharyngei muscles, covered by mucous membrane. The anterior and posterior pillars are separated below by a triangular interval, in which the tonsil is lodged. The space left between the arches of the palate on the two sides is called the isthmus of the fauces. It is bounded above by the free margin of the palate ; below, by the tongue ; and on each side, by the pillars of the soft palate and tonsils. The mucous membrane of the soft palate is thin, and covered with squamous epithelium on both surfaces, excepting near the orifice of the Eustachian tube, where it is columnar and ciliated. The palatine glands form a continuous layer on its posterior surface and round the uvula. The aponeurosis of the soft palate is a thin but firm fibrous layer, attached above to the hard palate, and becoming thinner towards the free margin of the velum. It is blended with the aponeurotic tendon of the Tensor palati muscle. The muscles of the soft palate are five on each side ; the Levator palati, Tensor palati, Palato-glossus, Palato-pharyngeus, and the Azygos uvulae. The tonsils {amygdalse) are two glandular organs, situated one on each side of the fauces, between the anterior and posterior pillars of the soft palate. They are of a rounded form, and vary considerably in size in different individuals. Externally, the tonsil is in relation with the inner surface of the Superior con- strictor, and with the internal carotid and ascending pharyngeal arteries, and corresponds to the angle of the lower jaw. Its inner surface presents from twelve to fifteen orifices, leading into small recesses, from which numerous follicles branch out into the substance of the gland. These follicles are lined by a con- tinuation of the mucous membrane of the pharynx, covered with epithelium, their walls being formed by a layer of closed capsules imbedded in the submucous tissue. These capsules are analogous to those of Peyer's glands ; they contain a thick grayish secretion. The arteries supplying the tonsil are the dorsalis linguae from the lingual, the ascending palatine and tonsillar from the facial, the ascending pharyngeal from the external carotid, and the descending palatine branch of the internal maxillary. The veins terminate in the tonsillar plexus, on the outer side of the tonsil. The nerves are derived from the fifth, and from the glossopharyngeal. The Salivaey Glands. The principal salivary glands communicating with the mouth, and pouring their secretion into its cavity, are the parotid, submaxillary, and sublingual. The Parotid gland (fig. 330), so called from being placed near the ear (*apa, near ; ovj, w ro { , the ear), is the largest of the three salivary glands, varying in weight from half an ounce to an ounce. It lies upon the side of the face, imme- diately below and in front of the external ear. It is limited above by the zygoma; below, by the angle of the jaw, and by an imaginary line drawn between it and the Sterno-mastoid muscle ; anteriorly, it extends to a variable extent over the Masseter muscle ; posteriorly, it is bounded by the external meatus, the mastoid process, and the Sterno-mastoid and Digastric muscles, slightly overlapping the former. Its anterior surface is grooved to embrace the posterior margin of the ramus of the lower jaw, and advances forwards beneath the ramus, between the two ptery- 654 ORGANS OF DIGESTION. goid muscles. Its outer surface, slightly lobulated, is covered by the integument and fascia, and lias one or two lymphatic glands resting on it. Its inner surface extends deeply into the neck, by means of two large processes, one of which dips behind the styloid process, and projects beneath the mastoid process and the Sterno-mastoid muscle ; the other is situated in front of the styloid process, and passes into the back part of the glenoid fossa, behind the articulation of the lower jaw. Imbedded in its substance is the external carotid, which ascends behind the ramus of the jaw ; the posterior auricular artery emerges from it behind ; the temporal artery above; the transverse facial in front; and the internal maxillary winds through it inwards, behind the neck of the jaw. Superficial to the external carotid is the trunk formed by the union of the temporal and internal maxillary veins ; a branch, connecting it with the internal jugular, also traversing the gland. It is traversed, from before backwards, by the facial nerve and its branches, which emerge at its anterior border ; the great auricular nerve pierces the gland to join the facial, and the temporal branch of the inferior maxillary nerve lies above the upper part of the gland. The internal carotid artery and internal jugular vein lie close to its deep surface. Steno's duct, the duct of the parotid gland, is about two inches and a half in length. It commences upon the inner surface of the cheek by a small orifice, Fig. 330.— The Salivary Gland. opposite the second molar tooth of the upper jaw ; running obliquely for a short distance beneath the mucous membrane, it pierces the Buccinator muscle, and crosses the Masseter to the anterior border of the gland, in the substance of which it subdivides into numerous branches. The direction of the duct corre- sponds to a line drawn across the face about a finger's breadth below the zygoma, from the lower part of the concha to midway between the free margin of the upper lip and the ala of the nose. While crossing the Masseter, it receives the duct of a small detached portion of the gland, socia parotidis, which occasionally exists as a separate lobe, just beneath the zygomatic arch. The parotid duct is SALIVARY GLANDS. Wfl dense, of considerable thickness, and its canal is about tlie size of a crow-quill ; it consists of an external or fibrous coat, of considerable density, containing con- . tractile fibres, and of an internal or mucous coat, lined with columnar epithelium. Vessels and Nerves. The arteries supplying the parotid gland are derived from the external carotid, and from the branches of that vessel in or near its substance. The veins follow a similar course. The lymphatics terminate in the superficial and deep cervical glands, passing in their course through two or three lymphatic glands, placed on its surface and in its substance. The nerves are derived from the carotid plexus of the sympathetic, the facial, superficial, temporal, and great auricular nerves. The Submaxillary gland is situated below the jaw, in the anterior part of the submaxillary triangle of the neck. It is irregular in form, and weighs about two drachms. It is covered by the integument, Platysma, deep cervical fascia, and the body of the lower jaw, corresponding to a depression on its inner surface, and lies upon the Mylo-hyoid, Hyo-glossus, and Stylo-glossus muscles, a portion of the gland passing beneath the posterior border of the Mylo-hyoid. In front of it is the anterior belly of the Digastric ; behind, it is separated from the parotid gland by the stylo-maxillary ligament, and from the sublingual gland in front by the Mylo-hyoid muscle. The facial artery lies in a groove in its posterior and upper border. Wharton's duct, the duct of the submaxillary gland, is about two inches in length, and its walls much thinner than those of the parotid duct. It commences by a narrow orifice on the summit of a small papilla, at the side of the fraenum linguae. Passing between the sublingual gland and the Genio-hyo-glossus mus- cle, it runs backwards and outwards between the Mylo-hyoid, and the Hyo-glossus and Genio-hyo-glossus muscles, and beneath the gustatory nerve, to the deep por- tion of the gland, where it divides into numerous branches. Vessels and Nerves. The arteries supplying the submaxillary gland are branches of the facial and lingual. Its veins follow the course of the arteries. The nerves are derived from the submaxillary ganglion, from the mylo-hyoid branch of the inferior dental, and from the sympathetic. The Sublingual gland is the smallest of the salivary glands. It is situated beneath the mucous membrane of the floor of the mouth, on either side of the fraenum linguae, in contact with the inner surface of the lower jaw, close to the symphysis. It is narrow, flattened, in shape somewhat like an almond, and weighs about a drachm. It is in relation, above, with the mucous membrane ; below, with the Mylo-rryoid muscle ; in front, with the depression on the side of the symphysis of the lower jaw, and with its fellow of the opposite side ; behind, with the deep part of the submaxillary gland; and internally, with the Genio- hyo-glossus, from which it is separated by the lingual nerve and Wharton's duct. Its excretory ducts (ductus Biviniani), from eight to twenty in number, open sepa- rately into the mouth, on the elevated crest of mucous membrane, caused by the projection of the gland, on either side of the fraenum linguae. One or more join to form a tube which opens into the Whartonian duct ; it is called the duct of Bartholin^. Vessels and Nerves. The sublingual gland is supplied with blood from the sub- lingual and submental arteries. Its nerves are derived from the gustatory. Structure. The salivary are conglomerate glands, consisting of numerous lobes, which are made up of smaller lobules, connected together by dense areolar tissue, vessels, and ducts. Each lobule consists of numerous closed vesicles, which open into a common duct ; the wall of each vesicle is formed of a delicate basement membrane, lined by epithelium, and covered on its outer surface with a dense capil- lary network. In the submaxillary and sublingual glands, the lobes are larger and more loosely united than in the parotid. 656 ORGANS OF DIGESTION. The Pharynx The Pharynx is that part of the alimentary canal which is placed behind the nose, mouth, and larynx. It is a musculo-membranous sac, somewhat conical in form, with the base upwards, and the apex downwards, extending from the under surface of the skull to the cricoid cartilage in front, and the fifth cervical vertebra behind. The pharynx is about four inches and a half in length, and broader in the transverse than in the antero-posterior diameter. Its greatest breadth is opposite the cornua of the hyoid bone; its narrowest point at its termination in the oesophagus. It is limited, above, by the basilar process of the occipital bone; below, it is continuous with the oesophagus ; posteriorly, it is connected by loose areolar tissue with the cervical portion of the vertebral column, and the Longi colli and Eecti capitis antici muscles ; anteriorly, it is incomplete, and is attached in succession to the internal pterygoid plate, the pterygo-maxillary ligament, the lower jaw, the tongue, hyoid bone, and larynx ; laterally, it is connected to the styloid processes and their muscles, and is in contact with the common and internal carotid arteries, the internal jugular veins, and the eighth, ninth, and sympathetic nerves, and, above, with a small part of the Internal pterygoid muscles. It has seven openings communicating with it; 'the two posterior nares, the two Eustachian tubes, the mouth, larynx, and oesophagus. The posterior nares are the two large apertures situated at the upper part of the anterior wall of the pharynx. The two Eustachian tubes open one at each side of the upper part of the pharynx, at the back part of the inferior meatus. Below the nasal fossae are the posterior surface of the soft palate and uvula, the large aperture of the mouth, the base of the tongue, the epiglottis, and the cordiform opening of the larynx. The oesophageal opening is the lower contracted portion of the pharynx. Structure. The pharynx is composed of three coats ; a mucous coat, a muscular layer, and a fibrous coat. The fibrous coat is situated between the mucous and muscular layers, and is called the pharyngeal aponeurosis. It is thick above, where the muscular fibres are wanting, and firmly connected to the basilar process of the occipital and petrous portion of the temporal bones. As it descends, it diminishes in thickness, and is gradually lost. The mucous coat is continuous with that lining the Eustachian tubes, the nares, the mouth, and the larynx. It is covered by columnar ciliated epithelium, as low down as a level with the floor of the nares ; below that point, it is of the squamous variety. The muscular coat has been already described (p. 262). The pharyngeal glands are of two kinds, the simple or compound follicular, which are found in considerable numbers beneath the mucous membrane, through- out the entire pharynx ; and the racemose, which are especially numerous at the upper part of the pharynx, and form a thick layer, across the back of the fauces, between the two Eustachian tubes. The (Esophagus. The (Esophagus is a membranous canal, about nine inches in length, extending from the pharynx to the stomach. It commences at the lower border of the cricoid cartilage, opposite the fifth cervical vertebra, descends along the front of the spine, through the posterior mediastinum, passes through the Diaphragm, and, entering the abdomen, terminates at the cardiac orifice of the stomach, opposite the ninth dorsal vertebra. The general direction of the oesophagus is vertical ; but it presents two or three slight curvatures in its course. At its commencement, it is (ESOPHAGUS. 65T placed in the median line ; but it inclines to the left side at the root of the neck, gradually passes to the middle line again, and, finally, again deviates to the left, as it passes forwards to the oesophageal opening of the Diaphragm. The oesophagus also presents an antero-posterior flexure, corresponding to the curvature of the cervical and thoracic portions of the spine. It is the narrowest part of the ali- mentary canal, being most contracted at its commencement, and at the point where it passes through the Diaphragm. Relations. In the neck, the oesophagus is in relation, in front, with the trachea ; and, at the lower part of the neck, where it projects to the left side, with the thyroid gland and thoracic duct ; behind, it rests upon the vertebral column and Longus colli muscle ; on each side, it is in relation with the common carotid artery (especially the left, as it inclines to that side), and part of the lateral lobes of the thyroid gland ; the recurrent laryngeal nerves ascend between it and the trachea. In the thorax, it is at first situated a little to the left of the median line : it passes across the left side of the transverse part of the aortic arch, descends in the posterior mediastinum, along the right side of the aorta, until near the Diaphragm, where it passes in front and a little to the left of this vessel, previous to entering the abdomen. It is in relation, in front, with the trachea, the arch of the aorta, the left bronchus, and the posterior surface of the pericardium; behind, it rests upon the vertebral column, the Longus colli, and + ,he intercostal vessels ; below, near the Diaphragm, upon the front of the aorta ; laterally, it is covered by the pleurae ; the vena azygos major lies on the right, and the descending aorta on the left side. The pneumogastric nerves descend in close contact with it, the right nerve passing down behind, and the left nerve in front of it. Surgical Anatomy. The relations of the oesophagus are of considerable practical interest to the surgeon, as he is frequently required, in cases of stricture of this tube, to dilate the canal by a bougie, when it becomes of importance that its direction and relations to surrounding parts should be remembered. In cases of malignant disease of the oesophagus, where its tissues have become softened from infiltration of the morbid deposit, the greatest care is requisite in directing the bougie through the strictured part, as a false passage may easily be made, and the instrument may pass into the mediastinum, or into one or the other pleural cavity, or even into the peri- cardium. The student should also remember that contraction of the oesophagus, and consequent symp- toms of stricture, are occasionally produced by an aneurism of some part of the aorta pressing upon this tube. In such a case, the passage of a bougie could only hasten the fatal issue. It occasionally happens that a foreign body becomes impacted in the oesophagus, which can neither be brought upwards nor moved downwards. When all ordinary means for its removal have failed, excision is the only resource. This, of course, can only be performed when it is not very low down. If the foreign body is allowed to remain, extensive inflammation and ulceration of the oesophagus may ensue. In one case with which I am acquainted, the foreign body ulti- mately penetrated the intervertebral substance, and destroyed life by inflammation of the mem- branes and substance of the cord. The operation of cesophagotomy is thus performed : — The patient being placed upon his back, with the head and shoulders slightly elevated, an incision, about four inches in length, should be made on the left side of the trachea, from the thyroid cartilage downwards, dividing the skin and Platysma. The edges of the wound being separated, the Omo-hyoid muscle and the fibres of the Sterno-hyoid and Sterno-thyroid muscles must be drawn inwards ; the sheath of the carotid vessels being exposed should be drawn outwards, and retained in that position by retractors; the oesophagus will then be exposed, and should be divided over the foreign body, which should then be removed. Great care is necessary to avoid wounding the thyroid vessels, the thyroid gland, and the laryngeal nerves. Structure. The oesophagus has three coats ; an external or muscular, a middle or cellular, and an internal or mucous coat. The muscular coat is composed of two planes of fibres of considerable thick- ness, an external longitudinal and an internal circular. The longitudinal fibres are arranged, at the commencement of the tube, in three fasciculi ; one in front, which is attached to the vertical ridge on the posterior surface of the cricoid cartilage, and one at each side, continuous with the fibres of the Inferior constrictor; as they descend they blend together, and form a uniform layer, which covers the outer surface of the tube. 42 658 ORGANS OF DIGESTION. The circular fibres are continuous above with the Inferior constrictor : thei r direction is transverse at the upper and lower parts of the tube, but oblique in the central part. The muscular fibres in the upper part of the oesophagus are of a red color, and consist chiefly of the striped variety ; but below, they consist entirely of the involuntary muscular fibre. The cellular coat connects loosely the mucous and muscular coats. The mucous coat is thick, of a reddish color above, and pale below. It is loosely connected with the muscular coat, and disposed in longitudinal plicas, which disappear on distension of the tube. Its surface is studded with minute papillae, and it is covered throughout with a thick layer of squamous epithelium. The oesophageal glands are numerous small compound glands, scattered through- out the tube ; they are lodged in the submucous tissue, and open upon the surface by a long excretory duct. They are most numerous at the lower part of the tube, where they form a ring round the cardiac orifice. The Abdomen". The Abdomen is the largest cavity of the trunk of the body, and is separated, below, from the pelvic cavity by the brim of the pelvis. It is of an oval form, the extremities of the oval being directed upwards and downwards ; it is wider above than below, and measures more in the vertical than in the transverse diameter. Fig. 331. — The Regions of the Abdomen and their Contents. (Edge of Costal Cartilages in dotted outline.) Boundaries. It is bounded, in front and at the sides, by the lower ribs, the Transversales muscles, and venter ilii ; behind, by the vertebral column, and the Psoae and Quadrati lumborum muscles ; above, by the Diaphragm ; below, by the ABDOMEN. 659 brim of the pelvis. The muscles forming the boundaries of this cavity are lined upon their inner surface by a layer of fascia, differently named according to the part to which it is attached. This cavity contains the greater part of the alimentary canal, some of the accessory organs 4 to digestion, the liver, pancreas, and spleen, and the kidneys and supra-renal capsules. Most of these structures, as well as the wall of the cavity in which they are contained, are covered by an extensive and complicated serous membrane, the peritoneum. The apertures found in the walls of the abdomen, for the transmission of structures to or from it, are the umbilicus, for the transmission (in the foetus) of the umbilical vessels ; the caval opening iu the Diaphragm, for the transmission of the inferior vena cava ; the aortic opening, for the passage of the aorta, vena azygos, and thoracic duct ; and the oesophageal opening, for the oesophagus and pneumogastric nerves. Below, there are two apertures on each side ; one for the passage of the femoral vessels, and the other for the transmission of the spermatic cord in the male, and the round ligament in the female. Regions. For convenience of description of the viscera, as well as of reference to the morbid condition of the contained parts, the abdomen is artificially divided into certain regions. Thus, if two circular lines are drawn round the body, the one parallel with the cartilages of the ninth ribs, and the other with the highest point of the crests of the ilia, the abdominal cavity is divided into three zones, an upper, a middle, and a lower. If two parallel lines are drawn from the cartilage of the eighth rib on each side, down to the centre of Poupart's ligament, each of these zones is subdivided into three parts, a middle and two lateral. The middle region of the upper zone is called the epigastric (Im, over, and yacrr^p, the stomach); and the two lateral regions, the right and left hypochondriac (irto, under, and xovSpot, the cartilages). The central region of the middle zone is the umbilical; and the two lateral regions, the right and left lumbar. The middle region of the lower zone is the hypogastric or pubic region ; and the lateral regions are the right and left inguinal. The parts contained in these different regions are the following (fig. 331): — Right Hypochondriac. The right lobe of the liver and the gall-bladder, the duodenum, hepatic flexure of the colon, upper part of the right kidney, and right supra-renal cap- sule. Right Lumbar. Ascending colon, lower part of the right kidney, and some convolutions of the small intestines. Right Inguinal. The caecum, appendix caeci, ureter, and spermatic vessels. Epigastric Region. The middle and pylo- ric end of the stomach, left lobe of the liver and lobus Spigelii, the hepa- tic vessels, cceliac axis, semilunar ganglia, pan- creas, parts of the aorta, vena cava, vena azygos, and thoracic duct. Umbilical Region. The transverse colon, part of the great omen- tum and mesentery, trans- verse part of the duode- num, and some convolu- tions of the jejunum and ileum. Hypogastric Region. Convolutions of the small intestines, the blad- der in children, and in adults if distended, and the uterus during preg- nancy. Left Hypochondriac. The splenic end of the stomach, the spleen and extremity of the pancreas, the splenic flexure of the colon, upper half of the left kidney, and left su- pra-renal capsule. Left Lumbar. Descending colon, lower part of left kidney, and some convolutions of the small intestines. Left Inguinal. Sigmoid flexure of the colon, ureter, and sper- matic vessels. 660 ORGANS OF DIGESTION. The Peritoneum. The Peritoneum (rtspitttvfiv, to extend around) is a serous membrane, and, like all membranes of this class, a shut sac. In the female, hoVever, it is not completely closed, the Fallopian tubes communicating with it by their free extremities; and thus the serous membrane is continuous with their mucous lining. The peritoneum partially invests all the viscera contained in the abdominal and pelvic cavities, forming the visceral layer of the membrane ; it is then reflected upon the internal surface of the parietes of these cavities, forming the parietal layer. (Fig. 332.) The free surface of the peritoneum is smooth, moist, and covered by a thin, squamous epithelium; its attached surface is rough, being connected to the viscera and inner surface of the parietes by means of areolar tissue, called the sub-peritoneal areolar tissue. The parietal portion is loosely connected with the fascia lining the abdomen and pelvis ; but more closely to the under surface of the Diaphragm, and in the middle line of the abdomen. In order to trace the reflections of this membrane (the abdomen having been Fig. 332.- -The Reflections of the Peritoneum, as seen in a vertical Section of the Abdomen. opened), the liver should be raised and supported in that position, and the stomach should be depressed, when a thin membranous layer is seen passing from the transverse fissure of the liver, to the upper border of the stomach ; this is the lesser or gastro-hepatic omentum. It consists of two thin, delicate layers of peri- toneum, an anterior and a posterior, between which are contained the hepatic PERITONEUM. 6«1 vessels and nerves. Of these two layers, the anterior should first be traced, and then the posterior 1 . The anterior layer descends to the lesser curvature of the stomach, and covers its anterior surface as far as the great curvature ; it descends for some distance in front of the small intestines, and, returning upon itself to the transverse colon, forms the external layer of the great omentum; it then covers the under surface of the transverse colon, and, passing to the back part of the abdominal cavity, forms the inferior layer of the transverse mesocolon. It then descends in front of the duodenum, the aorta, and vena cava, as far as the superior mesenteric artery, along which it passes to invest the small intestines, and, returning to the vertebral column, forms the mesentery; whilst, on either side, it covers the ascending and descending colon, and is thus continuous with the peritoneum lining the walls of the abdomen. From the root of the mesentery, it descends along the front of the spine into the pelvis, and surrounds the upper part of the rectum, which it holds in its position by means of a distinct fold, the mesorectum. Its course in the male and female now differs. In the male, it forms a fold between the rectum and bladder, the recto-vesical fold, and ascends over the posterior surface of the latter organ as far as its summit. In the female, it descends into the pelvis in front of the rectum, covers a small part of the posterior wall of the vagina, and is then reflected on to the uterus, the fundus and body of which it covers. From the sides of the uterus, it is reflected on each side to the wall of the pelvis, forming the broad ligaments ; and from its anterior surface it ascends upon the posterior wall of the bladder, as far as its summit. From this point it may be traced, as in the male, ascending upon the anterior parietes of the abdomen, to the under surface of the Diaphragm ; from which it is reflected upon the liver, forming the upper layer of the coronary, and the lateral and longitudinal ligaments. It then covers the upper and under sur- faces of the liver, and at the transverse fissure becomes continuous with the anterior layer of the lesser omentum, the point from whence its reflection was ori- ginally traced. The posterior layer of the lesser omentum descends to the lesser curvature of the stomach, and covers its posterior surface as far as the great curvature; it then descends for some distance in front of the small intestines, and, returning upon itself to the transverse colon, forms the internal layer of the great omentum ; it covers the upper surface of the transverse colon, and, passing backwards to the spine, forms the upper layer of the transverse mesocolon. Ascending in front of the pancreas and crura of the Diaphragm, it lines the back part of the under sur- face of this muscle, from which it is reflected on to the posterior border of the liver, forming the inferior layer of the coronary ligament. From the under surface of the liver, it may be traced to the transverse fissure, where it is continuous with the posterior layer of the lesser omentum, the point from whence its reflection was originally traced. The space included in the reflections of this layer of the peritoneum is called the lesser cavity of the peritoneum or cavity of the great omentum. It is bounded, in front, by the lesser omentum, the stomach, and the descending part of the great omentum ; behind, by the ascending part of the great omentum, the transverse colon, transverse mesocolon, and its ascending layer ; above, by the liver ; and below, by the folding of the great omentum. This space communicates with the general peritoneal cavity through the foramen of Winslow, which is situated be- hind the right free border of the lesser omentum. The foramen of Winslow is bounded in front by the lesser omentum, inclosing the vena portas and the hepatic artery and duct ; behinft, by the inferior vena cava ; above, by the lobus Spigelii ; below, by the hepatic artery curving forwards from the cceliac axis. This foramen is nothing more than a constriction of the general peritoneal cavity at this point, caused by the hepatic and gastric arteries passing forwards from the coeliac axis to reach their respective viscera. 662 ORGANS OF DIGESTION The viscera thus shown to be almost entirely invested by peritoneum are the liver, stomach, spleen, first portion of duodenum, jejunum, and ileum, transverse colon, sigmoid flexure, upper end of rectum, uterus, and ovaries. Those viscera partially covered by it are the descending and transverse portions of the duodenum, the caecum, the ascending and descending colon, the middle por- tion of the rectum, and the upper part of the vagina and posterior wall of the blad- der. The kidneys, supra-renal capsules, and pancreas, are covered by this mem- brane without receiving any special investment from it. The lower end of the rectum, the neck, base, and anterior surface of the bladder, and the lower part of the vagina, have no peritoneal investment. Numerous folds are formed by the peritoneum, extending between the various organs. These serve to hold them in position, and, at the same time inclose the - -Is and nerves proceeding to each part. Some of the folds are called liga- ments, from their serving to support the organs in position. Others, which connect certain parts of the intestine with the abdominal wall, constitute the mesenteries; and, lastly, those are called omenta, which proceed from one viscus to another. The Ligaments, formed by folds of the peritoneum, include those of the -iver, spleen, bladder, and uterus. They are described with their respective organs. The Omenta are the lesser or gastro-hepatic omentum, the great or gastro-colic omentum, and the gastro- splenic omentum. The lesser omentum (gastro-hepatic) is the duplicature which extends between the transverse fissure of the liver, and the lesser curvature of the stomach. It is extremely thin, and consists, as before said, of two layers of peritoneum. At the left border, its two layers pass on to the end of the oesophagus ; but, at the right border, where it is free, they are continuous, and form a free rounded margin, which contains between its layers the hepatic artery, the ductus communis chole- dochus, the portal vein, lymphatics, and hepatic plexus of nerves ; all these struc- tures being inclosed in loose areolar tissue, called Glisson's capsule. The great omentum {gastro-colic) is the largest peritoneal fold. It consists of four layers of peritoneum, two of which descend from the stomach, one from its anterior, the other from its posterior surface ; these, uniting at its lower border, descend in front of the small intestines, as low down as the pelvis ; and the same two ascend again as far as the transverse colon, where they separate and inclose that part of the intestine. These separate layers may be easily demonstrated in the young subject ; but in the adult, they are more or less inseparably blended. The left border of the great omentum is continuous with the gastro-splenic omen- tum ; its right border extends as far only as the duodenum. The great omentum is usually thin, presents a cribriform appearance, and always contains some adipose tissue, which, in fat subjects, accumulates in considerable quantity. Its use ap- pears to be to protect the intestines from cold, and to facilitate their movement upon each other during their vermicular action. The gastro-splenic omentum is the fold which connects the concave surface of the spleen to the cul-de-sac of the stomach, being continuous by its lower border with the great omentum. It contains the splenic vessels and the vasa brevia. The Mesenteries are the mesentery proper, the mesocsecum, the ascending, transverse, and descending mesocolon, the sigmoid mesocolon, and the meso- rectum. The mesentery (utaov, fttpov), so called from being connected to the middle of the cylinder of the small intestine, is the broad fold of peritoneum which connects the convolutions of the jejunum and ileum with the posterior wall of the abdomen. Its root, the part connected with the vertebral column, is narrow, about six inches in length, and directed obliquely from the left side of the second lumbar vertebra, to the right sacro-iliac symphysis. Its intestinal border is much longer ; and here its two layers separate, so as to inclose the intestine, and form its peritoneal coat. Its breadth, between its vertebral and intestinal border, is about four inches. Its upp>er border is continuous with the under surface of the STOMACH. 663 transverse mesocolon ; its lower border, with the peritoneum covering the caecum and ascending colon. It serves to retain the small intestines in their position, and contains between its layers the mesenteric vessels and nerves, the lacteal vessels, and mesenteric glands. The mesocsecum, when it exists, serves to connect the back part of the caecum with the right iliac fossa ; more frequently, the peritoneum passes merely in front of this portion of the large intestine. The ascending mesocolon is the fold which connects the back part of the ascend- ing colon with the posterior wall of the abdomen. The descending mesocolon retains the descending colon in connection with the posterior abdominal wall; more frequently, the peritoneum merely covers the anterior surface and sides of these two portions of the intestine. The transverse mesocolon is a broad fold, which connects the transverse colon with the posterior wall of the abdomen. It is formed of the two ascending layers of the great omentum, which, after separating to surround the transverse colon, join behind it, and are continued backwards to the spine, where they diverge in front of the duodenum, as already mentioned. This fold contains between its layers the vessels which supply the transverse colon. The sigmoid mesocolon is the fold of peritoneum which retains the sigmoid flexure in connection with the left iliac fossa. The mesorectum is the narrow fold which connects the upper part of the rectum with the front of the sacrum. It contains the hemorrhoidal vessels. The appendices epiploicas are small pouches of the peritoneum filled with fat, and situated along the colon and upper part of the rectum. They are chiefly appended to the transverse colon. The Stomach. The Stomach is the principal organ of digestion. It is the most dilated part of the alimentary canal, serving for the solution and reduction of the food, which constitutes the process of chymification. It is situated in the left hypochondriac, the epigastric, and part of the right hypochondriac regions. Its form is irregularly conical, curved upon itself, and presenting a rounded base, turned to the left side. It is placed immediately behind the anterior wall of the abdomen, above the transverse colon, below the liver and Diaphragm. Its size varies considerably in different subjects, and also according to its state of distension. When moderately full, its transverse diameter is about twelve inches, its vertical diameter about four. Its weight, according to Clendenning, is about four ounces and a half. It presents for examination two extremities, two orifices, two borders, and two surfaces. Its left extremity is called the greater or splenic end. It is the largest part of the stomach, and expands for two or three inches to the left of the point of entrance of the oesophagus. This expansion is called the great cul-de-sac or fundus. It lies beneath the ribs, in contact with the spleen, to which it is connected by the gastro-splenic omentum. The lesser or pyloric end is much smaller than the preceding, and situated on a plane anterior and inferior to it. It lies in contact with the wall of the abdomen, the under surface of the liver, and the neck of the gall-bladder. ^ The oesophageal or cardiac orifice communicates with the oesophagus ; it is the highest part of the stomach, and somewhat funnel-shaped in form. The pyloric orifice communicates with the duodenum, the aperture being guarded by a valve. The lesser curvature extends between the oesophageal and cardiac orifices, along the upper border of the organ, and is connected to the under surface of the liver by the lesser omentum. The greater curvature extends between the same points, along the lower border, 6G4 ORGANS OF DIGESTION. and gives attachment to the great omentum. The surfaces of the organ are limited by these two curvatures. The anterior surface is directed upwards and forwards, and is in relation with the Diaphragm, the under surface of the left lobe of the liver, and, in the epigas- tric region, with the abdominal parietes. Fig. 333. — The Mucous Membrane of the Stomach and Duodenum, with the Bile Ducts. Cyttie The posterior surface is directed downwards and backwards, and is in relation with the pancreas and great vessels of the abdomen, the crura of the Diaphragm, and the solar plexus. The stomach is held in position by the lesser omentum, which extends from the transverse fissure of the liver to its lesser curvature, and by a fold of peri- toneum, which passes from the Diaphragm on to the oesophageal end of the stomach, the gastro-phrenic ligament ; this constitutes the most fixed point of the stomach, whilst the pyloric end and greater curvature are the most movable parts : hence, when this organ becomes greatly distended, the greater curvature is directed forwards, whilst the anterior and posterior surfaces are directed, the former upwards, and the latter downwards. Alterations in Position. There is no organ in the body the position and connections of which present such frequent alterations as the stomach. During inspiration it is displaced downwards by the descent of the Diaphragm, and elevated by the pressure of the abdominal muscles during expiration. Its position to the surrounding viscera is also changed, according to the empty or distended state of the organ, When empty, it occupies only a small part of the left hypochon- driac region, the spleen lying behind it ; the left lobe of the liver covers it in front, and the under surface of the heart rests upon it above, and in front, being separated from it by the left lobe of the liver and pericardium. Hence it is, that, in gastralgia. the pain is generally referred to the heart, and is often accompanied by palpitation and intermission of the pulse. When the STOMACH. G65 stomach is distended the Diaphragm is forced upwards, contracting the cavity of the chest ; hence the dyspnoea complained of, from inspiration being impeded. The heart is also displaced upwards ; hence the oppression in this region, and the palpitation experienced in extreme disten- sion of the stomach. Pressure from without, as in the pernicious practice of tight lacing, pushes the stomach down towards the pelvis. In disease, also, the position and connections of the organ may be greatly changed, from the accumulation of fluid in the chest or abdomen, or when the size of any of the surrounding viscera undergoes alteration. On looking into the pyloric end of the stomach, the mucous membrane is found projecting inwards in the form of a circular fold, the pylorus, leaving a narrow circular aperture, about half an inch in diameter, by which the stomach commu- nicates with the duodenum. The pylorus is formed by a reduplication of the mucous membrane of the stomach, containing numerous muscular fibres, which are aggregated into a thick circular ring, the longitudinal fibres and serous membrane being continued over the fold without assisting in its formation. The aperture is occasionally oval. Sometimes, the circular fold is replaced by two crescentic folds, placed, one above, and the other below, the pyloric orifice ; and, more rarely, there is only one. Structure. The stomach consists of four coats ; a serous, a muscular, a cellular, and a mucous coat, together with vessels and nerves. The serous coat is derived from the peritoneum, and covers the entire surface of the organ, excepting along the greater and lesser curvature, at the points of attachment of the greater and lesser omenta ; here the two layers of peritoneum leave a small triangular space, along which the nutrient vessels and nerves pass. The muscular coat is situated immediately beneath the serous covering. It con sists of three sets of fibres, the longitudinal, circular, and oblique (fig. 334). Fig. 334. — The Muscular Coat of the Stomach. The longitudinal fibres are most superficial ; they are continuous with the longi- tudinal fibres of the oesophagus, radiating in a stellate manner from the cardiac orifice. They are most distinct along the curvatures, especially the lesser ; but are very thinly distributed over the surfaces. At the pyloric end, they are more thickly distributed, and continuous with the longitudinal fibres of the small intestine. G66 ORGANS OF DIGESTION The circular fibres form a "uniform layer over the whole extent of the stomach, "beneath the longitudinal fibres. At the pylorus, they are most abundant, and are aggregated into a circular ring, which projects into the cavity, and forms, with the fold of mucous membrane covering its surface, the pyloric valve. The oblique fibres are limited chiefly to the cardiac end of the stomach, where they are disposed as a thick uniform layer covering both surfaces, some passing obliquely from left to right, others from right to left, round the cardiac orifice. The cellular coat consists of a loose, filamentous, areolar tissue, connecting the mucous and muscular layers. It is sometimes called the submucous coat. It supports the bloodvessels previous to their distribution to the mucous membrane ; hence it is sometimes called the vascular coat. The mucous membrane of the stomach is thick; its surface smooth, soft, and velvety. During infancy, and immediately after death, it is of a pinkish tinge ; but in adult life, and in old age, it becomes of a pale straw or ash-gray color. It is thin at the cardiac extremity, but thicker towards the pylorus. During the contracted state of the organ, it is thrown into numerous plaits or rugoe, which, for the most part, have a longitudinal direction, and are most marked towards the lesser end of the stomach, and along the greater curvature. These folds are entirely obliterated when the organ becomes distended. Structure of the mucous membrane (fig. 835). When examined with a lens, the inner surface of the mucous membrane presents a peculiar honey-comb appearance, Fig. 335. — Minute Anatomy of Mucous Membrane of Stomach. Mouths of Tuliuli Orifice of Tuts EpitheJi'cUjoarticlrS from being covered with small shallow depressions or alveoli, of a polygonal or hexagonal form, which vary from l-100th to l-350th of an inch in diameter, and are separated by slightly elevated ridges. In the bottom of the alveoli are seen the orifices of minute tubes, the gastric follicles, which are situated perpendicu- larly side by side, in the entire substance of the mucous membrane. They are short, and simply tubular in character towards the cardiac end ; but at the pyloric end, they are longer, more thickly set, convoluted, and terminate in dilated saccular extremities, or subdivide into from two to six tubular branches. The gastric follicles are composed of a homogeneous basement membrane, lined upon its free surface by a layer of cells, which differ in their character in different parts of the stomach. Towards the pylorus, these tubes are lined throughout with columnar epithelium ; they are termed the mucous glands, and are supposed to secrete the gastric mucus. In other parts of the organ, the deep part of each tube is filled with nuclei, and a mass of granules ; above these is a mass of nucleated cells, the upper fourth of the tube being lined by columnar epithelium. These are called the peptic glands, the supposed agents in the secretion of the gastric juice. Simple follicles are found in greater or less number over the entire surface of the mucous membrane ; they are most numerous near the pyloric end of the stomach, and especially distinct in early life. The epithelium lining the mucous membrane of the stomach and its alveoli is of the columnar variety. SMALL INTESTINE. 6G7 Vessels and Nerves. The arteries supplying the stomach are, the gastric, pyloric and right gastro-epiploic branches of the hepatic, the left gastro-epiploic and vasa brevia from the splenic. They supply the muscular coat, ramify in the submucous coat, and are finally distributed to the mucous membrane. The veins accompany the arteries, and terminate in the splenic and portal veins. The lymphatics are numerous ; they consist of a superficial and deep set, which pass through the lym- phatic glands found along the two curvatures of the organ. The nerves are, the terminal branches of the right and left pneumogastric, the former being distributed upon the back, and the latter upon the front part of the organ. Branches from the sympathetic also supply the organ. The Small Intestine. The Small Intestine is that part of the alimentary canal in which the chyme is mixed with the bile, the pancreatic juice, and the secretions of the various glands imbedded in the mucous membrane of the intestines, and where the separation of the nutritive principles of the food, the chyle, is effected: this constitutes chyli- fication. The small intestine is a convoluted tube, about twenty feet in length, which gradually diminishes in size from its commencement to its termination. It is contained in the central and lower parts of the abdominal and pelvic cavities, surrounded above and at the sides by the large intestine ; in relation, in front, with the great omentum and abdominal parietes ; and connected to the spine by a fold of peritoneum, the mesentery. The small intestine is divisible into three portions ; the duodenum, jejunum, and ileum. The duodenum has received its name from being about equal in length to the breadth of twelve fingers (eight or ten inches.) It is the shortest, the widest, and the most fixed part of the small intestine; it has no mesentery, and is only partially covered by the peritoneum. Its course presents a remarkable curve, somewhat like a horseshoe in form ; the convexity being directed towards the right, and the concavity to the left, embracing the head of the pancreas. Commencing at the pylorus, it ascends obliquely upwards and backwards to the under surface of the liver ; it then descends in front of the right kidney, and passes nearly trans- versely across the front of the spine, terminating in the jejunum on the left side of the second lumbar vertebra. Hence the duodenum has been divided into three portions : ascending, descending, and transverse. The first or ascending portion, about two inches in length, is free, movable, and nearly completely invested by the peritoneum. It is in relation, above and in front, with the liver and neck of the gall-bladder ; behind, with the right border of the lesser omentum, the hepatic artery and duct, and vena porta). This por- tion of the intestine is usually found stained with bile, especially on its anterior surface. The second or descending portion, about three inches in length, is firmly fixed by the peritoneum and pancreas. It passes from the neck of the gall-bladder vertically downwards, in front of the right kidney, as far as the third lumbar vertebra. It is covered by peritoneum only on its anterior surface. It is in relation, in front, with the right arch of the colon and mesocolon ; behind, with the front of the right kidney ; at its inner side is the head of the pancreas, and the common choledoch duct. The common bile and pancreatic ducts perforate the inner side of this portion of the intestine obliquely, a little below its middle. The third or transverse portion, the longest and narrowest part of the duodenum, passes across the front of the spine, ascending from the third to the second lumbar vertebra, and terminating in the jejunum on the left side of this bone. In front, it is covered by the descending layer of the transverse mesocolon, and crossed by the superior mesenteric vessels ; behind, it rests upon the aorta, the vena cava, and the crura of the Diaphragm ; above it is the lower border of the pancreas, the superior mesenteric vessels passing forwards between the two. 668 ORGANS OF DIGESTION. Vessels and Nerves. The arteries supplying the duodenum are the pyloric and pancreatico-duodenal branches of the hepatic, and the inferior pancreatico- duodenal branch of the superior mesenteric. The veins terminate in the gastro- duodenal and superior mesenteric. Its nerves are derived from the solar plexus. The jejunum (jejunus, empty), so called from being usually found empty after death, includes the upper two-fifths of the rest of the small intestine. It com- mences at the duodenum on the left side of the second lumbar vertebra, and terminates in the ileum; its convolutions being chiefly confined to the umbilical and left iliac regions. The jejunum is wider, its coats thicker, more vascular, and of a deeper color than those of the ileum ; but there is no characteristic mark to distinguish the termination of the one, or the commencement of the other. The ileum (ei-ktiv, to twist), so called from its numerous coils or convolutions, includes the remaining three-fifths of the small intestine. It occupies chiefly the umbilical, hypogastric, right iliac, and occasionally the pelvic, regions, and ter- minates in the right iliac fossa by opening into the inner side of the commence- ment of the large intestine. The ileum is narrower, its coats thinner and less vascular than those of the jejunum; a given length of it weighing less than the same length of jejunum. Structure of the small intestine. The wall of the small intestine is composed of four coats ; serous, muscular, cellular, and mucous. The serous coat is derived from the peritoneum. The first or ascending por- tion of the duodenum is almost completely surrounded by this membrane ; the second or descending portion is covered by it only in front ; and the third or transverse portion lies behind the descending layer of the transverse mesocolon, by which it is covered in front. The remaining portion of the small intestine is surrounded by the peritoneum, excepting along its attached or mesenteric border ; here a space is left for the vessels and nerves to pass to the gut. The muscular coat consists of two layers of fibres, an external or longitudinal, and an internal or circular layer. The longitudinal fibres are thinly scattered over the surface of the intestine, and are most distinct along its free border. The circular fibres form a thick, uniform layer ; they surround the cylinder of the intestine in the greater part of its circumference, but do not form complete rings. The muscular coat is thicker at the upper, than at the lower part of the small intestine. The cellular or submucous coat connects together the mucous and muscular layers. It consists of a loose, filamentous, areolar tissue, which forms a nidus for the subdivision of the nutrient vessels, previous to their distribution to the mucous surface. The mucous membrane is thick and highly vascular at the upper part of the small intestine, but somewhat paler and thinner below. It presents for examina- tion the following constituents : — -rp vi r Simple follicles. Epithelium. ,f> s , , i -v/% i • , ( Duodenal glands. Valvuke conniventes. r>, -, ) v , -, & •, Y']V (jrlands. < Solitary glands. ( Agminate or Peyer's glands. The epithelium., covering the mucous membrane of the small intestine, is of the columnar variety. The valvulse conniventes (valves of Kerkring) are reduplications or foldings of the mucous membrane and submucous tissue, containing no muscular fibres. They extend transversely across the cylinder of the intestine for about three- fourths or five-sixths of its circumference. The larger folds are about two inches in length, and two-thirds of an inch in depth at their broadest part ; but the greater number are of smaller size. The larger and smaller folds alternate with each other. They are not found at the commencement of the duodenum, but begin SMALL INTESTINE. 669 Fig. 336.— Two Villi magnified. Artery to appear about one or two inches beyond the pylorus. In the lower part of the descending portion, below the point where the common choledoch and pancreatic ducts enter the intestine, they are very large and closely approximated. In the transverse portion of the duodenum and upper half pf the jejunum, they are large and numerous ; and from this point, as far as the middle of the ileum, they diminish considerably in size. In the lower part of the ileum, they almost entirely disappear ; hence the comparative thinness of this portion of the intes- tine, as compared with the duodenum and jejunum. The valvulae conniventes retard the passage of the food along the intestines, and afford a more extensive surface for absorption. The villi are minute, highly vascular processes, projecting from the mucous mem- brane of the small intestine throughout its whole extent, and giving to its surface a beautiful velvety appearance. In shape, some are triangular and laminated, others conical or cylindrical, with clubbed or fili- form extremities. They are largest and most numerous in the duodenum and jeju- num, and become fewer and smaller in the ileum. Krause estimates their number in the upper part of the small intestine, at from fifty to ninety in a square line ; and in the lower part, from forty to seventy ; the total number for the whole length of the intestine being four millions. In structure each villus consists of a network of capillary and lacteal vessels, with nuclear corpuscles and fat globules in their interstices, inclosed in a thin prolongation of basement membrane covered by a single layer of columnar epithelium, the particles of which are arranged perpendicularly to the surface. A layer of organic muscular fibre has been described forming a thin hollow cone round the central lacteal. It is possible that this assists in the propulsion of the chyle along the vessel. The mode of origin of the lacteals within the villi is un- known. The simple follicles or crypts of Lieberkuhn are found in considerable numbers over every part of the mucous membrane of the small intestine. They consist of minute tubular depressions of the mucous membrane, arranged perpendicularly to the surface, upon which they open by small circular apertures. They may be seen with the aid of a lens, their orifices appearing as minute dots, scattered between the villi. Their walls are thin, consisting of a layer of basement membrane, lined by cylindrical epithelium, and covered on their exterior by capillary vessels. Their contents vary, even in health, and the purpose served by their secretion is still very doubtful. The duodenal or Brunner's glands are limited to the duodenum and com- mencement of the jejunum. They are small, flattened, granular bodies, imbedded in the submucous areolar tissue, and open upon the surface of the mucous mem. brane by minute excretory ducts. They are most numerous and largest near the pylorus. They may be compared to the elementary lobules of a salivary gland, spread out over a broad surface, instead of being collected in a mass. In structure they resemble the pancreas. The solitary glands (glandulse solitarise) are found scattered throughout the mucous membrane of the small intestine, but are most numerous in the lower part of the ileum. They are small, round, whitish bodies, from half a line to a line in diameter, consisting of a closed saccular cavity, having no excretory duct, and containing an opaque white secretion. Their free surface is covered with villi, and each gland is surrounded by openings like those of the follicles of Lieberkuhn. Their use is not known. CTO ORGANS OF DIGESTION. Fig. 337— Patch of Peyer's Glands. From the lower part of the Ileum. i Peyer's glands may be regarded as aggregations of solitary glands, forming "ircular or oval patches from twenty to thirty in number, and varying in length from half an inch to four inches. They are largest and most numerous in the ileum. In the lower part of the jejunum they are small, of a circular form, and few in number ; they are occasionally seen in the duodenum. They are placed lengthwise in the intestine, covering the portion of the tube most distant from the attachment of the mesentery. Each patch is formed of a group of small, round, whitish vesicles, covered with mucous membrane. Each vesicle consists of a moderately thick ex- ternal capsule, having no excretory duct, and containing an opaque white secretion. Each is surrounded by a zone or wreath of simple follicles, and the interspaces between them are covered with villi. These vesicles are usually closed ; but it has been supposed that they open at intervals to discharge the secretion contained within them. The mu- cous and submucous coats of the intestine are intimately adherent, and highly vascular, opposite the Peyerian glands. Their use is not known [but they are now generally sup- posed to belong to the lymphatic system]. They are largest and most developed during the digestive process. The Large Intestine. Fig. 338.— A portion of the above magnified. The Large Intestine extends from the termination of the ileum to the anus. It is about five feet in length ; being one-fifth of the whole extent of the intestinal canal. It is largest at its commencement at the ceecum, and gradually diminishes as far as the rectum, where there is a dilatation of considerable size, just above the anus. It differs from the small intestine in its greater size, its more fixed position, and its saccu- lated form. The large intestine, in its course, describes an arch, which surrounds the convolutions of the small intestine. It commences in the right iliac fossa, in a dilatation of considerable size, the caecum. It ascends through the right lumbar and hypochondriac regions, to the under surface of the liver ; passes transversely across the abdomen, on the confines of the epigastric and umbilical regions, to the left hypochondriac region ; descends through the left lumbar region to the left iliac fossa, where it becomes convoluted, and forms the sigmoid flexure ; finally, it enters the pelvis, and descends along its posterior wall to the anus. The large intestine is divided into the caecum, colon, and rectum. The Caecum (csecus, blind) is the large blind pouch or cul-de-sac extending downwards from the commencement of the large intestine. It is the most dilated part of this tube, measuring about two and a half inches, both in its vertical and transverse diameters. It is situated in the right iliac fossa, immediately behind the anterior abdominal wall, being retained in its place by the peritoneum, which passes over its anterior surface and sides ; its posterior surface being connected by '&rXW-; M*m;m jf*:/!.-."^- .CviO •LARGE INTESTINE. 6U loose areolar tissue with the iliac fascia. Occasionally, it is almost completely surrounded by peritoneum, which forms a distinct fold, the mesocaecum, connecting its back part with the iliac fossa. This fold allows the caecum considerable freedom of movement. Attached to its lower and back part, is the appendix vermiformis, a long, narrow, worm-shaped tube, the rudiment of the lengthened caecum found in all the mammalia, except the ourang-outang and wombat. The appendix varies from three to six inches in length, its average diameter being about equal to that of a goose-quill. It is usually directed upwards and inwards behind the caecum, coiled upon itself, and terminates in a blunt point, being retained Fig. 339. — The Cfficnm and Colon laid open to show the ileo-caecal Valve. in its position by a fold of peritoneum, which sometimes forms a mesentery for it. Its canal is small, and communicates with the caecum by an orifice which is some- times guarded with an incomplete valve. Its coats are thick, and its mucous lining furnished with a large number of solitary glands. Ileo-csecal Valve. The lower end of the ileum terminates at the inner and back part of the large intestine, opposite the junction of the caecum with the colon. At this point, the mucous membrane forms two valvular folds, which pro- ject into the large intestine, and are separated from each other by a narrow elongate aperture. This is the ileo-caecal valve (valvula Bauhini). Each fold is semilunar in form. The upper one, nearly horizontal in direction, is attached by its convex border to the point of junction of the ileum with the colon; the lower segment being connected at the point of junction of the ileum with the caecum. Their concave margins are free, project into the intestine, separated from one an- other by a narrow slit-like aperture, transversely directed. At each end of this aperture, the two segments of the valve coalesce, and are continued, as a narrow membranous ridge, around the canal of the intestine for a short distance, forming the fraena or retinacula of the valve. The left end of this aperture is rounded ; the right end is narrow and pointed. Each segment of the valve is formed of a reduplication of the mucous mem- brane, and of the circular muscular fibres of the intestine, the longitudinal fibres and peritoneum being continued uninterruptedly across from one intestine to the 6T2 ORGANS OF DIGESTION. other. When these are divided or removed, the ileum may be drawn outwards, and all traces of the valve will be lost, the ileum appearing to open into the large intestine by a funnel-shaped orifice of large size. The surface of each segment of the valve directed towards the ileum is covered with villi, and presents the characteristic structure of the mucous membrane of the small intestine ; whilst that turned towards the large intestine is destitute of villi, and marked with the orifices of the numerous tubuli peculiar to this mem- brane. These differences in structure continue as far as the free margin of the valve. When the caecum is distended, the margins of the opening are approximated, so as to prevent any reflux into the ileum. The colon is divided into four parts, the ascending, transverse, descending, and the sigmoid flexure. The ascending colon is smaller than the caecum. It passes upwards from the right iliac fossa, to the under surface of the liver, on the right of the gall-bladder, where it bends abruptly inwards to the left, forming the hepatic flexure. It is retained in position with the posterior wall of the abdomen by the peritoneum, which covers its anterior surface and sides, its posterior surface being connected by loose areolar tissue with the Quadratus lumborum and right kidney ; sometimes the peritoneum almost completely invests it, and forms a distinct but narrow meso- colon. It is in relation, in front, with the convolutions of the ileum and the abdominal parietes; behind, it lies on the Quadratus lumborum muscle, and right kidney. The transverse colon, the longest part of the large intestine, passes transversely from right to left across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondriac region, where it curves downwards beneath the lower end of the spleen, forming its splenic flexure. In its course it describes an arch, the concavity of which is directed backwards towards the ver- tebral column ; hence the name, transverse arch of the colon. This is the most movable part of the colon, being almost completely invested by peritoneum and connected to the spine behind by a large and wide duplicature of this membrane, the transverse mesocolon. It is in relation, by its upper surface, with the liver and gall-bladder, the great curvature of the stomach, and the lower end of the spleen ; by its under surface, with the small intestines; by its anterior surface, with the anterior layers of the great omentum and the abdominal parietes ; by its posterior surface, with the transverse mesocolon. The descending colon passes almost vertically downwards through the left hypo- chondriac and lumbar regions to the upper part of the left iliac fossa, where it terminates in the sigmoid flexure. It is retained in position by the peritoneum, which covers its anterior surface and sides, its posterior surface being connected by areolar tissue with the left crus of the Diaphragm, the left kidney, and the Quad- ratus lumborum. It is smaller in calibre, and more deeply placed than the ascend- ing colon. The sigmoid flexure is the narrowest part of the colon ; it is situated in the left iliac fossa, commencing at the termination of the descending colon, at the margin of the crest of the ilium, and ending in the rectum, opposite the left sacro-iliac symphysis. It curves in the first place upwards, and then descends vertically, and to one or the other side like the letter/, hence its name; and is retained in its place by a loose fold of peritoneum, the sigmoid mesocolon. It is in relation, in front, with the small intestines and abdominal parietes; behind, with the iliac fossa. The Rectum is the terminal part of the large intestine, and extends from the sigmoid flexure to the anus ; it varies in length from six to eight inches, and has received its name from being somewhat less flexuous than any other part of the intestinal canal. It commences opposite the left sacro-iliac symphysis, passes obliquely downwards from left to right to the middle of the sacrum, forming a gentle curve to the right side. Regaining the middle line, it descends in front of LARGE INTESTINE. 673 tlie lower part of the sacrum and coccyx ; and, near the extremity of the latter bone, inclines backwards to terminate at the anus, being curved both in the lateral and anteroposterior directions. The rectum is, therefore, not straight, the upper part being directed obliquely from the left side to the median line, the middle portion being curved in the direction of the hollow of the sacrum and coccyx, the lower portion presenting a short curve in the opposite direction. The rectum is cylindrical, not sacculated like the rest of the large intestine ; it is narrower at its upper part than the sigmoid flexure, gradually increases in size as it descends, and immediately above the anus presents a considerable dilatation, capable of acquiring an enormous size. The rectum is divided into three portions, upper, middle, and lower. The upper portion, which includes about half the length of the tube, extends obliquely from the left sacro-iliac symphysis to the centre of the third piece of the sacrum. It is almost completely surrounded by peritoneum, and connected to the sacrum behind by a. duplicature of this membrane, the mesorectum. It is in relation behind with }t]ie Pyriformis muscle, the sacral plexus of nerves, and the branches of the internal iliac artery of the left side, which separate it from the sacrum and sacro-iliac symphysis ; in front, it is separated, in the male, from the posterior surface of the bladder, in the female, from the posterior surface of the uterus and its appendages, by some convolutions of the small intestine. The middle portion of the rectum is about three inches in length, and extends as far as the tip of the coccyx. It is closely connected to the concavity of the sacrum, and covered by peritoneum only on the upper part of its anterior surface. It is in relation, in front, with the triangular portion of the base of the bladder, the vesiculae seminales, and vasa deferentia ; more anteriorly, with the under sur- face of the prostate. In the female, it is adherent to the posterior wall of the vagina. The lower portion is about an inch in length ; it curves backwards at the fore part of the prostate gland, and terminates at the anus. This portion of the intestine receives no peritoneal covering. It is invested by the Internal sphincter, supported by the Levatores ani muscles, and surrounded at its termination by the External sphincter. In the male, it is separated from the membranous portion and bulb of the urethra by a triangular space ; and, in the female, a similar space intervener between it and the vagina. This space forms by its base the perineum. Structure of the large intestine. The large intestine has four coats ; serous, mus cular, cellular, and mucous. The serous coat is derived from the peritoneum, and invests the different portions of the large intestine to a variable extent. The caecum is covered only on its anterior surface and sides ; more rarely, it is almost completely invested, being held in its position by a duplicature, the mesocaecum. The ascending and descending colon are usually covered only in front. The transverse colon is almost completely invested, excepting at the points corresponding to the attach- ment of the great omentum and transverse mesocolon. The sigmoid flexure is nearly completely surrounded, excepting at the point corresponding to the attach- ment of the iliac mesocolon. The upper part of the rectum is almost completely invested by the peritoneum ; the middle portion is covered only on its anterior surface ; and the lower portion is entirely devoid of any serous covering. In the course of the colon, and upper part of the rectum, the peritoneal coat is thrown into a number of small pouches filled with fat, called appendices epiploicse. They are chiefly appended to the transverse colon. The muscular coat consists of an external longitudinal and an internal circular layer of muscular fibres. The longitudinal fibres are found as a uniform layer over the whole surface of the large intestine. In the caecum and colon, they are especially collected into three flat longitudinal bands, each being about half an inch in width. These bands commence at the attachment of the appendix vermiformis to the caecum : one, the posterior, is placed along the attached border of the intestine ; the anterior band, 43 674 ORGANS OF DIGESTION. the largest, becomes inferior along the arch of the colon, where it corresponds to the attachment of the great omentum, but is in front in the ascending and descending colon and sigmoid flexure ; the third or lateral band is found on the inner side of the ascending and descending colon, and on the under border of the transverse colon. These bands are nearly one-half shorter than the other parts of the intestine, and serve to produce those sacculi characteristic of the csecum and colon ; accordingly, when they are dissected offj the tube can be lengthened, and its sacculated character becomes lost. In the sigmoid flexure, the longitudinal fibres become more scattered, and upon its lower part, as well as round the rectum, they spread out, and form a thick uniform layer. The circular fibres form a thin layer over the caecum and colon, being especially accumulated in the intervals between the sacculi ; in the rectum, they form a thick layer, especially at its lower end, where they become numerous, and form the Internal sphincter. The cellular coat connects closely together the muscular and mucous layers. The mucous membrane, in the caecum and colon, is pale, and of a grayish or pale yellow color. It is quite smooth, destitute of villi, and raised into numerous crescentic folds, which correspond to the intervals between the sacculi. In the rectum, it is thicker, of a darker color, more vascular, and connected loosely to the muscular coat, as in the oesophagus. When the lower part of the rectum is contracted, its mucous membrane is thrown into a number of folds, some of which, near the anus, are longitudinal in direction, and are effaced by the distension of the gut. Besides these, there are three or four permanent folds, of a semilunar shape, described by Mr. Houston. 1 They are usually three in number ; sometimes a fourth is found, and, occasionally, only two are present. One is situated near the commencement of the rectum, on the right side ; another extends inwards from the left side of the tube opposite the middle of the sacrum ; the largest and most constant one projects backwards from the fore part of the rectum, opposite the base of the bladder. When a fourth is present, it is situated about an inch above the anus, on the back of the rectum. These folds are about half an inch in width, and contain some of the circular fibres of the gut. In the empty state of the intestine they overlap each other, as Mr. Houston remarks, so effectually as to require considerable manoeuvring to conduct a bougie or the finger along the canal of the intestine. Their use seems to be, " to support the weight of fecal matter, and prevent its urging towards the anus, where its presence always excites a sensation demanding its discharge." The mucous membrane of the large intestine presents for examination, epithelium, simple follicles, and solitary glands. Fig. 340. — Minute Structure of Large Intestine. Ti.Su/i Solitary Fo/hW. Section of Mtootur Mtoibrun* Tuhuli TriUmj Su-imucotu Cell. tits. Free Surf a The epithelium is of the columnar kind. . The simple follicles are minute tubular prolongations of the mucous membrane, arranged perpendicularly, side by side, over its entire surface ; they are longer, Dub. Hosp. Repoi-ts, vol. v. p. 163. J THE LIVER. 6T5 more numerous, and placed in much closer apposition than those of the small intestine ; and they open by minute rounded orifices upon the surface, giving it a cribriform appearance. The solitary glands in the large intestine are most abundant in the caecum and appendix vermiformis, being irregularly scattered over the rest of the intestine ; they are small, prominent, flask-shaped bodies, of a whitish color, perforated upon the central part of their free surface by a minute orifice, which, in the majority, is permanent. The Liver. The Liver is a glandular organ of large size, intended mainly for the secretion of the bile, but effecting also important changes in certain constituents of the blood in their passage through the gland. It is situated in the right hypochondriac region, and extends across the epigastrium into the left hypochondrium. It is the largest gland in the body, weighing from three to four pounds (from fifty to sixty ounces avoirdupois). It measures, in its transverse diameter, from ten to twelve inches; from six to seven in its antero-posterior ; and is about three inches thick at the back part of the right lobe, which is the thickest part. Its upper surface is convex, directed upwards and forwards, smooth, covered by peritoneum, and is in relation with the under surface of the Diaphragm ; and below, to a small extent, with the abdominal parietes. This surface is divided into two unequal lobes, the right and left, by a fold of peritoneum, the suspensory or broad ligament. Its under surface is concave, directed downwards and backwards, and in rela* tion with the stomach and duodenum, the hepatic flexure of the colon, and the right kidney and supra-renal capsule. This surface is divided by a longitudinal fissure, into a right and left lobe. The posterior border is rounded and broad, and connected to the Diaphragm by the coronary ligament; it is in relation with the aorta, the vena cava, and the crura of the Diaphragm. The anterior border is thin and sharp, and marked, opposite the attachment of the broad ligament, by a deep notch. In adult males, this border usually corre- sponds with the margin of.'the ribs ; but in women and children, it projects usually below this point. The right extremity of the liver is thick and rounded ; whilst the left is thin and flattened. Changes of Position. The student should make himself acquainted with the different circum- stances under which the liver changes its position, as they are of importance as a guide in deter- mining the existence of enlargement, or other disease of that organ. Its position varies according to the posture of the body; in the upright and sitting postures, its lower border may be felt beneath the edges of the ribs ; in the recumbent posture, it usually recedes beneath the ribs. Its position varies with the ascent or descent of the Diaphragm. In a deep inspiration, the liver descends below the ribs ; in expiration, it is raised to its ordinary level. Again, in emphy- sema, where the lungs are distended, and the Diaphragm descends very low, the liver is pushed down ; but in some other diseases, as phthisis, where the Diaphragm is much arched, the liver rises very high up. Pressure from without, as in tight lacing, by compressing the lower part of the chest, dis- places the liver considerably, its anterior edge often extending as low as the crest of the ilium ; and its convex surface is often, at the same time, deeply indented from pressure of the ribs. Its position varies greatly, according to the greater or less distension of the stomach and intestines. When the intestines are empty, the liver descends in the abdomen ; but when they are distended, it is pushed upwards. Its relations with surrounding organs may also be changed by the growth of tumors, or from collections of fluid in the thoracic or abdominal cavities. Ligamexts. The ligaments of the liver (fig. 341) are five in number : four are formed of folds of peritoneum ; the fifth, the ligamentum teres, is a round, fibrous cord, resulting from the obliteration of the umbilical vein. The ligaments are the longitudinal, two lateral, coronary, and round. 676 ORGANS OF DIGESTION. The longitudinal ligament (broad, falciform, or suspensory ligament) is a broad and thin antcro-posterior peritoneal fold, falciform in shape, its base being directed forwards, its apex backwards. It is attached by one margin to the under surface of the Diaphragm, and the posterior surface of the sheath of the right Rectus muscle as low down as the umbilicus ; by its hepatic margin, it extends from the notch on the anterior margin of the liver, as far back as its posterior border. It consists of two layers of peritoneum closely united together. Its anterior free edge contains between its layers the round ligament. The lateral ligaments, two in number, right and left, are triangular in shape. They are formed of two layers of peritoneum united, and extend from the sides of the Diaphragm to the adjacent margins of the posterior border of the liver. The left is the longer of the two, and lies in front of the oesophageal opening in the Diaphragm ; the right lies in front of the inferior vena cava. The coronary ligament connects the posterior border of the liver to the Diaphragm. It is formed by the reflection of the peritoneum from the Diaphragm on to the upper and lower margins of the posterior border of the organ. The coronary Fig. 341. — The Liver. Upper Surface. ligament consists of two layers, which are continuous on each side with the lateral ligaments, and, in front, with the longitudinal ligament. Between the layers, a large oval interspace is left uncovered by peritoneum, and connected to the Diaphragm by firm areolar tissue. This space is subdivided, near its left extremity, into two parts by a deep notch (sometimes a canal), which lodges the inferior vena cava, and into which open the hepatic veins. The round ligament is a fibrous cord, resulting from the obliteration of the umbilical vein. It ascends from the umbilicus in the anterior free margin of the longitudinal ligament, to the notch in the anterior border of the liver, from which it may be traced along the longitudinal fissure on the under surface of the liver, as far back as the inferior vena cava. Fissures. Five fissures are seen upon the under surface of the liver, which serve to divide it into five lobes. They are the longitudinal fissure, the fissure of the ductus venosus, the transverse fissure, the fissure for the gall-bladder, and the fissure for the vena cava. The longitudinal fissure is a deep groove, which extends from the notch on the anterior margin of the liver, to the posterior border of the organ. It separates the right and left lobes ; the transverse fissure joins it, at right angles, about THE LIVER. 677 one-third from its posterior extremity, and divides it into two parts. The anterior half is called the umbilical fissure; it is deeper than the posterior part, and lodges the umbilical vein in the foetus, or its fibrous cord (the round ligament) in the adult. This fissure is often partially bridged over by a prolongation of the hepatic substance, the p> ons hepatis. The fissure of the ductus venosus is the back part of the longitudinal fissure ; it is shorter and shallower than the anterior portion. It lodges in the foetus the ductus venosus, and in the adult a slender fibrous cord, the obliterated remains of that vessel. Via. 342.— The Liver. Under Surface. The transverse or portal fissure is a short but deep fissure, about two inches in length, extending transversely across the under surface of the right lobe, nearer to its posterior than its anterior border. It joins, nearly at right angles, with the longitudinal fissure. By the older anatomists, this fissure was considered the gateway (porta) of the liver ; hence the large vein which enters at this point was called the portal vein. Besides this vein, the fissure transmits the hepatic artery and nerves, and the hepatic duct and lymphatics. At their entrance into the fissure, the hepatic duct lies in front to the right, the portal vein behind, and the hepatic artery between the other two to the left. The fissure for the gall-bladder (fossa cystidis fellese) is a shallow, oblong fossa, placed on the under surface of the right lobe, parallel with the longitudinal fissure. It extends from the anterior free margin of the liver, which is occa- sionally notched for its reception, to near the right extremity of the transverse fissure. The fissure for the vena cava is a short deep fissure, occasionally a complete canal, which extends obliquely upwards from a little behind the right extremity of the transverse fissure, to the posterior border of the organ, where it joins the fissure for the ductus venosus. On slitting open the inferior vena cava which is contained in it, a deep fossa is seen, at the bottom of which the hepatic veins communicate with this vessel. This fissure is separated from the transverse fissure by the lobus caudatus ; and from the longitudinal fissure by the lobus Spi- gelii. Lobes. The lobes of the liver, like the ligaments and fissures, are also five in number ; the right lobe, the left lobe, the lobus quadratus, the lobus Spigelii, and the lobus caudatus. The right lobe is much larger than the left ; the proportion between them being 678 ORGANS OF DIGESTION. .is six to one. It occupies the right hypochondrium, and is separated from the left lobe, on its upper surface, by the longitudinal ligament; on its under surface, by the longitudinal fissure ; and in front, by a deep notch. It is of a quadrilateral form, its under surface being marked by three fissures, the transverse fissure, the fissure for the gall-bladder, and the fissure for the inferior vena cava ; and by two shallow impressions, one in front (impressio colica), for the hepatic flexure of the colon, and one behind {impressio renalis), for the right kidney and supra-renal capsule. The left lobe is smaller and more flattened than the right. It is situated in the epigastric and left hypochondriac regions, sometimes extending as far as the upper border of the spleen. Its upper surface is convex ; its under concave surface rests upon the front of the stomach ; and its posterior border is in relation with the car- diac orifice of the stomach. The lobus quadratus or square lobe is situated on the under surface of the right lobe, bounded in front by the free margin of the liver ; behind, by the transverse fissure ; on the right, by the fissure for the gall-bladder ; and, on the left, by the umbilical fissure. The lobus Sjrigelii projects from the back part of the under surface of the right lobe. It is bounded, in front, by the transverse fissure ; on the right, by the fissure for the vena cava ; and on the left, by the fissure for the ductus venosus. The lobus caudatus or tailed lobe is a small elevation of the hepatic substance, extending obliquely outwards, from the base of the lobus Spigelii, to the under surface of the right lobe. It separates the right extremity of the transverse fissure from the commencement of the fissure for the inferior vena cava. Vessels. The vessels connected with the liver are also five in number ; they are the hepatic artery, the portal vein, the hepatic vein, the hepatic duct, and lym- phatics. The hepatic artery, portal vein, and hepatic duct, accompanied by numerous lymphatic vessels and nerves, ascend to the transverse fissure, between the layers of the gastro-hepatic omentum ; the hepatic duct lying to the right, the hepatic artery to the left, and the portal vein behind the other two. They are enveloped in a loose areolar tissue, the capsule of Glisson, which accompanies the vessels in their course through the portal canals, which are hollowed out of the interior of the organ. The hepatic veins convey the blood from the liver. They commence at the cir- cumference of the organ, and proceed towards the deep fossa in its posterior border, where they terminate by two large, and several smaller branches, in the inferior vena cava. The hepatic veins have no cellular investment, consequently their parietes are adherent to the walls of the canals through which they run ; so that, on a section of the organ, these veins remain widely open and solitary, and may be easily dis- tinguished from the branches of the portal vein, which are more or less collapsed, and always accompanied by an artery and duct. The lymphatics are large and numerous, consisting of a deep and superficial set. They have been already described. Nerves. The nerves of the liver are derived from the hepatic plexus of the sympathetic, from the pneumogastric nerves, especially the left, and from the right phrenic. Structure. The substance of the liver is composed of lobules, held together by an extremely fine areolar tissue, of the ramifications of the portal vein, hepatic duct, hepatic artery^ hepatic veins, lymphatics, and nerves; the whole being invested by a fibrous and a serous coat. The serous coat is derived from the peritoneum, and invests the entire surface of the organ, excepting at the point corresponding to the attachment of its various ligaments, and at the bottom of the different fissures, where it is deficient. It is intimately adherent to the fibrous coat. STRUCTURE OF THE LIVER. 679 The fibrous coat lies beneath the serous investment, and covers the entire surface of the organ. It is difficult of demonstration, excepting where the serous coat is deficient. At the transverse fissure, it is continuous with the capsule of Glisson ; and, on the surface of the organ, with the areolar tissue separating the lobules. The lobules form the chief mass of the hepatic substance ; they may be seen either on the surface of the organ, or by making a section through the gland. They are small granular bodies, about the size of a millet-seed, measuring from one-twentieth to one-tenth of an inch in diameter. When divided longitudinally, they have a foliated margin, and, if trans- versely, a polygonal outline. The bases of the lobules are clustered round the smallest branches (sublobular) of the hepatic veins, to which each is connected by means of a small branch, which issues from the centre of the lobule (intra- lobular). The remaining part of the sur- face of each lob ale is imperfectly isolated from the surrounding lobules, by a thin stratum of areolar tissue, and by the smaller vessels and ducts. If one of the hepatic veins be laid open, the bases of the lobules may be seen through the thin wall of the vein, on which they rest, arranged in the form of a tessellated pavement, the centre of each polygonal space presenting a mi- nute aperture, the mouth of a sublobular vein. Each lobule is composed of a mass of cells ; of a plexus of biliary ducts ; of a venous plexus, formed by branches of the portal vein ; of a branch of an he- patic vein (intralobular); of minute arteries ; and probably, of nerves and lymphatics. The hepatic cells form the chief mass of the substance of a lobule, and lie in the interspaces of the capillary plexus, being probably contained in a tubular network, which forms the origin of the biliary ducts. The smallest branches of the vena portaa pass between the lobules, around which they form a plexus, the interlobular. Branches from this plexus enter the lobules, and form a network in their circumference. The radicles of the portal vein communicate with those of the hepatic vein, which occupy the centre of the lobule ; and the latter converge to form the intralobular vein, which issues from the base of the lobule, and joins the hepatic vein. The portal vein carries the blood to the liver, from which the bile is secreted; the hepatic vein carries H. Longitudinal section of an hepatic vein ; a, por- tion of the canal, from which the vein has been removed ; b, orifices of nltimate twigs of the vein (sub-lobular), situated in the centre of the lobules. After Kieruan. Longitudinal section of a small portal vein and canal, after Kiernan. a. Portions of the caual from which the vein has been removed ;• b, side of the portal vein in contact with the canal-, e, the side of the vein which is separated from the canal by the hepatic artery and d'uct, with areolar tissue (Glisson's capsule); d, lateral sur- face of the portal vein, through which are seen the outlines of the lobules and the openings of the interlobular veins ; /, vaginal voins of Kie* nan ; g, hepatic artery ; A,, hepatic. duct 680 ORGANS OF DIGESTION. from the liver the superfluous blood ; and the bile duct carries from the liver the bile secreted by the hepatic cells. The hepatic cells form the chief mass of each lobule : they are of a more or less spheroidal form ; but may be rounded, flattened, or many-sided, from mutual compression. They vary in size from the TTsW^h to the ^'^th of an inch in diameter, and contain a distinct nucleus in the interior, or even sometimes two. In the nucleus is a highly refracting nucleolus, with granules. The cell-contents are viscid, and contain yellow particles, the coloring matter of the bile, *ind oil globules. The cells adhere together by their surfaces, so as to form rows, which radiate from the centre towards the circumference of the lobule. These cells are probably the chief agents in the secretion of the bile. Biliary dwts. The precise mode of origin of the biliary ducts is uncertain. Mr. Kiernan's original view, confirmed as it is by the researches of Dr. Beale, shows that the ducts commence within the lobules, in a plexiform network (lobular biliary plexus), in which the hepatic cells lie. According to Henle, Handheld Jones, and Kolliker, the cells are packed in the interspaces of the capillary plexus, and, by means of temporary communications, transmit their contents into the minute bile ducts which originate in the spaces behveen the lobules, never entering within them. The ducts form a plexus (interlobular) between the lobules ; and the interlobular branches unite into vaginal branches, which lie in the portal canals, with branches of the portal vein and hepatic duct. The ducts finally join into two large trunks which leave the liver at the trans- verse fissure, and these joining form the hepatic duct. The Portal vein, on entering the liver at the transverse fissure, divides into primary branches, which are contained in the portal canals, together with branches of the hepatic artery and duct, and the nerves and lymphatics. In the larger portal canals, the vessels are separated from the parietes, and joined to each other by a loose cellular web, the capsule of Glisson. The veins, as they lie in the portal canals, give off vaginal branches, which form a plexus (vaginal plexus) in Glisson's capsule. From this plexus, and from the portal vein itself, small branches are given off, which pass between the lobules (interlobular veins) ; these cover the entire surface of the lobules, excepting their bases. The lobular branches are derived from the interlobular veins ; they penetrate into the lobule, and form a capillary plexus within them. From this plexus the intralobular vein arises. The Hepatic artery appears destined chiefly for the nutrition of the coats of the large vessels, the ducts, and the investing membranes of the liver. It enters the liver at the transverse fissure, with the portal vein and hepatic duct, and ramifies with these vessels through the portal canals. It gives off vaginal branches, which ramify in the capsule of Glisson ; and other branches, which are distributed to the coats of the vena portse and hepatic duct. From the vaginal plexus, inter- lobular branches are given off, which ramify through the interlobular fissures, a few branches being distributed to the lobules. Kiernan supposes, that the branches of the hepatic artery terminate in a capillary plexus, which communicates with the branches of the vena portse. The Hepatic veins commence in the interior of each lobule by a plexus, the branches of which converge to form the intralobular vein. The intralobular vein passes through the centre of the lobule, and leaves it at its base to terminate in a sublobular vein. Fig. 345 7-y A transverse section of a small portal canal and its vessels, after Kiernan. 1. Portal vein; 2, intrr- lobular branches ; 3, branches of the vein, termed, by Mr. Kiernan, vaginal, also giving off inter- lobular branches ; 4, hepatic duct ; 6, hepatic artery. GALL-BLADDER. 681 The sublobular veins unite with neighboring branches to form larger veins ; and these join to form the large hepatic trunks, which terminate in the vena cava. Gall-bladder. The Gall-bladder is the reservoir for the bile ; it is a conical or pear-shaped membranous sac, lodged in a fossa on the under surface of the right lobe of the liver, and extending from near the right extremity of the transverse fissure to the anterior free margin of the organ. It is about four inches in length, one inch in breadth at its widest part, and holds from eight to ten drachms. It is divided into a fundus, body, and neck. The fundus, the broad extremity, is directed down- wards, forwards, and to the right, and occasionally projects from the anterior border of the liver : the body and neck are directed upwards and backwards to the left. The gall-bladder is held in its position by the peritoneum, which, in the majority of cases, passes over its under surface, but it occasionally invests it, and is con- nected to the liver by a kind of mesentery. Relations. The body of the gall-bladder is in relation, by its upper surface, with the liver, to which it is connected by areolar tissue and vessels ; by its under surface, with the first portion of the duodenum, occasionally the pyloric end of the stomach, and the hepatic flexure of the colon. The fundus is completely invested by peritoneum; it is in relation, in front, with the abdominal parietes, immediately below the tenth costal cartilage ; behind, with the transverse arch of the colon. The neck is narrow, and curves upon itself like the Italic letter/; at its point of connection with the body and with the cystic duct, it presents a well-marked constriction. When the gall-bladder is distended with bile or calculi, the fundus may be felt through the abdominal parietes, especially in an emaciated subject ; the relations of this sac will also serve to explain the occasional occurrence of abdominal biliary fistulse, through which biliary calculi may pass out, and of the passage of calculi from the gall-bladder into the stomach, duodenum, or colon, which occasionally happens. Structure. The gall-bladder consists of three coats ; serous, fibrous and muscular, and mucous. The external or serous coat is derived from the peritoneum; it completely invests the fundus, but covers the body and neck only on their under surface. The middle or fibrous coat is a thin but strong fibrous layer, which forms the framework of the sac, consisting of dense fibres which interlace in all directions. Plain muscular fibres are also found in this coat, disposed chiefly in a longitudinal direction, a few running transversely. The internal or mucous coat is loosely connected with the fibrous layer. It is generally tinged with a yellowish-brown color, and is everywhere elevated into minute rugee, by the union of which numerous meshes are formed ; the depressed intervening spaces having a polygonal outline. The meshes are smaller at the fundus and neck, being most developed about the centre of the sac. Opposite the neck of the gall-bladder, the mucous membrane projects inwards so as to form a large valvular fold. The mucous membrane is covered with columnar epithelium, and secretes an abundance of thick viscid mucus; it is continuous through the hepatic duct with the mucous membrane lining the ducts of the liver, and through the ductus communis choledochus with the mucous membrane of the alimentary canal. The Biliary Ducts are the hepatic, the cystic, and the ductus communis choledochus. ^ The hepatic duct is formed of two trunks of nearly equal size, which issue from the liver at the transverse fissure, one from the right and one from the left lobe ; these unite, and pass downwards and to the right for about an inch and a half to join at an acute angle with the cystic duct, to form the common choledoch duct. • 682 ORGANS OF DIGESTION. The cystic duct, the smallest of the three biliary ducts, is about an inch in length. It passes obliquely downwards and to the left from the neck of the gall-bladder, and joins the hepatic duct to form the common duct. It lies in the gastro-hepatic omentum in front of the vena cava, the cystic artery lying to its left side. The mucous membrane lining its interior is thrown into a series of crescentic folds, from five to twelve in number, which project into the duct in regular succession, and are directed obliquely round the tube, presenting much the appearance of a continuous spiral valve. They exist only in the human subject. When the duct has been distended, the interspaces between the folds are dilated, so as to give to its exterior a sacculated appearance. The ductus communis 'choledochus, the largest of the three, is the common excre- tory duct of the liver and gall-bladder. It is about three inches in length, of the diameter of a goose-quill, and formed by the junction of the cystic and hepatic ducts. It descends along the right border of the lesser omentum, behind the first portion of the duodenum, in front of the vena portae, and to the right of the hepatic artery; it then passes between the pancreas and descending portion of the duodenum, and running for a short distance along the right side of the pancreatic duct, near its termination, passes with it obliquely between the mucous and muscular coats, the two opening by a common orifice upon the summit of a papilla, situated at the inner side of the descending portion of the duodenum, a little below its middle. Structure. The coats of the biliary ducts are composed of an external or fibrous, and an internal or mucous layer. The fibrous coat is composed of a strong areolar fibrous tissue. The mucous coat is continuous with the lining membrane of the hepatic ducts and gall-bladder, and also with that of the duodenum. It is provided with numerous glands, the orifices of which are scattered irregularly in the larger ducts, but in the smaller hepatic ducts are disposed in two longitudinal rows, one on each side of the vessel. These glands are of two kinds. Some are ramified tubes, which occasionally anastomose, and from the sides of which saccular dila- tations are given off; others are small clustered cellular glands, which open either separately into the hepatic duct, or into the ducts of the tubular glands. The Pancreas. Dissection. The pancreas may be exposed for dissection in three different ways : 1. By raising the liver, drawing down the stomach, and tearing through the gastro-hepatic omentum. 2. By raising the stomach, the arch of the colon, and great omentum upwards, and then dividing the inferior layer of the transverse mesocolon. 3. By dividing the two layers of peritoneum, which descend from the great curvature of the stomach to form the great omentum ; turning this organ upwards, and then cutting through the ascending layer of the transverse mesocolon. The Pancreas (*w-«pia$, all flesh) is a conglomerate gland, analogous in its structure to the salivary glands. In shape, it is transversely oblong, flattened from before backwards, and bears some slight resemblance to a hammer, its right extremity being broad, and presenting a sort of angular bend from above down- wards, called the head; its left extremity gradually tapers to form the tail, the intermediate portion being called the body. It is situated transversely across the posterior wall of the abdomen, at the back of the epigastric and both hypochon- driac regions. Its length varies from six to eight inches, its breadth is an inch and a half, and its thickness from half an inch to an inch, being thicker at its right extremity and along its upper border. Its weight varies from two to three and a half ounces, but it may reach six ounces. The right extremity or head of the pancreas (fig. 346) is curved upon itself from above downwards, and is embraced by the concavity of the duodenum. The common bile duct descends behind, between the duodenum and pancreas ; and the pancreatico-duodenal artery descends in front between the same parts. Upon its posterior part is a lobular fold of the gland, which passes transversely to the left, behind the superior mesenteric vessels, forming the back part of the canal, in PANCREAS. 683 which they are contained. It is sometimes detached from the rest of the gland, and is called the lesser pancreas. The lesser end or tail of the pancreas is narrow; it extends to the left as far as the spleen, and is placed over the left kidney and supra-renal capsule. The body of the pancreas is convex in front, and covered by the ascending layer of the transverse mesocolon and the posterior surface of the stomach. The posterior surface is concave, and has the following structures interposed between it and the first lumbar vertebra: — the superior mesenteric artery and vein, and commencement of the vena portee, the vena cava, the aorta, the left kidney, supra-renal capsule, and corresponding renal vessels. The upper border is thick, and has resting upon it, near its centre, the cceliac axis; the splenic artery and vein are lodged in a deep groove or canal in this Fig. 346. — The Pancreas and its Relations. border, and, to the right, the first part of the duodenum and the hepatic artery are in relation with it. The lower border, thinner than the upper, is separated from the transverse portion of the duodenum by the superior mesenteric artery and vein ; to the left of these the inferior mesenteric vein ascends behind the pancreas to join the splenic vein. The pancreatic duct, called also the canal of Wirsung from its discoverer, extends transversely from left to right through the substance of the pancreas, nearer to its lower than its upper border, and lying nearer its anterior than its posterior sur- face. In order to expose it, the superficial portion of the gland must be removed. It commences by an orifice common to it and the ductus communis choledochus upon the summit of an elevated papilla, situated at the inner side of the descending portion of the duodenum, a little below its middle. Passing very obliquely through the mucous and muscular coats, it separates itself from the common choledoch duct, and, ascending slightly, runs from right to left through the middle of the gland, giving off numerous branches, which pass to be distributed to its lobules. Sometimes the pancreatic and common choledoch ducts open separately into the 684 ORGANS OF DIGESTION. duodenum. The excretory duct of the lesser pancreas is called the ductus pan- creaticus minor ; it opens into the main duct near the duodenum, and sometimes separately into that intestine, at a distance of an inch or more from the termination of the principal duct. The pancreatic duct, near the duodenum, is about the size of an ordinary quill ; its walls are thin, consisting of two coats, an external fibrous and an internal mucous ; the latter is thin, smooth, and furnished, near its termination, with a few scattered follicles. Sometimes the pancreatic duct is double, up to its point of entrance into the duodenum. The Structure of the pancreas closely resembles that of the salivary glands ; but it is looser and softer in its texture. The fluid secreted by it is almost identical with saliva. Vessels and Nerves. The arteries of the pancreas are derived from the splenic, the pancreatico-duodenal branch of the hepatic, and the superior mesenteric. Its veins open into the splenic and superior mesenteric veins. Its lymphatics terminate in the lumbar glands. The nerves are filaments from the splenic plexus. The Spleen. The Spleen is usually classified together with the thyroid, supra-renal and thymus glands, as one of the ductless glands, from its possessing no excretory duct. It is of an oblong flattened form, soft, of very brittle consistence, highly vascular, of a dark bluish-red color, and situated in the left hypochondriac region, em- bracing the cardiac end of the stomach. It is invested by peritoneum, and connected with the stomach by the gastro-splenic omentum. Relations. Its external surface is convex, smooth, and in relation with the under surface of the Diaphragm, which separates it from the ninth, tenth, and eleventh ribs of the left side. The internal surface is slightly concave, and divided by a vertical fissure, the hilus, into an anterior or larger, and a posterior or smaller portion. The hilus is pierced by several large, irregular apertures, for the entrance and exit of vessels and nerves. At the margins of the hilus, the two layers of peritoneum are reflected from the surface of the spleen on to the cardiac end of the stomach, forming the gastro-splenic omentum, which contains between its layers the splenic vessels and nerves, and the vasa brevia. The internal surface is in relation, in front, with the great end of the stomach ; below, with the tail of the pancreas ; and behind, with the left crus of the Diaphragm and corresponding supra-renal capsule. ' Its upper end, thick and rounded, is in relation with the Diaphragm, to which it is connected by a fold of peritoneum, the suspensory ligament. Its lower end is pointed ; it is in relation with the left extremity of the trans- verse arch of the colon. Its anterior margin is free, rounded, and often notched, especially below. Its posterior margin is rounded, and lies in relation with the left kidney, to which it is connected by loose areolar tissue. The spleen is held in its position by two folds of peritoneum ; one, the gastro- splenic omentum, connects it with the stomach, and the other, the susjiensory ligament, with the under surface of the Diaphragm. The size and weight of the spleen are liable to very extreme variations at different periods of life, in different individuals, and in the same individual under different conditions. In the adult, in whom it attains its greatest size, it is usually about five inches in length, three or four inches in breadth, and an inch or an inch and a half in thickness, and weighs about seven ounces. At birth, its weight, in proportion to the entire body, is almost equal to what is observed in the adult, being as 1 to 350 ; whilst in the adult it varies from 1 to 320 to 1 to 400. In old age, the organ not only decreases in weight, but decreases considerably in pro- SPLEEN. ' 6S5 portion to the entire body, being as 1 to 700. The size of the spleen is increased during and after digestion, and varies considerably, according to the state of nutrition of the body, being large in highly fed, and small in starved animals. In intermittent and other fevers, it becomes much enlarged, weighing occasionally from 18 to 20 pounds. Structure. The spleen is invested by two coats ; an external serous, and an internal fibrous elastic coat. The external or serous coat is derived from the peritoneum; it is thin, smooth, and in the human subject intimately adherent to the fibrous elastic coat. It invests almost the entire organ, being reflected from it at the hilus, on to the great end of the stomach, and at the upper end of the organ on to the Dia- phragm. The fibrous elastic coat forms the framework of the spleen. It invests the exterior of the organ, and at the hilus is reflected inwards upon the vessels in the form of vaginae or sheaths. From these sheaths, as well as from the inner surface of the fibro-elastic coat, numerous small fibrous trabeculve or bands (fig. 347) are given off in all directions ; these, uniting, constitute the areolar framework of the spleen. The proper coat, the sheaths of the vessels, and the trabecule, consist of Fig. 347. — Transverse Section of the Spleen, showing the Trabecular Tissue and the Splenic Vein and its Branches. a dense mesh of white and yellow elastic fibrous tissues, the latter considerably predominating. It is owing to the presence of this tissue, that the spleen pos- sesses a considerable amount of elasticity, admirably adapted for the very con- siderable variations in size that it presents under certain circumstances. In some of the mammalia, in addition to the usual constituents of this tunic, there are found numerous pale, flattened, spindle-shaped, nucleated fibres, like unstriped muscular fibres. It is probably owing to this structure, that the spleen possesses, when acted upon by the galvanic current, faint traces of contractility. The proper substance of the spleen occupies the interspaces of the areolar frame- work of the organ ; it is a soft, pulpy mass, of a dark reddish-brown color, consist- ing of colorless and colored elements. The colorless elements consist of granular matter; nuclei, about the size of the red blood-disks, homogeneous or granular in structure, and nucleated vesicles in small numbers. These elements form, probably, one-half or two-thirds of the 686 ORGANS OF DIGESTION. whole substance of the pulp, filling up the interspaces formed by the partitions of the spleen, and lying in close contact with the walls of the capillary vessels, so as to be readily acted upon by the nutrient fluid which permeates them. These elements form a large part of the entire bulk of the spleen in well-nourished ani- mals ; whilst they diminish in number, and occasionally are wanting, in starved animals. The application of chemical tests shows that they are essentially a pro- tein compound. The colored elements of the pulp consist of red blood-globules and of colored corpuscles, either free, or included in cells. Sometimes, unchanged blood-disks are seen included in a cell ; but more frequently the included blood-disks are altered both in form and color. Besides these, numerous deep-red, or reddish- yellow, or black corpuscles and crystals, either single or aggregated in masses, are seen diffused throughout the pulp-substance ; these, in chemical composition, are closely allied to the hasmatin of the blood. Malpighian Corpuscles. — On examining the cut surface of a healthy spleen, a number of small semi-opaque bodies, of gelatinous consistence, are seen dissemi- nated throughout its substance ; these are the splenic or Malpighian corpuscles Fig. 348. — The Malpighian Corpuscles, and their Relation with the Splenic Artery and its Branches. (fig. 348). They may be seen at all periods of life ; but they are more distinct inearly life, than in adult life or old age ; and they are much smaller in man, than in most mammalia. They are of a spherical or ovoid form, vary considerably in size and number, and are of a semi-opaque whitish color. They are appended to the sheaths of the smaller arteries and their branches, presenting a resemblance to the buds of the moss rose. Each consists of a membranous capsule, composed of fine pale fibres, which interlace in all directions. In man, the capsule is homo- geneous in structure, and formed by a prolongation from the sheaths of the small arteries to which the corpuscles are attached. The bloodvessels ramifying on the surface of the corpuscles consist of the larger ramifications of the arteries to which the sacculus is connected ; and also of a delicate capillary plexus, similar to that surrounding the vesicles of other glands. These vesicles have also a close relation with the veins (fig. 349). These vessels, which are of considerable STRUCTURE OF THE SPLEEN. G87 size even at their origin, commence on the surface of each vesicle throughout the whole of its circumference, forming a dense mesh of veins, in which each of these Fig. 349.— One of the Splenic Corpuscles, showing its Relations with the Bloodvessels. bodies is inclosed. It is probable, that from the blood contained in the capillary network, the material is separated which is occasionally stored up in their cavity ; the veins being so placed as to carry off) under certain conditions, those contents Fig. 350. — Transverse Section of the Human Spleen, showing the Distribution of the Splenic Artery and its Branches. that are again to be discharged into the circulation. Each capsule contains a soft, white, semi-fluid substance, consisting of granular matter, nuclei similar to those found in the pulp, and a few nucleated cells, the composition of which is apparently 638 ORGANS OF DIGESTION. albuminous. These bodies are very large after digestion is completed, in well-fed animals, and especially in those fed upon albuminous diet. In starved animals, they disappear altogether. The splenic artery is remarkable for its large size, in proportion to the size of the organ ; and also for its tortuous course. It divides into from four to six branches, which enter the hilus of the organ, and ramify throughout its substance (fig. 350), receiving sheaths from an involution of the external fibrous tunic, the same sheaths also investing the nerves and veins. Each branch runs in the transverse axis of the organ, from within outwards, diminishing in size during its transit, and giving off, in its passage, smaller branches, some of which pass to the anterior, others to the posterior part ; these ultimately terminate in the proper substance of the spleen, in small tufts or pencils of capillary vessels, which lie in direct contact with the pulp. Each of the larger branches of the arteries supplies chiefly that region of the organ in which the branch ramifies, having no anasto- mosis with the majority of the other branches. The capillaries, supported by the minute trabecular, traverse the pulp in all directions, and terminate either directly in the veins, or open into lacunar spaces, from which the veins originate. The veins are of large size, as compared with the size of the organ, and their distribution is limited, like that of the arteries, to the supply of a particular part of the gland ; they are much larger and more numerous than the arteries. They originate, 1st, as continuations of the capillaries of the arteries ; 2dly, by inter- cellular spaces communicating with each other ; 3dly, by distinct carcal pouches. By their junction they form from four to six branches, which emerge from the hilus ; and these, uniting, form the splenic vein, the largest branch of the vena porta). The lymphatics form a deep and superficial set ; they pass through the lym- phatic glands at the hilus, and terminate in the thoracic duct. The nerves are derived from branches of the right and left semilunar ganglia, and right pneumogastric nerve. The Thorax. The Thorax is a conical, osseous framework, connected with the middle region of the spine. It is narrow above, broad below, flattened before and behind, and somewhat cordiform on a transverse section. Boundaries. It is bounded in front by the sternum, the six upper costal cartilages, the ribs, and intercostal muscles ; at the sides, by the ribs and inter- costal muscles ; and behind, by the same structures and the dorsal portion of the vertebral column. The superior opening of the thorax is bounded on each side by the first rib ; in front, by the upper border of the sternum ; and behind, by the first dorsal vertebra. It is broader from side to side, than from before backwards ; and its direction is backwards and upwards. The lower opening or base is bounded in front by the ensiform cartilage; behind, by the last dorsal vertebra ; and on each side by the last rib, the Dia- phragm filling in the intervening space. Its direction is obliquely downwards and backwards, so that the cavity of the thorax is much deeper on the posterior wall, than on the anterior. It is wider transversely than from before backwards, and its general direction is convex towards the chest ; but it is more flattened at the centre than at the sides, and rises higher on the right than on the left side, corresponding in the dead body to the upper border of the fifth costal cartilage, on the right side ; and to the corresponding part of the sixth cartilage on the left side. The parts which pass through the upper opening of the thorax are, from before backwards, the Sterno-hyoid and Sterno-thyroid muscles, the remains of the thymus gland, the trachea, oesophagus, thoracic duct, and the Longi colli muscles ; on the sides, the arteria innominata, the left carotid and left subclavian arteries, the internal mammary and superior intercostal arteries, the right and left vena? innominata?, and the inferior thyroid veins, the pneumogastric, sympathetic, phrenic, and cardiac nerves, and the recurrent laryngeal nerve of the left side. The apex of each lung, covered by the pleura, also projects through this aperture, a little above the margin of the first rib. The viscera contained in the thorax are, the great central organ of circulation, the heart, inclosed in its membranous bag, the pericardium ; and the organs of respiration, the lungs, invested by the pleura?. The Pericardium. The Pericardium is a conical membranous sac, in which the heart and the commencement of the great vessels are contained. It is placed behind the sternum, and the cartilages of the fourth, fifth, sixth, and seventh ribs of the left side, in the interval between the pleurae. Its apex is directed upwards, and surrounds the great vessels about two inches above their origin from the base of the heart. Its base is attached to the central tendon of the Diaphragm, extending a little farther to the left than the right side. In front, it is separated from the sternum by the remains of the thymus gland above, and a little loose areolar tissue below ; and is covered by the margins of the lungs, especially the left. Behind, it rests upon the bronchi, the oesophagus, and the descending aorta. Laterally, it is covered by the pleura? ; the phrenic vessels and nerve descending between the two membranes on either side. 44 689 690 THE THORAX. The pericardium is a fibre-serous membrane, and consists, therefore, of two layers ; an external fibrous and an internal serous. The fibrous layer is a strong, dense, fibrous membrane. Above, it surrounds the great vessels arising from the base of the heart, on which it is continued in the form of tubular prolongations, which are gradually lost upon their external coats; the strongest being that which incloses the aorta. Below, it is attached to the central tendon of the Diaphragm ; and, on the left side, to its muscular fibres. The vessels receiving fibrous prolongations from this membrane are the aorta, the superior vena cava, and the pulmonary arteries and veins. As the inferior cava enters the pericardium, through' the central tendon of the Diaphragm, it receives no covering from the fibrous layer. Fig. 351.— Front View of the Thorax. The Ribs and Sternum are represented in Relation to the Lungs, Heart, and other Internal Organs. The serous layer invests the heart, and is then reflected on the inner surface of the pericardium. It consists, therefore, of a visceral and a parietal portion. The former invests the surface of the heart, and the commencement of the great vessels, to the extent of two inches from their origin ; from these it is reflected upon the inner surface of the fibrous layerTtining, below, the upper surface of the central tendon of the Diaphragm. The serous membrane incloses the aorta and pulmonary artery in a single tube; but it only partially covers the superior and inferior venae cavse, and the four pulmonary veins. Its inner surface is smooth HEART. 691 and glistening, and secretes a thin fluid, which serves to facilitate the movements of the contained organ. The arteries of the pericardium are derived from the internal mammary, the bronchial, the oesophageal, and the phrenic. The Heart. The Heart is a hollow muscular organ, of a conical form, placed between the lungs, and inclosed in the cavity of the pericardium. Position. The heart is placed obliquely in the chest ; the broad attached end or base is directed upwards and backwards to the right, and corresponds to the interval between the fifth and eighth dorsal vertebrae ; the apex is directed for- wards and to the left, and corresponds to the interspace between the cartilages of the fifth and sixth ribs, one inch to the inner side, and two inches below the left nipple. The heart is placed beneath the lower two-thirds of the sternum, and projects further into the left than into the right cavity of the chest, extending from the median line about three inches in the former direction, and only one and a half in the latter. Its upper border would correspond to a line drawn across the sternum, on a level with the upper border of the third costal cartilages ; and its lower border, to a line drawn across the lower end of the gladiolus, from the costo-xiphoid articulation of the right side, to the part corresponding to the apex. Its anterior surface is rounded and convex, directed upwards and forwards, and formed chiefly by the right ventricle and part of the left. Its posterior surface is flattened, and rests upon the Diaphragm. The right border is long, thin, and sharp ; the left border short, but thick and round. Size. The heart, in the adult, measures about five inches in length, three inches and a half in breadth in its broadest part, and two inches and a half in thickness. The prevalent weight, in the male, varies from ten to twelve ounces, in the female, from eight to ten ; its proportion to the body being as 1 to 169, in males, 1 to 149 in females. The heart continues increasing in weight, and also in length, breadth, and thickness, up to an advanced period of life ; and this is more marked in men than in women. Component parts. The heart is subdivided by a longitudinal muscular septum, into two lateral halves, which are named respectively, from their position, right and left ; and a transverse constriction divides each half of the organ into two cavities, the upper cavity on each side being called the auricle, the lower the ventricle. The right is the venous side of the heart, receiving into its auricle the dark venous blood from the entire body, by the superior and inferior venae cava3, and coronary sinus. From the auricle, the blood passes into the right ventricle ; and from the right ventricle, through the pulmonary artery, into the lungs. The blood, arterialized by its passage through the lungs, is returned to the left side of the heart by the pulmonary veins, which open into the left auricle ; from the left auricle the blood passes into the left ventricle, and from the left ventricle is dis- tributed, by the aorta and its subdivisions, through the entire body. This con- stitutes the circulation of the blood in the adult. This, division of the heart into four cavities is indicated upon its surface in the form of grooves. Thus, the great transverse groove separating the auricles from the ventricles is called the auriculo-ventricular groove. It is deficient, in front, from being crossed by the root of the pulmonary artery, and contains the trunk of the nutrient vessels of the heart. The auricular portion occupies the base of the heart, and is subdivided into two cavities by a median septum. The two ventricles' are also separated into a right and left, by two longitudinal furrows, which are situated, one on its anterior, the other on its posterior surface ; these extend from the base to the apex of the organ, the former being situated nearer to the left border of the heart, and the latter to the right. It follows, therefore, that the right ventricle forms the greater portion of the anterior surface of the heart, and the left ventricle more of its posterior surface. 692 THE THORAX. Each of these cavities should now be separately examined. The Eight Aueicle is a little larger than the left, its walls somewhat thinner, measuring about one line; and its cavity is capable of containing about two ounces. It consists of two parts, a principal cavity or sinus, and an appendix auriculae. The sinus is the large quadrangular-shaped cavity, placed betAveen the two venge cavee ; its walls are extremely thin, and it is connected below with the right Fig. 352. — The Right Auricle and Ventricle laid open, the anterior walls of both being removed. Xn'stle yarseri th Jtigit Auricula -Ymtriculaj* evvniny ventricle, and, Internally, with the left auricle, being free in the rest of its extent. The appendix auriculae, so called from its fancied resemblance to a dog's ear, is a small conical muscular pouch, the margins of which present a dentated edge. It projects from the sinus forwards and to the left side, overlapping the root of the pulmonary artery. To examine the interior of the auricle, a transverse incision should be made along its ventri- cular margin, from its right border to the appendix ; and, from the middle of this, a second inci- sion should be carried upwards, along the inner side of the two venae cavae. The following parts present themselves for examination : — /'Superior vena cava. Relics of Foetal j Annulus ovalis. [Inferior vena cava. structure. \ Fossa ovalis. Openings. (Coronary sinus. Musculi pectinati. 'Foramina Thebesii. -r T ■, j Eustachian. v Auriculo-ventricular. { Coronary. HEART— RIGHT AURICLE. 693 OPENINGS. The superior vena cava returns the blood from the upper half of the body, and opens into the upper and front part of the auricle, the direcikm of its orifice being downwards and forwards. The inferior vena cava, larger than the superior, returns the blood from the lower half of the body, and opens into the lowest part of the auricle, near the septum, the direction of its orifice being upwards and inwards. The direction of a current of blood through the superior vena cava would consequently be towards the auriculo-ventricular orifice; whilst the direction of the blood through the inferior cava would be towards the auricular septum. This is the normal direc- tion of the two currents in foetal life. The tuberculum Lower i is a small projection on the right wall of the auricle, between- the two venae cavae. This is most distinct in the hearts of quadrupeds ; in man, it is scarcely visible. It was supposed, by Lower, to direct the blood from the superior vena cava towards the auriculo-ventricular opening. The coronary sinus opens into the auricle, between the inferior vena cava and the auriculo-ventricular opening. It returns the blood from the substance of the heart, and is protected by a semicircular fold of the lining membrane of the auricle, the coronary valve. The sinus, before entering the auricle, is considerably dilated. Its wall is partly muscular, and, at its junction with the great coronary vein, is somewhat constricted, and furnished with a valve, consisting of two unequal segments. The foramina Thebesii are numerous minute apertures, the mouths of small veins {venae cordis minimse), which open on various parts of the inner surface of the auricle. They return the blood directly from the muscular substance of the heart. Some of these foramina are minute depressions in the walls of the heart, presenting a closed extremity. The auriculo-ventricular opening is the large oval aperture of communication between the auricle and ventricle, to be presently described. Valves. The Eustachian valve is situated between the anterior margin of the inferior cava and the auriculo-ventricular orifice. It is semilunar in form, its convex margin being attached to the wall of the vein ; its concave margin, which is free, terminating in two cornua, of which the left is attached to the anterior edge of the annulus ovalis ; the right being lost on the wall of the auricle. The valve is formed by a duplicature of the lining membrane -of the auricle, containing a few muscular fibres. In the foetus, this valve is of large size, and serves to direct the blood from the inferior vena cava, through the foramen ovale, into the left auricle. In the adult, it is . occasionally persistent, and may assist in preventing the reflux of blood into the inferior vena cava ; more commonly, it is small, and its free margin presents a cribriform or filamentous appearance ; occasionally, it is alto- gether wanting. The coronary valve is a semicircular fold of the lining membrane of the auricle, protecting the orifice of the coronary sinus. It prevents the regurgitation of blood into the sinus during the contraction of the auricle. This valve is occasionally double. The fossa ovalis is an oval depression, corresponding to the situation of the foramen ovale in the foetus. It is situated at the lower part of the septum auricu- larum, above the orifice of the inferior vena cava. The annulus ovalis is the prominent oval margin of the foramen ovale. It is most distinct above, and at the sides; below, it is deficient. A small slit-like valvular opening is occasionally found, at the upper margin of the fossa ovalis, which leads upwards, beneath the annulus, into the left auricle ; it is the remains of the aperture between the two auricles in the foetus. The musculi pectinati are small, prominent muscular columns, which run across the inner surface of the appendix auriculae, and adjoining portion of the wall of the sinus. They have received the name, pectinati, from the fancied resemblance they bear to the teeth of a comb. 094 THE THORAX. The Right Ventkicle is triangular in form, and extends from the right auricle to near the apex. Its anterior or upper surface is rounded and convex, and forms the larger part of the front of the heart. Its posterior or under surface is flattened, rests upon the Diaphragm, and forms only a small part of this surface. Its inner wall is formed by the partition between the two ventricles, the septum ventricu- lorum, the surface of which is convex, and bulges into the cavity of the right ventricle. Superiorly, the ventricle forms a conical prolongation, the infundi- bulum or conus arteriosus, from which the pulmonary artery arises. The walls of the right ventricle are thinner than those of the left, the proportion between them being as 1 to 2 (Bizot). The thickest part of the wall is at the base, and it gradually becomes thinner towards the apex. Its cavity, which equals that of the left ventricle, is capable of containing about two fluid ounces. To examine its interior, an incision should be made a little to the right of the anterior ven- tricular groove from the pulmonary artery to the apex of the heart, and from thence carried up along the right border of the ventricle, as far as the auriculo-ventricular opening. The following parts present themselves for examination : — ~ . j Auriculo-ventricular. penings . . j Opening of the pulmonary artery. ■y i j Tricuspid. * ' * I Semilunar. And a muscular and tendinous apparatus connected with the tricuspid valves : — Columnae carneae. Chordae tendineEe. The auriculo-ventricular orifice is the large oval aperture of communication between the auricle and ventricle. It is situated at the base of the ventricle, near the right border of the heart, and corresponds to the centre of the sternum between the third costal cartilages. The opening is about an inch in diameter, oval from side to side, surrounded by a fibrous ring, covered by the lining mem- brane of the heart, and is rather larger than the corresponding aperture on the left side, being sufficiently large to admit the ends of three fingers. It is guarded by the tricuspid valve. The opening of the pulmonary artery is circular in form, and situated at the summit of the conus arteriosus, close to the septum ventriculorum. It is placed on the left side of the auriculo-ventricular opening, upon the anterior aspect of the heart, and corresponds to the upper border of the third costal cartilage of the left side, close to the sternum. Its orifice is guarded by tkje semilunar valves. The tricuspid valve consists of three segments of a triangular or trapezoidal shape, formed by a duplicature of the lining membrane of the heart, strengthened by a layer of fibrous tissue, and containing, according to Kurschner and Senac, muscular fibres. These segments are connected by their bases to the auriculo- ventricular orifice, and by their sides with one another, so as to form a continuous annular membrane, which is attached round the margin of the auriculo-ventricular opening, their free margins and ventricular surfaces affording attachment to a num- ber of delicate tendinous cords, the chordse tendinese. The largest and most mov- able segment is placed towards the left side of the auriculo-ventricular opening interposed between it and the pulmonary artery. Another segment corresponds to the front of the ventricle ; and. a third to its posterior wall. The central part of each segment is thick and strong ; and the lateral margins are thin and indented. The chordae tendineae are connected with the adjacent margins of the principal segments of the valve, and are further attached to each segment in the following manner : — 1. Three or four reach the attached margin of each segment, where they are continuous with the auriculo-ventricular tendinous ring. 2. Others, four to six in number, are attached to the central thickened part of each segment. 3. The most numerous and finest are connected with the marginal portion of each «egment. HEART— LEFT AURICLE. 695 The columnse carnese are the rounded muscular columns which project from nearly the whole of the inner surface of the ventricle, excepting near the opening of the pulmonary artery. They may be classified, according to their mode of connection with the ventricle, into three sets. The first set merely form prominent ridges on the inner surface of the ventricle, being attached by their entire length on one side, as well as by their extremities. Tho second set are attached by their two extremities, but are free in the rest of their extent ; whilst the third set (columnse papillares), three or four in number, are attached by one extremity to the Avail of the heart, the opposite extremity giving attachment to the chordse tendinese. The semilunar valves, three in number, guard the orifice of the pulmonary artery. They consist of three semicircular folds, formed by a duplicature of the lining membrane, strengthened by fibrous tissue. They are attached, by their convex margins, to the wall of the artery, at its junction with the ventricle, the straight border being free, and directed upwards in the course of the vessel, against the sides of which they are pressed during the passage of the blood along its canal. The free margin of each is somewhat thicker than the rest of the valve, is strengthened by a bundle of tendinous fibres, and presents, at its middle, a small projecting fibro- cartilaginous nodule, called corpus Arantii. From this nodule, tendinous fibres radiate through the valve to its attached margin, and these fibres form a consti- tuent part of its substance throughout its whole extent, excepting two narrow lunated portions, placed one on either side of the nodule, immediately behind the free margin ; here, the valve is thin, and formed merely by the lining membrane. During the passage of the blood along the pulmonary artery, these valves are pressed against the sides of its cylinder, and the course of the blood along the tube is uninterrupted ; but during the ventricular diastole, when the current of blood along the pulmonary artery is checked, and partly thrown back by its elastic walls, these valves become immediately expanded, and effectually close the entrance of the tube. When the valves are closed, the lunated portions of each are brought into contact with one another by their opposed surfaces, the three fibro-cartilagi- nous nodules filling up the small triangular space that would be otherwise left by the approximation of the three semilunar folds. Between the semilunar valves and the commencement of the pulmonary artery are three pouches or dilatations, one behind each valve. These are the pulmonary sinuses (sinuses of Valsalva). Similar sinuses exist between the semilunar valves and the commencement of the aorta ; they are larger than the pulmonary sinuses. The Left Auricle is rather smaller but thicker than the right, measuring about one line and a half; it consists of two parts, a principal cavity or sinus, and an appendix auriculae. The sinus is cuboidal in form, and concealed in front by the pulmonary artery and aorta ; internally, it is separated from the right auricle by the septum auricu- larum ; and behind, it receives on each side the pulmonary veins, being free in the rest of its extent. The appendix auriculae is somewhat constricted at its junction with the auricle; it is longer, narrower, and more curved than that of the right side, and its mar- gins more deeply indented, presenting a kind of foliated appearance. Its direction is forwards towards the right side, overlapping the root of the pulmonary artery. In order to examine its interior, a horizontal incision should be made along the attached border of the auricle to the ventricle ; and, from the middle of this, a second incision should be carried upwards. The following parts then' present themselves for examination : — The openings of the four pulmonary veins. Auriculo- ventricular opening. Musculi pectinati. 696 THE THORAX. The pulmonary veins, four in number, open, two into the right, and two into the left side of the auricle. The two left veins frequently terminate by a common opening. They are not provided with valves. The auriculo-ventricular opening is the large oval aperture of communication between the auricle and ventricle. It is rather smaller than the corresponding opening on the opposite side. The musculi pectinati are fewer in number and smaller than on the right side ; they are confined to the inner surface of the appendix. On the inner surface of the septum auricularum may be seen a lunated impres- sion, bounded below by a crescentic ridge, the concavity of which is turned upwards. This depression is just above the fossa ovalis in the right auricle. Ft* 353. — Tlie Left Auricle and Ventricle laid open, the Anterior Walls of both being removed. passed thro' Aortic opening The Left Yenteicle is longer and more conical in shape than the right ven- tricle. It forms a small part of the left side of the anterior surface of the heart, and a considerable part of its posterior surface. It also forms the apex of the heart by its projection beyond the right ventricle. Its walls are much thicker than those of the right ventricle, the proportion being as 2 to 1 (Bizot). They are also thickest in the broadest part of the ventricle, becoming gradually thinner towards the base, and also towards the apex, which is the thinnest part. Its cavity should be opened by making an incision through its anterior wall along the left side of the ventricular septum, and carrying it round the apex and along its posterior surface to the auriculo-ventricular opening. The following parts present themselves for examination : — Auriculo-ventricular. y 1 i Mitral. Aortic. • ( Semilunar Chordaa tendinere. Columnge carneas. Openings HEART— LEFT VENTRICLE. 697 he auricula-ventricular opening is placed to the left of the aortic orifice, be- neath the right auriculo-ventricular opening, opposite the centre of the sternum. It is a little smaller than the corresponding aperture of the opposite side ; and, like it, is broader in the transverse, than in the antero-posterior, diameter. It is surrounded by a dense fibrous ring, covered by the lining membrane of the heart and is guarded by the mitral valve. The aortic opening is a small circular aperture, in front and to the right side of the auriculo- ventricular, from which it is separated by one of the segments of the mitral valve. Its orifice is guarded by the semilunar valves. Its position corre- sponds to the sternum, on a line with the lower border of the third left costal cartilage. The mitral valve is attached to the circumference of the auriculo-ventricular orifice, in the same way that the tricuspid valve is on the opposite side. It is formed by a duplicature of the lining membrane, strengthened by fibrous tissue, and contains a few muscular fibres. It is larger in size, thicker, and altogether stronger than the tricuspid, and consists of two segments of unequal size. The larger segment is placed in front, between the auriculo-ventricular and aortic ori- fices, and is said to prevent the filling of the aorta during the distension of the ventricle. Two smaller segments are usually found at the angle of junction of the larger. The mitral valves are furnished with chordae tendineee ; their mode of attachment is precisely similar to those on the right side, but they are thicker, stronger, and less numerous. The semilunar valves surround the orifice of the aorta; they are similar in structure, and in their mode of attachment, to those of the pulmonary artery. They are, however, larger, thicker, and stronger than those of the right side ; the lunulas are more distinct, and the corpora Arantii larger and more prominent. Between each valve and the cylinder of the aorta is a deep depression, forming the sinus aortici (sinuses of Valsalva) ; they are larger than those at the root of the pulmonary artery. The columnse carnese admit of a subdivision into three sets, like those upon the right side ; but they are smaller, more numerous, and present a dense interlace- ment, especially at the apex, and upon the posterior wall. Those attached by one extremity only, the musculi papillares, are two in number, being connected one to the anterior, the other to the posterior wall ; they are of large size, and terminate by free rounded extremities, from which the chordas tendineoa arise. The Endocardium is the serous membrane which lines the internal surface of the heart ; it assists in forming, by its reduplications, the valves contained in this organ, and is continuous with the lining membrane of the great bloodvessels. It is a thin, smooth, transparent membrane, giving to the inner surface of the heart its glistening appearance. It is more opaque on the left than on the right side of the heart, thicker in the auricles than in the ventricles, and thickest in the left auricle. It is thin on the musculi pectinati, and on the columnae carneae ; but thicker on the smooth part of the auricular and ventricular walls, and on the tips of the musculi papillares. Structure of the Heart. The heart consists of muscular fibres, and of fibrous rings which serve for their attachment. The fibrous rings surround the auriculo-ventricular and arterial orifices ; they are stronger upon the left than on the right side of the heart. The auriculo- ventricular rings serve for the attachment of the muscular fibres of the auricles and ventricles, and also for the mitral and tricuspid valves ; the left one is closely connected, by its right margin, with the aortic arterial ring. Between these and the right auriculo-ventricular ring, is a fibro-cartilaginous mass ; and in some of the larger animals, as the ox and elephant, a portion of bone. The fibrous rings surrounding the arterial orifices serve for the attachment of the great vessels and semilunar valves. Each ring receives, by its ventricular margin, the attachment of the muscular fibres of the ventricles; its opposite 698 THE THORAX. margin presents three deep semicircular notches, within which the middle coat of the artery (which presents three convex semicircular segments) is firmly fixed; the attachment of the artery to its fibrous ring being strengthened by the thin cellular coat and serous membrane externally, and by the endocardium within. It is opposite the margins of these semicircular notches, in the arterial rings, that the endocardium, by its reduplication, forms the semilunar valves, the fibrous structure of the ring being continued into each of the segments of the valve at this part. The middle coat of the artery in this situation is thin, and the sides of the vessel dilated to form the sinuses of Valsalva. The muscular structure of the heart consists of bands of fibres, which present an exceedingly intricate interlacement. They are of a deep red color, and marked with transverse striae. The muscular fibres of the heart admit of a subdivision into two kinds, those of the auricles, and those of the ventricles, which are quite independent of one another. Fibres of the auricles. These are disposed in two layers, a superficial layer common to both cavities, and a deep layer proper to each. The superficial fibres are most distinct on the anterior surface of the auricles, across the bases of which they run in a transverse direction, forming a thin but incomplete layer. Some of these fibres pass into the septum auricularum. The internal or deep fibres proper 1 to each auricle consist of two sets, looped, and annular fibres. The looped fibres pass upwards over each auricle, being attached by both extremities to the corre- sponding auriculo- ventricular rings, in front and behind. The annular fibres sur- round the whole extent of the appendices auriculae, and are continued upon the walls of the venae cavae and coronary sinus on the right side, and upon the pul- monary veins on the left side, at their connection with the heart. In the appendices, they interlace with the longitudinal fibres. Fibres of the ventricles. These, as in the auricles, are disposed in layers, some of which' are common to both ventricular cavities, whilst others belong exclusively to one ventricle, the latter being chiefly found towards the base of the heart. The greater majority of these fibres are connected by both ends with the auriculo- ventricular fibrous rings, either directly or indirectly through the chordae ten- dineae ; some, however, are attached to the fibrous rings surrounding the arterial orifices. The superficial fibres are either longitudinal, or, more commonly, oblique or spiral in their direction, and towards the apex are arranged in the form of twisted loops ; the deeper fibres are circular. The spiral fibres .are disposed in layers of various degrees of thickness ; the most superficial, on the front of the ventricles, run obliquely from right to left, and from above downwards. On the back of the ventricles they are directed more vertically, and pass from left to right. The superficial fibres coil inwards at the apex of the heart, round which they are arranged in a whorl-like iorm, called the vortex, dipping beneath the edge of the deeper and shorter layers. If these fibres are carefully uncoiled, in a heart previously boiled, the cavity < f the left, and then that of the right ventricle, will be exposed at this point. The layers of fibres successively met with have a simi- lar arrangement ; the more superficial and longer turning inwards, and including the deeper and shorter bands. All these fibres ascend and spread out upon the inner surface of the ventricles, forming the walls, the septum, and the musculi papillares, which project from these cavities ; and they are finally inserted into the auriculo-ventricular fibrous rings, or, indirectly, through the chordae tendineae. Of these spiral fibres, some enter at the interventricular furrows, and surround either ventricle singly ; others pass across the furrows, and embrace both cavities. On tracing those which form the vortex, back into the interventricular septum, they become interlaced with similar fibres from the right ventricle, and ascend vertically upon the right side of the septum, as far as its base, in the form of a long and broad band. Circular fibres. The circular fibres are situated deeply in the substance of VASCULAR SYSTEM OF TIIE FCETUS. 699 the heart ; towards the base they enter the anterior and posterior longitudinal furrows, so as to include each cavity singly, or, passing across them, surround both ventricles, more fibres passing across the posterior than the anterior furrow. They finally ascend in the substance of the ventricle, to be inserted into the fibrous rings at its base. Vessels and Nerves. The arteries supplying the heart are the anterior and pos- terior coronary. The veins accompany the arteries, and terminate in the right auricle. They are the great cardiac vein, the small or anterior cardiac veins, and the venae cordis minimae (venae Thebesii). The lymphatics terminate in the thoracic and right lymphatic ducts. The nerves are derived from the cardiac plexuses, which are formed partly from the spinal, and partly from the sympathetic system. They are freely distributed both on the surface, and in the substance of the heart ; the separate filaments being furnished with small ganglia. These have been figured by Remak, but the more extended investigations of Dr. Robert Lee have shown them tp exist in great abundance, both in the nerves distributed to the surface, and in those in the interior of the organ. Peculiarities in the Vascular System of the Foetus. The chief peculiarities in the heart of the foetus are the direct communication between the two auricles by the foramen ovale, and the large size of the Eustachian valve. There are also several minor peculiarities. Thus, the position of the heart is vertical until the fourth month, when it commences to assume an oblique direction. Its size is also very considerable, as compared with the body, the proportion at the second month being as 1 to 50 : at birth, it is as 1 to 120 : whilst, in the adult, the average is about 1 to 160. At an early period of foetal life, the auricular portion 'of the heart is larger than the ventricular, the right auricle being more capacious than the left ; but, towards birth, the ventricular portion becomes the larger. The thickness of both ventricles is, at first, about equal ; but, towards birth, the left becomes much the thicker of the two. The foramen ovale is situated at the lower and back part of the septum auricularum. Through it the auricles communicate with each other. It attains its greatest size at the sixth month. The Eustachian valve is developed from the anterior border of the inferior vena cava, at its entrance in the auricle, and, rising up on the left side of the opening of this vein, serves to direct the blood from the inferior vena cava through the foramen ovale into the left auricle. The peculiarities in the arterial system of the foetus are the communication between the pulmonary artery and descending aorta, by means of the ductus arteriosus, and the communication between the internal iliac arteries and the placenta, by the umbilical arteries. The ductus arteriosus is a short tube, about half an inch in length at birth, and of the diameter of a goose-quill. It connects the left branch of the pulmonary artery with the termination of the arch of the aorta, just beyond the origin of the left subclavian artery. It conducts the chief part of the blood of the right ventri- cle into the descending aorta. The umbilical or hypogastric arteries arise from the internal iliacs, in addition to the usual branches given off' from these vessels in the adult. Ascending along the sides of the bladder to its fundus, they pass out of the abdomen at the umbilicus, and are continued along the umbilical cord to the placenta, coiling round the umbilical vein. They return the blood to the placenta which has been circulated in the system of the foetus. The peculiarity in the venous system of the foetus is the communication established between the placenta and the liver and portal vein, through the umbilical vein, and with the inferior vena cava by the ductus venosus. TOO THE THORAX. Fcetal Circulation. In the following plan the figured arrows represent the kind of \>lood, as well as the direction which it takes in the vessels. Thus — arterial blood is figured >» > ; venous blood, >» •••>; mixed (arterial and venous blood), #ti> i ' *if , Fig. 354.— Plan of the Foetal Circulation. Intrtml Mac JGC The arterial blood destined for the nutrition of the foetus is carried from the placenta to the foetus, along the umbilical cord, by the umbilical vein. The umbilical vein enters the abdomen at the umbilicus, and passes upwards along the FCETAL CIRCULATION. T01 free margin of the suspensory ligament of the liver, to the under surface of this organ, where it gives off two or three branches to the left lobe, one of which is of large size; and others to the lobus quadratus and lobus Spigelii. At the transverse fissure, it divides into two branches ; of these, the larger is joined by the portal vein, and enters the right lobe ; the smaller branch continues onwards, under the name of the ductus venosus, and joins the left hepatic vein at the point of junction of this vessel with the inferior vena cava. The blood, there- fore, which traverses the umbilical vein, reaches the inferior vena cava in three different ways. The greater quantity circulates through the liver with the portal venous blood, before entering the cava by the hepatic veins ; some enters the liver directly, and is also returned to the inferior cava by the hepatic veins ; the smaller quantity passes directly into the vena cava, by the junction of the ductus venosus witli the left hepatic vein. In the inferior cava, the blood carried by the ductus venosus and hepatic veins becomes mixed with that returning from the lower extremities and viscera of the abdomen. It enters the right auricle, and, guided by the Eustachian valve, passes through the foramen ovale into the left auricle, where it becomes mixed with a small quantity of blood returned from the lungs by the pulmonary veins. From the left auricle it passes into the left ventricle ; and, from the left ventricle, into the aorta, from whence it is distributed almost entirely to the head and upper extremities, a small quantity being probably carried into the descending aorta. From the head and upper extremities, the blood is returned by the branches of the superior vena cava to the right auricle, where it becomes mixed with a small portion of the blood from the inferior cava. From the right auricle, it descends over the Eustachian valve into the right ventricle; and, from the right ventricle, into the pulmonary artery. The lungs of the foetus being solid, and almost impervious, only a small quantity of blood is distributed to them, by the right and left pulmonary arteries, which is returned by the pulmonary veins to the left auricle ; the greater part passes through the ductus arteriosus into the commence- ment of the descending aorta, where it becomes mixed with a small quantity of blood transmitted by the left ventricle into the aorta. Along this vessel it descends to supply the lower extremities and viscera of the abdomen and pelvis, the chief portion being, however, conveyed by the umbilical arteries to the placenta. From the preceding account of the circulation of the blood in the foetus, it will be seen: — 1. That the placenta serves the double purpose of a respiratory and nutritive organ, receiving the venous blood from the foetus, and returning it again re-oxy- genated, and charged with additional nutritive material. 2. That nearly the whole of the blood of the umbilical vein traverses the liver before entering the inferior vena cava ; hence the large size of this organ, especially at an early period of foetal life. 3. That the right auricle is the point of meeting of a double current, the blood in the inferior vena cava being guided by the Eustachian valve into the left auricle, whilst that in the superior vena cava descends into the right ventricle. At an early period of foetal life, it is highly probable that the two streams are quite distinct ; for the inferior vena cava opens almost directly into the left auricle, and the Eustachian valve would exclude the current along the tube from entering the right ventricle. At a later period, as the separation between the two auricles becomes more distinct, it seems probable that some slight mixture of the two streams must take place. 4. The blood carried from the placenta to the foetus by the umbilical vein, mixed with the blood from the inferior vena cava, passes almost directly to the arch of the aorta, and is distributed by the branches of this vessel to the head and upper extremities; hence the large size and perfect development of these parts at birth. 5. The blood contained in the descending aorta, chiefly derived from that which has already circulated through the head and limbs, together with a small 102 THE THORAX. quantit}'- from the left ventricle, is distributed to the lower extremities; hence the small size and imperfect development of these parts at birth. Changes m the Vascular System at Birth. At birth, when respiration is established, an increased amount of blood from the pulmonary artery passes through the lungs, which now perform their office as respiratory organs, and, at the same time, the placental circulation is cut off. The foramen ovale becomes gradually closed by about the tenth day after birth, a valvular fold rising up on the left side of its margin, and ultimately above its upper part ; this valve becomes adherent to the margins of the foramen for the greater part of its circumference, but, above, a valvular opening is left between the two auricles, which sometimes remains persistent. The ductus arteriosus begins to contract immediately after respiration is estab- lished, becomes completely closed from the fourth to the tenth day, and ultimately degenerates into an impervious cord, which serves to connect the left pulmonary artery to the concavity of the arch of the aorta. Of the umbilical or hypogastric arteries, the portion continued on to the bladder from the trunk of the corresponding internal iliac remains pervious, as the supe- rior vesical artery ; and the part between the fundus of the bladder and the umbilicus becomes obliterated between the second and fifth days after birth, and forms the anterior true ligament of this viscus. The umbilical vein and ductus venosus become completely obliterated between the second and fifth days after birth, and ultimately dwindle to fibrous cords ; the former becoming the round ligament of the liver, the latfler the fibrous cord, which, in the adult, may be traced along the fissure of the ductus venosus. Organs of Voice and Eespiration. pi* 355.— Side View of the Thyroid and Cricoid Cartilages. The Larynx. The Larynx is the organ of voice, placed at the upper part of the air-passage. It is situated between the trachea and base of the tongue, at the upper and fore part of the neck, where it forms a considerable projection in the middle line. On either side of it lie the great vessels of the neck; behind, it forms part of the boundary of the pharynx, and is covered by the mucous membrane lining this cavity. The larynx is narrow and cylindrical below, but broad above, where it presents the form of a triangular box, being flattened behind and at the sides, whilst in front it is bounded by a prominent vertical ridge. It is composed of cartilages, connected together by ligaments, moved by numerous muscles, lined by mucous membrane, and supplied with vessels and nerves. The cartilages of the larynx are nine in number; — three single, and three pairs : — Thyroid. Two Arytenoid. Cricoid. Two Cornicula Laryngis. Epiglottis. Two Cuneiform. The Tliyroid (0vp«ov dSof, like a shield) is the largest cartilage of the larynx. It consists of two lateral lamellae or alae, united at an acute angle in front, forming a vertical projection in the middle line, which is prominent above, and called the pomum Adami. This projection is subcu- taneous, more distinct in the male than in the female, and occasionally separated from the integument by a bursa mucosa. Each lamella is quadrilateral in form. Its outer surface presents an oblique ridge, which passes downwards and for- wards from a tubercle, situated near the root of the superior cornu. This ridge gives attachment to the Ster no -thyroid and Thyro-hyoid muscles; the portion of cartilage included between it and the poste- rior border, to part of the Inferior constric- tor muscle. The inner surface of each ala is smooth, concave, and covered by mucous membrane above and behind ; but in front, in the re- ceding angle formed by their junction, are attached the epiglottis, the true and false chordae vocales, the Thyro-arytenoid and Thyro-epiglottidean muscles. The upper border of the thyroid carti- lage is deeply notched in the middle line, immediately above the pomum Adami, whilst on either side it is slightly concave. This border gives attachment throughout its whole extent to the thyro-hyoid membrane. The lower border is connected to the cricoid cartilage, in the median line, by the cri co-thyroid membrane ; and, on each side, by the Crico-thyroid muscle. 703 T04 ORGANS OF YOICE AND RESPIRATION. Fig. 356.— The Cartilajr^s of the Larynx. Posterior View. EPIGLOTTIS The posterior borders, thick and rounded, terminate, above, in the superior cornua ; and, below, in the inferior cornua. The two superior cornua are long and narrow, directed backwards, upwards, and inwards ; and terminate in a conical extremity, which gives attachment to the thyro-hyoid ligament. The two inferior cornua are short and thick ; they pass forwards and inwards, and present, on their inner surfaces, a small, oval, articular facet for articulation with the side of the cricoid cartilage. The posterior border receives the insertion of the Stylo-ph.aryngeus and Pal&to-pharyngeus muscles on each side. The Cricoid Cartilage is so called from its resemblance to a signet-ring (xpi'xoj «5o$, like a ring). It is smaller but thicker and stronger than the thyroid cartilage, and forms the lower and back part of the cavity of the larynx. Its anterior half is narrow, convex, affording attachment in front and at the sides to the Crico-thyroid muscles, and, be- hind those, to part of the Inferior constrictor. Its posterior half is very broad, both from side to side and from above downwards ; it presents in the middle line a vertical ridge for the attachment of the longitudinal fibres of the oesophagus, and on either side of this is a broad depression for the Crico-arytsenoideus posticus muscle. At the point of junction of the two halves of the cartilage on either side, is a small round elevation, for articulation with the inferior cornu of the thyroid cartilage. The lower border of the cricoid cartilage is horizontal, and con- nected to the upper ring of the trachea by fibrous membrane. Its upper border is directed ob- liquely upwards and backwards, owing to the great depth of its posterior surface. It gives at- tachment, in front, to the crico- thyroid membrane ; at the sides, to part of the same membrane and to the lateral Crico-aryte- noid muscle ; behind, the highest point of the upper border is surmounted on each side by a smooth, oval surface, for articulation with the arytenoid cartilage. Be- tween the articular surfaces is a slight notch, for the attachment of part of the Arytsenoideus muscle. The inner surface of the cricoid cartilage is smooth, and lined by mucous mem- brane. The Arytenoid Cartilages are so called from the resemblance they bear, when ruKi/j^wi CaTtlLafj, ARYTENOID- insertion *f CRlCO-AfirT*NOiO P«ftTlCl.SkTlATi*AM» CRICOID Arl/ettla r facet Ar-t/eufftr fnem, f separating the two bronchi, view of the interior. will be seen to occupy the left of the jn„£. median line, as was first shown by Mr. Goodall, of Dublin, so that any solid body descending the trachea, by virtue of the laws of gravity, would naturally be directed towards the right bronchus, and this tendency is undoubtedly aided by the larger size of this tube, as compared with its fellow. This fact serves to explain why a foreign sub- stance in the trachea almost universally falls into the right bronchus. The trachea is composed of imperfect cartilaginous rings, fibrous membrane, muscular fibres, longitudinal yellow elastic fibres, mucous membrane, and glands. The Cartilages vary from sixteen to twenty in number ; each forms an imper- fect ring, which surrounds about two-thirds of the cylinder of the trachea, being imperfect behind, where the tube is completed by fibrous membrane. The carti- lages are placed horizontally above each other, separated by narrow membranous intervals. They measure about two lines in depth, and half a line in thickness. Their outer surfaces are flattened, but, internally, they are convex, from being thicker in the middle than at the margins. The cartilages are connected together, at their margins, by an elastic fibrous membrane, which covers both their surfaces ; and in the space between their extremities, behind, forms a distinct layer. The peculiar cartilages are the first and the last. The first cartilage is broader than the rest, and sometimes divided at one end ; it is connected by fibrous membrane with the lower border of the cricoid cartilage, with which, or with the succeeding cartilage, it is sometimes blended. TRACHEA. 113 The last cartilage is thick and broad in the middle, in consequence of its lower border being prolonged downwards, and, at the same time, curved backwards, at the point of bifurcation of the trachea. It terminates on each side in an imper- fect ring, which incloses the commencement of the bronchi. The cartilage above the last is somewhat broader than the rest at its centre. Two or more of the cartilages often unite, partially or completely, and are sometimes bifurcated at their extremities. They are highly elastic, and seldom ossify, even in advanced life. In the right bronchus, the cartilages vary in number from six to eight ; in the left, from nine to twelve. They are shorter and narrower than those of the trachea. The Muscular Fibres are disposed in two layers, longitudinal and transverse. The longitudinal fibres are the most external, and arise by minute tendons from the termination of the tracheal cartilages, and from the fibrous membrane. The transverse fibres, the most internal, form a thin layer, which extends trans- versely between the ends of the cartilages, at the posterior part of the trachea. The muscular fibres are of the unstriped variety. The Elastic Fibres are situated beneath the mucous membrane, inclosing the entire cylinder of the trachea; they are most abundant at its posterior part, where they are collected into longitudinal bundles. The Mucous Membrane lining the tube is covered with columnar ciliated epithelium. It is continuous with that lining the larynx. The Tracheal Glands are found in great abundance at the posterior part of the trachea. They are small, flattened, ovoid bodies, placed between the fibrous and muscular coats, each furnished with an excretory duct, which opens on the surface of the mucous membrane. Some glands of smaller size are also found at the sides of the trachea, between the layers of fibrous tissue connecting the rings, and others immediately beneath the mucous coat. The secretion from these glands serves to lubricate the inner surface of the trachea. Vessels and Nerves. The trachea is supplied with blood by the inferior thyroid arteries. The veins terminate in the thyroid venous plexus. The nerves are derived from the pneumogastric and its recurrent branches, and from the sympa- thetic. Surgical Anatomy. The air-passage may be opened in three different situations ; through the crico-thyroid membrane (laryngotomy), through the cricoid cartilage and upper ring of the trachea (laryngo4racheotomy), or through the trachea below the isthmus of the thyroid gland (tracheotomy). The student should, therefore, carefully consider the relative anatomy of the air-tube in each of these situations. Beneath the integument of the laryngo-tracheal region, on either side of the median line, are the two anterior jugular veins. Their size and position vary; there is nearly always one, and frequently two : at the lower part of the neck they diverge, passing beneath the Sterno-mastoid muscles, and are frequently connected by a transverse communicating branch. These veins should, if possible, always be avoided in any operation on- the larynx or trachea. If cut through, considerable hemorrhage is the result. Beneath the cervical fascia are the Sterno-hyoid and Sterno-thyroid muscles, the contiguous edges of the former being near the median line, and beneath these muscles the following parts are met with, from above downwards ; the thyroid cartilage, the crico-thyroid membrane, the cricoid cartilage, the trachea, and the isthmus of the thyroid gland. The crico-thyroid space is very superficial, and may be easily felt, beneath the skin, as a depressed spot, about an inch below the pomum Adami : it is crossed transversely by a small artery, the crico-thyroid, the division of which is seldom accompanied by any troublesome hemorrhage. The isthmus of the thyroid gland usually crosses the second and third rings of the trachea ; above it, is found a large transverse communicating branch between the superior thyroid veins, and the isthmus is covered by a venous plexus, formed between the thyroid veins of opposite sides. On the sides of the thyroid gland, and below it, the veins converge to a single median vessel, or to two trunks which descend along the median line of the front of the trachea, to open into the innominate veins by valved orifices. In the infant, the thymus gland ascends a variable distance along the front of the trachea ; and the innominate artery crosses this tube obliquely at the root of the neck, from left to right. The arteria thyroidea ima, when that vessel exists, passes from below upwards along the front of the trachea. The upper part of the trachea lies comparatively superficial ; but the lower part passes obliquely downwards and backwards, so as to be deeply placed between the converging Sterno-mastoid muscles. In the child, the trachea 714 ORGANS OF VOICE AND RESPIRATION. is smaller, more deeply placed, and more movable than in the adult. In fat, or short-necked people, or in those in whom the muscles of the neck are prominently developed, the trachea is more deeply placed than in the opposite conditions. Fig. 363.— Surgical Anatomy of Laryngotracheal Region in the Infant. Cvioo-ikyroid Minnln le Artery Cricoid CartUagt &uj>eriar 2'Ayroul vein From these observations, it must be evident that laryngotomy is anatomically the most simple opei'ation, can most readily be performed, and should always be preferred when particular circumstances do not render the operation of tracheotomy absolutely necessary. The operation is performed thus: The head being thrown back and steadied by an assistant^ the finger is passed over the front of the neck, and the crico-thyroid depression felt for. A vertical incision is then made through the skin, in the middle line over this spot, and the crico-thyroid membrane is divided to a sufficient extent to allow of the introduction of a large curved tube. The crico- thyroid artery is the only vessel of importance crossing this space. If it should be of large size, its division might produce troublesome hemorrhage. Laryngo-tracheotomy, anatomatically considered, is more dangerous than tracheotomy, on account of the small interspace between the cricoid cartilage and the isthmus of the thyroid gland ; the communicating branches between the superior thyroid veins, which cover this spot, can hardly fail to be divided, and the greatest care will not, in some cases, prevent the division of part of the thyroid isthmus. If either of these structures is divided, the hemorrhage will be considerable. Tracheotomy below the isthmus of the thyroid gland is performed thus : The head being thrown back and steadied by an assistant, an incision, an inch and a half or two inches in length, is made through the skin, in the median line of the neck, from a little below the cricoid cartilage, to the top of the sternum. The anterior jugular veins should be avoided, by keeping exactly in the median line ; the deep fascia should then be divided, and the contiguous borders of the Sterno-hyoid muscles separated from each other. A quantity of loose areolar tissue, containing the inferior thyroid veins, must then be separated from the front of the trachea, with the handle of the scalpel ; and when the trachea is well exposed, it should be opened by inserting the knife into it, dividing two or three of its rings from below upwards. It is a matter of the greatest importance to restrain, if possible, all hemorrhage before the tube is opened ; otherwise, blood may pass into the trachea, and suffocate the patient. THE PLEURA. U5 The Pleura. Each lung is invested, upon its external surface, by an exceedingly delicate serous membrane, the pleura, which incloses the organ as far as its root, and is then reflected upon the inner surface of the thorax. The portion of the serous Fig. 364.— A Transverse Section of the Thorax, showing the Relative Position of the Viscera, and the Rellections of the Pleurae. TRIANGULARIS STCR luttrnaL JiLunmary Vessels Ltft Phrt'tie Ittrv* Plcuf^i fiulmonat** Pleura CoduUis Mediastinum- Posterior membrane investing the surface of the lung is called the -pleura pulmonalis (visceral layer of pleura), whilst that which lines the inner surface of the chest is called the pleura costalis (parietal layer of pleura). The interspace or cavity between these two layers is called the cavity of the pleura. Each pleura is therefore a shut sac, one occupying the right, the other the left half of the thorax; and they are perfectly separate, not communicating with each other. The two pleurae- do not meet in the middle line of the chest, excepting at one point in front ; an interspace being left between them, which contains all the viscera of the thorax, excepting the lungs : this is the mediastinum. Reflections of the pleura (fig. 364). Commencing at the sternum, the pleura passes outwards, covers the costal cartilages, the inner surface of the ribs and Intercostal muscles, and at the back of the thorax passes over the thoracic ganglia and their branches, and is reflected upon the sides of the bodies of the vertebras, where it is separated by a narrow interspace from the opposite pleura, the posterior mediastinum. From the vertebral column, the pleura passes to the side of the pericardium, which it covers to a slight extent ; it then covers the back part of the root of the lung, from the lower border of which a triangular fold descends vertically by the side of the posterior mediastinum to the Diaphragm. This fold is the broad ligament of the lung, the ligamentum latum pulmonis, and serves to retain the lower part of the organ in position. From the root, the 716 ORGANS OF VOICE AND RESPIRATION". pleura may be traced over the convex surface of the lung, the summit and base, and also over the sides of the fissures between the lobes. It covers its anterioi' surface, and front part of its root, and is reflected upon the side of the pericar- dium to the .;' P ncr- surface of the sternum. Below, it covers the upper surface of the Diaphragm. Above, its apex projects, in the form of a cul-de-sac, through the superior opening of the thorax into the neck, extending about an inch above the margin of the first rib, and receives the summit of the corresponding lung ; this sac is strengthened, according to Dr. Sibson, by a dome-like expansion of fascia, derived from the lower part of the Scaleni muscles. A little above the middle of the sternum, the contiguous surfaces of the two pleurae are in contact for a slight extent ; but, above and below this point, the interval left between them by their non-approximation forms the anterior mediastinum. The inner surface of the pleura is smooth, polished, and moistened by a serous fluid ; its outer surface is intimately adherent to the surface of the lung, and to the pulmonary vessels as they emerge from the pericardium ; it is also adherent to the upper surface of the Diaphragm ; throughout the rest of its extent it is somewhat thicker, and may be separated from the adjacent parts with extreme facility. The right pleural sac is shorter, wider, and reaches higher in the neck than the left. Vessels and Nerves. The arteries of the pleura are derived from the intercostal, the internal mammary, the phrenic, inferior thyroid, thymic, pericardiac, and bronchial. The veins correspond to the arteries. The lymphatics are very numerous. The nerves are derived from the phrenic and sympathetic (Luschka). Kolliker states that nerves accompany the ramifications of the bronchial arteries in the pleura pulmonalis. Mediastinum. The Mediastinum is the space left in the median line of the chest by the non- approximation of the two pleurae. It extends from the sternum in front to the spine behind, and contains all the viscera in the thorax, excepting the lungs. The mediastinum may be subdivided, for convenience of description, into the anterior, middle, and posterior. The anterior mediastinum is bounded in front by the sternum, on each side by the pleura, and behind by the pericardium. Owing to the oblique position of the heart towards the left side, this space is not parallel with the sternum, but directed obliquely from above downwards, and to the left of the median line ; it is broad oelow, narrow above, very narrow opposite the second piece of the sternum, the contiguous surfaces of the two pleurae being occasionally united over a small space. The anterior mediastinum contains the origins of the Sterno-hyoid and Sterno-thyroid muscles, the Triangularis sterni, the internal mammary vessels of the left side, the remains of the thymus gland, and a quantity of loose areolar tissue, containing some lymphatic vessels ascending from the convex surface of the liver. The middle mediastinum is the broadest part of the interpleural space. It contains the heart inclosed in the pericardium, the ascending aorta, the superior vena cava, the bifurcation of the trachea, the pulmonary arteries and veins, and the phrenic nerves. The posterior mediastinum is an irregular triangular space, running parallel with the vertebral column; it is bounded in front by the pericardium and roots of the lungs, behind by the vertebral column, and on either side by the pleura. It contains the descending aorta, the greater and lesser azygos veins and superior intercostal vein, the pneumogastric and splanchnic nerves, the oesophagus, thoracic duct, and some lymphatic glands. THE LUNGS. 717 The Lungs. The Lungs are the essential organs of respiration ; they are two in number, placed one in each of the lateral cavities of the chest, separated from each other by the heart and other contents of the mediastinum. Each lung is conical in shape, and presents for examination an apex, a base, two borders, and twc surfaces. The apex forms a tapering cone, which extends into the root of the neck, about an inch to an inch and a half above the level of the first rib. Fig. 365. — Front View of the Thorax. The Ribs and Sternum are represented in Relation to the Lungs, Heart, and other Internal Organs. The lose is broad, concave, and rests upon the convex surface of the Dia- phragm; its circumference is thin, and fits into the space between the lower ribs and the costal attachment of the Diaphragm, extending lower down externally and behind than in front. The external or thoracic surface is smooth, convex, of considerable extent, and corresponds to the form of the cavity of the chest, being deeper behind than in front. The inner surface is concave. It presents, in front, a depression corresponding to the convex surface of the pericardium, and, behind, a deep fissure, the hilum pulmonis, which gives attachment to the root of the lung. 718 ORGANS OF VOICE AND RESPIRATION The posterior border is rounded and broad, and is received in the deep con- cavity on either side of the spinal column. It is much longer than the anterior border, and projects below between the ribs and Diaphragm. The anterior border is thin and sharp, and overlaps the front of the peri- cardium. The anterior border of the right lung corresponds to the median line of the sternum, and is in contact with its fellow, the pleuras being interposed, as low as the fourth costal cartilage ; below this, the contiguous borders are separated by an irregularly-shaped interval, formed at the expense of the anterior border of the left lung, and corresponding to which the pericardium is exposed. Fig. 306. — Front View of the Heart and Lungs. Ductus Arter/orum Each lung is divided into two lobes, an upper and lower, by a long and deep fissure, which extends from the upper part of the posterior border of the organ, about three inches from its apex, downwards and forwards to the lower part of its anterior border. This fissure penetrates nearly to the root. In the right lung the upper lobe is partially divided by a second and shorter fissure, which extends from the middle of the preceding, forwards and upwards, to the anterior margin of the organ, marking off a small triangular portion, the middle lobe. The right lung is the largest ; it is broader than the left, owing to the inclination of the heart to the left side, and is also shorter by an inch, in consequence of the Diaphragm rising higher on the right side to accommodate the liver. The right lung has also three lobes. The left lung is smaller, narrower, and longer than the right, and has only two lobes. . . THE LUNGS. 719 A little above the middle of the inner surface of each lung, and nearer its pos- terior than its anterior border, is its root, by which the lung is connected to the heart and the trachea. It is formed by the bronchial tube, the pulmonary artery, the pulmonary veins, the bronchial arteries and veins, the pulmonary plexus of nerves, lymphatics, bronchial glands, and areolar tissue, all of which are inclosed by a reflection of the pleura. The root of the right lung lies behind the superior cava and upper part of the right auricle, and below the vena azygos. That of the left lung passes beneath the arch of the aorta, and in front of the descending aorta; the phrenic nerve and the anterior pulmonary plexus lie in front of each, and the pneumogastric and posterior pulmonary plexus behind each. The structures composing the root of each lung are arranged in a similar manner from before backwards on both sides, viz. ; — the pulmonary veins most anterior, the pulmonary artery in the middle, and the bronchus, together with the bronchial vessels, behind. From above downwards, on the two sides, their arrangement differs, thus: — On the right side, their position is, bronchus, pulmonary artery, pulmonary veins; on the left side, their position is, pulmonary artery, bronchus, pulmonary veins : this is accounted for by the bronchus being placed on a lower level on the left than on the right side. The weight of both lungs together is about forty-two ounces, the right lung being two ounces heavier than the left ; but much variation is met with according to the amount of blood or serous fluid they may contain. The lungs are heavier in the male than in the female, their proportion to the body being, in the former, as 1 to 37, in the latter as 1 to 43. The specific gravity of the lung tissue varies from 345 to 746, water being 1000. The color of the lungs at birth is of a pinkish white; in adult life, mottled in patches, of a dark slate color ; and, as age advances, this mottling assumes a dark black color. The coloring matter consists of granules of a carbonaceous substance, deposited in the areolar tissue near the surface of the organ. It increases in quantity as age advances, and is more abundant in males than in females. The posterior border of the lung is usually darker than the anterior. The surface of the lung is smooth, shining, and marked out into numerous poly- hedral spaces, which represent the lobules of the organ, and the area of each of these spaces is crossed by numerous lighter lines. The substance of the lung is of a light, porous, spongy texture ; it floats in water, and crepitates when handled, owing to the presence of air in the tissue. It is also highly elastic ; hence the collapsed state of these organs when they are removed from the closed cavity of the thorax. Structure. The lungs are composed of an external serous coat, a subserous areolar tissue, and the pulmonary substance or parenchyma. The serous coat is derived from the pleura; it is thin, transparent, and invests the entire organ as far as the root. The subserous areolar tissue contains a large proportion of elastic fibres ; it invests the entire surface of the lung, and extends inwards between the lobules. The "parenchyma is composed of lobules, which, although closely connected together by an interlobular areolar tissue, are quite distinct from one another, being easily separable in the foetus. The lobules vary in size : those on the surface are large, of a pyramidal form, the base turned towards the surface ; those in the interior are smaller, and of various forms. Each lobule is composed of one of the ramifications of the bronchial tube and its terminal air-cells, of the ramifications of the pulmonary and bronchial vessels, lymphatics, and nerves; all of these structures being connected together by areolar fibrous tissue. The bronchus, upon entering the substance of the lung, divides and subdivides dichotomously throughout the entire organ. Sometimes three branches arise together, and occasionally small lateral branches are given off from the sides of a main trunk. Each of the smaller subdivisions of the bronchi enters a pulmonary 720 ORGANS OF VOICE AND RESPIRATION. lobule (lobular bronchial tube), and, again subdividing, ultimately terminates in the intercellular passages and air-cells of which the lobule is composed. Within the lungs the bronchial tubes are circular, not flattened, and their constituent elements present the following peculiarities of structure. The cartilages are not imperfect rings, but consist of thin laminaa, of varied form and size, scattered irregularly along the sides of the tube, being most distinct at the points of division of the bronchi. They may be traced into tubes the dia- meter of which is only one-fourth of a line. Beyond this point, the tubes are wholly membranous. The fibrous coat and longitudinal elastic fibres are con- tinued into the smallest ramifications of the bronchi. The muscular coat is dis- posed in the form of a continuous layer of annular fibres, which may be traced upon the smallest bronchial tubes ; they consist of the unstriped variety of muscular fibre. The mucous membrane lines the bronchi and its ramifications throughout, and is covered with columnar ciliated epithelium. According to the observations of Mr. Rainey, 1 the lobular bronchial tubes, on entering the substance of the lobules, divide and subdivide from four to nine times, according to the size of the lobule, continuing to diminish in size until they attain a diameter of ^th to ^ D th of an inch. They then become changed in structure, losing their cylindrical form, and are continued onwards as irregular passages (intercellular passages), through the substance of the lobule, their sides and ex- tremities being closely covered by numerous saccular dilatations, the air-cells. This arrangement resembles most closely the naked eye appearances observed in the reticulated structure of the lung of the tortoise, and other reptilia. The air-cells are small, polyhedral, alveolar recesses, separated from each other by thin septa, and communicating freely with the intercellular passages. They are well seen on the surface of the lung, and vary from 5 ^th to ^th of an inch in diameter, being largest on the surface, at the thin borders, and at the apex, and smallest in the interior. At the termination of the bronchial tubes, in the intercellular passages, their constituent elements become changed ; their walls are formed by an interlacing of the longitudinal elastic bundles with fibrous tissue, the muscular fibres disappear, and the mucous membrane becomes thin and delicate, and lined with a layer of squamous epithelium. The latter membrane lines the air-cells, and forms by its reduplications the septa intervening between them. The Pulmonary Artery conveys the venous blood to the lungs ; it divides into branches which accompany the bronchial tubes and terminates in a dense capillary network upon the walls of the intercellular passages and air-cells. From this network, the radicles of the pulmonary veins arise ; coalescing into large branches, they accompany the arteries, and return the blood, purified by its passage through the capillaries, to the left auricle of the heart. In the lung, the branches of the pulmonary artery are usually above and in front of a bronchial tube, the vein below. The Pulmonary Capillaries form plexuses which lie immediately beneath the mucous membrane, on the walls and septa of the air-cells, and upon the walls of the intercellular passages. In the septa between the cells, the capillary network forms a single layer. The capillaries are very minute, the meshes being only slightly wider than the vessels ; their walls are also exceedingly thin. The Bronchial Arteries supply blood for the nutrition of the lung ; they are derived from the thoracic aorta, and, accompanying the bronchial tubes, are dis- tributed to the bronchial glands, and upon the walls of the larger bronchial tubes and pulmonary vessels, and terminate- in the deep bronchial veins. Others are distributed in the interlobular areolar tissue, and terminate partly in the dee]), partly in the superficial, bronchial veins. Lastly, some ramify upon the walls of the smallest bronchial tubes, and terminate in the pulmonary veins. The Superficial and Deep Bronchial Veins unite at the root of the lung, and 1 Medico-Chirurgical Transactions, vol. xxviii. 1845. THYROID GLAND. 121 terminate oi\ the right side in the vena azygos ; on the left side, in the superior intercostal vein. The Lymphatics consist of a superficial and deep set ; they terminate at the root of the lung, in the bronchial glands. Nerves. The lungs are supplied from the anterior and posterior pulmonary plexuses, formed chiefly by branches from the sympathetic and pneumogastric. The filaments from these plexuses accompany the bronchial tubes upon which they are lost. Small ganglia have been found by Eemak upon the smaller branches of these nerves. Thyroid Gland. The Thyroid Gland bears much resemblance in structure to other glandular organs, and is usually classified together with the thymus, supra-renal glands, and spleen, under the head of ductless glands, from its possessing no excretory duct. Its function is unknown, but, from its situation in connection with the trachea and larynx, is usually described with these, although taking no part in the function of respiration. It is situated at the upper part of the trachea, and consists of two lateral lobes, placed one on each side of this tube, connected together by a narrow transverse portion, the isthmus. Its anterior surface is convex, and covered by the Sterno-hyoid, Sterno-thyroid, and Omo-hyoid muscles. Its lateral surfaces, also convex, lie in contact with the sheath of the common carotid artery. Its posterior surface is concave, and embraces the trachea and larynx. The posterior borders of the gland extend as far back as the lower part of the pharynx. This gland is of a brownish-red color. Its weight varies from one to two ounces. It is larger in females than in males, and becomes slightly increased in size during menstruation. It occasionally becomes enormously hj'pertrophied, con- stituting the disease called bronchocele or goitre. Each lobe is somewhat conical in shape, about two inches in length, and three-quarters of an inch in breadth, the right lobe being rather the larger of the two. The isthmus connects the lower third of the two lateral lobes ; it measures about half an inch in breadth, and the same in depth, and usually covers the second and third rings of the trachea. Its situation presents, however, many variations, a point of some importance in the operation of tracheotomy. Sometimes the isthmus is altogether wanting. A third lobe, of conical shape, called the pyramid, occasionally arises from the left side of the upper part of the isthmus, or from the left lobe, and ascends as high as the hyoid bone. It is occasionally quite detached, or divided into two parts, or altogether wanting. A few muscular bands are occasionally found attached, above, to the body of the hyoid bone, and, below, to the isthmus of the gland, or its pyramidal process ; these were named by Soemmering, the Levator rjlandulve tltyroideve. Structure. The thyroid consists of numerous minute closed vesicles, com- posed of a homogeneous membrane, inclosed in a dense capillary plexus, and connected together into imperfect lobules by areolar tissue. These vesicles are spherical or oblong, perfectly distinct, and contain a yellowish fluid, in which are found floating numerous "dotted corpuscles" and cells. The fluid coa- gulates by heat or alcohol, but preserves its transparency. In the foetus and in young subjects, the corpuscles lie in a single layer, in contact with the inner surface of these cavities, and become detached during the process of growth. Vessels and Nerves. The arteries supplying the thyroid are the superior and inferior thyroid, and sometimes an additional branch from the arteria innominata, which ascends from this vessel upon the front of the trachea. The arteries arc 46 722 ORGANS OF YOICE AND RESPIRATION. remarkable for their large size and frequent anastomoses. The veins form a plexus on the surface of the gland, and on the front of the trachea, from which arise the superior, middle, and inferior thyroid veins ; the two former terminating in the internal jugular, the latter in the vena innominata. The lymphatics are numerous, of large size, and terminate in the thoracic and right lymphatic ducts. The nerves are derived from the pneumogastric, and from the middle and inferior cervical ganglia of the sympathetic. Chemical Composition. The thyroid gland consists of albumen, traces of gela- tin, stearin, olein, extractive matter, alkaline and earthy salts, and water. The salts are chloride of sodium, alkaline sulphate, phosphate of potash, lime, mag- nesia, and a trace of oxide of iron. Thymus Gland. The Thymus Gland presents much resemblance in structure to other glandular organs, and is classified under the head of the ductless glands, from its possessing no excretory duct. The thymus gland is a temporary organ, attaining its full size at the end of the second year, when it ceases to grow, and gradually dwindles, until, at puberty, it has almost disappeared. If examined when its growth is most active, it will be found to consist of two lateral lobes, placed in close contact along the middle line, situated partly in the anterior mediastinum, partly in the neck, and extending from the fourth costal cartilage upwards, as high as the lower border of the thyroid gland. It is covered by the sternum, and by the origins of the Sterno-hyoid and Sterno -thyroid muscles. In the mediastinum, it rests upon the pericardium, being separated from the arch of the aorta and great vessels, by the thoracic fascia. In the neck, it lies on the front and sides of the trachea, behind the Sterno-hyoid and Sterno-thyroid muscles. The two lobes generally differ in size ; they are occasionally united so as to form a single mass, and sometimes separated by an intermediate lobe. The thymus is of a pinkish-gray color, soft, and lobulated on its surfaces. It is about two inches in length, one and a half in breadth, below, and about three or four lines in thickness. At birth, it weighs about half an ounce. Structure. Each lateral lobe is composed of numerous lobules, held together by delicate areolar tissue, the entire gland being inclosed in an investing capsule of a similar, but denser, structure. The primary lobules vary in size from a pin's head to a small pea. Each lobule contains, in its interior, a small cavity, which is surrounded with smaller or secondary lobules, which are also hollow within. The cavities of the secondary and primary lobules communicate ; those of the latter opening into the great central cavity or reservoir of the thymus, which extends through the entire length of each lateral half of the gland. The central cavity is lined by a vascular membrane, which is prolonged into all the subordinate cavities, and contains a milk-white fluid resembling chyle. If the investing capsule and vessels, as well as the areolar tissue connecting the lobules, are removed from the surface of either lateral lobe, it will be seen that the •central cavity is folded upon itself, and admits of being drawn out into a lengthened tubular cord, around which the primary lobules are attached in a spiral manner, like knots upon a rope. Such is the condition of the organ at an early period of its development ; for Mr. Simon has shown, that the primitive form of the thymus is a linear tube, from which, as its development proceeds, lateral diverticula lead outwards, the tube ultimately becoming obscure, from its surface being covered with numerous lobules. According to Oesterlen and Mr. Simon, the cavities in the secondary lobules are surrounded by rounded saccular dilatations or vesicles, which open into it. These vesicles are formed of a homogeneous membrane, inclosed in a dense capil- lary plexus. The whitish fluid contained in the vesicles and central cavity of the thymus THYMUS GLAND. 723 contains numerous dotted corpuscles, similar to those found in the chyle. The corpuscles are flattened circular disks, measuring about T TyW of an inch in dia- meter. Vessels and Nerves. The arteries supplying the thymus are derived from the internal mammary, and from the superior and inferior thyroid. The veins termi- nate in the left vena innominata, and in the thyroid veins. The lymphatics are of large size, arise in the substance of the gland, and are said to terminate in the internal jugular vein. Sir A. Cooper considered that these vessels carried into the blood the secretion formed in the substance of the thymus. The nerves are exceedingly minute ; they are derived from the pneumogastric and sympathetic. Branches from the descendens noni and phrenic reach the investing capsule, but do not penetrate into the substance of the gland. Chemical Composition. The solid animal constituents of the thymus are albu- men and fibrin in large quantities, gelatin and other animal matters. The salts are alkaline and earthy phosphates, with chloride of potassium. It contains about 80 per cent, of water. The Urinary Organs. The Kidneys. The Kidneys are two glandular organs, intended for the secretion of the urine. They are situated at the back part of the abdominal cavity, behind the peri- toneum, one in each lumbar region, extending from the eleventh rib to near the crest of the ilium; the right one being lower than the left, from its vicinity to the liver. They are usually surrounded by a considerable quantity of fat, and are retained in their position by the vessels which pass to and from them. Relations. The anterior surface of the kidney is convex, partially covered by the peritoneum, and is in relation, on the right side, with the back part of the right lobe of the liver, the descending portion of the duodenum, and ascending colon ; and on the left side with the great end of the stomach, the lower end of the spleen, the tail of the pancreas, and the descending colon. The posterior surface is flattened, and rests upon the corresponding crus of the Diaphragm, in front of the eleventh and twelfth ribs, on the anterior lamella of the aponeurosis of the Transversalis which separates it from the Quadratus lum- borum, and on the Psoas magnus. The superior extremity, directed inwards, is thick and rounded, and embraced by the supra-renal capsule. It corresponds, on the left side, to the upper border of the eleventh rib, and on the right side to the lower border. The inferior extremity, small and flattened, extends nearly as low as the crest of the ilium. The external border is convex, and directed outwards towards the parietes of the abdomen. The internal border is concave, and presents a deep notch, the hilus of the kidney, more marked behind than in front. At the hilus, the vessels, excretory duct, and nerves pass into or from the organ ; the branches of the renal vein lying in front, the artery and its branches next, the excretory duct or ureter being behind and below. On the vessels the nerves and lymphatics ramify, and much cellular tissue and fat surrounds the whole. The hilus leads into a hollow space, the sinus, which occupies the interior of the gland. Each kidney is about four inches in length, two inches in breadth, and about one inch in thickness ; the left one being somewhat longer and thinner than the right. The weight of the kidney in the adult male varies from 4J oz. to 6 oz. ; in the female, from 4 oz. to 5| oz., the difference between the two being about half an ounce. The left is nearly always heavier than the right, by about two drachms. Their weight in proportion to the body is about 1 to 240. The renal substance is dense, firm, extremely fragile, and of a deep red color. The kidney is invested by a fibrous capsule, formed of dense fibro-areolar tissue. It is thin, smooth, and easily removed from its surface, to which it is con- nected by fine fibrous processes and vessels ; and at the hilus is continued inwards, lining the sides of the sinus, and at the bottom of that cavity forms sheaths around the bloodvessels and the subdivisions of the excretory duct. On making a vertical section through the organ, from its convex to its concave border, it appears to consist of two different substances, viz., an external or cor- tical, and an internal or medullary, substance. The cortical substance forms about three-fourths of the gland. It occupies the 724 THE KIDNEYS. 725 Fig. 367. — Vertical Section of Kidney, surface of the kidney, forming a layer about two lines in thickness, where it covers the pyramids, and sends numerous prolongations inwards, towards the sinus between the pyramids. The cortical substance is soft, reddish, granular, easily lacerated, and contains nu- merous small red bodies disseminated through it in every part, excepting towards the free surface. These are the Malpighian bodies. The cortical substance is composed of a mass of convoluted tubuli uriniferi, bloodvessels, lymphatics, and nerves, connected together by a firm, transparent, granular substance, which contains small granular cells. The medullary substance consists of pale, reddish-colored, conical masses, the pyra- mids of Malpighi, varying in number from eight to eighteen; their bases are directed towards the circumference of the organ, whilst their apices, which are free from the cortical substance, converge towards the sinus, and terminate in smooth, rounded ex- tremities, called the papillse (mammillae) of the kidney. Sometimes, two of the masses are joined, and have between them only one papilla. The kidney is thus seen to consist of a number of conical-shaped masses, each inclosed, excepting at the apex, by an invest- ment of the cortical substance ; these repre- sent the separate lobules of which the human kidney in the foetus consists, a condition observed permanently in the kidneys of many of the lower animals. - As the human kidney becomes developed, the adjacent lobules coalesce, so as to form a single gland, the surface of which, even in the adult, occasionally presents faint traces of a lobular subdivision. The medullary substance is denser in structure than the cortical, darker in color, and presents a striated appearance, from being composed of a number of minute diverging tubes (tubuli uriniferi). The tubuli uriniferi commence at the apices of the cones by small orifices, which vary from 3tf?y to 2 £ff of an inch; as they pass up in the medullary substance, towards the peri- phery, they pursue a diverging course, di- viding and subdividing at very acute angles, until they reach the cortical substance, when they become convoluted, anastomose freely with each other, and retain the same diameter. The number of orifices on the entire surface of a single papilla is, according to Huschke, about a thousand ; from four to five hundred large, and as many smaller ones. The tubuli uriniferi are formed of a transparent homo- geneous basement membrane, lined by sphe- roidal epithelium, which occupies about two- thirds of the diameter of the tube. The tubes are separated from one another, in the medullury cones, by capillary vessels, which form oblong meshes parallel with the tubuli, and by an intermediate parenchymatous substance composed of cells. As soon as the tubuli uriniferi enter the cortical substance (fig. 368), they Fig. 368. — Minute Structure of Kidney. >i"t# 726 URINARY ORGANS. become convoluted, and anastomose freely with each other ; they are sometimes called the tubes of Ferrein. At the bases of the pyramids, the straight tubes are described as being collected into small conical bundles, the tortuous tubuli cor- responding to which are prolonged upwards into the cortical portion of the kidney as far as the surface, forming a number of small conical masses, which are named the pyramids of Ferrein, several of which correspond to each medullary cone and its corresponding portion of cortical substance. According to Mr. Bowman, the tubuli uriniferi commence in the cortical substance as small, dilated, membranous capsules, the capsules of the Malpighian bodies ; they also form loops, either by the junction of adjacent tubes, or, according to Toynbee, by the union of two branches proceeding from the same tube ; they have also been seen to arise by free closed extremities. The Malpighian bodies are found only in the cortical substance of the kidney. They are small round bodies, of a deep red color, and of the average diameter of the yl^ of an inch. Each body is composed of a vascular tuft inclosed in a thin membranous capsule, the dilated commencement of a uriniferous tubule. The vascular tuft consists of the ramifications Of a minute artery, the afferent vessel, which, after piercing the capsule, divides, in a radiated manner, into several branches, which ultimately terminate in a finer set of capillary vessels. From these, a small vein, the efferent vessel, proceeds ; this pierces the capsule near the artery, and forms a close venous plexus, with the efferent vessels from other Malpighian bodies, round the adjacent tubuli. The capsular dilatation of the Malpighian body is not always placed at the commencement of the tube ; it may occupy one side (Gerlach) : hence their sub- division into lateral or terminal. The membrane composing it is thicker than that of the tubule ; the epithelium lining its inner surface is thin, and, in the frog, provided with ciliae at the neck of the dilated portion ; but in the human subject, ciliae have not been detected. According to Mr. Bowman, the surface of the vascular tuft lies free and uncovered in the interior of its capsule ; but, according to Gerlach, it is covered with a thick layer of nucleated cells, similar to those lining the inner surface of the capsule. Ducts. The ureter, as it approaches the hilus, becomes dilated into a funnel- shaped membranous sac, the pelvis. It then enters the sinus, and subdivides usually into three prolongations, the infundibula, one placed at each extremity, and one in the middle of the organ ; these subdivide into from seven to thirteen smaller tubes, the calyces, each of which embraces, like a cup-like pouch or calyx, the base of one of the papillae. Sometimes, a calyx incloses two or more papillae. The ureter, the pelvis, and the calyces consist of three coats, — fibrous, muscular, and mucous. The external or fibro-elastic coat is continuous, round the bases of the papillae, with the tunica propria investing the surface of the organ. The muscular coat is placed between the fibrous and mucous coats. It consists of an external or longitudinal, and an internal or circular stratum. The internal or mucous coat invests the papillae of the kidney, and is continued into the orifices upon their surfaces. It is lined by epithelium of the spheroidal kind. Vessels, and Nerves. The renal artery is large in proportion to the size of the organ which it supplies. Each vessel divides into four or five branches, which enter the hilus, and are invested by sheaths derived from the fibrous capsule ; they penetrate the substance of the organ between the papillae, and enter the cortical substance in the intervals between the medullary cones, dividing and subdividing in their course towards the bases of the pyramids, where they form arches by their anastomoses ; from these arches, numerous vessels are distributed to the cortical substance, some of which enter the Malpighian corpuscles, whilst others form a capillary network round the uriniferous tubes. The veins of the kidney commence upon the surface of the organ, where they have a stellate arrangement ; they pass inwards, and open into larger veins, which URETERS — SUPRA-RENAL CAPSULES. 727 unite into arches round the bases of the medullary cones. After receiving the venous plexus from the tubular portion, they accompany the branches of the arteries to the sinus of the kidney, where they finally unite to form a single vein, which terminates in the inferior vena cava. The lymphatics of the kidney consist of a superficial and deep set ; they accom- pany the bloodvessels, and terminate in the lumbar glands. The nerves are derived from the renal plexus, which is formed by filaments from the solar plexus and lesser splanchnic nerve ; they accompany the branches of the arteries. From the renal plexus, some filaments pass to the spermatic- plexus and ureter. The Ureters. The Ureter is the excretory duct of the kidney. It is a cylindrical mem- branous tube, from sixteen to eighteen inches in length, and of the diameter of a goose-quill. It is placed at the back part of the abdomen, behind the peritoneum ; and extends obliquely downwards and inwards, from the lower part of the pelvis of the kidney, enters the cavity of the pelvis, and then passes downwards, for- wards, and inwards, to the base of the bladder, into which it opens by a con- stricted orifice, after passing obliquely, for nearly an inch, between its muscular and mucous coats. Relations. In its course from above downwards, it rests upon the Psoas muscle, being covered by the peritoneum, and crossed in front very obliquely by the spermatic vessels ; the right ureter lying close to the outer side of the inferior vena cava. Opposite the sacrum, it crosses the common or the external iliac artery, lying behind the ileum on the right side, and the sigmoid flexure of the colon on the left. In the pelvis, it enters the posterior false ligament of the bladder, and runs below the obliterated hypogastric artery, the vas deferens, in the male, passing between it and the bladder. In the female, the ureter passes along the sides of the cervix uteri and upper part of the vagina. At the base of the bladder, it is situated about two inches from its fellow ; lying, in the male, about an inch and a half behind the base of the prostate, at the posterior angle of the trigone. Structure. The ureter is composed of three coats, fibrous, muscular, and mucous. The fibrous coat is continuous with that surrounding the pelvis. The muscular coat consists of two layers of longitudinal fibres, and an inter- mediate transverse layer. The mucous coat is smooth, and presents a few longitudinal folds, which become effaced by distension. It is continuous with the mucous membrane of the bladder below ; whilst, above, it is prolonged over the papillae into the tubuli uriniferi. The epithelial cells lining it are spheroidal. The arteries supplying the ureter are branches of the renal, spermatic, internal iliac, and inferior vesical. The nerves are derived from the inferior mesenteric, spermatic, and hypo- gastric plexuses. Supra-renal Capsules. The Supra-renal Capsules are usually classified, together with the spleen, thymus, and thyroid, under the head of "ductless glands," as they have no excre- tory duct. They are two small flattened glandular bodies, of a yellowish color, situated at the back part of the abdomen, behind the peritoneum, immediately in front of the upper end of either kidney ; hence their name. The right one is somewhat triangular in shape, bearing a resemblance to a cocked hat ; the left is more semilunar, and usually larger and higher than the right. They vary in size in different individuals, being sometimes so small as to be scarcely detected, at other times large. They measure from *>n inch and a quarter to nearly two 728 URINARY ORGANS. inches in length, are rather less in width, and from two to three lines in thickness. In weight, they vary from one to two drachms. Relations. The anterior surface of the right supra-renal capsule is in relation with the under surface of the liver ; that of the left with the pancreas and spleen. The posterior surface rests upon the crus of the Diaphragm, opposite the tenth dorsal vertebra. Their upper thin convex border is directed upwards and inwards. Their lower thick concave bonier rests upon the upper end of the kidneys, to which they are connected by areolar tissue. Their inner borders are in relation with the great splanchnic nerves and semilunar ganglia, and lie in contact on the right side with the inferior vena cava, and on the left side with the aorta. The surface of the supra-renal gland is surrounded by areolar tissue containing much fat, and closely invested by a thin fibrous coat, which is difficult to remove, on account of the numerous fibrous processes and vessels which enter the organ through the furrows on its anterior surface and base. Structure. On making a perpendicular section, the gland is seen to consist of two substances, external or cortical, and internal or medullary. The cortical substance forms the chief part of the organ ; it is of a deep yellow color, and v consists of narrow columnar masses placed perpendicularly to the surface. The medullary substance is soft, pulpy, and of a dark brown or black color ; hence the name, atrabiliary capsules, given to these organs. In its centre is often seen a space formed by the breaking down of its component parts. According to the researches of Oesterlen and Mr. Simon, the narrow columnar masses of which the cortical substance is composed measure about T J ^th of an inch in diameter, and consist of small closed parallel tubes of limitary membrane containing dotted nuclei, together with much granular matter, oil globules, and nucleated cells. According to Ecker, the apparent tubular canals consist of rows of closed vesicles placed endwise, so as to resemble tubes ; whilst Kolliker states, that these vesicles are merely loculi or spaces in the stroma of the organ, having no limitary membrane, and, from being situated endwise, present the appearance of linear tubes. Nucleated cells exist in large numbers in the supra-renal glands of ruminants, but more sparingly in man and other animals, but the granular matter appears to form their chief constituent; the granules vary in size, and they present the singular peculiarity of undergoing no change when acted upon by most of the chemical reagents. The columnar masses are surrounded by a close capillary network, which runs parallel with them. The medullary substance consists of nuclei and granular matter, uniformly scattered throughout a plexus of minute veins. The arteries supplying the supra-renal glands are numerous and of large size, and are derived from the aorta, the phrenic, and the renal ; they subdivide into numerous minute branches previous to entering the substance of the gland. The supra-renal vein returns the blood from the medullary venous plexus, and receives several branches from the cortical substance ; it opens on the right side into the inferior vena cava, on the left side into the renal vein. The lymphatics terminate in the lumbar glands. The nerves are exceedingly numerous; they are derived from the solar and renal plexuses, and, according to Bergmann, from the phrenic and pneumogastric nerves. They have numerous small ganglia developed upon them. The Pelvis. The Cavity of the Pelvis is that part of the general abdominal cavity which is below the level of the linea ilio-pectinea and the promontory of the sacrum. Boundaries. It is bounded, behind, by the sacrum, the coccyx, and the great sacro-sciatic ligaments ; in front and at the sides, by the pubes and ischia, covered by the Obturator muscles; above, it communicates with the cavity of the abdomen; and below, it is limited by the Levatores ani and Coccygei muscles, and the BLADDER. 729 visceral layer of the pelvic fascia, which is reflected from the wall of the pelvis on to the viscera. Contents. The viscera contained in this cavity are the urinary bladder, the lower end of the rectum, and some of the generative organs peculiar to each sex ; they are partially covered by the peritoneum, and supplied with blood and lymphatic vessels and nerves. The Bladder. The Bladder is the reservoir for the urine. It is a musculo-membranous sac, situated in the pelvis, behind the pubes, and in front of the rectum in the male, the uterus and vagina intervening between it and that intestine in the female. The shape, position, and relations of the bladder are greatly influenced by age, sex, and the degree of distension of the organ. During infancy, it is conical in shape, and projects above the upper border of the pubes into the hypogastric region. In the adult, when quite empty and contracted, it is a small triangular Fig. 369. — Vertical Section of Bladder, Penis, and Urethra. Covftr'k CI Prtpuo* sac, placed deeply in the pelvis, flattened from before backwards, its apex reaching as high as the upper border of the symphysis pubis. When slightly distended, it has a rounded form, and partially fills the pelvic cavity; when greatly distended it is ovoid in shape, rising into the abdominal cavity, often extending upwards nearly as high as the umbilicus. It is larger in its vertical diameter than from side to side, and its long axis is directed from above obliquely downwards and backwards in a line directed from some point between the pubes and umbilicus (according to its distension) to the end of the coccyx. The bladder, when distended, is slightly curved forwards towards the anterior wall of the abdomen, so as to be more 130 URINARY ORGANS. convex behind than in front. In the female, it is larger in the transverse than in the vertical diameter, and its capacity is said to be greater than in the male. "When moderately distended, it measures about five inches in length, and three inches across, and the ordinary amount which it contains is about a pint. The bladder is divided into a summit, body, base, and neck. The summit or apex of the bladder is rounded and directed forwards and upwards ; it is connected to the umbilicus by a fibro-muscular cord, the urachus, and also by means of two rounded fibrous cords, the obliterated portions of the hypogastric arteries, which are placed one on each side of the urachus. The summit of the bladder behind the urachus is covered by peritoneum, whilst the portion in front is uncovered by it, and rests upon the abdominal wall. The urachus is the obliterated remains of a tubular canal existing in the embryo, which connects the cavity of the bladder with a membranous sac placed external to the abdomen, opposite the umbilicus, called the allantois. In the infant at birth, it is occasionally found pervious, so that the urine escapes at the umbilicus, and calculi have been found in its canal. The body of the bladder in front is not covered by peritoneum, and is in relation with the triangular ligament of the urethra, the posterior surface of the symphysis pubis, the Internal obturator muscles, and, when distended, with the abdominal parietes. The posterior surface is covered by peritoneum throughout. It corresponds, in the male, with the rectum ; in the female, with the uterus, some convolutions of the small intestine being interposed. The side of the bladder is crossed obliquely from below, upwards and forwards, by the obliterated hypogastric artery ; above and behind this cord, the bladder is covered by peritoneum, but, below and in front of it, the serous covering is wanting, and it is connected to the pelvic fascia. The vas deferens passes, in an arched direction, from before backwards, along the side of the bladder, towards its base, crossing in its course the obliterated hypogastric artery, and passing along the inner side of the ureter. The base or fundus of the bladder is directed downwards and backwards. It varies in extent according to the state of distension of the organ, being very broad when full, but much narrower when empty. In the male, it rests upon the second portion of the rectum, from which it is separated by a reflection of the recto- vesical fascia. It is covered posteriorly, for a slight extent, by the peri- toneum, which is reflected from it upon the rectum, forming the recto-vesical fold. The portion of the bladder in relation with the rectum corresponds to a triangular space, bounded behind by the recto-vesical fold ; on either side, by the vesicula seminalis and vas deferens; and, in front, by the prostate gland. When the bladder is very full, the peritoneal fold is raised with it, and the distance between its reflection and the anus is about four inches, but this distance is much diminished when the bladder is empty and contracted. In the female, the base of the bladder lies in contact with the lower part of the cervix uteri, is adherent to the anterior wall of the vagina, and separated from the upper part of the anterior surface of the cervix uteri by a fold of the peritoneum. The cervix or neck of the bladder is the constricted portion continuous with the urethra. In the male, its direction is oblique in the erect posture, and it is surrounded by the prostate gland. In the female, its direction is obliquely down- wards and forwards. Ligaments. The bladder is retained in its place by ligaments, which are divided into true and false. The true ligaments are five in number, two anterior and two lateral, formed by the recto-vesical fascia, and the urachus. The false ligaments, also five in number, are formed by folds of the peritoneum. The anterior ligaments (pubo-prostatic) extend from the back of the pubes, one on each side of the symphysis, to the front of the neck of the bladder, and upper surface of the prostate gland. These ligaments contain a few muscular fibres, prolonged from the bladder. STRICTURE OF THE BLADDER. 731 The lateral ligaments, broader and thinner than the preceding, are attached to the lateral parts of the prostate, and to the sides of the base of the bladder. The urachus is the fibro-muscular cord already mentioned, extending between the summit of the bladder and the umbilicus. It is broad below, at its attachment to the bladder, and becomes narrower as it ascends. The false ligaments of the bladder are, two posterior, two lateral, and one superior. The two posterior pass forwards, in the male, from the sides of the rectum ; in the female, from the sides of the uterus, to the posterior and lateral aspect of the bladder : they form the lateral boundaries of the recto- vesical fold of peritoneum, and contain the obliterated hypogastric arteries, the ureters, and vessels and nerves. The two lateral ligaments are reflections of the peritoneum, from the iliac fossae to the sides of the bladder. The superior ligament is the prominent fold of peritoneum extending from the summit of the bladder to the umbilicus. It covers the urachus, and the obliterated hypogastric arteries. Structure. The bladder is composed of four coats : — a serous, a muscular, a cel- lular, and a mucous coat. The serous coat is partial, and derived from the peritoneum. It invests the posterior surface, from opposite the termination of the two ureters to its summit, and is reflected from this point and from the sides, on to the abdominal and pelvic walls. The muscular coat consists of two layers of unstriped muscular fibre, an external layer, composed of longitudinal fibres, and an internal layer of circular fibres. The longitudinal fibres are most distinct on the anterior and posterior surfaces of the organ. They arise, in front, from the anterior ligaments of the bladder, from the neck of the bladder, and, in the male, from the adjacent portion of the prostate gland. They spread out, and form a plexiform mesh, on the anterior surface of the bladder, being continued over the posterior surface and base of the organ to the neck, where they are inserted into the prostate in the male, and into the vagina in the female. Other longitudinal fibres arise, in the male, from the sides of the prostate, and spread out upon the sides of the bladder, intersecting with one another. The circular fibres are very thinly and irregularly scattered on the body of the organ ; but, towards its lower part, round the cervix and commencement of the urethra, they are disposed as a thick circular layer, forming the sphincter vesicae, which is continuous with the muscular fibres of the prostate gland. Two bands of oblique fibres, originating behind the orifices of the ureters, converge to the back part of the prostate gland, and are inserted, by means of a fibrous process, into the middle lobe of this organ. They are the muscles of the ureters, described by Sir C. Bell, who supposed that, during the contraction of the bladder, they served to retain the oblique direction of the ureters, and so prevent the reflux of urine into them. The cellular coat consists of a layer of areolar tissue, connecting together the muscular and mucous coats, being intimately connected with the latter. The mucous coat is thin, smooth, and of a pale rose color. It is continuous through the ureters with the lining membrane of the uriniferous tubes, and, below, with the urethra. It is connected loosely to the muscular coat, by a layer of areolar tissue, excepting at the trigone, where its adhesion is more close. It is provided with a few mucous tollicles, and numerous small racemose glands, lined with columnar epithelium, exist near the neck of the organ. The epithe- lium covering it is intermediate in form between the columnar and squamous varieties. Interior of the bladder. Upon the inner surface of the base of the bladder, immediately behind the urethral orifice, is a triangular, smooth surface, the apex T32 "URINARY ORGANS. Fig. 370.— The Bladder and Urethra laid open. Seen from above. Cwp"'> Gl* of which is directed forwards; this is the trigonum vesicse or trigone vesicale. It 's paler in color than the rest of the mucous membrane, and never presents any rugae, even in the collapsed condition of the organ, owing to its intimate adhesion to the subjacent tissues. It is bounded on each side by two slight ridges, which pass backwards and outwards to the orifices of the ureters, and correspond with the muscles of these tubes ; and at each posterior angle, by the orifices of the ureters, which are placed nearly two inches from each other, and about an inch and a half behind the orifice of the urethra. The trigone corresponds with the interval at the base of the bladder, bounded by the prostate in front, and the vesicula3 and vasa deferentia on the sides. Projecting from the lower and anterior part of the bladder, into the orifice of the urethra, is a slight elevation of mucous membrane, called the uvula vesicse. It is formed by a thickening of the prostate. The arteries supplying the bladder are the superior, middle, and inferior vesical, in the male, with additional branches from the uterine, in the female. They are all derived from the anterior trunk of the internal iliac. The veins form a complicated plexus round the neck, sides, and base of the bladder, and terminate in the internal iliac veins. The lymphatics accompany the bloodvessels, passing through the glands surrounding them. The nerves are derived from the hypogastric and sacral plexuses; the former supplying the upper part of the organ, the latter its base and neck. Male Urethra. The Urethra extends from the neck of the bladder to the meatus urinarius. It is curved in its course, so as to resemble, in its flaccid state, the Italic letter /; but in the erect state it forms only a single curve, the concavity of which is directed upwards. Its length varies from eight to nine inches ; and it is divided into three portions, the prostatic, membranous, and spongy, the structure and relations of which are essentially different. The Prostatic portion is the widest and most dilatable part of the canal. It passes through the prostate gland, from its base to its apex, lying nearer its upper than its lower surface. It is about an inch and a quarter in length, and the form of the canal is spindle-shaped, being wider in the middle than at either extremity, and narrowest in front, where it joins the membranous portion. A transverse section of the canal in this situation is triangular, the apex directed downwards. Upon the floor of the canal is a narrow longitudinal ridge, the veru montanum Ottflcr* cf Juct*. s/'Coitytrs Glands URETHRA. 733 or caput yallinaginis, formed by an elevation of the mucous membrane and its. subjacent tissue. It is eight or nine lines in length, and a line and a half in height, and contains, according to Kobelt, muscular and erectile tissues. When distended, it may serve to prevent the passage of the semen backwards into the bladder. On each side of the veru montanum is a slightly depressed fossa, the prostatic sinus, the floor of which is perforated by numerous apertures, the orifices of the prostatic ducts, the ducts of the middle lobe opening behind the crest. At the fore part of the veru montanum, in the middle line, is a depression, the sinus pocularis or vesicula prostalica; and upon or within its margins are the slit-like openings of the ejaculatory ducts. The sinus pocularis forms a cul-de-sac about a quarter of an inch in length, which runs upwards and backwards in the sub- stance of the prostate, beneath the middle lobe ; its prominent upper wall partly forms the veru montanum. Its walls are composed of fibrous tissue, muscular fibres, and mucous membrane ; and numerous small glands open on its inner sur- face. It has been called by Weber, who discovered it, the uterus masculinus, from its supposed homology with the female organ. The Membranous portion of the urethra extends between the apex of the pros- tate, and the bulb of the corpus spongiosum. It is the narrowest part of the canal (excepting the orifice), and measures three-quarters of an inch along its upper, and half an inch along its lower surface, in consequence of the bulb projecting backwards beneath it below. Its upper concave surface is placed about an inch beneath the pubic arch, from which it is separated by the dorsal vessels and nerves of the penis, and some muscular fibres. Its lower convex surface is separated from the rectum by a triangular space, which constitutes the perineum. The membranous portion of the urethra perforates the deep perineal fascia ; and two layers from this membrane are prolonged round it, the one forwards, the other backwards ; it is also surrounded by the Compressor urethraa muscle. Its cover- ings are mucous membrane, elastic fibrous tissue, a thin layer of erectile tissue, muscular fibres, and a prolongation from the deep perineal fascia. The Spongy portion is the longest part of the urethra, and is contained in the corpus spongiosum. It is about six inches in length, and extends from the termi- nation of the membranous portion to the meatus urinarius. Commencing below the symphysis pubis, it ascends for a short distance, and then curves downwards. It is narrow, and of uniform size in the body of the penis, measuring about a quarter of an inch in diameter ; being dilated behind, within the bulb, where it forms the bulbous portion, and again anteriorly, within the glans penis, forming the fossa navicularis. A cross section of this canal in the body has its diameter transverse, but in the glans the diameter is directed vertically. The meatus urinarius is the most contracted part of the urethra ; it is a vertical slit, about three lines in length, bounded on each side by two small labia. The inner surface of the lining membrane of the urethra, especially on the floor of the spongy portion, presents the orifices of numerous mucous glands and follicles, situated in the submucous tissue, and named the glands of Littre. They vary in size, and their orifices are directed forwards, so that they may easily intercept the point of a catheter in its passage along the canal. One of these lacunte, larger than the rest, is situated on the upper surface of the fossa navicularis, about an inch and a half from the orifice ; it is called the lacuna magna. Into the bulbous portion are found opening the ducts of Cowper's glands. Structure. The urethra is composed of three coats : a mucous, muscular, and erectile. The mucous coat forms part of the genito-urinary mucous membrane. It is continuous with the mucous membrane of the bladder, ureters, and kidneys, externally, with the integument covering the glans penis ; and is prolonged into the ducts of the numerous glands which open into the urethra, viz., Cowper's glands, and the prostate gland ; and, through the ejaculatory ducts, is continued into the vasa deferentia and vesiculse seminales. In the spongy and membranous portions, the mucous membrane is arranged in longitudinal folds when the organ 734 URINARY ORGANS. is contracted. Small papillae are found upon it, near the orifice ; and its epithe- lial lining is of the columnar variety, excepting near the meatus, where it is laminated. The muscular coat consists of two layers of plain muscular fibres, an external longitudinal layer, and an internal circular. The muscular tissue is most abundant in the prostatic portion of the canal. A thin layer of erectile tissue is continued from the corpus spongiosum round the membranous and prostatic portions of the urethra to the neck of the bladder. Male Generative Organs. Prostate Gland. The Prostate Gland (rtpoCat^fii, to stand before) is a pale, firm, glandular body, which surrounds the neck of the bladder and commencement of the urethra. It is placed in the pelvic cavity, behind and below the symphysis pubis, posterior to the deep perineal fascia, and upon the rectum, through which it may be distinctly felt, especially when enlarged. In shape and size it resembles a horse-chestnut. Its base is directed backwards towards the neck of the bladder. The apex is directed forwards to the deep perineal fascia, which it touches. Its under surface is smooth, and rests on the rectum, to which it is connected by a dense areolar fibrous tissue. Its upper surface is flattened, marked by a slight longitudinal furrow, and placed about three-quarters of an inch below the pubic symphysis. It measures about an inch and a half in its transverse diameter at the base, an inch in its antero-posterior diameter, and three-quarters of an inch in depth; and its weight is about six drachms. It is held in its position by the anterior ligaments of the bladder (pubo-prostatic) ; by the posterior layer of the deep perineal fascia, which invests the commencement of the membranous portion of the urethra and prostate gland ; and by the anterior portion of the Levator ani muscle {levator prostatae), which passes down on each side from the symphysis pubis and anterior ligament of the bladder to the sides of the prostate. The prostate consists of three lobes ; two lateral and a middle lobe. The two lateral lobes are of equal size, separated behind by a deep notch, and marked by a slight furrow upon their upper and lower surface, which indicates the bi-lobed condition of the organ in some animals. The third or middle lobe is a small, transverse band, occasionally a rounded or triangular prominence, placed between the two lateral lobes at the under and posterior part of the organ. It lies immediately beneath the neck of the bladder, behind the commencement of the urethra, and above the ejaculatory ducts. Its existence is not constant, but it is occasionally found at an early period of life, as well as in adults, and in old age. In advanced life it often becomes considerably enlarged, and projects into the bladder, so as to impede the evacuation of the urine. The prostate gland is perforated by the urethra and common seminal ducts. The urethra usually lies about one-third nearer its upper than its lower surface ; occasionally, the prostate surrounds only the lower three-fourths of this tube, and it more rarely runs through the lower than the upper part of the gland. The ejaculatory ducts pass forwards obliquely through a conical canal, situated in the lower part of the prostate, and open into the prostatic portion of the urethra. Structure. The prostate is inclosed in a thin but firm fibrous capsule, distinct from that derived from the posterior layer of the deep perineal fascia, and sepa- rated from it by a plexus of veins. Its substance is of a pale, reddish-gray color, very friable, but of great density. It consists of glandular substance and muscular tissue. The glandular substance is composed of numerous follicular pouches, opening into elongated canals, which join to form from twelve to twenty small excretory ducts. The follicles are connected together by areolar tissue, supported by pro- longations from the fibrous capsule, and inclosed in a delicate capillary plexus. The epithelium lining the canals is columnar, whilst that in the terminal vesicles is of the squamous variety. The muscular tissue of the prostate is arranged in the form of circular bands 735 736 MALE GENERATIVE ORGANS. round the urethra ; it is continuous behind with the circular fibres of the sphincter vesicae, and in front with the circular fibres of the urethra. The muscular fibres are of the involuntary kind. The prostatic ducts open into the floor of the prostatic portion of the urethra. Vessels and Nerves. The arteries supplying the prostate are derived from the internal pudic, vesical, and hemorrhoidal. Its veins form a plexus around the sides and base of the gland ; they communicate in front with the dorsal vein of the penis, and terminate in the internal iliac vein. The nerves are derived from the hypogastric plexus. The Prostatic Secretion is a milky fluid, having an acid reaction, and presenting, on microscopic examination, molecular matter, the squamous and columnar forms of epithelium, and granular nuclei. In old age, this gland is liable to be enlarged, and its ducts are often filled with innumerable small concretions, of a brownish-red color, and of the size of a millet-seed, composed of carbonate of lime and animal matter. Cowper's Glands. Cowper's Glands are two small rounded and somewhat lobulated bodies, of a yellowish color, about the size of peas, placed beneath the fore part of the membranous portion of the urethra, between the two layers of the deep perineal fascia. They lie close behind the bulb, and are inclosed by the transverse fibres of the Compressor urethras muscle. Each gland consists of several lobules, held together by a fibrous investment. The excretory duct of each gland, nearly an inch in length, passes obliquely forwards beneath the mucous membrane, and opens by a minute orifice on the floor of the bulbous portion of the urethra. Their existence is said to be constant ; they gradually diminish in size as age advances. The Penis. The Penis is the organ of copulation, and contains in its interior the larger portion of the urethra. It consists of a root, body, and the extremity or glans penis. The root is broad and firmly connected to the rami of the pubes by two strong tapering fibrous processes, the crura, and to the front of the symphysis pubis by a fibrous membrane, the suspensory ligament. The extremity or glans penis presents the form of an obtuse cone, flattened from above downwards. At its summit is a vertical fissure, the orifice of the urethra, meatus urinarius ; and at the back part of this orifice a fold of mucous membrane passes backwards to the bottom of a depressed raphe, where it is continuous with the prepuce ; this fold is termed the froenum preputii. The base of the glans forms a rounded projecting border, the corona glandis ; and behind the corona is a deep constriction, the cervix. Upon both of these parts numerous small lenticular sebaceous glands are found, the glandulse Tysonii sou odoriferve. They secrete a sebaceous matter of very peculiar odor, which probably contains casein, and becomes easily decomposed. The body of the penis is the part between the root and the extremity. In the flaccid condition of the organ it is cylindrical, but when erect has a triangular prismatic form with rounded angles, the broadest side being turned upwards, and called the dorsum. It is covered by integument remarkable for its thinness, its dark color, its looseness of connection with the deeper parts of the organ, and from containing no adipose tissue. At the root of the penis the integument is continuous with that upon the pubes and scrotum ; and at the neck of the glans it leaves the surface, and becomes folded upon itself to form the prepuce. The internal layer of the prepuce, which also becomes attached to the cervix, approaches in character to a mucous membrane ; it is reflected over the glans penis, and at the meatus urinarius is continuous with the mucous lining of the urethra. PE^IS. T37 Tlie mucous membrane covering the glans penis contains no sebaceous glands ; but projecting from its free surface are a number of small, highly sensitive papillae. , The penis is composed of a mass of erectile tissue, inclosed in three cylindrical fibrous compartments. Two of these, the corpora cavernosa, are placed side by side along the upper part of the organ ; the third or corpus spongiosum incloses the urethra, and is placed below. The Corpora Cavernosa form the chief part of the body of the penis. They consist of two fibrous cylindrical tubes, placed side by side, and intimately con- nected along the median line for their anterior three-fourths, their posterior fourth being separated to form the two crura, by which the penis is connected to the rami of the pubes. Each crus commences by a thick-pointed process in front of the tuberosity of the ischium ; and, near its junction with its fellow, presents a slight enlargement, named, by Kobelt, the bulb of the corpus cavernosum. Just beyond this point they become constricted, and retain an equal diameter to their anterior extremity, where they form a single rounded end, which is received into a fossa in the base of the glans penis. A median groove on the upper surface lodges the dorsal vein of the penis, and the groove on the under surface receives the corpus spongiosum. The root of the penis is connected to the symphysis pubis by the suspensory ligament. Structure. Each corpus cavernosum consists of a strong fibrous envelop, inclosing a fibrous reticular structure, containing erectile tissue in its meshes. It is separated from its fellow by an incomplete fibrous septum. The fibrous investment is extremely dense, of considerable thickness, and highly elastic ; it not only invests the surface of the organ, but sends off numerous fibrous bands (trabeculse) from its inner surface, as well as from the surface of the septum, which cross its interior in all directions, subdividing it into a number of separate compartments, which present a spongy structure, in which the erectile tissue is contained. The trabecular structure fills the interior of the corpora cavernosa. Its com- ponent fibres are larger and stronger round the circumference than at the centre of the corpora cavernosa; they are also thicker behind than in front. The inter- spaces, on the contrary, are larger at the centre than at the circumference, their long diameter being directed transversely ; and they are largest anteriorly. They are lined by a layer of squamous epithelium. The fibrous septum forms an imperfect partition between the two corpora caver- nosa ; it is thick and complete behind, but in front it is incomplete, and consists of a number of vertical bands of fibrous tissue, which are arranged like the teeth of a comb ; hence the name, septum pectiniforme. These bands extend between the dorsal and urethral surface of the corpora cavernosa. The fibrous investment and septum consist of longitudinal bands of white fibrous tissue, with numerous elastic and muscular fibres. The trabecule also consist of white fibrous tissue, elastic fibres, and plain muscular fibres, and inclose arteries and nerves. The Corpus Spongiosum incloses the urethra, and is situated in the groove on the under surface of the corpora cavernosa. It commences posteriorly in front of the deep perineal fascia, between the diverging crura of the corpora cavernosa, where it forms a rounded enlargement, the bulb ; and terminates, anteriorly, in another expansion, the glans penis, which overlays the anterior rounded extremity of the corpora cavernosa ; its central portion or body is cylindrical, and tapers slightly from behind forwards. The bulb varies in size in different subjects ; it receives a fibrous investment from the anterior layer of the deep perineal fascia, and is surrounded by the Accelerator urinse muscle. The urethra enters the bulb nearer its upper than its lower surface, being surrounded by a layer of erectile tissue, named, by Kobelt, the colliculi bulbi, a thin prolongation of which is continued backwards round the membranous and prostatic portions of the canal to the neck of the bladder, 47 738 MALE GENERATIVE ORGANS. lying immediately beneath the mucous membrane. The portion of the bulb below the urethra presents a partial division into two lobes, being marked externally by a linear raphe, whilst internally there projects inwards, for a short distance, a thin fibrous septum, most distinct in early life. Structure. The corpus spongiosum consists of a strong fibrous envelop, inclosing a trabecular structure, which contains in its meshes erectile tissue. The fibrous envelop is thinner, whiter in color, and more elastic than that of the corpus cavernosum. The trabeculse are delicate, uniform in size, and the meshes between them small ; their long diameter, for the most part, corresponding with that of the penis. A thin layer of muscular fibres, continuous behind with those of the bladder, forms part of the outer coat of the corpus spongiosum. Erectile tissue consists essentially of an intricate venous plexus, lodged in the interspaces between the trabeculse. The veins forming this plexus are so numerous, and communicate so freely with one another, as to present a cellular appearance when examined by means of a section; their walls are extremely thin, and lined by squamous epithelium. The veins are smaller in the glans penis, corpus spongiosum, and circumference of the corpora cavernosa, than in the central part of the latter, where they are of large size, and much dilated. They return the blood by a series of vessels, some of which emerge in considerable numbers from the base of the glans penis, and converge on the dorsum of the organ to form the dorsal vein ; others pass out on the upper surface of the corpora cavernosa, and join the dorsal vein ; some emerge from the under surface of the corpora cavernosa, and, receiving branches from the corpus spongiosum, wind round the sides of the penis to terminate in the dorsal vein ; but the greater number pass out at the root of the penis, and join the prostatic plexus and pudendal veins. The arteries of the penis are derived from the internal pudic. Those supplying the corpora cavernosa are the arteries of the corpora cavernosa, and branches from the dorsal artery of the penis, which perforate the fibrous capsule near the fore part of the organ. Those to the corpus spongiosum are the arteries of the bulb. Additional branches are described, by Kobelt, as arising from the trunk of the internal pudic ; they enter the bulbous enlargement on the corpora cavernosa and corpus spongiosum. The arteries, on entering the cavernous structure, divide into branches, which are supported and inclosed by the trabecular ; according to Muller, some of these branches terminate in a capillary network, which communicates with the veins as in other parts; whilst others are more convoluted, and assume a tendril- like appearance; hence the name, helicine arteries, which is given to these peculiar vessels. The helicine arteries are most abundant in the back part of the corpora cavernosa and corpus spongiosum ; they have not been seen in the glans penis. The existence of these vessels is denied by Valentin, who describes the smallest branches of the arteries as terminating by wide, funnel-shaped orifices, which open directly into the venous cavities. The lymphatics of the penis consist of a superficial and deep set ; the former terminate in the inguinal glands, the latter emerge from the corpora cavernosa and corpus spongiosum, and, passing beneath the pubic arch, join the deep lym- phatics of the pelvis. The nerves are derived from the internal pudic nerve and the hypogastric plexus. On the glans and bulb, some filaments of the cutaneous nerves have Pacinian bodies connected with them. The Testes. The Testes are two small glandular organs, which secrete the semen ; they are situated in the scrotum, being suspended by the spermatic cords. Each is of an oval form, compressed laterally and behind, and having an oblique position in the scrotum ; the upper extremity being directed forwards and a little outwards ; the lower, backwards and a little inwards; the anterior convex border looks forwards and downwards, the posterior or straight border, to which the cord is attached, backwards and upwards. COVERINGS OF THE TESTES. 739 The anterior and lateral surfaces, as well as both extremities of the organ, are convex, free, smooth, and invested by a serous covering called the tunica vaginalis. The posterior border, to which the cord is attached, receives only a partial invest- ment from this membrane. Lying upon the outer edge of this border, is a long, narrow, flattened body, named, from its relation to the testis, the epididymis («« AiSi^o;, testis). It consists of a central portion or body, an upper enlarged ex- tremity, the globus major or head ; and a lower pointed extremity, the tail or globus minor. The globus major is intimately connected with the upper end of the testicle by means of its efferent ducts ; and the globus minor is connected with its lower end by cellular tissue, and a reflection of the tunica vaginalis. The outer surface and upper and lower ends of the epididymis are free and covered by serous membrane ; the body is also completely invested by it, excepting along its posterior border, and connected to the back of the testis by a fold of the serous membrane. Attached to the upper end of the testis, or to the epididymis, is a small pedunculated body, the use of which is unknown. Size and Weight. The average dimensions of this gland are from one and a half to two inches in length, one inch in breadth, and an inch and a quarter in the antero-posterior diameter ; and the weight varies from six to eight drachms, the left testicle being a little the larger. Coverings. At an early period of foetal life, the testes are contained in the abdo- minal cavity, behind the peritoneum. Before birth, they descend to the inguinal canal, along which they pass with the spermatic cord, and, emerging at the external abdominal ring, they descend into the scrotum, becoming invested in their course by numerous coverings, derived from the serous, muscular, and fibrous layers of the abdominal parietes, as well as by the scrotum. The coverings of the testis are the Skin ) G , -p. , \ Scrotum. Dartos j Intercolumnar or External spermatic fascia. Cremaster muscle. Infundibuliform fascia, Fascia propria or Internal spermatic fascia. Tunica vaginalis. The Scrotum is a cutaneous pouch, which contains the testes and part of the spermatic cords. It is divided into two lateral halves, by a median line or raphe, which is continued forwards along the under surface of the penis, and backwards along the middle line of the perineum to the anus. Of these two lateral portions, the left is longer than the right, and corresponds with the. greater length of the spermatic cord on the left side. Its external aspect varies under different circumstances ; thus, under the influence of warmth, and in old and debilitated persons, it becomes elongated and flaccid ; but, under the influence of cold, and in the young and robust, it is short, corrugated, and closely applied to the testes The scrotum consists of two layers, the integument and the darto;-;. The integument is very thin, of a brownish color, and generally thrown into folds or rugae. It is provided with sebaceous follicles, the secretion of which has a peculiar odor, and is beset with thinly-scattered, crisp hairs, the roots of which are seen through the skin. The dartos is a thin layer of loose reddish tissue, endowed with contractility ; it forms the proper tunic of the scrotum, is continuous, around the base of the scrotum, with the superficial fascia of the groin, perineum, and inner side of the thighs, and sends inwards a distinct septum, septum scroti, which divides it into two cavities for the two testes, the septum extending between the raphe and under surface of the penis, as far as its root. The dartos is closely united to the skin externally, but connected with the subjacent parts by delicate areolar tissue, upon which it glides with the greatest facility. The dartos is very vascular, and consists of a loose areolar tissue, con- taining unstriped muscular fibre. Its contractility is slow, and excited by cold and mechanical stimuli, but not by electricity. ?40 MALE GENERATIVE ORGANS. Fig. 371.— The Testis in Situ : the Tunica Vaginalis having been laid open. Artery of Cord The intercolumnar fascia is a thin membrane, derived from the margin of the pillars of the external abdominal ring, during the descent of the testis in the foetus, being prolonged downwards around the surface of the cord and testis. It is separated from the dartos by loose areolar tissue, which allows of considerable movement of the latter upon it, but is intimately connected with the succeeding layer. The cremasteric fascia consists of scattered bundles of muscular fibres ( Cremaster muscle), derived from the lower border of the Internal oblique muscle, during the descent of the testis. The fascia propria is a thin membranous layer, which loosely invests the surface of the cord. It is a continuation downwards of the infundibuliform pro- cess of the fascia transversalis, and is also derived during the descent of the testis in the foetus. The tunica vaginalis is described more appropriately, as one of the proper coverings of the testis. A more detailed account of the coverings just described may be found in the description of the surgical anatomy of inguinal hernia. Proper coverings or investments of the Testis. The testis is invested by three tunics, the tunica vaginalis, tunica albu- ginea, and tunica vasculosa. The Tunica Vaginalis is the serous covering of the testis. It is a pouch of serous membrane, derived from the peri- toneum during the descent of the testis, in the foetus, from the abdomen into the scrotum. After its descent, that portion of the pouch which extends from the internal ring to near the upper part of the gland becomes obliterated, the lower portion remaining as a shut sac, which invests the outer surface of the testis, and is reflected on the internal surface of the scrotum ; hence it may be described as consisting of a visceral and parietal por- tion. The visceral portion {tunica vaginalis propria) covers the outer surface of the testis, as well as the epididymis, con- necting the latter to the testis by means of a distinct fold. From the posterior border of the gland, it is reflected on to the internal surface of the scrotum. The parietal portion of the serous membrane (tunica vaginalis reflexa) is far more extensive than the visceral portion, extending upwards for some distance in front, and on the inner side of the cord, and reaching below the testis. The inner surface of the tunica vaginalis is free, smooth, and covered by a layer of squamous epithelium. The interval between the visceral and parietal layers of this mem- brane constitutes the cavity of the tunica vaginalis. The Tunica ATbuginea is the fibrous covering of the testis. It is a dense fibrous membrane, of a bluish- white color, composed of bundles of white fibrous tissue, which interlace in every direction. Its outer surface is covered by the tunica vaginalis, except along its posterior border, and at the points of attachment of the epididymis ; hence the tunica albuginea is usually considered as a fibro-serous membrane, like the dura mater and pericardium. This membrane surrounds the glandular structure of the testicle, and, at its posterior and upper border, is reflected into the interior of the gland, forming an incomplete vertical septum, called the mediastinum testis {corpus Highmorianum). The mediastinum testis extends from the upper, nearly to the lower, border of