HX00060739 T" MR SB •■■;•*"-"■ (ftnlumbia ftmttWBttij tit % (Ettg of Ne ro fork (Enllpgr of pijjjHtriattH anfc g>urgwms Stefmnr? ICtbrarg .^ A}»"v jSf^Jp ANATOMY, DESCRIPTIVE AND'SURGICAL BY HENRY GRAY, F.R.S., FELLOW OF THE ROYAL COLLEGE OF SURGEONS ; LECTURER ON ANATOMY AT ST. GEORGE'S HOSPITAL MEDICAL SCHOOL. EDITED BY / T. PICKERING PICK, F.R.C.S., CONSULTING SURGEON TO ST. GEORGE'S HOSPITAL AND TO THE VICTORIA HOSPITAL FOR CHILDREN: H. M. INSPECTOR OF ANATOMY IN ENGLAND AND WALES, ROBERT HOWDEN, M.A., M.B., CM., PROFESSOR OF ANATOMY IN THE UNIVERSITY OF DURHAM; EXAMINER IN ANATOMY IN THE UNIVERSITIES OF DURHAM AND EDINBURGH, AND TO THE BOARD OF EDUCATION, SOUTH KENSINGTON. A REVISED AMERICAN, FJEJOM THE FIFTEENTH ENGLISH. EDITION. WITH 780 ILLUSTRATIONS, MANY OF WHICH ARE NEW. LEA BROTHEES & CO., PHILADELPHIA AND NEW YORK, 1901. ' A T TO SIR BENJAMIN COLLINS BRODIE, BART., F.R.S., D.C.L., SERJEANT-SURGEON TO THE QUEEN, CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE, Ubis Worfe is BeotcateO IN ADMIRATION OF HIS GREAT TALENTS AND IN REMEMBRANCE OF MANY ACTS OF KINDNESS SHOWN TO THE AUTHOR FROM AN EARLY PERIOD OF HIS PROFESSIONAL CAREER. PUBLISHERS' NOTE TO THE NEW AMERICAN EDITION. In his masterpiece Henry Gray left undying evidence of his anatomical knowledge and of his comprehension of the best method of imparting it to other minds. It is appropriate that a new and thoroughly revised edition of such a work should appear in the opening of the new century — for forty-five years it has easily held the front place among works on Anatomy, and its merits are only brightened by the numerous works which have endeavored to contest its supremacy. During that time it has had the benefit of the careful scrutiny of many leading anatomists of the English-speaking race. Anatomy is far from stationary, either in its facts or in improvements in the method of their presentation ; hence any work which would faithfully reflect the existing position of the science must be revised at comparatively frequent intervals. Fortunately for students and practitioners, Gray's Anatomy enjoys a continuous demand rendering frequent revision pos- sible. The splendid illustrations in Gray have long been known as the most effective and intelligible presentations of anatomical structures ever produced. In the present revision this series has been vastly improved, special attention having been given to those for the portion on General Anatomy and Embryology. The practical application of anatomical facts in medicine and surgery has always been a prominent feature of the work, and this distinctive characteristic has received especial care. This new century edition is presented to the medical public with the absolute confidence that it will be found worthy in every respect to maintain the exalted -^ioh a Avork has for so many years enjoyed as the most convenient and of its subject. PREFACE TO THE FIFTEENTH ENGLISH EDITION. In this edition the entire work has undergone a careful revision. The section on Embryology has been somewhat amplified, and its text rendered more intelligible by the introduction of some sixty additional illustrations after His, Kollmann, Duval, and others. Throughout the rest of the work a considerable number of the diagrams have been redrawn and new illustrations here and there added. The Editors are indebted to Dr. R. Bolam, Lecturer on Physiology and Histology, and to Dr. W. Turnbull, Demonstrator of Anatomy, both of the University of Durham College of Medicine, for their valuable help. The former kindly undertook the revision of the chapter on General Anatomy or Histology ; while the latter rendered great assistance in the revision and proof-reading of some of the other portions of the work. It is hoped that this edition will maintain the reputation which the work has for so many years enjoyed. 7 CONTENTS. DESCRIPTIVE AND SURGICAL ANATOMY. OSTEOLOGY.— THE SKELETON. " i PAGE The Skeleton 33 Number of the Bones 33 Form of Bones 315 The Spixe. General Characters of a Vertebra ...... 34 Characters of the Cervical Vertebrae 35 Atlas 30 Axis 37 Seventh Cervical 3!) Characters of the Dorsal Vertebrae 39 Peculiar Dorsal Vertebras 41 Characters of the Lumbar Vertebras 41 Structure of the Vertebrae 43 Development of the Vertebrae 43 Atlas 44 " " Axis 44 '' " Seventh Cervical .... 45 " " Lumbar Vertebrae .... 45 Progress of Ossification in the Spine 45 Sacral and Coccygeal Vertebrae 45 Sacrum 45 Coccyx 50 Of the Spine in General 51 Surface Form of Spine 53 Surgical Anatomy of Spine 53 The Skull. Bones of the Cranium 55 Occipital Bone 55 Parietal Bones 59 Frontal Bone 61 Temporal Bones 65 Sphenoid Bone 72 Ethmoid Bone 77 Development of the Cranium 80 The Fontanelles 80 Wormian Bones ' 81 Congenital Fissures and Gaps 81 Bones of the Face : Nasal Bones 81 Superior Maxillary Bones 83 Changes produced in Upper Jaw by Age . 88 Lachrymal Bones : 88 Malar Bones 89 Palate Bones 91 Inferior Turbinated Bones 94 Vomer 95 Inferior Maxillary Bone 96 Changes produced in the Lower Jaw by Age '. 99 Sutures of the Skull 101 Vertex of the Skull 103 Base of the Skull, Internal Surface 103 Anterior Fossa ]03 Middle Fossa 105 Posterior Fossa 106 Base of Skull, External Surface 106 Lateral Region of the Skull . 110 Temporal Fossa 110 Mastoid Portion Ill Zygomatic Fossa Ill PAGE Spheno-niaxillary Fossa 112 Anterior Region of the Skull 112 Orbits 11 3 Nasal Fossae 115 Surface Form of Skull 11- Surgical Anatoniv of Skull 119 Os Hyoides . . '. 122 The Thoeax. The Sternum 124 The Ribs 128 Peculiar Ribs 130 Costal Cartilages 132 Surface Form of Chest 132 Surgical Anatomy of Chest 133 The L'ppee Extremity. The Shoulder and Pelvic Girdles 134 The Clavicle 135 Surface Form I'M Surgical Anatomv 137 The Scapula ....'. 138 Surface Form 143 Surgical Anatomy 143 The Humerus 144 Surface Form 1-J!' Surgical Anatomy 149 The Forearm . . 150 The Ulna 150 Surface Form 155 The Radius 155 Surface Form 157 Surgical Anatomv of Bones of Forearm . 157 The Hand 158 The Carpus 158 Bones of the Upper Row 161 Bones of the Lower Row 163 The Metacarpus 165 Peculiar Characters of the Metacarpal Bones . 166 Phalanges 169 Surface Form of Bones of Hand .... 169 Surgical Anatomy of Bom- of Hand . . 170 Development of the Bones of the Hand. . 170 The Lower Extremity. Os Innominatum 171 Ilium 172 Ischium 171 Os Pubis 176 Development of the Os Innominatum . . . . 177 The Pelvis 179 Differences between the Male and Female Pelvis 182 Surface Form of Bones of Pelvis . . . 182 Surgical Anatomy of Bones of Pelvis . . 183 The Femur or Thigh-bone 183 Surface Form 190 Surgical Anatomv TheLeg 191 Patella 191 Surface Form 192 Surgical Anatomy 192 9 10 CONTENTS. PAGE Tibia 192 Surface Form 196 Fibula 196 Surface Form 198 Surgical Anatomy of Boues of Leg . . . 198 The Foot 199 Tarsus 199 Os Calcis 199 Astragalus 203 Cuboid . .■ 204 Navicular 205 Internal Cuneiform Middle " External " -ui Metatarsal Bones 208 Phalanges 210 Development of the Bones of the Foot . . . 211 Construction of the Foot as a whole . . . 211 Surface Form of Foot 213 Surgical Anatomy of Foot 213 Sesamoid Bones 214 THE ARTICULATIONS. Structures composing the Joints 217 Articular Lamella of Bone 217 Ligaments 217 Synovial Membrane 217 Bursse 218 Synovia 218 Forms of Articulation : Synarthrosis 218 Amphiarthrosis 219 Diarthrosis 219 Movements of Joints 220 Articulations of the Trunk. Articulations of the Vertebral Column . . . 223 " " Atlas with the Axis . . 227 " Spine with the Cranium 229 " Atlas with the Occipital Bone 229 Articulation of the Axis with the Occipital Bone 230 Surgical Anatomy of Articulations of the Spine 231 Tempero-mandibular Articulation 231 Surface Form 234 Surgical Anatomy 234 Articulations of the Ribs with the Vertebrae : Costo-central 234 Costo-transverse 236 Articulations of the Cartilages of the Bibs with the Sternum and Eusiform Cartilage . 238 Iuterchondral Articulations 239 Articulations of the Ribs with their Carti- lages 239 Ligaments of the Sternum 239 Articulation of the Pelvis with the Spine . . 240 Articulations of the Pelvis : Articulation of the Sacrum and Ilium . . 241 Ligament between the Sacrum and Is- chium 242 Articulation of the Sacrum and Coccyx . 244 Articulation of the Pubes 244 Articulations of the Upper Extremity. Sterno-clavicular 245 Surface Form 247 Surgical Anatomy 247 Acromio-clavicular 248 Surface Form 249 Surgical Anatomy 249 Proper Ligaments of the Scapula . . • ... 249 Shoulder-joint 251 Surface Form 254 Surgical Anatomy 254 Elbow-joint 255 Surface Form 258 Surgical Anatomy 358 Superior Eadio-ulnar Articulations 259 Middle Radio-ulnar Articulation 259 Inferior Radio-ulnar Articulation 260 Surface Form 261 Wrist-joint 262 Surface Form ' . 263 Surgical Anatomy 263 Articulations of the Carpus 263 " of the first row of Carpal Bones 263 of the second row of Carpal Bones 264 <: of the two rows of Carpal Bones 264 Carpo-metacarpal Articulations 265 of the Metacarpal Bone of Thumb and Trapezium 265 of the four inner Metacarpal Bones and Carpus 266 Articulations of the Metacarpal Bones 267 Metacarpophalangeal Articulations 267 Surface Form 268 Articulations of the Phalanges 268 Articulations of the Lower Extremity. Hip-joint 268 Surface Form 272 Surgical Anatomy 272 Knee-joint 274 Surface Form 280 Surgical Anatomy 280 Superior Tibio-fibular Articulation 282 Middle Tibio-fibular Articulation 282 Inferior Tibio-fibular Articulation 282 Articulations between the Tibia and Fibula . 282 Ankle-joint 283 Surface Form 285 Surgical Anatomy 285 Articulations of the Tarsus 287 " of the Os Calcis and Astragalus 287 of the Os Calcis and Cuboid . 287 " of the Os Calcis and Navicular 288 Surgical Anatomy .... 288 of the Astragalus and Navicular 289 " of the Navicular and Cuneiform 289 " of the Navicular and Cuboid . . 289 of the Cuneiform with each other 290 of the External Cuneiform and Cuboid 290 Tarso-metatarsal Articulations 299 Articulations of the Metatarsal Bones. . . . 291 Synovial Membranes in Tarsal and Metatarsal Joints 291 Metatarso-phalangeal Articulations 292 Articulations of the Phalanges 293 Surface Form 293 MUSCLES AND FASCIiE. General Description of Muscle 295 I Cranial Region. Tendons 296 , Dissection 298 Aponeuroses .... 296 Occipito-fron talis 298 " " Fascia 296 , . , „ . Auricular Region. Muscles and Fascia of the Cranium and Dissection * ACE- Attrahens Auriculum Subdivision into Groups 297 Attollens Auriculum CONTENTS. 11 PAGE Eetrahens Auriculum 301 Actions 301 Palpebral Region. Dissection 301 Orbicularis Palpebrarum 301 Corrugator Supercilii 30:2 Tensor Tarsi '. 302 Actions 302 Orbital Region. Dissection 303 Levator Palpebrre 303 Eectus Superior, Inferior. Internal, and Ex- ternal Eecti 304 Superior Oblique 304 Inferior Oblique 305 Actions 305 Surgical Anatomy 306 Nasal Region. Pyramidalis Nasi 306 Levator Labii Superioris Alseque Nasi .... 306 Dilatator Naris, Anterior and Posterior . . . 306 Compressor Nasi 306 Compressor Narium Minor 306 Depressor Ala? Nasi 306 Actions 307 Superior Maxillary Region. Levator Labii Superioris Proprius 307 Levator Anguli Oris 307 Zygomaticus, Major and Minor 307 Actions 307 Inferior Maxillary Region. Dissection 308 Levator Labii Inferioris 308 Depressor Labii Inferioris 308 Depressor Anguli Oris 308 Actions 308 Intermaxillary Region. Dissection 308 Orbicularis Oris 308 Buccinator 309 Eisorius 310 Actions 310 Temporo-mandibular Region. Masseteric Fascia 310 Masseter 310 Temporal Fascia 310 Dissection 311 Temporal 311 Pterygo-mandibidar Region. Dissection 312 External Pterygoid 312 Internal Pterygoid 312 Actions 313 Surface Form of Muscles of Head and Face . 313 Muscles and Fascia of the Neck. Subdivision in Groups 313 Superficial Region. Dissection 314 Superficial Cervical Fascia 314 Platysma Myoides 314 Surgical Anatomy 315 Actions 315 Deep Cervical Fascia 315 Surgical Anatomy .• 317 Stern o-mastoid 317 Boundaries of the Triangles of the Neck . . 318 Actions 319 Surface Form 319 Surgical Anatomy 319 Infra-hyoid Region. Dissection 319 Sterno-hyoid . , • . . 319 PAGE Sterno-thyroid 319 Thyro-byoid Onio-hyoid Actions Supra-hyoid Region. Dissection 301 Digastric 321 Stylo-liyoid 30-2 Stylo-hyoid Ligament 322 Mylo-byoid . ., • . . . . Genio-hyoid :;:■_> Actions 303 Lingual Region. Dissection 323 Genio-hyo-glossus 323 Hyo-glossus 324 Chrondro-glossus 324 Stylo-glossus 324 Palato-glossus 325 Muscular Substance of Tongue 325 Superior Lingualis 326 Transverse Lingualis 326 Vertical Lingualis 326 Inferior Lingualis 326 Surgical Anatomy 327 Actions 327 Pharyngeal Region. Dissection 327 Inferior Constrictor 327 Middle Constrictor 328 Superior Constrictor 328 Stylo-pharyngeus 329 Actions . 329 Palatal Region. Dissection 329 Levator Palati 329 Tensor Palati 329 Palatine Aponeurosis 330 Azygos Uvula? 330 Palato-glossus 331 Palato-pbaryngeus 331 Salpingo-pharyngeus 331 Actions 331 Surgical Anatomy 332 Vertebral Region (Anterior). Eectus Capitis Anticus Major 332 Eectus Capitis Anticus Minor 332 Eectus Capitis Lateralis 333 Longus Colli 333 Vertebral Region (Lateral). Scalenus Anticus 334 Scalenus Medius 335 Scalenus Posticus 335 Actions • 335 Surface Form of Muscles of Neck 335 Muscles and Fascle of the Trunk. Subdivision into Groups 336 The Back. Subdivision into Layers 336 First Layer. Dissection 336 Superficial and Deep Fascia? 3oi Trapezius jj«fi Ligameutuin Nucha? 339 Latissimus Dorsi «39 Second Layer. Dissection •';'" Levator Anguli Scapula 340 Ehomboideus Minor j^ 1 " Ehomboideus Major 340 Actions "*4" Third Layer. Dissection 341 Serratus Posticus Superior 341 12 CONTENTS. PAGE Serratus Posticus Inferior 341 Vertebral Aponeurosis 1 341 Lumbar Fascia 342 Splenius 342 Splenitis Capitis 342 Splenius Colli 342 Actions • • • • 342 Fourth Layer. Dissection 343 Erector Spinse * 343 Ilio-costalis 343 Musculus Accessorius ad Ilio-costalem .... 343 Cervical is Ascendens 345 Longissimus Dorsi •' 345 Trausversalis Cervicis 345 Trachelo-mastoid 345 Spinalis Dorsi 345 Spinalis Colli 345 Complexus 345 Bi venter Cervicis 346 Fifth Layer. Dissection 346 Semispinalis Dorsi et Colli 346 Multifidus Spinse 346 Eotatores Spinas 347 Supraspinales 347 Interspinals 347 Extensor Coccygis 347 Intertransversales 347 Eectus Capitis Posticus Major 347 Pectus Capitis Posticus Minor 348 Obliqaus Capitis Inferior 348 Obliquus Capitis Superior 34S Suboccipital Triangle 348 Actions 348 Surface Form of Muscles of Back 349 The Thorax. Intercostal Fascias . ." 350 Intercostal Muscles > . . . 350 External Intercostals 350 Internal Intercostals 350 Infracostales (subcostales) 351 Triangularis Stern i 351 Levatores Costarum 352 Diaphragm 352 Actions 354 Muscles of Inspiration and Expiration . . . 355 Superficial Muscles of the Abdomen. Dissection 356 Superficial Fascia 356 External or Descending Oblique 356 External Abdominal Ping . . . 357 The Intercolumnar Fibres 358 The Intercolumnar Fascia 359 Poupart's Ligament 359 Gimbernat's Ligament 359 Triangular Fascia 359 Ligament of Cooper 359 Internal or Ascending Oblique 360 Cremaster 361 Trausversalis 362 Pectus 362 Pyramidalis 364 Linea Alba 365 Lineas Semilunares, Lineas Transversa? . . . 365 Actions 365 Fascia Trausversalis 365 Internal Abdominal Ping 366 Inguinal Canal 366 Surface Form of Muscles of Abdomen . . . 366 Deep Muscle's of the Abdomen. Quadratus Lumborum 367 Actions 367 Muscles of the Pelvic Outlet. Corrugator Cutis Ani 368 External Sphincter Ani 368 PAGE Internal Sphincter Ani 368 Levator Ani 369 Coccygeus 369 Muscles of the Perinseum in the Male. Superficial Perineal Fascia 370 Transversus Perinsei 371 Accelerator Urinse 371 Erector Penis 372 Triangular Ligament 373 Compressor Urethras 374 Muscles of the Perinseum in the Female. Transversus Perinsei 375 Sphincter Vaginas 375 Erector Clitoridis 375 Triangular Ligament 375 Compressor Urethrse 375 Muscles axd Fascije of the Upper Extremity. Subdivision into Groups 376 Dissection of Pectoral Region and Axilla . . 376 Fascias of the Thorax 377 The Shoulder. Anterior Thoracic Eegion. Pectoralis Major 378 Costo-coracoid Membrane 378 Pectoralis Minor 379 Subclavius 360 Actions 3S1 Lateral Thoracic Eegion. Serratus Magnus 381 Actions 382 Superficial Fascia 382 Acromial Eegion. Deep Fascia 382 Deltoid 382 Actions 383 Surgical Anatomy 383 Anterior Scapular Eegion. Subscapular Fascia 383 Subscapularis_ 383 Actions . . '. 384 Posterior Scapular Eegion. Dissection 384 Supraspinous Fascia 384 Supraspinatus 384 Infraspinous Fascia 384 Infraspinatus 384 Teres Minor 385 Teres Major 386 Actions 386 The Arm. Anterior Humeral Eegion. Dissection 386 Deep Fascia of Arm 386 Coraco-brachialis 387 Biceps 3i = 7 Brachialis Anticus 368 Actions • 388 Posterior Humeral Eegion. Triceps 388 Subanconeus -}^ Actions 389 Surgical Anatomy 389 The Forearm. Dissection 389 Deep Fascia of Forearm 3SD Anterior Eadio-ulnar Eegion, Superficial Layer. N,^^ Pronator Radii Teres 390 Flexor Carpi Radialis 391 CONTENTS. 15 Superficial Temporal Artery. page Course and Kelations 495 Branches 495 Surgical Anatomy 496 Internal Maxillary Artery. Course and Relations 496 Branches from First Portion 496 " " Second Portion 498 " " Third Portion 499 Surgical Anatomy of the Triangles of the Neck. Anterior Triangular Space. Inferior Carotid Triangle 500 Superior Carotid Triangle 500 Submaxillary Triangle 501 Posterior Triangular Space. Occipital Triangle 501 Subclavian Triangle 502 Internal Carotid Artery. Cervical Portion 502 Petrous Portion 503 Cavernous Portion 503 Cerebral Portion 503 Peculiarities 504 Surgical Anatomy 505 Branches 505 Ophthalmic Artery 505 Cerebral Branches of Internal Carotid . 510 The Blood-vessels of the Brain , . 512 Arteries of the Upper Extremity. Subclavian Arteries. First Part of Right Subclavian Artery . First Part of Left Subclavian Artery . . Second Part of Subclavian Artery . . . Third Part of Subclavian Artery .... Peculiarities Surface Marking Surgical Anatomy Branches Vertebral Artery Basilar Artery Circle of Willis Thyroid Axis Inferior Thyroid Suprascapular Artery Transversal is Colli Internal Mammary Superior Intercostal The Axilla Surgical Anatomy of the Axilla 514 516 516 516 517 518 518 520 520 522 523 523 523 524 524 526 527 527 529 Axillary Artery. First Portion 530 Second Portion 530 Third Portion 531 Peculiarities 531 Surface Marking 531 Surgical Anatomy 531 Branches . 532 Brachial Artery. Relations 533 Bend of the Elbow 534 Peculiarities of Brachial Artery 534 Surface Form 535 Surgical Anatomy 535 Branches 536 Radial Artery. Relations 538 Deep Palmar Arch 533 Peculiarities 539 Surface Marking 539 Surgical Anatomy 539 Branches 539 Ulnar Artery. pa',e Relations 540 Peculiarities of Ulnar Artery Surface Marking 540 Surgical Anatomy r,4i Branches 543 Superficial Palmar Arch 544 Arteries of the Trunk. Descending Aorta 546 Thoracic Aorta. Course and Relations 546 Surgical Anatomy Branches 547 Abdominal Aorta. Coui-se and Relations 549 Surface Marking Surgical Anatomy 550 Branches 550 Coeliac Axis 551 Gastric Artery 551 Hepatic Artery 551 Splenic Artery 551 Superior Mesenteric Artery 553 Inferior Mesenteric Artery 555 Suprarenal Arteries Renal Arteries 556 Spermatic Arteries 557 Ovarian Arteries 557 Phrenic Arteries 557 Lumbar Arteries Middle Sacral Artery 558 Luschka's Gland - Common Iliac Arteries. Course and Relations Branches Peculiarities . . . . Surface Marking . . . Surgical Anatomy . . 559 559 559 560 560 Internal Iliac Artery. Course and Relations 561 Peculiarities 562 Surgical Anatomy 562 Branches 563 Vesical Arteries 563 Hemorrhoidal Arteries 563 Uterine Arteries 563 Vaginal Arteries 564 Obturator Artery 564 Peculiarities 565 Internal Pudic Artery 565 In the Male 565 Peculiarities Surgical Anatomy Branches 566 In the Female 567 Sciatic Artery •'''• Lumbar Artery Lateral Sacral Artery Gluteal Artery Surface Marking of Branches of Internal Iliac 569 Surgical Anatomy of Branches of Internal Iliac . 570 External Iliac Artery. Course and Relations Surgical Anatomy Deep Epigastric Artery Deep Circumflex Iliac Artery . . . . 570 571 572 Arteries of the Lower Extremity. Femoral Artery. Course and Relations Scarpa's Triangle Hunter's Canal 572 572 573 16 CONTENTS. PAGE Common Femoral 573 Superficial Femoral 574 Peculiarities 575 Surface Marking 575 Surgical Anatomy 575 Branches 578 Deep Femoral 578 Branches 579 Popliteal Artery. Popliteal Space 581 Course and Relations 581 Peculiarities 582 Surface Marking 582 Surgical Anatomy 582 Branches 583 Anterior Tibial Artery. Coarse and Relations 585 Peculiarities 586 Surface Marking 586 Surgical Anatomy 586 Branches 5S6 Dorsalis Pedis Artery. Course and Relations 587 Peculiarities 587 Surface Marking .' 587 Surgical Anatomy . . . 587 Branches 588 Posterior Tibial Artery. Course and Relations 588 Peculiarities 589 Surface Marking 589 Surgical Anatomy 589 Branches 590 Peroneal Artery. Course and Relations 590 Peculiarities 590 Plantar Arteries 591 Surface Marking 592 Surgical Anatomy 592 THE VEINS. General Anatomy. Subdivision into Pulmonary, Systemic, and Portal 593 Anastomoses of Veins 593 Superficial Veins 593 Deep Veins, Venae Comites 594 Sinuses 594 Pulmonary Veins 594 Systemic Veins 594 Veins of the Head and Neck. Frontal Vein 595 Facial Vein 596 Surgical Anatomy 596 Temporal Vein 596 Internal Maxillary Vein 596 Temporo-maxillary Vein . 597 Posterior Auricular Vein 597 Occipital Vein 597 Veins of the Neck. External Jugular Vein 597 Surgical Anatomy 597 Posterior External Jugular Vein 598 Anterior Jugular Vein 59H Internal Jugular Vein 598 Lingual Vein 598 PAwE Pharyngeal Vein 598 Thyroid Veins 598 Surgical Anatomy of Internal Jugular Vein . 599 Vertebral Veins 589 Veins of the Diploe 599 Cerebral Veins. Superficial Cerebral Veins 600' Deep Cerebral Veins 601 Cerebellar Veins 60L Sinuses of the Dura Mater. Superior Longitudinal Sinus 602 Inferior Longitudinal, Straight Sinuses . . . 602 Lateral Sinus 602 Occipital Sinuses 603 Cavernous Sinuses 603 Surgical Anatomy . . 604 Circular Sinus 604 Superior Petrosal Sinus 604 Inferior Petrosal Sinus 605 Transverse Sinuses 605 Emissary Veins 605 Surgical Anatomy 606 Veins of the Upper Extremity and Thorax. Superficial Veins 607 Deep Veins 607 Axillary Vein 609 Surgical Anatomy 609 Subclavian Vein 609 Innominate Veins 609 Peculiarities of 610 Internal Mammary Veins 610 Inferior Thyroid Veins 610 Superior Intercostal Veins 611 Superior Vena Cava 611 Azygos Veins 611 Bronchial Veins 611 Spinal Veins 612 Veins of the Lower Extremity — Abdomen and Pelvis. Internal Saphenous Vein . 614 External Saphenous Vein 614 Popliteal Vein 615 Femoral Vein 616 External Iliac Vein 616 Deep Epigastric Veins 616 Deep Circumflex Iliac Veins 616 Internal Iliac Vein 616 Internal Pudic Veins 616 Common Iliac Veins 617 Peculiarities 617 Inferior Vena Cava 617 Peculiarities 618 Lumbar Veins 618 Spermatic Veins 618 Surgical Anatomy 618 Ovarian Veins 618 Renal and Suprarenal Veins 619 Phrenic Veins 619 Hepatic Veins 619 Portal System of Veins. Superior Mesenteric Vein 619 Splenic Vein 619 Inferior Mesenteric Vein 619 Gastric Veins 619 Portal Vein 621 Cystic Vein 621 Cardiac Veins 621 Coronary Sinus 622 CONTENTS. 17 THE LYMPHATICS. General Anatomy. page Subdivision into Deep and Superficial .... 623 Lymphatic or Conglobate Glands 623 Thoracic Duct 624 Eight Lymphatic Duct 625 Lymyhatics of Head, Face, and Neck. Lymphatic Glands of Head 625 Lymphatics of the Head 625 Superficial Lymphatics of the Face 626 Deep Lymphatics of tbe Face 626 Lymphaties of the Cranium 626 Lymphatic Glands of the Neck 627 Superficial Cervical Glands 627 Deep Cervical Glands 628 Superficial and Deep Cervical Lymphatics . . 628 Surgical Anatomy 628 Lymphatics of the Upper Extremity. Superficial Lymphatic Glands 628 Deep Lymphatic Glands 628 Axillary Glands 628 Surgical Anatomy 629 Superficial Lymphatics of Upper Extremity . 630 Deep Lymphatics of Upper Extremity . . . 630 Lymphatics of the Lower Extremity. Superficial Inguinal Glands 630 Surgical Anatomy 630 Deep Lymphatic Glands 630 Anterior Tibial Gland 631 Popliteal Glands 631 Deep Inguinal Glands 631 Gluteal and Ischiatic Glands 631 Superficial Lymphatics of Lower Extremity 631 Internal Group 631 External Group 631 Deep Lymphatics of Lower Extremity . . . 632 Lymphatics of Pelvis and Abdomen. Lymphatic Glands of Pelvis 632 External Iliac Glands 632 Internal Iliac Glands ■ ■ ■ . . 632 Sacral Glands 632 Lumbar Glands 632 PAGE Superficial Lymphatics of Wall of Abdomen I of Gluteal Region . . 632 " of Scrotum and Peri- neum 633 " of Penis 633 " of Labia Nymphae, and Clitoris . . 634 Deep Lymphatics of Pelvis and Abdomen . . 634 Lymphatics of Bladder i;:;i of Eectum 634 of Uterus 634 of Testicle 634 of Kidney 634 of Liver 634 Lymphatic Glands of Stomach 635 Lymphatics of Stomach 635 Lymphatic Glands of Spleen 635 Lymphatics of Spleen G35 Lymphatic System of the Intestine. Lymphatic Glands of Small Intestine (Mesen- teric Glands) 635 Lymphatic Glands of Large Intestine .... 635 Lymphatics of Small Intestine (Lacteals) . . 635 of Large Intestine 635 Lymphatics of Thorax. Lymphatic Glands of Thorax 636 Intercostal Glands 636 Internal Mammary Glands 636 Anterior Mediastinal Glands 636 Posterior Mediastinal Glands 636 Superior Lymphatics on Front of Thorax . . 636 Deep Lymphatics of Thorax 636 Intercostal Lymphatics 636 Internal Mammary Lymphatics .... 636 Lymphatics of Diaphragm 636 Bronchial Glands 636 Lymphatics of Lung 637 Cardiac Lymphatics 637 Thymic Lymphatics 637 Thyroid Lymphatics 637 Lymphatics of CEsophagus 637 THE NERVOUS SYSTEM. Subdivision into Cerebro-spinal Centres, Ganglia, and Nerves, etc 639 The Brain and its Membranes. Membranes of the Brain 639 The Dura Mater. Structure 639 Arteries, Veins, Nerves 640 Processes of the Dura Mater \ 640 Falx Cerebri 640 Tentorium Cerebelli 640 Falx Cerebelli 641 Diaphragma Selli 641 The Arachnoid Membrane. General Description 641 Subdural Space 641 Subarachnoid Space 641 Cerebro-spinal Fluid . . . . 642 Structure 642 Glandulse Pacchioni . 642 The Pia Mater. General Description and Structure 642 Lymphatics and Nerves 643 The Brain. General Considerations and Divisions .... 643 2 The Hemispheres. Surface of the Cerebrum 643 Longitudinal Fissure 645 Sylvian Fissure 645 Fissure of Rolando 646 Parieto-occipital Fissure 646 Calloso-margiual Fissure 646 Internal Parieto-occipital Fissure 647 Calcarine Fissure 647 Collateral Fissure 647 Dentate or Hippocampal Fissure (>l~ Frontal Lobe 648 Parietal Lobe 650 Occipital Lobe 65] Temporal Lobe ,ir ''-' Central Lobe or Island of Reil 652 Limbic Lobe 652 Olfactory Lobe 654 Base of the Encephalon 655 Longitudinal Fissure 655 655 656 656 656 656 Corpus Callosuni Lamina Cinera Optic Commissure Tuber Cinereum Infundibulum Corpora Albicantia 656 Posterior Perforated Space ,, >~~ Pons Varolii 657 Crura Cerebri 659 Hemispheres of Cerebellum / 18 CONTENTS. PAGE The Interior of the Cerebrum. . . . 658 Corpus Callosum 659 Lateral Ventricles 660 Corpus Striatum 662 Xucleus Caudatus 662 Medulla Oblongata 656 Optic Tracts 657 Xucleus Lenticularis 662 Internal Capsule 663 External Capsule 66-4 Claustrum 664 Taenia Semicircularis 664 Fornix 664 Anterior Commissure 665 Septum Lucidum 665 Fifth Ventricle 666 Hippocampus Major 666 Corpus Fimbriatum 667 Choroid Plexus 667 Transverse Fissure 669 Velum Interpositum 669 The Inter-brain 669 Third Ventricle 670 Middle Commissure 671 Posterior Commissure 671 Optic Thalami 671 Pineal Gland 672 The Mid-brain 673 Orustse 674 Tegmentum 674 Substantia Xigra 675 Corpora Quadrigemina 675 Corpora Geniculata 676 Aqueduct of Sylvius 676 Subthalamic Eegion 676 The Structure of the Cerebrum . . . 677 White Matter of the Cerebrum 677 Projection Fibres 677 Commissural Fibres 677 Association Fibres 677 Gray Matter of the Cerebi-um 678 " of the Cortex 678 Special Types of Gray Matter 680 The Hind-brain 681 Pons Varolii 681 Superior Olivarv Xucleus . 683 Nuclei of the Fifth Nerve .683 Xucleus of the Sixth Xerve 683 Nucleus of the Facial Xerve 683 Nuclei of the Auditory Xerve 684 Xuclei Pontis 684 The. Cerebellum 684 Lobes 684 Upper Surface of the Cerebellum 686 Lingula 686 Lobulus Centralis 686 Culmen Monticuli 686 Clivus Monticuli 6S6 Folium Cacuminis 686 Under Surface of the Cerebellum 686 Nodule and Flocculus 688 Uvula and Amygdalae 688 Pyramid and Biventral Lobes 689 Tuber Valvules, and Posterior Inferior Lobes 6S9 Internal Structure of the Cerebellum .... 689 Peduncles 6S9 Gray Matter of the Cortex 691 Independent Centres 693 Weight of the Cerebellum 693 The Medulla Oblongata .... 693 Pyramids 694 Lateral Columns 694 Olivary Body 694 Funiculus of Eolando 694 Funiculus Cuneatus 694 PAGE- Funiculus Gracilis 696 Eestiform Body 696 Arciform Fibres 696 Fourth Ventricle 697 Internal Structure of the Medulla 699 Weight of the Encephalon 703 Cerebral Topography 705 The Spinal Coed and its Membeanes. Dissection 707 The Membranes of the Cord. . . . 707 Dura Mater 707 Arachnoid 708 Pia Mater 709 Ligamentum Denticulatum 709 The Spinal Cord 710 Fissures 711 Columns 711 Structure 712 Minute Anatomy 713 r - Neuroglia 713 White Substance 713 Gray Substance 715 Origin of the Spinal Nerves 717 Xerve-tracts 717 Motor, Efferent, or Descending Tract . . 718 Other Descending Tracts 719 Sensory, Afferent, Ascending Tract . . . 719 Other Ascending Tracts 719 The Cbanial Xeeve. Enumeration 720 Olfactory Xerve 720 Surgical Anatomy 721 Optic Xerve 721 Tracts 721 Commissure 721 Surgical Anatomy 722 Motor Oculi Xerve 722 Surgical Anatomy 724 Pathetic Xerve 725 Surgical Anatomy 725 Trifacial Xerve 725 Gasserian Ganglion 726 Ophthalmic Xerve 726 Lachrymal and Frontal Branches .... 726 Nasal Branches 727 Ophthalmic Ganglion 729 Superior Maxillary Nerve 729 Spheno-palatine Ganglion 732 Inferior Maxillary Xerve 734 Auriculo-temporal Branch 735 Lingual Branch 735 Inferior Dental Branch 736 Otic Ganglion 736 Submaxillary Ganglion 737 Surgical Anatomy of Fifth Xerve 738 Abducens Xerve 738 Eelations of the Orbital Xerves in the Cavern- ous Sinus 739 Eelations, etc., in the Sphenoidal Fissure . . 739 " in the Orbit 739 Surgical Anatomy 740 Facial Xerve 740 Branches of Facial Xerve 741 Surgical Anatomy 744 Auditory Xerve 745 Surgical Anatomy 746 Glosso-pharyngeal Xerve 746 Pneumogastric (Vagus) Xerve 749 Surgical Anatomy 752 Spinal Accessory Xerve 753 Surgical Anatomy 754 Hypoglossal Xerve 754 Surgical Anatomy 756 The Spinal Xeeves. Boots of the Spinal Xerves 756 Origin of Anterior Eoots 756 " of Posterior Eoots 756 CONTENTS. 19 Ganglia of the Spinal Nerves 757 Posterior Divisions of the Spinal Nerves . . 758 Anterior Divisions of the Spinal Nerves . . . 758 Points of Emergence of Spinal Nerves . . . 758 The Cervical Nerves. Eoots of the Cervical Nerves 758 Posterior Divisions of the Cervical Nerves . 759 Anterior Divisions of the Cervical Nerves . 760 The Cervical Plexus. Superficial Branches of the Cervical Plexus . 762 Deep Branches of the Cervical Plexus .... 763 The Brachial Plexus. Branches above the Clavicle. Posterior Thoracic 768 Suprascapular 768 Branches below the Clavicle. Anterior Thoracic 769 Subscapular Nerves 769 Circumflex Nerve . . 769 Musculocutaneous Nerve 770 Internal Cutaneous Nerve 770 Lesser Internal Cutaneous Nerve 771 Median Nerve 771 Ulnar Nerve 772 Musculo-spiral Nerve 774 Eadial Nerve 775 Posterior Interosseous Nerve 775 Surgical Anatomy of Brachial Plexus .... 776 The Dorsal Nerves. Eoots of the Dorsal Nerves 776 Posterior Divisions of the Dorsal Nerves . . 777 Anterior Divisions of the Dorsal Nerves . . 777 First Dorsal Nerve 777 Upper Dorsal Nerves 778 Lower Dorsal Nerves 779 Last Dorsal Nerve 780 Surgical Anatomy 780 Thr Lumbar Nerves. Boot of Lumbar Nerves 780 Posterior Divisions of Lumbar Nerves . . . 781 Anterior Divisions of Lumbar Nerves .... 781 The Lumbar Plexus. Branches of Lumbar Plexus 782 Ilio-hypogastric Nerve 782 Uio-inguinal Nerve 783 Genito-crural Nerve 783 External Cutaneous Nerve 785 Obturator Nerve 785 Accessory Obturator Nerve 786 Anterior Crural Nerve 786 Branches of Anterior Crural 786 Middle Cutaneous 786 Internal Cutaneous 786 Long Saphenous 787 Muscular and Articular Branches .... 787 The Sacral and Coccygeal Nerves, page Eoots of, origin of 788 Posterior Divisions of Sacral Nerves .... 788 Coccygeal Nerve 789 Anterior Divisions of Sacral Nerves .... 789 The Sacral Plexus. Superior Gluteal Nerve Inferior Gluteal Nerve Small Sciatic Nerve Pudic Nerve Great Sciatic Nerve Internal Popliteal Nerve External Saphenous Nerve Posterior Tibial Nerve Plantar Nerves External Popliteal or Peroneal Nerve .... Anterior Tibial Nerve Musculo-cutaneous Nerve Surgical Anatomy of Lumbar and Sacral Plexus 791 791 791 793 793 794 794 794 795 796 796 796 797 The Sympathetic Nerve. Subdivision of, into Parts 798 Branches of the Ganglia, General Description of 799 Cervical Portion of the Gangliated Cord 799 Superior Cervical Ganglion 799 Carotid Plexus 801 Cavernous Plexus 801 Middle Cervical Ganglion 803 Inferior Cervical Ganglion 803 Thoracic Part of the Gangliated Cord 801 Great Splanchnic Nerve 804 Lesser Splanchnic Nerve 804 Smallest Splanchnic Nerve 804 Lumbar Portion of the Gangliated Cord 805 Pelvic Portion of the Gangliated Cord 805 The Great Plexuses of the Sympathetic. Cardiac Plexuses 805 Great Cardiac Plexs 806 Superficial Cardiac Plexus 806 Coronary Plexuses 806 Epigastric, or Solar Plexus 806 Phrenic Plexus 808 Suprarenal Plexus 808 Eenal Plexus 808 Spermatic Plexus 808 Cceliac Plexus 808 Superior Mesenteric Plexus 809 Aortic Plexus 809 Inferior Mesenteric Plexus 809 Hypogastric Plexus £ Pelvic Plexus £ Inferior Hemorrhoidal Plexus 809 Vesical Plexus \ Prostatic Plexus 809 Vaginal Plexus * Uterine Plexus bl ° THE ORGANS OF SPECIAL SENSE. The Tongue. Structure of 811 Papillae of 813 Glands of 815 Fibrous Septum of 815 Hyo-glossal Membrane 815 Arteries and Nerves of 815 Muscles of 815 Nerves of 816 Surgical Anatomy 816 The Nose. ■Cartilages of 818 Muscles of 819 Skin Mucous Membrane Arteries, Veins, and Nerves The Xasal Fossse. Outer Wall of Mucous Membrane of . . . • ■ Superior, Middle, and Inferior Meatuses . . Arteries and Veins of Nasal Fossse .... Nerves of Nasal Fossse Surgical Anatomy of Nose and Nasal Fossse The Eye. Situation, Form of Capsule of Tenon 819 819 819 820 820 822 823 S23 824 824 20 CONTENTS. Tunics of, sclerotic 825 Cornea 826 Choroid 828 Biliary Body 829 Ciliary Muscle 830 Iris 830 Membrana Pupillaris 832 Ciliary Muscle 832 Retina 832 Structure of Retina 833 Structure of Retina at Yellow Spot 838 Arteria Centralis Retinae 839 The Humors of the Eye. Aqueous Humor 839 Anterior Chamber 839 Posterior Chamber 839 Vitreous Body 839 Suspensory Ligament of Lens 840 Canal of Petit 840 Crystalline Lens and its Capsule 840 Changes produced in the Lens by Age .... 841 Vessels of the Globe of the Eye 841 Nerves of the Eyeball 841 Surgical Anatomy of Eye 841 The Appendages of the Eye. Eyebrows 843 Eyelids 843 Eyelashes 843 Structure of the Eyelids 843 Tarsal Plates 843 Meibomian Glands 844 Conjunctiva 845 Carunculse Lachrymales 845 The Lachrymal Apparatus. Lachrymal Gland 846 " Canals 846 " Sac 847 Nasal Duct 847 Surface Form of Papebral Fissure 847 Surgical Anatomy ' 847 The Ear. The External Ear. Pinna, or Auricle 848 Structure of Auricle 849 PAGE Ligaments of the Pinna 849 Muscles of the Pinna ' , • 850 Arteries, Veins, and Nerves of the Pinna' . . 850 Auditory Canal 851 Surface Form 852 The Middle Ear, or Tympanum. Cavity of Tympanum , . 852 Roof of the Tympanic Cavity 853- Floor of the Tympanic Cavity 853 Outer Wall of the Tympanic Cavity .... 853- Internal Wall of the Tympanic Cavity . . . 853 Posterior Wall of the Tympanic Cavity . . . 854 Anterior Wall of the Tympanic Cavity . . . 854 Eustachian Tube 855 Membrana Tympani 855 Structure of ' . . 855 Ossicles of the Tympanum 85ft Ligaments of the Ossicula 857 Muscles of the Tympanum 857 Mucous Membrane of Tympanum ...... 858- Arteries of Tympanum 858 Veins and Nerves of Tympanum 858- The Internal Ear, or Labyrinth. Osseous Labyrinth 859" Vestibule :>.-.. 859- Semicircular Canals: Superior Semicircular Canal . . . . . . 560 Posterior Semicircular Canal . . . . . . 860 External Semicircular Canal . . .-■• i. . 860" Cochlea : Central Axis of, or Modiolus 861 Bony Canal of j« • 861 Osseous Lamina Spiralis * '. . 862 Membranous Labyrinth 862 Utricle and Saccule 862 Semicircular Canals 862 Cochlea . 863 Scala Tvmpaui, Scala Vestibuli. and Scala Media . 863: Organ of Corti 864 Vessels of the Labyrinth . 86ft Auditory Nerve 866- Vestibular Nerve ' - 867 Cochlear Nerve ■ 867 Surgical Anatomy 867 THE ORGANS OF DIGESTION. Subdivisions of the Alimentary Canal .... 869 The Mouth 869 The Lips . 869 The Cheeks 870 The Gums 870 The Teeth. General Characters of 871 Permanent Teeth 871 Incisors 871 Canine 872 Bicuspids 872 Molars 873 Temporary, or Milk Teeth 873 Structure of the Teeth 874 Ivory or Dentine 876 Enamel 877 Cortical Substance 878 Development of the Teeth 878 of the Permanent Teeth . . . 881 Eruption of the Teeth 881 The Palate. Hard Palate 883 Soft Palate 883 Uvula, Pillars of the Soft Palate 883 Mucous Membrane and Aponeurosis .... 883 Muscles of Soft Palate 884 The Tonsils. Arteries 884 Veins and Nerves of Tonsils 884 The Salivary Glands. Parotid Gland. Situation and Relations 884 Stenson's Duct ,...:. 885 Surface Form , .' . 886 Vessels and Nerves of Parotid Gland .... 886 The Submaxillary Gland. Situation and Relations 886 Wharton's Duct 886 Vessels and Nerves of Submaxillary Gland . 887 The Sublingual Gland. Situation and Relations 887 Vessels and Nerves of 887 Structure of Salivarv Glands 887 Surface Form of Mouth 888- The Pharynx and OZsophagtts. Situation and Relations 890- Structure of Pharynx 890" Surgical Anatomy 891 Relations of Oesophagus 891 Structure 892- CONTENTS. 21 PAGE Vessels 892 Nerves of 893 Surgical Anatomy 893 The Abdomen. Boundaries Apertures of Eegions . . . The Peritoneum. Eeflections traced Lesser Sac of Peritoneum Ligaments formed by Peritoneum Omenta Lesser Omentum Great Omentum Gastro-splenic Omentum Mesenteries Mesocolon, Mesorectum, Appendices Epi- ploicee Eetro-peritoneal Fossae The Stomach. Situation Surfaces Greater aud Lesser Curvatures Cardiac and Pyloric Orifices Alterations in Position Pylorus ' Structure of Stomach Serous Coat Muscular Coat and Mucous Membrane . . . Gastric Follicles Vessels aud Nerves of Stomach Surface Marking Surgical Anatomy 895 895 895 899 901 901 901 902 902 902 903 904 905 905 906 906 907 908 908 908 908 909 910 910 911 The Small Intestines. Duodenum First or Superior Portion . . . Second or Descending Portion Third or Transverse Portion . Fourth or Ascending Portion . Vessels and Nerves of Duodenum . Jejunum and Ileum Meckel's Diverticulum Structure of Small Intestines . . . Serous and Muscular Coats .... Mucous Membrane and Epithelium Valvulse Conniventes Villi — their Structure Simple Follicles Duodenal Glands Solitary Glands Peyer's Glands Vessels and Nerves The Large Intestine. Caecum Appendix Caeci Vermiformis . Ileo-csecal Valve .^. Colon . . . ' Ascending Transverse Descending Sigmoid Flexure Eectum Structure of Large Intestine . . . Serous Coat Muscular Coat Areolar and Mucous Coats .... Simple Follicles 912 912 912 914 914 914 914 915 915 915 915 916 917 918 918 919 919 921 922 922 923 923 923 924 925 925 925 928 928 928 928 929 Solitary Glands 929 Vessels and Nerves 929 Surface Form 930 Surgical Anatomy 930 The Liver. Size, Weight, Position of 933 Its Surfaces and Borders 934 Fissures. Longitudinal 935 Fissure of Ductus Venosus . .' 936 Portal Fissure 936 Fissure for Gall-bladder 936 Fissure for Inferior Vena Cava 93& Lobes. Eight 937 Quadratus 937 Spigelii 937 Caudatus 937 Left 937 Ligaments. Falciform 937 Lateral and Coronary 937 Eound Ligament 938 Vessels of Liver 938 Structure of Liver 938 Serous Coat 938 Fibrous Coat 938 Lobules 938 Hepatic Cells 939 Hepatic Artery 940 Portal Vein 940 Hepatic Veins 940 Biliary Ducts 940 Lymphatics of the Liver 941 Nerves of Liver 941 Excretory Apparatus of the Liver. Hepatic Duct 942 Gall-bladder 942 Structure 942 Cystic Duct 943 Ductus Communis Choledochus 943 Structure 943 Surface Marking of Liver 943 Surgical Anatomy 944 The Pancreas. Dissection 945 Eelations 945 Duct 947 Structure 948 Vessels and Nerves 948 Surface Marking 948 Surgical Anatomy 948 The Spleen. Eelations 949 Size and Weight 950 Structure of Serous and Fibrous Coats . . . 950 Proper Substance 951 Splenic Artery, Distribution 952 Malpighian Bodies 952 Capillaries of Spleen 953 Veins of Spleen 953 Lymphatics 953 Nerves 954 Surface Marking of Spleen 954 Surgical Anatomy 954 THE ORGANS OF VOICE AND RESPIRATION. The Larynx. I Cartilage of Wrisberg 958 Epiglottis 9o8 Cartilages of the Larvnx 955 | Ligaments of the Larynx 958 Thyroid Cartilage 955 Ligaments Connecting the Thyroid Cartilage Cricoid Cartilage 956 \ with the Hyoid Bone 958 Arytenoid Cartilages, Cartilages of Santo- Ligaments Connecting the Thyroid Cartilage rini 957 with the Cricoid 958 22 CONTENTS. PAGE Ligaments Connecting the Arytenoid Carti- lages to the Cricoid 959 Ligaments of the Epiglottis 959 Superior Aperture of the Larynx 959 Eima Glottidis 959 False Vocal Cords 960 True Vocal Cords 961 Ventricle of Larynx, Sacculus Laryngis ." . . 961 Muscles of Larynx 961 Crico-thyroid 961 Crico-arytenoideus posticus 962 Crico-arytenoideus lateralis 962 Arytenoideus 962 Thyro-arytenoideus 962 Muscles of the Epiglottis 963 Thyro-epiglottideus 963 Aryteno-epiglottideus, superior 963 " inferior 963 Actions of Muscles of Larynx 963 Mucous Membrane of Larynx 964 Glands, Vessels, and Nerves of Larynx . . . 964 The Trachea. Relations 965 Bronchi 966 Structure of Trachea 966 Cartilages 966 Fibrous Membrane 967 Muscular Fibres 967 Mucous Membrane 967 Glands 967 Vessels and Nerves 967 Surface Form 968 Surgical Anatomy of Laryngo-tracheal Eegion 968 The Pleura. Reflections . . 969 Vessels and Nerves 971 Surgical Anatomy 971 The Mediastina. page Superior Mediastinum 971 Anterior Mediastinum 972 Middle Mediastinum 972 Posterior Mediastinum 973 The Lungs Surfaces 973 Borders and Lobes 973 Boot of Lung 974 Weight, Color, and Properties of Substance of Lung 975 Structure of Lung 975 Serous Coat and Subserous Areolar Tissue . . 975 Parenchyma and Lobules of Lung 976 Bronchi, Arrangement of, in Substance of Lung 976 Structure of Smaller Bronchial Tubes .... 976 The Air-cells 976 Pulmonary Artery 976 Pulmonary Capillaries and Veins 976 Bronchial Arteries 976 Bronchial Veins 977 Lymphatics and Nerves of Lung 977 Surface Form of Lungs 977 Surgical Anatomy 977 The Thyroid Gland. Surface and Relations 979 Structure '. . 980 Vessels and Nerves 981 Surgical Anatomy 981 The Thymus Gland. Relations 981 Structure 982 Vessels and Nerves 982 THE URINARY ORGANS. The Kidneys. Relations 985 Dimensions, Weight 985 General Structure 986 Cortical Substance 987 Medullary Substance 987 Minute Structure 987 Malpigliian Bodies 988 Tufts 988 Capsule 988 Tubuli Uriniferi, Course 988 Structure 990 Renal Blood-vessels 992 Renal Veins 992 Vente Rectee 992 Nerves 993 Lymphatics 993 Surface Form * 993 Surgical Anatomy 993 The Ureters. Situation 994 Calices . 995 Course 995 Relations 995 Structure 995 Surgical Anatomy 996 The Suprarenal Capsides. Relations 997 Structure 997 Vessels and Nerves 998 The Pelvis. Boundaries 998 Contents 998 The Bladder. Shape, Position, Relations 998 Subdivisions 1001 Urachus 1002 Ligaments 1002 Structure 1002 Interior of Bladder 1003 Vessels and Nerves 1004 Surface Form 1004 Surgical Anatomy 1004 The Male Urethra. Divisions 1005 Structure 1006 Surgical Anatomy 1007 Bladder and Urethra in the Female .... 1007 THE MALE ORGANS OF GENERATION. Prostate Glands 1009 Structure - 1010 Vessels and Nerves 1010 Surgical Anatomy ... 1011 Cowper's Gland 1011 Structure 1011 The Penis. Root 1011 Glans Penis 1011 Body 1012 Structure of Penis 1012 Corpora Cavernosa 1012 Structure 1012 Arteries of the Penis 1013 Corpus Spongiosum 1013 The Bulb 1013 Structure of Corpus Spongiosum ....... 1014 Lymphatics of the Penis 1011 CONTENTS. 23 PAGE Nerves of the Penis 1014 Surgical Anatomy 1014 The Testes and their Coverings. Scrotum 1015 Coverings of the Testis . 1015 Vessels and Nerves of the Coverings of the Testis 1016 The Spermatic Cord. Its Composition 1016 Relations of, in Inguinal Canal 1016 Arteries of the Cord 1016 Veins of the Cord 1016 Lymphatics and Nerves of the Cord . . . .1017 Surgical Anatomy . 1017 The Testes. Form and Situation 1017 Size and Weight 1018 Coverings 1018 Tunica Vaginalis 1018 Tunica Albuginea 1018 Mediastinum Testis 1018 Tunica Vasculosa 1019 i Structure of the Testis 1019 Lobulus of the Testis mi'.i Tubuli Seminiferi 1019 Arrangement in Lobuli 1019 in Mediastinum Testis .... 1019 in Epididymis 1019 Spermatogenesis 1020 Vas Deferens, Course, Relations 1021 Structure 102] Vas Aberrans . 1021 Surgical Anatomy 1021 Vesiculse Seminales. Form and Size 1022 Relations 1022 Structure 1022 Ejaculatory Ducts 1023- THE FEMALE ORGANS OF GENERATION. Mons Veneris, Labia Majora 1025 " " Labia Minora 1026 Clitoris ' 1026 Meatus Urinarius 1027 Hymen, Glands of Bartholin 1027 The Vagina. Relations 1028 Structure 1028 The Uterus. Situation, Form, Dimensions 1028 Fundus, Body, and Cervix 1029 Ligaments 1029 Cavitv of the Uterus 1030 Cavitv of the Cervix 1031 Structure 1031 Vessels and Nerves 1032 Its Form, Size, and Situation in the Foetus . 1033 " " " at Puberty . . 1033 Its Form, Size, etc., during Menstruation . . 1033 Its Form during Pregnancy 1033 after Parturition 1033 in Old Age 103a The Appendages of the Uterus. Fallopian Tubes 1034 Structure 1035 Ovaries 1035 Structure 1036- Graafian Vesicles 1036 Discharge of the Ovum 1037 Ligament of the Ovary 1038 Round Ligaments 1038 Vessels and Nerves of Appendages . . . . 1038 The Mammary Glands. Situation and Size 1038 Nipple 1039 Structure of Mamma 1039 Vessels and Nerves 1040 THE SURGICAL ANATOMY OF HERNIA. INGUINAL HEENIA. Coverings of Inguinal Hernia. Dissection 1041 Superficial Fascia ; . . . . 1041 Superficial Vessels and Nerves 1041 Deep Layer of Superficial Fascia 1042 Aponeurosis of External Oblique . . .-. . . 1042 External Abdominal Ring 1043 Pillars of the Ring 1043 Intercolumnar Fibres 1043 " Fascia 1043 Poupart's Ligament 1044 Gimbernat's Ligament 1044 Triangular Ligament 1044 Internal Oblique Muscle 1045 Cremaster 1045 Transversalis Muscle 1045 Spermatic Canal 1046 Transversalis Fascia 1046 Internal Abdominal Ring 1047 Subperitoneal Areolar Tissue 1047 Deep Epigastric Artery 1047 Peritoneum 1047 Oblique Inguinal Hernia. Course and Coverings of Oblique Hernia . . 1049 Seat of Stricture 1051 Scrotal Hernia 1051 Bubonocele 1051 Congenita] Hernia 1051 Infantile and Encysted Hernia 1051 Hernia into the Funicular Process 1051 Direct Inguinal Hernia. Course and Coverings of the Hernia .... 1052 Seat of Stricture 1053 Incomplete Direct Hernia in,",:; Comparative Frequency of Oblique and Di- rect Hernia 1053 Division of Stricture in Inguinal Hernia . . 1053 FEMORAL HEENIA. Dissection 1053 Superficial Fascia 1053 Cutaneous Vessels 1054 Internal Saphenous Vein 1054 Superficial Inguinal Glands 1055 Cutaneous Nerves 1055 Deep Layer of Superficial Fascia 1055 Cribriform Fascia 1055 Fascia Lata 1055 Iliac Portion 1055 Pubic Portion 1056 Saphenous Opening 1056 ( 'rural Arch 1057 Gimbernat's Ligament 1058 Femoral Sheath 1059 Deep Crural Arch 1059 Crural Canal 1059 24 CONTENTS. PAGE Femoral or Crural Eing 1060 Position of Parts around the Eing 1060 Septum Crurale 1060 Descent of Femoral Hernia 1061 PAGE Coverings of Femoral Hernia 1061 Varieties of Femoral Hernia 1061 Seat of Stricture 1061 SURGICAL ANATOMY OF THE PERINvEUM. Ischio-rectal Region. Dissection of 1063 Boundaries of 1063 Superficial Fascia 1063 Ischio-rectal Fossa • • • . . 1064 Position of Parts contained in 1064 The Perinteum Proper in the Male. Boundaries and Extent 1064 Deep Layer of Superficial Fascia 1065 •Course taken by the Urine in Eupture of the Urethra 1065 JVEuscles of the Perinseum (Male) 1065 Deep Perineal Fascia 1065 Superficial Layer 1066 Deep Layer 1066 Parts between the two Layers 1066 Compressor Urethras 1067 Cowper's Glands 1067 Pudic Vessels and Nerves 1067 Artery of the Bulb 1067 Position of the Viscera at Outlet of Pelvis . 1067 Prostate Gland "... 1068 Surgical Anatomy of Lithotomy 1068 Parts divided in the Operation 1069 Parts to be avoided in the Operation .... 1069 Abnormal Course of Arteries in the Perinseum 1069 The Female Perinseum. Superficial Fascia 1069 Deep Fascia 1069 Compressor Urethras 1070 Perineal Body 1070 Pelvic Fascia • 1070 Obturator Fascia 1071 Eecto-vesical Fascia : . . 1071 GENERAL ANATOMY OR HISTOLOGY. The Animal Cell 1073 The Nutritive Fluids 1077 Blood 1077 Lvmph and Chyle 1082 Epithelium 1082 Connective Tissue 1086 The Connective Tissues proper 1086 Adipose Tissue 1091 Pigment 1092 ■Cartilage 1092 White Fibro-cartilage 1094 Yellow or Eeticular, Elastic Cartilage . 1094 The Bone 1096 Development of Bone 1099 Muscular Tissue 1104 Striped Muscle 1 . . . . 1105 Unstriped Muscle 1109 Cardiac Muscular Tissue 1110 Nervous Tissue 1111 The Brain ."~- 1118 The Nerves 1118 The Sympathetic Nerve 1120 Origin and Termination of Nerves . . . 1120 The Ganglia 1124 The Vascular System 1126 The Arteries 1126 The Capillaries 1128 The Veins 1130 The Lymphatics 1131 The Lymphatic Glands 1133 The Skin and its Appendages 1135 The Nails 1139 The Hair 1140 The Sebaceous Glands 1142 The Sudoriferous Glands 1142 Serous Membranes 1143 Synovial Membranes 1145 Mucous Membranes . . .' 1145 Secreting Glands 1146 EMBRYOLOGY. The Ovum 1149 Maturation of 1150 Impregnation of 1151 Segmentation of 1152 Formation of the Mesoblast 1154 First Eudiments of the Embryo 1155 Formation of Membranes 1160 The Amnion • 1160 The Chorion 1161 The Allantois . .1162 The Decidua 1162 The Placenta 1164 Development of the Embryo 11 65 The Spine 1165 The Eibs and Sternum 1166 The Cranium and Face 1166 The Nervous Centres 1172 The Nerves 1178 The Eye 1180 The Ear 1183 The Nose 1184 The Skin, Glands, and Soft Parts . . . .1186 The Limbs 1187 The Muscles 1187 The Blood-vascular System 1 187 Vitelline Circulation 1187 Placental Circulation . . . 1189 The Alimentary Canal and its Appendages . 1198 The Eespiratory Organs 1206 The Urinary and Generative Organs .... 1207 Ovaries and Testicles 1209 Descent of the Testes 1211 External Organs 1212 Chronological Tables of the Development of the Fetus 1215 INDEX 1217 DESCRIPTIVE AND SURGICAL ANATOMY. OSTEOLOGY-THE SKELETON. nnHE entire skeleton in the adult consists of 200 distinct bones. These are — The spine or vertebral column (sacrum and coccyx included) 26 Cranium 8 Face 14 Hyoid bone, sternum, and ribs 26 Upper extremities . . 64 Lower extremities 62 200 In this enumeration the patellae are included as separate bones, but the smaller sesamoid bones and the ossicula auditus are not reckoned. The teeth belong to the tegumentary system. These bones are divisible into four classes : Long, Short, Flat, and Irregular. The Long Bones are found in the limbs, where they form a system of levers, which have to sustain the weight of the trunk and to confer the power of locomo- tion. A long bone consists of a shaft and two extremities. The shaft is a hollow cylinder, contracted and narrowed to afford greater space for the bellies of the muscles ; the walls consist of dense, compact tissue of great thicknep" in the middle, but becoming thinner toward 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 not straight, but curved, the curve generally taking place in two directions, thus affording greater strength to the bone. The bones belonging to this class are the clavicle, humerus, radius, ulna, femur, tibia, fibula, metacarpal and metatarsal bones, and the phalanges. Short Bones. — Where a part of the skeleton is intended for strength and com- pactness, and its motion is 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 compressed, such as the bones of the carpus and tarsus. These bones, in their structure, are spongy throughout, excepting at their surface, where there is a thin crust of compact substance. The patella? also, together with the other sesamoid bones, are by some regarded as short bones. Flat Bones. — Where the principal requirement is either extensive protection or the provision of broad surfaces for muscular attachment, we find the osseous structure expanded into broad, flat plates, as is seen in the bones of the skull and the shoulder-blade. These bones are composed of two thin layers of compact tissue enclosing 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 3 33 34 THE SKELETON. 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, scapula, os innominatum, sternum, ribs, and patella. The Irregular or Mixed Bones are such as, from their peculiar form, cannot be orouped 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 vertebra?, sacrum, coccyx, temporal, sphenoid, ethmoid, malar, 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. 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 fossa?, grooves, furrows, fissures, notches, etc. These non-articular eminences and depressions serve to increase the extent of surface for the attachment of liga- ments and muscles, and are usually well marked in proportion to the muscularity of the subject. 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 anbipvaiz, an excrescence) ; but if such process is developed as a separate piece from the rest of the bone, to which it is afterward joined, it is termed an epiphysis (from In'upuoiz, an accretion). The main part of the bone, or shaft, which is formed from the primary centre of ossification, is termed the diaphysis, and is separated, during growth, from the epiphysis by a layer of cartilage, at which growth in length of the bone takes place. THE SPINE. The Spine is a flexuous and flexible column formed of a series of bones called x 7 (from vertere, to turn). ■ Vertebrae are thirty-three in number, and have received the names dorsal, lumbar, sacred, and coccygeal, according to the position which r -_ u py; 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 increased by an additional vertebra in one region, or the number may be diminished in one region, the deficiency being supplied by an additional vertebra in another. These observations do not apply to the cervical portion of the spine, the number of bones forming which is seldom increased or diminished. The vertebrae in the upper three regions of the spine are separate 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 or arch. The arch (neural) is formed of two pedi- cles and two lamina?, supporting seven processes — viz. four articular, two trans- verse, and one spinous. The bodies of the vertebrae are piled one upon the other, forming a strong CERVICAL VERTEBRJE. 35 pillar for the support of the cranium and trunk ; the arches forming a hollow cylinder behind the bodies for the protection of the spinal cord. The different vertebra? are connected together by means of the articular processes and the intervertebral fibro-cartilages ; while 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 vertebra? apertures exist through which the spinal nerves pass from the cord. Each of these constituent parts must now be separately examined. The Body or Centrum is the largest part of a vertebra. Above and below, it is flattened; its upper and lower surfaces are rough for the attachment of the intervertebral fibro-cartilages, and present a rim around their circumference. In front, it is convex from side to side, concave from above downward. Behind, it is flat from above downward and slightly concave from side to side. Its ante- rior surface is perforated by a few small apertures, for the passage of nutrient vessels ; whilst on the posterior surface is a single large, irregular aperture, or occasionally more than one, for the exit of veins from the body of the vertebra — the vence basis vertebrae. The Pedicles are two short, thick pieces of bone, which project backward, 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 vertebra? 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 and blood-vessels. The Laminae are two broad plates of bone which complete the neural arch by fusing together in the middle line behind. They enclose a foramen, the spinal 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 subfiava. The Spinous Process projects backward from the junction of the two lamina;, and serves for the attachment of muscles and ligaments. The Articular Processes, four in number, two on each side, spring from the junction of the pedicles with the lamina?. The two superior project upward, their articular surfaces being directed more or less backward; the two inferior project downward, their articular surfaces looking more or less forward. 1 The Transverse Processes, two in number, project one at each side from the point where the lamina joins the pedicle, between the superior and inferior articular processes. They also serve for the attachment of muscles and ligaments. Character of the Cervical Vertebrae (Fig. 1). The Cervical Vertebrae are smaller than those in any other region of the spine, and may readily be distinguished by the foramen in the transverse process, which does not exist in the transverse process of either the dorsal or lumbar vertebra?. The Body is small, comparatively dense, and broader from side to side than from before backward. The anterior and posterior surfaces are flattened and of equal depth ; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and fore part of the vertebra? below. Its upper surface is concave transversely, and presents a pro- jecting lip on each side; its lower surface is convex from side to side, concave from before backward, and presents laterally a shallow concavity which receives the corresponding projecting lip of the adjacent vertebra, The pedicles are directed outward and backward, and are attached to the body midway between the upper and lower borders, so that the superior intervertebral notch is as deep as the inferior, but it is, at the same time, narrower. The lamince are narrow. 1 It may, perhaps, be as well to remind the reader that the direction of a surface is determined by that of a line drawn at right angles to it. { 36 THE SKELETON. long, thinner above than below, and overlap each other, enclosing the spinal foramen, Avhich is very large, and of a triangular form. The spinous j^'ocess is short, and 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 articular processes are flat, oblique, and of an oval form : the superior are directed backward and upward ; the inferior forward and downward. The transverse processes are short, directed downward, outward, and forward, bifid at their extremity, and marked by a groove along their upper surface, which runs downward and outward from the superior intervertebral notch, and serves for the transmission of one of the cer- vical nerves. They are situated in front of the articular processes and on the outer side of the pedicles. The transverse processes are pierced at their base by a foramen, for the transmission of the vertebral artery, vein, and plexus of nerves. Anterior tubercle of tram- verse process. Foramen for vertebral artery Posterior tubercle of transverse process Transverse process. ^Superior articular process. Inferior articular process. Fig. 1.— Cervical vertebra. Each process is formed by two roots : the anterior root, sometimes called the costal process, arises from the side of the body, and is the homologue of the rib in the dorsal region of the spine; the posterior root springs from the junction of the pedicle with the lamina, and corresponds with the transverse process in the dorsal region. It is by the junction of the two that the foramen for the vertebral vessels is formed. The extremity of each of these roots forms the anterior and posterior tubercles of the transverse processes. 1 The peculiar vertebrae in the cervical region are the first, or Atlas ; the second, or Axis ; and the seventh, or Vertebra prominens. The great modifications in the form of the atlas and axis are designed 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 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; while the parts corresponding to the pedicles join in front to form the anterior arch. The atlas is ring-like, and consists of an anterior arch, a posterior arch, and two lateral masses. The anterior arch forms about one-fifth of the ring: 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 upper and lower borders give attachment to the anterior occipito-atlantal and the anterior atlanto-axial ligaments, which connect it with the occipital bone above and the axis below. The posterior arch forms about two-fifths of the circumference of the Done ; it terminates behind in a tubercle, 1 The anterior tubercle of the transverse process of the sixth cervical vertebra is of large size, and is sometimes known as " Chassaignac's " or the "carotid tubercle."' It is in ^ relation with the carotid artery, which lies in front and a little external to it so that, as w° | jinted out by Chnssaignac, the vessel can with ease be compassed against it. CEB VIC A L VEB TEBRjE. hich is the rudiment of a spinous process, and gives origin to the Rectus capitis osticus mir.or. The diminutive size of this process prevents any interference in ^he movements between the atlas and the cranium. The posterior part of the a tirch presents above and behind a rounded edge for the attachment of the posterior tpccipito-atlantal ligament, while in front, immediately behind each superior .articular process, is a groove, sometimes converted into a foramen by a delicate l %oiiy spiculum which arches backward 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 pr ocesses, instead of in front of them, as in the other vertebrae. They 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 backward and inward. They also transmit the suboccipital (first spinal) nerve. On the under sur- face of the posterior arch, in the same situation, are two other grooves, placed behind the lateral masses, and representing the inferior intervertebral notches of other vertebrae. They are much less marked than the superior. The lower border also gives attachment to the posterior atlanto-axial ligament, which con- nects it with the axis. 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 articu- lating processes above, and two below. The two superior are of large size, oval, Tubercle Diagram of section of odontoid process. Diagram of section of transverse ligament. Foramen for vertebral artery. Groove for vertebral artery and 1st cervical nerve. Rudimentary spinous process. Fig. 2. — First cervical vertebra, or atlas. concave, and approach each other in front, but diverge behind; they are directed upward, inward, and a little backward, each forming a kind of cup for the corre- sponding condyle of the occipital bone, and are admirably adapted to the nodding movements of the head. Not infrequently 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 downward and inward, 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 the transverse 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 p rior allowing the transmission of the spinal cord and its membranes. This part of the spinal canal is of considerable size, to afford space for the spinal cord; and hence lateral displacement of the atlas may occur without compression- of this structure. The transverse processes are of large size, project directly outward and downward from the lateral masses, and serve for the attachment of special muscles which assist in rotating the head. They are long, not bifid, and perfor- ated at their base by a eVnal for the vertebral artery, which is directed from below, upward and backward. The Axis (Fig. 3) is so named from forming the pivot upon which the first vertebra, carrying the head, rotates. The most distinctive character of this bone THE SKELETON. is the strong, prominent process, tooth-like in form (hence the name ■which rises perpendicularly from the upper surface of the body, deeper in front than behind, and prolonged downward anteriorly so the upper and fore part of the next vertebra. It presents in frc Odontoid process. Rough surface for check ligaments: Articular surface for transverse ligament. Articular surface Jo. atlas. Body. Spinous process.- ~ransverse process. Inferior articular process. Fig. 3. —Second cervical vertebra, or axis. longitudinal ridge, separating two lateral depressions for the attachment of the Longus colli muscle of either side. The odontoid process presents two, articulating surfaces : one in front, of an oval form, for articulation with the atlas ; another behind, for the transverse ligament — the latter frequently encroaching on the sides of the process. The apex is pointed, and gives attachment to the middle fasciculus of the odontoid or check ligaments (dig amentum suspensoriwni). Below the apex the process is somewhat enlarged, and presents on either side a rough impression for the attachment of the lateral fasciculi of the odontoid or check ligaments, which connect it to the occipital bone ; the base of the process, where it is attached to the body, is constricted, so as to prevent displacement from the transverse ligament, which binds Body. it in this situation to the anterior arch of the atlas. " Sometimes, however, this process does become displaced, especially in children, in whom the ligaments are more relaxed : instant death is the re- sult of this accident. The in- ternal structure of the odontoid process is more compact than that of the body. The pedicles are broad and strong, especially their anterior extremities, which coa- lesce with the sides of the body and the root of the odontoid process. The lamina? are thick and strong, and the spinal fora- men large, but smaller than that of the atlas. The transverse 'proc- esses are very small, not bifid, and perforated by the foramen for the vertebral artery, which is directed obliquely upward and outward. The superior articular surfaces are round, slightly convex, directed upward and outward, 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 vertebrae. The superior Fig. 4.- Spinous process. ■ Seventh cervical vertebra, or vertebra prominens. DORSAL VERTEBRA. 39 intervertebral notches are very shallow, and lie behind the^articular processes ; the inferior in front of them, as in the other cervical vertebrae. The spinous pr> 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 process; hence the name "vertebra prominens." This process is thick, nearly horizontal in direction, not bifurcated, and has attached to it the lower end of the ligamentum nuchae. The transverse process is usually of large size, its posterior tubercles are large and prominent, while the anterior are small and faintly marked; its upper surface has usually a shallow groove, and it seldom presents more than a trace of bifurcation at its extremity. The foramen in the transverse process is sometimes as large as in the other cervical vertebrae, but is usually smaller on one or both sides, and sometimes wanting. On the left side it occasionally gives passage to the vertebral artery ; more frequently the vertebral vein traverses it on both sides ; but the usual arrangement is for both artery and vein to pass in front of the transverse process, and not through the foramen. Occasionally the anterior root of the transverse process exists as a separate bone, and attains a large size. It is then known as a "cervical rib." Characters of the Dorsal Vertebrae. The Dorsal Vertebras are intermediate in size between those in the cervical and those in the lumbar region, and increase in size from above downward, the upper Superior articular process Demi-facet for head of rib. Facet for tubercle of rib. Demi-facet for head of rib. Inferior articular process. Fig. 5.— A dorsal vertebra. vertebrae in this segment of the spine being much smaller than those in the lower part of the region. The dorsal vertebrae may be at once recognized by the pres- ence on the sides of the body of one or more facets or half-facets for the heads of the ribs. The bodies of the dorsal vertebrae 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 as broad in the antero-posterior as 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, 40 THE SKELETON. near the root of the pedicle, by two demi-facets,. one above, the other below, are covered with cartilage in the recent state, and, when articulated with the ing vertebrae, form, with the intervening fibro-cartilage, oval surfaces reception of the heads of the corresponding ribs. The •pedicles are directed ward, and the inferior intervertebral notches are of large size, and deeper tha* any other region of the spine. The laminae, are broad, thick, and imbricated- that is to say, overlapping one another like tiles on a roof. The spinal foramen is | An entire facet above , \ a demi-facet below. —A demi-facet above. One entire facet. An entire facet, j No facet on transverse process, which is ru- [ dimentary. An entire facet. C No facet on trans- verse process. \ Inferior articular process, convex and turned out- ward. Fig. 6. — Peculiar dorsal vertebrae. small, and of a circular form. The spinous processes are long, triangular on transverse section, directed obliquely downward, and terminate in a tubercular extremity. They overlap one another from the fifth to the eighth, but are less oblique in direction above and below. The articular processes are flat, nearly vertical in direction, and project from the upper and lower part of the pedicles ; the superior being directed backward and slightly outward and upward, the inferior LUMBAR VERTEBRA. 41 forward and a little inward and downward. The transverse processes arise from the same parts of the arch as the posterior roots of the transverse processes in the neck, and are situated behind the articular processes and pedicles ; they are thick, strong, and of great length, directed obliquely backward and outward, presenting a clubbed extremity, which is tipped on its anterior part by a small concave surface, for articulation with the tubercle of a rib. Besides the articular facet for the rib, three indistinct tubercles may be seen rising from the transverse processes, one at the upper border, one at the lower border, and one externally. In man they are comparatively of small size, and serve only for the attachment of muscles. But in some animals they attain considerable magnitude, either for the purpose of more closely connecting the segments of this portion of the spine or for muscular and ligamentous attachment. 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 body is like that of a cervical vertebra, being broad trans- versely ; its upper surface is 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, however, the ninth has two demi-facets on each side ; when this occurs the tenth has only a demi-facet at the upper part. The Tenth. Dorsal has (except in the cases just mentioned) an entire articular facet on each side, above, which is partly placed on the outer surface of the pedicle. It has no demi-facet below. In the Eleventh Dorsal the body approaches in its form and size to the lumbar. 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 spinous process is short, and nearly horizontal in direction. The transverse processes are very short, tubercular at their extremities, and have no articular facets for the tubercles of the ribs. 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 outward, like those of the lumbar vertebrae ; by the general form of the body, laminae, and spinous process, approaching to that of the lumbar vertebrae ; and by the transverse processes being shorter, and marked by three elevations, the superior, inferior, and external tubercles, which correspond to the mammilla ry, accessory, and transverse processes of the lumbar vertebrae. Traces of similar elevations are usually to be found upon the other dorsal vertebrae (vide ut supra). Characters of the Lumbar Vertebrae. The Lumbar Vertebrae (Fig. 7) are the largest segments of the vertebral column, and can at once be distinguished by the absence of the foramen in the transverse process, the characteristic point of the cervical vertebrae, and by the absence of any articulating facet on the side of the body, the distinguishing mark of the dorsal vertebrae. The body is large, and has a greater diameter from side to side than from before backward, slightly thicker in front than 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 superincumbent weight. The pedicles are very strong, 'directed backward from the upper part of the bodies ; consequently, the inferior intervertebral notches are of considerable depth. The lamina? are broad, short, and strong, and the spinal foramen triangular, larger than in the dorsal, smaller than in the cervical, region. The spinous processes are thick and broad, somewhat quadrilateral, horizontal in direction, thicker below than above, and terminating by a rough, uneven border. 42 THE SKELETON. The superior articular processes are concave, and look backward and inwa. the inferior, convex, look forward and outward ; the former are separated by c much wider interval than the latter, embracing the lower articulating processes of the vertebra above. The transverse processes are long, slender, directed trans- Superior articular process. Fig. 7.— Lumbar vertebra. versely outward in the upper three lumbar vertebrae, slanting a little upward in the lower two. They are situated in front of the articular processes, instead of behind them as in the dorsal vertebrae, and are homologous with the ribs. Of the three tubercles noticed in connection with the transverse processes of the twelfth dorsal vertebra, the superior ones become connected in this region with the back Inf. articular process. Mammillary process. Accessory process. Sup. articular process. Fig. 8. — Lumbar vertebrae. part of the superior articular processes, and have received the name of mammillary processes ; the inferior are represented by a small process pointing downward, situated at the back part of the base of the transverse process, and called the accessory processes : these are the true transverse processes, which are rudimental in this region of the spine; the external ones are the so-called transverse processes, LUMBAR VERTERRJE. 43 the homologue of the rib, and hence sometimes called costal processes (Fig- 8). Although in man these are comparatively small, in some animals they attain con- siderable size, and serve to lock the vertebras more closely together. The Fifth Lumbar vertebra is characterized by having the body much thicker in front than behind, "which accords with 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 thick- ness of its transverse processes, which spring from the body as well as from the pedicles. Structure of the Vertebrae. — 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 of vessels ; its interior is traversed by one or two large canals, for the reception of veins, which con- verge toward a single large, irregular aperture or several small apertures at the posterior part of the body of each bone. The arch and processes projecting from it have, on the contrary, an exceedingly thick covering of compact tissue. Development. — Each vertebra is formed of four primary centres of ossification (Fig. 9), one for each lamina and its processes, and two for the body. 1 ' Ossifica- By If primary centres. I ivj \2 for body {8th week), j&ik \ i m By 4 secondary centres. lfor each lamina (6th week). Fig. 9. —Development of a vertebra. By 2 additional plates. ■1 for upper surface ' of body, 1 for under surface of body, Fig. 10. 21 years. 1 for each trans- verse process, 16 years. 2 (sometimes 1) for spinous process (16 years). Fig. 11. tion commences in the laminae about the sixth week of foetal life, in the situation where the transverse processes afterward project, the ossific granules shooting backward to the spine, forward into the pedicles, and outward into the transverse and articular processes. Ossification in the body commences in the middle of the cartilage about the eighth week by two closely approximated centres, which speedily coalesce to form one central ossific point. According to some authors, ossifica- tion commences in the lamina only in the upper vertebrae — i. e., in the cervical and upper dorsal. The first ossific points in the lower vertebrae are those which are to form the body, the osseous centres for the laminae appearing at a subsequent period. At birth these three pieces are perfectly separate. During the first year the laminae become united behind, the union taking place first in the lumbar region and then extending upward through the dorsal and lower cervical regions. About the third year the body is joined to the arch on each side in such a manner that the body is formed from the three original centres of ossification, the amount con- tributed by the pedicles increasing in extent from below upward. Thus the bodies of the sacral vertebrae are formed almost entirely from the central nuclei : the bodies of the lumbar are formed laterally and behind by the pedicles: in the dorsal region the pedicles advance as far forward as the articular depressions for the head of the ribs, forming these cavities of reception ; and in the neck the 1 By many observers it is asserted that the bodies of the vertebra are developed from a single centre which speedily becomes bilobed, so as to give the appearance of two nuclei ; but that there are two centres, at all events sometimes, is evidenced by the fact that the two halves of the body of the vertebra may remain distinct throughout life and be separated by a fissure through which a protru- sion of the spinal membrane may take place, constituting an anterior spina bifida. 44 THE SKELETON. By 3 centres. 1 for anterior arch (1st year), not constant. 1 for each "I , * , • ., lateral mass J ■' Fig. 12.— Atlas. 2d year. 6th month. 1 for each lateral mass. 1 for body (4-th month). 1 for under surface of body. Fig. 13.— Axis. 2 additional centres. lateral portions of the bodies are formed entirely by the advance of the pedicles. The line along which union takes place between the body and the neural arch is named the neuro-central suture. Before puberty no other changes occur, except- ing a gradual increase in the growth of these primary centres ; the upper and under surfaces of the bodies and the ends of the transverse and spinous processes being tipped with cartilage, in which ossific granules are not as yet deposited. At sixteen years (Fig. 11) three secondary centres appear, one for the tip of each transverse process, and one for the extremity of the spinous process. In some of the lumbar vertebrae, especially the first, second, and third, a second ossi- fying centre appears at the base of the spinous process. At twenty-one years (Fig. 10) a thin circular epiphysial plate of bone is formed in the layer of cartilage situated on the upper and under sur- faces of the body, the former being the thicker of the two. All these become joined, and the bone is com- pletely formed between the twenty- fifth and thirtieth year of life. Exceptions to this mode of de- velopment occur in the first, second, and seventh cervical, and in the vertebrae of the lumbar region. The Atlas (Fig. 12).— The num- ber of centres of ossification of the atlas is very variable. It may be developed from two, three, four, or five centres. The most frequent ar- rangement is by three centres. Two of these are destined for the two lateral or neural masses, the ossifica- tion of which commences about the seventh week near the articular pro- cesses, and extend backward ; these portions of bone are separated from one another behind, at birth, by a narrow interval filled in with carti- lage. BetAveen the third and fourth years thev unite either directly or through the medium of a separate centre developed in the cartilage in the middle line. The anterior arch, at birth, is altogether cartilaginous, and in this a sepa- rate nucleus appears about the end of the first year after birth, and, extending laterally, joins the neural processes in front of the pedicles. Sometimes there are two nuclei developed in the cartilage, one on either side of the median line, which join to form a single mass. And occasionally there is no separate centre, but the anterior arch is formed by the gradual extension forward and ultimate junction of the two neural processes. The Axis (Fig. 13) is developed by seven centres. The body and arch of this bone are formed in the same manner as the corresponding parts in the other ver- tebrae : one centre (or two, which speedily coalesce) for the lower part of the body, and one for each lamina. The centres for the laminae appear about the seventh or eighth week, that for the body about the fourth month. The odontoid process consists originally of an extension upward of the cartilag- inous 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 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 for tubercles on superior articular process. Fig. 14.— Lumbar vertebra. DORSAL VERTEBRA. -L9 gradually becomes ossified at its circumference, but remains cartilagin>n between centre until advanced age. 1 Finally, as Humphry has demonstrated, the the odontoid process has a separate nucleus, which appears in the second than the joins about the twelfth year. In addition to these there is a secondary < a thin epiphysial plate on the under surface of the body of the bone. ^-^ The Seventh Cervical. — The anterior or costal part of the transverse g\ of the seventh cervical is developed from a separate osseous centre aW abol \ sixth month of foetal life, and joins the body and posterior division of the tr.| verse process between the fifth and sixth years. Sometimes this process continu as a separate piece, and, becoming lengthened outward, constitutes what is known as a cervical rib. This separate ossific centre for the costal process has also been found in the fourth, fifth, and sixth cervical vertebrae. The Lumbar Vertebrae (Fig. 14) have two additional cents s (besides those peculiar to the vertebrae generally) for the mammillary tubercles, which project from the back part of the superior articular processes. The tr msverse process of the first lumbar is sometimes developed as a separate piece, which may remain permanently unconnected with the remaining portion of the bone, thus forming a lumbar rib — a peculiarity that is rarely met with. Progress of Ossification in the Spine generally. — Ossification of the laminae of the vertebrae commences in the cervical region of the spine, and proceeds gradually downward. Ossification of the bodies, on the other hand, commences a little beloAv the centre of the spinal column (about the ninth or tenth dorsal vertebra), and extends both upward and downward. Although, however, the ossific nuclei make their first appearance in the low r er dorsal vertebrae, the lumbar and first sacral are those in which these nuclei are largest at birth. Attachment of Muscles. — To the Atlas are attached nine pairs : the Longus colli, Rectus capitis anticus minor, Rectus lateralis, Obliquus capitis superior and inferior, Splenius colli, Levator anguli scapulae, First Intertransverse, and Rectus capitis posticus minor. To the Axis are attached eleven pairs : the Longus colli. Levator anguli scapulae, Splenius colli, Scalenus medius, Transversalis colli, Intertransversales, Obliquus capitis inferior, Rectus capitis posticus major, Semispinalis colli. Mul- tifidus spinae, Interspinals. To the remaining vertebrae, generally, are attached thirty-five pairs and a sin- gle muscle: anteriorly, the Rectus capitis anticus major, Longus colli, Scalenus anticus medius and posticus, Psoas magnus and parvus, Quadratus lumbo- rum, Diaphragm, Obliquus abdominis internus, and Transversalis abdominis — posteriorly, the Trapezius, Latissimus dorsi, Levator anguli scapulae, Rhomboideus major and minor, Serratus posticus superior and inferior, Splenius. Erector spinae, Ilio-costalis, Longissimus dorsi, Spinalis dorsi, Cervicalis ascendens. Transversalis colli, Trachelo-mastoid, Complexus, Biventer cervicis, Semispinalis dorsi and colli, Multifidus spinae, Rotatores spinae, Interspinales, Supraspinales, Intertransversales, Levatores costarum. Sacral and Coccygeal Vertebrae. The Sacral and Coccygeal Vertebrae consist, at an early period of life, of nine separate pieces, which are united in the adult so as to form two bones, five enter- ing into the formation of the sacrum, four into that of the coccyx. < Occasionally, the coccyx consists of five bones. 2 The Sacrum (sacer, sacred) is a large, triangular bone (Fig. 15). situated at the lower part of the vertebral column, and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two innominate bones : its upper part or base articulating with the last lumbar vertebrae, its apex with the coccyx. The sacrum is curved upon itself, and placed very obliquely, its upper 1 See Cunningham. Journ. Anat., vol. xx. p. 238. 2 Sir George Humphry describes this as the usual composition of the coccyx.— On the Skeleton, p. 456. THE SKELETON. 44 projecting forward, and forming, with the last lumbar vertebra, a very it angle, called the 'promontory or sacro-vertebral angle ; whilst its central lateral p&irected backward, so as to give increased capacity to the pelvic cavity. The line its for examination an anterior and posterior surface, two lateral surfaces, named tq, n apex, and a central canal. ing a g Anterior Surface is concave from above downward, and slightly so from undeito sidei In the middle are seen four transverse ridges, indicating the original beingion of the bone into five separate pieces. The portions of bone intervening Attween the ridges correspond to the bodies of the vertebrae. The body of the lirst segment 1$ of large size, and in form resembles that of a lumbar vertebra ; the succeeding ones, diminish in size from above downward, are flattened from before backward, and curved so as to accommodate 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 downward, and directed outward and forward ; they transmit the anterior branches of the sacral nerves and the lateral sacral arteries. External to these foramina is the lateral mass, consisting at an early period of life of separate segments; these become blended, in the adult, with the bodies, with each other, and with the posterior transverse processes. Each lateral mass is traversed by four broad, shallow grooves, which lodge the anterior sacral nerves as they pass outward, 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 sacrum (Fig. 16), the bodies are seen to be united at their circumference by bone, a wide interval being left centrally, which, in the recent state, is filled by intervertebral substance. In SACRAL AND COCCYGEAL VERTEBRsE. 19 some bones this union is more complete between the lower segments than between the upper ones. The Posterior Surface (Fig. 17) 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 sac- ral 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 downward ; the fourth usually, and the fifth always, remaining undevel- oped. External to the spinous processes on each side are the lamince, broad and well marked in the first three pieces ; sometimes the fourth, and generally the fifth, are only partially developed and fail to meet in the middle line. These partially developed laminae are prolonged downward as rounded processes, the sacral cornua, and are connected to the cornua of the coccyx. Between them the bony wall of the lower end of the sacral canal is imperfect, and is liable to be opened in the sloughing of bed-sores. 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 artic- ulating 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 and assist in forming the sacral cornua. External to the articular processes are the four 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 transverse processes of the sacral vertebrae. The first pair of transverse tubercles are large, very distinct, and correspond with each superior angle of the bone; t-hey together with the second pair, which are of small size, give attachment to the horizontal part of the sacro- iliac ligament; the third give attachment to the oblique fasciculi of the posterior sacro-iliac ligaments ; and the fourth and fifth to the great sacro-sciatic 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 Multifidus spinae. 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 surface, and in the fresh state is coated with fibro-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 terminates in a projection called the inferior lateral angle ; below this angle is a notch, which is converted into a foramen by articulation with the transverse process of the upper piece of the coccyx, and transmits the anterior Fig. 16.— Vertical section of the sacrum. THE SKELETON. division of the fifth sacral nerve. This lower, sharp border gives attachment to the greater and lesser sacro-sciatic ligaments, and to some fibres of the Gluteus maximus posteriorly, and to the Coccygeus in front. The Base of the sacrum, which is broad and expanded, is directed upward and forward. In the middle is seen a large oval articular surface, which is connected with the under surface of the body of the last lumbar vertebra by a fibro-carti- laginous disk. It is bounded behind by the large, triangular orifice of the sacral canal. The orifice is formed behind by the laminae and spinous process of _ the first sacral vertebra : the superior articular processes project from it on each side; they are oval, concave, directed backward and inward, like the superior articular processes of a lumbar vertebra ; and in front of each articular process is an inter- vertebral notch, which forms the lower part of the foramen between the last lumbar and first sacral vertebra. Lastly, on each side of the large oval articular Erector spinse _^ Upper half of fifth posterior sacral foramen. Fig. 17.— Sacrum, posterior surface. plate is a broad and flat triangular surface of bone, which extends outward, sup- ports the Psoas magnus muscle and lumbo-sacral cord, and is continuous on each side with the iliac fossa. This is called the ala of the sacrum, and gives attach- ment to a few of the fibres of the Iliacus muscle. The posterior part of the ala represents the transverse process of the first sacral segment. The Apex, directed downward and slightly forward, presents a small, oval, concave surface for articulation with the coccyx. The Spinal Canal runs throughout the greater part of the bone ; it is large and triangular in form above, small and flattened, from before backward, below. In this situation its posterior wall is incomplete, from the non-development of the laminae 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 externally by a thin layer of compact tissue. SACRAL AND COCCYGEAL VERTEBRA. 49 Differences in the Sacrum of the Male and Female. — The sacrum in the female is shorter and wider than in the male ; the lower half forms a greater angle with the upper, the upper half of the bone being nearly straight, the lower half pre- senting the greatest amount of curvature. The bone is also directed more obliquely- backward, which increases the size of the pelvic cavity ; but the sacro-vertebral angle projects less. In the male the curvature is more evenly distributed over the w T hole 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. Occasionally 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 development of the laminae and spinous processes. The sacrum, also, varies considerably 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 toward its middle. In a third set the degree of curvature was less marked, and affected especially the lower third of the bone. Development (Fig. 18). — The sacrum, formed by the union of five vertebrae, has thirty-five centres of ossification. The bodies of the sacral vertebrae have each three ossific centres : one for the central part, and one for the epiphysial plates on its upper and under surface. Occasionally the primary centres for the bodies of the first and second piece of the sacrum are double. The arch of each sacral vertebra is developed by two centres, one for each lamina. These unite with each other behind, and subsequently join the body. The lateral masses have six additional centres, two for each of the first three vertebrae. These centres make their appearance above and to the outer side of the anterior sacral foramina (Fig. 18), and are developed into separate segments Two epiphysial laminx for each lateral surface." Additional centres for the first three pieces.-'' At birth. At4i At 25th year Fig. 18.— Development of the sacrum. Fig. 19. Fig. 20. (Fig. 19) ; they are subsequently blended with each other, and with the bodies and transverse processes to form the lateral mass. Lastly, each lateral surface of the sacrum is developed by two epiphysial plates (Fig. 20) : one for the auricular 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 ossi- fication of the central part of the bodies of the first three vertebrae commences. and at a somewhat later period that of the last two. Between the sixth and eighth months ossification of the laminae takes place; and at about the same period the centres for the lateral masses for the first three sacral vertebrae make their appearance. The period at which the arch becomes completed by the junction 4 50 THE SKELETON. Cornua. of the laminae with the bodies in front and with each other behind varies in different segments. The junction between the laminae and the bodies takes place first in the lower vertebrae as early as the second year, but is not effected in the upper- most until the fifth or sixth year. About the sixteenth 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. The bodies of the sacral vertebrae are, during early life, separated from each other by intervertebral disks. But about the eighteenth year the two lowest segments become joined together by ossification extending through the disk. This process gradually extends upward until all the segments become united, and the bone is completely formed from the twenty-fifth to the thirtieth year of life. Articulations. — With four bones : the last lumbar vertebra, coccyx, and the two innominate bones. Attachment of Muscles. — To eight pairs : in front, the Pyriformis and Coccyg- eus, and a portion of the Iliacus to the base of the bone ; behind, the Gluteus maximus, Latissimus dorsi, Multifidus spinae, and Erector spinae, and sometimes the Extensor coccygis. The Coccyx. The Coccyx (xoxxvZ, cuckoo), so called from having been compared to a cuc- koo's beak (Fig. 21), is usually formed of four small segments of bone, the most rudimentary 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) is a mere nodule of bone, without distinct processes. All the segments are destitute of pedicles, laminae, and spinous processes, and, consequently, of intervertebral foramina and spinal canal. The first segment is the largest ; it resembles the lowermost sacral vertebra, and often exists as a separate piece ; the last three, diminishing in size from above downward, 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, the base of the triangle joining the end of the sacrum. It presents for examination an anterior and posterior sur- face, 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-coccygeal ligament and 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 lineal row of tubercles, the rudimentary articular processes of the coccygeal vertebrae. Of these, the supe- rior pair are large, and are called the cornua of the coccyx ; they project upward, and articulate with the cornua of the sacrum, the junction between these two bones completing the fifth posterior sacral foramen for the transmission of the pos- terior division of the fifth sacral nerve. The lateral borders are thin, and present a series of small eminences, which represent the transverse processes of the coccygeal vertebrae.. Of these, the first on each side is the largest, flattened from before backward, and often ascends to join the lower part of the thin lateral edge of the sacrum, thus completing the fifth anterior sacral foramen for the transmission of the anterior division of the fifth sacral nerve; the others diminish in size from above downward, and are often wanting. The borders *7"oR Anterior surface,. hi* '"ct'eR Posterior surface. Fig. 21.— Coccyx. THE SPINE IN GENERAL. 51 OL IS developed piece. Occa- pieces of this of the coccyx are narrow, and give attach- ment on each side to the sacro-sciatic liga- ments, to the Coccygeus muscles in front of the ligaments, and to the Gluteus maximus behind them. The base presents an oval sur- face 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 by four centres, one for each sionally one of the first three bone is developed by two centres, placed side by side. The ossific nuclei make their ap- pearance in the following order : in the first segment, shortly after 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 with each other from below upward, the union between the first and second segments being frequently delayed until after the age of twenty-five or thirty. At a late period of life, especially in females, the coccyx often becomes joined to the end of the sacrum. Articulation. — With the sacrum. Attachment of Muscles. — To four pairs and one single muscle : on either side, the Coccygeus ; behind, the Gluteus maximus and Extensor coccygis, when present ; at the apex, the Sphincter ani ; and in front, the Levator ani. The Spine in General. The Spinal Column, formed by the junc- tion of the vertebrae, is situated in the median line, at the posterior part of the trunk ; its average length is about two feet two or three I inches, measuring along the curved anterior surface of the column. Of this length the cervical part measures about five, the dorsal about eleven, the lumbar about seven inches, and the sacrum and coccyx the remainder. The female spine is about one inch less than that of the male. 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. When ex- amined more closely, the upper pyramid is seen to be formed of three smaller pyramids. The uppermost of these consists of the six 1st cervical or Atlas. Coccyx. Fig. 22.— Lateral view of the spine. 52 THE SKELETON. 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 commences at the fourth dorsal, and gradually increases in size to the fifth lumbar. Viewed laterally (Fig. 22), 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, and is the least marked of all the curves. The dorsal curve, which is concave forward, commences at the middle of the second, and terminates at the middle of the twelfth dorsal. Its most prominent point behind corresponds to the spine of the seventh dorsal vertebra. The lumbar curve commences at the middle of the last dorsal vertebra, and terminates at the sacro-vertebral angle. It is convex anteriorly ; the convexity of the lower three vertebrae being much greater than that of the upper two. The pelvic curve commences at the sacro- vertebral articulation and terminates at the point of the coccyx. It is concave anteriorly. The dorsal and pelvic curves are the primary curves, and begin to be formed at an early period of foetal life, and are due to the shape of the bodies of the vertebrae. The cervical and lumbar curves are compensatory or secondary, and are developed after birth in order to maintain the erect position. They are due mainly to the shape of the intervertebral disks. The spine has also a slight lateral curvature, the convexity of which is directed toAvard the right side. This is most probably produced, as Bichat first explained, chiefly by muscular action, most persons using the right arm in prefer- ence 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 individuals who were left-handed the lateral curvature was directed to the left side. The movable part of the spinal column presents for examination an an- terior, a posterior, and two lateral surfaces ; a base, a summit, and spinal 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 downward 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 extremities, in the cervical region. In the dorsal region they are directed obliquely above, assume almost a vertical direction in the middle, and are horizontal below, as are also the spines of the lumbar vertebrae. 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. Occasionally one of these processes deviates a little from the median line — a fact to be remembered in practice, as irregularities of this sort are attendant also on fractures or displacements of the spine. On either side of the spinous processes, extending the whole length of the column, is the vertebral groove formed by the laminae in the cervical and lumbar regions, where it is shallow, and by the laminae 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 process. In the dorsal region the latter processes stand backward, on a plane considerably 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 on the outer side of the pedicles, between the interver- THE SPINE IN GENERAL. 53 tebral foramina. In the dorsal region they are posterior to the pedicles, interver- tebral foramina, and articular processes. In the lumbar they are placed also in front of the articular processes, but behind the intervertebral 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 vertebrae, 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 intervertebral 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 that portion of the vertebral column formed by the twenty-four movable vertebras 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 or spinal canal follows the different curves of the spine ; it is largest in those regions in which the spine enjoys the greatest freedom of move- ment, as in the neck and loins, where it is wide and triangular ; and narrow and rounded in the back, where motion is more limited. Surface Form.— -The only part of the vertebral column which lies closely under the skin, and so directly influences surface form, is the apices of the spinous processes. These are always distin- guishable at the bottom of a median furrow, which, more or less evident, runs down the mesial line of the back from the external occipital protuberance above to the middle of the sacrum below. In the neck the fun'ow is broad, and terminates in a conspicuous projection, which is caused by the spinous process of the seventh cervical vertebra (vertebra prominens). Above this the spinous process of the sixth cervical vertebra may sometimes be seen to form a projection ; the other cervical spines are sunken, and . are not visible, though the spine of the axis can be felt, and generally also the spines of the third, fourth, and fifth cervical vertebrae. In the dorsal region the furrow is shallow, and during stooping disappears, and then the spinous pro- cesses become more or less visible. The markings produced by these spines are small and close together. In the lumbar region the furrow is deep, and the situation of the lumbar spines is frequently indicated by little pits or depressions, especially if the muscles in the loins are well developed and the spine incurved. They are much larger and farther apart than in the dorsal region. In the sacral region the furrow is shallower, presenting a flattened area which terminates below at the most prominent part of the posterior surface of the sacrum, formed by the spinous process of the third sacral vertebra. At the bottom of the furrow may be felt the irregular posterior surface of the bone. Below this, in the deep groove leading to the anus, the coccyx may be felt. The only other portions of the vertebral column which can be felt from the surface are the transverse processes of three of the cervical vertebrae — viz. the first, the sixth, and the seventh. The transverse process of the atlas can be felt as a rounded nodule of bone just below and in front of the apex of the mastoid process, along the anterior border of the sterno-mastoid. The transverse process of the sixth cervical vertebra is of surgical importance. If deep pressure be made in the neck in the course of the carotid artery, opposite the cricoid cartilage, the prominent anterior tubercle of the transverse process of the sixth cervical vertebra can be felt. This has been named Chassaignacs tubercle, and against it the carotid artery may be most conveniently compressed by the finger. The transverse process of the seventh cervical vertebra can also often be felt. Occasionally the anterior root, or costal process, is large and segmented off, forming a cervical rib. Surgical Anatomy. — Occasionally the coalescence of the lamina? is not completed, and con- sequently a cleft is left in the arches of the vertebrae, through which a protrusion of the spinal membranes (dura mater and arachnoid), and sometimes of the spinal cord itself, takes place, constituting a malformation known as spina bifida- This disease is most common in the lumbo- sacral region ; but it may occur in the dorsal or cervical region, or the arches throughout the whole length of the canal may remain unapproximated. In some rare cases, in consequence of the non-coalescence of the two primary centres from which the body is formed, a similar con- dition may occur in front of the canal, the bodies of the vertebrae being found cleft and the tumor projecting into the thorax, abdomen, or pelvis, between the lateral halves of the bodies affected. The construction of the spinal column of a number of pieces, securely connected together and enjoying only a slight degree of movement between any two individual pieces, though per- mitting of a very considerable range of movement as a whole, allows a sufficient degree of mobility without any material diminution of strength. The many joints of which the spine is composed, together with the very varied movements to which it is subjected, render it liable to 54 THE SKELETON. sprains ; but so closely are the individual vertebrae articulated that these sprains are rarely or ever severe, and any amount of violence sufficiently great to produce tearing of the ligaments would tend rather to cause a dislocation or fracture. The further safety of the column and its less liability to injury is provided for by its disposition in curves, instead of in onestraight line. For it is an elastic column, and must first bend before it breaks : under these circumstances, being made up of three curves, it represents three columns, and greater force is required to pro- duce bending of a short column than of a longer one that is equal to it in breadth and material. Again, the safety of the column is provided for by the interposition of the intervertebral disk between the bodies of the vertebrae, which act as admirable buffers in counteracting the effects of violent jars or shocks. Fracture-dislocation of the spine may be caused by direct or indirect violence, or by a combination of the two, as when a person, falling from a height, strikes against some prominence and is doubled over it. The fractures from indirect violence are the more com- mon, and here the bodies of the vertebrae are compressed, whilst the arches are torn asunder ; whilst in fractures from direct violence the arches are compressed and the bodies of the vertebrae separated from each other. It will therefore be seen that in both classes of injury the spinal marrow is the part least likely to be injured, and may escape damage even where there has been considerable lesion of the bony framework. For, as Mr. Jacobson states, ' ' being lodged in the centre of the column, it occupies neutral ground in respect to forces which might cause fracture. For it is a law in mechanics that when a beam, as of timber, is exposed to breakage and the force does not exceed the limits of the strength of the material, one division resists compression, another laceration of the particles, while the third, between the two, is in a negative condition." 1 Applying this principle to the spine, it will be seen that, whether the fracture-dislocation be pro- duced by direct violence or indirect, one segment, either the anterior or posterior, will be exposed to compression, the other to laceration, and the intermediate part, where the cord is situated, will be in a neutral state. When a fracture-dislocation is produced by indirect violence the dis- placement is almost always the same, the upper segment being driven forward on the lower, so that the cord is compressed between the body of the vertebra below and the arch of the vertebra above. The parts of the spine most liable to be injured are (1) the dorsi-lumbar region, for this part is near the middle of the column, and there is therefore a greater amount of leverage, and more- over the portion above is comparatively fixed, and the vertebrae which form it, though much smaller, have nevertheless to bear almost as great a weight as those below ; (2) the cervico-dorsal region, because here the flexible cervical portion of the spine joins the more fixed dorsal region ; and (3) the atlanto-axial region, because it enjoys an extensive range of movement, and, being near the skull, is influenced by violence applied to the head. In fracture-dislocation it has been proposed to trephine the spine and remove portions of the laminae and spinous processes. The operation can only be of use when the paralysis is due to the pressure of bone or the effusion of blood, and not to cases, wdiich are by far the most common, where the cord is crushed to a pulp. And even in those cases where the cord is compressed by bone the portion of displaced bone which presses on the cord is generally the body of the vertebra below, and is therefore inaccess- ible to operation. The operative proceeding is one of great severity, involving an extensive and deep wound and great risk of septic meningitis, and, as the advantages to be derived from it are exceedingly problematical and confined to a very few cases, it is not often resorted to. Trephin- ing has also been resorted to in some cases of paraplegia due to Pott's disease of the spine. Here the paralysis is due to the pressure of inflammatory products, and where this is new scar- tissue, formed by the organization of granulation tissue, its removal has been attended with a very considerable amount of success. THE SKULL. The Skull is supported on the summit of the vertebral column, and is of an oval shape, wider behind than in front. It is composed of a series of flattened or irregularly shaped bones which, with one exception (the lower jaw), .are immovably joined together. It is divided into two parts, the Cranium and the Face, the former of which constitutes a case for the accommodation and protection of the brain, while opening on the face are the orifices of the nose and mouth; between the cranium above and the face below the orbital cavities are situated. The Cranium (xpdvoz, 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 lachrymal, two malar, two palate, two inferior turbinated, vomer, and inferior maxillary. The ossiculi auditils, the teeth, and Wormian bones are not included in this enumeration. 1 Holmes's System of Surgery, vol. i., p. 529, 1883. THE CRANIUM. 55 Occipital. Two Parietal. Frontal. Uranium, c bones . < m m ^ lwo lemporal. Skull, 22 fowes < Face, 14 5owes Sphenoid. Ethmoid. Two Nasal. Two Superior Maxillary. Two Lachrymal. Two Malar. Two Palate. Two Inferior Turbinated. Vomer. Inferior Maxillary. The Hyoid Bone, situated at the root of the tongue and attached to the base of the skull by ligaments, has also to be considered in this section. THE CRANIUM. The Occipital Bone. The Occipital Bone (ob, caput, against the head) is situated at the back part Linea £Cr -^N J SUPERIOR '■^' T i£-jr j !l CONSTRICTOR of Pharynx. Fig. 23.— Occipital bone. Outer surface. and base of the cranium, is trapezoid in shape and is much curved on itself (Fig. 23). It presents at its front and lower part a large oval aperture, the foramen magnum, by which the cranial cavity communicates with the spinal canal. The portion of bone behind this opening is flat and expanded and forms the ,; ttr portion in front is a thick, elongated mass of bone, the basilar ss ; w either side of the foramen are situated processes bearing the 56 THE SKELETON. condyles, by which the bone articulates w \i ji the atlas. These processes are known as the condylar portions. It presents for Examination two surfaces, four borders, and four angles. The external surface is convex. Mid 1 . < -n the summit of the bone and the posterior margin of the foramen magmn ominent tubercle, the external occipital protuberance, and, descending from far as the foramen, a vertical ridge, the external occipital crest. This {protuberance and crest give attachment to the Ligamentum nuchae, and vary in prominence in different skulls. Passing outward from the occipital protuberance is a semicircular ridge on each side, the superior curved line. Above this line there is often a second less distinctly marked ridge, called the highest curved line (linea suprema) ; to it the epicranial aponeurosis is attached. The bone between these two lines is smoother and denser than the rest of the surface. Running parallel with these from the middle of the crest is another semicircular ridge on each side, the inferior curved lines. The surface of the bone above the linea suprema is rough and porous, and in the recent state is covered by the Occipito-frontalis muscle, while the superior and inferior curved lines, together with the surfaces of bone between and below them, serve for the attachment of several muscles. The superior curved line gives attachment inter- nally to the Trapezius, externally to the muscular origin of the Occipito-frontalis, and to the Sterno-cleido-mastoid to the extent shown in Fig. 23 ; the depressions between the curved lines to the Complexus internally, the Splenius capitis and Obliquus capitis 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 backward. It transmits the medulla oblongata and its membranes, the spinal accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the occipito-axial ligaments. Its back part is wide for the transmission of the medulla, and the corresponding margin rough for the attachment of the dura mater enclosing it ; the fore part is narrower, being encroached upon by the con- dyles ; it has projecting toward 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, oval, or reniform in shape, and directed downward and outward ; they converge in front, and encroach slightly upon the anterior segment of the foramen. On the inner border of each condyle is a rough 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, channelled in front by a deep notch, which forms part of the jugular foramen or foramen lacerum posterius. The under surface of this process presents an eminence Avhich represents the paramastoid process of some mammals. The eminence is occasionally large, and extends as low as the transverse process of the atlas. This surface affords attachment to the Rectus capitis lateralis muscle and to the lateral occipito-atlantal ligament ; its upper or cerebral^surface presents a deep groove which lodges part of the lateral sinus, whilst its external surface is marked by a quadrilateral rough facet, 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 fore part, is a foramen, the anterior con- dyloid ; it is directed downward, outward, and forward, and transmits the hypo- glossal nerve, and occasionally a meningeal branch of the ascending pharyngeal artery. This foramen is sometimes double. Behind each condyle is a fossa, 1 some- times perforated at the bottom by a foramen, the posterior condyloid, for the trans- mission 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, 1 This fossa presents many variations in size. It is usually shallow, and the foramen small ; occa- sionally 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. THE CRANIUM. ■ji the pharyngei for the attachment of the tendinous raphe and Superior constrictor of vnx ; and on each side of it rough depressions for the attachment of te Kectus capitis anticus, major and minor. The Internal or Cerebral Surface (Fig. 24) is deeply concave. The posterior part or tabulur is divided by a crucial ridge into four fossae. The two superior fossae receive the occipital lobes of the cerebrum, and present slight eminences and depressions corresponding to their convolutions. The two inferior, which receive the hemispheres of the cerebellum, are larger than the former, and com- paratively 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 upward to the superior angle of the bone ; it presents 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, Superior angle. Lateral i— Angle. Inferior angle. Fig. 24.— Occipital bone. Inner surface on the edge of which it becomes gradually lost ; this ridge, which is bifurcated below, serves for the attachment of the falx cerebelli. It is usually marked by a single groove, which commences at the back part of the foramen magnum and lodges the <~>or>inital sinus. Occasionally the groove is double where two sinuses exist. TL erse grooves pass outward to the lateral angles ; they are deeply channelled i lodgment of the lateral sinuses, their prominent margins afford- 58 THE SKELETON. ing attachment to the tentorium cerebelli. 1 At the point of meeting of these grooves is a depression, the torcular Uerophili, 2 placed a little to one or the other side of the internal occipital protuberance. More anteriorly is the foramen mag- num, and on each side of it, but nearer its anterior than its posterior part, the internal openings of the anterior condyloid foramen ; the internal openings of the posterior condyloid foramina are a little external and posterior to them, protected by a small arch of bone. At this part of the internal surface there is a very deep groove in which the posterior condyloid foramen, when it exists, has its termina- tion. This groove is continuous, in the complete skull, with the transverse groove on the posterior part of the bone, and lodges the end of the same sinus, the lateral. In front of the foramen magnum is the basilar process, presenting a shallow depression, the basilar groove, which slopes from behind, upward and forward, and supports the medulla oblongata and part of the pons Varolii, 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 corre- spond 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 border 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 por- tion of the temporal, forms the foramen lacerwn posterius or jugular foramen. This notch is occasionally subdivided into two parts by a small process of bone, , and it generally presents anjtperture at its upper part, the internal opening of the posterior condyloid foramen. Structure. — The occipital hone consists of two compact laminae, called the outer and inner tables, having between them the diploic tissue ; this bone is especially thick at the ridges, protuberances, condyles, and an- terior part of the basilar process; while at the bottom of the fossae, es- pecially the inferior, it is thin, semi- transparent, and destitute of diploe. Development (Fig. 25). — At birth the bone consists of four distinct parts : a tabular or expanded portion, which lies behind the foramen magnum ; two condylar parts, which form the sides of the foramen ; and a basilar part, which lies in front of the foramen. The number of nuclei for the tabular part vary. As 1 Usually one of the transverse grooves is deeper and broader than the other ; 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. 2 The columns of blood coming in different directions were supposed to be pressed together at this point (torcular, a wine-press). At birth the 4 pieces separate. H^/or occipital portion. 1 for each condyloid portion. > % U '1 for basilar portion. J rs Kig. 25.— Development of occipital bone. By seven centres. THE PARIETAL BONES. 59 *»""« >« v"£,™ j^v,^, "i.^u 10, i±^>.^v^i, udduicu in tutr uiicctiun indicate the figure. The basilar and two condyloid poitions are each developed : a single nucleus, which appears a little later. The upper portion of a rule, there are four, but there may be only one (Blandin) or as many as eight (Meckel). They appear about the eighth week of foetal life, and soon unite" to form a single piece, which is, however, fissured in the direction indicated in from ipper portion of the tabular surface — that is to say, the portion above the transverse fissure ia developed from membrane, and may remain separated from the rest of the bone throughout life, when it constitutes the interparietal bone : the rest of the bone is developed from cartilage. At about the fourth year the tabular 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 twelve pairs : to the superior curved line are attached the Occipito-frontalis, Trapezius, and Sterno-cleido-mastoid. To the space between the curved lines, the Complexus, 1 Splenitis capitis, and Obliquus capitis superior ; to the inferior curved line, and the space between it and the foramen magnum, the Rectus capitis posticus, major and minor; to the transverse process, the Rectus capitis lateralis ; and to the basilar process, the Rectus capitis anticus, major and minor, and Superior constrictor of the pharynx. Fig. 26. — Left parietal bone. External surface. The Parietal Bones. The Parietal Bones (paries, a Avail) form, by their union, the sides and roof of the skull. Each bone is of an irregular quadrilateral form, and presents for examination two surfaces, four borders, and four ano-les. 1 To these the Biventer cervicis should be added, if it is regarded as a separate muscle. 60 THE SKELETON. Surfaces. — The external surface (Fig. 26) is convex, smooth, and marked about its centre by an eminence called the parietal eminence, which indicates the point where ossification commenced. Crossing the middle of the hone in an arched direction are two well-marked curved lines or ridges, the upper and lower temporal ridges ; the former gives attachment to the temporal fascia, while the latter indicates the upper limit of the origin of the temporal muscle. Above these ridges the surface of the bone is rough and porous, and covered by the aponeurosis of the Occipito-frontalis ; between them the bone is smoother and more polished than the rest ; below them the bone forms part of the temporal fossa, and affords attach- ment 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, and sometimes a small branch of the occipital artery. Its existence is not constant, and its size varies considerably. The internal surface (Fig. 27), concave, presents depressions for lodging the convolutions of the cerebrum and numerous furrows for the ramifications of the middle meningeal artery; the latter runs upward and backward from the Posterior superior angle. Posterior inferior angle. ^.Anterior superior angle. §p Anterior inferior angle. Fig. 27. —Left parietal bone. Internal surface. 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, especially in the skulls of old persons ; they lodge the Pacchionian bodies. The internal opening of the parietal foramen is also seen when that aperture exists. Borders. — The superior, the longest and thickest, is dentated to articulate with its fellow of the opposite side, forming the sagittal suture. The inferior is divided into three parts : of these, the anterior is thin and pointed, bevelled at the e of the outer surface, and overlapped by the tip of the great wing of th< the middle portion is arched, bevelled at the expense of the ou -< THE FRONTAL BONE. 61 overlapped by the squamous portion of the temporal ; the posterior portion is thick and serrated for articulation with the mastoid portion of the temporal. The anterior border, deeply serrated, is bevelled at the expense of the outer surface above and of the inner below ; it articulates with the frontal bone, forming the coronal suture. The posterior border, deeply denticulated, articulates with the occipital, forming the lambdoid suture. Angles. — The anterior superior angle, thin and pointed, corresponds with that portion of the skull which in the foetus is membranous and is called the anterior fontanelle. The anterior inferior angle is thin and lengthened, being received in the interval between the great wing of the sphenoid and the frontal. Its inner surface is marked by a deep groove, sometimes a canal, for the anterior branch of the middle meningeal artery. The posterior superior angle corresponds with the junction of the sagittal and lambdoid sutures. In the foetus this part of the skull is membranous, and is called the posterior fontanelle. The posterior inferior angle articulates with the mastoid portion of the temporal bone, and generally presents on its inner surface a broad, shallow groove for lodging part of the lateral sinus. Development. — The parietal bone is formed in membrane, being developed by one centre, which corresponds with the parietal eminence, and makes its first appearance about the seventh or eighth week of foetal life. Ossification gradually extends from the centre to the circumference of the bone : the angles are conse- quently the parts last formed, and it is in their situation that the fontanelles exist previous to the completion of the groAvth of the bone. Occasionally the parietal bone is divided into two parts, upper and lower, by an antero-posterior suture. Articulations. — With five bones : the opposite parietal, the occipital, frontal, temporal, and sphenoid. Attachment of Muscles. — One only, the Temporal. The Frontal Bone. The Frontal Bone (frons, the forehead) resembles a cockle-shell in form, and consists of two portions — a vertical ox: frontal portion situated at the anterior part of the cranium, forming the forehead ; and a horizontal or orbito-nasal portion which enters into the formation of the roof of the orbits and nasal fossae. Vertical Portion. — External Surface (Fig. 28). — In the median line, traversing the bone from the upper to the lower part, is occasionally seen a slightly-elevated ridge, and in young subjects a suture, which represents the line of union of the two lateral halves of which the bone consists at an early period of life ; in the adult this suture is usually obliterated and the bone forms one piece ; traces of the obliterated suture are, however, generally perceptible at the lower part. On either side of this ridge, a little below the centre of the bone, is a rounded eminence, the frontal eminence. These eminences vary in size in different individuals, and are occasionally unsymmetrical in the same subject. They are especially prominent in cases of well-marked cerebral development. The w r hole surface of the bone above this part is smooth, and covered by the aponeurosis of the Occimto-frontalis muscle. Below the frontal eminence, and Separated from it by a slight groove i the superciliary ridge, broad internally, where it is continuous Avith the nasal eminence, but less distinct as it arches outward. These ridges are caused by the projection outward of the frontal air sinuses, 1 and give attachment to the Orbicu- laris palpebrarum and Corrugator supercilii. Between the two superciliary ridges is a smooth surface, the glabella or nasal eminence. Beneath the super- ciliary ridge is the supraorbital arch, a curved and prominent margin, which forms 1 Some confusion is occasioned to students commencing the study of anatomy by the name "sinuses" having been given to two perfectly different kinds of spaces connected with, the skull. It may be as well, therefore, to state here, at 'the outset, that the "sinuses" in the interior of the cranium which produce the grooves on the inner surface of the bones are venous channels along which the blood runs in its passage back from the brain, while the "sinuses" external to the cranial cavity (the frontal, sphenoidal, ethmoidal, and maxillary) are hollow spaces in the bones themselves which communicate with the nostrils, and contain air. 62 THE SKELETON. the upper boundary of the orbit and separates the vertical from the horizontal portion of the bone. The outer part of the arch is sharp and prominent, afford- ing to the eye, in that situation, considerable protection from injury; the inner part is less prominent. At the junction of the internal and middle third of this arch is a notch, sometimes converted into foramen, and called the supraorbital notch or foramen. It transmits the supraorbital artery, vein, and nerve. A small aperture is seen in the upper part of the notch, which transmits a vein from the diploe to join the. supraorbital vein. The supraorbital arch terminates externally in the external angular process and internally in the internal angular process. The external angular process is strong, prominent, and articulates with the malar bone; running upward and backward from it are two well-marked lines, which, commencing together from the external angular process, soon diverge from each other and run in a curved direction across the bone. These are the upper and lower temporal ridges ; the upper gives attachment to the temporal fascia, the Jntemal External angular process. angu i ar process. Nasal $ spine. Fig. 28.— Frontal bone. Outer surface. lower to the temporal muscle. Beneath them is a slight concavity that forms the anterior part of the temporal fossa and gives origin to the Temporal muscle. The internal angular processes are less marked than the external, and articulate with the lachrymal bones. Between the internal angular processes is a rough, uneven interval, the nasal notch, which articulates in the middle line with the nasal bone, and on either side with the nasal process of the superior maxillary bone. From the concavity of this notch projects a process, the nasal process, which extends beneath the nasal bones and nasal processes of the superior maxillary bones and supports the bridge of the nose. On the under surface of this-4s a long pointed process, the nasal spine, and on either side a small grooved surface enters into the formation of the roof of the nasal fossa. The nasal spine forms part of the septum of the nose, articulating in front with the nasal bones and behind with the perpendicular plate of the ethmoid. THE FRONTAL BONE. 63 Internal Surface (Fig. 29). — Along the middle line is a vertical groove, the edges of which unite below to form a ridge, the frontal crest; the groove lodges the superior longitudinal sinus, whilst its margins afford attachment to the falx cerebri. The crest terminates below at a small notch which is converted into a foramen by articulation with the ethmoid. It is called the foramen ccecnm, and varies in size in different subjects: it is sometimes partially or completelv impervious, lodges a process of the falx cerebri, and when open transmits a vein from the lining membrane of the nose to the superior longitudinal sinus. On either side of the groove the bone is deeply concave, presenting depressions for the convolutions of the brain, and numerous small furrows for lodging the ramifications of the anterior meningeal arteries. Several small, irregular fossse are seen also on either side of the groove, for the reception of the Pacchionian bodies. Horizontal Portion. — This portion of the bone consists of two thin plates, the orbital plates, which form the vault of the orbit, separated from one another by a median gap, the ethmoidal notch. The external surface of each orbital plate consists of a smooth, concave, triangular lamina of bone, marked vit its anterior and external part (immediately beneath the external angular «*fifflWjM%Khni With superior maxillary With nasal With perpendicular plate of ethmoid. Fig. 29.— Frontal bone. Inner surface Under surface of nasal process, forming part of roof of nose. process) by a shallow depression, the lachrymal fossa, for lodging the lachrymal gland; and at its anterior and internal part by a depression (sometimes a small tubercle), the trochlear fossa, for the attachment of the cartilaginous pulley of the Superior oblique muscle of the eye. The ethmoidal notch separates the two orbital plates- it is quadrilateral, and filled up, A\hen the bones are united, by the cribril »nn plate of the ethmoid. The margins of this notch present several half- cell^ which when united with corresponding half-cells on the upper surface of the ethmoid,