CoQege of S^tv^itiansi anti ^urgeonst TLibvaxv Digitized by tine Internet Arcliive in 2010 witli funding from Open Knowledge Commons (for the Medical Heritage Library project) http://www.archive.org/details/anatomydescriptOOgray ANATOMY DESCRIPTIVE AND APPLIED BY HENRY GRAY, F.R.S. FELLOW OF THE HOYAL COLLEGE OF SURGEONS; LECTUREB ON ANATOMY AT ST. GEORGE's HOSPITAL MEDICAL SCHOOL, LONDON A NEW AMERICAN EDITION THOROUGHLY REVISED AND RE-EDITED WITH THE ORDINARY TERMINOLOGY FOLLOA\'E» BY THE BASLE ANATOMICAL NOMENCLATURE IN LATIN BY EDWARD ANTHONY SPITZKA, M.D. DIRECTOR OF THE DANIEL. BAUGH INSTITUTE OF ANATOMY AND PROFESSOR OF GENERAL ANATOMY IN ' JEFFERSON MEDICAL COLLEGE, PHILADELPHIA HUustratet) witb 1225 lEnaravinos LEA & FEBIGER PHILADELPHIA AND NEW YORK Entered according to the Act of Congress, in the year 1913, by LEA & FEBIGER to the OfiB.ce of the Librarian of Congress. All rights reserved. THE FIRST EDITION OP THIS WORK WAS DEDICATED TO SIB BENJAMIN COLLINS BRODIE, Bart., F.R.S., D.C.L. IN ADMIRATION OF HIS GREAT TALENTS AND IN REMEMBRANCE OF MANY ACTS OF KINDNESS SHOWN TO THE ORIGINAL AUTHOR OF THE BOOK FROM AN EARLY PERIOD OF HIS PROFESSIONAL CAREER PREFACE. As a thoroughly practical treatise on the subject for the medical student, Gray's Anatomy, both in the original and its many succeeding editions, has long been held in the highest esteem. In this as in previous revisions the Editor has endeavored to adhere to the plan as much as possible, supplying such facts and views as the advances in the science of anatomy rendered it necessary to in- corporate. Descriptions of undue length have been curtailed, and any difficult passages in the text have been clarified; so that the essentials are here embodied into a fairly complete account of the structures of the human body and their development. It has also been the Editor's aim to achieve the utmost degree of uniformity in the mode of treatment throughout the work. Under the heading of Applied Anatomy many important medical and surgical considerations are discussed. In the use of descriptive terms, concerning which widely different opinions prevail, the Editor has sought to take a middle course, employing such designations as seem sanctioned by their usage in current medi- cal literature. The Basle Nomina A7iatomica Nomenclature, in italics, has been added in parentheses, except where the two nomenclatures are identical, and the terms are listed in the General Index. Here, also, they have been italicized, and thus distinguished they afford a working glossary of the BNA system. Other synonyms are printed in Roman type. Illustrations have been added from original drawings and preparations, and some from standard works, wherever it seemed that any important point could be made more clear. The Editor is greatly indebted to his assistants. Dr. Howard Dehoney, Demon- strator of Anatomy, and Dr. Henry E. Radasch, Assistant Professor of Histology and Embryology in the Jefferson Medical College, for valuable aid in the prepara- tion of this revision. The Editor also wishes to thank Mr. William A. Hassett, of Lea & Febiger, for indexing the book, for seeing it through the press, and for the valuable aid he has ungrudgingly given. E. A. S. Philadelphia, 1913. fv) PUBLISHERS' NOTE. Books, like men, have characters that can be analyzed- to a certain point, but beyond or below lies a quality, subtle as life, and incapable of analysis or imitation, which is called personality. The greater the author, and the more intense his mental action in creating his book, the more it partakes of this ele- ment. This principle, so clear as to be almost axiomatic, is illustrated to the fullest extent in the work in hand. Henry Gray combined two faculties, either one sufficient to make his name famous. He was a great anatomist and a great teacher. He possessed a thorough knowledge of anatomy and an equal insight into the best methods of imparting it to other minds. His text was unequalled in clearness, and he united with it a series of incomparable illustrations. He devised the method of engraving the names of the parts directly upon them, thereby exliibiting at a glance not only their nomenclature, but also their posi- tion, extent, and relations. His work, still unique in this respect, was also the first to employ colors. Summing all, it is hardly to be wondered at that students and teachers alike find their labors reduced and the permanence of knowledge increased by the use of such a book. On its original appearance, half a century ago, it immediately took the leading place, and it has not only maintained its position in its own subject, but has also become the best-known work in all medical literature in the English language. It is incomparably the greatest text-book in medicine, measured by the numbers of students who have used it, and it is unique also in being the one work which is certain to be carried from college to afi'ord guidance in the basic questions underlying practice. The consequent demand is evidenced in the number of editions, which collectively represent the labors of many of the leading anatomists since the early death of its talented author. In this new revision every line has been carefully considered, any possible obscurity has been clarified, the latest acces- sions to anatomical knowledge have been introduced, and much has been rewritten. Care has been exercised to make the text a homogeneous, sequen- tial, and complete presentation of the subject, sufficing for every need of the student, physician, or surgeon. As ample directions are given for dissecting, this volume will serve every requirement of the student throughout his course. The new nomenclature and that still in common use have been introduced in a manner rendering the work universal in the prime essential of terminology. The Table of Contents is so arranged as to give a complete conspectus of anatomy, a feature of ob^'ious value. The whole book is thoroughly organized in its headings and the sequence of subjects, so that the student receives his knowledge of the parts in their anatomical dependence. As a teaching instrument the new Gray's Anatomy embodies all that careful thought and unstinted expenditure can combine in book form. (vii) CONTENTS. DESCRIPTIVE AND APPLIED ANATOMY. OSTEOLOGY. Introduction 33 General Anatomy of the Skeleton The Skeleton 35 Number of the Bones 35 Form of Bones 35 Long Bones 35 Short Bones 36 Flat Bones 36 Irregular Bones 36 Surface of Bones 36 Structure of Bone 38 Bloodvessels of Bone 40 Chemical Composition of Bone 41 Ossification and Growth of Bone 42 Applied Anatomy of the Bones 46 SPECLA.L Anatomy of the Skeleton. The Vertebhal oh Spinal Column or the Spine. General Characters of a Vertebra. The Cervical VertebriB 49 Atlas 50 Axis : 52 Seventh Cervical 53 The Thoracic VertebrEe 53 Peculiar Thoracic Vertebrce 54 The Lumbar Vertebrae : ■ . . 56 The Sacral and Coccygeal Vertebrae 58 Sacrum 58 The Sacral Canal 61 Differences in the Sacrum of the Male and Female 61 Coccyx 61 Structure of the VertebrEe 62 Development of the Vertebrae 63 Development of the Atlas 63 Development of the Axis 64 Development of the Seventh Cervical , 64 Development of the Lumbar Vertebrae .... 64 The Vertebral Column as a Whole 66 Surface Form of the Vertebral Column .... 67 Applied Anatomy of the Vertebral Column. fi8 The Skull. The Cerebral Cranium. The Occipital Bone 70 The Parietal Bone 74 The Frontal Bone 76 Vertical Portion of the Frontal Bone. 76 Horizontal or Orbital Portion of the Frontal Bone 79 The Temporal Bone 80 The Squamous Portion 80 The Petromastoid Portion 81 The Mastoid Portion 82 The Petrous Portion 83 The Tympanic Portion 87 The Sphenoid Bone 89 The Body of the Sphenoid Bone 90 The Greater or Temporal Wings 92 The Lesser or Orbital Wings 93 The Pterygoid Processes 94 The Sphenoidal Turbinated Processes. . 95 The Ethmoid Bone 96 The Horizontal Lamina or Cribriform Plate 96 The Vertical Plate 97 The Lateral Mass or Labyrinth 97 The Bones of the Face. The Nasal Bones 99 The Maxillae 100 Changes Produced in the Upper Jaw by Age . 106 The Lacrimal Bone 106 The Malar Bone 107 The Palate Bone 109 The Turbinated Bone 113 The Vomer 114 The Mandible or Lower Jaw 115 Changes Produced in the Mandible by Age 119 Side Views of the Mandible at Different Periods of Life 119 The Sutures 121 The Skull Whole. The Vertex of the Skull 123 The Base of the Skull 123 The Lateral Region of the Skull 132 The Temporal Fossa 132 The Mastoid Portion 133 The Zygomatic Fossa 133 The Sphenomaxillary Fossa 134 The Anterior Region of the Skull 134 The Orbits 136 The Nasal Cavity 138 Development of the Skull 141 Differences in the Skull Due to Age 143 Obliteration of the Sutures 144 Differences in the Skull Due to Sex 144 Supernumerary, Wormian, Sutural or Epac- tal Bones 144 Craniology 144 Surface Form of the Skull 147 Applied Anatomy of the Skull 149 The Hyoid or Lingual Bone. The Thorax. 153 Boundaries of the Thorax 154 The Cavity of the Thorax 1^7 The Sternum or Breast Bone 157 The Ribs 161 Peculiar Ribs 163 The Costal Cartilages 16o Surface Form of Thorax 166 Applied Anatomy of Thorax 167 (ix) CONTENTS The Upper Extremity. The Shoulder Girdle. The Clavicle 169 Surface Form of the Clavicle 171 Applied Anatomy of the Clavicie 172 The Scapula or Shoulder Blade 172 Surface Form of the Scapula 177 Applied Anatomy of the Scapula 17S The Humerus or Arm Bone 178 Surface Form of the Humerus 184 Api^lied Anatomy of the Humerus 184 The Forearm. The Ulna or Elbow Bone 185 Surface Form of the Ulna . 190 The Radius 190 Surface Form of the Radius 192 Applied Anatomy of the Radius and Ulna 192 The Hand. The Carpus 195 Bones of the Upper Row 196 The Scaphoid or Navicular Bone.. 196 The Semilunar Bone 197 The Cuneiform Bone 197 The Pisiform Bone 198 Bones of the Lower Row 198 The Trapezium 198 The Trapezoid 199 The Os Magnum 199 The Unciform 200 The Metacarpus 201 Peculiar Characters of the Metacarpal Bones 202 The Phalanges of the Hand 204 Surface Form of the Bones of the Hand .... 205 Applied Anatomy of the Bones of the Hand 205 Development of the Bones of the Hand .... 206 The Lower Extremity. The Os Innominatum 207 The Ilium 207 The Ischium 210 The Pubis 212 The Cotyloid Cavity or Acetabulum.. . 213 The Obturator or Thyroid Foramen . . . 213 The Pelvis 215 Position of the Pelvis 217 Axes of the Pelvis 218 Differences between the Male and Female Pelvis 218 Surface Form of the Pelvis 219 Applied Anatomy of the Pelvis 220 The Thigh. The Femur or Thigh Bone 221 Surface Form of the Femur 228 Applied Anatomy of the Femur 229 The Leg. The Patella or Knee Cap 230 Surface Form of the Patella 231 Applied Anatomy of the Patella 231 The Tibia or Shin Bone 231 Surface Form of the Tibia 236 The Fibula or Calf Bone 236 Surface Form of the Fibula 238 Applied Anatomy of the Bones of the Leg. . 239 The Foot: The Tarsus 239 The Calcaneus 239 The Astragalus or Ankle Bone 244 The Cuboid 245 The Scaphoid or Navicular Bone 246 The Cuneiform or Wedge Bones 247 The Metatarsal Bones 249 Peculiar Characters of the Metatarsal Bones 250' The Phalanges of the Foot 252 Development of the Foot 254 Construction of the Foot as a Whole 254 Surface Form of the Foot 255 Applied Anatomy of the Foot 256 Sesamoid Bones 257 THE AETICULATIONS OR JOINTS. structures Composing the Joints 259 Bone 259 Cartilage 259 Ligaments 261 Synovial Membrane 261 Forms of Articulation : Synarthrosis (Immovable Articulation) 263 Amphiarthrosis (Mixed Articulation) . . 264 Diarthrosis (Movable Articulation) .... 264 Kinds of Movement Admitted in Joints. . . . 266 Ligamentous Action of Muscles 267 Articulations of the Trunk. Articulations of the Vertebral Column 268 The Ligaments of the Vertebral Bodies or Centra 268 The Ligaments Connecting the Laminae 271 The Ligaments Connecting the Articu- lar Processes 271 The Ligaments Connecting the Spinous Processes 272 The Ligaments Connecting the Trans- verse Processes 272 Articulations of the Atlas with Axis 273 Articulations of the Vertebral Column with Cranium-. Articulation of Atlas with Occipital Bone. . 275 Articulation of Axis with Occipital Bone . . . 277 Applied Anatomy of Articulations of the Vertebral Column 278 The Temporomandibular Articulation 279 Surface Form 281 Applied Anatomy 281 Articulations of the Ribs with the Vertebral or the Costovertebral Articulations . . 282 The Costocentral Articulations 282 The Costotransverse Articulations 284 The Costosternal Articulations 286 Articulations of the Cartilages of the Ribs with Each Other 288 Articulations of the Ribs with their Cartilages 288 Articulations of the Sternum 288 Articulation of the Vertebral Column with the Pelvis ■ 289 Articulations of the Pelvis 290 Articulation of the Sacrum and Ilium . . 290 Ligaments Passing between the Sacrum and Ischium 291 Articulation of the Sacrum and Coc- cyx 292 Articulation of the Pubic Bones 294 Articulations of the Upper Extremity. Sternocla-vdcular Articulation 295 Surface Form , 297 Applied Anatomy 297 Acromioclavicular Articulation or Scapulo- clavicular Articulation 297 Surface Form 299 Applied Anatomy 299 CONTENTS XI Proper Ligaments of the Scapula 299 The Shoulder-joint 301 Surface Form 304 Applied Anatomy 304 The Elbow-joint 306 Surface Form 309 Applied Anatomy 309 Radio-ulnar Articulation 310 Superior Artirulation 310 Surf:H-r I-(,nii 311 AiU'lii''! Anatomy 311 Middle Kadio-ulnar Ligaments 311 Inferior Articulation 312 Surface Form 314 The Radiocarpal or Wrist-joint 314 Surface Form 315 Applied Anatomy 315 Articulations of the Carpus 315 Articulations of the First Row of Carpal Bones 315 Articulations of the Second Row of Carpal Bones '. . 316 Articulations of the Two Rows of Carpal Bones with Each Other 316 Carpometacarpal Articulations 317 Articulation of the Metacarpal Bone of the Thumb with the Trapezium. . 317 Articulations of the Metacarpal Bones of the Four Inner Fingers with the Carpus 318 Articulations of the Metacarpal Bones with Each Other 319 Metacarpophalangeal Articulations 320 Surface Form. 321 Articulations of the Phalanges 321 Articulations of the Lower Extremity. The Hip-joint 322 Surface Form 329 The Hip-joint — Applied Anatomy 329 The Knee-joint 331 Surface Form 33y Applied Anatomy 338 Tibiofibular Articulation 340 Superior Tibiofibular Articulation 340 Middle Tibiofibular Ligament or Inter- osseous Membrane 341 Inferior Tibiofibular Articulation 341 The Tibiotarsal Articulation or Ankle-joint 342 Surface Form of Ankle-joint 346 Applied Anatomy of Ankle-joint 346 Articulations of the Tarsus 347 Articulation of the Calcaneus and Astragalus 347 Articulation of the Calcaneus with the Cuboid 347 The Ligaments Conneoting the Cal- caneus and Scaphoid 348 Applied Anatomy 349 Articulation of the Astragalus with the Scaphoid Bone 349 The Articulation of the Scaphoid with the Cuneiform Bones 349 The Articulation of the Scaphoid with the Cuboid 350 The Articulations of the Cuneiform Bones with Each Other or the Inter- cuneiform Articulations 350 The Articulation of the External Cuneiform Bone with the Cuboid 351 Applied Anatomy •. 351 Tarsometatarsal Articulations 351 Articulations of the Metatarsal Bones with Each Other 352 Metatarsophalangeal Articulations 353 Articulations of the Phalanges 354 Surface Form 354 Applied Anatomy 364 THE MUSCLES AND FASCIA. General Description of Muscles 355 Form and Attachment of Muscles 357 Applied Anatomy of Muscles 359 General Description of Tendons 360 General Description of Aponeurosis 360 General Description of Fasciae 360 Development of Skeletal Musculature 361 Muscles and Fascia of the Cranium and Face. Subdivision in Groups 362 The Cranial Region 362 The Skin of the Scalp 363 Superficial Fascia 363 The Occipitofrontalis 36.3 Applied Anatomy 365 The Auricular Region '. 365 Attrahens Aurem 366 Attolens Aurem 366 Retrahens Aurem 366 The Palpebral Region 366 Orbicularis Palpebrarum 366 Corrugator Supercilii 367 Tensor Tarsi or Horner's Muscle 367 Tlie Orbital Region 368 Orbital Septum 368 Levator Palpebrae Superioris 369 Recti 370 Superior Oblique 370 Inferior Oblique 370 Fasciae of the Orbit 371 Applied Anatomy 371 The Nasal Region 372 Py ramidalis Nasi 372 Levator Labii Superioris Alaeque Nasi . 372 Dilator Naris Posterior 372 Dilator Naris Anterior 372 Compressor Naris 372 Compressor Narium Minor 372 Depressor Alae Nasi 372 The Maxillary Region 373 Levator Labii Superioris 373 Levator Anguli Oris 373 Zygomaticus Major 373 Zygomaticus Minor 373 The Mandibular Region 374 Levator Menti 374 Depressor Labii Inferioris or Quad- ratus Menti 374 Depressor Anguli Oris 374 The Buccal Region 374 Orbicularis Oris 374 Buccinator 375 Risorius 377 The Temporomandibular Region 377 Masseteric Fascia 377 Masseter Muscle 377 Temporal Fascia 378 Temporal Muscle 378 The Pterygomandibular Region 379 External Pterygoid Muscle 379 Internal Pterygoid Muscle 380 Surface Form of Muscles of Head and Face. 381 Muscles and Fascia of the Neck. Subdivisions into Groups 381 The Superficial Cer\'ical Region 381 Superficial Cervical Fascia 381 Platysma 381 Deep Cervical Fascia 382 Applied Anatomy 384 Sternomastoid 385 Triangles of the Neck 386 Applied Anatomy 386 The Infrahyoid Region 386 Sternohyoid 386 Sternothyroid 387 Thyrohyoid 387 Omohyoid 3SS CONTENTS The Suprahyoid Region 388 Digastric 388 Stylohyoid 389 Mylohyoid 389 Geniohyoid 390 The Lingual Region 391 Geniohyoglossus 391 Hyoglossus 391 Chondroglossus 392 Styloglossus 392 The Muscle Substance of the Tongue. . 393 Applied Anatomy 394 The Pharyngeal Region 394 Inferior Constrictor 394 Middle Constrictor 395 Superior Constrictor 395 Stylopharyngeus 396 The Palatal Region 397 Levator Palati 397 Tensor Palati 397 Palatal Aponeurosis 397 Azygos Uvulae 398 Palatoglossus 398 Palatopharyngeus 398 Salpingopharyngeus 399 Applied Anatomy 399 The Anterior Vertebral Region 400 Rectus Capitis Anticus Major 400 Rectus Capitis Anticus Minor 400 Rectus Capitis Lateralis 400 Longus Colli 401 The Lateral Vertebral Region 401 Scalenus Anticus 401 Scalenus Medius 401 Scalenus Posticus 402 Surface Form of Muscles of Neck 402 Muscles and Fascia of the Trtjnk. Subdivision into Groups 403 Muscles of the Back. Subdivision into Groups 403 The First Layer 404 Superficial Fascia 404 Deep Fascia 404 Trapezius 404 Ligamentum Nuchae 406 Latissimus Dorsi 406 The Second Layer 407 Levator Anguli Scapulae 407 Rhomboideus Minor 407 Rhomboideus Major 407 The Third Layer 408 Serratus Posticus Superior 408 Serratus Posticus Inferior 408 Vertebral Aponeurosis 408 Splenius Capitis 409 Splenius Colli 409 The Fourth Layer 410 Erector Spinae 410 Iliocostalis 410 Musculus Accessorius 410 Cervicalis Ascendens 412 Longissimus Dorsi 412 Trans versalis Cervicis 412 Trachelomastoid 412 Spinalis Dorsi ." 412 Spinalis Colli 412 Complexus 412 The Fifth Layer 413 Semispinalis Dorsi 413 Semispinalis Colli 413 Multifidus Spinae 413 Rotatores Spinae 413 Supraspinales 414 Interspinales 414 Extensor Coccygis 414 Intertransversales 414 Rectus Capitis Posticus Major 414 Rectus Capitis Posticus Minor 414 Obliquus Inferior 415 Obliquus Superior 415 Suboccipital Triangle 415 Applied Anatomy 416 Muscles and Fascice of the Thorax. Intercostal Fascia 417 Intercostal Muscles 417 External Intercostals 417 Internal Intercostals 417 Infracostales 417 Triangularis Sterni 417 Levatores Costarum 417 Diaphragm 418 Muscles of the Abdomen. Antero-lateral Muscles of the Abdomen . . . 423 Superficial Fascia 424 Deep Fascia 424 External or Descending Oblique 424 Aponeurosis of the External Oblique 425 External Abdominal Ring 426 Applied Anatomy 427 Poupart's Ligament 427 Gimbernat's Ligament 428 Triangular Fascia 428 Ligament of Cooper 428 Internal or Ascending Oblique 428 Cremaster Muscle 430 Transversalis 432 Rectus Abdominis 433 Pyramidalis 435 Linea Alba 435 Linea Semilunares 436 Fascia Transversalis 436 Internal or Deep Abdominal Ring 437 Inguinal or Spermatic Canal 437 Surface Form 439 Posterior Muscles of the Abdomen 439 The Fascia Covering the Quadratus Lumborum 439 Quadratus Lumborum 439 Muscles and Fascice of the Pelvic Outlet The Central Tendinous Point of the Perineum 442 The Muscles of the Perineum in the Male. . 442 Superficial Transverse Perineal 442 Accelerator Urinae 443 Erector Penis 444 The Muscles of the Perineum in the Female 445 Superficial Transverse Perineal.. ....... 445 Sphincter Vaginae 445 Erector Clitoridis 446 The Triangular Ligament in the Male and in the Female 446 Compressor or Constrictor Urethrae. . . 448 The Pelvic Fascia 448 Levator Ani 450 Coccygeus 453 Muscles of the Ischiorectal Region 453 Corrugator Cutis Ani 453 External Sphincter Ani 453 Internal Sphincter Ani 454 Ischiorectal Fossa 454 Muscles and Fascia of the Upper Extremity. Subdivision into Groups 455 Dissection of Pectoral Region and Axilla . . . 455 Muscles and Fascice of the Thoracic Region. The Anterior Thoracic Region 455 Superficial Fascia 455 Deep Fascia 456 Pectoralis Major 456 Costocoracoid Membrane or the Clavi- pectoral Fascia 459 Pectoralis Minor 460 Subclavius 460 The Lateral Thoracic Region 461 Serratus Magnus 461 Applied Anatomy 461 CONTENTS Muscles and Fascim of the Shoulder and Arm. The Acromial Region 462 Deltoid 462 Applied Anatomy 463 The Anterior Scapular Region 463 Subscapularis 464 The Posterior Scapular Region 464 Supraspinatus 464 Infraspinatus 465 Teres Minor 466 Teres Major 466 Muscles and Fascice of the Arm, The Anterior Humeral Region 467 Deep Fascia 467 Coracobrachialis 468 Biceps or Biceps Flexor Cubiti 469 Brachialis Anticus 469 The Posterior Humeral Region 470 Triceps or Triceps Extensor Cubiti .... 470 Subanconeus 471 Muscles and Fascice of the Forearm. Deep Fascia 471 The Anterior Radioulnar Region 472 Superficial Layer 472 Pronator Teres 472 Applied Anatomy . . . '. 473 Flexor Carpi Radialis 473 Palmaris Longus 474 Flexor Carpi Ulnaris 474 Flexor Sublimis Digitorum 475 Deep Layer 476 Flexor Profundus Digitorum 476 Flexor Longus PoUicis 476 Pronator Quadratus 478 Applied Anatomy 478 The Radial Region 479 Brachioradialis 479 Extensor Carpi RadiaUs Longior 479 Extensor Carpi Radialis Brevior 479 The Posterior Radioulnar Region 480 Superficial Layer 480 Extensor Communis Digitorum . . . 480 Extensor Minimi Digiti 481 Extensor Carpi Ulnaris 482 Anconeus 482 Supinator (Brevis) 482 Extensor Ossis Metacarpi PoUicis. 482 Extensor Brevis PoUicis 483 Extensor Longus PoUicis 484 Extensor Indicis 484 Applied Anatomy 485 Muscles and Fascice of the Hand. Anterior Annular Ligament 486 The Synovial Membranes of the Flexor Tendons at Wrist 486 Applied Anatomy 487 Bursae about the Hand and Wrist 487 Posterior Annular Ligament 487 Superficial Transverse Ligament of Fingers . 489 The Radial Region 489 Abductor PoUicis 489 Opponens PoUicis 490 Flexor Brevis PoUicis ,. . . . 490 Adductor Obliquus PoUicis 490 Adductor Transversus PoUicis 492 The Ulnar Region 492 Palmaris Brevis 492 Abductor Minimi Digiti 492 Flexor Brevis Minimi Digiti 493 Opponens Minimi Digiti 493 The Middle Palmar Region 493 Lumbricales 493 Interossei 493 Dorsal Interossei 494 First Dorsal Interossei Muscle or Abductor Indicis 494 Palmar Interossei 494 Surface Form of Muscles of the Upper Ex- tremity 495 Applied Anatomy of Muscles of the Upper Extremity 497 Muscles and Fasci/E of the Lower Extremity. Subdivision into Groups 501 Muscles and Fascice of the Iliac Region. lUac Fascia 502 Psoas Magnus 504 Psoas Parvus 504 Iliacus 504 Applied Anatomy 505 Muscles and Fasciw of the Thigh. The Anterior Femoral Region 505 Superficial Fascia 506 Deep Fascia or Fascia Lata 506 Applied Anatomy 508 Tensor Fasciae Femoris 508 Sartorius 508 Quadriceps Extensor 509 Rectus Femoris 510 Vastus Externus 510 Vastus Internus 510 Crureus 511 Subcrureus 512 AppUed Anatomy 512 The Internal Femoral Region 512 Gracilis 512 Pectineus 513 Adductor Longus 513 Adductor Brevis 514 Adductor Magnus 514 Hunter's Canal 515 Applied Anatomy 515 The Muscles and Fascice of the Hip. The Gluteal Region 515 Gluteus Maximus 515 Gluteus Medius 516 Gluteus Minimus 517 Pyriformis 517 Obturator Membrane 517 Obturator Internus 518 GemelU 520 Quadratus Femoris 520 Obturator Externus 521 The Posterior Femoral Region 522 Biceps Femoris 522 Semitendinous 524 Semimembranous 524 Applied Anatomy 525 Muscles and Fascice of the Leg. The Anterior Tibiofibular Region 525 Deep Fascia of the Leg 525 Tibialis Anticus 526 Extensor Proprius Hallucis 527 Extensor Longus Digitorum 527 Peroneus Tertius 527 The Posterior Tibiofibular Region 528 Superficial Layer 528 Gastrocnemius 528 Soleus 529 Tendo Achillis 530 Plantaris 530 Deep Layer 531 Deep Transverse Fascia 531 Popliteus 531 Flexor Longus Hallucis 532 Flexor Longus Digitorum 533 Tibialis Posticus 533 The Fibular Region 534 Peroneus Longus 534 Peroneus Brevis 535 Applied Anatomy 535 CONTENTS Muscles and Fascice of the Foot. Anterior Annular Ligament 536 Internal Annular Ligament 536 External Annular Ligament 537 The Dorsal Region 537 Fascia of the Dorsal Region 537 Extensor Brevis Digitorum 537 The Plantar Region 537 Plantar Fascia 537 The First Layer 538 Abductor Hallucis 538 Flexor Brevis Digitorum 538 Fibrous Sheaths of Flexor Tendons 539 Abductor Minimi Digiti 539 The Plantar Region — The Second Layer 539 Flexor Accessorius 539 Lumbricales 540 The Third Layer 541 Flexor Brevis Hallucis 541 Adductor Obliquus Hallucis 541 Adductor Transversus Hallucis . . . 541 Flexor Brevis Minimi Digiti 541 The Fourth Layer 541 Interossei Muscles 541 Surface Form of Muscles of the Lower Extremity. 543 Applied Anatomy of Muscles of the Lower Extremity 544 THE VASCULAR SYSTEMS. The Heart and Bloodvessels. The Circulation of the Blood The Pericardium. Structure of the Pericardium Vestigial Fold of the Pericardium Applied Anatomy of the Pericardium. The Heart. Position of the Heart Component Parts of the Heart The Cavities of the Heart Right Auricle ". . . . Right Ventricle Left Auricle . 548 550 550 551 553 553 554 557 559 The Cavities of the Heart — Left Ventricle 560 Capacity of the Cavities of the Heart 561 Size and Weight of the Heart 562 Structure of the Heart 562 Endocardium 562 Myocardium 562 Fibres of Auricles 562 Fibres of Ventricles 563 The Cardiac Cycle and the Action of the Valves 565 Surface Form of the Heart 567 Applied Anatomy of the Heart 568 Peculiarities of the Vascular System in the Fetus 568 Fetal Circulation 570 Changes in the Vascular System at Birth . . 571 THE ARTEEIES. The Distribution of the Arteries 572 Anastomosis of the Arteries 572 Histology of Arteries and Capillaries 573 Bloodvessels of the Bloodvessel Wall 573 Lymphatics of the Arteries 574 Nerves of the Arteries 574 Arterial Sheath 574 Applied Anatomy of the Arteries 574 The Pulmonary Artery. Right Branch of the Pulmonary Artery. . . . 575 Left Branch of the Pulmonary Artery 575 Applied Anatomy of the Pulmonary Artery 575 The Aorta. The Ascending Aorta. Relations of the Ascending Aorta 576 Branches of the Ascending Aorta 578 The Coronary Arteries 578 Applied Anatomy of the Coronary Arteries 578 The Arch of the Aorta. Relations of the Arch of the Aorta Peculiarities of the Arch of the Aorta AppHed Anatomy of the Arch of the Aorta . Branches of the Arch of the Aorta The Innominate Artery Relations Branches Thyroidea Ima Applied Anatomy Peculiarities 579 580 580 581 582 582 582 582 582 583 The Arteries of the Head and Neck. The Common Carotid Artery. Relations of the Common Carotid Artery. . 583 Peculiarities of the Common Carotid Artery 586 Surface Marking of the Common Carotid Artery 586 Applied Anatomy of the Common Carotid Artery 586 The External Carotid Artery Relations Surface Marking Applied Anatomy Branches Superior Thyroid Artery Applied Anatomy Lingual Artery Applied Anatomy Facial Artery Applied Anatomy Occipital Artery Posterior Auricular Artery Ascending Pharyngeal Artery. . . . Applied Anatomy Superficial Temporal Artery Applied Anatomy Internal Maxillary Artery Applied Anatomy The Triangles of the Neck Anterior Triangle of the Neck Posterior Triangle of the Neck The Internal Carotid Artery Cervical Portion . Petrous Portion Cavernous Portion Cerebral Portion Peculiarities Applied Anatomy Branches Tympanic Vidian Arteriae Receptaculi Anterior Meningeal Ophthalmic Anterior Cerebral Middle Cerebral Posterior Communicating Artery. Choroid Artery The Arteries of the Brain. The Central GangUonic System The Cortical Arterial System The Vertebral Artery Applied Anatomy 588 588 588 589 589 590 590 591 592 595 595 596 597 597 597 598 598 600 602 603 605 606 607 607 609 609 609 610 614 616 617 617 618 619 619 620 CONTENTS The Ahteries of the Upper Extremity. The Subclavian Artery. First Part of the Right Subclavian Artery . . 623 First Part of the Left Subclavian Artery . . . 625 Second and Third Parts of the Subclavian Artery 625 Peculiarities of the Subclavian Artery 626 Surface Marking of the Subclavian Artery . . 626 Applied Anatomy of the Subclavian Artery . 627 Branches 628 Vertebral Artery 628 Thyroid Axis 628 Peculiarities 630 Internal Mammary Artery 631 Superior Intercostal Artery 633 The Axilla. Boundaries of the Axilla 633 Contents of the Axilla 634 Applied Anatomy 634 The Axillary Artery 635 Surface Marking 637 Applied Anatomy 637 Branches 638 Superior Thoracic 638 Acromiothoracic 638 Long Thoracic or External Mam- mary 638 Alar Thoracic 639 Subscapular 639 Circumflex Arteries 639 The Brachial Artery. Relations of the Brachial Artery 640 Anatomy of the Bend of the Elbow 641 Peculiarities of the Brachial Artery 641 Surface Marking of the Brachial Artery. . . . 641 Applied Anatomy of the Brachial Artery. . . 641 Branches of the Brachial Artery 642 Superior Profunda Artery 642 Nutrient Artery 643 Inferior Profunda Artery 643 Anastomotica Magna 643 Muscular Branches 644 The Anastomosis Around the Elbow- joint 644 The Radial Artery 644 The Deep Palmar Arch 645 Surface Marking 646 Applied Anatomy 646 Branches 646 Radial Recurrent 646 Muscular Branches 646 Anterior Radial Carpal 647 Superficialis Volae 647 Posterior Radial Carpal 647 Dorsalis Pollicis. 647 Dorsalis Indicis 647 Princeps Pollicis 647 Radialis Indicis ; 647 Perforating Arteries 648 Palmar Interosseous 648 Palmar Recurrent Branches 648 The Ulnar Artery 648 Surface Marking 649 Applied Anatomy 649 Branches 650 Anterior Ulnar Recurrent 650 Posterior Ulnar Recurrent 650 Interosseous Artery 650 Muscular Branches 651 Anterior Ulnar Carpal 651 Posterior Ulnar Carpal 651 Profunda Branch 651 Superficial Palmar Arch 652 Surface Marking 652 Applied Anatomy 652 The Arteries of the Trunk. The Descending Aorta. The Thoracic Aorta 653 Applied Anatomy 654 Branches 654 The Thoracic Aorta — Branches — Bronchial .VrtiTJfs 654 CEso|.h:ii;(M! ,\riiTies 654 Peric;ir.li;il \il-rirs 654 MediiisliiKil I'.iaiiches 654 Intercostal Arteries 655 Applied Anatomy 657 The Abdominal Aorta 657 Surface Marking 657 Applied Anatomy 658 Branches 658 Inferior Phrenic Arteries 658 The Cceliac Axis or Artery 659 Applied Anatomy 662 The Suprarenal Artery 662 The Lumbar Arteries 662 The Superior Mesenteric Artery... 663 The Renal Arteries 665 The Spermatic Arteries 665 The Ovarian Arteries 665 The Inferior Mesenteric Artery . . . 666 The Cojntnon Iliac Arteries. Relations of the Common Iliac Arteries. . . . 668 Branches of the Common Iliac Arteries .... 668 Peculiarities of the Common Iliac Arteries . 668. Surface Marking 669 Applied Anatomy of the Common Iliac Arteries 669 The Internal Iliac Artery 669 Applied Anatomy 671 Branches 671 Superior Vesical 671 Middle Vesical 672 Inferior Vesical 672 Middle Hemorrhoidal 672 Uterine Artery 672 Vaginal Artery 672 Applied Anatomy 673 Obturator Artery 673 Internal Pudic Artery 674 Sciatic Artery 677 Iliolumbar Artery 678 Lateral Sacral Arteries 678 Gluteal Artery 678 Surface Marking 679 Applied Anatomy 679 The External Iliac Artery 679 Surface Marking 680 Applied Anatomy 680 Branches 680 Deep Epigastric Artery 680 Applied Anatomy 681 Deep Circumflex Iliac Artery 682 The Arteries of the Lower Extremity. The Femoral Artery. The Femoral or Crural Sheath 683 The Femoral or Crural Canal 684 Scarpa's Triangle 685 Hunter's Canal or the Adductor Canal 685 Relations of the Femoral Artery 686 PecuUarities of the Femoral Artery 687 Surface Marking of the Femoral Artery .... 687 Applied Anatomy of the Femoral Artery. . . 687 Branches of the Femoral Artery 688 Superficial Epigastric ' 689 Superficial Circumflex Iliac 689 Superficial External Pudie.or the Supe- rior Superficial External Pudic 689 Deep External Pudic 689 Muscular Branches 6S9 Deep Femoral or the Profunda Femoris 689 The Popliteal Artery. The Popliteal Space 691 Boundaries 692 Contents 692 Position of Contained Parts 692 Peculiarities 693 Surface Marking 693 Applied Anatomy 693 Branches 694 CONTENTS The Popliteal Space — Branches — Superior Muscular Branches 694 Inferior Muscular or Sural Branches 694 Cutaneous Branches 694 Superior Articular Arteries 694 Azygos Articular Artery 695 Inferior Articular Arteries 695 Circumpatellar Anastomosis 696 The Anterior Tibial Artery 696 Surface Marking 697 Applied Anatomy 697 Branches 697 Posterior Recurrent Tibial 698 Superior Fibular 698 Anterior Recurrent Tibial 698 Muscular Branches 698 The Dorsalis Pedis Artery 698 Surface Marking 699 Applied Anatomy 699 Branches 699 The Dorsalis Pedis Artery — Branches — Cutaneous Branches 699 Tarsal Artery 699 Metatarsal Artery 699 Communicating Artery 700 The Posterior Tibial Artery. 700 Surface Marking 701 Applied Anatomy 701 Branches 701 Peroneal Artery 701 Cutaneous Branches 702 Nutrient Artery 702 Muscular Branches 703 Communicating Branch 703 Malleolar or Internal Malleolar. . . 703 Internal Calcaneal 703 Internal Plantar Artery 703 External Plantar Artery 703 Surface Marking 704 Apphed Anatomy 704 THE A^EINS. Subdivisions of the Veins 705 Histology of the Veins 706 Superficial or Cutaneous Veins 707 Deep Veins 707 Sinuses 707 The Pulmonary Veins. Applied Anatomy of the Pulmonary Veins . . 708 The Systemic Veins. The Cardiac Veins. The Coronary Sinus 708 The Veins of the Head and Neck. Veins of the Exterior of the Head and Face 710 Frontal Vein 710 Supraorbital Vein 710 Angular Vein 710 Facial Vein 710 Common Facial Vein 710 Applied Anatomy 711 Superficial Temporal Vein 712 Pterygoid Plexus 712 Internal Maxillary Vein 712 Temporomaxillary Vein 712 Posterior Auricular Vein 712 Occipital Vein 713 The Veins of the Neck 713 External Jugular Vein 713 Posterior External Jugular Vein 713 Anterior Jugular Vein 713 Internal Jugular Vein 714 Applied Anatomy 717 Vertebral Vein 717 The Veins of the Diploe 718 Meningeal or Dural Veins 719 The Cerebral Veins _ V19 Superficial Cerebral Veins 719 Deep Cerebral Veins or Veins of Galen 720 Superficial Cerebellar Veins 720 Deep Cerebellar Veins 720 Veins of the Pons 720 Veins of the Medulla Oblongata 721 The Sinuses of the Dura. Ophthalmic Veins and Emissary Veins 721 Superior Sagittal Sinus 721 Inferior Sagittal Sinus 722 Straight or Tentorial Sinus 722 Lateral Sinuses 722 Occipital Sinus 723 Cavernous Sinus 724 Applied Anatomy 724 Sphenoparietal Sinuses 725 Circular Sinus 726 Superior Petrosal Sinus 726 The Sinuses of the Dura. Ophthalmic Veins and Emissary Veins — Inferior Petrosal Sinus 726 Transverse or Basilar Sinus 727 Emissary Veins 727 Applied Anatomy 727 The Veins of the Upper Extremity and Thorax. The Superficial Veins of the Upper Ex- tremity 728 Superficial Veins of the Hand and Fingers 728 Anterior Ulnar Vein 729 Posterior Ulnar Vein 729 Common Ulnar Vein 729 Radial Vein 730 Median Vein 730 BasUic Vein 730 Cephalic Vein 730 The Deep Veins of the Upper Extremity. . . 731 Interosseous Veins 731 Deep Palmar Veins 731 Brachial Veins 731 Axillary Vein 731 Applied Anatomy 732 Subclavian Vein 732 Innominate or Brachiocephalic Veins . . 733 Internal Mammary Veins 734 Vertebral Vein 734 Inferior Thyroid Veins 734 Superior Intercostal Veins 735 Superior Vena Cava 735 Azygos Veins 736 Applied Anatomy 737 Bronchial Veins 737 The Vertebral Veins 737 Extravertebral Veins 737 Intravertebral Veins 738 Veins of the Bodies of the Vertebrae . . . 738 Veins of the Spinal Cord 739 Veins of the Lower Extremity, Abdomen, and j Superficial Veins of the Lower Extremity ... 739 Superficial Veins of the Foot 739 Internal or Long Saphenous Vein 740 External or Short Saphenous Vein 741 Applied Anatomy 741 Deep Veins of the Lower Extremity 741 Deep Veins of the Foot 741 Posterior Tibial Veins 742 Anterior Tibial Veins 742 Pophteal Vein 742 Femoral Vein 742 External Iliac Vein 742 Deep Epigastric Vein 742 Deep Circumflex Iliac Vein 742 CONTENTS XVII Deej) Veins of the Lower Extremity — Pubic Vein 743 Internal Iliac Vein 743 Hemorrhoidal Plexus 745 . Vesicoprostatic Plexus 745 Vesical Plexus 745 Applied Anatomy 745 Dorsal Veins of the Penis 746 Vaginal Plexuses and Veins 747 Uterine Plexuses 747 Common Iliac Veins 747 Inferior Vena Cava 748 Applied Anatomy 748 Lumbar Veins 749 Spermatic Veins 750 Applied Anatomy 750 Ovarian Veins 751 Deep Veins of the Lower Extremity — Renal Veins 751 Suprarenal Veins 751 Inferior Phrenic Veins 751 Hepatic Veins 751 The Portal System of Vkins. The Portal Vein 751 The Splenic Vein 752 The Superior Mesenteric Vein 753 The Cysrie Vein 754 Paraumbilical Veins 754 Anastomosis between Portal and Systemic Veins 754 Applied Anatomy 754 Development of the Blood-vascular System . 755 THE LYMPHATIC SYSTEM. Subdi\asions into Superficial and Deep Sets . 767 Lymph Nodes or Lymphatic Glands 768 Hemolymph Nodes 768 Structure of Lymphatics 769 Origin of Lymphatics 769 Termination of Lymphatics 769 Development of Lymphatic Vessels 769 Applied Anatomy 770 The Thoracic Duct. Structure of the Thoracic Duct 773 The Right Lymphatic Duct 773 Applied Anatomy 774 Lymphatics of the Head, Face, and Neck. The Lymphatic Nodes of the Head and Face 774 Occipital Nodes 774 Posterior Auricular or Mastoid Nodes.. 774 Parotid Ljonph Nodes 774 Internal Maxillary Nodes 776 Lingual Nodes 776 Retropharyngeal Nodes 776 Lymphatic Vessels of the Scalp 776 Lymphatic Vessels of the Pinna and Exter- nal Auditory Meatus 777 Lymphatic Vessels of the Face 777 Lymphatic Vessels of the Nasal Fossae 777 Lymphatic Vessels of the Mouth ■ . . 777 Lymphatic Vessels of the Tongue 777 Lymph Nodes of the Neck 777 Superficial Cervical Nodes 777 Submaxillary Nodes 778 Submental or Suprahyoid Nodes 779 Retropharyngeal Nodes 779 Deep Cervical Nodes 779 Lymphatic Vessels of the Skin and Muscles of the Neck 780 Applied Anatomy 780 The Lymph.atics of the Upper Extremity. The Lymph Nodes of the Upper Extremity . 781 Superficial Lymph Nodes 781 Deep Lymph Nodes or the Axillary Nodes 782 Lymphatic Vessels of the Upper Extremity 783 Superficial Lymphatic Vessels 783 Deep Lymphatic Vessels 784 Applied Anatomy 784 The Lymphatics of the Lower Extremity. The Lymph Nodes of the Lower Extremity 784 Anterior Tibial Node 784 Popliteal Nodes 784 Inguinal Nodes 785 Superficial Inguinal Nodes 785 Deep Inguinal Nodes 786 Applied Anatomy 786 The Lymphatic Vessels of the Lower Ex- tremity 786 Superficial Vessels 786 Deep Vessels 787 The Lymph.atics of the Pelvis .and Abdomen. The Parietal Nodes 787 External Iliac Nodes 787 Internal IKac or Hypogastric Nodes. . . 787 Common Iliac Nodes 788 Lumbar Nodes 788 Lateral Aortic Nodes 788 Lymphatic Vessels of the Abdomen and Pelvis 789 Superficial Vessels 789 Deep Vessels 790 Lymphatic Vessels of the Perineum and External Genitals 790 The Visceral. Nodes 790 The Superior Mesenteric Nodes 790 Mesenteric Nodes 790 Applied Anatomy 791 Ileocolic Nodes 791 Mesocolic Nodes 791 Inferior Mesenteric Nodes 791 Lymphatic Vessels of the Abdomen and Pelvic Viscera 792 Lymphatic Vessels of the Stomach 792 Applied Anatomy 793 Lymphatic Vessels of the Duodenum . . . 793 Lymphatic Vessels of the Small In- testine 793 Lymphatic Vessels of the Large Intes- tine 794 Lymphatic Vessels of the Anus and Rectum 794 Lymphatic Vessels of the Liver 794 Lymphatic Vessels of the Gall-bladder. 795 Lymphatic Vessels of the Pancreas .... 796 Lymphatic Vessels of the Spleen 796 Lymphatic Vessels of the , Suprarenal Glands 796 Lymphatic Vessels of the Urinary Organs 796 Lymphatic Vessels of the Kidney. 796 Lymphatic Vessels of the Ureter. . 796 Ljonphatic Vessels of the Bladder. 796 Lymphatic Vessels of the Prostate 796 Ljonphatic Vessels of the Urethra. 796 Lymphatic Vessels of the Reproductive Organs 796 Lymphatic Vessels of the Testes . . 796 Lymphatic Vessels of the Vas Deferens 797 Lymphatic Vessels of the Ovarj' . . 797 Lymphatic Vessels of the Fallopian Tube 797 Lymphatic Vessels of the Uterus . . 797 Lymphatic Vessels of the Vagina. . 797 The Lymphatics of the Thorax. The Parietal Lymph Nodes 798 Internal Mammary Nodes 798 Intercostal Nodes 798 Diaphragmatic Nodes 798 CONTENTS Superficial Lymphatic Vessels of the Tho- racic Wall ■• 'J* Lymphatic Vessels of the Mammary 'Gland .■•^;n ■ ■• Vtm Deep Lymphatics of the Thoracic Wall. ... 799 Lymphatic Vessels of the Diaphragm . . 799 Applied Anatomy '^ The Visceral Lymph Nodes «UU Anterior Mediastinal Nodes »uu Posterior Mediastinal Nodes »uu The Visceral Lymph Nodes— Tracheobronchial Nodes hUU Applied Anatomy ■ • • °0- Lymphatic Vessels of the Thoracic Viscera . 802 Lymphatic Vessels of the Heart 802 Lymphatic Vessels of the Lungs 802 Lymphatic Vessels of the Pleura 802 Lymphatic Vessels of the Thymus Gland ■^■■■- 802 Lymphatic Vessels of the (Esophagus. 802 THE NERVE SYSTEM. The Spinal Cord and Brain, with their Meninges. Fundamental Facts Regarding the Develop- | ment of the Nerve System 804 Development of Nerve Tissue »OD Structure of the Nerve System |U ' The Neurone ^ °Xn The Dendrites =Yn The Axone o^V The Collaterals ^^^ Nerve Cell Nidi or Nuclei 812 "Nerve Fibres" and Nerves. Origin and Termination of Nerves. ■••■■■■• 81* The Supporting Tissue Elements of the . Nerve System »{° The NeurogUa °J° Chemical Composition of Nerves oia The Central Nerve System. Preliminary Considerations 819 The Spinal Cord. External Morphology of the Spinal Cord. . . 822 The Enlargements of the Spinal Cord . . . »jA Fissures and Grooves of the Spinal Cord ... 82o Columns of the Spinal Cord . 82b Development of the Spinal Cord. 82^ Internal Structure of the Spinal Cord 8-9 Gray Substance of the Cord 829 White Substance of the Cord 8dd Tracts of the Spinal Cord .•■■•■• gg* Ground Bundle of the Dorsal Column . 837 Ground Bundle of the Lateral Column 839 Ground Bundle of the Ventral Column 840 Myelinization of the Axones of the Cord 840 Applied Anatomy of the Spinal Cord 842 The Membranes of the Cord. The Spinal Dura |43 The Arachnoid °** The Pia of the Cord ■ ■ ■ ■ o4& Applied Anatomy of the Membranes oi the Cord S46 847 The Brain or Encephalon. General Appearance and Topography of the Brain Dimensions of the Bram 849 Weight of the Brain .• • ■ ■ j' V tt ' ' 'i The Development of the Bram and the Usual Classifioations of its Subdivisions 850 Brief Consideration of the Phases of Devel- opment of the Brain Tube 852 Forebrain °52 Midbrain °°^ Hindbrain °°g Flexures of the Brain Tube :••;.■•, °°^ Dorsal and Ventral Laminai or Longitudinal Zones of the Brain ood Descriptive Anatomy of the Adult Human Brain. Parts Derived from the Hindbrain (Rhom- bencephalon) 861 The Medulla Oblongata 8bl Parts Derived from the Hindbrain— The Pons.. =64 Fourth Ventricle of the Brain 8o4 Internal Structure of the Medulla Oblongata 867 Internal Structure of the Pons and Pars Dorsalis Pontis /,' ' ■■ i Central Connections of the Cranial Nerves to the Hindbrain 8/ / The Cerebellum ; >; ' ' V „ ■ ' ' ' §So Internal Structure of Cerebellum. . 888 The Cerebellar Peduncles 889 Weight of the Cerebellum 893 The Midbrain 893 External Morphology 894 Corpora Quadrigemina 894 Superior Brachium 895 Internal Geniculate Body 895 Crura Cerebri 895 Taenia Pontis 895 Tractus Peduncularis Transversus 895 Internal Structure of Midbrain 896 The Aqueduct and Central Aque- duct Gray 897 Substantia Nigra or Intercalatum . 897 Corpora Quadrigemina 897 Tegmentum 897 Red Nucleus or Rubrum 898 Fountain Decussation 900 Crusta or Pes ■ • 900 Summary of the Gray Masses m the Midbrain ;■.■.• ^ Deep Origin of Cranial Nerves Arising in the Midbrain 900 Parts Derived from the Forebrain 902 External Morphology 9U2 TheThalami 902 The Pineal Body 9Ub Third Ventricle ■■■■_■ 90/ External Morphology of the Optic Portion of the Hypothalamus . . 908 Tuber Cinereum 90S Pituitary Body or Hypophysis 909 Lamina Terminahs or Terma 909 Optic Tract and its Central Con- nections 909 Optic Chiasm 910 The Cerebral Hemispheres 91- External Morphology ■ ■ . ■.■ ■'!'' Configuration of Each Cerebral Hemi- Cerebral Fissures and Gyres 915 Cerebral Lobes and Fissures 91b The Interlobar Fissures 916 Frontal Lobe 919 Parietal Lobe 922 Occipital Lobe 924 Temporal Lobe 924 The Island of Reil 925 The Rhinencephalon or Olfactory Lobe ■■■; ^^^ Internal Configuration of the Cerebral Hemispheres 931 The Cortex 932 The Corpus Callosum 933 The Lateral Ventricles 93b The Choroid Fissure or Rima 940 The Choroid Plexus of the Lateral Ventricles and Velum Interposi- turn 940 CONTENTS The Cerebral Hemispheres — Internal Con- figuration of — ■ The Hippocampus and Fornix .... 942 The Septum Lucidum 945 The Anterior Commissure 946 Gray Masses in the Cerebral Hemi- sphere 946 Intimate Structure of the Cerebral Cortex and its Special Types in Dif- ferent Regions 951 Summary of the Cerebral Fibre System 954 The Olfactory Pathways 958 Cortical Localization of Function. Motor Area , 959 Sensory Area 960 Language Area 960 Association Areas 961 Craniocerebral Typography 962 The Meninges or Meningeal Membranes of the Brain. The Dura of the Brain 964 Processes of the Dura 966 The Arachnoid of the Brain 968 Subarachnoid Space 969 The Arachnoid Villi or Pacchionian Bodies 970 The Pia of the Brain 971 Velum Interpositum or the Tela Chor- oidea Superior 971 The Cranial Nerves. The First or Olfactory Nerves. Applied Anatomy , 974 The Second or Optic Nerve. ■Optic Chiasm 974 Applied Anatomy 975 The Third or Oculomotor Nerve. Applied Anatomy 977 The Fourth or Trochlear Nerve. Applied Anatomy 978 The Fifth, Trigeminal, or Trifacial Nerve. Gasserian or Semilunar Ganglion 978 Ophthalmic Nerve 979 The Superior Maxillary Nerve 982 The Inferior Maxillary or Mandibular Nerve 987 Surface Marking 990 Apphed Anatomy 991 The Sixth or Abducent Nerve. Applied Anatomy 994 The Seventh or Facial Nerve. Applied Anatomy 999 The Eighth or Acoustic Nerve. The Cochlear Nerve 1000 The Vestibular Nerve 1000 Applied Anatomy 1001 The Ninth or Glossopharyngeal Nerve. The Superior or Jugular Ganglion 1002 The Inferior or Petrous Ganglion 1002 The Gustatory Path 1003 Applied Anatomy 1003 The Tenth, Vagus, or Pneumogastric Nerve. The Ganglion of the Root or the Jugular Ganglion 1005 The Ganglion of the Trunk or the Inferior Ganglion 1005 Applied Anatomy 1008 The Eleventh or Spinal Accessory Nerve. The Bulbar or Vagal Accessory Part 1009 The Spinal Portion 1009 Applied Anatomy 1009 The Twelfth or Hypoglossal Nerve. Applied Anatomy 1012 The Spinal Neeve.s. The Anterior or Ventral Root The Posterior or Dorsal Root Spinal Ganglia Points of Emergence of Spinal Nerves. Divisions of Spinal Nerves 1013 1013 1013 1014 1014 The Cervical Plexus. The Superficial Branches of the Cervical The Deep Branches of the Cervical Plexus, Internal Series Applied Anatomy The Deep Branches of the Cervical Plexus, External Series Applied Anatomy The Brachial Plexus. Applied Anatomy The Anterior or Ventral Divisions of Thor- acic Nerves Applied Anatomy The Lumbosacral Plexus. The Anterior or Ventral Di-visions of the Lumbar Nerves The Lumbar Plexus The Anterior or Ventral Divisions of the Sacral and Coccygeal Nerves The Sacral Plexus. Relations The Pudendal Plexus. Applied Anatomy 1023 1025 1025 1026 1040 1043 1044 1044 1051 1053 1062 The Sympathetic Nerve System. Structure of the Sympathetic System 1063 The Gangliated Cord. Cervicocephalic Portion of the Gangliated Cord 1066 The Superior Cervical Ganglion 1066 The Middle Cervical Ganglion 1069 The Inferior Cer^dcal Ganglion 1069 Applied Anatomy 1069 Thoracic Portion of the Gangliated Cord 1070 Lumbar Portion of the Gangliated Cord . . . 1071 Pelvic Portion of the Gangliated Cord ..... 1072 The Great Plexuses of the Sympathetic System. The Cardiac Plexus 1072 The CceUac or Solar Plexus 10/3 The Hypogastric Plexus 1077 The Pelvic Plexuses 1077 CONTENTS THE OEGANS OF SPECIAL SENSE. The Nose. The Outer Nose. Structure 1079 The Nasal Fossae. The Anterior Nares 1081 The Posterior Nares 1081 The Outer Wall 1082 The Inner Wall lOhS The Mucous Membrane 1083 AppUed Anatomy of the Nose 1085 The Eye. The Capsule of Tenon 1086 The Tunics of the Bye. The Solera and Cornea 1089 The Sclera 1090 The Cornea 1090 The Choroid, Ciliary Body, and Iris 1092 The Choroid 109.3 The Ciliary Body 1094 The Iris 1096 Membrana Pupillaris 1100 The Retina or Tunica Interna 1 100 The Refracting Media. The Aqueous Humor 1105 The Vitreous Body 1105 The Crystalline Lens 1106 Applied Anatomy of the Eye 1109 The Appendages of the Eye. The Eyebrows 1112 The EveHds 1112 The Eyelashes 1113 The Meibomian or Tarsal Glands 1114 The Conjunctiva 1114 The Lacrimal Apparatus 1115 The Lacrimal Gland 1115 The Lacrimal Canals 1116 The Lacrimal Sac 1116 The Lacrimal Apparatus — The Nasal Duct 1117' Surface Form HIT" Applied Anatomy 1118 The Ear. The External Ear. The Pinna or Auricula 1119 The Auditory Canal or Meatus 1122 Applied Anatomy 1124 The Middle Ear, Drum or Tympanum. The Tympanic Cavity 1125' The Membrana Tympani 1128 The Ossicles of the Tympanum 1131 The Malleus 1131 The Incus 1132 The Stapes 1133 Applied Anatomy •■ 1135 The Internal Ear or Labyrinth. The Osseous Labsointh 1136 The Vestibule 1136 The Bony Semicircular Canals 1137 The Modiolus 1138 The Membranous LabjTinth 1140 The Utricle 1140 The Saccule 1141 The Membranous Semicircular Canals. 1142 Structure 1142 The OHGAN.S of T.aste 1148 The Skin. The Cuticle, Scarf Skin, or Epidermis 1151 I The Corium, Cutis Vera, Derma, or True Skin llo3 I The Appendages of the Skin. The Nails.. 1156 The Hairs llg?- I The Sebaceous Glands 1161 The Sudoriferous or Sweat Glands 1161 THE OEGANS OF VOICE AND EESPIRATION. The Larynx. The Cartilages of the Larynx 1163 The Ligaments of the Larynx 1167 Interior of the Larj'nx 1169 Muscles of the Larynx 1172 The Trachea .and Bronchi. The Risht Bronchus 1176 The Left Bronchus 1177 Surface Form }}on Applied Anatomy 1180 The PLETjHa:. The Mediastinum or Interpleural Space. The Superior Mediastinum 1186 The Anterior Mediastinum 1186 The Middle Mediastinum 1186 The Posterior Mediastinum 1187 Applied Anatomy 1188 The Lungs. The Apex of the Lung 1188 The Base of the Lung 11|8 Surfaces of the Lung 1189 Borders of the Lung 1190 Fissures and Lobes of the Lung 1190 : The Root of the Lung 1193 Di«sions of the Bronchi 1194 Surface Form ll™ Applied Anatomy 1197 THE ORGANS OF DIGESTION. The Mouth, Oral or Buccal Cavity. ' I The CaHty of the Mouth Proper Floor of the Mouth The Lips 1200 The Palate The Vestibule of the Mouth 1200 The Teeth ^ • ,- ■ , ■ ,u ■ ,, • The Mucous Membrane 1200 Temporary. Deciduous, or Milk Teeth, The rVippks ; . . 1200 Permanent 1 eeth . .^. ..... . The Buccal Glands'. ■.■.■.■.;::: 1200 . Chemical Compo^tion o the Teeth . . . The Gums 1200 i Development of the Teeth 1201 1201 1202 1204 1205 1206 1210 1212 CONTENTS XXI The Tongue. The Body of the Tongue 1217 The Base or Root of the Tongue 1217 The Apex or Tip of the Tongue 1217 The Dorsum of the Tongue 1217 The Margin of the Tongue 1217 The Under or Inferior Surface of the Tongue 1217 Development of the Tongue 1221 Applied Anatomy 1222 The Salivary Glands. The Parotid Gland 1223 The Submaxillary Gland 1225 The Sublingual Gland 1226 Development of the Salivary Glands 1227 Surface Form 1227 Applied Anatomy 1229 The Pharynx. The Nasal Part or Nasopharynx 1229 The Oral Part 1230 The Tonsils 1230 Development 1232 Applied Anatomy 1233 The Laryngeal Part 1233 Development of the Pharynx 1234 Applied Anatomy of the Pharynx 1235 The (Esophagus. Applied Anatomy 1239 The Abdomen. Boundaries of the Abdomen 1241 Regions of the Abdomen 1242 The Peritoneum. Development of the Peritoneum and Alimentary Tract 1245 Retroperitoneal Fossas 1265 Applied Anatomy 1268 The Stomach. Openings of the Stomach 1271 Curvatures of the Stomach 1271 Surfaces of the Stomach 1271 ■Component Parts of the Stomach 1272 Interior of the Stomach 1273 Movement and Innervation of the Stomach . 127!) Surface Form 1280 Applied Anatomy ' 12)50 The Small Intestine. The Duodenum 1282 Interior of the Duodenum 1286 Applied Anatomy 1287 The Jejunum and Ileum 1287 Meckel's Diverticulum 1288 Structure of the Villi 1291 Applied Anatomy of the Small Intestine. . . 1295 The Large Intestine. The Cecum 1296 The Vermiform Appendix 1298 The Ileocecal Valve 1301 Applied Anatomy 1,302 The Colon 1,303 Apphed Anatomy 1.306 The Rectum 1306 The Anal Canal 1.309 The Anal Orifice or Anus 1309 Movements and Innervations of the Intes- tines 1312 Surface Form of the Intestines 1313 Applied Anatomy of the Intestines 1314 The Liver. Surfaces of the Liver 1320 Fissures of the Liver 1322 Lobes of the Liver 1323 Ligaments of the Liver 1324 Support and Movability of the Liver 1325 Abnormalities of the Liver 1326 The Excretory Apparatus of the Liver 1331 The Hepatic Duct 1332 The Gall-bladder 1332 The Cystic Duct 1333 The Common Bile Duct 1333 Surface Relations of the Liver 1334 Applied Anatomy of the Liver 1335 The Pancreas. Pancreatic Juice 1341 Surface Form of the Pancreas 1341 Applied Anatomy of the Pancreas 1341 THE UEINOGENITAL ORGANS. The Urinary Organs. The Kidneys. Relations of the Kidneys 1343 Anterior Surface of Right Kidney 1343 Anterior Surface of Left Kidney 1343 Posterior Surface of the Kidney 1345 Borders of the Kidney 1347 Extremities of the Kidney 1348 Fixation of the Kidney 1348 Minute Anatomy of the Kidney 1350 Variations and Abnormalities of the Kidney 1354 Surface Form of the Kidney ". 1354 Applied Anatomy of the Kidney 1355 The Ureters. Applied Anatomy of the Ureters 1358 The Urinary Bladder. Surfaces of the Bladder 1359 The Fundus or Base 1361 The Summit or Apex 1361 The Urachus or Middle Umbilical Ligament 1361 The Ligaments of the Bladder 1361 The Interior of the Bladder 1364 Surface Form of the Bladder 1365 Applied Anatomy of the Bladder 1366 The Male Urethra. The Prostatic Portion 1366 The Membranous Portion 1367 The Penile or Spongy Portion 1368 Apphed Anatomy 1369 The Female Urethra 1370 The Male Reproductive Organs. The Testicles. The Scrotum 1372 The Intercolumnar or External Spermatic Fascia _ 1374 The Cremasteric Fascia 1374 The Infundibuliform Fascia 1374 The Tunica Vaginalis 1374 The Inguinal or Spermatic Canal 1375 The Spermatic Cord 1375 The Testes 1377 The Epididymis 1378 The Tunics of the Testicle 1379 The Semen 1381 Applied Anatomy of the Testicle 1382 The Vas Deferens. Organ of Giraldfe 1384 The Seminal Vesicles. Applied Anatomy of the Seminal Vesicles. . 1385 The Ejttculatory Duels 13S6 xxu CONTENTS The Penis. The Root of the Penis 1388 The Body of the Penis 1388 AppUed Anatomy of the Penis 1390 The Prostate Gland. Applied Anatomy of the Prostate Gland . . . 1395 Cowper's Glands 1397 The Female Repboductive Organs. The Ovaries. The Ovary at Different Ages 1399 Applied Anatomy of the Ovaries 1401 The Fallopian Tube or Oviduct. Applied Anatomy of the Fallopian Tube . . . 1402 The Uterus or Womb. q'he Mammary Gland. The Fundus of the Uterus 1404 The Nipple 1428 The Body of the Uterus 1404 Variations in Mammte 1429 The Neck or Cervix Uteri 1405 Applied Anatomy 1432 Folds and Ligaments of the Uterus 1406 The Male Breast 1433 The Uterus at Different Ages 1408 Applied Anatomy 1433 Abnormalities of the Uterus 1408- Changes at a Menstrual Period 1408 Changes Induced by Pregnancy 1409 AppUed Anatomy of the Uterus 1411 The Vagina. Relations of the Vagina 1414 The External Organs. The Mods Veneris 1415 The Labia Majora 1415 The Labia Minora or Nymphse 1416 The Vestibule of the Vagina 1416 The Clitoris 1418 The Vaginal Bulb 1420 The Glands of Bartholin 1420 Development of the Urinary and Generative 1420 THE DUCTLESS GLANDS. The Thyhoid Gland oh Body. Accessory Thyroids 1436 Apphed Anatomy 1438 The Parathyroid Gland. Embryology. . . . r?T"^-r.._^.^j^^ 1440 Applied Anatomy ^TT^ : rr^-r^^ 1440 The Thymus Gland. Applied Anatomy 1442 The Spleen. Relations of the Spleen 1444 Surface Form of the Spleen 1446 Applied Anatomy 1447 The Suprabenal Gland ob Adbenal Capsule. Accessory Suprarenal Glands 1448 The Carotid Glands or Carotid Bodies. Applied Anatomy 1450 The Coccygeal Gland ob Body, or Luschka's Gland. Structure of the Coccygeal Gland 1450 The Parasympathetic Bodies. . . 1450 DESCRIPTIVE AND APPLIED ANATOMY. INTRODUCTION. ANATOMY (dva, apart, and re/iwco, I cut) is the name given to that division of natural science which deals with the structure or organization of living things. Human anatomy is that division of general anatomy which applies to the structure of man, bearing in mind the fact that man is distinguished as a sepa- rate genus among primate mammals, an order of vertebrates. Man, as a vertebrate, possesses an internal skeleton with a median longitudinal axis, which is divided transversely into segments called vertebrse. This vertebral axis (spinal column) in the habitually erect position of the human body is sup- ported by the pelvic limbs, and is surmounted by the skull. The pelvic limbs serve the purposes of progression, while the pectoral limbs are adapted as organs of prehension; a distinction common to nearly all primates is the possession of an opposable first digit or thumb. The possession of milk glands, rudimentary in the male, but well developed and important in the female, relegates the human species to the class of mammals. The present work is an account of the various parts and organs of the human body, being descriptive of their characteristics as revealed by dissection, and, with a view toward practical application, certain parts or regions of the body are examined in their entirety. These two methods of studying anatomy are conventionally termed descriptive anatomy and applied or topographic anatomy. Embryology deals with the origin and development of the body and its organs. Histology deals with the minute structure of the tissues and organs as revealed by the microscope. In the present work only brief accounts of the embryology and histology of the organs are interpolated in their proper places; the minute details must be sought for in special works upon these subjects. The systematic consideration of the parts of the human body requires a foreword as to the descriptive terms, nomenclature, and classification employed in anatomy. The descriptive terms are names indicative of position and direction. Despite the structural homologies discernible among vertebrates in general, there are wide differences regarding the natural attitude or position habitually assumed, so that whatever is situated " in front" in the erect man is " below" in the quadrupedal animal. The use of terms like anterior, posterior, superior, inferior, in front of, beneath, has given rise to great ambiguity and confusion whenever applied at one and the same time to homologous parts in man and other vertebrates. It is essential that the names used in designating structural parts shall be so definite that each of the terms shall have but one signification. The study of anatomy has been made unnecessarily difficult by a multiplicity of synonyms and compound names, when single words would answer all requirements. Further- more, many of the terms even now in general use are not equally applicable to lower animals and man, a condition which constitutes a great hindrance to ana- tomic progress. Various reforms have been proposed, chief of which has been that of a commission of the German Anatomic Society, which, in 1895, formulated a list of terms, the Basle Nomina Anatomica (BNA), which is unfortunately 3 (33) 34 DESCRIPTIVE AND APPLIED ANATOMY replete with serious imperfections and inconsistencies. Thus while one of the branches of the radial nerve is called the N. cutaneus brachii posterior, the nominal suffix of two other branches of the same nerve is dorsalis. It cannot be said that the BNA has as yet completely displaced some of the designations in common use to that degree which its enthusiastic advocates would wish. The ambiguous, confusing, and vague terms will gradually fall into disuse as time shows their inutility and better expressions achieve universal adoption. For descriptive purposes the liuman body is supposed to be in the erect position, the arms hanging by the sides and the palms of the hands directed forward. The body, as a whole, as with most vertebrates, consists of two general divisions, axial and appendicular; the former is the body proper (soma), the latter comprises the limbs (membra). The middle plane of the body is called the meson, from the Greek to ftiffou, the middle; while mesal and mesad (ad being the Latin ecjuiva- lent of the English -ward) are adjectival and adverbial inflections. The mesal plane is also the dorsoventral plane which passes approximately through the sagittal suture of the skull, and hence any plane parallel to it is termed a sagittal plane. A vertical plane at right angles to the mesal plane passes, roughly speaking, through the central part of the coronal suture or through a line parallel to it; such a plane is therefore called a coronal plane or frontal plane. A plane at right angles to both the mesal and coronal planes is termed a transverse plane. The terms anterior and posterior have been employed to indicate the relation of parts to the front or back of the body, and the terms superior and inferior to signify the relative levels of different structures; but the growing use of data derived from com- parative anatomy and embryology in the elucidation of the human structure makes it desirable that terms should be employed which may without ambiguity indicate relative position in both man and animals. Thus, ventral and dorsal, cephalic and caudal (together with their adverbial derivatives ending in -ad), are preferable and are thus sometimes used in this edition. Lateral and laterad are general terms per- taining to the sides of the body, while dextral and sinistral are specific terms for right and left respectively. The terms central (centrad) and peripheral (periph- erad) are in general use, though specially applicable to the bloodvessels and the nerve system. The common terms "inner" and "outer," "deep" and "superfi- cial," "beneath," "under," and so on, are too frequently ambiguous. The use of the words ental and ectal, derived respectively from ivzo:; (inward) and iy.ro; (outward), and their inflections entad and ectad often serve to avoid such ambi- guity. Wherever a series of organs embraces several similar parts, bearing like names, the general terms are combined with distinctive prefixes, as, for instance, sitpraspinatus and m/raspinatus. The terms proximal and distal refer to the attached and free ends of the limbs and their parts, being preferable to the less precise and sometimes confusing designations of upper and lower. The other aspects (borders or sides) of each limb are variously designated by the terms ulnar, radial, anconal, and thenar; tibial, fibidar, patellar, and popliteal. It is often convenient to speak of the flexor and extensor aspects of the limb divisions and their bones. The designation of parts in the limbs by anterior and posterior is still largely employed, though the demands of consistency and logic will probably compel the adoption of substitutes more in accord with the nomenclature of com- parative anatomy. The classification which is used in the present work is as follows : Osteology, or description of the bones. Syndesmology, or description of the joints and ligaments. Myology, or description of the muscles and fasciae. Angiology, or description of the heart and the bloodvessels and lymph vessels. Neiirology, or description of the nerve system and organs of special sense. Splanchnology, or description of the viscera, comprising the organs of respira- tion and phonation, digestion, reproduction, excretion, and internal secretion. OSTEOLOGY. GENEEAL ANATOMY OF THE SKELETON. THE general framework of the body is built up mainly of a series of bones, supplemented, however, in certain regions by pieces of cartilage; the bony part of the framework constitutes the skeleton. In comparative anatomy the term skeleton has a wider application, as in some of the lower animals hard, protective, and supporting structures are more exten- sively distributed, being developed in association with the integumentary system. In such animals the skeleton may be described as consisting of an internal or deep skeleton, the endoskeleton, and an external or superficial, the exoskeleton. In the human subject the exoskeleton is extremely rudimentary, its only important representatives being the teeth and nails. The term skeleton is, therefore, confined to the endoskeleton, and this is divisible into an axial part, which includes that of the head and trunk, and an appendicular part, which comprises that of the limbs. In the skeleton of the adult there are 206 distinct bones, as follows: f Vertebral column 26 Axial J Skull 22 Skeleton j Hyoid bone 1 iRil; libs and sternum 25 — 74 Appendicular f Upper limbs 64 Skeleton \ Lower limbs 62 — 126 Auditory ossicles 6 Total 206 The patellae are included in this enumeration, but the smaller sesamoid bones are not reckoned. Bones are divisible, according to their shape, into four classes — long, short, flat, and irrecjular. Long Bones. — The long bones are found in the limbs, where they form a system of levers, which sustain the weight of the trunk and confer the power of locomotion and prehension. A long bone consists of a shaft and two extremities. The shaft, or diaphysis, is a hollow cylinder, the central cavity being termed the medullary canal; the wall consists of dense, compact tissue of considerable thickness in the middle part of the shaft, but becoming thinner toward the extremities; the cancellous tissue is scanty. The extremities, or epiphyses, are generally ex- panded, for the purposes of articulation and to aiTord broad surfaces for muscle attachment. They are usually developed from separate centres of ossification termed epiphyses, and consist of cancellous tissue surrounded by a thin layer of compact bone. The long bones are not straight, but curved, the curve generally taking place in two planes, thus affording greater strength to the bone. The (35) 36 GENERAL ANATOMY OF THE SKELETON bones belonging to this class are the clavicle, humerus, radius, uhia, femur, tibia, fibula, metacarpal and metatarsal bones, and the phalanges. Short Bones. — Where a part of the skeleton is intended for strength and compactness, and its motion is at the same time slight and limited, it is divided into a number of small bones united by ligaments, and the separate bones are short and compressed, such as the bones of the carpus and tarsus. These consist of can- cellous tissue covered by a thin crust of com- pact substance. The patellae also, together with the other sesamoid bones, are by some regarded as short bones. Flat Bones. — Where the principal re- Cjuirement is either extensive protection or the provision of broad surfaces for the at- tachment of muscles, we find the osseous structure expanded into broad, flat plates, as is seen in the bones of the skull and the scapulae. Flat bones are composed of two thin layers of compact tissue enclosing be- tween them a variable quantity of cancellous tissue. In the cranial bones these layers of compact tissue are familiarly known as the tables of the skull; the outer table is thick and tough; the inner table is thinner, denser, and more brittle, and hence is termed the vitreous table. The intervening cancellous tissue is called the diploe. The flat bones are: the occipital, parietal, frontal, nasal, lacri- mal, vomer, scapula, os innominatum, sternum, ribs, and, according to some, the patella. Irregular Bones. — The irregular or mixed liones are such as, from their peculiar form, cannot be grouped under either of the pre- ceding 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 vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, malar, maxilla, mandible, palate, turbinated, and hyoid. Surfaces of Bones. — If the surface of any bone is examined, certain eminences and depressions are seen, to which descrip- tive anatomists have given the following names. These eminences and depressions are of two kinds: articular and nonarticular. 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. Nonarticular 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, line, or crest. Fig. 1, — General of the human skeleton. SURFACES OF BONES 37 The nonarticular depressions are also of very variable form, and are descril)eil as fossae, grooves, furrows, fissures, notches, sulci, etc. These nonarticular emi- nences and depressions serve to increase the extent of surface for the attachment of ligaments and muscles, and are usually well marked in proportion to the muscularity of the subject; the grooves, fissures, and notches often transmit vessels and nerves. FtG. 2. — Diagram of the structure of compact bone. A small part of a transverse section of the shaft of a long bone is shown. At the uppermost part is the periosteum covering the outside of the bone; at the lowermost part is the endosteum lining the marrow cavity. Between these is the compact tissue, consisting largely of a series of Haversian systems, each being circular in outline and perforated by a central canal. In the first one is shown only the area occupied by a system; in the second is seen the concentric arrangement of the lamellae; and in the others, respectively, canaliculi; lacuna?; lacunee and canaliculi; the contents of the canal, artery, vein, lymphatic and areolar tissue; lamellae, lacunse, and canaliculi; and, finally, all of the structures composing a complete system. Between the systems are circumferential and intermediate lamellfe, only a few of which are represented as lodging lacunse, though it is to be understood that the lacunie are in all parts. The periosteum is seen to be made up of a fibrous layer and a vascular layer, and to have upon its attached surface a stratum of cells. From the fibrous layer project inward the rivet-like fibres of Sharpey. (F. H. Gerrish.) 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 anotlnjae:;, 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 i7Tl(}n)acz, an accretion). The main part of the bone, or sliaft, 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. Some bones are hollow and contain sinuses, 38 GENERAL ANATOMY OF THE SKELETON which are spaces for air. Canals, or foramina, are channels or openings in bone through which nerves or vessels pass. Structure of Bone. — Bone is a highly speciaHzed form cf connective tissue. In reality, it is white filjrous tissue, calcified and structurally modified until it becomes osseous tissue. Bone is not simply a crude mass resulting from the calcification of cartilage or fibrous tissue; it is a distinct tissue, of a definite structure, the constituent parts of which are arranged symmetrically. There are two varieties of bone: dense or compact bone {substantia compacta), and can- cellous, loose, or spongy bone (substantia spongiosa). Compact bone is dense, and is always found upon the exterior of the bony tissue. Even this apparently compact tissue is porous; it differs from cancellous bone in its greater densitv and in the arrangement of its osseous substance into lamellae. It forms practically the entire shafts of the long bones and constitutes the outer portion of their extremities and of the short, flat, and irregular bones. With the exception of enamel and dentin it represents the hardest substance of the body, is tough and elastic, and much force is required to break it. Compact bone consists of an outer membrane, the periosteum, internal to which is seen the osseous tissue. The periosteum (Fig. 2) is a fibrous membrane adhering to the surface of the bone in nearly every part except at the cartilage-covered extremities. When strong tendons or ligaments are attached to the bone, the periosteum is incor- porated with them. By means of the periosteum many vessels reach and enter the hard bone through Volkmann's canals. This is shown by stripping the periosteum from the surface of living bone, when small bleeding points are seen, each of which marks the entrance of a vessel from Yia. 3. Fibres of Sharpey from the the periosteum. It thus becomes obvious that the loosen- p.irietal bone (adult man) isolated by Jng of the periosteum, bv depriving a portion of the bone dissociation. (After KoUiker.) r. -. ■ , ^ _. ' j „ ■ t^i, ._ ._u 01 Its nourishment, may produce necrosis, ine membrane is firmly attached to the bone by trabeculfe of fibrous tissue, Sharpey's fibres (Fig. 3), which penetrate the bone at right angles to its surface, and carry bloodvessels. They do not directly enter the Haversian systems, but only the circumferential and intermediate lamellje — parts that are formed by periosteal action. Prolongations from some of these vessels reach the Haversian canals, and even the bone marrow. In the extremities of Fig. 4. — Transverse section of compact tissue of bone. Magnified about 150 diameters. (Sharpey.) a long bone, vessels from the periosteum penetrate the layer of compact bone and reach the cancellous tissue. In the newborn and in the young the periosteum is composed of three layers: an outer or fibrous layer, containing some bloodvessels, and composed of bundles of white fibrous tissue; a middle or flbroelastic layer, containing some bloodvessels, fibrous tissue, and much elastic tissue; and an inner or osteogenetic layer, which is very vascular and contains numerous cells, which are converted into osteoblasts or bone-forming cells. TRANSVERSE SECTION OF COMPACT BONE 39 Transverse Section of Compact Bone (Fio;. 4). — The osseous tissue consists of cells, osteoblasts, and intercellular substance anun^iod in lamellae. In the osseous tissue are found Haversian systems, lacunae, canaliculi, and osteoblasts. In the middle of long bones is a space, the medullary or marrow cavity, containing the marrow. There are four varieties of lamella?: (1) The periosteal, peripheral, circumferential, or external; (2) the Haversian, or concentric; (3) the interstitial, ground, or intermediate; and (4) the perimeduUary, or internal. The ]5eriosteal lamellfe are sometimes called primary, as they are the first to appear, and are formed by the direct transformation of the inner layer of the periosteum into bone. In the shaft of a long bone there are several layers of periosteal lamellfe, but no one layer is extensive enough to surround the bone completely. Lacunje and canaliculi are present. _ _ In the outer surface of the layer of periosteal lamellaj depressions exist that are known as Howship's foveolae, or lacunae. These depressions a,re made by large cells, called osteoclasts, which destroy bone. There are no Haversian canals in this outer layer, but there are some larce channels, Volkmann's canals, that convey bloodvessels into the bone and run at right angles to the periosteal surface. Many small arteries from the periosteum enter the periphery bodi of the shaft and of the epiphyses. The Haversian or concentric lamellae are circular layers arranged around a central space, or canal, known as the Haversian canal. There is no fixed number of these layers, there being usually from five to ten. The layers of each system are parallel to one another. Fig. 5. — Nucleated bone cells (osteoblasts) and their processes, contained in the bone lacuna and their canaliculi respectively. From a section through the vertebra of an adult mouse. (Klein and Noble Smith.) Fig. 6. — Combined transverse and longitudinal section of compact bone. CH. Longitudinal Haversian canal and anastomosing canals, o. Communicating with medullary cavity. Si. Intermediate systems. Spe. Circumferential lamella?. Spi. PerimeduUary lamelte. os. Osteoblasts. (Poirier and Charpy.) but the layers of different systems cross at va rious angles. Between these layers are small, irreg- ular spaces called lacunae; and extending radially nut from the lacunte and piercing the various lamellas are delicate canals known as canaliculi, which connect the lacuna?. The lacuna nearest to the Haversian canal communicates with it by means of canaliculi; and canaliculi also com- municate with other Haversian systems. The Haversian canal contains bloodvessels— an artery or a vein, or both — and a nerve. The vessel in the canal is covered with endothelial cells, and the canal itself is lined with them. The space thus formed is a lymph channel, and into these chan- nels the canahculi empty. Beneath the periosteum and at the periphery of the medullary cavity there are lymph spaces that are in direct communication with the canaliculi of the Haversian systems. In each lacuna is a bone cell — a corpuscle that almost fills the space, and sends arms, or processes, out into the canaliculi (Fig. .5). This bone cell is an osteoblast. The interstitial or intermediate lamellae occupy the spaces between the Haversian systems. They represent the remains cf p. riiihcral lamell*. ' They are usually short and very irregular, but possess lacunae and canaliculi, which are arranged as in the Haversian systems. The perimeduUary lamellae are irregular and few in number. They surround the marrow cavity, and in areas mav be interrupted. Lacunse, canaliculi, and osteoblasts are present. Lining the marrow cavity surface of the bone is a membrane, the endosteum, that resembles the periosteum in structure, but is not cjuite so prominent. The osteoblasts are irregular, flattened, stellate masses of protoplasm, possessing a number of processes. The protoplasm is granular, and each cell contains a large and distinct nucleus. 40 GENERAL ANATOMY OF THE SKELETON Osteoblasts are met with in the deeper layer of the periosteum, in the endosteum, and in the lacunae. Longitudinal Section of Compact Bone (Figs. 6 and 8). — We do not see concentric rings, as in a transverse section, but rows of lacuna; parallel to the course of the Haversian canals — and these canals appear like half tubes instead of circular spaces. The tubes are seen to branch and communicate, so that each separate Haversian canal runs only a short distance. In other respects the structure closely resembles that of a transverse section. Cancellous bone is found in the interior of flat and irregular bones and forming the bulk of the extremities of the long bones. It consists of anastomosing spicules of bone forming a meshwork for the red marrow. The spicules have a fibrillar structure, and contain lacunae and canaliculi, but no Haversian systems. In the epiphyses the spicules are placed, as a rule, at right angles to the planes of the articular surface (the lines of greatest pressure) ; these are bound together by other spicules that correspond in direction to the planes of the articulation (the lines of greatest tension). Those spicules nearer the marrow cavity are usually heavier and stronger (Fig. 181). -Cells of red marrow of the gu i-t. Erythroblasts Marrow. — There are three varieties: red, yellow, and mucoid. Red marrow {medulla ossium rubra) is found in the diploe of the cranial bones, in the cancellous tissue of the vertebrse, ribs, and sternum, and in the extremities of the long bones. Red marrow contains much less fat and is less solid than yellow marrow. It consists of a delicate net- work of retiform connective tissue, supporting a dense capillary plexus; some fat; and numer- ous cellular elements. Surrounding the marrow is the endosteum. The cellular elements of red marrow (Figs. 7 and 12) comprise four main groups: (1) Marrow cells, or myelocytes, which are granular protoplasmic masses, capable of ameboid movements, and containing large nuclei. They are not found in normal blood, but are abundant in leukemia. (2) Small nucleated, reddish cells called erythroblasts are found; they resemble the nucleated red cells of the blood of the embryo; eventually by the loss of their nuclei they become normal red blood corpuscles. (3) Nonnucleated red blood corpuscles; and (4) giant cells, containing one or more nuclei — the osteoclasts — complete the cellular elements. In addition there are a large number of leukocytes, or white blood cells, i. e., polynuclear cells, eosinophiles, and basophiles. Yellow marrow is found in the shafts of long bones of adults, and differs from the preceding in the presence of a great quantity of fat and a corresponding decrease in the number of cellular elements. Gelatinous or mucoid marrow is formed by the absorption of the fat and the cellular elements of yellow marrow, and by the serous infiltration of the intercellular substance. It is produced by starvation, old age, and certain pathological conditions. Neither yellow nor mucciid marrow are blood-cell forming in function. Bloodvessels of Bone. — Small arteries derived from the periosteum enter Volkmann's canals and pass to the Haversian canals and ultimately to the marrow. The cancellous tissue is sup- plied by fewer but larger vessels, which are derived from the periosteum, and which often pene- trate the covering of the compact bone and ramify in the cavities of the spongy tissue. The marrow is supplied by a large artery (sometimes more than one) called the nutrient artery. It enters the bone by the nutrient foramen, which is usually near the centre of the shaft, runs in an oblique canal through the compact substance, giving off branches to this CHEMICAL COMPOSITION OF BONE 41 structure, and entering the medullary cavity, sends branches toward the extremities, thus forming capillary plexuses in the marrow. These branches communicate with branches from the periosteal vessels The walls of the \essels are ^erv thin, the venous blood enters the spaces of the led marrow and the current becomes extremely slow. Small \eins collect the venous blood and emii^c tiom the bone _. _ „iuuii lluiifeitudmal seLtioii thiouth tliL diapln Is ut tliL hu with pigment which la here black Ha\ ersian canalb aie cut longitudin \Uj \11 ctnals are filled 90 (tozymonowicz ) Veins emerge from the long bones in three places: (1) One or two large veins accompany the nutrient artery. (2) Numerous veins emerge at the articular extremities. (3) Many small veins arise in and emerge from compact substance. The latter two classes do not accompany arteries. The veins in the marrow and in the bone are devoid of valves; but immediately after emerging from the bone they have numerous valves. In the flat cranial bones the veins are numerous and large. The lymphatics are chiefly periosteal; but some have been demonstrated as entering the bone, nlong with the vessels, and running in the Haversian canals. Nerves, meduUated {myelinic) and nonmeduUated (amyelinic) , are found in bone. They are distributed freely to the periosteum, and some of the fibres terminate in this structure as Pacinian corpuscles. Nerves accompany the nutrient arteries into the interior of the bone, and also reach the marrow from the periosteum by w^ay of Volkmann's canals and the Haversian canals. They certainly supply the arterial coats and possibly ramify about the osteoblasts. Nerves are most numerous in the articular extremities of the long bones, in the vertebrae, and the large flat bones. Chemical Composition of Bone. — Bone consists of about 36 per cent, of animal {organic) and about 64 per cent, of earthy {inorganic) substance intimately combined. The animal part may be obtained by immersing the bone for a considerable time in dilute mineral acid, after which process the bone comes out exactly the same shape as before, but per- fectly flexible, so that a long bone (one of the ribs, for example) can easily be tied into a knot, if now a transverse section is made, the same general arrangement of the Ha\'ersian canals, 42 GENERAL ANATOMY OF THE SKELETON lamelliE. lacunte, and canaliculi is seen, though not so plainly as in the ordinary section. The animal basis is lararely composed of ossein, or fat collagen. When boiled with water, especially under pressure, fat collagen is almost entirely resolved into gelatin. The earthy part may be obtained by calcination, in which process the animal matter is com- pletely burned out. The bone will still retain its original form, but it will be white and brittle, will have lost about one-third of its original weight, and will crumble upon the slightest pressure. The earthy matter confers on bone its hardness and rigidity, and the animal matter its tenacity. The mineral matter consists chiefly of calcium phosphate, forming about two-thirds of the weight of bone. Ossification and Growth of Bone. — For the early development of the skeleton the reader is referred to text-books on embryology. Embryonic connective-tissue cells of the meso- blast develop membrane. Membrane may become bone directly or cartilage may be deposited, which cartilage by the process of ossification is changed into bone. The tissue which is eventually to become bone contains cellular elements which evolve into osteo- blasts, or bone-forming cells. Osteoblasts exist in the connective tissues which become bone by intramem- branous ossification, and in the deeper layers of the tissue called perichondrium which invests cartilage and which becomes the osteogenetic layer of the peri- osteum. In view of the fact that in the fetal skeleton some bones are preceded by membrane (parietal bones, frontal bone, upper part of tabular portion of occipital bone, most of the bones of the face), and others are pre- ceded by rods of cartilage (the long bones), two kinds of ossification are described — viz., the intramembra- nous and the intracartilaginous. Intramembranous Ossification. — In the case of bones which are developed in membrane no cartilagi- nous mould precedes the appearance of the bone tissue. The membrane, which occupies the place of the future bone, consists of white, fibrous connective tissue, and ultimately forms the periosteum. At this stage it is seen to be composed of fibres and granular cells in a matrix. The outer portion is more fibrous, while internally the cells or osteoblasts predominate; the whole tissue is quite vascular. At the outset of the process of bone formation a little network of bony spicules is first noticed radiating from the point or centre of ossification. When these rays of Fig. 9. — Schematic diagram, showing epi- physis and diaphysis and line of ossification, Ev. Epiphysis of endochondral bone. zpt. Zone of proliferation. 7C. Zone of calcifica- tion, ca. Cartilage. (Poirier and Charpy.) Union q adjacent Fig. 10, — Part of the grow V Bony ^^^iT^ " spicules. ng edge of the developing parietal bone of a fetal cat, (After J. Lawr growing bone are examined with a microscope they are found to consist at their growing point of a network of fine, clear fibres and granular corpuscles, with an intervening ground substance (Pig. 10). The fibres are termed osteogenetic fibres, and are made up of fine fibrils differing INTJRAMEMBBANO US OSSIFXCA TION 43 little from from those of white fibrous tissue. Like them, they are probably deposited in the matrix through the influence of the cells — in this case the osteoblasts. The osteogenetic fibres soon assume a dark and granular appearance from the deposition of calcareous granules in the fibres and in the intervening matrix, and as they calcify they are found to enclose some of the granular C'o^ Fig. 11. — Longitudinal section tlirnuch tlie second phalanx of tlie fincer of a seven months' human embryo. Stained in hematoxylin and eosin. X 104. A. Periosteum. B. Primary areola. C. Periosteal bone. D. Sec- ondary areola and marrow. E, Calcareous material. F^ Endochondral bone. (Szymonowicz.) corpuscles, or osteoblasts. By the fusion of the calcareous granules the bony tissue again assumes a more transparent appearance, but the fibres are no longer so distinctly seen. The involved osteoblasts form the corpu.scles of the future bone, the spaces in which they are enclosed con- stituting the lacuniE. As the osteogenetic fibres grow out to the periphery they continue to ossify and give rise to fresh bone spicules. Thus, a network of bone is formed, the meshes of Fig. 12. — Section through the red bone B. Eosinophiles. C. Nucleated red blood __ a rabbit. Biondi's stain. X 640. .4. Jlyelocytes. puscles. D. Giant cells. E. Myelocyte. (Szymonowicz.) which contain the bloodvessels and a delicate connective tissue crowded with osteoblasts. The bony trabecule thicken by the addition of fresh layers of bone formed by the osteoblasts on their surface, and the meshes are correspondingly encroached upon. Subsequently successive layers of bony tissue are deposited under the periosteum and around the larger vascular channels. 44 GENERAL ANATOMY OF THE SKELETON which become the Haversian canals, so that the bone increases much in thickness. The process spreads laterally to the region of the future suture, and here between the various bones a layer of fibrous tissue, the cambium layer, is maintained until the full size of the bone is reached. The cambium layer then ossifies and the bone ceases to grow at its edges. Intracartilaginous Ossification. — .Just before ossification begins the bone is entirely carti- laginous, and in the long bone, which may be taken as an example, the process commences in the centre and proceeds toward the extremities, which for some time remain cartilaginous. Subsequently a similar process commences in one or more places in those extremities and gradually ossifies them. The extremities do not, however, become joined to the shaft by bony tissue until growth has ceased, but are attached to it by a layer of cartilaginous tissue termed the epiphyseal cartilage. The first step {proliferation) in the ossification of the cartilage is that the cartilage cells, at the point where ossification is commencing and which is termed a centre of ossification, multiply, enlarge, and arrange themselves in rows (Fig. 11). The matrix in which they are embedded ■>^^ \-^ / Fig. 13. — Cross-section of a developing bone of a human fetus of four montlis, a. Periosteum, h. Boundary between endochondral and periosteal bone. c. Perichondral bone. d. Remains of area of e&lcification. c. Endochondral bone, f, f. Bloodvessels, g. g'. Developing Haversian spaces. A. Marrow, i. Bloodvessel. (Radasch, after Stohr's Histology.) increases in quantity, so that the cells become further separated from each other. A deposit of calcareous material (calcification) now takes place in this matrix, between the rows of cells, so that they become separated from each other by longitudinal coliunns of calcified matrix. These columns are connected to one another by transverse bars of calcareous substance, and present a granular and opaque appearance. In the calcareous areas the cartilage cells repro- duce so rapidly that a number of cells are seen in each large lacuna, or space, which is called a primary areola. This process is succeeded by destruction of some of the columns between the smaller spaces, forming thus a fewer number of larger spaces, the secondary areolae. Some of the cells within the areolse disappear, others become osteoblasts, which appty themselves to the columns and secrete a thin veneer of osseous tissue upon the calcareous matter; still others of these cells become osteoclasts. At the same time that this process is going on in the centre of the solid bar of cartilage of which the fetal bone consists, certain changes are taking place on its surface. This is covered by a very vascular membrane, the perichondrium, entirely similar to the embryonic connective tissue already described as constituting the basis of membrane bone, on the inner or cartilage INTRA CA R TIL A GINO US OSSIFICA TION 45 siirface of which the cells become osteoblasts, or bone-forming cells. By the agency of these cells a thin layer of bony tissue is being formed between the outer membrane, now the periosteum, and the cartilage by the intramembraiious mode of ossification just described; this constiiuics the first periosteal lamella. These two processes go on simultaneously. The second stan-e i vascularization) consists in the prolongation into the cartilage of processes of the deeper or osteogenetic layer of the periosteum, these processes consisting of bloodvessels and cells — osteoblasts, or bone formers, and osteoclasts, or bone destroyers. The latter are similar to the giant cells (myeloplaques) found in marrow, and they excavate passages through the new- formed bony layer by absorption, and ]3ass through it into the areolae. Wherever these processes come in contact with the calcified walls of the primary areolse they absorb it, and thus cau.se a fusion of the original cavities and assist in the formation of larger spaces, which are termed the secondary areolae (Sharpey), or medullary spaces. These secondary spaces become filled with enibryoni:' marrow, consisting of ostenlilasts, vessels, a few leukocytes, and a few myelocytes. Tiie first periosteal lamella is rapiiily followed by the formation of others of the same nature, the osteoblasts secreting the lamellre remaining between the successive layers with their pro- cesses passing from one to the other. The spaces occupied by these cells are the lacunae and the small channels occupied by the processes are the canaliculi. A periosteal lamella is not smooth and regular and does not extend completely around the developing bone, but meets others that aid in completing the circle. The irregularities are due to projecting processes of bone that meet others and enclose small, irregu- lar, longitudinal canals, which contain vessels and primitive marrow, and are the primitive Haversian canals. These are also seen at the junctions of the lamellae (Fig. 13). The osteo- clasts of the primitive marrow apply themselves to the walls of the canals and absorb the osseous tissue until a comparatively large and regular canal is formed, and within this canal the osteoblasts secrete successive concentric layers of bone until a small central canal alone remains which contains a little marrow and the vessels. This canal is the true Haversian canal. The concentric lamelke are the Haversian lamellae, between which the osteoblasts remain in their lacunae and radiating can- aliculi. The remains of the peri- osteal lamellae between the Haversian systems constitute the interstitial lamellae (Fig. 6). Within the centre of the rod of devebping bone the osteoclasts meanwhile destroy the trabeculae of calcific material covered by osseous tissue, and thus is formed one common cavity — the beyinning of ilie medullar!/ cavity. The marrow then forms one common mass in the centre of the bone, and the surrounding fibrous tissue becomes a second periosteum, or endosteum, which sur- rounds the marrow and secretes incomplete lamellae, thus bounding the marrow cavity as the perimedullary lamellae. All of the above osseous tissue is merely temporary in the growth of the bone thickness. As can now be readily seen, the long bones increase evenly in thickness by the periosteal method, while increase in length is due entirely to the intracartilaginous method. .Such are the changes which may be observed at one particular point, the centre of ossification. While they have been going on here a similar process has been set up in the surrounding parts and has been gradually proceeding toward the ends of the shaft, so that in the ossifying bone all the changes described above may be seen in different parts, from the true bone in the centre of the shaft to the hyaline cartilage at the extremities. The bone thus formed differs from the bone of the adult in being more spongy and less regularly lamellated. As more and more bone is removed by this process of absorption from the interior of the bone to form the medullary canal, so more and more bone is deposited on the e.xterior by the peri- osteum, until at length the bone has attained the shape and size which it is destined to retain during adult hfe. As the ossification of the cartilaginous shaft extends toward the articular ends it carries with it, as it were, a layer of cartilage, or the cartilage grows as it ossifies, and thus the bone is increased in length. During this period of growth the articular end, or cpiphyxis, remains for some time entirelv cartilaginous; then a bony centre appears in it, and it undergoes the same process of intracartilaginous ossification; the cancellous bone of the extremities of the processes of the bones is never completely removed to form a single marrow cavity, but the Fig. 14. — Osteoblasts from the parietal bone of a human eflfcryo thirteen weeks old. a. Bony septa with the cells of the lacunae. h. Layers of osteoblasts, c. The latter in transition to bone cor- puscles. (-\fter Gegenbaur.) 46 GENERAL ANATOMY OF THE SKELETON spaces become somewhat enlarged as the bones grow. The epiphyses remain separated from the shaft by a narrow cartilaginous {cambium) layer for a definite time (Fig. 9). This layer ulti- mately ossifies, the distinction between shaft and epiphysis is obliterated, and the bone assumes its completed form and shape. The same remarks also apply to the processes of bone which are separately ossified, such as the trochanters of the femur. The bones, having been formed, con- tinue to grow until the body has acquired its full stature. The number of ossific centres varies in different bones. In most of the short bones ossification commences at a single point in the centre, and proceeds toward the circumference. In the long bones there is a central point of ossification for the shaft or diaphysis; and one or more for each extremity, the epiphysis. That for the shaft is the first to appear. The union of the epiphyses with the shaft takes place in the reverse order to that in which their ossification began, with the exception of the fibula, and appears to be regulated by the direction of the nutrient artery of the bone. Thus, the nutrient arteries of the bones of the arm and forearm are directed toward the elbow, and the epiphyses of the bones forming this joint become united to the shaft before those at the shoulder and wrist. In the lower limb, on the other hand, the nutrient arteries pass in a direction from the knee; that is, upward in the femur, downward in the tibia and fibula; and in them it is observed that the upper epiphysis of the femur and the lower epiphysis of the tibia and fibula become first united to the shaft. Where there is only one epiphysis, the nutrient arter}' is directed toward that end of the bone where there is no additional centre, as toward the acromial end of the clavicle, toward the distal end of the metacarpal bone of the thumb and great toe, and toward the proximal end of the other metacarpal and metatarsal bones. Besides these epiphyses for the articular ends, there are others for projecting parts or processes, which are formed separately from the bulk of the bone. For an account of these the reader is referred to the description of the individual bones in the sequel. A knowledge of the exact periods when the epiphyses become joined to the shaft is often of great importance in medicolegal inquiries. It also aids the surgeon in the diagnosis of many of the injuries to which the joints are liable; for it not infrequently happens that on the application of severe force to a joint the epiphysis becomes separated from the shaft, and such an injur}' may be mistaken for a fracture or dislocation. Applied Anatomy. — It has been stated above that the bones increase first in length by ossi- fication continuing to extend in the epiphyseal cartilage, which goes on growing in advance of the ossifying process; and secondly in circumference by deposition of new bone from the deeper layer of the periosteum. A thorough realization of these facts is essential to the student, when he comes to consider the various pathological changes which affect bone. Anything which inter- feres with the growth at the epiphyseal line will lead to a diminution in the length which the bone should attain in adult life, and similarly anything which interferes with the growth from the deeper layer of the periosteum will result in a disproportion in the thickness of the bone. Thus, separation of the epiphyses, septic or tuberculous disease about the epiphyseal line, and excisions involving the epiphyseal line, will result in varying amounts of shortening of the bone, as com- pared with that of the opposite side; whereas separation or imperfect nutrition of the periosteum results in defective growth in circumference. It is thus obvious that a careful study of osseous development is of the very greatest utility in the proper understanding of bone disease; and, moreover, that an accurate knowledge of the blood supply of a long bone has many important bearings. The outer portion of the compact tissue being supplied by periosteal vessels, which reach the bone through muscle attachments, it follows that where the muscles or muscle attachments are well developed, and therefore amply supplied with blood, the periosteum will ako be well nourished and the bones proportionately well developed in girth; this is well seen L. strong, muscular men with well-marked ridges on the bones. Conversely, if the muscle development be poor, the bones are correspondingly thin and light, and if from any cause a limb has been paralyzed from early childhood, all of the bones of that extremity are remarkable for their extreme thinness — that is to say, the periosteal blood supply has been insufficient to nourish that membrane, and consequently very little new osseous tissue has been added to the bones from the outside. The best example of this condition is seen in connection with the disease known £(s infantile paralysis, where a limb becomes paralyzed at a very early period of childhood, where the muscles become flaccid and atonic, and where the blood supph' is in consequence very greatly diminished. In such cases, although the limb does continue to grow in length from the epiphyseal lines, its length is considerably less than on the normal side, as a result of the imperfect nutrition; but the most striking feature about all the long bones of the limb is their remarkable tenuity, little or no addition having been made to their diameters. In cases where the periosteum has been separated from the compact tissue by extensive injury or inflammatory exudation, necrosis or death of the underlying portion of bone takes place, due to interference with the blood supply, and the dead portion or sequestrum has to be subsequently separated and cast off. Cases, however, occur in which the inflammatory process affects the whole oi a great portion APPLIED ANATOMY 47 of the diaphysis of a long bone, and here extensive necrosis of the affected portion takes place, and the condition goes by the name of acute infective periostitis. Where this occurs the shaft of the bone dies very rapidly, especially if the singly nutrient artery be thrombosed at the same time. The pus which has formed beneath the periosteum is set free by timely excision, or burrows to the surface; the periosteum then falls back on the necrosed diaphysis and rapidly forms a layer of new periosteal bone, surrounding the sequestrum. This layer is called the involiicrum, and the openings in it through which the pus escapes the cloacw. When the inflammatory process affects mainly the medullary canal, the condition is spoken of as osteomyelitis, and the two conditions very frequently co-exist, and then go by the name of acute infective necrosis of hone or acute diaphysitis. When the medullary cavity is filled with pus, septic thrombosis of the veins in the Haversian canals takes place, and there is a very great danger of septic emboli being separated and carried into the general circulation, thus setting up a fatal pyemia. In fact, pyemia is more frequently due to septic bone conditions than to any other cause. In the preantiseptic days pyemia frequently resulted from amputations, when the medullary canal of a long bone was opened by the saw cut. Osteomyelitis ensued, and if the patient sur- vived, a tubular sequestrum of the divided shaft subsequently separated. A proper understanding of the epiphyses is of the utmost possible importance to the student, and greatly simplifies many of the problems in the pathology of bone disease. Speaking generally, the long bones have at either end an epiphysis from the cartilage of which growth occurs, and hence the shaft of the bone increases in length at both ends. In every case, however, one epiphysis is the more active, and also continues in its activity for a longer time. This actively growing epiphysis is always the one from which the nutrient foramen in the diaphy- sis is directed, and it unites to the shaft at a later date. It follows, therefore, that the increase in length of a long bolie is largely dependent on the epiphysis, and hence anything which inter- feres with the growth from this epiphyseal line at any time prior to the union of the epiphysis with the shaft must result in a cessation of growth in length of that bone. Thus, when dealing with disease in the neighborhood of this actively growing epiphysis very great care should be taken not to excise or destroy its line of union with the shaft. These epiphyses are particularly prone to become the seat of tuberculous disease, which especially tends to attack the soft, highly vascular cancellous tissue. Again, the actively growing epiphyseal line is the portion of a long bone which is in the vast majority of cases affected by tumor growth in bone, whether it be innocent or malignant, the former (viz., osteoma) usually appearing about puberty, and the latter (viz., sarcoma) usually toward the end of the active period of epiphyseal growth. Epiphyseal growth, moreover, has to be considered by the surgeon when he is about to ampu- tate in a child. If tlie amputation is being performed through a bone, the actively growing epiphysis of which is at the upper end, and which will continue to grow for many years (i. e., humerus and tibia), it will be necessary to make allowance for this and to cut the flaps long; as otherwise, owing to continued growth, the sawed end of the bone will ultimately project through the stump, and a condition known as "conical stump" will result. This requires removal of a further portion of the bone. An inflammatory condition termed acute epiphysitis also occurs, although it is not so frequent as the acute infective conditions of the diaphysis, owing to the freer blood supply of the epiphysis; in late years it has been shown that acute epiphysitis in children is very frequently the result of a pneumococcal infection, and it may pass on to complete separation of the epiphysis. In this connection it is worthy of note that some of the epiphyseal lines lie entirely within the capsules of their corresijonding joints, in other cases entirely without the capsules; and it must follow that in the former case epiphyseal disease, acute or chronic, becomes, ipso facto, practically synonymous with disease of that joint. The best examples of intracapsular epiphyses are those of the head of the femur and the head of the humerus, and the vast majority of all cases of tuberculous disease of the hip starts as a tuberculous epiphysitis about the intracapsular epiphyseal line of the femur; again, cases of acute septic arthritis of the shoulder- or hip-joint generally have their origins in these intracapsular epiphyseal lines, and often result in separa- tion of the affected epiphysis. The other class, or extracapsular epiphysitis, when diseased, do not tend to involve the neighboring joint so readily; and it should be the surgeon's duty to keep the disease from involving the joint. For example, the trochanteric epiphysis of the femur is extracapsular as regards the hip-joint, and the epiphyseal line of the head of the tibia is well below the level of the knee-joint, and should a chronic tuberculous abscess form in the latter situation, it should be attacked from the outside before it has time to spread up and involve the cartilage of the head of the tibia. It is, therefore, of great surgical interest to note in every case the relations which the various epiphyseal lines bear to their respective joint capsules. 48 SPECIAL ANATOMY OF THE SKELETON SPECIAL ANATOMY OF THE SKELETON. THE VERTEBRAL OR SPINAL COLUMN, OR THE SPINE (COLUMNA VERTEBRALIS). The vertebral column is a flexuous and flexible column formed of a series of bones called vertebrae. The vertebrse are thirty-three in number, and have received the names cervical, thoracic, lumbar, sacral, and coccygeal, according to the position which they occupy; seven are found in the cervical region, twelve in the thoracic, five in the lumbar, five in the sacral, and foui- in the coccygeaTf" 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 vertebral column, as the number of bones forming it is rarely increased or diminished. The vertebrse in the upper three regions of the spine remain separate through- out life, and are known as true or movable vertebra; but those found in the sacral and coccygeal regions are firmly united in the adult, 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 cocc3rx. The fused vertebra are known as false or immovable vertebrae. With the exception of the first and second cervical, the true or movable verte- brae present certain common characteristics which are best studied by examining one from the middle of the thoracic region. GENERAL CHARACTERS OF A VERTEBRA. A typic vertebra consists of two essential parts — an anterior solid segment, the body, and a posterior segment, the arch (arcus vertebrae), or the neural arch. The arch is formed of two pedicles &ad two laminae, supporting seven processes — viz., four articular, two transverse, and one spinous. The bodies of the vertebrse are placed one upon the other, forming a strong pillar for the support of the skull and trunk; the arches forming a hollow cylinder behind the bodies for the protection of the spinal cord. The different vertebrae are connected by means of the articular processes and the intervertebral fibrocartilages; while the transverse and spinous processes serve as levers for the attachment of muscles which move the different parts of the vertebral column. Lastly, between each pair of vertebrte apertures (foramina intervertehralia) exist through which the spinal nerves pass. The Body (corpus vertebrae) is the largest part of a vertebra. Its tipper and lower surfaces are flattened and rough for the attachment of the intervertebral fibrocartilages, and each presents a rim around its 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 anterior surface is perforated by a few small apertures, for the passage of nutrient vessels; while on the posterior surface is a single large, irregular aperture, or occasionally more than one, for the exit of veins, the venae basis vertebrae, from the body of the vertebra. Pedicles (radix arcus vertebrae). — The pedicles are two short, thick pieces of bone, which project backward, one on each side, from the upper part of the THE CERVICAL VERTEBRA 49 body of the vertebra, at the line of junction of its posterior and lateral surfaces and form the root of the vertebral arch. The concavities above and below the pedicles are the superior and inferior intervertebral notches [iucisura vertebralis superior et inferior); they are four in number, two on each side, the inferior onps being generalTj^Jhe-deeper. When the vertebrae are articulated the notches of each contiguous pair of bones form the intervertebral foramina (foramina inter- vertebralia), which communicate with the vertebral canal and transmit the spinal nerves and bloodvessels. Laminae. — ^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 or vertebral foramen {foramen vertehrale), which serves for the protection of the spinal cord. AVhen the vertebrte are joined they form, with their ligaments, the vertebral canal (canalis vertebralis). The laminae are connected to the body by means of the pedicles. Their upper and lower borders are rough, for the attachment of the ligamenta subfiava. Processes. Spinous Process (processus spinosvs). — The spinous process is a rather long, three-sided mass of bone which projects backward from the junction of the two laminae and may terminate in a tubercle, and serves for the attachment of muscles and ligaments. Articular Processes. — The articular processes (zygapophyses), four in number, two on each side, spring from the junction of the pedicles with the laminae. Each superior process (processus articularis superior) projects upward, its articular sur- face (fades articularis superior) being directed more or less backward; each inferior process (processus articularis inferior) projects downward, its articular surface (fades articularis inferior) looking more_i>z_l£ss-4©Fward.' Transverse Processes (processus transversa) . — 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 serve for the attachment of muscles and ligaments. The Cervical Vertebrae (Vertebrae Cervicales) (Fig. 15). The cervical vertebrte are smaller than those in any other region of the spine, and may be readily distinguished by the foramen in the transverse process, which does not exist in the transverse process of either a thoracic or lumbar vertebra. Body. — 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 projecting 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. Pedicles. — 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. Laminae. — The laminae are narrow, long, thinner above than below, and overlap each other,. enclosing the vertebral foramen, which is very large, and of a triangular form. Processes. Spinous Process. — The spinous process is short, and bifid at the extremity, to afi'ord greater extent of surface for the attachment of muscles, the ' It may, perhaps, be as well to remind the reader that the direction of a surface is determined by that of l line drawn at right angles to it. 50 SPECIAL ANATOMY OF THE SKELETON two divisions being often of unequal size. They increase in length from the fourth to the seventh vertebra. Articular Processes. — ^The articular processes are flat, oblique, and of an oval form ; the -superior are directed backward and upward, the inferior forward and downward. Transverse Processes. — ^The transverse processes are short, directed down- ward, outward, and forward, bifid at their extremity, and marked by a groove along the upper surface, which runs downward and outward from the superior intervertebral notch and serves for the transmission of one of the cervical 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 bases by a foramen, for the transmission of the vertebral artery, vein, and a plexus of sympathetic nerves. This foramen is known as the transverse foramen, the costotransverse foramen, and the vertebrarterial foramen (J'oramen iransversarium). Each process is formed by two roots — the anterior root, sometimes called the costal process, arising from the side of the body, and the homologue.of the rib in the thoracic region of the column ; the posterior root springs from the junction of the pedicle with the lamina, and corresponds to the transverse process in the thoracic region. Antenor tubercle of t) ajis- verse pi oces!> Costotransverse foramen for vertebral artery and vein and' sympathetic plexu Posterior tubercle of transverse process Costal process Ti anil eise process. 1 ^-^npei lor articular pi ocess. Infeiior articular pro Fig. 15. — Ce^^'ical vertebra. It is by the junction of the two that the foramen for the vertebral vessels is formed. The extremity of each of these roots form the anterior and posterior tubercles of the transverse processes. The peculiar vertebrae in the cervical regions are the first, or atlas; the second, or axis; and the seventh, or vertebra promlnens. The great modifications in the form of the atlas and axis are designed to admit of the nodding and rotatory movements of the head. Atlas. — ^The atlas (Fig. 16) is so named because it supports 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 (arcus anterior) forms about one-fifth of the ring; its anterior surface is convex, and presents about its centre a tubercle (tuberculum anterius) , for the attachment of the Longus colli muscle; posteriorly it is concave, and marked by a smooth, oval facet {fovea dentis), covered with cartilage, 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 CERVICAL VERTEBRAE 51 the occipital bone above and the axis below. The posterior arch {arcuH posterior) forms about two-fifths of the circumference of the bone; it terminates behind in a tubercle (iuberculum postenvs) , which is the rudiment of a spinous process, and gives origin to the Rectus capitis px^.st.ini.s minor. The diminutive size of this process prevents any interference in the movements between the atlas and the cranium. The posterior part of the arch presents above and behind a rounded edge for the attachment of the posterior occipitoatlantal ligament, while in front immediately behind each superior articular process, is a groove {sidcvs arteriae ■vertebralis) (Fig. 16), sometimes converted into a foramen by a delicate bony spiculum, which arches backward from the posterior extremity of the superior articular process. These grooves represent the superior intervertebral notches, and are peculiar in that they are situated behind the articular processes, instead of in front of them, as in the other vertebra;. They serve for the transmission of the vertebral artery, which, ascending through the foramen in the transverse process, winds around the lateral mass in a backward and inward direction. They also transmit the suboccipital (first spinal) nerve. On the under surface of the posterior arch, in the same situation, are two other grooves, placed behind the lateral, masses, and representing the inferior intervertebral notches of other vertebrae. They are much less marked than the superior. The lower border *" Dtaqram of section of odontoid, pt oce^s Diaqi am of section of t)ansieise hgamenL Foramen for vertebral artery. Groove for vertebral artery and 1st cermcal nerve. Endhnentary spinous process. Fig. 16. — First cervical vertebra, i\,_J,^\ CoJ^^'"^ j^aWti'-"-^ Vv^C^ftv also gives attachment to the posterior atlanto-axial ligament, which connects it with the axis. The lateral masses {massae laterales) are the most bulky and solid parts of the atlas, in order to support the weight of the head; they present two articulating surfaces above and two below. Each represents one-fifth of the ring. The superior articular surface {fovea articularis superior) of each is of large size, oval, concave, and approaches its companion in front, but diverges from it behind ; it is directed upward, inward, and a little backward, forming a kind of cup for the corresponding condyle of the occipital bone. The two processes are admirably adapted to the nodding movements of the head. Not infrequently they are par- tially subdivided by a more or less deep indentation, which encroaches upon each lateral margin. Each inferior articular process (fades articularis inferior) is circular in form, flattened or slightly concave, and directed downward and inward, articulating with the axis. The inferior processes permit 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 or arches; the anterior or smaller segment receiving the odontoid process of the axis, the posterior allowing the transmission of the spinal cord and its membranes. This part of the vertebral canal is of considerable size, to aft'ord space for the spinal cord; and hence lateral 52 SPECIAL ANATOMY OF THE SKELETON 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 perforated at their bases by a canal for the vertebral artery, which is directed from below, upward, and backward. Axis. — The axis (epistropheus) (Fig. 17) is the pivot upon which the first vertebra, carrying the head, rotates. The most distinctive character of this bone is the strong, prominent process, tooth-like in form, which rises perpendicularly from the upper surface of the body. The body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and fore part of the next vertebra. It presents in front a median longitudinal ridge, separating two lateral depressions, for the attachment of the Longus colli muscles of either side. The odontoid process presents two articulating surfaces covered with cartilage; one in front, of an oval form, for articulation with the atlas (fades articularis anterior) ; another behind (fades articularis posterior) , for the transverse Odontoidjprocess, Bough surface for checTc ligaments. — ,^i^, ■■^i^s it.,^ 1 j^Yfii^niar surface for atlas. Articular surf ace for ti ansierse ligament ^^i X\ i Spinous process.-^^i^ 'W'MW iJ ■/ I Transtiei »e process. Inferior articular process. Fig. 17. — Second c-ervical vertebra, or a.xis. ligament — the latter frequently encroaching on the sides of the process. The apex is pointed, and gives attachment to the middle odontoid ligament. 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, wliere it is attached to the body, is constricted, so as to prevent displacement from the transverse ligament, which binds it in this situation to the anterior arch of the atlas. The pedicles are broad and strong, especially their anterior extremities, which coalesce with the sides of the body and the root of the odontoid process. The laminas are thick and strong, and the spinal foramen large, but smaller than that of the atlas. The transverse processes are very small, not l^ifid, and each is perforated by the foramen for the vertebral artery, wErdi is directed obliquely upward and outward. The superior articular siu-faces (fades articulares superiores) are circular, slightly convex, directed upward and outward, and are peculiar in being supported on the body, pedicles, and transverse processes. The inferior articular surfaces (fades articulares inferiores) have the same direction as those of the other cervical vertebree. The superior 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 process is of large size, very strong, deeply channelled on its under surface, and presents a bifid, tubercular extremity' for the attachment of muscles which serve to rotate the headTipon the spine. THE THORACIC VEllTEBRjE 53 Seventh Cervical (Fig. 18).— The most distinctive character of this vcrtel)ra is the existence of a very long and prominent spinous process, hence the name, vertebra prominens. This pro- cess is thick, nearly horizontal in direction, not bifurcated, and gives attachment to the lower end of the ligamentum nuchae. The transverse process is usually of large size, its posterior tuber- cles 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 ex- tremity. The foramen in the transverse process is sometimes as large as in the other cervical vertebras, but is usually smaller on one or both sides, and is sometimes absent. Usually the vertebral artery and vein pass in front of the transverse process, but occasionally it is traversed on both sides by these vessels, or the left one alone may give passage to them. Occasionally the anterior root of the trans- verse process exists as a separate bone, and attains a large size. It is then called' a cervical rib. The Thoracic Vertebrae (Vertebrae Thoracales). The thoracic vertebrae are intermediate in size between those in the cervical and those in the lumbar region, and increase in size from above downward, the upper vertebrse in this segment of the column being much smaller than those in the lower part. A thoracic vertebra may be at once recognized by the presence on each side of the body of one or more facets or half-facets for the heads of the ribs. Bodies. — The bodies of the thoracic vertebrae resemble those in the cervical and lumbar regions at the respective ends of this portion of the vertebral column, but in the middle of the thoracic 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, near the root of the pedicle, by two demi-facets, one above, the other below (fovea costalis superior et inferior). These are covered by cartilage in the recent state, and, when articulated with the adjoining vertebrse, form, with the intervening fibrocartilage, oval surfaces for the reception of the heads of the corresponding ribs. Pedicles. — The pedicles are directed backward, and the inferior intervertebral notches are of large size, and deeper than in any other region of the spine. Laminae. — The laminae are broad, thick, and imbricated — that is to say, overlapping one another like tiles on a roof. The vertebral foramen is small, and of a circidar form. Processes. — Spinous Processes. — Each spinous process is long, triangular on transverse section, directed obliquely downward, and terminates in a tubercular 54 SPECIAL ANATOMY OF THE SKELETON extremity. They overlap one another from the fifth to the eighth vertebra, but are less oblique in direction above and below. Articular Processes. — 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 forward and a little inward and downward. Superior articulai pt ocesi Facet for tubercle of F-.o. 19.— A th Transverse Processes. — 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, and having on its anterior part near its tip a small concave surface, for articulation with the tubercle of a rib (fovea costalis transversalis). Besides the articular facet for the rib, three indistinct tubercles may be seen arising from the transverse processes — one at the upper border, one at the lower border, and one externally. In man they are of comparatively small size, and serve only for the attachment of muscles. But in some animals they attain con- siderable magnitude, either for the purpose of more closely connecting the segments of this portion of the vertebral column or for muscular and ligamentous attachment. The peculiar thoracic vertebrse are the first, ninth, tenth, eleventh, and twelfth (Fig. 20). First Thoracic Vertebra. — The first thoracic vertebra presents, on each side of the body, a sin^e^ntire articular facet for the head of the first rib and a demi- facet for the upper half of the second. The body is like that of a cervical vertebra, being broad transversely, its upper surface is concave, and lipped, pneach side. The articular surfaces are oblique,"and the spinous process thick, long, and almost horizontal. Ninth Thoracic Vertebra. — ^The ninth thoracic vertebra has no demi-facet below. In some subjects, however, the ninth has two demi-facets on eacTi side; when this occurs the tenth has only a demi-facet at the upper part. Tenth Thoracic Vertebra. — The tenth thoracic vertebra has (except in the case just mentioned) an entire articular facet on each side, above, which is partly THE THORACIC VERTEBRAE placed on the outer jurface-of-the-pedicle. It has no demi-facet below, times it has no facet on its transverse process. 55 Some- ( An entire facet above; \ a demi-facet below. —A demi-facet atiove. One entire facet. entire facet. J. No facet on rudimentary (_ transverse process. entire facet. No facet on trans- verse process. Inferior articidat Fig. 20.— Peculi; Eleventh Thoracic Vertebra. — The body of this vertebra approaches in its form and size that of the lumbar vertebra. 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 thoracic region. The spinous process is short, and nearly horizpntal in direction. The transverse processes are very short, Tubercular at their extrem- ities, and have no articiilar facets for the tubercles o? tbe ribs. Twelfth Thoracic Vertetra. — The twelfth thoracic vertebra has the same general characters as the eleventh, but may be distinguished from it by the in- 56 SPECIAL ANATOMY OF THE SKELETON ferior articular processes being convex and turned outward, like those of the lumbar vertebrae; and by the fact that this vertebra resembles the lumbar vertebrae in the general form of the body, laminae, and spinous process; and by the trans- verse processes being shorter, and marked by three elevations, the superior, inferior, and external tubercles, which correspond to the mammillary, accessory, and transverse processes of the lumbar vertebrae. There is no facet on its transverse process for the twelfth rib. The Lumbar Vertebrae (Vertebrae Lumbales) (Fig. 21). The lumbar vertebrae 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 articu- lating facet on the side of the body, the distinguishing mark of the thoracic vertebrae. Superioi a)ticula> pi ocas Fig. 21. — Lumbar vertebra. Body. — ^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 surface for the support of the superincumbent weight. Pedicles. — The pedicles are very strong, directed backward from the upper part of the bodies; consequently, the inferior intervertebral notches are of con- siderable depth. Laminaj.- The laminae are broad, short, and strong, and the vertebral foramen triangular, larger than in the thoracic, smaller than in the cervical, region. Processes. Spinous Processes. — The spinous processes are thick and broad, somewhat quadrilateral, horizontal in direction, thicker below than above, and terminating in a rough, uneven border. Articular Processes. — The superior articular processes are concave, and look backward and inward; the inferior are convex, and look forward and outward; the former are separated by a much wider interval than the latter, embracing the lower articulating processes of the vertebra above. Transverse Processes. — The transverse processes are long, slender, directed transversely 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 thoracic vertebrae, and are homologous with the ribs. Of the three tubercles noticed in connection with the transverse processes of the THE LUuMBAB VERTEBRA 57 twelfth thoracic vertebra, the superior one on each side becomes connected in tliis region witli the back part of the superior articular process, and has received tiie name of mammillary process {processus mamillaris) ; the inferior is represented by a small process pointing downward, situated at the back part of the base of the transverse process, and called the accessory process (processus accessorius); these are the true transverse processes, which are rudimentary in this region of the spine. The external one, the so-called transverse process, is the homoloo-ue of the rib, and constitutes the costal process (processus costarius) (Fig. 22). Although in man the costal processes are comparatively small, in some animals they attain considerable size, and serve to lock the vertebrte more closely together. Inferior articulaT process Transverse process Superior articular process StNf^ /«*V^P a Mammillary process \\\/ MvA.j^ S^^W.///Z^^ ^ ^ Accessory process- Fig. 22. — Lumbar vertebra, viewed obliquely. i'ifth Lumbar Vertebra. — The fifth lumbar vertebra is characterized by haing the body much thicker in front than behind, which accords with the promi- nence of the sacrovertebral articulation; by the smaller size of its spinous process; by t\e wide interval between the inferior articulating processes ; and by the greater size \nd thickness of its transverse processes, which spring from the body as well as fr^ the pedicles. Attahment of Muscles. — To the Atlas are attached nine pairs: the Longus colli, Rectus capitis ntieus minor, Rectus lateralis, Obliquus capitis superior and inferior, Splenius colli, Levator\nguli scapulae. First Intertransverse, and Rectus capitis posticus minor. To th* Axis are attached eleven pairs: the Longus colli. Levator anguli scapulae, Splenius colli, Scajnus medius, Transversalis colli, Intertransversales, Obliquus capitis inferior. Rectus capitis poiicus major, Semispinalis colli, Multifidus spinae, Interspinales. To the -emaining vertebrae, generally, are attached thirty-five pairs and a single muscle: anteriorly, he Rectus capitis anticus major, Longus colli. Scalenus anticus, medius, and posticus. Psoas magiis and parvus, Quadratus lumborum, Diaphragm, Obliquus abdominis internus, and Trans\rsalis abdominis; posteriorly, the Trapezius, Latissimus dorsi. Levator anguli scapulae, Rtimboideus major and minor, Serratus posticus superior and inferior, Splenius, Erector spirip, Iliocostalis, Longissimus dorsi. Spinalis dorsi, Cervicalis ascendens, Trans- versalis colli,Trachelomastoid, Complexus, Biventer cervicis, Semispinalis dorsi and colli, Multifidus spine, Rotatores spinae, Interspinales, Supraspinales, Intertransversales, Levatores costarum. \ 58 SPECIAL ANATOMY OF THE SKELETON The 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. ^ Sacrum (os sacrum). — The sacrum is a large, triangular bone (Fig. 23), 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 in- nominate bones; its upper part or base articulating with the last lumbar vertebra. Fig. 23. — Sacrum, anterior surface. its apex with the coccyx. It is composed of five segments of bone. The acrum is curved upon itself, and placed very obliquely, its upper extremity prqecting forward, and forming, with the last lumbar vertebra, a very prominent angle, called the promontory (promontorium), or sacrovertebral angle; while its central part is directed backward, so as to give increased capacity to the pelvi cavity. It presents for examination an anterior and posterior surface, two lateraburfaces, a base, an apex, and a central Canal. Surfaces. Anterior or Pelvic Surface (fades pelvina). — The antervr surface is concave from above downward, and slightly so from side to sid- In the middle are seen four transverse ridges (Imeae transversae) , indicating fle original division of the bone into five separate pieces. The portions of bonentervening ^ Sir George Humphry describes this ual composition of the coccyx. " On the Slie'fo THE SACRAL AND COCCTGEAL VERTEBRA 59 between the ridges correspoiui to the bodies of the vertebrae. The body of the first segment is of large size, and in form resembles that of a luml)ar 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 men- tioned are seen the anterior sacral foramina (foramina sacralia anteriora), analoo-ous • to the intervertebral foramina, four in number on each side, somewhat circular 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 fora- mina is the lateral mass (pars lateralis), consisting at an early period of life of separate segments ; these become blended, in the adult, vi^ith 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 divisions of the 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. 24), the bodies are seen to be united at their cir- cumference by bone, a wide interval being left centrally, which, in the recent state, is filled by intervertebral substance. In some bones this union is more com- plete between the lower segments than between the upper ones. Posterior or Dorsal Suriace (fades dor- salis). — The posterior suriace (Fig. 25) is convex and much narrower than the anterior. In the middle line are three or four tubercles, which represent the rudi- mentary spinous processes of the sacral vertebrae. Of these tubercles, the first is usually prominent, and perfectly dis- tinct from the rest; the second and third are either separate or united into a tubercular ridge (crista sacralis media), which diminishes in size from above downward; the fourth usually, and the fifth always, remaining undeveloped; being undeveloped, in this situation the lower end of the sacral canal is exposed. The gap is called the hiatus sacralis. External to the spinous processes on each side are the laminje, broad and well marked in the first three pieces; sometimes the fourth, and generally the fifth. External to the laminae is a linear series of indistinct tubercles representing the articular processes (crisfac sacrales artiat- lares); the upper pair are large, well developed, and correspond in shape and direction to the superior articulating processes of a lumbar vertebra; the second and third are small; the fourth and fifth (usually blended together) are situated on each side of the exposed part of the sacral canal and form downward project- ing processes^ the sacral cornua, and are connected to the cornua of the coccyx. -Vertical section of the sacrum. 60 SPECIAL ANATOMY OF THE SKELETON External to the articular processes are the four posterior sacral foramina {foram- ina sacralia posteriora) ; 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 vertebrse (cristae sacrales laterales). The first pair of transverse tubercles are large, very distinct, and correspond with each superior angle of the bone; they, together with the second pair, which are of small size, give attachment to the horizontal part of the posterior sacro- iliac ligament; the third gives attachment to the oblique fasciculi of the pos- terior sacroiliac ligaments; and the fourth and fifth to the great sacrosciatic ligaments. The interspace between the spinous and transverse processes on the back of the sacrum presents a wide, shallow concavity, called the sacral Erector spinse. |H— ia^iSSiOTua dorsl. ] — • Erector spinas. Upper half of fifth lor sacral foramen. Fig. 25. — Sacrum, dorsolateral view. groove; it is continuous above with the vertebral groove, and lodges the origin of the Multifidus spinae. Lateral Surface. — ^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 [fades auricularii), and in the fresh state is coated with fibrocartilage. It is bounded posteriorly by deep and uneven impressions, for the attachment of the posterior sacroiliac ligaments. The chief prominence is called the tuberosity {tuberositas sacralis). 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 THE SACRAL AND COCCYGEAL VERTEBRA 01 transmits the anterior division of the fifth sacral nerve. This lower, sharp border gives attachment to the greater and lesser sacrosciatic ligaments, and to some fibres of the Gluteus maximus posteriorly, and to the Coccygeus in front. Base (basis oss. sacri). — 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 fibrocartilaginous disk. It is bounded behind by the large, tri- angular 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 intervertebral 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 plate is a broad and flat triangular surface of bone, which extends outward, supports the Psoas magnus muscle and lumbosacral cord, and is continuous on each side with the iliac fossa. This is called the ala of the sacrum (ala sacralis), and gives attachment 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. Apex (apex OSS. sacri). — The apex, directed downward and slightly forward, presents a small, oval, concave surface for articulation with the coccyx. ^ The Sacral Canal (canalis sacralis) 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 (hiafus sacralis). It lodges the sacral nerves, and is perforated by the anterior and posterior sacral foramina, through which these pass out. I^ constitutes the sacral continuation of the vertebral canal (Fig. 24). Diflerences 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 presenting the greatest amount of curvature. The bone is also directed more obliquely backward, which increases the size of the pelvic cavity; but the sacrovertebral angle projects less. In the male the curvature is more evenly distributed over the whole length of the bone, and is altogether greater than in the female. Variations. — 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 laminse 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. Articulations. — With /our bones: the last hmibar vertebra, coccyx, and the two innominate bones. Attachment of Muscles. — To eight pairs: in front, the Pyriformis and Coccygeus, 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. Coccyx (os coccygis). — ^The coccyx (Fig. 26) is usually formed of four small segments of bone, the most rudimentary parts of the vertebral column (vertebrae coccygeae). In each of the first three segments may be traced a rudimentary body, articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone, without distinct processes. All the segments are desti- tute of pedicles, laminae, and spinous processes, and consequently of interverte- bral foramina and vertebral canal. The first segment is the largest; it resembles the lowermost sacral vertebra, and often exists as a separate piece; the last three, 62 SPECIAL ANATOMY OF THE SKELETON diminishing in size from above downward, are usually blended to form a single bone. The gradual diminution in the size of the pieces gives this bone a tri- angular form, the base of the triangle joining the apex of the sacrum. It presents for examination an anterior and posterior surface, two borders, a base, and an apex. ■'Tor ►" Antunor surface. Posterior surface. Fig. 26. — Coccyx, Surfaces. Anterior Surface. — The anterior surface is slightly concave and marked with three transverse grooves, indicating the points of junction of the differ- ent pieces. It has attached to it the anterior sacrococcygeal ligament and Levator ani muscle, and supports the lower end of the rectum. Posterior Surface. — 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 vertebrse. Of these, the superior pair are large, and are called the cornua of the coccjrx (cornua coccygea) ; 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 posterior division of the fifth sacral nerve. Borders. — The lateral borders are thin, and present a series of small emi- nences, 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 of the coccyx are narrow, and give attachment on each side to the sacrosciatic ligaments, to the Coccygeus muscles in front of the ligaments, and to the Gluteus maximus behind them. Base. — The base presents an oval surface for articulation with the sacrum. Apex. — ^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 the other side. 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. 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 of various sizes for the passage of vessels; its interior is traversed by one or two large canals (for the transmission of veins) , which converge toward a single large, irregular aperture or several small apertures at the posterior part of the body of each bone. The arch and processes pro- THE SACRAL AND COCCYGEAL VERTELU^K 63 jecting from it have, on the contrary, an exceedingly thick covering of compact tissue (Fig 27). The sacrum and coccyx consist mainly of spongy bone covered by a thin layer of compact bone. Fig. 27. — Bony structure of a lumbar vertebra. (Poirier and Charpy.) Development. — Each vertebra is formed of four primary centres of ossification (Fig. 28), one for each lamina and its processes, and two for the body.' Ossification commences in the laminae about the sixth week of fetal life, in the situation where the transverse processes afterw ard project, the ossific granules spreading backward to the spine, forward into the pedicles, and out- ward 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, ossification commences in the laminie only in the upper vertebrs; — i. e., in the cervical and upper thoracic. The first ossific points in the lower vertebrae are those which are to form the body, the osseous centres for the laminse appearing at a subsequent period. At birth these three pieces are entirely sepa- rate. During the first year the laminae become united behind, the union taking place first in the lumbar vertebrae and then extending upward through the thoracic and lower cervical verte- bras. 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 contributed by the pedicles increasing in extent from below upward. Thus, the bodies of the sacral vertebra are formed almost entirely from the central nuclei; the bodies of the lumbar are formed laterally and behind by the pedicles; in the thoracic 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 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 neurocentral suture. Before puberty no other changes occur, excepting a gradual increase in the gro\\th - 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 de- posited. At sixteen years (Fig. 30) three secondary centres appear, one for the tip of each trans- verse process, and one for the extremity of the spinous process. In some of the lumbar vertebrae, especially the first, second, and third, a second ossifying centre appears at the base of the spinous process. At twenty-one years (Fig. 29) a thin, circular, epiphyseal plate of bone is formed in the layer of cartilage situated on the upper and under surfaces of the body, the former being the thicker of the two. These represent two additional secondary centres of ossification. \\\ these become joined, and the bone is completely formed between the twenty-fifth and thirtieth year of life. Exceptions to this mode of development occur in the first, second, and seventh cervical, and in the vertebrae of the lumbar region. Atlas (Fig. 31).— The number of centres of ossification of the atlas is quite variable. It may be developed from iwo, three, four, or five centres. The most frequent method is from three centres. Two of these are destined for the two lateral or neural masses, the ossification of which commences about the seventh week near the articular processes, and extends backward; these portions of bone are separated from one another behind, at birth, by a narrow interval filled in with cartilage. Between the third and fourth vears they unite either directly or through the medium of a separate centre developed in the cartilage in the median line. The anterior > 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 eienta sometimes, is evidenced by the facts that the t-s-o h.alves of the body of the vertebra may remam distmct throughout life, and be separated by a fissure through which a protrusion of the spinal membrane may take place, constituting an anterior spina bijida. 64 SPECIAL ANATOMY OF THE SKELETON arch, at birth, is altogether cartilaginous, and in this a separate nucleus appears about the end of the first year after birth, and, extending laterally, joins the neural processes in front of the pedi- cles. Sometimes there are two centres developed in the cartilage, one on either side of the median line, which join to form a single mass. By If primary centres. 1 fui hud;/ (Sih week). 1 for each lamina (6th weeh). Fig. 28. — Development of a vertebra. I plates. 1 for upper surface "i of body, ■ 21 year^ ,1 for nn.der surface of body. By 4 secondary centres. 1 for each trans- verse process, 16 years. 2 (sometimes 1) for spinous process (16 years). Fig. 30 By S ccnir anterior arch (1st year), not c/mstant. before birth. 6th month. 1 for each lateral mass. 1 for body (4fh month). 1 'for under surface of body. Axis. jnr tubeicles on supenoi aiticulai process. Fig. 33. — Lumbar vertebra. 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 pro- cesses. Axis. — The axis (Fig. 32) is developed by seven centres, five primarij and tico secondary. The body and arch of this bone are formed in the same manner as the corresponding parts in the other vertebrae: one centre (or two, which speedily coalesce) for the lower part of the body, and one for each lamina. The centres for the laminre 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 cartilagi- nous mass in which the lower part of the body is formed. At about the sixth month of fetal life two centres make their appearance in the base of this pro- cess; they are placed laterally, and join before birth to form a conical bilobed mass deeply cleft above; the interval be- tween 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 car- tilaginous interval, which gradually be- comes ossified at its circumference, but remains cartilaginous in its centre until advanced age. Finally, the apex of the odontoid process has a separate (second- ary) centre, which appears in the second year and joins about the twelfth year. In addition to these there is a secondary centre for a thin epiphyseal plate on the under surface of the body of the bone. Seventh Cervical. — The anterior or costal part of the transverse process of the seventh cervical is developed from a separate osseous centre at about the sixth month of fetal life, and joijis the body and posterior division of the trans- verse process between the fifth and sixth years.. In rare instances this process continues as a separate piece, and, be- coming 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 vertebras. Lumbar Vertebree. — The hmibai- vertebrre (Fig. 33) have two additional centres (besides those peculiar to the vertebrae generally) for the mamraillary tubercles, which project from the back part of the superior articular processes. The transverse process of the first lumbar is sometimes developed as a separate piece, which ma}' remain per- THE SACRAL AND COCCYGEAL VETlTEBRjE 60 manently unconnected with the remaining portion of the bone, thus forming a himhar rib a peculiarity. 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 epiphyseal plates on its upper and under surface. Occasionally the iirimary centres for the bodies of the first and second piece of the sacrum are double. The arch of each sacral vertebra is developed from 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 vertebrte. These centres, representing costal elements, make their appearance above and to the outer side of the anterior sacral foramina (Fio;. 34), and are developed into separate segments (Fig. 3.5); 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 from two epiphyseal plates (Fig. 36) — one for the auricular surface, and one for the remaining part of the thin lateral edge of the bone. Additional cetitte^ for the /i)s( time piei Two epiphysial lamines for each lateral surface/'^ Fig. 34. — Development of the sacrum. Period of Development.— At about the eighth or ninth week of fetal life ossification of the central part of the bodies of the first three vertebrae commences, and between the fifth and eighth months in the last two. Between the si.xth and eighth months ossification of the lamina takes place; and at about the same period the centres for the lateral masses for the first three sacral vertebrfe make their appearance. The period at which the arch becomes completed by the junc- tion 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 uppermost 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. At about the eighteenth year the two lowest segments become joined 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. The coccyx is developed from four centres, one for each piece. Occasionally one of the first three pieces of this bone is developed from two centres, placed side by side. The ossific nuclei make their appearance in the following order: In the first segment, between the first and fourth years; in the second piece, at from five to ten years; in the third, from ten to fifteen years; inthe fourth from fourteen 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 fre- quently delayed until after the age of twenty-five or thirty. At a late period of life, especially in females, the coccyx often becomes ankylosed to the end of the sacrum. 'arly stage. 66 SPECIAL ANATOMY OF THE SKELETON Coccyx. Fig, 38. — Lateral view of the vertebral column. The Vertebral Column as a Whole. The vertebral column (columna verte- bralis), formed by the interarticulatioii of the vertebrae, is situated in the median line, in the posterior part of the trunk; its average length is about two feet two or three inches (65 to 67.5 cm.), measuring along the curved anterior surface of the column. Of this length, the cervical part measures about five, the thoracic about eleven, the lumbar about seven inches, and the sacrum and coccyx the remainder. The female column is about one inch less than that of the male. Viewed laterally (Fig. 38), the spinal column presents several curves which cor- respond to the different regions of the column, and are called cervical, thoracic, lumbar, and pelvic. The cervical curve commences at the apex of the odontoid process, and terminates at the middle of the second thoracic vertebra; it is convex in front, and is the least marked of all the curves. The thoracic curve, which is concave forward, commences at the middle of the second, and terminates at the middle of the twelfth thoracic vertebra. Its most prominent point behind corresponds to the spine of the seventh thoracic vertebra. The lumbar curve commences at the middle of the last thoracic vertebra, and terminates at the sacrovertebral angle. It is convex anteriorly; the convexity of the lower three vertebrae being much greater than that of the upper two. The pelvic curve com- mences at the sacrovertebral articulation and terminates at the point of the coccj^x. It is concave anteriorly. The thoracic and pelvic curves are the primary curves, and begin- to be formed at an early period of fetal life, and are due to the shape of the bodies of the vertebrae. The cervical and lumbar curves are compensatory or sec- ondary, and are developed after birth in order to maintain the erect position. They are due mainly to the shape of the in- tervertebral disks. Not uncommonly the thoracic portion of the vertebral column — even in healthy persons — deviates toward the right. This is due to the position of the heart and of the arch of the aorta. The movable part of the vertebral column presents for examination an anterior, a pos- terior, and two lateral surfaces; a base, a summit, and the vertebral canal. THE VERTEBBAL COLUMN AS A WHOLE 67 Surfaces. — The anterior or ventral surface presents the bodies of the vertebra; separated in the recent state by the intervertebral disks. The bodies are broad in the cervical region, narrow in the upper part of the thoracic, and broadest in the himbar region. The whole of this surface is convex transversely, concave from above downward in the thoracic region, and convex in the same direction in the cervical and lumbar regions. The posterior or dorsal surface presents in the median line the spinous pro- cesses. These are short, horizontal, with bifid extremities, in the cervical region. In the thoracic 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 thoracic region. On either side of the spinous processes, extending the whole length of the column, is the vertebral groove formed by the laminse in the cervical and lumbar regions, where it is shallow, and by the laminae and transverse processes in the thoracic region, where it is deep and broad. In the recent state these grooves lodge the deep muscles of the back. External to each vertebral groove are the articular processes, and still more externally are the transverse processes. In the thoracic region the latter processes stand backward, on a plane considerably posterior to that of like 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 intervertebral foramina. In the thoracic region they are posterior to the pedicles, inter- vertebral foramina, and articular processes. In the lumbar region they are placed in front of the articular processes, but behind the intervertebral foramina. The lateral surfaces are separated from the dorsal surface by the articular processes in the cervical and lumbar regions, and by the transverse processes in the thoracic region. These surfaces present in front the sides of the bodies of the vertebrse, marked in the thoracic 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 thoracic regions, and gradually increasing in size to the' last lumbar vertebra. 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. Base. — The base of that portion of the vertebral column formed by the twenty-four movable vertebrae is formed by the under surface of the body of the fifth lumbar vertebra; and the summit by the upper surface of the atlas. Vertebral Canal. — ^The vertebral canal follows the different curves of the verte- bral column; it is largest in those regions in which the vertebral column enjoys the greatest freedom of movement, as in the neck and loins, where it is wide and triangular; and is narrow and cylindrical in the back, where motion is more limited. Surface Form.— The only parts of the vertebral column -svhich lie closely under the skin, and so directly influence surface form, are the apices of the spinous processes. These are always distinguishable at the bottom of a median furrow, which, more or less evident, runs down the mesal line of the back from the external occipital protuberance above to the middle of the sacrum below. Occasionally one of these processes deviates a little from the median line — a fact to be remembered in practice, as irregularities of this kind are attendant also on fracture or displace- ments of the vertebral column. In the cervical region the furrow is between the Trapezii muscles; in the back and loins it is between the Erector spinae muscles. In the neck the furrow is broad, and terminates in a conspicuous projection, which is caused by the spinous process of the seventh cervical vertebra {vertebra promincns). Above this the spinous process of the sLxth cervical vertebra may sometimes be seen projecting; 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 vertebra;. In the thoracic region the furrow is shallow, and durmg stooping disappears, and then the spinous processes become more or less visible. The markmgs produced by these spines are small and close together. In the lumbar region the fm-row is deep, and the situation of the lumbar spines is frequently indicated by little pits, or depressions, 68 SPECIAL ANATOMY OF THE SKELETON especially if the muscles in the loins are well developed and the process incurved. They are much larger and farther apart than in the thoracic 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 processes 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 sLxth, 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 Sternomastoid. 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 Chassaignac's 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 ante- rior root, or costal process, is large and separate, forming a cervical rib. Applied Anatomy. — It is frequently necessary to locate certain vertebr». Several of them can be easily found and identified. The seventh cervical spine is conspicuously prominent, and when the skin over it has been marked with a blue pencil the spine of the sixth cervical above and of the first thoracic below may be located. The spine of the third thoracic vertebra is on a level with the root of the spine of the scapula. The spine of the fourth lumbar vertebra is on a level with the highest point of the iliac crest. When one or two vertebrae have been definitely recog- nized the other ones can be found by counting the spines from a fixed point or from fixed points. Over the fifth lumbar spine there is no prominence, but a depression. The third sacral spine is on a level with the posterior superior spines of the ilium. The level at which the spinal cord terminates should be known to the surgeon if he proposes to tap the spinal theca {lumbar punc- ture) for diagnostic or therapeutic purposes or for spinal anesthesia. In an adult the cord terminates at the lower border of the first lumbar vertebra, and the theca terminates opposite the body of the third sacral vertebra. In a young child the cord terminates opposite the body of the third lumbar vertebra, and the theca ends at about the same level as in an adult. Hence, in either a child or an adult, a puncture below the level of the fourth lumbar vertebra will infiict no injury upon the cord. In children the puncture is made just beneath the spinous process, and in adults about one-half an inch to either side of the spinous process, although the needle should be made to enter the dura in the median line. In either case the needle is directed upward and forward. As previously pointed out, the surgical anatomy of an infant's spine is not identical with the sur- gical anatomy of an adult's spine. The umbilicus of an infant is opposite the body of the fourth lumbar vertebra; in an adult it is opposite the spinous process of the third lumbar vertebra. In an infant the base of the sternum is on a level with the top of the seventh cervical spine, and in an adult of the second thoracic spine (A. H. Tubby). The vertebral column may be the seat of tuberculosis, which may destroy the bodies of the vertebrae; in such cases a deflection of the column may be directed either forward or backward. This deflection is produced by the great weight of the trunk on the diseased bone. If the deflection is directed forward, it is called lordosis; if backward, kyphosis. Scoliosis (lateral deviation of the vertebral column) is usually due to a faulty attitude of children while standing or while sitting at school desks. Occasionally the coalescence of the laminfe is not completed, and consequently 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 or hydrorhacliitis. This condition is most common in the lumbosacral region ; but it. may occur in the thoracic or cervical region, or the arches throughout the whole length of the canal may remain unapproximated. In some rare cases, in consequence of the noncoalescence of the two primary centres from which the body is formed, a similar condition 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 aft'ected. 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 individuals pieces, though permitting of a very considerable range of movement, as a whole, allows a sufficient degree of mobility without any material diminution of strength. The main joints of which the spine is composed, together with the very varied movements to which it is subjected, render it liable to sprains, which may complicate other injuries or may exist alone; but so closely are the individual vertebrae articulated that these sprains are seldom severe, and an amount of violence sufficiently great to produce tearing of the ligaments would tend 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 one straight 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 produce 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 inter- position of the intervertebral disks between the bodies of the vertebrae, which act as admirable THE SKULL 69 buffers in counteracting the effects of violent jars or shocks. Fracture didncation of the verteliral column 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 common, and here the bodies of the vertebrte are compressed, while the arches are torn asunder; while 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 cord is the part least likely to be injured, and may escape damage even when 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."' Applying this principle to the vertebral column, it will be seen that, whether the fracture dislocation be produced by direct violence or by indirect force, 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 displacement 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 vertebral column most liable to be injured are (1) the thoracolumbar region, for this part is near the middle of the column, and there is therefore a greater amount of leverage, and, moreover, 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- thoracic region, because here the flexible cervical portion of the vertebral column joins the more fixed thoracic region; and (3) the atlantoaxial 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, spinous processes and portions of the laminae may be removed {laminectomy) in order to free the spinal cord from pressure, and to permit the surgeon to explore, to arrest hemorrhage, to remove bone fragments, or to apply sutures. Laminectomy is also resorted to in some cases of paraplegia due to Pott's disease of the spine. THE SKULL. The Skull, or superior expansion of the vertebral cohimn, has been described as if composed of four vertebrae, the elementary parts of which are specially modified in form and size, and almost immovably connected, for the reception of the brain and special organs of the senses. These vertebrae are the occipital parietal, frontal, and nasal. Descriptive anatomists, however, divide the skull into two parts, the Cranium and the Face. The Cranium is composed of eight bones, viz., the occipital, two parietals, frontal, two temporals, sphenoid, and ethmoid. The Face is composed of fourteen bones, viz., the two nasals, two maxillce, two lacrimals, two malars, two palates, two turbinates, vomer, and mandible. The ossic- uli auditus, the teeth, and Wormian hones are not included in this enumeration. Occipital. Skull, 22 bones Two parietals. Cranium, 8 bones . ^ Twftemporals. Sphenoid. L Ethmoid. f Two nasals. Two maxillae. Two lacrimals. r, , . J I Two malars. Face, 14 bones . . < ^^^,^ ^.^^^^^^ Two turbinates. I Vomer. L Mandible. 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. ' Holmes' System of Surgery, 1883, vol. i, p. 529. 70 SPECIAL ANATOMY OF THE SKELETON THE CEREBRAL CRANIUM (CRANIUM CEREBRALE) The Occipital Bone (Os Occipitale). The occipital bone is situated at the back part and base of the cranium, is curved on itself, and is trapezoidal in shape. The bone presents for examination two surfaces, four borders, and four angles. Surfaces. — The external surface is convex. Midway between the summit of the bone and the posterior margin of the foramen magnum — a large oval opening for transmission of the spinal cord — is a prominent tubercle, the external occipital protuberance { protuberantia occipitalis externa), and, descending from it Lmea sup) as far as the foramen, a vertical ridge, the external occipital crest (crista occipitalis externa). This protuberance and crest give attachment to the ligamentum nuchae and Trapezius, and vary in prominence in different skulls. Passing outward from the occipital protuberance is a semicircular ridge on each side, the superior curved line (linea niiclme superior). Above this line there is often a second less distinctly marked ridge, called the highest curved line (linea nuchae suprema); to it tlie 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 line (linea nuchae inferior). The surface of the bone above the linea suprema is rough and porous, and in the recent state is covered by the Occipitofrontalis muscle. The superior and inferior curved lines, together with the surfaces of bone between and below them, serve for the attachment of several muscles. THE OCCIPITAL BONE 71 The superior curved line gives attachment internally to the Trapezius, externally to the muscular origin of the Occipitofrontalis, and to the Sternomastoid to the extent shown in Fig. 39; the depressions between the curved lines to the Com- plexus 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 {foramen occipitale magnum) is a large, oval apertiu'e, its long diameter extending from before backward. It transmits the lower por- tion of the medulla oblongata and its membranes, the spinal part of the spinal accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the occipitoaxial ligaments. Its back part is wide for the transmission of the medulla oblongata, and the corresponding margin rough for the attachment of the dura enclosing it; the fore part is narrower, being encroached upon by the condyles; it has projecting toward it, from below, the odontoid process, and its margins are smooth and bevelled internally to support the meclulla oblongata. On each side of the foramen magnum are the condyles for articulation with the atlas. Each condyle (condylus occipitalis) is convex, oval, or reniform in shape, and directed downward and outward. The condyles 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; while external to tliem is a rough tubercular prominence, the transverse or jugular process (processus jugularis), channelled in front by a deep notch (incisura jugularis), which forms, part of the jugular foramen (foramen lacerum posterius). The under surface of this process presents an eminence (processus intrajugularis) , which 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 attach- ment to the Rectus capitis lateralis muscle and to the lateral occipitoatlantal ligament; its upper or cerebral surface presents a deep groove, which lodges part of the lateral sinus, while 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 condylar foramen (canalis hypoglossi); it is directed downward, outward, and forward, and transmits the hypoglossal nerve, and occasionally a meningeal branch of the ascending pharyn- geal artery. This foramen is sometimes double. Behind each condyle is a fossa^ (fossa condyloideus), sometimes perforated at the bottom by a foramen, the posterior condylar foramen (canalis condyloideus), for the transmission of a vein to the lateral sinus. The basilar process (pars basilaris) is a strong quadri- lateral plate of bone, which is wider behind than in front, and is situated in front of the foramen magnum. Its under surface is rough, presents in the median line a tubercular ridge, the pharyngeal spine {tuherculuni pharyngeum), for the attach- ment of the tendinous raph^and Superior constrictor of the pharynx, and on each side of it rough depressions for the attachment of the Rectus capitis anticus, major and minor. The internal surface (Fig. 40) is deeply concave. The posterior part is divided by a crucial ridge into four fossa?. The two superior fossa; 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 comparatively smooth ; both are marked by slight grooves for the lodgement of arteries. At the point of meeting of the four > This fossa presents many variations in size. It is usually shallow, and the foramen small; occasionally wanting on one or both sides. Sometimes both fossa and foramen are large, but confined to one side only; more rarely, the fossa and foramenare very large on both sides. 72 SPECIAL ANATOMY OF THE SKELETON divisions of the crucial ridge is an eminence, the intemal occipital protuberance {yro- tuberantia occipitalis interna). It nearly corresponds to that on the outer surface, though it is often on a slightly higher level, 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, .the sagittal sulcus (sulcus sagittalis), for the superior saggittal sinus. The margins of the groove give attachment to the falx cerebri. The inferior division, the intemal occipital crest (crista occipitalis interna), runs to the posterior margin of the foramen magnum, on the edge of which it becomes gradually lost; this Superior Inferior angle. Fig. 40, — Occipital bone. Inner surface. 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 occipital sinus. Occasionally the groove is double where two sinuses exist. A transverse groove (sulcus transversus) passes outward on each side to the lateral angle. The grooves are deep channels for the lodgement of the lateral sinuses, their prominent margins affording attachment to the tentorium.^ At the point of meeting of these grooves is a depression, the torcular^ (confluens sinuum), placed a little to one or the other side of the internal 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 sagittal sinus, 2 The columns of blood coming in different directions were supposed to be pressed together at this point iiorcular, a wine press). THE OCCIPITAL BONE 73 occipital protuberance. More anteriorly is the foramen magnum, and on each side of it, but nearer its anterior than its posterior part, the internal openinn's of the anterior condylar foramen. On the superior aspect of the lateral portion of the bone the jugular tubercle (tuherculum jugulare) is seen. This corresponds to the portion of bone which roofs in the anterior condylar foramen. The internal openings of the posterior condylar foramina are a little external and posterio ■ to the openings of the anterior condylar foramina, protected by a small arch of bone. At this part of the internal surface there is a very deep groove in which the posterior condylar foramen, when it exists, has its termination. 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 lateral sinus. In front of the foramen magnum is the basilar process, presenting a shallow depression, the basilar groove (clivus), 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 (sulcus peiros'us inferior), which lodges the inferior petrosal sinus. Borders. — The superior border (viargo lambdoideus). 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 (marcjo mastoideus) is rough, and articulates with the mastoid portion of the tem- poral, forming the masto-occipital suture; the inferior half articulates with the petrous portion of the temporal, forming the petro-occipital suture ; these two por- tions are separated from each other by the jugular process. In front of this process is a deep notch, which with a similar one on the petrous portion of the temporal forms the jugular foramen (foramen, lacerum posterius). This notch is occasionally subdivided into two parts by a small process of bone (processus intrajugularis) , and it generally presents an aperture at its upper part, the internal opening of the posterior condylar foramen. 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 fetus which is called the posterior fontanelle. The inferior angle is represented by the square-shaped surface of the basilar process. At an early period of life a layer of cartilage separates this part of the bone from the sphenoid, but in the adult the union between them is osseous. The lateral angles correspond to the outer ends of the transverse grooves, and are received into the interval between the posterior inferior angles of the parietal and the mastoid portion of the temporal. Structure. — The occipital bone consists of two compact laminse, called the outer and inner tables, having between them the diploic tissue; this bone is especially thick at the ridges, protuberances, con- dyles, and anterior part of the basilar process; while at the bottom of the fossae, especially the inferior, it is thin, semitrans- parent, and destitute of diploe. Development (Fig. 41).— At birth the bone consists of four distinct parts — a tabular or squamous portion, which \&f^ -1 for basilar portion. ,. lies behind the foramen magnum; two ^ ,, x, , ^^"^ j. r ■ •» i v, -r =o„o„ , ,. , ■ I P P ■ , ,. Fig. 41. — Development of occipital bone. From seven condylic parts, which form the sides 01 centres, the foramen; and a basilar part, which lies in front of the foramen. The tabular portion is usually developed from four centres, though the number may vary from one to eight; two centres appear near the median line of the bone 74 SPECIAL ANA TOMY OF THE SKELETON during the second month, and two more a little lateral to the preceding during the third month. These parts tend to unite, but complete union does not occur until about the fourth month after birth. That part of the tabular portion above the highest curved line is developed by the iidramembranous method, and may exist in the adult as a separate element, the interparietal bone, or os incae, because of its frequent occurrence in Peruvian skulls. The remainder of the tabular portion and the basilar and two condyloid parts are developed from cartilage. Usually two centres appear in the basilar portion during the sixth fetal week, and by rapid coalescence give the appearance of a single centre. Each condylic portion develops from a single centre that appears at about the end of the eighth fetal week. At about the fourth year the tabular and the two condyloid pieces unite, and about the sixth year the bone consists of a single piece. 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 atks. Attachment of Muscles. — To twelve pairs — to the superior curved line are attached the Occipitofrontalis, Trapezius, and Sternomastoid. To the space between the curved lines, the Complexus,^ Splenius 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. The Parietal Bone (Os Parietale). The parietal bones are paired bones, and form, by their union, the sides and roof of the cranium proper. Each bone is of an irregular quadrilateral form, and presents for examination two surfaces, four borders, and four angles. Surfaces. — The external surface (fades parietalis) (Fig. 42) is convex, smooth, and marked about its centre by an eminence called the parietal eminence {tuber parietale), which indicates the point where ossification commenced. Crossing the middle of the bone in an antero-posterior direction are two well-marked curved ridges, the upper and lower temporal ridges (linea temporalis superior et inferior-) ; the former gives attachment to the temporal fascia, while the latter indicates the upper limit of the origin of the Temporal muscle. These lines form the temporal crest. Above these ridges the surface of the bone is covered by the aponeurosis of the Occipitofrontalis; below them the bone forms part of the temporal fossa, and affords attachment to the temporal muscle. At the back part, of the superior border, close to the sagittal suture, which separates the two parietal bones, is a small foramen (foramen parietale), which transmits the emissary vein of Santorini to the scalp from the superior sagittal sinus. It sometimes also transmits a small branch of the occipital artery. Its existence is not constant, and its size varies considerably. The internal or cerebral surface (fades cerebralis') (Fig. 43) is concave, presents depressions for the lodgement of the convolutions of the cerebrum, and numerous furrows for the branches of the middle meningeal artery; the latter runs upward and backward from the anterior inferior angle and from the central and posterior part of the lower border of the bone. Sometimes a distinct canal exists for the artery, but it never remains a canal for a long distance. Along the upper .margin of the bone is part of a shallow groove, which, when joined to the opposite parietal, forms a channel for the superior sagittal sinus. The elevated edges of the groove afford attachment to the falx cerebri. Near the groove are seen several depres- sions. Pacchionian depressions (foveolae granulares [Pacchioni]). They are most frequently foimd in the skulls of old persons, and lodge the arachnoid villi (Pacchi- onian bodies). The interna! opening of the parietal foramen is also seen when that aperture exists. On the inner surface of the posterior inferior portion of the bone is a portion of the groove for the lodgement of the lateral sinus. * To these the Biventer cervicis should be added, if it is regarded as a separate muscle. THE PARIETAL BONE 75 occipital bone. of te-Ki-V Fig. 42. — Left parietal bone. External surface. Fig. 43. — Left parietal bone. Internal surface. 76 SPECIAL ANATOMY OF THE SKELETON Borders. — The superior border (margo sagiUalis), the longest and thickest, is dentated to articulate with its fellow of the opposite side, forming the sagittal suture. The inferior border (niargo squamosus) is divided into three parts; of these, the anterior is thin and pointed, bevelled at the expense of the outer surface, and overlapped by the tip of the greater wing of the sphenoid; the middle portion is arched, bevelled at the expense of the outer surface, and 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 [margo frontalis), 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 (margo occipitalis), deeply denticulated, articulates with the occipital, forming the lambdoid suture. Angles. — The anterior superior angle (angulus frontalis), thin and pointed, corresponds with that portion of the skull which in the fetus is membranous, and is called the anterior fontanelle {bregma). The anterior inferior angle (angulus sphenoidalis) is thin and lengthened, being received in the interval between the greater 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. At the anterior inferior angle the parietal and frontal bones and the greater wing of the sphenoid bone meet. This spot is called the pterion. The posterior superior angle (angulus occipitalis) corresponds with the junction of the sagittal and lambdoid sutures. In the fetus this part of the skull is mem- branous, and is called the posterior fontanelle (lambda). The posterior inferior angle (angulus mastoideus) articulates with the mastoid portion of the temporal bone, and generally presents on its inner surface a broad, shallow groove for the lodgement of part of the lateral sinus. Development. — The parietal bone is formed in membrane, being developed from one centre, which corresponds with the parietal eminence, and makes its first appearance about the seventh or eighth week of fetal life. Ossification gradually extends from the centre to the circumference of the bone; the angles are consequently the parts last formed, and it is in their situation that the fontanelles exist previous to the completion of the growth 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.— 0»e only, the Temporal. ^ The Frontal Bone (Os Frontale). The frontal bone consists of two portions — a vertical or frontal portion, situated at the anterior part of the cranium proper, forming the forehead; and a horizontal or orbital portion, which enters into the formation of the roof of the orbits and nasal fossae. Vertical Portion. Surfaces. — External Surface (fades frontalis) (Fig. 44). — 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 (frontal or metopic 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. On either side of this ridge, a little below the centre of the bone, is a rounded prominence, the frontal eminence (tuber frontale). These eminences vary in size in different individuals, and are occasionally unsymmetrica! THE FRONTAL BONE 77 in the same subject. The whole surface of the bone above this part is sinootli, and covered by the aponeurosis of the Occipitofrontalis muscle. Below the frontal eminence and separated from it by a slight groove is the superciliary ridge (arcus super ciliar is), broad internally, where it is continuous with the nasal eminence, but less distinct as it arches outward. These ridges are caused by the projection outward of the frontal air sinuses/ and give attachment to the Orbicularis palpebrarum and Corrugator supercilii. Between the two superciliary ridges is a smooth, flat surface, the glabella. Beneath the superciliary ridge is the supraorbital arch (margo supraorbitalis), a curved and prominent margin, which forms the upper boundary of the orbit and separates the vertical fi-om the hori- zontal portion of the bone. The outer part of the arch is sharp and prominent, affording to the eye, in that sititation, 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 a foramen, and called the supraorbital notch {incistira supraorbitalis). 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. To the median side of the supraorbital notch there is often a notch (incisura frontalis) for the passage of the frontal artery and nerve. The supraorbital arch terminates externally in the external angular process and internally in the internal angular 1 Some confusion is occasioned to students commencing the study of anatomy by the name ' 'sinuses ha\ing bsen given to two perfectly different kinds of spaces connected with the sliull. It miiy be .is well, therefore, to state here, at the outset, that the "sinuses" in tne interior of the cranium which produce the grooves on the in"cr 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 contaiil air. 78 SPECIAL ANATOMY OF THE SKELETON 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, starting together from the external angular process as the temporal crest, soon diverge from each other and run in a curved direction across the ])one. These are the upper and lower temporal ridges ; the upper gives attachment to the temporal fascia, the 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 process is less marked than the external, articulates with the lacrimal bones, and gives attachment to the Orbicularis palpebrarum. With maxilla With nasal ii , , ^ j- 7 I ! nthi sm face of nasal pi ocess, With perpendicular plate of ethmoid ' foiming pait of loof of nose Fig. 45. — Frontal "bone. Inner surface. Internal Surface (cerebral surface, fades cerehralis) (Fig. 45). — Along the median line is a vertical groove, the sulcus sagittalis, the edges of which unite below to form a ridge, the frontal crest {crista frontalis'); the groove lodges the superior sagittal sinus, while 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 cecum, and varies in size in different subjects; it is sometimes partially or completely impervious, lodges a process of the falx, and when open transmits a vein from the mucous membrane of the nose to the superior sagittal 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 the ramifications of the anterior branches of the middle meningeal arteries. Several small, irregular fossse are seen also on either side of the groove, for the reception of the arachnoid villi. The border of the vertical portion is thick, deepl}' serrated, bevelled at the THE FRONTAL BONE 79 expense of the internal table above, where it rests upon the parietal iKjnes, and at the expense of the external table at each side, where it receives the lateral pressure of those bones; this border is continued below into a triangular rough surface which articulates with the greater wing of the sphenoid. Horizontal or Orbital Portion. — ^This portion of the bone consists of two thin plates, the orbital plates, wiiich form the vault of the orbit, separated from one another by a median gap, the ethmoidal notch. Surfaces. Orbital Surface. — The surface of each orbital plate {fades orhitali.s) consists of a smooth, concave, triangular lamina of bone, marked at its front and external part ( immediately beneath the external angular process) by a shallow depression, the lacrimal fossa {fossa cilandulae lacrimalis), occupied by the lacrimal gland; and at its anterior and internal part by a depression (sometimes a small tubercle), the trochlear fossa {fovea trochlearis), for the attachment of the carti- laginous pulley of the Superior oblique muscle of the eye. These plates are united in front by a roughened uneven surface called the nasal process, which articulates in front with the nasal bones, laterally with the nasal process of each maxilla. From the middle of the nasal process a thin lamina of bone (the nasal spine) projects downward and forward; on either side of this is a shallow groove, which enters into the formation of the nasal fossa. The nasal spine articulates in front with the nasal bones and behind with the perpendicular plate of the ethmoid, and by so doing assists in forming the septum of the nose. The ethmoidal notch (incisura ethvioidalis) separates the two orbital plates; it is quadrilateral, and occupied, when the bones are united, by the cribriform plate of the ethmoid. The margins of this notch present several half cells, which, when united with corresponding half cells on the upper surface of the ethmoid, complete the eth- moidal cells; two grooves are also seen crossing these edges obliquely; they are con\erted into canals by articulation with the ethmoid, and are called the anterior and posterior ethmoidal canals {foramen ethmoidale anterius and foramen ethvioidale posterius) ; they open on the inner wall of the orbit. The anterior one transmits the nasal nerve and anterior ethmoidal vessels; the posterior one, the posterior ethmoidal vessels. In front of the ethmoidal notch, on each side of the nasal process, is the opening of the frontal air sinus {sinus frontalis). These are two irregular cavities, which extend upward and outward, a variable distance, between the two tables of the skull, and are separated from each other by a thin bony septum {septum simnim frontalium) , which is often displaced to one side. Within the sinuses imperfect trabecule of bone often exist. The sinuses are beneath and gi\e rise to the prominences above the supraorbital arches called the super- ciliary ridges {arciis snperciliares). The frontal air sinuses are absent at birth, become apparent about the seventh year of life, and from this period until the age of twenty gradually increase in size. Sometimes, however, the sinuses remain very small or never develop at all — or one side may be large and the other small — or one may exist on one side and be absent on the other. The right sinus is usually the larger. These cavities are larger in men than in women. The floor of each sinus is very thin and is over the orbit and the upper border of the lateral mass ■of the ethmoid. The thinnest portion of the floor is at the upper and inner angle of the orbit. The frontal sinuses are lined by mucous membrane, and each sinus communicates with the middle meatus of the nose by the infundi- bulum. In some cases the sinuses communicate with each other by means of an aperture in the septum and occasionally join the sinus in the crista galli of the ethmoid. The internal surface {cerebral surface, fades cercbralis) of the horizontal portion presents the convex upper surfaces of the orbital plates, separated from each other in the median line by the ethmoidal notch, and marked by eminences and de- pressions for the convolutions of the frontal lobes of the cerebrum. 80 SPECIAL ANATOMY OF THE SKELETON The border of the horizontal portion is thin, serrated, and articulates with the lesser wing of the sphenoid. Structure. — The frontal portion and external angular processes consist of diploic tissue sur- rounded by compact bone. In the frontal sinus region the cancellous tissue is wanting. The horizontal portion is thin, translucent, and composed entirely of compact tissue. Development (Fig. 46). — The frontal bone is formed in membrane, being developed from two primary centres, one for each lateral half, which make their appearance about the seventh or eighth week, above the orbital arches. From this point ossification extends, in a radiating manner, upward into the forehead and backward over the orbit. The nasal spine is developed from two secondary centres, while additional cen- tres appear in the regions of the internal and external angular processes. Sometimes a centre appears on either side at the lower end of the coronal suture. This latter centre sometimes re- mains ununited, and is known as the pterion. , ossicle, or it may join with the parietal, sphenoid, ;. ° ° or temporal bone. At birth the bone consists of two pieces, which afterward become united, along the median line, by a suture (metopic) which runs from the vertex to the root of the nose. This suture usually becomes obliterated within a few years after birth, but it occasionally remains throughout life. Articulations. — With twelve bones — two parietal, the sphenoid, the ethmoid, two nasal, two maxillse, two lacrimal, and two malar. Attachment of Muscles. — To three pairs — the Corrugator supercilii, Orbicularis palpe- brarum, and Temporal, on each side. The Temporal Bone (Os Temporale). The temporal bone consists of three parts — (a) the squamous, (6) the petro- mastoid, and (c) the tympanic portions — which, though separate in early life, become united in the adult. The three parts meet and form a part of the outer wall and a part of the base of the skull and the external auditory meatus. The Squamous Portion {pars squamosa temporalis). — The squamous portion, the anterior and upper part of the bone, is scale-like in form, and is thin and translucent (Fig. 47). Its external surface is smooth, convex, and grooved at its back part for the deep temporal arteries; it affords attachment to the Tem- poral muscle and forms part of the temporal fossa. At its back part may be seen a curved ridge (part of the temporal ridge), which serves for the attachment of the temporal fascia, limits the origin of the Temporal muscle, and marks the boundary between the squamous and mastoid portions of the bone. Pro- jecting from the lower part of the squamous portion is a long, arched process of bone, the zygoma, or zygomatic process. This process is at first directed out- ward, its two surfaces looking upward and downward; it then appears as if twisted upon itself, and runs forward, its surfaces now looking inward and out- ward. The superior border of the process is long, thin, and sharp, and serves for the attachment of the temporal fascia. The inferior, short, thick, and arched, has attached to it some fibres of the Masseter muscle. Its outer surface is convex and subcutaneous; its inner is concave, and also affords attachment to the Masse- ter. The extremity, broad and deeply serrated, articulates with the malar bone. The zygomatic process is connected to the temporal bone by three divisions, called its roots — an anterior, middle, and posterior. The anterior, which is short, but broad and strong, is directed inward, to terminate in a rounded eminence. THE TEMl^ORAL BONE SI the emiiientia arti.cularis. This eminence forms the front boundary of tlie glenoid fossa, and in the recent state is covered with cartilage. The middle root (posfglenoid process) forms the posterior boundary of the mandibular portion of the glenoid fossa; while the posterior root, which is strongly marked, runs from the upper border of the zygoma, in an arched direction, upward and backward, forming the posterior part of the temporal ridge (s2ipramastoid crest). At the junction of the anterior root with the zygoma is a projection, called the tubercle, for the attachment of the external lateral ligament of the mandible; and between Groove for middle temporal artery Incisura parietalis / Supramental \ Uwn,,lc ^'-'^^ OCCIPITO- Zygomatic proc Lnunentta articulans- Postglenoid pi ocess Glenoid cavity Glaserian fissure Tympavic plate STYLOGLOSSU Occipital groove External auditory process stvlohyoi'd Styloid process Fig. 47.— Left tempoiLiI bo Lateral surface. the anterior and middle roots is an oval depression, forming part (mandibular) of the glenoid fossa, for the reception of the condyle of the mandible. Between the posterior wall of the external auditory meatus and the posterior root of the zygoma is the area called the suprameatal triangle (Macewen), often marked by a spinous process (spine of Henle). The internal surface of the squamous portion (Fig. 48) is concave, presents numerous eminences and depressions for the convolutions of the cerebrum, and two well-marked grooves for the branches of the middle meningeal artery. Borders. — The superior border is thin, bevelled at the expense of the internal surface, so as to overlap the lower border of the parietal bone, forming the squamous suture. The anterior inferior border is thick, serrated, and bevelled, alternately at the expense of the inner and outer surfaces, for articulation with the greater wing of the sphenoid. The Petromastoid Portion {partes petrosa ct mastoidea). — The petromastoid portion consists of (a) a mastoid portion, the thick conical posterior part behind 82 SPECIAL ANATOMY OF THE SKELETON the external auditory meatus, and (6) a pyramidal portion named the petrous portion, which contains the internal ear and forms part of the floor of the cranial cavity- ^to-l bone ETmnentia arcuata. Foramen Tnastoidev/m I Aquaeductus vestihuli AqiULeductus cockleie Meatus acusticus intemus Fig. 48. — Left temporal bone. Inner surface. The Mastoid Portion {pars mastoidea). — The mastoid portion is situated at the posterior part of the bone (Figs. 47 and 49). Surfaces. Outer Surface. — ^The outer surface of the mastoid is rough, and gives attachment to the Occipitofrontalis and Retrahens aurem muscles. It is perforated by numerous foramina; one of these, of large size, situated at the posterior border of the bone, is termed the mastoid foramen {foramen mastoidemii) ; it transmits a vein from the lateral sinus and a small artery from the occipital to supply the dura. The position and size of this foramen are very variable. It is not always present; sometimes it is situated in the occipital bone or in the suture between the temporal and the occipital. The mastoid portion is con- tinued below into a conical projection, the mastoid process {processus niastoidevs), the size and form of which vary somewhat. This process serves for the attach- ment of the Sternomastoid, Splenius capitis, and the Trachelomastoid. On the inner side of the mastoid process is a deep groove, the digastric fossa {incisura mastoidea), for the attachment of the Digastric muscle; and, running parallel with it, but more internal, the occipital groove {sulcus a. occipitalis), which lodges the occipital artery {fossa mastoidea). Internal Surface. — The internal surface of the mastoid portion presents a deep, cu^^'ed groove, the sigmoid fossa, which lodges part of the lateral sinus; and into THE TEMPORAL BONE 83 it may be seen opening the mastoid foramen, which transmits an emissary vein from the lateral' sinus to the posterior auricular or occipital vein and a small artery, the mastoid branch of the occipital artery. A section of the mastoid process (Figs. 49 and 50) shows it to contain a number of cellular spaces, com- municating with one another, called the mastoid cells (cellulae mastoideae), which exhibit the greatest possible variety as to their size and number. At the upper and front part of the bone these cells are large and irregular, and contain air. They diminish in size toward the lower part of the bone; those situated at the apex of the mastoid process are quite small, representing spaces of cancellous bone, and usually containing marrow. Occasionally they are entirely absent, and Mastoid antrum Tegmen tympani Prominence of extl. semicircular canal Prominence of facial canal Fenestra ovalis Bristle in canal for Tensor tympani Processus cocldeariformis Bnstle in hiaivs Fallopii Mastoid cells Carotid canal Bony pa} t of Eustachian tube Promontory Bristle in pyramid Fenestra rotunda Sulcus tympanicus Bristle in stylomastoid foramen. Fig. 49. — Section through the petrous and mastoid portions of the temporal bone, showing the communication of the cavity of the tympanum wiith the mastoid antrum. the mastoid is solid throughout. In addition to these pneumatic cells may be seen a large, irregular cavity, the mastoid antrum (Figs. 49 and 50), situated at the upper and front part of the section. This must be distinguished from the mastoid cells, though it communicates with them. The mastoid cells are not developed until after puberty, but the mastoid antrum is almost as large at birth as it is in the adult bone. The antrum and cells are filled with air, and are lined with a prolongation of the mucous membrane of the tympanum, which extends into them through an opening, by which they communicate with the cavity of the tympanum. In consequence of the communication which exists between the tympanum and mastoid cells, inflammation of the hning membrane of the former cavity may easily travel backward to that of the antrum, leading to caries and necrosis of their walls and the risk of transference of the inflammation to the lateral sinus or encephalon. The Petrous Portion {pars petrosa [pyramid]) (Fig. 48). — The petrous portion is a pyramidal process of bone wedged in at the base of the skull between the 84 SPECIAL ANAT03IY OF THE SKELETON sphenoid and occipital bones. Its direction from without is inward, forward, and a little downward. It presents for examination an apex, four surfaces, and four borders, and contains in its interior the essential parts of the organ of hearing. Apex {apex pyramidis) . — The apex of the petrous portion, rough and uneven, is recei^'ed into the angular interval between the posterior border of the greater wing of the sphenoid and the basilar process of the occipital ; it presents the ante- rior or internal orifice of the carotid canal (foramen caroticum internum), and forms the posterior and external boundary of the foramen lacerum medium. Surfaces. — The superior surface of the petrous portion (Fig. 48) forms the posterior part of the middle fossa of the skull; it looks upward and forward. This surface is continuous with the squamous portion, to which it is united by PANIC CANfl Fig. 50. — Right temporal bone cut open to show the anterior surface of the petrous portion. X 2. (Spalteholz.) a suture, the petrosquamous suture, the remains of which are distinct even at a late period of life. The superior surface presents five points for examination: (1) An eminence (eminentia arcuata) near the centre, which indicates the situation of the superior semicircular canal. (2) In front and a little to the outer side of this eminence a depression indicating the position of the tympanum; here the layer of bone which separates the tympanum from the cranial cavity is extremely thin, and is known as the tegmen tympani. The tliin inferior extremity of this plate drops downward and presents itself at the inner extremity of the Glaserian fissure, there making the fissure double; the anterior slit is called the canal of Huguier, and it transmits the chorda tympani nerve. (3) A shallow groove, sometimes double, leading outward and backward to an oblique opening, the hiatus Fallopii (liiatus caualis facialis), for the passage of the greater petrosal nerve and the petrosal branch of the middle meningeal artery. (4) A smaller opening (apertura superior canaliculi tympanici), occasionally seen external to the latter, for the passage of the smaller petrosal nerve. (5) A shallow depression, the trigeminal depression {impressio THE TEMPORAL BONE 85 trigemini), for the reception of the Gasserian ganghon, is placed at the inner extremity of this surface. The anterior or tympanic surface (Fig. 50) is mostly hidden by the tympanic por- tion of the bone, and is best studied either in very young skulls or in bones which have been cut behind the tympanic membrane. This surface forms the postero- internal wall of the tympanum and presents an oval foramen (fenestra ve.stibiili) , into which the base of the stapes is fitted. Just above and external to the fenestra ovalis is the mastoid antrum, leading from the tympanum to the mastoid cells. The antrum is roofed by the tegmen tym- pani. Below and internal to the fenestra 2 3 ovalis is a rounded eminence, the promon- tory, formed by the first turn of the cochlea. Below the promontory is situated the fe- nestra rotunda, which is closed in the recent state by a membrane. Internal to the fenestra ovalis is the orifice of the canal which transmits the Tensor tympani; below this is the Eusta- chian canal for the passage of air from the pharynx to the tympanum. The two canals are separated by the processus coch- leariformis. On this surface, just above, then external to the oval foramen, be- tween it and the antrum, is the facial canal {canalis facialis). This canal is traversed by the facial nerve on its way to the stylomastoid foramen. The portion of the anterior surface not covered by the tympanic plate is occupied by the termina- tion of the carotid canal (foramin caroti- cum internum), the wall of w'hich is defi- cient in front. The posterior surface forms the front part of the posterior fossa of the skull, and is continuous with the inner surface of the mastoid portion of the bone. It presents three points for examination: (1) About its centre a large orifice, the meatus auditorius internus {meatus acusticus internus), through which pass the facial, auditory and intermediate nerves, and the auditory artery. The size of this meatus varies considerably; its margins are smooth and rounded, and it leads into a short canal, about one-third inch in length, which runs directly outward and is closed by a vertical plate, the lamina cribrosa, which is divided by a horizontal crest, the falciform crest {crista transversa), into two unequal portions (Fig. 51). Each portion is subdivided by a small vertical crest into two parts, named, respectively, anterior and posterior. The lower portion presents three sets of foramina : one group just below the pos- terior part of the crest, the area cribrosa media, consisting of a number of small openings for the nerves of the saccule; below and posterior to this, the foramen singulare, or opening for the nerve of the posterior semicircular canal; in front and below the first, the tractus spiralis foraminosus, consisting of a number of small, spirally arranged openings which terminate in the canalis centralis cochleae and transmit the nerve of the cochlea; the upper portion, that above the crista, pre- sents behind a series of small openings, the area cribrosa superior, for the passage of filaments of the utricle and superior and external semicircular canal, and, in front, one large opening, the commencement of the aquaeductus Fallopii {canalis facialis), for the passage of the facial nerve. (2) External and below the meatus Fig. 5i. — Diagrammatic view of the fundus ol the internal auditory meatus: 1, Falciform crest, 2, Anterior superior cribriform area, 2', Internal opening of the aquaeductus Fallopii, 3, Vertical crest which ssparates the anterior and posterior superior cribriform areas, 4. Posterior superior cribriform area, with (4') openings for nerve filaments. 5. Anterior inferior cribriform area, 5'. Spirally arranged, sieve-like openings for the nerves to the cochlea. 5". Opening of the cen- tral canal of the cochlea. 6, Crest which sepa- rates t':c anterior and posterior inferior cribriform areas. 7. Posterior inferior cribriform area. 7'. Orifices for the branches of the nerve to the saccule. 8. Foramen singulare of Morgagni, with the anterior portion of the canal which gives passage to the nerve to the posterior semicircular canal. (Testut.) 86 SPECIAL ANATOMY OF THE SKELETON auditorius is a small slit (apertura externa aquaedudus vestibuli), almost hidden by a thin plate of bone, leading to a canal, the aquaeductus vestibuli, which trans- mits the ductus endolymphaticus, together with a small artery and vein. (3) In the interval between these two openings, but above them, is an angular depression {fossa subarcuata.) , which lodges a process of the dura, and transmits a small vein into the cancellous tissue of the bone. In the child this depression is represented by a large fossa, the floccular fossa, which extends backward as a blind tunnel under the superior semicircular canal. The inferior or basilar surface (Fig. 52) is rough and irregular, and forms part of the base of the skull. Passing from the apex to the base, this surface presents the following points for examination: (1) A rough surface, quadrilateral in form, which serves partly for the attachment of the Levator palati and Tensor tympani STYLOPHARYNGEUS Sough quadrilateral surface. _ External opening 0/"*'%^ carotid canal. -^ Canal for Jacobson^s nerve. Aquaeductus cochleae. Canal for Arnold' a nerve. Jugular fossa. Vaginal process. Styloid process. Stylomastoid foramen. Jugular surface. Auricular fissure. Fig. 52. — Petrous portion of the left temporal bone. Inferior surface. muscles. (2) The large circular aperture of the carotid canal, the external carotid opening (foramen caroticum externum) ; the canal ascends at first vertically, and then, making a bend, runs horizontally forward and inward; it transmits the internal carotid artery and the carotid sympathetic plexus. Within the carotid canal are several openings {canaliculi caroticotympanici) , which transmit tympanic branches of the internal carotid artery and of the carotid sympathetic plexus. (3) The opening of the aquaeductus cochleae {apertura externa canaliculi cochleae), a small, triangular opening, lying on the inner side of the latter, close to the pos- terior border of the petrous portion; it transmits a vein from the cochlea, which joins the internal jugular. (4) External to these openings a deep depression, the jugular fossa {fossa jugularis) , which varies in depth and size in different skulls ; it lodges the lateral sinus, and, with a similar depression on the margin of the jugular process of the occipital bone, forms the foramen lacerum posterius or THE TEMPORAL BONE 87 jugular foramen. (5) A foramen which is the opening of a small canal (canaliai- lu^ tympanicus) for the passage of Jacobson's nerve (the tympanic branch of the glossopharyngeal) ; this foramen is seen in front of the bony ridge dividing the carotid canal from the jugular fossa. (6) A small foramen on the wall of the jugular fossa, for the passage of the auricular branch of the vagus {Arnold's) nerve. (7) Behind the jugular fossa a smooth, square-shaped facet, the jugular surface; it is covered with cartilage in the recent state, and articulates with the jugular process of the occipital bone. (S) The stylomastoid foramen {joravien stylomastoidevm) , a rather large orifice, placed between the styloid and mastoid processes; it is the termination of the facial canal, and transmits the facial nerve and stylomastoid artery. Borders. — The posterosuperior border {angulus superior pyramidis), the longest, is grooved for the superior petrosal sinus, and has attached to it the tentorium cerebelli ; at its inner extremity is a semilunar notch, upon which the fifth nerve lies. The postero-inferior border is intermediate in length between the postero- superior and antero-inferior. Its inner half is marked by a groove, which, when completed by its articulation with the occipital, forms the channel for the infe- rior petrosal sinus. Its outer half presents a deep excavation, the jugular fossa {fossa jugularis), which, with a similar notch on the occipital, forms the foramen lacerum posterius. A projecting eminence of bone occasionally stands out from the centre of the notch, and divides the foramen into two parts. The anterosuperior border is divided into two parts — an outer, joined to the squamous portion by a suture, the remains of which are distinct; an inner, free, articulating with the spinous process of the sphenoid. At the angle of junction of the petrous and squamous portions is seen the opening of the canalis viuscvlo- tuharius. The antero-inferior border is also divided into two parts — the outer portion is hidden from view by the tympanic plate. The inner part is free and forms the inferior lip of the carotid canal and gives attachment to the Tensor tympani and Levator palati muscles. The Tympanic Portion {pars tympanica). — The tympanic portion is placed in front of the anterior surface of the petrous portion; its most internal part is narrow and forms the anterior wall of the Eustachian canal. Externally it broadens out and has an antero-inferior and a posterosuperior surface, an anterosuperior, an antero-inferior, and an external border. The antero-inferior surface looks forward and downward and forms the posterior part of the glenoid fossa. The posterosuperior surface forms the anterior wall of the external audi- tory canal. From this surface there continues on to the anterior part of the mastoid portion a U-shaped process, with its concavity upward; this process shares in forming the inferior and posterior wall of the external auditory canal. Between the upturned part of the U-shaped process and the mastoid is a foramen (fissura tympanoviastoidea) transmitting the tympanic (auricular nerve of Arnold) branch of the vagus. In the concavity of this U-shaped process is a furrow {sidcus tympanicus), in which is placed the tympanic membrane {membrana tympani), like a mirror in its frame. The anterosuperior border fuses with the middle zygomatic root. Internally, this border is continuous with the upper border of the narrow part of the bone, and is separated from the squamous portion of the bone by the Glaserian fissure and a small part of the tegmen tympani. The antero-inferior border is thin internally; externally it divides into two laminse and ensheaths the root of the styloid process — hence the name vaginal process given to this border. The external border is free and rough, and has attached to it the cartilaginous part of the ear. The glenoid fossa {fossa mandibular is) is a considerable hollow formed in front SPECIAL ANATOMY OF THE SKELETON by the squamous part of the temporal, and behind by the tympanic bone. The part of the fossa formed by the squamous portion is covered with cartilage and articulates with the condyle of the mandible. The posterior part of the fossa lodges part of the parotid gland, and is formed by the antero-inferior surface of the tym- panic portion. The fossa is crossed by an oblique fissure, the petrotympanic fissure (Glaserian fissure), which leads into the tympanum, lodges the processus gracilis of the malleus, and transmits the tympanic branch of the internal maxillary artery. This fissure is closed externally; at its inner extremity it is separated from the squamous portion by the downgrowth of a process of bone from the tegmen tympani {^processus inferior tegmini tympani) of the petrous portion between the squamous and tympanic plates, making the fissure at its internal extremity a double one. The anterior limb is known as the canal of Huguier {canaliculus chordae tympani), and transmits the chorda tympani nerve. The external auditory meatus is bounded in front, below, and behind by the tympanic portion. The roof and the upper part of the posterior wall are formed by the squamous portion. The canal is about three-quarters of an inch (18 mm.) in length, and is directed inward and forward. In vertical section it is of oval outline, the long axis of the oval being vertical in the outer segment and oblique in the inner segment. The styloid process is a sharp spine of varying length. It projects downward and forward from the vaginal process of the tympanic part, and gives origin to the stylohyoid and stylomandibular ligaments, and to the Styloglossus, Stylo- pharyngeus, and Stylohyoid muscles. Structure. — The squamous portion is like that of the other cranial bones; the mastoid portion, cellular; and the petrous portion, dense and hard. Development (Fig. 53). — The temporal bone is developed from ten centres, exclusive of those for the internal ear and the ossicles — viz., one for the squamous portion, including the zygoma, one for the tympanic plate, six for the petrous and mastoid parts, and two for the styloid process. Just before the close of fetal life the temporal bone consists of four parts: (1) The squamozygomatic part, ossified in membrane from a single nucleus, 'n'hich appears at its lower part about the second month. (2) The tympanic plate, an imper- fect ring, in the concavity of which is a groove, the sulcus tympanicus, for the at- tachment of the circumference of tlie tym- panic membrane. This is also ossified from a single centre, which appears in membrane about the third month. (3) The petromas- toid part, which is developed from six centres, appearing in the cartilaginous ear capsule about the fifth or sixth month. Four of these are for the petrous portion and are placed around the labyrinth, and two are for the mastoid (Vrolik). According to Huxley, the centres are more numerous and are disposed so as to form three portions: The first por- tion includes most of the labyrinth (part of the cochlea, vestibule, superior semicircular canals, and the inner wall of the tympanic cavity) and a part of the petrous and mastoid. This portion he has named the pro-otic. The second portion — the opisthotic — consists of the rest of the petrous, and is thus made up: the floor of the tympanum and vestibule surrounds the caro- tid canal and the outer and lower portions of the cochlea and spread inward below the internal auditory meatus. The third portion — the pteriotic — roofs the antrum and tympanic cavity. The fourth portion — the epiotic — includes the remainder of the mastoid. The petromastoid is ossified in cartilage. (4) The styloid process is also ossified in cartilage from two centres — one for the base, which appears before birth, and is termed the tympanohyal ; the other, comprising JS' 6 for petrous and mastoid portioiis. 2' for styloid p Fio. 53. — Developmi THE SPHENOID BONE 89 the rest of the process, is named the stylohyal, and does not appear until after birth. Shortly before birth the tympanic plate unites with the squamous. Tlie petrous and mastoid unite at puberty, and in some slculls never becomes united. The subsequent changes in this bone are, that the tympanic plate e.\tends outward and backward, so as to form the meattis auditorius. (1) The extension of the tympanic plate, however, does not take place at an equal rate all around the circumference of the ring, but occurs most rapidly on its anterior and posterior portions, and these outgrowths meet and blend, and thus, for a time, there exists in the floor of the meatus a foramen, the foramen of Huschke; this foramen, usually closed by the fifth year, may persist throughout life. (2) The glenoid cavity is at first extremely shallow, and looks outward as well as downward; it becomes deeper and is ultimately directed downward. Its change in direc- tion is accounted for as follows: the part of the squamous temporal which supports it lies at first hclmc the level of the zygoma. As, however, the base of the skull increases in width, this lower part of the squama is directed horizontally inward to contribute to the middle fossa of the skull, and its surfaces therefore come to look upward'and downward. (3) The mastoid portion is at first quite flat, and the stylomastoid foramen and rudimentary styloid process lie immediately behind the tympanic ring. With the development of the air cells the outer part of the mastoid portion grows downward and forward to form the mastoid process, and the styloid process and stylomastoid foramen now come to lie on the under surface. The descent of the foramen is necessarily accompanied by a corresponding lengthening of the aqueduct of Fallopius. Squamozis portion Petrosqua7nous sutute Squamous portion Peirosquonnous suture Eimneniia arcuata, Fig. 54. — Temporal bone at birth. Outer aspect. Fossa subarcuaia Meatus acusticus internus Fig. 55. — Temporal bone at birth. Inner aspect. (4) The downward and forward growth of the mastoid process also pushes forward the tympanic plate, so that the portion of it which formed the original floor of the meatus and containing the foramen of Huschke is ultimately found in the anterior wall. (5) With the gradual increase in size of the petrous portion the floccular fossa or tunnel under the superior semicircular canal becomes filled 'up and almost obliterated. Articulations. — With Jive bones — occipital, parietal, sphenoid, mandible, and malar. Attachment of Muscles.— To fifteeen—to the squamous portion, the Temporal; to the zygoma, the Masseter; to the mastoid portion, the Occipitofrontalis, Sternomastoid, Splenius <;apitis, Trachelomastoid, Digastric, and Posterior auricular; to the styloid process, the Stylo- pharyngeus, Stylohyoid, and Styloglossus; and to the petrous portion, the Levator palati, Tensor tympani. Tensor palati, and Stapedius. The Sphenoid Bone (Os Sphenoidale). The sphenoid bone is situated at the anterior part of the base of the skull, articulating with all the other cerebral cranial bones, which it binds firmly and solidly together. In its form it somewhat resembles a bat with its wings extended ; and is divided into a central portion or body, two greater and two lesser wir.gs 90 SPECIAL ANATOMY OF THE SKELETON extending outward on each side of the body, and two processes — the pterygoid processes — which project from the lower part of this body. The Body {corpus). — The body is of large size and hollowed out in its interior so as to form a mere shell of bone. It presents for examination four surfaces — a superior, an inferior, an anterior, and a posterior. Surfaces. — The superior surface (Fig. 56) presents in front a prominent spine, the ethmoidal spine, for articulation with the cribriform plate of the ethmoid; behind this is a smooth surface having in the median line a slight longitudi- nal eminence, with a depression on each side for the lodgment of the olfac- tory lobes. This surface is bounded behind by a ridge, which forms the ante- rior border of a narrow, trans^'erse groove, the optic groove {sulnis chiasmatis) ; behind the ridge lies the optic chiasm ; the groove is continuous on each side with the optic foramen (foramen opticum) ,ioT the passage of the optic nerve and ophthal- mic artery. Behind the optic groove is a small eminence, olive-like in shape, the Middle chnoid process. Posterior dinoid process. Ethmoidal Optic foramen. Sphenoidal fissure Foramen rotundum. Foramen Vesalii: Foramen oval^: Foramen spinosum. Fig. 56 — Sphenoid bone. Superior surface. olivary eminence (tuberculum sellae) ; and still more posteriorly a deep depression, the sella turcica (fossa hypophyseos) , which lodges the circular sinus and the hypophysis. This fossa is perforated by numerous foramina, for the transmission of nutrient vessels into the substance of the bone. It is bounded in front by the olivary eminence, and also by two small processes, one on either side, called the middle clinoid processes (processus clinoidei medii), which are sometimes connected by a spiculum of bone to the anterior clinoid processes. It is bounded behind by a square-shaped plate of bone, the dorsum sellae, terminating at each superior angle in a tubercle, the posterior clinoid process (processus clinoideus posterior'). The size and form of these processes vary considerably in different individuals. They deepen the sella turcica, and serve for the attachment of prolongations from the tentorium cerebelli. The sides of the dorsum sellae are notched for the passage of the abducent nerves, and below present a sharp process, the petrosal process, which is joined to the apex of the petrous portion of the temporal bone, forming the inner boundary of the middle lacerated foramen. Behind this plate the bone presents a shallow depression, which slopes obliquely backward, and is continuous with the basilar groove of the occipital bone; it is called the clivus, and supports the upper part of the pons. On either side of the body is THE SPHENOID BONE 91 a broad, /-shaped groove, which lodges the internal carotid artery and the cavernous sinus. (See page 724 for other structures in the sinus.) It is called the cavernous groove {sulcus caroiicus). Along the outer margin of this groo\'e, at its posterior part, is a ridge of bone in the angle between the body and greater wing, called the lingula (lingula sphenoidalis). The posterior surface, quadrilateral in form, is joined to the basilar process of the occipital bone. During childhood these bones are separated by a layer of cartilage; but later (between the eighteenth and twenty-fifth years) this becomes ossified from above downward, and the two bones then form one piece. The anterior surface (Fig. 57) presents, in the median line, a vertical ridge of bone, the ethmoidal crest {crista sphenoidalis), which articulates in front with the perpendicular plate of the ethmoid, forming part of the septum of the nose (Fig. 57). On either side of it are irregular openings leading into the sphenoidal sinuses (sinus sphenoidales), which are two large, irregular cavities of the hollowed out interior of the body of the sphenoid bone, and separated more or less completely from each other by a perpendicular bony septum {septum sinuuvi sphenoidalium). Occasionally they extend into the basilar process of the occipital nearly as far as the foramen magnum. Their form and size vary considerably; they are seldom Flerygoid ridge Jiiternal pterygoid plate. Hamv.lar process. symmetrical, and are often partially subdivided by irregular, osseous laminae. One or both sinuses may be absent. The septum is seldom quite vertical, being commonly bent to one or the other side. These sinuses do not exist in very young children, but appear, according to Laurent, in the seventh year. After once appearing they increase in size as age advances. They are partially closed, in front and below, by two thin, curved plates of bone, the sphenoidal turbinated processes {conchae sphenoidales). At the upper part of each is a round opening {aperttira sinus sphenoidalis), by which the sinus communicates with the upper and back part of the nose, and occasionally with the posterior ethmoidal cells or sinuses. The lateral margins of the surface present a serrated edge, which articulates with the os planum of the ethmoid, completing the posterior ethmoidal cells; the lower margin, also rough and serrated, articulates with' the orbital process of the palate bone. The inferior surface presents, in the middle line, a triangular spine, the rostrum 92 SPECIAL ANA TOMV OF THE SKELETON (rostrum sphenoidalis), which is continuous with the sphenoidal crest on the anterior surface, and is received into a deep fissure between the altie of the vomer. On each side may be seen a projecting lamina of bone, the vaginal process (pro- cessus vaginalis), which runs horizontally inward from near the base of the ptery- goid process and articulates with the edges of the vomer. Close to the root of the pterygoid process is a groove (sulcus plerygopalatinus), formed into a com- plete canal when articulated with the sphenoidal process of the palate bone; it is called the pterygopalatine canal, and transmits the pterygopalatine vessels and a pharyngeal branch of the sphenopalatine ganglion. The Greater or Temporal Wings {alae magna) . — The greater wings are two strong processes of bone which arise from the sides of the body, and are curved in a direction upward, outward, and backward, each being prolonged behind into a sharp-pointed extremity, the alar, or sphenoidal spine (spina angidaris). Each wing presents three surfaces and a circumference. Surfaces. — The superior surface (fades cerebralis) (Fig. 56) forms part of the middle fossa of the skull; it is deeply concave, and presents eminences and depressions for the convolutions of the cerebrum. At its anterior and internal part is seen a circular aperture, the foramen rotundum, for the transmission of the second division of the trigeminal nerve. Behind and external to this is a large oval foramen, the foramen ovale, for the transmission of the third division of the trigeminal nerve, the small meningeal artery, and sometimes the small petrosal nerve. At the inner side of the foramen ovale a small aperture may occasionally be seen opposite the root of the pterygoid process; it is the foramen Vesalii, transmitting a small vein. In the posterior angle, near to the spine of the sphenoid, is a short canal, sometimes double, the foramen spinosum, which transmits the middle meningeal artery and the meningeal branch of the superior maxillary nerve. Just to the inner side of the foramen spinosum a minute fora- men (canaliculus innominatum) is occasionally found, for the passage of the small petrosal nerve. The external surface (Fig. 57) is convex and divided by a transverse ridge, the pterygoid ridge (crista infratemporalis), into two portions. The superior or larger, convex from above downward, concave from before backward, enters into the formation of the temporal fossa, and gives attachment to part of the Temporal muscle. The inferior portion, smaller in size and concave, enters into the formation of the zygomatic fossa, and affords attachment to the External pterygoid muscle. It presents, at its posterior part, a sharp-pointed eminence of bone, the spine, to which are connected the internal lateral ligament of the mandible and the Tensor palati muscle. At its inner and anterior extremity is a triangular spine of bone, which serves to increase the extent of origin of the External pterygoid muscle. The anterior surface is divided into two parts, the orbital surface above and the sphenomaxillary below. The orbital surface is quadrilateral in form; it looks inward and forward, and assists in forming the outer wall of the orbit. It is bounded above by a serrated edge for articulation with the frontal bone. Internally this edge is sharp and free and forms the lower boundary of the sphenoidal fissure. At about the centre of the free part of this border a little tubercle projects, giving origin to one head of the External rectus muscle of the eyeball. At its outer part is a notch for the transmission of a recurrent branch of the lacrimal artery. The outer border is serrated for articulation with the malar bone. The lower border is rounded and enters into the formation of the sphenomaxillary fissure. This border separates the orbital surface above from the sphenomaxillary portion below. This latter portion is situated just above the pterygoid process and helps to form the posterior wall of the sphenomaxillary THE SPHENOID BONE 93 fossa in the articulated skull and exhibits the anterior extremity of the foramen rotundum. Circumference (Fig. 56). — Commencing from behind, that portion of the circum- ference of the body of the sphenoid to the spine is serrated and articulates by its outer half with the inner part of the antero-superior border of the petrous portion of the temporal bone, while the inner half forms the anterior boundary- of the mid- dle lacerated formaen, and presents the posterior aperture of the Vidian canal {canalis pterygoideus) , for the passage of the Vidian nerve and artery. In front of the spine, the circumference of the greater wing presents a serrated edge, bevelled at the expense of the inner table below and of the external above, which articulates with the squamous portion of the temporal bone. At the tip of the greater wing a triangular portion is seen, bevelled at the expense of the internal surface, for articulation with the anterior inferior angle of the parietal bone. Internal to this is a triangular, serrated surface, for articulation with the frontal Posterior view. bone ; this surface is continuous internally with the sharp inner edge of the orbital plate, which assists in the formation of the sphenoidal fissure, and externally with the serrated margin for articulation with the malar bone. The Lesser or Orbital Wings {alae parvae). — The lesser wings are two thin triangular plates of bone which arise, one on each side, from the upper part of the lateral surface of the body of the sphenoid, and, projecting transversely outward, terminate in a sharp point (Fig. 56). The superior surface of each forms part of the anterior fossa of the skull, is smooth, flat, broader internally than externally, and supports part of the frontal lobe of the cerebrum. The inferior surface forms the back part of the roof of the orbit and the upper boundary of the sphenoi- dal fissure, or foramen lacerum anterius. This fissure is of a triangular form, and leads from the cavity of the cranium into the orbit. It transmits the third, the fourth, the three branches of the ophthalmic di^■ision of the trigeminal, the abducent nerve, some filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lacri- mal artery to the dura and the ophthalmic vein. The anterior border of the lesser 94 SPECIAL ANATOMY OF THE SKELETON wing is serrated for articulation with the frontal bone ; the posterior border, smooth and rounded, is received into the sylvian fissure of the cerebrum. The inner extremity of this border forms the anterior clinoid process {processus dinoideus anterior). The lesser wing is connected to the side of the body by two roots, the upper thin and flat, the lower thicker, obliquely directed, and presenting on its outer side, near its junction with the body, a small tubercle, for the attachment of the common tendon of origin of three of the Extrinsic muscles of the eye. Be- tween the two roots is the optic foramen, for the transmission of the optic nerve and ophthalmic artery. The Pterygoid Processes {-processus pterygoidei). — ^The pterygoid processes, one on each side, descend perpendicularly from the place where the body and greater wing unite (Fig. 59). Each process consists of an external and an in- ternal plate, which are joined together by their anterior borders above, but are separated below, leaving an angular cleft, the pterygoid notch, in which the pterygoid tuberosity of the palate bone is received. The two plates diverge from each other from their line of connection in front, so as to form in conjunc- tion with the tuberosity of the palate bone a V-shaped fossa, the pterygoid fossa. The external pterygoid plate {laviina lateralis processus pterygoidei) is broad and Fig. 59. — Sphenoid bone. Posterior surface. thin, turned a little outward, and, by its outer surface, forms part of the inner wall of the zygomatic fossa, giving attachment to the External pterygoid; its inner sur- face forms part of the pterygoid fossa, and gives attachment to the Internal pterygoid. The posterior border of this plate frequently has one or more rough projections, to one of which is attached the pterygospinous ligament, when this is present. The internal pterygoid plate {lamina medialis processus pterygoidei) is much narrower and longer, curving outward, at its extremity, into a hook-like process of bone, the hamular process {haviulii-s pterygoideus) , around which turns the tendon of the Tensor palati muscle. The outer surface of this plate forms part of the pterygoid fossa, the inner surface forming the outer boundary of the posterior aperture of the nares. The posterior border of this plate gives attach- ment to the phar.yngeal aponeurosis throughout its entire length. The Superior constrictor muscle of the pharynx arises from its lower half. Projecting back- ward from the middle of this border is a spine {processus tuharius), which supports the pharyngeal end of the Eustachian tube. Above this the border divides into two lips; the space between is the scaphoid fossa ( fossa scaphoidea). In this fossa arises the Tensor palati muscle. The anterior margin articulates with the poste- rior border of the perpendicular plate of the palate bone. Superiorly, the internal pterygoid plate has a thin lamina of bone, the vaginal THE SPHENOID BOXE 95 process {processus vagiiialis), which runs inward on the under surface of the body of the sphenoid nearly to tlie rostrum. In the groove between the two in the articu- lated skull are seen the alae of the vomer. On the under surface of the vaginal process is a groove (svlciis pterygopalatimos), which in the articulated skull is con- verted into the pterygopalatal canal by union with the sphenoidal process of the palate bone. At the junction of the vaginal process and the inner plate is the pterygoid tubercle, just above which is the posterior opening of the Mdian canal. The anterior surface of the pterygoid process is quite broad at its base, and forms the chief part of the posterior wall of the sphenomaxillary fossa. The Sphenoidal Turbinated Processes (conchae sphenoidales). — The sphe- noidal turbinated processes are two thin curved plates of bone, which exist as separate pieces until puberty, and occasionally are not joined to the sphenoid in the adult. They are situated at the anterior part of the body of the sphe- noid, an aperture (aperiura sinus sjjhcnoidalis) of \ariable size being left in the anterior wall of each, through which the sphenoidal sinuses open into the nasal fossse. They are irregular in form and taper to a point behind, being broader and thinner in front. Their upper surface, which looks toward the cavity of the sinus, is concave; their under surface convex. Each bone articulates in front with the ethmoid, externally with the palate; its pointed posterior extremity is placed above the vomer, and is received between the root of the pterygoid process on the outer side and the rostrum of the sphenoid on the inner.' Development. — Up to about the eighth month of fetal life the sphenoid bone consists of two distinct parts — a posterior or postsphenoid part, which comprises the sella turcica, the greater wings, and the pterygoid processes; and an anterior or presphenoid part, to which the anterior part of the body and lesser wings belong. It is developed (ram fourteen centres — eight for the postsphenoid division and six for the presphenoid. All parts except the internal pterygoid plates have an intracartilaginous origin. Postsphenoid Division. — The first nuclei to appear are those for the greater wings (alt- sphenoids). They make their appearance between the foramen rotundum and foramen ovale about the eighth week, and from them the external pterygoid plates are also formed. Soon after, the nuclei for the posterior part of the body appear, one on either side of the sella turcica, and become blended together aljout the middle of fetal life. About the ninth or tenth week the centre for the internal pterygoid plate appears, followed by the centre for the hamiilar process; the centre for the lingula appears during the fourth month, and soon joins the rest of the body. The internal and external pterygoid plates become joined at about the sixth month. one for each two for anterior lesser wing, part of body. one for each tntemat - pterygoid plate one for /»' «««'' hngula v each greater wing and external ptery- [_goid plate, one/or each Sphenoidal turbinated process. Fig. 61. — Sphenoid bone at birth. Posterior aspect. Presphenoid Division. — The first nuclei to appear are those for the lesser wings (orbito- phenoids). They make their appearance about the ninth week, at the outer borders of the optic * -A. small portion of the sphenoidal turbinated process sometimes enters into the formation of the inner wall of the orbit, between the os planum of the ethmoid in front, the orbital plate of the palate below, and the frontal above. — Cleland, Roy. Soo. Trans., 1862. 96 SPECIAL ANATOMY OF THE SKELETON foramina. A second pair of nuclei appears on the inner side of the foramina shortly after, and, becoming united, form the front part of the body of the bone. The remaining two centres for the sphenoidal turbinated processes make their appearance about the fifth month. At birth they consist of small triangular laminse, and it is not until the third year that they become hollowed out and cone-shaped. About the fourth j-ear they become fused with the lateral masses of the ethmoid, and between the ninth and twelfth years they unite with the sphenoid bone. The presphenoid is united to the body of the postsphenoid about the eighth month, so that at birth the bone consists of three pieces — viz., the body in the centre, and on each side the great wings with the pterygoid processes. The lesser wings become joined to the body at about the time of birth. During the first year after birth the greater wings and l:>ody are united. From the ninth to the twelfth year the turbinated processes are partially united to the sphenoid, their junction being complete by the twentieth year. Lastly, the sphenoid joins the occipital from the eighteenth to the twenty-fifth year. Articulations. — The sphenoid articulates with all the bones of the cerebral cranium, and five pf the face — the two malar, the two palate, and vomer; the exact extent of articulation with each bone is shown in the accompanying figures.' Attachment of Muscles. — To elemn pairs — the Temporal, External pterygoid, Internal pterygoid, Superior constrictor, Tensor palati, Levator palpebrae, Superior oblique, Superior rectus. Internal rectus, Inferior rectus. External rectus. The Ethmoid Bone (Os Ethmoidale) . The ethmoid is an exceedingly light, spongy bone, of a cubical form, situated at the anterior part of the base of the cranium proper, between the two orbits at the root of the nose, and contributing to the formation of each of these cavi- ties. It consists of four parts — a horizontal plate, which forms part of the base of the cranium proper; a perpendicular plate, which forms part of the septum of the nose; and two lateral masses, containing a number of spaces. Slit for nasal nerv& Anterior ethmoidal cells Vertical plate {lamina perpendicularis) Unciform process Fig. 62. — Ethmoid bone. Outer surface of right lateral mass. (Enlarged.) The Horizontal Lamina, or Cribriform Plate {lamina cribrosa) (Fig. 62), forms part of the anterior fossa of the base of the skull, and is received into the eth- moid notch of the frontal bone between the two orbital plates. Projecting up- ward from the middle line of this plate is a thick, smooth, triangular process of bone, the crista galli. Its base joins the cribriform plate. Its posterior border, long, thin, and slightly curved, serves for the attachment of the falx cerebri. Its anterior border, short and thick, articulates with the frontal bone, and presents two small projecting alse {'processus alares), which are received into corresponding depressions in the frontal, completing the foramen cecum behind. Its sides are smooth and sometimes bulging, in which case it is found to enclose a small sinus. On each side of the crista galli the cribriform plate is narrow and deeply grooved, to support the bulb of the olfactory tract, and is perforated by foramina for the passage of the olfactory nerves. These foramina are arranged in three rows: The innermost, which are the largest and least numerous, are lost in grooves on the lit also sometimes articulates with the tuberosity of the maxilla. THE ETHMOID BONE 97 upper part of the septum ; the foramina of the outer row are continued on to the surface of the superior turbinated process. The foramina of the middle row are the smallest; they perforate the bone and transmit nerves to the roof of the nose. At the front part of the cribriform plate, on each side of the crista galli, is a small fissure, which transmits the nasal branch of the ophthalmic nerve; and at its posterior part a triangular notch, which receives the ethmoidal spine of the sphenoid. Cnsta galh Lamina crihrosa Lateral 7ii.ass Superior turhina ted process Superior meatus Piocessus uncinaius Biferior turbinated process Perpendicular plate Fig. 63. — Ethmoid bone from behind. Fig. 64. — Ethmoid bo (Spalteholz.) icitli EtlimoKfa/ The Vertical Plate {lamina perpendicular is) (Fig. 65) is a thin, flattened, lamella of bone, which descends from the under surface of the cribriform plate, and assists in forming the septum of the nose. It is much thinner in the middle than at the circumference, and is generally deflected a little to one side. Its anterior border articulates with the nasal spine of the frontal bone and crest of the nasal bones. Its pos- terior border, divided into two parts, articulates by its upper half with the sphenoidal crest of the sphenoid, by its lower half with the vomer. The inferior border serves for the attachment of the triangular cartilage of the nose. On each side of the perpendicular plate numerous grooves are seen, leading from the foramina on the cribriform plate; they lodge filaments of the olfactory nerves. The Lateral Mass, or Labyrinth (labyrinthus ethmoidalis), of the ethmoid consists of a number of thin-walled cellular cavities, the ethmoidal cells (celhdae ethvioidales), interposed between two vertical plates of bone, the outer one of which forms part of the orbit, and the inner one part of the outer wall of the nasal fossa Fig. 65. — Perpendicula ■ plate of ethmoid (enlarged) , showr the right lateral mass. 98 SPECIAL ANA TO MY OF THE SKELETON Fig. 66. — Ethmoid bone. Inner surface of right lateral of the corresponding side. There are two lateral masses, one on each side. The ethmoidal cells are not present at birth, but appear during the fifth year. In the disarticulated bone many of these cells appear to be broken ; but when the bones are articulated they are closed in at every part, except where they open into the nasal fossae. The upper surface of each lateral mass presents a number of apparently half-broken cellular spaces; these are closed in, when articulated, by the edges of the ethmoidal notch of the frontal bone. Crossing this surface are two grooves on each side, converted into canals by articulation with the frontal; they are the anterior and posterior ethmoidal canals (canalis ethmoidale anterius et posterius), and open on the inner wall of the orbit. The anterior transmits the nasal nerve and the anterior ethmoidal vessels; the posterior transmits the posterior ethmoidal A'essels. . The posterior surface also presents large irregular cellular cavities, which are closed in by articulation with the sphenoidal turbinated processes and the orbi- tal process of the palate. The cells at the anterior surface are completed by the lacrimal bone and nasal process of the maxilla, and those below also by the maxilla. The outer surface of each lateral mass consists chiefly of a thin, smooth, oblong plate of bone, called the OS planum (lamina papyracea); it forms part of the inner wall of the orbit, and articulates, above, with the orbital plate of the frontal; helow, with the maxilla; in front, with the lacrimal; and behind, with the sphenoid .and orbital process of the palate. In front of the os planum are found the anterior ethmoidal cells, which are completed by the lacrimal bone and the nasal process of the maxilla. From the inferior part of each lateral mass, immediately beneath the os planum, there projects downward and back'ward an irregular hook-like lamina of bone, called the unciform process (processus uncinatus); it serves to close in the upper part of the orifice of the antrum (Fig. 71), and articulates with the ethmoidal process of the turbinated bone. It is often broken in disarticulating the bones. The inner surface of each lateral mass forms part of the outer wall of the nasal fossa of the corresponding side. It is formed of a thin lamella of bone, which descends from the under surface of the cribriform plate, and terminates below in a free, convoluted margin, the middle turbinated process (concha nasalis media). The whole of this surface is rough and marked above by numerous grooves, which run nearly vertically downward from the cribriform plate; they lodge branches of the olfactory nerve, which are distributed on the mucous membrane covering the bone. The back part of this surface is subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate of bone, the superior turbinated process (concha nasalis superior). By means of an orifice at the upper part of this fissure the posterior ethmoidal cells open into the superior meatus. Below, and in front of the superior meatus, is seen the convex surface of the middle turbinated process. It extends along the whole length of the inner surface of each lateral mass. The middle of its lower margin is free and thick. The anterior portion articulates with the superior turbinated crest of the nasal process of the maxilla, and the posterior portion articulates with the superior tur- binated crest of the maxilla and palate bone. Its concavity, directed outward, assists in forming the middle meatus. It is by a large orifice at the upper and THE NASAL BONES 99 front part of the middle meatus that the anterior ethmoidal cells, and through them the frontal sinuses, communicate with the nose by means of a funnel- shaped canal, the infundibulum {infundihulum ethnoidale) (Fig. 62). The cell- ular cavities of each lateral mass, thus walled in by the os planum in the outer side and by the other bones already mentioned, are divided by a thin trans- verse bony partition into two sets, which do not communicate with each other; they are termed the anterior and posterior ethmoidal sinuses. The former, more numerous, communicate with the frontal sinuses above and the middle meatus; below by means of the infundibulum; the posterior, less numerous, open into the superior meatus and communicate (occasionally) with the sphenoidal sinuses. In some cases the ethmoidal sinuses communicate with the maxillary sinus. In some cases the os planum never develops, and the ethmoidal sinuses are separated from the orbit merely by membrane. Development. — The ethmoid is developed in cartilage from three centres — one for the per- pendicular lamella, and one for each lateral mass. The lateral masses are first developed, ossific granules making their appearance in the os planum between the fourth and fifth months of fetal life, and extending into the turbinated processes. At birth the bone consists of the two lateral masses, which are small and poorly developed. During the first year after birth the perpendicular plate and crista galli begin to ossify, from a single centre, and become joined to the lateral masses about the beginning of the second year. The cribriform plate is ossified partly from the perpendicular plate and partly from the lateral masses. The formation of the ethmoidal cells, which completes the bone, does not commence until the end of the fourth year. Articulations. — With thirteen bones — the sphenoid, the frontal, and eleven of the face, the two nasal, two palate, two maxillse, two lacrimal, two turbinated, and the vomer. No muscles are attached to this bone. THE BONES OF THE FACE (OSSA FACIEI). The facial bones are fourteen in number — viz., the Two nasal. Two palate. Two maxillse. Two turbinated. Two lacrimal. Vomer. Two malar. Mandible. The Nasal Bones (Ossa Nasalia). The nasal bones are two small oblong bones, varying in size and form in dif- ferent individuals; they are placed side by side at the middle and upper part of the face, forming by their junction "the bridge" of the nose (Fig. 67). Each bone presents for examination two surfaces and four borders. Surfaces. — The outer surface is concave from abo\'e downward, convex from side to side; it is covered by the Pyramidalis and Compressor nasi muscles. It is marked by numerous small arterial furrows, and perforated about its centre by a foramen {foramen nasale), sometimes double, for the transmission of a sinall vein. The inner sm'face is concave from side to side, convex from above downward, in which direction it is traversed by a longitudinal groove (sometimes a canal), for the passage of a branch of the nasal nerve. Borders. — The superior border is narrow, thick, and serrated, for articulation with the nasal notch of the frontal bone. The inferior border is broad, thin, sharp, inclined obliquely downward, out- ward, and backward, and serves for the attachment of the lateral cartilage of the nose. This border presents, about its middle, a notch, through which passes 100 SPECIAL ANATOMY OF THE SKELETON the branch of the nasal nerve above referred to, and is prolonged at its inner extremity into a sharp spine, which, when articulated with the opposite bone, forms the nasal angle. The external border is serrated, bevelled at the expense of the internal surface above and of the external below, to articulate with the nasal process of the maxilla. Mic. with malar. Groove for nasal nerve Inner Surface. Fig. 69.— Left nasal bone The internal border, thicker above than below, articulates with its fellow of the opposite side, and is prolonged behind into a vertical crest, which forms part of the septum of the nose; this crest articulates from above downward with the nasal spine of the frontal, the per- pendicular plate of the eth- moid, and the triangular septal cartilage of the nose. Development. — Of intramembranous origin and from one centre for each bone, which appears about the eighth week. Articulations. — With four bones — two of the cerebral cranium, the frontal and ethmoid, and two of the face, the opposite nasal and the maxilla. The nasal bone has no muscles attached to it. The Maxillae (Upper Jaw). The maxillae are the largest bones of the face, excepting the mandible, and form, by their union, the whole of the upper jaw. Each maxilla assists in the formation of the walls of three cavities, the roof of the mouth, the floor and outer wall of the nasal fossae, and the floor of the orbit, and also enters into the THE MAXILLA 101 formation of two fossae, the zygomatic and sphenomaxillary, and two fissures, the sphenomaxillary and pterygomaxillary. The bone presents for examination a body and four processes — malar, nasal, alveolar, and palatal. The Body (corpus maxillae). — The body is somewhat cuboid and is hollowed out in its interior to form a large cavity, the antrum of Highmore {sinus maxillaris). Its surfaces are four — an external or facial, a posterior or zygomatic, a superior or orbital, and an internal or nasal. Surfaces. — The facial surface (fades anterior) (Fig. 70) is directed forward and outward. It presents at its lower part a series of eminences corresponding to the position of the anterior five teeth. Just above those for the incisor teeth is a depression, the incisive fossa, which gives origin to the Depressor alae nasi ; and below it to the alveolar border is attached a slip of the Orbicularis oris. Above and a little external to it the Compressor naris arises. More external is another depression, the canine fossa (fossa canina), larger and deeper than the incisive fossa, from which it is separated by a vertical ridge, the canine eminence, corresponding to the socket of the canine tooth. The canine fossa gives origin to the Levator anguli oris. Above the canine fossa is the infraorbital foramen {foramen infraorbiiale), Outer Surface. Incisive fossa. Posterior dental canals. Maxillary tuberosity. Fig. 70. — Left maxilla. Outer surface. the termination of the infraorbital canal; it transmits the infraorbital vessels and nerve. Sometimes the infraorbital canal opens by two, very rarely by three, orifices on the face. Above the infraorbital foramen is the margin of the orbit {margo infraorhitalis), which affords partial attachment to the Levator labii superioris. To the sharp margin of bone which bounds this surface in front and separates it from the internal surface is attached the Dilatator naris posterior. The posterior (fades infratem-poralis) or zygomatic surface is convex, directed backward and outward, and forms part of the zygomatic fossa. It is sepa- rated from the facial surface by a strong ridge of bone, the malar process, which extends upward from the socket of the second molar tooth. It presents about its centre several apertures leading to canals in the substance of the bone; 102 SPECIAL ANATOMY OF THE SKELETON they are termed the posterior dental canals {foramina aheolaria), and transmit the posterior dental vessels and nerves. At the lower part of this surface is a rounded eminence, the maxillary tuberosity {tuber maxillare), especially prominent after the growth of the wisdom tooth, rough on its inner side for articulation with the tuberosity of the palate bone, and sometimes with the external pterygoid plate. It gives attachment to a few fibres of origin of the Internal pterygoid muscle. Immediately above this is a smooth surface, which forms the anterior boundary of the sphenomaxillary fossa; it presents a groove which, running ob- liquely downward, is converted into a canal by articulation with the palate bone, forming the posterior palatine or palatomaxillary canal for the descending palatine artery and great palatine nerve. The posterior border forms the anterior bound- ary of the pterygomaxillary fissure. The superior or orbital siu-face {fades orbitalis) is thin, smooth, triangular, and forms part of the floor of the orbit. It is bounded internally by an irregular margin, which in front presents a notch, the lacrimal notch {incisura lacrimalis), which receives the lacrimal bone; in the middle it articulates with the os planum of the ethmoid, and behind with the orbital process of the palate bone; bounded ex- ternally by a smooth, rounded edge which enters into the formation of the spheno- maxillary fissure, and which sometimes articulates at its anterior extremity with the orbital plate of the sphenoid; bounded in front by part of the circumference of the orbit, which is continuous on the inner side with the nasal, on the outer side with the malar process. Along the middle line of the orbital surface is a deep groove, the infraorbital groove {sidcus infraorbitalis) , for the passage of the infra- orbital vessels and nerve. The groove commences at the middle of the outer border of this surface, and, passing forward, terminates in a canal, which subdi- vides into two branches. One of the canals, the infraorbital canal, opens just below the margin of the orbit; the other, which is smaller, runs downward in the sub- stance of the anterior wall of the antrum; it is called the anterior dental canal, and transmits the anterior dental vessels and nerve to the front teeth of the maxilla. From the back part of the infraorbital canal a second small canal is sometimes given off, which runs downward in the outer wall of the antrum, and conveys the middle dental nerve to the biscupid teeth. Occasionally this canal is a branch of the anterior dental canal. At the inner and fore part of the orbital surface, just external to the lacrimal groove for the nasal duct, is a depression which gives origin to the Inferior oblique muscle of the eye. The internal surface (Fig. 71) is unequally divided into two parts by a horizontal projection of bone, the palatal process {processus palatinus); the portion above the palatal process is known as the nasal surface {fades nasalis). It forms part of the outer wall of the nasal fossa. Below the palate process is the cavity of the mouth. The superior division of the nasal surface presents a large, irregu- lar opening {hiatus maxillaris), leading into the maxillary sinus. At the upper border of this aperture are numerous broken cellular cavities, which in the articu- lated skull are closed by the ethmoid and lacrimal bones. Below the aperture is a smooth concavity which forms part of the inferior meatus of the nasal fossa, and behind it is a rough surface which articulates with the perpendicular plate of the palate bone, traversed by a groove which, commencing near the middle of the posterior border, runs obliquely downward and forward, and forms, when com- pleted by its articulation with the palate bone, the posterior palatine or palato- maxillary canal. In front of the opening of the antrum is a deep groove, con- verted into a canal {canalis nasolacrimalis) by the lacrimal and turbinated bones. The groove is called the lacrimal groove {sulcus lacrimalis), and lodges the nasal duct. More anteriorly is a well-marked rough ridge, the inferior turbinated crest {crista conchalis), for articulation with the turbinated bone. The shallow con- THE MAXILLJE 103 cavity above this ridge forms part of the middle meatus of the nose, while that below it forms part of the inferior meatus. The portion of this surface below the palatal process is concave, rough, and uneven, and perforated by numerous small foramina for the passage of nutrient vessels. It enters into the formation of the roof of the mouth. The antrum of Highmore (sinus maxillaris) is a pyramidal cavity hollowed out of the body of the maxilla. It varies much in size. It is in most cases a large cavity, but in some is very small. The apex of the antrum, directed outward, is formed by the malar process ; its base by the outer wall of the nose. Its walls are everywhere exceedingly thin, and correspond to the orbital, facial, and zygo- matic surfaces of the body of the bone. The floor is formed by the alveolar process of the maxilla. The roof corresponds to the orbital plate. Its inner wall, or base, presents, in the disarticulated bone, a large, irregular aperture (hiatus maxil- laris), which communicates with the nasal fossa. The margins of this aperture are thin and ragged, and the aperture itself in the articulated skull is much con- ■^jSi-/''-o^ £on^ partially closinff orifice of antrum marked in outline Ethmoid. Turbinated. Palate. Anterior nasal spine. Bristle passed through anterior palatine candl. ^"-^W^iwV^. Fig. 71. — Left maxilla. Internal surface. tracted by its articulation with the ethmoid above, the turbinated bone below, and the palate bone behind.^ In the articulated skull this cavity communicates with the middle meatus of the nasal cavity, generally by two small apertures left between the above-mentioned bones. In the recent state usually only one small opening exists, near the upper part of the cavity, sufficiently large to admit the end of a probe, the other being closed by the lining membrane of the sinus. Crossing the cavity of the antrum are often seen several projecting laminse of bone, similar to those seen in the sinuses of the cranium; on its posterior wall are the posterior dental canals, transmitting the posterior dental vessels and nerves to the teeth. Projecting into the floor are several conical processes, corresponding ' In some cases, at any rate, the lacrimal bone encroacfies 'slightly on the anterior superior portion of the opening, and assists in forming the inner wall of the antrum. 104 SPECIAL ANA TOMY OF THE SKELETON to the roots of the first and second molar teeth; in some cases the floor is per- forated by the teeth in this situation; projecting into the antrum from the roof is a ridge corresponding to the infraorbital canal. The Processes. — The malar process (^processus zygomaticus) is a rough, trian- gular eminence, situated at the angle of separation of the facial from the zygo- matic surface. In front it is concave, forming part of the facial surface; behind it is also concave, and forms part of the zygomatic fossa; above it is rough and serrated for articulation with the malar bone; while below a prominent ridge marks the division between the facial and zygomatic surfaces. A small part of the Masseter muscle arises from this process. The nasal process (processus frontalis) is a strong, triangular plate of bone, which projects upward, inward, and backward by the side of the nose, forming part of its lateral boundary. Its external surface is concave, smooth, perforated by numerous foramina, andgivesattachment totheLevatorlabiisuperiorisalaecjue nasi, the Orbicularis palpebrarum, and the Tendo oculi. Its infernal surface forms part of the outer wall of the nasal fossa; at its upper part it presents a rough, uneven surface, which articulates with the ethmoid bone, closing in the anterior ethmoidal cells; below this is a transverse ridge, the superior turbinated crest (crista ethmoi- dalis), for articulation with the middle turbinated process of the ethmoid; below the crest is a shallow, smooth concavity which forms part of the middle meatus; below this again is the inferior turbinated crest (already described), where the pro- cess joins the body of the bone. Its upper border articulates with the nasal notch of the frontal bone. The anterior border of the nasal process is thin, directed obliquely downward and forward, and presents a serrated edge for articulation with the nasal bone; its posterior border is thick, and hollowed into a groove, the lacrimal groove, for the nasal duct; of the two margins of this groove, the inner one articu- lates with the lacrimal bone, the outer one forms part of the circumference of the orbit. Just where the latter joins the orbital surface is a small tubercle, the lacrimal tubercle, which articulates with the hamular process of the lacrimal bone. The lacrimal groove in the articulated skull is converted into a canal {canalis lacrimalis) by the lacrimal bone and lacrimal process of the turbinated bene; it is directed downward, and a little backward and outward, is about the diameter of a goose-quill, slightly narrower in the middle than at either extremity, and terminates below in the inferior meatus. It lodges the nasal duct. The alveolar process (^processus alveolaris) is the thickest and most spongy part of the bone, broader behind than in front, and excavated into deep cavities for the reception of the teeth (alveoli dentales). These cavities are eight in number, and vary in size and depth according to the teeth they contain. That for the canine tooth is the deepest; those for the molars are the widest, and subdivided into minor cavities by septa; those for the incisors are single, but deep and narrow. The Buccinator muscle arises from the outer surface of this process as far forward as the first molar tooth. After the loss of the prominent teeth at any time, but especially in old age, this process, like that of the mandible, is absorbed. The palatal process (processus palatinus), thick and strong, projects horizon- tally inward from the inner surface of the body. It is much thicker in front than behind, and forms a considerable part of the floor of the nostril and the roof of the mouth. Its inferior surface (Fig. 72) is concave, rough and uneven, contains numerous little cavities for the glands of the mucous membrane, and forms part of the roof of the mouth. This surface is perforated by numerous foramina for the passage of the nutrient vessels, channelled at the back part of its alveolar border by a longitudinal groove, sometimes a canal, for the transmission of the posterior palatine vessels, and the great posterior palatine ner^'e from Meckel's ganglion, and presents little depressions for the lodgement of the palatine glands. When the two maxillae are articulated, a large fossa may be seen in the middle THE MAXILLJE 105 Anterior palatine canat. Foramina ofStens ^^-^^Fo) amen of Scarpa, Palate proceis uj maxilla K^ V 1 /- line, immediately behind the incisor teeth. This is the anterior palatine fossa. On examining the bottom of this fossa four canals are seen: two branch off laterally to the right and left nasal fossae, and two — one in front and one behind — lie in the middle line. Tlie former pair of these openings are named the incisor foramina, or foramina of Stenson; they are the openings of the forking incisor canal, through which pass the anterior or terminal branches of the descending or posterior palatine arteries, which ascend from the mouth to the nasal fossa?, and they contain the remains of Jacobson's organ. The canals in the middle line are termed the foramina of Scarpa, and transmit the nasopalatine nerves, the left passing through the anterior, and the right through the posterior, canal. Occasionally in adults' skulls, often in children's skulls, on the palatal surface of the process a delicate linear suture may sometimes be seen extending from the anterior palatine fossa to the interval between the lateral incisor and the canine tooth. This marks out the premaxillary bones (o.s incisivwn) on each side, and includes the whole thickness of the alveolus, the correspond- ing part of the floor of the nose, and the anterior nasal spine, and contains the sockets of the incisor teeth; in some animals it exists as a separate bone. The upper surface of the palatal process is concave from side to side, smooth, and forms part of the floor of the nose. It presents the upper orifices of the foramina of Stenson and Scarpa, the former being on each side of the middle line, the latter being situated in the intermaxillary suture, and therefore not visible unless the two bones are placed in apposition. The otder border of the palatal process is incorporated with the rest of the bone. The inner border is thicker in front than behind, and is raised above into a ridge, the nasal crest {crista uasalis), which, with the corresponding ridge in the opposite bone, forms a groove for the reception of the vomer. In front this crest rises to a considerable height, and this portion is named the incisor crest. The anterior margin is bounded by the thin, concave border of the opening of the nose, prolonged forward internally into a sharp process, forming, with a similar process of the opposite bone, the anterior nasal spine {spina nasalis anterior). The posterior border is serrated for articu- lation with the horizontal plate of the palate bone. palatine canals. Accessory palatine foramina. Fig. 72. — The palate and alveolar arch. Development.— This bone commences to ossify at a very early period, and ossification proceeds in it with great rapidity, so that it is difficult to ascertain with certainty ks precise number of centres. It appears, however, ]:)robable that it is ossified from six centres, which develop in membrane: (1) One, the ocit/oHn.raZ, which forms that portion of the body of the bone which lies internal to the infraorbital canal, including the floor of the orbit, the outer wall of the nasal fossa, and the nasal process. (2) A malar, which gives origin to that 106 SPECIAL ANATOMY OF THE SKELETON Anterior Surjace. portion of the bone which has external to the infraorbital canal and the malar process. (3) A palatal, from which is developed the palatal process posterior to Stenson's canal and the adjoining part of the nasal wall. 4. A premaxiUary, for the front part of the alveolus, which carries the incisor teeth and corresponds to the premaxillary bone of the lower animals. (5) A nasal, that gives rise to the nasal process and the portion above the canine tooth. (6) An infravomerine, that lies beneath the vomer and between the palatal and premaxillary centres. The premaxillary centre is in close association with the development of the perpendicular plate of the ethmoid and the vomer. According to Albrecht it develops from two centres of ossification, each having an incisive tooth. The one possessing the mesal segment he calls the endogiiatldon. The lateral segment he calls the mesognathion, while to the maxilla he gives the name exognathion. These seg- ments are separated by five sutures. The failure of union of any of these segments will lead to the various forms of cleft palate. These centres appear about the eighth week, and by the tenth week have become fused together so that the bone consists of two portions, one the maxilla proper, and the other the premaxillary portion. The suture between these two portions on the palate persists until middle life, but is not to be seen on the facial surface. This is believed by Callender to be due to the fact that the front wall of the sockets of the incisive teeth is not formed by the pre- maxillary bone, but by an outgrowth from the facial part of the maxilla. The antrum appears as a shallow groove on the inner surface of the bone at an earlier period than any of the other nasal sinuses, its development commencing about the fourth month of fetal life, and reaches its full size after the second dentition. The sockets for the teeth are formed by the growing downward of two plates from the dental groove, which subsequently becomes divided by partitions jutting across from the one to the other. If the two palatal processes fail to unite partially or completely, a partial or complete cleft palate results. Articulations. — With nine bones, two of the cerebral cranium, the frontal and ethmoid, and seven of the face — viz., the nasal, malar, lacrimal, turbinated, palate, vomer, and its fellow of the opposite side. Sometimes it articulates with the orbital plate of the sphenoid, and sometimes with its external pterygoid plate. Attachment of Muscles. — To twelve — the Orbicularis palpebrarum, Obliquus oculi infe- rior, Levator labii superioris alaeque nasi. Levator labii superioris, Levator anguli oris, Com- pressor naris. Depressor alae nasi. Dilatator naris posterior, Masseter, Buccinator, Internal pterygoid, and Orbicularis oris. Applied Anatomy. — It is from the extreme thinness of the walls of the antrum that we are enabled to explain how a tumor growing from the antrum encroaches upon the adjacent parts, pushing up the floor of the orbit and displacing the eyeball, projecting inward into the nose, protruding forward on to the cheek, and making its way backward into the zygomatic fossa and downward into the mouth. Inferior Surface. CHANGES PRODUCED IN THE UPPER JAW BY AGE. At birth and during infancy the diameter of the bone is greater in an antero-posterior than in a vertical direction. Its nasal process is long, its orbital surface large, and its tuberosity well marked. In the adult the vertical diameter is the greater, owing to the development of the alveolar process and the increase in size of the antrum. In old age the bone approaches again in character to the infantile condition; its height is diminished, and after the loss of the teeth the alveolar process is absorbed, and the lower part of the bone contracted and diminished in thickness. The Lacrimal Bone (Os Lacrimale). The lacrimal (lacrima, a, tear) is the smallest and most fragile bone of the face. There are two lacrimal bones. They are situated at the front part of the inner wall of the orbit (Fig. 67), and resemble somewhat in form, thinness, and size a finger nail ; hence, they are termed the ossa un^is. Each bone presents for exami- nation two surfaces and four borders. THE MALAB BONE ' 107 Surfaces. — The external or orbital surface (Fig. 74) is divided by a vertical ridge, the lacrimal crest {crista lacrimalis posterior), into two parts. The portion of bone in front of this ridge presents a smooth, concave, longitudinal groove (sulcus lacrimalis), the free margin of which unites with the nasal process of the maxilla, completing the lacrimal canal. The upper part of this groove {fossa sacci lacrimalis) lodges the lacrimal sac; the lower part lodges the nasal duct. The portion of bone behind the ridge is smooth, slightly concave, and forms part of the inner wall of the orbit. The ridge, with a part of the orbital surface immediately behind it, affords origin to the Tensor tarsi muscle ; it terminates below in a small hook-like projection, wuhfrmtai. the hamular process {hamulus lacrimalis), which articulates with the lacrimal tubercle of the maxilla and completes the upper orifice of the lacrimal canal. It sometimes exists as a separate piece, which is then called the lesser lacrimal bone. The internal or nasal surface presents a depressed furrow, corresponding to the ridge on its outer surface. The sur- face of bone in front of this forms part of the middle meatus, and that behind it articulates with the ethmoid bone, closing in the anterior ethmoidal cells. Borders. — Of the four borders, the anterior is the long- est, and articulates with the nasal process of the maxilla. ,^ fig. 74,— Left lacrimal f^^, , . , . , -11 bone. iivXternal surface. ihe postenor, thm and uneven, articulates with the os (Siightiy enlarged.) planum of the ethmoid. The superior, the shortest and thickest, articulates with the internal angular process of the frontal bone. The inferior is divided by the lower edge of the vertical crest into two parts; the posterior part articulates with the orbital plate of the maxilla; the anterior portion is prolonged downward into a pointed process, which articulates with the lacrimal process of the turbinated bone and assists in the formation of the lacrimal canal. Development. — From a single centre, which makes its appearance in membrane at about the eighth or ninth week. Articulations. — With four bones — two of the cerebral cranium, the frontal and ethmoid, and two of the face, the maxilla and the turbinated. Attachment of Muscles. — To one muscle, the Tensor tarsi. The Malar Bone (Os Zygomaticum). The malar bone is a quadrangular bone, situated at the upper and outer part of the face. It forms the prominence of the cheek, part of the outer wall and floor of the orbit, and part of the temporal and zygomatic fossae (Fig. 7.5). Each bone presents for examination an external and an internal surface; three processes, the frontal, orbital, and zygomatic processes; and four borders. Surfaces.— The external surface {fades malaris) (Fig. 76) is smooth, convex, perforated near its centre by a small aperture, the malar foramen, for the passage of nerves and vessels from the orbit. The malar surface is co-\-ered by the Orbicu- laris palpebrarum muscle, and affords attachment to the Zygomaticus major and minor muscles. The internal surface {fades temporalis) (Fig. 77), directed backward and inward, is conca-\'e, presenting anteriorly a rough, triangular surface, for articulation with the maxilla ; and behind, a smooth concave surface, which above forms the anterior boundary of the temporal fossa, and below, where it is wider, forms part of the zygomatic fossa. This surface presents, a little above its centre, the aperture of 108 SPECIAL ANATOMY OF THE SKELETON a malar canal {foramen zygomaticotemporale) , and affords attachment at its lower part to a portion of the Masseter muscle. Processes. — ^The frontal process (^processus frontosphenoidalis) is thick and serrated, and articulates with the external angular process of the frontal bone. To its orbital margin is attached the external tarsal ligament. Frontal pi Oct s'i Ert angular pi ocess Ki^ht inilir bone m s%tu The orbital process is a thick and strong plate, which projects backward from the orbital margin of the bone. Its supero-infernal surface (fades orbitalis), smooth and concave, forms, by its junction with the orbital surface of the maxilla and with the greater wing of the sphenoid, part of the floor and outer wall of the orbit. Its temporal surface, smooth and concave, forms part of the zygomatic and temporal yfiih froittal. Si-istl^s passed / through iempoi o- ^ e malar canals. , ^ &.) fossfe. Its anterior viargin is smooth and rounded, forming part of the circum- ference of the orbit. Its superior margin, rough and directed horizontally, artic- ulates with the frontal bone behind the external angular process. Its posterior THE PALATE BONE 109 inargin is rough and serrated for articulation with the sphenoid ; wtpniaUy it is also serrated for articulation with the orbital surface of the maxilla. At the angle of junction of the sphenoidal and maxillary portions a short, rounded, non- articular margin is generally seen; this forms the anterior boundary of the spheno- maxillary fissure; occasionally no such nonarticular margin exists, the fissure being completed by the direct junction of the maxilla and sphenoid bones or by the interposition of a small Wormian bone in the angular interval between them. On the supero-internal surface of the orbital process is seen the orifice of one of the temporomalar canals. This canal may be bifurcated, or there may be two canals from the beginning; one of these usually opens on the temporal surface, the other (occasionally two) on the facial surface; they transmit filaments of the orbital branch of the superior maxillary nerve. The zygomatic process {processus temporalis), long, narrow, and serrated, articu- lates with the zygomatic process of the temporal bone. Borders. — The antero-superior {orbital border) is smooth, arched, and forms a considerable part of the circumference of the orbit. The antero-inferior (maxil- lary border) is rough, and bevelled at the expense of its inner table, to articulate with the maxilla, affording attachment by its margin to the Levator labii superioris, just at its point of junction with the maxilla. The postero-superior (temporal border) curved like an italic letter/, is continuous above, with the commencement of the temporal ridge; below, with the upper border of the zygomatic arch; it affords attachment to the temporal fascia. The postero-inferior (masseteric border) is continuous with the lower border of the zygomatic arch, affording attachment by its rough edge to the Masseter muscle. Development. — The malar bone ossifies generally from three centres, which appear about the eighth week — one for the zygomatic and two for the orbital portion — and which fuse about the fifth month of fetal life. The bone is sometimes, after birth, seen to be divided by a horizontal suture into an upper and larger and a lower and smaller division. In some primates the malar bone consists of two parts, an orbital and a malar. Articulations. — With four bones — three of the cranium, frontal, sphenoid, and temporal; and one of the face, the maxilla. Attachment of Muscles. — To four — the Levator labii superioris proprius, Zygomaticus major and minor, and Masseter. The Palate Bone (Os Palatinum). The palatal bones' are situated at the back part of the nasal fossre ; they are wedged in between the maxilla and the pterygoid processes of the sphenoid (Fig. 78). Each bone assists in the formation of three cavities — the floor and outer wall of the nose, the roof of the mouth, and the floor of the orbit — and enters into the formation of two fossae, the sphenomaxillary and pterygoid fossae; and one fissure, the sphe- nomaxillary fissure. In form the palate bone somewhat resembles the letter L, and may be divided into an inferior or horizontal plate and a superior or vertical plate. The Horizontal Plate (pars liorizontaUs) (Figs. 79 and 80) is of a quadrilateral form, and presents two surfaces and four borders. Surfaces. — The superior or nasal surface (fades nasalis^, concave from side to side, forms the back part of the floor of the nasal cavity. The inferior or palatine surface (fades palatina), slightly concave and rough, forms the back part of the hard palate. At its posterior part may be seen a transverse ridge, more or less marked, for the attachment of part of the aponeurosis of the ' The word palate is frequently \ised as an adjective. Palatal is the correct form (froni palatum, the palate), but usage sanctions palatine in certain compounds, despite the fact that palatine is derived from palatium, ix palace. This is another example of what is charitably called a "late Latin" form, akin to hallux and hallucis. — [Editor.] 110 SPECIAL ANATOMY OF THE SKELETON Tensor palati muscle. At the outer extremity of this ridge is a deep groove, the pterygopalatine groove (sulcus pterygopalatinus) , converted into a canal by its articulation with the tuberosity of the maxilla, and forming the lower end of the posterior palatine canal {canalis ijterycjojjalatiniis) . Near this groove the orifices of one or two small canals, accessory posterior palatine canals (canales iKilatim), may be seen for the passage of the middle and posterior palatine nerves from the sphenopalatine (Meckel's) ganglion. Through the posterior palatine canal emerge the descending palatine artery and the great posterior palatine nerve. Borders. — ^The anterior is serrated, bevelled at the expense of its inferior sur- face, and articulates with the palatal process of the maxilla. The posterior is concave, free, and serves for the attachment of the soft palate. Its inner extremity is sharp and pointed, and when united with the opposite bone forms a Sphenopalatine notch. Sup. turbinated crest, n^? N-, MIDQ Inf. turbinated crest. Sup turbinated crest. Inf turbinated crest. Ant. nasal spiiie. projecting process, the palatine spine (.'.■piua nasalis fostcrior), for the attachment of the Azygos uvulae muscle. The external is united with the lower part of the perpendicular plate almost at right angles. The internal, the thickest, is serrated for articulation with its fellow of the opposite side; its superior edge is raised into a ridge, which, united with the opposite bone, forms a crest (crista nasalis), into which the vomer is received. The Vertical or Perpendicular Plate (pars perpend icidaris) (Figs. 79 and 80) forms the back part of the outer wall of the nasal fossa, is thin, of an oblong form, and directed upward and a little inward. It presents two surfaces, an external and an internal, and three borders. Surfaces. — The internal, medial, or nasal surface (fades nascdis) presents at its lower part a broad, shallow depression, which forms part of the inferior meatus of the nose. Immediately above this is a well-marked ridge, the inferior turbin- ated crest (crista conchali.s), for articulation with the turbinated bone; above this a second broad, shallow depression, which forms part of the middle meatus, sur- mounted above by a horizontal ridge less prominent than the inferior, the superior turbinated crest (crista ethmoidalis) , for articulation with the middle turbinated THE PALATE BONE 111 process. Above the superior turbinated crest is a narrow, horizontal groove, which forms part of the superior meatus. The external or lateral surface (J'aclesmaxillaris) is rough and irregular throughout the greater part of its extent, for articulation with the inner surface of the maxilla, its upper and back part being smooth where it enters into the formation of the sphenomaxillary fossa; it is also smooth in front, where it covers the orifice of the antrum. Toward the back Orbital process. Orbilal surface. Superior meatus Sphenopalatine /c Maxillary surface. Maxillary * process. Fig. 79. Horizontal Plate. -Left palate bone. Internal (Enlarged.) part of this surface is a deep groove, the pterygopalatine groove, converted into a canal, the posterior palatine canal, by its articulation with the maxilla. It transmits the posterior or descending pala- tine vessels and the great or anterior palatine nerve from Meckel's ganglion. Borders. ■ — The anterior border (Fig. 79) is thin, irreg- ular, and presents opposite the inferior turbinated crest a pointed, projecting lamina, the maxillary process (processiis maxillaris), which is directed forward, and closes in the lower and back part of the opening of the antrum. The posterior border (Fig. 80) presents a deep groove, the edges of which are serrated for articulation with the pterygoid process of the sphenoid. At the lower part of this border is seen a pyramidal process of bone, the tuberosity of the palate {processus pyramidalis), which is received into the angular interval between the two pterygoid plates of the sphenoid at their inferior extremity. This process presents at its back part a median groove and two lateral surfaces. The groove is smooth, and forms part of the pterygoid fossa, affording attachment to the Internal pterygoid muscle; while the lateral surfaces are rough and uneven, for articulation with the anterior border of each pterygoid plate. A few fibres of the Superior con- strictor of the pharynx arise from the tuberosity of the palate bone. The base of this process, continuous with the hori- zontal portion of the bone, presents the apertures of the accessory posterior pala- tine canals, through which pass the two smaller descending branches of Meckel's ganglion; while its outer surface is rough for articulation with the inner surface of the body of the maxilla. The superior border of the vertical plate presents two well-marked processes separated by an intervening notch. The ante- rior, or larger, is called the orbital pi-ocess ; the posterior, the sphenoidal process. Orbital process. ^^^^^sw tcce ^Sphenopalatine foramen, , Sphenoidal process. ~ Articular portion. J^on-artictdar portion. Fig. 80. — Left palate bone. Posterior (Enlarged.) 112 SPECIAL ANATOMY OF THE SKELETON Processes. — The orbital process {processus orhitalis) , directed upward and out- ward, is placed on a higher level than the sphenoidal. It presents five surfaces, which enclose a hollow cellular cavity, and is connected with the perpendicular plate by a narrow, constricted neck. Of these five surfaces, three are articular, two nonarticular or free surfaces. The three articular are the anterior or maxillary surface, which is directed forward, outward, and downward, is of an oblong forni, and rough for articulation with the maxilla. The posterior or sphenoidal surface is directed backward, upward, and inward. It ordinarily presents a small, open cell, the orbital sinus, which communicates with the sphenoidal cells, and the mar- gins of which are serrated for articulation with the vertical part of the sphe- noidal turbinated process. The internal or ethmoidal surface is directed inward, upward, and forward, and articulates with the lateral mass of the ethmoid bone. In some cases the cellular cavity opens on the internal surface of the bone ; it then communicates with the posterior ethmoidal cells. More rarely it opens on both surfaces, and then communicates with both the posterior ethmoidal and the sphenoidal cells. The nonarticular or free surfaces are the superior or orbital surface, directed upward and outward, of triangular form, concave, smooth, and forming the back part of the floor of the orbit; and the external or zygomatic surface, directed outward, backward, and downward, of an oblong form, smooth, lying in the sphenomaxillary fossa, and looking into the zygomatic fossa. The latter surface is separated from the orbital by a smooth, rounded border, which enters into the formation of the sphenomaxillary fissure. The sphenoidal process (processus sphenoidalis) of the palate bone is a thin, com- pressed plate, much smaller than the orbital, and directed upward and inward. It presents three surfaces and two borders. The superior surface, the smallest of the three, articulates with the under surface of the sphenoidal turbinated pro- cess; it presents a groove, which contributes to the formation of the pterygopala- tine canal. The internal surface is concave, and forms part of the outer wall of the nasal fossa. The external surface is divided into an articular and a nonartic- ular portion; the former is rough, for articulation with the inner surface of the internal pterygoid plate of the sphenoid; the latter is smooth, and forms part of the sphenomaxillary fossa. The anterior border forms the posterior boundary of the sphenopalatine notch. The posterior border, serrated at the expense of the outer table, articulates with the inner surface of the internal pterygoid plate. The orbital and sphenoidal processes are separated from each other by a deep notch, the sphenopalatine notch ( incisura sphenopalatina), which is converted into a foramen, the sphenopalatine foramen (foramen sphenopalatinum) , by articulation with the under surface of the body of the sphenoid bone. Sometimes the two pro- cesses are united above, and form between them a complete foramen (Figs. 79 and 80), or the notch is crossed by one or more spiculse of bone, so as to form two or more foramina. In the articulated skull this foramen is seen to pass from the sphenomaxillary fossa into the back part of the superior meatus. It trans- mits the sphenopalatine vessels and the superior nasal and nasopalatine nerves. Development. — From a single centre, which makes its appearance in membrane about the second month at the angle of junction of the two plates of the bone. From this point ossification spreads inward to the horizontal plate, downward into the tuberosity, and upward into the vertical plate. In the fetus the horizontal plate is much larger than the vertical, and even after it is fully ossified the whole bone is remarkable for its shortness. Articulations. — With six bones — the sphenoid, ethmoid, maxilla, turbinated, vomer, and opposite palate. Attachment of Muscles. — To four — the Tensor palati, Azygos uvulae, Internal pterygoid, and Superior constrictor of the pharynx. THE TURBINATED BONE \VA The Turbinated Bone (Concha Nasalis Inferior), The turbinated bones are situated one on each side of the outer wall of each nasal fossa. Each consists of a layer of thin, spongy bone, curled upon itself like a scroll — hence its name "turbinated" — and extends horizontally along the outer wall of the nasal fossa, immediately below the orifice of the antrum (Fig. SI). Each bone presents two surfaces, two borders, and two extremities. Fig. 81.~N;isal cavity, right lateral wall, from the left. (Spalteholz.) Surfaces. — ^The internal surface (Fig. 82) is convex, perforated by numerous apertures, and traversed by longitudinal grooves and canals for the lodgement of arteries and veins. In the recent state it is covered by the lining membrane of the nose. The external surface is concave (Fig. 83), and forms part of the inferior meatus. -Right turbinated bo Internal surface. Fic. S3. — Right turbinated bone. External surface. Borders. — Its upper border is thin, irregular, and connected to various bones along the outer wall of the nose. It may be divided into three portions; of these, tlie anterior articulates with the inferior turbinated crest of the maxilla ; the poste- rior with the inferior turbinated crest of the palate bone; the middle portion of the 114 SPECIAL ANATOMY OF THE SKELETON superior border presents three well-marked processes, which vary much in their size and form. Of these, the anterior and smallest is situated at the junction of the anterior fourth with the posterior three-fourths of the bone; it is small and pointed, and is called the lacrimal process {-processus lacrimal is); it articulates by its apex with the anterior inferior angle of the lacrimal bone, and by its margins with the groove on the back of the nasal process of the maxilla, and thus assists in forming the canal for the nasal duct. At the junction of the two middle fourths of the bone, but encroaching on its posterior fourth, a broad, thin plate, the eth- moidal process (processus ethmoidalis), ascends to join the unciform process of the ethmoid; from the lower border of this process a thin lamina of bone curves down- ward and outward, hooking over the lower edge of the orifice of the antrum, which it narrows below; it is called the maxillary process (processus maxillaris), and fixes the bone firmly to the outer wall of the nasal fossa. The inferior border is free and thick, more especially in the middle of the bone. Both extremities are more or less narrow and pointed, the posterior being the more tapering. If the bone is held so that its outer concave surface is directed backward (i. e., toward the holder), and its superior border, from which the lacrimal and ethmoidal processes project, upward, the lacrimal process will be directed to the side to which the bone belongs.' Development. — From a mngle centre, which makes its appearance about the middle of fetal life in the outer wall of the cartilaginous nasal septum. Articulations. — With four bones — one of the cerebral cranium, the ethmoid, and three of the face, the maxilla, lacrimal, and palate. No muscles are attached to this bone. The Vomer. The vomer is a single bone, situated vertically at the back part of the nasal fossae, forming part of the septum of the nose (Fig 84). It is thin, somewhat like a ploughshare in form; but varies in different individuals, being frequently bent to one or the other side ; it presents for examination two surfaces and four borders. Surfaces. — ^The lateral surfaces are smooth, marked by small furrows for the lodgement of bloodvessels, and by a groove on each side, sometimes a canal, the nasopalatine groove, or canal, which runs obliquely downward and forward to the intermaxillary suture; it transmits the nasopalatine nerve. Borders. — ^The superior border, the thickest, presents a deep groove, bounded on each side by a horizontal projecting leaf of bone; these leaves are the alse (alae vomeris). The groove formed by the alae receives the rostrum of the sphenoid, while the alse are overlapped and retained by the vaginal processes, which pro- ject on the under surface of the body of the sphenoid at the base of the pterygoid processes. At the front of the groove a fissure is left for the transmission of blood- vessels to the substance of the bone. The inferior border, the longest, is broad and uneven in front, where it articulates with the crests of the two maxillae ; thin and sharp behind, where it joins with the palate bones. The upper half of the anterior border usually consists of two laminse of bone, in the groove between which is received the perpendicular plate of the ethmoid ; the lower half, also separated into two lamellse, receives between them the lower margin of the septal cartilage of the nose. The posterior border is free, concave, and separates the nasal fossee behind. It is thick and bifid above, thin below. The surfaces of the vomer are covered by mucous membrane, which is inti- mately connected with the periosteum, with the intervention of very little, if any, submucous connective tissue. 1 If the lacrimal process is broken off, as is often the case, the side to which the bone belongs may be known by recollecting that the maxillary process is nearer the back than the front of the bone. THE MANDIBLE, OR LOWER JAW 115 Space for fnavqida) cartilage of septum '*^^^PI||| Lo'.ti urn of sphenoid. Fig. S4. — Vomer ; Development.— The vomer at an early period consists of two laminse, separated by a very considerable in- terval, and enclosing between them a plate of cartilage, the vomerine car- tilage, which is prolonged forward to form the remainder of the septum. Ossification commences, about the eighth week, in the membrane at the postero-inferior part of this cartilage from two centres, one on each side of the middle line, which extend to form the two laminse. The intervening cartilaginous plate is absorbed. They begin to coalesce at the lower part, but their union is not complete until after puberty. Articulations. — With nx bones — two of the cerebral cranium, the sphenoid and ethmoid, and four of the face, the maxillse and the two palate bones; and with the cartilage of the septum. The vomer has no muscles attached to it. With maxillae and palate. Fig. 85, — The vomer. The Mandible, or Lower Jaw (Mandibula). The mandible, the largest and strongest bone of the face, serves for the reception of the lower teeth. It consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which join the back part of the body nearly at right angles. The Body (corpus mandibulae) (Fig. 86). — The body is convex in its general outline, and curved somewhat like a horseshoe. It presents for examination two surfaces and two borders. , Surfaces. — ^The external surface is convex from side to side, concave from above downward. In the median line is a vertical ridge, the symphysis, which extends 116 SPECIAL ANATOMY OF THE SKELETON from the upper to the lower border of the bone, and indicates the point of junction of the two pieces of which the bone is composed at an early period of life. The lower part of the ridge terminates in a prominent triangular eminence, the mental process (protuberantia mentalis). This eminence is rounded below, and often Coronoid process. Condyle Groove for faaal aitery -The mandible. Outer surface. presents a median depression separating two processes, the mental tubercles (iubercula mentalia). It forms the chin, a feature peculiar to the human skull. On either side of the symphysis, just below the cavities for the incisor teeth, is a depression, the incisor fossa, for the attachment of the Levator menti; more externally is > ^''". Fig. 87. — The mandible. Inner surface. Side view. attached a portion of the Orbicularis oris, and still more externally, a foramen, the mental foramen (foramen meiitale), for the pas'sage of the mental vessels and nerve. This foramen is placed just below the interval between the two bicuspid teeth. Running outward from the base of the mental process on each side is a THE MANDIBLE, OB LOWER JAW II7 ridge, the external oblique line (linea obliqua). The ridge is at first nearly hori- zontal, but afterward inclines upward and backward, and is continuous with the anterior border of tire ramus; it aii'ords attachment to the Depressor labii inferioris and Depressor anguH oris; below it the Platysma is attached. The Internal surface (Fig. 87) is concave from side to side, convex from above downward. In the middle line is an indistinct linear depression, corresponding to the symphysis externally; on either side of this depression, just below its centre, are two prominent tubercles, one above and one below, the genial tubercles {spinae mentales) , which afford attachment, the upper pair to the Genio- hyoglossi, the lower pair to the Geniohyoidei, muscles. Sometimes the tubercles on each side are blended into one; at others they all unite into an irregular eminence; or, again, nothing but an irregularity may be seen on the surface of the bone at this part. On either side of the genial tubercles is an oval depression, the sublingual fossa (fovea sublingualis), for the lodgement of the sublingual gland; and beneath the fossa a rough depression, tlie digastric fossa (fossa digastrica), on each side, wliich gives attachment to the anterior belly of the Digastric muscle. At the back part of the sublingual fossa the internal oblique line, or mylohyoid ridge (linea mylohyoidea), commences; it is at first faintly marked, but becomes more distinct as it passes upward and outward, and is especially prominent opposite the last two molar teeth; it affords attachment throughout its whole extent to the Mylohyoid muscle; the Superior constrictor of the pharynx with the pterygomandibular ligament being attached above its posterior extremity, near the alveolar margin. The portion of the bone above this ridge is smooth and covered by the mucous membrane of the mouth; the portion below presents an oblong depression, the submaxillary fossa (fovea submaxillaris) , wider behind than in front, for the lodgment of the submaxillary gland. The external and internal oblique lines divide the body of the bone into a superior or alveolar and an infe- rior or basilar portion. Borders. — ^The superior or alveolar portion of the body (pars alveolaris) has above a narrow border which is wider and the margins of which are thicker behind than in front. It is hollowed into numerous cavities (alveoli dentales), for the reception of the teeth ; these cavities are sixteen in number, and vary in depth and size according to the teeth which they contain. To the outer side of the alveo- lar border the Buccinator muscle is attached as far forward as the first molar tooth. The inferior or basilar portion (basis mandibulae) is rounded, longer than the superior and thicker in front tlian behind; it presents a shallow groove, just where the body joins the ramus, over wliich the facial artery turns. The Perpendicular Portions or Rami (rami mandibulae). — ^The perpendicular portions or rami are of a quadrilateral form. Each presents for examination two surfaces, four borders, and two processes. Surfaces. — The external surface is flat, marked with ridges, and gives attachment throughout nearly the whole of its extent to the Masseter muscle. The internal surface presents about its centre an oblique foramen (foramen man- dibulare), the beginning of the inferior dental canal, which transmits the inferior dental vessels and nerve. The margin of this opening is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula (lingula mandibidae), which gives attachment to the internal lateral ligament of the mandible, and at its lower and back part a notch leading to a groove, the mylo- hyoidean groove (sulcus mylohyoideus) , which runs obliquely downward to the back part of the submaxillary fossa, and lodges the mylohyoid vessels and nerve. Be- hind the groove is a rough surface, for the insertion of the Internal pterygoid muscle. The inferior dental canal (canalis mandibulae) runs obliquely downward and forward in the substance of the ramus, and then horizontally forward in the body; it is here placed under the alveoli, with which it communicates by small 118 SPECIAL ANATOMY OF THE SKELETON openings. On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals, which run forward, to be lost in the cancellous tissue of the bone beneath the incisor teeth. This canal, in the poste- rior two-thirds of the bone, is situated nearer the internal surface of the jaw ; and in the anterior third, nearer its external surface. Its walls are composed of com- pact tissue at either extremity, and of cancellous in the centre. It contains the inferior dental vessels and nerve, from which branches are distributed to the teeth through small apertures at the bases of the alveoli. Borders. — ^The lower border of the ramus is thick, straight, and continuous with the body of the bone. At its junction with the posterior border is the angle of the jaw (angiilus mandihulae). The angle is either inverted or everted, and marked by rough, oblique ridges on each side, for the attachment of the Masseter externally and the Internal pterygoid internally; the stylomaxillary ligament is attached to the angle between these muscles. The anterior border is thin above, thicker below, and continuous with the external oblique line. The posterior border is thick, smooth, rounded, and covered by the parotid gland. The upper border of the ramus is thin, and presents two processes, separated by a deep concavity, the sigmoid notch. Of these processes, the anterior is the coronoid, the posterior, the condyloid. The coronoid process (processus coronoideus) is a thin, flat, triangular eminence, which varies in shape and size. Its anterior border is convex, and is continuous below with the anterior border of the ramus; its posterior border is concave, and forms the anterior boundary of the sigmoid notch. Its external surface is smooth, and affords attachment to the Temporal and Masseter muscles. Its internal surface gives insertion to the Temporal muscle, and presents a ridge which begins near the apex of the process and runs downward and forward to the inner side of the last molar tooth. Between this ridge and the anterior border is a grooved triangular area, the upper part of which gives attachment to the Temporal, the lower part to some fibres of the Buccinator. The condyloid process (^processus condyloideus), shorter but thicker than the coronoid, consists of two portions, the condyle (capitulum mandihulae), and the constricted portion which supports the condyle, the neck [collum mandihulae). The condyle is of an oblong form, its long axis being transverse, and set obliquely on the neck in such a manner that its outer end is a little more forward and a little higher than its inner. It is convex from before backward and from side to side, the articular surface extending farther on the posterior than on the anterior aspect. At its outer extremity is a small tubercle for the attachment of the external lateral ligament of the temporomandibular joint. The neck of the condyle is flattened from before backward, and strengthened by ridges which descend from the fore part and sides of the condyle. Its lateral margins are narrow, the external one giving attachment to part of the external lateral ligament. Its posterior surface is convex; its anterior is hollowed out on its inner side by a depression, the ptery- goid depression (fovea pterygoidea), for the attachment of the External pterygoid muscle. The sigmoid notch (incisura inandihulae), separating the two processes, is a deep semilunar depression, crossed by the masseteric vessels and nerve. Development. — The mandible is ossified in the fibrous membrane covering the outer surfaces of Meckel's cartilages. These cartilages, one on either side, form the cartilaginous bar of the mandibular arch, being joined at the symphysis by mesodermal tissue. The proximal end of each cartilage is connected with the periotic capsule, and here serves to form the malleus and incus. The next succeeding portion as far as the lingula is replaced by fibrous tissue to form the sphenomandibular ligament. Between the lingula and the canine tooth the cartilage disap- pears, while the portion near the symphysis becomes ossified and incorporated with the incisor division of the mandible. This ossific centre appears in about the sixth week of fetal life — i. e., earlier than in any other bone except the clavicle; ossification is practically complete by the tenth THE MANDIBLE, OR LO WEB JA W \ 19 week. Accessory nuclei develop to form the condyle and the coronoid process, in the front part of both alveolar walls and along the front of the lower border of the bone. These accessory nuclei possess no separate ossific centres, but ossification extends into them from the adjacent membrane bone and they undergo absorption. The inner alveolar border, usually described as arising from a separate ossific centre {splenial centre), is formed in the human mandible by an ingrowth from the main mass of the bone. At birth the bone consists of two halves, united by a fibrous symjihysis, in which ossification takes place during the first year. Articulation. — With the glenoid fossse of the two temporal bones. Attachment of Muscles. — To fifteen -pairs — to its external surface, commencing at the sym- physis, and proceeding backward: Levator menti, Depressor labii inferioris, Depressor anguli oris, Platysma, Buccinator, Masseter; a portion of the Orbicularis oris is also attached to this surface. To its internal surface, commencing at the same point: Geniohyoglossus, Geniohyoirl, Mylohyoid, Digastric, Superior constrictor, Temporal, Internal pterygoid, External pterygoid. Meckel's cartilage Fic. SS. — Scheme showing ossification of the mandible, inner side (Low). The membrane bone is colored red. The greater part of Meckel's cartilage is colored blue. The upturned, stippled portion near the symphysis represents the part of Meckel's cartilage, which is surrounded and invaded by the membrane bone. The accessory nuclei of cartilage in the condyle, coronoid process, alveolar border, and body are indicated by stippled areas. Fig. 89. — Scheme showing ossification of mandible from the outer side (Low). Membrane bone colored red. Accessory nuclei of cartilage stippled. CHANGES PRODUCED IN THE MANDIBLE BY AGE. The changes which the mandible undergoes after birth relate (1) to the alterations effected in the body of the bone by the first and second dentitions, the loss of the teeth in the aged, and the subsequent absorption of the alveoli; (2) to the size and situation of the dental canal; and (3) to the angle at which the ramus joins with the body. At birth (Fig. 90) the bone consists of lateral halves, united by fibrous tissue. The body is a mere shell of bone, containing the sockets of the two incisor, the canine, and the two tem- porary molar teeth, imperfectly partitioned from one another. The dental canal is of large size, and runs near the lower border of the bone, the mental foramen opening beneath the socket of the first molar. The angle is obtuse (17.5 degrees), and the condyloid portion nearly in the same horizontal line with the body; the neck of the condyle is short, and bent backward. The coronoid process is of comparatively large size, and situated at right angles with the rest of the bone. SIDE VIEW OF THE MANDIBLE AT DIFFERENT PERIODS OF LIFE. After birth (Fig. 91) the two segments of the bone become joined at the symphysis, from below upward, in the first year; but a trace of separation may be visible in the beginning of the second year near the alveolar margin. The body becomes elongated in its whole length, but more especially behind the mental foramen, to provide space for the three additional teeth developed in this part. The depth of the body becomes greater, owing to increased growth of the alveolar part, to afford room for the fangs of the teeth, and by thickening of the subdental portion, which enables the jaw to withstand the powerful action of the masticatory muscles; but the alveolar portion is the deeper of the two, and, consequently, the chief part of the body lies above the oblique line. The dental canal after the second dentition is situated just above the level of the mylohyoid ridge, and the mental foramen occupies the position usual to it in the adult. The angle becomes less obtuse, owing to the separation of the jaws by the teeth. (About the fourth year it is 140 degrees.) 120 SPECIAL ANA TOMY OF THE SKELETON Fig. 90. — Mandible in newborn. Fig. 91. — In child six to seven years of age. Fig. 92. — In the adult. Fig. 93.— In old age. (Spalteholz.) THE SUTURES 121 In the adult (Fig. 92) the alveolar and basilar portions of the body are usually of equal dejjth. The mental foramen opens midway between the upper and lower border of the bone, and the dental canal runs nearly parallel with the mylohyoid line. The ramus is almost vertical in direction, and joins the body nearly at right angles. In old age (Fig. 93) the bone becomes greatly reduced in size; for with the loss of the teeth the alveolar process is absorbed, and the basilar part of the bone alone remains, conseciuently, the chief part of the bone is heloiv the oblique line. The dental canal, with the mental foramen opening from it, is close to the alveolar liorder. The rami are oblique in direction, the angle obtuse, and the neck of the condyle more or less bent backward. The Sutures. The bones of the cerebral cranium and face are connected to each other by means of sutures. That is, the articulating surfaces or edges of the bones are more or less roughened or uneven, and are closely adapted to each other, a small amount of intervening fibrous tissue, the sutiual ligament, fastening them together. The cranial sutures may be divided into three sets: (1) Those at the vertex of the skull. (2) Those at the side of the skull. (3) Those at the base. The sutures at the vertex of the skull are four — the metopic, the sagittal, the coronal, and the lambdoid. The metopic or frontal suture (sutiira frontalis) (Fig. 44) is usually noted in adults as a trivial fissure, just above the glabella. At birth the two halves of the frontal bone are separated by the suture. This suture is, as a rule, almost com- pletely or completely closed during the fifth or sixth year, but occasionally it persists throughout life. The interparietal or sagittal suture {sutura sagittalis) is formed by the junction of the two parietal bones, and extends from the middle of the frontal bone back- ward to the superior angle of the occipital. This suture is sometimes perforated, near its posterior extremity, by the parietal foramen; and in front, where it joins the coronal suture, a space is occasionally left which encloses a large Wormian bone. The frontoparietal or coronal suture (sutura coronalis) (Fig. 99) extends trans- versely across the vertex of the skull, and connects the frontal with the parietal bones. It commences at the extremity of the greater wing of the sphenoid on one side, and terminates at the same point on the opposite side. The dentations of the suture are more marked at the sides than at the summit, and are so constructed that the frontal rests on the parietal above, while laterally the frontal supports the parietal. The occipitoparietal or lambdoid suture (sutura lamhdoidea) (Fig. 99), so called from its resemblance to the Greek letter A, connects the occipital with the parietal bones. It commences on each side at the mastoid portion of the temporal bone, and inclines upward to the end of the sagittal suture. The dentations of this suture are very deep and distinct, and are often interrupted by several small Wormian bones. The lateral sutures (Fig. 99) extend from the external angular process of the frontal bone to the lower end of the lambdoid suture behind. The anterior fortion is formed between the lateral part of the frontal bone above and the malar and greater wing of the sphenoid below, forming the frontomalar suture (sutura zygomaticofrontalis) and frontosphenoidal suture (sutura sphenofrontal is). These sutures can also be seen in the orbit, and form part of the so-called transverse facial suture. The posterior portion is formed between the parietal bone above and the greater wing of the sphenoid, the squamous and mastoid portions of the temporal bone below, forming the sphenoparietal, squamoparietal, and mastoparietal sutures. 122 SPECIAL ANA TOMY OF THE SKELETON The sphenoparietal (sutura sphenopariefalis) is very short; it is formed by the tip of the greater wing of the sphenoid, which overlaps the anterior inferior angle of the parietal bone. The squamoparietal (sutura squamosa) is arched, and is formed by the squamous portion of the temporal bone overlapping the middle division of the lower border of the parietal. The mastoparietal (sutura parietmnastoidea), a short suture, deeply dentated, is formed by the posterior inferior angle of the parietal and the superior border of the mastoid portion of the temporal. The sutures at the base of the ^kull (Fig. 98) are the basilar in the centre, and on each side the petro-occipital, the masto-occipital, the petrosphenoidal, and the squamosphenoidal. The basilar suture (Jissura spheiwoccipitalis) is formed by the junction of the basilar surface of the occipital bone with the posterior surface of the body of the sphenoid. At an early period of life a thin plate of cartilage exists between these bones, but in the adult they become fused into one (synchondrosis spheno- occipitalis). Between the outer extremity of the basilar suture and the termina- tion of the lambdoid an irregular suture exists, which is subdivided into two por- tions. The inner portion, formed by the union of the petrous part of the temporal with the occipital bone, is termed the petro-occipital fissure (fissiira petrooccipitalis). The outer portion, formed by the junction of the mastoid part of the temporal with the occipital, is called the masto-occipital suture (sutura occipitomastoidea) . Between the bones forming the petro-occipital suture a thin plate of cartilage exists; in the masto-occipital is occasionally found the opening of the mastoid foramen. Between the outer extremity of the basilar suture and the sphenoparietal an irregu- lar suture may be seen, formed by the union of the sphenoid with the temporal bone. The inner and smaller portion of this suture is termed the petrosphenoidal fissure (fissura sphenopetrosal; it is formed between the petrous portion of the temporal and the greater wing of the sphenoid; the outer portion, of greater length and arched, is formed between the squamous portion of the temporal and the greater wing of the sphenoid; it is called the squamosphenoidal suture (sutura sphenosquamosa). The bones of the cerebral cranium are connected with those of the face, and the facial bones with each other, by numerous sutures, which, though distinctly marked, have received no special names. The only remaining suture deserving especial consideration is the transverse suture. This extends across the upper part of the face, and is formed by the junction of the frontal with the facial bones; it extends from the external angular process of one side to the same point on the opposite side, and connects the frontal with the malar, the sphenoid, the ethmoid, the lacrimal, the maxillae, and the nasal bones on each side (suiura zygomatico- jrontalis; the orbital portion of the sutura sphenofrontalis, sutura frontoethmoidalis, sutura frontolacrimalis, sutura frontomaxillaris, sutura nasofrontalis) . The sutures remain separate for a considerable period after the complete for- mation of the skull. It is probable that they serve the purpose of permitting the growth of the bones at their margins, while their peculiar formation, together with the interposition of the sutural ligament between the bones forming them, prevents the dispersion of blows or jars received upon the skull. Humphry remarks, "that, as a general rule, the sutures are first obliterated at the parts in which the ossification of the skull was last completed — viz., in the neighborhood of the fontanelles; and the cranial bones seem in this respect to observe a similar law to that which regulates the union of the epiphyses to the shafts of the long bones." The same author remarks that the time of their disappearance is extremely variable; they are sometimes found well marked in skulls edentulous with age, while in others which have only just reached maturity they can hardly THE SKULL AS A WHOLE \ 23 be traced. The obliteration of the sutures takes place sooner on the inner ihun "on the outer surface of the skull. The sagittal and coronal sutures are, as a rule, the first to become ossified — the process starting near the posterior extremity of the former and the lower ends of the latter. THE SKULL AS A WHOLE. The skull, formed by the union of the several cranial and facial bones already described, when considered as a whole is divisible into five regions — a superior region or vertex, an inferior region or base, two lateral regions, and an anterior region, the face. The Vertex of the Skull. — The superior region, or vertex, presents two sur- faces, an external and an internal. Surfaces. — The external surface {norma verticalis) is bounded, in front, by the glabella and superciliary ridges; behind, by the occipital protuberance and superior curved lines of the occipital bone; laterally, by an imaginary line extending from the outer end of the superior curved line, along the temporal ridge, to the external angular process of the frontal bone. This surface includes the greater part of the vertical portion of the frontal, the greater part of the parietal, and the superior third of the occipital bone; it is smooth, convex, of an elongated oval form, crossed transversely by the coronal suture, and from before backward by the sagittal, which terminates behind in the lambdoid. The point of junction of the coronal and sagittal sutures is named the bregma. The point of junction of the sagittal and lambdoid sutures is called the lambda, and is about 2f inches (7 cm.) above the external occipital protuberance. From before backward may be seen the frontal eminences and remains of the suture connecting the two lateral halves of the frontal bone; on each side of the sagittal suture are the parietal foramen and parietal eminence, and still more posteriorly the convex surface of the occipital bone. In the neighborhood of the parietal foramen the skull is often flattened, and the name of obelion is sometimes given to that point of the sagittal suture which lies exactly opposite to the parietal foramen. The internal or cerebral surface is concave, presents depressions for the convolu- tions of the cerebrum, and numerous furrows for the lodgement of branches of the meningeal arteries. Along the middle line of this surface is a longitudinal groove, narrow in front, where it commences at the frontal crest, but broader behind, where it lodges the superior longitudinal sinus, and by its margin affords attachment ' to the falx cerebri. On either side of it are several depressions for the arachnoid villi, and at its back part the internal openings of the parietal foramina. This surface is crossed, in front, by the coronal suture; from before backward by the sagittal; behind, by the lambdoid. The Base of the Skull (the Skull being without the Mandible).— The inferior region, or base of the skull, presents two surfaces — an internal or cerebral, and an external or basilar. Siu'faces.— The internal or cerebral surface (Fig. 94) presents three fossa:", called the anterior, middle, and posterior fossw of the cranium. The anterior fossa (fossa cranii aiiterior) (Fig. 94) is formed by the orliital plates of the frontal, the cribriform plate of the ethmoid, the anterior third of the superior surface of the body, and the upper surface of the lesser wings of the sphenoid bone, and is situated at a higher level than the other fosste. It is the most elevated of the three fosste, convex externally where it corresponds to the roof of the orbit, con- cave in the median line in the situation of the cribriform plate of the ethmoid. It is traversed on either side by three sutures, the ethmofrontal, ethmosphenoidal, and frontosphenoidal, and lodges the frontal lobes of the cerebrum. It presents. 124 SPECIAL ANATOMY OF THE SKELETON in the median line, from before backward, the commencement of the groove for the superior sagittal sinus and the frontal crest for the attachment of the falx cerebri; Groove for superior sagittal sinus. Gi'OOves for anterior meningeal artery. Foramen csecum. Crista galli. Slit for nasal nerve. Groove for nasal nerve. Anterior ethmoidal foramen. Orifices for olfactory nerves. Posterior ethmoidal foramen. Ethmoidal spine. Olfactory grooves. Optic foramen.. Optic groove. Olivary process. Anterior clinoid process. Middle clinoid process. PosteHor clinoid process. Groove for 6th nerve. Foramen lacerum medinm. OHfiee of carotid canal. ion for Gasserian ganglion. Deprei Meatus auditorius inter Floccular fossa. Superior petrosal groove. Foramen lacerum posterius. Anterior condylar forarnen. Aquxducius vesiUndi. Posterior condylar foramen. i foramen. Posterior meningeal grooves. Fig. 94. — Base of the skull. Inner or cerebral surface. the foramen cecum, an aperture formed between the frontal bone and the crista gaUi of the ethmoid, which, if pervious, transmits a small vein from the nose to the sagittal sinus; behind tlae foramen cecum, the crista galli, the posterior mar- THE SKULL AS A WHOLE 125 gin of which affords attachment to the falx cerebri; on either side of the crista gaili, the cribriform plate, which supports the olfactory bulb, and presents three rows of foramina for the transmission of its nerve filaments, and in front a slit- like opening {nasal slit) for the nasal branch of the ophthalmic division of the trigeminal nerve. On the outer side of each olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina, the former situated about the middle of the outer margin of the olfactory groove. The anterior ethmoidal foramen transmits the anterior ethmoidal vessels and the nasal nerve, which latter runs in a depression along the surface of the ethmoid to the slit-like opening above mentioned ; while the posterior ethmoidal foramen opens at tlie })ack part of this margin under cover of the projecting lamina of the sphenoid, and trans- mits the posterior ethmoidal vessels. Farther back in the middle line is the eth- moidal spine, bounded behind by a slight elevation, separating two shallow longi- FiG. 95. — Base of the skull. Interior view. tudinal grooves which support the olfactory lobes. Behind this is a transverse sharp ridge, running outward on either side to the anterior margin of the optic foramen, and separating the anterior from the middle fossa of the base of the skull. The anterior fossa presents, laterally, depressions for the convolutions of the cere- brum and grooves for the lodgement of the anterior meningeal arteries. The middle fossa (fossa cranii media) (Fig. 94), deeper than the preceding, is narrow in the middle line, but becomes wider at the side of the skull. It is bounded in front by the posterior margin of the lesser wings of the sphenoid, the anterior clinoid processes, and the ridge forming the anterior margin of the optic groove; behind, by the superior border and anterior surface of the petrous portions of the temporal and the dorsum sellse; externally, by the squamous portions of the temporal and the anterior inferior angle of the parietal bones and greater wings of the sphenoid. On each side it is traversed by four sutures, the squamoparietal, sphenoparietal, 126 SPECIAL ANATOMY OF THE SKELETON squamosphenoidal, and petrosphenoidal. In the middle line, from before back- ward, is the optic groove, which supports the optic commissure; the groove terminates on each side in the optic foramen, for the passage of the optic nerve and ophthal- mic artery; behind the optic groove is the olivary process and laterally the anterior clinoid processes, to which are attached processes of the tentorium cerebelli. Farther back is the sella turcica, a deep depression which lodges the hypophysis and circular sinus, bounded in front by a small eminence on either side, the middle clinoid process, and behind by a broad, square plate of bone, the dorsum sellae, surmounted at each superior angle by a tubercle, the posterior clinoid process; beneath the latter process is a notch, for the abducent nerve. On each side of the sella turcica is the carotid groove; it is broad, shallow, and curved somewhat like the italic letter /,• it commences behind at the foramen lacerum medium, and Fig. 96. — Median sagittal section of tlie skull. terminates on the inner side of the anterior clinoid process, and presents along its outer margin a ridge of bone, the lingula. This groove lodges the cavernous sinus, the internal carotid artery, and the nerves which enter the orbit. The sides of the middle fossa are of considerable depth; they present depressions for the convolutions of the cerebrum and grooves for the branches of the middle men- ingeal artery; the latter commence on the outer side of the foramen spinosum, and consist of two large branches, an anterior and a posterior; the former passing upward and forward to the anterior inferior angle of the parietal bone, the latter passing upward and backward. The following foramina may also be seen on either side from before backward. Most anteriorly is seen the sphenoidal fissure {foramen lacerum ajiterius), formed above by the lesser wing of the sphenoid; below^ by the greater wing; internally, by the body of the sphenoid; and some- THE SKULL AS A WHOLE 127 times completed externally by the orbital plate of the frontal bone. It trans- mits the third, the fourth, the three branches of the ophthalmic division of the trigeminal, the abducent nerve, some filaments from the cavernous plexus of the sympathetics, the orbital branch of the middle meningeal artery, a recurrent branch from the lacrimal artery to the dura, and the ophthalmic vein. Behind the inner extremity of the sphenoidal fissure is the foramen rotundum, for the passage of the second division of the trigeminal nerve ; still more posteriorly is seen a small orifice, the foramen Vesalii, an opening situated between the foramen rotundum and the foramen ovale, a little internal to both; it varies in size in dift'erent indi- viduals, and is often absent; when present it transmits a small vein and opens below into the outer side of the scaphoid fossa. Behind and external to the latter open- ing is the foramen ovale, which transmits the third division of the trigeminal nerve, the small meningeal artery, and sometimes the small petrosal nerve. On the outer side of the foramen ovale is the foramen spinosum, for the passage of the middle meningeal artery; occasionally a small foramen (canaliculus innominatus) for the transmission of the small superficial petrosal nerve is seen internal to the fora- men spinosum. On the inner side of the foramen ovale is the foramen lacerum medium ( foramen lacerum) ; the lower part of this aperture is filled in the recent state with cartilage which is pierced by the Vidian nerve and a meningeal branch from the ascending pharyngeal artery. On the anterior surface of the petrous portion of the temporal bone is seen, from without inward, the eminence caused by the projection of the superior semicircular canal ; in front of and a little outside this is a depression, the tegmen tympani, corresponding to the roof of the tympa- num; the groove leading to the hiatus Fallopii, for the transmission of the greater petrosal nerve and the petrosal branch of the middle meningeal artery; beneath it, a smaller groove, for the passage of the lesser petrosal nerve; and, near the apex of the bone, the depression for the Gasserian ganglion; and the internal orifice of the carotid canal, for the passage of the internal carotid artery and carotid plexus of nerves. The posterior fossa ( fossa cranii posterior) , deeply concave, is the largest of the three, and situated on a lower level than either of the preceding. It is formed by the posterior third of the superior surface of the body of the sphenoid, by the occipital, the posterior surface of the petrous and the mastoid portions of the tem- poral, and the posterior inferior angle of the parietal bones; it is crossed on either side by four sutures, the petro-occipital, the masto-occipital, the mastoparietal, and the basilar; and lodges the cerebellum, pons, and medulla oblongata. It is separated from the middle fossa in the median line by the dorsum sellee, and on each side by the superior border of the petrous portion of the temporal bone. This border serves for the attachment of the tentorium cerebelli, is grooved for the supe- rior petrosal sinus, and at its inner extremity presents a notch, in which rests the trigeminal nerve. The circumference of the fossa is bounded posteriorly by the grooves for the lateral (transverse) sinuses. In the centre of this fossa is the fora- men magnum, bounded on either side by a rough tubercle, which gives attachment to the odontoid or cheek ligaments; and a little above these are seen the internal openings of the anterior condylar foramina,through which pass the hypoglossal ner\'e and meningeal branches from the ascending pharyngeal arteries. In front of the foramen magnum is a grooved surface, formed by the basilar process of the occipi- tal bone and by the posterior third of the superior surface of the body of the sphe- noid, which supports the medulla oblongata and pons; and articulates on each side with the petrous portion of the temporal bone, forming the petro-occipital suture, the anterior half of which is grooved for the inferior petrosal sinus, the posterior half being encroached upon by the foramen lacerum posterius {foramen jugulare). This foramen presents three compartments — through the anterior passes the infe- rior petrosal sinus; through the posterior, the lateral sinus and some meningeal 128 SPECIAL ANATOMY OF THE SKELETON branches from the occipital and ascending pharyngeal arteries; and through the middle, the glossopharyngeal, vagus, and spinal accessory nerves. Above the jugu- lar foramen is the internal auditory meatus, for the facial and auditory nerves and auditory artery; behind and external to this is the slit-like opening leading into the aquaeductus vestibuli, which lodges the ductus endolymphaticus; while between the two latter, and near the superior border of the petrous portion, is a small, tri- angular depression, the remains of the floccular fossa, which lodges a process of the dura and occasionally transmits a small vein from the substance of the bone. Be- hind the foramen magnum are the inferior occipital fossae, which lodge the hemi- spheres of the cerebellum, separated from each other by the internal occipital crest, which serves for the attachment of the falx cerebelli and lodges the occipital sinus. The posterior fossae are limited above by the deep transverse grooves for the lodgment of the lateral sinuses, which diverge forward on each side from a depression in the mesal plate, the torcular. These channels, in their passage outward, groove the occipital bone, the posterior inferior angles of the parietals, the mastoid portions of the temporals, and the jugular processes of the occipital, and terminate at the back part of the jugular foramen. Where the lateral sinus grooves the mastoid portion of the temporal bone (sigmoid fossa) the orifice of the mastoid foramen may be seen. Just previous to the termination of the groove the posterior condylar foramen opens into it. Neither foramen is constant. The basilar surface (norma basalis) (Fig. 97) of the skull is extremely irregular. It is bounded in front by the incisor teeth in the maxillae; behind by the inion and the superior curved lines of the occipital bone; and laterally by the alveolar arch, the lower border of the malar bones, the zygoma, and an imaginary line extending from the zygoma to the mastoid process and extremity of the superior curved line of the occiput. It is formed by the palatal processes of the maxillae and palate bones, the vomer, the pterygoid processes, under surface of the greater wings, spinous processes and part of the body of the sphenoid, the under surface of the squamous, mastoid, and petrous portions of the tempoi'als, and the under surface of the occipital bone. The anterior part of the base of the skull is raised above the le\el of the rest of this surface (when the skull is turned over for the purpose of examination), is surrounded by the alveolar process, which is thicker behind than in front, and excavated by sixteen depressions for the lodgement of the teeth of the maxillae, the cavities varying in depth and size according to the teeth they con- tain. Immediately behind the incisor teeth is the anterior palatine fossa. At the bottom of this fossa may usually be seen four apertures, two placed laterally, the foramina of Stenson, which open above, one in the floor of each nostril, and trans- mit the anterior branch of the posterior palatine vessels, and two in the median line in the intermaxillary suture, the foramina of Scarpa, one in front of the other, the anterior transmitting the left, and the posterior (the larger) the right, naso- palatine nerve. These two lateral canals are sometimes wanting, or they may join to form a single one, or one of them may open into one of the lateral canals above referred to. The palatine vault is concave, uneven, perforated by numerous foramina, marked by depressions for the palatine glands, and crossed by a crucial suture, formed by the junction of the four bones of which it is composed. At the front part of this surface a delicate linear suture may frequently be seen, passing outward and forward from the anterior palatine fossa to the interval between the lateral incisor and canine teeth, and marking off the premaxillary portion of the bone. At each posterior angle of the hard palate is. the posterior palatine foramen, for the transmission of the posterior palatine vessels and great descending palatine nerve; and running forward and inward from it a groove, for the same vessels and nerve. Behind the posterior palatine foramen is the tuberosity of the palate bone, perforated by one or more accessory posterior palatine canals, giving passage to the THE SKULL AS A WHOLE 129 middle and posterior palatine nerves from the sphenopalatine (Meckel's) ganglion, and marked by the commencement of a ridge which runs transversely inward, Anterior palatine fossa. Transmits left nasopalatine nerve. Transmits anterior palatine vessel. Transmits right nasopalatine nerve. Accessory palatine foramina. ■Sphenoid process of palate. Pterygopalatine canal. Fig. 97. — Base of the skuU. E.xternal surface. 9 130 SPECIAL ANATOMY OF THE SKELETON and serves for the attachment of the tendinous expansion of the Tensor palati muscle. Projecting backward from the centre of the posterior border of the hard palate is the posterior nasal spine, for the attachment of the Azygos uvulae muscle. Behind and above the hard palate is the posterior aperture of the nasal fossae (choanse), divided into two parts by the vomer, bounded above by the body of the sphenoid, below by the horizontal plate of the palate bone, and laterally by the internal pterygoid plate of the sphenoid. Each aperture measures about an inch in the vertical and about half an inch in the transverse direction. At the base of the vomer may be seen the expanded alse of this bone, receiving between them the rostrum of the sphenoid. Near the lateral margins of the vomer, at the root of the pterygoid processes, are the pterygopalatine canals, which transmit the pterygopalatine vessels and the pharyngeal nerve from the sphenopalatine (Meckel's) ganglion. The pterygoid process, which bounds the posterior nares on each side, presents near its base the pterygoid or Vidian canal, for the Vidian nerve and artery. Each process consists of two plates, which bifurcate at the extremity to receive the tuberosity of the palate bone, and are separated behind by the pterygoid fossa, which lodges the Internal pterygoid muscle. The internal Fig. 98.— Base of the skull. External surface. plate is long and narrow, presenting on the border of its base the scaphoid fossa, for the origin of the Tensor palati muscle, and at its extremity the hamular process, around which the tendon of this muscle turns. The external pterygoid plate is broad, forms the inner boundary of the zygomatic fossa, and affords attachment by its outer surface to the External pterygoid muscle. Behind the nasal fossse in the middle line is the basilar surface of the occipital THE SKULL AS A WHOLE 131 bone, presenting in its centre the pharyngeal spine, for the attachment of the Superior constrictor muscle of the pharynx, with depressions on each sifle for the insertion of the Rectus capitis anticus major and minor. At the base of the external pterygoid plate is the foramen ovale, for the transmission of the third divi- sion of the trigeminal nerve, the small meningeal artery, and sometimes the small petrosal nerve; behind this, the foramen spinosum, which transmits the middle meningeal artery, and the prominent spinous process of the sphenoid, which gi\es attachment to the internal lateral ligament of the mandible and the Tensor palati muscle. External to the spinous process is the glenoid fossa, divided into two parts by the Glaserian fissure (page 88), the anterior portion concave, smooth, bounded in front by the eminentia articularis, and serving for the articulation of the condyle of the mandible; the posterior portion rough, bounded behind by the tympanic plate, and serving for the reception of part of the parotid gland. Emerging from between the laminae of the vaginal process of the tympanic plate is the styloid process, and at the base of this process is the stylomastoid foramen, for the exit of the facial nerve and entrance of the stylomastoid artery. External to the stylo- mastoid foramen is the auricular fissure, for the exit of the auricular branch of the vagus, bounded behind by the mastoid process. Upon the inner side of the mas- toid process is a deep groove, the digastric fossa; and a little more internally the occipital groove, for the occipital artery. At the base of the internal pterygoid plate is a large and somewhat triangular aperture, the foramen lacerum medium, bounded in front by the greater wing of the sphenoid, behind by the apex of the petrous por- tion of the temporal bone, and internally by the body of the sphenoid and basilar process of the occipital bone; it presents in front the posterior orifice of the Vidian canal; behind, the aperture of the carotid canal. The basilar surface of this open- ing is filled in the recent state by fibrocartilaginous substance, which is pierced by the Vidian nerve and a meningeal branch of the ascending pharyngeal artery; across its upper or cerebral aspect passes the internal carotid artery. External to this aperture the petrosphenoidal suture is observed, at the outer termination of which is seen the orifice of the canal for the Eustachian tube and that for the Ten- sor tympani muscle. Behind this suture is seen the under surface of the petrous portion of the temporal bone, presenting from within outward, the quadrilateral, rough surface, part of which affords attachment to the Levator palati and Tensor tympani muscles; posterior to this surface is the orifice of the carotid canal and the orifice of the aquaeductus cochleae, the former transmitting the internal carotid artery and the ascending branches of the superior cervical ganglion of the sympa- thetic, the latter serving for the passage of a small artery to and a small vein from the cochlea. Behind the carotid canal is a large aperture, the jugular foramen, formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side, and is divided into three compartments by processes of dura. The anterior is for the passage of the inferior petrosal sinus; the posterior, for the lateral sinus and some meningeal branches from the occipital and ascending pharyngeal arteries; the central one, for the glosso- pharyngeal, vagus, and spinal accessory nerves. On the ridge of the bone dividing the carotid canal from the jugular foramen is the small foramen for the transmis- sion of Jacobson's nerve (tympanic branch of the glossopharyngeal) ; and on the wall of the jugular foramen, near the root of the styloid process, is the small aper- ture for the transmission of the auricular branch of the vagus nerve (Arnold's nerve) . Behind the basilar surface of the occipital bone is the foramen magnum, bounded on each side by the condyles, rough internally for the attachment of the check ligaments, and presenting externally a rough surface, the jugular process, which serves for the attachment of the Rectus capitis lateralis muscle and the lat- eral occipito-atlantal ligament. The middle of the anterior margin of the foramen magnum is called the basion. The mid-point of the posterior margin is called the 132 SPECIAL ANATOMY OF THE SKELETON opisthion. On either side of each condyle anteriorly is the anterior condylar fossa, continued as the anterior condylar foramen, for the passage of the hypoglossal nerve and often a meningeal branch of the ascending pharyngeal artery. Behind each condyle is the posterior condylar fossa, continued as the posterior condylar foramen, for the transmission of a vein to the lateral sinus. Behind the foramen magnum is the external occipital crest, terminating above at the external occipital protuberance, while on each side are seen the superior and inferior curved lines; these, as well as the surfaces of bone between them, are rough for the attachment of the muscles, which are enumerated on pages 70 and 71. The Lateral Region of the Skull. — The norma lateralis is of a somewhat triangular form, the base of the triangle being formed by a line extending from the external angular process of the frontal bone along the temporal ridge backward to the outer extremity of the superior curved line of the occiput; and the sides by two lines, the one drawn downward and backward from the external angular process of the frontal bone to the angle of the mandible, the other from the angle of the mandible upward and backward to the outer extremity of the superior curved line. This region is divisible into three portions — temporal fossa, mastoid portion, and zygomatic or infratemporal fossa. Fig. 99. — Lateral aspect of the skull. The Temporal Fossa (fossa temporalis). — The temporal fossa is bounded above and behind by the temporal ridges, which extend from the extei-nal angular process of the frontal upward and backward across the frontal and parietal bones, curving downward behind to terminate in the posterior root of the zygomatic process. In front it is bounded by the frontal, malar, and greater wing of the sphenoid ; externally by the zygomatic arch formed conjointly by the malar and temporal bones; heloiD, it is separated from the zygomatic fossa by the pterygoid ridge, seen on the outer THE SKULL AS A WHOLE 1.3:3 surface of the greater wing of the sphenoid. This fossa is formed by five bones, part of the frontal, greater wing of the sphenoid, parietal, squamous portion of the temporal and malar bones, and is traversed by six sutures, part of the frontomalar, sphenomalar, coronal, sphenoparietal, squamoparietal, and squamosphenoidal. The point where the coronal suture crosses the superior temporal ridge is named the stephanion; and the region where the four bones, the parietal, the frontal, the squamous portion of the temporal, and the greater wing of the sphenoid, meet, at the anterior inferior angle of the parietal bone, is named the pterion. This point is about on a level with the external angular process of the froii(*>■' >*''' ■ Fossa sub' « ' ^--^^&rya Optic foramen. ^ r^!& Greater wing of Eor. hypi Foramen magnum. Fig. I09.-Model of the chondrocranium of .a^human embryo. 8'^f„., The membrane bones are not represented. (From Hertwig's Handbuch der Entwickelungslehre.) the frontal the vomer, the internal pterygoid plates, and the bones of the face. Some of them remain diiinct throughout life (.. i parietal and frontal), while others 30m w>th the bones of thrchondrocrani^m (.. q.. interparietal, squamous temporals, arid internal pterygoid plate ). Recent Ob ervations have shown that, in mammals, the basicranial cartilage, both m the THE SKULL AS A WHOLE 143 chordal and prechordal regions of the base of the skull, is developed as a single plate, which extends from behind forward. In man, however, its posterior part shows an indication of its being developed from two chondrifying centres which fuse rapidly in front and below. The relation of this cartilaginous plate to the notochord differs in different animals. In the ral embryo it lies vcntrad of the notochord (Robinson); in the sheep, pig, calf, and ferret the cranial |i;irl of the notochord is enclosed within it; in man, the anterior and posterior thirds of (he carlilage surround the notochord, but its middle third lies on the dorsal aspect of the notochord, which in this region is placed between the cartilage and the wall of the pharynx. Optic foramen g of sphenoid Nasal capsule Nasal septu: Maxilla. Vomer Meckel s cartilage f^ ^^ / j \ i>tt/hid process Thyroid carlilagc'-^^^^^fj^lf^lJ Fen. cocldeae. Cricoid cartilage. ^^ For. h'jpogl. Fig. 110. — The same model as shown in Fig. 109 from the left side. Certain of the membrane bones of the right side are represented in yellow. Differences in the Skull Due to Age. — At birth the skull as a whole is large in pro- portion to the other parts of the skeleton, but its facial portion is small, and equals only about one-eighth of the bulk of the cranium as compared with one-half in the adult. The frontal and parietal eminences are prominent, and the greatest width of the skull is at the level of the latter; on the other hand, the glabella, superciliary ridges, and mastoid processes are not developed. Ossification of the skull bones is not completed, and many of them — e. g., the occipital, temporals, sphenoid, frontal, and mandible — consist of more than one piece. Unossified ^ . , Fig 112, — The lateral fontanelles. Fig. hi, — Skull at birth, showing the anterior and posterior fontanelles. membranous intervals, termed /o.ta.Wfes-, are seen at ^e angles of the parietal bones; th^ "The a,aerior or hreg.naiic fonianelle (Fig. Ill) is the largest, an A is ^^^ j^Z of the sagittal, coronal, and interfrontal sutures; U ,s '-^"g^-^J.^^'^^^'^i^J^^X V- -■"•"^ inch and a half in its antero-posterior and an mch in its transNerse diametei, / 144 SPECIAL ANATOMY OF THE SKELETON fontanelle is triangular in form and is situated at the junction of the sagittal and lambdoid sutures. The \?ittT?A fontanelles (Fig. 112) are small, irregular in shape, and correspond respectively with the antero-inferior and postero-inferior angles of the parietal bones. An additional fontanelle is sometimes seen in the sagittal suture at the region of the obelion. The fontanelles are usually closed by the growth and extension of the bones which surround them, but sometimes they are the sites of separate ossific centres which develop into Wormian bones. The posterior and lateral fontanelles are obliterated within a month or two after birth, but the anterior is not com- pletely closed until the first half of the second year; sometimes it remains open beyond the second year, a condition which is usually seen in rhachitis, and is due to malnutrition. A knowledge of the shape and position of the fontanelles is of service to the accoucheur in enabling him to deter- mine which part of the fetal head is presenting during parturition. The small size of the face at birth is mainly accounted for by the rudimentary condition of the ja\\»s, the noneruption of the teeth, and the small size of the maxillary air sinuses and nasal cavities. At birth the nasal cavities lie almost entirely between the orbits, and the lower border of the anterior nasal aperture is only a little below the level of the orbital floor. With the eru]3- tion of the milk teeth there is an enlargement of the face and jaws, and these changes are still more marked after the second dentition. The skull grows rapidly from birth to the seventh year, by which time the foramen magnum and petrous parts of the temporals have reached their full size and the orbital cavities are only a little smaller than those of the adult. Growth is slow from the seventh year until the approach of puberty, when a second period of activity takes place; this consists of an increase in all direc- tions, but it is especially marked in the frontal and facial regions, where it is associated with the development of the air sinuses. Obliteration of the Sutures.. — Obliteration of the sutures of the vault takes place as age advances, usually beginning during the fourth decade of life and first becoming manifest on the inner surface, appearing externally about ten years later; the posterior part of the sagittal suture is usually the first to become obliterated, next the coronal, and then the lambdoid. The most striking feature of an old skull is the marked diminution in the size of the jaws consequent on the loss of the teeth and the absorption of the alveolar processes, thus reducing the facial height and altering the mandibular angles. Differences in the Skull Due to Sex. — Until the age of puberty little difference exists be- tween the male and the female skull. The skull of an adult female is, as a rule, lighter and smaller. While the cranial capacity of white males averages 1560 c.c, that of females is nearly 200 c.c. less. The female skull has thinner walls, its ridges for muscle attachment are less strongly marked, the superciliary ridges, glabella, and mastoid processes are less prominent, and the corresponding air sinuses are smaller. The upper margin of the orbit is sharper, the frontal and parietal eminences are more prominent, and the vault is somewhat flattened as compared with the male skull. The contour of the face is more rounded, the facial bones are smoother, and the jaws and teeth are smaller. No single structural characteristic, however, serves to determine the sex, and the features enumerated above can guide in the examination only when they are sufficiently pronounced to justify a probable diagnosis.' Supernumerary, Wormian,- Sutural, or Epactal Bones (Ossa Triquetra). In addition to the constant centres of ossification of the skull, additional ones are occasion- ally found in the course of the sutures. These form irregular, isolated bones, interposed between the cranial bones, and have been termed Wormian bones, or ossa triquetra. They are most frecjuently found in the course of the lambdoid suture, but occasionally also occupy the situation of the fontanelles, especially the posterior and, more rarely, the anterior. Frequently one is found between the anterior inferior angle of the parietal bone and the greater wing of the sphe- noid, the epipteric bone, or the pterion ossicle (Fig. 113). They have a great tendency to be symmetrical on the two sides of the skull, and they vary much in size, being in some cases not larger than a pin's head, and confined to the outer table; in other cases so large that one pair of these bones maj' form the whole of the occipital bone above the superior cmwed lines. Craniology. Skulls vary in shape and size, and the term craniology is applied to the comparative study of these variations. By means of exact measurements and their correlation, skulls may be classified in various w-ays. ' See P. J. Mobius: Ueber die Verschiedenheit mannlicher und weiblicher Schiidel. Archiv fur Anthiopologie, 1907, N. F., vol. vi. 2 Wormiu3, a physician of Copenhagen, is said to have given the first detailed description of these bones. THE SKULL AS A WHOLE 145 I. According to capacity, measured by means of shot, mustard seed, etc. 1 Microcephalic, with a capacity of less than 1350 c.c. (e. g., Australians, Andamanese). 2. Mesocephalic, with a capacity of from 1350 to 1450 c.c. (e g., Negroes, Chinese). 3. Megacephalic, with a capacity of over 1450 c.c. (e. g., Europeans, Japanese, and Eskimos). F:g. 113. — Wormian bones. Fig. 114. — Brachycephalic cranium. (Poirier and Charpy.) Fig. 115. — Dolichocephalic cranium (Poirier and Charpy.) Fig. 116. — Brachycephalic and Charpy.) FiG. 1)7 — Dolichocephalic cranium. (Poirier and Charpy.) 146 SPECIAL ANATOMY OF THE SKELETON II. — To facilitate regional description and to compare the normae of one skull with those of another, the skull is placed in such a way that a plane passing through the inferior margin of the orbit and the superior margin of the external auditory meatus shall be horizontal (the horizontal line of the Frankfort agreement). Various linear and arc measurements are made between definite and easily localized points on the surface of the skull, and, although previously men- tioned, are here tabulated for convenience of reference. They are divided into two groups; (1) those in the mesal plane, and (2) those on either side of it. - The Points in the Mesal Plane are: Mental Point. — The most prominent point of the chin. Alveolar Point, or Prosthion. — The central point of the anterior margin of the upper alveolar arch. Subnasal Point. — The middle of the lower border of the anterior nasal aperture, at the base of the nasal spine. Nasion. — The central point of the frontonasal suture. Glabella. — The point in the middle line at the level of the superciliary ridges. Ophryon. — The point in the middle line at the level where the temporal lines most nearly approach each other. Bregma. — The meeting point of the coronal and sagittal sutures. Obelion. — A point in the sagittal suture on a level with the parietal foramina. Lambda. — The point of junction of the sagittal and lambdoid sutures. Occipital Point. — The point in the middle line of the occipital bone farthest from the glabella. Inion. — The external occipital protuberance. Opisthion. — The mid-point of the posterior margin of the foramen magnum. Basion. — The mid-point of the anterior margin of the foramen magnum. The Points on Either Side of the Mesal Plane are: Gonion. — The outer margin of the angle of the mandible. Dacryon. — The point of union of the antero-superior angle of the lacrimal with the frontal bone and the frontal process of the maxilla. Stephanion. — The point where the temporal line intersects the coronal suture. Pterion. — The point where the greater wing of the sphenoid joins the antero-inferior angle of the parietal. Auricular Point. — The centre of the orifice of the external auditory meatus. Asterion. — The point of meeting of the lambdoid, masto-occipital, and mastoparietal sutures. The horizontal circumference of the cranium is measured in a plane passing through the glabella (Turner) or the ophryon (Flower) in front, and the occipital point behind; it averages about twenty inches (50 cm.) in the female and twenty-one inches (52.5 cm.) in the male. The occipitofrontal or longitudinal arc is measured from the nasion over the middle line of the vertex to the opisthion; while the basinasal length is the distance between the basion and the nasion. These two measurements, plus the antero-posterior diameter of the foramen magnum, represent the vertical circumference of the cranium. The length is measured from the glabella to the occipital point, while the breadth, or greatest transverse diameter, is usually found near the external auditory meatus. The proportion of , ,, , , (breadth X 100) . , , , ,. . , breadth to length -. -r is termed the cephalic index, or index of breadth. The hei-ght is usually measured from the basion to the bregma, and the proportion of height , , (height X 100) to length j TT constitutes the vertical or height index. In studying the face the principal points to be noticed are the proportion of its length and breadth, the shape of the orbits and of the anterior nasal aperture, and the degree of projection of the jaws. The length of the face may be measured from the ophryon or nasion to the chin, or, if the man- dible be wanting, to the alveolar point; while its ividth is represented by the distance between the zygomatic arches. By comparing the length with the width of the face, skulls may be divided into two groups — dolichofacial, or leptoprosope (long-faced), and brachyfadal, or chemoprosnpe (short-faced). The orbital index signifies the proportion which the orbital height bears to the orbital width, thus: orbital height X 100 orbital width The na-sal index expresses the proportion which the width of the anterior nasal aperture bears to the height of the nose, the latter being measured from the nasion to the lower margin of the nasal aperture, thus: nasal width X 100 nasal height THE SKULL Afi A WHOLE 147 The degree of projection of the jaws is determined by the fjiiathic or alveolar index, which represents the proportion between the basialveolar and basinasal lengths, thus: basialveolar length X 100 basinasal length The following table, modified from that given by Duckworth, illustrates how these different indices may be utilized in the classification of skulls. Index. Classification. Nomenclature. Examples. 1. Cephalic . Below 75 Between 75 and SO Above 80 Dolichocephalic Mesaticephalic Brachycephalic Kaffirs and Native Australians Europeans and Chinese MongoUans and Andamans 2. Orbital . . Below 84 Between 84 and 89 Above 89 Microseme Mesoseme Megaseme Tasmanians and Nati\'e Australians Europeans Chinese and Polynesians 3. Nasal . . . Below 48 Between 48 and 53 Above 53 Leptorhine Mesorhine Platyrhine Europeans Chinese and Japanese Negroes and Native Australians 4. Gnathic . Below 98 Between 98 and 103 Above 103 Orthognathous Mesognathous Prognathous Europeans Chinese and Japanese Native Australians Surface Form. — The various bony prominences or landmarks which can be easily felt and recognized in the head and face, and which afford the means of mapping out the important struc- tures comprised in this region, are as follows: 1. Supraorbital arch. 2. Internal angular process. 3. E.xternal angular process. 4. Zygomatic arch. 5. Mastoid process. 6. External occipital protuberance. 7. Superior curved line of occipital bone. 8. Parietal eminences. 9. Temporal ridge. 10. Frontal eminences. 1 1 . Superciliary ridges. 12. Nasal bones. 13. Lower margin of orbit. 14. Mandible. (1) The supraorbital arches are to be felt throughout their entire extent, covered by the eye- brows. They form the upper boundary of the circumference or base of the orbits, and separate the face from the forehead. They are strong and arched, and terminate internally on each side of the root of the nose in the internal angular process, which articulates with the lacrimal bone. Externally they terminate in the external angular process, which articulates with the malar bone. This arched ridge is sharper and more defined in its outer than in its inner half, and forms an overhanging process which protects and shields the lacrimal gland. It thus protects the eye in its most exposed situation and in the direction from which blows are most likely to descend. ' The supraorbital arch varies in prominence in different individuals. It is more marked in the male than in the female, and in some races of mankind than others. In the less civilized races, as the forehead recedes backward, the supraorbital arch becomes more prominent, and approaches more to the characters of the monkey tribe, in which the supraorbital arches are very largely devel- oped, and acquire additional prominence from the oblique direction of the frontal bone. (2) The internal angular process is scarcely to be felt. Its position is indicated by the angle formed by the supraorbital arch with the nasal process of the maxilla and the lacrimal bone at the inner side of the orbit. Between the internal angular processes of the two sides is a broad surface which as.sists in furiiiiiig the root of the nose, and immediately above this a broad, smooth, somewhat ti-iaiiguhir suifiicc, the glabella, situated between the superciliary ridges. (3) The external angular process is much more strongly marked than the internal, and is plainly to be felt. It is formed by the junction or confluence of the supraorbital and temporal ridges, and, articulating with the malar bone, it serves to a very considerable extent to support the bones of the face. In carnivorous animals the external angular process does not articulate with the malar, and therefore this lateral support to the bones of the face is not present. (4) The zygomatic arch is plainly to be felt throughout its entire length, being situated almost immediately under tne skin. It is formed by the malar bone and the zygomatic process of the temporal bone. At its anterior extremity, where it is formed by the malar bone, it is broad arjfl forms the prominence 148 SPECIAL ANATOMY OF THE SKELETON of the cheek; the posterior part is narrower, and terminates just in front and a little above the tragus of the external ear. "I'he lower border is more plainly to be felt than the upper, in conse- quence of the dense temporal fascia being attached to the latter, which somewhat obscures its outline. Its shape differs very much in individuals and in different races of mankind. In the skulls of savages — as, for instance, in the skull of the negro of the Guinea Coast — the malar bones project forward and not outward, and the zygoma at its posterior extremity extends farther outward before it is twisted on itself to be prolonged forward. This makes the zygomatic arch stand out in bold relief, and affords greater space for the Temporal muscle. In skulls which have a more pyramidal shape, as in the Eskimos or Greenlanders, the malar bones do not pro- ject forward and downward under the eyes, as in the preceding form, but take a direction out- ward, forming with the zygoma a large, rounded sweep or segment of a circle. Thus it happens that if two lines are drawn from the zygomatic arches, touching the temporal ridges, they meet above the top of the head, instead of being parallel, or nearly so, as in the European skull, in which the zygomatic arches are not nearly so prominent. This gives to the face a more or less oval type. (5) Behind the ear is the mastoid portion of the temporal bone, plainly to be felt, and terminating below in a nipple-shaped process. Its anterior border can be traced immediately behind the concha, and its apex is on about a level with the lobule of the ear. It is rudimentary in infancy, but gradually develops in childhood, and is more marked in the negro than in the European. (6) The external occipital protuberance (inion) is always plainly to be felt just at the level where the skin of the neck joins that of the head. At this point the skull is thick for the purposes of safety, while radiating from it are numerous curved arches or buttresses of bone which give to this portion of the skull further security. (7) Running outward on either side from the external occipital protuberance is an arched ridge of bone, which can be more or less plainly perceived. This is the superior curved line of the occipital bone, and gives attachment to some of the muscles which keep the head erect on the vertebral column; accordingly, we find it more developed in the negro tribes, in whom the jaws are much more massive, and therefore require stronger muscles to prevent their extra weight carrying the head forward. Below this line the surface of bone at the back of the head is obscured by the overlying muscles. Above it the vault of the cranium is thinly covered with soft structures, so that the form of this part of the head is almost exactly that of the upper portion of the occipital, the parietal, and the frontal bones themselves; and in bald persons, even the lines of junction of the bones, especially the junction of the occipital and parietal at the lambdoid suture, may be defined as a slight depression caused by the thickening of the borders of the bones in this situation. (8) In the line of the greatest transverse diameter of the head, on each side of the middle line, are generally to be found the parietal eminences, one on each side of the middle line, though sometimes these eminences are not situated at the point of the greatest transverse diameter, which is at some other prominent part of the parietal region. They denote the point where ossification of the parietal bone began. They are much more prominent and well marked in early life, in consequence of the sharper curve of the bone at this period, so that it describes the segment of a smaller circle. Later in life, as the bone grows, the curve spreads out and forms the segment of a larger circle, so that the eminence becomes less distinguishable. In consequence of this sharp curve of the bone in early life, the whole of the vault of the skull has a squarer shape than it has in later life, and this appear- ance may persist in those suffering from rhachitis. The eminence is more apparent in the negro's skull than in that of the European. This is due to greater flattening of the temporal fossa in the former skull to accommodate the larger Temporal muscle which exists in these races. The parietal eminence is particularly exposed to injury from blows or falls on the head, but fracture is to a certain extent prevented by the shape of the bone, which forms an arch, so that the force of the blow is diffused over the bone in every direction. (9) At the side of the head may be felt the temporal ridge. Commencing at the external angular process, it may be felt as a curved ridge, passing upward and then curving backward, on the frontal bone, separating the forehead from the temporal fossa. It may then be traced passing backward in a curved direction, over the parietal bone, and, though less marked, still generally to be recognized. Finally, the ridge curves downward, and terminates in the posterior root of the zygoma, which separates the squamous from the subcutaneous mastoid portion of the temporal bone. (10) The frontal eminences vary a good deal in different individuals, being considerably more prominent in some than in others, and they are often not symmetrical on the two sides of the bodj', the one being much more pronounced than the other. This is often especially noticeable in the skull of the young child or infant, and becomes less marked as age advances. The prominence of the frontal eminences depends more upon the general shape of the whole bone than upon the size of the protuberances themselves. As the skull is more highly developed in consequence of in- creased intellectual capacity, so the frontal bone becomes more upright and the frontal eminences stand out in bolder relief. Thus they may be considered as affording, to a certain extent, an indication of the development of the hemispheres of the cerebrum beneath, and of the mental powers of the individual. They are not so much exposed to injury as the parietal eminences. In falls forward the upper extremities are involuntarily thrown out, and break the force of the fall, and tlius shield the frontal bone from injury. (11) Below the frontal eminences on the fore- THE 8KULL AS A WHOLE 149 head are the superciliary ridges, which denote the position of the frontal sinuses, and vary according to the size of the sinuses in different individuals, being, as a rule, small in the female, absent in children, and sometimes unusually prominent in the male, when the frontal sinuses are largely developed. They commence on either side of the glabella, and a( first present a rounded form, which gradually fades away at their outer ends. (12) The nasal bones form the promi- nence of the nose. They vary much in size and shape, and to them arc due the variations in contour of this organ and much of the character of the face. Thus, in the Mongolian or Ethio- pian they are flat, broad, and thick at their base, giving to these races the flattened nose by which they are characterized, and differing very decidedly from the Caucasian, in whom the nose, owing to the shape of the nasal bones, is narrow, elevated at the bridge, and elongated downward. Below, the nasal bones are thin and connected with .the cartilages of the nose, and the angle or arch formed by their union serves to throw out the bridge of the nose, and is nuuh more marked in some individuals than others. (13) The lower margin of the orbit, formed by the maxilla and the malar bone, is plainly to be felt throughout its entire length. It is continuous inter- nally with the nasal process of the maxilla, which forms the inner boundary of the orbit. At the point of junction of the lower margin of the orbit with the nasal process is to be felt a little tubercle of bone, which can be plainly perceived by running the finger along the bone in this situation. This tubercle serves as a guide to the position of the lacrimal sac, which is situated above and behind it. (14) The outline of the mandible may be felt throughout its entire length. Just in front of the tragus of the external ear, and below the zygomatic arch, the condyle can be made out. When the mouth is opened this prominence of bone can be perceived advancing out of the glenoid fossa on to the eminentia articularis, and receding again when the mouth is closed. From the condyle the posterior border of the ramus can be felt extending down to the angle. A line drawn from the condyle to the angle would indicate the exact position of this border. From the angle to the symphysis of the chin the lower, rounded border of the body of the bone may be plainly felt. At the point of junction of the two halves of the bone is a well-marked triangular eminence, the mental process, which forms the prominence of the chin. Applied Anatomy. — The thickness of the skull varies greatly in different regions of the same • skull and in different individuals. The average thickness of the skullcap is about one-fifth of an inch (-5 mm.). The thickest portions are the occipital protuberance, the inferior portion of the frontal bone, and the mastoid process. The thinnest portions are the occipital fossse, the squamous portion of the temporal bone, and over certain sinuses and arteries. An arrest in the ossifying process may give rise to deficiencies or gaps, or to fissures, which are of importance in a medicolegal point of view, as they are liable to be mistaken for fractures. The fissures gener- ally extend from the margin toward the centre of the bone, but gaps may be found in the middle as well as at the edges. In course of time they may become covered with a thin lamina of bone. Occasionally a protrusion of the brain or its membranes may take place through one of these gaps in an imperfectly developed skull. When the protrusion consists of membranes only, and is filled with cerebrospinal fluid, it is called a meningocele; when the protrusion consists of brain as well as membranes, it is termed an encephalocele; and when the protruded brain is a prolongation from one of the ventricles, and is distended by a collection of fluid from an accu- mulation in the ventricle, it is termed a hydrencephalocele. This latter condition is some- times found at the root of the nose, where a protrusion of the anterior horn of the lateral ventricle takes place through a deficiency of the frontonasal suture. These malformations are usually found in the middle line, and most frequently at the back of the head, the protrusion taking place through the fissures which separate the four centres of ossification from which the tabular portion of the occipital bone is originally developed (see page 73). They most frequently occur through the upper part of the vertical fissure, which is the last to ossify, but not uncommonly through the lower part, when the foramen magnum may be incomplete. More rarely these protrusions have been met with in other situations than those above mentioned, both through normal fissures, as the sagittal, lambdoid, and other sutures, and also through abnormal gaps and deficiencies at the sides, and even at the base of the skull. Force may be responsible in a young person for separating a suture. This accident, seldom met with even in the young, is only occasionally encountered in older persons. Fractures of the skull may be divided into those of the vault and those of the 5a.se. Frac- tures of the vault are usually produced by direct violence. This portion of the skull varies in thickness and strength in different individuals, but, as a rule, is sufficiently strong to resist a very considerable amount of violence without being fractured. This is due to several causes — the rounded shape of the head and its construction of a number of secondary elastic arches, each made up of a single bone; the fact that it consists of a number of bones, united at all events in early life by a sutural ligament, which acts as a sort of buffer and interrupts the continuity of any violence applied to the skull; the presence of arches or ridges, both on the inside and outside of the skull, which materially strengthen it; and the mobility of the head upon the vertebral column, which further enables it to withstand violence. The elasticity of the bones of the head is especially marked in the skull of the child, and this fact, together with the wide separation of 150 SPECIAL ANATOMY OF THE SKELETON the individual bones from each other, and the interposition between them of other and softer structures render fracture of the bones of the head a very uncommon event in infants and quite young children; as age advances and the bones become joined, fracture is more common, though still less liable to occur than in the adult. Fractures of the vault may, and generally do, involve the whole thickness of the bone; but sometimes one table may be fractured without any corre- sponding injury to the other. Thus, the outer table of the skull may be splintered and driven into the diploe, or in the frontal or mastoid regions into the frontal or mastoid cells, without any injury to the internal table. And on the other hand, the internal table has been fractured, and por- tions of it depressed and driven inward, without any fracture of the outer table. As a rule, in fractures of the skull the inner table is more splintered and comminuted than the outer, and this is due to several causes. It is thinner and more brittle; the force of the violence as it passes inward becomes broken up, and is more diffused by the time it reaches the inner table; the bone, being in the form of an arch, bends as a whole and spreads out, and thus presses the par- ticles together on the convex surface of the arch — i. e., the outer table — and forces them asunder on the concave surface or inner table; and lastly, there is nothing firm under the inner table to support it and oppose the force. Fractures of the vault may be simple fissures or starred and comminuted fractures, and these may be depressed or elevated. These latter cases of fracture with elevation of the fractured portion are uncommon, and can only be produced by direct wound. In comminuted fracture a portion of the skull is broken into several pieces, the lines of fracture radiating from a centre where the chief impact of the blow was felt; if depressed, a fissure circumscribes the radiating line, enclosing a portion of skull. If this area is circular, it is termed a pond fracture, and would in all probability have been caused by a round instru- ment, as a blackjack or hammer; if elliptical in shape, it is termed a gutter fracture, and would owe its shape to the instrument which had produced it, as a poker. A fracture may take place along the line of an ossified or partly ossified suture. When a surgeon explores the vault of the skull through a wound he must not mistake a Wormian bone for a fragment produced by a fractiu'e. A Wormian bone which may lead to mistake is encountered at the anterior inferior angle of the parietal bone. Fractures of the base are most frequently produced by the extension of a fissure from the vault, as in falls on the head, where the fissure starts from the part of the vault which first struck the ground. Sometimes, however, they are caused by direct violence, when foreign bodies have been forced through the thin roof of the orbit, through the cribriform plate of the ethmoid from being thrust up the nose, or through the roof of the pharynx. Other cases of fracture of the base occur from indirect violence, as in fracture of the occipital bone from impaction of the spinal column against its condyles in falls on the buttocks, knees, or feet, or in cases where the glenoid cavity has been fractured by the violent impact of the condyle of the mandible against it from blows on the chin. The most common place for fracture of the base to occur is through the middle fossa, and here the fissure usually takes a fairly definite course. Starting from the point struck, which is generally somewhere in the neighborhood of the parietal eminence, it runs downward through the parietal bone and the squamous portion of the temporal bone and across the petrous portion of this bone, frequently traversing and implicating the internal auditory meatus, to the middle lacerated foramen. From this it may pass across the body of the sphenoid, through the pituitary fossa to the middle lacerated foramen of the other side, and may indeed travel round the whole cranium, so as completely to separate the anterior from the posterior part. The course of the fracture should be borne in mind, as it explains the symptoms to which fracture in this region may give rise; thus, if the fissure pass across the internal auditory meatus, injury to the facial and auditory nerves may result, with consequent facial paralysis and deafness; or the tubular pro- longation of the arachnoid around these nerves in the meatus may be torn, and thus permit of the escape of the cerebrospinal fluid should there be a communication between the internal ear and the typanum and the membrana tympani be ruptured, as is frequently the case; again, if the fissure passes across the pituitary fossa and the mucoperiosteum covering the under surface of the body of the sphenoid is torn, blood will find its way into the pharynx and be swallowed, and after a time vomiting of blood will result. Fractures of the anterior fossa, involving the bones forming the roof of the orbit and nasal fossa, are generally the results of blows on the forehead; but fracture of the cribriform plate of the ethmoid may be a complication of fracture of the nasal bone. When the fracture implicates the roof of the orbit, the blood finds its way into this cavity, and, travelling forward, appears as a subconjunctival ecchymosis. Subconjunctival ecchymosis can also be caused by fracture of the malar bone. If the roof of the nasal fossa be fractured, the blood escapes from the nose. In rare cases there may be also escape of cerebrospinal fluid from the nose where the dura and arachnoid have been torn. In fractures of the posterior fossa extravasation of blood takes place beneath the deep fascia, and discoloration of the skin is soon observed in the course of the posterior auricular artery, the discoloration first appearing in the skin over the tip of the mastoid process of the temporal bone (Battle's sign). Some of the blood which was extra vasated beneath the deep fascia approaches the surface through the open- ings in the deep fascia for the passage of vessels and nerves. THE SKULL AS A WHOLE 151 The bones of the skull are frequently the seat of nodes, and not uncommonly necrosis results from this cause, also from injury. Necrosis may involve the entire thickness of the skull, but is usually confined to the external table. Necrosis of the internal table alone is rarely met with. The bones of the skull are also sometimes the seat of sarcomatous tumors. The skull in rachitis is peculiar — the forehead is high, square, and projecting, and the antero- posterior diameter of the skull is long in relation to the transverse diameter. The bones of the face are small and ill-developed, and this gives the appearance of a larger head than actually exists. The bones of the head are often thick, expecially in the neighborhood of the sutures, and the anterior fontanelle is late in closing, sometimes remaining unclosed until the fourth year. The condition of craniotabes has by some been also believed to be the result of rachitis, by others is believed to be due to inherited syphilis. In all probability it is due to both. In these cases the bone undergoes atrophic changes in patches, so that it becomes greatly thinned in places, generally where there is pressure, as from the pillow or nurse's arm. It is, therefore, usually met with in the parietal bone and vertical plate of the occipital bone. In congenital syphilis deposits of porous bone are often found at the angles of the parietal bones and two halves of the frontal bone which bound the anterior fontanelle. These deposits are separated by the coronal and sagittal sutures, and give to the skull the appearance of a hot cross bun. They are known as Parrot's nodes, and such a skull has received the name of natifonn, Fia. 118. — Division of the aiastoid prottss into four tquil parts An opening in the upper anterior quadrant reaches the mastoid antrum into the upper posterior quadrant reaches the lateral sinus the lower anterior quad- rant into mastoid cells; a superficial opening into the lower posterior quadrant reaches mastoid cells; a deep open- ing reaches the descending limb of the lateral sinus. (A. E. bchmitt.) from its fancied resemblance to the buttocks. The cells of the mastoid are sometimes the seat of suppuration as the result of infection extending backward from the tympanic cavity. In such cases the antrum of the mastoid must be opened in order that the pus escape. This is done by applying the gouge between the posterior wall of the external auditory meatus and the posterior root of the zygoma. This space is called the siiprameatal^ triangle of Macewen. In connection with the bones of the face a common malformation is cleft palate, o^ying to the nonunion of the palatal processes of the maxillary or preoral arch. This cleft may involve the whole or only a portion of the hard palate, and usually involves the soft palate also. The cleft is in the middle line, except it involves the alveolus in front, when it follows the suture between the main portion of the bone and the premaxillary bone. Sometimes the cleft runs on either side of the premaxillary bone, so that this bone is quite isolated from the maxillary bones and hangs from the end of the vomer. In such a case the premaxillary bone usually contains the germs of the central incisors only. In some cases there is no premaxillary bone and the great gap in the lip is in the median line. Cleft palate (page 106) is usually associated with harelip, which, when single, is almost always on one side, corresponding to the position of the suture between the lateral incisor and canine tooth. Some few cases of median harelip have been described. In double harelip there is a cleft on each side of the middle line. The outlines and the height of the arch of the palate vary greatly in different persons. A narrow palate with a high arch is common in idiots and certain degenerates. The bones of the face are sometimes fractured as the result of direct violence. The two 152 SPECIAL ANATOMY OF THE SKELETON most commonly broken are the nasal bone and the mandible, and of these, the latter is by far the most frequently fractured of all the bones of the face. Fracture of the nasal bone is for the most part transverse, and takes place about half an inch from the free margin. The broken portion may be displaced backward or more generally to one side by the force which produced the lesion, as there are no muscles here which can cause displacement. The malar bone is probably never broken alone; that is to say, unconnected with a fracture of the other bones of the face. The zygomatic arch is occasionally fractured, and when this occurs from direct violence, as is usually the case, the fragments may be displaced inward. This lesion is often attended with great diffi- culty or even inability to open and shut the mouth, and this has been stated to be due to the depressed fragments perforating the temporal muscle, but would appear rather to be caused by the injury done to the bony origin of the Masseter muscle. Fractures of the maxilla may vary much in degree, from the chipping off of a portion of the alveolar arch, to an extensive comminu- tion of the whole bone from severe violence, as the kick of a horse. The most common situa- tion for a. fracture of the mandible is in the neighborhood of the canine tooth, as at this spot the jaw is weakened by the deep socket for the fang of this tooth; it is next most frequently fractured at the angle; then at the symphysis, and finally the neck of the condyle or the coronoid process may be broken. Occasionally a double fracture may occur, one in either half of the bone. The fractiu-es are usually compound, from laceration of the mucous membrane covering the gums. The displacement is mainly the result of the same violence as produced the injury, but may be fiu-ther increased by the action of the muscles passing from the neighborhood of the sym- physis to the hyoid bone. The maxilla and mandible are both of them frequently the seat of necrosis, though the disease affects the latter much more frequently than the former. It may be the result of periostitis, from tooth irritation, injury, or the action of some specific poison, as syphilis, or from salivation by mercury; it not infrequently occurs in children after attacks of the exanthematous fevers, and a special form occurs from the action of the fumes of phosphorus in persons engaged in the manufacture of matches. Tumors attack the jaw bones not infrequently, and these may be either innocent or malig- nant; in the upper jaw cysts may occur in the antrum, constituting the so-called dropsy of the antrum ; or, again, cysts may form in either jaw in connection with the teeth — either cysts con- nected with the roots of fully developed teeth, the "dental cyst;" or cysts connected with imper- fectly developed teeth, the "dentigerous cyst." Solid innocent tumors include the fibroma, the chondroma, and the osteoma. Of malignant tumors there are the endotheliomata, the sarcomata, and the epitheliomata. The sarcomata are of various kinds, the spindle-celled, the round-celled, which are of a very malignant character, and the myeloid sarcomata, prin- cipally affecting the alveolar margin of the bone. Of the epitheliomata we find the squamous variety spreading to the bone from the palate or gum, and the cylindrical epithelioma origi- nating in the antrum or nasal fossEe. Both mandible and maxilla occasionally recjuire excision for tumors and in some other condi- tions. The maxilla is removed by an incision from the inner canthus of the eye, along the side of the nose, around the ala, and down the middle line of the upper lip. A second incision is carried outward from the inner canthus of the line along the lower margin of the orbit as far as the prominence of the malar bone. The flap thus formed is reflected outward and the surface of the bone exposed, and the central incisor of the diseased side is removed. The connections of the bone to the other bones of the face are then divided with a narrow saw and bone-cutting forceps. They are (1 ) the junction with the malar bone, passing into the sphenomaxillary fissure; (2) the nasal process; a small portion of its upper extremity, connected with the nasal bone in front, the lacrimal bone behind, and the frontal bone above, being left; (3) the connection with the bone on the opposite side and the palate in the roof of the mouth. The bone is now firmly grasped with lion-jaw forceps, and by means of a rocking movement upward and downward the remaining attachments of the orbital plate with the ethmoid and the back of the bone with the palate, broken through. The soft palate is first separated from the hard with a scalpel, and is not removed. Occasionally in removing the maxilla it will be found that the orbital plate can be spared, and this should always be done if possible. A horizontal saw-cut is to be made just below the infraorbital foramen and the bone cut through with a chisel and mallet. Lockwood has pointed out that in removing the maxilla the surgeon must be careful in dividing the nasal process of the maxilla to preserve the internal orbital or palpebral ligament (Tendo oculi), because this ligament arises from the palpebral fascia, and if it is interfered with the eye will inevitably drop downward. Removal of one-half of the mandible is sometimes required. If possible, the section of the bone should be made to one side of the symphysis, so as to save the genial tubercles and the origin of the Geniohyoglossus muscle, as otherwise the tongue tends to fall backward and may produce sufl^ocation. Having extracted the central or preferably the lateral incisor tooth, a vertical incision is made down to the bone, commencing at the free margin of the lip, and carried to the lower border of the bone; it is then carried along its lower border to the angle and up the posterior margin of the ramus to a level with the lobule of the ear. The flap THE II VOID OB LINGUAL BONE 153 thus formed is raised by separating; all the structures attached to the outer surface of the l)one. The jaw is now sawed through at the point where the tooth has been extracted, and the knife passed along the inner side of the mandible, separating the structures attached to this surface. The mandible is then grasped by the surgeon and strongly depressed, so as to bring down the coronoid process and enable the operator to sever the tendon of the Temporal muscle. The mandible can be now further depressed, care being taken to not evert it nor rotate it outward, which would endanger the internal maxillary artery, and the External pterygoid muscle is torn through or divided. The capsular ligament is now opened in front and the lateral ligaments divided, and the mandible removed with a few final touches of the knife. The antrum of Highmore occasionally requires tapping for suppuration. This may be done through the socket of a tooth, preferably the first molar, the fangs of which are most intimately connected with the antrum, or through the facial aspect of the bone above the alveolar pro- cess. This latter method does not perhaps afford such efficient drainage, but there is less chance of food finding its way into the cavity. The operation may be performed by incising the mucous membrane above the second molar tooth, and driving a trocar or any sharp-pointed instrument into the cavity. THE HYOID OR LINGUAL BONE (OS HYOIDEUM). The hyoid bone (Fig. 119) is a bony arch, shaped like a horseshoe, and consist- ing of five segments — a body, two greater cornua, and two lesser cornua. It is suspended from the tips of the styloid processes of the temporal bones by ligamentous bands, the stylohyoid ligaments. The Body, or basihyal {corpus ossei hyoidei), forms the central part of the bone, and is of a quadrilateral form. Surfaces. — Its anterior surface (Fig. 119), convex, directed forward and upward, is divided into two parts by a vertical ridge which descends along the median Fia. H9. — Hyoid bone. Anterior line and is crossed at right angles by a horizontal ridge, so that this surface is divided into four spaces or depressions. At the point of meeting of these two lines is a prominent elevation, the tubercle. The anterior surface gives attach- ment to the Geniohyoid in the greater part of its extent; above, to the Genio- hyoglossus; belotv, to the Mylohyoid, Stylohyoid, and the aponeurosis of the Digastric (suprahyoid aponeurosis); and between these to part of the Hyo- glossus. The posterior surface is smooth, concave, directed backward and downward, and separated from the epiglottis by the thyrohyoid membrane and by a quantity of loose areolar tissue. The lateral surfaces are joined to the greater cornua. In early life they are connected with the cornua by cartilaginous surfaces, and held together by ligaments, and occasionally a synovial membrane is found between them. 154 SPECIAL ANATOMY OF THE SKELETON Borders. — The superior border is rounded, and gives attachment to the thyro- hyoid membrane, part of the Geniohyoglossi and Chondroglossi muscles. The inferior border gives attachment, in front, to the Sternohyoid; behind, to the Omo- hyoid and to the part of the Thyrohyoid at its junction with the great cornua. It also gives attachment to the Levator glandulae thyroideae when this muscle is present. The Greater Cornua (cornua viajora), or thyrohyals, project backward from the lateral surfaces of the body; they are flattened from above downward, diminish in size from before backward, and terminate posteriorly in a tubercle for the attachment of the lateral thyrohyoid ligament. The outer surface gives attachment to the Hyoglossus, their upper border to the Middle constrictor of the pharynx, their lower border to part of the Thyrohyoid muscle. The Lesser Cornua (cornua minora), or ceratohyals, are two small, conical- shaped eminences attached by their bases to the angles of junction between the body and greater cornua, and giving attachment by their apices to the stylohyoid ligaments.' The smaller cornua are connected to the body of the bone by a distinct diarthrodial joint, which usually persists throughout life, but occasion- ally becomes ankylosed. Development. — From six centres — two (sometimes one) for the body, and one for each cornu. Ossification commences in the body about the eighth month, and in the greater cornua toward the end of fetal Ufe. Ossification of the lesser cornua commences in the first or second year after birth. Attachment of Muscles. — Sternohyoid, Thyrohyoid, Omohyoid, aponeurosis of the Digastric, Stylohyoid, Mylohyoid, Geniohyoid, Geniohyoglossus, Chondroglossus, Hyoglossus, Middle constrictor of the pharynx, and occasionally a few fibres of the Inferior lingualis. It also gives attachment to the thyrohyoidean membrane and the stylohyoid, thyrohyoid, and hyoepiglottic ligaments. Surface Form. — The hyoid bone can be felt in the receding angle below the chin, and the finger can be carried along the whole length of the bone to the greater cornu, which is situated just below the angle of the mandible. This process of bone is best perceived by making pressure on one cornu, and so pushing the bone over to the opposite side, when the cornu of this side will be distinctly felt immediately beneath the skin. This process of bone is an important landmark in ligation of the lingual artery. Applied Anatomy. — The hyoid bone is occasionally fractured, generally from direct vio- lence, as in the act of garroting or throttling. It is frequently found broken in those who have been hanged. The greater cornu is the part of the bone most frequently broken, but sometimes the fracture takes place through the body of the bone. In consequence of the muscles of the tongue having important connections with this bone, there is great pain upon any attempt being made to move the tongue, as in speaking or swallowing. THE THORAX. The thorax, or chest, is an osseocartilaginous cage, the cavity of which (cavum thoracis) contains and protects the principal organs of respiration and circula- tion. It is conical in shape, being narrow above and broad below, flattened from before backward, and longer behind than in front. It is somewhat reni- form on transverse section. Boundaries. — The posterior surface is formed by the twelve thoracic vertebrae and the posterior part of the ribs. It is concave from above downward, and pre- sents on each side of the middle line a deep groove, the vertebral groove, in conse- quence of the direction backward and outward which the ribs take from their vertebral extremities to their angles. The anterior surface is flattened or slightly convex, and inclined forward from above downward. It is formed by the sternum 1 These ligaments in many animals are distinct bones, and in man are occasionally ossified to a certain extent. THE THORAX 155 and costal cartilages. The lateral sxirfaces are convex; they are formed by the ribs, separated from each other by spaces. Each space is called an intercostal space (sfatiwm inter costale). These are eleven in number, and are occupied by the intercostal muscles. Fir'it thoracic Fig. 120.— The thor: The superior or upper aperture of the thorax, the inlet (apertura thoracis supe- rior), is reniform in shape, being broader from side to side than from before back- ward. It is formed by fhe first thoracic vertebra behind, the upper margin of the sternum in front, and the first rib on each side. It slopes downward and forward, so that the anterior boundary is on a lower level than the posterior. The antero-posterior diameter is about two inches (5 cm.), and the transverse about Jour (10 cm.). The parts which pass through the upper opening of the thorax are, froiri' tefore backward in or near the middle line, the Sternohyoid and Sternothyroid muscles, the remains of the thymus gland, the trachea, oesophagus, thoracic duct, the inferior thyroid veins, and the Longus colli muscle of each side; at the sides, the innominate artery, the left common carotid, and 156 SPECIAL ANATOMY OF THE SKELETON left subclavian arteries, the internal mammary and superior intercostal arteries, the right and left innominate veins, the vagus, cardiac, phrenic, and sympathetic nerves, the anterior branch of the first thoracic nerve, and the recurrent laryngeal nerve of the left side. The apex of each lung, covered by the pleura, also projects through this aperture, a little above the margin of the first rib. Fig. 121. — The thorax. Dorsal view. (Spaltcholz.) The inferior or lower opening (apertura thoracis inferior) is formed by the twelfth thoracic vertebra behind, by the twelfth ribs at the sides, and in front by the eleventh, tenth, ninth, eighth, and seventh costal cartilages, which ascend on either side and form an angle, the subcostal angle (angulus infrasternalis), from the apex of which the ensiform cartilage projects. It is wider transversely than from before backward. It slopes oblicjuely downward and backward, so that the cavity of the thorax is much deeper behind than in front. The Diaphragm closes in the opening forming the floor of the thorax. THE STEBNU3I, OB BREAST BONE I57 The Cavity of the Thorax (caviim thoracis). — The capacity of the cavity of the thorax does not correspond with its apparent size externally, because (1) the space enclosed by the lower ribs is occupied by some of the abdominal viscera; and (2) the cavity extends above the first rib into the neck. The size of the cavity of the thorax is constantly varying during life, with the movements of the ribs and Diaphragm, and with the degree of distention of the abdominal viscera. From the collapsed state of the lungs, as seen when the thorax is opened, in the dead body, it would appear as if the viscera only partly filled the cavity of the thorax, but during life there is no vacant space, that which is seen after death being filled up during life by the expanded lungs. In the female the thorax differs as follows from the male: (1) Its general capacity is less. (2) The sternum is shorter. (3) The upper margin of the sternum is on a level with the lower part •of the body of the third thoracic vertebra, whereas in the male it is on a level with the lower part of the body of the second thoracic vertebra. (4) The upper ribs are more movable, and so allow a greater enlargement of the upper part of the thorax than in the male. The Sternum, or Breast Bone. The sternum, or breast bone (Figs. 122 and 123), is a flat, narrow bone, situated in the median line of the front of the chest, and consisting, in the adult, of three portions. It has been likened to an ancient sword; the upper piece, representing the handle, is termed the manubrium sterni (presternum) ; the middle and largest piece, which represents the chief part of the blade, is termed the gladiolus (corpus sterni or mesosternum) ; and the inferior piece, which is hkened to the point of the sword, is termed the ensiform appendix {processus xiphoideus or meta- sternum). In its natural position its inclination is oblique from above down- ward and forward. It is slightly convex in front, concave behind, broad above, becoming narrowed at the point where the first and second pieces are connected, after which it again widens a little, and is pointed at its extremity. Its average length in the adult is abouL,§£.ven inches (17.5 cm.), being rather longer IiTthe male than in the female. At the junction of the manubrium and gladiolus is a distinct angle {angulus Ludovici), the gladiolus looking forward, the manubrium also looking forward, but to a less degree. This angle is on a level with the second rib, and is produced by retraction of the upper portion of the thorax. First Piece. — The manubrium sterni is of a somewhat triangular form, broad and thick above, narrow below at its junction with the middle piece. Surfaces. — Its anterior surface, convex from side to side, concave from above downward, is smooth, and affords attachment on each side to the Pectoralis major and sternal origin of the Sternomastoid muscle. In well-marked bones the ridges limiting the attachment of these muscles are very distinct. Its posterior surface, concave and smooth, affords attachment on each side of the Sternohyoid and Sternothyroid muscles. Borders. — The superior border, the thickest, presents at its centre the prestemal notch (i)icisura jiigularis), and on each side an oval articular surface, the clavicular facet (incisura clavicidaris), directed upward, backward, and outward, for articulation with the sternal end of the~clavicle. The inferior border presents an oval, rough surface, covered in the recent state with a thin layer of cartilage, for articulation with the second portion of the bone (synchondrosis sternalis). The junction of the manubrium with the gladiolus is marked by a transverse ridge, which corresponds to the attachment on each side of the cartilage of the second rib. The lateral borders are marked above by a depression (iiicisura cosfalis I) for the first costal cartilage, and below by a small facet, which, with a 158 SPECIAL ANATOMY OF THE SKELETON i\G. 122.— Anterior (ventral) surface of sternum and Fig. 123.— Posterior (dorsal) surface of sternum, costal cartilages. THE STERNUM, OB BREAST BONE 159 similar facet on the upper angle of the middle portion of the bone, forms a notch {incisura costalis II) for the reception of the costal cartilage of the second rib. These articular surfaces are separated by a narrow, curved edge, which slopes from abo\'e downward and inward. Second Piece. — The gladiolus, considerably longer, narrower, and thinner than the first piece, is broader below than above. Surfaces. — Its anterior surface (planum sternale) is nearly flat, directed upward and forward, and marked by three transverse lines which cross the bone opposite the third, fourth, and fifth articular depressions. These lines are produced by the union of the four separate pieces of which this part of the bone consists at an early period of life. At the junction of the third and fourth pieces is occasionally seen an orifice, the sternal foramen; it varies in size and form in different individuals and pierces the bone from before backward. This surface affords attachment on each side to the sternal origin of the Fectoralis major. The posterior surface, slightly concave, is also marked by three transverse lines, but they are less dis- tinct than those in front; this surface affords attachment below, on each side, to the Triaogularis sterni muscle, and occasionally presents the posterior opening of the sternal foramen. Borders. — The superior border presents an oval surface for articulation with the manubrium. The inferior border is narrow, and articulates with the ensiform appendix. Each lateral border presents, at each superior angle, a small facet, which, with a similar facet on the manubrium, forms a cavity for the cartilage of the second rib; the four succeeding angular depressions receive the cartilages of the third, fourth, fifth, and sixth ribs; while each inferior angle presents a small facet, which, with a corresponding one on the ensiform appendix, forms a notch for the cartilage of the se\'enth rib. They are separated by a series of curved interarticular intervals, which diminish in length from above downward, and correspond to the intercostal spaces. Most of the cartilages belonging to the true ribs, as will be seen from the foregoing description, articulate with the sternum at the line of junction of two of its primitive component segments. This is well seen in many of the lower animals, where the separate parts of the bone remain ununited longer than in man. In this respect a striking analogy exists between the mode of connection of the ribs with the vertebral column and the connection of the costal cartilages with the sternum. Third Piece. — The ensiform or xiphoid appendix is the smallest of the three ; it is thin and elongated in form, cartilaginous in structure in youth, but more or less ossified at the upper part in the adult. Surfaces. — Its anterior surface affords attachment to the chondroxiphoid liga- ment; its posterior surface, to .some of the fibres of the Diap^liragm and Triangii^ laris sterni muscles; its lateral borders, to the aponeurosis of the abdominal muscles. Above Tf articulates with the lower end of the gladiolus, and at each superior angle presents a facet (incisura costalis VII), for the lower half of the cartilage of the seventh rib; below, by its pointed extremity, it gives attachment to the linea alJDa. This portion of the sternum varies much in appearance, being some- times pointed, broad, and thin, sometimes bifid or perforated by a circular open- ing, occasionally curved or deflected considerably to one or the other side. Structure. — The bone is composed of delicate cancellous structure, covered by a thin layer of compact tissue, which is thickest in the manubrium between the articular facets for the clavicles. Development. — The cartilaginous sternum originally consists of two bars, situated one on either side of the mesal plane and connected with the rib cartilages of its own side. It is usual for the eighth cartilage to lose its attachment to the sternum and become attached to the seventh cartilage. The sternal end of the ninth cartilage divides longitudinally, the mesal part remains 160 SPECIAL ANATOMY OF THE SKELETON attached to the sternum and becomes the ensiform process. The remaining part acquires attachment to the eighth cartilage. These two bars fuse with each other along the middle line, and the bone, including the ensiform appendix, is usually developed from six centres, one for the first piece or manubrium, four for the second piece or gladiolus, and one for the ensiform appendix. Up to the middle of fetal life the sternum is entirely cartilaginous, and when ossification takes place the ossific granules are deposited in the middle of the intervals between the articular depressions for the costal cartilages, iu the following order (Fig. 125): In the manubrium and first piece of the gladiolus, during the sixth month; in the second and third pieces of the gladiolus between the seventh and ninth months; the fourth piece of the gladiolus ossifies toward the latter part of the first year; the ensiform process ossifies Vjetween the fifth and eighteenth years. The centres appear in the upper part of each segment and proceed gradually downward. To these may be added the occasional existence, as described by Breschet, of two episternal centres, which make their appearance one on each side of the presternal notch. They are probably vestiges of the episternal bone of the monotremata and lizards. It occasionally happens that some of the segments are formed from more than one centre, the number and position of which vary (Fig. 127). Thus, the first piece may have two, three, or even six centres. When two are present, they are generally situated one above the other, the upper one being the larger;' the second piece has seldom more than one; the Fig. 124. — Showing ventral ends of the upper seven (cartilaginous) ribs fused to form a pair of longitudinal sternal bars. 1 for mannbriiim 4 for gladiobisJ^ \ 7th month 5 1st year after birth '^z::^r\'''^'' ''"''""- [ Barely unite, Sijrii'" ■ '^ 1 except in old age. Between puberty and the 25th year. Soon after puberty. Partly cartilaginous to advanced life. Fig. 126. — Time of unioa of for first piece, two or more centres. 12^ V""^ f<^^' second piece, usually one. %T~ for third 1 '0 u tO for fourth \ 2, placed laterally. f^^ K) for fifth J Arrest of development of lateral pieces, producing Sternal fissure, and Sternal foramen. Fig, 127. — Peculiarities in number of centres of sternum. Fig. 128. — Peculiarities in mode of union of sternum. ^ Sir George Humphry states that this is "probably the more complete condition." THE RIBS 101 Non-articular pari of tubercle Angle I I 1^ Articular part of lulerclc third, fourth, and fifth pieces are often formed from two centres placed laterally, the irregular union of which will serve to explain the occasional occurrence of the sternal fora- men (Fig. 126), or of the vertical sternal fissure, which occa- sionally intersects this part of the bone (Fig. 126), and which is further explained by the manner in which the cartilaginous matrix, in which ossification takes place, is formed. Union of the various centres of the gladiolus com- mences about puberty, from below, and proceeds upward, so that by the age of twenty-five they are all united, and this portion of bone consists of one piece. The ensiform cartilage becomes joined to the gladiolus about forty. The manubrium is occasionally but seldom joined to the gladiolus in advanced life by bone. When this union takes place, however, it is generally only superficial, a portion of the centre of the sutural cartilage remaining unossified. Articulations. — With the clavicles and seven costal carti- lages on each side. Attachment of Muscles.— To nine pairs and one single muscle — the Pectoralis major, Sternomastoid, Sternohyoid, Sternothyroid, Triangularis sterni, aponeuroses of the ■Shaft Obliquus externus abdominis, Obliquus internus abdominis, Transversalis, Rectus abdominis muscles, and Diaphragm. The Ribs (Costae). Tlie ribs are elastic arches of bone, which form the chief part of the thoracic wails. They are twelve in number on each side; but this number may be increased by the development of a cervical or lumbar rib, or may be diminished to eleven. The first^ .seven are connected behind with the spine and in front with the sternum, through the intervention of the costal cartilages; they are called true (vertebrosternal) ribs (costae verae)} The remaining five are false ribs {costae spuriae); of these, the first three have '<,\ their cartilages attached to the cartilage of the rib \\ ^ above, the vertebrochondral ribs; the last two are free V\ ^ \ ^' '^heir anterior extremities, the floating or vertebral \ \ \ \ ribs. The ribs vary in their direction, the upper ones •d l^i|/ ^Demifacet for vertebra. Subcostal groove Fig. 130. — A central rib of the left side, viewed from bebind. articulation with the costal cavity formed by the junction of the bodies of two contiguous thoracic vertebras; the upper facet is small, the inferior one of larger size; the ridge separating them serves for the attachment of the interarticular ligament. The neck (collum costae) is that flattened portion of the rib which extends out- ward from the head; it is about an inch long, and is placedLjnJi'ont of thejracs- verse process of the lower of the two vertebrae with which the head articulates. Its anterior surface is flat and smooth, its posterior surface is rough for the attach- ment of the middle costotransverse ligament,^^JKt is perforated by nimierous foramina, the direction of which is less constant than those found on the inner surface of the shaft. Of its two borders, the superior border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse liga- ment; its inferior border is rounded. On the posterior surface of the neck, just where it joins the shaft, and nearer the lower than the upper border, is an eminence — the tuberosity, or tubercle. The tuberosity (tuhrrciilnm costae) consists of an articular and a nonanicular portion. The articular portion (fades articularis tubercidi costae), the more in- ternal and inferior of the two, presents a small, oval surface or articulation with the extremity of the transverse process of the lower of the two vertebrse to which the head is connected. The nonarticular portion is a rough elevation, which THE RIBS 153 affords attachment to the posterior costotransverse ligament. The tiihercle is much more prominent in the upper than in tlie lower ril)s. Anterior Extremity. — The anterior or sternal extremity is flattened, and presents a porous, oval, concave depression, into which the costal cartilage is received. The shaft (cor-pus costae) is thin and flat, so as to present two surfaces, an external and an internal, and two borders, a superior and an inferior. The external surface is convex, smooth, and marked at its back part, a little in front of the tuberosity, by a prominent line, directed obliquely from above downward and outward; this gives attachment to a tendon of the Iliocostalis_ muscle or of one of its accessory portions, and is called the angle (anc/ulus costae). At this point the rib is bent in two directions. If the rib is laid upon its lower border, it will be seen that the portion of the shaft in front of the angle rests upon this border, while the portion of the shaft behind the angle is bent inward and at the same time tilted upward. The interval between the angle and the tuberosity increases gradually from the second to the tenth rib. The portion of bone between these two parts is rounded, rough, and irregular, and serves for the attachment of the Longissimus dorsimuscle. The portion of bone between the tubercle and sternal extremity is also slightly twisted upon its own axis, the external surface looking downward behind the angle, a little upward in front of it. This surface presents toward its sternal extremity an oblique line, the anterior angle. The internal surface is concave, smooth, directed a little upward behind the angle, a little downward in front of it. This surface is marked by a ridge which com- mences at the lower extremity of the head; it is strongly marked as far as the inner side of the angle, and gradually becomes lost at the junction of the anterior with the middle third of the bone. The interval between it and the inferior border presents a groove, subcostal groove {sulcus costae), for the intercostal vessels and nerve. At the back part of the bone this groove belongs to the inferior border, but just in front of the angle, where it is deepest and broadest, it corresponds to the internal surface. The superior edge of the groove is rounded; it serves for the attachment of the Internal intercostal muscle. The inferior edge corresponds to the lower margin of the rib and gives attachment to the External intercostal muscle. Within the groove are seen the orifices of numerous small foramina which traverse the wall of the shaft obliquely from before backward. The superior border, thick and rounded, is marked by an external and an inter- nal lip, more distinct behind than in front; they serve for the attachment of the External and Internal intercostal muscles. The inferior border, thin and sharp, has attached to it the External intercostal muscle. Peculiar Ribs. — The ribs which require especial consideration are five in number, viz., the first, second, tenth, eleventh, and twelfth. First Rib. — The first rib (Fig. 131) is the shortest and the most curved of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward. The head is of small size, rounded, and presents only a single articular facet for articulation with the body of the first thoracic ver- tebra. The neck is narrow and rounded. The tuberosity, thick and prominent, rests on the outer border. There is no angle, but in this situation the rib is slightly bent, with the convexity of the bend upward, so that the head of the bone is directed downward. The upper surface of the shaft is marked by two shallow depressions, separated by a small rough surface (tuberculum scaleni) for the attach- ment of the Scalenus anticus muscle — the shallow groove in front of it trans- mitting the subclavian vein, the deeper groove behind it (sulcus subclaviae^ the subclavian artery. Between the groove for the subclavian artery and the tuberosity is a rough surface, for the attachment of the Scalenus medius muscle. The under surface is smooth, and destitute of the groove observed on the other 164 SPECIAL ANATOMY OF THE SKELETON ribs The outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first serration of the Serratus magnus; the inner is con- cave thin and sharp, and marked about its centre by the commencement ot Bm^i^^^^'''' Single articular facet — SinjZe arftCM/rtr/ncrf.— ^^^^ Tuberosity 11 Single articular facet. Figs. 131 to 135.— Pecul the rough surface for the Scalenus anticus. The anterior extremity is larger and thicker than any of the other ribs. Second Rib.— The second rib (Fig. 132) is much longer than the first, but bears a very considerable resemblance to it in the direction of its curvature. The non- THE COSTAL CARTILAGES 165 articular portion of the tuberosity is occasionally only slightly marked. The angle is slight and situated close to the tuberosity, and the shaft is not twisted, so tliat both ends touch any plane surface upon which it may be laid; but there is a similar though slighter bend, with its convexity upward, to that found in the first rib. The shaft is not horizontal, like that of the first rib, its outer surface, which is convex, looking upward and a little outward. It presents, near the middle, a rough emi- nence {tuberositas costae II), for the attachment of part of the first and all of the second digitations of the Serratus magnus; behind and above which is attached the Scalenus posticus. The inner surface, smooth and concave, is directed down- ward and a little inward; it presents a short groove tow^ard its posterior part. Tenth Rib. — The tenth rib (Fig 133) has only a single articular facet on its head. Eleventh and Twelfth Ribs.— The eleventh and twelfth ribs (Figs. 134 and 135) have each a single articular facet on the head, which is of rather large size; they have no neck or tuberosity, and are pointed at the extremity. The eleventh has a slight angle and a shallow groove on the lower border. The twelfth has neither, and is much shorter than the eleventh, and the head has a slight inclina- tion downward. Sometimes the twelfth rib is even shorter than the first. Structure. — The ribs consist of cancellous tissue enclosed in a thin layer of compact bone. Development. — Each rib, with the exception of the last two, is developed from three centres, one for the shaft near the angle, one for the head, and one for the tubercle. The last two ribs have only two centres, that for the tubercle being wanting. Ossification commences in the shaft of the ribs between the ninth and eleventh weeks before its appearance in the vertebrje. The epiphysis of the head, which is of slightly angular shape, and that for the tubercle, of a lenticular form, make their appearance between the sixteenth and twentieth years, and are not united to the rest of the bone until about the twenty -fifth year. Attachment of Muscles. — To nineteen — the Intercostales externi et interni, Scalenus anticus, Scalenus uicdius, Sc^ilenus posticus, Pectoralis minor, Serratus magnus, Obliquus externus ulidominis, (^uadratus lumborum. Diaphragm, Latissimus dorsi, Serratus posticus superior, Serratus posticus inferior, Iliocostalis, Musculus accessorius ad iliocostalem, Lon- gissimus dorsi, Cervicalis ascendens, Levatores costarum, and Infracostales. The Costal Cartilages. The costal cartilage (cartilago costalis) (Fig. 122) is white, hyaline cartilage. The cartilages serve to prolong the ribs forward to the front of the thorax, and they contribute very materially to the elasticity of its walls. The first seven are con- nected with the sternum, the next three with the lower border of the cartilage of the preceding rib. The cartilages of the last two ribs have pointed extremities, W'hich terminate in free ends in the walls of the abdomen. Like the ribs, the costal cartilages vary in their length, breadth, and direction. They increase in length from the first to the seventh, then gradually diminish to the last. They diminish in breadth, as well as the intervals between them, from the first to the last. They are broad at their attachment to the ribs, and taper toward their sternal extremities, excepting the first two, which are of the same breadth throughout, and the sixth, seventh, and eighth, which are enlarged where their margins are in contact. In direction they also vary; the first descends a little, the second is horizontal, the third ascends slightly, while all the rest follow the course of the ribs for a short extent, and then ascend to the sternum or preceding cartilage. Each costal cartilage presents two surfaces, two borders, and two extremities. Surfaces. — The anterior surface is convex, and looks forward and upward; that of the first gives attachment to the costoclavicular ligament and the Subclavius muscle; that of the second, third, fourth, fifth, and sixth, at their sternal ends, to the Pectoralis major.' The others are covered by, and give partial attachment to, some of the great flat muscles of the abdomen. The posterior surface is con- 1 The first and seventh also, occasionally, give origin to the same muscle. 166 SPECIAL ANATOMY OF THE SKELETON cave, and directed backward and downward, the first giving attachment to the Sternothyroid, the third to the sixth inclusive to the Triangularis sterni, and the six or seven inferior ones to the Transversalis muscle and the Diaphragm. Borders. — Of the two borders, the superior border is concave, the inferior con- vex; they afford attachment to the Internal intercostal muscles, the upper border of the sixth giving attachment to the Pectoralis major muscle. The contiguous borders of the sixth, seventh, and eighth, and sometimes the ninth and tenth, costal cartilages present small, smooth, oblong-shaped facets at the points where they, articulate. Extremities. — Of the two extremities, the outer extremity is continuous with the osseous tissue of the rib to which it belongs. The inner extremity of the first is continuous with the sternum; the six succeeding ones have rounded extremities, which are received into shallow concavities on the lateral margins of the sternum. The inner extremities of the eighth, ninth, and tenth costal cartilages are pointed, and are connected with the cartilage above. Those of the eleventh and twelfth are free and pointed. The costal cartilages are most elastic in youth, those of the false ribs being more so than the true. In old age they become of a deep yellow color, and are prone to calcify. Attachment of Muscles. — To nine — the Subclavius, Sternothyroid, Pectoralis major, Internal oblique, Transversalis, Rectus abdominis. Diaphragm, Triangularis sterni, and Internal intercostals. Surface Form. — The bones of the thorax are to a very considerable extent covered by mus- cles, so that in the strongly developed muscular subject they are for the most part concealed. In the emaciated subject, on the other hand, the ribs, especially in the lower and lateral region, stand out as prominent ridges with the sunken, intercostal spaces between them. In the median line, in front, the superficial surface of the sternum is to be felt throughout its entire length, at the bottom of a deep median furrow- (the sternal furrow) situated between the two great pectoral muscles. These muscles overlap the anterior surface somewhat, so that the whole of the sternum in its entire width is not subcutaneous; and this overlapping is greater opposite the centre of the bone than above and below, so that the furrow is wider at its upper and lower parts, but narrower in the middle. The centre of the upper border of the ster- num is visible, constituting the prestemal notch, but the lateral parts of this border are obscured by the tendinous origins of the Sternomastoid muscles, which present themselves as oblique tendinous cords, which narrow and deepen the notch. Lower down on the sub- cutaneous surface, a well-defined transverse ridge, the angulus Ludovici, is always to be felt. This denotes the line of junction of the manubrium and the body of the bone, and is a useful guide to the second costal cartilage, and thus to the identity of any given rib. The second rib being found through its costal cartilage, it is easy to count downward and find any other. From the middle of the sternum the furrow spreads out, and, exposing more of the surface of the body of the bone, terminates below in a sudden depression, the infrastemal depression, or pit of the stomach {scrohiculus cordis), which corresponds to the ensiform cartilage. This depression lies between the cartilages of the seventh ribs, and in it the ensiform cartilage may be felt. The sternum in its vertical diameter presents a general convexity forward, the most prominent point of which is at the joint between the manubrium and gladiolus. On each side of the sternum the costal cartilages and ribs on the front of the thorax are par- tially obscured by the great jiectoral muscles, through which, however, they are to be felt as ridges, with yielding intervals between them, corresponding to the intercostal spaces. Of these spaces, the one between the second and third ribs is the widest, the next two somewhat nar- rower, and the remainder, with the exception of the last two, comparatively narrow. The lower border of the Pectoralis major muscle corresponds to the sixth rib, and below this, on the front of the thorax, the broad, flat outline of the ribs as they begin to ascend, and the more rounded outline of the costal cartilages, are often visible. The lower boundary of the front of the thorax, the abdominothoracic arch, which is most plainly seen by arching the body backward, is formed by the ensiform cartilage and the cartilages of the seventh, eighth, ninth, and tenth ribs, and the extremities of the eleventh and twelfth ribs or their cartilages. On each side of the thorax, from the axilla downward, the flattened external surfaces of the ribs may be defined in the form of oblique ridges, separated by depressions corresponding to the intercostal spaces. They are, however, covered by muscles, which obscure their outline to a certain extent in the strongly developed. Nevertheless, the ribs, with the exception of the first, can generally be followed over the front and sides of the thorax without difficulty. The first rib, being almost completely covered by the clavicle and scapula, can only be distinguished in a THE COSTAL CARTILAGES 107 small portion of its extent. At the back the angles of the ribs form a slightly marked oblique line on each side of and some distance from the vertebral spines. This line diverges some- what as it descends, and external to it is a broad, convex surface caused by the projection of the ribs beyond their angles. Over this surface, except where covered by the scapula, the individual ribs can be distinguished. Applied Anatomy. — Malformations of the sternum present nothing of surgical importance beyond the fact that abscesses of the mediastinum may sometimes escape through the sternal foramen. Fractures of the sternum are by no means common, due, no doubt, to the elasticity of the ribs and their cartilages, which support it like so many springs. When broken it is fre- quently associated with fracture of the vertebral column, and may be caused by forcibly bending the body either backward or forward until the chin becomes impacted against the top of the sternum. It may also be fractured by direct violence or by muscular action. The fracture usually occurs in the upper half of the body of the bone. Dislocation of the gladiolus from the manubrium also takes place, and is sometimes described as a fracture. The bone, cancellous in structure and being subcutaneous, is frequently the seat of (jiimma- tous tumors, and not uncommonly is affected with caries. Occasionally the bone, and especially its ensiform appendix, becomes altered in shape and driven inward, in workmen, by the pressure of tools against the chest. The rihs are frequently broken, though from their connections and shape they are able to withstand great force, yielding under the injury and recovering themselves like a spring. The middle of the series are the ones most liable to fracture. The first, and to a less extent the second, being protected by the clavicle, are rarely fractured; and the eleventh and twelfth, on account of their loose and floating condition, enjoy a like immunity. The fracture generally occurs from indirect violence, from forcible compression of the thoracic wall, and the bone then gives way at its weakest part — i. e., just in front of the angle. But the ribs may also be broken by direct violence, when the bone gives way and is driven inward at the point struck, or they may be broken by muscular action. It seems probable, however, that in the latter case the bone has undergone some atrophic changes. Fracture of the ribs is frequently complicated by some injury to the viscera contained within the thorax or upper part of the abdominal cavity, and this is most likely to occur in fractures from direct violence. Occasionally supernumerary ribs exist. They may come from the lumbar vertebrse or from the cervical vertebrse. A cervical rib is due to excessive development of the costal element of the seventh cervical vertebra. In nearly two-thirds of the reported cases the condition is bilateral. It rarely produces symp- toms until after the twentieth year. The symptoms are a superficial pulsation of the sub- clavian artery, a prominence which can be felt, and evidences of pressure in the brachial plexus (Carl Beck). Beck divides the different types of the condition as follows: (a) Slight degree: The cervical rib reaches beyond the transverse process. (6) More advanced : The cervical rib reaches beyond the transverse process, either with a free end or touching the first rib. (c) Almost complete: The connection between the cartilage of the first rib is formed either by means of a distinct band or by the end of its long body, {d) Complete: It has become a true rib and possesses a true cartilage which unites with the cartilage of the first rib.' A very rare condition is a rib from the sixth cervical vertebra. The diagnosis is confirmed by the .r-rays. The treatment of cervical rib is excision. Fracture of the costal cartilages may also take place, though it is a comparatively rare injury. The thorax is frequently found "to be altered in shape in certain diseases. The shape of the thorax in those suffering from rhachitis is produced chiefly by atmospheric pressure. The balance between the air on the inside of the thorax and the air on the outside during some stage of respiration is not equal, the preponderance being in favor of the air outside; and this, acting on the softened ribs, causes them to be forced in at the junction of the carti- lages with the bones, which is the weakest part. In consequence of this the sternum projects forward with a deep depression on either side caused by the sinking in of the softened ribs. The depression is less on the left side, on account of the rijas being supported by the heart. The condition is known as pigeon-h-east. The lower ribs, however, are not involved in this deform- ity, as they are prevented from falling in by the presence of the stomach, liver, and spleen. And when the liver and spleen are enlarged, as they sometimes are in rhachitis, the lower ribs may be pushed outward; this causes a transverse constriction just above the costal arch. The anterior extremities of the ribs are usually enlarged in rhachitis, giving rise to what has been termed the rhachitio rosary. The phthisical chest is often long and narrow, flattened from before backward, and with great obliquity of the ribs and projection of the scapute. In pulmonary emphysrma the thorax is enlarged in all its diameters, and presents on section an almost circular outline. It has received the name of the barrel-shaped chest. In severe cases of lateral curvature of the spine the thorax becomes much distorted. In consequence of the rotation of the bodies of the vertebrre which takes place in this disease the ribs opposite the convexity of the thoracic curve become extremely convex behind, being thrown out and bulging, and at the same time flattened ' Jour. .\mer. Med. Assoc, June 17, 1905. 168 SPECIAL ANATOMY OF THE SKELETON in front, so that the two bends of the same rib are almost parallel. Coincident with this, the ribs on the opposite side, on the concavity of the curve, are sunken and depressed behind and bulging and convex in front. In addition to this the ribs become occasionally welded together by bony material. The ribs are frequently the seat of caries leading to abscesses and sinuses, which may burrow- to a considerable extent over the wall of the thorax. The only special anatomical point in con- nection with abscesses and sinuses is that care must be taken in dealing with them that the intercostal space is not punctured and the pleural cavity opened or the intercostal vessels wounded, as the necrosed portion of bone is generally situated on the internal surface of the rib. In cases of empyema the thorax requires opening to evacuate the pus. There is considerable difference of opinion as to the best position to do this. Probably the best place for intercostal drainage is between the fifth and sixth ribs, in or a little in front of the mid-axillary line. This is the last part of the cavity to be closed by the expansion of the lung; it is not thickly covered by soft parts; the space between the two ribs is sufficiently great to allow of the introduction of a fair-sized drainage tube, and when the patient is confined to bed he does not lie upon the drainage tube as he does when the opening is posterior. Better than intercostal drainage in the vast majority of cases is rib resection and drainage. A portion of the fifth or sixth rib should be removed in the mid-axillaiy line. In chronic empyema the lung becomes shrunken and ad- herent, and simple drainage will not bring about a cure. It is necessary in such cases to do an operation that will permit of collapse of the chest wall. Estlander s operation consists in resect- ing a portion of every rib which overlies the cavity of the empyema. Schede's operation consists in removing ribs from the second rib down over the empyema cavity. The ribs are removed from cartilages to angles, and intercostal muscles and the parietal layer of the pleura are also taken away. Fowler and de Lorme not only practise extensive rib resection and remove the parietal layer of the pleura, but also remove pulmonary pleura (total pleurectomy or pulmonary decortication). THE EXTREMITIES. The extremities, or limbs, are those long, jointed appendages of the body which are connected to the trunk by one end and free in the rest of their extent. They are four in number: an upper or thoracic pair, connected with the thorax through the intervention of the shoulder and subservient mainly to prehension; and a lower or pelvic pair, connected with the pelvis, intended for support and locomotion. Both pairs of limbs are constructed after one common type, so that they present numerous analogies, while at the same time certain differences are observed between the upper and lower pair, dependent on the peculiar offices they have to perform. The bones by which the upper and lower limbs are attached to the trunk are named, respectively, the shoulder and pelvic girdles, and they are constructed on the same general type, though presenting certain modifications relating to the diflerent uses to which the upper and lower limbs are respectively applied. The shoulder girdle is formed by the scapula and clavicles, and is imperfect in front and behind. In front, however, the girdle is completed by the upper end of the sternum, with which the inner extremities of the clavicle articulate. Behind, the girdle is widely imperfect and the scapula is connected to the trunk by muscles only. The pelvic girdle is formed by the innominate bones, and is completed in front through the symphysis pubis, at which the two innominate bones articulate with each other. It is imperfect behind, but the intervening gap is filled in by the upper part of tlie sacrum. The pelvic girdle, therefore, presents, with the sacrum, a complete ring, massive and comparatively rigid, in marked contrast to the lightness and mobility of the shoulder girdle. THE UPPER EXTREMITY. The bones of the upper extremity consist of the clavicle and scapula (pectoral girdle), the humerus (arm), the radius and ulna (forearm), the carpal bones (wrist), the metacarpal bones (palm), and the phalanges (digits). THE CLA VICLE, OB COLLAR BONE ](J9 THE SHOULDER GIRDLE. The shoulder girdle consists of the clavicle and the scapula. The Clavicle, or Collar Bone (Clavicula). The clavicle forms the anterior portion of the shoulder girdle. It is a long bone, curved somewhat like the italic letter /, and placed nearly horizontally at the upper and anterior part of the thorax, immediately over the first rib. It articulates by its inner extremity with the upper border of the sternum, and by its outer extremity with the acromion process of the scapula, serving to sustain the upper extremity in the various positions which it assumes, while at the same time it allows of great latitude of motion in the arm.' It presents a double curva- ture when looked at in front, the convexity being forward at the sternal end and the concavity at the scapular end. Its outer third is flattened from above downward, and extends, in the natural position of the bone, from a point opposite the cora- coid process to the acromion. Its inner two-thirds are of a prismatic form, and extend from the sternum to a point opposite the coracoid process of the scapula. Outer or Flattened Portion. — The outer third is flattened from above down- ward, so as to present two surfaces, an upper and a lower; and two borders, an anterior and a posterior. Surfaces. — The upper surface is flat, rough, marked by impressions for the attachment of the Deltoid in front and the Trapezius behind; between these two impressions a small portion of the bone is subcutaneous. The under surface is flattened. At its posterior border, a little external to the point where the pris- matic joins with the flattened portion, is a rough eminence, the conoid tubercle (tuberositas coracoidea) ; this, in the natural position of the bone, surmoimts the coracoid process of the scapula and gives attachment to the conoid ligament. From' this tubercle an oblique line, occasionally a depression, passes forward and outward to near the outer end of the anterior border; it is called the oblique line or trapezoid ridge, and aflfords attachment to the trapezoid ligament. Borders. — The anterior border is concave, thin, and rough, and gives attachment to the Deltoid; it occasionally presents, at its inner end, at the commencement of the deltoid impression, a tubercle, the deltoid tubercle. The posterior border is convex, rough, broader than the anterior, and gives attachment to the Trapezius. Inner or Prismatic Portion. — The prismatic portion forms the inner two- thirds of the bone. It is curved so as to be convex in front, concave behind, and is marked by three borders, separating three surfaces. Borders. — The anterior border is continuous with the anterior margin of the flat portion, and separates the anterior surface from the inferior; at the inner half of the clavicle it forms the lower boundary of an elliptical space for the attach- ment of the clavicular portion of the Pectoralis major, and approaches the pos- terior border of the bone; it coincides with the anterior margin of the subclavian groove. The superior border is continuous with the posterior margin of the flat portion, and separates the anterior from the posterior surface. At its commence- ment it is smooth and rounded, becomes rough toward the inner third for tlie attachment of the Sternomastoid muscle, and terminates at the upper angle of the sternal extremity. The posterior or subclavian border separates the posterior > The clavicle acts especially as a fulcrum to enable the muscles to give lateral motion to the arm. It is accordingly absent in those animals in which the fore limbs are used only for progression, but is present for the most part in those animals in which the anterior extremities are clawed and used for prehension, though m some of them— as, for instance, in a large number of the carnivora— it is merely a rudimentary bone suspended among the muscles, and not articulating with the scapula or sternum. 170 SPECIAL ANA TOMY OF THE SKELETON from the inferior surface, and extends from the conoid tubercle to the rhomboid impression. It forms the posterior boundary of the groove for the Subclavius muscle, and gives attachment to a layer of cervical fascia covering the Omohyoid muscle. Surfaces. — The anterior surface is included betw^een the superior and anterior borders. It is directed forward and a little upward at the sternal end, outward and still more upward at the acromial extremity, where it becomes continuous with the upper surface of the flat portion. Externally, it is smooth, convex, nearly subcutaneous, being covered only by the Platysma; but, corresponding to the inner half of the bone, it is divided by a more or less prominent line into two parts — a lower portion, elliptical in form, rough, and slightly convex, for the attachment of the Pectoralis major; and an upper part, which is rough, for the attachment of the Sternomastoid. Between the two muscular impressions Aaonual exfremiti/. Sternal extremity. Fig. 136. — Left clavicle. Superior surface. Capsidar ligament Fig. 137. — Left clavicle. Inferior surface. is a small subcutaneous interval. The posterior or cervical surface is smooth, flat, and looks backward toward the root of the neck. It is limited, above, by the superior border; below, by the posterior border; internally, by the margin of the sternal extremity; externally, it is continuous with the posterior border of the flat portion. It is concave from within outward, and is in relation, by its lower part, with the suprascapular vessels. This surface, at about the junction of the inner and outer curves, is also in close relation with the brachial plexus and subclavian vessels. It gives attachment, near the sternal extremity, to part of the Sternohyoid muscle; and presents, at or near the middle, a nutrient foramen. It opens into a nutrient canal, which is directed obliquely outward and transmits the chief nutrient artery of the bone. Sometimes there are two foramina on the poste- rior surface, or one on the posterior and one on the inferior surface. The infe- rior or subclavian surface is bounded, in front, by the anterior border; behind, THE CLAVICLE, OR COLLAR BONE 171 by the posterior border. It is narrow internally, but gradually increases in width externally, and is continuous with the under surface of the flat portion. Commencing at the sternal extremity may be seen a small facet, the costal facet, for articulation with the cartilage of the first rib. This is continuous with the articular surface at the sternal end of the bone. External to this is a broad, rough surface, the rhomboid impression (tuberositas costalis), rather more than an inch in length, for the attachment of the costoclavicular (rhomboidj ligament. The remaining part of this surface is occupied by a longitudinal groove, the subclavian groove, broad and smooth externally, narrow and more uneven internally; it gives attachment to the Subclavius muscle, and by its margins to the costocoracoid membrane, which splits to enclose the muscle. Not infrequently this groove is subdivided into two parts by a longitudinal line, which gives attachment to the intermuscular septum of the Subclavius muscle. Internal or Sternal Extremity (extremitas sternalis). — The internal or sternal extremity of the clavicle is triangular in form, directed inward and a little down- ward and forward; and presents an articular facet (fades articularis sternalis), concave from before backward, convex from above downward, which articulates with the sternum through the intervention of an intra-articular fibrocartilage; the circumference of the articular surface is rough, for the attachment of numer- ous ligaments. The posterior border of this surface is prolonged backward, so as to increase the size of the articular facet; the upper border gives attachment to the intra-articular fibrocartilage, and the lower border is continuous with the costal facet on the inner end of the inferior surface, which articulates with the cartilage of the first rib. Outer or Acromial Extremity (extremitas acromialis). — The outer or acromial extremity, directed outward and forward, presents a small, flattened, oval facet, acromial surface (fades articularis acromialis), which looks obliquely downward, and which articulates with the acromion process of the scapula. The circum- ference of the articular facet is rough, especially above, for the attachment of the acromioclavicular ligaments. Peculiarities of the Bone in the Sexes and in Individuals.— In the female the clavicle is generally shorter, thinner, less curved, and .siiioolhei- than in the male; in the female it is placed almost, if not quite, horizontal, while in the male it inclines slightly downward and inward. In those persons who perform considerable manual labor, which brings into constant action the muscles connected with this bone, it becomes thicker and more curved, its ridges for muscle attachment become prominently marked. The right clavicle is generally longer, thicker, and rougher than the left. Structure. — The shaft, as well as the extremities, consists of cancellous tissue, invested by a coni|ia(t layer much thicker in the middle than at either end. It has no true medullary cavity. Development. — From two centres, one for the shaft and outer extremity and one for the statissimus dorsi glides; sometimes the latter muscle takes origin by a few fibres from this part. The broad and narrow portions of bone above alluded to are separated by an oblique line which runs from the axillary border, downward and backward, to meet the elevated ridge; to it is attached the aponeurosis separating the two Teres muscles from each other. Coracohumeral ligament Coracoacromial ligament Trapezoid ligament Conoid ligament Fig. 139.— Left scapula Posterior surface or dorsum. The spine (spina scapulae) is a prominent plate of bone which crosses obliquely the inner four-fifths of the dorsum of the scapula at its upper part, and separates the supra- from the infraspinous fossa; it commences at the vertebral border by a smooth, triangular surface, over which the Trapezius glides, and; gradually be- coming more elevated as it passes outward, terminates in the acromion process which overhangs the shoulder-joint- The spine is triangular and flattened from THE SCAPULA, OB SHOULDER BLADE 175 above downward, its apex corresponding to the vertebral border, its base (which is directed outward) to the neck of the scapula. It presents two surfaces and three borders. Its superior surface is concave, assists in forming tiie supraspinous fossa, and affords attachment to part of the Supraspinatus muscle. Its inferior surface forms part of the infraspinous fossa, gives origin to part of the Infraspi- natus muscle, and presents near its centre the orifice of a nutrient canal. Of the three borders, the anterior is attached to the dorsum of the bone; the posterior, or crest of the spine, is broad, and presents two lips and an intervening rough interval. To the superior lip is attached the Trapezius to the extent shown in Fig. 139. A rough tubercle is generally seen occupying that portion of the spine which receives the insertion of the middle and inferior fibres of this muscle. From the inferior Up, throughout its whole length, arises the Deltoid. The interval between the lips is also partly covered by the tendinous fibres of these muscles. The external border, or base, the shortest of the three, is slightly concave, its edge thick and round, continuous above with the under surface of the acromion process, below with the neck of the scapula. The narrow portion of bone external to this border, and separating it from the glenoid cavity, is called the great scapular notch, and serves to connect the supra- and infraspinous fosste. The acromion process (acromion) is a large and somewhat triangular or oblong process, flattened from behind forward, directed at first a little outward, and then curving forward and upward, so as to overhang the glenoid cavity. Its upper surface, directed upward, backward, and outward, is convex, rough, and gives origin to some fibres of the Deltoid, and in the rest of its extent it is subcutaneous. Its under surface is smooth and concave. Its outer border is thick and irregular, and presents three or four tubercles for the tendinous origins of the Deltoid muscle. Its inner margin, shorter than the outer, is concave, gives attachment to a portion of the Trapezius muscle, and presents about its centre a small oval surface for articulation with the acromial end of the clavicle. Its apex, which corresponds to the point of meeting of these two borders in front, is thin, and has attached to it the coracoacromial ligament. Margins, or Borders of the Scapula. — The superior border (margo superior) is the shortest and thinnest of the three borders; it is concave and extends from the internal ang'e to the coracoid process. At its outer part is a deep, semicircular notch, the suprascapular notch (i.ncisura scapxdae), formed partly by the base of the coracoid process. The notch is converted into a foramen by the supra- scapular ligament, and serves for the passage of the suprascapular nerve. Some- times this foramen is entirely surrounded by bone. The adjacent margin of the superior border affords attachment to the Omohyoid muscle. The external or axillary border (margo axillaris) is the thickest of the three. It commences above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle. Immediately below the glenoid cavity is a rough impression, the infraglenoid tubercle {tuberositas itifraglenoidalis), about an inch in length, which affords origin to the long head of the Triceps muscle; in front of this is a longitudinal groove, which extends as far as the lower third of the external border and afl^ords origin to part of the Subscapularis muscle. The inferior third of this border, which is thin and sharp, serves for the origin of a few fibres of the Teres major behind and the Subscapularis in front. The internal or vertebral border (margo vertebralis) is the longest of the three, and extends from the internal to the inferior angle of the bone. It is arched, is intermediate in thickness between the superior and the external borders, and the portion of it above the spine is bent considerably outward, so as to form an obtuse angle with the lower part. The internal border presents an anterior lip, a posterior lip, and an intermediate space. The anterior lip affords attachment to the Serratus magnus; the posterior lip, an origin to the Supraspinatus above the spine, the 176 SPECIAL ANATOMY OF THE SKELETON Infraspinatus below; to the interval between the two lips, the Levator anguli scapulae is inserted; above the triangular surface at the commencement of the spine, the Rhomboideus minor to the edge of that surface; the Rhomboideus major is attached by means of a fibrous arch connected above to the lower part of the triangular surface at the base of the spine, and below to the lower part of the posterior border. Angles.— The internal angle (angulus medialis), formed by the junction of the superior and internal borders, is thin, smooth, rounded, somewhat inclined outward, and gives attachment to a few fibres of the Levator anguli scapulae muscle. The inferior angle (angulus inferior), thick and rough, is formed by the union of the vertebral and axillary borders, its posterior surface affording origin to the Teres major and frequently to a few fibres of the Latissimus dorsi. The external angle {angulus lateralis) is the thickest part of the bone, and forms what is called the head of the scapula. The head presents a shallow, pyriform, articular surface, the glenoid surface (cavitas glenoi'dalis) , the longest diameter of which is from above downward, and its direction outward and forward. It is broader below than above. Just above it is a rough surface, the supra- glenoid tubercle {tuberositas supraglenoidalis) , from which arises the long tendon of the Biceps muscle. The glenoid cavity is covered with cartilage in the recent state; and its margins are slightly raised and give attachment to a fibrocartilaginous structure, the glenoid ligament, by which its cavity is deepened. The neck of the scapula {collum scapulae) is the slightly depressed surface which surrounds the head; it is more distinct on the posterior than on the anterior surface, and below than above. In the latter situation it has arising from it a thick promi- nence, the coracoid process. The coracoid process {processus coracoideus) is a thick, curved process of bone which arises by a broad base from the upper part of the neck of the scapula; it is directed at first upward and inward, then, becoming smaller, it changes its direction and passes forward and outward. The ascending portion, flattened from before backward, presents in front a smooth, concave surface over which passes the Subscapularis muscle. The horizontal portion is flattened from above downward, its upper surface is convex and irregular; its under surface is smooth; its inner border is rough, and gives attachment to the Pectoralis minor; its outer border is also rough for the coracoacromial ligament, while the apex is embraced by the conjoined tendon of origin of the short head of the Biceps and of the Coracobrachialis and gives attachment to the costocoracoid ligament. At the inner side of the root of the coracoid process is a rough impression for the attach- ment of the conoid ligament; and running from it obliquely forward and outward on the upper surface of the horizontal portion, an elevated ridge for the attachment of the trapezoid ligament. Structure. — In the head, processes, and all the thickened parts of the bone the scapula is composed of cancellous tissue covered by compact bone, while in the rest of its extent it is com- posed of a thin layer of dense, compact tissue. The central part of the supraspinous fossa and the upper part of the infraspinous fossa, but especially the former, are usually so thin as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent muscles come into contact. Development (Fig. 140). — From seven, or more centres — one for the body, two for the coracoid process, two for the acromion, one for the vertebral border, and one for the inferior angle. Ossification of the body of the scapula commences about the second month of fetal life by the formation of an irregular quadrilateral plate of bone immediately behind the glenoid cavity. This plate extends itself so as to form the chief part of the bone, the spine growing up from its posterior surface about the third month. At birth a large part of the scapula is osseous, but the glenoid cavity, coracoid and acromion processes, the posterior border, and inferior angle are cartilaginous. From the fifteenth to the eighteenth month after birth THE SCAPULA, OB SHOULDER BLADE 177 ossification takes place in the middle of the coracoid process, which usually becomes joined wilii the rest of the bone at the time when the other centres make their appearance. Between the fourteenth and twentieth years ossification of the remaining centres takes place in quick succession, and in the following oviei-: fir.-it, in the root of the coracoid process, in the form of a broad scale; second, near the base of the acromion process; third, in the inferior ande and contiguous part of the posterior hor Aev; fourth, near the extremity of the acromion; fifth, in the posterior border. The acromion process, besides being formed of two separate nuclei, has its base formed by an extension into it of the centre of ossification which belongs to the spine, the extent of which varies in different cases. The two separate nuclei unite and then join with the extension from the spine. These various epiphyses become joined to the bone between the ages of twenty-two and twenty-five years. Sometimes fail- ure of union between the acromion process and spine occurs, the junc- tion being effected by fibrous tissue or by an imperfect articulation; in some cases of supposed fracture of the acromion with ligamentous union it is probable that the de- tached segment was never united to the rest of the bone. The upper third of the glenoid cavity is usually ossified from a separate centre {suh- coracoid) which makes its appearance between the tenth and eleventh years. Very often, in addition, an epiphysis appears for the lower part of the glenoid cavity. Articulations. — With the hu- merus and clavicle. Attachment of Muscles. — To seventeen — to the anterior surface, theSubscapularis; posterior surface, Supraspinatus, Infraspinatus; spine. Trapezius, Deltoid; superior border. Omohyoid; vertebral border, Serra- tus magnus. Levator anguli scapulae, Rhomboideus, minor and major; axillary border. Triceps, Teres minor, Teres major; apex of glen- oid cavity, long head of the Biceps; coracoid process, short head of the Biceps, Coracobrachialis, Pectoralis minor; and to the inferior angle oc- casionally a few fibres of the Latissi- mus dorsi. Surface Form.— The only parts of the scapula which are truly sub- cutaneous are the spine and acro- mion process, but, in addition to these, the coracoid process, the internal or vertebral border and inferior angle, and, to a less extent, the axillary border, may be defined. The acro- mion process and spine of the scapula are easily felt throughout their entire length, forming, with the clavicle, the arch of the shoulder. The acromion can be ascertained to be connected to the clavicle at the acromioclavicular joint by running the finger along it, its position being often indicated by an irregularity or bony outgrowth from the clavicle close to the joint. The acromion can be felt forming the point of the shoulder, and from this can be traced backward to join the spine of the scapula. The place of junction is usually denoted by a prominence, which is sometimes called the acromial angle. From here the spine of the scapula can be felt as a prominent ridge of bone, marked on the surface as an oblique depression, which becomes less and less distinct, and terminates a little external to the spinous processes of the vertebra?. Its termination is usually indicated by a slight dimple in the skin on a level with the interval be- tween the third and fourth thoracic spines. Below this point the vertebral border of the scapula may be traced, running downward and outward, and thus diverging from the vertebral spines, to the inferior angle of the bone, which can be recognized, although covered by the Latissimus dorsi muscle. From this angle the axillary border can usually be traced through this thick muscular covering, forming, with the muscles, the posterior fold of the axilla. The coracoid ifenof Fig. 140. — Plan of the development of the scapula. From seven centres. The epiphyses (except one for the coracoid pro- cess) appear from fifteen to seventeen years, and unite between twenty-two and twenty-five years of age. 178 SPECIAL ANA TOMY OF THE SKELETON process may be felt about an inch below the junction of the middle and outer thirds of the clavicle. Here it is covered by the anterior border of the Deltoid and lies a little to the outer side of a slight depression which corresponds to the interval between the Pectoralis major and Deltoid muscles. When the arms are hanging by the side, the upper angle of the scapula corresponds to the upper border of the second rib or the interval between the first and second thoracic spines, the inferior angle to the upper border of the eighth rib or the interval between the seventh and eighth thoracic spines. Applied Anatomy. — Fractures of the body of the scapula are rare, owing to the mobility of the bone, the thick layer of muscles \>y which it is encased on both surfaces, and the elasticity of the ribs on which it rests. Fracture of the neck of the bone is also uncommon. The most fre- quent course of a line of fracture of the neck is from the suprascapular notch to the infraglenoid tubercle (surgical neck), and it derives its principal interest from its simulation to a subglenoid dislocation of the humerus. The diagnosis can be made by noting the alteration in the position of the coracoid process. A fracture 'of the neck external to, and not including, the coracoid process (anatomical neck) is said to occur, but it is exceedingly doubtful whether such an accident ever takes place. The acromion process is more frequently broken than any other part of the bone, and there is sometimes, in young subjects, a separation of the epiphysis. It is believed that many of the cases of supposed fracture of the acromion, with fibrous union, which have been found on postmortem examination are really cases of imperfectly united epiphysis. Sir Astley Cooper believed that most fractures of this bone are united by fibrous tissue, and the cause of this mode of union is the difficulty that arises in keeping the fractured ends in constant apposition. The coracoid process is occasionally broken oft', either by direct violence or perhaps, rarely, by muscular action. Tumors of various kinds grow from the scapula. Of the innocent form of tumors, probably the osteomata are the most common. ' When an osteoma grows from the anterior surface of the scapula, as it sometimes does, it is of the compact variety, such as usually grows from mem- brane-formed bones, as the bones of the skull. This would appear to afford evidence that this portion of the bone is formed from membrane, and not, like the rest of the bone, from cartilage. Sarcomatous tumors sometimes grow from the scapula, and may necessitate removal of the bone, with or without amputation of the upper limb. Removal of the upper limb with the scapula and the outer two-thirds of the clavicle is known as the mterscaqndothoracic amputafion. The scapula may be partially resected or completely excised. There are several methods of complete excision. The bone may be excised by a T-shaped incision, and, the flaps being reflected, the removal is commenced from the vertebral border, so that the subscapular vessels which lie along the axillary border are among the last structures divided, and can be at once secured. THE ARM. The arm is that portion of the upper extremity which is situated between the shoulder and the elljow. Its skeleton consists of a single bone, the humerus. The Humerus, or Arm Bone (Figs. 141, 142). The humerus is the longest and largest bone of the upper extremity; it presents for examination a shaft and two extremities. Upper or Proximal Extremity. — The upper extremity presents a large, rounded head, joined to tlie shaft by a constricted portion, called the neck, and two other eminences, the greater and lesser tuberosities. The Head (caput humeri). — ^The head, nearly hemispherical in form,^ is dii'ected upward, inward, and slightly backward, and articulates with the glenoid surface of the scapula; its surface is smooth and coated with cartilage in the recent state. The circumference of its articular surface is slightly constricted, and is termed the anatomical neck, in contradistinction to the constriction which exists below the tuberosities. The latter is called the surgical neck (collum chirurgicuvi) , as it is often the seat of fracture. The anatomical neck (collum anatomicum) is obliquely directed, forming an 1 Though the head is nearly hemispherical in form, its margin, as Sir G. Humphry has shown, is by no means a true circle. Its greatest measurement is from the top of the bicipital groove in a direction downward, inward, and backward. Hence, it follows that the greatest elevation of the arm can be obtained by rolling the articular surface in this direction — that is to say, obliquely upward, outward, and forward. THE HUMERUS, OB ABM BONE 179 Capsular ligament [brevis]. Fig. 141. — Left humerus. Anterior view. ISO SPECIAL ANATOMY OF THE SKELETON obtuse angle with the shaft. It is more distinctly marked in the lower half of its circumference than in the upper half, where it presents a narrow groove, separating tlie head from the tuberosities. Its circumference affords attachment to the capsular ligament and is perforated by numerous vascular foramina. The Greater Tuberosity (tubercuhim majus). — The greater tuberosity is situated on the outer side of the head and lesser tuberosity. Its upper surface is rounded and marked by three flat facets, separated by two slight ridges; the highest facet gives attachment to the tendon of the Supraspinatus; the middle one, to the Infra- spinatus ; the inferior facet and the shaft of the bone below it, to the Teres minor. The outer surface of the greater tuberosity is convex, rough, and continuous \\ath the outer side of the shaft. The Lesser Tuberosity (t'uberculum minus). — The lesser tuberosity is more prominent, although smaller than the greater; it is situated in front of the head, and is directed inward and forward. Its summit presents a prominent facet for the insertion of the tendon of the Subscapularis muscle. The tuberosities are separated from each other by a deep groove, the bicipital groove (sulcus inter- iuhercularis). This groove lodges the long tendon of the Biceps muscle, accom- panied by a branch of the anterior circumflex artery. It commences above be- tween the two tuberosities, passes obliquely downward and a little inwai'd, and terminates at the junction of the upper with the middle third of the bone. It is deep and narrow at the commencement, and becomes shallow and a little broader as it descends. In the recent state it is covered with a thin layer of cartilage, lined by a prolongation of the synovial membrane of the shoulder-joint, and receives the tendon of insertion of the Latissimus dorsi muscle. The Shaft (corpus humeri). — The shaft of the humerus is almost cylindrical in the upper half of its extent, prismatic and flattened below, and presents three borders and three surfaces for examination. The anterior border runs from the front of the greater tuberosity above to the coronoid depression below, separating the internal from the external surface. Its upper part is very prominent and rough, forms the outer Up of the bicipital groove, and serves for the attachment of the tendon of the Pectoralis major. About its centre it forms the anterior boundary of the rough deltoid impression j below, it is smooth and rounded, affording attachment to the Brachialis anticus. muscle. The external border (iiiargo lateralis) runs from the back part of the greater tuberosity to the external condyle, and separates the external from the posterior surface. It is rounded and indistinctly marked in its upper half, serving for the attachment of the lower part of the insertion of the Teres minor muscle, and below this of the external head of the Triceps muscle; its centre is traversed by a broad, but shallow, oblique depression, the musculospiral groove (sulcus nervi radialis); its lower part is marked by a prominent, rough margin, a little curved from behind forward, the external supracondylar ridge, which presents an anterior lip for the attachment of the Brachioradialis above and Extensor carpi radialis longior below, a posterior lip for the Triceps, and an intermediate space for the attachment of the external intermuscular septum. The internal border {margo medialis) extends from the lesser tuberosity to the internal condyle. Its upper third is marked by a prominent ridge, forming the internal lip of the bicipital groove, and gives attachment to the tendon of the Teres major. About its centre is an impression for the attachment of the Coraco- brachialis, and just below this is seen the entrance of the nutrient canal, directed downward. Sometimes there is a second canal situated at the commencement of the musculospiral groove, for a nutrient artery derived from the superior pro- funda branch of tlie brachial artery. The inferior third of this border is raised into a slight ridge, the internal supracondylar ridge, which becomes very prominent THE HUMERUS, OR ARM BONE 181 below; it presents an anterior lip for the attachment of the Brachialis anticus muscle, a posterior lip for the internal head of the Triceps muscle, and an intermediate space for the attachment of the internal intermus- cular septum. The external surface (fades anterior later- alis) is directed outward above, where it is smooth, rounded, and covered by the Del- toid muscle; forward and outward below, where it is slightly concave from above downward, and gives origin to part of the Brachialis anticus muscle. About the mid- dle of this surface is seen a rough, triangular impression for the insertion of the Deltoid muscle, deltoid impression {tuberositas deltoi- dea), a.nd below this the musculospiral groove, directed obliquely from behind forward and downward, and transmitting the musculo- spiral nerve and superior profunda artery. The internal surface (fades anterior medi- alis), less extensive than the external, is directed inward above, forward and inward below ; at its upper part it is narrow and forms the floor of the bicipital groove; to it is attached the Latissimus dorsi. The middle part of this surface is slightly roughened for the attachment of some of the fibres of the tendon of insertion of the Coracobrachialis; its lower part is smooth, concave from above downward, and gives attachment to the Brachialis anticus mus- cle.^ A little below the middle of the shaft is the nutrient foramen. This leads into a nutrient canal, which is directed toward the elbow-joint. The posterior surface (fades posterior) (Fig. 142) appears somewhat twisted, so that its upper part is directed a little inward, its lower part backward and a little outward. Nearly the whole of this surface is covered by the external and internal heads of the • A sm;ill hook-shaped process of bone, the supracondylar process, varying from i/io to 3/4 of an inch in length, is not in- frequently found projecting from the inner surface of the shaft of the humerus two inches above the internal condyle. It is curved downward, forward, and inward, and its pointed extremity is connected to the internal border, just above the inner condyle, by a ligament or fibrous band, which gives origin to a portion of the Pronator teres; through the arch completed by this fibrous band the median nerve and brachial artery pass when these structures deviate from their usual course. Sometimes the nerve alone is transmitted through it, or the nerve may be accompanied by the ulnar artery in cases of high division of the brachial. A well-marked groove is usually found behind the process in which the nerve and artery are lodged. This space is anal- ogous to the supracondyloid foramen in many animals, and probably serves in them to protect the nerve and artery from compression during the contraction of the muscles in this region. Fig. 142. — Left humerus. Posterior surface. 182 SPECIAL ANATOMY OF THE SKELETON Triceps, the former of which is attached to its upper and outer part, the latter to its inner and back part, the two being separated by the musculospiral groove. The Lower or Distal Extremity is flattened from before backward, and curved sHghtly forward; it terminates below in a broad, articular surface which is divided into two parts by a slight ridge. Projecting on either side are the external and internal condyles. By some anatomists the external condyle is called the external epicondyle and the internal condyle is called the internal epicondyle. The articular surface extends a little lower than the condyles, and is curved slightly forward, so as to occupy the more anterior part of the bone; its greatest breadth is in the transverse diameter, and it is obliquely directed, so that its inner extremity occupies a lower level than the outer. The outer portion of the articular surface presents a smooth, rounded eminence, which has received the name of the capitellum, or radial head of the humerus (capitulum humeri) ; it articulates with the cup-shaped depression on the head of the radius, and is limited to the front and lower part of the bone, not extending as far back as the other portion of the articular surface. On the inner side of this eminence is a shallow groove, in which is received the inner margin of the head of the radius. Above the front part of the capitellum is a slight depression, the radial fossa (fossa radialis), which receives the anterior border of the head of the radius when the forearm is flexed. The inner portion of the articular surface, the trochlea (trochlea humeri), presents a deep depression between two well-marked borders. This surface is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the bone. The external border, less prominent than the internal, corresponds to the interval between the radius and the ulna. The internal border is thicker, more prominent, and consequently of greater length, than the external. The grooved portion of the articular surface fits accurately within the greater sigmoid cavity of the ulna; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely from behind forward and from without inward. Above the front part of the trochlear surface is seen a smaller depression, the coronoid fossa (J'ossa coronoidea), which receives the coronoid process of the ulna during flexion of the forearm. Above the back part of the trochlear surface is a deep, triangular depression, the olecranon fossa (J'ossa olecrani), in which is received the summit of the olecranon process in extension of the forearm. These fossae are separated from one another by a thin, transparent lamina of bone, which is sometimes perforated by a foramen, the supratrochlear foramen; their upper margins afi'ord attachment to the anterior and posterior ligaments of the elbow-joint, and they are lined, in the recent state, by the synovial membrane of this articulation. The articular surfaces, in the recent state, are covered with a thin layer of hyaline cartilage. The external condyle (epicondi/his lateralis) is a small, tubercular eminence, less prominent than the internal, curved a little forward, and giving attachment to the external lateral ligament of the elbow- joint, and to a tendon common to the origin of some of the Extensor and Supinator muscles. The internal condyle (epifrochlea or epicondyhis medialis), larger and more prominent, is directed a little backward; it gives attachment to the internal lateral ligament, to the Pronator teres, and to a tendon common to the origin of some of the Flexor muscles of the forearm. The ulnar nerve runs in a groove, the ulnar groove (sulcus nervi ulnaris), at the back of the internal condyle, or between It and the olecranon process. These condyles are directly continuous above with the external and internal supracondylar ridges. Structure. — The extremities consist of cancellous tissue, covered with a thin compact layer; the shaft is composed of a cylinder of compact tissue, thicker at the centre than at the extremities, and hollowed out by a large medullary canal, which extends along its whole length. In the head of the humerus the plates of the cancellous tissue are arranged in curves (Fig. 143), known as pressure curves. Most of the bone plates are at right angles to the plane of the THE HUMERUS, OR ARM BONE ]S3 articular surface (the lines of greatest pressure), and they are bound togetlier l)y other bone fibres, which usually correspond to the plane of the articulation (the lines of greatest tension). This arch-like arrangement strengthens the head of the bone, and it is further strengthened by the binding fibres. Development. — From eiyht centres (Fig. 144), one for each of the following parts: The shaft, head, each tuberosity, the radial head, the trochlear portion of the articular surface, and each condyle. The nucleus for the shaft appears near the centre of the bone in the eighth week, and soon extends toward the extremities. At birth the humerus is ossified ncarjv in its whole length, the extremities remaining cartilaginous. During the first year, sometimes even before birth, ossification commences in the head of the bone, and during the third year the centre for the greater tuberosity makes its appearance, that for the lesser being small and not appearing until tlie fifth year. By the sixth year the centres for the head and tuberosities have increased in size and become joined, so as to form a single large epiphysis. Epiphyseal line. _ > of head and tuberosities blend at Bth year, and unite with shaft at 20th Fig. 144. — Plan of the development of the humerus from eight centres. The lower end of the humerus is developed in the following manner: At the end of the second year ossification commences in the capitellum, and from this point extends inward, so as to form the chief part of the articular end of the bone, the centre for the inner part of the trochlea not appearing until about the age of twelve. Ossification commences in the internal condyle about the fifth year, and in the external one not until about the thirteenth or fourteenth year. About the sixteenth or seventeenth year the outer condyle and both portions of the articulating surface (which have already joined) unite with the shafi ; M \\\r rit^hieenth year the inner condyle l)ecomes joined; while the upper epiphysis, although the Hr.s( formed, is not united until about the twen- tieth year. Articulations. — With the glenoid cavity of the scapula and with the ulna and radius. Attachment of Muscles. — To twenty-four — to the greater tuberosity, the Supraspinafus, Infraspinatus, and Teres minor; to the lesser tuberosity, the Subscapularis; to the externa! bicipital ridge, the Pectoralis major; to the internal bicipital ridge, the Teres major; to the bicip- ital groove, the Latissimus dorsi; to the shaft, the Deltoid, Coracobrachialis, Brachialis anticus, external and internal heads of the Triceps; to the internal condyle, the Pronator teres, and com- mon tendon of the Fle.xor carpi radialis, Palmaris longus. Flexor sublimis digitorum, and Flexor carpi ulnaris; to the external, supracondylar ridge, the Brachioradialis and Extensor carpi radi- 184 SPECIAL ANATOMY OF THE SKELETON alls longior; to the external condyle, the common tendon of the Extensor carpi radialis brevior, Extensor communis digitorum, Extensor minimi digiti, Extensor carpi ulnaris, and Supinator [brevis]; to the back of the external condyle, the Anconeus. Surface Form. — The humerus is almost entirely clothed by the muscles which surround it, and the only parts of this bone which are strictly subcutaneous are small portions of the inter- nal and external condyles. In addition to these, the tuberosities and a part of the head of the bone can be felt under the skin and muscles by which they are covered. Of these, the greater tuberosity' forms the most prominent bony point of the shoulder, extending beyond the acromion process and covered by the Deltoid muscle. It influences materially the surface form of the shoulder. It is best felt while the arm is lying loosely by the side; if the arm be raised, it recedes from under the finger. The lesser tuberosity, directed forward and inward, is to be felt to the inner side of the greater tuberosity, just below the acromioclavicular joint. Between the two tuberosities lies the bicipital groove. This can be defined by placing the finger and making firm pressure just internal to the greater tuberosity; then, by rotating the humerus, the groove will be felt to pass under the finger as the bone is rotated. With the arm abducted from the side, by pressing deeply in the axilla the lower part of the head of the bone is to be felt. On each side of the elbow-joint, and just above it, the internal and external condyles of the bone may be felt. Of these, the internal is the more prominent, but the ridge passing upward from it, the internal supracondylar ridge, is much less marked than the external, and, as a rule, is not to be felt. Occasionally, however, we find along this border the hook-shaped process men- tioned in the foot-note on page 181. The external condyle is most plainly to be seen diu-ing semiflexion of the forearm, and its position is indicated by a depression between the attachment of the adjacent muscles. From it is to be felt a strong bony ridge running up the outer border of the shaft of the bone. This is the external supracondylar ridge; it is concave forward, and corresponds with the curved direction of the lower extremity of the humerus. Applied Anatomy. — There are several points of surgical interest connected with the humerus. First, as regards its development. The upper end, though the first to ossify, is the last to join the shaft, and the length of the bone is mainly due to growth from this upper epiphysis. Hence, in cases of amputation of the arm in young subjects the humerus continues to grow con- siderably, and the end of the bone, which immediately after the operation was covered with a thick cushion of soft tissue, begins to project, thinning the soft parts and rendering the stump conical. This may necessitate another operation, which consists in the removal of a couple of inches or so of the bone, and even after this operation a recurrence of the conical stump may take place. There are several points of surgical interest in connection with fractures. First, as regards their causation, the bone may be broken by direct or indirect violence like the other long bones, but, in addition to this, it is probably more frecjuently fractm-ed by muscular action than any other of this class of bone in the body. It is usually the shaft, just below the insertion of the Deltoid, which is thus broken. Fractures of the upper end may take place through the anatomical neck, through the surgical neck, or separation of the greater tuberosity may occur. Fracture of the anatomical neck is a very rare accident ; in fact, it is doubted by some whether it ever occurs. These fractures are usually considered to be intracapsular, but they are probably partly within and partly without the capsule, as the lower part of the capsule is inserted some little distance below the anatomical neck, while the upper part is attached to it. They may be impacted or nonimpacfed. In most cases there is little or no displacement on account of the capsule, in whole or in part, remaining attached to the lower fragment. Separation of the upper epiphysis of the humerus sometimes occurs in the young subject, and is marked by a character- istic deformity by which the lesion may be at once recognized. This consists in the presence of an abrupt projection at the front of the joint a short distance below the coracoid process, caused by the upper end of the lower fragment. In fractures of the shaft of the huvterus the lesion may take place at any point, but appears to be more common in the lower than in the upper part of the bone. The points of interest in connection with these fractures are: (1) That the musculospiral nerve may be injured as it lies in the groove on the bone, or may become involved in the callus which is subsequently thrown out; and (2) the frequency of nonunion. This is believed to be more common in the humerus than in any other bone, and various causes have been assigned for it. It would seem most probably to be due to the difiiculty that there is in fixing the shoulder-joint and the upper fragment, and possibly the elbow-joint and lower fragment also. Other causes which have been assigned for the nonunion are: (1) That in attempt- ing passive motion of the elbow-joint to overcome any rigidity which may exist, the movement does not take place at the articulation, but at the seat of fracture; or that the patient, in con- sequence of the rigidity of the elbow, in attempting to flex or extend the forearm moves the fragment and not the joint. (2) The presence of small portions of muscle tissue between the broken ends. (3) Want of support to the elbow, so that the weight of the arm tends to drag the lower fragment away from the upper. An important distinction to make in fractures of the loiver end of the humerus is between those that involve the elbow-joint and those which do not; the former are always serious, as they may lead to stiffness of the joint and impairment of the THE ULNA, Oli ELBOW BONE 185 utility of the limb. They include the T-shaped fracture and oblique fractures which involve the articular surface. The fractures which do not involve the joint are the transverse above the condyles and the so-called epitrochlear fracture, in which the tip of the internal condyle is broken off, genei-ally by direct violence. Under the head of i-eparation of the lower epiphysis two separate injuries have been described: (1) Where the whole of the four ossific centres which form the lower extremity of the bone are separated from the shaft; and (2) where the articular portion is alone separated, the two condyles remaining attached to the shaft of -the bone. The epiphyseal line between the shaft and lower end runs across the bone just above the tips of the condyles, a point to be borne in mind in performing the operation of excision. Shortening may follow epiphysitis. Tumors originating from the humerus are of frequent occurrence. A not uncommon place for a chondroma to grow from is the shaft of the bone somewhere in the neighborhood of the insertion of the deltoid. Sarcomata frequently grow from this bone. THE FOREARM. The forearm is that portion of the upper extremity which is situated between tlie elbow and the wrist. Its skeleton is composed of two bones, the ulna and radius. The Ulna, or Elbow Bone (Figs. 14-5, 147). The ulna is a long bone, prismatic in form, placed at the inner side. of the forearm, parallel with the radius. It is the larger and longer of the two bones. Its upper extremity, of great thickness and strength, forms a large part of the articulation of the elbow-joint; it diminishes in size from above downward, its lower extremity being very small, and excluded from the wrist-joint by the inter- position of an intra-articular fibrocartilage. It is divisible into a shaft and two extremities. The Upper or Proximal Extremity, the strongest part of the bone, presents for examination two large, curved processes, the olecranon process and the coronoid process; and two concave, articular cavities, the greater and lesser sigmoid cavities. The olecranon process {i •lecranon) is a large, thick, curved eminence situated at the upper and back part of the ulna. It is curved forward at the summit so as to present a prominent tip which is received into the olecranon fossa of the humerus in extension of the forearm, its base being contracted where it joins the shaft. This is the narrowest part of the upper end of the ulna. The posterior surface of the olecranon, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its zipper surface is of a quadrilateral form, marked behind by a rough impression for the attachment of the Triceps muscle; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, covered with cartilage in the recent state, and forms the upper and back part of the greater sigmoid cavity. The lateral borders present a continuation ' of the same groove that was seen on the margin of the superior surface ; they serve for the attachment of ligaments — viz., the back part of the internal lateral ligament internally, the posterior ligament externally. To the inner border is also attached a part of the Flexor carpi ulnaris, while to the outer border is attached the Anconeus muscle. The coronoid process {processus coronoideus) is a triangular eminence of bone which projects horizontally forward from the upper and front part of the ulna. Its base is continuous with the shaft, and of considerable strength; so much so that fracture of it is an accident of rare occurrence. Its apex is pointed, slightly curved upward, and is received into the coronoid depression of the hiuneriis in 186 SPECIAL ANATOMY OF THE SKELETON Ulna. , cr a>i 'C^imiiar ligamtnt. Radius. PRONATOR TERES Occasional ongm of y. . . ^r rUEXOR tONQUS POLL CIS *' / \ \ V 1 \ I Radial origin of flexor DIGITORUM Oapstdar Styloid pi ocess Styloid process. Fig. 145, — Bones of the left forearm, Antei'ior view. THE ULNA, OB ELBOW BONE 187 Olecranon process \ flexion of the forearm. Its upper surface is smooth, concave, and forms the lower part of the greater sigmoid cavity. The under siirface is concave; and marked by an impression internally for the insertion of the Brachialis anticus. At the junc- tion of this surface with the shaft is a rough eminence, the tubercle of the ulna (tuberositas ulnae), for the attachment of the oblique ligament of the middle radio-ulnar articulation. Its outer surface presents' a narrow, oblong, articular depression, the lesser sigmoid cavity. The inner surface, by its prominent free margin, serves for the attachment of part of the internal lateral ligament. At the front part of this surface is a small, rounded eminence for the attach- ment of one head of the Flexor sublimis digitorum; behind the eminence, a depression for part of the origin of the Flexor profundus digitorum; and, descend- ing from the eminence, a ridge which gives attachment to one head of the Pro- nator teres. Generally, the Flexor longus pollicis has an origin from the lower part of the coronoid process by a rounded bundle of muscle fibres. The greater sigmoid cavity (incisura semilunaris) is a semilunar depression of large size, formed by the olecranon and coronoid processes, and serving for articulation with the trochlear surface of the humerus. About the middle of either lateral border of this cavity is a notch which con- tracts it somewhat, and serves to indicate the junction of the two processes of which it is formed. The cavity is concave from above downward, and divided into two lateral parts by a smooth, elevated ridge which runs from the summit of the olecranon to the tip of the coronoid process. Of these two portions, the internal is the larger, and is slightly concave transversely; the external portion is convex above, slightly concave be- low. The articular surface, in the recent state, is covered with a thin layer of hyaline cartilage. The lesser sigmoid cavity {incisura radi- alis) is a narrow, oblong, articular depres- sion, placed on the outer side of the coronoid process, and receives the lateral articular sur- face of the head of the radius. It is concave from before backward, and its extremities, which are prominent, serve for the attach- ment of the orbicular ligament. In the recent state it is covered with a thin layer of hyaline cartilage. The Shaft (corpus ulnae), at its upper part, is prismatic in form, and curved from behind forward and from without inward, so as to be convex behind and externally; its central part is quite straight; its lower part rounded, smooth, and bent a little outward; it tapers gradually from above downward, and presents for examination three borders and three surfaces. The anterior or palmar border (marcjo volaris) commences above at the prominent inner angle of the coronoid process, and terminates below in front of the styloid process. It is well marked above, smooth and rounded in the middle of its extent,' and affords origin to the Flexor profundus digitorum; its lower fourth, marked off from the rest of the border by the commencement of an oblique ridge on the anterior surface, serves for the origin of the Pronator quadratus. It separates the anterior from the internal surface. The posterior or dorsal border (margo dorsalis) commences above at the apex of the triangular subcutaneous surface at the back part of the olecranon, and 188 SPECIAL ANATOMY OF THE SKELETON Ulna. Capsular ligament LIMIS DIGITORUM, ■Capsular ligament Fig. 147. — Bones of the left forearm. Posterior view. THE ULNA, OR ELBO W BONE 1,S9 terminates below at the back part of the styloid process; it is well marked in the upper three-fourths, and gives origin to the aponeurosis common to the Flexor carpi ulnaris, the Extensor carpi ulnaris, and the Flexor profundus digitonim muscles; its lower fourth is smooth and rounded. This border separates the internal from the posterior surface. The external or interosseous border (crista interossea) commences above by the union of two lines, which converge one from each extremity of the lesser sigmoid cavity, enclosing between them a triangular space for the origin of part of the Supinator [brevis], and terminates below at the middle of the. lower extremity. Its two middle fourths are very prominent; its lower fourth is smooth and rounded. This border gives attachment to the interosseous membrane, and .separates the anterior from the posterior surface. The anterior or palmar surface {fades volaris') lies between the anterior and external borders, is much broader above than below, is concave in the upper three- fourths of its extent, and affords origin to the Plexor profundus digitorum; its lower fourth, also concave, is covered by the Pronator quadratus. The lower fourth is separated from the remaining portion of the bone by a prominent ridge (pronator ridge) directed obliquely from above downward and inward; this ridge marks the extent of attachment of the Pronator quadratus. At the junction of the upper with the middle third of the bone is the nutrient foramen. It opens into the nutrient canal, which is directed obliquely inward and upward (proximally). The posterior or extensor surface (fades dorsalis) is bounded externally by the interosseous border, internally by the posterior border, and is directed backward and outward; it is broad and concave above, somewhat narrower and convex in the middle of its course, narrow, smooth, and rounded below. It pre- sents, above, an oblique ridge, which runs from the posterior extremity of the lesser sigmoid cavity, downward to the posterior border; the triangular surface above this ridge receives the insertion of the Anconeus muscle, while the upper part of the ridge itself aiYords origin to the Supinator. The surface of bone below this is subdivided by a longitudinal ridge into two parts; the internal part is smooth, and covered by the Extensor carpi ulnaris; the external portion, wider and rougher, gives origin from above downward to part of the Supinator, the Extensor ossis metacarpi pollicis, the Extensor longus pollicis, and the Extensor indicis muscles. The internal surface (Jades medialis) is broad and concave above, narrow and convex below. It gives origin by its upper three-fourths to the Flexor profundus digitorum muscle; its lower fourth is subcutaneous. The anterior and the inner surfaces constitute the flexor surface. The Distal or Lower Extremity is of small size, and excluded from the articulation of the wrist-joint. It presents for examination two eminences, tlie outer and larger of which is a rounded, articular eminence, termed the head (capitulum ulnae), the inner, narrower and more projecting, is a nonarticular eminence, the styloid process (processus sti/loideus). The head presents an articular facet, part of which, of an oval form, is directed downward, and plays on the upper surface of the triangular fibrocartilage which separates it from the wrist-joint; the remaining portion, directed outward, is narrow, convex, and received into the sigmoid cavity of the radius. The styloid process projects from the inner and back part of the bone, and descends a little lower than the head, terminating in a rounded summit, which affords attachment to the internal lateral ligament of the wrist. The head is separated from the styloid process by a depression for the attachment of the triangular intra-articular fibrocartilage; and behind, by a shallow groove for the passage of the tendon of the Extensor carpi ulnaris. 190 SPECIAL ANATOMY OF THE SKELETON Appears at^^ 10th year. Olecranon. -Joins shaft a 16th year. Stracture. — Similar to tliat of the other long bones. Development. — From thrive centres — one for the shaft, one for the inferior extremity, and one for the olecranon (Fig. 148). Ossification commences near the middle of the shaft about the eighth week, and soon extends through the greater part of the bone. At birth the ends are cartilaginous. About the fourth year a separate osseous nucleus appears in the middle of the head, which soon extends into the styloid process. About the tenth year ossific material appears in the olecranon near its extremity, the chief part of this process being formed from an extension of the shaft of the bone into it. At about the sixteenth year the upper epiphysis becomes joined to the shaft, and at about the twentieth year the lower one. Articulations. — With the humerus and radius. Attachment of Muscles. — To sixteen: To the olecranon, the Triceps, Anconeus, and one head of the Flexor carpi ulnaris. To the coronoid process, the Brachialis anticus. Pronator teres. Flexor sublimis digitorum, and Flexor profundus digitorum; generally also the Flexor longus pollicis. To the shaft, the Flexor profundus digitorum, Pronator quadratus, Flexor carpi ulnaris. Extensor carpi ulnaris. Anconeus, Supinator [brevis], Extensor ossis metacarpi pollicis. Extensor longus pollicis, and Extensor indicis. Surface Form. — The most prominent part of the ulna on the surface of the body is the olecranon process, which can always be felt at the back of the elbow-joint. When the fore- arm is flexed, the upper quadrilateral surface can be felt, directed backward; during extension it recedes into the olec- ranon fossa, and the contracting fibres of the triceps prevent its being perceived. At the back of the olecranon is the smooth, triangular, subcutaneous surface, which below is continuous with the posterior border of the shaft of the bone, and felt in every position of the forearm. During extension the upper border of the olecranon is slightly above the level of the internal condyle, and the process itself is nearer to this condyle than the outer one. Running down the back of the forearm, from the apex of the triangular surface which forms the posterior surface of the olecranon, is a prominent ridge of bone, the posterior border of the ulna. This may be felt throughout the entire length of the shaft of the bone, from the olecranon above to the styloid process below. As it passes down the forearm it pursues a sinuous course and inclines to the inner side, so that, though it is situated in the middle of the back of the limb above, it is on the inner side of the wrist at its termination. It becomes rounded off in its lower third, and may be traced below to the small, subcutaneous surface of the st3'loid process. Internal to this border the lower fourth of the inner surface ma)' be felt. The styloid process may be felt as a prominent tubercle of bone, continuous above with the posterior subcutaneous border of the ulna, and terminating below in a blunt apex, which lies a little internal and behind, but on a level with, the wrist-joint. The styloid process is best felt when the hand is in the same line as the bones of the forearm, and in a position midway between supination and pronation. If the forearm is pronated while the finger is placed on the process, it will be felt to recede, and another prominence of bone will appear just behind and above it. This is the head of the ulna, which articulates with thejower end of the radius and the triangular intra-articular fibrocarti- lage, and now projects between the tendons of the Extensor carpi ulnaris and the Extensor minimi dij;iti muscles. 8th' ^ Appears aij Jfth year. ^Joins shaft at Both year. Inferior extremity. Fig, 148. — Plan of the development of the ulna. From three centres. The Radius. The radius is situated on the outer side of the forearm, lying side by side with the ulna, which exceeds it in length and size (Fig. 145). Its upper end is small, and forms only a small part of the elbow-joint; but its lower end is large, and forms the chief part of the wrist. It is one of the long bones, prismatic in form, slightly curved longitudinally, and, like other long bones, has a shaft and two extremities. The Proximal or Upper Extremity presents a head, neck, and tuberosity. The head (capituluni radii) is of a cylindrical form, depressed on its upper surface into a shallow cup (fovea capituli radii), which articulates with the capitel- lum or radial head of the humerus. In the recent state it is covered with a layer THE RADIUS 191 of hyaline cartilage which is thinnest at its centre. Around the circumference of the head is a smooth, articular surface {circumferentia articularis) , broad internally, where it articulates with the lesser sigmoid cavity of the ulna; narrow in the rest of its circumference, where it rotates within the orbicular ligament. It is coated with hyaline cartilage in the recent state. The head is supported on a round, smooth, and constricted portion of bone, called the neck (collum radii), which presents, behind, a slight ridge, for the attachment of part of the Supinator [brevis]. Beneath the neck, at the inner and front aspect of the bone, is a rough eminence, the bicipital tuberosity {tuberositas radii). Its surface is divided into two parts by a vertical line — a posterior, rough portion, for the insertion of the tendon of the Biceps muscle; and an anterior, smooth portion, on which a bursa is interposed between the tendon and the bone. The Shaft {corpus radii) is prismoid in form, narrower above than below, and slightly curved, so as to be convex outward. It presents three surfaces, separated by three borders. The anterior border {marcjo volaris) extends from the lower part of the tuber- osity above to the anterior part of the base of the styloid process below. It separates the anterior from the external surface. Its upper third is very promi- nent; and from its oblique direction, downward and outward, has received the name of the oblique line of the radius. It gives insertion externally at the Supinator [brevis] internally, it limits the origin of the Flexor longus pollicis, and between these, arising from it, is the radial origin of the Flexor sublimis digitorum. The middle third of the anterior border is indistinct and rounded. Its lower fourth is sharp, prominent, affords attachment to the Pronator quadratus and to the posterior annular ligament of the wrist, and terminates in a small tubercle at the base of the styloid process, into which is inserted the tendon of the Brachioradialis. The posterior border {margo dorsalis) commences above at the back part of the neck of the radius, and terminates below at the posterior part of the base of the styloid process; it separates the posterior from the external surface. It is indistinct above and below, but well marked in the middle third of the bone. The internal border {crista interossea) commences above at the back part of the tuberosity, where it is rounded and indistinct, becomes sharp and prominent as it descends, and at its lower part divides into two ridges, which descend to the anterior and posterior margins of the sigmoid cavity. This border separates the anterior from the posterior surface, and has the interosseous membrane attached to it throughout the greater part of its extent. The anterior or flexor surface {fades volaris) is concave for its upper three- fourths, and gives origin to the Flexor longus pollicis muscle; it is broad and flat for its lower fourth, and gives attachment to the Pronator quadratus. A promi- Bent ridge limits the attachment of the Pronator quadratus below, and between this and the inferior border is a triangular rough surface for the attachment of the anterior ligament of the wrist-joint. At the junction of the upper and middle third of this surface is the nutrient foramen, the opening of the nutrient canal, which is directed obliquely upward (proximally). The posterior or extensor surface {fades dorsalis) is rounded, convex, and smooth in the upper third of its extent, and covered by the Supinator [brevis] muscle. Its middle third is broad, slightly concave, and gives origin to the Extensor ossis metacarpi pollicis above, the Extensor brevis pollicis below. Its lower third is broad, convex, and covered by the tendons of the muscles, which subsequently run in the grooves on the lower end of the bone. The external surface {fades lateralis) is rounded and convex throughout its entire extent. Its upper third gives attachment to the Supinator [brevis] muscle. About its centre is seen a rough ridge, for the insertion of the Pronator teres muscle. Its lower part is narrow, and covered by the tendons of the Extensor ossis metacarpi pollicis and Extensor brevis pollicis muscles. 192 SPECIAL ANATOMY OF THE SKELETON The Lower Extremity is large, of. quadrilateral form, and provided with two articular surfaces — one at the extremity, for articulation with the carpus, and one at the inner side of the bone, for articulation with the ulna. The carpal articular surface (fades articularis carpea) is of triangular form, concave, smooth, and divided by a slight antero-posterior ridge into two parts. Of these, the external is of a tri- angular form, and articulates with the scaphoid bone; the inner is quadrilateral and articulates with the semilunar bone. The articular surface for the head of the ulna is called the sigmoid cavity of the radius (incisura ulnaris) ; it is narrow, con- cave, smooth, and articulates with the head of the ulna. The circumference of this end of the bone presents three surfaces — an anterior, external, and posterior. The anterior surface, rough and irregular, affords attachment to the anterior ligament of the wrist-joint. The external surface is prolonged obliquely downward into a strong conical projection, the styloid process (processus styloideus), which gives attachment by its base to the tendon of the Brachioradialis, and by its apex to the external lateral ligament of the wrist-joint. The outer surface of this process is marked by a flat gi-oove, which runs obliquely downward and forward, and gives passage to the tendons of the Extensor ossis metacarpi pollicis and the Extensor brevis pollicis. The posterior surface is convex, affords attachment to the posterior ligament of the wrist, and is marked by three grooves. Proceeding from without inward, the first groove is broad but shallow, and subdivided into two by a slightly elevated ridge; the outer of these two transmits the tendon of the Extensor carpi radial is longior, the inner the tendon of the Extensor carpi radialis brevior. The second, which is near the centre of the bone, is a deep but narrow groove, bounded on its outer side by a sharply defined ridge; it is directed obliquely from above, downward and outward, and transmits the tendon of the Extensor longus pollicis. The third, lying most internally, is a broad groove, for the passage of the tendons of the Extensor indicis and Extensor communis digitorum. Structure. — Similar to that of the other long bones. Development (Fig. 149). — From three centres, one for the shaft and 07ie for each extremity. That for the shaft makes its appearance near the centre of the bone, about the eighth week of fetal life. About the end of the second year ossification commences in the lower epiphysis, and about the fifth year in the upper end. At the age of seventeen or eighteen the upper epiphysis becomes joined to the shaft, the lower epiphysis becoming united about the twentieth year. Some- times an additional centre appears about the fourteenth year in the bicipital tuberosity. Articulation. — With four bones — the humerus, idna, scaphoid, and semilunar. Attachment of Muscles. — To nitie: To the tuberosity, the Biceps; to the oblique ridge, the Supinator [brevis], Flexor sublimis digitorum, and Flexor longus pollicis; to the shaft (its anterior surface), the Flexor longus pollicis and Pronator quadratus; (its posterior surface), the Extensor ossis metacarpi pollicis and Extensor brevis pollicis; (its outer surface), the Pronator teres; and to the styloid process, the Brachioradialis. Surface Form. — Just below and a little in front of the posterior surface of the external con- dyle a part of the head of the radius may be felt, covered by the orbicular and external lateral ligaments. There is in this situation a little dimple in the skin, which is most visible when the arm is extended, and which marks the position of the head of the bone. If the finger is placed on this dimple and the forearm pronated and supinated, the head of the bone will he distinctly perceived rotating in the lesser sigmoid cavity. The upper half of the shaft of the radius can- not be felt, as it is sturounded by the fleshy muscles arising from the external condyle. The lower half of the shaft can be readily examined, although covered by tendons and muscles and not strictly subcutaneous. If traced downward, the shaft will be felt to terminate in a lozenge- shaped, convex surface on the outer side of the base of the styloid process. This is the only subcutaneous part of the bone, and from its lower extremity the apex of the styloid process will be felt bending inward toward the wrist. About the middle of the posterior aspect of the lower extremity of the bone is a well-marked ridge, best perceived when the hand is slightly flexed on the A\Tist. It forms the outer boundary of the oblique groove on the posterior surface of the bone, through which the tendon of the Extensor longus pollicis runs, and serves to keep that tendon in place. Applied Anatomy of the Radius and Ulna. — The two bones of the forearm are more often broken together than is either the radius or ulna separately. It is, therefore, convenient to consider fractures of both bones in the first instance, and subsequently to mention the principal fractures THE RADIUS 193 Apyears a 5th year. Unites with shaft - about 18th or 20th year. which take place in each bone individually. These fractures may be produced bv either direct or indirect violence, though more commonly by direct violence. When indirect force i.s ap|)lied to the forearm the radius generally alone gives way, though both bones may suffer. The fracture from indirect force generally takes place somewhere about the middle of the bones; fracture from direct violence may occur at any part, more often, however, in the lower half of the bone. The fracture is usually transverse, but may be more or less oblique. A point of interest in con- nection with these fi-actures is the tendency that there is for the two bones to unite across the interosseous membrane; the limb should therefore be put up in a position midway between supi- nation and pronation, which is not only the most comfortable position, but also separates the bone-s most widely from each other, and therefore diminishes the risk of the bones becoming united across the inter- osseous membrane. The splints, anterior and posterior, which are applied in these cases should be rather wider than the limb, so as to prevent any lateral pressure on the bones. In these cases there is a greater liability to gangrene from the pressure of the splints than in other parts of the body. This is no doubt due princijially to two causes: (1) The flexion of the forearm compressing to a certain extent the brachial artery and retarding the flow of blood to the limb; and (2) the superficial position of the two main arteries of the forearm in a part of their course, and their liability to be compressed by the splints. The special fractures of the ulna are: (1) Fracture of the olecranon. This may be caused by direct violence, falls on the elbow with .the forearm flexed, or by muscular action by the sudden contraction of the triceps. The most common place for the frac- ture to occur is at the constricted portion where the olecranon joins the shaft of the bone, and the fracture may be either transverse or oblique; but any part may be broken, even a thin shell may be torn off. Fractures from direct violence are occasionally comminuted. The displacement is sometimes very slight, owing to the fibrous structures around the process not being torn. (2) Fracture of the coronoid process sometimes occurs as a complication of dislocation backward of the bones of the forearm, but it is doubtful if it ever occurs as an xmcomplicated injury. (3) Fractures of the shaft of the ulna may occur at any part, but usually takes place at the middle of the bone or a little below it. They are usually the result of direct violence. (4) The styloid process may be knocked off by direct violence. Fractures of the radius consist of: (1) Fracture of the head of the bone; this generally occurs in conjunction with some other lesion, but may occur as an uncomplicated injury. (2) Fracture of the neck may also take place, but is generally complicated with other injury. (3) Fractures of the shaft of the radius are very common, and may take place at any part of the bone. They may take place from either direct or indirect violence. In fractures of the upper third of the shaft of the bone, that is to say, above the insertion of the Pronator teres, the displacement is very great. The upper fragment is strongly supinated by the Biceps and Supinator, and flexed by the Biceps, while the lower fragment is pronated and drawn toward the ulna by the two pronators. If such a fracture is put up in the ordinary position, midway between supination and pronation, the fracture will unite with the upper fragment in a position of supination, and the lower one in the mid-position, and thus considerable impairment of the movements of the hand will result. The limb should be put up with the forearm supinated. (4) The most impor- tant fracture of the radius is that of the lower end (Colles' fracture). The fracture is transverse, and generally takes place about an inch from the lower extremity. It is caused by falls on the ]5alm of the hand, and is an injury of advanced life, occurring more frequently in the female than the male. In consequence of the manner in which the fracture is caused, the upper frag- ment becomes driven into the lower, and impaction is the result; or else the lower fragment becomes split up into two or more pieces, so that no fixation occurs. Separation of the lower epiphysis of the radius may take place in the young. This injury and Colles' fracture may be distinguished from other injuries in this neighborhood — especially dislocation, with W'hich it is liable to be confounded — by observing the relative positions of the styloid processes of the ulna and radius. In the natural condition of parts, with the arm hanging by the side, the styloid process of the radius is on a lower level than that of the ulna; that is to say, nearer the groiuid. After fracture or separation of the epiphysis this process is on the same or a higher level than that of the ulna, whereas it would be unaltered in position in dislocation. 13 .ippeari 2d yea I Unites with shaft about 20th year. Lowei extiemity. 194 SPECIAL ANATOMY OF THE SKELETON THE HAND, The skeleton of the hand is subdivided into three segments — the carpus, or wrist bones; the metacarpus, or bones of the palm; and the phalanges, or bones of the digits. FLEXOR ^ PROFUNDUS f I DIGITORUM Fio. 150. — Bones of the left hand. Palmar surface. THE CARPUS 195 The Carpus (Ossa Carpi) (Figs. 150, 151). The bones of the carpus, eight in number, are arranged in two rows. Those of the upper row, enumerated from the radial to the uhiar side, are the scaphoid. '-^Aj^a EXTENSOR COMMUNIS DiGiTORUM and EXTENSOR INDICIS. Fig. 151.— Bonea of the left hand. Dorsal surface. 196 SPECIAL ANATOMY OF THE SKELETON semilunar, cuneiform, and pisiform; those of the lower row, enumerated in the same order, are the trapezium, trapezoid, os magnum, and unciform. Common Characters of the Carpal Bones. — Each bone (excepting the pisi- form) presents six surfaces. Of these the anterior, palmar, or volar, and the posterior or dorsal are rough for hgamentous attachment, the dorsal surface being the broader, except in the scaphoid and semilunar. The superior or proximal and inferior or distal are articular, the superior generally convex, the inferior concave; and the internal and external are also articular when in contact with contiguous bones, otherwise rough and tubercular. The structure of all is similar, consisting of cancellous tissue enclosed in a layer of compact bone. Vad'^'' With 1 Fig. 152. — Diagram to show articulations Bones of the Upper Row. — The scaphoid or navicular bone {os naviculare manus) (Fig. 1.5.3) is the largest bone of the first row. It is situated at the upper and outer part of the carpus, its long axis being from above downward, outward, and forward. For radius For semilunar Tuberosity For trapesimn For OS magnum. tor f)apezoid A B Fig. 153. — The left scaphoid. A, seen from behind; B, seen from in front. Surfaces. — The superior surface is convex, smooth, of triangular shape, and articulates with the lower end of the radius. The inferior surface, directed down- ward, outward, and back\i'ard, is smooth, convex, also triangular, and divided by a slight ridge into two parts, the external of which articulates with the trapezium, the inner with the trapezoid. The posterior or dorsal surface presents a narrow, rough groove which runs the entire length of tlie bone and serves for the attachment of ligaments. The anterior or palmar siu-face is concave above, and elevated at its lower and outer part into a prominent rounded tuberosity (tuberculum ossis iiavicidaris), which projects forward from the front of the carpus and gives attach' THE CARPUS 197 ment to the anterior annular ligament of the wrist and sometimes a few fibres of the Abductor poUicis. The external surface is rough and narrow, and gives attachment to the external lateral ligament of the wrist. The internal surface presents two articular facets; of these, the superior or smaller one is flattened, of semilunar form, and articulates with the semilunar; the inferior or laro-er is concave, forming, with the semilunar bone, a concavity for the head of the os magnum. To ascertain to which side the bone belongs, hold the convex radial articular surface upward, and the dorsal surface backward; the prominent tubercle will be directed to the side to which the bone belongs. Articulations. — With five bones — the radius above, trapezium and trapezoid l)elo\v, os magnum and semilunar internally. Attachment of Muscles. — Occasionally a few fibres of the Abductor pollicis. The semilunar bone (Fig. 154) may be distinguished by its deep concavity and crescentic outline. It is situated in the centre of the upper row of the carpus, between the scaphoid and cuneiform. For cuneiform For scaphoid For unciform For os magnum A B Fig. 154. — The left semilunar. A, anterior and internal surfaces; B, external surface. Surfaces. — The superior surface, convex, smooth, and bounded by four edges, articulates with the radius. The inferior surface is deeply concave, and of greater extent from before backward than transver,sely ; it articulates with the head of the OS magnum and by a long, narrow facet (separated by a ridge from the general surface) with the unciform bonc^^fhe anterior or palmar and posterior or dorsal surfaces are rough, for the attachment of ligaments, the former being the broader and of a somewhat rounded form. The external surface presertts a narrow, flat- tened, semilunar facet for articulation with the scaphoid. The internal surface js marked by a smooth, quadrilateral facet, for articulation with the cuneiform. To ascertain to which hand this bone belongs, hold it with the dorsal surface upward, and the convex articular surface backward; the quadrilateral articular facet will then point to the side to which the bone belongs. Articulations. — With five bones — the radius above, os magnum and unciform below, sca])hoid externally, and cuneiform internally. For pisifor The cuneiform (os f.riquetrum) (Fig. 155) may be distinguished by its pyramidal shape, and by 'its having an oval, isolated facet for articulation with the pisiform bone. It is situated at the upper and inner side of the carpus. Surfaces. — ^The superior surface presents an internal, i'ough, nonarticular portion, and an external or articular portion, which is convex, smooth, and articu- lates with the triangular intra-articular fibrocartilage of the wrist. The inferior surface, directed outward, is concave, sinuously curved, and smooth for articulation with the unciform. The posterior or dorsal surface is For unciform Fig. 155. — The left cuneiform. 198 SPECIAL ANATOMY OF THE SKELETON rough, for the attachment of ligaments. The anterior or palmar surface presents. at its inner side, an oval facet, for articulation with the pisiform, and is rough externally, for ligamentous attachment. The external surface, the base of the pyramid, is marked by a flat, quadrilateral, smooth facet, for articulation with the semilunar. The internal surface, the summit of the pyramid, is pointed and roughened, for the attachment of the internal lateral ligament of the wrist. To ascertain to which hand this bone belongs, hold it so that the base is directed backward, and the articular facet for the pisiform bone upward; the concave articular facet will point to the side to which the bone belongs. Articulations. — With three bones — the semilunar externally, the pisiform in front, the unci- form below; and with the triangular, interarticular fibrocartilage which separates it from the lower end of the ulna. The pisiform (os pisiforme) (Fig. 156) may be known by its small size and by its presenting a single articular facet. It is situated on a plane anterior to the other bones of the carpus; it is spheroidal in form, with its long For cuneiform ,. , ,. , , j.- n , ' diameter directed vertically. Surfaces. — Its posterior surface is a smooth, oval facet, for articulation with the cuneiform. This facet approaches the superior, but not the inferior border of the bone. The anterior Fig. 156.— The left or palmar surface is rounded and rough, and gives attachment to posterior and lateral the anterior annular ligament and to the Flexor carpi ulnaris sur aces. ^^^ Origin to the Abductor minimi digiti. The outer and inner surfaces are also rough, the former being concave, the latter usually convex. To ascertain to which hand this bone belongs, hold the bone with its posterior or articular facet downward and the nonarticular portion of the same surface backward; the inner concave surface will point to the side to which it belongs. Articulations. — With one bone, the cuneiform. Attachment of Muscles. — To two — the Flexor carpi ulnaris and Abductor minimi digiti; and to the anterior annular ligament. Bones of the Lower Row. — The trapezium (os multangtdum majus) (Fig. 157) is of very irregular form. It may be distinguished by a deep groove, for the tendon of the Flexor carpi radialis muscle. It is situated at the external and inferior part of the carpus between the scaphoid and first metacarpal bone. For scaphoid For trapezoid ^,.r». / ,-5;:^^?>C n ± -j ■^ , . — -^"^Ss. / .^i^'-- «^ For trapezoid For 2nd Al-.M metacarpal ^ ' '^ Bidge \ For 1st metacarpal F°^ ^'«^ metacarpal A B Fig. 157. — The left trapezium. A, as seen from in front; B, from above and mesal side. Surfaces. — The superior surface, concave and smooth, is directed upward and inward, and articulates with the scaphoid. The inferior surface, directed down- ward and inward, is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface, for articulation with the base of the first metacarpal bone. The anterior or palmar surface is narrow and rough. At its upper part is a deep groove running from above obliquely downward and inward; it transmits the tendon of the Flexor carpi radialis, and is bounded externally THE CARPUS 199 by a prominent ridge, the oblique ridge of the trapezium {hiherruluni ossis mul- tanguli majoris). This surface gives origin to the Abductor pollicis, Opponens poUicis, sometimes to a portion of the superficial head of the Flexor bre\-is pollicis muscles, and the anterior annular ligament. The posterior or dorsal surface is rough. The external surface is also broad and rough, for the attachment of ligaments. The internal surface presents two articular facets; the upper one, large and concave, articulates with the trapezoid; the lower one, small and oval, with the base of the second metacarpal bone. To ascertain to which hand this bone belongs, hold it with the grooved palmar surface upward, and the external broad, nonarticular surface backward; the saddle-shaped surface will then be directed to the side to w-hich the bone belongs. Articulations. — With four bones — the scaphoid above, the trapezoid and second metacarpal bones internally, the first metacarpal below. Attachment of Muscles. — Abductor pollicis, Opponens pollicis, and sometimes the superficial head of the Flexor brevis pollicis. The trapezoid (os multangidum minus) (Fig. 158) is the smallest bone in the second row. It may be known by its wedge-shaped form, the broad end of the wedge forming the dorsal, the narrow end the palmar, surface, and by its having four articular surfaces 'touching each other and separated by sharp edges. Palmar For surface trapesium Fig. 158. — The left trapezoid. A, as seen from above, inner side and behind; B, from in front. Surfaces. — The superior surface, quadrilateral in form, smooth, and slightly con- cave, articulates with tiie .scaphoid. The inferior surface articulates with the upper end of the second metacarpal bone; it is convex from side to side, concave from before backward, and subdivided by an elevated ridge into two unequal lateral facets. The posterior or dorsal and anterior or palmar surfaces are rough, for the attachment of ligaments, the former being the larger of the two. The external surface, convex and smooth, articulates with the trapezium. The internal surface is concave and smooth in front, for articulation with the os magnum; rough behind, for the attachment of an interosseous ligament. To ascertain to which hand this bone belongs, let the broad dorsal surface be held upward, and the inferior concavo-convex surface forward; the internal concave surface will then point to the side to which the bone belongs Articulations. — With four bones — the scaphoid above, second metacarpal bone below, trape- zium externally, os magnum internally. The OS magnum {os capitatum) (Fig. 159) is the largest bone of the carpus, and occupies the centre of the wrist. It presents, above, a rounded portion or head, which is recei\"ed into the conca^'ity formed by the scaphoid and semilunar bones; a constricted portion or neck; and, below, the body. Surfaces. — The superior surface is rounded, smooth, and articulates with the semi- lunar. The inferior surface is divided by two ridges into three facets for articu- lation with the second, third, and fourth metacarpal bones, that for the third (the middle facet) being the largest of the three. The posterior or dorsal surface is broad and rough; the anterior or palmar, narrow, rounded, and also rough, for the 200 SPECIAL ANATOMY OF THE SKELETON attachment of ligaments, and it gives origin to a part of the Adductor obHquus polHcis. The external surface articulates with the trapezoid by a small facet at its anterior inferior angle, behind which is a rough depression for the attach- ment of an interosseous ligament. Above this is a deep and rough groove, which forms part of the neck and serves for the attachment of ligaments, bounded supe- riorly by a smooth, convex surface for articulation with the scaphoid. The For scaphoid For trapezoid For semilunar For 3rd For %nd metacarpal metacarpal For 4th metacarpal Palmar surface Fig. 159. — The left os magnum. A, outer side seen from below; B, internal posterior surface. internal surface articulates with the unciform by a smooth, concave, oblong facet which occupies its posterior and superior parts, and is rough in front, for the attachment of an interosseous ligament. To ascertain to which hand this bone belongs, the rounded head should be held upward, and the broad dorsal surface forward; the internal concave articular surface will point to the side to which the bone belongs. Articulations. — With seven bones — the scaphoid and semilunar above; the second, third, and fourth metacarpal below; the trapezoid on the radial side; and the unciform on the ulnar side. Attachment of Muscles. — Part of the Adductor obliquus pollicis. The unciform {os hamahim) (Fig. 160) may be readily distinguished by its wedge-shaped form and the hook-like process that projects from its palmar surface. It is situated at the inner and lower angle of the carpus, with its base downward, resting on the two inner metacarpal bones, and its apex directed upward and outward. For semilunar For cuneifor? For OS magnum — For ith metacarpal For 5th metacarpal Unciform process For 5th metacarpal A B Fig. 160. — The left unciform. A, internal surface; B, outer and distal surfaces. Surfaces. — The superior surface, the apex of the wedge, is narrow, convex, smooth, and articulates with the semilunar. The inferior surface articulates with the fourth and fifth metacarpal bones, the concave surface for each being sepa- rated by a ridge which runs from before backward. The posterior or dorsal surface is triangular and rough, for ligamentous attachment. The anterior or palmar surface presents, at its lower and inner side, a curved, hook-like process of bone, the imciform process (hamulus ossis hamati), directed from the palmar sur- face forward and outward. It gives attachment by its apex to the annular liga- THE METACARPUS 201 ment and insertion to some of the fibres of the Flexor carpi uhiaris; by its inner surface it gives origin to the Flexor brevis minimi digiti and the Opponens niininii digiti; and is grooved on its outer side, for the passage of the Flexor tendons into the palm of the hand. This is one of the four eminences on the front of the carpus to which the anterior annular ligament is attached, the others being the pisiform internally, the oblique ridge of the trapezium and the tuberosity of the scaphoid externally. The internal surface articulates with the cuneiform by an oblong facet cut obliquely from above, downward and inward. The external surface articulates with the os magnum by its upper and posterior part, the remaining portion being rough, for the attachment of ligaments. To ascertain to which hand it belongs, hold the apex of the bone upward, and the broad dorsal surface backward; the concavity of the process will be on the side to which the bone belongs. Articulations. — With five bones — the semilunar above, the fourth and fifth metacarpal below, the cuneiform internally, the os magnum externally. Attachment of Muscles. —To three — the Flexor brevis minimi digiti, the Opponens minimi digiti, the Flexor cari)! ulnaris. The Metacarpus (Ossa Metacarpalia) (Figs. 150, 151). The metacarpal bones are five in number, and they.are numbered from 1 to 5 inclusive, the first being the metacarpal bone of the thumb, the fifth the meta- carpal bone of the little finger. They are long, cylindrical bones, presenting for examination a shaft and two extremities. Common Characters of the Metacarpal Bones. — The shaft (corpus) is pris- moid in form, and curved longitudinally, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces — two lateral and one posterior. The two lateral surfaces constitute the palmar or volar aspect. The lateral surfaces are concave, for the origin of the Interossei inuscles, and separated from one another by a prominent anterior ridge. The posterior or dorsal surface presents in its distal half a smooth, triangular, flattened area which is covered, in the recent state, by the tendons of the Extensor muscles. This triangular surface is bounded by two lines, which commence in small tubercles situated on the dorsal aspect on either side of the digital extremity, and, running backward, converge to meet some distance behind the centre of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal ex- tremity. This ridge separates two lateral, sloping surfaces for the origin of the Dorsal interossei muscles.' To the tubercles on the digital extremities are attached the lateral ligaments of the metacarpophalangeal joints. On the pal- mar surface of each metacarpal bone is a nutrient foramen, which opens into a nutrient canal. In the first metacarpal the direction of this foramen is toward the phalanges (distad). In each of the other metacarpals it is from the phalanges (proximad). The carpal or proximal extremity (bask) is of a cuboidal form, and broader behind than in front; it articulates above with the carpus, and on each side with the adjoining metacarpal bones; its dorsal and palmar surfaces are rough, for the attachment of tendons and ligaments. The distal extremity (capltulum) presents an oblong surface, markedly con- vex from before backward, less so from side to side, and flattened laterally; it articulates with the proximal phalanx; it is broader and extends farther forward on the palmar than on the dorsal aspect. It is longer in the antero-posterior than in the transverse diameter. On either side of the head is a tubercle for the attach- the hand mav be at once differentiated from the metatarsal 202 SPECIAL ANATOMY OF THE SKELETON ment of the lateral ligament of the metacarpophalangeal joint. The posterior surface, broad and flat, supports the Extensor tendons; the anterior surface is grooved in the middle line for the passage of the Flexor tendons, and marked on each side by an articular eminence continuous with the terminal articular surface. The metacarpal spaces (spatia interossea metacarpi) are the intervals between the metacarpal bones. They are occupied by the Interossei muscles. The broadest space is between the metacarpal bones of the thumb and index finger. Peculiar Characters of the Metacarpal Bones. — The metacarpal bone of the thumb (o« metacar- pale I) (Fig. 161) is shorter and wider than the rest, diverges to a greater degree from the carpus, and its palmar surface is directed inward toward the palm. The shaft is flattened and broad on its dorsal aspect, and does not present the ridge which is found on the other metacarpal bones; it is concave from above downward, on its palmar surface. The carpal extremity, or base, presents a concavo-convex surface, for articulation with the trapezium; it has no lateral facets, but presents externally a tubercle for the insertion of the Extensor ossis metacarpi poUicis. The distal extremity is less convex than that of the other metacarpal bones, broader from side to side than from before backward. It presents on its palmar aspect two distinct articular eminences for the two sesamoid bones in the tendons of the Flexor brevis pollicis, the outer one being the larger of the two. Tubercle Foi ti ape'sium. For trape: Fig. 161.— The first metacarpal. (Left.) The side to which this bone belongs may be known by holding it in the position it occupies in the hand, with the carpal extremity upward and the dorsal surface backward; the tubercle for the Extensor ossis metacarpi pollicis will point to the side to which it belongs. Attachment of Muscles. — To four — the Opponens pollicis, the Extensor ossis metacarpi pollicis, the Flexor brevis pollicis, and the First dorsal interosseous. The metacarpal bone of the index finger (os metacarpaJe II) (Fig. 162) is the longest and its base the largest of the other fcfir. Its carpal extremity is prolonged upward and inward, forming a prominent ridge. The dorsal and palmar surfaces of this extremity are rough, for the attachment of tendons and ligaments. It pre- sents four articular facets — three on the upper aspect of the base; the middle one of the three is the largest, concave from side to side, convex from before back- ward, for articulation with the trapezoid; the external one is a small, flat, oval facet, for articulation with the trapezium; the internal one on the summit of the ridge is long and narrow, for articulation with the os magnum. The fourth facet is on the inner or the ulnar side of the extremity of the bone, and is for articulation with the third metacarpal bone. The side to which this bone belongs is indicated by the absence of the lateral facet on the outer (radial) side of its base, so that if the bone is placed with the base toward the student and the palmar surface upward, the side on which there is no lateral facet will be that to which it belongs. Attachment of Muscles. — To six — Flexor carpi radialis, Extensor carpi radiahs longior, the deep portion of the Flexor brevis pollicis. First and Second dorsal interosseous, and First palmar interosseous. The metacarpal bone of the middle finger (os metacarpale III) (Fig. 163) is a little smaller than the preceding; it presents a pyramidal eminence, the styloid THE METACARPUS 203 process {processus styloideus), on the radial side of its base (dorsal aspect), wliicl) extends upward behind the os magnum; immediately below this, on the dorsal aspect, is a rough surface for the attachment of the Extensor carpi radialis brevior. The carpal, articular facet is concave behind, flat in front, and articulates with the OS magnum. On the radial side is a smooth, concave facet, for articulation with the second metacarpal bone, and on the ulnar side two small, oval facets, for articu- lation with the fourth metacarpal. _ The side to which this bone belongs is easily recognized by the styloid process on the radial side of its base. With the palmar surface uppermost and the base toward the student, this process points toward the side to which the bone belongs. Attachment of Muscles.— To s?.r~E\-tensor carpi radialis brevior. Flexor carpi radialis. Adductor transversus pollicis, Adductor obliquus pollicis, and Second and Thu-d dorsal inter- osseous. . For third metacarpal Sor trapezoid. For os magiiuvi. Fig. 162. — The second metacirp.il. (Left.) For fourlh metacarpal. SlyloiH For second process, metacarpal. For OS magnum. Fig. 163.— The third metacarpal. (Left.) The metacarpal bone of the ring finger (os metacarpale IV) (Fig. 164) is shorter and smaller than the preceding, and its base small and quadrilateral; the carpal surface of the base presenting two facets, a large one internally, for articulation with the unciform, and a small one externally, for the os magnum. On the radial side are two oval facets, for articulation with the third metacarpal bone; and on the ulnar side a single concave facet, for the fifth metacarpal. If this bone is placed with the base toward the student and the palmar surface upward, the radial side of the base, which has two facets for articulation with the third metacarpal bone, wili be on the side to which it belongs. If, as sometimes happens in badly marked bones, one of these facets is indistinguishable, the side may be known by selecting the surface on which the larger articular facet is present. This facet is for the fifth metacarpal bone, and would therefore be situated on the ulnar side— that is, the one to which the bone does not belong. Attachment of Muscles.— To three— the Third and Fourth dorsal and Second palmar inter- The metacarpal bone of the little finger (os meiacarfaJe V) (Fig. 165) presents on its base one facet, which is concavo-convex, and which articulates with the unciform bone, and one lateral, articular facet, which articulates with the fourth metacarpal bone. On its ulnar side is a prominent tubercle, for the insertion of 204 SPECIAL ANATOMY OF THE SKELETON the tendon of the Extensor carpi ulnaris. The dorsal surface of the shaft is marived by an obhque ridge which extends from near the ulnar side of the upper extremity to the radial side of the lower. The outer division of this surface serves for the attachment of the Fourth dorsal interosseous muscle; the inner division is smooth and covered by the Extensor tendons of the little finger. L-'^N For third metacarpal. For os magnum. For fift h meta- carpal For unciform. Fig. 164.— The fourth metacarpal. (Left.) For unciform, metacarpal. Fig. 16S.— The fifth metacarpal. (Left.) If thi.s Vione is placed with its base toward the student and its pahnar surface upward, the side of the head wiiich has a lateral facet will be that to which the bone belongs. Attachment of Muscles. — To five — the E.xtensor carpi ulnaris, Fle.xor carpi ulnaris, Oppo- nens minimi digiti. Fourth dorsal, and Third palmar interossei. Articulations. — Besides the phalangeal articulations, the first metacarpal bone articulates with the trapezium; the second with the trapezium, trapezoid, os magnum, and third metacarpal bones; the third with the os magnum and second and fourth metacarpal bones; the fourth with, the OS magnum, unciform, and third and fifth metacarpal bones; and the fifth with the unciform and fourth metacarpal. Th.^ first has no lateral facets on its carpal extremity; the second has no lateral facet on its radial side, but one on its ulnar side; the third has one on its radial and two on its ulnar side; the fourth has two on its radial and one on its. ulnar side; and the fifth has only one on its radial side. The Phalanges of the Hand (Phalanges Digitorum Manus). The phalanges (phalanges digitorum manus) are fourteen in number, three for each finger, and two for the thumb. In numbering them the proximal bone is designated as the first phalanx (phalan.v I). They are long bones, and present for examination a shaft and two extremities. The shaft (corpus phaJangis) tapers from above downward, is convex posteriorly, concave in front from above downward, flat from side to side, and marked laterally by rough ridges, which give attachment to the fibrous sheaths of the Flexor tendons. A nutrient foramen on the palmar surface leads into a nutrient canal which runs toward the periphery (distad). The metacarpal extremity, or base (basis plialangis), of each phalanx in the first row presents an oval, concave, articular surface, broader from side to side than from before backward; and the same extremity in the other two rows, a double concavity, separated by a longitudinal median ridge, extending from before backward. The distal extremity of the first phalanx of the thumb THE PHALANGES OF THE HAND 205 and of the first and second phalanx of each of the fingers is smaller than the base, and terminates in two small, lateral condyles, separated by a slight groove (trochlea phahnqis); the articnlar surface being prolonged farther forward on the palmar than on the dorsal surface, especially in the first row. The ungual phalanges (distal) are convex on their dorsal, flat on their palmar, surfaces; they are recognized by their small size and by a roughened, elevated surface of a horseshoe form on the palmar aspect of their ungual extremity (tuber- ositas luujuicularis), which serves to support the sensitive pulp of the finger. Articulations. — The first row, with the metacarpal bones and the second row of phalanges; the second row, with the first and third; the third, with the second ro^\'. Attachment of Muscles.— To the base of the first phalanx of the thumb, ^w muscles— the Extensor brevis [joUicis, Flexor brevis poliicis. Abductor pollicis, Adductores transversus and Obliquus pollicis. To the second phalanx, two — the Flexor longus pollicis and the Extensor Jongus pollicis. To the base of the first phalanx of the index finger, the First dorsal and the First palmar interosseous; to that of the middle finger, the Second and Third dorsal interosseous; to that of the ring finger, the Fourth dorsal and the Second palmar interossei; and to that of the little finger, the Third palmar interosseous, the Flexor brevis minimi digiti, and Abductor minimi digiti. To the second phalanges, the Flexor sublimis digitorum. Extensor communis digitorum, and, in addition, the Extensor indicis to the index finger, the Extensor minimi digiti to the little finger. To the third phalanges, the Flexor profundus digitorum and Extensor communis digitorum. Surface Form of Carpal and Metacarpal Bones and of the Phalanges.— On the front of tlie wrist are two subcutaneous eminences, one on the radial side, the larger and flatter, due to the tuberosity of the scaphoid and tlie ridge on the trapezium; the other, on the ulnar side, caused by the pisiform bone. The tubercle of the scaphoid may be felt just below and in front of the apex of the styloid process of the radius. It is best perceived by ■extending the hand on the forearm. Immediately below may be felt another prominence, better marked than the tubercle; this is the ridge on the trapezium which gives attachment to some of the short muscles of the thumb. On the inner side of the front of the wrist the pisiform bone may be felt, forming a small but prominent projection in this situation. It is some distance below the styloid process of the ulna, and may be said to be just below the level of the styloid process of the radius. The rest of the front of the carpus is covered by tendons and the annular ligament, and entirely concealed, with the exception of the hooked process of the unciform, which can only be made out with difficulty. The back of the carpus is convex and covered by the Extensor ten- dons, so that none of the posterior surfaces of the bones are to be felt, with the exception of the cuneiform on the inner side. Below the carpus the dorsal surfaces of the metacarpal bones, except the fifth, are covered by tendons, and are scarcely visible e.xcept in very thin hands. The dorsal surface of the fifth is, however, subcutaneous throughout almost its whole length, and may be plainly perceived and felt. In addition to this, slightly external to the middle line of the hand, is a prominence, frequently well marked, but occasionally indistinct, formed by the base of the metacarpal of the middle finger. The heads of the metacarpal bones may be plainly felt and seen, rounded in contour and standing out in bold relief under the skin, when the fist is clenched. It should be borne in mind that when the fingers are flexed on the hand, the articular surfaces of the first phalanges glide off the heads of the metacarpal bones on to their anterior surfaces, so that the head of these bones form the prominence of the knuckles and receive the force of any blow which may be given. The head of the third metacarpal bone is the most prominent, and receives the greater part of the shock of the blow. This bone articulates with the os magnum, so that the concussion is carried through this bone to the scaphoid and semilunar, with which the head of the os magnum articulates, and by these bones is transferred to the radius, along which it may be carried to the capitellum of the humerus. The enlarged extremities of the phalanges may be plainly felt; they form the joints of the fingers. When the digits are bent the proximal phalanges of the joints form prominences, which in the joint between the first and second pha- langes is slightly hollowed, in accordance with the grooved shape of their articular surfaces, while at the last row the prominence is flattened and square-shaped. In the palm of the hand the four inner metacarpal bones are covered by muscles, tendons, and the palmar fascia, and no part of them but their heads is to be distinguished. With regard to the thumb, on the dorsal aspect the base of the metacarpal bone forms a prominence below the styloid process of the radius; the shaft is to be felt, covered by tendons, terminating at its head in a flattened pi'ominence, in front of which can be felt the sesamoid bones. Applied Anatomy. — The carpal bones are not very liable to fracture, except from extreme violence, when the parts may be so comminuted as to necessitate amputation. Occasionally they are the seat of tubemdous disease. The metacarpal bones and the phalanges are not infre- quently broken by direct violence. The first metacarpal bone is the one most commonly frae- 206 SPECIAL ANATOMY OF THE SKELETON tured; then the second, the fourth, and the fifth, the third being the one least frequently broken. There are two diseases of the metacarpal bones and phalanges which require special mention on account of the frequency of their occurrence. One is tuberculous dactylitis, consisting in a deoosit of tuberculous material in the medullary canal, expanding the bone, with subsequent caseadon and resulting necrosis. The other is chondroma, which is perhaps more frequently found in connection with the metacarpal bones and phalanges than with any other bones. When chon- dromatous growth takes place there are usually multiple tumors, and they may spring either from the medullary canal or from the periosteum. • ■ Development of the Bones of the Hand. — The carpal bones are each developed from a single centre. At birth they are all cartilaginous. Ossification proceeds in the following order (Fig. 166): In the os magnum and unciform an ossific point appears during the first year, the former preceding the latter; in the cuneiform, at the third year; in the trapezium and semilunar, at the -fifth year, the latter preceding the former; in the scaphoid, in the si.\th to the eighth year; in the trapezoid, during the eighth year; and in the pisiform, about the twelfth year. Appears 3rd year. Unite Wth year. Appears 8th week. Carpus. One centre for each bone Alt cartilaginous at butti. Metacarpus. Two centres for each tone • One for shaft, One for distal extremity, except first. Phalanges. Two centres for eacli bone [IJ One for shaft, One for metacarpal extremity. ^Appears ttih-Sth year. Unite IStli-SOth year. §, ^l^i—Apnears 8th week. Appears Uh-Sth year. Unite ISth-SO year. .^ I [-^Appears 8th week. Fig. 166. — Plan of the development of the bones of the hand. Occasionally an additional bone, the os centrale, is found in the carpus, lying between the scaphoid, trapezoid, and oS magnum. During the second month of fetal life it is represented by a small cartilaginous nodule, which, however, fuses with the cartilaginous scaphoid about the third month. Sometimes the styloid process of the third metacarpal is detached and forms an additional os.sicle. The metacarpal bones are each developed from ttvo centres, one for the shaft and one for the distal extremity for the four inner metacarpal bones; one for the shaft and one for the base for the metacarpal bone of the thumb, which in this respect resembles the phalanges.' Ossi- fication commences in the centre of the shaft about the eighth or ninth week, the centre for the first metacarpal bone being the last to appear; ossification gradually proceeds to either end of ' Allan Thomson has demonstrated the fact that the first metacarpal bone is often developed from three centres; that is to say, there is separate nucleus for the distal end, forming a distinct epiphysis, visible at the age of seven or eight years. He also states that there are traces of a proximal epiphysis in the second metacarpal bone. — Journal of . Anatomy and Physiology, 1S69. THE OS INNOMINA TUM 207 the bone: about the third year the distal extremities of the four inner nietaoarpal bones and the base of the first metacarpal begin to ossify, and they unite with the shaft about the twentieth year. The phalanges are each developed from two centres, one for the shaft and one for the base. Ossification commences in the shaft, in all three rows, at about the eighth week, and gradually involves the whole bone excepting the upper extremity. Ossification of the base commences in the first row between the third and fourth years, and a year later in those of the second and third rows. The two centres become united, in each row, between the eighteentli and twentieth years. In the ungual phalanges the centre for the shaft appears at the distal extremity of the phalanx, instead of at the middle of the shaft, as is the case with the other phalanges. The ungual phalanges are the first boiies of the hands to begin to ossify. THE LOWER EXTREMITY. The lower extremity consists of the following bones: Ossa innominata (with the sacrum and coccyx forming the pelvis), the femur (thigh), the tibia and fibula (the leg), the tarsus, the metatarsus and phalanges {(ht foot). THE OS INNOMINATUM, CALLED ALSO OS COXAE, HIP BONE (Figs. 167, 168). The OS iimonunatlun is a large, irregularly shaped, flat bone, constricted in the centre and expanded above and below. With its fellow of the opposite side it forms the sides and anterior wall of the pelvic cavity. In young subjects it consists of three separate parts, which meet and form the large, cup-like cavity, the acetabulum, situated near the middle of the outer surface of the bone; and, although in the adult these have become united, it is usual to describe the bone as divisible into three portions — the ilium, the ischium, and the pubis. The ilium is the superior, broad, and expanded portion which runs upward from the acetabulum and forms the prominence of the hip. The ischium is the inferior and strongest portion of the bone ; it proceeds down- ward from the acetabulum, expands into a large tuberosity, and then, curving forward, helps to bound, with the descending ramus of the os pubis, a large aperture, the obturator foramen. The OS pubis is that portion which extends inward and downward from the acetabulum to articulate in the middle line with the bone of the opposite side; it forms the front of the pelvis and supports the external organs of generation. The Ilium (os ilium) presents for examination two surfaces, an external and an internal, a crest, and two borders, an anterior and a posterior. The external surface (Fig. 167) is divided into two parts — an upper or gluteal and a lower or acetabular. The upper portion — known as the dorsum ilii — is directed backward and outward behind, and downward and outward in front. It is smooth, convex in front, deeply concave behind; bounded above by the crest, beloio by the upper border of the acetabulum; in front and behind by the anterior and posterior borders. This surface is crossed in an arched direction by three semicircular lines — the superior, middle, and inferior curved lines. The superior curved line (linea glutaea posterior), the shortest of the three, commences at the crest, about two inches in front of its posterior extremity; it is at ftrst distinctly marked, but as it passes downward and backward to the upper part of the great sacrosciatic notch, where it terminates, it becomes less marked, and is often alto- gether lost. Behind this line is a narrow semilunar surface, the upper part of vyhich is rough and affords origin to part of the Gluteus maximus; the lower part is smooth and has no muscle fibres attached to it. The middle curved line (linea glutaea anterior), the longest of the three, commences at the crest, about an inch behind its anterior extremity, and, taking a curved direction downward and backward, terminates at the upper part of the great sacrosciatic notch. The 208 SPECIAL ANATOMY OF THE SKELETON space Ijetween the superior and middle curved lines and the crest is concave, and affords origin to the Gluteus medius muscle. Near the central part of this line may often be observed the orifice of a nutrient foramen. The inferior curved Anterior superior CTOR LONGUS GEMELLUS INFERIOR Fig. 167. — Right os innominatum. E.xternal surface. line {linea glutaea inferior), the least distinct of the three, commences in front at the notch on the anterior border, and, taking a cun'ed direction backward and downward, terminates at the middle of the great sacrosciatic notch. The surface of bone included between the middle and inferior curved lines is concave from above downward, convex from before backward, and affords origin to the Gluteus minimus muscle. Beneath the inferior curved line, and corresponding to the upper part of the acetabulum, is a roughened surface (sometimes a depres- sion), from which arises the reflected tendon of the Rectus femoris muscle. The lower or acetabular part of the external surface enters into the formation THE OS INNOMINATUM 209 of the acetabulum, of which it forms rather less than two-fifths. It is separated from tlie gluteal portion by a prominent rim, which forms part of the margin of the acetabular cavity. COMPRESSOR L Cnts penis/ erector penje Fig. 168. — Right os innominatum. Internal surface. The internal surface (Fig. 168) is bounded above by the crest; belotv it is con- tinuous with the pelvic surface of the os pubis and ischium, a faint line only indicating the place of union; and before and behind it is bounded by the anterior and posterior borders. It presents a large, smooth, concave surface, called the iliac fossa (fossa iliaca), which lodges the Iliacus muscle, and presents at its lower part the orifice of a nutrient canal, and below this a smooth, rounded border, the iliopectineal line (linea arcuata). which separates the iliac fossa from that portion of the internal surface which enters into the formation of the true pelvis, and which gives origin to part of the Obturator internus muscle. Behind the iliac fossa is a rough surface divided into two portions, an anterior and a posterior 14 210 SPECIAL ANATOMY OF THE SKELETON The anterior or auricular portion { fades aiiricidaris) , so called from its resemblance in shape to the ear, is coated with cartilage in the recent state, and articulates with a surface of similar shape on the side of the sacrum. The posterior portion (ivherositas iliaca) is rough, for the attachment of the posterior sacroiliac ligaments an,d for a part of the origin of the Erector and Multifidus spinae. The crest of the ilium (crista iliaca) is convex in its general outline and sinuously curved, being concave inward in front, concave outward behind. It is longer in the female than in the male, very thick behind, and thinner at the centre than at the extremities. It terminates at either end in a prominent eminence, the anterior superior and posterior superior spinous process {spina iliaca anterior superior el spina iliaca posterior superior). The surface of the crest is broad, and divided into an external lip (labium externmn), an internal lip (labium internum), and- an intermediate space (linea intermedia). About two inches behind the anterior superior spinous process there is a prominent tubercle on the outer lip. To the external lip is attached the Tensor fasciae femoris, Obliquus externus abdominis, and Latissimus dorsi, and along its whole length, the fascia lata; to the space between the lips, the Internal oblique; to the internal lip, the Transversalis, Quadratus lumborum, and Erector spinae, the Iliacus, and the iliac fascia. The anterior border of the ilium is concave. It presents two projections, sepa- rated by a notch. Of these, the uppermost, situated at the junction of the crest and anterior border, is called the anterior superior spinous process of the ilium, the outer border of which gives attachment to the fascia lata and the origin of the Tensor fasciae femoris; its inner border, to the Iliacus; while its extremity affords attachment to Poupart's ligament and the origin of the Sartorius. Beneatli this eminence is a notch which gives origin to the Sartorius muscle, and across which passes the external cutaneous nerve. Below the notch is the anterior inferior spinous process (spina iliaca anterior inferior), which terminates in the upper lip of the acetabulum; it gives origin to the straight tendon of the Rectus femoris muscle and the iliofemoral ligament. On the inner side of the anterior inferior spinous process is a broad, shallow groove, over which passes the Ilio- psoas muscle. This groove is bounded internally by an eminence, the iliopectineal eminence (eminentia iliopectinea) , which marks the point of union of the ilium and OS pubis. The posterior border of the ilium, shorter than the anterior, also presents two projections separated by a notch, the posterior superior spinous process (spi7ia iliaca posterior superior) and the posterior inferior spinous process (spina iliaca posterior inferior). The former corresponds \\ith that portion of the inner surface of the ilium which serves for the attachment of the oblique portion of the sacroiliac ligaments and the Multifidus spinae muscle; the latter, to the auricular portion which articulates with the sacrum. Below the posterior inferior spinous, process the posterior border forms the upper part of a deep notch, the great sacrosciatic notch. The Ischium (os ischii) forms the lower and back part of the os innominatum. It is di^'isible into a thick and solid portion — the body; a large, rough eminence, on W'hich the trunk rests in sitting — the tuberosity; and a thin part which passes inward and slightly upward — the ramus. The body (corpus ossis ischii), somewhat triangular in form, presents three surfaces, antero-external, internal, and postero-external ; and three borders, ex- ternal, internal, and posterior. The antero-external surface corresponds to that portion of the acetabulum formed by the ischium; it is smooth and concave, and forms a little more than two-fifths of the acetabular cavity; its outer margin is bounded by a prominent rim or lip, the external border, to which the cotyloid fibrocartilage is attached. Below the acetabulum, between it and the tuberosity, is a deep groove, along w-hich the tendon of the Obturator externus muscle runs THE OH INNOMINATUM 211 as it passes outward to be inserted into the trochanteric fossa of the femur. The internal surface is smooth, concave, and enters into the formation of the lateral boundary- of the true peh'ic canity. This surface is perforated by two or three large, vascular foramina, and affords origin to part of the Obturator internus muscle. The postero-external surface is quadrilateral in form, broad and smooth. Below, where it joins the tuberosity, it presents a groove, the obturator groove (sulcus ohturatorius) , continuous with that on the antero-external surface; in this groo\'e is received the posterior fleshy part of the Obturator externus muscle when the thigh is flexed. The lower edge of this groove is formed by the tuberosity of the ischium, and affords origin to the Gemellus inferior muscle. The postero- external surface is limited, externally, by the margin of the acetabulum; behind, by the posterior border; it supports the Pyriformis, the two Gemelli, and the Obturator internus muscles in their passage to the great trochanter. The ex- ternal border separates the postero-external from the antero-external surface. The internal border is thin, and forms the outer circumference of the obturator foramen. The posterior border of the body of the ischium is continuous with the posterior border of the ilium; it presents, a little below the centre, a thin and pointed triangular eminence, the spine of the ischium {spina ischiadica), more or less elongated in different subjects; its external surface gives origin to the Gemellus superior, its internal surface to the Coccygeus and Levator ani; while to the pointed extremity is connected the lesser .sacrosciatic ligament. Above the spine is a notch of large size, the great sacrosciatic notch, converted into a foramen, the great sacrosciatic foramen (foramen ischiadicum majus), by the lesser and greater sacrosciatic ligaments; it transmits the Pyriformis muscle, the gluteal vessels, and superior and inferior gluteal nerves; the sciatic vessels, the greater and lesser sciatic nerves, the internal pudic vessels and nerve, and the nerves to the Obturator internus and Quadratus femoris. Of these, the gluteal vessels and superior gluteal nerve pass out above the Pyriformis muscle, the other structures, below it. Below the spine is a smaller notch, the lesser sacrosciatic notch (incisura ischiadica minor); it is smooth, coated in the recent state with cartilage. It is converted into a foramen, the lesser sacrosciatic foramen (foramen ischiadicum minus), by the sacrosciatic ligaments, and transmits the tendon of the Obturator internus, the nerve which supplies that muscle, and the internal pudic vessels and nerve. The tuberosity of the ischium (tuber ischiadicum) is the portion of bone between the body and the ramus. The tuberosity presents for examination three sur- faces— external, internal, and posterior. The external surface is quadrilateral in shape and rough, for the attachment of muscles. It is bounded above by the groove for the tendon of the Obturator externus; in front it is limited by the posterior margin of the obturator foramen, and below it is continuous with the ramus of the bone; behind, it is bounded by a prominent margin which separates it from tlie posterior surface. In front of this margin the surface gives origin to the Quadratus femoris, and anterior to this some of the fibres of origin of the Obturator externus. The lower part of the surface gives origin to part of the Adductor magnus. The internal surface forms part of the bony wall of the true ^ pelvis. In front it is limited by the posterior margin of the obturator foramen; behind, it is bounded by a sharp ridge, for the attachment of a falciform pro- longation of the great sacrosciatic ligament; it sometimes presents a groove on the inner side of this ridge for the lodgement of the internal pudic vessels and nerve ; and, more anteriorly, has attached the Transversus perinaei and Erector penis vel clitoridis muscles. The posterior surface is divided into two portions — a lower rough, somewhat triangular part, and an upper smooth, quadrilateral portion. The lower portion is subdivided by a prominent y-ertical ridge, passing from base to apex, into two parts; the outer one gives origin to the Adductor magnus; 212 SPECIAL ANAT03fY OF THE SKELETON the inner, to the great sacrosciatic hgament. The upper portion is subdivided into two facets by an obUque ridge which runs downward and outward ; from the upper and outer facet arises the Semimembranosus; from the lower and inner, the Biceps and Semitendinosus. The ramus {raimis inferior ossis ischii) is the thin, flattened part of the ischium which ascends from the tuberosity upward and inward, and joins the descending ramus of the os pubis, their point of junction being indicated in the adult by a rough line. The outer surface of the ramus is rough, for the origin of the Obtura- tor externus muscle, and also some fibres of the Adductor magnus; its inner sur- face forms part of the anterior wall of the pelvis. Its inner border is thick, rough, slightly everted, forms part of the outlet of the pelvis, and presents two ridges and an intervening space. The ridges are continuous with similar ones on the de- scending ramus of the os pubis; to the outer one is attached the deep layer of the superficial perineal fascia, and to the inner, the superficial layer of the tri- angular ligament of the perineum. If these two ridges are traced backward, they will be found to join with each other just behind the point of origin of the Transversus perinei muscle; here the two layers of fascia are continuous behind the posterior border of the muscle. To the intervening space, just in front of the point of junction of the ridges, is attached the Transversus perinei muscle, and in front of this arises a portion of the crus penis vel clitoridis and the Erector penis vel clitoridis muscle. Its outer border is thin and sharp, and forms part of the inner margin of the obturator foramen. The Pubis (os pubis) forms the anterior part of the os innominatum, and, with the bone of the opposite side, forms the front boundary of the true pelvic cavity. It is divisible into a body, a superior or ascending and an inferior or descending ramus. The body (corpus ossis pubis) is the broad portion of bone formed at the junc- tion of the two rami. It is somewhat quadrilateral in shape, and presents for ex- amination two surfaces and three borders. The anterior surface is rough, directed downward and outward, and serves for the attachment of various muscles. From the upper and inner angle, immediately below the upper border, arises the Adduc- tor longus; lower down, from without inward, arise the Obturator externus, the Adductor brevis, and the upper part of the Gracilis. The posterior surface, convex from above downward, concave from side to side, is smooth, and forms part of the anterior wall of the pelvis. It gives origin to the Levator ani, Obturator internus, a few muscle fibres prolonged from the bladder, and the puboprostatic ligaments. At the outer part of the upper border is a prominent tubercle, which projects forward and is -called the spine (tuberciduvi ptibicimi); to it is attached Poupart's ligament. Passing upward and outward from this is a prominent ridge, forming part of the iliopectineal line (linea arcuata). It marks the brim of the true pelvis; to it are attached a portion of the conjoined tendon of the Internal oblique and Transversalis muscles, Gimbernat's ligament, and the triangular fascia. Internal to the spine the upper border is called the crest, which ex- tends from this process to the inner extremity of the bone. It affords attach- ment to the conjoined tendon of the Internal Oblique and Trans^"e^salis, and to the Rectus abdominis and Pyramidalis muscles. The point of junction of the crest with the inner border of the bone is called the angle ; to it, as well as to the symphysis, is attached the internal pillar of the external abdominal ring. The internal border is articular; it is oval, covered by eight or nine transverse ridges, which serve for the attachment of a thin layer of cartilage. This surface is united to its fellow of the opposite side in the whole pelvis. The joint is called the symphysis pubis. The outer border presents a sharp margin, which forms part of the circumference of the obturator foramen and afi'ords attachment to the obturator membrane. The ascending ramus (ramus superior ossis pubis) extends from the body to THE OS INNOMINATUM 213 the point of junction of the os pubis with the ihum, and forms the upper part of the circumference of the obturator foramen. It presents for examination a superior, inferior, and posterior surface, and an outer extremity. The supe- rior surface presents a continuation of the iliopectineal Hne, already mentioned as commencing at the pubic spine. In front of this ridge the surface of bone is triangular in form, wider externally than internally, smooth, and is covered by the Pectineus muscle. The surface is bounded externally by a rough eminence, the iliopectineal eminence {eminentia iliopectinea), which serves to indicate the point of junction of the ilium and os pubis, and gives attachment to the Psoas parvus, when this muscle is present. The triangular surface is bounded ijelow by a prominent ridge, the obturator crest (crista obturatoria), which extends from the cotyloid notch to the spine of the os pubis. The inferior surface forms the upper boundary of the obturator foramen, and presents externally a l)road and deep oblique groove, the obturator groove (sulcus obturaforius), for the passage of the obturator vessels and nerve; and internally a sharp margin which forms part of the circumference of the obturator foramen, and to which the obturator membrane is attached. The posterior surface forms part of the anterior boundary of the true pelvis. It is smooth, convex from above downward, and affords origin to some fibres of the Obturator internus. The outer extremity, the thickest part of the ramus, forms one-hfth of the cavity of the aceta!)ulum. The descending ramus (ramus inferior ossis pubis) is thin and flattened. It passes outward and downward, becoming narrower as it descends, and joins with the ramus of the ischium. Its anterior surface is rough, for the origin of muscles — the Gracilis along its inner border; a portion of the Obturator externus where the ramus enters into the formation of the obturator foramen; and be- tween these two muscles the Adductores brevis and magnus from within out- ward. The posterior surface is smooth, and gives origin to the Obturator internus, and, close to the inner margin, to the Compressor urethrae. The inner border is thick, rough, and everted, especially in females. It presents two ridges, separated by an intervening space. The ridges extend downward, and are continuous with similar ridges on the ascending ramus of the ischium; to the external one is attached the deep layer of the superficial perineal fascia, and to the internal one the superficial layer of the triangular ligament of the perineum. The outer border is thin and sharp, forms part of the circumference of the obturator fora- men, and gives attachment to the obturator membrane. The Cotyloid Cavity, or Acetabulum, is a deep, cup-shaped, hemispherical depression, directed downward, outward, and forward; formed internally by the os pubis, above by the ilium, behind, externally, and beloic by the ischium, a little less than two-fifths being formed by the ilium, a little more tlian two-fifths by the ischium, and the remaining fifth by the pubic bone. It is bounded by a prominent uneven rim, which is thick and strong above, and serves for the attachment of the cotyloid ligament, which contracts its orifice and deepens the surface for articula- tion. It presents below and internally a deep notch, the cotyloid notch (incisura ucetabuli), which is continuous with a circular depression, the fossa of the ace- tabulum (fossa acetabuli), at the bottom of the cavity; this depression is perforated by numerous apertures, lodges a mass of fat, and its margins, as well as those of the notch, serve for the attachment of the ligamentum teres. The fossa acetabuli is partly surrounded by a concave rim of bone (fades lunata). The cotyloid notch is converted, in the natural state, into a foramen by a dense ligamentous band, the transverse ligament, which passes across it. Through this foramen the nu- trient vessels and nerA'cs of the joint pass. The Obturator, or Thyroid Foramen (foramen obturatum), is a large aperture situated between the ischium and os pubis. In the male it is large, of an oval form, its longest diameter being obliquely from before backward; in the female 214 SPECIAL ANATOMY OF THE SKELETON it is smaller and more triangular. It is bounded by a thin, uneven margin, to which a strong membrane is attached, and presents, anteriorly, a deep groove, the obturator groove (sulcus obtiiratorius), which runs from the pelvis obliquely inward and downward. This groove is converted into a foramen by a ligamentous band, a specialized part of the obturator membrane, attached to two tubercles, one (tuberculum obturatorium posterkis) on the internal border of the ischium, just in front of the cotyloid notch, the other (tubercuhim obturatorium anterius) on the inferior margin of the posterior surface of the ascending ramus of the pubis, and transmits the obturator vessels and nerve. Structure. — This bone consists of much cancellous tissue, especially where it is thick, enclosed between two layers of dense, compact tissue. In the thinner parts of the bone, as at the bottom of the acetabulum and centre of the iliac fossa, it is usually semitransparent, and composed entirely of compact tissue. Development (Fig. 169). — From eight centres — three primary, one for the ilium, one for the ischium, and one for the os pubis; and five secondary, one for the crest of the ilium, one for the anterior inferior spinous process (said to occur more frequently in the male than in the female), one for the tuberosity of the ischium, one for the symphysis pubis (more frequent in the female than the male), and one or more for the Y-shaped piece at the bottom of the acetabulum. These „ ■ ,, J \ Three primary {Ilium, Ischium, and Os Pubis). F'-om eight centres ip^^^^^^y^^ S. Symphysis pub/: The three primary centres unite through a V-shaped piece about puberty. Epiphyses appear about puberty, and unite about the twenty-Jifth year. Fig. 169. — Plan of the development of the os innominatum. various centres appear in the following order: First, in the ilium, at the lower part of the bone, immediately above the sciatic notch, at about the eighth or ninth week; secondly, in the body of the ischium, at about the third month of fetal life; thirdly, in the body of the os pubis, between the fourth and fifth months. At birth the three primary centres are quite separate, the crest, the bottom of the acetabulum, the ischial tuberosity, and the rami of the ischium and pubes being still cartilaginous. At about the seventh or eighth year the rami of the os pubis and ischium are almost completely united by bone. About the twelfth year the three divisions of the bone have extended their growth into the bottom of the acetabulum, being separated from each other by a Y-shaped portion of cartilage, which now presents traces of ossification, often by two or more centres. One of these, the os acetahuli, appears about the age of twelve, between the ilium and os pubis, and fuses with them about the aeeof eighteen. It forms the pubic part of the acetabulum. The ilium and ischium then become joined, and lasdy the os pubis to the ischium, through the THE PELVIS 215 intervention of this Y-shaped portion. At about the age of puberty ossification, takes place in each of the remaining portions, and they become joined to the rest of the bone between the twentieth and twenty-fifth years. Separate centres are frequently found for the pubic and ischiiil .spines. Articulations. — ^Yith its fellow of the opposite side, the sacrum, and femur. Attachment of Muscles.— To the ilium, sixteen. To the outer lip of the crest, the Tensor vaginae femoris, Obliquus externus abdominis, and Latissimus dorsi; to the internal lip, the Iliacus, Transversalis, Quadratus lumborum, and Erector spinae; to the intenspace between the lips, the Obliquus internus. To the outer surface of the ilium, the Gluteus maximus. Gluteus medius. Gluteus minimus, reflected tendon of the Rectus femoris; to the upper part of the great sacrosciatic notch, a portion of the Pyriformis; to the internal surface, the Iliacus; to that portion of the internal surface below the iliopectineal line, the Obturator internus to the internal surface of the posterior superior spine, and the Multifidus spinae; to the anterior border, the Sartoi'ius and straight tendon of the Rectus femoris. To the ischium, thirteen. To the outer surface of the ramus, the Obturator e.xternus and Adductor magnus; to the internal surface, the Obturator internus and Erector penis. To the spine, the Gemellus superior, Levator ani, and Coccygeus. To the tuberosity, the Biceps, Semitendinosus, Semimembranosu.s, Quadi'atus femoris. Adductor magnus, Gemellus inferior, Transversus perinei. Erector penis. To the pubis, sixteen: Obliquus externus, Obliquus internus, Transversalis, Rectus abdominis, Pyramidalis, Psoas parvus, Pectineus, Adductor magnus, Adductor longus. Adductor brevis. Gracilis, Obturator externus and internus. Levator ani, Compressor urethrae, and occasionally a few fibres of the Accelerator urinae. THE PELVIS (Figs. 170, 171). The pelvis is stronger and more massively constructed than either the cranial or thoracic cavity; it is a bony ring, interposed between the lower end of the verte- bral column, which it supports, and the lower extremities, upon which it rests. It is composed of four bones — the two ossa innominata, which boiuid it on either side and in front, and the sacrum and cocc3rx, which complete it behind. The pelvis is divided by an oblique plane passing through the prominence of the sacrum, the iliopectineal line, and the upper margin of the syinphysis pubis into the false and true pelvis. The False Pelvis {pelvis major) is the expanded portion of the pelvic cavity which is situated above this plane. It is bounded on each side by the ossa ilii; in front it is incomplete, presenting a wide interval between the spinous proces.ses of the ilia on either side, which is filled up in the recent state by the parietes of the abdomen; behind, in the middle line, is a deep notch. This broad, shallow cavity is fitted to support the intestines and to transmit part of their weight to the anterior wall of the abdomen, and is, in fact, really a portion of the abdominal cavity. The term false pelvis is incorrect, and this space ought more properly to be regarded as part of the hypogastric and iliac regions of the abdomen. The True Pelvis (pelvis minor) is that part of the pelvic cavity which is situated below the iliopectineal line. It is smaller than the false pelvis, but its walls are more perfect. For convenience of description it is divided into a superior circumference, or inlet, an inferior circumference, or outlet, and a cavity. Tiie superior circumference, or inlet (apertura pelvis superior), forms the brim of the pelvis, the included space being called the inlet. It is formed by the ilio- pectineal line, completed in front by the crests of the pubic bones, and behind by the anterior margin of the base of the sacrum and sacrovertebral angle. Tlie inlet of the pelvis is somewhat heart-shaped, obtusely pointed in front, diverging on either side, and encroached upon behind by the projection forward of the promontory of the sacrum. It has three principal diameters — antero-posterior (sacropubic), transverse, and oblique. The antero-posterior or conjugate diameter (conjugata) extends from the sacrovertebral angle to the symphysis pubis. Its average measurement is four inches in the male and four and three-fifths inches in the female. The transverse diameter {diameter transversa) extends across the greatest width of the inlet, from the middle of the brim on one side to the 216 SPECIAL ANATOMY OF THE SKELETON same point on the opposite; its average measurement is five inches in the male, five and one-fourth inches in the female. The oblique diameter (diameter ohliqua) extends from the margin of the pelvis, corresponding to the iliopectineal eminence 170.— Male pelvis (adult). on one side, to the sacroiliac articulation on the opposite side; its average measure- ment is four and one-fourth inches in the male and five in the female. The cavity of the true pelvis is bounded in front by the symphysis pubis; behind, by the concavity of the sacrum and coccyx, vt'hich, curving forward above and Fig. 171. — Female pelvis (adult). belovv^, contracts the inlet and outlet of the canal; and laterally it is bounded by a broad, smooth, quadrangular surface of bone, corresponding to the inner surface of the body of the ischium and that part of the ilium which is below the ilio- THE PEL Vm 217 pectineal line. The cavity is sliallow in front, measuring at the symphysis an inch and a half in depth, three inches and a half in the middle, and four inches and a half posteriorly. From this description it will be seen that the cavity of the pelvis is a short, curved canal, considerably deeper on its posterior thaii on its anterior wall. This cavity contains, in the recent subject, the rectum, bladder, and some of the organs of generation. The rectum is placed at the back of the pelvis, and corresponds to the curve of the sacrococcygeal segment of the vertebral column; the bladder in front, behind the symphysis pubis. In the female the uterus and vagina occupy the interval between these viscera. The lower circumference is very irregular; the space enclosed by it is called the outlet (apertura pelvis inferior). It is bounded by three prominent emi- nences— one posterior, formed by the point of the coccyx; and one on each side, the tuberosities of the ischia. These eminences are separated by three notches; one in front, the pubic arch (arciis pubis), formed by the convergence of the rami of the ischia and pubic bones on each side. The other notches, one on each side, are formed by the sacrum and coccyx behind, the ischium in front, and the ilium above ; they are called the sacrosciatic notches ; in the natural state they are converted into foramina by the lesser and greater sacrosciatic ligaments. In the recent state, when the ligaments are in situ, the oudet of the pelvis is lozenge-shaped, bounded in front by the subpubic ligament and the rami of theos pubis and ischium; on each side by the tuberosities of the ischia; and behind by the great sacrosciatic ligaments and the tip of the coccyx. The diameters of the outlet of the pelvis are two, antero-posterior and trans- verse. The antero-posterior diameter extends from the tip of the coccyx to the lower part of the symph}'sis pubis; its average measurement is three and three- quarter inches in the male and four and one-half inches in the female. The antero-posterior diameter varies with the length of the coccyx, and is capable of increase or diminution on account of the mobility of that bone. During labor the coccyx may be bent back so that the conjugate is increased one inch, or even one and one-fourth inches. The transverse diameter extends from the posterior part of one ischiatic tuberosity to the same point on the opposite side; the average measurement is three and one-half inches in the male and four and three-fourths in the female.' Position of the Pelvis. — In the erect posture the pelvis is placed obliquely with regard to the trunk of the body; the bony ring, which forms the brim of the true pelvis, is placed so as to form an angle of about 60 to 65 degrees with the ground on which we stand (inclinatio pelvis). The pelvic surface of the symphysis pubis looks upward and backward, the concavity of the sacrum and coccyx down- ward and forward, the base of the sacrum in well-formed female bodies being nearly four inches above the upper border of the symphysis pubis, and the apex of the coccyx a little more than half an inch above its lower border. In conse- quence of the obliquity of the pelvis the line of gravity of the head, which passes through the middle of the odontoid process of the axis and through the points of junction of the curves of the vertebral column to the sacrovertebral angle, descends toward the front of the cavity, so that it bisects a line drawn transversely through the middle of the heads of the thigh bones. And thus the centre of gravity of the head is placed immediately over the heads of the thigh bones on which the trunk is supported. ' The measurements of the pelvis given above are, I believe, fairly accurate, but different measurements are given by various authors, no doubt due in a great measure to differences in the physique and stature of the population from whom the measurements have been taken. The accompanying table has been formulated to show the measurements of the pelvis which are adopted by many obstetricians. — [Editor.] Diameters of the True Pelvis in Woman. Antero-posterior. Oblique. Transrerse. Of inlet . . 4';5 inches (118 mm.) 5 inches (127 mm.) SVt inches (135 i Of outlet. . 4'/.., inches (115 mm.) 4»;i inches (120 i 218 SPECIAL ANATOMY OF THE SKELETON Axes of the Pelvis (Fig. 172). — The plane of the inlet of the true pelvis will be represented by a line drawn from the base of the sacrum to the upper margin of the symphysis pubis. A line carried at right angles with this at its middle would correspond at one extremity with the umbilicus, and at the other with the middle of the coccyx; the axis of the inlet is therefore directed downward and backward. The axis of the outlet, prolonged upward, would touch the base of the sacrum, and is therefore directed downward and forward. The axis of the cavity is curved like the cavity itself; this curve corresponds to the concavity of the sacrum and coccyx, the extremities being indicated by the central points of the inlet and outlet. A knowledge of the direction of these axes serves to explain the course of the fetus in the passage through the pelvis during parturition. Differences between the Male and Female Pelvis. — The female pelvis, looked at as a whole, is distinguished from the male by the bones being more delicate, by its width being greater and its depth smaller. The whole pelvis is less massive, and its bones are lighter and more slender, and its muscular impressions are slightly marked. The iliac fossae are shallow, and the anterior iliac spines widely separated; hence the greater prominence of the hips. The inlet in the female is larger than in the male; it is more nearly circular, and the sacrovertebral angle projects less forward. The cavity is shallower and wider; the sacrum is shorter, wider, and less curved; the obturator foramina are triangular, and smaller in size than in the male. The outlet is larger and the coccyx more movable. The Plane 0/ outlet. Fig. 172. — Vertical section of the pelvis, with lines indicating the axis of the pelvis. Fig. 173. — Diameters of the pelvic inlet in the female. spines of the ischia project less inward. The tuberosities of the ischia aud the acetabula are wider apart. The pubic arch is wider and more rounded than in the male, where it is an angle rather than an arch. In consequence of this the THE PELVIS 219 width of the fore part of the pelvic outlet is much increased and the passage of the fetal head facilitated. The size of the pelvis varies not only in the two sexes, but also in different members of the same sex. This does not appear to be influenced in any way by the height of the individual. Women of short stature, as a rule, have broad pelves. Occasionally the pelvis is equally contracted in all its dimensions, so much so that all its diameters measure an inch less than the average, and this even in women of average height and otherwise well formed. The principal divergences, however, are foimd at the inlet, and affect the relation of the antero- posterior to the transverse diameter. Thus we may have a pelvis the inlet of which is elliptical either in a transverse or antero-posterior direction; the trans- verse diameter in the former and the antero-posterior in the latter greatly exceeding the other diameters. Again, the inlet of the pelvis in some instances is seen to be almost circular. The same differences are found in various races. European women are said to have the most roomy pelves. That of the negress is smaller, circular in shape, and with a narrow pubic arch. The Hottentots and Bushwomen possess the smallest pelves. Fig. 174. — Diameters of the pelvic outlet in the female. In the fetus and for several years after birth the pelvis is small in proportion to that of the adult. The cavity is deep and the projection of the sacrovertebral angle less marked. The generally accepted opinion that the female pelvis does not acquire its sexual characters until after puberty has been shown by recent observations^ to be erroneous, the characteristic differences between the male and female pelvis being distinctly indicated as early as the fourth month of fetal life. At birth these differences are distinct (Romiti), the female pelvis possessing less straight ilia, a broader subpubic arch, and less height than the male. Surface Form.— The pelvic bones are so thickly covered with muscles that it is only at cer- tain points that they approach the surface and can be feU through the skin. In front, the anterior superior spinous process is easily recognized; a portion of it is subcutaneous, and in thin sub- jects may be seen to stand out as a prominence at the outer extremity of the fold of the groin, in fat subjects its position is marked by an oblique depression among the surrounding fat, at the bottom of which the bony process may be felt. Proceeding upward and outward from this process, the crest of the ilium may be traced throughout its whole length, sinuously curved. It is represented, in muscular subjects, on the surface, by a groove or furrow, the iliac furrow, caused by the projection of fleshy fibres of the External oblique muscles of the abdomen ; the niik.. Band ix and x; and Arthur Thomson, Journ.al of .Anatomy and 220 SPECIAL ANATOMY OF THE SKELETON iliac furrow lies slightly below the level of the crest. It terminates behind in the posterior supe- rior spinous process, the position of which is indicated by a slight depression on a level with the spinous process of the second sacral vertebra. Between the two posterior superior spinous processes, but at a lower level, is to be felt the spinous process of the third sacral vertebra (see page 68). Another part of the bony pelvis easily accessible to touch is the tuberosity of the ischium, situated beneath the gluteal fold, and, when the hip is flexed, it is easily felt, as it is then to a great extent uncovered by muscle. Finally, the spine of the os pubis can always be readily felt, and constitutes an important surgical guide, especially in connection with the subject of hernia. It is nearly in the same horizontal line with the upper edge of the great trochanter. In thin subjects it is very apparent, but in the obese it is obscured by the pubic fat. It can, however, be detected by everting the thigh and following up the tendon of origin of the Adductor longus muscle. Applied Anatomy. — There is arrest of development in the bones of the pelvis in cases of extroversion of the bladder; the anterior part of the pelvic girdle being deficient, the bodies of the pubic bones imperfectly developed, and the symphysis absent. The pubic bones are separated to the extent of from two to four inches, the superior rami shortened and directed forward, and the obturator foramen diminished in size, narrowed, and turned outward. The iliac bones are straightened out more than normal. The sacrum is very peculiar. The lateral curve, instead of being concave, is flattened out or even convex, with the iliosacral facets turned more outward than normal, while the vertical curve is straightened.' Fractures of the pelvis are divided into fractures of the false pelvis and of the true pelvis. Frac- tures of the false pelvis vary in extent: a small portion of the iliac crest may be broken or one of the spinous processes may be torn off, and this may be the result of muscular action; or the bone may be extensively comminuted. This latter accident is the result of some crushing vio- lence, and may be complicated with fracture of the true pelvis. These cases may be accompanied by injury to the intestine as it lies in the hollow of the bone, or to the iliac vessels as they course along the margin of the true pelvis. Fractures of the true pelvis generally occur through the ascending ramus of the os pubis and the ramus of the ischium, as this is the weakest part of the bony ring,, and may be caused either by crushing violence applied in an antero-posterior direction, when the fracture occurs from direct force, or by compression laterally, when the acetabula are pressed together, and the bone gives way in the same place from indirect violence. Occasionally the injury may be double, a break occurring on both sides of the body. In fracture of. the true pelvis the contained viscera are liable to be damaged; the small intestines, the urethra, the bladder, the rectum, the vagina, and even the uterus, in the female, have all been lacerated by a dis- placed fragment. Fractures of the acetabulum are occasionally met with; either a portion of the rim may be broken off, or a fracture may take place through the bottom of the cavity, and the head of the femur may be driven inward and project into the pelvic cavity. Separation of the Y-shaped cartilage at the bottom of the acetabulum may also occur in the young subject, dispersing the bone into its three anatomical portions. The sacrum, is seldom broken. The cause is direct violence — i. e., blows, kicks, or falls on the part. The lesion may be complicated with injury to the nerves of the sacral plexus, leading to paralysis and loss of sensation in the lower extremity or to incontinence of feces from paralysis of the Sphincter ani. Fracture of the coccyx is a very rare injury, but does occasionally take place. Some sup- posed dislocations of this bone have been fractures and so have some of the cases diagnosticated as coccygodynia. A fracture of the coccyx is due to direct force. The pelvic bones often undergo important deformity in rhachiti-s, the effect of which in the adult woman may interfere seriously with childbearing. The deformity is due mainly to the weight of the spine and trunk, which presses on the sacrovertebral angle and greatly increases it, so that the antero-posterior diameter of the pelvis is diminished. But, in addition to this, the weight of the viscera on the venter ilii causes the ilia to expand and the tuberosities of the ischia to incurve. In osteomalacia also great deformity may occur. The weight of the trunk causes an increase in the sacrovertebral angle and a lessening of the antero-posterior diameter of the inlet, and at the same time the pressure of the acetabula on the heads of the thigh bones causes these cavities, with the adjacent bone, to be pushed upward and backward, so that the oblique diameters of the pelvis are also diminished, and the cavity of the pelvis assumes a tri- radiate shape, with the symphysis pubis pushed forward. THE THIGH. The thigh is that portion of the lower extremity which is situated between the pelvis and the knee. It consists in the skeleton of a single bone, the fenmr. 1 Wood, Heath's Dictionary of Practical Surgery, i, 426. THE FE31VB, OR THIGH BONE 221 The Femur, or Thigh Bone (Figs. 175, 177). The femur (femur) is tiie long- est,' largest, and strongest bone in the skeleton, and almost per- fectly cylindrical throughout the greater part of its extent. In the erect posture it is not vertical, being separated from its fellow above by a considerable interval, which corresponds to the entire breadth of the pelvis, but inclin- ing gradually downward and in- ward, so as to approach its fellow toward its lower part, for the purpose of bringing the knee-joint near the line of gravity of the body. The degree of this incli- nation varies in different persons, and is greater In the female than the male, on account of the greater breadth of the pelvis. The femur, like other long bones, is divisible into a shaft and two extremities. The Upper or Proximal Ex- tremity presents for examination S head, a neck, and a greater and a lesser trochanter. The head {caput femor is) ,v\\\ch. is globulai^ and forms rather more than a hemisphere, is directed up- ward, inward, and a little forward, the greater part of its convexity being above and in front. Its surface is smooth, coated with hyaline cartilage in the recent state, except at a little behind and below its centre, where there is an ovoid depression {fovea capitis femoris), for the attachment for the ligamentum teres. The neck {collum femoris) is a flattened pyramidal process of bone which connects the head with the shaft. It varies in length and obliquity at various periods in life and under different circum- stances. The angle is widest in infancy, and becomes lessened during growfh, so that at puberty it forms a gehtle curve from the 1 In a man six fee^ high it measures eighteen inches — one-fourth of the whole body stature. DepreMion for LIGAMENTUM TERES. '"■e/- CoiliW "Ve. Fig. 175. — Right femu Anterior surfacei '222 SPECIAL ANATOMY OF THE SKELETON axis of the shaft. In the adult it forms an angle of about 125 degrees with the shaft, but varies in inverse proportion to the development of the pelvis and the stature. In consequence of the prominence of the hips and widening of the pelvis in the female, the neck of the thigh bone forms more nearly a right angle with the shaft than it does in the male. The neck is flattened from before backward, contracted in the middle, and broader at its outer extremity, where it is connected with the shaft, than at its summit, where it is continuous with the head. The vertical diameter of the outer half is increased by the thickening of the lower edge, which slopes downward to join the shaft at the lesser trochanter; as a result of this the outer half of the neck is flattened from before backward, and its vertical diameter measures one-third more than the antero-posterior. The inner half is smaller and of a more circular shape. The anterior surface of the neck is per- forated by numerous vascular foramina. The posterior surface is smooth, and is broader and more concave than the anterior; it gives attachment to the posterior part of the capsular ligament of the hip-joint, about half an inch above the posterior intertrochanteric line. The superior border is short and thick, and ter- minates externally at the great trochanter; its surface is perforated by large foramina. The inferior border, long and narrow, curves a little backward, to terminate at the lesser trochanter. Obturator intemus and GemelU Pip if 01 nns 4'^^ Insertion of Obturator " c^&^ extemus Greater trochanter Fig. 176. — Upper extremity of the femur \iewed from behind and abov The trochanters are prominent processes of bone which afford leverage to the muscles which rotate the thigh on its axis. They are two in number, the greater and the lesser. The greater trochanter (trochanter major) is a large, irregular, quadrilateral emi- nence, situated at the outer side of the neck, at its junction with the upper part of the shaft. It is directed a little outward and backward, and in the adult is about three-quarters of an inch lower than the head. It presents for examination two surfaces and four borders. The external surface, quadrilateral in form, is broad, rough, convex, and marked by a prominent diagonal impression, which extends from the posterior superior to the anterior inferior angle, and serves for the attachment of the tendon of the Gluteus medius. Above the impression is a triangular surface, sometimes rough for part of the tendon of the same muscle, sometimes smooth for the interposition of a bursa between that tendon and the bone. Below and behind the diagonal line is a smooth, triangular surface, over which the tendon of the Gluteus maximus muscle plays, a bursa being inter- posed. The internal surface is of much less extent than the external, and presents THE FEMUR, OR THIGH BONE 223 at its base a deep depression, the digital or trochanteric fossa {fossa Irochauterica), for the attachment of the tendon of the Obturator externus muscle; above and in front of this an impression for the attachment of the Obtura- tor internus and Gemelli. The superior border is free; it is thick and irregular, and marked near the centre by an impression, which extends onto the internal surface, for the attachment of the Pyri- formis. The inferior border cor- responds to the point of junction of the base of the trochanter with the outer surface of the shaft; it is marked by a rough, prominent, slightly curved ridge, which gives origin to the upper part of the Vastus externus muscle. The anterior border is prominent, somewhat irregular, as well as the surface of bone immediately be- low it ; it affords attachment at its outer part to the Gluteus mini- mus. The posterior border is veiy prominent, and appears as a free, rounded edge, which forms the back part of the digital fossa. The lesser trochanter (trochan- ter minor) is a conical eminence which varies in size in different subjects; it projects from the lower and back parts of the base of the neck. Its base is triangular, and connected with the adjacent parts of the bone by three well-marked borders; two of these are above — the internal border, continuous with the lower border of the neck, the external border, with the pos- terior intertrochanteric line — while the inferior border is con- tinuous with the middle division of the linea aspera. Its summit, which is directed inward and backward, is rough and gives insertion to the tendon of the Iliopsoas. The Iliacus is also inserted into the shaft below the lesser trochanter between the Vastus internus in front and the Pectineus behind. ^ Groove for tendon of Tic 177. — Eight femur Posterior surface. 224 SPECIAL ANATOMY OF THE SKELETON A well-marked prominence of variable size, which projects from the upper and front part of the neck at its junction with the great trochanter, is called the tubercle of the femur; it is the point of meeting of five muscles — the Gluteus mini- mus externally, the Vastus externus below, and the tendon of the Obturator internus and Gemelli internally. Running obliquely downward and inward from the tubercle is the spiral line of the femur, or anterior intertrochanteric line (linea inter- Irochanierica); it winds around the inner side of the shaft, below the lesser tro- chanter, and terminates about two inches below this eminence in the linea aspera. Its upper half is rough, and affords attachment to the iliofemoral ligament of the hip-joint; its lower half is less prominent, and gives origin to the upper part of the Vastus internus. Running obliquely downward and inward from the summit of the great trochanter on the posterior surface of the neck is a very prominent, well-marked ridge, the posterior intertrochanteric a, .& line (crista intertrochavf erica). Its upper half forms the posterior border of the great tro- chanter, and its lower half runs down\\"ard and inward to the upper and back part of the lesser trochanter. A slight ridge sometimes com- mences about the middle of the posterior intertro- chanteric line, and passes vertically downward for about two inches along the back part of the shaft; it is called the linea quadrati, and gives attachment to the Quadratus femoris and a few fibres of the Adductor magnus muscles.' The Shaft (corpus femoris). — The shaft, almost cylindrical in form, is a little broader above than in the centre, and somewhat flattened below, from before backward. It is slightly arched, so as to be convex in front and concave behind, where it is strengthened by a prominent longitudinal ridge, the linea aspera. It presents for examination three borders, separating three surfaces. Of the three borders, one, the linea aspera, is poste- rior; the other two are placed laterally. The linea aspera (Fig. 178) is a prominent longitudinal ridge or crest, on the middle third of the bone, presenting an external lip (labium laterale), an internal lip (labium mecliale), and a rough intermediate space. Above, this crest is prolonged by three ridges. The most external ridge is very rough, and is continued almost vertically upward to the base of the great trochanter. It is sometimes termed the gluteal ridge (tuberositas glutaea), and gives attachment to part of the Gluteus maximus muscle; its upper part is sometimes elongated into a roughened crest, on which is a more or less well-marked, rounded tubercle, a rudimental third trochanter (trochanter tertius). The middle ridge (linea pectinea), the least distinct, is continued to the base of the lesser trochanter, and the internal ridge is lost above in the spiral line of the femur. Below, the linea aspera is prolonged by two ridges, which pass to the condyles and enclose between them a triangular space, the popliteal surface (planum popliteum), upon which rests the popliteal artery. Of these two ridges, the outer one is the more prominent, and descends to the summit of the outer condyle. The inner one is less marked, especially at ADDUCTOR TUBERCLE Fig. 178. — Diagram of linea aspera of the right femur, {.\fter Birmingham.) ' Generally there is merely a slight thickening about the centre of the intertrochanteric line, marking the point of attachment of the Quadratus femoris. This is termed by some anatomists the tubercle of the Quadratus. THE FEMUR, OR THIGH BONE 225 its upper part, where it is crossed by the femoral artery. It terminates, below, at the summit of the internal condyle, in a small tul^ercle, the adductor tubercle, which affords attachment to the tendon of the Adductor magnus. To the inner lip of the linea aspera and its inner prolongation above and below arises the Vastus internus, and to the outer lip and its outer prolongation above arises the Vastus externus. The Adductor magnus is attached to the linea aspera, to its outer prolongation above and its inner prolongation below. Between the Vastus externus and the Adductor magnus are attached two muscles — viz., the Gluteus maximus above, and the short head of the Biceps femoris below. Between the Adductor magnus and the Vastus internus four muscles are attached — the Iliacus and Pectineus above, the Adductor brevis and Adductor longus below (Fig. 178). A little below the centre of the linea aspera is the nutrient foramen, the orifice of the nutrient canal, which is directed obliquely upward (proximally). The two lateral borders of the femur are only slightly marked, the outer one ex- tending from the anterior inferior angle of the great trochanter to the anterior extremity of the external condyle; the inner one from the spiral line at a point opposite the lesser trochanter, to the anterior extremity of the internal condyle. The internal border marks the limit of origin of the Crureus muscle internally. The anterior surface includes that portion of the shaft which is situated bet\\een the two lateral borders. It is smooth, convex, broader above and below than in the centre, slightly twisted, so that its upper part is directed forward and a little outward, its lower part forward and a little inward. From the upper three-fourths of this surface the Crureus takes origin; the lower fourth is separated from the muscle by the intervention of the synovial membrane of the knee-joint and a bursa, and affords origin to the Subcrureus to a small extent. The external surface includes the portion of bone between the external border and the outer lip of the linea aspera; it is continuous above with the outer surface of the great trochanter, below with the outer surface of the external condyle; from its upper three fourths arises the outer portion of the Crureus muscle. The internal surface includes the portion of bone between the internal border and the inner lip of the linea aspera; it is continuous above with the lower border of the neck, below with the inner side of the internal condyle; it is covered by the Vastus internus muscle. Lower or Distal Extremity. — The lower extremity, larger than the upper, is of a cuboidal form, flattened from before backward, and divided into two large eminences, the condyles, by an interval which presents a smooth depression in front called the trochlea {fames ■patellaris), and a notch of consideraljle size behind — the intercondyloid notch (fossa intercondyloidea). The external condyle (condyles lateralis) is the more prominent anteriorly, and is the broader both in the antero- posterior and transverse diameters. The internal condyle (condylus medialis) is the longer, and more prominent inferiorly. This difference in the length of the two condyles is only observed when the bone is perpendicular and depends upon the obliquity of the thigh bones, in consequence of their separation above at the articulation with the pelvis. If the femur is held obliquely, the surfaces of the two condyles will be seen to be nearly horizontal. The two condyles are directly continuous in front, and form a smooth, trochlear surface, tjie trochlea. The trochlea and the inferior surface of the condyles constitute the articular surface of the lower end of the femur, and are covered by hyaline cartilage in the recent state. The trochlea articulates with the patella. It presents a median groove, which extends downward and backward to the intercondyloid notch; and two lateral convexities, of which the external is the broader, more prominent, and pro- longed farther upward upon the front of the outer condyle. The external border of this articular surface is also more prominent, and ascends higher than the internal one. The inferior surfaces of the condyles are convex from side to side 15 226 ^FECIAL ANATOMY OF THE SKELETON and from before backward, and articulate with the corresponding surfaces of the tibia. They are marked off from the trochlea by two irregular grooves. The outer groove runs obliquely outward and forward from the anterior extremity of the intercondyloid notch to the outer side of the external condyle. The inner is less well marked and placed farther forward than the one on the external condyle; it extends obliquely inward and backward. In the grooves the semilunar cartilages fit when the knee is extended. The opposed surfaces of the condyles form the lateral walls of the intercondyloid notch. _ / ■ groove. ^ .Inner tuberosity. » ^Semilunar area. Outer tuberosity. . ,- , y Fig. 179. — Lower extremity of riglit femur viewed from below. The outer surface of the external condyle presents, a little behind its centre, an eminence, the outer tuberosity (epico7idylus lateralis); it is less prominent than the inner tuberosity, and gives attachment to the external lateral ligaments of the knee. Immediately beneath it is the popliteal groove, which commences at a depression a little behind the centre of the lower border of this surface; the front part of this depression gives origin to the Popliteus muscle, the tendon of which is lodged in the groove during flexion of the knee. The groove is smooth, covered with hyaline cartilage in the recent state, and runs upward and back- ward to the posterior extremity of the condyle. The posterior extremity is con- vex and smooth; just above and to the outer side of the articular surface is a de- pression for the tendon of the outer head of the Gastrocnemius, above which is the origin of the Plantaris. The inner surface of the inner condyle presents a convex eminence, the inner tuberosity {epicondyliw medialis) , rough, for the attachment of the internal lateral ligament. Just above the articular surface of this condyle, behind, is a depres- sion for the tendon of origin of the inner head of the Gastrocnemius. The intercondyloid notch is bounded laterally by the opposed surfaces of the .condyles, and lodges the crucial ligaments of the knee-joints. The inner wall of the notch at its front part has attached to it the posterior crucial ligament. The external wall at its upper and back part affords attachment to the anterior crucial ligament. Above, it is separated from the popliteal surface by a ridge — the linea inter condyloidea. Structure. — ^The shaft of the femur is a cylinder of compact tissue, hollowed by a large med- ullary canal. The cyhnder is of great thickness and density in the middle third of the shaft, where the bone is narrowest and the medullary canal well formed; but above and below this the cavity gradually becomes smaller, owing to a separation of the layers of the bone into cancelli, which project into the medullary canal and finally obliterate it, so that the upper and lower ends of the shaft, and the articular extremities more especially, consist of cancellated tissue invested by a thin, compact layer. The arrangement of the cancelli in the ends of the femur is remarkable. In the upper end they are arranged in two sets. One, starting from the top of the head, the upper surface of the neck. THE FEMUR, OR THIGH BONE 227 and the great trochanter, converge to the inner circumference of the shaft (Figs. ISO and ISl); these are placed in the direction of greatest pressure, and serve to support the vertical weight of the body. The second set are planes of lamellae intersecting the former nearly at right angles, and are situated in the line of the greatest tension — that is to say, along the lines in which the muscles and ligaments exert their traction. In the head of the bone these planes are arranged in a cur\'ed form, in order to strengthen the bone when exposed to pressure in all directions. In the midst of the cancellous tis- sue of the neck is a vertical plane of compact bone, the femoral spur (calcar femorale), which commences at the point where the neck joins the shaft just exter- nal to the lesser trochanter, and extends in the direc- tion of the digital fossa (Fig. 1S2). This materially strengthens this portion of the bone. Another point in connection with the structure of the neck of the femur requires mention, especially on accoimt of its influence on the production of fracture in this situation. It wdll be noticed that a considerable portion of the great trochanter lies behind the level of the posterior sur- face of the neck; and if a section be made tlirough the trochanter at this level, it will be seen that the posterior wall of the neck is prolonged into the tro- chanter. This prolongation is termed by Bigelow the true neck,' and forms a thin, dense plate of bone, which passes beneath the posterior intertrochanteric ridge toward the outer sur- face of the bone. In the lower end the cancelU spring on all sides from the inner surface of the Fig. 180. — Scheme showing disposition of principal cancellous lamellEe in upper extrem- ity of femur. Epiphyseal line. Fig. ISl. — Longitudinal section of head and necic of femur. cylinder, and descend in a perpendicidar direction to the articular surface, the cancelli being strongest and ha\'ing a more accurately perpendicular course above the condyles. In addition the Hip, p. 121. 228 SPECIAL ANATOMY OF THE SKELETON to this, however, horizontal planes of cancellous tissue are to be seen, so that the spongy tissue in this situation presents an appearance of being mapped out into a series of rectangular areas. Articulations. — With tkree bones — the os innominatum, tibia, and patella. Development (Fig. 1 S3). — The femur is developed from five centres — one for the shaft, one for each extremity, and one for each trochanter. Of all the long bones, except the clavicle, it is the first to show traces of ossification; this commences in the shaft, at about the seventh week of fetal life, the centres of ossification in the epiphyses appearing in the following order: First, in the lower end of the bone, at the ninth month of fetal life' (from this the condyles and tuber- osities are formed) ; in the head at the end of the first year after birth ; in the great trochanter, during the foiu'th year; and in the lesser trochanter, between the thirteenth and fourteenth years. The order in which the epiphyses are joined to the shaft is the reverse of that of their appearance; their junction does not commence until after puberty, the lesser trochanter being first joined, then the great, then the head, and lastly the inferior extremity (the first in which ossification commenced), which is not united until the twentieth year. Because of this late union, the lower extremity of the femur has been called the "growing end" of the bone, and early arrest of ossifi- cation here results in more or less marked diminution of stature. Great trochanter. ^ Digital fossa. Appears at Ifth year; joins shaft ^ ahout 18th year. i= '^ Joins shaft at SOth 9th mon ' i ^J^ J^^ year. (fetaC). \=f Lower extremity. J^iG, 182. — Calcar femorale. Attachment of Muscles.— To tiventy-three. To the great trochanter: the Gluteus medius, ■Gluteus minimus, Pyriformis, Obturator internus. Obturator externus, Gemellus superior, and Gemellus inferior. To the lesser trochanter: the Psoas magnus and the Iliacus below it. To the shaft: the Quadratus femoris, Vastus externus, Gluteus maximus, short head of the Biceps femoris. Vastus internus. Adductor magnus, Pectineus, Adductor brevis. Adductor longus, Crureus, and Subcrureus. To the condyles: the Gastrocnemius, Plantaris, and Popliteus. Surface Form. — The femur is covered with muscles, so that in fairly muscular subjects the shaft is not to be detected through its fleshly covering, and the only parts accessible to the touch are the outer surface of the great trochanter and the lower expanded end of the bone. The external surface of the great trochanter may be felt, especially in certain positions of the limb. Its position is generally indicated by a depression, owing to the thickness of the Gluteus medius and ^ This is said to be the only epiphysis in which ossification begins before birth; though, according to observers, the centre for the upper epiphysis of the tibia also appears before birth. THE FEMUR, OB THIGH BONE 229 minimus, which project above it. When, however, the thigh is flexed, and espeeiully if crossed over the opposite one, the trochanter produces a blunt eminence on the surface. The upjjer border is about on a hne with the spine of the os pubis, and its exact level is indicated by a line drawn from the anterior superior spinous process of the ilium, over the outer side of the liip, to the most prominent point of the tuberosity of the ischium. This is known as N§laton's line. The outer and inner condyles of the lower extremity may easily be felt. The outer one is more subcutaneous than the inner one, and readily felt. The tuberosity on it is comparatively little developed, but can be more or less easily recognized. The inner condyle is more thickly covered, and this gives a general convex outline to this part, especially when the knee is flexed. The tuberosity on it is easily felt, and at the upper part of the condyle the sharp tubercle for the insertion of the tendon of the Adductor magnus can be recognized without difficulty. Occa- sionally, exostoses develop in the tendon of insertion of the Adductor magnus; these are the "rider's hones" of cavalry soldiers and horsemen (pp. 360, 515). When the knee is flexed, and the patella situated in the interval between the condyles and the upper end of the tibia, a part of the trochlear surface of the femur can be made out above the patella. Applied Anatomy. — There are one or two points about the ossification of the femur bear- ing on practice to which allusion must be made. It has been stated above that the lower end of the femur is the only epiphysis in which ossification has commenced at the time of birth. The presence of the ossific centre in newly born children found dead is, therefore, a proof that the child has arrived at the full period of uterogestation. However, according to Hartman, at term this centre is absent in 12 per cent, of cases. The position of the epiphyseal line should be carefully noted. It is on a level with the adductor tubercle, and the epiphysis does not, therefore, form the whole of the cartilage-clad portion of the lower end of the bone. It is essen- tial to bear this point in mind in performing excision of the knee, since growth in length of the femur takes place chiefly from the lower epiphysis, and any interference with the epiphyseal cartilage in a young child would involve such ultimate shortening of the limb, from want of growth, as to render it almost useless. Separation of the loiver epiphysis may take place up to the age of twenty, at which time it becomes completely joined to the shaft of the bone; but, as a matter of fact, few cases occur after the age of sixteen or seventeen. The epiphysis of the head of the femur is of interest principally on account of its being the seat of origin of a large number of cases of tiiberciilous disease of the hip-joint. The disease commences in the majority of cases in the highly vascular and growing tissue in the neighborhood of the epiphysis, and from here extends into the joint. In the condition known as coxa tarn the head of the femur falls to a lower level than normal. The angle between the neck and shaft is greatly diminished and may become a right ^ngle, or the head may actually descend to a lower level than that of the trochanter. The neck is also bent with a convexity forward ; coxa vara is due to rachitis. Fractures of the femur are divided, like those of the other long bones, into fractures of the upper end, of the shaft, and of the lower end. The fractures of the upper end may be classi- fied into (1) fracture of the neck; (2) fracture at the junction of the neck with the great trochanter; (.3) fracture of the great trochanter; and (4) separation of the epiphysis, either of the head or the great trochanter. The first of these, fracture of the neck, is usually termed intracapsular fracture, but this is scarcely a correct designation, as, owing to the attachment of the capsular ligament, the fracture may be partly within and partly without the capsule, when the fracture occurs at the lower part of the neck. It generally occurs in old people, principally women, and usually from a very slight degree of indirect violence. Probably the main cause of the fracture taking" place in old people is in consequence of the degenerative changes which the bone has undergone. Merkel believes that it is mainly due to the absorption of the calcar femorale. These fractures are occasionally impacted. As a rule, they unite by fibrous tissue, and frequently no union takes place, and the surfaces of the fracture become smooth and eburnated. The lack of reparative power in intracapsular fracture is due to lack of apposition of the fragments and diminution in the amount of blood sent to the smaller fragment. The head of the bone receives blood from the neck through the reflected portions of the capsule and through the ligamentum teres. A fracture cuts off the supply by the neck and by the reflected portions of the capsule. Fractures at the junction of the rieck with the great trochanter are usually termed extracap- sular, but this designation is also incorrect, as the fracture is partly within the capsule, owing to its attachment in front to the anterior intertrochanteric line, which is situated below die line of fracture. These fractures are produced by direct violence to the great trochanter, as from a blow or fall laterally on the hip. From the rnanner in which the accident is caused, the neck of the bone is driven 'into the trochanter, where it may remain impacted or the trochanter may split up into two or more fragments, and thus no fixation takes place. Fractures of the great trochanter may be either "oblique fracture through the trochanter major, without implicating the neck of the bone" (Astley Cooper), or separation of the great trochanter. Most of the "recorded cases of this latter injury occurred in young persons, and were probably cases of separation of the epiphysis of the great trochanter. Sepai-ation of_ the epiphysis of the head of the femur has been said to occur, but has probably never been verified by postmortem examination. 230 SPECIAL ANATOMY OF THE SKELETON Fracture of the shaft may occur at any part, but the most usual situation is at or near the centre of the bone. They may be caused by direct or indirect violence or by muscular action. Fractures of the upper third of the shaft are almost always the result of indirect violence, while those of the lower third are the result, for the most part, of direct violence. In the middle third fractures occur from both forms of injury in about equal proportions. Fractures of the shaft are generally oblique, but they may be transverse, longitudinal, or spiral. The transverse frac- ture occurs most frequently in children. The fractures of the lower end of the femur include transverse fracture above the condyles, the most common; and this may be complicated by a vertical fracture between the condyles, constituting the T-shaped fracture. In these cases the popliteal artery is in danger of being wounded. Oblique fracture, separating either the internal or external condyle, and a longitudinal incomplete fracture between the condyles, may also take place. The femur and also the bones of the leg are frequently the seat of acute osteomyelitis in young children. This is no doubt due to their greater exposure to injury, which is often the exciting cause of this disease. Tumors not infrequently are found growing from the femur, the most common forms being sarcoma, which may grow either from the periosteum or from the medullary tissue within the interior of the bone; and exostosis, which is commonly found originating in the neighborhood of the epiphyseal cartilage of the lower end. Genu varum is a form of how-leg in which the tibia and femur are curved outward, the knees being widely separated. Both extremities are usually affected. In early life the disease is due to rhachitis. In elderly people it may be due to arthritis deformans. Genu valgum (knock-knee) is a condition in which the knees are close together, the feet are wide apart, and the internal lateral ligament of the knee-joint is stretched. It is due to excessive growth of the inner con- dyle of the femur, the shaft of the femur curving inward. It may be due to rhachitis, attitude of an occupation, or flat-foot, and one or both knees may be affected. THE LEG. The skeleton of the leg consists of three bones — the patella, a large sesamoid bone, placed in front of the knee; the tibia; and the fibula. The Patella, or Kneecap (Fig. 184). The patella is a flat, triangular bone, situated at the anterior part of the knee- joint. It is usually regarded as a sesamoid bone, developed in the tendon of the Quadriceps extensor. It serves to protect the front of the joint, and in- creases the leverage of the Quadriceps extensor by making it act at a greater angle. It presents an anterior and a pos- terior surface, three borders, and an apex. Surfaces. — The anterior sur- face is convex, perforated by small apertures, for the passage of nutrient vessels, and marked by numerous rough, longitudi- FlQ. 184.— Right patella. A. Anterior surface. B. Posterior yisI StrisB This SUrfaCC is COV- surface. i • 'i ered, ni the recent state, by an expansion from the tendon of the Quadriceps extensor, which is continuous below with the superficial fibres of the ligamentum patellae. It is separated from the integument by a bursa. The posterior surface presents a smooth, oval-shaped, articular surface {fades articidaris), covered with hyaline cartilage in the recent state, and divided into two facets by a vertical ridge, which descends from the superior border toward the inferior angle of the bone. The ridge corresponds to the groove on the trochlear THJiJ TIBIA, OB. SHIN BONE 231 surface of the femur, and the two facets to the articular surfaces of the two con- dyles; the outer facet, for articulation with the outer condyle, being broader and deeper. This character serves to indicate the side to which the bone belongs. Below the articular surface is a rough, convex, nonarticular depression, the lower half of which gives attachment to the ligamentum patellae, the upper half being separated from the head of the tibia by adipose tissue. Borders. — The superior border (basis patellae) is thick, and sloped from Ijehind, downward and forward; it gives attachment to that portion of the Quadriceps extensor which is derived from the Rectus femoris and Crureus muscles. The lateral borders are thinner, converging below. They give attachment to that portion of the Quadriceps extensor derived from the external and internal Vasti muscles. The apex (ape.r patellae) is pointed, and gives attachment to the ligamentum patellae. Structure. — This bone resembles a sesamoid bone (1) in being developed in a tendon; (2) in its centre of ossification presenting a knotty or tuberculated outline; (3) in its structure being composed mainly of dense cancellous tissue. It consists of a nearly uniform, dense cancellous tissue covered by a thin compact lamina. The cancelli immediately beneath the anterior surface are arranged parallel with it. In the rest of the bone they radiate from the posterior articular surface toward the other parts of the bone. Development. — From a single centre, which makes its appearance in the second or third, but may not ajjpear until the sixth year. More rarely, the bone is developed by two centres, placed side by side. Ossification is completed about the age of puberty. Articulations. — With the two condyles of the femur. Attachment of Muscles. — To four — the Rectus, Crureus, Vastus internus, and Va.stus externus. These muscles, joined at their insertion, constitute the Quadriceps extensor cruris. Surface Form. — The external surface of the patella can be seen and felt in front of the knee. In the extended position of the limb the internal border is a little more prominent than the outer, and if the Quadriceps extensor is relaxed the bone can be moved from side to side and appears to be loosely fixed. If the joint is flexed, the patella recedes into the hollow between the condyles of the femur and the upper end of the tibia, and becomes firmly fixed against the femur. Applied Anatomy. — The main surgical interest about the patella is in connection with frac- tures, which are of common occurrence. They may be produced by muscular action; that is to say, by violent contraction of the Quadriceps extensor while the limb is in a position of semi- flexion, so that the bone is snapped across the condyles; or by direct violence, such as falls on the knee. Most fractures are due to muscular action; in fact, the patella is more often broken by muscular action than is any other bone. In fractures by muscular action the line of fracture is transverse. In fractures by direct force the line of fracture may be oblique, longitudinal, stellate, or the bone variously comminuted. The principal interest in these cases attaches to their treatment. Owing to the wide separation of the fragments, and the difficulty there is in maintaining them in apposition, union takes place by fibrous tissue, and this may subsequently stretch, producing wide separation of the fragments and permanent lameness. Various plans, including opening the joint and suturing the fragments, have been advocated for overcoming this difficulty. In many cases a portion of fascia or capsule gets between the fragments. In such a condition operation is necessary. In the larger number of cases of fracture of the patella the l>nee-joint is involved, the car- tilage which covers its posterior surface being torn, the s3'novial membrane lacerated, the lateral fibrous expansions ruptured, and the patellar bm-sa torn open. In cases of fracture from direct violence, however, this need not necessarily happen, the lesion may involve only the superficial part of the bone; and, as Morris has pointed out, it is an anatomical possibility, in complete fracture, if the lesion involve only the lower and nonarticular part of the bone, for it to take place without injury to the synovial membrane. The Tibia, or Shin Bone (Figs. 185, 186). The tibia is situated at the front and inner side of the leg, and, excepting the femur, is the longest and largest bone in the skeleton. It is prismoid in form, expanded above, where it enters into the knee-joint, more slightly enlarged below. 232 SPECIAL ANATOMY OF THE SKELETON Capsular ligament Sti/loid -y, External malleohts. Capsular ligament Fig. 1S5. — Bones of the right leg. .interior surface. Fig. 186.— Bones of the right leg. Posterior surface. THE TIBIA, OR SHIN BONE 233 In the male its direction is vertical and parallel with the bone of the opposite side; but in the female it has a slightly oblique direction downward and outward, to compensate for the oblique direction of the femur inward. It presents for examination a shaft and two extremities. The Proximal or Upper Extremity.— The upper extremity, or head, is large, and expanded on each side into two lateral eminences, the internal and external tuberosities (coiidijlus medialis and condylus lateralis). Superiorly, each tuberosity presents a smooth, concave surface {fades articularis superior), which articulates with a condyle of the femur. The internal articular surface is oval in shape and concave from side to side; the external one is circular, concave from side to side, but slightly convex from before backward, especially at its posterior part, where it is prolonged on to the posterior surface for a short distance; the central portions of these surfaces articulate with the condyles, while the peripheral portions are overlaid by the semilunar cartilages of the knee. Between the two articular surfaces, and nearer the posterior than the anterior aspect of the bone, is an eminence, the spine of the tibia (eminentia intercondijloidea); surmounted by a prominent tubercle on each side (the tuherculum intercond.yloideum mediale and the tuherculum intercondyloideuni laterale), on to the lateral aspect of which External semilunar cartilage. Po-iterior crucial llqatntnt External semilunar cartilage. Anterior crucial ligament. Internal scmiluruir cartilage. Internal semilunar cartilage. Fig. 187. — Upper surfaces of right tibia, showing attachment of crucial ligaments cartilages have been partly cut away. nd semilunar cartilages. The the facets just described are prolonged; in front and behind the spinous process is a rough depression (fossa intercondyloidea anterior and the fossa intercondy- loidea posterior) for the attachment of the anterior and posterior crucial ligaments and the semilunar fibrocartilages (Fig. 187). The anterior surfaces of the tuberosities are continuous with one another, form- ing a single large surface, which is somewhat flattened; it is triangular, broad above, and perforated by large vascular foramina; narrow below, where it ter- minates in a prominent oblong elevation of large size, the tubercle of the tibia {tuberositas tibiae); the lower half of this tubercle is rough, for the attachment of the ligamentura patellae; the upper half presents a smooth facet supporting, in the recent state, a bursa which separates the ligament from the bone. Poste- riorly the tuberosities are separated from each other by a shallow depression, the popliteal notch {incisura poplitea), which gives attachment to part of the pos- terior crucial ligament and part of the posterior ligament of the knee-joint. The inner tuberosity presents posteriorly a deep transverse groove, for the insertion of one of the fasciculi of the tendon of the Semimembranosus (Fig. 266) . Its lateral surface is convex, rough, and prominent, and gives attachment to the internal lateral ligament. The outer tuberosity presents posteriorly a flat articular facet {fades articidaris fibidaris) , nearly circular in form, directed downward, backward. 234 SPECIAL ANATOMY OF THE SKELETON and outward, for articulation with the fibula. Its lateral surface is convex and rough, more prominent in front than the internal, and presents a prominent rough eminence, situated on a level with the upper border of the tubercle of the tibia at the junction of its anterior and outer surfaces, for the attachment of the iliotibial band. Just below this the Extensor longus digitorum arises, and a slip from the Biceps femoris cruris is attached. x Shaft of the Tibia (corpus tibiae). — The shaft of the tibia is of a triangular prismoid form, broad above, gradually decreasing in size to its most slender part, the commencement of its lower fourth; it then enlarges again toward its lower extremity. It presents for examination three borders and three surfaces. The anterior border, the most prominent, is called the crest of the tibia (crista anterior) ; it commences above at the tubercle, and terminates below at the anterior margin of the inner malleolus. This border is very prominent in the upper two-thirds of its extent, smooth and rounded below. It presents a very sinuous course, being usually curved outward above and inward below; it gives attachment to the deep fascia of the leg. The internal border (margo medialis) is smooth and rounded above and below, but more prominent in the centre; it commences at the back part of the inner tuber- osity, and terminates at the posterior border of the internal malleolus; its upper part gives attachment to the internal lateral ligament of the knee to the extent of about two inches, and to some fibres of the Popliteus muscle, and its middle third to some fibres of origin of the Soleus and Flexor, longus digitorum muscles.. The external border (crista interossea), or interosseous ridge, is thin and prominent, especially its central part, and gives attachment to the interosseous membrane; it commences above in front of the fibular articular facet, and bifurcates below, to form the boundaries of a triangular rough surface, for the attachilient of the interosseous ligament connecting the tibia and fibula. The internal surface (fades medialis) is smooth, convex, and broader above than below; its upper third, directed forward and inward, is covered by the aponeurosis derived from the tendon of the Sartorius, and by the tendons of the Gracilis and Semitendinosus, all of which are inserted nearly as far forward as the anterior border; in the rest of its extent it is subcutaneous. The external surface (fades lateralis) is narrower than the internal; its upper two-thirds presents a shallow groove for the origin of the Tibialis anticus muscle; its lower third is smooth, convex, curves gradually forward to the anterior aspect of the bone, and is covered from within outward by the tendons of the following muscles: Tibialis anticus. Extensor proprius hallucis. Extensor longus digitorum. The posterior surface (fades posterior) (Fig. 186) presents, at its upper part, a prominent ridge, the oblique line of the tibia (l.inea poplitea), which extends from the back part of the articular facet for the fibula obliquely downward, to the in- ternal border, at the junction of its upper and middle thirds. It marks the lower limit for the insertion of the Popliteus muscle, and serves for the attachment of the popliteal fascia and part of the Soleus, Flexor longus digitorum, and Tibialis posticus muscles; the triangular concave surface, above and to the inner side of this line, gives attachment to the Popliteus muscle. The middle third of the posterior surface is divided by a vertical ridge into two lateral halves; the ridge is well marked at its commencement at the oblique line, but becomes gradually indistinct below; the inner and broader half gives origin to the Flexor longus digitorum, the outer and narrower to part of the Tibialis posticus. The remaining part of the bone presents a smooth surface covered by the Tibialis posticus. Flexor longus digitorum, and Flexor longus hallucis muscles. Immediately below the oblique line is the nutrient foramen, which is large and directed obliquely downward. It is the opening of the nutrient canal, which is directed toward the ankle. THE TIBIA, OB SHIN BONE 235 Upper rxtmnity. The Distal or Lower Extremity.— The lower extremity, much smaller than the upper, presents five surfaces; it is prolonged downward, on its inner side, to a strong process, tiie internal malleolus (malleolus medialis). The inferior surface (Jacicn cniiciilaris inferior) of the bone is cjuadrilateral, and smooth for articulation with the astragalus. This surface is concave from before backward, and broader in front than behind. It is traversed from before backward by a slight elevation, separating two lateral depressions. It is narrow internally, where the articular surface becomes continuous with that on the inner malleolus. The anterior surface of the lower extremity is smooth and rounded above, and covered by the tendons of the Extensor muscles of the toes; its lower margin presents a rough transverse depression, for the attachment of the anterior ligament of the ankle-joint. The posterior surface presents a superficial groove directed obliquely downward and inward, continuous with a similar groove on the posterior surface of the as- tragalus, and serving for the passage of the tendon of the Flexor longus hallucis. The external surface presents a triangular rough depression for the attachment of the interior interosseous ligament, connecting it with the fibula; the lower part of this depression, the iiicisura fibularis, is smooth, covered with cartilage in the recent state, and articulates with the fibula. This surface is bounded by two prominent borders, continuous above with the interosseous ridge; they afford attachment to the anterior inferior and posterior inferior tibiofibular ligaments. The internal surface of the lower extremity is prolonged downward to form a strong pyramidal process, flattened from without inward — the internal malleolus (malleolus medialis). The inner surface of this process is convex and subcu- taneous; its outer surface is smooth and slightly concave, and articulates with the astragalus; its anterior border is rough, for the attachment of the anterior fibres of the internal lateral or deltoid ligament; its posterior border presents a broad and deep groove (sulcus malleolar is), directed obliquely downward and inward, which is occasionally double; this groove trans- mits the tendons of the Tibialis posticus and Flexor longus digitorum muscles. The apex of the internal malleolus is marked by a rough depression behind, for the attachment of the internal lateral ligaments of the ankle-joint. Structure.— Like that of the other long bones. At the junction of the middle and lower third, where the bone is smallest, the wall of the shaft is thicker than in other parts, in order to com- pensate for the smallness of the calibre of the bone. Development. — From three centres (Fig. 1 88), one for the shaft and one for each extrem- ity. Ossification commences in the centre of the shaft about the seventh week, and gradually ex- tends toward either extremity. The centre for the upper epiphysis appears before or shortly after birth; it is flattened in form, and has a thin, tongue-shaped process in front which forms the tubercle. That for the lower epiphysis appears in the second year. The lower epiphysis joins the shaft at about the eighteenth, and the upper one about the twentieth year. T\yo additional centres occasionally exist — one for the tongue-shaped process of the upper epiphysis, which forms the tubercle, and one for the inner malleolus. Appenrs shorily after birth. Appears at Snd_ year. Joins shaft ahout 20th year. _Joins shaft about ISlh year. 236 SPECIAL ANATOMY OF THE SKELETON Articulations. — With three bones — the femur, fibula, and astragalus. Attachment of Muscles. — To twelve: To the inner tuberosity, the Semimembranosus; to the outer tuberosity, the Tibialis anticus and Extensor longus digitorum and Biceps femoris, to the shaft, its internal surface, the Sartorius, Gracilis, and Semitendinosus; to its external surface, the Tibialis anticus; to its posterior surface, the Popliteus, Soleus, Flexor longus digitorum, and Tibialis posticus; to the tubercle, the ligamentum patellae, by which the Quadriceps extensor muscle is inserted into the tibia. In addition to these muscles, the Tensor fasciae femoris is inserted indirectly into the tibia, through the iliotibial band, and the Peroneus longus occasionally derives a few fibres of origin from the outer tuberosity. Surface Form. — A considerable portion of the tibia is subcutaneous and easily felt. At the upper extremity the tuberosities are to be recognized just below the knee. The internal one is broad and smooth, and merges into the subcutaneous surface of the shaft below. The external one is narrower and more prominent, and on it, about midway between the apex of the patella and the head of the fibula, may be felt a prominent tubercle for the insertion of the iliotibial band. In front of the upper end of the bone, between the tuberosities, is the tubercle of the tibia, forming an oval eminence which is continuous below with the anterior border or crest of the bone. This border can be felt, forming the prominence of the shin, in the upper two- thirds of its extent as a sharp and sinuous ridge, curved outward above and inward below. In the lower third of the leg the border disappears, and the bone is concealed by the tendons of the muscles on the front of the leg. Internal to the anterior border is to be felt the broad internal surface of the tibia, slightly encroached upon by the muscles in front and behind. It com- mences above at the wide expanded inner tuberosity, and terminates below at the internal malle- olus. The internal malleolus is a broad prominence situated on a higher level and somewhat farther forward than the external malleolus. It overhangs the inner border of the arch of the foot. Its anterior border is nearly straight; its posterior border presents a sharp edge which forms the inner margin of the groove for the tendon of the Tibialis posticus muscle. The Fibula, or Calf Bone (Figs. 185, 186). The fibula is situated at the outer side of the leg. It is the smaller of the two bones, and, in proportion to its length, the most slender of all the long bones; it is placed on the outer side of the tibia, with which it is connected above and below. Its upper extremity is small, placed toward the back of the head of the tibia and below the level of the knee-joint, and excluded»4i'om its formation; the lower extremity inclines a little forward, so as to be on a plane anterior to that of the upper end, projects below the tibia, and forms the outer ankle. It presents for examination a shaft and two extremities. The Proximal or Upper Extremity. — The upper extremity, or head (capitu- limi fibulae), is of an irregular quadrate form, presenting above a flattened articular facet, directed upward, forward, and inward, for articulation with a corresponding facet on the external tuberosity of the tibia. On the outer side is a thick and rough prominence, continued behind into a pointed eminence, the styloid process of the fibula (apex capituli fibulae), which projects upward from the posterior part of the head. The prominence gives attachment to the tendon of the Biceps femoris muscle and to the long external lateral ligament of the knee, the ligament dividing the tendon into two parts. The apex of the styloid process gives at- tachment to the short external lateral ligament. The remaining part of the circumference of the head is rough, for the attachment of muscles and ligaments. It presents in front a tubercle for the origin of the upper and anterior part of the Peroneus longus, and the adjacent surface gives attachment to the anterior superior tibiofibular ligament; and behind, another tubercle for the attachment of the posterior superior tibiofibular ligament and the upper fibres of origin of the Soleus muscle. The Shaft (corpus fibulae).^ — The shaft presents four borders — the antero- external, the antero-internal, the postero-external, and the postero-internal; and four surfaces — anterior, posterior, internal, and external. • Authorities differ as to the best description of the borders and surfaces of the shaft of the fibula. The editor has followed the scheme in general use at the present time. A more appropriate plan might be afforded by the consid- eration of three surfaces: extensor, peroneal, and flexor, the last being subdivided by the oblique ridge. — Editor. THE FIBULA, OR CALF BONE 237 The antero-external border (crista anterior) commences above in front of the head, runs vertically downward to a little below the middle of the bone, and then, curving somewhat outward, bifurcates so as to embrace the triangular subcutane- ous surface immediately above the outer surface of the external malleolus. This border gives attachment to an intermuscular septum, which separates the Extensor muscles on the anterior surface of the leg from the Peroneus longus and brevis muscles on the outer surface. The antero-intemal border (crista iuterossea), or interosseous ridge, is situated close to the inner side of the preceding, and runs nearly parallel with it in the upper third of its extent, but diverges from it so as to include a broader space in the lower two-thirds. It commences above, just beneath the head of the bone (sometimes it is quite indistinct for about an inch below the head), and terminates below at the apex of a rough triangular surface immediately above the articular facet of the external malleolus. It serves for the attachment of the interosseous membrane, which separates the Extensor muscles in front from the Flexor muscles behind. The postero-extemal border (crista lateralis) is prominent; it commences above at the base of the styloid process, and terminates below in the posterior border of the outer malleolus. It is directed outward, above, backward in the middle of its course, backward and a little inward below, and gives attachment to an aponeurosis which separates the Peronei muscles on the outer surface of the shaft from the Flexor muscles on its posterior surface. The postero-intemal border (crista medialis) sometimes called the oblique line, commences above at the inner side of the head, and terminates by becoming continuous with the interosseous ridge at the lower fourth of the bone. It is well marked and prominent at the upper and middle parts of the bone. It gives attachment to an aponeurosis which separates the Tibialis posticus from the Soleus above and the Flexor longus hallucis below. The anterior siirface {Jacies anterior) is the interval between the antero-external and antero-internal borders. It is extremely narrow and flat in the upper third of its extent, broader and grooved longitudinally in its lower third; it serves for the origin of three muscles, the Extensor longus digitorum, Peroneus tertius, and Extensor proprius hallucis. The external surface Q'acies lateralis) is the space between the antero-external and postero-external borders. It is much broader than the preceding, and often deeply grooved, is directed outward in the upper two-thirds of its course, backward in the lower third, where it is continuous with the posterior border of the external malleolus. This surface is completely occupied by the Peroneus longus and brevis muscles. The internal surface (fades medialis) is the interval included between the antero- internal and the postero-internal borders. It is directed inward, and is grooved for the origin of the Tibialis posticus muscle. The posterior surface (Jacies posterior) is the space included between the postero- external and the postero-internal borders; it is continuous below with the rough triangular surface above the articular facet of the outer malleolus; it is directed backward above, backward and inward at its middle, directly inward below. Its upper third is rough, for the origin of the Soleus muscle; its lower part presents a triangular rough surface, connected to the tibia by a strong interosseous ligament, and between these two points the entire surface is covered by the fibres of origin of the Flexor longus hallucis muscle. At about the middle of this surface is the nutrient foramen. It opens into the nutrient canal, which is directed downward. The Distal or Lower Extremity.— The lower extremity, or external malleolus (malleolus lateralis), is of a pyramidal form, somewhat flattened from without in- ward, and is longer, and descends lower than the internal malleolus. Its external surface is convex, subcutaneous, and continuous with the triangular (also sub- 238 SPECIAL ANATOMY OF THE SKELETON cutaneous) surface on the outer side of the shaft. The internal surface presents in front a smooth triangular facet {fades artlcularis malleoli), broader above than below, and convex from above downward, which articulates with a corresponding surface on the outer side of the astragalus. Behind and beneath the articular surface is a rough depression which gives attachment to the posterior fasciculus of the external lateral ligament of the ankle. The anterior border is thick and rough, and marked below by a depression for the attachment of the anterior fasciculus of the external lateral ligament. The posterior border is broad and marked by a shallow groove (sulcus malleolaris), for the passage of the tendons of the Peroneus longus and brevis muscles. The ai:iex is rounded, and gives 'attachment to the middle fasciculus of the external lateral ligament. Interosseous I "fi border Upper extremity. Appears atout ^ 4th year. ^ . Unites about ' S5th year. For post, fascic. of extl. lateral ligt. Appeals at JSM Unites about Sndyea, ~\W\ -Othyear. I.oirer erfremify. -Lower extremity of right fibula. Internal aspect. In order to distinguish ttie side to wliich the bone belongs, hold it with the lower extremit}^ downward and the broad groove for the Peronei tendons backward — i. e., toward the holder; the triangular subcutaneous surface will then be directed to the side to which the bone belongs. Development. — From three centres (Fig. 190) — one for the shaft and one for each extremity. Ossification commences in the shaft about the eighth week of fetal life, a little later than in the tibia, and extends gradually toward the extremities. At birth both ends are cartilaginous. Ossifi- cation commences in the lower end in the second year, and in the upper one about the fourth year. The lower epiphysis, the first in which ossification commences, becomes united to the shaft about the twentieth year; the upper epiphysis joins about the twenty-fifth year. Ossifi- cation appearing first in the lower epiphysis is contrary to the rule which prevails with regard to the commencement of ossification in epiphyses — viz., that epiphysis toward which the nutrient artery is directed commences to ossify last; but it follows the rule which prevails with regard to the union of epiphyses, by uniting first. Articulations. — With two bones: the tibia and astragalus. Attachment of Muscles.— To nine: To the head, the Biceps femoris, Soleus, and Peroneus longus; to the shaft, its anterior surface, the Extensor longus digitorum, Peroneus tertius, and Extensor proprius hallucis; to the internal surface, the Tibialis posticus; to the posterior surface, the Soleus and Flexor longus hallucis, to the external surface, the Peroneus longus and brevis. Surface Form. — The only parts of the fibula which may be fe't are the head and the lower part of the externa! surface of the shaft and the external malleolus. The head may be seen THE FOOT 239 and felt behind and to the outer side of the outer tuberosity of the tibia. It presents a small, prominent triangular eminence slightly above the level of the tubercle of the tibia. The exter- nal malleolus presents a narrow elongated prominence, situated on a plane posterior to the internal malleolus and reaching to a lower level. From it may be traced the lower third or half of the external surface of the shaft of the bone in the interval between the Peroneus tertius in front and the other two Peronei tendons behind. Applied Anatomy. — In fractures of the bones of the ley both bones are usually fractured, but either bone may be broken separately, the fibula more frequently than the tibia. Fracture of both bones may be caused either by direct or indirect violence. When it occurs from indirect force the fracture in the tibia is usually at the junction of the middle and lower third of the bone. Many causes conduce to render this the weakest part of the bone. The fracture of the fibula is usually at rather a higher level. These fractures present great variety, both as regards their direction and condition. They may be oblique, transverse, longitudinal, or spiral. When oblique, they are usually the result of indirect violence, and the direction of the fracture is from behind, downward, forward, and inward in many cases, but may be downward and outward or downward and backward. When transverse, the fracture is often at the upper part of the bone, and is the result of direct violence. The spiral fracture usually commences as a vertical fissure, involving the ankle-joint, and is associated with fracture of the fibula higher up. It is the result of torsion, from twisting of the body while the foot is fixed. Fractures of the tiliia alone are almost always the result of direct violence, except where the malleolus is broken off by twists of the foot. Fractures of the fibula alone may arise from indi- rect or direct force, those of the lower end being usually the result of the former, and those higher up being caused by a direct blow on the part. The tibia and fibula, like the femur, are frequently the seat of acute osteomyelitis. Tuhemdoiis abscess is more frequently met with in the cancellous tissue of the head and lower end of the tibia than in any other bone of the body. The abscess is of small size, very chronic, and prob- ably the result of tuberculous osteitis in the highly vascular growing tissue at the end of the shaft near the epiphyseal cartilage in the young subject. Such an abscess in bone is called Brodie's abscess. The tibia is the bone which is most frequently and most extensively distorted in rhachitis. It gives way at the junction of the middle and lower third, its weakest part, and presents a curve forward and outward. Boto-leg is due to outward curvature of the femur, tibia, and fibula, the bend being about the junction of the shafts and lower extremities. THE FOOT (Figs. 191, 192). The skeleton of the foot consists of three divisions — the tarsus, metatarsus, and phalanges. The Tarsus (os.m tarsi). — The hones of the tarsus are seven in number — viz., tlie calcaneus, or os calcis, astragalus, cuboid, scaphoid, internal, middle, and external cvmeiform. The Calcaneus (os calcis) (Fig. 194). — The heel bone is the largest and strongest of the tarsal bones. It is irregularly cuboidal in form, having its long axis directed forward and outv\ard. It is situated at the lower and back part of the foot, serving to transmit the weight of the body to the ground, and forming a strong lever for the muscles of the calf. It presents for examination six surfaces — superior, inferior, external, internal, anterior, and posterior. The superior surface is formed, behind, by the upper aspect of that part of the OS calcis which projects backward to form the heel. It varies in length in different individuals; is convex from side to side, concave from before backward, and cor- responds above to a mass of adipose substance placed in front of the tendo Achillis. In the middle of the superior surface are two (sometimes three) articular facets, separated by a broad shallow groove (sulcus calcanei), which is directed obliquely forward and outward, and is rough for the attachment of the interosseous ligament connecting the astragalus and os calcis. When the calcaneus is in contact with the astragalus this groove is converted into a canal (sinus tarsi). Of the articular surfaces, the posterior articular siu-face (fades articularis posterior) is th^ larger, and is situated on the body of the bone; it is of an oblong form, wider behind than in 240 SPECIAL ANA TOMY OF THE SKELETON Fig. 191. — Bones of the right foot. Dorsal surface. THE FOOT 241 AOOESSOniU&. ,rLExcR snevis hallucis. Fig. 192. — Bones of the right foot. Plantar surface. 16 242 SPECIAL ANA T03IY OF THE SKELETON front, and convex; it articulates with the posterior articular area of the astragalus. The anterior articular stirf ace is usually divided into two facets, the anterior of which (fades articularis anterior) supports the head of the astragalus. The more pos- teriorly situated facet (fades articularis calcanea media) articulates with the middle facet on the under surface of the astragalus. The anterior articular surface is supported on a projecting process of bone, called the lesser process of the cal- caneus (sustentaculum tali); it is oblong, concave longitudinally, and sometimes subdivided into two parts, which differ in size and shape. IMore anteriorly is seen the upper surface of the greater process of the calcaneus, marked bv a rough depression for the attachment of numerous ligaments, and a tubercle for the origin of the Extensor brevis digitorum muscle. The inferior surface is narrow, rough, uneven, wider behind than in front, and convex from side to side; it is bounded posteriorly by two tubercles separated by a rough de- pression; the external tubercle (pro- cessus lateralis tuberis calcanei), small, prominent, and rounded, gives origin to part of the Abductor minimi digiti; the internal tubercle (processus medialis tuberis calcanei), broader and larger, for the support of the heel, gives origin, by its prominent inner margin, to the Abductor hallucis, and in front to the Flexor brevis digitorum muscle and plantar fascia; the de- pression between the tubercles gives origin to the Abductor minimi digiti. The rough surface in front of the tubercles gives attachment to the long plantar ligament and origin to the outer head of the Flexor accessorius muscle; while to a prominent tubercle nearer the anterior part of this sur- face, as well as to a transverse groove in front of it, is attached the short plantar ligament. The external surface is broad, flat, and almost subcutaneous; it presents near its centre a tubercle, for the attachment of the middle fasciculus of the exter- nal lateral ligament. At its upper and anterior part this surface gives attach- ment to the external calcaneo-astragaloid ligament; and in front of the tubercle it presents a narrow surface marked by two oblique grooves; separated by an elevated ridge which varies much in size in different bones, it is named the peroneal spine {processus trochlear is), and gives attachment to a fibrous process from the external annular ligament. The superior groo-ve transmits the tendon of the Peroneus brevis; the inferior groove the tendon of the Peroneus longus. The internal surface is deeply concave; it is directed obliquely downward and forward, and serves for the transmission of the plantar vessels and nerves into the sole of the foot; it affords origin to part of the Flexor accessorius muscle. At its upper and fore part it presents an eminence of bone, the sustentaculum tali, Fig. 193, — Schematic representation of the articula- tions of the tarsus. Occasional articulations shown hy THE FOOT 243 which projects horizontally inward, and to it a slip of the tendon of the Tibialis posticus is attached. This process is concave above, and supports the anterior articular surface of the astragalus; below, it is grooved for the tendon of the Flexor longus hallucis. Its free margin is rough, for the attachment of part of the internal lateral ligament of the ankle-joint. The anterior surface {fades articularis cuhoidea), of a somewhat triangular form, articulates with the cuboid. It is concave from above downward and out- ward, and convex in the opposite direction. Its inner border gives attachment to the inferior calcaneoscaphoid ligament. Groove for Peroneus bre. A. Feroneal tubercle Groove for Feroneus longus tendo AchiUia External- tubercle B For posterim- facet of astragal:is For middle facet of astragalus For ntitei tor facet of astragalus Internal tubercle Groove for Flexor longus hallucis Sustentaculum tali Groove for interosseous ligament Fig. 194. — The left calcaneus. A. Postero-external view. B. Antero-internal view. The posterior surface is rough, prominent, convex, and wider below than above. The posterior extremity is the projection of the heel. It is called the tuberosity (tuber calcanei). Its lower part is rough, for the attachment of the tendo Achillis and the tendon of the Plantaris muscle; its upper part is smooth, and is covered .by a bursa which separates the tendons from the bone. 244 SPECIAL ANA TOMY OF THE SKELETON Articulations. — With two bones — the astragalus and cuboid. Attachment of Muscles. — To eight, part of the TibiaHs posticus, the tendo Achilhs, Plan- taris, Abductor hallucis, Abductor minimi digiti, Flexor brevis digitorum, Flexor accessorius, and Extensor brevis digitorum. For scaphoid Neck A Sup. surface, for tibia ' For inferior tibiofibular ligament For ext. malleolus For int. malleoUu Sup. surface, fur tihia Groove for Flexor longus \ . ^ hallucis For inferior calcaneo navicular ligament Middle calcaneal facet Posterior calcaneal facet Groove for Flex, long, hallucis For scaphoid 'For scaphoid j{ ~~~^~i^ZW -interior calcaneal facet Groove for interosseous ligaynent Fig. 195. — The left astragalus. A. Supero-external C. Inferior view. The Astragalus, or Ankle Bone {talus) (Fig. 195).— The astragaliLS is the second largest of the tarsal bones. It occupies the middle and upper part of the tarsus, supporting the tibia above, articulating with the malleoli on either side, resting below upon the calcaneus, and joined in front to the scaphoid. This bone may THE FOOT 245 be easily recognized by its large rounded head, by the broad articular facet on its upper convex surface, and by the two articular facets separated by a deep groove on its under concave surface. It presents six surfaces for examination. The superior surface presents, behind, a broad smooth trochlear surface {trochlea tali) for articulation with the tibia. The trochlea is broader in front than behind, convex from before backward, slightly concave from side to side; in front of it is the upper surface of the neck of the astragalus, rough for the attachment of ligaments. The inferior surface presents two articular areas separated by a deep groove {svlcits tali). The groove runs obliquely forward and outward, becoming gradu- ally broader and deeper in front; it corresponds with a similar groove upon the upper surface of the calcaneus, and forms, when articulated with that bone, a canal, filled up in the recent state by the calcaneo-astragaloid ligament. Of the two articular areas, the posterior (fades articularis calcanea posterior) is the larger, of an oblong form, and deeply concave from side to side ; it rests on the posterior articular surface of the os calcis; the anterior articular area is shorter and narrower, of an elongated oval form, convex longitudinally, and most often subdivided into two facets by an elevated ridge; of these, the posterior (fades articularis calcanea media) articulates with the hinder portion of the anterior articular surfaces of the calcaneus; the anterior (fades articularis calcanea anterior) rests upon the anterior portion of the anterior articular surface of the calcaneus just mentioned. The internal surface presents at its upper part a pear-shaped articular facet (fades malleolaris medialis) for the inner malleolus, continuous above with the trochlear surface; below the articular surface is a rough depression, for the attachment of the deep portion of the internal lateral ligajnent. The external surface presents a large triangular facet (fades malleolaris lateralis), concave from above downward for articulation with the external malleolus; it is continuous above with the trochlear surface; and in front of it is a rough depression for the attachment of the anterior fasciculus of the external lateral ligament of the ankle-joint. The anterior surface (fades articularis navicularis) forms the head of the astrag- alus, is convex and rounded, smooth, of an oval form, and directed obliquely inward and downward; it articulates with the scaphoid. On its under and inner surface is a small facet, continuous in front with the articular surface of the head, and behind with the anterior articular area for the calcaneus. This rests on the inferior calcaneoscaphoid ligament, being separated from it by the syno\ial mem- brane. The head is attached to the rest of the bone by a constricted portion, the neck of the astragalus (collum tali). The posterior surface is traversed by a groove (sidcus m. flexoris hallucis longi), which runs obliquely downward and inward, and transmits the tendon of the Flexor longus hallucis, external to which is the prominent external tubercle (pro- cessus posterior tali), to which the posterior fasciculus of the external lateral ligament is attached. This tubercle is sometimes separated from the rest of the astragalus, and is then known as the os trigonum. To ascertain to which foot the bone belongs, hold it with the broad articular surface upward, and the rounded head forward; the lateral triangular articular surface for the external malleolus will then point to the side to which the bone belongs. Articulations. — With four bones — tibia, fibula, calcaneus, and scaphoid. The Cuboid (os cuboideum) (Fig. 196). — The cuboid is placed on the outer side of the foot, in front of the calcaneus, and behind the fourth and fifth meta- tarsal bones. It is of a pyramidal shape, its base being directed inward, its apex outward. It may be distinguished from the other tarsal bones by the existence 246 SPECIAL ANATOMV OF THE SKELETON of a deep groove on its under surface, for the tendon of the Peroneus longus muscle. It presents for examination six surfaces, three articular and three nonarticular. The nonarticular surfaces are the dorsal, plantar, and external. The dorsal surface, directed upward and outward, is rough, for the attachment of numerous ligaments. The plantar surface presents in front a deep groove, the peroneal groove (sulcus m. peroiiei loncji), which runs obliquely from without, forward and inward; it lodges the tendon of the Peroneus longus, and is bounded behind by a prominent ridge, to which is attached the long calcaneocuboid ligament. The ridge terminates externally in an eminence (tuberositas ossi-s cuboidei), the surface of which presents a convex facet, for articulation with the sesamoid bone of the tendon contained in the groove. The surface of bone behind the groove is rough, for the attachment of the short plantar ligament, a few fibres of origin of the Flexor brevis hallucis, and a fasciculus from the tendon of the Tibialis posticus. The external surface, the smallest and narrowest of the three, presents a deep notch formed by the commencement of the peroneal groove. For ext. cuneiform For 4tk -metatarsal Occasional facet for scaphoid Fui 5th tatarsal Groovefor Tubeiositij Foi ralcaneni Peroneus longus B Fig. 196. — The left cuboid. .-1. .\ntero-internaI view. B. Postero-external view. The articular surfaces are the posterior, anterior, and internal. The posterior surface is smooth, triangular, and concavo-convex, for articulation with the anterior surface of the calcaneus. The anterior surface, of smaller size, but also irregularly triangular, is divided by a vertical ridge into two facets : the inner one, quadrilateral in form, articulates with the fourth metatarsal bone; the outer one, larger and more triangular, articulates with the fifth metatarsal. The internal surface is broad, rough, irregularly quadrilateral, presenting at its middle and upper part a smooth oval facet, for articulation with the external cuneiform bone; and behind this (occasionally) a smaller facet, for articulation with the scaphoid; it is rough in the rest of its extent, for the attachment of strong interosseous liga- ments. To ascertain to which foot the bone belongs, hold it so that its under surface, marked by the peroneal groove, looks downward, and the large concavo-convex articular surface backward toward the holder: the narrow nonarticular surface, marked by the Commencement of the peroneal groove, will point to the side to which the bone belongs. Articulations. — With foiir bones — the calcaneus, external cuneiform, and the fourth and fifth metatarsal bones; occasionally with the scaphoid. Attachment of Muscles. — Part of the Flexor brevis hallucis and a slip from the tendon of the Tibialis posticus. Scaphoid or Navicular Bone (os naviculare pedis) (Fig. 197). — The scaphoid is situated at the inner side of the tarsus, between the astragalus behind and the three cuneiform bones in front. It may be distinguished by its form, being con- cave behind, convex and subdivided into three facets in front. The anterior surface, of an oblong form, is convex from side to side, and sub- divided by two ridges into three facets, for articulation with the three cuneiform bones. The posterior surface is oval, concave, broader externally than internally. THE FOOT 247 and articulates with the rounded head of the astragalus. The dorsal surface is convex from side to side, and rough for the attachment of ligaments. The plantar is irregular, and also rough for the attachment of ligaments. The internal surface presents a rounded tubercular eminence, the tuberosity {tuberositas ossis navicu- laris), the lower part of which projects, and gives attachment to part of the tendon of the Tibialis posticus. The external surface is rough and irregular, for the attachment of ligamentous fibres, and occasionally presents a small facet for articulation with the cuboid bone. For viid. cuneiforin For int. cuneifoi m Fig. 197 —The left scaphoid For astragalus Tubercle eternal view. B. Postero-internal view. For Znd For For 1st metatarsal metatarsal mid-cuneiform To ascertain to which foot the bone belongs, hold it" with the concave articular surface back- ward, and the convex dorsal surface upward; the external surface — i. e., the surface opposite the tubercle — will point to the side to which the bone belongs. Articulations. — With four bones — astragalus and three cuneiform; occasionally also with the cuboid. Attachment of Muscles. — Part of the Tibialis posticus. Cuneiform or Wedge Bones. — The cuneiform bones have received their name from their wedge-like shape. They form, with the cuboid, the distal row of the tarsus, being placed between the scaphoid behind, the three innermost meta- tarsal bones in front, and the cuboid externally. They are called the first, second, and third, counting from the inner to the outer side of the foot, and, from their position, in- ternal, middle, and external. Internal or First Cuneiform {OS cuneiforms primum) (Fig. 198). — The internal cuneiform is the largest of the three. It is situated at the inner side of- the foot, between the scaphoid behind and the base of the first metatarsal in front. It may be distinguished from the other two by its large size, and by its not presenting such a distinct wedge-like form. Without the others it may be known by the large, kidney-shaped anterior articu- lating surface and by the prominence on the inferior or plantar surface for the attachment of the Tibialis posticus. It presents for examination six surfaces. The internal surface is subcutaneous, and forms part of the inner border of the foot; it is broad, quadrilateral, and presents at its anterior inferior angle a smooth oval facet, into which the tendon of the Tibialis anticus is partially inserted; in the rest of its extent it is rough, for the attachment of ligaments. The external For tendon of Tibialis anticus For scapticrid Antero-internal view. 248 SPECIAL ANATOMY OF THE SKELETON surface is concave, presenting, along its superior and posterior borders, a narrow, reversed, I>-shaped surface, for articulation with the middle cuaeiform behind and second metatarsal bone in front; in the rest of its extent it is rough, for the attachment of ligaments, and part of the tendon of the Peroneus longus. The anterior surface, kidney-shaped, much larger than the posterior, articulates with the metatarsal bone of the great toe. The posterior surface is triangular, concave, and articulates with the innermost and largest of the three facets on the anterior surface of the scaphoid. The plantar surface is rough, and presents a prominent tuberosity at its back part for the attachment of part of the tendon of the Tibialis posticus. It also gives attachment in front to part of the tendon of the Tibialis anticus. The dorsal surface is the narrow-pointed end of the wedge, which is directed upward and outward; it is rough for the attachment of ligaments. To ascertain to which side the bone belongs, hold it so that its dorsal narrow edge looks upward, and the long, kidney-shaped, articular surface forward; the external surface, marked by its vertical and horizontal articular facets, will point to the side to which it belongs. Articulations. — With four bones: scaphoid, middle cuneiform, first and second metatarsal bones. Attachment of Muscles. — To three — the Tibialis anticus and posticus, and Peroneus longus. Middle or Second Cuneiform (os cuneiforme secundum) (Fig. 199). — The middle cuneiform, the smallest of the three, is of very regular wedge-like form, the broad extremity being placed upward, the narrow end downward. It is situated between the other two bones of the same For int. cuneiform p^^ scaphoid "ame, and articulates with the scaphoid behind and the second metatarsal in front. It is smaller than the external cuneiform bone, from which it may be further dis- tinguished by the L-shaped artic- ular facet, which runs around the „ „ , \ , • T. . .t^„ upper and back part of its inner .For 2nd metatarsal For ext cuneiform ff r surface. Fig. 199. — The left middle cuneiform. A. Antero-mtern.il rr^, . . , view. B. Postero-externai view. i he anterior surface, triangular in form and narrower than the posterior, articulates with the base of the second metatarsal bone. The posterior surface, also triangular, articulates with the scaphoid. The internal surface presents an L-shaped articular facet, running along the superior and posterior borders, for articulation with the internal cuneiform, and is rough in the rest of its extent, for the attachment of ligaments. The external surface presents posteriorly a smooth facet for articulation with the external cuneiform bone. The dorsal surface forms the base of the wedge; it is quadrilateral, broader behind than in front, and rough for the attachment of ligaments. The plantar surface, pointed and tubercular, is also rough for ligamentous attachment and for the insertion of a slip from the tendon of the Tibialis posticus. To ascertain to which foot the bone belongs, hold its superior or dorsal surface upward, the broadest edge being toward the holder; the smooth facet (limited to the posterior border) will then point to the side to which it belongs. Articulations. — With four bones — scaphoid, internal and external cuneiform, and second metatarsal bone. Attachment of Muscles. — A slip from the tendon of the Tibialis posticus is attached to this bone. External or Third Cuneiform (os cuneiforme terfium) (Fig. 200). — The external cuneiform, intermediate in size between the two preceding, is of a very regular wedge-like form, the broad extremity being placed upward, the narrow end down- TH13,vt of the Tibialis posticus, and Flexor brevis hallucis. The number of tarsal bones may be reduced owing to congenital ankylosis which may occur between the os calcis and cuboid, the os calcis and scaphoid, the os calcis and astragalus, or the astragalus and scaphoid. The Metatarsal Bones (ossa metatarsalia). — The metatarsal bones are five in number, and are numbered one to five, in accordance with their position from within outward; they are long bones, and present for examination a shaft and two extremities. 250 SPECIAL ANATOMY OF THE SKELETON Common Characters. — The shaft (corpus) is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is slightly curved longitudinally, so as to be concave below, slightly convex above. On the plantar surface of the shaft of each bone is a nutrient foramen corresponding to the nutrient foramen in each meta- carpal bone. The proximal extremity, or base (basis), is wedge-shaped, articulating by its terminal surface with the tarsal bones, and by its lateral surfaces with the contiguous metatarsal bones, its dorsal and plantar surfaces being rough for the attachment of ligaments. The distal extremity, or head (capitvlvvi) , presents a terminal rounded articular surface, oblong from above downward, and ex- tending farther backward below than above. Its sides are flat- tened and present a depression, surmounted by a tubercle, for ligamentous attachment. Its under surface is grooved in the middle line for the passage of the Flexor tendon, and marked on each side by an articular eminence continuous with the terminal articular surface. Occasional Jati t joi second metatarsal. For internal cuneiform, Fig. 201. — The first metatarsal. (Left.) Occii'^iimnl I /ai et for first „ , , I metatarsal. ^"'^ external For middle cuneiform. cimeijorm. \ For second metatarsal. For middle cuneiform. For fourth metatarsal. Fig. 202. — The second metatar.sal. (Left.) Fig. 203. — The third metatarsal. (Left.) Peculiar Characters. — The metatarsal bone of the great toe (os metatarsale I) (Fig. 201) is remarkable for its great thickness, but is the shortest of all the metatarsal bones. The shaft is strong and of well-marked prismoid form. The THE FOOT 251 proximal extremity presents, as a rule, no lateral articular facet, but occasionally on the outer side there is an oval facet by which it articulates with the second metatarsal bones. Its proximal articular surface is of large size and kidney shaped; it corresponds to the distal extremity of the internal cuneiform; its cir- cumference is grooved, for the tarsometatarsal ligaments, and internally gives attachment to part of the tendon of the Tibialis anticus muscle; its inferior angle presents a rough oval prominence, the tuberosity {tuberositas ossis metatarsalis I), for the insertion of the tendon of the Peroneus longus. The head is of large size; on its plantar surface are two grooved facets, over which glide sesamoid bones; the facets are separated by a smooth elevated ridge. This bone is known by the single kidney-shaped articular surface on its base, the deeply grooved appearance of the plantar surface of its head, and its great thickness relatively to its length. When it is placed in its natural position, the concave border of the kidney-shaped articular surface on its l)ase points to the side to which the bone belongs. Attachment of Muscles. — To three — part of the Tibialis anticus, the Peroneus longus, and the First dorsal interosseous. The second metatarsal (os metaiarsale II) (Fig. 202) is the longest and largest of the remaining metatarsal bones, being prolonged backward into the recess formed between the three cuneiform bones. Its tarsal extremity is broad above, narrow and rough below. It presents four articular surfaces — one behind, of a triangular form, for articulation with the middle cuneiform; one at the upper part of its internal lateral surface, for articulation with the internal cuneiform; and two on its external lateral surface — an upper and a lower, separated by a rough nonarticular interval. Each of these articular surfaces is divided by a vertical ridge into two facets, thus making four facets; the two anterior of these articulate with the third metatarsal; the two posterior (sometimes continuous) with the external cuneiform. In addition to these articular surfaces there is occasionally a fifth when this bone articulates with the first metatarsal bone. It is oval in shape, and is situated on the inner side of the shaft near the base. The facets on the tarsal extremity of the second metatarsal bone serve at once to distinguish it from the rest, and to indicate the foot to which it belongs; there being one facet at the upper angle of the internal surface, and two facets, each subdivided into two parts, on the external surface, pointing to the side to which the bone belongs. The fact that the two posterior subdi- visions of these external facets sometimes run into one should not be forgotten. Attachment of Muscles.— To /o((r— the Adductor obliquus hallucis, First and Second dorsal interossei, and a slip from the tendon of the Tibialis posticus; occasionally also a slip from the Peroneus longus. The third metatarsal (os metatarsale III) (Fig. 203) articulates proximally, by means of a triangular smooth surface, with the external cuneiform; on its inner side, by two facets, with the second metatarsal; and on its outer side, by a single facet, with the fourth metatarsal. The latter facet is of circular form and situated at the upper angle of the base. The third metatarsal is known by possessing at its tarsal end two undivided facets on the inner side, and a single facet on the outer. This distinguishes it from the second metatarsal, in which the two facets, found on one side of its tarsal end, are each subdivided into two. The single facet (when the bone is put in its natural position) is on the side to which the bone belongs. Attachment of Muscles.— To five — Adductor obliquus hallucis, Second and Third dorsal and First plantar interossei, and a slip from the tendon of the Tibialis posticus. The fourth metatarsal {os metatarsale IV) (Fig. 204) is smaller in size than the preceding; its tarsal extremity presents a terminal quadrilateral surface, for articu- lation with the cuboid; a smooth facet on the inner side, divided by a ridge into an anterior portion for articulation with the third metatarsal, and a posterior 252 SPECIAL ANATOMY OF THE SKELETON portion for articulation with the external cuneiform; on the outer side a single facet, for articulation with the fifth metatarsal. The fourth metatarsal is known by its having a single facet on either side of the tarsal extrem- xty, that on the inner side being divided into two parts. If this subdivision be not recognizable, the fact that its tarsal end is bent somewhat outward will indicate the side to which it belongs. Attachment of Muscles.^To five — Adductor obliquus hallucis. Third and Fourth dorsal, and Second plantar interossei, and a slip from the tendon of the Tibialis posticus. The fifth metatarsal bone, or the metatarsal bone of the little toe {os metatarsale V) (Fig. 205), is recognized by the tubercle (tuberositas ossis metatarsalis V) on the outer side of its base. It articulates behind, by a triangular surface cut obliquely from without inward, with the cuboid, and internally with the fourth metatarsal. For cuboid* For ext. cuneiform. Fig. 204.— The fourth metatarsal. (Left.) Tuberosity. For fourth \ vietatarsal. For cuboid. Fig. 205. — The fifth metatarsal. (Left.) The projection on the outer side of this bone at its tarsal end at once distinguishes it from the others, and points to the side to which it belongs. Attachment of Muscles. — To si.v — the Peroneus brevis, Peroneus tertius, Flexor brevis minimi digiti, Adductor transversus hallucis, Fourth dorsal, and Third plantar interossei. Articulations. — Each bone articulates with the tarsal bones by one extremity (proximal), and by the other (distal) extremity with the first row of phalanges. The number of tarsal bones with which each metatarsal articulates is one for, the first, three for the second, one for the third, tw'o for the fourth, and one for the fifth. The Phalanges of the Foot (Phalanges Digitorum Pedis). The phalanges of the foot, both in number and general arrangement, resemble those in the hand-; there being two in the great toe and three in each of the other toes. The nutritive foramina correspond to those in the phalanges of the hand. The first or proximal phalanx (phalanx prima) resembles closely the corre- sponding bone of the hand. The shaft also is compressed from side to side, convex above, concave below. The proximal extremity is concave; and the distal extremity presents a trochlear surface, for articulation with the second phalanx. THE FOOT 253 The second phalanx (phalanx secwida) is remarkably small and short, but rather broader than the first phalanx. The ungual or distal phalanx (phalanx terfia) in form resembles the bone of the corresponding finger, but is smaller, flattened from above downward, presenting a broad base for articulation with the second phalanx, and an expanded extremity for the support of the nail and end of the toe. y s I s. > Appears 10th year ; imites after puberty. Tarsus. One centre for each toiie, except calcaneus Two centres for each totie One for shaft, One for digital cMtreit except 1st. Phalanges Two centres for each hone : One for shaft. One for proximal extremity. 3d year. Unite ISth-SO year. Appears 7th week. Appeal s 9th week Unite 18th 20th yeai Appears Sth-Sth year. Appears M^i year. Unite 17-18th year. | Appears Snd-4th month. Appears 6th-7lh year. Unite 17th-18th year. ■, Appears Snd-4th month.~^-~J fi \ / Appears 6th year.^ 3 ^^ Unite 17th-18th year.AW S Appears 10th week.—vj'^ Fig. 206. — Plan of the development of the foot. Articulation. — The first row, with the metatarsal bones behind and second phalanges in front; the second row of the four outer toes, with the first and third phalanges; of the great toe, with the fir.st plialanx; tlie third row of the four outer toes, with the second phalanges. Attachment of Muscles. — To the first phalanges: Great toe, five muscles— innermost tendon of E.xteiisor l)ievis diijitorum, Abductor hallucis. Adductor obliquus hallucis. Flexor brevis hallucis, Adductor transversus hallucis. Second toe, three muscles — First and Second dorsal interosseous and First lumbrical. Third toe, three muscles — Third dorsal and First plantar inter- osseous and Second lumbrical. Fourth toe, three muscles — Fourth dorsal and Second plantar interosseous and Third lumbrical. Fifth toe, four muscles — Flexor brevis minimi digiti, Abduc- tor minimi digiti, and Third plantar interosseous, and Fourth lumbrical. Second phalanges: Great toe — Extensor longus huUucis, Flexor longus hallucis. Other toes — Flexor brevis digitorum, one slip of the common tendon of the Extensor longus and brevis digitorum.' Third phalanges: Two slips from the common tendon of the Extensor longus and Extensor brevis digitorum, and the Flexor longus digitorum. Except the second phalanx of the fifth toe, which no slip from the Extensor brevis digitorum. 254 SPECIAL ANATOMY OF THE SKELETON Development of the Foot (Fig. 206). The tarsal bones are each developed from a single centre, excepting the calcaneus, which has an epiphysis for its posterior extremity. The centres make tlieir appearance in the following order: calcaneus, at the sixth month of fetal life; astragalus, about the seventh month; cuboid, at the ninth month; external cuneiform, during the first year; internal cuneiform, in the third year; middle cuneiform and scaphoid, in the fourth year. The epiphysis for the posterior tuberosity of the calcaneus appears at the tenth year, and unites with the rest of the bone soon after puberty. When this part remains as a separate bone, it is called the oa trigonum. The metatarsal bones are each developed from two centres — one for the shaft and one for the digital extremity in the four outer metatarsal; one for the shaft and one for the base in the metatar- sal bone of the great toe.^ Ossification commences in the centre of the shaft about the ninth week, and extends toward either extremity. The centre in the proximal end of the first metatarsal bone appears about the third year, the centre in the distal end of the other bones between the fifth and eighth years; they unite with the shaft between the eighteenth and twentieth years. The phalanges are de\'eloped from two centres for each bone — one for the shaft and one for the proximal extremity. The centre for the shaft appears about the tenth week, that for the epiphysis between the fourth and tenth years ; they join the shaft about the eighteenth year. Construction of the Foot as a Whole (Figs. 207, 208). The foot is constructed on the same principles as the hand, but modified to form a firm Ijasis of support for the rest of the body when in the erect position. It is more solidly constructed, and its component parts are less movable on each other than in the hand. This is especially the case with the great toe, M'hich has to assist in supporting the body, and is therefore constructed with greater solidity; it lies parallel with the other toes, and has a very limited degree of mobility, whereas the thumb, which is occupied in numerous and varied movements, is constructed in such a manner as to permit of great mobility. Its metacarpal bone is directed away from the others, so as to form an acute angle with the second, and it enjoys a considerable range of motion at its articulation with the carpus. The foot is placed at right angles to the leg — a position which is almost peculiar to man, and has relation to the erect position which he maintains. In order to allow of its supporting the weight of the whole body in this position with the least expenditure of material, it is constructed in the form of an arch. This antero-posterior or longitudinal arch is made up of two unequal limbs. The hinder one, which is made up of the calcaneus and the posterior part of the astrag- alus, is about half the length of the anterior limb, and measures about three inches. The anterior limb consists of the rest of the tarsal and the metatarsal bones, and measures about seven inches. It may be said to consist of two parts, an inner segment made up of the head of the astragalus, the scaphoid, the three cuneiform, and the three inner metatarsal bones; and an outer segment composed of the calcaneus, the cuboid, and the two outer metatarsal bones. The summit of the arch is at the superior articular surface of the astragalus; and its two extremi- ties— that is to say, the two piers on which the arch rests in standing^are the internal tubercle on the under surface of the calcaneus posteriorly, and the heads of the metatarsal bones anteriorly. The weakest part of the arch is the joint between the astragalus and scaphoid; and here it is more liable to yield in those who are overweighted, and in those in whom the ligaments which complete and preserve the arch are' relaxed. This weak point in the arch is braced on its con- cave surface by the inferior calcaneoscaphoid ligament, which is more elastic than most other ligaments, and thus allows the arch to yield from jars or shocks applied to the anterior portion of the foot and quickly restores it to its pristine ' As was noted in the first metacarpal bone, so in the first metatarsal, there is often to be observed a tendency to the formation of a second epiphysis in the distal extremity. CONSTRUCTION OF THE FOOT AS A WHOLE 255 condition. This ligament is supported internally by blending with the deltoid ligament, and inferiorly by the tendon of the Tibialis posticus muscle, which is spread out into a fan-shaped insertion, and prevents undue tension of the liga- ment or such an amount of stretching as would permanently elongate it. In addition to this longitudinal arch the foot presents a transverse arch, at the anterior part of the tarsus and hinder part of the metatarsus. This, however, can scarcely be described as a true arch, but presents more the character of a half- dome. The inner border of the central portion of the longitudinal arch is elevated Fig. 207. — Skeleton of the foot, internal border. (Poirier and Charpy.) from the ground, and from this point the bones arch over to the outer border, which is in contact with the ground, and, assisted by the longitudinal arch, pro- duce a sort of rounded niche on the inner side of the foot, which gives the appear- ance of a transverse as well as a longitudinal arch. The line of the foot, from the point of the heel to the toes, is not quite straight, but is directed a little outward, so that the inner border is a little convex and the outer border concave. This disposition of the bones becomes more marked when the longitudinal arch of the foot is lost, as in the condition known under the name of "flat-foot." OLE CUNEIFORM ST METATARSAL Fig. 20S. — Skeleton of the foot, external border. (Poirier and Charpy.) Surface Form. — On the dorsum of the foot the individual bones are not to be distinguished ■with the e.x'ception of the head of the astragalus, which forms a rounded projection in front of the ankle-joint when the foot is forcibly extended. The whole surface forms a smooth convex outline, the summit of which is the ridge formed by the head of the astragalus, the scaphoid, the middle cuneiform, and the second metatarsal bones; from this it gradually inclines outward and more rapidly inward. On the inner side of the foot, the internal tubercle of the calcaneus and the ridge separating the inner from the posterior surface of the bone may be felt most pos- teriorly. In front of this, and below the internal malleolus, may be felt the projection of the sustentaculum tali. Passing forward is the well-marked tuberosity of the scaphoid bone, situ- ated about an inch or an inch and a quarter in front of the internal malleolus. Further toward the front, the ridge formed by the base of the first metatarsal bone can be obscurely felt, and from this the shaft of the bone can be traced to the expanded head articulating with the base 256 SPECIAL ANATOMY OF THE SKELETON of the first phalanx of the great toe. Immediately beneath the base of this phalanx, the internal sesamoid bone is to be felt. Lastly, the expanded ends of the bones forming the last joint of the great toe are to be felt. On the outer side of the foot the most posterior bony point is the external tubercle of the calcaneus, with the ridge separating the posterior from the outer surface of the bone. In front of this the greater part of the external siu^face of the calcaneus is subcu- taneous; on it, below and in front of the external malleolus, may be felt the peroneal spine when this is present. Farther forward, the base of the fifth metatarsal bone forms a prominent and well-defined landmark, and in front of this the shaft of the bone, with its expanded head, and the base of the first phalanx may be defined. The sole of the foot is almost entirely covered by soft parts, so that but few bony parts are to be made out, and these somewhat obscurely. The hinder part of the under surface of the calcaneus and the heads of the metatarsal bones, with the exception of the first, which is concealed by the sesamoid bones, may be recognized. Applied Anatomy. — Considering the injuries to which the foot is subjected, it is surpris- ing how seldom the tarsal bones are fractured. This is no doubt due to the fact that the tarsus is composed of a number of bones, articulated by a considerable extent of surface and joined together by very strong ligaments, which serve to mitigate the intensity of violence applied to this part of the body. When fracture does occur, these bones, being composed for the most part of a soft cancellous structure, covered only by a thin shell of compact tissue, are often extensively comminuted, especially as most of the fractures are produced by direct violence. As the bones have only a very scanty amount of soft parts over them, fractures are very often compound, and amputation is frequently necessary. CALCANEUS of Chopart's amputation. Fig. 210. — Line of Lisfranc's amputation, (Poirier.) (Poirier.) When fracture occurs in the anterior group of tarsal bones, it is almost invariably the result of direct violence, but fractures of the posterior group, that is, of the calcaneus and astragalus, are most frequently produced by falls from a height on to the feet; though fracture of the cal- caneus may be caused by direct violence or by muscular action. The posterior part of the bone, that is, the part behind flie articular surfaces, is almost always the seat of the fracture, though some few cases of fracture of the sustentaculum tali and of vertical fracture between the two articulating facets have been recorded. The neck of the astragalus, being the weakest part of the bone, is most frequently fractured, though fractures may occur in any part and almost in any direction, either associated or not with fracture of other bones. In cases of club-foot, especially in congenital cases, the bones of the tarsus become altered in shape and size, and displaced from their proper positions. This is especially the case in congenital equinovarus, in which the astragalus, particularly about the head, becomes twisted and atrophied, and a similar condition may be present in the other bones, more especially the scaphoid. The tarsal bones are peculiarly liable to become the seat of tuberculous caries, and this condition may arise after comparatively trivial injuries. There are several reasons to account for this. They are composed of a delicate cancellated structure, surrounded by intricate synovial membranes. They are situated at the farthest point from the central organ of the circulation and exposed to vicissitudes of temperature; and, moreover, on their dorsal surface are thinly clad with soft parts which have but a scanty blood-supply. And finally, after slight injuries, they are not maintained in a condition of rest to the same extent as structures suffering from similar injuries in some other parts of the body. Caries of the calcaneus or astragalus may remain limited to the one bone for a long period, but when one of the other bones is affected, the remainder frequently become involved, in consequence of the disease spreading through the large and complicated synovial membrane which is more or less common to these bones. Amputation of the whole or a part of the foot is frequently required either for injury or disease. The principal amputations are as follows: (1) Syme's amputation at the ankle-joint by a heel- flap, with the removal of the malleoli and a thin slice from the lower end of the tibia. (2) Pirogoff's amputation: removal of the whole of the tarsal bones, except the posterior part of the SESAMOID BONES 257 calcaneus. A thin slice is sawed from the tibia and fibula, including the two malleoli. The sawed surface of the calcaneus is then turned up and united to the similar surface of the tibia. (.3) Subastragaloid amputation: removal of the foot below the astragalus through the joint between it and the calcaneus. The bones of the tarsus occasionally recjuire removal individually. This is especially the case with the astragalus and calcaneus for disease limited to the one bone, or again the astragalus may require excision in cases of subastragaloid dislocation. In cases of in\'eterate talipes the head of the astragalus and greater process of the calcaneus is often removed, some- times the scaphoid is also taken out. Finally, Mikulicz and Watson have devised operations for the removal of more extensive portions of the tarsus. Mikulicz's operation consists in the re- moval of the calcaneus and astragalus, along with the articular surfaces of the tibia and fibula, and also of the scaphoid and cuboid. The remaining portion of the tarsus is then brought into contact with the sawed surfaces of the tibia and fibula, and fixed there. The result is a position of the shortened foot resembling talipes ecjiiinus. Watson's operation is adapted to those cases where the disease is confined to the anterior tarsal bones. By two lateral incisions he saws through the bases of the metatarsal bones in front and opens up the joints between the scaphoid and astragalus, and the cuboid and calcaneus, and removes the intervening bones. Fractures of the metatarsal bones and phalanges are nearly always due to direct violence, and in many cases the injury is the result of severe crushing accidents, necessitating amputation. The metatarsal bones, and especially the metatarsal bone of the great toe are frequently dis- eased, either in tuberculous subjects or in perforating ulcer of the foot. Sesamoid Bones (Ossa Sesamoidea) (Figs. 211, 212). These are small rounded masses, cartilaginous in early life, osseous in the adult, which are developed in those tendons which exert a great amount of pressure upon Fig. 211 —Sesamoid bones of the hand. (Poirier and Charpy.) the parts over which they glide. It is said that they are more commonly found in the male than in the female, and in persons of an active muscular habit than in those who are weak and debilitated. They are invested throughout their whole surface by the fibrous tissue of the tendon in which they are found, excepting upon that side which lies in contact with the part over which they play, where they present a Iree articular facet. They may be divided into two kinds — those 258 SPECIAL ANATOMY OF THE SKELETON which glide over the articular surfaces of the joints, and those which play over the cartilaginous facets found on the surfaces of certain bones. The sesamoid bones of the joints in the upper extremity are two on the palmar surface of the metacarpophalangeal joint in the thumb, developed in the tendons of the Flexor brevis poUicis; one on the palmar surface of the interphalangeal joint of the thumb; occasionally one or two opposite the metacarpophalangeal articulations of the fore and little fingers; and, still more rarely, one opposite the same joints of the third and fourth fingers. In the lower extremity, the patella, which is developed in the tendon of the Quadriceps extensor; two small sesamoid bones, found in the tendons of the Flexor brevis hallucis, opposite the metatarso- phalangeal joint of the great toe; one sometimes over the interphalangeal joint of the great toe; and occasionally one in the metatarsophalangeal joint of the second toe, the little toe, and, still more rarely, the third and fourth toes. Those found in the tendons which glide over certain bones occupy the following situations: One sometimes found in the tendon of the Biceps brachii, opposite the tuberosity of the radius; one in the tendon of the Peroneus longus, where it glides through the groove in the cuboid bone; one appears late in life in the tendon of the Tibialis anticus, opposite the smooth facet of the internal cuneiform bone; one is found in the tendon of the Tibialis posticus, opposite the inner side of the head of the astragalus; one in the outer head of the Gastrocnemius, behind the outer condyle of the femur; and one in the conjoined tendon of the Psoas and Iliacus, where it glides over the os pubis. Sesamoid bones are found occasionally in the tendon of the Gluteus maximus, as it passes over the great trochanter, and in the tendons which wind around the inner and outer malleolL THE AETICULATIONS, OE JOINTS. THE various bones of which the skeleton consists are connected at different parts of their surfaces, and such connections are designated hv the name of joints, or articulations. Certain joints are immovable, as all those between the cranial bones excepting the temporomandibular joint. In an immovable joint the adjacent margins of the Ijones are applied in close contact, a thin layer of fibrous membrane, the sutural ligament, or, as at the base of the skull, in certain situations, a thin layer of cartilage, being interposed. Where slight movement is required, combined with great strength, the osseous surfaces are united by tough and elastic fibrocartilages, as in the joints between the vertebral bodies and in the interpubic articulation; but in the movable joints the bones forming the articulation are generally expanded for greater convenience of mutual connection, covered by hyaline cartilage, held together by strong bands or capsules of fibrous tissue called ligaments, and partially lined by a membrane, the synovial membrane, which transudes a fluid to lubricate the various parts of which the joint is formed; so that the structures which enter into the formation of a joint are bone, hyaline cartilage, fibrocartilage, ligament, and synovial membrane Bone. — Bone constitutes the fundamental element of all the joints In the long bones the extremities are the parts which form the articulations; they' are generally somewhat enlarged, and consist of spongy, cancellous tissue, with a thin coating of compact substance. The layer of compact bone which forms the articular surface, and to which the cartilage is attached, is called the articular lamella. It is of a white color, extremely dense, and varies in thickness. Its structure differs from ordinary bone tissue in this respect, that it contains no Haversian canals, and its lacunae are much larger than in ordinary bone and have no canaliculi The vessels of the cancellous tissue, as they approach the articular lamella, turn back in loops, and do not perforate it; this layer is conse- quently more dense and firmer than ordinary bone, and is evidently designed to form a firm and unyielding support for the articular cartilage. In the flat bones the articulations usually take place at the edges, and, in the short bones, at various parts of their surface. Cartilage. — There are three varieties of cartilage — ^1, hyaline; B, fibrocartilage; and C, yellow elastic cartilage; of these, but two, hyaline and fibrocartilage are utilized in the structure of a joint. In general, cartilage consists of a genetic investing membrane, the perichondrium, surrounding the cartilage substance proper. The latter consists of the cellular elements, or chondroblasts, and the intercellular substance, or matrix. The perichondrium is composed chiefly of white fibrous connecti^'e tissue ivith a few added yellow elastic fibres and cellular elements. The outer part contains few cells, and is called the fibrous layer. The inner part, or (jenetic Inijer, contains the bloodvessels, and is rich in flat- tened, elongated, or spindle-shaped cells, the chondroblasts. The chondroblasts vary in shape; those immediately beneath the perichondrium are flat and elongated, while those farther in become larger and o\'al in form. Each cell contains a prominent nucleus embedded in a clear protoplasm that may contain one or more vacuoles. Each cell is sharply outlined, and lies in a space called the lacuna, but two or more cells may be seen to occupy the same lacuna. The matrix immediately surrounding the lacuna is somewhat differentiated from the remaining matrix, and is called the capsule of the lacuna. (259) 260 THE ARTICULATIONS, OR JOINTS The matrix varies in the different varieties of cartilage. In hyaline cartilage it is bluish or ]5early in appearance, and under low magnification is apparently homogeneous; in the fibro- cartilage the matrix consists mainly of white fibrous tissue arranged in bundles of varying size with islands of hyaline matrix and cartilage cells at intervals; the matrix of elastic cartilage is mainly yellinv clastic lis.sue with islands of hyaline matrix and cartilage cells. A. Hyaline cartilage is surrounded by its perichondrium, internal to which is found the apparently homogeneous or slightly granular matrix. If the latter be examined by polarized light or be first treated with potassium hydrate, the fundamental fibrillse are discernible. The fibrils form a meshwork that contains the hyaline substance and cells. In joints the hyaline cartilage is found as a thin layer covering the articular surfaces of the bones concerned, and is here called articular cartilage. In this form the peripheral cells are parallel to the surface; deeper in toward the bone the cells become arranged in rows at right angles to the surface. The latter condition may account for the vertical splitting of articular cartilage that occurs in certain diseases. Hyaline cartilage is also found in the costal, tracheal, bronchial, and most of the larjmgeal cartilages. It tends to calcify and even ossify in old age, and upon boiling yields a substance called chondrin. The hyaline cartilage that covers the joint surfaces of the bones, by its elasticity enables it to break the force of any concussion, while its smoothness affords ease and freedom of move- ment. It varies in thickness according to the shape of the articular surface on which it lies; where this is convex the cartilage is thickest at the centre, where the greatest pressure is received; the reverse is the Case on the concave articular surfaces. : rr \'>-' __•==" g _.^ Fig. 213. — Sections of cartilage. A. Hyaline cartilage, a. Fibrous layer of perichondrium. 6. Genetic layer of perichondrium, c. Youngest chondroblasts. d. Older chondroblasts. e. Capsule, f. cells, g. Lacuna. B. Elastic cartilage. C. Wnite fibrocartilage. (Radasch.) 5. Fibrocartilage is surrounded by a perichondrium; its matrix differs from that of the hyaline variety in consisting chiefly of white fibrous tissue arranged in bundles with little islands of hyaline substance and cells scattered here and there. It is found in the intra-articular car- tilages, deepening joint cavities, and in the intervertebral disks. It is arranged in three groups — (1) intra-articular, (2) connecting, and (.3) circumferential. 1. The articular flbrocartilages, or articular disks (menisci artindares), are flattened, fibro- cartilaginous plates, of a round, oval, triangular, or sickle-like form, interposed between the articular cartilages of certain joints. They are free on both surfaces, thinner toward their centre than at their circumference, and held in position b}' the attachment of their margins and extremities to the surrounding ligaments. The synovial membrane of the joint is prolonged over them a short distance from their attached margins. They are found in the temporo- mandibular, sternoclavicular, acromioclavicular, wrist- and knee-joints. These cartilages are LIGAMENTS 261 usually found in those joints which are most exposed to violent concussion and subject to fre- quent movements. Their use is to maintain the apposition of the ojjposed surfaces in their various motions; to increase the depth of the articular surfaces and give ease to the gliding movement; to moderate the effects of great pressure and deaden the intensity of the shocks to which the parts may be subjected. Iluraphry has pointed out that these intra-arlicular fil)ro- cartilages serve an important purpose in increasing the variety of movements in a joint. Thus, in the knee-joint there are two kinds of motion — viz., angular movement and rotation— although it is a hinge-joint, in which, as a rule, only one variety of motion is permitted; the former movement takes place between the condyles of the femur and the articular cartilages, the latter between the cartilages and the head of the tibia. So, also, in the temporomandibular joint, the upward and downward movement of opening and shutting the mouth takes place between the fibrocartilage and the mandible, the grinding movement between the glenoid cavity and the fibrocartilage, the latter moving with the mandible. Intra-articular cartilages may divide the joint into two distinct cavities, as in the temporo- mandibular articulation. The periphery of an articular cartilage is attached particularly to the capsule, and may also be attached to the nonarticular portion of the bone. The semilunar cartilages of the knee resemble tendon more than they do cartilage. The fibres are arranged in dense, more or less parallel bundles, separated by small, scattered hyaline cells, and the disks are attached to the bone by thin layers of hyaline cartilage. 2. The connecting fibrocaitilages are interposed between the bony surfaces of those joints which admit of only slight moliility, as between the bodies of the vertebras and between the pubic bones. They form disks which adhere closely to both of the opposed surfaces, and are composed of concentric rings of fibrous tissue, with cartilaginous laminte interposed, the former tissue predominating toward the circumference, the latter toward the centre. 3. The circumferential fibrocartilages consist of a rim of fibrocartilage, which surrounds the margin of sonu- ol' the ariicular caviiii-s, as the cotyloid cavity of the hip and the glenoid cavity of the shoulder; tliey serve (o deepen the articular surface, and to protect its edges. Elastic cartilage, although not utilized in joints, may be considered here. It is surrounded by a perichondrium, and its matrix differs from the preceding varieties in being composed chiefly of yellow elastic tissue. It is found in the pinna of the ear, Eustachian tube, epiglottis, and small cartilages of the larynx. It does not ossify or calcify. Cartilage, in the adult, is an avascular tissue, and although vessels at times are seen in the costal cartilages, they do not nourish it, as no branches are given off. Nerves are likewise absent. Ligaments consist of bands of various forms, serving to connect the articular extremities of bones, and are composed mainly of coarse bundles of very dense, white, fibrous tissue placed parallel with, or closely interlaced with, one another, and presenting a white, shining, silvery aspect. A ligament is pliant and flexible, so as to allow of the most perfect freedom of movement, but it is strong, tough, and inextensile, so as not readily to yield under the most severely applied force; it is consequently well adapted to serve as the connecting medium between the bones. Some ligaments consist entirely of yellow elastic tissue, as the ligamenta subflava, which connect together the adjacent arches of the verte- brae in man, and the ligamentum nuchae in the lower animals are composed of yellow elastic tissue. In these cases it will be observed that the elasticity of the ligament is intended to act as a substitute for muscular power. Synovial membrane is a thin, delicate, serous membrane, arranged in its simplest form like a short, wide tube, attached by its open ends to the margins of the articular cartilages and covering the inner surfaces of the various ligaments which connect the articulating surfaces, so that, along with cartilages, it completely encloses the joint-cavity. Its transudate is thick, viscid, and glairy, like the white of an egg, hence it is termed synovia. It is composed of a single layer of endothelial cells resting upon a thin layer of fibroelastic (subendothelial) tissue. The synovial membranes found in the body admit of subdivision into three kinds — articular, bursal, and vaginal. Articular synovial membrane is found in every freely movable joint. It lines the capsule of the joint and is reflected upon the nonarticular intracapsular portion of the bones which enter iiito the formation of the joint. In the fetus this membrane is said, by Toynbee, to 262 THE ARTICULATIONS, OR JOINTS be continued over the surface of the cartilages ; but in the adult it merely encroaches for a short distance upon the margins of the cartilages, to which it is firmly attached; it then invests the inner surface of the capsular or other ligaments enclosing the joint, and is reflected over the surface of any tendons passing through its cavity, as the tendons of the Popliteus in (he knee and the tendon of the Sleeps in the shoulder. In some of the joints the synovial membrane is thrown into folds, which pass across the cavity. They are called synovial ligaments, and are especially distinct in the knee. These folds, when large, frequently contain con- siderable quantities of fat, which acts as a cushion between the two articular surfaces and serves a valuable purpose in filling up gaps. In some joints there are flattened folds, sub- divided at their margins into fringe-like processes (sjoiovial villi), the vessels of which have a convoluted arrangement. These latter generally project from the synovial membrane near the margin of the cartilage and lie flat upon its surface. They consist of fibroelastic tissue covered with endothelium, and contain fat-cells in variable quantities, and, more rarely, isolated cartilage-cells. Under certain diseased conditions similar processes are found covering the entire surface of the synovial membrane, forming a mass of pedunculated fibrofatty growths which project into the joint. Similar structures are also found in some of the bursal and vaginal synovial membranes. The bursal synovial membranes are sacs interposed between surfaces w hich move upon each other, producing friction, as in the gliding of a tendon or of the integument o^er projecting bony surfaces. There are two groups of synovial bursse designated according to situation: (1) Sub- cutaneous synovial bursse {btirsae mucosae suhndaneae) (Fig. 214) are those situated between the integument and a prominent process of bone. Subcutaneous bursge are found between the integument and the front of the patella, over the olecranon, the malleoli, and other prominent parts. (2) Subtendinous synovial bursas (hursae mucosae subtendineae) (Fig. 214) are those situ- ated between tendons or muscles and the bony or cartilaginous surfaces over which the tendons or muscles glide. For example, a bursa is placed between the Glutei muscles and the surface Fig. 214. — Scheme of a serous bursa. (Poirier and Charpj-.) of the great trochanter. Subtendinous bursfe are found often about joints and not unusually com- municate directly with the cavity of the joint by means of an opening in the joint capsule, the synovial membrane of the joint being continuous with the synovial membrane of the bursa. For instance, the bursa between the tendon of the Psoas and Iliacus muscles and the capsular ligament of the hip communicates with the hip-joint; and the bursa between the under surface of the Subscapularis muscle and the neck of the scapula communicates with the shoulder-joint. Bursse consist of a thin wall of connective tissue, lined by endothelial cells, and contain a viscid fluid. The vaginal synovial membrane (Figs. 257 and 365), which is the synovial sheath or the thecal synovial bursa ( I'dt/tna mucosa tendinis), serves to facilitate the gliding of a tendon in the osseofibrous canal through \\hich it passes. The membrane is here arranged in the form of a sheath, one layer of which adheres to the w all of the canal, and the other is reflected upon the surface of the contained tendon, the space between the two surfaces of the membrane containing synovia. These sheaths are chiefly found surrounding the tendons of the Flexor and Extensor rnuscles of the fingers and toes as they pass through the osseofibrous canals in the hand or foot. A vaginal sheath covers the long head of the Biceps brachii muscle from its origin to the surgical neck of the humerus (Fig. 247). Subjacent to the synovial membrane of certain joints are found pads of adipose tissue, the synovial pads. These serve to fill up large spaces, and by adapting themselves to changes of position maintain the form of the joint during movement. SYNARTHROSIS 2(53 The articulations are divided into tliree classes — synarthrosis, or immovable; amphiarthrosis, or mixed; and diarthrosis, or movable joints. Synarthrosis (Immovable Articulation). — Synarthrosis includes all those artic- ulations in which tlie surfaces of the bones are in almost direct contact, being fastened together by an intervening mass of connective tissue, and in which there Sutural ligament Fig. 215, — Section across the sagittal suture. Cartilage Perichondrium -Section through the occipitosphenoid synchondrosis of an infant. is no joint cavity and no appreciable motion. Examples of synarthrosis are the joints between the bones of the cranium and of the face, excepting those of the mandible. The varieties of synarthrosis are four in number — sutura, schindylesis, gomphosis, and synchondrosis. Lifjament Intervertehral disk of fibrocartUage Articular cartilage -rT^?||%(Spo Fig. 217. — Diagrammatic section of a symphysis. The sutura is that form of articulation met with only in the skull, where the contiguous margins of flat bones are apparently but not really in immediate contact, a thin layer of fibrous tissue, sutural membrane, being interposed. This membrane is continuous externally with the pericranium and internally with the Articular cartilage Synovial membrane Capsular ligament Synovial membrane Articular cartilage Intra-articidar fibrocartUage Capsular ligament Fig. 219. — Diagrammatic section of a diarthrodial joint, with an intra-articular fibrocartilage. dura. In some of the sutures the sutural membrane gradually disappears as age advances and the two bones form an osseous fusion. Where the articulating surfaces are connected by a series of processes and indentations interlocked. 264 THE ARTICULATIONS, OB JOINTS it is termed a true suture, or sutura vera, of which there are three varieties — sutura dentata, serrata, and limbosa. The sutura dentata is so called from the tooth-liive form of the projecting articular processes, as in the suture between the parietal bones. In the sutura serrata the edges of the two bones forming the articulation are serrated like the teeth of a fine saw, as between the two portions of the frontal bone. In the sutura limbosa besides the dentated processes, there is a certain degree of bevelling of the articular surfaces, so that the bones overlap each other, as in the suture between the parietal and frontal bones. When the articulation is formed by roughened surfaces placed in apposition with one another, it is termed the false suture, of which there are two kinds — the sutura squamosa, formed by the overlapping of two contiguous bones by broad bevelled margins, as in the squamoparietal (squamous) suture; and the sutura harmonia, where there is simple apposition of two contiguous, rough, bony surfaces, as in the articulation between the two maxilla; or of the horizontal plates of the palate bones. Schindylesis is that form of articulation in which a thin plate of bone is received into a cleft or fissure formed by the separation of two laminse in another bone, as in the articulation of the rostrum of the sphenoid and perpendicular plate of the ethmoid mth the vomer, or in the reception of the latter in the median fissure between the maxillse and palate bones. i A gomphosis is an articulation formed by the insertion of a conical process into a socket, as a nail is driven into a board; this is not illustrated by any articu- lation between bones, properly so called, but is seen in the articulation of the teeth with the alveoli of the maxillae and mandible. A synchondrosis is a joint in which the connecting medium is hyaline cartilage. This is a temporary form of joint, because the hyaline cartilage becomes con- verted into bone before adult life. Such joints are found between the epiphyses and shafts of long bones, between the occipital and the sphenoid at, and for some years after birth. Amphiarthrosis (Mixed Articulation). — In this form of articulation the con- tiguous osseous surfaces are either connected by broad flattened disks of fibro- cartilage which adhere to the end of each bone, as in the articulation between the bodies of the vertebrae, or else the articular surfaces are co^'ered with fibro- cartilage, partially lined by synovial membrane, and connected by external liga- ments, as in the pubic symphysis, both of these joints being capable of limited motion. The articulation between the bodies of the vertebrae resemble the synarthrodia! joints in the continuity of their surfaces and the absence of a synovial sac; the symphysis pubis resembles the diarthrodial articulation. Diarthrosis (Movable Articulation). — This form of articulation includes the greater number of the joints in the body, mobility being their distinguishing character. They are formed by the approximation of two contiguous bony surfaces covered with cartilage, connected by ligaments and lined with synovial membrane. The varieties of joints in this class have been determined by the kind of motion permitted in each. There are two varieties in which the move- ment is uniaxial; that is to say, all movements take place around one axis. In one form, the ginglymus, or hinge-joint, this axis is, practically speaking, trans- verse; in the other, the trochoid, or pivot-joint, it is longitudinal. There are two varieties where the movement is biaxial or around two horizontal axes at right angles to each other or at any intervening axis between the two. These are the condyloid joint and the saddle-joint. There is one form of joint where the move- ment is polyaxial, the enarthrosis, or ball-and-socket joint. And finally there are the arthrodia, or gliding joints. In a diarthrosis there is always a joint cavity lined with synovial membrane — the articular surfaces of the bones are covered with hyaline cartilage, and the bones are held in contact by ligaments. S VNA B TIIR OSIS 265 The ginglymus, or hinge-joint, is that form of joint in which the articular surfaces are moulded to eacii other in such a manner as to permit motion only in one plane, forward and backward; the extent of motion at the same time being coi^siderahle. The direction which the distal bone takes in this motion is never in the same plane as that of the axis of the proximal bone, and there is always a certain amount of alteration from the straight line during flexion. The articular surfaces are connected together by strong lateral ligaments, which form their chief bond of union. The most perfect forms of ginglymus are the interphalangeal joints. A trochoid, or pivot-joint or rotary joint, is one in which the movement is limited to rotation; the joint is formed by a pivot-like process turning within a ring, or the ring on the pivot, the ring being formed partly of bone, partly of ligament. In the superior radioulnar articulation the ring is formed partly by the lesser sigmoid cavity of the ulna and in the rest of its extent by the orbicular ligament; here the head of the radius rotates within the ring. In the articulation of the odontoid process of the axis with the atlas the ring is formed in front by the anterior arch of the atlas; behind, by the transverse ligament; here the ring rotates around the odontoid process. Condyloid or biaxial articulation is that form of joint in which an ovoid artic- ular head, or condyle, is received into an elliptical cavity in such a manner as to permit of flexion and extension, adduction and abduction and circumduction, but no axial rotation. The articular surfaces are connected together by anterior, posterior, and lateral ligaments. An example of this form of joint is found in the wrist. Articulation by reciprocal reception, or saddle-joint, is that variety in which the articular surfaces are concavo-convex; that is to say, they are inversely convex in one direction and concave in the other. The movements are the same as in the preceding form; that is to say, there is flexion, extension, adduction, abduction, and circumduction, but no axial rotation. The articular surfaces are connected by a capsular ligament. The best example of this form of joint is the carpo- metacarpal joint of the thumb. An enarthrosis, or ball-and-socket joint, is that form of joint in which the distal bone is capable of motion around an indefinite number of axes which have one common centre. It is formed by the reception of a globular head into a deep cup-like cavity, the parts being kept in apposition by a capsular ligament strength- ened by accessory ligamentous bands. Examples of this form of articulation are found in the hip- and shoulder-joints. Arthrodia. — Arthrodia is that form of joint which admits of a gliding move- ment; it is formed by the approximation of plane surfaces or of one slightly con- cave to one slightly convex, the amount of motion between them being limited by the ligaments, or osseous processes, surrounding the articulation; as in the articular processes of the vertebrte, the carpal joints, except that of the os magnum with the scaphoid and semilunar bones. Below, in tabular form, are the names, distinctive characters, and examples of the different kinds of articulations: 266 IHE ARTICULATIONS, OR JOINTS Synarthrosis, or Im- movable Joint. Sur- faces separated by fibrous membrane or by a line of cartilage, without any interven- ing synovial cavity, and immovably con- nected 'with each other. As in joints of cran- ium and face (except mandible). Amphiarthrosis, Mixed Articulation. Suiura. Articu- lation by processes and indentations '' interlocked. Diarthrosis, ^Movable Joint. f Dentaia, having tooth- I like processes. I As in interparietal suture. Serrata, having serrated Sutura vera (true) I ^'^S^^ ^'^^ ^^ ^eeth of a articulate bv indent- -1 ^^^'' ... ed borders. " "^ mtertrontal suture. Limbosa, having bevelled margins and dentated pro- cesses. As in frontoparietal su- l ture. I Squamosa, formed by thin bevelled margins, over- lapping each other. Sutura notha ^J"^^ ''^ squamoparietal (false), articulate hy { tt ' ■ „ , , UP ■' ' Harmonia, formed bv rough surfaces. ^, .,.' „ . •■ " the apposition of contigu- ous rough surfaces. As in intermaxillary su- [ ture. Schindylesis. — Articulation formed by the reception of a thin plate of one bone into a fissure of another. As in articulation of rostrum of sphenoid with vomer. Gomphosis. — Articulation formed by the insertion of a conical process into a socket — the teeth. Synchondrosis — (1) Surfaces connected by fibrocartilage and not separated by synovial membrane. Has limited motion. As in joints between bodies of vertebrse. (2) Surfaces covered by fibrocartilage, lined by partial synovial membrane. As in pubic symphysis. Ginglymus. — Hinge-joint; motion limited to two directions, for- ward and backward. Articular surfaces fitted together so as to permit of movement in one plane. As in the interphalangeal joints. Trochoid, or Pivoi-joint. — Articulation by a pivot process turning within a ring or ring around a pivot. As in superior radioulnar articu- lation and atlanto-axial joint. Condyloid. — Ovoid head received into elliptical cavity. Movements in every direction except axial rotation. As the wrist-joint. Reciprocal Reception (saddle-joint). — Articular surfaces inversely con- vex in one direction and concave in the other. Movement in e\"ery direction except axial rotation. As in the carpometacarpal joint of the thumb. Enart.hrosis. — Ball-and-socket joint ; capable of motion in all directions. Articulations by a globular head received into a cup-like cavity. As in hip- and shoulder-joints. Arthrodia. — Gliding joint; articulations by plane surfaces, which glide upon each other. As in carpal and tarsal articulations. The Einds of Movement Admitted in Joints. The movements admissible in the joints may be divided into four kinds — ghding, angular movement, circumduction, and rotation. These movements are often, however, more or less combined in the various joints, so as to produce an infinite variety, and it is .seldom that we find only one kind of motion in any particular joint. Gliding movement is the most simple kind of motion that can take place in a joint, one surface gliding or moving over another without any angular or rotatory movement. It is common to all movable joints, but in some, as in the articu- lations of the carpus and tarsus, it is the only motion permitted. This movement is not confined to plane surfaces, but may exist between any two contiguous TliU KINDS OF MO VE3IENT ADMITTED IN JOINTS 2G7 surfaces, of whatever form, limited by the ligaments which enclose the articu- lation. Gliding over a wide range, as is seen in the sliding of the patella over the condyles of the femur, is called coaptation. Angular movement occurs only between the long bones, and by it the angle between the two bones is increased or diminished. It may take place in four directions — forward and backward, constituting flexion or bending and extension or straightening, or inward toward and outward from the medial line of the body, constituting adduction and abduction. Al)duction of a limb is movement away from the medial line of the body. Adduction of a limb is movement toward the medial line of the body. In the fingers and toes the significance of the terms are different; abduction means movement of the fingers away from the middle finger or of the toe away from the second toe; adduction means movement of fingers toward the middle finger or of the toes toward the second toe. The strictly gingly- moid or hinge-joints admit of flexion and extension only. Abduction and adduc- tion, combined with flexion and extension, are met with in the more movable joints; as in the hip-, shoulder-, and metacarpal-joint of the thumb, and partially in the wrist. When two anterior surfaces are brought nearer together, as by bending the elbow or wrist, we speak of the movement as anterior or ventral flexion. Ventral flexion of the wrist is also called volar or palmar flexion. If two posterior surfaces are brought nearer together, as by bending the knee or extending the wrist, we speak of the movement as posterior or dorsal flexion. At the wrist-joint the bending of the ulnar margin of the hand toward the ulnar side of the forearm is ulnar flexion; the bending of the radial margin of the hand toward the radial side of the forearm is radial flexion. Circumduction is that limited degree of motion which takes place between the head of the bone and its articular cavity, while the extremity and sides of the limb are made to circumscribe a conical space, the base of which corresponds with the inferior extremity of the limb, the apex with the articular cavity; this kind of motion is best seen in the shoulder- and hip-joints. Rotation is the movement of a bone upon an axis, which is the axis of the pivot on which the bone turns, as in the articulation between the atlas and axis, when the odontoid process serves as a pivot around which the atlas turns; or else is the axis of a pivot-like process which turns within a ring, as in the rotation of the radius upon the humerus. Ligamentous Action of Muscles. — The movements of the different joints of a limb are com- bined by means of the long muscles which pass over more than one joint, and which, when relaxed and stretched to their greatest extent, act as elastic ligaments in restraining certain movements of one joint, except when combined with corresponding movements of the other, these latter movements being usually in the opposite direction. Thus, the shortness of the Hamstring muscles prevents complete flexion of the hip, unless the knee-joint is also flexed, so as to bring their attachments nearer together. The uses of this arrangement are threefold : (1 ) It coordinates the kinds of movement which are the most habitual and necessary, and enables them to be per- formed with the least expenditure of power. "Thus, in the usual gesture of the arms, whether in grasping or rejecting, the shoulder and the elbow are fiexed simultaneously, and simultaneously extended," in consequence of the passage of the Biceps and Triceps brachii over both joints. (2) It enables the short muscles which pass over only one joint to act upon more than one. "Thus, if the Rectus femoris remain tonically of such length that, when stretched over the extended hip, it compels extension of the knee, theia the Gluteus maximus becomes not only an extensor of the hip, but an extensor of the knee as well." (3) It provides the joints with ligaments which, while, they are of very great power in resisting movements to an extent incompatible with the mechan- ism of the joint, at the same time spontaneously yield when necessary. "Taxed beyond its strength, a ligament will be ruptured, whereas a contracted muscle. is easily relaxed; also, if neighboring joints be united by ligaments, the amount of flexion or extension of each must remain in constant proportion to that of the other; while, if the union be by muscles.the seijaration of the points of attachment of those muscles may vary considerably in different varieties of move- ment, the muscles adapting themselves tonically to the length required."' Dr. W. W. Keen points out how important it is " that the stu-geon should remember this ligamentous action of ' Dr. Cleland, in Journal of Anatomy and Physiology, 1S66, No. 1, p. 85. 268 THE ARTICULATIONS, OR JOINTS muscles in making passive motion — for instance, at tlie wrist after Colles' fracture. If the fingers be extended, tlie wrist can be fiexed to a right angle. If, however, thev be first flexed, as in 'making a fist.' flexion at the wrist is stricti}' limited to from 40 to 50 degrees in difTerent per- sons, and is very painful beyond that point. Hence, passive motion here should be made with the fingers extended. In the leg, when flexing the hip, the knee should be flexed." Dr. Keen further points out that "a beautiful illustration of this is seen in the perching of birds, whose toes are forced to clasp the perch by just such a passive ligamentous action so soon as they stoop. Hence, they can go to sleep and not fall off the perch." The articulations may be arranged into those of the trunk, those of the upper extremity, and those of the lower extremity. ARTICULATIONS OF THE TRUNK. These may be divided into the following groups, viz. : I. Of the Vertebral Column. II. Of the Atlas with the Axis. III. Of the Atlas with the Occipital Bone. IV. Of the Axis with tiae Occipital Bone. V. Of the Mandible. VI. Of the Ribs with the Vertebrae. VII. Of the Cartilages of the Ribs with the Sternum and with Each Other. VIII. Of the Sternum. IX. Of the Vertebral Column with the Pelvis. X. Of the Pelvis. I. Articulations of the Vertebral Column. The different segments o*^ the vertebral column are connected by spinal ligaments iQigamenta coluninae vertehralis), which may be divided into five sets: (1) Those connecting the bodies of the vertebrse. (2) Those connecting the laminae. (3) Those connecting the articular processes. (4) Those connecting the spinous processes. (5) Those of the transverse processes (the last four kinds being known as interneural) . The articulations of the bodies of the vertebrfe with each other form a series of amphiarthrodial joints; those between the articular processes form a series of arthrodial joints. 1. Ligaments of the Vertebral Bodies or Centra (Intercentral Ligaments). Anterior Common Ligament. Posterior Common Ligament. Intervertebral Substance. The anterior common ligament {Ugamentum longitidinale anterms) (Figs. 222, 225, and 228) is a broad and strong band of longitudinal fibres which extends along the anterior (ventral) surface of the bodies of the vertebrfe from the axis to the sacrum. It is broader below than above, thicker in the thoracic than in the cervical or lumbar regions, and somewhat thicker opposite the front of the body of each vertebra than opposite the intervertebral substance. It is attached, above, to the body of the axis by a pointed process, where it is continuous with the .anterior atlanto-axial ligament, is connected with the tendon of insertion of the Longus colli muscle, and extends down as far as the upper bone of the sacrum. It consists of dense longitudinal fibres, which are intimately adherent to the ^intervertebral substance and the prominent margins of the vertebrfe, but less ARTICULATIONS OF THE VERTEBRAL COLUMN 269 closely to the middle of the bodies. In the latter situation the fibres are exceed- ingly thick, and serve to fill up (he concavities on their front surface and to make the anterior surface of the vertebral column more even. This ligament is com- posed of several layers of fibres, which vary in length, but are closely interlaced with each other. The most superficial or longest fibres extend between four or five vertebrse. A second subjacent set extends between two or three vertebrte, while a third set, the shortest and deepest, extends from one vertebra to the next. At the side of the bodies the ligament consists of a few short fibres, which pass from one vertebra to the next, separated from the median portion by large oval apertures for the passage of vessels. The posterior common ligament {ligamentum lomjitudinale posferius) (Figs. 227 and 228) is situated within the vertebral canal, and extends along the posterior (dorsal) surface of the liodies of the vertebrae from the body of the axis above, where nterverte- jral fibro- :artilage LIGAMENT -Vertebral bodies with ligaments behind. (Spalteholz.) ith the adjacent. (Spalteholz.) it is continuous with the posterior occipito- axial ligament, to the sacrum below. It is broader above than below, and thicker in the thoracic than in the cervical or lumbar regions. In the situation of the interver- tebral substance and contiguous margins of the vertebrfe, where the ligament is more intimately adherent, it is broad, and presents a series of dentations with intervening concave margins; but it is narrow and thick over the centre of the bodies, from which it is separated by the vente basis vertebrte. This ligament is composed of smooth, shining, longitudinal fibres, denser and more compact than those of the anterior ligament, and formed of a superficial layer occupying the interval between three or four vertebrre, and of a deeper layer which extends between one vertebra and the next adjacent to it. It is separated from the dura of the spinal cord by loose connective tissue. The Intervertebral Fibrocartilages {fibrocartilagines inienertebralcs) (Figs. 221 and 222). — Each fibrocartilaginous disk is of lenticular form and of composite structure. The disks are interposed between the adjacent surfaces of the bodies of the vertebrse from the axis to the sacrum, and form the chief bonds of connec- tion between those bones. In young children intervertebral substance exists in the coccyx. These disks vary in shape, size, and thickness in dift'erent parts of the vertebral column. In shape they accurately correspond with the surfaces of the bodies between which they are placed, being oval in the cervical and lumbar regions, and circular in the thoracic. Their size is greatest in the lumbar region. 270 THE ABTJCULATIONS, OB JOINTS In thickness they vary not only in the different regions of the vertebral column, but in different parts of the same disk; thus, they are thicker in front than behind in the cervical and lumbar regions, while they are uniformly thick in the thoracic reo-ion. The intervertebral disks form about one-fourth of the vertebral column, exclusive of the first two vertebrae; they are not equally distributed, however, between the various bones; the thoracic portion of the vertebral column having, in proportion to its length, a much smaller quantity than in the cervical and lumbar right half of sectic regions, which necessarily gives to the latter parts greater pliancy and freedom of movement. The intervertebral disks are adherent, by their surfaces, to a thin layer of hyaline cartilage which covers the upper and under surfaces of the bodies of the vertebrse, and in which, in early life, the epiphyseal plates develop, and by their circumference are closely connected in froat to the anterior, and behind to the posterior common ligament; while in the thoracic region they are connected laterally, by means of the interarticular ligament, to the heads of those ribs which articulate with two vertebrae; they, consequently, form part of the articular cavities in which the heads of these bones are received. Structure of the Intervertebral Substance. — The outer portion of the intervertebral sub- stance is composed of many layers of fibrous connective tissue. This enveloping; portion is called the annulus fibrosus. The central portion of the disk is composed of soft, pulpy, highly elastic fibrocartilage, containing some bands of connective tissue. It is called the nucleus pulposus, is of a yellowish color, and rises up considerably above the surrounding level when the ilisk is divided horizontally. This pulpy substance, which is especially well developed in the lumliar region, is the remains of the notochord, and, according to Luschka, contains a small synovial cavity in its centre. The outer layers of the disk are arranged concentrically one within the other, the outer- most consisting of ordinary fibrous tissue, but the others and more numerous consisting of white fibrocartilage. These plates are not quite vertical in their direction, those near the circumference being curved outward and closely approximated; while those nearest the centre curve in the opposite direction, and are somewhat more widely separated. The fibres of which each plate is composed are directed, for the most part, obliquely from above downward, the fibres of adjacent plates passing in opposite directions and varying in every layer; so that the fibres of one layer are directed across those of another, like the limbs of the let'tei; X. This laminar arrangement belongs to about the outer half of each disk. The pulpy substance presents no concentric arrange- ment, and consists of a fine fibrous matrix, containing angular cells, united to form a reticular ARTICULATIONS OF THE VERTFAiBAL COLUMN 271 structure. J. Bland Sutton' calls attention to the fact that in the human fetus a transverse ligamentous band crosses the dorsal aspect of the intervertebral disk and is continuous with the interosseous ligaments of the heads of the riljs; and also that a fetal ligamentous band exists in the ventral surface of the intervertelwal disiv which, after development, becomes the middle fasciculus of the stellate ligament. These liands are named by Sutton the posterior conjugal ligaments and the anterior conjugal ligaments. Intemeural articulations inciiule tiie ligaments of the laminse; articular pro- cesses, spinous processes, and transverse processes. 2. Ligaments Connecting the Lamin.e. Ligamenta Subflava. •The ligamenta subflava {Ibjamenta intercmralia) (Figs. 222 and 223) are inter- posed between the lamina? of the vertebrse, from the axis to tlie sacrum. They are most distinct wlien seen from tlie interior of tlie vertebral canal; when viewed from the outer surface they ap- pear sliort, being overlapped by the laminae. Each ligamentum subfiavum consists of two lateral portions, which commence on each side at the root of either articular process, and pass back- ward to the point where the laminfe converge to form the spinous process, where their mar- gins are in contact and to a certain extent united; slight in- tervals being left for the passage of small vessels. These ligaments consist of yellow elastic tissue, the fibres of which, almost per- pe:idicular in direction, are at- tached to the anterior surface of the laminse above, some distance from its inferior margin, and to the posterior surface, as well as to the margin of the lamina below. In the cervical region they are thin in texture, but very broad and long; they become thicker in the thoracic region, and in the lumbar acquire very considerable thickness. Their highly elastic property serves to preserve the upright posture and to assist in resuming it after the spine has been flexed. These ligaments do not exist between the occiput and atlas or between the atlas and axis. 3. Ligaments Connecting the Articular Processes. Capsular Ligaments. The capsular ligaments {ca-psidae articiikires) (Fig. 225) are thin and loose ligamentous sacs, attached to the contiguous margins of the articulating processes • Ligaments: Their Nature and Morphology, 1887. 272 THE ARTICULATIONS, OR JOINTS of each vertebra through the greater part of their circumference, and completed internally by the ligamenta subflava. They are longer and looser in the cervical than in the thoracic or lumbar regions. The capsular ligaments are lined on their inner surface with synovial membrane. 4. Ligaments Connecting the Spinous Processes. Supraspinous Ligament. Ligamentum Nuchae. Interspinous Ligaments. The supraspinous ligament (ligamentum sicprasfinale (Fig. 222) is a strong fibrous cord, which connects the apices of the spinous processes from the seventh cervical to the spinous processes of the sacrum. It is thicker and broader in the lumbar than in the thoracic region, and intimately blended, in both situa- tions, with the neighboring aponeurosis. The most superficial fibres of this ligament connect three or four vertebrae; those deeper-seated pass between two or three vertebrae; while the deepest connect the contiguous extremities of neigh- boring vertebrae. It is continued upward to the external occipital protuberance as the ligamentum nuchae. The ligamentum nuchae is a fibrous membrane which, in the neck, represents the supraspinous ligaments of the lower vertebrte. It extends from the external occipital protuberance and crest to the spinous process of the seventh cervical vertebra. From its anterior border a fibrous lamina is given off, which is attached to the posterior tubercle of the atlas, and to the spinous processes of all the cervical vertebrae, so as to form a septum between the muscles on either side of the neck. In man it is merely a rudiment of an important elastic band which, in some of the lower animals, serves to sustain the weight of the head. The interspinous ligaments {ligamenta interspinalia) (Fig. 222), thin and membranous, are interposed between the spinous processes. Each ligament extends from the root to the summit of each spinous process and connects their adjacent margins. They meet the ligamenta subflava in front and the supraspin- ous ligament behind. They are narrow and elongated in the thoracic region; broader, Cjuadrilateral in form, and thicker in the lumbar region; and only slightly developed in the neck. 5. Ligaments Connecting the Transverse Processes. Intertransverse Ligaments. The intertransverse ligaments {ligamenta intertransversaria) (Fig. 235) consist of bundles of fibres interposed between the transverse processes. In the cervical region they consist of a few irregular, scattered fibres; in the thoracic, they are rounded cords intimately connected with the deep muscles of the back; in the lumbar region they are thin and membranous. Movements of the Vertebral Column. — The movements permitted in the vertebra column are flexion, exteiision, lateral movement, circumduction, and rotation. In flexion (forward flexion), or movement of the vertebral column forward, the anterior common ligament is rela.\ed, and the intervertebral substances are compressed in front, while the posterior common ligament, the ligamenta subflava, and the inter- and supraspinous liga- ments are stretched, as well as the posterior fibres of the intervertebral disks. The interspaces between the laminte are widened, and the inferior articular processes of the vertebrse above glide upward upon the articular processes of the vertebrae below. Flexion is the most extensive of all the movements of the vertebral column. In extension (backward flexion), or movement of the vertebral column backward, an exacdy opposite disposition of the parts take place. This movement is not extensive, being limited by the anterior common ligament and by the approximation of the spinous processes. ARTICULATION OF THE ATLAS WITH THE AXIS 273 Flexion and extension are greatest in the lower part of the lumbar region between the third and fourth and fourth and fifth lumbar vertebroe; above the third they are much diminished, and reach their minimum in the middle and upper part of the back. They increase again in the neck, the capability of motion backward from the upright position being in this region greater than that of the motion forward, whereas in the lumbar region the reverse is the case. In lateral flexion, the sides of the interveitebral disks are compressed, the extent of motion being liiiiiicd by the resistance offered by the surrounding ligaments and by the approximation of the traiisxcrse i)rocesses. This movement may take place in any part of the vertebral column, but has the greatest range in the neck and loins. Circumduction is limited, and is produced merely by a succession of the preceding movements. Rotation is produced by the twisting of the intervertebral substances; this, although only slight between any two vertebrre, produces a considerable extent of movement when it takes place in the whole length of the vertebral column, the front of the upper part of the column being turned to one or the other side. This movement takes place only to a slight extent in the neck, but is more .pronounced in the upper part of the thoracic region, and is altogether absent in the lumbar region. It is thus seen that the cervical region enjoys the greatest extent of each variety of movement, flexion and extension, especially, being very extensive. In the thoracic region the three movements of flexion, extension, and circumduction are permitted only to a slight extent, while rotation is very extensive in the upper part and ceases below. In the lumbar region there is extensive flexion, extension, and lateral movement, but no rotation. The movements permitted are mainly due to the shape and position of the articulating pro- cesses. In the loins the inferior articulating processes are turned outward and are embraced by the superior; this renders rotation in tliis region of the vertebral column impossible, while there is nothing to prevent a sliding upward and downward of the surfaces on each other, so as to allow of flexion and extension. In the thoracic region, on the other hand, the articulating processes, by their direction and mutual adaptation, especially at the upper part of the series, permit of rotation, but prevent extension and flexion, while in the cervical region the greater obliquity and lateral slant of the articular processes allow not only flexion and extension, but also rotation. The principal muscles which produce flexion are the Sternomastoid, Rectus capitis anticus major, and Longus colli ; the Scaleni ; the abdominal muscles and the Psoas magnus. Extension is produced by the fourth layer of the muscles of the back, assisted in the neck by the Splenius, Semispinales dorsi et colli, and the Multifidus spinae. Lateral motion is produced by the fourth layer of the muscles of the back, by the Splenius and the Scaleni, the Quadratus lumborum and Psoas magnus, the muscles of one side only acting; and rotation by the action of the fol- lowing muscles of one side only — viz., the Sternomastoid, the Rectus capitis anticus major, the Scaleni, the Multifidus spinae, the Complexus, and the abdominal muscles. II. Articulation of the Atlas with the Axis (Articulatio Atlantoepistrophica). The articulation of the atlas with the axis is of a complicated nature, compris- ing no fewer than four distinct joints. There is a pivot articulation between the odontoid process of the axis and the ring formed between the anterior arch of Fig. 224. — Articulation between odontoid process and atlaa. the atlas and the transverse ligament (Fig. 224). Here there are two joints — one in front between the posterior surface of the anterior arch of the atlas and the front 18 274 THE ARTICULATIONS, OR JOINTS of the odontoid process (atlanto-odontoid joint); the other between the anterior surface of the transverse ligament and the back of the process (syndosmo-odon- toid joint). Between the articular processes of the two bones there is a double arthroidal or gliding joint. The ligaments which connect these bones are the Anterior Atlanto-axial. Posterior Atlanto-axial. Transverse. Two Capsular. The anterior atlanto-axial ligament (Figs. 225 and 228) is a strong, membranous layer, attached, above, to the lower border of the anterior arch of the atlas; below, to the base of the odontoid process and to the front of the body of the axis. It is ■ strengthened in the middle line by a rounded cord, which is attached, above, to the tubercle on the anterior arch of the atlas, and heloiv to the body of the axis, being a continuation upward of the anterior common ligament of the vertebral column. The ligament is in relation, in front, with the Recti antici majores. The posterior atlanto-axial ligament (Figs. 225 and 228) is a broad and thin membranous layer, attached, above, to the lower border of the posterior arch of the atlas; below, to the upper edge of the laminte of the axis. This ligament supplies the place of the ligamenta subflava, and is in relation, behind, with the Inferior oblique muscles. The transverse ligament of the atlas' (ligamentum transversum atlantis) (Figs. 227 and 228) is a thick, strong band, which arches across the ring of the atlas, and serves to retain the odontoid process in firm connection with its anterior «L LIGAMENT f "^'^ rtl'Sj ANTERIOR CONDYLAR Fig. 225. — Occipital bone TRANSVERSE CESS OF ATLAS JOIN- r BETWEEI lODY Of ■VERT "EBR AND INTEI =tVER TEBHAL F IBRO CARTI LAGI TRANSVERSE PROCESS THrRD CERVICAL HTEBRA ical vertebra with ligaments, from in front. (Spalteholz.) arch. This ligament is flattened from before backward, broader and thicker in st,',rw''^n,?r»!S^^t°''tr^t"f •*" describe the transverse ligament with those of the atlas and axis; but the ?h^ ,forteb.,1 n^t^^"'''''' *''*, 'I '5 ™''"^ ^ •i°''"°" °f 'he mechanism by which the movements of the head on «?;l'/^LTlire\trw;?nt£i1^tt^e°r*b^ "^<^ ^"^^ '^^ ^^^ --^^^ ^'^^^^ '<> "-^ ^'^^^^ ARTICULATION OF THE ATLAS WITH THE OCCIPITAL BONE 275 the middle than at either extremity, and firmly attached on each side to a small tubercle on the inner surface of the lateral mass of the atlas. As it crosses the odontoid process, a small fasciculus is derived from its upper, and another from its lower border; the former passing upward, to be inserted into the anterior sur- face of the foramen magnum of the occipital bone; the latter, downward, to be attached to the posterior surface of the body of the axis; hence, the whole ligament has received the name of cruciform ligament {Ugamentum cnwiahim atlantis). A synovial surface is interposed between the odontoid process and the trans- verse ligament, and one is placed between the anterior surface of the odontoid process and the anterior arch of the atlas. The transverse ligament divides the vertebral foramen of the atlas into two unequal compartments; of these, the pos- terior and larger serves for the transmission of the cord and its membranes and the spinal accessory nerves; the anterior and smaller contains the odontoid pro- cess. Since the space between the anterior arch of the atlas and the transverse ligament is smaller at the lower part than the upper (because the transverse lio-ament embraces tightly the narrow neck of the odontoid process), this process is retained in firm connection with the adas after all the other ligaments have been divided. The capsular ligaments (capsulae articulares) (Figs. 226 and 227) are two thin and loose capsules, connecting the lateral masses of the adas with the superior articular surfaces of the axis, the fibres being strengthened at the posterior and inner part of each articulation by an accessory ligament, which is attached below to the body of the axis near the base of the odontoid process. Synovial Membranes (Fig. 224). — There are four sjoiovial membranes in this articulation — one linhig; the inner surface of each of the capsular Hgaments; one between the anterior surface of the odontoid process and- the anterior arch of the atlas; and one between the posterior surface of the odontoid process and the transverse ligament. The latter often communicates with those between the condyles of the occipital bone and the articular surfaces of the atlas. Movements. — This joint allows the rotation of the atlas (and, with it, of the cranium) upon the axis, the extent of rotation being limited by the odontoid ligaments. The principal muscles by which this action is produced are the Sternomastoid and Com- plexus of one side, acting with the Rectus capitis anticus major, Splenius, Trachelomastoid, Rectus capitis posticus major, and Inferior oblique of the other side. ARTICULATIONS OF THE VERTEBRAL COLUMN WITH THE CRANIUM. The ligaments connecting the vertebral column with the cranium may be divided into two sets — those connecting the occipital bone with the atlas, and those con- necting the occipital bone with the axis. III. Articulation of the Atlas with the Occipital Bone (Articulatio Atlanto-occipitalis) . This articulation is a double condyloid joint. Its ligaments are the Anterior Occipito-atlantal. Posterior Occipito-atlantal. Two Capsular. The anterior occipito-atlantal ligament (viembrana atlanfooccipitalis anterior) (Figs. 225 and 22S) is a broad membranous layer, composed of densely woven fibres, which passes between the anterior margin of the foramen magnum above, and the whole length of the upper border of the anterior arch of the atlas below. Laterally, it is continuous with the capsular ligaments. In the middle line in 276 THE ARTICULATIONS, OB JOINTS front it is strengthened by a strong, narrow, rounded cord, which is attached, above, to the basilar process of the occiput, and, below, to the tubercle on the anterior arch of the atlas, and which is a continuation of the anterior common ligament. This ligament is in relation, in front, with the Recti antici minores; hehiyid, with the odontoid ligaments. The posterior occipito-atlantal ligament (membrana atlanto-occipitalis posterior, posterior occipito-atloid ligament) (Figs. 226 and 228) is a very broad but thin membranous lamina intimately blended with the dura. It is connected, above, to the posterior margin of the foramen magnum; heloic, to the upper border of the posterior arch of the atlas. This ligament is incomplete at each side, and forms, with the groove in the upper surface of the posterior arch, an opening for the vertebral artery and suboccipital nerve. The fibrous band which arches over the artery and nerve sometimes becomes ossified. The ligaments are in relation, behind, with the Recti postici minores and Obliqui superiores; in front, with the dura of the vertebral canal, to which they are intimately adherent. POSTERIOR OC CIPITO-ATLANTA LIGAMEN POSTERIOR OC- CIPITO-ATLANTAL LIGAMENT TRANSVERSE PROCESS OF ATLAS Fig. 226. — Occipital bone, first and second cervical vertebree with ligaments from behind. (Spalteholz.) The capsular ligaments (capsulae articulares) (Fig. 227) surround the condyles of the occipital bone, and connect them with the articular processes of the atlas; they consist of thin and loose capsules, which enclose the synovial membranes of the articulations. Synovial Membranes. — There are two synovial membranes in this articulation, one lining the inner surface of each of the capsular ligaments. These occasional!)' communicate with that between the posterior surface of the odontoid process and the transverse ligament. Movements. — The movements permitted in this joint are flexion and extension, which give rise to the ordinary forward and backward nodding of the head. Slight lateral motion to one or the other side may also take place. When either of these actions is carried beyond a slight extent, the whole of the cervical portion of the spine assists in its production. Flexion \s mainly produced by the action of the Rectus capitis anticus major et minor and the Sternomastoid muscles; extension by the Rectus capitis posticus major et minor, the Obliquus superior, the Complexus, Splenius, and upper fibres of the Trapezius. The Recti laterales are concerned in the lateral movement, assisted by the Trapezius, Splenius, Complexus, and the Sternomastoid of the same side, all acting together. According to Cruveilhier, there is a slight amount of rotation in this joint. ARTICULATION OF THE AXIS WITH THE OCCIPITAL BONE 277 IV. Articulation of the Axis with the Occipital Bone. The ligaments of this articulation are the Occipito-axial. Three Odontoid. To expose these ligaments the vertebral canal should be laid open by removing the posterior arch of the atlas, the laminae and spinous process of the axis, and the portion of the occipital bone behind the foramen magnum, as seen in Fig. 227. Fig. 227. — Occipito-axial and atlanto-axial ligaments. Posterior view, obtained by the vert«bri3e and the posterior part of the skull. ^•ing the arches of The posterior occipito-axial ligament (membrana tectoria) (Figs. 227 and 22^) is situated within the vertebral canal. It is a broad, strong band, which covers the odontoid process and its ligaments, and appears to be a prolongation upward of, or a membrane due to fusion with, the posterior common ligament of the spine. It is attached, below, to the posterior surface of the body of the axis, and, becom- ing expanded as it ascends, is inserted into the basilar groove of the occipital bone, in front of the foramen magnum, where it becomes blended with the dura of the skull. Relations. — By its anterior surface with the transverse Hgament; by its 'posterior surface with the posterior common ligament. The lateral odontoid ligaments (ligamenta alaria) (Figs. 227 and 228) are strong, rounded, fibrous cords, which arise one on either side of the upper part of the odontoid process, and, passing obliquely upward and outward, are inserted into the rough depressions on the inner side of the condyles of the occipital bone. In the triangular interval left between these ligaments another strong fibrous 278 THE ARTICULATIONS, OR JOINTS cord, the middle odontoid ligament (ligavientum apicis dentis), may be seen, which passes ahnost perpendicularly from the apex of the odontoid process to the anterior margin of the foramen magnum, being intimately blended with the deep portion of the anterior occipito-atlantal ligament and upper fasciculus of the transverse ligament of the atlas. Movements. — The odontoid ligaments serve to limit tlie extent to which rotation of the cranium may be carried; hence, they have received the name of check ligaments. In addition to these ligaments, which connect the atlas and axis to the skull, the ligamentum nuchae must be regarded as one of the ligaments by which the vertebral column is connected with the cranium. It is described on page 272. L-VE- OF POSTERIOR COMMON Lf T L PARATED FROM THE LH OH OCCrPITO-AXIAL LIGAMENT ANTERIOR OCCIFITO ■ Js ^^Li ITLANTAL LIGA^ ENT ' (v^ V ANTERIOR COM Fig. 228.— Median sagittal section through the occipital bone and first three cervical vertebrae with ligaments. (Spalteholz). Applied Anatomy.— The ligaments which unite the component parts of the vertebrre together are.so strong, and these bones are so interlocked by the arrangement of their articulating processes, that dislocation is very uncommon, and, indeed, "unless accompanied hy fracture, seldom occurs, except in the upper part of the neck. Dislocation of the occiput from the atlas has only been recorded m one or two cases; but dislocation of the atlas from the axis, with rupture of the trans- verse ligament, is much more common; it is the mode in which death is produced in some cases ot execution by hanging. In the lower part of the neck— that is, below the third cervical vertebra —dislocation unattended by fracture occasionally takes place. TEMPOBOMANDIB ULAR ARTICULATION 279 V. Temporomandibular Articiilation (Articulatio Mandibularis) . This is a ginglymo-arthrodial joint; the parts entering into its formation on each side are, above, the anterior part of the glenoid cavity of the temporal bone and the eminentia articularis; and, below, the condyle of the mandible. The ligaments are the following: External Lateral. Internal Lateral. Articular Disk Stylomandibular. Capsular. The external lateral ligament {ligamenium temporomaitdibulare) (Fig. 229) is a short, thin, and narrow fasciculus, attached, above, to the outer surface of the zygoma and to the tubercle on its lower border; beloiv, to the outer border of the neck and to the tubercle at the outer extremity of the condyle of the mandible. It is broader above than below; its fibres are placed parallel to one another, ss»m\ ^ ^^^^ Temporal bone. k\ , ,A Fig. 229. — Tempoi and directed obliquely downward and backward. Externally, it is covered by the parotid gland and by the integument. Internally it is in relation with the capsular ligament, of which it is an accessory band, and from which it is not separable. The internal lateral ligament (licfamentum sphenomandibulare) (Fig. 230) is .a flat, thin band which is attached above to the spine of the sphenoid bone, and, becoming broader as it descends, is inserted into the margin of the dental foramen and the portion of bone, the lingula, which overhangs the foramen in front. This ligament is not a true articular ligament, but is an accessory band, contrib- uted to the capsule by the deep cervical fascia. Its outer surface is in relation, above, with the External pterygoid muscle; lower down it is separated from the neck of the condyle by the internal maxillary artery; and still more inferiorly, the inferior dental vessels and nerve separate it from the ramus of the mandible. The inner surface is in relation with the Internal pterygoid. 280 THE ARTICULATIONS, OB JOINTS Fig. 230. — Temporomandibular articulation. Internal The stylomandibular ligament Qigamentum stylomandibulare) (Fig. 230) is a specialized band of the cervical fascia, which extends from near the apex of the styloid process of the temporal bone to the angle and posterior border of the ramus of the mandible, between the Masseter and Internal pterygoid muscles. This ligament separates the parotid from the submaxillary gland, and has attached to its inner side part of the fibres of origin of the Stylo- glossus muscle. Although usually classed among the ligaments of the mandible, it can be considered only as an accessory to the articu- lation. The capsular ligament {cap- sula articularis) (Figs. 229 and 230) forms a thin and loose cap- sule, passing from the circum- ference of the glenoid cavity and the articular surface immediately in front to the upper margin of the articular disk, and from the lower margin of the articular disk to the neck of the condyle of the mandible. It consists of very thin fibres, and is complete. It forms two joint cavities, distinct from each other, and separated by the articular disk. So thin is it that it is hardly to be considered as a distinct ligament; it is thickest at the back part, and thinnest on the inner side of the articulation.' The articular meniscus (discus articularis) (Fig. 231) is a thin plate of an oval form, placed horizontally between the condyle of the mandible and the glenoid cavity. Its upper surface is con- cavo-convex from before backward, and a little convex transversely, to accommodate itself to the form of the glenoid cavity. . Its under sur- face, where it is in contact with the condyle, is concave. Its circumfer- ence is connected to the capsular ligament, and in front to the tendon of the External pterygoid muscle. It is thicker at its circumference, especially behind, than at its centre. The fibres of which it is composed have a concentric arrangement, more apparent at the circumference than at the centre. Its surfaces are smooth. It divides the joint into two cavities, each of which is furnished with a separate synovial membrane reflected from the capsular ligament. Synovial Membranes (Fig. 231). — The synovial membranes, tivo in number, are placed, one above, and the other below, the articular disk. The upper one, the larger and looser of the two, is continued from the margin of the cartilage covering the glenoid cavity and eminentia ' Sir G. Humphry describes the internal portion of the capsular ligament separately as the short internal lateral ligament; and it certainly seems as deserving of a separate description as is the external lateral ligament. THE TEMPOROMANDIBULAR ARTICULATION 281 articularis on to the upper surface of the articular disk. The lower one passes from the under surface of the articular disk to the neck of the condyle of the mandible, being prolonged down- ward a little farther behind than in front. The articular disk is sometimes perforated in its centre; the two synovial sacs then communicate with each other. The nerves of this joint are derived from the auriculotemporal and masseteric branches of the inferior maxillary. The arteries are derived from the temporal branch of the external carotid. Movements. — The movements possible in this articulation are very extensive. Thus, the mandible may be depressed or elevated, or it may be carried forward or backward. It must be borne in mind that there are two distinct joints in this articulation — that is to say, one between the condyle of the mandible and the articular disk, and another between the disk and the glenoid fossa; when the mandible is depressed, as in o])e'ning the mouth, the movements which take place in these two joints are not the same. In the lower compartment, that between the condyle and the articular disk, the movement is of a ginglymoid or hinge-like character, the condyle rotating on a transverse axis on the articular disk; while in the upper compartment the movement is of a gliding character, the articular disk, together with the condyle, gliding forward on to the eminentia articularis. These two movements take place simultaneously — the condyle and articular disk move forward on the eminence, and at the same time the condyle revolves on the articular disk. In the opposite movement of shutting the mouth the reverse action takes place; the articular disk glides back, carrying the condyle with it, and this at the same time revolves back to its former position. When the mandible is carried horizontally forward, as in protruding the lower incisors in front of the upper, the movement takes place principally in the upper compartment of the joint — the articular disk, carrying with it the condj'le, glides forward on the glenoid fossa. This is because this movement is mainly effected by the External pterygoid muscles, which are inserted into both condyle and articular disk. The grinding or chewing movement is produced by the alternate movement of one condyle, with its disk, for- , ward and backward, while the other condyle moves simultaneously in the opposite direction; at the same time the condyle undergoes a vertical rotation on its own axis on the disk in the lower compartment. One condyle advances and rotates, the other condyle recedes and rotates, in alternate succession. The mandible is depressed by its own weight, assisted by the Platysma, the Digastric, the Mylohyoid, and the Geniohyoid muscles. It is elevated by the anterior part of the Temporal, Masseter, and Internal pterygoid muscles. It is drawn forward by the simultaneous action of the External pterygoid and the superficial fibres of the Masseter; and it is drawn backward by the deep fibres of the Masseter and the posterior fibres of the Temporal muscles. The grinding movement is caused by the alternate action of the two External pterygoids. Surface Form. — The temporomandibular articulation is quite superficial, situated below the base of the zygoma, in front of the tragus and external auditory meatus, and behind the posterior border of the upper part of the Masseter muscle. Its exact position can be at once ascertained by feeling for the condyle of the mandible, the working of which can be distinctly felt in the movements of the mandilile in opening and shutting the mouth. When the mouth is opened wide, the condyle advances out of the glenoid fossa on to the eminentia articularis, and a depres- sion is felt in the situation of the joint. Applied Anatomy. — Genuine dislocation of the mandible is almost always forward. Croker, King, and Theim, however, have reported posterior displacement. Dislocation is caused by vio- lence or muscular action. When the mouth is open, the condyle is situated on the eminentia articularis, and any sudden violence, or even a sudden muscular spasm, as during a convulsive yawn, may displace the condyle forward into the zygomatic fossa. The displacement may be unilateral or bilateral, according as one or both of the condyles is displaced. The latter of the two is the more common. The articular disk adheres to the condyle until it passes over the eminentia articularis, but at this point remains behind. Sir Astley Cooper described a condition which he termed "subluxation." It occurs princi- pally in delicate women, and is belived by some to be due to the relaxation of the ligaments, permitting too free movement of the bone. Others believe it is due to displacement of the articular disk. Still others attribute the symptoms to gouty or rheumatic changes in the joint. In close relation to the condyle of the mandible is the external auditory meatus and the tympanum; any force, therefore, applied to the bone is liable to be attended with damage to these parts, or inflammation in the joint may extend to the ear, or, on the other hand, inflammation of the middle ear may involve the articulation and cause its destruction, thus leading to ankylosis of the joint. In children, arthritis of this joint may follow the exanthemata, and in adults it occurs as the result of some constitutional conditions, as rheumatism or gout. The temporomandibular joint is also occasionally the seat of osteoarthritis, leading to great suffering during efforts of mas- tication. A peculiar affection sometimes attacks the neck and condyle of the mandible, consisting in hypertrophy and elongation of these parts and consequent protrusion of the chin to the opposite side. 282 THE ARTICULATIONS, OR JOINTS VI. Articulations of the Ribs with the Vertebrae or the Costovertebral Articulations (Articulationes Costovertebrales). The articulations of the ribs with the vertebral column may be divided into two sets: (1) Those which connect the heads of the ribs with the bodies of the vertebrae — costocentral. (2) Those which connect the necks and tubercles of the ribs with the transverse processes — costotransverse. 1. Costocentral Articulations (Articulationes Capitulorum) (Figs. 232 and 233). These constitute a series of arthrodial joints, formed by the articulation of the heads of the ribs with the cavities on the contiguous margins of the bodies of the Fig. 232.— Vertebral column (Spalteholz.) thoracic vertebras and the intervertebral substance between them, except in the case of the first, tenth, eleventh, and twelfth ribs, where the cavity is formed by a single vertebra. The bones are connected by the following ligaments: Anterior Costovertebral or Stellate. Capsular. Intra-articular The anterior costovertebral or stellate ligament (ligamentum capituli costae radiatum) (Figs. 232 and 235) connects the anterior part of the head of each rib with the sides of the bodies of two vertebrae and the intervertebral disk between them. It consists of three flat bundles of ligamentous fibres, which are attached to the anterior part of the head of the rib, just beyond the articular ARTICULATIONS OF THE BIBS WITH THE VEBTEBBJE 283 surface. The superior fibres pass upward to be connected with the body of the vertebra above; the inferior one descends to the body of the vertebra below; and the middle one, the smallest and least distinct, passes horizontally inward, to be attached to the intervertebral substance. On the first rib, which articulates with a single vertebra, this ligament does not present a distinct division into three fasciculi; its fibres, however, radiate, and are attached to the body of the last cervical vertebra, as well as to the body of the vertebra with which the rib articulates. In the tenth, eleventh, and twelfth ribs also, which likewise articulate with a single vertebra, the division does not exist; but the fibres of the ligament in each case radiate and are connected with the vertebra above, as well as that with which the ribs articulate. Relations. — In front, with the thoracic ganglia of the sympathetic, the pleura, and, on the right side, with the vena azygos major; behind, with the interarticular ligament and synovial membranes. The capsular ligament (capsula articularis) is a thin and loose ligamentous bag, which surrounds the joint between the head of the rib and the articular cavity formed by the inter- vertebral disk and the ad- jacent vertebra. It is very thin, firmly connected with the anterior ligament, and most distinct at the upper and lower parts of the articulation. Behind, some of its fibres pass through the intervertebral foramen to the back of the inter- vertebral disk. This is the }\om.o\ogueoH\\e.liga'mentum conjugale of some mammals, which unites the heads of opposite ribs 'across the back of the intervertebral disk. The intra-articular liga- ment (Jigamentum capifidi costae interarticidare) (Figs. 23.3 and 234) is situated in the interior of the joint. It consists of a short band of fibres, flattened from above downward, attached by one extremity to the sharp crest which separates the two articular facets on the head of the rib, and by the other to the intervertebral disk. It divides the joint into two cavities, which have no communication with each other. For the first, tenth, eleventh, and twelfth ribs the intra-articular ligament does not exist; consequently there is but one synovial membrane. Synovial Membranes (Figs. 233 and 234). — There are two syno\'iaI membranes in each of the articulations in which there is an intra-articular ligament, one on each side of this structure. 284 THE ARTICULATIONS, OB JOINTS 2. Costotransverse Articulations (Articulationes Costotransversariae) (Fig. 234). The articular portion of the tubercle of the rib and adjacent transverse process form an arthrodial joint. For the eleventh and twelfth rihs this articulation is wanting. The ligaments connecting these parts are the Anterior or Superior Costotransverse. Middle Costotransverse (Interosseous). Posterior Costotransverse. Capsular. The anterior or superior ligament (ligamentum costotransversarium anterius) (Figs. 234 and 235) consists of two sets of fibres; the one (anterior) is attached below to the sharp crest on the upper border of the neck of each rib, and passes Fig. 234. — Costotransverse articulation. Seen from above. obliquely upward and outward to the lower border of the transverse process immediately above; the other (posterior) is attached below to the neck of the rib, and passes upward and inward to the base of the transverse process and outer border of the lower articular process of the vertebra above. The first rib has no anterior costotransverse ligament. For the twelfth rib the ligament is absent or is a mere vestige. Relations. — This ligament is in relation, in front, with the intercostal vessels and nerves; behind, with the Longissimus dorsi muscle. Its internal border is thickened and free, and bounds an aperture through which pass the posterior branches of the intercostal vessels and nerves. Its external border is continuous with a thin aponeurosis which covers the External intercostal muscle. The middle costotransverse or interosseous ligament (ligamentum colHcostae} (Fig. 234) consists of short but strong fibres which pass between the rough surface on the posterior part of the neck of each rib and the anterior surface of the ad- jacent transverse process. In order to fully expose this ligament, a horizontal VERSE LIG INTER! VERSE LIGAMENT ARTICULATIONS OF THE BIBS WITH THE VERTEBRA 285 section should be made across the transverse process and corresponding part of the rib; or the rib may be forcibly separated from the transverse process and the fibres of tlie ligament put on the stretch. For the eleventh and twelfth ribs this ligament is quite rudimentary or wanting. The posterior costotransverse ligament (ligamentum costotransversarmm pos- ierius) (Fig. 234) is a short but thick and strong fasciculus which passes obliquely from the summit of the transverse process to the rough nonarticular portion of the tubercle of the rib. This ligament is shorter ^\o. and more oblique in the upper than in the lower ribs. Those correspon- ding to the superior ribs ascend, while those of the inferior ribs descend slightly. For the eleventh and twelfth ribs this ligament is M-anting. The capsular liga- ment (capsula artic'ular- is) is a thin, membranous sac attached to the cir- cimiference of the articu- lar surfaces, and enclos- inga syno\-ial membrane. For the eleventh and twelfth ribs this ligament is absent. Movements.~The heads of the ribs are so closely connected to the bodies of the vertebrae by the stellate and intra-articular hgaments, and the necks and tubercles of the ribs to the transverse Fig. 235. — Ribs and corresponding -vertebra; with ligaments, processes, that only a slight ^^^ "sht. (Spaltehoh.) gliding movement of the ar- ticular surfaces on each other can take place in these articulations. The result of this gliding movement with respect to the six upper ribs consists in, an elevation of the front and middle portion of the rib with a consequent enlargement of the antero-posterior diameter of the thorax, the hinder part being prevented from performing any upward movement by its close connection with the vertebral column. In this gliding movement the rib rotates on an axis corresponding to a line drawn through the two articulations, costocentral and costotransverse, which the rib forms with the vertebral column. None of the ribs lie in a truly horizoiKal plane; they are all directed more or less obliquely, so that their anterior extremities lie at a lower level than their posterior; this obliquity increases from the first to the seventh, and then again decreases. If we examine any one rib — say that in which there is the greatest obliquity — we shall see that it is obvious that as its sternal extremity is carried upward it must also be thrown forward; so that the rib may be regarded as a radius moving on the vertebral joint as a centre, and causing the .sternal attachment to describe an arc of a circle in the vertical plane of the body. Since all the ribs are oblique and connected in front to the sternum by the flexible costal cartilages, they must have a tendency to thrust the sternum forward, and so increase the antero-posterior diameter of the thorax. With respect to the seventh, eighth, ninth, and tenth ribs, each one, besides rotating in a similar manner to the upper six, also rotates on an axis corresponding with a line drawn from the head of the rib to the sternum. By this movement an elevation of the middle portion of the rib takes place, and consequently an increase in the transverse diameter of the thorax. For the ribs not only slant downward and forward from their vertebral attachment, but they are also oblique in relation to their transverse plane — that is to say, their middle is at a lower level than INFERIOR AHTIC ULAfl PROCESS 286 THE ARTICULATIONS, OB JOINTS either their vertebral or sternal extremities. It results from this that when the ribs are raised, the central portion is thrust outward, somewhat after the fashion in which the handle of a bucket is thrust away from the side when raised to a horizontal position, and the lateral I ijl diameter of the thorax is increased (see Fig. 236). The mobility of the diflerent ribs varies greatly. The first rib is more fixed than the others, on account of the weight of the upper extremity and the strain of the ribs beneath; but on the freshly dissected thorax it moves as freely as the others. From the same causes the movement of the second rib is also not very extensive. In the other ribs this mobility increases successively down to the last two, which are very movable. The ribs are generally more movable in the female than in the male. VII. Costosternal Articulations (Articulationes Sternocostales) (Fig. 237). ^ Fig. 236. — I)i:im:njis .showing the axis of rotation of the ribs in the moveiiieiiU ut respiration. The one axi.s of rota- tion corresponds with the Une drawn through the two articula- tions which the rib forms with the vertebral column (a, 6), and the other with a line drawn from the head of the rib to the sternum (A, B). (From Kirke's Handbook of Physiology.) The articulations of the carti- lages of the true ribs with the sternum are arthrodial joints, with the exception of the first, in which the cartilage is almost always directly united with the sternum, and which must therefore be re- garded as a synarthrodial articu- lation. Tlae ligaments connecting them are the Anterior Chondrosternal. Capsular. Posterior Chondrosternal. Intra-articular Chondrosternal. Chondroxiphoid. The anterior chondrosternal ligament (liganientum sternocostale radiatum) (Fig. 237) is a broad and thin membranous band that radiates from the front of the inner extremity of the cartilages of the' true ribs to the anterior surface of the sternum. It is composed of fasciculi which pass in different directions. The superior fasciculi ascend obliquely, the inferior fasciculi pass obliquely downward, and the middle fasciculi pass horizontally. The superficial fibres of this ligament are the longest; they intermingle with the fibres of the ligaments above and below them, with those of the opposite side, and with the tendinous fibres of origin of the Pectoralis major, forming a thick fibrous membrane which covers the surface of the sternum (inembraiia sterni). This is more distinct at the lower than at the upper part. The capsular ligament (capsida articidaris) surrounds the joint formed between the cartilage of a true rib and the sternum. It is very thin, intimately blended with the anterior and posterior ligaments, and strengthened at the upper and lower part of the articulation by a few fibres which pass from the cartilage to the side of the sternum. These ligaments protect the synovial membranes. The posterior chondrosternal or sternocostal ligament (ligamentum sterno- costale radiatum), less thick and distinct than the anterior, is composed of fibres COSTOSTERNAL ARTICULA TI0N8 287 which radiate from the posterior surface of the sternal end of the cartilages of the true ribs to the posterior surface of the sternum, becoming blended with the periosteum. The intra-articular chondrosternal ligament {ligamentum sternocostale inier- articulare) (Fig. 237) is found between the second costal cartilage and the sternum. The cartilage of the second rib is connected with the sternum by means of an Fig. 237. — Sternum and ribs with ligaments, from in front. In the right half of the figure the most anterior layer has been removed and the joint cavities have been opened; the parts are separated somewhat from one another on the left side. (Spalteholz.) intra-articular ligament attached by one extremity to the cartilage of the second rib, and by the other extremity to the cartilage which unites the first and second pieces of the sternum. This articulation is provided with two synovial membranes. The cartilage of the third rib is also occasionally connected with the sternum by means of an intra-articular ligament which is attached by one extremity to the cartilage of the third rib, and by the other extremity to the sternum. This 288 THE ARTICULATIONS, OB JOINTS articulation may be provided with two synovial membranes. In the other joints intra-articular ligaments may exist, but they rarely completely divide the joint into two cavities. The anterior chondroxiphoid ligament (ligamentum costoxiphoideum anterius) (Fig. 237) is a band of ligamentous fibres which connects the anterior surface of the seventh costal cartilage, and occasionally also that of the sixth, to the anterior surface of the ensiform cartilage. It varies in length and breadth in different subjects. A similar band of fibres on the posterior surface, though less thick and distinct, may be demonstrated. It is spoken of as the posterior chondroxiphoid ligament. Synovial Membranes (Fig. 2.37). — There is no synovial membrane between the first costal cartilage and the sternum, as this cartilage is directly continuous with the manubrium. There are tioo synovial membranes, both in the articulation of the second and third costal cartilages to the sternum. There is generally one synovial membrane in each of the joints between the fourth, fifth, sixth, and seventh costal cartilages to the sternum; but it is sometimes absent in the sixth and seventh chondrosternal joints. Thus, there are usually eiyht synovial cavities on each side in the articulations between the costal cartilages of the true ribs and the sternum. After middle life the articular surfaces lose their polish, become roughened, and the synovial membranes appear to be wanting. In old age the articulations do not exist, the cartilages of most of the ribs becoming continuous with the sternum. Movements. — The movements which are permitted in the chondrosternal articulations are limited to elevation and depression, and these only to a slight extent. Articulations of the Cartilages of the Ribs with Each Other {articulationes interchondrales) (Fig. 237). — The contiguous borders of the sixth, seventh, and eighth, and sometimes the ninth and tenth, costal cartilages articulate with each other by small, smooth, oblong-shaped facets. Each articulation is enclosed in a thin capsular ligament lined by synovial membrane, and strengthened externally and internally by ligamentous fibres, external and internal interchondral ligaments (ligamenta intercostalia externa et interna), which pass from one cartilage to the other. Sometimes the fifth costal cartilage, more rarely that of the ninth, articu- lates, by its lower border, with the adjoining cartilage by a small oval facet; more frequently they are connected by a few ligamentous fibres. Occasionally the articular surfaces above mentioned are wanting. Articulations of the Ribs with their Cartilages (Fig. 237).— The outer extremity of each costal cartilage is received into a depression in the sternal ends of the ribs, and the two are held together by the periosteum. There is no real joint. Occasionally a synovial membrane exists between the first rib and the corresponding cartilage. VIII. Articulations of the Sternum (Fig. 237) The first piece of the sternum is united to the second either by an amphi- arthrodial joint — a single piece of true fibrocartilage uniting the segments — or by a diarthrodial joint, in which each bone is clothed with a distinct lamina of hyaline cartilage, adherent on one side, free and lined with synovial membrane on the other. In the latter case the cartilage covering the gladiolus is continued without interruption on to the cartilages of the second ribs. The two segments are further connected by an Anterior Intersternal I^igament. Posterior Intersternal Ligament. The anterior intersternal ligament consists of a lajer of fibres, having a longi- tudinal direction ; it blends with the fibres of the anterior chondrosternal liga- ments on both sides, and with the tendinous fibres of origin of the Pectoralis ARTICULATION OF VERTEBRAL COLUMN WITH THE PELVIS 289 major muscle. This ligament is rough, irregular, and much thicker below than above. The posterior intersternal ligament is disposed in a somewhat similar manner on the posterior surface of the articulation. IX. Articulation of the Vertebral Column with the Pelvis. The ligaments connecting the last lumbar vertebra with the sacrum are similar to those which connect the segments of the vertebral column with each other — viz. : (1) The continuation downward of the anterior and posterior common liga- ments. (2) The intervertebral substance connecting the flattened oval surfaces of the two bones and forming an amphiarthrodial joint. (.3) Ligamenta subflava, connecting the arch of the last lumbar vertebra with the posterior border of the sacral canal. (4) Capsular ligaments connecting the articulating processes and forming a double arthrodia. (5) Inter- and supraspinous ligaments. Occasional aperture of communication with Bursa 0/ psoas and iliacus. Femur. Fig. 238. — Articulations of the pelvis and hip. Anterior ' The two proper ligaments connecting the pelvis with the vertebral column are the lumbosacral and iliolumbar. The lumbosacral ligament (Fig. 2.38) is a short, thick, triangular fasciculus, which is connected above to the lower and front part of the transverse process of the last lumbar vertebra; it passes obliquely outward and is attached below to the lateral surface of the base of the sacrum. It is closely blended with the anterior sacroiliac and the iliolumbar ligaments, and is to be regarded as a portion ■ of the iliolumbar ligament. This ligament is in relation, in frojit, with the Psoas muscle. The internal border of the lumbosacral ligament margins the foramen of the last lumbar nerve. 290 THE ARTICULATIONS, OB JOINTS The iliolumbar ligament (Hgamentum iliolumhale) (Fig. 238) passes horizontally outward from the apex of the transverse process of the last lumbar vertebra to the crest of the ilium immediately in front of the sacroiliac articulation. It is of a triangular form, thick and narrovsf internally, broad and thinner externally. It is in relation, in front, vi'ith the Psoas muscle; behind, with the muscles occupy- ing the vertebral groove; above, with the Quadratus lumborum. It blends in places with the lumbosacral ligament, and its crescentic inner margin marks the limit of the foramen for the fourth limibar nerve. These ligaments are thick prolongations from the anterior layer of the lumbar fascia. X. Articulations of the Pelvis. The ligaments connecting the bones of the pelvis with each other may be divided into four groups: (1) Those connecting the sacrum and ilium. (2) Those passing between the sacrum and ischium. (3) Those connecting the sacrum and coccyx. (4) Those between the tv/o pubic bones. 1. Articulation of the Sacrum and Ilium (Articulatio Sacroiliaca). The sacroiliac articulation is an amphiarthrodial joint, formed between the lateral surfaces of the sacrum and ilium. The anterior or auricular portion of each articular surface is covered with a thin plate of hyaline cartilage, thicker on the sacrum than on the ilium. These ai'e in close contact with each other, and to a certain extent united together by irregular patches of softer fibro- cartilage, and at their upper and posterior part by fine fibres of interosseous fibrous tissue. Throughout a considerable part of their extent, especially in advanced life, they are not connected together, but are separated "by a space containing a synovial-like fluid, and hence the joint presents the characters of a diarthrosis. The ligaments connecting these surfaces are the Anterior Sacroiliac. Posterior Sacroiliac. The anterior sacroiliac ligament (Ugamenta sacroiliaca anteriora) (Fig. 238) consists of numerous thin bands which connect the anterior surfaces of the sacrum and ilium. The posterior sacroiliac ligament Qigamentum sacroUiacum posterius) (Fig. 239) is a strong ligament, situated in a deep depression between the sacrum and ilium behind, and forming the "chief bond of connection between those bones. It consists of numerous strong fasciculi which pass between the bones in various directions. The upper part of the ligament, the short sacroiliac {Hgamentum sacroiliacuni posterius breve) is nearly horizontal in direction and passes from the first and second transverse tubercles on the posterior surface of the sacrum to the rough, uneven surface at the posterior part of the inner surface of the ilium. The lower part (Hgamentum sacroUiacum posterius longum), oblique in direction, is attached by one extremity to the third transverse tubercle on the posterior surface of the sacrum, and by the other to the posterior superior spine of the ilium; it is sometimes called the oblique sacroiliac ligament. Surface Form. — The position of the sacroiliac joint is indicated by the posterior superior spine of the ilium. This process is immediately behind the centre of the articulation. ARTICULATIONS OF THE PELVIS 291 2. Ligaments Passing between the Sacrum and Ischium (Fig. 239). The Great Sacrosciatic (Posterior). The Small Sacrosciatic (Anterior). The great or posterior sacrosciatic ligament {Ugamentum sacroiuberosum) (Figs. 239 and 240) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the extremities; attached by its broad base to the posterior inferior spine of the ilium, to the fourth and fifth transverse tubercles of the sacrum, and to the lower part of the lateral margin of that bone and the coccyx. Passing obliquely downward, outward, and for- ^ Femm Fig. 239. — .Articulations of pelvis and hip. Posterior Mew ward, it becomes narrow and thick, and at its insertion into the inner margin of the tuberosity of the ischium it increases in breadth, and is prolonged forward along the inner margin of the ramus, forming what is known as the falciform process of the great sacrosciatic ligament {processus falciformis) . The free concave edge of this prolongation has attached to it the obturator fascia, with which it forms a kind of groove, protecting the internal pudic vessels and nerve. One of its surfaces is turned toward the perineum, the other toward the Obturator internus muscle. Relations. — The superficial surface of this ligament gives origin, by its whole extent, to fibres of the Gluteus ma.xiraus muscle. Its deep surface is united to the lesser sacrosciatic ligament. Its external border forms, above, the posterior boundary of the great sacrosciatic foramen, and, below, the posterior boundary of the lesser sacrosciatic foramen. Its loioer border forms part of the boundary of the perineum. It is pierced by the coccygeal branch of the sciatic artery and the coccygeal nerve. 292 THE ARTICULATIONS, OB JOINTS The small or anterior sacrosciatic ligament {ligamentum sacrospinosuTri) (Figs. 239 and 240), much shorter and smaller than the preceding, is thin, triangular in form, attached by its apex to the spine of the ischium, and internally, by its broad base, to the lateral margin of the sacrum and coccyx, anterior to the attacli- ment of the great sacrosciatic ligament, with wliich its fibres a're intermingled. -ANT. SACI aOILlAC LIGAMENT. -GREAT SA CRO- SCIATIC LIGA- MENT. .SMALL SA< CRO- SCIATIC LIGA- MENT. .GREAT SA CRO- SCIATIC LIGA' MENT. Obtu. membrane. Fig. 240. — Side view of pelvis, showing the greater and lesser sacrosciatic ligaments. Relations. — Its deep surface is in relation with the Cotcygeus muscle; its superficial surface is covered by the great sacrosciatic ligament and crossed by the internal pudic vessels and nerve. Its superior harder forms the lower boundary of the great sacrosciatic foramen; its inferior border, part of the lesser sacrosciatic foramen. These two ligaments convert the sacrosciatic notches into foramina. The superior or great sacrosciatic foramen (foramen ischiadicmn majiis) (Figs. 239 and 240) is bounded, in front and above, by the posterior border of the os innominatum;fcp/«"?!fi, by the great sacrosciatic ligament; and below, by the lesser sacrosciatic ligament. It is partially filled in the recent state by the Pyriformis muscle, which passes through it. Above this muscle the gluteal vessels and superior gluteal nerve emerge from the pelvis, and, below it, the sciatic vessels and nerves, the internal pudic vessels and nerve, the inferior gluteal nerve, and the nerves to the Obturator internus and Quadratus femoris. The inferior or lesser sacrosciatic foramen (foramen ischiadicum minus) (Figs. 239 and 240) is bounded, in front, by the tuber ischii; above, by the spine and lesser sacro- sciatic ligament; behind, by the greater sacrosciatic ligament. It transmits the tendon of the Obturator internus muscle, its nerve, and the internal pudic vessels and nerve. 3. Articulation of the Sacrum and Coccyx (Symphysis Sacrococcygea). This articulation is an amphiarthrodial joint, formed between the oval surface at the apex of the sacrum and the base of the coccyx. It is analogous to the joints between the bodies of the vertebrae. The ligaments are the Anterior Sacrococcygeal. Posterior Sacrococcygeal. Lateral Sacrococcygeal. Interposed Fibrocartilage. ABTICULATIONS OF THE PELVIS 293 The anterior sacrococcygeal ligament {llgamentum sacrococcygemn anierius) consists of a few irre Made near its posterior surface. STERNOCLAVICULAR ARTICULATION 295 part of the joint, but it occasionally reaches to the front, and may extend the entire length of the cartilage. This cavity may sometimes be demonstrated by making a vertical section of the symphysis pubis near its posterior surface (Fig. 242). The obturator ligament is more properly regarded as analogous to the mus- cular fasciae, with which it will be described. ARTICULATIONS OF THE UPPER EXTREMITY. The articulations of the upper extremity may be arranged in the following groups : I. Sternoclavicular Articulation. II. Acromioclavicular Articulation. III. Ligaments of the Scapula. IV. Shoulder-joint. V. Elbow-joint. VI. Radioulnar Articulations. VII. Wrist-joint. VIII. Articulations of the Carpal Bones. IX. Carpometacarpal Articulations. X. Metacarpophalangeal Articula- tions. XI. Articulations of the Phalanges. I. Sternoclavicular Articulation (Articulatio Stemoclavicularis) (Fig. 243). The sternoclavicular is an arthrodial joint. The parts entering into its forma- tion are the sternal end of the clavicle, the upper and lateral part of the first piece of the sternum, and the cartilage of the first rib. The articular surface of the Fig. 243. — Sternoclavicular articulation. Anterior sternum is covered with hyaline cartilage. The articular surface of the clavicle is much larger than that of the sternum, and invested with a layer of hyaline cartilage' which is considerably thicker than that on the latter bone. The liga- ments of this joint are the Capsular. Anterior Sternoclavicular. Posterior Sternoclavicular. Interclavicular. Costoclavicular. Articular Disk. 1 According to Bruch, the sternal cartilaginous in structure. nd of the clavicle is covered by a tissue which is rather fibrous than 296 THE ARTICULATIONS, OB JOINTS The capsular ligament {capsula articularis) completely surrounds the articula- tion, consisting of fibres of varying degrees of thickness and strength. Those in front and behind are of considerable thickness, and form the anterior and posterior sternoclavicular ligaments; but those above and below, especially in the latter situation, are thin and scanty. The anterior sternoclavicular ligament (Ikjamenium, sternodavicnlare) (Fig. 243) is a part of the capsule. It is a broad band of fibres which covers the anterior surface of the articulation, being attached, above, to the upper and front part of the inner extremity of the clavicle, and, passing obliquely downward and inward, is attached, below, to the upper and front part of the first piece of the sternum. This ligament is covered, m front, by the sternal portion of the Sterno- mastoid and the integument; behind, it is in relation with the articular disk and the two synovial membranes. The posterior sternoclavicular ligament, also a part of the capsule, is a band of fibres which covers the posterior surface of the articulation, being attached, above, to the upper and back part of the inner extremity of the clavicle, and. passing obliquely downward and inward, is attached, below, to the upper and back part of the first piece of the sternum. It is in relation, in fro7it, with the articular disk and synovial membranes; behind, with the Sternohyoid and Sternothyroid muscles. The interclavicular ligament (ligamentum interdaviculare) (Fig. 243) is a flat- tened band which varies considerably in form and size in different individuals; it passes in a curved direction from the upper part of the inner extremity of one clavicle to the other, and is also attached to the upper margin of the sternum. It is in relation, in front, with the integument; behind, with the Sternothyroid muscles. The costoclavicular or rhomboid ligament Qicjamentum costoclavicidare) (Fig. 243) is short, flat, and strong; it is of a rhomboid form, attached, belotv, to the upper and inner part of the cartilage of the first rib; it ascends obliquely back- ward and outward, and is attached, above, to the rhomboid depression on the under surface of the clavicle. It is in relation, in front, with the tendon of origin of the Subciavius; behind, with the subclavian vein. The articular disk (discus articularis) (Fig. 243) is a flat and nearly circular meniscus, interposed between the articulating surfaces of the sternum and clavicle. It is attached, above, to the upper and posterior border of the articular surface of the clavicle; beloiv, to the cartilage of the first rib, at its junction with the sternum; and by its circumference, to the anterior and posterior sternoclavicular and the interclavicular ligaments. It is thicker at the circumference, especially its upper and back part, than at its centre or below. It divides the joint into two cavities, each of which is furnished with a separate synovial membrane. Synovial Membrane. — Of the two synovial membranes found in this articulation, one is reflected from the sternal end of the clavicle over the adjacent surface of the articular disk and cartilage of the first rib; the other is placed between the articular surface of the sternum and adjacent surface of the articular disk; the latter is the larger of the tT\-o. Movements. — This articulation is the centre of the movements of the shoulder, and admits of a limited amount of motion in nearly every direction — upward, downward, backward, for- ward— as well as circumduction. When these movements take place in the joint, the clavicle in its motion carries the scapula with it, this bone gliding on the outer surface of the thorax. This joint therefore forms the centre from which all movements of the supporting arch of the shoulder originate, and is the only point of articulation of this part of the skeleton with the trunk. "The movements attendant on elevation and depression of the shoulder take place between the clavicle and the articular disk, the bone rotating upon the ligament on an axis drawn from before back- ward through its own articular facet. When the shoulder is moved forward and backward, the clavicle, with the articular disk, rolls to and fro on the articular surface of the sternum, revolving, ■with a gliding movement, around an axis drawn nearly vertically through the sternum. In the circumduction of the shoulder, which is compounded of these two inovements, the clavicle revolves ACROMIOCLAVICULAR ARTICULATION 297 upon the articular disk, and the latter, with the clavicle, rolls upon the sternum."' Elevation of the clavicle is principally limited by the costoclavicular ligament; depression by the inter- clavicular. The muscles which raise the clavicle, as in shrugging the shoulder, are the upper fibres of the Trapezius, the Levator anguli scapulae, the clavicular head of the Sternomastoid, assisted to a certain extent by the two Rhomboids, which pull the vertebral border of the scapula backward and upward, and so rai^c (he clavicle. The ilrjircssioii iif (lie chivicle is principally effected by gravity, assisted liy iln- SuUclavius, Pec'omlis niiimi-, ;iiiil Idwcr fibres of the Trape- zius. It is drawn backward \i\ the ifhomboids and the middle and luwcr liUrcs of the Trapezius; smA forward by theSerratus magnus and Pectoralis minor. Surface Form. — The position of the sternoclavicular joint may be easily ascertained by feeling the enlarged sternal end of the collar-bone just external to the long, cord-like, sternal origin of the Sternomastoid muscle. If this muscle is relaxed by bending the head forward, a depres- sion just internal to the end of the clavicle, and between it and the sternum, can be felt, indi- cating the exact position of the joint, which is subcutaneous. When the arm hangs by the side, the cavity of the joint is V-shaped. If the arm is raised, the bones become more closely approxi- mated, and the cavity becomes a mere slit. Applied Anatomy. — The strength of this joint mainly depends upon its ligaments, and it is because of the ligaments and because the force of a blow is generally transmitted along the long axis of the clavicle, that dislocation so rarely occurs, and that the bone is generally broken rather than displaced. When dislocation does occur, the course which the displaced bone takes depends more upon the direction in which the violence was applied than upon the anatomical construction of the joint; it may be either forward, backward, or upward. A complete upward dislocation is also inward. A complete forward or backward dislocation is also inward and downward. The chief point worthy of note, as regards the construction of the joint, in regard to dislocations, is the fact that, owing to the shape of the articular surfaces being so little adapted to each other, and that the strength of the joint mainly depends upon the ligaments, the dis- placement when reduced is very liable to recur, and hence it is extremely difficult to keep the end of the bone in its proper place, and it may be necessary to incise the soft parts and wire the bone in place. II. Acromioclavicular or Scapuloclavicular Articulation (Articulatio Acromioclavicularis) (Fig. 244). The acromioclavicular is an arthrodial joint formed between the outer ex- tremity of the clavicle and the inner margin of the acromion process of the scapula. The ligaments which surround the joint form a capsule. The ligaments of this articulation are the Superior Acromioclavicular. f Trapezoid Inferior Acromioclavicular. Coracoclavicular -! and Articular Disk. [ Conoid. Tlie superior acromioclavicular ligament (Ugamentum acromiodavindare) (Figs 244 and 245) is a portion of the joint capsule. It is a quadrilateral band which covers the superior part of the articulation, extending between the upper part of the outer end of the clavicle and the adjoining part of the upper surface of the acromion. It is composed of parallel fibres which interlace with the aponeurosis of the Trapezius and Deltoid muscles; below, it is in contact with the articular disk (when it exists) and the synovial membranes. The inferior acromioclavicular ligament, somewhat thinner than the preceding, and, like it, a portion of the capsule, covers the under part of the articulation and is attached to the adjoining surfaces of the two bones. It is in relation, above, with the synovial membranes, and in rare cases with the articular disk; below, with the tendon of the Supraspinatus. These two ligaments are con- tinuous with each other in front and behind, and form a complete capsule around the joint. ' Humphry, On the Human Skeleton, p. 402. 298 THE ARTICULATIONS, OB JOINTS The articular disk {discus articularis) is frequently absent in this articulation. When the meniscus exists it is generally incomplete and only partially separates the articular surfaces, and occupies the upper part of the articulation. More jarely it completely separates the joint into two cavities. The Synovial Membrane. — There is usually only one synovial membrane in this articu- lation, but when a complete articular disk exists there are two synovial membranes. The coracoclavicular ligament (ligamentum coracoclaviculare) (Figs. 244 and 245) serves to connect the clavicle with the coracoid process of the scapula. It does not properly belong to this articulation, but as it forms a most efficient means in retaining the clavicle in contact with the acromial process, it is usually described with it. It consists of two fasciculi, called the trapezoid and conoid ligaments. Fig. 244. — The left shoulder-joint, scapuloclavicular articulations, and proper ligaments of the scapula. The trapezoid ligament (ligamentum trapezoidcum), the anterior and external ■fasciculus, is broad, thin, and quadrilateral; it is placed obliquely between the coracoid process and the clavicle. It is attached, below, to the upper surface of the coracoid process; above, to the oblique line on the under surface of the clavicle. Its anterior border is free; its posterior border is joined with the conoid ligament, the two forming by their junction a projecting angle. The conoid ligament (ligamentum conoideum), the posterior and internal fas- ciculus, is a dense band of fibres, conical in form, the base being directed upward, the summit downward. It is attached, below, by its apex to a rough impression at the base of the coracoid process, internal to the trapezoid ligament ; above, by its expanded base, to the conoid tubercle on the under surface of the clavicle, and ■ to a line proceeding internally from it for half an inch. These ligaments are PBOPEB LIGAMENTS OF THE SCAPITLA 299 in relation, in front, with the Subclavius and Deltoid; behind, with the Trapezius. They serve to limit rotation of the scapula, the trapezoid limiting rotation forward, and the conoid backward. Movements. — The movements of this articulation are of two kinds: (1 j A gliding motion of the articular end of the clavicle on the acromion. (2) Rotation of the scapula forward and back- ward upon the clavicle, the extent of this rotation being limited by the two portions of the coraco- ■clavicular ligament. The acromioclavicular joint has important functions in the movements of the upper extremity. It has been well pointed out by Sir George Humphry that if there had been no joint between the clavicle and scapula the circular movement of the scapula on the ribs (as in throwing both shoulders backward or forward) would have been attended with a greater alteration in the direction of the shoulder than is consistent with the free use of the arm in such position, and it would have been impossible to give a blow straight forward with the full force of the arm ; that is tisay, with the combined force of the scapula, arm, and forearm. "This joint," as he happily says^'is so adjusted as to enable either bone to turn in a hinge-like manner upon a vertical Axis drawn through the other, and it permits the surfaces of the scapula, like the baskets in a roundabout swing, to look the same way in every position, or nearly so." Again, when the whole Arch formed by the clavicle and scapula rises and falls (in elevation or depression of the shoul- ders), the joint between these two bones enables the scapula still to maintain its lower part in ■contact with the ribs. Surface Form. — The position of the acromioclavicular joint can generally be ascertained by the sli^tly enlarged extremity of the outer end of the clavicle, which causes it to project above the leva^f the acrDuiion process of the scapula. Sometimes this enlargement is so considerable as to form a mundcd eminence, which is easily to be felt. The joint lies in the plane of a vertical line passing u|) the middle of the front of the arm. Applied Anatomy. — Owing to the slanting shape of the articular surfaces of this joint, the ■commonest didocation is the passing of the acromion process of the scapula under the outer end of the clavicle; but dislocations in the opposite direction have been described. The first form of dislocation is produced by violent force applied to the scapula so as to drive the shoulder forward. The displacement in acromioclavicular dislocation is often incomplete, on account of the strong coracoclavicular ligaments which remain untorn. The same difficulty exists, as in the sternoclavicular dislocation, in maintaining the ends of the bone in apposition after reduction, and it may become necessary to wire them in place after incision of the soft parts. III. Proper Ligaments of the Scapula (Figs. 244, 245). The proper ligaments of the scapula pass between portions of that bone, but are not parts of an articulation. They are the Coracoacromial. Superior Transverse. Inferior Transverse. The coracoacromial ligament (ligamentum coracoacromiale) is a strong triangular band, extending between the coracoid and acromial processes. It is attached, by its apex, to the summit of the acromion just in front of the articular surface for the clavicle, and by its broad base to the whole length of the outer border of the coracoid process. Its posterior fibres are directed inward, its anterior fibres forward and inward. This ligament completes the vault formed by the coracoid and acromion processes for the protection of the head of the humerus. It is in relation, above, with the clavicle and under surface of the Deltoid muscle; below, with the tendon of the Supraspinatus muscle, a bursa being interposed. Its ■Older border is continuous with a dense lamina that passes beneath the Deltoid upon the tendons of the Supra- and Infraspinatus muscles. This ligament is sometimes described as consisting of two marginal bands and a thinner inter- vening portion, the two bands being attached, respectively, to the apex and base of the coracoid process, and joining together at their attachment into the acromion process, ^^^len the Pectoralis minor is inserted, as sometimes is the case, into 300 THE ARTICULATIONS, OR JOINTS the capsule of the shoulder-joint instead of into the coracoid process, it passes between these two bands, and the intervening portion is then deficient. The superior transverse or suprascapular ligament (lit/amentum transversum scapulae swperius) (Figs. 245 and 246) converts the suprascapular notch into a Fig, 245. — Right clavicle and scapula with ligament, from without and somewhat from in front. (Spalteholz.) ELTOID. SUPHASPINATUS. TERES MAJ TEBEs MAJOR. Circumflex vessels. Fig. 246. — Vertical sections through the shoulder-joint, the Circumflex vessels. being vertical and hor SCAPULARIS. ntal. (.\fter Henle.) foramen. It is a thin and flat fasciculus, narrower at the middle than at the extremities, attached by one end to the base of the coracoid process, and by the other to the inner extremity of the scapular notch. The suprascapular nerve passes through the foramen; the suprascapular vessels pass over the ligament. SHO ULDER-JOINT 30 1 An additional ligament, the inferior transverse or spinoglenoid ligament (Ji(j(i- mentum traiisversum scapulae Inferius), is sometimes found on the scapula, stretching from the outer border of the spine to the margin of the glenoid cavity. When present, it forms an arch under which the suprascapular vessels and nerve pass as they enter the infraspinous fossa. Movements. — The scapula is capable of being moved upward and downward, forward and backward, or, by a combination of these movements, circumducted on the wall of the thorax. The muscles which raise the scapula are the upper fibres of the Trapezius, the Levator anguli scapulae, and the two Rhomboids; those which depress it are the lower fibres of the Trapezius, the Pec- toralis minor, and, through the clavicle, the Subclavius. The scapula is drawn hackicard by the Rhomboids and the middle and lower fibres of the Trapezius, and forward by the Serratus magnus and Pectoralis ininor, assisted, when the arm is fixed, by the Pectoralis major. The mobility of the scapula is very considerable, and greatly assists the movements of the arm at the shoulder-joint. Thus, in raising the arm from the side the Deltoid and Supraspinatus can only lift it to a right angle with the trunk, the further elevation of the limb being effected by the Trape- zius and Serratus magnus moving the scapula on the wall of the thorax. This mobility is of special importance in ankylosis of the shoulder-joint, the movement of this bone compensating ito a very great extent for the immobility of the joint. IV. Shoulder-Joint (Articulatio Humeri) (Figs. 245, 246). The shoulder-joint is an enarthrodial or ball-and-socket joint. The bones enter- ing into its formation are the large globular head of the humerus, which is received into the shallow glenoid cavity of the scapula — an arrangement which permits of very considerable movement, while the joint itself is protected against dis- placement by the tendons which surround it and by atmospheric pressure. The ligaments do not maintain the joint surfaces in apposition, because when they alone remain the humerus can be separated to a considerable extent from the glenoid cavity; their use, therefore, is to limit the amount of movement. Above, the joint is protected by an arched vault, formed by the under surfaces of the coracoid and acromion processes, and the coracoacromial ligament. The articular surfaces are covered by a layer of hyaline cartilage; that on the head of the humerus is thicker at the centre than at the circumference, the reverse being the case in the glenoid cavity. The ligaments of the shoulder are the Capsular. Transverse Humeral. Coracohumeral. Glenoid.' The capsular ligament (capsula articularis) (Figs. 245 and 247) completely encircles the articulation, being attached, above, to the circumference of the glenoid cavity beyond the glenoid ligament, below, to the anatomical neck of the humerus, approaching nearer to the articular cartilage above than- in the rest of its extent. It is thicker above and below than elsewhere, and is remarkably loose and lax, and much larger and longer than is necessary to keep the bones in contact, allowing them to be separated from each other more than an inch — an evident provision for that extreme freedom of movement which is peculiar to this articulation. Its superficial surface is strengthened, above, by the Supra- spinatus; below, by the long head of the Triceps; behind, by the tendons of the Infraspinatus and Teres minor; and in front, by the tendon of the Subscapularis. The capsular ligament usually presents three openings: One anteriorly, below the coracoid process, establishes a communication between the synovial mem- brane of the joint and a bursa beneath the tendon of the Subscapularis muscle. 1 The long tendon of origin of the Biceps brachii muscle also acts as one of the ligaments of this joint. See the observations on p. 267 on the function of the muscles passing over more than one joint. 302 THE ARTICULATIONS, OB JOINTS The second, which is not constant, is at the posterior part, where a communica- tion sometimes exists between the joint and a bursal sac belonging to the Infra- spinatus muscle. The third is seen between the two tuberosities, for the passage of tlie long tendon of the Biceps brachii muscle. It transmits a sac-like prolonga- tion of the synovial membrane, which ends as a blind pouch opposite the surgicaL neck of the bone. The coracohumeral ligament (ligamentum coracohumerale) (Fig. 244) is a broad band which strengthens the upper part of the capsular ligament. It arises from the outer border of the coracoid process, and passes obliquely downward and outward to the front of the gi'eat tuberosity of the humerus, being blended with the tendon of the Supraspinatus muscle. This ligament is intimately united tO' the capsular ligament throughout the greater part of its extent. SUPERIOR TRANSVERSE LIGAMENT Fig. 247. — Right shoulder-joint, frontal section, from behind. (Spalteholz.) Supplemental Bands of the Capsular Ligament. — In addition to the coracohumeral ligament, the capsular ligament is strengthened by supplemental bands in the interior of the joint, and can be best studied by opening the capsule from behind and removing the head of the humerus. One of these bands (Flood's ligament) passes from the anterior edge of the glenoid cavity to the lower part of the lesser tuberosity of the humerus. It is supposed to correspond with the ligamentum teres of the hip-joint. A second of these bands (Schlemm's ligament), is situated at the lower part of the joint, and passes from the under edge of the glenoid cavity to the under part of the neck of the humerus. A third, called the glenohumera.l ligament, is situated at the upper part of the joint. It is attached, above, to the apex of the glenoid cavity, close to the root of the coracoid process, and, passing downward along the inner edge of the tendon of the Biceps brachii, is attached, below, above the lesser tuberosity of the humerus, where it forms the inner boundary SHOULDER-JOINT 303 of the upper part of the bicipital groove. It is a thin, ribbon-like band, occasion- ally quite free from the capsule. The transverse humeral ligament is a prolongation of the capsular ligament. It is a broad hand of fibrous tissue passing from the lesser to the greater tuber- osity of the humerus, and always limited to that portion of the bone which lies above the epiphyseal line. It converts the bicipital groove into an osseoaponeu- rotic canal, and is the homologue of the strong process of bone which connects the summits of the two tuberosities in the musk o.x. The glenoid ligament {labrum glenoidale) (Figs. 245 and 247) is a fibrocartilagi- nous rim, attached around the margin of the glenoid cavity. It is triangular on section, the thickest portion being fixed to the circumference of the cavity, the free edge being thin and sharp. It is continuous above with the long tendon of the Biceps muscle, which bifurcates at the upper part of the cavity into two fasciculi, and becomes continuous with the fibrous tissue of the glenoid ligament. This ligament deepens the cavity for articulation, and protects the edges of the bone. Synovial Membrane (Fig. 247). — The synovial membrane is reflected from the margin of the glenoid cavity over the fibrocartilaginous rim surrounding it; it is then reflected over the internal surface of the capsular ligament, covers the lower part and sides of the anatomical neck of the humerus as far as the cartilage covering the head of the bone. The long tendon of the Biceps brachii, which passes through the capsular ligament, is enclosed in a tubular sheath of synovial membrane (vagina mucosa intertubercularis), which is reflected upon it at the point vvhere it perforates the capsule, and is continued around it as far as the level of the surgical neck of the humerus. The tendon of the Biceps is thus enabled to traverse the articulation, but it is not contained in the interior of the synovial cavity. Bursse. — A large bursa, the subscapular bursa, exists between the joint capsule and the ten- don of the Subscapularis muscle. I'liis sa<' communicates with the shoulder-joint by means of an opening at the inner side of the ciipsular ligament. Occasionally another and smaller bursa, the infraspinatus bursa, exists beneath the tendon of the Infraspinatus. It communicates with the shoukier-joint by means of an opening in the outer surface of the capsule. The subdeltoid or subacromial bursa is placed between the under surface of the Deltoid muscle and the outer surface of the capsule. It does not communicate with the joint. The subcutaneous acromial bursa is between the surface and the summit of the acromion process. There is a bursa beneath the Coracobrachialis muscle, one beneath the Teres major, and one beneath the tendinous portion of the Latissimus dorsi. There is also a bursa between the tendon of insertion of the Pectoralis major muscle and the long head of the Biceps. The muscles in relation with the joint are, above, theSupraspinatus; beloiv, the long head of the Triceps; mfronf, the Subscapularis; behind, the Infraspinatus and Teres minor; wiihiii, the long tendon of the Biceps. The Deltoid is placed most externally, and covers the articulation on its outer side, as well as in front and behind. The arteries supplying the joint are articular branches of the anterior and posterior circum- flex, and the suprascapular. The nerves are derived from the circumflex and suprascapular. Movements. — The shoulder-joint is capable of movement in every direction, forward, back- ward, abduction, adduction, circumduction, and rotation. The humerus is drawn fonvard by the Pectoralis major, anterior fibres of the Deltoid, Coracobrachialis, and by the Biceps when the forearm is flexed; backward, by the Latissimus dorsi. Teres major, posterior fibres of the Del- toid, and by the Triceps when the forearm is extended; it is abducted (elevated) by the Del- toid andSupraspinatus; it is adducted (depressed) by the Subscapularis, Pectoralis major, Latis- simus dorsi, and Teres major; it is rotated outward by the Infraspinatus and Teres minor; and it is rotated inward by the Subscapularis, Latissimus dorsi. Teres major, and Pectoralis major. The most striking peculiarities in this joint are: (1 ) The large size of the head of the humerus in comparison with the depth of the glenoid cavity, even when supplemented by the glenoid ligament. (2) The looseness of the capsule of the joint. (3) The intimate connection of the cap- sule with the muscles attached to the head of the humerus. (4) The peculiar relation of the Biceps tendon to the joint. It is in consequence of the relative size of the two articular surfaces that the joint enjoys such free movement in every possible direction. When these movements of the arm are arrested in the shoulder-joint by the contact of the bony surfaces and by the tension of the corresponding fibres of the capsule, together with that of the muscles acting as accessory ligaments, they can be carried considerably farther by the movements of the scapula, involving, of course, motion at 304 THE ARTICULATIONS, OR JOINTS the acromio- and sternoclavicular joints. These joints are therefore to be regarded as accessory structures to the shoulder-joint.' The extent of these movements of the scapula is very con- siderable, especially in extreme elevation of the arm, which movement is best accomplished when the arm is thrown somewhat forward and outward, because the margin of the head of the humerus is by no means a true circle; its greatest diameter is from the bicipital groove downward, inward, and backward, and the greatest elevation of the arm can be obtained by rolling its articular surface in the direction of this measurement. The great width of the central portion of the humeral head also allows of very free horizontal movement when the arm is raised to a rifht ancle, in which movement the arch formed by the acromion, the coracoid process, and the coracoacromial ligament constitutes a sort of supplemental articular cavity for the head of the bone. The looseness of the capsule is so great that the arm will fall about an inch from the scapula when the muscles are dissected from the capsular ligament and an opening made in it to remove the atmospheric pressure. The movements of the joint, therefore, are. not regulated by the capsule so much as by the surrounding muscles and by the pressure of the atmosphere — an arrangement which "renders the movements of the joint much more easy than they would otherwise have been, and permits a swinging, pendulum-like vibration of the limb when the muscles are at rest" (Humphry). The fact, also, that in all ordinary positions of the joint the ■capsule is not put on the stretch enables the arm to move freely in all directions. Extreme movements are checked by the tension of appropriate portions of the capsule, as well as by the interlocking of the bones. Thus it is said that "abduction is checked by the contact of the great tuberosity with the upper edge of the glenoid cavity, adduction by the tension of the coraco- humeral ligament" (Beaunis et Bouchard). Cleland^ maintains that the limitations of move- ment at the shoulder-joint are due to the structure of the joint itself, the glenoid ligament fitting, in different positions of the elevated arm, into the anatomical neck of the humerus. Cathcart^ has pointed out that in abducting the arm and raising it above the head, the scapula TOtates throughout the whole movement with the exception of a short space at the beginning and at the end; that the humerus moves on the scapula not only from the hanging to the horizontal position, but also in passing upward as it approaches the vertical above; that the clavicle moves not only during the second half of the movement but in the first as well, though to a less extent — i. p., the scapula and clavicle are concerned in the first stage as well as in the second; and that the humerus is partly involved in the second as well as chiefly in the first. The intimate union of the tendons of the four short muscles with the capsule converts these muscles into elastic and spontaneously acting ligaments of the joint, and it is regarded as being also intended to prevent the folds into which all portions of the capsule would alternately fall in the varying positions of the joint from being driven between the bones by the pressure of the atmosphere. The peculiar relations of the Biceps tendon to the shoulder-joint appear to subserve various purposes. In the first place, by its connection with both the shoulder and elbow the muscle harmonizes the action of the two joints, and acts as an elastic ligament in all positions, in the manner previously adverted to.* .\^ext, it strengthens the upper part of the articular cavity, and prevents the head of the humerus from being pressed up against the acromion process, when the Deltoid contracts, instead of forming the centre of motion in the glenoid cavity. By its passage .along the bicipital groove it assists in rendering the head of the humerus steady in the various movements of the arm. ^Vhen the arm is raised from the side it assists the Supra- and Infra- spinatus in rotating the head of the humerus in the glenoid cavity. It also holds the head of the bone firmly in contact with the glenoid cavity, and prevents its slipping over its lower edge, or lieincf displaced by the action of the Latissimus dorsi and Pectoralis major, as in climbing and many other movements. Surface Form. — The direction and position of the shoulder-joint may be indicated by a line •drawn from the middle of the coracoacromial ligament, in a curved direction, with its con- vexity inward, to the innermost part of that portion of the head of the humerus which can be -felt in the axilla when the arm is forcibly abducted from the side. When the arm hangs by the side, not more than one-third of the head of the bone is in contact with the glenoid cavity, and three-quarters of its circumference is in front of a vertical line drawn from the anterior border •of the acromion process. Applied Anatomy. — Owing to the construction of the shoulder-joint and the freedom of movement which it enjoys, as well as in consequence of its exposed situation, it is more fre- ■quently dislocated than any other joint in the body. Dislocations of the shoulder contribute about forty per cent, of the cases in tables of dislocations. Dislocation occurs when the arm is thrown into extreme abduction, and when, therefore, the head of the humerus presses against ithe lower and front part of the capsule, which is the thinnest and least supported part of the liga- i See p. 299. ^ Journal of Anatomy and Physiology, 1884, vol. xviii. 8Ibid.,voI. xviii. < See p. 267. SHOULDEE^ JOINT 305 ment. The rent in the capsule ahnost invarialily takes jilace in this situation, between the tendon of the Subscapularis and the Triceps, and thn)ui:i;h it the head of the bone escapes, so that the dislocation in most instances is primarily subijlinoid. The head of the bone does not usually remain in this situation, but generally assumes some other position, which varies accord- ing to the direction and amount of force producing the dislocation and the relative strength of the muscles in front and behind the joint. In consequence of the muscles at the back being weaker than those in front, and especially on account of the long head of the Triceps preventing the bone passing backward, dislocation forward is much more common than backward. The most frequent position which the head of the humerus ultimately assumes is on the front of the neck of the scapula, beneath the coracoid process, and hence named subcoracoid dislocation. Occasionally, in consequence, probably, of a greater amount of force being brought to bear on the limb, the head is driven farther inward, and rests on the upper part of the front of the thorax, beneath the clavicle (subclamcular). If the head of the bone passes under the Subscapularis muscle and also under the Teres major or the lower border of the Pectoralis major, the arm remains abducted, or even with the elbow raised above the head (luxatio erecta). Sometimes the humerus remains in the position in which it was primarily displaced, resting on the axillary border of the scapula {subijlenoid), and rarely it passes backward and remains in the infra- spinous fossa beneath the spine (subspinous). If dislocation frequently recurs the condition may be amended in some cases by exposing the capsule and putting tucks in it by means of sutures. An old unreduced dislocation is sometimes treated by incising the soft parts and returning the head of the humerus into the glenoid cavity. In other cases the head of the humerus is excised. Dislocation oi the long tendon of the Biceps muscle from the bicipital groove is a rare accident. When it occurs the arm is rigid in abduction, but the head of the humerus is found to be in the glenoid cavity. It is reduced by flexion of the elbow and rotation of the arm. Rup- ture of the long tendon of the Biceps is more common than dislocation of the tendon. After this injury the belly of the muscle is relaxed and is nearer than normal to the elbow; flexion of the forearm is much weakened, and is weaker in supination than it is in pronation. The head of the humerus passes forward and inward, and the condition is often mistaken for dislocation of the bone. If we desire to aspirate the shoulder-joint, place the arm against the side, flex the forearm at a right angle to the arm, carry the forearm across the front of the thorax, and enter the trocar below the acromion (De Vos). The shoulder-joint is sometimes the seat of all those inflammatory affection,?, both acute and chronic, which attack joints, though perhaps it suffers less frequently than some other joints of equal size and importance. Acute synovitis may result from injury, rheumatism, or pyemia, or may follow secondarily on the so-called acute epiphysitis of infants. It is attended with effusion into the joint, and when this occurs the capsule is evenly distended and the contour of the joint rounded. Special projections may occur at the site of the openings in the capsular ligament. Thus, a swelling may appear just in front of the joint, internal to the lesser tuberosity, from effusion into the bursa beneath the Subscapularis muscle; or, again, a swelling which is some- times bilobed may be seen in the interval between the Deltoid and Pectoralis major muscles, from effusion into the diverticulum, which runs down the bicipital groove with the tendon of the Biceps. The effusion into the synovial membrane can be best ascertained by examination from the axilla, where a soft, elastic, fluctuating swelling can usually be felt. The bursa beneath the Deltoid is sometimes ruptured by violence, and sometimes inflames, suppurates, or becomes tuberculous. Tuberculous arthritis not infrequently attacks the shoulder-joint, and may lead to total destruction of the articulation, when ankylosis may result or long-protracted suppuration may necessitate excision. This joint is also one of those which is most liable to be the seat of osteo- arthritis, and may also be affected in gout and rheumatism; or in locomotor ataxia, when it occasionally becomes the seat of Charcot's disease. E.xdsion of the shoulder-joint may be required in cases of arthritis (especially the tubercu- lous form) which have gone on to destruction of the articulation; in compound di^locaticms and fractures, particularly those arising from gunshot injuries, in which there has been extensive injury to the head of the bone; in some cases of old unreduced dislocation, where there is much pain; and possibly in some few cases of growth connected with the upper end of the bone. The operation is best performed by making an incision from the middle of the coracoacromial liga- ment down the arm for about three inches; this will expose the- bicipital groove and the tendon of the Biceps, which may be either divided or hooked out of the way, according as to whether it is implicated in the disease or not. The capsule is then freely opened, and the muscles attached to the greater and lesser tuberosities of the humerus divided. The head of the bone can then be thrust out of the wound and sawed off, or divided with a narrow saw in situ and subsequently removed. The section should be made, if possible, just below the articular surface, so as to leave the bone as long as possible. The glenoid cavity must then be examined, and gouged if carious. 20 306 THE ARTICULATIONS, OB JOINTS V. Elbow-joint (Articulatio Cubiti) (Figs. 248, 249). The elbow is a ginglymus or hinge-joint. The bones entering into its forma- tion are the trochlea of the humerus, which is received into the greater sigmoid cavity of the ulna, and admits of the movements peculiar to such a joint — viz., flexion and extension; while the capitellum or radial head of the humerus articu- lates with the cup-shaped depression on the head of the radius; the circum- ference of the head of the radius articulates with the lesser sigmoid cavity of the ulna, allowing of the movement of rotation of the radius on the ulna, the chief action of the superior radioulnar articulation. The articular surfaces are covered by a thin layer of hyaline cartilage, and connected by a capsular Fig. 248. — Left elbow-joint, showing anterior and internal ligaments. Fig. 249. — Left elbow-joint, showing posterior and external ligaments. ligament (capsula articulafis) (Fig. 250) of unequal thickness, being especially thickened on its two sides and, to a less extent, in front and behind. These thickened portions are usually described as distinct ligaments under the following names: Anterior. Posterior. Internal Lateral. External Lateral, ELBOW JOINT 307 The orbicular ligament of the upper radio-ulnar articulation must also be reckoned among the ligaments of the elbow (see p. 310). The anterior ligament (Fig. 248) is a broad and thin fibrous layer which covers the anterior surface of the joint. It is attached, above, to the front of the internal condyle and to the front of the humerus immediately above the coronoid and radial fossae; belotv, to the anterior surface of the coronoid process of the ulna and to the orbicular ligament, being continuous on each side with the lateral ligaments. Its superficial fibres pass obliquely from the inner condyle of the humerus outward to the orbicular ligament. The middle fibres, vertical in direction, pass from the upper part of the coronoid depression and become partly blended with the preceding, but are mainly inserted into the anterior surface of the coronoid process. The deep or transverse set inter- sects these at right angles. This ligament is in relation, in front, with the Brachialis anticus muscle, except at its outermost part. The posterior ligament (Fig. 249) is a thin and loose membranous fold, attached, above, to the lower end of the humerus, above and at the sides of the olecranon fossa; below, to the groove on the upper and outer sur- faces of the olecranon. The superficial or transverse fibres pass between the adjacent margins of the olecranon fossa. The deeper portion consists of vertical fibres, some of which, thin and weak, pass from the upper part of the olecranon fossa to the margin of the olecranon; others, thicker and stronger, pass from the back of the capltellum of the humerus to the posterior border of the lesser sigmoid cavity of the ulna. This ligament is in relation, behind, with the tendon of the Triceps muscle and the Anconeus muscle. The internal lateral ligament (ligamentum collaterale ulnare) (Fig. 248) is a thick triangular band consisting of two portions, an anterior and posterior, united by a thinner intermediate portion. The anterior portion, directed obliquely forward, is attached, above, by its apex, to the front part of the internal condyle of the humerus; and, below, by its broad base, to the inner margin of the coronoid process. The posterior portion, also of triangular form, is attached, above, by its apex, to the lower and back part of the internal condyle; below, to the inner margin of the olecranon. Between these two bands a few intermediate fibres descend from the internal condyle to blend with a transverse band of ligamentous 50. — Right elbow-joint, cut tlirough at right angles to the of the trochlea humeri, from the ulnar side. (Spalteholz.) 308 THE ARTICULATIONS, OR JOINTS tissue which bridges across the notch between the olecranon and coronoid pro- cesses. This ligament is in relation, internally, with the Triceps and Flexor carpi ulnaris muscles and the ulnar nerve, and gives origin to part of the Flexor sublimis digitorum muscle. The external lateral ligament {ligamenhmi collatemle radiale) (Fig. 249) is a short and narrow fibrous band less distinct than the internal, attached, above, to a depression below the external condyle of the humerus; below, to the orbicular ligament, some of its most posterior fibres passing over that ligament, to be inserted into the outer margin of the ulna. This ligament is intimately blended with the tendon of origin of the Supinator [brevis] muscle. Synovial Membrane (Fig. 250). — The synovial itiembrane is very extensive. It covers the margin of the articular surface of the humerus, and lines the coronoid and olecranon fossae on that bone; from these points it is reflected over the anterior, posterior, and lateral ligaments, and forms a pouch (recessus sacciformis) between the lesser sigmoid cavity, the internal surface of the orbicular ligament, and the circumference of the head of the radius. Projecting into the cavity is a crescentic fold of synovial membrane, between the radius and ulna, suggesting the division of the joint into two — one the humeroradial, the other the humeroulnar. Between the capsular ligament and the synovial membrane are three masses of fat — one, the largest, above the olecranon fossa, which is pressed into the fossa by the Triceps during flexion; a second, over the coronoid fossa; and a third, over the radial fossa. The two last-named pads are pressed into their respective fossse during extension. The muscles (Fig. 251) in relation with the joint are, in front, the Brachialis anticus; behind, the Triceps and Anconeus; externally, the Supinator [brevis] and the common tendon of origin of the Extensor muscles; internally, the common tendon of origin of the Flexor muscles, and the Flexor carpi ulnaris, with the ulnar nerve. The arteries supplying the joint are derived from the anastomosis between the superior pro- funda, inferior profunda, and anastomotica magna, branches of the brachial, with the anterior, pos- terior, and interosseous recurrent branches of the ulnar and the recurrent branch of the radial. These vessels form a complete chain of anasto- moses around the joint. The nerves are derived from the ulnar as it passes between the internal condyle and the olec- ranon ; a filament from the musculocutaneous, and two filaments from the median. Bursse.^The olecranon hva&a, {bursa snbcnfanea olecrani) is placed between the olecranon process and the cutaneous surface. A bursa exists between the tendon of the Biceps brachii and the tubercle of the radius (bursa bicipitoradialis); another between the Triceps tendon and the olecranon process {bursa subtendinea olecrani) ; a third between the cutaneous surface and the external condyle {bursa subcuianea epicondyli humeri lateralis) ; a fourth between the cutaneous surface and the internt,! condyle {bursa subcutanea epicondyli humeri ?nedialis); and a fifth internal to the Triceps ttndon at its insertion on the olecranon {bursa intratendi?iea olecrani). Movements. — The elbow-joint comprises three different portions — viz., the joint between the ulna and humerus, that between the head of the radius and the humerus, and the superior radioulnar articulation, described below. All these articular surfaces are invested by a common synovial membrane, and the movements of the whole joint should be studied together. The com- bination of the movements of flexion and extension of the forearm with those of pronation and supination of the hand, which is insured by the two being performed at the same joint, is essential to the accuracy of the various minure movements of the hand. The portion of the joint between the ulna and humerus is a simple hinge-joint, and allows Fig 2d1 ^ It I ) , I joint taken somewhat obhquelj d the radial aspect (A.fter Braune ) ELBOW-JOINT 309 of movements of flexion and extension only. Owing to the obliquity of the trochlear surface of the humerus, this movement does not take place in a straight line. When the forearm is extended and supinated the axis of the arm is not in the same line as the axis of the forearm, but the axis of the arm forms an angle with the axis of the forearm, and the hand, with the forearm, is directed outward. During flexion, on the other hand, the forearm and the hand tend to approach the middle line of the body, and thus enable the hand to be easily carried to the face. The shape of the articular surface of the humerus, with its prominences and depressions accurately adapted to the opposing surface of the olecranon, prevents any lateral movement. Flexion is produced by the action of the Biceps and Brachialis anticus, assisted by the muscles arising from the inter- nal condyle of the humerus and by the Brachioradialis; extension, by the Triceps and Anconeus, assisted by the Extensors of the wrist and by the Extensor communis digitorum and Extensor minimi digiti. The joint between the head of the radius and the capitellum or radial head of the humerus is an arthrodial joint. The bony surfaces would of themselves constitute an enarthrosis, and allow- of the movement in all directions were it not for the orbicular ligament by which the head of the radius is bound down firmly to the lesser sigmoid cavity of the ulna, an arrangement which prevents any lateral separation of the two bones. It is to the same ligament that the head of the radius owes its security from dislocation, which would otherwise constantly occur as a con- sequence of the shallowness of the cup-like surface on the head of the radius. In fact, but for this ligament the tendon of the Biceps would be liable to pull the head of the radius out of joint.' In complete extension the head of the radius glides so far back on the outer condyle that its edge is plainly felt at the back of the articulation. Flexion and extension of the elbow-joint are limited by the tension of the structures on the front and back of the joint, the limitation of flexion being also aided by the soft structures of the arm and forearm coming in contact. In combination with any position of flexion or extension the head of the radius can be rotated in the upper radioulnar joint, carrying the hand with it. The hand is directly articulated to the lower surface of the radius only, and the concave or sigmoid surface on the lower end of the radius travels around the lower end of the ulna. The latter bone is excluded from the wrist-joint (as will be seen in the sequel) by the articular disk. Thus, rotation of the head of the radius around an axis which passes through the centre of the radial head of the humerus imparts circular movement to the hand through a very considerable arc. Surface Form. — If the forearm be slightly flexed on the arm, a curved crease or fold with its convexity downward may be seen running across the front of the elbow, extending from one condyle to the other. The centre of this fold is some slight distance above the line of the joint. The position of the radiohumeral portion of the joint can be at once ascertained by feeling for a slight groove or depression between the head of the radius and the capitellum of the humerus at the back of the articulation. Applied Anatomy. — From the great breadth of the joint, and the manner in which the articular surfaces are interlocked, and also on account of the strong lateral ligaments and the support which the joint derives from the mass of muscles attached to each condyle of the humerus, lateral displacement of the bones is very uncommon, whereas antero-posterivr dislocation, on account of the shortness of the antero-posterior diameter, the weakness of the anterior and posterior ligaments, and the want of support of muscles, much more frequently takes place, dislocation backward taking place when the forearm is in a position of extension, and forward when in a position of flexion. For, in the former position, that of extension, the coronoid process is not interlocked into the coronoid fossa, and loses its grip to a certain extent, whereas the olecranon process is in the olecranon fossa, and entirely prevents displacement forward. On the other hand, during flexion, the coronoid process is in the coronoid fossa, and prevents dis- location backward, while the olecranon loses its grip and is not so efficient, as during extension, in preventing a forward displacement. When lateral dislocation does take place, it is generally incomplete. Dislocation of the elbow-joint is of common occurrence in children, far more common than dislocation of any other articulation. In lesions of this joint there is often very great difficultv in ascertaining the exact nature of the injury. Sprain of the elbow is a very common injury in child- hood. Injury to the radiohumeral joint is frequently ]>roduced by lifting a child by the hand, as in swinging it over a gutter. The Supinator [brevis], which under normal circumstances would retain the head of the radius against the capitellum of the humerus, is unable to do so, the radio- humeral articulation receives the force and the orbicular ligament undergoes upward displace- ment, is caught between the head of the radius and the capitellum, and jams the joint. This injury is often called subluxation of the head of the radius. The elbow-joint is occasionally the seat of acute synovitis. The synovial membrane then becomes distended with fluid, the bulging showing itself principally around the olecranon process; that is to say, on its inner and outer sides and above, in consequence of the laxness of the ' Humphry, op. cit.. p. 419. 310 THE ARTICULATIONS, OB JOINTS posterior ligament. Occasionally, a weE-marked, triangular projection may be seen on the outer side of the olecranon, from bulging of the synovial membrane beneath the Anconeus muscle. A^ain, there is often some swelling just above the head of the radius, in the line of the radio- humeral joint. There is generally not much swelling at the front of the joint, though sometime'^ deep-seated fulness beneath the Brachialis anticus may be noted. When suppuration occurs rlifj abscess usually points at one or other border of the Triceps muscle; occasionally the pus dis- charges itself in front, near the insertion of the Brachialis anticus muscle. Chronic synovitis, usually of tuberculous origin, is of common occurrence in the elbow-joint; under these circum- stance's the forearm tends to assume the position of semiflexion, which is that of greatest ease and relaxation of ligaments. It should be borne in mind that should ankylosis occur in this or the extended position, the limb will not be nearly so useful as if it becomes ankylosed in a position of rather less than a right angle. Loose cartilages- are sometimes met with in the elbow-joint, not so commonly, however, as in the knee; nor do they, as a rule, give rise to such urgent symp- toms. They rarely require operative interference. The elbow-joint is also sometimes affected with osteoarthritis, but this affection is less common in this articulation than in some other of the larger joints. Bursitis about the elbow, generally known as miners' elboiv, is not uncommon. Excision of the elbow is principally required for one of three conditions — viz., tuberculous arthritis, injury and its results, and ankylosis in a positior. which greatly impairs the useful- ness of the limb; but may be necessary for some other rarer conditions, such as disorganizing arthritis after pyemia, unreduced dislocation, and osteoarthritis. The results of the operation are, as a rule, more favorable than those of excision of any other joint, and it is one, therefore, that the surgeon should never hesitate to perform, especially in the first three of the conditions mentioned above. The operation is best performed by a single vertical incision down the back of the joint, a transverse incision, over the outer condyle, being added if the parts are much thickened and fixed. A straight incision is made about four inches long, the mid-point of which is on a level with and a little to the inner side of the tip of the olecranon. This incision is made down to the bone, through the substance of the Triceps muscle. The operator with the point of his knife, and guarding the soft parts with his thumb-nail, separates them from the bone. In doing this there are two structures which he should carefully avoid — the ulnar nerve, which lies parallel to his incision, but a little internal, as it courses down between the internal condyle and the olecranon process, and the prolongation of the Triceps into the deep fascia of the fore- arm over the Anconeus muscle. Having cleared the bones and divided the lateral and posterior lio-aments, the forearm is strongly flexed and the ends of the bone turned out and sawed off. The section of the humerus should be through the base of the condyles, that of the ulna and radius should be just below the level of the lesser sigmoid cavity of the ulna and the neck of the radius. In this operation the object is to obtain such fibrous union as shall allow free motion of the bones of the forearm: and, therefore, passive motion must be commenced early, that is to say, about the tenth day. VT. Radioulnar Articulation (Articulatio Radioulnaris) . The articulation of the radius with the ulna is effected by ligaments which connect both extremities as well as the shafts of these bones. It may, conse- quently, be subdivided into three articulations: (1) The superior radioulnar, which is a portion of tlie elbow-joint; (2) the middle radioulnar; and (3) the inferior radioulnar articulations. 1. Superior Articulation (Articulatio Radioulnaris Proximalis). This articulation is a trochoid or pivot-joint. The bones entering into its forma- tion are the inner side of the circumference of the head of the radius rotating within tlie lesser sigmoid cavity of the ulna. Its only ligament is the annular or orbicular. The orbicular or annular ligament (Jigamenium annulare radii) (Figs. 248, 249, and 2.52) is a strong, flat band of ligamentous fibres which surrounds the head of the radius and retains it in firm connection with tire lesser sigmoid cavity of the ulna. It fonns about four-fifths of an osseofibrous ring, attached by each end to tlie extremities of the lesser sigmoid cavity, and is smaller at the lower part of its BA DIO ULNAR A R TICULA TION 311 ORBICULAR circumference than above, by which means the head of the radius is more securely held in its position. Its outer surface is strengthened by the external lateral ligament of the elbow, and affords origin to part of the Supinator [brevis] muscle. Its inner surface is smooth, and lined with synovial membrane. The synovial mem brane is continuous with that which lines the elbow-joint. Movements. — The movement which takes place in this articulation is limited to rotation of the head of the radius within the orbicular ligament, and upon the lesser sigmoid cavity of the ulna; the axis of rotation passes through the centre of the capitellum of the humerus. Rotation forward is called pronation; rota- tion backward, supinaiion. Supination is performed by the Biceps and Supinator [brevis], assisted to a slight extent by the Ex- tensor muscles of the thumb and, in certain positions, by the Brachioradialis. Pronation is effected by the Pronator teres and Pronator quadratus, assisted, in some positions, by the BrJichioradialis. Surface Form. — The position of the su- perior radioulnar joint is marked on the surface of the body by the little dimple on the back of the elbow, which indicates the position of the head of the radius. Applied Anatomy.— D;.?/oca(?o». of the head of the radius alone is not an uncommon accident, and occurs most frequently in young persons from falls on the hand when the fore- arm is extended and supinated, the head of the bone being displaced forward. It is at- tended by rupture of the orbicular ligament. Occasionally a peculiar injury, which is sup- posed to be a subluxation, occurs in young children in lifting them from the ground by the hand or forearm. It is believed that the head of the radius is displaced downward or the orbicular ligament upward, and the upper border of the ligament becomes folded over the head of the radius, between it and the capitellum of the humerus. 2. Middle R.\dioulnar Lig.\ments. ' The interval between the shafts of the radius and ulna is occupied by two ligaments. Oblique. Interosseous. The oblique ligament (chorda ohli- ^'°- '""-^^eX ^4lt\■s1LV'°Ts^™teh;lz^ *'"' "'"" qua) (Figs. 248 and 252) is a small, flat- tened fibrous band which extends obliquely downward and outward from the tubercle of the ulna at the base of the coronoid process to the radius a little below the bicipital tuberosity. Its fibres run in the opposite direction to those of the 312 THE ARTICULATIONS, OB JOINTS interosseous ligament, and it appears to be placed as a substitute for it in the upper part of the interosseous interval. This ligament is sometimes wanting. The interosseous membrane (membrana interossea antehrachii) (Fig. 252) is a broad and thin plane of fibrous tissue descending obliquely downward and inward, from the interosseous ridge on the radius to that on the ulna. It is deficient above, commencing about an inch beneath the tubercle of the radius; is broader in the middle than at either extremity; and presents an oval aperture just above its lower margin for the passage of the anterior interosseous vessels to the back of the forearm. This ligament serves to connect the bones and to increase the extent of surface for the attachment of the deep muscles. Between its upper border and the oblique ligament an interval exists through which the posterior inter- osseous vessels pass to the dorsum of the forearm. Two or three fibrous bands are occasionally found on the dorsal surface of this membrane which descend obliquely from the ulna toward the radius, and which have consequently a direc- tion contrary to that of the other fibres. It is in relation, in front, by its upper three-fourths with the Flexor longus pollicis on the outer side, and with the Flexor profundus digitorum on the inner, lying upon the interval between which are the anterior interosseous vessels and nerve; by its lower fourth, with the Pro- nator quadratus; behind, with the Supinator [brevis]. Extensor ossis metacarpi pollicis, Extensor brevis pollicis. Extensor longus pollicis. Extensor indicis; and, near the wrist, with the anterior interosseous artery and posterior interosseous 3. Inferior Articulation (Articulatio Radioulnaris Distalis). This is a pivot-joint, formed by the sigmoid cavity at the inner side of the lower end of the radius receiving the head of the ulna. The articular surfaces are covered by a thin layer of hyaline cartilage, and connected by a capsule, portions of which are usually described as distinct ligaments. The ligaments of the articulation are: Anterior Radioulnar. Posterior Radioulnar. Triangular Articular Disk. The anterior radioulnar ligament (Fig. 253) is a narrow band of fibres extending from the anterior margin of the sigmoid cavity of the radius to the anterior surface of the head of the ulna. The posterior radioulnar ligament (Fig. 254) extends between similar points on the posterior surface of the articulation. The triangular articular disk (discus articularis) (Figs. 252 and 256) is triangular in shape, and is placed transversely beneath the head of the ulna, binding the lower end of this bone and the radius firmly together. Its periphery is thicker than its centre, which is thin and occasionally perforated. It is attached by its apex to a depression which separates the styloid process of the ulna from the head of that bone; and by its base, which is thin, to the prominent edge of the radius, which separates the sigmoid cavity from the carpal articulating surface. Its margins are united to the ligaments of the wrist-joint. Its upper surface, smooth and concave, articulates with the head of the ulna, forming an arthrodial joint; its under surface, also concave and smooth, forms part of the wrist-joint and articu- lates with the cuneiform and inner part of the semilunar bone. Both surfaces are covered by a synovial membrane — the upper surface by one peculiar to the radioulnar articulation; the under surface, by the synovial membrane of the wrist. RADIOULNAR ARTICULATION 3l3 Synovial Membrane. — The synovial membrane (Fig. 256) of this articulation has been called, from its extreme looseness, the membrana sacciformis. It projects horizontally inward between the head of the ulna and the articular disk, and upward' between the radius and the ulna, forming a very loose cul-de-sac {reccssus sacciformis). The quantity of synovia which it contains is usually considerable. The inferior radioulnar joint does not communicate with the wrist-joint. radioulnar articulation. Carpometacarpal iculatimis. Fig. 253, — Ligaments of wrist and hand. Anterior viewv Inferior radioulnar articulation Wrist-joint Carpal articulations Carpometacarpal articulation Fig. 254. — Ligaments of wrist and hand. Posterior i Movements.— These consist of a movement of rotation through about 1 60 degrees of the lower end of the radius around an axis which corresponds to the centre of the head of the ulna. When the radius rotates forward, pronation of the forearm and hand is the result; and when backwaid, snpinaiion. It will thus be seen that in pronation and supination of the forearm and hand the radius describes a segment of a cone, the axis of which extends from the centre of the head 314 THE ARTICULATIONS, OR JOINTS of the radius to the middle of the head of the ulna. In this movement, however, the ulna is not quite stationary, but rotates a little in the opposite direction. So that it also describes the segment of a cone, though of smaller size than that described by the radius. The movement ■n-hich causes this alteration in the position of the head of the ulna takes place principally at the shoulder-joint by the rotation of the humerus, but possibly also to a slight extent at the elbow- joint.' Surface Form. — The position of the inferior radio-ulnar joint may be ascertained by feeling for a slight groove at the back of the ^\Tist, between the prominent head of the ulna and the lower end of the radius, when the forearm is in a state of almost complete pronation. VII. Radiocarpal or Wrist-joint (Articulatio Radiocarpea) (Figs. 253, 254). The wrist is a condyloid articulation. The parts entering into its formation are the lower end of the radius and under surface of the articular disk, which form together the receiving cavity, and the scaphoid, semilunar, and the cunei- form bones, which form the condyle. The articular surface of the radius and the under surface of the articular disk are the receiving cavity, forming together a transversely elliptical concave surface. The articular surfaces of the scaphoid, semilunar, and cuneiform bones form together a smooth, convex surface, the con- dyle, which is received into the concavity above mentioned. All the bony surfaces of the articulation are co\'ered by hyaline cartilage, and are connected by a capsule, which is divided into the following ligaments: External Lateral. Anterior. Internal Lateral. Posterior. The external lateral ligament Qigamentum collaterale carpi radiale) (Fig. 253) extends from the summit of the styloid process of the radius to the outer side of the scaphoid, some of its fibres being prolonged to the trapezium and annular ligament. The internal lateral ligament (llgamenttim collaterale carpi ulnars) (Fig. 253) is a rounded cord, attached, above, to the extremity of the styloid process of the ulna, and dividing, below, into two fasciculi, which are attached, one to the inner side of the cuneiform bone, the other to the pisiform bone and annular ligament. The anterior or volar ligament (ligamentum, radiocarpeum volare) (Fig. 253) is a broad, membranous band, attached, above, to the anterior margin of the lower end of the radius, to its styloid process, and to the ulna; its fibres pass down- ward and inward to be inserted into the palmar surface of the scaphoid, semilunar, and cuneiform bones. Some of the fibres are' continued to the os magnum. In addition to this broad membrane there is a distinct rounded fasciculus, superficial to the rest, which passes from the base of the styloid process of the ulna to the semi- lunar and cuneiform bones. This ligament is perforated by numerous apertures for the passage of vessels, and is in relation, in front, with the tendons of the Flexor profundus digitorum and of the Flexor longus pollicis. The posterior or dorsal ligament {ligamentum radiocarpeum dorsale) (Fig. 254), thinner and weaker than the anterior, is attached, above, to the posterior border of the lower end of the radius ; its fibres pass obliquely downward and inward, to be attached to the dorsal surface of the scaphoid, semilunar, and cuneiform bones, and are continuous with those of the dorsal carpal ligaments. This ligament is in relation, behind, with the Extensor tendons of the fingers. Synovial Membrane.— The synovial membrane (Fig. 255) lines the inner surface of the ligaments above described, extending from the lower end of the radius and articular disk above ' See Hultkrantz, Das Ellenbogen Gelenk und seine Mechanik, Jena, 1S97. ARTICULATIOJ^ti OF THE CARPUS 315 to the articular surfaces of the carpal bones below. It is loose and lax, and presents numerous fdlils, cs])ccia]ly behind. The arteries supplying the joint are the anterior and posterior carpal branches of the radial and ulnar, the anterior and posterior interosseous, and some ascending branches from the deep palmar arch. The nerves are derived from the ulnar and posterior interosseous. Movements. — The movements permitted in this joint are volar flexion, dorsi-flexion, abduction, addudion, and circumduction. Its actions will be further studied with those of the carpus, with which they are combined. Surface Form. — The line of the radiocarpal joint is on a level with the apex of the styloid process of the ulna. Applied Anatomy. — The wrist-joint is rarely dislocated, its strength depending mainly upon the numerous strong tendons which surround the articulation. Its security is further pro- vided for by the number of small bones of which the carpus is made up, and which are united by very strong ligaments. The slight movement which takes place between the several bones serves to break the jars that result from falls or blows on the hand. Dislocation backward, which is the more common dislocation, simulates to a considerable extent CoUes' fracture of the radius, and is apt to be mistaken for it. The diagnosis can be easily made out by observing the relative position of the styloid processes of the radius and ulna. In the natural condition the styloid process of the radius is on a lower level — i. e., nearer the ground — when the arm hangs by the side, than that of the ulna, and the same would be the case in dislocation. In Colles' fracture, on the other hand, the styloid process of the radius is on the same or even a higher level than that of the ulna. The wrist-joint is occasionally the seat of acute synovitis, the result of traumatism or con- sequent upon rheumatic or pyemic conditions. When the synovial sac is distended with fluid, the swelling is greatest on the dorsal aspect of the wrist, and shows a general fulness, with some bulging between the tendons. The inflammation is prone to extend to the intercarpal joints and to attack also the sheaths of the tendons in the neighborhood. Chronic inflammation of the wrist is generally tuberculous, and often leads to similar disease in the synovial sheaths of adjacent tendons and of the intercarpal joints. The disease, therefore, when progressive, frequently leads to necrosis of the carpal bones, and the result is often unsatisfactory. VIII. Articulations of the Carpus (Articulatio Intercarpea) (Figs. 253, 254). These articulations may be subdivided into three sets: 1. The Articulations of the First Row of Carpal Bones. 2. The Articulations of the Second Row of Carpal Bones. 3. The Articulations of the Two Rows with each other. 1. Articulations of the First Row of Carpal Bones These are arthrodial joints. The ligaments connecting the scaphoid, semi- lunar, and cuneiform hones are: Dorsal. Palmar. Two Interosseous. The dorsal ligaments (llgameida intercarpea dorsalia) are placed transversely behind the bones of the first row; they connect the scaphoid and semilunar and the semihuiar and cimeiform. The palmar or volar ligaments (Ugamenta intercarpea volaria) connect the scaphoid and semilunar and the semilunar and cuneiform bones; they are weaker than the dorsal, and placed very deeply below the anterior ligament of the wrist. The interosseous ligaments (ligamenta intercarpea interossea^ (Fig. 255) are tvi'o narrow bundles of fibrous tissue connecting the semilunar bone on one side with the scaphoid, and on the other with the cuneiform. They are on a level with the superior surfaces of these bones, and close the upper part of the spaces 316 THE ARTICULATIONS, OB JOINTS between them. Their upper surfaces are smooth, and form with the bones the convex articular surfaces of the wrist-joint. The hgaments connecting the pisiform bone are: Capsular. Two Palmar Ligaments. The capsular ligament is a thin membrane which connects the pisiform bone to the cuneiform. It is lined by a separate synovial membrane. The two palmar ligaments are two strong fibrous bands which connect the pisiform to the unciform {ligamentum pisohamatum) , and to the base of the fifth metacarpal bone {ligainentum pisometacarpeum). 2. Articulations of the Second Row of Carpal Bones. These are also arthrodial joints. The articular surfaces are covered with hyaline cartilage, and connected by the following ligaments: Dorsal. Palmar. Three Interosseous. The dorsal ligaments {ligamenta iniercarpea dorsalia) extend transversely from one bone to another on the dorsal surface, connecting the trapezium with the trape- zoid, the trapezoid with the os magnum, and the os magnum with the unciform. The palmar ligaments (^ligamenta iniercarpea volaria) have a similar arrange- ment on the palmar surface. The three interosseous ligaments (ligamenta intercarpea inierossea) (Fig. 255),. much thicker than those of the first row, are placed one between the os magnum and the unciform, a second between the os magnum and the trapezoid, and a third between the trapezium and trapezoid. The first of these is much the strongest, and the third is sometimes wanting. 3. Articulations of the Two Rows of Carpal Bones with Each Other (Figs. 253, 254). The joint between the scaphoid, semilunar, and cuneiform, and the second row of the carpus, or the midcarpal joint, is made up of three distinct portions; in the centre the head of the os magnum and the superior surface of the unciform articulate with the deep, cup-shaped cavity formed by the scaphoid and semilunar bones, and constitute a sort of ball-and-socket joint. On the outer side the trape- zium and trapezoid articulate with the scaphoid, and on the inner side the unci- form articulates with the cuneiform, forming gliding joints. Sometimes a small ligament joins the navicular to the neck of the os magnum and is representative of the os centrale (p. 206) (Sutton). The ligaments are: Anterior. External Lateral. Posterior. Internal Lateral. The anterior or palmar ligaments (ligamenta intercarpea volaria) consist of short fibres, which pass, for the most part, from the palmar surface of the bones of the first row to the front of the os magnum. CARPOMETACARPAL ARTICULATIONS 317 The posterior or dorsal ligaments (ligmnenta intercarpea dorsalis) consist of short, irregular bundles of fibres passing between the bones of the first and second row on the dorsal surface of the carpus. The lateral ligaments are very short; they are placed, one on the radial, the other on the ulnar side of the carpus; the former, the stronger and more distinct, ■connecting the scaphoid and trapezium, the latter the cuneiform and unciform; they are continuous with the lateral ligaments of the wrist-joint. In addition to these ligaments, a slender interosseous band sometimes connects the os magnum and the scaphoid. Synovial Membrane (Fig. 255). — The synovial membrane of the carpus is very extensive; it passes from under the surface of the scaphoid, semilunar, and cuneiform bones to the upper sm-face of the bones of the second row, sending upward two prolongations — between the scaphoid and semilunar and the semilunar and cuneiform; sending downward three prolongations between the four bones of the second row, which are further continued onward into the carpometacarpal joints of the four inner metacarpal bones, and also for a short distance between the metacarpal bones. There is a separate synovial membrane between the pisiform and the cuneiform bones. Movements. — The articulation of the hand and wrist, considered as a whole, is divided into three parts: (1) The radius and the articular disk, (2) the meniscus,'^ formed by the scaphoid, semilunar, and cuneiform, the pisiform bone having no essential part in the movements of the hand; (.3) the hand proper, the metacarpal bones with the four carpal bones on which they are svipported — viz., the trapezium, trapezoid, os magnum, and unciform. These three elements form two joints: (1) The superior, wrist-joint proper, between the meniscus and bones of the forearm; (2) the inferior, transverse or midcarpal joint, between the hand and nHiiiscus. 1. The articulation between the forearm and carpus is a true condyloid articulation, and therefore all movements but rotation are permitted. Flexion and extension are the most exten- sive, and of these a greater amount of extension than flexion is permitted on account of the articulating surfaces extending farther on the dorsal than on the palmar aspect of the carpal bones. In this movement the carpal bones rotate on a transverse axis drawn between the tips of the styloid processes of the radius and ulna. A certain amount of adduction (or ulnar flexion) and abduction (or radial flexion) is also permitted. Of these movements, the former is consider- ably greater in extent than the latter. In these movements the carpus revolves upon an antero- posterior axis drawn through the centre of the wrist. Finally, circumduction is permitted by the consecutive movements of adduction, extension, abduction, and flexion, with intermediate movements between them. There is no rotation, but this is provided for by the supination and pronation of the radius on the ulna. The movement of volar flexion is performed by the Flexor carpi radialis, the Flexor carpi ulnaris, and by the Palmaris longus; dorsi-flexion, by the Extensor carpi radialis longior et brevior and the Extensor carpi ulnaris; adduction (ulnar flexion), by the Flexor carpi ulnaris and the Extensor carpi ulnaris; and abduction (radial flexion), by the Extensors of the thumb and the Extensores carpi radialis longior et brevior and the Flexor carpi radialis. 2. The chief movements permitted in the transverse or midcarpal joint are flexion, extension, and a slight amount of rotation. In flexion, and extension, which are the movements most freely enjoyed, the trapezium and trapezoid on the radial side and the unciform on the ulnar side glide forward and backward on the scaphoid and cuneiform respectively, while the head of the OS magnum and the superior surface of the unciform rotate in the cup-shaped cavity of the scaphoid and semilunar. Flexion at this joint is of greater range than extension. A very trifling amount of rotation is also permitted, the head of the os magnum rotating around a vertical axis drawn through its own centre, while at the same time a slight gliding movement takes place in the lateral portions of the joint. IX. Carpometacarpal Articulations (Articulationes Carpometacarpeae) (Fig. 254). 1. Articulation of the Metacarpal Bone of the Thumb with the Trapezium (Articulatio Carpometacarpea Pollicis). This is a joint of reciprocal reception, and enjoys great freedom of movement, on account of the configuration of its articular surfaces, which are saddle-shaped, ' Called meniscus because the bones composing it serve the essential purposes of an articular disk. 318 THE ARTICULA TIONS, OR JOINTS so that, on section, each bone appears to be received into a cavity in the other, according to the direction in which they are cut. The joint is surrounded by a capsular ligament. The capsular ligament is thick and fibrous, but loose, and passes from the cir- cumference of the upper extremity of the metacarpal bones to the rough edge bounding the articular surface of the trapezium; it is thickest externally and behind, and lined with a separate synovial membrane. Movements. — In the articulation of the metacarpal bone of the thumb with the trapezium, the movements permitted are flexion, extension, adduction, abduction, and circumduction. When the joint is flexed the metacarpal bone is brought in front of the palm and the thumb is gradu- ally turned to the fingers. It is by this peculiar moveaent that the tip of the thumb is opposed to the other digits; for by slightly flexing the fiiif^ers the palmar surface oi the thumb can be brought in contact with their palmar surfaces. 2. Articulations of the Metacarpal Bones of the Four Inner Fingers WITH THE Carpus (Articulationes Carpometacarpeae). The joints formed between the carpus and four inner metacarpal bones are arthrodial joints. The ligaments are: Dorsal. Palmar. Interosseous. The dorsal ligaments (Jigamenta carpometacarpea dorsalis), the strongest and most distinct, connect the carpal and metacarpal bones on their dorsal surface. The second metacarpal bone receives two fasciculi — one from the trapezium, the other from the trapezoid; the third metacarpal receives two — one from the trapezoid and one from the os magnum; the fourth, two — one from the os magnum and one from the unciform; the fifth receives a single fasciculus from the unciform bone, which is continuous with a similar ligament on the palmar surface, thus forming an incomplete capsule. The palmar ligaments (Ugamenta carpometacarpea volaria) have a somewhat similar arrangement on the palmar surface, with the exception of the third meta- carpal, which has three ligaments — an external one from the trapezium, situated above the sheath of the tendon of the Flexor carpi radialis; a middle one, from the OS magnum; and an internal one, from the unciform. The interosseous ligaments consist of short, thick fibres, which are limited to one part of the carpometacarpal articulation; they connect the contiguous inferior angles of the os magnum and unciform with the adjacent surfaces of the third and fourth metacarpal bones. Synovial Membrane. — The synovial membrane is a continuation of that between the two rows of carpal bones. Occasionally, the articulation of the unciform with the fourth and fifth metacarpal bones has a separate synovial membrane. The synovial membranes of the wrist and carpus (Fig. 255) are thus seen to be five in number. The first, the membrana saccifonnis of the inferior radioulnar articulation, passes from the lower end of the ulna to the sigmoid cavity of the radius, and lines the upper surface of the articular disk. The second passes from the lower end of the radius and articular disk above to the bones of the first row below. The third, the most extensive, passes between the contig- uous margins of the two rows of carpal bones — between the bones of the second row to the carpal extremities of the four inner metacarpal bones. The. fourth passes from the margin of the trapezium to the metacarpal bone of the thumb. The fifth passes between the adjacent margins of the cuneiform and pisiform bones. \ CA RPOMETA CA RPA L AR TICULA T10N8 31& Movements. — The movement permitted in the carpometacarpal articulations of the four inner fingers is limited to a slight gliding of the articular surfaces upon each other, the extent of which varies in the different joints. Thus, the articulation of the metacarpal bone of the little finger is most movable, then that of the ring linger. The metacarpal bones of the index and middle fingers are almost immovable. MEMBRANA SACCI- FORMIS OF INFERIOR RADIO-ULNAR ARTICULATION TRIANGULAR ARTICULAR DISK STYLOID PROCESS OF ULNA ARTICULATION OF TRAPEZIUM AND METACARPAL BONE OF THUMB METACARPAL BONES Fig. 255.— Joints of the right hand, from the back of the hand. (Spalteholz.) 3. Articulations of the Metacarpal Bones with Each Other (Articu- LATioNES Intermetacarpeae (Figs. 254, 255). The carpal extremities of the four inner metacarpal bones articulate with one another at each side by small surfaces covered with cartilages, and connected by dorsal, palmar, and interosseous ligaments. The dorsal ligaments {ligamenta hasium oss. metacarp. dorsalia) and palmar ligaments (liejamenta hasium oss. vietacarp. volaria) pass transversely from one bone to another on the dorsal and palmar surfaces. The interosseous ligaments (lujamenta hasium oss. metacarp. interossea) pass between their contiguous surfaces, just beneath their lateral articular facets. 320 THE ARTIGULA TIONS, OB JOINTS S3movial Membrane (Fig. 255). — ^The synovial membrane between the lateral facets is a reflection from that between the two rows of carpal bones. ANTERIOR >R VAGINAL LIGAMENT TRANSVERS METACARPAL kiGAMENT SECOND PALMAR MTER05SE0US MUSCLE Fig. 256. — Metacarpal bones and first phalanges of the second to the fifth finger of the right hand, with ligaments, from the volar surface. (Spaltebolz.) The transverse metacarpal ligament Qigamentum capitidorum oss. metacar- ■paliuvi transversum) (Fig. 256) is a narrow, fibrous band which passes trans- Tersely across the anterior surfaces of the digital extremities of the four inner metacarpal bones, connecting them. It is blended anteriorly with the palmar ligaments of the metacarpophalangeal articulations. To its posterior border is connected the fascia which covers the Interossei muscles. Its anterior surface is concave where the Flexor tendons pass over it. Behind it the tendons of the Interossei muscles pass to their insertion. X. Metacarpophalangeal Articulations (ArticulationesMetacarpophalangeae) (Figs. 256, 257). These articulations are of the condyloid variety, formed by the reception of the rounded head of the metacarpal bone into a shallow cavity in the extremity of the first phalanx. The expansion of the Extensor communis digitorum tendoii acts as a dorsal ligament. There is a capsular ligament which at certain points has strengthening ligaments. The ligaments are: Anterior. Two Lateral. ARTICULATIONS OF THE PHALANGES 321 The palmar or vaginal ligament {li(/amentum vagmale, glenoid ligament of Cru- veilhier) is a thick, dense, fibrous structure, placed on the palmar surface of the joint in the interval between the lateral liga- ments, to which it is connected; it is loosely united to the metacarpal bone, but very firmly to the base of the first phalanx. Its palmar surface is intimately blended with the transverse metacarpal ligament, and presents a groove for the passage of the Flexor tendons, the sheath surrounding which is connected to each side of the groove. By its deep surface it forms part of the articular surface for the head of the meta- carpal bone, and is lined Ijy a synovial mem- brane. The lateral ligaments (Ucjamcnta coUateralia) are strong, rounded cords placed one on each side of the joint, each being attached by one extremity to the posterior tubercle on the side of the head of the metacarpal bone, and by the other to the ahticu contiguous extremity of the phalanx. Movements. — The movements which occur in these joints are flexion, extension, adduction, abduction, and circumduction; the lateral movements are very extensive. Surface Form. — The prominences of the knuckles do not correspond to the position of the joints either of the metacarpophalangeal or interphalangeal articulations. These prominences are invariably formed by the distal ends of the proximal bone of each joint, and the line indicating the position of the joint must be sought con- siderably in front of the middle of the knuckle. ARTICULAR CAPSULE XI. Articulations of the Phalanges (Articu- lationes Digitorum Manus) (Fig. 257) These are ginglymus joints. Each joint has a capsule, and certain accentuated portions are re- garded as definite ligaments. These ligaments Anterior or Palmar. Two Lateral {ligamenta coUateralia). The arrangement of these ligaments is similar to those in the metacarpophalangeal articula- tions; the Extensor tendon supplies the place of a dorsal ligament. Fig. 257. — Metacarpal bones and first phalanges of the third finger of the right nand. with ligaments, from the radial side, (Spalteholz.) Movements. — The only movements permitted in the phalangeal joints are flexion and extension; these movements are more extensive between the first and second phalanges than between the second and third. The movement of flexion is very considerable, but extension is limited by the anterior and lateral ligaments. •21 322 THE ARTICULATIONS, OR JOINTS ARTICULATIONS OF THE LOWER EXTREMITY. The articulations of the lower extremity comprise the following groups: I. The Hip-joint. 11. The Knee-joint. III. The Articulations between the VI. The Tarsometatarsal Articulations, VII. Articulations of the Metatarsal Bones with each other. Tibia and Fibula. I \^III. The Metatarsophalangeal Articu- IV. The Ankle-joint. i lations. V. The Articulations of the Tarsus, j IX. TheArticulations of the Phalanges. I. The Hip-joint (Articulatio Coxae) (Figs. 258, 2.59). This articulation is an enarthrodial or ball-and-socket joint, formed by the reception of the head of the femur into the cup-shaped cavity of the acetabulum. The articulating surfaces are covered by hyaline cartilage, that on the head of the femur being thicker at the centre than at the circumference, and covering the entire surface with the exception of a depression just below its centre for the attachment of the ligamentum teres; that covering the acetabulum is much thinner at the centre than at the circumference. This cartilage forms an incomplete ring of a horseshoe shape, being deficient below, where there is a circular depres- sion, which in the recent state is occupied by a mass of fat covered by synovial membrane. The ligaments of the joints are the Capsular. Teres. Iliofemoral. Cotyloid. Transverse. The capsular ligament (capsula articularis) (Figs. 258 and 259) is a strong, dense, ligamentous capsule, embracing the margin of the acetabulum above and surround- ing the neck of the femur below. Its upper circumference is attached to the acetab- ulum a short distance above and behind the cotyloid ligament, but in frotit it is attached to the outer margin of the ligament, and opposite to the notch, where the margin of this cavity is deficient, it is connected to the transverse ligament, and by a few fibres to the edge of the obturator foramen. Its loioer circumference surrounds the neck of the femur, being attached, in front, to the spiral or anterior intertrochanteric line; above, to the base of the neck; behind, to the neck of the lione, about half an inch above the posterior intertrochanteric line. From this insertion the fibres are reflected upward over the neck of the femur, forming a sort of tubular sheath, the cervical reflection, which blends with the periosteum and can be traced as far as the cartilage which covers the head of the femur. On the surface of the neck of the femur some of these reflected fibres are raised into longitudinal folds, termed retinacula. It is much thicker at the upper and fore part of the joint, where the greatest amount of resistance is required, than below and internally, where it is thin, loose, and longer than in any other part. It consists of two sets of fibres, circular and longitudinal. The circular fibres, zona orbicularis (Fig. 261), are most abundant at the lower and back part of the capsule, and form a sling or collar around the neck of the femur. Anteriorly they blend with the deep surface of the iliofemoral ligament, and through this medium reach the anterior inferior spine of the ilium. The longitudinal fibres are greatest in amount at the upper and front part of the capsule, where THE HIP-JOINT 323 they form distinct bands or accessory ligaments, of which the most important is the iliofemoral. Other accessory bands are iinown as the pubofemoral (Jiga- mentum pubocapsidare), passing from the outer portion of the horizontal pubic ramus, the iliopectineal eminence, the obturator crest and the obturator mem- M OFEMORAL 1_ I G AM E ?MT ANTERIOR INTERTRO CHANTERIC LINE Fig. 258. — Right hip-joint, from in front. (Spalteholz.) brane, to the front of the capsule; and the ischiocapsular ligament or ligament of Bertin (ligamentum ischiocapsulare), which passes from the ischium, just laelow the acetabulum, to blend with the circular fibres at the lower part of the joint. The external surface is rough, covered by numerous muscles, and separated in front from the Psoas and Iliacus muscles by a synovial bursa, which not infre- quently communicates, by a circular aperture, with the cavity of the joint. It differs from the capsular ligament of the shoulder in being much less loose and lax, and in not being perforated for the passage of a tendon. The iliofemoral (ligamentum iliofemorale) (Figs. 261 and 262) is an accessory band of fibres extending obliquely across the front of the joint; it is intimately connected with the capsular ligament, and serves to strengthen it in this situa- 324 THE ARTICULATIONS, OB JOINTS tion. It is attached, above, to the lower part of the anterior inferior spine of the ihum and the adjacent rim of the acetabulum; and, diverging below, forms two bands, of which one passes downward to be inserted into the lower part of the anterior intertrochanteric line; the other passes downward and outward to be inserted into the upper part of the same line and the adjacent part of the neck of the femur. Between the two bands is a thinner part of the capsule. Some- times there is no division, but the ligament spreads out into a flat, triangular Fig. 259.— Right hip-joint, from behind. (The band, which is attached below into the whole length of the anterior intertrochan- teric line. This ligament is frequently called the Y-shaped ligament of Bigelow; and the outer or upper of the two bands is sometimes described as a separate ligament, under the name of the iliotrochanteric ligament. The ligamentiun teres {ligamentuin teres femoris) (Figs. 261 and 262) is a tri- angular band implanted by its apex into the depression a little behind and below THE HIP JOINT 325 the centre of the head of the femur, and by its broad base into the margins of the cotyloid notch, where it blends with the transverse ligament. It is formed of white fibrous connective tissue, surrounded by a tubular sheath of synovial mem- brane. Sometimes only the synovial fold exists. Very rarely it is absent. The ligament is made tense when the hip is semiflexed, and the limb adducted and rotated outward; it is, on the other hand, relaxed when the limb is abducted. It has, however^ but little influence as a ligament, and though it may to a certain extent limit movement, it would appear to be merely a "vestigial and practically useless ligament.'" Fig. 260. — Right hip-joint from the mesal side. (The bottom of the acetabulum has been chiselled away sufficiently to make the head of the femur visible.) (Spalteholz.) The cotyloid ligament {labruvi glenoidale (Fig. 263) is a fibrocartilaginous rim attached to the margin of the acetabulum, the cavity of which it deepens; at the same time it protects the edges of the bone and fills up the inequalities on its sur- face. It bridges over the notch as the transverse ligament of the acetabulum, and thus forms a complete circle, which closely surrounds the head of the femur, and assists in holding it in its place. It is prismoid on section, its base being attached to the margin of the acetabulum and its opposite edge being free and sharp. Its two surfaces are invested by synovial membrane, the external one being in contact with the capsular ligament, the internal one being inclined inward, so as to narrow the acetabulum and embrace the cartilaginous surface of the Tiead of the femur. It is much thicker above and behind than below and in front, and consists of close, compact fibres, which arise from different points of the 1 J. Bland Sutton, Ligaments: Their Nature and Morphology, 1887. 326 THE ARTICULATIONS, OR JOINTS circumference of the acetabulum and interlace with each other at very acute angles. The transverse ligament of the acetabulum Qigamentum transversum acetahidi) (Figs. 260 and 263) is in reality a portion of the cotyloid hgament, though difFering from it in having no cartilage cells among its fibres. It consists of strongs flattened fibres, which cross the notch at the lower part of the acetabulum and convert it into a foramen. Thus an interval is left beneath the ligament for the passage of nutrient vessels to the joint. R LIGAMENT CAPSULA FIBRO CAPSULA SYNOV OPER'S LIGAMENT )F PUBIS Fig. 261. — The right hip-joint, seen from before. (Toldt.) The synovial membrane (Figs. 261 and 262) is very extensive. Commencing at the margin of the cartilaginous surface of the head of the femur, it covers all that portion of the neck which is contained within the joint; from the neck it is reflected on the internal surface of the capsular ligament; it covers both surfaces of the cotyloid ligament and the mass of fat contained in the depression at the bottom of the acetabulum, and it is prolonged as far as the head of the femur in the form of a tubular sheath around the ligamentum teres. It sometimes communicates through an aperture in the capsular ligament between the inner band of the Y-shaped ligament and the pubofemoral ligament with a bursa situated on the under surface of the Iliopsoas muscle. The muscles in relation with the joint (Fig. 263) are, in front, the Psoas and Iliacus, sepa- rated from the capsular ligament by a synovial bursa; above, the reflected head of the Rectus femoris and Gluteus minimus, the latter being closely adherentto the capsule; internally, the THE HIP-JOINT •i21 Obturator externus and Pectineus; behind, the Pyriformis, Gemellus superior, Obturator internus, Gemellus inferior, Obturator externus, and Quadratus femoris. The arteries supplying the joint are derived from the obturator, sciatic, internal circumflex, and gluteal. The nerves are articular branches from the sacral plexus, great sciatic, obturator, accessory obturator, and a filament from the branch of the femoral (anterior crural) supplying the Rectus femoris. Bursas. — Numerous bursse exist in the neighborhood of the hip-joint. Some anatomists have counted twenty-one (Synnestredt). The chief ones are: (1) The iliopectineal bursa (bursa ilio- pcctinea) (Fig. 264), between the Iliopsoas tendon and the capsule of the joint. This bursa often communicates with the hip-joint. (2) The subtendinous iliac bursa (biirxa iliaca .lub- tendiiiea), between the tendon of the Psoas and Iliacus and the lesser trochanter. (3) The ischio- FiG. 262.— Right hip-joint. Frontul section. Posterior half, viewed from in front. The joint surfaces hiive been somewhat pulled apart. (Spalteholz.) gluteal bursa (bursa ischiadica m. glutaei maximi), between the Gluteus maximus muscle and the tuberosity of the ischium (not constant). (4) The bursa of the greater trochanter (bursa trochanierica m. glutaei maximi), between the greater trochanter and the Gluteus maximus muscle near the muscular insertion. (.5) Two or three gluteofemoral bursae (bursae (/lufaiofimornles) below. (6) The obturator bursa (bursa m. ohtiirattu-ii iiilrnii), between the margin of the great sacrosciatic notch and the tendon of the Obturatdv internus muscle. (7) The subcutaneous trochanteric bursa (bursa trochanterica subcutanea), between the cutaneous surface and the great 328 THE ARTICULATIONS, OB JOINTS trochanter. Besides these there is a bursa between the greater trochanter and the anterior part of the Gluteus medius; between the greater trochanter and the posterior part of the Gluteus medius; between the greater trochanter and the Gluteus minimus; beneath the PjTiformis muscle; between the lesser trochanter and the Quadratus femoris muscle; and there are bursse beneath the Biceps femoris muscle. Movements. — The movements of the hip are very extensive, and consist of flexion, exten- s-ion, adducfion, abduction, circumduction, and rotation. The hip-joint presents a very striking contrast to the shoulder-joint in the much more com- plete mechanical arrangements for its security and for the limitation of its movements. In the shoulder, as we have seen, the head of the humerus is not adapted at all in size to the glenoid cavity, and is hardly restrained in any of its ordinary movements by the capsular ligament. In the hip-joint, on the contrary, the head of the femur is closely fitted to the acetabulum for a distance extending over nearly half a sphere, and at the margin of the bony cup it is still more closely embraced by the cotyloid ligament, so that the head of the femur is held in its place by that ligament even when the fibres of the capsule have been cjuite divided (Humphry). The anterior portion of the capsule, described as the iliofemoral ligament, is the strongest of all the ligaments in the body, and is put on the stretch by any attempt to extend the femur beyond a straight line with the trunk. That is to say, this ligament is the chief agent in main- taining the erect position without muscular fatigue; for a vertical line passing through the Fig. 263. — Relation oi ii i U t , t le capsule of the hip-joint. (From a drawing by Mr. F. A. Barton.) centre of gravity of the trunk falls behind the centres of rotation in the hip-joint, and therefore the pelvis tends to fall backward, but is prevented by the tension of the iliofemoral and capsular ligaments. The security of the joint may be also provided for by the two bones being directly united through the ligamentum teres; but it is doubtful whether this so-called ligament can have much influence upon the mechanism of the joint. Flexion of the hip-joint is arrested by the soft parts of the thigh and abdomen being brought into contact when the leg is flexed on the thigh ; and by the action of the Hamstring muscles when the leg is extended.' Extension is arrested by the tension of the iliofemoral ligament and the front of the capsule; adduction, by the thighs coming into contact; adduction loith flexion, by the outer band of the iliofemoral ligament, and the outer part of the capsular ligament; abduction, by the inner band of the ilio- • The hip-joint cannot be completely fieved, in most persons, without at the same time flexing the knee, on account of the shortness of the Hamstring muscles. — Cleland, Jour, of Anat. and Physiol, No. l.Old Series, p. 87. THE HIP-JOINT 329 femoral ligament and the pubofemoral band ; rotation outward, by the outer band of the iliofemoral ligament; and rotation inward, by the isehiocapsular ligament and the hinder part of the cap- sule. The muscles which flex the femur on the pelvis are the Psoas, Iliacus, Rectus femoris, Sartorius, Pectineus, Adductor longus and brevis, and the anterior fibres of the Gluteus medius and minimus. Extension is mainly performed by the Gluteus maximus, assisted by the Ham- string muscles. The thigh is atlducted by the Adductores magnus, longus, and brevis, the Pectineus, the Gracilis, and the lower part oi' the Gluteus maximus, and abducted by the Gluteus medius and minimus and the upper part of the Gluteus maximus. The muscles which rotate the thio-h inward are the anterior fibres of the Gluteus medius, the Gluteus minimus, and the Tensor fasciae femoris; while those which rotate it outward are the posterior fibres of the e described with the anatomy of the eyeball. Applied. Anatomy. — The position and exact point of insertion of the tendons of the Inter- nal and External recti muscles into the globe should be carefully examined from the front of the eyeball, as the surgeon is often required to divide the one or the other muscle for the cure of strabismus (squint). In convergent strabismus, which is the more common form of the disease, the eye is turned inward, requiring the division of the Internal rectus. In the divergent form which is more rare, the eye is turned outward, the External rectus being especially implicated. The deformity produced in either case is to be remedied by division of one or the other muscle. The operation is thus performed: The lids are to be well separated; the eyeball being rotated outward or inward, the conjunctiva should be raised by a pair of forceps and divided immedi- ately beneath the lower border of the tendon of the muscle to be divided, a littie behind its insertion into the sclera; the submucous areolar tissue is then divided, and into the small aper- ture thus made a blunt hook is passed upward between the muscle and the globe, and the tendon of the muscle and conjunctiva covering it divided by a pair of blunt-pointed scissors. Or the tendon may be divided by a subconjunctival incision, one blade of the scissors being passed upward between the tendon and the conjunctiva, and the other between the tendon and the sclera. Inflammation of the synovial membrane lining the trochlea of the Superior oblique may lead to the formation of a cyst of considerable size. 1 See F. Groyer, in the Vienna Sitzungsberiohte der Kaiserliohen Akademie der Wissenschaften, 1903, Band 372 THE MUSCLES AND FASCIA In performing enucleation of the eyeball the conjunctiva is clipped with scissors near the cornea and the capsule of T6non is divided with it. One Rectus muscle after another is caught up on a blunt hook and divided. The scissors are now pushed well in along the outer orbital wall and the optic nerve is divided. Finally, the Oblique muscles, the ciliary vessels and nerves, and fragments of tissue helping to retain the globe are cut and the eyeball is enucleated. An orbital abscess is evacuated by making an incision close to the border of the orbit, above or below the eyeball. Exophthalmos, or abnormal protrusion of the eyeball, is believed to be due to hypersecretion of the thyroid (as in goitre), which, through the cervicocephalic division of the sympathetic, stimulates the nonstriated tarsal muscles to sustained contraction. These muscles are arranged like a cuff, and may be regarded as having their origin in the orbital septum and their insertion at the equator of the eyeball. In their action they are antagonists of the Recti, and of the Levator palpebrae superioriS; and open wide the palpebral fissure and draw the eyeball forward. (Consult J. Landstrom, Ueber Morbus Basedowii, Thesis, Stockholm, 1907.) 5. The Nasal Region (Fig. 287). Pyramidalis nasi. Dilatator naris anterior. Levator labii superioris alaeque nasi. Compressor nasi. Dilatator naris posterior. Compressor narium minor. Depressor alae nasi. The Pyramidalis nasi (m. frocerus) is a small pyramidal slip placed over the nasal bone. Its origin is by tendinous fibres from the fascia covering the lower part of the nasal bone and upper part of the cartilage, where it blends with the Compressor nasi, and it is inserted into the skin over the lower part of the forehead between the two eyebrows, its fibres decussating with those of the Occipitofron- talis (see page 364). The Levator labii superioris alaeque nasi is a thin triangular muscle placed by the side of the nose, and extending between the inner margin of the orbit and upper lip. It arises by a pointed extremity from the upper part of the nasal process of the maxilla, and, passing obliquely downward and outward, divides into two slips, one of which is inserted into the cartilage of the ala of the nose; the other is prolonged into the upper lip, becoming attached to the under surface of the skin and blended with the Orbicularis oris and Levator labii superioris proprius. The Dilatator naris posterior is a small muscle which is placed partly beneath the elevator of the nose and lip. It arises from the margin of the nasal notch of the maxilla and from the sesamoid cartilages, and is inserted into the skin near the margin of the nostril. The Dilatator naris anterior is a thin, delicate fasciculus passing from the cartikge of the ala of the nose to the integument near its margin. This muscle is situated in front of the preceding. The Compressor naris (m. nasalis) is a small, thin, triangular muscle arising by its apex from the maxilla, above and a little external to the incisive fossa; its fibres proceed upward and inward, expanding into a thin aponeurosis which is attached to the fibrocartilage of the nose and is continuous on the bridge of the nose with that of the muscle of the opposite side and with the aponeurosis of the Pyramidalis nasi. The Compressor narium minor is a small muscle attached by one end to the alar cartilage, and by the other to the integument at the end of the nose. The Depressor alae nasi (m. depressor septi) is a short radiated muscle arising from the incisive fossa of the maxilla; its fibres ascend to be inserted, into the septum and back part of the ala of the nose. This muscle lies between the mucous membrane and muscular structure of the lip. THE MAXILLA B I ' REGION 373 Nerves. — All of the muscles of this group are supplied by the facial nerve. Actions. -The Pj'ramidalis nasi draws down the inner angle of the eyebrows and produces transverse wrinkles over the bridge of the nose. The Levator labii superioris alaec|ue nasi draws upward the upper lip and ala of the nose; its most important action is upon the no.se, which it dilates to a considerable e.xtent. The action of this muscle produces a marked influence over the countenance, and it is the principal agent in the e.xpression of contempt and disdain. The two Dilatatores nasi enlarge the aperture of the nose. Their action in ordinary breathing is to resist the tendency of the nostrils to close from atmospheric pressure, but in difficult breath- ing they may be noticed to be in violent action, as well as in some emotions, as anger. The Depressor alae nasi is a direct antagonist of the other muscles of the nose, drawing the ala of the nose downward, and thereby constricting the aperture of the nares. The Compressor naris depresses the cartilaginous part of the nose and compresses the alee together. 6. The Maxillary Region (Fig. 287). Levator labii superioris. Zygomaticu.s major. Levator anguli oris. Zygomaticus minor. In the BNA term musculus quadratus labii superioris tliree muscles are in- cluded. The caput aiigulare is called in this book the Levator labii superioris alaeque nasi. The capiit iiifraorbitale is called the Levator labii superioris. The capiit zi/c/omaticum is called the Zygomaticus minor.' The Levator labii superioris is a thin muscle of a quadrilateral form. It arises from the lower margin of the orbit immediately above the infraorbital foramen, some of its fibres being attached to the maxilla, others to the malar bone; its fibres converge to be inserted into the muscular substance of the upper The Levator anguli oris (m. camnus) arises from the canine fossa immediately below the infraorbital foramen; its fibres incline downward and a little outward, to be inserted into the deep surface of the skin and into the subcutaneous tissue near the angle of the mouth and intermingles with the fibres of the Zygomaticus major, the Depressor anguli oris, and the Orbicularis oris. The Zygomaticus major (m. zygomaticus) is a slender fasciculus which arises from the malar bone, in front of the zygomatic suture, and, descending obliquely downward and inward, is inserted into the deep surface of the skin and subcutaneous tissue at the outer portion of the upper lip and into the angle of the mouth, where it blends with the fibres of the Levator anguli oris, the Orbicu- laris oris, and the Depressor anguli oris. The Zygomaticus minor, which is often absent, arises from the malar bone immediately behind the maxillary suture, and, passing downward and inward, is inserted internal to the angle of the mouth and is continuous with the Orbicularis oris at the outer margin of the Levator labii superioris. It lies in front of the Zygomaticus major. Nerves. — This group of muscles is supplied by the facial nerve. Actions, — The Levator labii superioris is the proper elevator of the upper lip, carrying it at the same time a little forward. It assists in forming the nasolabial ridge which passes from the side of the nose to the upper lip and gives to the face an expression of sadness. The Levator anguli oris raises the angle of the mouth and draws it inward, and assists the Levator labii su- perioris in producing the nasolabial ridge. The Zygomaticus major draws the angle of the mouth backward and upward, as in laughing; while the Zygomaticus minor, being inserted into the outer part of the upper lip and not into the angle of the mouth, draws it backward, upward, and outward, and thus gives to the face an expression of sadness. I That this grouping is quite artificial and morphologically unwarranted has been shown by McMurrich American Journal of Anatomy, vol. iii, Proceedings, p. iii. 374 THE MUSCLES AND FASCIA 7. The Mandibular Region (Fig. 287). Levator menti. Depressor labii inferioris. Depressor anguli oris. Dissection. - -Tlie muscles in this region may be dissected by maliing a vertical incision tlirough the integument from the margin of the lower lip to the chin; a second incision should then be carried along the margin of the mandible as far as the angle, and the integument carefully removed in the direction shown in Fig. 286. The Levator menti (m. mentalis) is a small conical fasciculus placed on the side of the frenum of the lower lip. It arises from the mandibular incisive fossa, external to the symphysis of the mandible; its fibres descend to be inserted into the integument of the chin. The Depressor labii inferioris, or Quadratus menti (m. quadrafus labii inferioris) (Fig. 294), is a small quadrilateral muscle. It arises from the external oblique line of the mandible, between the symphysis and mental foramen, and passes obliquely upward and inward, to be inserted into the integument of the lower lip, its fibres blending with the Orbicularis oris and with those of its fellow of the opposite side. It is continuous with the fibres of the Platysma at its origin. This muscle contains much fat intermingled with its fibres. The Depressor anguli oris (?re. triangularis) (Fig. 287) is triangular in shape, arising, by its broad base, from the external oblique line of the mandible, from whence its fibres pass upward, to be inserted, by a narrow fasciculus, into the angle of the mouth. It is continuous with the Platysma at its origin and with the Orbicularis oris and Risorius at its insertion, and some of its fibres are directly continuous with those of the Levator anguli oris.^ Nerves. — This group of muscles is supplied by the facial nerve. Actions. — The Levator menti raises the lower lip and protrudes it forward, and at the same time wrinkles the integument of the chin, expressing doubt or disdain. The Depressor labii inferioris draws the lower lip directly downward and a little outward, as in the expression of irony. The Depressor anguli oris depresses the angle of the mouth, being the antagonist to the Levator anguli oris and Zygomaticus major; acting with the Levator anguli oris, it will draw the angle of the mouth directly inward. 8. The Buccal Region. Orbicularis oris. Buccinator. Risorius. Dissection. — Tie dissection of these muscles may be considerably facilitated by filling the cavity of the mouth with tow, so as to distend the cheeks and lips; the mouth should then be closed by a few stitches and the integument carefully removed from the surface. The Orbicularis oris (Figs. 287 and 293) is not a simple sphincter muscle, like the Orbicularis palpebrarum, but consists of numerous strata of muscle fibres, having different directions, which surround the orifice of the mouth. These fibres are partially derived from the other facial muscles which are inserted into the lips, and are partly fibres proper to the lips themselves. Of the former, a considerable number are derived from the Buccinator and form the deeper stratum of the Orbicularis. Some of the Buccinator fibres — namely, those near the middle of the muscle — decussate at the angle of the mouth, those arising from the maxilla passing to the lower lip, and those from the mandible to the ' Muscle fibres connecting the two muscles below the chin are occasionally met with; they constitute the Husculus transversus menti of His and Waldeyer. THE BUCCAL It EG ION 375 upper lip. Other fibres of the muscle, situated at its upper and lower part, pass across the lips from side to side without decussation. Superficial to this stratum is a second, formed by the Levator and Depressor anguli oris, which cross each other at the angle of the mouth, those from the Depressor passing to the upper lip, and those from the Levator to the lower lip, along which they run to be in- serted into the skin near the median line. Li addition to these there are fibres from the other muscles inserted into the lips — the Levator labii superioris, the Levator labii superioris alaeque nasi, the Zygomatici, and the Depressor labii inferioris; these intermingle with the transverse fibres above described, and have principally an oblique direction. The proper fibres of the lips are oblique, and pass from the under surface of the skin to the mucous membrane through the thickness of the lip. In addition to these are fibres by which the muscle is connected directly with the maxilla and mandible and with the septum of the nose. Li the upper lip these consist of two bands, an inner and an older, on each side of the nasal plane; the outer band (m. incisivus superior) arises from the alveolar border of the maxilla, opposite the lateral incisor tooth, and, arching outward on each side, is continuous '•e:vatoh *ryBUCCINATOF» E. A. S. Fig. 293. — Plan of the fibres constituting the Orbicularis nuscle. at the angle of the mouth with the other muscles inserted into this part. The inner band (m. nasolabialis) connects the upper lip to the septum of the nose. The interval between the two inner bands corresponds with the depression called the philtrum seen on the surface of the skin beneath the septum of the nose. The additional fibres for the lower lip (in. incisivus inferior) arise from the mandible, externally to the Levator menti, and arch outward to the angles of the mouth to join the Buccinator and the other muscles attached to this part. The Buccinator (Fig. 294) is a broad, thin muscle, quadrilateral in form, which occupies the interval between the jaws at the side of the face. It arises from the outer surface of the alveolar processes of the maxilla and mandible, corresponding to the three molar teeth, and, behind, from the anterior border of the pterygomandibular ligament, which separates it from the Superior constrictor of the pharynx. The fibres converge toward the angle of the mouth, where the central fibres intersect each other, those from below being continuous with the upper segment of the Orbicularis oris, and those from above with the inferior segment; the highest and lowest fibres continue forward uninterruptedly into the corresponding segment of the lip, without decussation. 376 THE MUSCLES AND FASCIA Relations. — By its xwperfidal surface, behind, with a large mass of fat, the sucking pad (i-or- pus adiposum buc.cae), which separates it from the ramus of the mandible, the Masseter, and a small portion of the Temporal muscle. The sucking pad is much more developed, relatively, in children than in adults. It assists sucking by aiding the cheek to resist atmospheric pressure. The Buccinator muscle is in relation, anteriorly, with the Zygomatici, Risorius, Levator anguli Fig. 294. — ^Temporal and deep muscles about the mouth. (Testut.) oris, Depressor anguli oris, and the parotid duct, which pierces it opposite the second molar tooth of the ma.xilla; the facial artery and vein cross it from below upward; it is also crossed by the branches of the facial and buccal nerves. By its deep surface it is in relation with the buccal glands and mucous membrane of the mouth. The pterygomandibular ligament {raphe pferygomandibularis) is a tendinous thickening of the buccopharyngeal fascia, attached by one extremity to the apex of the internal pterygoid plate, and by the other to the posterior extremity (lingula) THE TEMPOROMANDIBULAR REGION 377 of the internal oblique line of the mandible. Its deep surface corresponds to the cavity of the mouth, and is lined with mucous membrane. Its superficial surface is separated from the ramus of the mandible by a quantity of adipose tissue. Its posterior border gives attachment to the Superior constrictor of the phapaix; its anterior border, to the fibres of the Buccinator. Tlie buccopharyngeal fascia (fascia huccopharyngea) is a thin fascia covering the superficial surface of the Buccinator muscle. It is gradually lost in front of the angle of the mouth. Posteriorly, it is continued over the superficial surface of the Constrictor muscles. Its thickened cord-like portion is the stylomandibular ligament. The Risorius (m. risorius) (Fig. 287) consists of a narrow bundle of fibres which arises in the fascia over the Masseter muscle, and, passing horizontally forward, is inserted with the Depressor anguli oris into the subcutaneous and muscular tissue at the angle of the mouth. It is placed superficial to the Platysma, and is broadest at its outer extremity. This muscle varies much in its size and form. Nerves. — The muscles in this group are all supplied by the facial nerve. Actions. — The Orbicularis oris in its ordinary action produces the direct closure of the lips; by its deep fibres, assisted by the oblique ones, it closely applies the lips to the alveolar arch. The superficial part, consisting principally of the decussating fibres, brings the lips together and also protrudes them forward. The Buccinators contract and compress the cheeks, so that, during the process of mastication, the food is kept under the immediate pressure of the teeth. When the cheeks have been previously distended with air, the Buccinator muscles expel it from between the lips, as in blowing a trumpet. Hence the name {buccina, a trumpet). The Risorius retracts the angles of the mouth, and produces the unpleasant expression which is sometimes seen in tetanus, and is known as risus sardonicus, the sardonic laugh. 9. The Temporomandibular Region. Masseter. Temporal. The masseteric fascia (fascia parotideomasseterica) covers the Masseter muscle. It is firmly connected with this muscle and is derived from the deep cervical fascia. Above, this fascia is attached to the lower border of the zygoma, and behind, it invests the parotid gland, constituting the parotid fascia. The Masseter muscle {m. masseter) (Fig. 287) is a short, thick muscle, somewhat quadrilateral in form, consisting of two portions, the superficial and the deep. The superficial portion, the larger, arises by a thick, tendinous aponeu- rosis from the malar process of the maxilla, and from the anterior two-thirds of the lower border of the zygomatic arch; its fibres pass downward and backward, to be inserted into the angle and lower half of the outer surface of the ramus of the mandible. The deep portion is much smaller and more muscular in texture; it arises from the posterior third of the lower border and the whole of the deep surface of the zygomatic arch; its fibres pass downward and forward, to be inserted into the upper half of the ramus and outer surface of the coronoid process of the mandible. The deep portion of the muscle is partly concealed, in front by the superficial portion; behind, it is covered by the parotid gland. The fibres of the two portions are continuous at their insertion. Relations. — By its superficial surface, •^\nth the Zygomatic!, the parotid gland (the socia paro- tidis), the parotid duct, the branches of the facial nerve and the transverse facial vessels, which cross it; the masseteric fascia; the Risorius, Piatysma, and the integument. By its deep surface it is in relation with the Temporal muscle at its insertion, the ramus of the mandible, the Buc- cinator and the long buccal nerve, from which it is separated by a mass of fat (sucking pad). The masseteric nerve and artery enter in on its deep surface. Its posterior margin is overlapped by the parotid gland. Its anterior margin, which projects over the Buccinator muscle, is crossed below by the facial vein. 378 THE MUSCLES AND FASCIA The temporal fascia (Jascia temporalis) covers the Temporal muscle. It is a strong, fibrous investment, covered, on its superficial surface, by the Attrahens and AttoUens aurem muscles, the aponeurosis of the Occipitofrontalis, and by part of the Orbicularis palpebrarum. The temporal vessels and the auriculo- temporal nerve cross it from below upward. Above, it is a single layer, attached to the entire extent of the upper temporal ridge; but below, where it is attached to the zygoma, it consists of two layers, one of which is inserted into the outer, and the other into the inner, border of the zygomatic arch. A small quantity of fat, the orbital branch of the temporal artery, and a filament from the orbital, or temporomalar, branch of the superior maxillary nerve are contained between these two layers. It affords attachment by its deep surface to the superficial fibres of the Temporal muscle. Dissection. — In order to expose the Temporal muscle, remove the temporal fascia, which may be effected by separating it at its attachment along the upper border of the zygoma and dissecting it upward from the surface of the muscle. The zygomatic arch should then be divided in front at its junction with the malar bone, and behind near the externa! auditory meatus, and drawn downward with the Masseter, which should be detached from its insertion into the ramus and angle of the mandible. The whole extent of the Temporal muscle is then exposed 29.5. — The Temporal muscle, the zygoma and Masseter having been removed. The Temporal muscle (m. temporalis) (Figs. 294 and 295) is a broad, radiating muscle situated at the side of the head and occupying the entire extent of the tem- poral fossa. It arises from the whole of the temporal fossa except that portion of it which is formed by the malar bone. Its attachment extends from the external angular process of the frontal in front to the mastoid portion of the temporal behind, and from the curved line on the frontal and parietal bones above to the pterygoid ridge on the greater wing of the sphenoid below. It is also attached to the inner surface of the temporal fascia. Its fibres converge as they descend, and terminate in a flat tendon, which is inserted into the inner and outer surfaces, apex, and anterior border of the coronoid process and the anterior border of the ramus of the mandible, nearly as far forward as the last molar tooth. Relations. — By its superficial surface, with the integument, the Attrahens and Attollens aurem muscles, the temporal vessels and nerves, the aponeurosis of the Occipitofrontalis, the temporal THE PTERYGOMANDIBULAR REGION 379 fascia, the zygoma, and Masseter; by its Aeej) surface, with the temporal fossa, the External pterygoid and part of the Buccinator muscles, the internal maxillary artery and its deep tem- poral branches, and the deep temporal nerves. Behind the tendon are the masseteric vessels and nerve, and in front of it the buccal vessels and nerve. Its anterior border is separated from the malar bone by a mass of fat. Nerves. — Both the Masseter and Temporal muscles are supplied by branches of the inferior maxillary division of the trigeminal nerve. 10. The Pterygomandibular Region (Figs. 296, 297). External pterygoid. ■ Internal pterygoid. Dissection, — The Temporal muscle having been examined, saw through the base of the coronoid process and draw it upward, together with the Temporal muscle, which should be detached from the surface of the temporal fossa. Divide the ramus of the mandible just below the condyle, and also, by a transverse incision extending across the middle, just above the dental foramen; remove the fragment, and the Pterygoid muscles will be exposed. Fig. 296. — The Pterygoid muscles, the zygomatic arch, and a portion of the ramus of the mandible having been removed. The External pterygoid muscle (m. fterygoideus externus) is a short, thick muscle, somewhat conical in form, which extends almost horizontally between the zygomatic fossa and the condyle of the mandible. It arises by two heads, sepa- rated bya slight interval ; the upper head arises from the inferior surface of the greater wing of the sphenoid and from the pterygoid ridge which separates the zygomatic from the temporal fossa; the lower head arises from the outer surface of the external pterygoid plate. Its fibres pass horizontally backward and outward, to be inserted into a depression in front of the neck of the condyle of the mandible and into the front of the articular disk of the temporomandibular articulation. Relations. — By its swperfinal s«r/ac?, with the ramus of the mandible, the internal maxillary artery, which crosses it,' the tendon of the Temporal muscle, and the Masseter; by its deep surface it rests against the upper part of the Internal pterygoid muscle, the internal lateral liga- ment, the middle meningeal artery, and inferior maxillary nerve; by its upper border it is in relation with the temporal and masseteric branches of the inferior maxillary nerve; by its lower border it is in relation with the inferior dental and lingual nerves. Through the interval between the two portions of the muscle, the buccal nerve emerges and the internal maxillary artery passes, when the trunk of this vessel lies on the muscle (Fig. 292). 1 This is the usual relation, but in many cases the artery will be found below the muscle. 380 THE MVSCLES AND FASCIA The Internal pterygoid muscle {m. -pterygoideus iniernits) is a thick, quadri- lateral muscle, and resembles the Masseter in form. It arises from the pterygoid fossa, being attached to the inner surface of the external pterygoid plate and to the grooved surface of the tuberosity of the palate bone, and by a second slip from the outer surface of the tuberosities of the palate and maxilla : its fibres pass downward, outward, and backward, to be inserted, by a strong, tendinous lamina, into the lower and back part of the inner side of the ramus and angle of the mandible as high as the dental foramen. Relations. — By its superficial surface, with the ramus of the mandible, from which it is sep- arated, at its upper part, by the External pterygoid muscle, the internal lateral ligament, the internal maxillary artery, the dental vessels and nerves, and the lingual nerve, and a process of the parotid gland. By its deep surface, with the Tensor palati, being separated from the Superior constrictor of the pharynx by a cellular interval. Nerves. — These muscles are supplied by branches of the mandibular division of the tri- geminal nerve. Actions. — The Temporal, Masseter, and Internal pterygoid raise the mandible against the maxillse with great force. The External pterygoids assist in opening the mouth, but their main action is to draw forward the condyles and articular disks so that the mandible is protruded and the inferior incisors are projected in front of the upper; in this action they are assisted by the Internal pterygoids. The mandible is retracted by the posterior fibres of the Temporal. If the Internal and External pterygoids of one side act, the corresponding side of the mandible is drawn for- ward, while the opposite condyle remains comparatively fixed, and lateral movement, such as occurs during the trituration of the food, takes place. Surface Form. — The outline of the muscles of the head and face cannot be traced on the siu-face of the body, except in the case of two of the masticatory muscles. Those of the head are thin, so that the outline of the bone is perceptible beneath them. Those in the face are small, covered by soft skin, and often by a considerable layer of fat, so that their outline is con- cealed, but they serve to round off and smooth prominent borders and to fill up what would be otherwise unsightly angular depressions. Thus, the Orbicularis palpebrarum rounds off the prominent margin of the orbit, and the Pyramidalis nasi fills in the sharp depression beneath the glabella, and thus softens and tones down the abrupt depression which is seen on the un- clothed bone, In like manner, the labial muscles, converging to the lips and assisted by the superimposed fat, fill in the sunken hollow of the lower part of the face. Although the muscles of the face are usually described as arising from the bones and inserted into the nose, lips, and corners of the mouth, they have fibres inserted into the skin of the face along their whole extent, so that almost every point of the skin of the face has its muscular fibre to move it; hence it is that when in action the facial muscles produce alterations in the skin-surface, giving rise to the formation of various folds or wrinkles, or otherwise altering the relative position of the parts, so as to produce the varied expressions with which the face is endowed; hence these muscles are termed the muscles of expression.'- The only two muscles in this region which greatly influence surface form are the Masseter and the Temporal. The Masseter is a quadi'ilateral muscle, which imparts fulness to the hinder part of the cheek. When the muscle is firmly contracted, as when the teeth are clenched, its outline is plainly visible; the anterior border forms a prominent vertical ridge, behind which is a considerable fulness, especially marked at the lower part of the muscle; this fulness is entirely lost when the mouth is opened and the muscle no longer in a state of contraction. The Temporal muscle is fan-shaped, and fills the temporal fossa, sub- stituting for it a somewhat convex form, the anterior part of which, on account of the absence of hair over the temple, is more marked than the posterior, and stands out in strong relief when the muscle is in a state of contraction. MUSCLES AND FASCIA OF THE NECK. The muscles of the neck may be arranged into groups corresponding with the region in which they are situated. These groups are nine in number: 1. Superficial Cervical Region. 5. Pharyngeal Region. 2. Infrahyoid Region. 6. Palatal Region. 3. Suprahyoid Region. 7. Anterior Vertebral Region. 4. Lingual Region. 8. Lateral Vertebral Region. 9. Muscles of the Larynx. Man and Animals, and several articles in the Journal of MUSCLES AND FASCIA OF THE NECK 381 The muscles contained in each of these groups are the following: 1. Superficial Region. Platysma. Sternomastoid. 2. Infrahyoid Region. Sternohyoid. Sternothyroid. Thyrohyoid. Omohyoid. 3. Suprahyoid Region. Digastric. Stylohyoid. Mylohyoid. Geniohyoid. 4. Lingual Region. Geniohyoglossus. Hyoglossus. Chondroglossus. Styloglossus. Palatoglossus. ^ f Superior lingual. g J Inferior lingual. 5 1 Transverse lingual. E\ t Vertical lingual. W 5. Muscles of the Pharynx. Inferior constrictor. Middle constrictor. Superior constrictor. Stylopharyngeus. Palatopharyngeus. Salpingopharyngeus. 6. Muscles of the Soft Palate. Levator palati. Tensor palati. Azygos uvulae. Palatoglossus. Palatopharyngeus. Salpingopharyngeus. 7. Muscles of the Anterior Vertebral Region. Rectus capitis anticus major. Rectus capitis anticus minor. Rectus capitis lateralis. Longus colli. 8. Muscles of the Lateral Vertebral Region . Scalenus anticus. Scalenus medius. Scalenus posticus. 9. Muscles of the Larynx {Intrinsic). Included in the description of the Larynx (page 1172.) 1. The Superficial Cervical Region. Platysma. Sternomastoid. Dissection. — A block having been placed at the back of the neck, and the face turned to the side opposite that to be dissected, so as to place the parts upon the stretch, make two trans- verse incisions, one from the chin, along the margin of the mandible, to the mastoid process, and the other along the upper border of the clavicle. Connect these by an oblique incision made in the course of the Sternomastoid muscle, from the mastoid process to the sternum; the two flaps of integument having been removed in the direction shown in Fig. 286, the superficial fascia will be exposed. The superficial cervical fascia is a thin, aponeurotic lamina which is hardly demonstrable as a separate membrane. It invests the Platysma. The Platysma (^platysma) (Fig. 287) is a broad, thin plane of muscle fibres situated on the side of the neck. It arises by thin, fibrous bands from the fascia covering the upper part of the Pectoral and Deltoid muscles; its fibres pass 382 THE MUSCLES AND FASCIA over the clavicle and proceed obliquely upward and inward along the side of the neck. The anterior fibres interlace, below and behind the symphysis menti, with the fibres of the muscle of the opposite side; the posterior fibres pass over the mandible, some of them are attached to the bone below the external oblique line, others pass on to be inserted into the skin and subcutaneous tissue of the lower part of the face, and many of these fibres blend with the muscles about the angle and lower part of the mouth. Sometimes fibres can be traced to the Zygo- matic muscles or to the margin of the Orbicularis oris. Beneath the Platysma the external jugular vein may be seen descending in a line from the angle of the mandible to the middle of the clavicle. Relations, — By its superficial surface, with the integument, to which it is united more closely below than above; by its deej} surface, with the Pectoralis major and Dehoid, and with the clavicle. In the nech, with the external and anterior jugular veins, the deep cervical fascia, the superficial branches of the cervical plexus, the Sternomastoid, Sternohyoid, Omohyoid, and Digastric muscles. Behind the Sternomastoid muscle the Platysma covers in the posterior tri- angle of the neck; on the /ace it is in relation with the parotid gland, the facial artery and vein, and the Masseter and Buccinator muscles. Nerves. — The lower division of the facial nerve supplies this muscle. Action. — The Platysma produces a slight wrinkling of the surface of the skin of the neck in an oblique direction, when the entire muscle is brought into action. Its anterior portion, the thickest part of the muscle, depresses the mandible; it also serves to draw down the lower lip and the angle of the mouth on each side, thus being one of the chief agents in the expression of melancholy. In the pressure upon the bloodvessels of the neck induced by strong inspira- tory effort, this muscle draws away the skin and fascia, and by so doing greatly diminishes the pressure on the veins. The deep cervical fascia {fascia colli) (Fig. 297) lies under cover of the Platysma muscle and constitutes a complete investment for the neck. It also forms a sheath for the carotid vessels, and, in addition, is prolonged deeply in the shape of certain processes or lamellae, which come into close relation with the structures situated in front of the vertebral column. The investing portion of the fascia is attached, behind, to the ligamentum nuchae and to the spine of the seventh cervical vertebra. It forms a thin investment for the Trapezius muscle, at the anterior border of which it is continued forward as a loose areolar layer, which covers the posterior triangle of the neck; thence it passes to the posterior border of the Sternomastoid, where it begins to assume the appearance of a fascial membrane. Along the hinder edge of the Sternomastoid tlie membrane divides to enclose this muscle, at the anterior edge of which it once more forms a single lamella, which roofs in the anterior triangle of the neck, and, reaching forward to the middle line, is continuous with the corresponding part from the opposite side of the neck. In the middle line of the neck it is attached to the symphysis menti and to the body of the hyoid bone. Above, the fascia is attached to the superior curved line of the occiput, to the mastoid process of the temporal, and to the whole length of the body of the man- dible. Opposite the angle of the mandible the fascia is very strong, and binds the anterior edge of the Sternomastoid firmly to that bone. Between the mandible and the mastoid process it ensheaths the parotid gland — the layer which covers the gland extending upward (parotid fascia) to be fixed to the zygomatic arch. The parotid fascia is prolonged forward to cover the Masseter muscle, the masse- teric fascia. From the layer which passes under the parotid a strong band, the stylomandibular ligament, reaches from the styloid process to the angle of the mandible. Three other bands may be defined — the internal lateral ligament of the temporomandibular articulation (p. 279), the pterygomandibular, and the pterygospinous ligaments. The pterygospinous ligament stretches across from the upper half of the posterior free border of the external pterygoid plate to the spinous process of the sphenoid. It occasionally ossifies, producing an adventi- THE SUPERFICIAL CERVICAL REGION 383 tious pterygospinous foramen, which transmits the branches of the mandibular division of the trigeminal nerve to the muscles of mastication. Below, the cervical fascia is attached to the acromion process, the clavicle, and to the manubrium sterni. Some little distance above the last-named point, how- ever, it splits into two layers, superficial and deep. The former is attached to the anterior border of the manubrium, the latter to its posterior border and to the interclavicular ligament. Between these two layers is a slit-like interval, the suprasternal space (spatium suprasternale). It contains a small quantity of Trochlear process of deep cervical fascia for Omohyoid tendon. OMOHYOID. Thyioid body ' Common caiohd ai teiy Internal jugidai vein TERNOMASTO Vagus} nerve. y~ U" '/, External "] jugtdar > 0^- Anterior jugular vein. STERNOHYOID. -STERNOTHYROID, Pretracheal fascia. Ti achea. (Esophagus. Prevertebral fascia. LONGUS COLLI, ■61h cervical. Vertebral vessels. TRAPEZIUS — -SEMISPINALIS COLLL COMPLEXUS. SPLENIUS CAPITIS. Fig. 297.— Section of the i ck at about the level of the sixth cervical vertebr; deep cervical fascia. Showing the arrangement of the areolar tissue, sometimes a lymph node, the lower portions of the anterior jugular veins and their transverse connecting branch, and also the sternal heads of the Sternomastoid muscles. The fascia which covers the deep aspect of the Sternomastoid gives off certain im- portant processes, viz. : (1) A trochlear process to envelop the tendon of the Omohy- oid, and bind it down to the sternum and first costal cartilage. (2) A strong sheath, the carotid sheath, for the large vessels of the neck, enclosed within which are the carotid artery, internal Jugular vein, the vagus, and descendens hypoglossi nerves. 384 THE MUSCLES AND FASCIA (3) The prevertebral fascia {fascia praevertebralis) , which extends inward behind the carotid vessels, where it assists in forming their sheath, and passes in front of the prevertebral muscles. It thus forms the posterior limit of a fibrous compart- ment which contains the larynx and trachea, the thyroid gland, and the pharynx and oesophagus. The prevertebral fascia is fixed above to the base of the skull, while below it is continued into the thorax in front of the Longus colli muscles. Parallel to the carotid vessels and along their inner aspect it gives off a thin lamina, the buccopharyngeal fascia, which closely invests the Constrictor muscles of the pharynx, and is continued forward from the Superior constrictor on to the Buccinator. The prevertebral fascia is attached to the prevertebral layer by loose connective tissue only, and thus an easily distended space, the retropharyngeal space, is found between them. This space is limited above by the base of the skull, while below it extends behind the oesophagus into the thorax, where it is continued into the posterior mediastinum. This fascia is also prolonged downward and outward behind the carotid vessels and in front of the Scaleni muscles, and forms a sheath for the brachial plexus of nerves and for the subclavian vessels in the posterior triangle of the neck, and, continuing under the clavicle as the axillary sheath, it becomes attached to the deep surface of the costocoracoid membrane. Immediately above the clavicle an areolar space exists between the investing layer and the sheath of the subclavian vessels, and in it are found the lower part of the external jugular vein, the descending clavicular nerves, the suprascapular and transversalis colli vessels, and the posterior belly of the Omohyoid muscle. This space extends downward behind the clavicle, and is limited below by the fusion of the costocoracoid membrane with the anterior wall of the axillary sheath. (4) The pretracheal fascia, which extends inward in front of the carotid vessels, and assists in forming the carotid sheath. It is further continued behind the Depressor muscles of the hyoid bone, and, after enveloping the thyroid body, is prolonged in front of the trachea to meet the corresponding layer of the opposite side. Above, it is fixed to the hyoid bone, while below it is carried downward in front of the trachea and large vessels at the root of the neck, and ultimately blends with the fibrous pericardium. This layer is fused on either side with the prevertebral layer, with which it completes the compartment containing the larynx and trachea^ the thyroid gland, the pharynx, and oesophagus. Applied Anatomy. — The deep cervical fascia is of considerable importance from a surgical point of view. As will be seen from tlie foregoing description, it may be divided into tliree layers : (1) A superficial layer; (2) a layer passing in front of the trachea, and forming with the super- ficial layer a sheath for the Depressors of the hyoid bone; (3) a prevertebral layer passing in front of the bodies of the cervical vertebrae, and forming with the second layer a space in which are contained the trachea, oesophagus, etc. The superficial layer forms a complete investment for the neck. It is attached behind to the ligamentum nuchae and the spine of the seventh cer- vical vertebra; above, it is attached to the external occipital protuberance, to the superior curved !ine of the occiput, to the mastoid process, to the zygoma and the mandible; below, it is attached to the manubrium sterni, the clavicle, theacromion process, and the spine of the scapula; in front it blends with the fascia of the opposite side. This layer opposes the extension of abscesses or new growths toward the surface, and pus forming beneath ithas a tendency to extend laterally. If pus is in the posterior triangle, it might extend backward under the Trapezius, forward under the Sternomastoid, or downward under the clavicle for some distance, until stopped by the junction of the cervical fascia to the costocoracoid membrane. If the pus is contained in the anterior triangle, it might find its way into the anterior mediastinum, being situated in front of the layer of fascia which passes down into the thorax to become continuous with the peri- cardium; but owing to the lesser density and thickness of the fascia in this situation it more frequently finds its way through it and points above the sternum. The second layer of fascia, is connected above with the hyoid bone. It passes down beneath the Depressors and in front of the thyroid body and trachea to become continuous with the fibrous layer of the pericardium. Laterally it invests the great vessels of the neck and is connected with the superficial layer beneath the Sternomastoid. Pus forming beneath this layer would in all probability find its way into the posterior mediastinum. The third layer (the prevertebral fascia) is connected above to the base of the skull. Pus forming beneath this layer, in cases, for instance, of caries of the bodie? THE SUPEB.FICIA L CER VIVA L REGION .385 of the cervical vertebrae, mislit extend toward the posterior and lateral part of the neck and point in this situation, or inifjht ])ertorate this layer of fascia and the pharyngeal fascia and point into the pharynx {riiropharyngcal ahsccss). In cases of cut throat the cervical fascia is of considerable importance. When the v>ound involves only the superficial layer the injury is usually trivial, the only special danger being injury to the external jugular vein, and the only special complication being diffuse cellulitis. But where the second of the two layers has been opened up, and where important structures may have been injured, serious results may ensue. The Sternomastoid (?n. siernocleidomasfoideus) (Fig. 298) is a large, thick muscle, which passes obliquely across the side of the neck, being enclosed between two layers of the deep cervical fascia. It is thick and narrow at its central part, but is broader and thinner at each extremity. It arises, by two heads, from the sternum and clavicle. The sternal portion is a rounded fasciculus, tendinous in front, fleshy behind, which arises from the upper and anterior part of the first piece of the sternum, and is directed upward, outward, and backward. The clavicular portion arises from the inner tliird of the superior border and anterior surface of the clavicle, being composed, of fleshy and aponeurotic fibres; it is directed almost vertically upward. These two portions are separated from each Fig. 29S. — Muscles of the neck and boundaries of the triangles. other, at their origin, by a triangular cellular interval, but become gradually blended, below the middle of tlie neck, into a thick, rounded muscle, which is inserted, by a strong tendon, into the outer surface of tlae mastoid process of tlie temporal bone, from its apex to its superior border, and by a thin aponeurosis into the outer half of the superior curved line of the occipital bone. The Sterno- mastoid varies much in its extent of attachment to the clavicle; in one case the clavicular may be as narrow as the sternal portion ; in another, the former, may be 386 THE MUSCLES AND FASCIA as much as three inches in breadth. When the clavicular origin is broad, it is occasionallj' subdivided into numerous slips separated by narrow intervals. More rarely, the corresponding margins of the Sternomastoid and Trapezius have been found in contact. Triangles of the Neck. — The Sternomastoid muscle divides the quadrilateral area of the side of the neck into two triangles, an anterior and a posterior. The boundaries of the anterior triangle are, \n front, the median Hne of the neck; above, the lower border of the body of the mandible, and an imaginary line drawn from the angle of the mandible to the mastoid process; behind, the anterior border of the Sternomastoid muscle. The apex of the triangle is at the upper border of the sternum. The bdundaries of the posterior triangle are, in front, the pos- terior border of the Sternomastoid; helow, the middle third of the clavicle; behind, the anterior margin of the Trapezius.' The apex corresponds with the meeting of the Sternomastoid and ' Trapezius on the occipital bone. Relations. — By its superfieial surface, with the integument and Platysma, from which it is separated by the external jugular vein, some of the superficial branches of the cervical plexus, and the superficial layer of the deep cervical fascia. By its deep surface it is in relation with the Sternoclavicular articulation; a process of the deep cervical fascia; the Sternohyoid, Sterno- thyroid, Omohyoid, posterior belly of the Digastric, Levator anguli scapulae, Splenius and Scaleni muscles;- common carotid artery, internal jugular vein, commencement of the internal and external carotid arteries, the occipital, subclavian, transversalis colli, and suprascapular arteries and veins; the phrenic, vagus, hypoglossal, descendens and communicans hypoglossi nerves; the spinal accessory nerve, which pierces its upper third; the cervical plexus, parts of the thyroid and parotid glands, and deep lymph nodes. Nerves. — The Sternomastoid is supplied by the spinal accessory nerve and deep branches of the cervical plexus. Actions. — When only one Sternomastoid muscle acts, it draws the head toward the shoulder of the same side, assisted by the Splenius and the Obliquus capitis inferior of the opposite side. At the same time it rotates the head so as to carry the face toward the opposite side. When the two muscles act together they flex the head upon the neck. If the head is fixed, the two muscles assist in elevating the thorax in forced inspiration. Applied Anatomy. — The applied anatomy of the Sternomastoid muscle is of importance chieflv in connection with the deformity known as wrij-neck (torticollis). Wry-neck may be either acquired, congenital, or spasmodic. The acquired may be caused by acute glandular enlargement, cellulitis of the neck, myositis of the Sternomastoid, or cervical caries. The con- genital variety is due to injury of the Sternomastoid during birth, which probably causes a subsequent chronic fibrous myositis (Mikulicz). This is best remedied by making an open horizontal incision over the origin of the muscle and exposing it. A director is then passed underneath and the muscle clearly divided, making sure that any tense bands of fascia are thor- oughly divided. Spasmodic torticollis is a condition of adult life. It is marked by clonic or tonic spasm, first of the Sternomastoid, then of many of the other neck muscles. It is thought to be a disease of the central nerve system. 2. The Infrahyoid Region (Figs. 298, 299). Depressors of the Hyoid Bone and Larynx. Sternohyoid. , Thyrohyoid. Sternothyroid. Omohyoid. Dissection. — The muscles in this region may be exposed by removing the deep fascia from the front of the neck. In order to see the entire extent of the Omohyoid it is necessary to divide the Sternomastoid at its centre, and turn its ends aside, and to detach the Trapezius from the clavicle and scapula. This, however, should not be done until the Trapezius has been dissected. The Sternohyoid (m. stemohyoideus) is a thin, narrow, ribbon-like muscle, which arises from the inner extremity of the clavicle, the posterior sternoclavicular ligament, and the upper and posterior part of the first piece of the sternum; passing upward and inward, it is inserted, by short, tendinous fibres, into the lower border of the body of the hyoid bone. This muscle is separated, below, from ' The anatomy of these triangles will be more exactly described with that of the vessels of the neck. THE INFRAHYOID REGION 387 its fellow by a considerable interval; but the two muscles come into contact with each other in the middle of their course, and from this upward lie side by side. It sometimes presents, immediately above its origin, a transverse tendinous intersection, like those in the Rectus abdominis. As a rule, two bursa? (hursae sternohyoidii) lie between the cricothyroid membrane and the Sternohyoid muscle. Relations. — By its superficial surface, below, with the sternum, the sternal end of the clavicle, and the Sternomastoid; and above, with the Platysma and deep cervical fascia; by its deep sur- face, with the Sternothyroid, Cricothyroid, and Thyrohyoid muscles, the thyroid gland, the superior thyroid vessels, the thyroid cartilage, the cricothyroid and thyrohyoid membranes. The Sternothyroid (m. sternothyreoideus) is situated beneath the preceding muscle, but is shorter and wider than it. It arises from the posterior surface of the first piece of the sternum, below the origin of the Sternohyoid, and from the edge of the cartilage of the first rib, occasionally of the second rib also, and is inserted into the oblique line on the side of the ala of the thyroid cartilage. This muscle is in close contact with its fellow at the lower part of the neck, and is occa- FlG. 299. — Muscles of the neck. Anterior view. sionally traversed by a transverse or oblique tendinous intersection, like those in the Rectus abdominis. Relations.— By its superficial surface, with the Sternohyoid, Omohyoid, and Sternomastoid; by its deep surface, from below upward, with the trachea, innominate veins, common carotid (and on the right side the innominate artery), the thyroid gland and its vessels, and the lower part ofthe larynx and pharynx. The inferior thyroid vein lies along its inner border, a relation which it is important to remember in the operation of tracheotomy. On the left side the deep surface of the muscle is in relation to the oesophagus. The Thyrohyoid {m. thyreohyoideus) is a small, quadrilateral muscle appear- ing like a continuation of the Sternothyroid. It arises from the oblique line on 388 THE MUSCLES AND FASCIA the side of the thyroid cartilage, and passes vertically upward to be inserted into the lower border of the body and greater cornu of the hyoid bone. Relations. — By its superficial surface, with the Sternohyoid and Omohyoid muscles; by its deep surface, with the thyroid cartilage, the thyrohyoid membrane, and the superior laryngeal vessels and nerve. The Omohyoid (m. omoliyoideus) passes across the side of the neck, from the scapula to the hyoid bone. It consists of two fleshy bellies, united by a central tendon. It arises from the upper border of the scapula, and occasionally from the transverse ligament which crosses the suprascapular notch, its extent of attach- ment to the scapula varying from one-sixth of an inch to an inch. From this origin the posterior belly {venter inferior) forms a flat, narrow fasciculus, which inclines forward and slightly upward across the lower part of the neck, behind the Sternomastoid muscle, where it becomes tendinous; it then changes its direc- tion, forming an obtuse angle, and terminates in the anterior belly {venter superior), which passes almost vertically upward, close to the outer border of the Sternohyoid, to be inserted into the lower border of the body of the hyoid bone, just external to the insertion of the Sternohyoid. The central tendon of this muscle, which varies much in length and form, is held in position by a process of the deep cervical fascia, which includes it in a sheath. This process is prolonged down, to be attached to the clavicle and first rib. It is by this means that the angular form of the muscle is maintained. The posterior belly of the Omohyoid divides the posterior triangle of the neck into an upper or occipital, and a lower or subclavian triangle, while its anterior belly divides the anterior triangle of the neck into an upper or carotid, and a lower or muscular triangle. Relations. — By its superficial surface, with the Trapezius, the Sternomastoid, deep cervical fascia, Platysma, and integument; by its deep surface, with the Scaleni muscles, phrenic nerve, lower cervical nerves which go to form the brachial plexus, the suprascapular vessels and nerve, sheath of the common carotid artery and internal jugular vein, the Sternothyroid and Thyro- hyoid muscles. Nerves. — The Depressors of the hyoid bone are supplied by branches from the ansa ceni- calis formed by the first three cervical nerves. Actions. — These muscles depress the larynx and hyoid bone, after they have been drawn up with the pharynx in the act of deglutition. The Omohyoid muscles not only depress the hyoid bone, but carry it backward and to one side. This bone is concerned especially in pro- longed inspiratory efforts; for by rendering the lower part of the cervical fascia tense it lessens the inward suction of the soft parts, which would otherwise compress the great vessels and the apices of the lungs. This action is synergistic with that of the Platysma. The Thyrohyoid may act as an elevator of the thyroid cartilage when the hyoid bone ascends, drawing u]jward the thyroid cartilage, behind this bone. The Sternothyroid acts as a depressor of the thyroid cartilage. 3. The Suprahyoid Region (Figs. 298, 299). Elevators of the Hyoid Bone — Depressors of the Mandible. Digastric. Mylohyoid. Stylohyoid. Geniohyoid. Dissection. — To dissect these muscles a block should be placed beneath the back of the neck, and the head drawn backward and retained in that position. On the removal of the deep fascia the muscles are at once exposed. The Digastric (m. digastricus) consists of two fleshy bellies united by an inter- mediate, rounded tendon. It is a small muscle, situated below the side of the body of the mandible, and extending, in a curved form, from the side of the head to the symphysis of the mandible. The posterior belly {venter posterior), longer than the anterior, arises from the digastric groove on the inner side of the mastoid process of the temporal bone, and passes downward, forward, and inward. THE >SUmAHYOn) REGION 3S9 The anterior belly {venter anterior) arises from a depression on the inner side of the lower border of the mandible, close to the symphysis, and passes downward and backward. The two bellies terminate in the central tendon which per- forates the Stylohyoid, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, lined with a synovial mem- brane. A broad aponeurotic layer is given off from the tendon of the Digastric on each side, which is attaciied to the body and greater cornu of the hyoid bone; this is termed the suprahyoid aponeurosis. It forms a strong layer of fascia between the anterior portions of the two muscles, and a firm investment for the other muscles of the suprahyoid region which lie deeper. Relations. — By its superficial surface, with the mastoid process, the Platysma, Sternomastoid, part of the Splenius, Trachelomastoid, and Stylohyoid muscles, and the parotid gland. By its deep surface, the anterior belly lies on the Mylohyoid; the posterior belly on the Styloglossus, Stylopharyngeus, and Hyoglossus muscles, the external carotid artery and its occipital, lingual, facial, and ascending pharyngeal branches, the internal carotid artery, internal jugular vein, and hypoglossal nerve. The Stylohyoid (m. stylohyoideus) is a small, slender muscle, lying in front of and above the posterior belly of the Digastric. It arises from the back and outer surface of the styloid process of the temporal bone, near the base; and, passing downward and forward, is inserted into the body of the hyoid bone, just at its junction with the greater cornu, and immediately above the Omohyoid. This muscle is perforated, near its insertion, by the tendon of the Digastric. Fig. 300.— Mylohyoid muscle. (P. d Charpy.) Relations. — By its superficial surface, above, -viilh- the parotid gland and deep cervical fascia; below, this muscle is superficial, being situated immediately beneath the deep cervical fascia. By its deep surface, with the posterior belly of the Digastric, the external carotid artery, with its lingual and facial branched, the Hyoglossus muscle, and the hypoglossal nerve. The Stylohyoid Ligament (licjamentum stylohyoideus). — In connection with the Stylohyoid muscle may be described a ligamentous band, the stylohyoid ligament. It is a fibrous cord, often containing a little cartilage in its centre, which continues the styloid process down to the hyoid bone, being attached to the tip of t!ie former and to the lesser cornu of the latter. It is often more or less ossified, and in many animals forms a distinct bone, the epihyal. The Mylohyoid (?ra. mylohyoideus) (Fig. 300) is a flat, triangular muscle, 390 THE MUSCLES AND FASCIA situated immediately beneath the anterior belly of the Digastric, and forming, with its fellow of the opposite side, a muscular floor for the cavity of the mouth. It arises from the whole length of the mylohyoid ridge of the mandible, extending from the symphysis in front to the last molar tooth behind. The posterior fibres pass inward and slightly downward, to be iiiserted into the body of the hyoid bone. The middle and anterior fibres are inserted into a median fibrous raphe, extending from the symphysis of the mandible to the hyoid bone, where they join at an angle with the fibres of the opposite muscle. The median raphe is sometimes wanting; the muscle fibres of the two sides are then directly continuous with one another. Relations. — By its superficial surface, with the Platysma, the anterior belly of the Digastric, the suprahvoid aponeurosis, the submaxillary gland, submental vessels, and mylohyoid vessels and nerve; by its deep surface, with the Geniohyoid, part of the Hyoglossus and Styloglossus muscles, the hypoglossal and lingual nerves, the submaxillary ganglion, the sublingual gland, the deep portion of the submaxillary gland and duct; the sublingual and ranine vessels, and the buccal mucous membrane. Fig. 301. — Muscles of the tongue. Left side.i Dissection. — The Mylohyoid should now be removed, in order to expose the muscles which lie beneath; this is effected by reflecting it from its attachments to the hyoid bone and man- dible, and separating it by a vertical incision from its fellow of the opposite side. The Geniohyoid (?«. geniohyoideus) (Fig. 301) is a 'narrow, slender muscle, situated immediately beneath^ the inner border of the Mylohyoid. It arises from the inferior genial tubercle on the inner side of the symphysis of the mandible, and passes downward and backward, to be inserted into the anterior surface of the body of the hyoid bone. This muscle lies in close contact with its fellow of the opposite side, and increases slightly in breadth as it descends. ' The muscles and ligaments attached to the styloid process have been termed the " bouquet of Riolanua." - This refers to the depth of the muscles from the skin in the order of dissection. In the erect position of the bodj' the Geniohyoid is above the Mylohyoid. THE LINGUAL RF.GION 391 Relations. — It is covered by the Mylohyoid and lies along the lower border of the Genio- hyoglossus. Nerves. — The anterior belly of the Digastric is supplied by the mylohyoid "Sranch of the inferior dental; its posterior belly, by the facial; the Stylohyoid is su|)plicd by the facial; tlie Mylohyoid, by the mylohyoid branch of the inferior dental; the Geniohyoid, by a branch from the ansa cervicalis which accompanies the hypoglossal in a common sheath. Actions. — This group of muscles performs two very important actions. They raise the hyoid bone, and with it the base of the tongue, during the act of deglutition; or, when the hyoid bone is fixed by its Depressors and those of the larynx, they depress the mandible. During the first act of deglutition, when the mass is being driven from the mouth into the pharynx, the hyoid bone, and with it the tongue, is carried upward and forAvard by the anterior belly of the Digastric, the Mylohyoid, and Geniohyoid muscles. In the second act, when the mass is passing through the pharynx, the direct elevation of the hyoid bone takes place by the combined action of all the muscles; and after the food has passed, the hyoid bone is carried upward and backward by the posterior belly of the Digastric and Stylohyoid muscles, w-hich assist in preventing the return of the bolus into the mouth. ''- 4. The Lingual Region (Figs. 301, 302). Geniohyoglossus. Styloglossus. Hyoglossus. Palatoglossus.' Chondroglossus. Dissection. — After completing the dissection of the preceding muscles, saw through the mandible just external to the symphysis. Then draw the tongue forw'ard, and attach it, by a stitch, to the nose; when its muscles, which are thus put on a stretch, may be examined. ^ The Geniohyoglossus {m. genioglossus) has received its name from its triple attachment to the mandible, hyoid bone, and tongue. It is a flat, triangular muscle, placed vertically on either side of the middle line, its apex corresponding with its point of attachment to the mandible, its base with its insertion into the tongue and hyoid bone. It arises by a short tendon from the superior genial tubercle on the inner side of the symphysis of the mandible, immediately above the Geniohyoid; from this point the muscle spreads out in a fan-like form, a few of the inferior fibres passing downward, to be attached by a thin aponeurosis into the upper part of the body of the hyoid bone, a few fibres passing between the Hyoglossus and Chondroglossus to blend with the Constrictor muscles of the pharynx; the middle fibres passing backward, and the superior ones upward and forward, to enter the whole length of the under surface of the tongue, from the base to the apex. The two muscles lie on either side of the median plane; behind they are quite distinct from each other, and are separated at their insertion into the under surface of the tongue by a tendinous raphe, which extends through the middle of the organ. In front the two muscles are more or less blended; distinct fasciculi are to be seen passing off from one muscle, crossing the middle line, and intersecting with bundles of fibres derived from the muscle on the other side. Relations. — By its deep surface this muscle is in contact with its fellow of the opposite side; by its superficial surface, with the Inferior lingualis, the Hyoglossus, the lingual artery and hypoglossal nerve, the lingual nerve, and sublingual gland; by its upper border, with the mucous membrane of the floor of the mouth (fremnn linguae); by its loiver border with the Geniohyoid. The Hyoglossus (m. hyoc/lossus) is a thin, flat, quadrilateral muscle which arises from the side of the body and whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, I The Palatoglossus, or constrictor isthmi faucitim, although one of the muscles of the tongue which serA'es to draw the base of that organ upward during the act of deglutition, is more nearly associated, both in situation and function, with the soft palate. It will consequently be described with the group of Palatal muscles. 392 THE MUSCLES AND FASCIA between the Stj'loglossus and Lingualis. The fibres of this muscle which arise from the body are directed upward and backward, overlapping those arising from the greater cornu, which are directed upward and forward. Relations. — By its superficial surface, with the Digastric, the Stylohyoid, Styloglossus, and Mylohyoid muscles, the submaxillary ganglion, the lingual and hypoglossal nerves, the sub- maxillary duct, the ranine vein, the sublingual gland, and the deep portion of the submaxillary gland. By its deep surface, with the Stylohyoid ligament, the Geniohyoglossus, Lingualis, and Sliddle constrictor, the lingual vessels, and the glossopharyngeal nerve. The Chondroglossus (m. choiidroglossus) is a distinct muscular slip, though it is sometimes described as a part of the Hyoglossus, from which, however, it is sepa- rated by the fibres of the Geniohyoglossus, which pass to the side of the pharynx. It is about three-quarters to an inch in length; it arises from the inner side and base of the lesser cornu and contiguous portion of the body of the hyoid bone, and passes directly upward to blend with the Intrinsic muscle fibres of the tongue, between the Hyoglossus and Geniohyoglossus. The Styloglossus (m. styloglossus), the shortest and smallest of the three styloid muscles, arises from the anterior and outer side of the styloid process, near the apex, and from the stylomandibular ligament, to which its fibres, in most cases, are attached by a thin aponeurosis. Passing downward and forward between the internal and external carotid arteries, and becoming nearly horizontal in its direction, this muscle divides upon the side of the tongue into two portions — one longitudinal, which enters the .^-9 ^^OffilpiU*^ OUT EDGE OF SUPERIOR LINGUALIS. Fig. 302. -Muscles on the dorsum of the tongue. Fig. 303. — Coronal section of tongue. Showing intrinsic muscles, a. Lingual artery. 6. Inferior lingualis. cut through, c. Fibres of Hyoglossus. d. Oblique fibres of Styloglossus, e. Inser- tion of Transverse lingualis. f. Superior lingualis. g. Papillse of tongue, h. Vertical fibres of Geniohyglossus intersecting Trans- verse lingualis. i. Septum. (Altered from Krause.) side of the tongue near its dorsal surface and blends with the fibres of the Lingualis in front of the Hyoglossus; the other oblique, which overlaps the Hyoglossus muscle and decussates with its fibres. Relations. — By its superficial surface, from above downward, with the parotid gland, the Internal pterygoid muscle, the lingual nerve, and the mucous membrane of the mouth; by its deep surface, with the tonsil, the Superior constrictor, and the Hyoglossus muscle. Nerves. — The muscles of this group are supplied by the hypoglossal nerve. THE LINGUAL RECflON 393 The Muscle Substance of the Tongue (Figs. 302 and 303).— The muscle fibres of the tongue run in \:irii)us directions. These fibres are divifled into two sets — Extrinsic and Intrinsic. The Extrinsic muscles of the. tongue are those which have their origin external to, and only their terminal fibres contained ipilhin, the substance of the organ. They are: the Styloglossus, the Ilyoglossus, the Palatoglossus, the Geniohyoglossus, and part of the Superior constrictor of the pharynx (Pharyngoglossus). The Intrinsic muscles are those which are contained entirely irithin the tongue, and which form the giM'alcr pari of its muscular structure. The tiinguc consists of .synnuelrical halves separated from each other in the middle line by a fibrous septum [srpium liiii/iiar). Kach half is composed of muscle fibres arranged in various directions, containing much interposed fat, and .supplied by vessels and nerves. Immediately beneath the mucous membrane is a submucous fibrous layer, into which the muscle fibres whicSi terminate in this stratum of the tongue are inserted. Upon removing this, with the mucous membrane, the first stratum of muscle fibres is exposed. This belongs to the group of Intrinsic muscies, and has been named the Superior lingualis (m. longitiidinnli.y .sw(/«r/«/-). It consists of a thin layer of oblique and longitudinal fibres which arise from the siilniiiicous fibrous layer, close to the epiglottis, and fVoiii the fibrous septum, and which pass forward and outward to the edges of the tongue. Between lis fibres pass some vertical fibres derived from the Geniohyo- glossus and from the vertical Intrinsic muscle, which will be described later on. Beneath this layer is the second stratum of muscle fibres, derived principally from the Extrinsic muscles. In front this stratum is formed by the fibres derived from the Styloglossus, which run along the side of the tongue and which in turn send out two sets of fibres. The first of these two latter sets of fibres extends over the dorsum and runs obliquely forward and inward to the middle line. The second set of fibres goes on to the under surface of the sides of the anterior part of the tongue, and runs between the fibres of the Hyoglossus muscle forward and inward to the middle line. Behind this layer of fibres, derived from the Styloglossus, are fibres derived from the Hyoglossus, assisted by some few fibres of the Palatoglossus. The Hyoglossus, enter- ing the side of the under surface of the tongue, between the Styloglossus and Inferior lingualis, passes around its margin and spreads out into a layer on the dorsum, which occupies the middle third of the organ, and runs almost transversely inward to the septum. It is reenforced by some fibres from the Palatoglossus; other fibres of this muscle pass more dee|jly and inter- mingle with the next layer. The posterior part of the second layer of the muscle fibres of tlie tongue is derived from those fibres of the Hyoglossus which arise from the lesser cornu of the hyoid bone, and are here described as a separate muscle — the Chondroglossus. The fibres of this muscle are arranged in a fan-shaped manner, and spread out over the posterior third of the tongue. Beneath this layer is the third layer, the great mass of Intrinsic muscles of the tongue, which is intersected at right angles by the terminal fibres of one of the Extrinsic muscles — the Genio- hyoglossus. This portion of the tongue is paler in color and softer in texture than that already described, and is sometimes designated the medullary portion in contradistinction to the firmer superficial part, wliich is lerneil the cnrliral portion. The medullary portion consists largely of Iransvi-rsc fibres, the Trail, verse liimualis, and of vertical fibres, the Vertical lingualis. The Transverse Mngualis (m. traii^versus linguae) forms the largest portion of the third layer of muscle fibres of the tongue. The fibres arise from the median septum, and pass outward to be inserted into the submucous fibrous layer at the sides of the tongue. Intermingled with these trans- \erse intrinsic fibres are transverse extrinsic fibres derived from the Palatoglossus and the Superior constrictor of the pharynx. These transverse extrinsic fibres, however, run in the opposite direction, passing inward toward the septum. Intersecting the transverse fibres are a large number of vertical fibres derived partly from the Geniohyoglossus and partly from intrinsic fibres, the Vertical lingualis. The fibres derived from the Geniohyoglossus enter the under surface of the tongue on each side of the median septum from base to apex. They ascend in a radiating manner to the dorsum, being inserted into the submucous fibrous layer covering the tongue on each side of the middle line. The Vertical lingualis (m. verticalis linguae) is found only at the borders of the forepart of the tongue, external to the fibres of the Geniohyo- glossus. Its fibres extend from the upper to the under surface of the organ, and decussate with the fibres of the other muscles, and especially with those of the Transverse lingualis. The fonrth layer of muscle fibres of the tongue consists partly of' extrinsic fibres derived from the Styloglossus, and partly of intrinsic fibres, the Inferior lingualis. At the sides of the under surface of the organ are some fibres derived from the Styloglossus, which, as it runs forward at the side of the tongue, gives off fibres which, passing forward and inward between the fibres of the Hyoglossus, form an inferior oblique stratum which joins in front with the anterior fibres of the Inferior lingualis. The Inferior lingualis (7?;. longitndinalis inferior) is a longitudinal band, situated on the under surface of the tongue, and extending from the base to the apex of the organ. Behind, some of its fibres are connected with the body of the hyoid bone. It lies between the Hyoglossus and the Geniohyoglossus, and in front of the Hyoglossus it enters into relation with the Styloglossus, with the fibres of which it blends. It is in relation by its under surface with the ranine artery. 394 THE MUSCLES AND FASCIuE Applied Anatomy. — The fibrous septum which exists between the two halves of the tongue is almost complete, so that the anastomosis between the two lingual arteries is not very free, a fact often illustrated by injecting one-half of the tongue with colored. gelatin, while the other half is left uninjected or may be injected with gelatine of a different color. This is a point of considerable importance in connection with removal of one-half of the tono-ue for cancer, an operation which is now frequently resorted to when the disease is strictly confined to one side of the anterior portion of the tongue. If the mucous membrane is divided lon^ituilinallv exactly in the middle line, the tongue can be split into halves along the median rapht' witli:>ut any appreciable hemorrhage, and the diseased half can then be removed. Actions. — The movements of the tongue, although numerous and complicated, may be under- stood by carefully considering the direction of the fibres of its muscles. The Geniohyoglossi muscles, by means of their posterior fibres, draw the base of the tongue forward, so as to pro- trude the apex from the mouth. The anterior fibres draw the tongue back into the mouth. The whole length of these two muscles, acting along the middle line of the tongue, draw it down- ward, so as to make it concave from side to side, forming a channel along which fluids may pass toward the pharynx, as in sucking. The Hyoglossi muscles depress the tongue and draw down its sides, so as to render it convex from side to side. The Styloglossi muscles draw the tongue upward and backward. The Palatoglossi muscles draw the Isase of the tongue upward. With regard to the Intrinsic muscles, both the Superior and Inferior lingualis tend to shorten the tongue, but the former, in addition, turn the tip and sides upward so as to render the dorsum concave, while the latter pull the tip downward and cause the dorsum to become convex. The Transverse lingualis narrows and elongates the tongue, and the Vertical lingualis flattens and broadens it. The complex arrangement of the muscle fibres of the tongue, and the various directions in which they run, give to this organ the power of assuming the various forms neces- sary for the enunciation of the different consonantal sounds. 5. The Pharyngeal Region (Figs. 304, 305). Inferior constrictor. Superior constrictor. Middle constrictor. Stylopharyngeus. Palatopharyngeus. ) ,f^ , ,. s Q 1 • 1 I (See next section.) balpingopharyngeus. ) ^ -' Dissection (Fig. 304). — In order to examine the muscles of the pharynx, cut through the trachea and oesophagus just above the sternum, and draw them upward by dividing the loose areolar tissue connecting the pharynx with the front of the vertebral column. The parts being drawn well forward, apply the edge of the saw immediately behind the styloid processes, and saw the base of the skull through from below upward. The pharynx and mouth should then be stuffed with tow, in order to distend its cavity and render the muscles tense and easier of dissection. Tlie Inferior constrictor {m. constrictor pharyngis inferior), the most superficial and thickest of the three Constrictors, arises from the side of the cricoid cartilages, in the interval between the Cricothyroid muscle in front and the articular facet for the thyroid cartilage behind; from the oblique line on the side of the ala of the thyroid cartilage, the cartilaginous surface behind it, nearly as far as its posterior border, and from the inferior cornu. From these origins the fibres spread back- ward and inward, to be inserted into the fibrous raphe in the posterior median line of the pharynx. The inferior fibres are horizontal, and continuous with the fibres of the oesophagus; the rest ascend, increasing in obliquity, and overlap the ^Middle constrictor. Relations. — The Inferior Constrictor is covered by a thin membrane which surrounds the entire pharynx, the buccopharyngeal fascia (fascia buccopharyngea). Behind, this fascia is in relation with the vertebral column and the prevertebral fascia and muscles; laterally, with the thyroid gland, the common carotid artery, and the Sternothyroid muscle; by its deep surface, with the Middle constrictor, the Stylopharyngeus, Palatopharyngeus, the fibrous coat and mucous membrane of the pharynx. The internal laryngeal nerve and the laryngeal branch of the superior thyroid artery pass near the upper border, and the recurrent laryngeal nerve and the laryngeal branch of the inferior thyroid artery, beneath the lower border of this muscle, previous to their entering the larynx. THE PHARYNGEAL REGION 395 The Middle constrictor (in. constrictor pharyngis medius) is a flattened, fan- shaped muscle, smaller than the preceding. It arises from the whole length ol the upper border of the greater cornu of the hyoid bone, from the lesser cornu, and from the stylohyoid ligament. The fibres diverge from their origin, the lower ones descending beneath the Inferior constrictor, the middle fibres passing trans- versely, and the upper fibres ascending and overlapping the Superior constrictor. The muscle is inserted into the posterior median fibrous raph^, blending in the middle line with its fellow of the opposite side. Relations. — Between this muscle and the Superior constrictor are the glossopharyngeal ner\'e, the Stylopharyngeus muscle and the stylohyoid Hgament; and between it and the Inferior con- strictor is the superior laryngeal nerve. Behind, the Middle constrictor lies on the vertebral column, the Longus colli, and the Rectus capitis anticus major. 0?^ each side it is in relation with the carotid vessels, the pharyn- geal plexus, and some lymph nodes. Near its origin it is covered by the Hyoglossus, the lingual vessels being placed between the two muscles. It lies upon the Superior constric- tor, the Stylopharyngeus, the Palatopharyn- geus, the fibrous coat, and the mucous membrane of the pharynx. The Superior constrictor (m. con- strictor pliarijiKjis superior) is a quadri- lateral muscle, thinner and paler than the other Constrictors, and situated at the upper part of the pharynx. It arises from the lower half of the posterior margin of the internal pterygoid plate and its hamular process, from the con- tiguous portion of the palate bone and the reflected tendon of the Tensor palati muscle, from the pterygomandibular ligament, from the ah'eolar process above the posterior extremity of the mylohyoid ridge, and by a few fibres from the side of the tongue. From these points the fibres curve backward, to be inserted into the median raphe, being also prolonged by means of a fibrous aponeurosis to the pharyngeal spine on the basilar process of the occipital bone.^ The superior fibres arch beneath the Levator palati and the Eustachian tube. The interval between the upper border of the muscle and the basilar process is deficient in muscle fibres and is closed by a portion of the pharyngeal aponeurosis. This interval is known as the sinus of Morgagni (Fig. 305). cles of the pharynx. Relations. — By its superficial surface the Superior constrictor is in relation with the prever- tebral fascia and muscles, the vertebral column, the internal carotid and ascending pharyngeal arteries, the internal jugular vein and pharyngeal venous plexus, the glossopharyngeal, vagus, spinal accessory, hypoglossal, lingual, and sympathetic nerves, the Middle constrictor and Internal pterygoid muscles, the styloid process, the stylohyoid ligament, and the Stylopharyn- geus. By its deep surface, it is in relation with the Palatopharyngeus, the tonsil, the fibrous, coat, and the mucous membrane of the pharynx. liddle lacerated toramen and descend 396 THE 3IUSCLES AND FASCIAE The Stylopharyngeus (m. stylopharyngeus) is a long, slender muscle, cylindrical above, broad and thin below. It arises from the inner side of the base of the styloid process of the temporal bone, passes downward along the side of the pharynx between the Superior and Middle constrictors, and spreads out beneath the mucous membrane, where some of its fibres are lost in the Constrictor muscles; and others, joining with the Palatopharyngeus, are inserted into the posterior border of the thyroid cartilage. The glossopharyngeal nerve runs on the outer side of this muscle, and crosses over it in passing forward to the tongue. Acces FRO OF TEMPOR ilD PROCE"- -)■;,' \ \ V= STYLOPHARYNGEUS Fig. 305. — The muscles of the pharynx. On the right side most of the Inferior constrictor has been removed, on the left side the Digastric and Stylohyoid have been removed. (Spalteholz.) Relations. — By its superficial surface, with the Styloglossus muscle, the parotid gland, the external carotid artery, and the Middle constrictor; by its deep surface, with the internal carotid, the internal jugular vein, the Superior constrictor, Palatopharyngeus, and pharyngeal mucous membrane. Nerves. — The Constrictors are supplied by branches from the pharyngeal plexus formed by the vagus, glossopharyngeal, and sympathetic nerves. The Inferior constrictor also receives an additional branch from the external laryngeal nerve and one from the recurrent laryngeal The Stylopharyngeus is supplied by a branch from the glossopharyngeal nerve. THE PALATAL BEG TON 397 Actions. — When deglutition is about to be performed, the pharynx is drawn upward and dilated in different directions, to receive the bolus propelled into it from the mouth. The Stylo- pharyngei, which are much farther removed from one another at their origin than at their inser- tion, draw the sides of the pharynx upward and outward, and so increase its transverse diameter; its breadth in the antero-posterior direction is increased by the larynx and tongue being carried forward in their ascent. As soon as the bolus is received in the pharynx, the Elevator muscles relax, the bag descends, and the Constrictors contract upon the bolus, and convey it gradually downward into the (Esophagus. Besides its action in deglutition, the pharynx also exerts an important influence in the modulation of the voice, especially in the production of the higher tones. 6. The Palatal Region (Fig. 306). Levator palati. Palatoglossu.s. Tensor palati. Palatopharyngeus. Azygos uvulae. Salpingopharyngeus. Dissection (Fig. 306). — Lay open the pharynx from behind by a vertical incision extending from its upper to its lower part, and partially divide the occipital attachment by a transverse incision on each side of the vertical one; the posterior surface of the soft palate is then exposed. Having fixed the uvula so as to make it tense, the mucous membrane and glands should be carefully removed from the posteriar surfa:'e of the soft palate, and the muscles of this part are at once exposed. The Levator palati (m. levator veli palatini) is a long, thick, rounded muscle, placed on the outer side of the posterior nares. It arises from the under surface of the apex of the petrous portion of the temporal bone, and from the lower margin of the cartilaginous portion of the Eustachian tube; after passing into the pharynx, above the upper concave margin of the Superior constrictor, it passes obliquely downward and inward, its fibres spreading out into the soft palate as far as the middle line, where they blend with those of the opposite side. Relations. — By its superficial surface, this muscle is in relation with the Tensor palati, the Superior constrictor, and the Eustachian tube; by its deep surface, with the mucous membrane of the pharynx; posteriorly, with the posterior fasciculus of the Palatopharyngeus, the Azygos uvulae, and the mucous membrane of the soft palate. The Tensor palati (m. tensor veli palatini) is a broad, thin, ribbon-like muscle, placed on the outer side of the Levator palati, and consisting of a vertical and a horizontal portion. The. vertical portion arises by a flat lamella from the scaphoid fossa at the base of the internal pterygoid plate; from the spine of the sphenoid and from the outer side of the cartilaginous portion of the Eustachian tube; it descends vertically between the internal pterygoid plate and the inner surface of the Liternal pterygoid muscle, and terminates in a tendon, which winds around the hamular process, being retained in this situation by some of the fibres of origin of the Liternal pterygoid muscle. Between the hamular process and the tendon is a small bursa (bursa m. tensoris veli palati). The tendon or horizontal portion then passes horizontally inward, and is inserted into a broad aponeurosis, the palatal aponeurosis, and into the transverse ridge on the horizontal portion of ' the palate bone. Relations, — By its superficial surface, this muscle is in relation with the Internal pterygoid; by its deep surface, with the Levator palati, from which it is separated by the Eustachian tube and Superior constrictor, and with the internal pterygoid plate. In the soft palate its tendon and the palatal aponeurosis are anterior to those of the Levator palati, being covered by the Palatoglossus and the mucous membrane. Palatal Aponeurosis. — Attached to the posterior border of the hard palate is a thin, firm, fibrous lamella which supports the muscles and gives strength to the 398 THE MUSCLES AND FASCIJE soft palate. It is thicker above than below, where it becomes very thin and difficult to define. Laterally, it is continuous with the pharyngeal aponeurosis. The Azygos uvulae {in. uvulae) is not a single muscle, as would be inferred from its name, but a pair of narrow cylindrical fleshy fasciculi placed on either side of the median line of the soft palate. Each muscle arises from the posterior nasal spine of the palate bone and from the contiguous tendinous aponeurosis of the soft palate, and descends to be inserted into the uvula. Relations. — Anteriorly, with the tendinous expansion of the Levatores palati; 'posteriorly, with the posterior fasciculus of the Palatopharyngeus and the mucous membrane. The next two muscles are exposed by removing the mucous membrane from the pillars of the fauces throughout nearly their whole extent. « p I a Fig. 306. — Muscles of the soft palate, the pharynx being laid open from behind and The Palatoglossus (??;.. c/lossopalatinus) is a small fleshy fasciculus, narrower in the middle than at either extremity, forming, with the mucous membrane covering its surface, the anterior pillar of the soft palate. It arises from the ante- rior surface of the soft palate on each side of the uvula, and, passing downward, forward, and outward in front of the tonsil, is inserted into the side of the tongue, some of its fibres spreading over the dorsum, and others passing deeply into the substance of the organ to intermingle with the Transverse lingualis. In the soft palate the fibres of this muscle are continuous with those of the muscle of the opposite side. The Palatopharyngeus (/». pharyngopalatinus) is a long, fleshy fasciculus, narrower in the middle than at either extremity, forming, with the mucous. THE PALATAL REGION ;399 membrane covering its surface, the posterior pillar of the soft palate. It is sepa- rated from the Palatoglossus by an angular interval, in which the tonsil is lodged. It arises from the soft palate by an expanded fasciculus, which is divided into two parts by the Levator palati and Azygos uvulae. The posterior fasciculus lies in contact with the mucous membrane, and also joins with the corresponding muscle in the middle line; the anterior fasciculus, the thicker, lies in the soft palate between the Levator and Tensor, and joins in the middle line the corresponding part of the opposite muscle. Passing outward and downward behind the tonsil, the Palatopharyngeus joins the Stylopharyngeus, and is inserted with that muscle into the posterior border of the thyroid cartilage, some of its fibres being lost on the side of the pharynx, and others passing across the middle line posteriorly to decussate with the muscle of the opposite side. Relations. — In the soft palate its posterior surface is covered by mucous membrane, from which it is separated by a layer of palatal glands. By its anterior surface it is in relation -with the Tensor palati. Where it forms the posterior pillar of the fauces it is covered by mucous membrane, excepting on its outer surface. In the pharynx it lies between the mucous membrane and the Constrictor muscles. The Salpingopharyngeus {m. salpingopharyngeus) arises from the inferior part of the Eustachian tube near its orifice; it passes downward and blends with the posterior fasciculus of the Palatopharyngeus. In a dissection of the soft palate from its posterior or nasal surface to its anterior or oral sur- face, the muscles would be exposed in the following order — viz., the posterior fasciculus of the Palatopharyngeus, covered over by the mucous membrane reflected from the floor of the nasal fossEe; the Azygos uvulae; the Levator palati; the anterior fasciculus of the Palatopharvngeus; the aponeurosis of the Tensor palati, and the Palatoglossus, covered over by a reflection from the oral mucous membrane. Nerves. — The Tensor palati is supplied by a branch from the otic ganglion; tlie remaining muscles of this group are in all probability supplied by the internal branch of the spinal accessory, the fibres of which are distributed along with certain branches of the vagus through the pharyn- geal plexus.' Actions. — During the first stage of deglutition the bolus of food is driven back into the fauces by the pressure of the tongue against the hard palate; the base of the tongue is, at the same time, retracted, and the larynx is raised with the pharynx, and carried forward under it. During the second stage the entrance to the larynx is closed, not, as was formerly supposed, by the folding backward of the epiglottis over it, but, as Anderson Stuart has shown, by the draw- ing forward of the arytenoid cartilages toward the cushion of the epiglottis — a movement produced by the contraction of the outer portion of the TlijToarytenoid, the Arytenoid, and Aryteno-epiglottidean muscles. The bolus of food after leaving the tongue passes on to the posterior or laryngeal surface of the epiglottis, and glides along this for a certain distance;' then the Palatoglossi muscles, the constrictors of the fauces, contract behind the food; the soft palate is slightly raised by the Levatores palati, and made tense by the Tensores palati; and the Palatopharyngei, by their con- traction, pull the pharynx upward over the bolus of food, and at the same time come nearly together, the uvula filling up the slight interval between them. By these means the food is prevented from passing into the upper part of the larynx or the posterior nares; at the same time the latter muscles form an inclined plane, directed oblicjuely downward and backward, along the under surface of which the bolus descends into the lower part of the pharynx. Each Salpingopharyngeus raises the upper and lateral part of the pharynx — i. e., that part which is above the point where the Stylopharyngeus is attached to the pharynx. Applied Anatomy. — After operation for cleft palate the Tensor palati and I,ev:ifor palati retard union by causing undue tension along the line of suture. In order to overcome this it is necessary to divide these muscles, and this is done by making longitudinal incisions on either side, parallel to the cleft and just internal to the hamular process, in such a position as to avoid the posterior palatine artery. 1 Journal of .\natomy and Physiology, vol. x.xiii, p. .52.3. 2 We now know that normal deelutjtion can be carried out when the epiglottis is so small that it cannot cover the opening into the larynx, or when it has been removed surgically. In such cases the sphincter muscles which surround the laryngeal aperture contract during swallowing and prevent the entrance of foreign bodies into the larynx. 400 THE MUSCLES AND FASCIAE 7. The Anterior Vertebral Region (Fig. 307). Rectus capitis anticus major. Rectus capitis anticus minor. Rectus capitis lateralis. Longus colli. The Rectus capitis anticus major (/;i. longus capitis), broad and thick above and narrow below, appears like a continuation upward of the Scalenus anticus. It arises by four tendinous slips from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebra, and ascends, convei'ging toward its fellow of the opposite side, to be inserted into the basilar process of the occipital bone. Relations. — By its anterior surface, this muscle is in relation with the pharynx, the inferior cer- vical sympathetic ganglion and nerve, and the sheath enclosing the internal and common cai-otid artery, internal jugular vein, and vagus nerve; by its posterior surface, with the Longus colli, the Rectus capitis anticus minor, and the upper cervical vertebrae. Fig. 307. — The prevertebral muscles (ventral view). The Rectus capitis anticus minor (m. rectus capitis anterior) is a short, flat muscle, situated immediately behind the upper part of the preceding. It arises from the anterior surface of the lateral mass of the atlas and from the root of its transverse process, and, passing obliquely upward and inward, is inserted into the basilar process immediately behind the rectus capitis anticus major. The Rectus capitis lateralis (m. rectus capitis lateralis) is a short, flat muscle, which arises from the upper surface of the transverse process of the atlas and is THE LATERAL VERTEBRAL REGION 401 inserted into the under surface of the jugular process of the occipital bone. This muscle lies behind the internal jugular vein, and in front of the upper portion of the vertebral artery. The LongUS colli (/«. longus colli) is a long, flat muscle, situated on the anterior surface of the vertebral column, between the atlas and the third thoracic vertebra. It is broad in the middle, narrow and pointed at each extremity, and consists of three portions — a superior oblique, an inferior oblique, and a vertical portion. The superior oblique portion arises from the anterior tubercles of the transverse processes of the third, fourth, and fifth cervical vertebrae, and, ascending obliquely inward, is inserted by a narrow tendon into the tubercle on the anterior arch of the atlas. The inferior oblique portion, the smallest part of the muscle, arises from the front of the bodies of the first two or three thoracic vertebrae, and, ascend- ing obliquely outward, is inserted into the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebrae. The vertical portion lies directly on the front of the vertebral column; it arises, below, from the front of the bodies of the upper three thoracic and lower three cervical vertebrae, and is inserted above into the front of the bodies of the second, third, and fourth cervical vertebrae. Relations. — By its superficial surface, with the prevertebral fascia, the pharynx, oesophagus, sympathetic nerve, the sheath of the great vessels of the neck, the inferior thyroid artery, and the recurrent laryngeal nerve; by its deep surface, with the cervical and thoracic portions of the \ertebral cohimn. Its inner border is separated from the opposite muscle by a considerable interA-al below, but they approach each other above. Nerves. — The Rectus capitis anticus minor and the Rectus lateralis are supplied from the loop between the first and second cervical nerves; the Rectus capitis anticus major, by branches from the second, third, and fourth cervical; the Longus colli, by branches from the second to the seventh cervical nerves. Actions. — The Rectus anticus major and minor are the direct antagonists of the muscles at the back of the neck, serving to restore the head to its natural position after it has been drawn backward. These muscles also serve to flex the head, and, from their obliquity, rotate it, so as to turn the face to one or the other side. The Longus colli flexes and slightly rotates the •cervical portion of the vertebral column. 8. The Lateral Vertebral Region (Figs. 307, 308). Scalenus anticus. Scalenus medius. Scalenus posticus. The Scalenus anticus {m. scalenus anterior) is a conical-shaped muscle, situated deeply at the side of the neck, behind the Sternomastoid. It arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and, descending almost vertically, is inserted by a narrow, flat tendon into the scalene tubercle on the inner border and upper surface of the first rib. The lower part of this muscle separates the subclavian artery and vein, the latter being in front, and the former, with the brachial plexus, behind. Relations. — By its superficial surface, this muscle is in relation with the clavicle, the Sub- •clavius, Sternomastoid, and Omohyoid muscles, the transversalis colli, and the suprascapular arteries, the subclavian vein, and the phrenic nerve; by its deep surface, with the Scalenus medius, pleura, subclavian artery, and brachial plexus of nerves. It is separated from the Longus colli, on the inner side, by the vertebral artery. On the anterior tubercles of the transverse processes of the cervical vertebr.'e, between the attachments of the Scalenus anticus and Longus colli lies the ascending cervical branch of the inferior thyroid artery. The Scalenus medius (m. scalenus medius), the largest and longest of the three Scaleni, arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae, and, descending along the side of the vertebral column. 402 THE MUSCLES AND FASCIJE is inserted by a broad attachment into the upper surface of the first rib, behind the o-roove for the subclavian artery, as far back as the tubercle. It is separated from the Scalenus anticus by the subclavian artery below and by the cervical nerves above. The posterior thoracic, or nerve of Bell, is formed in the substance of the Scalenus medius and emerges from it. The nerve to the Rhomboids also pierces it. Relations. — By its superficial surface, with the Sternomastoid; it is crossed by the clavicle, the Omohyoid muscle, subclavian artery, and cervical nerves. To its outer side is the Levator anguli scapulae and the Scalenus posticus muscle. The Scalenus posticus (m. scalenus posterior), the smallest of the three Scaleni, arises, by two or three separate tendons, from the posterior tubercles of the trans- verse processes of the lower two or three cervical vertebra, and, diminishing as it descends, is inserted by a thin tendon into the outer surface of the second rib, behind the attachment of the Ser- ratus magnus. This is the most deeply ~ ^"^i \ placed of the three Scaleni, and is occasionally blended with the Scalenus medius. Nerves. — The Scalenus anticus receives branches from the fourth to the seventh cervical; the Scalenus medius from the third to the eighth cervical; and the Scalenus posticus, from the fom-th to the eighth cer- vical nerves. Actions. — The Scaleni muscles, when they take their fixed point from above, elevate the first and second ribs, and are, therefore, inspiratory muscles. When they take their fixed point from below, they bend the verte- bral column to one or the other side. If the muscles of both sides act, lateral movement is prevented, but the vertebral column is slightly flexed. The Rectus lateralis, acting on one side, bends the head laterally. Surface Form. — The muscles in the neck, with the exception of the Platysma, are in- vested by the deep cervical fascia, which softens down their form, and is of consid- erable importance in connection with deep cervical abscesses and tumors, modifying the direction of the growth of tumors and of the enlargement of abscesses, and causing them to extend laterally instead of toward thfc surface. The Platysma does not influence surface form except when in action, when it produces wrinkling of the skin of the neck, which is thrown into oblique ridges parallel with the fasciculi of the muscle. Sometimes this contraction takes place suddenly and repeatedly as a sort of spasmodic twitching, the result of a nervous habit. The Sternomastoid is the most important muscle of the neck as regards its surface form. If the muscle is put into action by drawing the chin downward and to the opposite shoulder, its surface form will be plainly out- lined. The sternal origin will stand out as a sharply defined ridge, while the clavicular origin will present a flatter and not so prominent outline. The fleshy middle portion will appear as an oblique roll or elevation, with a thick, rounded anterior border gradually becoming less marked above. On the opposite side — i. e., on the side to which the head is turned — the outline is lost, its place being occupied by an oblique groove in the integument. When the muscle is at rest its anterior border is still visible, forming an oblique rounded ridge, terminating below in a sharp outline of the sternal head. The posterior border of the muscle does not show above the clavicular head. The anterior border is defined by drawing a line from the tip of the mas- toid process to the sternoclavicular joint. It is an important surface-marking in the operation Fig. 308. — Scaleni muscles. (Poirier and Charpy.) MUSCLES AND FASCIAE OF THE TRUNK 403 of ligation of the common carotid artery and in some other operations. Between the sternal and clavicular heads is a slight depression, most marked when the muscle is in action. This is bounded below by the prominent sternal extremity of the clavicle. Between the sternal origins of the two muscles is a V-shaped space, the suprasternal notch, more pronounced below, and becoming toned down above, where the Sternohyoid and Sternoth , roid muscles, lying upon the trachea, become more prominent. Above the hyoid bone, in the middle line, the anterior belly of the Digastric to a certain extent influences surface form. It corresponds to a line drawn from the symphysis of the mandible to the side of the body of the hyoid bone, and renders convex this part of the hyomental region. In the posterior triangle of the neck, the posterior belly of the Omohyoid, when in action, forms a conspicuous object, especially in thin necks, presenting a cord-like form running across this region, almost parallel with, and a little above, the clavicle. MUSCLES AND FASCIiE OF THE TRUNK. The muscles of the Trunk may be arranged in four groups, corresponding with the region in which they are situated. I. The Back. II. The Thorax. III. The Abdomen. IV. The Perineinn. I. MUSCLES OF THE BACK. The muscles of the back are very numerous, and may be subdivided into five layers: First Layer. Trapezius. Latissimus dorsi. Second Layer. Levator anguli scapulae. Rhomboideus minor. Rhomboideus major. Third Layer. Serratus posticus superior. Serratus posticus inferior. Splenius capitis. Splenius colli. Fourth Layer. Sacral and Lumbar Regions. Erector spinae Dorsal Region. Iliocostalis. Musculus accessorius ad iliocostalem Longissimus dorsi. Spinalis dorsi. Cervical Region. Cervicalis ascendens. Transversalis cervicis. Trachelomastoid. Complexus. Biventer cervicis. Spinalis colli. Fifth Layer. Semispinalis dorsi. Semispinalis colli. Multifidus spinae. Rotatores spinae. Supraspinales. Interspinales. Extensor coccygis. Intertransversalis. Rectus capitis posticus major. Rectus capitis posticus minor. Obliquus capitis inferior. Obliquus capitis superior. 404 THE 3IUSCLES AND FASCIA The First Layer (Fig. 310). Trapezius. Latissimus dorsi. Dissection (Fig. 309). — Place the body in a prone position, with the arms extended over the sides of the table, and the thorax and abdomen supported by several blocks, so as to render the muscles tense. Then make an incision along the middle line of the back from the occipital protuberance to the coccyx. Make a transverse incision from the upper end of this to the mas- toid process, and a third incision from its lower end, along the crest of the ilium to about its middle. This large intervening space should, for convenience of dissection, be subdivided by a fourth incision, extending obliquely from the spinous process of the last thoracic vertebra, upward and outward, to the acromion process. This incision corresponds with the lower border of the Trapezius muscle. The flaps of integument are then to be removed in the direction shown in the figure. The superficial .fascia is exposed upon removing the skin from the back. It forms a layer of considerable thickness and strength, in which a quantity of granular pinkish fat is contained. It is con- tinuous with the superficial fascia in other parts of the body. The deep fascia is a dense fibrous layer attached to the occipital bone, the spines of the vertebriB, the crest of the ilium, and the spine of the scapula. It covers over the supei-ficial muscles, forming sheaths for them, and in the neck forms the posterior part of the deep cervical fascia; in the thorax it is con- tinuous with the deep fascia of the axilla and thorax, and in the abdomen with that covering the abdominal muscles. In the back of the thoracic region the deep fascia is called the vertebral aponeurosis. It covers the Erector spinae muscles, and is the dorsal layer of the lumbar fascia. The Trapezius (m. trapezius) is a broad, flat, triangular muscle, placed immediately beneath the skin and fascia, and covering the upper and back part of the neck and shoulders. It arises from the external occipital protuberance and the inner third of the superior curved line of the occipital bone; from the ligamentum nuchae, the spinous process of the seventh cer- vical, and the spinous processes of all the thora- cic vertebrae ; and from the corresponding portion of the supraspinous ligament. From this origin the superior fibres proceed downward and out- ward, the inferior ones upward and outward, the middle fibres horizontally, and are inserted, the superior ones into the outer third of the posterior border of the clavicle and into the adjacent part of its upper surface. The middle fibres pass into the inner margin of the acromion process, and into the superior lip of the posterior border or crest of the spine of the scapula; the inferior fibres converge near the scapula, and terminate in a triangular aponeurosis, which glides over a smooth surface at the inner extremity of the spine, to be inseHed into a tubercle at the outer part of this smooth surface. The Trapezius is fleshy in the greater part of its extent, but tendinous at its origin and insertion. At its occipital origin Fig. 309, — Dissection of the muscles of OF THE BACK 405 TiGi 310. — Muscles of the back. On the left side is exposed the first layer; on the right side, the second '.ayer and part of the third. 406 THE MUSCLES AND FASCIA it is connected to the bone by a thin fibrous lamina, firmly adherent to the skin, and wanting the lustrous, shining appearance of aponeuroses. At its origin from the spines of the vertebrae it is connected to the bones by means of a broad semi- elliptical aponeurosis, which occupies the space between the sixth cervical and the third thoracic vertebrae, and forms, with the aponeurosis of the opposite muscle, a tendinous ellipse. The rest of the muscle arises by numerous short tendinous fibres. If the Trapezius is dissected on both sides, the two muscles resemble a trapezium or diamond-shaped quadrangle; two angles corresponding to the shoulders; a third to the occipital protuberance; and the fourth to the spinous process of the last thoracic vertebra. The clavicular insertion of this muscle varies as to the extent of its attachment; it sometimes advances as far as the middle of the clavicle, and may even become blended with the posterior edge of the Sternomastoid or may overlap it. This should be borne in mind in the operation for tying the third part of the subclavian artery. Relations. — By its superficial surface, the Trapezius is in relation with the integument; by its deep surface, in the neck, with the Complexus, Splenius, Levator anguli scapulae, and Rhom- boideus minor; in the back, with the Rhomboideus major, Supraspinatus, Infraspinatus, and vertebral aponeurosis (which separates it from the prolongations of the Erector spinae), and the Latissimus dorsi. The spinal accessory nerve and the superficial cervical artery and branches from the third and fourth cervical nerves pass beneath the anterior border of this muscle. The anterior margin of its cervical portion forms the posterior boundary of the posterior triangle of the neck, the other boundaries being the Sternomastoid in front and the clavicle below. The Ligamentum nuchae (Fig. 310) is a fibrous membrane, which, in the neck, represents the supraspinous and interspinous ligaments of the lower vertebrae. It extends from the external occipital protuberance to the spinous process of the seventh cervical vertebra. From its anterior border a fibrous lamina (fascia nuchae) is given off, which is attached to the external occipital crest, the posterior tubercle of the atlas, and the spinous process of each of the cervical vertebrae, so as to form a septum between the muscles on each side of the neck. In man it is merely the rudiment of an important elastic ligament, which, in some of the lower animals, serves to sustain the weight of the head. The Latissimus dorsi (m. latissimus dorsi) is a broad, flat muscle, which covers the lumbar and the lower half of the thoracic regions, and is gradually contracted into a narrow fasciculus at its insertion into the humerus. It arises by tendinous fibres from the spinous processes of the six inferior thoracic vertebrae and from the dorsal layer of the lumbar fascia (see page 410), by which it is attached to the spines of the lumbar and sacral vertebrae and to the supraspinous ligament. It also arises from the external lip of the crest of the ilium, behind the insertion of the External oblique muscle, and by fleshy digitations from the three or four lower ribs, which are interposed between similar processes of the External oblique (Fig. 317, page 425). From this extensive origin the fibres pass in different directions, the upper ones horizontally, the middle obliquely upward, and the lower vertically upward, so as to converge and form a thick fasciculus, which crosses the inferior angle of the scapula, and which usually receives a few fibres of origin from it. The muscle curves around the lower border of the Teres major, and is twisted upon itself so that the superior fibres become at first posterior and then inferior, and the vertical fibres at first anterior and then superior. It ter- minates in a short quadrilateral tendon, about three inches in length, which, passing in front of the tendon of the Teres major, is inserted into the bottom of the bicipital groove of the humerus, its insertion extending higher on the humerus than that of the tendon of the Pectoralis major. The lower border of the tendon of this muscle is united with that of the Teres major, the surfaces of the two being separated near their insertions by a bursa ; another bursa is sometimes interposed OF THE BACK 407 between the muscle and the inferior angle of the scapula. This muscle at its insertion gives off an expansion to the deep fascia of the arm. A fleshy slip, the axillary arch, varying from 3 to 4 inches in length, and from \ to J of an inch in breadth, occasionally arises from the upper edge of the Latissimus dorsi about the middle of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, to join the under surface of the tendon of the Pectoralis major, the Coracobrachialis, or the fascia over the Biceps. The position of this abnormal slip is a point of interest in its relation to the axillary artery, as it crosses the vessel just above the spot usually selected for the applica- tion of a ligature, and may mislead the surgeon during the operation. It may be easily recog- nized by the transverse direction of its fibres. Dr. Struther found it, in 8 out of 105 subjects, occurring seven times on both sides. In most subjects there is a fibrous axillary arch, in only a few is the arch composed of muscle tissue. There is usually a fibrous slip which passes from the lower border of the tendon of the Latis- simus dorsi, near its insertion, to the long head of the Triceps. This is occasionally fleshy, and is the representative of the Dorso-rpitrorhlcnris muscle of apes. Relations. — The superficial surface of the Latissimus dorsi is subcutaneous, excepting at its upper part, where it is covered by the Tra|)ezius, and at its insertion, where its tendon is crossed by the axillary vessels and the brachial plexus of nerves. By its deep surface it is in relation with the lumbar fascia, the Serratus Dosticus inferior, the lower External intercostal mus- cles and ribs, the inferior angle of the scapula, Rhomboideus major. Infraspinatus, and Teres major muscles. Its outer margin is separated below from the External oblique by a small triangular interval, the triangle of Petit (trii/oimm lumbate [Petiii]); and another triangular interval exists between its upper border and the margin of the Trapezius in which the Rhom- boideus major muscle is exposed. Nerves. — The Trapezius is supplied by the spinal accessory, and by branches from the anterior divisions of the third and fourth cervical nerves: the Latissimus dorsi by the sixth, seventh and eighth cervical nerves through the middle or long subscapular nerve. The Second Layer (Fig. 310). Levator anguli scapulae. Rhomboideus minor. Rhomboideus major. Dissection. — The Trapezius must be removed, in order to expose the next layer; to effect this, detach the muscle from its attachment to the clavicle and spine of the scapula, and turn it back toward the vertebral column. The Levator anguli scapulae (m. levator sca-pulae) is situated at the hack part and side of the neck. It aris.es by tendinous slips from the transverse process of the atlas, and from the posterior tubercles of the transverse processes of the second, third, and fourth cervical vertebrae ; these, becoming fleshy, are united so as to form a flat muscle, which, passing downward and backward, is inserted into the posterior border of the scapula, between the superior angle and the triangular smooth surface at the root of the spine. The Rhomboideus minor (m. rhomboideus minor) arises from the ligamentum nuchae and spinous processes of the seventh cervical and first thoracic vertebrae. Passing downward and outward, it is inserted into the margin of the triangular smooth surface at the root of the spine of the scapula. This small muscle is usually separated from the Rhomboideus major by a slight cellular interval. The Rhomboideus major (m. rhomboideus 7najor) is situated immediately below the preceding, the adjacent margins of the two being occasionally united. It arises by tendinous fibres from the spinous processes of the four or five upper thoracic vertebrae and the supraspinous ligament, and is inserted into a narrow tendinous arch attached above to the lower part of the triangular surface at the root of the spine; below, to the inferior angle, the arch being connected to the border of the scapula by a thin membrane. When the arch extends, as it occa- sionally does, a short distance, the muscle fibres are inserted into the scapula itself. 408 THE MUSCLES AND FASCIA Nerves. — The Rhomboid muscles are supplied by branches from the anterior division of the fifth cervical nerve; the Levator anguli scapulae, by the anterior divisions of the third and fourth cervical nerves, and frequently by a branch from the nerve to the Rhomboids. Actions. — The movements effected by the preceding muscles are numerous, as may be con- ceived from their extensive attachment. The whole of the Trapezius when in action retracts the scapula and braces back the shoulder; if the head is fixed, the upper part of the Trapezius will elevate the point of the shoulder, as in supporting weights; when the lower fibres are brought into action, they assist in depressing the bone. The middle and lower fibres of the muscle rotate the scapula, causing elevation of the acromion process. If the shoulders are fixed, both Trapezii, acting together, will draw the head directly backward; or if only one acts the head is drawn to the corresponding side. The Latissimus dorsi, when it acts upon the humerus, depresses it, draws it backward, adducts, and at the same time rotates it inward. It is the muscle which is principally employed in giving a downward blow, as in felling a tree or in sabre practice. If the arm is fixed, the muscle may act in various ways upon the trunk; thus, it may raise the lower ribs and assist in forcible inspiration; or, if both arms are fixed, the two muscles may assist the Abdominal and great Pectoral muscles in suspending and drawing the whole trunk for- ward, as in climbing or walking on crutches. The Levator anguli scapulae raises the superior angle of the scapula, and by so doing depresses the point of the shoulder. It assists the Trape- zius in bearing weights and in shrugging the shoulders. If the shoulder be fixed, the Levator anguli scapulae inclines the neck to the corresponding side and rotates it in the same direction. The Rhomboid muscles carry the inferior angle backward and upward, thus producing a slight rotation of the scapula upon the side of the thorax, the Rhomboideus major acting especially on the lower angle of the scapula through the tendinous arch by which it is inserted. The Rhom- boid muscles, acting together with the middle and inferior fibres of the Trapezius, will draw the scapula directly backward toward the vertebral column. The Third Layer. Serratus posticus superior. Serratus posticus inferior, c 1 • f Splenius capitis. * ^ ( Splenius colli. Dissection. — To bring into view the third layer of rnuscles, remove the whole of the second, together with the Latissimus dorsi, by cutting through the Levator anguli scapulae and Rhom- boid muscles near their origin, and reflecting them downward, and by dividing the Latissimus dorsi in the middle by a vertical incision carried from its upper to its lower part, and reflecting the two halves of the muscle. The Serratus posticus superior {m. serratus posterior superior) is a thin, flat quadrilateral muscle situated at the upper and back part of the thorax. It arises by a thin and broad aponeurosis from the ligamentum nuchae, and from the spinous processes of the last cervical and two or three upper thoracic vertebrEe and from the supraspinous ligament. Inclining downward and outward, it becomes muscular, and is inserted, by four fleshy digitations, into the tipper borders of the second, third, fourth, and fifth ribs, a little beyond their angles. The Serratus posticus inferior (m. serratus posterior inferior) (Fig. 310) is situated at the junction of the thoracic and lumbar regions; it is of an irregularly quadrilateral form, broader than the preceding, and separated from it by a con- siderable interval. It arises by a thin aponeurosis from the spinous processes of the last two thoracic and two or three upper lumbar vertebrae, and from the supra- spinous ligaments. Passing obliquely upward and outward, it becomes fleshy, and divides into four flat digitations, which are inserted into the lower borders of the four lower ribs, a little beyond their angles. The thin aponeurosis of origin is intimately blended with the lumbar fascia. The vertebral aponeurosis is a thin, fibrous lamina, extending along the whole length of the back part of the thoracic region, serving to bind down the long Extensor muscles of the back which support the vertebral column and head, and separate them from those muscles which connect the vertebral column to the upper OF THE BA CK 409 extremity. It consists of longitudinal and transverse fibres blended together, forming a thin lamella, which is attached, in the median line, to the spinous jjroc- esses of the thoracic vertebrae; externally, to the angles of the ribs; and is contin- uous with the intercostal fascia. It is continuous below with the aponeurosis of the Serratus posticus inferior and a portion of the lumbar fascia, which gives origin to the Latissimus dorsi; above, it passes beneath the Serratus posticus superior and the Splenius, and blends with the deep fascia of the neck. The lumbar fascia or aponeurosis (Figs. 310 and 325), which may be regarded as the posterior aponeurosis of the Transversalis abdominis muscle, consists of three laminte, which are attached as follows: The dorsal layer, to the spines of the lumbar and sacral vertebrte and their supraspinous ligaments; the middle layer, to the tips of the transverse processes of the lumbar vertebrae and their intertransverse ligaments; the ventral layer, to the roots of the lumbar transverse processes. The dorsal layer is continued above as the vertebral aponeurosis, while inferiorly it is fixed to the outer lip of the iliac crest. With this layer are blended the aponeurotic origin of the Serratus posticus inferior and part of that of the Latissimus dorsi. The middle layer is attached above to the last rib, and below to the iliac crest; the ventral layer is fixed below to the iliolumbar ligament and iliac crest; while above it is thickened to form the external arcuate ligament of the Diaphragm, and stretches from the tip of the last rib to the transverse pro- cess of the first or second lumbar vertebra. These three layers, together with the vertebral column, enclose two spaces, the posterior of which is occupied by the Erector spinae muscle, and the anterior by the Quadratus lumborum. Now detach the Serratus posticus su])erior from its origin, and turn it outward, when the Splenius muscle will be brought into view. The Splenius muscle mass (Fig. 310) is situated at the back of the neck and upper part of the thoracic region. At its origin it is a single muscle, which soon after its origin becomes broad, and divides into two portions, which have separate insertions. It arises, by tendinous fibres, from the lower half of the ligamentum nuchae, from the spinous processes of the last cervical and of the six upper tho- racic vertebrte, and from the supraspinous ligament. From this origin the fleshy fibres proceed obliquely upward and outward, forming a broad, flat muscle sheet, which divides as it ascends into two portions, the Splenius capitis and Splenius colli. The Splenius capitis (m. splenius capitis) is inserted into the mastoid process of the temporal bone, and into the rough surface on the occipital bone, just beneath the superior curved line. The Splenius colli {m. splenius cervicis) is inserted, by tendinous fasciculi, into the posterior tubercles of the transverse processes of the two or three upper cervical vertebrae. The Splenius muscles are separated from their fellows of the opposite side by a triangular interval, in which is seen the Complexus. Nerves. — The Splenius capitis and colli muscles are supplied from the external branches of the posterior primary divisions of the middle and lower cervical nerves; the Serratus posticus, superior is supplied by the external branches of the upper three or four intercostal nerves; the Serratus posticus inferior by branches of the ninth, tenth, and eleventh intercostal nerves. Actions. — The Serrati are respiratory muscles. The Serratus posticus superior elevates the ribs; it is therefore an inspiratory muscle; while the Serratus inferior draws the lower ribs down- ward and backward, and thus elongates the thorax. It also fixes the lower ribs, thus aiding the downward action of the Diaphragm and resisting the tendency which it has to draw the lower ribs upward and forward. It must therefore be regarded as a muscle of inspiration. This muscle is also probably a tensor of the vertebral aponeurosis. The Splenii muscles of the two sides, acting together, draw the head directly backward, assisting the Trapezius and Com- plexus; acting separately, they draw the head to one or the other side, and slightly rotate it, turning; the face to the same side. They also assist in supporting the head in the erect position. 4i0 THE MUSCLES AND FASCIA The Fourth Layer (Fig. 311). I. Erector spinae. a. Outer Column. b. Middle Column Iliocostalis. Longissimus dorsi. Musculus accessorius. Transversalis cervicis. Cervicalis ascendens. Trachelomastoid. c. Inner Column. Spinalis dorsi. Spinalis colli. II. ComplexLis. Dissection. — To expose the muscles of the fourth layer, remove entirely the Serrati and the vertebral and lumbar fascife. Then detach the Splenius by separating its attachment to the spinous processes and reflecting it outward. The Erector spinae (m. sacrospinalis) and its prolongations in the thoracic and cervical regions fill up the vertebral groove on each side of the vertebral column. It is covered in the lumbar region by the lumbar fascia; in the thoracic region, by the Serrati muscles and the vertebral aponeurosis; and in the cervical region, by a layer of cervical fascia continued beneath the Trapezius and the Splenius. This large muscular and tendinous mass varies in size and structure at different parts of the vertebral column. In the sacral region the Erector spinae is narrow and pointed, and its origin is chiefly tendinous in structure. In the lumbar region the muscle becomes enlarged, and forms a large, fleshy mass. In the thoracic region it subdivides into two parts, which gradually diminish in size as they ascend to be inserted into the vertebrse and ribs. The Erector spinae arises from the anterior surface of a very broad and thick tendon, the erector spinae aponeurosis, which is attached, iniernally, to the spines of the sacrum, to the spinous processes of the lumbar and the eleventh and twelfth thoracic vertebrae, and to the supraspinous ligament; externally, to the back part of the inner lip of the crest of the ilium, and to the series of eminences on the pos- terior part of the sacrum, which represents the transverse processes, where it blends with the great sacrosciatic and posterior sacroiliac ligaments. Some of its fibres are continuous with the fibres of origin of the Gluteus maximus. The muscle fibres form a single large fleshy mass, bounded in front by the transverse processes of the lumbar vertebrse and by the middle lamella of the lumbar fascia. Opposite the last rib it divides into three parts: (1) The Iliocostalis; (2) the Longis- simus dorsi; and (3) the Spinalis dorsi, 1. The Iliocostalis (?n.. iliocostalis liimborum), the external portion of the Erector spinae, is inserted, generally, by six or seven flattened tendons into the inferior borders of the angles of the six or seven lower ribs. The number of the tendons of this muscle is, however, quite variable, and therefore the number of ribs into which it is inserted varies. Internally this muscle is reinforced by a series of muscle slips which arise from the angles of the ribs; by means of these the Iliocostalis is continued upward to the upper ribs and to the cervical portion of the vertebral column. These accessory portions form two additional muscles, the Musculus accessorius and the Cervicalis ascendens. The Musculus accessorius (m. iliocostalis dorsi) arises, by separate flattened tendons, from the upper borders of the angles of the six lower ribs ; these become muscular, and are finally inserted, by separate tendons, into the upper borders of the angles of the six upper ribs and into the back of the transverse processes of the seventh cervical vertebra. OF THE BACK Occipital hone. 411 MULTIFIDUS SPIN* First thoracic vertebra First lumbar verteb: First sacral vertebra Fig. 311.— Muscles of the back. Deep layer 412 THE MUSCLES AND FASCIA The Cervicalis ascendens (m. illocostalis cervicis) is the continuation of the Acces- sorius upward into the neck; it is situated on the inner side of the tendons of the Accessorius, arising from the angles of tlie four or five upper ribs, and is inserted by a series of slender tendons into the posterior tubercles of the transverse pro- cesses of the fourth, fifth, and sixth cervical vertebrae. 2. The Longissimus dorsi is the middle and largest portion of the Erector spinae. In the lumbar region, where it is as yet blended with the Iliocostalis, some of the fibres are attached to the whole length of the posterior surface of the transverse processes and the accessory processes of the lumbar vertebrse, and to the middle layer of the lumbar fascia. In the thoracic region the Longissimus dorsi is inserted, by long, thin tendons, into the tips of the transverse processes of all the thoracic vertebra, and into from seven to eleven of the lower ribs between their tubercles and angles. This muscle is continued upward to the cranium and cer- vical portion of the vertebral column by means of two additional muscles, the Transversalis cervicis and Trachelomastoid. The Transversalis cervicis (m. longissimus cervicis), placed on the inner side of the Longissimus dorsi, arises by long, thin tendons from the summits of the trans- verse processes of the six upper thoracic vertebrte, and is inserted by similar tendons into the posterior tubercles of the transverse processes of the cervical vertebrte, from the second to the sixth inclusive. The Trachelomastoid (m. longissimus capitis') lies on the inner side of the pre- ceding, between it and the Complexus muscle. It arises, by tendons, from the transverse processes of the five or six upper thoracic vertebrse, and the articular processes of the three or four lower cervical vertebra?. The fibres form a small muscle, which ascends to be inserted into the posterior margin of the mastoid process, beneath the Splenius and Sternomastoid muscles. This small muscle is almost always crossed by a tendinous intersection near its insertion into the mastoid process.^ 3. The Spinalis dorsi is situated at the inner side of the Longissimus dorsi, with which it is intimately blended. It arises, by three or four tendons, frpm the spinous processes of the first two lumbar and the last two thoracic vertebrse; these, uniting, form a small muscle, which is inserted, by separate tendons, into the spinous processes of the thoracic vertebrae, the number varying from four to eight. It is intimately united with the Semispinalis dorsi, which lies beneath it. The Spinalis colli (jn. spinalis cervicis) is a small muscle, connecting the spinous processes of the cervical vertebrse, and analogous to the Spinalis dorsi in the thoracic region. It varies considerably in its size and in the extent of its attachment to the vertebrffi, not only in difl^erent bodies, but on the two sides of the same body. It usually arises by fleshy or tendinous slips, varying from two to four in ninnber, from the spinous processes of the fifth, sixth, and seventh cervical vertebrte, and occasionally from the first and second thoracic, and is inserted into the spinous process of the axis, and occasionally into the spinous processes of the two vertebrse below it. This muscle was found absent in five cases out of twenty-four. The Complexus (m. semispinalis capitis) is a broad thick muscle, situated at the upper and back part of the neck, beneath the Splenius, and internal to the Transversalis cervicis and Trachelomastoid. It arises, by a series of tendons, from the tips of the transverse processes of the upper six or seven thoracic and the last cer^'ical vertebrse, and from the articular processes of the three cervical vertebrse above this. The tendons, uniting, form a broad muscle, which passes obliquely upward and inward, and is inserted into the innermost depression be- tween the two curved lines of the occipital bone. At about its middle it is traversed 1 These two muscles (Transversalis cervicis and Trachelomastoid) are sometimes described as one having a common origin, but dividing above at their insertion. The Trachelomastoid is then termed the Transversalis capitis. OF THE JiA CK 413 by a transverse tendinous intersection. The iimer portion of this muscle is usually separate and is called the biventer cervicis, from the intervention of a tendon between its two fleshy bellies. The Fifth Layer (Fig. 311). Semispinalis dorsi. Extensor coccygis. Semispinalis colli. Intertransversales. Multifidus spinae. Rectus capitis posticus major. Rotatores spinae. Rectus capitis posticus minor. Supraspinales. Obliquus inferior. Interspinales. Obliquus superior. Dissection. — Remove the muscles of the preceding layer by dividing and turning aside the Complexus; then detach the Spinahs and Longissimus dorsi from their attachments, divide the Erector spinae at its connection below to the sacral lumbar vertebrae and turn it outward. The muscles filling up the interval between the spinous and transverse processes are then exposed. The Semispinalis dorsi (m. semispi)ialis dorsi) consists of thin, narrow, fleshy fasciculi interposed between tendons of considerable length. It arises by a series of small tendons from the transverse processes of the lower thoracic vertebrte, from the tenth or eleventh to the fifth or sixth; and is inserted, by five or six tendons, into the spinous processes of the upper four thoracic and lower two cervical vertebne. The Semispinalis colli {m. semispinalis cervicis), thicker than the preceding, arises by a series of tendinous and fleshy fibres from the transverse processes of the upper five or six thoracic vertebrae, and is inserted into the spinous processes of four cervical vertebrae, from the axis to the fifth cervical. The fasciculus connected with the axis is the largest, and is chiefly muscular in structure. Superficial to this muscle and the preceding are the profunda cervicis artery, the princeps cervicis artery, and the internal branches of the posterior divisions of the first, second, and third cervical nerves; their deep surfaces lie upon the ]\'Iultifidus spinae. The Multifidus spinae (m. multifidus) consists of a number of fleshy and ten- dinous fasciculi which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. In the sacral region these fasciculi arise from the back of the sacrum, as low as the fourth sacral foramen, and from the aponeurosis of origin of the Erector spinae; from the inner surface of the pos- terior superior spine of the ilium and posterior sacro-iliac ligaments; in the lumbar regions from the mammillary processes; in the thoracic region, from the transverse processes; and in the cervical region, from the articular processes of the three or four lower vertebrae. Each fasciculus, passing obliquely upward and inward, is inserted into the whole length of the spinous process of one of the vertebrae above. These fasciculi vary in length; the most superficial, the longest, pass from one vertebra to the third or fourth above; those next in order pass from one vertebra to the second or third above; while the deepest connect two contiguous vertebriB. Its superficial surface is covered by the Semispinalis dorsi, and the Semispinalis colli, and its deep surface, lies upon the laminse and spinous processes of the vertebrfe. The Rotatores spinae (mm. rotatores) are found only in the thoracic region of the spine, beneath the Multifidus spinae; they are eleven in number on each side. Each muscle is small and somewhat quadrilateral in form; and arises from the 414 THE 3IUSCLES AND FASCIjE upper and back part of the transverse process, and is inserted into the lower border and outer surface of the lamina of the vertebra above, the fibres extending as far inward as the root of the spinous process. The first is found between the first and second thoracic; the last, between the eleventh and twelfth. Sometimes the number of these muscles is diminished by the absence of one or more from the upper or lower end. The Supraspinales {mm. supraspinales) consist of a series of fleshy bands which lie on the spinous processes in the cervical region of the vertebral column. The Interspinales (mm. interspinales) are short muscular fasciculi, placed in pairs between the spinous processes of the contiguous vertebrae, one on each side of the interspinous ligament. In the cervical region they are most distinct, and consist of six pairs, the first being situated between the axis and the third vertebra, and the last between the last cervical and the first thoracic vertebra. They are small narrow bundles, attached, above and below, to the apices of the spinous processes. In the thoracic region they are found between the first and second vertebrae, and occasionally between the second and third; and below, between the eleventh and twelfth. In the lumbar region there are four pairs of these muscles in the intervals between the five lumbar vertebrae. There is also occasionally one in the interspinous space betw^een the last thoracic and first lumbar, and between the fifth lumbar and the sacrum. The Extensor coccygis is a slender muscular fasciculus, occasionally present, -nhicli extends over the lower part of the posterior surface of the sacrum and coccyx. It arises by tendinous fibres from the last bone of the sacrum or first piece of the coccyx, and passes downward to be ituerted into the lower part of the coccyx. It is a rudiment of the Extensor muscle of the caudal vertebrae of the lower animals. The Intertransversales (mm. iniertransversarii) are small muscles placed between the transverse processes of the vertebrae. In the cervical region they are most developed, consisting of rounded muscular and tendinous fasciculi, which are placed in pairs, passing between the anterior and the posterior tubercles of the transverse processes of two contiguous vertebrae, separated from one another by the anterior division of the cervical nerve, which lies in the groove between them. In this region there are seven pairs of these muscles, the first pair being between the atlas and axis, and the last pair between the seventh cervical and first thoracic vertebrae. In the thoracic region they are least developed, consisting chiefly of rounded tendinous cords in the intertransverse spaces of the upper thoracic verte- brae; but between the transverse processes of the lower three thoracic vertebrae, and between the transverse processes of the last thoracic and the first lumbar, they are muscular in structure. In the lumbar region they are arranged in pairs, on either side of the vertebral column, one set occupying the entire interspace between the transverse processes of the lumbar vertebrae, the intertransversales laterales; the other set, intertransversales mediales, passing from the accessory process of one vertebra to the mammillary process of the next below. The Rectus capitis posticus major [m. rectus capitis posterior major) arises by a pointed tendinous origin from the spinous process of the axis, and, becoming broader as it ascends, is inserted into the inferior curved line of the occipital bone and the surface of bone immediately below it. As the muscles of the two sides pass upward and outward, they leave between them a triangular space, in which are seen the Recti capitis postici minores muscles. The siiperficial surface is crossed by the Complexus; its deep surface lies on the posterior occipito-atlantal ligament. The Rectus capitis posticus minor (m. rectus capitis posterior minor), the small- est of the four muscles in this region, is of a triangular shape; it arises by a narrow pointed tendon from the tubercle on the posterior arch of the atlas, and, becom- ing broader as it ascends, is inserted into the rough surface beneath the inferior OF THE BACK 415 curved line, nearly as far as the foramen magnum, and nearer to the middle line than the preceding. The Obliquus inferior (m. ohliquus capitis inferior), the larger of the two Oblique muscles, arises from the apex of the spinous process of the axis, and passes outward and slightly upward, to be inserted into the lower and back part of the transverse process of the atlas. The Obliquus superior (?n. ohliquus capitis superior), narrow below, wide and expanded above, arises by tendinous fibres from the upper surface of the transverse process of the atlas; it joins with the insertion of the preceding, and, passing obliquely upward and inward, is inserted into the occipital bone, between the two curved lines, external to the Complexus. The Suboccipital triangle is the triangular interval between the two oblique muscles and the Rectus capitis posticus major. This triangle is bounded, above and internally, by the Rectus capitis posticus major; above and externally, by the Obliquus superior; below and externally, by the Obliquus inferior. It is covered in by a layer of dense fibrofatty tissue, situated beneath the Complexus muscle. The floor is formed by the posterior occipito-atlantal ligament and the posterior arch of the atlas. It contains the vertebral artery, as it runs in a deep groove on the upper surface of the posterior arch of the atlas, and the posterior division of the sub- occipital nerve. Nerves. — The fourth and fifth layers of the muscles of the back are supplied by the posterior primary divisions of the spinal nerves. Actions. — When both the Spinales dorsi contract, they extend the thoracic region of the vertebral column; when only one muscle contracts, it helps to bend the thoracic portion of the vertebral column to one side. The Erector spinae, comprising the Iliocostalis and the Longissimus dorsi with their accessory muscles, serves, as its name implies, to maintain the vertebral column in the erect posture; it also serves to bend the trunk backward when it is required to counterbalance the influence of any weight at the front of the body, as, for instance, when a heavy weight is suspended from the neck, or when there is any great abdominal dis- tention, as in pregnancy or dropsy; the peculiar gait under such circumstances depends upon the vertebral column being drawn backward by the counterbalancing action of the Erector spinae muscles. The muscles which form the continuation of the Erector spinae upward steady the head and neck, and fix them in the upright position. If the Iliocostalis and Lon- gissimus dorsi of one side act, they serve to draw down the thorax and vertebral column to the corresponding side. The Cervicales ascendens, taking their fixed points from the cervical vertebrte, elevate those ribs to which they are attached; taking their fixed points from the ribs, both muscles help to extend the neck; while one muscle bends the neck to its own side. The Transversales cervicis, when both muscles act, taking their fixed point from below, bend the neck backward. The Trachelomastoid, when both muscles act, taking their fixed point from below, bend the head backward; while if only one muscle acts, the face is turned to the side on which the muscle is acting, and then the head is bent to the shoulder. The two Recti muscles draw the head backward. The Rectus capitis posticus major, owing to its obliquity, rotates the cranium, with the atlas, around the odontoid process, turning the face to the same side. The Multifidus spinae acts successively upon the different parts of the vertebral column; thus, the sacrum furnishes a fixed point from which the fasciculi of this muscle act upon the lumbar region; these then become the fixed points for the fasciculi moving the thoracic region, and so on throughout the entire length of the vertebral column; it is by the successive contraction and relaxation of the separate fasciculi of this and other muscles that the spine preserves the erect posture without the fatigue that would necessarily have been produced had this position been maintained by the action of a single muscle. The Multifidus spinae, besides preserving the erect position of the vertebral column, serves to rotate it, so that the front of the trunk is turned to the side opposite to that from which the muscle acts, this muscle being assisted in its action by the Obliquus externus abdominis. The Com]ilexi draw the head directly backward; if one muscle acts, it draws the head to one side, and rotates it so that the face is turned to the opposite side. The Superior oblique draws the head backward, and, from the obliquity in the direction of its fibres, will slightly rotate the cranium, turning the face to the opposite side. The Inferior oblique rotates the atlas, and with it the cranium, around the odontoid process, turning the face to the same side. The Semispinales, when the muscles of the two sides act together, help to extend the vertebral column; when the muscles of one side only act, they rotate the thoracic and cervical parts of the vertebral column, turning the body to the opposite side. The Supraspinales and Interspinales by approximating the spinous processes help to extend the vertebral column. The. Intertransversales approximate the transverse processes, and help- 416 THE MUSCLES AND FASCIA to bend the vertebral column to one side. The Rotatores spinae assist the Multifidus spinae to rotate the vertebral column, so that the front of the trunk is turned to the side opposite to that from which the muscle acts. Surface Forms. — The surface forms produced by the muscles of the back are numerous and difficult to analyze unless they are considered in systematic order. The most superficial layer, consisting of large strata of muscle tissue, influences to a certain extent the surface form, and at the same time reveals the forms of the layers beneath. The Trapezius at the upper part of the back, and in the neck, covers over and softens down the outline of the underlying muscles. Its anterior border forms the posterior boundary of the posterior triangle of the neck. It forms a slight undulating ridge which passes downward and forward from the occiput to the junction of the middle and outer third of the clavicle. The tendinous ellipse formed by a part of the origin of the two muscles at the back of the neck is always to be seen as an oval depression, more marked when the muscle is in action. A slight dimple on the skin opposite the interval between the spinous processes of the third and fourth thoracic vertebrae marks the triangular aponeurosis by which the inferior fibres are inserted into the root of the spine of the scapula. From this point the inferior border of the muscle may be traced as an undulating ridge to the spinous process of the twelfth thoracic vertebra. In like manner the Latissimiis dorsi softens down and modulates the underlying structures at the lower part of the back and lower part of the side of the thorax. In this waj' it modulates the outline of the Erector spinae; of the Serratus posticus inferior, which is sometimes to be discerned through it. The anterior border of the muscle is the only part which gives a distinct surface form. This border may be traced, when the muscle is in action, as a rounded edge, starting from the crest of the ilium, and passing obliquely forward and upward to the posterior border of the axilla, where it combines with the Teres major in forming a thick rounded fold, the posterior boundary of the axillary space. The muscles in the second layer influence to a very considerable extent the surface form of the back of the neck and upper part of the trunk. The Levator anguli scapulae reveals itself as a prominent divergent line, running downward and outward, from the transverse proc- esses of the upper cervical vertebrae to the angle of the scapula, covered over and toned down by the overlying Trapezius. The Rhomboidei produce, when in action, a vertical eminence between the vertebral border of the scapula and the vertebral furrow, varying in intensity according to the condition of contraction or relaxation of the Trapezius muscle, by which they are for the most part covered. The lowermost part of the Rhomboideus major is not covered by the Trapezius, and forms on the surface an oblique ridge running upward and inward from the inferior angle of the scapula. Of the nmscles of the third layer of the back, the Serratus posticus superior does not in any way influence surface form. The Serratus posticus inferior, when in strong action, may occasionally be revealed as an elevation beneath the Latis- simus dorsi. The Splenii by their divergence serve to broaden out the upper part of the back of the neck and produce a local fulness in this situation, but do not otherwise influence surface form. Beneath all these muscles those of the fourth layer — the Erector spinae and its continua- tions— influence the surface form in a decided manner. In the loins, the Erector spinae, bound down by the lumbar fascia, forms a rounded vertical eminence, which determines the depth of the vertebral furrow, and which below tapers to a point on the posterior surface of the sacrum and becomes lost there. In the back it forms a flattened plane which gradually becomes lost. In the neck the only part of this group of muscles which influences surface form is the Trachelo- mastoid, which produces a short convergent line across the upper part of the posterior triangle of the neck, appearing from under cover of the posterior border of the Sternomastoid and being lost below beneath the Trapezius. Applied Anatomy. — In cases of tuberculous caries of the vertebral bodies, and in other diseases affecting the vertebral column, rigidity of the spinal muscles is one of the earliest and most constant symptoms. A child with commencing vertebral disease always maintains the affected portion of the column in a state of absolute rigidity, to prevent the inflamed structures from being moved against each other; this is one of the best examples of nature's method of producing rest of the affected part. II. MUSCLES AND FASCI.a! OF THE THORAX. The muscles belonging exclusively to this region are few in number. They are the Intercostales externi. Triangularis sterni. Intercostales interni. Levatores costarum. Infracostales. Diaphragm. OF THE THORAX 417 Intercostal Fascia.— A thin but firm layer of fascia covers the outer surface of the P^xternal intercostal and the inner surface of the Internal intercostal muscles; and a third layer, more delicate, is interposed between the two planes of muscle fibres. These are the intercostal fasciae, external, middle, and iiiferiial; they are best marked in those situations where the muscle fibres are deficient, as between the External intercostal muscles and sternum, in front, and between the Internal intercostals and vertebral column, behind. The Intercostal muscles (Figs. 319 and 347) are two thin planes of muscle and tendon fibres, place.d one over the other. They fill up the intercostal spaces, and are directed oblic|uely Ijetween the margins of the adjacent libs. They have received the name external and internal from the position they bear to each other. Between them in the grooved under surface of the rib run the intercostal vessels and nerve. The tendon fibres are longer and more numerous than the muscle fibres; hence the walls of the intercostal spaces possess very considerable strength, to which the crossing of the muscle fibres materially contributes. The External intercostals (mm. intercostales externi) are eleven in number on each side. They extend from the tubercles of the ribs, behind, to the commence- ment of the cartilages of the ribs, in front, where they terminate in a thin mem- brane, the anterior intercostal membrane, which is continued forward to the sternum. They arise from the lower border of the rib above, and are inserted into the upper border of the rib below. In the two lowest spaces they extend to the ends of the cartilages, and in the upper two or three spaces they do not quite extend to the ends of the ribs. Their fibres are directed obliquely downward and forward, in a similar direction with those of the External oblique muscle of the abdomen. They are thicker than the Internal intercostals. The Internal intercostals (mm. intercostales interni) are also eleven in number on each side. They commence anteriorly at the sternum in the interspaces between the cartilage of the true ribs, and from the anterior extremities of the cartilages of the false ribs, and extend backward as far as the angles of the ribs, whence they are continued to the vertebral column by a thin aponeurosis, the -posterior intercostal membrane. They arise from the ridge on the inner surface of the rib above, as well as from the corresponding costal cartilage, and are inserted into the upper border of the rib below. Their fibres are directed obliquely downward and backward, passing in the opposite direction to the fibres of the External intercostal muscle. The Infracostales (mm. subcostales) consist of muscular and aponeurotic fas- ciculi, which vary in number and length; they are placed on the inner surface of the ribs, where the Internal intercostal muscles cease; they arise from the inner surface of one rib, and are inserted into the inner surface of the first, second, or third rib below. Their direction, like the Internal intercostals, is usually oblique. They are most frequently found between the lower ribs. The Triangularis sterni (m. transversus thoracis) (Fig. 312) is a thin plane con- sisting of muscle and tendon fibres, and is situated upon the inner wall of the front of the thorax. It arises from the lower third of the posterior surface of the sternum, from the posterior surface of the ensiform cartilage, and from the sternal ends of the costal cartilages of the three or four lower true ribs. Its fibres diverge upward and outward, to be inserted by digitations into the lower borders and inner surfaces of the costal cartilages of the second, third, fourth, fifth, and sixth ribs. The lowest fibres of this muscle are horizontal in their direction, and are continuous with those of the Transversa lis; those which succeed are oblique, while the superior fibres are almost vertical. This muscle varies much in its attachment, not only in different bodies, but on opposite sides of the same body. The internal mammary artery runs between this muscle and the costal cartilages. The Levatores COStarum (mm. levafores costarum) (^Fig. 311), tivelve in mmiber on each side, are small tendinous and fleshy bundles which arise from the extrem- 418 THE MUSCLES AND FASCIA ities of the transverse processes of the seventh cervical and the eleven upper thoracic vertebra. They pass obliquely downward and outward and are inserted into the upper border, between the tubercle and the angle of the rib, immediately below its vertebra of origin. In some instances the muscle divides into two fascicuH, one of which is inserted as above described; the other fasciculus passes down to the second rib below its origin. Nerves. — The muscles of this group are supplied by the intercostal nerves. STERNOMASTO SUBCLAVIUS Fig. 312.— Posteric • surface of sternum and costal cartilages, showing Triangularis sterni muscle ration in the Museum of the Royal College of Surgeons of England. ) (From a prepa- The Diaphragm (diaphragma) (Figs. 313 and 314) is a thin, musculofibrous septum placed at the junction of the upper with the middle third of the trunk; it separates the thoracic from the abdominal cavity, its convex upper surface forming the floor of the former, and its concave under surface the roof of the latter. Its peripheral part consists of muscle fibres which arise from the internal circumference of the thoracic outlet, as well as from certain lumbar vertebrje, and pass upward and inward to converge to a central tendon. Anteriorly, the Diaphragm arises from the dorsal surface of the ensiform cartilage by two fleshy strips (pars sternalis); on either side, from the inner surfaces of the six lower costal cartilages (seventh to twelfth) {pars cosfalis), interdigitating with slips of origin of the Transversalis abdominis. Behind, it takes origin from certain OF THE THORAX 419 lumbar vertebrte by two crura; and from aponeurotic arches named the arcuate ligaments {jpars lumbalis). The criira are situated on the bodies of the hmibar vertebrae, on each side of the aorta. Tlie crura, at their origin, are tendinous in structure; the right crus, larger and longer than the left, arises from the anterior surface of the bodies and articular disks of the four upper lumbar vertebra?; the left crus arises from the three upper lumbar vertebrae; both blend with the anterior common ligament of the vertebral column. The tendinous portion of each crus passes forward and inward to meet the corresponding portion of the opposite side, thus forming the tendinous arch known as the middle arcuate ligament. From this arch diverging muscle fil^res arise, the outermost portion of wliich is directed upward and outward to the central tendon; the innermost portion decussate in front of the aorta, diverge in order to surround the oesophagus, and likewise end in the central tendon. The filires derived from the right crus are the more numerous and pass in front of those derived from the left. Each crus, in its tendinous portion, is perforated by the great and lesser splanchnic nerves and sometimes the ascending lumbar radicle of the azygos veins. The internal arcuate ligament (arcus lumbocosiaUs medialis) is a tendinous arch in the fascia covering the upper part of the Psoas magnus muscle, on each side of the vertebral column. This tendinous arch is connected mesad to the body of the first (or second) lumbar vertebrae, laterad to the front of the tip of the transverse process of the first (or second) lumbar vertebrae. The external arcuate ligament (arcus lumhocostalis lateralis) is the thickened upper margin of the anterior lamella of the lumbar fascia; it arches across the upper part of the Quadratus lumborum from the front of the transverse process of the first (or second) lumbar vertebra to the apex and lower margin of the twelfth rib. The fibres of the Diaphragm derived from these sources vary in length; those arising from the ensiform cartilage are short and occasionally aponeurotic, con- tinuous with the posterior layer of the Rectus abdominis sheath. Those arising from the arcuate ligaments, and more especially those from the cartilages of the ribs at the side of the thorax, are longer, describe well-marked curves as they ascend, and finally converge to be inserted into the margin of the central tendon. The central tendon of the Diaphragm (centrum tendineum) (Fig. 314) is a thin but strong tendinous aponeurosis, situated at the centre of the \R\\\t formed by the muscle, immediately below the pericardium, with which it is partly blended. It is shaped somewhat like a trefoil leaf, consisting of three divisions, or leaflets, sepa- rated from one another by slight indentations. The right leaflet is the largest ; the middle one, directed toward the ensiform cartilage, the next in size; and the left, the smallest. In structure, the tendon is composed of several planes of fibres which intersect one another at various angles, and unite into straight or curved bundles — an arrangement which aft'ords it additional strength. The openings in the Diaphragm are three large and several smaller apertures. The former are the aortic, the oesophageal, and the opening for the inferior vena cava. The aortic opening (hiatus aorticus) is the lowest and the most posterior of the three large apertures connected with this muscle, being at the level of the first lumbar vertebra. It is situated slightly to the left of the middle line, immediately in front of the bodies of the vertebrae; and is, therefore, behind the Diaphragm, not in it. It is an osseoaponeurotic aperture, formed by a tendinous arch (middle arcuate ligament) thrown across the front of the bodies of the vertebrae, from the crus on one side to that on the other, and it transmits the aorta, the vena azygos 420 THE MUSCLES AND FASCIAE major, and the thoracic duct. Sometimes the vena azygos major is transmitted upward through the right crus. Occasionally some tendinous fibres are.pro- CESOPHAGUS AOHTA Fig. 313.^ — The Diaphragm, seen from above. (Poirier and Charpy.) ""'iiinii ' *■ tcndom Fig. 314. — The Diaphragm, viewed from in front. (Testut.) longed across the bodies of the vertebrfe from the inner part of the lower end of the crura, pass behind the aorta, and thus convert the opening into a fibrous ring OF THE THORAX 421 The oesophageal opening {li'iatnH oesophageus) is situated at the level of the tenth liioracic vertebra; it is elliptical in form, oblique in direction, muscular in structure, and is formed by the decussating fibres of the two crura. It is placed above, and at the same time anterior, and a little to the left of the aortic opening. It transmits the oesophagus and vagus nerves and some small oesophageal arteries. The anterior margin of this aperture is occasionally tendinous, being formed by the margin of the central tendon. The posterior and lateral margins are thick and the gullet is in contact with them for about half an inch. The right margin of the CESophageal opening is particularly prominent and lies in the oesophageal groove on the posterior surface of the left lobe of the liver. The opening for the inferior vena cava (foramen, venae cavae) is the highest open- ing, being about on the level of the dislv between the eighth and ninth thoracic vertebrae; it is quadrilateral in form, tendinoi^s in structure, and is placed at the junction of the right and middle leaflets of the central tendon, its margins being adherent to the wall of the inferior vena cava. " " ^ A \\ Fig. 315. — The Diaphragm, viewed from below. (Testut.) The right crus transmits the greater and lesser splanchnic nerves of the right side; the left crus transmits the greater and lesser splanchnic nerves of the left side, and the vena azygos minor (inferior). The gangliated cords of the sympa- thetic usually enter the abdominal cavity by passing behind the internal arcuate ligaments. Serous Membranes. — The serous membranes in relation with the Diaphragm are four in number, three covering its upper or thoracic surface, and one its abdominal surface. The three serous membranes on its upper surface are the two pleurre on either side and the pericardium, which covers the middle portion of the tendinous centre. The greater portion of the under surface of the Diaphragm is covered by the peritoneum. Nerves. — The Diaphragm is supplied by the right and left phrenic nerves, derived from the anterior primary divisions of the third, fourth, and fifth cervical nerves. The nerve filaments which pass to the Diaphragm from the lower four intercostal nerves are sensor in function and supply only the peritoneum. Actions. — Each External intercostal muscle elevates the rib below. Owing to the oblique axis of the costovertebral articulation, the curved obliquity of the ribs themselves, and the 422 THE 3IUSCLES AND FASCIJE angular arrangement of the lower costal cartilages, the sternum is lifted upward and forward, the ribs upward and slightly outward, and the diameters of the thorax are thus increased. The action of the Internal intercostals is in dispute. Haller long ago taught that they act together with the External intercostals as inspiratory muscles. Investigators have since endeav- ored to show that they act as expiratory muscles.' Others believe that the Intercostal muscles contract simultaneously and serve merely as strong septal supports which prevent the inter- costal spaces from being pushed out or drawn in during respiration. Masoin and Du Bois Rey- mond,- in experiments on animals, proved that the intercartilaginous portions of the Internal intercostals contracted synchronously with the Diaphragm. The Diaphragm is the principal muscle of inspiration, and presents the form of a dome con- cave toward the abdomen. The central part of the dome is tendinous, and the pericardium is attached to its upper surface; the circumference is muscular. During inspiration the lowest ribs are fLxed, and from these and the crura the muscle fibres contract and draw downward and forward the central tendon with the attached pericardium. In this movement the curva- ture of the Diaphragm is scarcely altered, the dome moving downward nearly parallel to its original position and pushing before it the abdominal viscera. The descent of the abdominal viscera is permitted by the elasticity of the abdominal wall, but the limit of this is soon reached. The central tendon applied to the abdominal viscera then becomes a fixed point for the action of the Diaphragm, the effect of which is to elevate the lower ribs and through them to push forward the sternum and the upper ribs. The right cupola of the Diaphragm, lying on the liver, has a greater resistance to overcome than the left, which lies over the stomach, but to compensate for this the right crus and the fibres of the right side generally are stronger than those of the left. In all expulsive acts the Diaphragm is called into action to give additional power to each expulsive effort. Thus, before sneezing, coughing, laughing, crying, or vomiting, and previous to the expulsion of urine or feces, or of the fcetus from the uterus, a deep inspiration takes place. The height of the Diaphragm is constantly varying during respiration; it also varies with the degree of distention of the stomach and intestines and with the size of the liver. After a forced expiration the right cupola is on a level in front with the fourth costal cartilage, at the side with the fifth, sixth, and seventh ribs, and behind with the eighth rib; the left cupola is a little lower than the right. Halls Dally states that the absolute range of movement between deep inspiration and deep expiration averages in the male and female 30 mm. on the right side and 28 mm. on the left; in quiet respiration the average movement is 12.5 mm. on the right side and 12 mm. on the left.^ Skiagraphy shows that the height of the Diaphragm in the thorax varies considerably with the position of the body. It stands highest when the body is horizontal and the patient on his back, and in this position it performs the largest respiratory excursions with normal breathing. When the body is erect the dome of the Diaphragm falls, and its respiratory movements become less. The dome falls still lower when the sitting posture is assumed, and in this position its respiratory excursions are least in extent. These facts may, perhaps, explain v.'hy it is that patients suffering from severe dyspnea are most comfortable and least short of breath when they sit up. When the body is horizontal and the patient on his side, the two halves of the Diaphragm do not behave alike. The uppermost half sinks to a level lower even than when the patient sits, and moves little with respiration; the lower half rises higher in the thorax than it does when the patient is supine, and its respiratory excursions are much increased. In unilateral disease of the pleura or lungs analogous interference with the position or movement of the Diaphragm can generally be observed skiagi-aphically. It appears that the position of the Diaphragm in the thorax depends upon three main factors, viz.: (1) The elastic retraction of the lung tissue, tending to pull it upward; (2) the pressure exerted on its under surface by the viscera; this naturally tends to be a negative pressure, or a downward suction, when the patient sits or stands, and a positive or an upward pressure when he lies; (3) the intra-abdominal tension due to the abdominal muscles. These are in a state of contraction in the standing position and not in the sitting position; hence, the Diaphragm when the patient stands is pushed up higher than when he sits. The Levatores costarum being inserted near the fulcra of the ribs can exert but little action on them; they act as rotators and lateral flexors of the vertebral column. The Triangularis sterni draws down the costal cartilages, and is therefore a muscle of expi- ration. Mechanism of Respiration. — The respiratory movements must be examined during (a) quiet respiration, and during (b) forced respiration. 1 Consult articles by Cleland in the Journal of Anatomy and Physiology. May, 1867. p. 209; B.aumler, Obser- vations on the Action of the Intercostal Muscles, Erlangen, 1860 fRef. in New Syd. Soc.'s Year-Book for 1861, p. 69); Keen, Trans. Coll. of Phys., Phila., Third series, vol. i, 1875. p. 97; Flusser, Ueber die Wirkung der Mus- culi Intercostales, Anat. Anz., April 16. 1908; Boecker, -Anat. Anz.. .June 27, 1908. ^ ZuT Lehre von der Function der Musculi intercostales interni, Archiv fur Physiologic. 1896, p. 8.5. ^ Inquiry into the Physiological Mechanism of Respiration, journal of Anatomy and Physiology, vol. xliii^ 1908. OF THE ABDOMEN 423 Quiet Respiration. — The first and second pairs of ribs are fixed by the Scaleni and Ijy the resistiiricc of llu' cervical structures; the last pair, and through it the eleventh pair, are fixed by the Quadratus lumborum muscles. The other ribs are elevated, so that the first two inter- costal spaces are diminished while the other spaces are increased in width. It has already been shown (p. 285) that elevation of the third, fourth, fifth, and sixth ribs leads to an increase in the antero-posterior and transverse diameters of the thorax; the vertical diameter is increased by the descent of the diaphragmatic dome so that the lungs are expanded in al! directions exce)jt backward and upward. Elevation of the eighth, ninth, and tenth ribs is accompanied by an outward and backward movement, leading to an increase in the transverse diameter of the upper part of the abdomen; the elasticity of the anterior abdominal wall allows a slight increase in the antero-posterior diameter of this part, and in this way the decrease in the vertical diameter of the abdomen is compensated and space provided for its displaced viscera. Expiration is effected by the elastic recoil of the abdominal walls and by the action of the abdominal muscles, which push back the viscera displaced downward by the Diaphragm. Forced Respiration. — All the movements of quiet respiration are here carried out, but to a greater extent. In inspiration the shoulders and the vertebrai borders of the scapulte are fixed and the limb muscles, Trapezius, Serratus magnus, Pectorals, and Latissimus dorsi, are called into play. The Scaleni are in stronger action, and the Sternomastoids also assist, when the head is fixed, by drawing up the sternum and by fixing the clavicles. The first rib is there- fore no longer stationary, but, with the sternum, is raised; with it all the other ribs except the last are raised to a higher level. In conjunction with the increased descent of the Diaphragm this provides for a considerable augmentation of all the thoracic diameters. The anterior abdom- inal muscles come into action so that the umbilicus is drawn upward and backward, and this allows the Diaphragm to exert a more powerful infiuence on the lower ribs; the transverse diameter of the upper part of the abdomen is greatly increased and the subcostal angle is opened out. The deeper muscles of the back, e. g., the Serrati postici superiores and the Erectores spinae, are also brought into action; the thoraciccurve of thevertebral column is partially straight- ened, and the whole column, above the lower lumbar vertebrse, is drawn backward. This increases the antero-posterior diameters of the thorax and of the upper part of the abdomen and widens the intercostal spaces. Forced expiration is effected by the recoil of the abdominal walls, by the contraction of the antero-lateral muscles.of the abdominal wall, and of the Serrati postici inferiores and Triangularis sterni. Halls Dally {op. cit.) gives the following figures as representing the average changes which occur during deepest possible respiration. The manubrium moves 30 mm. in an upward, and 14 mm. in a forward direction; the width of the subcostal angle, at a level of 30 mm. belciw the articulation of the manubrium with the gladiolus, is increased by 26 mm.; the umbilicus is retracted and drawn upward for a distance of 1 3 mm. Artificial Respiration. — By the "prone pressure" method of Prof. E. A. Schafer advantage is taken of the contour of the diapliragm and of the elastic recoil of the thoracic wall in providing for a tidal air exchange in the lungs. III. MUSCLES OF THE ABDOMEN. The muscles of the abdomen may be divided into two groups: (1) The antero-lateral muscles of the abdomen. (2) The posterior muscles of the abdomen. 1. The Antero-lateral Muscles of the Abdomen. The muscles of this group are the External oblique. Transversalis. Internal oblique. Rectus. Pyramidalis. Dissection (Fig. 316). — To dissect the abdominal muscles, make a vertical incision from the ensiform cartilage to the symphysis pubis; a second incision from the umbilicus obliquely upward and outward to "the outer surface of the thorax, as high as the lower border of the fifth or sixth rib; and a third, commencing midway between the umbilicus and pubes, transversely outward to the anterior superior iliac spine, and along the crest of the ilium as far as its posterior third. 424 THE MUSCLES AND FASCIA Then reflect the three flaps included between these incisions from within outward, in tne lines of direction of the muscle fibres. If necessary, the abdominal muscles may be made tense bj inflating the peritoneal cavity tlirough the umbilicus. , The superficial fascia of the abdomen consists, over the greater part of the abdominal wall, of a single layer of fascia, which contains a variable amount of fat; but as this layer approaches the groin it is easily divisible into two layers, between which are found the superficial vessels and nerves and the superficial inguinal lymph nodes. The superficial layer of the superficial fascia {fascia of Camper) is thick, areolar in texture, and contains in its meshes adipose tissue, the quantity of which varies in different subjects. Below, it passes over Poupart's ligament, and is continuous with the outer layer of the superficial fascia of the thigh. In the male this fascia is continued over the penis and outer surface of the cord to the scrotum, where it helps to form the dartos. As it passes to the scrotum it changes its character, becoming thin, destitute of adipose tissue, and of a pale reddish color, and in the scrotum it acquires some nonstriated muscle fibres. From the scrotum it may be traced back- ward to be continuous with the superficial fascia of the perineum. In the female this fascia is con- tinued into the labia majora. The deep layer of the superficial fascia (fascia of Scarpa) is thinner and more membranous in character than the superficial layer, and contains a considerable quantity ef yellow elastic fibres. In the middle line it is intimately adherent to the linea alba and to the symphysis pubis, and is prolonged, in the male, on to the dorsum of the penis, forming the suspensory ligament of the penis; above, it joins the superficial layer and is continuous with the superficial fascia over the rest of the trunk ; heloio, •it blends with the fascia lata of the thigh a little below Poupart's ligament; and below and in- ternally it is continued over the penis and spermatic cord to the scrotum, where it helps to form the dartos. From the scrotum it may be traced backward to be continuous with the deep layer of the superficial fascia of the perineum (fascia of Colles). In the female it is continued into the labia majora. The deep fascia invests the External oblique muscle, but is so thin over the aponeurosis of the muscle as to be scarcely recognizable. The External or Descending oblique muscle (m. obliquus extemus abdominis) (Fig. 317) is situated on the side and fore part of the abdomen; being the largest and the most superficial of the three flat muscles in this region. It is broad, thin, and irregularly quadrilateral, its muscular portion occupying the side, its aponeu- rosis the anterior wall, of the abdomen. It arises, by eight fleshy digitations, from the external surface and lower borders of the eight inferior ribs; these •digitations are arranged in an oblique line running downward and backward; the upper ones being attached close to the cartilages of the corresponding ribs; the lowest, to the apex of the cartilage of the last rib ; the intermediate ones, to the ribs at some distance from their cartilages. The five superior serrations increase in size from above downward, and are received between corresponding processes of the Serratus magnus; the three lower ones diminish in size from above downward, receiving between them corresponding processes from the Latis- simus dorsi. From these attachments, the fleshy fibres proceed in various direc- tions. Those from the lowest ribs pass nearly vertically downward, to be inserted Fig. 316. — Dissection of abdomen. OF THE ABDOMEN 425 into the anterior half of the outer Hp of the crest of the ilium; the middle and upper fibres, directed downward and forward, terminate in an aponeurosis, oppo- site a line drawn from the prominence of the ninth costal cartilage to the anterior superior spine of the ilium. The aponeurosis of the External oblique is a thin, but strong membranous apon- eurosis, the fibres of which are directed obliquely downward and inward. It is joined with that of the oj^posite muscle along the median line and covers the whole of the front of the abdomen; above, it is covered by and gives origin to the lower border of the Pectoralis major; below, some of its fibres are inserted into the symphy- External abdo- minal ring. Giinb&rnaVs Fig. 317. — The External oblique muscle. sis pubis, while others pass deeply through the middle line to be attached to the crest and iliopectineal line of the opposite side; these latter fibres are termed the triangular fascia. But the great majority of the fibres below are closely aggre- gated, and extend obliquely across from the anterior superior spine of the ilium to the spine of the os pubis and the iliopectineal line. In the median line it inter- 426 THE MUSCLES AND FASCIAE laces with the aponeurosis of the opposite muscle, forming the linea alba, which extends from the ensiform cartilage to the symphysis pubis. That portion of the aponeurosis which extends between the anterior superior spine of the ilium and the spine of the os pubis is a broad band, folded inward, and continuous below with the fascia lata; it is called Poupart's ligament. The inner half inch of this ligament is reflected and attached to the subjacent pectineal line. This reflected part is called Gimbernat's ligament. In the aponeurosis of the External oblique, immediately above the crest of the OS pubis, is a triangular space, the external abdominal ring, formed by a thinning of the fibres of the aponeurosis in this situation. ^COLUMNAR RIIV G im ^B INIBE HNAT s__— — -^ liiii IH LIGAME^ T 1 nil 1 '111 ^^s SAPh P^ml s w 1 ^^^ \ M \ I^K^ MOR Lor L *7 T» j«^K^ SAPl- G — K' Fig. 318. — Right external abdominal ring and saphenous opening in the male. (Spalteholz.) Relations. — By its superficial surface, the External oblique muscle is in relation with the superficial fascia, superficial epigastric and circumflex iliac vessels, and some cutaneous nerves; by its deep surface, with the Internal oblique, the lower part of the eight inferior ribs, and Intercostal muscles, the Cremaster, the spermatic cord in the male, and round ligament in the female. Its posterior border, extending from the last rib to the crest of the ilium, is fleshy throughout and free; it is occasionally overlapped by the Latissimus dorsi, though generally a triangular interval exists between the two muscles near the crest of the ilium, in which is seen a portion of the Internal oblique. This triangle, Petit's triangle {trigonum lumhale) is there- fore bounded in front by the External oblique, behind by the Latissimus dorsi, below by the crest of the ilium, and its floor is formed by the Internal oblique muscle (Fig. 317). The following parts of the aponeurosis of the External oblique muscle require to be further described: External Abdominal Ring. Intercolumnar Fibres and Fascia. Poupart's Ligament. Gimbernat's Ligament. Triangular Fascia of the Abdomen. The External Abdominal Ring {annulus inguinalis subcutaneous) (Figs. 318 and 321). — Just above and to the outer side of the crest of the os pubis an interval OF THE ABDOMEN 427 known as the external abdominal ring is seen in the aponeurosis of the External oblique muscle. The interval is oblique in direction, corresponding with the course of the fibres of the aponeurosis, is somewhat triangular in form, and usually measures about an inch (2.5 cm.) from base to apex and about half an inch (1.25 cm.) transversely. It gives passage to the spermatic cord in the male and to the round ligament in the female. It is bounded helow by the crest of the os pubis; above, by a series of curved fibres, the external spermatic or the inter- coluninar fibres which pass across the upper angle of the ring, thus increasing its strength; and on each side, by the margins of the opening in the aponeurosis, which are called the columns or pillars of the ring. The external pillar (crus inferius) is inferior from the obliquity of its direction. It is stronger than the internal pillar; it is formed by that portion of Poupart's ligament which is inserted into the spine of the os pubis; it is curved so as to form a kind of groove, upon which the spermatic cord rests. The internal pillar (cms sjtperijis), a broad, thin, flat band, is formed by the fibres of the aponeurosis which are inserted into the crest and the symphysis pubis. The intercolumnar fibres {fibrae iiitercrurales) (Fig. 318) are a series of curved tendinous fibres, which arch across the lower part of the aponeurosis of the External oblicjue. They have received their name from stretching across between the two pillars of the external ring, describing a curve with the concavity downward. They are much thicker and stronger at the -outer margin of the external ring, where they are connected to the outer third of Poupart's ligament, than internally, where they are inserted into the linea alba. They are more strongly developed in the male than in the female. The intercolumnar fibres increase the strength of the lower part of the aponeurosis, and prevent the divergence of the pillars from each other. These intercolumnar fibres as they pass across the external abdominal ring are themselves connected together by delicate fibrous tissue, thus forming a fascia, the intercolumnar fascia or the external spermatic fascia, which, as it is attached to the piliai's of the ring, covers it in. This intercolumnar fascia is continued down as a tubular prolongation around the outer surface of the cord and testis or of the round ligament, and encloses them in a distinct sheath. Applied Anatomy .^The sac of an inguinal hernia, in passing through the external abdominal ring, receives an investment from the intercolumnar fascia. If the finger is introduced a short distance into the external abdominal ring and the limb is then extended and rotated outward, the aponeurosis of the External oblique, together with the iliac portion of the fascia lata, will be felt to become tense, and the external ring much contracted; if the limb is, on the contrary, flexed upon the pelvis and rotated inward, this aponeurosis will become lax and the external abdominal ring sufficiently enlarged to admit the finger with comparative ease; hence the patient should always be put in the latter position when the taxis is applied for the reduction of an inguinal hernia in order that the abdominal walls may be relaxed as much as possible. Poupart's Ligament (ligamentum inguinale). — Poupart's ligament is the lower border of the aponeurosis of the External oblique muscle, and extends from the anterior superior spine of the ilium to the pubic spine. From this latter point it is reflected to the iliopectineal line for about half an inch, thus forming Gimbernat's ligament. Its general direction is curved downward toward the thigji, where it is continuous with the fascia lata. Its outer half is rounded and oblique in direction and gives partial origin to the Internal oblique and Trans- versalis muscles. Its inner half gradually widens at its attachment to the os pubis, is more horizontal in direction, and lies beneath the spermatic cord. Nearly the whole of the space included between the femoral arch and the innominate bone is filled in by the parts which descend from the abdomen into the thigh (Fig. 326). These are referred to again on a subsequent page. 428 THE MUSCLES AND FASCIA Gimbernat's ligament {ligamentum lacunare) (Figs. 318 and 326) is that part of Poupart's ligament which is reflected to the iliopectineal Hne. It is about half an inch in length, more prominent in the male than in the female, almost hori- zontal in direction in the erect posture, and of a triangular form with the base directed outward. Its base, or outer margin, is concave, thin, and sharp, and lies in contact with the crural sheath, forming the inner boimdary of the femoral or crural ring {annulus femoralis). Its a-pex corresponds to the spine of the os pubis. Its deep margin is attached to the iliopectineal line, and is continuous with the pubic portion of the fascia lata. Its superficial margin is continuous with Pou- part's ligament. Its surfaces are directed upward andclownward. Triangular Fascia {ligamentum inguinale reflexwn). — The triangular fascia of the abdomen is a triangular layer of tendinous fibres, which comes from the aponeurosis of the opposite External oblique, and is attached b_y its apex to the iliopectineal line, where it is continuous with Gimbernat's ligament. It lies beneath the spermatic cord, behind the inner pillar of the external abdominal ring, and in front of the conjoined tendon. Ligament of Cooper (Fig. 328). — This is a strong ligamentous band, which was first described by Sir Astley Cooper. It extends upward and backward from the base of Gim- bernat's ligament along the iliopectineal line, to which it is attached. It is strengthened by the fascia transversalis, by the iliopectineal aponeurosis, and by a lateral expansion from the lower attachment of the linea alba (adminiculum lineae albae). Dissection. — Detach the External oblique by dividing it across, just in front of its attach- ment to the ribs, as far as its posterior border, and separate it below from the crest of the ilium as far as the anterior superior spine; then separate the muscle carefully from the Internal oblique, which lies beneath, and turn it toward the opposite side. The Internal or Ascending oblique muscle (m. ohliquus iniernus abdominis) (Fig. 319), thinner and smaller than the preceding, beneath which it lies, is of an irregularly quadrilateral form, and is situated at the side and fore part of the abdomen. It arises, by fleshy fibres, from the outer half of Poupart's ligament, to the groove on the upper surface of which it is attached; from the anterior two- thirds of the middle lip of the crest of the ilium, and from the posterior lamella of the lumbar fascia (Fig. 325). From this origin the fibres diverge; those from Pou- part's ligament, few in number and paler in color than the rest, arch downward an.d inward across the spermatic cord in the male and across the round ligament in the female, and, becoming tendinous, are inserted, conjointly with those of the Transversalis, into the crest of the os pubis and iliopectineal line, to the extent of half an inch or more, forming what is known as the conjoined tendon of the Internal oblique and Transversalis. The fibres from the anterior third of the iliac origin are horizontal in their direction, and, becoming tendinous along the lower fourth of the linea semilunaris, pass in front of the Rectus muscle to be inserted into the linea alba; those which arise from the middle third of the origin from the crest of the ilium pass obliquely upward and inward, and terminate in an aponeurosis which divides at the outer border of the Rectus muscle into two lamella? (Fig. 326), and are continued forward, in front and behind this muscle, to be inserted into the linea alba. The posterior lamella is also connected to the cartilages of the seventh, eighth, and ninth ribs; the fibres arising most posteriorly pass almost vertically upward, to be inserted into the lower borders of the cartilages of the three lower ribs, and are continuous with the Internal intercostal muscles. The lower fibres of this muscle are continuous with the Cremaster. The aponeurosis of the Internal oblique is continued forward to the middle of the abdomen, where it joins with the aponeurosis of the opposite muscle at the linea alba, and extends from the costal arch to the os pubis. At the outer margin of the Rectus muscle this aponeurosis, for the upper three-fourths of its extent. OF THE ABDOAIEN 429 Conjoined tendon CnCMASTER Fig. 319.— The Internal oblique muscle. VER5ALI5 DEEP E( GASTRIC ARTEI AND VE LIGAMENT OF HENLE LIGAMENT OF HESSELBACH Fig. 320. — The deep epigastric artery and veins, ligament of Henle and ligament of Hesselbach, seen from in front. (Modified from Braune.) 430 THE 3IU8CLE8 AND FASCIA divides into two lamellae, which pass, one in front and the other behind the muscle, enclosing it in a kind of sheath, and reuniting on its inner border at the linea alba; the anterior layer is blended with the aponeurosis of the External oblique muscle; the posterior layer with that of the Transversalis. Along the lower fourth the aponeurosis passes altogether in front of the Rectus without any separation. Where the aponeurosis ceases to split, and passes altogether in front of the Rectus muscle, a deficiency is left in the sheath of the Rectus behind; this is marked above by a sharp lunated margin which has its concavity downward, and is known as the semilunar fold of Douglas Qiiwa semicircularis) (Fig. 32.3) . Relations. — By its superficial surface the Internal oblique is in relation with the External oblique, Latissinius dorsi, spermatic cord, and external ring; by its deep surface, with the Trans- versalis muscle, the lower intercostal vessels and nerves, the iliohypogastric and the ilioinguinal nerves. Near Poupart's ligament it lies on the fascia transversalis, internal ring, and spermatic cord. Its lower border forms the upper boundary of the inguinal canal. Fig. 321.— Diagram of sheath of Rectus. External oblique Internal oblique TranRrprsalis Fig. 322. — Diagram of a transve section through the anteri fold of Douglas. abdominal wall, below the semilu The Cremaster muscle (m. cremaster) (Fig. 319) is a thin layer of muscle, com- posed of a number of fasciculi which arise from the inner part of Poupart's liga- ment, where its fibres are continuous with those of the Internal oblique and also occasionally with the Transversalis. It passes along the outer side of the spermatic cord, descends with it through the external abdominal ring upon the front and sides of the cord, and forms a series of loops which differ in thickness and length in different subjects. Those at the upper part of the cord are exceedingly short, but they become in succession longer and longer, the longest reaching down as low as the testicle, where a few are inserted into the tunica vaginalis. These loops are united by areolar tissue, and form a thin covering, the cremasteric fascia, over the cord and testis. The fibres of this muscle ascend along the inner side of the cord, and are inserted by a small pointed tendon into the crest of the os pubis and in front of the sheath of the Rectus muscle. It will be observed that the origin and insertion of the Cremaster is precisely similar to that of the lower fibres of the Internal oblique. This fact affords an easy explanation of the manner in which the testicle and cord are invested by this muscle. At an early period of fetal life the testis is placed at the lower and back part of the abdominal cavity, but during its descent toward the_ scrotum, which takes place before birth, it passes beneath the arched fibres of the Internal oblique. As the testis and cord go to their destination in the scrotum they pass beneath this OF THE ABDOMEN 431 muscle and carry with them and retain fibres from its lower part. It occasionally happens that the loops of the Cremaster surround the cord, some lying behind as well as in front. It is probable that under these circumstances the testis, in its descent, passed through instead of beneath the fibres of the Internal obliciue. In the descent of an inguinal hernia, which takes the same course as the spermatic cord, the Cremaster muscle forms one of its coverings. This muscle becomes largely developed in cases of hydrocele and large old scrotal hernia. The Cremaster muscle is found only in the TERIOR LEAF SHEATH OF CTU5 ABDOMINIS Fig. 32.3.— The i cles of the abdomen, showing the semilu (Spalteholz.) Viewed from in front. male, but almost constantly in the female a few muscle fibres may be seen on the surface of the round ligament which correspond to this muscle, and in cases of inguinal hernia in the female a considerable amount of muscle tissue may be found covering the sac. Relations. — By its superficial surface, with the External oblique, Latissimus dorsi, spermatic cord, and external ring; by its deep surface, with the Transversalis muscle, the lower intercostal 432 THE MVSCLES AND FASCIA vessels and nerves, the iliohypogastric and the ilioinguinal nerves. Near Poupart's ligament the Cremaster lies on the fascia transversalis, internal ring, and spermatic cord. Its lower border forms the upper boundary of the spermatic canal. Dissection, — Detach the Internal oblique in order to expose the Transversalis beneath. This mav be effected by dividing the muscle, above, at its attachment to the ribs: below, at its con- nection with Poupart's ligament and the crest of the ilium; and behind, by a vertical incision extending from the last rib to the crest of the ilium. The muscle should previously be made Fig, 324. — The Transversalis, Rectus, and Pyramidalis muscles. tense by drawing upon it with the fingers of the left hand, and if its division be carefully effected, the cellular interval between it and the Transversalis, as well as the direction of the fibres of the latter muscle, will afford a clear guide to their separation; along the crest of the ilium the cir- cumflex iliac vessels are interposed between them, and form an important guide in separating *iiem. The muscle should then be thrown inward toward the linea alba. The Transversalis muscle (m. transversus abdominis) (Fig. 324), so called from the direction of its fibres, is the deepest flat muscle of the abdominal wall. OF THE ABDOMEN 433 being placed immediately beneath the Internal oblique. It arises by fleshy fibres from the outer third of Poupart's ligament; from the inner lip of the crest of the ilium for its anterior three-fourths; from the inner surface of the cartilages of the six lower ribs, interdigitating with the Diaphragm; and from the lumbar fascia (Fig. 325), which may be regarded as the posterior aponeurosis of the muscle. The muscle terminates in front in a broad aponeurosis, the lower fibres of which curve downward and inward, and are inserted, together with those of the Internal oblique, on the crest of the os pubis and iliopectineal line, thus forming what is known as the conjoined tendon of the Internal oblique and Transversalis muscles. Throughout the rest of its extent the aponeurosis passes horizontally inward, and is inserted into the linea alba, its upper three-fourths passing behind the Rectus abdominis muscle, blending with the posterior lamella of the Internal oblique; its lower fourth passing in front of the Rectus. The conjoined tendon of the Internal oblicjue and Transversalis is chiefly formed by the lower part of the tendon of the Transversalis, and is inserted into the crest of the OS pubis and iliopectineal- line, immediately behind the external abdominal ring, thus serving to protect what would otherwise be a weak point in the abdominal wall. The conjoined tendon is sometimes divided into an outer and an inner portion — the /ormer termed the ligament of Hesselbach {ligamentwn imerfoveolare) ; the latter, the ligament of Henle (Fig. 320). Relations. — By its superficial surface, with the Internal oblique, the lower intercostal nerves, and the inner surface of the cartilages of the lower ribs; by its deep surface, with the fascia transversalis, which separates it from the peritoneum. Its lower border forms the upper boundary of the inguinal canal. Dissection. — To expose the Rectus abdominis muscle, open its sheath by a vertical incision extending from the costal arch to the os pubis, and then reflect the two portions from the surface of the muscle, which is easily done, excepting at the lineae transversae, where so close an adhesion exists that the greatest care is requisite in separating them. Now raise the outer edge of the muscle, in order to examine the posterior layer of the sheath. By dividing the muscle in the centre, and turning its lower part downward, the point where the posterior wall of the sheath terminates in a thin curved margin will be seen. The Rectus abdominis (m. rectus abdominis) (Figs. 323 and 324) is a long flat muscle, which extends along the whole length of the front of the abdomen, being separated from its fellow of the opposite side by the linea alba. It is much broader, but thinner, above than below, and arises by two tendons; the external or larger is attached to the crest of the os pubis, the internal, smaller portion interlaces with its fellow of the opposite side, and is connected with the ligaments covering the front of the symphysis pubis. The fibres ascend, and the muscle is inserted by three portions of unequal size into the cartilages of the fifth, sixth, and seventh ribs. The longest portion attached principally to the cartilage of the fifth rib, usually has some fibres of insertion into the anterior extremity of the rib itself. Some fibres are occasionally connected with the costoxiphoid ligaments and side of the ensiform cartilage. The Rectus muscle is traversed by tendinous intersections, three in number, which have received the name of lineae transversae (inscriptiones tendineae). One of these is usually situated opposite the umbilicus, and two above that point; of the latter, one corresponds to the extremity of the ensiform cartilage, and the other to the interval between the ensiform cartilage and the umbilicus. These inter- sections pass transversely or obliquely across the muscle in a zigzag course; they rarely extend completely through its substance, sometimes they pass only half- way across it, and are intimately adherent in front to the sheath in which the muscle is enclosed. Sometimes one or two additional lines may be seen, one usually below the umbilicus; the position of the other, when it exists, is variable. These additional lines are for the most part incomplete. 434 THE 3WSCLE8 AND EASCI^ The Rectus is enclosed in a sheath, the rectus sheath (vagina m. recti abdominis) (Figs. 325 and 326), formed by the aponeurosis of the Obhque and Transversalis Fig. 325. — A transverse section of the abdomen in the lumbar region. muscles, which are arranged in the following manner. Wien the aponeurosis of the Internal oblique arrives at the outer margin of the Rectus it divides into two (anterior leaf) Posterior k-af Anterior leaf SHEATH OF RECTUS ABDOMINIS Fig. 326. — Transition of the tendon of the right internal oblique into the sheath of the rectus. (Spalteholz.) lamellae, one of which passes in front of the Rectus, blending with the aponeurosis of the External oblique; the other, behind it, blending with "the aponeurosis of the OF THE ABDOMEN 435 Transversalis; and these, joining again at its inner border, are inserted into the hnea alba. This arrangement of the aponeuroses exists along the upper three-fourths of the muscle; at the commencement of the lower fourth, the posterior wall of the sheath terminates in a thin curved margin, the semilunar fold of Douglas (liiiea seviicircularis) (Fig. 323), the concavity of which looks downward toward the pubes; the aponeuroses of all three muscles pass in front of the Rectus without any separation. A very thin aponeurotic layer does pass behind the lower one-fourth of the muscle, but it is trivial as compared with the thickness of the layer behind the upper three-fourths of the muscle. This sudden thinning causes the semilunar fold of Douglas. The extremities of the fold of Douglas descend as pillars to the os pubis. The inner pillar is attached to the symphysis pubis; the outer pillar passes downward as a distinct band on the inner side of the internal abdominal ring to join with the outer fibres of the con- joined tendon, and assist in forming the ligament of Hesselbach (Fig. 320). There its fibres divide into two sets, internal and external; the internal fibres are attached to the ascending ramus of the os pubis; the external fibres pass to the psoas fascia, to the deep surface of Poupart's ligament, and to the tendon of the Transversalis on the outer side of the ring. The Rectus muscle, in the situ- ation where its sheath is deficient, is separated from the peritoneum by the trans- versalis fascia. Since the tendon of the Internal oblique and the Transversalis only reach as high as the costal margin, it follows that above this level the sheath of the Rectus is also deficient behind, the muscle resting directly on the cartilages of the ribs, being covered merely by the aponeurotic tendon of the External oblique. The convex outer border of the Rectus muscle corresponds to the linea .semilunaris. The Pyramidalis (m. pyramidalis) is a small muscle, triangular in shape, placed at the lower part of the abdomen, in front of the Rectus, and is contained in the same sheath. It arises by tendinous fibres from the front of the os pubis and the anterior pubic ligament; the fleshy portion of the muscle passes upward, diminishing in size as it ascends, and terminates by a pointed extremity, which is inserted into the linea alba, midway between the umbilicus and the os pubis. This muscle is sometimes found wanting on one or both sides; the lower end of the Rectus then becomes pi-oportionately increased in size. Occasionally it has been found double on one side, or the muscles of the two sides are of unequal size. Its length varies slightly. Besides the Rectus and Pyramidalis muscles, the sheath of the Rectus contains the superior and deep epigastric arteries, the terminations of the lumbar arteries and of the lower intercostal arteries and nerves. Nerves. — The abdominal muscles are supplied by the lower intercostal nerves. The Trans- versalis and Internal oblique also receive filaments from the hypogastric branch of the ilio- hypogastric and sometimes from the ilioinguinal. The Cremaster is supplied by the genital branch of the genitofemoral. The Pyramidalis is supplied by the twelfth thoracic nerve. The linea alba (Figs. 324 and 325) is a tendinous raphe seen along the middle line of the abdomen, extending from the ensiform cartilage to the superior pubic ligament, to which it is attached. It is placed between the inner borders of the Recti muscles, and is formed by the blending of the aponeuroses of the Obliqui and Transversales muscles. It is narrow below, corresponding to the narrow interval existing betvi'een the Recti, but broader above, as these muscles diverge from one another in their ascent ; it becomes of considerable breadth when there is great distention of the abdomen from pregnancy or from ascites. It presents numerous aper- tures for the passage of vessels and nerves; the largest of these is the umbilicus (Fig. 327). The umbilicus is a fibrous ring formed by the fibres of the aponeurosis of the linea alba', in the fetus it transmits the umbilical vein, the two hypogastric arteries, the allantoic duct, and the vitello-intestinal duct; but in the adult the aperture is filled with scar tissue and is obliterated; the resulting cicatrix is stronger than the neighboring parts; hence umbilical hernia occurs in the adult near the umbilicus, while in the fetus it occurs at the umbilicus. The remains of the fetal structures are cord-like in character; and they diverge from the umbilicus within the abdomen. 436 THE MUSCLES AND FASCIA UMBILICUS YPOGASTRIC — URACHUS Fig. 327. — The umbilicus of the fetus seen from within the abdomen. (Poirier and Charpy.) The remains of the umbilical vein constitute the round ligament of the liver, and this cord passes upward (Fig. 327). The remains of the hypogastric arteries pass dowiiward (Fig. 327). The remains of the allantois become the lu-achus, which passes to the summit of the bladder (Fig. 327). The depression of the umbilicus is created by the virachus. The lineae semilunares (Figs 317 and 323) are two curved tendinous lines placed one on each side of the linea alba. Each corresponds with the outer border of the Rectus muscle, and each extends from the cartilage of the ninth rib to the pubic spine, and is formed by the aponeurosis of the Internal oblique at its point of division to enclose the Rectus, where it is reinforced in front by the External obli(|ue and behind by the Transversalis. Actions. — The abdominal muscles perform a three- fold action: When the pelvis and thorax are fixed, they compress the abdominal viscera, by constricting the cavity of the abdomen, in which action they are materially assisted by the descent of the Diaphragm. By these means assist- ance is given in expelling the fetus from the uterus, the feces from the rectum, the urine from the bladder, and the contents of the stomach in vomiting. If the pelvis and vertebral column be fixed, these muscles compress the lower part of the thorax, mate- rially assisting expiration. If the pelvis alone is fixed, the thorax is bent directly forward when the muscles of both sides act, or to either side when those of the two sides act alternately, rotation of the trunk at the same time taking place to the opposite side. If the thorax be fixed, these muscles, acting together, draw the pelvis upward, as in climbing, or, acting singly, they draw the pelvis upward, and bend the vertebral column to one side or the other. The Recti muscles, acting from below, depress the thorax, and consequently fiex the vertebral column ; when acting from above, they fiex the pelvis upon the vertebral column. The Pyramidales are tensors of the linea alba. The fascia transversalis {fascia transversalis) is a thin aponeurotic membrane which lies betM^een the deep surface of the Transversalis muscle and the extra- peritoneal fat. It forms part of the general layer of fascia which lines the interior of the abdominal and pelvic cavities, and is directly continuous with the iliac and pelvic fasciae. In the inguinal region the transversalis fascia is thick and dense in structure, and joined by fibres from the aponeurosis of the Transversalis muscle, but it becomes thin and cellular as it ascends to the Diaphragm, and blends with the fascia covering this muscle. In front, it unites across the middle line with the fascia on the opposite side of the body, and behind it becomes lost in the fat which covers the posterior surfaces of the kidneys. Beloiv, it has the following attachments: Posteriorly, it is connected to the whole length of the crest of the ilium, between the attachments of the Transversalis and Iliacus muscles; between the anterior superior spine of the ilium and the femoral vessels it is connected to the posterior margin of Poupart's ligament, and is there continuous with the iliac fascia. Internal to the femoral vessels it is thin and attached to the pubis and to the iliopectineal line, behind the conjoined tendon, with which it is united; and, corresponding to the point where the femoral vessels pass into the thigh, this fascia descends in front of them, and forms the anterior wall of the femoral sheath. Beneath Poupart's ligament the transversalis fascia is strengthened by a band of fibrous tissue, which is only loosely connected to Poupart's ligament, and is specialized as the deep femoral arch. The spermatic cord in the male and the round ligament in the female pass through this fascia; the point where they pass through is called the internal abdominal ring. This opening is not visible exter- nally, owing to a prolongation of the transversalis fascia on these structures, which forms the infmidibuliform fascia. OF THE ABDOMEN 437 The internal or deep abdominal ring {anmdus inguinalis abdominis) (Figs. 320 and 328) is situated in the transversalis fascia, midway between the anterior superior spine of the ilium and the symphysis pubis, and about iialf an inch above Poupart's ligament. It is of an oval form, the extremities of the oval directed upward and downward, varies in size in different subjects, and is much larger in the male than in the female. The internal ring is bounded, abocc and externally, by the arched fibres of the Trans^■e^salis; below and internally, by the deep epigastric vessels. It transmits the spermatic cord in the male and the round ligament in the female. From its circumference a thin funnel-shaped membrane, the infundibuliform or internal spermatic fascia, is continued around the cord and testis, enclosing them in a distinct covering. EMORAL AHTERY GIMBERNAT-S LIGAMENT LIGAMENT Fia. 328. — The relation of the femoral and internal abdominal rings, seen fn removal of the peritoneum. (Poirier and Charpy.) 'ithin the abdomen after Wien the sac. of an oblique inguinal hernia passes through the internal or deep abdominal ring, the infundibuliform process of the transversalis fascia, .forms one of its coverings. The Inguinal or Spermatic Canal (canalis inguinalis) (Figs. 329 and 330). — ^The inguinal or spermatic canal contains the spermatic cord (Junicuhis sperinaticus) in the male and the round ligament (ligamentum teres uteri) in the female. It is an oblique canal about an inch and a half in length, directed downward and inward, and placed parallel to and a little above Poupart's ligament. It commences above at the internal or deep abdominal ring, which is the point where the cord enters the spermatic canal, and terminates below at the external ring. It is bounded in front by the aponeurosis of the External oblique throughout its whole length, and by the Internal oblique for its outer third; behind, from within outward, by the triangular fascia (when this is present), the conjoined tendon, and the trans- versalis fascia; below, by Gimbernat's ligament, and by the union of the fascia transversalis with Poupart's ligament. The deep epigastric artery passes upward and inward behind the canal lying close to the inner side of the internal abdominal ring (Fig. 320). The interval between this artery and the outer edge of the Rectus abdominis is named Hesselbach's triangle, the base of which is formed by Pou- part's ligament. 438 THE MUSCLES AND FASCIJE ien_xe:.jh_im A,i.^ 'v" EXTERNAL OBLIQUE (reflected inward) Fig. 329. — The right inguinal canal m the m-le, second layer, vu\\( Fig 318 ) (Spalteholz unt (The first layer is shown i Fig. 330.-The right inguinal canal in the male, third layer, viewed from in front. (Spalteholz.'! OF THE ABDOMEN 439 That form of protrusion in which the intestine follows the course of the spermatic cord along the spermatic canal is called oblique inguinal hernia. Surface Form. — The only two muscles of this group which have any considerable influence on surface form are the External oblique and the Rectus muscles of the abdomen. With regard to the E.xternal oblique, the upper digitations of its origin from the ribs are well marked, and are intermingled with the serrations of the Serratus magnus; the lower digitations are not visible, as they are covered by the thick border of the Latissimus dorsi. The attachment of the External ob- lique to the crest of the ilium, in conjunction with the Internal oblique, forms a thick oblique roll, which determines the iliac furrow. Sometimes on the front of the lateral region of the abdomen an undulating outline marks the spot where the muscle fibres terminate and the aponeurosis commences. The outer border of the Rectus is defined by the lima xiniilunaris, which may be exactly located by putting the muscle into action. It corresponds wiili ;i curved line, with its convexity outward, drawn from the end of the cartilage of the ninth rib to the spine of the os pubis, so that the centre of the line, at or near the umbilicus, is three inches from the median line. The inner border of the Rectus corresponds to the linea alba, marked on the surface of the body by a groove, the abdominal furrow, which extends from the infrasternal fossa to, or to a little below, the umbilicus, where il grailuiiUy becomes lost. The surface of the Rectus presents three transverse fiurows, the tiiirac innisvcrsae. The upper two of these, one opposite or a little below the tip of the ensiform cartilage, and another, midway between this point and the umbilicus, are usually well marked; the third, opposite the umbilicus, is not so distinct. The umbilicus, situated in the linea alba, varies very much in position as regards its level. It is always situated above a zone drawn around the body opposite the highest point of the crest of the ilium, generally being from three-quarters of an inch to an inch above this line. It usually corresponds, therefore, to the articular disk between the third and fourth lumbar vertebrae. 2. The Posterior Muscles of the Abdomen. Psoas magnus. Iliacus. Psoas parvus. Quadratus lumborum. The Psoas magnus, the Psoas parvus, and the Iliacus muscles, with the fascia covering them, will be described with the Muscles of the Lower Extremity. The Fascia Covering the Quadratus Lumborum (Fig. 325). — ^This is the most anterior of the three layers of the lumbar fascia. It is a thin layer of fascia, which, passing over the anterior surface of the Quadratus lumborum, is attached, inter- nally, to the bases of the transverse processes of the lumbar vertebrse; below, to the iliolumbar ligament; and above, to the apex and lower border of the last rib. The portion of this fascia which extends from the transverse process of the first lumbar vertebra to the apex and lower border of the last rib constitutes the ligamentum arcuatum externum of the Diaphragm. The Quadratus lumborum (w. quadratus hnnhormn) (Fig. 311) is situated in the lumbar region. It is irregularly quadrilateral in shape, and broader below than above. It arises by aponeurotic fibres from the iliolumbar ligament and the adjacent portion of the crest of the ilium for about two inches, and is inserted into the lower border of the last rib for about half its length, and by four small tendons, into the apices of the transverse processes of the four upper lumbar vertebrae. Occasionally a second portion of this muscle is found situ- ated in front of the preceding. This arises from the upper borders of the trans- verse processes of three or four of the lower lumbar vertebrae, and is inserted into the lower margin of the last rib. The Quadratus lumborum is contained in a sheath formed by the anterior and middle lamellte of the lumbar fasciae. Relations. — Its deep surface (or rather the fascia which covers its anterior surface) is in relation with the colon, the kidney, the Psoas muscle, and the Diaphragm. Between the fascia and the muscle are the last thoracic, iliohypogastric, and ilioinguinal nerves. Its superficial surface is in relation with the middle lamella of the lumbar fascia, which separates it from the 440 THE MUSCLES AND FASCIA Erector spinae. The Quadratus luinborum extends, however, beyond the outer border of the Erector spinae. Nerve-supply. — The anterior branches of the last thoracic and the first lumbar nerves,- sometimes also a branch from the second lumbar nerve. Actions. — The Quadratus lumborum draws down the last rib. It acts as a muscle of inspi- ration by helping to fix the origin of the Diaphragm. If the thorax and vertebral column are fixed, it may act upon the pelvis, raising it toward its own side when only one muscle is put in action; and when both muscles act together, either from below or above, they flex the trunk. IV. MUSCLES AND FASCI.® OF THE PELVIC OUTLET. The muscles and fasciae of the pelvic outlet are those structures which form the floor of the pelvis. Perineum is a term used to designate that segment of the structure lying dorsal to the pubic arch and subpubic ligament and ventral to a line drawn transversely, in front of the anus, between the anterior part of the tuberosity of the ischium of each side. The ischiorectal space is the name given to the segment dorsal to the line above mentioned and ventral to the tip of the coccyx. This space is bounded laterally by the Gluteus maximus muscle. Fig. 331. — The perineum. The integliment and superficial layer of superficial fascia reflected. The fascia of the pelvic outlet is most easily understood if it is considered in the order of its dissection. Considered thus, it resolves itself into three strata — the superficial fascia, the triangular ligament, and the pelvic fascia. The su'per- ficial fascia is made up, as in other regions of the body, of a superficial and a deep layer. The fascia over the ischiorectal region is arranged in fatty layers, which fill the ischiorectal fossa on each side of the rectum and anus. In the region of the perineum the fascia requires fuller consideration; here it is definitely arranged into two layers — superficial and deep. The superficial layer is thick, loose, areolar in texture, and, except toward the scrotum, contains in its meshes OF THE PELVIC OUTLET 441 some adipose tissue, the amount of which varies in different subjects. In front this layer is continuous with the dartos of the scrotum, in the mid-hne of which it dips deeply to form the scrotal septum. In the female this structure enters SUPERFICIAL LAYER OF TRIANGULAR \ LIGAMENT TRANSVERSUS SUPERFICIALIS ANOCOCCYGEAL LIGAMENT Fig. 332. — The muscles of the male perineum, viewed from below. (Spalteholz.) into the formation of the mons veneris and the labia majora. The superficial layer is continuous on either side with the fatty fascia on the inner side of the thighs. The deep layer of the superficial fascia, or the fascia of CoUes (Fig. 331), is thin, aponeurotic in structure, and of considerable strength. It serves to bind 442 THE MUSCLES AND FASCIA down the muscle of the root of the penis. It is continuous with the dartos of the scrotum, with the fascia of the penis, and with Scarpa's fascia on the anterior surface of the abdomen; on either side it is firmly attached to the outer lip of the ischiopubic ramus. Posteriorly (dorsally) the deep layer curves around the superficial transverse perineal muscle to blend with the base of the triangular ligament. The deep (cephalic) surface of this fascia covers the superficial mus- cles and the superficial bloodvessels and nerves of the perineum (Fig. 333). From its deep surface a septum which is incomplete in front is given off and divides the adjacent space in two. The Central Tendinous Point of the Perineum. — This is a fibrous point in the middle line of the pelvic outlet, between the urethra and the rectum, and about half an inch in front of the anus. At this point four muscles converge and are attached — viz., the External sphincter ani, the Accelerator urinae, and the two Superficial transverse perineal ; so that by the contraction of these muscles, which extend in opposite directions, it serves as a fixed point of support (Fig. 333). Transversiis perine superjiciahs Central tendinous point of perineum. Superficial perineal artery. Superficial perineal nerve. Internal pudic nerve. Internal pudic artery. Fig. 333, — The superficial muscles and vessels ot the perineum. The Muscles of the Perineum in the Male (Figs. 332, 333). Superficial transverse perineal. Accelerator urinae. Erector penis. Compressor urethrae. The Superficial transverse perineal muscle (to. transversus perinei superficialis) is a narrow muscular slip, which passes more or less transversely across the pelvic outlet. It arises by a small tendon from the inner and fore part of the tuberosity of the ischium, and, passing inward, is inserted into the central tendinous point of the perineum, joining in this situation with the muscle of the opposite side, the External sphincter ani behind, and the Accelerator urinae in front. The base of the triangular ligament lies under cover of this muscle. Nerve-supply. — The perineal branch of the internal pudic. Actions. — By their contraction they serve to fix the central tendinous point of the perineum. OF THE PERINEUM IN THE 31 ALE 443 The Accelerator urinae (m. bulbocavernosus) is placed in the middle line of the perineum, immediately in front of the anus. It consists of two symmetrical Superficial layer of deep perineal fascia removed showing __ COMPRESSOR URETHHAE _Jniernal piidic artery. Artery of the bidb. 'Cowper^s gland. Fig. 334.— Triangular ligament or deep perineal fascia. On the left side the anterior layer has been removed. Artery of corpus cavet nosum Dorsal artery of J)ei^)^ Artery of bulb. Internal pudic artery. Cowper's gland Fig. 335.— a view of the position of the viscera at the outlet of the pelvis. halves, united along the median line by a tendinous raphe. It arises from the central tendon of the perineum, and from the median raphe in front. From this 444 THE MUSCLES AND FASCIA point its fibres diverge symmetrically; the most posterior form a thin layer, which is lost on the superficial surface of the triangular ligament; the middle fibres encircle the bulb and adjacent parts of the corpus spongiosum, and join with the fibres of the opposite side, on the upper part of the corpus spongiosum, in a strong aponeurosis. The anterior fibres, the longest and most distinct, spread out over the sides of the corpus cavernosum, and are inserted partly into that body, anterior to the Erector penis (occasionally extending to the os pubis), and partly terminate in a tendinous expansion, which covers the dorsal vessels of the penis. The latter fibres are best seen by dividing the muscle longitudinally, and dissect- ing it outward from the surface of the urethra. Many fibres of the External sphincter ani and of the Superficial transverse perineal muscles pass into this muscle. This muscle is sometimes so developed that it may be arranged under four distinct layers. In such subjects the posterior and greatest part of the muscle is composed of two layers. The deeper invests the bulb of the corpus spongiosum in a cap-like manner. It is called the Com- pressor hemisphaerium bulbi. The superficial portion, called the Compressor bulbi, arises in the central tendon of the perineum, where it blends with the Superficial transversus perinei and the External sphincter ani muscles, and from the greater portion of the median tendinous raphe. The muscle spreads out to cover the bulb and adjacent portion of the corpus spongiosum, and meets its fellow of the opposite side in the strong aponeurosis on the upper part of the corpus spongiosum. The hindmost fibers are attached to the inferior surface of the subjacent triangular ligament. The Constrictor radicis penis consists of the most anterior fibers of the Accelerator urinae. They take origin from the portion of the median raphe not occupied by the Compressor bulbi, and spread outAvard. forward, and upward over the Corpus cavernosum, anterior to the insertion of the Erector penis, and are inserted partly into the Corpus cavernosum; other fibers terminate in a tendinous expansion which encircle the root of the penis, and, therefore, cover the dorsal vessels of this organ. The Ischiobulbosus lies superficial to the Compressor bulbi; it arises from the tuberosity of the ischium and passes upward and forward to be inserted into that part of the median raphe which has to do with the bulb. Action. — This muscle serves to empty the canal of the urethi-a, after the bladder has expelled its contents; during the greater part of the act of micturition its fibres are relaxed, and it only comes into action at the end of the process. The middle fibres are supposed, by Krause, to assist in the erection of the corpus spongiosum, by compressing the erectile tissue of the bulb. The anterior fibres, on each side, according to Tyrrel, also contribute to the erection of the penis, as they are inserted into, and are continuous with, the fascia of the penis, and thus com- press the dorsal vein during the contraction of the muscle. The Erector penis {m. ischiocavernosus) covers part of the crus penis. It is an elongated muscle, broader in the middle than at either extremity, and situated on either side of the lateral boundary of the perineum. It arises by tendinous and fleshy fibres from the inner surface of the tuberosity of the ischium and the great sacro-sciatic ligament behind the crus penis, and from the adjacent portion of -the ramus of the ischium and pubis. From these points fleshy fibres succeed, which end in an aponeurosis which is inserted into the sides and under surface of the crus penis. Occasionally some of the fibres of this muscle that arise from the pubic ramus pass to the dorsum of the penis. To these fibres is given the name Pubo- cavernosus or Levator penis. Nerve-supply. — ^The perineal branch of the internal pudic. Actions. — This muscle compresses the crus penis and retards the return of the blood through the veins, and thus serves to maintain the organ erect. Between the muscles just examined a triangular space exists, bounded internally by the Accelerator urinae, externally by the Erector penis, and behind by the Transversus perinei superficialis. The floor of this space is formed by the triangular ligament of the perineum (deep perineal fascia), and running in it from behind forward (toward the pubis) are the superficial perineal vessels and nerves, the long pudendal nerve, and the transverse perineal artery, which courses along the posterior boundary of the space on the Superficial transverse perineal muscle. OF THE PERINEUM IN THE FEMALE 445 The Muscles of the Perineum in the Female. Superficial transverse perineal. Sphincter vaginae. Erector clitoridis. Compressor urethrae. The Superficial transverse perineal {m. transversus perinei superficialis) in the female is a narrow slip which passes more or less transversely across the back part of the perineal space. It arises by a small tendon from the inner and fore part of the tuberosity of the ischium, and, passing inward, is inserted into the central point of the perineum, joining in this situation with the muscle of the opposite side, the External sphincter ani behind, and the Sphincter vaginae in fi'ont. Sn^penso}^/ Ugainent of cliiorh Glans clitoris Xexternal sphincter ani muscle MUSCLE Os coccyx Fig. 336.— The female perineum after removal of the skin and superficial fascia. (BardeleDen.) Nerve-supply.— The perineal branch of the internal pudic. Actions.— By their contraction these muscles serve to fix the central tendinous point of the perineum. The Sphincter vaginae (m. hulhocavernosus) surrounds the orifice of the vagina; it is homologous v ith the Accelerator urinae in the male. It arises posteriorly from the central tendiuous point of the perineum, where it blends with the External sphincter ani. Its fibres pass forward on each side of the vagina, where it covers 446 THE MUSCLES AND FASCIA the A-aginal bulb, to be inserted into the corpora cavernosa of the clitoris; a fas- ciculus crosses over the body of the organ and compresses the dorsal vein. Nerve-supply. — The perineal branch of the internal pudic. Actions. — It diminishes the orifice of the vagina. The anterior fibres contribute to the erection of the clitoris, as they are inserted into and are continuous with the fascia of the clitoris and compress the dorsal vein during the contraction of the muscle. The Erector clitoridis (m. ischiocavernosus) resembles the Erector penis in the male, but is smaller. It covers the unattached part of the crus clitoridis. It is an elongated muscle, broader at the middle than at either extremity, and situated on either side of the lateral boundary of the perineum. It arises by tendinous and fleshy fibres from the inner surface of the tuberosity of the ischium, behind the crus clitoridis from the surface of the crus, and from the adjacent portion of the ramus of the ischium. From these points fleshy fibres succeed, ending in an aponeurosis, which is inserted into the sides and under surface of the crus clitoridis. Nerve-supply. — The perineal branch of the internal pudic. Actions. — It compresses the crus clitoris and retards the return of blood through the veins, and thus serves to maintain the organ erect. The Triangular Ligament in the Male and in the Female. The triangular ligament or the deep perineal fascia (diaphragma urogenitale) (Figs. 336, 337, 338) is stretched almost horizontally across the pubic arch, so as to close in the front part of the outlet of the pelvis. It consists of two dense membranous laminae, which are united along their dorsal borders, but are sep- arated ventrally by intervening structures. The superficial layer {fascia diaphrag- matis urogenitalis inferior) is triangular in shape and about an inch and a half in depth. Its apex is directed forward, and is separated from the subpubic liga- ment by an oval opening for the transmission of the dorsal vein of the penis. A strengthening band, the transverse pelvic ligament {ligavientum transversum pelvis), passes from one pubic bone to the other below the vein. The lateral mar- gins of the inferior layer of the triangular ligament are attached on each side to the rami of the ischium and os pubis, above the crura penis. The base is directed toward the rectum, and connected to the central tendinous point of the perineum. It is continuous with the deep layer of the superficial fascia behind the Superficial transverse perineal muscles (Fig. 337), and with a thin fascia which covers the cutaneous surface of the Levator ani muscle, the anal or ischiorectal fascia (Fig. 341). This layer of the triangular ligament is perforated, about an inch below the symphysis pubis, by the urethra, the aperture for which is circular in form; by the arteries to the bulb and by the ducts of Cowper's glands close to the urethral aperture ; by the arteries to the corpora cavernosa — one on each side, close to the pubic arch and about half-way along the attached margin of the ligament; and by the dorsal arteries and nerves of the penis near the apex of the ligament. Its base is also perforated by the superficial perineal vessels and nerves, while between its apex and the subpubic ligament passes the dorsal vein of the penis. When this superficial layer of the triangular ligament is detached, the follow- ing structures will be seen between it and the deeper layer: The membranous portion of the urethra and the Compressor urethrae muscle; Cowper's glands and their ducts; the pudic vessels and dorsal nerve of the penis; the artery and nerve of the bulb, and a plexus of veins (Fig. 334). The triangular ligament in the female (Fig. 336) is not so strong as in the male. It is divided in the middle line by the aperture of the vagina, with the external coat of which it becomes blended; between the vaginal orifice and the pubis it is THE TRIANGULAR LIGAMENT IN MALE AND IN FEMALE 447 EXTE SPHINC- TER ANI DEEP LAYEB OF SUPERFICIAL FASCU OF PERINEUM (CoHes' fascia) Fig. 337. — The triangular ligament of the perineu DORSAL VEIN OF PENIS' Y DORSAL NERVE I DORSAL ARTERY_ / OF PENIS ARTERY TO Fig. 338.— The superficial layer of the triangular ligament. The Compressor urelhrae muscle lies behind the superficial layer of the triangular ligament and is shown la the figure for convenience. (Poirier and Charpy.) 448 THE MUSCLES AND FASCIJE perforated by the urethra. Its base is continuous, as in the male, with the deep layer of the superficial fascia surrounding the Transversus perinei muscles. Like the triangular ligament in the male, it consists of two layers, between which are to be found the following structures: The dorsal vein and nerves of the clitoris, a portion of the urethra and the Compressor urethrae muscle, the glands of Bartholin and their ducts, the pudic vessels, the arteries of the vestibular bulbs, and a plexus of veins. The deep layer of the triangular ligament is a part of the pelvic fascia, and is described on page 449. The Compressor or Constrictor urethrae {m. sphincter urethrae membranacea) in the male surrounds the whole length of the membranous portion of the urethra, and is contained between the two layers of the triangular ligament. It arises, by apon- eurotic fibres, from the junction of the rami of the os pubis and ischium, to the extent of half or three-quarters of an inch — the point where the crura penis join the transverse ligament of the perineum and the layers of the triangular liga- ment; each segment of the muscle passes inward, and divides into two fasciculi, which surround the membranous urethra and unite, at the upper and lower surfaces of this tube, with the muscle of the opposite side by means of a tendinous raphe. This muscle is frequently discovered in two portions, an anterior and a posterior, separated by a distinct interval. In such cases the posterior fibres are called the transversus perinei profundus, and the anterior fibres are called the sphincter urethrae membranaceae. The Compressor urethrae in the female arises as in the male; passing mesally, likewise, it divides into two fasciculi; these latter, however, have not the same intimate functional relationship to the urethra as has the muscle of the male. One fasciculus passes ventrad of the urethra to blend with its opposite fellow; the posterior fascicle inserts itself into the lateral vaginal wall. Nerve-supply. — The perineal branch of the internal pudic. Actions. — The muscles of both sides act together as a sphincter, compressing the mem- branous portion of the urethra. During the transmission of fluid they, like the Acceleratores urinae, are relaxed, and come into action only at the end of the process, to eject the last drops of the fluid. The Pelvic Fascia. The pelvic fascia binds strongly together the pelvic structures, supports the bloodvessels, nerves, and lymphatics, and strengthens the floor of the cavity. Above, it is loosely connected to the back part of the iliopectineal line, and is continuous here with the iliac fascia. Posteriorly, over the sacrum, it is very thin and lies ventrad to the Pyriformis muscle and to the sacral plexus of nerves. This part is often called the fascia of the Pyriformis, and extends outward along the muscle into the gluteal region. At its sacral attachments around the margins of the sacral foramina it comes into intimate association with and en- sheathes the nerves as they emerge from these foramina. Anterior to its ilio- pectineal attachment the pelvic fascia sinks in its attachment below the brim of the pelvis. It arches below the obturator vessels and nerves, completing the obturator canal, and at the front of the pelvis the line of attachment is depresesd on the posterior surface of the os pubis, so that at the symphysis it lies just above the inferior border of this bone. From this line of attachment the posterior part is prolonged outward on the Obturator internus into the gluteal region. The middle portion descends on the visceral surface of the Obturator internus to be- come attached to the falciform process of the great sacrosciatic ligament. Be- cause of this relation with the Obturator internus this part is called the Obturator fascia (Fig. 340). The part attached to the body of the pubis descends to be attached to the ischiopubie ramus, and here becomes blended with the base of the triangular ligament (Fig. .341). From the ischiopubie ramus it is continued THE PELVIC FASCIA 449 onward behind the Compressor urethrae muscle across the pubic arch, to be con- tinuous with the fascia of the opposite side. Here it takes a special name, the ANTERIOR- SUPERIOR SPINES EATER CROSCIftTIC iAMENT FASCIA OF LEVATOR ANI MUSCLE Fig. 339. — Pelvic fascia (semidiagrammatic). deep layer of the triangular ligament {fascia diaphragmatis urogenitalis superior) (Figs. 337 and 341). This part of the fascia is perforated by the urethra; a por- Jnternal pitdic vessels and nerve. Fig. 340. — A transverse section of the pelvis, sliowing tiie pelvic fascia from beliind. tion of it turns backward around the anterior extremity of the Levator ani mus- cle to join the visceral layer next to be considered. At the level of a line extending from the back part of the syniphysis pubis to the spine of the ischium is a thick, whitish band termed the white line (arms 29 450 THE MUSCLES AND FASCIA tendinexis) (Fig. 339). Above this line the fascia hes in contact with the perito- neum and belongs to the pelvic cavity. Below this line the obturator fascia has to do with the ischiorectal space. The pudic vessels and nerves cross this area enclosed in a special sheath (Alcock's canal). At the white line the obturator fascia gives off a special layer to the pelvic viscera, Rectovesical fascia (fascia endopelmna) ; where these two layers diverge partly arises the Levator ani (Figs. 339 and 340). The Rectovesical fascia lies superior (cephalad) to the Levator ani (Fig. 340). Traced forward it is seen to be attached to the posterior surface of the body of the pubis three-fourths of an inch higher than the pelvic fascia. Traced internally it approaches the bladder and rectum; here it splits into several layers. The upper layer invests the bladder and constitutes the lateral trite lic/a- vient of the bladder; another prolongation invests the seminal vesicle, passes be- tween the bladder and rectum, being continuous with the same fascia on the Fig. 341— Side of the male subject, showing the pelvic and perineal fasi opposite side; a third in^•estment is also prolonged downward on the rectum within the insertion of the Levator ani muscle. In front of the bladder the fascia closely ensheathes the prostate gland and prostate plexus of veins, forming the capsule of the prostate. That portion of the fascia which is attached to the body of the pubis passes backward as a narrow cord-like band to the upper part of the prostate and upper part of the neck of the bladder; this is the anterior true ligament of the bladder, or puboprostatic ligament (Figs. 340, 341). The Anal fascia is a thin, aponeurotic fascia which clothes the under surface of the Levator ani muscle. It arises from the obturator fascia just below the origin of the Levator ani, and extends inward and downward and separates this muscle from the ischiorectal fossa. (See page 454.) The Levator ani (Fig. 343) is a broad, thin muscle, situated on the side of the pelvis. It is attached to the inner surface of the side of the true pelvis, and descends to unite with its fellow of the opposite side. Together these structures THFj pel VIC FASCIA 451 form the greater part of the floor of the pelvic cavity. They support the viscera in this cavity and surround the various structures which pass through it. This muscle arises, in front, from the posterior surface of the body of the pubis on the outer side of the symphysis; behind, from the inner surface of the spine of the ischium; and between these two points, from the obturator fascia. Posteriorly, this fascial origin corresponds, more or less closely, with the white line (page 449), GLANDS Fig. 342. — The right Levator ani in the male, viewed from the left. (Spalteholz.) • but in front the muscle arises from the fascia at a varying distance above the white line, in some cases reaching nearly as high as the canal for the obturator vessels and nerve. The fibres pass downward to the middle line of the floor of the pelvis; the most posterior are inserted into the sides of the last two segments of the coccyx; those placed more anteriorly unite with the muscle of the opposite side, in a median fibrous raph^ (anococcygeal raphe), which extends between the coccyx and the margin of the anus. The middle fibres are inserted into the side of the rectum. 452 THE MUSCLES AND FASCI.^ blending with the fibres of the Sphincter muscles; lastly, the anterior fibres descend upon the side of the prostate gland to unite beneath it with the muscle of the opposite side, joining with the fibres of the External sphincter and Trans- versus perinei muscles at the central tendinous point of the perineum. The anterior portion is occasionally separated from the rest of the muscle by connective tissue. From this circumstance, as well as from its peculiar relation with the prostate gland, descending by its side, and surrounding it as in a sling, it has been described by Santorini and others as a distinct muscle, under the name of Levator prostatae. In the female the anterior fibres of the Levator ani descend upon the side of the vagina. I \ ' ^ l.t.VHIUH MNI r \ - ™,„„ .» '//RC- TOCt-tYGEUSlM ILIOCLl. i HU i Tjr fjL ^ ill I ■' ^ ,lcvatob\ /- ^cii^is- FiG. 343.— The levator a Spalteholz.) Relations. — By its deep, upper, or pehic surface the Levator ani is in relation with the rectovesical fascia, which separates it from the bladder, prostate, rectum, and peritoneum. By- its superficial, lower, or perineal surface it forms the inner boundary of the ischiorectal fossa, and is covered by a thin layer of fascia, the anal fascia, given off from the obturator fascia. Its posterior border is free and separated from the Coccygeus mviscle by a cellular interspace. Its anterior border is separated from the muscle of the opposite side by a triangular space, through which the uretlora, and in the female the vagina, pass from the pelvis. The Levator ani may be divided into iliococcygeal and pubococcygeal parts. (Fig. 343.) The Iliococcygeus arises from the ischial spine and from the posterior part of the pelvic fascia, and is attached to the coccyx and anococcygeal raph^; it is usually thin, and may fail entirely, or be largely replaced by fibrous tissue. An accessory slip at its posterior part is sometimes named the Iliosacralis. The Pubococcygeus arises from the back of the pubis and from the anterior part of the pelvic fascia, and " is directed backward almost horizontally along the side of the anal canal toward the coccyx and sacrum, to which it finds attachment. Between the termination of the vertebral column and the anus the two pubococcygeal muscles come together and form a thick, fibromuscular layer lying on the raphe formed by the iliococcygei " (Thompson), The greater part of this muscle is inserted into the coccyx and into the last one or two pieces of the sacrum. This insertion into the vertebral column is, however, not admitted by all observers. The fibres which form a sling for the rectum are named the Puborecialis or Sphincter recti. THE PEL VIC FASCIA 453 They arise from the lower part of the symphysis pubis, and from the upper layer of the triangular ligament. They meet with the corresponding fibres of the opposite side around the lower part of the rectum, and form for it a strong sling. Nerve-supply. — The Levator ani is supplied by a branch from the fourth sacral nerve and by a branch which is sometimes derived from the perineal, sometimes from the inferior hemor- rhoidal division of the pudic nerve. The Coccygeus (?«. coccygeiis) (Fig. 343) is situated behind and parallel with the preceding. It is a triangular plane of muscular and tendinous fibres, arising by its apex from the spine of the ischium and lesser sacrosciatic ligament, and inserted by its base into the margin of the coccyx and into the side of the lower piece of the sacrum. It assists the Levator ani and Pyriformis in closing in the back part of the outlet of the pelvis. Nerve-supply. — The Coccygeus is supplied by a branch from the fourth and fifth sacral nerves. Actions. — The Levatores ani constrict the lower end of the rectum and vagina. They elevate and invert the lower end of the rectum after it has been protruded and everted during the expul- sion of the feces. The Coccygei muscles pull forward and support the coccyx, after it has been pressed backward during defecation or parturition. The Levatores ani and Coccygei together form a muscular diaphragm which supports the pelvic viscera. Muscles cf the Ischiorectal Region. Corrugator cutis ani. Internal sphincter ani. External sphincter ani. Levator ani (described on page 450). Coccygeus (described above). The Corrugator Cutis Ani. — Around the anus is a thin stratum of involuntary muscle fibre which radiates from the orifice. hiteriiaUy, the fibres fade into the submucous tissue, while externally they blend with the true skin. By its con- traction it raises the skin into ridges around the margin of the anus. The External sphincter ani (?/;. sphincter ani externus) (Figs. 332, 333, 3.36, and 342) is a thin, flat plane of muscle fibre, elliptical in shape and intimately adher- ent to the integument surrounding the margin of the anus. It measures about three or four inches in length from its anterior to its posterior extremity, being about an inch in breadth opposite the anus. It consists of two strata, super- ficial and deep. The superficial, constituting the main portion of the muscle, arises from a narrow tendinous band, the anococcygeal raphe, which stretches from the tip of the coccyx to the posterior margin of the anus; it forms two flattened planes of muscle tissue, which encircle the anus and meet in front of be inserted into the central tendinous point of the perineum, joining with the Transversus perinei, the Levator ani, and the Accelerator urinae. The deeper portion forms a complete sphincter to the anal canal. Its fibres surround the canal, closely applied to the Internal sphincter, and in front blend with the other muscles at the central point of the perineum. In a considerable proportion of cases the fibres decussate in front of the anus, and are continuous with the Transversus perinei. Posteriorly, they are not attached to the coccyx, the fibres of opposite sides being continuous behind the anal canal. The upper edge of the muscle is ill-defined, since fibres are given off from it to join the Levator ani. Nerve-supply. — A branch from the fourth sacral and twigs from the inferior hemorrhoidal branch of the internal pudic supply the muscle. Actions. — The action of this muscle is peculiar: (1) It is, like other muscles, always in a state of tonic contraction, and having no antagonistic muscle it keeps the anal canal and orifice closed. (2) It can be put into a condition of greater contraction under the influence of the will, so as more firmlv to occlude the anal aperture in expiratory efforts, unconnected with defecation. (3) Taking its fixed point at the coccyx, it helps to 6x the central point of the perineum, so that the Accelerator urinae may act from this fixed point. 454 THE 3IUSCLES AND FASCIJE The Internal sphincter ani (m. sphincter ani internus) is a ring of muscle which surrounds the anal canal for about an inch ; its inferior border being con- tiguous with, but quite separate from, the External sphincter. This muscle is about a sixth of an inch in thickness, and is formed by an aggregation of the involuntary circular fibres of the intestine. It surrounds the canal for about an inch, its lower border being about a quarter of an inch from the external orifice. It is paler in color and less coarse in texture than the External sphincter. Actions. — Its action is entirely involuntary. It helps the External sphincter to occlude the anal aperture. The Ischiorectal fossa {fossa ischiorectalis) (Figs. 332 and 342) is situated between the end of the rectum and the ischial tuberosity. It is triangular in shape; its base, directed to the surface of the body, is formed by the integument of the ischiorectal region; its apex, directed upward, corresponds to the point of division of the obturator fascia and the thin membrane given off from it, which covers the outer surface of the Levator ani (anal fascia). Its dimensions are about an inch in breadth at the base and about two inches in depth, being deeper behind than in front. It is bounded, internally, by the Sphincter ani, Levator ani, and the Coccygeus muscles; externally, by the tuberosity of the ischium and the obturator fascia, which covers the inner surface of the Obturator internus muscle; in front, it is limited by the line of junction of the deep layer of the super- ficial fascia with the base of the triangular ligament; and behind, by the margin of the Gluteus maximus muscle and the great sacrosciatie ligament. This space is filled with a large mass of adipose tissue, which explains the frequency with which abscesses in the neighborhood of the rectum burrow to a considerable depth. The fascia covering the inferior surface of the pelvic diaphragm is knoM'n as the anal fascia (fascia inferior diaphragrnatis pelvis). It is attached above to the obturator fascia along the line of origin of the Levator ani, while below it is contin- uous with the deep layer of the triangular ligament and with the fascia on the Inter- nal sphincter ani. The layer covering the upper surface of the pelvic diaphragm (pais diaphragmatica fasciae pelvis) follows, above, the line of origin of the Levator ani, and is therefore somewhat variable. In f7-ont it is attached to the back of the symphysis pubis about three-quarters of an inch above its lower border. It can then be traced outward across the back of the body of the pubis for a distance of about half an inch, where it joins the obturator fascia. It is attached to this fascia along a line which pursues a somewhat irregular course to the spine of the ischium. The irregularity of this line is due to the fact that the origin of the Levator ani, which in lower forms is from the pelvic brim, is in man lower down, on the obturator fascia. Tendinous fibres of origin of the muscle are therefore often found extending up toward, and in some cases reaching^ the pelvic brim, and on these the fascia is carried. MUSCLES AND FASCI.ffi OF THE UPPER EXTREMITY. The muscles of the upper extremity are divisible into groups, corresponding with the different regions of the limb. I. Of the Thoracic Region. II. Of the Shoulder and Arm. 1. Anterior Thoracic Region. 3. Acromial Region. Pectoralis major. Pectoralis minor. Deltoid. Subclavius. 2. Lateral Thoracic Region. 4. Anterior Scapular Region. Serratus magnus. Subscapularis. THE ANTERIOR THORA CIG REGION 455 5. Posterior Scapular Regie Supraspinatus. Infraspinatus. Teres minor. Teres major. 6. Anterior Humeral Region. Coracobrachialis. Biceps. Brachialis anticus. 7. Posterior Humeral Region. Triceps. Subanconeus. III. Of the Forearm. 8. Anterior Radioulnar Region. . [ Pronator teres. "o c Flexor carpi radialis. u >^ \ ralmaris longus. Flexor carpi ulnaris. Flexor sublimis digitorum. Fiexor profundus digitorum. Flexor longus pollicis. Pronator quadratus. 9:'v^ O 9. Radial Region. Brachioradialis. Extensor carpi radialis longior. Extensor carpi radialis brevior. a- cs' 10. Posterior Radioulnar Region. Extensor communis digitorum. Extensor minimi digiti. Extensor carpi ulnaris. Anconeus. Supinator [brevis]. ■ Extensor ossis metacarpi pollicis. Extensor brevis pollicis. Extensor longus pollicis. . Extensor indicis. IV. Of the Hand. 11. Radial Region. Abductor pollicis. Opponens pollicis. Flexor brevis pollicis. Adductor oblic(uus pollicis. Adductor transversus pollicis. 12. Ulnar Region. Palmaris brevis. Abductor minimi digiti. Flexor brevis minimi digiti. Opponens minimi digiti. 13. Middle Palmar Region. Lumbricales. Interossei palmares. Interossei dorsales. Dissection of Pectoral Region and Axilla (Fig. 344).— The arm being drawn away from the side nearly at right angles with the trunk and rotated outward, make a vertical incision through the integument in the median hne of the thorax, from the upper to the lower part of the sternum; a second incision along the lower border of the Pectoral muscle, from the ensiform cartilage to the inner side of the axilla; a third, from the sternum along the clavicle, as far as its centre; and a fourth, from the middle of the clavicle obliquely downward, along the interspace between the Pectoral and Deltoid muscles, as low as the fold of the axilla. The flap of integu- ment is then to be dissected ofi' in the direction indicated in the figure, but not entirely removed, as it should be replaced on completing the dissection. If a transverse incision is now made from the lower end of the sternum to the side of the thorax, as far as the posterior fold of the axilla, and the integument reflected outward, the axillary space will be more completely exposed. I. THE MUSCLES AND FASCIA OF THE THORACIC REGION. 1. The Anterior Thoracic Region. Pectoralis major [Sternalis.] Pectoralis minor. Subclavius. The superficial fascia of the thoracic region is a loose cellulofibrous layer en- closing masses of fat in its spaces. It is continuous with the superficial fascia of the neck and upper extremity above, and with that of the abdomen below. Oppo- 456 THE 3IUSCLES AND FASCIAE 3. Dissection of Shoulder and Arm. site the mamma it divides into two layers, one of which passes in front, the other behind that gland; and from both of these layers numerous septa pass into its substance, supporting its various lobes; from the anterior layer fibrous processes pass forward to the integument and nipple. These processes were called by Sir A. Cooper the suspensory ligaments, from, the support they afford to the gland in this situation. The deep thoracic fascia is a thin aponeurotic lamina, covering the surface of the oreat Pectoral muscle, and sending numerous prolongations between its fascicuH; it is attached, in the mid-line, to the front of the sternum, and above to the clavicle; externally and below it becomes continuous with the fascia over the shoulder, axilla, and thorax. It is very thin over the upper part of the muscle, thicker in the interval between the Pectoralis major and Latissimus dorsi, where it closes in the axillary space, and is known as the axillary fascia {fas- cia axillaris). It passes behind into the fascia of the Latissimus dorsi and Teres major, in front into the fascia of the Deltoid and outward into the fascia of the arm. The fascia of the Latissimus dorsi divides at the outer margin of the muscle into two layers, one of which passes in front and the other behind it; these proceed as far as the spinous processes of the thora- cic vertebrse, to which they are attached. As the axillary fascia leaves the lower edge of the Pecto- ralis major to pass across the floor of the axilla it sends a layer up- ward under cover to the muscle, the deep pectoral fascia; this lamina splits to envelop the Pectoralis minor, at the upper edge of which it becomes continuous with the costocoracoid membrane (claripec- toral fascia). The hollow of the axilla, seen when the arm is ab- ducted, is mainly produced by the traction of this fascia on the axillary floor, the axillary fascia hence it is sometimes named the suspensory ligament of the axilla. The axillary fascia is not a distinct and complete rigid floor of the axillary space. Like all Qther fascise, it follows muscular planes, and splits to encompass vessels, nerves, and muscles. In it are numerous perforations. At the lower part of the thoracic region the deep thoracic fascia is well developed, and is continuous with the fibrous sheath of the Recti abdominis. The Pectoralis major (m. pectoralis major) (Fig. 345) is a broad, thick, triangular muscle, situated at the upper and fore part of the thorax, in front of the axilla. It arises from the anterior surface of the sternal half of the clavicle; from half the breadth of the anterior surface of the sternum, as low down as the attachment of the cartilage of the sixth or seventh rib; this portion of its origin consists of aponeurotic fibres, which intersect with those of the opposite muscle ; it also arises from the cartilages of all true ribs, with the exception, frequently, of the first 3. Bend of Elbow. 4= Forearm. 5. Palm of Hand. Fig. 344. — Dissection of the upper extremity. THE ANTERIOR THORACIC REGION 457 or the seventh, or both ; and from the aponeurosis of the External oblique muscle of the abdomen. The fibres from this extensive origin converge toward its in- sertion, giving to the muscle a radiated appearance. Those fibres which arise from the clavicle pass oblicjuely outward and downward and are usually separated from the rest by a cellular interval; those from the lower part of the sternum, and the cartilages of the lower true ribs, pass upward and outward, while the middle fibres pass horizontally. They all terminate in a flat tendon, about two inches Fig. 343.— Muscles of the tho nd front of the broad, which is inserted into the outer bicipital ridge of the humerus. This tendon consists of two laminae, placed one in front of the other, and usually blended together below. The superficial, the thicker, receives the clavicular and upper half of the sternal portion of the muscle; and its fibres are inserted in the same order as that in which they arise ; that is to say, the outermost fibres of origin from the clavicle are inserted at the uppermost part of the tendon; the upper fibres 458 THE MUSCLES AND FASCIjE of origin from the sternum pass down to the lowermost part of this superficial lamina of the tendon and extend as low as the tendon of the Deltoid and join with it. The deef lamina of the tendon receives the attachment of the lower half of the sternal portion and the deeper part of the muscle from the costal cartilages. These deep fibres, and particularly those from the lower costal cartilages ascend, the higher turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted. The deep lamina reaches higher on the humerus than the superficial one, and from it an expansion is given ofl^ which covers the bicipital groove and blends with the capsule of the shoulder-joint. From the deepest fibres of this lamina at its insertion an expansion is given off which lines the bicipital groove of the humerus, while from the lower border of the tendon a third expansion passes downward to the fascia of the arm. Between the posterior surface of the tendon of the Great pectoral and the ^terior surface of the long head of the Biceps there is usually a bursa (bursa m. pectoralis majoris). IC BRANCH O^ ACIC NERVE PECTORALIS MAJOR ^. Fig. 346. — Costocoracoid membrane. Relations. — By its swperficial surface, with the integument, the superficial fascia, the Platysma, some of the branches of the descending cervical nerves, the mammary gland, and the deep fascia; by its deep surface: its thoracic portion, with the sternum, the ribs and costal cartilages, the costocoracoid membrane, the Subclavius, Pectoralis minor, Serratus magnus, and the Intercostals; its axillary portion forms the anterior wall of the axillary space, and covers the axillary vessels and nerves, the Biceps brachii and Coracobrachialis muscles. Its upper harder lies parallel with the Deltoid, from which it is separated by a slight interspace in which lie the cephalic vein and humeral branch of the acromial thoracic artery. Its lower border forms the anterior margin of the axilla, being at first separated from the Latissimus dorsi by a considerable interval ; but both muscles gradually converge toward the outer part of the space. THE ANTERIOR THORACIC REGION 459 A Stemalis muscle is occasionally found in the pectoral region; it may be confined to one side, or may be bilateral. It is sometimes represented by delicate scattered fibres overlying a normal Pectoralis major, or by a well-developed muscle associated with a defective Pectoralis major. It is often attached to the sternal end of the Sternomastoid; below, it becomes lost in the presternal fascia or in the aponeurosis of the External oblique. This variant is regarded as a displaced and rotated segmt-nt of the Pectoralis major; it is supplied by branches from the anterior tiioracic nerve. Dissection. — Detach the Pectoralis major by dividing the muscle along its attachment to the clavicle, and by making a vertical incision through its substance a little external to its line of attachment to the sternum and costal cartilages. The muscle should then be reflected outward, and its tendon carefully examined. The Pectoralis minor is now exposed, and immediately above it, in the interval between its upper border and the clavicle, a strong fascia, the costo- coracoid membrane. ^ Vr, S Fig. 347. — Muscles of the thorax and front of the arm, showing e ! of the bounda The Costocoracoid Membrane, or the Clavipectoral Fascia (fascia coraco- clavicularis) (Fig. 346), is a strong fascia, situated under cover of the clavicular portion of the Pectoralis major muscle. It occupies the interval between the Pectoralis minor and Subclavius muscle, and protects the axillary ■s'essels and nerves. Traced upward, it splits to enclose the Subclavius muscle, and its two layers are attached to the clavicle, one in front of and the other behind the muscle; the deep layer fuses with the deep cervical fascia and with the sheath of the axillary vessels. Mesially, it blends w'ith the fascia, co^'ering the first two intercostal spaces, and is attached also to the first rib internal to the origin of the Subclavius muscle. Laterally, it is very thick and dense, and is attached to the coracoid 460 THE MUSCLES AND FASCIA process. The portion extending from its attachment to the first rib to the cora- coid process is often whiter and denser than the rest; this is sometimes called the costocoracoid ligament. Below, it is thin, and at the upper border of the Pectoralis minor it splits into two layers to invest this muscle; from the lower border of the Pectoralis minor it is continued downward to join the axillary fascia, and outward to join the fascia o\'er the short head of the Biceps. The costocoracoid mem- brane is pierced by the cephalic vein, the acromiothoracic artery and vein, supe- rior thoracic artery, and anterior thoracic nerve. The Pectoralis minor {m. pectoralis minor) (Fig. 347) is a thin, flat, triangular muscle, situated at the upper part of the thorax, beneath the Pectoralis major. It arises by three tendinous digitations from the upper margin and outer surface of the third, fourth, and fifth ribs, near their cartilages, and from the aponeurosis covering the Intercostal muscles; the fibres pass upward and outward, and con- verge to form a flat tendon, which is inserted into the inner border and upper surface of the coracoid process of the scapula. Relations. — By its superficial surface, with the Pectoralis major and the thoracic branches of the acromiothoracic artery. By its deep surface, with the ribs. Intercostal muscles, Serratus magnus, the axillary space, and the axillary vessels and brachial plexus of nerves. Its upper border is separated from th^ clavicle by a narrow triangular interval, occupied by the costocoracoid membrane, behind which are the axillary vessels and nerves. The long thoracic artery runs parallel to the lower border of this muscle and the anterior thoracic nerve pierces it. The costocoracoid membrane should now be removed, and the Subclavius muscle will be exposed. The Subclavius (m. subclavius) is a small triangular muscle, placed in the interval between the clavicle and the first rib. It arises in front of the rhomboid ligament by a short, thick tendon from the first rib and its cartilage at their junction; the fleshy fibres proceed obliquely upward and outward, to be inserted into the groove on the under surface of the clavicle. An extension from the apon- eurosis of this muscle lies upon the subclavian vein. Relations. — Its deep surface is separated from the first rib by the subclavian vessels and brachial plexus of nerves. Its superficial surface is separated from the Pectoralis major by the costocoracoid membrane, which, with the clavicle, forms an osseofibrous sheath in which the musole is enclosed. If the costal attachment of the Pectoralis minor be divided across, and the muscle reflected outward, the axillary vessels and nerves are brought fully into view, and should be examined. Nerves. — The Pectoral muscles are supplied by the external and internal anterior thoracic nerves; the Pectoralis major through these nerves receives filaments from all the spinal nerves entering into the formation of the brachial plexus; the Pectoralis minor receives its fibres from the eighth cervical and first thoracic nerves tlirough the internal anterior thoracic nerve. The Subclavius is supplied by a filament derived from the fifth and sixth cervical nerves. Actions. — If the arm has been raised by the Deltoid, the Pectoralis major will, conjointly with the Latissimus dorsi and Teres major, depress it to the side of the thorax. If acting alone, it adducts and draws forward the arm, bringing it across the front of the thorax, and at the same time rotating it inward. The Pectoralis minor depresses the point of the shoulder, drawing the scapula downward and inward to the thorax, and throwing the inferior angle backward. The Subclavius depresses the shoulder, drawing the clavicle downward and forward. When the arms are fixed, all three muscles act upon the ribs, drawing them upward and expanding the thorax, and thus becoming very important agents in forced inspiration. During an attack of asthma patients always assume an attitude which fixes the shoulders, so that all these muscles may be brought into action to assist in increasing the capacity of the thorax. THE LATERAL TIIOBACIC REGION 46] 2. The Lateral Thoracic Region. Serratus magnus. The Serratus magnus (m. serratus anterior) (Fig. 347) is a thin, irregularly quadrilateral muscle, situated between the ribs and the scapula at the upper and lateral part of the thorax. It arises by fleshy digitations or slips from the outer surfaces and upper borders of the upper eight or nine ribs, and from the aponeu- roses covering the intervening intercostal muscles. Each digitation (except the first) arises from the corresponding rib; the first digitation arises from the first and second ribs and from the fascia covering the first intercostal space. From this extensive attachment the fibres pass backward, closely applied to the thoracic wall, and reach the vertebral border of the scapula, and are inserted into its ventral aspect in the following manner. The first digitation, arising from the first and second ribs, is inserted into a triangular area on the ventral aspect of the superior angle. The next two digitations (from the second and third ribs) spread out to form a thin triangular sheet, the base of which is directed backward and is inserted into nearly the whole length of the ventral aspect of the vertebral border. The lower five or six digitations converge to form a fan-shaped mass, the apex of which is inserted, by muscular and tendinous fibres, into a triangular impression on the ventral aspect of the inferior angle. The lower four slips interdigitate at their origin with the upper five slips of the External oblicjue muscle of the abdomen. Relations. — This muscle is partly covered, in front, by the Pectoral muscles; behind, by the Subscapularis. The axillary vessels and nerves lie upon its upper part, while its deep surface rests upon the ribs and intercostal muscles. Nerves. — The Serratus magnus is supplied by the posterior thoracic nerve, which is derived from the fifth, sixth, and seventh cervical nerves. Actions. — Tlie Serratus magnus, as a whole, carries the scapula forward, and at the same time raises the vertebral border of the bone. It is therefore concerned in the action of pushing. Its lower and stronger fibres move forward the lower angle and assist the Trapezius in rotating the bone around an axis through its centre, and thus assist this muscle in raising the acromion and supporting weights upon the shoulder. It also assists the Deltoid in raising the arm, inasmuch as during the action of this latter muscle it fixes the scapula and so steadies the glenoid cavity in which the head of the humerus rotates. After the Deltoid has raised the arm to a right angle with the trunk, the Serratus magnus and the Trapezius, by rotating the scapula, raise the arro into an almost vertical position. It is possible that when the shoulders are fixed the lower fibres of the Serratus magnus may assist in raising and everting the ribs; but it is not the important inspiratory muscle which it was formerly believed to be. Applied Anatomy. — ^Vhen the muscle is paralyzed, the vertebral border, and especially the lower angle of the scapula, leaves the ribs and stands out prominently on the surface, giving a peculiar "winged" appearance to the back. The patient is unable to raise the arm, and an attempt to do so is followed by a further projection of the lower angle of the scapula from the back of the thorax. Dissection. — After completing the dissection of the axilla, if the muscles of the back have been dissected, the upper extremity should be separated from the trunk. Saw through the clavicle at its centre, and then cut through the muscles which connect the scapula and arm with the trunk — viz., the Pectoralis minor in front, Serratus magnus at the side, and the Levator anguli scapulae, the Rhomboids, Trapezius, and Latissimus dorsi behind. These muscles sliould be cleaned and traced to their respective insertions. Then make an incision through the integu- ment, commencing at the outer third of the clavicle, and extending along the margin of that bone, the acromion process, and spine of the scapula; the integument should be dissected from above downward and outward, when the fascia covering the Deltoid will be exposed (Fig. 344, No. 3) II. MUSCLES AND FASCI.a: OF THE SHOULDER AND ARM. The superficial fascia of the upper extremity is a thin cellulofibrous layer, con- taining the superficial veins and lymphatics, and the cutaneous nerves. It is 462 THE MUSCLES AND FASCIA most distinct in front of the elbow, and contains very large superficial veins and nerves; in the hand it is hardly demonstrable, the integument being closely ad- herent to the deep fascia by dense fibrous bands. Small subcutaneous bursse are found in this fascia over the acromion, the olecranon, and the knuckles. The deep fascia of the upper extremity comprises the aponeurosis of the shoulder, arm, and forearm, the anterior and posterior annular ligaments of the carpus, and the palmar fascia. These will be considered in the description of the muscles of the several regions. 3. The Acromial Region. Deltoid. The deep fascia covering the Deltoid invests this muscle and sends down numer- ous prolongations between its fasciculi. In front, it is continuous with the fascia covering the great Pectoral muscle; behind, with that covering the Infraspinatus; above, it is attached to the clavicle, the acromion, and spine of the scapula; heloiv, it is continuous with the deep fascia of the arm. The Deltoid (vi. deUoideus) (Fig. 345) is a large, thick, triangular muscle, which gives the rounded outline to the shoulder, and has received its name from its resem- blance to the Greek letter J {delta) inverted. It covers the shoulder-joint in front, behind, and on its outer side. It arises from the outer third of the anterior border and upper surface of the clavicle; from the outer margin and upper surface of the acromion process, and from the lower lip of the posterior border of the spine of the scapula, as far back as the triangular surface at its mesal end. From this extensive origin the fibres converge toward their insertion, the middle passing vertically, the anterior obliquely backward, the posterior obliquely forward, they unite to form a thick tendon, which is inserted into a rough triangular promi- nence on the middle of the outer side of the shaft of the humerus. At its insertion the muscle gives off an expansion to the deep fascia of the arm. This muscle is remarkably coarse in texture, and the arrangement of its muscle fibres is some- what peculiar; the central portion of the muscle^-that is to say, the part arising from the acromion process — consists of fibres having an oblique direction, which arise in a bipenniform manner from the sides of tendinous intersections, generally four in number, which are attached above to the acromion process and pass downward parallel to one another in the substance of the muscle. The oblique muscle fibres thus formed are inserted into similar tendinous intersec- tions, generally three in number, which pass upward from the insertion of the muscle into the humerus and alternate with the descending septa. The portions of the muscle which arise from the clavicle and spine of the scapula are not arranged in this manner, but pass from their origin above, to be inserted into the margins of the inferior tendon. Relations. — By its superficial surface, the Deltoid is in relation with the integument, the superficial and deep fascije, Platysma, and supra-acromial nerves. Its deep surface is separated from the capsule of the shoulder-joint by a large sacculated synovial bursa, the subdeltoid bursa (bursa stibdeltoidea) . This bursa often communicates with the subacromial bursa (bursa subacromialis) , which is between the acromial process and the coraco-acromial ligament above and the capsule of the shoulder-joint and the Supraspinatus muscle below. The deep surface of the Deltoid covers the coracoid process, coraco-acromial ligament, Pectoralis minor, Coraco- brachialis, both heads of the Biceps, the tendon of the Pectorahs major, the insertions of the Supraspinatus, Infraspinatus, and Teres minor, the scapular and external heads of the Triceps, the circumflex vessels and nerve, and the humerus. Its anterior border is separated at its upper part from the Pectoralis major by a cellular interspace, which lodges the cephalic vein and humeral branch of the acromiothoracic artery; lower down the two muscles are in close con- tact. Its posterior border rests on the Infraspinatus and Triceps muscles. Nerves. — The Deltoid is supplied by the fifth and sixth cer\-ical tlirough the circumflex nerve. THE ANTERIOR SCAPULAR REGION 463 Actions. — The Deltoid raises the arm directly from the side, so as to bring it to a right angle nith the trunk, but this act cannot be performed without the aid of the Serratus magnus, which muscle steadies the lower angle of the scapula. Its anterior fibres, assisted by the Pectoralis major, draw the arm forward; and its posterior fibres, aided by the Teres major and Latissimus dorsi, draw it backward. Applied Anatomy. — The Deltoid is very liable to atrophy, and when in this condition dislo- cation of the shoulder-joint is simulated, as there is flattening of the shoulder and apparent prominence of the acromion process; upon examination, however, it will be found that the relative position of the greater tuberosity of the humerus to the acromion and coracoid process is unchanged. Atrophy of the Deltoid may be due to disuse or loss of trophic influence, either from injury to the circumflex nerve (as in " cruich-palsy") or from spinal cord lesions, as m infantile paralysis. In the operation performed for the obliteration of the subdeltoid bursa, the incision through the Deltoid should be as far anterior as possible, in order to avoid severing the nerves which enter the muscle from behind. 4. The Anterior Scapular Region. Subscapularis. Dissection. — Divide the Deltoid across, near its upper part, by an mcision carried along the margin of the clavicle, the acromion process and spine of the scapula, and reflect it downward, when the structures under cover of it will be seen. eUPRASPINATUS 8UB6CAPULARIS Fig. 348. — Diagra L showing attachment of muscles of the shoulder and arm. Origins, red; insertions, blue. Anterior aspect. The subscapular fascia (fascia subscapularis) is a thin membrane attached to the entire circumference of the subscapular fossa, and affording attachment by its inner surface to some of the fibres of the Subscapularis muscle. 464 THE MUSCLES AND FASCIA The Subscapularis {m. sithsca-pularis) (Fig. 347) is a large triangular muscle which fills up the subscapular fossa, arising from its internal two-thirds, with the exception of a narrow margin along the internal border, and the surfaces at the superior and inferior angles which afford attachment to the Serratus magnus; it also arises from the lower two-thirds of the groove on the axillary border of the bone. Some fibres arise from the tendinous laminae, which intersect the muscle, and are attached to ridges on the bone; and others form an aponeurosis, which separates the muscles from the Teres major and the long head of the Triceps. The fibres pass outward, and, gradually converging, terminate in a tendon, which is inserted into the lesser tuberosity of the humerus and into the neck of the humerus just behind this tuberosity and into the capsular ligament of the shoulder-joint. The tendon of the muscle is in close contact with the anterior part of the capsular ligament of the shoulder-joint, and glides over a large bursa {bursa m. subscapularis), which separates it from the base of the coracoid process. This bursa communicates with the cavity of the joint by an aperture in the cap- sular ligament. Relations. — Its deep surface forms a considerable part of the posterior wall of the axilla, and is in relation with the Serratus magnus, Coracobrachialis, and Biceps, the axillary vessels and brachial plexus of nerves, and the subscapular vessels and nerves. By its superficial sur- face, with the scapula and the capsular ligament of the shoulder-joint. Its lower border is con- tiguous to the Teres major and Latissimus dorsi. Nerves. — It is supplied by the fifth and sixth cervical nerves through the upper and lower subscapular nerves. Actions. — The Subscapularis rotates the head of the humerus inward; when the arm is raised, it draws the humerus forward and downward. It is a powerful defence to the front of the shoulder-joint, preventing displacement of the head of the bone. 5. The Posterior Scapular Region (Figs. 349, 350). Supraspinatus. Teres minor. Infraspinatus. Teres major. Dissection. — To expose these muscles, and to examine their insertion into the humerus, detach the Deltoid and Trapezius from their attachment to the spine of the scapula and acromion process. Remove the clavicle by dividing the ligaments connecting it with the coracoid process, and separate it at its articulation wdth the scapula; divide the acromion process near its root with a saw. The fragments being removed, the tendons of the posterior Scapular muscles will be fully exposed. A block should be placed beneath the shoulder-joint, so as to make the muscles tense. The supraspinatus fascia (fascia supraspinata) is a thick and dense membranous layer, which completes the osseofibrous case in which the Supraspinatus muscle is contained; it affords attachment, by its deep surface, to some of the fibres of the muscle. It is thick internally, but thinner externally under the coraco- acromial ligament. The Supraspinatus muscle (m. supraspinatus) occupies the whole of the supra- spinous fossa, arising from its internal two-thirds and from the strong fascia which covers the surface of the muscle. The muscle fibres converge to a tendon which passes across the upper part of the capsular ligament of the shoulder-joint, to which it is intimately adherent, and is inseried into the highest of the three facets on the greater tuberosity of the humerus. Relations. — By its superficial surface, with the Trapezius, the clavicle, the acromion, the coraco- acromial ligament, and the Deltoid; by its deep surface, with the scapula, the suprascapular vessels and nerve, and upper part of the shoulder- joint. The infraspinatus fascia (fascia infraspinata) is a dense fibrous membrane, covering in the Infraspinatus muscle and attached to the circumference of the THE POSTERIOR SCAPULAR REGION 465 infraspinous fossa; it aft'o''ds attachment, by its inner surface, to some fibres of tliat muscle. At tiie point where the Infraspinatus commences to be covered by the Deltoid, this fascia divides into two layers; one layer passes over the Deltoid muscle, helping to form the deltoid fascia already described; the other passes beneath the Deltoid to the capsule of the shoulder-joint. Fig. 349. — Diagram showing attachment of muscles of shoulder and arm. Posterior aspect. Origins, red; insertions, blue. The Infraspinatus (m. wfraspinahis) is a thick, triangular muscle, which occupies the chief part of the infraspinous fossa, arising by fleshy fibres from its internal two-thirds, and by tendinous fibres from the ridges on its surfaces; it also arises from a strong fascia which covers it externally, and separates it from the Teres major and minor. The fibres converge to a tendon which glides over the external border of the spine of the scapula, and, passing across the posterior part of the capsular ligament of the shoulder-joint, is inserted into the middle impres- sion on the greater tuberosity of the humerus. The tendon of this muscle is sometimes separated from the capsule of the shoulder-joint by a synovial bursa (bursa m. infraspinati), which may communicate with the joint-cavity. Relations. — By its superfieial surface, with the Deltoid, the Trapezius, Latissimus dorsi, and the integument; by its deep surface, with the scapula, from which it is separated by the supra- scapular and dorsalis scapulae vessels, and with the capsular ligament of the shoulder-joint. Its loiver border is in contact with the Teres minor, occasionally united with it, and with the Teres maior. ^ 30 466 THE MU8CLE8 AND FASCIA The Teres minor (m. teres minor) is a narrow, elongated muscle, which arises from the dorsal surface of the axillary border of the scapula for the upper two- thirds of its extent, and from the two aponeurotic lamina, one of which separates this muscle from the Infraspinatus, the other from the Teres major; its fibres pass obliquely upward and outward, and terminate in a tendon which is inserted into the lowest of the three facets on the greater tuberosity of the humerus, and by fleshy fibres, into the humerus immediately below it. The tendon of this muscle passes across the posterior part of the capsular ligament of the shoulder- joint. Relations. ^By its superficial surfcwe, with the Deltoid and the integument; by its deep surface, with the scapula and dorsal branch of the subscapular artery, the long head of the Triceps, and the shoulder-joint; by its upper border, with the Infraspinatus; by its lower border, with the Teres maior, from which it is separated anteriorly by the long head of the Triceps. Fig. 350. — Muscles on the dorsum of the Scapula and the Triceps. The Teres major (m. teres major) is a thick but somewhat flattened muscle, which arises from the oval surface on the dorsal aspect of the inferior angle of the scapula, and from the fibrous septa interposed between it and the Teres minor and Infraspinatus; the fibres are directed upward and out^vard, and termi- nate in a flat tendon, about two inches in length, which is inserted into the inner bicipital ridge of the humerus. The tendon of this muscle, at its insertion into the humerus, lies behind that of the Latissimus dorsi, from which it is separated by a synovial bursa, the two tendons being, however, united along their lower borders for a short distance. A bursa {bursa m. teretis majoris) is found between the tendon of the Teres major and the bone. THE ANTERIOR HUMERAL REGION 467 Relations. — By its superficial surface, with the Latissimus dorsi below, and the long head of the Ti-iceps above. By its deep surface, with the Subscapularis, Latissimus dorsi, Coraco- brachialis, short head of the Biceps brachii, the axillary vessels, and brachial plexus of nerves. Its upper border is at first in relation with the Teres minor, from which it is afterward separated by the long head of the Triceps. Its lower border forms, in conjunction with the Latissimus dorsi, part of the posterior boundary of the axilla. The Latissimus dorsi at first covers the orio-in of the Teres major, then wraps itself obliquely around its lower border, so that its tendon ultimately comes to lie in front of that of the Teres major. Nerves. — The Supra- and Infraspinatus muscles are supplied by the fifth and sixth cervical nerves through the suprascapular nerve; the Teres minor, by the fifth cervical, through the circumflex; and the Teres major, by the fifth and sixth cervical, through the lower subscapular. Actions.— The Supraspinatus assists the Deltoid in raising the arm from the side, and fixes the head of the humerus in the glenoid cavity. The Infraspinatus and Teres minor rotate the head of the humerus outward; when the arm is raised, they assist in retaining it in that position and carrying it backward. One of the most important uses of these three muscles is the great protection they afford to the shoulder-joint, the Supraspinatus supporting it above, and pre- venting displacement of the head of the humerus upward, while the Infraspinatus and Teres ■minor protect it behind, and prevent dislocation backward. The Teres major assists the Latis- simus dorsi in drawing the humerus downward and backward, when previously raised, and in rotating it inward; when the arm is fixed, it may assist the Pectoral and Latissimus dorsi muscles in drawing the trunk forward. THE MUSCLES AND FASCI.® OF THE ARM. 6. The Anterior Humeral Region (Fig. 347). Coracobrachialis. Biceps. Brachialis anticus. Dissection. — The arm being placed on the table, with the front surface uppermost, make a vertical incision through the integument along the middle line, from the clavicle to about Lwo inches below the elbow-joint, where it should be joined by a transverse incision, extending from the inner to the outer side of the forearm; the two flaps being reflected on either side, the fascia should be examined (Fig. 344). The deep fascia (fascia brachii) of the arm is continuous with that covering the Deltoid and the great Pectoral muscles, by means of which it is attached, above, to the clavicle, acromion, and spine of the scapula, and it is also continuous with the axillary fascia. It forms a thin, loose, membranous sheath investing the muscles of the arm, sending down septa between them, and is composed of fibres disposed in a circular or spiral direction, and connected by vertical and oblique fibres. It differs in thickness at different parts, being thin over the Biceps brachii, but thicker where it covers the Triceps, and over the condyles of the humerus; it is strengthened by fibrous aponeuroses, derived from the Pectoralis major and Latissimus dorsi, on the inner side, and from the Deltoid externally. On either side it gives off a strong intermuscular septuvi, whicla is attached to the supracon- dylar ridge and to the condyle of the humerus. These septa serve to separate the muscles of the anterior froin those of the posterior brachial region. The external intermuscular septum extends from the lower part of the external bicipital ridge, along the external supracondylar ridge, to the outer condyle; it is blended with the tendon of the Deltoid, gives attachment to the Triceps behind, to the Brachialis anticus, Brachioradialls, and Extensor carpi radialis longior in front. It is perforated by the musculospiral nerve and the anterior terminal branch of the superior profunda artery. The internal intermuscular septum,, thicker than the preceding, extends from the lower part of the internal lip of the bicipital groove below the Teres major, along the internal supracondylar ridge to the inner condyle, it is blended with the tendon of the Coracobrachialis, and aft'ords attachment to the Triceps behind, and the Brachialis anticus in front. It is perforated by the ulnar nerve and the inferior profunda and anastomotica magna arteries. At 468 THE MUSCLES AND FASCIAE the elbow the deep fascia is attached to all the prominent points around the joint — viz., the condyles of the humerus and the olecranon process of the ulna — and is continuous with the deep fascia of the forearm. Just below the middle of the arm, on its inner side, in front of the intermuscular septum, is an oval opening in the deep fascia which transmits the basilic vein and some lymphatic vessels. Fig. 351. — Horizontal section at middle of right arm — upper surface of lower segment. B. V., basilic vein. CEPH. v., cephalic vein. I. C. N.. internal cutaneous nerve. I. P. -4., inferior profunda artery. M. C. N., mus- culocutaneous nerve. M. N., median ner\'e. M. .S. N., musculospiral nerve. S. P. A., superior profunda artery. U. N., uln:.r nerve. (.A.fter Braune.) The Coracobrachialis (m. coracobrachialis), the smallest of the three muscles in this region, is situated at the upper and inner part of the arm. It arises by fleshy fibres from the apex of fhe coracoid process, in common with the short head of the Biceps, and from the intermuscular septum between the two muscles; the fibres pass downward, backward, and a little outward, to be inserted by means of a flat tendon into an impression at the middle of the inner surface and internal border of the shaft of the humerus between the origins of the Triceps and Brachi- alis anticus. It is perforated by the musculocutaneous nerve. The inner border of the muscle forms a guide to the position of the terminal portion of the axillary and upper part of the brachial arteries. Relations. —By its superficial surface, with the Pectorahs major above, and at its insertion with the brachial vessels and median nerve which cross it; by its deep surface, with the tendons of the Subscapularis, Latissimus dorsi, and Teres major, the inner head of the Triceps, the THE ANTERIOR HUMERAL REGION 469 humerus, and the anterior circumflex vessels; by its inner border, with the brachial artery, and the median and musculocutaneous nerves; by its outer border, with the short head of the Biceps and Brachialis anticus. The Biceps, or the Biceps flexor cubiti (m. biceps brachii), is a long fusiform muscle, occupying the whole of the anterior surface of the arm, and divided above into two portions or heads, from which circumstance it has received its name. The short head (ca'put breve) arises by a thick flattened tendon from the apex of the coracoid process, in common with the Coracobrachialis. The long head (caput loiir/um) arises from the upper margin of the glenoid cavity, and is continu- ous with the glenoid ligament. This tendon arches over the head of the humerus, being enclosed in a special sheath of the synovial membrane of the shoulder-joint; it then passes through an opening in the capsular ligament at its attachment to the humerus, and descends in the bicipital groove, in which it is retained by a fibrous prolongation from the tendon of the Pectoralis major. Each tendon is succeeded by an elongated muscle belly, and the two bellies, although closely applied to each other, can readily be separated until within about three inches of the elbow-joint. Here they end in a flattened tendon, which is inserted into the back part of the tuberosity of the radius, a synovial bursa, being interposed between the tendon and the front of the tuberosity; another bursa is often inter- posed between the ulna and the tendon. As the tendon of the muscle approaches the radius it becomes twisted upon itself, so that its anterior surface becomes external and is applied to the tuberosity of the radius at its insertion; opposite the bend of the elbow the tendon gives off, from its inner side, a broad aponeurosis, the bicipital fascia (lacertus fibrosus), which passes obliquely downward and in- ward across the brachial artery, and is continuous with the deep fascia covering the origins of the superficial Flexor muscles of the forearm (Fig. 340). ^ Relations. — Its superficial surface is overlapped above by the Pectoralis major and Deltoid; in the rest of its extent it is covered by the superficial and deep fasciae and the integument. Its deey surface rests above on the shoulder-joint and upper part of the humerus; below it rests on the Brachialis anticus, with the musculocutaneous nerve intervening between the two, and on the Supinator [brevis]. Its inner border is in relation with the Coracobrachialis, and overlaps the brachial vessels and median nerve; its outer border, with the Deltoid and Brachioradialis. The Brachialis anticus (m. brachialis) is a broad muscle, which covers the elbow-joint and the lower half of the front of the humerus. It is somewhat com- pressed from before backward, and is broader in the middle than at either extrem- ity. It arises from the lower half of the outer and inner surfaces of the shaft of the humerus, and commences above at the insertion of the Deltoid, which it embraces by two angular processes. Its origin extends below, to within an inch of the margin of the articular surface, and is limited on each side by the external and internal borders of the shaft of the humerus. It also arises from the inter- muscular septa on each side, but more extensively from the inner, from which it is separated below by the Brachioradialis and Extensor carpi radialis longior.' Its fibres converge to a thick tendon, which is inserted into a rough depression on the anterior surface of the coronoid process of the ulna, being received into an interval between two fleshy slips of the Flexor profundus digitorum. Relations. — By its superficial surface, with the Biceps, the brachial vessels, musculocutaneous and median nerves; by its deep surface, with the humerus and front of the elbow-joint; by its inner border, with the Triceps, ulnar nerve, and Pronator teres, from which it is separated by the intermuscular septum; by its outer border, with the musculospiral nerve, radial recurrent artery, the Brachioradialis, and Extensor carpi radialis longior. ' A third head to the Biceps is occasionally found (Theile says as often as once in eiijht or nine subjectsi , arising at the upper and inner part of the Brachialis anticus, with the fibres of which it is continuous, and inserted into the bicipital fascia and inner side of the tendon of the Biceps. In most cases this additional slip passes behind the brachial artery in its course down the arm. Occasionally the third head consists of two slips which pass down, one in front of, the other behind, the artery, concealing the vessel in the lower half of the arm. 470 THE MUSCLES AND EASVIJE Nerves. — The muscles of this group are supphed by the musculocutaneous nerve. The Bracliialis anticus usually receives an additional filament from the musculospiral. The Coraco- brachialis receives its supply primarily from the seventh cervical, the Biceps and Brachialis anticus from the fifth and sixth cervical nerves. Actions. — The Coracobrachial is draws the humerus forward and inward, and at the same time assists in elevating it toward the scapula. The Biceps is a flexor of the forearm; it is also a powerful supinator, and serves to render tense the deep fascia of the forearm by means of the broad aponeurosis given off from its tendon. The Brachialis anticus is a flexor of the forearm, and forms an important defence to the elbow- joint. When the forearm is fixed, the Biceps and Brachialis anticus flex the arm upon the forearm, as is seen in efforts at climbing. 7. The Posterior Humeral Region. Triceps. Subanconeus. The Triceps, or the Triceps extensor cubiti (m. friceps brachii) (Fig. 352) is situated on the back of the arm, extending the entire length of the posterior surface of the humerus. It is of large size, and is divided above into three parts; hence its name. These three portions have been named: (1) the middle, scapular, or long head; (2) the external or long humeral head; and (3) the internal or short humeral head. The middle or scapular head (caput longurri) arises by a flattened tendon from a rough triangular depression on the scapula, immediately below the glenoid cavity, being blended at its upper part with the capsular ligament; the muscle fibres pass downward between the two other portions of the muscle, and join with them in the common tendon of insertion. The external head {caput laterale) arises from the posterior surface of the shaft of the humerus, between the insertion of the Teres minor and the upper part of the musculospiral groove; from the external border of the humerus and the external intermuscular septum; the fibres from this origin converge toward the common tendon of insertion. The internal head (caput mediale) arises from the posterior surface of the shaft of the humerus, below the groove for the musculospiral nerve; commencing above, narrow and pointed, below the insertion of the Teres major, and extending to within an inch of the trochlear surface; it also arises from the internal border of the humerus, and from the back of the whole length of the internal and lower part of the external intermuscular septum. Certain fibres of this portion of the muscle are directed downward to the olecranon, while others converge to the tendon of insertion. The tendon of the triceps commences about the middle of the back part of the muscle; it consists of two aponeurotic laminae, one of which is subcutaneous and covers the posterior surface of the muscle for the lower half of its extent ; the other is more deeply seated in the substance of the muscle; after receiving the attachment of the muscle fibres, they join above the elbow, and are inserted, for the most part, into the back part of the upper surface of the olecranon process; a band of fibres is, however, continued downward, on the outer side, over the Anconeus, to blend with the deep fascia of the forearm. Relations. — By its superficial surface, the Triceps is in relatiori with the Deltoid above; in the rest of its extent it is subcutaneous; by its deep surface, with the humerus, musculospiral nerve, superior profunda vessels, and back part of the elbow-joint. Its middle or long head is in relation, behind, with the Deltoid and Teres minor; in front, with the Subscapularis, Latissimus dorsi, and Teres major. The long head of the Triceps descends between the Teres minor and Teres major, di\"iding the triangulai' space between these two muscles and the humerus into two smaller spaces, one triangular, the other quadrangular (B'ig. 350). The triangular space contains the dorsalis THE POSTERIOR HUMERAL REGION 471 scapulae vessels; it is bounded by the Teres minor above, the Teres major below, and the scapular head of the Triceps externally; the quadrang^ular space transmits the posterior circumflex vessels and the circumflex nerve; it is bounded Ijy the Teres minor above, the Teres major below, the scapular head of the Triceps internally, and the humerus externally. The Subanconeus is a name given to a few fibres from the under surface of the lower part of the Triceps muscle, which are inserted into the posterior ligament of the elbow-joint. By some authors it is regarded as the homotype of the Subcrureus in the lower limb, but it is not a separate muscle. Nerves. — The Triceps is supplied by the seventh and eighth cervical nerves through the musculospiral nerve. Actions. — The Triceps is the great Extensor muscle of the forearm, serving, when the forearm is flexed, to extend the elbow-joint. It is the direct antagonist of the Biceps and Brachialis anticus. When the arm is extended the long head of the muscles may assist the Teres major and Latissimus dorsi in drawing the humerus backward and in adducting it to the thorax. The long head of the Triceps protects the under part of the shoulder-joint, and prevents displacement of the head of the humerus downward and backward. The Subanconeus draws up the'synovial membrane of the elbow-joint out of the way of the advancing olecranon process during exten- sion of the forearm. Applied Anatomy. — The existence of the band of fibres from the Triceps to the fascia of the forearm is of importance in excision of the elbow, and should always be carefully preserved from injury by the operator, as by means of these fibres the patient is enabled to. extend the forearm, a movement which would otherwise mainly be accomplished by gravity — that is to say, allowing the forearm to drop from its own weight. III. MUSCLES AND FASCI.a: OF THE FOREARM. ■ Dissection. — To dissect the forearm, place the limb in the position indicated in Fig. 344, make a vertical incision along the middle line from the elbow to the wrist, and a transverse incision at the extremity of this; the superficial structures being removed, the deep fascia of the forearm is exposed. The deep fascia of the forearm {fascia antibrachii'),^ continuous above with that enclosing the arm, is a dense, highly glistening aponeurotic investment, which forms a general sheath enclosing the muscles in this region; it is attached, behind, to the olecranon and posterior border of the ulna, and gives off from its inner surface numerous intermuscidar septa, which enclose each muscle separately. Below, it is continuous in front with the anterior amndar ligament, and forms a sheath for the tendon of the Palmaris longus muscle, which passes over the annular ligament to be inserted into the palmar fascia. Behind, near the wrist-joint, it becomes much thickened by the addition of many transverse fibres, and forms the posterior annular ligament. It consists of circular and oblique fibres, con- nected by numerous vertical fibres. It is much thicker on the dorsal than on the palmar surface, and at the lower than at the upper part of the forearm, and is strengthened above by tendinous fibres derived from the Brachialis anticus and Biceps in front, and from the Triceps behind. Its deep surface gives origin to muscle fibres, especially at the upper part of the inner and outer sides of the forearm, and forms the boundaries of a series of conical-shaped cavities, in which the muscles are contained. Besides the vertical septa separating each muscle, transverse septa are given off on the anterior and posterior surfaces of the forearm, separating the deep from the superficial layer of muscles. Numerous apertures exist in the fascia for the passage of vessels and nerves; one of these, of large size, situated at the front of the elbow, serves for the passage of a communicating branch between the superficial and deep veins. This fascia is also perforated on its anterior surface, near the wrist, by the ulnar artery and nerve. * The correct spelling is antebrachium, not antibrachium. as is gi\'en in the list of the BNA. — [Editor.] 472 THE MUSCLES AND FASCIJE The muscles of the forearm may be subdivided into groups corresponding to the region they occupy. One group occupies the inner and anterior aspect of the forearm, and comprises the Flexor and Pronator muscles, xlnother group occupies its outer side, and a third its posterior aspect. The two latter groups include all the Extensor and Supinator muscles. RADIAL ARTERY PALMARIS MEDIAN NERVE Fig. 352. — Transverse section through the middle of the right forearm, in the position of semipronation. (After Braune.) 8. The Anterior Radioulnar Region. The muscles in this region are divided for convenience of description into two groups or layers, superficial and deep. The Superficial Layer. Pronator teres. Palmaris longus. Flexor carpi radialis. Flexor carpi ulnaris. Flexor sublimis digitorum. These muscles take partial origin from the internal condyle of the humerus by a common tendon. The Pronator teres (m. pronator teres) has two heads. One (caput humerale), the larger and more superficial, arises from the humerus, immediately above the internal condyle, from the tendon common to the origin of the other muscles; and from the fascia of the forearm and the intermuscular septum between it and the Flexor carpi radialis. The deep head (caput uhiare) is a thin fasciculus THE ANTEBIOlt RADIOULNAR REGION 473 which arises from the inner side of the coronoid process of the uhia, joining the preceding at an acute angle. The median nerve enters the forearm between the two heads of the muscle and is separated from the ulnar artery by the deep head. The muscle passes obliquely across the forearm from the inner to the outer side, and terminates in a flat tendon, which turns over the outer margin of the radius, and is inserted into a rough impression at the middle of the outer surface of the shaft of that bone. BRACHI0RAD1ALI6 EXT. CARPI RAD. Fig. 353. — Diagram showing attachments of the muscles of the forearm and hand. Anterior aspect. Origins, red; insertions, blue. The origins and insertions of the Palmar interosseous muscles are omitted. (See Fig. 150.) Relations, — By its superficial surface, throughout the greater part of its extent, with the deep fascia; at its insertion the muscle is crossed by the radial vessels and nerve, and is covered by the Brachioradialis; by its deep surface, with the Brachiahs anticus, Flexor sublimis digitorum. the median nerve, and ulnar artery, the small or deep head being interposed between the two latter structures. Its outer border forms the inner boundary of a triangular space (anieeuhital (space) (page 641), in which are placed the brachial artery, median nerve, and the tendon of the Biceps muscle. Its inner border is in contact with the Flexor carpi radiaUs. Applied Anatomy. — This muscle, when suddenly brought into very active use, as in the game of lawn tennis, is liable to be strained, producing slight swelling and tenderness, and pain on putting the muscle into action. This is known as lawn-tennis arm. The Flexor carpi radialis (m. flexor car-pi radialis) lies on the inner side of the preceding muscle. It arises from the internal condyle by the common tendon, from the fascia of the forearm, and from the intermuscular septa between it and the Pronator teres, on the outside, the Palmaris longus internally, and the Flexor sublimis digitorum beneath. Slender and aponeurotic in structure at 474 THE MUSGLEfi AND FASCIJE its commencement, it increases in size, and terminates in a tendon which forms rather more than the lower half of its length. This tendon passes through a canal on the outer side of the annular ligament, runs through a groove in the os trapezium (which is converted into a canal by a fibrous sheath, and is lined with a synovial membrane), and is inserted into the base of the metacarpal bone of the index finger, and by a slip into the base of the metacarpal bone of the middle finger. Relations. — By its superficial surface, with the deep fascia and the integument; by its deep surface, with the Flexor sublimis digitorum. Flexor longus poUicis, and wrist- joint; by its outer border,, with the Pronator teres and the radial vessels; by its inner border, with the Pal- maris longus above and the median nerve below. The Palmaris longus (m. palmaris longus) (Fig. 354) is a slender, fusiform muscle, lying on the inner side of the preceding. It arises from the in- ner condyle of the humerus by the common tendon, from the deep fascia, and the intermuscular septa between it and the adjacent muscles. It terminates in a slender flattened tendon, which passes over the upper part of the annular ligament, to end in the central part of the palmar fascia and lower part of the annular ligament, frequently sending a tendi- nous slip to the short muscles of the thumb. This muscle is often absent, and is subject to very con- siderable variations; it may be tendinous above and muscular below; or it may be muscular in the centre, with a tendon above and below; or it may present two muscle bundles with a central tendon ; or, finally, it may consist simply of a mere tendinous band. Relations. — By its superficial surface, with the ■ deep fascia. By its deep surface, with the Flexor sublimis digi- torum. Internally, with the Flexor carpi ulnaris. Exter- nally, with the Flexor carpi radialis. The median nerve lies close to the tendon, just above the wrist, on its inner and posterior side. The Flexor carpi ulnaris (m. flexor carpi ulnaris) (Fig. 354) lies along the ulnar side of the forearm. It arises by two heads, connected by a tendinous arch, beneath which pass the ulnar nerve and posterior ulnar recurrent artery. One head (caput humerale) arises from the inner condyle of the humerus, by the common tendon; the other (caput ulnare), from the inner margin of the olecranon and from the upper two-thirds of the posterior border of the ulna, by an aponeu- rosis, common to it and the Extensor carpi ulnaris and Flexor profundus digi- torum; and from the intermuscular septum between it and the Flexor sublimis digitorum. The fibres terminate in a tendon which occupies the anterior part of the lower half of the muscle, and is inserted into the pisiform bone, and is prolonged from this to the unciform and fifth metacarpal bones by the piso- FlG. 354. — Front of the left forearm. Superficial muscles. THE ANTERIOR RADIOULNAR REGION 475 unciform and pisometacarpal ligaments; it is also attached by a few fibres to the annular ligament. Relations. — By its superficial surface, with the deep fascia, with which it is intimately con- nected for a considerable extent; by its deep surface, with the Flexor sublimis digitorum, the Flexor profundus digitorum, the Pronator quadratus, and the ulnar vessels and nerve; by its outer or radial border, with the Palmaris longus above and the ulnar vessels and nerve below. The Flexor sublimis digitorum (m. flexor digitorum sublimis) (Fig.- 354 > is placed beneath the preceding muscles, which therefore must be removed in order to bring its attachment into view. It is the largest of the muscles of the super- ficial layer, and arises by three heads. One head (caput humerale) arises from the internal condyle of the humerus by the common tendon, from the internal lateral ligament of the elbow-joint, and from the intermuscular septum common to it and the preceding muscles. The second head (caput ulnare) arises from the inner side of the coronoid process of the ulna, above the ulnar origin of the Pronator teres (Fig. 14.5, p. 186). The third head (caput radiale) arises from the oblique line of the radius, extending from the tuberosity to the insertion of the Pronator teres. The fibres pass vertically downward, forming a broad and thick muscle, which speedily divides into two planes of muscle fibres, superficial and deep; the superficial plane divides into two parts which end in tendons for the middle and ring fingers; the deep plane also divides into two parts, which end in tendons for the index and little fingers, but previously to having done so it gives off a muscular slip, which joins that part of the superficial plane which is intended for the ring finger. As the four tendons thus formed pass beneath the annular ligament into the palm of the hand, they are arranged in pairs, the superficial pair corresponding to the middle and ring fingers, the deep pair to the index and little fingers. The tendons diverge from one another as they pass onward. Opposite the bases of the first phalanges each tendon divides into two slips (chiasma tendinurn) to permit the passage of the corresponding tendon of the Flexor profundus digitorum; the tv/o portions of the tendon then unite arid form a grooved channel for the reception of the accompanying deep Flexor tendon. Finally, they subdivide a second time, to be inserted into the sides of the second phalanges about their middle. The inser- tion in the index finger is shown in Fig. 361. After leaving the palm the tendons of the superficial Flexor, accompanied by the deep Flexor tendons, lie in osseo- j,^^ sss.-Section passing through the middle aponeurotic canals (Fig. 356). Each third of the first phalanx of the middle finger (frozen ^ 1 1? 1 section). The tendon of the Flexor sublimis digi- Canal or theca extends from the metacar- torum is divided into two small bands, which spread , , , , • 1 , • , , 1 • laterally and engage themselves between the osss- pophalangeal articulation to the proXl- ous plane .and the Flexor profundus digitorum. mal end of the distal phalanx (Fig. 256). ^''°'"'' "°'' ^''"''^■' It is formed by strong fibrous bands, which arch across the tendons, and are attached on each side to the margins of the phalanges. Opposite the middle of the proximal and second phalanges the sheath is very strong, and the fibres pass transversely; but opposite the joints it is much thinner, and the fibres pass obliquely. It is very thin over the metacarpo- phalangeal articulation, and is absent over the distal phalanx. Each sheath is lined by a synovial membrane, which is reflected on the contained tendons. Relations. — In the forearm, by its superficial surface, with the deep fascia and all the pre- ceding superficial muscles; by its deep surface, with the Flexor profundus digitorum. Flexor FLEXOn PROFUNDI JS DIGITORUM SHEATH or I /FLEXOR FLEXOR ~> SUBLIMIS TENDONS ,^ 5^>N. DIGITORUM fKith DIGITAL ARTERIES C f/^^M AND NERVES i^^4 COMMON TENDON C \^~^^y EXTENSOR MUSCLE ~] — OF FINGERS FIRST PHALANX 476 THE MUSCLES AND FASCIA longus pollicis, the ulnar vessels and nerve, and the median nerve. In the hand its tendons are in relation, superficially, with the palmar fascia, superficial palmar arch, and the branches of the median nerve; deeply, with the tendons of the deep Flexor and the Lumbricales. The Deep Layer (Fig. 356). Flexor profundus digitorum. Flexor longus pollicis. Pronator quadratus. Dissection. — Divide each of the superficial muscles at its centre, and turn either end aside; the deep layer of muscles, together with the median nerve and ulnar vessels, will then be exposed. The Flexor profundus digitorum {m. flexor digitorum profimdus) (Fig. 356) is situated on the ulnar side, of the forearm, immediately beneath the superficial Flexors. It arises from the upper three-fourths of the anterior and inner surfaces of the shaft of the ulna, embracing the insertion of the Brachialis anticus above, and extending, below, to within a short distance of the Pronator quadratus. It also arises from a depression on the inner side of the coronoid process; by an aponeurosis from the upper three-fourths of the posterior border of the ulna, in common with the Flexor and Extensor carpi ulnaris; and from the ulnar half of the interosseous membrane. The fibres form a fleshy belly of considerable size, which divides into four tendons; these pass under the annular ligament beneath the tendons of the Flexor sublimis digitorum. Opposite the first phalanges the tendons pass through the openings in the tendons of the Flexor sublimis digitorum, and are finally inserted into the bases of the last phalanges. The portion of the muscle for the index finger (Fig. 360) is usually distinct throughout, but the tendons for the three inner fingers are connected by cellu- lar tissue and tendinous slips p.s far as the palm of the hand. The tendons of this muscle and those of the Flexor sublimis digitorum, while contained in the osseoaponeurotic canals of the fingers, are invested in a synovial sheath, and are connected to each other and to the phalanges by slender tendinous filaments, called vincula accessoria tendinum (vincida tendineae). Of these there are two sets: (a) The ligamenta brevia — two in each finger — are composed of triangular bands of fibres which connect respectively (1) the tendon of the Flexor sublimis digitorum to the front of the first interphalangeal joint, and (2) the head of the first phalanx and the tendon of the Flexor profundus digitorum to the front of the second interphalangeal joint and to the head of the second phalanx, (b) The ligavienta longa connect the under surfaces of the Flexor sublimis digitorum to the proximal end of the palmar surface of the first phalanx, and the under surface of the Flexor profundus digitorum to those of the subjacent Flexor sublimis digitorum after the tendons of the former have passed through the latter (Fig. 361). Four small muscles, the Lumbricales, are connected with the tendons of the Flexor profundus in the palm. They will be described with the muscles in that region. Relations. — By its superficial surface, in the forearm, with the Flexor sublimis digitorum. the Flexor carpi ulnaris, the ulnar vessels, and nerve, and the median nerve; and in the hand, with the tendons of the superficial Flexor; by its deep surface, in the forearm, with the ulna, the interosseous membrane, the Pronator quadratus; and in the hand, with the Interossei, Adductor pollicis, and deep palmar arch; by its ulnar border, with the Flexor carpi ulnaris; by its radial border, with the Flexor longus pollicis, the anterior interosseous vessels and nerve being inter- posed. The Flexor longfus pollicis (m. flexor pollicis longus) (Fig. 356) is situated on the radial side of the forearm, lying on the same plane as the preceding. It arises from the grooved anterior surface of the shaft of the radius, commencing above, THE ANTERIOR RADIOULNAR REGION 477 Fig. 356. — Front of the left forearm. Deep muscles. Fig. 357. — Posterior surface of the left forea Superficial muscles. 478 THE 3IUSCLES AND FASCIA immediately below the tuberosity and oblique line, and extending below to within a short distance of the Pronator quadratus. It also arises from the ad- jacent part of the interosseous membrane and generally by a fleshy slip from the inner border of the coronoid process or from the internal condyle of the humerus. The fibres pass downward, and terminate in a flattened tendon which passes beneath the annular ligament, is then lodged in the interspace between the super- ficial head of the Flexor brevis pollicis and the Adductor obliquus poUicis, and, entering an osseoaponeurotic canal similar to those for the other Flexor tendons, is inserted into the base of the last phalanx of the thumb. Relations. — By its superficial surface, with the Flexor sublimis digitorum, Flexor carpi radialis, Brachior'adialis, and radial vessels; by its dee-p surface, with the radius, interosseous membrane, and Pronator quadratus; by its ulnar border, with the Flexor profundus digitorum, from which it is separated by the anterior interosseous vessels and nerve. The Pronator quadratus {m. pronator quadratics) (Figs. 356 and 365) is a small, flat, quadrilateral muscle, extending transversely across the front of the radius and ulna, above their carpal extremities. It arises from the oblique ridge on the lower part of the anterior surface of the shaft of the ulna; from the lower fourth of the anterior surface and the anterior border of the ulna; and from a strong aponeurosis which covers the inner third of the muscle. The fibres pass outward and slightly downward, to be inserted into the lower fourth of the anterior surface and anterior border of the shaft of the radius. Relations. — By its superficial surface, with the Flexor profundus digitorum, the Flexor longus pollicis. Flexor carpi radialis, and the radial vessels; by its deep surface, with the radius, ulna, and interosseous membrane. Nerves. — All the muscles of the superficial layer are supplied by the median nerve, excepting the Flexor carpi ulnaris, which is supplied by the ulnar nerve. The Pronator teres and the Flexor carpi radialis derive their supply primarily from the sixth and seventh cervicals; the Palmaris longus from the eighth cervical; the Flexor sublimis digitorum from the seventh and eighth cervical and first thoracic, and the Flexor carpi ulnaris from the eighth cervical and first thoracic nerves. Of the deep layer, the Flexor profundus digitorum is supplied by the seventh and eighth cervicals and first thoracic through the ulnar and anterior interosseous branch of the median. The remaining two muscles, the Flexor longus pollicis and Pronator quadratus, are also supplied by the eighth cervical and first thoracic through the anterior interosseous branch of the median. Actions. — These muscles act upon the forearm, the wrist, and hand. The Pronator teres helps to rotate the radius upon the ulna, rendering the hand prone; when the radius is fixed it assists the other muscles in flexing the forearm. The Flexor carpi radialis is one of the Flexors of the wrist; when acting alone it flexes the wrist, inclining it to the radial side. It can also assist in pronating the forearm and hand, and, by continuing its action, in bending the elbow. The Flexor carpi ulnaris is one of the flexors of the wrist; when acting alone it flexes the wrist, inclining it to the ulnar side (adducting the wrist), and, bv continuing to contract, it bends the elbow. The Palmaris longus is a tensor of the palmar fascia. It also assists in flexing the wrist and elbow. The Flexor sublimis digitorum flexes first the middle and then the proximal pha- langes. It assists in flexing the wrist and elbow. The Flexor profundus digitorum is one of the Flexors of the phalanges. After the Flexor sublimis has bent the second phalanx, the Flexor profundus flexes the terminal one, but it cannot do so until after the contraction of the superficial muscle. It also assists in flexing the wrist. The Flexor longus pollicis is the flexor of the distal phalanx of the thumb. ^Vhen the thumb is fixed it also assists in flexing the wrist. The Pronator quadratus helps to rotate the radius upon the ulna, rendering the hand prone. Applied Anatomy. — ^^'hen a finger is amputated so that the fibrous sheath of the Flexor ten- dons is divided in a region in which it is firm and dense, the tendon contracts but the theca does not, and the rigid theca constitutes a permeable passage to the palm. If the parts should be infected the theca will draw pus toward the palm. Hence, it is best to close the theca by sutures. "Over the terminal phalanx, and over the joint between the middle and terminal phalanges, there is no fibrous sheath. In front of the metacarpophalangeal joint it is scarcely evident. Over the first and second (proximal and middle) phalanges, and in front of the joint between these bones, the fibrous sheath is well marked, and appears as a rigid tube when cut across. As the sheath crosses the metacarpophalangeal and first interphalangeal joints it is adherent THE RADIAL REGION 479 to tlie glenoid (anterior metacarpophalangeal) ligament, and is easily closed by two fine cat- gut sutures passed vertically — i. e., from the dorsal to the palmar wall. Opposite the shafts of the first and second phalanges, however, there is much difficulty in effecting closure, since the sheath is united to the periosteum, and that membrane is very thin. In these situations the periosteum should be stripped up a little from the palmar aspect of the bone, and the orifice of the tube secured by two fine sutures passed either vertically or transversely, as may appear the more convenient. This stripping off of periosteum should be effected before the bone is divided."' 9. The Radial Region (Figs. 354, 357). Brachioradialis [Supinator longus]. Extensor carpi radialis longior. Extensor carpi radialis brevier. Dissection. — Divide the integument in the same manner as in the dissection of the anterior brachial region, and, after having- examined the cutaneous vessels and nerves and deep fascia, remove all those structures. The muscles will then be exposed. The removal of the fascia will be considerably facilitated by detaching it from below upward. Great care should be taken to avoid cutting across the tendons of the muscles of the thumb, which cross obliquely the larger tendons running down the back of the radius. Tlie Brachioradialis (m. brachioradialis, formerly Supinator longus) (Fig. 354) is the most superficial muscle on the radial side of the forearm; it is fleshy for the upper two-thirds of its extent, and becomes tendinous below. It arises from the upper two-thirds of the external supracondylar ridge of the humerus, and from the external intermuscular septum, being limited above by the musculospiral groove. The fibres terminate above the middle of the forearm in a flat tendon, which is inserted into the outer side of the base of the styloid process of the radius. Relations. — By its superficial surface, with the integument and fascia for the greater part of its extent; near its insertion it is crossed by the Extensor ossis metacarpi pollicis and the Extensor brevis pollicis; by its deep surface, with the humerus, the Extensor carpi radialis longior and brevior, the insertion of the Pronator teres, and the Supinator [brevis]; by its inner border, above the elbow, with the Brachialis anticus, the musculospiral nerve, and the radial recurrent artery; and in the forearm with the radial vessels and nerve. The Extensor carpi radialis longior (m. extensor carpi radialis longus') (Fig. 357) is placed partly beneath the preceding muscle. It arises from the lower third of the external supracondylar ridge of the humerus, and from the external intermuscular septum by a few fibres from the common tendon of origin of the Extensor muscles of the forearm. The fibres terminate at the upper third of the forearm in a flat tendon, which runs along the outer border of the radius, beneath the Extensor tendons of the thimib ; it then passes through a groove com- mon to it and the Extensor carpi radialis brevior, immediately behind the styloid process, and is inserted into the base of the metacarpal bone of the index finger, on its radial side. Relations. — By its superficial surface, with the Brachioradialis and fascia of the forearm; its outer side is crossed obliquely by the Extensor tendons of the thumb; by its deep surface, with the elbow-joint, the Extensor carpi radialis brevior, and back part of the wrist. The Extensor carpi radialis brevior (m. extensor carpi radialis brevis) (Fig. 357) is shorter, as its name implies, and thicker than the preceding muscle, beneath which it is placed. It arises from the external condyle of the humerus by a tendon common to it and the three following muscles; from the external lateral ligament of the elbow-joint, from a strong aponeurosis which covers its surface, and from 1 Operative Surgery. By Sir Frederick Treves. 480 THE MUSCLES AND FASCIJE the intermuscular septa between it and the adjacent muscles. The fibres termi- nate about the middle of the forearm in a flat tendon which is closely connected with that of the preceding muscle, and accompanies it to the %vrist, lying in the same groove on the posterior surface of the radius; it passes beneath the Extensor tendons of the thumb, then beneath the annular ligament, and, diverging some- what from its fellow, is inserted into the base of the metacarpal bone of the middle finger, on its radial side. There is often a bursa between a portion of the base of the bone and the tendon. The tendons of the two preceding muscles pass through the same compartment of the annular ligament, and are lubricated by a single synovial membrane, but are separated from each other by a small vertical ridge of bone as they lie in the groove at the back of the radius. Relations. — By its superficial surface, with the Extensor carpi radialis longior, and with the Extensor muscles' of the thumb which cross it; by its deef surface, with the Supinator [brevis], tendon of the Pronator teres, radius, and wrist-joint; by its ulnar border, with the Extensor communis digitorum. 10. The Posterior Radioulnar Region (Fig. 357). The muscles in this region are divided for purposes of description into two groups or layers, superficial and deep. The Superficial Layer. Extensor communis digitorum. Extensor carpi ulnaris. Extensor minimi digiti. Anconeus. The Extensor communis digitoruni (m. extensor digitorum communis) is situ- ated at the back part of the forearm. It arises from the external condyle of the humerus by the common tendon, from the deep fascia, and the intermuscular septa between it and the adjacent muscles. It divides below into four tendons which pass, together with that of the Extensor indicis, through a separate com- partment of the annular ligament, lubricated by a synovial membrane. The tendons then diverge, pass across the back of the hand, and are inserted into the second and third phalanges of the fingers in the following manner: The outermost tendon, accompanied by the Extensor indicis, goes to the index finger (Figs. 357 and 360) ; the second tendon is sometimes connected to the first by a thin transverse band, and receives a slip from the third tendon (Fig. 357) ; it goes to the middle finger; the third tendon gives off the slip to the second (Fig. 357), and receives a very considerable part of the fourth tendon; the fourth, or innermost tendon, divides into two parts; one goes to join the third tendon, the other, rein- forced by the Extensor minimi digiti, goes to the little finger. Each tendon opposite the metacarpophalangeal articulation becomes narrow and thickened, and gives off a thin fasciculus upon each side of the joint, which blends with the lateral ligaments and serves as the posterior ligament; after having passed the joint it spreads out into a broad aponeurosis, which covers the whole of the dorsal surface of the first phalanx, being reinforced, in this situation, by the tendons of the Interossei and Lumbricales. Opposite the first phalangeal joint this aponeu- rosis divides into three slips, a middle and two lateral; the former is inserted into the base of the second phalanx, and the two lateral, which are continued onw-ard along the sides of the second phalanx, unite by their contiguous margins, and are inserted into the dorsal surface of the last phalanx. As the tendons cross the phalangeal joints they furnish them with posterioi ligaments. The accessory THE POHTEEIOR RADIOULNAR REGION 481 slips or lateral vincula which join the tendon of the ring finger to the tendon of the little finger and to the tendon of the middle finger are constant. If the middle and little fingers are held flexed the lateral vincula greatly limit the range of exten- sion possible in the ring finger. Relations. — By its superficial surface, with the fascia of the forearm and hand, the posterior annular Ufjauient, and integument; by its deep surface, with the Supinator [brevis], the Extensol muscles of the thumb and index finger, the posterior interosseous vessels and nerve, the wrist- joint, carpus, metacarpus, and phalanges; by its radial border, with the Extensor carpi radialis brevior; by its ulnar border, with the Extensor minimi digiti and Extensor carpi ulnaris. [brevis] EXTENSOR LONGU Origin of f aponeurosis < common to : (.flexor EXTENSOR C EXTENSOR INDICIS Fig. 358. — Diagram showing attachments of muscles of forearm and hand. Posterior aspect. Origins, red; insertions, blue. The origins and insertions of the Dorsal interossei muscles are omitted. ^See Fig. 151.) The Extensor minimi digiti (m. extensor digiti quinti proprius) is a slender muscle placed on the inner side of the Extensor communis, with which it is gen- erally connected. It arises from the common Extensor tendon by a thin, tendin- ous slip, and from the intermuscular septa between it and the adjacent muscles. Its tendon runs through a separate compartment in the annular ligament behind the inferior radioulnar joint, then divides into two as it crosses the hand, the outermost division being joined by the slip from the innermost tendon of the common Extensor, The two slips thus formed spread into a broad aponeurosis, which, after receiving a slip from the Abductor minimi digiti, is inserted into the second and third phalanges of the little finger. The tendon is situated on the ulnar side of, and is somewhat more superficial than, the common Extensor. 482 THE MUSCLES AND FASCIA ■ The Extensor carpi ulnaris is the most superficial muscle on the ulnar side of the forearm. It arises from the external condyle of the humerus by the common Extensor tendon ; by an aponeurosis from the posterior border of the ulna in common with the Flexor carpi ulnaris and the Flexor profundus digitorum; and from the deep fascia of the forearm. This muscle terminates in a tendon which runs through a groove behind the styloid process of the ulna, passes through a separate compartment in the annular ligament, and is inserted into the prominent tubercle on the ulnar side of the base of the metacarpal bone of the little finger. The Anconeus (m. anconaeus) is a small triangular muscle placed behind and below the elbow-joint, and appears to be a continuation of the external portion of the Triceps. It arises by a separate tendon from the back part of the outer condyle of the humerus, and is inserted into the side of the olecranon and upper fourth of the posterior surface of the shaft of the ulna; its fibres diverge from their origin, the upper ones being directed transversely, the lower obliquely inward. The Deep Layer (Fig. 362). Supinator [brevis]. Extensor brevis pollicis. Extensor ossis metacarpi pollicis. Extensor longus pollicis. Extensor indicis. The Supinator [brevis] (m. supinator) (Figs. 359 and 360) is a broad muscle, of hollow cylindrical form, curved around the upper third of the radius. It con- sists of two distinct planes of muscle fibres, between which lies the posterior interosseous nerve (Fig. 359). The two planes' ame in common — the superficial one by tendinous, and the deeper by muscle fibres from the external condyle of the humerus, from the external lateral ligament of the elbow-joint and the orbic- ular ligament of the radius; from the ridge on the ulna, which runs obliquely downward from the posterior extremity of the lesser sigmoid cavity; from the triangular depression in front of the cavity; and from a tendinous expansion which covers the surface of the muscle. The superficial fibres surround the upper part of the radius, and are inserted into the outer edge of the bicipital tuberosity and into the oblique line of the radius, as low down as the insertion of the Pronator teres. The upper fibres of the deeper plane form a sling-like fasciculus, which encircles the neck of the radius above the tuberosity and is attached to the back part of its inner surface; the greater part of this portion of the muscle is inserted into the posterior and external surface of the shaft, midway between the oblique line and the head of the bone. Between the insertion of the two planes the posterior interosseous nerve lies on the shaft of the bone (Fig. 359). Relations. — By its superficial surface, with the superficial Extensors and the Brachioradialis muscles, and the radial vessels and nerve; by its deep surface, with the elbow-joint, the inter- osseous membrane, and the radius. The Extensor ossis metacarpi pollicis (m. abductor pollicis longus) is the most external and the largest of the deep Extensor muscles; it lies immediately below the Supinator [brevis], with which it is sometimes united. It arises from the outer part of the posterior surface of the shaft of the ulna below the insertion of the Anconeus, from the interosseous membrane, and from the middle third of the posterior surface of the shaft of the radius. Passing obliquely downward and outward, it terminates in a tendon which runs through a groove on the outer side of the styloid process of the radius, accompanied by the tendon of the Extensor brevis pollicis, and is inserted into the base of the metacarpal bone of the thumb. THE POSTERIOR RADIOULNAR REGION 483 It occasionally gives ofF two slips near its insertion — one to the trapezium, and the other to blend with the origin of the Abductor pollicis. Fig. 359 — Supinator [brevis]. (From a prepa- ration in the Mubeum of the Royal College of Surgeons of England.) Relations. — By its superficial surface, with the Extensor communis digitorum, Ex- tensor minimi digiti, and fascia of the fore- arm, and with the branches of the posterior interosseous artery and nerve which cross it; by its deep surface, witli the ulna, the interosseous membrane, the radius, the ten- dons of the Extensor carpi radialis longior and brevior, which it crosses obliquely, and at the outer side of the wrist, with the radial vessels; by its upper border, with the Supinator [brevis]; by its lower harder, with the Extensor brevis pollicis. The Extensor brevis pollicis (m. extensor pollicis brevis), the smallest muscle of this group, lies on the inner side of the preceding. It arises from the posterior surface of the shaft of the radius, below the Extensor ossis metacarpi pollicis, and from the interosseous membrane. Its direction is similar to that of the Extensor ossis metacarpi 484 THE MUSCLES AND FASCIJE pollicis, its tendon passing through the same groove on the outer side of the styloid process, to be inserted into the base of the first phalanx of the thumb. Relations. — The same as those of the Extensor ossis metacarpi polHcis. The Extensor longus pollicis {m. extensor -pollicis longus) is much larger than the preceding muscle, the origin of which it partly covers in. It arises from the outer part of the posterior surface of the shaft of the ulna, below the origin of the Extensor ossis metacarpi pollicis, and from the interosseous mem- brane. It terminates in a tendon which passes through a separate compartment Tendon of Ext. carpi rad. longior Tendon of Ext. conimutiis digitoru7n Wendon of Extensor indicis First LumMcal Ligamenta irevia Tendon of Ext. ossis tnetacarpi pollicis Trapezium ■Badial artery Tendon of Ext. brevis pollicis Tendon of Ext. long, pollicis Fhior suhlimis digiiorutn Flexor p) of undus digitorum Fig. 361. — The tendons attached to the right index finger. in the annular ligament, lying in a narrow, oblique groove at the back part of the lower end of the radius. It then crosses oblicjuely the tendons of the Extensor carpi radialis longior and brevior, being separated from the other Extensor tendons of the thumb, by a triangular interval, in which the radial artery is found, and is finally inserted into the base of the last phalanx of the thumb. Relations. — By its superficial surface, with the same parts as the Extensor ossis metacarpi polHcis; by its deep surface, with the ulna, interosseous membrane, the posterior interosseous nerve, radius, the wrist, the radial vessels, and metacarpal bone of the thumb. The Extensor indicis (m. extensor indicis froprins) (Figs. 357 and 360) is a narrow, elongated muscle placed on the inner side of, and parallel with, the THE POSTERIOR RADIOULNAR REGION 485 preceding. It arises from the posterior surface of the siiaft of the ulna, below the origin of the Extensor longus pollicis and from the interosseous membrane. Its tendon passes with the Extensor communis digitorum through the same canal in the annular ligament, and subsequently joins the tendon of the Extensor communis which belongs to the index finger, opposite the lower end of the corre- sponding metacarpal bone, lying to the ulnar side of the tendon from the common Extensor. Nerves. — The Brachioradialis is supplied by the fifth and sixth, the Extensor carpi radialis li)ngior by the sixth and seventh, and the Anconeus by the seventh and eighth cervical nerves, all through the musculospiral nerve; the remaining muscles of the radial and posterior brachial region are supplied through the posterior interosseous nerve, the Supinator [brevis] being sup- plied by the sixth cervical, the Extensor carpi radialis brevior by the sixth and seventh cervicals, and all the other muscles by the seventh cervical. Actions. — The muscles of the radial and posterior brachial regions, which comprise all the Extensor and Supinator muscles, act upon the forearm, wrist, and hand; they are the direct antagonists of the Pronator and Flexor muscles. The Anconeus assists the Triceps in extending the forearm. The chief action of the Brachioradialis is that of a Flexor of the elbow-joint, but in addition to this it may act both as a Supinator or a Pronator; that is to say, if the forearm is forcibly pronated it will act as a Supinator, and bring the bones into a position midway between supination and pronation; and, vice versa,ii the arm is forcibly supinated, it will act as a pro- nator, and bring the bones into the same position, midway between supination and pronation. The action of the muscle is therefore to throw the forearm and hand into the position they naturally occupy when placed across the chest. The Supinator [brevis] is a true supinator; that is to say, when the radius has been carried across the ulna in pronation and the back of the hand is directed forward, this muscle carries the radius back again to its normal position on the outer side of the ulna, and the palm of the hand is again directed forward. The Extensor carpi radialis longior extends the wrist and abducts the hand. It may also assist in bending the elbow-joint; at all events, it serves to fix or steady this articulation. The Extensor carpi radialis brevior assists the Extensor carpi radialis longior in extending the wrist, and may also act slightly as an abductor of the hand. The Extensor carpi ulnaris helps to extend the hand, but •when acting alone inclines it toward the ulnar side; by its continued action it extends the elbow- joint. The Extensor communis digitorum extends the phalanges, then the wrist, and finally the elbow. It acts principally on the proximal phalanges, the middle and terminal phalanges being extended by the Interossei and Lumbricales. It has also a tendency to separate the fingers as it extends them. The Extensor minimi digiti extends similarly the little finger, and by its continued action it assists in extending the wrist. It is owing to this muscle that the little finger can be extended or pointed while the others are flexed. The chief action of the Extensor ossis metacarpi pollicis is to carry the thumb outward and backward from the palm of the hand, and hence it has been called the Abductor pollicis longus. By its continued action it helps to extend and abduct the wrist. The Extensor brevis pollicis extends the proximal phalanx of the thumb. By its continued action it helps to extend and abduct the wrist. The Extensor longus pollicis extends the terminal phalanx of the thumb. By its continued action it helps to extend and abduct the wrist. The Extensor indicis extends the index finger, and by its continued action assists in extending the wrist. It is owing to this muscle that the index finger can be extended or pointed while the others are flexed. Applied Anatomy. — The tendons of the Extensor muscles of the thumb are liable to become strained and their sheaths inflamed after excessive exercise, producing a sausage-shaped swell- ing along the course of the tendon, and giving a peculiar creaking sensation to the finger when the muscle acts; it is known as fenosynovitis. In piano-players the slips which join the tendons of the Extensor communis digitorum may limit freedom of motion in individual fingers. Their complete extension, without operative interference, can only be brought about by long-continued exertion in practice, when elongation of certain accessory, but restricting, tendons is made by nutritive growth. If there is much limitation, division of the hindering slips is advisable.' Par- alysis of the Extensor muscles of the hand is common in lead poisoning, and causes the well- known "wrist drop." Curiously enough, the Brachioradialis and Extensor ossei metacarpi pollicis muscles escape. The paralysis is due to a neuritis of the musculospiral nerve. 1 Prof. William S. Forbes, in the Philadelphia Medical Journal, January 15. 1898. 486 THE MUSCLES AND FASCIA IV. MUSCLES AND FASCIA OF THE HAND. The muscles of the hand are subdivided into three groups: (1) Those of the thumb, which occupy the radial side and produce the thenar eminence. (2) Those of the little finger, which occupy the ulnar side and give rise to the hypothenar eminence. (3) Those in the middle of the palm and within the interosseous spaces. Dissection (Fig. 344). — Make a transverse incision across the front of the wrist, and a second across the heads of the metacarpal bones; connect the two by a vertical incision in the middle line, and continue it through the centre of the middle finger. The anterior and posterior annular ligaments and the palmar fascia should then be dissected. ANTERIOR A N N U LA R LIGAMENT, flexor longus pollicis flexor carpi radial1 :les of thumb Median nerve. Ulnar 1st Metacarp Ead al i EXT. CARP R EXTENSOR EXTENSOR Os magnuni. EXTENSOR COMMUN S D G TORUM CIS of the tendons, vessels, and The Anterior Annular Ligament (ligamentuvi carpi transverswn) (Fig. 362) is a strong, fibrous band which arches over the carpus, converting the deep groove on the front of the carpal bones into a canal, beneath which pass the Flexor tendons of the fingers. It is attached, internally, to the pisiform bone and the hook of the unciform bone, and externally to the tuberosity of the scaphoid and to the inner part of the anterior surface and the ridge of the trapezium. It is continuous, above, with the deep fascia of the forearm, of which it may be regarded as a thick- ened portion, and, below, with the palmar fascia. It is crossed by the ulnar ves- sels and nerve and the cutaneous branches of the median and ulnar nerves. At its outer extremity is the tendon of the Flexor carpi radialis, which lies in the groove on the trapezium between the attachments of the annular ligaments to the bone. It has inserted into its anterior surface a part of the tendon of the Palmaris longus and part of the tendon of the Flexor carpi ulnaris, and has arising from it, below, the small muscles of the thumb and little finger. Beneath it pass the tendons of the Flexores sublimis and Profundus digitorum, the tendon of the Flexor longus pollicis, and the median nerve. The Synovial Membranes of the Flexor Tendons at the Wrist. — There are two vaginal synovial membranes which enclose all the tendons as they pass beneath this ligament — one for the Flexores sublimis and Profundus digitorum, the other for the Flexor longus pollicis. They extend up into the forearm for about an inch above the annular ligament, and downward about half-way along the metacarpal bone, where they terminate in a blind diverticulum around each pair OF THE HAND 487 of tendons, with the exception of those of the thumb and little finger; in each of these two digits the diverticulum is continued on, and communicates with the synovial sheath of the tendons in the fingers. In the other three fingers the syno- vial sheath of the tendons begins as a blind pouch without communication with the large synovial sac (Fig. 363). Applied Anatomy. — This arrangement of the synovial sheaths explains the fact that thecal abscess in the thumb or little finger is liable to be followed by abscesses of the forearm, from extension of the inflammation along the continuous synovial sheaths. Tuberculous inflamma- tion is liable to occur in this situation, constituting compound palmar ganglion; it presents an hour-glass outline, with a swelling in front of the wrist and in the palm of the hand, and a constriction corre- sponding to the annular ligament between the two. The fluid can be forced from the one swelling to the other under the liga- ment. Bursae about the Hand and Wrist.— BursEe usually exist between the distal ex- tremities of the metacarpal bones (bursae intermetacarpophalangeae), and a subcuta- neous bursa often exists over the dorsal surface of the head of the fifth metacarpal bone. Subcutaneous digital dorsal bursse occur "almost constantly in the first finger- joints (between the first and second pha- lanx), occasionally in the second joint of the second and fourth fingers"' (bursae sub- cutaneae digitorum, dorsales). A bursa exists between the tendon of the Extensor carpi radialis brevior and the base of the third metacarpal bone; another between the Flexor carpi ulnaris and the pisiform bone; another between the Flexor carpi radialis and the base of the second metacarpal bone. 363. — Diagram showing the arrangement of the synovial sheaths of the palm and fingers. The Posterior Annular Ligament (ligamentum carpi dorsale) is a strong fibrous band extending obliquely downward and inward across the back of the wrist, and consisting of the deep fascia of the back of the forearm, strengthened by the addition of some transverse fibres. It binds down the Extensor tendons in their passage to the fingers, being attached, internally, to the styloid process of the ulna, the cuneiform and pisiform bones; externally, to the margin of the radius; and, in its passage across the wrist, to the ridges on the posterior surface of the radius. It presents six compartments for the passage of ten- dons, each of which is lined with a separate synovial membrane (Fig. 364) . These are, from without inward: (1) On the outer side of the styloid process, for the tendons of the Extensor ossis metacarpi and Extensor brevis pollicis. (2) Behind the styloid process, for the tendons of the Extensor carpi radialis longior and Fig. 364.— Transverse section through the wrist, show- ing the annular ligamenta and the canals for the passage of the tendons. > Hand .\tlas of Human Anatomy. By Werner Spalteholz. Translated and edited by Lewellys F. Barker. 488 THE MVSCLES AND FASCIJE brevior. (3) About the middle of the posterior surface of the radius, for the ten- don of the Extensor longus pollicis. (4) To the inner side of the latter, for the tendons of the Extensor communis digitorum and Extensor indicis* (5) Oppo- site the interval between the radius and ulna, for the Extensor minimi digiti. (6) Grooving the back of the ulna, for the tendon of the Extensor carpi ulnaris. The synovial membranes lining these sheaths are usually very extensive, reaching from above the annular ligament down upon the tendons for a variable distance on the back of the hand. Fig. 365.— Palm preparation in the Museum of the Royal College of Surgeons of England.) The deep palmar fascia (^aponeurosis palmaris) (Fig. 365) forms a common sheath which invests the muscles of the hand. It consists of a central and two lateral portions. The central portion occupies the middle of the palm, is triangular in shape, of great strength and thickness, and binds down the tendons and protects the vessels and nerves in this situation. It is narrow above, where it is attached to the lower margin of the annular ligament, and receives the expanded tendon of the Pal- maris longus muscle. Below, it is broad and expanded, and divides into four slips for the four fingers. Each slip gives off superficial fibres, which are inserted THE RADIAL REGION 489 into the skin of the palm and finger, those to the palm joining the skin at the furrow corresponding to the metacarpophalangeal articulation, and those to the fingers passing into the skin at the transverse fold at the base of the fingers. The deeper part of each slip subdivides into two processes, which are inserted into the lateral margins of the anterior ligament of the metacarpophalangeal joint. From the sides of these processes portions are sent backward (dorsal) to be attached to the bor- ders of the lateral surfaces of the metacarpal bones at their distal extremities. By this arrangement short channels are formed on the front of the lower ends of the metacarpal bones, through which the Flexor tendons pass.^ The intervals left in the fascia between the four fibrous slips transmit the digital vessels and nerves and the tendons of the Lumbricales. At the points of division of the palmar fascia into the slips above mentioned numerous strong, transverse fibres bind the separate processes together. The palmar fascia is intimately adherent to the integument by dense, fibroareolar tissue, forming the superficial palmar fascia, and gives origin by its inner margin to the Pal maris brevis; it covers the superficial palmar arch, the tendons of the Flexor muscles, and the branches of the median and ulnar nerves, and on each side it gives off a vertical septum, which is continu- ous with the interosseous aponeurosis and separates the two lateral from the middle palmar group of muscles. The lateral portions of the palmar fascia are thin, fibrous layers, which cover, on the radial side, the muscles of the ball of the thumb, and, on the ulnar side, the muscles of the little finger; they are continuous with the dorsal fascia, and in the palm with the central portion of the palmar fascia. The Superficial Transverse Ligament of the Fingers is a thin band of transverse fibres (fasciculi transversi); it stretches across the roots of the four fingers, and is closely attached to the skin of the clefts, and internally to the fifth metacarpal bone, forming a sort of rudimentary web. Beneath it the digital vessels and nerves pass onward to their destination. Applied Anatomy. — The palmar fascia is liable to undergo contraction, producing a very inconvenient deformity known as Diipuytren's contraction. The ring and little fingers are most frequently implicated, but the middle, the index, and the thumb may be involved. The proximal phalanx is flexed and cannot be straightened, and the two distal phalanges become similarly flexed as the disease advances. 11. The Radial Region (Figs. 366, 367). Abductor pollicis. Flexor brevis pollicis. Opponens pollicis. Adductor obliquus pollicis. Adductor transversus pollicis. The Abductor pollicis (m. abductor pollicis brevis) (Fig. 357) is a thin, flat muscle, placed immediately beneath the integument. It arises from the anterior annular ligament, the tuberosity of the scaphoid, and the ridge of the trapezium, frequently by two distinct slips; and, passing outward and downward, is inserted by a thin, flat tendon into the radial side of the base of the first phalanx of the thumb, sending a slip to join the tendon of the Extensor longus pollicis. Relations. — By its superficial surface, with the palmar fascia and superficialis volae artery, which frequently perforates it. By its deep surface, with the Opponens pollicis. Its inner border is separated from the Flexor brevis pollicis by a narrow cellular interval. * Dr. Keen describes a fifth slip as frequently found passing to the thumb. 490 THE MUSCLES AND FASCIA The Opponens pollicis {vi. opponens pollicis) (Figs. 366 and 367) is placed beneath and partially to the outer side of the preceding. It atises from the ridge on the trapezium and from the anterior annular ligament, passes down- ward and outward, and is inserted into the whole length of the metacarpal bone of the thumb on its radial side. Relations. — By its superficial surface, with the Abductor and Flexor brevis pollicis. By its deep surface, with the first metacarpal bone. By its inner border, with the Adductor obliquus poUicis. The Flexor brevis pollicis (vi. flexor pollicis brevis) (Fig. 367) consists of two portions, superficial and deep. The superficial portion arises from the outer two- thirds of the lower border of the anterior annular ligaments and sometimes from EXT. LONGUS POLLIC] Mrst metacarpal hont- FlG. 366.- Ill I I lie thumb. the ridge of the trapezium, and passes along the outer side of the tendon of the Flexor longus pollicis; and, becoming tendinous, has a sesamoid bone developed in its tendon, and is inserted into the outer side of the base of the first phalanx of the thumb. The deeper portion of the muscle is very small, and arises from the ulnar side of the first metacarpal bone beneath the Adductor obliquus pollicis, and is inserted into the inner side of the base of the first phalanx with this muscle. Relations. — By its superficial surface, with the palmar fascia. Its deep surface is separated from the Adductor obhquus pollicis by the tendon of the Flexor longus polHcis. By its external (radial) surface, with the Abductor pollicis. The Adductor obliquus pollicis {m. adductor pollicis) (Figs. 366 and 367) arises by several slips from the os magnum, the bases of the second and third THE RADIAL REGION 491 metacarpal bones, the anterior carpal ligaments, and the sheath of the tendon of the Flexor carpi radialis. From this origin the greater number of fibres pass obliquely downward and converge to a tendon, which, uniting, with the tendons of the deeper portion of the Flexor brevis pollicis and the Adductor transversus, Fia. 367.— Muscles of the left hand. Palmar surface. is inserted into the inner side of the base of the first phalanx of the thumb, a sesamoid bone being developed in the tendon of insertion. A considerable fas- ciculus, however, passes more obliquely outward beneath the tendon of the long Flexor to join the superficial portion of the short Flexor and the Abductor pollicis.' • This muscle is described by some as the deep portion of the Flexor brevis pollicis. 492 THE MUSCLES AND FASCIJE Relations. — By its superficial surface, with the Flexor longus pollicis and the superficial head of the Flexor brevis pollicis. Its deep surface is in relation with the deep palmar arch, which passes between the two Adductors. The Adductor transversus pollicis (m. adductor transversus i)ollicis) (Figs. 366 and 367) is the most deeply seated of this group of muscles. It is of a tri- angular form, arising, by its troad base, from the lower two-thirds of the meta- carpal bone of the middle finger on its palmar surface; the fibres, proceeding outward, converge to be inserted, with the deeper part of the Flexor brevis pollicis, and the Adductor obliquus pollicis, into the ulnar side of the base of the first phalanx of the thumb. From the common tendon of insertion a slip is prolonged to the Extensor longus pollicis. Relations. — By its superficial surface, with the tendons of the Flexor profundus and the Lumbricales. Its deep surface covers the first two interosseous spaces, from which it is separated by a strong aponeurosis. Three of these muscles of the thumb, the Abductor, the Adductor transversus, and the Flexor brevis pollicis, at their insertions give off fibrous expansions which join the tendon of the Extensor longus pollicis. This permits of flexion of the pro:dmal phalanx and extension of the terminal phalanx at the same time. Nerves. — The Abductor, Opponens, and superficial head of the Flexor brevis pollicis are supplied by the sixth cervical through the median nerve; the deep head of the Flexor brevis, and the Adductors, by the eighth cervical through the ulnar nerve. Actions. — The actions of the muscles of the thumb are almost sufficiently indicated by their names. This segment of the hand is provided with three Extensors — an Extensor of the metacarpal bone, an Extensor of the first, and an Extensor of the second phalanx ; these occupy the dorsal surface of the forearm and hand. There are also three Flexors on the palmar surface — a Flexor of the metacarpal bone, a Flexor of the proximal, and a Flexor of the terminal phalanx; there is also an Abductor and two Adductors. The Abductor pollicis moves the metacarpal bone of the thumb outward; that is, away from the index finger. The Opponens pollicis flexes the first metacarpal bone — that is, draws it inward over the palm — so as to turn the ball of the thumb toward the fingers, thus producing the movement of opposition. The Flexor brevis pollicis flexes and adducts the proximal phalanx of the thumb. The Adductores pollicis move the metacarpal bone of the thumb inward; that is, toward the index finger. These muscles give to the thumb its extensive range of motion. It will be noticed, however, that in conse- quence of the position of the first metacarpal bone, these movements differ from the corre- sponding movements of the metacarpal bones of the other fingers. Thus extension of the thumb more nearly corresponds to the motion of abduction in the other fingers, and fiexion ' to adduction. 12. The Ulnar Region (Fig. 367). Palmaris brevis. Flexor brevis minimi digiti. Abductor minimi digiti. Opponens minimi digiti. The Palmaris brevis (m. palmaris brevis) is a thin quadrilateral muscle placed beneath the integument on the ulnar side of the hand. It arises by tendinous fasciculi from the anterior annular ligament and palmar fascia; the fleshy fibres pass inward, to be inserted into the skin on the inner border of the palm of the hand. The Abductor minimi digiti (m. abductor digiti quinti) is situated on the ulnar border of the palm of the hand. It arises from the pisiform bone and from the tendon of the Flexor carpi ulnaris, and terminates in a flat tendon, which divides into two_ slips; one is inserted into the ulnar side of the base of the first phalanx of the little finger. The other slip is inserted into the ulnar border of the aponeurosis of the Extensor minimi digiti. THE MIDDLE PALMAR REGION 493 Relations. — By its superficial surface, with the inner portion of the palmar fascia and the Palmnris brevis; by its deep surface, with the Opponens minimi digiti; by its outer border, with tlie Flexor brevis minimi digiti. The Flexor brevis minimi digiti (in. flexor digifi quinti hrevh) lies on the same plane as the preceding muscle, on its radial side. It arises from the convex aspect of the hook of the unciform bone and anterior surface of the annular ligament, and is inserted into the inner side of the base of the first phalanx of the little finger. It is separated from the Abductor at its origin by the deep branches of the idnar artery and nerve. This muscle is sometimes wanting; the Abductor is then, usually, of large size. Relations. — By its superficial surface, with the internal portion of the palmar fascia and the Palmaris brevis; by its deep surface, with the Opponens. The deep branch of the ulnar artery and the corresponding branch of the uhiar nerve pass between the Abductor and Flexor brevis minimi digiti muscles. The Opponens minimi digiti (m. opponens digiti quinti) (Fig. 356) is of a triangular form, and placed immediately beneath the preceding muscles. It arises from the convexity of the hook of the unciform bone and the contiguous portion of the anterior annular ligament; its fibres pass downward and inward, to be inserted into the whole length of the metacarpal bone of the little finger, along its ulnar margin. Relations. — By its superficial surface, with the Flexor brevis and Abductor minimi digiti; by its deep surface, with the Interossei muscles in' the fourth metacarpal space, the metacarpal bone, and the Flexor tendons of the little finger. Nerves. — All the muscles of this group are supplied by the eighth cervical nerve through the ulnar nerve. Actions. — The Abductor minimi digiti abducts the little finger from the middle line of the hand. It corresponds to a dorsal interosseous muscle. It also assists in flexing the proximal phalanx and extending the second and third phalanges. The Flexor brevis minimi digiti abducts the little finger from the middle line of the hand. It also assists in flexing the proximal phalanx. The Opponens minimi digiti draws forward the fifth metacarpal bone, so as to deepen the hollow of the palm. The Palmaris brevis corrugates the skin on the inner side of the palm of the hand and probably serves to protect the ulnar nerve and artery from damage by the pressure of grasping a hard object. 1.3. The Middle Palmar Region. Lumbricales. Interossei dorsales. Interossei palmares. The Lumbricales (?nm. lumbricales) (Fig. 367) are four small fleshy fasciculi, accessories to the deep Flexor muscle. They arise from the tendons of the Flexor profundus digitorum; the^ir.s'^ and second, from the radial side and palmar surface of the tendons of the index and middle fingers, respectively; the third, from the contiguous sides of the tendons of the middle and ring fingers; and the fourth, from the contiguous sides of the tendons of the ring and little fingers. They pass to the radial side of the corresponding fingers and opposite the meta- carpophalangeal articulation each tendon is inserted into the tendinous expansion of the Extensor communis digitorum, covering the dorsal aspect of each finger. The Interossei muscles {mm. interossei) (Figs. 368 and 369) are so named from occupying the intervals between the metacarpal bones, and are divided into two sets, dorsal and palmar. 494 THE 3IUSCLES AND FASCIJE The Dorsal interossei (mm. interossei dorsales) are four in number, larger than the palmar, and occupy the intervals between the metacarpal bones. They are bipenniforra muscles, arising by two heads from the adjacent sides of the meta- carpal bones, but more extensively from the metacarpal bone of the finger into which the muscle is inserted. They are inserted into the bases of the first phalanges and into the aponeurosis of the common Extensor tendon. Between the double orio-in of each of these muscles is a narrow triangular interval, through the first of which passes the radial artery; through each of the other three passes a per- forating branch from the deep palmar arch. The First dorsal interosseous muscle, or Abductor indicis, is larger than the others. It is flat, triangular in form, and arises by two heads, separated by a fibrous arch, for the passage of the radial_ artery from the dorsum to the palm of the hand. The outer head arises from the upper half of the ulnar border of the first meta- carpal bone; the inner head, from almost the entire length of the radial border of the second metacarpal bone; the tendon is inserted into the radial side of the index finger. The Second and Third dorsal interossei are inserted into the middle finger, the former into its radial, the latter into its ulnar side. The Fourth is inserted into the ulnar side of the ring finger. The Palmar interossei (mm. interossei volares), three in number, are smaller than the Dorsal, and placed upon the palmar surface of the metacarpal bones, rather than between them. Each muscle arises from the entire length of the meta- carpal bone of one finger, and- is inserted into the side of the base of the first Fig. 368.— The Dorsal interossei of left hand. The line marked by an * is that from which abduction is made. Fig. 369. — The Palmar interossei of left hand. The line marked by an * is that to which adduction is made. phalanx and aponeurotic expansion of the common Extensor tendon of the same finger. The First arises from the ulnar side of the second metacarpal bone, and is inserted into the same side of the first phalanx of the index finger. The Second arises from the radial side of the fourth metacarpal bone, and is inserted into the same side of the ring finger. The Third arises from the radial side of the fifth metacarpal bone, and is inserted into the same side of the little finger. From SURFACE FORM OF THE UPPER EXTREMITY 495 this account it may be seen that each finger is provided with two Interosseous muscles, with the exception of the little finger, in which the Abductor muscle takes the place of one of the pair. Nerves. — -The two outer Lumbricales are supplied by the sixth cervical nerve, through the third and fourth digital branches of the median nerve; the two inner Lumbricales and all the Interossei are supplied by the eighth cervical nerve, through the deep palmar branch of the ulnar nerve. The third Lumbrical frequently receives a twig from the median. Actions. — The Palmar interossei muscles adduct the finger to an imaginary line drawn longitudinally through the centre of the middle finger; and the Dorsal interossei abduct the fingers from that line. In addition to this, the Interossei, in conjunction with the Lumbricales, flex the first phalanges at the metacarpophalangeal joints, and extend the second and third phalanges in consequence of their insertion into the expansion of the Extensor tendons. The Extensor communis digitorum is believed to act almost entirely on the first phalanges. SURFACE F0R:\I OF THE UPPER EXTREMITY. The Pectoralis major muscle largely influences surface form and conceals a considerable part of the thoracic wall in front. Its sternal origin presents a festooned border which bounds and determines the width of the sternal furrow. Its clavicular origin is somewhat depressed and flattened, and between the two portions of the muscle is often an oblique depression which differentiates the one from the other. The outer margin of the muscle is generally well marked above, and bounds the infraclavicular fossa (Fossa of Mohi-enheim), a triangular interval which separates the Pectoralis major from the Deltoid. It gradually becomes less marked as it approaches the tendons of insertion, and becomes more closely blended with the Deltoid muscle. The lower border of the Pectoralis major forms the rounded anterior axillary fold, and corresponds with the direction of the fifth rib. The Pectoralis minor muscle influences surface form. When the arm is raised its lowest slip of origin produces a local fulness just below the border of the anterior fold of the axilla, and so serves to break the sharp line of the lower border of the Pec- toralis major muscle, which is produced when' the arm is in this position. The origin of the Serratus magnus muscle produces a very characteristic surface marking. When the arm is raised from the side in a well-developed subject, the five or six lower serrations are plainly discernible, forming a zigzag line, caused by the series of digitations, which diminish in size from above downward, and have their apices arranged in the form of a curve. When the arm is lying by the side, the first serration to appear, at the lower margin of the Pectoralis major, •is the one attached to the fifth rib. The Deltoid muscle, with the prominence of the upper extremity of the humerus, produces the rounded outline of the shoulder. It is rounder and fuller in front than behind, where it presents a somewhat flattened foi-m. Its anterior border, above, presents a rounded, slightly curved eminence, w'hich bounds externally the infraclavicular fossa; below, it is closely united with the Pectoralis major. Its posterior border is thin, flattened, and scarcely marked above; below, it is thicker and more prominent. When the muscle is in action, the middle portion becomes irregular, presenting alternate longitudinal elevations and depressions, the elevations corresponding to the fleshy portions, the depressions to the tendinous intersections of the muscle. The insertion of the Deltoid is marked by a depression on the outer side of the middle of the arm. Of the scapular muscles, the only one which materially influences surface form is the Teres major, which assists the Latissimus dorsi in forming the thick, rounded fold of the posterior boundary of the axilla. When the arm is raised, the Coraco- ■ brachialis reveals itself as a long, narrow elevation which emerges from under cover of the anterior fold of the axilla and runs downward, internal to the shaft of the humerus. When the arm is hanging by the side, its front and inner part presents the prominence of the Biceps, bounded on either side by an intermuscular depression. This muscle determines the contour of the front of the arm, and extends from the anterior margin of the axilla to the bend of the elbow. Its upper tendons are concealed by the Pectoralis major and the Deltoid, and its lower tendon sinks into the space at the bend of the elbow, \^^len the muscle is in a state of complete con- traction— that is to say, when the forearm has been flexed and supinated — it presents a rounded convex form, bulged out laterally, and its length is diminished. On each side of the Biceps, at the lower part of the arm, the Brachialis anticus is discernible. On the outer side it forms a narrow eminence which extends some distance up the arm along the border of the Biceps. On the inner side it shows itself only as a little fulness just above the elbow. On the back of the arm the long head of the Triceps may be seen as a longitudinal eminence emerging from under cover of the Deltoid, and gradually merging into the longitudinal flattened plane of the tendon of the muscle on the lower part of the back of the arm. The tendon of insertion of the 496 THE MUSCLES AND FASCIAE muscle extends about half-way up the back of the arm, where it forms an elongated flattened plane when the muscle is in action. Under similar conditions the surface forms produced by the three heads of the muscle are well seen. On the anterior aspect of the elbow are to be seen two muscular elevations, one on each side, separated above and converging below so as to form a triangular space. Of these, the inner elevation, consisting of the Flexors and Pronators, forms the prominence along the inner side and front of the forearm. It is a fusiform mass, pointed above at the internal condyle and gradually tapering off below. The Pronator teres, the innermost muscle of the group, forms the boundary of the triangular space at the bend of the elbow. It is shorter, less prominent, and more oblique than the outer boundary. The most prominent part of the eminence is produced by the Flexor carpi radialis, the muscle next in order on the inner side of the preceding one. It forms a rounded prominence above, and can be traced down- ward to its tendon, which can be felt lying on the front of the wrist, nearer to the radial than to the ulnar border, and to the inner side of the radial artery. The Palmaris longus pre- sents no surface marking above, but below is the most prominent tendon on the front of the wrist, standing out, when the muscle is in action, as a sharp, tense cord beneath the skin. The Flexor subliinis digitorum does not directly influence surface form. The position of its four tendons on the front of the lower part of the forearm is indicated by an elongated depression between the tendons of the Palmaris longus and the Flexor carpi ulnaris. The Flexor carpi ulnaris occupies a small part of the posterior surface of the forearm, and is separated from the Extensor and Supinator group, which occupies the greater part of this surface, by the ulnar furrow, produced by the subcutaneous posterior border of the ulna. Its tendon can be perceived along the ulnar border of the front of the forearm, and is most marked when the hand is flexed and adducted. The deep muscles of the front of the forearm have no direct influence on sur- face form. The external group of muscles of the forearm, consisting of the Extensors and Supi- nators, occupy the outer and a considerable portion of the posterior surface of this region. It has a fusiform outline, which is altogether on a higher level than the Pronator teres and Flexors. Its apex emerges from between the Triceps and Brachialis anticus muscles some distance above the elbow-joint, and acquires its greatest breadth opposite the external condyle, and thence gradually shades off into a flattened surface. About the middle of the forearm it divides into two longitudinal eminences which diverge from each other, leaving a triangular interval between them. The outer of these two groups of muscles consists of the Brachioradialis arid the Fxtensores carpi radialis longior et brevior, which form a longitudinal eminence descending from the external condylar ridge in the direction of the styloid process of the radius. The other and more pos- terior group consists of the Extensor communis digitorum, the Extensor minimi digiti, and the Extensor carpi ulnaris. It commences above as a tapering form at the external condyle of the humerus, and is separated behind at its upper part from the Anconeus by a well-marked furrow, and below, from the Pronato-flexor mass, by the ulnar furrow. In the triangular interval left between these two groups the Extensors of the thumb and index finger are seen. ' The only two muscles of this region which require special mention as independently influencing surface form are the Brachioradialis and the Anconeus. The inner border of the Brachio- radialis forms the outer boundary of the triangular space at the bend of the elbow. It com- mences as a rounded border above the condyle, and is longer, less oblique, and more prominent than the inner boundary. Lower down, the muscle forms a full fleshy mass on the outer side of the upper part of the forearm, and below tapers into a tendon, which may be traced down to the styloid process of the radius. The Anconeus presents a well-marked and characteristic surface form in the shape of a triangular, slightly elevated surface, immediately external to the subcutaneous posterior surface of the olecranon, and diff'erentiated from the common Extensor group by a well-marked oblique longitudinal depression. The upper angle of the triangle corresponds to the external condyle, and is marked by a depression or dimple in this situation. In the interval caused by the divergence from each other of the two groups of muscles into which the Extensor and Supinator group is divided at the lower part of the forearm an oblique elon- gated eminence is seen, caused by the emergence of two of the Extensors of the thumb from their deep origin at the back of the forearm. This eminence, full above and becoming flattened out and partially subdivided below, runs downward and outward over the back and outer sur- face of the radius to the outer side of the wrist-joint, where it forms a ridge, especially marked when the thumb is extended, which passes onward to the posterior aspect of the thumb. The tendons of most of the Extensor muscles are to be seen and felt at the level of the wrist-joint. Most externally are the tendons of the Extensor ossis metacarpi poUicis and the Extensor brevis 2|)ollicis, forming a vertical ridge over the outer side of the loint from the styloid process of the radius to the thumb. Internal to this is the oblique ridge produced by the tendon of the Extensor longus poUicis, very noticeable when the muscle is in action. The Extensor carpi radialis longior is scarcely to be felt, but the Extensor carpi radialis brevior can be distinctly perceived as a vertical ridge emerging from under the inner border of the tendon of the Extensor longus pollicis, when the hand is forcibly extended at the wrist. Internal to this, again, can be felt APPLIED ANATOMY OF THE UPPER EXTREMITY 497 the tendons of the Extensor indicis, Extensor communis digitorum, and Extensor minimi digiti; the latter tendon being separated from those of the common Extensor by a sh(i;ht furrow. The muscles of the hand ai-e ]irinci|)ally concerned, so far as regards surface form, in producing the thenax and hypothenar eminences, and individually are not to be distinguished, on the sur- face, from each other. The Adductor transversus pollicis is, however, an exception to this; its anterior border gives rise to a ridge across the web of skin connecting the thumb to the rest of the hand. The thenar eminence is much larger and rounder than the hi/poiliciicir, which presents a longer and narrower eminence along the ulnar side of the hand. When the Palmaris brevis is in action it produces a wrinkling of the skin over the hypothenar eminence, and a deep dimple on the ulnar border of the hand. The anterior extremities of the Lumbrical muscles help to produce the soft eminences just behind the clefts of the fingers, sejjarated from each other by depressions corresponding to the Flexor tendons in their sheaths. Between the thenar and hypothenar eminences, at the wrist-joint, is a slight groove or depression, widening out as it approaches the fingers; beneath this we have the strong cenli'al part of the palmar fascia. On the back of the hand the Dorsal interossei produce elongated markings between the meta- carpal bones. When the thumb is adducted the First dorsal interosseous forms a prominent fusiform bulging; the other Interossei are not so marked. The skin over the inner side and front of the forearm is thin, smooth, and sensitive; it contains few hairs and many sweat glands. Over the outer side and back of the arm and forearm it is thicker, denser, and less sensitive, and contains more hairs and fewer sweat glands. Over the olecranon the cuticle is thick and rough; the skin is loosely connected to the underlying tissues and becomes transversely wrinkled when the forearm is extended. At the front of the wrist the skin presents three transverse furrows, which correspond from above downward to the position of the styloid process of the ulna, the wrist-joint, and the midcarpal joint, respectively. The skin of the palm of the hand differs considerably from that of the forearm. At the wrist it suddenly becomes hard and dense, and covered by a thick layer of cuticle. The skin in the thenar region presents these characteristics less than elsewhere. In spite of this hardness and density, the skin of the palm is exceedingly sensitive and very vascular. It is destitute of hair, and no sebaceous follicles have been found in this region. It is tied down by fibrous bands along the lines of flexion of the digits, producing certain furrows of a permanent character. One of these, starting from about the tubercle of the scaphoid, curves around the thenar eminence, and ends on the radial border of the hand, a little above the metacarpophalangeal joint of the index finger. It corresponds to the outer border of the central portion of the palmar fascia, and is produced by the movements of the thumb at the carpometacarpal joint. A second line begins at the end of the first and extends oblicjuely across the palm upward and inward, to the ulnar margin about the middle of the fifth metacarpal bone. A third commences at the ulnar border of the hand about an inch below the termination of the second and extends outward across the palm over the heads of the third, fourth, and fifth metacarpal bones. These last two lines are caused by the flexion of the fingers at the metacarpophalangeal joints. Over the fingers the skin again becomes thinner, especially at the flexures of the joints, and over the terminal phalanges it is thrown into numerous ridges in consequence of the arrangement of the papillse in it. .These ridges form, in different individuals, distinctive and permanent patterns, which may be used for purposes of identifi- cation. (See page 1150.) The superficial fascia in the palm is made up of dense fibrofatty tissue. This tissue binds down the skin so firmly to the deep palmar fascia that very little movement is permitted between the two. APPLIED ANATOMY OF THE UPPER EXTREMITY. The student, having completed the dissection of the muscles of the upper extremity, should consider the effects likely to be produced by the action of the various muscles in fracture of the bones. In considering the action of the various muscles upon fractures of the upper extremity, the most common forms of injury have been selected both for illustration and description. Fracture of the middle of the clavicle (Fig. 370) is always attended with considerable dis- placement; the inner end of the outer fragment is displaced inward and backward, while the outer end of the same fragment is rotated forward. The whole outer fragment is somewhat depressed. The deformity is described by saying that the shoulder goes downward, forwari^, and inward. "^ The displacement is produced as follows: inward, by the muscles passing from the thorax to the outer fragment of the clavicle, to the scapula, and to the humerus— viz., the Subclavius and the Pectoralis minor, and, to a less extent, the Pectoralis major and the Latissimus dorsi; back- ward, in consequence of the rotation of the outer fragment. The Serratus magnus causes the 32 498 THE MUSCLES AND FASCIA scapula to rotate on the thoracic wall; this carries the acromion and outer end of the outer fragment of the clavicle forward and causes the piece of bone to rotate around a vertical axis through its centre, and so carries the inner end of the outer portion backward. The depression of the whole outer fragment is produced by the weight of the arm and by the contraction of the Deltoid. The outer end of the inner fragment appears to be elevated, the skin being drawn tensely over it; this is owing to the depression of the outer fragment, as the inner fragment is usually kept fixed by the costoclavicular ligament and by the antagonism between the Sterno- mastoid and Pectoralis major muscles. But it may be raised by an unusually strong Sterno- mastoid, or by the inner end of the outer fragment getting below and behind it. The causes of displacement having been ascertained, it is easy to apply the appropriate treatment. The outer fragment is to be drawn outward, and, together with the scapula, raised upward to a level with the inner fragment, and retained in that position. This deformity is corrected by carrying the shoulder upward, outward, and backward. In fracture of the acromial end of the clavicle, between the conoid and trapezoid ligaments onlv slight displacement occurs, as these ligaments, from their oblique insertion, serve to hold both portions of the bone in apposition. Fracture, also, of the sternal end, internal to the costoclavicular liga- ment, is attended with only slight displacement, this ligament serving to retain the fragments in close ap- position. Fracture of the acromion process usually arises from violence applied to the upper and outer part of the shoulder; it is generally known by the rotundity of the shoulder being lost, from the Deltoid drawing -7 /m\ \M^'t'Vl"*if'S will he found resting on the front and upper part of the head of the humerus. In order to relax the anterior and outer fibres of the Deltoid (the opposing muscle), the arm should be drawn forward across the thorax and the elbow well raised, so that the head of the bone may press the acromion process upward and retain it in its position. Fracture of the coracoid process is an extremely rare accident, and is usually caused by a sharp blow on the point of the shoulder. Displacement is here produced by the combined actions of the Pectoralis minor, the short head of the Biceps, and the Coraco- brachialis, the former muscle drawing the fragment inward, and the latter muscles directly downward, the amount of displacement being limited by the connection of this process to the acromion by means of the coraco-acromial ligament. In many cases there appears to have been little or no displacement, from the fact that the coracoclavicular ligament has remained intact, and has kept the separated fragment from displacement. In order to relax these muscles and replace the frag- ments in close apposition, the forearm should be flexed so as to relax the Biceps^ and the arm drawn forward and inward across the chest, so as to relax the Coracobrachialis; the humerus should then be pushed upward against the coraco-acromial ligament, and the arm retained in that position. Fracture of the surgical neck of the humerus (Fig. 371) is very common, is attended with considerable displacement, and its appearances correspond somewhat with those of dislocation of the head of the humerus into the axilla. The upper fragment is slightly elevated under the coraco-acromial ligament by the muscles attached to the greater and lesser tuberosities; the lower fragment is drawn inward by the Pectoralis major, Latissimus dorsi, and Teres major; and the humerus is thrown obliquely outward from the side by the Deltoid, and occasionally elevated so as to cause the upper end of the lower fragment to project beneath and in front of the coracoid process. The deformity is reduced by fixing the shoulder, and drawing the arm outward and downward. To counteract the opposing muscles, and to keep the fragments in position, a conical-shaped pad should be placed with the apex in the axilla; while the forearm is flexedto an angle of 90 degrees the shoulder is padded with cotton, a shoulder-cap of plaster of Paris is applied to cover the shoulder, a portion of the thorax and back, and the arm down to the external condyle (Scudder). The arm, with the elbow slightly forward, is bandaged to the side. In some cases a splint is placed between the axillary pad and the inner side of the arm. APPLIED ANATOMY OF THE UPPER EXTREMITY 499 In fracture of the shaft of the humerus below the insertion of the Pectoralis major, Latissimus dorsi, and Teres major, and above the insertion of the Deltoid, there is also considerable deformity, the upper fragment being drawn inward by the first-mentioned muscles, and the lower fragment upward and outward by the Deltoid, pro- ducing shortening of the limb and a considerable promi- nence at the seat of fracture, from the fractured ends of the bone riding over one another, especially if the fracture takes place in an oblique direction. The fragments may be brought into apposition by extension from the elbow, and are retained in that position by adopting the same means as in the )jreceding injury, or by the use of an internal angular splint with three short humeral splints. In fractures of the shaft of the hmiierus immediately be- low the insertion of the Deltoid, the amount of deformity depends greatly upon the direction of the fracture. If it occurs in a transverse direction, only slight displacement takes place, the upper fragment being drawn a little for- ward; but in oblic|ue fracture the combined actions of the Biceps and Brachialis anticus muscles in front and the Triceps behind draw upward the lower fragment, causing it to glide over the upper fragment, either backward or for- ward, according to the direction of the fracture. Simple extension reduces the deformity, and the application of an internal angular splint and three short humeral splints will retain the fragments in apposition. Care should be taken not to raise the elbow, but the forearm and hand may be sup- ported in a sling. Fracture of the humerus (Fig. 372) above the condi/le deserves very attentive consideration, as the general appearances correspond somewhat with those produced by separation of the epiphysis of the humerus, and with those of dislocation of the radius and ulna backward. If the direction of the fracture is oblique from above, downward and forward, the lower fragment -Fracture of the h the condyle. Fig. .373. — Fracture of the olecranon. is drawn upward by the Brachialis anticus and Biceps in front and the Triceps behind; and at the same time is drawn backward behind the upper fragment by the Triceps. This injury may be differentiated from dislocation by the increased mobility in fracture, the existence of crepitus, and the fact of the deformity being remedied by extension, on the discontinuance of which it is reproduced. The age of the patient is of importance in distinguishing this form of injury from separation of the epiphysis. If fractui'e occurs in the opposite direction to that shown in Fig. 362, the lower fragment is drawn upward and forward, causing a considerable prominence in front, and the upper fragment projects backward beneath the tendon of the Triceps muscle. 500 THE MUSCLES AND FASCIA Fracture of the olecranon process (Fig. 373) is a frequent accident. The detached fragment is displaced upward, by the action of the Triceps muscle, from half an inch to two inches; the prominence of the elbow is consequently lost, and a deep hollow is felt at the back part of the joint, which is much increased on flexing the limb. The patient at the same time loses, more or less, the power of extending the forearm. The treatment consists in relaxing the Triceps by extending the limb, and retaining it in the extended position by means of a long straight splint applied to the front of the arm; the fragments are thus brought into close appo- sition, and may be further approximated by drawing down the upper fragment. The frag- ments may be wired together and thus prevent the formation of a ligamentous union, as is generally the case when wiring is not em- ployed; passive motion must be instituted at the end of the third week to prevent ankylosis. Fracture of the neck of the radius is an exceedingly rare accident, and is generally caused by direct violence. Its' diagnosis is somewhat obscure, on account of the slight deformity visible, the injured part being surrounded by a large number of muscles; but the movements of pronation and supination are entirely lost. The upper fragment is drawn outward by the Supinator [brevis], the extent of displacement being limited by the attachment of the orbicular ligament. The lower fragment is drawn forward and slightly upward by the Biceps, and inward by the Pronator teres, its displacement forward and upward fjeing counteracted in some degree by the Supinator. The treatment essentially consists in relaxing the Biceps, Supinator, and Pro- nator teres muscles by flexing the forearm, and placing it in a position midw'ay between pronation and supination, extension having been previously made so as to bring the parts in apposition. Fig. 374.— Fracture of the shaft of th. Fig. 375. — Fracture of the lower end of the radius. In fracture of the radius below the insertion of the Biceps, but above the insertion of the Pronator teres, the upper fragment is strongly supinated by the Biceps and Supinator, and at the same time drawn forward and flexed by the Biceps; the lower fragment is pronated and drawn inward toward the ulna by the Pronators. Thus, there is extreme displacement with very little deformity. In treating such a fracture the arm must be put up in a position of supination, otherwise union will take place with great impairment of the movements of the hand. In fractures of the radius below the insertion of the Pronator teres (Fig. 374), the upper fragment is drawn upward by the Biceps and inward by the Pronator teres, holding a position midway between pronation and supination, and a degree of fulness in the upper half of the fore- arm is thus produced; the lower fragment is drawn downward and inward toward the ulna by the Pronator quadratus, and thrown into a state of pronation by the same muscle; at the same time, the Brachioradialis, by elevating the styloid process, into which it is inserted, will serve to depress the upper end of the lower fragment still more toward the ulna. In order to relax the opposing muscles the forearm should be bent, and the limb placed in a position midway between pronation and supination; the fracture is then easily reduced by extension from the wrist and elbow; well-padded splints should be applied on both sides of the forearm from the elbow to the wrist; the hand, being allowed to fall, will, by its own weight, counteract the action of the Pronator quadratus and of the Brachioradialis, and elevate the lower fragment to the level of the upper one. In fracture of the shaft of the ulna the upper fragment retains its usual position, but the lower fragment is drawn outward toward the radius by the Pronator quadratus, producing a well- OF THE LOWER EXTREMITY 501 niarked depression at the seat of fracture and some fulness on the dorsal and palmar surfaces of the forearm. The fracture is easily reduced by extension from the wrist and forearm. The forearm should be flexed, and placed in a position midway between pronation and supination, and well-padded splints applied from the elbow to the ends of the fingers. In fracture of the shajts of the radius and ulna together the lower fragments are drawn ujiward, sometimes forward, sometimes backward, according to the direction of the fracture, by the combined actions of the Flexor and Extensor muscles, producing a degree of fulness on the dorsal or palmar surface of the forearm; at the same time the two fragments are drawn into contact by the Pronator quadratus, the radius being in a state of pronation; the upper fragment of the radius is drawn upward and inward by the Biceps and Pronator teres to a higher level than the ulna; the upper portion of the ulna is slightly elevated by the Brachialis anticus. The fracture may be reduced by extension from the wrist and elbow, and the forearm should be placed in the same position as in fracture of the ulna. In fracture of the lower end of the radius (Colles' fracture) (Fig. 375) the displacement which is produced is very considerable, and bears some resemblance to dislocation of the carpus back- ward, from which it should be carefully distinguished. The lower fragment is displaced back- ward and upward, but this displacement is probably due to the force of the blow driving the portion of the bone into this position and not to any muscular influence. The upper fragment projects forward, often lacerating the substance of the Pronator quadratus, and is drawn by this muscle into close contact with the lower end of the ulna, causing a projection on the anterior surface of the forearm, immediately above the carpus, from the Flexor tendons being thrust forward. This fracture may be distinguished from dislocation by the deformity being removed on making sufficient extension, when crepitus may be occasionally detected; at the same time, on extension being discontinued, the parts immediately resume their deformed appearance. The age of the patient will also assist in determining whether the injury is fracture or separation of the epiphysis. Reduction is effected by hyperextension, longitudinal traction, and forced flexion.' The posterior straight splint with suitable pads is the best dressing. MUSCLES AND FASCIA OF THE LOWER EXTREMITY. The muscles of the lower extremity are subdivided into groups corresponding with the different regions of the limb. I. Iliac Region. 2. Internal Femoral Region. Psoas magnus. Psoas parvus. Iliacus. Gracilis. Pectineus. Adductor longus. Adductor brevis. Adductor magnus. II. Thigh. 1. Anterior Femoral Region. Tensor fasciae femoris. Sartorius. [■ Rectus femoris. Quadriceps J Vastus externus. extensor. | Vastus internus. I Crureus. Subcrureus. III. Hip. 3. Gluteal Region. Gluteus maximus. Gluteus medius. Gluteus minimus. Pyriformis. Obturator internus. Gemellus superior. Gemellus inferior. Quadratus femoris. Obturator externus. 502 THE MUSCLES AND FASCIA 4. Posterior Femoral Region. -TT • ,. f Biceps femor is. Hamstring o •* i- , '^ i bemitendinosus. muscles. j o • u bemimem branosus. .IV. Leg. 5. Anterior Tibiofibular Region. Tibialis anticus. Extensor proprius hallucis. Extensor longus digitorum. Peroneus tertius. 6. Posterior Tibiofibular Region. Superficial Layer. Gastrocnemius. Soleus. Plantaris. Deep Layer. Popliteus. Flexor longus hallucis. Flexor longus digitorum. Tibialis posticus. 7. Fibular Region. Peroneus longus. Peroneus brevis. V. Foot. 8. Dorsal Region. Extensor brevis digitorum. 9. Plantar Region. First Layer. Abductor hallucis. Flexor brevis digitorum. Abductor minimi digiti. Second Layer. Flexor accessorius. Lumbricales. Third Layer. Flexor brevis hallucis. Adductor obliquus hallucis. Flexor brevis minimi digiti. Adductor transversus hallucis. Fourth Layer. Interossei. I. MUSCLES AND FASCIiE OF THE ILIAC REGION. Psoas magnus. Psoas parvus. Iliacus. Dissection. — No detailed description is required for the dissection of these muscles. On the vemoval of the viscera from the abdomen they are exposed, covered by the peritoneum and a thin layer of fascia, the iliac fascial The iliac fascia (fascia iliaca) is the aponeurotic layer which lines the back part of the abdominal cavity, and covers the Psoas and Iliacus muscles throughout their whole extent. It is thin above, and becomes gradually thicker below as it approaches the femoral arch. The portion covering the Psoas is thickened, above, to form the ligamentum arcuatum internum; internally it is attached, by a series of arched processes, to the intervertebral substances, to the prominent margins of the bodies of the vertebrae, and to the upper part of the sacrum, the intervals so left, opposite the constricted portions of the bodies, transmitting the lumbar arteries and veins and the fila- ments of the sympathetic cord. Externally, above the crest of the ilium, this portion of the iliac fascia is continuous with the anterior lamella of the lumbar fascia covering the front of the Quadratus lumborum, but below the crest of the ilium it is continuous with the fascia covering the Iliacus. OF THE ILIA C REGION 503 The portion investing the Iliacus is connected externally to the whole length of the inner border of the crest of the ilium, and internally to the brim of the true pelvis, where it is continuous with the periosteum; at the iliopectineal emi- nence it receives the tendon of insertion of the Psoas parvus, when that muscle exists. External to the external iliac vessels, this fascia is intimately connected to the posterior margin of Poupart's ligament, and is continuous with the fascia transversalis. Immediately to the outer side of the external iliac vessels, as they pass beneath Poupart's ligament, the fascia iliaca is prolonged backward and inward from Poupart's ligament as a band, the iliopectineal ligament (Fig. 376), and is attached to the iliopectineal eminence. The ligament divides the space between Poupart's ligament and the horizontal ramus of the pubis into two parts, the inner of which {lacuna vaso- rum) transmits the femoral vessels, and the femoral branch of the genitofemoral nerve is bounded internally by the base of Gimbernat's ligament and contains the femoral ring. The outer part (lacuna mus- culorum) transmits the Ilio- psoas and the femoral nerve and the external cutaneous nerve (Fig. 376). Internal to the vessels the iliac fascia is at- tached to the iliopectineal line behind the conjoined tendon, where it is again continvious with the transversalis fascia; and, corresponding to the point where the femoral vessels pass into the thigh, this fascia de- scends behind them, forming the posterior wall of the fem- oral sheath. This portion of the iliac fascia which passes behind the femoral vessels is also attached to the iliopec- tineal line beyond the limits of the attachment of the con- joined tendon; at this part it is continuous with the pubic portion of the fascia lata of the thigh. The external iliac vessels lie in front of the iliac fascia, but all the branches of the lumbar plexus lie behind it; it is separated from the peritoneum by a quantity of loose areolar tissue. The femoral sheath (fascia cruris) is formed by the transversalis fascia in front of the vessels and the iliac fascia behind them. In the thigh the fasciae join to the inner side of the femoral vein, a space, the femoral canal (canalis femoralis) (Fig. 376), intervening between the vein and their junction. Between the femoral vein and the edge of Gimbernat's ligament is the femoral or crmal ring (annulus femoralis) (Fig. 376). It is the upper opening of the femoral canal, just mentioned, and leads into the cavity of the abdomen. It is bounded in front by Poupart's ligament; behind by the horizontal ramus of the pubes covered by the Pectineus muscle; internally by the base of Gimbernat's ligament; externally by the fibrous septum lying in the inner side of the femoral vein. The PECTINEUS ligament and the relation of the parts pass- ath it. (Poirier and Charpy.) 504 THE MUSCLES AND FASCIJE femoral ring is closed by the septum crurale of Cloquet (septum femorale [Cloqueti]), which is a process of transversalis fascia (Fig. 378). The femoral canal is the interval between the femoral vein and the inner wall of the femoral sheath. This canal extends from the femoral ring to the saphenous opening. The Psoas magnus (m. psoas major) (Fig. 379) is a long fusiform muscle placed on the side of the lumbar region of the vertebral column and the margin of the pelvis. It arises from the front of the bases and lower borders of the transverse processes of the lumbar vertebrae by five fleshy slips; also from the sides of the bodies and the corresponding intervertebral substances of the last thoracic and all the lumbar vertebrte. The muscle is connected to the bodies of the vertebrae by five slips; each slip is attached to the upper and lower margins of two vertebrae, and to the intervertebral substance between them, the slips themselves being connected by the tendinous arches which extend across the constricted part of the bodies, and beneath which pass the lumbar arteries and veins and filaments of the sympathetic cord. These tendinous arches also give origin to muscle fibres, and protect the bloodvessels and nerves from pressure during the action of the muscle. The first slip is attached to the contiguous margins of the last thoracic and first lumbar vertebrte; the last to the contiguous margins of the fourth and fifth lumbar ver- tebrae, and to the intervertebral substance. From these points the muscle descends across the brim of the pelvis, and, diminishing gradually in size, passes beneath Poupart's ligament, and terminates in a tendon which, after receiving nearly =the whole of the fibres of the Iliacus, is inserted into the lesser trochanter of the femur. Relations. — In the lumbar region, by its anterior surface, wliich is placed behind the peri- toneum, the Psoas magnus is in relation with the fascia which covers it, with the ligamentum arcuatum internum, the kidney, Psoas parvus, renal vessels, ureter, spermatic vessels, genito- femoral nerve, and the colon. In many cases the vermiform appendix rests upon the right Psoas muscle (page 505). By its posterior surface, with the transverse processes of the lumbar ver- tebrte and the Quadratus lumborum muscle, from which it is separated by the anterior lamella of the lumbar fascia. The lumbar plexus is situated in the posterior part of the substance of the muscle. By its inner side the muscle is in relation with the bodies of the lumbar vertebrae, the lum'bar arteries, the ganglia of the sympathetic cord, and their branches of communication with the spinal nerves; the lumbar nodes; the inferior vena cava on the right and the aorta on the left side, and along the brim of the pelvis with the external iliac artery. In the thigh it is in relation, superfidaUy, with the fascia lata; deeply, with the capsular ligament of the hip, from which it is separated by a synovial bursa {bursa iliopectinea), which frequently communi- cates with the cavity of the joint through an opening of variable size; between the tendon and part of the lesser trochanter is the bursa iliaca suhtendinea; by its inner border, with the Pectineus and internal circumflex artery, and also with the femoral artery, which slightly overlaps it; by its outer border, with the femoral nerve and Iliacus muscle. The Psoas parvus (m. psoas minor) (Fig. 379) is a long, slender muscle placed in front of the Psoas magnus. It arises from the sides of the bodies of the last thoracic and first lumbar vertebrae and from the intervertebral substance between them. It forms a small, flat, fleshy bundle, which terminates in a long flat tendon inserted into the iliopectineal eminence, and, by its outer border, into the iliac fascia. This muscle is most often absent, and is sometimes double. The Iliacus (in. iliacus) (Fig. 379) is a fiat, triangular muscle which fills up the whole of the iliac fossa. It arises from the upper two-thirds of this fossa and from the inner margin of the crest of the ilium; behind, from the iliolumbar liga- ment and base of the sacrum; in front, from the anterior superior and anterior inferior spinous processes of the ilium, from the notch between them. The fibres converge to be inserted into the outer side of the tendon of the Psoas, some of them' being prolonged and attached to the shaft of the femur for about an inch below and in front of the lesser trochanter.' The most external fibres are inserted into the capsule of the hip-joint. ' The Psoas and Iliacus are often regarded as a single muscle — the Iliopsoas — having two heads of origin and a single insertion. THE ANTERIOR FEMORAL REGION 505 Relations. — Within the abdomen, by its anterior surface, with the ihac fossa, which separates the muscle from the peritoneum, and with the external cutaneous nerve; on the right side, with the cecum; on the left side, with the pelvic colon; by its posterior surface, with the iliac fossa; by its inner border, with the Psoas magnus and femoral nerve. In the thigh, it is in relation, by its superficial surface, with the fascia lata, the Rectus and Sartorins muscles, and the profunda femoris artery; by its deep surface, with the capsule of the hip-joint, a synovial bursa common to it and the Psoas magnus being interposed. Nerves. — The Psoas magnus is supplied by the anterior branches of the second and third lumbar nerves; the Psoas parvus, when it exists, is supplied by the anterior branch of the first lumbar nerve; and the Iliacus, by the anterior branches of the second and third lumbar nerves through the femoral. Actions. — The Psoas and Iliacus muscles, acting from above, flex the thigh upon the pelvis. Actincf from below, the femur being fixed, the muscles of both sides bend the lumbar portion of the vertebral column and pelvis forward. They also serve to maintain the erect position, by supporting the vertebral column and pelvis upon the femur, and assist in raising the trunk when the body is in the recumbent posture. The Psoas par\'us is a tensor of the iliac fascia. It assists in flexing the lumbar portion of the vertebral column laterally, the pelvis being its fixed point. Applied Anatomy. — There is no definite septum between the portions of the iliac fascia covering the Psoas and Iliacus, respectively, and the fascia is only connected to the subjacent muscles by a quantity of loose connective tissue. When an abscess forms beneath this fascia, as it is very liable to do, the pus is contained in an osseofibrous cavity, which is closed on all sides within the abdomen, and is open only at its lower part, where the fascia is prolonged over the muscle into the thigh. Abscess within the sheath of the Psoas muscle (Psoas abscess) is generally due to tuberculous caries of the bodies of the lower thoracic or of the lumbar vertebrae. When the disease is in the thoracic region, the pus courses down the posterior mediastinum, in front of the bodies of the vertebrae, and, passing beneath the ligamentum arcuatum internum, enters the sheath of the Psoas muscle, down which it passes as far as the pelvic brim; it then gets beneath the iliac portion of the fascia and fills up the iliac fossa. In consequence of the attachment of the fascia to the pelvic brim, it rarely finds its w'ay into the pelvis, but passes by a narrow opening under Poupart's ligament into the thigh, to the outer side of the femoral vessels. It thus follows that a Psoas abscess may be described as consisting of four parts: (11 A somewhat narrow channel at its upper part, in the Psoas sheath; (2) a dilated sac in the iliac fossa; (.3) a constricted neck under Poupart's ligament; and (4) a dilated sac in the upper part of the thigh. When the lumbar vertebrte are the seat of the disease, the pus finds its way directly into the substance of the muscle. If a Psoas abscess forms, the muscle fibres are destroyed, and the nerve cords contained in the abscess are isolated and exposed in its interior; the femoral vessels which lie in front of the fascia remain intact, and the peritoneum seldom becomes implicated. All Psoas abscesses do not, however, pursue this course; the pus may leave the muscle above the crest of the ilium, and, tracking backward, may point in the loin (lumbar abscess); or it may point above Poupart's ligament in the inguinal region; or it may follow the course of the iliac vessels into the pelvis, and, passing through the great sacrosoiatic notch, discharge itself on the back of the thigh; it may open into the bladder or find its way into the perineum, or it may pass down the thigh to the popliteal space or even lower. Straiti of the Psoas muscle is not unusual, and induces pain which may be mistaken for appendicitis. The bursa beneath the tendon of the Psoas and Iliacus and the hip-joint or that between the tendon and the lesser trochanter may greatly enlarge and produce pain and disablement. Byron Robinson^ pointed out that trauma of the Psoas muscle may be an important factor in the etiology of appendicitis, as it may induce periappendicular adhesions which interfere with the circulation of blood and feces. Robinson says, in the previously quoted article, that in 46 per cent, of men and in 20 per cent, of women the appendix rests on the Psoas muscle. II. MUSCLES AND FASCIA OF THE THIGH. 1. The Anterior Femoral Region. ( Rectus femoris. Tensor fasciae femoris. Quadriceps J Vastus externus. Sartorius. extensor. | Vastus internus. t Crureus. Subcrureus. Dissection. — To expose the muscles and fasciae in this region, make an incision along Poupart's ligament, from the anterior superior spine of the ilium to the spine of the os pubis; 'Annals of Surgery. April, 1901. 506 THE MUSCLES AND FASCIyE a vertical incision from the centre of this, along the middle of the thigh to below the knee-joint; and a transverse incision from the inner to the outer side of the leg, at the lower end of the ver- tical incision. The flaps of integument having been removed, the superficial and deep fasciae should be examined. The more advanced student should commence the study of this region by an examination of the anatomy of femoral hernia and Scarpa's triangle, the incisions for the dissection of which are marked out in Fig. 377. ■ 1. Dissection of femoral hernia, and Scarpa's triangle. 2. Front of thigh. Superficial Fascia. — The superficial fascia forms a continuous layer over the whole of the thigh. It consists of areolar tissue, containing in its meshes much fat, and is capable of being separated into two or more layers, between which are found the superficial vessels and nerves. It varies in thickness in difl^erent parts of the limb; in the groin it is thick, and the two layers are separated from one another by the superficial inguinal lymph nodes, the internal \ I '^ v' / ^. ^~»t.i-i..."... >|ic;iriin(c.s presented by the tendon of this muscle, it must be dividrd near ils iiiscrlioii and rcllcclcil inward. Relations. --fr/////» the prlri.^ (his muscle is in relation, by its decj) surface, with the obturator membrane and inner surface of the anterior wall of the pelvis; by its superficial surface, with the pelvic and obturator fascise, which separate it from the Levator ani ; and it is crossed by the internal pudic vessels and nerve. This surface forms the outer boundary of the ischio- i\'ed from without and below. The quadratus having !o not shown. (Spalteholz.) rectal fossa. External to the pelvis it is covered by the Gluteus maximus, is crossed by the great sciatic nerve, and rests on the back part of the hip-joint. As the tendon of the Obturator internus emerges from the lesser sacrosciatic foramen it is overlapped by the two Gemelli, while nearer its insertion the Gemelli pass in front of it and form a groove in which the tendon lies. A synovial bursa, narrow and elongated in form, is usually found' between the tendon of this muscle and the capsular ligament of the hip ; it occasionally communicates with the bursa between the tendon and the tuberosity of the ischium, the two forming a single sac. 520 THE MUSCLES AND FASCIA The Gemelli (Fig. 375) are two small muscular fasciculi, accessories to the tendon of the Obturator internus, which is received into a groove between them. They are called superior and inferior. The Gemellus superior (m. gemellus superior), the smaller of the two^ arises from the outer surface of the spine of the ischium, and, passing horizontally outward, becomes blended with the upper part of the tendon of the Obturator internus, and is inserted with it into the inner surface of the great trochanter. This muscle is sometimes wanting. Relations, — By its superficial surface, with the Gluteus maximus and the sciatic vessels and nerves; by its deep surface, with the capsule of the hip-joint; by its upper border, with the lower margin of the Pyriformis; by its lower border, with the tendon of the Obturator internus. Anterior division of obtuiato) ne)ve Ante) 10) jnfettor iliac smne the Museum of the Royal College of The Gemellus inferior (m. gemellus inferior) arises from the upper part of the tuberosity of the ischium, where it forms the lower edge of the groove for the Obturator internus tendon, and, passing horizontally outward, is blended with the lower part of the tendon of the Obturator internus, and is inserted with it into the inner surface of the great trochanter. Relations. — By its superficial surface, with the Gluteus maximus and the sciatic vessels and nerves; by its deep surface, with the capsular ligament of the hip- joint; by its upper border, with the tendon of the Obturator internus; by its lower border, with the tendon of the Obturator externus and Quadratus femoris. The Quadratus femoris (m. quadratus femoris) (Fig. 384) is a short, flat muscle, quadrilateral in- shape, situated between the Gemellus inferior and the upper margin of the Adductor magnus. It arises from the upper part of the exter- nal lip of the tuberosity of the ischium, and, proceeding horizontall}^ outward, is OF THE HIP 521 inserted into the upper part of the Hnea quadrata; that is, the line which crosses the posterior intertrochanteric Hne. Relations. — By its superficial surface, with the Gluteus maximus and the sciatic vessels and nerves; bv its deej) surface, with the tendon of the Obturator externus and trochanter minor and with the capsule of' the hip-joint; by its upper border, with the Gemellus inferior. Its lower border is separated from the Adductor magnus by the terminal branches of the internal circumflex vessels. A synovial bursa is often found between the under surface of this muscle and the lesser trochanter, which it covers. Dissection. — In order to expose the next muscle (the Obturator externus) it is necessary to remove the Psoas, Iliacus, Pectineus, and Adductores brevis and longus muscles from the front and inner side of the thigh, and the Gluteus maximus and Quadratus femoris from the back part. Its dissection should, consequently, be postponed until the muscles of the anterior and internal femoral regions have been explained. The Obturator externus (m. obturator externus) (Figs. .385 and 386) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis. It arises from the margin of bone immediately around the inner side of the obturator foramen — viz., from the body and ramus of the os pubis and the ramus of the ischium; it also arises from the inner two-thirds of the outer surface of the obturator membrane, and from the tendinous arch which completes the canal for the passage of the obturator vessels and nerves. The fibres from the pubic arch extend on to the inner surface of the bone, from which they obtain a narrow origin between the margin of the foramen and the attachment of the membrane. The fibres converging pass backward, outward, and upward, and terminate in a tendon which rims across the back part of the hip-joint, and is inserted into the digital fossa of the femur. Relations. — In front, with the Psoas, Iliacus, Pectineus, Adductor magnus, and Adductor brevis; and more externally, with the neck of the femur and capsule of the hip-joint. The external and internal terminal branches of the obturator artery and accompanying veins lie between this muscle and the obturator membrane; the superficial part of the obturator nerve lies above the muscle, and the deep branch perforates it; by its deep surface, with the obturator membrane and Quadratus femoris at its insertion. Nerves. — The Gluteus maximus is supplied by the fifth lumbar and first and second sacral nerves through the inferior gluteal nerve from the sacral plexus; the Gluteus medius and mini- mus, by the fom'th and fifth lumbar and first sacral nerves, through the superior gluteal; the Pyriformis is supplied by the first and second sacral nerves; the Gemellus inferior and Quad- ratus femoris by the last lumbar and first sacral ner\-e; the Gemellus superior and Obturator internus by the fifth lumbar and first and second sacral nerves, and the Obturator externus by the second, third, and fourth lumbar nerves through the obturator nerve. Actions. — The Gluteus maximus, when it takes its fixed point from the pelvis, extends the femur and brings the bent thigh into a line with the body. Taking its fixed point from below, it acts upon the pelvis, supporting it and the whole trunk upon the head of the femur, which is especially obvious in standing on one leg. Its most powerful actions are to hold the head of the femur in close approximation to the acetabulum in walking and to cause the body to regain the erect position after stooping by drawing the pelvis backward, being assisted in this action by the Biceps, Semitendinosus, and Semimembranosus. The Gluteus maximus is a tensor of the fascia lata, and by its connection with the ihotibial band it steadies the femur on the articular surface of the tibia during standing, when the Extensor muscles are relaxed. The lower part of the muscle also acts as an Adductor and External rotator of the limb. The Gluteus medius and minimus abduct the thigh when the limb is extended, and are principally called into action in supporting the body on one limb, in conjunction with the Tensor fasciae femoris. Their anterior fibres, by drawing the great trochanter forward, rotate the thigh inward, in which action they are also assisted by the Tensor fasciae femoris. The remaining muscles are power- ful Rotators of the thigh outward. In the sitting posture, when the thigh is flexed upon the pelvis, their action as Rotators cease, and they become Abductors, with the exception of the Obturator externus, which still rotates the femur outward. When the femur is fixed, the Pyriformis and Obturator muscles serve to draw the pelvis forward if it has been inclined backward, and assist in steadying it upon the head of the femm-. 522 THE MUSCLES AND FASCIA 4. The Posterior Femoral Region. {Hamstring Muscles.) Biceps femoris. Semitendinosus. Semimembranosus. Dissection (Fig. 383). — Make a vertical incision along the middle of the back of the thigh, from the lower fold of the buttock to about three inches below the back of the knee-joint, and there connect it with a transverse incision, carried from the inner to the outer side of the leg. Make a third incision transversely at the junction of the middle with the lower third of the thigh. The integument having been removed from the back of the knee, and the boundaries of the popliteal space having been examined, the removal of the integument from the remaining part of the thigh should be continued, when the fascia and muscles of this region will be exposed. GLUTE ADDUCTOR MAGNUS SEMIMEMBRANOSUS P0PLITEU8 Fig. 387. — Diagram showing the attachments of the muscles of the thigh. Posterior aspect. Origins, red; insertions, blue. The Biceps femoris (m. biceps femoris) is a large muscle, of considerable length, situated on the posterior and outer aspect of the thigh (Figs. 384 and 388). It arises by two heads. One, the long head (capid longum), arises from the lower and inner impression on the back part of the tuberosity of the ischium, by a tendon THE POSTERIOR FEMORAL REGION 523 common to it and the Semitendinosiis, and from the lower part of the great sacro- sciatic Hgament. The femoral or short head (caput breve) arises from the outer lip of the linea aspera, between the Adductor magnus and Vastus externus, extend- ing up almost as high as the insertion of the Gluteus maximus; from the outer prolongation of the linea aspera to within two inches of the outer condyle, and from the external intermuscular septum. The fibres of the long head form a fusi- Fig. 38S.— Region of the knee, seen obliquely from behind and within Right limb. (Toldt.) form belly, which, passing obliquely downward and a little outward, terminates in an aponeurosis which covers the posterior surface of the muscle, and receives the fibres of the short head; this aponeurosis becomes gradually contracted into a tendon, which is inserted into the outer side of the head of the fibula, and by a small slip into the lateral surface of the external tuberosity of the tibia. At its insertion the tendon divides into two portions, which embrace the long external lateral ligament of the knee-joint. From the posterior border of the tendon a 524 THE MUSCLES AND FASCIjE thin expansion is given off to the fascia of the leg. The tendon of this muscle forms the outer Hamstring. Relations. — By its superficial surface, with the Gluteus maximus and the small sciatic nerve, the fascia lata, and integument. By its deep surface, with the Semimembranosus, Adductor magnus, and Vastus externus, the great sciatic nerve, and, near its insertion, with the external head of the Gastrocnemius, the Plantaris, the superior external articular arterj', and the external popliteal nerve. A bursa {bursa m. bicijntis femoris inferior) is found between the long tendon of origin of this muscle and the Semitendinosus and Semimembranosus. Sometimes there is a bursa {bursa bieipitogastrocneynialis) between the tendon of the insertion of the Biceps and the origin of the Gastrocnemius, and there is a bursa {bursa m. bicipitis femoris inferior) between the tendon of the Biceps and the external lateral ligament. The Semitendinosus (m. semitendinosus) (Figs. 384 and 388), remarkable for the great length of its tendon, is situated at the posterior and inner aspect of the thigh. It arises from the lower and inner impression on the tuberosity of the ischium by a tendon common to it and the long head of the Biceps femoris; it also arises from an aponeurosis which connects the adjacent surfaces of the two muscles to the extent of about three inches after their origin. The Semitendi- nosus is a fusiform muscle, which, passing downward and inward, terminates a little below the middle of the thigh in a long round tendon which lies along the inner side of the popliteal space, then curves around the inner tuberosity of the tibia, and is inserted into the upper part of the inner surface of the shaft of that bone nearly as far forward as its anterior border. At its insertion it gives off from its lower border a prolongation to the deep fascia of the leg. This tendon lies behind the tendon of the Sartorius, and below that of the Gracilis, to which it is united. A tendinous intersection is usually observed about the middle of the muscles. The bursa anserina lies between the tendon of the Semitendinosus and the tibia. The Semimenibranosus (m. semimembranosis) (Figs. 384 and 388), so called from its membranous tendon of origin, is situated at the back part and inner side of the thigh. It arises by a thick tendon from the upper and outer impression on the back part of the tuberosity of the ischium, above and to the outer side of the Biceps femoris and Semitendinosus, and is inserted into the groove on the inner and back part of the inner tuberosity of the tibia, beneath the internal lateral ligament. The tendon of the muscle at its origin expands into an apon- eurosis which covers the upper part of its anterior surface; from this aponeurosis muscle fibres arise, and converge to another aponeurosis, which covers the lower part of its posterior surface and contracts into the tendon of insertion. The tendon of the muscle at its insertion gives off certain fibrous expansions; one of these, of considerable size, passes upward and outward, to be inserted into the back part of the outer condyle of the femur, forming part of the posterior ligament of the knee-joint; a second is continued downward to the fascia which covers the Popliteus muscle. The tendon also sends a few fibres to join the internal lateral ligament of the joint. The tendons of the two preceding muscles, with that of the Gracilis, form the inner Hamstrings. Nerves. — The muscles of this region are supplied by the fourth and fifth lumbar and the first, second, and third sacral nerves through the great sciatic nerve. Actions. — The Hamstring muscles flex the leg upon the thigh. When the knee is semiflexed, the Biceps, in conseciuence of its oblique direction downward and outAvard, rotates the leg slightly outward; and the Semitendinosus, and to a slight extent the Semimembranosus, rotate the leg inward, assisting the Popliteus. Taking their fixed point from below, these muscles, especially the Semimembranosus, serve to support the pelvis upon the head of the femur and to draw the trunk directly backward, as in raising it from the stooping position or in feats of strength, when the body is thrown backward in the form of an arch. X'Slien the leg is extended on the thigh, they limit the amount of flexion of the trunk on the lower limbs. THE ANTERIOR TIBIOFIBULAR REGION 525 Applied Anatomy. — The Hamstring tendons are occasionally ruptured. In disease of the knee-joint the Hamstrings may contract, flexing the knee, drawing the tibia backward, and some- times causing incomplete dislocation. The tendons of these muscles occasionally require sub- cutaneous division in some forms of spurious ankylosis of the knee-joint dependent upon per- manent contraction and rigidity of the Flexor muscles, or from stiffening of the ligamentous other tissues surrounding the joint, the result of disease. Division of a tendon is effected by putting the tendon upon the stretch, and inserting a narrow sharp-pointed knife between it and the skin; the cutting edge being then turned toward the tendon, it should be divided, taking great care that the wound in the skin is not at the same time enlarged. The relation of the external popliteal nerve to, the tendon of the Biceps must always be borne in mind in dividing this tendon; in fact, a complete exposure of the tendon is much to be preferred. IV. MUSCLES AND FASCI.ffi OF THE LEG. These may be divided into three groups: those on the anterior, those on the posterior, and those on the outer side of the leg. 5. The Anterior Tibiofibular Region (Fig. 390). Tibialis anticus. Extensor longus digitorum. Extensor proprius halhicis.^ Peroneus tertius. Dissection (Fig. 377). — The knee should be bent, a block placed beneath, it, and the foot kept in an extended position; then make an incision through the integument in the middle line of the leg to the ankle, and continue it along the dorsum of the foot to the toes. Make a second incision transversely across the ankle, and a third in the same direction across the bases of the toes; remove the flaps of integimient included between these incisions in order to examine the deep fascia of the leg. The deep fascia of the leg (fascia cruris) forms a complete investment to tlie muscles, but is not continuous over the subcutaneous surfaces of the bones. It is continuous above witli the fascia lata, receiving an expansion from the tendon of the Biceps femoris, (jn the outer side, and from the tendons of the Sartorius Gracilis, and Semitendinosus on the inner side; in front, it blends with the peri- osteum covering the subcutaneous surface of the tibia, and witli that covering the head and external malleolus of the fibula; belotc, it is continuous with the annular ligaments of the ankle. It is thick and dense in the upper and anterior part of the leg, and gives attachment, by its deep surface, to the Tibialis anticus and Extensor longus digitorum muscles, but is thinner behind, where it covers the Gastrocnemius and Soleus muscles. Over the popHteal space it is much strengthened by trans- verse fibres which stretch across from the inner to the outer Hamstring muscles, and it is here perforated by the external saphenous vein. Its deep surface gives off, on the outer side of the leg, two strong intermuscular septa which enclose the Peronei mu.scles, and separate them from the muscles of the anterior and posterior tibial regions. It also gives off several smaller and more slender processes which enclose the individual muscles in each region; at the saine time a broad transverse, intermuscular septum, called the deep transverse fascia of the leg, intervenes between the superficial and deep muscles in the posterior tibiofibular region. ^There is no such word as "Hallux, -cis." It is the result of some ignorant blunder, copied until it has become established by usage; it has been thought better, therefore, to retain it. According to Lewis and Short, the word is Allex, masculine; genitive, Allicis, the great toe, and the correct rendering would be Extensor proprixis allicis. It is a rare word, and is sometimes spelt, but not so correctly, " Hallex." It is used by Plautus, in the " Pcenulus," V, v. 31, of a little man, as we might say, " a hop-o'-my-thumb." " Tunc hie amator audes esse, allex viri" (To think of you daring to make up to her, you hop-o'-my-thumb!). The word " alex.** sometimes spelt " allex," a fish sauce, is probably a different word altogether. It is used by Horace and Pliny. 526 THE MUSCLES AND FASCIA Remove the fascia by dividing it in the same direction as the integument, excepting opposite the ankle, where it should be left entire. Commence the removal of the fascia from below, opposite the tendons, and detach it in the line of direction of the muscle fibres. The Tibialis anticus (m. tibialis anterior) is situated on the outer side of the tibia; it is thick and fleshy at its upper part, tendinous below. It arises from the outer tuberosity and upper two-thirds of the external surface of the shaft of the tibia; from the adjoining part of the interosseous membrane; from the deep surface Fig. 389. — Diagram showing the attachments of the muscies of the leg. Anterior aspect. Origins, red; insertions, blue. of the fascia; and from the intermuscular septum between it and the Extensor longus digitorum; the fibres pass vertically downward, and terminate in a tendon which is apparent on the anterior surface of the muscle at the lower third of the leg. After passing through the innermost compartment of the anterior annular ligament, it is inserted into the inner and under surface of the internal cuneiform bone and base of the metatarsal bone of the great toe. There is usually a bursa (bursa subtendinea m. tibialis anterioris) between the tendon of the Tibialis anticus and the internal cuneiform bone. At the upper part of the leg this muscle over- laps the anterior tibial vessels and nerve. THE ANTERIOR TIBIOFIBULAR REGION 527 The Extensor proprius hallucis (m. extensor hallu- cislougiis) is a thin, elongated, and flattened muscle situated between the Tibialis anticus and Extensor longus digitorum. It arises from the anterior surface of the fibula for about the middle two-fourths of its extent, its origin being internal to that of the Exten- sor longus digitorum; it also arises from the inter- osseous membrane to a similar extent. The fibres pass downward, and terminate in a tendon which occupies the anterior border of the muscle, passes through a distinct compartment in the lower portion of the annular ligament, crosses the anterior tibial vessels near the bend of the ankle, and is inserted into the base of the last phalanx of the great toe. Op- posite the metatarsophalangeal articulation the tendon : gives off a thin prolongation on each side, which covers the surface of the joint. It usually sends an expan- sion from the inner side of the tendon, to be inserted into the base of the first phalanx. The Extensor longus digitorum (m. extensor dicji- torum longus) is an elongated, flattened, penniform muscle situated the most externally of all the muscles on the fore part of the leg. It arises from the outer tuberosity of the tibia ; from the upper three-fourths of the anterior surface of the shaft of the fibula ; from the interosseous membrane; from the deep surface of the fascia; and from the intermuscular septa bet^\een it and the Tibialis anticus on the inner and the Peronei on the outer side. The tendon enters a canal in the annular ligament with the Peroneus tertius, and divides into four slips, which run across the dorsum of the foot and are inserted into the second and third pha- langes of the four lesser toes. The mode in which the tendons are inserted is the following: Each of the three inner tendons opposite the metatarsophalangeal articulation is joined, on its outer side, by a tendon from the Extensor brevis digitorum. The outer ten- don does not receive such a tendinous slip. They all receive a fibrous expansion from the Interossei and Lumbricales, and then spread out into a broad aponeu- rosis, which covers the dorsal surface of the first pha- lanx; this aponeurosis, at the articulation of the first with the second phalanx, divides into three slips — a middle one, which is inserted into the base of the second phalanx, and two lateral slips, which, after imiting on the dorsal surface of the second phalanx, are continued onward, to be inserted into the base of the third. The Peroneus tertius (m. jwronaens tertius) is a part of the Extensor longus digitorum, and might be described as its fifth tendon. The fibres belonging to this tendon arise from the lower fourth of the anterior surface of the fibula, from the lower part of the interosseous membrane, and from an intermus- tJ- „nU'" Fig. 390.— Muscles of the front of the leg. 528 THE iVUSCLES AXD FASCIA cular septum between it and the Peroneus brevis. The tendon, after passing throiigli the same canal in the annular ligament as the Extensor longus digito- rum, is inserted into the dorsal surface of the base of the metatarsal bone of the little toe. This muscle is sometimes wanting. Nerves. — These muscles are supplied by the fourth and,fifth lumbar and first sacral nerves through the anterior tibial nerve. Actions. — The Tibialis anticus and Peroneus tertius are the direct Flexors of the foot at the ankle-joint; the former muscle, when acting in conjunction with the Tibialis posticus, raises the inner border of the foot {i. e., inverts the foot); and the latter, acting with the Peroneus brevis and longus, draws the outer border of the foot upward, and the sole outward (i. e., everts the foot). The Extensor longus digitorum and Extensor proprius hallucis extend the phalanges of the toes, and, continuing their action, flex the foot upon the leg. Taking their fixed point from below, in the erect posture, all these muscles serve to fix the bones of the leg in the perpendicular position, and give increased strength to the anlde-joint. 6. The Posterior Tibiofibular Region (Figs. 388, 394). Dissection (Fig. .383) . — Make a vertical incision along the middle line of the back of the leg, from the lower part of the popliteal space to the heel, connecting it below by a transverse incision extending between the two malleoli; the flaps of integument being removed, the fascia and muscles should be examined. The muscles in this region of the leg are subdivided into two layers — superficial and deep. The superficial layer constitutes a powerful muscular mass, forming the calf of the leg. Their large size is one of the most characteristic features of the muscular apparatus in man, and bears a direct connection with his ordinary- attitude and mode of progression. The Superficial Layer. Gastrocnemius. Soleus. Plantaris. The Gastrocnemius (m. gastrocnemius) is the most superficial muscle, and forms the greater part of the calf. It arises by two heads, which are connected to the condyles of the femur by two strong flat tendons. The inner and larger head (caput mediale) arises from a depression at the upper and back part of the inner condyle and from the adjacent part of the femur. The outer head (caput laterale) arises from an impression on the outer side of the external condyle and from the posterior surface of the femur immediately above the condyle. Both heads, also, arise by a few tendinous and fleshy fibres from the ridges which are continued upward from the condyles !o the linea aspera. Each tendon spreads out into an aponeurosis, which covers the posterior surface of that portion of the muscle to which it belongs; the muscle fibres of the inner head form a thicker mass and extend lower than those of the outer. From the anterior surface of these tendinous expansions muscle fibres are given off. The fibres in the median line, which correspond to the accessory portions of the muscle derived from the bifur- cations of the linea aspera, unite at an angle upon a median tendinous raphe below; the remaining fibres converge to an aponeurosis which covers the anterior surface of the muscle, and this, gradually contracting, unites with the tendon of the Soleus, and forms with it the tendo Achillis. Relations. — By its superficial surface, with the fascia of the leg, which separates it from the external saphenous vein and nerve; by its deep surface, with the posterior ligament of the knee- joint, the Popliteus, Soleus, Plantaris, popliteal vessels, and internal popliteal nerve. The tendon of the inner head corresponds with the back part of the inner condyle, from which it is THE POSTERIOR TIBIOFIBULAR REGION 529 SEMIMEMBRANOSUS GASTROCNEMIUS AND SOLEU8 (Teudo Achillis) Fig. 391. — Diaerara showing the attachments of nauscles of leg. Posterior aspect. OrijsiDS, red; insertions, blue, .The attachments of muscles of bones of foot are given in detail in Figs. 191 and 192. separated by a synovial bursa, which, in some cases, commu- nicates with the cavity of the knee-joint. The tendon of the outer head contains a sesamoid fibrocartilage (rarely osseous), where it plays over the corresponding outer condyle; and one is occasionally found in the tendon of the inner head. The Gastrocnemius should be divided across, just belo\? its origin, and turned downward, in order to expose the next two muscles. /' --f bursa betwe FASCIA AND The Soleus {m. soleus) is a broad flat muscle situated immediately beneath the Gastrocnemius. It lias received its name from its resemblance in shape to a sole-fish. It arises by tendinous fibres from the back part of the head of the fibula and from the up- per third of the posterior surface of its shaft; from the oblique line of the tibia and from the middle third of its internal border; some fibres also arise from a tendinous arch placed between the tibial and fibular origins of the muscle, beneath which the popliteal vessels and internal popliteal nerve pass. to an aponeurosis which covers the posterior surface of the muscle, and this, 34 BURSA BETWEEN TENDON AND CALCANEUS -Bursae of the tendo (Poirier and Charpy.) The fibres pass backward 530 THE MUSCLES AND FASCIA gradually becoming thicker and narrower, joins with the tendon of the Gastroc- nemius, and forms with it the tendo Achillis. Relations. — By its superficial surface, with the Gastrocnemius and Plantaris; by its deef surface, with the Flexor longus digitorum, Flexor longus hallucis, Tibialis posticus, and posterior tibial vessels and nerve, from which it is separated by the transverse intermuscular septum or deep transverse fascia of the leg. The Tendo Achillis {tendo calcaneus), the common tendon of the Gastrocnemius and Soleus,' is the thickest and strongest tendon in the body. It is about six- inches in length, and commences about the middle of the leg, but receives fleshy fibres on its anterior surface nearly to its lower end. Gradually becoming con- tracted below, it is inserted into the lower part of the posterior surface of the Fig. 393. — Transverse section at the middle of the leg. In front of the interosseous membrane are the ante- rior tibial vessels and nerve; in front of the Soleus, the posterior tibial vessels and nerve; and close^to the fibula, the peroneal vessels. (After Braune.) calcaneus, a synovial bursa {bursa tendinis calcanei [Achillis]) (Fig. 392) being interposed between the tendon and the upper part of this surface. The tendon spreads out somewhat at its lower end, so that its narrowest part is usually about an inch and a half above its insertion. The tendon is covered by the fascia and the integument, a bursa (bursa subcutanea calcanea) (Fig. 392) being often inter- posed between the tendon and the fascia. The tendon is separated from the deep muscles and vessels by a considerable interval filled up with areolar and adipose tissues. Along its outer side, but superficial to it, is the external saphenous vein. The Plantaris {m. plantaris) is an extremely diminutive muscle placed between the Gastrocnemius and Soleus, and remarkable for its long and delicate tendon. 1 These two muscles with a common tendon are by some anatomists classed together as one muscle, the Triceps surae, the two heads of origin of the Gastrocnemius and the Soleus constituting the three heads of the Triceps, and the tendo Achillis the single tendon of insertion. THE POSTERIOR TIBIOFIBULAR REGION 531 It arises from the lower part of the outer prolongation of the linea aspera and from the posterior ligament of the knee-joint. It forms a small fusiform belly, about three or four inches in length, terminating in a long slender tendon which crosses obliquely between the two muscles of the calf, and, running along the inner border of the tendo Achillis, is inserted with it into the posterior part of the cal- Oaneus. This muscle is occasionally double, and is sometimes wanting. Occa- sionally its tendon is lost in the internal annular ligament or in the fascia of the leg. Nerves. — The Gastrocnemius is supplied by the first and second sacral nerves, and the Plantaris by the fourth and fifth lumbar and first sacral nerves through the internal popliteal. The Soleus is supplied by the fifth lumbar and first and second sacral nerves through the internal popliteal and posterior tibial. Actions. — The muscles of the calf are the chief Extensors of the foot at the ankle-joint. They possess considerable power, and are constantly called into use in standing, walking, dancing, and leaping; hence, the large size they usually present. In walking, these muscles draw power- fully upon the calcaneus, raising the heel, and with it the entire body, from the ground; the body being thus supported on the raised foot, the opposite limb can be carried forward. In standing, the Soleus, taking its fixed point from below, steadies the leg upon the foot, and prevents the body from falling forward, to which there is a constant tendency from the superincumbent weight. The Gastrocnemius, acting from below, serves to flex the femur upon the tibia, assisted by the Popliteus. The Plantaris is the rudiment of a large muscle which exists in some of the lower animals and is continued over the os calcis to be inserted into the plantar fascia. In man it is an accessory to the Gastrocnemius, extending the ankle if the foot is free, or bending the knee if the foot is fixed. Possibly, acting from below, by its attachment to the posterior liga- ment of the knee-joint, it may pull that ligament backward during flexion, and so protect it from being compressed between the two articular surfaces. The Deep Layer (Fig. 395). Popliteus. Flexor longus digitorum. Flexor longus hallucis. Tibialis posticus. Dissection. — Detach the Soleus from its attachment to the fibula and tibia, and turn it down- ward, when the deep layer of muscles is exposed, covered by the deep transverse fascia of the leg. The deep transverse fascia of the leg is a transversely placed, intermuscular septum, between the superficial and deep muscles in the posterior tibiofibular region. On either side it is connected to the margins of the tibia and fibula. Above, where it covers the Popliteus, it is thick and dense, and receives an expan- sion from the tendon of the Semimembranosus ; it is thinner in the middle 61 the leg, but below, where it covers the tendons passing behind the malleoli, it is thick- ened and continuous with the internal annular ligament. This fascia should now be removed, commencing from below opposite the tendons, and detaching it from the muscles in the direction of their fibres. The Popliteus (m. popliteus) (Fig. 388) is a thin, flat, triangular muscle, which forms part of the floor of the popliteal space. It arises by a strong tendon, about an inch in length, from a deep depression on the outer side of the external condyle of the femur, and from the posterior ligament of the knee-joint. The muscle is inserted into the inner two-thirds of the triangular surface above the oblique line on the posterior surface of the shaft of the tibia, and into the tendinous expansion covering the surface of the muscle. The tendon of the muscle is covered by that of the Biceps femoris and by the external lateral ligament of the knee-joint; it grooves the posterior border of the external semilunar fibrocartilage, and is invested by the synovial membrane of the knee-joint. Relations. — By its superficial surface, with the fascia covering it, which separates it from the Gastrocnemius, Plantaris, popliteal vessels, and internal popliteal nerve; by its deep surface, with the knee-joint and back of the tibia. 532 THE MUSCLES AND FASCIA The Flexor longus hallucis {in. flexor halliwis longus) is situated on the fibular side of the leg, and is. the most superficial and largest of the three next muscles. illbO* -^ Tendons of ERONEUS LONGU6 BRCVIS. Fig. 394. — Muac!e3 of the back of the right leg. Superficial layer. Fig. 395. — Muscles of the back of the right leg. Deep layer. It arises from the lower two-thirds of the posterior surface of the shaft of the fibula, with the exception of an inch at its lowest part; from the lower part of the interosseous membrane; from an intermuscular septum between it and the THE POSTERIOR TIBIOFIBULAR REGION 533 Peronei, externally; and from the fascia covering the Tibialis posticus internally. The fibres pass obliquely downward and backward, and terminate in a tendon which occupies nearly the whole length of the posterior surface of the muscle. This tendon occupies a groove on the posterior surface of the lower end of the tibia; it then lies in a second groove on the posterior surface of the astragalus, and finally in a third groove, beneath the sustentaculum tali of the calcaneus, and passes into the sole of the foot, where it runs forward between the two heads of the Flexor brevis hallucis, and is inserted into the base of the last phalanx of the great toe (Fig. 397). The grooves in the astragalus and calcaneus, which contain the tendon of the muscle, are converted by tendinous fibres into distinct canals lined by synovial membrane; and as the tendon crosses the sole of the foot, it is connected to the Common Flexor by a tendinous slip. Relations. — By its superficial surface, with the Soleus and tendo Achillis, from which it is separated by the deep transverse fascia ; by its deep surface, with the fibula, Tibialis posticus, the peroneal vessels, the lower part of the interosseous membrane, and the ankle-joint; by its outer border, with the Peronei; by its inner border, with the Tibialis posticus and posterior tibial vessels and nerve. In the sole of the foot it lies above the Abductor hallucis and Flexor longus digitorura. The Flexor longus digitorum (??i. flexor digitorum longus) is situated on the tibial side of the leg. At its origin it is thin and pointed, but gradually increases in size as it descends. It arises from the posterior surface of the shaft of the tibia, immediately below the oblique line to within three inches of its extremity, internal to the tibial origin of the Tibialis posticus; some fibres also arise from the fascia covering the Tibialis posticus. The fibres terminate in a tendon which runs nearly the whole length of the superficial surface of the muscle. This tendon passes behind the internal malleolus in a groove, common to it and the Tibialis posticus, but separated from the latter by a fibrous septum, each tendon being contained in a special sheath lined by a separate synovial membrane. It then passes obliquely forward and outward, superficial to the internal lateral ligament, into the sole of the foot (Fig. 397), where, crossing superficially to the tendon of the Flexor longus hallucis,^ to which it is connected by a strong tendinous slip, it becomes expanded, is joined by the Flexor accessorius, and finally divides into four tendons, which are inserted into the bases of the last phalanges of the four lesser toes, each tendon passing through a fissure in the tendon of the Flexor brevis digitorum opposite the base of the first phalanges (Fig. 396). Relations. — In the leg, by its superficial surface, with the posterior tibial vessels and nerve, and the deep transverse fascia, which separates it from the Soleus muscle; by its deep surface, •Kith the TilDia and Tibialis posticus. In the foot it is covered by the Abductor hallucis and Flexor brevis digitorum, and crosses superficial to the Flexor longus hallucis. The Tibialis posticus (m. tibialis 'posterior) lies between the two preceding muscles, and is the most deeply seated of all the muscles in the leg. It com- mences above by two pointed processes, separated by an angular interval, through which the anterior tibial vessels pass forward to the front of the leg. It arises from the whole of the posterior surface of the interosseous membrane, excepting its lowest part, from the outer portion of the posterior surface of the shaft of the tibia, between the commencement of the oblique line above, and the junction of the middle and lower third of the shaft below; and from the upper two-thirds of the internal surface of tlae fibula; some fibres also arise from the deep transverse fascia and from the intermuscular septa, separating it from the adjacent muscles on each side. This muscle, in the lower fourth of tlie leg, passes in front of the Flexor longus digitorum, and terminates in a tendon which passes tlirough a groove behind the inner malleolus with the tendon of that muscle, but enclosed in a separ- • That is, in the order of dissection of the sole of the foot. 634 THE MUSCLES AND FASCIA ate sheath; it then passes through another sheath, over the internal lateral ligament into the foot, and then beneath the inferior calcaneoscaphoid ligament. Beyond this sheath the tendon passes between the sustentaculum tali and the tubercle of the scaphoid to the plantar aspect and divides into two main slips. The stronrjer medial slip is inserted into the tubercle of the scaphoid and into the internal cunei- form and sends an expansion to the plantar surface of the sustentaculum tali. The weaker lateral slip divides into lesser slips, which are inserted into the middle and external cuneiform, the cuboid and the base of the second, third, and fourth meta- tarsal bones. The stronger tendon as it passes over the scaphoid contains a sesamoid bone. A bursa is often situated between the tendon and the scaphoid. Relations. — By its superficial surface, with the Soleus, from which it is separated by the deep transverse fascia, the Flexor longus digitonim, the posterior tibial vessels and nerve, and the peroneal vessels; by its dee-p surface, with the interosseous ligament, the tibia, fibula, and ankle-joint. Nerves. — The Popliteus is supplied by the fourth and fifth lumbar and first sacral nerves, through the internal popliteal; the Flexor longus digitorum and Tibialis posticus by the fifth lumbar and first and second sacral ; and the Flexor longus hallucis by the fifth lumbar and first and second sacral nerves through the posterior tibial. Actions. — The Popliteus assists in flexing the leg upon the thigh; when the leg is flexed, it will rotate the tibia inward. It is especially called into action at the commencement of the act of bending the knee, inasmuch as it produces a slight inward rotation of the tibia, M'hich is essen- tial in tlie early stages of this movement. The Tibialis posticus is a direct Extensor of the foot at the ankle-joint; acting in conjunction with the Tibialis anticus, it turns the sole of the foot inward (i. e., inverts the foot), antagonizing the Peronei, which turn it outward (evert it). In the sole of the foot the tendon of the Tibialis posticus lies directly below the inferior calcaneo- scaphoid ligament, and is therefore an important factor in maintaining the arch of the foot. The Flexor longus digitorum and Flexor longus hallucis are the direct Flexors of the phalanges, and, continuing their action, extend the foot upon the leg; the_y assist the Gastrocnemius and Soleus in extending the foot, as in the act of walking or in standing on tiptoe. In consequence of the oblique direction of the tendon of the long Flexor, the toes would be drawn inward were it not for the Flexor accessorius muscle, which is inserted into the outer side of its tendon and draws it to the middle line of the foot during its action. Taking their fixed point from the foot, these muscles serve to maintain the upright posture by steadying the tibia and fibula perpendicularly upon the ankle-joint. They also serve to raise these bones from the oblique position they assume in the stooping posture. 7. The Fibular Region (Fig. 381). Peroneus longus. Peroneus brevis. Dissection. — The muscles are readily exposed by removing the fascia covering their surface, from below upward, in the line of direction of their fibres. The Peroneus longus (in. peronaeus longus) is situated at the upper part of the outer side of the leg, and is the more Superficial of the two muscles. It arises from the head and upper two-thirds of the outer surface of the shaft of the fibula, from the deep surface of the fascia, and from the intermuscular septa between it and the muscles on the front, and those on the back of the leg, occasionally also by a few fibres from the outer tuberosity of the tibia. Between its attachment to the head and to the shaft of the fibula there is a small interval of bone from which no muscle fibres arise; through this gap the external popliteal nerve passes beneath the muscle. The muscle terminates in a long tendon, which passes be- hind the outer malleolus, in a groove common to it and the tendon of the Peroneus brevis, behind which it lies, the groove being converted into a canal by a fibrous band, and the tendons being invested by a common synovial membrane; it is then reflected obliquely forward across the outer side of the calcaneus, below its peroneal tubercle, being contained in a separate fibrous sheath, lined by a pro- longation of the synovial membrane which lines the groove behind the malleolus. Having reached the outer side of the cuboid bone, it runs in a groove on the under THE POSTERIOR TIBIOFIBULAR REGION 535 surface of that bone, which is converted into a canal by the long calcaneocuboid ligament, and is lined by a synovial membrane; the tendon then crosses the sole of the foot obliquely, and is inserted into the outer side of the base of the meta- tarsal bone of the great toe and the internal cuneiform bone (Figs. 397 and 398). Occasionally it sends a slip to the base of the second metatarsal bone. The tendon changes its direction at two points — first, behind the external malleolus; secondly, on the outer side of the cuboid bone; in both of these situations the tendon is thickened, and in the latter a sesamoid fibrocartilage, or sometimes a bone, is usually developed in its substance. Relations. — By its superficial surface, with the fascia and integument; by its deep surface, with the fibula, external popHteal nerve, the Peroneus brevis, calcaneus, and cuboid bone; by its nnferior border, with an intermuscular septum, which intervenes between it and the Extensor longus digitorum; by its posterior border, with an intermuscular septum, which separates it from the Soleus above and the Flexor longus hallucis below. The Peroneus brevis (m. peronaeus brevis) lies beneath the Peroneus longus, and is shorter and smaller than it. It arises from the lower two-thirds of the external surface of the shaft of the fibula, internal to the Peroneus longus, and from the intermuscular septa separating it from the adjacent muscles on the front and back part of the leg. The fibres pass vertically downward, and termi- nate in a tendon which runs in front of that of the preceding muscle through the same groove, behind the external malleolus, being contained in the same fibrous sheath and lubricated by the same synovial membrane. It then passes through a separate sheath on the outer side of the calcaneus, above that for the tendon of the Peroneus longus, the two tendons being here separated by the peroneal tuber- cle, and is finally inserted into the tuberosity at the base of the metatarsal bone of the little toe, on its outer side. Relations. — By its superficial surface, with the Peroneus longus and the fascia of the leg and foot; by its deep surface, with the fibula and outer side of the os calcis. Nerves. — The Peroneus longus and brevis are supplied by the fourth and fifth lumbar and first sacral nerves through the musculocutaneous branch of the external popliteal nerve. Actions. — The Peroneus longus and brevis extend the foot upon the leg, in conjunction with the Tibialis posticus, antagonizing the Tibialis anticus and Peroneus tertius, which are Flexors of the foot. The Peroneus longus also everts the sole of the foot; hence, the extreme eversion occasionally observed in fracture of the lower end of the fibula, where that bone offers no resist- ance to the action of this muscle. From the oblique direction of the Peroneus longus tendon across the sole of the foot it is an important agent in the maintenance of the transverse arch of the foot. Taking their fixed point below, the Peronei serve to steady the leg upon the foot. This is especially the case when standing upon one leg, when the tendency of the superincumbent weight is to throw the leg inward; the Peroneus longus overcomes this tendenc_v by drawing on the outer side of the leg, and thus maintains the perpendicular direction of the limb. Applied Anatomy. — The student should now consider the position of the tendons of the various muscles of the leg, their relation with the ankle-joint and surrounding bloodvessels, and especially their action upon the foot, as their rigidity and contraction give rise to one or other of the kinds of deformity known as club-foot. The most simple and common deformity, and one that is rarely, if ever, congenital, is the talipes equinus, the heel being raised by rigidity and con- traction of the Gastrocnemius muscle, and the patient walking upon the ball of the foot. In the talipes varus the foot is forcibly adducted and the inner side of the sole raised, sometimes to a right angle with the ground, by the action of the Tibialis anticus and posticus. In the talipes valgus the outer edge of the foot is raised by the Peronei muscles, and the patient walks on the inner ankle. In the talipes calcaneus the toes are raised by the Extensor muscles, the heel is depressed, and the patient walks upon it. Other varieties of deformity are met with, as the talipes equinovarus, equinovalgus, and ealcaneovaUjus, whose names sufficiently indicate their nature. Of these, the talipes equinovarus is the most common congenital form; the heel is raised by the tendo Achillis, the inner border of the foot drawn upward by the Tibialis anticus, the anterior two-thirds twisted inward by the Tibialis posticus, and the arch increased by the contraction of the plantar fascia, so that the patient walks on the middle of the outer border of the foot. Each of these deformities may sometimes be successfully relieved by divi- sion of the opposing tendons and fascia; by this means the foot regains its proper position, 536 THE MUSCLES AND FASCIA and the tendons subsequently heal. The operation is easily performed by putting thecontracted tendon upon the stretch, and dividing it by means of a narrow, sharp-pointed knife inserted beneath it. Pes caviis, or hollow foot, is accentuation of the longitudinal arch. Pes planus, or flat-foot, has been discussed on page 349. Rupture of a few of the fibres of the Gastrocnemius may take place._ Rupture of the Plantaris tendon not uncommonly occurs, especially in men somewhat advanced in life, from some sudden exertion, and frequently occurs during the game of lawn tennis, and is hence known as lawii- tennis leg. The accident is accompanied by a sudden pain, and produces a sensation as if the individual had been struck a violent blow on' the part. The tendo Achillis is also sometimes rup- .tured. It is stated that John Hunter ruptured his tendo Achillis while dancing at the age of forty. The bursa interposed between the posterior surface of the os calcis and the tendo Achillis, just above the point of insertion of the tendon, may become inflamed, producing a disabling pain {achillodynia, or Albert's disease). V. MUSCLES AND FASCIA OF THE FOOT. The fibrous bands, or thickened portions of the fascia of the leg, which bind down the tendons in front of and behind the ankle in their passage to the foot, are termed the annular ligaments, and are three in number — anterior, internal, and external. The Anterior Annular Ligament (Fig. 390) consists of a superior or transverse portion (ligamentum transversum cruris), which binds down the Extensor tendons as they descend on the front of the tibia and fibula; and an inferior or Y-shaped portion (ligamentum cruciatum cruris), which retains them in connection with the tarsus, the two portions being connected by a thin intervening layer of fascia. The transverse portion is attached externally to the lower end of the fibula and internally to the tibia; above it is continuous with the fascia of the leg; it contains only one' synovial sheath, for the tendon of the Tibialis anticus; the other tendons and the anterior tibial vessels and nerve passing beneath it, but without any dis- tinct synovial sheath. The Y-shaped portion is placed in front of the ankle- joint, the stem of the Y, the fundiform ligament of Retzius, being attached externally to the upper surface of the calcaneus, in front of the depression for the interosseous ligament; it is directed inward, as a double layer, one lamina passing in front, and the other behind, the tendons of the Peroneus tertius and Extensor longus digitorum. At the inner border of the latter tendon these two layers join, forming a sheath in which the tendons are enclosed, surrounded by a synovial membrane. From the inner extremity of this sheath the two limbs of the Y diverge; one passes upward and inward, to be attached to the internal malleolus, passing over the Extensor proprius hallucis and the vessels and nerves, but en- closing the Tibialis anticus and its synovial sheath by a splitting of its fibres. The other limb extends downward and inward to be attached to the inner border of the plantar fascia, and passes over the tendons of the Extensor proprius hallucis and Tibialis anticus and also the -vessels and nerves. These two tendons are con- tained in separate synovial sheaths situated beneath the ligament. The Internal Annular Ligament (ligamentum laciniatum) is a strong fibrous band which extends from the inner malleolus above to the internal margin of the calcaneus below, converting a series of grooves in this situation into canals for the passage of the tendons of the Flexor muscles and vessels into the sole of the foot. It is continuous by its upper border with the deep fascia of the leg, and by its lower border with the plantar fascia and the fibres of origin of the Abductor hallucis muscle. The four canals which the ligament completes transmit, counting from before backward, first, the tendon of the Tibialis posticus; second, the tendon of the Flexor longus digitorum; third, the posterior tibial vessels and nerve, which run through a broad space beneath the ligament; lastly, in a canal formed partly by the astragalus, the tendon of the Flexor longus hallucis. The canals for the tendons are lined by a separate synovial membrane. THE DORSAL REGION 537 The External Annular Ligament is divided into two portions — a superior portion (retinaculum mm. peronaeorum su2)erius), which extends from the extremity of the outer malleohis to the outer surface of the calcaneus; it binds down the tendons of the Peroneus longus and brevis muscles in their passage behind the external malleolus. The two tendons are enclosed in one synovial sac. An inferior portion (retinacvlum mm. peronaeorum inferius), which bridges the Peronei on the side of the clacaneus and is attached to the bone above and below them. 8. The Dorsal Region (Fig. 390). Extensor brevis digitorum. Fascia (fascia dorsalis pedis). — The fascia on the dorsum of the foot is a thin membranous layer continuous above with the anterior margin of the annular ligament; it becomes gradually lost opposite the heads of the metatarsal bones, and on each side blends with the lateral portions of the plantar fascia ; it forms a sheath for the tendons placed on the dorsum of the foot. On the removal of this fascia the muscle and tendons of the dorsal region of the foot are exposed. The Extensor brevis digitorum (m. extensor digitorum brevis) (Fig. 390) is a broad thin muscle which arises from the fore part of the upper and outer sur- faces of the calcaneus, in front of the groove for the Peroneus brevis, from the exter- nal calcaneo-astragaloid ligament, and from the common limb of the Y-shaped portion of the anterior annular ligament. It passes obliquely across the dorsum of the foot, and terminates in four tendons. The innermost, which is the largest, is inserfed into the dorsal surface of the base of the first phalanx of the great toe, crossing the dorsalis pedis artery; the other three, into the outer sides of the long Extensor tendons of the second, third, and fourth toes. Nerves. — It is supplied by the anterior tibial nerve. Actions. — The Extensor brevis digitorum is an accessory to the long Extensor, extending the phalanges of the four inner toes, but acting only on the first phalanx of the great toe. The obliquity of its direction counteracts the oblique movement given to the toes by the long Extensor, so that, both muscles acting together, the toes are evenly extended. 9. The Plantar Region (Figs. 396, 397). The plantar fascia (aponeurosis plantaris), the densest of all the fibrous mem- branes, is of great strength, and consists of pearly white glistening fibres, dis- posed, for the most part, longitudinally; it is divided into a central and two lateral portions. The central portion, the thickest, is narrow behind and attached to the inner tubercle of the calcaneus, posterior to the origin of the Flexor brevis digitorum, and, becoming broader and thinner in front, divides near the heads of the meta- tarsal bones into five processes, one for each of the toes. Each of these processes divides opposite the metatarsophalangeal articulation into two strata, superficial and deep. The superficial stratum is inserted into the skin of the transverse sulcus which divides the toes from the sole. The deeper stratum divides into two slips which embrace the sides of the Flexor tendons of the toes, and blend with the sheaths of the tendons, and laterally with the transverse metatarsal ligament, thus forming a series of arches through which the tendons of the short and long Flexors pass to the toes. The intervals left between the five processes allow the digital vessels and nerves and the tendons of the Lumbricales muscles to become super- ficial. At the point of division of the fascia into processes and slips numerous transverse fibres are superadded, which serve to increase the strength of the fascia 538 THE MUSCLES AND FASCIA at this part by binding the processes together and connecting them with the integu- ment. The central portion of the plantar fascia is continuous with the lateral portions at each side, and from its deep surface sends upward two strong vertical intermuscular septa, which separate the middle from the external and internal groups of plantar muscles; from these, again, thinner transverse septa are derived, which separate the various layers of muscles in this region. The deep surface of this fascia gives attachment behind to the Flexor brevis digitorum muscle. The lateral portions of the plantar fascia are thinner than the central division, and cover the sides of the foot. The outer portion covers the under surface of the Abductor minimi digiti; it is thick behind, thin in front, and extends from the calcaneus to the base of the fifth metatarsal bone, to the outer side of which it is attached; it is continuous internally with the central portion of the plantar fascia, and externally with the dorsal fascia. The inner portion is very thin, and covers the Abductor hallucis muscle; it is attached to the internal annular ligament, and is continuous around the side of the foot with the dorsal fascia, and externally with the middle portion of the plantar fascia. The muscles in the plantar region of the foot may be divided into three groups, in a similar manner to those in the hand: (1) Those of the internal plantar region are connected with the great toe, and correspond with those of the thumb; (2) those of the external plantar region are connected with the little toe, and corre- spond with those of the little finger; and (3) those of the middle plantar region are connected with the tendons intervening between the two former groups. But in order to facilitate the dissection of these muscles it will be found more convenient to divide them into four layers, as they present themselves, in the order in which they are successively exposed. The First Layer. Abductor hallucis. Flexor brevis digitorum. Abductor minimi digiti. Dissection. — Remove the fascia on the inner and outer sides of the foot, commencing in Sront over the tendons and proceeding backward. The central portion should be divided transversely in the middle of the foot, and the two flaps dissected forward and backward. The Abductor hallucis {m. abductor hallucis) lies along the inner border of the foot and covers the first parts of the plantar vessels and nerves. It arises from the inner tubercle on the under surface of the calcaneus (Fig. 396); from the internal annular ligament ; from the plantar fascia ; and from the intermuscular septum between it and the Flexor brevis digitorum. The fibres terminate in a tendon which is iyiserted, together with the innermost tendon of the Flexor brevis hallucis, into the inner side of the first phalanx of the great toe. The Flexor brevis digitorum {m. flexor digitorum brevis) lies in the middle of the sole of the foot, immediately beneath^ the plantar fascia, with which it is firmly united. Its deep surface is separated from the extern.al plantar vessels and nerves by a thin layer of fascia. It arises by a narrow tendinous process, from the inner tubercle of the calcaneus (Fig. 396), from the central part of the plantar fascia, and from the intermuscular septa between it and the adjacent muscles. It passes forward, and divides into four tendons, one for each of the four outer toes. Opposite the bases of the first phalanges each tendon divides into two slips, to allow of the passage of the corresponding tendon of the Flexc longus digitorum ; the two portions of the tendon then unite and form a grooved channel for the reception of the accompanying long Flexor tendon. Finally, iThat is, in order of dissection of tlie sole of the foot. THE PLANTAR REGION 539 they divide a second time, to be inserted into the middle of the sides of the second phalanges. The mode of division of the tendons of the Flexor brevis digitorum and their insertion into the phalanges is analogous to the division and insertion of the Flexor sublimis digitorum in the hand. Fibrous Sheaths of the Flexor Tendons.— These are not so well marked as in the fingers. The Flexor tendons of the toes as tliey run along the phalanges are retained against the bones by a fibrous sheath, forming osseoaponeurotic canals. These sheaths are formed by strong fibrous bands which arch across the tendons and are attached on each side to the margins of the phalan- ges. Opposite the middle of the proximal and sec- ond phalanges the sheath is very strong, and the fibres pass transversely, but opposite the joints it is much thinner, and the fibres pass obliquely. Each sheath is lined by a synovial membrane which is re- flected upon the contained tendon. The Abductor minimi digiti (m. abductor digiti quinti) lies along the outer border of the foot, and is in relation by its inner mar- gin with the external plantar vessels and nerves. It arises, by a very broad origin, from the outer tubercle of the calcaneus, from the under surface of the calcaneus be- tween the two tubercles, from the fore part of the inner tubercle (Fig. 396), from the plantar fascia and the intermuscular septum, between it and the Flexor brevis digitorum. Its tendon, after gliding over a smooth facet on the under surface of the base of the fifth metatarsal bone, is inserted with the short Flexor of the little toe into the outer side of the base of the first phalanx of this toe. Dissection. — The muscles of the superficial layer shovild be divided at their origin by inserting the . knife beneath each, and cutting obliquely backward, so as to detach them from the bone; they should then be drawn forward, in order to expose the sec- ond layer, but not cut away at their insertion. The two layers are separated by a thin membrane, the deep plantar fascia, on the removal of which is seen the tendon of the Flexor longus digitorum, the Flexor accessorius, the tendon of tlie Flexor longus hallucis, and the Lumbricales. The long Flexor tendons diverge from each other at an acute angle; the Flexor longus hallucis runs along the inner side of the foot, on a plane superior to that of the Flexor longus digitorum, the direction of the latter being obliquely outward. The Second Layer. Flexor accessorius. Lumbricales. The Flexor accessorius {m. quadratus plantae) is separated from the muscles of the first layer by the external plantar vessels and nerves. It arises by two heads, which are separated from each other by the long plantar ligament; the inner or larger head, which is muscular, arises from the inner concave surface of the cal- 540 THE MUSCLES AND FASCIAE caneus below the groove which lodges the tendon of the Flexor longus digitorum; the outer head, flat and tendinous, arises from the outer surface of the calcaneus, in front of its lesser tubercle (Fig. 397), and from the long plantar ligament; the two portions join at an acute angle, and are inserted into the outer margin and upper and under surfaces of the tendon of the Flexor longus digitorum, forming a kind of groove in which the tendon is lodged.^ The Lumbricales {vi. lumbricales) are four small muscles accessory to the tendons of the Flexor longus digitorum; they arise from the tendons of the long FlQ 397 — Muscles of the sole of the right foot. Second layer. FiQ. 398.— Muscles of the sole of the right foot. Third layer. Flexor, as far back as their angle of division, each arising from two tendons, except the internal one. Each muscle terminates in a tendon, which passes forward on the inner side of the four lesser toes and is inserted into the expansion of the long Extensor tendon on the dorsum of the first phalanx of the corresponding toe. Dissection. — The Flexor tendons should be divided at the back part of the foot, and the riexor accessorius at its origin, and drawn forward, in order to expose the third layer. * According to Turner, the fibres of the Flexor accessorius end : the second, third, and fourth digits. aponeurotic bands, which contribute slips to THE PLANTAR REGION 541 The Third Layer. Flexor brevis hallucis. Flexor brevis minimi digiti. Adductor obliquus hallucis. Adductor transversus hallucis. The Flexor brevis hallucis {vi. flexor halbwis brevis) arises, by a pointed tendinous process, from the inner part of the under surface of the cuboid bone, from the contiguous portion of the external cuneiform, and from the prolongation of the tendon of the Tibialis posticus, which is attached to that bone. The muscle divides in front into two portions which are inserted into the inner and outer sides of the base of the first phalanx of the great toe, a sesamoid bone being developed in each tendon at its insertion. The inner portion of this muscle is blended with the Abductor hallucis previous to its insertion, the outer portion with the Adductor obliquus hallucis, and the tendon of the Flexor longus hallucis lies in a gi'oove between them. The Adductor obliquus hallucis (cafut ohliquum m. adductoris hallucis) is a large, thick, fleshy mass passing obliquely across the foot and occupying the hollow space between the four inner metatarsal bones. It arises from the tarsal extrem- ities of the second, third, and fourth metatarsal bones, and from the sheath of the tendon of the Peroneus longus, and is inserted, together with the outer portion of the Flexor brevis hallucis, into the outer side of the base of the first phalanx of the great toe. The small muscles of the great toe, the Abductor, Flexor brevis, Adductor obliquus, and Adductor transversus, like the similar muscles of the thumb, give off fibrous expansions, at their insertions, to blend with the long Extensor tendon. The Adductor transversus hallucis (caput trangversum m. adductoris hallucis) is a narrow, flat, muscular fasciculus, stretched transversely across the heads of the metatarsal bones, between them and the Flexor tendons. It arises from the inferior metatarsophalangeal ligaments of the three outer toes, sometimes only from the third and fourth and from the transverse ligament of the metatarsus; and is inserted into the outer side of the first phalanx of the great toe, its fibres being blended with the tendon of insertion of the Adductor obliquus hallucis. The Flexor brevis minimi digiti {m. flexor digiti quinti brevis) lies on the meta- tarsal bone of the little toe, and much resembles one of the Interossei. It arises from the base of the metatarsal bone of the little toe, and from the sheath of the Peroneus longus; its tendon is inserted into the base of the first phalanx of the little toe on its outer side. Occasionally some of the deeper fibres of the muscle are inserted into the outer part of the distal half of the fifth metatarsal bone; these are described by some as a distinct muscle, the Opponens minimi digiti. The Fourth Layer. * The Interossei. The Interossei muscles (mm. interossei) in the foot are similar to those in the hand, with this exception, that they are grouped around the middle line of the second digit, instead of the middle line of the third digit, as in the hand. They are seven in number, and consist of two groups. Dorsal and Plantar. The Dorsal Interossei (???. interossei dorsales), four in number, are situated be- tween the metatarsal bones. They are bipenniform muscles, arising by two heads from the adjacent sides of the metatarsal bones, between which they are placed; their tendons are inserted into the bases of the first phalanges, and into the apon- eurosis of the corresponding slip of the common Extensor tendon. In the angular interval left between the heads of each muscle at its posterior extremity the per- forating arteries pass to the dorsum of the foot, except in the First interosseous muscle, where the interval allows the passage of the communicating branch of the 642 THE MUSCLES AND FASCIA dorsalis pedis artery. The First dorsal interosseous muscle is inserted into the inner side of the second toe; the other three are inserted into the outer sides of the second, third, and fourth toes. The Plantar Interossei (m. interossei plantares), three in number, lie beneath, rather than between, the metatarsal bones. They are single muscles, and each arises from but one metatarsal bone. They arise from the base and inner sides of the shaft of the third, fourth, and fifth metatarsal bones, and are inserted into the inner sides of the bases of the first phalanges of the same toes, and into the aponeurosis of the corresponding slip of the common Extensor tendon. Nerves. — The Flexor brevis digitorum, the Flexor brevis and Abductor hallucis, and the innermost Lumbrical are supplied by the medial plantar nerve. All the other muscles in the sole of the foot by the lateral plantar. The First dorsal interosseous muscle frequently receives an extra filament from the internal branch of the anterior tibial nerve on the dorsum of the foot, and the Second dorsal interosseous a twig from the external bi'anch of the same nerve. Actions. — All the muscles of the foot act upon the toes, and for purposes of description as regard their action may be grouped as Abductors, Adductors, Flexors, or Extensors. The Abduc- tors are the Dorsal interossei, the Abductor hallucis, and the Abductor minimi digiti. The Dorsal interossei are Abductors from an imaginary line passing through the axis of the second toe, so that the first muscle draws the second toe inward, toward the great toe; the second muscle draws the Fig. 399. — The Dorsal interossei. Left foot. The line marked by an * is that from which abduction is performed. Fig. 400. — The Plantar interossei. Left foot. The line marked by an * is that to which adduction is made. same toe outward ; the third draws the third toe, and the fourth draws the fourth toe, in the same direction. Like the Interossei in the hand, they also help to flex the proximal phalanges and to extend the two terminal phalanges. The Abductor hallucis abducts the great toe from the others, and also flexes the proximal phalanx of this toe. And in the same way the action of the Abductor minimi digiti is twofold — as an Abductor of this toe from the others, and also as a Flexor of the prox- imal phalanx. The Adductors are the Plantar interossei, the Adductor obliquus hallucis, and the Adductor transversus hallucis. The Plantar interosseous muscles adduct the third, fourth, and fifth toes toward the imaginary line passing through the second toe, and by means of their inser- tion into the aponeurosis of the Extensor tendon they, with the Dorsal interossei, flex the prox- imal phalanges and extend the two terminal phalanges. The Adductor obliquus hallucis is chiefly concerned in adducting the great toe toward the second one, but also assists in flexing this toe. The Adductor transversus hallucis approximates all the toes, and thus increases the curve of the transverse arch of the metatarsus. The Flexors are the Flexor brevis digitorum, the Flexor accessorius, the Flexor brevis hallucis, the Flexor brevis minimi digiti, and the Lum- bricales. The Flexor brevis digitorum flexes the second phalanges upon the first, and, con- SURFACE FORM OF THE LOWER EXTBEMFFY 543 tinuing its action, may flex the first phalanges also and bring the toes together. The Flexor accessorius assists the long Flexor of the toes, and converts the oblique pull of the tendons of th;u muscle into a direct backward jmll upon the toes. The Flexor brevis halluces flexes and slightly adducts the first phalanx of the great toe. The Plexor brevis minimi digiti flexes the little toe and draws its metatarsal bone downward and inward. The Lumbricales, like the corresponding muscles in the hand, assist in flexing the proximal |ihalanx, and by their insertion into the long Extensor tendon aid in straightening the two terminal phalanges. The only muscle in the Extensor group is the Extensor brevis digitorum. It extends tlie first phalanx of the great toe, and assists the long Extensor in extending the next three toes, and at the same time gives to the toes an outward direction when they are extended. SURFACE FORM OF THE LOWER EXTREMITY. Of the muscles of the thigh, those of the iliac region have no influence on surface form, while those of the anterior femoral region, being to a great extent superficial, largely contribute to the surface form of this part of the body. The Tensor fasciae femoris produces a broad elevation immediately below the anterior portion of the crest of the ilium and behind the anterior supe- rior spinous process. From its lower border a longitudinal groove, corresponding to the ilio- tibial band, may be seen running down the outer side of the thigh to the outer side of the knee- joint. The Sartorius muscle, when it is brought into action by flexing the leg on the thigh and the thigh on the pelvis, and rotating the thigh outward, presents a well-marked surface form. At its upper part, where it constitutes the outer boundary of Scarpa's triangle, it forms a prominent oblique ridge, which becomes changed into a flattened plane below, and this grad- ually merges in a general fulness on the inner side of the knee-joint. When the Sartorius is not in action, a depression exists between the Quadriceps extensor and the Adductor muscles, running obliquely downward and inward from the apex of Scarpa's triangle to the inner side of the knee, which depression corresponds to this muscle. In the depressed angle formed by the divergence of the Sartorius and Tensor fasciae femoris muscles, just below the anterior superior spinous process of the ilium, the Rectus femoris muscle appears, and, below this, deter- mines to a great extent the convex form of the front of the thigh. In a well-developed subject the borders of the muscle, when in action, are clearly to be defined. The Vastus externus forms a long flattened plane on the outer side of the thigh, traversed by the longitudinal gruo\'e formed by the iliotibial band. The Vastus intemus, on the inner side of the lower half of the thigh, gives rise to a considerable prominence, which increases toward the knee and terminates somewhat abruptly in this situation with a full, curved outline. The Crureus and Subcrureus are completely hidden, and do not directly influence surface form. The Adductor muscles, constituting the internal femoral group, are not to be individually distinguished from each other, with the exception of the upper tendon of the Adductor longus and the lower tendon of the Adductor magnus. The upper tendon of the Adductor longus, when the muscle is in action, stands out as a prominent ridge, which runs oblicjuely downward and outw'ard from the neigh- > borhood of the pubic spine, and forms the inner boundary of a flattened triangular space on the upper part of the front of the thigh, known as Scarpa's triangle. The lower tendon of the Adductor magnus can be distinctly felt as a short ridge extending down to the Adductor tubercle on the internal condyle, between the Sartorius and Vastus internus. The Adductor group of muscles fills in the triangular space at the upper part of the thigh, formed between the oblique femur and the pelvic wall, and to them is due the contour of the inner border of the thigh, the Gracilis largely contributing to the smoothness of the outline. These muscles are not marked off on the surface from those of the posterior femoral region by any intermuscular marking, but on the outer side of the thigh these latter muscles are defined from the Vastus externus by a distinct marking, corresponding to the external intermuscular septum. The Gluteus maximus and a part of the Gluteus medius are the only muscles of the buttock which influence surface form. The other part of the Gluteus medius, the Gluteus minimus, and the external Rotators are completely hidden. The Gluteus maximus forms the full rounded outline of the buttock; it is more prominent behind, compressed in front, and terminates at its tendinous insertion in a depression immediately behind the great trochanter. Its lower border does not correspond to the gluteal fold, but is much more oblique, being marked by a line drawn from the side of the coccyx to the junction of the upper with the lower two-thirds of the thigh on the outer side. From beneath the lower margin of this muscle the Hamstring muscles appear, at first narrow and not well marked, but as they descend becoming more prominent and widened out, and eventually dividing into two well-marked ridges, which constitute the upper boundai'ies of the popliteal space, and are formed by the tendons of the inner and outer Hamstring muscles, respectively. In the upper part of the thigh these muscles are not to be individually distin- guished from each other, but lower dow-n the separation between the Semitendinosus and Semi- membranosus is denoted by a slight intermuscular marking. The external hamstring tendon, formed by the Biceps is seen as a thick cord running down to the head of the fibula. The inner Hamstring tendons comprise the Semitendinosus, the Semimembranosus, and the Gracilis. The Seniit(mdinosus is the most internal of these, and can be felt, in certain positions of the 544 THE MUSCLES AND FASCIA limb, as a sharp cord; the Semimembranosus is thick, and the Gracilis is situated a little farther forward than the other two. All (lie iimsilcs on the front of the leg appear to a certain extent somewhere on the surface, but the form of (his region is mainly dependent upon the Tibialis anticus and the Extensor longus digitorum. The Tibialis anticus is well marked, and presents a fusiform enlargement at the outer side of the tibia, and projects beyond the crest of the shin bone. Frotn the muscular mass its tendons may be traced downward, standing out boldly, when the muscle is in action, on the front of the tibia and ankle-joint, and coursing down to its insertion along the inner border of the foot. A well-marked groove separates this muscle exter- nally from the Extensor longus digitorum, which fills up the rest of the space between the upper part of the shaft of the tibia and fibula. It does not present so bold an outline as the Tibialis anticus, and its tendon below, diverging from the tendon of the Tibialis anticus, forms with the latter a sort of plane, in which may be seen the tendon of the Extensor proprius hallucis. A groove on the outer side of the Extensor longus digitorum, seen most plainly when the muscle is in action, separates the tendon from a slight eminence corresponding to the Peroneus tertius. The fleshy fibres of the Peroneus longus are strongly marked at the upper part of the outer side of the leg, especially when the muscle is in action. It forms a bold swelling, separated by furrows from the Extensor longus digitorum in front and the Soleus behind. Below, the fleshy fibres terminate abruptly in a tendon which overlaps the more flattened form of the Peroneus brevis. At the external malleolus the tendon of the Peroneus brevis is more marked than that of the Peroneus longus. On the dorsum of the foot the tendons of the Extensor muscles, emerging from beneath the anterior annular ligament, spread out and can be distinguished in the following order: The most internal and largest is the Tibialis anticus, then the Extensor proprius hallucis; next comes the Extensor longus digitorum, dividing into four tendons to the four outer toes; and lastly, most externally, is the Peroneus tertius. The flattened form of the dorsum of the foot is relieved by the rounded outline of the fleshy belly of the Extensor brevis digitorum, which forms a soft fulness on the outer side of the tarsus in front of the external malleolus, and by the Dorsal interossei, which bulge between the metatarsal bones. At the back of the knee is the popliteal space, bounded above by the tendons of the Hamstring muscle; below, by the two heads of the Gastrocnemius. Below this space is the prominent fleshy mass of the calf of the leg, produced by the Gastrocnemius and Soleus. When these muscles are in action, as in standing on tiptoe, the borders of the Gastrocnemius are well defined, presenting two curved lines, which converge to the tendon of insertion. Of these borders, the inner is more prominent than the outer. The fieshy mass of the calf terminates somewhat abruptly below in the tendo Achillis, which stands out prominently on the lower part of the back of the leg. It presents a somewhat tapering form in the upper three-fourths of its extent, but widens out slightly below. When the muscles of the calf are in action, the lateral portions of the Soleus may be seen, forming curved eminences, of which the outer is the longer, on either side of the Gastrocnemius. Behind the inner border of the lower part of the shaft of the tibia a well- marked ridge, produced by the tendon of the Tibialis posticus, is visible when this muscle is in a state of contraction. On the sole of the foot the superficial layer of muscles influences surface form; the Abductor minimi digiti most markedly. This muscle forms a narrow rounded elevation along the outer border of the foot, while the Abductor hallucis does the same, though to a less extent, on the inner side. The Flexor brevis digitorum, botmd down by the plantar fascia, is not very apparent; it produces a flattened form, covered by the thickened skin of the sole, which is here throwm into numerous wrinkles. APPLIED ANATOMY OF THE LOWER EXTREMITY. The student should now consider the efi^ects produced by the action of the various muscles in fractures of the bones of the lower extremity. The more common forms of fractures are selected for illustration and description. In fracture of the neck of the femur internal to the capsular ligament (Fig. 401) the charac- teristic marks are slight shortening of the limb and eversion of the foot, neither of which symp- toms occurs, however, in certain cases until some time after the injury. The eversion is caused by the weight of the limb rotating it outward. The shortening is produced by the action of the Glutei, and by the Rectus femoris in front and the Biceps, Semitendinosus, and Semimem- branosus behind. In fracture of the femur just below the trochanters (Fig. 402) the upper fragment, the portion chiefly displaced, is tilted forward almost at right angles with the pelvis by the combined action of the Psoas and Iliacus, and, at the same time, everted and drawm outward by the external Rotator and Glutei muscles, causing a marked prominence at the upper and outer side of the thigh, and much pain from the bruising and laceration of the muscles. The limb is shortened, in consequence of the lower fragment being drawn upward by the Rectus in front, and the Biceps, Semimembranosus, and Semitendinosus behind, and is at the same time everted. This fracture may be reduced by direct relaxation of all the opposing muscles, to effect which the limb shoidd be put up in such a manner that the thigh is flexed on the pelvis and the leg on the thigh. Oblique fracture of the femur immediately above the condyles (Fig. 403) is a formidable injury, and attended with considerable displacement. On examination of the limb the lower frag- APPLIED ANATOMY OF THE LOWER EXTREMITY 545 ment may be felt deep in the popliteal space, being drawn backward by the Gastrocnemius and Plantaris muscles, and upward by the Hamstring and Rectus femoris muscles. The pointed Fig. 403. — Fracture of the femur above the condyles. Fig. 404. — Fracture of the patella. 546 THE 2IUSCLES AND FASCIA end of the upper fragments is drawn inward by the Pectineus and Adductor muscles, and tilted forward by the Psoas and Iliacus, piercing the Rectus muscle and occasionally the integument. The greatest care is requisite in keeping the pointed extremity of the upper fragment in proper position; otherwise, after union of the fracture, the power of extension of the limb is partially destroyed from the Rectus femoris muscle being held down by the fractured end of the bone, and from the patella, when elevated, being drawn upward against the projecting fragment. In fracture of the patella (Fig. 404) the fragments are separated by the effusion whichtakes place into the joint, and by the action of the Quadriceps extensor; the extent of separation of the two fragments depending upon the degree of laceration of the ligamentous structures around the bone. The tibia is fractured most commonly by indirect force at the junction of the middle third with the lower third of the shaft. Compound fractures are more common in the leg than in any other region of the body because the tibia is such a superficial bone and is so much, exposed to injury. Most fractures from indirect force are oblique. In oblique fracture of the shaft of the tibia (Fig. 405), if the fracture has taken place obliquely from above, downward and forward, the fragments override each other, the lower fragments being drawn backward and upward by the powerful action of the muscles of the calf; the pointed extremity of the upper fragment projects forward immediately beneath the integu- ment, often protruding through it and rendering the fracture a compound one. If the direc- tion of the fractui'e is the reverse of that shown in the figure, the pointed extremity of the lower fragment projects forward, riding upon the lower end of the upper one. By bending the knee, which relaxes the opposing muscles, and making extension from the ankle and counterexten- sion at the knee, the fragments may be brought into apposition. Fig. 406. — Fracture of the fibula, with dislocation of the foot outward — "Pott's fracture." Fracture of the fibula tvith dislocation of the foot outward (Fig. 406), commonly known as Pott's fracture, is one of the most frequent injuries of the ankle-joint. The fibula is fractured about three inches above the ankle; in addition to this the internal malleolus is broken off, or the deltoid ligament torn through, and the end of the tibia displaced from the corresponding surface of the astragalus. The foot is markedly everted, and the sharp edge of the upper end of the fractured malleolus presses strongly against the skin; at the same time, the heel is drawn up by the muscles of the calf. This injury can generally be reduced by flexing the leg at right angles with the thigh, which relaxes all the opposing muscles, and by making extension from the ankle and counterextension at the knee. THE VASCULAR SYSTEMS. rpHE vascular systems comprise the heart and bloodvessels (blood-vascular I system) for the circulation of the blood, and the lymphatics and lacteals (lymph-vascular system), which collect the lymph from the tissues and the chyle from the digestive tract and conveying them to the great veins. THE HEART AND BLOODVESSELS. Pulmonary Cajitllaries The heart is the central organ of the blood-vascular system, and consists of a hollow mass of muscle tissue; by its contraction the blood is forced to all parts of the body through a complicated series of tubes, termed arteries. The arteries undergo enormous ramification in their course throughout the body, and end in very minute vessels, called arterioles, which, in their turn, open into a close- meshed network of microscopic vessels, termed capillaries. After the blood has passed through the capillaries it enters into minute vessels called venules and from them it is collected into a series of larger vessels, called veins, by which it is again returned to the heart. The passage of the blood through the heart and bloodvessels consti- tutes what is termed the circulation of the blood, of which the following is an outline: The human heart is divided by a septum into right and left halves, and each half is further separated into two cavities, termed the auricle and the ventricle. The heart, therefore, consists of four chambers, two, the right auricle and right ventricle, form- ing the right half, and two, the left auricle and left ventricle, forming the left half. The right half of the heart contains venous or deoxygenated blood; the left, arterial or oxygenated blood. From the cavity of the left ventricle the aerated blood passes into a large artery, the aorta, through the numerous branches of which it is dis- tributed to all parts of the body. In its passage through the capillaries of the body the blood carries to the tissues the mate- rials necessary for their growth and nourish- ment, and at the same time receives from the tissues the waste products resulting from their metabolism. In doing so it becomes changed from arterial into venous Fig. 407. — Diagram showing the course of the circulation of the blood. This diagram does not show that the liver also receives blood through the hepatic artery. (547) 548 THE VASCULAR SYSTEMS blood, which is collected by the veins and through them returned to the right auricle of the heart. From this cavity the deoxygenated blood passes into the right ventricle, from which it is conveyed through the pulmonary arteries to the lungs. In the capillaries of the lungs it again becomes oxygenated, and is then carried to the left auricle by the pulmonary veins. From this cavity it passes into that of the left ventricle, from which the cycle once more begins. The course of the blood from the left ventricle through the body generally to the right side of the heart constitutes the greater or systemic circulation, while its passage from the right ventricle through the lungs to the left side of the heart is termed the lesser or pulmonary circulation. It is necessary, however, to state that the blood which circulates through the spleen, pancreas, stomach, small intestine, and the greater part of the large intes- tine is not returned directly from these organs to the heart, but is collected into a large vein, termed the portal vein, by which it is carried to the liver. In the liver this vein divides, after the manner of an artery, and ultimately ends in capil- lary vessels, from which the rootlets of a series of veins, called the hepatic veins, arise, these carry the blood into the inferior vena cava (postcava), whence it is conveyed to the right auricle. From this it will be seen that the blood contained in the portal vein passes through two sets of capillary \'essels — (1) those in the spleen, pancreas, stomach, etc., and (2) those in the liver. Speaking generally, the arteries may be said to contain pure and the veins im- pure blood. This is true of the systemic, but not of the pulmonary vessels, since it has been seen that the impure blood is conveyed from the heart to the lungs by the pulmonary arteries, and the pure blood returned from the lungs to the heart by the pulmonary veins. Arteries, therefore, must be defined as vessels which convey blood from the heart, and veins as vessels which return blood to the heart. The heart and lungs are contained within the cavity of the thorax, the walls of which afford them protection (Fig. 421). The heart lies between the two lungs, and is there enclosed within a serofibrous bag, the pericardium, while each lung is invested by a serous membrane, the pleura. The skeleton and cavity of the thorax were described on page 154. THE PERICARDIUM. The pericardium (Fig. 408) is a conical serofibrous sac in which the heart and the commencement of the great vessels are contained. It is placed in the middle mediastinum and lies on and is somewhat attached to the Diaphragm. It consists of two layers, an external fibrous, the fibrous pericardium, and an internal serous, the serous pericardium. The fibrous pericardium is a strong, dense connective tissue layer and forms the outer wall of the pericardial sac. Of conical shape, its base is applied to the muscular substance and central tendon of the diaphragm; to the latter a small portion is inseparably blended, the base is pierced by the inferior vena cava, the apex is directed upward and posteriorly, and is closed by fusion with the external coat of the great vessels and is continuous with the pretracheal layer of the deep cervical fascia. In front, it is separated from the anterior wall of the thorax, in the greater part of its extent, by the lungs and pleurae ; but a small area, somewhat variable in size, and usually corresponding with the left half of the lower portion of the gladiolus of the sternum and the inner extremities of the cartilages of the fourth and fifth ribs of the left side, comes into direct relationship with the thoracic wall. The sac is attached to the posterior surface of the sternum by two fibrous bands, the superior and inferior sternopericardial ligaments {lig. sternopericardica) (Fig. 408); THE PEBTCARDIUM 549 the upper passing to the manubrium, and the lower to the ensiform cartilage. Behind, it rests upon the bronchi, the oesophagus, and the descending aorta. Laterally, it is covered by the pleurse, and is in relation to the inner surface of the lungs; the phrenic nerve with its accompanying vessels descends between the pericardium and pleura on either side (Fig. 409). The vessels receiving fibrous prolongation from this membrane are the aorta, the superior vena cava, the right and left pulmonary arteries, the four pulmonary veins, and the impervious ductus arteriosus. The inferior vena cava enters the pericardium through the central tendon of the Diaphragm, and consequently it receives no covering from the fibrous layer. LIGAMENTS Fig. 408. — Ligaments of the pericardium. (Modified from Teutleben.) Right lateral view, showing the right vertebropericardial ligamentS; the right phrenopericardial, and the superior and inferior sternopericardial liga- ments. (Poirier and Charpy.) The Serous pericardium is a closed sac which lines the fibrous pericardium and is invaginated by the heart; it therefore consists of a msceral and a parietal portion. The visceral portion or epicardium covers the heart and the great vessels, and from the latter is continuous with the parietal layer which lines the fibrous pericardium. The serous pericardium encloses the aorta and pulmonary artery in a single tube, but it only partially covers the superior and inferior vena cava and the four pul- monary veins. From these vessels the serous pericardium is reflected to the parietal layer and presents the shape of an inverted fl (Fig. 409). The cul-de-sac enclosed between the limbs of the fl is known as the oblique sinus, while the passage between the venous and arterial mesocardia — i. e., between the aorta and pulmonary artery 550 THE VASCULAR SYSTEMS in front and the auricles behind — is termed the transverse sinus {simis transversus pericardii). The serous pericardium is smooth and glistening, and transudes a serous fluid, which serves to facilitate the movements of the heart. The Vestigial Fold of the Pericardium. — Between the left pulmonary artery and subjacent pulmonary vein and behind the left extremity of the transverse sinus is a triangular fold of the serous pericardium; it is known as the vestigial fold of Marshall (ligavientum v. cavae sinistrae). It is formed by the duplicature of the serous layer over the remnant of the lower part of the fetal left superior vena cava (». cam sinistra), or the duct of Cuvier, which becomes impervious after bu-th, and remains as a fibrous band stretching from the left superior intercostal vein Fig. 409. — Posterior wall of the pericardial c, showing the lines of reflection of the s great veaaeU. ! pericardium from the to the left auricle, where it is continuous with a small vein, the oblique vein of Marshall (v. obliqua atrii sinistri [Marshalli]), which opens into the coronary sinus. The arteries of the pericardium are derived from the internal mammary and its mtisculo- phrenic branch, and from the descending thoracic aorta. The nerves of the pericardium are derived from the vagi, the phrenics, and the sympathetics. Applied Anatomy. — The effusion of fluid into the pericardial sac often occurs in acute rheu- _matism or pneumonia, or in patients with chronic vascular and renal disease, embarrassing the heart's action and giving rise to signs of cardiac distress, such as pallor, a rapid and feeble pulse, dyspnea, and restlessness. On examination, the apical cardiac impulse is absent, or replaced by a more extensive indefinite and wavering pulsation; it may appear to be in the second, third, or fourth left space, and is then not an apex impulse, as Potain has stated, but due to the impact of some portion of the heart wall nearer its base. In childi-en the precordial intercostal spaces may bulge outward. The most striking sign, however, is the great increase in all directions of the precordial dulness on percussion. This becomes pear-shaped, the stalk THE HEART 551 of the pear reaching up to about the left sternodavioular articulation; the dulness also extends some distance to the right of the sternum, particularly in the fifth interspace (Rotch). The fluid collects mainly on either side of the heart, and below it, especially on the left side, where the Diaphragm can yield more readily to pressure than it can on the right. Paraccnlcsis of the "pericardium is often required to relieve the urgent cardiac or respiratory distress in these cases, and should be performed without hesitation and before the patient is in extremis. It may also be required when the pericardium is filled with blood or pus, and as it is advisable to perform this operation without transfixing the pleura, the puncture should be made either in the fifth or sixth intercostal space on the left side and close to the sternum, so as to avoid wounding the internal mammary artery, which descends about half an inch from the sternal margin; or the needle may be entered -at the left costoensiform angle and made to pass upward and backward behind the lower end of the body of the sternum into the pericardial sac. It must be remembered that even in the largest pericardial effusions, the heart itself lies almost in contact with the anterior wall of the thorax, and great care must be exercised to avoid piercing this organ. Pericardiotomy is required when the effusion is of a purulent nature. In this operation a .portion of the fifth or sixth costal cartilage is excised. An incision is made along the left border of the sternum from the upper border of the fourth cartilage to the seventh. Trans- verse incisions an inch long are then made outward from either extremity of this, and the rect- angular flap thus formed reflected outward. The fifth costal cartilage is now separated from the sternum by means of a gouge, great care being taken not to let the instrument slip and pene- trate too deeply. The cartilage is then seized with lion forceps and raised, the tissues beneath it being peeled off, so as to avoid wounding the internal mammary artery or the pleura. The Triangularis sterni is now scratched through with a director or the nail of the index finger close to the sternum, and the pericardium felt for and opened, the finger guarding the pleura and left internal mammary artery. THE HEART (COR). The heart is a hollow muscular organ of a somewhat conical form, placed be- tween the lungs, and occupying the cavitj' of the pericardium. Position (Fig. 410). — The heart is placed obliquely in the thorax; the broad attached end or base {basis cordis) is directed backward and corresponds with the thoracic vertebrae, from the fifth to the eighth inclusive, the apex (ape.r cordis) is directed downward, forward, and to the left, and corresponds to the space between the cartilages of the fifth and sixth ribs, about three and a quarter inches from the middle line of the sternum. The heart projects farther into the left than into the right half of the cavity of the chest, extending from the median line over three inches in the former direction, and only one and one-half in the latter ; about one- third of the heart lies to the right ancl two-thirds to the left of the mesial plane. The base of the heart is formed by the auricles and forms the whole of the posterior surface. It is separated from the fifth, sixth, seventh, and eighth thoracic vertebrae by the oesophagus, aorta, and thoracic duct. Somewhat quadrilateral in form, it is in relation above with the bifurcation of the pulmonary artery, and is bounded below by the posterior part of the auriculoventricular sulcus, containing the coronary sinus. On the right it is limited by the sulcus terminalis (page 554) of the right auricle. This corresponds to a ridge in the interior of the auricle, called the crista terminales. The entrance of the two left pulmonary veins into the left auricle forms the left limit of the base. The four pulmonary veins, two on either side, open into the left auricle, while the superior vena ca^'a opens into the upper and the inferior vena cava into the lower part of the right auricle. The apex is directed downward, forward, and to the left, and is overlapped by the left lung and pleura; it lies behind the fifth left intercostal space, three and a quarter inches (8 cm.) from the midsternal line, or about an inch and a half (4 cm.) below and three-quarters of an inch (2 cm.) to the inner side of the left nipple in the male. The apex is wholly made up of the left ventricle. The antero-superior surface {fades sternocostalis) (Fig. 412) is directed forward, ■wpicard, and to the left. Its lower part is convex, formed chiefly by the right 552 THE VASCULAR SYSTEMS ventricle, together with a small part of the left ventricle. It lies behind the middle portion of the sternum and the costal cartilages of the third, fourth, fifth, and sixth ribs of both sides, but, on account of the heart's inclination to the left, only a small part of it lies behind the cartilages of the right ribs (Fig. 412). The postero-inferior surface (fades diaphragmatica) (Fig. 412), which looks downward and slightly backward, is formed by the ventricles, chiefly the left, and rests upon the central tendon and a small part of the left muscular portion of the Diaphragm. It is separated from the base by the posterior part of the auriculo- FlG. 410. — Position of the heart. The pericardium laid open. Adult male and Charpy.) ventricular furrow, and is traversed obliquely by the posterior interventricular groove. This surface is flattened or slightly convex. The right margin of the heart is long, and is formed by the right auricle above and the right ventricle below. The auricular portion is almost vertical, and is situated behind the third, fourth, and fifth right costal cartilages about 3 cm. from the middle line. The ventricular portion, thin and sharp, is named the nmrfio acutus; it is nearly horizontal, and extends from the sternal end of the sixth right costal cartilage behind the lower end of the gladiolus to the apex of the heart. The left margin, or margo obtusus, is short, thick, and rounded; it is formed mainly by the left ^'entricle, but to a slight extent, above, by the left auricle. It extends from a point in the second left intercostal space, about 4.5 cm. from THE HEART 553 the mesal (middle) line, obliquely downward, with a convexity to the left, to the apex of the heart. Component Parts. — The heart cavity is subdivided by a muscular septum into two lateral halves, which are named, respectively, the right or pulmonary heart and the left or systemic heart; and a transverse constriction subdivides each half of the organ into two cavities, the posterior cavity on each side being called the auricle; the anterior, the ventricle. The heart, therefore, consists oi jour cham- bers— viz., the right and left auricles, and right and left ventricles. The course of the blood through the heart cavities and bloodvessels has already been de- scribed (page 547). The division of the heart into four cavities is indicated upon its surface by grooves. The groove scparatiuu' the auricles from the ventricles is called the LIFT APPENDIX AURICULAE LEFT AURICULO- VENTRICULAR Fig. 411 — Base of the heart tuned m red. auriculoventricular groove (sulcus coronarius) . It contains the trunks of the nutrient vessels of the heart, but is obliterated in front, where it is crossed by the root of the pulmonary artery. The interauricular groove, separating the two auricles, is scarcely marked on the postero-inferior aspect,- while superiorly it is hidden by the pulmonary artery and aorta. The ventricles are separated by two furrows, the interventricular grooves (sulci longitudinales) , one of which (sulcus longitudmalis anterior) is situated on the antero-superior surface close to the left margin of the heart, the other (sulcus longitudinalis posterior) on the postero-inferior surface near the right margin; these grooves extend from the base of the ventricular portion to a point n little to the right of the apex of the heart. i The Cavities of the Heart. — Each of the cavities of the heart is lined by the endocardium, a thin, smooth membrane which gives the glistening appearance to their internal surfaces and by reduplications forming the valves (mitral and 554 THE VASCULAR SYSTEMS tricuspid) guarding the orifices of communication and the semilunar valves of the aorta and pulmonary artery. The Right Auricle^ {airium dextnm) is the larger of the two auricles, although its walls are somewhat thinner than those of the left, measuring about 2 min. It consists of two parts, a principal cavity, the sinus venosus, situated posteriorly, and an antero-superior, smaller portion, the auricular appendix. The sinus venosus {sinus venarum) is the large quadrangular cavity, placed between the two venae cavse. Its walls, which are extremely thin, are connected in front and to the left with the right ventricle, and mesally with the left auricle, but are free in the rest of their extent. The right auricular appendix {auricula dextra), so called from its fancied resem- blance to a dog's ear, is a small conical muscular pouch, the margins of which Fig. 412. — Showing relations of opened heart to front of thor; present a dentated edge. It projects from the sinus forward and toward the left side, overlapping the root of the aorta. The separation of the appendix from the sinus venosus is indicated externally by a groove, the sulcus terminalis (His), which extends from the front of the supe- rior vena cava to the front of the inferior vena cava, and represents the line of union of the sinus venosus of the embryo with the primitive auricle. In the cavity of the auricle the separation is marked by a vertical, smooth, muscular ridge on the anterior wall, the crista terminalis (His) (Fig. 414). Behind the crista the internal surface of the auricle is smooth, while in front of it the muscle fibres of the wall are raised into parallel ridges resembling the teeth of a comb, and hence named the musculi pectinati. ilature the auricle is called the atr: , and the auricular appendix is called the auricle. THE HEART 555 To examine the interior of the rifjht auricle, an incision should be made along its right bor- der from the entrance of the superior vena cava to that of the inferior vena cava. A second cut is to be made from the centre of the first incision to the tip of the auricular appendix, and the flap raised. The interior of the right auricle (Fig. 413) presents the following parts for examination : Openii Superior vena cava. Inferior vena cava. Coronary sinus. Foramina Thebesii. Auriculoventricular. Anterior cardiac veins. Fossa ovalis. Annulus ovalis. Tuberculum Loweri. Musculi pectinati. Crista terminalis. Y 1 f Eustachian. 1 Coronary. The superior vena cava (precava) returns the blood from the upper half of the body, and opens into the upper and back part of the auricle, the direction of its orifice being downward and for- ward. Its opening has no valves. The inferior vena cava (post- cava), larger than the superior vena cava, returns the blood from the lower half of the-, body, and opens into the lowest part of the auricle near the septum, the direc- tion of its orifice being upward and inward, and guarded by a rudimentary valve, the Eusta- chian valve. The blood which enters the auricle through the superior vena cava is directed downward and forward, i. e., to- ward the auriculoA'entricular ori- fice, while that entering it through the inferior vena cava is directed upward and backward toward the auricular septum. This is the normal direction of the two cur- rents in fetal life. The coronary sinus (sijiiis coro- narius) opens into the auricle, be- tween the inferior vena cava and the auriculoventricular opening. It returns the blood from the sub- stance of the heart, and is protected by an incomplete semicircular fold of the lining membrane of the auricle, the coronary valve, or valve of Thebesius. The foramina Thebesii ( foramina venarum minimarum) are depressions in the walls of the auricle; the majority of these are culs-de-sac, but about one-third are the orifices of minute veins (venae viinimae cordis), which return the blood directly from the muscle substance of the heart. Bristle passed throuah right am iruloventriculaj opening 413 — The nglit auricle and ventricle laid open anterior walls of both being remo\ ed 556 THE VASCULAR SYSTEMS The anterior cardiac veins open into the lower fore part of the right auricle. The right auriculoventricular opening, or the tricuspid orifice {ostium venosum dexirum), is the large oval aperture of communication between the right auricle and the ventricle; it will be described with the right ventricle. The Eustachian valve (valvula venae cavae inferioris [Eustachii]) is situated in front of the orifice of the inferior vena cava. It is semilunar in form, its convex margin being attached to the anterior margin of the inferior caval orifice; its con- cave margin, which is free, terminates in two cornua, of which the left is continuous with the anterior edge of the annulus ovalis, while the right is lost on the wall of Fig. 414. — Heart opened to show the interior of the right auricle and of the two ventricles, from in front. The wall of the right auricle is turned back to show- the musculi pectinati and the crista terminalis. The ven- tricular walls and the ventricular septum have been cut. The aortic \-alve is made more prominently visible in the drawing than it really is in nature. auricle, containing a few muscle fibres. In the fetus this valve is of large size, and tends to direct the blood from the inferior vena cava, through the foramen ovale, into the left auricle. In the adult it is occasionally large, and may assist in preventing the reflux of blood into the inferior vena cava; more commonly it is small, and its free margin presents a cribriform or filamentous appearance; occa- sionally it is altogether wanting. The coronary valve or valve of Thebesius (valvidae sinus coronarii [Thebesii]) is a semicircular fold. of the lining membrane of the auricle, protecting the orifice of the coronary sinus. It prevents the regurgitation of blood into the sinus during the contraction of the auricle. This valve is occasionally double. THE HEART 557 The fossa ovalis is an oval depression corresponding to the situation of the foramen ovale in the fetus. It is situated at the lower part of the interauricular septum, above and to the left of the orifice of the inferior vena cava. In fetal life an opening, the foramen ovale, exists at this point between the two auricles; almost immediately after birth the valve-like edge is pressed down by the increased pressure in the left auricle, and by the tenth day it passes to the annulus and closes the opening. The amiulus ovalis (limbns fossae ovalis [Vieussenii]) is the prominent oval margin of the fossa ovalis. It is most distinct above and at the sides; below, it is deficient. A small, slit-like, valvular opening is occasionally found, at the upper anterior margin of the fossa ovalis, which leads upward beneath the annulus into the left auricle; it is the remains of the fetal aperture between the two auricles. The tubercle of Lower {tvhercvlvm intervenosvm [Loweri]) is a small projection on the inter- auricular septum between the fossa ovalis and the opening of the superior vena cava. It is most distinct in the hearts of quadrupeds; in man it is scarcely visible. It was supposed by Lower to direct the blood from the superior vena cava toward the auriculoventricular opening. The internal surface of the right auricle is smooth, except in the appendix and adjacent part of the anterior wall of the sinus venosus, where the muscular wall is thrown into parallel ridges resembling the teeth of a comb, and hence named the musculi pectinati. These end behind in a vertical smooth ridge, the crista termi- nalis (Fig. 414). The Right Ventricle (^ventriculus dexter) is pyramidal in form, and extends from the right auricle to near the apex of the heart. Its antero-swperior surface is rounded and convex, and forms the larger part of the front of the heart. Its under surface is flattened, rests upon the Diaphragm, and forms a small part of the postero- inferior surface of the heart. Its 'posterior wall is formed by the septum between the two ventricles, the interventricular septum (septum ventriculorum) , which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline. The basal and inner angle of the ventricle is prolonged into a conical pouch, the infundibulum {conns arteriosus), from which the pulmonary artery arises. The balance of the ventricle, the body, is the portion into which the auriculo- ventricular orifice opens. The conus arteriosus is marked off from the body of the ventricle by a muscular projection (crista supraventricidaris). The walls ■of the right ventricle are thinner than those of the left, the proportion between them being as 1 to 3. The wall is thickest at the base, and gradually becomes thinner toward the apex. To examine the interior of the right ventricle, its anterior wall should be turned downward and to the right in the form of a triangular flap. This is accomplished by making two incisions: (1) From the pulmonary artery to the apex of -the ventricle parallel to, but a little, to the right of, the anterior interventricular furrow; (2) another, starting from the upper extremity, of the first and carried outward parallel to, but a little below, the auriculoventricular furrow, care being taken not to injure the auriculoventricular valve. The interior of the right ventricle presents for examination: ( Auriculoventricular. Openings < Opening of the pulmonary artery, t Foramina Thebesii. Valves I Tricuspid. [ bemilunar. Columnae carneae. Chordae tendineae. The right auriculoventricular opening, or the tricuspid orifice (ostium venosum wntriculi dextri), is the large oval aperture of communication between the auricle and ventricle. It is situated at the base of the ventricle, near the right border of 558 THE VA&'CULAB SYSTEMS the heart. The plane of this opening is nearly vertical. It is oval and about 3.75 cm. (1.5 inches) in diameter from side to side, surrounded by a fibrous ring (annuhis fibrosvs) and co^'e^ed by the lining membrane of the heart; it is consider- ably larger than the corresponding aperture on the left side, being sufficient to admit the ends of four fingers. The circumference of the orifice is about 12 cm. (4.8 inches) in the male, and 10.5 cm. (4.2 inches) in the female. It is guarded by the tricuspid valve. The opening of the pulmonary artery {ostium arteriosum -pulmonis) is circular in form, and is situated at the summit of the conus arteriosus, close to the ventricular septum. It is placed above and to the left of the auriculo ventricular opening, and is guarded by the pulmonary valve. Foramina Thebesii are scattered over the interior of the right ventricle. The tricuspid valve (vciMda trinispidalis) consists of three segments or cusps {cuspides) of a triangular or trapezoidal shape, each formed by a duplicature of the lining membrane of the heart, strengthened by intervening layers of fibrous tissue. The largest and most movable segment is placed toward the left side of the auriculoventricular opening, and is interposed between that opening and the infundibulum; hence it is called the left or infundibular cusp {cuspis medialw). Another segment is in relation with the right part of the front of the ventricle, the right or marginal cusp {cuspis anterior), and a third with its posterior wall, the posterior or septal cusp {cuspis posterior). The central part of each segment is thick and strong; the lateral margins are thin and translucent. These segments are connected by their bases to the oval fibrous ring surrounding the auriculoven- tricular orifice {annidus fibrosus dexter), and by their sides with one another, so as to form a continuous annular membrane, which is attached around the margin of the auriculoventricular opening; their serrated free margins and ventricular surfaces afford attachment to a number of delicate tendinous cords, the chordae tendineae. The chordae tendineae are connected with the adjacent margins of the principal segments of the valve, and are further attached to each segment in the following manner: (1) Three or four reach the attached margin of each segment, where they are continuous with the auriculoventricular tendinous ring. (2) Others, four to six in number, are attached to the central thickened part of each segment. (3) The most numerous and finest are connected with the marginal portion of each segment. The columnae cameae {trabecidae carneae) are the rounded muscle columns which project from nearly the whole of the inner surface of the ventricle, except- ing near the opening of the pulmonary artery, where the wall is smooth. They may be classified, according to their mode of connection with the ventricle, into three sets. The first set merely forms prominent ridges on the inner surfaces of the ventricle, being attached by their entire length on one side, as well as by their extremities. The second set are attached by their two extremities, but are free in the rest of their extent, forming arches; while a third set {muscidi papUlares) are continuous by their bases with the wall of the ventricle, while their apices give origin to the chordae tendineae, the papillary muscles. There are usually two papillary muscles or groups of muscles, the anterior and the posterior; of these, the anterior is the larger, its chordae tendineae are connected with the right and left segments of the tricuspid valve. The posterior sometimes consists of two or three muscle columns; its chordae tendineae are connected with the posterior and the right segments of the tricuspid valve. In addition to these, some few chordae spring directly from the ventricular septum, or from small eminences on it, and pass to the left and posterior segments. A fleshy band, well marked in the sheep and some other animals, is frequently seen passing from the base of the anterior papillary muscle to the interventricular septum. From its attachments it may assist in preventing overdistention of the ventricle, and so has been named the moderator band. THE HEART 659 The pulmonary valve (Fig. 414) consists of three semilunar segments (valvulae scmiluiiart'.t a. piilmoiialls), two of which are anterior and one of which is posterior, formed by dupiicatures of the hning membrane of the ventricle, strengthened by fibrous tissue. They are attached, by their outer convex margins, to the wall of the artery, at its junction with the ventricle, their inner borders being free, and directed upward in the lumen of the vessel. The free and attached margins of each are strengthened by a bundle of tendinous fibres, and the former presents, at its middle, a small projecting thickened nodule, consisting of bundles of inter- lacing connective-tissue fibres with branched connective-tissue cells and some few elastic fibres. Such a nodule is called the corpus Arantii {nodulus valvulae semi- lunaris [Arantii]). From this nodule tendinous fibres radiate through the valve to its attached margin, but are absent from two narrow crescentic portions, the lunulas {I'unulae valvularum semilunarium), placed one on either side of the nodule immediately adjoining the free margin. The basal end of the pulmonary artery presents three dilatations opposite to the valve. These are the pulmonary sinuses of Valsalva. Similar sinuses exist between the semilunar valves and the commencement of the aorta; they are larger than the pulmonary sinuses. In order to examine the interior of the left auricle, make an incision on the posterior surface of the auricle from the pulmonary veins on one side to those on the other, the incision being carried a little way into the vessels. Make another incision from the middle of the horizontal one to the auricular appendix. The Left Auricle (atrium sinistrum) is rather smaller than the right, but its walls are thicker, measuring about 3 mm.; it consists, like the right, of two parts, a principal cavity and an am^icular appendix. Tlie principal cavity is cuboidal in form, and concealed in front by the pulmonary artery and aorta; in front and to the right, it is separated from the right auricle by the interauricular septum {septum atriorum); behind, it receives on either side two pidmonary veins. The left auricular appendix (auricula sinistra) is somewhat constricted at its junction with the principal cavity; it is longer, narrower, and more curved than that of the right side, and its margins are more deeply indented. It is directed forward and toward the right and overlaps the root of the pulmonary artery. The interior of the left auricle presents the following parts for examination: The openings of the four pulmonary veins. Auriculoventricular opening. Musculi pectinati. Foramina Thebesii. The pulmonary veins, four in number, open into the upper part of the posterior surface of the left auricle — two on either side of its middle line. They are not provided with valves. The two left veins frequently terminate by a common opening. The left auriculoventricular opening, or mitral orifice (ostium venosum ventriculi sinistri), is the aperture of communication between the left auricle and the left ventricle. It is rather smaller than the corresponding opening on the right side. The musculi pectinati, fewer and smaller than in the right auricle, are confined to the inner surface of the auricular appendix. On the interauricular septum may be seen a lunated impression bounded below by a crescentic ridge the concavity of which is turned upward. The depression is just above the fossa ovalis of the right auricle. The inner surface of the left auricle also shows foramina Thebesii and venae minimae cordis. 660 THE VASCULAR SYSTEMS To examine the interior of the left ventricle, make an incision a little to the left of the anterior interventricular groove from the base to the apex of the heart, and carry it up from thence, a little to the left of the posterior interventricular groove, nearly as far as the auriculoventricular groove. The Left Ventricle (yenfriculus sinister) is longer and more conical in shape than the right ventricle, and on transverse section its cavity presents an oval or nearly circular outline. It forms a small part of the anterior surface of the heart and a considerable part of its postero-inferior surface. It also forms the apex of the heart by its projection beyond the right ventricle. Its walls are much thicker than those of the right side, the proportion being as 3 to 1. Its interior (Fig. 415) presents the following parts for examination: ( Auriculoventricular. Openings < Aortic ( Foramina Thebesii. Chordae tendineae. -rr , f Mitral or Bicuspid. Valves \ c> •! t bemilunar. Columnae carneae. The left auriculoventricular opening, or the mitral orifice (ostium venosum ven- iriculi sinistri), is placed below and to the left of the aortic orifice. It is a little smaller than the corresponding aperture of the opposite side, admitting only two Fig. 415.— The left auricle Bi isfle passed through left auriculoventricular opening. Passed thiough aoitic opening. utricle laid open, the posterior walls of both being removed. fingers ; but, like it, is broader in the transverse than in the antero-posterior diameter. Its right, posterior, and left sides are surrounded by a dense horseshoe-shaped, fibrous ring (annuius fibrosus sinister). The orifice is guarded by the mitral or bicuspid valve. The aort;ic opening (ostium arteriosum) is a circular aperture, in front and to the right side of the auriculoventricular opening, from which it is separated by the aortic cusp of the mitral valve. Its orifice is guarded by the aortic valve, which THE HEART 561 consists of three semilunar segments. The portion of the ventricle immediately below the aortic orifice is often termed the aortic vestibule, and ]30ssesses fibrous instead of muscular walls. The inner walls of the left ventricle are dotted with foramina Thebesii. The mitral or bicuspid valve (valvida hicuspidalis) is attaclied to the circumfer- ence of the auriculoventricular orifice in the same way that the tricuspid valve is on the opposite side. It consists of two triangular cusps, formed by duplicatures of the lining membrane, strengthened by fibrous tissue, and containing a few muscle fibres. The cusps are of unequal size, and are larger, thicker, and stronger than those of the tricuspid valve. The larger segment, the anterior or aortic cusp (cuspis anterior), is placed in front and to the right between the auriculoventricular and aortic orifices; the smaller, the posterior or marginal cusp (cuspis posterior), is placed to the left and behind the opening. Two smaller cusps are usually found at the angles of junction of the larger. The cusps of the mitral valve are furnished with chordae tendineae, which are attached in a manner similar to those on the right side; they are, however, thicker, stronger, and less numerous. The aortic valve consists of three semilunar segments (valvulae semilunares aortae), which surround the orifice of the aorta; two are posterior (right and left) and one anterior. They are simi- lar in structure and in their mode of attachment to those of the pulmonary ^'alve, but are larger, thicker, and stronger; the lunulee are more distinct and the corpora Arantii thicker and more promi- nent. Opposite the segments the wall of the aorta presents slight dilatations, the sinuses of Val- salva, which are larger than those at the origin of the pulmonary artery. The columnae carneae are of three kinds, like those upon the right side; but they are more numerous, and present a dense interlacement, especially at the apex, and upon the posterior wall. The musculi papillares are two in number, one being connected to the anterior, the other to the posterior wall; they are of large size, and terminate by free rounded extremities, from which the chordae tendineae arise. The chordae tendineae from each papillary muscle are con- nected to both cusps of the mitral valve. The interventricular septum (septum, ventriculorum) is directed obliquely back- ward and to the right, and is curved with the convexity toward the right ventricle; its margins correspond with the interventricular grooves. The greater portion of it is thick and fleshy (septmn musculare ventriculorum) , but its upper and posterior part, which separates the aortic vestibule from the lower part of the right auricle and upper part of the right ventricle is thin and fibrous, and is termed the undefended or membranous part of the interventricular septum (septum mem- branaceum ventriculorum). It is deri\'ed from the lower part of the aortic septum of the fetus, and an abnormal communication may exist at this part, owing to defective development of this septum. Capacity of the Cavities of the Heart. — Each of the cavities of the heart is capable of holding about 100 c.c, but this is subject to considerable variation among different individuals. 36 Fig. 415. — Base of ventr possd by removal of the auricles. 562 THE VASCULAR SYSTEMS Size and Weight of the Heart. — The normal heart, in the adult, measures five inches in length, three inches and a half in breadth at the broadest part, and two inches and a half in thickness. The prevalent weight, in the male, varies from ten to twelve ounces (average, eleven ounces) ; in the female, from eight to ten; its proportions to the body being as 1 to 160 in males; 1 to 150 in females. The heart continues to increase in weight and in size up to an advanced period of life ; this increase is more marked in men than in women. Structure of the Heart. — The heart is a hollow muscular organ, and its walls are divisible into three coats — the endocardium, myocardium, and epicardium, or visceral layer of the peri- cardium (page .549). The endocardium is a thin, smooth, serous membrane which lines and gives the glistening appearance to the internal surface of the heart; it assists in forming the valves by reduplications and is continuous with the endothelial coat of the bloodvessels which pass to and emerge from the heart. It is composed of endothelial cells resting upon a fibro-elastic membrane which contains some unstriated muscle cells. The endocardium is more opaque on the left than on the right side of the heart, thicker in the auricles than in the ventricles, and thickest in the left auricle. It is thin on the musculi pectinati and on the columnae carneae, but thicker on the smooth parts of the auricular and ventricular walls and on the tips of the musculi papillares. The fibrous rings {annuli fibrosi) surround the auriculoventricular and arterial orifices; they are stronger upon the left than on the right side of the heart, and are composed of dense white fibrous connective tissue. The auriculoventricular rings serve for the attachment of the muscle fibers of the auricles and ventricles, and also for the mitral and tricuspid valves; the rino- on the left side is closely connected by its right margin with the aortic arterial ring. Be- tween these and the right auriculoventricular ring is a mass of fibrous tissue (irigoniim Jibrosum), and in some of the larger animals, as the ox and elephant, a nodule of bone, the os cordis. The fibrous rings surrounding the arterial orifices serve for the attachment of the great vessels and semilunar valves. Each ring receives, at its ventricular margin, the attachment of the muscle fibres of the ventricles; its opposite margin presents three deep semicircular notches, within which the middle coat of the artery (which presents three convex semicircular segments) Fig. 417.— The ( Poirior and Charpy. ) is firmly fixed, the attachment of the artery to its fibrous ring being strengthened by the thin fibrous "coat and serous membrane externally and by the endocardium within. It is opposite the margins of these semicircular notches, in the arterial rings, that the endocardium by its reduplication, strengthened by white fibrous tissue, forms the semilunar valves, the fibrous structure of the ring being continued into each of the segments of the valve. The middle coat of the artery in this "situation is thin, and the sides of the vessels are dilated to form the sinuses of Valsalva. The myocardium of the heart consists of bands and layers of muscle tissue which present an exceedingly intricate interlacement. It consists of (a) the fibres of the auricles, {b) the fibres of the ventricles, and (c) the auriculoventricular bundle of His. Fibres of the Auricles (Fig. 417). — These are disposed in two layers — a superficial layer common to both cavities, and a deep laj^er proper to each. The superficial fibres are more distinct on the anterior surface of the auricles, across the bases of which they run in a transverse THE HEART 563 Fig. 418.— The i lacular arrangement of the apex {Poirier and Charpy. ) direction, forminf; a thin but incomplete layer. Some of these fibres pass into the septum atrioriun. The internal or deep fibres proper to each auricle consist of two sets, looped and annular fibres. The looped fibres pass upward over each auricle, being attached by two ex- tremities to the corresponding auriculoventricular rings in front and behind. The annular fibres surroimd the auricular ap- pendices, and form annular bands around the terminations of the veins and around the fossa ovalis. The fibres of the ventricles are arranged in a complex manner, and various accoimts have been given of their course and connections. The following description is based on the work of McCallum.' They consist of superficial and deep layers, all of which, with the ex- ception of two, are inserted into the papillary muscles of the ven- tricles. The superficial layers con- sist of the following: (a) Fibres which spring from the tendon of the conus arteriosus and sweep downward and toward the left across the anterior interventricular furrow and around the apex of the heart, where they pass upward and inward to terminate in the papil- lary muscles of the left ventricle. Those which spring from the upper half of the tendon of the conus ar- teriosus pass to the anterior papil- lary muscle, those from the lower half to the posterior papillary mus- cle and the papillary muscles of the septum. (6) Fibres which arise from the right auriculoventricular ring and nm diagonally across the back of the right ventricle and around its right border on to its anterior surface, where they dip beneath the fibres just described, and, crossing the interventricular groove, wind aroimd the apex of the heart and terminate in the pos- terior papillary muscle of the left ventricle, (c) Fibres which spring from the left auriculoventricular ring, and, crossing the posterior interventricular fm-row, pass suc- cessively into the right ventricle and end in its papillary muscles. The deep layers are tliree in num- ber; they arise in the papillary mus- cles of one ventricle and, curving in an S-shaped manner, turn in at the interventricular furrow and end in the papillary muscles of the other ventricle. The layer which is most superficial in the right ven- tricle lies next the lumen of the left, and rice versa. Those of the first layer almost encircle the right ventricle, and, crossing in the septum to the left, unite with the superficial fibres from the right auriculoventricujai ring to form the posterior papillary muscle. Those of the second layer have a less extensive course in the wall of the right ventricle, and a correspondingly greater course in the left, where they join with the superficial fibres from the anterior half of the tendon of the conus arteriosus I Johns Hopkins Hospital Reports, vol. ix. Fig. 419. — The arrangement of the muscle of the (Poirier and Charpy.) 564 THE VASCULAR SYSTEMS to form the papillary muscles of the septum. Those of the third layer pass almost entii-ely around the left ventricle and unite with the superficial fibres from the lower half of the tendon of the conus arteriosus to form the anterior papillary muscle. Besides the layers just described there are two bands which do not end in papillary muscles. One springs from the right auriculoventricular ring and crosses in the auriculoventricular septum; it then encircles the deep laj-ers of the left ventricle and ends in the left auriculoventricular ring. The second band is apparently confined to the left ventricle; it is attached to the left auriculoventricular ring, and encircles the portion of the ventricles adjacent to the aortic orifice. The auriculoventricular bundle of His {fasciculus atrioventricularis) (Fig. 420) is the only direct muscle ronnection known to exist between the auricles and ventricles. It arises near the opening of the coronary sinus, where it is connected with the annular and septal fibres of the right auricle. These fibres converge, form anode {node of Tawara), and continue Fig. 420. — Schematic representation of the auriculoventricular bundle of His. The bundle, represented in red, originates near the orifice of the coronarj' sinus, undergoes slight enlargement to form a node, passes forward to the interventricular septum, and divides into two limbs. The ultimate distribution cannot be completely shown as a compact bundle which passes forward in the lower part of the pars memhranacea scpti to the upper limit of the muscle portion of the ventricular septum, and divides into right and left fasciculi. These run down to the right and left ventricles, one on either side of the inter- ventricular septum, the left limb being just covered by endocardium, while the right limb, for a part of its course, is more deeply placed in the muscle layer. Each limb is enclosed in a layer of connective tissue, which isolates it from the musculature of the interventricular sep- tum, but in the lower parts of the ventricles each fasciculus separates into numerous strands which enter the papillary muscles and spread over the entire internal surface of the ventricular muscle and form histological connections with the true cardiac muscle fibres. The right limb is the smaller of the two and usually reaches the anterior papillary muscle by passing along the moderator band when this is present. The undivided portion of the auriculoventricular bundle consists of narrow, somewhat fusiform fibres, but its two divisions and their terminal THE HEART 565 strands are composed of Purkinje fibres. The bundle is not always easily recognized in the human heart, but is readily demonstrated in the heart of the sheep or calf. A constant bursa or lubricating mechanism is in relation with the main bundle, according to Curran,' and a special artery, arising from the right coronary, enters the bundle at its begin- ning and follows it in direction. The Purkinje fibres are very much larger in size than the cardiac cells, and differ from them in several ways. In longitudinal section they are quadrilateral in shape, being about twice as long as they are broad. The central portion of each fibre contains one or more nuclei and is made up of granular protoplasm, with no indication of striations, while the peripheral portion is clear and has distinct transverse striations. The fibres are intimately connected with each other, possess no definite sarcolemma, and do not branch. The epicardium, or visceral layer of the pericardium, is a serous membrane analogous in structure to the endocardium, but contains no smooth muscle tissue. It is thin, smooth, glisten- ing, and transparent, and is reflected over the roots of the great vessels to the inner surface of the pericardial sac, forming there the parietal layer of the pericardium. Applied Anatomy. — Clinical and experimental evidence go to prove that the auriculoven- tricular bundle conveys the impulse to systolic contraction from the auricular septum to the ventricles, and much attention has recently been paid to it, because it appears to become attacked by various disease processes and to lose much of its conducting power in many cases of Stokes-Adams disease (heart block). This condition is characterized by a slow pulse, a tendency to syncopal or epileptiform seizures, and the fact that while the cardiac auricles beat at a normal rate, the ventricles contract much less frequently. The existence of a bursa in relation with the bundle suggests the possibility of a bursitis, in view of which these cardiac symptoms may be the result of acute rheumatism or other febrile diseases. Vessels and Nerves. — The arteries supplying the heart are the right and left coronary from the aorta. The veins terminate in the right auricle, and will be described with the general venous system. The lymphatics end in the thoracic and right lymphatic ducts. The nerves are derived from the superficial and deep cardiac plexuses, and from these plexuses obtain fibres of the vagus, spinal accessory, and sympathetic. The superficial cardiac plexus lies under the arch of the aorta. The deep cardiac plexus is in front of the tracheal bifurcation. The nerves from the plexuses are freely distributed both on the surface and in the substance of the heart, the separate filaments being furnished with small ganglia. A special system of gan- glion cells and nerve fibres has been found- in the auriculoventricular bimdle. The Cardiac Cycle and the Action of the Valves.' — By the contractions and pump- ing action of the heart the blood is forced through the arteries, capillaries and veins of the systemic and pulmonic v.ascular systems. Normally, these contractions are rhythmic in character and occur at the rate of about seventy per minute. Each period of activity is followed by a period of rest, and during these two periods certain events take place in the various parts of the heart in regular sequential order. The period included between the occurrence of any one of these events and the recurrence of the same event constitutes a cardiac cycle, or cardiac revolution. The cardiac cycle may be conveniently divided into three phases, which succeed one another, as follows: (1) A short, practically simultaneous contraction of both auricles, termed the miricular systole, followed, after a slight pause, by (2) a simul- taneous, but more prolonged, contraction of both ventricles, named the venfriciilar systole, and (3) a period of rest during which the whole heart is relaxed, i. e., in a state of diastole. The contraction process begins at the venous openings or in an area in the right auricle between the venae cavae, whence it spreads, in the form of a wave, over the auricles and then to and over the ventricles. The quick contraction of the auricles forces the blood contained in these chambers, through the auriculoventricular openings into the relaxed ventricles, which become fully distended. The contraction of the ventricles follows almost immediately. There ensues a rapid compression of the contained mass of blood and a rela- ti\'ely high pressure is thus developed which occasions the forcible closure of the auriculoventricular valves. These are prevented from being everted into the auricular cavities by their attachment to the papillary muscles through the intermediation of the chordae tendineae. The diminution in size of the ventricular •The Anatomical Record, December, 1909, vol. iii, No. 12. 2.T. Gordon Wilson, Proceedings of the Royal Society, B., 1909, vol. Ixxxi. 3 Re\d3ed by Dr. G. Bachmann. 566 THE VASCULAR SYSTEMS cavities might be followed by a slackening of these tendinous cords were it not for the compensating effect of the active shortening of the papillary muscles which takes place shortly after the onset of the contraction of the general ventricular musculature. The pressure in the ventricles soon rises above that in the pul- monary artery and aorta. At that moment the valves at the orifices of these vessels are forced open and the blood is driven, by a sustained contraction, from the right ventricle into the pulmonary artery and from the left ventricle into the aorta. As soon as the ventricular systole ceases and the pressure in the pulmonary artery and aorta exceeds that in the ventricles the pulmonary and aortic valves close, thus preventing a regurgitation of the blood into the ventricles. While the ventricle? are contracting blood is flowing from the veins into the auricles, where it accumu- lates and distends them. As the ventricles relax, the pressure of the blood in the auricles opens the auriculoventricular valves and blood now flows passively from the veins into the auricles and from these into the ventricles. The rapid accumu- lation of the blood in the ventricles leads to a floating up of the auriculoventricular valves which are shortly afterward pushed aside during the next succeeding auricular contraction. It will be observed that each set of chambers contracts and relaxes alternately. However, the time occupied by the auricular contraction is short, while that occu- pied by the relaxation is long in comparison with the time occupied by the similar events in the ventricles. From the beginning of the ventricular diastole until the beginning of the next auricular systole the entire heart is at rest — the so-called common pause of the heart's chambers. The average duration of a cardiac cycle is about 3^ of a second, which may be divided, approximately, among its different phases as follows: Auricular systole, ^. Auricular diastole, ^. Ventricular systole, -=^5-. Ventricular diastole, ^^. Common pause -pj. As mentioned before, the contraction process, which begins at the mouths of the great veins, spreads with great rapidity, over the auricles, and then to and over the ventricles. A slight delay is experienced by the contraction wave in passing from the auricles to the ventricles. This is due in all probability to the circumstance that the contraction wave must be conducted along a narrow bridge of muscle tissue which is more or less embryonic in character. This bridge of mus- cle tissue connecting the auricles with the ventricles, morphologically and physio- logically, is the auriculoventricular bundle of His (page 564). In accordance with this view, the origin and conduction of the contraction process is a property of the muscle tissue, and the theory which embodies this view is known as the myo- genic theory of the heart beat. Inasmuch as nerve cells and their axones are found in many parts of the heart, the auriculoventricular bundle included, it is thought by some that the origin and conduction of the stimulus giving rise to the contraction process is a property of the nerve tissue. The theory embodying this view is known as the neurogenic theory of the heart beat. It must be said, however, that many facts tend to demonstrate that the myogenic theory is the cor- rect one. Whatever be the tissue in which the heart beat originates, the cause of the contraction must be sought in the heart itself; for the mammalian heart can be made to beat for a relatively long time when completely isolated from the body of the animal. • The cardiac muscle, therefore, does not depend for its contractions on the dis- charge of nerve impulses by the central nerve system, although the latter, 'through the extracardiac nerves, exercises a regulative influence on the heart's action, increasing or decreasing the rate or force of the heart beats in accordance with the physiological needs of the body. THE HE ART 567 Surface Form.— In order to show the exlmt of the heart in relation to the front of the thorax, draw a line from a point in the second Icl'l intn-co.slal sjiace, 4.5 cm. (nearly two inches) from the median line to the upper border of the third rjoht costal cartilage, .3 cm. (one inch and a quarter) from the median line. This represents the base line or upper limit of the organ. Take a point in the fifth left intercostal space 8 cm. from the median line (about three and a quarter inches) ; this represents the apex of the heart. Draw a line from this apex point, with a slight convexity downward, to the junction of the seventh right costal cartilage to the sternum 2..5 cm. from the median line. Thi.s represents the lower limit of the heart. Join the right extremity of the first line— that is, the base line— with the right extremity of this line— that is, to the seventh right chondrosternal joint— with a slight curve outward, so that it projects about 3.5 cm. (one inch and a half) from the mid-line of the sternum. Lastly, join the left extremity of the base line and the apex point by a line curved slightly to the left. , showing relation of the heart, lungs, etc., to the ribs and sternum. P. Pul- M. Left auriculoventricular orifice. Tr. Right auriculoventricular orifice. A portion of the area of the heart thus mapped out is uncovered by lung, and therefore gives a dull note on percussion; the remainder, being overlapped by the lung, gives a more or less resonant note. The former is known as the are:i of complete cardiac dulness. The area of complete cardiac dulness is included between a line drav^n from the centre of the sternum, on a level with the fourth costal cartilage, to the apex of the heart, and a line drawn from the same point down the lower third of the midline of the sternum. Below, this area merges into the dulness which corresponds to the liver. Topography of the various orifices is as follows — viz., the pulmonary orifice is situated in the upper angle formed by the articulation of the third left costal cartilage with the sternum; the aortic orifice is a little below and internal to this, behind the left border of the sternimi, close to the articulation of the third left costal cartilage to this bone. The left avriculore7itricular opening is behind the sternum, rather to the left of the median line, and opposite the fourth costal cartilages. The right auricidoventricular opening is a little lower, opposite the fourth interspace and in the middle line of the body (Fig. 421). 568 THE VASCULAR SYSTEMS Applied Anatomy. — Wounds of the heart are often immediately fatal, but not necessarily so. Thev nia\' be nonpenetrating, when death may occur from hemorrhage, if one of the coro- nary vessels has been wounded, or subsequently from pericarditis; or, on the other hand, the patient may recover. Even a penetrating wound is not necessarily fatal, if the wound is a small one. An attempt should be made to save the patient by means of a surgical operation. A trap-door flap comprising the whole thickness of the thoracic wall should be made. The hinges of the trap-door are the rib cartilages. The pericardium is exposed and freely opened, clots are removed, the wound in the heart is sought for, and when discovered is sutured. In a pene- trating wound the sutures include the whole thickness of the heart, except the endocardium. Interrupted sutures should be used, and each one had better be tied during diastole. A number of successful operations of this character have been performed. Peculiarities in the Vascular System of the Fetus (Fig. 423). The chief peculiarities in the heart of the fetus are the direct communication between the two auricles through the foramen ovale, and the large size of the Eustachian valve. There are also several minor peculiarities. Thus, the position of the heart is vertical until the fourth month, when it commences to assume an oblique direction. Its size is also very considerable as compared with the body, the proportion at the second month being 1 to 50; at birth it is as 1 to 120; while in the adult the average is about 1 to 160. At an early period of fetal life the auric- ular portion of the heart is larger than the ventricular, the right auricle being more capacious than the left; but toward birth the ventricular portion becomes the larger. The thickness of both ventricles is at first about equal, but toward birth the left becomes much the thicker of the two. Fig. 422. — The right auricle of a fetal heart (eighth month). Enlarged. (Spalteholz.) The foramen ovale (Fig. 422) is situated at the lower and back part of the inter- auricular septum, forming a communication between the auricles. It remains as a free oval opening until the middle period of fetal life. About this period a fold grows up from the posterior wall of the auricle to the left of the foramen ovale, and advances over the opening so as to form a sort of valve, which allows the blood to pass only from the right to the left auricle, but not in the opposite direction. The Eustachian valve (Fig. 422) projects upward in front of the opening of the inferior vena cava, and tends to direct the bl.ood from this vessel through the foramen ovale into the left auricle. THE HEART 569 The peculiarities in the arterial system of the fetus are the communication between the pulmonar.y artery and the descending aorta by means of the ductus arteriosus, and the continuation of the internal iliac arteries as the umbilical arteries to the placenta. Pndus arteriosus. Infe) nal iliac arteri Fig. 423. — Plan of the fetal circulation. In this plan the figured arrows represent the kind of blood, as well as the direction which it takes in the vessels. Thus, arterial blood is figured >> — - -> ; venous blood, >> >; mixed (arterial and venous) blood, >>••• — ••• — >. The ductus arteriosus (Fig. 423) is a short tube, about 10 mm. (half an inch) in length at birth, and 2 mm. (one-twelfth of an inch) in diameter. In the early condition it forms the continuation of the pulmonary artery, and opens into the descending aorta just below the origin of the left subclavian artery, and so con- 570 THE VASCULAR SY8TEM8 ducts the greater part of the blood from the right ventricle into this vessel. When the branches of the pulmonary artery have become relatively larger to the ductus arteriosus, the latter is chiefly connected to the left pulmonary artery; and the fibrous cord {ligamentum arteriosum) , which is all that remains of the ductus arteriosus in later life, will be found to be attached to the root of that vessel. Occasionally a small lumen persists in the ligamentum arteriosum. The umbilical or hypogastric arteries are continued from the internal iliacs, along the sides of the bladder to its apex; they pass out of the abdomen at the umbilicus and are carried in the umbilical cord to the placenta. They convey the blood which has circulated in the system of the fetus to the placenta. The peculiarities in the venous system of the fetus are the communications established between the placenta and the liver and portal vein, through the umbil- ical vein; and between the umbilical vein and the inferior vena cava through the ductus venosus. Fetal Circulation (Fig. 423). — ^The blood destined for the nutrition of the fetus is returned from the placenta to the fetus by the umbilical vein. This vein enters the abdomen at the umbilicus, and passes upward along the free margin of the suspensory ligament of the liver to the under surface of that organ, where it gives off two or three branches to the left lobe, one of which is of large size, and others to the quadrate and Spigelian lobes. At the transverse fissure it divides into two branches; of these, the larger is joined by the portal vein and enters the right lobe; the smaller branch continues outward, under the name of the ductus venosus, and joins the left hepatic vein at the point of junction of that vessel with the inferior vena cava. The blood, therefore, which traverses the umbilical vein reaches the inferior vena cava in three different ways ; the greater quantity circu- lates through the liver with the portal venous blood before entering the inferior vena cava by the hepatic veins ; some enters the liver directly, and is also returned to the inferior vena cava by the hepatic veins ; the smaller quantity passes directly into the inferior vena cava by the junction of the ductus venosus with the left hepatic vein. In the inferior vena cava (postcava) the blood carried by the ductus venosus and hepatic veins becomes mixed with that returning from the lower extremities and wall of the abdomen. It enters the right auricle, and, guided by the Eustachian valve, passes through the foramen ovale into the left auricle, where it becomes mixed with a small quantity of blood returned from the lungs by the pulmonary veins. From the left auricle it passes into the left ventricle, and from the left ventricle into the aorta, by means of which it is distributed almost entirely to the head and upper extremities, a small quantity being probably carried into the descending aorta. From the head and upper extremities the blood is returned by the tributaries of the superior vena cava to the right auricle, where it becomes mixed with a small portion of the blood from the inferior vena cava. From the right auricle it descends over the Eustachian valve into the right ventricle, and from the right ventricle passes into the pulmonary artery. The lungs of the fetus being inactive, only a small quantity of the blood of the pulmonary artery is distributed to them by the right and left pulmonary arteries, and is returned by the pulmonary veins to the left auricle; the greater part passes through the ductus arteriosus into the commencement of the descending aorta, where it becomes mixed with the blood transmitted by the left ventricle into the aorta. Through this vessel it descends to supply the lower extremities and viscera of the abdomen and pelvis, the chief portion being, however, conveyed by the umbilical arteries to the placenta. From the preceding account of the circulation of the blood in the fetus it will be seen — 1. That the placenta serves the purposes of nutrition, respiration, and excretion, THE HEART 571 receiving the impure blood from the fetus, and returning it charged with addi- tional nutritive material. 2. That nearly the whole of the blood of the umbilical vein traverses the liver before entering the inferior vena cava; hence the large size of this organ, especially at an early period of fetal life. 3. That the right auricle is the point of meeting of a double current, the blood in the inferior vena cava being guided by the Eustachian valve into the left auricle, while that in the superior vena cava descends into the right ventricle. At an early period of the fetal life it is somewhat probable that the two streams are distinct, for the inferior vena cava opens almost directly into the left auricle, and the Eusta- chian valve would tend to exclude the current along the vein from entering the right ventricle. At a later period, as the separation between the two auricles becomes more distinct, it seems more probable that mixture of the two streams must take place. 4. The pure blood carried from the placenta to the fetus by the umbilical vein, mixed with the blood from the portal vein and the inferior vena cava, passes almost directly to the arch of the aorta, and is distributed by the branches of that vessel to the head and upper extremities; hence the large size and advanced development of those parts at birth. 5. The blood contained in the descending aorta, largely derived from that which has already circulated through the head and upper limbs, together with a small quantity from the left ventricle, is distributed to the lower extremities; hence the small size and less advanced development of these parts at birth. Changfes in the Vascular System at Birth. — At birth, when respiration is established, an increased amount of blood from the pulmonary artery passes through the lungs, which now perform their office as respiratory organs, and at the same time the placental circulation is cut off. Soon after birth the foramen ovale is closed by the valvular edge being pressed against the annulus ovalis, the pressure being due to respiration, which increases the pressure in the left auricle. The structures fuse, and closure is usually complete by about the tenth day after birth. The valvular fold above mentioned becomes adherent to the margins of the foramen for the greater part of its circumference, but above a slit-like opening is left between the two auricles which sometimes remains persistent. The ductus arteriosus begins to contract immediately after respiration is estab- lished, usually becomes completely closed from the fourth to the tenth day, and •ultimately degenerates into an impervious cord {Kg. arteriosuvi) which serves to connect the left pulmonary artery to the arch of the aorta. Of the umbilical or hypogastric arteries, the portion continued on to the bladder from the trunk of the corresponding internal iliac remains pervious as the superior vesical artery, and the part extending from the side of the bladder to the umbilicus becomes impervious between the second and fifth days after birth, and projects as a fibrous cord toward the abdominal cavity, carrying on it a fold of peritoneum. The umbilical win and the ductus venosus become impervious between the second and fifth days after birth, and ultimately dwindle to fibrous cords, the former becoming the rowul ligament of the liver, the latter the ligamentum venosum of the liver. THE AETERIES. The arteries are cylindrical tubular vessels which serve to convey blood from both ventricles of the heart to every part of the body. These vessels were named arteries {i^p, air; r/jpslu, to contain) from the belief entertained by the ancients tliat they contained air. Galen is believed to have been the first to show that during life they contain blood. The distribution of the systemic arteries is like a highly ramified tree, the common trunk of which, formed by the aorta, commences at the left ventricle of the heart, the smallest ramifications corresponding to the periphery of the body and the contained organs. The arteries are found in nearly every part of the body, with the exception of the hairs, nails, epidermis, cartilages, and cornea; and the larger trunks usually occupy the most protected situations, running, in a limb, along the flexor side, where they are less exposed to injury. There is considerable variation in the mode of division of the arteries; occasion- ally a short trunk subdivides into several branches at the same point, as we observe in the celiac and thyroid axes; or the j^ B vessel may give off several branches in succession, and still continue as the main trunk, as is seen in the arteries of the limbs; but the usual division is dichotomous; as, for instance, the aorta dividing into the two common iliacs, and the common carotid into the exter- nal and internal carotids. A branch of an artery is smaller than the trunk from which it arises; but if an artery divides into two branches, the combined cross-section area of the two vessels is, in nearly every instance, somewhat greater than that of the trunk; and the combined cross-section area of all the arterial branches greatly exceeds that of the aorta ; so that the arteries collectively may be regarded as a cone, the apex of which corresponds to the aorta, the base to the capillary system. The arteries, in their distribution, communicate with one another, forming what are called anastomoses or inosculations ( Fig. 424) ; and these communications are very free between the large as well as between the smaller branches. An anasto- mosis between trunks of equal size is found where great activity of the circulation is requisite, as at the base of the brain; here the two vertebral arteries unite to form the basilar, and the two internal carotid arteries are connected by a short communicating trunk; it is also found in the abdomen, the intestinal arteries having very ample anastomoses between their larger branches. In the limbs the anasto- moses are most numerous and of largest size around the joints, the branches of an artery above anastomosing with branches from the vessels below ; these anastomoses are of considerable interest to the surgeon, as it is by their enlargement that a (572) Fig. 424. — Diagram showing the anastomosis of arteries. (Poirier and Charpy.) THE ARTERIES 573 collateral circulation is established after the application of a ligature to an artery. The smaller branches of arteries anastomose more frequently than the larger, and between the smallest twigs these inosculations become so numerous as to constitute a close network that pervades nearly every tissue of the body. A ter- minal artery is one which forms no anastomoses. Such vessels are believed to exist in the brain, spleen, kidneys, lungs, mesentery, and papillary layer of the skin. Throughout the body generally the larger arterial branches usually pursue a straight course, but in certain situations they are tortuous; thus, the facial arteries in their course over the face, and the arteries of the lips, are extremely tortuous in their course, to accommodate themselves to the movements of the parts. The uterine arteries are also tortuous, to accommodate themselves to the increase of size which the organ undergoes during pregnancy. The arteries are dense in structure, of considerable strength, highly elastic, and, when divided, they usually preserve, although empty, their cylindrical form. Histology of Arteries and Capillaries.— An artery consists of an endothelial tube covered by certain accessory coats. The coats of an artery are: (1) internal coat, or tunica intima; (2) a middle coat, or tunica media; and (3) an external coat, or tunica adventitia (Fig. 409). 1. The inner coat ifiiiiira intima) consists of endothehal cells resting upon some subendo- thelial fibroelastic tissue. Limiting the intima is a "n-avy band of yellow elastic tissue called the internal elastic lamina. In small arteries the endothelial cells rest upon the elastic lamina. In large arteries (aorta, pulmonary a.) the elastic tissue forms the fenestrated membrane of Henle. 2. The middle coat (tunica media) consists of muscle, elastic tissue, and white fibrous tissue. In medium-sized arteries the smooth muscle tissue is circularly arranged, with only a small quantity of elastic tissue here and there. In small arteries the elastic tissue is absent; in the large arteries the elastic tissue predomi- nates; in some vessels (retinal, first part of aorta, and pulmonary artery) the elastic tissue may entirely replace the muscle tissue. Occasionally longitudi- nally arranged muscle tissue is seen in the media. In medium-sized arteries the media is bounded by a layer of clastic „ ^^ ^ ^- _ tissue called (he external elastic lamina. D-fe*CT'^^^*^^'~-§^^ -''^^^^■i "^ '-'' '^O 3. The external coat (inniea ndvnititia) Q^^M^^^^^^^^^-^^-^^ is called the fibrous coat. It contains ^'^="-^^&^^^^^^^^^^^^^° fibroelastic tissues, and in some arteries Fig. 425.— Transverse section of part of the wall of the fibres of nonstriated muscle longitudi- posterior tibial artery. X 75. A. Endothelial and sub- 11 J Ti i ■ ii X • i endothehal layers of inner coat. B. Elastic layer (fenes- nally arranged, tt COntams the nutrient trated membrane) of inner coat, appearing as a bright line vessels, nerves, and lymphatics of the in section. C. Muscle layer (middle coat) Z). Outer coat, , . i ,, + ' rl* * ■ V, ■ consistmg of connective-tissue bundles. In the interstices arteries, as tne arteries aiminisn m of the bundles are some connective-tissue nuclei, and, espe- size the coats likewise become thinner. I'ial'y near the muscular coat, a number of elastic fibres cut The endothelial cells rest upon the in- ternal elastic lamina; the media becomes reduced to a few layers of muscle fibres, and the adventitia is represented by some bundles of fibroelastic tissue. This represents the precapillary arteriole, and it gradually becomes the capillary. Capillaries are small endothelial tubes connecting arterial and venous systems. They vary from joVo to 2oVo of an inch (5 /j. to 13/i) in diameter, and about zs of an inch (500 /i) in length. The endothelial cells are thin, flat, and irregular in outline; the darkly staining nucleus usually causes a bulging of the cell, as it is thicker than the protoplasmic portion of the cells. These cells are held together by a small amount of cement substance, and are considered by many to have the property of 'phagocytosis. These cells are also said to be contractile. Small openings called stomata are frecjuently noted between these cells, but they are considered arti- facts. Capillaries anastomose and form vast networks. AmpuUse, sinusoids, retia mirabilia, sinuses, and anastomoses are forms of capillaries seen in certain organs and tissues. Bloodvessels of the Bloodvessel Wall. — Many small bloodvessels, the vasa vasorum, enter the adventitia; from these vessels branches are sent into the media, but not the intima. The latter is nourished bj' the blood that flows over it. They may arise from the vessels to which they are distributed or take origin from an adjacent vessel. The blood is returned from the walls of the vessels by small veins. 574 THE VASCULAR SYSTEMS Lymphatics. — Distinct lymphatic vessels may exist in the adventitia, but are represented by li/inph spaces in the other coats. Lymph capillaries often surround small bloodvessels, or a small bloodvessel may lie in a perivascular Ijrmph space. Nerves. — Arteries are supplied with nerves, myelinic and amyelinic. A network of nerve fibres may surround a vessel, and usually capillaries are so surrounded. In the arteries a network of nerves exists in the media. These nerves supply the muscle fibres, and are called vasomotor nerves. According to Stohr, nerve endings are found in the endothelium of the capillaries, giving them the power of contractility. The Arterial Sheath {vagina vasis) surrounds the artery. It is composed of connective tissue, and is attached to the vessel at numerous points by fibrous tissue. Fig. 426. — Capillaries from the Fig. 427. — Finest vessels on the arterial side. From the human mesentery of a guinea-pig after brain. Magnified 300 times. 1. Small artery. 2. Transition vessel, treatment with a solution of nitrate 3. Coarsei capillaries. 4. Finer capillaries, a. Structureless mem- of silver, a. Cells, b. Their nuclei. brane still with some nuclei, representative of the tunica adven- titia. h. Nuclei of the muscle fibre cells. c. Nuclei within the small artery; perhaps appertaining to an endothelium, d. Nuclei in the transition vessels. Applied Anatomy. — Arteries are liable to a degenerative process known as atheroma or ar- teriosclerosis. It is essentially a senile change, although it may begin at any age and is predis- posed by renal disease, gout, diabetes mellitus, and many other morbid states, and results in the replacement of the arterial elastic tissue by fibrous tissue. The process results in the rise of the arterial blood-pressure with a corresponding hypertrophy of the heart. The weakening of the vessel wall, with reduction of the calibre, renders such affected arteries liable to rupture. THE PULMONAEY ARTERY (A. PULMONALIS) (Figs. 429, 433). The pulmonary artery conveys the venous blood from the heart to the lungs. It is a short, wide vessel, about two inches (5 cm.) in length and one and one- fifth inches (30 mm.) in diameter, arising from the left side of the base (conns arteriosus) of the right ventricle, in front of the aorta. At its origin are three dilatations, the sinuses of Valsalva, described on page 559. It extends obliquely upward and backward, passing at first in front of and then to the left of the ascending aorta, as far as the under surface of the arch, where it divides, about on a level with the intervertebral disk between the fifth and sixth thoracic ver- tebrse, into right and left branches of nearly equal size. Relations. — The whole of the vessel is contained, together with the ascending aorta, in the pericardium. It is enclosed with the aorta in a single tube of the serous pericardium, which is continued upward upon them from the base of the heart and connects them together. The TI-IE AORTA 675 fibrous layer of the pericardium becomes gradually lost upon the external coats of its two branches. In front, the pulmonary artery is separated from the anterior extremity of the second left inter- costal space by the pleura and left lung, in addition to the pericardium; it rests at first upon the ascending aorta, and higher up lies in front of the left auricle on a plane posterior to the ascending aorta. On either side of its origin is the appendix of the corresponding auricle and a coronary artery, the left coronary artery passing, in the first part of its course, behind the vessel. The superficial cardiac plexus lies above its bifurcation, between it and the arch of the aorta. The right branch of the pulmonary artery (ramus dexter a. ■pulmonalis), longer and larger than the left, runs liorizontally outward to the root of the right lung, where it divides into two branches, of which the lower and larger supplies the middle and lower lobes; the upper and smaller is distributed to the upper lobe. It has ill front of it the ascending aorta, the superior vena cava, and the right phrenic nerve. It has behind it the right bronchus. Above it is the arch of the aorta. Beloiv it is the right auricle. The left branch of the pulmonary artery (ramus sinister a. pidmonalis), shorter and somewhat smaller than the right, passes horizontally to the root of the left lung, where it divides into two branches for the two lobes. In front of it and below it are the pulmonary veins of the left side. Behind are the descending aorta and the left bronchus. Above it are the arch of the aorta, the left recurrent laryn- geal nerve, and the ligamentum arteriosum. The left bronchus in a portion of its course lies below as well as behind. The root of the left pulmonary artery is connected to the under surface of the arch of the aorta by a short fibrous cord, the ligamentum arteriosum; this is the remains of a vessel peculiar to fetal life, the ductus arteriosus. The terminal branches of the pulmonary artery will be described with the anatomy of the lung. Applied Anatomy. — Stenosis of the pulmonary artery, either with, or, more rarely, without defective formation of the interventricular septum, is one of the commonest congenital defects of the heart. It may be due either to fetal endocarditis or to maldevelopment of the bulbus cordis. As in most forms of congenital heart disease, the child is cyanosed (morbus coervleus), especially when excited or on exertion, and rarely lives to adolescence, commonly dying of heart failure in infancy, or of pulmonary tuberculosis or intercurrent disease in childhood. The chief signs of the condition .ii-e the loud, harsh systolic cardiac murmur best heard over the second left costal cartilage, cyanosis, clubbing of the finger tips, and the presence of an excess of red corpuscles in the blood. Embolism of the pulmonary artery by a clot of blood coming from the right side of the heart in patients with heart disease, or from a thrombosed vein in cases, for example, of influenza, enteric fever, puerperal sepsis, or fractured limbs, is a common cause of sudden or rapid death. The patient may cry out with sudden excruciating pain in the precordia when the detached embolus lodges, and after a brief period of intense dyspnea, pallor, and anguish, die. A few cases of surgical interference in embolism of the pulmonary artery are on record. Sev- eral were in a measure successful, death being usually due to septic complications, such as pleurisy and pericarditis. (Cf. Kreuzer, Centralblatt fiir Chirurgie, No. 21, 1909.) THE AORTA (Figs. 428, 429). The aorta, or arteria magna, is the main trunk of a series of vessels which convey the oxygenated blood to the tissues of the body for their nutrition. It commences at the upper part of the left ventricle, where it is about one and one-eighth inches (28 mm.) in diameter, and, after ascending for a short distance, arches backward and to the left side, over the root of the left lung, then descends within the thorax on the left side of the vertebral column, passes through the aortic opening in the Diaphragm, and, entering the abdominal cavity, terminates, considerably dimin- ished in size, about seven-tenths of an inch (17.5 mm.) in diameter, opposite the lower border of the fourth luitibar vertebra, where it divides into the right and left common iliac arteries. Hence, it is divided into the ascending aorta, the arch of the aorta, and the descending aorta, which last is again divided into the thoracic aorta and the abdominal aorta, from the position of these parts. 576 THE VASCULAR SYSTEMS THE ASCENDING AORTA (AORTA ASCENDENS). The ascending aorta is about two inches (5 to 6 cm.) in length. It commences at the base of the left ventricle, on a level with the lower border of the third costal cartilage, behind the left half of the sternum; it passes obliquely upward, forward, and to the right, as high as the upper border of the second right costal cartilage, VAGUS NERVE CARDIAC NERVE SUPERIOR INTER- ^ COSTAL VEIN CARDIAC NERVE \ LIGAMENTUA RTERIOSUh Fig. 428.— The th describing a slight curve in its course, and being situated, when distended, about a quarter of an inch behind the posterior surface of the sternum. At its origin it presents, opposite the segments of the aortic valve, three small dilatations called the sinuses of Valsalva, described on page 561. At the union of the ascending with the transA'erse part of the aorta the caliber of the vessel is increased, owing to a dilatation of its right wall. This dilatation is termed the great sinus of the aorta (bulbous aortae). A section of the aorta through this part is somewhat oval in outline. The ascending aorta is contained within the pericardium, and, to- gether with the pulmonary artery, is invested in a tube of serous membrane, con- tinued on to them from the surface of the heart. Relations. — The ascending aorta is largely covered (ventrad) at its commencement by the trunk of the pulmonary artery and the right auricular appendix, and, higher up, is separated from the sternum by the pericardium, the right pleura, and anterior margin of the right lung, THE ASCENDING AORTA bll some loose areolar tissue, and the remains of the thymus gland; behind, it rests upon the right pulmonary artery, left auricle, and the right bronchus. On the rirjht side it is in relation with the superior vena cava and right auricle; on the left side, with the pulmonary artery. Riqht lagiis Fig. 430. — Plan of the branches. Fig. 429. — The arch of the aorta and its branches. Plan of the Relations of the Ascending Aorta. In front. Pulmonary artery. Right auricidar appendix. Pericardium. Right pleura and lung. Remains of the thymus gland. Right side. Superior vena cava. Right auricle. Behind. Right pulmonary artery. Left auricle. Right bronchus. 37 Left side. Pulmonary artery. 578 THE VASCULAR SYSTEMS Branches. — The only branches of the ascending aorta are the coronary arteries which supply the heart. They are two in number, right and left, arising near the commencement of the aorta immediately above the attached margin of the semi- lunar valves. The Coronary Arteries (Fig. 429). — The right coronary artery (a. caronoria Ycordis] dextra), about the size of a crow's quill, arises from the anterior sinus of Valsalva. It passes forward between the pulmonary artery and the right auricular appendix, then runs obliquely to the right side, in the groove between the right auricle and ventricle, and, curving around the right border of the heart, runs to the left along its postero-inferior surface as far as the postero-inferior interventricular groove, where it divides into two branches, one of which, the transverse, continues onward in the groove between the left auricle and ventricle, and anastomoses with the left coro- nary ; the other, the descending (ramus descendens posterior a. coronariae [cordis] dextrae^, courses along the postero-inferior inter- ventricular furrow, supplying branches to both ventricles and to the septum, and anastomosing at the apex of the heart with the descending branches of the left coronary. This vessel sends a large branch, the marginal, along the thin margin of the right ventricle, to the apex, which in its course RIGHT AURICLE Fig. 431. — Horizont.il section through the sixth thoracic . ™ nil vertebra— upper surface of the lower segment— showing the glVCS Oil IlUmerOUS Small braUChcS ascending portion of the aortic arch, the tlioracic aorta, and r .i , i ] i* i ■• related structures. to the stcmal and diaohragmatic surfaces of the risht ventricle. It also gives off a branch, the infundibular, which ramifies over the front part of the conus arteriosus of the right ventricle. A small branch of the right coronary is said to supply the auriculoventricular bundle of His (see page 564). The left coronary artery (a. roronaria [cordis] sinistra), larger than the former, arises from the left posterior sinus of ^''alsalva; it passes forward between the pul- monary artery and the left auricular appendix, and divides into two branches. Of these, one, the transverse, passes transversely outward in the left auriculo- ventricular groove, and winds around the left border of the heart to its diaphrag- matic surface, where it anastomoses with the transverse branch of the right coronary; the other, the descending (ramus descendens anterior a. coronariae [cordis'] sinistrae), passes along the antero-superior interventricular groove to the apex of the heart, where it anastomoses with the descending branches of the right coronary. The left coronary supplies the left auricle and its appendix, gives branches to both ventricles, and numerous twigs to the pulmonary artery and commencement of the aorta. Peculiarities. — These vessels occasionally arise by a common trunk, or their number may be increased to three, the additional branch being of small size. More rarely there are .two additional branches. Appued Anatomy. — The sudden blocking of a coronary artery by an embolus, or its more gradual obstruction by arterial disease or thrombosis, are common causes of sudden death in persons past middle age. If the obstruction to the passage of blood is incomplete, true Angina pectoris may occur. In this condition the patient is suddenly seized with a spasm of agonizing pam in the precordial region and down the left arm, together with an indescribable sense of anguish. He may die in such an attack, or succumb a few hours or days later from heart failure, or he may survive a number of attacks. THE ARCH OF THE AORTA 579 THE ARCH OF THE AORTA (ARCUS AORTAE). The arch, or transverse aorta, commences at the level of the upper border of the second chondrosternal articulation of the right side, and passes at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left side of the trachea, and finally passes downward on the left side of the Ijody of the fourth thoracic vertebra, at the lower border of which it becomes continuous with the descending aorta. It thus forms two curvatures, one with its convexity upward, the other with its convexity forward and to the left. Its upper border is usually about an inch below the upper margin of the ster-' num. Relations. — The arch of the aorta is covered m frorit by the pleurae and anterior margins of the lungs, and by the remains of the thymus gland. As the vessel runs backward its left side is in contact with the left lung and pleura. Passing downward on the left side of this part of the arcli are four nen-es; in order from be- fore backward these are the left phrenic, the inferior cervical cardiac branch of the left vagus, the superior cardiac branch of the left sympathetic, and the trunk of the left vagus. As the left vagus crosses the arch it gives off its recurrent laryngeal branch, which hooks around below the vessel and then passes upward on its right side. The left superior intercostal vein runs obliquely upward and forward, on the left side of the arch between the phrenic and vagus nerves. On the right are the deep car- diac plexus, the left recurrent laryngeal nerve, the oesophagus, and thoracic duct; the trachea lies behind and to the right of the vessel. Above are the innominate, left common carotid, and left subclavian arteries, which arise from the convexity of the arch and are crossed close to their origins by the left innominate vein. Below are the bifurcation of the pulmonary artery, the left bronchus, the ligamentum arteriosum, the superficial cardiac plexus, and the left recurrent laryngeal nerve. As already stated, the ligamentum arteriosum connects the commencement of the left pulmonary artery to the aortic arch. RIGHT PLEURA MAMMARY ARTERY Fig. 435. — Horizontal section through the fourth thoracic vertebra — upper surface of the lower segment. The cut is made at the lower part of the transverse portion of the aortic arch. Plan of the Rel.^tions of the Arch of the Aorta. Above. In Front. Left innominate vein. Innominate artery. Left carotid. Left subclavian. Behind. Pleurse and lungs. Remains of thymus gland. Left vagus nerve. Left phrenic nerve. Superficial cardiac nerves. Left superior intercostal vein. [ Arch of \ 1 Aorta. j Trachea. Deep cardiac plexus. Oesophagus. Thoracic duct. Left recurrent nerve. Below. Bifurcation of pulmonary artery. Ligamentum arteriosum. Superficial cardiac plexus. Left recurrent nerve. Left bronchus. 580 THE VASCULAR SYSTEMS Between the origin of the left subclavian artery and the attachment of the liga- mentum arteriosum the kimen of the fetal aorta is considerably narrowed, forming what is termed the aortic isthmus {isthmus aortae), while immediately beyond the liga- mentum arteriosus the vessel presents a fusiform dilatation which His has named the aortic spindle (aorfenspinder) — the point of junction of the two parts being mai'ked in the concavity of the arch by an indentation or angle. These conditions persist, to some extent, in the adult, where His found that the average diameter of the spindle exceeded that of the isthmus by 3 mm. (about one-eighth of an inch). Peculiarities. — The height to which the aorta rises in the thorax is usually about an inch below the upper border of the sternum; but it may ascend nearly to the top of that bone. Occa- sionally it is found an inch and a half, more rarely two or even three inches, below this point. In [Direction. — Sometimes in man, as is normal in birds, the aorta arches over the root of the right instead of the left lung, and passes down on the right side of the vertebral column; such an arrangement is usually found to be associated with transposition of other viscera. Less frequently, the aorta, after arching over the root of the right lung, is directed to its usual position on the left side of the vertebral column, this peculiarity not being accompanied by any transposition of the viscera. In Conformation. — The aorta occasionally divides, as in some quadrupeds, into an ascending and descending trunk, the former of which is directed vertically upward, and subdivides into three branches, to supply the head and upper extremities. Sometimes the aorta subdivides soon after its origin into two branches, which soon reunite. In one of these cases the oesophagus and trachea were found to pass through the interval left by the division of the aorta; this is the normal condition of the vessel in the reptilia. Applied Anatomy.— Of all the vessels of the arterial system, the aorta, and more especially its arch, is most fre- quently the seat of disease; hence it is important to con- sider some of the consequences that may ensue from aneurism of this part. Aortic aneurisms usually occur along a spiral line, the so-called "surf-line of the aorta," which begins at the anterior sinus of Valsalva and is lost in the dorsomesal wall of the descending aorta, as shown in Fig. 433. it will be remembered that the ascending aorta is con- tained in the pericardium, just behind the sternum, being crossed at its commencement by the pulmonary artery and right auricular appendix, and having the right pulmonary artery behind, the superior vena cava on the right side, and the pulmonary artery and left auricle on the left side. Aneurism of the asceiiding aorta, in the situation of the sinuses of Valsalva, in the great majority of cases, affects the anterior sinus; this is mainly owing to the fact that the regurgitation of blood upon the sinuses seems to take place aorta, " showing the commoner points chiefly on the anterior aspect of the vessel. As the aneuris- of origin of aneurisms. mal sac enlarges it may compress any or all of the structures in immediate proximity to it, but chiefly project toward the right anterior side, and, consequently, interferes mainly with those structures' which have a corresponding relation with the vessel. In the majority of cases it bursts into the cavity of the pericardium, the patient suddenly drops dead, and', upon a postmortem examination, the pericardial sac is found full of blood; or it may compress the right auricle, or the pulmonary artery and adjoining part of the right ventricle,' and open into one or the other of these parts, or may press upon or even rupture into the superior vena cava. Aneurism of the ascending aorta, originating above the sinuses, most frequently implicates the right anterior wall of the vessel, where, as has been explained, there exists a normal dilata- tion, the great sinus of the aorta; this is probably mainly owing to the blood being impelled agamst this part. The direction of the aneurism is also chiefly toward the right of the median line. It attains a large size and projects forward, it may cause absorption of the sternum and the cartilages of the ribs, usually on the right side, and appears as a pulsating tumor on the front of the thorax, just below the manubrium; or it may burst into the pericardium, or mav compress or open into the right lung, the trachea, bronchi, or oesophagus. Regarding the arch of the aorta, the student is reminded that the vessel lies on the trachea, the oesophagus, and thoracic duct; that the left recurrent laryngeal nerve winds around it; and that from its upper part are given off three large trunks, which supply the head, neck, and upper Fig. 433.— The "surf-lii THE ARCH OF THE AORTA 581 extremities. An aneurismal tumor, taking origin from the posterior part of the vessel, may press upon the trachea, impede the breathing, or produce cough, hemoptysis, or stridulous breathing, or it may ultimately burst into that tube, producing fatal hemorrhage. Again, its pressure on the laryngeal nerves may give rise to symptoms which so accurately resemble those of laryngitis that the operation of tracheotomy has in some cases been resorted to, from the supposition that disease existed in the larynx; or it may press upon the thoracic duct and destroy life by inanition; or it may involve the oesophagus, producing dysphagia; or may burst into the oesophagus, when fatal hemorrhage will occur. Again, the innominate artery, or the sub- clavian, or left carotid, may be so obstructed by clots as to produce a weakness, or even a disap- pearance, of the pulse in one or the other wrist or in the left temporal artery; or the tumor may present itself at or above the manubrium, generally either in the median line or to the right of the sternum, and may simulate an aneurism of one of the arteries of the neck. Branches (Figs. 429 and 430). — The branches given off from the arch of the aorta are three in number — the innominate, the left common carotid, and the left subclavian arteries. RigJit pulmonaty vein. Right pulmonai y- vein. T.pp. subclavian ffi*/o\ a)tery. Left . carotid artery. Inf 6)101 thyroid I em artery. Bight common carotid artery. -Relation of great vessels at base of a fetal heart, seen from above (enlarged). (From a preparation in the Museum of the Royal College of Surgeons of England.) Peculiarities. Position of the Branches. — The branches, instead of arising from the highest part of the arch (their usual position), may be moved more to the right, arising from the commencement of the transverse or upper part of the ascending portion; or the distance from one another at their origin may be increased or diminished, the most frequent change in this respect being the approximation of the left carotid toward the innominate artery. The number of the primary branches may be reduced to a single vessel, or more commonly two, the left carotid arising from the innominate artery, or (more rarely) the carotid and sub- clavian arteries of the left side arising from the innominate artery. But the number may be increased to four, from the right carotid and subclavian arteries arising directly from the aorta, the innominate being absent. In most of these latter cases the right subclavian has been found to arise from the left end of the arch; in other cases it was the second or third branch given off instead of the first. Another common form in which there are four primary branches is that in which the left vertebral artery arises from the arch of the aorta between the left carotid and subclavian arteries. Lastly, the number of trunks from the arch may be increased to five or six; in these instances, the external and internal carotids arise separately from the arch, the common carotid being absent on one or both sides. In some cases six branches have been found, and this condition is associated with the origin of both vertebral arteries from the arch. Number Usual, Arrangement Different. — When the aorta arches over to the right side, the three branches have an arrangement the reverse of that which is usual, the innominate sup- 582 THE VASCULAR SYSTEMS plyino- the left side, and the carotid and subclavian (which arise separately) the right side. In other'^cases, where the aorta takes its usual course, the two carotids may be joined in a common trunk, and'the subclavians arise separately from the arch, the right subclavian generally arising from the left end of the arch. In some instances other arteries are found to arise from the arch of the aorta. Of these the most common are the bronchial, one or both, and the thyroidea ima ; also the internal mammary and the inferior thyroid have been seen to arise from this part of the vessel. The Innominate Artery (A. Anonyma) (Figs. 429 and 4.30). The innominate or brachiocephalic artery is the largest branch given off from the arch of the aorta. It arises, on a level with the upper border of the second right costal cartilage, from the commencement of the arch of the aorta in front of the left carotid, and, ascending obliquely to the upper border of the right sterno- clavicular articulation, divides into the right common carotid and right subclavian arteries. This vessel varies from an inch and a half to two inches in length. Relations. — In front, it is separated from the first piece of the sternum by the Sternohyoid and Sternothyroid muscles, the remains of the thymus gland, the left innominate and right inferior thyroid veins which cross its root, and sometimes the inferior cervical cardiac branch of the right vagus. Behind, it lies upon the trachea, which it crosses obliquely, and continuing upward it lies in the right pleura. On the right side is the right innominate vein, right vagus nerve, and the pleura; and on the left side, the remains of the thymus gland, the origin of the left carotid artery, the left inferior thyroid vein, and the trachea. Plan of the Relations of the Innominate Artery. In front. Sternum. Sternohyoid and Sternothyroid muscles. Remains of the thymus gland. Left innominate and right inferior thyroid veins. Inferior cervical cardiac branch from right vagus nerve. Right side. ^'' \ Left side. Right innominate vein. / innominate ^ Remains of thymus. Right vagus nerve. \ Artery. ' Left carotid. Pleura. V / Left inferior thyroid vein. ^~-__^^^ Trachea. Behind. Trachea. Right pleura. Branches. — The innominate usually gives off no branches, but occasionally a small branch, the thyroidea ima, is given off from this vessel. It also sometimes gives off a thymic or bronchial branch. The thyroidea ima (a. thyroidea ima), which is occasionally present, ascends in front of the trachea to the lower part of the thyroid body, which it supplies. It varies greatly in size, and appears to compensate for the deficiency or absence of one of the other thyroid vessels. It occasionally is found to arise from the right common carotid or from the aorta, the subclavian, or internal mammary vessels. Applied Anatomy. — Ligation of the innominate artery is an extremely grave operation. Thiswas first done by Mott. The " operation of clioice " seems to be that done by Burrell. "An incision is made at the anterior edge of the right Sternomastoid muscle, extending from the level of the cricoid cartilage to two inches below the upper border of the sternum. From this point another incision, extending outward four inches in length to the junction (right) of the outer THE COMMON CAROTID ARTERY 583 and middle thirds of the clavicle. The skin flap with the fascia and Platysma muscle is turned back. The Sternomastoid is severed close to its insertion into clavicle and sternum. The Sterno- thyroid, Sternohyoid, and Omohyoid are also divided." The sternoclavicular joint and the right side of the manubrium are honeycombed by means of a surgical engine or trephine. A flat retractor is slid underneath the joint while the trephining is done to protect the underlying parts. The block of bone is now removed. The right and left innominate veins going down to form the superior vena cava, with the vagus and right recurrent laryngeal nerves resting on the innominate artery, are all Jilainly to be seen. The sheath of the innominate artery is now opened and a ligature is applied. Burrell states that the exposure which is given by the removal of a part of the sternum is extremely satisfactory, and he fails to understand how a ligature can be applied to the innominate artery with any safety without a clear view of the anatomical structures involved. Peculiarities in Point of Division.— When the bifurcation of the innominate artery varies from the point above mentioned it sometimes ascends a considerable distance abo\'e the sternal end of the clavicle; less frequently it divides below it. In the former class of cases its length may exceed two inches, and in the latter be reduced to an inch or less. These are points of con- siderable interest for the surgeon to remember in connection with the operation of tying this vessel. Position. — When the aorta arches over to the right side, the innominate is directed to the left side of the neck instead of the right. Collateral Circulation. — Allan Burns demonstrated, on the dead subject, the possibility of the establishment of the collateral circulation after ligation of the innominate artery, by tying and dividing that artery, after which, he says, "Even coarse injection, impelled into the aorta, passes freely by the anastomosing branches into the arteries of the right arm, filling them and all the vessels of the head completely." ' The branches by which this circulation would be carried on are very numerous; thus, all the communications across the middle line between the branches of the carotid arteries of opposite sides would be available for the supply of blood to the right side of the head and neck; while anastomosis between the superior intercostal of the subclavian and the first aortic intercostal (see page 654 on the collateral circulation after ob- literation of the thoracic aorta) would bring the blood, by a free and direct course, into the right subclavian; the numerous connections, also, between the intercostal arteries and the branches of the axillary and internal mammary arteries would, doubtless, assist in the supply of blood to the right arm, while the deep e|5igastric, from the external iliac, would, by means of its anasto- mosis with the internal mammary, compensate for any deficiency in the vascularity of the wall of the thorax. ARTERIES OF THE HEAD AND NECK. The chief artery which supplies the head and neck on each side is the common carotid; it ascends in the necli and divides into two branches: (1) The external carotid, supplying the superficial parts of the head and face and the greater part of the neck; (2) the internal carotid, supplying to a great extent the parts within the cranial cavity. THE COMMON CAROTID ARTERY (A. CAROTIS COMMUNIS) (Figs. 428, 429). The common carotid arteries differ in length and in their mode of origin. The right common carotid (a. carotis communis dextra) begins at the bifurcation of the innominate artery, behind the right sternoclavicular articulation, and is confined to the neck. The left common carotid (a. carotis communis sinistra) arises from the highest part of the arch of the aorta to the left of and on a plane posterior to the innominate artery, and therefore consists of a thoracic and a cervical portion. The thoracic portion of the left common carotid artery ascends from the arch of the aorta through the superior mediastinum to the level of the left sternoclavicular joint, where it continues as the cervical portion. Relations. — In front, it is separated from the first piece of the sternum by the Sternohyoid ami Sterudlhyroid muscles, the anterior portions of the left pleura and lung, the left innominate vein, and (he remains of the thymus gland; behind, it lies on the trachea, oesophagus, thoracic * Surgical Anatomy of the Head and Neck, p. 62. 584 THE VA&CVLAB SYSTEMS duct, and the left recurrent laryngeal nerve. To its right side, it is in relation with the innomi- nate artery, inferior thyroid veins, and remains of the thymus gland. To its left side, with the left vagus nerve, left pleura, and left lung. The left subclavian artery is posterior and slightly external to it. Plan of the Relations of the Left Common Carotid. Thoracic Portion. In front. 1 Sternum. Sternohyoid and Sternothyroid muscles. Left innominate vein. Remains of the thymus gland. Intemallv. / \ Externally. ^ I 1 .aft P^mmnTi \ "^ Innominate artery. I Thoracic Left vagus nerve. Inferior thyroid veins. \ Portion. / Left pleura and lung. Remains of the thymus gland. \_^ / Left subclavian artery. Behind. Trachea. Oesophagus. Thoracic duct. Left recurrent laryngeal nerve. The cervical portions of the two common carotids resemble each other so closely that one description will apply to both. Each vessel passes obliquely upward from behind the sternoclavicular articulation to a level with the upper border of the thyroid cartilage, opposite the fourth cervical vertebra, where it divides into the external and internal carotid arteries. At the lower part of the neck the two common carotid arteries are separated from each other by a small interval, which contains the trachea; but at the upper part, the thyroid body, the larynx, and pharynx project forward between the two vessels, and give the appearance of their being placed farther back in this situa- tion. The common carotid artery is contained in a sheath derived from the deep cervical fascia, which also encloses the internal jugular vein and vagus nerve, the vein lying on the outer side of the artery, and the nerve between the artery and vein, on a plane posterior to both. On opening the sheath these three struc- tures are seen to be separated from one another, each being enclosed in a separate fibrous investment. Relations. — At the lower part of the neck the common carotid artery is very deeply seated, being covered by the integument, superficial fascia, Platysma, and deep cervical fascia, the Sternomastoid, Sternohyoid, and Sternothyroid muscles, and by the Omohyoid, opposite the cricoid cartilage; but in the upper part of its course, near its termination, it is more superficial, being covered merely by the integument, the superficial fascia, Platysma, deep cervical fascia, and inner margin of the Sternomastoid, and, when the latter is drawn backward, it is seen to be contained in a triangular space, bounded behind by the Sternomastoid, abote by the pos- terior belly of the Digastric, and below by the anterior belly of the Omohyoid. This part of the artery is crossed obliquely, from within outward, by the sternomastoid artery; it is crossed also by the superior and middle thyroid veins, which terminate in the internal jugular; and, descending on its sheath in front, is seen the descendens hypoglossi nerve, this filament being joined by one or two branches from the cervical nerves, which cross the vessel from without inward. Sometimes the descendens hypoglossi is contained within the sheath. The middle thyroid vein crosses the artery about its middle, and the anterior jugular vein below; the latter, however, is separated from the artery by the Sternohyoid and Sternothyroid muscles. Behind, the artery is separated from the transverse processes' of the vertebree by the Longus colli and THE COMMON CAROTID ARTERY 585 Rectus capitis anticus major muscles, the sympathetic cord being interposed between it and the muscles. The recurrent laryngeal nerve and inferior thyroid artery cross behind the vessel at its lower part. Internally, it is in relation with the trachea and thyroid gland, the latter overlapping it, the inferior thyroid artery and recurrent laryngeal nerve being interposed; higher up, with the larynx and pharynx. On its outer side are placed the internal jugular vein and vagus nerve. At the lower part of the neck the internal jugular vein on the right side diverges Fig. 435. — Applied anatomy of the arteries of the homing the carotid and subcla\ian arteries ^ from the artery, but on the left side it approaches it, and often overlaps its lower part. This is an important fact to bear in mind during the performance of any operation on the lower part of the left common carotid artery. In this region the relation which the right and left recurrent laryngeal nerves bear to the arteries is not identical. The left recurrent laryngeal nerve lies behind the thoracic portion of the left common carotid artery and internal to the cervical portion of the vessel. The right nerve passes obliquely upward and inward behind the right common carotid to reach its inner side. 1 The hypoglossal nerve is not rightly placed in this drawinR. It forms the upper side of a triangle, the two lower sides of which are the two bellies of the Diga.stric. The lingual artery would then run under the Hyoglossus muscle, below the hypoglossal nerve. (See Fig. 437.) 586 THE VASCULAR SYSTE3IS Plan of the Relations of the Common Carotid Artery. In front. Integument and superficial fascia. Omohyoid. Deep cervical fascia. Descendens and communicans hypoglossi Platysma. nerves. Sternomastoid. Sternomastoid artery. Sternohyoid. Superior and middle thyroid veins. Sternothyroid. Anterior jugular vein. Externally. Internally. Internal jugular vein. Vagus nerve. I Common | 1 Carotid. ) Trachea. Thyroid gland. Recurrent laryngeal nerve. Inferior thyroid artery. Larynx. Pharynx. Behind. Longus colli. Sympathetic cord. Rectus capitis anticus major. Inferior thyroid artery. Recurrent laryngeal nerve. On the posterior aspect of the angle of bifurcation of the common carotid is a reddish-brown oval body known as the caiotid gland. (See Ductless Glands.) Peculiarities as to Origin. — The right common carotid may arise above or below the upper border of the sternoclavicular articulation. This variation occurs in one out of about eight cases and a half, and the origin is more frequently below than above; or the artery may arise as a separate branch from the arch of the aorta or in conjunction with the left carotid. The left common carotid varies more frequently in its origin than the right. In the majority of abnor- mal cases it arises with the innominate artery, or, if the innominate artery is absent, the two carotids arise usually by a single trunk. It rarely joins with the left subclavian, except in cases of transposition of the arch. Peculiarities as to Point of Division. — In the majority of abnormal cases this occurs higher than usual, the artery dividing into two branches opposite the hyoid bone, or even higher; more rarely it occurs below, opposite the middle of the larynx or the lower border of the cricoid car- tilage; and one case is related by Morgagni where the common carotid, only an inch and a half in length, divided at the root of the neck. Very rarely the common carotid ascends in the neck without any subdivision, the internal carotid being wanting; and in a few cases the com- mon carotid has been found to be absent, the external and internal carotids arising directly from the arch of the aorta. This peculiarity existed on both sides in some instances, on one side in others. Occasional Branches. — Each common carotid usually gives off no branch previous to its bifurcation; but it occasionally gives origin to the superior thj'roid or its laryngeal branch, the ascending pharyngeal, the inferior thyroid, or, more rarely, the vertebral artery. Surface Marking. — The course of each common carotid artery is indicated by a line drawn from the sternal end of the clavicle below, to a point midway between the angle of the mandible and the mastoid process above. That portion of the line below the level of the upper border of the thyroid cartilage would represent the course of the vessel. Applied Anatomy. — The operation of tying the common carotid artery may be necessary in a case of woimd of that vessel or its branches, in aneurism, or in a case of pulsating tumor of the orbit or skull. If the wound involves the trunk of the common carotid, it will be necessary to tie the artery through the wound above and below the wounded part. If the wound is too small to admit of safe and rapid work it must be enlarged. In cases of aneurism, or where one of the branches of the common carotid is wounded in an inaccessible situation, it may be judged necessary to tie the trunk. In such cases the whole of the artery is accessible, and any part may be tied except close to either end. When the case is such as to allow of a choice being made, the lower part of the carotid should never be selected as the spot upon which to place a ligature, for not only is the artery in this situation placed very deeply in the neck, but it is covered by three layers of muscles, and, on the left side, in the great majority of cases, the interna! jugular vein passes obliquely in front of it. Neither should the upper end be selected, for here the superior thyroid vein and its tributaries would give rise to very considerable difficulty in the appli- cation of a ligature. The point most favorable for the operation is that part of the vessel which is at the level of the cricoid cartilage. It occasionally happens that the carotid artery bifm-cates THE COMMON CAROTID ABTEBY 587 below its usual position; if the artery be exposed at its point of bifurcation, both divisions of the vessel should be tied near their origin, in preference to tying the trunk of the artery near its termination; and if, in consequence of the entire absence of the common carotid or from its early division, two arteries, the external and internal carotids, are met with, the ligature should be placed on that vessel which is found on corajiression to be connected with the diseased area. Ligation of the Carotid at the Level of the Cricoid Cartilage {Lujation in. fhc Triangle of Election).' — The triangle of election is bounded posteriorly hy the anterior edge of the Ster- nomastoid; is bounded above by the posterior belly of the Digastric; is bounded below hy the anterior belly of the Omohyoid. In this operation the direction of the vessel and the inner margin of the Sternomastoid are the chief guides to its performance. The patient should be placed on his back with the head thrown back and tui-ned slightly to the opposite side; an incision is to be made, three inches long, in the direction of the anterior border of the Sterno- mastoid, so that the centre corresponds to the level of the cricoid cartilage; after dividing the inteo-ument, superficial fascia, and Platysma, the deep fascia must be cut through on a director, so as to avoid wounding numerous small veins that are usually found beneath. The head may now be brought forward so as to relax the parts somewhat, and the margins of the wound are held asunder by retractors. The descendens hypoglossi nerve may now be exposed, and must be avoided, and, the sheath of the vessel having been raised by forceps, is to be opened to a small extent over the artery at its inner side. The internal jugular vein may present itself alternately distended and relaxed; this should be compressed both above and below, and drawn outward, in order to facilitate the operation. The aneurism needle is passed from the outside, care being taken to keep the needle in close contact with the artery, and thus avoid the risk of injuring the internal jugular vein or including the vagus nerve. Before the ligature is tied it should be ascertained that nothing but the artery is included in it. Ligation of the Common Carotid at the Lower Part of the Neck (Ligation in the Triangle of Necessity)} — Tlie triangle of necessity is bounded aljove by the anterior belly of the Omo- hyoid; is bounded behind by the anterior margin of the Sternomastoid; is bounded in front by the mid-line of the neck. This operation is sometimes required in cases of aneurism of the upper part of the carotid, especially if the sac is of large size. It is best performed by dividing the sternal origin of the Sternomastoid muscle, but may be done in some cases, if the aneurism is not of very large size, by an incision along the anterior border of the Sternomastoid, extending down to the sternoclavicular articulation, and by then retracting the muscle. The easiest and best plan, however, is to make an incision two or three inches long down the lower part of the anterior border of the Sternomastoid muscle to the sternoclavicular joint, and a second incision, starting from the termination of the first, along the upper border of the clavicle for about two inches. This incision is made through the superficial and deep fascia, and the sternal origin of the muscle is exposed. This is to be divided on a director, and turned up, with the super- ficial structures, as a triangular flap. Some loose connective tissue is to be divided or torn through, and the outer border of the Sternohyoid muscle exposed. In doing this care must be taken not to wound the anterior jugular vein, which crosses the muscle to reach the external jugular or subclavian vein. The Sternohyoid, and with it the Sternothyroid, are to be drawn inward by means of a retractor, and the sheath of the vessel is exposed. This must be opened with great care on its inner or tracheal side, so as to avoid the internal jugular vein. This_ is especially necessary on the left side, where the artery is commonly overlapped by the vein. On the right side there is usually an interval between the artery and the vein, and not the same risk of wounding the latter. The common "carotid artery, being a long vessel without any branches, is particularly suitable for the performance of Brasdor's operation for the cure of an aneurism of the lower part of the vessel. Brasdor's procedure consists in ligating the artery on the distal side of the aneurism, and in the case of the common carotid there are no branches given off from the vessel between the aneurism and the site of the ligature; hence, the flow of blood through the sac of the aneurism is diminished, and cm-e takes place in the usual way, by the deposit of laminated fibrin. Collateral Circulation. — After ligation of the common carotid the collateral circulation can be perfectly established by the free communication which exists between the carotid arteries of opposite" sides, both without and within the cranium, and by enlargement of the branches of the subclavian artery on the side corresponding to that on which the vessel has been tied — the chief communication outside the skull taking place between the superior thyroid from the external carotid and the inferior thyroid from the subclavian, the profunda cervicis from the subclavian and the superior intercostal with the arteria princeps cervicis of the occipital; the vertebral taking the place of the internal carotid within the cranium. 1 For description of the triangles of the neck, see page 602. 588 THE VASCULAR SYSTEMS The External Carotid Artery (A. Carotis Externa) (Figs. 434, 435). The external carotid artery commences opposite the upper border of the thyroid cartilage, and, taking a slightly curved course, passes upward and forward, and then inclines backward to the space between the neck of the condyle of the man- dible and the external meatus, where it divides into the superficial temporal and internal maxillary arteries. It rapidly diminishes in size in its course up the neck, owing to the number and large size of the branches given off from it. In the child it is somewhat smaller than the internal carotid, but in the adult the two vessels are of nearly equal size. At its origin this artery is more superficial and placed nearer the. middle line than the internal carotid, and is contained in the triangular space bounded by the Sternomastoid behind, the anterior belly of the Omohyoid below, and the posterior belly of the Digastric and the Stylohyoid above (i. e., the superior carotid triangle). Relations. — It is covered by the skin, superficial fascia, Platysma, deep fascia, and anterior margin of the Sternomastoid, and is crossed by the hypoglossal nerve, and by the lingual and facia] veins; it is afterward crossed by the Digastric and Stylohyoid muscles, and higher up passes deeply into the substance of the parotid gland, where it lies beneath the facial nerve and the junction of the temporal and internal maxillary veins. Internally is the hyoid bone, wall of the pharynx, the superior laryngeal nerve, and the ramus of the mandible, from which it is separated by a portion of the parotid gland. Externally, in the lower part of its course, is the internal carotid artery. Behind it, near its origin, is the superior laryngeal nerve; and higher up, it is separated from the internal carotid by the Styloglossus and Stylopharyngeus muscles, the glossopharyngeal nerve, and part of the parotid gland. Plan of the Relations of the External Carotid. In front. Skin, superficial fascia. Platysma and deep fascia. Anterior border of Sternomastoid. Hypoglossal nerve. Lingual and facial veins. Digastric and Stylohyoid muscles. Parotid gland with facial nerve and temporomaxillary vein in its substance. Internally. Hyoid bone. Pharynx. Superior laryngeal nerve. Parotid gland. Ramus of mandible. Externally. Internal carotid artery (lower part). Behind. Superior laryngeal nerve. Styloglossus. Stylopharyngeus. Glossopharyngeal nerve. Parotid gland. Surface Marking. — The position of the external carotid artery may be marked out with sufficient accuracy by a line drawn from the front of the meatus of the external ear to the side of the cricoid cartilage, slightly arching the median line. Applied Anatomy. — The application of a ligature to the external carotid may be required m case of wounds of this vessel, or of its branches when these cannot be tied, and in some cases of pulsating tumor of the scalp or face. The operation has not received the attention which it THE EXTERNAL CAROTID ARTERY 589 deserves, owing to the fear which surgeons have entertained of secondary hemorrhage, on account of the number of branches given off from the vessel. This fear, however, has been shown by Mr. Cripps not to be well founded.' I^igation is often very useful as a means of preventing excessive hemorrhage in operations about the face, jaws, and mouth. It is sometimes employed with the hope of lessening the growth of tumors by cutting off the blood supply, but ligation is useless for this purpose. Ligation of one external carotid artery arrests the circulation for only a brief period, and within a very few days the circulation is practically freely reestablished. This result is seen to be inevitable when we recall the numerous branches of the external carotid, their free anastomoses, and the fact that a very great number of extremely minute vessels in the middle line join the external carotid system of one side to that of the other side. Robert H. M. Dawbarn points out that ligation of both external carotids produces only temporary anemia, for " inside of a week or ten days thereafter the pulse can again be felt in the temporals and facials upon both sides."' Dawbarn points out that even after excision of the external carotids, with separate ligation of each of the eight branches, blood can still reach the nose, tongue, etc., from outside systems by twenty-nine distinct routes. Whereas ligation of even both carotids will not prevent the growth of a malignant tumor, excision of each external carotid, with separate control of its eight branches, will sometimes prove of great value in retarding the progress of a growth. It "starves" the growth and may cause it to shrink (Dawbarn 's oper- ation). To tie the external carotid near its origin, below the point where it is crossed by the Digastric, an incision about three inches in length should be made along the margin of the Sterno- mastoid, from the angle of the mandible to the upper border of the thyroid cartilage. The ligature should be applied between the lingual and superior thyroid branches. To tie the vessel above the Digastric, between it and the parotid gland, an incision should be made, from the lobe of the ear to the greater cornu of the hyoid bone, dividing successively the skin, Platysma, and fascia. By drawing the Sternomastoid outward, the posterior belly of the Digastric and Stylohyoid muscles downward, and separating them from the parotid gland, the vessel will be exposed, and a ligature may be applied to it. The circulation is at once reestablished by the free com- munication between most of the large branches of the artery (facial, lingual, superior thyroid, occipital) and the corresponding arteries of the opposite side and by the anastomosis of its branches with those of the internal carotid, and of the occipital with the branches of the sub- clavian, etc. Branches. — The external carotid artery gives off eight branches, which, for convenience of description, may be divided into four sets. (See Fig. 436, Plan of the Branches.) Anterior. Posterior. Ascending. Terminal. Superior Thyroid. Occipital. Ascending Phar- Superficial Temporal. Lingual. Posterior Auric- yngeal. Internal Maxillary. Facial. ular. The student is here reminded that many variations are met with in the number, origin, and course of these branches in different subjects; but the above arrange- ment is that which is found in the great majority of cases. 1. The superior thyroid artery (a. thyroidea superior) (Figs. 435 and 436) arises from the external carotid artery, just below the greater cornu of the hyoid bone, and terminates in the thyroid gland. Relations. — From its origin under the anterior border of the Sternomastoid it runs upward and forward for a short distance in the superior carotid triangle, where it is covered by the integument, fascia, and Platysma; it then arches downward and forward beneath the Omo- hyoid, Sternohyoid, and Sternothyroid muscles. To the inner side are the Inferior constrictor of the pharynx and the external branch of the laryngeal nerve. It distributes numerous branches to the upper part of the gland, anastomosing with its fellow of the opposite side and with the inferior thyroid arteries. The terminal branches supplying the gland are generally two in number; one, the largest, the anterior branch (ramus anterior), descends at the anterior border of the lateral lobe of the gland, reaches the upper border of the isthmus, and then passes in the substance of the isthmus to the middle line of the neck, where it anastomoses with the corre- sponding artery of the opposite side; the posterior branch {ramus fosterior) descends along 590 THE VASCULAR SYSTEMS the posterior border of the lateral lobe of the gland, the anterior and posterior branches anasto- mose with each other and with branches of the inferior thyroid, and both of them send branches to the thyroid gland (rami glandidares) . Besides the arteries distributed to the muscles by which it is covered and to the substance of the gland. Branches. — The branches of the superior thyroid are the following: Infrahyoid. Sternomastoid. Superior Laryngeal. Cricothyroid. The infrahyoid branch (ramus hyoideus) is small, and runs along the lower border of the hyoid bone beneath the Thyrohyoid muscle; after supplying the muscles connected to that bone, it forms an arch, by anastomosing with the vessel of the opposite side. The sternomastoid branch (ramus stern ocleidomastoideus') runs downward and out- ward across the sheath of the common carotid artery, and supplies the Sterno- mastoid and neighboring muscles and integument. There is frequently a separate branch from the external carotid distributed to the Sternomastoid muscle. The superior laryngeal (a. laryngea sujxrior), larger than either of the preceding, accompanies the internal branch of the superior laryngeal nerve, beneath the Thyrohyoid muscle; it pierces the thyrohyoid membrane, and supplies the muscles, mucous membrane, and glands of the larynx, anastomosing with the branch from the opposite side. The cricothyroid (ramus cricothyreoidetis) is a small branch which runs trans- versely across the cricothyroid membrane, and communicates with the artery of the opposite side. Applied Anatomy. — The superior thyroid, or one of its branches, is often divided in. cases of cut throat, giving rise to considerable hemorrhage. In such cases the artery should be secured, the wound being enlarged for that pur- pose, if necessary. The operation may be easily performed, the position of the artery being very superficial, and the only structures of importance covering it being a few small veins. The superior and inferior thyroid arteries of the involved side are ligated before extirpating a goitrous lobe of the thyroid gland. The position of the superficial descending branch is of importance in connection with the operation of ligation of the common carotid artery. It crosses and lies on the sheath of this vessel, and may be wounded in opening the sheath. The position of the cricothyroid branch should be remembered, as it may prove the source of troublesome hemorrhage during the operation of laryngotomy. In performing the operation of quick laryngotomy the cricothyroid membrane should be incised transversely in order to avoid this vessel. 2. The lingual artery (a. Ungualis) (Figs. 435 and 436) arises from the external carotid between the superior thyroid and facial; it first runs obliquely upward and inward to the great cornu of the hyoid bone; it then curves downward and forward, forming a loop which is crossed bv the hypoglossal nerve, and pass- ing beneath the Digastric and Stylohyoid muscles, it runs horizontally forward, beneath the Hyoglossus, and finally, ascending almost perpendicularly to the tongue, turns forward on its under surface as far as the tip, under the name of the ranine artery. Fig. 437.— Showing the relation of the hngua) artery and hypoglossal nerve; Lesser's triangle is liounded above by the nerve, below by the posterior belly of the Digastric, and in front by the posterior border of the Mylohyoid, indicated by a solid line. The floor of the triangle is occupied by the Hyoglossus. THE EXTERNAL CAROTID ARTERY 591 Relations. — Xi^jirst, or oblique, portion is superficial, being contained in the same triangular space as the superior thyroid artery, resting upon the Middle constrictor of the pharynx, and covered by the Platysma and fascia of the neck. Its second, or curved, portion also lies upon the Middle constrictor, being covered at first by the tendon of the Digastric and the Stylohyoid muscle, and afterward by the Hyoglossus, the latter muscle separating it from the hypoglossal nerve. Its third, or horizontal, portion lies between the Hyoglossus and Geniohyoglossus muscles. The fourth, or terminal, part, under the name of the ranine, runs along the under surface of the tongue to its tip; it is very superficial, being covered only by the mucous mem- brane, and rests on the Lingualis on the outer side of the Geniohyoglossus. The hypoglossal nerve crosses the lingual artery, and then becomes separated from it, in the second part of its course, by the Hj'oglossus muscle. Branches. — The branches of the lingual artery are the Suprahyoid. Sublingual. Dorsalis Linguse. Ranine. The suprahyoid branch (ramus hyoideus) runs along the upper border of the hyoid bone, supplying the muscles attached to it and anastomosing with its fellow of the opposite side. The dorsalis linguae {ramus dorsalis linguae) (Fig. 496) arises from the lingual artery beneath the Hyoglossus muscle; it ascends to the back of the dorsum of the tongue, and supplies the mucous membrane, the tonsil, soft palate, 'and epiglottis, anastomosing with its fellow from the opposite side. This artery is frequently represented by two or three small branches. The sublingual (a. sublingualis), which may -be described as a branch of bifur- cation of the lingual artery, arises at the anterior margin of the Hyoglossus muscle, and runs forward between the Geniohyoglossus and the sublingual gland. It supplies the substance of the gland, giving branches to the Mylohyoid and neigh- boring muscles, the mucous membrane of the mouth and gums. One branch runs behind the alveolar process of the mandible in the substance of the gum to anas- tomose with a similar artery from the other side. The ranine, or deep lingual (a. profunda linguae), may be regarded as the other branch of bifurcation. It is usually described as the continuation of the lingual artery; it runs along the under surface of the tongue, resting on the Inferior lin- gualis, and covered by the mucous membrane of the mouth; it lies on the outer side of the Geniohyoglossiis, accompanied by the lingual nerve. On arriving at the tip of the tongue it is said to anastomose with the artery of the opposite side, but this is denied by Hyrtl. In the mouth these vessels are placed one on either side of the frenum. Applied Anatomy. — The lingual artery may be divided near its origin in cases of cut throat, a complication that not infrequently happens in this class of wounds; or severe hemorrhage which cannot be restrained by ordinary means may ensue from a wound or deep ulcer of the tongue. In the former case the primary wound may be enlarged if necessary, and the bleeding vessels secured. In the latter case it has been suggested that the lingual artery should be tied near its origin. Ligation of the lingual artery is also occasionally practised, as a palliative measure, in cases of cancer of the tongue, in order to check the progress of the disease by starving the growth and it is often tied as a preliminary measure to removal of the tongue. The operation is a somewhat difficult one, on account of the depth of the artery, the number of important structures by which it is surrounded, the loose and yielding nature of the parts upon which it is supported, and its occasional irregularity of origin. An incision is to be made in a curved direc- tion from a point one finger's breadth external to the symphysis of the mandible downward to the cornu of the hyoid bone, and then upward to near the angle of the mandible. Care must be taken not to carry this incision too far backward, for fear of endangering the facial vein. In the first incision the skin, superficial fascia, and Platysma will be divided, and the deep fascia exposed. The deep fascia is then to be incised, and the submaxillary gland exposed and pulled upward by retractors. A triangular space is now exposed. Leaser's triangle (Fig. 437), bounded internally by the posterior border of the Mylohyoid muscle; below and externally, by the tendon of the Digastric; and above, by the hypoglossal nerve. The floor of the space is formed by the 592 THE VASCULAB SYSTEMS Hyoglossus muscle, beneath which the artery lies. The fibres of this muscle are now to be cut through horizontally and the vessel exposed, care being taken, while near the vessel, not to open the pharynx. Troublesome hemorrhage may occur in the division of the frenum in children if the ranine arteries, which lie on each side of it, are wounded. The student should remember that the oper- ation is always to be performed with a pair of blunt-pointed scissors, and the mucous membrane only is to be divided by a very superficial cut, which cannot endanger any vessel. The scissors, also, should be directed toward the floor of the mouth. Any further liberation of the tongue which may be necessary can be effected by tearino-. 3. The facial artery (a. maxillaris externa) (Figs. 435 and 438) arises a little above the lingual, and passes obliquely upward, beneath the Digastric and Stylo- hyoid muscles, and frequently beneath the hypoglossal nerve; it now runs forward 1 teria septi nasi, uperior coronary. Inferior coronary. Infei ior labial. Fig. 438. — The arteries of the face and scalp. The muscle tissue of the lips must be supposed to have beea cut away, in order to show the course of the coronary arteries. under cover of the body of the mandible, lodged in a groove on the posterior surface of the submaxillary gland; this may be called the cervical part of the artery. It then curves upward over the body of the mandible at the anterior inferior angle of the Masseter muscle; passes forward and upward across the cheek to the angle of the mouth, then upward along the side of the nose, and terminates at the inner canthus of the eye, under the name of the angular artery. The facial artery, both in the neck and on the face, is remarkably tortuous; in the former situation its tor- tuosity enables it to accommodate itself to the movements of the pharynx in deglu- tition, and in the latter to the movements of the mandible and the lips and cheeks. THE EXTERNAL CAROTID ARTERY 593 Relations. — In the neck its orlp;in is .su|)erfieial, being covered by the integument, Piatysnia, and fascia; it then passes beneath ihc ])igaslric and Stylohyoid muscles and part of the sub- maxillary gland. It lies upon the ^Middle constrictor of the pharynx, and is separated from the Styloglossus and Hyoglossus muscles by a portion of the submaxillary gland. On the face, where it passes over the body of the mandible, it is comparatively superficial, lying immediately beneath the Platysma. In this situation its pulsation may be distinctly felt, and compression of the vessel against the bone can be eflectually made. In its course over the face it is covered by the integument, the fat of the cheek, and, near the angle of the mouth, by the Platysma, Risorius, and Zygomatic muscles. It rests on the Buccinator, the Levator anguli oris, and the Levator labii superioris (sometimes piercing or else passing under this last muscle). The facial vein lies to the outer side of the artery, and takes a more direct course across the face, where it is separated from the artery by a considerable interval. In the neck it lies superficial to the artery. The branches of the facial nerve cross the artery, and branches of the infra- orbital nerve lie beneath it. Branches. — The branches of this vessel may be divided into two sets — those given off below the mandible (cervical), and those on the face (facial). Cervical Branches. Facial Branches. Ascending Palatine. Inferior labial. Tonsillar. Inferior labial coronary. Submaxillary. Superior labial coronary. Submental. Lateral nasal. Angular. Muscular. The ascending palatine (a. palatine ascendens) passes up between the Styloglossus and Stylopharyngeus to the outer side of the pharynx, along which it is continued between the Superior constrictor and the Internal pterygoid to near the base of the skull. It divides, near the Levator palati, into two branches; one follows the course of the Levator palati, and, winding over the upper border of the Superior constrictor, supplies the soft palate and the palatal glands, anastomosing with its fellow of the opposite side and with the posterior palatine branch of the internal maxillary artery; the other pierces the Superior constrictor and supplies the tonsil and Eustachian tube, anastomosing with the tonsillar and ascending pharyngeal arteries. The tonsillar branch (ramus tonsillaris) passes up between the Internal pterygoid and Styloglossus, and then ascends along the side of the pharynx, perforating the Superior constrictor, to ramify in the substance of the tonsil and root of the tongue. The submaxillary or glandular branches (ra^ni glandulares) consist of three or four large vessels, which supply the submaxillary gland, some being prolonged to the neighboring muscles, lymph nodes, and integument. The submental (a. submentalis) (Fig. 435), the largest of the cervical branches, is given off from the facial artery just as that vessel emerges from the submaxillary gland; it runs forward upon the Mylohyoid muscle, just below the body of the mandible and beneath the Digastric; after supplying the surrounding muscles, and anastomosing with the sublingual artery by branches which perforate the Mylohyoid muscle, it arrives at the symphysis of the mandible, where it turns over the border of the mandible and divides into a superficial and a deep branch; the former passes between the integument and Depressor labii inferioris, supplies both, and anastomoses with the inferior labial. The deep branch passes between the latter muscle and the bone, supplies the lip, and anastomoses with the inferior labial and mental arteries. The inferior labial (a. labialis inferior) (Fig. 438) passes beneath the Depressor anguli oris, to supply the muscles and integument of the chin and lower lip, anasto- mosing with the inferior labial coronary and submental branches of the facial, atehal aiteiy Supi ascapula) at te) y \ ,^^^ ^..cl net i€ Subclavian at tery Extei nal jugu- lai letn Eiqht ttmomi- nate lein Jnnomi nate aitety. \ -■S -Subscapular artery. -Musculospiral nerve. Fig. 456. — The subclavian artery, showing its relations. (From a preparatic College of Surgeons of England.) the Museum of the Royal Plan op the Relations of First Portion of the Right Subclavian Artery. In front. Skin, superficial fascia. Platysma, deep fascia. Clavicular origin of Sternomastoid. Sternohyoid and Sternothyroid. Anterior jugular, internal jugular, and vertebral veins. Vagus and cardiac nerves. Loop from the sympathetic. Beneath. Pleura. Recurrent laryngeal nerve. Behind. Recurrent laryngeal nerve. Sympathetic. Pleura and apex of lung. Longus colli. First thoracic vertebra. THE SUBCLAVIAN ARTERY 625 First Part of the Left Subclavian Artery (Figs. 428 and 429).— The first part of the left subclavian artery ariaes from the arch of the aorta, behind the left common carotid, and at the level of the fourth thoracic vertebra; it ascends nearly vertically to the root of the neck and then arches outward to the inner margin of the Scalenus anticus muscle. Relations. — It is in relation, in front, with the vagus, cardiac, and phrenic nerves, which lie parallel with it, the left carotid artery, left internal jugular and vertebral veins, and the com- mencement of the left innominate vein, and is covered by the Sternothyroid, Sternohyoid, and Sternomastoid muscles. A loop of the sympathetic encircles the artery, forming the an-sa snb- clavia. Behind', it is in relation with the oesophagus, thoracic duct, inferior cervical ganglion of the sympathetic, and Longus colli muscle; higher up, however, the oesophagus and thoracic duct lie to its right side; the latter ultimately arching over the vessel to join the angle of union between the subclavian and internal jugular veins. To its inner side are the oesophagus, trachea, thoracic duct, and left recurrent laryngeal nerve; to its outer side, the left pleura and lung. Plan of the Relations of First Portion of the Left Subclavian Artery. In front. Vagus, cardiac, and phrenic nerves. Left carotid artery. Thoracic duct. Left internal jugular, vertebral, and innominate veins. Sternothyroid, Sternohyoid, and Sternomastoid muscles. Inner side. Older side. Pleura and left lung. Trachea. (Esophagus. Thoracic duct. Left recurrent laryngeal nerve. 3chind. (Esophagus and thoracic duct. Inferior cervical ganglion of sympathetic. Longus colli. Second and Third Parts of the Subclavian Artery (Figs. 432 and 456). — The second portion of the subclavian artery lies behind the Scalenus anticus muscle; it is very short, and forms the highest part of the arch described by that vessel. Relations. — It is covered, in front, by the skin, superficial fascia, Platysma, deep cervical fascia, the Sternomastoid and the Scalenus anticus muscles. On the right side the phrenic nerve is separated from the second part of the artery by the Scalenus anticus muscle, while on the left side the nerve crosses the first part of the artery immediately to the inner edge of the muscle. Behind, it is in relation with the pleura and the Scalenus medius muscle. Above, is the brachial plexus of nerves; below, the pleura. The subclavian vein lies below and in front of the artery, separated from it by the Scalenus anticus muscle. Plan of the Relations of Second Portion of Subclavian Artery. In front. Skin and superficial fascia. Platysma and deep cervical fascia. Sternomastoid. Phrenic nerve. Scalenus anticus. Subclavian vein. Above. Brachial plexus. Below. Pleura. Behind. Pleura and Middle Scalenus. 10 626 2!£rz; VASCULAB SYSTEMS The third portion of the subclavian artery passes downward and outward from the outer margin of the Scalenus anticus muscle to the outer border of the first rib, where it becomes the axillary artery. This portion of the vessel is the most superficial, and is contained in tlie subclavian triangle (see page 606). Relations. — It is covered, in front, by the skin, the superficial fascia, the Platysma, the descending clavicular branches of the cervical plexus, and the deep cervical fascia; by the clavicle, the Subclavius muscle, the suprascapular artery and vein, and the transverse cervical vein; the nerve to the Subclavius muscle passes vertically downward in front of the artery. The external jugular vein crosses the artery at its inner side, and receives the suprascapular and transverse cervical veins, which frequently form a plexus in front of it. The subclavian vein is below and in front of the artery, lying close behind the clavicle. Behind, it lies on the Middle Scalenus muscle and the lowest cord of the brachial plexus, formed by the union of the last cervical and first thoracic nerves. Above and to its outer side are the upper trunks of the brachial plexus and the Omohyoid muscle. Below, it rests on the upper surface of the first rib, or on the cervical rib if one be present. Plan of the Relations of Third Portion of Subclavian Artery. In front. Skin and superficial fascia. Platysma and deep cervical fascia. Descending branches of cervical plexus. Nerve to Subclavius muscle. Subclavius muscle, suprascapular artery, and vein. The external jugular and transverse cervical veins. The clavicle. Above. / Subclavian \ BeloW Brachial plexus. [ ™J'^'l j First rib. Omohyoid. , Behind. Scalenus medius. Lower cord of brachial plexus. Peculiarities. — The subclavian arteries vary in their origin, their course, and the height to which they rise in the neck. The origin of the right subclavian from the innominate takes place, in some cases, above the sternoclavicular articulation, and occasionally, but less frequently, in the cavity of the thorax, below that point. Or the artery may arise as a separate trunk from the arch of the aorta. In such cases it may be either the first, second, third, or even the last branch derived from that vessel; in the majority of cases it is the first or last, rarely the second or third. When it is the first branch, it occupies the ordinary position of the innominate artery; when the second or third, it gains its usual position by passing fjehind the right carotid; and when the last branch, it arises from the left extremity of the arch, at' its upper or back part, and passes obliquely toward the right side, usually behind the trachea, oesophagus, and right carotid, sometimes between the oesophagus and trachea to the upper border of the first rib, whence it follows its ordinary course. Its manner of development is such that the inferior laryngeal nerve is not looped under the ves- sel, but passes in a nearly straight course on its way to the larynx. In very rare instances this vessel arises from the thoracic aorta, as low down as the fourth thoracic vertebra. Occasionally it perforates the Scalenus anticus muscle; more rarely it passes in front of that muscle. Some- times the subclavian vein passes wdth the artery behind the Scalenus anticus muscle. The artery may ascend as high as an inch and a half above the clavicle or any intermediate point between this and the upper border of the bone, the right subclavian usually ascending higher than the left. The left subclavian is occasionally joined at its origin with the left common carotid. Surface Marking. — The course of the subclavian artery in the neck may be mapped out by describing a curve, with its convexity upward at the base of the posterior triangle. The inner THE SVBCLA VIAN ARTERY 627 end of this curve corresponds to the sternoclavicular joint, the outer end of the centre of the lower border of the clavicle. The curve is to be drawn with such an amount of convexity that its mid-point reaches half an inch above the upper l^order of the clavicle. The left subclavian artery is more deeply placed than the right in the first part of its course, and, as a rule, does not reach quite as high a level in the neck. It should be borne in mind that the posterior border of the Sternomastoid muscle corresponds to the outer border of the Scalenus anticus muscle, so that the third portion of the artery, that part most accessible for operation, lies immediately external to the posterior border of the Sternomastoid muscle. Applied Anatomy. — The relations of the subclavian arteries of the two sides having been examined, the student should direct his attention to a consideration of the best position in which compression of the vessel may be effected, or in what situation a ligature may be best applied in cases of aneurism or wound. Compression of the subclavian artery is required in cases of operation about the shoulder, in the axilla, or at the upper part of the arm; and the student will observe that there is only one situation in which it can be effectually applied — viz., where the artery passes across the upper surface of the first rib. In order to compress the vessel in this situation, the shoulder should be depressed, and the surgeon, grasping the side of the neck, should press with his thumb in the angle formed by the posterior border of the Sternomastoid with the upper border of the clavicle, downward, backward, and inward against the rib; if from any cause the shoulder cannot be sufficiently depressed, pressure may be made from before backward, so as to compress the artery against the Scalenus medius muscle and the transverse process of the seventh cervical vertebra. In appropriate cases a preliminary incision may be made through the cervical fascia, and the finger may be pressed down directly upon the artery. Ligation of the subclavian artery may be required in cases of wounds or of aneurism in the axilla, or in cases of aneurism on the cardiac side of the point of ligation; and the third part of the artery is that which is most favorable for an operation, on account of its being compara- tively superficial and most remote from the origin of the large branches. In those cases where the clavicle is not displaced, this operation may be performed with comparative facility; but where the clavicle is pushed up by a large aneurisaial tmnor in the axilla the artery is placed at a great depth from the surface, which materially increases the difficulty of the o]ieration. Under these circumstances it becomes a matter of importance to consider the height to which this vessel reaches above the bone. In ordinary cases its arch is about half an inch above the clavicle, occasionally it is as high as an inch and a half, and sometimes so low as to be on a level with the upper laorder of the clavicle. If the clavicle is displaced, these variations will necessarily make the operation more or less difficult, according as the vessel is more or less accessible. The procedure in the operation of tying the third portion of the subclavian artery is as fol- lows: The patient being placed on a table in the supine position, with the head drawn over to the opposite side and the shoulder depressed as much as possible, the integument should be drawn downward over the clavicle, and an incision made through it, upon that bone, from the anterior border of the Trapezius to the posterior border of the Sternomastoid, to which may be added a short vertical incision meeting the inner end of the preceding. The object in drawing the skin downward is to avoid any risk of wounding the external jugular vein, for as it perforates the deep fascia above the clavicle, it cannot be drawn downward with the skin. The soft parts should now be allowed to glide up, and the cervical fascia should be divided upon a director, and if the interval between the Trapezius and Sternomastoid muscles be insufficient for the per- formance of the operation, a portion of one or both may be divided. The external jugular vein will now be seen toward the inner side of the wound; this and the suprascapular and transverse cervical veins, which terminate in it, should be held aside. If the external jugular vein is at all in the way and exposed to injury, it should be tied in two places and divided. The suprascapular artery should be avoided, and the Omohyoid muscle held aside if necessary. In the space beneath this muscle careful search must be made for the vessel; a layer of deep fascia and some connective tissue having been divided carefully, the outer margin of the Scalenus anticus muscle must be felt for, and, the finger being guided by it to the first rib, the pulsation of the subclavian artery will be felt as it passes over the rib. The sheath of the vessels having been opened, the aneurism needle may then be passed around the artery from above downward and inward, so as to avoid including any of the branches of the brachial plexus. If the clavicle is so raised by the tumor that the application of the ligature cannot be effected in this situation, the artery may be tied above the first rib, or even behind the Scalenus anticus muscle; the difficulties of the operation in such a case will be materially increased, on account of the greater depth of the artery and the alteration in position of the surrounding parts. The second part of the subclavian artery, from being that portion which rises highest in the neck, has been considered favorable for the application of the ligature when it is difficult to tie the arterv in the third part of its course. There are, however, many objections to the oper- ation in this situation. It is necessary to divide the Scalenus anticus muscle, upon which lies the phrenic nerve, and at the inner side of which is situated the internal jugular vein; and a 628 THE VASCULAR SYSTEMS wound of either of these structures might lead to the most dangerous consequences. Again, the artery is in contact, below, witli the pleura, which must also be avoided; and, lastly, the proximity of so many of its large branches arising internal to this point must be a still further objection to the operation. In cases, however, where the sac of an axillary aneurism encroaches on the neck, it may be necessary to divide the outer half or two-thirds of the Scalenus anticus musdle, so as to place the ligature on the vessel at a greater distance from the sac. The oper- ation is performed exactly in the same way as a ligation of the third portion, until the Scalenus anticus is exposed, when it is to be divided on a director (never to a greater extent than its outer two-thirds), and it immediately retracts. The operation is therefore merely an extension of ligation of the third portion of the vessel. In those cases of aneurism of the axillary or subclavian artery in which the aneurism encroaches upon the outer portion of the Scalenus muscle to such an extent that a ligature cannot be applied in that situation, it may be deemed advisable, as a last resource, to tie the first portion of the subclavian artery. On the left side this operation has been regarded as almost impracticable; the great depth of the artery from its surface, its intimate relation with the pleura, and its close proximity to the thoracic duct and to so many important veins and nerves, presents a series of difficulties which it is very difficult to overcome. Nevertheless, it has been successfully done several times. The main objection to the operation in this situation is the smallness of the interval which usually exists between the commencement of the vessel and the origin of the nearest branch. The operation may be performed in the following manner: The patient being placed on the table in the supine position witli the neck extended, an incision should be made along the upper border of the inner part of the clavicle, and a second along the inner border of the Sternoinastoid, meeting the former at an angle. The attachment of both heads of the Sternomastoid must be divided on a director and turned outward; a few small arteries and veins, and occasionally the anterior jugular vein, must be avoided, or, if necessary, ligated in two places and divided, and the Sternohj'oid and Sternothyroid muscles are to be divided in the same manner as the preceding muscle. After tearing through the deep fascia, the internal jugular vein will be seen crossing the subclavian artery; this should be pressed aside and the artery secured by passing the needle from below upward, by which the pleura is more effectually avoided. The exact position of the vagus, the recurrent laryngeal, the phrenic and sympathetic nerves should be remembered, and the ligature should be applied near the origin of the verte- bral, in order to afford as much room as possible for the formation of a coagulum between the ligature and the origin of the vessel. It should be remembered that the right subclavian artery is occasionally deeply placed in the first part of its course when it arises from the left side of the aortic arch, and passes in such cases behind the cesophagus or between it and the trachea. Branches. — The branches given ofF from the subclavian artery are: Vertebral. Internal mammary. Superior intercostal. ( Inferior thyroid. Thyroid axis-fi'='<'^'' ' the middle of the arm; piercing the internal intermuscular septum, it descends on the surface of the inner head of the Triceps muscle to the space between the inner condyle and olecranon, accompanied by the ulnar nerve, and terminates by anastomos- ing with the posterior ulnar recurrent and anastomotica magna. It some- times supplies a branch to the front of the internal condyle, which anas- tomoses with the anterior ulnar re- current. The anastomotica magna (a. collat- eralis ulnaris inferior) arises from the brachial about two inches above the elbow-joint. It passes transversely inward upon the Brachialis anticus, and, piercing the internal intermuscular septum, winds Fig. 461. — The radial and ulnar arteries. 644 THE VASCULAR SYSTEMS around the back of the humerus between the Triceps and the bone, forming an arch above the olecranon fossa by its junction with the posterior articular branch of the superior profunda. As this vessel lies on the Brachialis anticus, branches ascend to join the inferior profunda, and others descend in front of the inner condyle to anastomose with the anterior ulnar recurrent. Behind the internal condyle an offset is given off which anastomoses with the inferior profunda and posterior ulnar recurrent arteries and supplies the Triceps. The muscular (rami musculares) are three or four large branches, which are distributed to the muscles in the course of the artery. They supply the Coraco- brachialis, Biceps, and Brachialis anticus muscles. The Anastomosis around the Elbow-joint (Fig. 462). — The vessels engaged in this anastomosis may be conveniently divided into those situated in front and behind the internal and external condyles. The branches anasto- mosing in front of the internal condyle are the anastomotica magna, the anterior ulnar recur- rent, and the anterior terminal branch of the inferior profunda. Those hehind the internal condyle are the anastomotica magna, the posterior ulnar recurrent, and the posterior terminal branch of the inferior profunda. The branches anastomosing in front of the ex- ternal condyle are the radial re- current and the anterior terminal branch of the superior profunda. Those hehind the external condyle (perhaps more properly described as being situated between the ex- ternal condyle and the olecranon) are the anastomotica magna, the interosseous recurrent, and the posterior terminal branch of the superior profunda. There is also a large arch of anastomosis above the olecranon, formed by the in- terosseous recurrent, joining with the anastomotica magna and posterior ulnar recurrent. From this description it will be observed that the anastomotica magna is the vessel most engaged, the only part of the anastomosis in which it is not employed being that in front of the external condyle. Anterior branch of superior profunda Posterior branch oj superior profunda Radial recurrent Interosseous g I recurrent. 11 Superior profunda. M \\ Inferior profunda. Anastomotica 7nagna. Anterior ulnar recurrent. Posterior idnar recurrent. Interosseous. Postei lor znterosseous. ^ Anterior interosseous. i 462. — Diagram of the anastomosis around the right elbow-joint. The Radial Artery (A. Radialis) (Figs. 461, 463). The radial artery appears, from its direction, to be the continuation of the brachial, but in size it is smaller than the ulnar. It commences at the bifurcation of the brachial, just below the bend of the elbow, and passes along the radial side of the forearm to the wrist; it then winds backward, around the outer side of the carpus, beneath the Extensor tendons of the thumb, to the upper end of the THE RADIAL ARTERY 645 space between the metacarpal bones of the thumb and index finger, and finally passes forward, between the two heads of the First dorsal interosseous muscle, into the palm of the hand, where it crosses the metacarpal bones to the ulnar border of the hand, to form the deep palmar arch. At its termination it anastomoses with the profunda branch of the ulnar artery. The relations of this vessel may thus be conveniently divided into three parts — viz., in the forearm, at the back of the wrist, and in the hand. Relations. — In the forearm this vessel extends from opposite the neck of the radius to the fore part of the styloid process, being placed to the inner side of the shaft of the bone above and in front of it below. It is overlapped in the upper part of its course by the fleshy belly of the Brachioradialis muscle; throughout the rest of its course it is superficial, being covered by the integument, the superficial and deep fascije. In its course downward it lies upon the tendon of the Biceps, the Supinator [brevis], the Pronator teres, the radial origin of the Flexor subliniis digitorum, the Flexor longus polHcis, the Pronator quadratus, and the lower extremity of the radius. In the upper third of its course it lies between the Brachioradialis and the Pronator teres; in the lower two-thirds, between the tendons of the Brachioradialis and the Flexor carpi radialis. The radial nerve lies close to the outer side of the artery in the middle third of its course, and some filaments of the musculocutaneous nerve, after piercing the deep fascia, run along the lower part of the artery as it winds around the wrist. The vessel is accompanied by venae comites throughout its whole course. Plan of the Relations of the Radial Artery in the Forearm. In front. Skin, superficial and deep fasciae. Brachioradialis. Inner side. / \ Outer side. Pronator teres. I pore'i'rm" ] Brachioradialis. Flexor carpi radialis. \ J Radial nerve (middle third). Behind. Tendon of Biceps. Supinator [brevis]. Pronator teres. Flexor sublimis digitorum. Flexor longus pollicis. Pronator quadratus. Radius. At the wrist, as it winds around the outer side of the carpus from the styloid process to the first interosseous space, it lies upon the external lateral ligament, and then upon the scaphoid bone and trapezium, being covered by. the Extensor tendons of the thumb, subcutaneous veins, some filaments of the radial nerve, and the integument. It is accompanied by two veins and a filament of the musculocutaneous nerve. In the hand it passes from the upper end of the first interosseous space, between the heads of the Abductor indicis or First dorsal interosseous muscle, transversely accross the palm, to the base of the metacarpal bone of the little finger, where it anastomoses with the communi- cating branch from the ulnar artery, forming the deep palmar arch. The deep palmar arch (arcus volaris frofundus) (Fig. 463) lies upon the carpal extremities of the metacarpal bones and the Interossei muscles, being covered by the Adductor obliquus pollicis, the Flexor tendons of the fingers, the Lumbricales, the Opponens, and Flexor brevis minimi digiti. Alongside of it, but running in the opposite direction — that is to say, from within outward — is 646 ' THE VASCULAR SYSTEMS the deep branch of the ulnar nerve. The branches of the deep palmar arch are the palmar interosseous, perforating and palmar recurrent vessels (page 648). Peculiarities. — The origin of the radial artery, according to Quain, is, in nearly one case in eight, higher than usual; more frequently arising from the axillary or upper part of the brachial, than from the lower part of this vessel. The variations in the position of this vessel in the arm and at the bend of the elbow have been already mentioned. In the forearm it deviates less fre- quently from its position than the ulnar. It has been found lying over the fascia instead of beneath it. It has also been observed superficial to the Brachioradialis, instead of under its inner border; and in turning around the wrist it has been seen lying over, instead of beneath, the Extensor tendons of the thumb. Surface Markiug. — The position of the radial artery in the forearm is represented by a line drawn from the outer border of the tendon of the Biceps in the centre of the hollow in front of the elbow-joint with a straight course to the inner side of the forepart of the styloid process of the radius. Aj^lied Anatomy. — The radial artery is much exposed to injury in its lower third, and is frequently wounded. The injury is often followed by a traumatic aneurism, for which the operation of extirpation or laying open the sac after securing the vessel above and below is required. The operation of tying the radial artery is required in cases of wounds either of its trunk or of some of its branches, or for aneurism; and it will be observed that the vessel may be exposed in any part of its course through the forearm without the division of any muscle fibres. The operation in the middle or inferior third of the forearm is easily performed, but in the upper third, near the elbow, it is attended with some difficulty, from the greater depth of the vessel and from its being overlapped by the Brachioradialis muscle.. To tie the artery in the upper third an incision three inches in length should be made thi-ough the integument, in a line drawn from the centre of the bend of the elbow to the front of the styloid process of the radius, avoiding the branches of the median vein; the fascia of the arm being divided and the Brachioradialis drawn a little outward, the artery will be exposed. The venae comites should be carefully separated from the vessel, and the hgature passed from the radial to the ulnar side. In the middle third of the forearm the artery may be exposed by making an incision of similar length on the inner margin of the Brachioradialis. In this situation the radial nerve lies in close relation with the outer side of the artery, and should, as well as the veins, be carefully avoided. In the lower third the artery is easily secured by dividing the integument and fascia in the interval between the tendons of the Brachioradialis and Flexor carpi radialis muscles. Branches (Figs. 461 and 463). — ^The branches of the radial artery may be divided into three groups, corresponding with the three regions in which the vessel is situated. f Radial recurrent. C Posterior radial carpal. In the J Muscular. At the J First dorsal interosseous. Forearm ] Anterior radial carpal. Wrist ] Dorsales pollicis. t Superficialis volae. I. Dorsalis indicis. r Princeps pollicis. Radialis indicis. In the Hand ■{ Perforating. Palmar interos.seous. . Palmar recurrent. The radial recurrent (a. recurrens radialis) (Fig. 463) is given off imme- diately below the elbow. It ascends between the branches of the musculospiral nerve lying on the Supinator [brevis], and then between the Brachioradialis and Brachialis anticus, supplying these muscles and the elbow-joint, and anastomosing with the anterior terminal branch of the superior profunda. The muscular branches (rami musculares) are distributed to the muscles on the radial side of the forearm. THE RADIAL ARTERY 647 The anterior radial carpal {ramus carpeus volaris) (Fig. 463) is a small vessel which arises from the radial artery near the lower border of the Pronator quad- ratus, and, running inward in front of the radius, anastomoses with the ante- rior carpal branch of the ulnar artery. In this way an arterial anastomosis, the anterior carpal arch (rete carpi volare) is formed in front of the wrist; it is joined by branches from the anterior interosseous above, and by recurrent branches from the deep palmar arch below, and gives off branches which descend to supply the articulations of the wrist and carpus. The superficialls volae (ramus volaris superficialis) (Fig. 463) arises from the radial artery, just where this vessel is about to wind around the wrist. Running forward, it passes between, occasionally over, the muscles of the thumb, which it supplies, and sometimes anastomoses with the palmar portion of the ulnar artery, completing the superficial palmar arch. This vessel varies considerably in size; usually it is very small, and terminates in the muscles of the thumb; sometimes it is as large as the continuation of the radial. The posterior radial carpal (ramus carpeus dorsalis) (Fig. 464) is a small vessel which arises from the radial artery beneath the Extensor tendons of the thiunb; crossing the carpus transversely to the inner border of the hand, it anasto- moses with the posterior carpal branch of the ulnar, forming the posterior carpal arch (i-ete carpi dorsale), which is joined by the termination of the anterior inter- osseous artery. From this arch are given off descending branches, the dorsal interosseous arteries (aa. metacarpeae do'rsales) for the second, third, and fourth interosseous spaces, which run forward on the Second, Third, and Fourth dorsal interossei muscles, and divide into dorsal digital branches (aa. digitales dorsales), which supply the adjacent sides of the index, middle, ring, and little fingers, respectively, communicating with the digital arteries of the superficial palmar arch. The dorsal interosseous arteries anastomose with the perforating branches from the deep palmar arch. The first dorsal interosseous arises beneath the Extensor tendons of the thumb, sometimes with the posterior radial carpal; running forward on the Second dorsal interosseous muscle, it divides into two dorsal digital branches, which supply the adjoining sides of the index and middle fingers; it forms anastomoses similar to those of the two other dorsal interosseous arteries. The dorsales poUicis (Fig. 464) are two vessels which run along the sides of the dorsal aspect of the thumb. They usually ari.se separately, but occasionally by a common trunk, near the base of the first metacarpal bone. The dorsalis indicis (Fig. 464), also a small branch, runs along the radial side of the back of the index finger, sending a few branches to the Abductor indicis. The princeps pollicis (a. princeps pollicis) (Fig. 463) arises from the radial just as it turns inward to the deep part of the hand; it descends between the Abductor indicis and Adductor oblicjuus pollicis, then between the Adductor transversus pollicis and Adductor obliquus pollicis, along the ulnar side of the metacarpal bone of the thumb, to the base of the first phalanx, where it lies beneath the tendon of the Flexor longus pollicis and divides into two branches. These make their ap- pearance between the inner and outer insertions of the Adductor obliquus pollicis, and run along the sides of the palmar aspect of the thumb, forming on the palmar surface of the last phalanx an arch, from which branches are distributed to the integument and subcutaneous tissue of the thiunb. The radialis indicis (a. volaris indicis radialis) (Fig. 463) arises close to the pre- ceding, descends between the First dorsal interosseous and Adductor transversus pollicis, and runs along the radial side of the index finger to its extremity, where it anastomoses v/ith the collateral digital artery from the s uperficial palmar arch. At the lower border of the Adductor transversus pollicis this vessel anastomoses with the princeps pollicis, and gives a communicating branch to the superficial palmar arch. 648 THE VASCULAR SYSTEMS Anastomotica magna. Anterior ulnar recurrent. Posterior tdnar recurrent. The perforating arteries {rami perforantes) (Fig. 463), three in number, pass backward from the deep palmar arch through the second, third, and fourth inter- osseous spaces and between the » .v, heads of the corresponding Inter- ossei, to anastomose with the dorsal interosseous arteries. The palmar interosseous (aa. vietacarpeae volares) (Fig. 463), three or four in number, arise from the convexity of the deep palmar arch; they run downward upon the Interossei muscles, and anastomose at the clefts of the fingers with the digital branches of the superficial arch. The palmar recurrent branches arise from the concavity of the deep palmar arch. They ascend in front of the wrist, supplying the carpal articulations and anas- tomosing with the anterior carpal arch. The Ulnar Artery (A. Ubiaris) (Figs. 461, 463). The ulnar artery, the larger of the two terminal branches of the brachial, commences a little below the bend of the elbow, and passes obliquely across the inner side of the forearm to a point about mid- way between the elbow and the wrist. It then runs along the ulnar border to the wrist, crosses the annular ligament on the radial side of the pisiform bone, and immediately beyond this bone divides into two branches which enter into the formation of the superficial and deep palmar arches. Fig. 463 — Ulnar and radial arteries Deep view. Relations. — In the Forearm. — In its upper half it is deeply seated, being covered by all the superficial Flexor muscles, excepting the Flexor carpi ulnaris; the median nerve is in relation with the inner side of the artery for about an inch and then crosses the vessel, being separated from it by the deep head of the Pronator teres; it lies upon the Brachialis anticus and Flexor profundus digitorum muscles. In the lower half of the forearm it lies upon the Flexor profundus, being covered by the integument, the superficial and deep fasciae, and is placed between the Flexor carpi ulnaris and Flexor sublimis digitorum muscles. It is accom- panied by two venae comites; the ulnar nerve lies on its inner side for the lower h\'0-thirds of its extent, and a small branch from the nerve descends on the lower part of the vessel to the palm of the hand. THE ULNAR ARTERY 649 Plan of Relations of the Ulnar Artery in the Forearm. In front. TJnn r H 7/ .(Superficial layer of Flexor muscles. "' •' (Median nerve. Lower Half — Superficial and deep fasciae. Inner side. Outer side. Flexor carpi uluaris. ... Ulnar nerve (lower two-thirds). \ !''"«"'"• / Flexor sublimis digitorum. Behind. Brachialis anticus. Flexor profundus digitorum. At the wrist (Fig. 461) the ulnar artery is covered by the integument and fascia, and lies upon the anterior annular ligament. On its inner side is the pisiform bone, and somewhat behind the artery, the ulnar nerve. The nerve and artery are crossed by a band of fibres, which extends from the pisiform bone to the anterior annular ligament. Peculiarities. — The idnar artery has been found to vary in its origin nearly in the propor- tion of one in thirteen cases, in one case arising lower than usual, about two or three inches below the elbow, and in all other cases much higher, the brachial being a more frequent source of origin than the axillary. Variations in the position of this vessel are more frequent than in the radial. When its origin is normal, the course of the vessel is rarely changed. When it arises high up it is almost in- variably superficial to the Flexor muscles in the forearm, lying commonly beneath the fascia, more rarely l)et\\ een the fascia and integument. In a few cases its position was subcutaneous in the upper ]iai-t of the forearm, subaponeurotic in the lower part. Surface Marking. — On account of the curved direction of the ulnar artery the line on the surface of the body which indicates its course is somewhat complicated. First, draw a line from the front of the internal condyle of the hmnerus to the radial side of the pisiform bone; the lower two-thirds of this line represents the course of the middle and lower third of the ulnar artery. Secondly, draw a line from the centre of the antecubital fossa to the Junction of the upper and middle third of the first line; this represents the course of the upper third of the artery. Applied Anatomy. — The application of a ligatiu-e to this vessel is required in cases of wound of the artery or of its branches, or in consequence of aneurism. In the upper half of the fore- arm the artery is deeply seated beneath the Superficial Flexor muscles, and the application of a ligature in this situation is attended with some difficulty. An incision is to be made in the course of a line drawn from the front of the internal condyle of the humerus to the outer side of the pisiform bone, so that the centre of the incision is three fingers' breadth below the internal condyle. The skin and superficial fascia having been divided and the deep fascia exposed, the white line which separates the Flexor carpi ulnaris from the other Flexor muscles is to be sought for, and the fascia incised in this line. The Flexor carpi ulnaris is now to be carefully separated from the other muscles, when the ulnar nerve will be exposed, and must be drawn aside. Some little distance below the nerve the artery will be found accompanied by its venae comites, and it may be ligated by passing the needle from within outward. In the middle and lower third of the forearm this vessel may be easily secured by making an incision on the radial side of the tendon of the Flexor carpi ulnaris; the deep fascia being divided, and the Flexor carpi ulnaris and its companion muscle, the Flexor sublimis, being separated from each other, the vessel will be exposed, accompanied by its venae comites, the ulnar nerve lying on its inner side. The veins being separated from the artery, the ligature should be passed from the ulnar to the radial side, taking care to avoid the ulnar nerve. 650 THE VASCULAR SYSTEMS Branches (Figs. 463 and 464). — The branches of the ulnar artery may be arranged in the following groups: Anterior ulnar recurrent. Posterior ulnar recurrent. Forearm { t , f Anterior interosseous, interosseous i u . • • ^ 1^ rostenor mterosseous. L Muscular. Tu- ■ f j Anterior ulnar carpal. \ Posterior ulnar carpal. rr if Profunda. \ Superficial palmar arch. The anterior ulnar recurrent (a. recurrentes ulnaris anterior) (Fig. 463) arises im- mediately below the elbow-joint, passes upward and inward between the Brachialis anticus and Pronator teres, supplies twigs to those muscles, and, in front of the inner condyle, anastomoses with the anastomotica magna and inferior profunda. The posterior ulnar recurrent (a. recurrentes ulnaris posterior) (Figs. 463 and 464) is much larger, and arises somewhat lower than the preceding. It passes backward and inward, beneath the Flexor sublimis, and ascends behind the inner condyle of the humerus. In the interval between this process and the olecranon it lies beneath the Flexor carpi ulnaris, and ascending between the heads of that muscle, in relation with the ulnar nerve; it supplies the neighboring muscles and joint, and anastomoses with the inferior profunda, anastomotica magna, and interosseous recurrent arteries. The interosseous artery (a. interossea communis) (Fig. 463) is a short trunk about half an inch in length, and of considerable size, which arises immediately Ijelow the tuberosity of the radius, and, passing backward to the upper border of the intei'osseous membrane, divides into two branches, the anterior and posterior interosseous. The anterior interosseous (a. interossea volaris) (Fig. 463) passes down the fore- arm on the anterior surface of the interosseous membrane, to which it is connected by a thin aponeurotic arch. It is accompanied by the interosseous branch of the median nerve, and overlapped by the contiguous margins of the Flexor profundus digitorum and Flexor longus pollicis muscles, giving off in this situation muscular - branches and the nutrient arteries of the radius and ulna. At the upper border of the Pronator quadratus a branch, anterior communicating artery, descends beneath the muscle to anastomose in front of the carpus with the anterior carpal arch. The continuation of the artery passes behind the Pronator quadratus, and, piercing the interosseous membrane, reaches the back of the forearm, and anasto- moses with the posterior interosseous artery (Fig. 464) . It then descends to the back of the wrist to join the posterior carpal arch. The anterior interosseous gives off a long, slender branch, the comes nervi mediana artery (a. mediana), which accompanies the median nerve and gives branches to its substance. This artery is sometimes much enlarged, and accompanies the nerve into the palm of the hand. The posterior interosseous artery (a. interossea dorsales) (Figs. 463 and 464) passes backward through the interval between the oblique ligament and the upper border of the interosseous membrane. It appears between the contiguous borders of the Supinator [brevis] and the Extensor ossis metacarpi pollicis, and runs down the back part of the forearm, between the superficial and deep layer of muscles, to both of which it distributes branches (Fig. 464). Where it lies upon the Extensor ossis metacarpi pollicis and the Extensor brevis pollicis, it is accompanied by the posterior interosseous nerve. At the lower part of the forearm it anastomoses with the termination of the anterior interosseous artery and with the posterior carpal arch. Then, continuing its course over the head of the ulna, THE ULNAR ARTERY 051 superior profunda. Ana.itomotica magna. Posterior ulnar recurrent. Posterior ntierosseous. it joins the jjosterior carpal l^raneh of the uhiar artery. This artery gives ofF, near its origin, the interosseous recurrent l)ranch. The interosseous recurrent artery (a. intcrossea recurrens) (Fig. 464) is a large vessel which ascends to the interval between the external condyle and olecranon, on or through the fibres of the Supinator [brevis], but beneath the Anconeus, anastomosing with a branch from tire superior profunda, / J^ _ Descending branch from and with the posterior ulnar / recurrent and anastomotica magna. The muscular branches (rami musculares) are dis- tributed to the muscles along the ulnar side of the forearm. The anterior ulnar carpal {ramus carpeus volaris) (Fig. 463) is a small vessel which crosses the front of the car- pus beneath the tendons of the Flexor profundus and in- osculates with a correspond- ing branch of the radial artery. The posterior ulnar carpal (ramus carpeus dorsalis) (Fig. 464) arises immediately above the pisiform bone, and winds backward beneath the tendon of the Flexor carpi ulnaris; it passes across the dorsal surface of the carpus be- neath the Extensor tendons to anastomose with a corre- sponding branch of the radial artery and complete the pos- terior carpal arch (rete carpi dorsale) (Fig. 464). Imme- diately after its origin it gives off a small branch, which runs along the ulnar side of the fifth metacarpal bone, and supplies the ulnar side of the dorsal sur- face of the little finger. The profunda branch (rom- us volaris profundus) (Fig. 463) passes deeply inward be- tween the Abductor minimi digiti and Flexor brevis min- imi digiti, near their origins; it anastomoses with the termi- nation of the radial artery, completing the deep palmar arch. The continuation of the trimk of the ulnar artery in the hand forms the greater part of the superficial palmar arch. Termination of an^ tenor interosseous. Posterior carpal (radial). Radial. ^Do7'saUs poinds, ■salis indicis. Fig. 464. — Artertes of the back of the forearm 652 THE VASCULAR SYSTEMS The superficial palmar arch (circus volaris superficialis) (Fig. 461) is formed by the uhiar artery in tlie hand, and is usually completed on the outer side by a branch from the radialis indicis, but sometimes by the superficialis volae or the princeps pollicis of the radial artery. The arch passes across the palm, describing a curve, with its convexity downward. Relations. — The superficial palmar arch is covered by the skin, the Palmaris brei'is, and the palmar fascia. It lies upon the annular ligament, the Flexor brevis and Opponens minimi digiti, the tendons of the Flexor sublimis digitorum, the Lumbrical muscles, and the divisions of the median and ulnar nerves. Plan of the Relations of the Superficial Palmar Arch. Behind. Annular ligament. Flexor brevis minimi digiti. Opponens minimi digiti. Tendons of Flexor sublimis digitorum. Lumbrical muscles. Branches of median and ulnar nerves. Branches. — The branches of the Superficial palmar arch are: Four Digital Arteries. Four digital arteries (aa. dig Hales volares covnntines') (Fig. 461) are given off from the convexity of this arch. The innermost accompanies the inner digital branch of the ulnar nerve, and runs along the ulnar side of the little finger; it is joined by a twig from the deep palmar arch or from the innermost palmar inter- osseous artery. The three outer run downward in front of the three inner inter- osseous spaces, superficial to the corresponding nerves and Lumbrical muscles. A little above the interdigital clefts they are joined by the palmar interosseous arteries, and by the inferior perforating branches of the dorsal interosseous arteries. Each then divides into coliateral digital arteries (aa. digitales volares propriae) for the supply of the contiguous sides of the index, middle, ring, and little fingers. These collateral branches lie behind the corresponding digital nerves; they anastomose freely in the subcutaneous tissue of the finger tip and by smaller branches near the interphalangeal joints. Each supplies a couple of dorsal branches which anastomose with the dorsal digital arteries, and supply the soft parts on the back of the second and third phalanges, including the matrix of the finger nail. Surface Marking. — The superficial palmar arch is represented by a curved line, starting from the outer side of the pisiform bone and carried downward as far as the middle third of the palm, and then ciu-ved outward on a \exe\ with the upper (proximal) end of the cleft between the thumb and index finger. The deep palmar arch is situated about half an inch nearer to the carpus. Applied Anatomy. — Wounds of the palmar arches are of special interest, and are always difficult to deal with. When the superficial arch is wounded it is generally possible, by enlarging the wound if necessary, to secure the vessel and tie it; or in cases where it is found impossible to THE DESCENDING AORTA 653 encircle the vessel with a ligature, a pair of hemostatic forceps may be applied and left on for twenty-four or forty-eight hours. Wounds of the deep arch are not so easily dealt with. It may be possible to secure the vessel by ligature or by forcipressure forceps, which may be left on; or, failing in this, the wound may be carefully plugged with gauze and an outside dressing care- fully bandaged on. The plug should be allowed to remain untouched for three or four days. In wounds of the deep palmar arch a ligature may be ap])lied to the bleeding points from the dorsum of the hand by resection of the upper part of the third metacarpal bone. It is useless in these cases to ligate one of the arteries of the forearm alone, and, indeed, simultaneous liga- tion of both radial and ulnar arteries above the wrist is often unsuccessful, on account of the anastomosis carried on by the carpal arches. Therefore, if unable to ligate the divided ends of the arch, upon the failure of pressure to arrest hemorrhage, it is expedient to apply a ligature to the brachial artery. ARTERIES OF THE TRUNK. . THE DESCENDING AORTA (Figs. 465, 466). The descending aorta is divided into two portions, the thoracic and abdominal, in correspondence with the two great cavities of the trunk in which it is situated. The Thoracic Aorta [aorta thoracalis) (Fig. 465). — The thoracic aorta is contained in the back part of the posterior mediastinum and commences at the lower border of the fourth thoracic vertebra, on the left side, and terminates at the aortic opening in the Diaphragm, in front of the lower border of the last thoracic vertebra. At its commencement it is situated on the left side of the vertebral column; it approaches the median line as it descends, and at its termination lies directly in front of the vertebral column. The direction of this vessel being influenced by the vertebral column, upon which it rests, it describes a curve which is concave forward in the thoracic region. As the branches given off from it are small, the diminution in the size of the vessel' is inconsiderable. Relations. — It is in relation, in front, from above downward, with the root of the left lung, the pericardium, the oesophagus, and the Diaphragm; behind, with the vertebral column and the azygos minor veins; on the right side, with the vena azygos major and thoracic duct; on the left side, with the left pleura and lung. The oesophagus, with its accompanying nerves, lies on the right side of the aorta above; but at the lower part of the thorax it passes in front of the aorta, and close to the Diaphragm is situated to its left side. Plan of the Relations of the Thoracic Aorta. In front. Root of left lung. Pericardium. (Esophagus (middle). Diaphragm. Right side. / >v Left side. CEsophagus (above). ( Thoracic I Pleura. Vena azygos major. I '^°'''*" j Left lung. Thoracic duct. \ / CEsophagus (below). Behind. Vertebral column. Superior and inferior azygos minor veins. Peculiarities. — The aorta is occasionally found to be obliterated at a particular spot — viz., at the junction of the arch with the thoracic aorta just below the ligamentum arteriosum. Whether this is the result of disease or of congenital malformation is immaterial to oiu- present purpose; it affords an interesting opportunity of observing the resoiu-ces of the collateral circulation. 654 THE VASCULAR SYSTEMS The course of the anastomosing vessels, by which the blood is brought from the upper to the lower part of the artery, will be found well described in an account of two cases in the Fafho- logical Transactiowt, vols, viii and x. In the former (p. 162) Mr. Sydney Jones thus sums up the detailed description of the anastomosing vessels: "The principal communications by which the circulation was carried on were: First, the internal mammary, anastomosing with the intercostal arteries, with the phrenic of the abdominal aorta by means of the musculophrenic and comes nervi phrenici, and largely with the deep epigastic. Secondly, the superior inter- costal, anastomosing anteriorly by means of a large branch with the first aortic intercostal, and posteriorly with the posterior branch of the same artery. Thirdly, the inferior thyroid, by means of a branch about the size of an ordinary radial, formed a communication with the first aortic intercostal. Fourthly, the transverse cervical, by means of very large communi- cations with the posterior branches of the intercostals. Fifthly, the branches (of the subclavian and axillary) going to the side of the thorax were large, and anastomosed freely with the lateral branches of the intercostals." In the second case also (vol. x, p. 97) Mr. Wood describes the anastomoses in a somewhat similar manner, adding the remark that "the blood which was brought into the aorta through the anastomoses of the intercostal arteries appeared to be ex- pended principally in supplying the abdomen and pelvis, while the supply to the lower extremities had passed through the internal mammary and epigastrics." Applied Anatomy. — The student should now consider the effects likely to be produced by aneurism of the thoracic aorta, a disease of common occurrence. When we consider the great depth of the vessel from the surface and the number of important structures which surround it on every side, it may easily be conceived what a variety of obscure symptoms may arise from dis- ease of this part of the arterial system, and how they may be liable to be mistaken for those of other affections. Aneurism of the thoracic aorta most usually extends backward along the left side of the vertebral column, producing absorption of the bodies of the vertebrte, with curvature of the spine; while the irritation or pressure on the spinal cord will give rise to pain, either in the thorax, back, or loins, with radiating pain in the left upper intercostal spaces, from pressure on the intercostal nerves; at the same time the tumor may project backward on each side of the vertebral column, beneath the integument, as a pulsating swelling, simulating abscess connected with diseased bone, or it may displace the oesophagus and compress the lung on one or the other side. If the tumor extend forward, it may press upon and displace the heart, giving rise to palpitation and other symptoms of disease of that organ ; or it may displace, or even com- press, the oesophagus, causing pain and difficulty of swallowing, as in stricture of that tube; and ultimately even open into it by ulceration, producing fatal hemorrhage. If the disease extends to the right side, it may press upon the thoracic duct; or it may burst into the pleural cavity or into the trachea or lung; and, lastly, it may open into the posterior mediastinum. The diagnosis of thoracic aneurism is facilitated by the use of the a-'-rays. Branches of the Thoracic Aorta. — I Bronchial. ^f , ^ , ^ , , I Intercostal. n ■ r ^ ' Parietal ■{ Subcostal, rencardial. 1 ^ • i Mediastinal. I Superior phrenic. The bronchial arteries (aa. hronchiales) are the nutrient vessels of the lungs, and vary in number, size, and origin. There is, as a rule, only one right bronchial artery, which arises from the first aortic intercostal, or from the left bronchial. The left bronchial arteries, usually two in number, arz.se from the thoracic aorta, one a little lower than the other. Each vessel runs along the back part of the corresponding bronchus, dividing and subdividing along the bronchial tubes, supplying them, the cellular tissue of the lungs, the bronchial nodes, and the oesophagus. The oesophageal arteries (aa. oesophageae), usually four or five in number, arise from the front of the aorta, and pass obliquely downward to the oesophagus, forming a chain of anastomoses along that tube, anastomosing with the oesopha- geal branches of the inferior thyroid arteries above, and with ascending branches from the phrenic and gastric arteries below. The pericardial (rami pericardiaci) are a few small vessels, irregular in their origin, distributed to the pericardium. The mediastinal branches (rami mediastinales) are numerous small vessels which supply the nodes and loose areolar tissue in tne posterior mediastinum. THE DESCENDING AORTA 655 The intercostal arteries {aa. intercostales) (Fig. 465) arise from the back of the aorta. The aortic intercostals are usually nine in number on each side, the two superior intercostal spaces being supplied by the superior intercostal, a branch of the subclavian. The right aortic intercostals are longer than the left, on account of the position of the aorta on the left side of the vertebral column; they pass across the bodies of the vertebrte, behind the oesophagus, thoracic duct, and the vena azygos major, and are covered by the right lung and pleura. The left aortic intercostals run backward on the sides of the vertebrae and are covered by the left lung and 'pleura; the two upper are crossed by the left superior intercostal vein, the lower vessels by the azygos minor veins. Opposite the heads of the ribs the sympathetic cord passes downward in front of them, and the splanchnic nerves also descend in front of the lower arteries. Each artery crosses the cor- responding intercostal space obliquely toward the angle of the upper rib and thence is continued forward in the sub- costal groove. It is placed at first be- tween the pleura and the posterior inter- costal membrane, then pierces this membrane and lies between it and the External intercostal muscle as far as the rib angle; from this onward it runs be- tween the External and Internal inter- costal muscles and anastomoses with the anterior intercostal branches of the inter- nal mammary or musculophrenic. Each intercostal artery is accompanied by a vein and nerve, the former being above, and the latter below, except in the upper intercostal spaces, where the nerve is at first above the artery. The first aortic intercostal anastomoses with the superior intercostal branch of the subclavian, and the last two intercostals continue anteriorly from the intercostal spaces into the abdominal wall, anastomosing with the superior epigastric, subcostal and lumbar arteries. Branches. — Each intercostal artery gives off numerous muscular and cutaneous branches. Fig. 465. — Thoncic aorta (Testut.) Posterior or dorsal. Muscular. Collateral intercostal. Lateral cutaneous. The posterior or dorsal branch {ramus posterior') runs with the posterior division of a spinal nerve and passes backward through a small opening which is bounded above and helow by the necks of the ribs and adjacent transverse processes, internally by the vertebral body, and externally by the anterior costotransverse ligament. It gives off a spinal branch, which enters the vertebral canal through the intervertebral foramen, is distributed to the spinal cord and its membranes. 656 THE VASCULAR SYSTEMS and to the bodies of the vertebrae in the same manner as the lateral spinal branches from the vertebral. The collateral intercostal branch comes off from the intercostal artery near the angle of the rib, and descends to the upper border of the rib below, along which it courses to anastomose with the anterior intercostal branch of the internal mam- mary. Fig. 466. — The abdominal aorta and its branches. Muscular branches {rami musculares) are given to the Intercostal and Pectoral muscles and to the Serratus magnus; they anastomose with the superior and long thoracic branches of the axillary artery. The lateral cutaneous branches (rami cutanei lateraJes) accompany the lateral cutaneous branches of the intercostal nerves, and divide into anterior and posterior branches. THE ABDOMINAL AORTA G57 Mammary branches are given off by the intercostal arteries in the third, fourth, and fifth spaces. They supply the mammary gland, and increase considerably in size during the period of lactation. Applied Anatomy. The liusitinn of the intercostal vessels should be borne in mind in perforniini;- tin- (i|iciaiiiin of pnran iili:-;ix tJioracis. The puncture should never be made nearer the middle hue pnstc-riorly thnii .he angle of the rib, as the artery crosses the space internal to this point. In the lateral portion of the thorax, where the puncture is iisually made, the artery lies at the upper part of the intercostal space, and therefore the puncture should be made just above the upper border of the rib forming the lower boundary of the space. The Abdominal Aorta (aorta ahdominalis) (Fig. 466). — The abdominal aorta commences at the aortic opening of the Diaphragm, in front of the lower border of the body of the last thoracic vertebra, and, descending a little to the left side of the vertebral column, terminates on the body of the fourth lumbar vertebra, usually a little to the left of the middle line,' by dividing into the two common iliac arteries. It diminishes rapidly in size, in consequence of the many large branches which it gives off. As it lies upon the bodies of the vertebra?, the curve which it describes is convex forward, the greatest convexity corresponding to the third lumbar vertebra, which is a little above and to the left side of the umbilicus. Relations. — It is covered, in front, by the lesser omentum and stomach, behind which are the branches of the coeliac axis and the solar plexus; below these, by the splenic vein, the pan- creas, the left renal vein, the transverse portion of the duodenum, the mesentery, and aortic plexus. Behind, it is separated from the lumbar vertebrae and intervening disks by the anterior common ligament and left lumbar veins. On the riyht side it is in relation with the inferior vena cava (the right crus of the Diaphragm being interposed above), the vena azygos major, thoracic duct, and right semilunar ganglion; on the left side, with the gangliated cord of the sympathetic and left semilunar ganglion the fourth part of the duodenum and some coils of the small intestine. Plan of the Relations of the Abdominal Aorta. In front. Lesser omentum and stomach. Branches of the coeliac axis and solar plexus. Splenic vein. Pancreas. Left renal vein. Transverse duodenum. Mesentery. Aortic plexus. Right side. Left side. Right crus of Diaphragm. / \ Gangliated cord. Inferior vena cava. j Abdominal \ Left semilunar ganglion. Vena azygos major. Thoracic duct. Right semilunar ganglion. Belmid. Left lumbar veins. Vertebral column. Surface Marking.— In order to map out the abdominal aorta on the surface of the abdomen, a line must be drawn from the middle line of the body, on a level with the costal extremity ol the seventh costal cartilage, doAvnward and slightly to the left, so that it just skirts the umbilicus, to a zone drawn around the body opposite the highest point of the crest of the ilium. This point 1 Lord Lister, having accurately examined 30 bodies in order to 'ascertain the exact point of termination of this vessel, found it "either absolutelj', or almost absolutely, mesal in 15. while in 13 it deviated more or les8 to the left, and in 2 was slightly to the right" (System of Surgery, edited by T. Holmes. 2d ed., \-ol. v. p 632). 658 THE VASCULAR SYSTEMS is generally half an inch below and to the left of the umbilicus, but as the position of this struc- ture varies with the obesity of the individual, it is not a reliable landmark as to the situation oi the bifurcation of the aorta. Applied Anatomy. — Aneurisms of the ahdominal aorta near the coeliac axis communicate in nearly equal proportion with the anterior and posterior parts of the artery. When an aneurismal sac is connected with the back part of the abdominal aorta, it usually produces absorption of the bodies of the vertebrae, and forms a pulsating tumor that presents itself in the left hypochondriac or epigastric regions, and is accompanied by symptoms of dis- turbance in the alimentary canal. Pain is invariably present, and is usually of two kinds — a fixed and constant pain in the back, caused by the tumor pressing on or displacing the branches of the solar plexus and splanchnic nerves; and a sharp lancinating pain, radiating along those branches of the lumbar nerves which are pressed on by the tumor; hence the pain in the loins, the testes, the hypogastrium, and in the lower limb (usually of the left side). This form of aneurism usually bursts into the peritoneal cavity or behind the peritoneum in the left hypo- chondriac region; or it may form a large aneurismal sac, extending down as low as Poupart's ligament; hemorrhage in these cases being generally very extensive, but slowly produced, and not rapidly fatal. When an aneurismal sac is connected with the front of the aorta near the coeliac axis it forms a pulsating tumor in the left hypochondriac or epigastric region, usually attended with symptoms of disturbance of the alimentary canal, as nausea, dyspepsia, or constipation, and is accom- panied by pain, which is constant, but nearly always fixed in the loins, epigastrium, or some part of the abdomen; the radiating pain being rare, as the lumbar nerves are seldom implicated. This form of aneurism may burst into the peritoneal cavity or behind the peritoneum, between the layers of the mesentery, or, more rarely, into the duodenum; it seldom extends backward so as to affect the vertebral column. The abdominal aorta has been tied several times, and although none of the patients perma- nently recovered, still, as Prof. Keen's lived forty-eight days, the possibility of the reestablish- ment of the circulation is proved. In the lower animals this artery has been often successfully tied. The chief difficulty consists in isolating the artery in consequence of its great depth; and the embarrassment resulting from the proximity of the aneurismal tumor, and the great prob- ability of disease in the vessel itself, add to the dangers and difficulties of this formidable opera- tion. The collateral circulation would be carried on by the anastomosis between the internal mam- mary and the deep epigastric; by the free communication between the superior and inferior mesenteries if the ligature were placed above the latter vessel: or by the anastomosis between the inferior mesenteric and the internal pudic when (as is more common) the point of ligation is below the origin of the inferior mesenteric; and possibly by the anastomoses of the lumbar arteries with the branches of the internal iliac. Branches. — The branches of the abdominal aorta comprise visceral, parietal, and terminal arteries. The branches in order of origin are as follows : 1. Right and left inferior phrenics (p). ( Gastric ~1 2. Coeliac axis < Hepatic >{v.). (Splenic j 3. Right and left suprarenals (v.). 4. Right and left first lumbars (p.). 5. Superior mesenteric {v.). 6. Right and left renal («.). 7. Right and left spermatics or ovarian (».). 8. Right and left second lumbars {p.). 9. Inferior mesenteric (d.). 10. Right and left third lumbars (p.). 11. Right and left fourth lumbars {p.). 12. Right and left common iliac it.). 13. Middle sacral (^p.). {]}.), Parietal; (».), visceral; (t.), terminal. The inferior phrenic arteries (aa. phrenicae inferiores) (Fig. 466) are two small vessels which present much \'ariety in their origin. They may arise separately THE ABDOMINAL AORTA 659 from the front of the aorta, immediately above the coeliac axis, or by a common truniv, which may spring either from the aorta or from the coehac axis. Some- times one is derived from tlie aorta, and the other from one of the renal arteries. In only one out of thirty-six cases examined did these arteries arise as two separate vessels from the aorta. They diverge from one another across the crura of the Diaphragm, and then pass obliquely upward and outward upon the under surface of the Diaphragm. The left phrenic passes behind the oesophagus and runs for- ward on the left side of the oesophageal opening. The right phrenic passes behind the inferior vena cava, and ascends along the right side of the aperture for trans- mitting that vein. Near the back part of the central tendon each vessel divides into two branches. The internal branch runs forward to the front of the thorax, supplying the Diaphragm, and anastomosing with its fellow of the opposite side, and with the musculophrenic and comes nervi phrenici branches of the internal mammary. The external branch passes toward the side of the thorax and anasto- moses with the intercostal arteries and with the musculophrenic. The internal branch of the right phrenic gives off a few vessels to the inferior vena cava, and the left one some branches to the oesophagus. Each vessel also sends glandular Cy»tic artery Fio. 467— The ccel and its branches, the liver having been raised and the lesser omentum removed. branches {rami suprarenales superior) to the suprarenal glands of its own side. The spleen and the liver also receive a few branches from the left and right vessels respectively. The coeliac axis, or artery (a. coeliaca) (Figs. 467 and 468), is a short, thick trunk, about half an inch in length, which arises from the aorta, close to the margin of the opening in the Diaphragm, behind the posterior parietal perito- 660 THE VASCULAR SYSTEMS neum, above the pancreas, and below the twelfth thoracic vertebra, and, passing nearly horizontally forward (in the erect posture), divides into three large branches, the gastric, hepatic, and splenic, occasionally giving off one of the phrenic arteries. Relations. — It is covered by the lesser omentum. On the right side it is in relation with the right semilunar ganglion; on the left side, with the left semilunar ganglion and cardiac end of the stomach. Below, it rests upon the upper border of the pancreas. Great Fig. 468.— The cceli: } and its branches, the stomach having been raised and the transverse mesocolon removed ( semidiagrammatic ) . The gastric or coronary artery (a. gastrica siyiistra) (Figs. 467 and 468), the small- est of the three branches of the coeliac axis, passes upward and to the left side, behind the peritoneum of the lesser peritoneal cavity. It continues this course until it nearly reaches the lesser curvature of the stomach just below the cardia. It then turns to the front and curves forward, distributing branches to the oesoph- agus which anastomose with the aortic oesophageal arteries; others supply the cardiac end of the stomach, anastomosing with branches of the splenic artery; it then passes from left to right, along and upon the lesser curvature of the stomach and beneath the peritoneum to the pylorus, lying in its course between the layers of the lesser omentum, and sometimes dividing into two vessels, which run along each side of the lesser curvature. One vascular arch gives branches to the antero-superior wall of the stomach and the other to the postero-inferior wall; at its termination it anastomoses with the pyloric branches of the hepatic. The THE ABDOMINAL AORTA 661 (Esophageal branches {rami oesophagel) anastomose with the oesoj^haj^eal hranchcs from the thoracic aorta and the inferior phrenic. Occasionally the j^astric artery gives off an hepatic branch of variable size, which is usually distributed to the left lobe of the liver. The hepatic artery (a. hepatica) (Figs. 467 and 468) in the adult is intermediate in size between the gastric and splenic; in the fetus it is the largest of the three branches of the coeliac axis. It runs forward and to the right, to be distributed to the upper margin of the pyloric end of the stomach; in its course it forms the lower boundary of the foramen of ^^'i^slow. It then passes upward between the layers of the lesser omentum, and in front of the foramen of Winslow, to the trans- verse fissure of the liver, where it divides into two branches, right and left, which supply the corresponding lobes of that organ, accompanying the ramifications of the portal vein and hepatic duct. The hepatic artery, in its course along the right border of the lesser omentum, is in relation witli the common bile duct and portal vein, the duct lying to the right of the artery and the portal vein behind. Its branches (Figs. 467 and 468) are: Pyloric. rrastrndundenal I ^'S^* gastroepiploic. I buperior pancreaticoduodenal. Cystic. The pyloric (a. gastrica dextrd) arises from the hepatic, above the pylorus, descends between the layers of the lesser omentum to the pyloric end of the stomach, and passes from right to left along its lesser curvature, supplying it with branches and anastomosing with the terminal branches of the gastric artery. The gastroduodenal {a. gastrodvodenalis) (Fig. 468) is a short but large branch, which descends near the pylorus, behind the first portion of the duodenum, and divides at the lower border of this viscus into two branches, the right gastro- epiploic (a. c/astroepiploica dextra) and the superior pancreaticoduodenal. Previous to its division, it gives off two or three small inferior pyloric branches, to the pyloric end of the stomach and pancreas. The right gastroepiploic runs from right to left along the greater curvature cf the stomach, between the layers of the great omentum, anastomosing about the middle of the greater curvature of the stomach with the left gastro-epiploic from the splenic artery. This vessel gives off numerous branches, some of which ascend to supply both surfaces of the stomach, while others descend to supply the great omentum (rami epiploici). The superior pancreaticoduodenal (a. pancreaticoduodenalis superior) descends between the contiguous margins of the duodenum and pancreas. It supplies the head of the pancreas by means of the ravii pancreatica, and the duodenum by means of the rami duodenalis, and anastomoses with the inferior pancreatico- duodenal branch of the superior mesenteric artery and with the pancreatic branches of the splenic. The cystic artery (a. cystica) (Fig. 467), usually a branch of the right hepatic, passes downward and forward along the cystic duct to the gall-bladder and divides into two branches, one of whicla ramifies on its free surface beneath the peritoneum, the other between the gall-bladder and the substance of the liver. The splenic artery (a. lienalis) (Figs. 467 and 468), in the adult, is the largest of the three branches of the coeliac axis, and is remarkable for the extreme tortuosity of its course. It passes horizontally to the left side, behind the peritoneum and along the upper border of the pancreas, accompanied by the splenic vein, which lies below it; it crosses in front of the upper part of the left kidney, and on arriving near the spleen divides into branches, some of which enter the hilum of that organ between the two layers of the lienorenal ligament to be distributed to its 662 THE VASCULAR SYSTEMS structure; some branches, given off along its course, are distributed to the pan- creas, while others pass to the greater curvature of the stomach between the two layers of the gastrosplenic omentum. Its branches are: Pancreatic. Vasa brevia. Left gastroepiploic. The pancreatic branches (rami pancreatici) are numerous small branches derived from the splenic as it runs behind the upper border of the pancreas, supplying its middle and left parts. One of these, larger than the rest, is sometimes given off from the splenic near the left extremity of the pancreas; it runs from left to right near the posterior surface of the gland, following the course of the pancreatic duct, and is called the pancreatica magna. These vessels anastomose with the pancreatic branches of the pancreaticoduodenal arteries, derived from the hepatic on the one hand and the superior mesenteric on the other. The vasa brevia (aa. gastricae breves) consist of from five to seven small branches, which arise either from the end of the splenic artery or from its terminal branches. They pass from left to right, between the layers of the gastrosplenic omentum, are distributed to the greater curvature of the stomach, anastomosing with branches of the gastric and left gastroepiploic arteries. The left gastroepiploic (a. gastroepiploica sinistra^, the largest branch of the splenic, runs from left to right along but distinctly below the greater curvature of the stomach, between the layers of the great omentum, and anastomoses with the right gastroepiploic. In its course it distributes several ascending branches to both surfaces of the stomach; others descend to supply the greater omentum. Applied Anatomy. — The operation of pylorectomy can be made an almost bloodless pro- cedure by tying the gastric, the pyloric, and the right and left gastroepiploic arteries. "The gastric is doubly tied about one inch below the cardiac orifice at a point where it joins the lesser curvature and is divided between the ligatures. The pyloric is doubly tied and di\'ided. The fingers are passed beneath the pylorus, raising the gastrocolic omentum from the transverse mesocolon, and in this way safe ligation behind the pylorus of the right gastro-epiploic artery, or in most cases its parent vessel, the gastroduodenal, is secured. The left gastro-epiploic is now tied at an appropriate point, and the necessary amount of gastrocolic omentum doubly tied and cut."' EmboHsm of branches of the splenic artery is not uncommon in heart disease, the embolus coming from the left side of the heart. It is characterized by the occurrence of a sudden sharp pain or "stitch" in the splenic region, with subsequent local enlargement of the spleen from the formation of an infarct in its substance. The suprarenal artery (a. suprarenalis media) (Fig. 466), or capsular artery, arises, one from each side of the aorta, opposite the superior mesenteric artery. It is a small vessel which passes obliquely upward and outward, over the corre- sponding crus of the Diaphragm, to the under surface of the suprarenal gland, to which it is distributed, anastomosing with capsular branches from the phrenic and renal arteries. In the adult these arteries are of small size; in the fetus they are as large as the renal arteries. The lumbar arteries (aa. liimbales) are in series with the intercostals. They are usually four in number on either side, and arise from the back part of the aorta opposite the bodies of the upper four lumbar vertebrte. A fifth pair, small in size, is occasionally present; it arises from the middle sacral artery. They run outward and backward on the bodies of the lumbar vertebrae, behind the sympa- thetic cord, to the intervals between the adjacent t^ans^"erse processes, and are then continued into the abdominal wall. The arteries of the right side pass behind the inferior vena cava, and the upper two on each side run behind the corresponding crus of the Diaphragm. The arteries of both sides pass beneath the tendinous arches which give origin to the Psoas magnus, and are then continued behind this 'William J. Mayo, Annals of Surgery, March, 1904. THE ABDOMINAL AORTA 663 muscle and the lumbar plexus. They- now cross the Quadratus lumborum, the upper three arteries running behind, the last usually in front of the muscle. At the outer border of the Quadratus lumborum they pierce the posterior aponeurosis of the Transversalis abdominis and are carried forward between this muscle and the Internal oblique. They anastomose with the lower intercostals, the sub- costal, the iliolumbar, the deep circumflex iliac, and the deep epigastric arteries. Branches. — In the interval between the adjacent transverse processes each lumbar artery gives off a dorsal branch {ramus dorsalis), which is continued back- ward between the transverse processes and is distributed to the muscles and skin of the back. It gives off a spinal branch (ramus sjnnalis) which enters the verte- bral canal and is distributed in a similar manner to the lateral spinal branches of the vertebral (page 620). Muscular branches are supplied from each lumbar artery and from its dorsal branch to the neighboring muscles. The superior mesenteric artery (a. mesenterica superior) (Figs. 466 and 470) is a vessel of large size which supplies the whole length of the small intestine, except the first part of the duodenum; it also supplies the cecum and the ascending and transverse parts of the colon. It arises from the front of the aorta about half, an inch below the coeliac axis, and is covered at its origin by the splenic vein and the neck of the pancreas. It passes downward and forward in front of the lower part of the head of the pancreas — processus uncinatus — and the third portion of the duodenum, and descends between the layers of the mesentery to the right iliac fossa, where, considerably diminished in size, it anastomoses with one of its own branches — viz., the ileocolic. In its course it forms an arch, the convexity of which is directed forward and downward to the left side, the concavity backward and upward to the right. It is accompanied by the superior mesenteric vein, and is surrounded by the superior mesenteric plexus of nerves. Dissection. — In order to expose the superior mesenteric artery raise the great omentum and transverse colon, draw down the small intestines, and cut through the peritoneum where the transverse mesocolon and mesentery join; the artery -n-ill then be exposed just as it issues from over the unciform process of the head of the pancreas. Branches. — Its branches are: Inferior pancreaticoduodenal. Ileocolic. Vasa intestini tenuis. Right colic. Middle colic. The inferior pancreaticoduodenal (a. fancreaticoduodenalis inferior') is given off from the superior mesenteric, or from its first intestinal branch behind the pan- creas. It courses to the right between the head of the pancreas and duodenum, and then ascends to anastomose with the superior pancreaticoduodenal artery. It distributes branches to the head of the pancreas and to the second and third portions of the duodenum. The vasa intestini tenuis (aa. intestinales) arise from the convex side of the superior mesenteric artery. They are usually from twelve to fifteen in number, and are distributed to the jejunum (aa. jejunales) and ileum {aa. ileae). They run parallel with one another between the layers of the mesentery, each vessel dividing into two branches, which iniite with similar branches on each side, forming a series of arches the convexities of which are directed toward the intes- tine. From this first set of arches branches arise, which again unite with similar branches from either side, and thus a second series of arches is formed; and from these latter, a third and a fourth, or even a fifth, series of arches is constituted, diminishing in size the nearer they approach the intestine. From the terminal arches numerous small straight vessels arise which encircle the intestine, upon which they are distributed, ramifying between its coats. Throughout their 664 THE VASCULAR SYSTEMS course small branches are given ofF to the nodes and other structures between the layers of the mesentery. (See the description of the vascular loops in the section upon the Intestines.) The ileocolic artery (a. ileocolica) is the lowest branch given off from the con- cavity of the superior mesenteric artery. It descends between the layers of the mesentery to the right iliac fossa, where it divides into two branches. Of these, the inferior division anastomoses with the termination of the superior mesen- teric artery, forming with it an arch, from the convexity of which branches proceed to supply the termination of the ileum, the cecum, the vermiform appen- dix, and the ileocecal valve. The superior division anastomoses with the right colic and supplies the commencement of the colon. Fig. 469. — Arteries and appendix seen from behind. (Poirier and Cliarpy > The descending branch of the ileocolic runs toward the upper border of the ileocecal junction and gives off the following branches: (a) Colic, which passes upward on the ascending colon; (h) anterior and posterior cecal (or ileocecal), which are distributed to the front and back of the cecum; (c) appendicular [a. appendicularis) , which passes downward behind the terminal part of the ileum and runs in the mesoappendix close to its free margin for the supply of the appendix; and {d) ileal, which runs upward and to the left on the terminal part of the ileum and anastomoses with the termination of the superior mesenteric (Fig. 469). The right colic artery (a. colica dextra) arises from about the middle of the concavity of the superior mesenteric artery; it passes to the right behind the peritoneum to the middle of the ascending colon, and divides into two branches — a descending branch, which anastomoses with the ileocolic, and an ascending branch, which anastomoses with the middle colic. These branches form arches, from the convexity of which vessels are distributed to the ascending colon. The middle colic artery (a. colica media) arises from the upper part of the concavity of the superior mesenteric, and, passing downward and forward between the layers of the transverse mesocolon, divides into two branches, the one on the right side anastomosing with the right colic; that on the left side, with the left colic, a branch of the inferior mesenteric. From the arches formed by their anastomosis branches are distributed to the transverse colon. The branches of this vessel lie between the two layers of the transverse mesocolon. THE ABDOMINAL AORTA 665 The renal arteries (are. renales) (Fig. 466) are two larjje trunks which arise from the sides of the aorta immediately below the superior mesenteric artery. Each is directed outward across the corresponding crus of the Diaphragm, so as to form nearly a right angle with the aorta. The right is longer than the left, on account of the position of the aorta; it passes behind the inferior ^ena cava. The left is somewhat higher than the right. Before reaching the hilum of the kidney, each artery usually di-\'ides into four branches. Two of these vessels enter the anterior portion and two the posterior portion of the kidney. The anterior branches supply three-fourths of the kidney, the posterior supply one-fourth. Each vessel gives off a small branch to the suprarenal gland {a. supraraialis inferior) and branches to the ureter, ureteral branches, and to the surrounding cel- lular tissue and muscles, perirenal branches. The two circulations are distinct and do not anastomose even at the periphery. Between these two sets of vessels is a nearly bloodless zone, the exsanguinated renal zone of Hyrtl, which does not correspond to the lateral border, but is one-half inch dorsal to the external border of the kidney. The ventral or anterior segment is much the larger. In very rare instances the bloodless zone corresponds to the lateral border (Kiimmel) . Applied Anatomy. — An incision of the middle third of the kidney exactly at the junction of the two segments does not divide large vessels. As the incision approaches either pole there is danger of cutting a large branch (Schede). Frequently there is a second renal artery, which is gi\en off from the abdominal aorta either above or below the renal artery proper, the former being the more common position. Instead of entering the kidney at the hilum, one or more accessory renal arteries often pierce the upper or the lower part of the gland. The spermatic arteries (aa. spermaticae internae) (Fig. 466) are distributed to the testes. They are two slender vessels of considerable length, which arise from the front of the aorta a little below the renal arteries. Each artery passes obliquely outward and downward behind the peritoneum, resting on the Psoas muscle, the right spermatic lying in front of the inferior vena cava, the left behind the sigmoid flexure of the colon. It then crosses obliquely over the ureter (to which it sends a few branches) and the lower part of the external iliac artery to reach the internal abdominal ring, through which it passes, and accompanies the other constituents of the spermatic cord along the inguinal canal to the scrotum, where it becomes tortuous and divides into several branches. Two or three of these accompany the vas deferens, anastomosing with the artery of the vas defer- ens, and are distributed to the epididymis ; others pierce the back part of the tunica albuginea and supply the substance of the testis. The spermatic artery in the inguinal canal gives off cremasteric branches to supply the Cremaster muscle. In the canal and scrotimi the artery lies behind the pampiniform plexus and in front of the vas deferens. The ovarian arteries {aa. ovaricae) (Fig. 473) in the female correspond to the spermatic arteries in the male. They supply the ovaries, and are shorter than the spermatic. The origin and course of the first part of each artery are the same as the spermatic in the male, but on arriving at the margin of the pelvis the o^•arian artery passes inward, between the two layers of the broad ligament of the uterus, to be distributed to the ovary. Small branches go to the Fallopian tube, the ureter, and the broad ligament; and one passes on to the side of the uterus and anastomoses with the uterine artery. Other offsets are continued along the round ligament through the inguinal canal, to the integument of the labium and groin. At an early period of fetal life, when the testes or ovaries lie at the side of the vertebral column below the kidneys, the spermatic or ovarian arteries are short; but as these organs descend from the abdomen into the scrotum or pelvis, the arteries gradually become lengthened. 666 THE VASCULAR SYSTEMS The inferior mesenteric artery {a. mesenterica inferior) (Figs. 466 and 471) supplies the descending colon, the sigmoid flexure of the colon, and the greater part of the rectum. It is smaller than the superior mesenteric, and arises from the front and toward the left side of the aorta, between one and two inches above the division of that vessel into the common iliacs. It passes downward to the left iliac fossa, and then descends between the layers of the mesorectum, into the pelvis, under the name of the superior hemorrhoidal artery. It lies at first in close relation with the left side of the aorta, and then passes as the superior hemor- rhoidal in front of the left common iliac artery. Fig. 470. — The superior mesenteric artery and its branches. Dissection. — In order to expose the inferior mesenteric artery clraw the small intestines and mesentery over to the right side of the abdomen, raise the transverse colon toward the thorax, and divide the peritoneum covering the front of the aorta. Branches. — Its branches are: Left colic. Superior hemorrhoidal. Sigmoid. The left colic artery (a. colica sinistra) passes behind the peritoneum, in front of the left kidney, to reach the descending colon; it divides into an ascending THE ABDOMINAL AORTA 667 branch which anastomoses with the middle colic, and a descending branch which anastomoses with the upper sigmoid artery. From the arches formed by these anastomoses, branches are distributed to the descending colon. The sigmoid arteries {aa. sigvioideae) run obliquely downward and outward behind the peritoneum across the Psoas muscle to the sigmoid flexure of the colon. They divide into branches which supply the lower part of the descending colon and the sigmoid flexure, anastomosing above with the left colic, and below with the superior hemorrhoidal artery. Inferior liemorrhmda! iiJA Fig. 471. — The inferior raesent The superior hemorrhoidal artery (a. hemorrhoidalis superior) (Figs. 471 and 472), the terminal portion of the inferior meseixteric, descends into the pelvis between the layers of the mesorectum, crossing, in its course, the left ureter and left common iliac vessels. Opposite the middle of the sacrum it divides into two branches, which descend one on either side of the rectum, and about five inches from the anus break up into several small branches, which pierce the muscular coat of the bowel and run downward, as straight vessels, placed at regular intervals from each other in the wall of the intestine between its muscular and mucous coat, to the level of the Internal sphincter; here they form a series of loops around the lower end of the rectum, and communicate with the middle hemorrhoidal arteries, which are branches of the internal iliac, and with the inferior hemorrhoidal branches of the internal pudic. 668 THE VASCULAR SYSTEMS THE COMMON ILIAC ARTERIES (AA. ILIACAE COMMUNES) (Figs. 466, 472). The abdominal aorta divides on the left side of the body of the fourth lumbal vertebra into the two common iliac arteries. Each is about two inches in length. They diverge from the termination of the aorta, pass downward and outward to the margin of the pelvis, and divide, opposite the intervertebral disk, between the last Umibar vertebra and the sacrum, into two branches, the internal and external iliac arteries, the latter supplying the lower extremity; the former, the viscera and parietes of the pelvis. The right common iliac is somewhat longer than the left, and passes more obliquely across the body of the last lumbar vertebra. In front of it are the peri- toneum, the small intestines, branches of the sympathetic cord, and, at its point of division, the ureter. Behind, it is separated from the bodies of the fourth and fifth lumbar vertebrae, and the intervening intervertebral disk, by the two common iliac veins. On its outer side, it is in relation above with the inferior vena cava and the right common iliac vein; and below, with the Psoas magnus muscle. On its inner side, above, is the left common iliac vein. The left common iliac is in relation, iji front, with the peritoneum, small intes- tines, branches of the sympathetic cord, and the superior hemorrhoidal artery; and is crossed at its point of bifurcation by the ureter. It rests on the bodies of the fourth and fifth lumbar vertebrae, with the intervening disk. The left common iliac vein lies partly on the inner side, and partly behind the corresponding artery; on its outer side, the artery is in relation with the Psoas magnus muscle. Plan of the Relations of the Common Iliac Arteries. In front. Peritoneum. Small intestines. Sympathetic cord. Ureter. In front. Peritoneum. Sympathetic cord. Superior hemorrhoidal artery. Ureter. ^ ~\ Onter side. ' Inner side. /^ N ^ -. / Right \ Common I Iliac. J , Inferior vena cava. 1 Right common iliac vein. Psoas muscle. Left common / iliac vein. 1 ' . ,^ \ Outer side. Left \ ^mS"" j Psoas magnus y ' / muscle. Behind. Behind. Fourth and fifth lumbar vertebrae. Right and left common iliac veins. Fourth and fifth lumbar vertebrae. Left common iliac vein. Branches. — The common iliac arteries give off small branches to the perito- neum. Psoas magnus, ureters, and the surrounding areolar tissue, and occasionally give origin to the iliolumbar or to the accessory renal arteries. Peculiarities. — The -point of origin varies according to the bifurcation of the aorta. In three-fourths of a large number of cases the aorta bifurcated either upon the fourth lumbar vertebra or upon the intervertebral disk between it and the fifth, the bifurcation being, in one case out of nine below, and in one out of eleven above, this point. In ten out of every thirteen cases the vessel bifurcated within half an inch above or below the level of the crest of the ilium, more frequently below than above. The point of division is subject to great variety. In two-thirds of a large number of cases it was between the last lumbar vertebra and the upper border of the sacrum, being above that point in one case out of eight and below it in one case out of six. The left common iliac artery- divides lower down more frequently than the right. The relative lengths, also, of the two common iliac arteries vary. The right common iliac was the longer in sixty-three cases, the left in fifty-two, while they were both equal in fifty-three. The length of the arteries varied in five-sevenths of the cases examined from an inch and a half THE INTEltXAL ILIAC ARTERY 669 .to three inches; in about half of the remaining cases the artery was longer and in the other half shorter, the iTiiniraura length being less than half an inch, the maximum four and a hall inches. In two insiaiK-es the right common iliac has been found wanting, the external and internal iliaes arising dirccily from the aorta. Surface Marking. -Draw a line between the highest points of the iliac crests; this is usually half an inch below the umbilicus; in this line take a point lialf an inch to the left of the middle line. From this draw two lines to points midway between the anterior superior sjjines of the ilium and the symphysis pubis. These two diverging lines will represent the course of the common and external iliac arteries. Draw a second line corresponding to the level of the ante- rior su]5erior spines of the ilium; the portion of the diverging lines between these two levels will represeiil the course of the common iliac artery; the portion below the lower zone, that of the external iliac artery. Applied Anatomy. — The application of a ligature to the common iliac artery may be re- quired on account of aneurism or hemorrhage implicating tlie external or internal iliacs; The abdomen is opened by an incision in either the semilunar line or the hnea alba; the intestines are drawn to one side and the peritoneum covering the artery divided. The sheath is then opened, and the needle passed from within outward. On the right side great care must be exercised in passing the needle, since both the common iliac veins lie behind the artery. After the vessel has been tied the incision in the peritoneum over the artery sliould be sutured. In amputation of the hip-joint the common iliac can be compressed most certainly and safely by opening the abdomen and compressing the vessel by means of the fingers against the Psoas muscle (McBurney's method). Collateral Circulation. — The principal agents in carrying on the collateral circulation after the application of a ligature to the common iliac are the anastomoses of the hemorrhoidal branches of the internal iliac with the superior hemorroidal from the inferior mesenteric; the anastomoses of the uterine and ovarian arteries and of the vesical arteries of opposite sides; of the lateral sacral with the middle sacral artery; of the epigastric with the internal mammary inferior intercostal, and lumbar arteries; of the circumflex iliac with the lumbar arteries; of the iliolumbar with the last lumbar artery; of the obturator artery, by means of its pubic branch, with the vessel of the opposite side and with the deep epigastric. From the back part of the aorta, just at its bifurcation, arises the middle sacral artery (a. sacralis media) (Fig. 472). It is a small vessel, and descends upon the last lumbar vertebra, along the middle line of the front of the sacrum, to the upper part of the coccyx, where it anastomoses with the lateral sacral arteries, and terminates in the coccygeal body. From it minute branches arise which run through the mesorectura to supply the posterior surface of the rectum. Other branches are given off on each side, which anastomose with the lateral sacral arteries, and send branches into the anterior sacral foramina. It is crossed by the left common iliac vein, and is accompanied by a pair of venae comites; these unite to form a single vessel which opens into the left common iliac vein. This artery and its lateral branches probably represent fused segmental arteries (see page 763). The Internal Iliac Artery (Figs. 466, 472). The internal iliac or hypogastric artery (a. hypogastrica) supplies the walls and viscera of the pelvis, the l)uttock, the generative organs, and inner side of the thigh. It is a short thick vessel, smaller in the adult than the external iliac, and about an inch and a half in length. It arises at the bifurcation of the common iliac, opposite the lumbosacral articulation, and, passing downward to the upper margin of the great sacrosciatic foramen, divides into two large trunks, an anterior and a posterior. From its anterior division a partially impervious cord, a part of the fetal hypogastric artery, extends forward to the bladder. Relations.— 7n front, with the ureter, which is between the artery and the peritoneum. Behind, with the internal iliac vein, the lumbosacral cord, and Pyritormis muscle. On its outer side, near its origin with the external iliac vein, which lies between it and the Psoas magnu3 muscle; lower down, with the obturator nerve. 670 THE VASCULAR SYSTEMS Plan of the Relations of the Internal Iliac Artery. Outer side. Psoas masnus. Behind. Internal iliac vein. Lumbosacral cord. Pyfiformis muscle. Fig. 472. — Arteries of the pel In the fetus the hypogastric artery is twice as large as the external iliac, and appears to be the continuation of the common iliac. Instead of dipping into the pelvis, it passes forward to the bladder, and ascends along the sides of that viscus to its summit, to which it gives branches; it then passes upward along the back part of the anterior wall of the abdomen to the umbilicus, converging toward its fellow of the opposite side. Having passed through the umbilical opening, THE INTERNAL ILIAC ARTERY - 671 the two arteries, now termed umbilical, enter the umbilical cord, where they are coiled around the umbilical vein and ultimately ramify in tlie placenta. At birth, when the placental circulation ceases, the portion of tlie hypogastric artery which extends from the summit of the bladder to the umbilicus, contracts, and ultimately dwindles to a solid fibrous cord, the impervious hypogastric artery (lig. umbilicale laferalc), but the lower portion, extending from its origin Jn what is now the internal iliac artery) for about an inch and a half to the wall of tlie bladder, and thence to the summit of that organ, is not totally impervious, though it becomes considerably reduced in size, and serves to convey blood to the bladder under the name of the superior vesical artery. Peculiarities as Regards Length. — In two-thirds of a large number of cases the length of the internal iliac varied between an inch and an inch and a half: in the remaining third it was more frequently longer than shorter, the maximum length being three inches, the minimum half an inch. The lengths of the common and internal iliac arteries bear an inverse proportion to each other, the internal iliac arfcrv being long when the common iliac is short, and vice versa. As Regards its Place of Division.— The place of division of the internal iliac varies between the upper margin of the siicnnn ami llie upper border of the sacrosciatic foramen. The arteries of the two .sides in a series of cases often differed in length, but neither seemed constantly to exceed the other. Applied Anatomy. — The application of a ligature to the internal iliac artery may b« required in cases of aneurism or hemorrhage affecting one of its branches. The best method of tying the internal iliac artery is by an abdominal section in the median line and reaching the vessel through the peritoneal cavity. This plan has been advocated by Dennis, of New York, on the following grounds; (1) It in no way increases the danger of the operation; {'2) it prevents a series of acci- dents which have occurred during ligature of the artery by the older methods; (3) it enables the surgeon to ascertain the exact extent of disease in the main arterial trunk, and select. his spot for the application of the ligature; and (4) it occupies much less time. ' Collateral Circulation. — The circulation after ligature of the internal iliac artery' is carried on by the anastomoses of the uterine and ovarian arteries; of the opposite vesical arteries; of the hemorrhoidal branches of the internal iliac with those from the inferior mesenteric; of the obturator artery, by means of its pubic branch, with the vessel of the opposite side and with the epigastric and internal circumflex; of the circumflex and perforating branches of the profunda femoris with the sciatic; of the gluteal with the posterior branches of the sacral arteries; of the iliolumbar with the last lumbar; of the lateral sacral with the middle sacral; and of the cir- cumflex iliac with the iliolumbar and gluteal. Branches (Fig. 472). — The branches of the internal iliac are: From the Anterior Trunk. From the Posterior Trunk. Superior vesical. Iliolumbar. Middle vesical. Lateral sacral. Inferior vesical. Gluteal. Middle hemorrhoidal. Obturator. Internal pudic. Sciatic. vlgiiml } ^«*''«/e'^^«««- The superior vesical (a. ■vesicalis superior) (Fig. 472) represents the pervious portion of the fetal hypogastric artery. It extends to the side of the bladder, distributing numerous branches to the apex and body of the organ. From one of these a slender vessel is deriv'ed which accompanies the ^'as deferens in its course to the testis, where it anastomoses with the spermatic artery. This is the artery of the vas deferens. Other branches supply the ureter. ^ For a description of a case in which Owen made a dissection ten years after ligature of the internal iliac artery, see Medico-Chirurgical Transactions, vol. xvi. 672 THE VASCULAB SYSTEMS The middle vesical (a. vesicalis medialis) (Fig. 472), usually a branch of the superior, is distributed to the base of the bladder and under surface of the seminal vesicles. The inferior vesical (a. vesicalis inferior) (Fig. 472) frequently arises in com- mon with the middle hemorrhoidal, and is distributed to the base of the bladder, the prostate gland, and seminal vesicles. The branches distributed to the pros- tate communicate with the corresponding vessel of the opposite side. The middle hemorrhoidal artery (a. haemorrhoidalis media) (Fig. 472) usually arises together with the preceding vessel. It is distributed to the rectum, anasto- mosing with the superior and inferior hemorrhoidal arteries. It gives branches to the seminal vesicle and prostate gland. Vaginal arterie. Fig. 473. — The arteries of the internal organs of generatic of the female, seen from behind. (After Hyrtl.) The uterine artery {a. uterina) (Fig. 473) arises from the anterior division of the internal iliac and runs inward on the Levator ani to the neck of the uterus. About three-quarters of an inch from the cervix it crosses the front of the ureter, to which it supplies a small branch. Ascending in a tortuous course on the side of the uterus, between the layers of the broad ligament, it distributes branches to its substance and to the round ligament and the Fallopian tube (ramus tubarius), anastomosing near its termination with the ovarian artery. It gives a branch to the ovary (ramus ovarii), which anastomoses with a branch from the ovarian branches to the cen^ix of the uterus, cervicouterine, and a branch which descends on the vagina, the cervicovaginal, and, joining with branches from the vaginal arteries, form a median longitudinal vessel both in front and behind; these descend on the anterior and posterior surfaces of the vagina, and are named the azygos arteries of the vagina. The vaginal artery (a. vaginalis) usually corresponds to the inferior vesical in the male; it descends upon the vagina, supplying its mucous membrane, and sends branches to the bulb of the vestibule, the neck of the bladder, and the contiguous THE INTERNAL ILIAC ARTERY G73 part of the rectum. It assists in forming the azygos arteries of the vagina, which are anterior and posterior vessels, running longitudinally, and due to anastomoses of the branches of the vaginal from each side and the cervicovaginal artery. The vaginal artery is frequently represented by two or three branches. Luschka, HyrtI, Waldeyer, Robinson, and others, instead of describing the ovarian and uterine arteries as two distinct vessels, regard them as constituting the chief parts of one vessel, the arterja uterina ovarica. What has been called "the circle of Robinson" is composed of a spiral segment (the arteria uterina ovarica), with a portion of the abdominal aorta, common iliacs, and internal iliacs. Robinson' has made a careful study of this vascular circle; he shows that it is of gfeat impor- tance in certain surgical procedures, and that its remarkable "capacity for extension" saves it from damage when the uterus is enormously distended by pregnancy, or when it is "drawn through the pudendum with traction forceps for palpation, inspection, or repair." The author just quoted says further that the utero-ovarian artery has three origins, because it develops from the Wolffian body: The ovarian segment ariseif from the abdominal. aorta. The uterine segment arises from the anterior branch of the internal iliac artery. The artery of the round ligament arises from the deep e[)igastric. The arteria uterina ovarica secures nutrition to the uterus by bringing blood from three sources. It is spiral throughout its entire course, in certain parts is convoluted or looped, and it is accompanied by the pampiniform plexus of veins. The three origins of this vessel are freely united by anastomoses, and rami laterales are given off, which unite the bilateral vessels in the median line. Robinson describes three bifurcations of the utero-ovarian artery. The distal bifurcation, which is "about midway between the uterus and the pelvic wall," forms an acute angle with the main vessel. This bifurcation indicates the point of division of the external from the internal genitals. The cervicovaginal artery supplies the external genitals. The proximal bifurcation marks the situation of the ovary. The artery bifurcates at an acute angle into two branches to supply the ovary and Fallopian tube. The middle bifurcation consists of (1) the division of the uterine segment at the angle formed by the uterus and oviduct ("forming the ramus oviductus and ramus ovarii"), and (2) "the bifurcation of the ramus oviductus forming the ramus oviductus and the ramus ligamenti teretis, or the segment of the round ligament."' Applied Anatomy. — As pointed out by Robinson, the source of bleeding after vaginal hys- terectomy is usually the torn and undamped cervicovaginal artery. As previously mentioned, the spiral and convoluted course of the utero-ovarian artery allows the uterus, ovary, and tube to be drawn into the vagina without injury to the vessels. Robinson points out that in vaginal hysterectomy the genital circle is not divided and only the rami laterales which go to the uterus are cut, the ovaries retaining a normal blood supply and continuing to fimctionate. The obturator artery (a. obturator ia) (Fig. 472) passes forward and down- ward on the lateral wall of the pelvis, to the upper part of the obturator foramen, and, escaping from the pelvic cavity through a short canal, formed by a groove on the under surface of the ascending ramus of the os pubis and the arched border of the obturator membrane, it divides into an internal and external branch. In the pelvic cavity this vessel is in relation, externally, with the obturator fascia; internally, with the ureter, vas deferens, and peritoneum; while a little below it is the obturator nerve. Branches. — Within the pelvis, the obturator artery gives off an iliac branch (ramus iliacus) to the iliac fossa, which supplies the bone and the Iliacus muscle, and anastomoses with the iliolumbar artery; a vesical branch (ramus vesicalis), which runs backward to supply the bladder; and a pubic branch (ramus pubicus), which is given off from the vessel just before it leaves the pelvic cavity. The pubic branch ascends upon the back of the pubis, communicating with offshoots from the deep epigastric artery and with the corresponding vessel of the opposite side; it is sometimes placed on the inner side of the femoral ring. Outside the pelvis, the obturator artery divides into an internal and an external branch, which are deeply situated between the Obturator externus and the pelvis. • F. BjTon Robinson. The Utero-ovarian Artery, or the Genital Vascular Circle, 1903. 674 THE VASCULAB SYSTEMS The internal branch {ramus anterior) curves backward along the inner margin of the obturator foramen, lying between it and the Obturator externus muscle ; it distributes branches to the Obturator externus, Pectineus, Adductors and Gracilis, and anastomoses with the external branch, and with the internal circumflex artery. The external branch {ramus posterior) curves backward around the outer margin of the obturator foramen, also lying between the obturator foramen and the Obturator externus muscle, to the space between the Gemellus inferior and Quadratus femoris, where it divides into two branches. One, the smaller, courses inward around the lower margin of the foramen and anastomoses with the internal branch and with the internal circumflex; the other inclines outward in the groove below the acetabulum (a. acetabulis) , and supplies the muscles attached to the tuberosity of the ischium and anastomoses with the sciatic artery. It sends through the cotyloid notch a branch to the hip-joint, which ramifies on the ligamentum teres as far as the head of the femur. Peculiarities (Figs. 474 and 475). — The obturator artery sometimes arises from the main stem or from the posterior trunk of the internal iUac, from the deep epigastric (28 per cent.), or it may arise from the external iliac (1.2 per cent.). Figs. 474 and 475. — Variations in origin and course of the obturator artery. When the obturator artery arises at the front of the pelvis from the deep epigastric, it descends almost vertically to the upper part of the obturator foramen. The artery in this course usually lies in contact with the external iliac vein and on the outer side of the femoral ring (Fig. 474) ; in such cases it would not be endangered in the operation for femoral hernia. Occasionally, however, it curves inward along the free margin of Gimbernat's ligament (Fig. 475), and under such circumstances would almost completelj' encircle the neck of the hernial sac, and would be in great danger of being wounded if an operation were performed for strangulation. The internal pudic artery {a. pudenda interna) (Figs. 476 and 477) is the smaller of the two terminal branches of the anterior trunk of the internal iliac, and supplies the external organs of generation. Though the course of the artery is the same in the two sexes, the vessel is much smaller in the female than in the male, and the distribution of its branches somewhat different. The description of its arrangement in the male will first be given, and subsequently the differences which it presents in the female will be mentioned. The internal pudic artery in the male passes downward and outward to the lower border of the great sacrosciatic foramen, and emerges from the pelvis be- tween the Pyriformis and Coccygeus muscles; it then crosses the spine of the ischium and enters the pelvis through the lesser sacrosciatic foramen. The artery now crosses the Obturator internus muscle along the outer wall of the ischio- rectal fossa, being situated about an inch and a half above the lower margin of the ischial tuberosity. It gradually approaches the margin of the ramus of the ischium, passes forward between the two layers of the triangular ligament of the perineum ; it then runs forward along the inner margin of the ramus of the pubis and about half an inch behind the subpubic ligament it pierces the superficial layer of the triangular ligament and divides into its two terminal branches, the dorsal artery of the penis and the artery of the corpus cavemosum. THE INTERNAL ILIAC ARTERY 675 Relations. — Within the pelvis, at its beginning, it lies in front of the Pyrifomiis muscle and sacral plexus of nerves, and the sciatic artery, and on the outer side of the rectum (on the left side). As it crosses the spine of the ischium it is covered by the Gluteus maximus and over- lapped by the great sacrosciatic ligament. Here the pudic nerve lies to the inner side and the nerve to the Obturator interniis to the outer side of the vessel. On entering the pelvis it lies on the outer side of the ischiorectal fossa, upon the surface of the Obturator internus muscle, contained in a fibrous canal (Alcock's canal), formed by the splitting of the obturator fascia. It is accompanied by the pudic veins and the pudic nerve. Peculiarities. — The internal pudic is sometimes smaller than usual, or fails to give off one or two of its usual branches; in such cases the deficiency is supplied by branches derived from an additional vessel, the accessory pudic, which generally arises from the internal pudic artery before its exit from the orcat .siu ru.sciatic foramen. It passes forward along the lower part of the bladder and across the side of tlie prostate gland to the root of the penis, where it perforates the triangular ligament and gives off the branches usually derived from the pudic artery. The deficiency most frequently met with is that in which the internal pudic ends as the artery of the bulb, the artery of the corpus cavernosum and dorsal artery of the penis being derived from the accessory pudic. Or the pudic may terminate as the superficial perineal, the artery of the bulb being derived, with the other two branches, from the accessory vessel. Occasionally the acces- sory pudic artery is derived from one of the other branches of the internal iliac, most frequently the inferior vesical or the obturator. Branches. — The branches of the internal pudic artery are: Muscular. Artery of the bulb. Inferior hemorrhoidal. Urethral artery. Superficial perineal. Artery of the corpus cavernosum. Transverse perineal. Dorsal artery of the penis. The muscular branches consist of two sets — one given off in the pelvis, the other as the vessel crosses the ischial spine. The former are several small offshoots which supply the Levator ani, the Obturator internus, the Pyriformis, and the Coccygeus muscles. The branches given off outside the pelvis are distributed to the adjacent part of the Gluteus maximus and External rotator muscles. They anastomose with branches of the sciatic artery. The inferior hemorrhoidal artery (a. haernorrhoidalis inferior) arises from the internal pudic as it passes above the tuberosity of the ischium. Crossing the ischiorectal fossa it is distributed by two or three terminal branches to the muscles and integument of the anal region. Instead of one inferior hemor- rhoidal artery two or three small vessels may arise from the internal pudic. The superficial perineal artery (a. periiiei) (Fig. 476) supplies the scrotum and the muscles and integument of the perineum. It arises from the internal pudic in front of the preceding branches, and turns upward, crossing either over or under the Transversus perinei superficialis muscle, and runs forward, parallel to the pubic arch, in the interspace between the Accelerator urinae (??i. bidbocavernosus) and Erector penis (m. ischiocavernosus) muscles, both of which it supplies, and is finally distributed to the skin and dartos of the scrotum. In its passage through the perineum it lies beneath the superficial perineal fascia. The transverse perineal artery is a small branch which arises either from the internal pudic or from the superficial perineal artery as it crosses the Transversus perinei muscle. It runs transversely inward along the cutaneous surface of the Transversus perinei superficialis muscle and anastomoses with the like vessel of the opposite side, and with the superficial perineal and inferior hemorrhoidal arteries. It supplies the Transversus perinei and the structures between the anus and bulb of the urethra. The artery of the bulb (o. bulbi urethrae) is a short vessel of large caliber which arises from the internal pudic between the two layers of the triangular ligament; it passes nearly transversely inward, through the fibres of the Compressor urethrae muscle, pierces the superficial layer of the triangular ligament, and gives oft' 676 THE VASCULAR SYSTEMS branches which ramify in the bulb of the urethra. It is then continued forward in the corpus spongiosum to the glans penis. It gives off a small branch to Cowper's gland. The urethral artery (a. urethralis) is a small vessel which passes to the corpus spongiosum at the angle of the converging crura of the penis. It reaches the glans penis and anastomoses with the artery of the corpus cavernosum and the dorsal artery of the penis. This vessel is quite often absent. The artery of the corpus cavernosum (a. profunda penis), one of the terminal branches of the internal pudic, arises just after that vessel has perforated the superficial triangular ligament, and, quickly entering the crus penis obliquely, runs forward in the centre of the corpus cavernosum, to which its branches are distributed. Transversus peniin ficialf. ■Superficial perineal artery. ■Superficial perineal nerve. Internal pudic nerve. Internal pudic artery. Fig. 476. — The superficial muscles and vessels of the perine The dorsal artery of the penis (a. dorsalis penis) ascends between the crus and pubic symphysis, and passes between the two layers of the suspensory ligament of the penis, and runs forward on the dorsum of the penis to the glans, where it divides into two branches which supply the glans and prepuce. On the dorsum of the penis it lies immediately beneath the integument, between the dorsal nerve and the deep dorsal vein, the former being on its outer side. It supplies the integ- ument and fibrous sheath of the corpus cavernosum, sending branches through the sheath to anastomose with the preceding vessel. The internal pudic artery in the female is smaller than in the male. Its origin and course are similar, and there is considerable analogy in the distribution of its branches. The superficial perineal artery supplies the labia pudendi; the artery of the bulb supplies the bulbi vestibuli and the erectile tissue of the vagina; the artery of the corpus cavernosum (a. profunda cUtoridis) supplies the cavernous body of the clitoris; and the dorsal artery of the clitoris (o. dorsalis clitoridis) supplies the dorsum of that organ, and terminates in the glans and in the mem- branous fold corresponding to the prepuce of the male. THE INTERNAL ILIAC ARTERY 677 The sciatic artery (a. ghitaea inferior) (Fig. 477), the larger of the two terminal branches of tiie anterior trunk of the internal iliac, is distributed chiefly on the buttock and back of the thigh. It passes down to the lower part of the great sacrosciatic foramen behind the internal pudic artery, resting on the sacral plexus of nerves and Pyriformis muscle, and escapes from the pelvis through this foramen between the Pyriformis and Coccygeus. ' It then descends in the interval between the tro- chanter major and tuberosity of the ischium, accompanied by the sciatic nerves, and covered by the Gluteus maxi- mus, and is continued down the back of the thigh supplying the skin, and anastomosing with branches of the perfora- ting arteries. Within the pelvis it distrib- utes branches to the Pyriformis, Coccygeus, and Levator ani muscles; some hemorrhoidal branches, which supply the rectum, and occasionally take the place of ithe middle hemor- rhoidal artery; and vesical branches to the base and neck of the bladder, seminal vesicles, and prostate gland. Outside the pelvis it gives off the fol- lowing branches: Muscular. Coccygeal. Comes nervi ischiadic!. Anastomotic. Articular. Cutaneous. The muscular branches sup- ply the Gluteus maximus, anastomosing with the gluteal artery in the substance of the muscle; the External rotators, anastomosing with the internal pudic artery; and the muscles attached to the tuberosity of the ischium, anastomosing with the external branch of the obturator and the internal circumflex arteries. The coccygeal branch runs inward, pierces the great sacrosciatic ligament, and supplies the Gluteus maximus, the integument, and other structures on the back of the coccyx. The comes nervi ischiadic! (a. comitans n. ischiadici) is a long, slender vessel which accompanies the great sciatic nerve for a short distance; it then penetrates it and runs in its substance to the lower part of the thigh. Superior intet md, artictilai . Superior external articular. Inferior muscular Fig. 477.— The arter">3 of the gluteal and posterior femoral regionb 678 THE VASCULAR SYSTEMS The anastomotic artery is directed downward across the External rotators and assists in forming the so-called crucial anastomosis by anastomosing with the superior perforating and the internal and external circumflex arteries. The articular branch, generally derived from the anastomotic, is distributed to the capsule of the hip-joint. The cutaneous branches are distributed to the skin of the buttock and back of the thigh. The iliolumbar artery (a. iliolumhalis), given off from the posterior trunk of jhe internal iliac, turns upward and outward between the obturator nerve and lumbosacral cord, to the inner margin of the Psoas muscle, behind which it divides into a lumbar and an iliac branch. The lumbar branch (ramus lumhalis) supplies the Psoas and Quadratus lum- borum muscles, anastomosing with the last lumbar artery, and sends a small spinal branch (ramus spinalis) through the intervertebral foramen, between the last lumbar vertebra and the sacrum, into the vertebral canal, to supply the Cauda equina. The iliac branch (ramus iliacus) descends to supply the Iliacus muscle; some offshoots, running between the muscle and the bone, anastomose with the iliac branch of the obturator; one of these enters an oblique canal to supply the diploe, while others run along the crest of the ilium, distributing branches to the Gluteal and Abdominal muscles, and anastomose in their course with the gluteal circum- flex iliac, and external circumflex arteries. The lateral sacral arteries (a. sacralis lateralis) (Fig. 472) are usually two in number — superior and inferior. The superior, which is of large size, passes inward, and, after anastomosing with branches from the middle sacral, enters the first or second anterior sacral foramen, supplies branches to the contents of the sacral canal, and, escaping by the corresponding posterior sacral foramen, is distributed to the skin and muscles on the dorsum of the sacrum, anastomosing with the gluteal. The inferior passes obliquely across the front of the Pyriformis muscle and sacral nerves to the inner side of the anterior sacral foramina, descends on the front of the sacrum, and anastomoses over the coccyx with the middle sacral and opposite lateral sacral artery. In its course it gives off branches which enter the anterior sacral foramina (rami spinales); these, after supplying the contents of the sacral canal, escape by the posterior sacral foramina, and are distributed to the muscles and skin on the dorsal surface of the sacrum, anastomosing with the gluteal. The gluteal artery (a. glutaea superior) (Fig. 477) is the largest branch of the internal iliac, and appears to be the continuation of the posterior division of that -s-essel. It is a short, thick trunk which runs backward between the lumbo- sacral cord and the first sacral nerve, and, passing out of the pelvis above the upper border of the Pyriformis muscle, immediately divides into a superficial and a deep branch. AVithin the pelvis it gives off a few muscular branches to the Iliacus, Pyriformis, and Obturator internus, and, just previous to emerging from that cavity, a nutrient artery which enters the ilium. The superficial branch enters the deep surface of the Gluteus niaximus, and divides into numerous branches, some of which supply the muscle, while others per- forate its tendinous origin, and supply the integument covering the posterior sur- face of the sacrum, anastomosing with the posterior branches of the sacral arteries. The deep branch lies under the Gluteus medius and almost immediately sub- divides into two. Of these, the superior division (ramus superior), continuing the original course of the vessel, passes along the upper border of the Gluteus mini- mus to the anterior superior spine of the ilium, anastomosing with the circumflex iliac and ascending branches of the external circumflex artery. The inferior division (ramus inferior) crosses the Gluteus minimus obliquely to the trochanter THE EXTERNAL ILIAC ARTERY 679 major, distributing branches to the Gluteus muscles, and anastomoses with the external circumflex artery. Some branches pierce the Gluteus minimus to supply the hip-joint. Surface Marking. — The position of the three main branches of the internal iliac, the sciatic, internal pudic, and gluteal, which may occasionally be I he objcil of siii-;.i(al inlcrference, is indicated on the surface in the following way: A line is to br drau n Iniin ilji' |ii»(iTior suije- rior iliac spine to the posterior superior angle of the great troehanlcr, willi the hinb .slightly fie.xed and rotated inward; the point of emergence of the gluteal artery from the upper part of the sciatic notch will correspond with the junction of the upper with the middle third of this line. A second line is to be drawn from the same point to the outer part of the tuberosity of the ischium; the junction of the lower with the middle third marks the point of emergence of the sciatic and pudic arteries from the great sciatic notch. Applied Anatomy. — Any of these three vessels may require ligating for a wound or for aneurism, which is generally traumatic. The gluteal artery is ligated by turning the patient two-thirds over on his face and making an incision from the posterior superior spine of the ilium to the upper and posterior angle of the great trochanter. This must expose the Gluteus maxi- mus muscle, and its fibres are to be separated through the whole thickness of the muscle and pulled apart with retractors. The contiguous margins of the Gluteus medius and Pyriformis are now to be separated from each other, and the artery will be exposed emerging from the sciatic notch. In ligation of the sciatic artery, the incision should be made parallel with that for ligation of the gluteal, but one inch and a half lower down. After the fibres of the Gluteus maximus have been separated, the vessel is to be sought for at the lower border of the Pyri- formis; the great sciatic nerve, which lies just above it, forms the chief guide to the artery. The internal pudic can be reached through the incision used to reach the sciatic. The External Iliac Artery (A. Iliaca Externa) (Fig, 472). The external iliac artery is larger in the adult than is the internal iliac. It passes obliquely downward and outward along the inner border of the Psoas muscle, from the bifurcation of the common iliac to a point beneath Poupart's ligament, midway between the anterior superior spine of the ilium and the sym- physis pubis, where it enters the thigh and becomes the femoral artery. Relations. — In front, the artery is in relation with the peritoneum, subperitoneal areolar tissue, the termination of the ileum on the right side, and the sigmoid flexure on the left, and a thin layer of fascia derived from the iliac fascia, which surrounds the artery and vein. At its origin it is crossed by the ovarian artery in the female, and occasionally by the ureter. The spermatic vessels descend for some distance upon it near its termination, and it is crossed in this situation by the genital branch of the genitofemoral nerve and the deep circumflex iliac vein; the vas deferens in the male, and the round ligament in the female, curve down along its inner side. Behind, it is in relation with the inner border of the Psoas muscle, from which it is separated by the iliac fascia. At the upper part of its course, the external iliac vein lies partly behind it, but lower down lies entirely to its inner side. Externally, it rests against the Psoas muscle, from which it is separated by the iliac fascia. Numerous lymphatic vessels and nodes are found lying on the front and inner side of the vessel. Plan of the Relations of the External Iliac Artery. In front. Peritoneum, intestines, and fascia. vr ( Lymphatic vessels and nodes. p t' J Spermatic vessels. J . " , j Genitofemoral nerve (genital branch). " ' V Deep circumflex iliac vein. Outer side. / \ Inner side. Psoas magnus. I iiiac. External iliac vein and vas deferens Iliac fascia. \ / near Poupart's ligament. Behind. External iliac vein. Psoas magnus. 680 THE VASCULAB SYSTEMS Surface Marking. — The surface line indicating the course of the external iliac artery has been already given (see page 669). Applied Anatomy. — The application of a ligature to the external iliac may be reciuired in cases of aneurism of the femoral artery or for a wound of the artery. This vessel may be secured in any part of its course, excepting near its upper end, which is to be avoided on account of the proximity of the internal iliac, and near its lower end, which should also be avoided, on account of the proximity of the deep epigastric and circumflex iliac vessels. The patient having been placed in the supine position, an incision should be made, commencing below at a point about three-quarters of an inch above Poupart's ligament, and a little external to its middle, and run- ning upward and outward, parallel to Poupart's ligament, to a point one inch internal and one inch above the anterior superior spine of the ilium. When the artery is deeply seated more room will be required, and may be obtained by curving the incision from the point last named inward toward the umbilicus for a short distance. The Abdominal muscles and transversalis fascia having been cautiously divided, the peritoneum should be separated from the iliac fossa and raised toward the peh-is; and on introducing the finger to the bottom of the wound, the artery may be felt pulsating along the inner border of the Psoas muscle. The external iliac vein is generally found on the inner side of the artery, and must be cautiously separated from it by the finger nail or handle of the knife, and the aneurism needle should be introduced on the inner side, between the artery and the vein. Ligation of the external iliac artery is also performed by a transperitoneal method. An incis- ion four inches in length is made in the semilunar line, commencing about an inch below the um- bilicus and carried tlu-ough the abdominal wall into the peritoneal cavity. The intestines are then pushed upward and held out of the way by a broad abdominal retractor, and an incision is made through the peritoneum at the brim of the pelvis in the course of the arterj-, and the vessel is seciu'ed in any part of its course which may seem desirable to the operator. The advan- tages of this operation appear to be that if it is found necessary the common iliac artery can be ligated instead of the external iliac without extension or modification of the incision: and secondly, that the vessel can be ligated without in any way interfering with the co\-erings of the sac of an aneurism. Possibly a disadvantage may exist in the greater risk of hernia after this method. Collateral Circulation. — The principal anastomoses in carrying on the collateral circulation, after the application of a ligature to the external iliac, are the iliolumbar with the circumflex iliac; the gluteal with the external circumflex; the obturator with the internal circumflex; the sciatic with the superior perforating and circumflex branches of the profunda artery; and the internal pudic with the external pudic. When the obturator arises from the epigastric it is supplied with blood by branches, either from the internal iliac, the lateral sacral, or the internal pudic. The epigastric receives its supply from the internal mammary and inferior intercostal arteries, and from the internal iliac by the anastomoses of its branches with the obturator.' Branches. — Besides several small branches to the Psoas muscle and the neigh- boring lymph nodes, the external iliac gives oflf two branches of considerable size — the deep epigastric and deep circumfle.^ iliac arteries. ( The deep epigastric artery (a. epigasfrica inferior) (Fig. 472) arises from the external iliac above Poupart's ligament. It curves forward below the peri- toneum, and then ascends obliqtiely along the inner margin of the internal ab- dominal ring, Ij'ing between the transversalis fascia and peritoneum; continuing its course upward, it pierces the transversalis fascia, and passing over the semi- lunar fold of Douglas, ascends between the Rectus and the posterior lamella of its aponeurotic sheath. It finally divides mto numerous branches which anasto- mose, above the umbilicus, with the superior epigastric branch of the internal mammary and with the lower intercostal arteries (Fig. 458). As the deep epi- gastric artery passes obliquely upward and inward from its origin it lies along the lower and inner margin of the internal abdominal ring and behind the commence- ment of the spermatic cord. This part of the vessel is crossed by the vas deferens in the male and the round ligament of the uterus in the female. Branches. ^The branches of this vessel are: The cremasteric (a. spermafica externa in the male, a. ligamenti teretis uteri in the female), which accompanies the spermatic cord, and supplies the Cremaster muscle and other coverings of the 1 Sir Astley Cooper describes the dissection of a limb eighteen years after successful ligation of the external iliac artery in Vol. I of Guy's Hospital Reports. THE EXTERNAL ILIAC ARTERY 681 spermatic cord, anastomosing with the spermatic artery in the male, and which accompanies the round ligament in the female; a pubic branch {ramus puhicu.i), which runs along Poupart's ligament, and then descends behind the os pubis to the inner side of the femoral ring, and anastomoses with offshoots from the obturator artery; muscular branches, some of which are distributed to the Abdominal muscles and peritoneum, anastomosing with the lumbar and circumflex iliac arteries; cutaneous branches, which perforate the tendon of the External oblique, and supply the integument, anastomosing with branches of the superficial epi- gastric. . Fig. 478. — Femoral sheath laid open to sh compartments. : portion of fascia lata removed. Peculiarities. — The origin of the deep epigastric may take place from any part of the external iliac between Poupart's ligament and two inches and a half above it, or' it may arise below this ligament, from the common femoral or from the deep femoral. It frequentl_y arises from the external iliac by a common trunk with the obturator. Sometimes the epigastric arises from the obturator, the latter vessel being furnished by the internal iliac, or the epigastric may be formed by two branches, one derived from the external iliac, the other from the internal iliac. Applied. Anatomy. — The deep epigastric artery follows a line drawn from the middle of Poupart's ligament toward the umbilicus; but shortly after this line cro.sses the linea semilunaris the direction changes, and the course of the vessel is directly upward in the line of junction of the inner third with the outer two-thirds of the Rectus muscle. It has important surgical rela- tions, in addition to the fact that it is one of the principal means, through its anastomosis with the internal mammary, in establishing the collateral circulation after ligation of either the com- mon or external iliac arteries. It lies close to the internal abdominal ring, and is therefore internal to an oblique inguinal hernia, but external to a direct inguinal hernia, as the hernip emerges from the abdomen. It forms the outer boundary of Hesselbach's triangle. It is ii. close relationship with the spermatic cord, which lies in front of it in the inguinal canal, separatefl only by the transversalis fascia. The vas deferens curves round its outer side. 682 THE VASCULAR SYSTEMS The deep circumflex iliac artery (o. cireumflexa ilium -profunda) (Fig. 471) arises from the outer side of the external ihac nearly opposite the epigastric artery. It ascends obliquely outward behind Poupart's ligament, contained in a fibrous sheath formed by the junction of the transversalis and iliac fascite, to the anterior superior spinous process of the ilium. It then runs along the inner surface of the crest of the ilium to about its middle, where it pierces the Transversalis, and runs backward between that muscle and the Internal oblique, to anastomose with the iliolumbar and gluteal arteries. Opposite the anterior superior spine of the ilium it gives off a large branch which ascends between the Internal oblique and Transversalis muscles, supplying them, and anastomosing with the lumbar and epigastric arteries. It also gives off cutaneous branches. Femoral Pouimrt's hgament. branch Femoral ; External cutaneous nerve. Iliac portion of Sheath of fascia lata. Femoral vein. Femoral rifig.^ GimberiviV Femoral artery. Fig. 479. — Structures which pass beneath the crural arch. ARTERIES OF THE LOWER EXTREMITY The artery which supplies the greater part of the lower extremity is the direct continuation of the external iliac. It continues as a single trunk from Poupart's ligament to the lower border of the Popliteus muscle, and here divides into two branches, the anterior and posterior tibial. For convenience of description, the upper part of the main trunk is named femoral, the lower part, popliteal. THE FEMORAL ARTERY G83 THE FEMORAL ARTERY (A. FEMORALIS) (Figs. 4S1 and 4S-2). The femoral artery commences immediately behind Poupart's ligament, midway between the anterior superior spine of the ilium and the symphysis pubis, and, passing down the fore part and inner side of the thigh, terminates at the opening in the Adductor raagnus, at the junction of the middle with the lower third of the thigh, where it becomes the popliteal artery. The vessel, at the upper part of the thigh, lies in front of the hip-joint, on a line with the innermost part of the head of the femur; in the lower part of its course it is in close relation with the inner side of the shaft of the bone, and between these two parts the vessel is some distance from the bone. The first inch and a half of the vessel is enclosed, together with the femoral vein, in a fibrous sheath — the femoral sheath. In the upper third of the thigh it is contained in a triangular space called Scarpa's triangle, and in this space it gives off its largest branch, the deep femoral. In the middle third of the thigh it is contained in an aponeurotic canal called Hunter's canal. That portion of the femoral artery which extends from Poupart's ligament to the origin of the deep femoral is sometimes called the common femoral; its continua- tion is the superficial femoral. Fig. 480.— The relation of the femoral and internal abdominal rings, seen from within the abdomen. Right side. The femoral or crural sheath (Fig. 479) is a continuation downward of the fasciffi that line the abdomen, the transversalis fascia passing down in front of the femoral vessels, and the iliac fascia descending behind them ; these fascia^ are directly continuous on the iliac side of the femoral artery, but a small space exists between the femoral vein and the point where they are continuous on the pubic side of that vessel, which constitutes the femoral or crural canal (Fig. 479). The femoral sheath is closely adherent to the contained vessels about an inch below the saphe- nous opening, tjcing blended with the sheath of the vessels, but opposite Pou- part's ligament it is much larger than is required to contain them; hence the funnel-shaped form which it presents. The outer border of the sheath is perfo- rated by the femoral nerve. Its inner border is pierced by the internal saphenous vein and numerous lymphatic vessels. In front it is covered by the iliac portion of the fascia lata; and behind it is the pubic portion of the same fascia. 684 THE VASCULAR SYSTEMS The anterior wall of the sheath is a thickened band of fascia continuous above Poupart's ligament with the transversalis fascia, called the deep crural arch. From it stretch two septa, one between the femoral artery and the vein, the other lying just internal to the vein, and cutting off a small space between the vein and the inner wall of the sheath. The septa are stretched between the anterior and posterior walls of the sheath, so that each vessel is enclosed in a separate compart- ment. The interval left between the vein and the inner wall of the sheath is not CIRCUMFLEX DEEP EXTERNAL PUDIC INTERNAL CIRCUMFLEX SUPERIOR EXTER NAL ARTtCULAI BRANCH O POPLITEAL Fig. 4S1. — Scheme of the femoral artery. and Charpy.) filled up by any structure, excepting a little loose areolar tissue, a few lymphatic vessels, and occasionally by a small lymph node; this is the femoral or crural canal through which the intestine descends in femoral hernia. The femoral or crural canal (canalis femoralis) (Figs. 479 and 480) is the narrow interval between the femoral vein and the inner wall of the femoral sheath. It exists as a distinct canal only when the sheath has been separated from the vein by dissection or by the pressure of a hernia or tumor. Its length is from a quarter THE FEMORAL ARTERY G85 to half an inch, and it extends from the femoral ring to the upper part of (he saphenous opening. This canal has two orifices — an, upper one, tiie femoral or crural ring, closed by the septum crurale; and a lower one, the saphenous opening, closed l)y the cribri- form fascia. - The femoral or crural ring (afinulus femoralis) (Figs. 462 and 463) is the upper opening of the femoral canal, and leads into the cavity of the abdomen. It is of an oval form; its long diameter, directed transversely, measures about half an inch, and it is larger in the female than in the male, which is one of the reasons of the greater frequency of femoral hernia in the former sex. Scarpa's triangle (trigomim femorale) corresponds to the de- pression seen immediately below the fold of the groin. It is a triangular space, the apex of which is directed downward, and the sides formed externally by the Sartorius, internally by the inner margin of the Adductor longus, and above by Poupart's ligament. The floor of the space is formed from without inward by the Ilia- cus, Psoas, Pectineus (in some cases a small part of the Adduc- tor brevis), and the Adductor longus muscles; and it is divided into two nearly equal parts by the femoral vessels, which extend from the middle of its base to its apex, the artery giving off in this situation its superficial and pro- funda branches, the vein receiving the deep femoral and internal saphenous. On the outer side of the femoral artery is the femoral nerve dividing into its branches. In the outer corner of the space is the external cutaneous nerve. Within the sheath of the artery, and lying upon the outer side of the vessel, is the femoral branch of the genitofemoral nerve. At the base of the triangle the vein is to the inner side of the artery; at the apex of the triangle it is passing behind the artery. Besides the vessels and nerves, this space contains some fat and lymphatics. Hunter's canal, or the adductor canal (canalis adductorius [HtDtteri]) (Fig. 381), is the aponeurotic space in the middle third of the thigh, extending from Lonq •saphenous net ve. ■inastomotica magna Ana'itomotica Iiifetio} internal ailicithty. Fig. 4S2. — The femoral artery. 686 THE VASCULAR SYSTEMS the apex of Scarpa's triangle to the femoral opening in the Adductor magnus muscle. It is bounded, externally, by the Vastus internus; internally, by the Adductors longus and magnus muscles; and is covered in by a strong aponeurosis which extends transversely from the Vastus internus across the femoral vessels to the Adductor longus and magnus; lying on which aponeurosis is the Sartorius muscle. It contains the femoral artery and vein enclosed in their own sheath of areolar tissue, the vein being behind and on the Outer side of the artery, and the internal or long saphenous nerve lying at first on the outer side and then in front of the vessels. Relations. — The relations of the artery differ along its course. In Scarpa's triangle the femoral artery is very superficial, being covered by the skin and superficial fascia, superficial inguinal lymph nodes, the iliac portion of the fascia lata, and the anterior part of the femoral sheath. The femoral branch of the genitofemoral nerve courses for a short distance within the outer compartment of the femoral sheath and lies at first in front and then on the outer side of the artery. Near the apex of Scarpa's triangle the internal cutaneous nerve crosses the artery from without inward. Behind the artery are the posterior part of the femoral sheath, the pubic portion of the fascia lata, the inner part of the tendon of the Psoas, the Pectineus and Adductor longus. The artery is separated from the capsule of the hip-joint by the tendon of the Psoas, from the Pectineus by the femoral vein and profunda vessels, and from the Adductor longus by the femoral vein. The nerve to the Pectineus passes inward behind the artery. On the outer side of the artery, but separated from it by some fibres of the Psoas, is the femoral nerve. The femoral vein is on the inner side of the upper part of the artery, but is behind the vessel in the lower part of Scarpa's triangle. Plan of the Relations of the Femoral Artery in Scarpa's Triangle. In front. Skin and superficial fascia. Superficial inguinal nodes. Iliac portion of fascia lata. Prolongation of transversalis fascia. Femoral branch of genitofemoral nerve. • Superficial circumflex iliac vein. Superficial epigastric vein. Inner side. Outer side. Small part of Psoas muscle, Femoral vein. \ Artery, j separating the artery from the femoral nerve. Behind. Prolongation of fascia covering the Iliacus muscle. Pubic portion of fascia lata. Nerve to Pectineus. Tendon of Psoas muscle. Pectineus muscle. Capsule of hip-joint. In Hunter's canal the femoral artery is more deeply situated, being covered by the integument, the superficial and deep fascite, the Sartorius and the fibrous roof of the canal; it is crossed from without inward by the long saphenous nerve. Behind the artery are the Adductores longus et magnus; in front and to its outer side is the Vastus internus. The femoral vein lies behind the upper part, and on the outer side of the lower part of the artery. As the artery passes out of Scarpa's THE FEMORAL ARTERY 687 it for triangle into Hunter's canal, the Iliacus and Pectineus muscles lie heliiiu a short distance (Fig. 482). That portion of the femoral artery which extends from Poupart's ligament to the origin of the profunda is sometimes named the common femoral. Plan of the Relations of the Femoral Artery in Hunter's Canal. In front. Skin, superficial and deep fasciie. Internal cutaneous nerve. Sartorius. Aponeurotic covering of Hunter's canal. Internal saphenous nerve. Inner side. Adductor longus. Adductor magnus. Sartorius. • Behind. Outer side. Long saphenous nerve. Nerve to Vastus internus. Vastus internus. Femoral vein (below). Femoral vein (above). Profunda artery and vein. Pectineus and Iliacus (high up). Adductor longus. Adductor magnus. Peculiarities, Double Femoral Reunited.— Several cases are recorded in which the femoral artery divided into two trunl;s below the origin of the profunda, and became reunited near the opening of the Adductor magnus so as to form a single popliteal artery. One of them occurred in a patient operated upon for popliteal aneurism. Change of Position.— A few cases have been recorded in which the femoral artery was situated at the back of the thigh, the vessel being continuous above with the internal iliac, escap- ing from the pelvis through the great sacrosciatic foramen, and accompanying the great sciatic nerve to the po])Hteal space, where its division occurred in the usual manner. The external iliac in these cases was small, and terminated in the profunda. Position of the Vein. — The femoral vein is occasionally placed along the inner side of the artery, throughout the entire extent of Scarpa's triangle, or it may be divided so that a large vein is placed on each side of the artery for a greater or less extent. Surface Marking. — The upper two-thirds of a line drawn from a point midway between the anterior superior spine of the ilium and the symphysis pubis to the adductor tubercle on the inner condyle of the femur, with the thigh abducted and rotated outward, will indicate the course of the femoral artery. AppUed Anatomy. — Compression of the femoral artery, which is constantly requisite in amputations and other operations on the lowerlimbs, and also for the cure of popliteal aneurisms, is most effectually made immediately below Poupart's ligament. In this situation the artery is very superficial, and is merely separated from the ascending ramus of the os pubis by the Psoas muscle; so that the surgeon, by means of his thumb or a compressor, may effectualiy control the circulation through it. This vessel may also be compressed in the middle third of the thigh by placing a compress over the artery, beneath the tourniquet, and directing the pressure from within outward, so as to compress the vessel against the inner side of the shaft of the femur. The application of a ligature to the femoral artery may be required in the cases of wound or aneurism of the arteries of the leg, of the popliteal or femoral;' and the vessel may be exposed and tied in any part of its course. The great depth of this vessel at its lower part, its close con- nection with important structures, and the density of its sheath render the operation in this situation one of much greater difficulty than the application of a ligature at its upper part, where it is more superficial. Ligation of the common femoral artery is usually considered unsafe, on account of the con- nection of large branches with it — viz., the deep epigastric and the deep circumflex iliac arising just above Poupart's ligament; on account of the number of small branches which arise, from it in its short course; and on account of the uncertainty of the origin of the profunda femoris, which, if it arise high up, would be too close to the ligature for the formation of a firm coag- ulum. The profunda sometimes arises higher than the point above mentioned, and rarely ' Ligation of the femoral artery has been also recommended and performed for elephantiasis of the leg and acute inflammation of the knee-joint (Maunder, CUn. See. Trans., vol. ii, p. 37). 688 THE VASCULAR SYSTEMS between two or three inches (in one case four) below Poupart's ligament. It would appear, then, that the most favorable situation for the application of a ligature to the femoral is on the super- ficial femoral at the apex of Scarpa's triangle. In order to expose the artery in this situation, an incision between three and four inches long should be made in the course of the vessel, the patient lying in the recumbent position, with the limb slightly flexed and abducted, and rotated outward. A large vein is frequently met with, passing in the course of the artery to join the internal saphenous vein; this must be avoided, and the fascia lata having been cautiously divided and the Sartorius exposed, that muscle must be drawn outward in order to expose fully the sheath of the vessels. The finger being introduced into the wound and the pulsation of the artery felt, the sheath should be opened on the outer side of the vessel to a sufficient extent to allow of the introduction of the ligature, but no farther; otherwise the nutrition of the coats of the vessel may be interfered with, or muscular branches which arise from the vessel at irregular intervals may be divided. In this part of the operation the long saphenous nerve and the nerve to the Vastus internus, which is in close relation with the sheath, should be avoided. The aneurism needle must be carefully introduced and kept close to the artery, to avoid the femoral vein, which lies behind the vessel in this part of its course. To expose the artery in Hunter's canal, an incision should be made between three and four inches in length, a finger's breadth internal to the line of the artery, in the middle of the thigh ' — i. e., midway between the groin and the knee. The integument is first divided. The fascia lata having been divided, and the outer border of the Sartorius muscle exposed, it should be draAvn inward, when the strong fascia which is stretched across from the Adductors to the Vastus internus will be exposed, and must be freely divided; the sheath of the vessels is now seen, and must be opened, and the artery secured by passing the aneurism needle between the vein and artery in the direction from without inward. The femoral vein in this situation lies on the outer side of the artery and the long saphenous nerve on the anterior and outer side of the artery. It has been seen that the femoral artery occasionally divides into two trunks below the origin of the profunda. If in the operation for tying the femoral two vessels are met with, the surgeon should alternately compress each, in order to ascertain which vessel is connected with the aneurismal tumor or with the bleeding from the wound, and that one only should be tied which controls the pulsation or hemorrhage. If, however,, it is necessary to compress both vessels before the circulation in the tumor is controlled, both .should be tied, as it would be probable that they became reunited, as in the instances referred to above. In wounds of the femoral artery the question of the mode of treatment is of considerable importance. If the wound in the superficial structures is a large one, the injured vessel must be exposed and tied; but if the wound is a punctured one and the bleeding has ceased, the ques- tion will arise whether to cut down upon the artery or to trust to pressure. Mr. Cripps advises that if the wound is in the " upper part of the thigh — that is to say, in a position where the fem- oral artery is comparatively superficial — the surgeon may enlarge the opening with a good prospect of finding the wounded vessel without an extensive or prolonged operation. If the wound be in the lower half of the thigh, owing to the greater depth of the artery and the possi- bility of its being the popliteal that is wounded, the search is rendered a far more severe and hazardous operation, and it should not be undertaken until a thorough trial of pressure has proved ineffectual." Great care and attention are necessary for the successful application of pressure. The limb should be carefully bandaged from the foot upward to the wound, which is not covered, and then onward to the groin. The wound is then dusted with iodoform or boracic powder and a conical pad applied o\'er the wound. Rollers the thickness of the index finger are then placed along the course of the vessel above and below the wound, and the whole carefully bandaged to a back splint with a foot piece. Collateral Circulation. — After ligation of the femoral artery, the main channels for carry- ing on the circulation are the anastomoses between (1) the gluteal and sciatic branches of the internal iliac with the internal and external circumflex and superior perforating branches of the profunda femoris; (2) the obturator branch of the internal iliac with the internal circumflex of the profunda; (.3) the internal pudic of the internal iliac with the superficial and deep external pudic of the common femoral; (4) the deep circumflex iliac of the external iliac with the external circumflex of the profunda and the superficial circumflex iliac of the femoral; and (.5) the sciatic and comes nervi ischiadici of the internal iliac with the perforating branches of the profunda. Branches (Figs. 481 and 482). — The branches of the femoral artery are: Superficial epigastric. Muscular. Superficial circumflex iliac. ( External circumflex. Superficial external pudic. Profunda femoris < Internal circumflex. Deep external pudic. ( Three perforating. Anastomotica magna. THE FEMOR. \L AR TER Y GS9 The superficial epigastric (a. cpigasirica superficialis) arises from the fem- oral about lialF an inch helow Poiipart's ligament, and, passing through the saphenous opening in the fascia lata, ascends on the abdomen in the superficial fascia covering the External oblique muscle, nearly as high as the umbilicus. It distributes branches to the superficial inguinal nodes, the superficial fascia, and the integument, anastomosing with branches of the deep epigastric. The superficial circumflex iliac (a. circumflexa ilium superficialis), the smallest of the cutaneous branches, arises close to the preceding, and, piercing the fascia lata, runs outward, parallel with Poupart's ligament, as far as the crest of the ilium, dividing into branches which supply the integument of the groin, the superficial fascia, and the superficial inguinal lymph nodes, anastomosing with the deep circumflex iliac and with the gluteal and external circumflex arteries. The superficial external pudic (a. pudenda externa superficialis) arises from the inner side of the femoral artery, close to the preceding vessels, and, after passing through the saphenous opening, courses inward, across the spermatic cord or round ligament, to be distributed to the integument on the lower part of the abdomen, the penis and scrotum in the male, and the labium majus in the female, anastomosing with branches' of the internal pudic. The deep external pudic (a. p^idenda externa profunda), more deeply seated than the preceding, passes inward across the Pectineus and Adductor longus muscles, covered by the fascia lata, which it pierces at the inner border of the thigh, its branches being distributed, in the male, to the integument of the scrotum and perineum; and in the female to the labium majus, anastomosing with branches of the superficial perineal artery. Muscular branches (rami musculares) are supplied by the femoral to the Sartorius, Vastus internus, and Adductors. The deep femoral, or the profunda femoris (a. profunda femoris) (Fig. 481 and 482), is a large vessel arising from the outer and back part of the femoral artery, from one to two inches below Poupart's ligament. It at first lies on the outer side of the superficial femoral, and then passes behind it and the femoral vein to the inner side of the femur, and, passing downward beneath the Adductor longus, terminates at the lower third of the thigh in a small branch which pierces the Adductor magnus (and from this circumstance is sometimes called the fourth perforating artery), and is distributed to the Flexor muscles on the back of the thigh, anastomosing with branches of the popliteal and inferior perforating arteries. The deep femoral supplies all the tissues on the back and outer side of the thigh not supplied by the sciatic and gluteal arteries. Relations. — Behind, it lies first upon the Iliacus, and then on the Pectineus, Adductor brevis, and Adductor magnus muscles. In front, it is separated from the superficial femoral artery, above by the femoral and profunda veins, and below by the Adductor longus. On its outer side the origin of the Vastus internus separates it from the femur. Plan of the Relations of the Profunda Artery. In front. Superficial femoral artery. Femoral and profunda veins. Adductor longus. Outer side. Vastus internus. Beliind. Iliacus. Pectineus. Adductor brevis. Adductor magnus. 44 690 THE VASCULAR SYSTEMS Peculiarities of Origin of the Profunda.— This vessel occasionally arises from the inner side, and, more rarely, from the back of the common trunk; but the more important peculiarity, from a surgical point of view, is that which relates to the height at which the vessel arises from the femoral. In three-fourths of a large number of cases it arose between one to two inches below Poupart's ligament; in a few cases the distance was less than an inch; more rarely, opposite the ligament; and in one case, above Poupart's ligament, from the external iliac. Occasionally, the distance between the origin of the vessel and Poupart's ligament exceeds two inches, and in one case it was found to be as much as four inches. Branches. — The profunda gives off the following-named branches: External circumflex. Four perforating. Internal circumflex. Muscular. The external circumflex artery (a. circumflexa femoris lateralis) supplies the muscles on the front of the thigh. It arises from the outer side of the profunda, passes horizontally outward, between the divisions of the femoral nerve and behind the Sartorius and Rectus muscles, and divides into three sets of branches — ascending, transverse, and descending. The ascending branch {ramus ascendens) passes upward, beneath the Tensor fasciae femoris muscle, to the outer side of the hip, anastomosing with the terminal branches of the gluteal and deep circumflex iliac arteries. It sends out muscular branches. The descending branch (ramus descendens) passes downward, behind the Rectus, upon the Vasti muscles, to which its branches are distributed, one or two passing beneath the Vastus externus as far as the knee, anastomosing with the superior articular branches of the popliteal artery. These are accompanied by the branch of the femoral nerve to the Vastus externus. The transverse branch, the smallest, passes outward over the Crureus, pierces the Vastus externus, and winds around the femur to its back part, just below the great trochanter, anastomosing at the back of the thigh with the internal circum- flex, sciatic, and superior perforating arteries. The internal circumflex artery (a. circumf.exa femoris medialis), smaller than the external, arises from the inner and back part of the profunda, and winds around the inner side of the femur, between the Pectineus and Psoas muscles. On ' reaching the upper border of the Adductor brevis it gives off two muscular branches, one of which passes inward to be distributed to the Adductor muscles, the Gracilis, and Obturator externus, anastomosing with the obturator artery; the other descends, and passes beneath the Adductor brevis, to supply it and the great Adductor; while the continuation of the vessel passes backward and divides into an ascending and a transverse branch (Fig. 386). The ascending branch (ramius -profundus) passes obliquely upward upon the tendon of the Obturator externus and under cover of the Quadratus femoris toward the digital fossa, where it anastomoses with twigs from the gluteal and sciatic arteries. The transverse branch {ramus superficialis), larger than the ascending, appears between the Quadratus femoris and upper border of the Adductor magnus, anastomosing with the sciatic, external circumflex, and superior perforating arteries, the crucial anas- tomosis. Opposite the hip-joint the artery gives off an articular vessel {ramus acetabuli), which enters the joint beneath the transverse ligament; and, after sup- plying the adipose tissue, passes along the round ligament to the head of the bone. The perforating arteries (Figs. 481 and 482), usually three in number, are so called from their perforating the tendon of the Adductor magnus muscle to reach the back of the thigh. They pass backward close to the linea aspera of the femur, under cover of small tendinous arches in the Adductor magnus. The first is given off above the Adductor brevis, the second in front of that muscle, and the third immediately below it THE POPLITEAL ARTERY G91 The first perforating artery (a. perfnrans prima) passes backward between the Pectineus and Adductor brevis (sometimes perforates the hxtter); it then pierces the Adductor magnus close to the linea aspera. It gives off branches whicli supply the Adductor brevis, the Adductor magnus, the Biceps, the Ghiteus maximus muscles, and anastomoses with the sciatic, internal and external circumflex, and second perforating arteries. The second perforating artery (a. perforans secunda), larger than the first, pierces the tendons of the Adductor brevis and Adductor magnus muscles, and divides into ascending and descending branches, which supply the Flexor muscles of the thigh, anastomosing with the first and third perforating arteries. The second artery frequently arises in common with the first. The nutrient artery of the femur (a. nidricia femoris) is usually given off from this branch. The third perforating artery (a. perforans tertia) is given off below the Adductor brevis; it pierces the Adductor magnus, and divides into branches which supply the Flexor muscles of the thigh; anastomosing above with the higher perforating arteries, and below with the terminal branches of the profunda and the muscular branches of the popliteal. A fourth perforating artery is represented by the termination of the profunda femoris artery. Numerous muscular branches arise from the profunda; some of these end in the Adductor muscles, others pierce the Adductor magnus, give branches to the Ham- string muscles, and anastomose with the internal circumflex artery and with the upper muscular branches of the popliteal. The anastomotica magna (a. genu suprema) (Figs. 481 and 482) arises from the femoral artery just before it passes through the tendinous opening in the Adductor magnus muscle, and immediately divides into a superficial and deep branch. The superficial branch {ramus saphenus) pierces the aponeurotic covering of Hunter's canal, and accompanies the long saphenous nerve to the inner side of the thigh. It passes between the Sartorius and Gracilis muscles, and, piercing the fascia lata, is distributed to the integument of the upper and inner part of the leg, anastomosing with the inferior internal articular artery. The deep branch (ramus musculoarticularis) descends in the substance of the Vastus internus, lying in front of the tendon of the Adductor magnus, to the inner side of the knee, where it anastomoses with the superior internal articular artery and the anterior recurrent branch of the anterior tibial. A branch from this vessel crosses outward above the articular surface of the femur, forming an anas- tomotic arch with the superior external articular artery, and supplies branches to the knee-joint. THE POPLITEAL ARTERY (A. POPLITEA) (Figs. 477 and 481). The popliteal artery commences at the termination of the femoral at the opening in the Adductor magnus, and, passing obliquely downward and outward behind the knee-joint to the lower border of the Popliteus muscle, divides into the anterior and posterior tibial arteries. A portion of the artery lies in the popliteal space; but above and below, to a considerable extent, it is covered by the muscles which form the boundaries of the space, and is therefore beyond the confines of the space. The Popliteal Space (Fig. 483). Dissection. — A vertical incision about eight inches in length should be made along the back part of the knee-joint, connected above and below by a transverse incision from the hiner to the outer side of the limb. The flaps of integument included between these incisions should be reflected in the direction shown in Fig. 3S3, p. 518. 692 THE VASCULAR SYSTEMS Boundaries. — The popliteal space is a lozenge-shaped space, widest at the back part of the knee-joint, and deepest above the articular end of the femur. It is bounded externaMy, above the joint, by the Biceps, and below the joint by the Plantaris and external head of the Gastroc- nemius. Internally, above the joint, by the Semimembranosus, Semitendinosus, Gracilis, and Sartorius; below the joint, by the inner head of the Gastrocnemius. Above, it is limited by the apposition of the inner and outer Hamstring muscles; below, by the junction of the two heads of the Gas- trocnemius. The floor is formed by the lower part of the posterior surface of the shaft of the femur, the posterior ligament of the knee-joint, the upper end of the tibia, and the fascia covering the Popliteus muscle, and the space is covered in by the fascia lata. Contents. — It contains the popliteal vessels and their branches, together with the termi- nation of the external saphenous vein, the internal and external popliteal nerves and some of their branches, the lower extremity of the small sciatic nerve, the articular branch from the obturator nerve, a few small lymph nodes, and a considerable quantity of loose adipose tissue. Position of Contained Parts. — The in- ternal popliteal nerve descends in the middle line of the space lying superficial and cross- ing the artery from without inward. The external popliteal nerve descends on the outer side of the upper part of the space, lying close to the tendon of the Biceps muscle. More deeply at the bottom of the space are the popliteal vessels, the vein lying superficial to the artery, to which it is closely united by dense areolar tissue; it is a thick- walled vessel, and lies at first to the outer side of the artery, and then crosses it to gain the inner side below; sometimes the vein is double, the artery lying between the two venae comites, which are usua'ly connected ■ by short transverse branches. More deeply and, at its upper part, close to the surface of the bone is the popliteal artery, and passing off from it at right angles are its articular branches. The articular branch from the obturator nerve descends upon the popliteal artery to supply the knee, and occasionally there is found deep in the space an artic- ular filament from the great sciatic nerve. The popliteal lymph nodes, four or five Fig. 483.— The popliteal, posterior tibial, and in number, are found surrouuding the artery; peroneal arteries. The external popliteal (or per- ,, ,. r • i , ,^ 'i oneal) nerve has been removed. (See Fig. 776.) 0116 USUally llCS Superficial tO the VCSSel; THE POPLITEAL ARTERY 693 another is situated between it and the bone, and the rest are placed on either side of it. The popliteal artery, in its course downward from the aperture in the Adductor magnus to the lower Ijorder of the Popliteus muscle, rests hrst on the inner surface of the femur, and is then separated by a little fat from the hollowed popliteal surface of the bone; in the middle of its course it rests on the posterior ligament of the knee-joint, and below on tlie fascia covering the Popliteus muscle. Super- ficiallij, it is covered above by the Semimembranosus; in the middle of its course, by a quantity of fat, whicli separates it from the deep fascia and integument; and below it is overlapped by the Gastrocnemius, Plantaris, and Soleus muscles, the popliteal vein, and the internal popliteal nerve. The popliteal vein, which is intimately attached to the artery, lies superficial and external to it above; it then crosses it and lies to its inner side. The internal popliteal nerve is still more super- ficial and external above, but below the joint it crosses the artery and lies on its inner side. Laterally, the artery is bounded by the muscles which are situated on either side of tlie popliteal space. Plax of the Rel.\tions of the Popliteal Artery. Inner side. Semimembranosus. Internal condyle. Gastrocnemius (inner In front. Femiu-. Posterior ligament. Popliteus. Outer side. Biceps. External condyle. Gastrocnemius (outer head). Plantaris. Behind. Semimembranosus. Fascia. Popliteal vein. Internal popliteal nerve. Gastrocnemius. Plantaris. Soleus. Peculiarities in Point of Division.— Occasionally the popliteal artery divides prematurely into its terminal branches; this unusual division occurs most frequently opposite the knee-joint. The anterior tibial under these circumstances may pass in front of the Popliteus muscle. Unusual Branches. — The artery sometimes divides into the anterior tibial and peroneal, the posterior tibial being wanting or very small. Occasionally the popliteal is found to divide into three branches, the anterior and po.sterior tibial and peroneal. Surface Marking. — The course of the upper part of the popliteal artery is indicated by a line di'awn from the outer border of the Semimembranosus muscle at the junction of the middle and lower third of the thigh obliquely downward to the middle of the popliteal space, exactly behind the knee-joint. From this point it passes vertically downward to the level of a line drawn through the lower part of the tubercle of the tibia. Applied Anatomy. — The popliteal artery is not infrequently the seat of injury. It mav be torn by direct violence, as by the passage of a cart-wheel over the knee or by hyperextension of the knee; and in the dead body, at all events, the middle and internal coats may be ruptured by extreme flexion. It may also be lacerated by fracture of the lower part of the shaft of the femur or by antero-posterior dislocation of the knee-joint. It has been torn in breaking down adhesions in cases of fibrous ankylosis of the knee, and is in danger of being wounded, and, in fact, has been wounded, in performing Macewen's operation for osteotomy of the lower end of the femur for genu valgum. In addition, Spencer records a case in which the popliteal artery was woimded from in front by a stab just below the knee, the knife passing through the interosseous space. 694 THE VASCULAR SYSTEMS The popliteal artery is more frequently the seat of aneurism than is any other artery in the body, with the exception of the thoracic aorta. This is due, no doubt, in a great measure, to the amount of movement to which it is subjected, and to the fact that it is supported b}' loose and lax tissue only, and not by muscles, as is the case with most arteries. Ligation of the popliteal artery is required in cases of wound of that vessel, but for aneurism of the posterior tibial it is preferable to tie the superficial femoral. The popliteal may be tied in the upper or lower part of its course; but in the middle of its course the operation is attended with considerable difficulty, from the great depth of the artery and from the extreme degree of tension of the lateral boundaries of the space. In order to expose the vessel in the upper part of its course, the patient should be placed in the supine position, with the knee flexed and the thigh rotated outward, so that it rests on its outer surface; an incision three inches in length, beginning at the junction of the middle and lower third of the thigh, is to be made parallel to and immediateh- behind the tendon of the Adductor magnus, and the skin, superficial and deep fascia divided. The tendon of the muscle is thus exposed, and is to be drawn forward and the Hamstring tendons backward. A quantity of fatty tissue will now be exposed, in which the artery will be felt pulsating. This is to be separated with the point of a director until the artery is exposed. The vein and nerve will not be seen, as they lie to the outer side of the artery. The sheath is to be opened and the aneurism needle passed from before backward, keeping its point close to the artery for fear of injuring the vein. The only structure to avoid is the long saphenous vein in the superficial incision. The upper part of the popliteal artery may also be tied by an incision on the back of the limb, along the outer margin of the Semimembranosus, but the operation is a more difficult one, as the internal popliteal nerve and the popliteal vein are first exposed, and great care has to be exercised in separating them from the artery. To expose the vessel in the lower part of its course, w'here the artery lies between the two heads of the Gastrocnemius, the patient should be placed in the prone position with the limb extended. An incision should then be made through the integument in the middle line, com- mencing opposite the bend of the knee-joint, care being taken to avoid the external saphenous vein and nerve. After dividing the deep fascia and separating some dense cellular membrane, the artery, vein, and nerve will be exposed, descending between the two heads of the Gastroc- nemius. Some muscular branches of the popliteal should be avoided if possible, or, if divided, tied immediately. The leg being now flexed, in order the more effectually to separate the two heads of the Gastrocnemius, the nerve should be drawn inward and the vein outward, and the aneurism needle passed between the artery and vein from without inward. Branches. — The branches of the popliteal artery are: - , J Superior. Superior external articular. Muscular ^^ inferior or sural. Azygos articular. Cutaneous. Inferior internal articular. Superior internal articular. Inferior external articular. The superior muscular branches, two or three in number, arise from the upper part of the popliteal artery, and are distributed to the lower part of the Adductor magnus and Flexor muscles of the thigh, anastomosing with the fourth perforating branch of the profunda. The inferior muscular or sxiral (aa. surales) are two large branches which are distributed to the two heads of the Gastrocnemius and to the Plantaris muscle They arise from the popliteal artery opposite the knee-joint. The cutaneous branches arise separately from the popliteal artery or from some of its branches; they descend between the two heads of the Gastrocnemius muscle, and, piercing the deep fascia, are distributed to the integument of the calf. One branch usually accompanies the short, or external, saphenous vein, the superficial sural artery. The superior articular arteries, two in number, arise one on each side of the popliteal, and wind around the femur immediately above its condyles to the front of the knee-joint. The internal branch (a. genu superior medialis) winds inward beneath the Hamstring muscles, to which it supplies branches, above the inner head of the Gastrocnemius, and, passing beneath the tendon of the Adductor magnus, divides into two branches, one of which supplies the Vastus internus. THE POPLITEAL ARTERY 695 anastomosing with the anastoraotica magna and inferior internal articular; the other ramifies close to the surface of the femur, supplying it and the knee-joint, and anastomosing with the superior external articular artery. This branch is frequently of small size, a condition which is associated with an increase in the size of the anastomotica magna. The external branch (a. cjenu superior lateralis) passes above the outer condyle, beneath the tendon of the Biceps, and divides into a superficial and deep branch; the superficial branch supplies the Vastus externus, and anastomoses with the descending branch of the external circumflex and the inferior external articular arteries; the deep branch supplies the lower part of the femur and knee-joint, and forms an anastomotic arch across the bone with the anastomotica magna and the inferior internal articular arteries. The azygos articular (o. (jenu media) is a small branch arising from the pop- liteal artery opposite the bend of the knee-joint. It pierces the posterior ligament, and supplies the ligaments and synovial membrane in the interior of the articu- lation. Descending branch f \\ external circumflex Superior e eternal articular Inferior external J^^/ articular i iC Superior fibular -4- Anterior recurrent tibial. Ana'^tomotica magna Deep branch of anas~ iomoiica magna. Superficial branch of anastomotica magna. ^\^ V^ Superior internal articular. Inferior internal articular. Fig 484 — Circumpatellar anastomosis. The inferior articular arteries, two in number, arise from the popliteal be- neath the Gastrocnemius, and wind around the head of the tibia below the joint. The internal branch {a. genu inferior medialis) first descends along the upper mar- gin of the Popliteus muscle, to which it gives branches; it then passes below the inner tuberosity, beneath the internal lateral ligament, at the anterior border of which it ascends to the front and inner side of the joint, to supply the head of the tibia and the articulation of the knee, anastomosing with the inferior external articular and superior internal articular arteries. The external branch (a. genu inferior laterali.s) passes outward alx)ve the head of the fibula, to the front of the knee-joint, passing in its course beneath the outer head of the Gastrocnemius, the 696 THE VASCULAB SYSTEMS external lateral ligament, and the tendon of the Biceps muscle, and divides into branches which anastomose with the inferior internal articular artery, the superior external articular artery, and the anterior recurrent branch of the anterior tibial. Circumpatellar Anastomosis. — Around and above the patella, and on the contiguous ends of the femur and tibia, is a large network of vessels, forming a superficial and a deep plexus. The superficial plexus is situated between the fascia and skin around about the patella; the deep Infetim internal plgxus, which forms a close network mti,r.ular i^„ it i n n i or vessels, lies on the surtace ot the lower end of the femur and upper end of the tibia around their articular surfaces, and sends numerous off- shoots into the interior of the joint. The arteries from which this plexus is formed are the two internal and two external articular branches of the popliteal, the anastomotica magna, the terminal branch of the profunda, the descending branch from the ex- ternal circumflex, and the anterior re- current branch of the anterior tibial. The Anterior Tibial Artery (A. Tibialis Anterior) (Fig. 485). The anterior tibial artery com- mences at the bifurcation of the popliteal at the lower border of the Popliteus muscle, passes forward be- tween the two heads of the Tibialis posticus, and through the large oval aperture above the upper border of the interosseous membrane to the deep part of the front of the leg; it here lies close to the inner side of the neck of the fibula; it then descends on the anterior surface of the inter- osseous membrane, gradually ap- JDroaching the tibia; and at the lower part of the leg lies on this bone, and then on the anterior ligament of the ankle to the bend of the ankle-joint, where it lies more superficially, and becomes .the dorsalis pedis. Relations. — In the upper two-thirds of its extent it rests upon the interosseous membrane, to which it is connected by deli- cate fibrous arches thrown across it; in the lower third, upon the front of the tibia and Communicating. -Applied anatomy of the anterior tibial and dorsalis pedis arteries. THE ANTERIOR TIBIAL ARTERY 097 ihe anterior ligament of the ankle-joint. In the upper third of its course it lies between the Tibialis anticus and Extensor longus digitorum; in the middle third, between the Tibialis anti- cus and Extensor proprius hallucis. At the bend of the ankle it is crossed by the tendon of the Extensor proprius hallucis, and lies between it and the innermost tendon of the Extensor longus digitorum. It is covered, in the upper two-thirds of its course, by the muscles which lie on either side of it and by the deep fascia; in the lower third, by the integument anterior annular ligament and fascia. The anteriot tibial artery is accompanied by two veins, venae comites, which lie one on each side of the artery; the anterior tibial nerve, coursing around the outer side of the neck of the fibula, comes into relation with the outer side of the artery shortly after it has passed through the opening in the interosseous membrane; about the middle of the leg it is placed superficial to it; at the lower part of the artery the nerve is generally again on the outer side. Plan op the Relations of the Anterior Tibial Artery. In front. Integument, superficial and deep fasciiB. Anterior tibial nerve. Tibialis anticus (overlaps it in the upper part of the leg). Extensor longus digitorum \ / „„i„„ % „r„ i,*i \ T, ^ ^ • 7 II • ? (overlap it slightly), iixtensor proprius hallucis i ' s j / Anterior annular ligament. Inner s-ide. ' ^ v Outer side. Tibialis anticus. / .„,„,,„, \ Anterior tiliial nerve. . 1 11 . I Anterior \ . ,. . Extensor proprius hallucis 1 Tibial. I Extensor longus digitorum. (crosses it at its lower \ / Extensor proprius hallucis. , part). v^^_^/ Behind. Interosseous membrane. Tibia. Anterior ligament of ankle-joint. Peculiarities in Size. — This vessel may be very small, may be deficient to a greater or less extent, or may be entirely wanting, its place being supplied hy perforating branches from the posterior tibial or by the anterior division of the peroneal artery. Course. — The artery occasionally deviates in its course toward the fibular side of the leg, regaining its usual position beneath the annular ligament at the front of the ankle. In two instances the vessel has been found to approach the surface in the middle of the leg, being covered merely by the integument and fascia below that point. Surface Marking. — Draw a line from the inner side of the head of the fibula to midway between the two malleoli. In this line take a point one inch and a quarter below the head of the fibula, and the portion of the line below this point will mark the course of the artery'. Applied Anatomy. — The anterior tibial artery may be tied in the upper or lower part of the leg. In the upper part the operation is attended with great difficulty, on account of the depth of the vessel from the surface. An incision, about four inches in length, should be made through the integument, midway between the tubercle of the tibia and the outer margin of the fibula, and the deep fascia exposed. The wound must now be carefully dried, its edges retracted, and the white line separating the Tibialis anticus from the Extensor longus digitorum sought for. When this has been clearly defined, the deep fascia is to be divided in this line, and the Tibialis anticus separated from the adjacent muscles with the handle of the scalpel or a director until the interosseous membrane is reached. The foot is to be flexed in order to relax the muscles, and upon drawing them apart the artery will be found lying on the interosseous membrane with the nerve on its outer side or on top of the artery. The nerve should be drawn outward, and the venae comites separated from the artery and the needle passed around it. To tie the vessel in the lower third of the leg above the ankle-joint an incision about three inches in length should be made through the integument between the tendons of the Tibialis anticus and Extensor proprius hallucis muscles, the deep fascia being divided to the same extent. The tendon on either side should be held aside, when the vessel will be seen lying upon the tibia, K'ith the nerve on the outer side and one of the venae comites on either side. Branches. — The branches of the anterior tibial artery are: Posterior recurrent tibial. Muscular. * Superior fibular. Internal malleolar. Anterior recurrent tibial. External malleolar. 698 THE VASCULAR SYSTEMS The posterior recurrent tibial (a. recurrens tibialis posterior) is not a constant branch, and is given off from the anterior tibial before that vessel passes through the interosseous space. It ascends beneath the Popliteus muscle, which it supplies, and anastomoses with the lower articular branches of the popliteal artery, giving an offshoot to the superior tibiofibular joint. The superior fibular is sometimes given off from the anterior tibial, sometimes' from the posterior tibial. It passes outward, around the neck of the fibula, through the Soleus, which it supplies, and ends in the substance of the Peroneus longus. The anterior recurrent tibial (a. recurrens tibialis anterior) arises from the anterior tibial as soon as that vessel has passed through the interosseous space; it ascends in the Tibialis anticus muscle, and ramifies on the front and sides of the knee-joint, anastomosing with the articular branches of the popliteal, with the anastomotica magna, and the external articular branches of the popliteal assisting in the formation of the circumpatellar plexus. The muscular branches are numerous; they are distributed to the muscles which lie on each side of the vessel, some cutaneous branches piercing the deep fascia to supply the integument, others passing through the interosseous mem- brane, and anastomosing with branches of the posterior tibial and peroneal arteries. The internal malleolar branch (a. malleolaris anterior mediaUs) arises about two inches above the articulation, and passes beneath the tendons of the Extensor proprius hallucis and Tibialis anticus to the inner ankle, upon which it ramifies, anastomosing with branches of the posterior tibial and internal plantar arteries and with the internal calcanean from the posterior tibial. The external malleolar branch (a. malleolaris anterior lateralis) passes beneath the tendons of the Extensor longus digitorum and Peroneus tertius, and supplies the outer ankle, anastomosing with the anterior peroneal artery and with ascending branches from the tarsal branch of the dorsalis pedis. The Dorsalis Pedis Artery (A. Dorsalis Pedis) (Figs. 485, 486). The dorsalis pedis, the continuation of the anterior tibial, passes forward from the ankle along the tibial side of the foot to the back part of the first intermetatarsal space, where it divides into two branches, the dorsalis hallucis and communicating. Relations. — This vessel, in its course forward, rests upon the astragalus, navicular, and middle cuneiform bones and the ligaments connecting them, being covered by the integument and fascia, anterior annular ligament, and crossed near its termination by the innermost tendon of the Extensor brevis digitorum. On its tibial side is the tendon of the Extensor proprius hallucis; on its. fibular side, the innermost tendon of the Extensor longus digitorum, and the termination of the anterior tibial nerve. The nerve is, however, quite as often upon the tibial side of the artery. The artery is accompanied by two veins. Plan of the Relations of the Dorsalis Pedis Artery. 7/1 front. Integument and fascia. Anterior annular ligament. Innermost tendon of Extensor brevis digitorum. Tibial side. Fibular side. Ts , • i_ 11 • \ f eaiB. 1 Extensor longus digitorum. Extensor proprius hallucis. ^ J Anterior tibial nerve. Behind. Astragalus. Navicular. Middle cuneiform. And their ligaments. THE BORSALIS PEDIS ARTERY 699 Peculiarities in Size. — The dorsal artery of the foot may be hirger than usual, to compen- sate for a deficient plantar artery; or it may be deficient in its terminal branches to the toes, which are then derived from the internal plantar; or its place may be supplied altogether by a large anterior peroneal artery. Position. — This artery frequently curves outward, lying external to the line between the middle of the ankle and the back part of the first interosseous space. Surface Marking. — The dorsalis pedis artery is indicated on the surface of the dorsum of the foot by a line drawn from the centre of the space between the two malleoli to the back of the first intermetatarsal space. Applied Anatomy. — This artery may be tied, by making an incision through the integu- ment between two and three inches in length, on the fibular tide of the tendon of the Extensor proprius hallucis, in the interval between it and the inner border of the short Extensor muscle. The incision should not ex- tend farther forward than the back part of the first inter- metatarsal space,as the artery divides in that situation. The deep fascia being divided to the same extent, the artery will be exposed, the nerve lying upon its outer side. Branches. — The branches of the dorsalis pedis are: Cutaneous. Tarsal. Metatarsal — Interos- seous. Dorsalis hallucis. Communicating. Cutaneous branches go to the skin of the dor- sum and inner surface of the foot. The tarsal artery (o. tarsea lateralis) arises from the dorsalis pedis, as that vessel crosses the navicular bone; it passes in an arched direction outward, lying upon the tarsal bones, and covered by the Extensor brevis digitorum; it supplies that muscle and the articulations of the tarsus, and anastomoses with branches from the metatarsal, external malleolar, peroneal, and external plantar arteries. The metatarsal (a. arcuata) arises a little anterior to the preceding; it passes outward lu the outer part of the foot, over the bases of the metatarsal bones, beneath the tendons of the short Extensor, its direction being influenced by its point of origin; and it anastomoses with the tarsal and external plantar arteries. This vessel gives off three branches, the dorsal interosseous arteries (aa. meta- tarseae dorsales), which pass forward upon tlie three outer Dorsal interossei mus- cles, and, in the clefts between the toes, divide into two dorsal collateral branches for the adjoining toes (aa. digitales dorsales). At the back part of each inter- osseous space these vessels receive the posterior perforating branches from the plantar arch, and at the fore part of each interosseous space they are joined by Fig. 486. — Diagram of the arteries of the dorsal surface of the foot. (Poirjer and.Charpy.) 700 THE VASCULAR SYSTEMS the anterior perforating branches from the digital arteries. The outermost inter- osseous artery gives oil a branch which suppHes the outer side of the Httle toe. The dorsalis hallucis, or the first dorsal interosseous (a. dorsalis hallucis), is one of the terminal branches of the dorsalis pedis. It runs forward along the outer border of the first metatarsal bone, and at the cleft between the first and second toes divides into two branches, one of which passes inward, beneath the tendon of the Extensor proprius hallucis, and is distributed to the inner border of the great toe; the outer branch bifurcates, to supply the adjoining sides of the great and second toes. The communicating artery (ramus plantaris profundus), the other terminal branch of the dorsalis pedis, dips down into the sole of the foot, between the two heads of the First dorsal interosseous muscle, and anastomoses with the termina- tion of the external plantar artery, to complete the plantar arch. It here gives off its plantar digital branch, which is named the arteria magna hallucis, or the princeps hallucis. This artery passes forward along the first interosseous space, and, after sending a branch along the inner side of the great toe, bifurcates for the supply of the adjacent sides of the great and second toes. The Posterior Tibial Artery (A. Tibialis Posterior) (Fig. 4S3). The posterior tibial is an artery of large size, which extends obliquely down- ward from the lower border of the Popliteus muscle, along the tibial side of the leg, to the fossa between the inner malleolus and the heel, where it divides beneath the origin of the Abductor hallucis, on a level with a line drawn from the point of the internal malleolus to the centre of the convexity of the heel, into the internal and external plantar arteries. At its origin it lies opposite the interval between the tibia and fibula; as it descends, it approaches the inner side of the leg, lying behind the tibia, and, in the lower part of its course, is situated midway between the inner malleolus and the tuberosity of the os calcis. Relations. — The posterior tibial artery lies successively upon the Tibialis posticus, the Flexor longus digitorum, the tibia, and the back part of the ankle-joint. It is covered by the deep transverse fascia, which separates it above from the Gastrocnemius and Soleus muscles; at its termination it is covered by the Abductor hallucis muscle. In the lower third, where it is more superficial, it is covered only bj' the integument and fascia, and runs parallel with the inner border of the tendo Achillis. It is accompanied by two veins and by the posterior tibial nerve, which lies at first to the inner side of the artery, but soon crosses it, and is, in the greater part of its course, on its outer side. Plan of the Relations of the Posterior Tibial Artery. In front. Tibialis posticus. Flexor longus digitorum. Tibia. Ankle-joint. Inner side. / \ Outer side. Posterior tibial nerve, I T'}'^^^ j Posterior tibial nerve, upper third. \ ' / lower two-thirds. Behind. Integument and fascia. Gastrocnemius. Soleus. Deep transverse fascia. Posterior tibial nerve. Abductor hallucis. THE POSTERIOR TIBIAL ARTERY 701 Behind the inner malleolus the tendons and bloodvessels are arranged, under cover of the internal annular ligament, in the following order, from within outward: First, the tendons of the Tibialis posticus and Flexor longus digitorum, lying in the same groove, behind the inner malleolus, the former being the more internal. External to these is the posterior tibial artery, having a vein on either side, and, still more externally, the posterior tibial nerve. About half an inch nearer the heel is the tendon of the Flexor longus hallucis. Peculiarities in Size. — The posterior tibial is not infrequently smaller than usual, or absent, its place being supplied by a large peroneal artery which passes inward at the lower end of the tibia, and either joins the small tibial artery or continues alone to the sole of the foot. Surface Marking. — The course of the posterior tibial artery is indicated by a line drawn from a point one inch In-low the centre of the popliteal space to midway between the tip of the internal mallc:ilus anil the c<'ntre of the convexity of the heel. Applied Anatomy. — The appliration of a ligature to the posterior tibial may be required in cases of wound of the sole of the foot attended with great hemorrhage, when the vessel should be tied at the inner ankle. In cases of wound of the posterior tibial it will be necessary to enlarge the opening so as to expose the vessel at the woimded point, excepting where the vessel is injured by a punctured wound from the front of the leg. In cases of aneurism from wound of the artery low down, the vessel should be tied in the middle of the leg. But in aneurism of the posterior tibial high up it would be better to tie the femoral artery. To tie the posterior tibial artery at the ankle, a semUunar incision, convex backward, should be made through the integument, about two inches and a half in length, midway between the ' heel and the inner ankle or a little nearer the latter. The subcutaneous cellular tissue having been divided, a strong and dense fascia, the internal annular ligament, is exposed. This liga- ment is continuous above with the deep fascia of the leg, covers the vessels and nerves, and is intimately adherent to the sheaths of the tendons. This having been cautiously divided upon a director, the sheath of the vessels is exposed, and, being opened, the artery is seen with one of the venae comites on each side. The aneurism needle should be passed around the vessel from the heel toward the ankle, in order to avoid the posterior tibial nerve, care being taken at the same time not to include the venae comites. The vessel may also be tied in the lower third of the leg by making an incision, about three inches in length, parallel with the inner margin of the tendo Achillis. The internal saphenous vein being carefully avoided, the two layers of fascia must be divided upon a director, when the artery is exposed along the outer margin of the Flexor longus digitorum, with one of its venae comites on either side and the nerve lying external to it. To tie the posterior tibial in the middle of the leg is a very difficult operation, on account of the great depth of the vessel from the surface. The patient being placed in the recumbent posi- tion, the injured limb should rest on its outer side, the knee being partially bent and the foot extended, so as to relax the muscles of the calf. An incision about four inches in length should then be made through the integument a finger's breadth behind the inner margin of the tiljia, taking care to avoid the internal saphenous \ein. The deep fascia having been divided, the margin of the Gastrocnemius is exposed, and must be drawn aside, and the tibial attachment of the Soleus divided, a director being previously passed beneath it. The artery may now be felt pulsating beneath the deep fascia about an inch from the margin of the tibia. The fascia having been divided, and the limb placed in such a position as to relax the muscles of the calf as much as possible, the veins should be separated from the artery, and the aneurism needle passed around the vessel from without inward, so as to avoid wounding the posterior tibial nerve. Branches. — The branches of the posterior tibial artery are: Peroneal. Cutaneous. Nutrient. Communicating. Muscular. Internal calcaneal. Malleolar cutaneous. The peroneal artery (a. pcronaea) (Fig. 483) lies, deeply seated, along the back part of the fibular side of the leg. It arises from the posterior tibial about an inch below the lower border of the Popliteus muscle, passes obliquely outward to the fibula, and then descends along the inner border of that bone, contained in a fibrous canal between the Tibialis posticus and the Flexor longus hallucis, or in the substance of the latter muscle to the lower third of the leg, where it gives off' the anterior peroneal. It then passes across the articulation between the til>ia and filjula to the outer side of the os calcis, where it gives off its terminal branches, the external calcaneal. 702 THE VASCULAB SYSTEMS Relations. — This vessel rests at first upon the Tibialis posticus, and then, for the greater part of its course, in a fibrous canal between the origins of the Flexor longus hallucis and Tibialis posticus, covered or surrounded by the fibres of the Flexor longus hallucis. It is covered, in the upper pmi of its course, by the Soleus and deep transverse fascia; below, by the Flexor longus hallucis. Plan of the Relations of the Peroneal Artery. hi front. Tibialis posticus. Flexor longus hallucis. Outer side. Fibula. Flexor longus hallucis. Inner side. Flexor longus hallucis. Behind. Soleus. Deep transverse fascia. Flexor longus hallucis. Peculiarities in Origin. — The peroneal artery may arise three inches below the Popliteus, or from the posterior tibial high up, or even from the popliteal. Its size is more frequently increased than diminished; and then it either reinforces the poste- rior tibial by its junction with it, or altogether takes the place of the posterior tibial in the lower part of the leg and foot, the latter vessel only existing as a short muscular branch. In those rare cases where the peroneal artery is smaller than usual a branch from the posterior tibial supplies its place, and a branch from the anterior tibial compensates for the diminished anterior peroneal artery. In one case the peroneal artery has been found entirely wanting. The anterior peroneal is sometimes enlarged, and takes the place of the dorsal artery of the foot. Branches. — ^The branches of the peroneal are: Muscular. Communicating. Nutrient. Posterior peroneal. Anterior peroneal. External calcaneal. Muscular Branches. — The peroneal artery in its course gives off branches to the Soleus, Tibialis posticus, Flexor longus hallucis, and Peronei muscles. The nutrient artery (a. nutricia fibulae) supplies the fibula. The anterior peroneal (ramus perforans) (Fig. 486) pierces the interosseous membrane, about two inches above the outer malleolus, to reach the fore part of the leg, and, passing down beneath the Peroneus tertius to the outer ankle, rami- fies on the front and outer side of the tarsus, anastomosing with the external malleolar and tarsal arteries. The communicating (ramus cominunicans) is given off from the peroneal about an inch from its lower end, and, passing inward, joins the communicating branch of the posterior tibial. The posterior peroneal passes down behind the outer ankle to the back of the external malleolus, to terminate in branches which ramify on the outer surface and back of the os calcis. The external calcaneal (ramus calcaneus lateralis) are the terminal branches of the peroneal artery; they pass to the outer side of the heel, and communicate with the external malleolar, and, on the back of the heel, with the internal calcaneal arteries. Cutaneous branches come from the posterior tibial and supply the skin of the inner side and back of the leg. The nutrient artery of the tibia (a. nutricia tibiae) arises from the posterior tibial near its origin, and, after supplying a few muscular branches, enters the THE POSTERIOR TIBIAL ARTERY 703 nutrient canal of that bone, which it traverses obliquely from above downward. This is the largest nutrient artery of bone in the body. The muscular branches of the posterior tibial are distributed to the Soleus and deep muscles along the back of the leg. The communicating branch (ramus communicans), to join a similar branch of the peroneal, runs transversely across the back of the tibia, about two inches above its lower end, passing beneath the Flexor longus hallucis. The malleolar or internal malleolar (a. malleolar is posterior medialis) lies upon the tibia, sends branches over the inner ankle, and anastomoses with the inner malleolar branch of the anterior tibial. The internal calcaneal (rami calcanei mediales') are several large arteries which arise from the posterior tibial just before its division; they are distributed to the fat and integument behind the tendo Achillis and about the heel, and to the muscles on the inner side of the sole, anastomosing with the peroneal and internal malleolar, and, on the back of the heel, with the external calcaneal arteries. CoMmunieating branch of dorsalis pedis. Its digilal branches. Fig. 487. — The plantar arteries. Superficial view. Fig. 488. — The plantar arteries. Deep The internal plantar artery (a. planfaris medialis) (Figs. 487 and 488), much smaller than the external, passes forward along the inner side of the foot. It is at first situated above^ the Abductor hallucis, and then between it and the Flexor brevis digitorum, both of which it supplies. At the base of the first metatarsal bone, where it has become much diminished in size, it passes along the inner border of the great toe, anastomosing with its digital branch. Small superficial digital branches (ramus superficialis) accompany the digital branches of the medial plantar nerve and join the plantar digital arteries of the three inner spaces. In addition, this vessel gives off numerous cutaneous branches. The external plantar artery (a. plantaris lateralis) (Figs. 487 and 488), much larger than the internal, passes obliquely outward and forward to the base of the > This refers to the erect position of the body. In the ordinary position for dissection the artery is deeper than the muscle. 704 THE VASCULAR SYSTEMS fifth metatarsal bone. It then turns obHquely inward to the interval between the bases of the first and second metatarsal bones, where it anastomoses with the communicating branch from the dorsalis pedis artery, thus completing the plantar arch (areas plantaris) (Fig. 488). As this artery passes outward, it is first placed between the os calcis and Abductor hallucis, and then between the Flexor brevis digitorum and Flexor accessorius, and as it passes forward to the base of the little toe it lies more superficially between the Flexor brevis digitorum and Abductor minimi digiti, covered by the deep fascia and integument. The remaining portion of the vessel is deeply situated; it extends from the base of the metatarsal bone of the little toe to the back part of the first interosseous space, and forms the plantar arch; it is convex forward, lies below or on the plantar aspect of the tarsal ends of the second, third, and fourth metatarsal bones and the correspond- ing Interosseous muscles and upon the Adductor obliquus hallucis. Surface Marking. — The course of the internal plantar artery is represented by a line drawn from the mid-point between the tip of the internal malleolus and the centre of the con- \'exity of the heel to the middle of the under suface of the great toe; the external plantar by a line from the same point to within a finger's breadth of the tuberosity of the fifth metatarsal bone. The plantar arch is indicated by a line drawn from this point — i. e., a finger's breadth internal to the tuberosity of the fifth metatarsal bone transversely across the foot to the back of the first interosseous space. Applied Anatomy. — Wounds of the plantar arch are always serious, on account of the depth of the vessel and the important structures which must be interfered with in an attempt to ligate it. They must be treated on similar lines to those of wounds of the palmar arches (see page 654). Delorme has shown that the plantar arch may be ligated from the dorsum of the foot in almost any part of its course by removing a portion of one of the three middle meta- tarsal bones. Branches. — The plantar arch, besides distributing numerous branches to the muscles, integument, and fasciae in the sole, gives off the following branches: Posterior perforating. ■ Digital. The posterior perforating (raini perforanfes posferiores) are three small branches which ascend through the back part of the three outer interosseous spaces, between the heads of the Dorsal interossei muscles, and anastomose with the interosseous branches from the metatarsal artery. The digital branches (aa. metatarseae plantares) are four in number, and supply the three outer toes and half the second toe. It will be remembered that the arteria princeps hallucis is the plantar digital branch of the communicating rami in the first interosseous space and supplies the adjacent sides of the great and second toes. The first digital branch of the plantar arch passes outward from the outer side of the plantar arch, and is distributed to the outer side of the little toe, passing in its course beneath the Abductor and short Flexor muscles. The second, third, and fourth run forward along the interosseous spaces, and on arriving at the clefts between the toes each divides into collateral digital branches {aa. digitales plantares), which supply the adjacent sides of the three outer toes and the outer side of the second. At the bifurcation of the toes each digital artery sends upward, through the fore part of the corresponding interosseous space, a small branch which anastomoses with the interosseous branches of the metatarsal artery. These are the anterior perforating branches (rami perforantes anteriores). From the description given it will be seen that both sides of the three outer toes and the outer side of the second toe are supplied by branches from the plantar arch; both sides of the great toe and the inner side of the second are supplied by the communicating branch of the dorsalis pedis (princeps hallucis). THE VEINS. The Veins convey the blood from the capillaries of the different parts of the body toward the heart. They consist of two distinct sets of vessels, the pulmonary and systemic veins, and an appendage to the systemic, the portal system. The Pulmonary Veins are concerned in the circulation of the blood through the lungs. Unlike other vessels of this kind, they contain arterial blood, which they return from the lungs to the left auricle of the heart. \ Fig. 489. — Valves of a vein. In the lower part of the figure are seen the parietal valves; the upper part shows the mouth of a vein guarded by a valve. (Poirier and Charpy.) La. X. Fig, 490. — Collateral anastomosis of veins. The arrows indicate the direction of the flow of blood (schematic). (Poirier and Charpy.) The Systemic Veins are concerned in the general circulation; they return the venous blood from the body generally to the right auricle of the heart. The Portal Vein and its radicles constitute the portal system. The portal system is in reality an appendage to the systemic venous system, and is confined to the abdominal cavity, returning the venous blood from the viscera of the digestive system, and carrying it to the liver by a single trunk of large size, the portal vein. This vessel ramifies in the substance of the liver and breaks up into a minute network of capillaries. These capillaries then re-collect to form the hepatic veins, by which the blood is conveyed to the inferior vena cava. The veins, like the arteries, are found in nearly every tissue of the body. They commence by minute plexuses which receive the blood from the capillaries. The 45 (705) 706 THE VASCULAR SYSTEMS branches which have their commencement in these plexuses unite into trunks, and these, in their passage toward the heart, constantly increase in size as they receive tributaries or join other veins. The veins are larger and altogether more numerous than the arteries; hence the capacity of the venous system is much greater than that of the arterial, the pulmonary veins excepted, which only slightly exceed in capacity the pulmonary arteries. From the combined area of the smaller venous tributaries being greater than the main trunks, it results that the venous system represents a cone, the summit of which corresponds to the heart, its base to the periphery of the body. In form the veins are cylindrical, like the arteries, their walls collapsing when empty, and the uniformity of their surface being interrupted at intervals by slight dilatations, which indicate the existence of valves in their interior (Fig. 489). They usually retain, however, about the same calibre as long as they receive no tributaries, but not so uniformly as do the arteries. The veins communicate very freely with one another (Fig. 491), especially in certain regions of the body, and this communication exists between the larger trunks as well as between the smaller tributaries. Thus, in the cavity of the cranium and between the veins of the neck, where obstruction would be at- tended with imminent danger to the cerebral venous system, we find that the sinuses and larger veins have large Fig. 491.— The venous circle of Braune (schematic). The_ arrows indicate the direction of the blood current. (Poirier and Charpy.) Fig. 492.— Part of I inferior of section of the vena (Szymonowicz.) and very frequent anastomoses (Fig. 490). The same free communication exists throughout the whole extent of the vertebral canal, and between the veins composing the various venous plexuses in the abdomen and pelvis, as the sper- matic, uterine, vesical, and prostatic plexuses. Veins have thinner walls than arteries, the difference in thickness being due to the small amount of elastic and muscular tissues which the veins contain. The superficial veins usually have thicker coats than the deep veins, and the veins of the lower limb are thicker than those of the upper. Histology of the Veins. — As previously stated, capillaries enter into venules orpost- capiUary veins. ^ The venules empty into larger veins. Vein walls are much thinner than arterial walls. The coats are: tunica intima, tunica media, and tunica adventitia. A vein has a much thinner media and much less elastic tissue than an artery, and a very strongly THE PULMONARY VEINS 707 developed adventitia. The intima is a connective-tissue layer containing a small num- ber of elastic fibers and lined with endothelium. The internal elastic lamina is usually poorly developed. The valves are duplications of the intima. The media consists chiefly of white fibrous tissue containing some circular muscle fibres and some fine elastic fibres. In some veins the media is thoroughly well developed (veins of the lower extremities), in others it is practically absent (veins of the retina, of the pia, of bone, the superior vena cava). The adventitia is dense and strong, and is composed of fibre-elastic tissue and non-striated muscle fibres longitudinally placed. Fig. 492 shows a transverse section of part of the wall of a vein. The large veins and the veins of medium size possess vasa vasorum in the adven- titia and to some extent in the media. The walls of veins contain vasomotor ner^•es. LjTnjjh capillaries often surround the smaller bloodvessels and sometimes by spaces lined with endo- thelium and which are in communication with the lymphatic system; these spaces are called perivascular lymph spaces. The systemic veins are subdivided into three sets — superficial, deep, and sinuses. The Superficial or Cutaneous Veins are found between the layers of the super- ficial fascia, immediately beneath the integument; they return the blood from these structures, and communicate with the deep veins by perforating the deep fascia. The Deep Veins accompany the arteries, and are usually enclosed in the same sheath with tho.se vessels. With the smaller arteries — as the radial, ulnar, brachial, tibial, and peroneal — they exist generally in pairs, one lying on each side of the vessel, and are called venae comites. The larger arteries — as the axillary, sub- clavian, popliteal, and femoral — have usually only one accompanying vein. In certain organs of the body, however, the deep veins do not accompany the arteries; for instance, the veins in the skull and vertebral canal, the hepatic veins in the liver, and the larger veins returning blood from the osseous tissue. Sinuses are venous channels which, in their structure and mode of distribution, differ altogether from the veins. They are found only in the interior of the skull, and consist of channels formed by a separation of the two layers of the dura, their outer coat consisting of fibrous tissue, their inner of an endothelial layer con- tinuous with the lining membrane of the veins. THE PULMONARY VEINS (V. PULMONALES) (Fig. 493). The pulmonary veins return the arterialized blood from the lungs to the left auricle of the heart. They are four in number, two for each lung, and are destitute of valves. They commence in a capillary network upon the walls of the air-cells, where they are continuous with the capillary ramifications of the pulmonary artery, and uniting, form one vessel for each lobule. These vessels, uniting successively form a single trunk for each lobe, three for the right and two for the left lung. Each venous trunk is about 1.5 cm. in length and of about the same calibre. The vein from the middle lobe of the right lung generally unites with that from the upper lobe. Thus, two trunks are formed on each side, which'open separately into the left auricle. Occasionally the three veins on the right side remain sepa- rate. Not infrequently the two left pulmonary veins terminate by a common opening. Within the lung, the tributaries of the pulmonary artery are in front, the veins behind, and the bronchi between the two. At the root of the lung, the upper pulmonary vein lies in front of and a little below the pulmonary artery; the lower is situated below the other structures in the lung root, and on a plane posterior to the upper vein; behind the pulmonary artery is the bronchus. Within the pericardium, their anterior surfaces are invested by the serous layer of this membrane. The right pulmonary veins pass behind the right auricle and ascending aorta and superior vena cava; the left pass in front of the thoracic aorta. 708 THE VASCULAR SYSTEMS Applied Anatomy. — Thrombosis of larger or smaller tributaries of the pulmonary veins is common in inflamed areas of the lung; or as a consequence of pressure from tumors, but it does not give rise to any special symptoms. ENTRANCE OF VENA AZYGOS BRANCH OF PUL- MONARY ARTERY Fig. 493. — Pulmonary veins, seen in a dorsal view of the heart and lungs lie iett lui g is pulled to the left, and the right lung has been partly cut away to show the ramifications of the air tubes and bloodvessels. (Testut.) THE SYSTEMIC VEINS. The systemic veins may be arranged into three groups: (1) The cardiac veins, which open directly into the right auricle of the heart. (2) Those of the head and neck, upper extremity, and thorax, which terminate in the superior vena cava. (3) Those of the lower extremity, abdomen, and pelvis, which terminate in the inferior vena cava. THE CARDIAC VEINS. The coronary sinus (sinus coronarius) is a wide venous channel about an inch in length which receives the majority of the veins draining the blood from the substance of the heart. It is situated in the posterior part of the auriculo- ventricular groove, and is partly covered by muscle fibres from the left auricle. It terminates in the right auricle between the opening of the inferior vena cava and the auriculoventricular aperture, its orifice being guarded by a semilunar A'ahe, the coronary valve, or valve of Thebesius. Tributaries. — Great cardiac or left coronary. Middle or posterior cardiac. Small cardiac or right coronary. Posterior vein of the left ventricle. Oblique vein of Marshall. CARDIAC VEINS 709 1. The great cardiac or left coronary vein {v. cordis magna) begins at the apex of the heart and ascends along the anterior interventricular groove to the base of the ventricles. It then curves to the left in the auriculoventricular groove to the back of the heart, and opens into the left extremity of the coronary sinus. It receives tributaries from the left auricle, and from both ventricles; one of these, the left marginal vein, is of considerable size, and ascends along the left margin of the heart. 2. The small cardiac or right coronary vein {v. cordis parva) runs in the groove between the right auricle and ventricle, and opens into the right extremity of the coronary sinus. It receives blood from the back of the right auricle and ventricle; its largest tributary, the right marginal vein, ascends along the right margin of the heart and joins it in the auriculoventricular groove. 3. The middle, or posterior, cardiac vein (v. cordis media) commences at the apex of the heart, ascends in the posterior interventricular groove, and ends in the coronary sinus near its right extremity. ..PULMONARY VEINS LEFT AURICLE Fig, 494. — Cardiac veina, dorsal view. (Testut.) 4. The posterior vein of the left ventricle (v. posterior ventriculi sinistri) ascends on the back of the left ventricle to the coronary sinus, but may end in the great cardiac vein. 5. The oblique vein of Marshall (v. ohliqiia airii sinistri) is a small vessel which descends obliquely on the back of the left auricle and ends in the coronary sinus near its right extremity; it is continuous above with the vestigial fold of Marshall, and the two structures form the remnant of the left Cuvierian duct. The following cardiac veins do not terminate in the coronary sinus: (1) The anterior cardiac veins (uv. cordis anteriores), comprising three or four small vessels which collect blood from the front of the right ventricle and open into the right auricle. The right marginal vein frequently opens into the right auricle, and is therefore sometimes regarded as belonging to this group. (2) The veins of Thebesius (vv. cordis minimae), consisting of a number of minute veins which arise in the muscular wall of the heart; the majority open into the auricles, but a few empty their blood into the ventricles. 710 THE VASCULAB SYSTEMS VEINS OF THE HEAD AND NECK. The veins of the head and neck may be subdivided into three groups: (1) The veins of the exterior of tlie head and face. (2) The veins of the neck. (3) The veins of the diploe and the interior of the cranium. Veins of the Exterior of the Head and Face (Fig. 495). The veins of tlie exterior of the head and face are: Frontal. Superficial temporal. Supraorbital. Internal maxillary. Angular. Temporomaxillary. Facial. Posterior auricular. Occipital. The frontal vein {v. frontalis) commences on the anterior part of the skull in a venous plexus which communicates with the anterior tributaries of the super- ficial temporal vein. The veins converge to form a single trunk, which runs downward near the middle line of the forehead parallel with the vein of the oppo- site side. The two veins are joined, at the root .of the nose, by a transverse branch called the nasal arch (_v. nasofrontalis), which receives some small veins from the dorsum of the nose. Occasionally the frontal veins join to form a single trunk, which bifurcates at the root of the nose into the two angular veins. At the root of the nose the veins diverge and join the supraorbital vein, at the inner angle of the orbit, to form the angular vein. The supraorbital vein (y. supraorbitalis) commences on the forehead, com^ municating with the anterior temporal vein, and runs downward and inward, superficial to the Occipitofrontalis muscle, receiving tributaries from the neigh- boring structures, and from the frontal vein of the diploe, and joins the frontal vein at the inner angle of the orbit to form the angular vein. Previous to its junction with the frontal vein, it sends through the supraorbital notch into the orbit a branch which communicates with the ophthalmic vein. As this vessel passes through the notch, it receives a diploic vein from the diploe of the frontal bone, through a foramen at the bottom of the notch. The angular vein (u. angularis), formed by the junction of the frontal and supraorbital veins, runs obliquely dowaiward and outward on the side of the root of the nose to the level of the lower margin of the orbit, where it becomes the facial vein. It receives the veins of the ala nasi on its inner side and the superior pal- pebral veins on its outer side; it, moreover, communicates with the ophthalmic vein, thus establishing an important anastomosis between the facial vein and the cavernous sinus. The facial vein (v. facialis anterior) commences at the side of the root of the nose, being a direct continuation of the angular vein. It lies behind and follows a less tortuous course than the facial artery. It passes obliquely downward and out- ward, beneath the Zygomaticus major and minor muscles, descends along the anterior border of the Masseter, crosses over the body of the mandible with the facial artery to beneath the angle, and unites with the anterior division of the temporomaxillary vein to form the common facial vein. The common facial vein iv. facialis communis) is formed hy the union of the facial and the anterior division of the temporomaxillary vein, just beneath the angle of the mandible. The vein is covered by the Platysma, runs downward and backward beneath the Sternomastoid muscle, crosses the external carotid artery, VEINS OF THE EXTERIOR OF THE HEAD AND FACE 711 and empties into the internal jugular vein at the level of the iiyoid line. It receives a large communicating branch at the anterior border of the Sternomastoid muscle, which comes from tlie anterior jugular vein in the suprasternal fossa. Tributaries of Facial Veins. — The facial vein receives, near the angle of tlie mouth, communicating tributaries of considerable size, the deep facial (or anterior in- ternal maxillary vein), from the pterygoid plexus. It is also joined by the inferior palpebral, the superior and inferior bbial veins, the buccal veins from the cheek, Interior facial. ( uDunon 1 1 ml A^Supeuor iJiywid. Fig. 495. — Veins of the head and neck. and the masseteric veins. The common facial vein receives the submental; the inferior palatine, which returns the blood from the plexus around the tonsil and soft palate; the submaxillary vein, which commences in the submaxillary gland; and, generally, the ranine vein. Applied Anatomy. — There are some points about the facial vein which render it of great importance in sui'oery. It is not so flaccid as are most superficial veins, and, in consequence of this, remains more patent when divided. It has, moreover, no valves. It communicates freely with the intracranial channels, not only at its commencement by its tributaries, the angulai' and supraorbital veins, communicating with the ophthalmic vein, a tributary of the cavernous 712 THE VASCULAR SYSTEMS sinus, but also by its deep tributaries, which communicate through the pterygoid plexus with the cavernous sinus by tributaries which pass through the foramen ovale and foramen lacerum medium. These facts have an important bearing upon the surgery of some diseases of the face, for on account of its patency the facial vein favors septic absorption, and therefore any phlegmonous inflammation of the face following a poisoned wound is liable to set up thrombosis in the facial vein, and detached portions of the clot may give rise to purulent foci in other parts of the body. On account of its communications with the cerebral sinuses these thrombi are apt to extend upward into them and so induce a fatal issue. The superficial temporal vein {w. temporales superficiales) commences by a minute plexus on the side and vertex of the skull, which communicates with the frontal and supraorbital veins in front, the corresponding vein of the opposite side, and the posterior auricular and occipital veins behind. From this network anterior and posterior branches are formed which unite above the zygoma, form- ing the trunk of the vein. The trunk is joined in this situation by a large vein, the middle temporal (v. temporalis media), which receives blood from the sub- stance of the Temporal muscle and pierces the fascia at the upper border of the zygoma. The junction of the superficial temporal and the middle temporal vein forms the common temporal vein which descends between the external auditory meatus and the condyle of the mandible, enters the substance of the parotid gland, and unites with the internal maxillary vein to form the temporomaxillary vein. Tributaries. — The common temporal vein receives in its course some parotid veins, an articular branch from the articulation of the mandible, anterior auricular veins from the external ear, and a vein of large size, the transverse facial {v. trans- versa faciei) , from the side of the face. The middle temporal vein, previous to its junction with the temporal vein, receives a branch, the orbital vein (i'. orbitalis), which is formed by some external palpebral branches, and passes backward between the layers of the temporal fascia. The pterygoid plexus {plexus pterygoideus) is of considerable size, and is situ- ated between the Temporal and External pterygoid, and partly between the two Pterygoid muscles. It receives tributaries corresponding with the branches of the internal maxillary artery. Thus, it receives the middle meningeal veins, the deep temporal, the pterygoid, masseteric, buccal, alveolar, some palatine veins, the inferior dental, and a branch which communicates with the ophthalmic vein through the sphenomaxillary fissure. This plexus communicates very freely with the facial vein and with the cavernous sinus by branches through the foramen Vesalii, foramen ovale, and foramen lacerum medium, at the base of the skull. The internal maxillary vein (i'. maxillaris interna) is a short trunk which accompanies the first part of the internal maxillary artery. It is formed by a confluence of the veins of the pterygoid plexus, and passes backward between the internal lateral ligament and the neck of the mandible, and unites with the superficial temporal vein to form the temporomaxillary vein. The temporomaxillary vein (v. facialis posterior), formed by the union of the superficial temporal and internal maxillary veins, descends in the substance of the parotid gland, superficial to the external carotid artery, but beneath the facial nerve between the ramus of the mandible and the Sternomastoid muscle. It divides into two vessels, an anterior, sometimes called the deep facial vein, which passes inward to join the facial vein, and a posterior, which is joined by the posterior auricular vein and becomes the external jugular. The posterior auricular vein (v. auricidaris posterior) commences upon the side of the head by a plexus which communicates with the tributaries of the tem- poral and occipital veins. It descends behind the external ear, and joins the posterior division of the temporomaxillary vein, forming the external jugular. It receives the stylomastoid vein and some tributaries from the back part of the external ear. THE VEINS OF THE NEVK 713 The occipital vein (y. occipitalis) commences in a plexus at the back part of the vertex of tlie skull. From the plexus the vein follows the course of the occipital artery, passing deeply beneath the muscles of the back part of the neck, and ter- minating in the suboccipital triangle by becoming continuous with the posterior vertebral vein (v. cervicalis profunda). Sometimes it is more superficial, and in this case is a tributary of the external jugular vein. As it passes across the mastoid portion of the temporal bone, it receives the mastoid vein, which thus establishes a communication with the lateral sinus. The Veins of the Neck (Fig. 495). The veins of the neck, which return the blood from the head and face, are: External jugular. Anterior jugular. Posterior external jugular. Internal jugular. Vertebral. The external jugular vein (v. jugularis externa) receives the greater part of the blood from the exterior of the cranium and deep parts of the face, and is formed by the junction of the posterior division of the temporomaxillary and the posterior auricular veins. It commences in the substance of the parotid gland, on a level with the angle of the mandible, and runs perpendicularly down the neck in the direction of a line drawn from the angle of the mandible to the middle of the clavicle. In its course it crosses the Sternomastoid muscle, and runs parallel with its posterior border as far as its attachment to the clavicle, where it perforates the deep fascia, and terminates in the subclavian vein, on the outer side of, or in front of, the Scalenus anticus muscle. It is separated from the Sternomastoid by the investing layer of the deep cervical fascia, and is covered by the Platysma, the superficial fascia, and the integument. This vein crosses about its middle the superficial cervical nerve, and throughout the upper half of its course is accompanied by the great auricular nerve. The external jugular vein varies in size, bearing an inverse proportion to that of the other veins of the neck; it is occasionally double. It is provided with two pairs of valves, the lower pair being placed at its entrance into the subclavian vein, the upper pair in most cases about an inch and a half above the clavicle. The portion of vein between the two sets of valves is often dilated, and is termed the sinus. These valves do not prevent the regurgitation of the blood or the passage of injection masses from below upward. Tributaries. — This vein receives the occipital occasionally, the posterior external jugular, and, near its termination, the suprascapular, transverse cervical, and anterior jugular veins; in the substance of the parotid gland a large branch of communication from the internal jugular joins it. The posterior external jugular vein (r. jugularis posterior) commences in the occipital region, and returns the blood from the integument and superficial muscles in the upper and back part of the neck, lying between the Splenius and Trapezius muscles. It runs down the back part of the neck, and opens into the external jugular just below the middle of its course. The anterior jugular vein (v. jugularis anterior) commences near the hyoid bone from the convergence of the inferior labial coronary, the submental and the mental veins, and communicating branches. It passes down between the median line and the anterior border of the Sternomastoid, and at the lower part of the neck passes beneath that muscle to open into the termination of the external jugular, or, in some instances, into the subclavian vein (Fig. .514). It varies con- siderably in size, bearing almost always an inverse proportion to the external 714 THE VASCULAR SYSTEMS jugular. Most frequently there are two anterior jugulars, a right and left, but occasionally only one. Its tributaries are some laryngeal veins, and occasionally a small thyroid vein. Just above the sternum the two anterior jugular veins com- municate by a transverse trunk, which receives tributaries from the inferior thyroid veins; each also communicates with the internal jugular. There are no valves in this vein. The internal jugular vein (v. jug^daris interna) collects the blood from the interior of the cranium, from the superficial parts of the face, and from the neck. It is directly continuous with the lateral sinus, and commences in the posterior compartment of the jugular foramen, at the base of the skull (Fig. 507). At its origin it is somewhat dilated, and this dilatation is called the sinus or bulb of the internal jugular vein (bulbus v. fugularis superior). The vein runs down the side of the neck in a vertical direction, lying at first on the outer side of the internal carotid artery, and then on the outer side of the common carotid artery, and at HYPOGLOSS Fig. 496. — Veins of the tongue. (Testut, modified from Hirschfeld.) Note. — The hypoglossal nerve has been displaced downward in this preparation. The cor- rect relations of the nerve and the lingual artery are shown in Fig. 437. the root of the neck unites with the subclavian vein to form the innominate vein. Just before its termination it is again distinctly dilated (bulbus v. fugularis in- ferior). The internal jugular vein, at its commencement, lies upon the Rectus capitis lateralis, and behind the internal carotid artery and the nerves passing through the jugular foramen; lower down, the vein and artery lie upon the same plane, the glossopharyngeal and hypoglossal nerves passing forward between them; the vagus descends between and behind them in the same sheath, and the spinal accessory passes obliquely outward, behind or in front of the vein. At the root of the neck the vein of the right side is placed at a little distance from the artery; on the left side it usually lies over the artery at its lower part. The right internal jugular vein crosses the first part of the subclavian artery. The internal jugular vein is of considerable size, but varies in different individuals, the left one being usually the smaller. It is provided with a pair of valves, which are placed about an inch above its termination. Tributaries. — This vein receives in its course the inferior petrosal sinus, the common facial, lingual, pharyngeal, superior, and middle thyroid veins, and sometimes the occipital. A tributary from the cochlea opens into the bulb of the internal jugular vein. A venous plexus from the lateral sinus {^plexus venosus caroticus internus) surrounds the internal carotid artery in the carotid canal and THE VEINS OF THE NECK 715 empties into the internal jugular vein. At its point of junction with the com- mon facial vein it becomes increased in size. (See Facial Veins, p. 710.) The inferior petrosal sinus leaves the skull through the anterior compartment of the jugular foramen, and joins the vein near its commencement. Sometimes the inferior petrosal sinus is not a direct tributary of the internal jugular vein, the blood being conveyed to it by a venous plexus in the hypoglossal canal. TEMPORO- SUBCLAVIAN Fig. 497.— The veins of the neck, viewed from in front. (Spalteholz.) The lingual veins (lu'. linguales) (Fig. 496) commence on the dorsum, sides, and under surface of the tongue, and, passing backward along the course of the lingual artery and its branches, terminate in the Internal jugular. The ranine vein, a tributary of considerable size commencing below the tip of the tongue, may join the lingual; generally, however, it passes backward on the Hyoglossus muscle in company with the hypoglossal nerve, and joins the facial. The lingual veins receive the sublingual and the dorsal lingual veins. The pharyngeal veins {vv. phari/iigeae) commence in the pharyngeal plexus on the wall of the pharynx, and, after receiving meningeal tributaries, the dural or meningeal veins, the Vidian veins, and the sphenopalatine veins, terminate in the internal jugular. They occasionally open into the facial, lingual, or superior thyroid vein. The superior thyroid vein (v. thyreoidea superioris) (Fig. 497) commences in the substance and on the surface of the thyroid gland by tributaries corresponding 716 THE VASCULAR SYSTEMS mth the branches of the superior thyroid artery, and terminates in the upper part of the internal jugular vein. It receives the superior laryngeal and crico- thyroid veins. Fig, 498. — Diagram showing common arrangement of thyroid ' (Kocher.) SUPERIOR Fig. 499.— The fasci Ivoclier the thjreoidea The \eins here desismted the mfenor thjroid are called by (.Poiner and Charpj ) The middle thyroid vein (Fig. 483) collects the blood from the lower part of the lateral lobe of the thyroid gland, and after being joined by some veins from the larynx and trachea, terminates in the lower part of the internal jugular vein. Often THE VEINS OF THE NECK 717 in place of the middle thyroid vein there are two veins, the superior and inferior accessory thyroid. These veins pass into the internal jugular. The facial and occipital veins have been described on pages 710 and 713. Applied Anatomy. — The internal jugular vein occasionally requires ligation in cases of septic thrombosis of the lateral sinus from suppuration of the middle ear. This is done in order to prevent septic emboli being carried into the general circulation. This operation has been per- formed in a number of cases, with satisfactory results. The cases are generally those of chronic disease of the middle ear, with discharge of pus which perhaps has existed for many years. The patient is seized with acute septic inflammation, spreading to the mastoid cells, and, con- sequent on this, septic thrombosis of the lateral sinus extending to the internal jugular vein. Such cases are always extremely grave, for there is danger that a portion of the septic clot will be detached and cause septic embolism in the thoracic viscera. If thrombophlebitis of the sinus is suspected the mastoid should be opened and cleansed and the sinus should be at once exposed and explored. If the sinus is found to be thrombosed the surgeon should at once pro- ceed to ligate the internal jugular vein, by an incision along the anterior border of the sterno- mastoid, the centre of which is on a level with the greater cornu of the hyoid bone. The vein should be ligated in two places or opened between. After the vessel has been secured and divided the lateral sinus is to be thoroughly cleared out, and, by removing the ligature from the upper end of the divided vein, all septic clots may be removed by syringing from the sinus through the vein. If hemorrhage occurs from the distal end of the sinus, it can be arrested by careful plugging with gauze. The internal jugular vein is also surgically important, because it is surrounded by a large number of the deep chain of cervical lymph nodes; and when these are enlarged in tuloerculous or malignant disease, they are liable to become adherent to the vessel, rendering their removal difficult and often dangerous. The proper course to pursue in these cases is to ligate the vessel above and below the glandular mass, and resect the included portion together with the nodes. Cardiac pulsation is often demonstrable in the internal jugular vein at the root of the neck. There are no valves in the innominate veins or superior vena cava; in consequence, the systole of the right auricle causes a wave to pass up these vessels, and when the conditions are favorable this wave appears as a somewhat feeble flicker over the internal jugular vein at the root of the neck, quite distinct from, and just preceding, the more -forcible impulse transmitted from the underlying common carotid artery and due to the ventricular s\'stole.' This auricular systolic venous impulse is much increased in conditions in which the right auricle is abnormally distended with blood or is hypertrophied,. as is often the case in disease of the auriculoventricular valves. In Stokes-Adams' disease (p. 56.5) it is this pulsation which gives evidence of the fact that the auricles are beating faster — often two or three times faster — than the ventricles. The vertebral vein (v. vertebralis) (Fig. 500) is formed in the suboccipital iriangle, from numerous small tributaries which spring from tlie intraspinal venous plexuses (plexus venosi ■vertehrales) and issue from the vertebral canal above the posterior arch of the atlas. They unite with small veins from the deep muscles at the upper and back part of the neck, and form a vessel which passes outward and enters the foramen in the transverse process of the atlas, and descends, forming a dense plexus around the vertebral artery, in the canal formed by the foramina in the transverse processes of the cervical vertebrte. This ple.xus unites at the lower part of the neck into a single trunk, which emerges from the foramen in the transverse process of the sixth cervical vertebra, and terminates at the root of the neck in the back part of the innominate vein near its origin, its mouth being guarded by a pair of valves. On the right side, it crosses the first part of the sub- clavian artery. Tributaries. — In its course the vertebral vein communicates with a vein trans- mitted from the lateral sinus of the skull through the posterior condylar foramen. It anastomoses with the occipital vein and receives muscular veins from the muscles in the prevertebral region; intraspinal veins, from the back part of the cervical portion of the vertebral column; meningorachidian veins, from the interior of the vertebral canal; the anterior and posterior vertebral veins; and close to its termination it is sometimes joined by the first intercostal vein. The ascending cervical or anterior vertebral vein commences in a plexus around the transverse processes of the upper cervical vertebrae, descends in company with the 'The Interpretation of the Venous Pulse, by G. Bachmann, Amer. Jour. Med. Sei., November, 1908. 718 THE VASCULAR SYSTEMS ascending cervical artery between the Scalenus anticus and Rectus capitis anticus major muscles, and opens into the vertebral vein just before its termination. VERTEBRAL- ERTEBRAL POSTERIOR EXTERNAL JUGULAR POSTERroR DEEP CERVICAL Fig. 500.— The vertebral The posterior vertebral or posterior deep cervical vein (v. cervicalis profunda^ (Fig. 500) accompanies the deep cervical artery, lying between the Complexus and Semispiiialis colli. It commences in the suboccipital region by communicating branches from the occipital vein and tributaries from the deep muscles at the back of the neck. It receives tributaries from the plexuses around the spinous processes of the cervical vertebrae; and terminates in the lower end of the vertebral vein. The Veins of the Diploe (Venae Diploicae) (Fig. 501). The diploic spaces of the cranial bones in the adult contain a number of tortuous canals, the diploic canals (canales diploid [Brescheti]), which are bounded by a more or less complete layer of compact osseous tissue. The veins they contain are large and capacious, their walls being thin, and formed only of endothelium resting upon a layer of elastic tissue; they present at irregular intervals pouch-like dilatations, or culs-de-sac, which serve as reservoirs for the blood. In adult life, so long as the cranial bones are distinct and separable, these veins are confined to the particular bones; but in old age, when the sutures are united, they communicate with one another and increase in size. They communi- cate, in the interior of the cranium, with the veins and the sinuses of the dura, and on the exterior of the skull with the veins of the pericranium. They consist of (1) the frontal diploic vein (v. di.ploica frontalis), which opens into the supra- orbital vein by an aperture in the supraorbital notch; (2) the anterior temporal diploic vein (v. di.ploica temporalis anterior), which is coniined chiefly to the frontal bone, and opens into one of the deep temporal veins through an aper- ture in the greater wing of the sphenoid; (3) the posterior temporal vein (v. diploica THE CEREBRAL VEINS 719 temporalis posterior), which is situated in the parietal bone, and terminates in the lateral sinus through an aperture at the postero-inferior angle of the parietal bone or through the mastoid foramen; and (4) the occipital diploic vein (v. diploica occipitalis), the largest of the four, which is confined to the occipital bone, and opens into the lateral sinus or the torcular Herophili. The emissary veins are considered on page 727. Fig. 501 — Veins of the diplo as displived by the remo\aI of the outer table of the skull. The meningeal or dural veins (w. meningeae) chiefly correspond with the middle meningeal artery and its branches, as its two venae comites. The veins accompany the middle meningeal artery, are united to the sphenoparietal sinus, pass through the foramen spinosum, and join the pterygoid plexus. The other dural veins correspond somewhat to the anterior and posterior meningeal distribu- tion and empty into the neighboring sinuses. The Cerebral Veins (Venae Cerebri). The cerebral veins possess no valves, and their walls, owing to the absence of muscle tissue, are extremely thin. They pierce the arachnoid membrane and the inner or meningeal layer of the dura and open into the cranial venous sinuses. They may be divided into two sets, cerebral and cerebellar. The cerebral veins consist of (a) the superficial veins, which are placed on the surface of the brain, and (/j) the deep veins, which lie in its interior. The superficial cerebral veins ramify upon the surface of the brain, being lodged in the fissures between the convolutions, a few running across the convolutions. They receive tributaries from the substance of the brain and terminate in the sinuses. They are divisible into two sets, superior and inferior. The superior cerebral veins {vv. cerebri superiores), eight to twelve in number on each side, return the blood from the convolutions on the superior surface of the hemisphere; they pass forward and inward toward the intercerebral fissure, where they receive the veins from the mesal surface of the hemisphere ; near their terminations they become invested with tubular sheaths of the arachnoid, and open into the longitudinal sinus in the opposite direction to the course of the cur- rent of the blood in the sinus. 720 THE VASCVLAR SYSTEMS The inferior cerebral veins {\w. cerebri mferiores) ramify on the lower part of the outer and on the under surfaces of the cerebral hemisphere. Some, collecting tributaries from the under surface of the frontal lobes of the brain, terminate in the cavernous sinus. One vein of large size, the middle cerebral or superficial sylvian vein (y. cerebri media), commences on the under surface of the temporal lobe, and, running along the sylvian fissure, opens into the cavernous sinus. Another large vein, the great anastomotic vein of Trolard, connects the supe- rior sagittal sinus with the cavernous sinus by Ijecoming continuous above with one of the superior cerebral veins and below by joining the middle cerebral vein. A third, the posterior anastomotic vein connects the middle cerebral vein with the lateral sinus by coursing over the temporal lobe. A fourth, the basilar vein (v. basilis [Rosenthali]), is formed at the anterior perforated spot by the union of (a) a small anterior cerebral vein, which accompanies the anterior cerebral artery (6) the deep sylvian vein, which receives tributaries from the island of Reil (or insula) and neighboring convolutions, and runs in the lower part of the sylvian fissure; and (c) the inferior striate veins, which leave the corpus striatum through the anterior perforated substance. The basilar vein passes backward around the crus cerebri, and ends in the vein of Galen; it receives tributaries from the inter- peduncular space, the descending horn of the lateral ventricle, the uncinate gyre, and the midbrain. Small inferior cerebral veins from the under surface of the frontal lobe end in the cavernous sinus; others from the temporal lobe terminate in the superior petrosal and lateral sinuses. The deep cerebral veins, or veins of Galen (vv. cerebri internae) (Fig. 725), are two in number. Each is formed by the union of two veins, the vena cor- poris striati, and the choroid vein, on either side. They run backward, parallel with each other, between the layers of the velum interpositum, and beneath the splenium, and in the region of the pineal body unite to form a short trunk, the vena magna Galeni {v. cerebri magna), which passes out of the brain at the great transverse fissure, and ends in the anterior extremity of the straight sinus. The two velar veins receive tributaries from the callosal region, from a portion of the occipital lobe, and just before their union each vein receives the corresponding basilar vein. Each vena magna Galeni also receives the superior cerebellar veins. The vena corporis striati on each side coimnences in the groove between the corpus striatum and thalamus, receives numerous veins from both of these parts, and unites, behind the anterior pillars of the fornix, with the choroid vein to form one of the deep cerebral veins. The choroid vein {v. choroidea) originates in the extreme end of the middle horn of the lateral ventricle and runs along the whole length of the outer border of the choroid plexus, receiving veins from the hippocampus, the fornix, and corpus callosum, and unites, at the anterior extremity of the choroid plexus, with the vein of the corpus striatum to form the deep cerebral veins of that side. The superficial cerebellar veins (Fig. 723) occupy the surface of the cerebellum, and are disposed in two sets, superior and inferior. The superior superficial cerebellar veins (ra. cerebelli siiperiores) pass partly for- ward and inward, across the superior vermis (prevermis), to terminate in lateral branches which pass partly to the tentorial sinus and partly outward to the lat- eral and superpetrosal sinuses. The subcerebellar or inferior superficial cerebellar veins (vv. cerebelli inferiores), of large size, terminate in the lateral, subpetrosal, and occipital sinuses. The deep cerebellar veins bring blood from the interior of the cerebellum to the superficial veins. Veins of the Pons. — Veins come from the interior of the pons, the deep veins, and enlpty into a plexus of superficial veins. From this superficial venous plexus a superior vein passes to the basilar vein, and an inferior vein either into a cere- bellar vein or into the superpetrosal sinus. THE SIiYUSUS OF THE DURA 721 Veins of the Medulla Oblongata. — ^'ein.s jjass from the interior of the medulla oblongata and end in a plexus on the surface. From this plexus comes an anterior median vein, which is a prolongation of a like vein of the spinal cord — a posterior median vein corresponding to a lilve vein of the cord — and small branches which pass with the roots of the glossopharyngeal, -vagus, spinal accessory, and hvpo- glossal nerves, and empty into the occipital and the subpetrosal sinuses. The perivascular lymph spaces are especially found in connection with the vessels of the brain. These vessels are enclosed in a sheath, which acts as a lymphatic channel, through which the lymph is carried to the subarachnoid and subdural spaces, from which it is returned into the seneral circulation. The Sinuses of the Dura (Sinus Durae Matris) (Figs. 502, 503). Ophthalmic Veins and Emissary Veins. The sinuses of the dura are venous channels which drain the blood from the brain; they are situated between the two layers of the dura and are lined by endothelium continuous with that which lines the veins. They are sixteen in number, of which six are single and situated in the mesal plane; the other ten are paired, five being placed on either side of the mesal plane. They are divided into two sets: {\) Those situated at the upper and back part of the skull; (2) those at the base of the skull. The former are : Superior sagittal sinus. Tentorial or straight sinus. Inferior sagittal sinus. Lateral sinuses. Occipital sinus. The superior sagittal sinus (sinus sagittalis superior) (Figs. 502 and 50.3) oc- cupies the attached margin of the falx cerebri. Commencing at the foramen cecum, through which it usually communicates by a small branch with the veins of the nasal fossse, it runs from before backward, grooving the inner sur- face of the frontal, the adjacent margins of the two parietals, and the supe- rior division of the crucial ridge of the occipital; near the internal occipital protuberance it usually deviates toward the right, and is continued as the corre- sponding lateral sinus. The sinus is triangular on transverse section, is narrow in front, and gradually increases in size as it passes backward. Its inner surface presents the internal openings of the superior cerebral veins, which run, for the most part, from behind forward, and open chiefly at the back part of the sinus, their orifices being concealed by valve-like folds; numerous fibrous bands, chordae Willisii (Fig. 504), are also seen extending transversely across the inferior angle of the sinus; and some small, white, projecting bodies, the glandulae Pacchioni (granulationes arachuoidales). This sinus communicates by numerous small apertures with spaces in the dura known as lacunae laterales, or parasinoidal spaces (Fig. 504). The arachnoid villi project into these spaces. The superior sagittal sinus receives the superior cerebral veins, numerous veins from the diploe and dura, the outlets of the parasinoidal spaces, and, at the posterior extremity of the sagittal suture, veins from the pericranium, which pass through the parietal foramina. Sometimes the sagittal sinus receives a twig from the nose which passes through the foramen cecum. The inferior sagittal sinus (sirms sagittalis inferior, s. falcialis) (Fig. 503) is con- tained in the posterior half or two-thirds of the free margin of the falx cerebri. It is of a cylindric form, increases in size as it passes backward, and terminates in the straiglit sinus. It receives several A-eins from the falx cerebri, and occa- sionally a few from the mesal surface of the hemispheres. 46 722 THE VASCULAR SYSTEMS The straight or tentorial sinus {sinus rectus, s. tentorii) (Figs. 502 and 503) is situated at tiie line of junction of the falx cerebri with tiie tentorium cerebelli. It is triangular on section, increases in size as it proceeds backward, and runs obliquely downward and backward from the termination of the inferior sagittal Fig. 502. — Coronal i ction of the skull to show the situatious (Poirier and Charpy.) nd shapes of the chief i sinus to the lateral sinus of the opposite side to that into which the sagittal sinus is prolonged. Its terminal part communicates by a cross-branch with the torcular Herophili (confluence of the sinuses). Besides the inferior sagittal sinus, it re- ceives the vena magna Galeni and the superior cerebellar veins. A few transverse bands cross its lumen. Torcular herophili. Foramen cecum. Fig. 503. — Sagittal section of the skull, showing the sinuses of the du: The lateral sinuses (Figs. 502 and 503) are of large size and commence at the internal occipital protuberance; one, generally the right, being the direct continua- tion of the superior sagittal sinus, the other of the straight sinus. Each lateral sinus {sinus transversus) passes outward and forward, describing a slight curve with its convexity upward, to the base of the petrous portion of the temporal THE SINUSES OF THE D URA 723 bone, and is situated, in this part of its course, in the attached margin of the tentorium cerebelli; it then leaves the tentorium, curves downward and inward to reach the jugular foramen, where it terminates in the internal jugular vein. In its course it rests upon the inner surface of the occipital, the postero-inferior angle of the parietal, the mastoid portion of the temporal bone, and on the occipital again, at the jugular process, just before its termination. The portion of the sinus which occupies the groove on the mastoid portion of the temporal bone is known as the sigmoid sinus. The lateral sinuses are frequently of unequal size, that formed by the sagittal sinus being the larger, and they increase in size as they proceed from behind forward. The horizontal portion is triangular on section, the curved portion semicylindric. Their inner surface is smooth, and not crossed by the fibrous bands found in the other sinuses. The lateral sinuses receive the blood from the superior petrosal sinuses at the base of the petrous portion of Fig 504. — Sagittal sinus seen from above after removal of the skullcap. The chordae Willisii are clearly ■'/isible. The parasinoidal sinuses are also well shown. Probes passing from the latter to the longitudinal sinus show that they communicate. (Poirier and Charpy.) the temporal bone, and they unite with the inferior petrosal sinus, just external to the jugular foramen, to form the internal jugular vein (Fig. 50S). They com- municate with the veins of the pericranium by means of the mastoid and posterior condylar veins, and they receive some of the inferior cerebral and inferior cere- bellar veins, some veins from the diploe, and often veins from the internal ear (yv. audiiivae internae), which come out of the internal auditory meatus. The petrosquamous sinus, when present, runs backward along the junction of the petrous and squamous portions of the temporal bone, and opens into the lateral sinus. The occipital sinus (sinus occipitalis) (Fig. 503) is the smallest of the cranial .sinuses. It is generally single, but occasionally there are two. It is situated in 724 THE VASCULAR SYSTEMS the attached margin of the falx cerebelH. It commences by several small veins around the margin of the foramen magnum, one of which joins the termination of the lateral sinus; it communicates with the posterior spinal veins and terminates in the torcular Herophili. The torcular Herophili, or confluence of the sinuses (confluens simmm), is the term applied to the dilated extremity of the superior sagittal sinus. It is of irreg- ular form, and is lodged on one side (generally the right) of the internal occipital protuberance. From it the lateral sinus of the side to which it is deflected is derived. It also receives the blood from the occipital sinus, and is connected across the middle line with the commencement of the lateral sinus of the opposite side. The sinuses at the base of the skull are: Two cavernous sinuses. Two superior petrosal sinuses. Two sphenoparietal sinuses. Two inferior petrosal sinuses. Circular sinus. Transverse sinus. The cavernous sinuses (Figs. 507 and 508) are so named because they present a reticulated structure, due to their being traversed by numerous interlacing filaments (Fig. 505). They are of irregular form, larger behind than in front, and are placed one on each side of the sella turcica, extending from the sphenoidal fissure to the apex of the petrous portion of the temporal bone. Each cavernous sinus (sinus cavernosus) receives anteriorly the superior ophthalmic vein through the sphenoidal fissure, and opens behind into the petrosal sinuses. On the inner wall of each sinus is the internal carotid artery, accompanied by filaments of the carotid plexus and by the abducent nerve; and on its outer wall, the oculomotor, trochlear, ophthalmic, and superior maxillary divisions of the trigeminal nerve (Fig. 505). These parts are separated from the blood fiowing along the sinus by the lining membrane, which is continuous with the inner coat of the veins. Each cavernous sinus receives some of the cerebral veins, and also the spheno- parietal sinus. It communicates with the lateral sinus by means of the superior petrosal sinus; with the internal jugular vein through the inferior petrosal sinus and through a plexus of veins on the internal carotid artery; with the pterygoid plexus through the foramen ovale, and with the angular vein through the ophthal- mic vein. The two sinuses also communicate with each other by means of the circular sinus. Applied Anatomy. — An arteriovenous communication may be established between the cavernous sinus and the internal carotid artery, as it lies in it, giving rise to a pulsating tumor in the orbit. Such a communication may be the result of injury, such as a bullet wound, a stab, or a blow or fall sufficiently severe to cause a fracture of the base of the skull in this situation, or it may occur from the rupture of an aneurism or a diseased condition of the internal carotid artery. The disease begins with sudden noise and pain in the head, followed by exophthalmos, swelling and congestion of the lids and conjunctivEe. A pulsating tumor develops at the margin of the orbit, with thrill and the characteristic bruit; accompanying these symptoms there may be impairment of the sight, paralysis of the iris and orbital muscles, and pain of varying intensity. In some cases the opposite orbit becomes affected by the passage of the arterial blood into the opposite sinus by means of the circular sinus. Or the arterial blood may find its way through the emissary veins into the pterygoid plexus, and thence into the veins of the face. Pulsating tumors of the orbit may also be due to traumatic aneurism of one of the orbital arteries, and symptoms resembling those of pulsating tumor may be produced by pressure on the ophthalmic vein, as it enters the sinus, by an aneurism of the internal carotid artery. Ligation of the internal or the common carotid artery has been performed in these cases with some degree of success. Of recent years more attention has been paid to thrombosis of the cavernous sinus than for- merly, and it is now well established that caries in the upper parts of the nasal fossae and sup- puration in certain of the accessory sinuses of the nose, are frequently responsible for septic tlu-ombosis of the cavernous sinuses, in exactly the same way as lateral sinus thrombosis is due to septic disease in the mastoid process. Manj' deaths from meningitis, hitherto unaccounted for, are in reality due to the spread of an infection from an ethmoidal or sphenoidal air cell to the cavernous sinus, and thence to the meninges. It is obvious, therefore, that no case of clu-onic nasal suppuration should be left untreated. THE SINUSES OF THE DURA 725 The sphenoparietal sinuses may be regarded, together with the ophthalmic veins, as the commencement of the corresponding cavernous sinuses. Each of these sinuses {sinus sphenoparidaUs) is lodged in the dura on the under surface of the lesser wing of the sphenoid bone. It takes origin from one of the middle meningeal TRANSVERSE Fig. 505. — Frontil section through the light ( enlarged. (Spalteholz.) veins, usually receives l^lood from the diploe of the skull, passes inward, and ends in the anterior part of the cavernous sinus. The ophthalmic veins are two in number, superior and inferior. The superior ophthalmic vein {v. ophfhalmica superior) (Fig. 506) begins as the nasofrontal vein ( v. nasofrontalis), which communicates with the angular vein at the inner angle of the orbit. It joins the angular vein with the cavernous sinus; Fig. 506. — Veins of the orbit. (Poirier and Charpy.) it pursues the same course as the ophthalmic artery, and receives tributaries cor- responding to the branches derived from that vessel. Forming a short single trunk, it passes through the inner extremity of the sphenoidal fissure, and termi- nates in the cavernous sinus. It anastomoses with the inferior ophthalmic vein and receives lacrimal, anterior and posterior ethmoidal, and muscular branches, and veins of the eyelids and of the eyeball (vv. wrticosae) . 726 THE VASCULAR SYSTEMS The inferior ophthalmic vein {v. ophthalmica inferior) (Fig. 506) arises in the veins of the eyehds and lacrimal sac, receives the veins from the floor of the orbit, and either passes out of the orbit through the sphenoidal fissure to join the pterygoid plexus of veins, or else, passing backward through the sphenoidal fissure, it enters the cavernous sinus, either by a separate opening, or, more fre- quently, in common with the superior ophthalmic vein. It receives muscular tributaries and veins of the eyeball, and anastomoses with the superior ophthal- mic and deep facial vein. The circular sinus (sinus circularis) (Figs. 505 and 507) is formed by two transverse vessels, the anterior and posterior intracavernous sinuses (sinus inter- cavernosus anterior and si7itis intercavernosus posterior), which connect the two cavernous sinuses; one passes in front of and the other behind the pituitary body, and thus they form with the cavernous sinuses a venous circle around that body. The anterior one is usually the larger of the two, and one or other is occasionally absent. The superior petrosal sinus (sifius petrosus superior) (Figs. 503 and 507) is situated along the superior border of the petrous portion of the temporal bone, in the front part of the attached margin of the tentorium cerebelli. It is small and narrow, and connects the cavernous and lateral sinuses at each side. It receives some cerebellar and inferior cerebral veins, and veins from the tympanic cavity. The inferior petrosal sinus (sijiits petrosus infe- rior) (Fig. 503) is situated in the groove formed by the junction of the pos- -openmgof mastoid teTioT border of the pe- trous portion of the tem- poral with the basilar process of the occipital bone. It commences in front at the termination of the cavernous sinus, and, passing through the anterior compartment of the jugular foramen, ends in the commencement of the internal jugular vein. The inferior petrosal sinus receives a vein from the internal ear {vv. auditavae internae) and also veins from the medulla oblongata, pons, and under surface of the cerebellum. The exact relation of the parts to one another in the foramen is as follows : The inferior petrosal sinus is in front, with the meningeal branch of the ascending pharyngeal artery, and is directed obliquely downward and backward; the lateral sinus is situated at the back part of the foramen with a meningeal branch of the occipital artery, and between the two are the glossopharyngeal, vagus, and spinal accessory nerves. These three sets of structures are divided from each other by two processes of fibrous tissue. The junction of the inferior petrosal sinus with the internal jugular vein takes place superficial to the nerves, so that these latter lie a little internal to the venous channels in the foramen. YTorcular Serophili. Fig. 507. — The sinuses at the base of the skull. VEINS OF THE UPPER EXTREMITY AND THORAX 727 The transverse or basilar sinus {'plexus basilarin) (Fig. 507) consists of se\erai interlacing veins between the layers of the dura over the basilar process of the occipital bone, which serve to connect the two inferior petrosal sinuses. They communicate with the anterior spinal veins. The emissary veins (emissaria) are vessels which pass through apertures in the cranial wall and establish communications between the sinuses inside the skull and the diploic veins in the diploe, and the veins external to the skull. Some of these are always present, others only occasionally so. They vary much in size in difi'erent individuals. The principal emissary veins are the following: (1) A vein (emissarium mastoideum) almost always present, runs through the mastoid foramen and connects the lateral sinus with the posterior auricular or with the occipital vein. (2) A vein (emissarium pariefale) which passes through the parietal foramen and connects the superior sagittal sinus with the veins of the scalp. (.3) A plexus of minute veins (rete canalis hypoglossi), which pass through the anterior condylar (hypoglossal) foramen and connect the occipital sinus with the vertebral vein and deep veins of the neck. (4) An inconstant vein {emissarium condyloideum) which passes through the posterior condylar foramen and connects the lateral sinus with the deep veins of the neck. (5) A plexus of veins (rete foraminis ovalis) connects the cavernous sinus with the pterygoid and pharyngeal plexuses through the foramen ovale. (6) Two or three small veins run through the foramen lacerum medium and connect the cavernous sinus with the pterygoid and pharyngeal plexuses. (7) There is some- times a small vein connecting the same parts and passing through the inconstant foramen of Vesalius opposite the root of the pterygoid process of the sphenoid bone. (8) A plexus of veins {plexus venosus caroticus internus) traverses the carotid canal and connects the cavernous sinus with the internal jugular vein. (9) A small vein {emissarium occipitale) usually connects the occipital vein with the lateral sinus or the torcular Herophili and the occipital diploic vein. (10) A vein is usually transmitted through the foramen cecum and connects the superior sagittal sinus with the veins of the mucous membrane of the nose. Applied Anatomy. — These emissary veins are of great importance in surgery. In addition to them there are, however, other communications between the intra- and extracranial chan- nels, as, for instance, the communication of the angular and supraorbital veins with the ophthal- mic vein at the inner angle of the orbit, and the communication of the veins of the scalp with the diploic veins. Through these communications inflammatory processes commencing on the outside of the skull may travel inward, leading to osteophlebitis of the diploe and inflammation of the membranes of the brain. This is one of the principal dangers of scalp wounds and other injuries of the scalp. By means of these emissary veins blood may be abstracted almost directly from the intra- cranial vessels. For instance, leeches applied behind the ear abstract blood almost directly from the lateral sinus by means of the vein passing through the mastoid foramen. Again, epis- taxis in children will frequently relieve severe headache, the blood which flows from the nose being derived from the superior sagittal sinus by means of the vein which passes through the foramen cecum. VEINS OF THE UPPER EXTREMITY AND THORAX. The veins of the upper extremity are divided into two sets, superficial and deep. The Superficial. Veins are placed immediately beneath the integument between the layers of the superficial fascia. The Deep Veins accompany the arteries, and constitute the venae comites of those vessels. Both sets of vessels are provided with valves, which are more numerous in the deep than in the superficial veins. 728 THE VASCULAR SY8TE3IS Fig. 508.— The on the dorsum of the hand. (Bourgery.) The Superficial Veins of the Upper Extremity (Fig. 509). The superficial veins of the upper extremity are: Superficial veins of the hand. Median. Anterior ulnar. Median cephalic Posterior ulnar. Median basilic. Common ulnar. Basilic. Radial. Cephalic. The superficial veins of the hand and fingers (Figs. 508 and 509) are prin- cipally situated on the dorsal surface. These dorsal veins begin in each finger as a venous plexus, in which are distinct veins running in a longitudinal direction and called dorsal digital veins {vv. digitales dorsales propriae). The dorsal digital veins terminate over the first phalanges in the venous arches of the fingers {amis THE SUPERFICIAL VEINS OF THE UPPER EXTREMITY 729 venosi diriifalcs). From these arches take origin the four dorsal interosseous or the interdigital veins (m. metacarpeae dorsales). These veins form tlie dorsal venous plexus of the hand {rete venosum dorsalc manus). This plexus hes in a hne with the lower ends of the shafts of the metacarpal bones. It receives the dorsal interosseous veins, the radial digital vein of the index finger, and numerous superficial veins from the back of the hand. It gives origin to the superficial radial vein and the posterior ulnar vein. The superficial veins of the palmar surface are of less size and number than the dorsal veins. They arise from each of the phalanges by a plexus ivv. digiiales volares projmae). Vessels at the borders of the fingers take most of the blood to the dorsal veins. There are also veins in the finger webs {m. intercajyitidares) , which convey the blood from the palm to the dorsum. A superficial plexus, the palmar plexus, lies upon the palmar fascia, the fascia of the thenar emi- nence, and the fascia of the hypothenar eminence. The anterior ulnar vein (Fig. 509) commences on the anterior surface of the ulnar side of the hand and wrist, and ascends along the anterior surface of the ulnar side of the forearm to the bend of the elbow, w^here it joins with the posterior ulnar vein to form the common ulnar. Occasionally it opens separately into the median basilic vein. It communicates with tributaries of the median vein in front and with the pos- terior ulnar behind. The posterior ulnar vein (Fig. 508) commences on the posterior surface of the ulnar side of the wrist. It runs on the posterior surface of the ulnar side of the forearm, and just below the elbow unites with the anterior ulnar vein to form the common ulnar, or else joins the median basilic and helps to form the basilic. It communicates with the deep veins of the palm by a vein which emerges from beneath the Abductor minimi digiti muscle. The common ulnar vein (Fig. 509) is a short trunk which is not constant. TjTi . , • j_ -J. ■ J- J u J.1 Fig. 509. — The superficial veins of the flexor aspect of When it exists it is JOnned by the the upper extremity. Median cephalic Evtet nal cutaneous nei ve 730 THE VASCULAR SYSTEMS junction of the two preceding veins, and, passing upward and outward, joins the median basihc to form the basilic vein. When it does not exist the anterior and posterior ulnar veins open separately into the median basilic vein. The radial vein {v. radialis) (Figs. 509 and 510) commejices upon the dorsal surface of the wrist, and communicates with the deep veins of the palm by a branch which passes through the first interosseous space. The radial vein soon forms a large. vessel, which ascends along the radial side of the forearm and receives numerous veins from both its surfaces. At the bend of the elbow it unites with the median cephalic to form the cephalic vein. The median vein {v. mediana cubiti) (Fig. 509) ascends on the front of the forearm, and communicates with the anterior ulnar and radial veins. At the bend of the elbow it receives a branch of communication from the deep veins, the deep median vein, and divides into two trunks, the median cephalic and median basilic, which diverge from each other as they ascend. The median cephalic (v. mediana cephalica) (Fig. 509), usually the smaller of the two, passes outward in the groove between the Brachioradialis and Biceps muscles, and joins with the radial to form the cephalic vein. The branches of the external cutaneous nerve pass beneath this vessel. The median basilic vein {v. mediana basilica) (Fig. 509) passes obliquely in- ward, in the groove between the Biceps and Pronator teres muscles, and joins the common ulnar to form the basilic. This vein passes in front of the brachial artery, from which it is separated by a fibrous expansion, the bicipital fascia, which is given off from the tendon of the Biceps to the fascia covering the Flexor muscles of the forearm. Filaments of the internal cutaneous nerve pass in front as well as behind this vessel. Venesection is usually performed at the bend of the elbow, and as a matter of practice the largest vein in this situation is commonly selected. This is usually the median basilic, and there are anatomical advantages and disadvantages in selecting this vein. The advantages are, that, in addition to its being the largest, and therefore yielding a greater supply of blood, it is the least movable and can be easily steadied on the bicipital fascia on which it rests. The dis- advantages are, that it is in close relationship with the brachial artery, separated only by the bicipital fascia; and formerly, when venesection was frequently practised, arteriovenous aneu- rism was no uncommon result of this practice. Another disadvantage is, that the median basilic is crossed by some of the branches of the internal cutaneous nerve, and these may be divided in the operation, giving rise to "traumatic neuralgia of extreme intensity" (Tillaux). Intravenous infusion of normal saline solution is very frequently required for all conditions of severe shock and after profuse hemorrhages. The patient's arm is surrounded by a tight band- age so as to impede the venous return, and a small incision is made over the largest vein visible in front of the elbow; a double ligature is now passed around the vein, and the lower one is tied; the vein is then opened and a cannula connected with a funnel by tubing and filled with warm saline solution is inserted. The bandage is next removed from the arm, and two, three, or more pints of fluid are allowed to flow into the vein ; when a sufficient quantity has gone in, the upper ligatiffe around the vein is tied and a stitch put in the skin wound. The basilic vein (v. basilica) (Figs. 509 and 511) is of considerable size and is formed by the coalescence of the common ulnar vein with the median basilic. It passes upward along the inner side of the Biceps muscle and pierces the deep fascia a little below the middle of the arm. The opening in the fascia is known as the semilunar hiatus. The vein ascends in the course of the brachial artery to the lower border of the tendons of the Latissimus dorsi and Teres major muscles, and is continued onward as the axillary vein. The cephalic vein («. cephalica) (Fig. 509) is formed by the union of the median cephalic and the radial veins. It courses along the outer border of the Biceps muscle, lying in the same groove with the upper external cutaneous branch of the musculospiral nerve, to the upper third of the arm ; it then passes in the inter- val between the Pectoralis major and Deltoid muscles, lying in the same groove THE DEEP VEINS OF THE UPPER EXTREMITY 731 with the descending or humeral branch of tiie acromiothoracic artery. It pierces the costocoracoid membrane, and, crossing the axillary artery, terminates in the axillary vein just below the clavicle. This vein is occasionally connected with the external jugular or subclavian by a branch which passes from it upward in front of the clavicle. The accessory cephalic vein (y. cephalica accessoria) arises either from a small tributary plexus on the back of the forearm or from the ulnar side of the dorsal venous arch; it joins the cephalic above the elbow. In some cases the accessory cephalic springs from the cephalic above the wrist and joins it again higher up. A large oblique branch frequently connects the basilic and cephalic veins on the back of the forearm.^ The Deep Veins of the Upper Extremity, The deep veins of the upper extremity (Fig. 510) follow the course of the arteries, forming their venae comites, or companion veins. Usually there is one vein lying on each side of the corresponding artery, and they are connected at intervals by short transverse branches. Two digital veins accompany each artery along the sides of the fingers; these, uniting at their base, pass along the interosseous spaces in the palm, and terminate in the two venae comites which accompany the superficial palmar arch. Branches from these vessels on the radial side of the hand accompany the superficialis volae, and on the ulnar side terminate in the deep ulnar veins (Fig. 510). The deep ulnar veins, as they pass in front of the wrist, communicate with the inter- osseous and superficial veins, and at the elbow unite with the deep radial veins to form the venae comites of the brachial artery. The venae comites of the brachial communicate by numerous transverse branches, which cross over or under the artery. The interosseous veins (Fig. 510) accompany the anterior and posterior interosseous arteries. The anterior interosseous veins commence in front of the wrist, where they communicate with the deep radial and ulnar veins; at the upper part of the forearm they receive the posterior interosseous veins, and terminate in the venae comites of the ulnar artery. The deep palmar veins accompany the deep palmar arch, being formed by tributaries which accompany the ramifications of that vessel. At the wrist they receive a dorsal and a palmar tributary from the thumb. The deep palmar veins communicate with the deep ulnar veins at the inner side of the hand, and on the outer side terminate in the deep radial veins (Fig. 510), which are the venae comites of the radial artery. Accompanying the radial artery the deep radial veins ter- minate in the venae comites of the brachial artery. The brachial veins {vv. brachiales) (Fig. 510) are placed one on each side of the brachial artery; receiving tributaries corresponding with the branches given off from that vessel ; at the lower margin of the Subscapularis muscle they join the axillary vein. These deep veins have numerous anastomoses, not only with each other, but also with the superficial veins. One of the brachial veins empties into the axillary, the other, usually the smaller, generally unites with the basilic. The axillary vein (v. axillaris) (Fig. 511) is of large size, and is the continuation upward of the basilic vein. It comviences at the lower border of the tendon of the Teres major muscle, increases in size as it ascends, by receiving tributaries corre- ' Concerning the variations in the arrangement and course of the veins of the upper extremity, consult the article by W. Krause in Henle's Handbuch der Anatomic. 732 THE VASCULAR SYSTEMS spending with the branches of the axillary artery, and terminates immediately beneath the clavicle at the outer border of the first rib, where it becomes the subclavian vein. This vessel is covered in front by the Pectoral muscles and costo- coracoid membrane, and lies on the thoracic side of the axillary artery, which it par- tially overlaps. Near the lower margin of the Subscapularis it receives the venae comites of the brachial artery, and, near its termination, the ceph- alic vein. This vein is pro- vided with a pair of valves iTEs oppositethe lowerborderof the "■ Subscapularis muscle; valves are also found at the termina- tion of the cephalic and sub- scapular veins. Other tributaries of the axil- lary vein are : The long thoracic vein (y. thoracalis lateralis) (Fig. 511), which receives the thoracico- epigastric vein {v. fhoracoepi- (jastrica), and which comes from the superficial epigastric or from the femoral vein; and the costoaxillary veins (yv. costoaxillares) (Fig. 511), which come from the first six intercostal spaces and convey the blood from the intercostal veins to the axillary. ANASTOMOSIS Fig. 510. — The deep ^ems of the upper extremity. (Bourgery.) Applied Anatomy.— There are several points of surgical interest in connection with the axillary vein. Being more superficial, larger, and slightly overlapping the axillary artery, it is more liable to be wounded in the operation of extirpation of the axillary nodes, especially as these nodes, when diseased, are liable to become adherent to the vessel. When wounded there is always danger of air being drawn into its interior, in which case death is usually the result. This is due not only to the fact that it is near the thorax, and therefore liable to be influenced by the respiratory movements, but also because it is adherent by its anterior surface to the costocoracoid membrane, and therefore if wounded is likely to remain patulous and favor the chance of air being sucked in. This adhesion of the vein to the fascia prevents its collapsing, and therefore favors the furious bleeding which takes place in these cases. To avoid wounding the axillary vein in the extirpation of nodes from the axilla no undue force should be used in isolating the nodes. If the vein is found to be so embedded in the malignant deposit that the latter cannot be removed without taking away a part of the vein, this must be done, the vessel having been first ligated above and below the diseased area. The subclavian vein {v. subclavia) (Figs. 512 and 513), the continuation of the axillary, extends from the outer border of the first rib to the inner end of the clav- icle, where it unites with the internal jugular to form the innominate vein. It is in relation, m front,' Wii\\ the clavicle and the Subclavius muscle; behind and above, with the subclavian artery, from which it is separated internally by the Scalenus anticus muscle and phrenic nerve. Beloiv, it rests in a depression on the first rib and upon the pleura. Above, it is covered by the cervical fascia and integu- ment. THE DEEP VEINS OF THE UPPER EXTREMITY 733 An expansion of the aponeurosis of the Subclavius muscle lies upon the vein (Fig. 512). The subclavian vein occasionally rises in the neck to a level with the third part of the subclavian artery, and in two instances has been seen passing with this vessel behind the Scalenus anticus. It is usually provided with a pair of valves about an inch from its termination. O^ Fig. 511.— The COSTOAXILLARY LONG THORACIC i of the right axilla, viewed from in front. (Spalteholz.) PECTORALIS Fig. 512. — The aponeurotic expansion of the Subclaviuf muscle over the subclavian vein. (Poirier and Charpy.) Tributaries. — It receives the ex- ternal jugular vein, sometimes the anterior jugular vein, and occasion- ally a small branch from the ceph- alic. At the angle of junction with the internal jugular the left sub- clavian vein receives the thoracic duct (Fig. 513), while the right subclavian vein receives the right lymphatic duct. The innominate or brachio- cephalic veins (yv. anonymae) (Fig. 514) are two large trunks, placed one on either side of the root of the neck, and formed by the union of the internal jugular and subclavian veins of the corresponding side. The right innominate vein (y. anonyma dextra) is a short vessel, an inch in length, which commences at the inner end of the clavicle, and, passing almost vertically downward, joins with the left innominate vein just below the cartilage of the first rib, close to the right border of the sternum, to form the superior vena cava. It lies superficial and external to the innominate artery; on its right side is the phrenic nerve, and the pleura is here interposed between it and the apex of the lung. This vein, at the angle of junction of the internal jugular with the 734 THE VASCULAR SYSTEMS subclavian, receives the right vertebral vein, and, lower down, the right internal mammary, right inferior thyroid, and sometimes the right thyroidea ima and the right superior intercostal veins. The left innominate vein (v. anonyma sinistra), about two and a half' inches in length, and larger than the right, passes from left to right across the upper and front part of the thorax, at the same time inclining downward, and unites with the right innominate vein to form the superior vena cava. It is in relation, in front, with the first piece of the sternum, from which it is separated by the Sterno- hyoid and Sternothyroid muscles, the thymus gland or its remains, and some loose areolar tissue. Behind it are the three large arteries arising from the arch of the aorta, together with the vagus and phrenic nerves. This vessel is joined by the left vertebral, left internal mammary, left inferior thyroid, left thyroidea ima, and the left superior intercostal veins, and occasionally some thymic and peri- cardiac veins. There are no valves in the innominate veins. LONGUS COLLI MUSCLE COMMON CAROTID AHTERV LEFT VAGUS NERVE VERTEBRAL ARTERY VERTEBRAL VEIN THORACIC DUCT INTERNAL JUGULAR VEIN EXTERNAL JUGULAR VEIN ANTERIOR JUGULAR VEIN SUBCLAVIAN VEIN Fig. 513. — The bend of the thoracic duct at its termination in the subclavian vein. (Poirier and Charpy.) Peculiarities. — Sometimes the innominate veins open separately into the right auricle; in such cases the right vein takes the ordinary course of the superior vena cava; but the left vein — the left superior vena cava, as it is termed — after communicating by a small branch with the right one, passes in front of the root of the left lung, and, turning to the back of the heart, receives the cardiac veins, and terminates in the back of the right auricle. This occasional condition in the adult is due to the persistence of the early fetal condition, and is the normal state of things in birds and some mammalia. The internal mammary veins (w. mammariae internae), two to each internal mammary artery, follow the course of that vessel, and receive tributaries corre- sponding to the branches of the artery. The two veins unite into a single trunk which terminates in the corresponding innominate vein. It receives the twelve anterior intercostal veins from the upper six intercostal spaces of the corresponding side — six anterior perforating veins (rami perforantes) — veins from the surface of the sternum (rami sternales) — muscular veins, and vessels from the mediastinum and pleura. The internal mammary veins anastomose below with the venae comites of the musculophrenic and superior epigastric arteries. The superior phrenic vein (i. e., the vein accompanying the arteria comes nervi phrenici) usually opens into the internal mammary vein. The vertebral vein (see p. 717). The inferior thjToid veins (vv. thyreoideae inferiores) (Fig. 499), two, frequently three or four, in number, arise in the venous plexus on the thyroid body (plexus thyreoideus imfar), communicating with the middle and superior thyroid veins. They form a plexus in front of the trachea, behind the Sternothyroid muscles. THE DEEP VEINS OF THE UPPER EXTREMITY 735 Superior thyroid. Middle thyioul f _ II al jugular From this plexus a left vein descends and joins the left innominate trunk, and a right vein passes obliquely downward and outward across the innominate artery to open into the right innominate vein, just at its junction with the superior vena cava. The thyreoidea ima vein (v. thyreoidea ima) passes downward in front of the trachea and termi- nates in the left innomi- nate vein. These veins receive tributaries from the tracheal veins (vv. irache- ales), from the oesophageal veins (vv. oesophageae), from the inferior laryngeal veins (v. lari/iif/ea inferior). The superior intercos- tal veins (right and left) drain the blood from two or three of the intercostal spaces below the first. The right superior inter- costal vein ( V. intercostalis sufrema dextra) passes downward and inward and opens into the vena azygos major; the left superior intercostal vein (v. intercos- talis swprema sinister) runs across the arch of the aorta and opens into the left innominate vein. It usually receives the left bronchial and left superior phrenic vein, and commu- nicates below with the vena azygos minor supe- rior. The vein from the first intercostal space opens directly into the corre- sponding vertebral or in- nominate vein. The superior vena cava {v. cava superior; precava) (Fig. 514)- receives the blood which is conveyed io the heart from the whole of the upper half of the body. It is a short trunk, varying from two inches and a half to three inches in length, formed by the junction of the two innominate veins. It com- ■mences at the level of the Fig. 514. — The A-ense cav 736 THE VA8GULAR SYSTEMS lower border of the cartilage of the first rib close to the sternum on the right side, and, descending vertically, enters the pericardium about an inch and a half above the heai-t, and terminates in the upper part of the right auricle opposite the upper border of the third right costal cartilage. In its course it describes a slight curve, the convexity of which is to the right side. Relations, — In front, with the pericardium and process of cervical fascia which is con- tinuous with it; these separate it from the thymus gland, the sternum, and the second and third right costal cartilages; behind, with the root of the right lung. On its right side, it is in relation with the phrenic nerve and right pleura; on its left side, with the commencement of the innom- inate artery and ascending part of the aorta, the latter somewhat overlapping it. The portion contained within the pericardium is covered in front and laterally by the serous layer of that membrane. It receives the .vena azygos major just before it enters the pericardium, and several small veins from the pericardium and parts in the mediastinum. The superior vena cava has no valves. The azygos veins are three in number; they collect the blood from the majority of the intercostal spaces, and connect the superior and inferior vense cavse. The vena azygos major {v. azygos) (Fig. 514) commences opposite the first or second lumbar vertebra by a branch from the right lumbar veins, called the right ascending lumbar vein {v. lumbalis ascendens); sometimes by a branch from the right renal vein or from the inferior vena cava. It enters the thorax through the aortic opening in the Diaphragm, and passes along the right side of the ver- tebral column to the fourth thoracic vertebra, where it arches forward over the root of the right lung, and terminates in the superior vena cava just before that vessel enters the pericardium. While passing through the aortic opening of the Diaphragm it lies with the thoracic duct on the right side of the aorta; and in the thorax it lies upon the intercostal arteries on the right side of the aorta and thoracic duct, and is partly covered by pleura. Tributaries. — It receives the lower ten posterior intercostal veins of the right side, the upper two or three of these opening, first of all, into the right superior inter- costal vein. On the left side the first posterior intercostal vein follows the same course as the right and empties into the vertebral or innominate vein. The second, third, and fourth posterior intercostal veins unite and form the left superior intercostal vein. This vein then passes forward across the arch of the aorta and unites with the left innominate vein. The fifth, sixth, and seventh posterior intercostals of the left side contribute to the vena azygos minor superior. The rest of the posterior intercostal veins of the left side terminate in the vena azygos minor inferior. It receives the azygos minor veins, several oesophageal mediastinal and pericardial veins; near its termination, the right bronchial vein. A few imperfect valves are found in this vein; but its tributaries are provided with complete valves. The intercostal veins {m. intercostalis) are divided into anterior and pos- terior intercostals. The anterior intercostal veins are tributaries of the internal mammary or the musculophrenic veins (p. 734). The posterior intercostal veins (Fig. 514) number eleven on each side, there being one vein in each intercostal space. Each vein lies in the groove at the lower margin of the rib above the corresponding intercostal artery. On the right side the first posterior intercostal vein crosses the neck of the first rib anteriorly and opens into the vertebral vein or the innominate vein. The posterior inter- costals of the right side, from the fifth to the eleventh inclusive, open individually into the vena azygos major. The second, third, and fourth intercostals of this side unite to form a common trunk, the right superior intercostal vein, which then joins the vena azygos major. The vena azygos minor inferior {v. lieviiazygos) (Fig. 514) commences in the lumbar region by a branch from one of the lumbar veins, ascending lumbar («. THE SPINAL VEINS 737 lumhalis ascendens), or from the left renal. It enters the thorax through the left crus of the Diaphragm, and, ascending on the left side of the vertebral column as high as the eighth or ninth thoracic vertebra, passes across the vertebral column, behind the aorta, oesophagus, and thoracic duct, to terminate in the major azygos vein. It receives the four or five lower intercostal veins of the left side, and some oesophageal and mediastinal veins. The vena azygos minor superior {v. hemiazygos accessoria) varies inversely in size with the left superior intercostal. It receives veins from the intercostal spaces between the left superior intercostal vein and highest tributary of the vena azygos minor inferior. They are usually three or four in number, usually the fifth, sixth, and seventh left posterior intercostal veins. They join to form a trunk which ends in the major azygos vein or in the vena azygos minor inferior. When this vein is small or altogether wanting, the left superior intercostal vein will extend as low as the fifth or sixth intercostal space. It sometimes receives the left bronchial vein. Applied Anatomy. — In obstruction of the inferior vena cava, the azygos veins are one of the principal means by which the venous circulation is carried on, connecting as they do the superior and inferior venae cavae, and communicating with the common iliac veins by the ascend- ing lumbar veins and with many of the tributaries of the inferior vena cava. Thrombosis of the superior vena cava is oftenest due to pressure exerted on the vessel by an aneurism or a tumor; it may also occur by propagation of clotting from a tributary peripheral vein. If occlusion of the vessel take jjlace slowly, a collateral venous circulation may be estab- lished; the patient will have some oedema with dilatation and congestion of the veins about the head and neck, and may also suffer from attacks of dyspnea and recurrent pleural effusion. In most cases, however, the blockage of the superior vena cava takes place rapidlj', and is rapidly fatal. The bronchial veins (vv. bronchiales anteriores et posteriores) return the blood from the larger bronchi and from the structures at the roots of the lungs ; that of the right side opens into the vena azygos major, near its termination; that of the left side opens into the left superior intercostal vein or the vena azygos minor superior. A considerable quantity of the blood which is carried to the lungs through the bronchial arteries is returned to the left side of the heart by the pul- monary veins. The Vertebral Veins. The vertebral veins may be arranged into four groups — viz.: 1. The extra vertebral veins. 2. The intravertebral veins. 3. The veins of the bodies of the vertebrae. 4. The veins of the spinal cord. 1. The extravertebral veins (plexus venosi vertebrales eiierni) commence by small branches which receive their blood from the integument of the back of the vertebral column and from the muscles in the vertebral grooves. They form two plexuses, an anterior plexus {plexus venosi vertebrales anteriores), upon the vertebral bodies, and a posterior plexus (plexv^ venosi vertebrales posteriores) , which surrounds the spinous processes, the laminae, and the transverse and articular processes of all the vertebrae. At the bases of the transverse processes they communicate, by means of ascending and descending branches, with the veins surrounding the contiguous vertebrae, and they join with the veins in the vertebral canal by branches which perforate the ligamenta subflava. Other branches pass obliquely forward, between the transverse processes, and com- municate with the intravertebral veins through the intervertebral foramina {vv. intervertebrales) . The extravertebral veins terminate by joining the \ertebral veins in the neck, the intercostal veins in the thorax, and the lumbar and lateral sacral veins in the loins and pelvis. 47 738 THE VASCULAR SYSTEMS 2. The intravertebral veins {plexus venosi vertebrales interni) are situated between the spinal dura and the vertebrae. They consist of two longitudinal plex- uses, one of which runs along the posterior surface of the bodies of the vertebrae, anterior longitudinal vertebral veins. The other plexus, posterior longitudinal ver- tebral veins, is placed on the inner or anterior surface of the laminae of the vertebrae. The anterior longitudinal vertebral veins (sinus vertebrales longitudinales) consist of two large, tortuous veins which extend along the whole length of the vertebral column, from the foramen magnum, where they communicate with each other by a venous ring around that opening and with the basilar and occipital sinuses through the foramen, to the base of the coccyx, being placed one on each side of the posterior surface of the bodies of the vertebrae along the margin of the posterior common ligament. These veins communicate opposite each vertebrae by transverse trunks which pass beneath the ligament. Each transverse trunk receives the large vena basis vertebrae {v. basivertebralis) from the interior of the body of the vertebra. The anterior longitudinal vertebral veins are least devel- oped in the cervical and sacral regions. They are not of uniform size throughout. The exfra-vertehral veins. Fig. 515. — Transverse section of a showing the vertebral Vertical section of two thoracic vertebrce showing the vertebral veins. being alternately enlarged and constricted. At the intervertebral foramina they communicate with the extravertebral veins, and with the vertebral veins in the neck, with the intercostal veins in the thoracic region, and with the lumbar and sacral veins in the corresponding regions. The posterior longitudinal vertebral veins, smaller than the anterior, are situated one on either side, between the inner surface of the laminte and the theca yerte- bralis. They communicate (like the anterior) opposite each vertebra by trans- verse trunks, and with the anterior longitudinal veins by lateral transverse branches which pass from behind forward. The posterior longitudinal veins, by branches which perforate the ligamenta subflava, join with the extravertebral veins. From them branches are given off which pass through the intervertebral foramina and join the vertebral, intercostal, lumbar, and sacral veins. The intervertebral veins (vv. intervertebrales) accompany the spinal nerves in the intervertebral foramina, receive veins from the spinal cord, and join the intra- and extravertebral veins. 3. The veins of the bodies of the vertebrae (vv. basivertehrales) emerge from the foramen on the posterior surface of each vertebra and join the transverse THE SUPERFICIAL VEINS OF THE LOWER EXTREMITY 739 trunk connecting the anterior longitudinal vertebral veins. They are contained in large, tortuous channels in the substance of the bones, similar in every respect to tiiose found in the diploe of the cranial bones. These canals lie parallel to the upper and lower surfaces of the bones. They commence by small openings on the front and sides of the bodies of the vertebrffi, through which communicating branches from the veins external to the bone pass into its substance, and converge to the principal canal, which is sometimes double toward its posterior part. They open into the corresponding transverse branch uniting the anterior longitudinal veins. They become greatly enlarged in advanced age. 4. The veins of the spinal cord iyv. spinales) emerge from the cord substance and form a minute, tortuous, venous plexus which covers the entire surface of the cord, being situated between the pia and arachnoid. In this plexus there are (1) two median longitudinal veins, one in front of the ventral fissure, and the other behind the dorsal groove of the cord; and (2) four lateral longitudinal veins which run behind the nerve roots; These vessels are largest in the lumbar region. Near the base of the skull they unite, and form two or three small trunks, which communicate with the vertebral veins, and terminate in the inferior cerebellar veins or in the inferior petrosal sinuses. Each of the spinal nerves is accompanied by a radicular efferent vessel as far as the intervertebral foramina, where it joins the other veins from the vertebral canal. There are no valves in the vertebral veins. . VEINS OF THE LOWER EXTREMITY, ABDOMEN, AND PELVIS (Figs. 517, 518). The veins of the lower extremity are subdivided, like those of the upper, into two sets, superficial and deep; the superficial veins are situated beneath the integu- ment, between the two layers of superficial fascia, the deep veins accompanying the arteries, and forming the venae comites of those vessels. Both sets of veins are provided with valves, which are more numerous in the deep than in the super- ficial set. These valves are also more numerous in the lower than in the upper limb. The Superficial Veins of the Lower Extremity. The Superficial Veins of the Foot. — In the sole of the foot there is a sub- cutaneous venous plexus {rele venosum plantare cutaneuni), from which some branches go to the deep veins, but most of the branches pass around the margins to the dorsum of the foot. There is a transverse venous arch at the root of the toes which receives plantar vessels from the toes and sends branches between the toes {yv. intercapitulares) to the venous arch of the dorsum. On the dorsum of each toe the veins gather into two vessels, known as the dorsal digital veins (vv. digitales pedis dorsalis). The dorsal digital veins from the opposed margins of t^Ao toes unite to form a dorsal intercligital vein. There are four dorsal inter- digital veins (I'f . digitales communes pedis), and they pass into the venous arch of the dorsum. The dorsal digital vein, fi'om the inner surface of the great toe, passes directly into the internal saphenous vein, and the dorsal digital vein, from the outer surface of the little toe, passes directly into the external saphenous vein. The venous arch of the dorsum of the foot {arciis venosus dorsalis pedis) is sit- uated in the superficial structures over the anterior extremities of the metatarsal bones. It has its convexity directed forward, and receives digital tributaries from the upper surface of the toes ; at its concavity it is joined by numerous small veins which form a plexus on the dorsum of the foot (rele venosum dorsale pedis cutaneum). The arch terminates internally in the long saphenous, externally in the short saphenous vein. 740 THE VASCULAR SYSTEMS The chief superficial veins of the lower extremity are the internal or long saphenous and the external or short saphenous. The internal or long saphenous vein {v. saphena magna) (Figs. 517 and 520) commences at the inner side of the arch on the dorsum of the foot; it ascends in i /.'Ss7 Pig. 517. — The internal or long saphenous vein and its tributaries. Fig. 518. — External or short saphenous vein. front of the inner malleolus and along the inner side of the leg, behind the inner margin of the tibia, ac- companied by the internal saphenous nerve. At the knee it passes backward behind the inner condyle of the femur, ascends along the inside of the thigh, and, passing through the saphenous opening in the fascia lata, terminates in the femoral vein about an inch and a half below Poupart's ligament. This vein receives in its course cutaneous tributaries from the leg and thigh, and at the saphenous opening receives the superficial epigastric, superficial circumflex iliac, and external pudic veins. The veins from the inner and back part of the thigh frequently unite to form a large vessel, which enters the main trunk near the saphenous opening; and sometimes those on the outer THE DEEP VEINS OF THE LOWER EXTREMITY 741 side of the thigh join to form another large vessel ; so that occasionally three large veins are seen converging from different parts of the thigh toward the saphenous opening. The internal saphenous vein communicates in the foot with the internal plantar vein; in the leg, with the posterior tibial veins by branches which perforate the tibial origin of the Soleus muscle, and also with the anterior tibial veins; at the knee, with the articular veins; in the thigh, with the femoral vein by one or more branches. The valves in this vein vary from two to six in number; they are more numerous in the thigli than in the leg. The external or short saphenous vein {v. saphena parva) (Fig. 518) com- mences at the outer side of the arch on the dorsum of the foot; it ascends behind the outer malleolus, and along the outer border of the tendo Achillis, across which it passes at an acute angle to reach the middle line of the posterior aspect of the leg. Passing directly upward, it perforates the deep fascia in the lower part of the popliteal space, and terminates in the popliteal vein, between the heads of the Gastrocnemius muscle. It receives numerous large tributaries from the back part of the leg, and communicates with the deep veins on the dorsum of the foot and behind the outer malleolus. Before it perforates the deep fascia it gives off a communicating branch, which passes upward and inward to join the internal saphenous vein. This vein contains from nine to twelve valves, one of which is always found near its termination in the popliteal vein. The external saphenous nerve lies close beside this vein. Applied Anatomy. — A varicose condition of the saphenous veins is more frequently met with than in the other veins of the body, except perhaps the spermatic and hemorrhoidal veins. The course of the internal saphenous is in front of the tip of the inner malleolus, over the sub- cutaneous surface of the lower end of the tibia, and then along the internal border of this bone to the back part of the internal condyle of the femur, whence it follows the course of the Sar- torius musde, and, is represented on the surface by a line drawn from the posterior border of the Sartorius on a level with the internal condyle to the saphenous opening. The external saph- enous lies behind the external malleolus, and from this follows the middle line of the calf to just below the ham. It is not generally so apparent beneath the skin as the internal saphenous. Both these veins in the leg are accompanied by nerves, the internal saphenous being joined by its companion nerve just below the level of the knee-joint. No doubt much of the pain of vari- cose veins in the leg is due to this fact. Operations for the relief of varicose veins are frequently required, portions of the veins being removed after having been ligated above and below. It is important to note whether the main varicose area drains into the internal or the external saphenous vein — the former condition being much the more common — and to control the venous return by removing a small portion of the main trunk just before it opens into the deep vein by passing through the deep fascia; thus in most cases a piece should be removed from the internal saphenous just before it passes through the saphenous opening, and in addition the affected veins should be excised just above and just below the level of the knee-joint. In other cases the external saphenous will have to be dealt with immediately below the point where it pierces the fascial roof of the popliteal space. The Deep Veins of the Lower Extremity. The deep veins of the lower extremity accompany the arteries and their branches and are called the venae comites of those vessels. The venae comites in the lower extremity pass into one trunk, the popliteal vein, whereas in the upper extremity the venae comites continue with the artery to the axilla. The Deep Veins of the Foot. — The plantar digital veins (vv. digifales plantares) form the plantar metatarsal veins (ri\ mctalarscac plaiifarc.s-), which communicate with the veins of the dorsinii of the foot by perforating veins and also communicate with the deep venous arch of the sole of the foot {amis venosus plantaris). The plantar arch gives oft' lateral or external plantar veins, which unite with median or internal plantar veins to form the posterior tibial veins. On the dorsum of the foot the deep \eins begin as the dorsal metatarsal veins {m. metafarseae dorsales jxdis), which form the venae comites of the dorsalis pedis artery. 742 THE VASCULAR SYSTEMS The posterior tibial veins {vv. tihiales posteriores) accompany the posterior tibial artery and are joined by the peroneal veins. The. anterior tibial veins (vv. tibialis anteriores) are formed by a continuation upward of the venae comites of the dorsalis pedis artery. They pass lietween the tibia and fibula, through the large oval aperture above the interosseous membrane, and form, by their junction with the posterior tibial, the popliteal vein. The valves in the deep veins are very numerous. The popliteal vein (v. poplitea) (Fig. 519) is formed by the junction of the anterior and posterior tibial veins; it ascends through the popliteal space to the aperture in the Adductor magnus tendon, where it becomes the femoral vein. In the lower part of its course it is placed internal to the artery; between the heads of the Gastrocnemius it is superficial to that vessel; but above the knee-joint it is close to the outer side of the artery. It receives the sural veins from the Gastrocnemius muscle, the articular veins, and the external saphenous veins. The valves in this vein are usually four in niunber. The femoral vein (y. femoralis) (Figs. 520 and 521) accompanies the femoral artery through the upper two-thirds of the thigh. In the lower part of its course it lies external to the artery; higher up it is behind it; and at Poupart's ligament it lies to its inner side and on the same plane. It receives numerous muscular tributaries, and about an inch and a half below Poupart's ligament it is joined by the deep femoral; near its termination it is joined by the internal saphenous vein. The valves in the femoral vein are four or five in number. The deep femoral vein (v. profunda femoris) Teceives tributaries corresponding to the perforating branches of the profunda artery, and through these establishes communications with the popliteal vein below and the sciatic vein above. It also receives the internal and external circumflex veins. The external iliac vein (v. iliaca externa) (Figs. 521 and 523) commences at the termination of the femoral, beneath the crural arch, and, passing upward along the brim of the pelvis, terminates opposite the sacroiliac joint by uniting with the internal iliac to form the common iliac vein. On the right side it lies at first along the inner side of the external iliac artery, but as it passes upward gradually inclines behind it. On the left side it lies altogether on the inner side of the artery. It receives, immediately above Pou- part's ligament, the deep epigastric and deep circumflex iliac veins and a small pubic vein, corresponding to the pubic branch of the obturator artery. It fre- quently contains one and sometimes two valves. Tributaries. — The external iliac vein receives the deep epigastric, deep circumflex iliac, and pubic veins. The deep epigastric vein (v. epigastrica inferior) (Fig. 521) is formed by the anion of the venae comites of the deep epigastric artery, which communicates above with the superior epigastric vein; it joins the external iliac about half an inch above Poupart's ligament. The deep circumflex iliac vein (v. circumflexa ilium profunda) (Fig. 521) is formed b}' the union of the venae comites of the deep circumflex iliac artery, Fig. 519. — The popliteal vein. (Poirier and Charpy.) THE BEEP VETNS OF THE LOWER EXTREMITY 74.3 and joins the external iliac vein about three-quarters of an inch above Poupart's ligament. The pubic vein communicates with the obturator \em in the obturator fora- men, and ascends on the back of the pubis to terminate in the external iliac \-ein. The internal iliac vein {v. hypoc/astrica) commences near the upper part of the great sacrosciatic foramen, passes upward behind and slightly to the inner side of the internal iliac artery, and at the brim of the pelvis joins with the external iliac to form the common iliac. UMBfLICUS SUPERFICIAL EXTERNAL CIRCUMFLEX SUPERFICIAL INTERNAL CIRCUMFLEX Fig. 520.— The femoral Dtl its tributaries. (Poirier and Charpy.) Tributaries. — With the exception of the fetal umbilical vein, which passes up- ward and backward from the umbilicus to the liver, and the iliolumbar vein which usually joins the common iliac vein, the tributaries of the internal iliac vein corre- spond with the branches of the internal iliac artery. It receives (a) the gluteal, sciatic, internal pudic, and obturator veins, which have their origins outside the pelvis; (b) the lateral sacral veins, which lie in front of the sacrum; and (c) the middle hemorrhoidal, vesical, uterine, and vaginal veins, which originate in venous plexuses connected with the pelvic viscera. I. The gluteal veins (vv. glutaeae super lores) or venae comites of the gluteal artery, receive tributaries from the buttock corresponding with the branches of 744 THE VASCULAR SYSTEMS the artery; they enter the pelvis through the great sacrosciatic foramen, above the Pyriformis, and frequently unite before ending in the internal iliac vein. 2. The sciatic veins {m. glidaeae inferiores) , or venae comites of the sciatic artery, begin on the upper part of the back of the thigh, where they anastomose with the internal circumflex and first perforating veins. They enter the pelvis through the lower part of the sacrosciatic foramen and join to form a single stem which opens into the lower part of the internal iliac vein. 3. The internal pudic veins are the venae comites of the internal pudic artery. They covimejice in the veins which issue from the corpus cavernosum, accom- pany the internal pudic artery, and unite to form a single vessel, which ends in the internal iliac vein. They receive the veins from the bulb of the urethra, the superficial perineal, and the inferior hemorrhoidal veins {m. hemorrhoidales inferiores). The deep dorsal vein of the penis communicates with the internal pudic veins, but ends mainly in the vesicoprostatic venous plexus. veins. (Poirier and Charpy.) 4. The obturator vein (v. obturatoria) begins in the upper portion of the adductor region of the thigh and enters the pelvis through the anterior part of the obturator foramen. It runs backward and upward on the lateral wall of the pelvis below the obturator artery, and then passes between the ureter and the internal iliac artery, to end in the internal iliac vein. 5. The lateral sacral veins (vv. sacrales laterales) accompany the lateral sacral arteries on the anterior surface of the sacrum and terminate in the internal iliac vein. 6. The middle hemorrhoidal vein {v. hemorrhoidal is media) takes origin in the hemorrhoidal plexus and receives tributaries from the bladder, prostate gland, and seminal vesicle; it runs outward on the pelvic surface of the Levator ani to end in the internal iliac vein. THE DEEP VEINS OF THE LOWER EXTREMITY 745 The hemorrhoidal plexus surrounds the rectum, and communicates in front with the vesicoprostatic plexus in the male, and the uterovaginal plexus in the female. It consists of two parts, an internal in the submucosa, and an external outside the muscular coat. Below, the internal plexus presents a series of dilated pouches which are arranged in a circle around the tube immediately above the anal orifice and are connected by transverse branches. The lower part of the external plexus is drained by the inferior hemorrhoidal veins into the internal pudic; its middle part by the middle hemorrhoidal vein, which joins the internal iliac; and its upper part by the superior hemorrhoidal vein, which forms the commencement of the inferior mesenteric vein, a tributary of the portal vein. A free communication between the portal and systemic venous systems is established through the hemorrhoidal plexus. Fig. 522. — Scheme of the anastomosis of the veins of the rectum. (Poirier and Charpy.) The vesicoprostatic plexus surrounds the prostate gland and the neck of the bladder, and lies partly in the fascial sheath of the prostate and partly between the sheath and the capsule of the gland. In front it receives the deep dorsal vein of the penis; behind, it Cv->mmunicates with the hemorrhoidal and vesical plexuses, and derives tributaries from the vasa deferentia and seminal vesicles. It is drained into the internal iliac veins by one or more vessels on either side. The correspond- ing plexus in the female is named the vesicovaginal. The vesical plexus lies on the muscular coat of the bladder, and is best marked toward the base and sides of this viscus; it drains into the vesicoprostatic plexus. Applied Anatomy. — The veins of the hemorrhoidal plexus are liable to become dilated and varicose, and form piles. This is due to several anatomical reasons: the ve.ssels are contained in verj' loose, lax connective tissue, so that they get less support from surrounding structures than most other veins, and are less capable of resisting increased blood pressure; the condition is favored by gravitation, being influenced by the erect posture, either sitting or standing, and by the fact that the superior hemorrhoidal and portal veins have no valves; the veins pass 746 THE VASCULAR SYSTEMS through muscle tissue and are liable to be compressed by its contraction, especially during the act of defecation; they are affected by every form of portal obstruction. The prostatic plexus of veins is liable to become congested in many inflammatory conditions in the neighborhood, such as acute gonorrheal prostatitis. It is owing to the free communi- cation which exists between this and the middle hemorrhoidal plexus that great relief can be given by free saline purgation. Hemorrhage may be very profuse from the prostatic plexus after operations on that gland, but can usually be checked by hot fluid irrigation. Septic thrombosis sometimes occurs after operations, and infected emboli may find their way into the general circulation. THIRD LUMBAR VESICAL PLEXUS Fig. 523. — The veins of the male pelvis, right half, viewed from the left. The Psoas n and the rectum drawn down somewhat to the side. (Spalteholz.) cle has been removed The dorsal veins of the penis are two in number, a superficial and a deep. The superficial vein drain.? the prepuce and skin of the penis, and, running back- ward in the subcutaneous tissue, incHnes to the right or left, and opens into the corresponding superficial external pudic vein, a tributary of the internal or long saphenous vein. The deep vein receives the blood from the glans penis and corpora cavernosa; it courses backward in the middle line between the dorsal arteries, beneath the deep fascia, and near the root of the penis passes between THE DEEP VEINS OF THE LOWER EXTREMITY 747 SUPERFICIAL DOR- SAL VEIN ARTERV I .DEEP DORSAL VEIN the two parts of the suspensory ligament and then through an aperture between the subpubic hgament and the apex of the triangular ligament, and divides into two branches, which enter the vesicoprostatic plexus. The dorsal vein of the clitoris corresponds in woman to the dorsal vein of the penis in man, and empties into the inferior vesical plexus. The Vaginal Plexuses and Veins (Fig. 525). — The vaginal plexuses are placed at the sides of the vagina, being especially developed at the orifice of the canal. They receive vessels from the vaginal walls. The plexuses communicate with the uterine plexus above, with the bulbar veins below, with the inferior vesical plexus in front, and with the hemorrhoidal plexus be- hind, and are drained by the vaginal veins, one on either side, into the internal iliac veins. The uterine plexuses (Fig. 525) are situated along the sides and superior angles of the uterus, between the two layers of the broad ligament, and communicate with the ovarian and vaginal plexuses. They are drained by the uterine veins Fig. 524. — The penis in transverse section, showing the the blood-vesaels. (Testut.) VAGINAL VENOUS PLEXUS OS UTERI VAGINA CUT OPEN BEHIND Fig 525 — \ essels of the uterus and its appendages rear view. (Testut.) (ot. uterinae) (Fig. 525) which arise from the lower part of the plexus. There are usually two veins on each side, and they are not provided with vah'es. These veins for the first portion of their course are placed in the base and inner portion of the broad ligament; they then pass back with the uterine artery and terminate in the internal iliac vein. During pregnancy the uterine veins become greatly enlarged. The common iliac veins (Figs. 521 and 523) are formed by the union of the external and internal iliac veins in front of the sacroiliac articulation; passing obliquely upward toward the right side, each ^-ein terminates upon the inter\-erte- bral substance between the fourth and fifth lumbar vertebrje, where the -veins of 748 THE VASCULAR SYSTEMS the two sides unite at an acute angle to form the inferior vena cava. The right common iliac (y. iliaca communis dextra) is shorter than the left, nearly vertical in its direction, and ascends behind and then to the outer side of its corresponding artery. The left common iliac (v. iliaca communis sinistra), longer than the right, and more oblique in its course, is at first situated on the inner side of the corre- sponding artery, and then behind the right common iliac. Each common iliac receives the iliolumbar, and sometimes the lateral sacral veins. The left receives, in addition, the middle sacral vein. No valves are found in these veins. The middle sacral veins (Figs. 521 and 522) accompany the corresponding artery along the front of the sacrum, and join to form a single vein {y. sacralis media), which terminates in the left common iliac vein; occasionally in the angle of junction of the two iliac veins. The middle sacral veins communicate with the inferior hemorrhoidal. The iliolumbar veins (vv. ilioluvibales) receive branches from the iliac fossae, spinal muscles, and vertebral canal. One vein on each side runs with the artery, passes posterior to the Psoas muscle, and joins the common iliac vein. Peculiarities. — The left common iliac vein, instead of joining with the right in its usual position, occasionally ascends on the left side of the aorta as high as the kidney, where, after receiving the left renal vein, it crosses over the aorta, and then joins with the right vein to form a short inferior vena cava. In these cases the two common iliacs are connected by a small communicating branch at the spot where they are usually united. The inferior vena cava (v. cava inferior; postcava) (Figs. 514 and 521) returns to the heart the blood from nearly all the parts below the Diaphragm. It is formed by the junction of the two common iliac veins on the right side of the intervertebral substance between the fourth and fifth lumbar vertebrae. It passes upward along the front of the vertebral column on the right side of the aorta, and, having reached the liver, is contained in a groove on its posterior surface. It then passes through the Diaphragm between the mesal and right portions of the central tendon; it subsequently inclines forward and inward for about an inch, and, piercing the fibrous pericardium, passes behind the serous pericardium to open into the lower and back part of the right auricle. In front of its auricular orifice is a semilunar valve, the Eustachian valve; this is rudimentary in the adult, but is of large size and exercises an important function in the fetus. Relations.— /ra/ron/, from below upward, with the mesentery, right spermatic artery, trans- verse portion of the duodenum, the pancreas, portal vein, and the posterior surface of the liver, which, in most cases, partly and occasionally completely surrounds it; behind, with the verte- bral column, the right crus of the Diaphragm, the right renal and lumbar arteries, the right semilunar ganghon, and the inner part of the right suprarenal gland; on the right, side, with the right kidney and ureter; on the left side, with the aorta. The thoracic portion is short and covered anterolaterally by the serous layer of the pericardium. Peculiarities. — In Position. — This vessel is sometimes placed on the left side of the aorta, as high as the left renal veins, after receiving which it crosses over to its usual position pn the right side; or it may be placed altogether on the left side of the aorta, as far upward as its ter- mination in the heart; in such cases the abdominal and thoracic viscera, together with the great vessels, are all transposed. The vessel may be double, due to the bilateral persistence of the cardinal veins. Point of Termination. — Occasionally the inferior vena cava joins the vena azygos major, which is then of large size. In such cases the superior vena cava receives the whole of the blood from the body before transmitting it to the right auricle, except the blood from the hepatic veins, which passes directly into the right auricle. Applied Anatomy.— Thrombosis of the inferior vena cava is due to much the same causes as that of the superior (see page 737). It usually causes edema of the legs and back, without ascites; if the renal veins are involved, blood and albumin will often appear in the urine. An extensive collateral venous circulation is soon estabhshed by enlargement either of the super- ficial or of the deep veins, or of both. In the first case the epigastric, the circumflex iliac, the THE DEEP VEINS OF THE LOWER EXTREMITY 749 long thoracic, the internal mammary, the intercostals, the external pudic, and the lumbcvertebral anastomotic veins of Braune effect the communication with the superior cava; in the second, the deep anastomosis is made by the azygos major and minor and the lumbar veins. Tributaries. — It receives in its course the following veins: Lumbar. Right spermatic, or ovarian. Renal. Suprarenal. Inferior phrenic. Hepatic. The lumbar veins (vv. himhales), four in number on each side, collect the blood by dorsal tributaries from the muscles and integument of the loins and by abdominal tributaries from the walls of the abdomen, where they communicate with the epigastric veins. At the vertebral column they receive veins from the spinal plexuses, and then pass forward, around the sides of the bodies of the Fig. 526.— Spermatic veins. (Testut.) vertebrae beneath the Psoas magnus muscle, and terminate at the back part of the inferior vena cava. The left lumbar veins are longer than the right, and pass behind the aorta. The lumbar veins of either side are connected by a longitudinal vein which passes in front of the transverse processes of the lumbar vertebrae, and is called the ascending lumbar vein (c. lumbalis ascendens) (Fig. 514). It forms the most frequent origin of the corresponding azygos vein, and 750 THE VASCULAR SYSTEMS serves to connect the common iliac, iliolumbar, lumbar, and azygos veins of the corresponding side of the body. The spermatic veins {m. sperviaticae) (Fig. 526) emerge from the back of the testis, and receive tributaries from the epididymis; they unite and form a convo- luted plexus called the spermatic plexus {plexus pampiniformis), which constitutes the greater mass of the cord; the vessels composing this plexus are very numerous, and ascend along the cord in front of the vas deferens; below the external abdom- inal ring they unite to form three or four veins, which pass along the inguinal canal, and, entering the abdomen through the internal abdominal ring, coalesce to form two veins, which ascend on the Psoas muscle behind the peritoneum, lying one on either side of the spermatic artery. These unite to form a single vein, which opens on the right side into the inferior vena cava at an acute angle; on the left side into the left renal vein at a right angle (Fig. 527). The spermatic Fig. 527. — Terminations of tlie right and left spermatic veins. (Poirier and Charpy.) veins are provided with valves, particularly at the termination. The left sper- matic vein passes behind the sigmoid flexure of the colon. ^ Applied Anatomy. — The spermatic veins are very frequently varicose, constituting the dis- ease known as varicocele. Though it is quite possible that the originating cause of this affection may be a congenital abnormality either in the size or number of the veins of the spermatic plexus, still it must be admitted that there are many anatomical reasons why these veins should become varicose — viz., the imperfect support afforded to them by the loose tissue of the scrotum; their great length; their vertical course; their dependent position; their plexiform arrangement in the scrotum, with their termination in one small vein in the abdomen; their few and imperfect valves; and the fact that they may be subjected to pressure in their passage through the abdom-. inal wall. The left veins more often become varicose than the right veins, probably, as Brinton suggests, because the right spermatic vein practically always has a valve and opens into the inferior vena cava at an acute angle, whereas the left spermatic vein is not unusually destitute of a valve at its opening and passes into the left renal vein at a right angle. The operation for the removal of a varicocele consists in making a small incision just over the external abdominal ring and passing an aneurism needle around the mass of veins, taking care that the vas deferens is not included. The veins are isolated from the vas and ligated above and below, as high and as low as possible, and the intermediate portion cut away"; the divided ends are fixed together with a suture, and the skin wound closed. THE PORTAL SYSTEM OF VEINS 751 The ovarian veins {w. ovaricae) (Fig. 525) correspond with the spermatic in the male; they form a plexus in the broad ligament near the ovary and about the Fallopian tube, and communicate with the uterine plexus. They terminate in the same way as the spermatic veins in the male. Valves are occasionally found in these veins. Like the uterine veins, these vessels become greatly enlarged during pregnancy. The renal veins (vu. renales) (Fig. 515) are of large size, and are placed in front of the renal arteries. The left is longer than the right, and passes in front of the aorta, just below the origin of the superior mesenteric artery. It receives the left spermatic, the left inferior phrenic, and, generally, the left suprarenal veins. It opens into the inferior vena cava a little higher than the right. The suprarenal veins (yy. suprarenales) (Fig. 514) are two in number; that on the right side terminates in the inferior vena cava; that on the left side, in the left renal or in the left phrenic vein. The inferior phrenic veins (vv. phrenicae inferiores) follow the course of the phrenic arteries; the right ends in the inferior vena cava, the left in the left renal vein. The hepatic veins (dv. hepaticae) commence in the substance of the liver, in the capillary terminations of the portal vein and hepatic artery, iatralobular veins; these tributaries, gradually uniting into sublobular veins, usually form three large hepatic veins, which converge toward the posterior surface of the liver and open into the inferior vena cava, where that vessel is situated in the groove at the back part of this organ. Of these three veins, one from the right and another from the left lobe open obliquely into the inferior vena cava, that from the middle of the organ and lobulus Spigelii having a straight course. The hepatic veins run singly, and are in direct contact with the hepatic tissue. They are destitute of valves. THE PORTAL SYSTEM OF VEINS (Fig. 528). The portal system includes all the veins which drain the blood from the abdom- inal part of the alimentary canal (with the exception of the lower part of the rectum) and from the spleen, pancreas, and gall-bladder. From these viscera the blood is conveyed to the liver by the portal vein. In the substance of the liver the portal vein ramifies like an artery and terminates in the portal capillaries (sinusoids), from which the blood is conveyed to the inferior vena cava by the hepatic veins. From this it will be seen that the blood of the portal system passes through two sets of capillary vessels — viz., (a) the capillaries of the alimen- tary canal, spleen, pancreas, and gall-bladder; and (b) the portal capillaries in the substance of the liver. The portal vein and its tributaries are destitute of valves. The portal vein (vena portae) is about three inches in length, and is formed at the level of the second lumbar vertebra by the junction of the superior mesen- teric and splenic veins, the union of these veins taking place in front of the inferior vena cava and behind the neck of the pancreas. It passes up-\\-ard behind the first part of the duodenum and then ascends near the right border of the lesser omentum to the right extremity of the transverse fissure of the liver, where it divides into right and left branches, which accompany the corresponding branches of the hepatic artery into the substance of the liver. In the lesser omentum it is placed behind and between the common bile duct and the hepatic artery, the former lying to the right of the latter. It is surrounded by the hepatic plexus of nerves, and is accompanied by numerous lymphatic vessels and some lymph nodes. The right branch of the portal vein enters the right lobe of the liver, but before doing so generally receives the cystic vein. The left branch, longer but of smaller caliber than the right, crosses the longitudinal fissure, gives branches 752 THE VASCULAR SYSTEMS to the caudate and Spigelian lobes, and then enters the left lobe of the liver. As it crosses the longitudinal fissure it is joined in front by a fibrous cord, the liga- mentuvi teres of the liver or impervious umbilical vein, and is united to the inferior vena cava by a second fibrous cord, the ligamentum venosum or impervious ductus venosus. The tributaries of the portal vein are: Splenic. Superior mesenteric. Gastric. Pyloric. Cystic. Parumbilical, Fig. 528. — Portal vein and its tributaries. Note. — In this diagram the right gastroepiploic vein opens into the splenic vein; generally it empties into the superior mesenteric, close to its termination. The splenic vein {v. lienalis) (Fig. 528) covimences by five or six large branches which return the blood from the substance of the spleen. These, uniting, form a THE PORTAL SYSTEM OF VEINS 753 single vessel, which passes from left to right, grooving the upper and back part of the pancreas below the artery, and terminates at its greater end by uniting at a right angle with the superior mesenteric to form the portal vein. The splenic vein is of large size, and not tortuous like the artery. Tributaries. — The splenic vein receives the vasa brevia from the left extremitv of the stomach, the left gastroepiploic vein, the pancreatic veins, and the inferior mesenteric vein. (a) The short gastric veins (yv. gastricae breves), some four or five in number, drain the fundus and left part of the greater curvature of the stomach, and pass between the two layers of tiie gastrosplenic omentum to terminate in the splenic vein or in one of its large trii)Utaries. (b) Tiie left gastroepiploic vein (v. gastroepiploica sinistra) receives tributaries from the anterior and posterior surfaces of the stomach and from the great omen- tum; it runs from right to left along the greater curvature of the stomach and ends in the commencement of the splenic vein. (c) The pancreatic veins (iw. pancreaticae) consist of several small vessels which ■drain the body and tail of the pancreas, and open into the trunk of the splenic vein. {d) The inferior mesenteric vein (v. mesenterica inferior) returns blood from the rectum, and the pelvic, iliac, and descending parts of the colon. It begins in the rectum as the superior hemorrhoidal vein (v. haemorrhoidalis superior), which has its origin in the hemorrhoidal plexus, and through this plexus communicates with tiie middle and inferior hemorrhoidal veins. The superior hemorrhoidal vein leaves the pelvis and crosses the iliac vessels in company with the superior hemorrhoidal artery, and is continued upward as the inferior mesenteric vein. This vein lies to the left of the inferior mesenteric artery, and ascends behind the peritoneum and in front of the left Psoas; it then passes behind the body of the pancreas and opens into the splenic vein; sometimes it terminates in the angle of imion of the splenic and superior mesenteric veins. Tributaries. — ^The inferior mesenteric vein receives the sigmoid veins (vv. sig- mojdeae) from the sigmoid flexure and the left colic vein (v. colica sinistra) from the descending colon and splenic flexure. The superior mesenteric vein (v. mesenterica. superior) returns the blood from the small intestine, and from the cecum and ascending and transverse portions of the colon. It begins in the right iliac fossa by the union of the veins which drain the terminal part of the ileum, the cecum, and vermiform appendix, and ascends between the two layers of the mesentery on the right side of the supe- rior mesenteric artery. In its upward course it passes in front of the right ureter, the inferior vena cava, the third part of the duodenum, and the uncinate process of the head of the pancreas. Behind the neck of the pancreas it unites with the splenic vein to form the portal vein. Tributaries. — Besides the tributaries which correspond with the branches of the superior mesenteric artery — viz., the veins of the small intestine (vv. intesti- nalcs), the ileocolic (v. ileocolica), the right colic (ra. colica dextrac), and the middle coUc (v. colica media) — the superior mesenteric vein is joined by the right gastro- epiploic and pancreaticoduodenal veins. The right gastroepiploic vein {v. gastroepiploica dextra) receives tributaries from the great omentum and from the lower parts of the anterior and posterior surfaces of the stomach ; it runs from left to right along the greater cur^-ature of the stomach between the two layers of the great omentum. The pancreaticoduodenal veins {vv. pancrealicoduodenales) accompany their cor- responding arteries; the lower of the two frequently joins the right gastroepiploic vein. The gastric vein {v. coronaria ventriculi) derives tributaries from both surfaces 48 754 THE VASCULAR SYSTEMS of the stomach ; it runs from right to left along the lesser curvature of the stomach, between the two layers of the gastrohepatic omentum, to the oesophageal end of the stomach, where it receives some oesophageal veins. It then turns backward and passes from left to right behind the lesser sac of the peritoneum and ends in the portal vein. The pyloric vein is of small size, and runs from left to right along the pyloric portion of the lesser curvature of the stomach, between the two layers of the gastro- hepatic omentum, to terminate in the portal vein. The cystic vein {v. cystica) (Fig. 528) drains the blood from the gall-bladder, and, ascending along the cystic duct, usually terminates in the right branch of the portal vein. Parumbilical Veins (yv. parumbilicales). — In the course of the ligamentum teres of the liver and of the urachus small veins (panimbilicar) are found, which establish an anastomosis between the veins of the anterior abdominal wall and the portal and iliac veins. The best marked of these small veins is one which commences at the umbilicus and runs backward and upward in, or on the surface of, the ligamentum teres between the layers of the falciform ligament to terminate in the left branch of the portal vein. Anastomoses between the Portal and Systemic Veins. — Some tributaries of the portal vein communicate with certain neighboring systemic veins. The more important communications are between (a) the gastric veins and the (jesophageal veins which empty into the vena azygos minor; (b) the parumbilical veins, which anastomose with the deep epigastric and internal mammary veins; (c) the superior and middle hemorrhoidal veins, the latter opening into the internal iliacs. Applied Anatomy. — Obstruction to the portal vein may produce ascites, and this may arise from many causes, as (1) the pressure of a tumor on the portal vein, such as cancer or hydatid cyst, in the Uver, enlarged lymph nodes in the lesser omentum, or cancer of the head of the pancreas; (2) from cirrhosis of the liver, when the radicles of the portal vein are pressed upon by the contracting fibrous tissue in the portal canals; (3) from valvular disease of the heart, and back pressure on the hepatic veins, and so on the whole of the circulation through the liver. In this condition the prognosis as regards life and freedom from ascites may be much improved by the establishment of a good collateral venous circulation to relieve the portal obstruction in the liver. This is effected by communications between (a) the gastric veins, and the oesophageal veins emptying themselves into the vena azygos minor inferior, which often project as a varicose bunch into the stomach; (b) the veins of the colon and duodenum, and the left renal vein; (c) the accessory portal system of Sappey, branches of which pass in the round and falciform ligaments (particularly the latter), to unite with the epigastric and internal mammary veins, and through the diaphragmatic veins with the azygos; a single large vein shown to be a parumbilical vein, may pass from the hilus of the liver by the round ligament to the umbilicus, producing there a bunch of prominent varicose veins known as the Caput Medusae; (d) the veins of Retzius, which connect the intestinal veins with the inferior vena cava and its retroperitoneal branches; (e) the inferior mesenteric veins, and the hemorrhoidal veins that open into the internal iliacs; (f) very rarely the ductus venosus remains patent, affording a direct connection between the portal vein and the inferior vena cava. An operation for the relief of portal obstruction on these lines has been advocated by Ruther- ford Morison and by Talma. It consists in curetting the opposed surfaces of the liver and diaphragm and stitching them together, so as to secure vascular inflammatory adhesions between the two. The great omentum may with advantage be interposed between them, so as to increase the amount of the adhesions, and the spleen has been similarly scraped and sutured to or into the abdominal wall. The operation should not be deferred until the patient is moribund. Thrombosis of the portal vein, or pylethrombosis, is a very serious event, and is oftenest due to pathological processes causing compression of the vessel or injury to its wall, such as tumors or inflammation about the pylorus, head of the pancreas, or appendix, or to gallstones or cir- rhosis of the liver. If the thrombus is infected with bacteria, as is often the case when it is due to appenaicitis, septic or suppurative pylephlebitis results; this condition is known also as portal pyemia. Fragments of the infected clot break off and are carried away to lodge in the smaller veins in the liver, with the development of multiple abscesses in its substance and a rapidly fatal result. When the thrombus is sterile, the chief signs produced are enlargement of the spleen, recurrent ascites, and the establishment of a collateral venous circulation, the case clinically resembling one of atrophic cirrhosis of the liver. DEVELOPMENT OF THE BLOOD-VASCVLAR SYSTEM 755 DEVELOPMENT OF THE BLOOD-VASCULAR SYSTEM. There are three distinct stages in the develo])im'iit of the C'irculatory system, each in accord- ance with the manner in which nourishment is i)r()\idcd for ;it different periods of the existence of the individual. In the first stage there is the eitcUinc circulation, during which nutriment is extracted from the vitellus or contents of the yolli sac. In the second stage there is the placental circulation, during which nutriment is obtained by means of the placenta from the blood of the mother. In the third stage, commencing after birth, there is the complete circu- lation of the adult, during which nutrition is provided for by the organs of the individual.' I Mesoderm. Entoderm. Blood-island. Fig. 529. — Section through vascular area to show commencing development of bloodvessel. (Semidiagrammatic.) Bloodvessels first make their appearance in the mesodermal wall of the yolk sac, i. e., outside the body of the embryo. Here the cells become arranged into solid strands or cords which join to form a close-meshed network. The peripheral cells of these strands become flattened and joined to each other by their edges to form the walls of the primitive bloodvessels. Fluid col- lects within the strands and converts them into tubes, and the more centrally situated cells of the cell cords are thus pushed to the sides of the vessels and appear as masses of loosely arranged cells which project toward the lumen of the tube. These masses are termed hlood islands (Fig. 529); their cells acquire coloring matter (hemoglobin), and are then detached to form the blood- corpuscles or erythroblasts (Fig. 530).^ Later, red cells are formed in organs where the circulation Vessel wall. Blood-corpuscles. Fig. 530. — Later stage. is sluggish, as liver, spleen, and bone-marrow. At birth this function is lost by the liver and spleen. The earliest blood corpuscles are all nucleated; they are also capable of subdivision and of executing ameboid movements, and in these respects resemble colorless blood corpuscles. Soon, however, true colorless blood corpuscles make their appearance, and, according to Beard,' are first derived from the rudiments of the thymus. Coincidently with the development of the bloodvessels in the vascular area, the first rudi- ment of the heart appears as a pair of tubular vessels which are developed in the splanchno- pleure of the pericardial area in the precephalic part of the embryonic area. These are named the primitive aorta;, and a direct continuity is soon established between them and the vessels of the vascular area. Each receives precardially a vein — the vitelline vein — from the yolk sac, and is prolonged backward on the lateral aspect of the notochord under the name of the dorsal aorta. The dorsal aortfe end at first on the yolk sac; but with the development of the allantois, they are continued onward through the body stalk as the umbilical arteries to the villi of the chorion frondosum. By the forward growth and flexure of the head the pericardial area and the precardial portions of the primitive aortse are folded caudad on the ventral aspect of the fore-gut, and the original 1 That the umbilical circulation precedes the vitelline in the human embryo seems to be shown by Eternod's and Dandy's independent observations. CoTisult the latter's article, A Human Embryo with Seven Pairs of Somites, American Journal of Anatomy, January, 1910. - -Iticording to Dandy (loc. cil.) there is at first no apparent connection between this blood-formmg area and the vascular system of the very young human embryo, and that the presence of blood corpuscles in the latter is probably explained by endothelial proliferation from the capillaries in the chorionic membrane. ^ .Anatomischer Anzeiger, December, 19D0. 756 THE VASCULAR SYSTEMS relation of the layers of the pericardial area is reversed. Each primitive aorta now consists of a ventral and a dorsal part connected cephalad by an arched vessel traversing the first or man- dibular branchial arch. In each succeeding branchial arch a similar vessel develops, so that in all nx pairs of aortic arches are formed, of which the fifth atrophies early. Primitive jugu lar vein Chorionic villi Pig. 531. — Human embryo of about fourteen days old with yolk sac. (After His, from Kollmann's Entwickelungsgeschiclite.) In the pericardial region the two primitive aortse grow together and fuse to form the single- chambered primitive heart tube (Fig. 532), the caudal end of which receives the two vitelline veins, while from its cephalic end the two ventral aortje emerge. By the rhythmic contraction of the tubular heart the blood is forced through the aortre and bloodvessels of the vascular area, Auricle' Sinus venosus- Vitelline veins Fig. 532.— Diagram to illustrate the simple tubular condition of the heart. (Drawn from Ecker-Ziegler model.) Vitelline veins Fig. 533. — Heart further advanced than in Fig. 532. (Drawn from Ecker-Ziegler model.) from_ which it is returned to the heart by the vitelline veins; by this vitelline circulation the nutriment is absorbed from the vitellus. Umbilical or Placental Circulation.— With the atrophy of the yolk sac the vitelline circu- lation diminishes and ultimately ceases, while an increasing amount of blood is carried through DEVELOPMENT OF THE BLOOD-VASCULAR SYSTEM 757 the umbilical arteries to the villi of the chorion. Subsequently, as the nonplacental chorionic villi atrophy, their vessels disappear, and then the umbilical arteries convey the whole of the blood to the placenta, whence it is returned to the heart by the umbilical veins. In this manner the placental circulation is established, and by means of it nutritive materials are absorbed from, and waste products given up to, the maternal blood. ■ Optic reside. Auricle.-— yi.- -- T OmphaloTtiesen- feric veins. ed from the ventral surface. X 26. The umbilical veins, like the vitelline, become interrupted by the liver, and the blood returned by them passes through this organ before reaching the heart. Ultimately the right umbilical vein largely disappears, being represented in the adult by a small vein of the belly wall. During the occurrence of these changes great alterations take place in the primitive heart and bloodvessels, and now r('(|iiirc description. Further Development of the Heart.— The simple tubular heart, already described, be- comes elongated and bent on itself so as to form an S-shaped loop, the cephalic part bending to the right and the caudal part to the left. The intermediate portion arches transversely from right to left, and then turns sharply forward into the cephalic part of the loop. Slight con- Ventricle.' Vena cava siiperio Umtilical vein.- Maxillary process. StomodEeum. Mandibular 2)rocess. Fig. 535. — Heart of human embryo of about fifteen days. (Reconstruction by His.) strictions make their appearance in the tube and divide it from behind forward into four parts, viz.: (1) The sinus venosus; (2) the primitive auricle; (3) the primitive ventricle; (4) the aortic bulb, which consists of two portions, a proximal muscular portion known as the bulbiis cordis, and a distal portion, the primitive aortic stem (Figs. 532 to 534). The constriction between the auricle and ventricle constitutes the auricular canal, and indicates the site of the future auriculo- ventrieular valves. The sinus venosus is at first situated in the septum transversum behind the common auricle, and is formed by the union of the vitelline veins. The veins or ducts of Cuvier from the body of 758 THE VASCULAR SYSTEMS the embryo and the umbilical veins from the placenta subsequently open into it (Fig. 54.5). The sinus is at first placed transversely, and opens by a median aperture into the common auricle. Soon, however, it assumes an oblique position, and becomes crescentic in form; its right half or horn increases more rapidly than the left, while the opening into the auricle now communi- cates with the right portion of the auricular cavity. The right horn ultimately becomes incor- porated with and forms a part of the right auricle, the line of union between it and .the auricle proper being indicated in the interior of the adult auricle by a vertical crest {crista terminalis of His). The left horn, which ultimately receives only the left duct of Cuvier, persists as the Right auricle- Bulhus cordi —Left auricle Fig. 536. — Heart showing expansion of auricles. (Drawn from Edier-Ziegler model.) coronary sinus (Fig. 494). The vitelline and umbilical veins are soon replaced by a single vessel, the inferior vena cava, and the three veins (inferior vena cava and right and left Cuvierian ducts) open into the dorsal aspect of the auricle by a common slit-like aperture (Fig. 542). The upper part of this aperture represents the opening of the adult superior vena cava, the lower that of the inferior vena cava, and the intermediate part the orifice of the coronary sinus. The slit-like aperture lies obliquely, and is guarded by two valves, the right and left venous valves, which unite with each other above the opening and are continuous with a fold named the septum spurium. The left venous valve practically disappears, while the right is subsequently divided to form the Eustachian and Thebesian valves. At the lower extremity Aortic bitlb Left auricle Left rentricle.^ Might auricle. .Superior vena cava. •Septum transversitm. ■Umbilical vein. Vitelline or Omphalomesenteric vein. Fig. 537. — Heart of human embryo, 4.2 mm. long, seen from behind. fHis.) of the slit is a triangular thickening, the spina vestibuli of His, which partly closes the aperture between the two auricles, and, according to His, takes a part in the formation of both the inter- auricular and interventricular septa. The auricular canal is at first a short straight tube connecting the auricular with the ven- tricular portion of the heart, but its growth is relatively slow, and it becomes overlapped by the auricles and ventricles so that its position on the surface of the heart is indicated only by an annular constriction. (Fig. 536). Its lumen is reduced to a transverse slit, and two thickenings appear, one on its dorsal and another on its ventral wall. These thickenings, or evdocardial cushions (Fig. 542), as they are termed, project into the canal, and, meeting in the middle line. DEVELOPMENT OF THE BLOOD- VASCULAR SYSTEM 759 iirjite to form the septum inlermedium which divides the canal into two channels, the future right and left auriculo\entricular orifices. The primitive aurirular ca\ ity becomes subdivided into right and left auricles by an incom- plete septum, the septum primiim (Fig. 542), which grows downward into the auricular cavity. For a time the two auricles communicate with each other by an opening, the ostium primum of Born, below the free margin of the septum. This opening is, however, closed by the union of the septum primum with the septum intermedium, and the communication between the auricles is reestablished through an opening which is developed in the upper part of the septum primum; Aortic sepiiim. Common aurioulo- ventricular orifice. ■ Right veyiiricle. Septum inferius. Figs. 538 and 539.— Diagn .•entride. ^J**"™ inferius. ventricle. t to show the development of the septum of the aortic bulb and of the ventricles. (Born.) this opening is known as the foramen ovale (ostium secimdum of Born), and persists until shortly after birth. A second septinn, the septum secundum, semilunar in shape, grows downward from the upper wall of the auricle to tlie right of the primary septum and foramen ovale, forming the ventral and lower boundary of the latter. This fold becomes continuous with the Eustachian valve and forms the adult annulus ovalis. Shortly after birth it fuses with the primary septum, and by this means the foramen ovale is closed, but sometimes the fusion is incomplete and the upper part of the foramen remains patent. The primitive ventricle becomes divided bj^ a septum, the septum inferius or interventricular septum (Figs. 538, 539, 542), which grows upward from the lower part of the ventricle, its position Fig. 540. — Diagrams to illustrate the transformation of the bulbus cordis. Ac. Primitive aortic stem. Au. Auricle. B. Bulbus cordis. RV. Right ventricle. LV. Left ventricle. P. Pulmonary artery. (Keith.) being indicated on the surface of the heart by a fiu^row. Its dorsal part grows more rapidly than its ventral portion, and fvises with the dorsal part of the septum intermedium. For a time an interventricular foramen exists above its ventral portion, but this foramen is ultimately closed by the fusion of the aortic septum with the interventricular septum. As already stated, the aortic hnlh consists of a proximal muscular portion, the hidhns cordis, and a distal portion, the primitive aortic stem. When the heart assumes its S-shaped form the bulbus cordis lies ventral to or in front of the primitive ventricle. The adjacent walls of the bulbus cordis and ventricle approximate, fuse, and finally disappear, and the bulbus cordis now communicates freely with the right ventricle, while the jimction of the bulbus with the primitive 760 THE VASCULAR SYSTEMS aortic stem is brought directly ventral to and applied to the auricular canal. By the upgrowth of the interventricular septum the bulbus cordis is in great measure separated from the left ventricle, but remains an integral part of the right ventricle, of which it forms the infundibidum. The primitive aortic stem is divided by the aortic septum (Fig. 541). This makes its appear- ance as two lateral ridge-like thickenings which project into the lumen of the tube from just above the level of the sixth arch vessels; these increase in size, and ultimately meet and fuse to form the septum and thus the primitive aortic stem is divided into the pulmonarv artery and Fig. 541. — Transverse sections through the aortic bulb to show the growth of the aortic septum. The lowest section is on the left, the highest on the right of the figure. (After His.) the aorta. The aortic septum takes a spiral course toward the proximal end of the stem, so that the two vessels lie side by side above, but near the heart the pulmonary artery is in front of the aorta (Fig. 414). The septum grows down into the ventricle as an oblique partition, which ul- timately blends with the interventricular septum in such a way as to bring the bulbous cordis into communication with the pulmonary artery, and through the latter with the sixth pair of aortic arches; while the left ventricle is brought into continuity with the aorta which communi- cates with the remaining aortic arches. Sej}tain spitrium Opening of sinus venosus Left venous valve mn p)u. Sejjtum inferius Fig 542. — Interior of dorsal half of heart from a human embryo 10 mm. long. (His.) The Valves of the Heart. — The auriculoventricular valves are developed in relation to the auricular canal. By the upward expansion of the bases of the ventricles the canal becomes invaginated into the ventricular cavities. The invaginated margin forms the rudiments of the lateral cusps of the auriculoventricular valves; the mesal or septal cusps of the \-alves are developed as downward prolongations of the septum intermedium. The aortic and pulmonary valves are formed from four endocardial thickenings — an anterior, a posterior, and two lateral — which appear at the proximal end of the primitive aortic stem. As the aortic se|)tum grows dow-nward it divides each of the lateral thickenings into two, thus giving rise to six thickenings — the rudiments of the semilunar valves — three at the aortic and three at the pulmonary orifice. DEVELOPMENT OF THE BLOOD-VASCULAR SYSTEM 761 Further Development of the Arteries. — It has been seen (p. 756) that each primitive aorta consists of a ventral and a dorsal stem, which are continuous tlirough the first aortic acch. The dorsal aortis at first run backward separately on either side of the notochord, but about the third week they fuse from about the level of the fourth thoracic to that of the foitfth lumbar segment to form a single trunk, the descending aorta. The first aortic arches pass through the mandibular arches, and caudad of them five additional pairs are developed within the branchial arches; so that, in all, six pairs of aortic arches are formed (Fig. 544). The first and second arches pass between the ventral and dorsal aortse, while the others arise at first by a common trunk from the aortic bulb, but terminate separately in the dorsal aortse. As the neck elongates, the ventral aort« are lengthened, and the third and fourth arches arise directly from these vessels. Second aortic arch. Third aortic arch. Auditor!/ vesicle Primitive jugular veiti.^^-^ Fourth aortic arch. Fifth aortic arch. Cardinal vein.- First aortic arch. ■Olfactory pit. Maxillary process. Hyomandihular cleft. •Mandibular arcli. ■Aortic hidb. Auricle. ■Duct of Cuvier. .Ventricle. Allantois. Umbilical {allantoi< rtery). Fig. 543. — Profile view of a human erabryo estimated at twenty or twenty-one days old, (.\fter His.) In fishes these arches persist and give off branches to the gills, in ^^■hieh the blood is oxygenated. In mammals some of them remain as permanent structures, while others disappear or become imi>ervious (Fig. 544). The Ventral Aortae. — These persist on both sides. The right forms (a) the innominate artery, (6) the right common and external carotid arteries. The left give's rise to (a) the short portion of the aortic arch, which reaches from the origin of the innominate artery to that of the left common carotid artery; (6) the left common and external carotid trunks. The Aortic Arches.— The first and second disappear; the third {carotid arch) constitutes the commencement of the internal carotid artery. The fourth right arch forms the right sub- clavian as far as the origin of its internal mammary branch; while the fourth left arr-h con- stitutes the arch of the aorta between the origin of the left carotid artery and the termination of the ductus arteriosus. The fifth arch disappears on both sides. The sixth right arch disappears ; 762 THE VASCULAR SYSTEMS the sixth left arch gives off the pulmonary arteries and forms the ductus arteriosus; this duct remains pervious throughout fetal life, but becomes impervious a few days after birth.' The Dorsal Aortae. — Cephalad of the third aortic arches the dorsal aortse persist and form the headward continuation of the internal carotid arteries. Caudad of the third arch the right dorsal aorta disappears as far as the point where the two dorsal aortfe fuse to form the descending aorta. The part of the left dorsal aorta which intervenes between the third and fourth arches disappears, while the remainder persists to form the descending part of the arch of the aorta. A constriction, the aortic isthmus, is sometimes seen in the aorta between the origin of the left subclavian and the attachment of the ligamentum arteriosum. Below this isthmus the aorta expands slightly to form the aortic spindle. Sometimes the right subclavian artery arises from the aortic arch beyond the origin of the left subclavian and passes upward and to the right behind the trachea and oesophagus. This con- dition may be explained by the persistence of the right dorsal aorta and the obliteration of the fourth right arch. In birds the fourth right arch forms the arch of the aorta; in reptiles the foiu-th arch on both sides persists and gives rise to the double aortic arch in these animals. The heart originally lies on the ventral aspect of the pharynx, immediately caudad of the stoma- todeum. With the elongation of the neck and development of the lungs it recedes within the thorax, and, as a consequence, the anterior ventral aortee are drawn out and the original position of the fourth and fifth arches is greatly modified. Thus, on the right side the fourth recedes to -External carotid Ventral aorta Internal carotid Common carotid Aortic arch Right subclavian artery Right piil?nonary artery Trunk of pulmonary, artery Ductus arteriosus Vertebral artery Subclavian artery Left pulmonary artery Fig. 544. — Scheme of the aortic arches and their derivatives. (Modified from Kollmann.) the root of the neck, while on the left side it is withdrawn within the thorax. The recurrent laryngeal nerves originally pass to their distribution under the sixth pair of arches, and are therefore pulled backward with the descent of these structures, so that in the adult the left hooks around the ligamentum arteriosum; owing to the disappearance of the fifth and the sixth right arches the right nerve hooks around that immediately above them, i. e., the commencement of the subclavian artery. A series of segmental arteries arises from the primitive dorsal aortas, those in the neck alternating with the cervical segments of the vertebral column. The seventh segmental artery, which lies between the sixth and seventh cervical segments, is of special interest, since it forms the lower part of the vertebral artery and, when the forelimb bud appears, sends a branch to it (i. e., the subclavian artery); the upper part of the vertebral artery is formed by an inter- segmental anastomosis between the higher segmental arteries. From the seventh segmental arteries the entire left subclavian and the greater part of the right subclavian are formed. The subclavian artery is prolonged into the limb under the names of the axillary and brachial arteries, and these together constitute the arterial stem for the upper arm. The direct con- tmuation of this stem into the forearm forms the anterior interosseous artery; while the radial and ulnar vessels, which ultimately exceed this artery in size, are in reality lateral branches of the main stem. The formation of the primary caudal branches has already been referred to (p. 755), and the fusion of the dorsal aortse to form the greater part of the systemic aorta has been pointed out 1 His found that in the young embryo the right and left sixth arches each give that later both pulmonary arteries take origin from the left arch. L branch to the lungs, but DEVELOPMENT OF THE JSLOOB-VASCULAJi SYSTEM 763 (page 761). The middle sacral artery of the adult was formerly regarded as the direct con- tinuation of the adult aorta, but Young and Robinson' maintain that it is a secondary branch, probably representing fused segmental arteries. The caudal continuations of the aortte in the adult are the common iliac, internal ihac, and the partially impervious hypogastric arteries. The hypogastric arteries are continued into the umbiUcal cord as tlie imabilical arteries. After birth they become impervious cords from the umbilicus as far as the origin of the superior vesical arteries. The primary arterial stem for the lower limb is formed by the sciatic artery, which accom- panies the great sciatic nerve along the posterior aspect of the thigh to the back of the knee, where it is continued as the peroneal artery. The femoral artery arises later as a branch of the common iliac, and, passing down the front and inner side of the thigh to the bend of the knee, joins the sciatic artery. The femoral quickly enlarges, and coincidently with this the part of the sciatic immediately above the knee undergoes atrophy. The anterior and posterior tibial arteries are branches of the main arterial stem. Eight '•primitive jugular rein. Right cardinal Right duct of Cuviei Sinus venosits Right hepatic r^in. Portal Portal vein- Right umbiUcal vein Umbilical cord. _, ;,___>. -'Le/^ cardinal vein. 'Left duct of Cuvier, -Left hepatic dcih. -Ductus venosus. Left umbilical vein. Fig. S45. — Human embryo with heart and anterior body wall removed to show the sinus venosus and its tributaries. (After His, from Kollmann's Entwickelungsgeschichte.) Further Development of the Veins. — The formation of the great veins of the embryo maj be best considered by dividing them into two groups, visceral and parietal. The visceral, veins are the two vitelline or omphalomesenteric veins bringing the blood from the yolk sac, and the two umbilical or allantoic veins returning the blood from the placenta; these four veins open close together into the sinus venosus (Fig. 547). The vitelline veins run cephalad at first in front, and subsequently on either side of the intestinal canal. They unite on the ventral aspect of the canal, and beyond this are connected to one another by two cross branches, the first on the dorsal, the second on the ventral aspect of the duodenal portion of the intestine, which is thus encircled by two venous rings (Fig. 546). The portions of the veins above the upper ring become invaded by the developing liver and broken up by it into a plexus of small capillary-like vessels termed sinusoids (Minot). The branches conveying the blood to this plexus are named the venae advehentes, and become the branches of the I Journal of .^atomy and Physiology, vol. xxxii 764 THE VASCULAR SYSTEMS portal vein; while the vessels draining the plexus into the sinus venosus are termed the venae, revehentes, and form the future hepatic veins (Figs. 545 and 546). Ultimately the left vena revehens no longer communicates directly with the sinus venosus, but opens into the right vena revehens. The lower part of the yortal vein is formed from the fused vitelline veins which receive the veins from the alimentary canal; its upper part is derived from the venous rings by the persistence of the left half of the lower and the right half of the upper ring, so that the vessel forms a spiral turn round the duodenum (Fig. 546). The two umbilical veins fuse early to form a single trunk in the body stalk, but remain separate within the embryo and pass forward to the sinus venosus in the side walls of the body. Like the vitelline veins, their direct connection with the sinus venosus becomes interrupted by the inva- sion of the liver, and thus at this stage the whole of the blood from the yolk sac and placenta passes through the substance of the liver before it reaches the heart. The right umbilical vein becomes disconnected from the sinus venosus, shrivels, and forms a small vein of belly wall; the left, on the other hand, becomes enlarged and opens into the upper venous ring of the vitelline veins. Finally, a direct channel is established between this ring and the heart; this channel is called the ductus venosus, and, enlarging rapidly, forms a wide channel tlirough which most of the blood, returned from the placenta, is carried directly to the heart without being obliged to pass through the liver. The left umbilical vein and ductus venosus become impervious after birth, and form, respectively, the Ugamentum teres and Ugamentinn venosimi of the liver (Fig. 1071). Ventral detached portions of umbilical veins. y- , Stomach. Venae advehentes. - ~ Pancreas. -' Bile duct. -- Obliterated portions of venous rings. Right umbilical vein. Ductus venosits. Left umbilical vein. Fig. 546. — The liver, and the veins in connection with it, of a human embryo, twenty-four or twenty-five days old, as seen from the visceral surface. (After His.) (Copied from Milnes Marshall's Embryology.) The Parietal Veins. — The first indication of a parietal system consists in the appearance of two short transverse veins (the ducts of Cuvier), which open, one on either side, into the sinus >'enosus. Each of these ducts receives an ascending and descending vein. The ascending veins return the blood from the parietes of the trunk and from the mesonephroi, and are called postcardinal veins. The descending veins return the blood from the head and upper limbs, and are called the precaxdinal or primitive jugular veins (Fig. 547). The blood from the lower limbs is collected by the right niid li'I'l iliar veins, which, in the earlier stages of develop- ment, ojien into the corresponding right and left pustcardinals (Fig. 548); later on, a transverse channel (the left common iliac vein) is developed between the caudal parts of the two post- cardinal veins (Fig. 549), and through this the blood is carried to the right postcardinal vein. The portion of the left postcardinal vein below the level of the left renal vein atrophies and dis- appears up to the point of entrance of the left spermatic vein; above this level the left post- cardinal persists as the superior and inferior azygos minor veins. The right postcardinal vein, which now j-eceives the blood from both lower limbs, forms a large venous trunk along the posterior abdominal wall. Above the level of the renal veins the right postcardinal vein persists as the vena azygos major, and receives the right intercostal veins, while the azygos minor veins are brought into communication with it by the develo]3ment of transverse anastomotic channels in front of the vertebral column (Fig. 514). DEVELOPMENT OF THE' BLOOD-VASCULAR SYSTEM 765 Inferior Vena Cava. — The development of the inferior vena cava is associated with the formation of two pairs of veins, the snhnirdhinl and .suj)racar(iiual veins (Figs. 548 and 549), and with the ductus venoms. The subcardinal veins lii- piirnllel to, and ventrad of, the postcardinal veins and originate as longitudinal anasloniosing channels which communicate with the post- Sinus venosus Precardinal Subclavian Duct of Cuvier Vitelline Umbilical ^Postcardinal Subcardinal ■RcJial External iliac Internal iliac Fig. 547. — Scheme of arrangement cf parietal veins. Internal Jugular ■External jugular Subclavian Duct of Cuvier Left postcardinal -Ductus venosus Benal Subcardinal ■External iliac — Internal iliac Fig. 548. — Scheme showing early stages of development of the inferior vena cava. cardinals above and below and also with each other by a series of transverse channels. Of the transverse channels, only one persists to join each renal vein. The left subcardinal vein practi- cally disappears, while the right subcardinal enlarges and joins the ductus venosus cephalad and the right postcardinal caudad. At this stage the blood draining the lower extremities passes along a right-sided channel which courses ventrad of the lu-eter. Internal jugular '^'Subclavian Suprarenal Benal Simrynatie A B Fig. 549. — Diagram illustrating the development of the inferior vena cava in the cat. The cardinal and subcardinal veins and ductus venosus are blue and the supracardinal black. (Adapted from McClure and Huntington.) The supracardinal veins develop as bilaterally symmetrical channels dorsomesad of the postcardinals, l>y lonoitudinal anastomoses between parietal postcardinal tributaries fHuntington and McClure). Each vein extends from where the posterior limb veins open into the post 766 THE VASCULAR SYSTEMS cardinals to the junction of the primitive renal vein with the transverse subcardinal segment, and is situated dorsad of the corresponding ureter. The two supracardinals fuse almost wholly into a single channel and largely replace the postrenal segment of the primitive postcardinal sys- tem. To review, it is seen that the inferior vena cava is a composite vessel made up of the fol- lowing parts, enumerated in order from the heart: (1) The part of the ductus venosus between the hepatic veins and the heart; (2) the cephalic part (renal level) of the right subcardinal; (3) the fused supracardinals, the caudal portions only remaining separate to drain the right and left Uiacs (Fig. 549). In consequence of the atrophy of the Wolffian bodies the postcardinal veins diminish in size; the precardinal veins, on the other hand, become enlarged, owing to the rapid development of the head and brain. They are further augmented by receiving the veins (subclavian) from the upper extremities, and so come to form the chief veins of the Cuvierian ducts; these ducts gradually assume an almost vertical position in consequence of the descent of the heart into the thorax. The right and left Cuvierian ducts are originally of the same diameter, and are frequently termed the right and left superior venae cavae. By the development of a transverse channel (the left hrachiocephalic vein) between the two precardinal veins, the blood is carried across from the left to the right precardinal (Fig. 547). The portion of the right primitive jugular vein between the left brachiocephalic and the vena azygos major forms the upper part of the superior vena cava of the adult; the lower part of this vessel {i. e., below the entrance of the vena azygos major) is formed by the right Cuvierian duct. Below the origin of the trans- verse channel the left primitive jugular vein and left Cuvierian duct atrophy, the former con- stituting the upper part of the left superior intercostal vein, while the latter is represented by the vestigial fold and oblique vein of Marshall. Both right and left superior venae cavae are present in some animals, and are occasionally found in the adult human being. The oblique vein of Marshall passes downward across the back of the left auricle to open into the coronary sinus, which, as already indicated, represents the persistent left horn of the sinus \ enosus. The primitive jugular or precardinal veins are situated on the ventral surface of the brain, on the mesal side of the cranial nerve roots. A considerable portion of each of these veins disappears and is replaced by a vein which is developed on the lateral aspect of the cranial nerves from the fifth to the twelfth, inclusive. This new vein (vena capitis lateralis) leaves the skull in company with the facial nerve. The blood from the hind-brain is collected into a vein (the fidure lateral sinus) which passes through the foramen jugulare on the lateral aspect of the vagus nerve; here the two vessels join to form the internal jugular vein. On the dorsal aspect of the ear capsule an anastomotic channel is opened up between the vena capitis lateralis and the lateral sinus; and, coincident with this, the ])ortion of the former vein which extends from the fifth to the tenth cranial nerve becomes obliterated, and thus the whole of the blood from the brain is ultimately drained away by the lateral sinuses. The primitive jugular vein is therefore represented in the adult by the internal jugular, and not by the external jugular, as is usually stated.' The external jugular vein is a vessel of later formation, which at first drains the region behind the ear (posterior auricular) and enters the primitive jugular as a lateral tributary. A group of veins from the face and lingual region converge to form a common vein, the linguofacial,- which also terminates in the primitive jugular. Later, cross communications develop between the external jugular and the linguofacial, with the result that the posterior group of facial veins are transferred to the external jugular. The development of the lymphatics will be described at the beginning of the section on the lymph-vascular system. 1 Consult Die Entwickelung des Blutgefitss-sy stems, by Hochstetter. in Hertwig's Entwicltelungslelire; and also an article by Mall in the American Journal of Anatomy, December, 1904, vol. iv. 2 Heuer, American Journal of Anatomy, February, 1909, vol. ix. No. 1. THE LYMPHATIC SYSTEM. The lymphatic system' includes the lymphatic vessels and lymph nodes or lymphatic glands. The lymphatic vessels of the small intestine receive the special designation of lacteals or chyliferous vessels; they differ in no respect from the lymphatic vessels, except that during digestion they contain a milk-white fluid, the chyle. It is now generally held that the lymphatic system is a closed system peripher- ally, and that the tissue spaces are not in direct communication with lymphatics, although Mall has shown that granules injected into the portal vein are returned by both lymphatics and veins. Elsewhere, apparently, the absorption of the lymph is carried on by transudation through the endothelial lining of the lymph vessels and not by permanent openings (the so-called stomata) between the endo- thelial cells. The tissue spaces {lymph spaces) are found in practically all tissues and organs, and may be classified as pericellular or intercellular, perivascular and perineural spaces, which are not lined by endothelium. The lymph exudes into these spaces out of the blood capillaries and transudes into the lymphatic capillaries wherever such exist. Spaces like the subdural and subarachnoid, and the serous cavities of the body (pleural, pericardial, peritoneal, synovial bursse) are lined by endo- thelium, through which the lymph transudes by osmosis, while the lymphocytes may actually traverse the membrane. The ventricles of the brain and the central canal of the spinal cord, lined by the ependyma, contain a similar fluid derived from the plasma of the blood in the choroid plexuses, and they communicate with the subarachnoid space through the foramen of Magendie and those of Key and Retzius. Lymph is a transparent, colorless or slightly yellow fluid of a specific gravity of 1.015, more dilute than the blood plasma from which it is derived, containing only about 5 per cent, of proteins and 1 per cent, of salts and extractives. It contains formed elements of the lymphocyte class, and is slightly coagulable. Chyle is the intestinal lymph which is of a milky appearance during digestion on account of the emulsified fats absorbed by the lacteals. The lymphatic vessels are arranged into a superficial and a deep set. On the surface of the body the superficial lymphatic vessels are placed immediately beneath the integument, accompanying the superficial veins; they join the deep lymphatics in certain situations by perforating the deep fascia. In the interior of the body the lymphatics lie in the submucous areolar tissue throughout the whole length of the gastropulmonary and genitourinary tracts, and in the subserous tissue of the thoracic and abdominal cavities. In the cranial cavity the perivascular sheaths are lymph spaces. A plexiform network of minute, closed, capillary lymphatics may be found interspersed among the proper elements and bloodvessels of the several tissues, the vessels composing which, as well as the meshes between them, are much larger than those of the capillary bloodvessel plexus. From these networks small collecting vessels emerge, pass to a neighboring node, and divide • In the revision of the section on the lymphatic system, the editor has consulted the work by Poirier and Cundo, translated by Cecil H. Leaf, 1904; the articles by Sabin, Lewis, and Heuer in the American Journal of Anatomy, February 1, 1909; and the articles by Huntington, McClure, and others (symposium) in the Anatom- ical Record, May, 1908. Consult also G. S. Huntinffton and C. F. W. McClure, on the Anatomy and Develop- ment of the Jugular Lymph Sacs in the Domestic Cat (Fells domestica), American Journal of Anatomy, April, 1910, vol. X, No. 2, and several articles by various authors in the Anatomical Record, vol. vi. No. 6, June 20, 1912. (767) THE VASCULAR SYSTEMS into a capillary network in the node. Numerous small vessels emerge from the node, which unite into one lymphatic vessel, which joins a larger lymphatic trunk, which empties into a tributary of the superior vena cava. The deep lymphatics, fewer in number and larger than the superficial, accompany the deep bloodvessels. Their mode of origin is probably similar to that of the superficial vessels. The lymphatics of any part or organ exceed the veins in number and in capacity, but in size they are much smaller. Their anastomoses also, especially those of the large trunks, are more frequent, and are effected by vessels equal in calibre to those which they conneci, the continuous trunks retaining the same diameter throughout. The lymph nodes, or lymphatic glands (lymphoglandulae) , are small, solid, gland- like bodies situated in the course of the lymphatic and lacteal vessels. They vary from microscopic dimensions to the size of an olive, and their color, on section, is of a pinkish-gray tint, excepting the bronchial nodes, which in the adult are mottled with black, the hepatic nodes, which are yellow, and the splenic nodes, which are brown. Each node has a layer or capsule of cellular tissue investing it, from which prolongations dip into its substance, forming parti- tions. The lymphatic and lacteal vessels traverse these nodes in their passage to the lymphatic ducts. Before entering a node a lymphatic or lacteal vessel divides into several small branches, which are named afferent vessels (yasa affereniia). As they enter, the external coat becomes continuous with the capsule of the node, and the vessels becoming much thinned, and consisting only of their internal or endothelial coat, pass into the node, and branch out upon and in the tissue of the capsule, these branches opening into the lymph sinuses of the node. There is an ex- tensive sinus beneath the capsule; from this subcap- sular sinus numerous channels run inward to a central sinus. From both sinuses fine branches proceed to form a plexus, the vessels of which unite to form a single efierent vessel {yas efferens), which, on emerg- ing from the node, is again invested with an external coat from the gland capsule. The lymph nodes are filters or traps through which lymph and chyle flow, and also have a cytogenic function. In the nodes are masses of newly formed lymphocytes which attack any bacteria in the lymph or chyle. Like the lymphatics, the lymph nodes are arranged in superficial and deep sets; they are usually embedded in fat and are distinctly movable. Occasionally a node exists alone, but, as a rule, from eight to twelve, or even more, are assembled in communities or chains, and are usually arranged around bloodvessels. The nodes have a plentiful blood supply, and contain not only vasomotor nerves, but definite nerve plexuses. Besides the nodes, the body contains numerous lymphoid areas, which, in structure and function, are allied to lymph nodes (tonsils, Beyer's patches, etc.). Hemolymph nodes exist in various regions, but are most common in the abdomen in front of the vertebrae. They are like ordinary lymph nodes in form and also in size, but differ from them in being deep red instead of light pink. Their func- tion is to destroy red blood cells and to form lymphocytes, phagocytes, and eosino- philes. Hemolymph nodes develop like the ordinary lymphatic nodes except that the sinuses are blood channels. Fig. 550, — A lymph node with its afferent and efferent vessels. (Tes- tut.) rilE LYMPHATIC SYSTEM 769 Structure of Lymphatics. — The lymphatic \essels, including in this term the lacteal vessels, which are identical in structure with them, are composed of three coats. The internal is an endothelial and elastic coat. It is thin, transparent, slightly elastic, and ruptures more easily than the other coats. It is composed of a layer of elongated endothelial cells with ' serrated margins, by which the adjacent cells are dovetailed into one another. These are supported on a fibro-elastic membrane. The middle coat is composed of smooth muscle and fine elastic fibres, disposed in a transverse direction. The external coat consists of connective tissue, inter- mixed with smooth muscle fibres, longitudinally or obliquely disposed. It forms a protective covering, to the other coats, and serves to connect the vessel with the neighboring structures. The above description applies only to the larger lymphatics; in the smaller vessels there is no mus- cular or elastic coat, and the wall consists only of a connective-tissue coat, Kned by endothelium. The thoracic duct has a more complex structure than the other lymphatics; it presents a distinct subendothelial layer of branched cells, similar to that foimd in the arteries, and m the middle coat is a layer of connective tissues with its fibres arranged longitudinally. The lymphatics are supplied by nutrient vessels, which are distributed to their outer and middle coats; and here also have been traced many amyelinic nerve fibres in the form of several fine plexuses of fibrils. The lymphatics are very generally provided with valves, which assist materially in effecting the flow of the lymph. These valves are formed of thin layers of fibrous tissue, covered on both surfaces by endothelium, which presents the same arrangement upon the two surfaces as was described in connection with the valves of veins. In form they are semikmar; they are attached by their convex edges to the sides of the vessel, the concave edges being free and directed along the course of the contained current. Usually two such valves, of equal size, are found oppo- site each other; but occasionally exceptions occiu", especially at or near the anastomoses of lymphatic vessels. Thus, one valve may be of very rudimentary size and the other increased in proportion. The valves in the lymphatic vessels are placed at much shorter intervals than in the veins. They are most numerous near the lymphatic nodes, and are found more frecjuently in the lym- phatics of the neck and upper extremity than in those of the lower extremity. The wall of a l^'mphatic immediately above the point of attachment of each segment of a valve is expanded into a pouch or sinus, which gives to these vessels, when distended, the knotted or beaded appearance which they present. Valves are wanting in the vessels composing the plexiform network in which the lymphatics usually originate on the surface of the body. Lymphatic vessels have been found in nearly every tissue and organ of the body which con- tains bloodvessels; nonvascular structures, such as cartilage, the nails, cuticle, and hair, have none. Lymphatic vessels have not been demonstrated in the brain, spinal cord, eyeball, and internal ear; the pathway of the lymph is apparently along the intercellular and perivascular tissue spaces. Origin of Lymphatics. — The finest lymphatic ve.ssels (lymphatic capillaries) form a plexiform network in the tissues and organs, and their walls consist of a single layer of endothelial plates, with more or less sinuous margins; the vessels of the lymphatic system, therefore, form a series of closed tubes similar to those of the blood-vascular system. The lymphatic vessels, for the most part, accompany the arteries or veins throughout the body; sometimes a minute artery may be seen to be ensheathed for a certain distance by a lymphatic capillary vessel, which is often many times wider than a blood capillary. These are known as perivascular lymphatics. Terminations of Lymphatics. — The lymphatics, including the lacteals, dis- charge their contents into the veins at two points, namely, at the angles of junction of the subclavian and internal jugular veins — on the left side by means of the thoracic duct, and on the rig-lit side by the right lymphatic duet. Development of the Lymphatic Vessels. — The lymphatic system begins as a series of sacs at the points of junction of certain of the embryonic veins. These lymph spaces are developed from their first inception as independent perivenous mesenchymal intercellular clefts. The cells lining these spaces develop into a lymphatic intimal endothelium.' In the human embryo thp lymph sacs from which the lymphatic vessels are derived are six in number — two paired, the jugular and the caudal lymph sacs; and two unpaired, the retro- peritoneal and the cisterna chyli. In lower mammals an additional pair, subclavian, is present, but in the human embryo these are merely extensions of the jugular sacs. 'Cf. Huntington, Anatomical Record, vol. iv, No. 11, November, 1910, 49 770 THE VASCULAR SYSTEMS The position of the sacs is as follows: (1) jugular sac, at the junction of the subclavian vein with the primitive jugular; (2) caudal sac, at the junction of the iliac vein with the postcardi- nal; (3) retroperitoneal, in the position of the cross-branch between the renal veins; (4) cistema chyli, at the site of the cross-branch between the two iliac veins (Fig. 551). From the lymph sacs the lymphatic vessels bud out along fixed lines corresponding more or less closely to the course of the embryonic bloodvessels. Both in the body wall and in the wall of the intestine the deeper plexuses are the first to be developed; by continued growth of these the vessels in the superficial layers are gradually formed. By the confluence of peri-azygos lymphatic segments the thoracic duct is formed; this gains connection with the venous system at the site of the jugular lymph sac. At its connection with the cistema chyli it is at first double, but the right vessel soon joins with the left. All the lymph sacs except the cisterna chyli are, at a later stage, divided up by slender connective-tissue bridges and transformed into groups of lymph nodes. The lower portion of the cisterna chyli is similarly converted, but its upper portion remains as the receptaculum chyli. Ijeft innominate Jiigular lymph-sac Bight innominate Vena cava superior^ In ternaljugular External jugular. Duct of Cuvier Left •postcardirwl Prerenal part of vena cava inferior j; ^1^ Left capsular ' '^^\r°^ Left renal J Retroperitoneal Postrenal part of lymph-sac vena cava inferior ' Cistema chyli Caudal lymph-sac — ■ External iliac ~ Internal iliac Fig. 551. — Scheme showing relative positions of primary lymphatic sacs based on the description given by Florence Sabin. Applied Anatomy. — The lymphatic channels and nodes draining any infected area of the body are very liable to become infected, and do so with the production of acute or chronic lymph- angitis aud lijmphadenitis. In acute cases the paths of the superficial lymphatics are often marked out on the skin by the appearance over them of the four cardinal signs of inflammation — pain, redness, heat, and swelling — while the nodes swell and may suppurate. Chronic inflam- mation leads to growth and fibrosis of the lymphatics and the connective tissue around thepi; obstruction to the passage of the lymph results, as the fibrous tissue contracts and causes stenosis or obliteration of the lymphatic channels, and hard edema of the involved skin and subcutaneous tissue follows {pachydermia lymphangiectatica). Chronic lymphangitis, together with the blocking of numerous lymphatic vessels by the escaped ova of the minute parasitic worm Micro- filaria nocturna, is the cause of elephantiasis, a condition common in the tropics and subtropics, and characterized by enormous enlargement and thickening of the integument of some part of the body, most frequently the leg. Tubercular and syphilitic enlargements of the lymphatics and nodes are both very commonly met with. Primary tumors of the lymphatics are lymphan- gioma and endothelioma; the so-called "congenital cystic hygroma" of the neck, arm, trimk, or thigh is a cystic lymphangioma. .Primary tumors of the lymph nodes may be benign (lymph- adenoma, myxoma, chondroma) or malignant (lymphosarcoma); cancer is an extremely common secondary affection. In an operation for cancer it is not sufficient to cut wide of the growth and remove it; it is imperatively necessary to remove the lymph nodes which receive lymph from the diseased THE L YMPHATIC SYSTEM 771 area, and also, when possible, the lymphatic vessels between the cancer and the nodes. Nodes are diseased very early in cancer, long before they are palpably enlarged, and are usually infected by emboli of cancer cells. The rule is in any cancer, however recent, to regard the associated nodes as diseased, whether en- larged or not^ and to remove them thor- oughly, if possible, in one piece, with the interveuiiii; Iviiiph vessels and the area of primary malignant growth. THE THORACIC DUCT. The thoracic duct (ductus thorac- icus) (Fig. 552) conveys the great inass of lymph and chyle into the blood. It is the common trunk of all the lymphatic vessels of the body, excepting those of the right side of the head and neck, the right upper extremity, the right lung, right side of the heart, and part of the convex surface of the liver. In the adult it varies in length from 15 to 18 inches (38-45 cm.), and extends from the second lumbar vertebra to the root of the neck. It commences in the abdomen at a triangular or fusi- form dilatation, the receptaculum chyli, which is situated upon the front of the bodies of the first and of the second lumbar vertebra?, to the right side and behind the aorta, overlapped by the Tight crus of the Diaphragm. It enters the thorax through the aortic opening in the Diaphragm, lying to the right of the aorta, and is then placed in the posterior mediastinum between the aorta and vena azygos major. Here it lies in front of the vertebral column, from which it is separated by the right intercostal arteries, and by the azygos minor veins as they cross the middle line to open into the vena azygos major. Op- posite the fifth thoracic vertebra it inclines toward the left side, enters the superior mediastinum, and ascends behind the arch of the aorta on the left side of the oesophagus, and behind the first portion of the left sub- clavian artery, to the upper opening of the thorax. Opposite the seventh cer^'ical vertebra it turns outward in front of the vertebral artery and vein, behind the left common carotid artery and vagus nerve, and then curves downward over the subclavian artery and in front of the Scalenus anticus muscle and the phrenic nerve, so as to form an arch; it terminates in the angle of junction of the left Fig. 552. — The thoracic and right lymphatic ducts. 772 THE VASCULAR SYSTEMS subclavian artery and in front of tiie Scalenus anticus muscle and the phrenic- nerve, so as to form an arch; it terminates in the angle of junction of the left subclavian vein with the left internal jugular vein. It usually opens at the apex of the angle in the superior and outer surface, but may open on the posterior surface. Sometuiies it terminates by two or more branches. Figs. 552 and 554 show the termination of the thoracic duct. The thoracic duct, at its commence- ment, is about 2 to 3 mm. in diameter, diminishes considerably in its caliber in the middle of the thorax, and is again dilated just before its termination, the ampulla. It is generally flexuous in its course, the older the person the greater the flexuosity, and it is constricted at intervals so as to present a varicose appear- ance. The thoracic duct not infrequently divides in the middle of its course into two branches of unequal size, which soon reunite, or divides into several branches, which form a plexiform interlacement. It occasionally divides, at its upper part, into two vessels, of which the one on the left side terminates in the usual manner, while that on the right opens into the right subclavian vein, in connection with the right lymphatic duct. The thoracic duct has several valves throughout its whole course, but they are more numerous in the upper than in the lower part, and the lower valves are not competent; at its termination it is provided with a pair of competent valves, the free borders of which are turned toward the vein, so as to prevent the passage of venous blood into the duct. Fig. 553. — Modes of origin of the thoracic duct: a. Thoracic duct. a'. Receptaculum chyli. 6, c. Efferent trunks from lateral aortic nodes, d. An efferent passing through the left crus of the diaphragm, e, f. Lateral aortic nodes, g. Preaortic node. h. Retroaortic node. i. Common intestinal trunk, j. Descending tributary from intercostal lymphatics. (Poirier and Charpy.) The receptaculum chyli (cisterna chyli) (Figs. 552 and 553) receives the two lumbar lymphatic trunks, right and left, and the intestinal lymphatic trunk. The lumbar lymphatic trunks (trunci lumhales) are formed by the union of the efferent vessels from the lateral aortic lymph nodes. They receive the lymph from the lower limbs, from the walls and viscera of the pelvis, from the kidneys and suprarenal bodies, and the deep lymphatics of the greater part of the abdominal wall. The intestinal lymphatic trunk (truncus intestinalis) receives the lymph from the stomach and small intestine, from the pancreas and spleen, and from the lower and front part of the liver. Tributaries. — Opening into the commencement of the thoracic duct, on either side, is a descending trunk from the posterior intercostal nodes of the lower six or seven intercostal spaces. In the thorax the duct is joined, on either side, by a trunk which drains the upper lumbar nodes and pierces the crus of the Dia- phragm. It also receives the efferents from the posterior mediastinal nodes and from the posterior intercostal nodes of the upper six left spaces. In the neck it is joined by the left jugular, left siibclaman, and internal mammary trunks, and some- times by the left hronchoviediastinal trunk; the last named, howe^'er, usually opens independently into the junction of the left subclavian and internal jugular Aeins. THE RIGHT LYMPHATIC DUCT 112, Structure. — The thoracic duet is composed of three coats, which differ in some respects from those of the lymphatic vessels. The internal coat consists of a single layer of flattened endothelial cells; of a subendothelial layer, similar to I hut found in the arteries; and an elastic fibrous layer, the fibres of which run in a longituer, are situated upon the mastoid insertion of the Sternomastoid muscle. Their afferents drain the posterior part of the temporoparietal region, the upper part of the internal surface of the pinna, and the posterior surface of the external auditory canal ; their efferents pass to the upper deep cervical nodes. The parotid lymph nodes {lymphocjlandulae parotideae) (Figs. 556 and 557) are divided into three groups, superficial, deep, and the subparotid. THE LYMPH NODES OF THE HEAD AND FACE 775 The superficial parotid or preauricular lymph nodes {lymphoylandulae avricvlares anteriores) are situated between the parotid fascia and the parotid sahvary gland. DEEP CERVICAL- CHAIN 0 n\/?vw, 6 ^ Fig. 556. — General arrangen 1'^ of the head and neck. (Poirier and Charpy.) UBMAXILLARY NODE OF INTERNAL JUGULAR CHAIN Fig. 557. — The lymphatics of the neck. (Kuttner.) The deep parotid lymph nodes, from fifteen to twenty in number, are embedded in the substance of the parotid gland. The afferents of the superficial and deep 776 THE VASCULAR SYSTEMS parotid nodes drain the eyelids, eyebrows, the root of the nose, upper portion of the cheek, frontotemporal portion of the scalp, from the outer surface of the pinna, from the external auditory canal, and from the tympanum. Their efferents pass to the upper deep cervical nodes. The subparotid nodes lie beneath the parotid gland, on the lateral wall of the pharynx, and they are close to the internal carotid artery and the internal jugular vein. Their afferents drain the posterior part of the nasal fossa, nasopharynx, and Eustachian tube; their efferents pass to the upper deep cervical nodes. The facial nodes comprise three groups in the course of the afferents of the submaxillary nodes. (1) A maxillary, over the infraorbital region; (2) a buccal, upon the outer surface of the Buccinator where that muscle is pierced by the parotid duct; (3) a mandibular group, upon the outer surface of the mandible, at the anterior margin of the Masseter muscle, beneath the Platysma and in contact with the facial vessels. Their afferent vessels drain the eyelids, the conjunctiva, integument, and mucous membrane of the nose and cheek. Their efferents pass to both submaxillary and upper deep cervical nodes. The internal maxillary nodes (lymphoglandulae faciales profundae) are deeply placed beneath the ramus of the mandible on the outer surface of the External Fig, 558. — The retropharyngeal nodes. (Poirier and Charpy.) pterygoid, in relation with the internal maxillary artery. Their afferent vessels drain the temporal and zygomatic fossae and the nasopharynx; their efferents pass to the upper nodes of the deep cervical group and to the submaxillary nodes. The lingual nodes (lymqihoglandulae lingitales) are two or three small nodules lying on the Hyoglossus and under the Geniohyoglossus. They form merely nodal substations in the course of the lymphatic vessels of the tongue. The retropharyngeal nodes (Fig. 558) lie in the buccopharyngeal fascia, behind the upper part of the pharynx and in front of the arch of the atlas, being separated, however, from the latter by the Rectus capitis anticus major. Their afferents drain an extensive area, comprising the nasal fossae, the nasopharynx, and the Eustachian tube as far as the tympanum; their efferents pass to the upper nodes of the deep cervical group. The lymphatic vessels of the scalp are divisible into (a) those of the frontal region, which terminate in the parotid nodes; ih) those of the temporoparietal region, which end in the parotid and postauricular nodes; and (c) those of the THE LYMPH NODES OF THE HEAD AND FACE 777 occipital region, which terminate partly in the occipital nodes and partly in a trunk which runs down along the posterior border of the Sternomastoid to end in the lower group of deep cervical nodes. The lymphatic vessels of the pinna and external auditory meatus are also divisible into three groups: (a) an anterior, from the outer surface of the pinna and anterior wall of the canal to the parotid nodes; {h) a posterior, from the margin of the pinna, the upper part of its inner surface, the internal surface and posterior wall of the meatus to the postauricular and upper deep cervical nodes ; (c) an inferior, from the floor of the canal and from the lobule to the external jugular and upper deep cervical nodes. The lymphatic vessels of the face are more numerous than those of the scalp. Those from the eyelids and conjunctivae terminate partly in the submaxillary, but mainly in the parotid nodes. The vessels from the posterior part of the cheek also pass to the parotid nodes, while those of the anterior portion of the cheek, the side of the nose, the upper lip, and the lateral portions of the lower lip terminate in the submaxillary nodes. The deeper vessels from the temporal and zygomatic fossag pass to the internal maxillary and upper deep cervical nodes. The deeper vessels of the cheek and lips terminate, like the superficial, in the submaxillary nodes. Both superficial and deep vessels of the central part of the lower lip run to the suprahyoid nodes. The lymphatic vessels of the nasal fossae can be injected from the subdural and subarachnoid spaces. Those from the anterior parts of the fossae terminate in the submaxillary nodes; those from the posterior two-thirds of the fossae and from the communicating air sinuses pass partly to the retropharyngeal nodes and partly to the upper deep cervical nodes. The lymphatic vessels of the mouth terminate as follows: (a) Those of the gums terminate in tlie submaxillary nodes; (b) those of the hard palate terminate in the upper deep cervical and subparotid nodes; (c) those of the soft palate, in the retropharyngeal and upper deep cervical nodes; (d) those of the anterior part of the floor of the mouth pass through the submental and suprahyoid nodes to the upper deep cervical group; (e) those from the rest of the floor of the mouth ter- minate in the submaxillary and upper deep cervical nodes. The lymphatic vessels of the tongue (Fig. 559) are drained chiefly into the deep cervical nodes lying between the posterior belly of the Digastric and the posterior belly of the Omohyoid; one node situated at the bifurcation of the common carotid artery is so intimately associated with these vessels that it is known as the principal node of the tongue. The apical vessels of the tongue pass to the suprahyoid nodes and principal node of the tongue; the marginal vessels pass partly to the submaxillary and partly to the upper deep cervical nodes. The base of the tongue in the region of the circumvallate papillae is drained by vessels which terminate in the upper deep cervical nodes. The lymph nodes of the neck include the following groups: I. The Superficial Cervical, including — (a) External Jugular. (6) Anterior Cervical (superficial). (c) Submaxillary. (f^) Submental or Suprahyoid. II. The Deep Cervical, including — (a) Anterior Cervical (deep). (6) Retropharyngeal. (c) Sternomastoid. (d) Supraclavicular. The superficial cervical nodes {hjmphoriktndulaecervicalessiiperficialcs) (Fig. 557) are composed of two groups, the external jugular and the anterior cervical nodes. 778 THE VASCZILAM SYSTEMS The external jugular nodes (Figs. 557 and 560) are superficial to the Sterno- mastoid muscle. They are four to six in number and lie along the external jugular vein upon the outer surface of the deep cervical fascia, each node occupy- inc- a depression in the fascia. They are usually gathered in a group a little below the parotid gland, but sometimes extend to the middle of the vein. Their afferents drain the lower part of the pinna and parotid region, while their efferents pass around the anterior margin of the Sternomastoid and terminate in the upper deep cervical nodes. MARGINAL COL- LECTING TRUNKS TRUNKS OF ^ TRUNKS FROM r MARGIN OF J TONGUE Fig. 559.— The lymphatics of the tongue, lateral view. (Poirier and Charpy.) The submaxillary nodes (lympJioglandulae submaxillar es) (Figs. 556 and 557), three to sLx in number, are placed in the submaxillary triangle beneath the body of the mandible in the submaxillary triangle and rest on the superficial surface of the sheath of the submaxillary gland. One node (the middle gland of Stahr), which lies on the facial artery as it turns over the mandible, is the most constant of the series. Small lymph nodes are sometimes found on the deep surface of the submaxillary gland. Their afi'erents drain the inner canthus of the eye, the cheek, the side of the nose, the upper lip, the outer part of the lower lip, the gums, and the anterior part of the margin of the tongue; efferent vessels from the facial and suprahyoid nodes also enter the submaxillary nodes. Their efferent vessels pass to the upper nodes of the deep cervical group. THE LYMPH NODES OF THE HEAD AND FACE 779 The submental or suprahyoid nodes (Figs. 556 and 559) are usually two nodes situated between the anterior bellies of the two Digastric muscles and upon the IMylohyoid muscle. They receive lymph from the cutaneous surface of the ch.in, from the cutaneous and mucous surfaces of the central portion of the lower lip, from the central portion of the gums, from the floor of the mouth, and from the tip of the tongue. They send some vessels to the submaxillary lymph nodes, and frequently a node is interposed on the anterior belly of the Digastric muscle. They send other vessels to the upper deep cervical nodes. The anterior cervical nodes form an irregular and inconstant group on the front of the larynx and trachea. They may be divided into (a) a superficial set, placed on the anterior jugular vein; (6) a deeper set, which is further sub- divided into prelaryngeal, on the cricothyroid membrane, and pretracheal, on the front of the trachea. The superficial set receives lymph from the posterior auricular and occipital nodes; their efferents empty into the upper deep cervical nodes. The deeper set drains the lower part of the larynx, the thyroid body, and the upper part of the trachea; their efferents pass to the lower nodes of the upper deep cervical group. The retropharyngeal nodes have been described on page 776. MASTOID NODES , STERNOMA5TOID -i^NODE (extcmul If group) I. JUGULAR Fig. 560.— Deep cervical ch.ain. (Po The deep cervical nodes (lymphoglandulae cervicales profimdae) (Figs. 556 and 560) are nimaerous and of large size; they form a chain along the carotid sheath lying by the side of the pharynx, oesophagus, and trachea, and extending from the base of the skull to the root of the neck. They are usually described in two groups: (1) an upper or substemo mastoid group {lymphoglandulae cervi- cales profimdae superiores) lying under the Sternomastoid in close relation with the spinal accessory nerve and the internal jugular vein, some of the nodes lying in front of and others behind the vessel; (2) a lower or supraclavicular group (lympho- glandulae cervicales profundae inferiores) extending beyond the posterior margin of the Sternomastoid into the supraclavicular triangle, where they are closely related to the brachial plexus and subclavian vein. A few minute nodes are situated alongside the recurrent laryngeal nerves on the lateral aspects of the; trachea and oesophagus. The upper deep cervical nodes drain the occipital portion of the scalp, the pinna, and the back of die neck, the tongue, larynx, thyroid body, trachea, nasopharynx, nasal fossEe, palate, and oesophagus. They 780 THE VASCULAR SYSTEMS receive also the efferent vessels from all the other nodes of the head and neck, except those from the lower deep cervical group. The lower deep cervical nodes drain the back of the scalp and neck, the superficial pectoral region, part of the arm (see page 783), and occasionally part of the upper surface of the liver. In addition, they receive vessels from the upper group. The efferents of the upper deep cervical nodes pass partly to the lower group and pardy to a trunk which unites with the efferent trunk of the lower deep cervical nodes and forms the jugular trunk {truncus jugularis). This trunk, on the right side, ends in the junc- tion of the internal jugular and subclavian veins, while on the left side it joins the thoracic duct. The lymphatic vessels of the skin and muscles of the neck pass to the deep cervical nodes. From the upper part of the pharynx the lymphatic vessels pass to the retropharyngeal, from the lower part to the deep cervical nodes. From the larynx two sets of vessels arise, an upper and a lower. The vessels of the upper set pierce the thyrohyoid membrane and join the upper deep cervical nodes. Of the lower set, some pierce the cricothyroid membrane and join the pretracheal and prelaryngeal nodes; others run between the cricoid and first tracheal ring and enter the lower deep cervical nodes. The lymphatic vessels of the thyroid body consist of two sets, an upper, which accompanies the superior thyroid artery and enters the upper deep cervical nodes, and a lower, which runs partly to the pretracheal and partly to the small nodes which accompany the recurrent laryn- geal nerve. These latter nodes receive also the lymphatic vessels from the cervical portion of the trachea. Applied Anatomy. — The cervical nodes are very frequently the seat of tuberculous dis- ease. This condition is most usually set up by some lesion in those parts from which they receive their lymph. It is very desirable, therefore, that the surgeon, in dealing with these cases, possess a knowledge of the relation of the respective groups of nodes to the periphery, while in order to eradicate them by operation a long and difficult dissection may be required. Sir Frederick Treves prepared a table to show to what group lymph from each region is sent. The table is practically as follows: ■ i . i Sfo/p— Posterior part = suboccipital and mastoid nodes. Frontal and parietal portions = parotid nodes. Lymphatic vessels from the scalp also enter the superficial cervical set of nodes. Skin of face and neck = submaxillary, parotid, and superficial cervical nodes. External ear = superficial cervical nodes. Lower lip = submaxillary and suprahyoid nodes. Buccal cavity = submaxillary and upper set of deep cervical nodes. ■ Gums of lower jaw = suhmaniWavy nodes. Tongue — Anterior portion = suprahyoid and submaxillary nodes. Posterior portion = upper set of deep cervical nodes. Tonsils and palate = upper set of deep cervical nodes. Pharynx. — Upper part = parotid and retropharyngeal nodes. Lower part = upper set of deep cervical nodes. Larynx, orbit, and roof of mouth = upper set of deep cervical nodest Nasal fossce = retropharyngeal nodes, upper set of deep cervical nodes. Some lymphatic vessels from posterior part of the fossse enter the parotid nodes. Treves' table indicates the nodes usually involved, but the seat of primary disease cannot invariably be affirmed from a knowledge 'of the seat of glandular_ involvement, because the course of the lymphatic vessels is sometimes varied from that which usually maintains; for instance, in sorne cases lymphatics from the right side of the tongue pass to nodes in the left side of the neck. A retropharyngeal abscess begins laterad of the pharynx. It enlarges toward the centre rather than from it, because the Constrictors of the pharynx limit the outward progTcss of the pus. The nodes withiii the parotid salivary glands not unusually become tuberculous, and the surgeon may be led to believe that the salivary gland is the seat of primary disease. Sometimes, though seldom, after the extensive removal of lymph nodes the region drained by their tributaries' becomes the seat of persistent hard edema (lymph edema). It used to be thought that wounds of the thoracic duct were of necessity fatal, but it is now loiown that, unless close"to the vein, they are seldom even very dangerous. It may be possible to suture a partly divided duct. In an unsutured wound of the duct recovery follows if a collateral lymphatic circulation is established. THE LYMPH NODES OF THE UPPER EXTREMITY 781 THE LYMPHATICS OF THE UPPER EXTREMITY. The Lsrmph Nodes of the Upper Extremity. The lymph nodes of the upper extremity are divided into two sets, superficial and deep. Axillary nodes. X.,. ^i^- Fig. 561, — The superficial Iwiipbatics and nodes of the upper extremity. The superficial Ijonph nodes (Fig. 561) of the upper extremity are few in number and small in size. They lie in the subcutaneous tissue. They are not receiving depots of great areas, but interrupt lymphatic vessels here and there. The nodes in the axilla receive all of the lymphatic vessels, superficial and deep. There may be three sets of superficial nodes. One set, the antecubital nodes, lie in front of the elbow. These nodes are often absent. When these nodes are pres- ent they receive vessels from the anterior portion of the forearm and the middle 782 THE VASCULAR SYSTEMS of the palm. The vessels from them pass along the front and inner aspect of the arm. One or two superficial nodes lie above the internal condyle. This is the supratrochlear or epitrochlear group of nodes. There is usually but one node, but there may be two or more. It receives vessels from the three inner fingers, the inner portion of the hand, and the inner portion of the forearm, but, because of free anastomoses, also may receive lymph from any portion of the hand and fore- arm. Lymph vessels from the supratrochlear node pass up along the basilic vein to the axillary nodes. There are sometimes several small nodes along the cephalic vein in the groove between the Deltoid and the great Pectoral muscle. These are called infra- clavicular nodes, the efferents of which drain into the subclavian nodes. IN EXTERNAL GRO EXTE MAMMARY LYMPHATIC ENDING IN SUB- CLAVIAN NODES PECTORAL GROUP MAMMARY COL- LECTING TRUNKS CUTANEOUS COLLECTING TRUNK FROM THE THORACIC WALL LLECTING TRUNKS SSING TO INTERNAL AMMARY NODES Fig. 562. — Axillary nodes and lymphatics of the breast. (Poirier and Charpy.) The Deep Lyniph Nodes of the Upper Extremity or the Axillary Nodes (lymphoglandulae axillares) (Figs. 562 and 563). — The chief deep nodes are situ- ated adjacent to the axillary vessels. There are also a few small nodes along the radial, ulnar, and brachial arteries which receive deep lymphatics from bones, muscles, and ligaments, and send lymphatics to the axillary nodes. The axillary nodes number from fifteen to thirty-five in each axilla. They are embedded in the axillary fat and receive the lymphatic vessels from the upper extremity, from the skin of the upper portion of the thorax, from the Pectoral muscles, and from the mammary gland. They may be arranged in the following groups: (1) An external group, the humeral chain, lying on the inner surface of the vessels and nerves, particularly the axillary vein, to the sheath of which they are adherent. Occasionally one or several of these nodes are found beneath the vein. Some of the vessels from these nodes pass into the central group of lymph nodes; others enter the subclavian nodes; others pass above the clavicle and terminate in nodes situated in that region. (2) An anterior or pectoral group (lymphoglaiididae pectorales), situated along the lower border of the Pectoralis minor and in relation THE L YMPH NODES OF THE UPPER EXTREMITY 783 with the long thoracic artery. The afierents of this group drain the skin and muscles of the pectoral and subaxillary regions of the thorax and part of the mammary gland; their eft'erents pass to the central and subclavicular nodes. (3) A posterior group, the subscapular chain, lying along the subscapular artery. Their afferents drain the skin and muscles of the lower part of the neck and of the posterior thoracic wall; their ett'erents pass to the central axillary group of nodes. (4) A central or intermediate group of three or four large nodes situated in the adi- pose tissue near the base of the axilla, their afferents draining all the preceding groups of axillary nodes; their efferent vessels end in the subclavicular nodes. The nodes of the central group in many individuals protrude through the opening in the axillary fascia known as the foramen of Langer. (5) A subclavian group, situated behind the upper margin of the Pectoralis minor. From the axillary nodes come many vessels which, by anastomosing, form the infraclavicular plexus; they then unite into a trunk, the subclavian trunk {truncus subclavius), which courses between the subclavian vein and Subclavius muscle. On the right side it empties into the junction of the internal jugular and subclavian vein or unites with the jugular trunk to form the right lymphatic duct. On the left side it may empty into the venous junction or into the thoracic duct. PECTORAL GROUP Fig. 563. — Scheme of the axillary nodes. The dotted line indicates the position of the clavicle. The Lymphatic Vessels of the Upper Extremity (Figs. 561, 564). The lymphatic vessels of the upper extremity are divided into the superficial and the deep. The superficial lymphatic vessels of the upper extremity begin as plexuses in the skin and form vessels which ascend in the subcutaneous tissue. These plexuses are particularly plentiful in the palm and palmar surface of the digits (Fig. 564). On each side of each finger two lymph vessels are formed; they ascend toward the hand, cross the dorsum, and anastomose frecjnently with each other. The vessels from the dorsum of the hand join the lymph vessels of the forearm, which ascend chiefly along the superficial veins. The lymph vessels which ascend with the superficial ulnar vein pass into the supratrochlear node. The vessels which accompany the median veins pass into the antecubital or supratrochlear nodes. Some of the lymph vessels on the radial side of the fore- arm run up along the cephalic vein and terminate in the infracla^'icular nodes. All the other lymph vessels of the upper extremity pass direct to the axillary 784 THE VASCULAR SYSTEMS nodes. In the forearm there are about thirty vessels, in the middle of the arm there are from fifteen to eighteen (Sappey). The deep lymphatic vessels of the upper extremity convey the lymph from bone, periosteum, muscle, ligament, etc. They pass up the limb with the chief vessels, there usually being two trunks to each artery. In the arm there are two or three vessels. Some few vessels terminate in the small nodes along the radial, ulnar, and brach- ial arteries, but most of them pass directly to the axillary nodes. Applied Anatomy. — In malignant diseases, or other affections implicating the upper part of the back and shoulder, the front of the thorax and mammae, the upper part of the front and side of the abdomen, or the hand, forearm, or arm, the axillary nodes are liable to be found enlarged. In secondary syphilis 'the supratroch- lear node is found to be enlarged. This node is subcutaneous and readily palpa- ble against the subjacent bone when enlarged. Normal axillary nodes cannot be palpated. The axilla is a passage- way for structures between the neck or thorax and the upper extremity, and purulent collections or tumors may extend from the neck or thorax into the axilla or from the axiUa into the neck or thorax. The axillary nodes are involved early in cases of cancer of the mammary gland, and later the lower deep cervical nodes are involved, and, as Snow has pointed out, regurgitation of lymph containing cancer cells leads to retrosternal involve- ment and to secondary cancer of the head of the humerus. In operating for cancer of the breast, follow the principle of Hal- sted and remove the breast, the skin over it, the muscles and fascia, the lymph vessels, and the axillary nodes in one piece. By this plan thorough removal is possible, and as lymph vessels containing carcinoma cells are not cut across, the wound is not grafted with malignant epithelial cells. Diseased axillary nodes are apt to adhere to the sheath of the vein. In removing cancerous nodes always excise the sheath of the vein. Fig. 564.- -Lymphatic vessels of the dorsal surface of the hand. (Sappey.) THE LYMPHATICS OF THE LOWER EXTREMITY. The Lymph Nodes of the Lower Extremity. The lymph nodes of the lower extremity consist of the anterior tibial node and the popliteal and inguinal nodes, all deeply situated. The anterior tibial node (lynrphoc/Iandida tibialis anterior) is small and lies on the interosseous membrane in relation to the upper part of the anterior tibial vessels, and constitutes a substation in the course of the anterior tibial lymphatic trunks. Its efferents cross to the inner side of the leg just below the knee and pass to the superficial inguinal nodes. The popliteal nodes (lymphoglandulae popliteae), small in size and some six or seven in number, are embedded in the fat contained in the popliteal space. 'THE LYMPH NODES OF THE LOWER EXTREMITY 785 One lies immediately beneath the popliteal fascia, near the terminal part of the external saphenous vein, and drains the region from which this vein derives its tributaries. Another is placed between the popliteal artery and the posterior ligament of the knee; it receives the lymphatic vessels from the knee-joint together with those which accompany the articular arteries. The others lie at the sides of the popliteal vessels, and receive as afferents the trunks which accompany the anterior and posterior tibial vessels. The efferents of the pop- liteal nodes pass almost entirely alongside of the femoral vessels to the deep inguinal nodes, but a few may accompany the internal saphenous vein, and end in the nodes of the superficial inguinal group. The inguinal nodes vary from twelve to twenty in number and are arranged in two groups, superficial and deep. Fig. 565. — Nodes of the inguinal region with the afferent and some of the efferent lymphatics. (Poirier and Charpy.) The superficial inguinal lymph nodes (Figs. 565 and 566), placed immediately beneath the superficial fascia in Scarpa's triangle, are of large size, and vary in number from ten to twenty. It is customary to divide these nodes into groups according to the region in which they are found. A horizontal line carried through the saphenous opening divides the nodes into two groups, a superior group and an inferior group. The nodes of the superior group (lymphoglandulae ingumales) form a chain immediately below Poupart's ligament. They ^ecei^'e as afferents lymphatic vessels from the integument of the penis, scrotum, perineum, buttock, and lower abdominal wall. The nodes of the inferior group (lymphoglandulae suhinguinales) are placed on either side of the upper part of the saphenous vein, and receive as afferents the lymphatic vessels of the lower extremity and also some lymphatics from the penis, scrotum, clitoris, labia, perineum, and buttock. 50 786 THE VASCULAR SYSTEMS Fig. 566. — The superficial lymphatics and nodet of the lower extremity. The deep inguinal nodes (lymphoglan- dulae suhinc/uinales profundae) (Fig. 565) vary from one to three in number, and are placed under the fascia lata, on the inner side of the femoral vein. When three are present, the lowest is situated just below the junction of the internal saphenous and femoral veins, the middle in the femoral (crural) canal, and the highest in the outer part of the femoral ring. The middle is the most incon- stant of the three, but tlie highest one, tlie node of Cloquet, or Rosenmiiller, is also frequently absent. They receive as afferents the deep lymphatic trunks which accompany the femoral vessels, the lymphatics from the glans penis or glans clitoridis, and also some efferents from the superficial inguinal nodes. Applied Anatomy. — Inflammation and sup- puration of the popliteal nodes are most com- monly due to a sore on the outer side of the heel. The inguinal nodes frequently become en- larged in diseases implicating the parts from which their lymphatics originate. Thus, in malignant or syphilitic affections of the prepuce and penis, or labia majora, in cancer scroti, in abscess in the perineum, or in similar diseases affecting the integument and superficial struc- tures in those parts, or the subumbilical part of the abdominal wall, or the gluteal region, the upper chain of nodes is almost invariably enlarged, the lower chain being implicated in diseases affecting the lower limb. The Lymphatic Vessels of the Lower Extremity. The lymphatic vessels of the lower extremity consist of two sets, superficial and deep, and in their distribution corre- spond closely with the veins. The superficial lymphatic vessels of the lower extremity are placed beneath the integument in the superficial fascia, and are divisible into three sets — trunks which follow the course of the internal saphenous vein, trunks which accompany the external saphenous, and trunks from the gluteal region. (1) Trunks which fol- low the course of the internal saphenous vein arise from a plexus on the dorsum of the foot, which plexus obtains lym- phatics from all the toes, the sole, and both THE LYMPHATICS OF THE PELVIS AND ABDOMEN 787 borders of the foot. The internal trunks, three or four in number, pass to the superficial inguinal nodes. The external trunks run upward and inward and end in the internal trunks. (2) The trunks which follow the external saphenous vein numlter two or three, and they take origin from the heel and from the posterior half of the outer edge of the foot. They empty into the superficial inguinal nodes. (3) The lymph trunks from the gluteal region join vessels from the anus a-nd enter the superficial inguinal nodes. The deep lymphatic vessels of the lower extremity are few in number, and accompany tiie deep bloodvessels. In the leg they consist of three sets, the anterior tibial, peroneal, and posterior tibial, which accompany the corresponding blood- vessels, two or three to each artery; they ascend with the bloodvessels and enter the lymph nodes in the popliteal space; the efferent vessels from these nodes accompany the femoral vein and join the deep inguinal nodes; from these nodes vessels pass beneath Poupart's ligament and communicate with the chain. of nodes surrounding the external iliac vessels. The deep lymphatic vessels of the gluteal and sciatic regions follow the course of the bloodvessels, and join the gluteal and sciatic nodes at the great sacrosciatic foramen. THE LYMPHATICS OF THE PELVIS AND ABDOMEN. The lymphatics of the pelvis and abdomen may be divided from their situation into (a) parietal, lying retroperitoneally and in close association with the larger bloodvessels; and (6) visceral, which are found in relation to the visceral arteries. The parietal nodes (Fig. 567) include the following groups: External iliac. ( Lateral aortic. Internal iliac. Lumbar < Preaortic. Common iliac. ( Retroaortic. The external iliac nodes form three chains around the external iliac vessels. An external chain of three or four nodes lies between the artery and the Psoas muscle. A middle chain of three nodes lies upon the front surface of the external iliac vein. An internal chain of three or four nodes is placed to the inner side of the external iliac vein. An obturator node belongs to the inner chain of external iliac nodes. The external iliac nodes receive vessels from the superficial and deep inguinal nodes, from the glans penis or glans clitoris, deep lymphatics from the umbilicus and lower part of the belly wall, vessels from the superior portion of the vagina, the uterine cervix, the prostate gland, the bladder, the membranous portion of the urethra, and the internal iliac nodes, and the obturator node receives deep lymph vessels from along the course of the obturator vessels. The external iliac nodes send vessels direct to the common iliac nodes and also lymphatics to join vessels from the internal iliac nodes on their way to the comnoon iliac group. The nodes along the epigastric artery and those along the deep circumflex iliac artery are accessory chains to the main group of external iliac nodes. The internal iliac or hypogastric nodes (lymphoglandulae hypogasfricae) sur- round the internal iliac vessels, and receive the lymphatics corresponding to the distribution of the branches of the internal iliac artery; ?'. e., lymphatics from all the pelvic viscera, from the deeper parts of the perineum including the mem- branous and penile portions of the urethra, from the deep tissues of the posterior portion of the thigh, and from the buttocks. Their efferents pass to the common iliac nodes and also to the external iliac nodes. 788 THE VASCULAR SYSTEMS The sacral nodes belong to this group, but are placed in the concavity of the sacrum; they receive lymphatics from the rectum and posterior wall of the pelvis. The common iliac nodes are found about the common iliac artery and are divided into an external group, which lies upon the inner edge of the Psoas muscle; a middle group, behind the artery, and an internal group, which lies upon the front of the body of the fifth lumbar vertebra or upon the sacrovertebral articulation. They receive vessels from the external and internal iliac nodes and their efferents pass to the lateral aortic nodes. ,-r PHOMONTORV n COMMON ILIAC 1 , (external cliain) / l/>,/r,t, -COMMON ILIAC -EXTERNAL ILIAC _EXTfHNAL ILIAC (middle chain) OBTURATOR NERVE OBTURATOR . ARTERY Fig. 567. — Iliopelvic lymph nodes. (Po The lumbar nodes (lympJioglandulae lumbales) are very numerous, and consist of right and left lateral aortic, preaortic, and retroaortic groups. The right lateral aortic nodes are situated partly in front of the inferior vena cava, near the termination of the renal vein, and partly behind it on the origin of the Psoas, and on the right crus of the Diaphragm. The left lateral aortic nodes form a chain on the left side of the abdominal aorta in front of the origin of the Psoas and left crus of the Diaphragm. The nodes on either side receive (o) the efferents of the common iliac nodes; (6) the lymphatics from the testicle in the male and from the ovary. Fallopian tube, and body of the uterus in the female; (c) the lymphatics from the kidney and suprarenal body; and (d) the THE LYMPHATIC VESSELS OF THE ABDOMEN AND PELVIS 789 lymphatics draining the lateral abdominal muscles and accompanying tlie luml)ar veins. Most of the efferent vessels of the lateral aortic nodes converge to form the right and left lumbar trunks (trunci lumbales) which join the receptaculum chyli, but some enter the preaortic and retroaortic nodes, and others pierce the crura of the Diaphragm to join the lower end of the thoracic duct. The preaortic nodes lie in front of the aorta, and may be divided into celiac, superior mesenteric, and inferior mesenteric groups, arranged around the origins of the corresponding RNAL ILIAC * j- INTERNAL ILIAC SATELLITE TRUNK OF INTERNAL PUDIC VESSELS L VESSELS 7^ PROSTATIC COL- LECTING TRUNK Fig. 568. — The iliopelvic nodes (lateral view). (Poirier and Charpy.) arteries. They receive a few vessels from the lateral aortic nodes, but their principal afferents are derived from the viscera supplied by the 'three arteries with which they are associated. Some of their efl'erents pass to the retroaortic nodes, but the majority unite to form a common trunk, the truncus intestinalis, which enters the receptaculum chyli. The retroaortic nodes are placed below the receptaculum chyli, on the bodies of the third and fourth lumbar vetebrie. They receive lymphatic trunks from the lateral and preaortic nodes, while their efferents terminate in the receptaculum chyli. The Lymphatic Vessels of the Abdomen and Pelvis. The lymphatic vessels of the walls of the abdomen and pelvis may be divided into two sets, superficial and deep. The superficial vessels follow the course of the superficial bloodvessels and converge to the upper group of the superficial inguinal nodes. Those derived from the integument of the front of the abdomen below the umbilicus follow 790 - THE VASCULAB SYSTEMS the course of the superficial epigastric vessels, and those from the sides of the lum- bar part of the abdominal wall pass along the crest of the ilium, with the super- ficial circumflex iliac vessels. The superficial lymphatic vessels of the gluteal region turn horizontally round the outer side of the buttock, and join the super- ficial inguinal nodes. The deep vessels run alongside the principal bloodvessels. Those of the parietes of the pelvis, which accompany the gluteal, sciatic, and obturator vessels, follow the course of the internal iliac artery, and ultimately join the lateral aortic nodes. Lymphatic Vessels of the Perineum and External Genitals. — The lymphatic vessels of the perineum and of the integument of the penis, and of the scrotum (or vulva), follow the course of the external pudic vessels, and terminate in the superficial inguinal nodes. Those of the glans penis (or glans clitoridis) termi- nate partly in the deep inguinal nodes and partly in the external iliac nodes. The visceral nodes are associated with the branches of the coeliac axis, superior and inferior mesenteric arteries. Those related to the branches of the coeliac axis artery form three chains, gastric, hepatic, and splenic, which accom- pany the corresponding branches of the artery. The nodes of the gastric chain (lymphoglandtdae gastricae swperiores) are divisible into three groups— viz. : (a) upper gastric, on the stem of the artery; (h) lower gastric, accompanying the descending branches of the artery along the cardiac half of the lesser curvature of the stomach, between the two layers of the small omentum; and (c) paracardial, "outlying members of the coronary chain, disposed in a manner comparable to a chain of beads around the neck of the stomach" (Jamieson and Dobson*). The nodes of the gastric chain receive their aflerents from the lesser curvature and contiguous surfaces of the stomach; their eflerents pass to the coeliac group of preaortic nodes. The nodes of the hepatic chain (lymfJioglandulae hepaticae) (Fig. 574) consist of the following groups: (a) hepatic, on the stem of the hepatic artery and along the common bile duct, between the two layers of the gastrohepatic omentum as far as the transverse fissure of the liver; the cystic node, a member of. this group, is placed near the neck of the gall-bladder; (6) subpyloric, four or five in number, at the bifurcation of the gastroduodenal artery at the angle between the first and second parts of the duodenum; (c) one or two retropyloric nodes along the pyloric artery; (cl) right gastroepiploic (lymphoglavdvlae gastricae infer lores), four to seven in number, between the two layers of the greater omentum, along the pyloric half of the greater curvature of the stomach. The nodes of the hepatic chain receive afferents from the pyloric portion of the stomach, duodenum, liver, gall-bladder, and the head of the pancreas; their efPerents pass to the coeliac group of preaortic nodes. - The splenic nodes {lymphoglandidae pancreaticolienales) accompany the splenic artery and are situated in relation to the dorsal surface and upper border of the pancreas and in the lienorenal ligament. Their afferents are derived from the fundus of the stomach, from the spleen, and from the pancreas; their efferents pass to the coeliac group of preaortic nodes. The superior mesenteric nodes comprise three groups — mesenteric, ileocolic, and mesocolic. The mesenteric nodes (lymphoglamhdae mesenfericae) (Fig. 572) lie between the layers of the mesentery, and vary from one hundred to one hundred and fifty in number. One set is situated close to the wall of the small intestine, among the terminal twigs of the superior mesenteric artery; a second is in relation with the 1 Lancet, April 20 to 27, 1907. THE LYMPHATIC VESSELS OF THE ABDOMEN AND PELVIS 791 loops and primary branches of the vessel; while a third set of larger nodes lies along the trunk of the artery. Applied Anatomy. — Enlargement of the mesenteric lymph nodes is seen in most diseased conditions of the intestinal tract, and is well marked in enteric fever, tuberculous ulceration or malignant growths of the bowel. The enlarged nodes can often be palpated through the wall of the abdomen. The ileocolic nodes (Fig. 573), from ten to twenty in number, form a chain around the ileocolic artery, but show a tendency to subdivision into two groups, one near the duodenum and another on the lower part of the trunk of the artery. Where the vessel divides into its terminal branches the chain is broken up into sev- eral groups — viz. : (a) ileal, in relation to the ileal branch of the artery; (&) anterior ileocolic, usually of three or more nodes, in the ileocolic fold, near the wall of the Fig. 569. — Lymphatics of cot cecum; (c) posterior ileocolic, mostly placed in the angle between the ileum and the colon, but partly lying behind the cecum at its junction with the ascending colon; (d) appendicular, usually a single node, between the layers of the meso- appendix, near its free edge; (e) right colic, along the inner side of the ascending colon. The mesocoUc nodes are numerous, and lie between the layers of the transverse mesocolon, in close relation to the transverse colon; they are best developed in the neighborhood of the hepatic and splenic flexures. One or two small nodes are occasionally seen along the trunk of the right colic artery, and others are found in relation to the trunk and branches of the middle colic artery. The superior mesenteric nodes receive afferents from the jejunum, ileum, cecum, appendix, and the ascending and transverse parts of the colon; their efferents pass to the superior mesenteric nodes. The inferior mesenteric nodes (Fig. 569) consist of: («) Small nodes on the branches of the left colic and sigmoid arteries; (6) a group in the pelvic mescolon 792 THE VASCULAR SYSTEMS around the superior hemorrhoidal artery; and (c) a pararectal group in contact with the muscle coat of the rectum. Their afFerents drain the descending colon, sigmoid flexure, and upper portion of the rectum; their efFerents pass to the inferior mesenteric nodes. SUBPYLORI NODE /^ "M_J Fig. 570. — General view of the subperitoneal lymphatic plexus of the stomach prepared by the nicthod of Gerota. (Cun^o.) The Lymphatic Vessels of the Abdominal and Pelvic Viscera, These consist of: (1) Those of the subdiaphragmatic portion of the alimentary canal and its associated glands, the liver and pancreas; (2) those of the spleen and suprarenal bodies; (3) those of the urinary organs; (4) those of the repro- ductive organs. 1. The lymphatic vessels of the subdiaphragmatic portion of the alimentary canal are situated partly in the mucosa and partly in the seromuscular coats, but as the former system drains into the latter, the two may be considered as one. The lymphatic vessels of the stomach (Fig. 570) are continuous at the cardiac end with those of the oesophagus, and at the pyloric end with those of the duo- denum. They mainly follow the bloodvessels, and may be arranged in four sets. Those of the first set accompany the branches of the gastric artery, receiving tributaries from a large area on either surface of the stomach, and terminate in the nodes of the gastric chain. Those of the second set drain the fundus of the stomach, draining the area supplied by the vasa brevia and left gastroepiploic arteries, and ending in the splenic nodes. The vessels of the third set drain L Y3IPHA TIC VESSELS OF ABDOMINAL AND PEL VIC VISCERA 793 the right portion of the greater curvature and end in the right gastroepiploic nodes, the eft'erents of which pass to the subpyloric group. Those of tlie fourth set drain the pyloric canal and pass to the hepatic and subpyloric nodes, and, in part, also to the coronary chain, thence to the coeliac group. RIGHT GASTnO-EPIPLOIC CURRENT Fig. 571. — Lymphatic of the stomach, (Cundo.) Applied Anatomy. — Mikulicz pointed out the early infection of the nodes of the lesser curva- ture in pyloric cancer, and insisted that in operation for pyloric cancer the entire lesser curvature must be removed. Cuneo showed that in pyloric cancer the fundus and two-thirds of the greater curvature usually remain free from disease, because the lymph current is toward the pylorus and not from it. Of course, if the lymphatics become blocked, the lymph current may be reversed (regurgitation), and then infection of these parts can occur. William J. Mayo has noted the "lymphatic isolation" of the dome of the stomach. In operating for cancer of the pylorus, make the section of the stomach as directed by Hartmann, that is, a section which removes all of the lesser curvature and cuts the greater curvature well to the left of the subpyloric nodes. Fig. 572. — Lymphatics of the small intestine, (Poirier and Charpy.) The lymphatic vessels of the duodenum consist of an anterior and a pos- terior set which open into a series of small pancreaticoduodenal nodes on the anterior and posterior aspects of the groove between the head of the pancreas and the duodenum. The efferents from these nodes run in two directions, upward to the hepatic nodes and downward to the superior mesenteric nodes. The lymphatic vessels of the small intestine (Fig. 572) are called lacteals, from the milk-white fluid thev usually contain. Thev take origin in the intestinal 794 THE VASCULAR SYSTEMS villi and in lymphatic sinuses around the bases of the solitary nodules. Lymphatic plexuses exist in the submucous tissue, the muscular coat, and the subserous tissue. The lymphatic vessels pass between the layers of the mesentery, enter the mesenteric nodes, and finally unite to form two or three large trunks which terminate separately in the receptaculum chyli; frequently, however, they unite to form a single large trunk, termed the intestinal lymphatic trunk (Figs. 553 and 576). The lymphatic vessels of the large intestine consist of three sets — those of the cecum, ascending and transverse colon, which, after passing through their proper nodes, enter the mesenteric nodes; those of the descending colon and sigmoid flexure, which pass to the lumbar nodes, and those of the rectum and anus, which pass to the sacral and superficial inguinal nodes. Fig. 573. — Ventral The lymphatic vessels of the anus and rectum take origin from two net- works, one from the skin and mucous membrane and the other from the mus- cular coat. The lymph vessels from the skin at the anal margin pass to the super- ficial inguinal nodes. Some vessels from the skin of the anus ascend and reach the submucous plexus of the rectum, from which region lymph vessels pass to the pararectal nodes, to the nodes along the middle hemorrhoidal artery, and along the inferior hemorrhoidal artery, and to a pelvic node near the origin of the internal pudic artery. The efferents from these nodes terminate in the inferior mesenteric nodes. The lymphatic vessels of the liver are divisible into two sets, superficial and deep. The former arise in the subperitoneal areolar tissue over the entire sur- face of the organ, and may be grouped into (a) those on the convex surface, (b) those on the inferior surface. (a) On the convex surface. The vessels from the back part of this surface reach their terminal nodes by three different routes; the vessels of the middle set, five or six in number, pass through the canal opening in the Diaphragm and end in one or two nodes which are situated around the terminal part of the inferior vena cava; a few vessels from the left side pass backward toward L YMPHA TIC VESSELS OF A BD OMINA L A ND PEL VIC VISCERA 795 the oesophageal opening, and terminate in the paracardial nodes of the gastric chain; the vessels from the right side, one or two in number, run on the abdominal surface of the Diaphragm, and, after crossing its right cms, terminate in the coeliac nodes {lymphoglandulae codiacae). From the portions of the right and left lobes adjacent to the falciform ligament, the lymphatic vessels converge to form two trunks, one of which accompanies the inferior vena cava through the Diaphragm, and ends in the nodes around the terminal part of this vessel ; the other runs downward and forward, and, turning around the anterior sharp margin of the liver, accompanies the upper part of the ligamentum teres, and ends in the upper hepatic nodes. From the anterior surface a few additional vessels turn around the anterior sharp margin to reach the upper hepatic nodes. Some of the lymph of the upper part of the li^ver traverses the Diaphragm along several lymphatic vessels which drain into the anterior diaphragmatic nodes on the superior surface of the Diaphragm, just behind the ensiform cartilage and also LEFT LATERAL Fig. 574. — Lymphatics of the inferior surface of the liver. (Sappey.) near the termination of the inferior vena cava, and some to the middle diaphragm- atic, some to the posterior mediastinal groups. The efferents from the anterior diaphragmatic nodes pass to the internal mammary chain, a fact which may ex- plain the involvement of the supraclavicular nodes, particularly of the left side,^ secondary to an abdominal carcinoma. Q>) On the inferior surface. The vessels from this surface mostly converge to the transverse fissure, and accompany the deep lymphatics emerging from this fissure to the hepatic nodes; one or two from the posterior parts of the right and Spigelian lobes accompany the inferior vena cava through the Diaphragm, and end in the nodes around the terminal part of this vein. The deep lymphatics of the li'S'er converge to ascending and descending trunks. The ascending tnniks accompany the hepatic veins and pass through the Dia- phragm to end in the nodes around the terminal part of the inferior vena cava. The descending trunks emerge from the transverse fissure, and end in the hepatic nodes. The lymphatic vessels of the gall-bladder pass to the hepatic nodes in the * Osier, Principles and Practice of Medicine, 7th edition, 1909, page 4S5. 796 THE VASCULAR SYSTEMS transverse fissure of the liver; those of the common bile duct to the hepatic nodes along the duct and into the upper pancreaticoduodenal nodes. The lymphatic vessels of the pancreas arise from a network about the pan- creatic lobules. The collecting trunks anastomose freely among themselves and with the lymphatics of the duodenum, spleen, and in the mesentery and meso- colon ;i some end in the pancreaticoduodenal nodes, and others in the superior mesenteric nodes. 2. The lymphatics of the spleen and suprarenal glands. The lymphatic vessels of the spleen, both superficial and deep, pass to the splenic nodes in the lienorenal ligament and along the superior border of the pancreas. The lymphatic vessels of the suprarenal glands usually accompany the supra- renal veins, and end in the lateral aortic nodes; occasionally some of them pierce the crura of the Diaphragm and terminate in the nodes of the posterior medi- astinum. 3. The lymphatic vessels of the urinary organs. The lymphatic vessels of the kidney form three plexuses — one in the substance of the kidney, a second beneath its fibrous capsule, and a third in the perinephric fat; the second and third communicate freely with each other. The vessels from the plexus in the kidney substance converge to form four or five trunks which issue at the hilum. Here they are joined by vessels from the plexus under the capsule, and, following the course of the renal vein, end in the lateral aortic nodes. The perinephric plexus is drained directly into the upper lateral aortic nodes. The lymphatic vessels of the ureter run in different directions. Those from its upper portion end partly in the efferent vessels of the kidney and partly in the lateral aortic nodes; those from the portion immediately above the pelvic brim are drained into the common iliac nodes; while the vessels from the intrapelvic portion of the tube join the eft'erents from the bladder, or terminate in the internal iliac nodes. The lymphatic vessels of the bladder (Fig. 575) originate in two plexuses, an intramuscular and an extramuscular, it being generally admitted that the mucous membrane is devoid of lymphatics.^ The efferent vessels are arranged in two groups, one from the anterior and another from the posterior surface of the bladder. The vessels from the anterior surface pass to the external iliac nodes, but in their course minute nodes are situated. These minute nodes are arranged in two groups, an anterior vesical group, in front of the bladder, and a lateral vesical, in relation to the hypogastric artery. The vessels from the posterior surface pass to the internal, external, and common iliac nodes; those draining the upper part of this surface traverse the lateral vesical nodes. The lymphatic vessels of the prostate (Fig. 575) terminate chiefly in the internal iliac and sacral nodes, but one trunk from the posterior surface ends in the external iliac nodes, and another from the anterior surface joins the vessels which drain the membranous part of the urethra. Lymphatic Vessels of the Urethra. — The lymphatics of the fenile portion of the urethra accompany those of the glans penis, and terminate with them in the deep inguinal and external iliac nodes. Those of the membranous and prostatic portions, and those of the whole urethra in the female, pass to the internal iliac nodes. 4. The lymphatic vessels of the reproductive organs. The lymphatic vessels of the testes consist of two sets, superficial and deep, the former commencing on the surface of the tunica vaginalis, the latter in the epididymis and body of the testis. They form several large trunks which ascend ' p. Bartels, Ueber die Lymphgetasse des Pankreas, Arohiv f. Anat, u. Physiol., 1907. - Some authorities maintain that a plexus of lymphatic vessels does exist in the mucous membrane of tli^ bladder (consult Medecine op^ratoire des Voies urinaires, par J. Albarran, Paris. 1909). LYMPHATIC VESSELS OF ABDOMINAL AND PELVIC VISCERA 797 with the spermatic cord, and, accompanying the spermatic vessels into the abdo- men, terminate in the lateral aortic nodes. The lymphatic vessels of the vas deferens pass to the external iliac nodes; those of the vesiculae seminales partly to the internal and partly to the external iliac nodes. P'''''"t'\;lllV^il", Node in front of sacral promontory \ \\ External iliac \ ' \ ' node External iliac nodes Vessd draining into external iliac nodes lymph nodes Vessels draining into node on sacral promontory ^ Vessels draining into node on sacral promontory Middle hemor- rhoidal node Middle hemor- rhoidal lymphatic Fig 575 — Lymphatics of the prostate. (Cuneo and Ma The lymphatic vessels of the ovary are similar to those of the testicle, and ascend with the ovarian artery to the lateral aortic nodes. The lymphatic vessels of the Fallopian tube pass partly with those of the ovary and partly with those of the uterus. The lymphatic vessels of the uterus (Fig. 1149) consist of two sets, superficial and deep, the former being placed beneath the peritoneum, the latter in the sub- stance of the organ. The lymphatics of the cervix uteri run in three directions — transversely to the external iliac nodes, postero-Jaterally to the internal iliac nodes, and posteriorly to the common iliac nodes. The majority of the vessels of the body and fundus of the uterus pass outward in the broad ligaments, and are con- tinued up with the ovarian vessels to the lateral aortic nodes; a few, however, run to the external iliac nodes, and one or two to the superficial inguinal nodes. In the unimpregnated uterus the lymphatic vessels are very small, but during gestation are greatly enlarged. The l3Tnphatic vessels of the vagina extend in three directions — those of the upper part to the external iliac nodes, those of the middle part to the internal iliac nodes, and those of the lower part to the common iliac nodes. On the course of those from the middle and lower parts small nodes are situated. Some lymphatics from the lower part of the vagina join those of the vulva and pass to the superficial inguinal nodes. The lymphatics of the vagina anastomose with those of the cervix uteri, vulva, and rectimi, but not with those of the bladder. 798 THE VASCULAB SYSTEMS THE LYMPHATICS OF THE THORAX. The lymph nodes of the thorax may be divided into parietal and visceral — the former being situated in the thoracic wail, the latter in relation to the viscera. The parietal Isrmph nodes include the internal mammary, intercostal, and diaphragmatic nodes. 1. The internal mammary nodes are placed at the anterior extremities of the intercostal spaces, by the side of the internal mammary artery. They derive aft'erents from the mammary gland, from the deeper structures of the anterior abdominal wall above the level of the umbilicus, from the upper surface of the liver through a small group of nodes which lie behind the ensiform cartilage, and from the deeper parts of the anterior portion of the thoracic wall. Their efferents usually unite to form a single trunk on either side; this may open directly into the junction of the internal jugular and subclavian veins, or that of the right side may join the right subclavian trunk and that of the left the thoracic duct. 2. The intercostal nodes (lymphoglandulae intercostales) occupy the posterior parts of the intercostal spaces, in relation to the intercostal vessels. They receive the deep lymphatics from the postero-lateral aspect of the thorax; some of these vessels are interrupted by small lateral intercostal nodes. The efl'erents of the nodes in the lower four or five spaces unite to form the descending lumbar trunk, which descends and opens either into the receptaculum chyli or into the commence- ment of the thoracic duct. The efferents of the nodes in the upper spaces of the left side terminate in the thoracic duct; those of the corresponding right spaces, in the right lymphatic duct. 3. The diaphragmatic nodes lie on the thoracic aspect of the Diaphragm, and consist of three sets — anterior, middle, and posterior. The anterior set consists of (a) two or three small nodes behind the base of the ensiform (xiphisternum), which receive afferents from the convex surface of the liver, and (b) one or two nodes on either side near the junction of the seventh rib with its cartilage, which receive lymphatic vessels from the front part of the Diaphragm. The efferent vessels of the anterior set pass to the chain of internal mammary nodes. The middle set consists of two or three nodes on either side close to where the phrenic nerves enter the Diaphragm. On the right side some of the nodes o( this group lie within the fibrous sac of the pericardium, in front of the inferior vena cava. The afferents of this set are derived from the middle part of the Diaphragm, those on the right side also receiving afferents from the convex surface of the liver. Their efferents pass to the posterior mediastinal nodes. The posterior set consists of a few nodes situated on the back of the diaphrag- matic crura, and connected on the one hand with the lumbar nodes and on the other with the posterior mediastinal nodes. The superficial lymphatic vessels of the thoracic wall ramify beneath the skin and converge to the axillary nodes. Those over the Trapezius and Latis- simus dorsi run forward and unite to form ten or twelve trunks which end in the subscapular group. Those over the pectoral region, including the vessels from the skin covering the peripheral part of the mamma, run backward, and those over the Serratus magnus upward, to the pectoral group. Others near the lateral margin of the sternum pass inward between the rib cartilages and end in the internal mammary nodes, while the vessels of opposite sides anastomose across the front of the sternum. A few vessels from the upper part of the pectoral region pass upward over the clavicle to the supraclavicular group of cervical nodes. The lymphatic vessels of the mammary gland (Fig. 562) originate in a plexus in the interlobular spaces and on the walls of the galactiferous ducts. Those from the central part of the gland pass to an intricate plexus beneath the areola (suh- THE LYMPHATICS OF THE THORAX 799 areolar plexus), a plexus which also receives the lymphatics from the skin o'v-er the central part of the gland. Its efl'erents are collected into two trunks which pass to the pectoral group of axillary nodes. The vessels which drain the inner (mesal) part of the gland pierce the thoracic wall and end in the internal mammary nodes, while a vessel may occasionally emerge from the upper part of the gland and, piercing the Pectoralis major, terminate in the subclavian nodes (Fig. 562). The deep lymphatics of the thoracic wall consist of: 1. The lymphatics of the muscles which lie on the ribs; most of these terminate in tlie axillary nodes, but some from the Pectoralis major pass to the internal mammary nodes. 2. The intercostal lymphatic vessels which drain the Intercostal muscles and parietal pleura. Those draining the External intercostal muscles run backward and, after receiving the vessels which accompany the posterior branches of the intercostal arteries, terminate in the posterior intercostal nodes. Those of the Internal intercostal muscles and parietal pleura consist of a single trunk in each space. These trunks run forward in the subpleural tissue and the upper six open separately into the internal mammary nodes or into the vessels which unite them; those of the lower spaces unite to form a single trunk which terminates in the lowest of the internal mammary nodes. 3. The lymphatic vessels of the Diaphragm, which form two plexuses, one on its thoracic and another on its abdominal surface. These plexuses anasto- mose freely with each other, and are best marked on the parts covered respectively by the pleurte and peritoneum. That on the thoracic surface communicates with the lymphatics of the costal and mediastinal parts of the pleura, and its efferents consist of three groups: (a) anterior, passing to the nodes which lie near the junction of the seventh rib with its cartilage; (b) middle, to the nodes on the oesophagus and to those around the termination of the inferior vena cava; and (c) posterior, to the nodes which surround the aorta at the point where this vessel leaves the thoracic cavity. The plexus on the abdominal surface is composed of fine vessels, and anasto- moses with the lymphatics of the liver and, at the periphery of the Diaphragm, with those of the subperitoneal tissue. The efferents from the right half of this plexus terminate partly in a group of nodes on the trunk of the corresponding inferior phrenic artery, while others end in the right lateral aortic nodes. Those from the left half of the plexus pass to the preaortic and lateral aortic nodes and to the nodes on the terminal portion of the oesophagus. AppUed Anatomy. — The fact emphasized by Robinson that the peritoneum is a great lymph sac expkuns the quick absorption of septic material and the rapid spread of infectious pro- cesses. If the exudate clots and blocks the lymph channels, absorption is slow and life may be saved. If it does not clot, absorption is rapid and death is certain. Whether it clots or not depends on the nature of the bacteria present. Fowler, impressed by the fact that absorption takes place most rapidly from the diaphragmatic region and least rapidly from the pelvic region, advises placing the victim of peritonitis in bed, with his head and body elevated. A knowledge of the lymphatics of the breast and of the nodes into which the lymphatics drain is of the first importance to a surgeon. Certain surgical deductions from the anatomj' of this region are perfectly obvious — viz.: (1) If the skin of the mammary gland is involved in carci- noma, the thoracic group of axillary nodes of the same side is involved. If the skin over the sternal margin of the gland is involved, the nodes of the opposite axilla may be cancerous, as from this point lymph vessels rise and pass across the midline. If the skin of the sternal margin is involved the prognosis is worse than if it is free, the opposite axilla may be cancerous, and the opposite breast may become diseased. (2) When lymphatic vessels become blocked by cancer cells the lymph backs up, flows backward instead of in its proper direction, and may cause infec- tion in the most unsuspected situations. For instance, a block in the cutaneous lymphatics of a portion of the breast may lead to infection of the opposite breast and axilla, though, of course, it is not so likely to as is cancer of the skin of the sternal margin. By regurgitation of lymph 800 THE VASCULAR SYSTEMS the head of the humerus or the retrosternal structures may become diseased in mammary cancer. (3) If the nipple or areola is cancerous, the entire gland is sure to be diseased, as the lymphatic network of this region empties into the subareolar plexus, and most of the trunks coming from the gland also enter this plexus. (4) If the mammary gland is cancerous, all of the axillary nodes are regarded as diseased, as the main lymphatic channel from the breast reaches the nodes on the inner wall of the axilla upon the third digitation of the Serratus magnus. Further- more, in many cases an accessory lymph channel comes off from the lower portion of the mam- mary gland and passes directly to the axilla. (5) The subclavian nodes are to be regarded as diseased, because in a certain proportion of cases (the exact proportion being uncertain) an accessory lymph channel comes off from the posterior surface of the mammary gland, passes through the great Pectoral muscle, and ascends between the greater and lesser Pectorals to reach the subclavian nodes. (6) The element which greatly interferes with the cure of mammary carcinoma is the existence of lymph channels which arise from the inner portion of the mam- mary gland, pierce the greater Pectoral and Internal intercostal muscles, and reach the internal mammary nodes. Mediastinal involvement is apt to be earlier in carcinoma of the inner por- tion of the breast than in carcinoma of other portions, and the prognosis is particularly bad in cancer of the inner portion of the breast. What is known as the sternal symptom, of Snow is bulging of the sternum due to involvement of the thymus gland. (7) The sternal portion of the great Pectoral and the tissue between it and the lesser Pectoral muscle are to be regarded as diseased, because in some cases an accessory lymph channel from the breast penetrates the greater Pectoral and ascends to the subclavian nodes. This trunk has several interrupting or satellite nodes, the retropectoral nodes, in the tissue back of the great Pectoral muscle. (8) When the great Pectoral muscle is diseased, cancer cells soon spread widely through the sternal portion of the muscle, and this entire portion of the muscle becomes cancerous. The clavicular portion does not suffer early, but escapes until the cancer becomes extensive, as it is anatomically distinct from the sternal portion. If the fibres of the great Pectoral are extensively diseased, the thoracic group of axillary nodes, the subclavian nodes, and possibly the internal mammary nodes are involved. (9) The only operation in cancer of the breast which offers any real hope of cure is one which is done early and is radical. (10) It must be done early, because delay permits in\'olvement of the mediastinum, and if the disease has entered the mediastinum opera- tion is hopeless. If the sternum is bulged operation is useless, and nothing short of amputation at the shoulder-joint could be of help if the head of the humerus is enlarged by the disease. Even this radical procedure is of no avail, because the mediastinum is certainly involved if the head of the humerus is diseased. (11) If the lymph nodes above the clavicle are extensively diseased operation is useless, as in such cases the mediastinum is sure to be involved. (12) A radical operation means the removal of the skin of the breast with the nipple and areola, the subcutaneous tissue of this region, the entire breast, the sternal portion of the great Pectoral with its fascia, the retropectoral nodes and tissue, all the contents of the axilla except vessels and nerves, the nodes and cellular tissue beneath the anterior margin of the Latissimus dorsi, and the subclavian nodes. It is probably always wisest to open above the clavicle as well as below to facilitate the removal of nodes. It is seldom necessary to remove the clavicular por-. tion of the greater Pectoral. The lesser Pectoral does not require removal, but it should be taken away, because of the added safety and speed thus obtained in cleaning the great vessels and because its retention does not improve the functional result. The surgeon must remember that the female mammary gland is a much larger organ than we used to think, and all of its irregular projections and outlying lobules must be removed (p. 784). Formerly, surgeons did not com- pletely remove the breast, but only got rid of a large portion of it. The visceral lymph nodes consist of three groups — viz., anterior, mediastinal, posterior mediastinal, and tracheobronchial. The anterior mediastinal nodes (lymphoglandulae mediastinales anteriores) are placed in the anterior part of the superior mediastinum, in front of the arch of the aorta and in relation to the innominate veins and the large arterial trunks which arise from the aortic arch. They receive afferents from the thymic nodes; their efferents unite with those of the tracheobronchial nodes, to form the right and left bronchomediastinal trunks. The posterior mediastinal nodes {lympJio gland ulae mediastinales posteriores) lie behind the pericardium in relation to the oesophagus and descending thoracic aorta. Their afferents are derived from the oesophagus, the posterior part of the pericardium, the Diaphragm, and convex surface of the liver. Their efferents mostly terminate in the thoracic duct, but some join the tracheobronchial nodes. The tracheobronchial nodes form three main groups in relation to the bifurca- tion of the trachea — one on either side of the trachea above the bronchi and THE LYMPHATICS OF THE THORAX 801 one in the angle between the bronchi {lymphoglandulae tracheales) ; other nodes, termed interbronchial {lymphoglandulae bronchiales) , are found at the points of division of the larger bronchi. The afferents of the tracheobronchial nodes drain the lungs and bronchi, the thoracic part of the trachea and the heart; some MEDIASTINAL NODES AND VESSELS INTERCOSTAL NODES AND VESSELS RECEPTACULUM "•"" \ ,1 ^M^-^A ryy ^ \ 'w^/jii tinaltrut Fig. 576. — Deep lymph nodes and vessels of the thorax and abdomen (diagrammatic). Afferent i represented by continuous lines, and efferent and internodular vessels by dotted lines. (Cunnin of the efferents of the posterior mediastinal nodes also terminate in this group. Their efferent vessels ascend upon the trachea and unite with efferents of the internal mammary and anterior mediastinal nodes to form the right and left bronchomediastinal tninks. The right bronchomediastinal trunk may join the right lymphatic duct, and the left the thoracic duct, but more frequently they 802 THE VAHGULAB SYSTEMS open independently of these ducts into the junction of the internal jugular and subclavian veins of their own side. Applied Anatomy. — In all town dwellers there are continually being swept into those nodes from the bronchi and alveoli large quantities of the dust and black carbonaceous pigment that are so freely inhaled in cities. At first the nodes are moderately enlarged, firrij, inky black, and gritty on section; later they enlarge still further, often becoming fibrous from the irritation set up by the minute foreign bodies with which they are crammed, and may break down into a soft slimy mass or may calcify. In tuberculosis of the lungs these nodes are practically always infested; they enlarge, being filled with tuberculous deposits that may soften, or become fibrous, or calcify. Not infrequently an enlarged tuberculous node perforates into a bronchus, dis- charging its contents into the tube. When this happens there is great danger of acute pul- monary tuberculosis, the infecting node-substance being rapidly spread throughout the bronchia! system by the coughing its presence in the air-passages excites. The lymphatic vessels of the thoracic viscera consist of those of the heart and pericardium, lungs and pleura, thymus and oesophagus. The lymphatic vessels of the heart consist of two plexuses: (a) deep, immediately under the endocardium, and (5) superficial, subjacent to the visceral pericardium. The deep plexus opens into the superficial, the efferents of which form right and left collecting trunks. The left trunks, two or three in number, ascend in the anterior interventricidar furrow, receiving, in their course, aft'erents from both ventricles. On reaching the auriculoventricular furrow they are joined by a large trunk from the back of the heart, and then unite to form a single vessel which descends between the pulmonary artery and the left auricle and ends in one of the tracheobronchial nodes. The right trunk receives its afi'erents from the right auricle and from the right border and posterior surface of the right ventricle. It ascends in the posterior auriculoventricular groove and then runs forward in the auriculoventricular groove, and passes up behind the pulmonary artery, to end in one of the tracheobronchial nodes. The lymphatic vessels of the lungs originate in two plexuses, a superficial and a deep. The superficial plexus is placed beneath the visceral pleura. The deep accompanies the branches of the pulmonary vessels and the ramifications of the bronchi. In the case of the larger bronchi the deep plexus consists of two net- works, one, submucous, beneath the mucous membrane, and another, peribron- chial, outside the walls of the bronchi. In the smaller bronchi there is but a single plexus, which extends as far as the bronchioles, but fails to reach the alveoli, in the walls of which there are no traces of lymphatic vessels. The superficial efferents turn around the borders of the lungs and the margins of their fissures, and converge to end in some nodes situated at the hilum; the deep efferents are conducted to the hilum along the pulmonary vessels and bronchi, and end in the tracheobronchial nodes. Little or no anastomosis occurs between the superficial and deep lymphatics of the lungs, except in the region of the hilus. The lymphatic vessels of the pleura consist of two sets — one in the visceral and another in the parietal part of the membrane. Those of the visceral pleura drain into the superficial efferents of the lung, while the lymphatics of the parietal pleura have three modes of ending — viz. : (a) those of the costal portion join the lymphatics of the Internal intercostal muscles and so reach the internal mammary nodes; (6) those of the diaphragmatic part are drained by the efferents of the Diaphragm; while (c) those of the mediastinal portion terminate in the posterior mediastinal nodes. The lymphatic vessels of the thymus gland terminate in the superior medias- tinal, tracheobronchial, and internal mammary nodes. The lymphatic vessels of the oesophagus form a plexus around that tube, the collecting vessels from which drain into the posterior mediastinal nodes. THE NEEVE SYSTEM. THE SPINAL CORD AND BRAIN, WITH THEIR MENINOES. THE nerve system of man is an apparatus by means of which he appreciates and becomes influenced by impressions from the outer world, reacts on tliese impressions, and Iience is enabled to adapt himself to his environment. It is the organic substratum for those manifestations of nerve force engaged in the characteristic attributes of animal life — sensation and motion. Broadly stated, the nerve system connects the various parts of the body with one another and coordinates them into one harmonious whole in order to carry on the bodily functions methodically and to control the physiological division of labor through- out the organism. With the evolution of the higher forms of animal life through an immense phylogenetic past the nerve system has undergone remarkable differ- entiation and specialization, attaining its maximum as to dominant position and complexity of structure in the human species. The description of the nerve system is assisted by the accommodation of physio- logical data to the anatomical basis in order to demonstrate more clearly and to render more practical our knowledge of the mutual relations of its structure and function. The cycle of events which accompanies nerve action is determined by impressions received by the peripheral organs, apperception and reflexes of tliese impressions in the lower nerve centres, correlation of these with other impressions in higher centres, as well as voluntary reactions or inhibitions, liber- ated in compliance with the organic or higher needs of the individual. Conventionally, the nerve system is usually considered as consisting of (1) the cerebrospinal system, comprising (a) the central nerve axis (brain and spinal cord) and (7;) the peripheral nerves (cranial and spinal), and (2) the sympathetic nerve system. This subdivision, like others formulated by various authors, is an arbitrary one. No part of the system stands isolated, and the manifold groupings and chainings of the units of the system intimately connect the central nerve organs with the peripheral nerve endings, the organs of special sense and the vegetative organs. The distinction between the central and the sympathetic systems has been too absolute, and the only justification for adhering to the classification given above is based upon the fact that the sympathetic system is prepondei'atingly related to the interconnection and coordination of the nutritive (digestive, respiratory, and blood and lymph) apparatus, and, therefore, exer- cises a special control over its activities. Structurally considered, the nerve system consists of cell-elements peculiarly differentiated from all other tissue cells in that their protoplasm is extended, often to great distances from the nuclear region, in the form of processes. The cell- elements are held in place by supporting tissues, partly of ectodermal and partly of mesodermal origin, and receive an abundant blood supply. The cell element of the nerve system is called the neurone. The neurone is (803) 804 THE NEB VE SYSTEM the developmental, structural, rwA functional unit of the nen'e system. It is in reality a single cell presenting unusual structural modifications. It comprises not only the nerve-cell body with its numerous protoplasmic processes or dendrites, but also the axone, which may vary in length from a fraction of a millimetre to fully half a man's stature; so that, despite the delicacy of the axone, its bulk may be almost two hundred times greater than that of the cell body from which it pro- ceeds. The long axones serve to make a connection with a peripheral or distant nerve cell, muscle cell, or gland cell, while the shorter axones of certain neurones divide into terminal branches in the immediate vicinity of its cell body, presumably to come into relation with other nerve cells in the same or adjacent groups. Neurones, being devoted to the maintenance of functions manifested by various phenomena of nerve force, are differentiated in their polarity, both structurally and dynamically. Receptive neurones are so arranged as to receive afferent nerve impulses from other tissues; emissive or excitor neurones give out efferent nerve impulses. The former are generally termed sensor neurones, the latter motor (excitomotor) neurones if connected with muscle, excito glandular if connected with gland cells. Were the nei-ve system made up solely of such initial and ter- minal neurones, the apparatus would be merely a system of reflex arcs. Such it is in low forms of animal life which, by their very organization, and because of the close juxtaposition of their sensor and motor elements, are compelled to react to stimuli from without. In higher forms, with more profoundly differ- entiated nerve systems, the sensor impression must pass through an interposed medium which is capable of either transmitting the molecular change in the form of an excitomotor impulse or, on the other hand, is capable of reducing or check- ing the impulse. In other words, reaction is not imperative; there is a freedom of choice exercised by intermediate neurones endowed with inhibitory function. The simple arc, composed of an afferent sensor neurone and an efferent motor neurone, would act independently of all other arcs were it not for the interposition of this intermediate neurone and of other association neurones which, hy their relations toward similar arc elements, produce harmony of action. The basis, then, of the nerve system is a series of neurones, with projecting and association processes, coordinated for the purpose of performing specific actions manifested either by motion, by trophic changes, or by the apperception of stimuli of a chemical, mechanical (tactile and auditory), thermal, or photic nature. When we consider the profoundly complex manifestations of nerve phenomena in the mental and physical life of man it is not surprising to learn that his nerve system is made up of an immense multitude of aggregations of neurones. Fundamental Facts Regarding the Development of the Nerve System. — The nerve system is formed by a remarkable metamorphosis of the ectodermic layer of the developing ovum. Along the mid-dorsal line of the embryonic mass a thickening of the ectoderm forms a well-defined layer of cells, the neural plate. The proliferative process passes rapidly from the cephalic toward the caudal end, and as development advances it is seen that the most intense growth energy takes place at the cephalic end, indicative of the higher functional potentiality of what is to become the brain. The neural plate undergoes a trough-like for- mation as its edges become elevated cephalad and laterally to form the neural groove (Fig. 577). The edges become more and more elevated and bend toward the median line until the margins of the groove coalesce to form a tube, the neural tube, which sinks into the subjacent mesodermal tissues. The fusion of the mar- gins of the neural plate occurs first in the cervical region and rapidly continues both cephalad and caudad. The cephalic portion, destined to become the brain, expands and grows considerably, while the caudal portion elongates to form the spinal cord. Eventually the neural tube, as it sinks into the subjacent mesodermal tissue. THE SPINAL CORD AND BBAIN 805 severs all connection with the ectoderm from which it developed; but for a brief period the continuity is preserved in an attenuated septal mass, the neural crest (Fig. 577). The cell elements of this crest subsequently become detached from the superficial ectoderm, the continuity of which is again restored to form the integument. They then pass ventrad to either side of the neural tube, prolifer- NEURAL PLAT 30MAT0PLEURE- RNCHNOPLEURE-i ENTODERM Fig. 577. — Diagrams showing development of neural tube and crest. ate by mitosis, and accumulate in paired masses, corresponding in number to the segments of the body, to become, in part at least, the cerebrospinal ganglion cells of the afferent system, while other similarly paired masses migrate farther ventrad to a prevertebral position to form the gangliated cord and widely spread plexuses of the sympathetic system. From the tissues of the wall of the neural NEURAL TU ENTRAL ROOT MOTOCHOR MESONEPHROS MESENTERY Fig. 578. — Diagram showing development of a spinal nerve and its components, together with the spinal and sympathetic ganglia. tube and its temporary crest the entire nerve system of complex and intricate structure is developed. The cavity of the tube shares in the developmental growth changes to become the ventricular .system of the brain and central canal of the spinal cord. The major details of the development of the principal divisions will be considered in appropriate chapters. §06 THE NERVE SYSTEM Development of Nerve Tissue. 1 . In the Wall of the Neural Tube.-The single layer of nucleated epithelial cells of ectodermal origin whi.h makes up the wall of the neural tube early becomes modified into a layer of tall columnar cells called spongioblasts (Fig. o/9). Their protoplasmic ends undergo differentiation in that the central ends become elongated and atten- uated or collapsed to form a series of striated pillars with intervening spaces. The central ends retain their breadth, however, and form an internal limiting membrane. The ectal ends undergo differentiation to form a spongy reticulum (myelospongium net- work); eventually these spongioblasts become (a) ciliated ependymal cells and (6j neuroglia. In the intercellular spaces of the central zone there appear spherical cells of different structure and density. These are the germinal cells, seen in very early stages and proliferating lapidly by karyokine- sis. " They soon lose their sjiherical form, becoming pear-shaped as a protoplasmic process extends ectad. These pear-shaped cells are now termed neuroblasts (Fig. 579), the protons of the neurones, and as development advances they leave the central zone and migrate into the marginal reticulum to the positions in which they are found in the gray substance of the brain and spinal cord. The proto- n plasmic process is at first slightly bulbous and elon- ■Myelospongium networlc. ^^^^ Fig. 579. — Transverse section of the spinal cord of a human embryo at the beginning of the fourth week. Top of figure corresponds to hning of central canal. (.«ter His.) Fig. 580. — Scheme of central motor neurone. (I. type of Golgi.) The motor cell body, together with all its protoplasmic processes, its axis-cylinder process, collaterals, and end ramifications, repre- sent parts of a single cellorneuroTie. a.h. Axone- hillock devoid of Nissl bodies, and showing fibril- ation. c. Cytoplasm showing Nissl bodies and lighter ground substance, n'. Nucleolus. (Barker.) gates to form the axone extending toward other nerve-cells or to the peripheral tissue elements with which they become associated by the contiguity of the terminal arborizations into which the bulbous extremity develops. The precision w'ith which the axones travel toward their allotted goal is one of the most remarkable manifestations of organic development. An American experi- menter, Ross G. Harrison, has devised a method for directly observing the living, growing nerve. In isolated pieces of frog embryos the differentiation of the living nerve elements could be observed from day to day during several weeks. The bulbous end of the outflowing pro- toplasmic fibre, showing a faint fibrillation, was seen to reveal a continuous change of form particularly in a number of fine simple and branched filaments which w-ere in constant ameboid THE SPINAL COBD AND BRAIN 807 movement. Tlarrison's demonstration' is of great significance in connection with the "retraction theory" and oll.cr ideas related to the neurone doctrine. 2. In the Neural Crest Tissues. — The nerve tissue elements of the sympathetic system and of the ganglia of the cranial nerves and dorsal roots of the s]>inal nerves are derived from the neural crest. Omitting, for the present, the development of the sympathetic system, it is found that the cells of the paired masses which eventually become the cerebrospinal ganglia are at first somewhat spherical, then oval in form, sending out from cither extremity or pole a protoplasmic process. One process mi- grates centrad, the other towarii the tissues of the periphery. The central process penetrates the tissues of the neural tube and, assuming the typical form of an axone with its collaterals and end arborizations, comes into contiguous association with cer- tain cells of the central axis. The periph- eral process is in reality an unusually long dendrite, for it is centripetal in func- tion; but owing to the fact that it is usually provided with a myelin sheath it is also termed the peripheral axone of an afferent (or sensor) neurone. The central processes of the cells of a single spinal nerve ganglion form the dorsal nerve roots; the peripheral processes constitute the afferent portion of a spinal nerve. The cells them- selves are transformed from bipolar into apparently unipolar cells by the migration of the cell body to one side and the con- sequent approximation of the two pro- cesses to form a common pedicle in a T-shaped manner (Fig. 586). Structure of the Nerve System.— The whole of the nerve system is composed of nerve tissue and supporting connective tissue. The neurones constitute the nerve tissue, while the supporting tissue is com- posed of the neuroglia and of white fibrous tissue derived either from the investing membrane or from the sheaths of its numerous vascular channels. The Neurone. — The neurone or nerve cell element, whose individuality has already been pointed out, exhibits remark- able variations as to external characters, dimensions, and form. The neurone pre- sents a concentrated or swollen cell mass and nucleus, formerly known as the nerve cell (ganglion cell) and still retaining the name. From this cell body are given off a number of processes of two distinct kinds: (1) protoplasmic processes which are commonly branched and generally- called the dendrites ; (2) a single, thinner, and paler process, the axone (axis-cylinder proc(>ss; iicuraxone). Varied Forms of Neurones. — Bearing in mind that each neurone includes not onlj' the cell body and its dendritic processes, but also the axone or axis-cylinder process with all its rami- fications, we may consider each of these divisions under separate heads. 1. Nerve Cell Body. External Morphology. — The bodies of nerve cells vary much in size, measuring from 4 to 135 microns or more in diameter. The largest cells are found in the ventral horns of the spinal cord, in the spinal ganglia, in the large pyramidal cell layer of the cere- bral cortex, in the Purkinjean cell layer of the cerebellum, and in the cohmm of Clarke (dorsal nucleus) of the spinal cord. Very small cells are found in the olfactory bulbs, in the granular layers of the cerebral and the cerebellar cortex, and in the caput gliosum of the cord. Although all nerve cells begin in the embryonic ectoderm as spherical germinal cells, they later assume, in different regions, very different shapes. These external morphological relations Fig. 581. — Showing some varieties of cell bodies of neurones (diagrnmniatic.) A. Unipolar (amacrine) cell from the retina. B. Bipolar cell from vestibular gang- lion. C Multipolar ceil, with long axone, from spinal cord. D. "Golgi cell," with short axone breaking up into nmnerous terminal twigs. E. Pyramidal cell from cere- bral cortex, a. Axone. clt. Collaterals, t, Telodendria. al of Anatomy, June 1, 1907, vii, 1. (Anatomical Record, p. UC ; 808 THE NERVE SYSTEM have been liest revealed by the methods of Ehrlich and Golgi. According to the number ot processes arising from the cell body, neurones are referred to as (1) unipolar, (2) bipolar, and (3) multipolar nerve cells. 1. Unipolar cells are met with frequently in early stages of embryonic development, but are rare in the adult, being found only in the retina, olfactory bulb, and within the baskets of the Purkinjean cells of the cerebellum. They are called amacrine cells. The cells of the cerebro- spinal ganglia (excepting the cochlear and vestibular) are apparently unipolar, but they are developmentally and functionally of bipolar nature. 2. Bipolar cells are found almost exclusively in the peripheral sensor systems, as in the olfactory membrane, in the retina, in the cochlear and vestibular ganglia, and in the cerebro- spinal ganglia of the embryo. .3. Multipolar cells are the most numerous and form the principal elements of nerve centres throughout the system. They are termed multipolar because of the greater or less number of dendrites given ofT in addition to the single axone.' The terms "unipolar" and "multipolar" must be restricted to the morphological sense; dynamic- ally all nerve cells are bipolar. According to the relations of the axone we distinguish, after Golgi, two kinds of neurones: I. Neurones with long axones which become the axis cylinder of a central or peripheral nerve fibre. The axones give off several collaterals v/hich, like the parent stem, break into finely branched terminals or telodendria. II. Neurones with relatively short axones which do not go into the formation of a nerve fibre, but break up into terminal twigs in the vicinity of the cell-bodies from which they arise. Type II is genially termed, for brevity's sake, the Golgi ceU. Fig. 582. — Purkinjean cell from human cerebellu: plane transverse to tbe long axis of a cerebellar iolii clt. Collaterals. (Golgi method.) Fig. 583.— Profile view of Purkin- jean cell, in the plane of the long axis of a cerebellar folium. According to the morphological relations of the dendrites, neurones are classified as follows: (a) Stellate cells, the dendrites of which spring at intervals from the whole circumference of the cell body and pass toward all directions (motor cells in ventral horn and tract cells of the cord). (6) Cells with one principal stout dendrite (among other lesser dendrites) which gives off side branches and ends in fine terminal twigs (pyramidal cells of ' cerebral cortex; mitral cells of olfactory bulb). (c) Arboriform cells, giving off branched dendrites from both base and apex, resembling the roots and the branches of a tree; the axone often springs from the base of one of the root-like dendrites (pyramidal cells of the hippocampus). ; axone has been observed arising from a single cell, as in the Cajal cells of the THE SPINAL CORD AND BRAIN 809 (d) Cells with monopolar dendrites. Several main dendritic steins spring from one pole of the cell and, undergoing frequent subdivision, break up into a fine terfninal arborization. '^I'he axone .springs from the opposite pole (Purkinjean cells of the cerebellum; granular cells of the fasciola cinerea). 2. Nerve Cell Body. Internal Morpholocjy. — The nucleus of the nerve cell differs in no essen- tial from the typic nuclear structure. Regarding the organization of the cytoplasm several conflicting views exist. In the present state of our knowledge concerning this still obscure field of investigation it may be said that the nerve cell protoplasm is roughly di\'ided into a peripheral exoplasmic portion and a central endoplasmic portion. There is shown throughout the ex'toplasm a tendency to fibrillar structure, more pronounc'cd in the exoplasmic portion. Within the meshes of a more or less homogeneous ground substance, which pervades the whole, are deposited larger and smaller masses of a granular substance. Nerve cells fixed and stained by the methods of Nissl and Held show that the granuic m.Tsses are "stainable" (chromatophiles; tigroid bodies; Nissl bodies), probably of the nature of a nucleoproleid (Mact 'allum) and looked upon as a sort of nutritive reserve. Many of the lai-ger cells possess more or less pigmented material, adjacent to the nucleus. The cells of the substantia nigra (intercalatnm) and of the locus caeruleus contain an abundance of such pigment granules. The " unstainable" homogeneous ground substance of the cytoplasm is probably the more important functionally, for numerous delicate neurofibrils have, by special methods, been shown to traverse the cell body and its processes, crossing and interlacing, perhaps anastomosing with each other, and traceable into the axone.' Nissl, after years of painstaking investigation, has classified nerve cells into a great many different species in accordance with their reaction to staining agents. Fig. 584. — Motor nerve cell from ventral horn of spinal cord of rabbit. The angular and spindle-shaped Nissl bodies are well shown. (After Nissl.) -Axone. 'Mil sheath. Pig. 585. — Bipolar nerve cell from a spinal ganglion Fig. 586. — Three stages in the development of a cell of the pike.' (After Kblliker.) from a spinal ganglion. The Dendrites. — The dendrites are attenuated processes, usually numerous, resembling in structure and staining reactions the cytoplasm, of which, as extensions, they increase the functional expanse of the surface of the cell body. Emerging by a broad base, they become 1 That the neurofibrils form such an intracellular network and that the axones arise therefrom is disputed ■by Ramon y Cajal, Bielschowsky, and others. 810 THE NERVE SYSTEM narrower as they divide into many branches in a dichotomous or arborescent manner to end free, according to most observers, or to be joined with the dendrites of other neurones by means of minute fibrillaj (as claimed by Apathy) or by concrescence (Held). The contour of the dendrite, while occasionally irregular in some specimens, with varicosities along its course, is, as a rule, beset with numerous lateral buds called gemmules. ^'arious hypotheses have been advanced in explanation of these appearances, it being held by some investigators that they are related to- conditions of activity as contrasted to those of repose, while others believe them' to be artefacts produced by the fixing and staining methods at present employed. However, it is no longer disputed that the function of the dendrites is receptive and conductive (or cellulipetal) for nerve impulses, although they probably serve the nutritional requirements of the cell body as well. This functional distinction gives the clue to the correct interpretation of the central and peripheral prolongations of the cerebrospinal ganglionic neurones. The cells of these ganglia are at first bipolar in form, but gradually undergo transformation into apparently unipolar cells by the migration of the cell body to one side and the consequent approximation of the two processes to form a common pedicle in a T-shaped manner so typical of the spinal ganglion cell of the adult (Fig. 586). The central branch invariably remains cellulifugal, the peripheral branch invariably remains cellulipetal, and as such is equivalent to the dendrites of all other neurones. It is merely a modified dendrite in that it courses a longer distance without branching until it reaches the periphery and is usually myelinic. Such a peripheral prolongation of the ganglioa cell is also termed a centripetal nerve fibre or myelinic (medullaied) peripheral axone of an afferent B Fig. 587. — A. Myelinic axones in fresh state, showing a few nodes, B. Portion of a myelinic axone treated with iioiling ether and alcohol to remove the myelin and leaving the neurokeratin network, a, Axone. The Axone. — The axone is usually much longer than any of the dendrites, thin, pale, smooth, emerging from the nerve cell as a direct continuation of the neurofibrillar ground substance of the cell body, and devoid, so far as at present known, of chromatophile granules. Its calibre varies for the different cells, corresponding in general to the length of its course, but it is practically of uniform diameter throughout its extent. Axones may be extremely short or fully a meter in length. Most cells give rise to only one axone (monaxonic neurones), but in certain localities diaxonic (two axones) and polyaxonic (several axones) neurones are found. In a Golgi preparation axones stand out like pieces of black thread, taking a more direct course than do the irregular dendrites, and rarely branching before reaching the ultimate termination, although giving off collaterals along their course. The central axones of spinal ganglion (sensor) neurones are the principal exception to this rule in that they bifurcate in a Y-shaped manner after their entrance into the central nerve system. In the case of another group of neurones, Golgi's Cell, Type II, the axone is observed to break up into numerous THE SPINAL CORD AND BRAIN 811 branches soon after its tlqwrture from the cell; such axoncs ai\- called dendraxones. The axones and their collaterals end in terminal arborizations, tlu' telodendria. The axone is the distriljulive or emissive (cellulifugal) conductor of nerve im|)ulses. There is, therefore, a functional opposition attributable to the two extremities of the neurone, based upon its dynamic polarity and upon a physiologic principle which is established by all experi- ments to which the nerve system is submitted, namely, that nerve impulses pass through the neu- a d rone in a definite direction which is invariable and admitting of anatomic localization. The majority of the peripheral spinal and cerebral axones as well as those constituting the white sub- stance of the brain and cord are invested by a myelin sheath. The Collaterals (para.vones). — The collaterals are accessory branchings of the axones which are more numerous in the cyto]5roximal portion and are usually directed at right angles to the parent stem. Some axones possess few or no collaterals, while others possess many. The collaterals, especially those in the gray substance of the central axis, are frequently mye- linic. They unquestionably play an important part in the grouping and chaining of neurones within the system, in yielding up to neighboring neurones a por- tion of the impulse that the cell has received by its dendrites and transmits along its axone to a distance. Varieties of Axones.— Axones are divided into two main groups depending upon the ]3resence or absence of a myelin sheath — (I) myelinic axones and (II) amyelinic axones, or medullated and nomnedul- lated axones. Myelinic axones or medullated axis-cylinder processes are axones enveloped by a relatively thick sheath composed of semifluid phosphorized fat, which gives to the bundles of these structiu'es their opaque, white appearance. The myelin sheath is in tm-n invested by a delicate membrane (neurilemma) in one group, while another group is devoid of such covering, giving rise to the further subdivision into (a) myelinic axones with a neurilemma; (h) myelinic axones without a neurilemma. (I, a) Myelinic axones with a neurilemma consti- tute the bulk of the cerebr(jsi>iiial iiervc,^, and, in lesser proportion, of the syin))athetic nerves. The myelin sheath {medullary sheath of Schwarm) (Figs. 587 aiul 588) does not invest the axone tluoughout its course nor in a uniform manner. The axone after its emergence from the cell body and likewise in its preterminal por- tion is naked; and the delicate external membrane or neurilemma comes in contact with the axone. The myelin sheath consists of a number of tubular segments tleuiarcated by nodal intersections which are only 0.08 mm. apart in the very small myelinic axones, while for large axones the intervals may be 1 mm. or more. At the nodes {constrictions of Ran- vier) the neurilemma dips into the constriction to come in contact with the" axone, and any branches of the axone are invariably given off at such points. The interruptions in the continuity of the myelin sheath have been assumed to be provisions facilitating nutritive diffusion lietween the axone and the surrounding lymph, and here only may collaterals be given off. Each internodal myelinic segment is further' char- acterized by oblique clefts, irregularly distributed — the incisures of Schmidt-Lantermann — seen only in fixed specimens and probably artifacts. Extraction of the fatty substance of the myelin sheath by boiling alcohol and ether brings out a fine network which resists trypsin digestion, and is termed neurokeratin on account of its resemblance to the keratin of epidermal structures. The neurilemma {primitive sheath of Schwann; neurolemma), a delicate structureless mem- brane, encloses the myelin and the axone, wherever the myelin sheath is wanting. Against the Flo. .588. — A. Amyelinic axones with a neurilemm.i only, the nuclei of which can be seen. B. Diagram showing structure of a myelinic axone and illustrating two views regarding the relations of the sheaths at the node (compare the two sides). C. Trans- section of a group of myelinic axones, stained with osmic acid, showing: NF. Axonic neu- rofibrils. M. Myelin. F. Endon 812 THE NERVE SYSTEM inner surface of the neurilemma, and embedded as it were in the myelin, usually midway between two nodes, lies the oval-shaped nucleus of the neurilemma. Myelinic axones are usually from 4 to 10 microns in diameter; the extremes range from 2 to 20 microns. (I, 6) Myelinic axones without a neurilemma constitute the white substance of the brain and spinal cord, as well as the optic nerves. They differ from the axones just described in twd particulars — the neurilemma is absent and there are no nodes interrupting the continuity of the mj'elin sheath. A network of neuroglia replaces the neurilemma as a supporting tissue. (11, a) Amyelinic axones with a neurilemma (Remak's fibres; sympathetic nerve fibres) constitute the majority of the sympathetic axones and the axones of the olfactory nerves. The myelin sheath is absent and the axone is invested, more or less completely, by a nucleated cellular sheath or neurilemma. (II, h) Amyelinic axones without a neurilemma are naked axones, most numerous in the central ganglia. Most axones of longer course are devoid of any sheath in the cytoproximal and preterminal portions, whatever investment they may receive in the intermediate portion. NERVE CELL NIDI OR NUCLEI. Nerve cells are more or less definitely grouped in the gray substance of tlie brain and cord to form what are conventionally termed "nuclei." Inasmuch as the term nucleus has long been given to the vesicular body in the interior of all cells, ambiguity would be avoided by designating such nerve cell groups by the term nidi (plural of nidus, "a nest"). "NERVE FIBRES" AND NERVES. Prior to the general adoption of the neurone concept it was customary to desig- nate the conducting elements of the nerve system by the term nerve fibres in dis- tinction from the nerve cells. As has been pointed out above, the distinction no longer holds, but the designation "nerve fibre" is still retained in anatomic vocabulary and recurs so frequently in common parlance that, even with the new conception which has been formed of the architecture of the nerve system, the term cannot yet be entirely discarded in favor of "axone," although it probably will eventually. Nerves are round or flattened bundles of axones which serve to bring the central axis into relation with the periphery and other tissues of the body. The nerves of the body are subdivided into two great classes — the cerebrospinal, which are attached to the cerebrospinal axis, and the sympathetic or ganglionic nerves, which are attached to the ganglia of the sympathetic. The cerebrospinal nerves con- sist of numerous nerve fibres (myelinic axones) collected together into small or large bimdles or fasciculi and enclosed in a membranous sheath. Structure of Nerves. — In structure the common membranous investment, or sheath of the whole nerve, which is called the epineuriiun, as well as the septa given off from it, and which separate the fasciculi, consists of connective tissue, composed of white and yellow elastic fibres, the latter existing in great abundance. The tubular sheath of the smaller fasciculi composing the nerve trunk, called the perineurium, consists of a fine, smooth, transparent membrane, which may be easily separated, in the form of a tube, from the fibres it encloses; in structure it consists of connective tissue which has a distinctly lamellar arrangement, being composed of several lamellae, separated from each other by spaces containing lymph. The nerve fibres are held together and supported within the fascicuhis by delicate connective tissue called the endo- nem-ium (sheath of Henle). It is continuous with septa which pass inward from the innermost layer of the perineurium, and consists of a ground substance in which are embedded fine bundles of fibrous connective tissue which run for the most part longitudinally. It serves to support the capillary vessels, which are arranged so as to form a network with elongated meshes. The cerebrospinal nerves consist almost e.xclusively of myelinic axones, the amyelinic axones existing in very small proportions. NERVE FIBRES AND NERVES 81 3 The bloodvessels supplying a nerve terminate in a minute capillary plexus, the vessels com- posing which pierce the perineurium and run, for the most part, parallel with the fibres; they are connected by short, transverse vessels, forming narrow, oblong meshes, similar to the capillary system of muscle. Fine amyelinic axones accompany these cajjillary vessels, the vasomotor fibres, and break up into elementary fibrils, which form a network around the vessel. Horsley has also demonstrated certain myelinic fibres as running in the epineurium and terminating in small bulboid tactile corpuscles or end-bulbs of Krause. These nerve fibres, believed to be sensor, and termed nervi nervorum, are considered to have an important bearing upon certain neuralgic pains. Nerves, in their course, subdivide into branches, and these frequently communicate with branches of a neighboring nerve. The axones, so far as is at present known, do not coalesce, but pursue an uninterrupted course from the centre to the periphery. In separating a nerve, however, into its component fasciculi, it may be seen that they do not pursue a perfectly insulated course, but occasionally join at a very acute angle with other fasciculi proceeding in the same direction; from this branches are given off, to join again in like manner with other fasciculi. It must be distinctly understood, how- ever, that in these communications the axones do not coalesce, but merely pass into the sheath of the adjacent nerve, become intermixed with its axones, and again pass on, to become blended with the axones in some adjoining fasciculus. The communications which take place between two or more nerves form what is called a plexus. Sometimes a plexus is formed by the primary branches of the trunks of the nerves — as the cervical, brachial, lumbar, and sacral plexuses — and occasionally by the terminal fasciculi, as in the plexuses formed at the periphery of the body. In the formation of a plexus the com- ponent nerves divide, then join, and again subdivide in such a complex manner that the indi- vidual fasciculi become interlaced most intricately; so that each branch leaving a plexus may contain filaments from each of the primary nerve-trunks which form it. In the formation also of smaller plexuses at the periphery of the body there is a, free interchange of the fasciculi and primitive fibres. In each case, however, the individual filaments or axones remain separate and distinct. It is probable that through this interchange of fibres, every branch passing oif from a plexus has a more extensive connection with the spinal cord than if it had proceeded to its distribution without such connections with other nerves. Consequently the parts supplied by these nerves have more extended relations with the nerve centres; by this means, also, groups of muscles may be associated for combined action, as is best exemplified in the formation of the limb plexuses. The sympathetic nerves are constructed in the same manner as the cerebrospinal nerves, but consist mainly of amyelinic axones, collected into fasciculi and enclosed in a sheath of con- nective tissue. There is, however, in these nerves a certain admixture of myelinic axones, and the amount varies in different nerves, and may be known by their color. Those branches of the sympathetic which present a well-marked reddish-gray color are composed more especially of amyelinic axones, intermixed with a few myelinic axones; while those of a white color contain more of the latter and a few of the former. Occasionally, the gray and white cords run together in a single nerve, without any intermixture, as in the branches of communication between the sympathetic ganglia and the spinal nerves, or in the communicating cords between the ganglia. The nerves, both of the cerebrospinal and sympathetic systems, convey impressions of a two- fold kind. The afferent or centripetal nerves, generally called sensor, transmit to the nerve centres impressions made upon the peripheral ends of their components, to produce reflexes in the lower centres while the mind, through the medium of the brain, becomes conscious of environmental conditions or changes. The efferent or centrifugal (in large part "motor") nerves transmit impulses from the centres to the parts to which the nerves are distributed; these impulses either excite muscle contraction or influence the processes of nutrition, growth, and secretion. The ganglia may be regarded as separate small aggregations of nerve cells, connected with each other, with the cerebrospinal axis, and with the nerves in various situations. They are found on the dorsal root of each of the spinal nerves ; on the sensor root of the trigeminus; on the facial and auditory nerves; and on the glossopharyngeal and vagus nerves. They are also found in a connected series along each side of the vertebral column, forming the gangliated cord or trunk of the sympathetic; and on the branches of that nerve, generally in the plexuses or at the point of junction of two or more nerves with each other or with branches of the cerebrospinal system. On section they are seen to consist of a reddish-gray substance, traversed by nimierous white nerve fibres; they vary 814 THE NER VE SYSTEM considerably in form and size; the largest are found on the sensor root of the trigeminus and in the cavity of the abdomen; the smallest, not visible to the naked eye, exist in considerable numbers upon the nerves distributed to the different viscera. The ganglia are invested by a smooth and firm, closely adhering mem- branous envelope, consisting of dense areolar tissue; this sheath is continuous with the perineurium of the nerves, and sends numerous processes into the interior of the ganglion, which support the bloodvessels supplying its substance. Origin and Termination of Nerves. — To the central and the peripheral ending 'of a nerve are usually given the names of "origin" and "termination." These designations have been rendered inappropriate, in many cases, by the newer concept of neuronic arrangement. They have not yet become obsolete, however, particularly in dissecting-room anatomy, and warrant description here with a certain degree of reserve alluded to above. Fig. 5S9. — Diagrams of motor nerve endings in A. Striated muscle. B. Cardiac muscle. C. Nonstriated muscle, a. Axone. (. Telodendria. (After Huber, Bolim and Davidoff, and others.) Origin. — The origin in some cases is single — that is to say, the whole nerve emerges from the nerve centre by a single root; in other instances the nerve arises by two or more roots, which come off from different parts of the nerve centre, sometimes widely apart from each other; and it often happens, when a nerve arises in this way by two roots, that the functions of these two roots are different; as, for example, in the spina! nerves, each of which arises by two roots, the ventral of which is motor and the dorsal sensor. The point where the nerve root or roots emerge from the nerve centre is named the superficial or apparent origin, but the axones of which the nerve consists can be traced for a certain distance into the nerve centre to some portion of the gray substance, which constitutes the deep or real origin of the nerve. The manner in which these fibres arise at their deep crigin varies with their functions. The centrifugal or efferent nerve fibres originate in the nerve cells of the gray substance, the axones of these cells being prolonged to form the fibres. In the case of the centripetal or afferent nerves the axones grow inward either from nerve cells in the organs of special sense (e. g., the retina) or from nerve cells in the ganglia. Having entered the nerve NERVE FIBRES AND NERVES 815 centre, they branch and send their uUimate twigs among the cells, without, how- ever, uniting with thera. Termination. — Axones terminate periplierally in various ways and may he most conveniently studied in the efferent and afferent systems respectively. The so-called periph-eral terminations of afferent neurones are Ijetter called peripheral nerve beginnings, on account of their functional relations; the impulse is excited in the peripheral end and conducted centrad through the rest of the neurone. Fig. 590. — Showing some v.-xrieties of peripheral terminations of afferent neurones (or "peripheral nerve beginnings"): A. Terminal fibrillEe in epithelium (after Retzius). B. Tactile corpuscle (Meissner's, after Dogiel). C. Bulboid corpuscle (Krause's, after Dogiel). D. Lamellated corpuscle (Pacini's, after Dogiel. Sala, and others). E. Genital nerve corpuscle from human glans penis (after Dogiel). a, Axone. /. Telodendria. Modes of Termination of Axones. — The ultimate terminals of the axones and their collaterals are called telodendrions (or telodendria). So far as can be determined by present methods they invariably end "free," commonly by exhaustion through multiple division. This manifold branching presumably puts the neurone in a condition to influence the proce.sses of many other neurones ("avalanche con- duction" of Ramon y Cajal). In some localities the formation by axonic terminals of pericellular and peridendritic networks has been observed. Upon muscle 816 THE NERVE SYSTEM fibres the axone terminals form chains of flattened disks, the motor end plates. Among gland cells the terminal fibrils form more or less intricate plexuses. Peripheral Nerve Beginnings of Centripetal Neurones. — Nerve beginnings of the centripetal (sensor) fibres are found in nearly all the tissues of the body. They are peculiarly differentiated and of various forms in different localities, and their function is apparently the conversion of mechanical, thermal, chemical, and other stimuli into nerve impulses. The organs of vision, hearing, smell, and taste possess variously modified nerve beginnings which are described under appro- priate titles in the chapter on the Organs of Special Sense. The organs of the centripetal neurones collecting bodily impressions (tactile sense, muscle sense) and connected with the central axis are often very complicated structures. The principal varieties are : ' Terminal (peripheral) fibrillse. Tactile corpuscles (Meissner's). "Ruffini's endings." , <| Lamellated corpuscles (Pacini's). I Bulboid corpuscles (Krause's). Genital (nerve) corpuscles. L Articular (nerve) corpuscles. ^^ f Neuromuscular spindles (Ruffini). ■ I Neurotendinous spindles (Golgi). (I, a) Peripheral fibrillse are best demonstrable in the epithelium of the skin, mucous membranes, and cornea. The axone is seen to break up into its con- stituent fibrillae, which often present regular varicosities and anastomose with each other in a plexiform manner. (I, h) Tactile corpuscles (corpuscula tactus; touch corpuscles of Meissner and Wagner) consist of elongated oval lobules of delicate epithelioid tissue invaded by one or more axones which divide into their primitive fibrils, each terminal branch ending free usually as a somewhat flattened, disk-like plate in among the wedge- shaped cells of the corpuscle. Tactile corpuscles occur in large numbers in the cutaneous papilla; of the finger-tips, in the conjunctiva, and, less abundantly, in the rest of the skin; they appear to be concerned with the finer tactile sensations. Nerve fibres. Connective-tissue sheath. ending of Ruffini. (After Ruffini.) (I, c) Ruffini has described a special variety of sensor ner-\-e beginning in the sub- cutaneous tissue of the human finger (Fig. 591). They are principally situated at the junction of the cerium with the subcutaneous tissue; they are of oval shape, and consist of a strong connective-tissue sheath within which the axone divides into numerous varicose fibrils ending in small, free knobs. (I, d) Lamellated corpuscles {corpusnda lamellosa; Pacinian corpuscles; Vater's corpuscles; Herbst's corpuscles) are among the largest of the tactile end organs and are found chiefly in the palmar surface of the hand, the sole of the foot, the NERVE FIBRES AND NERVES 817 genital organs, the serous membranes, and many other structures. Each cor- puscle consists of a number of capsular connective-tissue lamellEe arranged more or less concentrically around a central granular protoplasmic core, pierced by a single axone which usually divides into two or more branches giving off col- laterals of beaded appearance and terminating in rounded knobs. (I, e) Bulboid corpuscles {corpuscida bidboidea; Krause's end bulbs) are minute cylindrical or oval bodies, consisting of a capsule continuous with the perineurium which encloses a core (inner bidb) of semifluid, finely granular protoplasm. The axone is bulbed peripherally and quite free distally, or, as is frequently observed, di^•ides into a number of branches, to each of which is attached an end bulb. Dendritic branchinqs. Spirals J ■' Fig. 592. — Middle third of a terminal plaqu the muscle spindle of an adult cat. (.\fter Rufiini.) (I,/) The genital corpuscles (corpuscida nervonim genitcdia) and the articular cor- puscles (corpuscida nervorum articidaria) very much resemble the bulboid cor- puscles just described. The genital corpuscles form aggregations of from two to six knob-like masses in the penis and clitoris. The articular corpuscles are found in the syno\'ial membranes of the joints. II, a) Neuromuscular spindles (muscle spindles of Kiihne) are found in nearly all the skeletal muscles and are most numerous in the Extrinsic muscles of the tongue, in the small muscles of the hand and foot, and in the Intercostal muscles. jMost elaborate investigations upon these spindles have been conducted recently by RufBni in Italy, Sihler, Huber, and De Witt in America. Neuromuscular spindles are usually found in the fibrous septa of the perimysium, and consist of the flattened nerve fibrils of centripetal axones arranged in one or all of three ways: (1) annular, where the fibrils surround the muscle fibres in rings; (2) spiral, and (3) dendritic or branched (Fig. 592) . They are doubtlessly concerned with the so-called muscle sense. (II, b) Neurotendinous Spindles (organs of Golgi). — The nerves convejdng sensor impulses from the tendons have a special modification of the peripheral fibres, in the form of numerous fibrils with branching end plates or of an annular and spiral arrangement resembling the neuromuscular spindles. They usually occur at the junction of the tendon bundles with the muscle fibres (Fig. 593). 818 THE NEB VE SYSTEM The Neurone Doctrine. — The results of the investigations of Golgi, Cajal, Forel, and others prompted Waldeyer to enunciate a theory with regard to the nerve mechanism of the neurone. This hypothesis is generally known as the neurone theory and assumes that (1) each neurone is a distinct and separate entity; (2) the collaterals and other terminals of the neurone form no connections among themselves; (3) neurones are associated, and impulses conveyed, by contact or contiguity of the axonic terminals of one axone with the cell body or dendrites of another neurone. The theory postulates a nerve cell amebism analogous to the extension and retraction of the pseudopodia of an ameba, and the "retraction theory" has been propounded in explanation of certain functional dissociation phenomena attending nerve force manifestations. ■Nerve fibres. Organ of Golgi, showing Tendon bundles, ramification of nerve fibrils. Muscle fibres. Fig. 593. — Neurotendinous spindle organ of Golgi from the human tendo calcaneus (Achillis). (After Ciaccio.) Opposed to the "neurone theory" or "contact theory" is the more recent continuity theory which is being earnestly advocated by Apathy, Bethe, and Nissl. In behalf of this theory it is claimed that the neurofibrils are continuous not only within the cell and its processes, but through an extracellular network as well. The dispute now being waged does not, however, affect our funda- mental ideas regarding the individuality of neurones with regard to their dynamic condition. The Supporting Tissue Elements of the Nerve System.— A fine meshwork of non-neural tissue, more or less dense in different localities, but apparently restricted to the central axis, serves to support the neurones. This sustentacular tissue is of two kinds: (1) the neuroglia; (2) . connective-tissue trabeculse derived from (a) the pia or (b) vascular channels. The Neuroglia. — The neuroglia consists of glia cells of varied forms and glia fibres. Glia cells are divisible into two species — ependjrmal cells and astrocytes of long-rayed and short- rayed type. Ependymal cells are the columnar epithelial cells which line the neural canal throughout. In the embryonic condition each cell is seen to project a long multibranched filament toward the periphery of the neural tube, while the free end carries a tuft of cilia. In adult life both the cilia and the radial filament are apparently lost or very much reduced. Regarding the structure of the glia cells proper as well as of the glia fibres there is a variance of opinion among different investigators. The astrocytes, as they are commonly revealed in Golgi preparations, may, as pointed out by Weigert and others, be due to an extension of the silver deposit upon glia-cell nuclei as well as upon adjacent filaments. Huber,' Hardesty,^ and others regard neuroglia tissue as a syncitium resulting from an early fusion of the protoplasm of the cells of the neural tube which at first were individual and definitely bounded. The fila- mentous reticulum of glia fibres ordinarily seen in adult tissues seems to result from an increase of the fine threads of the spongioplasmic network of the original cell protoplasm. Neuroglia occurs in both gray and white substances as an all-pervading supporting tissue. In certain localities, as upon the surface of the brain and cord, the neuroglia tissue is disposed in the form of a thin layer. ' American Journal of Anatomy, 1901, pp. 45 to 61. ' Aid., 1904, pp. 229 to 268. THE CENTRAL NER VE SYSTEM 819 Besides the neuroglia, the central nerve system contains as supporting tissues numerous fine and coarse septa or tralieeulfe derived from the investing pia, or from the sheaths of bloodvessels. Chemical Composition. — The amount of water in nerve tissue varies with the siUiation. Thus, in the gray substance of the cerebrum it constitutes about 83 per cent., in the white sub- stance from tiie same region about 70 per cent., while in the peripheral nerves, such as the sciatic, it may fall to (iO per cent. The solids consist of neuroalbumins, neuroglobulins, nucleoproteins, neurokeratin (in the gray substance proteins constitute about one-third of the total solids), lecithins, cerebrosides (chiefly phrenosin), cholesterin, unidentified organic sulphocompounds, aminofatty sub- stances, nitrogenous extractives, and inorganic salts with some collagen, fat, etc., in the adherent connective tissue (W. J. Gies). THE CENTRAL NERVE SYSTEM. The central nerve system, as it is convention- ally distinguished from the sympathetic system, is composed of a central axial aggregation of ganglia forming the brain and spinal cord, which are connected with the other tissues of the body by 43 pairs of nerves, of which 12 pairs are attached to the brain and 31 pairs to the spinal cord. The functional relations of the central mechanisms with the periphery are inaintained by the essential cell elements of the nerve tissues, the neurones. The chief task in the study and analysis of the structure of the nerve system lies in the dovetailing of features visible to the naked eye with those visible only imder high magnifying powers. By the com- l)ination of macroscopic with microscopic fea- tures the attentive student is enabled to resolve or reconstruct in the three dimensions of space, and see with his mental eye the opaque interior transparently resolved into intricate yet well- defined projecting and associating mechanisms. Assistance in sucli study may be derived from illustrations depicting hidden structures in ac- cordance with this principle. Preliminary Considerations. White Substance and Gray Substance. — The central axis of the nerve system contains two categories of sub- stance, their difference to the eye being one of color. They are coitventionally designated the white and gray substance. The white substance (substantia alba), which forms about two-thirds of the neural axis, is the conducting substance, and its characteristic appearance is due to the myelin sheaths which invest the axones in it. The gray substance (substantia grisea; cinerea) is the sentient and reacting mass containing the cell bodies of neurones. Its color is due to its translucency, its greater vascularity, and to a certain amount of pigment material in the cell ele- ments. The white and the gray substance is not sharply demarcated everywhere, Fig. 594. — Neuroglia cells of brain shown by Golgi's method. A. Cell with branched processes. B. Spider-cell with unbranched processes. _(.\fter Andriezen.) (From Schafer's Essentials of Histology.) 820 THE NERVE SYSTE3I for although the white substance is exclusively conducting substance, the gray is not exclusively ganglionic, for the former encroaches on the latter; in some local- ities, as in the ventral horns of the spinal gray, in parts of the cerebral cortex, in the reticular formation of the pons and medulla oblongata, and in the column of Clarke (dorsal nucleus), the admixture of myelinic fibres is considerable. Both white and gray substance is pervaded by the neuroglia. The specific graAaty of the cortical gray substance is 1.021; of the great gan- glia, 1.034; of the gray substance in the cerebellum and mesencephalon, 1.040; and of the white substance, 1.028. For convenience of study, and somewhat in correspondence with phyletic development, the central axis of the nerve system is divided into (1) the spinal cord and (2) the brain, grossly subdivided into (a) medulla oblongata, pons, and cerebellum; (6) mid-brain; and (c) fore-brain. This gross subdivision is arbitrary and the interrelations of the parts would be obscured were two much stress laid upon any mode of separation. THE SPINAL CORD (MEDULLA SPINALIS; MYELON). The spinal cord is the attenuated, nearly cylindrical part of the cerebrospinal axis which lies in the vertebral canal, occupying its upper two-thirds in the adult. It extends from about the level of the atlooccipital articulation (or lower bor- der of the pyramid decussation) to the level of the lower border of the body of the first lumbar vertebra, where it terminates in a slender filament of gray substance enveloped by pia, and, further caudad, by a sheath of dura which is attached to the dorsum of the coccyx. The spinal cord is continuous J'l'i^'^ 8 OENTICULATUM LIGAMENTU^ Fig. 595. — Showing the relation of the spinal cord to the dorsal surface of the trunk. The vertebrae are shown in red outlines. -^ fi E. A. S. Fig. 596. — Ventral view of medulla oblongata nd upper part of spinal cord. Dura and arach- oid cut along median line and folded aside. .1 nd B are fairly constant velar folds of the arach- oid. (.-Vfter Key and Retzius.) THE SPINAL CORD 821 cephalad with the medulla oblongata. Its length is 45 cm. (44 to 50 cm.) or eighteen to twenty inches in the male and 43.5 cm. (39.5 to 47 cm.) or sixteen to nineteen inches in the female. In the course of fetal development the spinal cord occupies the entire length of the vertebral canal up to the third month, but after this period it gradually recedes cephalad owing to the more rapid growth of the vertebral column, so that at Ijirth the caudal end of the spinal cord has risen to the level of the third lumbar vertebra. The spinal cord does not entirely hi! the vertebral canal. A wide space or rather a concentric series of spaces intervene between its surface and the walls of the canal, affording a marked freedom of movement of the vertebral column without exerting undue tension upon the spinal cord. These spaces, three in number, which concentrically surround the cord, are demarcated by the three protective membranes — (1) pia, (2) arachnoid, and (3) dura — which are continuous with the like meninges of the brain. The arrangement of the spaces and the membranes may be shown thus: Epidural space. (Areolo- fatty tissue and plexus of veins.) Subdural space. (Cerebro- spinal fluid.) Subarachnoid space and subarachnoid reticulum. (Cerebrospinal fluid.) The pia {pia mater spinalis) closely invests the entire surface of the spinal cord and sends septal ingrowths into its substance as well as a fold occupying the an- terior median fissure. A leaf-like, serrated fold of pia, the ligamentum denticula- tum, passes from each lateral border to the inner surface of the dural sheath and helps to support the cord within the subarachnoid space. The arachnoid and the pia are not separable in gross dissection as they merge insensibly, though usually described as distinct membranes. The arachnoid (araclmoidea spinalis) is in reality an exceedingly delicate and transparent web-like reticulum whose meshes constitute a relatively wide cavity filled with cerebrospinal fluid. The dura (dura mater spinalis) constitutes the outermost and thickest sheath, while the narrow interval between the dura and the vertebral canal is filled by a fine ^'enous plexus, together with soft, areolofatty tissue. The tubular sheath of dura ends in a pointed cul-de-sac at the level of the lower border of the second sacral segment. Of the three spaces which surround the cord, only the two innermost contain fluid, and that of a serous character; the amount in the subdural space is ^^ery small, just sufficient to moisten the contiguous endothelial surfaces of the dura and arachnoid; that in the subarachnoidal space is considerable. (For detailed description see section on the Meninges.) Weight. — The weight of the spinal cord, exclusive of all nerve roots, averages 28 grams, or 1 ounce avoirdupois, being slightly less in the female. Including the nerve roots as ordinarily cut in postmortem procedure, the weight averages 45 822 THE NEB VE SYSTEM grams in the male and 40 grams in the female. The ratio of weight in proportion to that of the brain among mammalia is lowest in the human species, being 1 to 51 in the male and 1 to 49.8 in the female. In the newborn the ratio is 1 to 115. Its specific gravity is 1.038. External Morphology. — In situ the spinal cord exhibits slight curvatures in the sagittal plane, lieing convex ventrad in the transition from cervical to thoracic portion and slightly concave ventrad to the lumbar portion. Its position varies also according to the degree of curvature of the spinal column, being raised slightly (a few millimeters only) in flexion of the vertebral column. The intrinsically segmental nature of the spinal cord is expressed by the association of each definite segment with the somatic segment supplied by its nerves. Thirty-one pairs of spinal nerves are commonly enumerated, thoracic- Fig. 597. — Showing the relations of the cord and erve origins to the levels at which the nerves emerge irough the intervertebral foramina (diagrammatic). Fig. 59S.— The c althougli two additional, rudimentary pairs, relics of a tailed vertebrate ancestry, are demonstrable. The first pair of spinal nerves emerges between the occiput and atlas, and is designated the first cervical; the other cervical pairs are named after the lower of the two vertebrse which form the intervertebral foramen through which the THE SPINAL CORD 823 nerve emerges. Very inconsistently the pair emerging between the seventh cervi- cal and first thoracic vertebrte is called the eighth cervical pair. The remaininp- spinal nerves are named after the upper of the two vertebrte forming the corre- sponding foramen. In all there are: Cervical pairs 8 Thoracic pairs 12 Lumbar pairs 5 Sacral pairs 5 Coccygeal pairs 1 31 All spinal nerves are made up of two roots by which they spring from the lateral aspects of the cord, symmetrically arranged, and these nerve root attachments are the only guides to the demarcation of the various segments of the spinal cord. The two roots are generally termed the posterior or dorsal (afferent or sensor) root, which enters the cord along the dorsolateral fissure, and the anterior or ventral (efferent or motor) root, which emerges along the ventrolateral fissure. Although the cervical nerves pass outward through the intervertebral foramina at nearly a right angle to the long axis of the cord, those of the lower series slope more and more caudad or downward, so that the fifth lumbar pair emerges six vertebral bodies lower than it originates. In fact, the lumljar and sacral nerves descend as parallel bundles in a brush-like manner to form the cauda equina, enclosed by the dural sheath as far as about the middle of the sacral canal. The topographical relations of the levels of origin and exit of the spinal nerves to the spinous processes of the vertebra are shown in Fig. 597. Corresponding with the degree of development of the periphery, the spinal cord is more massive in those segments which are associated with the limbs. Thus, in the ground-mole, the cervical portion is very much enlarged in conformity with the powerfully developed forelimbs, while in the kangaroo or the ostrich, with powerful legs, the lumbar portion of the spinal cord is proportionately enlarged. In man, both the cervical and lumbar portions are enlarged, and while the bulk of the lower limbs exceeds that of the upper, the cervical enlargement of the spinal cord is greater because it innervates a limb which is functionally niore differentiated, capable of much more skilful and complex movements, and endowed with more acutely developed tactile sensibility. The Enlargements of the Spinal Cord. — The spinal cord is marked by two spindle-shaped enlargements in its cervical and lumbar portions, while the inter- vening thoracic portion is nearly cylindrical, being slightly I'educed in its antero- posterior diameter. The cervical enlargement (intumescentia cerviccilis) extends from the first or second cervical segment to the level of the second thoracic vertebra, acquiring a maximum breadth (13 to 14 mm.) at the sixth cervical ver- tebra. At its junction with the medulla oblongata its breadth is about 11 mm. The thoracic portion is about 10 mm. in breadth (minimum at a little below its middle) while its sagittal diameter is 8 mm. The lumbar enlargement (intumescen- tia lumbalis) begins at the level of the tenth thoracic vertebra, and acquires its maximum breadth (12 mm.; sagittal diameter = 9 mm.) opposite the twelfth thoracic vertebra. Below the lumbar enlargement the cord gradually tapers to form a cone (conus), the apex of which, at the level of the lower border of the body of the first lumbar vertebra, is continuous with the attenuated filum. The cervical enlargement is characterized by a relatively greater breadth than the remaining portions of the cord which, on section, appear nearly circular. Conus (conns medullaris). — The conus is the conical extremity of the cord. The lower three sacral segments and the coccygeal segment are usually included 824 THE NERVE SYSTEM under this term. Its diameter becomes reduced to 2 mm. (y^g- inch), to be con- tinued below as the filum. C.l C2. C5. C.8: TA2. ma. Th.l2. L.5. S.2. Coc. *4LARGEMENT Ventral aspect. Dorsal aspect. Pig. 600. — Diagram of the spinal cord and its fissures. THE SPINAL CORD 825 Filum ifilum terminale) .—The delicate terminal thread called the filum, contin- uous with the tapered end of the conus, is about 24 cm. (10 inches) in length. As far as the level of the second sacral vertebral segment it is enclosed, together with the Cauda equina, in the tapering sheath of the dura. Within the dural sac it is called the filum internum, in contradistinction to the filum externum, which is an attenuated process of connective and glia tissue closely invested by a prolonga- tion of the dura, which finally attaches to the periosteum of the dorsum of the cocc>-x. The filum externum occupies one-third of the total length of the filum. Morphologically, the filum is the caudal representative of the cord, and its Intra- dural portion is usuallj' accompanied by slender fascicles of nerve fibres, which are rudimentary second and third coccygeal pairs of spinal nerves. Central canal. — Nuclei of spongio^ .. , .— , , Neuroblasts. *^^ >.. ^;^x^j^ Processes of neuroblasts ~~''"' ' growing out to form ventral nerve root. Ventral column- fiOl. — Section of spinal cord of a four weeks* embryo. (His.) Fissures and Grooves. — The spinal cord is a bilaterally symmetrical structure and exhibits a deep ventral fissure and a slight dorsal groove partially subdividing the cord into the right and left halves. The ventral fissure (/. mediana anterior) extends throughout the entire length of the cord, being shallower in the cervical and thoracic portions (less than one-third of the sagittal diameter) than in the lumbar portion. It is surfaced by a fold of pia which conveys the more im- portant nutritive vessels to the depths of the cord substance. In the depth of this fissure lies the white (ventral) commissure of the cord. The dorsal groove (sulcus medianus posterior) has been regarded, erroneously, as being analogous to the ven- tral fissure. Unlike the ventral fissure, however, the pia does not descend into its depths, but passes continuously over it. The shallow groove marks the site of a septum made up of neuroglial and ependyma) elements. An actual groove is best demonstrable in part of the lumbar cord and in the medulla oblongata, where it constitutes a veritable fissure between the clavse. Each lateral half is marked by the lines of root attachment of the spinal nerves. The dorsal nerve root fascicles enter the cord in linear series and in a depression or true sulcus termed the dorsolateral fissiu'e {.sulcus lateralis posterior). The ventral nerve root fascicles emerge, irregularly scattered, out of a greater circum- ferential area, and no true ventrolateral fissure can be said to exist. The line of emergence of the outermost fascicles is usually taken as an arbitrary boundary between the ventral and lateral districts of the cord, while the dorsolateral fissure more distinctly maps off the lateral from the dorsal district. An additional fissure. 826 THE NERVE SYSTEM observed most distinctly in the cervical and upper thoracic portions, termed the dorsoparamedian fissure (sulcus intermedms -posterior), demarcates the two principal divisions of the dorsal columns, the gracile and the cuneate columns. The dorso- SOMATIC SENSOR VISCERAL SENSOR VISCERAL MOTOR SOMATIC MOTOR Fig. 602. — A diagram of the component elements in tile spinal cord and the nerve roots in a trunk segment to illustrate the four functional divisions of the nerve system. (After Johnston.) paramedian fissure is an exceedingly shallow groove and is best denoted in sections of the cord by its continuance as a connective-tissue {glia) septum into the sub- stance of the dorsal column. An analogous ventroparamedian fissure (sulcus inter- SPONGIOBLAST- GERMINAL CELL Fig. 603. — Trans-section through neural tube, early and later stages, diagrammatic. Earliest stages shown on left side. On the right, the maturing neuroblasts are seen sending their axonic processes toward the periphery or to other regions of the central axis, and the central processes of the spinal ganglionic cells are seen to invade the dorsolateral region. medius anterior) is sometimes observable close to the ventral fissure, demarcating the ventral (or direct) pyramidal fasciculus. Columns of the Cord (funiculi medullae spinalis). — Each half of the spinal cord is thus divided, with respect to its white substance, into three chief columns THE SPINAL CORD 827 or funiculi. The dorsal column occupies the area between the dorsal septum and groove and the line of attachment of the dorsal nerve roots; this column in its turn is generally subdivided into the column of GoU {funiculus gracilis) and the column of Burdach {funiculus cuneatus) by the shallow dorsoparamedian groove and o-lia septum referred to above. The ventral column {funimdus axterinr) occupies the area between the ventral fissure and the outermost fascicles of the ventral nerve roots — an arbitrary boundary line. The lateral column (funiculus lateralis) constitutes the remainder of the cord, between the posterior and anterior nerve root attachments. Each of these columns is subdivided into its component bundles or fasciculi, best studied in sections of the cord. LOCATION OF THE SEGMENTS FOR SIBILITY. MOTILITY. .VtiscUs 0/ expression {tower facial) Palatal and pharyngeal musctr* Muscles of tlie larynx Muscles of tlie tongue Diaphragm Delt., liceps, pectoral, maj. iclavic. portion) "i Brachial, antic, supinator longus > Triceps, latis.dorsifPect. maj. {costal " )) Extenaores carpi et digitoruvft digitorum j ^■"■"•"^ Interossei, lumhricales \ Thenar, hypothenar i Fig. 604.— Explanation of abbreviations: tr. olf., olfactory tract; c. (7. I., lateral geniculate body; P, r, cr, .4, indicate approximately the location of the reflex centres for the pupillary (p), the respiratory (r), cremasteric (cr). patellar (.pat), and tendo-Achillis (A) reflexes. The vesical centre lies in the third and fourth sacral seg- ments; the anal centre in the fourth and fifth (represented by circles); the centres for erection, ejaculation, labor pains (?) are probably also situated in this region. In reality, the divisions between the various seg- ments are, of course, not so sharp as they are shown in the diagr.am,so that a given muscle or cutaneous region derives some of its controlling nerve-roots from the segments lying immediately above and below the principal segment. The sensor segment for any given region is regularly somewhat higher than the corresponding motor segment. (.Jakob.) Development of the Spinal Cord. — The elongated postcranial portion of the neural tube becomes the spina! cord, while the primitive cavity within is preserved as the central canal of 828 THE NERVE SYSTEM the cord. The metamorphosis of the neuroepithelial columnar cells has been described (p. 806). The lateral walls thicken considerably, the central slit-like canal widens as the walls bulge out- ward in an angular manner, and the central tubular gray becomes a fluted column with dorsal and ventral ridges (or horns) enveloped by a rapidly growing mantle of axone bundles which become myelinic in successive stages. The bulging of the thickening walls in the dorsal and ventral as well as lateral directions produces the ventral fissure and the postseptum. The segmental nature of the spinal cord has been alluded to before with regard to the seg- mental derivation of the cerebrospinal ganglia and the disposition of the outgrowing nerve Ventral aspect. Dorsal aspect. Fig. 605. — Distribution of cutaneous nerves. btmdles. There is a further mode of division into longitudinal systems based upon functional relationships. Two main categories of acti\'ity characterize the mechanism of the nerve system and find somatic expression in its architectural plan: First, actions in relation to the external world (somatic — involving skin, muscle, skeleton, etc.); second, internal activities concerned with the processes of nutrition and reproduction (visceral — involving the alimentary tract, vas- cular [blood and lymph], excretory, and reproductive systems). In each there is a twofold activity on the part of the nerve system: reception of stimuli and motor responses. In the cord (and to some extent in the brain as well) the following functional divisions may be distinguished and located anatomically (Fig. 602): Somatic sensor elements. Somatic motor elements. Visceral sensor elements. Visceral motor elements. THE SPINAL CORD 829 This functional differentiation of the neural axis into sensor and motor divisions apparently finds organic expression in an important modification of the developing neural tube. Each lateral wall of the neural tube is early demarcated into a dorsal and a ventral lamina and the slit-like central canal becomes more or less lozenge-shaped on trans-section, owing to the forma- tion of a lateral longitudinal furrow within. The dorsal lamina or zone is preponderatingly sensor in function, while the ventral zone is principally motor in function. This fundamental fact has been of the greatest aid in the correct interpretation of many hitherto obscure facts re- garding the mechanism of the nerve system, and will be found to underlie our method of descrip- tion throughout. The muscular supply from motor segments of the cord is shown in Fig. 604, and the cutaneous supply in Fig. 605. Internal Structure of the Spinal Cord. — If a transverse section of the spinal cord be made, it will be seen to consist of white and gray nerve substance. The white substance is made up of myelinated axones; the gray contains the cell bodies of neurones and nonmyelinated axones with only few myelinated axones. The color of the gray substance, so-called, varies according to the degree of capil- lary injection and the age of the individual. It is usually of a faint, reddish-gray tinge, the gray preponderating in older persons, but various shades of red, yellow, -LATERAL ERAL HORN TRAL HORN *''V7-R),L BOC* VENTRAL FISSURE Fig. 606. — Trans-section of the spinal cord at the mid-thoracic region. and light slate-color may be noted. Nor is the color uniform even in the same section. Around the central canal and at the periphery of the dorsal horn the gray substance is very translucent and is termed, according to its situation, the gelatinosa centralis (gliosa centralis) and gelatinosa Rolandi or caput gliosum (gliosa cornualis). The white substance surrounds the gray column as a variously thickened tunic, closely invested by the pia, which sends numerous delicate, vessd- bearing ingrowths into the substance of the cord. The relative area of the white substance, as seen on section, (increases cephalad; the absolute area of both white and gray is the largest in the region of the enlargements (Fig. 607). Gray Substance of the Cord (siibstantia grisea centraUs; entocinerea). — A plastic conception of the gray substance of the cord is essential to an understanding of the internal architecture. The gray core must be imagined not alone in the relations in which it is conventionally studied, as exposed in trans-sections, but 830 THE NER VE SYSTEM also as a fluted column having a continuous extent throughout the cord. This oray column is drawn into ventral and dorsal ridges, connected respectively with the ventral and dorsal nerve roots, while the white substance fills out the irregularities and completes the nearly cylindrical outline of the cord (Fig. 608). On viewing a trans-section, it is seen that the gray substance is so arranged as to present, in each lateral half of the cord, a crescentic or comma-shaped mass, the concavity of which is directed laterad. The two lateral masses are connected by a transverse bar or band of gray substance, termed the gray commissure (com- missura cinerea [griseaj), and containing the central canal, which extends the entire length of the cord. The dorsal septum of the cord reaches quite to the gray commissure, there being but a few white com- 40 20 0 20 M missural fibres in the dorsal zone. Ventrad, however, a lamina of white substance, the commissura ventralis alba, separates the gray commissure from the ventral fissure (Fig. 606). In trans-sections of the cord it is seen that the lateral crescentic gray masses, united across the middle line by a gray commissure, have the aggregate appear- ance of the letter H. Each crescentic mass presents projections which are more or less pronounced accord- ing to the segment of the cord under consideration. Broadly stated and without reference to special levels, the most marked projections are the dorsal and ventral horns or comua. The dorsal horn, directed dorsolaterad, is elongated and narrow, and its apex is composed of a trans- lucent, V-shaped mass termed the caput gelatinosa Bolandi. The attenuated apex of the dorsal cornu approaches the surface of the cord along the line of entrance of th'e dorsal nerve roots. The apex of the dorsal horn is wider in the regions of the enlargements and the gelat- inosa is most marked in the higher cervical segments. The base or cervix of the dorsal horn is constricted somewhat except in the thoracic portion, where its greater breadth is due to the presence of Clarke's col- umn (micleus dorsalis). The ventral horn is shorter, thicker, and more blunt, and is separated from the ventral and lateral surfaces of the cord by a tolerably thick lamina of white substance. Its margin, in trans-sections, presents a dentate or stellate appearance due to the emergence of fascicles of efferent or ventral root axones on their way to the ventral surface of the cord. What is known as the lateral horn projects as a lateral peninsular extension of the central gray nearly on the line of the gray commissure. It is best marked as a triangular projection in the upper thoracic segments. In the cervical enlarge- ment it is merged with the greatly expanded ventral horn, but it again becomes prominent in the upper cervical segments. The gray substance of the cord is not everywhere sharply demarcated from the white owing to the invasion of myelinic and amyelinic nerve fibres. Facing the lateral column, in the angle between the dorsal and ventral horns, small fascicles of white fibres are embedded in the gray so that it is broken up in a peculiar basket-work pattern termed the reticular formation. This gray network is best Fig. 607. — Pro.iection upon a plane of the absolute and relative extent of the gray and white sub- stance of the cord as determined by successive sectional areas. Gray substance shown in black, (Adapted from the measurements of Stilling.) THE SPINAL CORD 831 marked in the cervical region and becomes more abundant in the medulla oblon- gata. The mode of arrangement of the gray substance and its amount in proportion to the white vary in different parts of the cord. Thus, the dorsal horns are long and narrow in the cervical region; short and narrower in the thoracic; short but wider in the lumbar region. In the cer\-ical region the crescentic portions are small, and the white substance more abundant than in any other region of the cord. In the thoracic region the gray substance is least developed, the white substance being also small in quantity. In the lumbar region the gray substance is more abundant than in any other region of the cord. Toward the lower end of the cord the white substance gradually ceases. The crescentic portions of the gray substance soon blend into a single mass, which forms the only constituent of the lower extremity of the cord. E. A. S. VENTRAL FISSURE Fig. 608. — Showing origin of two pairs of spinal nerves (schematic). The gray commissure which connects the two crescentic masses of gray substance consists of myelinic and amyelinic nerve fibres and neuroglia. The fibres pass transversely, spreading out at various angles, into the lateral gray masses. In the gray commissure, and extending the whole length of the cord, is a minute channel, the central canal {canalis centralis; myelocele), which is barely visible to the naked eye, but is proportionately larger in some of the lower vertebrates. Cephalad, in the medulla oblongata, it opens out into the fourth ventricle; caudad it is continued for a short distance into the filum, in which it ends blindly. The canal is very minute, less than 0.1 mm. (g^o^inch), except in the terminal part of the conns, where it expands into a fusiform dilatation, the sinus terminalis. The central canal is lined by a layer of columnar cells which are seen to be ciliated in the embryo and are in all respects identical with the ependymal cells lining the ventricles of the brain. Surrounding the ependymal lining of the central canal and gradually merging into the spongy substance which constitutes the remainder of the gray commissure is a finely granular and reticulated substance, the gelatinosa centralis, almost entirely composed of neuroglia, with a few fine fibrils apparently proceeding from the ependymal cells, and having a translucent, gelatinous appearance. The gray substance of the cord is composed of (1) the gelatinosa or gliosa, which envelops the head of the dorsal horn and which encircles the central canal of the cord ; (2) the spongiosa, which forms the crescentic horns (except the heads of the posterior horns and the envelope of the central canal). Further, it may be stated that the gray substance consists of nerve-fibres of variable but smaller 832 THE NERVE SYSTEM average diameter than those of the white columns; (3) nerve cells of various shapes and sizes, with few or many processes; (4) bloodvessels, lymphatic channels, and connective tissue. The nerve fibres of the gray substance of the -pos- terior horn are for the most part composed of a dense interlacement of minute fibrils, intermingled with nerves of a larger size. This interlacement is formed partly by the axones and dendrites of the cells of the gray substance, and partly by fibres which enter the gray substance and which come from various sources. The nerve cells of the gray substance are collected into groups {iiidi or nuclei) as seen on transverse section, but they really form columns of cells placed longitudinally ; or else they are found scat- tered throughout the whole of the gray substance (Fig. 609). In the ventral horn four main groups of cells may be distinguished which are not wholly represented, how- ever, in all regions of the cord: (1) A ventral group of cells, separable in the cervi- cal and lumbar regions into ventromedial and ventro- lateral sub-groups; (2) a dorsomedial group, situated in the cervix of the ventral horn, usually demonstrable in the thoracic portion as well as a few contiguous cervical and lumbar seg- ments; (3) a lateral group, separable in the lower cer- vical and lumbar regions into ventrolateral and dorsolateral sub-groups, and supplying the muscles of the extremities; (4) a central group of cells in the lumbar and sacral regions. In the lateral horn, which is most prominent in the thoracic and upper cervical segments, lies an intermediate group of cells, a long, slender column which is nearly restricted to the thoracic portion of the cord, but is seen to reappear in the TRO-MEDIAL Fig. 609. — Trans-sections of the spinal cord at different levels to show the topographical arrangement of the principal cell groups. THE SPINAL CORD 833 upper three cervical and in the third and fourth sacral segments. The axones from these cells probably do not pass out with the ventral nerve roots, but rather course within the cord to terminate at various levels on the same as well as on the opposite side. A close connection with the sympathetic nerve system, and with vasomotor and sweat-gland nerves, has been suggested. In the dorsa) horn the most conspicuous group of cells is a columniform nucleus commonly termed Clarke's column (nucleus dorsalis), which extends between the seventh cervical and second (or third) lumbar segments of the cord. The cells are large and the group presents an oval outline in trans-sections, lying in the medial part of the cervix of the dorsal horn. The axones of these cells pass out of the gray into the lateral column of the cord to form the spinocerebellar tract, and convey tactile impulses to the cerebellum. It is repre- sented in other regions of the cord by scat- tered cells which are aggregated to form the cervical nucleus opposite the third cer- vical nerve, and a sacral nucleus in the middle and lower part of the sacral region. The axones of these cells form the homolateral direct cerebellar tract. The cells of the dorsal horn are not grouped very definitely, and for the purposes of description they are subdivided accord- ing to their location. The cells vary much in form and size and their branched axones pass toward other regions within the gray substance at various levels on the same or on opposite sides, or via the ground bun- dles. Many fibres of the dorsal nerve roots are in relation with the dorsal horn cells. The various groups of cells enumerated above are frecjuently demarcated from neighboring groups by nerve fibre intervals, which may be straight, curved, interlaced, or loop-shaped. Through the gelatinosa Rolandi (gliosa corimalis) pass niunerous fine fibrils, chiefly the afferent dorsal nerve root fibres, but in addition this peculiar, gelatinous, and semitranslucent substance contains numerous small, stellate cells; the region is so densely filled with axones and collaterals, as well as neuroglia cells, that until staining methods became sufficiently developed the importance of this substance remained in dispute. In man the gelatinosa Rolandi shows convolutions feebly imitating those of the olivary body, and its structure is analogous. Dorsad of the gliosa lies the ultimate zone of the dorsal horn; this gray substance resembles the spongiosa in its essential characters. The White Substance of the Cord {substantia alba). — The white substance of the cord, consisting chiefly of longitudinally disposed myelinic fibres, with blood- vessels, neuroglia, and connective-tissue septa, forms a thick mantle which invests the central gray column. When stained with carmine, a transverse section of the white substance is seen to be studded all over with minute dots surrounded by unstained circular areas. The dots are the transversely cut axones ; the lighter areas are the myelin sheaths. The mass of white substance is closely invested by E. A. S. Fig. 610. — Showing the dorsal nucleus (of Clarke), and its cervical and sacral extensions on one side, and the direct spinocerebellar tract on the other. The fibres of the tract ascend on the same side as the nucleus in which they 834 THE NERVE SYSTEM a sheath of neuroglia immediately beneath the pia. Numerous septa, derived from the pia, but always coated by a thin layer of neuroglia, pass into the white sub- stance to separate the respective bundles of fibres and are often interwoven between individual nerve fibres, acting as a supporting framework in which they are em- bedded. In addition to the longitudinal fibres there are shorter and less numerous trans\-erse fibres forming the white commissure. The longitudinal fibres constitute the conducting tracts. Although a purely anatomical examination fails to reveal the functional relations in these fibre bundles, the structural alterations which ensue (in accordance with the laws of Waller) in the distal portion of a neurone whose proximal portion has been destroyed, the progressive myelinization of separate tracts in the embryo and infant (as proved by the researches of jMeynert and Flechsig), the comparative anatomy method and electrophysiological experimentation have rendered possible the demonstration of the origin and destination of the various conducting systems or tracts with almost mathematical accuracy. While some fibres pursue a lengthy course, serving as conduction paths between the brain centres and the various spinal centres, others are shorter and serve to associate different spinal levels — in juxtaposition or relatively not far distant. It rhust be borne in mind that the gray substance, intercalated as it is in the course of the impulses which pass to and fro in the cord, contains the neural elements which are either (a) the source or (b) the destination of these impulses, and thus complete the ner^'e cycle requisite for the organization of the functions belonging to the cord. The motor and sensor phenomena, though interacting, depend upon distinct nerve elements which, because of their functional relationships, or because of the direction in which they convey impulses, are generally referred to as motor or efferent and sen- sor or afferent neurones; and in the spinal cord usage has sanctioned the employ- ment of the terms descending and ascending for tracts conveying motor and sensor impulses, respectively. Anatomically speaking, however, it is preferable to de- scribe the tracts with reference to their origins and termini (as cerebrospinal, spinothalamic, etc.), when known, or to their topographical relations as studied in trans-sections of the cord. For the purposes of description it is convenient to classify the longitudinal fibres into three general systems: (1) The cerebrospinal system of axones forming conduction paths for efferent impulses from the cerebrum to the spinal centres for peripheral organs, and axones for afferent impulses received in the spinal centres from the periphery and conveyed in turn to the cerebrum. (2) The spinocerebellar system, consisting of conduction paths, afferent and eft'erent between the cerebellum and the spinal centres. (3) Numberless association systems strictly confined within the cord (or only extending into the medulla oblongata), composed of shorter or longer axones which serve to associate not only different levels of the same spinal segment, but also the dift'erent segments that are in juxta- position or more remotely situated. These spinal association axones form bundles in close contact with the central gray column and are termed the fasciculi proprii or ground bundles. Tracts of the Spinal Cord. — In the dorsal column there are the following tracts: Ascendinj: 1. Fasciculus gracilis (Golli). 2. Fasciculus cuneatus (Burdachi). Descending : 1. Comma tract (Schultze). 2. Median oval tract (Flechsig). Associating : 1. Fasciculus dorsalis proprius. 2. Dorsal cornucommissural tract. 3. Septomarginal tract (Bruce). THE SPINAL CORD 835 Another tract, usually described as belonging to the lateral column, but functionally more intimately related to the sensor neurone system of the dorsai column is the fasciculus marginalis (of Spitzka and Lissauer, described on page 836). The great majority of the axones constituting the dorsal column are the afferent (sensor) axones arising from the spinal ganglion cells, entering the cord by the dorsal roots. These dorsal root axones bifm'cate in the region of the dorsal horn, one branch ascending a little obliquely at first, then vertically, while the other branch takes a similar downward course for a shorter distance (Fig. 613). As additional groups of fibres are contributed by each successive dorsal nerve root the mass of white substance in the dorsal column accumulates as the cord is ascended, though it must be noted that not all of these afferent fibres traverse the whole of the cord above, but end in relation with cells in the gray substance at various levels. The succes- sive accessions of afferent fibres are disposed in a laminated manner so that the lumbar fibres come to lie laterad of the sacral bundle, the thoracic laterad of the lumbar, and so on as the cord is ascended. A section of the cord at its highest level would therefore traverse a collection of bundles derived from all of the dorsal nei-ve roots of the cord, arranged as shown in Fig. 611. In the upper segments of the cord it is possible to distinguish a division of the dorsal column into two principal fasciculi owing to the presence of a distinct connective-tissue septum which passes into the substance of the dorsal column along the dorsoparamedian groove. These fasciculi are termed the fasciculus gracilis, or Goll's column, and the fasciculus cuneatus, or Burdach's column; in the consideration of the external morphology of the cord, these have already been referred to as the funiculus gracilis and funiculus cuneatus, respec- tively. It has been noted that even in the fresh cord, when sectioned, the gracile bundle has a different tinge and stains more deeply with carmine than does the cuneate bundle. The caudal or descending branches of tlie bifur- cate dorsal root axones are considerably shorter than the ascending branches. They terminate in the gray substance in relation with its cells and, by numerous collaterals which are shorter or longer and given off at various intervals, serve to asso- ciate different levels of the cord. Some of these collaterals cross the median line in the dorsal (gray) commissure to come into relation with neurones of the opposite side. Certain of the longer descending branches show a tendency to collect into a feebly marked bundle along the mesal border of the cuneate fasciculus, called, because of its outline in trans-sections — as seen in cases of descending degeneration from injury at a higher level — the comma tract of Schultze. A similar bundle, situated along the dorsal septum, best demonstrable in the lumbar cord, and with its fellow ^ Lumbar \\ neries Fig 611 — Formation of the fascic- ulus gracilis Spmil cord viewed from behmd To the left the fasciculus gracilis is> shaded. To the right, the drawing shows that the fasciculus gracilis is formed by the long fibres of the posterior roots, and that in this tract the sacral nerves lie next the mesal plane, the lumbar to their outer side, and the thoracic still more later- ally. (Poirier.) 836 THE NER VE SYSTEM of the opposite side of tlae oval outline as seen on section, is called the oval bundle of Flechsig (fractus cervkolumbalis [Edinger]; dorsomediales Sakralfeld [Obersteiner]). WHrXE VENT ?' ?i — Sc.ctions of the spinal cord at the level of the sixth cervical, sixth thoracic, and third lumbar seg- ments, the conductmg tracts being indicated on the right side of each section: C. Comma tract of Schultze. tl. Ulivospinal tract of Helweg. .1/. Marginal tract of Spitzka-Lissauer. O. Oval field of Flechsig. Marginal Tract. — Not all the axones of the dorsal nerve root enter the dorsal column. Another group elsewhere described passes into the dorsal horn as THE SPINAL CORD 837 well as toward Clarke's column, while a third group of fibres forms the so-called marginal tract/ situated close to or among the entering fibres of the dorsal roots, but frec[uently described as lying in the lateral column. The tract is demonstrable in all levels and is made up of successive increments of relatively short axones (traversing not more than three or four segments) to end in relation with the cells in the gdafiiiosa Rolandi. Ground Btindle of the Dorsal Column. — A zone of fibres contiguous with the dorsal face of the gray column, and termed the fasciculus dorsalis proprius or dorsal D.R D.R D.R. -n D.R Fig. 613. — Ramifications of the central processes (axones) of afferent neurones entering the spinal cord as seen in longitudinal section (schematic) : D.R. Axones of dorsal roots, b. Their bifurcation. cU. Collaterals. t. Telodendria ending in proximity of cells in the gray substance. F.C. Axones of gracile and cuneate fasciculi. ground bundle, is composed of axones arising from the smaller cells of the dorsal horn, which, after entering the white substance and bifurcating into ascending and descending branches, come into relation with other levels of the gray column by means of collaterals and terminating in it after a comparatively short course. They are therefore to be regarded purely as association or "longitudinal com- missural" fibres. The dorsal comucommissural tract (ventrales Hinterstrangs- hundel [Striimpell]; zone cor nucommiss urate [Marie]), occupying a triangular interval at the apex of the trans-sected dorsal column, and the septomarginal tract [of Bruce], in apposition with the postseptum, belong to this category of asso- ciation bundles. Both tracts are most evident in the lumbar portion of the cord. First described by E. C Spitzka (1885) and Lissauer (1886), and usually bearing the name of the latter. g3§ THE NERVE SYSTEM In the lateral column the following tracts may be enumerated: Ascending : 1. Dorsolateral spinocerebellar tract (Flechsig). 2. Superficial ventrolateral spinocerebellar tract (Gowers). 3. Spinothalamic tract. 4. Spinomesencephalic tract. Descending : 1. Crossed pyramidal tract. it! [2. Rubrospinal tract. "S^ I 3. Cerebellospinal tract (Marchi and Lowenthal). I i I 4. Lateral vestibulospinal tract. "- Is. Olivospinal tract of Hehveg. Associating: 1. Fasciculus lateralis proprius. The dorsolateral spinocerebellar or direct cerebellar tract (fasc. cerebellosjnnalis) lies at the periphery, laterad of the crossed pyramidal tract. Its axones arise from the cells of Clarke's column and ascend uninterruptedly to the medulla oblongata, and thence to the vermis of the cerebellum in its inferior or post- peduncle. The tract becomes more massive as the cord is ascended (Fig. 610). The superficial ventrolateral spinocerebellar tract, or tract of Gowers (fasc. antero- lateralis superfidalis [Gowersi]), also courses along the periphery, but farther ventrad. The origin of its axones is yet in dispute; they probably arise from cells in the gray substance of both sides, in the zone between the dorsal and ventral horns as well as from some of the ventral horn cells. The destination of the ax- ones of this tract is equally uncertain, but most of the fibres have been traced through the dorsolateral region of the medulla oblongata and the pontile retioula, whence it turns dorsimesad, to enter the cerebellum through the superior medullary velum and ends in the dorsal vermis. A lesser portion of the tract has been traced to the quadrigeminal bodies, while other groups of axones end in various levels of the gray substance. The spinothalamic and spinomesencephalic (tractus spinotectalis) tracts are not gathered into compact bundles, but are rather scattered among the fibres of the lateral column just mesad of the superficial ventrolateral spinocerebellar tract (Gowers). The axones of both systems arise from cells in the dorsal horn and its cervix of the opposite side, coursing through the white ventral commissure and ascending the cord, the spinothalamic fibres ending in the thalamus, the spinomesencephalic fibres ending in the region of the quadrigeminal bodies. The two tracts are collectively called tractus spinotectalis et thalamicus. The crossed P3n:amidal tract (fasciculus cerebrospinalis lateralis) occupies an ap- proximately triangular or oval area in the dorsal portion of the lateral column, just mesad of the direct cerebellar tract, except in the lumbar cord, where it lies at the surface. The axones of this tract arise from the pyramidal cells of the cerebral cortex (motor area) of the opposite side. After having descended through the internal capsule, crusta, pons, to the pyramis of the medulla oblongata, the major portion (85 to 90 per cent.) of the fibres derived from one-half of the brain decussate with those of the other half, crossing the median line to descend in the lateral column of the cord. The fibres which do not decussate constitute the direct pyramidal tract in the ventral column. As the crossed pyramidal tract descends it diminishes in size as its axones become distributed to the ventral horn, where they terminate either in contiguity with the ventral motor cells which give rise to the fibres of the ventral (motor) nerve roots, or else in contiguity with the dendrites of interposed neurones, which, in turn, convey the impulse to several associated niotor neurones presiding over the actions of associated muscles. The bundle becomes exliausted as a distinct strand at the level of the fourth sacral seament. THE SPTNAL CORD 839 The rabrospinal, cerebellospinal, lateral vestibulospinal, and olivospinal tracts consist of descending axones which are intermingled so that their mutual topo- graphical relations cannot at present be described. Collectively they constitute the fasciculus intermedius of Lowenthal and Bechterew (intermediolateral tract of Bruce and Campbell) and they lie ventrad of the crossed pyramidal tract and mesad of the combined spinothalamic and spinomesencephalic tracts. The rubrospinal tract (^lonakow's tract; prepyramidal tract) originates in the red nucleus in the tegmentum of the mid-brain of the opposite side and its axones terminate in relation with ventral horn cells! In their course these fibres are seen to invade the area of the crossed pyramidal tract. The cerebellospinal tract (Marchi's tract) is supposed to arise in the cortex of the cerebellar hemispheres, to become distributed to the motor centres in the ventral horn. The lateral vestibulospinal tract arises in the lateral nucleus of the vestibular nerve (Deiters' nucleus), and by its relations with spinal centres establishes a connection with the equilibratory apparatus. The olivospinal tract of Helweg (Helweg's Dreikantenbahn ; Bechterew's Oliven- biindel) is found only in the higher segments of the cord, at its periphery and just laterad of the emergence of the ventral nerve roots. Its connections and functional direction are uncertain; some investigators have traced its fibres between the olive and certain ventral horn cells; Obersteiner suggests a relationship with the pyram- idal tract. The coincidence, in point of time, of the myelinization of both tracts' is significant in this connection. Several other descending tracts ending in the spinal cord and arising in higher centres like the corpora quadrigemina, central gray substance of the mesencephalon, and the cerebellum have been recently described by Held, Boyce, and Bechterew. Ground Bundle of the Lateral Column {fasciculus lateralis proprius). — This lies in the concavity of the lateral aspect of the gray column and consists of axones of neurones having a purely commissural function. In the regions where the reticula is best marked it is subdivided into a group of smaller bundles by numerous glial septa. In the ventral column are described the following tracts: Descending: 1. Direct pyramidal tract. 2. Sulcomarginal tract. 3. Ventral vestibulospinal tract. Associating : 1. Association axones between spinal centres and several cranial nerve nuclei. 2. Fasciculus ventralis proprius. The direct P3n-amidal tract {fasciculus cerebrospinalis anterior) is the uncrossed portion of the pyramidal tract below the decussation in the medulla oblongata, and constituting only 10 to 15 per cent, of the fibre system arising in the motor cortex of the same side. It is a small, oblong bundle, as seen on trans-section, lying parallel with the ventral fissure, from which it is separated in the higher segments by the relatively narrow sulcomarginal tract. The tract diminishes in bulk as the cord is descended, to disappear in the thoracic portion of the cord; though, in rare instances, it has been obser\ed to extend throughout the lumbar portion as well. This diminution and eventual disappearance of the tract is due to the successive decussation of its fibres throughout its course, for, with a few exceptions, these cross in the ventral white commissure to come into relation with the ^"entral horn cells (motor cells) of the opposite side. This partial longitudinal extension of the pyramidal decussation and consequent formation of an uncrossed, ventrally situated pyramidal tract is peculiar to the primate order of verte- brates. 840 THE NERVE SYSTEM The sulcomarginal tract (tractus tectospinalis) is a thin bundle whose axones arise in the corpora quadrigemina of the opposite side, immediately decussating and descending through the medulla oblongata, to be distributed to various spinal centres in a manner not yet accurately ascertained. This tract, which is most developed in the cervical region of the cord, is assumed because of its proximity to the lower optic, ocular muscle, and acoustic nuclei. The ventral vestibulospinal tract (liowenthal's tract; anterior marginal fascic- ulus; ventral cerebellospinal tract) lies at the periphery of the ventral column, extending, as seen on trans-section, from the ventral root zone to the ventral fissure. Its axones arise from (1) the lateral (Deiters') and (2) superior (Bech- terew's) nuclei of the vestibular nerve; and (3) from the nucleus fastigii of the cerebellum. Their termination about the ventral horn cells has been traced as far as the sacral region of the cord. As in the lateral column, and continuous with the like formation, there is in the ventral column an intermediate zone of mixed systems of axones which serve to associate various levels of the cord with ganglionic masses in the medulla oblongata, as well as with the cerebellum and corpora quadrigemina. The nuclei of the tri- geminus, facial, auditory, glossopharyngeal, and vagus nerves, together with the olive and the cerebellum, seem most intimately associated with the spinal centres for movements of the head and neck. Ground Bundle of the Ventral Column. — The white substance of the ventral column contiguous with the central gray is made up of intersegmental axones of associa- tion connecting different levels of the cord. The ventral (white) commissure (coviviissura anterior alba) is composed of myelinic fibres which decussate with or cross each other and, on trans-section, are seen to form a narrow band connecting the ventral columns of the two sides. The axones composing it are chiefly (1) those arising from ventral horn cells, which after crossing the midline, course horizontally or cephalad and caudad to come into relation with neurones at the same or at different levels of the gray substance; (2) the decussating axones of the direct pyramidal tract; (3) numerous collaterals from the ventral and lateral column axones. The white commissure is most massive in the enlargements where the associations of the limb centres are neces- sarily greater in number. Myelinization of the Axones of the Cord. — The acquisition of the myelin sheath is not cotemporary for all axones in the cord, but is characterized by a regular progression in the myelinization of separate fasciculi. As a rule, those axone systems which are concerned with simpler or intrinsically spinal reflexes become myelinic or "mature" at an earlier stage of fetal development than do those con- cerned in the more elaborate connections of the cord with the Ijrain. According to Flechsig and Trepinski the order of myelinization is as follows: I. a, b. Ventral and dorsal roots during fifth month. II. a, b, c. Ground bundles and intermediolateral tracts during sixth month. III. a, b, c. Dorsal columns during fifth to seventh month. IV. Direct spinocerebellar tract, seventh month. V. Ventral spinocerebellar (Gowers') tract, seventh to eighth month. VI. Pyramidal (crossed and direct) tracts, at or soon after birth. VII. Olivospinal (Helweg's) tract, ninth month or later. The order of myelinization of the separate fasciculi is indicated in Fig. 614. Summary. — The Gray Substance. — The gray substance consists, aside from its supporting tissues, of sentient and reacting nerve cells, with their dendrites and axones, and of the terminals of axones entering from without. These nerve cells may be classified as follows: (a) Nerve cells whose axones pass directly out of the cord. These lie in the ventral horn, are "motor" in function, and their axones form the ventral nerve THE SPINAL CORD 841 roots. Certain nerve cells situated in the cervix of the ventral horn are believed to send splanchnic efferent axones in company with the motor axones in the ven- tral root, while very few similar efferent axones leave by means of the dorsal root. (h) Nerve cells whose axones pass into the white substance, usually bifurcating into a shorter descending and a longer ascending branch. Two kinds of cells are distinguished: , 1. Strand or tract cells whose axones (ascending branches) traverse the cord, to come into relation with higher centres in the brain. 2. Association cells whose axones, after a comparatively brief course in the white substance, reenter the gray substance and serve to coordinate different levels of the cord. Fig. 614. — Diagram showing the order of myelinization of the various tracts in the spinal cord (cervical level). The tracts are named on the right side; the Roman numerals on the left side correspond with the enumeration given in the text, H. Olivospinal tract of Helweg. M. Marginal tract. O. Oval tract of Flechsig. The tract cells may be further divided into two categories — homolateral and contralateral tract cells. Homolateral cells are those whose axones enter the white columns of the same side; contralateral cells are those whose axones traverse the white (ventral) commissure to the other side. Tract cells exist in all parts of the gray substance, and are termed, according to their situation, ventral, lateral, and dorsal horn cells. The contralateral tract cells preponderate in the dorsal horn, its cervix, and in the intermediate zone, and, on account of their course, are also called commissural cells. (c) Nerve cells of Golgi's type II, or cells with short, multibranched axones. The motor ventral horn cells and the splanchnic efferent cells differ, therefore, from the other categories in that they alone send their axones out of the centra! axis to the periphery. The tract cells, commissural cells, and the Golgi type II cells are strictly confined to the central axis; the tract cells serve to coordinate the separate units of the spinal neurone system with higher centres; the asso- ciation cells maintain the paths of conduction between higher and lower cell complexes; while the cells of Golgi's type II are limited to a narrower field of nerve activity as nerve links in the chaining together of neurones. White Substance. — The white substance consists essentially of axones the great majority of which are disposed longitudinally. These axones comprise : 842 THE NEB VE SYSTEM (a) Axones arising in the cerebral cortex, the gray ganglionic masses in the mid-brain, pons, and cerebellum, and descending to their terminations in different levels of the cord. (b) Axones which, conversely, arise in the gray substance of the cord (tract cell axones), to terminate in the higher brain centres. (c) Axones which coordinate difiFerent levels of the cord with each other (associa- tion cell axones). (d) Axones which, arising from the spinal ganglion cells of the dorsal nerve roots, enter the cord and ascend in the dorsal columns. Dissection. — ^To dissect the cord and its membranes it will be necessary to lay open the whole length of the vertebral canal. For this purpose the muscles must be separated from the vertebral grooves, so as to expose the spinous processes and laminae of the vertebrae; and the latter must be sawed through on each side, close to the roots of the transverse processes, from the third or fourth cervical vertebra above to the sacrum below. The vertebral arches having been displaced by means of a chisel and the separate fragments removed, the dura will be ex- posed, covered by a plexus of veins and a quantity of loose areolar tissue, often infiltrated with serous fluid. The arches of the upper vertebrae are best divided by means of a strong pair of cutting bone-forceps or by a rachitome. Applied Anatomy. — Contusion of the spine may cause an efFusion of blood or traumatic zonal inflammation of the spinal cord with paralysis which may disappear without surgical intervention. Concussion ("railway spine") is followed by temporary or rarely permanent impairment of function. Punctured wounds are usually caused by the knife, and are most com- monly inflicted upon the cervical and upper thoracic divisions and more often involving one- half of the cord. The course is generally an aseptic one; operation is indicated when infection of the cord ensues or when there is a compression from hemorrhage. This may be relieved by lumbar puncture (p. 68) with a large needle. Hemorrhage into the substance of the cord (hematomyelia) usually occurs in the 4-6 cervical segments. If the hemorrhage is confined to the gray substance, there is wasting of muscle and anesthesia of the pectoral limb; the reflexes below the lesion are abolished. If the white substance is involved, paraplegia below the level of the lesion ensues. The cord may be injured by fracture or dislocation of vertehroe (p. 69). Gunshot ivounds are usually of serious nature. Operation is indicated by symptoms of com- pression by the bullet or by fragments of bone. If the compression is due to accumulated blood, lumbar puncture may be resorted to. The cord usually shares in the congenital malformation known as spina bifida, resulting from failure of coalescence of the margins or lateral ridges of the neural plate. The defect may be complete {rachischisis totalis) or confined to a few segments of the cord. Tumors of many varieties, originating in the vertebra, meninges, or even in the substance of the cord itself (glioma, tuberculoma, etc.), give rise to many sensor and motor disturbances which afford a clue to the localization of such growths as indicated on page 831. Inflammation of the spinal cord (myelitis) may follow any of the acute specific fevers, occasioning more or less complete paralyses and anesthesia. In infantile spinal paralysis {acute anterior poliomyelitis) due to an infection which results in the destruction of ventral horn (motor) cells and consequent permanent paralysis and nutritional disturbances of the limbs whose centres are thus affected. Further, the muscles which normally antagonize the affected groups of muscles tend to assume a state of spastic contraction. The deformity thus produced may be relieved by tenotomy, transplan- tation of tendons, or even amputation. Syringomyelia is a chronic condition in which an abnormal prohferation of the spinal neuroglia takes place, generally near the central canal and in the cervical enlargement, and later this mass becomes absorbed, leaving an irregular cavity in its place. This gives rise to a number of interesting symptoms, such as analgesia (or insen- sitiveness to pain), inability to distinguish between heat and cold, progressive atrophy of the muscles of the hands and arms, trophic changes in the bones and joints, and painless whitlows. THE MEMBRANES OF THE CORD. The membranes which envelop the spinal cord are three in number. The most external is the dura, a strong fibrous membrane which forms a loose sheath around the cord. The most internal is the pia, a cellulovascular membrane which closely invests the entire surface of the cord. Between the two is the arachnoid, an avascular membrane which envelops the cord and is connected to the pia by slender filaments of connective tissue. THE SPINAL DURA 843 The Spinal Dura (Dura Mater Spinalis) (Figs. G15, 617). The spinal dura represents only the meningeal or supporting layer of the cranial dura. The endocranial or endosteal layer ceases at the foramen magnum dor- sally, but reaches as low as the third cervical vertebra ventrad; below these levels its place is taken by the periosteum. The dura forms a loose sheath which surrounds the cord and the cauda equina, and is loosely connected with the vertebral periosteum and the ligaments by a quantity of lax areolar tissue and a plexus of veins, the meningorachidian veins (plexus venosi vertebrales intern i). The space containing the fat and veins is called the epidural space {cavum epidurale). The situation of the veins between the dura and the periosteum of the vertebra corresponds therefore to that of the cranial sinuses between the endocranial and sup- porting layers. The dura is attached to the circumference of the foramen mag- num and to the axis and third cervical vertebra; it is also fixed to the posterior Fig. Clo. — The spinal cord and its membranes. Fig file — ihe dentate ligament. The dura has been opened and turned back. The ventral surface is seen. (Hirscbfeld.) common ligament, especially near the lower end of the spinal canal, by fibrous slips; it extends below as far as the second or third piece of the sacrum, where its cavity terminates, and, ensheathing the filum terminale, constitutes the fllum durae matris spinalis (Fig. 598), and descends to the dorsum of the coccyx, to blend with the periosteum. This part of the dura is called the coccygeal ligament (Fig. 617). The dura is much more capacious than is necessary for its contents, and its size is greater in the cervical and lumbar regions than in the thoracic. Its inner surface is smooth. On each side may be seen the double openings which transmit the two roots of the corresponding spinal nerve, the fibrous layer of the dura being continued in the form of a tubular prolongation on them as they pass through these apertures. These prolongations of the dura are short in the upper part of the vertebral column, but gradually become longer below, forming a number of tubes of fibrous membrane, which enclose the sacral nerves, and are contained in the vertebral canal. 844 THE NERVE SYSTEM The chief peculiarities of the dura of the cord, as compared with that investing the brain, are the following: The dura of the cord is not closely adherent to the bones of the vertebral canal, and is not, as is the cranial dura, the internal peri- osteum of the vertebrae. The vertebrae have an independent periosteum. It does Fig. 617. — The filum terminale (schematic). (Poirier and Charpy.) not send partitions into the fissures of the cord, as the cranial dura sends partitions into certain fissures of the brain. Its fibrous laminae do not separate to form venous sinuses, as in the cranium. It contains no arachnoid villi [Pacchionian bodies). Structure. — The dura consists of white fibrous and elastic tissue arranged in bands or lamellse, which, for the most part, are parallel with one another and have a longitudinal arrange- ment. Each surface is covered by a layer of endothelial cells. It is sparingly supplied with vessels, and some few nerves have been traced into it. The Arachnoid (Arachnoidea Spinalis) (Figs. 596, 615). The arachnoid is exposed by slitting the dura and reflecting that membrane to either side. It is a thin, delicate, tubular membrane which invests the surface of the cord, and is connected to the pia by slender filaments of connective tissue. Above, it is continuous with the cranial arachnoid; on each side it is continued on the various nerves, so as to form a sheath for them as they pass outward to the intervertebral foramina. The outer surface of the arachnoid is in contact with the inner surface of the dura, and the two are, here and there, joined together by isolated connective-tissue trabeculae. These trabeculae are especially numerous on the dorsal surface of the cord. For the most part, however, these membranes THE PIA OF THE CORD 845 are not connected together, and the interval between them is named the subdural space (c.avivm suhduralc). The subdural space contains a very small amount of lymph-like fluid. There is no communication between the .nibdural and the nuh- arachnoid spaces. The subdural space is prolonged laterad for a short distance on each emerging nerve and communicates with the lymph tract of the nerve. The inner surface of the arachnoid is separated from the pia by a considerable interval, which is called the subarachnoid space {cavum suharachnoideale). The space is largest at the lower part of the spinal canal, and encloses the mass of nerves which forms the cauda equina. Cephalad it is continuous with the cranial subarachnoid space, and communicates with the general ventricular cavity of the brain by means of openings in the pia, in the roof of the fourth ventricle, the foramen of Majendie or metapore and foramina of Key and Retzius. It contains an abundant serous secretion, the cerebrospinal fluid. This secretion is sufficient in amount to expand the arachnoid, and thus to distend completely the whole of the space included in the dura. The subarachnoid space is occupied by trabeculse of delicate endothelial-covered connective tissue, connecting the pia on the one hand with the arachnoid on the other. This is named subarachnoid tissue. In addition to this the space is partially subdivided by a longitudinal mem- branous partition, the septum posticum or the dorsal fenestrated septum, which serves to connect the arachnoid with the pia, opposite the dorsoniedian fissure of the spinal cord. It is a partition, but an incomplete and cribriform partition, which consists of bundles of white fibrous tissue interlacing with each other, and is coated with endothelium. The dentate ligament {ligamentwn denticiilatwn) , which runs from the pia to the dura on either side of the cord, divides the subarach- noid space into an anterior or ventral and a posterior or dorsal space, which joins like spaces in the cavity of the cranium. The external spinal veins {venae spinales externae) lie in the subarachnoid space. Structure. — The arachnoid is a delicate membrane made up of closely arranged interlacing bundles of connective tissue in several layers. It contains many elastic fibers, and is covered on each side by endothelial cells. The arachnoid contains neither vessels nor nerves. The Pia of the Cord (Pia Mater Spinalis). The pia of the cord is exposed on the removal of the arachnoid (Figs. 615 and 616). It covers the entire surface of the cord, to which it is very intimately adherent, forming its neurilemma, and sending a fold into its ventral fissure. It also forms a sheath for each of the filaments of the spinal nerves, and invests the nerves themselves. A longitudinal fibrous band extends along the middle line on its ventral surface, the linea splendens; and a somewhat similar band, which forms the ligamentum denticulatum, is situated on each side. At the point where the cord terminates the pia becomes contracted, and is continued caudad as a long, slender filament, the iilum terminate (Fig. 617), which descends within the sheath of the dura and the arachnoid and through the centre of the mass of nerves forming the cauda equina. It unites with tlie dura and arachnoid altout the level of the third sacral vertel)ra, and as the central ligament of the spinal cord, the coccy- geal ligament, or the filum dm-ae spinalis the fused membranes extend caudad as far as the base of the coccyx, where they blend with the periosteum. It assists in maintaining the cord in its position during the movements of the trunk. It contains a little gray nerve substance, which may be traced for some distance into its upper part, and is accompanied by a small artery and vein. At the upper part of the cord the pia presents a grayish, mottled tint, which is due to yellow or brown pigment cells scattered among the elastic fibres. 846 THE NERVE SYSTEM Arachnoid Dorsal root Ventral root Fig. 618. — Transverse section of th cord and its membranes. (Gegenbg spinal r.) Structure.— The pia of the cord is less vascular in structure, but thicker and denser, than the pia of the brain, with which it is continuous. It consists of two layers; an outer, resembling the arachnoid, composed of bundles of connective-tissue fibres, arranged for the most part longi- tudinally; and an inner (intima pia), consisting of stiff circular bundles of the same tissue, which present peculiar angular bends. It is covered on both surfaces by a layer of endothelium. Between the two layers are a number of cleft-like lymphatic spaces which communicate with the subarachnoid cavity, and a number of bloodvessels which are enclosed in perivascular sheaths, derived from the inner layer of the pia, into which the lymphatic s|xices ojm'u. The pia contains the anterior or ventral spinal artery and its branches, the two posterior or dorsal spinal arteries, and numerous veins which pass to the external spinal veins. It is also supplied with nerves, which are derived in part from the sym- pathetic and in part from the cerebrospinal nerves. These nerves supply the walls of the bloodvessels and enter the cord with the vessels. Both the arachnoid and the pia may be referred to by the compound name pia-arachnoid, inasmuch as these meningeal components are with difficulty separable from each other. va^a veriebraiia rpj^^ dentate ligament (ligamentum denti- culaimii) (Figs. 596 and 616) is a narrow, fibrous band, situated on each side of the spinal cord, throughout its entire length, running from the pia to the dura, and separating the ventral from the dorsal roots of the spinal nerves. It has received its name from the serrated appearance Vi^hich it presents. Its inner border is continuous with the pia at the side of the cord. Its outer border presents a series of triangular, dentated serrations, the points of which are fixed at intervals to the dura. These serrations are twenty- one in number on each side, the first being attached to the dura opposite the margins of the foramen magnum between the vertebral artery and the hypoglossal nerve, and the last near the lower end of the cord. Its use is to support the cord. Applied Anatomy. — Evidence of value in the diagnosis of meningitis may be obtained by the operation of lumbar punciiirc, that is, by puncturing the theca of the cord and withdrawing some of the cerebrospinal fluid, and the operation is regarded by some as curative, under the supposition that the draining away of the cerebrospinal fluid relieves the patient by diminish- ing the intercranial pressure. Lumbar puncture may give important diagnostic aid after a head injury by disclosing bloody cerebrospinal fluid. The operation is performed by inserting a trocar of the smallest size below the level of the fourth lumbar vertebra. In an adult the cord terminates- at the lower border of the first lumbar vertebra, and in a child opposite the body of the third lumbar vertebra. The canal may be punctured below the fourth vertebra without much risk of injuring its contents. The point of puncture is indicated by laying the child on its side and dropping a perpendicular line from the highest point of the crest of the ilium; this will cross the upper border of the spine of the fourth lumbar vertebra. In a child the puncture is made just below this spine; in adults, one-half an inch to one side of the end of this spine. However the preliminary puncture is made, the needle penetrates the dura in the midline. In entering the needle it should be directed upward and forward in a child; upward, forward, and slightly inward in an adult. THE BRAIN OR ENCEPHALON. The brain is that greatly modified and enlarged portion of the cerebrospinal axis which, with its membranes, almost completely fills the cavity of the cranium. It is a complex organ in which reside the highest functions — consciousness, ideation, judgment, volition, and intellect — together with the centres of special sense and for the mechanisms of life (respiration and circulation), and it is the a2:ent of the will. THE BRAIN OB ENCEPHALON 847 General Appearance and Topography of the Brain. — Corresponding to the varieties of cranial form, the shape of tlie fresh or the successfully preserved brain varies from the ovoid to the nearly spherical form, as viewed dorsally. The frontal pole is usually narrower, though more squarely formed; while the parieto- occipital portion is more massive, but more sharply pointed in each half. The outline is often rather that of an irregular pentagon with its angles rounded off. A dorsal view (Fig. 672) shows only the extensive convex surface of the two great convoluted cerebral hemispheres (hemicerebra) separated by a median cleft, the intercerebral fissure (fissura hngitudinalis cerebri). On divaricating the cerebral halves it is seen that the separation is not a total one, for in the depths of the fissure a broad commissural mass of white fibres — the corpus callosum — joins the cerebral hemispheres. Frontad the longitudinal fissure is continued to the ventral or basal aspect of the brain; caudad it passes into the fissura transversa cerebri (tentorial hiatus) or interval, separating the cerebrum from the cerebellum. In a lateral view (Fig. 67.3) the continuity of the spinal cord with the medulla oblongata, then the pons and cerebellum are seen in part, overlapped by the cere- brum. Prominent is the temporal lobe with its rounded pole, separated from the frontal and parietal lobes by a deep cleft, the sylvian fissure, in whose depths — overlapped by the opercula of the adjacent lobes — lies the island of Reil or insula. A ventral view (Fig. 619) presents many of the subdivisions of the brain. Here is seen the continuity of the spinal cord, with the short and slightly expanding medulla oblongata lying ventrad of the cerebellum and somewhat buried in its val- lecula or depression between the lateral hemispheres, which alone are visible. The cerebellum is a grayish-colored mass of considerable size and easily recognized by its foliated appearance, due to the numerous parallel and closely set curved fissures. A mass of white fibres, the pons, passes transversely from one cere- bellar hemisphere to the other, ventrad of the upper portion of the medulla oblongata. Above the pons are seen two large bundles, the crura cerebri, one on either side, diverging to pass into the cerebral halves. The inter\'al between the divergent crura cerebri and temporal poles laterad and the orbital portions of the cerebrum frontad contains a number of important structures. Encircling the crura cerebri and meeting in the fore part of the fossa are the optic tracts, decussating in the median plane to form the optic chiasm and continuing frontad as the optic nerves. The arch of the optic tracts and optic chiasm and the crura cerebri enclose the intercnnal space, in which may be seen (1) the posterior per- forated space (substantia perforata -posterior; postperforatum) ; (2) the corpora albicantia (c. mamillaria); (3) the tuber cinereum and the stalk of the pituitary body. A groove marking the lateral boundary of the fossa along each crus is termed the oculomotor sulcus, as the root fibres of the oculomotor nerve have their superficial origin therein. The posterior perforated space is a gray area with numerous minute apertures for the entrance of postperforant branches of the posterior cerebral artery. The corpora albicantia are two small, pea-like, white eminences closely set side by side. The tuber cinereum is a conical projection between the corpora albicantia and the optic chiasm, to which the hypophysis (pituitary body), resting in the sella of the sphenoid, is attached. In the re- moval of the brain from the skull the stalk of the hypophysis is usually torn through and an orifice, the lura, leading to the infundibular recess of the third ventricle, is thus exposed. In the interval between the optic tract and the orbital surface of each cerebral hemisphere is a small, depressed, triangular area of gray substance leading laterad into the basisylvian fissure and dotted with numerous apertures for the minute basal branches of the middle cerebral artery and called the anterior perforated space (preperf oratum) . If the optic chiasm be drawn somewhat ventrad, a delicate gray lamina, the lamina terminalis (terma), is seen attached to the dorsal surface of the optic 848 THE NERVE SYSTEM chiasm and passing dorsad into the intercerebral cleft to the region of the anterior commissure. Parallel to the mesal border of the orbital surface of each cerebral hemisphere lie the olfactory tract and bulb, torn away from the fila olfactoria as these pass through the lamina cribrosa of the ethmoid. The olfactory tract may be traced to its root area, the olfactory trigone, just frontad of the anterior perforated space. The superficial origin of nearly all of the cranial nerves may be seen upon the basal aspect of the brain (Fig. 619). These nerves, their superficial attachments to the brain, and the foramen of exit in the skull are enumerated in the following table : Tabulation of the Cranial Nerves, their Superficial Attachments to THE Brain, and the Foramina of Exit in the Skull. I. II. III. IV. V. Olfactory fila. Optic nerve. Oculomotor nerve. Trochlear nerve. Trigeminal nerve. TI. Abducent nerve. \ll. Facial nerve. VIII. Acoustic nerve. IX. Glossopharyngeal nerve. X. Vagus nerve. XL Spinal Accessory nerve. SnPERFici.\L, "Origin" or At- tachment TO THE Brain. XII. Hypoglossal nerve. Olfactory bulb and tract. Optic chiasm. Oculomotor groove along medial border of crus. Valve of Vieussens laterad of fren- ulum. Prelateral part of pons. Postpontile groove (prepyram- idal part). Postpontile groove (laterad of abducent nerve in preolivary . part) . Postpontile groove (laterad of facial nerve). Dorsolateral groove of medulla oblongata. Dorsolateral groove of medulla oblongata. (a) Encephalic part : Dorsolateral groove of medulla oblongata. (6) Spinal part: Lateral column of spinal cord, between ven- tral and dorsal roots of cer- vical nerves as far as the fifth and sixth cervical nerves. Pyramido-olivary groove. Foramen of Exit from the Skull. Ethmoidal cribrosa. Optic foramen. Sphenoidal fissure. Sphenoidal fissure. (o) Ophthalmic ramus, sphe- noidal fissure. (6) Maxillar}- ramus, foramen rotundum. (e) Mandibular ramus, foramen ovale. Sphenoidal fissure. Porus acusticus internus; meatus ■ acusticus internus ; facial canal; stylomastoid foramen. Porus acusticus internus. Jugular foramen. Jugular foramen. Jugular foramen. Canalis hypoglossi (" anterior condylar foramen"). The olfactory, optic, and acoustic nerves are afferent or sensor nerves. The trigeminal, glossopharyngeal, and vagus nerves are mixed nerves. The oculomotor, trochlear, abducent, facial, spinal accessory, and hypoglossal nerves are or motor nerves. THE BBAiy OR ENCEPHALON .S4.>...c, o=6."=— .^.^B"- .» the region, however, no more deserves uld the cephalic constriction even if it were dignified by the term ulhmua 852 THE NERVE SYSTEM stages and the disposition of certain of the cranial nerves afford a clue to the defi- nitive segmentation of the brain. According to the most recent researches, as many as eleven, sixteen, and even more neuromeres have been established in various vertebrate brains. The hind-brain alone shows from six to eight such neural segments (Figs. 620 and 621). The whole matter is yet so obscUre that confusion will be avoided by restricting our description to the three primary divisions and their derivatives without insisting upon the recognition of further definitive segments proposed by various authors in consequence of preconceived ideas obtained from the complicated adult structure of the brain. At this transi- tional period the student is, however, obliged to be familiar with the commonly accepted — yet provisional — schemes of segmentation and a comparative view is given in the following table: Table Showing Comparison of the Segmental Schemas Adopted by The Anatomische Gesellschaft in 1895. Partes ventrales. Partes dorsales. VI. Telencephalox. -n 4-- 1, ii, 1 „• (Corpus striatum; rhinen- Pars optica hypothalami. | cephalon; paUium. V. DiENCEPHALON. ■D „ „„•! ■ u j-u 1 „• (Thalamus; metathala- Pars mammilaris hypothalami. | ^^s gpithalamus. IV. Mesencephalon. Pedunculi cerebri. Corpora quadrigemina. III. Isthmus Rhombencephali. Pedunculi cerebri. f Brachia conjunctiva; ve- \ lum meduUare anterius. II. Metencbphalon. Pons. Cerebellum. I. Myelencephalon. Medulla oblongata. The Association of American Anatomists in 1897. I. Rhinencephalon. Bulbi olfactorii with their tracts; part of the aula and of the pre- commissure. II. Pkosbncephalon. Palliums, connected by part of the aula and part of the precommis- sure. III. DiENCEPH.A-LON. ' Thalami, including the chiasm; geniculate bodies. IV. Mesencephalon. Crura and quadrigeminum. V. Epbncephalon. Cerebellum: pons; preoblongata. . VI. Metencbphalon. Postoblongata. Brief Consideration of the Phases of Development of the Brain Tube, I. Fore-brain. — The cephalic or fore-brain vesicle widens and expands most rapidly and attains to a comparatively large size even before the mid- and hind- brain vesicles become markedly defined. A series of remarkable developmental changes ensue in the following order : (o) Optic vesicles appear as two diverticula, each budding from either side of the primary fore-brain vesicle, their distal ends growing considerably and coming into contact with the overlying epidermis, while the proximal or attached ends assume a stalk-like shape. The distal sac-like end becomes invaginated and forms the retina of the eye, while the stalk upon obliteration of its cavity forms the optic nerve. It is necessary to state here that as development proceeds the optic stalks become relatively shifted caudad and form more intimate connections with the thalamus and mid-brain. (b) A second pair of budding vesicles arises cephalad in the dorsal portion of the fore-brain vesicle and is destined to develop into the ponderous cerebral hemi- THE BRAIN OR ENCEPHALON 853 spheres with their great gangha, growing with great rapidity and exceeding in this respect all other parts of the brain. The growth of these secondary fore- brain vesicles is principally in the distal parts, and in this manner each forms a great pouch whose interior communicates with the primary neural cavity through a small opening, the foramen of Monro (i)orta). It must be remembered that in MUlbmm. Hindifdin Auditory vesicle. Head fold of amnion. Forehraiii. ' — Optic vesicle. -I -j-- Heart. •Omphalo-mesenteric vein -A-4--- ) Profovertebrie or [ mesoblastic somites. 'f-,-3— ^-S---Sjn«s rhomboidalis. Remains of primitive - streak. Fig. 623. — Chick embryo of thirty-three hours' incubation, viewed from the dorsal aspect. X 30. (From Duval's Atlas d'Embryologie.) these initial stages the vesicles are all extremely thin-walled, but later the walls thicken or hypertrophy to a marked degree, so that the neural cavity becomes relatively small. (c) Meanwhile (in the fourth week) the most ceplialic portion of the fore-brain also becomes differentiated. As the enlarging vesicles of the cerebral hemisphere crowd upon the median, slower-growing portion, there is observed, on either 854 THE NERVE SYSTEM side, the development of a groove or furrow, the primary arcuate fissure, which demarcates the olfactory region (^rhiiioicephalon) into a cephalic and a caudal portion. The cephalic portion develops into a blind tubular diverticulum, which grows cephalad to form the olfactory bulb and tract, its central cavity becoming obliterated (persist- ent in certain other mammals), while the caudal portion forms the roots of the olfactory nerves, the anterior perforated space or preperforatum and the subcallosal gyre. (d) At the ventral margin of the hemicerebral or secondary fore-brain vesicle an excessive proliferation of cells results in the production of several ganglionic masses — the basal ganglia, of which the largest are the lenticular nucleus (lenticula) and caudate nucleus (caudatum). (e) The median cephalic terminal wall inter- vening between the large hemicerebral vesicles persists as a thin and relatively undeveloped lamina, the lamina terminalis. (J) The remainder of the fore-brain undergoes great hypertrophy in its lateral walls to form the optic thalami, while the ventral portion develops moderately to form the hypothalamus, tuber cine- reum, posterior lobe of pituitary body, and corporffl albicantia. The dorsal wall fails to develop, and remains epithelial except at a point imme- diately adjacent to the quadrigeminal lamina of the mid-brain; here a diverticulum grows out to forin the pineal body or epiphysis (a rudi- mentary structure in man, but undoubtedly of functional use in ancestral vertebrates). (cj) The cavity of the primary fore-brain vesicle ode of undergoes alterations in form as the secondary \) Fig. 624.— Plan showing the m iaTtt°cenlli''earaf ofthetin-5 cSrS! metamorphoscs of its walls procccd in the course c;'lS'e?ere^pt\on.''-fl^^ of development. The hollow cerebral buds so E. Myeiencephaion. F. Central canal of rapidly outstrip all Other parts of thc braiu that cord. G. Lateral ventricle. H. Foramen ^. ■'. <: . . ^ of Monro. (After Gerrish.) their mternal cavities, the lateral ventricles, Netiral canal Neural i Pie tonial caLity ^ Splauchnopleure Omphalo- mesenteric vein Fig. 625. — Transverse section of a portion of a chick embryo of twenty-nine hours incubation, (From Duval's Atlas d'Embryologie.) become the most spacious of the ventricular system. The great hypertrophy of the thalamic ganglia in the lateral walls of the primary for^-brain determine the THE BRAIN OB ENCEPHALON 855 sagittally placed, slit-like form of the so-called third ventricle. The cavities of the optic and olfactory buds become obliterated. II. Mid-brain. — The second primary vesicle becomes .somewhat later differen- tiated and takes a less prominent part in the adult brain. Its dorsal wall goes into the formation of four eminences, the corpora quadrigemina, while the lateral and ventral sections grow considerably to form the crura cerebri. The neural cavity within the mid-brain persists as the narrow aqueduct joining the third and fourth ventricles. III. Hind-brain. — ^The third primary brain vesicle is demarcated from the mid- brain by a marked constriction to which has been given the term isthmus rhomb- encephali. The hind-brain is specially characterized by the great expansion of its thinned-out, membranous dorsal wall caudad, while cephalad the dorsal wall becomes very much thickened as the proton or " anlage " of the cerebellum. The ventral and lateral parts undergo thickening to form the pons and medulla oblongata. Invaglnatioti of Ectoderm to form the tens ntdimenf Fig, 626. — Trans-section of head of chick embryo of forty-eight hours' incubation. X 55. (From Duval's Atlas d'Embryologie.) Flexures of the Brain Tube. — The difference in growth rate of the differ- ent parts of the brain tube and the marked disproportion between the rapid brain growth and slower head growth causes the encephalic neural tube to become sharply bent upon itself at certain points. The first flexure to occur is involved in a bending of the entire head and takes place in the region of the mid-brain; this flexure is termed the cephalic flexure. A second bending of the tube occurs at the junction of the spinal cord and hind-brain; this is termed the cervical flexure, and is so pronounced in the fifth week of intrauterine life that the lirain tube and spinal cord form a right angle with each other. A third flexure is produced, in consequence of the other two, in the region of the future pons, and is therefore called the pontile flexure. Subsequently the cervical and j^ontile flexures are obliterated by a gradual straightening of this portion of the l)rain axis. Dorsal and Ventral Laminae or Longitudinal Zones of the Brain.— Quite like the longitudinal division of the developing spinal cord, there is a differ- entiation of the brain tube into dorsal and ventral zones, though much less clearly shown. The limiting furrow between the two is not demonstrable in the fore- brain; at least it is disputed, on good grounds, that it exists there. It is claimed even that three such longitudinal divisions exist on each side (Kupfi'er) and the formation of the cranial nerves is not quite comparable to the spinal nerves, although there is a fair homology with their dorsal-sensor and ventral-motor func- tional differentiation, despite their frequent admixture in some cranial nerves or the total absence of the one category in others. Thus the motor elements do not extend higher than the mid-brain and the dorsal division preponderates in the more highly organized parts of the brain, becoming predominant in the higher vertebrate species — particularly in man. 856 THE NERVE SYSTEM In its simplest expression the brain is a tube like the rest of the central nerve axis, but a remarkably modified one. There is the same primitive ependymal ^(0^R4,^ 3LFACTORY FOLD Fig. 627. — Profile view of the brain of hum A. Brain of an embryo of about fifteen days. Brain of an embryo about seven and a half weeks' old embryos at three several stages, reconstructed from sections: B. Brain of an embryo about three and a half weeks old. C. • ' (After His.) lining throughout its interior; there is likewise a central tubular gray mass of ganglionic tissue which, however, undergoes nuclear differentiation in some THE BBAIN OR ENCEPHALON 857 portions, atrophies in others, while in certain localities it is crowded away from the central cavity by the intrnsion of white fibre masses which are chiefly com- missural. A total atrophy occurs in a part of the dorsal wall of both fore-brain and hind-brain; partial atrophy is ol)servable in the floor of the third ventricle, near the optic chiasm, once perhaps the optic centre in the earliest of the ancestral vertebrates, but atrophied in higher forms as the visual tract became secondarily projected in the thalamus and mid-brain. Great hypertrophy characterizes the growth of the ganglionic gray in the floor of the lateral ventricle (cerebral vesicle), resulting in the formation of nugget-like masses, the caudate, lenticular, and amyg- daline nuclei. The central gray of the primary fore-brain also undergoes great hypertrophy, but in the lateral walls only, to form the large, compact thalami. Thalamus. Foramen of Monro, Posterior cnmmi. Pineal body. Quadrigeminai plate. ' Cerebellum. IT. Ventricle. Cerebral hemisphere. Olfactory lobe or :■; • ] rhinencephalor . . '^ , | Lamina terminalis. 1 ' | J Optic nerve. J i , Optic chiasm.^ i | Pitnilary body.'^ Tuber cinereum. 1 Pons. MedulJa j oblongata. Corpus ilbicans. Spinal cord. Fig. 628. — Median section of brain of human fetus during the third month. (After His.) As in the cord, fibre masses develop ectad of the central tubular gray in some localities, while in other regions the ganglionic gray remains at the surface and the white conducting substance is developed on its inner aspect. Thus we have, secondarily, the formation of superficial gray substance as the cortex (or rind) of the cerebrum and cerebellum. The isolation of ganglionic gray masses from the primitive central tubular gray and their difi^erentiation into nerve cell nidi is also observable in the reticular ganglionic formation of the medulla oblongata and pons as well as in the roof of the mid-brain. Certain aggregations of gray ganglionic tissue are intercalated in the course of fibre strands, receive an admixture of these, and are regarded as terminal, interrupting, or as condensing stations not unlike some very complex relay telegraph system. The olive, dentate nucleus, red nu- cleus, the nuclei of the gracile and cuneate funiculi, the basketwork intercalations of the reticular and lemniscus fields belong to this intrafascicular type of ganglionic structures. 858 THE NEB VE SYSTEM The plan of structure of the brain differs, tlierefore, from the comparatively sim 3le arrangement of the gray and white substance in the spinal cord. In the brain tlie gray substance is not centrally situated throughout, and there is a tendency to nuclear differentiation of great and small ganglionic masses. These are con- nected with each other and with the centres in the cord by longitudinal strands of fibres of greater and less length, as well as by transverse associating fibres RHOMBOIDAL Fig. 629. — Three stages in the development of the medulla oblongata, showing the metamorphosis of the rhomboidal lip. (Modified after His.) uniting the bilateral nuclei of the same ganglionic category; with the periphery they gain connection through the cranial nerves and [via the spinal cord) the spinal nerves. In tracing the various structures of the brain from the medulla oblongata to the cerebral cortex we follow anatomically what nature has done in the evolution of the highest type of brain from that of the simplest and most ancient vertebrate. In the medulla oblongata lie the centres which exert a very direct influence over those of the entire cord. The striate bodies and the thalami form a connecting link between the higher cerebral cortex and the medulla oblongata and cord below. The extensive cerebral cortex, an aggregation of psychic centres and therefore the seat of the will, controls the activities of the fore-brain ganglia (corpus striatum, thalamus) and the cerebellar cortex, and these in turn preside over the functions THE BRAIN OR ENCEPIIALON 859 of lower centres, as in the way of motor responses to external impressions; such reactions may be delayed or immediate according to the exercise of the will power residing in the cerebral cortex. This control by the will is intensified the higher we ascend the animal scale; the pyramidal tract, which originates in the cerebral cortex and threads its way to the motor centres of tiie spinal cord without interruption along the brain axis, is better developed in man than in any other animal. In the course of evolution the lower or more automatic ganglia and tracts remain relatively about the same in mass as in other mammalia, but the higher, more intellectual ganglia surpass these in growth, so that there is an apparent but not real diminution of the auto- matic systems observed in the human brain. oeR£.^RO-co,j J5>t (floor of iicle and queduct) Fig. 630. — Schematic representation of the chief ganglionic categories {I to V). Accurate topographical relations and interconnections are shown in other figures. It has been seen from the foregoing brief accounts of the development of the nerve system that the most prominent feature is the redundant growth of the cephalic or brain end of the neural tube. Comparative neuroanatomic re- searches have thrown much light upon the probable genesis of this remarkable characteristic. The ancestral vertebrate, built upon the segmental type, was a swimming animal, and its locomotion took place in the direction of its long axis. In its progress through the water the cephalic (or anterior) segments were those which first encountered the foreign objects floating in the same medium. It was for these segments to determine the quality of the objects encountered — whether 860 THE NERVE tiYHTEM they were inimical or indifferent or beneficial to its individual ends. The sensor periphery, in consequence of the demands of evolution, underwent specialization in the development of olfactory and gustatory organs for testing the quality of the food and of the surrounding medium; optic organs for perceiving rays of light; auditory organs for the appreciation of certain oscillations of the surrounding medium; while others, strictly tactile in nature, underwent elaboration as such in the development of sensitive antenna or tentacles. Motor contrivances, useful in the quest for food or in encounters with the enemy, were developed in the way of powerful jaws and masticatory muscles. In brief, a remarkable specialization and differentiation of structure attended the development of the head end, and with it the central organ of control kept pace. In the human species we find certain of these structural characteristics in a highly developed condition, while others have dwindled or disappeared in the course of evo- lution. Thus, in the myxinoid fishes and the lamprey the cere- bral hemispheres themselves are mere appendages of the olfactory lobes; the sense of smell was prob- ably the most important in lower animals. In the brain of man conditions are reversed and the olfactory system is seen to have dwindled to an extreme degree as compared with the immense size of the cerebrum; this in conformity with the relatively slight use made of the smell sense in the mental life of man. Other organs of special sense, however, became augmented, and these, together with the nerve mechanisms controlling the vital functions (respiration, circulation), required a more and more elaborate central nerve organ for the harmonious interaction of the several elements. This central organ or brain developed, in bulk and complexity, hand in hand with the increase of the intellectual faculties. Man's most manifest distinction from other animals has resulted from a remarkable evolutionary growth in brain size and brain power; and as the brain is the material organ of mental and moral manifesta- tions, we find in mankind the highest degree of superiority and culture — not only as compared with the nearest related apes, but of the civilized and progressive races as compared with the primitive and unprogressive races. ^'^j—MiO.dXe peduncle -Inferior peduncle -Medulla oblongata -Scheme showing the connection of the parts of the brain. DESCRIPTIVE ANATOMY OF THE ADULT HUMAN BRAIN. Morphologically considered, the brain consists of a common trunk (or brain axis) from which the two cerebral hemispheres crop out like swollen terminal buds, while the cerebellum is an excrescence of the trunk itself. The axially situated brain axis or ^'brain stem"^ comprises, roughly speaking, the axial parts of all ■ Also "brain isthmus," a loosely used term. It may here be remarked that most extant accounts of the anatoray of the brain overemphasize the distinction of brain parts from each other. Some authors follow one or anotjier system based upon the theories of the segmentation of the brain tube; others divide the brain into (a) rhombencephalon or hind-brain and {b) cerebrum, comprising mid- and fore-brain. None of the classifications proposed are, as already pointed out, quite satisfactory. The continuity of the parts can only be interrupted arbitrarily, and such procedure leads, to a too narrow conception of brain structures single and apart rather than serial and connected. PARTS DERIVED FROM THE HJXD-BRAIN -SGI three primary divisions of tiie l)r;un tuhe — (a) medulla oblongata, (h) pons, (r) mid- brain, (d) thalamic division of fore-brain. In this brain stem lie tiie majority i.f (he ganglionic masses enumerated al)ove, togetiier witii tiie nerve tracts uniting the various ceil nests in (presumable) automatic coordination as well as the great nerve tracts connecting the spinal gray with the cerebral hemispheres, the thalami, cerebellum, and the ganglia of the medulla oblongata (including the cranial nerve nuclei), and still other tracts connecting the medulla oblongata with the cerebral hemispheres, the cerebellum, and the special ganglia of the pons and mid-brain. Parts Derived from the Hind-brain (Rhombencephalon). Morphology. External The Medulla Oblongata (myelencephalon oblongata; spina! bulb; postoblon- gata of Wilder). — The medulla oblongata is the continuation cephalad of the spinal cord, the transition lying at the level of the foramen magnum and marked by the decussation of the pyramids. Its cephalic limit is sharply defined ventrad by the rounded margin of the pons, while its dorsal surface is sunk into the cere- bellar vallecula. The length of the medulla oblongata along its ventral surface is f to 1 inch (20 to 25 mm.) ; its maximum width at the pontile end is | inch (17 to 18 mm.), and half as much at its transition into the spinal cord; its maximum OF TRIGEMINAL NERVE FACIAL NERVE N. INTEBMEDIUS ACOUSTIC NERVE GLOSSO PHARYNGEAL NERVE VAGUS NERVE SPINAL ACCESSORY NERVE HYPOGLOSSAL NERVE I. CERVICAL NERVE ASILAR GROOVE Fig. 632. — Ventral view of pons and medulla oblongata, showing the attachments of certain cr.inial nerves on one side. * The inter-radieular pons tract or corpus pontobulbare, described in the text. thickness is about 15 mm. (| inch). Its expansion as it approaches the pons gives it the form of a truncated cone. The ventral surface rests upon the basilar groove of the occipital bone. Fissures. — The ventral and dorsal fissures of the cord are continued upon the medulla oblongata, making it a bilaterally symmetrical structure. The ventral or ventromedian fissiu-e (fissura mediana anterior) at the level of the foramen magnum is interrupted by a number of obliquely intercrossing fibres, called the 862 THE NERVE SYSTEM decussation of the pyramids. Beyond this interruption the ventral fissure passes cephalad to end at the ventrocaudal border of the pons in a recess called the postpontile recess or foramen cecum. The dorsal or dorsomedian fissure (fissura mediana posterior) is of short extent upon the medulla oblongata, for the neural cavity is here expanded into a rhom- boidal fossa whose dorsal wall, profoundly atrophied, is represented only by a delicate membranous lamina; the dorsal fissure rapidly becomes shallower as it ascends, to cease at the caudal apex of the "fourth ventricle." Like the spinal cord, the surface of each half of the medulla oblongata is divided into three longitudinal districts by fissures called the ventrolateral and dorsolateral fissures. Of these, the latter only is a continuation of the fissure of the same name in the spinal cord. The ventrolateral fissure (sulcus lateralis anterior) of the medulla oblongata demarcates the ventral column (pyramid) from the lateral column as well as the oli\'e, and the roots of the hypoglossal nerve, arranged in linear order, emerge from this fissure. (The ventrolateral fissure of the spinal cord becomes obscured as it ascends into the oblon- gata! region, for cephalad of the emergence of the ventral roots of the first cervical nerve a band of superficial arcuate fibres usually obliterates all traces of the furrow.) The dorsolateral fissure {sulcus lateralis posterior) of the medulla oblongata is directly continuous with the same-named fissure of the spinal cord, and the root bundles of the spinal accessory, vagus, and glossopharyngeal nerves are attached along the bottom of this fissure. Unlike the dorsal roots of the spinal nerves, the root bundles of these three cranial nerves are not all composed of afferent fibres arising in extraneous ganglionic cells and entering the medulla oblongata, for the accessory nerve is purely efferent and the vagus contains both afferent and efferent fibres. Areas. — The ventrolateral and dorsolateral fissures with their rows of nerve fascicles divide the surface of the medulla oblongata on each side into three dis- tricts which appear to be continuous with the three columns of the spinal cord; they are not so in reality, however, owing to the rearrangement of the fibre tracts and the central ganglionic mass in the myel-oblongatal transition. This portion of the brain axis is sculptured into several eminences and depressions ; of the emi- nences, some, like the olives, the tubercula cinerefe, and the clavse, are due to the accumulation of gray substance beneath the surface at that point; others, like the pyramids and restiform bodies, are due to the prominence at certain points of the surface of the great nerve tracts. Areas of the Medulla Oblongata. I. Ventral Area: Pyramid. II. Lateral Area: (a) Lateral tract. (b) Olive. III. Dorsal Area, marked by slight furrows dividing it into: (a) Funiculus gracilis. (b) Funiculus cuneatus. (c) Funiculus lateralis and tuberculum cinereum. The last three structures mentioned appear to become fused cephalad to continue as the restiform body or restis; in reality the restiform body is formed in a different manner. AREAS OF THE MEDULLA OBLONGATA 863 I. The Pyramids {pyramides meduUae oblongafae) constitute the ohlongatal portion of the direct cerebrospinal efferent tracts conveying (voluntary) motor impulses from the precentral cortex, through the internal capsule, crusta, and ventral pons to descend in the crossed and direct pyramidal tracts to the efferent (motor) cell groups in the ventral horns of the spinal gray. In their external appearance in the medulla oblongata they are moderately constricted at their pontile ends, appear to become somewhat expanded, to again taper as they pass, partlv into the ventral columns of the cord, partly, by decussation, into the lateral columns. The pyramids are separated from each other by the ventral (or ventro- median) fissure except where this is more or less completely obliterated by the decussating bundles. Each pyramid is bounded laterally by a slight furrow, the ventrolateral or pyramido-olivary groove, in which arise the hypoglossal nerve roots and which separates the pyramid from the olive. The pontile end of each pyramid is frequently traversed by a band of arched fibres {fibrae amiatae externae); ponticulus of Arnold (not the ponticulus of Henle), the ectal arcuate fibres. The decussation of the pyramids (decussatio pyramidum) is a term given to the obliquely intercrossing bundles seen at the oblongata-myelon transition. The extent to which this decussation occurs and the degree of its visibility varies in different individuals. While in most cases the majority (90 per cent.) of the fibres cross the median line in this decussation to continue as the crossed or lateral pyramidal tract, it is sometimes observed that a larger share of the fibres pass into the direct or uncrossed pyramidal tract with a corresponding reduction of the crossed tract. Occasionally the decussating bundles are so deeply situated in the ventral fissure as not to be visible. II. The Lateral Area of the medulla oblongata is continuous with that of the spinal cord, and is bounded by the dorsolateral and ventrolateral fissures. It is composed of the tract of Gowers (fa.tricvhts antrrnlaferaJis superficialis) , the ventrolateral ground bimdle {jaficiruhis jirajirius anicrolutrntUs), and the direct spinocerebellar tract {fasciculus cerebellospinal is [Flechsig]), while it is invaded from above by the crossed pyramidal tract. The olive is interpolated in the cephalic part of this area. The olive (oliva; olivary body) is a prominent, elongated oval mass bulging from the cephalic part of the la teral area of the medulla oblongata, bounded by shallow grooves, of which one, for the hypoglossal nerve roots (ventrolateral fissure) separates it from the pyramid, while the other, containing the nerve fascicles of the vagus, glossopharyngeal and spinal accessory nerves, separates the olive from the restiform body. From the pons it is separated by a shallow groove in which a band of arched fibres is sometimes seen. Numerous white fibres (external or ectal arcuate fibres) emerging from the ventral fissure and traversing the pyramid loop across the lower parts of the olive to enter the restiform body. The olive is formed by the olivary nucleus, embedded in a thin layer of white substance. The olive is about 12 mm. (| inch) in length and 5 mm. (^ inch) in breadth. III. Dorsal Area. — (a) The funiculus gracilis is the direct continuation of the tract of the same name in the spinal cord. It is a narrow white band placed along the dorsomedian fissure, and separated from the funiculus cuneatus by the dorso- paramedian furrow (sulcus intermedius posterior). At the caudal apex of the rhom- boidal fossa (fourth ventricle) each funiculus gracilis diverges from the median plane, presenting at this point a club-like enlargement, the clava. The promi- nence of the funiculus gracilis (and clava) is due to the gray nucleus funiculi gracilis beneath the surface. {//) The fimiculus cuneatus is the direct continuation of the tract of the same name in the spinal cord. It enlarges as it ascends, exhibiting a slight eminence or enlargement, the cuneate tubercle, which is marked only in the medulla ob- longata of young individuals, and is due to the nucleus funiculi cuneati beneath the surface. 864 THE NER VE SYSTEAr (c) The funiculus lateralis is a longitudinal prominence which gradually en- larges cephalad into a slight tubercle, the tuberculum cinereum, marking the ap- proach of the gelatinosa to the surface so as to form a prominence at a level with the lower border of the olive. The restiform body {corpus restiforme; restis) occupies the upper dorsolateral area of the medulla oblongata on each side, lying between the floor of the fourth ventricle and the roots of the vagus and glossopharyngeal nerves. This structure might at first glance appear to be the continuation of the three funiculi just described. But as a matter of fact it is made up of the direct spinocerebellar tract, a set of external or ectal arcuate fibres {fibrae arcuatae externae) and a set of internal or ental arcuate fibres {fibrae arcuatae internae). Each restiform body assists in forming the lower part of the lateral boundaries of the fourth ventricle and then enters the cerebellum as the inferior peduncle of that body. The Pons {pons [Varolii]) . — The pons is a prominent white mass on the ventral aspect of the brain stem which is interposed between the medulla oblongata and the crura cerebri. It is convex from side to side, and its fibres, running chiefly in a transverse arched direction, are gathered into rounded, compact strands on either side, to continue as the middle peduncles into the white substance of the corresponding cerebellar hemisphere. The fibre bundles of the pyramidal tracts thread their way through the pons on either side of the median plane and small aggregations of gray substance {nuclei pontis) are packed in the intervals between the transverse pontile and longitudinal pyramidal fibre bundles. The Basilar or Ventral Surface of the pons is in relation with the basilar process of the occipital and the dorsum sellae of the sphenoid. A shallow mesal groove lies between the eminences produced by the pyramidal tracts in their course through the pons. The groove is called the basilar groove {sulcus basilaris), as the basilar artery is usually accommodated in it; the artery is not, however, a factor in the production of the groove. The large sensor and small motor root bundles of the trigeminal nerve pierce the mass of the pons near the anterior pontile border, and a line drawn from this nerve root to that of the facial nerve is usually employed as an arbitrary boundary between the pons proper and the middle peduncle of the cerebellum. The abducent nerve emerges from the posterior pontile bor- der (prepyramidal part) ; the facial and acoustic nerves are attached farther laterad. While most of the superficial fibre bundles -of the pons are seen to arch trans- versely, certain small compact bundles' are seen to extend in an obliquely longitu- dinal direction from the region of the trigeminal nerve root to and among the roots of the facial and acoustic nerves. The Pars DorsaUs Pontis {pars metencephalica viedullae oblongatae; preoblongata). — The pars dorsalis pontis, or tegmental part, is not sharply demarcated from the medulla oblongata or the tegmentum and crusta of the mid-brain, and the margins of the pons on the ventral surface afford only arbitrary boundary lines; for in the vertebrate series the pons varies greatly in width and its margins can hardly be accepted as the boundaries of a definite brain segment. The dorsal surface of the pars dorsalis pontis is continuous with that of the oblongatal ventricular surface, and its description more properly belongs to a consideration of the anatomy of the fossa rhomboidalis or "floor of the fourth ventricle." Fourth Ventricle of the Brain {ventriculus quartus). — ^In a previous section on brain development it has been pointed out how the growth changes and differ- entiations in the hind-brain differ from those of the rest of the neural tube in that there is a marked disproportion in the degree of growth in the dorsal and ventral walls. While the ventral wall thickens greatly throughout to form the pons-oblon- ^ Called the inter-radicular pons tract by E. C. Spitzka (1884), and more recently described as part of the corpus pontobulbare by Essick (American Journal of Anatomy, vii, 1). AREAS OF THE MEBVLLA OBLONGATA 866 gata, the dorsal wall hypertrophies in its cephalic portion to form the cerebellum, while caudad thereof the roof atrophies and expands and becomes so attenuated as to be represented merely by a thin epithelial membrane. The outward folding of the walls of the neural tube in this region creates an expansion of the central cavity in the form of a rhomboidal fossa roofed in by the cerebellum and a thin epithelial layer. A time-honored custom enumerates this as the fourth of a system of ventricles of which the other three lie in the fore-brain. A cast of the cavity (Fig. 696) shows it to be irregularly pyramidal, with a lozenge-shaped base and ridge-like apex extending from side to side, corresponding to the acute-angled recessus tecti in the fastigium ("gable roof") formed by the valve of Vieussens and inferior medullary velum. Such a cast also indicates the ventral extension of the cavity from the lateral angles of the rhomboidal base in the form of the lateral recesses. It is customary to describe for the fourth ventricle a roof and a floor, although an examination of a sagittal section of a brain hardened in situ shows the floor to be in a vertical 'plane in the erect attitude. Caudad the cavity is continuous wi(h the minute central canal of the spinal cord and postoblongata (in part); cephalad it passes into the aqueduct or mesocele. The dorsal wall or "roof" is formed by the valvula (velum medullare anterius), the superior peduncles, tela choroidea ventriculi quarti, and fastigium of the cerebellum. The ventral wall or "floor" is the rhomboidal fossa occupied by the expanded central gray of the pre- and post- oblongatal portions of the hind-brain. "Floor" of the Fourth Ventricle {fossa rhomboidea). — The "floor" of the fourth ventricle is lozenge-shaped and exhibits regional elevations, depressions, and color differences which are in relation with the deep anatomy of the medulla ob- longata and tegmentum of the pons (preoblongata). It is divided longitudinally into symmetrical hah'es by a median groove, and each lateral half is subdivided into a larger cephalic and a smaller caudal triangle by white, transverse striae, composed of bundles of myelinic fibres connected with the acoustic tract and ap- pearing to sink beneath the surface near the median groove. The portion occupied by these striae acusticae {striae medullares) is termed by His the pars intermedia as distinguished from the pars superior and pars inferior, or frontal and caudal tri- angles respectively. Much variation is met with in regard to the course and degree of prominence of the striae acusticae (Fig. 633). There may be none visible or as many as twelve distinct bundles; bilateral symmetry is the exception, and not infrequently one or more bundles run obliquely cephalolaterad — the striae 866 THE NER VE SYSTEM obliquae (conductor sonorus). This irregularity of the acoustic strise has led to another mode of division of the "floor" for descriptive purposes — each side to be divided into a median and a lateral area, indicated by a more or less well- marked groove, the lateral furrow {sulcus limitans), connecting the superior and inferior (ala cinerea) foveae. This groove probably corresponds to one of the interzonal sulci of the embryonic tube, and in a gross way it separates the motor and sensor fields of the "floor." The median area is usually a continuous ridge which is quite accentuated in the cephalic division as the eminentia abducentis, while caudad it becomes narrowed as it approaches the closed part of the medulla oblongata. The convergence of the median and lateral furrows at the caudal apex of the rhomboidal fossa gi^'es the appearance of the point of an ancient writ- ing reed or quill pen; hence the term calamus scriptorius. In the caudal quarter triangle a middle area is occupied by an elongated tri- angular field whose depressed apex is directed frontad. A slight oblique ridge, the fxmiculus separans, composed chiefly of neuroglia, separates the area postrema caudally from the trigonum vagi or ala cinerea of a pronounced grayish color. The whole depression has been termed the fovea inferior. Mesally lies a narrow triangular field with its apex directed caudad and with slightly raised surface — • the trigonum hypoglossi. This area is resolved into two fields by a single or double formation of oblique rugae affording a " feathered" appearance to the lateral field, the area plumiformis. I^aterad of the trigonum vagi lies the caudal portion of the lateral area of the "floor," also called (in part) the area vestibularis (area acustica) and crossed over its middle by the striae acusticae when these are present. The area vestibularis is an irregularly triangular raised surface with its convex base toward the median line, and extending laterally to the attachment of the tela choroidea and into the lateral recess. In the fetus and in certain lower vertebrates the area is more prominent and is designated the tuberculum acusticum s. vestibu- laris. The "frontal" division of the floor or triangular quarter-field is marked by a depression at about its middle, the superior fovea {fovea trigemini),iTom which the slight "lateral furrow" runs caudad, and but for the intervention of the striae would reach the inferior fovea. Cephalad of the superior fovea, and continuing some distance along the aqueduct, is the locus caeruleus, which owes its color to the refraction of the pigmented cells, the substantia ferruginea, by the milky-white ependyma. At this altitude, the medial elevation between the superior fovea and the median sulcus is accentuated into a fairly pronounced eminence, the eminentia abducentis {eminentia medialis; e. teres), overlying the nucleus of the abducent nerve and the genu of the root of the facial nerve. The portion of the median sul- cus intervening between the eminentia abducentia is correspondingly depressed to form the fovea mediana. The ventricular features enumerated above correspond in a crude way to the deep structures of the pons-oblongata, and most of the cranial nerve nuclei are held in a rhomboidal frame formed by the superior and inferior peduncles. The surface markings are only imperfect replicas of the subjacent structures ; the various cell nests overlap each other more or less and their relations can best be studied in the projection drawing in Fig. 6.34. Membranous Portion of the "Roof" of the Fourth Ventricle. — The caudal exten- sion of the hypertrophied cerebellum hides from view the whole of the rhomboidal fossa, but this structure, as before stated, forms but a part of the actual dorsal wall or "roof." This includes the converging superior peduncles, the velum medul- lare anterius intervening between these, the fastigium of the cerebellum, tlie velum medullare posterius, and the tela choroidea ventriculi quarti. The velum medullare posterius is a thin and narrow lamina of white substance continued laterad as the flocculi of the cerebellum. At its caudal edge, /. e., where nerve tissue ceases, the ependymal or ventricular lining epithelium and the AREAS OF THE MEDULLA OliLONdATA 8(37 pia over this portion coalesce to form a delicate membrane — the tela choroidea — attached along the caudolateral boundary line of the rhomboidal fossa. Along this attachment there is another intrusion of nerve substance between the ependynial and pial layers; this reenforced lamina is usually termed the Ugula and may be traced to the clava and cuneate tubercle, thence laterad over the restiform body to bound the lateral recess. The structure is probably a vestige of the secondar). rhomboidal lip and has actually been found to be a part of the pontobulbar body referred to above. Another small semilunar lamina of nerve tissue bridges the caudal apex of the fourth ventricle and is called the obex. This structure is often devoid of nerve tissue, and is then a mere membranous lamina. Except in rare instances, the tela choroidea is perforated a short distance from the calamus region. The opening is of variable shape and size; it permits of communication between the ventricular cavity and the subarachnoid space and is termed the foramen of Majendie {apertura medialis v'entricidi qvarti; metapore). N. V STRIA PONTIS LOCUS CfRULEUS FOVEA MEDIANA FOVEA TRIGEMINI AREA VESTIBULA EMINENT NUCL GRACILIS -Surface markings and topography of the principal nuclei of the floor of the fourth ^ (Modified from Streeter.) Similar apertures at the extremities of the lateral recesses, and called the foramina Luschkae (apertura lateralis ventriculi quarti) also permit of a tidal flow of the cerebrospinal fluid. The choroid plexuses of the fourth ventricle (metaplexuses) are highly ^•ascular infoldings of the tela choroidea, one on either side of the median plane, from each of which offshoots extend laterad into the lateral recesses. As the choroid plexuses of the brain are always formed by infoldings or invaginations of the membranous portions of the brain tube, the ependymal continuity upon them is interrupted only at the margins of the foramina. liiternal Structure of the Medulla Oblongata. — While the spinal cord remains a closed tube with centrally situated gray, the medulla oblongata opens out on the dorsal aspect so as to uncover its part of the neural canal as the "floor" of the fourth 868 THE NEB YE SYSTEM ventricle. This involves a tilting of the functionally differentiated gray segments and, after a gradual transition in the medulla oblongata, the motor gray is to be Inferior medullary velum Choroid plexus Cisterna basalis of subarachnoid apace Central canal Fig- 635. — Scheme of roof of fourth ventricli DECUSSATION Fig. 636. — Schema of the pyramidal decussation Cisterna pontis of suharach^wid space the foramen of Majendie. sought nearest the middle line, the mixed gray just ectad, while the sensor is the outermost of all. Instead of the ventral, lateral, and dorsal horns of each half of the spinal cord, we have an ental, middle, and ectal comu in each half of the medulla oblongata. The positions alone have changed ; the functional relations to nerve roots having corresponding func- tions are homologous. Thus, the motor hypoglossal nucleus is placed in the mesal part of the ventricular floor, while the termi- nal nuclei of the aflferent vagus, glossopharyngeal, and auditory nerves lie in the lateral part. Another cardinal change in the internal structure of the mpdulla oblongata, accompanying the pre- ponderating development of the cerebrum and great basal gan- glia, is caused by interrupting and decussating fibre systems which seek passage through the brain stem and encroach more or less on its primitive architecture. While in the spinal cord there is a perfect continuity of the central tubular grav, we find in the medulla oblongata more pronounced peninsular and isolated insular nuclei or ganglionic gray masses. AREAS OF THE MEDULLA OBLONGATA 869 Pyramidal Decussation {decussatio pyramidum). — An important change in the internal structure is caused by the passage of the fibres of the pyramidal tract as these pass to the same and opposite sides of the cord, the latter category forming the pyramidal decussation. In consequence of this passage of white (crossed DORSO-MED "ixaiw Fig. 637. — Transverse section of the medulla oblongata at its lower end. (Testut.) Fig. 638. — Transverse section of the medulla oblongata at the decussation of the pyramids. (Testut, after Duval.) TRAPEZIUM' Fig, 639. — Diagram showing thi of the lemnisci (fillets) and their decussation. 870 THE NERVE SYSTEM pyramidal) fibres through its substance the ventral gray horn is broken up into a coarse network, while one portion of it, the caput comu, is entirely separated from the rest; only a small portion of the base of the cornu remains intact close to the ventrolateral aspect of the central canal. The caput cornu, thus separated, is displaced laterally, and comes to lie close to the caput cornu dorsalis, which has also shifted its position. In consequence of this breaking up of the greater part -HEAD OF DORSAL HORN BASE OF VENTRAL HORN HEAD OF VENTRAL HORN ^HYPOGLOSSAL NERVE Fig. 640. — Tr.^nsverse section of the medulla oblongata at the crossing of the lemnisci or fillets. (Testut.) of the ventral gray cornu by white fibres a coarse network is formed in the anterior and lateral areas of the medulla oblongata, which is named the formatio reticularis. The gelatinosa Rolandi {gliosa cornualis) of the dorsal horn is continued into the oblongata, but becomes insignificant, relatively, in the pars dorsalis pontis. The spinal root of the trigeminal nerve is in ectal relation with the gelatinosa Rolandi; at higher levels the spinal root of the vestibular nerve intervenes. FLOOR OF FOURTH VENTRICLE UCLEUS GRACILIS NUCLEUS CUNEATUS 3F DORSAL HORN AGUS NERVE EAD OF VENTRAL HORN TRAL PYRAMID Fig. 641.— Transv of of the fourth Decussation of the Lemnisci {fillets). — ^A similar change, dorsad and cephalad of the pyramidal decussation, is caused by the decussation of axone bundles arising in the nuclei of the gracile and cuneate fasciculi (Goll and Burdach). At this level the base of the dorsal gray cornu undergoes change in the form of two thick dorsal peninsular outgrowths which form the nuclei of termination of the axones in the gracile and cuneate fasciculi ; externally these gray masses produce the emi- nences of the clava and cuneate tubercle. The axones from these nuclei stream mesad and cephalad in a series of concentric arches, decussating in the raph^ with the bundles of the opposite side to form the decussation of the lemnisci' or sensor decussation. Cephalad of this decussation the lemnisci are two bundles of fibres coursing on either side of the raphe between the olives, and just dorsad 1 Also called "mesal lemnisci" in contradistinction to the "lateral lemnisci" — of different origin. AREAS OF THE MEDULLA OBLONGATA 871 of the pyramids; their further course toward the cerebrum will be described farther on. Fasciculi • jiyramidales Fig. 642. — Trans-section of the medulla oblongata at the decussation of the pyramidal tracts. Canalis centralis Nucleus nervi hypoglossi Nucleus alae cinereae Nucleus fasciculi gracilis Nucleus fatciculi 'cimeati iiuileus aicuatus Raphe Fig. 043. — Trans-section of the medulla oblongata at the lower end of the olives. With the extension of the central gray to form the floor, of the fourth ventricle, the caput cornu dorsale is displaced ectad so as to almost reach the surface, 872 THE NERVE SYSTEM where it forms a projection, the funiculus lateralis (Rolandi), which enlarges cephalad into a distinct prominence, the tuberculum cinereum. At a higher level the caput is separated from the surface by the spinal root of the trigeminal nerve and by the external arcuate fibres (Fig. 644). The cervix of the cornu becomes broken up into a reticular formation by the decussating fibres. A portion of the base is placed ectad of the nucleus funiculi cuneati and is called the accessory cuneate nucleus, supposed to be a continuation of Clarke's column. The formatio reticularis (Fig. 644) consists of diffusely scattered gray substance in a meshwork of white fibres. It is far more abundant in the medulla oblongata than in the cord. In trans-sections of the medulla oblongata it is seen to be divided by the hypoglossal nerve root fascicles into a mesal and a lateral field. In the mesal field the gray substance is scanty, and white fibres — principally longitudinal ones — preponderate; this is called the formatio reticularis alba in contradistinction to the lateral grayer reticulated field, the formatio reticularis grisea. Its numerous nerve cells mostly possess short axones and for the most part exercise associative DESCENDING ROOT VIII dorsal|^ accessor* ( OLIVE MESIAL ) EXT. ARCUATE FIBERS HYPOGLOSSAL NERVE HILUM OLIVjE ARCUATE NUCLEUS Fig. 644. — Trans-section of the medulla oblongata at about the middle of the olive. functions for the constantly active centres of respiration (nuclei of the vagus, phrenic, facial, etc.). Certain axones of longer course are collected into a small compact bundle just ventrad of the ventricular floor and central canal (and aque- duct in the mid-brain), and known as the medial longitudinal fasciculus (posterior longitudinal bundle). This tract is in intimate association with the cranial nerve nuclei. The formatio alba is principally made up of this tract and the lemniscus (interolivary stratum). The raphe (Fig. 644) is situated in the middle line of the medulla oblongata above the decussation of the pyramids. It consists of nerve fibres intermingled with nerve cells. The fibres have different directions, which can only be seen in suitable microscopic sections, thus: (1) Some run dorsoventrad ; these are con- tinuous with the external or superficial arcuate fibres. (2) Some are longitu- dinal; these are derived from the arcuate fibres, which on entering the raphe change their direction and become longitudinal. (3) Some are oblique; these are continuous with the internal or deep arcuate fibres which pass from the raphe. AREAS OF THE MEDULLA OBLONGATA 873 The nerve cells of the raphe are multipolar; some are connected with tlie dorso- ventral fibres, others with the superficial arcuate fibres. The restiform body succeeds the gracile and cuneate nuclei, in the dorsolateral part of the medulla oblongata. Its fibres converge from various sources and ultimately enter the cerebellum as its inferior peduncle. For a description of these fibre systems see the section on the "peduncles of the cerebellum." The nucleus of the olive or inferior olivary nucleus (nucleus olivarius inferior) is a corrugated lamina of gray substance whose extent nearly corresponds to that of the external elevation called the olive. It can be compared to a hollow oval sac or purse, slit on its mesal aspect and the edges of the slit everted. The opening is called the hilum. Numerous fibres stream into the interior through the hilum, while others cut through the lamina to join the fibre arches of the reticular field and then pass toward the restiform body. What are known as accessory olivary nuclei (nuclei olivarii accessorii) are smaller detached or semidetached portions of the olivary nucleus named, according to their position, the dorsal and medial accessory olivary nuclei (nuclei olivarii accessorii, dorsalis et medialis). The olivary nuclei play an important part as relay stations in cerebellar, con- nections. A considerable mass of fibres, the olivocerebellar fibres (fibrae ccrehello- olivares), originate in the olivary nucleus of one side to enter the cerebellum along the restiform body of the opposite side. A much less number of fibres, running contrariwise, reach the olivary nuclei from the opposite cerebellar hemi- spheres— the cerebello-olivary (vestibulo-olivary tract) fibres. Each olivary nucleus is the terminus of the thalamo-olivary fibres, and Helweg's olivospinal tract is believed to originate therein. The Arcuate Fibre Systems. — The arcuate fibre systems comprise two sets of fibres according as they course dorsad or ventrad of the olivary nuclei : 1. The internal or deep arcuate fibres comprise the olivocerebellar fibres, just described, and a number of commissural systems for the association of the teg- mental reticular gray ganglia and cranial-nerve nuclei. Others pass cerebralward. others to the cerebellum. 2. The external or superficial arcuate fibres take origin (a) from the gracile and cuneate nuclei and enter the restiform body of the same side; (h) from the same nuclei of the opposite side, decussating in the raphe and sweeping ventrad over the pyramid and olive,, forining a thin layer over them and ultimately reaching the restiform body. Many of these fibres are interrupted, on each side, in the nucleus arcuatus, a thin, isolated lamina of gray substance lying on the ventral aspect of the pyramid. The nucleus lateralis is seen in the lateral column (lower part of medulla ob- longata) as a difl^use gray mass lying between the gelatinosa Rolandi and tlie olive; it gradually disappears cephalad. The nucleus intercalatus (of Staderini and Van Gehuchfen) forms the elongated, wedge-shaped elevation in the medial triangle of the caudal portion of the ventric- ular floor called the area plumiformis (p. 869); the nucleus derives its name from its (intercalated) position between the hypoglossal and dorsovagal nuclei. Its functional connections are not yet precisely known. A nucleus postremus has been described (J. T. Wilson) as lying subjacent to the area postrema. The nucleus funiculi teretis lies close to the median sulcus in the altitude of the acoustic striie, and seems to bear an intimate relation to these. Summary of the Gray Masses in the Medulla Oblongata: *Central tubular gray (in "closed" part). *Gray floor of fourth ventricle (in "open" part). *Gelatinosa Rolandi or gliosa. ^Nucleus funiculi gracilis. 874 THE NERVE SYSTEM *Nucleus funiculi cuneatus. *Nucleus funiculi cuneati accessorius. *Nucleus lateralis. *Nucleus olivaris inferior. *Nucleus olivaris accessorius dorsalis. *Nucleus olivaris accessorius medialis. ^Nucleus arcuatus. Nucleus nervi hypoglossi. ^Nucleus intercalatus. *Nucleus postremus. Nucleus vagi (alae cinereae). Nucleus vestibularis (spinal division). ^Nucleus funiculi teretis. Nucleus ambiguus. Nucleus tractus solitarii. Nucleus tractus spinalis n. trigemini. *Formatio reticularis. In the foregoing enumeration of the gray masses of the medulla oblongata, those marked with an asterisk have been described above; the remaining structures relate to the deep connections of the cranial nerves, and will be discussed in detail under that head. Internal Structure of the Pons and Pars Dorsalis Pontis. — ^Trans-sections of the pons also pass through the tegmental part of the pons. To consider first the Fourth ventricU Forniatio reticularis I Nucleus emiTientiae \ medialis Fasciculus \ lonqitudmahs \ ^-fF mediahs \ JjCmniscus mediahs Fasciculi pyramidales Corpus trapezoideum apesoides Fig. 645. — Trans-section of the pons at its middle, showing the trapezoid body. internal structure of the pons proper (or jjcirs basilaris imntis): The pons is com- posed chiefly of (1) transverse fibres arranged in coarse bundles, (2) longitudinal fibres gathered in compact bundles, and (3) diffusely scattered masses of gray substance among the fibre bundles, the nuclei pontis. The transverse fibres, corresponding to the large size of the cerebellum, are more AREAS OF THE MEDULLA OBLONGATA 875 Fourth ventricle: its ependyma m yellow abundant in man, relatively, than in any other animal. They form a massive series of bundles coursing ventrad of the brain axis from one cerebellar hemisphere Valve of Vieussens Su-frior medullary velum lAngida Section of superior. ' _ cerebellar peduncle Sylvian root of trigeminal Nene cells^^ Posterior lonqitudmal f fasciculus ^- ' Lateral lemm^cti Formatio retxcidaiv Lateral sulcu^^^^z:^ Medial //^S^ lemniscus /^r^X Transverse I / ^ ■'•'< fibres of ' ^^ pons ji^ Trigeminal ^/-* iramidal fibres tiaphi """-^i^J^iL-bdC*""-^ Transverse fibres of pons Fig. 646. — Section of the pons, at its upper part. to the other. At the caudal border of the pons they embrace the pyramidal tracts as well, but farther cephalad the transverse pontile fibres are seen to intersect Decussation of trochlear nerves Locus c(eruleu5 Mesencephalic root of trigeminal nerve Medial longitudinal bundle Lateral lemniscus ■Gower's tract Rubrospinal tract Beginning of decussation ■of superior peduncles of cerebellum Fig. 647.— Section of the ta junction with mid-brain. (Higher leve! than Fig. 646.) the pyramidal tracts, breaking these up into pyramidal fasciculi; still farther cephalad the pyramidal tracts are wholly embedded in the mass of t^ans^•e^se pontile fibres, so that these in turn, with reference to the location of the pyramidal 876 THE NEBVE SYSTEM tracts, may be divided into a superficial and a deep set. Laterad they are gathered together to form the middle peduncles (described on p. 890). The longitudinal fibres consist chiefly of the pyramidal tracts, M'hich are solid strands at their entrance to and exit from the pons, but are broken up into lesser bundles at its middle. A certain number of the pyramidal fibres, as well as other cerebropontile fibre tracts, terminate in relation with the cells of the nuclei pontis, as well as certain of the efferent cranial nerve nuclei. This fact accounts for the demonstrable diminution in bulk of the pyramidal tract in its course through the pons. The nuclei pontis are small aggregations of gray substance (which in serial sections show them to be continuations of the arcuate nuclei) diffusely scattered among the fibre systems of the pons proper. They are intercalated in the course (1) of tracts passing from one cerebellar hemisphere to the other, and (2) of de- scending cerebropontile tracts. The cells of the pontile nuclei send their axones chiefly to the opposite cerebellar hemisphere and play an important part as links in the complex chain of the neurone systems which make the cerebellum such an important organ of sensomotor coordination. In the contact zone of pons proper and the pontile tegmentum lies a group of transversely decussating fibres with interspersed gray masses with large cells called the trapezium. This body will be more fully described in connection with the central auditory paths. The tegmental part of the pons is of much smaller bulk than the pons proper, as seen on trans-sections. On the dorsal surface is spread a layer of gray substance covered by ependyma, which forms the floor of the cephalic part of the fourth ventricle. Beneath this gray substance lies the formatio reticulans divided into symmetrical halves by the raphe — continued from the medulla oblongata. Em- bedded in the formatio reticularis are various isolated masses of gray substance and various more or less compact fibre tracts. Among the gray masses are several of the cranial nerve nuclei, to be described in a separate section, and the following: The superior olivary nucleus {nucleus olivarius superior) is a small gray mass or aggregation of several smaller masses situated laterad of the trapezium, inter- calated in the path of the trapezial fibres and forming a link in the central acoustic chain (Fig. 651). The nucleus incertus (Streeter) is an aggregation of gray substance in the floor of the fourth ventricle near the median sulcus and forming a slight, rounded elevation which extends to the aqueduct. Its functional relations are unknown. Fibre Tracts in the Pars Dorsalis Pontis. — Among the fibre tracts in the tegmental part of the pons the chief ones are (1) the medial lemnisci, (2) the lateral lemnisci, (3) the medial longitudinal bundle, and (4) the superior peduncles of the cerebellum. Each medial lemniscus, or medial fillet, in its passage through the tegmental part of the pons is gathered into a compact, ribbon-like bundle along the contact zone of the tegmentum and pons proper, lateroventrad of the trapezium, some fibres of which traverse it on their way toward the raphe. The medial lemniscus has been described in the medulla oblongata as occupying the field between raphe and inferior olivary nucleus (the interolivary stratum); in its ascent the medial lemniscus gradually trends laterad, so that it almost reaches the surface (Figs. 639 and 647). The lateral lemniscus is a constituent of the central auditory path, and will be described more fully on pages 881 and 898. In trans-sections above the level of the trigeminal nuclei the lateral lemniscus is seen as a flattened band spreading over the surface (externally the trigonum lemnisci) ectad of the superior peduncle. Its fibres are interrupted by an intercalated nucleus of the lateral lemniscus. The medial longitudinal bimdle (posterior longitudinal bundle) maintains its position just \'entrad of the central gray, close to the raphe. The superior peduncle of the cerebellum or prepeduncle is seen in trans-sections AREAS OF THE MEDULLA OBLONGATA 877 to be a very compact bundle of crescentic outline with the concavity turned toward the ventricular cavity. Its dorsimesal edge is joined to the superior medullary velum; its ventral border is sunk into the tegmentum, and in its ascent it becomes submerged laterally beneath the lateral lemniscus, dorsally beneath the quadrigeminal plate of the mid-brain. Summary of the Gray Masses in the Pars Dorsalis Pontis: Nucleus of Abducent Nerve. Nucleus of Facial Nerve. Afferent and Efferent Nuclei of Trigeminal Nerve. Nucleus of Spinal Root of Trigeminal Nerve. o ui T-\- • • / Dorsal Nucleus. Cochlear Division \ -.j . , ^.y , [ Ventral Nucleus. {Medial Nucleus. Lateral Nucleus. Superior Nucleus. Nuclei of Acoustic Nerve *Superior Olivary Nucleus. Nucleus of Trapezium. *Reticular Ganglionic Formation. *Nucleus Incertus. Nucleus of Lateral Lemniscus. Those marked with an asterisk have already been described; the remaining structures relate to the deep connections of several cranial nerves to be described in the succeeding section. Central Connections of the Cranial Nerves Attached to the Hind-brain.— Eight of the twelve pairs of cranial nerves are attached to the hind-brain portion of the central axis. Their superficial or apparent origin and the cranial foram- ina of exit are enumerated in the table on page 848. In coordination with the internal descriptive anatomy of the hind-brain the central connections of these eight cranial nerves must now be considered. They comprise : Purely efferent or motor nerves .... Mixed nerves Purely afferent or sensor XII. Hypoglossal nerve. XI. Spinal accessory nerve. VII. Facial nerve (proper). VI. Abducent nerve. X. Vagus nerve. IX. Glossopharyngeal nerve. V. Trigeminal nerve. fVIII. Acoustic nerve. 1 Motor to muscles of tongue. (a) Motor accessory to vagus nerve : (b) Motor to Trapezius and Sterno- mastoid muscles. Motor to muscles of scalp and face. Motor to External rectus muscle of eyeball. Sensomotor to respiratory tract and upper part of alimentary tract. Sensor to tongue (and motor?) to Stylopharyngeal muscle. Sensor to face, tongue, teeth; motor to muscles of mastica- tion. (a) Cochlear division forbearing. (b) Vestibular division for equi- librium. Another nerve which pursues a remarkably aberrant course, becoming asso- ciated with three of the above-mentioned cranial nerves, is the nervus intermedius, known peripherally as the chorda tyiapani. It is chiefly sensor (taste) in function, but also contains eiferent fibres which are exdtoglandulaf for the submaxillary and sublingual salivary glands. In the hind-brain axis lie certain gray masses which are functionally homol- ogous with the nuclear masses in the different parts of the spinal central gray. 878 THE NEB VE 8YSTEM These defined nests of nerve elements, from their relations to the cranial nerve roots, are called the cranial nerve nidi or nuclei. Their analogy to the origins of the spinal nerves extends to the shape and character of their cell elements and their differentiation into (a) nuclei of origin and (b) nuclei of termination or recipient nuclei. The nuclei of origin or motor nuclei are cell clusters from which arise the axones of efferent nerves or the efferent components of the mixed nerves. Some of these nuclei are in line with the basal portion of the ventral gray horn in the cord below and are termed, owing to their situ- ation near the mesal plane, the medial nuclei of origin. Other nuclei are isolated cell columns in the line of the caput comu ventrale detached by the ducussation of the pyramids, termed, from their position in the tegmental substance, the lateral nuclei of origin. The different nuclei of origin of the efferent cranial nerves are under the dominance of the cere- bral cortex by way of the cortico- tegmental (or corticobulbar) path — usually included in the pyramidal tract. The nuclei of termination or sen- sor cranial nerve nidi are likewise repetitions in structure of the dorsal horn of the spinal gray, but with less regularity and definiteness of posi- tion. Thus, while the gelatinosa Rolandi of the cord is continuous with the nucleus of the spinal root of the trigeminal nerve, other recipient or afferent nuclei are more or less isolated in the tegmental substance, while the two (lateral and ventral) nuclei of the cochlear nerve actually lie on the surface of the brain stem. The afferent impulses carried in by the sensor cranial nerves excite impulses in the neurones of the nuclei of termination; their axones enter the tegmental substance as arcuate fibres, cross the mesal plane to join the lemnisci to connect with the thal- amus and posterior quadrigeminal body and via thalamus and posterior quadrigeminal body with the cerebral cortex. The location of the various cranial nerve nuclei in the brain stem may be understood by a reference to the diagrams in Figs. 634, 648, 649, and 650. Hypoglossal Nerve Nucleus. — The nucleus of origin of the hypoglossal nerve is a rod-like cell column close to the mesal plane, extending for about 7 mm. (^ inch) in the caudal portion of the fourth ventricle, while its extraventricular portion extends about 5 mm. (i inch) caudad of the tip of the calamus. Its efferent axones course ventrad between the formatio reticularis alba and grisea, thence Fig. 64S. — The crani-al nerve nuclei schematically repre- sented in a supposedly transparent brain stem, dorsal view. Motor nuclei in red; primary terminal nuclei of afferent (sensor) nerves in blue, (Optic and olfactory centres are omitted,) AREAS OF THE MEDULLA OBLONGATA 879 between the olivary and medial accessory olivary nuclei, sometimes mesad of the latter, to emerge between pyramid and olive. None of the ribres decussate across the middle line, but the nuclei are coordinated by commissural fibres. x\xones from cerebrocortical cells (ventrad third of precentral gyre) terminate in relation with the cells of the hypoglossal nucleus. The hypoglossal nucleus permits of subdivision into groups: (a) a medial and (6) a lateral sub-group. The lateral group innervates the Palatoglossus and Pharyngoglossus, while the medial nuclear group innervates the remainder of the tongue muscles (Lingualis transversus and inferior, Genioglossus and Hyoglossus). The Spinal Accessory Nerve Nucleus. — The spinal accessory nerve is also a purelv motor or efferent nerve whose axones arise from an attenuated nucleus, with large multipolar cells, in direct continuation with the nucleus ambiguus (of the CERVICAL NERVES ' Fig. 649. — Nuclei of origin of the cranial motor nerves schematically represented : transparent brain stem, lateral view. a supposedly ninth and tenth nerves) cephalad, and with the dorsolateral cell column of the ventral horn of the upper five or six segments of the cord. The oblongatal portion of the nucleus gives rise to the encephalic root of the accessory nerve and its axones join the vagus to innervate the laryngeal muscles. Hence it may also be termed the nidus laryngei (in contradistinction to the nidus pharyngei or nucleus ambiguus, whose axones join the vagus and glossopharyngeal nerves to be distributed to the pharynx). The ventrolateral division of this cell column is believed to be the cardioinhibitor centre. The axones from the spinal nucleus are distributed to the Trapezius and Sternomastoid muscles. The nucleus of the spinal accessory nerve is likewise under the dominion of the cerebral cortex by way of the pyramidal tract, and a reflex arc is completed by afferent axones from the dorsal roots of the spinal nerves. 880 THE NEB VE SYSTEM The Vagus and GlossopharjTigeal Nuclei are usually considered in their aggregate, justified not only by their similarity in origin and central connections, but also by the uncertainty which prevails regarding their peripheral interlacement and complex terminations. Both nerves are in greater part afFerent, but also contain efferent axones. 1. Afferent Portions. — The afferent axones of the vagus arise from the cells in the jugular ganglion and ganglion nodosum (ganglion of the trunk); the afferent axones of the glossopharyngeal arise from the cells in its ganglion superius and ganglion petrosum. The root fascicles of both nerves enter the medulla oblongata along its dorsolateral groove, and the axones then undergo bifurcation into ascending and descending rami, similar to those of the dorsal roots of the spinal nerves. Fig. 650. — Primary terminal nuclei of the afferent (sensor) cranial nerves schematically represented in a. sup- posedly transparent brain stem, lateral view. The optic and olfactory centres are omitted. The ascending rami end in the nucleus alae cinereae {jiudeus vagi et glossopharyn- cjei); the descending rami collect to form a compact bundle called the tractus solitarius or trineural fasciculus,' and terminating in a gray cell column called the nucleus of the solitary tract- — a caudal prolongation of the nucleus alae cinereae. Both tract and nucleus become attenuated caudad, to disappear in the fourth cervical segment (relation with phrenic nerve nucleus), while cephalad it has been traced as far as the region of the locus caeruleus (relation with trigeminaS nerve nuclei). From the cells of the nucleus alae cinereae and nucleus tractus solitarii axones pass across the raphe to the contralateral interolivary stratum to join the medial 'There are other "solitary" fasciculi in the nerve system, and the name "trineural fasciculus" aptly characterizes a tract which has for its object the mutual interchange of functions among the central nuclei of the accessory, vagus, and glossopharyngeal nerves. - The nucleus of the solitary tract lies to the mesal side of the tract. Another nucleus has been described by Melius, lying laterad of the tract. AREAS OF THE MEDULLA OBLONGATA 881 lemniscus, establishing connections with the thalamus and c(jrtex; other axones join the tractus nucleocerebellaris. 2. Efferent Portions. — The efferent components of the vagus and glossopharyn- geal ner\cs come from two sources — (a) the dorsal efferent (vagal) nucleus and (&) the nucleus ambiguus. The dorsal efferent nucleus lies ventromesad of the principal nucleus alae cinereae and laterad of the hypoglossal nucleus. The axones from its cells pass obliquely ventrolaterad to enter the root fascicles of the vagus and to become distributed to the oesophagus, stomach, trachea, and bronchi. Whether the glossopharyngeal nerve receives efferent axones or not is still in debate. The nucleus ambiguus (nidus pharyngei — so termed in contradistinction to the nidus laryngei) is a rod-like mass of large, multipolar cells seen, in trans-sections, lying in the gray, reticular formation midway between olive and fasciculus soli- tarius and apparently a cephalic continuation of the accessory nerve nucleus. The axones arising from its cells run dorsimesad at first, then turn abruptly ectad to join the vagus (and glossopharyngeal ?) nerve-root fascicles, becoming dis- tributed to the pharyngeal muscles, oesophagus. Cricothyroid, and the other Laryngeal muscles. The Acoustic Nerve Nuclei. — The acoustic nerve consists of a cochlear and a vestibular divisioi); the former is concerned with the sense of hearing, the latter with the sense of equilibrium. 1. The cochlear or true auditory nerve arises in the bipolar cells of the cochlear spiral ganglion; its axones terminate in (o) the dorsal nucleus (tuberculum acusti- cum), a pyriform mass on the dorsolateral aspect of the restiform body, and (b) the ventral nucleus, somewhat detached from the former. From the dorsal nucleus cells arise the axones which compose the striae acusticae, myelinic fibre bundles traversing the ventricular surface to near the median sulcus, dipping into the tegmental substance, crossing to the opposite side in the raphe, and eventually joining the lateral lemniscus to end in the posterior quadri- geminal body and internal geniculate body. From the ventral nucleus cells arise the axones which course transversely to form the trapezium at the contact zone of the pons proper and tegmentum. Additional axones from cells in the superior olives of both sides and in the trapezium itself increase the bulk of this tract; some of the primary axones end in relation with these cells. These axone groups form the contralateral lemniscus lateralis, which contains the intercalated nucleus of the lateral lemniscus as a relay station, to be continued to the posterior quadrigeminal and to the internal geniculate bodies and thence to the cortical auditory "centre" in the supertemporal gyre. 2. The vestibular nerve axones arise in the bipolar vestibular ganglion cells (G. of Scarpa), enter the brain stem, and bifurcate into ascending and descending rami, which terminate as follows: The ascending rami end in the medial nucleus (Schwalbe's); the descending rami end in the spinal vestibular nucleus, which extends clown to the gracile and cuneate nuclear level; another group of axones ends in the lateral nucleus (nucleus magnocellularis) (Deiters'); while a fourth and last group ends in the superior nucleus (Bechterew's). From the cells of all these nuclei of termination axones proceed toward the cortex, dentate nucleus, and nucleus fastigii of the cerebellum, as part of the nucleocerebellar tract, to the nuclei of the abducent, trochlear, trigeminal, and oculomotor nerves by collaterals from axones in the medial longitudinal bundle, to the thalamus, and to the ventral horn nuclei of the spinal cord along the tractus vestibulospinalis (ventral and lat- eral). The far-reaching and complex connections of the vestibular nerve with the cerebellum and the centres for eye muscles and the spinal centres for bodily mo\-e- ments make this cranial nerve a most interesting subject for the active research now going on. 56 882 THE NERVE SYSTEM The Facial Nerve Nucleus. — The facial nerve proper is to be distinguished from its so-called sensor root, or pars intermedia, or nervus intermedius. The axones of the efferent facial nerve arise from cells forming the facial nucleus in the ventrolateral region of the reticular formation, in line with the nucleus ambiguus or nidus pharyngei, a little over 4 mm. {\ inch) from the \-entricular floor. These axones converge toward the ventricular floor to form a compact bundle which curves over the abducens nucleus from behind, overlying it like a horseshoe over a ball {genu facialis internum) ; not as a straight but as a bent horseshoe, bent so that its cephalic branch is directed more laterad than its caudal branch. After having encircled the abducens nucleus, the facial root passes ventrolaterad, passing its own nucleus ectad, and emerging in the postpontile groove (recessus facialis).^ Pyramidal fibres from the precentral cortex place this nucleus under the in- fluence of the will; it also receives fibres from the trigeminal and acoustic central systems. The nervus intermedius is a mixed nerve, containing afferent (taste) fibres and efferent (excitoglandular or secretory) fibres. With respect to its afferent com- ponent it may be regarded as an aberrant portion of the glossopharyngeal nerve. Bestiform Nucleus .of cerebellar Beckterew. fibres.\ jf.^^eus ofFil -Raphe. Fillet. Inf. sensory . „ of trigeminal Fibres taking oblique course. Pyramidal tract.' linal nuclei of the vestibular root of the auditory nerve, (Schematic.) (Testut.) 'ith their upper 1. Afferent Portion.- — These axones arise from the cells of the geniculate ganglion, implanted upon the genu facialis externum, and terminate in a nuclear extension cephalad of the nucleus tractus solitarii. They probably convey gustatory sense impulses from the anterior two-thirds of the tongue and the pillars of the soft palate. 2. Efferent Portion. — A nucleus of origin for the excitoglandular elements has been described as a group of cells extending beneath the ventricular floor from the level of the facial nucleus to that of the motor trigeminal nerve, close to the raphe, and called the nucleus salivatorius. (Fig. 745). Peripherally we shall study this nerve as the chorda tympani. The mixed nature of the nervus intermedius and of the geniculate ganglion makes it probable that they combine the elements of a sympathetic and a spinal ganglion; the nerve, at least, contains both vegetative and sensorial elements. ' The peculiar course of the deep root of the facial ffandering of the facial nucleus in the embryonic period. has been shown by Streeter to be due to a AREAS OF THE MEDVLLA OBLONGATA 883 The Abducent Nerve Nucleus. — The abducent nerve is a small motor ner\-e, supplying the External rectus muscle of the eyeball. Its nucleus of origin with large, multipolar cells, lies close to the median plane beneath the eminentia abducentis. The axones from these cells pass ventrad through the tegmentum and trapezium, and laterad of the pyramidal tract, to emerge in the postpontile groove. The nuclei are brought under the dominion of the cerebral cortex by pyramidal fibres of the opposite side. They are likewise brought into intimate relation with the trigeminal, acoustic, and opposite oculomotor nerve nuclei. Demssaling fibres Direct fiires to Restiform^fff'^f fi'"!^^ to sup. olivary sup. olivary body. <>f ("i^rculun body of opposite body of same side. N side. of tuberculum acusticum. Efferent fibres of accessory nucleus. Superior olivary^ body. Central acoustic tract {lateral fillet). Tuberculum acusticum. Accessory nucleus \\ of auditory nerve. Decussating fibres to sup. olivary body of oppo- site side. Trapezoid body. Trapezoid nucleus. Pyramidal tract. Fig. 652. — Terminal nuclei of the cochlear nerve, with their upper connections. (Schematic.) The vestib- ular root with its terminal nuclei and thin efferent fibres have been suppressed. On the other hand, in order not to obscure the trapezoid body, the efferent fibres of the terminal nuclei on the right side have been resected in a considerable portion .of their e.xtent. The trapezoid body, therefore, shows only one-half of its fibres — viz., those which come from the left. (Testut.) The Trigeminal Nerve Nucleus. — The trigeminal is relatively enormous and has correspondingly extensive central connections, including nuclei in the mid-brain, pars dorsalis pontis and oblongata, and spinal cord. It is a mixed sensomotor nerve and the afferent and efferent divisions must be considered separately. 1. Afferent Portion. — The axones of the afferent or sensor root arise in the cells of the large semilunar (Gasserian) ganglion. As in the dorsal roots of the spinal nerves, these axones bifurcate, on entering the brain axis, into ascending and descending rami. These terminate in a cephalic nuclear extension of the gela- tinosi Rolandi of the cord; the ascending rami terminate in the so-called sensor nucleus of the trigeminus, the descending rami in the nucleus of the spinal tract of the trigeminus, which extends as far as the second cervical segment of the cord. The sensor nucleus, at the level of the entrance of the nerve, is quite massive, becoming attenuated cephalad. The spinal tract, in its descent, likewise decreases rapidly as it gives off its terminal axones to the nucleus of the tract. The cells of these terminal nuclei send out axones which cross the median plane, giving off collaterals to the facial nucleus, to join the medial lemniscus to reach the thal- amus, and, via thalamus, the somestlietic cerebral cortex. Other axones are distributed (a) to the motor or efferent nucleus of the trigeminus and (5) to the motor or efferent cranial nerve nuclei. 2. Efferent Portion. — The eiferent or motor component of the trigeminal nerve consists of axones arising from cells in two nidi: (a) the principal nucleus in the 884 THE NERVE SYSTEM dorsolateral part of the pontile tegmentum, dorsomesad of the sensor nucleus; (b) a small, slender, so-called mesencephalic root nucleus (nucleus radicis asceiid- entis nervi trigemini) extending cephalad of the region of the locus coeruleus»to lie along the aqueduct in the mid-brain. The fibres from the principal nucleus supply the muscles of mastication. The distribution of the fibres from the mesen- cephalic root is not precisely known. Kolliker suggests that they may supply the Tensor veli palatini, Tensor tympani. Mylohyoid, and anterior belly of the Digastric. Like other motor nuclei, these efferent divisions of the trigeminus are under the dominion of the cerebral cortex via pyramidal fibres. The Cerebellum. — The cerebellum occupies the greater part of the posterior fossa or cerebellar part of the skull, and is the largest portion of the hind-brain. It is overlapped by the occipital poles of the cerebrum, being separated from these by the tentorium. It lies dorsad of the pons oblongata and partly embraces this portion of the brain stem. It is composed of a white central core with scattered gray masses and a surface layer of gray substance that is of darker hue than the cerebral cortex. Ala lobuli centralis. I centralis. > Great horizontal 'Jissure. Pre-clival fissure. clival ] Fig. 6o3.- — Upper surface of the cerebellum. (Schiifer.) The cerebellum is convoluted on a plan entirely different from that of the cere- brum. Each primary fold is folded by secondary and these in turn by tertiary folds, so that on sagittal section a cypress-leaf appearance is noted, the arbor vitae cerebelli. The interior or medullary white substance follows all these branchings and sub-branchings, forming a skeleton of the minute folds which are called folia. These folia are demarcated on the surface by numerous curved and more or less parallel fissures of various depths. The cerebellum is connected to the brain stem by three pairs of peduncles and by vestigial portions of the primitive dorsal wall of the brain tube. Among the latter the medullary vela or laminae are most important; they are the superior medullary velum (valvula), and the inferior medullary velum (velum) which enter into the formation of the "roof" of the fourth ventricle. The rounded margin of the cerebellum demarcates two surfaces looking re- spectively "upward" and "downward," or cephalic and caudal surfaces. Both are convex, the inferior or caudal surface more so than the upper or cephalic. The inferior surface shows a deep median depression, the vallecula, into which the medulla oblongata is sunk. The ventral margin is widely notched to partly embrace the brain stem (tegmental part of the pons and corpora quadrigemina) ; a dorsal notch {incisura cerebelli posterior), which is smaller and narrower and THE CEREBELLUM 885 lodges the cerebellar falx, separates the hemispheres as tliese project beyond the inferior vermis. ♦^rhe cerebellum is arbitrarily subdivided into a medial segment, the vermis or worm, from its annulated appearance, and two lateral portions, commonly called the cerebellax "hemispheres." The vermis may, according to the aspect in which it is viewed, be divided into the superior vermis or prevermis on the upper or cephalic surface, and the inferior vermis or postvermis on the inferior or caudal aspect. The superior vermis is hardly distinguished from the adjacent sloping surfaces of the hemispheres; occasionally a slight furrow exists on either side. Ordinarily the term is to be restricted to the high median elevation usually called the mon- ticulus cerebelli. The inferior vermis is more distinctly bounded by a deep fissure, the sulcus valleculae, on each side, separating it from the corresponding lateral hemisphere. Among the many fissures which traverse the surface of the cerebellum, one is particularly conspicuous as a deep cleft which may be traced along the dorso- lateral margin from the dorsal notch to the point of entrance of the cerebellar Post-noclular Jis. Great zontal ssnre. pyramidal fissure. ■ valvulse. Fig. 654. — Under surface of the cerebellu (Schafer.) peduncles. This is the peduncular sulcus or great horizontal sulcus (sulcus horizon- talis cerebelli), and it divides the cerebellum into a cephalic or upper and caudal or lower part. The sulcus is usually quite deep in the hemispheral portion, but it frequently fails to traverse the vermis. Other deep fissures demarcate the lobes or major subdivisions of the intricately convoluted surface of the cerebellum. Conventionally the lobes and fissures or sulci are described upon the "upper" and "lower" surfaces respectively, and this mode of description is partially adhered to here. A better idea of the topographical relations of the lobes and sulci in the vermis and the hemispheres may be gained frorn a study of the divisions of the cerebellum as if extended in one plane as well as on sagittal sections through the mesal and lateral planes. Lobes and Fissures of the Cerebellum. — The surface of the cerebellum is traversed by eight more or less curved and deep fissures demarcating nine lobar subdivisions. Distinctive names are given to the portions of each lobe in the hemispheres as contrasted with that in the vermis, although often without warrant, as the two are quite continuous and merit no such distinction. This burdensome nomenclature seems so firmly rooted in descriptive anatomy that the vai-ioiis terms must be 886 THE NEBVE 8rSTE3I repeated here. The arrangement of the fissures and lobes will be understood by reference to the following schema, in which structures are named from "before backward," or cephalocaudad : • ^"ER1IIS. Hemisphere. Lingula. Vincula lingualae. <: — — Precentral Fissure. ^ Lobulus centralis. Ala lobuli centralis. <: Postcentral Fissure. > Culmen monticuli. Anterior crescentic lobe.' < — ' — Preclival Fissure. > Clivus monticuli. Posterior crescentic lobe. < Postdival Fissure. > Folium cacuminis. Superior semilunar lobe. < Peduncular Fissure. ^ ( Inferior semilunar lobe. ") Tuber vermis. ^ < Postgracile fissure. > [ Postero-inferior lobule. (, Gracile lobe. j <$- Postpyramidal Fissure. >■ Pj'ramis. Biventral lobe. •< Prepyramidal Fissure. > . Uvula. Tonsilla (Amygdala). C ■ ' Postnodular Fissure. • • > I- Xodulus. Flocculus. The lingula (lingula cerebelli) is a tongue-shaped process of the vermis lying in the ventral cerebellar notch, ventrad of the central lobe, and is partially or com- pletely concealed by it. It consists of five, six, or seven lamellffi lying upon and connected with the dorsum of the valvula. At either side the lingula gradually shades off, being prolonged only for a short distance toward the region of the peduncles as the vincula Ungulae. The central lobe (lobulus centralis) is a small median mass situated in the ventral notch, dorsad of and overlapping the lingula. Its lateral, wing-iike prolongation is called the ala lobuli centralis. The culminal lobe is much larger than the two lobes just described, and con- stitutes, with the succeeding lobe (the clival lobe), the bulk of the superior vermis and "upper" surface of the cerebellum. It pardy overlaps the central lobe. Its lateral extensions are also termed the anterior crescentic lobes. The clival lobe is of considerable size, separated from the culminal lobe by the preclival fissure and from the cacuminal lobe by the postclival fissure. Its lateral extensions are also termed the posterior crescentic lobes. ^ The anterior and posterior crescentic lobes of either side have been described by sonie writers as the pars anterior and pars posterior of the quadrate lobe or lobulus quadr annularis. The cacuminal lobe or superior semilunar lobe (folium vermis) is a short, narrow band at the dorsal margin of the \-ermis, which expands in either hemisphere into a lobe of considerable size, of semilunar shape, and bounded caudad by the peduncular fissure. 'The anterior and posterior crescentic lobes are often called the para anterior and pars posterior, respectively, of the "lobulus quadrangularis." THE CEREBELLUM 887 The tuberal lobe is of small size in the region of the inferior vermis, but laterally spreads out into the large inferior semilunar (lobulus semilunaris Inferior) and g^acile lobes demarcated by the intervening postgracile fissure. These lol^es com- prise at least two-thirds of the "inferior" surface of the cerebellar hemispheres. Fig. 655. — Diagram showing fissures ( U. UA'ula. Pu. Pyramid. nder surface of the cerebellum. F. Flocculus. A^. Nodule. I. Amygdala or Tonsilla. Bivent. Biventral lobe. The gracile lobe is often divided by an intragracile fissure into pre- and post- gracile lobes. The pyramidal lobe is a conical projection, forming the largest prominence of the inferior vermis. It is continued laterad into the hemisphere as the biventral lobe {lobulus biventer); the demarcation between the latter and the pyramis proper is accentuated by the deep sulcus valleculfe. • peduncles ebellum. Grea horhoih Jisstf Amygdala or TousiUa. Nodtile. Fig. 656. — Sagittal section of the cerebellum, near the junction of the (Schafer.) Foiu-tli ventricle. I'ith the hemisphere. The uvular lobe (uvula vermis) occupies a considerable portion of the inferior vermis as the uvula, while its lateral extension in either hemisphere, the amygdala or tonsilla {tonsilla cerebelli; amygdaline nucleus), is a rounded mass lying in a deep fossa between the uvula and biventral lobe. (This fossa was termed by the THE NERVE SYSTEM older anatomists the nidus avis or "bird's nest" [Reil and Vieq d'Azyr].") The junction of uvula and tonsilla is an attenuated isthmus marked by a few shallow furrows and termed the furrowed band. The nodular lobe comprises the nodulus (nodulus vermis) (in the inferior vermis) and the flocculus {flocculi secondarii) of each side, connected by a delicate lamina of white substance, the velum medullare posterius. Each flocculus lies adjacent to the ventrolateral surface of the peduncular mass, extending into the ventral ex- tremity of the peduncular fissure. The flocculi of the two sides are connected with each other by a band of white substance, termed the posterior medullary velum in its medial portion, while its lateral expansions toward the flocculi are termed the peduncles of the flocculli. Sulcus preclivalis Sidms pustcVivalis Sulcus postgrneii [ Sulcus piegracilis Sulcus intragracilis Fig. 657. — Internal structure of the cerebellum. The Internal Structure of the Cerebellum. — In any section of the cerebellum we may recognize the interior white substance, corpus medullare, and the periph- eral gray cortex. The white substance in each lateral hemisphere is more bulky than in the median vermis, while the cortex is of more uniform thick- ness throughout. In a sagittal section in the mesal plane the central white core is seen to divide into two main branches — anterior ramus or preramus and posterior ramus or postramus; these main branches divide and subdivide into a series of medullary laminte surmounted by the foliated cortex, and presenting the charac- teristic appearance known as the arbor vitae cerebelli. Isolated Gray Masses or Nuclei of the Cerebellum. — Embedded in the white matter of the cerebellum are several gray masses. They are four in number on each side: 1. Dentate nucleus or dentatum. 2. Nucleus emboliformis or embolus. 3. Nucleus globosus or globulus. 4. Nucleus fastigii or fastigatum. The nucleus dentatus is the largest and best studied of the cerebellar nuclei. It is located in the mesal part of the corresponding cerebellar hemisphere, in the direct prolongation of the superior peduncle of the cerebellum, which appears to enter it. It consists of a folded lamina of gray substance convoluted like the similar nucleus of the olive, and opens cephalomesad where its hilum (hilus nuclei dentati) permits of the entrance and exit of fibres from various sources. THE CEREBELLUM 889 The nucleus emboliformis is a small mass of gray substance, elongated cephalo- caudad, and placed entad of the dentate nucleus, partly covering its hilum. The nucleus globosus consists of several small round or oval masses connected with each other and lying entad of the preceding. The nucleus fastigii (nucleus of the "roof") is second in size to the dentate nucleus, situated close to the mesal plane directly dorsad of the fourth ventricle, or in the fastigium of the cerebellum, and within the inferior vermis. The nuclei of opposite sides approach each other so nearly as almost to fuse. The Cerebellar Peduncles. — Three pairs of peduncles constitute the chief avenues for the entrance and emergence of the fibres composing the white substance of Fig. 658. — Diagram showing the origin and ( JHed.jpL rse of the fibres of the peduncles of the cerebellum. (Edinger.) the cerebellum and connecting adjacent parts of the brain stem therewith. The peduncles are, on each side, the superior, middle, and inferior peduncles. The inferior peduncle {corpus restifonne; postpedunculus) is the continuation of the restiform body of the medulla oblongata. It contains both afferent and efferent fibres, connecting the cerebellar cortex with structures situated caudad; (1) The dorsal or direct spinocerebellar tract, composed of axones arising in Clarke's column (spinal cord) and terminating in the cortex of the superior vermis on both sides of the median line, but chiefly on the opposite side. (2) The olivocerebellar 890 THE NERVE SYSTEM tract, composed of axones (chiefly internal arcuate fibres) arising in the (niferior) ohvary nuclei— principally from the contralateral or opposite olive, and termniat- ing in the cortex of the superior vermis and adjacent hemispheral portions, as well Fig. 659. — The peduncles of the cerebellum. On the left the three peduncles have been cut at their entrance into the cerebellum; on the right side they are shown penetrating the cerebellar hemisphere. (Poirier and Charpy.) as in the dentate nucleus. (3) External arcuate fibres from the homolateral and contralateral nuclei of the gracile and cuneate funiculi. (4) The nucleocerebellar tract, composed of axones from the recipient nuclei of certain cranial nerves {vestibular, trigeminal). (5) The cere- bellospinal (descending) tract, termi- nating in relation with the ventral horn cells at various levels of the spinal cord. The middle peduncles {bracJiia pontis; medipedunculi) are the largest of the three pairs. They consist of a mass of curved fibres comprising the pons and entering either cerebellar hemi- sphere between the parted lips of the ventral end of the peduncular fissure, just ectad of the inferior peduncle. Each peduncle contains axones cours- ing in opposite directions and in large part may be considered as purely com- missural fibres. Some of the axones terminate, however, in the nuclei pontis to convey impulses to the cells therein ; these in turn send their axones (tractus pontocerebellares) into the opposite mid- dle peduncle, and therefore constitute interrupted commissural systems. A few Fig. 660. — Semidiagram of the three cerebella peduncles. (Testut.) THE CEREBELLU3I 891 fibre systems in the middle peduncles establish relations with certain other structures in the brain stem, notably the nuclei of the oculomotor, trochlear, and abducent cranial nerves. The superior peduncles {brachia conjimcim; prepedunculi) emerge cephalad from the cerebellum entad of the middle peduncles. As they extend cephalad thev converge to form the lateral boundaries of the fourth ventricle and partly roof it in. On trans-section they appear of oval outline, somewhat concave toward the cavity of the ventricle. The superior medullary velum or valvula, a thin lamina of white substance, spans the interval between the converging superior peduncles, and thus completes the roofing-in of the cephalic portion of the fourth ventricle. The superior peduncles consist almost wholly of axones arising from the cells of the dentate nucleus, the ectal part of the nucleus fastigii of the same side, and mesal part of the nucleus fastigii of the opposite side. In their course, converging cephalad, tliese bundles pass into the tegmentum of the mid-brain ventrad of the inferior corpora quadrigemina, and decussate almost wholly. The fibres of each pedimcle terminate in the red nucleus of the opposite side, although a few continue to enter the thalamus. This system of fibres is also called the tractus cerebellotegmentalis, and axones of inverse functional direction have been included therein. The ventrolateral spinocerebellar tract (Gowers' tract) is in relation with the supe- rior peduncle and superior medullary velum. Unlike the dorsal or direct spinocere- bellar tract, it does not enter the cerebellum along the inferior peduncle. Its fibres pass farther cephalad, through the reticular formation of the pars dorsalis pontis and medulla oblongata, to become reflected dorsocaudad at the level of the isthmus of the hind-brain, and entering the superior medullary velum, proceed with the superior peduncle into the cerebellum. The medullary vela are two thin, relatively undeveloped laminse of white sub- stance, representatives of the mid-dorsal wall of the brain tube adjacent to the cerebellar proton, and in the adult brain appear as prolongations of the white central core of the cerebellum. They are the anterior or superior medullary velum (valvula; or valve of Meussens) and the posterior or inferior medullary velum (velum). The superior medullary velum is a thin lamina of white sul^stance spanning the interval between the converging superior peduncles, and with these assisting in the formation of tlie "roof" of the fourth ventricle. Caudad it is continuous with the white substance of the cerebellum, while on its dorsal surface lie the five to seven folia of the lingula. Cephalad it narrows as the corpora quadrigemina are approached, and a slight median ridge, the frenulum, descends upon the dorsal surface of its apical portion from between the posterior quadrigemina; on either side of the frenulum may be seen the superficial origin of the trochlear nerve. The majority of the fibres in the superior medullary velum are longitudinal; as already described (p. 838), the ventral spinocerebellar (Gowers') tract reaches the cerebellum along the superior medullary velum. The inferior medullary velum is a still thinner lamina of white substance which 6ears the same relations to the nodulus that the superior medullary velum pre- sents to the lingula. Laterad it extends to the flocculus of either side. The inferior medullary velum ends in a free crescentic edge and its ependymal and pial coverings continue as a fused, delicate membrane, the tela choroidea ven- triculi quarti. The superior and inferior medullary vela enter the cerebellum at an acute angle, forming the peaked roof (fastigium), while the tent-like recess is called the recessus tecti. The Fibres Proper of the Cerebellum. — The librae propriae of tiie cerebellum are of two kinds: (1) commissural fibres, which cross the middle line to connect the 892 THE NER VE SYSTEM opposite halves of the cerebellum, some at the anterior part and others at the posterior part of the vermis; (2) association fibres, whicli are homolateral fibres connecting adjacent lamina with each other. Microscopic Appearance of the Cerebellar Cortex. — The cerebellar cortex, on • section, presents two marked layers — an outer, of a pale gray color, the molecular layer, and an inner, of a rusty-brown tint, the granular layer. At the contact line of these two layers, but more within the molecular than the granular, are found the characteristic nerve elements of the cerebellum, the flask-shaped Purkinjean nerve cells. The molecular or ectal layer consists of cells and delicate fibrillse embedded in a neuroglial network. The cells are small and are characterized by the course of PURKINJEA ^MOLECULAR OLGI CELL SMALL CELL OF MOLECULAR' LAYER eaSKET CELL Fig. 661. — Trans-section of a cerebellar folii AXONE OF MOSSY FIBRE (Diagrammatic after Cajal and Kolliker.) their branching axones which run parallel with the surface of the folium, give off numerous collaterals which pass in a vertical direction toward the cell bodies of the Purkinjean elements and embrace these in a basket-like network. Hence these cells are called basket cells (Fig. 661). The Purkinjean cells are flask-shaped, and form a stratum at the junction of the molecular and granular layers, their bases directed toward the latter. Each THE MID-BBAIN 893 cell gives off an axone entad, while ectad it gives off numerous dichotomously branching dendrites covering a very large field of the molecular layer. The axone, after giving oft' several collaterals which pass toward different parts of the granular layer, becomes myelinic not far from the cell body and passes into the white substance to establish connections with other folia within the cerebellum or with more distinct brain structures. The granular or ental layer is characterized liv containing numerous small nerve cells or granules of a reddish-brown color, together with many nerve fibrils. Most of the cells are nearly spherical and provided with short dendrites, which spread out in a spider-like manner in the granular layer. Their axones pass outward into the molecular layer, and, bifurcating at right angles, run horizontally for some distance. In the outer part of the granular layer are also to be observed some larger cells, of the type termed Golgi cells (Fig. 661). Their axones undergo frequent division as soon as they leave the nerve cells, and pass into the granular layer, while their dendrites ramify chiefly in the molecular layer. Finally, in the gray substance of the cerebellar cortex fibres are to be seen which come from the white centre and penetrate the cortex. The cell origin of these fibres is unknown, though it is believed that it is probably in the gray substance of the spinal cord. Some of these fibres end in the granular layer, by dividing into numerous branches, on which are to be seen peculiar moss-like appendages; hence they have been termed by Ramon y Cajal the moss fibres (Fig. 661); they form an arborescence around the cells of the granular layer. Other fibres derived from the medullary centre can be traced into the molecular layer, where their branches cling around the dendrites of Purkinje's cells, and hence they have been named the clinging or tendril fibres (Fig. 661). The cerebellum is an important sensomotor organ, transmuting sensor im- pressions into motor impulses under the dominance of the cerebral centres. Its connections with other brain portions and the spinal cord are established by the peduncular fibres. It is essentially an apparatus for the coordination of movements and the space-sense perceptions or orientation of the body and its parts in space. These functions depend principally upon the reception of sensor impulses frorn (1) the vestibular nerve (from, the semicircular canals) and (2) the spinocerebellar (ascending) tracts conveying sensor impulses from the skin, muscles and joints. Motor impulses pass along (1) the cerebellospinal (descend- ing) tracts to the ventral horn nuclei of the cervical cord; (2) the tractus rubro- spinalis, which arises in the red nucleus — an intercalated ganglionic mass con- nected with the cerebellar cortex by the superior peduncles, or tractus cerebello- tegmentalis. The tractus rubrospinalis is a tract for voluntary motor impulses next in importance to the pyramidal tract. Weight of the Cerebellum. — Its average weight in the male is 165 grams (5.8 ounces avoirdupois) and 155 grams (5.4 ounces avoirdupois) in the female. It attains its maximum between the twenty-fifth and thirty-fifth years, its increase in weight after the fourteenth year being relatively greater in the female than in the male. The proportion between the cerebellum and the cerebrum is as 1 to 7.5; among eminent men it is 1 to 8.5, owing to the preponderance in bulk of the cerebrum or thought-apparatus proper. In the newborn the ratio is as 1 to 20. The Mid-brain (Mesencephalon). The mid-brain is the short and constricted portion of the brain which lies in the opening of the tentorium cerebelli {incisura \entoni) and which connects the pons with the inter-brain and hemispheres, and hence it is frequently called the isthmus cerebri. It is developed from the second brain vesicle, the canity of which becomes the aqueduct. It comprises the crura cerebri, the corpora quadri- 894 THE NERVE SYSTEM gemina, the internal geniculate bodies, and the aqueduct. Its two surfaces are ven- tral and dorsal. They are free, but concealed; the ventral surface by the apices of the temporal lobes which overlap it; the dorsal, by the overhanging cerebral hemi- spheres. The ventral surface, when exposed by drawing aside the temporal lobes, is seen to consist of two cylindrical bundles of white substance, which emerge from the pons and diverge as they pass forward and outward, to enter the inner and under part of either hemisphere. They are the crura cerebri, and between them is a triangular area, the intercfural space;' near the point of divergence of the crura cerebri the roots of the third nerve are seen to emerge in several bundles from a groove, the sulcus oculomotorius (sulcus nervi oculomotorii) (Fig. 619). The dorsal surface is not visible until a considerable portion of the cerebral hemi- spheres and other overlying structures have been removed. It then presents four rounded eminences placed in pairs, two cephalad and two caudad, and sepa- rated from one another by a crucial depression. These are termed the corpora FRENULUM-- ' -^..r-TAENlA PONTIS TROCHLEAR NERVe' ^B TRIGEMINAL NERVE SUPERIOR MEDULLAR ^/^^^ VELUM (cut) ^^^ 1ERVE USTIC NERVE RESTIFORM BODY ^ ^±J ^iHBI^3^ GLOSSOPHARYNGEAL AND VAGUS NERVES CUNEATC TUBERCLE -^' Wi--^^^ ^^S/^ HYPOGLOSSAL NERVE TUBERCULUM CINEREUIV Fig. 662. — The brain stem, showing medulla oblongata, pons, mid-brain, and part of- the optic thalami. quadrigemina (Fig. 662). The ventral and dorsal surfaces meet on the side of the mid-brain, and are separated from each other by a furrow, the lateral groove {sulcus lateralis viesencejjhali) , which runs caudocephalad (Fig. 662). External Morphology. Dorsal Surface. — The corpora quadrigemina are four rounded eminences placed in pairs separated by a shallow median groove and a more sharply cut transverse- furrow. The cephalic pair, the superior quadrigeminal bodies (superior collicuR; pregemina; the nates of older authors), are the larger, and the pineal body rests in the flattened depression between them. The superior quadrigeminal bodies are oval, their long diameter being directed cephalolaterad, and are of a yellowish-gray color. The inferior quadrigeminal bodies (colliculi in- ^ Also called interpeduncular space, or posterior perforated space. THE MID-BRAIN 895 feriores; postgemina; the testes of older authors) are hemispherical in form and lighter in color than the preceding. The lamina quadrigemina, comprising the whole of the dorsal wall of the mid-brain, extends from the root region (posterior commissure) of the pineal body to the cephalic end of the superior medullary velum. Each superior and inferior quadrigeminal body is continued lateroventrad in prominent white bands, the brachia. The band from the superior quadrigeminal body is termed the superior brachium or prebrachium ; that from the inferior quad- rigeminal body is called the inferior brachium or postbrachium. The superior brachium or prebrachium (brachium quadricjeminum siiperius) proceeds cephaloventrad between the overhanging pulvinar and a light-gray eminence, the internal geniculate body. In reality it is a continuation of a part of the optic tract. The inferior brachium or postbrachium (brachmm quadricjem- inum inferius) proceeds in a similar direction to disappear beneath the internal geniculate body. Of the two geniculate bodies, on either side, the external geniculate body belongs rather to the thalamus (p. 905), while the internal geniculate body may properly be considered here among the structures of the mid-brain. The internal geniculate body or postgeniculum {corpus geniculatum mediale) is a small oval eminence of the lateral surface of the mid-brain in which the mesal root of the optic tract appears to terminate. The inferior brachium like- wise appears to run into this body; as a matter of fact, so far as is known, the internal geniculate body is (1) a way-station for auditory impulses in their course toward the cerebrum; (2) the origin and terminus for the infracommissure of Gudden (commissura mferior [Guddeni]), by means of which circuitous path, through the optic chiasm, and along the mesal root of the optic tract, the internal geniculate bodies of the two sides are connected. The quadrigeminal lamina is continuous caudad with the superior peduncles of the cerebellum and the intervening superior medullary velum. A slight, median ridge-like projection, the frenulum valvulae, descends from between the inferior quadrigeminal bodies onto the superior medullary velum; on either side of the frenulum emerge the slender trochlear nerves. The crura cerebri constitute the bulk of this portion of the brain stem. Upon the ventral aspect of the brain they appear as two large, white, rope-like strands emerging from the pons and diverging to either cerebral hemisphere, becoming embraced by the optic tracts. Each crus is composed of a dorsal tegmental part — a continuation of the tegmentum of the hind-brain — and a ventral crusta or pes. These parts are demarcated from each other on the external surface by the oculomotor sulcus ventrad (which looks into the intercrural space) and the sulcus lateralis mesencephali on the lateral aspect. The lateral surface shows dor- sally the superior cerebellar peduncle dipping into the substance of the mid-brain, while between it and the crusta is a small triangular field of oblique fibre strands, not always well defined, called the trigonum lemnisci because the lateral lemniscus tends to reach the surface of the brain stem at this situation (Fig. 662) . The surface of the crura cerebri shows a rope-like twist in the course of its fibre bundles. Oblique or transverse fasciculi are sometimes seen upon the sur- face, two of which are fairly constant. They are (1) the taenia pontis, and (2) Gudden's tractus peduncularis transversus (cimbia). The taenia pontis, as Horsley has shown, takes origin contralaterally in the gray substance continuous with the "interpeduncular ganglion," but ventral to it. The taenia then passes over the lateral lemniscus and superior cerebellar peduncle to the dentate nucleus and nucleus fastigii. The tractus peduncularis transversus, or cimbia,^ may be traced from the supe- ^ In architecture, a band or fillet about a column. Also called fasciculus arciformis pedis. 896 THE NERVE SYSTEM rior quadrigeminal body and internal geniculate body over the surface of the crus cerebri to near the ventromeson, disappearing from view in the oculomotor sulcus. Internal Structures of the Mid-brain. — If a cross-section be made through the mesencephalon it will be seen that each lateral half is divided into two unequal portions by a lamina of deeply pigmented gray substance, named the substantia nigra (intercalatum; ganglion of Soemmering). The postero-superior portion of LEMNISCUS Fig. 663. — Trans-section of the mid-brain through the level of the inferioi quadrigeminal body. the crus is named the tegmentum, and the antero-inferior the crusta or pes. The substantia nigra is curved on section with its concavity upward, and extends from the lateral groove externally to the oculomotor sulcus internally. The two crustae are in contact in front of the pons, from which point they diverge from each other, but the two halves of the tegmentum are joined to each other in the mesal AQUEDUCT CLEUS OF MOTOR ERVE 3RACHIUM EDIAL LONQI- JDINAL FASCIC- ULUS OCULOMOTOR NERVE Fig. 664. — Trans-section of the mid-brain through the level of the superior quadrigeminal body. plane by a forward prolongation of the raphe or median septum of the pons. Laterally the tegmenta are free, but dorsally they blend with the corpora quadri- gemina. Traversing the mid-brain in the median plane and nearer the dorsal surface is the aqueduct, surrounded by the central tubular gray, which in this brain seg- THE MID-BUAIN ■ 897 ment has retained the comparathely primitive arrangement of the embryonic brain tube. The Aqueduct (mesocele) and Central Aqueduct Gray. — The aqueduct is a nar- row canal connecting the third with the fourth -ventricle, and demarcating the lamina quadrigemina dorsad from the tegmental zone. Its shape on trans- section varies at diiferent levels, being T-shaped caudad, oval or quadrangular along its middle, and triangular cephalad. It is lined by the ependyma (columnar ciliated epithelium) and surrounded by the central aqueduct gray. The central gray is separated dorsally from the corpora quadrigemina by the stratum lemnisci; ventrad near the median plane lie the medial longitudinal bundles. Within the gray substance lie certain well-defined cell clusters, the nuclei of origin of the oculomotor and trochlear nerves and the mesencephalic root of the trigeminal nerve. These will be described in detail later. The substantia nigra or intercalatum is a crescentic layer of deeply pigmented gray substance interpolated between the crusta and the tegmentum. IVIesad it nearly touches its fellow of the opposite side, being separated by the rudimentary ganglionic gray (the posterior perforated substance or postperforatum) in the inter- crural space. Its ventral face sends numerous ramifying prolongations among the fasciculi of the crusta. It extends from the cephalic border of the pons to the subthalamic region, while its lateral edge reaches the surface along the lateral sulcus. Its cells are medium-sized, multipolar, their bodies approaching the fusiform or angular in outline. The cells are characterized by a pigment (marked only in man) which varies from a pale brown in the young to an absolute blackness in the \'ery aged. The axones arising from the cells proceed in various directions toward the tegmentum and crusta, but their exact course is not known. Experi- mental excitation of this ganglionic mass elicits movements of deglutition accom- panied by respiratory changes. JNIellus has found in the monkey that a portion of the pyramidal tracts is interrupted in the substantia nigra. The corpora quadrigemina are largely composed of gray substance, but the superior and inferior corpora quadrigemina differ distinctly in structure. The inferior corpora quadrigemina or postgemina are more homogeneous in texture, comprising a pair of compact ganglia which on trans-section have the shape of biconvex lenses, encapsulated by white substance. The cells are small, multipolar, and very numerous, embedded in a fine molecular groundwork. The white stratum zonale is principally derived from the fibres of the lateral lemniscus, which terminate in the central gray of the inferior quadrigeminal body as well as in the internal geniculate body. The axones of the cells in the inferior quadrigeminal body coiu'se cephalad in the inferior brachium, dip beneath the internal geniculate body into the tegmentum, and proceed to the thalamus. The inferior quadrigeminal bodies are important links in the chain of the auditory neurone system, and are special localities for the reflexion of auditory impulses. The tegmentum of the mid-brain is continuous with the like formations in the hind-brain stem and consists of longitudinal fibre bundles intersected by transverse arched fibre systems with gray substance irregularly scattered in the interstices, composing the formatio reticularis. In its ventral portion, on either side, and at the level of the superior quadrigeminal body, lies a gray ganglionic mass, the red nucleus. The superior corpora quadrigemina or pregemina present a true cortical type, which is more evident in the optic lobes of lower vertebrates. In man the thin, outermost white layer — the stratum zonale — is an expansion of the optic tract. Beneath this lies a gray nucleus, with numerous small cells — the stratum cinereum — • a cup-like layer of crescentic outline on trans-section. The succeeding ental layer is a white stratum, also derived from the optic tract — the stratum opticum. Between this and the underlying stratum lemnisci is a second gray layer, less defined because of the diffuse interlacinff of white fibres. 898 THE NERVE SYSTEM Each superior quadrigeminal body is one of a series of primary centres of vision related more to eye-muscle reflexes resulting from optic and auditory stimuli than to actual light and color perception. Fibres from the retina, for the most part, form the stratum zonale and end in the ganglionic gray; others enter into the formation of the stratum opticum. Return fibres from the occipital cortex also enter the stratum opticum. The retinal and occipital fibers determine the forma- tion of the superior brachium. Other fibres reach the superior quadrigeminal body through the lateral and medial lemnisci — from both sides — to end in rela- tion with the deeper cells of the stratum cinereum. The connections of the superior quadrigeminal body with the cochlear centres aft'orded by the lateral lemniscus establishes the so-called optic-acoustic reflex path. The red nucleus or rubrum (nucleus iegmenti; nucleus ruber), so termed from its reddish tinge in the fresh brain, which it owes to the pigmentation of its cells as well as to its great vascularity, is found subjacent to the superior quadrigeminal body in tliose section-levels where the substantia nigra has its greatest expansion. In trans-sections its outline is irregularly circular; in sagittal sections an elongated oval. The red nucleus is the end station for the majority of the decussated fibres of the superior peduncles of the cerebellum, for fibres from the cerebral cortex, and from the corpus striatum. These fibre bundles form for the nucleus a capsule which is thicker on its ental surface. From the cells of each of the nuclei arise axones which pass (1) to the thalamus and cerebral cortex (links in the cerebello-cortical neurone-chain), and (2) axones which descend into the spinal cord to form the tractus rubrospinalis (Monakow's) — a continuation of an indirect motor path from the cerebral cortex to the peripheral motor nerve. The tracts arising from the red nuclei of the two sides decussate with each other and descend in the tegmentum. In the intercrural space lies a primitive gray ganglionic mass, the posterior perforated substance or postperforatum. In this posterior perforated substance, cephalad of the pons and in the median line, lies a cluster of cells, the interpeduncu- lar nucleus (Gudden). The fasciculus retroflexus (^leynert), whose fibres arise in the habenal ganglion, descends to end in the interpeduncular ganglion. The principal longitudinal fibre tracts in the tegmentum of the mid-brain are (1) the medial longitudinal fasciculus, (2) the lateral lemniscus, (3) the medial lenmiscus., (4) the decussating superior cerebellar peduncles, (5) the decussating rubrospinal tracts, and (6) the central tegmental tracts. The medial longitudinal bimdle lies on each side of the median plane, just ventrad of the central aqueduct gray in the mid-brain and continuous throughout the brain stem in its formatio reticularis. It is the continuation and the equivalent, but in a more differentiated form, of the ventral basis bundle of the spinal cord. It is formed by association neurones and acts as an associating agent with regard to many cranial and spinal nerve centres for the performance of certain definite functions. Its neurones receive impulses from afferent elements and transmit them to motor or efferent elements. It particularly brings into relation the sensor cranial nerve nuclei and the corpora quadrigemina with the motor nerves of the eye (III, IV, and VI), of the face (VII), and of the trunk. A special nucleus for the bundle is described as being situated in the gray floor of the third ventricle, at its junction with the aqueduct. The axones from the cells of this nucleus cross to the opposite side through the posterior commissure (Fig. 665). The lateral lemniscus, we have learned, is a continuation of the auditory path in its course to the cerebral cortex. Its formation is described on page 884. In the mid-brain the fibres of the lateral lemniscus course through the lateral part of the tegmentum, near the surface, and most of them end in the gray nucleus of the inferior corpora quadrigemina and in the internal geniculate body. A few fibres are carried into the superior quadrigeminal body. THE MID-BRAIN 899 The medial lemniscus, or principal conduction path for sensor impulses from the trunk and extremities, and already discussed in the preceding (p. 876), ascends in the tegmentum of the mid-brain in the contact zone with the crusta. In its ascent it is deflected slightly dorsolaterad by the red nucleus. The lateral border of the ribbon-like bundle is in contact with the lateral lemniscus, and forms an angle with it, as seen on trans-section (Figs. 663 and 664). Fig. 665. — The medial longitudinal bundle in black and red. Lateral lemniscus i identified by comparison with Fig. 648.) Many of the fibres of the medial lemniscus terminate in the superior quadri- geminal body; the remainder proceed to the thalamus. The superior peduncles or prepeduncles of the cerebellum sink into the mid-brain tegmentum in a cephaloventral direction, the two superior peduncles converging and their fibres undergoing a complete decussation (Wernekinck's commissure) subjacent to the inferior quadrigeminal body. The crossed fibres end, for the most part, in the red nucleus of each side; others circumvent the nucleus forming 900 , THE NERVE SY>STE3I a white capsule for it which is thicker on its ental surface, and proceed to the thalamus. The tractus nibrospinalis (Monakow's) is composed of axones arising in the red nucleus, decussating with those of the opposite tract, and descending in the tegmentum to the lateral intermedial fasciculus of the cord, to terminate in relation with ventral-horn cells. The central tegmental tract (olivary fasciculus) probably arises in the inferior olivary nucleus and ascends in the tegmentum. In the pars dorsalis pontis it is best seen in trans-sections as a compact longitudinal bundle along the dorsi- m^sal aspect of the superior olive. Cephalad it is said to end in the lenticular nucleus. Fountain Decussation.' — A dense decussation may be found in the space between the two red nuclei. The fibres composing the decussating bundles arise from cells in the superior corpora quadrigemina and central aqueduct gray. After having crossed the middle line they descend as the tectospinal tract, join the medial longitudinal fasciculus, and give off collaterals to, or terminate in the nuclei of, the eye muscle nerves, as well as to spinal centres for movements of the head and neck. The crusta or pes is somewhat crescentic in outline on section and is composed of longitudinal fibre bundles — the continuation of the internal capsule — divisible into three sectors. The middle sector comprises three-fifths of the cross-section area of the crusta, and comprises the pyramidal tract on its way from the cerebral cortex (motor area) to cranial and spinal centres below. The ectal sector, or lateral one-fifth, comprises the tempore pontile tract;' its axones arise from the cortical cells in the temporal lobe and end in fine terminal arborizations in relation with cells of the nuclei pontis. The ental sector, or mesal one-fifth of the crusta, comprises the frontopontile tract; its axones arise from cells in the cortex of the frontal lobe and terminate in the nuclei pontis. The pyramidal tract is a direct voluntary motor tract; the two corticopontile tracts enumerated above are links in a chain of neurones which constitute an indirect motor tract. The series of neurones in the chain of the indirect motor tract may be shown in the following order: Corticopontile tract; nuclei pontis; cerebellocortex ; dentate nucleus; superior cerebellar peduncle; red nucleus; tractus rubrospinalis ; spinal gray; spinal nerve; muscle. Summary of the Gray Masses in the Mid-brain: *Central aqueduct gray. (a) Oculomotor n. nucleus. (b) Trochlear n. nucleus. Nucleus radicis descendentis nervi trigemini. ^Nucleus of medial longitudinal bundle and postcommissure, *Formatio reticularis. *Substantia nigra (intercalatum). *Red nucleus (rubrum). ^Stratum cinereum of superior corpora quadrigemina. *Nucleus of inferior corpora quadrigemina. *" Interpeduncular" ganglion. Structures marked with an asterisk have been considered in the preceding description. The central connections of the oculomotor, trochlear, and trigem- inal nerves may now be described. Deep Origin of Cranial Nerves Arising in the Mid-brain. —The mesen- cephalic root of the trigeminal nerve has been described on page 884. ^Decussatio fontinalis, so called because of the resemblance of the scattering strands to the jets of a fountain. THE MID-BRAIN 001 The Trochlear Nerve Nucleus. — The trochlear nerve iiiicleu.s is situated in the level of the cephalic half of the inferior quadrigeminal body. It is a small oval mass of gray substance in the ventral part of the central acjueduct gray. The cells are large, sometimes stellate in appearance. The root fibres pursue a peculiar course; they accumulate in the lateroventral angle of the aqueduct gray, run caudad, gradually rising dorsad, and suddenly turn mesad to undergo a complete decussation with the root of the opposite side in the superior medul- lary velum, emerging laterad of the frenulum, or at the inner border of the superior peduncle. The nucleus is placed under the dominion of the cerebral cortex by pyramidal fibres, and it is associated with other nuclei in the brain stem by the medial longitu- dinal bundle. The Oculomotor Nerve Nucleus. — The oculomotor nerve nucleus is a group of cell clusters in the ventral portion of the aqueduct gray, subjacent to the superior quadrigeminal body, and extending cephalad to become lost in the gray wall of the third ventricle at the slope formed by the opening out of the aqueduct. Its nerve elements are arranged in definite groups. The most cephalic of these is composed of smaller elements, closely crowded and embedded in deeply staining Antero-exteriial nuclcu^.-^ Aniero-internaZ nu Nucleus of Bdingt Westphal. Third ventricle. Central nucleus. A nterior dorsal nucleus. Anterior ventral nucleus. _Posierior ventral nucleus. -Posterior dorsal nucleus. -Crossed fibres. ^Xucleus of origin of trochlear nerve. Decussation of trocMear nerve. -Trochlear nerve. riG. 666. — Showing the different groups of cells, which constitute, according to Perlia. the nucleus of origin of the oculomotor nerve. (Testut. ) molecular ground substance. In a flat-wise section of the brain stem the outline of this nucleus resembles an inverted L or the tip of a boat hook; the axones from the cells of this nucleus (of Edinger and Westphal) supply the Ciliary muscle and Sphincter iridis (pupillary motion). The main nucleus, composed of several sub-groups, lies caudolaterad of the preceding, and is composed of larger cell elements. The root fibre bundles from this nuclear group pass ventrad, breaking through the medial longitudinal fasciculus, separating like the strands of a horse's tail by the interference of the red nucleus, to become gathered into more compact bun- dles between the mesal edge of the substantia nigra and intercrural region, and emerging by eight to twelve fascicles which compose the trunk of the oculomotor nerve. 902 THE NERVE SYSTEM External rectus The origin of each nerve is not Hmited to the nuclei of its side; a part is decus- sated and the decussated origin is related to the innervation of the Internal rectus. By means of association neu- juteniai rones in the medial longitu- dinal fasciculus the oculo- motor and abducens nuclei of one side are brought into relation, affording an organic basis for the synergism exist- ing between the Internal and External recti muscles in the conjugated lateral eye move- ments. The paradox of the facial nerve supplying muscles un- der the reflex dominion of the retina (Orbicularis oculi) instead of the oculomotor may be explained by the assumed existence of fibres emerging from the oculomotor nucleus, entering the medial longitudinal fasciculus and joining the root of the facial. Parts Derived from the Fore-brain. The fore-brain or prosencephalon includes those portions of the brain which are derived from the cephalic one of the three primary brain vesicles. It includes, according to prevailing schemas, a thalamic portion (the thalamencephalon or diencephalon) and the telencephalon. The two' divisions constitute a structural continuity and exhibit a mutual dependency so close that the arbitrary distinction now in vogue tends to mislead. The relations of "diencephalon" and "telen- cephalon" are further complicated by the intimate fusion of the sides of the former (thalami) with the floors of the latter; this caudatothalamic fusion, in the adult brain, gives rise to some difficulty in distinguishing the two segments. The internal capsule which intervenes between thalamus and lenticular nucleus also in- tervenes between lenticular nucleus and caudate nucleus, both telencephalic parts. External Morphology. — The diencephalon or thalamencephalon comprises the thalami, the pineal body or epiphysis and habenulse, the external geniculate bodies, and the pars mamillaris hypothalami. (Other classifications include also the pars optica, with tuber cinereum, infimdibulum, optic chiasm, and pituitary body or hypophysis. It is also defined as so much of the fore-brain as does not enter into the formation of the cerebral hemispheres.) Caudad it is continuous with the mid-brain, cephalad with the cerebral hemispheres. Its primitive cavity becomes metamorphosed in the adult into the third ventricle or diacele as the lateral walls hypertrophy to form the thalami. Its ventral surface is the relatively insignificant gray lamina in the intercrural space. Its dorsal surface is concealed from view by the massive hemispheres and their great commissure, the corpus callosum, and by the fornix. Its actual roof, separating it from the overlapping cerebral parts, is a delicate membranous fold, the velum interpositum or diatela. The Thalami.' — The thalami constitute the bulk of this portion of the brain. They are large ovoid masses of gray substance so named by the ancients after their resemblance to a pair of couches. Each thalamus is smaller frontad than caudad and the caudal ends are more widely separated from each other. The mesal or ^ Thalamos, bed or couch; bed-chamber. PARTS DERIVED FROM THE FORE-BRAIN 903 ventricular surface is largely free, except for an area, of variable size, by which the two thalami are fused in 90 per cent, of brains. The thalamic fusion is also called the middle commissure or medicommissure. The free surface is co\'ered by ependyma and is of smooth contour. Its dorsal limit is marked by an ependymal ridge, usually torn through in dissection, the taenia thalami or ripa,' fortified by a subjacent narrow band of fibres called the stria meduUaris, which may be traced to the habenular nucleus and habenular commissure (or "stalk" of the pineal body) . Caudad lies a depressed triangular area — the trigonum habenulae, situated cephalad of the superior cjuadrigeminal body. The dorsal surface is usually described as being free, but only a narrow ectal portion can be so described, the ependyma of the lateral ventricle being slightly rORAMEN OF MONRO LE COMMISSURE HOROIO PLEXUS OF HIHD VENTRICLE l/ENTRICLE Fig. 668. — Mesal aspect of a brain sectioned in the median sagittal plane. reflected upon it (the lamina affixa) before entering into the formation of the choroid plexus of the lateral ventricle. The rest of the dorsal surface is not lined by ependyma, but is in contact with the pial fold called the velum interpositum. This surface is of a whitish color owing to a thin layer, of white fibres, the stratum zonale. A faint oblique groove crosses this surface in a caudolateral direction, corresponding to the ectal edge of the fornix. Laterad it is demarcated from the caudate nucleus by a groove which is occupied by the striatal vein and a slender band of fibres, called the taenia semicircularis or stria terminalis. The surface is not of e^en contour throughout, usually showing three eminences (in addition to the puh'inar) corresponding to the main nuclear aggregations within the thal- amus— viz.: Tuberculum anterius, mediahs, and lateralis. 3 formed by tiie rupture of the ependyma along the lines of its reflection from entoccelian ^ventricular) 904 THE NERVE SYSTEM The tuberculum anterius forms a marked bulging frontal extremity, which helps to form the boundary of the foramen of Monro or aperture of communication between lateral and third ventricles. The caudal extremity of the thalamus is a prominent bolster-like projection which overhangs the brachia of the corpora quadrigemina and is called the pul- vinar. A smaller oval prominence, situated ventrolaterad of the pulvinar, is termed the external geniculate body or pregeniculum (corpus geniculatum lateral e) ■ — a partial end station for the optic tract. ■ FIFTH VENTRICLE SEPTUM LUCIDUM ENULAE TERIOR COMMISSURE SUPERIOR QUADRI' FRENULUM -Dissection showing the two th; clei, and adjacent parts. The lateral surface of the thalamus is in contact with the internal capsule — that great concentration of fibre tracts coursing to and from cerebral centres and forming the crusta below. To this white stratum the thalamus itself contributes fibres destined to reach the cortex, and in return it receives fibres from the cortex. These thalamocortical and corticothalamic sets of fibres constitute the thalamic radiation, forming a more or less distinct reticulated capsular zone {stratum reticulatum; external medullary lamina) for the thalamus. PARTS DERIVED ER03I THE FORE-BRAIN 905 The ventral or inferior stirface is continuous with the hypothalamic tefjmental substance and with the central gray substance of the third ventricle lining its sides and floor. Internal Structure of the Thalamus. — The thalamus is composed of gray substance, with large multipolar cells, which is subdivided into a number of distinct nuclei; twenty such have been described; three are universally recognized. They are separated from each other by a white layer (lamina medullaris interna) which runs parallel to the wall of the third ventricle for its greater length; caudally it runs mesad, overlapped by the ectal nucleus, and numerous sub-laminie run into it. Frontad the internal medullary lamina subdivides into two branches, thus permitting the intrusion of the nucleus anterius between the two main nuclei (medial and lateral). The nucleus anterius lies fronto4orsad ; in it terminate the axones of the fasciculus thalamomamillaris (fasciculus albicantiothalami ; bundle of Vicq d'Azyr). The nucleus medialis is lined mesad by the central gray of the third ventricle and is usually fused with its fellow of the opposite side (middle commissure). A special spheroidal cell cluster in this nucleus is called the centrum medianum (Luys). The nucleus lateralis is the largest of the three, extending the entire length of the thalamus and including the pulvinar. A special semilunar cluster of cells in the ventral portion of this nucleus is called the nucleus semilunaris (Flechsig). The Connections of the Thalamus. — The thalamus is a ganglion interposed between the sensor tracts in the tegmentum and the cerebral cortex, as well as an important link in the optic path. It also gives rise to motor tracts concerned with instinctive movements of an emotional nature. It is a relay station for the various tracts which convey sensations of touch, temperature, and pain from the body, extremities, head and neck, of muscle cense, and of the special senses. It transmits these impulses to, and, reciprocally, receives impulses from the cerebral cortex. As an "emotional" centre it is also under the inhibitory influence of the cerebral cortex, which, if the emotion be not too strong, prevents its external manifestation. The thalamocortical and corticothalamic fibres, with the internal capsule, enter into the corona radiata or fan-like formation of the white substance of the cerebral hemisphere. Although there is no anatomic subdivision into distinct groups of these fibres as they stream to and from the thalamus, it is customary to distinguish a frontal, a parietal, an occipital, and a ventral stalk. The frontal and parietal stalks, as their names indicate, pass between the thalamus and frontoparietal cortex, as well as to the lenticular nucleus and caudate nucleus. The occipital stalk is composed of fibres passing in both directions between the pulvinar and occipital cortex, constituting the so-called optic radiation. The ventral stalk comprises the ansa lenticularis (thalamolenticxdar) and the ansa peduncularis (thalamotemporal and thalamoinsular). They will be described in detail farther on. The external geniculate body, or pregeniculum (corpus geniculatum laterale) is an intercalar ganglion proper to the optic ner\e, derived from the thalamus. On section it is seen to be characterized by the regular alternation of deeply gray and white laminae. The latter are thicker and composed of fibres which enter the external geniculate body from the optic tract and optic radiation. The nerve cells in the gray substance are large, multipolar, and pigmented. [Note. — The external geniculate body and the more isolated internal genicu- late body are generally included under the head of metathalaimis .] The hypothalamic tegmental substance, continuous with the mid-brain tegmen- tum, is interpolated between the ventral face of the thalamus, the red nucleus, and a continuation of the substantia nigra known as the corpus hypothalamicus or body of Luys. Through the hypothalamic tegmentum stream the fibres of 906 THE NERVE SYSTEM the medial lemniscus, of the superior peduncle of the cerebellum, and from the red nucleus, to end in relation with thalamic cells. The corpus hypothalamicus is a grayish-brown, lentiform mass which lies in the ideal continuation frontad of the lateral part of the substantia nigra, and, like it, situated between pes and teg- mentum. It is made up of fine myelinated fibres crowded in great profusion and confusion, with numerous delicate, coiled capillaries and sparse, multipolar, more or less pigmented, nerve elements of moderate size. The outline of the body is defined by a white capsule, some of the fibres of which are seen to decussate in the floor of the third ventricle with those of the opposite side, dorsocaudad of the corpora albicantia. The Pineal Body {corpus pineale; epiphysis) (Figs. 668 and 669). — The pineal body (from its shape resembling a fir-cone — pinus) is a small, reddish-gray body placed between the caudal ends of the thalami and occupying the depression between the two superior quadrigeminal bodies. It is covered by the velum inter- positum, which intervenes between it and the splenium of the corpus callosum. It is an outgrowth which is not regarded as an important neural ingredient of the human brain and is generally believed to be a rudimentary relic, representing a Cyclopean eye' of some extinct ancestral vertebrate, homologous with the parietal organ, resembling a molluscan eye of a living species of Prosaurlan (the Hatteria of New Zealand). Its attached base is a hollow peduncle divisible into a dorsal and ventral part by the intrusion of the epiphyseal recess {recessus pinealis) of the third ventricle. The dorsal stalk continues on either side and upon each thalamus as the stria medullaris; it is reenforced by commissural fibres joining the habenulte of the two sides; hence another name for the dorsal stalk is the habenular com- missure (supracommissure of Osborn). The ventral stalk is folded over another commissural band — the posterior commissure. Structure. — The pineal body consists of a number of follicles, lined by epithelium and connected by ingrowths of connective tissue. The follicles contain a transparent viscid fluid and a quantity of sabulous matter named brain sand (acervus cerebri), composed of phos- phate and carbonate of lime, phosphate of magnesia and ammonia, with a little animal matter. These concretions are almost constant in their existence, and are present at all periods of life. In the interval between the pineal body and the caudal end of the thalamus lies a small triangular depression (sometimes an elevation) known as the tri- gonum habenulae, marking the position of the nidus, or ganglion habenulae, a group of small angular cells. The axones from these cells are collected ventrad into the fasciculus retroflexus (Meynert), which courses through the tegmentum mesad of the red nucleus to end in the interpeduncular ganglion (Gudden) in the posterior perforated sulistance. In addition to this fasciculus, the habenula is the reunion point for two other sets of fibres: (1) the stria medullaris and (2) habenular commissure. The stria medullaris (p. 903) is made up of axones arising from two sources: (1) cells in the hippocampus {via fornix) and (2) cells in the ganglion opticum basale. These join near the anterior pillar of the fornix and run caudad on the mesal thalamic surface, to end in the habenular ganglion of the same side and, by crossing in the dorsal stalk of the epiphysis, help to form the habenular commissure, to end in the corresponding nidus habenulae of the opposite side. The posterior commissure is a round band of white fibres crossing from side to side in the ventral stalk of the pineal body bridging the aqueduct at its continua- 1 Although most vertebrates show a single pineal body or parietal organ, it is double in the lamprey and certain reptiles; the two bodies lie one in front of the other — not side by side (although probably paired organs originally). The frontal organ sends its fibres into the habenular nucleus: the caudal organ to the region of the posterior com- missure (tectum opticum). PARTS DERIVED FROM THE FORE-BRAIN 907 tion into the third ventricle. The posterior commissure shares rehition with both fore-brain and mid-brain structures and is formed of decussating jfibres which may be enumerated in the following systems: (o) fibres arising in the special nucleus (described on p. 898) for the medial longitudinal bundle; (6) fibres con- necting the two thaland; (c) fibres connecting the habenular nidi; {d) fibres connect- ing the superior quadrigemina. [Note. — The habenular, pineal body, and posterior commissure are generally included under the head of epitkalamus.] The posterior perforated substance or postperforatum has be,en described on page 898. It marks the situation of the "interpeduncular ganglion," which is small in man, but very large in rodent brains. From the cells in this primitive gray lamina arise the fibre tracts already described as the taenia pontis (p. 895), and often -vdsible at the point of emergence from the gray substance of the intercrural space. The corpora albicantia (Fig. 673), or corpora mamiUaria, are two symmetrical, I jinirhjmal lininrj of veiHricle V em of corpus / - ^■a.~-i\ -^ striatum Lateral ventricle '''^ \ / // BKSti -run! amuc / Choroid plexus of lateral ventricle Velum interpositum Veins of Galen Ependymal lining of' ventricle Choroid plexuses of third ventricle Third ventricle Fig. 670. — Coronal section of lateral and third ventricles. (Diagrammatic.) small, round, white protuberances situated side by side in the intercrural space cephalad of the posterior perforated substance, at a point where the floor of the third ventricle rapidly decreases in thickness to form the tuber cinereum. The color of each corpus albicans is white, owing to a superficial stratum of fibres derived from the fornix. Within lie three nuclear masses — two medial, consti- tuting the main mass, and a smaller lateral nucleus applied against the former, so as to represent a crescent on cross-section. The fibres of the fornix terminate in the corpus albicans. From its cells arise two fasciculi which have a common neurone origin. Cajal discovered, and Kolliker confirmed the fact, that the axones from the medial nucleus cells bifurcate; one set of limbs passes fronto-dorsad to form the bundle of Vicq d'Azyr (fasciculus thalamomamiUaris), which ends in the nucleus anterius of the thalamus, while the other set of limbs of the primary axones passes caudad to form the fasciculus pedunculomamillaris in the mid-brain tegmentum; its destination is doubtful. The axones from the lateral nucleus join the latter bundle. [Note. — The posterior perforated substance and the corpora albicantia are generally included under the head of the Pars Mainillaris Hypothalami.] Third Ventricle {ventriculus tertius) (Fig. 668). — The third ventricle is the adult representative of the cavity of the primary fore-brain vesicle, but only so 908 THE NERVE SYSTEM much of it as is not carried laterad, on either side, in the rapidly growing, eventually huge cerebral hemisphere buds to form the lateral ventricles. It is a narrow, cleft-like interval between the two thalami and hypothalamic gray, limited f rontad by the terma, continuous caudad with the aqueduct and laterad, through the foramina of Monro, with the lateral ventricles. Its roof is destitute of nerve tissue and is formed by a delicate, fused ependymal and pial layer, invaginated on either side of the median plane by the plexuses of the lateral ventricle. The pial layer is one of the constituents of the fold known as the velum interpositum. The floor of the ventricle is formed by structures already described on the basal aspect in the intercrural ^pace — viz., the tuber cinereum, corpora albicantia, and posterior perforated substance, as well as the optic chiasm and a portion of the tegmentum of the crura cerebri. Much of the floor, it may be noted, is formed by the primitive, undifferentiated central gray; and although the optic vesicle develops from its ventrocephalic portion, the caudal shifting of central optic connections to thalamus and mid-brain has made this portion of the neural tube wall comparatively insignificant. The lateral avails are formed in part by the thalami, in part by the hypothalamic gray ventral extension. The fornix may be seen, shining through a thin lamina of gray substance and the ependyma, coursing caudoventrad to the corpus albicans. A slight furrow, the aulix or sulcus of Monro, may sometimes be traced from the aqueduct to the foramen of Monro, curving ventrad of a bridge-like fusion of the two thalami — the middle commissure (medicommissvire) . (The term commissure is inappropriate, as no commissural fibres appear to pass from one thalamus to the other in this "thalamic fusion"; it is absent in about 10 per cent, of brains examined.) The cephalic wall is formed by the lamina terminalis or terma, the rudimentary mediancephalic wall of the neural tube. The terma is attached to the dorsum of the optic chiasm; dorsally it is reinforced by the anterior commissure. As seen in mesal section or as shown by a cast of the ventricle (Fig. 696) it is seen to be of irregular outline. Frontad is the optic recess, dorsad of the optic chiasm; caudad thereof is the infundibular recess in the tuber. The epi- physeal recess is seen between the habenular commissure and the posterior com- missure. Dorsad of the pineal body is a diverticular recess of variable extent {recessus siqjrapinealis) . If the segmentation of the fore-brain into two divisions be adopted ultimately, il will be necessary to allot one portion of the third ventricle (between the thalami) to the diencephalon (hence diacele), and the rest to the telencephalon (the medial cavity of which is termed the aula by Wilder). In anticipation of the description of the cerebral hemispheres we may consider here the remaining structures in the floor of the third ventricle, usually included under the head of the pars optica hypothalami of the telencephalon, in order to lead up to a description of the cerebral connections of the optic tract. External Morphology of the Optic Portion of the Hypothalamus. This in- cludes the tuber cinereum and pituitary body or hypophysis, the lamina terminalis, the optic chiasm, and the optic tracts. The tuber cinereum (Fig. 668) is a thin-walled conical projection in the inter- crural space cephalad of the corpora albicantia. Its apical portion is attenuated to form the stalk of the pituitary body; this is generally termed the infundibulum, while the cavity of the funnel-shaped diverticulum is called the infundibular recess of the third ventricle. The gray lamina composing the tuber is continuous with the central ventricular gray, and therefore with the lamina terminalis. PARTS DERIVED FROM THE FORE-BRAIN 909 The pituitary body or hypophysis^ is a structure of twofold origin, giving rise to a division into a prehypophysis and a posthjrpophysis. Tlie po.sthypophysis alone is of neural origin, developing as a ventral diverticulum from the primitive neural tube. The prehypophysis or epithelial lobe, develops from the stomodeum, or buccal cavity, as a tubular diverticulum (Rathke's), which eventually loses its connection^ with the oral tissues to become included within the cranial cavity and intimately attached to the neural bud. Both pre- and posthypophysis are therefore of ectodermal origin and have developed from a conjunction of surface tissues which have migrated from opposed (ventral and dorsal) parts through the head! The prehypophysis is much the larger and somewhat embraces the post- hypophysis; the two are insepai-able, however, and together occupy the fossa hypophyseos of the sphenoid. CORPUS ALBICANS POSTERIOR CEREBF Fig. 671.— The pituitar\ boch ■LM,uphx-i- i median sagittal section. (Testut.) The two parts of the pituitary body are as distinct in structure as they are in embryonic origin. The posthypophysis consists of a mass of nerve cells, neuj-ogha, connective tissue, and bloodvessels; the structure of the prehypophysis is distinctly glandular, resembling that of the parathjToid bodies. It is surmised that the latter is the functional part of the pituitary body — concerned with the internal secretions, and usually involved in the pathological form of giantism called acromegaly. The lamina terminalis or terma (Fig. 668) is a thin, easily torn lamina between the optic chiasm and the anterior commissure, limited laterally by the closely ap- proximated cerebral hemispheres and constituting the primitive, undifferentiated cephalic boundary of the original neural tube. The Optic Tract and its Central Connections. — In the section on the development of the brain it was learned that the optic nerve is not a peripheral nerve; it is rather a central brain tract extruded from the neural tube. E\idence is at hand that in ancestral vertebrates the general cutaneous sensor system was also capable of light perception. With the recession of the neural tube from the surface and in company with the morphological differentiation of the head end, a light- perceiving pair of organs arose as a special development. The distal end of the optic brain vesicle becomes the retina, in structure like the brain wall, whose cell axones carry afferent impulses to the brain. Although the optic fibres enter the • F. Tilney : Study of the hypophysis cerebri with especial reference to its comparative histology. 2 of Wistar Institute of Anatomy and Biology, 1912. 2 Occasionally the channel persists as the craniopharyngeal canal. 910 THE NERVE SY,STE3I ventral wall of the brain, the retina is originally derived from the dorsolateral (sensor) wall of the second neuromere (Fig. 627). The parietal organs, also light-perceiving, likewise developed as paired dorsal buds farther caudad, eventu- ally to atrophy, as the more frontal optic organs better subserved the purposes of the organism. The remarkable and as yet unexplained fact regarding the optic apparatus is that the afferent fibres from the retinal cells pass into the ventral wall to cross to the opposite side, forming a decussation which is total, or nearly so, in verte- brates below the mammals ; the more laterally placed the eyes are the more nearly total is the decussation.' Although the optic vesicle is a diverticulum of the fore-brain in its cephalic portion, the optic tract in its central connections becomes intimately related with the external geniculate body and pulvinar, the occipital cortex of the cerebrum, and with the superior quadrigeminal body of the mid-brain. Some of these central structures are way-stations in reflex paths; the occipital cortex alone is the actual visual centre, though visual perceptions are here brought into association with tactile, auditory, and other impulses. Optic Chiasm. — From the retina of each eye the so-called optic ner^^es converge to partially decussate at the base of the brain to form the optic chiasm, a white quad- rangular plate which presses in the primitive central gray floor of the third ven- tricle, as previously described. Approximately one-third of the fibres of each optic nerve do not cross to the opposite side. The optic chiasm is further re- enforced by the infracommissure (of Gudden) and other lesser fibre tracts (com- missura superior [^Nleynerti] and commissura ansata [Kolliker]). The fibres in the chiasm are so complexly interwoven that only through exhaustive experi- mental development and pathological studies has it been possible to under- stand its structure. Broadly stated, the fibres from the medial (or nasal) halves of the retinae decussate in Mo, while those from the lateral (or tempo- ral) halves do not cross. Leaving the optic chiasm, the crossed medial and uncrossed lateral fibres form the slightly flattened optic tracts coursing caudo- laterad, embracing the crura cerebri and dividing in the neighborhood of the lateral geniculate body into two "roots," a mesal and a lateral root. The mesal root is in reality not a part of the true optic path; it is a separate fascicu- lar representation of the infracommissure of Gudden, composed of fibres form- ing a reciprocal bond of union (commissural) between the internal geniculate bodies of the two sides and coursing through the chiasm (Fig. 672) . The lateral root of the optic tract is the true visual path, composed of (a) the uncrossed fibres from the lateral half of the retina of the same side and (b) the crossed fibres from the mesal half of the retina of the opposite side. The fibres of the lateral root are distributed to the primary or lower optic centres as follows: (1) INIost fibres end in the external geniculate body; (2) a less number end in the pulvinar; (3) the remainder end in the nucleus of the superior quadrigeminal body. The lateral geniculate body and pulvinar are ganglionic way-stations or inter- nodes in which visual impulses are reflected, in large part, to the visual cortex in the occipital lobe; the superior quadrigeminal body, on the other hand, plays no part in the conduction of impulses perceived as light or color; it presides rather over the eye-muscle reflexes to visual- stimuli, and in its turn is under the dominion of the higher cortical centre. Reflex impulses are sent to the oblongata and spinal centres along axones entering into the formation of the medial longitudinal bundle. 1 Possibly the reflex contraction of the muscles on one side of the body in the ancestral vertebrate followed the perception of a menacing object by the eye of the opposite side; hence the advantage of a decussation. 2 And auditory stimuli as well ( see p. 898). JPAMTS DERIVED FROM THE FORE-BRAIN mi The axones of corticifiigal neurones proceed to the nucleus of the superior quadri- geminal body along the optic radiation/ Some fibres are detached from the optic tract and course through the crus cerebri to the oculomotor nucleus. These fibres are small, and are believed to he afjferent branches for the Sphincter pupillse and Ciliary muscles. The connections of the external geniculate body and pulvinar with the higher cortical centre of vision are established by neurones, the cells of which lie in the two ganglia just mentioned, and whose a.xones stream in an arched, more or less PULVINAR — 1 LAT. GENICULI MEDIAL GENICU- LATE BODY SUPERIOR QUADRI- GEMINAL BODY OCULOMOTOR OCCIPITAL CORTEX Fig. 672. — Scheme showing central connections of the optic nerve and optic tract. compact bundle in the white substance of the cerebral hemisphere toward the occipital cortex. Another system of neurones, whose cells lie in the cortex, sends its axones in the reverse direction (cortifugal) to the two lower centres. The cerebral tract thus formed between primary and secondary (cortical) centres is called the optic radiation (Fig. 712), to be studied more fully in the sequel. The components of the optic path are delineated schematically in Fig. 672. * Centrifugal fibres ending in the retina, and probably arising from cells been discovered in the optic tracts. I the superior quadrigeininal body, have 912 THE NEBVE SYSTESr The Cerebral Hemispheres. External Morphology. — Of all the component parts of the brain, the cerebral hemispheres form the largest part, and their preponderance and remarkable specialization underlie the extraordinary manifestations of the intellect so highly amplified in man. Fig. 673. — ^Tesal aspect of a brain sectioned in the median sagittal plane. The term cerebrum, often employed loosely as embracing several brain parts, is here intended to include the brain mantle and the olfactory lobe — equivalent to the telencephalon of His, with the exception of the pars optica hypothalami. As already indicated in the section on brain development, there has occurred, in the evolutionary history of man's vertebrate ancestry, a progressive increase of the secondary fore-brain, with concomitant reduction of the rkinencephalon, or smell brain — the most archaic portion because of the important relations of the smell sense to the life history of the earliest \'ertebrates.^ In a mesal view of a hemisected brain (Fig. 673) may be seen the various parts of the brain stem and the cerebellum overlapped by the preponderatingly greater cerebrum. Among the many notable features exposed to view in this brain section are certain fibre masses, commissures, extending across the meson, and therefore divided by the knife in this preparation. Of the commissures pertaining to the cerebrum one is conspicuous for its size and firm consistency. This great fore-brain commissure is the corpus callosum already mentioned as being demon- strable in the depths of the intercerebral cleft on divaricating the lips of this fissure. The corpus callosum constitutes a massive system of association fibres for the bilateral coordination of corresponding cortical parts. It is thickened caudally, forming the splenium of the corpus callosum; frontad it bends on itself • For a more thorough discussion on the natural subdi-vision of the fore-brain, based upon comparative morphol- ogy, see the paper by G. Elliott Smith, Journal of Anatomy and Physiology, 1901. THE CEREBRAL HEMISPHERES 913 ventrocaudad to form the genu ("knee"), including; an interval, between the two limbs, which is flanked on both sides by a thin lamina (hemiseptum) and bounded ventrad by the fornix, constituting a closed cavitj', the pseudocele icamim seyti 'peUucidi). The recurved ventral part of the genu tapers into a thinner, beak- shaped part, the rostrum. The rostrum is joined to the lamina terminalis, frontad of the anterior commissure, by a thin lamina, the copula {lamina rostralis) . Fig. 674. — The cerebral hemispheres viewed from above. (Spalteholz.) An arched structure composed of longitudinal fibre bundles comes to view in front of and below the junction of the splenium with the body of the corpus callosum, proceeds frontoventrad with its convexity frontad, to sink from view in the substance of the hypothalamic gray at a point just caudad of the anterior commissure. This white arched bundle is the fornix. Between it and the corpus callosum, rostrum, and copula stretches a thin, translucent lamina of nerve tissue — the hemiseptum. The hemisepta of the two sides together have usually been termed the septum pellucidum, while the enclosed narrow cavity is called the pseudocele or fifth ventricle. The subjacent parts revealed in this section have already been described; the morphology and internal relations of the corpus callosum, fornix, and hemiseptum will be described at a later stage. 58 914 THE NERVE SYSTEM The cerebral hemispheres together, as viewed from above or dorsally, appear as two symmetrical masses in close apposition, conforming in outline to that of the cranial cavity, which they so nearly fill. The frontal extremities or poles are massive and rounded, preponderatingly so in comparison with the brains of any related primate species. The occipital poles are each more pointed but expand frontad into the widest part of the cerebrum — the parietal lobes. The cerebral hemispheres or, briefly, the hemicerebra are partially separated from each other by the intercerebral cleft or great longitudinal fissure (fissura longitudinalis cerebri), into which fits a fold of the dura — the falx cerebri. By means of a large com- missural band of white fibres — the corpus callosum — the cerebral halves are joined together in the depths of the intercerebral cleft. All adjacent parts of the brain are overlapped by the ponderous cerebrum so as to entirely conceal the thalamic portion and the mid-brain, while the occipital lobes overlap the cerebellum with Fig. 675. — Principal fissures and lobes of the cerebrum the intervening tentorium — another fold of the dura. Further description will be restricted to each cerebral hemisphere. Configuration of Each Cerebral Hemisphere. — ^Each cerebral hemisphere presents an outer convex surface {fades convexa cerebri), applied to the correspond- ing half of the cranial vault; a mesal flattened surface (fades medialis cerebri), which lies in a sagittal plane, applied to the corresponding surface of the opposite cerebral hemisphere, with the great longitudinal fissure intervening, and for the most part in contact with the falx cerebri; and a basal or ventral surface, of irregular form, resting frontad upon the floors of the anterior and middle cranial fossae, and caudad upon the tentorium cerebelli. Prominent in the lateral and ventral views is the blunt projection of the temporal pole, while at the ventrolateral border, nearer the occipital pole, is a slightly marked indentation usually called the preoccipital notch. The deep vallecular depression between the orbital surface and the temporal pole accommodates the lesser wing of the sphenoid. More or less distinct borders demarcate the surfaces. The arched dorsimesal THE CEREBRAL IIE3nSPHERES 915 border intervenes between the mesal and the convex surfaces; a straight rncsorhifal border intervenes between the orbital and mesal surfaces of the frontal lobe; a ventrolateral border separates the tentorial siu'face from the lateral, convex sur- face of the occipital and temporal lobes; v/hile an obtuse border — the mesoventral or internal oecipital border — separates the tentorial from the mesal siu'faces. Cerebral Fissures and Gyres. — -The surface of each cerebral hemisphere presents alternatino- depressions or fissures which demarcate gyral elevations — the convolu- tions or gyres} The fissures vary in depth from that of a mere shallow groove to as much as 30 mm., and may attain a length of 15 cm. They are more or less sinuous and ramified. They mark the surface with fairly approximate uniformity, that is, one rarely finds an unfissured surface more than 15 to 20 mm. (|^ inch to f inch) in width. Numerous functional and mechanical influences must be credited with bringing about the complex foldings of the cerebral surface, prin- cipally (a) resistance of the cranium to the expanding brain or "mechanical packing;" (b) difl:'erences of growth rate in different parts of the cortical surface; (c) differences of growth rate of different fibre bundles retarding cortical expansion along the fissure lines and elongating to help in the formation of the gyres. The obvious result, whatever the influences may be, is an expansion of the cerebral cortex to an enormous degree, so that, instead of having a surface area of only 60,000 sq. mm. (if unconvoluted), the average adult cerebrum has a cortical area of 200,000 sq. mm. or more. Furthermore, the vascular pia, closely investing the surface and dipping into every fissure, is expanded in a like manner, affording an ample and uniform supply of blood for the entire cerebral cortex. The cerebral vesicle of the fetal brain presents a smooth surface during the first half of intrauterine life," except for the depressed fossa at the site of the future island of Reil — destined to become buried in the depths of the sylvian cleft formed by the apposition of the more energetically growing contiguous parts of the cerebral mantle. Some of the cerebral fissures develop early as infoldings of the com- paratively thin wall of the vesicle, and hence produce corresponding projections into the cerebral cavity; these are termed the total or complete fissures. The remaining fissures are only linear depressions of the surface not involving the entire thickness of the wall — the partial or incomplete fissures. The complete fissures and their correlative projections into the cerebral cavity (lateral ventricle) are: Fissure. Internal Eminence. Hippocampal fissure. Hippocampus. Calcarine fissure. Calcar. Collateral fissure. Collateral eminence. Occipital fissure. Occipital eminence. Among the remaining cerebral fissures, of which over fifty have been recog- nized and named, some are constant in representation in all normal brains, while others are of variable occurrence in diii'erent individual specimens. The constant fissures are those which regularly exist as interlobar and intergyral boundary lines forming a common pattern for all normal brains, but these, like all cerebral fissures, are subject to many individual variations as to course, depth, length, I Consistent with the use of the English Johe and lohes (for lohus and lohi), the English gyre and gyres are preferable to gyrus and gyri. The term iissure is here uniformly employed for all anfractuosities of the sur- face, though sulcus (pi. sulci) is quite as generally used; sometimes both terms are indiscriminately mi.xed in other works on this subject. - The so-called transitory fissures of older descriptions may be neglected, since the researches of Retzius, Hochstetter, and Mall have shown these to be iii reality artifacts due to postmortem swelling. 916 THE NERVE SYSTEM mode of branching, and anastomosis with neighboring fissures or manner of interruption by gyral isthmuses. The range of individual variations is so great that no two brains can be said to be exactly ahke; in fact, one may find numberless stages of complexity in the cerebral surface configuration from the simply fissured brains of mentally inferior individuals and races to the complexly fissured and more highly organized brains of vigorous thinkers and talented geniuses among the highly intellectual races of man. INTERCEREBRAL F. FISSURE GYRE Fig. 676. — Cerebral fissures and gyres ■< Cerebral Lobes and Fissures. — The cerebral surface is divided into five prin- cipal areas, called lobes, demarcated by certain constant fissures which are more or less conspicuous, and were therefore selected by the older anatomists as arbi- trary boundary lines; these are termed the interlobar fissures. The lobes are: (1) the frontal; (2) the parietal; (3) the temporal; (4) the occipital; (5) the island of Rail or insula. The interlobar fissures are: (1) the sylvian; (2) the central; (3) the occipital; (4) the calcarine; (5) the circuminsular. A series of fissures demarcating die rhinencephalon from the pallium or cerebral mantle proper will be considered at a later stage. The Interlobar Fissures. The Sylvian Fissure and Its Rami [fissura cerebri later- alis [SylmiJ). — This fissure is a well-marked cleft on the base and side of the cerebral hemisphere. Traced laterad from the region of the anterior perforated substance, it begins as a deep depression between the orbital surface of the frontal lobe and the temporal pole, corresponding to the bony ridge formed by the lesser wing of the sphenoid and extending to the convex surface. This portion of the THE CEREBRAL HEMISPHERES 917 fissure is termed the basisylvian fissure or vallecula sylvii, as far as the sylvian point.' The sylvian point marks tlie fonjunction of the main portion of the sylvian fissure with its basisylvian part as well as one or two rami. These rami are (!) the presylvian ramus and (2) the subsylvian ramus. The presylvian ramus" usually proceeds dorsad, slightly inclined frontad, for a distance of 2 to .') cm. into the subfrontal gyre. The subsylvian ramus {anterior horizontal limh) extends frontad for a distance of 1.5 to 2 cm., parallel to the orbitofrontal (superciliary) margin. These two rami often spring as shorter branches from a common stem, and both may be replaced by a single unbranched limb. The sylvian fissure proper is the most conspicuous part. It extends from the sylvian point in a caudal direction, inclined slightly dorsad,^ on the lateral surface of the cerebrum for a distance averaging 6 cm. (2| inches). It separates the temporal lobe wholly from the frontal and partly from the parietal lobe. It usu- ally ends in an upturned manner, in the parietal lobe, the change of direction being oftener abrupt than gi-adual; this terminal piece receives the name of epi- sylvian ramus. Occasionally a short ramus is sent ventrad into the supertemporal gyre and is called the hyposylvian ramus. The sylvian fissure ranges in depth from 15 mm. or less at the presylvian point to 25 or 30 mm. (1 inch to li inches) at the postsylvian point, correlative with the contour of the island of Reil, which lies in its depths. If the lips of the sylvian fissure be divaricated, the island of Reil is revealed as a cortical district, of tetra- hedral form, which is normally completely concealed by overlapping portions of the cerebral hemisphere called the opercula. These are four in number: (1) the operculum proper, (2) the preoperculum, (3) the suboperculum, and (4) the post- operculum. The operculum (frontoparietal operculum) is composed of the adjacent portions of the ventral border of the frontal and parietal lobes, the syh'ian fissure inter- vening between it and the postoperculum, which is the overlapping part of the temporal lobe. The preoperculum is a small triangular portion embraced by the presylvian and subsyh'ian rami, and is also called the pars triangularis or Broca's cap. The suboperculum (orbital operculum) is small, demarcated by the sub- sylvian ramus, and, for the most part, on the orbital face of the frontal lobe, projecting slightly over the frontal part of the island of Reil, with its margin separated from the temporal pole by the basisylvian cleft. The overlapping opercula are demarcated from the island of Reil by the cir- cuminsular fissure {sulcus circularis Reili). Development of the Island of Reil and the Sylvian Cleft. — The insular cortical district is topographically correlative with the great gray ganglia of the cerebral hemisphere, particularly the lenticular nucleus, from whose ectal surface the insular cortex is but little removed. As will be learned at a later stage, few if any pro- jection fibres pass to and from the island of Reil; its function is almost wholly associative for adjacent parts of the cerebral mantle. The island of Reil there- fore becomes buried beneath the more energetically growing and bulging parts immediately around it. There is at first a slight fossa (observable in the tenth to twelfth week) which, as development proceeds, and as the overhanging opercula encroach upon the island of Reil, becomes more deeply situated as a cleft-like depression until at birth the fossa has become a fissure, with the island of Reil perhaps slightly exposed near its cephalic extremity, where the incomplete apposi- ' So called in cranial topography. , . „ ' Also called the anterior ascending limh. In BNA terms the name for this fissural brtvnch is Ramus anlenor ascendens iissvrae cerebri lateralis. 5 Its inclination to the horizontal plane is called the sylvian angle, approximately 15 degrees. 918 THE NERVE SYSTEM tion of the opercula leaves a triangular space. This space is usually obliterated in childhood, but is commonly met with in certain races (negro, Australian) and in brains showing developmental defects or arrest. The mechanics of the formation of the surface outline of the sylvian fissure by the apposition of the growing and plastic opercula may be understood by a reference to Fig. 682. POSTCENT INTERLOCKING Fig. 677. — Central fissure fully opened up, so as to exhibit the interlocking gyres. The central fissure {fissure of Rolando [sulcus ce7itralis]) is situated at about the middle of the convex surface, and, coursing obliquely laterofrontad, divides this surface into approximately equal parts, intervening between the frontal and parietal lobes. It may be traced from a point at or near the dorsimesal border, about' 1 cm. (f inch) caudad of the mid-point of the occipitofrontal arc. It then runs sinuously laterofrontad to within a short distance of the sylvian fissure, about 2 cm. (A inch) caudad of the sylvian point; its line of general direction makes an angle of about 70 degrees with the median line (Rolandic angle). If measured ■along its sinuosities, its length averages 10.5 cm. (4 inches). Its curved course may be analyzed into five alternate curves (sometimes more or less), of which three are convex frontad and two caudad. It is rarely very much branched and does not often anastomose with neighboring fissures. Its dorsal end bears a con- stant relation to the caudal limb of the paracentral, frontad of which it can be found as a hook-like curve (Figs. 676 and 679) . If the lips of the central fissure be divari- cated, interdigitating sub-gyres are commonly seen in its depths (Fig. 677). These interlocking gyres are often fused to a greater or less degree, and a total interruption of the fissui-e has, in rare instances, been observed. The central fissure develops at about the end of the fifth month of intrauterine life, not as a single integer, but as the result of the union of two segments — a short dorsal and a longer ventral segment. As development proceeds these segments eventually unite end to end, and at the site of this union a vadum (or shallow uprising of the floor of the fissure) or even a complete isthmus may be demonstrated in the adult brain. Only three cases of bilateral interruption are on record. The occipital fissure (fissura occipitalis) is a deep cleft across the dorsimesal border trans-secting the occipitofrontal arc at about 5 cm. (2 inches) from the occipital pole, and extending upon both the mesal and the convex surfaces. On the meson it attains a length of .3 to 3.5 cm. (li to If inches) (to its junction with the calcarine fissure) while its lateral extent is shorter (2 to 2.5 cm., f to 1 inch). It is quite deep throughout and usually shows a number of interdigitating sub- gyres. THE CEREBRAL HEMISPHERES 919 The calcarine fissure {fissura calcarina) is a slightly arched fissure wiiich is usually Joined with die occipital fissure at the apex of the cuneus and extends caudad to the occipital pole, ending in a bifurcation. The fissure is composed of two integers which may be partially or completely separated (by a vadum or an isthmus); the caudal segment may then be distinguished as the postcalcarine fissure. The occipital and calcarine fissures join to form a Y-shaped junction; the two limbs of the Y embrace the cuneus, while the stem is continued as the occipito- calcarine stem for a distance of about .3 cm. This fissural stem is allotted to the occipital fissure by some and to the calcarine fissure by other authors. As there is no greater frequency of confluence with one as against the other, so far as present statistics go, it is preferable to assign no special relationship for this stem to one or the other principal fissure. I. Frontal Lobe. FissuKES of the Frontal Lobe. — 1. The lateral surface is bounded by the dorsimesal arched border, by the fronto-orbital (or superciliary) border, by the sylvian fissure (in part), and by the central fissure. The principal fissures marking this surface demarcate four gyres: (1) the precentral, (2) super- frontal, (3) medifrontal, and (4) subfrontal gyres. The fissures are (1) the pre- central, (2) superfrontal, and (3) subfrontal fissures. In addition must be described certain fissures which are intragyral and of more or less constant occurrence. The Precentral Fissural Complex (sulcus praecentralis). — Two fissural integers which are sometimes joined extend more or less parallel with the central fissure. The mesally situated piece is usually of zygal (^yoke-shaped) shape or triradiate, and usually anastomoses with the superfrontal fissure. From its position it is termed the supercentral or superior precentral fissure (sulcus praecentralis superior). The laterally situated piece is of longer extent, sometimes straight or slightly sinuous, sometimes arched like an inverted L, or T-shaped. It usually anastomoses with the subfrontal fissure. The two precentral segments demarcate the precentral gyre from the remaining three gyres of the lateral surface of the frontal lobe. The superfrontal fissiu'e (sulcus frontalis superior) usually springs from the supercentral and pursues a sinuous course frontad, to become lost, as a rule, in the zigzag or transverse ramifications of the prefrontal region. It is usually cjuite ramified and often anastomoses with other fissures. It demarcates the superfrontal from the medifrontal gyre. The subfrontal fissure {sulcus frontalis inferior) is most often confiuent with the precentral, less often with the supercentral fissure. It proceeds frontad in an arched course, to end either in a bifurcation or by anastomosing with other fissures (radiate fissure,' orbitofrontal fissure, or medifrontal fissure). The subfrontal fissure demarcates the medifrontal from the subfrontal gyre. Both the superfrontal and medifrontal gyres are characterized by a more or less pronounced longitudinal subdivision by less constant fissural segments. They are: (1) the paramesal fissure occupying an intermediate position between the superfrontal fissure and the dorsimesal border, in the superfrontal gyre, more often composed of a series of short segments which become lost in the more complex configuration of the prefrontal region; (2) the medifrontal fissure situated in the prefrontal part of the medifrontal gyre, rarely extending throughout, and usually ending cephalad in a widely spread bifurcation which constitutes the orbitofrontal fissure when independent. The medifrontal fissure is usually very much ramified and frecjuently anastomoses with neighboring fissures. The fissure is a char- acteristic of human and anthropoid brains only. By the occurrence of either or both paramesal and medifrontal fissures, the ordinary three-tier type of frontal lobe is converted into a four-tier and five-tier type; the latter more often in the brains of the more highly intellectual — a feature 920 THE NERVE SYSTEM which is concomitant with the comparatively late phyletic and embryonic develop- ment of the two secondary fissures described. Other, less important, fissures are: (1) the inflected fissure (fissura inflexa), incising the dorsimesal border between the central fissure and the cephalic limb of the paracentral; (2) the radiate fissure, near the lateral orbitofrontal border; (3) the transprecentral, a short oblique piece ventrad of the central and usually dipping into the syhian cleft; and (4) the diagonal fissure between the presylvian ramus and the ventral end of the central, and often confluent with the precentral (Fig. 678). 2. The mesal surface of the frontal lobe is bounded by the dorsimesal border, the mesorbital border, and the callosal fissure An arcuate fissure or system of fissures intermediate between the dorsimesal margin and the supercallosal fissure divides this surface into the superfrontal gyre, mesal aspect, and the callosal gyre. The name "callosomarginal" was usually applied to this fissure, but an examination of many brains reveals a certain integrality of fissural parts, which are not always connected. One constant segment from its relations with the central fissure is called the paracentral fissure, composed of a main stem with a cephalic and a caudal limb, embracing the paracentral gyre. Frontad thereof extends the supercallosal fissure, often in two segments, running a concentric course between the arched dorsimesal border and the genu of the callosum. The supercallosal may be confluent with the paracentral. The supercallosal is. SUPERCENTRAL F. f, = FISSURE G. = GYRE R. = RAMUS Fig. 678.— Fissures and gyres of the lateral surface of the left hemicerebrum. as a rule, quite ramified, its branches transcribing the superfrontal gyre. In the prefrontal region and ventrad of the genu of the corpus callosum lie one or two fissures, more or less parallel to the mesorbital border, and called, respect- ively, the rostral and subrostral fissures. 3! The orhiial surface of the frontal lobe is constantly marked by a straight fissure, the olfactory fissure {sulcus olfactoriiis) , which runs parallel to the mesorbital border and is occupied h\ the olfactory bulb and tract. It is about 5 cm. in length and demarcates the mesorbital gyre from the remaining orbital gyres. This THE CEREBRAL HEMISPHERES 921 orbital surface is marlved by a fissural system (^sulci orhitales) that is usually of zygal type, H-shaped or K-shaped, quadriradiate, or, rarely, triradiate. Wlien tlie transverse element is sufficiently pronounced it merits the name of transorbital fissure, demarcating the preorbital from the postorbital gyral field. Gyres of the Frontal Lobe (lobus frontalis). 1. Lateral Surface. — The pre- central gyre {gyrus centralis anterior), one of the chief motor areas of the cerebi-al cortex, is a moderately sinuous gyre extending from the dorsimesal border to the sylvian fissure and demarcated by the central and the precentral fissures (supercentral + precentral). G, = GYRE F.= FISSURE E. A. S. Fig. 679. — Fissures and gyres of the mesal surface of the left hemicerebrum. The superfrontal gyre is limited laterally by the superfrontal fissure, while it is continuous over the dorsimesal border with its mesal surface.' It merges insensibly with the medifrontal gyre in the prefrontal region, while it may be partially subdivided by the paramesal fissure. The medifrontal gyre {gyrus frontalis medius) is broader than the preceding, demarcated by the superfrontal and subfrontal fissures, and often marked by the medifrontal fissure in its prefrontal portion. The subfrontal gyre {gyrus frontalis inferior) is limited by the subfrontal fissure and the basisylvian + sylvian proper. It is traversed by the presylvian and sub- sylvian rami, embracing the preoperculum or pars triangularis. The gyre is of historic importance since Broca, in 1861, declared it to be the seat of speech con- trol. (See Cerebral Localization.) 2. Mesal Surface. — On the mesal surface of the frontal lobe and embracing the dorsal end of the central fissure lies an oval lobule or gyre called the paracentral gyre (lobulus paracentralis), limited by the paracentral fissure with its caudal and cephalic limbs. Frontad tliereof extends the large arched mesal surface of the superfrontal gyre {gyrus frontalis superior), limited by the supercallosal fissure. Between the latter fissure and the callosal fissure, concentrically situated with respect to the superfrontal, lies the callosal gyre {the "gyrus fornicatus" of other authors). ' There being no fissure at this border, it is improper to give the mesal surface of this gyre a different name e., "marginal gyrus" of the authors). 922 THE NERVE SYSTEM Frontad these two gjTes arch around the genu of the corpus callosum, to become merged through the disappearance of the intervening supercallosal fissure, and the rostral fissures alone mark this surface. INTERCEREBRAL F. SSURE GYRE Fig. 680. — Fissures and gyres of the basal surface of the cerebrum. 3. Orbital Surface. — ^The olfactory fissure and the mesorbital border boiuid the mesorbital gyre (gyrus rectus). The remaining orbital surface is not regularly divisible on account of the great variability of the orbital fissures; when the trans- orbital fissure is pronounced, a pre- and postorbital gyre may be distinguished. The postorbital limbus is a formation occasionally met with on the orbital sur- face. It consists of a curved, welt-shaped eminence demarcated by an incisure created by the lesser wing of the sphenoid, and due, apparently, to the intrusion of the postorbital portion into the middle fossa of the skull. II. Parietal Lobe (lobus ■parietalis). Fissures of the Parietal Lobe. — 1. The lateral surface is bounded by the dorsimesal border above, by the central fissure in front, and by a part of the sylvian fissure below; it is only partially de- marcated from the occipital lobe by the occipital fissure, and merges gradually into the temporal lobe. The principal fissures marking its surface consist of a group of integral segments showing various degrees of confluence . in different individuals and formerly known in the aggregate as the intraparietal sulcus of Turner (sulcus interparietalis. Two of the fissural segments present mucli the same parallelism to the central fis- sure which was noted for the precentral group, and hence these are termed the postcentral fissural complex. The postcentral fissural complex comprises a longer mesal and a shorter lateral THE CEREBRAL HEMISPHERES 923 (and ventral) segment, which are confluent in about 75 per cent, of brains and then very much resemble in length, continuity, and course the central fissure. This appearance has given rise to reports of alleged duplication of the central; an analysis of the relations of the dorsal ends of the fissures in question with the caudal limb of the paracentral removes all doubt. The postcentral fissure (proper) is the longer mesal (and dorsal) segment. Its dorsal end is frequently bifurcated and then usually embraces the dorsal exten- sion of the caudal limb of the paracentral. The subcentral fissure constitutes the shorter lateroventral segment. The parietal fissure is usually a slightly arched fissure inclining mesocaudad, sometimes independent but more often confluent, with one or both of the post- central segments just described. It demarcates the parietal gyre from the sub- parietal district. The paroccipital fissure, in whole or in part, probably represents a part of the simian exoccipital or " Att'enspalte," isolated by the upgrowth of gyral protons which are totally submerged in the ape brain, but rose to the surface concomitant with the rise in functional dignity of cortical areas so important in the human brain. The fissure is almost invariably of zygal shape, its stem directed sagittally, its ends bifurcated. Its confluence with the parietal fissure seems to be subject to some morphologic law; continuity is the rule on the left side (77 per cent.), and occurs less often on the right. The combination of continuity on the right and separation on the left is a rare one (6 per cent.). Less constant fissures are the transparietal, in the parietal lobe, and the inter- medial (Fig. 678). In the subparietal district terminate the upturned ends of the sylvian (i. e., episylvian ramus) of the supertemporal and the meditemporal fissures. 2. The mesal surface of the parietal lobe is equivalent to the quadrangular precuneus, limited by the paracentral and occipital fissures, while ventrad it is imperfectly separated from the callosal gyre by the precuneal fissure (postlimbic sulcus), usually of zygal or triradiate form and occasionally confluent with the paracentral. Gyres of the Parietal Lobe. 1. Lateral Surface. — The postcentral gyre {gyrus centralis posterior) is one of the chief somesthetic areas of the cortex. It is a long, more or less sinuous convolution extending obliquely from the dorsimesal- border to the sylvian fissure and demarcated by the central and the postcentral + subcentral fissures. The parietal gyre {lobulus parietalis superior) lies between the- dorsimesal border and the parietal fissure, bounded cephalad by the postcentral, caudad partly by the occipital fissure, the transition to the occipital lobe being maintained by the arched paroccipital gyre. The subparietal district or lobule (lobulus parietalis inferior) is divided into three convolutions which arch around the upturned ends of the sylvian, super- temporal, and meditemporal, and merge insensibly with the adjacent temporo- occipital gyres. The marginal gyre {gyrus supramarginalis) arches over the ex- tremity of the episylvian ramus and is connected frontad with the postcentral gyre, ventrad with the supertemporal gyre. The angular gyre {gyrus a)igularis) arches over the upturned extremity of the supertemporal fissure, and its limbs fuse with the supertemporal and meditemporal gyres. The postparietal gyre is not always clearly defined; it arches around the upturned end of the meditem- poral or its representative segment; mesally it is bounded by the paroccipital fissure. Variable intermedial fissures sometimes help to define the angular gyre from its two neighbors. 2. The mesal surface of the parietal lobe has already been described as equiva- 924 THE NERVE SYSTEM lent to the precuneus, from its position in " front" of the cuneus or quadrate lobo from its general shape. It is sometimes marked by a mesal extension of the transparietal fissure or by intraprecuneal fissures. III. Occipital Lobe (lohus ocripilolis). Fissures of the Occipital Lobe. — 1. The lateral surface of the occipital lobe is imperfectly demarcated from the adjacent parietal and temporal lobes in most brains. The sharply defined exoccipital fissure or " AiTenspalte" of other primates has, in the ancestry of man, been reduced to a series of fissural segments by the upgrowth of submerged cor- tical parts. The paroccipital fissure, we have already learned, probably repre- sents one of the gaps in the series; another may be the sulcus lunatus (Elliott Smith), usually termed the lateral occipital by the authors; lastly, a fissure some- times called the inferior occipital (suboccipital), and usually embraced, on the occipital pole, by the bifurcate limbs of the postcalcarine, may complete the series. Further researches are necessary to elucidate the morphology of this region. 2. The mesal surface is equivalent to the wedge-shaped region embraced by the occipital and calcarine fissures, and called the cuneus. A fairly constant cuneal fissure traverses its surface parallel to the calcarine. If it is ever determined that the morphological boundary of the occipital lobe is as outlined above, the lobe is practically excluded from the basal surface of the hemicerebrum. IV. Temporal Lobe (lobus temporalis). Fissures of the Temporal Lobe. — 1. The lateral surface of the temporal lobe is bounded by the basisylvian and sylvian fissures and by the ventrolateral border; caudally it merges into the adjacent parietal and occipital lobes. The supertemporal fissure {sulcus temporalis superior) is a deep, long (10 to 12 cm.), and usually continuous fissure which begins near the temporal pole, proceeds ventrad of but parallel with the sylvian, to become upturned in the parietal lobe and embraced by the arched angular gyre. The meditemporal fissure (sulcus temporalis medius) is rarely continuous; more often it is represented by a series of segments, two, three, or four in number, the caudal segment running more vertically into the parietal lobe to be embraced by the postparietal gyre. The meditemporal fissural segments run nearly parallel with the supertemporal and demarcate the meditemporal from the subtemporal gyre. 2. Tentorial or Ventral Surface. — Close to the ventrolateral margm and more or less parallel with it runs the subtemporal fissure (sulcus temporalis inferior), extending from near the temporal to near the occipital pole. It is rarely continu- ous, being usually broken up into two or more segments. It demarcates the sub- temporal from the subcollateral gyre. The collateral fissure (fissura collateralis) is a well-marked, long (8 to 12 cm.), and deep fissure extending from near the occipital to near the temporal pole. Caudally it demarcates the subcalcarine gyre from the subcollateral; frontad it intervenes between the latter gyre and the hippocampal gyre. Its middle part is correlative with the collateral eminence. On the ventromesal aspect of the temporal lobe and near its pole, cephalad of the uncus, is a moderately marked fissure or groove, called, because of its topographic relation to the amygdaline nucleus — a gray, ganglionic mass — the amygdaline fissure (fissura ectorhinalis s. postrhinalis), or incisura temporalis. 3. The dorsal or opercular surface of the temporal lobe enters into the formation ' of the sylvian cleft. It is but slightly marked by a few oblique or transverse furrows (transtemporal fissures) demarcating slightly elevated transtemporal gyres. Gyres of the Temporal Lobe. — The five principal fissures named subdivide the lobe into five gyres. On the lateral surface lie the supertemporal, meditemporal, THE CEREBRAL HEiMISPHERES 925 and subtemporal gyres (c/f/. feiiif oralis superior, mcdius cf inferior); on the ten- torial surface are the subcalcarine (gyrus lingualis), subcollateral (gyrus fusiformis; g. occipitoteruporalis) and part of the subtemporal. The hippocampal gyre (gyrus hippocampi), formerly inchided in the " limbic lobe," but morphologically belonging to the neopallium, occupies the dorsimesal part of the ventral surface of the temporal lobe. The longer or shorter extension of the occipitocalcarine stem partially (forming the isthmus gyri hippocampi) interrupts its continuity with the callosal gyre. It is demarcated by the collateral fissure (in part) and the hippocampal fissure, broadens out toward the temporal pole, and appears to become bent upon itself dorsally to form the uncinate gyre (uncus). As will be learned in the sequel, the hippocampal gyre is demarcated from the uncus proper by the intervention of the frenulum Giacomini — an exten- sion of the narrow, gray, dentate gyre. Fig. 681. — Brain of a six-months' hu natural size, right side. The insula (Kolliker.) . Fig. 682. — Cerebrum of an eight-months' human embryo, leftside. The insula is nearly covered in. (Testut.j Near the temporal pole it is demarcated from the subcollateral gyre by the fissura rhinica,^ or postrhinal fissure; this fissure is not infrequently confluent with the collateral. The surface of the hippocampal g,yre, particularly in the zone along the liippo- campal fissure, is of a more whitish color than is characteristic of other cerebral gyres; this is due to a white reticular stratum of fibres, the substantia reticularis alba. The con-\'ex, broader part of the gyre is marked by numerous small, wart-like eminences, resembling the skin of an amphibian, and called by Retzius the verrucae gyri hippocampi. Just ventrad of the uncinate portion, or the ter- minus of the hippocampal fissure, lies a groove marking the impression of the free edge of the tentorium cerebelli. The Island of Reil (insula; central lobe) (Figs. 682, 683).— The island of Reil lies deeply in the sylvian cleft and can only be seen when the lips of that cleft are widely separated, since it is overlapped by the opercula already described. With the opercula removed, the island of Reil presents a tetrahedral shape with its apex or pole directed fronto ventrad. Its borders are sharply outlined by the cir- cuminsular fissure except in the depths of the basisylvian cleft, where the insular cortex is continuous with the gray substance of the anterior perforated substance — the threshold or limen insulae (belonging to the rhinencephalon). An oblique transinsular or central insular fissure divides this district into a larger preinsula and a smaller postinsula. The postinsula is usually a single long gyre (gyrus longxis iiisulae), while the preinsula is subdivided by shallow fissures into three. 1 Called by Wilder, calls it tin part) the 'ith the amygdaline nucleus, the amygdaline fissure. Schwalbe 926 THE NER VE SYSTEM four, or five shorter preinsular gyres {gyri breves insulae), built upon a radiate plan, converging in the region of the insular pole. As already hinted, the island of Reil represents an area of the brain mantle whose growth did not keep pace with that of the surrounding parts; hence its submergence by them. The close appo- sition of the insular region to the subjacent basal ganglia, and the failure of devel- opment of great masses of projection fibres so prominent elsewhere, were doubt- lessly factors therein. The insular cortex is uninterruptedly continuous with the rest of the cortex, but it has become specialized into the purest association centre in the cerebrum, and we shall learn of its intimate relations to the faculty of speech on page 961. L supposedly transparent cerebral hemisphere, w by the opercLila. The Rhinencephalon, or Olfactory Lobe {lobus olfactorius) (Figs. 684, 685). — The grouping of the parts constituting the central olfactory structures under the term "rhinencephalon" as distinguished from the rest of the fore-brain (pallium) was first clearly made by Turner and proved by His to be embryologically well founded and by Edinger to agree with phylogenetic development. More light has been thrown upon the subject recently by Retzius and Elliott Smith. The sense of smell, while highly useful in the quest for food in earlier and lower forms of vertebrates, is relatively litde used in the mental life of man. The enormous preponderance of the cerebral mantle and the concomitant atrophy of the rhinen- cephalon in the human brain afford one of the most striking contrasts in brain morphology. This relatively feeble development in bulk of the olfactory apparatus in the human brain by no means renders its description simple. In fact, not until its development in lower macrosmatic animals was studied could anatomists form even an approximately clear conception of the seemingly disjointed remnants in the human brain of an olfactory apparatus so relatively huge in lower animals. The great expansion of the cerebral hemispheres and of the great commissure which connects them (the corpus callosum) has been an important factor in widely displacing primitively connected parts. The developmental history must be sought for in the writings of Edinger, Retzius, and Elliott Smith. THE CEREBRAL HEMISPHERES 927 The Rhinencephalon comprises: 1. Peripheral parts. 2. Central or Cortical parts. A comprehensive term for the peripheral part is lobus olfactorius, divisible into pre- and postolfactory parts. Preolfactory lobe 1. Bulbus olfactorius. 2. Tractus olfactorius. 3. Tuberculum olfactorium and trigonum. 4. Area parolfactoria (Br oca). 5. Stria olfactoria medialis. 6. Stria olfactoria intermedialis. . 7. Stria olfactoria lateralis. p If f 1 K / ^" ^'^terior perforated substance. i'ostoltactory lobe | g g^^^^ suhcallosm and Broca's diagonal hand. Fig. 684. — Schematic representation of the rhinencephalon, basal aspect. The Preolfactory Division. — The olfactory bulb and tract form a long and slender band with a bulbous extremity situated on the basal aspect of the frontal lobe and constituting a rudimentary remnant of a relatively large diverticulum, developed from the sensor ectoderm close to the border of the neural plate before it becomes converted into the neural tube and situated on either side of the neu- ropore at the extreme frontal end. Although hollow at first, the cavity (rhinocele) soon becomes obliterated. The olfactory bulb (bulbus olfactorius) is an oval mass of reddish-gray color, which rests on the cribriform plate of the ethmoid and is received in the olfactory fissure on the orbital surface of the frontal lobe. It receives the numerous olfactory nerves (fila olfactoria) from the nasal mucous membrane. The olfactory tract (trachis olfactorius) is a band of white substance, of prismatic outline on 928 THE NERVE SYSTEM section, its apical ridge fitting into the olfactory fissure. Toward its root region it is somewhat narrowed. The medial and lateral olfactory gyres are also termed the medial and lateral roots of the tract, and diverge in the region of the trigonum. The olfactory tubercle is best seen if the bulb and tract be lifted away from the olfactory fissure ; the tubercle appears as a small pyramidal elevation, its apex buried in the olfac- tory fissure, its irregularly triangular base forming the trigonum olfactorium, a small gray area frontad of the anterior perforated substance. This area is marked by ridge-like elevations which appear like radiating roots of the tract, and named, according to their position, the medial, intermediate, and lateral roots, striae or gyres. The lateral olfactory stria is continuous with the limen insulae in the depths of the basisyh-ian cleft, and thence passes to the uncus to end in the gyrus ambiens and gyrus semilunaris. The sharp turn made at the limen insulae is called the angulus lateralis. The medial olfactory stria, a narrow gyral band, proceeds mesad and merges with the adjacent cerebral surface; its extension on the mesal surface is known as the parolfactory area (Broca) limited frontad by the anterior parolfactory sulcus {sulcus parolfadoriiis anterior) and separated from the subcallosal gyre by the posterior parolfactory sulcus (stdcns parolfactorius 'posterior). The intermediate stria is not always very distinct; when present it may be traced from the proximal end of the olfactory tract for a short distance over the gray field of the trigonum, to plunge into the gray of the anterior perforated sub- stance. PosTOLFACTORY DIVISION. — The anterior perforated substance or space oc- cupies an irregular quadrate field between the olfactory trigone and the optic chiasm and tract. A more or less marked groove {sulcus parolfactorius posterior), which is identical with the fissitra prima (His) of the embryo, separates the trigo- num from the anterior perforated substance. Its frontal part, much perforated, is of a darker color than the hind portion; the latter is distinguished by the name of Broca's diagonal band. This courses obliquely laterad along the optic tract toward the uncus; mesally the bands of the two sides converge, frontad of the lamina terminalis, and proceed toward the rostrum of the corpus callosum as narrow fields which taper to curve around the genu and continue in the indusium of the corpus callosum as the striae longitudinales. The narrow field seen on the mesal aspect frontad of the lamina terminalis and anterior commissure is known as the gyrus subcallosus {formerly peduncle of the corpus callosum). The con- tinuity of the various parts may be understood by reference to Figs. 684 and 685. The cortical and central part of the rhinencephalon comprise: 1. The hippocampus.' 2. The uncus. 3. Gyrus dentatus. 4. Fasciola cinerea. 5. Indusium, medial and lateral longitudinal strise upon the corpus callosum. 6. Gyri Andreae Retzii. [ 7. Gyri subcallosi. 18. Fornix and fimbria. 9. Corpus albicans and albicantiothalamic tract. 10. Part of anterior commissure (precommJ.ssure). 11. Part of septum pellucidum. > Not to be confounded with the hippocampal gyre of the pallium* Cortical THE CEREBRAL HEMISPHERES 929 Central or Cortical Parts of the Rhinencephalon. — Following the sug- gestion made by Broca in 187S, it has been customary to designate these various parts by the comprehensive term limbic lobe. Broca's notion of the limbic lobe in man was founded upon attempts to homologize the human cerebral con- figurations with those found in lower animals. More recent researches have proved that Broca's "limbic lobe" included parts belonging to the neopalliimi and not to the rhinencephalon. The term is therefore inappropriate in a morphologic sense. The hippocampus is the submerged, peculiarly folded margin of the cerebral hemisphere produced by the hippocampal fissure. Its architecture can best be understood by referring to a frontal section (Fig. 686). It is seen that the whole cerebral marginal wall is pushed into the ventricular cavity (middle cornu) as a fold caused by the intrusion of the hippocampal fissure. A secondary fold not produced by a fissure, however — constitutes the gyrus dentatus. Super- imposed lies a prominent white band — the fimbria — composed of axones from INOUSIUM AND STRI/E FUSION OF FASCIOLA CINEREA AND D E N- E GVHE L FISSURE Fig. 685. — Schematic representation of the rhinencephalon. mesal aspect. the hippocampal cells, assisting in the formation of a white lamina, subjacent to the ependyma of the ventricle, and called the alveus. The whole formation is characteristic of this region, and from its fancied resemblance to a ram's horn — a symbol used on the temple of Jupiter Ammon — the name of cornu ammonis' has been given; the name hippocampus was applied because of a fancied resem- blance to the marine animal of the same name. The ventricular relations and internal structm-e of the hippocampus will be given farther on (p. 942). The uncus, with the atrophied lateral olfactory stria, is all that remains in the human brain of the relatively large pyriform lobe of lower forms. It appears to be a hook-like retroflexion of the hippocampal gyre which is partially encircled by the gyrus dentatus. Morphologically speaking, it is only the apical portion, or that which lies caudad of the dentate gyre which is the true uncus (the ciyrus intralimbicus of Retzius); the remainder is neopallial and a part of the hippo- campal gyre. The uncinate or intralimbic gyre may be traced caudad in the ^ FreQuently, but incorrectly, gi\'€ 930 THE NER VE SYSTEM depths of the fimbriodentate fissure, along the dentate gyre, the dentatofasciolar groove intervening, to be continued as the fasciola cinerea (gyrus fasciolaris of lletzius) over the splenium of the corpus callosum. If the hippocampal gyre be depressed for the purpose of examining the depths of the hippocampal fissure, there is revealed a narrow, gray band whose surface is scored by numerous incisures and whose edge is notched at frequent intervals. This corrugated band is the dentate gyre or fascia dentata. Partly overlapping it, but farther laterad, lies a white band — the fimbria — extending caudad from the uncus to become continued as the fornix. Fig. 686. — Trans-section of the hippocampal gyrus, (Edinger.) The dentate gyre is demarcated from the hippocampal gyre by the hippocampal fissure, from the fimbria by the fimbriodentate fissure, in whose depths lies the narrow continuation of the uncus or gyrus intralimbicus — the fasciola cinerea. Extending caudad, and for the most part parallel with the fimbria, it loses its corrugated appearance on approaching the splenium, then fuses with the fasciola cinerea, parting company with the fimbria (which now becomes fornix), to be continued upon the corpus callosum as a thin, broad plate of gray substance — the indusium or gyrus epicallosus. At the uncus the dentate gyre makes an abrupt turn to appear upon the mesal surface, out of the depths of the hippocampal fissure, and encircles the neck of the uncus, forming the frenulum Giacomini. Beyond this point it can be traced, in rare instances, to the gyrus semilunaris. The gyri Andreae Retzii are rudimentary gyral formations consisting of small, rounded, oval or spirally corrugated eminences situated ventrad of the splenium in the angular interval between the dentate and the hippocampal gyres. Struc- turally they have been shown to belong to the hippocampal formation. THE CEREBRAL HEMISPHERES 931 The indusium (gyrus epicallosus s. supracallosus), considered to be a vestige of the hippocampus, is a thin strip of gray substance superimposed upon the corpus caUosum and raised into two paired ridges by longitudinal fibre bundles which constitute the mesal and lateral longitudinal striae.' The indusium and its striae are continued cephalad into the gyrus subcallosus; perhaps, also, into the parolfactory area (Fig. 685). The central connections of the rhinencephalon will be considered in the de- scription of the internal configuration of the hemisphere. (See Fornix, Anterior Commissure, etc.) Internal Configuration. — Each cerebral hemisphere contains a cavity, the lateral ventricle (paracele), an extension of the primitive neural cavity carried outward, its contours modified by the developmental changes in the growth history of the secondary fore-brain vesicle. This central cavity is surrounded by the thick, convoluted walls of nerve tissue which make up the bulky cerebral hemispheres. The cerebral tissue, as elsewhere in the central axis, is made up of gray and white Z'' Fig. 687. — Mesal , partly dissented cerebral hemisphere, to show the relation cinerPa. dentate gyre, and uncus. of fimbria, faaciola substances. Two well-marked types of gray substance are recognizable: (a) the cortical, so named because its situation upon an interior white centre invites comparison with the rind (cortex) of a fruit; (b) the massive ganglionic or nugget- like masses not dissimilar from the thalamus already described, comprising, in this division of the brain, the caudate, lenticular, and amygdaline nuclei. The •white substance fills out the entire space intervening between the cortex, the cavity of the lateral ventricle, and the great basal ganglia, and is composed of myelinic axones which connect the elements of the cortex with other parts of the nerve system, or with other regions of the cortex of the same or the opposite cerebral hemisphere. If a brain, resting upon its basal surface, be sliced by successive horizontal sections from above, the peripheral gray and internal white are brought into view. ' The mesal stri:p are also called Striae Lancisii; the lateral stria;, Teniae lectae. 932 THE NERVE SYSTEM The more superficial sections reveal relatively more gray than white substance; deeper sections show a reverse condition, and a section immediately dorsad of the corpus callosum reveals, in each cerebral hemisphere, a very extensive semioval field of white substance, the centrum semiovale, surrounded on all sides by a narrow, convoluted margin of gray substance, the cortex. A close examination of the cut surface, in a fresh and normal brain, shows it to be studded with numerous minute red dots (puncta vasculosa) produced by the escape of blood from divided blood- vessels. The Cortex. — The cortex, as revealed in such a section, is not of uniform thickness throughout; difi^erent regions show different cortical thicknesses. In general, the cortex is somewhat thicker at the summit of a gyre than in the depths of an adjoining fissure, and it is thicker upon the convex than upon the mesal or basal surfaces. The maximum thickness is observed in the cortex of the central gyres t IG bSb — Corpus callosum ( and the insula; the minimum at the frontal and occipital poles, notably the latter. Not only is the cortex not of uniform thickness, but it is not of homogeneous structure as seen with the naked eye. An alternation of gray and white stripes is discernible, particularly in the occipital cortex, where a white band runs parallel with the cortical surface between two gray strata; this while stripe, first described by Gennari and usually bearing his name, is also called the band of Vicq d'Az3rr. The preponderance of white substance over gray substance in the cerebrum is a human charac- teristic concomitant with the relative increase of the association cortex, in turn demanding a more intricate interconnection of the ma-ny nerve cells by a multitude of association neurones. These THE CEREBRAL HEMISPHERES 933 coordinating fibre systems are as truly representative of the complexity of man's thought appa- ratus as the number of interconnecting wires within a telephone " central" station is indicative of the amplitude of connections possible in that system. The proportions of gray and -n'hite substances are expressed in the following tabulation: Gray substance | Cortex 33 per cent. •' ( Ganglia b per cent. White substance 61 per cent. The removal, by successive slices, of the dorsal parts of the cerebrum soon brings into view the large expanse of transverse myelinic fibres, the corpus callosum, which connects the two hemispheres. The Corpus Callosum (Trabs cerebri ; commissura maxima) . — ^The corpus callosum is a thick stratum of transversely directed nerve fibres, by which almost e\'ery part of one cerebral hemisphere is connected with the corresponding part of the other cerebral hemisphere (Figs. 689 and 690). The axones composing it arise from the Fig. 689. — Diagram of coronal section of cerebrum to show course of fibres of corpus callosum. (Testut.) i. 690.— Diagr, . to show (Testut.) small pyramidal or the polymorphous cells of the cerebral cortex, or they may be collaterals from the long association or even the projection neurones. They pass in both directions and within the centrum semiovale radiate in various direc- tions (radiatio callosi) between the fibres of the corona radiata to terminate in the layer of small pyramidal cells of the cortex, thus forming a great transverse commissural system, and at the same time roofing in the greater part of the lateral ventricle in each half. A portion of the dorsal surface is free for a width of about 1 cm. on either side of the mesal plane, partly covered by the indusium and overlapped by the callosal gyres of the two sides, a fold of pia intervening. The mass of radiating fibres may, for convenience of description, be sub- divided into a pars frontalis, a pars parietalis, and a pars occipitotemporalis. The frontal and occipitotemporal portions are compressed or thickened mesally because the fibres cannot pass directly across, but curve, respectivelv, frontad and caudad in each hemicerebrum to form two tong-like bundles, the forceps anterior s. minor (pref creeps) , and forceps posterior s. major (postforceps). The pars parietalis constitutes the greater part of the "body" of the corpus callosum. The fibres traversing the body {frimcus corporis callosi) and the adjacent part of the splenium curve around the posterior cornu and trigonum \'entriculi of the lateral ventricle, to form a thin but definite white stratum, the tapetum, in the roof and ectal wall of these parts of the cavity. The transverse direction of the fibres is rendered apparent in a dorsal view of the exposed corpus callosum in the form of the striae transversae. These are 934 THE NER VE SYSTEM but little obscured by a thin, gray lamina — the indusiiun — which is thickened longitudinally by two symmetrically situated fibre strands, the mesal (striae Lancisii) and lateral longitudinal striae (teniae tectae), already mentioned as rudi- ments of the rhinencephalon. The best conception of the size and form of the corpus callosum is obtained from a view of a mesal section. It is then seen to be a long, thick, somewhat flattened arch which bends sharply upon itself frontad to form the genu (^c/enu corporis callosi), while its caudal end is rounded and somewhat folded closely upon itself to form the splenium. The corpus callosum ranges in length from 7 to 10 cm., its cross-section area from 5 to 10 sq. cm., being longer and larger in heavier brains and in those of the highly intellectual as compared with smaller and less highly efficient brains. It extends to within 4 cm. of the frontal pole and to within 6 cm. of the occipital pole. The thickness of the "body" averages 5 mm.; of the splenium, 9 mm. or more, while the maximum thickness of the genu is about 13 to 15 mm. The reflected portion or rostrum (rostrum corporis callosi) gradually tapers into a very thin lamina, the copula {lamina rostralis), which in turn joins the lamina terminalis frontad of the anterior commissure. The splenium (splenium corporis callosi) projects as a rounded welt over the mid-brain, but is separated from it by a pial fold — the velum interpositum. Farther frontad the fornix becomes fused to the ventral surface of the corpus callosum for a short distance, to again leave it in its more arched course toward the corpus albicans. Two thin laminse, one on either side of the median plane, but closely applied to each other and frequently partially fused, occupy the interval between corpus callosum and the fornix of each side. The laminse together are termed the septum lucidum of the authors, each one being called a hemiseptum; the enclosed cavity is called the fifth ventricle or pseudocele, though not derived from the original neural cavity. .COMMISSURE J ^ — / / 7^ E. A. S. REGION OF ANT. COM. RMINALIS Fig. 69J. — Schemata showing the development of the corpus callosum and its relations to hippocampus, fornix, and anterior commissure. Lamina terminalis (terma) in heavy black, corpus callosum dotted. * Rep- resents the attenuated indusium and longitudinal strise already described. Development. — The corpus callosum develops as a mass of commissural fibres which grow from side to side in the lamina terminaHs (terma). The lamina terminalis serves as a matrix for several commissural systems — viz., the hippocampal commissure and the anterior commissure, in addition to the corpus callosum. The last develops rapidly in higher mammalian brains, thrusts aside the hippocampal margin of the pallium so that it atrophies in large part, and stretches out within its sharply bent arch a portion of the precommissural wall of each cerebral vesicle. It thus withdraws a part of the intercerebral cleft, eventually enclosing it entirely as the fifth ventricle. The stages of development are shown schematically in Fig. 691 and its development in the human embryo is shown in Fig. 692. The corpus callosum is most fully developed in man and does not appear below the marsupials. Its growth kept pace with the preponderatingly greater development of the neopallium in higher forms, and it may be looked upon as an index of the elaboration of at least one division of the association systems^ those concerned with bilateral coordinations. THE CEREBRAL HEMLHPIIEREH 935 Figs. 692-695. — Brains of human embryos; mesa! aspects of median sagittal section show the development of the corpus callosum. Fig. 692. Fourth month. Fig. .693. Fifth month. Fig. 694. Sixth month. Fig. 695. Seventh month. 936 THE NERVE SYSTEM The Lateral Ventricles. — An incision through the corpus callosum, on either side of the median plane, will expose two large, irregular, symmetrically situated cavities, the lateral ventricles, extending through a great part of each cerebral hemisphere. Each lateral ventricle communicates with the third ventricle through a small opening, the foramen of Monro, situated between the forni- column (anterior pillar of fornix) and frontal end of thalamus. The cavity is lined throughout by ependyma; it is narrow in some and wide in other localities, and contains cerebrospinal fluid. The shape of the lateral ventricle is best understood by reference to a cast of its interior, and its location within the cerebrum may be appreciated by a study of Figs. 696 and 697. Conventionally the lateral ventricle or paracele is described as being composed of a body or cella and three horn-like extensions or comua. Viewed laterally its contour corresponds to that of the cerebral hemisphere and its cornua project toward the three poles — viz., frontal, occipital, and temporal. . — Showing tbe ventricular system of the brain as a sohd cast as if seen through a transparent brain. The body {jpars centralis ventriculi lateralis) or cella of the lateral ventricle is defined as that portion which extends from the foramen of Monro to the region of the splenium. Its frontal prolongation is called the anterior horn or precomu. Near the splenium the cavity may be traced ventrolaterad into a capacious part (trigonum ventriculi), from which the posterior horn (postcornu) and middle horn (medicornu) are prolonged, respectively, toward the occipital and temporal poles. The anterior horn or precomu {cornu anterius) passes frontad, inclined slightly ventrolaterad. Its floor is the head (caput) of the caudate nucleus, forming a rounded incline sloping mesad toward a trench-like recess floored by the rostrum of the corpus callosum. Its roof is the anterior forceps of the corpus callosum. Its mesal wall is formed by a portion of the hemiseptum of the septum lucidum^ Laterally it is limited by the apposition, at an acute angle, of the corpus callosum and the caudate nucleus. Its apex reaches the ventricular surface of the genu of THE CEREBRAL HEMISPHERES 937 the corpus callosum. The general outhne of this part of the ventricle, in a .frontal section, is triangular (Fig. 707). The body of the cavity is curved with its convexity dorsad; its outline in trans- sections varies from the triangular to a mere slit which slopes slightly meso- ventrad. It is wholly roofed in by the corpus callosum {'pars fronioparietalis). Its floor is formed by the following structures named in order from its ectal toward COMMISSUR Fig. 697. — Dissection showing the left lateral posed. its ental limit: (1) caudate nucleus or caudatum; (2) a groove which marks the line of coalescence of caudate nucleus and thalamus and lodges the iaenial rein and a narrow fibre strand — the taenia semicircularis, beneath the ependyma; (3) a reflexion of the ependyma onto a narrow area of the thalamus; (4) the choroid plexus of the lateral ventricle; (5) the thin, sharp (fimbriated) edge of the fornix. The caudate nucleus narrows rapidly as it passes caudad. The taenia 938 THE NER VE SYSTEM semicircularis, lying along the ental border of the ventricular surface of the caudate nucleus, is a small band of white fibres arching from the amygdaline nucleus (near the temporal pole) to the anterior perforated substance. The entrance of a part of the thalamus into the formation of the floor of the lateral ventricle is apparent enough, but morphologically it should be strictly excluded therefrom. The thalamus is in no way formed from the parietes of the secondary fore-brain vesicles (telencephalon), for it is, in fact, excluded by a layer of ependyma (lamina afRxa) reflected onto, and often separable from, the surface of the thala- mus, so that it appears as a constituent of the floor because of the transparency of the ependymal sheet. The choroid plexus of the lateral ventricle is a richly vascular invagination over which the ependyma is continuous to again become reflected onto the fornix along its sharp edge. A reference to Fig. 670, show- ing the topographical relations of these structures in a frontal section, may be of assistance. The cavity is thence continued ventrolaterad in a bold sweep to become ex- panded as an obliquely pyramidal space of a somewhat triangular outline on section, and placed subjacent to the parietal lobe — the trigonum ventriculi (tri- gonuin coUaterale). A conspicuous feature in its floor is the collateral eminence, correlated with the collateral fissure. From the trigonum, the most capacious part of the lateral ventricle, the cavity is prolonged in opposite directions as the middle and posterior cornua. Tail of caudate nucleui Choroid lylexus Ex>iihelial lining of ventricle Pia mater Fimbria Fintbrio-dentate, fissure Alveus Dentate gyrus' Dentate fissure/ Fig. 698. — Coronal section of descending horn of tlie lateral ventricle. (Diagrammatic.) The middle horn or medicomu (cornu inferius) is a prolongation of the ventricular cavity, from its trigone toward the temporal pole, which pursues a curved course with its convexity directed ventrolaterad (Figs. 696 and 697), corresponding to the curved contour of the temporal lobe, and situated at a depth of about 3 cm. from its lateral surface as well as from the temporal pole. The roof is formed by (a) the tapetum of the corpus callosum; (h) the Cauda (tail) of the caudate nucleus; (c) the taenia semicircularis. The medial wall is principally composed of the hippocampus, a prominent welt-like eminence bulging into the cavity, largely filling it, and produced by the hippocampal fissure. The hippocampus nearly conceals from view the actual floor, which is of variable extent in different brains and usually marked by an extension of the collateral eminence previously described. Surmounting the corrugated hippocampal formation and projecting slightly into the cavity, is the fimbria, and from its sharp edge the ventricular ependyma THE CEREBRAL HEMISPHERES 939 Is reflected upon the invaginated choroid plexus of the lateral ventricle. The choroid plexus of the middle cornu is more voluminous than that of the body of the ventricle, and must be lifted in order to expose the whole of the ventricular aspect of the hippocampus. At the apex of the middle cornu the roof presents a more or less pronounced bulging, the amygdaloid tubercle, due to the presence of -the amygdaline nucleus, a small mass of ganglionic gray from which the taenia semicircularis arises and in which the caudate nucleus apparendy ends. The posterior cornu or postcomu is a shorter diverticulum which passes toward the occipital pole in a gently curved course, with its convexity directed laterad. It is not very capacious, usually slit-like on section, and tapers to a point within 2 or 3 cm. of the occipital pole. Its roof, slanting lateroventrad, is formed by the Fig. 609.— Diag: tapetum of the corpus callosum. On the inner or mesal ivall two elongated bulgings may be observed. The upper or dorsal elevation, called the occipital bulb or bulb of the cornu (bulbus cornu posterioris, callosal eminence [Wilder]), is formed by the compact arched posterior forceps of the corpus callosum as it curves around the very deep occipital fissure. The occipital bulb is not always well marked. Ventrad of it lies a more constant limbus or welt-like elevation, the calcar (calcar avis; hippocampus minor), a projection produced by the infolding of the cerebral wall along the calcarine fissure. The floor is continuous with the col- lateral eminence in front. The choroid plexus does not enter the posterior cornu. 940 THE NERVE SYSTEM The choroid fissure or rima (fissure of Bichat) is not a true fissure, and only becomes one when the choroid plexus of the lateral ventricle is torn from its connections. The choroid fissure is nevertheless a gap between the diencephalic part and the overlapping and recurved telencephalon produced by the extension of the secondary fore-brain vesicles in an arcuate manner. It is along this arcuate and fissure-like gap (Fig, 700) that the richly vascular (pial) choroid plexus invag- inates the atrophied parietes of the secondary fore-brain to form the choroid plexus which is everywhere covered by ependyma. The choroid fissure extends from the foramen of Monro to near the tip of the middle cornu in an arcuate course, and ependymal reflections everywhere close in this gap except at the foramen of Monro. The manner in which this is accomplished may best be understood by a study of a trans-section showing the ependymal reflections from the ventricular wall onto the invaginated choroid plexus (Figs. 670 and 698). The caudatothalamic fusion and the intrusion of the great fibre masses constituting the cerebral crura play their parts in complicating the relations in brains of higher type. Fig. 700. — Diagram showing the choroid fissure. (BichAt.) The Choroid Plexus of the Lateral Ventricle and Velum Interpositum. — The cho- roid plexus is a highly vascular, fringe-like structure composed of pia which is invaginated into the lateral ventricle along the choroid fissure, or gap between cerebral hemisphere and diencephalon. The portion of the choroid plexus protruding into the "body" of the lateral ventricle is the fringed vascular bor- der— a triangular fold of pia — the velum interpositum {tela choroidea superior), which, as its name implies, is interposed between the relatively small primary fore-brain and the enormous overlapping secondary fore-brain, and is produced by the overgrowth of the latter onto the former. Inasmuch as the nerve tissue in the roof of the third ventricle atrophies totally, the ventral fold of the pia comes into contact with the ependyma of that ventricle and here permits a similar vascular invagination in the form of two parallel fringes hanging into the cavity (diaplexus or choroid plexuses of the third ventricle). The dorsal leaf of the pial fold is in contact with the ventral face of the body of the fornix. Frontad, the velum interpositum tapers toward the region of the two foramina of Monro, where the choroid plexuses of the two sides are continuous with each other. The ventricular surface of the choroid plexuses is everywhere covered by ependyma which is reflected from it to the fimbriated edge of the fornix on the one hand and to the line of the taenia semicircularis (over the thalamus by the lamina affixa) on the other. Its vascular components, in addition to undefined lymphatic channels, are the anterior choroid artery, a branch of the internal carotid, entering THE CEREBRAL IIEBIISPHERES 941 Fornix Thalamus Corpora qnadr Fig. 701. — Diagram showing the mode of formation of the velum interpositura. Fig. 702.— The fornix, velum iuterpositum, and middle cornu of the lateral ventricle 942 THE NERVE SYSTE3I the plexus of the middle cornu ; and the posterior choroid artery from the posterior cerebral artery reaching the choroid plexus in the neighborhood of the splenium. The venules of the plexus join to form a tortuous middle cornual vein which terminates frontad by joining one of the velar veins. The velar veins (veins of Galen), one on either side close to the median line, running in the fold of the velum interpositum, are formed by the union of the tenial, striatal, and middle cornual veins. The two velar veins unite to form a common trunk which empties into the straight sinus. The Hippocampus and Fornix. — The hippocampus and the fornix merit special description. The hippocampus, as seen in the middle cornu, is a white eminence about 5 cm. (2 inches) in length, of a curved elongated form, enlarging cephalad and tapering caudad as the hippocampal fissure decreases in depth. The enlarged extremity is marked by alternate elevations and depressions, usually three in number, the hippocampal digitations; because of its resemblance to a lion's paw it is sometimes called the pes leonis or pes hippocampi. The white appearance of the ventricular aspect of the hippocampus is due to a stratum of white substance, the alveus, made up of myelinic axones from hippocampal cells and continued into the fimbria. The fimbria is folded so that its sharp margin is directed Choroid plexus Bulb of posterior cornu Ccdcar Fissure o/, Sylvius Fig. 703. — Posterior and descending Eminentia collateralis Fimbria Hippocatnpus of left lateral ventricle exposed from the aide. toward the cavity of the middle cornu; eventually its fibres will be seen to enter into the formation of the fornix. The formation of the hippocampus is best ob- served in a coronal section (Fig. 686). In this view it is seen to be a peculiarly folded margin of the cerebral cortex, corrugated by the intrusion of the hippo- campal and fimbriodentate fissures. Morphologically it is a vestigial sub- merged portion of the rhinencephalon, as a part of which it has already been described (p. 929). The fornix (Figs. 704, 705) is really a paired structure consisting of bilaterally symmetrical halves composed of longitudinally directed fibres which arch on each side from the region of the uncus to the corpus albicans. The two lateral parts join each other in the mesal plane along the summit of the arch to form the body of the fornix {corpus fornicis). Frontad they diverge slightly as they proceed THE CEREBRAL HEMISPHERES 943 toward the corpus albicans; caudacl they diverge more widely. The paired diverging portions are called respectively the anterior and posterior pillars of the fornix. The fibres of each half fornix arise from the pyramidal cells in the hippo- campus, and their course will be traced from this source to the ending in the corpus POCAMPAL Fig. 704. — The fornix, hippoc.ampal commissure, sple n, and dentate gyre seen from tiie basal aspect. albicans. Beginning at first as a stratum of white substance {alvevs) consti- tuting the ectal surface of the ventriculor bulge of the hippocampus, the fibres become collected along its medial border in a narrow but distinct folded band, the fimbria. This increases in diameter as increments are added to it along Fia. 70.5.— Diagram of the fornix. (E. A. S,) its course, until, at the apical region of the trigonum ventriculi, it leaves the dwindling hippocampus to ascend in a curved course (dorsimesad) toward the subsplenial callosal surface as a thick, flattened band. Once free from the hippo- campus on each side, the two converging bands of opposite sides are called the 944 THE NERVE SYSTEM posterior pillars or crura fornicis. The majority of the fibres continue frontad in each half fornix, but a number course transversely to enter the crus fornicis of the opposite side to end in the hippocampal formation. These fibres, of transverse course, form a thin lamina filling in the small triangular space in the subsplenial region between the converging crura fornicis and constituting the hippocampal commissure (lyra; psalterium). Occasionally a small recess called Verga's ventricle is formed between the corpus callosum and the hippocampal commissure. The two half fornices now become joined in the mesal plane and, leaving the subsplenial surface of the corpus callosum, dip frontoventrad in an arch — the body of the fornix. Its caudal part is broad and each half is of triangular outline (on section) with a sharp edge directed laterad. Where it is not in contact with the corpus callosum it affords attachment, on each side of the mesal plane, to the hemiseptum of the septum lucidum. Laterad of these lines of attachment the dorsal surface of each fornix enters into the formation of the floor of the lateral corpus callosum caudate nucleus Icaput) ANTERIOR CORNl LATERAL VENTRICLE^ E. A. S. PSEUDOCELE I section of the brain slightly caudad of the genu of the corpus callosum. ventricle and is covered by ependyma (Fig. 697). The ventral surface rests upon the velum interpositum, which separates it from the third ventricle and the dorsal surface of the thalamus (Fig. 670). Near the region of the anterior commissure the fornix again divides into its constituent lateral halves, separating as rounded strands called the anterior pillars. These curve ventrad to form the frontal boundary of the foramen of Monro and thence plunge into the hypothalamic gray, inclined slightly caudad, to end in the corpus albicans. The terminals of the fornix fibres come into rela- tion with the cells of the nucleus of the corpus albicans, which, in turn, give off the bifurcating Y-shaped axone bundles already described (p. 907). In rare instances each anterior pillar has been seen to divide on approaching the anterior commissure a part passing frontad thereof as an anomalous pre- commissural pillar of the fornix. The fornix, in its course from hippocampus to corpus albicans, gives oft", in addition to those described as hippocampal commissural fibres, axones (a) to the opposite half fornix, decussating in the fused portion (body), (6) to the hemiseptum of the septum lucidum, and (c) to THE CEREBRAL HEMISPHERES 945 the gray tissues of the anterior perforated substance (Fig. 685). It constitutes an inner olfactory arc as distinguished from the epicallosal or outer arc, repre- sented by the atrophied indusium and its longitudinal striae. LATERAL VENTRICLE CORPUS CALLOSUNl (rostrum) Fig. 708.— a coronal section of the brain in the plane of the anterior commissure. The Septum Lucidum {septum pelhwidum). -The so-called septum lucidum reallv consists of two vertically placed lamina or hemisepta. Between them hes a narrow, enclosed space, the cavum septi pellucidi (pseudocele; fifth ^ent^lclej, 60 946 THE NERVE SYSTEM roofed in by the corpus callosum, while the floor consists of the fused fornices and the rostrum. Each hemiseptum bounds a part of the anterior cornu and body of the lateral ventricle in its mesal wall, and in a lateral view is of triangular out- line. The hemisepta represent the thin, undeveloped parts of the mesal walls of the cerebral vesicles, which were enclosed within the rapidly developing arch of the corpus callosum. The cavum septi pellucidi is therefore a closed-off part of the original intercerebral cleft and not a part of the neural cavity, as its older name, "fifth ventricle," seems to imply. The Anterior Commissure. — The anterior commissure, or precommissure, is a bun- dle of white fibres, of oval outline in a sagittal section, which crosses the midline as a localized reenforcement of the lamina terminalis, slightly bulging into the frontal part (aula) of the third ventricle and clothed by its ependyma. It is a comparatively insignificant intercerebral commissure in the human brain, having become dimin- ished as the corpus callosum increased in mammalian development. It courses from side to side frontad of the anterior pillars of the fornix, ventrad of the head of the caudate nucleus, and passes, in part, through the frontal end of the lenticular nucleus (Fig. 708) . Its fibres radiate chiefly to the cortex of the temporal lobe and to certain parts of the rhinencephalon. The bundle is slightly twisted in each lateral, buried part. Two divisions are distinguishable: (1) The pars anterior or frontal part (in the median plane) con- tains two groups of fibres belonging to the olfactory apparatus — (a) fibres arising from the mitral cells in the olfactory bulb of one side to the same layer in the opposite bulb; (6) fibres which associate the uncus of one side with that of the other. (2) The pars posterior contains the fibres passing between the cortices of the two temporal lobes. Gray Masses in the Cerebral Hemisphere. — Aside from the cortex, the cerebral hemisphere contains certain gray ganglionic masses in its interior, more or less embedded in the white centrum, and called, because of their proximity to the base of the cerebrum, the basal ganglia. These comprise the caudate, the lenticular^ and the amygdaline nuclei. It i*^ usual to include the claustrum among the basal ganglia, but morphologically this structure belongs rather to the insular cortex of the island of Reil. Conventionally the caudate nucleus and lenticular nucleus together are described as the corpus striatum (striatum), a ganglionic mass which in earlier vertebrate brains bore intimate relations with the olfactory apparatus, but later, with the rise in functional dignity and growth of the neopallium, underwent specialization and difi^erentiation concomitant with the reduction of the rhinencephalon. The intrusion of great projection fibre masses, thrusting the cortical gray outward, has not been everywhere uniform, and we still find, in the human brain, a common ground in which the neopahial cortical gray, the corpus striatum, rhinencephalon, and amygdaline nucleus meet^the site of fusion being in the gray substance of the anterior perforated substance. To the cortical mantle they are regarded as bearing the relation of subordinate (subcortical) centres. In the human brain the corpus striatum — so called because of its striated appearance in sections — is composed of two masses, the caudate and lenticular nuclei, directly continuous with each other at their frontal ends (Fig. 710). The connecting gray bridge becomes broken up into numerous small bands of gray substance as the fibre masses of the internal capsule insinuate themselves between the two nuclei (Fig. 707). The caudate nucleus (nucleus caudatiis; caudatum) (Figs. 709, 710) presents a ventricular and a capsular surface; the ventricular surface, covered by ependyma, forms part of the floor of the body and anterior cornu of the lateral ventricle, while in the middle cornu it is a constituent of its roof, owing to its arched contour in cor- respondence with the sweeping curve of the ventricle itself. It is of a pyriform THE CEREBRAL HEMISPHERES 947 shape with a very much attenuated tail. The large, thick head projects into the anterior cornu, while its thinner tail is prolonged caudolaterad, separated from the thalamus by the narrow taenia semicircularis. Following the curved contour of the A'entricle it is prolonged as a narrow gray band in the roof of the middle cornu, where it joins the amygdaline nucleus. The nonventricular or capsular surface is embedded in the white substance of the cerebral hemisphere, and is chiefly related to the internal capsule. The ventricular surface shows, in microscopic sections, a dense ependymal lining. The capsular face is not sharply outlined, numerous strands of fibres, to and from the internal capsule, entering it obliquely so as to appear as streaks which extend to about the middle of the ganglion, there separating into finer and finer strands which become lost to the naked eye. The lenticular nucleus (lenticula) (Figs. 708 and 709) is wholly embedded in the white substance, and must be studied in sections. In its shape it resembles an irregular triangular pyramid with its convex base directed laterad and parallel with and near to the cortical expanse of the island of Reil and of about the same extent. Its ental, apical portion is directed toward the interval between caudate nucleus 948 THE NERVE SYSTE3I -AMYGDALA (head) and thalamus. The contour and slope of the surfaces of the ental pyra- midal face may be judged from the model pictured in Fig. 710. Its outline, as revealed in sections passing in different planes, is shown in Figs. 708 and 711. Sections of the lenticular nucleus show it to be composed of three^ concentric segments separated by two white medullary laminae. The segments are known as articuli; the ectal one is designated the putamen; the two ental zones constitute the globus pallidas (pallidum) . The puta- men is the larger and of a deeper reddish- gray tint; the two mesal divisions are lighter in color owing to a greater pro- portion of radiating streaks of white fibres passing to and from the internal capsule. The ectal outline of the puta- men is sharply defined against a white lamina, the external capsule. The amygdaline nucleus (amygdala) is usually regarded as an hypertrophied aggregation of the temporal cortex which has become nearly isolated from its cortical connection by intruding white substance. It is a rounded, gray, striated mass situated in the fore part of the temporal lobe in the roof of the middle cornu at its apex, where it produces the bulging called the amygdaloid tubercle. Caudad it is joined by the tail of the caudate nucleus; frontad it is continuous with the putamen. Except for the marked streaking shown in sections, its structure is like that of the cortex. Its cells apparently give rise to the narrow band of fibres — the taenia semicircularis — which courses along the mesal margin of the ventricular surface of the caudate nucleus throughout its arched course and ends in the gray of the anterior perforated substance, so that it nearly completes a circle. The claustrum is a thin plate of gray substance embedded in the white substance which intervenes between the putamen and the cortex of the island of Reil, and corresponds in extent to these. Its dorsal edge is very much attenuated; traced ventrad it thickens considerably and becomes continuous with the surface gray at the anterior perforated substance. Its ectal surface presents alternate ridges and depressions which correspond to the corrugations of the cortex of the island of Reil. The "external capsule" intervenes between its ental face and the putamen of the lenticular nucleus. From the cortex of the island of Reil proper it is separated by a white lamina which may be termed the periclaustral lamina or capsula extrema. Apparently the claustrum is the thickened and isolated spindle-cell stratum of the cortex of the island of Reil, a feature which may be of significance in relation to the preponderatingly associative function of the insular region. Internal Capsule- (Fig. 711). — Between the lenticular nucleus on the one hand and the caudate nucleus and thalamus on the other lies the internal capsule, a broad 1 Four and eveu five have been observed. ^ The terms internal capsule and external capsule owe their derivation to the fact that the lenticular nucleus is almost completely enveloped by white substance in the form of a capsule. Of these the internal or mesal portion is relatively massive, while the external or lateral portion is thin. Fig. 710. -Two views of Lateral aspect. I model of the striatum; A. B. Mesal aspect. (E. A. S.) THE CEREBRAL HEMISPHERES 949 band of white fibres which, as seen on horizontal section, appears bent, very much as a leg is bent on the thigh, with the knee (genu) directed mesad. The frontal or caudatolenticular division or limb is confined between the opposed faces of the caudate nucleus and lenticular nucleus. The genu receives the mesal apex of the lenticular nucleus in its hollow, while the caudal or thalamolenticular limb lies between the opposed faces of lenticular nucleus and thalamus. The frontal limb constitutes about one-third, the caudal limb two-thirds of the internal capsule mass. LAT. VEN CAVUM SE PELLUC CORTEX OF ISLfl EPIPHYSIS TAIL OF CAUDATE NUCLEUS HIPPOCAMPUS CHOROID PLEXUS. OPTIC RADIATIO -Horizontal section through the cerebrum appearance on the right sidi The term "internal capsule" is often loosely employed and is variously stated to include fibre tracts which do not course between the cerebral cortex and the "lower" brain centres. In a strict sense it is a mass of fibres which converge, like the sticks of a fan, toward the cerebral base and into the crusta. Dorsad of the basal ganglia the fibres radiate in various directions, streaming among the radiating callosal fibres and forming the so-called corona radiata. Yet other fibre tracts leave and enter the great ganglia at various altitudes along the internal capsule, and we must therefore distinguish the following cerebral fibre systems. Projecting systems, ascending and descending (in the functional sense), of longer and shorter course, connecting the cerebral cortex with (a) spinal gray centres; (h) mid-brain and pontile nuclei; (c) basal ganglia and thalamus. The 950 THE NEBVE SYSTEM last-mentioned system traverses the internal capsule to a greater or less extent, but does not continue into the crusta. These various systems are summarized on page 956. It may here be mentioned that the internal capsule, topographically, exhibits a functional dissociation in that its frontal or lenticulocaudate limb is composed of preponderatingly corticipetal fibres, while corticifugal fibres form the major portion of the thalamolenticular limb (Fig. 712). In the frontal limb are the thalamofrontal and thala- mostriate fibres, the former ending in the cortex of the frontal lobe, the latter in the caudate and lenticular nuclei. The chief cor- ticifugal components are the fron- topontile tract, and fewer fronto- thalamic and striatothalamic fibres. The frontopontile tract arises in the cortex of the prefrontal region, traverses the frontal limb of the internal capsule, forms the ental sector (one-fifth) of the crusta, and ends in the nuclei pontis. In the genu and the thalamo- lenticular limb of the internal capsule course several important fibre tracts which are chiefly cor- ticifugal. The pyramidal (motor) tract, in its course from the precentral cortex to the lower motor centres, occupies the frontal half of this limb. The portion in the genu, often designated the geniculate tract, comprises the pyramidal fibres which are destined to go to the facial and hypoglossal nerve nuclei; farther caudad lie, in suc- cession, the fibres going to the motor centres for the upper and the lower extremity and trunk. More posteriorly pass the corti- cipetal fibre-systems conveying sensor impressions from the per- iphery via thalamus (Fig. 712). The most caudal segment (also called the retrolenticular part) of the internal capsule contains (a) the optic radiation, composed of fibres coursing in both directions between the occipital cortex and the pulvinar, external geniculate and superior quadrigeminal bodies; (6) the auditory radiation, composed of fibres passing in both directions between the cortex of the temporal lobe (auditory centre) and the posterior quadrigeminal and internal geniculate bodies; (c) the occipito- pontile and temporopontile tracts from the occipital and part of the temporal cortex, coursing through the caudal segment of the internal capsule, constituting the ectal (one-fifth) sector of the crusta and ending in the nuclei pontis. In ad- dition there are scattered fibre bundles which arise from the ventral portion of Fig. 712. — Diagram of the tracts in the internal capsule. Motor tract red. The sensor tract (blue) is not direct, but formed of neurones receiving impulses from below in the thala- mus and transmitting them to the cortex. The optic radiation (occipitothalamic) is shown in violet. THE CEREBRAL IIEAIISPIIERES 951 the thalamus, enter the internal capsule to pass toward the cortex, in part through the lenticular nucleus, in part in the sublenticular zone, to form the ansa lenticu- laris. The reenforcement of this sublenticular white-fibre tract by cortico- thalamic fibres from the temporal lobe to thalamus forms the ansa peduncularis. The topographic relations of the various tract masses as seen in a flatwise section is schematically shown in Fig. 713; on the whole, they cori'espond to the cortical areas with which they are connected. Fig. 713. — The motor tract. (Modified from Poirier.) The external capsule (Fig. 711) is a thin lamina of white substance interposed between the ectal face of the lenticular nucleus and the claustrum. Dorsally, frontad and caudad, at the corresponding borders of the lenticular nucleus, it joins the internal capsule mass, while ventrally it is continuous with the white centrum of the temporal lobe. Its comparatively few projection fibres course to and from the ventral parts of the thalamus; its chief constituents are associa- tion axones for the circuminsular cortical areas. Minute Structure of the Cerebral Cortex and its Special Types in Different Regions (Fig. 714). — A section of the cerebral cortex reveals a tendency on the part of its constituent cells to arrange themselves in layers which alternate with zones less rich in cellular elements. Among the cells course the axones arising from them or terminating in their neighborhood. The axones are chiefly amyelinic, though some are myelinic for a part of their intracortical 952 THE NER VE SYSTEM j?r- ■1' y MOLECULAR LAVCH T' wMm mm Mm W m f course. The cells, of various sizes and shapes, together with their dendrites and axones, are embedded in a matrix of neuroglia. The nerve cells in a ti/pical section of the cortex are arranged in five tangential layers, as fol- lows: (1) the molecular layer; /2) the ectal poljrmorphous cell layer; ^.3) the layer of small pyramidal cells; (4J the layer of large pyramidal cells; (5) the ental polymorphous cell layer. The molecular layer {neuroglia layer) lies imme- diately subjacent to the pia, and is chiefly made up of glia cells and fibres, among which the dendrites of the subjacent layer of cells intrude. The ectal poljrmorphous layer cells are polygonal, triangular, and fusiform in shape, and tend to gather in groups in certain cortical regions. The fusiform cells are placed with their long axes parallel (i. e., tangential) to the gyral surface and are presumably associative in function. The Layer of Small and the Layer of Large Pyramidal Cells. — The cells in the second and third layers may be studied together, since, with the excep- tion of the difference in size and the more superficial position of the smaller cells, they resemble each other. The body of each cell is pyramidal in shape, its base being directed to the deeper parts and its apex toward the surface. It contains granular pig- ment, and stains deeply with ordinary reagents. The nucleus is nucleolated, of large size, and round or oval in shape. The base of the cell gives off the axone, and this passes into the central white substance, giving off collaterals in its course to be distributed as a projection, commissural, or asso- ciation fibre. Both the apical and basal parts of the cell give off dendrites. The apical dendrite is directed toward the surface, and ends in the molec- ular layer by dividing into numerous branches, all of which may be seen to be studded with projecting bristle-like processes when prepared by the silver or methylene-blue method. The larger pyramidal cells, especially in the precentral gyre, may exceed 50 // in length and 40 /i in breadth, and are termed giant cells. The chief function of the small pyramidal cells is commissural and associative. The chief function of the large pyramidal cells in the pre- central and paracentral cortex is motor, but they have also commissural and associative functions. Layer of Ental Polymorphous Cells.— The cells in this layer, as their name implies, vary greatly in contour, the commonest varieties being of a spindle, (, \X\i]yC't//'i ^,1 star, oval, or triangular shape. Their dendrites are 1 yn \^\\'TiSli'i directed outward, toward, but do not reach, the ' ' ■* molecular layer; their axones pass into the subjacent white substance. From this layer come commissural fibres, long association fibres, and some projection fibres. There are two other kinds of cells in the cerebral cortex, but their axones pass in a direction opposite to that of the pyramidal and polymorphous cells, among which they lie. They are: (a) the cells of Golgi, the axones of which do not become myelin- ated, but divide immediately after their origin into a large number of branches, which are directed toward the surface of the cortex; (6) the cells of Martinotti, which are chiefly found in the polymorphous layer. Their dendrites are short, and may have an ascending or descending course, while their axones pass out into the molec- ular layer and form an extensive horizontal arborization. Nerve Fibres in the Cortex.— These fill up a large part of the intervals between the cells. Some of these fibres form fasciculi; some are isolated, and others are arranged in plexuses. They may be myelinic or amyelinic, the latter comprising the axones of the smallest pyramidal cells and the cells of Golgi. In their direction the fibres may be either transverse, the transverse m i '•f, ^7« \m^i\ 714. — Typical arrangement of the cell layers in the cerebral cortex. THE CEREBRAL HEMISPHERES 953 tangential or horizontal fibres, or vertical, the vertical or radial fibres. The tangential fibres run parallel to the .surface of the hemisphere, intersecting the vertical fibres at a riirht an^le. They consist of several strata, of which the following are the most important: (1) A stratum of white fibres covering the superficial aspect of the molecular layer; (2j the band of Bech- terew, found in certain parts of the superficial portion of the layer of the smaller pyramidal cells; (3) the external or outer band of Badllarger or the band of Gennari, which runs through the layer of large pyramidal cells; (4) the internal band of Baillarger, which intervenes between the layer of large pyramidal cells and the polymor]jhous layer. According to Cajal, the tangen- tial fibres consist of (a) the collaterals of the pyramidal and polymorphous cells and of the cells of Martinotti; (6) the arborizations of the axones of Golgi's cells; (c) the collaterals and terminal arborizations of the projection, commissural, or association fibres. The vertical fibres: Some of these — viz., the axones of the pyramidal and polymorphous cells — are directed toward the central white substance, while others — the terminations of the commissural, projection, or association fibres — pass outward to end in the cortex. The axones of the cells of Martinotti are also ascending fibres. In certain parts of the cortex this typical structure is departed from. The chief of these regions are (1) the occipital lobe, (2) tlie transtemporal gjnres, (3) the hippocampus, (4) the dentate gyre, and (.5) the olfactory bulb. Special Types of Gray Substance. 1. The Occipital Lobe.— In the cuneus and the calcarine fissure of the occipital lobe Cajal has recently described as many as nine layers. Here the inner band of Baillarger is absent; the outer band of Baillarger or band of Gennari is, on the other hand, of considerable thickness. If a section be examined microscopically, an additional layer is seen to be interpolated between tire molecular layer and the layer of small pyramidal cells. This extra layer consists of two or three strata of fusiform cells, the long axes of which are at right angles to the surface. Each cell gives off two dendrites, external and internal, from the latter of which the axone arises and passes into the white central substance. In the layer of small pyramidal cells, fusiform cells, identical with the above, are seen, as well as ovoid or star- like elements with ascending axones, the cells of Martinotti. This area of the cortex forms the visual centre, and it has been shown by Dr. .1. S. Bolton' that in old-standing cases of optic atrophy the thickness of Gennari's band is reduced by nearly .50 per cent. 2. The Transtemporal Gyres are distinguished by a reduction of thickness of the pyramidal cell layer with closer approximation of the giant cells to each other, while the fusiform cell layer is more deeply situated than elsewhere. This cortical formation is the end station for cochlear nerve projections. 3. In the Hippocampus (Fig. 6S6) the molecular layer is very thick and contains a large number of Golgi cells. It has been divided into three strata : (a) S. convolutum or S. granulosimi, con- taining many tangential fibres; (6) S. lacunosum, presenting numerous lymphatic or vascular spaces; (c) S. radiatum, exhibiting a rich plexus of fibrils. The two layers of pyramidal cells are condensed into one, and these are mostly of large size. The axones of the cells in the polymorphous layer may run in an ascending, descending, or horizontal direction. Between the polymorphous layer and the ventricular ependyma is the white substance of the alveus. 4. The Dentate Gyre. — In the rudimentary dentate convolution the molecular layer contains some pyramidal cells, while the pyramidal layer is almost entirely represented by small ovoid elements. 5. The Olfactory Bulb (Fig. 715). — In many of the lower animals tliis contains a cavity which communicates through the hollow olfactory stalk with the cavity of the lateral ventricle. In man the original cavity is filled by neuroglia and its wall becomes thickened, but much more so on its ventral than on its dorsal aspect. Its dorsal part contains a small amount of gray and white substance, but this is scanty and ill defined. A section through the ventral part shows it to consist of the following layers from without inward: (1) A layer of olfactory nerve fibres, which are the myelinated axones prolonged from the olfactory cells of the nose, and which reach the bulb by passing through the cribriform plate of the ethmoid bone. At first they cover the bulb, and then penetrate it to end by forming synapses with the dendrites of the mitral cells, presently to be described. (2) Glomerular layer {stratum glomerulosinn): This contains numerous sphe- roidal reticulated enlargements, termed glomeruh, which are produced by the branching and arborization of the processes of the olfactory nerve fibres with the descending dendrites of the mitral cells. (3) Molecular layer: This layer is formed of a matrix of neuroglia, embedded in which are the mitral cells. These cells are pyramidal in shape, and the basal part of each gives off a thick dendrite which descends into the glomerular layer, where it arborizes as above, or, on the other hand, interlaces with similar dendrites of neighboring mitral cells. The axones pass through the next layer into the white substance of the bulb, from which, after becoming bent on themselves at a right angle, they are continued into the olfactory tract. (4) Xervc fibre layer: This lies next the central core of neuroglia, and its fibres consist of the axones or aflerent processes of the mitral cells which are passing on their way to the brain; some efferent fibres are, however, ' Phil. Trans, of Royal Society, Series B, vol. cxciii, p. 165. 954 THE NERVE SYSTEM also present, and terminate in the molecular layer and presumably come via the anterior com- missure from the mitral cells of the opposite bulb. The claustrum, although usually enumerated among the basal ganglia, is probably the thick- ened and isolated deepest layer of fusiform cells belonging to the cortex of the island of Reil. The white lamina' intervening between it and the cortex proper consists of association axones of longer and shorter course Summary of the Cerebral Fibre Systems. — ^The white substance of the cerebrum consists of myelinic fibres intricately interwoven but permitting of classification into three systems arranged according to the course they take. These systems comprise: (1) association fibres, which connect neighboring or distant parts within the same cerebral hemisphere; (2) commissural fibres, which unite allied parts in the two cerebral halves and come transversely across the midline to form the commissures; (3) projection fibres, which connect the cerebral cortex with lower centres in the brain and spinal cord, and, conversely, those fibres which connect lower centres with the cerebral cortex. 'Wliite substance {dorsal part) Neuroglia ance [ventral- part) Medullary layer Mitral cells Glomerular layer Layer of olfactory nerve fibres Fig. 715. — Coronal section of olfactory bulb. (Schwalbe.) 1. The association fibres (Fig. 716) connect different structures in the same hemi- spheres, and are in or near to the cortex. They take origin from the small pyram- idal and polymorphous cells of the deep layer of the cortex. Their direction is parallel to the surface of the hemisphere, and in their course they cross the pro- jection and commissural fibres. They are of two kinds: (1) Those which unite adjacent convolutions, short association fibres; (2) those which pass between more distant parts in the same hemisphere, long association fibres. The short association fibres are situated immediately beneath the gray cortex of the hemispheres, and connect adjacent convolutions. Tlaey constitute subcortical tracts and are divided into arcuate fibres and tangential fibres. Thus, some of these fibres connect the "visual sensor area with the visual memory area, and the auditory sensor with the auditory memory area." The long association fibres associate cerebral centres which are far apart. They are gathered into bundles and dip down deep into the centrum ovale. They include the following: (o) the uncinate fasciculus; (b) the superior longitudinal fasciculus; (c) the inferior longitudinal fasciculus (doubtful); (d) the cingulum; and (e) the fasciculus rectus. ' Previously described as the periclaustral Ian capsula extrema (p. 94S\ THE CEREBRAL HEMISPHERES 955 (a) The uncinate fasciculus (/. uncinatvs) passes between the uncinate gyre and the orbital portion of the frontal lobe; in its course it curves beneath the depths of the basisylvian fissure (Fig. 716). (b) The superior longitudinal fasciculus (/. longitudinal is superior) (Fig. 716) is beneath the convex surface of the hemisphere arching over the lenticular nucleus. It joins the frontal cortex with the parietal and temporal cortex and brings into relation the motor speech centres and the centres of auditory and visual memories. (c) The inferior longitudinal fasciculus (f. longitudinalis inferior) is usually described as a tract associating the centres of auditory and visual memory. Such association fibres undoubtedly exist, but it is doubtful whether they are collected into a distinct fasciculus. The bundle which is usually designated by this term E. A. S. Fig. 716. — Diagram showing the principal systems of associating fibres in the cerebrum. has been proved to be in part the projection system between the occipital cortex and" the thalamus and external geniculate body (E. Redlich) and in part also the fibres from the temporal cortex (meditemporal and subtemporal gyre) to the crusta.' (d) The cingulum, also called the fornix periphericus, is a band of white fibres that course in the white substance of the callosal gyre and runs excentrically to the corpus callosum. Its fibres may be traced frontad into the mesal olfactory stria and the anterior perforated substance, while caudad they radiate into the hippocampus. It may be regarded as an association tract of the rhinencephalon akin to the fornix. (e) The fasciculus rectus or perpendicular fasciculus runs dorsoventrad in the occipitoparietal transition and associates the subparietal gyres with the medi- and subtemporal gyres; a part of the fasciculus associates the dorsal occipital region with its ventral part and with the subcollateral gyre (Fig. 716). ■ The fornix, previously described, may be enumerated among the long associa- tion tracts; it belongs exclusively to the olfactory apparatus. 2. The commissural fibres are grouped under the following heads: (a) the corpus callosum, described on page 933; (h) the anterior commissure, described on page 946; and (c) the hippocampal commissure, described on page 944. ^E. J. Curran (Jour. Comp. Neurol, and Psychol., : ferior " coursing ventrolaterad of the lenticular nuclei . 6, Dec, 1909) describes a "fasciculus occipitofrontalis 956 THE NERVE SYSTEM 3. The projection fibres connect the cerebral cortex with lower brain centres (caudate and lenticular nuclei, thalamus, hypothalamic region, corpora quadri- gemina, pons, medulla oblongata), and with the spinal cord centres. They either project impulses from the cortex to the periphery or bring in impressions from without. Their radiations to and from the cortex, together with the radia- tions of the callosal fibres, give rise to the characteristic appearance of the corona radiata. We may distinguish the projection tracts of long course from those of short course, and, in the functional sense, those that are centrifugal, descending, or motor, from those that are centripetal, ascending, or sensor. The last mode of classification is more desirable. PRECENTB. Visual tract from the thalamus (OT) to the occipital lobe. E. Auditory tract from the internal geniculate body (to which a tract passes from the VIII N. nucleus) to the temporal lobe. F. Superior peduncle. G. Middle peduncle. H. Inferior peduncle. CN. Caudate nucleus. CQ. Corpora quadrigemina. The numerals refer to the cranial nerves. (Starr.) 1. Descending (corticifugal) tracts are composed of axones arising from the cortical pyramidal cells. (a) The pyramidal or motor tract from the "motor area," comprising the pre- central gyre and paracentral gyre, courses through the genu and frontal two- thirds of the thalamolenticular limb of the internal capsule, forms the middle (three-fifths) sector of the crusta, and passes through the pons into the medulla oblongata and spinal cord. The tract may be subdivided into a corticobulbar and a corticospinal division. The corticobulbar division is the pyramidal tract to the efferent cranial nerve nuclei. Only those fibres which are destined to go to the facial and hypoglossal can be traced throughout. They originate in the ventral part of the precentral gyre (face and tongue centre), course through the genu of the internal capsule. THE CEREBRAL HEMISPHERES 957 and end, contralaterally, in relation with the facial and hypoglossal nerve nuclei (also called the emissary speech tract). The corticospinal division arises from the remainder of the motor area, courses throuoh the frontal two-thirds of the posterior limb of the internal capsule, through crusta, pons, and medulla oblongata, to form the pyramids, and, under- going partial decussation, forms the direct and the crossed pyramidal tracts described in the spinal cord. (h) The frontopontile tract {Arnold's bundle) arises in the midfrontal cortex, courses through the internal capsule (caudal part of frontal limb), forms the mesal sector (one-fifth) of the crusta, and ends in the nuclei pontis. (c) The temporopontile tract {Tiirck's bundle) arises in the cortex of the tem- poral lobe, descends through the internal capsule (caudal segment), forms the ectal (one-fifth) sector of the crusta, and ends in the nuclei pontis. The existence of occipitopontile fibres is denied by Archambault in a recent contribution (1906). (d) The occipitomesenceph{ilic tract arises in the visual area (cuneus and cal- carine formation), courses through the retrolenticular part of the internal capsule, to end in the superior quadrigeminal body and in relation with the nuclei for move- ments of the eyeball. (e) Part of the fibres composing the optic radiation are corticipetal, arising in the occipital cortex and ending in the pulvinar of the thalamus and the external geniculate body. GRANULE Fig. 71S. — Schema of the olfactory bulb and tract neurones. 2. Ascending (corticipetal) tracts arise mostly from the nuclei of the thalamus and hj'pothalamus, mid-brain, and cerebellum. (a) The terminal or cerebral part of the general sensor pathway of the body comprises the axones arising in the cells of the lateral nucleus of the thalamus and the hypothalamic nucleus — interposed way-stations which transfer the im- pressions carried along the medial lemniscus from the nuclei of the gracile and cuneate fasciculi in the myeloblongata transition. They convey sensor impres- sions from the body periphery to the somesthetic area of the cortex — chiefly the postcentral and parietal gyres. (b) The terminal or cerebral part of the general sensor pathway of the head and neck comprises the axones which arise from the alferent cranial nerve nuclei (excepting the auditory) and course along the medial lemniscus to the thalamus and hypothalamic nucleus, to be thence projected to the somesthetic cerebral cortex. (c) The terminal or cerebral part of the auditory pathway from the inferior quadri- geminal body, internal geniculate body, and the interposed nucleus of the lateral lemniscus, ending in the auditory sphere of the cerebral cortex. (d) The terminal part of the visual pathway, described on pages 909-911. 958 THE NEB VE SYSTEM (e) The terminal (ascending) cerebellocortical pathway, arising as the fibres of the superior peduncles of the cerebellum, decussating and ending in the red nucleus and lateral nucleus of thalamus, is thence directly projected by new axones to the somesthetic cortical area, or indirectly projected via thalamus (lateral nucleus). Connections of the Corpus Striatum. — The connections of the caudate and len- ticular nuclei with each other and with the cortex may be summarized as follows: (a) Fibres from the cortex to the caudate and lenticular nuclei, entering into the formation of the corona radiata. (6) Fibres from the caudate nucleus and putamen of the lenticular nucleus coursing to the thalamus and hypothalamic region. Those from the caudate nucleus pass through the internal capsule to traverse the globus pallidus, are joined by the fibres from the putamen to again traverse the internal capsule and end in the thalamus, forming the striatothalamic radiation. (c) Fibres coursing ventrad in the medullary laminse of the lenticular nucleus, and reenforced by additional fibres from the globus pallidus, course mesad to the hypothalamic region to form the subthalamic radiation or ansa lenticularis (described on p. 951). This radiation is further reenforced by the ventral stalk of the thalamocortical radiation to form the ansa peduncularis (described on p. 951). The Olfactory Pathways. 1. Peripheral Pathway. — Impressions from the upper portion of the Schneiderian mucous membrane pass along the olfactory fila (central processes of the intraepithelial bipolar olfactory cells) to the glomeruli olfactorii in the olfactory bulb (Fig. 718). 2. Central Pathway. — In the glomeruli the impression is transmitted to the brush-like, dendritic endings of the mitral ceils and brush cells; the axones of these cells carry the impression centrad to the gray masses of the olfactory tract, trigonum olfactorium, anterior perforated substance, and adjacent parts (Fig. 713). These constitute the primary centres. The primary centres are connected with secondary or cortical centres (hippo- campus, gyrus dentatus, uncus) by the following tracts: (1) Lateral olfactory strise, from the olfactory trigone to the uncus, ending in the gyrus ambiens and gyrus semilunaris (p. 928). (2) Axones from cells in the olfactory trigonal gray through the fornix to hippocampus. (3) Striae mediales (Lancisii) from the trigone into gyrus subcallosus around the corpus callosum to gyrus dentatus and hippocampus. The amygdaline nucleus is by some regarded as a cortical centre to which impressions are carried by the taenia semicircularis. The fornix fibres arise from the pyramidal cells in the hippocampus and the polymorphous cells of the dentate gyre. Some fibres traverse the median plane as the hippocampal commissure to the opposite hippocampus; the remainder end in the corpus albicans, gray nucleus, or, in small part, are retroflexed as the stria medullaris thalami to the habenular ganglion. In the corpus albicans impressions are transmitted to the cells of two nuclear masses; from the medial nucleus arise axones constituting the fasciculus albicantis princeps, each axone bifurcating and the diverging bundles forming, respectively, the albicantiothalamic and the albicantiotegraental fasciculi (p. 907). The stria medullaris thalami consists of the following bundles ending in the habenular ganglion: (a) Axones from hijppocampus via fornix — the cortico- habenular tract; (b) axones from the hemiseptum of the septum lucidum and olfactory gray — the olfactohabenular tract; (c) axones from the thalamus to the habenular ganglion — the thalamohabeoular tract. In the habenular ganglion axones arise which pass as a distinct bundle ventrad through the tegmentum to the gray of the posterior perforated substance (ganglion interpeduncidare [inter- crurale] of Gudden) — the fasciculus retroflexus of Meynert. The primary olfactory centres of the two sides are connected by the 'pars CORTICAL LOCALIZATION OF FUNCTION 959 olfacforia of the anterior commissure, a bundle of fibres passing from side to side to end in the tract, granular stratum, and glomerular layer of the bulb. Further connections are established with the tuber cinereura, mid-brain, and even spinal centres; one division has been named the olfactomesencephalic tract (Wallenberg). The cingulum or fornix periphcricus is an arcuate association bundle, or rather an arcuate series of short bundles which establishes the connections of the rhinencephalon with the adjacent cortical areas (p. 955). CORTICAL LOCALIZATION OF FUNCTION. Patient researches conducted along clinicopathological, experimental, physiological, and de- velopmental lines have furnished us with a topographic map of the somesthetic and sense areas, and, inferentially, of the association areas of the cerebral cortex. The somesthetic and sense areas constitute less than one-third of the cortical area, while the remainder is presumed to be devoted to the elaboration of the higher mental activities manifested by abstract thought, ideation, reasoning, and language. The acquisition of these specifically human mental attri- butes has been the chief factor in bringing about the superior structure of the human brain, and those cortical regions which were subjected to increased associations rose in functional dignity and increased in size. With over nine billion functional nerve cells in the human cerebral cortex devoted to the mental processes, and less than one-third of these concerned with emissary and receptive functions, the intricacy and capacity of the human brain for the manifold registra- tion of sensations and the numerous transformations that characterize man's mental processes far exceed that of any other animal. -Mesal view of left cerebral hemisphere, showing localization of functions, fissin-es and gyres is the same as in Fig. 679. The schema of the The delineation of areas called motor, visual, auditory, etc., is not to be deemed as mathe- matically accurate or sharply defined as the boundaries of a State, county, or township. The areas rather shade off in a'difi'use manner, and the arbitrary demarcations employed in the appended figures merely show the maximum concentration of those cortical parts which most distinctly appertain to the function alleged for them. The ]>rliii'i|ial areas that are known to be functionally differentiated are the following: 1. Motor Area.— The motor area comprises the precentral gyre and parts of the frontal gyres adjacent thereto, together with the paracentral gyre and the adjacent portion of the superfrontal gyre on its mesal face. Stimulation of various parts of this area causes movement, while their destruction impairs or abolishes voluntary movements. Within this motor area may be defined districts which are cortical projections of the muscular systems of the body. Thus, movements of the lower limb seem to be controlled by the dorsal part of the precentral and the paracentral gyre; the trunk musculature by the area lying frontad both on the mesal aspect and in the dorsal 960 THE NER VE SYSTEM superfrontal; the upper limb seems to be controlled by the midportion of the precentral; while the facial musculature is projected in the ventral part. The motor regions for the tongue, larynx, muscles of mastication, and pharynx lie in the frontal opercular part; and the movements of the head and eye are dominated by the medifrontal gyre, adjacent to the precentral. Re- calling the fact that the pyramidal (motor) tract decussates in its course to the primary motor centres, it follows that the motor centres in one cerebral hemisphere control the movements of the opposite side of the body. As elsewhere in the cortex, these motor areas gradually pass one into the other and the boundaries are indeterminate. The localization of motor function is rather for coordinated groups of muscles than for individual muscles; as a rule, the most powerful articulation, as the thigh and the shoulder, is localizable frontad in the respective limb centres, while the smaller articulations and those differentiated as regards motility (digits, etc.) are local- izable more posteriorly. 2. Sensor Areas. — (a) The area for tactile and temperature impressions is more intensely localized in the postcentral gyre and in corresponding order with its neighboring precentral motor areas; that is to say, there is the most intimate intercommunication between the sensor and the motor regions which preside over corresponding parts of the body. So closely coupled are the related sensor and motor cells in the highest category of the reflex arc system represented in the cerebral cortex that both sensor and motor areas are included under the term of somes- thetic or sensomotor area, devoted to the registration of cutaneous impressions, impressions The schema of the fissures from the muscles, tendons, and joints; in short, the sense of movement. The cortical area embraced by the parietal gyre, together with its extension in the precuneus on the mesal aspect, appears to be devoted to the concrete perception of the form and solidity of objects, and is therefore termed the stereognostic sense area. (6) The auditory area is localized in the middle and posterior thirds of the supertemporal gjTe and in the adjacent transtemporal gyres in the sylvian cleft. (c) The visual area is most intensely localizable in the region of the calcarine fissure as well as in the cuneus as a whole. There seems to be an interrelation between the visual function and the special type of cortex already described, and chiefly characterized by the stripe of Gennari. {d) The olfactory area comprises the uncus, frontal part of hippocampus, indusium, sub- callosal g}Te, |iarolfactory area, and anterior perforated substance. (e) The gustatory area has not yet been accurately localized; presumably it lies in the neigh- borhood of the olfactory area in the temporal lobe (uncinate and hippocampal gyre?). 3. The Language Areas. — The cortical zone of language comprises certain specialized areas which take part in the intimate relations of speech to thought expression, to memory, in its reading form to sight, in writing to manual muscular innervation, and in "word understanding" to hearing. (a) The emissive {articular) centre for speech is localized in the region of the junction of the subfioiital gyie with the precentral gyre — a region known to be intimately related to the control CORTICAL LOCALIZA TION OF FUNCTION 961 of the muscles used in speech (larynx, tongue, jaw muscles). Destruction of this region at least causes a loss or disturbance of articulation of words. (6) The auditory perceptive centre, clinically known as the centre of "word deafness," is localized in the marginal gyre and adjacent parts of the super- and meditcMi])oral gyres, espe- cially the latter. A patient suffering with a lesion of this area may cicaiiy liciir hut not under- stand the spoken word. This division of the centre might also be called the lalognmtic (word- understanding) centre. (c) The visual perceptive centre, clinically known as the centre of "word blindness," is local- ized in the angular gyre Lesion of this area renders the patient incapable of understand- ing the significance of the words and objects which he sees. (d) An emissive "writing" centre, not positively proved to exist, has been localized in the medifrontal gyre, frontad of the motor area for the upper limb. ((?) Of not a lift le importance with reference to the intellectual control of the faculty of language is the island of Reil, purely an association centre, serving to connect the various receptive sense areas relating to the understanding of the written and spoken word with the somesthetic emissary centre related to articulate speech and writing; in other words, a centre for language-arrangement. divaricated to expose the island of Reil. The union of the various centres enumerated above forms the cortical zone of language, and is most intensely, if not exclusively, localized, or at least, active, in the left cerebral hemi- sphere in right-handed persons, and vice versa in left-handed persons, 4. The Association Areas. — The remaining area of the cerebral cortex is presumably the organic substratum for the higher psychic activities. At the present time not much is known about them, but broadly stated the frontal association area is concerned rather with the powers of thought in the abstract — creative, constructive, and philosophic. The parieto-occipito- temporal association area, on the other hand, seems to be more concerned with the powers of concepliim of the concrete, for the comprehension of analogies, comparing, generalizing, and systemaliziiig things heard, observed, and felt. The great extent of the association areas in the human brain is a somatic expression of man's possession of an associative memory or ability to register and compare sensations far greater than that of the highest ape. The pattern of the ifissures and gyres in the brains of the higher anthro- poids and man presents the same general features in all these types. In the course of evolution, however, the regions known as association areas assumed a greater energy of growth and ex- panded in proportion to the rise in functional dignity of these areas. They are regions of " un- stable equilibrium" which afford greater and more complex associations as mental development goes on in the species, and concomitant with this great cortical expansion the associating or coordinating fibre systems became more elaborate, complex, and far-reaching. With the aid of the microscope the matin-ing of the brain elements can be followed from the earliest stages of embryonic life to the adult period. The Flechsig method has shown how the function of nerve fibres within the brain is only established when the myelin sheath has developed. 61 962 THE NERVE SYSTEM But this development of mature nerve fibres does not occur simultaneously throughout the brain, but step by step in a definite order of succession; equally important bundles are myelinated simultaneously, but those of dissimilar importance develop one after another in accordance with Flechsig's law. The successive myelinization of fibre bundles to and from the cerebral cortex corresponds to the successive awakenings of mental activities and faculties in the growing child. Flechsig's method of investigation has been of great service in the elucidation of the problems of cerebral localization. Craniocerebral Topography. — The position of the principal fissures and convolutions of the cerebrum and their relation to the outer surface of the scalp (Fig. 677) have been the subject of much investigation, and many systems have been devised by which one may localize these parts from an exploration of the external surface of the head. These plans can only be regarded as approximately correct for several reasons; in the first place, because the relations of the convolutions and fissures to the surface are found to be quite Fig. 722. — Drawing to illustrate t-r.-iniocerebra] topography. (Taken from a cast in the Museu College of Surgeons of Kngland, prepared by Professor Cunningham.) I of the Royal variable in different individuals; secondly, because the surface area of the scalp is greater than the surface area of the brain, so that lines drawn on the one cannot correspond exactly to fissures or convolutions on the other; thirdly, because the fissures and convolutions in two individuals are never precisely alike. Nevertheless, the principal fissures and convolutions can be mapped out with sufficient accuracy for all practical purposes, so that any particular convolution can be generally exposed by removing with the trephine, or by the flap method, a certain portion of the skull. An excellent method is given by Chipault in his Chirurgie operatoire du systeme nerveux, 1894, vol. i. The following systems have been the longest in vogue: The various landmarks on the outside of the skull, which can be easily felt, and which serve as indications of the position of the parts beneath, have been already referred to, and the rela- tion of the fissures and convolutions to these landmarks is as follows: Intercerebral or Longitudinal Fissure. — ^This corresponds to a line drawn from the glabella at the root of the nose to the external occipital protuberance. | CORTICAL LOCALIZATION OF FUNCTION 963 The Sylvian Fissure. — The position of the sylvian fissure is marked by a Hne starting from a point 3 cm. (I5 inches) horizontally behind the external angular process of the frontal bone to a point 2 cm. (5 inch) below the most prominent point of the parietal eminence. The first 2 cm. (5 inch) will represent the basisylvian fissure, the remainder the sylvian fissure proper. The sylvian point is therefore 5 cm. (2 inches) behind and about 1 cm. (| inch) above the level of the external angular process. The presylvian ramus of the fissure passes upward from this point parallel to, and immediately behind, the coronal suture. The Tentorial Hiatus or Transverse Fissure.— This is between the cerebrum and cere- bellum, and corresponds to a line drawn from the inion to the external auditory meatus. A r a/ s Supra orbital line (Superior Horizontal) K Ax B K' Orbital-auricular line ( Base line } Z A M Fig. 723. — Kronlein's method for determining the portions of certain fissures of the brain. Central Fissure. — To find the dorsal end of the central fissure, a measurement should be taken from the glabella to the external occipital protuberance. The position of the top of the fissure will be, measuring from in front, .5.5.6 per cent, of the whole distance from the glabella to the external occipital protuberance. Professor Thane adopts a somewhat simpler method. He divides the distance from the glabella to the external occipital protuberance over the top of the head into two equal parts, and, having thus defined the middle point of the vertex, he takes a point half an inch behind it as the top of the sulcus. This is not quite so accurate as the former method; but it is sufficiently so for all practical purposes, and on account of its simplicity is very generally adopted. From this point the fissure runs downward and forward for 9 to 10 cm. (3$ to 4 inches), its axis making an angle of about 70 degrees with the middle line. In order to mark this groove, two strips of metal may be employed — one, the shorter, being fixed to the middle of the other at the angle mentioned. If the longer strip is now placed along the sagittal suture so that the junction of the two strips is over the point corresponding to the top of the furrow , 964 THE NEB VE SYSTEM the shorter, oblique strip will indicate the direction and 9 to 10 cm. will mark the length of the furrow. Dr. Wilson has devised an instrument, called a cyrtometer, which combines the scale of measurements for localizing the fissure with data for representing its length and direction.' The Occipital Fissure on the dorsal surface of the cerebrum runs outward at right angles to the great longitudinal fissure for about 2 to 3 cm. (f to li inches), from a point 0.5 cm. (j inch) in front of the lambda. Reid states that if the sylvian line be continued onward to the sagittal suture, the last 2 to 3 cm. of this line will indicate the position of the fissure. The Precentral Fissure begins 2 cm. (| inch) in front of the middle of the central fissure and extends nearly, but not quite, to the sylvian fissure. The Superfrontal Fissure runs backward from the supraorbital notch, parallel with the line of the longitudinal fissure to 1 cm. (-| inch) in front of the line indicating the position of the central fissure. The Subfrontal Fissure follows the course of the supertemporal ridge on the frontal bone. The Intraparietal Fissure, comprising the parietal, subcentral, and paroccipital fissm-es, begins on a level with the junction of the middle and lower third of the central fissure, on a line carried across the head from the back of the root of one auricle to that of the other. After passing up- ward it curves backward, lying parallel to the longitudinal fissure, midway between it and the parietal eminence; then curves downward to end midway between the posterior fontanelle (lambda) and the parietal eminence. Kronlein's method for determining the portions of certain fissures of the brain is very useful and easy of application (Fig. 723). It is as follows: (1) The base line, Z M, is a horizontal line running at the level of the lower border of the orbit and the upper border of the e.xternal auditory meatus. (2) Another horizontal line, K K', is drawn parallel to Z M. The second horizontal line is on a level with the supraorbital ridge. (3) A vertical line, Z K, is erected from Z M at the middle of the zygoma and is carried to the line K K'. (4) Another vertical line, A R, is erected from the base line at the level of the articulation of the mandible and is carried to R. (5) A third vertical line, M P, is erected from the base line at the posterior border of the mastoid process and is carried to the middle line of the skull, which is marked P. (6) A line is drawn from K to P. The portion of this line between R and P' corresponds to the central fissure. (7) The angle P K K' is bisected by the line K S. K S corresponds to the sylvian fis- sure, and K is directly over the sylvian point. To reach the a^nterior branch of the middle meningeal, apply the trephine at K; to reach the posterior branch, apply it at K'. In abscess of the temporal lobe the trephine should be applied, according to von Bergmann, in the region AaKM. THE MENINGES, OR MENINGEAL MEMBRANES OF THE BRAIN (MENINGES ENCEPHALI). Dissection. — To examine the brain with its membranes, the skullcap must be removed. In order to effect this, saw through the external table, the section commencing, in front, about 2 cm. (i inch) above the margin of the orbits, and extending, behind, to a little above the level of the occipital protuberance. Then break the internal table with the chisel and hammer, to avoid injuring the investing membranes or brain; loosen and forcibly detach the skullcap, and the dura will be exposed. The adhesion between the bone and the dura often is very intimate, particularly along the sutures. The membranes of the brain are from without inward — tlie dura, arachnoid, and the pia. The Dura of the Brain (Dura Mater Encephali) (Figs. 724, 729). The dura of the brain is a thick and dense, inelastic, fibrous membrane which lines the interior of the sicull. It is a covering for the brain and is also the internal cranial periosteum. It is composed of two layers closely connected, except in certain situations, where, as already described (p. 721), they separate to form sinuses for the passage of venous blood. Upon the outer surface of the cranial dura, in the situation of the longitudinal sinus, may be seen numerous small whitish bodies, the glandulae Pacchionii (gramdationes arachnoideales). Its outer surface is rough and fibrillated, and adheres closely to the inner surface I Lancet. 1888, vol. i. d. 408 THE DURA OF THE BRAIN 965 of the bones, the adhesion being most marked opposite the sutures and at the base of the skuH. Its inner surface is smooth and Hned by a layer of endothelium. It sends inward four processes which divide the cavity of the skull into a series of freely communicating compartments, for the lodgement and protection of the different parts of the brain; and it is prolonged to the outer surface of the skull, through the various foramina whicii exist at the base, and thus becomes continuous with the pericranium; its fibrous layer forms sheaths for the nerves which pass through these aper- tures. At the base of the skull it sends a fibrous prolongation into the foramen cecum; it sends a series of tubular prolongations around the fila- ments of the olfactory nerves as they pass through the cribriform plate, and another around the nasal nerve as it passes through the nasal slit; a prolongation is also continued through the sphenoidal fissure into the orbit, and another is carried into the same cavity through the optic foramen, forming a sheath for the optic nerve, which is continued as far as the eyeball. In the posterior fossa it ^1 LAYER DOTHEI.IAL LINING Fig. 724. — The structure of the dura. Section through the cranial vault of a child, slightly enlarged. (Poirier and Charpy.) HRAGMA SELL AE Fig. 725.— The tentorium oerebell sends a process into the internal auditory meatus, ensheathing the facial and auditory nerves; another through the jugular foramen, forming a sheath for the structures which pass through this opening; and a third through the anterior con- dylar foramen. Around the margin of the foramen magnum it is closely adherent to the bone, and is continuous with the spinal dura. 966 THE NERVE SYSTEM Processes of the Dura {processus durae matris). — The processes of the dura which project into the cavity of the skull are formed by reduplication of the inner or meningeal layer of the membrane, and are four in number — the falx cerebri, the tentorium cerebelli, the falx cerebelli, and the diaphragma sellae. The falx cerebri (Figs. 725 and 726), so named from its sickle-like form, is a strong arched process which descends vertically in the intercerebral fissure between the two hemispheres of the brain. It is narrow in front, where it is attached to the crista galli of the ethmoid bone, and broad behind, where it is connected with the upper surface of the tentorium cerebelli. Its upper margin is convex, and attached to the inner surface of the skull, in the middle line, as far back as the internal occipital protuberance; it contains the superior or great longitudinal sinus {sinus sagittalis superior). Its lower rnargin is free, concave, and NTERNAL JUGULAR Fig. 726, --Falx cerebri and tentorium cerebelli. left lateral view. (Testut.) presents a sharp, curved edge, which contains the falcial or inferior longitudinal sinus {sinus sagittalis inferior). The tentorial or straight sinus {sinus rectus) is formed by the attachment of the falx cerebri to the tentorium cerebelli. The tentorium cerebelli (Figs. 725 and 726) is an arched lamina of dura, elevated in the middle and slightly inclined toward the circumference. It intervenes between the upper surface of the cerebellum and the occipital lobes of the cerebrum. It is attached, Isehind, by its convex border to the transverse ridges upon the inner surface of the occipital bone, and there encloses on each side the transverse or lateral sinus (sinus transversus); frontad, to the superior margin of the petrous por- tion of the temporal bone on either side, there enclosing the superpetrosal sinus {sinus petrosus superior); and at the apex of this bone the free or internal border and the attached or external border meet, and, crossing one another, are continued forward, to be attached to the anterior and posterior clinoid processes respectively. THE DURA OF THE BBAIN 967 Along the middle line of its upper surface the posterior border of the falx is attached, the tentorial or straight sinus being placed at their point of junction. Its frontal border is free and concave, and with the dorsum sellae forms a large oval opening. This opening is called the incisura tentorii and transmits the mesencephalon. The falx cerebelli (falcula) (Fig. 725) is a small triangular process of dura received into the indentation tjetween the two lateral lobes of the cereljellum behind. Its base is attached, above, to the under and back part of the tentorium cerebelli; its posterior margin, to the lower division of the vertical crest on the inner surface of the occipital bone. As it descends it sometimes divides into two smaller folds, which are lost on the sides of the foramen magnum. The diaphragma sellae (Fig. 725) is a small, circular, horizontal fold, which constitutes a roof for the sella turcica. This almost completely covers the hypophysis, presenting merely a small central opening (foramen diaphrac/matis sellae) for the passage of the infundibulum. Structure (Fig. 724). — The dura consists of \yhite fibrous tissue with connective-tissue cells and elastic fibres arranged in flattened lamintie, which are imperfectly sejiarated by lacunar spaces and bloodvessels into two layers, endosteal and meningeal. The endosteal layer is the internal periosteum for the cranial bones and contains the bloodvessels for their supply FALX CEREBELLI 1. Frontal section passing through the tentorium seen in the centre. (Poirier and Charpy.) FiQ. 727. — Crucial prolongation of the dui torcular herophili i At the margin of the foramen magniun it l)econies continuous with the periosteum lining the vertebral canal. The meningeal or supporting layer is lined on its inner surface by a layer of nucleated endothelium, similar to that found cm serous membranes. By its reduplication the meningeal layer forms the falx cerebri, the tentorium cerebelli and falx cerebelli, and the diaphragma sellae. The two layers are connected by fibres which intersect each other obliquely. The arteries of the dura (see section on Arteries) are very numerous, but are chiefly distributed to the bones. Those found in the anterior fossa are the anterior meningeal branches of the anterior and posterior ethmoidal and internal carotid, and a branch from the middle meningeal. Those in the middle fossa are the middle and small meningeal branches of the internal maxil- lary; a branch from the ascending pharyngeal, whiiii cnlcrs the .skull through (lie foramen lacerum medium; branches from the internal carotid, and a recurrent branch from the lac- rimal. Those in the jiosterior fossa are meningeal branches from the occipital, one of which enters the skull through the jugular foramen, and the other through the mastoid foramen; the posterior meningeal from thie vertebral; occasional meningeal branches from the ascending pharyngeal, which enter the skull through the jugular and anterior condylar foramina; and a branch from the middle meningeal. The veins which return the blood from the dura (see p. 717), and partly from the bones, anastomose with the diploic veins (see p. 727). They terminate in the various sinuses, with the exception of two which accompany the middle meningeal artery, and pass out of the skull at the foramen spinosum to join the internal maxillary vein; above, the meningeal veins communicate with the superior longitudinal sinus. The sinuses are considered on pages 721 to 727 inclusive. 968 THE NERVE SYSTE3I On either side of the superior longitudinal sinus, especially near its middle, and also near the lateral and straight sinuses, are numerous spaces in the dura which communicate with the sinus, either by a small opening or a distinct venous channel. These spaces are the parasinoidal sin- uses (lacunae laterales). Many of the meningeal veins do not open directly into the sinuses, but indirectl.Y tlu-ough the parasinoidal sinuses. These venous lacunae are often invaginated by arachnoid villi, and they communicate with the underlying cerebral veins, and also with the diploic and emissary veins. The nerves of the dura are filaments from the trochlear, the ophthalmic division of the tri- geminal, the semilunar or Gasserian ganghon, the vagus, the hypoglossal, and the sjonpa- thetic. The Arachnoid (Arachnoidea Encephali) (Fig. 728). The cranial arachnoid is a delicate membrane which envelops the brain, lying between the pia internally and the dura externally; from this latter membrane it is separated by a very fine slit or space, the subdural space (cavum subdurale). The subdural space contains a very minute quantity of fluid of the nature of lymph. OLFACTORY ARACHNOID FlQ. 728. — The arachnoid upon the base of the brain. On the right the arachnoid has been partly removed to show the cerebrum and cerebellum with their superficial veins. (Poirier and Charpy.) The arachnoid is prolonged upon emerging nerves and joins the lymph spaces of the nerves. The subdural space does not communicate with the subarachnoid space. The arachnoid invests the brain loosely, being separated from direct contact with the cerebral substance by the pia, and a quantity of loose areolar tissue, the subarachnoidean areolar tissue. On the upper surface of the cerebrum the arachnoid THE ARACHNOID 969 is thin and transparent, and may be easily demonstrated by injecting a stream of air beneath it by means of a blowpipe; it passes over the convolutions without dipping down into the fissures between them, but does pass into the sylvian and intercerebral fissures and is prolonged upon the nerves as a sheath. At the base of the brain the arachnoid is thicker, and slightly opaque toward the central part; it covers the orbital surface of the anterior lobes and extends across between the two temporal lobes so as to leave a considerable interval between it and the brain, the cistema basalis. The subarachnoid space (cavum subarachnoideale) (Fig. 729) is the interval between the arachnoid and pia. It is not only on the surface, but dips between the convolutions. It is not, properly speaking, a space, for it is occupied every- where by a spongy tissue consisting of trabecular of delicate connective tissue covered with endothelium, which pass from the pia to the arachnoid, and in the meshes of which the subarachnoid fluid is contained. This so-called space is small on the surface of the cerebrum ; but at the base of the brain the subarachnoid tissue is less abundant and its meshes larger. Emusarp vein Venous lacuna \ Cerebral vein Sup. longitufUnnl sinit^ Pacchionian body Subdural space Subaraclinoid space Dura mater Arachnoid Cerebral cortex -Diagrammatic representation of a section across the top of the skull, etc. (Modified from Testut.) the membranes of the brain, In certain regions the arachnoid and pia are farther apart than was pre\"iously indicated, and these spaces are called subarachnoid cisternse (cisternae svbarach- noidales). The largest space is the continuation of the posterior part of the sub- arachnoid space of the spinal cord. It is called the postcistema or cistema magna {cisierna cerebellomeduUaris) . It is a space formed by the arachnoid passing across the back and under portions of the medulla oblongata and cerebellum. It com- municates with the fourth ventricle by three foramina. The largest opening is the foramen of Magendie (apertura medialis ventrindi quarti; metapore). It is in the middle line of the tela choroidea. At the end of each recessus lateralis of the fourth ventricle there is also an opening, and each opening is called the foramen of Luschka or of Key and Retzius {apertura lateralis ventriculi quarti). The cisterna 970 THE NERVE SYSTEM pontis is the continuation upward of the anterior part of the subarachnoid space of the cord. About the medulla oblongata it is continuous with the postcisterna, so this important nerve centre is surrounded by a large subarachnoid space. The cistema basalis {cisterna interi)eduncularis) is formed by the arachnoid extending between the two temporal lobes. There is a cisterna between the inferior edge of the falx cerebri and the superior surface of the corpus callosum which contains the anterior cerebral arteries, a cisterna in the sylvian fissure {cisterna sijhiana) which contains the middle cerebral artery, and a cisterna between the corpora quadrigemina which contains the vena magna Galeni. The cerebrospinal fluid (coeliolympha; liquor cerebrosplnalis) fills the subarach- noid space. It is a clear, limpid fluid, having a saltish taste and a slightly alkaline reaction. According to Lassaigne, it consists of 98.5 parts of water, the remaining 1.5 per cent, being solid matters, animal and saline. It varies in quantity, being most abundant in old persons, and is quickly reproduced. Its chief use is probably to afford mechanical protection to the nerve centres, and to prevent the effects of concussions communicated from without. Structure. — The arachnoid consists of bundles of connective tissue, the fine fibres of which form one layer and cross each other in every direction. At the level of the large fissures, and especially around the circle of Willis, it is reenforced by thick fibrous tissue. Both surfaces are covered with endothelium. There are no bloodvessels in the arachnoid; the vessels which appear to be in it are really in the pia. There is no positive proof that nerves are present in the arachnoid. It is true that Bochdalek and Luschka long ago described arachnoid nerves, but these observations have never been corroborated. The Arachnoid Villi or Pacchionian Bodies (Granulationes Arachnoideales). The arachnoid villi, erroneously called glandulae Pacchioni, are numerous small whitish or purplish projections, usually collected into clusters of variable size, which are found in the following situations: (1) Upon the outer surface of the dura, in the vicinity of the superior longitudinal sinus, being received into small depressions on the inner surface of the calvarium. (2) On the inner surface of the dura. (3) In the superior longitudinal sinus and the other sinuses. A hasty examination would lead us to suppose that these bodies spring from the dura, but, as a matter of fact, they originate from the arachnoid. They are not glandular in structure, but are simply enlarged normal villi of the arachnoid. In their growth they appear to perforate the dura, and when a group of villi is of large size it causes absorption of the bone, and comes to be lodged in a pit or depression (foveola gramdaris [Pacchioni]) on the inner table of the skull. Their manner of growth is as follows: At an early period they project through minute holes in the inner layer of the dura, which open into large venous spaces situated in the tissues of the membrane, on either side of the longitudinal sinus and com- municating with it. In their onward growth the villi push the outer layer of the dura before them, and this forms over them a delicate membranous sheath. In structure they consist of spongy trabecular tissue, covered over by a membrane, which is continuous with the arachnoid. The space between these two coverings, derived from the dura and arachnoid respectively, corresponds to and is con- tinuous Avith the subdural space. The spongy tissue of which they are composed is continuous with the trabecular tissue of the subarachnoid space; so that fluid injected into the subarachnoid space finds its way into the Pacchionian bodies, and through their coverings filters into the superior longitudinal sinus. They are supposed to be a means of getting rid of an excess of cerebrospinal fluid when its quantity is increased £^bove normal, or for replenishing the cerebrospinal fluid from the blood plasma when needed. Another means of getting rid of THE PI A OF THE BRAIN 971 cerebrospinal fluid is absorption by the lymph spaces of the cranial nerves, which possess sheaths of arachnoid up to the points at which they emerge from the skulh These bodies are not found in infancy, and very rarely until the third year. They are usually found after the tenth year; and from this period they increase in number as age advances. Occasionally they are wanting. GALCNI Fig 730 — \ elum interpositum. (Poirier and Charpy.) The Pia of the Brain (Pia Mater EncephaU) (Figs. 729, 730). The pia of the brain is a vascular membrane, and derives its blood from the internal carotid and vertebral arteries. It consists of a minute plexus of blood- vessels held together by an extremely fine areolar tissue. It invests the entire surface of the brain, dipping down between the convolutions and laminae, and is prolonged into the interior, forming the velum interpositum and the choroid plexuses of the lateral and fourth ventricles. The velum interpositum or the tela chorioidea superior (tela chorioidea xen- triculi tertii) (Fig. 730) is the prolongation of the pia into the interior of the brain through the medium of the transverse fissure. It is a double triangular vascular fold, that lies between the body of the fornix above and the thalami and the epithelial roof of the third ventricle below, and passes forward to the foramen of Monro. At each edge of the velum interpositum is the choroid plexus {-plexus chorioideus ventriculi laieralis; paraplexus) of the corresponding lateral ventricle. In front the two plexuses join behind the foramen of Monro, and at the point of junction two lesser choroid plexuses pass back along the under surface of the velum interpositum to the third ventricle, the diaplexus or median plexus (plexus chorioideus ventriculi tertii). The velar veins or veins of Galen (p. 720) are two veins which lie on either side of the middle of the velum interpositum and pass back. Each velar vein is formed by the union of the vein from the corpus striatum and the choroid vein from the choroid plexuses. The two velar veins unite and form the vena magna (Galeni) , which empties into the straight sinus. The pia of the surfaces of the hemispheres, where it covers the gray substance 972 THE NEB VE SYSTEM of the convolutions, is very vascular, and gives off from its inner surface a multi- tude of minute vessels, which extend perpendicularly for some distance into the cerebral substance. At the base of the brain, in the situation of the anterior and posterior perforated substance, a number of long, straight vessels are given off, which pass through the white substance to reach the gray substance in the interior. On the cerebellum the membrane is more delicate, and the vessels from its inner surface are shorter. The pia of the spinal cord is thicker, firmer, and less vascular than that of the brain, and as it is traced upward over the medulla oblongata it is seen to preserve these characters. At the upper border of the medulla ob- longata it is prolonged over the lower half of the fourth ventricle, forming, before it is reflected onto the imder surface of the cerebellum, a covering for the fourth ^•ent^icle called the tela chorioidea inferior {tela chorioidea ventricidi quarti; metatela) ; this carries the choroid plexus of the fourth ventricle {plexus chorioideus ventricidi quarti). The arteries of the pia (see pp. 614, 617, and 621) (Figs. 4.50 and 451) are the anterior, middle, and posterior cerebral, anterior choroid and choroid, superior, anterior inferior, and posterior inferior cerebellar. (The vessels of the cerebral ganglionic system and of the cortical arterial system are considered on p. 618.) The veins of the pia (see pp. 719, 720, and 721) are the basilar vein, the velar veins (Fig. 730), the veins constituting the choroid plexuses of the third ventricle, the lateral ventricles, and the fourth ventricle; the cerebral veins (Fig. 728) and the cerebellar veins (Fig. 728). The nerves of the pia accompany the branches of the arteries and are derived chiefly from the sympathetic. A few fibres are derived from certain cranial nerves, all of which are prob- ably of the afferent variety. THE CRANIAL NERVES (NERVI CEREBRALES). The irregularities of origin and distribution of the cranial nerves, as compared with the relatively simple spinal nerves, are so great and their functions were for- merly so little known that the older anatomists contented themselves with number- ing them in order, beginning at the frontal end of the brain, and named them with reference to their anatomic connections. The enumeration of the cranial nerves was as variously given, almost, as there were writers upon the subject; the systems of Willis and of Sommering were most in vogue for a time, but the latter prevails today. In Sommering's arrangement twelve pairs of cranial nerves are recognized, but, on morphological and functional grounds, the nerves of the seventh and eighth pairs should each be considered as being composed of two nerves, the eleventh pair should be included with the nerves of the tenth, and the optic "nerve" is rather a diverticulum of the brain itself than a nerve in the strict sense. Furthermore, while some of the nerves are sensor or motor in a sense strictly comparable with the spinal nerves, others are mixed in function, and yet others constitute nerves of special sense and lack general sensibility. The numerical names, based upon the order in which they pass through the foramina in the base of the cranium, are being abandoned gradually for the more appro- priate functional names, but not yet entirely so. Thus glossopharyngeal has not yet given way to '''gustatory;" "vagus" is shorter than " pneumogastric" — a term which is misleading for a nerve which is distributed not only to lungs and stomach, but also to the meninges, the pharynx and oesophagus, larynx and trachea, heart and pericardium, liver and spleen. The cranial nerves, as usually enumerated, together with their superficial "origin" or attachment to the brain and their foramina of exit from the skull, are tabulated on page 849. The central olfactory pathway is described on page 958, and the central connections of the optic tracts are given on page 911. The central connections of the remaining cranial nerves are described on pages 877 to 902. THE FIRST OR OLFACTORY NERVE 973 The following is a brief summary of the twelve pairs of cranial nerves, indicating their functional nature: No. Name. Functional nature. I. Olfactory (fila). Smell sense. II. Optic. Visual sense. III. Oculomotor. Motor to muscles of eyeball and orbit. IV. Trochlear. Motor to Superior oblique muscle of eyeball. V. Trigeminal. Mixed: Sensor to face, tongue, and teeth; motor to muscles of mastication. VI. Abducent. Motor to External rectus muscle of eyeball. VII. Facial. Motor to muscles of scalp and face. Nervus intermedins. Mixed: Sensor (gustatory) to tongue; excitoglandular to submaxillary and sublingual salivary glands. VIII. Acoustic: I. Cochlearis. Hearing sense. II. Vestibularis. Equilibratory. IX. Glossopharyngeal. Mixed- Sensor (and gustatory) to tongue and pharynx; motor ( ?) to Stylopharyngeus muscle. X. Vagus. Mixed : Sensorimotor to respiratory tract and part of ali- mentary tract. XI. Spinal accessory. I. Accessory to vagus. Motor to muscles of palate, pharynx, etc.; respiratory or- gans; inhibitory to heart. II. Spinal part. Motor to Trapezius and Sternomastoid muscles. XII. Hypoglossal. Motor to muscles of tongue. THE FIRST OR OLFACTORY NERVE (N. OLFACTORIUS). The olfactory nerves or fila are the special nerves of the sense of smell, and are about twenty in number on each side. These filaments constitute the first or olfactory nerves and are the axones of the olfactory cells, lying in the small olfac- tory region in the upper part of the superior turbinated process of the ethmoid and corresponding portion of the nasal septum and are macroscopically differenti- ated from the respiratory region in being of a more brownish hue (Fig. 731)., The olfactory fila are arayelinic and exhibit a plexiform arrangement in the deeper layers. After piercing the cribriform plate of the ethmoid they become attached to the under surface of the olfactory bulb, an oval mass of a grayish color, which rests on the cribriform plate of the ethmoid bone and forms the anterior expanded extremity of a slender process of brain substance, named the olfactory tract. The olfactory tract and bulb have already been described (p. 927). The olfactory tubercle (trigonum olfactoriunn) is a small triangular mass of gray substance between the diverging roots of the optic tract (p. 928). Each nerve is surroimded by tubular prolongations from the dura and pia, the former being lost on the periosteum lining the nose, the latter in the neuri- lemma of the nerve. The nerves, as they enter the nares, are divisible into two groups — an inner group, larger than those on the outer wall, spread out over the upper third of the septum; and an outer set, which is distributed over the superior turbinated process and the surface of the ethmoid in front of it. As the filaments descend, they appear to unite in a plexiform network, and are believed by most observers to terminate by becoming continuous with the deep extremities of the olfactory cells. The olfactory nerves differ in structure from other nerves in being composed exclusively of amyelinic fibres. They are deficient in the white substance of Schwann, and consist of axones with a distinct nucleated sheath, in which there are, however, fewer nuclei than in ordinary amyelinic fibres. The central olfactory pathways are described on page 958). 974 THE NER VE SYSTEM Applied Anatomy. — Destruction of the olfactory tract of one side causes loss of smell {anos- mia) on the side of the injury, because the olfactory tract is practically uncrossed. In severe injuries to the head the olfactory bulb may become separated from the olfactory nerves, thus producing loss of the sense of smell, and with this a considerable loss in the sense of taste, as much of the perfection of the sense of taste is due to the sapid substances, being also odorous and Fig. 731. — Extent of true olfactory mucous membrane simultaneously exciting the sense of smell. When the sense of smell is lost, an individual cannot distinguish the flavor of food, but he can distinguish that a substance is salt, or sweet, or bitter, or acid. The most usual cause of injury to the olfactory nerve is fracture of the base of the skull, the line of fracture passing through the cribriform plate of the ethmoid bone, but a blow upon the face, forehead, or back of the head which does not produce fracture may injure the nerves. THE SECOND OR OPTIC NERVE (N. OPTICUS). The fibres of the optic nerve, the special nerve of the sense of sight, are the central processes of the retinal ganglion cells which, after converging to the optic papilla, leave the eyeball by piercing its fibrous and vascular tunics as a cylindric cord. The point of emergence is situated a little mesad (3 to 4 mm. — \ to ^ inches) of the posterior pole of the globe. Behind the eyeball the nerve passes back- ward and inward through the orbital fat and optic foramen to enter the middle fossa of the cranium. The total length of the nerve averages 45 to 50 mm. (If to 2 inches). The two nerves converge to decussate partially, forming the chiasm. The optic chiasm (chiasma opticum) (Figs. 732 and 733 and p. 910) is somewhat quadrilateral in form, rests upon the olivary eminence and on the anterior part of the diaphragma sellae, being bounded above by the lamina terminalis; behind by the tuber cinereum; on either side by the anterior perforated substance. Within the commissure the optic nerves of the two sides undergo a partial decussation (Figs. 672 and 733), described in detail on pages 910 and 911. THE SECOND OR OPTIC NER VE 975 From the optic chiasm the optic tracts wind as flattened bands obliquely caudo- laterad around the crura cerebri to subdivide, each into two bands, one (mesal root) passing to the medial geniculate body and not a true continuation of the optic path (see Gudden's commissure, p. 910), the other (lateral root) passing to the lateral geniculate body, the pulvinar, and the superior quadrigeminal body (p. 910). The optic path has been described on pages 909 to 911. Applied Anatomy. — The optic nerve is peculiarly liable to become the seat of neuritis or undergo atrophy in affections of the central nerve system, and, as a rule, the pathological rela- tionship between the two affections is exceedingly difficult to trace. There are, however, certain points in connection with the anatomy of this nerve which tend to throw light upon the frequent association of these affections with intracranial disease: (1) From its mode of development and from its structure the optic nerve must be regarded as a prolongation of the brain substance, rather than as an ordinary cerebrospinal nerve. (2) As it passes from the brain it receives sheaths from the three cerebral membranes — a perineural sheath from the pia, an intermediate sheath from the arachnoid, and an outer sheath from the dura, which is also connected with the periosteum as it passes through the optic foramen. These sheaths are separated from each other by spaces which communicate with the subdural and subarachnoid spaces respectively. The innermost or perineural sheath sends a process around the arteria centralis retinae into the interior of the nerve, and enters immediately into its structure. Thus, inflammatory infections of the meninges or of the brain may readily extend themselves along these spaces or along the interstitial connective tissue in the nerve. To optic nerve ^^^ of same side. ^^^0/ opposite side. Fig. 732.— The left optic nerve and optic tracts. Fig. 733. — Course of the fibres in the optic chiasm. The course of the fibres in the optic chiasm has an important pathological bearing, and has been the subject of much controversy. Microscopic examination, experiments, and pathology all seem to point to the fact that there is a partial decussation of the fibres, each tract supplying the corresponding half of each eye, so that the right tract supplies the right half of each eye, and the left tract the left half of each eye. At the same time, Charcot believes — and his view has met with general acceptation — that the fibres which do not decussate at the optic chiasm will decussate in the corpora quadrigemina, so that lesion of the cerebral centre of one side causes complete blindness of the opposite eye, because both sets of decussating fibres are destroyed. Whereas should one tract — say the right — be destroyed by disease, there will be blindness of the right half of both retinte. A sagittal section through the optic chiasm would divide the decussating fibres, and would therefore produce blindness of the inner half of each eye; while a section at the margin of the side of the optic chiasm would produce blindness of the external half of the retina of the same side. The optic nerve may also be affected in injuries or diseases involving the orbit, in fractures of the anterior fossa of the base of the skull, in tumors of the orbit itself, or those invading this cavity from neighboring parts. 976 THE NEBVE SYSTEM Tnfratrochlem nerve. ~~ THE THIRD OR OCULOMOTOR NERVE (N. OCULOMOTORroS) (Figs. 734, 735). The third or oculomotor nerve supplies all the muscles of the orbit except the Superior oblique and External rectus; it also supplies, through its connection with the ciliary ganglion, the Sphincter muscle of the iris and the Ciliary muscle. It is a rather large nerve, of cylindric form and firm texture. Its apparent origin is from the oculomotor groove along the ventromesal border of the crus. The deep origin may be traced through the substantia nigra, red nucleus, and tegmentum of the crus to a nucleus situated on either side of the median line beneath the floor of the aqueduct. The nucleus of the oculomotor nerve also receives fibres from the abducent nerve of the opposite side. The nucleus of the oculomotor nerve, considered from a physiological standpoint, can be subdivided into several smaller groups of cells, each group controlling a particular muscle (see p. 901). On emerging from the brain, the nerve is invested with a sheath of pia, and enclosed in a prolongation from the arachnoid. It passes between superior cerebellar and posterior cerebral arteries, and then pierces the dura in front of and external to the posterior clinoid process, passing between the two processes from the free and attached borders of the tentorium, which are prolonged forward to be con- nected with the anterior and poste- rior clinoid processes of the sphe- noid bone. It passes along the outer wall of the cavernous sinus (Figs. 505 and 506); above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympa- thetic, and a communicating branch from the first division of the tri- geminal nerve. It then divides into two branches, which enter the orbit through the sphenoidal fissure, be- tween the two heads of the External rectus muscle (Fig. 734). On passing through the fissure, the nerve is placed below the trochlear nerve and the frontal and lacrimal branches of the ophthalmic nerve, while the nasal nerve is placed between its two divisions (Fig. 743). The superior division (ramus superior) (Fig. 735), the smaller, passes inward over the optic nerve, and supplies the Superior rectus and Levator palpebrae muscles. The inferior division (ramus inferior) (Fig. 735), the larger, divides into three branches. One passes beneath the optic nerve to the Internal rectus; another, to the Inferior rectus; and the third, the longest of the three, passes forward between the Inferior and External recti to the Inferior oblique. From Motor » Sensory root. Fig. 734. — Nerves of the orbit, seen from above. iciirrent filo^ment to dura mater. THE FOURTH OR TROCHLEAR NERVE 977 this latter a short, thick branch, radix brevis ganglii ciliaris, is given off to the lower ])art of the ciliary or lenticular ganglion and forms its short or motor root (Figs. 735 and 738). All these branches enter the muscles on their ocular surface, except that to the Inferior oblique, which enters its posterior border. Applied Anatomy. — Paralysis of the oculomotor nerve may be the result of many causes: as cerel)ral disease; conditions causing pressure on the cavernous sinus; periostitis of the bone entering into the formation of the sphenoidal fissure; fracture of the orbit. It results, when complete, in (1) ptosis, or drooping of the upper eyelid, in consequence of the Levator palpebrae being paralyzed; (2) external strabismus, on account of the unopposed action of the External rectus muscle, which is not supplied by the oculomotor nerve, and is not therefore paralyzed; (.3) dilatation of the pupil, because the sphincter fibres of the iris are paralyzed; (4) loss of power of accommodation, as the Sphincter pupillje, the Ciliary muscle, and the Internal rectus are paralyzed; (5) slight prominence of the eyeball, owing to most of its muscles being relaxed. ^^Ocutomotor Nerve Fig. 735.— Plan of the oculomotor nerve. Occasionally paralysis may affect only a part of the nerve; that is to say, there may be, for ex- ample, a dilated and fixed pupil, with ptosis, but no other signs. Irritation of the nerve causes spasm of one or other of the muscles supplied by it; thus, there may be internal strabismus from spasm of the Internal rectus; accommodation for near objects only from spasm of the Ciliary muscle, or contraction of the pupil (myosis), from irritation of the sphincter of the pupil. The oculomotor nerve is particularly liable to become involved in a syphilitic periarteritis where it passes between the superior cerebellar and posterior cerebral arteries; associated with locomotor ataxia various partial or complete paralyses of the nerve are often seen. THE FOURTH OR TROCHLEAR NERVE (N. TROCHLEARIS) (Figs. 633, 734). The fourth or trochlear nerve is, with the exception of the n. intermedius, the smallest of the cranial nerves, and supplies the Superior oblique muscle. It arises from a nucleus in the floor of the mid-brain aqueduct at t!ie level of the inferior quadrigeminal body. From its origin the nerve runs outward, curving around the central aqueduct gray to turn inward and l)ackward into the superior medullary velum, decussating with the corresponding nerve of the opposite side and emerging from the surface laterad of the frenulum veli, immediately behind (or caudad of) the posterior quadrigeminal body. Emerging from the superior medullary velum, the nerve is directed outward across the superior peduncle of the cerebellum, and then winds forward around the outer side of the crus cerebri, immediately above the pons, pierces the dura in the free border of the tentorium, just behind, and external to, the posterior clinoid process, and passes forward in the outer wall of the cavernous sinus, between the oculomotor nerve and the ophthalmic division of the trigeminal nerve (Figs. 505 and 506). It crosses the oculomotor nerve and enters the C2 978 THE NEB VE SYSTEM orbit through the sphenoidal fissure (Fig. 743). It now becomes the highest of all the nerves, lying at the inner extremity of the fissure internal to the frontal nerve. In the orbit it passes inward, above the origin of the Levator palpe- brae, and finally enters the orbital surface of the Superior oblique muscle. Branches of Communication. — In the outer wall of the cavernous sinus it forms communications with the cavernous plexus of the sympathetic and with the ophthalmic division of the trigeminal nerve. In the sphenoidal fissure it occa- sionally gives oS a branch to assist in the formation of the lacrimal nerve. Branches of Distribution. — It gives off a recurrent branch, which passes backward between the layers of the tentorium cerebelli, dividing into two or three filaments whicli may be traced as far back as the wall of the lateral sinus. Applied Anatomy. — The trochlear nerve when paralyzed causes loss of function in the Su- perior oblique, so that the patient is unable to turn his eye downward and outward. Should the patient attempt to do this, the eye on the affected side is twisted inward, producing diplopia or double vision. Accordingly, it is said that the first symptom of this disease which presents itself is giddiness when going down hill or in descending stairs, owing to the double vision produced by the patient looking at his steps while descending. THE FIFTH, TRIGEMINAL, OR TRIFACIAL NERVE (N. TRIGEMINUS) (Figs. 737, 738). The fifth, trigeminal, or trifacial nerve is the largest cranial nerve. It resembles a spinal nerve (1) in having two roots, motor and sensor; (2) in having a ganglion developed on its sensor root. It is the great sensor nerve of the head and face and the motor nerve of the muscles of mastication ; its upper two divisions are entirely sensor, the third division is partly sensor and partly motor. It arises by two roots; of these, the ventral is the smaller, and is the motor root (Fig. 649) ; the dorsal, the larger and sensor root. It emerges from the side of the pons near the upper border, by a small motor and a large sensor root. The small root consists of three or four bundles; the large root consists of numerous bundles of fibres, varying in number from seventy to a hundred. The two roots are separated from each other by a few of the transverse fibres of the pons. The deep termination of the large or sensor root is chiefly in a long tract in the medulla oblongata, the lower sensor nucleus, which is continuous below with the substantia gelatinosa Rolandi. The fibres from this nucleus form the so-called ascending root of the fifth nerve ; they pass upward through the pons and join with fibres from the upper sensor nucleus (Fig. 650), which is situated to the outer side of the motor nucleus, from which the lower part of the motor root takes origin. The deep origin of the small or motor root is derived partly from a nucleus embedded in tlie gray substance of the upper part of the floor of the fourth ventricle and partly from a collection of nerve cells situated at the side of the aqueduct from which the fibres pass caudad under the name of the mesencephalic or descending root of the fifth nerve (Fig. 650). The two roots of the nerve pass forward below the tentorium as it bridges over the notch on the inner part of the superior border of the petrous portion of the temporal bone (Fig. 737) ; they then run between the bone and the dura to the apex of the petrous portion of the temporal bone, where the fibres of the sensor root appear to enter into the formation of the large semilunar or Gasserian ganglion (Figs. 736 and 737), while the motor root passes beneath the ganglion without having any connection with it, and joins outside the cranium with one of the trunks derived from it (Figs. 736 and 737). The Gasserian or semilunar ganglion^ (ganglion semilunare) (Figs. 736 and 737) is lodged in an osteofibrous space, the cavum Meckelii (Fig. 726), near the 1 A Viennese anatomist, Raimund Balthasar Hirsch (1765), was the first who recognized the ganglionic nature of the swelling on the sensor root of the fifth nerve, and called it, in honor of his otherwise unlinown teacher, Jon. Laur, Gasser, the "Ganglion Gasseri." Julius Casserius. whose name is given to the musculocutaneous nerve of the arm, was professor at Padua, 1.545 to 1605. (See Hyrtl. Lehrbuch der Anatomis, p. 895 and p. 55.) THE FIFTH, TRIGEMINAL, OB TRIFACIAL NERVE 979 apex of the petrous portion of the temporal bone. The ganglion is of somewhat crescentic form, with its convexity turned forward. Its upper surface is intimately adherent to the dura. Besides the small or motor root, the large superficial petrosal nerve lies underneath the ganglion. MOTOR PORTION Fig. 736.— The right semilunar or G; NERVE on, viewed from the medial aide. (Enlarged.) (Spalteholz.) Branches of Communication. — This ganglion receives on its inner side filaments from the carotid plexus of the sympathetic. Branches of Distribution. — It gives off minute branches to the tentorium cerebelli and the dura in the middle fossa of the cranium. From its anterior (convex) harder, which is directed forward and outward, three large branches proceed — • the ophthalmic, superior maxillary, and inferior maxillary. The ophthalmic and superior maxillary consist exclu- sively of fibres derived from the large root and ganglion, and are solely nerves of common sensation. The third division, or inferior maxillary, is joined outside the cranium by the motor root, and is, therefore, strictly speaking, the only portion of the tri- geminal nerve which can be said to resemble a spinal nerve. Associated with the three divisions of the trigeminal nerve are four small ganglia — the ophthalmic, sphenopala- tine, otic, and submaxillary ganglia. The ophthalmic nerve (/(. ophthal- micus), or first division of the tri- geminal, is a sensor nerve. It supplies sensor branches to the cornea, ciliary muscle, and iris^ to the lacrimal gland, to a part of the mucous lining of the nasal fossae, and to the integument of the eyelids, eyebrow, forehead, and nose (Fig. 742). It is the smallest of the three divisions of the fifth, arising from the upper part of the Gasserian ganglion. It is a short, flattened band, about 2 cm. (4 inch) in length, which passes forward PETROSAL SINUS SENSOR ROOT -The course of the motor root of the trigeminal nerve. (Poirier and Charpy.) 980 THE NERVE SYSTEM along the outer wall of the cavernous sinus (Figs. 505 and 506) , below the oculo- motor and trochlear nerves (Fig. 736), and just before entering the orbit, through the sphenoidal fissure, divides into three branches — lacrimal, frontal, and nasal. Branches of Communication. — The ophthalmic nerve is joined by filaments from the cavernous plexus of the sympathetic, and gives off minute branches to communicate with the oculomotor and abducent nerves, and not infrequently with the trochlear. Branches of Distribution. — It gives off recurrent filaments {n. tentorii) which pass between the layers of the tentorium cerebelli, and then divides into — Lacrimal. Frontal. Nasal. The lacrimal nerve (n. lacrimalis) (Figs. 738 and 739) is the smallest of the three branches of the ophthalmic. It sometimes receives a filament from the trochlear nerve, but this is possibly derived from the branch of communication which passes from the ophthalmic to the trochlear. It passes forward in a separate tube of dura, and enters the orbit through the narrowest part of the sphenoidal fissure (Fig. 743). In the orbit it runs along the upper border of the External rectus muscle, with the lacrimal artery, and communicates with the temporomalar branch of the superior maxillary nerve. It enters the lacrimal gland and gives ofl^ several filaments, which supply the gland and the conjunctiva. Finally, it pierces the superior palpebral ligament, and terminates in the integument of the upper eyelid, joining with filaments of the facial nerve. The lacrimal nerve is occasionally absent, when its place is taken by the temporal branch of the superior maxillary. Sometimes the latter branch is absent, and a continuation of the lacrimal is substituted for it. The frontal nerve (ji. frontalis) (Figs. 734 and 738) is the largest division of the ophthalmic, and may be regarded, both from its size and direction, as the continu- ation of the nerve. It enters the orbit above the muscles, through the sphenoidal fissure (Fig. 738), and runs forward along the middle line, between the Levator palpebrae and the periosteum. Midway between the apex and the base of the orbit it divides into two branches, supratrochlear and supraorbital. The supratrochlear branch («. supratrochlearis) (Fig. 734) the smaller of the two, passes inward, above the pulley of the Superior oblique muscle, and gives off a descending filament, which joins with the infratrochlear branch of the nasal nerve. It then leaves the orbit between the pulley of the Superior oblique and the supraorbital foramen, curves up on to the forehead close to the bone, ascends beneath the Corrugator supercilii and Occipitofrontalis muscles, and, dividing into branches which pierce these muscles, it supplies the integument of the lower part of the forehead on either side of the middle line and sends filaments to the conjunctiva and skin of the upper eyelid. The supraorbital branch (/l swpraorhitalis) (Fig. 743) passes forward through the supraorbital foramen, and gives off, in this situation, palpebral filaments to the upper eyelid. It then ascends upon the forehead, and terminates in cutaneous and pericranial branches. The cutaneous branches, two in number, an inner and an outer, supply the integument of the cranium as far back as the vertex. They are at first situated beneath the Occipitofrontalis, the inner branch perforating the frontal portion of the muscle, the outer branch its tendinous aponeurosis. The pericranial branches are distributed to the pericranium over the frontal and parietal bones. The nasal nerve («. nasociliaris) (Figs. 734 and 738) is intermediate in size between the frontal and lacrimal, and is more deeply placed than the other branches of the ophthalmic. It enters the orbit by way of the sphenoidal fissure (Fig. 743) between the two heads of the External rectus, and passes obliquely inward across the optic nerve, beneath the Superior rectus and Superior oblique muscles, THE FIFTH, TRIGEMINAL, OB TRIFACIAL NERVE 981 to the inner wall of the orbit. Here it passes through the anterior ethmoidal foramen, and, entering the cavity of the cranium, traverses a shallow groove on the front of the cribriform plate of the ethmoid bone, and passes down, through the slit by the side of the crista galli, into the nose (Fig. 740), where it divides into two branches, an internal and an external branch. The internal branch (rami nasales mediales) supplies the mucous membrane near the fore part of the septum of the nose. The external branch (rami nasales laterales) descends in a groove on the inner surface of the nasal bone, and supplies a few filaments to the mucous membrffne covering the fore part of the outer wall of the nares as far as the inferior turbinate process; it then leaves the cavity of the nose, between the. lower border of the nasal bone and the upper lateral cartilage of the nose, and, passing down beneath the Compressor nasi, supplies the integument of the ala and the tip of the nose, joining with the facial nerve. The branches of the nasal nerve are the ganglionic, long ciliary, and infratrochlear. The ganglionic branch or the long root of the ciliary ganglion [radix loiiga (janglii ciliaris) (Figs. 735 and 738) is a slender branch, about 1 to 2 cm. in length, which usually arises from the nasal nerve, between the two heads of the External rectus Fig. 738. — Nerves of the orbit and ophthalmic ganglion, side muscle. It passes forward on the outer side of the optic nerve, and enters the postero-superior angle of the ciliary ganglion, forming its long root. It is some- times joined by a filament from the cavernous plexus of the sympathetic or from the superior division of the oculomotor nerve. The long ciliary nerves (nn. ciliares longi), two or three in number, are given off from the nasal as it crosses the optic nerve. They accompany the short ciliary nerves (Figs. 735 and 738) from the ciliary ganglion, pierce the posterior part of the sclera, and, running forward between it and the choroid, are distributed to the Ciliary muscle, iris, and cornea. The infratrochlear branch (n. infratrochlear is) (Fig. 734) is given off just before the nasal nerve passes through the anterior ethmoidal foramen. It runs forward along the upper border of the Internal rectus muscle, and is joined, beneath the pulley of the Superior oblique, by a filament from the supratrochlear nerve. It then passes to the inner angle of the eye, and supplies the integument of the eyelids and side of the nose, the conjunctiva, the lacrimal sac, and the cariuicula lacrimalis. 982 THE NERVE SYSTEM The ophthalmic, lenticular, or ciliary ganglion (ganglion ciliare) is a small, quad- rangular, flattened ganglion of a reddish-gray color, and about the size of a pin's head, situated at the back part of the orbit between the optic nerve and the External rectus muscle, lying generally on the outer side of the ophthalmic artery. It is enclosed in a quantity of loose fat, which makes its exposure by dissection some- what difficult. Its branches of communication or roots are three, all of which enter its posterior border. One, the long or sensor root (radix longa gamjlii ciliaris), is derived from the nasal branch of the ophthalmic and joins its postere-superior angle. The second, the short or motor root (radix brevis ganglii ciliaris), is a short, thick nerve, occasionally divided into two parts, which is derived from the branch of the oculomotor to the Inferior oblique muscle, and is connected with the postero- inferior angle of the ganglion. The third, the sympathetic root (radix sympa- thetica ganglii ciliaris), is a slender filament from the cavernoua plexus of the sympathetic. This is frequently blended with the long root, although it some- times passes to the ganglion separately. The ganglion occasionally receives a filament of communication from the sphenopalatine ganglion. Its branches of distribution are the short ciliary nerves (nu. ciliares breves) (Figs. 735 and 738). These are delicate filaments, from six to ten in number, which arise from the fore part of the ganglion in two bundles, connected with its superior and inferior angles; the lower bundle is the larger. They run forward with the ciliary arteries in a wavy course, one set above and the other below the optic nerve, and are accompanied by the long ciliary branches of the nasal nerve. They pierce the sclera at the back part of the globe, pass forward in delicate grooves on its inner surface, and are distributed to the Ciliary muscle, iris, and cornea. One small branch is said to penetrate the optic nerve with the arteria centralis retinae. The superior maxillary nerve (u. maxillaris) (Figs. 734 and 737), or second division of the trigeminal, is a sensor nerve. It is intermediate, both in position and size, Ijetween the ophthalmic and inferior maxillary. It commences at the middle of the Gasserian ganglion as a flattened plexiform band, and, passing horizontally forward, it leaves the skull through the foramen rotundum, where it becomes more cylindrical in form and firmer in texture. It then crosses the sphenomaxillary fossa (Fig. 67), inclines outward on the back of the maxilla, and enters the orbit through the sphenomaxillary fissure; it traverses the infra- orbital canal in the floor of the orbit, and appears upon the face at the infra- orbital foramen.^ At its termination the nerve lies beneath the Levator labii superioris muscle, and divided into a leash of branches, which spread out upon the side of the nose, the lower eyelid, and upper lip, joining with filaments of the facial nerve. Branches of Distribution. — The branches of this nerve may be divided into four groups: (1) Those given off in the cranium. (2) Those given off in the spheno- maxillary fossa. (3) Those in the infraorbital canal. (4) Those on the face. In the cranium .... Meningeal or dural. ( Orbital or temporomalar. Sphenomaxillary fossa . j Sphenopalatine. V Posterior superior dental. Infraorbital canal . . . | Middle superior dental ( Anterior superior dental, r Palpebral. On the face . . . . j Nasal. V Labial. ' After it enters the mfrax>rbital canal the nerve is usually called the infraorbital (n. infraorhitalis), and is, therefore, the terminal branch, of the superior maxillary nerve (Fig. 742J. THE FIFTH, TRIGEMINAL, OB TRIFACIAL NERVE 983 The Meningeal or Dural Branch (n. meiiiiigeiis medius) is given off from the supe- rior maxillary nerve directly after its origin from the Gasserian ganglion; it accom- panies the middle meningeal artery and supplies the dura of the middle fossa of the base of the skull. The Orbital or Temporomalar Branch {n. zygomaticus) (Figs. 738 and 739) arises in the sphenomaxillary fossa, enters the orbit by the sphenomaxillary fissure, and divides at the back of that cavity into two branches, temporal and malar. The temporal branch (ramus zygomaticotemporalis) runs along the outer wall of the orbit in a groove in the malar bone, receives a branch of communication from the lacrimal, and, passing through a foramen in the malar bone, enters the temporal fossa. It ascends between tlae bone and the substance of the Temporal muscle, pierces this muscle and the temporal fascia about an inch above the 739. — Distribution of the second and third divisions of the trigeminal d submaxillary ganglion. zygoma, and is distributed to the integument coveiing the temple and side of the forehead, communicating with the facial and the auriculotemporal branch of the inferior maxillary nerve. As it pierces the temporal fascia it gives oft" a slender twig, which runs between the two layers of the fascia to the outer angle of the orbit. The malar branch (ramus zygomaticofacialis) passes along the external inferior angle of the orbit, emerges upon the face through a foramen in the malar bone, and, perforating the Orbicularis palpebrarum muscle, supplies the skin on the prominence of the cheek, where it is named the subcutaneus malae. It joins with the facial and the palpebral branches of the superior maxillary. The Sphenopalatine Branches (/(/(. sphetwpalafiiu (Fig. 739), two in number, descend to the sphenopalatine ganglion, of which ganglion they are the sensor or short roots. 984 THE NERVE SYSTEM The Posterior Superior Dental Branches {rami aheolares superiores jMsteriores) (Fig. 739) arise from the trunk of the nerve just as it is about to enter the infra- orbital canal; they are generally two in number, but sometimes arise by a single trunk, and immediately divide and pass downward on the tuberosity of the maxilla. They give off several twigs to the gums and neighboring parts of the mucous membrane of the cheek, superior gingival branches (rami gingivales superiores). They then enter the posterior dental canals on the zygomatic surface of the maxilla, and, passing from behind forward in the substance of the bone, communicate with the middle dental nerve by a plexus formation, and give off branches to the lining membrane of the antrum and three twigs to each molar tooth. These twigs enter the foramina at the apices of the fangs and supply the pulp. The Middle Superior Dental Branch (ramus alveolaris superior medius) is given off from the superior maxillary nerve in the back part of the infraorbital canal, and runs downward and forward in a special canal in the outer wall of the antrum to supply the two bicuspid teeth. It communicates with the posterior and anterior dental branches by a plexus formation {plexus dentalis superior). At its point of communication with the posterior branch, above the root of the second bicuspid tooth, is a slight thickening which is the so-called ganglion of Valentin; and at its point of communication with the anterior branch is a second enlargement, which is called the ganglion of Bochdalek. Neither of these is a true ganglion. The Anterior Superior Dental Branch {ramus alveolaris superior anteriores), of large size, is given off from the superior maxillary nerve just before its exit from the infraorbital foramen; it enters a special canal in the anterior wall of the antrum, and divides into a series of branches which supply the incisor and canine teeth. It communicates with the middle dental nerve by a plexus, and gives off a nasal branch, which passes through a minute canal into the nasal fossa, and supplies the mucous membranes of the fore part of the inferior meatus and the floor of the cavity, commimicating with the nasal branches from the sphenopalatine ganglion. The Palpebral Branches {rami palpebrales inferiores) pass upward beneath the Orbicularis palpebrarum muscle. They supply the integument and conjunctiva of the lower eyelid, joining at the outer angle of the orbit with the facial nerve and the malar branch of the orbital. The Nasal Branches (rami nasales interni) pass inward; they supply the integu- ment of the side of the nose and join with the nasal branch of the ophthalmic. The Labial Branches (rami labiales superiores), the largest and most numerous, descend beneath the Levator labii superioris muscle, and are distributed to the integument of the upper lip, the mucous membrane of the mouth, and the labial glands. All these branches are joined, immediately beneath the orbit, by filaments from the facial nerve, forming an intricate plexus, the infraorbital plexus. The Sphenopalatine or Meckel's Ganglion {ganglion sphenopalafiimm) (Fig. 740), the largest of the ganglia associated with the branches of the trigeminal nerve, is deeply placed in the sphenomaxillary fossa, close to the sphenopalatine foramen. It is triangular or heart-shaped, of a reddish-gray color, and is situated just below the superior maxillary nerve as it crosses the fossa. Branches of Communication. — Like the other ganglia of the trigeminal nerve, it possesses a motor, a sensor, and a sympathetic root. Its sensor root is derived from the superior maxillary nerve through its two sphenopalatine branches (p. 983). These branches of the nerve, given off in the sphenomaxillary fossa, descend to the ganglion. Their fibres, for the most part, pass in front of the ganglion, as they proceed to their destination, in the palate and nasal fossa, and are not incorporated in the ganglionic mass; some few of the fibres, however, THE FIFTH, TRIGEMINAL, OR TRIFACIAL NERVE 985 enter the ganglion, constituting its sensor root. Its motor root is derived from tlie facial nerve through the large superficial petrosal nerve, and its sympathetic root from the carotid plexus, through the large deep petrosal nerve. These two nerves join together before their entrance into the ganglion to form a single nerve, the Vidian. The large or great superficial petrosal branch (h. petrosus superficialis major) (Fig. 744) is given off from tlie geniculate ganglion implanted on the external genu of the facial nerve in the facial canal or aquaeductus Fallopii; it passes through the hiatus canalis facialis, enters the cranial cavity, and runs forward, being contained in a groove on the anterior surface of the petrous portion of the temporal bone, and lies beneath the dura. It then enters the cartilaginous substance which fills in the foramen lacerum medium, and, joining with the large deep petrosal nerve, forms the Vidian nerve. Fig. 740. — The sphenopalatine or Meckel's ganglion and its branches The large deep petrosal nerve (?i. pefrosus profundus) (Fig. 745) is given off from the carotid plexus of the sympathetic upon the internal carotid artery, and runs through the carotid canal on the outer side of the internal carotid artery. It then enters the cartilaginous substance which fills in the foramen lacerum medium, and joins with the large superficial petrosal nerve to form the Vidian. The Vidian nerve (;i. canalis pterygoidei) (Fig. 740), formed by the junction of the two preceding nerves in the cartilaginous substance which fills in the middle lacerated foramen, passes forward, through the Vidian canal, with the artery of the same name, and is joined by a small ascending nerve branch, the sphenoidal branch, from the otic ganglion. Finally, it enters the sphenomaxillary fossa, and joins the posterior angle of the sphenopalatine ganglion. Branches of Distribution of the Sphenopalatine Ganglion. — These are divisible into four groups — ascending, which pass to the orbit; descending, to the palate; internal, to the nose; and posterior branches, to the nasopharynx. 986 THE NERVE SYSTEM The ascending branches (rami orhitales) are two or three delicate filaments which enter the orbit by the sphenomaxillary fissure, and supply the periosteum and the nonstriated muscle parts of the Levator palpebrae or Superior tarsal muscle, the Inferior tarsal muscle, and the Orbital muscle of Miiller. According to Luschka, some filaments pass through foramina in the suture between the os planum of the ethmoid and frontal bone to supply the mucous membrane of the posterior ethmoidal and sphenoidal sinuses. The descending or palatine branches {nn. palatini) (Fig. 740) are distributed to the roof of the mouth, the soft palate, tonsil, and lining membrane of the nose. They are almost a direct continuation of the sphenopalatine branches of the superior maxillary nerve, and are three in number — anterior, middle, and posterior. The anterior palatine nerve' (n. palatinus anterior) descends through the posterior palatine canal, emerges upon the hard palate at the posterior palatine foramen, and passes forward in a groove in the hard palate, nearly as far as the incisor teeth. It supplies the gums, the mucous membrane, and glands of the hard palate, and communicates in front with the termination of the nasopalatine nerve (see below). While in the posterior palatine canal it gives off inferior nasal branches (rami nasales posteriores inferiores), which enter the nose through openings in the palate bone and ramify over the turbinated bone and middle and inferior meatuses; and, at its exit from the canal, a palatine branch is distributed to both surfaces of the soft palate. The middle palatine nerve (n. palatinus medius) descends through one of the accessory posterior palatine canals, distributing branches to the uvula, tonsil, and soft palate. It is occasionally wanting. The posterior palatine nerve (?i. palatinus posterior) descends with a minute artery through the posterior palatine canal, and emerges by a separate opening behind the posterior- palatine foramen. It supplies the soft palate, tonsil, and uvula. The middle and posterior palatine join with the tonsillar branches of the glossopharyngeal to form a plexus around the tonsil (circulus tonsillaris). The internal branches are distributed to the septum and oucer M'all of the nasal fossae. They are the superior nasal and the nasopalatine. The superior nasal branches (rami nasales posteriores superiores), four or five in number, enter the back part of the nasal fossa by the sphenopalatine foramen. They supply the mucous membrane covering the superior and middle turbinated processes, and that lining the posterior ethmoidal cells, a few being prolonged to the upper and back part of the septum. The nasopalatine nerve (n. nasopalatinus) also enters the nasal fossa through the sphenopalatine foramen; it passes inward across the roof of the nose, below the orifice of the sphenoidal sinus, to reach the septum, and then runs obliquely downward and forward along the lower part of the septum, to the anterior palatine foramen, lying between the periosteum and mucous membrane. It descends to the roof of the mouth through the anterior palatine canal (Fig. 740). The two nerves are here contained in separate and distinct canals, situated in the inter- maxillary suture, and termed the foramina of Scarpa, the left nerve being usually anterior to the right one. In the mouth they become united, supply the mucous membrane behind the incisor teeth, and join with the anterior palatine nerves. The nasopalatine nerve furnishes a few small filaments to the mucous membrane of the septum. Posterior Branch. — The pharyngeal or pterygopalatine nerve (Fig. 740) is a small branch arising from the back part of the sphenopalatine ganglion. It passes through the pterygopalatine canal with the pterygopalatine artery, and is dis- tributed to the mucous membrane of the upper part of the pharynx, behind the Eustachian tube. * Formerly called the great palatine nerve. THE FIFTH, TRIGEMINAL, OB TRIFACIAL NERVE 987 The Inferior Maxillary or Mandibular Nerve {n. mandihularis) (Figs. 738 and 739). — The inferior maxillary or third division of the trigeminal nerve dis- tributes branches to the teeth and gums of the mandible, the integument of the temple and external ear, the lower part of the face and lower lip, and the muscles of mastication; it also supplies the tongue with a large branch. It is the larcrest of the three divisions of the trigeminal, and is made up of two roots — a large or sensor root, proceeding from the inferior angle of the Gasserian ganglion; and a small or motor root, wliich passes beneath the ganglion and unites with the sensor root just after its exit from the skull through the foramen ovale (Figs. 736 and 739). Immediately beneath the base of the skull this nerve divides into two trunks, anterior and posterior. Previous to its division the primary trunk gives off from its inner side a recurrent (meningeal) branch and the nerve to the Internal ptery- goid muscle. The Recurrent or Meningeal Branch (ii. spinosus) is given off directly after its exit from the foramen ovale. It passes backward into the skull through the foramen spinosura with the middle meningeal artery. It divides into two branches, anterior and posterior, which accompany the main divisions of the artery and supply tlie dura. The posterior branch also supplies the mucous lining of the mastoid cells. The anterior branch communicates with the dural branch of the superior maxillary nerve. The Internal Pterygoid Nerve («. pterygoideus interims), given off from the inferior maxillary previous to its division, is intimately connected at its origin with the otic ganglion. It is a long and slender branch, which passes inward to enter the deep surface of the Internal pterygoid muscle. The anterior and smaller division of the inferior maxillary nerve, which receives nearly the whole of the motor root of the trigeminal nerve, divides into branches which supply the muscles of mastication. They are the masseteric, deep temporal, buccal, and external pterygoid branches (Fig. 739). The masseteric branch {a. massetericus) passes outward, above the External pterygoid muscle, in front of the temporomandibular articulation and behind the tendon of the Temporal muscle; it crosses the sigmoid notch with the masse- teric artery, to the deep surface of the Masseter muscle, in which it ramifies nearly as far as its anterior border. It gives a filament to the temporoman- dibular joint. The deep temporal branches (nii. iemporales profundi), two in number, anterior and posterior, supply the deep surface of the Temporal muscle. The posterior branch (n. temporalis profundus posterior), of small size, is placed at the back of the temporal fossa. It sometimes arises in common with the masseteric branch. The anterior branch (n. temporalis profundus anterior) is frequently given off with the buccal nerve; it is reflected upward, at the pterygoid ridge of the sphenoid, to the front of the temporal fossa. Frequently a third branch (middle deep tem- poral) is present. The buccal or buccinator branch (n. buccinatorius) passes foi'ward between the two heads of the External pterygoid; and downward beneath or through the fibres of the Temporal muscle; it gives a branch to the External pterygoid during its passage through that muscle, and a few ascending filaments to the Temporal muscle, one of which occasionally joins with the anterior branch of the deep tem- poral nerve. The superior or upper branch supplies the integument and upper part of the Buccinator muscle, joining with the facial nerve around the facial vein. The inferior or lower branch passes forward to the angle of the mouth; it supplies the integument and Buccinator muscle, as well as the mucous membrane lining the inner surface of that muscle, and joins the facial nerve.' ' There seems to be no reason to doubt that the branch supplying the Buccinator muscle is entirely a nerve of ordinary sensation, and that the true motor supply of this muscle is from the facial. 988 THE NEB VE SYSTE3I The external pterygoid nerve (». pterygoideus externus) is most frequently derived from the buccal, but it may be given off separately from the anterior trunk of the inferior maxillary nerve. It enters the muscle on its inner surface. The posterior and larger division of the inferior maxillary nerve is for the most part sensor, but receives a few filaments from the motor root. It divides into three branches — auriculotemporal, lingual, and inferior dental (Fig. 739). The auriculotemporal nerve (ji. auriculotemporalis) (Fig. 741) generally arises by two roots, between which the middle meningeal artery passes. It runs back- ward beneath the External pterygoid muscle to the inner side of the neck of the mandible. It then turns upward with the temporal artery, between the external auditory canal and the condyle of the mandible, under cover of the parotid gland, and, escaping from beneath this structure, ascends over the zygoma and divides into two temporal branches. The branches of communication of the auriculotemporal nerve are with the facial and with the otic ganglion. The branches of communication with the facial (rami anastomotici cum n.faciali), usually two in number, pass forward from behind the neck of the condyle of the mandible, to join this nerve at the posterior border of the Masseter muscle. The filaments of communication with the otic ganglion are derived from the commencement of the auriculotemporal nerve. The branches of distribution are: Anterior auricular. Parotid. Articular. Superficial temporal. Branches to the external auditory meatus. The anterior auricular branches (nn. auricnlares arderiores) are usually two in number. They supply the front of the upper part of the pinna, being distributed principally to the skin covering the front of the helix and tragus. A branch to the temporomandibular articulation, the articular branch, is usually derived from the auriculotemporal nerve. The parotid branches (rami.parotidei) supply the parotid gland. The superficial temporal branches (rami temporales superficiales) accompany the temporal artery to the vertex of the skull, and supply the integument of the tem- poral region, communicating with the facial nerve, and with the temporal branch of the temporomalar from the superior maxillary nerve. The branches to the external auditory meatus (n. meatus auditorii externi), two in number, enter the canal between the bony and cartilaginous portion of the meatus. They supply the skin lining the meatus; the upper one sending a filament to the membrana tympani (ramus memhranae tympani). The lingual nerve (n. lingualis) (Fig. 739) supplies the papilla and mucous membrane of the anterior two-thirds of the tongue, and is deeply placed throughout the whole of its course. It lies at first beneath the External pterygoid muscle, being placed to the inner side and in front of the inferior dental nerve, and is occasionally joined to this nerve by a branch which may cross the internal maxil- lary artery. The chorda tympani nerve also joins it at an acute angle in this situ- ation. The nerve then passes between the Internal pterygoid muscle and the inner side of the ramus of the mandible, and crosses obliquely to the side of the tongue over the Superior constrictor of the pharynx and the Styloglossus muscles, and then between the Hyoglossus muscle and the deep part of the submaxillary gland; the nerve finally runs across the submaxillary or Wharton's duct, and along the side of the tongue to its apex, lying immediately beneath the mucous membrane. The branches of communication are with the inferior dental and hypoglossal nerves and the submaxillary ganglion, and, apparently only, with the facial through the chorda tympani. The branches to the submaxillary ganglion are two or three THE FIFTH, TRIGEMINAL, OB TRIFACIAL NERVE 989 in number; those connected with the hj'poglossal nerve form a plexus at the anterior margin of the Hyoglossus muscle. The branches of distribution supply the mucous membrane of the mouth, the gums, the sublingual gland, and the mucous membrane of the anterior two- thirds of the tongue; the terminal filaments communicate at the tip of the tongue, with the hypoglossal nerve. The chorda tympani fibres which join the lingual nerve are probably taste fibres and excitoglandular for the submaxillary and sub- lingual salivary glands. The inferior dental nerve (»,. alveolaris inferior) (Fig. 739) is the largest of the branches of the inferior maxillary nerve. It passes downward with the inferior dental artery, at first beneath the External pterygoid muscle, and then between the internal lateral ligament and the ramus of the mandible to the dental foramen. It then passes forward in the dental canal of the mandible, lying beneath the teeth, as far as the mental foramen, where it divides into two terminal branches, incisor and mental. The branches of the inferior dental are the mylohyoid, dental, incisor, and mental. The mylohyoid (/;. mijlohi/oideus) is derived from the inferior dental just as that nerve is about to enter the dental foramen. It descends in a groove on the inner surface of the ramus of the mandible, in which it is retained by a process of fibrous membrane. It reaches the under surface of the Mylohyoid muscle, and supplies it and the anterior belly of the Digastric. The dental branches supply the molar and bicuspid teeth. They correspond in number to the fangs of those teeth, each nerve entering the orifice at the point of the fang and supplying the pulp of the tooth. The incisor branch is continued onward within the bone to the middle line, and supplies the canine and incisor teeth. The dental branches and the incisor branch form a plexus (plexus dentalis infe- rior), and from this plexus come the branches to the teeth (rami dentales inferiores) and to the gums {rami gingivales inferiores). The mental branch («. menialis) emerges from the bone at the mental foramen, and divides beneath the Depressor anguli oris muscle into two or three branches; one descends to supply the skin of the chin, and another (sometimes two) ascends to supply the skin and mucous membrane of the lower lip. These branches com- municate freely with the facial nerve. Two small ganglia are connected with the inferior maxillary nerve — the otic ■with the trunk of the nerve, and the submaxillary with its lingual branch. The Otic Ga,nglion( gang! ion oticum) (Fig. 739) is a small, oval-shaped, flattened ganglion of a reddish-gray color, situated immediately below the foramen ovale, on the inner surface of the inferior maxillary nerve, and surrounding the origin of the internal pterygoid nerve. It is in relation, externally, with the trunk of the inferior maxillary nerve, at the point where the motor root joins the sensor portion; internally, with the cartilaginous part of the Eustachian tube, and the origin of the Tensor palati muscle; behind, it lies in relation with the middle meningeal artery. Branches of Communication. — ^This ganglion is connected with the internal pterygoid branch of the inferior maxillary nerve by two or three short, delicate filaments. From this nerve the ganglion may obtain a motor root, and possibly also a sensor root, as these filaments from the nerve to the Internal pterygoid perhaps contain sensor fibres. The otic ganglion communicates with the glosso- pharyngeal and facial nerves through the small superficial petrosal nerve (Figs. 741 and 744) continued from the tympanic plexus, and through this communication it probably receives its sensor root from the glossopharjmgeal and its motor root from the facial; its communication with the symoathetic is effected by a filament 990 THE NERVE SYSTEM from the plexus surrounding the middle meningeal artery. The ganglion also communicates with the auriculotemporal nerve (ramus anastomoticus cum n. auriculotemporali). This communicating filament is probably a branch from the glossopharyngeal which passes to the ganglion, and through it and the auriculo- temporal nerve to the parotid gland. A slender filament, the sphenoidal, ascends from it to the Vidian nerve. Branches of Distribution. — Its branches of distribution are a filament to the Tensor tympani (n. tensoris tympani) and one to the Tensor palati (n. tensoris veil palatini). The former passes backward on the outer side of the Eustachian tube; the latter arises from the ganglion, near the origin of the internal pterygoid nerve, and passes forward. The fibres of these nerves are, however, mainly derived from the nerve to the Internal pterygoid muscle. The Submaxillary Ganglion (ganglion submaxillare) (Fig. 739) is of small size, fusiform in shape, and situated above the deep portion of the submaxillary gland, near the posterior border of the Mylohyoid muscle, being connected by filaments with the lower border of the lingual nerve. Fig. 741. — The otic ganglion and its branches Branches of Communication. — ^This ganglion is suspended from the lingual nerve by two filaments (rami communicanies cum n. linguali), which join it separately at its fore and back part. It also receives a branch from the chorda tympani, and communicates with the sympathetic by filaments from the sympathetic plexus around the facial artery. Branches of Distribution. — These are five or six in number; they arise from the lower part of the ganglion, and supply the mucous membrane of the mouth and the submaxillary or Wharton's duct, some being lost in the submaxillary gland (rami submaxillar es). The branch of communication from the lingual nerve to the fore part of the ganglion is by some regarded as a branch of distribution, by which filaments of the chorda tympani pass from the ganglion to the lingual nerve, and by it are conveyed to the sublingual gland and the tongue. Surface Marking. — It will be seen from the above description that the three terminal branches of the three divisions of the trigeminal nerve emerge from foramina in the bones of the skull and pass on to the face; the terminal branch of the first division emerging through the THE FIFTH, TRIGEMINAL, OR TRIFACIAL NERVE 991 supraorbital foramen; that of the second through the infraorbital foramen; and the third throujjh the mental foramen. The supraorbital foramen is situated at the junction of the internal and middle third of the supraorbital arch. If a straight line is drawn from this point to the lower border of the mandibfe, so that it passes between the two bicuspid teeth of the mandible, it will pass over the infraorbital and mental foramina, the former being situated about one centimetre (two-fifths of an inch) below the margin of the orbit, and the latter varying in jjosition according to the age of the individual. In the adult it is midway between the upper and lower borders of the mandible; in the child it is nearer the lower border; and in the edentulous jaw of old age it is close to the upper margin. Applied Anatomy. — In fracture of the hose of the skull the trigeminal nerve or one of its brandies may be injured. It seems certain that occasionally, though seldom, the trigeminal nerve may be actually divided by such an injury. The trigeminal nerve may be aft'ected in its entirety, or its sensor or motor root may be affected, or one of its primary main divisions. In injury to the sensor root there is anesthesia of the half of the face on the side of the lesion, with the exception of the skin over the parotid gland; insensibility of the conjunctiva, followed, if the eye is not temporarily protected with a watch glass, by destructive inflammation of the cornea, MENTAL NtRVE- FlG. 742. — Sensor areas of the head, showing the general distribution of the three dii nerve. Gerrish'3 Anatomy. (Modified from Testut.) partly, it is held, from loss of trophic influence, and partly it is certain, from the irritation pro- duced by the presence of foreign bodies on it, which are not perceived by the patient, and there- fore not e.xpelled by the act of winking; dryness of the nose, loss to a considerable extent of the sense of taste, and diminished secretion of the lacrimal and salivary glands. In injury to the motor root there is impaired action of the mandible from paralysis of the muscles of mastication on the affected side. The trigeminal nerve is often the seat of neuralgia, and each of the three divisions has been divided or a portion of the nerve excised for this affection. The supraorbital nerve may be ex- posed by making an incision an inch and a half in length along the supraorbital margin below the eyebrow, which is to be drawn upward, the centre of the incision corresponding to the supra- orbital notch. The skin and Orbicularis palpebrarum having been divided, the nerve can be easily found emerging from the notch and lying in some loose cellular tissue. It should be drawn up by a blunt hook and divided, or, what is better, a portion of it should be removed. The infraorbital nerve has been divided at its exit by an incision on the cheek; or the floor of the orbit has been exposed, the infraorbital canal opened up, and the anterior part of the nerve resected; or the whole nerve, together with Meckel's ganglion as far back as the foramen rotun- dum, has been removed. This latter operation, though undoubtedly a severe proceeding, appears to have been followed by better results than has nerve resection. The ojieration is per- formed as fellows. The maxilla is first exposed by a T-shaped incision, one limb of the incision 992 THE NER VE SYSTEM passing along the lower margin of the orbit, the other from the centre of the first cut vertically down the cheek toward the angle of the mouth. The nerve is then found, is divided, and a piece of silk is tied to it as a guide. A small trephine (one-half inch) is then applied to the bone below, but including the infraorbital foramen, and the antrum opened. ' The trephine is now applied to the posterior wall of the antrum, and the sphenomaxillary fossa exposed. The infraorbital canal is now opened up from below by fine cutting pliers or a chisel, and the nerve drawn down into the trephine hole, it being held on the stretch by means of the piece of silk; it is severed with fine curved scissors as near the foramen rotundum as possible, any branches coming off from the ganglion being also divided.' The mental branch of the inferior dental nerve may be divided at its exit from the foramen through an incision made through the mucous inembrane where it is reflected from the alveolar process on to the lower lip ; or a portion of the trunk of the inferior dental nerve may be resected through an incision on the cheek through the Masseter muscle, exposing the outer sm'face of the ramus of the mandible. A trephine is then applied over the position of the inferior dental foramen and the outer table removed, so as to expose the inferior dental canal. The nerve is dissected out of the portion of the canal exposed, and, having been divided after its exit from the mental foramen, it is by traction on the end exposed in the trephine hole, drawn out entire, and cut off as high up as possible.^ The inferior dental nerve has also been divided through an in- cision within the mouth, the bony point guarding the inferior dental foramen forming the guide to the nerve. The buccal nerve may be divided by an incision through the mucous membrane of the mouth and the Buccinator muscle just in front of the anterior border of the ramus of the mandible (Stimson). In inveterate neuralgia of one or two of the branches of the trigeminal nerve a peripheral operation may cure the case, but seldom does. It often gives relief, perhaps for months. In neuralgia of the second division or third division, or of the second division and third division, Abbe, of New York, opens the skull and divides the nerve or nerves by an intracranial opera- tion, removes a piece of nerve so that the foramen of exit is empty, and covers the foramen with rubber tissue, to hinder regrow'th of the nerve. Other operators, after removing a piece from each nerve, have plugged the foramina of the exit with dentists' cement or silver foil. Rose's method of neurectomy is very valuable for neuralgia of the second division. It is a modification of the Braun-Lossen method. The infraorbital nerve is exposed, a ligature is tied about it, the roof of the infraorbital canal is chiselled open, and the nerve is freed as far back as possible. An incision is made from below the external angular process outward along the zygoma to in front of the lobule of the ear, downward to just above the angle of the mandible, and forward for two inches. The flap is raised and the zygoma is exposed. The root of the zygoma is drilled at two points, and the zygomatic process of the temporal bone is drilled at two points. The bone is sawed in two places between the drill holes. The freed arch is lifted down and back, the tendon of the Temporal muscle is drawn backward, and the pterygomaxillary fossa is thus exposed. The internal maxillary artery is divided between two ligatures. The External pterygoid muscle is separated from the greater wing of the sphenoid and from the root of the external pterygoid process. The superior maxillary nerve is grasped and twisted off as near the ganglion as possible. The entire nerve is then drawn back from the infraorbital foramen and removed. The wound is then closed. If the third division is also haunted by neuralgia, it too should be removed a few weeks after the performance of Rose's operation. If a peripheral operation fails, or if all the branches of the trigeminal are involved, the Gas- serian ganglion must be removed, or the sensor root of the trigeminal must be divided, as sug- gested by Frazier and Spiller. Removal of the Gasserian ganglion was suggested by J. Ewing Mears in 1884, and was first carried out by Rose in 1890. The method chiefly in vogue was devised by Hartley, and was first performed by him in 1891. An osteoplastic flap is made in front of the ear, the dura is exposed and lifted. FoUowing Krause's advice, the third division is exposed and clamped. The second division is exposed and clamped. The nerves are loosened from their beds and then are rolled about the clamps. This twisting pulls out the ganglion intact along with the motor root, and also the sensor root from the pons. A difficulty in the Hartley operation is the danger of division of the middle meningeal artery. If this happens, the surgeon may be able to arrest bleeding and proceed with the operation. If the vessel is torn off at the foramen spi- nosum, it will be necessary to pack the wound and postpone any further operative manipulation for forty-eight hours. Dr. Harvey Gushing has modified Hartley's operation by trephining the wall of the temporal fossa very low down. He opens the skull below the arch of the meningeal vessels, and thus avoids the middle meningeal artery at the foramen spinosum, and also the sulcus arteriosus of the parietal bone. After the removal of the ganglion. Professor Keen, in order to prevent undue inflammation of the eye, sews the eyelids of the affected side together, leaving a space open at each angle, and covers the eye with a watch crystal. Boric acid solution 1 Carnochan, American .Journal of the Medical Sciences, 1858, p 136. 2 Hears, Transactions of the American Surgical Association, vol. ii, p, 469. THE SIXTH OR ABDUCENT NERVE 993 is flushed into tde opening at the external angle at frequent intervals. The stitches are removed from the lid in from eight to ten days. The lingual nerve is occasionally divided with the view of relieving the pain in cancerous disease of the tongue. This may be done in that part of its course where it lies below and behind the last molar tooth. If a line is drawn from the middle of the crown of the last molar tooth to the angle of the mandible, it will cross the nerve, which lies about half an inch behind the tooth, parallel to the bulging alveolar ridge on the inner side of the body of the bone. If the knife is entered three-quarters of an inch behind and below the last molar tooth and carried down to the bone, the nerve will be divided. Hilton divided it opposite the second molar tooth, where it is covered only by the mucous membrane, and Lucas pulls the tongue forward and over to the opposite side, when the nerve can be seen standing out as a firm cord under the mucous mem- brane by the side of the tongue and can be easily seized with a sharp hook and divided or a portion excised. This is a simple enough operation on the cadaver, but when the disease is extensive and has extended to the floor of the mouth, as is generally the case when division of the nerve is thought of, the operation is not practicable. THE SIXTH OR ABDUCENT NERVE (N. ABDUCENS) (Fig. 738). The sixth or abducent nerve supplies the External rectus muscle. Its super- ficial origin is by several filaments from the postpontile groove, between pons and pyramid. Its deep origin is from the upper part of the floor of the fourth ventricle, close to the median line, beneath the eminentia abducentis (Fig. 650). From the nucleus of the abducent nerve some fibres are supposed to pass through the medial longitudinal bundle to the oculomotor nucleus of the opposite side and into the oculomotor nerve, along which they are carried to the Internal rectus muscle. See, however, the description already given on page 901). The nerve pierces the dura on the basilar surface of the sphenoid bone, runs through a notch immediately below the posterior clinoid process, and enters the cavernous sinus. It passes forward through the sinus, lying on the outer side of the internal carotid artery (Fig. 505). It enters the orbit through the sphenoidal fissure, and lies above the oph- thalmic vein, from which it is separated by a lamina of dura (Fig. 743). It then passes be- tween the two heads of the External rectus muscle, and is distributed to that muscle on its ocular surface. Branches of Communication. — It is joined by several fila- ments from the carotid and cavernous plexuses, and by one from the ophthalmic nerve. Relations to One Another of the Oculomotor, Trochlear, Oph- thalmic Division of the Trigeminal, and Abducent Nerves as they Pass to the Orbit. — The oculomotor, trochlear, the ophthalmic division of the trigeminal, and tlie abducent nerves, as they pass to the orbit, bear a certain relation to one another in the cavernous sinus, at the sphenoidal fissure, and in the cavity of the orbit, which will now be described. In the cavernous sinus (Figs. 505 and 506) the oculomotor, trochlear, and ophthalmic division of the trigeminal are placed on the outer wall of the sinus, in their numerical order, both from above downward and from within outward. The abducent nerve lies at the outer side of the internal carotid artery. As these nerves pass forward to the sphenoidal fissure, the oculomotor and trigeminal nerves become divided into branches, and the abducent nerve approaches the rest so that their relative position becomes considerably changed. 63 lufur Aliihicen Ophthalmic vein ^upm } division of ociilo-motor, division of oculo-motor. -Relations of structures passing through the sphenoidal fissure 994 THE NERVE SYSTEM In the sphenoidal fissure (Fig. 743) the trochlear nerve and the frontal and lacrimal branches of the ophthalmic division of the trigeminal lie upon the same plane, the former being most internal, the latter external, and they enter the cavity of the orbit above the muscles. The remaining nerves enter the orbit between the two heads of the External rectus muscle. The superior division of the oculomotor nerve is the highest of these; beneath this lies the nasal branch of the ophthalmic nerve; then the inferior division of the oculomotor nerve; and the abducent nerve lowest of all. In the orbit (Figs. 734 and 738) the trochlear nerve and the frontal and lacrimal divisions of the ophthalmic nerve lie on the same plane immediately beneath the periosteum, the trochlear nerve being internal and resting on the Superior oblique muscle, the frontal nerve resting on the Levator palpebrae muscle, and the lacrimal nerve on the External rectus muscle. Next in order comes the superior division of the oculomotor nerve, lying immediately beneath the Superior rectus muscle, and then the nasal branch of the ophthalmic nerve, crossing the optic nerve from the outer to the inner side of the orbit. Below these is found the optic nerve, surrounded in front by the ciliary nerves, and having the ciliary ganglion on its outer side, between it and the External rectus muscle. Below the optic nerve is the inferior division of the oculomotor nerve and the abducent nerve which lie on the outer side of the orbit. Applied Anatomy. — It is often stated that the abducent nerve is more frequently involved in fractures of the hose of the skull than any other of the cranial nerves. As a matter of fact, however, it is injured in only about 2 per cent, of cases of fracture of the skull (Putscher). Cases have been reported in which the nerve was actually severed. The nerve may be injured by traction, pressure of a blood clot, of a tumor, or of an arteriovenous aneurism. The result of paralysis of this nerve is internal or convergent squint. When injured so that its function is destroyed, there is, in addition to the paralysis of the External rectus muscle, often a certain amount of contrac- tion of the pupil, because some of the sympathetic fibres to the radiating muscle of the iris pass along with this nerve. THE SEVENTH OR FACIAL NERVE (N. FACIALIS) (Figs. 744, 745). The seventh or facial nerve is the motor nerve of all the muscles of expression in the face, and of the Platysma and Buccinator; the muscles of the external ear, the posterior belly of the Digas- E=cten^alsuperfiaalpe^rosal.ff2C2^'^^r'^''f||§A *"''' """"^ the Stylohyoid. The Brancii to join smau ««pf';\\L£_jL/viW.-^S«a»^ '/ \ chorda tvmpani (or nervus mter- fieial petrosal>A^l. I TV~'iA-g'^c> ^^aSi;, \ __ ■'. ^ . ^ . Large mperfidca petrosal.- \ .|f w^A U N^^>\ ' \ medius) IS reterreci to as the sen- Geniculate ganglion. ~\^J^^=:^^^^^^ | SOr portion of the facial.- Its superficial origin is from the upper end of the medulla oblon- gata, in the groove between the Fig. 744,-The ™;;[7^^1.^^°™|f «™^°f '•>« ^^"^1 ""^ olive and restiform body. Its deep origin is from a nucleus situated in the floor of the fourth ventricle, beneath the superior fovea (Fig. 650). The facial nucleus is deeply placed in the reticular formation of the lower part of the pars dorsalis pontis, a litde external and ventral to the nucleus of the abducent nerve. From this origin the fibres pursue a curved course in the substance of the pars dorsalis pontis. They first pass backward and inward, and then turn upward and forward, forming the genu internum, which with the nucleus abducentis produces an eminence, the eminentia teres or abducentis, on the floor of the fourth ventricle, and finally bend sharply downward and outward around the upper erid of the nucleus of origin of the abducent nerve, to reach their superficial origin between the olive and restiform body. From the nucleus of the oculomotor THE SEVENTH OB FACIAL NERVE 095 nerve some fibres arise which descend in the medial longitudinal Ijundle and join the facial just before it leaves the pars dorsalispontis; these fibres are said to supply the anterior belly of the Occipitofrontalis, the Orbicularis palpebrarum, and the Corrugator supercilii, as these muscles have been observed to escape paralysis in lesions of the nucleus of the facial nerve. _ The acoustic or auditory nerve lies to the outer side of the facial nerve; and betv.een the two Is a small fasciculus, the nervus intermedius or pars intermedia of Wrisberg, which apparently arises from the medulla oblongata and joins the farial nerve in the internal auditory meatus. The central processes of the ganglion cells, known as the nervus intermedius, end in the upper end of the nucleus of the glossopharyngeal nerve. If it is to be classified as part of the facial then the nervus intermedius may be regarded as the sensor root of the facial nerve, analogous to the sensor root of the trigeminal, and its real nucleus of origin consists of the geniculate ganglion (see p. 882). It will be remembered that a portion of the nervus inter- medius is efferent (excitoglandular), arising from the nucleus salivatorius (p. 882). Nucleus Salivator Spheno- ^„rjf palatine \> 4 Oanglton Communicating Branch To Digastric To Styio-hijoid E. A. S. Fig. 745. — Plan of the facial and intermediate i Ajferent Uastc) fibers ' Efferent iexcito-glanduiari fibers to submaxillary and sublingual ganglia and glands ommunication with other nerves. The facial nerve, firmer, rounder, and smaller than the auditory, passes forward and outward upon the middle peduncle of the cerebellum, and enters the internal auditory meatus with the auditory nerve and artery. Within the meatus the facial nerve lies in a groove along the upper and anterior part of the auditory nerve, and the nervus intermedius is placed between the two and joins the inner angle of the geniculate ganglion. Beyond the ganglion its fibres are generally regarded as forming the chorda tympani (see p. 997). At the bottom of the meatus the facial nerve enters the canalis facialis or aquae- ductus Fallopii and follo^^s the course of that canal through the petrous portion of the temporal bone, from its commencement at the internal meatus to its termina- tion at the stylomastoid foramen (Figs. 50 and 744). It is at first directed outward between the cochlea and vestibule toward the inner wall of the tympanum; it In the internal auditory meatus 996 THE NERVE 8Y8TEM then bends suddenly backward and arches downward behind the tympanum to the stylomastoid foramen. At the point in the aqueduct of Fallopius where the nerve changes its direction (geiiiculum n. facialis), it presents a reddish, gangli- form swelling, the geniculate ganglion (ganglion geniculi) or intumescentia ganglio- formis (Fig. 744). The geniculate ganglion receives a branch from the vestibular division of the auditory nerve. On emerging from the stylomastoid foramen the facial nerve runs forward in the substance of the parotid gland, crosses the external carotid artery, and divides behind the ramus of the mandible into two primary branches, temporofacial and cervicofacial, from which numerous offshoots are distributed over the side of the head, face, and upper part of the neck, supply- ing the superficial muscles in these regions. As the primary branches and their offshoots diverge from each other, they present somewhat the appearance of a bird's claw; hence the name of pes anserinus is given to the divisions of the facial nerve in and near the parotid gland. Branches of Communication (Fig. 745). — The communications of the facial nerve may be thus arranged : 'With the acoustic nerve. The nervus intermedins, which is between the facial and acoustic, is supposed to give branches to both. The branch given to the acoustic accompanies it for a certain distance, and then departs from it to join the geniculate ganglion. With the acoustic as explained above. With the sphenopalatine ganglion by the large superficial petrosal nerve. With the otic ganglion by the small superficial petrosal nerve. With the sympathetic, on the middle meningeal artery by the external super- ficial petrosal nerve. In the canalis facialis or Fallopian 1 -itt-.i ^i • i u \ e ^\. , ^ '^ - With the auricular brancii or the vagus. aqueduct j ° iWith the glossopharyngeal. With the vagus. With the great auricular. With the auriculotemporal. Behind the ear With the small occipital. On the face With three divisions of the trigeminal. In the neck . With the superficial cervical. In the internal auditory meatus some minute filaments pass between the facial and acoustic nerves. The large superficial petrosal nerve arises from the geniculate ganglion and con- sists chiefly of sensor branches which are distributed to the mucous membrane of the soft palate. It probably also contains a few motor fibres which form the motor root of the sphenopalatine (Meckel's) ganglion. It passes forward through the hiatus canalis facialis (Fallopii) and runs in a groove on the anterior surface of the petrous portion of the temporal bone beneath the Gasserian ganglion to the foramen lacerum medium. It receives a twig from the tympanic plexus, and in the foramen is joined by the great deep petrosal, from the sympathetic plexus on the internal carotid artery, to form the Vidian nerve. This nerve passes through the Vidian canal and ends in the sphenopalatine (Meckel's) ganglion. The geniculate ganglion is connected with the otic ganglion by a branch which From the geniculate ganglion THE SEVENTH OR FACIAL NERVE 997 joins the small superficial petrosal nerve; and also with the sympathetic filaments accompanying the middle meningeal artery, by the external petrosal nerve (Bidder). From the gangliform enlargement, according to Arnold, a twig is sent back to the auditory nerve. Just before the facial nerve emerges from the stylomastoid foramen it generally receives a twig of commimication from the auricular branch of the vagus. After its exit from the stylomastoid foramen, it sends a twig to the glosso- pharyngeal, another to the vagus nerve, and communicates with the great auricular branch of the cervical plexus, with the auriculotemporal branch of the inferior maxillary^ nerve in the parotid gland, with the small occipital nerve behind the ear, on the face with the terminal branches of the three divisions of the fifth, and in the neck with the transverse cervical. Branches of Distribution (Fig. 745). — ^The branches of distribution of the facial nerves may be thus arranged: Within the canalis facialis or aquae- J Tympanic, to the Stapedius muscle, ductus Fallopii \ Chorda tympani. At its exit from the stylomastoid f Posterior Auricular. e •{ Digastric. foramen c^ i i -j 1^ btylohyoid. {Temporal. Malar. ^..... , Infraorbital. I Jjuccal. [^ Cervicofacial . . < Mandibular. (^ Cervical. The Tympanic Branch (n. stapedius) (Fig. 745) arises from the nerve opposite the pyramid; it passes through a small canal in the pyramid and supplies the Stapedius muscle. The Chorda Tympani (Figs. 744 and 745) is apparently given off from the facial as it passes vertically downward at the back of the tympanum, about 5 mm. (3- inch) before its exit from the stylomastoid foramen. It passes from below upward and forward in a distinct canal, and enters the cavity of the tympanum through an aperture (iter chordae posterius) on its posterior wall between the open- ing of the mastoid cells and the attachment of the membrana tympani, and be- comes invested with mucous membrane. It traverses the cavity of the tympanum, between the fibrous and mucous layers of the membrana tympani, crosses over the handle of the malleus, emerges from the cavity through a foramen at the inner end of the Glaserian fissure, which is called the canal of Huguier (iter chordae anterius). It then descends between the two Pterygoid muscles on the inner aspect of the spine of the sphenoid, which it sometimes grooves, and joins the lingual nerve at an acute angle. A portion of the nerve (excitoglandular division) passes to the submaxillary ganglion; the rest is continued onward through the muscular substance of the tongue to the mucous membrane covering its anterior two-thirds. These constitute the nerves of taste for this portion of the tongue. A few of its fibres probably pass through the submaxillary ganglion to the sublin- gual gland. Before joining the lingual nerve it receives a small communicating branch from the otic ganglion. As already stated, the chorda tympani nerve is regarded as the peripheral portion of the nervus intermedins (see p. 989). The Posterior Auricular Nerve {n. auricularis postenor) (Figs. 745 and 746) arises close to the stylomastoid foramen, and passes upward in front of the mastoid process and between the mastoid process and the external ear, where it is joined by a filament from the auricular branch of the vagus, and communicates with the 998 THE NER VE SYSTEM mastoid branch of the great auricular and with the small occipital. As it ascends between the external auditory meatus and the mastoid process it divides into two branches, the auricular and the occipital branches. The auricular branch sup- plies the Retrahens aurem and the small muscles on the cranial surface of the pinna. The occipital branch (ramus occipitalis), the larger, passes backward along the superior curved line of the occipital bone, and supplies the occipital portion of the Occipitofrontalis. The Digastric Branch of the Facial Nerve (ramus digastricus) arises close to the stylomastoid foramen; it divides into several filaments, which supply the posterior belly of the Digastric; one of these perforates that muscle to join the glo^opharyn- geal nerve. The Stylohyoid Branch (ramus stylohyoideus) frequently arises by a common trunk with the digastric; it is long and slender, and passes inward to enter the Stylohyoid muscle about its middle. The Temporo facial Division (Figs. 745 and 746), the larger of the two terminal branches of the facial, passes upward and forward through the parotid gland, crosses the external carotid artery and temporomaxillary vein, and passes over the neck of the condyle of the mandible, being connected in this situation with the auriculotemporal branch of the inferior maxillary nerve. It breaks up into branches which are distributed over the temple and upper part of the face; these are divided into three sets — temporal, malar, and infraorbital. The temporal branches (rami temporales) cross the zygoma to the temporal region, supplying the Attrahens and Attollens aurem muscles, and join with the temporal branch of the temporomalar division of the superior maxillary nerve, and with the auriculotemporal branch of the inferior maxillary nerve. The more anterior branches supply the frontal portion of the Occipitofrontalis, the Orbicularis palpebrarum, and Corrugator supercilii muscles, and join with the supraorbital and lacrimal branches of the ophthalmic. The malar branches (rami zygomatici) pass across the malar bone to the outer angle of the orbit, where they supply the Orbicularis palpebrarum muscle and join with filaments from the lacrimal nerve and the malar branch (subcutaneus malae) of the superior maxillary nerve. The infraorbital branches of larger size than the rest, pass horizontally forward to be distributed between the lower margin of the orbit and the mouth. The superficial branches run beneath the skin and above the superficial muscles of the face, which they supply; some branches are distributed to the Pyramidalis nasi, joining at the inner angle of the orbit with the infratrochlear and nasal branches of the ophthalmic. The deep branches pass beneath the Zygomatici and the Levator labii superioris, suppljang the Levator anguli oris, the Levator labii superioris alaeque nasi, and the small muscles of the nose, and form a plexus, infraorbital plexus, by joining with the branches of the infraorbital branch of the superior maxillary nerve and the buccal branches of the cervicofacial. The Cervicofacial Division of the facial nerve passes obliquely downward and forward through the parotid gland, crossing the external carotid artery. In this situation it is joined by branches from the great auricular nerve. Opposite the angle of the mandible it divides into branches which are distributed on the lower half of the face and upper part of the neck. These may be divided into three sets — buccal, mandibular, and cervical. The buccal branches (rami buccales) cross the Masseter muscle. They supply the Buccinator and Orbicularis oris, and join with the infraorbital branches of the temporofacial division of the nerve, and with filaments of the buccal branch of the inferior maxillary nerve. The mandibular branch (ramus marginalis mandihulae) passes forward beneath THE SEVENTH OR FACIAL NERVE 999 the Platysma and Depressor anguli oris, supplying the muscles of the lower lip and chin, and communicating with the mental branch of the inferior dental nerve. The cervical branch (ramtis colli) runs forward beneath the Platysma, and forms a series of arches across the side of the neck over the suprahyoid region. A branch descends vertically to join with the superficial cervical nerve from the cervical plexus; others supply the Platysma. Fig. 746. — ^The nerves of the scalp, face, and side of thi Applied Anatomy. — The facial nerve is more frequently paralyzed than any of the other of the cranial nerves. The paralysis [facial 'palsy) may depend either upon (1) central causes — i. e., blood clots or intracranial tumors pressing on the nerve before its entrance into the internal auditory meatus. It is also one of the nerves involved in bulbar -paralysis. Or (2) it may be paralyzed in its passage through the petrous bone by damage due to middle-ear disease or by fractures of the base of the skull. Or (3) it may be afl'ected at or after its exit from the stylomastoid foramen. This is commonly known as Bell's paralysis. It may be due to exposure to cold or to injury of the nerve, either from accidental wounds of the face or during some surgical operation, as removal of parotid tumors, opening of abscesses, or operations on the mandible. When the cause is central, the abducent nerve is usually paralyzed as well, and there is also hemiplegia on the opposite side. In these cases the electric reactions are the same as in health; whereas, when the paralysis is due to a lesion in the course of the nerve, the reactions of degenera- tion develop. When the nerve is paralyzed in the petrous bone, in addition to the paralysis of the muscles of expression, there is loss of taste in the anterior part of the tongue, and the patient is 1000 THE NERVE SYSTEM unable to recognize the difference between bitters and sweets, acids and salines, from involvement of the chorda tympani. The mouth is dry, because the salivary glands are not secreting; the sense of hearing is affected from paralysis of the Stapedius, but there is no hemiplegia. When the cause of the paralysis is from fracture of the base of the skull, the acoustic nerve and the petrosal nerves, which are connected with the intumescentia ganglioformis, are also involved. When the injury to the nerve is after its exit from the stylomastoid foramen, all the muscles of expression except the Levator palpebrae, together with the posterior belly of the Digastric and Stylohyoid, are paralyzed. There is smoothness of the forehead, and the patient is unable to frown; the eyelids cannot be closed, and the lower lid droops, so that the punctum is no longer in contact with the globe, and the tears run down the cheek; there is smoothness of the cheek and loss of the nasolabial furrow; the nostril of the paralyzed side cannot be dilated; the mouth is drawn to the sound side, and there is inability to whistle; food collects between the cheek and gum from paralysis of the Buccinator. The facial nerve is at fault in cases of so-called histrionic spasm, which consists in an almost constant and uncontrollable twitching of the muscles of the face. This twitching is sometimes so severe as to cause great discomfort and annoyance to the patient and to interfere with sleep, and for its relief the facial nerve has been stretched. The operation is performed by making an incision behind the ear from the root of the mastoid process to the angle of the mandible. The parotid is turned forward, and the dissection carried along the anterior border of the Sterno- mastoid muscle and mastoid process until the upper border of the posterior belly of the Digas- tric is found. The nerve is parallel to this on about a level with the middle of the mastoid process. When found, the nerve may be stretched by passing a blunt hook beneath it and pulling it for- ward and outward. Too great force must not be used, for fear of permanent injury to the nerve. In facial paralysis of extracerebral origin it may be advisable to expose the nerve, cut it across, and anastomose the distal end of the paralyzed nerve to the accessory nerve, or, better, to the hypo- glossal nerve (facioaccessory anastomosis or faciohypoglossal anastomosis). The idea was first proposed by Ballance, and has been put in practice by Ballance and Stewart, Keen, Gushing, Paure, Kennedy, and others. THE EIGHTH OR ACOUSTIC NERVE (N. ACUSTICUS) (Fig. 747). The eighth or acoustic or auditory nerve comprises two distinct sets of fibres which, although both are devoted to the transmission of afferent impulses, differ in their peripheral distribution and in their central connections. The two divi- sions appear blended in the interval between the medulla oblongata and the in- ternal auditory meatus, running obliquely laterofrontad in company with the facial nerve and internal auditory artery. At the internal auditory meatus the two divisions of the nerve are separable, the vestibular division above, the cochlear below. The cochlear nerve (radix cochlearis) is the true nerve of hearing, lacking general sensibility, however, and therefore a nerve of special sense. The fibres of this division arise from the cells of the spiral ganglion of the cochlea as axones of bipolar cells whose dendrites or peripheral processes terminate about the (auditory) hair cells of the organ of Corti (p. 1143). The central connections of the cochlear division are described on page 881. The vestibular nerve (radix vestibidaris) conducts impulses of equilibratory sense from the semicircular canals, utricle, and saccule to the vestibular nuclei. The ganglion of origin of this nerve differs from ordinary sensor ganglia in that its cells are of bipolar structure, having retained this embryonic characteristic of the ganglion cells throughout life. The central processes of the cells of the vestibular ganglion (or ganglion of Scarpa) enter the medulla oblongata with the trunk of the cochlear nerve in the postpontile groove, laterad of the facial nerve, to establish central connections already described on page 881. The peripheral processes constitute the two main branches of the nerve — viz., (a) the utriculo- ampullar and (b) the sacculoampuUar. The upper or utriculoampullar branch divides into: (a) The utricular branch, passing through the superior macula cribrosa of the vestibule to end in the macula acustica of the utricle. THE EIGHTH OR ACOUSTIC NEIiVE 1001 (b) The superior ampullar branch, accomjjanying the utricular l^ranch, to end in the crista acustica of the ampulla of the superior semicircular canal. (c) The lateral ampullar, to the ampulla of the lateral semicircular canal. The lower or sacculoampuUar branch is somewhat longer and divides into: (a) The posterior ampullar, passing through the foramen singulare and the inferior macula cribrosa to end in the ampulla of the posterior semicircular canal. (b) The saccular branch, passing through the middle macula cribrosa to end in the macula acustica of the sacculus. Fig. 747. — Distribution of the acoustic nerve. (Semidiagrammatic.) (Testut.) Applied Anatomy. — The acoustic nerve is frequently injured, together with the facial nerve, in fractures of the middle fossa of the base of the skull implicating the internal auditory meatus. Tiie nerve may be either torn across, producing permanent deafness, it may be bruised, or it may be pressed upon by extravasated blood or inflammatory exudation, when the deafness will in all probability be temporary. The nerve may also be injured by violent blows on the head without fracture, and deafness may follow loud explosions of dynamite, etc., probably from some lesion of this nerve, which is more liable to be injured than the other cranial nerves on account of its structure. The test that the nerve is destroyed and that the deafness is not due to some lesion of the auditory apparatus is obtained by placing a vibrating tuning-fork on the head. The vibrations will be heard in cases where the auditory apparatus is at fault, but not in cases of destruction of the auditory nerve. Tinnitus aurium is commonly present in cases of ear disease. The sounds are variable in intensity and nature — buzzing, hissing, whistling, rushing, bell-ringing, and so forth. In the insane, tinnitus is associated with delusions and hallucinations of hearing, and may be due to nothing more than impacted cerumen in the meatus. Meniere's disease is discussed in the Applied Anatomy of the Labyrinth. THE NINTH OR GLOSSOPHARYNGEAL NERVE (N. GLOSSOPHARYNGEUS) (Figs. 748, 749). The ninth or glossopharyngeal nerve is distributed, as its name implies, to the tongue and pharynx, being the nerve of ordinary sensation to the mucous mem- brane of the pharynx, fauces, and tonsil; and the nerve of taste to all parts of the tongue to which it is distributed. 1002 THE NEB VE SYSTEM Its (apparent) superficial origin is hy three or four filaments, closely connected, from the upper part of the medulla oblongata, in the dorsolateral groove (Fig. 748) . The central connections are described on page 880. The small motor component arises from cells in the nucleus ambiguus. The real origin of the sensor fibres of the glossopharyngeal must be looked for in the jugular and petrosal ganglia which are developed from the neural crest. From its superficial origin it passes outward across the flocculus, and leaves the skull at the central part of the jugular foramen, in a separate sheath of the dura external to and in front of the vagus and spinal accessory nerves (Fig. 749). In its passage through the jugular foramen it grooves ju.guiiiraa^i. the lower border of the petrous portion of the temporal rvMoaf^i. bone, and at its exit from the skull passes forward Tympa^ . bgt^ggjj ]^^ jugular vciu and internal carotid artery, and descends ventrad of the latter vessel, and beneath the styloid process of the temporal bone and the muscles connected with it, to the lower border of the Stylopharyngeus muscle. The nerve now curves in- ward, forming an arch on the side of the neck, and lying upon the Stylopharyngeus muscle and the ^liddle vagui constrictor of the pharynx. It then passes beneath eomm JS&n'if tbe1fiSfh% the Hyoglossus musclc, and is finally distributed to and eleventh cranial nerves. the mucous membrane of the fauccs and base of the tongue, and the mucous glands of the mouth and tonsil. In passing through the jugular foramen the nerve presents, in succession, two gangliform enlargements. The superior and smaller is called the jugular ganglion; the inferior and larger, the petrous ganglion or the ganglion of Andersch. The superior or jugular ganglion (ganglion superius) is situated in the upper part of the groove in which the nerve is lodged during its passage through the jugular foramen. It is of very small size, and involves only part of the trunk of the nerve. It is usually regarded as a detached portion from the lower ganglion. The inferior or petrous ganglion (ganglion inferius) is situated in a depression in the lower border of the petrous portion of the temporal bone; it is larger than the superior ganglion and involves the whole of the fibres of the nerve. From this ganglion arise those filaments which connect the glossopharyngeal with the vagus and sympathetic nerves. Branches of Communication. — The branches of communication are with the vagus, sympathetic, and facial. The branches to the vagus are two filaments, arising from the petrous ganglion, one of which passes to the auricular branch ,of the vagus, and one to the upper ganglion of the vagus. The petrous ganglion is connected by a filament with the superior cervical ganglion. The branch of communication with the facial perforates the posterior bell}^ of the Digastric muscle. It arises from the trunk of the nerve below the petrous ganglion, and joins the facial just after its exit from the stylomastoid foramen. Branches of Distribution. — The branches of distribution are the tympanic, carotid, pharyngeal, muscular, tonsillar, and lingual. The Tympanic Branch or Jacobson's Nerve (;(. tympanicus) arises from the petrous ganglion, and enters a small bony canal {canaJicithis tympanicus) in the lower surface of the petrous portion of the temporal bone, the lower opening of which is situated on the bony ridge which separates the carotid canal from the jugular fossa. It ascends to the tympanum, enters that cavity by an aperture in its floor close to the inner wall, and divides into branches which are contained in grooves upon the surface of the promontory. These branches form a tympanic THE TENTH, VAGUS, OR PNEUiMOGASTRIC NERVE 1003 plexus {plexus tyvipanicus). This plexus gi^^es off (1) the small superficial petrosal nerve (Fig. 745); (2) a branch to join the great superficial petrosal nerve; and (3) branches to the tympanic cavity, all of which will be described in connection with the anatomy of the ear. The Carotid Branches (u. caroticofympanicus superior and u. caroticotympaiiicus inferior) descend along the trunk of the internal carotid artery as far as its com- mencement, communicating with the pharyngeal branch of the vagus and with branches of the sympathetic. The Pharyngeal Branches (rami pharyngei) are three or four filaments which unite opposite the Middle constrictor of the pharynx with the pharyngeal 1)ranches of the vagus and sympathetic nerves to form the pharyngeal plexus, brandies from which perforate the muscular coat of the pharynx to supply tlie muscles and mucous membrane. The Muscular Branch (ramus sfylophari/ngeus) is distributed to the Stylo- pharyngeus muscle. The Tonsillar Branches (rami tonsillares) supply the tonsil, forming a plexus (circulus tonsillaris) around this body, from which branches are distributed to the soft palate and fauces, where they communicate with the palatine nerves. The Lingual Branches {rami linguales) are two in number; one supplies the cir- cumvallate papillsB and the mucous membrane covering the surface of the base of the tongue; the other perforates its substance, and supplies the mucous mem- brane and follicular glands of the posterior one-third of the tongue and communi- cates with the lingual nerve. The Gustatory Path. — The impressions of taste reach the glossopharyngeal nucleus in the medulla oblongata in two ways. From the posterior one-third of the tongue and from the palate they reach the nucleus by the glossopharyngeal nerve. From the anterior two-thirds of the tongue impulses of taste are conveyed by the chorda tympani or portion of the nervus intermedius. From the glosso- pharyngeal nucleus gustatory impressions pass by way of the medial fillet to the thalamus of the opposite side, and from the thalamus through ventral thalamo- cortical radiation to the gyrus hippocampi, where the cortical gustatory centre is situated. Applied Anatomy. — Injury may produce hemorrhage about the roots of the nerve. Berg- mann reported such a case. The patient died from edema of the glottis after presenting evi- dences of disorder of speech and difSculty in swallowing. Disease of the glossopharyngeal nerve alone cannot usually be diagnosticated. THE TENTH, VAGUS, OR PNETJMOGASTRIC NERVE (N. VAGUS) (Figs. 748, 749). The tenth, vagus, or pneumogastric nerve has a more extensive distribution than any of the other cranial nerves, passing through the neck and thorax to the upper part of the abdomen. It is composed of both motor and sensor fibres. It supplies the organs of voice and respiration with motor and sensor fibres, and the pharynx, oesophagus, stomach, and heart with motor fibres. Its superficial origin (Fig. 748) is by eight or ten filaments from the groove between the olive and the restiform body below the glossopharyngeal; its central connections are described on page 880. The real origin of the sensor fibres of the vagus is to be found in the cells of the ganglia on the nerve — viz., the ganglion of the root and the ganglion of the trunk. The filaments become united and form a flat cord, which passes outward beneath the flocculus to the jugular foramen, through which it emerges from the cranium (Fig. 749). In passing through this opening the vagus accompanies the spinal accessory nerve, being contained in the same sheath of dura with it, a 1004 THE NERVE SYSTEM Gh'!Sophari/ngeal \ Spinal membranous septum separating them from the glossopharyngeal, which lies in front (Fig. 749). The nerve in this situation presents a well-marked ganghonic enlargement, which is called the superior ganglion, or jugular ganglion; to it the vagal ac- cessory part of the spinal ac- cessory nerve is connected by one or two filaments. After its exit from the jugular fora- men the nerve is joined by the accessory portion of the spinal accessory nerve and enlarges into a second gangliform swell- ing, called the inferior ganglion or the ganglion of the trunk of the nerve, through which the fibres of the spinal accessory nerve pass unchanged, being principally distributed to the pharyngeal and superior laryn- geal branches of the vagus ; but some of the filaments from it are continued into the trunk of the vagus below the ganglion to be distributed with the re- current laryngeal nerve, and probably also with the cardiac nerves. The vagus nerve passes vertically down the neck within the sheath of the carotid ves- sels lying between the internal carotid artery and the internal jugular vein as far as the thy- roid cartilage, and then between the same vein and the common carotid to the root of the neck (Fig. 749). From here the course of the nerve differs on the two sides of the body. On the right side (Fig. 749) the nerve passes across the sub- clavian artery between it and the right innominate vein, and descends by the side of the trachea to the back part of the root of the right lung, where it spreads out in a plexiform net- work, the posterior pulmonary plexus (plexus pulmonalis pos- terior), from the lower part of which two cords descend upon the oesophagus, on which tube they divide, forming, with branches from the opposite nerve, the oesophageal plexus (plexus gulae); below, these branches are collected into a single cord, which runs along the back part of the oesophagus, enters the abdomen, and is distributed to the Vagus -Course and distribution of the glossopharyngeal, ' and spinal accessory ] THE TENTH, VAGUS, OB, PNEUMOGA8T11IC NEliVE 1005 posterior surface of the stomach, joining the left side of the solar plexus, and send- ing filaments to the splenic plexus and a considerable branch to the coeliac plexus. On the left side the vagus nerve enters the thorax between the left carotid and subclavian arteries, behind the left innominate vein. It crosses the arch of the aorta and descends behind the root of the left lung, forming the posterior pul- monary plexus [plexus fulvionalis posterior), and along the anterior surface of the oesophagus, where it unites with the nerve of the right side in forming the oesopha- geal plexus. It passes to the stomach, distributing branches over the anterior surface of that viscus, some extending over the fundus, and others along the lesser curvature. Filaments from these branches enter the gastrohepatic omentum and join the hepatic plexus. The ganglion of the root or the jugular ganglion (ganglion jugulare) is of a grayish color, circular in form, about 4 mm. or ^ inch in diameter. Branches of Communication. — To this ganglion the accessory portion of the spinal accessory nerve is connected by several delicate filaments; it also communi- cates by a twig with the petrous ganglion of the glossopharyngeal, with the facial nerve by means of its auricular branch, and with the sympathetic by means of an ascending filament from the superior cervical ganglion. The ganglion of the trunk or the inferior ganglion (ganglion nodosum) is a plexiform cord, cylindrical in form, of a reddish color, and about an inch (2 cm.) in length; it involves the whok of the fibres of the nerve, and passing through it is the vagal accessory portion of the spinal accessory nerve, which blends with the vagus below the ganglion, to be then continued principally into its pharyngeal and superior laryngeal branches. Branches of Communication. — This ganglion is connected with the hypoglossal, the superior cervical ganglion of the sympathetic, and the loop between the first and second cervical nerves. Branches of Distribution. — The branches of the vagus are: In the jugular fossa . . . } Meningeal or dural. ■' ° ( Auricular. r Pharyngeal. In the neck \ Superior laryngeal. I Recurrent laryngeal. L Cervical cardiac. [ Thoracic cardiac. In the thorax .... _ Fig. 754. — A portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots. (Testut.) 1014 THE NEBVE SYSTEM Structure. — The ganglion in an embryo is composed of bipolar nerve cells. In an adult the bipolar nerve cells by fusion of their two poles form unipolar elements. The process of each unipolar cell divides' into two a short distance from the cell. One of the processes from each cell passes to the spinal cord, and the other passes into the spinal nerve. Two other forms of cells are, however, present — viz.: (a) the cells of Dogiel, whose axones ramify close to the cell (type II of Golgi), and are distributed entirely within the ganglion; and (6) multipolar cells similar to those found in the sympathetic ganglia. On the posterior roots of the lumbar and sacral nerves, between the spinal ganglia and the cord, small cellular masses occasionally exist. They are called accessory or aberrant ganglia (gaiujlia abermntia). Each tvpic spinal nerve contains somatic and splanchnic fibre systems, as well as fibres connecting these systems with each other. 1. The somatic fibres are eft'erent and afferent. The efferent fibres originate in the cells of the anterior cornu of the spinal gray substance, and run outward through the anterior nerve roots to the spinal nerve. They convey impulses to the voluntary muscles and are continuous from their origin to their peripheral distribution. The afferent fibres (peripheral axones) convey impres- sions from the -skin, etc., and originate in the unipolar nerve cells of the spinal ganglia. The central axones enter the spinal cord through the posterior nerve roots, to be continued to the medulla oblongata, to end in the nuclei of the gracile and cuneate funiculi (Goll and Burdach), or they may end by arborization around efferent neurones in the same or opposite side of the cord, completing in this way reflex arcs. 2. The sympathetic fibres are also efferent and afferent. The efferent fibres originate in the visceral motor gray substance of the spinal cord and are conveyed through the anterior nerve root and the white ramus communicans to the corresponding ganglion of the sympathetic chain; here they may end by forming synapses around its cells, or may run through the ganglion to end in another "of the chain or in a' more distally placed ganglion in one of the sympathetic plexuses, the impulses being relayed in other neurones to be carried to the bloodvessels of the trunk and limbs or to the viscera. , The afferent fibres are derived partly from unipolar and partly from the multipolar cells of the spinal ganglia. Their peripheral processes are carried outward through the white rami communicantes, and after passing through one or more sympathetic ganglia without interruption, terminate in the tissues of the viscera. The central processes of the Imipolar cells enter the spinal cord thi-ough the posterior nerve root and form synapses around either somatic or visceral efferent neurones, thus completing reflex arcs. The dendrites of the multipolar nerve cells form synapses around the cells of Dogiel in the spinal ganglia, and by this path the original impulse is transferred from the sympathetic to the somatic system, through which it is conveyed to the sensorium. Points of Emergence of the Spinal Nerves. — ^The roots of the spinal nerves from their origin in the cord run obliquely caudad to their point of exit from the intervertebral foramina, the amount of obliquity varying in different regions of the spine, and being greater in the lower than in the upper part. The level of their emergence from the cord is within certain limits variable, and of course does not correspond to the point of emergence of the nerve from the intervertebral foramina (Fig. 757). Each nerve root receives a covering from the pia, and is loosely invested by the arachnoid, the latter being prolonged as far as the points where the roots pierce the dura. The two roots pierce the dura separately, each receiving a sheath from this membrane; this sheath is continuous with the epineurium of the nerve where the roots join to form the spinal nerve. Divisions. — Immediately beyond the ganglion the two roots coalesce, their fibres intermingle, and the trunk thus formed constitutes the spinal nerve; it passes out of the intervertebral foramen, and divides into a posterior or dorsal primary division for the supply of the dorsal part of the body, and an anterior or ventral primary division for the supply of the ventral part of the body (Fig. 755). Each division contains fibres from both roots. Before dividing, each spinal nerve gives off a small recurrent or meningeal branch (ramus meningeus) (Fig. 755) which reenters the vertebral canal through the intervertebral foramen and supplies the membranes and bloodvessels of the cord, the vertebrae, and the vertebral ligaments. The posterior or dorsal primary divisions (rami posteriores) (Fig. 755) of the spinal nerves are generally smaller than the anterior; they arise from the trunk THE SPINAL NERVES 1015 resulting from the union of tlie roots, in the intervertebral foramina; and, passing dorsad, divide into internal or medial and external or lateral branches, which are distributed to the muscles and integument behind the spine. The posterior Fig. 755. — Plan of the constitution of a spinal nerve. (W. Keiller, in Gerrish's Text-book of Anatomy.) primary divisions of the spinal nerves form two small plexuses, the posterior cervical plexus and the posterior sacral plexus. The first cervical, the fourth and fifth sacral, and the coccygeal nerves do not divide into external and internal branches. Sympathetic ganglion Fig. 756. — Scheme showing structure of a typical spinal nerve. The anterior or ventral primary divisions {rami anteriores) (Fig. 755) of the spinal nerves supply the parts of the body ventrad of the spine, including the limbs. They are for the most part larger than the posterior primary divisions. Each division, soon after its origin, receives a slender filament from the sympathetic which is called the gray ramus commimicans. In the thoracic region the anterior 1016 THE NERVE 8YS2EM primary divisions of the spinal nerves are quite separate from each other, and are uniform in their distribution; but in the cervical, lumbar, and sacral regions they form intricate plexuses previous to their distribution. The anterior primary divisions of certain thoracic, lumbar, and sacral nerves give off a delicate col- lection of nerve filaments to the sympathetic cord. These are called the white rami communicantes or the visceral branches of the spinal nerves. Posterior or Dorsal Primary Divisions of the Spinal Nerves. — ^The posterior or dorsal primary divisions are here described together, inasmuch as they do not enter into the formation of the important plexuses (cervical, lumbar, and sacral) exclusively made up of the anterior primary divisions. Fig. 757. — Ventral aspect. Figs. 757 and 758. — Distributii Fig. 758. — Dorsal aspect, utaneous nerves. The Posterior or Dorsal Divisions of the Cervical Nerves {rami postcriores). — The posterior division of the first cervical nerve (Fig. 759) differs from the pos- terior divisions of the other cervical nerves in not dividing into an internal and external branch. It is larger than the anterior division, and escapes from the vertebral canal between the occipital bone and the posterior arch of the atlas and beneath the vertebral artery. It enters the suboccipital triangle formed by THE SPINAL NERVES 1017 the Rectus capitis posticus major, the Obliquus superior and Obiiquus inferior; it gives branches also to the Rectus capitis posticus minor and to the Complexus. From the branch which supplies the Inferior oblicjue a communicating filament is given off which joins the second cervical nerve. This nerve also occasionally gives off a cutaneous filament, which accompanies the occipital artery and com- municates with the occipitalis major and minor nerves. The posterior division of the second cervical nerve is much larger than the anterior division, and is the largest of all the posterior cervical divisions. It emerges from the vertebral canal between the anterior arch of the atlas and lamina of. the axis, below the Inferior oblique. It supplies a twig to this muscle, and receives a communicating filament from the first cervical. It then divides into an internal or medial and an external or lateral branch. The internal or medial branch, called, from its size and distribution, the great occipital nerve (?i. occipitalis major) {Pig. 759), ascends obliquely inward between the Obliquus inferior and the Complexus, and pierces the latter muscle and the Trapezius near their attachments to the occipital bone. It is now joined by a filament from the posterior division of the third cervical nerve, the anastomotic, and, ascending on the back part of the head with the occipital artery, divides into two branches, which supply the integument of the scalp as far forward as the vertex, communicating with the occipitalis minor. It gives ofT an auricular branch to the back part of the ear and muscular branches to the Complexus. The external or lateral branch is often joined by the external branch of the pos- terior division of the third cervical nerve, and supplies the Splenius, Trachelo- mastoid, and Complexus. VERTEBRAL ARTERY Fig. 759. — Posterior primary divisions of the upper three cervical nerves, (Testut.l The posterior division of the third cervical nerve (Fig. 759) is intermediate in size between those of the second and fourth. Its internal or cutaneous branch passes between the Complexus and Semispinalis, and, piercing the Splenius and Trapezius, supplies the skin over the latter muscle; while under the Trapezius it gives off a branch called the third occipital nerve (n. occipitalis iertius), which pierces the Trapezius and supplies the skin on the lower and back part of the head. It lies to the inner side of the occipitalis major, with which it is connected. The external branch often joins that of the second cervical. The posterior division of the suboccipital nerve and the internal branches of the posterior divisions of the second and third cervical nerves are occasionally 1018 THE NEBVE SYSTEM Joined beneath the Complexus by communicating loops to form the posterior cervical plexus (Cruveilhier). The posterior divisions of the lower five cervical nerves pass dorsad, and divide, behind the Intertransversales muscles, into internal or medial and external or lateral branches. The internal branches, the larger, are distributed differently in the upper and lower part of the neck. Those derived from the fourth and fifth nerves pass between the Complexus and Semispinalis muscles, and, having reached the Spinous processes, perforate the aponeurosis of the Splenius and Trapezius, and are con- tinued outward to the integument over the Trapezius, while those derived from the three lowest cervical nerves are the smallest, and are placed beneath the Semi- spinalis colli, which they supply, and then pass into the Interspinalis, Multifidus spinae, and Complexus, and send twigs through this latter muscle to supply the integument near the spinous processes. The external branches supply the muscles at the side of the neck — viz., the Cervicalis ascendens, Transversalis colli, and Trachelomastoid. The Posterior Divisions of the Thoracic Nerves (rami foster lores). — ^The posterior divisions of the thoracic nerves are smaller than the anterior, pass dorsad between the transverse processes, and divide into internal or medial and external or lateral branches. The internal or medial branches of the posterior divisions of the six upper thoracic nerves pass inward between the Semispinalis dorsi and Multifidus spinae muscles, which they supply, and then, piercing the origins of the Rhpmboidei and Trapezius muscles, become cutaneous by the side of the spinous processes and ramify in the integument. The medial branches of the six lower thoracic nerves are dis- tributed to the Multifidus spinae, without giving off any cutaneous filaments. The external or lateral branches increase in size from above downward. They pass through the Longissimus dorsi muscle to the cellular interval between it and the Iliocostalis muscle, and supply those muscles, as well as their continuations upward to the head, and also the Leva tores costarum muscles; the five or six lower nerves also give off cutaneous filaments, which pierce the Serratus posticus inferior and Latissimus dorsi muscles in a line with the angles of the ribs, and then ramify in the integument. The cutaneous branches of the posterior primary divisions of the thoracic nerves are twelve in number. From each ramus medialis of the upper six nerves comes a ramus cutaneus medialis, and from each ramus lateralis of the lower six nerves comes a ramus cutaneus lateralis. The six upper cutaneous nerves are derived from the internal branches of the posterior divisions of the thoracic nerves. They pierce the origins of the Rhomboidei and Trapezius muscles, and become cutaneous by the side of the spinous processes, and then ramify in the integument. They are frequently furnished with gangliform enlargements. The six lower cuta- neous nerves are derived from the external branches of the posterior divisions of the thoracic nerves. They pierce the Serratus posticus inferior and Latissi- mus dorsi muscles in a line with the angles of the ribs, and then ramify in the integument. The Posterior Divisions of the Lumbar Nerves (rami posteriores). — The posterior divisions of the lumbar nerves diminish in size from above downward; they pass postero-laterad between the transverse processes, and divide into internal or medial and external or lateral branches. The internal branches (rami mediales), the smaller, pass inward close to the articular processes of the vertebrae, and supply the Multifidus spinae and Inter- spinales muscles. The external branches (rami laterales) supply the Erector spinae and Inter- transverse muscles. The three upper branches give off cutaneous nerves which THE SPINAL NUBVES ' 1019 pierce the aponeurosis of the Latissimiis dorsi muscle and descend over the back part of the crest of the ilium, to be distributed to the integument of the gluteal region, some of the filaments^assing as far as the trochanter major (Fig. 778). The posterior division of the fifth lumbar nerve usually sends a branch which forms a loop with the posterior division of the first sacral nerve. The Posterior Divisions of the Sacral Nerves (rami posteriores) (Fig. 779). — ■ The posterior divisions of the sacral nerves are small, diminish in size from above downward, and emerge, except the last, from the sacral canal by the posterior sacral foramina. The upper three are covered at their exit from the sacral canal by the IMultifidus spinae muscle, and divide into internal or medial and external or lateral branches. The internal branches (rarni mediales) are small, and supply the Multifidus spinae muscle. The external branches (rami laterales) join with one another, and with the last lumbar and fourth sacral nerves, in the form of loops on the posterior surface of the sacrum, constituting the posterior sacral plexus. From these loops branches pass to the outer surface of the great sacrosciatic ligament, where they form a second series of loops beneath the Gluteus maximus muscle. Cutaneous branches from this second series of loops, usually two or three in number, pierce the •Gluteus maximus muscle along the line drawn from the posterior superior spine of the' ilium to the tip of the coccyx. They supply the integument over the posterior part of the gluteal region. , The posterior divisions of the lower two sacral nerves are small and lie below the Multifidus spinae muscle. They do not divide into internal and external branches, but join with each other, and \\\i\\ the posterior division of the coccygeal nerve to form the posterior sacrococcygeal nerve, which passes through the sacro- sciatic ligament, and forms loops on the back of the sacrum, filaments from which supply the integument over the coccyx. The Posterior Division of the Coccygeal Nerve. — ^The coccygeal nerve divides into its anterior and posterior divisions in the vertebral canal. The posterior division is the smaller, and it does not divide into internal and external branches, but receives, as already stated, a communicating branch from the last sacral, and is lost in the integument over the dorsum of the coccyx. Anterior or Ventral Primary Divisions of the Spinal Nerves. — ^l"'he anterior primary divisions of the spinal nerves (rami anteriores) supply the antero-lateral parts of the trunks and the limbs; they are, for the most part, larger than the posterior divisions. In the thoracic region they run independently of one another, but in the cervical, lumbar, and sacral regions they unite near their origins to form plexuses. The Anterior or Ventral Divisions of the Cervical Nerves (rami anteriores). — The anterior primary divisions of the cervical nerves, with the exception of the first, pass laterad between the anterior and posterior Intertransverse muscles, lying on the grooved upper surfaces of the transverse processes, and emerge between the muscles attached to the anterior and posterior tubercles of these processes. The anterior primary division of the first or suboccipital nerve issues from the vertebral canal above the posterior arch of the atlas and runs forward around the lateral aspect of its superior articular process, internal to the vertebral artery. In most cases it descends internal to and in front of the Rectus lateralis, but in some cases it pierces the muscle. The anterior primary divisions of the upper four cervical nerves unite to form the cervical plexus, and each receives a gray ramus communicans from the superior cervical ganglion of the sympathetic cord. Those of the lower four cervical, together with the greater part of the first thoracic, form the brachial plexus. They 1020 THE NEBVJE SYSTEM each receive a gray ramus communicans, those for the fifth and sixth being derived from the middle, and those for the seventh and eighth from the inferior, cervical ganglion of the sympathetic. THE CERVICAL PLEXUS (PLEXUS CERVICALIS) (Figs. 760, 761). The cervical plexus is formed by the anterior divisions of the four upper cervical nerves. It is situated opposite the four upper cervical vertebrae, resting upon the Levator anguli scapulae and Scalenus medius muscles, and covered in by the Sternomastoid. Its branches may be divided into two groups, superficial and deep, which may be thus arranged: 2,C. 2, 3, C. 2. 3, C. 3,4,C. 3. 4, C. 3, 4, C. 1,2,C. 1,2,C. , 2, 3, 4, C. 1,C. 1,2,C. 2, 3, C. 3, 4, 5, C. 2, 3, 4, C. 2,C. 3, 4, C. 3, 4, C. 3, 4, C. [Ascending /Small occipital " (^ (jreat auricular Superficial \ Transverse Superficial cervical [ Sternal . [ Descending or Supraclavicular \ Clavicular [ Acromial f with hypoglossal r Communicating I with vagus . i with sympathetic f Rectus lateralis . Deep . Internal L Muscular '■ External I Anterior Recti .... j Communicantes hypoglossi 1^ Phrenic Communicating with spinal accessory . r Sternomastoid Muscular Trapezius . . . . . JLevator anguli scapulae I Scalenus medius The Superficial Branches of the Cervical Plexus. — ^The Small Occipital Nerve {n. occipitalis minor) (Fig. 760) arises from the second cervical nerve, sometimes also from the third ; it curves around the posterior border of the Sternomastoid, and ascends, running parallel to the posterior border of the muscle, to the back part of the side of the head. Near the cranium it perforates the deep fascia, and is continued upward along the side of the head behind the ear, supplying the integument, and communicating with the great occipital, great auricular, and with the posterior auricular branch of the facial. This nerve gives off an auricular branch, which supplies the integument of the upper and back part of the auricle, communicating with the mastoid branch of the great auricular. The auricular branch is occasionally derived from the great occipital nerve. The small occipital varies in size; it is occasionally double. The Great Auricular Nerve (?i. auricularis magnus) (Fig. 760) is the largest of the ascending branches. It arises from the second and third cervical nerves, winds around the posterior border of the Sternomastoid, and, after perforating the deep fascia, ascends upon that muscle beneath the Platysma to the parotid gland, where it divides into facial, auricular, and mastoid branches. The facial branches are distributed to the integument of the face over the parotid gland; others penetrate the substance of the gland and communicate with the facial nerve. The auricular branches ascend to supply the integument of the back of the pinna, except at its upper part, communicating with the auricular branches of the facial and vagus nerves. A filament pierces the pinna to reach its outer surface, where it is distributed to the lobule and lower part of the concha. The mastoid branch communicates with the small occipital and the posterior THE CERVICAL PLEXUS 1021 auricular branch of the facial, and is distributed to the integument l)ehind the ear. The Superficial or Transverse Cervical Nerve (n. cutaneus colli) (Fig. 760) arises from the second and third cer\ical nerves, turns around the posterior border of the Sternomastoid about its middle, and, passing obliquely forward beneath the external jugular vein to the ventral border of the muscle, perforates the deep cervical fascia, and divides beneath the Platysma into two branches, which are distributed to the antero-lateral parts of the neck. BRANCHEa. OF FAC1A6, " NERVE \ VI f/JA, 'fk " ''''''^'^^° Fig. 760.— The cutaneous branches of the right cervical plexus viewed from the right. The Platysma h.a.s been partly removed. (Spalteholz.) The ascending' branch (ramus superior) gives a filament which accompanies the external jugular vein; it then passes upward to the submaxillary region, and divides into branches, some of which form a plexus with the cervical branches of the facial nerve beneath the Platysma; others pierce that muscle and are distributed to the integument of the upper half of the neck, at its fore part, as high as the chin. The descending branches (rami inferiores), usually represented by two or more filaments, pierce the Platysma, and are distributed to the integument of the side and front of the neck, as low as the sternum. 1022 THE NERVE SYSTEM The Descending or Supraclavicular Branches {nn. supraclavicular es) (Fig. 760) arise from the third and fourth cervical nerves; emerging beneath the posterior border of the Sternomastoid, they descend in the posterior triangle of the neck beneath the Platysma and deep cervical fascia. Near the clavicle they perforate the fascia and Platysma to become cutaneous, and are arranged, according to their position, into three groups. Fig. 761.— Plan of the 'al plexus. _ (Gerrish.) The Inner or Sternal Branches {nn. supraclaviculare.s anteriores) cross obliquely over the external jugular vein and the clavicular and sternal attachments of the Sternomastoid muscle, and supply the integument as far as the median line. They furnish one or two filaments to the sternoclavicular joint. The Middle or Clavicular Branches {nn. supraclaviculares medii) cross the clavicle, and supply the integument over the Pectoral and Deltoid muscles, communicating with the cutaneous branches of the upper intercostal nerves. The External or Acromial Branches {nn. supraclaviculares posferiores) pass THE CERVICAL PLEXUS 1023 obliquely across the outer surface of the Trapezius and the acromion, and supply the integument of the upper and back part of the shoulder. The Deep Branches of the Cervical Plexus (Fig. 761). Internal Series.— The Communicating Branches consist of several filaments which pass from the loop between the first and second cervical nerves to the vagus, hypoglossal, and sympa- thetic. The branch accompanying the hypoglossal in its sheath ultimately leaves PP«'-HI-l / V t , \x INFERIOR Wt \ CERVICAL V /gsnglion • ""■vV INFERIOR Vv.iSX'LAByNGEAL UNICATING ROM PLEXUS C CARDIAC *, /^ J \laryngeal Fig. 762.— The phn rith the vagus nerve. (Toldt.) that nerve as a series of branches — viz., the descendens cervicalis, the nerve to the Thyrohyoid, and the nerve to the Geniohyoid (see p. 1011). Branches (gray rami communicantes) from all four cervical nerves pass to the superior cervical ganglion of the sympathetic, while another communicating branch passes from the fourth to the fifth cervical. Muscular branches supply the Anterior recti and Rectus lateralis muscles. Those to the Anterior recti proceed from the first cervical nerve, and from the loop formed between it and the second. The Rectus lateralis is supplied by the second, third, and fourth cervical nerves. The Communicantes Cervicales (Hypoglossi) (Fig. 761) consist usually of two 1024 THE NERVE SYSTEM filaments, one being derived from the second and the other from the third cervical. These filaments usually join to form the descendens cervicis, which passes down- ward on the outer side of the internal jugular vein, crosses in front of the vein a little below the middle of the neck, and forms a loop {ansa hypoglossi; ansa cer- vicalis) with the descendens hypoglossi in front of the sheath of the carotid vessels. Occasionally, the junction of these nerves takes place within the sheath. DESCENDING BRANCH OF HYPOGLOSSAL '/W/''^m Fig. 763. — The right brachial plexus with its short branches, viewed from in front. The _ Sternomastoid and Trapezius muscles have been completely, the Omohyoid and Subclavius have been partially, removed; a piece has been sawed out of the clavicle; the JPectoralis muscles have been incised and reflected. (Spalteholz.) The Phrenic or the Internal Respiratory Nerve of Bell {n. phrenicus) (Figs. 761 and 762) arises chiefly from the fourth cervical nerve, with a few filaments from the third and a branch from the fifth, although this branch is occasionally derived from the nerve to the Subclavius. It descends to the root of the neck, running obliquely across the front of the Scalenus anticus, and beneath the Sternomastoid, the posterior belly of the Omohyoid muscles, and the transversalis colli and suprascapular vessels. It next passes over the first part of the subclavian artery, between it and the subclavian vein, and, as it enters the thorax, crosses the internal mammary artery near its origin. Within the thorax it descends nearly vertically in front of the root of the lung and by the side of the pericardium, between it and the mediastinal portion of the pleura, to the Diaphragm, where it divides into branches, some few of which are distributed to its thoracic surface, but most of which separately pierce that muscle and are distributed to its under surface (rami phren.icoabdominales). In the thorax it is accompanied by a branch of the internal mammary artery, the arteria comes nervi phrenici. The two phrenic nerves differ in their length, and also in their relations at the upper part of the thorax. The right phrenic nerve is situated more deeply, and is shorter and more vertical in direction than the left; it lies on the outer side of the right innominate vein and superior vena cava. THE CERVICAL PLEXUS 1025 The left phrenic nerve is rather longer than the right, from the inclination of the heart to the left side, and from the Diaphragm being lower on this than on the opposite side. It enters the thorax behind the left innominate vein, and crosses in front of the vagus and the arch of the aorta and the root of the hmg. Each nerve supplies filaments to the pericardium and pleura, and near the thorax is joined by a filament from the sympathetic, and, occasionally, by one from the ansa cervicalis. Branches have been described as passing to the peri- toneum. MUSCULOCUTANEOUS 3 ■t ^ ,1 LflTrPAL CUTANEOUS I ~i. Jl I Inr ■vr th of 5^^^ THIRD INTERCOSTAL Fig. 764. — The right brachial plexus (infraclavicular portion) in the axillary fossa, viewed from below and in front. The Pectoralis major and minor muscles have been in large part removed; their attachments have been reflected. (Spalteholz.) From the right nerve one or two filaments pass to join in a small ganglion with phrenic branches of the solar plexus; and branches from this ganglion are dis- tributed to the hepatic plexus, the suprarenal gland, and inferior vena cava. From the left nerve filaments pass to join the phrenic plexus of the sympathetic, but without any ganglionic enlargement. Applied Anatomy. — Irritation of the phrenic nerve causes hiccough and persistent cough. Bilateral paralysis of the phrenic causes death from paralysis of the Diaphragm. This form of death is seen by the surgeon in fracture dislocation of the third cervical vertebra. Division of the phrenic on one side is not fatal, and is occasionally practised by the surgeon in removing a tumor of the neck. In Hearn's and Franklin's cases of removal of the vagus the phrenic was also divided. Unilateral division of the phrenic nerve causes paralysis of the corresponding half of the Diaphragm, which is difficult of recognition, because, as Gowers points out, the patient can still take deep inspirations, the thoracic muscles not being paralyzed. The Deep Branches of the Cervical Plexus. External Series. Communi- cating Branches, — The deep branches of the external series of the cervical plexus 65 1026 THE NERVE SYSTEM communicate with the spinal accessory nerve, in the substance of the Sterno- mastoid muscle, in the posterior triangle, and beneath the Trapezius. Muscular branches are distributed to the Sternomastoid, Trapezius, Levator anguli scapulae, and Scalenus medius. The branch for the Sternomastoid is derived frojn the second cervical; the Trapezius and Levator anguli scapulae receive branches from the third and fourth. The branch for the Scalenus medius is derived sometimes from the third, sometimes from the fourth, and occasionally from both nerves. SCULO SPIRAL Fig. 765. — Plan of the brachial plexus. (Gerrish.) Applied Anatomy. — The cervical plexus may be damaged by wounds or contusions, which may or may not be associated with fracture of the clavicle. Paralysis ensues, the extent depend- ing on the degree of damage. After a contusion the paralysis is apt to be temporary and to be followed by pain and muscular spasm in the arm. Paralysis of the arm due to plexus injury may be partial or complete. In some cases there is complete motor palsy and partial sensor palsy, the sensor impulses passing along undamaged collaterals. In certain spasmodic diffi- culties the surgeon occasionally stretches the cervical plexus. It is reached by an incision at the posterior margin of the Sternomastoid muscle. This incision begins t\vo inches below the level of the tip of the mastoid and is carried downward for three inches. THE BRACHIAL PLEXUS (PLEXUS BRACHIALIS) (Figs. 763, 764). The brachial plexus is formed by the union of the anterior primary divisions of the lower four ce^^'^cal nerves and the greater part of the first thoracic nerve, receiving usually a fasciculus from the fourth cervical nerve, and frequently one from the second thoracic nerve. It extends from the lower part of the side of the neck to the axilla. It is very broad, and presents little of a plexiform arrangement at its commencement. It is narrow opposite the clavicle, becomes broad and forms a more dense interlacement in the axilla, and divides opposite the coracoid process into numerous branches for the supply of the upper limb. The nerves which form the plexus are all similar in size, and their mode of communication is subject to considerable variation, so that no one plan can be given as applying to THE BRACHIAL PLEXUS 1027 every case/ The following appears, however, to be the most constant arrangement : above the clavicle {'pars supraclavicularis) the fifth and sixth cervical unite soon after their exit from the intervertebral foramina to form a common trunk. The eighth cervical and first thoracic also unite to form one trunk. So that the nerves Fig. 766. — Cutaneous nerves of right upper Fig. 767. — Cutaneous nerves of right upper extremity Anterior view extremity. Posterior view. forming the plexus, as they lie on the Scalenus medius at the outer border of the Scalenus anticus muscle, are blended into three trunks — an upper one, formed ' Kerr, Bardeen, and Elting, from a study of 175 brachial plexuses, recognized seven types. In 58 per cent, the outer cord was formed from the fourth to the seventh, the inner cord froni the eighth to the ninth spina] nerve, and the posterior or dorsal cord from the fourth to the ninth. In 30 per cent, the outer cord was formed from the fifth to the seventh, the inner cord from the eighth to the ninth, and the posterior cord frcm the fiftl« to the ninth. 1028 THE NEB VE SYSTEM by the junction of the fifth and sixth cervical nerves; a middle one, consisting of the seventh cervical nerve; and a lower one, formed by the junction of the eighth cervical and first thoracic nerves. As they pass beneath the clavicle, to compose the infraclavicular part of the plexus (pars infraclavicular is), each of these three trunks divides into two branches, an anterior and a posterior. The anterior divi- sions of the upper and middle trunks then unite to form a common cord, which is situated on the outer side of the middle part of the axillary artery, and is called the outer cord of the brachial plexus (fasciculus lateralis). The anterior division of the lower trunk passes distally on the inner side of the axillary artery in the middle of the axilla, and forms the inner cord of the brachial plexus (fasciculus medialis). The posterior divisions of all three trunks unite to form the posterior cord of the brachial plexus (fasciculus posterior), which is situated behind the second portion of the axillary artery. From this posterior cord are given off the two lower subscapular nerves, the upper subscapular nerve being given off from the posterior division of the upper trunk prior to its junction with the posterior division of the lower and middle trunks. The posterior cord divides into the circumflex and musculospiral nerves. Branches of Communication. — ^The brachial plexus communicates with the cer- vical plexus by a branch from the fourth to the fifth cervical nerve, and with the phrenic nerve by a branch from the fifth cervical, which joins that nerve on the Anterior scalenus muscle; the fifth and sixth cervical nerves are joined by filaments to the middle cervical ganglion of the sympathetic, the seventh and eighth cervical to its inferior ganglion, and the first thoracic nerve to its first thoracic ganglion. Close to their exit from the intervertebral foramina the nerves give ofT the filaments to the ganglia. Relations, — In the neck, the brachial plexus lies in the posterior triangle, being covered by the skin, Platysma, and deep fascia; it is crossed by the posterior belly of the Omohyoid muscle and by the transversalis colli artery. When the dorsalis scapulae artery arises from the third part of the subclavian it usually passes between the roots of the plexus. The plexus lies at first between the Scalenus anticus and medius, and then above and to the outer side of the subclavian artery; it next passes behind the clavicle and Subclavius muscle, lying upon the first serration of the Serratus magnus, and the Subscapularis muscles. It is in close relation with the apex of the lung (Luschka). In the axilla it is placed on the outer side of the first portion of the axillary artery; it surrounds the artery in the second part of its course, one cord lying upon the outer side of that vessel, one on the inner side, and one behind it, and at the lower part of the axillary space gives off its terminal branches to the upper extremity. Branches of Distribution. — ^The branches of the brachial plexus are arranged in two groups — viz., those given off above the clavicle, and those below the clavicle. SuPBACLA^^cuLAH Branches. Communicating /with phrenic „ ^ 5' S" " (^ with sympathetic 5, 6, 7, 8, C. 1, T. Rhomboids (posterior scapular) 5, C. Supraspinatus ) „ , _ „ ^ Infraspinatus [Suprascapular ...... 5, 6, C. Muscular . . ^Subclavius 5,6,C. Serratus magnus (posterior thoracic) ..... 5, 6, 7, C. Longus colli 5, 6, 7, 8, C. LScaleni 5, 6,7,8. C. The Communicating Branch (Figs. 762 and 765) with the phrenic is derived from the fifth cervical nerve or from the loop between the fifth and sixth; it joins the phrenic on the Anterior scalenus muscle. The communications with the sympa- thetic have already been referred to. The Muscular Branches (rami nvusculares) supply the Longus colli, Scaleni, Rhomboidei, and Subclavius muscles. Those for the Loneus colli and Scaleni THE BRACHIAL PLEXUS 1029 arise from the four lower cervical nerves at their exit from the intervertebral . foramina. The nerve to the Subclavius {ti. subclavius) is a small filament which arises from the fifth cervical at its point of junction with the sixth nerve; it descends in front of the third part of the subclavian artery to the Subclavius muscle, and is usually connected by a filament with the phrenic nerve. The posterior scapular nerve (k. dorsalis scapulae) (Figs. 763 and 765) arises from the fifth cervical, pierces the Scalenus medius, and passes beneath the Levator anguli scapulae, which it occasionally supplies to the Rhomboid muscles. The Long Thoracic or the External Respiratory Nerve of Bell or Posterior Thoracic Nerve (;;. fhoracalis longus) (Figs. 763 and 770) supplies the Serratus magnus muscle, and is remarkable for the length of its course. It usually arises by three roots from the. fifth, sixth, and seventh nerves, but the root from the seventh may be absent. The roots from the fifth and sixth nerves pierce the Scalenus medius, while that from the seventh emerges in front of that muscle. The nerve passes down behind the brachial plexus and the axillary vessels, resting on the outer surface of the Serratus magnus. It extends along the side of the thorax to the lower border of that muscle, supplying filaments to each of the muscular digitations. The Suprascapular Nerve (n.. suprascapularis) (Figs. 765 and 770) arises from the trimk formed by the fifth and sixth cervical nerves; passing obliquely outward beneath the Trapezius and the Omohyoid, it enters the supraspinous fossa below the transverse or suprascapular ligament, passes beneath the supraspinatus muscle, and curves around the external border of the spine of the scapula to the infraspinous fossa. In the supraspinous fossa it gives ofF two branches to the Supraspinatus muscle, and an articular filament to the shoulder-joint; and in the infraspinous fossa it gives off two branches to the Infraspinatus muscle, besides some filaments to the shoulder-joint and scapula. The Infraclavicular Branches (Figs. 764 and 765) are derived from the three cords of the brachial plexus. The fasciculi of which they are composed may be traced through the plexuses to the spinal nerves from which they originate. They are as follows: f Musculocutaneous 5, 6, C. Outer cord . External anterior thoracic 5, 6, 7, C. I Outer head of median 6, 7, C. f Internal anterior thoracic 8, C. 1,T. Internal cutaneous 8, C.1,T. Inner cord . •! Lesser internal cutaneous . (8, C.)1,T. j Ulnar S,C. 1,T. I Inner head of median 8, C. 1,T. r Upper subscapular 5, 6, C. Middle " 5, 6, 7, C. Posterior cord -j Lower " '. 5, 6, C. Circumflex 5, 6, C. I Musculospiral . . . (.5), 6, 7, 8, C. (1, T). These branches from below the clavicle may be arranged according to the parts they supply: To the thorax Anterior thoracic. To the shoulder ...... / Subscapulars. \ Circumflex. r Musculocutaneous. Internal cutaneous. To the arm, forearm, and hand . J Cesser internal cutaneous. I Median. Ulnar. _^ Musculospiral. 1030 THE NEBVE SYSTEM The Anterior Thoracic Nerves {nn. thoracales anteriores) (Figs. 764 and 765), two in number, supply the Pectoral muscles. The external anterior thoracic nerve (Figs. 763 and 770), the larger of the two, arises from the outer cord of the brachial plexus, through which its fibres may be traced to the fifth, sixth, and seventh cervical nerves. It passes inward, across the axillary artery and vein, pierces the costocoracoid membrane, and is dis- tributed to the under surface of the Pectoralis major muscle. It sends down a communicating filament to join the internal anterior thoracic nerve, and this communicating filament forms a loop around the inner side of the axillary artery. The internal anterior thoracic nerve arises from the inner cord and through it from the eighth cervical and first thoracic nerves. It passes behind the first part of the axillary artery, then curves forward between the axillary artery and vein, and joins with the filament from the external nerve. It then passes to the under surface of the Pectoralis minor muscle, where it divides into a number of branches, which supply the muscle on its under surface. Some two or three branches pass through the muscle and reach the Pectoralis major. The Subscapular Nerves Qui. subscapulares) (Figs. 764 and 765), three in number, arise from the posterior cord of the plexus and supply the Subscapularis, Teres major, and Latissimus dorsi muscles, and give filaments to the shoulder-joint. The fasciculi of which they are composed may be traced to the fifth, sixth, seventh, and eighth cervical nerves. The upper or short subscapular nerve, the smallest, arises from the posterior divi- sion of the upper trunk of origin of the brachial plexus, and enters the upper part of the Subscapularis muscle; this nerve is frequently represented by two branches. The lower subscapular nerve arises from the posterior cord of the brachial plexus, enters the axillary border of the Subscapularis, and terminates in the Teres major. The latter muscle is sometimes supplied by a separate branch. The middle or long subscapular nerve (n. thoracodorsalis) (Fig. 764), the largest of the three, arises from the posterior cord of the brachial plexus and follows the course of the subscapular artery, along the posterior wall of the axilla to the Latissimus dorsi muscle, through which it may be traced as far as its lower border. The Circumflex Nerve (n. axillaris) (Figs. 765 and 771) supplies some of the muscles, the shoulder-joint, and the integument of the shoulder (Figs. 767 and 768). It arises from the posterior cord of the brachial plexus, in common with the musculospiral nerve, and its fibres may be traced through the posterior cord to the fifth and sixth cervical nerves. It is at first placed behind the axillary artery, between it and the Subscapularis muscle, and passes downward and out- ward to the lower border of that muscle. It then winds posteriorly in company with the posterior circumflex artery, through a quadrilateral space bounded above by the Teres minor muscle, below by the Teres major muscle, internally by the long head of the Triceps muscle, and externally by the neck of the humerus. The nerve then divides into two branches. The upper branch (Fig. 771) winds posteriorly around the surgical neck of the humerus, beneath the Deltoid, with the posterior circumflex vessels, as far as the an- terior border of that muscle, supplying it, and giving off cutaneous branches, which pierce the muscle and ramify in the integument covering its lower part (Fig. 768), The lower branch (Fig. 771). at its origin, distributes filaments to the Teres minor and back part of the Deltoid muscles. Upon the filaments to the former muscle an oval enlargement usually exists. The nerve then pierces the deep fascia, and supplies the integument over the lower two-thirds of the posterior surface of the Deltoid (n. cidaneus brachii lateralis), as well as that covering the long head of the Triceps (Fig. 772). The circumflex nerve, before its division, gives off an articular filament, which enters the shoulder- joint below the Subscapularis muscle. THE BRACHIAL PLEXUS 1031 The Musculocutaneous (n. nuisculocutaneus) (Figs. 765 and 770) arises from the outer cord of the brachial plexus, opposite the lower border of the Pectoralis minor muscle, receiving fila- ments from the fifth, sixth, and seventh cervical nerves. It perforates the Coraco- brachialis muscle (Fig. 770), passes obliquely betvi^een the Biceps and Brachialis anticus muscles to the outer side of the arm, and, a little above the elbow, winds around the outer border of the tendon of the Biceps, and, perforating the deep fascia, becomes cu- taneous (Fig. 766). In its course through the arm this nerve supplies the Coraco- brachialis, Biceps, and the greater part of the Brachialis anticus muscles. The branch to the Coracobrachialis is given off from the nerve close to its origin, and in some instances as a separate filament from the outer cord of the plexus. The branches to the Biceps and Brachialis anticus are given off after the nerve has pierced the Coraco- brachialis. The nerve also, sends a small branch to the humerus, which enters the nutrient foramen with the accompanying artery, and a filament from the branch supplying the Brachialis anti- cus goes to the elbow-joint. The musculocutaneous fur- nishes the chief nerve supply to this joint. The cutaneous portion of the musculocutaneous nerve (?!. cutaneus antebrachii lat- eralis) passes behind the median cephalic vein, and divides, opposite the elbow- joint, into an anterior and a posterior branch. The anterior branch de- scends along the radial border of the forearm to the wrist, and supplies the integument over the outer half of its anterior surface. At tlie wrist-joint it is placed in front of the radial artery, and some filaments, piercing the deep fascia, accompany that vessel to the dorsum of Fig. 708 — Cutaneous (W Keillcr I 1032 THE NERVE SYSTEM the wrist, supplying tlie carpus. The nerve then passes downward to the ball of the thumb, where it terminates in cutaneous filaments. It communicates with a branch from the radial nerve and with the palmar cuta- neous branch of the median. The posterior branch passes downward along the back part of the radial side of the forearm to the wrist. It sup- plies the integument of the lower third of the forearm, communicating with the radial nerve and the external cutaneous branch of the mus- culospiral. The cutaneous areas supplied by the mus- culocutaneous nerve are in- dicated in Figs. 768 and 769. Variations. — The musculocu- taneous nerve presents frequent irregularities. It may adhere for some distance to the median and then pass outward, beneath the Biceps, instead of through the Coracobrachialis. Frequently some of the fibres of the median run for some distance in the mus- culocutaneous and then leave it to join their proper trunk. Less frequently the reverse is the case, and the median sends a branch to join the musculocutaneous. In- stead of piercing the Coracobra- chialis muscle the nerve may pass under it or through the Biceps. Occasionally it gives a filament to the Pronator teres muscle, and it has been seen to supply the back of the thumb when the radial nerve was absent. The Internal Cutaneous Nerve {n. cutaneus antebrachii. medialis) (Figs. 765 and 770). or medial cutaneous nerve of the forearm, is one of the smallest branches of the bra- chial plexus. It arises from the inner cord in common with the ulnar nerve and internal head of the median nerve, and, at its commence- ment, is placed on the inner side of the axillary artery, and afterward of the brachial artery. It derives its fibres from the eighth cervical and first thoracic nerves. This nerve gives off, near the axilla, a cutaneous filament, which pierces the fascia and supplies the integument covering the Biceps 769. —Cutaneous nerves of the upper limb, posterior aspect. CW. Keiller, in Gerrish's Text-book of Anatomy.) THE BRACHIAL FLEXU8 1033 muscle nearly as far as the elbow. This filament lies a little external to the common trunk, from which it arises. It passes down the inner side of the arm, Eit") nal ante) lor thoracic. lull 1 nal anterior thoracic, MvKculocutaneoas, Mu'iculospiral. Paste) lor mte) osseous. Old terms. t.)tte)ior i))te)Oi,seou3. New terms Intercostohumeral = Intercostobrachial. Posterior thoracic = Long thoracic. Kerve of Wrisberg = Medial cutaneous nerve of upper arm, (N. cutaneus brachii medialis.) Internal cutaneous = lledial nerve of forearm. (N. cutaneus antebrachii mediahs.) Fig. 770. — Nerves of the left upper extremity. 1034 THE NERVE SYSTEM pierces the deep fascia with the basih'c vein, about the middle of the limb, and, becoming cutaneous, divides into two branches, anterior and posterior. The anterior branch, the larger of the two, passes usually in front of, but occa- sionally behind, the median basilic vein. It then descends on the anterior surface of the ulnar side of the forearm, distributing filaments to the integument as far as the wrist, and communicating with a cutaneous branch of the ulnar nerve (Fig. 766). The posterior branch passes obliquely downward on the inner side of the basilic vein, passes in front of, or over, the internal condyle of the humerus to the back of the forearm, and descends on the posterior surface of its ulnar side as far as the wrist, distributing filaments to the integument (Fig. 767). It communicates, above the elbow, with the lesser internal cutaneous nerve, the lower external cutaneous branch of the musculospiral, and above the wrist with the posterior cutaneous branch of the ulnar nerve. The cutaneous areas supplied by the internal cutaneous nerve are indicated in Figs. 768 and 769). The Lesser Internal Cutaneous Nerve, or the Nerve of Wrisberg (?;,. cutaneus brachii medialis) (Figs. 765 and 770), is distributed to the integument on the inner side of the arm. It is the smallest of the branches of the brachial plexus, and, arising from the inner cord, receives its fibres from the first thoracic "herve. It passes through the axillary space, at first lying behind, and then on the inner side of, the axillary vein, and communicates with the intercostohumeral nerve. It descends along the inner side of the brachial artery to the middle of the arm, where it pierces the deep fascia, and is distributed to the integument of the back of the lower third of the arm, extending as far as the elbow (Figs. 767 and 768), where some filaments are lost in the integument in front of the inner condyle, and others over the olecranon. It communicates with the posterior branch of the internal cutaneous nerve. In some cases the nerve of Wrisberg and the intercostohumeral nerve are con- nected by two or three filaments which form a plexus at the back part of the axilla. In other cases the intercostohumeral is of large size, and takes the place of the nerve of Wrisberg, receiving merely a filament of communication from the brachial plexus, which filament represents the latter nerve. In other cases this filament is wanting, the place of the nerve of Wrisberg being supplied entirely by the intercostohumeral. The Median Nerve (n. medianus) (Figs. 764 and 770) extends along the middle of the arm and forearm to the hand, lying between the ulnar and musculospiral nerves, and the ulnar and the radial nerves. It arises by two roots, one from the outer and one from the inner cord of the brachial plexus ; these embrace the lower part of the axillary artery, uniting either in front or on the outer side of that vessel. The median nerve receives filaments from the sixth, seventh, and eighth cervical and the first thoracic nerves, and sometimes from the fifth cervical as well. - As it descends through th* arm, it lies at first on the outer side of the brachial artery, crosses that vessel in the middle of its course, usually in front, but o(jcasionaliy behind it, and lies on its inner side to the bend of the elbow, where it is situated beneath the bicipital fascia, and is separated from the elbow-joint by the Brachialis anticus muscle. In the forearm it passes between the two heads of the Pronator teres muscle and crosses the ulnar artery, but is separated from that vessel by the deep head of the Pronator teres. It descends beneath the Flexor sublimis muscle, lying on the Flexor profundus muscle, to within two inches (5 cm.) above the annular ligament, where it becomes more superficial, lying between the tendons of the Flexor sublimis and Flexor carpi radialis muscles, beneath, and rather to the radial side or under the tendon of the Palmaris longus, covered by the integu- ment and fascia. It tlien passes through the carpal canal beneath the annular ligament into the palm of the hand. In its course through the forearm iz is •THE BRACHIAL PLEXUS 1035 accompanied by the arteria comes nervi mediani, a branch of the anterior interos- seous artery. Branches. — ^With the exception of the nerve to the .Pronator teres muscle, which sometimes arises above the elbow-joint, and filaments to tlie elbow-joint, the median nerve gives off no branches in the arm. In the forearm its branches are the muscular, anterior interosseous, and palmar cutaneous. The muscular branches (rami musculares) are derived from the nerve near the elbow and supply all the superficial muscles on the front of the forearm except the Flexor carpi ulnaris. The anterior or volar interosseous (n. interosseiis [antebrachii] volaris) (Fig. 770) supplies the deep muscles on the front of the forearm, except the inner half of the Flexor profundus digitorum. It accompanies the anterior interosseous artery along the interosseous membrane, in the interval between the Flexor longus pollicis and Flexor profundus digitorum muscles, both of whicli it supplies, and terminates below in tlie Pronator quadratus muscle, sending filaments to the inferior radioulnar articulation and the wrist-joint. The palmar cutaneous branch (ramus cutaneus palmaris n. mediani) arises from the median nerve at the lower part of the forearm. It pierces the fascia above the annular ligament, and, descending over that ligament, divides into two branches, of which the outer branch supplies the skin over the ball of the thumb, and com- municates with the anterior cutaneous branch of the musculocutaneous nerve; and the inner branch supplies the integument of the palm of the hand, communi- cating with the cutaneous branch of the ulnar. In the palm of the hand the median nerve is covered by the integument and palmar fascia and is crossed by the superficial palmar arch. It rests upon the tendons of the flexor muscles. In tliis situation it becomes enlarged, somewhat flattened, of a reddish color, and divides into two branches. Of these, the external branch supplies a muscular branch to some of the muscles of the thumb and digital branches to the thumb and radial side of the index finger; the internal branch supplies digital branches to the contiguous sides of the index and middle and of the middle and ring fingers. Tlie digital branches, before they subdivide, are called common palmar digital branches of the median nerve (nn. digitales volares communes). The branch to the muscles of the thumb (ramus mucularis) is a short nerve whicli divides to supply the Abductor, Opponens, and the superficial head of the Flexor brevis pollicis muscles, the remaining muscles of this group being supplied by the ulnar nerve. The digital branchss (hh. digitales volares proprii) are five in number. The first and second pass along the borders of the thumb, the external branch communi- cating with branches of the radial nerve. The third passes along the radial side of the index finger, and supplies the First lumbricalis muscle. The fourth sub- divides to supply the adjacent sides of the index and middle fingers, and sends a branch to the Second lumbricalis muscle. The fifth supplies the adjacent sides of the middle and ring fingers, and communicates with a branch from the ulnar nerve. Each digital nerve, opposite the base of the first phalanx, gives oft' a dorsal branch, which joins the dorsal digital nerve from the radial nerve and runs along the side of the dorsum of the finger, to end in the integument over the last phalanx. At the end of the finger the digital nerve divides into a palmar and a dorsal branch, the former of which supplies the extremity of the finger, and the latter ramifies around and beneath the nail. The digital nerves, as they run along the fingers, are placed superficial to the digital arteries. The cutaneous areas supplied by the median nerve are shown in Figs. 768 and 769). * 1036 THE NERVE SYSTEM The Ulnar Nerve {n. ulnaris) (Figs. 764 and 770) is situated along the inner or ulnar side of the upper limb, and is distributed to the muscles and integument of the forearm and hand. It is smaller than the median, behind which it is placed, diverging from it in its course down the arm. It arises from the inner cord of the brachial plexus, in common with the inner head of the median and the internal cutaneous nerves, and derives its fibres from the eighth cervical and first thoracic nerves. At its origin it lies to the inner side of the axillary artery, and liolds the same relation with the brachial artery to the middle of the arm. Here it pierces the intermuscular septum, runs obliquely across the internal head of the Triceps, and descends to the groove between the internal condyle and the olec- ranon, accompanied by the inferior profunda artery. At the elbow it rests upon the back of the inner condyle, and passes into the forearm between the two heads of the Flexor carpi ulnaris muscle. In the forearm it descends in a perfectly straight course along the ulnar side of the extremity, lying upon the Flexor pro- fundus digitorum muscle, its upper half being covered hy the Flexor carpi ulnaris muscle, its lower half lying on the outer side of the muscle, being covered by the integument and fascia. In the upper third of its course, it is separated from the ulnar artery by a considerable interval, but in the rest of its extent the nerve lies to the inner side of the artery. At the wrist the ulnar nerve crosses the annular ligament on the outer side of the pisiform bone, to the inner side of and a little behind the ulnar artery, and immediately beyond this bone divides into two branches, the superficial and the deep palmar. Branches. — ^The branches of the ulnar nerve are: In the forearm Articular (elbow). Muscular. , p, n ■ i , Cutaneous. In the hand / Superficial palmar. -P, I J. I Deep palmar. Dorsal cutaneous. "^ ^ ^ ^ Articular (wrist). The articular branches to the elbow-joint consist of several small filaments. They arise from the nerve as it lies in the groove between the inner condyle of the humerus and the olecranon. The muscular branches (rami musculares), two in number, arise from the trunk of the nerve near the elbow; one supplies the Flexor carpi ulnaris; the other, the inner half of the Flexor profundus digitorum. The cutaneous branches are two in number, palmar and dorsal. The palmar cutaneous branch (ramus cutaneus palmaris) arises from the ulnar nerve at about the middle of the forearm and runs downward on the ulnar artery, giving off some filaments entwining around the vessel. Just above the annular ligament it pierces the deep fascia and ends in the integument of the palm, com- municating with the palmar cutaneous branch of the median nerve. The dorsal cutaneous branch {ramus dorsalis manus) arises about two inches aI)ove the wrist; it passes posteriorly beneath the Flexor carpi ulnaris, perforates the deep fascia, and, running along the ulnar side of the back of the wdst and hand, divides into branches (nn. digitales dorsales) ; one of these supplies the inner side of the little finger; a second supplies the adjacent sides of the little and ring fingers; a third joins the branch of the radial nerve which supplies the adjoining sides of the middle and ring fingers, and assists in supplying them; a fourth is distributed to the metacarpal region of the hand, communicating with a branch of the radial nerve. On the little finger the posterior digital branches extend only as far as the base of the terminal phalanx, and on the ring finger as far as the base of the second phalanx; the more distal parts of these digits are supplied by posterior branches derived from the palmar digital branches of the ulnar. THE BRACHIAL PLEXUS 1037 The superficial palmar branch (ramus superficialis n. tdnaris) supplies the Palmaris brevis and the integument on the inner side of the iiand, and terminates in two digital branches, which are distributed, one to the ulnar side of the litde finger, the other to the adjoining sides of the little and ring fingers, the latter communicating with a branch from the median. The digital branches are dis- tributed to the fingers in the same manner as the digital branches of the median. The deep palmar branch (ramus profundus n. idnaris), accompanied by the deep branch of the ulnar artery, passes between the Abductor and Flexor brevis minimi digiti muscles; it then perforates the Opponens minimi digiti and follows the course of the deep palmar arch beneath the flexor tendons. At its origin it supplies the muscles of the little finger. As it crosses the deep part of the hand it sends two branches to each interosseous space, one for the Dorsal and one for the Palmar interosseous muscle, the branches to the Second and Third palmar interossei supplying filaments to the two inner Lumbrical muscles. At its ter- mination between the thumb and index finger it supplies the Adductores trans- versus et obliquus poUicis and the inner head of the Flexor brevis pollicis. It also sends articular filaments to the wrist-joint. It will be remembered that the inner part of the Flexor profundus digitorum muscle is supplied by the ulnar nerve; the two inner Lumbricales, which are connected with the tendons of this part of the muscle, are therefore supplied by the same nerve. The outer part of the Flexor profundus is supplied by the median nerve; the two outer Lumbricales, which are connected with the tendons of tiiis part of the muscle, are therefore supplied by the same nerve. Brooks states that in twelve instances out of twenty-one he found that the Third lumbrical received a twig from the median nerve, in addition to its branch from the ulnar. The cutaneous areas supplied by the ulnar nerve are shown in Figs. 768 and 769. The Musculospiral Nerve (n. radialis) (Figs. 770 and 771), the largest branch of the brachial plexus, supplies the muscles of the back part of the arm and forearm, and the integument of the same parts, as well as that of the back of the hand (Figs. 768 and 769). It arises from the posterior cord of the brachial plexus, of which it may be regarded as the continuation. Its fibres are derived from the sixth, seventh, and eighth, and sometimes also from the fifth cervical and first thoracic nerves. At its commencement it is placed first behind the axil- lary artery and then behind the upper part of the brachial artery, passing down in front of the tendons of the Latissimus dorsi and Teres major. It winds around from the inner to the outer side of the humerus in the musculospiral groove with the superior profunda artery, between the internal and external heads of the Triceps muscle (Fig. 771). It pierces the external intermuscular septum, and descends between the Brachialis anticus and Braehioradialis muscles to the front of the external condyle of the humerus, where it divides into the radial and pos- terior interosseous nerves. The branches of the musculospiral nerve are: Muscular. Radial. Cutaneous. Posterior interosseous. The muscular branches {rami musculares n. radialis) are derived from the nerve at the inner side, back part, and outer side of the arm respectively; they supply the Triceps, Anconeus, Braehioradialis, Extensor carpi radialis longior, and Bra- chialis anticus muscles. The internal muscular branches supply the inner and middle heads of the Triceps muscle. That to the inner head of the Triceps is a long, slender filament which lies close to the ulnar nerve, as far as the lower tliird of the arm, and is therefore frecjuently spoken of as the ulnar collateral branch. The posterior muscular branch, of large size, arises from the nerve in the groove between the Triceps muscle and the humerus. It divides into branches which 1038 THE NERVE SYSTEM Circumfiex. supply the outer and Inner heads of the Triceps and Anconeus muscles. _ The branch for the latter muscle is a long, slender filament which descends in the substance of the Triceps to the Anconeus. The external muscular branches supply the Brachioradialis, Extensor Suprascapuiary\ carpi radialis longior, and (usually) the outer part of the I3rachialis anticus muscles. The cutaneous branches are three in number, one internal and two external. The inter- nal cutaneous branch (n. cuia- neus brachii posterior) arises in the axillary space with the inner muscular branch. It is of small size, and passes through the axilla to the inner side of the arm, supplying the integument on its posterior aspect nearly as far as the olecranon. In its course it crosses beneath the intercosto- humeral nerve, with which it communicates. The external cutaneous branch (n. cutaneus antehrachii dorsalis) divides into two branches, and each one perforates the outer head of the Triceps muscle at its attachment to the humerus. The upper and smaller one passes to the front of the elbow, lying close to the cephalic vein, and supplies the integument of the lower half of the arm on its anterior aspect. The lower branch pierces the deep fascia below the insertion of the Deltoid muscle, and passes down along the outer side of the arm and elbow, and then along the back part of the radial side of the fore- arm to the wrist, supplying the integument in its course, and joining, near its termi- nation, with the posterior cutaneous branch of the mus- culocutaneous nerve. The Radial Nerve (ramus superficialis n. radialis) (Fig. 770), passes along the front of the radial side of the forearm to the commencement of its lower third. It lies at first a little to the outer side of the radial artery, concealed beneath the Brachioradialis. In the middle third of the forearm it lies beneath the same muscle, in close relation with the outer side of the artery. It leaves the artery about three inches above the wrist, passes beneath the tendon of the Brachio- FiG. 771. — The suprascapular, circumflex, and mu THE BRACHIAL PLEXU8 1039 radialis, and, piercing the deep fascia at the outer border of the forearm, divides into two branches. The external branch, the smaller of the two, supplies the integument of the radial side and ball of the thumb, joining with the anterior branch of the musculocutaneous nerve. The internal branch communicates, above the wrist, with the posterior cutaneous branch from the musculocutaneous, and on the back of the hand forms an arch with the dorsal cutaneous branch of the ulnar nerve. It then divides into four digital nerves {tin. digitales dorsales), which are distributed as follows: The first supplies the ulnar side of the thumb; the second, the radial side of the index finger; the third, the adjoining sides of the index and middle fingers; and the fourth, the adjacent borders of the middle and ring fingers.^ The latter nerve communicates with a filament from the posterior branch of the ulnar nerve. The Dorsal or Posterior Interosseous Nerve (ji. interosseous [antebrachii] dorsalis) (Figs. 770 and 771) winds to the back of the forearm around the outer side of the radius, passes between the two planes of fibres of the Supinator [brevis] muscle, and is prolonged downward, between the superficial and deep layer of muscles, to the middle of the forearm. Considerably diminished in size, it descends on the interosseous membrane, beneath the Extensor longus pollicis muscle, to the back of the carpus, where it presents a gangliform enlargement from which fila- ments are distributed to the inferior radioulnar articulation, to the wrist-joint, and to the ligaments and articulations of the carpus. It supplies all the muscles of the radial and posterior cubital regions, excepting the Anconeus, Supinator longus, and Extensor carpi radialis longior. Applied Anatomy. — The brachial plexus may be severed by traction on the limb, leading to complete paralysis. Bristow^ has reported three cases of avulsion of the plexus and has described twenty-four cases. In these cases it is generally believed that the lesion is rather a tearing away of the nerves from the spinal cord than a solution of continuity of the nerve fibres themselves. In a case operated upon by Bristow it was found that the plexus had given way where the four cervical nerves and the first thoracic nerve unite to form three trunks. In supra- clavicular division of the brachial plexus, not only will there be motor and sensor paralysis in the limb, but the Serratus magnus muscle will probably be paralyzed, because of injury to the poste- rior thoracic nerves. In the axilla any of the nerves forming the brachial plexus may be injured by a wound of this part, the median being the one which is most frequently damaged from its exposed position. The musculospiral, on account of its sheltered and deep position, is least often wounded. The brachial plexus in the axilla is often damaged from the pressure of a crutch, producing the condition known as crutch paralysis. In these cases the musculospiral is the nerve most frequently implicated; the ulnar nerve being the one that appears to suffer next in frequency. The circumflex nerve is of particular surgical interest. On account of its course around the surgical neck of the humerus, it is liable to be torn in fractures of this part of the bone, and in dislocations of the slioulder-joint, leading to paralysis of the Deltoid, and, according to Erb, inflammation of the shoulder-joint is liable to be followed by a neuritis of this nerve from exten- sion of the inflammation to it. Hilton takes the circumflex nerve as an illustration of a law which he lays down, that " the same trunks of nerves whose branches supply the groups of muscles moving a joint furnish also a distribution of nerves to the skin over the insertions of the same muscles, and the interior of the joint receives its nerves from the same source." In this way he explains the fact that an inflamed joint becomes rigid, because the same nerves which supply the interior of the joint supply the muscles which move that joint. The median nerve is liable to injury in wounds of the forearm. When paralyzed, there is loss of flexion of the second phalanges of all the fingers and of the terminal phalanges of the index and middle fingers. Flexion of the terminal phalanges of the ring and middle fingers can still be effected by that portion of the Flexor profundus digitorum which is supplied by the ulnar nerve. There is power to flex the proximal phalanges through the Interossei. The thumi) cannot be flexed or opposed, and is maintained in a position of extension and adduction. All power of pronation is lost. The wrist can be flexed, if the hand is first adducted, by the action ^ According to Hutchinson, the digital nerve to the thumb reaches only as high asthe root of the nail; the one to the forefinoter as high as the middle of the second phalanx, and the one to the middle and ring fingers not higher than the first phalangeal joint (London Hospital Gazette, vol. iii, p. 319). 2 Annals of Surgery, September, 1902. 1040 THE NERVE SYSTEM of the Flexor carpi ulnaris. There is loss or impairment of sensation on the palmar surface of the thumb, index, middle, and outer half of the ring fingers, and on the dorsal surface of the same fingers over the last two phalanges; except in the thumb, where the loss of sensation is limited to the back of the last phalanx. In order to expose the median nerve for the purpose of stretching it an incision should be made along the radial side of the tendon of the Palmaris longus muscle, which serves as a guide to the nerve. The ulnar nerve is liable to be injured in wounds of the forearm. When paralyzed, there is loss of power of flexion in the ring and little fingers; there is impaired power of ulnar flexion and adduction of the hand; there is inability to spread out the fingers from paralysis of the Interossei; and there is inability to adduct the thumb. The fingers cannot be flexed at the first joints, and cannot be extended at the other joints. A daw hand develops, the first phalanges being overextended and the others flexed. Sensation is lost or impaired in the skin of the ulnar side of the hand anteriorly and posteriorly, involving the little finger, the ring finger, and the ulnar half of the middle finger posteriorly, and anteriorly involving the little finger and the ulnar half of the ring finger. In order to expose the nerve in the lower part of the forearm, an incision should be made along the outer border of the tendon of the Flexor carpi ulnaris, and the nerve will be found lying on the ulnar side of the ulnar artery. The 7nusculospiral nerve is probably more frequently injured than any other nerve of the upper extremity. In consequence of its close relationship to the humerus as it lies in the mus- culospiral groove, it is frequently torn or injured in fractures of this bone, or subsequently involved in the callus that may be thrown out around a fracture, and thus pressed upon and its functions interfered with. It is also liable to be squeezed against the bone by kicks or blows; it may be divided by wounds of the arm. When paralyzed, the hand is flexed at the wrist and lies flaccid. This condition is known as drop wrist. The fingers are also flexed, and on an attempt being made to extend them the last two phalanges only will be extended through the action 'of the Interossei, the first phalanges remaining flexed. There is no power of extending the wrist. Supination is completely lost when the forearm is extended on the arm, but is possible to a certain extent if the forearm is flexed so as to allow of the action of the Biceps. The power of extension of the forearm is lost on account of paralysis of the Triceps. Loss of sensation may be considerable or slight. Its area is shown in Fig. 769. The best position in which to expose the nerve for the purpose of stretching is to make an incision along the inner border of the Brachioradialis muscle, just above the level of the elbow-joint. The skin and superficial structures are to be divided and the deep fascia exposed. The white line in this structure indi- cating the border of the muscle is to be defined, and the deep fascia divided in this line. By now raising the Brachioradialis the nerve will be found lying beneath it, on the Brachialis anticus muscle. Postajiesthctic paralf/sis. When a person emerges from the influence of a general anesthetic palsy of the arm may be found to exist. The brachial plexus may have been compressed during the operation by drawing the arm strongly from the body or elevating it by the side of the head. In such a case the plexus was compressed by the head of the humerus (Braun). The median nerve is stretched when the arm is rotated externally and drawn backward and outward. The ulnar nerve is stretched when the forearm is flexed and supinated (Braun). Garrigues believes that in most cases of postanesthetic paralysis the brachial plexus was squeezed between the collar bone and the first rib by the head of the patient being drawn to the opposite side or being allowed to fall back. The Anterior or Ventral Divisions of the Thoracic Nerves (rami anteriores). — The anterior primary divisions of the thoracic nerves are twelve in number on each side. Eleven of them are situated between the ribs, and are therefore termed intercostal; the twelfth lies below the last rib. Each nerve is connected with the adjoining ganglion of the sympathetic by one or two filaments (ramus communicans). The intercostal nerves are distributed chiefly to the parietes of the thorax and abdomen and differ from the anterior divisions of the other spinal nerves in that there is no plexus formation, each nerve running an inde- pendent course. The first two nerves supply fibres to the upper limb in addition to their thoracic branches; the next four are limited in their distribution to the parietes of the thorax; the five lower supply the parietes of the thorax and abdomen; the twelfth thoracic is distributed to the abdominal wall and the skin of the buttock. The Anterior Division of the First Thoracic Nerve divides into two branches; one, the larger, leaves the thorax in front of the neck of the first rib, and enters into the formation of the brachial plexus; the other and smaller branch runs along the first intercostal space, forming the first intercostal nerve (n. intercostalis I), ANTERIOR THORACIC NERVE8 1041 giving off muscular branches, and terminates on the anterior part of the thorax by forming the first anterior cutaneous nerve (ramus cutaneus anterior n. inter- costalis I) of the thorax. Occasionally this anterior cutaneous branch is wanting. The first intercostal nerve, as a rule, gives off no lateral cutaneous branch, but sometimes a small branch is given off which communicates with the intercosto- humeral. It frequently receives a connecting twig from the second thoracis? nerve, which passes upward over the neck of the second rib. Fig. 772. — Anterior aspect. Figs. 772 and 773. — Distribution of cutaneous nerves. Fig. 773.— Posterior aspect. The Anterior Divisions of the Second, Third, Fourth, Fifth, and Sixth Thoracic Nerves and the Small Branch from the First Thoracic Nerve (nn. intercostales) are confined to the parietes of the thorax, and are named thoracic intercostal nerves. They pass forward in the intercostal spaces below the intercostal vessels. At the back of the thorax they lie between the pleura and the posterior intercostal membrane, piercing the latter, and course between the two planes of Intercostal muscles as far as the middle of the rib. They then enter the substance of the Internal intercostal muscles, and, running amidst their fibres as far as the costal cartilages, they gain the inner surface of the muscles, and lie between them and the pleura. 1042 THE NEB VE SYSTEM Near the sternum, they cross in front of the internal mammary artery and Tri- ano-ularis sterni muscle, pierce the Internal intercostal muscles, the anterior intercostal membrane, and Pectoralis major muscle, and supply the integument of the anterior wall of the thorax and over the mammary gland, forming the anterior cutaneous nerves of the thorax; the branch from the second nerve is joined with the supraclavicular nerves of the cervical plexus. Branches. — ^Numerous slender muscular filaments {rami musculares) supply the ""Intercostals, the Infracostales, the Levatores costarum, the Serratus posticus superior, and the Triangularis sterni muscles. At the front of the thorax some of these branches cross the costal cartilages from one intercostal space to another. ANTERIOR CUTANEOUS Fig. 774. — Plan of a typical intercostal nerve The lateral cutaneous nerves (rami cidanei laterales) are derived from the inter- costal nerves, midway between the vertebrfe and sternum; they pierce the External intercostal and Serratus magnus muscles, and divide into anterior and posterior branches. The anterior branches (rami anteriores) are reflected forward to the side and fore part of the thorax, supplying the skin of the thorax and mamma; those of the fifth and sixth nerves supply the upper digitations of the External oblique. The posterior branches (rami posteriores) are reflected posteriorly to supply the integument over the scapula and over the Latissimus dorsi muscle. The lateral cutaneous branch of the second intercostal nerve (n. intercostohrachialis) is of large size, and does not divide, like the other nerves, into an anterior and a posterior branch. It is named, from its origin and distribution, the intercosto- humeral or intercostobrachial nerve (Figs. 757 and 770). It pierces the External intercostal muscle, crosses the axilla to the inner side of the arm, and joins with a filament from the lesser internal cutaneous nerve of the upper arm (nerve of Wrisherg). It then pierces the fascia, and supplies the skin of the upper half of ANTERIOR THORACIC NERVES 1043 the inner and back part of the arm (Figs. 768 and 769), communicating with the internal cutaneous branch of the musculospiral nerve. The size of this nerve is in inverse proportion to the size of the other cutaneous nerves, especially the nerve of Wrisberg. A second intercostohumeral nerve is frequently given ofi from the third intercostal. It supplies filaments to the armpit and inner side of the arm. It may or may not send a branch to the intercostohumeral. The Anterior Divisions of the Seventh, Eighth, Ninth, Tenth, and Eleventh Thoracic Nerves are continued anteriorly from the intercostal spaces into tlie al)dominal wall; hence these nerves are named thoracoabdominal intercostal nerves. They have the same arrangement as the upper ones as far as the anterior extremities of the intercostal spaces, where they pass behind the costal cartilages, and between the Internal oblicjue and Transversalis muscles, to the sheath of the Rectus, which they perforate. They supply the Rectus muscle, and terminate in branches which become subcutaneous near the linea alba. These branches are named the anterior or ventral cutaneous nerves of the abdomen. They are directed outward as far as the lateral cutaneous nerves, supplying the integument of the front of the belly. The lower intercostal nerves supply the Intercostals, Serratus posticus inferior, and Abdominal muscles, and, about the middle of their course, give off lateral cutaneous branches which pierce the External intercostal and External oblic|ue muscles, in the same line as the lateral cutaneous nerves of the thorax, and divide into anterior and posterior branches, which are distributed to the integu- ment of the abdomen and l:)ack; the ventral branches supply the digitations of the External oblique and extend downward and forward nearly as far as the margin of the Rectus muscle; the posterior branches pass backward to supply the skin over the Latissimus dorsi. The Anterior Division of the Last Thoracic Nerve is larger than that of the other thoracic nerves; it runs along the lower border of the last rib, and passes under the external arcuate ligament of the Diaphragm. It then runs in front of the Quadratus lumborum muscle, perforates the Transversalis muscle, and passes between it and the Internal oblique muscle, to be distributed in the same manner as the lower intercostal nerves. It communicates with the iliohypogastric branch of the lumbar plexus, and is frequently connected with the first lumbar nerve by a slender branch, the thoracicolumbar nerve, which descends in the substance of the Quadratus lumborum muscle. It gives a branch to the Pyramidalis muscle. The lateral cutaneous branch of the last thoracic is remarkable for its large size. It does not divide into an anterior and a posterior branch, like the other lateral cutaneous branches of the intercostal nerves, but perforates the Internal and Ex- ternal oblique muscles, passes over the crest of the ilium in front of the iliac branch of the iliohypogastric, and is distributed to the integument of the front part of the gluteal region, some of its filaments extending as low down as the trochanter major. Applied Anatomy. — The lower seven intercostal nerves and the iliohypogastric from the first lumbar nerve supply the skin of the abdominal wall. -They run downward and inward fairly equidistant from each other. Tlie sixth and seventh supply the skin over the "pit of the stomach;" the eighth corresponds to about the position of the middle linea transversa; the tenth to the umbilicus; and the iliohypogastric supplies the skin over the pubes and external abdominal ring. There are several points of surgical signiScance about the distribution of these nerves, and it is important to remember their origin and course, for in many diseases affecting the nerve trunks at or near their origin the pain is referred to their peripheral origin?. Thus, in Pott's disease of the spine children will often he brought to the surgeon sufTering from pain in the belly. This is due to the fact that the nerves are irritated at the seat of disease as they issue from the vertebral canal. When the irritation is confined to a single pair of nerves, the sen- sation complained of is often a feeling of constriction, as if a cord ^ere tied around the abdomen; and in these cases the situation of the sense of constriction may serve to localize the disease in 10-14 THE NER VE SYSTEM the spinal column. In other cases, where the bone disease is more extensive and two or more nerves are involved, a more diffused pain in the abdomen is complained of. A similar condition is sometimes present in affections of the cord itself, as in tabes dorsalis. Again, it must be borne in mind that the same nerves which supply the skin of the abdomen supply also the muscles which constitute the greater part of the abdominal wall. Hence it follows that any irritation applied to the peripheral terminations of the cutaneous branches in the skin of the abdomen is immediately followed by reflex contraction of the abdominal muscles. A good practical illustration of this may sometimes be seen in watching two surgeons examine the abdomen of the same patient. One, whose hand is cold, causes the muscles of the abdom- inal wall to contract at once and the belly to become rigid, and thus not nearly so suitable for examination; the other, who has taken the precaution to warm his hand, examines the abdomen without exciting any reflex contraction. The supply of both muscles and skin from the same source is of importance in protecting the abdominal viscera from injury. A blow on the abdomen, even of a severe character, will do no injury to the viscera if the muscles are in a condition of firm contraction; whereas in cases where the muscles have been taken unawares, and the blow has been struck while they were in a state of rest, an injury insufficient to produce any lesion of the abdominal wall has been attended with rupture of some of the abdominal con- tents. The importance, therefore, of immediate reflex contraction upon the receipt of an injury cannot be overestimated, and the intimate association of the cutaneous and muscular fibres in the same nerve produces a much more immediate response on the part of the muscles to any peripheral stimulation of the cutaneous filaments than would be the case if the two sets of fibres were derived from independent sources. Again, the nerves supplying the aljdominal muscles and skin are derived from the lower inter- costal nerves and are intimately connected with the sympathetic supplying the abdominal viscera through the lower thoracic ganglia from which the splanchnic nerves are derived. In conse- quence of this, in rupture of the abdominal viscera and in acute peritonitis the muscles of the belly wall become firmly contracted, and thus as far as possible preserve the abdominal contents in a condition of rest. THE LUMBOSACRAL PLEXUS. The anterior primary divisions of the lumbar, sacral, and coccygeal nerves form the hunbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic. For descriptive purposes this plexus is usually divided into three parts — the lumbar, sacral, and pudendal plexuses. The Anterior or Ventral Divisions of the Lumbar Nerves (rami anteriores). — The anterior divisions of the lumbar nerves increase in size from above downward. They are joined, near their origins, hy gray rami communicaiifes from the lumbar ganglia of the sympathetic cord. These consist of long, slender filaments, which accompany the lumbar arteries around the sides of the bodies of the vertebrae beneath the Psoas magnus muscle. Their arrangement is somewhat irregular; one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive rami from two ganglia. The first and second and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic cord by a ivhite ramus communicans. The nerves pass obliquely outward behind the Psoas magnus, or between its fasciculi, distributing filaments to it and the Quadratus lumborum muscles. The first three and the greater part of the fourth are connected together in this situation by anastomotic loops, and form the lumbar plexus. The anterior division of the fifth lumbar, joined with a branch from the fourth, descends across the base of the sacrum to join the anterior division of the first sacral nerve and assists in the formation of the sacral plexus. The cord resulting from the union of the fifth lumbar and the branch from the fourth is called the lumbosacral cord {truncus lumbosacralis) (Figs. 776 and 781). The Lumbar Plexus {plexus lumhalis) (Figs. 775 and 776). — The lumbar plexus is formed by the loops of communication between the anterior divisions of the four upper lumliar nerves. The plexus is narrow above, and often con- nected with the last thoracic nerve by a slender branch. The plexus is broad below, where it is joined to the sacral plexus by the lumbosacral cord. The lumbar plexus is situated in the substance of the Psoas magnus muscle near its posterior part, in front of the transverse processes of the lumbar vertebrae. THE LUMBOSACRAL PLEXUS 1045 The mode in which the plexus is arranged varies in different subjects.^ It differs from the brachial plexus in not forming an intricate interlacement, but the several nerves of distribution arise from one or more of the spinal nerves in the following manner: The first lumbar nerve receives a branch from the last tho- racic, gives off a larger, upper branch, which sub- divides into the iliohypo- gastric and ilioinguinal nerves; and a smaller lower branch which unites with a branch of the second lumbar, to form — --i-— :=S-^/ / i- " the genitofemoral nerve. iuiohvpogasth The remainder of the ilio-inguin — ^ ^^^ / •/ ^^ y. m second nerve and the third and fourth lumbar ... . GENITOFEMOI,-^ - ^ , i_ / / ^ ^ 1 lu nerves divide mto anterior ^^^^ ^ ' /t^//^/ ^^ l iv and posterior divisions. cutaneous The anterior division of the second unites with the / /^ /^/ j// // ..-■- l v anterior division of the third nerve and a part of ^° '"^"I.Tacosv the anterior division of femoral (antei the fourth nerve to form cruraO^^^ obturator^ the obturator nerve. The Fig. 775.— Diagram of the lumbar plexus. remainder of the anterior division of the fourth nerve passes down to communicate with the fifth lumbar nerve. The posterior divisions of the second and third nerves divide into two branches, a smaller branch from each uniting to form the external or lateral cutaneous nerve, and a larger branch from each, joining with the posterior division of the fourth lumbar nerve to form the femoral or anterior crural nerve. The accessory obturator, when it exists, is formed by the union of two small branches given off' from the third and fourth nerves. The branches of the lumbar plexus may therefore be arranged as follows: Iliohypogastric • ^ 1,L. Ilioinguinal 1,L. Genitofemoral 1,2, L. Dorsal Divisions. External (or lateral) cutaneous 2, .3, L. Femoral (or anterior crural) 2, 3, 4, L. . Ventral Divisions. Obturator \ • • 2, 3,4,L. ' Accessory obturator 3, 4, L. The Iliohypogastric Nerve (?;. iliohypogastricus) (Figs. 775 and 776) arises from the first lumbar nerve. It emerges from the lateral border of the Psoas magnus muscle at its upper part, and crosses obliquely in front of the Quadratus lumborum to the crest of the ilium. It then perforates the Transversalis muscle posteriorly near the crest of the ilium. It gives oft" muscular branches (rami musculares) to the abdominal wall, and divides between the Transversalis and the Internal oblique into two cutaneous branches, iliac and hypogastric. 1 For statistical studies of the variations the American Journal of Anatomy, vol. vi. tered in different individuals, see the article by Bardeen, in 1046 THE NERVE SYSTEM The iliac branch (ramus cutaneus lateralis) pierces the Internal and External oblique muscles immediately above the crest of the ilium, and is distributed to the, integument of the gluteal region, behind the lateral cutaneous branch of the last thoracic nerve (Fig. 782). The size of this nerve bears an inverse proportion to that of the lateral cutaneous branch of the last thoracic nerve. The hypogastric branch (ramus cutaneus anterior) (Fig. 777) continues onward between the Internal oblique and Transversalis muscles. It then pierces the Internal oblique, and becomes cutaneous by perforating the aponeurosis of the External oblique, about an inch (2.5 cm.) above and a little laterad of the external abdominal ring, and is distributed to the integument of the hypogastric region. The iliohypogastric nerve communicates with the last thoracic and ilioinguinal nerves. Fig 776 — ^The lumbar plexus and its branches. The Ilioinguinal Nerve (n. ilioinguinalis) (Figs. 776 and 777), smaller than the preceding, arises with it from the first lumbar nerve. It emerges from the lateral border of the Psoas magnus muscle just below the iliohypogastric nerve, and, passing obliquely across the Quadratus lumborum and Iliacus muscles, perforates the Transversalis near the fore part of the crest of the ilium, and communicates with the iliohypogastric nerve between that muscle and the Internal oblique. The nerve then pierces the Internal oblique, distributing muscular branches (rami musculares) to it, and, accompanying the spermatic cord through the external abdominal ring, is distributed to the integument of the upper and inner part of the thigh, to the skin covering the root of the penis, and to the scrotum in the THE LUMBOSACRAL PLEXUS 1047 male (jin. scrotates auteriores) and to the skin covering the mons veneris and labium majus in the female (//«. lahiales anteriores). The size of this nerve is in inverse proportion to that of the iliohypogastric. Occasionally it is very small, and ends by joining the iliohypogastric; in such cases a branch from the iliohypo- gastric takes the place of the ilioinguinal, or the ilioinguinal nerve may be alto- gether absent. The genitofemoral or genitocrural nerve (h. genitofemoralis) (Figs. 775 and 776) arises from the first and second lumbar nerves. It passes oblicjuely through the substance of the Psoas magnus muscle, and emerges from its inner border at a level corresponding to the intervertebral substance between the third and fourth lumbar vertebrfe; it then descends on the surface of the Psoas muscle, under cover of the peritoneimi, and divides into a genital and a femoral branch. The genital branch or external spermatic nerve (n. spermaticus externus) passes outward on the Psoas magnus, and pierces the fascia transversalis,- or passes through the internal abdominal ring; in the male it then descends along the back part of the spermatic cord to the scrotum, and supplies the Cremaster muscle. In the female it accompanies the round ligament, and is lost upon it. The femoral branch or lumboinguinal nerve {ii. lumhoingidnalis) (Fig. 777) descends on the external iliac artery, sending a few filaments around it, and, passing beneath Poupart's ligament to the thigh, enters the sheath of the femoral vessels, lying superficial and a little external to the femoral artery. It pierces the anterior layer of the sheath of the vessels, and, becoming superficial by passing through the fascia lata, it supplies the skin of the anterior aspect of the thigh as far as midway between the pelvis and knee. On the front of the thigh it com- municates with the outer branch of the middle cutaneous nerves, derived from the femoral nerve. A few filaments from this nerve may be traced on to the femoral artery; they are derived from the nerve as it passes beneath Poupart's ligament. The External or Lateral Cutaneous Nerve {n. cutaneus femoris lateralis) (Figs. 776 and 777) arises from the second and third lumbar nerves. It emerges from the lateral border of the Psoas magnus muscle, about its middle, and crosses the Iliacus muscle obliquely, toward the anterior superior spine of the ilium. It then passes under Poupart's ligament and over the Sartorius muscle into the thigh, where it divides into two branches, anterior and posterior. The anterior branch descends in an aponeurotic canal formed in the fascia lata, becomes superficial about four inches below Poupart's ligament, and divides into branches which are distributed to the integument along the anterior and outer part of the thigh, as far down as the knee. The terminal filaments of this nerve frequently communicate with the middle and internal cutaneous and with the patellar branch of the long saphenous nerve, forming with them the patellar plexus. The posterior branch pierces the fascia lata, and subdivides into branches which pass backward across the outer and posterior siu'face of the thigh, supplying the integument from the level of the great trochanter to the middle of the thigh. The Obturator Nerve {n. ohturatorius) (Figs. 776 and 778) supplies the Obturator externus and Adductor muscles of the thigh, the articulations of the hip and knee, and occasionally the integument of the thigh and leg. It arises from the second, the third, and the fourth lumbar nerves. Of these, the branch from the third is the largest, while that from the second is often very small. It descends through the inner fibres of the Psoas magnus muscle, and emerges from its inner border near the brim of the pelvis; it then passes behind the external iliac vessels, which separate it from the ureter, and runs along the lateral wall of the pelvis, above the obturator vessels, to the upper part of the obturator foramen. Here it enters the thigh, and divides into anterior and posterior branches, which are separated by some of the fibres of the Obturator externus muscle, and lower down by the Adductor brevis muscle. 1048 THE NERVE SYSTEM Femoral or anteri crural. -Anterior tiiidL Anterior division of obturator. Internal cutaneous. Fig. 777. — Cutaneous nerves of right lower extremity. Front view. THE LUMBOSACRAL PLEXUS 1049 The anterior branch (ramus anterior) (Fig. 778) passes down in front of the Adductor hrevis, being covered by the Pectineus and Adductor longiis; at the lower border of the latter muscle, it communicates with the internal cutaneous and internal saphenous nerves, forming a kind of plexus. It then descends upon the femoral artery, upon ^^■hich it is finally distributed. The nerve, near the obturator foramen, gives off an articular branch to the hip-joint. Behind the Pectineus it distributes muscular branches to the Adductor longus and Gracilis, and usually to the Adductor brevis, and in rare instances to the Pectineus, and receives a communicating branch from the accessory obturator nerve when that nerve is present. Occasionally the communicating branch to the internal cutaneous and interna! saphenous nerves is continued down, as a cutaneous branch (ramus cutaneus), to the thigh and leg. ^^^len this is so, it emerges from beneath the lower border of the Adductor longus, descends along the posterior margin of the Sartorius to the inner side of the knee, where it pierces the deep fascia, communicates with the internal or long saphenous nerve, and is distributed to the integument of the inner side of the leg as low down as its middle. When this communicating branch is small its place is supplied by the internal cutaneous nerve. The posterior branch (ramus posterior') pierces the anterior part of the Obturator externus, sending branches to supply this muscle, and passes behind the Adductor brevis on the front of the Adductor magnus, where it divides into numerous muscular branches, which supply the Adductor magnus, and the Adductor brevis when the latter does not receive a branch from the anterior division of the nerve. It also gives off a filament to the knee-joint. The articular branch for the knee-joint is sometimes absent; it either perforates the lower part of the Adductor magnus, or passes through the opening which transmits the femoral artery, and enters the popliteal space; it then descends upon the popliteal artery, as far as the back part of the knee-joint, where it perforates the posterior ligament, and is distributed to the synovial membrane. It gives filaments to the artery in its course. The Accessory Obturator Nerve (n. obturatorius accessorms) (Fig. 781) is present in about 29 per cent, of cases. It is of small size, and arises by separate filaments from the third and fourth lumbar nerves. It descends along the inner border of the Psoas magnus muscle, crosses the ascending ramus of the os pubis, and passes under the outer border of the Pectineus muscle, where it divides into numer- ous branches. One of these supplies the Pectineus, penetrating its deep surface; another is distributed to the hip-joint; while a third communicates with the anterior branch of the obturator nerve. When this nerve is absent the hip-joint receives two branches from the obturator nerve. Occasionally it is very small, and becomes lost in the capsule of the hip-joint. The Femoral or Anterior Crural Nerve (n. femoralis) (Figs. 776 and 778) is the largest branch of the lumbar plexus. It supplies muscular branches to the Iliacus, Pectineus, and all the muscles on the front of the thigh, excepting the Tensor fasciae femoris; cutaneous filaments to the front and inner side of the thigh, and to the leg and foot (Fig. 772) ; and articular branches to the hip- and knee-joint. It arises from the second, third, and fourth lumbar nerves, sometimes from the first or fifth as well. It descends through the fibres of the Psoas magnus, emerging from this muscle at the lower part of its outer border, and passes downward be- tween it and the Iliacus muscle, and beneath Poupart's lig&ment, into the thigh, where it becomes somewhat flattened, and divides into an anterior and a posterior part. Under Poupart's ligament it is separated from the femoral artery by a portion of the Psoas magnus. Within the abdomen the femoral nerve gives off from its outer side some small muscular branches to the Iliacus, and a branch to the femoral arterj' which is 1050 THE NERVE SYSTEM distributed upon the upper part of that vessel. The origin of this branch varies; it occasionally arises higher than usual, or it may arise lower down in the thigh. In the thigh the following branches are given off: From the Anterior Division. From the Posterior Division. Middle cutaneous. Long saphenous. Internal cutaneous. Muscular. Muscular. Articular. The middle and internal cutaneous branches of the femoral nerve are the rami cutanei anteriores n. femoralis of the BNA. The middle cutaneous nerve (Figs. 777 and 778) pierces the fascia lata (and generally the Sartorius) about three inches (8 cm.) below Poupart's ligament, and divides into two branches (Fig. 777), which descends in immediate proximity along the fore part of the thigh, to supply the integument as low as the front of the knee. Here they communicate with the internal cutaneous nerve and the patellar branch of the internal saphenous nerve, to form the patellar plexus. In the upper part of the thigh the outer division of the middle cutaneous nerve communicates with the femoral branch of the genitofemoral nerve. The internal cutaneous nerve (Fig. 777) passes obliquely across the upper part of the sheath of the femoral artery, and divides in front or at the inner side of that vessel into two branches, anterior and posterior or internal. The internal cutaneous nerve, before dividing, gives off a few filaments, which pierce the fascia lata (accompanying the long saphenous vein) to supply the integument of the inner side of the thigh. One of these filaments passes through the saphenous opening; a second becomes subcutaneous about the middle of the thigh (Fig. 777); and a third pierces the fascia at its lower third (Fig. 777). The anterior branch runs downward on the Sartorius, perforates the fascia lata at the lower third of the thigh, and divides into two branches, one of which supplies the integument as low down as the inner side of the knee; the other crosses to the outer side of the patella, communicating in its course with the nervus cutaneus patellae, a branch of the long or internal saphenous nerve. The posterior or internal branch descends along the inner border of the Sartorius muscle to the knee, where it pierces the fascia lata, communicates with the long saphenous nerve, and gives off several cutaneous branches. It then passes down to supply the integ- ument of the inner side of the leg. Beneath the fascia lata, at the lower border of the Adductor longus, it joins with branches of the long saphenous and obturator nerves to form a plexiform network (suhsartorial flex-US') (Fig. 778). When the communicating branch from the obturator nerve is large and continued to the integument of the leg, the internal branch of the internal cutaneous is small and terminates in the plexus, occasionally giving off a few cutaneous filaments. The Muscular Branches of the Anterior Division (rami viuscidares).'— The nerve to the Pectineus arises from the femoral nerve immediately below Poupart's liga- ment, and passes inward behind the femoral sheath to enter the anterior sm-face of the muscle; it is often duplicated. The nerve to the Sartorius arises in common with the middle cutaneous. The long or internal saphenous nerve (n. saphenus) (Figs. 777 and 778) is the largest of the cutaneous branches of the femoral nerve. It approaches the femoral artery where this vessel passes beneath the Sartorius, and lies in front of it, beneath the aponeurotic covering of Hunter's canal, as far as the opening in the lower part of the Adductor magnus. It then leaves the artery, and proceeds distally along the inner side of the knee, beneath the Sartorius muscle, pierces the fascia lata opposite the interval between the tendons of the Sartorius and Gracilis muscles, and becomes THE LUMBOSACRAL PLEXUS 1051 subcutaneous. The nerve then passes along the inner side of the leg (Fig. 777), accompanied by the internal saphenous vein, descends behind the internal border of the tibia, and at the lower third of the leg divides into two branches; one continues its course along the margin of the tibia, terminating at the inner ankle; the other passes in front of the ankle, and is distributed to the integument along the inner side of the foot, as far as the great toe, communicating with the internal branch of th'e musculocutaneous nerve. The long saphenous nerve about the middle of the thiyh gives off a communicating branch which joins the subsartorial plexus. At the inner side of the knee it gives off a large patellar branch (ramus infrapatel- laris), which pierces the Sartorius and fascia lata, and is distributed to the integu- ment in front of the patella. This nerve commimicates above the knee with the anterior branch of the internal cutaneous and with the middle cutaneous; below the knee, with other branches of the long saphenous; and on the outer side of the joint, with branches of the external cutaneous nerve, forming a plexiform network, the patellar plexus. The patellar branch is occasionally small, and terminates by joining the internal cutaneous, which supplies its place in front of the knee. Below the knee the branches of the long saphenous nerve are distributed to the integument of the front and inner side of the leg, communicating with the cutaneous branches from the internal cutaneous or from the obturator nerve. The Muscular Branches of the Posterior Division supply the four parts of the Quadriceps extensor muscle. The branch to the Rectus femoris enters its under surface high up, sending oft' a small filament to the hip-joint. The branch to the Vastus extemus, of large size, follows the course of the descend- ing branch of the external circumflex artery to the lower part of the muscle. It gives off an articular filament to the knee-joint. The branch to the Vastus internus is a long branch which runs down on the outer side of the femoral vessels in company with the long saphenous nerve. It enters the muscle about its middle, and gives off a filament which can usually be traced downward on the surface of the muscle to the knee-joint. The branches to the Crureus are two or three in number, and enter the muscle on its anterior surface about the middle of the thigh;'a filament from one of these descends through the muscle to the Subcrureus and the knee-joint. The articular branch to the hip-joint is derived from the nerve to the Rectus muscle. The articular branches to the knee-joint are three in number. One, a long slender filament, is derived from the nerve to the Vastus externus muscle; it penetrates the capsular ligament of the joint on its anterior aspect. Another is derived from the nerve to the Vastus internus muscle. It can usually be traced downward on the surface of this muscle to near the joint; it then penetrates the muscle and accompanies the deep branch of the anastomotica magna artery, pierces the cap- sular ligament of the joint on its inner side, and supplies the synovial membrane. The third branch is derived from the nerve to the Crureus. The Anterior or Ventral Divisions of the Sacral and Coccygeal Nerves (rami aiiteriores) (Fig. 781). — ^The anterior primary divisions of the sacral and coccygeal nerves form the sacral and pudendal plexuses. The anterior divisions of the upper four sacral nerves enter the pelvis through the anterior sacral foramina, that of the fifth between the sacrum and coccyx, while that of the coccygeal nerve curves forward below the rudimentary transverse process of the first piece of the coccyx. The first and second sacral are large; the third, fourth, and fifth diminish progressively from above downward. Each nerve receives a c/ray ramus conmiunicans from the corresponding ganglion of the sympathetic cord, 1052 THE NERVE SYSTEM ^ Bi to COCCYGEUS, _ I i tu ( t/qeal. ^B\ to' j Bi to LEVATOR ANI. SPHINSTER ANI Fig. 7S0. — Side view of pelvis, sbowina: sacral nervea THE SACIiAL PLEXUS 1053 while from the third, and frequendy from the second and fourth anterior sacral divisions, tohite rami communicanies are given to the pelvic plexuses of the sym- pathetic. THE SACRAL PLEXUS (PLEXUS SACRALIS) (Fig. 781). The sacral plexus is formed liy the lumbosacral cord, the anterior primary division of the first and portions of the anterior primary divisions of the second and third sacral nerves. The lumbosacral cord comprises the whole of the anterior primary division of the fifth and a part of the anterior primary division of the fourth lumbar nerves, it appears at the inner margin of the Psoas magnus and runs downward (caudad) over the pelvic brim to join the first sacral nerve. The third sacral nerve divides into an upper and a lower branch, the former entering the sacral and the latter the pudendal plexus FOURTH LUMBAR FTH LUMBAR SECOND SACRAL THIRD SACRAL FOURTH SACRAL EAL Bn. TO SPHINCTEl A LEVATOR ANI FTH SACRAL TO COCCYGEUS -COCCYGEAL with the pudendal plexus. CGerrish.) (See text for variations in origin of the perforating cutaneous nerve.) The branches or divisions forming the sacral plexus converge toward the lower part of the great sacrosciatic foramen, and unite to form a flattened band, from the anterior and posterior surfaces of which several branches arise. The band itself is continued as the great sciatic nerve, which splits on the back of the thigh into the internal and external popliteal nerves; these two nerves sometimes arise separately from the plexus, and in all cases their independence can be shown by dissection. Relations. — The sacral plexus lies on the anterior or ventral surface of the pelvic part of the Pyriformis and is covered in front by the pelvic fascia, which separates it from the internal iliac vessels, the ureter and the pelvic colon. The gluteal vessels run between the lumbosacral cord and the first sacral nerve, and the sciatic vessels between the second and third sacral nerves. 1054 THE NERVE SYSTEM All the nerves entering the plexus, with the exception of the third sacral, split into anterior and posterior divisions, and the nerves arising from these are as follows: Anterior or Ventral Posterior or Dorsal Divisions. Divisions. Nerve to Quadratus femoris and Gemellus inferior 4, 5, L. 1, S. Nerve to Obturator internus and Gemellus superior 5, L. 1,2, S. Nerve to Pyriformis (1),2, S. Superior gluteal 4, 5, L. 1 , S. Inferior gluteal 5, L. 1,2, S. Small sciatic 1, 2, 3, S. „ , . ,. f Internal popliteal 4, 5, L. 1.2. 3, S. Great sciatic | External popliteal 4,5,L.1,2,S. The nerve to the Quadratus femoris and Gemellus inferior arises from the anterior divisions of the fourth and fifth kimbar and first sacral nerves; it leaves the pelvis through the great sacrosciatic foramen, below the Pyriformis, and runs downward beneath the great sciatic nerve, the Gemelli, and the tendon of the Obturator internus, enters the anterior surface of these muscles; it gives off an articular branch to the hip-joint. The nerve to the Obturator internus arises from the anterior divisions of the fifth lumbar and first and second sacral nerves; it leaves the pelvis throiigh the great sacrosciatic foramen below the Pyriformis muscle, crosses the ischial spine, reenters the pelvis through the small sacrosciatic foramen, and ends in the Obturator internus, after entering the pelvic surface of that muscle. The branch to the Gemellus superior enters the upper part of the posterior surface of that muscle. The nerve to the Pyriformis arises from the posterior division of the second, or the posterior divisions of the first and second sacral nerves, and enters the anterior surface of the muscle; this nerve may be double. The Superior Gluteal Nerve {n. giutaeus superior) (Figs. 781 and 783) arises from the posterior divisions of the fourth and fifth lumbar and first sacral nerves; it leaves the pelvis through the great sacrosciatic foramen above the Pyri- formis, accompanied by the gluteal vessels, and divides into a superior and an inferior branch. The superior branch accompanies the upper branch of the deep division of the gluteal artery, and ends in the Gluteus minimus after giving off branches to supply a part of the Gluteus medius. The inferior branch accompanies the lower branch of the gluteal artery across the Gluteus minimus; it gives fila- ments to the Gluteus medius and Gluteus minimus, and ends in the Tensor fasciae femoris. The Inferior Gluteal Nerve (?!. giutaeus inferior) (Fig. 781) arises from the posterior divisions of the fifth lumbar and first and second sacral nerves ; it leaves the pelvis through the great sacrosciatic foramen, below the Pyriformis muscle, and divides into branches, which enter the deep surface of the Gluteus maximus. The Small Sciatic [n. cutaneus femoris posterior) (Figs. 781 and 783), or post- femoral cutaneous nerve supplies the integument of the perineum and back part of the thigh and leg. It arises partly from the anterior and pardy from the pos- terior divisions of the first, second, and third sacral nerves, and emerges from the pelvis through the great sacrosciatic foramen below the Pyriformis. It then descends beneath the Gluteus maximus with the sciatic artery, and passes down the back part of the thigh beneath the fascia lata, and over the long head of the Biceps to the lower part of the popliteal region, here it pierces the fascia and accompanies the external saphenous vein {v. saphena parva) to about the middle of the back of the leg, its terminal filaments communicating with the sural or external saphenous nerve. The branches of the small sciatic nerve are all cutaneous, and are grouped as follows: gluteal, perineal, and femoral. THE SACBAL PLEXUS 1055 The gluteal cutaneous branches {nn. chmium inferiores [laterales]), two or three in number, turn upward around the lower border of the Gluteus maximus to supply the skin covering the lower and outer part of that muscle. The perineal cutaneous branches {rami perineales) are distributed to the skin at the upper and inner side of the thigh, on its posterior aspect. One branch, longer than the rest, the inferior pudendal or long scrotal nerve (Fig. 783), curves forward below the ischial tuberosity, pierces the fascia lata, and runs forward beneath the superficial fascia of the perineum to be distributed to the skin of tire scrotum in the male and the labium majus in the female, communicating with the superficial perineal and inferior liemorrhoidal nerves. The femoral cutaneous branches consist of numerous descending filaments derived from botli sides of the nerve, and are distributed to the back and inner sides of the thigh, to the skin covering the popliteal space, and to the upper part of the leg. The Great Sciatic Nerve (n. ischiadicus) (Figs. 781 and 883) supplies nearly the whole of the integument of tlie leg, the muscles of the back of the thigh, and those of the leg and foot. It is tlie largest nerve cord in the body, measuring three-quarters of an inch in breadth, and is the continuation of the flattened band of the sacral plexus. It passes out of the pelvis through the great sacrosciatic foramen, below the Pyriformis muscle. It descends between the great trochanter of the femur and the tuberosity of the ischium, along the back part of the thigh, to about its lower third, where it divides into two large branches, the internal popliteal or tibial and external popliteal or peroneal nerves (Fig. 783). This division may take place at any point between the sacral plexus and the lower third of the thigh. When the division occurs at the plexus (in 10 per cent, of cases) the two nerves descend together side by side; or they may be separated, at their commencement, by the interposition of part or the whole of the Pyriformis muscle. As the nerve descends along the back of the thigli, it rests upon the posterior surface of the ischium, the nerve of the Quadratus femoris. and the External rotator muscles of the thigh, in company with the small sciatic nerve and arteryji^lt^: and is covered by the Gluteus maximus; lower down, it lies upon the Adductor magnus, and is covered by the long head of the Biceps. The branches of the nerve, before its division, are articular and muscular. The articular branches (rami ariiculares) arise from the upper part of the nerve; they supply the hip-joint, perforating the posterior part of its fibrous capsule. Tliese branches are sometimes derived directly from the sacral plexus. The muscular branches (rami inusculares) are distributed to the flexors of the leg — ^viz., the Biceps, Semitendinosus, and Semimembranosus, and to the Adductor magnus. The nerve to the short liead of the Biceps comes from the external popliteal part of the great sciatic, while the other muscular branches arise from tlie internal popliteal portion, as may be seen in those cases where the two popliteal nerves emerge separately on the buttock. The Internal Popliteal or Tibial Nerve {n. tibialis) (Figs. 781 and 783), the larger of the two terminal branches of the great sciatic, arises from the anterior primary branches of tlie last two lumbar and first three sacral nerves. It descends along the back part of the thigh, tlirough the middle of the popliteal space, to the lower part of tlie Popliteus muscle, where it passes with the artery beneath the arch of the Soleus and becomes the posterior tibial. It is overlapped by the Hamstring muscles above, and then becomes more superficial, and lies to the outer side of, and some distance from, the popliteal vessels; opposite the knee-joint it is in close relation with tlie vessels, and crosses to the inner side of the artery. Below, it is overlapped by the Gastrocnemius. The branches of this nerve are the articular and muscular, and a cutaneous branch, the commimicans tibialis. 1056 THE NER VE SYSTEM f\ Piidic Nerve to obturaior intemus Fig. 7S2.— Cut; extremity. Posti ^N. B. — In this diagram the communicans tibialis and communicans peronei are not in their normal position. They have been displaced by the removal of the superficial muscles. The external saphenous nerve is formed by the junction of the two communicantes. THE SACRAL PLEXUS 1057 The articular branches {rami ariiculares), usually three in number, supply the knee-joint; two of these branches accompany the superior and inferior internal articular arteries, and a third, the azygos articular artery. The muscular branches (rami muficularea), four or five in number, arise from the nerve as it lies between the two heads of the Gastrocnemius; they supply that muscle and the Plantaris, Soleus, and Popliteus. The branch which supplies the Popliteus turns around its lower border and is distributed to the deep surface of the muscle. The communicans tibialis (n. cutaneus surae medialis) descends between the two heads of the Gastrocnemius, and about the middle of the back of the leg pierces the deep fascia, and joins a communicating branch (ramus anastomoiicus pero- naeus) from the external popliteal nerve to form the short or external saphenous nerve (Fig. 783). The external saphenous nerve, formed by the communicating branches of the internal and external popliteal nerves, passes downward and out- ward near the outer margin of the tendo Achillis, lying close to the external saphe- nous vein, to the interval between the external malleolus and the os calcis. It divides into two branches, the posterior of which breaks up into lateral calcaneal branches (rami calcanei lateralcs). The anterior branch (n. cutaneus dorsalis lateralis) winds around the outer malleolus, and is distributed to the integument along the outer side of the foot and little toe, communicating on the dorsum of the foot with the musculocutaneous nerve. In the leg its branches communicate with those of the small sciatic. The cutaneous area supplied by the external saphenous nerve is indicated in Fig. 785. The Posterior Tibial Nerve (Fig. 783), the direct continuation of the internal pop- liteal nerve, commences at the lower border of the Popliteus muscle, and passes along the back part of the leg with the posterior tibial vessels to the interval between the inner malleolus and the heel, where it divides into the external and internal plantar nerves. It lies upon the deep muscles of the leg, and is covered above by the muscles of the calf, lower down by the skin and fascia. In the upper part of its course it lies to the inner side of the posterior tibial artery, but it soon crosses that vessel, and lies to its outer side as far as the ankle. In the lower third of the leg it is placed parallel with the inner margin of the tendo Achillis. The branches of the posterior tibial nerve are muscular, internal calcaneal, and articular. The muscular branches {rami musculares) arise either separately or by a common trunk from the upper part of the nerve. They supply the Soleus, Tibialis pos- ticus. Flexor longus digitorum, and Flexor longus hallucis muscles; the branch to the latter muscle accompanies the peroneal artery. The branch to the Soleus enters the deep surface of the muscle, while that from the internal popliteal enters the superficial surface. The internal calcaneal branches (rami calcanei mediales) perforate the internal annular ligament, and supply the integument of the heel and inner side of the foot (Fig. 785)_. The articular branch (ramus articidaris ad articulationem talocruralem) is given oft' just above the bifurcation of the nerve and supplies the ankle-joint. The Internal Plantar Nerve (n. plantaris medialis) (Fig. 784), the larger of the two terminal branches of the internal popliteal, accompanies the internal plantar artery along the inner side of the foot. From its origin at the inner ankle it passes beneath the Abductor hallucis, and then forward between this muscle and the Flexor brevis digitorum; it divides opposite the bases of the metatarsal bones into four plantar digital branches (nn. digifales plantares communes) and communicates with the plantar nerve. Branches. — In its course the internal plantar nerve gives oft' cutaneous branches, which pierce the plantar fascia and supply the integument of the sole of the foot 1058 THE ]S,ERVE SYSTEM (Fig. 785); muscular branches, \\hich supply the Abductor hallucis and Flexor brevis digitorum; articular branches, to the articulations of the tarsus and meta- tarsus; and four plantar digital branches (/;«. digitales plantares proprii). The first (innermost) branch becomes cutaneous about the middle of the sole, between the Adductor hallucis and Flexor brevis digitorum; the three outer branches pass between the divisions of the plantar fascia in the clefts between the toes. They are distributed in the following manner: The first supplies the inner border of the great toe, and sends a filament to the Flexor brevis hallucis muscle; the second bifurcates, to supply the adjacent sides of the great and second toes, sending a fila- ment to the First lumbrical muscle ; the third supplies the adjacent sides of the second and third toes; the fourth supplies the corresponding sides of the third and fourth toes, and receives a communicating branch from the external plantar nerve (Fig. 784). Each digital nerve gives off cutaneous and articular filaments; and opposite the last phalanx sends a dorsal branch, which supplies the structures around the nail, the continuation of the nerve being dis- tributed to the ball of the toe. It will be observed that the distribution of these branches is precisely similar to that of the median nerve in the hand. The External Plantar Nerve (n. plantaris later- alis) (Fig. 784), the smaller of the two, completes the nerve supply to the structures of the sole of the foot (Fig. 785), being distributed to the little Lateral plantar. Fig 784. — The plantar nervea Fig, 785. — Areas of distribution of the cutaneous nerves of the sole (W Keiller, in Gerrish's Text-book of Anatomy. 5 toe and outer half of the fourth, as well as to most of the deep muscles, its dis- tribution being similar to that of the ulnar nerve in the hand. It passes obliquely forward with the external plantar artery to the outer side of the foot, lying between the Flexor brevis digitorum and Flexor accessorius ; and in the interval between the former muscle and Abductor minimi digiti, divides into a superficial and a deep branch. Before its division it supplies the Flexor accessorius and Abductor minimi digiti. The superficial branch {ramus superficialis) separates into two digital nerves. One, the smaller of the two, supplies the outer side of the little toe, the Flexoi brevis minimi digiti, and the two Interosseous muscles of the fourth metatarsal THE SACRAL PLEXUS 1059 space; the other and larger digital branch supplies the adjoining sides of the fourth and fifth toes, and communicates with the internal plantar nerve. The deep or muscular branch (ramus profundus) accompanies the external plantar artery into the deep part of the sole of the foot, beneath the tendons of the Flexor muscles, and Adductor obliquus hallucis, and supplies all the Interossei (except those in the fourth metatarsal space), the three outer Lumbricales, the Adductor obliquus hallucis, and the Adductor transversus hallucis. The External Popliteal or Peroneal Nerve (/(. peronaeiis communis) (Figs. 781 and 783), about one-half the size of the internal popliteal, is derived from the posterior branches of the last two lumbar and first two sacral nerves. It descends obliquely along the outer sides of the popliteal space to the head of the fibula, close to the inner margin of the Biceps muscle. It is easily felt beneath the skin behind the head of the fibula at the inner side of the tendon of the Biceps. It passes between the tendon of the Biceps and outer head of the Gastrocnemius, winds around the neck of the fibula, between the Peroneus longus and the bone, and divides beneath the muscle into the anterior tibial and musculocutaneous nerves. The branches of the external popliteal nerve, previous to its division, are articular and cutaneous. The articular branches (rami articulares) are three in number: two of these accompany the superior and inferior external articular arteries to the outer side of the knee. The upper one occasionally arises from the great sciatic nerve before its bifurcation. The third (recurrent) articular nerve is given off at the point of division of the external popliteal nerve; it ascends with the anterior recurrent tibial artery through the Tibialis anticus muscle to the front of the knee, which it supplies. The Lateral Cutaneous Branch (?;. cutaneous surae lateralis). — There may be two or three of these branches. They supply the integument along the back part and outer side of the leg. The largest cutaneous branch of the peroneal is the communicans peronei (ramus anastomoticus -peronaeu-s) , which arises near the head of the fibula, crosses the external head of the Gastrocnemius to the middle of the leg, and joins with the communicans tibialis to form the external saphenous nerve. This nerve occasionally exists as a separate branch, which is continued as far down as the heel. The Anterior Tibial Nerve or Deep Peroneal (n. peronaeus profundus) (Fig. 778) commences at the bifurcation of the peroneal nerve, between the fibula and upper part of the Peroneus longus, passes obliquely downward beneath the Extensor longus digitorum muscle to the fore part of the interosseous membrane, and gets into relation with the anterior tibial artery above the middle of the leg; it then descends with the artery to the front of the ankle-joint, where it divides into an external and an internal branch. This nerve lies at first on the outer side of the anterior tibial artery, then in front of it, and again at its outer side at the ankle-joint. The branches of the anterior tibial nerve in its course through the leg are the muscular branches (rami miiscidares) to the Tibialis anticus. Extensor longus digitorum, Peroneus tertius, and Extensor proprius hallucis muscles, and an articular branch to the ankle-joint. The external or tarsal branch of the anterior tibial nerve passes outward across the tarsus, beneath the Extensor brevis digitorum, and, having become enlarged like the posterior interosseous nerve at the wrist, supplies the Extensor brevis digitorum muscle. From the enlargement three minute interosseous branches are given off which supply the tarsal joints and the metatarsophalangeal joints of the second, third, and fourth toes. The first of these sends a filament to the Second dorsal interosseous muscle. 1060 THE NERVE 8YBTEM The internal branch, the continuation of the nerve, accompanies the dorsalis pedis artery along the inner side of the dorsum of the foot, and at the first inter- osseous space divides into two dorsal digital branches {nn. digitales dorsales hal- lucis lateralis et digiti secundi medialis), which supply the adjacent sides of the great and second toes, communicating with the internal branch of the musculo- cutaneous nerve. Before it divides it gives off to the first space an interosseous branch which supplies the metatarsophalangeal joint of the great toe and sends a branch to the First dorsal interosseous muscle. The Musculocutaneous Nerve (;;. peronaeus superficialis) (Fig. 778) supplies the muscles on the fibular side of the leg and the integument over the greater part of the dorsum of the foot. It passes forward between the Peronei muscles and the Extensor longus digitorum, pierces the deep fascia at the lower third of the leg on its front and outer side, and divides into two branches. This nerve in its course between the muscles gives off muscular branches to the Peroneus longus and brevis, and cutaneous branches to the integument of the lower part of the leg. The internal dorsal cutaneous branch (n. cutaneus dorsalis medialis) of the muscu- locutaneous nerve passes in front of the ankle-joint and divides into three dorsal digital branches («;;. digitales dorsales pedis). The internal branch supplies the skin of the dorsum of the foot and the inner side of the great toe, and communicates with the internal saphenous nerve. The intermediate branch runs to the space between the great and second toes, supplies the adjacent sides of these, and com- municates with the anterior tibial nerve. The external branch passes to the space between the second and third toes and supplies the adjacent sides of these. The external dorsal cutaneous branch (h. cutaneus dorsalis intermediu-s), the smaller, passes along the outer side of the dorsum of the foot, and divides into two dorsal digital branches, the inner being distributed to the adjacent sides of the third and fourth toes, the outer to the adjacent sides of the fourth and fifth toes. It also supplies the integument of the outer ankle and outer side of the foot and communicates with the external saphenous nerve. The branches of the musculocutaneous nerve supply all the toes excepting the outer side of the little toe, which is supplied by the small saphenous nerve. The adjoining sides of the great and second toes are also supplied by the internal branch of the anterior tibial. It frequently happens that some of the outer branches of the musculocutaneous are absent, their place being then taken by branches of the external saphenous nerve. THE PUDENDAL PLEXUS (PLEXUS PUDENDUS), The pudendal plexus (Fig. 781) is not sharply marked off from the sacral plexus, some of the branches which spring from it may arise in conjunction with those of the sacral plexus. It lies on the posterior wall of the pelvis and is usually formed by branches from the ventral primary divisions of the second and third sacral nerves the whole of the anterior primary divisions of the fourth and fifth sacral nerves, and the coccygeal nerve. It gives off the following branches; Perforating cutaneous (variable) . (2, 3. S.) (3, 4, S.) (4, 5, S.) Pudic , .,„... 2, 3, 4, S, Visceral . ' . . . 3, 4, S. Muscular . , . . 4, S. Anococcygeal , 4, 5, S, and Cocc. The Perforating Cutaneous Nerve (Fig. 781) is not always present. It sometimes arises from the second and third sacral nerves, or from the third and fourth, or • THE PUDENDAL PLEXUS 1061 even fourth and fifth sacral nerves, and is of small size. When present, it pierces the lower part of the great sacrosciatic ligament, and, winding around the lower border of the Gluteus maximus, supplies the integument covering the inner and lower part of that muscle. When absent, its place is taken either by a cutaneous branch of the small sciatic, or by the greater coccygeal jxrforafing nerve of Eisler. The Pudic Nerve (h. imdendus) (Figs. 781 and 783) derives its fibres from the anterior branches of the second, third, and fourth sacral nerves. It leaves the pelvis below the Pyriformis through the great sacrosciatic foramen. It then crosses the spine of the ischium, and enters the pelvis through the lesser sacrosciatic foramen. It accompanies the pudic vessels upward and forward along the outer wall of the ischiorectal fossa, being contained in a sheath of the obturator fascia, termed Alcock's canal, and divides into two terminal branches, the perineal nerve, and the dorsal nerve of the penis or clitoris. Before its division it gives off the inferior hemorrhoidal nerve. The inferior hemorrhoidal nsrve {ii. hemorrhoidalis inferior) is occasionally derived separately from the sacral plexus (3d S.). It passes across the ischio- rectal fossa, with its accompanying vessels, toward the lower end of the rectum, and is distributed to the Sphincter ani externus and to the integument around the anus. Branches of this nerve communicate with the inferior pudendal and super- ficial perineal nerves at the fore part of the perineum. The perineal nerve (n. perinei), the inferior and larger of the two terminal branches of the pudic, is situated below the pudic artery. It accompanies the superficial perineal artery in the perineum, dividing into cutaneous and muscular branches. The cutaneous branches (superficial perineal) are two in number, posterior and anterior. The posterior or external branch pierces the base of the triangular liga- ment of the urethra, and passes forward along the outer side of the urethral triangle in company with the superficial perineal artery; it is distributed to the skin of the scrotum (nn. scrotales posteriores) or to the labium majus in the female (mi. labiales posteriores). It communicates with the inferior hemorrhoidal, the inferior pudendal, and the other superficial perineal nerve. The anterior or internal branch also pierces the base of the triangular ligament, and passes forward nearer to the middle line, to be distributed to the inner and back part of the scro- tum. Both these nerves supply the labium majus in the female. The muscular branches are distributed to the Transversus perinaei, Accelerator urinae. Erector penis, and Compressor urethrae. A distinct branch is given off from the nerve to the Accelerator urinae, pierces this muscle, and supplies the corpus spongiosum, ending in the mucous membrane of the urethra. This is the nerve to the bulb. The Dorsal Nerve of the Penis (??. dorsalis penis) is the deepest division of the pudic nerve; it accompanies the pudic artery along the ramus of the ischium; it then runs forward along the inner margin of the ramus of the os pubis, between the superficial and deep layers of the triangular ligament. Piercing the superficial layer, it gives a branch to the corpus cavernosum, and passes forward, in company with the dorsal artery of the penis, between the layers of the suspensory ligament, on to the dorsum of the penis, along which it is carried as far as the glans on which it ends. In the female the dorsal nerve is very small, and supplies the clitoris (/(. dorsalis cliforidis). The visceral branches arise from the third and fourth, and sometimes the second, sacral nerves and are distributed to the bladder and rectum, and, in the female, to the vagina; they communicate with the pelvic plexuses of the sympathetic. The muscular branches are derived from the fourth sacral, and supply the Levator ani, Coccygeus, and Sphincter ani externus. The branches to the Levator ani 1062 THE NEB VE SYSTEM and Coccygeus enfer their pelvic surfaces; that to the Sphincter ani externu? (perineal branch) reaches the ischiorectal fossa by piercing the Coccygeus or by passing between it and the Levator ani. Cutaneous branches from this branch supply the skin between the anus and the coccyx. Anococcygeal Branches (nn. anococcygei). — The fifth sacral nerve receives a communicating branch from the fourth, and unites with the coccygeal nerve to form the coccygeal plexus (plexus coccygeus). From this plexus the anococcygeal nerves take origin; they consist of a few fine filaments which pierce the great sacrosciatic ligament to supply the skin in the region of the coccyx. Applied Anatomy. — The lumbar plexus is formed in the Psoas magnus, and, therefore, in Psoa,s abscess any or all of its branches may be irritated, causing severe pain in the parts to which the irritated nerves are distributed. The genitofemoral nerve is the one which is most frequently implicated. Tiie nerve is also of importance, as it is concerned in one of the reflexes employed in the investigation of diseases of the spine. If the skin over the inner side of the thigh just below Poupart's ligament, the part supplied by the femoral branch of the genitofemoral nerve, be gently tickled in a male child, the testicle will be noticed to be drawn upward through the action of the Cremaster, which is supplied by the genital branch of the same nerve. The same result may sometimes be noticed in adults, and can almost always be produced by severe stimu- lation. This reflex, when present, shows that the portion of the cord from which the first and second lumbar nerves are derived is in a normal condition. The femoral or anterior crural nerve is in danger of being injured in fractures of the true pelvis, since the fracture most commonly takes place through the ascending ramus of the os pubis, at or near the point where this nerve crosses the bone. It is also liable to be injured in fractures and dislocations of the femur, and in some tumors growing in the pelvis is likely to be pressed upon, and its functions impaired. Moreover, on account of its superficial position, it is exposed to injury in wounds and stabs in the groin. When this nerve is paralyzed, the patient is unable to flex his hip completely, on account of the loss of motion in the Iliacus; or to extend the knee on the thigh, on account of paralysis of the Quadriceps extensor cruris; there are complete paralysis of the Sartorius and partial paralysis of the Pectineus. There is loss of sensation down the front and inner side of the thigh, except in that part supplied by the femoral branch of the genitofemoral nerve, and by the ilioinguinal nerve. There is also loss of sensation down the inner side of the leg and foot as far as the ball of the great toe. The obturator nerve is of special surgical interest. It is rarely paralyzed alone, but occa- sionally is paralyzed in association with the femoral (anterior crural). The principal interest attached to it is in connection with its supply to the knee; pain inthe knee being symptomatic of many diseases in which the trunk of this nerve, or one of its branches, is irritated, Thus, it is well known that in the earlier stages of hip-joint disease the patient does not complain of pain in that articulation, but on the inner side of the knee, or in the knee-joint itself, botli these articu- lations being supplied by the obturator nerve, the final distribution of the nerve being to the knee-joint. Again, the same thing occurs in sacroiliac disease: pain is complained of in the knee-joint or on its inner side. The obturator nerve is in close relationship with the sacroiliac articulation, passing over it, and, according to some anatomists, distributing filaments to it. Again, in cancer of the sigmoid flexure, and even in cases where masses of hardened feces are impacted in this portion of the gut, pain is complained of in the knee. The left obturator nerve lies beneath the sigmoid flexure, and is readily pressed upon and irritated when disease exists in this part of the intestine. Finally, pain in the knee forms an important diagnostic sign in ob- turator hernia. The hernial protrusion as it passes through the opening in the obturator mem- brane presses upon the nerve and causes pain in the parts supplied by its peripheral filaments. \Vlien the obturator nerve is paralyzed, the patient is unable to press his knees together or to cross one leg over the other, on account of paralysis of the Adductor muscles. Rotation outward of the thigh is impaired from paralysis of the Obturator externus. Sometimes there is loss of sensation in the upper half of the inner side of the thigh. The great sciatic nerve is liable to be pressed upon by various pelvic tumors, giving rise to pain along its trunk, to which the term sciatica is applied. Tumors growing from the pelvic viscera, or bones, aneurisms of some of the branches of the internal iliac artery, calculus in the bladder, when of large size, accumulation of feces in the rectum, may all cause pressure on the nerve inside the pelvis, and give rise to sciatica. Outside the pelvis exposure to cold, violent movements of the hip-joint, exostoses or other tumors, growing from the margin of the sacro- sciatic foramen, may also give rise to the same condition. When paralyzed there is loss of motion in all the muscles below the knee, and loss of sensation in the same situation, except the upper half of the back of the leg, supplied by the small sciatic and the upper half of the inner side of the leg, when the communicating branch of the obturator is large. The great sciatic nerve has been frequently cut down upon and stretched, or has been acU' THE SYMPATHETIC NERVE SYSTEM 1063 punctured for the relief of sciatica. The nerve has also been stretched in cases of locomotor ataxia, the anesthesia of leprosy, etc. In order to define it on the surface, a point is taken at the junction of the middle and lower third of a line stretching from the posterior superior spine of the ilium to the outer part of the tuber ischii, and a line is drawn from this point to the middle of the upper part of the popliteal space. The line must be slightly curved with its convexity outward, and as it passes downward to the lower border of the Gluteus maximus is slightly nearer the tuberosity of the ischium than to the great trochanter, as it crosses a line drawn between these two points. The operation of stretching the sciatic nerve is performed by making an incision over the course of the nerve about the centre of the thigh. The skin, superficial struc- tures, and deep fascia having been divided, the interval between the inner and outer Hamstrings is to be defined, and these muscles respectively pulled inward and outward with retractors. The nerve will be found a little to the inner side of the Biceps. It is to be separated from the surrounding structures, hooked up with the finger, and stretched by steady and continuous trac- tion for two or three minutes. The sciatic nerve may also be stretched by what is known as the " dry" method. The patient is laid on his back, the foot is extended, the leg flexed on the thigh, and the thigh strongly flexed on the abdomen. While the thigh is maintained in this position the leg is forcibly extended to its full extent, and the foot as fully flexed on the leg. This last- named method is uncertain. The position of the external popliteal nerve, close behind the tendon of the Biceps on the outer side of the ham, should be remembered in subcutaneous division of the tendon. After it is divided, a cord often rises up close beside it, which might be mistaken for a small undivided portion of the tendon, and the surgeon might be tempted to reintroduce his knife and divide it. This must never be done, as the cord is the external popliteal nerve, which becomes prominent as soon as the tendon is divided. (See also page 52.5). THE SYMPATHETIC NERVE SYSTEM (SYMPATHICUS) (Fig. 786). The distinction of the sympathetic nerve system from the cerebrospinal system is made merely for reasons of convenience. The two systems are intimately connected and the sympathetic is morphologically a derivative of the central axis disseminated in connection with the nutritive apparatus and establishing relation- ships among the vegetative organs. The sympathetic nerve system consists of (1) a series of central ganglia (gan- glia trunci sympathici) connected by a great ganglionic cord, the gangliated cord (truncus sympathicus), extending from the base of the skull to the coccyx, one gangliated cord on each side of the middle line of the body, ventrolaterad of the vertebral column; (2) of three great gangliated plexuses (plexus sympathici) or aggregations of nerves and ganglia, situated ventrolaterad of the vertebral column in the thoracic, abdominal, and pelvic cavities respectively; (3) of smaller or terminal ganglia, situated in relation with the abdominal viscera;' and (4) of numerous nerve fibres. These latter are of two kinds — communicating, by which the ganglia communicate with each other and with the cerebrospinal nerves; and distributory, supplying the internal viscera and the coats of the bloodvessels. Each gangliated cord may be traced upward from the base of the skull into the cranial cavity by an ascending branch, which passes through the carotid canal, forms a plexus on the internal carotid artery and in the cavernous sinus (Fig. 789), and communicates with certain cranial nerves (p. 1067); the lower ends of the two cords converge and end in a single ganglion, the ganglion impar (ganglion coccygeum impar), situated ventrad of the coccyx. The ganglia of the cord are distinguished as cervical, thoracic, lumbar, and sacral, and except in the neck they closely correspond in number to the vertebra against which they lie. They are arranged thus: Cervical portion 3 pairs of ganglia. Thoracic " 10 to 12 " " Lumbar " 4 " " Sacral " 4 or 5 " " 1 The ciliary, sphenopalatine, otic, and submaxillary ganglia, already described in connection with the tri- geminal nerve, may be regarded as belonging to the sympathetic system. 1064 THE NERVE SYSTEM MIDDLE CEHVI- In the neck the ganglia are situated in front of the transverse processes of the vertebra ; in the thoracic region, in front of the heads of the ribs ; in the lumbar region, on the sides of the bodies of the spifOL vertebrae; and in the sacral region, in front of the sacrum. Connections with the Spinal Nerves. — Communications are established between the sym- pathetic and spinal nerves through' what are known as gray and white rami communi- cantes (Fig. 786), the gray rami conveying sympathetic fibres into the spinal nerves, and the white rami transmitting afferent and efferent fibres to the sym- pathetic. Each spinal nerve receives a gray ramus com- municans from the gangliated cord of the sympathetic, but white rami are not supplied by all the spinal nerves. The white rami are derived from the first thoracic to the first lum- bar, inclusive, while the visceral branches which run from the second, third and fourth sacral nerves directly to the pelvic plex- uses of the sympathetic belong to this category. The majority of the fibres which spring from the sympathetic ganglia are amyelinic (_^6res of Remak); the fibres which reach the sympa^ thetic through the white ramus communicans are myelinated. The branches of distribution, or sympathetic nerves, derived from the gangliated cords from the prevertebral plexuses, and also from the smaller ganglia, are principally destined for the bloodvessels and thoracic and abdominal viscera, supplying the involuntary muscle fibres of the coats of the vessels and the hollow viscera, and the se- creting cells, as well as the Fio. 786.-Anterior surface of the spinal cord, showing the mUSCular COatS of the Vessds in Bpinal nerves and their connections with the sympathetic trunk on j^q o-landular VlSCera. 1 ney one side. (Testut.) -^ i> n. , ^ a: j. consist of efferent and aiierent fibres, for the origin and course of which see pages 1014 and 1015 (Fig. 756). The three great gangliated plexuses (collateral ganglia) are situated m front of tne vertebral column in the thoracic, abdominal, and pelvic regions, and are named, MBAR GANGLIA THE SYMPATHETIC NERVE SYSTEM 1065 respectively, the cardiac, the solar or coeliac, and the hypogastric plexus. They consist of collections of nerves and ganglia, the nerves being derived from the ga'no-Iiated cords and from the cerebrospinal nerves. They distribute branches to the v-iscera. Carotid plex 3Iiddle cemcnl qannhon / Inferior cervical ganglion ■^Pharyngeal hranche. Ca) diac branches. Deep ca> diac plexus. Supeificial cardiac plexus. f^olar plexus. Aortic plexus. Hypogastric plexus Sacral gangh Ganglion impai Fig. 7S7.— The sympathetic nerve syste 1066 THE NEB VE SYSTEM THE GANGLIATED CORD (TRUNCUS SYMPATHETICUS). Cervicocephalic Portion of the Gangliated Cord (Figs. 788, 789). The cervicocephalic portion of each gangliated cord {ipars cephalica et cervicalis s. sympathici) consists of three ganglia, distinguished, according to their position, as the superior, middle, and inferior cervical, connected by intervening cords. This portion of the sympathetic cord receives no white rami communicantes from the cervical spinal nerves, its spinal fibres being derived from the white rami of the upper thoracic nerves which enter the corresponding thoracic ganglia of the sympathetic and through these ascend into the cervical portion. The superior cervical ganglion (ganglion cervicale superius) (Figs. 787 and 788), the largest of the three, is about three-quarters of an inch in length. It is placed opposite the second and third cervical vertebrte. It is of a reddish-gray color, is usually fusiform in shape, is sometimes broad and flattened, and is occasionally constricted at intervals; it is believed that it is formed by the coales- cence of the four ganglia corresponding to the four upper cervical nerves. It is in relation, in front, Avith the sheath of the internal carotid artery and internal jugular vein; behind, it lies on the Rectus capitis anticus major. Its branches may be divided into superior, inferior, eJrtemal, internal, and anterior. The superior branch (n. caroiicus iniernus) (Fig. 744) appears to be a direct prolongation of the ganglion. It is soft in texture and of a reddish color. It ascends by the side of the internal carotid artery, and, entering the carotid canal in the temporal bone, divides into two branches, which lie, one on the outer, and the other on the inner, side of that vessel. The outer branch, the larger of the two, distributes filaments to the internal carotid artery and forms the carotid plexus. The inner branch also distributes filaments to the internal carotid artery, and, continuing onward, forms the cavernous plexus. The Carotid Plexus (plexus caroiicus intermis) (Figs. 787 and 788) is situated on the outer side of the internal carotid artery. Filaments from this plexus occa- sionally form a small gangliform swelling, the carotid ganglion, on the under surface of the artery. The carotid plexus communicates with the Gasserian ganglion, the abducent nerve, and the sphenopalatine ganglion; it distributes filaments to the wall of the carotid artery, and also communicates with Jacobson's nerve (the tympanic branch of the glossopharyngeal). The communicating branches to the abducent nerve consist of one or two filaments which join that nerve as it lies upon the outer side of the internal carotid artery. The communication with the sphenopalatine ganglion is efFected by a branch, the large deep petrosal nerve (Fig. 745), given off from the plexus on the outer side of the artery; this branch passes through the cartilage filling up the foramen lacerum medium, and joins the large superficial petrosal from the facial to form the Vidian nerve (Figs. 740 and 745). The Vidian nerve then proceeds through the Vidian canal to the sphenopalatine ganglion. The communication with Jacobson's nerve is effected by two branches, one of which is called the deep petrosal nerve, and the other the caroticotympanic nerve; the latter may consist of two or three delicate filaments. The Cavernous Plexus (plexus cavernosus) (Fig. 788) is situated below and in- ternal to that part of the internal carotid which is placed by the side of the sella turcica, in the cavernous sinus, and is formed chiefly by the internal division of the ascending branch from the superior cervical ganglion. It commimicates with the oculomotor, the trochlear, the ophthalmic division of the trigeminal. CERVICOCEPHALIC PORTION OF THE GANGLIATED CORD 1067 and the abducent nerves, and with the ciliary or lenticular ganglion, and distri- butes filaments to the wall of the internal carotid artery, and to the hypophysis. The branch of communication with the oculomotor nerve joins it at its point of division; the branch to the trochlear nerve joins it as it lies on the outer wall of the cavernous sinus; other filaments are connected with the under surface of the trunk of the ophthalmic nerve; and a second filament of communication joins the abducent nerve. EXTERN CVIUSC CILIARY ^ SENSORY OF CILIARY — GANGLIO OPHTHALMIC N. GASSERIAN GANGLION (lurned forward) TEMPORO- MAXILLARY ARTICULATION CAHOTICOTYMPAN C I ANGLION MOTOR 1ANCH MOTOR fMPATHETIC ROOT OF LIARY GANGLION OCULOMOTOR NERVE ABDUCENT NERVE UCENT NERVE INTE CAROTID ARTERY Fig. 788. — The cephalic portion of the sympathetic nerve system, seen obliquely from above and behind. (Toldt.) The filaments of connection with the ciliary ganglion (Fig. 735) arise from the anterior part of the cavernous plexus and enter the orbit through the sphenoidal fissure; they may join the nasal Id ranch of the ophthalmic nerve or be continued forward as a separate branch. The terminal filaments from the carotid and cavernous plexuses are prolonged along the internal carotid artery, forming plexuses which entwine around the anterior and middle cerebral arteries and the ophthalmic artery; along the former vessels they may be traced on to the pia; along ;he latter, into the orbit, where they accompany each of the branches of the vessel. The filaments prolonged to the anterior communicating artery connect the sympathetic nerves of the right and left sides. The so-called inferior branch of the superior cervical ganglion communicates with the middle cervical ganglion. The external branches are comimmicaling, and consist of gray rami communi- cantes to the upper four cervical nerves and to certain of the cranial nerves. Sometimes the btanch to the fourth cervical nerve may come from the cord connecting the superior and middle cervical ganglia. The branches to the cranial nerves consist of delicate filaments, which run to the ganglion of the trunk of 1068 THE NERVE SYSTEM CAVERNOUS PLEXUS the vagus, and to the hypoglossal nerve. A separate filament {nenus jugidaris) passes upward to the base of the skull, and subdivides to join the petrous ganglion of the glossopharyngeal, and the ganglion of the root of the vagus in the jugular foramen. The internal branches' are per- ipheral, and consist of the pharyn- geal and laryngeal branches, and the superior cardiac nerve. The pharyngeal branches (rajni pharyngei) (Fig. 787) pass in- ward to the side of the pharynx, where they join with branches from the glossopharyngeal, vagus, and external laryngeal nerves to form the pharyngeal plexus. The laryngeal branches join the superior laryngeal nerve and its branches. The superior cardiac nerve {71. cardiacus superior) (Figs. 787) arises by two or more branches from the superior cervical gan- glion, and occasionally receives a filament from the cord of communication between the first and second cervical ganglia. It runs down the neck behind the common carotid artery, lying upon the Longus colli, and crosses in front of the inferior thyroid artery and recurrent laryngeal nerve. The course of the nerves on the two sides then differs. The right superior cardiac nerve, at the root of the neck, passes either in front of or behind the subclavian artery^ and along the in- nominate artery, to the back part of the arch of the aorta, where it joins the deep cardiac plexus. It is connected with other branches of the sympathetic; about the middle of the neck it receives filaments from the external laryngeal nerve; lower down it obtains one or two twigs from the vagus, and as it enters the thorax it is joined by a filament from the recurrent laryngeal. Filaments from the nerve com- municate with the thyroid branches from the middle cervical ganglion. The left superior cardiac nerve, in the thorax, runs by the side of the left common carotid artery, and in front of the arch of the aorta to the superficial cardiac plexus. The anterior branches (nil. carotid externi) (Fig. 789) ramify upon the external carotid artery and its branches, forming around each a delicate plexus, on the EIGHTH CERVrCA NERVE FIRST THORACIC NERVE Fig. 789. — Diagra : of the cervical sympathetic cord. (Testut,) CERVICAL GANGLION Fig. 790. — The subclavian loop passing from the middle to the inferior cervical ganglia. CERVICOCEPHALIC POUTION OF THE GANGLIATED VOUD 1069 nerves composing which small ganglia are occasionally found. The plexuses accompanying some of these arteries have important communications with other nerves. That surrounding the external carotid artery (^plexus caroticus externus) is connected with the branch of the facial nerve to the Stylohyoid muscle; that surrounding the facial artery communicates with the submaxillary ganglion by one or two filaments; and that accompanying the middle meningeal artery sends an ofi'shoot which passes to the otic ganglion and a second, the external superficial petrosal nerve (Fig. 745), to the geniculate ganglion of the facial nerve. The middle cervical ganglion (ganglion, cervicale medium) (Figs. 787 and 789) is the smallest of the three cervical ganglia, and is occasionally altogether wanting. It is placed opposite the sixth cervical vertebra, usually upon, or close to, the inferior thyroid artery. It is probably formed b}^ the coalescence of two ganglia corresponding to the fifth and sixth cervical nerves. It is joined by gray rami communicantes to the fifth and sixth cervical nerves. It gives off the thyroid and middle cardiac nerves. The thyroid branches are small filaments which accompany the inferior thyroid artery to the thyroid gland, forming the inferior thjrroid plexus (plexus thyroideus inferior); they communicate, on the artery, with the superior cardiac nerve, and, in the gland, with branches from the recurrent and external laryngeal nerves. The middle or great cardiac nerve (n. cardiacus medius) (Fig. 787), the largest of the three cardiac nerves, arises from the middle cervical ganglion or from the cord between the middle and inferior ganglia. On the right side it descends behind the common carotid artery, and at the root of the neck passes either in front of or behind the subclavian artery; it then descends on the trachea, receives a few filaments from the recurrent laryngeal nerve, and joins the right side of the deep cardiac plexus. In the neck it communicates with the superior cardiac and re- current laryngeal nerves. On the left side the middle cardiac nerve enters the thorax between the left carotid and subclavian arteries, and joins the left side of the deep cardiac plexus. If the middle cervical ganglion is absent^ the above- named branches arise from the gangliated cord. The inferior cervical ganglion (ganglion cervicale inferius) (Figs. 787 and 789) is situated between the base of the transverse process of the last cervical vertebra and the neck of the first rib on the inner side of the superior intercostal artery. Its form is irregular; it is larger in size than the preceding, and is frequently joined to the first thoracic ganglion. It is probably formed by the coalescence of two ganglia which correspond to the last two cervical nerves. It is connected to the middle ganglion by two or more cords, one of which forms a loop around the subclavian artery and supplies offshoots to it. This loop is named the ansa subclavii (Vieussenii). , The ganglion is joined to the seventh and eighth cervical and the first thoracic nerves by gray rami communicantes. It gives off the inferior cardiac nerve and offshoots to bloodvessels. The inferior cardiac nerve (n. cardiacus inferior) arises from the inferior cervical or first thoracic ganglion. It passes down behind the subclavian artery and along the front of the trachea to join the deep cardiac plexus. It communicates freely behind the subclavian artery with the recurrent laryngeal and middle cardiac nerves. The offshoots to bloodvessels accompany the vertebral artery, and form a plexus around it; this plexus (plexus vertebralis) supplies filaments to the vessel, and is continued up the vertebral and basilar arteries to the cerebral and cerebellar arteries. Applied Anatomy.— The situation of the cervical sympathetic makes wounds of it rare. Thirteen cases of traumatic injury to the cervical symija'thetics were collected by Seeligmtiller. In ten cases paralysis existed; in three, irritation. Tumors of the neck may cause irritation or 1070 THE NERVE SYSTE3I paralysis. In irritation of the sympathetic the corresponding side of the face becomes pale, the pupil" dilates, the palpebral fissure widens, and the eyeball protrudes. In many cases there is acceleration of the heart beats. In paralysis of the sympathetic the pupil contracts, the pal- pebral fissure is narrowed by partial ptosis, the corresponding side of the face reddens, there is an increase in the flow of tears, and recession of the eyeball. The surgeon occasionally resects the sympathetic. Jonnesco recommends bilateral removal of the superior cervical ganglia for glaucoma, and bilateral removal of all the cervical sympa- thetic ganglia for epilepsy and for exophthalmic goitre. The results of resection do not appear to justify the operation. The Thoracic Portion (Pars Thoracalis) of the Gangliated Cord (Fig. 791). The thoracic portion of the gangliated cord consists of a series of ganglia which usually correspond in number to that of the vertebrae; but, from the occa- RENAL PLEXUS Fig. 791. — Plan of the right sympathetic cord and splanchnic nerves. (Testut.) sional coalescence of two, their number is uncertain. The ganglia are placed on each side of the spine, resting against the heads of the ribs, and are covered by THE LUMBAR PORTION OF THE GANGLIATED CORD 1071 the costal pleura; the last two ganglia are, however, anterior to the rest, being placed on the side of the bodies of the eleventh and twelfth thoracic vertebrte. The ganglia are small in size and of a grayisli color. The hrst ganglion, larger than the others, is of an elongated form and is frequently blended with the last cervical ganglion. They are connected by the intervening portions of the cord. Two rami communicantes, one white and the other gray, connect each ganglion with its corresponding spinal nerve. The branches from the uf per five ganglia are very small; they supply filaments to the thoracic aorta and its branches, and to the bodies of the vertebrae and their ligaments. Branches from the second, third, and fourth ganglia enter the posterior pulmonary plexus. The branches from the lower seven ganglia are large, and white in color; they distribute filaments to the aorta, and unite to form the three splanchnic nerves. These are named the great, the lesser, and the smallest, or renal splanchnic. The great splanchnic nerve (/;. splanchnicus major) is white in color, firm in texture, and is formed by branches from the thoracic ganglia between the fifth or sixth and the ninth or tenth; but the fibres in the higher roots may be traced upward in the sympathetic cord as far as the first or second thoracic ganglion. These roots unite to form a cord of considerable size. It descends oblicjuely inward in front of the bodies of the ve tebrte along the posterior mediastinum, perforates the crus of the Diaphragm, and terminates in the semilunar ganglion of the solar plexus (Fig. 791), distributing filaments to the renal and suprarenal plexuses. A ganglion {ganglion splanchnicum) exists on this nerve opposite the eleventh or twelfth thoracic vertebra. The lesser splanchnic nerve (h. splanchnicus minor) is formed by filaments from the tenth and eleventh ganglia, and from the cord between them. It pierces the Diaphragm near or with the preceding nerve, and joins the aorticorenal ganglion of the solar plexus (Fig. 791). It communicates in the thorax with the great splanchnic nerve, and ends in the solar plexus. The least splanchnic nerve (n. splanchnicus imus) arises from the last thoracic ganglion, and, piercing the Diaphragm, terminates in the renal plexus. It occa- sionally communicates with the preceding nerve. A striking analogy appears to exist between the splanchnic and the cardiac nerves. The cardiac nerves are three in number, they arise from the three cer- vical ganglia, and are distributed to a large and important organ in the thoracic cavity. The splanchnic nerves, also three in number, are connected probably with all the thoracic ganglia, and are distributed to important organs in the abdominal cavity. The Lumbar Portion (Pars Lumbalis) of the Gangliated Cord (Fig. 787). The lumbar portion of the gangliated cord is situated in front of the vertebral column along the inner margin of the Psoas magnus. It consists usually of four ganglia, connected together by interganglionic cords. It is continuous above with the thoracic portion beneath the internal arcuate ligament of the Diaphragm, and below with the sacral portion behind the common iliac artery. The ganglia are of small size, and placed much nearer the median line than the thoracic ganglia. Gray rami communicantes connect all the ganglia with the lumbar spinal nerves. There may be two from each ganglion, but the arrangement is not so uniform as in other regions. The first and second, and sometimes the third, lumbar nerves send white rami communicantes to the upper two or three ganglia. From the situation of the lumbar ganglia these branches are longer than in the other regions. They accompany the lumbar arteries around the sides of the bodies 1072 THE NER VE SYSTEM of the vertebrae, passing beneath the fibrous arches from which some of the fibres of the Psoas magnus arise. Of the branches of distribution some branches pass inward, in front of the aorta, and lielp to form the abdominal aortic plexus {plexus aorticus abdominalis) (Fig. 787). Other branches descend in front of the common iliac arteries, and, joining over the promontory of tlie sacrum, assist in forming the hypogastric plexus {'plexus hypogastricus) (Fig. 787). Numerous delicate filaments are also distributed to the bodies of the vertebras and the ligaments connecting them. Pelvic Portion (Pars Pelvina) of the Gangliated Cord (Fig. 787). The pelvic portion of the gangliated cord is situated in front of the sacrum along the inner side of the anterior sacral foramina. It consists of four or five small ganglia on each side, connected by interganglionic cords. Below, these cords converge and unite on the front of the coccyx by means of a small ganglion, the coccygeal ganglion or ganglion impar {ganglion coccygeuvi impar) (Fig. 787). Gray rami comraunicantes pass from the ganglia to the sacral and coccygeal nerves. No white rami communicantes join this part of the gangliated cord, but the visceral brandies which arise from the third and fourth, and sometimes from the second, sacral are regarded as homologous witli white rami communi- cantes The branches of distribution communicate on the front of the sacrum with the corresponding branches from the opposite side; some, from the first two ganglia, pass to join the pelvic plexus, while others form a plexus which accompanies the middle sacral artery, from which plexus filaments pass to the coccygeal gland. THE GREAT PLEXUSES OF THE SYMPATHETIC SYSTEM. The great plexuses of the sympathetic are the large aggregations of nerves and ganglia, previously alluded to, situated in the thoracic, abdominal, and pelvic cavities respectively, and named the cardiac, pulmonary, oesophageal, coeliac, and hypogastric plexuses respectively. They consist not only of sympathetic fibres derived from tlie ganglia, but also of fibres from the central nerve system which are conveyed through the white rami communicantes. i'rom them are derived the branches which supply the viscera. The Cardiac Plexus (Plexus Cardiacus) (Fig. 787). The cardiac plexus is situated at the base of tht heart, and is divided into a superficial part, which lies in tlie concavity of the arch of the aorta, and a deep part, which lies between the trachea and aorta. The two plexuses are, however, closely connected. The superficial cardiac plexus lies beneath the arch of the aorta, in front of the riglit pulmonary artery. It is formed by the left superior cardiac nerve, the left (and occasionally also the right) inferior cervical cardiac branches of the vagus, and filaments from the deep cardiac plexus. A small ganglion, the cardiac ganglion of Wrisberg {ganglion cardiacum [Wrisbergi]) is occasionally found connected with these nerves at their point of junction. This ganglion, when present, is situated immediately beneath the arch of the aorta on the right side of the ductus arteriosus. The superficial cardiac plexus gives branches to the deep cardiac plexus beneath the arcli of the aorta to the right or anterior coronary plexus and to tlie left anterior pulmonary plexus. The deep cardiac plexus is situated in front of the trachea at its bifurcation,. THE CCELIAC OB SOLAR PLEXUS 1073 above the point of division of the puhnonary artery and behind the arch of the aorta. It is formed by the cardiac nerves derived from the cervical ganglia of the sympathetic and the cardiac branches of the recurrent laryngeal and vagus. The only cardiac nerves which do not enter into the formation of this plexus are the left superior cardiac nerve and the inferior cervical cardiac branch from the left vagus. The branches from the right side of this plexus pass, some in front of, and others behind, the right pulmonary artery; the former, the more numerous, transmit a few filaments to the anterior pulmonary plexus, and are then continued onward to form part of the right coronary plexus; those behind the pulmonary artery dis- tribute a few filaments to the right auricle, and are then continued onward to form a part of the left coronary plexus. The left side of the plexus is connected with the superficial cardiac plexus and gives filaments to the left auricle of the heart, and to the anterior pulmonary plexus, and is then continued to form the greater part of the left coronary plexus. The left coronary plexus (plexus coronarius posterior) is larger than the right, and accompanies the left coronary artery; it is chiefly formed by filaments pro- longed from the left side of the deep cardiac plexus, and by a few from the right side. It gives branches to the left auricle and ventricle. The right coronary plexus {plexus coronarius anterior) is formed partly from the superficial and partly from the deep cardiac plexus. It accompanies the right coronary artery, and gives branches to the right auricle and ventricle. Although sympathetic filaments enter into the formation of the anterior and posterior pulmonary and the oesophageal plexuses, these are usually regarded as portions of the vagus nerve (p. 1007). The Coeliac or Solar Plexus (Plexus Coeliacus) (Figs. 787, 792). The coeliac or solar plexus supplies the viscera in the abdominal cavity. It consists of a great network of nerves and ganglia, situated behind the pancreas and the lesser peritoneal cavity and in front of the aorta and crura of the Diaphragm. It surrounds the coeliac axis and root of the superior mesenteric artery, extending downward as low as the pancreas and outward to the suprarenal glands. This plexus, and the ganglia connected with it, receive the great, the small, and the least splanchnic nerves of both sides, and some filaments from the right vagus nerve. It distributes filaments which accompany, under the name of plexuses, all the branches from the front of the abdominal aorta. Of the ganglia of which the solar plexus is partly composed the principal are the two semilunar ganglia {ganglia coeliaca) (Figs. 792 and 793), which are situated one on each side of the plexus, and are the largest ganglia in the body. They are large, irregular, gangliform masses formed by the aggregation of smaller ganglia, having interspaces between them. They are situated in front of the crura of the Diaphragm, close to the suprarenal glands; the one on the right side lies beneath the inferior vena cava. The upper part of each ganglion is joined by the great splanchnic nerve, and to the inner side of each the branches of the solar plexus are connected. The lower portion of each semilunar ganglion is detached, and is named the aorticorenal ganglion. From the coeliac plexus are derived the following: Phrenic or Diaphragmatic plexus. Gastric plexus. Suprarenal plexus. Splenic plexus. Renal plexus. Hepatic plexus. Spermatic | i , Superior mesenteric plexus. Ovarian j " ' ' ^^ Aortic plexus. 1074 THE NERVE SYSTEM The Phrenic Plexus {plexus phrenicus) (Fig. 792) accompanies the inferior phrenic artery to the Diaphragm, some filaments passing to the suprarenal gland. It arises from the upper part of the semilunar ganglion, and is larger on the right than on the left side. It receives one or two branches from the phrenic nerve. At the point of junction with the phrenic nerve is a small ganglion, the phrenic ganglion (ganglion phrenicum) (Fig. 793), which lies on the under surface of the Diaphragm, near the right suprarenal. Its branches are distributed to the inferior vena cava, suprarenal, and hepatic plexus. There is no phrenic ganglion on the left side. CCELIAC LEFT PHRENrC PLEXUS VAGU PLEXUS Fig. 792.— The semilunar gaogli; FEHIOR :SENTERIC LEXUS 'ith the sympathetic plexuses of the abdominal viscera radiating from the gangha. (Toldt.) The Suprarenal Plexus (plexus suprarenalis) (Fig. 792) is formed by branches from the coeliac plexus, from the semilunar ganglion, and from the phrenic and great splanchnic nerves, a ganglion being formed at the point of junction of the latter nerve. It supplies the suprarenal gland, being chiefly distributed to its medullary portion. The branches of this plexus are remarkable for their large size in comparison with the size of the organ they supply. THE CCELIAC OR SOLAR PLEXUS 1075 The Renal Plexus {plexus renalis) (Figs. 792 and 793) is formed bj' filaments from the ca-Hac plexus, the lower part of the semilunar ganglion (aorticorenal o-ancdion) and the aortic plexus. It is also joined by the least splanclinic Phrenic qanqhon Suprarenal plexus Ltft lenal artery, &upei wi mesenteric ganglion. Infei lot mesenteric artery. .Infeno) mesenteric ganglion. Sacioiettebral angle. ( ommon ihac vein. -Common iliac artery. Fig. 793.— Lumbar portion of the gangliated cord, with the ccsliac and hypogastric plextises. (.\fter Henle.) 1076. THE NEJRVi: SYSTEM nerve. The nerves from these sources, fifteen or twenty in number, have numerous ganglia developed upon them. They accompany the branches of the renal artery into the kidney, some filaments on the right side being distributed to the inferior vena cava, and others, on both sides, to the spermatic plexuses. The Spermatic Plexus (plexus sfermaticus) (Fig. 792) is derived from the renal plexus, receiving branches from the aortic plexus. It accompanies the spermatic vessels to the testis. In the female the ovarian plexus {plexus arteriae ovaricae) arises like the sper- matic plexus, and is distributed to the ovaries. Fallopian tubes, and fundus of the uterus. The Gastric or Coronary Plexus {plexus gastricus superior) (Fig. 792) accompa- nies the gastric artery along the lesser curvature of the stomach, and joins with branches from the left vagus nerve. The Splenic Plexus {plexus lienalis) (Fig. 792) is formed by branches from the coeliac plexus, the left semilunar ganglion, and from the right vagus nerve. It accompanies the splenic artery and its branches to the substance of the spleen, giving off, in its course, filaments to the pancreas, the pancreatic plexus, and the left gastroepiploic plexus, which accompanies the left gastroepiploic artery along the greater curvature of the stomach. The Hepatic Plexus {plexus hepaticus) (Fig. 792), the largest offshoot from the coeliac plexus, receives filaments from the left vagus and right phrenic nerves. It accompanies the hepatic artery, ramifying in the substance of the liver upon the branches of the portal vein within the substance of the liver. Branches from this plexus accompany all the divisions of the hepatic artery. Thus, there is a pyloric plexus accompanying the pyloric branch of the hepatic, which joins with the gastric plexus and vagi nerves. There is also a gastro- duodenal plexus, which subdivides into the pancreaticoduodenal plexus, which accompanies the pancreaticoduodenal artery, to supply the pancreas and duo- denum, joining with branches from the mesenteric plexus. The gastroepiploic plexus, which accompanies the right gastroepiploic artery along the greater curvature of the stomach, and which is said to anastomose with branches from the splenic plexus, is in reality derived from the splenic plexus. A cystic plexus, which supplies the gall-bladder, also arises from the hepatic plexus near the liver. The Superior Mesenteric Plexus {plexus mesentericus superior) (Fig. 792) is a continuation of the lower part of the great solar plexus, receiving a branch from the junction of the right vagus nerve with the coeliac plexus. It surrounds the superior mesenteric artery, which it accompanies into the mesentery, and divides into a number of secondary plexuses, which are distributed to all parts supplied by the artery — ^viz., pancreatic branches to the pancreas; intestinal branches, which supply the whole of the small intestine ; and ileocolic, right colic, and middle colic branches, which supply the corresponding parts of the large intestine. The nerves composing this plexus are white in color and firm in texture; in the upper part of the plexus close to the origin of the superior mesenteric artery is a ganglion {ganglion mesen- tericum super ius). The Abdominal Aortic Plexus {plexus aorticus abdominalis) (Figs. 792 and 79.3) is formed by branches derived, on either side, from the coeliac plexus, receiving filaments from some of the lumbar ganglia. It is situated upon the sides and front of the aorta, between the origins of the superior and inferior mesenteric arteries. From this plexus arise part of the spermatic, the inferior mesenteric, and the hypo- gastric plexuses ; it also distributes filaments to the inferior vena cava. The Inferior Mesenteric Plexus {plexus mesentericus inferior) (Fig. 792) is derived chiefly from the left side of the aortic plexus. It surrounds the inferior mesenteric artery, and divides into a number of secondary plexuses, which are distributed to all the parts supplied by the artery — viz., the left colic and sigmoid plexuses, which THE PELVIC PLEXUSES 1077 supply the descending and sigmoid flexure of the colon; and the superior hemor- rhoidal plexus (plexus hemorrhoidalis superior), which supplies the upper part of the rectum and joins in the pelvis with l)ranches from the pelvic plexus. The Hypogastric Plexus (Plexus Hypogastricus) (Figs. 787, 793). The hypogastric plexus supplies the viscera of the pelvic cavity. It is situated in front of the promontory of the sacrum, between the two common iliac arteries, and is formed by the union of numerous filaments, which descend on each side from the abdominal aortic plexus and from the lumbar ganglia. This plexus con- tains no evident ganglia; it bifurcates, below, into two lateral portions, right and left, which form the pelvic plexuses. The Pelvic Plexuses. The pelvic plexuses supply the viscera of the pelvic cavity, and are situated at the side of the rectum in the male, and at the sides of the rectum and vagina in the female. They are formed by a continuation of the hypogastric plexus, by the visceral branches from the second, third, and fourth sacral nerves, and by a few filaments from the first two sacral ganglia. At the points of junction of these nerves small ganglia are found. From these plexuses numerous branches are distributed to the rectum and bladder in the male, and to the rectum, bladder, uterus, and vagina in the female. They accompany the branches of the internal iliac artery. These secondary plexuses are (1) the inferior hemorrhoidal, (2) vesical, (3) prostatic, (4) vaginal, and (5) uterine plexuses. The Inferior Hemorrhoidal Plexus (plexus haemorrhoidalis inferior) arises from the upper part of the pelvic plexus. It supplies the rectum, joining with branches of the superior hemorrhoidal plexus. The Vesical Plexus {plexus vesicalis) arises from the fore part of the pelvic plexus. The nerves composing it are nmnerous, and contain a large proportion of spinal nerve fibres. They accompany the vesical arteries, and are distributed to the side and base of the bladder. Numerous filaments also pass to the vesiculae seminales and vasa deferentia; those accompanying the vas deferens join, on the spermatic cord, with branches from the spermatic plexus. The Prostatic Plexus (plexus prostaticus) is continued from the lower part of the pelvic plexus. The nerves composing it are of large size. They are distributed to the prostate gland, seminal vesicles, and erectile tissue of the penis. The nerves supplying the erectile tissue of the penis consist of two sets, the small and large cavernous nerves. They are slender filaments, which arise from the fore part of the prostatic plexus, and, after joining with branches from the internal pudic nerve, pass for%\'ard beneath the pubic arch. The small cavernous nerves (jin. cavernosi penis minores) perforate the fibrous covering of the penis, near its root. The large cavernous nerve (n. cavernosus penis major) passes forward along the dorsum of the penis, joins with the dorsal nerve of the penis, and is distributed to the corpora cavernosa and corpus spongiosum. The uterine and vaginal plexuses in reality constitute one plexus, the utero- vaginal plexus (plexus uferovagiualis). The Vaginal Plexus arises from the lower part of the pelvic plexus. It is dis- tributed to the walls of the vagina, to the erectile tissue of the vestibule, and to the clitoris. The nerves composing this plexus contain, like the vesical, a large proportion of spinal nerve fibres. The Uterine Plexus accompanies the uterine artery to the side of the uterus between the layers of the broad ligament; it communicates with the ovarian plexus. THE OEGANS OF SPECIAL SENSE. m, ^HE organs of the senses {orgaiia scnsuuin) are five in number — those of I smell, sight, hearing, taste, and touch. THE NOSE. The nose is the peripheral portion of the organ of smell (prganon olfactus); by means of the peculiar properties of its nerves it protects the lungs from the inhala- tion of deleterious gases and assists the organ of taste in discriminating the prop- erties of food. The organ of smell consists of two parts — one external, the outer nose, which projects from the centre of the face, and an internal, the cavum nasi, which is divided by a septum into the right and left nasal fossae. THE OUTER NOSE (NASUS EXTERNUS). The outer nose is the more anterior and prominent part of the organ of smell. Of a pyramidal form, it is directed downward, and projects from the centre of the face immediately above the upper lip. Its root (radix nasi) is connected directly with the forehead. Its base (basi^ nasi) presents two elliptical orifices, the nostrils or anterior nares (nares), separated from each other by an antero- posterior septum, the columna (septum mobile nasi). The margins of the nostrils are provided with a number of stiff hairs or vibrissas, which arrest the passage of foreign substances carried with the current of air intended for respiration. The point (apex nasi) is the free extremity of the nose. The lateral surfaces of the nose form, by their union in the middle line, the dorsum (dorsum nasi), the direction of which varies considerably in different individuals. The portion of the dorsum over the nasal bones is the bridge. Each lateral surface terminates below in a rounded eminence, the wing or ala nasi, which, by its lower margin (margo nasi), forms the outer boundary of the corresponding nostril. Above the ala is a depression, the alar sulcus. Structure. — ^The nose is composed of a framework of bones and cartilages, the latter being slightly acted upon by certain muscles. It is covered externally by the integument, internally by mucous membrane, and is supplied with vessels and nerves. The bony framework occupies the upper part of the organ; it consists of the nasal bones and the nasal processes of the maxillae ("pp. 99 and 104). The cartilaginous framework {cartilagiiu's nasi) (Figs. 794 and 795) consists of five pieces — the two upper and the two lower lateral cartilages and the cartilage of the septvun. The upper lateral cartilage (cartilago 7iasi lateralis) of each side is situated below the free margin of the nasal bone and is flat and triangular in shape. Its anterior margin is thicker than the posterior, and continuous aliove with the cartilage of the septum. Its posterior margin is attached to the nasal process of the maxilla. Its inferior margin is connected by fibrous tissue with the lower lateral cartilage; one surface is tiu-ned outward, the other inward toward the nasal cavity. The lower lateral cartilage (cartilago alaris major) is a thin, fiexible plate situated immediately below the preceding, and bent upon itself in such a manner as to form the inner and outer walls of the orifice of the nostril. The portion which forms the inner wall {cms mediale), thicker than the rest, is loosely connected with the corresponding portion of the opposite cartilage to (1079) 1080 THE ORGANS OF SPECIAL SENSE form a small part of the columna. Its inferior border, free, rounded, and projecting, forms, with the thickened integimient and subjacent tissue and the corresponding parts of the opposite side, the mobile septum. The part of the cartilage which forms the outer wall {cms laterale) is Seen from below. le view. ■cer lateral cart Sesamoid cartilages. Figs. 794 and 795. — Cartilages of the curved to correspond with the ala of the nose; it is oval and flattened, narrow behind, where it is connected with the nasal process of the maxilla by a tough fibrous membrane, in which are found three or four small cartilaginous plates, the sesamoid or lesser alar cartilages {cartilagines dares minores). _ Above, it is connected by fibrous tissue to the upper lateral cartilage and front part of the cartilage of the septum; below, it falls short of the margin of the nostril; the ala being completed by dense cellular tissue covered by skin. In front the lower lateral cartilages are separated by a notch which corresponds with the point of the nose. The cartilage of the septum (carfilago septi nasi) (Figs. 794 and 796) is somewhat quadrilateral in form, thicker at its margins than at its centre, and completes the sepa- ration between the nasal fossa in front. Its anterior margin, thickest above, is connected with the nasal bones, and is continuous with the anterior margins of the two upper lateral cartilages. Below, it is connected to the inner portions of the lower lateral cartilages by fibrous tissue. Its posterior margin is connected with the perpendicular lamella of the ethmoid; its inferior margin with the vomer and the palate processes of the max- illa? (Fig. 796). It may be prolonged backward (especially In children) for some distance between the vomer and perpendicular plate of the eth- moid, forming what is termed the sphenoidal process (processus sphenoidalis septi cartila- ginei). The septal cartilage does not reach as far as the lower part of the nasal septum. This i.i formed by the thinnest portions of the lower lateral cartilages and by the skin; it is freely movable, and hence is termed the mobile septum. Along the lower margin of the anterior half of the cartilage of the septum is another cartilage which is attached to the vomer and is known as the vomerine cartilage, or cartilage of Jacobson (cartilagovomeronasalis). These various cartilages are connected to each other and to the bones by a tough fibrous membrane, which allows the utmost facility of movement between them. The muscles of the nose are situated beneath the integument; they are (on each side) the Pyramidalis nasi, the Levator labii superiores alaeque nasi, the Dilatator naris, anterior and pos- -Bones and cartilacce of Right side. eptum of the nose. THE NASAL F088M 1081 terior, the Compressor nasi, the Compressor narium minor, and the Depressor alae nasi. They have been previously described (p. 372). The integiunent co\'ering the dorsum and the .sides of the nose is thin, and loosely connected with the subjacent parts; but the integument of the tip and the alas of the nose is thicker and more firmly adherent, and is furnished with a large number of sebaceous follicles, the orifices of which are usually very distinct. The mucous membrane lining the interior of the nose is continuous with the skin externally and with the mucous membrane which lines the nasal fossse within. The arteries of the nose are the lateralis nasi from the facial, and the inferior artery of the septum from the superior coronarij, which supply the alii? and septum, the sides and dorsum being supplied from the nasal branch of the ophthalmic and the infraorbital. The veins of the nose terminate in the facial and ophthalmic. The Ijrmphatics of the outer nose are shown in Fig. 557. They empty chiefly into the submaxillary lymph nodes. The nerves for the muscles of the nose are derived from the facial, while the skin receives its branches from the infraorbital, infratrochlear, and na^al branches of the ophthalmic. THE NASAL FOSS.ffi (CAVUM NASI). The nasal fossae are two irregular cavities situated in the middle of the face, one on each side of the mesal plane. They open in front, when the soft parts are in place, by the two nostrils or anterior nares, and terminate, behind, in the nasopharynx by the posterior nares. Bccessus splieno ethmoidalis Orifice of Eustachian tube Fossa of Rosenmilller Fig. 797. — Outer wall of nasal fossa. The anterior nares (nares) are somewhat pear-shaped apertures, each measur- ing about one inch (2.5 cm.) antero-posteriorly and half an inch (1.2 cm.) trans- versely at their widest part. The nasal fossae in the dry skull open in front by the anterior nasal aperture (aperhira pyriformis). The posterior nares (choanae) are two oval openings, which are smaller in the living or recent subject than in the skeleton, because they are narrowed by the 1082 THE ORGANS OF SPECIAL SENSE mucous membrane. Each measures an inch (2.5 cm.) in the vertical and half an inch (1.2 cm.) in the transverse direction in a M^ell-developed adult skull. For the description of the bony boundaries of the nasal fossae see page 138. Inside the aperture of the nostril is a slight dilatation, the vestibule (vestibulum nasi), which extends as a small pouch, the ventricle, toward the point of the nose. Above and behind the vestibule is surrounded by a prominence (limen nasi). Below the prominence the vestibule ic lined with skin; above and behind it the fossa is lined with mucous membrane. The fossa, above and behind the vesti- bule, has been divided into two parts — an olfactory portion (regio olfactoria), a slit- PROBE P^g SINUS THfloJl^O ''""it. Fig. 798. — External wall of right nasal fossa, parts of the turbinates having been cut away to show the orifices of the sinuses which open into the meatuses. (Testut.) like cavity, comprising the upper and central part of the septum and the superior turbinated process, and a respiratory portion {regio respiratoria), which comprises the rest of the fossa. The Outer Wall (Figs. 797 and 798). — The superior, middle, and inferior meati (meatus nasi superior, niediiis, and inferior) are described on page 141. The sphenoidal air sinus opens into the sphenoethmoidal recess (recessus sphenoeth- moidalis), a narrow recess above the superior turbinated process (Fig. 798). The posterior ethmoidal cells open into the front and upper part of the superior meatus (Fig. 797). Where the middle turbinated process joins the nasal process of the maxilla there is often an elevation, agger nasi, presumably a representative of another turbinate. On raising or cutting away the middle turbinated process the outer wall of the middle meatus is fully exposed (Figs. 798 and 799) and pre- sents (1) a rounded elevation, termed the bulla ethmoidalis, opening on or immedi- ately above which are the orifices of the middle ethmoidal cells; (2) a deep, narrow, curved groove, in front of the bulla ethmoidalis, termed the hiatus semilunaris, into which the anterior ethmoidal cells and the maxillary sinus open, the orifice of the latter being placed near the level of its roof. The middle meatus is pro- longed, above and in front, into the infxmdibulum, which leads into the frontal sinus. The anterior extremitj^ of the meatus is continued into a depressed area which lies above the vestibule and is named the atrium {atrium meatus medii nasi). THE NASAL FOSS^ 1083 The nasal duct opens into the anterior part of the inferior meatus, the opening being frequently overlapped by a fold of mucous membrane.' The Inner Wall (Fig. 799). — The inner wall or septum is frequently more or less deflected from the mesal plane (Fig. 799), thus limiting the size of one fossa and increasing that of the other. Ridges or spurs of bone growing outward from the septum are also sometimes present. Immediately over the incisi\e foramen at the lower edge of the cartilage of the septum a depression, the nasopalatine recess {recessus nasopalathms) , may be seen. In the septum close to this recess a minute orifice may be discerned; it leads into a blind pouch, the rudimentary organ of Jacobson {organon wmeronasale) , which is well developed in some of the lower animals, but is rudimentary in man. The organ is supported by a plate Eye ball J oijve (hiatus semilunaris) leading to infundibiUum Middle turbinated vrocejis Middle meatus Turbinated boiie f Buccal cai ity \ ^pace beiueen cheek and gum Molai tooth upper jaw Root t-J molar tooth Fig. 799— Tr: Tongue Hard palnf' Nasal septum ^ vertical section of the nasal fossje. Tlie section i processes. (Cryer.) made anterior to the superior turbinated of cartilage, distinct from the cartilage of the septum, tlie cartilage of Jacobson (p. 1080). The cartilage of Jacobson is to the outer side of the lower edge of the cartilage of the septum. Just below the opening of the blind poucli is an ele- vation, tlie eminence of Jacobson. The Mucous Membrane (membrana mucosa nasi). — The mucous membrane lining the nasal fossse is sometimes called the Schneiderian membrane.- It is closely adherent to the periosteum or perichondrium, upon \Ahich it lies. It is continuous externally with the skin through the anterior nares, and with the mucous mem- brane of the nasopharynx through the posterior nares. From the nasal fosste its continuity may be traced with the conjuncti-\-a through the nasal duct and lacrimal canals; with the lining membrane of the tympanum and mastoid cells I J. p. Schaeffer: " Types of Ostia Nasolacrimalia, etc.," Amer. Jour, of Anat., vol. xiii. No. 2, 1912. 2After Conrad Victor Schneider (1614-16S0), Professor of Anatomy at Wittemberg. 1084 THE ORGANS OF SPECIAL SENSE through the Eustachian tube; and with the frontal, ethmoidal, and sphenoidal sinuses, and the maxillary sinus through the several openings in the meatuses. The mucous membrane is thickest and most vascular over the turbinated processes and bone. It is also thick over the septum, but in the intervals between the spongy bones and on the floor of the nasal fossae it is very thin. Where it lines the various sinuses it is thin and pale. Owing to the great thickness of this mem- brane, the nasal fossae are much narrower, and the turbinated processes and bones appear larger and more prominent than in the dried skull. From the same cir- cumstance, also, the various apertures com- municating with the meatuses are consid- erably narrowed. Epithelial hvier Branch of olfactory nerre'f Tunica propr Olfactory gland- C'ross-section of nerve' Fig. 800. — Vertical i Suppm-ting cell Structure of the Mucous Membrane (Figs. 800 and 801). — The epithelium covering the mucous membrane differs in its character according to the functions of the part of the nose in which it is found. In the respirator}' portion of the nasal cavity the epithelium is columnar and ciliated, which is also the type found in the accessory sinuses, with the exception of the maxillary, where the epithelium is of the simple polygonal variety. Interspersed among the columnar ciliated cells are gob- let or mucin cells, while between their bases are found smaller pyramidal cells. In this region, beneath the epithelium and its base- ment membrane, is a fibrous layer infil- trated with leukocytes, so as to form in many parts diffuse lymphoid tissue, which is particularly plentiful in children ; beneath this is a nearly continuous layer of smaller and larger glands, some mucous and some serous, the ducts of which open upon the surface. In the respiratory portion of the mucous membrane there is an extensive anastomosing plexus of veins, which in some regions forms a distinct cavernous tissue (plexus caveniosus concharum). The cav- ernous tissue is particularly distinct over the inferior turbinated bones. In the olfactory region the mucous membrane is yellowish in color and the epithelial cells are columnar and non-ciliated; they are of two kinds, supporting cells and olfactory cells. The supporting cells are irregular pigmented elements that contain oval nuclei, situated in the deeper parts of the cells; the free surface of each cell presents a sharp outline, and its deep extremity is prolonged into a process which runs inward, branching to communicate with similar processes from neighboring cells, so as to form a network in the deep part of the mucous mem- brane. Lying between these central processes of the supporting cells are a large number of spindle-shaped cells, the olfactory cells, which consist of a large spherical nucleus surrounded by a small amount of granular protoplasm, and possessing two processes, of M'hich one runs outward between the columnar epithelial cells, and projects on the surface of the mucous mem- brane as a fine, hair-like process, the olfactory hair; the other or deep process runs inward, is frequently beaded, and is continuous with one of the filaments of the olfactory nerves. Beneath the epithelium, extending through the thickness of the mucous membrane, is a layer of tubular. Fig. 801. — From a vertical section through the mucous embrane of the regio olfactoria of a quite young dog. Gol- 's method. X -ioO. (Szymonowitz.) THE NASAL F088JE 1085 often branched, glands, the glands of Bowman (glandulac olfadoriac), identical in structure with serous glands. The accessory spaces, sphenoidal, frontal, maxillary, sinuses, and ethmoidal cells are lined by an extension of the nasal mucosa. The mucosa is thin, and consists of stratified ciliated and goblet cells upon a basement membrane and supported by a thin fibroelastic tunica propria. The glands are few in number and racemose in structiu'e. The arteries of the nasal fossae are the anterior and posterior ethmoidal, from the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof of the nose; the sphenopalatine, from the internal maxillary, which supplies the mucous membrane covering the spongy bones, the meatuses, and septum; the inferior artery of the septum, from the superior coronary of the facial; and the infraorbital and alveolar branches of the internal maxillary, which supply the lining membrane of the antrum. The ramifications of these vessels form a close, plexiform network, beneath and in the substance of the mucous membrane. The veins of the nasal fossse form a close, cavgrnous-like network beneath the mucous mem- brane. This cavernous appearance is especially well marked over the lo« er part of the septum and over the middle turbinated process and inferior turbinated bones. Some of the veins pass, with those accompanying the sphenopalatine artery, through the sphenopalatine foramen; and others, tlirough the alveolar branch, to join the facial vein; some accompany the ethmoidal arteries, and terminate in the ophthalmic vein; and, lastly, a few communicate with the veins in the interior of the skull, through the foramina in the cribriform plate of the ethmoid bone, and the foramen cecum. The lymphatics have already been described (p. 777). The nerves of ordinary sensation are the nasal branch of the ophthalmic, filaments from the anterior dental branch of the superior maxillary, the Vidian, the nasopalatine, the large or anterior ])alatine, and nasal branches of the sphenopalatine ganglion. The nasal branch of the ophthalmic ilivision of the trigeminal nerve distributes filaments to the fore part of the septum and outer wall of the nasal fossre. Filaments from the anterior dental branch of the superior max- illary supply the inferior meatus and inferior turbinated bone. The Vidian nerve supplies the upper and back part of the septum and superior turbinated process, and the upper anterior nasal branches from the sphenopalatine ganglion have a similar distribution. The nasopalatine nerve supplies the middle of the septum. The larger or anterior palatine nerve supplies the lower nasal branches to the middle turbinated process and the turbinated bone. The olfartori/ nn vrs, the special nerves of the sense of smell, are distributed to the olfactory region, and ha\e liccn already referred to (p. 973). Applied Anatomy. — Instances of congenital deformity of the nose are occasionally met with, such as complete absence of the nose, an aperture only being present; or perfect development on one side, and suppression or malformation on the other; or there may be imperfect apposi- tion of the nasal bones, so that the nose presents a median cleft or furrow. Deformities which have been acquired are much more common, such ils flattening of the nose {saddle nose), the result of syphilitic necrosis, imperfect development of the nasal bones in cases of congenital syphilis, or a lateral deviation of the nose may result from fracture. The skin over the ahe and tip of the nose is thick and closely adherent to subjacent parts. Inflammation of this part is therefore very painful, on account of the tension. The skin is largely supplied with blood, and the circulation here being terminal, vascular engorgement is liable to occur, especially in women at the menopause and in both sexes from disorders of digestion, ex- posure to cold, etc. The skin of the nose also contjtins a large number of sebaceous glands, and these, as a result of intemperance, are apt to become affected, and the nose becomes reddened, congested, and irregularly swollen. To this condition the term grog blossom is popularly' applied- [n some of these cases there is enormous hypertrophy of the skin and subcutaneous tissues, pro- ducing pendulous masses, termed lipomata nasi. Ordinary epithelioma and rodent ulcer may attack the nose, the latter being the more common of the two. Lupus and syphilitic ulceration frecfuently attack the nose, and may destroy the whole of the cartilaginous portion. In fact, lupus vulgaris begins more frequently on the ala of the nose than in any other situation. Cases of congenital occlusion of one or both nostrils, or adhesion betw'een the ala and septum may occur, and may recjuire immediate operation, since the obstruction much interferes with niu-sing. Bony closure of the posterior nares may also occur. To examine the nasal cavities, the head should be thrown back and the nose drawn upward, the parts being dilated by some form of speculum. The posterior nares can be exjilored by the aid of reflected light from the mouth, by which the posterior nares can be illuminated. The examination is very difficult to carry out, and, as a rule, sufficient information regarding the presence of foreign bodies or tumors in the nasopharynx can be obtained by the introduction of the finger behind the soft palate through the mouth. The septmn of the nose is sometimes dis- placed or deviates from the middle line; this may be the result of an injury or some congenital defect in its development; in the latter case the deviation usually occurs along the line of union of the vomer and mesethmoid, and rarely occurs before the seventh year. Sometimes the de\'ia- tion may be so great that the septum may come in contact with the outer wall of the nasal fossa, and may even become adherent to it, thus producing complete obstruction. Perforation, of the 1086 THE ORGANS OF SPECIAL SENSE septum is not an uncommon affection and may arise from several causes — syphilitic or tubercu- lous ulceration, blood tumor or abscess of the septum, and especially in workmen exposed to the vapor of bichromate of potash, from the irritating and corrosive action of its fumes. When small, the perforation may cause a peculiar whisthng sound during respiration. When large, it may lead to the falling in of the bridge of the nose. Epistaxis is a very common affection in children. It is rarely of much consequence, and will almost always subside, but in the more violent hemorrhages of later life it may be necessary to plug the posterior nares. In performing this operation it is desirable to remember the size of the posterior nares. A ready method of regulating the size of the plug to fit the opening is to make it of the same size as the terminal phalanx of the thumb of the patient to be operated on. Foreign bodies, such as boot buttons, are frequently inserted into the nostrils by children, and require some care in their removal, as unskilled attempts only result in pushing the foreign body farther into the nasal fossa. Bodies which remain in the nose any length of time are apt to set up an ulceration of the mucosa, which may spread to the bone; a unilateral nasal discharge in a child is always suggestive of the presence of a foreign body. A foreign body is best removed under anesthesia, placing the left forefinger in the nasopharynx to prevent the passage of the body into the air-passages, and then removing the foreign body through the anterior naris by a suitable scoop or forceps manipulated by the right hand. Nasal poll/pus is a very common disease, and presents itself in three forms — the gelatinous, the fibrous, and the malignant. The first is by far the most common. It grows from the mucous membrane of the outer wall of the nasal fossa, where there is an abundant layer of highly vas- cular submucous tissue; rarely from the septum, where the mucous membrane is closely adher- ent to the cartilage and bone, without the intervention of much, if any, submucous tissue. The most common seat of gelatinous polyps is probably the middle turbinated process. The fibrous polypus generally grows from the base of the skull behind the posterior nares or from the roof of the nasal fossae. The malignant polypi, both sarcomatous and carcinomatous, may arise in the nasal cavities and the nasopharynx; or they may originate in the antrum, and protrude through its inner wall into the nasal fossa. Rhiiwlitlis or nose-stones may sometimes be found in the nasal cavities. They arise from the deposition of phosphate of lime upon either a foreign body or a piece of inspissated secretion. The nasal passages furnish a secretion of their own and receive secretion from other parts (tears and secretions of the accessory sinuses). The nasal cavities contain the ethmoidal laby- rinths, the lateral masses of the ethmoid (which form the superior and middle turbinated processes), and the inferior turbinated bones. The nasal cavity is surrounded by four pairs of pneumatic spaces, the accessory sinuses. These are the maxillary sinuses (p. 103), the fron- tal sinuses (p. 79), the sphenoidal sinuses (p. 99), and the cells of the ethmoidal labyrinth (p. 97). The lacrimal duct opens into the inferior meatus Inflammation of the air-cells may fol- low inflammation of the nasal mucous membrane or bone disease One set of cells or many may suffer. Suppuration may occur; pus may be retained; death of bone may ensue. The most serious conditions may follow (abscess of brain, sinus thrombosis, septicemia), and an operation is necessary to obtain relief. THE EYE. The eyeball or globe {bidhiis oculi) (Figs. 802 and 804) is contained in the ante- rior part of the cavity of the orbit. In this situation it is securely protected from injury, while its position is such as to insure the most extensive range of sight. It is acted upon by nimierous muscles, by which it is capable of being directed to different parts; it is supplied by vessels and nerves, and is additionally pro- tected in front by the orbital margins, eyelids, etc. The eyeball is embedded in the fat of the orbit, but is partly surrounded by II thin membranous sac, the capsule of T€non, which isolates it, so as to allow of free movement. The Capsule of T6non (fascia bulbi [Tenoni]) (Figs. 802 and 803) consists of a thin membrane which envelops the eyeball from the optic nerve to the ciliary region, separating it from the orbital fat and forming a socket in which it plays. Its inner surface is smooth, and is in contact with the outer siu-face of the sclera, the periscleral or suprascleral lymph space only intervening. This lymph space is continuous with the subdural and sul>arachnoid spaces, and is traversed by delicate bands of connecti^^e tissue which extend between the capsule and the sclera. This lymph space forms a flexible pocket, in which the globe rotates. The capsule is perforated behind by the ciliary vessels and nerves and by the optic nerve, being continuous with the sheath of the latter. In front it blends with THE EYE 1087 the ocular conjunctiva, and with it is attached to the clhary region of the eyeball. It is perforated by the ocular muscles, and is reflected backward on each as a tubular sheath. The sheath of the Superior oblique is carried as far as the fibrous ERtOR TARSAL MUSCLE OPTIC NERV Fig. 802. — The right eye in sagittal section, showing the capsule of T6non (semidiagrammatic*. (Testut.) pulley of that muscle; that on the Inferior oblique reaches as far as the floor of the orbit, to which it gives off a slip. The sheaths on the Recti are gradually lost in the epimysium, but they give off important expan- sions. The expansion from the Superior rectus blends with the ten- don of the Levator palpebrae; that of the Inferior rectus is attached to the inferior tarsal plate. These two Recti, therefore, will exercise some influence on the movements of the eyelids. The expansions from the sheaths of the Internal and External recti are strong, especially the one from the latter muscle, and are at- tached to the lacrimal and malar bones respectively. As they probably check the action of these two Recti, they liave been named the internal and external check ligaments. Lockwood has also described a thickening of tlie lower part of the capsule of Tenon which he has named the suspensory ligament of the eye. It is slung like a Fig. S03.— The capsule of Ti^non. The aponeurosis is seen from behind forward on the posterior hemisphere of the globe, a. Cellulofibrous intermuscular lamina. 6. Deep leaf of the sheath incised at the point where it leaves the muscle to fold itself on the posterior hemisphere when it forms the posterior capsule, d. Partly incised, c. Serous membrane. (Poirier and Charpy.) 1088 THE ORGANS OF SPECIAL SENSE hammock below the eyeball, being expanded in the centre, and narrow at its extremities, which are attached to the malar and lacrimal bones respectively.' The anterior one-third of the globe is covered by the conjunctiva, or mucous membrane, reflected from the inner surfaces of the lids (Fig. 805). A lateral view of the globe shows that it is composed of segments of two spheres of different sizes (Figs. 804 and 805). The anterior segment is one of a small sphere, and forms about one-sixth of the eyeball. It is more prominent than the posterior seg- ment, which is one of a much larger sphere, and forms about five-sixths of the globe. Between the small, anterior or corneal segment and the large, posterior or scleral segment is a shallow and narrow groove, the scleral sulcus {sulcus sclerae). The anterior pole is the centre of the anterior portion of the cornea. The posterior pole is the centre of the posterior portion of the sclera. A straight line joining OCULAR CO ^ CTIVA CILlftRY -^"MUSCLE =«= ^4 >\^PARSCIL ARIS •^ Sr\ RETINAE ^,\ ORA SERRATA EXCAVATION Fig. 804. — The right ey MACULA LUTEA AND FOVEA CENTRALIS tal section. (Toldt.) these two poles is the sagittal or optic axis (cixis optica) (Fig. 804). A line drawn around the eyeball equally distant at all points from the two poles is called the equator (Fig. 804). The plane of the equator divides the globe in an anterior and a posterior hemisphere. The visual axis (linea visus) (Fig. 804) passes in a straight line from the first nodal point on the cornea to the fovea centralis of the yellow spot on the retina. A nodal point is the point of intersection of convergent rays with the visual axis. The first nodal point is 6.9685 mm. behind the summit of the cornea. The axes of the eyeballs are nearly parallel to the mesal plane, and therefore do not correspond to the axes of the orbits, which are inclined to this plane, forming with it an anterior angle of about 30 degrees. The optic nerves * See a paper by C. B. Lockwood, Journal of Anatomy and Physiology, vol. xx, part i, p. 1. THE SCLERA AND CORNEA 1089 follow the direction of the axes of the orbits and are therefore oot parallel, each nerve either leaves or connects with its eyeball about 1 mm. below and 3 mm, to the inner or nasal side of the posterior pole (Fig. 804). The eyeball measures rather more in its transverse and antero-posterior diameters than in its vertical diameter, the former amounting to about 24 mm. (nearly an inch), the latter to about 23.5 mm. (nine-tenths of an inch). The diameters in the female are some- what less than in the male. At birth the eyeball has a transverse diameter of about 17,5 mm., while at puberty it measures from 20 to 21 mm. The eyeball is composed of three investing tunics and of three main refracting media. Fig. 805. — Di.igram of a horizontal section of the right eye, showing the upper surface of the lower segment. (Testut.) THE TUNICS OF THE EYE. From without inward the three tunics are: I. Sclera and Cornea. II. Choroid, Ciliary Body, and Iris. III. Retina. I. The Sclera and Cornea (Tunica Fibrosa Oculi). The sclera and cornea (Figs. 805 and SOG) form the external tunic of the eyeball; they are essentially fibrous in structure, the sclera being opaque, and forming the posterior five-sixths of the globe; the cornea, which forms the remaining sixth,, is transparent. 1090 THE ORGANS OF SPECIAL SENSE The Sclera {ayXrjpb-, hard). — The sclera has received its name from its extreme density and toughness; it is a firm, unyielding, opaque, fibrous membrane serving to maintain the form of the globe. It is much thicker behind than in front. Its external surface is of a white color, and is in contact with the inner surface of the capsule of Tenon, a lymph space intervening; it is C]uite smooth, except one- quarter of an inch back of the sclerocorneal junction, at the points where the Recti and Obliqui muscles are attached to it, and its anterior part is covered by the conjunctival membrane (Fig. 829); hence the whiteness and brilliancy of the front of the eyeball. Its inner surface is stained a brown color, marked by grooves, in which are lodged the ciliary nerves and vessels (Figs. 814 and 815); the inner surface of the sclera is loosely connected with the outer surface of the choroid by a layer of exceedingly fine cellular pigmented tissue (lamina fusca), which traverses an extensive lymph space, the perichoroidal space (spatium perichoroideale) (Figs. 814 and 829) intervening between the sclera and choroid. Behind, the sclera is pierced by the optic nerve and is continuous with the fibrous sheath of the nerve, which is derived from the dura (Fig. 809). At the point where the optic nerve passes through the sclera, the lamina fusca is represented by an arrangement of the fibrous tissue which forms a thin network, the cribriform lamina (lamina cribrosa sclerae) (Fig. 819); the minute orifices in this lamina serve for the transmission of nerve filaments, and the fibrous septa dividing them from one another are continuous with the membranous processes which separate the bundles of nerve fibres. One of these openings (jporus opticus), larger than the rest, occupies the centre of the lamella; it transmits the arteria centralis retinae to the interior of the eyeball (Fig 819). Around the cribriform lamella are numerous small apertures for the trans- mission of the ciliary nerves and the short ciliary arteries, and about midway between the margin of the cornea and the entrance of the optic nerve are four or five large apertures, for the transmission of veins {venae vorticosae) (Fig. 809). In front, the fibrous tissue of the sclera is continuous with the substantia propria of the cornea (Fig. 829), but the opaque sclera slightly overlaps the outer surface of the transparent cornea. Structure. — The sclera is formed of white fibrous tissue int'^rmixed with fine elastic fibres, and of flattened connective-tissue cells, some of which are pigmented, contained in cell spaces between the fibres (Fig. 819). These fibres are aggregated into bundles, some of which are arranged in layers having an equatorial direction, but most of which are arranged in layers lying in meridian lines. Its vessels (Figs. 809 and 810) are not numerous, the capillaries being of small size and uniting at long and wide intervals. It obtains arterial blood from the short posterior ciliary and the anterior ciliary arteries. The venous blood is removed by the vetiae vorticosae and the anterior ciliary vein^. There are lymph spaces between the cells which empty into the periscleral (Fig. 802 and p. 1086) and perichoroidal lymph spaces (Fig. 814). Its nerves are derived from the ciliary nerves (Fig. 808) . They lose their myelin sheaths and enter among the bundles of fibrous tissue, but it is not known how they terminate. The Cornea (Figs. 804 and 809). — The cornea is the projecting transparent part of the external tunic of the eyeball, and forms the anterior sixth of the surface of the globe. It is almost, but not quite, circular in shape, occasionally a little broader in the transverse than in the vertical direction. It is convex anteriorly, and projects forward from the sclera in the same manner that a watch-glass does from the case. Its degree of curvature varies in difi^erent individuals, and in the same individual at different periods of life, it being more prominent in youth than in advanced life. Usually the curvature is slighdy greater in the vertical plane than in the horizontal plane; at its centre than at its periphery, and at its temporal than at its nasal side. The cornea is dense and of uniform thickness throughout; its posterior surface is perfectly circular in outline, and exceeds the anterior surface slightly in extent, as the latter is overlapped by the sclera. The anterior surface is covered with conjunctival epithelium (Fig. 814). THE SCLERA AND CORNEA 1091 Structure (Fig. S06). — The cornea consists of five layers — namely: (1) the anterior or epi- thelial layer; (2) the anterior elastic membrane; (3) the substantia propria; (4)the posterior elastic membrane; (5) the posterior or endothelial layer. 1. The anterior layer (epilhdium corneae) is composed of stratified epithelium and is contin- uous witli the cells iif till- conjunctiva at the borders of the cornea. There are from five to eight strata of nuclcutcd cells in the epithelium Anterior elastic membrane \^Substantia f propria anterior layer. The deepest are columnar. Above the columnar cells are several layers of polygonal cells, most of which have finger- like processes and are called jirh-kle cells. At the surface the cells and nuclei become flat. 2. The anterior elastic or anterior limiting membrane, or Bowman's \. membrane (lamina clasfica anterior), is less than half the thickness of the laj'er of stratified epithelium. It re- sembles in some respects, but is not, elastic tissue, and is thicker in the centre than at the periphery. It shows evidences of fibrillary struc- ture, and does not display a tendency to curl inward or to undergo frac- tiu'e when detached from the other layers of the cornea. It consists of extremely close interwoven fibrils, similar to those found in the rest of the cornea proper, but contains no corneal corpuscles. It ought, there- fore, to be regarded as a part of the proper tissue of the cornea, appar- ently representing a basement mem- brane. 3. The substantia propria or proper substance of the cornea forms the main thickness of that structure. It is fibrous, tough, un- yielding, perfectly transparent, and continuous with the sclera. It is composed of about sixty flattened lamellae, superimposed one on another. These lamellae are made up of bundles of modified connec- tive tissue, the fibres of which are directly continuous with the fibres of the sclera. The fibres of each lamella are for the most part parallel with each other; those of alternating lamellEe at right angles to each other. Fibres, however, frequently pass obliquely from one lamella to the next (fibrae arcnatae). The lamella? are connected with each other by an interstitial cement substance, in which are spaces, the corneal spaces (Fig. SOT). The spaces are stellate in shape, and have numerous off'shoots or cailaliculi (Fig. sOT). Iiy which they communicate with one another. Each space contains a cell, the large corneal corpuscle (Fig. 807), which resembles in form the space in which it is lodged, but it does not entirely fill it, the remainder of the space containing lymph. In the aged the margin of the cornea becomes opaque gray. This rim is called the arcus senilis, and is due to fat deposit in the lamella; and corneal corpuscles. 4. The posterior elastic membrane, the membrane of Descemet, or of Demours {lamina elasiica posterior), which covers the posterior surface of the substantia propria of the cornea, presents no structure recognizable under the microscope. It consists of an elastic and perfectly trans- parent homogeneous membrane of extreme thinness, which is not rendered opaque by either water, alcohol, or acids. It is very brittle, but its most remarkable property is its extreme elas- FlG. 806.— Vertical ction through the cornea of X 200. (Szymonowicz.) Posterior epithelium newborn child. 1092 THE ORGANS OF SPECIAL SENSE Fig. 807. — From a horizontal section of an ox's cornea. Positive picture of the canal system drmonstrated by the gold chloride method. X 450. (Szymouowicz.) licity and the tendency which it presents to curl up, or roll upon itself, with the attached surface innermost, when separated from the proper substance of the cornea. Its use appears to be "to preserve the requisite permanent correct curvature of the flaccid cornea proper" (Jacob). At the margin of the cornea this posterior elastic membrane breaks up into fibres to form a reticular structure at the outer angle of the anterior chamber, the intervals between the fibres forming small cavernous spaces, Corneal cell in the spaces of Fontana (spatia Lymph canaliculi lymph space anguli iridis) (Fig. S14). These ]!< — • — ~7" — 1 little spaces communicate with a circular canal in the deeper parts of the corneoscleral junction. This is the canal of Schlemm {sinus venosus sderae) (Figs. 814 and 829) ; it communicates inter- nally with the anterior chamber through the spaces of Fontana, and externally with the scleral veins. Some of the fibres of this reticulated structure are continued into the front of the iris, forming the Ugamentum pectinatum iri- dis; while others are connected with the fore part of the sclera and choroid. 5. The posterior layer or the corneal endothelium (endothelium cainerae anterioris) lines the aqueous chamber and prevents the absorption of the aqueous humor. It covers the posterior surface of the elastic lamina, is reflected upon the front of the iris, and also lines the spaces of Fontana. It consists of a single layer of polygonal, flattened, transparent, nucleated cells, similar to those lining other serous cavities. Arteries and Nerves. — The fetal cornea contains bloodvessels which pass from the margin almost to the centre. The adult cornea contains no bloodvessels, except at its margin. The capillaries from the sclera and conjunctiva form loops at the corneal margin, and many of these loops enter the cornea for a distance of 1 mm. (Fig. 810). The balance of the cornea is non- vascular and obtains its nourishment from the lymph in the laeunae and canaliculi. Lymphatic vessels have not as yet been demonstrated in it, but are represented by the channels in which the bundles of nerves run; these channels are lined by endothelium and are continuous with the cell spaces. The nerves are numerous, and they are derived from the ciliary nerves; they form the annular plexus, at the corneal margin, and enter the laminated tissue of the cornea, lose their myelin sheaths, and ramify tliroughout the substantia propria as the plexus of the stroma. From this deep plexus come perforating fibres, which pass tlirough the anterior elastic lamina and form the subepithelial plexus, and from it fibres are given off which ramify between the epi- thelial cells, forming a network which is termed the intra-epithelial plexus. Nerve fibres from the annular plexus and from the plexus of the stroma come into close relation with the corneal corpuscles. Dissection. — In order to separate the sclera and cornea, so as to expose the second tunic, the eyeball should be immersed in a small vessel of water and held between the finger and thumb. The sclera is then carefully incised, in the equator of the globe, till the choroid is exposed. One blade of a pair of probe-pointed scissors is now introduced through the opening thus made, and the sclera divided around its entire circumference, and removed in separate portions. The front segment being then drawn forward, the handle of the scalpel should be pressed gently against it at its connection with the iris, and, these being separated, a quantity of perfectly trans- parent fluid will escape; this is the aqueous humor. In the course of the dissection the ciliary nerves (Fig. 808) may be seen lying in the loose cellular tissue between the choroid and sclera or continued in delicate grooves on the inner surface of the latter membrane. II. The Choroid, Ciliary Body, and Iris (Tunica Vasculosa Oculi) (Figs. SOS, S29). The middle tunic of the eye is formed from behind forward by the choroid, the ciliary body, and the iris. The choroid invests the posterior five-sixths of the globe, and extends as far forward as the ora serrata of the retina; the ciliary body connects the choroid THE CHOROID, CILIARY BODY, AND IRIS 1093 to the circumference of the iris. The iris is the circular septum, which hangs vertically behind the cornea, presenting in its centre a large rounded aperture, the pupil. The Choroid (chorioidea) is a thin, highly vascular membrane, of a dark-brown or chocolate color, which invests the posterior five-sixths of the globe, and is pierced behind by the optic nerve, and in this situation is firmly adherent to the sclera. It is thicker behind than in front. Externally, it is loosely connected by the lamina fusca with the inner surface of the sclera (p. 1090). Its inner surface is attached to the retina. Structure. — The choroid consists of a dense capillary plexus and of small arte- ries and veins, carrying the blood to and returning it from this plexus (Fig. SIO), and of branched and pigmented cells which lie in connective tissue. There are three layers in the choroid. Named from without inward, they ai'e the lamina suprachoroidea, the choroid proper, and lamina basalis. 1. The lamina suprachoroidea is on the external surface, that is, the surface next to the sclera. It resembles the lamina fusca of the sclera. It is com- posed of delicate nonvascular lamellas, each lamella consisting of a network of fine elastic fibres, among which are branched pigment cells. The spaces between the lamellfe are lined by endo- thelium, and open freely into the peri- choroidal lymph space, which, in its turn, communicates with the periscleral space by the perforations in the sclera through which the vessels and nerves are trans- mitted. 2. The choroid proper is internal to the lamina suprachoroidea. In consequence of the small arteries and veins of the choroid proper being arranged on the outer surface of the capillary network, it is customary to describe this as consisting of two layers — the outer {lamina vasculosa), composed of small arteries and veins, with pigment cells interspersed between them, and the imier {lamina choriocapiUaris), consisting of. a capillary plexus. The external layer of the choroid proper or the lamina vasculosa consists, in part, of the larger branches of the short posterior ciliary arteries (Figs. 809 and 812), which run forward between the veins, before they bend inward to terminate in the capillaries; but this layer is formed principally of veins, which have a whorl-like arrangement and empty into four or five large equidistant trunks, the venae vorticosae (Figs. 809 and 810), which pierce the sclera midway between the margin of the cornea and the attachment of the optic nerve. Interspersed between the vessels are dark star-shaped pigment-cells, the processes of which, communicating with similar branchings from neighboring cells, form a delicate network of stroma, which toward the inner surface of the choroid loses its pigmentary character. The inner layer of the choroid proper consists of an exceedingly fine capillary plexus, formed by the short ciliary vessels (Fig. 810), and is known as the membrane of Ruysch {lamina choriocapiUaris). The network is close, and finer at the hinder jiart of the choroid than in front. About 1.2 cm. behind the cornea its meshes become larger, and are con- tinuous with those of the ciliary processes. These two laminae are connected by an interme- diate stratmn {boundary zone), which is destitute of pigment cells and consists of fine elastic fibres. On the inner svu-face of the lamina choriocapiUaris is a very thin, structiu-eless, or faintly fibrous membrane, called the lamina basalis (membrane of Bruch) ; it is closely connected with the stroma of the choroid, and separates it from the pigmentary layer of the retina; the cells of the latter are found attached to this membrane. Dissection. — The ciliary body should now be examined. It may be exposed either by de- taching the iris from its connection with the CiUary muscle or by making a transverse section of the globe and examining it from behind. Fig. 80S.— The choroid ; (Enlarged.) 1094 THE ORGANS OF SPECIAL SENSE The Ciliary Body (corpus ciliare) (Fig. 813) joins the choroid to the margin of the iris. It is in reality a process of the choroid and comprises the orbicularis ciliaris, the ciliary processes, and the Ciliary muscle. The orbiculus ciliaris (Figs. 811 and 812) is a zone of about 4 mm. (| inch) in width, directly continuous -Rath the anterior part of the choroid; it presents numerous ridges arranged in a radial manner. The depressions between the ridges are filled with retinal pigment epithelium (Szymonowicz). The orbiculus contains no lamina choriocapillaris. ANTERrOR CILIARY RTERY Fig. 809. — Vessels and nerves of the choroid and iris, seen from above been largely removed. (Testut.) The sclera and cornea have The ciliary processes (processus ciliares) (Figs. 813 and 829) are formed by the plaiting and folding inward of the various layers of the choroid (i. e., the choroid proper and the lamina basalis) at its anterior margin, and are received between corresponding foldings of the suspensory ligament of the lens, thus establishing a connection between the choroid and inner tunic of the eye. They are arranged in a circle, and form a sort of plaited frill, the corona ciliaris, behind the iris, round the margin of the lens (Figs. 813 and 829). They vary between sixty and eighty in number, lie side by side, and may be divided into large and small; the latter, consisting of about one-third of the entire number, are situated in the spaces between the former, but without regular alternation. The larger processes are each about 2.5 mm. (one-tenth of an inch) in length, and are attached by their periphery to three or four of the ridges of the orbiculus ciliaris, and are continuous with the layers of the choroid; the opposite margin is free, and rests upon the circumference of the lens. Their anterior surface is turned toward the back of the iris, with the circumference of which they are continuous. The posterior surface is connected with the suspensory ligament of the lens. THE CHOROID, CILIARY BODY, AND IRIS 1095 Structure. — The ciliary processes are similar in structure to the choroid, but the vessels are larger, and have chiefly a longitudinal direction. They constitute the most vascular portion of the eyeball. The processes are covered on their inner surface by two strata of black pigment cells, which are continued forward from the retina, and are named the pars ciliaris retinae (Fig. 814). In the stroma of the ciliary processes there are also stellate pigment cells, which, how- ever, are not so numerous as in the choroid itself. ''//i Fig. 810. — Diagram of the bloodvessels of the eye, as seen in a horizontal section. (Leber, after Stohr.) Course of vasa centralia retinae: a. Al-teria. ai. Vena centralis retinae. /^. Anastomosis with vessels of outer coats 7. Anastomosis with branches of short posterior ciliary arteries, ri. Anastomosis with chorioideal vessels. Course of vasa ciliar. postic. brev. : I. Arteriae, and Ii. Venae ciliar. postic. brev. II. Episcleral artery. IIi. Episcleral vein. III. Capillaries of lamina choriocapiilaris. Course of vasa ciliar. postic. long.: 1. a. ciliar. post, longa. 2. Circulus iridis major cut across. 3. Branches to ciliary body. 4. Branches to iris. ' Course of vasa ciliar. ant.: a. Arteria. ai. Vena ciliar. ant. b. Junction with the circulus iridis major. c. Junction with lamina choriocapill. d. Arterial, and d\. Venous episcleral branches, e. Arterial, and ei. Venous branches to conjunctiva sclerae. f. Arterial, and fi. Venous branches to corneal border. V. Vena vorticosa. S. Transverse section of sinus venosus sclerae. The Ciliary muscle (Bowman's muscle) (m. ciliaris) (Figs. 814 and 816) con- sists of unstriped fibres; it forms a grayish, semitransparent, circular band, about 3 mm. (one-eighth of an inch) broad, on the outer surface of the fore part of the choroid, between the choroid and the iris and back of the sclerocorneal junction. It is thickest in front and gradually becomes thinner behind. It consists of two sets of fibres, radial and circular. The radial fibres (fibme meridiauales) (Figs. 1096 THE ORGANS OF SPECIAL SENSE INNER SURFACE' OF SCLERA terior surface) Fig. 811. — The middle or vascular coat of the eye- ball exposed from without. Left eye, seen obliquely from above and before. (Toldt.) 814 and 829), the more numerous, arise at the point of Junction of the cornea and sclera, and partly also from the ligamentum pectinatum iridis, and, passing backward, are attached to the choroid opposite to the ciliary processes. One bundle, according to Waldeyer, is continued backward to be inserted into the sclera. The circular fibres (fibrae circulares [Mulleri]) (Figs. 814 and 829) are internal to the radial ones and to some extent unconnected with them, and have a circular course around the at- tachment of the iris. They are some- times called the "ring muscle" of Miiller, and were formerly described as the ciliary ligament. They are well devel- oped in hypermetropic, but are rudi- mentary or absent in myopic eyes. The Ciliary muscle is admitted to be the chief agent in accommodation — i. e., in adjusting the eye to the vision of near objects. When the Ciliary muscle contracts, it draws the choroid for- ward, and relaxes the suspensory ligament. The elasticity of the lens at once allows it to bulge forward until it is again checked by the tension of the capsule;' the pupil is at the same time slightly contracted. The Iris (iris, a rainbow) (Figs. 815 and 817) has received its name from its various colors in different individuals. It is a thin, circular contractile curtain, suspended in the aq.ueous humor between the cornea and the lens, being perfo- rated a little to the nasal side of its centre by a circular aperture, the pupil (pMpiYZa) (Fig. 817), for the transmission ©f light. The pupil of a living person varies in size under the influence of light and in efforts at accommodation. In looking at a near object the pupil is small; in looking at a distant object it is large. In light the" pupil contracts, in darkness it dilates; hence the pupil is a window which permits light to pass into the interior of the eye. The size of this window depends on the contraction or relaxation of the iris. The iris divides the aqueous chamber (the space between the cornea and lens) into an anterior chamber and a posterior chamber which com- municate through the pupil (Fig. 804). By its circumference or ciliary margin (margo ciliaris) (Figs. 814 and 815) the iris is continuous with the ciliary body, and it is also connected with the posterior elastic lamina of the corneaby means of the pectinate ligament {ligamentum pecfliia- tum iridis) (Fig. 829) . The pectinate ligament of the iris is derived from the posterior ; of the choroid and iris. The sclera has )stiy removed. (Enlarged.) > Stewart, Manual ot Physiology. THE CHOROID, CILIARY BODY, AXD IRIS 1097 elastic layer of the cornea. In this hgament are numerous lymph spaces, the spaces of Fontana (spatia angidi iridis) [Fo7ita7iae]) (Fig. 814), and they join the canal of Fig. 813. — A portion of the corona eiliaris magnified. The ciliary processes and the ciliary folds, CToldt.) Schlemm to the anterior chamber of the eye. The inner or free edge of the iris forms the margin of the pupil, and is called the pupillary margin (jnargo pupillaris) (Fig. 815). The surfaces of the iris are flattened, and look forward and backward, the anterior toward the cornea, the posterior toward the ciliary processes and lens. Circ. fibres of Oitiwy musilc Fig. 814. — Section of the eye, showing the relations of the cornea, sclera, and iris, together with the Ciliarj niuscle and the cavernous spaces near the angle of the anterior chamber. ^\^ aldeyer.) The iris is pigmented and the color of an individual's eyes depends upon this pigment. The anterior surface (fades anterior) (Figs. 815 and 829) of the iris 1098 THE ORGANS OF SPECIAL SENSE is variously colored in different individuals, and is marked by lines which converge toward the pupil. The posterior surface {fades posterior) (Figs. 813 and 829) is of a deep purple tint, from being covered by two layers of pigmented, columnar epithelium, which layers are continuous posteriorly with the pars ciliaris retinae. This pigmented epithelium is termed the pars iridica retinae, though it is sometimes named uvea, from its resemblance in color to a ripe grape. CILIARY MA ATTACHED REMNANT Op CORNEAL MARGIN E BORDER 'IGMENTARY LAYER Fig. 815. — Section of the i Anterior surface magnified. (Toldt.) Structure. — The iris is composed of the following structures: 1. In front is a layer of flattened endothelial cells placed on a delicate hyalin basement membrane. This layer is continuous with the endothelial layer covering the membrane of Descemet, and in men with dark-colored irides the cells contain pigment granules. CILIARY GANGLIATEO EXUS POSTER LONG CILIARY ARTER OR RADICLES OF THE VORTICOSE VEINS -The ciliary gangliated plexus and the ciliary nerves entering the plexus, middle or vascular coat of the eyeball. (Toldt.) Outer surface of the 2. The stroma (stroma iridis) consists of fibres and cells. The former are made up of fine, deli- cate bundles of fibrous tissue, of which some few fibres have a circular direction at the circum- ference of the iris, but the chief mass consists of fibres radiating toward the pupil. They form, by their interlacement, delicate meshes, in which the vessels and nerves are contained. Inter- spersed between the bundles of connective tissue are numerous stellate cells with fine processes. THE CHOROID, CILIARY BODY, AND IRIS 1099 Many of them in dark eyes contain pipjmcnt njranules, but in blue eyes and the pink eyes of albinos they are unpigraented. The muscle fibres are unstriated and consist of circular and radial fibres. The circular fibres (»;. spliindcr pupillae) surround the margin of the pupil on the posterior surface of the iris, like a sphincter, forming a narrow band about one-thirtieth of an inch (0.8 mm.) in width, those near the free margin being closely aggregated; those more external somewhat separated, and forming less complete circles. The radial fibres (m. dilatator pupillae) converge from the circumference toward the centre, and blend with the circular fibres near the margin of the pupil. These fibres are regarded by some as elastic, not muscular. 3. Pigmented epithelium (pars iridica retinae). This is a continuation of the pars ciliaris retinae, and consisls of two layers of pigmented, columnar epithelial cells. The situation of the pigment differs in different irides. In the various shades of blue eyes the only pigmentation is that of the pigmented epithelium. The color of the eye in these individuals is due to this coloring matter showing more or less through the te.xture of the iris. In the albino even this pigment is absent. In the gray, brown, and black eye there are, as mentioned above, pigment granules to be found in the connective tissue cells of the stroma and in the endothelial layers on the front of the iris; to these the dark color of the eye is due. ANTERIOR CILIARY ARTERIES ANTERIOR CILIARY ARTERIES Fig. S17.— Iris, front view. (Testut.) The arteries of the Choroid and Iris (Figs. 809 and 817). — The short posterior ciliary arteries, from six to twelve in number, arise from the ophthalmic, or some of its branches; they pass for- ward around the optic nerve to the posterior part of the eyeball, pierce the sclera around the entrance of the nerve, and supply the choroid coat and ciliary processes. The arteries of the iris are derived from the long posterior ciliary and anterior ciliari/ arteries and from the vessels of the ciliary processes (see p. 613). The long posterior ciliary arteries (Figs. 809 and SIO), two in number, pass through the sclera, one on the inner and one on the outer side of the optic nerve, and pass forward between the sclera and choroid, and, having reached the attached margin of the iris (Figs. 809 and 817), divide into an upper and a lower branch, and. encircling the iris, anastomose with corresponding branches from the opposite side; into this vascular zone (eirculus i-ridis major) (Fig. 829) the anterior ciliary arteries (Fig. 829), from the lacrimal and anterior cUiary from the muscular branches of the ophthalmic, pour their blood. From this zone vessels converge to the free margin of the iris, and these communicate by branches from one to another and thus form a second zone (circuhis iridis minor) in this situation. The veins pass toward the ciliary margin and communicate with the veins of the ciliary processes and of the canal of Schlemm (Pigs. 809 and 810). The nerves of the Choroid and Iris (Fig. 808) are the short ciliary, the ciliary branches of the lenticular ganglion, and the long ciliary from the nasal branch of the ophthalmic division of the trigeminal. They pierce the sclera around the entrance of the optic nerve, and run for- 1100 THE ORGANS OF SPECIAL SENSE ward in the perichoroidal lymph space, in which they form a plexus, from which plexus filaments pass to supply the bloodvessels of the choroid. After reaching the iris they form a plexus around its attached margin; from this are derived amyelinic fibres which terminate in the circular and radial muscle fibres. Their exact mode of termination has not been ascertained. Other fibres from the plexus terminate in a network on the anterior surface of the iris. The fibres derived from the motor root of the lenticular ganglion (oculomotor nerve) supply the circular fibres, while those derived from the sympathetic supply the radial fibres. Membrana Pupillaris. — In the fetus the pupil is closed by a delicate transparent vascular membrane, the membrana pupillaris, which divides the space into which the iris is suspended into two distinct chambers. This membrane contains numer- ous minute vessels, continued from the margin of the iris to those on the front part of the capsule of the lens. These vessels have a looped arrangement, and converge toward each other without anastomosing. Between the seventh and eighth months the membrane begins to disappear, by gradual absorption from the centre toward the circumference, and at birth only a few fragments remain. It is said sometimes to remain permanent and produce blindness. III. The Retina, or Tiuiica Interna (Figs. 808, 809). The retina is a delicate nerve membrane, in which the fibres of the optic nerve are spread out and upon the surface of which the images of external objects are received. Its outer surface is in contact with the choroid; its inner with the vitre- ous body. Behind, it is continuous with the optic nerve; it gradually diminishes in thickness from behind forward; and, in front, extends nearly as far as the ciliary body, where it appears to terminate in a jagged margin, the ora serrata (Figs. 810 and 829). Here the nerve tissues of the retina end, but a thin pro- longation of the jnembrane extends forward over the back of the ciliary processes and iris, forming the pars ciliaris retinae and pars iridica reti- nae, already referred to. This for- ward prolongation consists of the pigmentary layer of the retina, to- gether with a stratum of columnar epithelium. The retina is soft, semi- transparent, and of a purple tint in the fresh state, owing to the presence of a coloring material named rhodopsin or visual ptu:ple; but it soon becomes clouded, opaque, and bleached when exposed to sunlight. Exactly in the centre of the front surface of the posterior part of the retina, corresponding to the visual axis, and at a point in which the sense of vision is most perfect, is an oval yellowish spot, called the yellow spot {macula lute a) (Figs. 804 and 818), having a central depression, the fovea centralis. The retina in the situation of the fovea centralis is exceedingly thin, and the dark color of the choroid is distinctly seen through it Itexistsonly in man, the quadrumana, and some saurian reptiles. About 3 mm. (one eighth of an inch) to the nasal side of the yellow spot, and about 1 mm. below it, is the point of attachment of the optic nerve, the optic disk {jporus opticus) Figs. 818 and 819), the circumference of which is slightly raised so as to form Fig. SIS.^ — The arteria centralis retinae, yellow spot, etc., the anterior half of the eyeball being removed. (iEnlarged.) THE RETINA, OB TUNICA INTERNA 1101 an eminence, the optic papilla (colliculiis nervi optici); the central portion is depressed and is called the optic cup (excavatio papillae nervi optici). The arteria centralis retinae pierces its centre. This is the only part of the surface of the retina from which the power of vision is absent, and is termed the blind spot. CHOROID POSTERIOR HORT CILIARY ARTERY AND~ VEIN Fig. 819. — The terminal portion of the optic nerve and its entrance into the eyeball, : (Toldt.) , Structure. — The retina is an exceedingly complex structure, and, when examined micro- scopically by means of sections made perpendicularly to its surface, is found to consist of many layers of nerve elements bound together and supported by the sustentacula! fibres. The layers of the retina are: 1. Membrana limitans interna. 2. Layer of nerve fibres (stratum opticum). 3. Ganglionic layer, consisting of nerve cells. 4. Inner plexiform layer. 5. Inner nuclear layer, or outer ganglionic layer. 6. Outer plexiform layer. 7. Outer nuclear layer, or layer of outer granules. 8. Membrana limitans externa. 9. Jacob's membrane (layer of rods and cones). 10. Pigmentary layer (tapetiun nigrimi). 1. The membrana limitans interna is the most internal layer of the retina and is in contact ■with the hyaloid membrane of the vitreous humor. It is derived from the supporting frame- work of the retina, with which tissue it will be described. 2. The layer of the nerve fibres consists of the axones proceeding from the nerve cells in the inner ganglionic layer. They are amyelinic, and, concentrating at the porus opticus, pass through all the layers of the retina except the membrana hmitans interna. On passing through the lamina cribrosa of the sclera these axones acquire myelin sheaths and leave the eyeball as a com- pact rounded bundle called the optic nerve A few of the fibres in tliis layer are centrifugal, being axones of ganglion cells within the brain, to terminate in the inner plexiform and outer ganglionic layers. The layer of nerve fibers is thickest at the optic nerve exit and gradually diminishes in thickness toward the ora serrata. 3. The ganglionic layer consists of a single layer of large ganglion cells, except in the macula lutea, where there are several strata. The cells are somewhat flask-shaped, the rounded internal surface of each cell resting on the preceding layer and sending off an axone which is prolonged as a nerve fibre into the fibre layer. From the opposite extremity numerous dendritesextend into the inner plexiform layer, where they branch out into flattened arborizations at different levels (Fig. 820). The ganglion cells vary much in size, and the dendrites of the smaller ones. 1102 THE ORGANS OF SPECIAL SENSE as a rule, arborize in the inner plexiform layer as soon as they enter it; while the processes of the (arger cells ramify close to the inner nuclear layer. 4. The inner plexiform layer is made up of a dense reticulum of minute fibrils, formed by the interlacement of the dendrites of the ganglion cells with those of the cells contained in the next layer, immediately to be described. Within the reticulum formed by these fibrils, a few branched spongioblasts are sometimes embedded. Membrana limitans ijifema Nerve-fibre layer Ganglionic layer — Inner plexiform.... layer Centrifugal fibre'' Outer nuclear layer Metnbrana limitans externa Layer of rods and cones Diffuse amacrine cell ''Amacrine cells ••Horizontal cell 7 Bod bipolars --•."Cone bipolars '—Pigmented layer Fig. 820.' — Plan of retinal neurones. (After Cajal.) 5. The inaer nuclear or inner granular layer consists of a number of closely packed cells, of which there are three varieties — viz.: (1) A large number of oval cells, which are commonly regarded as bipolar nerve cells, and are much more numerous than either of the other kind. They each consist of a large oval body placed vertically to the surface, and containing a distinct nucleus. The protoplasm is prolonged into two processes; one of these passes inward into the inner plexiform layer, is varicose in appearance, and ends in a terminal ramification, which is often in close proximity to the ganglion cells. The outer process passes outward into the outer plexiform layer, and there breaks up into a number of branches. There are two varieties of these bipolar cells — one in which the outer process arborizes around the knobbed ends of the rod fibres, and the inner around the cells of the ganglionic layer; these are called rod bipolars (Fig. 820); the others are those in which the outer process breaks up in a horizontal ramification, in contact with the end of a cone fibre; these are the cone bipolars, and their inner process breaks up into its terminal ramification in the inner molecular layer. (2) At the innermost part of this inner nuclear layer is a stratum of cells, which are named amacrine cells (of Cajal), from the fact that they have no axis-cylinder process, but they give a number of short proto- plasmic processes which extend into the inner plexiform layer and there ramify (Fig. 820). There are also at the outermost part of this layer some cells, the processes of which extend into and ramify in the outer molecular layer. These are the horizontal cells (of Cajal). (3) Some few cells are also found in this layer, connected with the fibres of ]Miiller, and will be described with those structures. 6. The outer plexiform layer is much thinner than the inner plexiform layer; but, like it, consists of a dense network of minute fibrils, derived from the processes of the horizontal cells of the preceding layer and the outer processes of the bipolar cells, which ramify in it, forming arborizations around the ends of the rod fibres and with the branched foot plates of the cone fibres. In the neighborhood of the macula lutea, elongations from the inner segments of rod fibres and cone fibres form the so-called Henle's fibre layer. THE RETINA, OR TUNICA INTERNA 1103 7. The outer nuclear or outer granular layer, like the inner nuclear layer, contains several strata of clear oval nuclear bodies; they are of two kinds, and on account of their being respec- tively connected with the rods and cones of Jacob's membrane (rod fibres and cone fibres) are named rod granules and cone granules. The rod granules are much the more numerous, and are jjlaced at different levels throufihout the layer. Their nuclei present a peculiar cross-striped appearance, and prolonged from either extremity of the granule isa fine process; the outer process is continuous with a single rod of Jacob's membrane; the inner passes inward toward the outer -Jio plexiform layer and terminates in an I 4,7 it. enlarged extremity, and is embedded X)2.5jt in the tuft into which the outer pro- cess of the rod bipolars break up. In its course it presents numerous varicosities. The cone granules, fewer in number than the rod gran- ules, are placed close to the mem- brana limitans externa, througl which they are continuous with th: cones of Jacob's membrane. Thej^ do not present any cross-striping, but contain a pyriforra nucleus which almost completely fills the cell. From their inner extremity a thick process passes inward to the outer plexiform layer, upon which it rests by a somewhat pyramidal enlargement, from which are given External segment Intermediary (Use- ElUptoid- Myoid- — ^^ ' ' * Fig. 822. — Cones in the different regions of the retina. 7. Near the era serrata. 11. At 3 mm. from the ora serrata. ///. At an equal distance from the ora serrata and the papilla. IV. At the periphery of the fovea centralis. V. In the fovea centralis. VI. Fig. 821. — The cells of the rods of the At the centre of the fovea centralis. E. Length of the external retina in the frog. A. Red rod. B. Green segment. /. Length of the internal segment. D. Diameter of rod. (Poirier and Charpy.) the internal segment. (Poirier and Charpy.) off numerous fine fibrils, which enter the outer plexiform layer, where they come in contact ■with the outer processes of the cone-bipolars. 8. The membrana limitans externa, like the membrana limitans interna, is derived from the fibres of Miiller, with which structures it will be described. 9. Jacob's membrane, or the layer of rods and cones, consists of visual cells, and the ele- ments which compose it are of two kinds, rod cells and cone cells, the former being much more numerous than the latter. The rod cells (Fig. S21) are of nearly uniform size, and arranged perpendicularly to the surface. A rod cell consists of a rod and a rod fibre, and the fibre con- tains the nucleus. The rods are cylindrical and each consists of two portions, an outer segment and an inner segment, which are of about equal length. The segments differ from each other as regards refraction and in their behavior with coloring reagents, the inner portion becoming stained by carmine, iodine, etc., the outer portion remaining unstained with these reagents, but staining yellowish brown with osmic acid. The outer portion of each rod is marked by trans- 1104 THE ORGANS OF SPECIAL SENSE verse strise, and is made up of a number of thin disks superimposed on one another. It also exhibits faint longitudinal marliings. The inner portion of each rod, at its deeper part where it is joined to the outer process of the rod granule, is indistinctly granular; its more superficial part presents a longitudinal striation, being composed of fine, bright, highly refracting fibres. The visual purple, or rhodopsin, is found only in the outer segments of the rods. At its inner end each rod is prolonged into a very fine fibre, the rod fibre, which contains a nucleus, and which terminates in the outer nuclear layer, being somewhat enlarged at its termination. The cone cells (Fig. 822) are conical, or flask-shaped, their broad ends resting upon the mem- brana limitans externa, the narrow pointed extremity being turned to the choroid. Each cone cell consists of two parts, the cone and the cone fibre. The outer segment or cone is a short conical process, which, like the outer segment of a rod, presents transverse stria". The inner segment (cone fibre) resembles the inner portion of the rods in structure, but differs from it in size, being shorter and bulged out laterally in a flask-shaped manner, and at the junction of the cone with the fibre is the nucleus of the cone cell. The cone fibre passes to the outer nuclear layer, and terminates as an expansion from which very minute fiorils are given off. The chem- ical and optical characters of the rod cells and cone cells are identical. 10. The pigmentary layer or tapetum nignmi, the most external layer of the retina, for- merly regarded as a part of the choroid, consists of a single layer of hexagonal epithelial cells, loaded with pigment granules. Each cell contains a flattened nucleus in the outer portion of the cell which is free from pigment at this point. These cells are smooth externally, where they are in contact with the choroid, but internally they are prolonged into fine, straight processes, which extend between the rods, this being especially the case when the eye is exposed to light. The pigment changes its position under the influence of light, and is distributed through the entire cell. In the eyes of albinos, the cells of the pigmentary layer are present, but they contain no coloring matter. Supporting Framework of the Retina. — Almost all these layers of the retina are con- nected by a supporting framework, formed by the supporting cells or supporting fibres of Miiller or radiating fibres, from which the membrana limitans interna et externa are derived. These fibres are found stretched between the two limiting layers, "like columns between a floor and a roof," and they pass through all the neural layers except Jacob's membrane^ Each com- mences on the inner surface of the retina by a conical hollow base, which sometimes contains a spheroidal body which stains deeply with hematoxylin, the edges of the bases of adjoining fibres being united and thus forming a boundary line, which is the membrana limitans interna. As they pass through the nerve fibre and ganglionic layers they give off few lateral branches; in the inner nuclear layer they give off numerous lateral processes for the support of the inner granules, while in the outer nuclear layer they form a network, the fibre baskets, around the rod and cone fibrils, and unite to form the external limiting membrane at the bases of the rods and cones. In the inner nuclear layer each fibre of Miiller presents a clear oval nucleus, which is sometimes situated at the side of, sometimes altogether within, the fibre. The supporting framework of the retina contains neuroglia cells. The Path of Light Stimuli. — The stimulus is supposed to be first received by the rod and cone cells (the visual cells), and is transmitted to the bipolar cells of the inner nuclear layer and then to the cells of the ganglionic layer, which send fibres by way of the optic nerve and tract to the brain (see p. 909). Macula Lutea and Fovea Centralis.— The structure of the retina at the yellow spot presents some modifications. In the macula lutea (1) the nerve fibres are wanting as a continuous layer; (2) the ganglionic layer consists of several strata of cells, instead of a single layer; (.3) in Jacob's membrane there are no rods, but only cones, and these are longer and narrower than in other parts; and (-1) in the outer nuclear layer there are only cone fibres, which are very long and arranged in curved lines. At the fovea centralis the only parts which exist are the cones of Jacob's membrane, the outer nuclear layer, the cone fibres of which are almost horizontal in direction, and an exceedingly thin inner granular layer, the pigmentary layer, which is thicker and its pigment more pronounced than elsewhere. The color of the macula seems to imbue all the layers except .Facob's membrane; it is of a rich yellow, deepest toward the centre, and does not appear to consist of pigment cells, but simply a staining of the constituent parts. At the ora serrata (Fig. 810) the nerve layers of the retina terminate abruptly, and the retina is continued onward as a single layer of elongated columnar cells covered by the pigmentary layer. This prolongation is known as the pars ciliaris retinae (Fig. 814), and can be traced for- ward from the ciliary processes on to the back of the iris, where it is termed the pars iridica retinae or uvea. From the description given of the nerve elements of the retina it will be seen that there is no direct continuity between the structures which form its different layers except between the ganglionic and nerve fibre layers the majority of the nerve fibres being formed of the axones of the ganglionic cells. In the inner molecular layer the dendrites of the ganglionic layer inter- lace with those of the cells of the inner nuclear layer, while in the outer molecular layer a THE VITREOUS BODY 1105 likf synapsis occurs between the processes of the inner granules and the rofl and cone elements. The arteria centralis retinae (Fig. SIO) and its accompanying vein, vena centralis retinae, pierce the optic nerve, and enter the globe of the eye through the porus opticus. They bifurcate on the surface of the papilla or just beneath it into an upper and a lower branch, and each of these again divides into an inner or nasal, and an outer or temporal branch; these at first run between the hyaloid membrane and the nerve layer; but they soon enter the latter, and pass forward, dividing dichotomously. From these branches a minute capillary plexus is given off, which does not extend beyond the inner nuclear layer. The macula receives small twigs from the temporal branches and others directly from the central artery; these do not, however, reach as far as the fovea centralis, which has no bloodvessels. The branches of the arteria centralis retinae do not anastomose with each other — in other words, they are "terminal arteries." In the fetus, a small vessel passes forward, through the hyaloid canal in the vitreous body, to the posterior surface of the capsule of the lens (Fig. 805). THE REFRACTING MEDIA. The Refracting media are three — viz.: Aqueous humor. Vitreous body. Crystalline lens, I. The Aqueous Humor (Humor Aqueus). The aqueous humor completely fills the lymph space known as the aqueous chamber, the space which is bounded in front by the cornea and behind by the lens and its suspensory ligament and the ciliary body (Fig. 829). The aqueous chamber is partly divided by the iris into two communicating parts, the anterior and posterior chambers (Figs. 805 and 829). The posterior chamber (camera oculi posterior') is only a narrow chink between the peripheral part of the iris, the suspensory ligament of the lens, and the ciliary processes. The anterior chamber (camera oculi anterior) is bounded in front by the cornea and behind by the iris. The external angle of the anterior chamber is bounded by the periphery of the cornea and of the iris. It is called the angle . , ,, „,, .. ,/ 7 •■7-\ Ti'l which the lens lies. Seen obliquely from or the filtration angle (a?i(/?/ms (r;rf;.s). It is by way the side and before. (Toidt.) of the filtration angle that any excess of aqueous humor passes by way of the spaces of Fontana and the canal of Schlemm (Fig. 814) to the anterior ciliary veins and relieves tension. The aqueous humor is small in quantity, has an alkaline reaction, in composition is litde more than water, less than 2 per cent, of its weight being solid matter, chiefly sodium chloride. Fig. 823. — The vitreous body removed from the eye in the fresh state, with the shaped hollow ( fossa hyaloidea) II. The Vitreous Body (Corpus Vitreum) (Figs. 805, 825). The vitreous body occupies about four-fifths of the entire globe. It is composed of a jelly-like tissue containing 98 per cent, water, some salts, and a litde albumin, and called the vitreous humor (humor vitreus), connective-tissue fibres, and con- nective-tissue cells. It fills the concavity of the retina, and is hollowed in front, forming a deep concavity, fossa hyaloidea (Fig. 82.3), for the reception of the lens. It is perfectly transparent, of the consistence of thin jelly, and is composed of an albuminous fluid enclosed in a deliciite transparent membrane, the hyaloid mem- brane (membrana hyaloidea), the outside of which is in contact with the membrana limitans interna of the retina. In the fetus a peculiar fibrous texture pervades the mass, the fibres joining at the numerous points, and presenting minute nuclear 1106 THE ORGANS OF SPECIAL SENSE granules at their point of junction. In the centre of the vitreous humor, running from the entrance of the optic nerve to the posterior surface of the lens, is a canal, filled with fluid and lined by a prolongation of the hyaloid membrane. This is the hyaloid canal (canalis hyaloideus) (Fig. 805), which in the embryonic vitreous humor conveyed the minute vessel from the central artery of the retina to the back of the lens. The hyaloid membrane encloses the whole of the vitreous humor. In front of the ora serrata it is thickened by the accession of radial fibres and is termed the zonule of Zinn (zonula ciliaris) (Figs. 824 and 829). Here it presents a series of radially arranged furrows, in which the ciliary processes are accommodated and to which they are adherent, as evidenced by the fact that when removed some of their pigment remains attached to the zonule.^ The zonule of Zinn splits into two CHORIOIDEA Fig. 824.— The zonule of Zi] • suspenboiv lig iment of the len=i Mew he lens and the cihary bod\ (Toldt ed from behind in connection with layers, one of which is thin and lines the fossa hyaloidea; the other is named the suspensory ligament of the lens; it is thicker, and passes over the ciliary body to be attached to the capsule of the lens a short distance in front of its equator. Scattered and delicate fibres are also attached to the region of the equator itself. This ligament retains the lens in position, and is relaxed by the contraction of the radial fibres of the Ciliary muscle, so that the lens is allowed to become more convex. Behind the suspensory ligament there is a sacculated canal, the canal of Petit (spatia zonularia), which encircles the margin of the lens and which can be easily inflated through a fine blowpipe inserted through the suspensoiy ligament. It is bounded in front by the anterior layer of the suspensory ligament of the lens, behind by the membrana hyaloidea, and internally by the capsule of the lens. The canal of Petit is a lymph space. All of the spaces of the canal of Petit com- municate with the posterior chamber of the eye. No vessels penetrate the vitreous body, although a lymph channel remains; so that its nutrition must be carried on by the vessels of the retina and ciliary processes, situated upon its exterior. III. The Crystalline Lens (Lens Crystallina) (Figs. 825, 826). The crystalline lens, enclosed in its capsule, is situated immediately behind the pupil, in front of the vitreous body, and is encircled by the ciliary processes, which slightly overlap its margin. ' F. A. Woll: A Simple Technique for the Removal of the Hyaloid Me Intact. Anat. Rec, vol. 6, No. 9, September, 1912. "ith Contents and Attachments THE CRYSTALLINE LENS 1107 The capsule of the lens {capsuhi kntis) (Fig. 785) is a transparent, liiglily elastic, and brittle niemljranc, which closely surrounds the lens, and is composed in part of cuticular and in part of connective tissues. It is not white fibrous tissue, anfi is not true elastic tissue (Szymonowicz). Its outer surface is composed of lamella' and possesses transverse striations. It rests, hehind, in the fossa hyaloidea in the fore part of the vitreous body (Fig. 823) ; in front, it is in contact with the free border of the iris, this latter receding from it at the circumference, thus forming the posterior chamber of the eye (Fig. 829); and it is retained in its position chiefly by the suspensory ligament of the lens, already described (Fig. 829). The capsule is much thicker in front than behind, and when ruptured the edges roll up with the outer surface innermo.st, like the elastic lamina of the cornea. Fig. 825. — The crystalline lens, hardened and divided. (Enlarged.) Fig. 82G. — The terms used in the orientation of the lens. (Toldt.) The lens is a transparent, biconvex body, the convexity of the posterior surface being greater than that of the anterior, "^rhe central points of these surfaces are termed respectively the anterior and posterior poles (pohis anterior et polus posterior lentis). A line connecting the poles constitutes the axis of the lens (axis leniis), while the marginal circumference is termed the equator (aequator lentis). The lens measures from 9 to 10 mm. in the transverse and vertical diameters and about 4 mm. from anterior to posterior pole. Figs. 827 and 828 -Diagram to show the direction and arrangement of the radiating lines on the front and back of the fetal lens. Fig. 827. From the front. Fig. 828. From the back. Structure. — The lens consists of an outer, soft part, easily detached (siibstanfia cortical is) , and a central, firm part (nucleus leniis) (Fig. 82.5). Faint lines (radii lentis) radiate from the poles to the equator. In the adult there may be six or more of these lines, but in the fetus they are only three in number and diverge from each other at angles of 120 degrees (Figs. 827 and 828). On the anterior surface one line ascends vertically and the other two diverge downward and outward. On the posterior surface one ray descends vertically and the other two diverge upward. They correspond with the free edges of an equal number of septa composed of an amorphous sub- stance, which dip into the substance of the lens. When the lens has been hardened (as in alcohol), it is seen to consist of concentric layers, or laminae, each of which is interrupted at the septa. Each lamina is built up of a number of parallel, hexagonal lens fibres {fihrae lentis), the edges of which are serrated to fit similar serrations of adjacent lens fibres, while the ends of the fibres 1108 THE ORGANS OF SPECIAL SENSE come into apposition with the septa. The fibres run in a curved manner from the septa on the anterior surface to those on the posterior surface. No fibres pass from pole to pole, but ihey are arranged in such a way that filj«-es which commence near the pole on the one aspect of the lens terminate near the peripheral extremity of the plane on the other, and vice versa. Each ■ fibre of the outer layers of the lens contains a nucleus, and these nuclei form a layer, the nuclear layer, on the surface of the lens. The nuclear layer is most distinct toward the circumference of the lens. The anterior surface of the lens is covered by a single layer of transparent, columnar, nucleated epithelial cells {epithelium lentis). At the equator these cells become elongated and their gradual transition into lens fibres can be traced. rrjsE TENDON OF S RECTOS POSTERIOR Fig. 829. — The upper half of a sagittal section through the front of the eyeball. fToldt.J The changes produced in the lens by age are the following : In the fetus its form is nearly spherical, its color of a slightly reddish tint, it is not perfectly transparent, and is so soft as to disintegrate readily on the slightest pressure. A small branch from the arteria centralis retinae runs forward, as already mentioned, tlirough the vitreous humor to the posterior part of the capsule of the lens, where its branches radiate and form a. plexiform network, wliich covers its surface, and they are continuous around the margin of the capsule with the vessels of the pupillary membrane and "ndtli those of the iris. In the adult the posterior surface is more convex than the anterior; it is colorless, transparent, firm in texture, and devoid of bloodvessels. In old age it becomes flattened on both surfaces, slightly opaque, of an amber tint, and in- creases in density. Vessels and Nerves of the Globe of the Eye. — The arteries of the globe of the eye are the short posterior ciliary, long posterior ciliary, and anterior ciliary arteries, and the arteria centralis retinae. They have been already described (p. 613). THE CRYSTALLINE LENS 1109 The ciliary veins are seen on the outer surface of the choroid, and are named from tlieir arrangement, the venae vorticosae (p. 1094). They converge to four or five equidistant trunlcs, which pierce the sclera midway between the margin of the cornea and the porus opticus. An- otlier set of veins accompanies the aiilerior ciliary arteries and opens into the ophthalmic vein. The Lymphatic Passages of the Eyeball.— The conjunctiva contains lymph vessels. The eyeball contains lymph spaces, i)ut no lymph vessels. There are two sets of lymph spaces in the eyeball, the anterior and posterior. The anterior l5miph spaces are the spaces of the cornea, of the iris, of the anterior chamber, and of the posterior chamber. The lymph from the intralamellar lymph spaces of the cornea enters the conjunctival lymphatics at the margin of the cornea. The lymph spaces of the iris open into the anterior chamber by the crypts of the iris, and at the margin of the iris join the spaces of Fontana. The aqueous humor fills the anterior and posterior chambers, but is furnished by the vessels in the posterior chamber; in part by the vessels of the ciliary body, and in part by the vessels of the posterior surface of the iris. The lymph passes by way of the ))upil into the anterior chamber, and then is taken up by the spaces of Fontana, the canal of Schlemm, and the anterior ciliary veins. The posterior Ijraiph spaces are the hyaloid canal, the perichoroidal lymph space, the space of Tenon, the intervaginal space of the optic nerve, and the supravaginal space. The hyaloid canal (Figs. S02 and 805). passes between the posterior surface of the lens and the optic disk. The hyaloid canal opens into the intervaginal space of the optic nerve. Between the sclera and the choroid is the perichoroidal lymph space (Fig. 829). It is around the choroid vessels and the venae vorticosae, and empties into I'enon's space by means of openings through the sclera about the venae vorticosae. Tenon's space (Figs. 802 and 803) is between the sclera and the capsule of Tenon. It receives lymph from the perichoroidal space, and empties into the supravaginal space. The optic nerve (Fig. S19) has a sheath of dura and a sheath of pia, and between these sheaths is the intervaginal lymph space. It is divided by a prolongation of the cerebral arachnoid into a subdural space and a subarachnoid space, which empty into the corresponding spaces of the membranes of the lirain. The supravaginal space is lictHcen the dural portion of the sheath of the optic nerve and a posterior jirolongation of Tenon's capsule.' The Nerves of the Globe of the Eye. — The long cihary nerves (tm. ciliares longi), two in number, are derived from the nasal branch of the ophthalmic, and the short ciliary nerves {nn. ciliares breves), twelve to fifteen in number, are derived from the ciliary or ophthalmic gan- glion. Both the long and short ciliary nerves perforate the sclera in the neighborhood of the optic nerve (Fig. 809). They pass along the perichoroidal lymph space, forming a plexus which sends filaments to the choroidal vessels. In front of the Ciliary muscle they form a second plexus, and from it come branches which go to the Ciliary muscle and the muscle fibres and vessels of the iris, sclera, choroid, ciliary body, and iris (Fig. 816). The ciliary nerves supply the cornea. The circular fibres of the iris are innervated by the oculomotor nerve and the radial fibres by the sympathetic. Applied Anatomy. — From a surgical point of view the cornea may be regarded as consist- ing of three layers: (1) Of an external epithelial laj'er, developed from the ectoderm, and con- tinuous with the external epithelial covering of the rest of the body, and therefore its lesions resemble those of the epidermis; (2) of the cornea proper, derived from the mesoderm, and associated in its diseases with the fibrovascular structures of the body; and (.3) the posterior elastic layer with its endothelium, also derived from the mesoderm and having the characters of a serous membrane, so that inflammation of it resembles inflammation of the other serous and synovial membranes of the body. The corn-ea contains no bloodvessels, except at its periphery, where numerous delicate loops, derived from the anterior ciliary arteries, may be demonstrated on the anterior surface of the cornea. The rest of the cornea is nourished by lymph, which gains access to the proper sub- stance of the cornea and the posterior layer through the spaces of Fontana (spatia anguli iridis). This lack of direct blood supply renders the cornea very apt to become inflamed in the cachectic and ill-nourished. In spite of the absence of bloodvessels, wounds of the cornea usually heal rapidly. A wound which penetrates the cornea opens the anterior chamber, and aqueous humor escapes. An ulcer may also open the anterior chamber. Through a wound or a perforated ulcer the papillary margin of tlie iris may prolapse. A trivial injury of the cornea is repaired by -transparent tissue. A severe injury is repaired by fibrous tissue, and opaciti/ results. A slight opacity resembling a cloud of gray smoke is called nebula; a more marked white opacity is called leuc.oma. In abscess of the cornea pus gravitates between the layers to the lower part of the cornea and the purulent collection assumes a crescentic shape (om/x). The arciis senilis, seen in the aged, is a condition of haziness or opacity at the corneal margin due to fatty degeneration of the tissues of the cornea. It signifies interference with the blood supply, because of senile degeneration of adjacent vessels. In cases of trachoma there is a peculiar affection of the cornea, called pannus, in which the anterior layers of the cornea become vascularized, and a rich network ■ For the lymphatic channels of the eyeball see Deaver's Surgical .\natomy, vol. ii, p. 392. 1110 THE ORGANS OF SPECIAL SENSE of bloodvessels may be seen on the cornea; and in interstitial keratitis new vessels extend into the cornea, giving it a pinkish hue, to which the term salmon patch is applied. The cornea is richly iupplied with nerves, derived from the ciliary nerves, which enter the cornea through the fore part of the sclera and form plexuses in the stroma, terminating between the epithelial cells by free ends or in corpuscles. In cases of glaucoma the ciliary nerves may be pressed upon as they course between the choroid and sclera (Fig. 808), and in consequence of the pressure upon them, the cornea, to which they are distributed, becomes anesthetic. When a scar forms on the cornea and the iris becomes adlierent, the scar and the iris, and sometimes even the lens, may bulge forward from intraocular tension. This condition is staphyloma of the cornea. In con- ditions of impaired nutrition the cornea may be bulged forward by intraocular pressure. The line of least resistance is a little below the centre of the cornea, and it is bulged forward and strongly curved. This condition is known as conical cornea. The sclera has very few bloodvessels and nerves. The bloodvessels are derived from the anterior ciliary, and form an open plexus in its substance. As they approach the corneal margin this arrangement is peculiar. Some branches pass through the sclera to the ciliary body; others become superficial and lie in the episcleral tissue, and form arches, by anastomosing with each other, some little distance behind the corneal margin. From these arches nimaerous straight vessels are given off, which run forward to the cornea, forming its marginal plexus. In inflamma- tion of the sclera and episcleral twsue these vessels become conspicuous, and form a pinkish zone of straight vessels radiating from the corneal margin, commonly known as the zone of ciliary injection. In inflammation of the iris and ciliary body, this zone is present, since the sclera speedily becomes involved when these structures are inflamed. But in inflammation of the cornea the sclera is seldom much affected, though the cornea and sclera are structurally continuous. This would appear to be due to the fact that the nutrition of the cornea is derived from a different source from that of the sclera. The sclera may be ruptured subcutaneously without any lacer- ation of the conjunctiva, and the rupture usually occurs near the corneal margin, where the tunic is thinnest. It may be complicated with lesions of adjacent parts — laceration of the choroid, retina, iris, or suspensory ligament of the lens — and is then often attended with hemor- rhage into the anterior chamber, which masks the nature of the injury. In some cases the lens has escaped through the rent in the sclera, and has been found under the conjunctiva. Wounds of the sclera, if they do not perforate, usually heal readily. If they extend through the sclera they cause diminished tension, are always dangerous, and are often followed by inflammation, suppuration, and by sympathetic ophthalmia. The sclera may be weakened by injury, inflam- mation, etc., and the weakened portion may bulge from intraocular pressure, and even a healthy sclera may bulge from excessive intraocular pressure. According to its situation the lesion is known as ciliary staphyloma, equatorial staphyloma, or posterior staphyloma. One of the functions of the choroid is to provide nutrition for the retina. and to convey ves- sels and nerves to the ciliary body and iris. Inflammation of the choroid is therefore followed by grave disturbance in the nutrition of the retina, and is attended with early interference with vision. Purulent choroiditis is not confined to the choroid; the retina, the vitreous, and the entire uveal tract become involved, and even other structures may suiTer. In its diseases it bears a con- siderable analogy to those which aff'ect the skin, and, like it, is one of the places from which melanotic sarcomata may grow. These tumors contain a large amount of pigment in their cells, and grow only from those parts where pigment is naturally present. The choroid may be rup- tured without injury to the other tunics, as well as participating in general injuries of the eyeball. In cases of uncomplicated rupture the injury is usually at its posterior part, and is the result of a blow on the front of the eye. It is attended by considerable hemorrhage, which for a time may obscure vision, but in most cases this is restored as soon as the blood is absorbed. The iris is the seat of a malformation, termed coloboma, which consists in a deficiency or cleft, which in a great number of cases is clearly due to an arrest in development. In these cases it is found at the lower aspect, extending directly downward from the pupil, and the gap frequently extends through the choroid to the attachment of the optic nerve. In some rarer eases the gap is round in other parts of the iris, and is then not associated with any deficiency of the choroid. The iris is abundantly supplied with bloodvessels and nerves, and is therefore very prone to become inflamed. When inflamed, in consequence of the fact that the iris and ciliary body are continuous, and that their vessels communicate, iritis is usually associated with cyclitis, the dis- ease being called iridocyclitis. And, in addition, inflammation of adjacent structures, the cornea and sclera, is apt to spread into the iris. The iris is covered with endothelium, and partakes of the character of a serous membrane, and, like these structures, is liable to pour out a plastic exuda- tion when inflamed, and contract adhesions, either to the cornea in front (synechia anterior), or to the capsule of the lens behind (synechia posterior). In iritis the lens may become involved, and the condition known as secondary cataract may be set up. Tumors occasionally commence in the iris; of these, cysts, which are usually congenital and sarcomatous tumors, are the most common and require removal. Gummata are not infrequently found in this situation. In some forms of injury of the eyeball, as the impact of a spent shot, a flying cork, the rebound of a twig, or a blow with a whip, the iris may be detached from the Ciliary muscle, the amount of detach- THE CRYSTALLINE LENS 1111 ment varying from the slightest degree to the separation of the whole iris from its ciliary con- nection. The Argyll-Robertson pupil shows no reaction to light, but retains reaction to accommodation and vision remains good. The retina, with the exception of its pigment layer, and its vessels is perfectly transparent, and is invisible when examined by the ophthalmoscope, so that its diseased conditions are rec- ognized by its loss of transparency. In rctiniii.'i, for instance, there is more or less dense and extensive opacity of its structure, and not infrequently extravasations of blood info its sub- stance. Hemorrhages may also take place into the retina from rupture of a bloodvessel without inflammation. In optic neuritis, papillitis, or choked .disk, the ophthalmoscope shows increase in vascularity, and swelling and opacity of the nerve, which extend beyond the disk margins. Optic atrophy is apt to follow. (Fig. S.30 shows a normal optic disk.) The retina may become displaced from effusion of serum between it and the choroid or by blows on the eyeball, or may occur without apparent cause in progressive mijopia, and in this case the ophthalmoscope shows an opac|ue, tremulous cloud. Glioma, a form of sarcoma, and essentially a disease of early life, is occasionally met with in connection with the retina. The lens has no bloodvessels, nerves, or connective tissue in its structure, and therefore is not subject to those morbid changes to which tissues containing these structures are liable. It does, however, present certain morbid or abnormal conditions of various kinds. Thus, variations in shape, absence of the whole or a part of the lens, and displacements are among its congenital defects. Opacities may occur from injury, senile changes, malnutrition, or errors in growth or development. An opacity of the capsule, of the lens, or of both, is known as a cataract. Senile changes may take place in the lens, impairing its elasticity and rendering it harder than in youth, Fig. S30. — Ophthalmoscopic appearance of healthy fundus in a person of very fair complexion. Scleral ring well marked. Left eye, inverted image. (Wecker and Jaeger.) Fig. 831. — Ophthalmoscopic appearance of severe recent papillitis. Several elongated patches of blood near border of disk. (After Hughlings Jackson.) SO that its curvature can only be altered to a limited extent by the Ciliary muscle. And, finally, the lens may be dislocated or displaced by blows upon the eyeball, and its relations to surround- ing structures altered by adhesions or the pressure of newgrowths. There are two particular regions of the eye which require special notice; one of these is known as the " filtration area," and the other as the " dangerous area." The filtration area is the circum- corneal zone immediately in front of the iris. Here are situated the cavernous spaces of Fon- tana, which communicate with the canal of Schlemm, through which the chief transudation of fluid from the eye is now believed to take place. The dangerous area of the eye is the region in the neighborhood of the ciliary body, and wounds or injuries in this situation are peculiarly ■dangerous; for inflammation of the ciliary body is liable to spread to many of the other structures of the eye, especially to the iris and choroid, which are intimately connected by nerve and vas- cular supplies. Moreover, wounds which involve the ciliary region are especially liable to be followed by sympathetic ophthalmia, in which destructive inflammation of one eye is excited by some irritation in the other. Emmctropia is normal vision. In normal vision the practically parallel light rays from distant olijects focus on the retina without effort; divergent rays from near objects are focussed on th« retina by an effort of accommodation. Hyperopia or hypermctropia is far-sightedness. In this condition the retina is in front of th^ principal focus when the eye is at rest. The patient endeavors to correct the failure by constant 1112 THE ORGANS OF SPECIAL SENSE and tiresome efforts at accommodation. The condition is usually due to inordinate shortness of the axis of the eye, but may be due to loss of the lens, decreased convexity of the refractive sur- faces, or lessened refractive power in the refractive media of the eye. It is corrected by the use of convex glasses. Myopia is near-sightedness. In this condition the rays of light come to a focus in front of the retina, and the patient is subjected to continued eye-strain. It is usually due to too great length of the axis of the eye, but may result from increase in refractive power of refractive media. It is. corrected by concave glasses. Sometimes, as a person with hyperopia begins to age, an increased refractive power of the lens causes myopia. The occurrence of myopia in a hyperopic eye is called second sirjM, and it enables the individual to cease wearing convex glasses. Exenteration of the contents of the orbit means removal of all the contents except those at the orbital apex. Even the periosteum is taken away. It is performed for malignant disease. Evisceration of the eyeball is performed by making a circular incision at the corneal margin and removing the internal and middle coats and the contents of the globe. The sclera is not removed. A glass ball is inserted into the scleral sheath, and the sclera is closed over the ball by vertical stitches, and the conjunctiva is closed over it by transverse stitches. The operation is performed for leucoma or staphyloma of the cornea. An artificial eye (a shell) is placed over the stump- when healing is complete. Enucleation, or excision of the eyeball, differs from exenteration of the orbital contents in the- fact that only the eyeball is removed. A circular incision through the ocular conjunctiva is carried around and near to the corneal margin. The conjunctiva and capsule of Tenon are- pushed back and the Rectus muscles are clamped and divided back of the clamp. Traction is made upon the globe in a forward and inward direction, and the optic nerve and adjacent structures are cut with scissors from the outer aspect of the globe. The eye is then pulled out of the orbit, and all structures which tend to retain it are divided. The stumps of the Recti muscles are sewed tosiether. THE APPENDAGES OF THE EYE (ORGANA OCULI ACCESSORIA). The appendages of the eye include the eyebrows, the eyelids, the conjunctiva, and the lacrimal apparatus — viz., the lacrimal gland, the lacrimal sac, and the nasal duct. The Eyebrows (supercilia) are two arched eminences of integument wliich sur- mount the upper circumference of the orbit on each side, and support numerous short, thick hairs, directed obhquely on the surface. The hairs may entangle foreign bodies and lessen somewhat the force of blows. In structure the eyebrows consist of thickened integument, connected beneath with the Orbicularis palpe- brarum, Corrugator supercilii, and Occipitofrontalis muscles. These muscles serve, by their action on this part, to control to a certain extent the amount of light admitted into the eye. The Eyelids (palpebrae) (Figs. 832 and 833) are two thin, movable folds placed in front of the eye, and protecting it from injury by their closure. The eyelids are composed of skin, superficial fascia, and areolar tissue, fibres of the Orbicu- laris palpebrarum muscle, palpebral and orbitotarsal ligaments, tarsal plates, and conjunctiva. The upper lid also contains the Levator palpebrae superioris muscle. In the lids are bloodvessels, lymph vessels, nerves, and ^Meibomian glands. There are two lids, the upper (palpebra superior) and the lower {palpehra inferior); the groundwork of both lids is made up of a fascial membrane called the orbital septum {septwn orbitale). The upper lid is the larger and the more movable of the two, and is furnished with a separate elevator muscle, the Levator palpebrae superioris. The orbital septum, in each lid, consists of two portions. The part near the orbital margin is called the orbital portion. The part in which the tarsus lies is called the tarsal portion. Between the two portions in each lid ^% a sulcus, called, in the upper lid, the superior orbitopalpebral sulcus, and in the rower lid, the inferior orbitopalpebral sulcus. When the eyelids are opened an elliDtical space, the interpalpebral slit {rima palpebrarum), is left between their THE APPENDAGES OF THE EYE 1113 margins, the angles of which eorrespond to tlie junction of the upper and lower lids, and are called canthi. The outer canthus (commissura palpebrarum laterallii) is more acute than the inner, and the lids here lie in close contact with the globe; but the inner canthus (commissura palpebrarum medialis) is prolonged for a short distance inward toward the nose, and the two lids are separated at the inner canthus by a triangular space, the lacus lacrimalis. At the commencement of the lacus lacrimalis, on the margin of each eyelid, is a small conical elevation, the lacrimal papilla, the apex of which is pierced by a small orifice, the punctum lacrimale ( Fig. 8o7), the commence- ment of the lacrimal canal (Fig. 835). AVhen the lids are closed a space remains between them and the globe to permit of the flow of tears inward (rivus lacri- malis). The Eyelashes (cilia) (Fig. 833) are attached to the free edges of the eyelids; they are short, thick, curved hairs, arranged in a double or triple row at the margin of the lids; those of the upper lid, more numerous and longer than the lower, curve upward; those of the lower lid curve downward. Because of this arrange- ment the two sets do not interlace in closing the lids. Near the attachment of the eyelashes are the openings of sebaceous glands (glandulae sebaceae) (Fig. 833) and of a number of glands, glands of Moll (glandulae ciliares [Molli]) (Fig. 833), arranged in several rows close to the free margin of the lid. They are regarded as enlarged and modified sweat glands. Fig. 832.— T1 (Testut.) Structure of the Eyelids (Fig. 791). — The eyelids are composed of the following structures, taken in their order from without inward : Integument, areolar tissue, fibres of the Orbicularis muscle, tarsal plate, and its ligament, Meibomian glands, and conjunctiva. The upper lid has, in addition, the aponeurosis of the Levator palpebrae, while both lids contain a certain amount of non-striated muscle, called, res])('ctlvcly, the Superior and Inferior tarsal muscles (see p. 369) (Fig. 802). The integument is cxtrcinrly thin, and coiitinuoii-; at flu- inaruiu of the hds with the conjunctiva. The subcutaneous areolar tissue is very lax and delicate, selilom contains any fat, and is extremely liable to serous infiltration. The Palpebral fibres of the Orbicularis oculi muscle (m. ciliaris [Riolani]) are thin, pale in color, and possess an involuntary action. The tarsal plates (Fig. 832) are two thin, elongated, wedge-shaped plates of dense connective tissue about 2.5 cm. (1 inch) in length. They are placed one in each lid, beneath the conjunc- tival siu-face, contributing to their form and support. The superior tarsal plate, superior tarsus, or superior tarsal body (famus siipcrioi) (Fig. 832), the larger, is of a semilunar form, about 8 mm. (J inch) in breadth at the centre, and becoming gradually narrowed at each extremity. To the anterior siu-face of this jjlate the aponeurosis of the Levator palpebrae is attached. The inferior tarsal plate, inferior tarsus, or inferior tarsal body (fare».y inferior} 1114 THE ORGANS OF SPECIAL SENSE (Fig. 832), the smaller of the two, is thinner and of an elliptical form. The free or ciliary margin of these plates is thick, and presents a perfectly straight edge. The attached or orbital margin is connected to the circumference of the orbit by the fibrous membrane of the lids, with which it is continuous. The outer angle of each plate is attached to the malar bone bj' the ex- ternal tarsal ligament {raphe palpebralis lateralis) (Fig. 832). The inner angles of the two plates terminate at the commencement of the lacus lacrimalis; they are attached to the nasal process of the superior maxilla by the internal tarsal ligament or the tendo oculi {ligamentiim palpebrale mediale) (Fig. 832) . In reality these so-called ligaments are fascial expansions situated one in each lid, and are attached marginally to the edge of the orbit, where they are continuous \Aith the periosteum. The superior ligament blends with the tendon of the Levator palpe- brae, the inferior with the inferior tarsal plate. Externally, the superior and infei'ior ligaments fuse to form the external tarsal ligament just referred to; internally they are much thinner, and, becoming separated from the internal tarsal ligament, are fixed to the lacrimal bone imme- diately behind the lacrimal sac. The whole fascial sheet spanning the orbit, and reenforced by these ligaments, constitutes the orbital sep- tum {septum orbitale), which is perforated by the vessels and nerves which pass from the orbital cavity to the face and scalp. The Meibomian or Tarsal Glands {glandulae tarsales [Meihomi^) (Figs. 833 and 835) are situated in the tarsal plates, and may be distinctly seen through the conjunctiva on everting the eyelids, pre- senting the appearance of parallel strings of pearls. They are about thirty in number in the upper eyelid, and some- what fewer in the lower. They corre- spond in length with the breadth of each plate, and are, consequently, longer in the upper than iit the lower eyelid. Their ducts open on the free margin of the lids by minute foramina, which correspond in number to the follicles. The use of their secretion is to prevent adhesions of the lids. Structure. — These glands are a variety of the cutaneous sebaceous glands, each consisting of a single straight tube or duct, having a cecal termination, and with numerous small alveoli opening into it. The tubes consist of basement membrane, lined at the mouths of the tubes by stratified epithelium; the deeper parts of the tubes and the alveoli are filled with polyhedral cells. They are thus identical in structure with the sebaceous glands. Fig. 833.- — Vertical section through the upper eye- lid, a. Skin. h. Orbicularis palpebrarum, h' . Mar- ginal fasciculus of Orbicularis (ciliary bundle), c. Levator palpebrae. rf. Conjunctiva, e. Tarsal plate, f. Meibomian gland, ff. Sebaceous gland, h. Eye- lashes, i. Small hairs of skin. j. Sweat-glands, h. Ac- ' lacrimal glands. (After Waldeyer.) The Conjunctiva (Figs. 834 and 835) is the mucous membrane of the eye. It lines the inner surface of the eyelids, is reflected over the fore part of the sclera and cornea, and joins the lids to the eyeball. In each of these situations its struc- ture presents some peculiarities. The palpebral portion (tunica coiijuucfiva palpebrarum) (Fig. 835) of the con- junctiva lines the posterior surface of the lids. It is thick, opaque, highly vascular, and covered with numerous papillre, its deeper parts presenting a considerable amount of lymphoid tissue. At the margins of the lids it becomes continuous THE APPENDAGES OF THE EYE 1115 with the lining memhrane of the ducts of the Meibomian glands, and, through the lacrimal canals, with the lining membrane of the lacrimal sac and nasal duct. At the outer angle of the upper lid the lacrimal ducts open on its free siu-face; and at the inner angle of the eye it forms a semilunar fold, the plica semilunaris {■plica semilunaris conjunctivae) (Fig. 837). The folds formed by tlie reflection of the conjunctiva from the lids on to the eye are called the superior and inferior palpebral folds, the former being the deeper of the two. These folds form the superior and inferior conjunctival fornix (Fig. 834). The Bulbar Portion {tunica conjunctiva bulbi). — ^Llpon the sclera the conjunc- tiva is loosely connected to the globe; it becomes thinner, loses its papillary struc- ture, is transparent, and only slighdy vascular in health. Upon the cornea the con- junctiva consists only of epithelium, constituting the anterior layer of the cornea (conjunctival epithelium) already described (p. 1091). Lymphatics arise in the conjunctiva in a delicate zone around the cornea, from which the vessels run to the ocular conjunctiva. Fornices of Conjunctiva. — At the line of reflection of each fold of the conjunctiva from each lid on to the globe of the eye a pocket or arch is formed. These arches are termed the fornices conjunctivae, superior and inferior ' "^^^^ ^inferior fohnjx (rig. bo4). j-jQ 834.— Sagittal section Glands of Conjunctiva. — In the conjunctiva there are ?f/y?' showing superior and , '' •' ^ '-w T • ^ inferior fornices of the con- a number ot mucous glands {gl. mucosae [Krausei\) which junctiva. (Xestut.) are much convoluted. They are chiefly found in the up- per lid. Other glands, analogous to lymphoid follicles, and called by Henle trachoma glands, are found in the conjunctiva, and, according to Stromeyer, are chiefl>' situated near the inner canthus of the eye. The caruncula lacrimalis is a small, reddish, conical-shaped body, situated at the inner cantlius of the eye, and filling up the small triangular space in this situ- ation, the lacus lacrimalis. It consists of an island of skin containing sebaceous and sweat glands, and is the source of the whitish secretion which constantly collects at the inner angle of the eye. A few slender hairs are attached to its surface. On the outer side of the caruncula is a slight semilunar fold of conjunc- tiva, the concavity of which is directed toward the cornea; it is called the plica semilunaris (Fig. 837). Miiller found smooth muscle fibres in this fold, and in some of the domesticated animals a thin plate of dense white fibrous tissue has been discovered. This structure is considered to be the rudiment of the third eyelid in birds, the membrana nictitans. The nerves in the conjunctiva are numerous and form rich plexuses. Accord- ing to Krause they terminate in a peculiar form of tactile corpuscle, the "terminal bulb." The Lacrimal Apparatus {apparatus lacrimalis) (Figs. 835 and 837) consists of the lacrimal gland, which secretes the tears, and its excretory ducts, which con- A-ey the fluid to the surface of the eye. This fluid is carried away by the lacrimal canals into the lacrimal sac, and along the nasal duct into the cavity of the nose. The Lacrimal Gland {glandula lacrimalis) is lodged in a depression at the upper and outer angle of the orbit, on the inner side of the external angular process of the frontal bone. It is of an oval form, about the size and shape of an almond. Its upper convex surface is in contact with the periosteum of the orbit, to which it is connected by a few fibrous bands. Its under concave surface rests upon the convex- ity of the eyeball and upon the Superior and External recti muscles. Its vessels and nerves enter its posterior border, while its anterior margin is closely adherent 1116 THE ORGANS OF SPECIAL SENSE to the back part of the upper eyelid, where it is covered to a slight extent hy the reflection of the conjunctiva. The fore part of the gland is separated from the rest by a fibrous septum; hence it is sometimes described as a separate lobe, called the inferior lacrimal gland (glandula lacrimalis inferior), the back part of the gland then being called the superior lacrimal gland {glandula lacrimalis superior)^ The ducts of the lacrimal gland, from six to twelve in number, run obliquely beneath the mucous membrane for a short distance, and, separating from each other, open by a series of minute orifices on the upper and outer half of the con- junctiva near its reflection on to the globe. These orifices are arranged in a row, so as to disperse the secretion over the surface of the membrane. Fig. 835. — The Meibomian surface of the eyelids. Structure. — In structure and general appearance the lacrimal resembles the serous salivary glands. In the recent state the cells are so crowded with granules that their limits can hardly be defined. Each cell contains an oval nucleus, and the cell protoplasm is finely fibrillated. The Lacrimal Canals (Fig. 837) commence at the minute orifices, puncta lacri- malia, on the summit of small conical elevations, the lacrimal papillae (papillae lacrimalis), seen on the margin of the lids at the outer extremity of the lacus lacrimalis. The superior canal (ductus lacrimalis superior), the smaller and shorter of the two, at first ascends, and then bends at an acute angle, and passes inward and downward to the ampulla of the lacrimal sac. The inferior canal (ductus lacrimalis inferior) at first descends, and then passes almost horizontally inward to the ampulla. These canals are dense and elastic in structure and somewhat dilated at their angles. The mucous membrane is covered with stratified epithelium upon a basement membrane. Outside the latter is a layer of striped muscle continuous with the Tensor tarsi. The two canals join in a dilatation, the ampulla (ampulla ductus lacrimalis), which empties into the lacrimal sac. The Lacrimal Sac (saccus lacrimalis) (Fig. 837) is the upper dilated extremity of the nasal duct, and is lodged in a deep groove formed by the lacrimal bone and the nasal process of the maxilla bone. It is oval in form, its upper extremity being closed in and rounded, while below it is continued into the nasal duct. It is covered by a fibrous expansion derived from the tendo oculi, and on its deep oli of lacrimal gland. THE APPENDAGES OF THE EYE 1117 surface it is crossed by the Tensor tarsi muscle (Horner's muscle, p. 367), which is attached to the ridge on the lacrimal bone. Structure. — The lacrimal sac consists of a fibrous elastic coat, lined internally by mucous memlirane, the latter being continuous, through the ampulla and lacrimal canals, with the mucous lining of the conjunctiva, and, through the nasal duct, with the mucous membrane of the nose. Fig. S37 — The lacrimal apparatus. Eight The Nasal Duct (ductus nasolacrimalis) (Fig. 837) is a membranous canal, about 2 cm. (three-quarters of an inch) in length, which extends from the lower part of the lacrimal sac to the inferior meatus of the nose, where it terminates by a somewhat expanded orifice, provided with an imperfect valve, the valve of Hasner (plica lacrhnalis [Hasneri]), formed by a fold of mucous mem- brane. It is contained in an osseous canal formed by the maxilla, the lac- rimal, and the turbinated bones, is narrower in the middle than at each extremity, and takes a direction down- ward, backward, and a little out- ward. It is lined by mucous mem- brane, which is continuous below with that of the nasal fossae. The mem- brane in the lacrimal sac and nasal duct is coA'ered with columnar epithelium, as in the nose; this epithelium is in places ciliated. Surface Form.— The palpebral fissure, or opening between the eyelids, is elliptic in shape, and differs in size in different individ- uals and in different races of mankind. In the Mongolian races, for instance, the opening is very small, merely a narrow fissure, and this makes the eyeball appear small in these races, whereas the size of the eye is relatively very constant. The normal direction of the fissure is slightly oblique, in a direction upward and out- ward, so that the outer angle is on a slightly higher level than the inner. This is especially noticeable in the Mongolian races, in whom, owing to the upward projection of the malar bone and the shortness of the external angular process of the frontal bone, the tarsal plate of the upper lid is raised at its outer part and gives an oblique direction to the palpebral fissure. When the eyes are directed forward, as in ordinary vision, the upper part of the cornea is covered by the upper lid, and the lower margin of the cornea corresponds to the level of the lower lid, so that about the lower thi-ee-fourths of the cornea is exposed under ordinary circumstances. On the margin of the lids, about 1 cm. from the inner canthus, are two small openings, the puiicta lacrimalia, the commencement of the lacrimal canals. They are best seen by everting the eyelids. In the natural condition they are in- contact with the conjunctiva of the eyeball, and are maintained in this position by the Tensor tarsi muscle, so that the tears running over the surface of the globe easily find their way into the lacrimal canals. The position of the lacrimal sac into which the canals open is indicated by a little tubercle, which is plainly to be felt on the lower margin of the orbit. The lacrimal sac lies immediately above and to the inner side of this tubercle, and a knife passed through the skin in this situation would open the cavity. The posi- tion of the lacrimal sac may also be indicated by the tendo ociili or internal tarsal ligament. If both lids be drawn outward, so as to tighten the skin at the inner angle, a prominent cord will be seen beneath the tightened skin. This is the tcndo oculi, which lies immediately over the lacrimal sac, bisecting it, and thus forming a useful guide to its situation. A knife entered immediately beneath the tense cord would open the lower part of the sac. A probe introduced through this opening can be readily passed downward through the duct into the inferior meatus of the nose. The direction of the duct is downward, outward, and backward, and this course should be borne in mind in passing the probe, otherwise the point may be driven through the thin bony walls of the canal. A convenient plan is to direct the probe in such a manner that if it were pushed •onward it would strike the first molar tooth of the lower jaw on the same side of the body. In other words, the surgeon standing in front of his patient should carry in his mind the position of 1118 THE ORGANS OF SPECIAL SENSE the first molar tooth, and should push his probe onward in such a way as if he desired to reach this structure. Beneath the internal aiigular process of the frontal bone the pulley of the Superior oblique muscle of the eye can be plainly felt by pushing the finger backward between the upper and inner angle of the eye and the roof of the orbit; passing backward and outward from this pulley, the tendon can be felt for a short distance. Applied Anatomy. — The eyelids are composed of various tissues, and consequently are liable to a variety of diseases. The skin which covers them is exceedingly thin and delicate, and is supported on a cjuantity of loose and lax subcutaneous tissue which contains no fat. In conse- quence of this it is very freely movable, and is liable to be drawn down by the contraction of neio-hboring cicatrices. Such contractions may produce an eversion of the lid known as ectropion. Inversion of the lids {entropion) from spasm of the Orbicularis palpebrarum or from chronic inflammation of the palpebral conjunctiva may also occur. In some individuals there is an. extra row of eyelashes on the inner margin of the lid, directed toward the cornea (distichiasis). Trichiasis is a condition in which the lashes are directed toward the eye, but there is not inversion of the lid. The eyelids are richly supplied with blood, and are often the seat of vascular growths, such as noevi. Rodent ulcer also frequently connnences in this situation. The loose cellular tissue beneath the skin is liable to become extensively infiltrated either with l)lood or inflammatory products, producing very great swelling. Even from very slight injuries to this tissue the extrava- sation of blood may be so great as to produce considerable swelling of the lids and complete closure of the eye, and the same is the ease when the inflammatory products are poured out. The follicles are liable to become inflamed, constituting the disease known as marginal blepharitis, blepharitis ciliaris, or "blear-eye." Irregular or disorderly growth of the eyelashes not infre- quentlv occurs, some of them being turned toward the eyeball and producing inflammation and follicles of the eyelashes, or the sebaceous glands associated with these follicles may be the seat of inflammation, constituting the ordinary hordeolum or "sty." The Meibomian glands are aft'ected in the so-called "tarsal tumor;" the tumor, according to some, being caused by the retained secre- tion of these glands; by others it is believed to be a neoplasm connected with the gland. The Orbicularis palpebrarum may be the seat of spasm (blepharospasm), either in the form of slight quivering of the lids or repeated twitchings, most commonly due to errors of refraction in children, or more continuous spasm, due to some irritation of the trigeminal or facial nerves. The Orbicu- laris may be paralyzed, generally associated with paralysis of the other facial muscles. Under these circumstances the patient is unable to close the lids, and if he attempts to do so, rolls the eyeball upward under the upper lid. The tears overflow from displacement of the lower lid, and the conjunctiva and cornea, being constantly exposed and the patient being unable to wink, become irritated from dust and foreign bodies. As a result there may be ulceration of the cornea, and possibly eventually complete destruction of the eye. In paralysis of the Levator palpebrae superioris there is drooping of the upper eyelid (ptosis) and other symptoms of impli- cation of the oculomotor nerve. The eyelids may be the seat of bruises, wounds, or burns. After wounds or burns adhesions of the margins of the lids to each other or adhesion of the lids to the globe may take place. The eyelids are sometimes the seat of emphysema after fracture of some of the thin bones forming the inner wall of the orbit. If shortly after such an injury the patient blows his nose, air is forced from the nostrils through the lacerated structure into the connective tissue of the eyelids, which suddenly swell up and present the peculiar crackling on pressure v^hich is characteristic of this affection. Foreign bodies frequently get into the conjunctival sac and cause great pain, especially if they come in contact with the corneal surface, during the movements of the lid and the eye on each other. The conjunctiva is frequently involved in severe injuries of the eyeball, but is seldom ruptured alone; the most common form of injury to the conjunctiva alone is from a burn, either from fire, strong acids, or lime. In these cases the union is apt to take place between the eyelid and the eyeball. The conjunctiva is often the seat of inflammation arising from many different causes, and the arrangement of the conjunctival vessels should be remembered as affording a means of diagnosis between this condition and injection of the sclera, which is present in inflam- mation of the deeper structures of the globe. The inflamed conjunctiva is bright red; the vessels are large and tortuous, and greatest at the circumference, shading off toward the corneal margin; they anastomose freely and form a dense network, and they can be emptied by gentle pressure. The lacrimal gland is occasionally, though rarely, the seat of inflammation (dacryoademtis). either acute or chronic; it is also sometimes the seat of tumors, benign or malignant, and for these may require removal. This may be done by an incision through the skin just below the eyebrow ; and the gland, being invested with a special capsule of its own, may be isolated and removed without opening the general cavity of the orbit. The canals may be obstructed, either as a con- genital defect or by some foreign body, as an eyelash or a dacryolith, causing the tears to run over the cheek. The canals may also become occluded as the result of burns or injury: over- flow of tears may, in addition, result from deviation of the puncta or from chronic inflammation of the lacrimal sac. When there is failure of the lacrimal tubes to drain off the tears and the THE EXTERNAL EAR 1119 fluid gathers beneath and flows over the Hds, the condition is known as epiphora or stUlicidium. This latter condition is set up by some obstruction to the nasal duct frequently occurring in tuber- culous subjects. In consequence of this the tears and mucus accumulate in the lacrimal sac, distending it. Suppuration in the lafrimal sac (daeryocystiiis) is sometimes met with; this may be the sequel of a chronic inflammation; or may occur after some of the eruptive fevers in cases where the lacrimal jjassages were previously quite healthy. It may lead to lacrimal fistula. THE EAR (ORGANON AUDITUS). The organ of hearing is divisible into three parts — the external ear. the middle ear or tympanum, and the internal ear or labyrinth. THE EXTERNAL EAR (AURIS EXTERNA). . The external ear consists of an expanded portion named pinna or auricula, and the auditory canal or meatus. The former serves to collect the vibrations of the air by which sound is produced; the latter conducts those vibrations to the tympanum. DARWINIAN Fig. 838. — The right pinna thout. (Spalteholz.) The Pinna, or Auricula (Fig. 838), is attached to the side of the head midway between the forehead and occiput. It is of an ovoid form, with its larger end directed upward. Its outer surface is irregularly concave, directed slightly for- ward, and presents numerous eminences and depressions which result from the foldings of its fibrocartilaginous element. To each of these, names have been assigned. Thus, the external prominent rim of the auricle is called the helix. Another curved prominence, parallel with and in front of the helix, is called the 1120 THE OBGANS OF SPECIAL SENSE INSERTION -antihelix; this bifurcates above and forms the crura (crura anthelicis), which en- close a triangular depression, the fossa of the antihelix (fossa triangularis [auric- ulae]). The narrow curved depression between the helix and antihelix is called the fossa of the helix or the scaphoid fosSa (scapha); the antihelix describes a curve around a deep, capacious cavity, the concha auriculae, which is partially divided into two parts by the crus of the helix (crus helicis), or the commencement of the helix; the upper part is termed the cymba conchae, the lower part the cavum conchae. In front of the concha, and projecting back- ward over the meatus, is a small pointed eminence, the tragus, so called from its being generally covered on its under surface with a tuft of hair resembling a goat's beard. Opposite the tragus, and separated from it by a deep notch (incisura intertragica), is a small tubercle, the antitragus. Below this is the lobule (lohulus auricu- lae), composed of tough areolar and adipose tissue, wanting the firmness and elas- ticity of the rest of the pinna. Sometimes the lobule does not hang freely, but is adherent. CARTILAGE ■ EXTERNAL AUDITORY MEATUS TRANSVERSE AURICULAR MUSCLE iFiG. 839. — The cartilage of the right pinna, isolated, with the muscles, viewed from the inside. (Spalteholz.) Where the helix turns downward a small tubercle, tubercle of Darwin (hiberculum auriculae 'IDarwiniJ), is frequently seen. This tubercle is very evident about the sixth month of fetal life; at this stage the human pinna has a close resemblance to that of some of the adult monkeys. The cranial surface of the pinna presents elevations which correspond to the depressions on its outer surface and after which they are named, e. g., 'eminentia conchae, eminentia fossae triangularis, etc. Structure. — The pinna is composed of a thin plate of yellow fibrocartilage, covered with integument and connected to the surrounding parts by the extrinsic ligaments and muscles, and to the com- mencement of the external auditory ■canal by fibrous tissue. The integument is thin, closely ad- herent to the cartilage, and covered with hairs furnished with sebaceous glands which are most numerous in. the concha and scaphoid fossa. The hairs are most numerous and largest on the tragus and antitragus. The cartilage of the pinna (cartilago ■auriculae) (Fig. 840) consists of one single piece; it gives form to this part of thS ear, and upon its surface are found all the eminences and depressions above described. It does not enter into the construction of all parts of the pinna; thus, it does not form a constituent part of the lobule; it is deficient also between the lamina of the tragus and beginning of the crus helix, the notch between them (incisura ferminalis auris) being filled up by dense fibrous tissue. At the front part of the pinna, where the helix bends upward, is a small projection of cartilage, called the spine of the helix (spina helicis), while the lower part of the helix is prolonged downward as a tail-like process, the Cauda helicis; this is separated from the antihelix by a fissure, the fissura antitragohelicina. The cranial aspect of the cartilage FISSURA ANTITHAGICO- HELICINA INCISURA TERMINALIS AUniS ANTITRAGUS -The right ear cartilage, isolated, without. (Spalteholz.) THE EXTERNAL EAR 1121 exhibits a transverse furrow, the sulcus antihelicus transversus, which separates the prominenee produced by the concha from that caused by the fossa triangularis. A vertical ridge {iion- ticiiliis) upon the eminentia conchae gives attachment to the Retrahens aurem muscle. The fissure of the helix is a short vertical slit, situated at the fore part of the pinna. Another fissure, the fissure of the tragus, is seen upon the anterior siu-face of the tragus. Anteriorly and infe- riorly the ciirUhi^r of the pinna is continuous with the cartilage of the external auditory canal b\- a cartilaginous isthmus (isihmiis cartilaginis auris). Some authors regard the tragus as part of the cartilanc of the canal. The cartilage of the pinna is very pliable, elastic, of a yel- lowish color, and belongs to that form of cartilage wlucli is known under the name of yellow fibrocartilage. The ligaments of the pinna {ligamenii auricularia [Valsalvae]) consist of two sets: 1. The extrinsie set, or those connecting it to tlie siile of the head. 2. The intrinsic .set, or those connecting the various parts of its cartil:ij,'c toi^cthcr. The extrinsic ligaments, the most important, are three in number — superior, anterior, and posterior. The superior ligament {lignmenUim auriculare superius) extends from the suprameatal spine to the s]jine of the helix. The anterior ligament {ligamentum auriculare anterius) extends from the spina helicis and tragus to the root of the zygoma. The posterior ligament (ligamentum. auriculare posterius) passes from the posterior surface of the concha to the outer surface of the mastoid process of the temporal bone. The chief intrinsic ligaments are: (1) A strong fibrous band stretching across from the tragus to the commencement of the helix, completing the meatus in front, and partly encircling the boundary of the concha; and (2) a band which extends between the anti- helix and the cauda helicis. Other less important bands are found on the cragial surface of the pinna . The muscles of the pinna (Figs. 839 and 841) consist of two sets: (1) The extrinsic, which connect it with the side of the head, moving the pinna as a whole — viz., the Attollens, Attrahens, and Retrahens aurem (p. 366). (2) The intririsic, which extend from one part of the auricle to another — viz.: Helicis major. Helicis minor. Tragicus. Antitragicus. Transversus auriculae. Obliquus auriculae. The Helicis major {m. helicis major) is a narrow vertical band of muscle fibres, situated upon the anterior margin of the helix. It arises, below, from the spina hehcis, and is inserted into the anterior border of the helix, just where it is about to curve backward. Tlie Helicis minor {m. helicis minor) is an oblique fasciculus which covers the crus helicis. The Tragicus (?». tragicus) is a short, flattened band of muscle fibres situated upon the outer surface of the tragus, the direction of its fibres being vertical. The Antitragicus (m. antitragicus) arises from the outer part of the antitragus; its fibres are inserted into the cauda helicis and antihelix. This muscle is usually very distinct. The Transversus auriculae (m. trans- versus auriculae) is placed on the cranial surface of the pinna. It consists of scat- tered fibres, partly tendon and partly muscle, extending from the convexity of the concha to the prominence correspond- ing with the groove of the helix. The Obliquus auriculae (Tod) (m. obliquus auriculae) consists of a few fibres extending from the upper and back part of the concha to the convexity immediately above it. The arteries of the pinna are the pos- terior auricular from the external carotid, the anterior auricular from the temporal, and an auricular branch from the occip- ital artery. The veins of the pinna ac- company the corresponding arteries. The Fig. S4l.-The muscles of the pinna. 1122 THE ORGANS OF SPECIAL SENSE lymphatics enter into the preauricular nodes and the nodes upon the Sternomastoid muscle at its insertion. Tlie nerves of the pinna are the great auricular, from the cervical plexus; the auricular branch of the vagus; the auriculotemporal branch of the inferior maxillai'v nerve; the small occipital from the cervical plexus, and the great occipital or internal branch of the dorsal division of the second cervical nerve. The muscles of the pinna are supplied by the facial nerve. The Auditory Canal, or Meatus (meatus acusticus extemus), extends from the bottom of the concha to the membrana tympani (Figs. 842 and 843). It is about 3.7 cm. (an inch and an half) in length if measured from the tragus ; from the bottom of the concha its length is about 2.5 cm. (an inch). It forms a sort of S-shaped curve, and is directed at first inward, forward, and slightly upward (pans externa); it then passes inward and backward {jpars media), and lastly is carried inward, forward, and slightly downward {jpars interna). It forms an oval cylindrical canal, the greatest diameter being in the vertical direction at the external orifice, but in the transverse direction at the tympanic end. It pre- sents two constrictions, one near the inner end of the carti- laginous portion, and another, the isthmus, in the osseous portion, about 2 cm. (three- quarters of an inch) from the bottom of the concha. The membrana tympani (Figs. 842 and 843), which closes the inner end of the canal, is directed obliquely, in conse- quence of which the floor of the canal is longer than the roof, and the anterior wall longer than the posterior. The auditory canal is formed partly by cartilage and membrane, partly by bone, and is lined by perichondrium and periosteum, covered by skin. The cartilaginous portion (meatus acusticus extemus cartilagineus) is about 8 mm. (one-third of an inch) in length; it is formed by the cartilage of the pinna, prolonged inward, and firmly attached to a greater portion of the circimiference of the auditory process of the temporal bone. The cartilage is deficient at its upper and back part, its place being supplied by a fibrous membrane. This part of the canal is rendered extremely movable by two or three deep fissures, the fissures of Santorini (incisurae cartilaginis meatus acustici externi YSantoriniJ), which extend through the cartilage in a vertical direction. The osseous portion (meatus acusticus extemus osseus) is about 16 mm. (two- thirds of an inch) in length, and narrower than the cartilaginous portion. It is directed inward and a little forward, forming a slight curve in its coiu'se, the con- vexity of which is upward and backward. Its inner end, which communicates, in the dry bone, with the cavity of the tympanum, is smaller than the outer and sloped, the anterior wall projecting beyond the posterior about 4 mm. (one-sixth of an inch); it is marked, except at its upper part, by a narrow groove, the tympanic sulcus (sulcus tynipanicus), in which the circumferential margin of the membrana tympani is attached. Its outer edge is dilated and rough in the greater part of its circumference, for the attachment of the cartilage of the pinna. Its transverse section is oval, the greatest diameter being from above downward and backward. The front and lower parts of this canal are formed by a curved plate of bone. Cat tilags of (he ezt auditory meatui, Fig. S42. — Transverse section of external auditorj" panum. Leftside. (Gegenbaur.) THJ<: EXTERNAL EAR 1123 the tympanic plate, which, in the fetus, exists as a separate ring (avmilii.s- tijin- panicus), incomplete at its upper part. (See Section on Osteology, p. 87.) The skin lining the meatus is very thin, adheres closely to the cartilaginous and osseous portions of the tube, and covers the surface of the membrana tympani, forming a very thin outer layer. After maceration the thin pouch of epidermis, when withdrawn, preserves the form of the canal. In the thick subcutaneous tissue of the cartilaginous part of the meatus are numerous ceruminous glands (glandulae ceruminosae) which secrete the ear ivax or ceruvien. They resemble in structure sweat glands, and their ducts open on the surface of the skin. -Vertical section through the external auditory canal and tympanum, passing i ovalis. (Testut.) , front of the fenestra Relations of the Canal. — In front of the osseous part is the glenoid fossa, which receives the condyle of the mandible (Fig. 100), which, however, is separated from the cartilaginous part by the retromandibular part of the parotid gland. The movements of the mandible influence to some extent the lumen of the cartilaginous portion. Behind tlie osseous part are the mastoid air cells {cellulae mastoideae), separated from it by a thin layer of bone (Fig. S4o). The arteries supplying the external canal are branches from the posterior am-iciilar, internal maxillary, and superficial temporal. The veins of the external canal accompany the corresponding arteries and pass to the in- ternal maxillary, temporal, and posterior auricular veins. The lymphatics accompany the veins and enter the parotid and posterior auricular lymph nodes. The nerves are chiefly derived from the auriculotemporal branch of the inferior maxillary nerve, the auricularis magnus, and the auricular branch of the vagus. The point of junction of the osseous and cartilaginous portions of the tube is an obtuse angle, which projects into the canal at its antero-inferior wall. This produces a sort of constriction in this situation, and renders it the narrowest portion of the canal — an important point to be borne in mind in connection with the presence of foreign bodies in the ear. The cartilaginous is connected to the bony part by fibrous tissue, which renders the outer part of the tube very movable, and therefore by drawing the pinna upward and backward the canal is rendered almost straight. At the external orifice are a few short crisp hairs which serve to prevent the entrance of small particles of dust, flies, or other insects. In the external auditory canal the secretion of the ceruminous glands serves to catch any small particles which may find their way into the canal, and prevent their reaching the membrana tympani, where their presence might excite irritation. In young children the canal is short, the osseous part being very deficient, and consisting merely of a bony ring {annulus tympanicus), which supports the membrana tympani. In the fetus the osseous part is entirely absent. The shortness of the canal in children 1124 THE ORGANS OF SPECIAL SENSE should be borne in mind in introducing the aural speculum, so that it shall not be pushed in too far, at the risk of injuring the membrana tympani; indeed, even in the adult the speculum should never be introduced beyond the constriction which marks the junction of the osseous and cartilaginous portions. In using this instrument it is advisable that the pinna should be drawn upward, backward, and a little outward, so as to render the canal as straight as possible, and thus assist the operator in obtaining, by the aid of reflected light, a good view of the membrana tympani. .Just in front of the membrane is a well-marked depression, situated on the floor of the canal and bounded by a somewhat prominent ridge; in this foreign bodies may become lodged. By aid of the speculum, combined with traction of the auricle upward and backward, the whole of the membrana tympani is rendered visible. It is a pearly-gray membrane, slightly glistening in the adult, placed obliquely, so as to form with the floor of the canal a very acute angle (about 5.5 degrees), while with the roof it forms an obtuse angle. At birth it is more hori- zontal— being situated in almost the same plane as the base of the skull. About midway between the anterior and posterior margins of the membrane, and extending from the centre obliquely upward, is a reddish-yellow streak; this is the handle of the malleus, which is attached to the membrane (Fig. 846). At the upper part of this streak, close to the roof of the canal, a little white rounded prominence is plainly to be seen; this is the processus brevis of the malleus, projecting against the membrane. The membrana tympani does not present a plane surface; on the contrary, its centre is drawn inward, on account of its connection with the handle of the malleus, and thus the external surface is rendered concave. The connections of the nerves of the auditory canal explain the fact that the occurrence, in cases of any irritation of the canal, of constant coughing and sneezing from implication of the vagus, or of yawning from implication of the auriculotemporal, of vomiting which may follow syring- ing the ears of children, and the occasional heart faihu-e similarly induced in elderlj' persons. No doubt also the association of earache with toothache in cancer of the tongue is due to im- plication of the inferior maxillary, which supplies also the teeth and the tongue. The upper half of the membrana tympani is much more richly supplied with blood than the lower half. For this reason, and also to avoid the chorda tympani nerve and ossicles, incisions through the viemhraiii- should 'ne made at the lower and posterior part. Applied Anatomy. — Malformations, such as imperfect development of the external parts, absence of the canal, or supernumerary auricles, are occasionally met with. Or the pinna may present a congenital fistula, "which is due to defective closure of the first visceral cleft, or rather of that portion of it which is not concerned in the formation of the Eustachian tube, tympanum, and meatus. In some cases the cephaloauricular angle is almost absent; in others, it is nearly a rio-ht angle. Projecting ears and long ears are said by some observers to be more common among degenerates, criminals, and the insane than among the normal, the non-criminal, and the sane. The skin of the auricle is thin and richly supplied with blood, but in spite of this it is frequently the seat oi frost-bite, due to the fact that it is much exposed to cold, and lacks the usual underlying subcutaneous fat found in most other parts of the body. A collection of blood is sometimes found between the cartilage and perichondrium {hematoma auris), usuall_v the result of traumatism, but not necessarily due to this cause. It is said to occur most frequently in the ears of the insane. Keloid sometimes grows in the auricle around the puncture made for ear-rings, and epithelioma occasionally affects this part. Deposits of urate of soda are often met with in the pinna in gouty subjects. The external auditory canal can be most satisfactorily examined by light reflected tlirough a funnel-shaped speculum; by gently moving the latter in different directions and by gently drawing the pinna upward, backward, and a little outward, so as to render the canal as straight as possible, the whole of the canal and membrana tympani can be brought into view. The points to be noted are the presence of wax or foreign bodies, the size of the canal, and the con- dition of the membrana tympani. The accumulation of wax (impacted cerumen) is often the cause of deafness, and may give rise to very serious consequences, causing ulceration of the membrane and even absorption of the bony wall of the canal. Foreign bodies are not infrequently introduced into the ear by children, and, when situated in the first portion of the canal, maj' be removed with tolerable facility by means of a minute hook or loop of fine wire, the parts being illuminated with reflected light; but when they have slipped beyond the narrow middle part of the meatus, their removal is in nowise easy, and attempts to efi'ect it, in inexperienced hands, may be followed by destruction of the membrana tympani arid possibly injury of the contents of the tympanum. The caliber of the external auditory canal may be narrowed by inflammation of its lining membrane, running on to suppuration; by periostitis; by polypi., sebaceous tumors, and exostoses. THE MIDDLE EAR, DRUM, OR TYMPANUM (AURIS MEDIA) (Figs. 844, 848). The middle ear or tympanum is an irregular cavity, compressed laterally, and situated within the petrous portion of the temporal bone. It is placed above THE MIDDLE EAR, DRUM, OR TYMPANUM 1125 the jugular fossa; the carotid canal lying in front, the mastoid cells behind, the external auditory canal externally, and the labyrinth internally. It is lined with mucous membrane, is filled with air, and communicates ^\■ith the mastoid cells, through the mastoid antrum, and with the nasopharynx by the Eustachian tube. The tympanum is traversed by a chain of movable bones, which connect the membrana tympani with the labyrinth, and serve to convey the vibrations communicated to the membrana tympani across the cavity of the tympanum to the internal ear. In shape it is roughly biconcave, the concave surfaces being placed vertically and forming the external and internal walls. The cavity forms an angle of 45 degrees with the sagittal plane. The Tympanic Cavity {cavum tym'pani) (Figs. 848 and 849) consists of two parts — the atrium or tympanic cavity proper (Fig. 849), opposite the tympanic mem- brane, and the attic or epitympanic recess {rccessus epitympanicKs) (Figs. 847 and 848), above the level of the upper part of the membrane; the latter contains the upper half of the malleus and the greater part of the incus. The diameter of the tympanic cavity, including the attic, measures about 15 mm. (three-fifths of an inch) vertically and anteroposteriorly. From without inward it measures about G mm. (one-quarter of an inch) above and 4 mm. (one-sixth of an inch) below; opposite the centre of the tympanic membrane it is only about 2 mm. (one- twelfth of an inch). It is bounded externally by the membrana tympani and meatus; internally, by the outer surface of the internal ear; it communicates behind \\\t\\ the mastoid antrum and through it with the mastoid cells, and in from with the Eustachian tube. Chorda tympnm Fig S4-i — \ ie\\ of the inner w all of the tympanum (enl The roof of the tympanum (paries tegmentalis) is broad, flattened, and formed of a thin plate of bone (legmen tympani) (Fig. 848), which separates the cranial and tympanic cavities. It is situated on the anterior surface of the petrous portion of the temporal bone, close to its angle of junction with the squamous portion of the same bone, and is prolonged backward so as to roof in the mastoid antrum; it is also carried forward to cover in the canal for the Tensor tympani muscle. Its outer edge corresponds with the remains of the petrosquamous suture. The floor (paries jugularis) (Fig. 848) is narrow, and is separated by a thin plate of bone (fundus tympani) from the jugular fossa. It presents, near the inner wall, a small aperture, the opening of the canaliculus tympanicus, for the transmission of Jacobson's nerve (». tympanicus). On the floor near the posterior wall there is often to be found a slight bony projection (prominentia styloideae). The outer wall (Fig. 843) is formed mainly by the membrana tympani, partly by the ring of bone into which this membrane is inserted. This ring of bone is. incomplete at its upper part, forming a notch (incisura tympanica [Riviiii]) 1126 THE ORGANS OF SPECIAL SENSE (Fig. S44), close to whicli are three small apertures — the iter chordae posterius, the Glaserian fissure, and the iter chordae anterius. The iter chordae posterius {canaliculus chordae tympani) (Fig. 804) is in the angle of junction between the posterior and external walls of the tympanum, immediately behind the membrana tympani and on a level with the upper end of the handle of the malleus; it leads into a minute canal, which descends in front of the facial canal and terminates in the aqueduct near the stylomastoid foramen. Through it the chorda tympani nerve enters the tympanum. The Glaserian or petrotympanic fissure {fissura petrotympanica.) [Glaseri]) (Fig. 847) opens just above and in front of the ring of bone into which the membrana tympani is inserted; in this situation it is a mere slit about 2 mm. in length. It lodges the long process and anterior ligament of the malleus, and gives passage to the tympanic branch of the internal maxillary artery. The iter chordae anterius or canal of Huguier (Fig. 847) is seen at the inner end of the preceding fissure; through it the chorda tympani nerve leaves the tympanum. The inner wall of the tympanum (paries labyrinthica) (Figs. 844 and 848) is adjacent to the labyrinth; it is vertical in direction, and looks direcdy outward. It presents for examination the following parts: Fenestra ovalis. Promontory. Fenestra rotunda. Ridge of the facial canal. Prominence of the lateral semicircular canal. The fenestra ovalis {fenestra vestibuli) (Fig. 844) is a reniform opening leading from the tympanum into the vestibule of the internal ear. Its long diameter is directed horizontally, and its convex border is upward. In the recent state it is occupied by the base of the stapes (Figs> 843 and 849), the circumference of which is connected to the margin of the foramen by an annular ligament. The fenestra rotunda {fenestra cochleae) (Fig. 844) is situated below and a little behind the fenestra ovalis, from which it is separated by a rounded elevation, the promontory; at its border is a narrow ridge of bone {crista fenestrae cochleae). The fenestra rotunda is closed in the recent state by a membrane (membrana tympani secundaria) ; this membrane is concave toward the tympanum, convex toward the cochlea. It consists of three layers — the external or mucous, derived from the mucous lining of the tympanum; the internal, from the lining membrane of the cochlea; and an intermediate or fibrous layer. The promontory (promontorium) (Fig. 848) is a rounded hollow prominence, formed by the projection outward of the first turn of the cochlea; it is placed between the fenestrte, and is furrowed on its surface {sulcus promontorii) for the lodgement of the tympanic plexus. A minute spicule of bone frequently connects the promontory to the pyramid. The prominentia canalis facialis (Fig. 848) indicates the position of the b.ony canal in which the facial nerve is contained; this canal traverses the inner wall of the tympanum above the fenestra ovalis, and behind that opening curves nearly vertically downward along the posterior wall. The posterior wall of the tympanum {paries mastoidea) (Fig. 848) is wider above than below, and presents for examination the — Opening of the antrum. Fossa incudis. Pyramid. The opening of the antrum is a large irregular aperture, which extends back- ward from the epitympanic recess and leads into a considerable air space, the mastoid antrum {antrum tympanicwn) (see p. 83). The antrum communicates THE MIDDLE EAR, DRUM, OB TrMPANUM 1127 witli lartje irregular cavities contained in the interior of the mastoid process, the mastoid air cells. These cavities vary considerably in nuinher, size, and form; they are Hned by mucous membrane continuous with that Hning the cavity of the tympanum. Tlie fossa incudis (Fig. 848) is placed in the posterior and inferior part of the epitympanic recess. It lodges the short process of the incus. The pyramid (emine)tti.a pijramidalis) (Fig. 844) is a conical eminence situated immediately behind the fenestra ovalis, and in front of the vertical portion of the facial canal; it is hollow in the interior, and contains the Stapedius muscle; its summit projects forward toward the fenestra ovalis and presents a small aper- ture which transmits the tendon of the muscle. The cavity in the pyramid is prolonged into a minute canal, which communicates with the facial canal and transmits the twig from the facial nerve which supplies the Stapedius. The anterior wall of the tympanum (paries carotica) is wider abo^-e than below; it corresponds with the carotid canal, from which it is separated by a thin plate of bone (Fig. 848), perforated by the caroticotympanic canaliculus, which transmits the tympanic branch of the internal carotid artery and the caroticotympanic nerves. It presents for examination the — Canal for the Tensor tympani. Orifice of the Eustachian tube. The processus cochleariformis. The orifice of the canal foi- the Tensor tympani and the orifice of the Eustachian tube are situated at the upper part of the anterior wall, being incompletely sepa- rated from each other by a thin, delicate, horizontal plate of bone, the processus cochleariformis (septum canalis musculotubarii) _(Figs. 844 and 848). The canalis musculotubarius is divided by this long process into the canal for the Tensor tympani and the canal for the Eustachian tube. These canals run from the tympanum forward, inward, and a little downward, to the angle between the squamous and petrous portions of the temporal bone. The canal for the Tensor tympani (semicanalis m. tensor is tympani) (Figs. 844 and 848) is the superior and the smaller of the two; it is rounded and lies beneath the forward prolongation of the tegmen tympani. It extends on to the inner wall of the tympanum and ends immediately above the fenestra ovalis. The processus cochleariformis passes backward below this part of the canal, forming its outer wall and floor; it expands above the anterior extremity of the fenestra ovalis and terminates by curving outward so as to form a pulley over which the tendon passes. The bony wall of this canal is incomplete, and the osseous vacancy is filled by tough connective tissue. The Eustachian tube (tuba audiiiva [Eustackii]) (Figs. 844 and 845) is the channel through which the tympanum communicates with the nasopharynx. Its length is 36 mm. (an inch and a half), and its direction downward, inward, and forward, forming an angle of about 4.5 degrees with the sagittal plane and one of from .30 to 40 degrees with the horizontal plane. The canal for the Eustachian tube (semicanalis tuhae auditivae) (Fig. 845) is formed partly of bone, partly of cartilage and fibrous tissue. The osseous portion (pars ossea tubae aiiditivae) is about 12 mm. (half an inch) in length. It is the outer portion of the tube. It commences in the anterior wall of the tympanum, below the processus cochleariformis. and, gradually narrowing, terminates at the angle of junction of the petrous and squamous portions of the temporal bone, its extremity presenting a jagged margin which ser^•es for the attach- ment of the cartilaginous portion. The cartilaginous portion (pars cartilaginea iuhae auditivae), about 2.5 cm. (an inch) in length, is formed of a triangular plate of elastic fibrocartilage (cartilago 1128 THE ORGANS OF SPECIAL SENSE tuhae aiiditivae), the apex of which is attached to the margin of the inner extremity of the osseous canal, while its base lies directly under the mucous membrane of the nasopharynx, where it forms an elevation or cushion above and behind the pharyngeal orifice of the tube. The upper edge of the cartilage is curled upon itself, being bent outward so as to present on transverse section the appearance of a hook (lamina lateralis); a groove or furrow is thus produced, which opens below and externally, and this part of the canal is completed by fibrous membrane. On transverse section the cartilage exhibits the laminse which above are continuous with each other — the hard, thick lamina medialis and the thin and hooked lamina lateralis. The cartilage of the Eustachian tube, with a hood plate of cartilage, forms the posterior portion of the inner wall (the lamina medialis). The cartilage is fixed to the base of the skull, and lies in a groove (sulcus tuhae auditivae) between Fig. 845. — Eustachian tube, laid open by a cut in its long axis. (Testut.) the petrous portion of the temporal and the greater wing of the sphenoid; this groove ends opposite the middle of the internal pterygoid plate, in a projection, the processus tubarius. The cartilaginous and bony portions of the tube are not in the same plane, the former inclining downward a little more than the latter. They join each other at a large obtuse angle, open below. The diameter of the canal is not uniform throughout, being greatest at the pharyngeal orifice and least at the junction of the bony and cartilaginous portions, where it is named the isthmus (isthmus tuhae auditivae^ ; it again expands somewhat as it approaches the tympanic cavity. The position and relations of the pharyngeal orifice are described with the anatomy of the nasopharynx. The mucous membrane of the tube is continuous in front with that of the nasopharynx, and behind with that which lines the tympanum; it is covered with ciliated epithelium and is thin in the osseous portion, while in the cartilaginous portion it contains many mucous glands and near the pharyngeal orifice a considerable amount of lymphoid tissue, which has been named by Gerlach the tubal tonsil. The tube is opened during deglutition by the Salpingopharyngeus and Dilatator tubse muscles. The Membrana Tympani (Figs. 846 and 847) separates the cavity of the tym- panum from the bottom of the external canal. It is a thin, semitransparent THE MIDDLE EAR, DRUM, OR TYMPANUM 1129 POSTERIOR TYMPANIC^ SPINE MARGIN OF MEMBRANA 1 ITMPANI OR LIMBUS TENSE PORTION OF MEMBRANA TYMPANI Fig. 846.— The right membrana tympani, viewed from the oulside, from in front, and from below. (Spalteholz.) SUPERIOR LIGAMENT NECK OF MALLEUSV ANTERIOR LIGAMENT AND ANTERIOR PROCESS OF MALLEOLUS INSERTION OF TENSOR TYMPANI Fig. 847. — The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above. (Spalteholz.) 1130 THE ORGANS OF SPECIAL SENSE membrane, nearly oval in form, somewhat broader above than below, and directed A'ery obliquely downward and inward, so as to form an angle of about 55 degrees with the floor of the canal (Fig. 843). The antero-inferior portion is) therefore, placed at the greatest distance from the external orifice of the meatus. In a new- born child the membrana tympani is almost horizontal. The greatest diameter of the membrana tympani is from 9 to 10 mm.; its least diameter is from 8 to 9 mm. The greater part of its circumference (limbiis memhranae tymimnae) is thickened and fixed in a groove, the sulcus tympanicus, at the inner extremity of the external meatus. This sulcus is deficient superiorly at the incisure or notch of Rivinus (Fig. 846). From the extremities of the notch two folds, the anterior and posterior malleolar folds, are prolonged to the short process of the malleus (Fig. 846). The small, somewhat triangular part of the membrane situated RECESS PROMINENCE OF EXTERNAL SEMICIRCULAR CANAL E OF AQUEDUCT OF FALLOPIUS TENDON OF STAPEDIUS MUSCLE PLICA STAP / / X PROCESSUS COCHLCARIFORMI5 ^ TENSOR TYMPANI uscLE (cut through) Fig. 848. — The medial wall and part of the posterior and anterior walls of the right tympanic cavity, lateral ^ (Spalteholz.) above these folds is lax and thin, and is named the membrana fiaccida of Shrapnell (Figs. 846 and 847); in it a small orifice is sometimes seen. The larger lower portion of the tympanic membrane is stretched tightly, and is called the tense portion or pars tensa (Figs. 846 and 847). The handle of the malleus is firmly attached to the inner aspect of the mem- brana tympani as far as its centre (Fig. 847), which it draws inward toward the tympanic cavity. The most depressed part of the concavity is called the umbo {itinbo memhranae tympanae) (Fig. 846). On the outer surface of the drum membrane a light stripe {stria malleolaris) is seen. It runs from in front and above downward and backward, and is produced by the handle of the malleus, showing through the membrane (Fig. 846). Structure. — The tympanic membrane is composed of tliree layers — an external {cutwular) , a middle {fibrous), and an internal {mvcous). The cuticular layer {stratum cuianeiim) is derived from the integument lining the external canal. The fibrous or middle layer {membrana propria) THE MIDDLE EAR, DRUM, OR TYMPANUM lV.il consists of two strata — an external, of radiating fibres (sfrafiim rndiatiim), whirh diverge from the handle of the malleus, and an internal, of circular fibres {xlralmii rin'iilarr), which are plenti- ful around the circumference, but sparse and scattei'cd ncai' the centre of the membrane. Branched i>r dendritic fibres, as pointed out by Grliber, are also present, especially in the pos- terior half (if the iiiciiiKi-ane. The arteries arc ilcriwd from the deep auricular branch of the internal maxillary, which ramifies beneath the cuticular layer and from the stylomastoid branch of the posterior auricular and tympanic branch of the internal maxillary, which are distributed on the mucous surface. The arteries of the cutaneous set anastomose with the arteries of the mucous set by minute branches which penetrate the drum membrane near its margin. The superficial veins open into the external jugular; those on the mucous surface drain partly into the lateral sinus and veins of the dura and partly into a plexus on the Eustachian tube. The outer surface of the drum membrane receives its nerve supply from the auriculotemporal branch of the inferior maxillary and the auricular branch of the vagus. The inner surface is supplied by the tym- panic branch of the glossopharyngeal. There are two sets of lymphatics, the cutaneous and mucous, which freely communicate. Tht spaces between the dendritic fibres of Grliber are lymph spaces (Kessel). The Ossicles of the Tympanum (ossicida aiditus) (Fig, 849).— The tym- panum contains in its upper part a chain of movable bones, three in number, the malleus, incus, and stapes. The first is attached to the membrana tympani, the last to the fenestra ovalis, the incus being placed between the two, and connected to both by delicate articulations. The Malleus (Fig. 850), so named from its fancied resemblance to a hammer, is placed farthest in front and outward. It consists of a head, neck, and three processes — the handle, or manubrium, the processus gracilis, and the processus brevis. The head (capitulum mallei) is the large upper extremity of the bone, and is situated in the epitympanic recess (Fig, 847). It is oval in shape, and articulates posteriorly with the incus, being free in the rest of its extent. The facet for articulation with the incus is covered by cartilage; it is constricted near the middle, and is divided by a ridge into an upper, greater, and a lower, lesser part; which form nearly a right angle with each other. Opposite the constriction the lower margin of the facet projects in the form of a process, the cog tooth, or spur of the malleus. On the back of the head below the spur is a crest (crista mallei), to which the posterior ligament of the malleus is attached. The neck (c-ollum mallei) is the narrow contracted part just beneath the head; below this is a prominence, to which the various processes are attached. The chorda tympani nerve crosses the inner surface (Fig. 847). The handle (^manubrium mallei) is a vertical process of bone, which is connected by its outer margin with the fibrous layer of the membrana tympani, its entire length being fastened to the fibrous layer of the drum membrane by its own peri- osteum and by a layer of cartilage (Figs. 847 and 849). It is directed downward, inward, and backward; it decreases in size toward its extremity, where it is curved slightly forward, and is flattened from within outward. The handle forms a variable angle with the head of the hammer. It averages about 130 degrees, . but is always greater in the right ear than in the left. It forms an angle -nith the Fig. 849 — Chain of ossicles and their liga- ments, seen from the front in a vertical, transverse section of the tympanum. (Testut.) 1132 THE ORGANS OF SPECIAL SENSE horizontal, averaging on the right side 50 degrees and on the left side 45 degrees (Spalteholz). Internally the handle is covered by the mucous membrane of the tympanum. On the inner side, near its upper end, is a slight projection, into which the tendon of the Tensor tympani is inserted (Fig. 847). The processus gracilis (processus anterior [Folii]) is a long and delicate process, which springs from the eminence below the neck and is directed forward and outward to the Glaserian fissure, to which it is connected by ligamentous fibres. In the fetus this is the longest process of the malleolus, and is in direct continuity with the cartilage of Meckel. MANUBRIUM INSERTION OF TENSOR TYMPANI MUSC INSERTION Ol EXTERNAL LIGAMENT OF MALLEUS PROCESS Fig. 850.— Viewed fr< in front. Fig. Sol. — Viewed from behind. (Spalteliolz.) Figs. 850 and 851. — The right malleus (enlarged). The processus brevis (processus lateralis) is a slight conical projection, which springs from the root of the manubrium; it is directed outward and is attached to the upper part of the tympanic membrane by cartilage and to the margins of the notch of Rivinus by the two tympanomalleolar folds. The Incus (Figs. 852 and 853) has received its name from its supposed resemblance to an anvil, but it is more like a bicuspid tooth with two roots. ARTICULAR ^ SURFACE FOR ■ ' HEAD OF MALLEUS ARTICULAR SURFACE FOR HEAD OF MALLEUS Fig. 852. — Lateral view. Fig. 853. — Medial and front view. (Spalteholz Figs. 862 and 853. — The right incus (enlarged.) which differ in length, and are widely separated from each other. It consists of a body and two processes. The body and the short process are placed in the epitympanic recess (Fig. 849). The body (corpus incudis) is somewhat quadrilateral, but compressed laterally. On its anterior surface is a deeply concavo-convex facet, which articulates with the head of the malleus, and the lower part is hollowed for the spur of the malleus. The two processes diverge from each other at an angle of from 90 to 100 degrees. THE MIDDLE EAR, DRUM, OB TYMPANUM 1133 The short process (crus breve), somewhat conical in shape, projects almost, horizontally backward, and articulates with a depression, the fossa incudis, in the lower and back part of the epitympanic recess. The long process (crus longuvi), longer and more slender than the preceding, descends nearly vertically behind and parallel to the handle of the malleus, and, bending inward, terminates in a rounded globular projection, the os orbiculare or lenticular process (processus lenticular is), which is tipped with cartilage, and articulates with the head of the stapes. In the fetus the os orbiculare exists as a separate bone. anter The Stapes (Figs. 854 and 855), so "' called from its close resemblance to a stirrup, consists of a head, neck, two qase or stapes crura, and a base. The stapes is the p^^ gg^ only one of the tympanic ossicles that Fiqs. 854 and SSS.— The right stapes (enlarged). Fig. ■I •, 854. Viewed from above. Fig. 855. Medial view. lias a marrow cavity. rspaitehoiz.) The head (capituhim stapedis) pre- sents a depression, tipped with cartilage, which articulates with the os orbiculare. The neck, the constricted part of the bone succeeding the head, receives the insertion of the Stapedius muscle. The two crura (crus anterius and crus posterius) diverge fron^ i,he neck and are connected at their extremities by a flattened, oval-shaped plate, the base (basis stapedis), which forms the foot-plate of the stapes and is fixed to the margin of the fenestra ovalis by ligamentous fibres. The foot-plate almost fills the oval window (Fig. 843). Of the two crura, the anterior is shorter and less curved than the posterior. In a recent specimen a membrane will be observed filling the space between the crura and the foot-plate. This membrane is connective tissue and is called the membrana obturatoria stapedis. The stapes lies practically horizontal. Articulations of the Ossicles of the Tympanum {articulationes ossicuhrum auditus) (Fig* 840). —These small bones are t onnected with each other and with the walls of the tympanum by ligaments, and are moved by small muscles. The articular surfaces of the malleus and incus and the orbicular process of the incus and head of the stapes are covered by cartilage, con- nected by delicate capsular ligaments and lined by synovial membrane. Ligaments Connecting the Ossicula with the Walls of the Tympanum dig. osdculorum auiUtus). — The malleus is fastened to the wall of the tympanum by three ligaments — the anterior, superior, and external ligaments. The anterior ligament of the malleus {tig. mallei anterius) is attached by one extremity to the neck of the malleus just aljove the jirocessus gracilis, and by the other to the anterior wall of the tympanum, ilo.sc to tlic (ilascrlau fi.ssure, some of its fibres being prolonged through the fisstue to reach the alar sjiiuc of the ^j)lnii(ji(l. The superior ligament of the malleus [Ug. mallei supcrius) is a delicate round bundle of fibres which descends perpendiculaily lidni the roof of the epitympanic recess to the head of the malleus. It is sometimes callcil the suspensory ligciment. The external ligament of the malleus (tig. mallei latcralc) is a triangular plane of fibres passing from the posterior part of the notch in the tympanic ring to the head of the malleus. The mal- leus rotates around an a.xis composed of the external and anterior ligaments, hence these two ligaments constitute what Helmholtz called the axis ligament of the malleus. Tlie incus is fastened to the wall of the tympanum by two ligaments, the posterior and the superior. The posterior hgament of the incus {Ug. incudis posterius) is a short, thick, ligamentous band ■which connects the extremhy of the short process of the incus to the posterior and lower part of the epitympanic recess, near the margin of the opening of the mastoid cells. A superior ligament of the incus (Kg. incudis superius) has been described, but it is little more than a fold of mucous membrane. The vestibular surface and the circumference of the base of the stapes are covered by hyaline cartilage, and the annular ligament of the stapes {Kg. annulare baseos stapedis) connects the circumference of the base to the margin of the fenestra ovalis. 1134 THE ORGANS OF SPECIAL SENSE • The muscles of the tympanum (?re. ossiculorum avditus) are two :* Tensor tympani. Stapedius. The Tensor tympani (m. tensor tympani) (Fig. 848), the larger, is contained in the bony canal above the osseous portion of the Eustachian tube, from which it is separated by the pro- cessus cochleariformis. It arises from the under surface of the petrous bone, from the carti- laginous portion of the Eustachian tube, and from the osseous canal in which it is contained. Passing backward through the canal, it terminates in a slender tendon which enters the tym- panum and makes a sharp bend outward around the extremity of the processus cochleariformis, and is inserted into the handle of the malleus near its root. Its nerve supply is from the motor root of the trigeminal nerve by way of the otic ganglion. The Stapedius (m. stapedius) (Fig. 848), the smallest constant muscle in the body, weighing only 1 grain, arises from the side of a conical cavity hollowed out of the interior of the pjTamid; its tendon emerges from the orifice at the apex of the pjo-amid, and, passing forward, is inserted into the neck of the stapes. Its surface is aponeurotic, its interior fleshy, and its tendon occasion- ally contains a slender bony spine, which is constant in some mammalia. It is supplied by the tympanic branch of the facial nerve. Actions. — The Tensor tympam draws the handle of the malleus inward and thus increases the tension of the tympanic membrane. When the Stapedius contracts it draws the head of the stapes backward, and in consequence the anterior end of the foot-plate passes outward toward the tympanum, and the posterior end inward toward the vestibule, and the annular ligament is made tense. It probably com]iresses the contents of the vestibule. Movements of the Ossicles of the Tympanum. — The chain of bones is a lever-like arrange- ment, by means of which the vibrations of the membrana tympani are transferred to the mem- brane covering the oval window, and from this to the perilymph in the labyrinth. When the tympanic membrane moves inward, the handle of the malleus moves with it. The movement of the malleus moves the incus, and the movement of the incus drives the foot of the stapes toward the labyrinth. When the handle of the malleus moves inward, the spur on the head becomes locked with the body of the incus. During outward movement it is unlocked. The ordinary outward movement of the drum membrane causes the above-described movements to be reversed. When there is overforcible outward movement the incus does not go outward quite as far as the malleus, but slides at the joint between the malleus and incus. This reluctance of the incus saves the foot of the stapes from being pulled away from the oval window. The mucous membrane of the tjrmpanum (tunica mucosa tympanica) is continuous with that of the nasopharynx through the Eustachian tube. It invests the ossicles, and the muscles and nerves contained in the tympanic cavity, forms the internal layer of the membrana tympani, and is reflected into the mastoid antrum and air cells, which it lines throughout. It forms several vascular folds {plicae), which extend from the walls of the tympanum to the ossicles, enveloping these as well as the chorda tympani nerve and the Tensor tympani muscle. The anterior malleolar fold {plica malleolaris anterior) comes off from the membrana tympani between the anterior edge of the notch of Rivinus and the handle of the malleus, envelops the processus gracilis of the malleus, the anterior ligament of the malleus, and the anterior portion of the chorda tympani nerve, and terminates in a free concave edge. The posterior malleolar fold {plica malleolaris posterior) is the larger of the two It comes off from the margin of the notch of Rivinus, envelopes the external ligament of the malleus, the posterior part of the chorda tympani nerve, is attached to the handle of the malleus, and ends in a free concave margin. The fold of the incus {plica inciidis) takes origin from the roof of the epitympanic recess and passes to the body and short process of the incus; and a similar fold passes from the head of the malleus to the anterior wall of the epitympanic recess. The entire stapes, with its obtiu-ator membrane, is enwrapped by the fold of the stapes {plica stapedis). This fold also ensheaths the tendon of the Stapedius muscle and often reaches to the posterior wall of the cavity of the tympanum. These folds separate off pouch-like cavities, and give the interior of the tympanum a somewhat honeycombed appearance. The inferior external pouch of the tympanmn or the pouch of Frussak (recessus mcmhranae tympani superior) is between the flaccid portion of the membrana tympani, the external liga- ment of the malleus, and the neck of the malleus. The anterior and posterior malleolar folds with the tymiianic membrane form two pouches. These are the anterior and posterior pouches or recesses of Troeltsch {ncrxxn.i nn'mbranae tympani, anterior and posterior). The anterior pouch is lilind alxne and has a slit-like opening below. The posterior pouch is continued into the blind superior pouch of the tympanic membrane. In the tympanum this membrane is pale, thin, slightly vascular, and covered for the most part with columnar ciliated epithelium, but that * Two additional muscles have been described as the Mm. laxator tympani major et minor; they correspond to the anterior and lateral ligaments of the malleus, but often show striated muscle tissue. (D. G. Methenj-.} THE MIDDLE EAR, DRUM, OR TYMPANUM 1135 covering the pyramid, ossicula, and membrana tympani possesses a flattened, nonciliated epi- thelium. In the antrum and mastoid cells its epithelium is also nonciliated. In the osseous portion of the Eustachian tube the membrane is thin, but in the cartilaginous jiortion it is very thick, highly vascular, covered with ciliated epithelium, and provided with numerous mucous glands. Vessels and Nerves. — The arteries supplying the tympanum are six in number. Two of them are larger than the rest — viz., the tympanic branch of the internal maxillary, which enters by way of the petrotympanic or Glaserian fissure and supplies the membrana tympani; and the stylomastoid branch of the posterior auricular, which passes through the stylomastoid foramen and the facial canal, and supplies the inner wall and floor of the tympanum, the mastoid cells and antrum, and the Stapedius muscle. This vessel anastomoses around the tympanic mem- brane with the tympanic. The middle meningeal sends a small branch to the Tensor tympani muscle near its origin. The petrosal branch of the middle meningeal enters the tympanum by way of the hiatus canalis facialis. Minute branches from the posterior branch of the middle meningeal pass through the petrosquamous fissure and are distributed to the antrum and epi- tympanic recess. Two tympanic branches come off from the internal carotid artery in its course through the carotid canal. A branch from the ascending pharyngeal and another from the Vidian accompany the Eustachian tube. The two tympanic branches from the internal carotid are given off in the carotid canal and perforate the thin anterior wall of the tympanum. The veins of the tympaniun terminate in the pterygoid plexus, the middle meningeal vein, and the superior petrosal sinus. The nerves of the tympanum constitute the tjmipanic plexus (plexus tympanicus [Jacobsoni]), which ramifies upon the surface of the promontory (Fig. 848). The plexus is formed by (1) the tympanic branch of the glossopharyngeal; (2) the small deep petrosal nerve; (.3) the small super- ficial petrosal nerve; and (4) a branch which joins the great superficial petrosal. The t3rmpanic branch of the glossopharjmgeal or Jacobson's nerve {n. fijmpanicus) enters the tympanum by an aperture in its flcior close to the inner wall and divic'e^ info branches, which ramify on the promontory and enter into the formation of the plexus. The small deep petrosal nerve (;i. pelrosiis profundus), from the carotid plexus of the sympathetic, passes through the wall of the carotid canal, and joins the branches of Jacobson's nerve. The branch to the great superficial petrosal passes through an opening on the inner wall of the tympanum in front of the fenestra ovalis. The small superficial petrosal nerve (n. pdrosus siiperjicmlis minor), derived from the otic ganglion, passes through a foramen {canaliculus innominafus) in the middle fossa of the base of the skull (sometimes through the foramen ovale), passes backward and enters the petrous bone through a small aperture, situated external to the hiatus canalis facialis on the anterior surface of this bone; it then courses downward through the bone, and, passing by the geniculate ganglion, receives a connecting filament from it (Fig. 845) and enters the tympanic cavity, where it communicates with Jacobson's .nerve, and assists in forming the tympanic plexus. The branches of distribution of the tympanic plexus are supplied to the mucous membrane of the tympanum; one special branch passing to the fenestra ovalis, another to the fenestra ro- tunda, and a third to the Eustachian tube. The small superficial petrosal may be looked "upon as the continuation of the tympanic nerve (Jacobson's) through the plexus to the otic ganglion. In addition to the tympanic plexus there are the nerves supplying the muscles. The Tensor tympani is supplied by a branch from the third division of the trigeminal through the otic gan- glion, and the Stapedius by the tympanic branch of the facial. The chorda tympani (Figs. 835 and 838) crosses the tympanic cavity. It is apparently given off from the facial as it passes vertically downward at the back of the tympammi, about 6 mm. (a quarter of an inch) before its exit from the stylomastoid foramen. It passes from below upward and forward in a distinct canal, and enters the cavity of the tympanum through an aperture, iter chordae posterius, already described (p. 1 126), and becomes invested with mucous membrane. It passes forward, through the cavity of the tympanum, crossing internal to the membrana tympani and over the handle of the malleus to the anterior inferior angle of the tym- panum, and emerges from that cavity through the iter chordae anterius or canal of Hugtiier (p. 1126). Applied Anatomy. — The principal point in connection with the surr/ical anatomy of the ti/mpanum is its relations to other parts. Its roof is formed by a thin plate of bone, which, with the dura, is all that separates it from the temporal lobe of the brain. Its floor is immediately above the jugular fossa and the carotid canal, the fossa being behind and the canal in front. Its posterior wall presents the opening of the viastoid cells. On its anterior wall is the opening of the Eustachian tube. Thus, it follows that in disease of the middle ear we may get subdural abscess, septic meningitis, or abscess of the cerebrum or cerebellum, from extension of the inflam- mation through the bony roof; thrombosis of the lateral si7ius, with or without pyemia, by ex- tension through the floor; or mastoid abscess by extension backward. In addition to this, there may be fatal hemorrhage from the internal carotid in destructive changes of the middle ear; and in tliroat disease we may get the inflammation extending up the Eustachian tube to the 1136 THE ORGANS OF SPECIAL SENSE . middle ear. The Eustachian tube is accessible from the nose. If the nose and mouth be closed and an attempt made to expire air, a sense of pressure with dulness of hearing is produced in both ears, from the air finding its way up the Eustachian tube and bulging out the membrana tympani. During the act of swallowing, the pharyngeal orifice of the tube, which is normally closed, is opened, probably by the action of the Dilatator tubse muscle. This fact was employed by Politzer in devising an easy method of inflating the tube. The nozzle of a rubber swinge is inserted into the nostril ; the patient takes a mouthful of water and holds it in his mouth, both nostrils are closed with the finger and thumb to prevent the escape of air, and the patient is then requested to swallow; as he does so the surgeon squeezes the bulb and the air is forced out of the syringe into the nose, and is driven into the Eustachian tube, which is now open. The impact of the air against the membrana tympani can be heard by the surgeon, if the membrane is intact, sound being conveyed by means of a piece of rubber tubing, one end of which is inserted into the meatus of the patient's ear, the other into that of the surgeon. The direct examination of the Eustachian tube is made by the Eustachian catheter. This is passed along the floor of the nostril, close to the septum, with the point touching the floor, to the posterior wall of the pharynx. ^Vhen this is felt, the catheter is to be withdrawn about half an inch, and the point rotated out- ward through a quarter of a circle, and pushed again slightly backward, when it will enter the orifice of the tube, and will be found to be caught, and air forced into the catheter will be heard impinging on the tympanic membrane if the ears of the patient and surgeon are connected by a rubber tube. THE INTERNAL EAR, OR LABYRINTH (AURIS INTERNA). The internal ear is the essential part of the organ of hearing and of orientation in space. It is called the labyrinth, from the complexity of its shape, and consists of two parts, the osseous labyrinth, a series of cavities channelled out of the sub- stance of the petrous portion of the temporal bone, and the membranous labyrinth, the latter being contained within the former. Opening of aqiiedudui leibbuh Bristle passed thi ough fot amen lotundum Opening of aqueductus coUileje Fig. 856. — The osseous labyrinth laid open (enlarged.) The Osseous Labyrinth (labyrinthus osseus) (Fig. 856) consists of three parts • — the vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the substance of the bone, and lined by periosteum and endothelium. A clear fluid is contained in the space between the osseous labyrinth and the membranous labyrinth. The space is called the perilymph space, and the fluid is called peri- lymph. The Vestibule {testihidiim) (Figs. 849 and 856) is the common central cavity of communication between the parts of the internal ear. It is situated on the inner side of the tympanum, behind the cochlea, and in front of the semicircular canals. THE INTERNAL EAR, OR LABYRINTH 1137 It is somewhat ovoid in shape, flattened from within outward, and measures about 5 mm. (one-fifth of an inch) from before backward, as well as from above downward, and about 3 mm. (one-eiolith of an inch) from without inward. On its outer or tympanic wall is the fenestra ovalis {fenestra vesfibuli), closed, in the recent state, by the base of the stapes, and its annular ligament. On its inner wall, at the fore part, is a small circular depression, the spherical recess (recessus sphaeri- cus), in which the saccule is placed. This recess is perforated, at its anterior and inferior part, by about a dozen minute holes ( macula cribrosa media), for the passage of filaments of the vestibular nerve to the saccule. Above and behind this depression is an oblique ridge, the crista vestibuli, the anterior extremity of which is called the pyramid {pyramis vestibuli). This ridge bifurcates posteriorly to enclose a small depression, the recessus cochlearis, which is perforated by eight small holes for the passage of filaments of the auditory nerve which supply the basal end of the ductus cochlearis. An oval depression is placed in the roof and inner wall of the vestibule above and behind the crista vestibuli. It is called the fovea hemielliptica, elliptical recess, or spherical recess (recessus ellipticus), and receives the utricle. The pyramid and the adjacent elliptical recess are per- forated by numerous minute foramina {macula cribrosa superior). The openings in the pyramid transmit filaments from the vestibular nerve to the utricle; the openings in the elliptical recess transmit filaments from the vestibular nerve to the ampullse of the superior and lateral semicircular canals. Below and behind the elliptical recess is a groove which deepens into a canal and is called the aquae - ductus vestibuli. This canal passes to the posterior surface of the petrous portion of the temporal bone and opens as a mere crack between the internal auditory meatus and the groove for the lateral sinus. It transmits a small vein, and con- tains a tubular prolongation of the lining membrane of the vestibule, the ductus endolymphaticus, which ends in a cul-de-sac between the layers of the dura mater within the cranial cavity. Behind, the semicircular canals open into the vestibule by five orifices. In froiit is an elliptical opening, which communicates with the scala vestibuli of the cochlea by an orifice, apertura scalae vestibuli cochleae. This opening is bounded below by a thin plate of bone (lamina spiralis ossea), which takes origin from the vestibular floor external to the spherical recess and in the cochlea forms the bony portion of the partition between the scala tympani and the scala vestibuli. In the anterior portion of the vestibular floor is a fissure (fissura vestibuli), which passes into the bony part of the canal of the cochlea. The external boundary of this fissure is a small, thin plate of bone (lamina spiralis secundaria). The Bony Semicircular Canals (canales semicirculares ossei ) (Fig. S56) are three bony canals situated above and behind the vestibule. They are of unequal length, compressed from side to side, and each describes the greater part of a circle. They measure about 0.8 mm. (one-thirtieth of an inch) in diameter, and each presents a dilatation at one end, called the ampulla ossea, which measures more than twice the diameter of the tube. These canals open into the vestibule by five orifices, one of the apertiu'es being common to two of the canals. The superior semicircular canal (canalis semicircidaris superior), 15 to 20 mm. in length, is vertical in direction, and is placed transversely to the long axis of the petrous portion of the temporal bone, on the anterior surface of which its arch forms a round projection. It describes about two-thirds of a circle. Its outer extremity, which is ampullated, communicates by a distinct orifice with the upper part of the vestibule; the opposite end of the canal, which is not dilated, joins Math the corresponding part of the posterior canal to form the cms commune, which opens into the upper and inner part of the vestibule. The posterior semicircular canal (canalis semicircidaris posterior), also vertical in direction, is directed backward, nearly parallel to the posterior surface of the 1138 THE ORGANS OF SPECIAL SENSE petrous bone; it is the longest of the three, measuring from 18 to 22 mm. ; its ampul- iated end commences at the lower and back part of the vestibule, its opposite end joining to form the common canal already mentioned. In the wall of the ampulla of the posterior canal are a number of small openings (macula cribrosa inferior) for the passage of nerves to the ampulla. The lateral or horizontal canal (canalis semicircidaris lateralis) is the shortest of the three. It measures from 12 to 15 mm., and its arch is directed outward and backward; thus each semicircular canal stands at right angles to the other two. Its ampullated end corresponds to the upper and outer angle of the vesti- bule, just above the fenestra ovalis, where it opens close to the ampullar^ end of the superior canal; its opposite end opens by a distinct orifice at the upper and back part of the vestibule. The cochlea (Figs. 856 and 857) bears some resemblance to a common snail- shell; it forms the anterior part of the labyrinth, is conical in form, and placed almost horizontally in front of the vestibule; its apex (cufula) is directed forward and outward, with a slight inclination downward, toward the upper and front part Fig. 857. — Osseous cochlea in vertical section. The broken, white lines indicate the position of the basilar membrane of the canal of the cochlea. Semidiagrammatic. (Testut.) of the inner wall of the tympanum; its base (basis cochleae) corresponds with the anterior depression at the bottom of the internal auditory meatus, and is perforated by numerous apertures for the passage of the cochlear divisions of the auditory nerve. It measures nearly a quarter of an inch (5 mm.) from base to apex, and its breadth across the base is somewhat greater (about 9 mm.). It consists of a conical-shaped central axis, the modiolus; of a canal, the bony canal of the cochlea, the inner wall of which is formed by the central axis, wound spirally around it for two turns and three-quarters, from the base to the apex, and of a delicate lamina, the lamina spiralis ossea, which projects from the modiolus, and, following the windings of the canal, partially subdivides it into two. In the recent state a mem- brarie, the membrana basilaris, stretches from the free border of this lamina, to the outer wall of the cochlea, and separates this canal into two passages, except where they communicate with each other at the apex of the modiolus by a small opening, named the heUcotrema. The Modiolus (Figs. 858 and 859) is the central axis or pillar of the cochlea. It is conical in form, and extends from the base to the apex of the cochlea. Its base (basis modioli) is broad, and appears at the bottom of the internal auditory THE INTERNAL EAB, OB LAB YBINTH 1139 meatus, where it corresponds with the area cochleae. It is perforated hy numerous orifices, which transmit fihxments of the cochlear division of tiie audi- tory nerve, the nerves for the first turn and a half being transmitted through the foramina of the tractus spiralis f oraminosus ; those for the apiCal, turn through the TRACTUS SPIRALIS FORAMINOSUS LAMINA SPIRALIS OSSEA Fig. 858. — Vertical section through the right cochleo, medial portio 1 the lateral side. (Spalteholzj. foramen centrale. The foramina of the tractus spiralis foraminosus pass up through the modiolus and successively bend outward to reach the attached margin of the lamina spiralis ossea. Here they become enlarged, and by their apposition form a spiral canal (canalis spiralis modioli), which follows the course of the attached Fig. 859. — The cochlea laid open (enlarged). margin of the lamina spiralis ossea and lodges the ganglion spirals (of Corti) (ganglion spirale cochleae). The foramen centrale is continued as a canal up the middle of the modiolus to its apex, and from this canal numerous minute foramina pass outward to the unattached edge of the lamina spiralis. In the foramina are vessels and nerves. The modiolus diminishes rapidly in size in the second and succeeding' coil. 1140 '^'HE ORGANS OF SPECIAL SENSE The bony canal or the spiral canal of the cochlea (canalis spiralis cochleae) (Fig. 859) takes two turns and three-quarters around the modiolus. The first turn of the canal is called the basal coil, the second is called the central coil, the third turn is called the apical coil. The promontory on the inner wall of the tympanic cavity is caused by the basal coil. The bony canal of the cochlea is a little over an inch (about 30 mm.) in length, and diminishes gradually in size from the base to the summit, where it terminates in the cupola (cupula), which forms the apex of the cochlea. The commencement of this canal is about a tenth of an inch (2.5 mm.) in diameter; it diverges from the modiolus toward the tympanum and vesti- bule, and presents three openings. One, the fenestra rotunda, communicates with the tympanum; in the recent state this aperture is closed by a membrane, the mem- brana tympani secundaria. Another aperture, of an elliptical form, opens into the vestibule. The third is the aperture of the aquaeductus cochleae, leading to a minute funnel-shaped canal, which opens on the basilar surface of the petrous bone internal to the jugular fossa, and transmits a small vein, and also forms a communication between the subarachnoidean space of the skull and the peri- lymph space in the scala tympani. The lamina spiralis ossea is a bony shelf or ledge which projects outward from the modiolus into the interior of the spiral canal, and, like the canal, takes nearly two and three-quarter turns around the modiolus. It reaches about half-way toward the outer wall of the spiral canal, and partially divides its cavity into two passages or scalae, of which the upper is named the scala vestibuli, while the lower is termed the scala tympani. Near the summit of the cochlea the lamina terminates in a hook-shaped process, the hamulus {hamulus laminae spiralis), which assists in forming the boundary of a small opening, the helicotrema, by which the two scalae communicate with each other. From the canalis spiralis modioli numerous foramina pass outward through the osseous spiral lamina as far as its outer or free edge. In the lower part of the first turn a second bony lamina (lamina spiralis secundaria) projects inward from the outer wall of the bony tube; it does not, however, reach the primary osseous spiral lamina, so that if viewed from the vestibule a narrow fissure, the fissura vestibuli, is seen between them. The fundus of the internal auditory meatus is described on page 85. The Membranous Labyrinth (lahyrinthus viembranaceus) (Figs. 860 and 861) is contained within the bony cavities just described, having the same general form as the cavities in which it is contained, though considerably smaller, being separated from the bony walls by a quantity of fluid, the perilymph (perilympha). It does not, however, float loosely in this fluid, but in places is fixed to the walls of the cavity. The membranous sac contains fluid, the endolymph (endolympha), and on the sac the ramifications of the auditory nerve are distributed. Within the osseous vestibule the membranous labyrinth does not quite preserve the form of the bony cavity, but presents two membranous sacs, the utricle and the saccule. The Utricle (utricidtis) is the larger of the two, of an oblong form, compressed laterally, and occupies the upper and back part of the vestibulcj lying in contact with the fovea semielllptica and the part below it. The highest portion of the utricle is called the recess (recessus utriculi); it is placed in the elliptical recess, and opening into it are the ampullae of the superior and lateral semicircular canals. The central portion of the recess of the utricle receives upon the side the lateral semicircular canal. This opening has no ampulla. The superior sinus is a prolongation upward and backward from the central portion of the utricle and in the superior sinus the crus commune and the superior and posterior semi- circular canals open. The lower and inner portion of the utricle is the inferior sinus, and into it the ampulla of the posterior semicircular canal opens. The floor and anterior wall of the recess of the utricle are much thicker than else- THE INTERNAL EAR, OR LAB YRINTH 1141 where, and form the macula acustica utriculi, which receives the utricular filaments of the auditory nerve and has attached to its internal surface a layer of calcareous particles which are called otoliths, The cavity of the utricle communicates behind ^ Ductus Endolymphaticus Fig. S60. — The membranous labyrinth (enlarged). with the membranous semicircular canals by five orifices. From its anterior wall is given off a small canal (ductus utriculosaccularis), which joins with a canal from the saccule, the ductus endolymphaticus. The Saccule {sacculiis) is the smaller of the two sacs; it is globular in form, lies in the recessus sphaericus near the opening of the scala vestibuli of the coch- BRANCH OF VESTIBULAR NERVE DUCT OF SUPERIOR SEMICIRCULAR CANAL AMPULLA OF EXTERNAL MEMBRANO Fig. 861. — The right membranous labyrinth of an adult, isolated, medial and poste view. (Spalteholz.) lea. Its anterior part exhibits an oval thickening, the macula acustica sac- culi, to which are distributed the saccular filaments of the auditory nerve. Its cavity does not directly communicate with that of the utricle. From the pos- 1142 THE ORGANS OF SPECIAL SENSE terior wall is given off a canal, the ductus endolymphaticus. This duct is joined by the ductus utriculosaccularis, and then passes along the aquaeductus vestibuli and ends in a blind pouch on the posterior surface of the petrous portion of the tem- poral bone, where it is in contact with the dura. From the lower part of the saccule a short tube, the canalis reuniens of Hensen {ductus reuniens [Henseni]), passes downward and outward to open into the ductus cochlearis near its vestibular extremity. The Membranous Semicircular Canals (ductus seniicircidares) are about one-third the diameter of the osseous canals, but in number, shape, and general form they are precisely similar, and each presents at one end an ampulla (ampullae mem- branaceae). The canals open by five orifices into the utricle, one opening being common to the inner end of the superior and the upper end of the posterior canal. In the ampulla; the wall is thickened, and projects into the cavity as a fiddle-shaped, transversely placed elevation, the septum transversum, in which the nerves end. The utricle, saccule, and membranous canals are attached here and there to the bone by numerous fibrous bands, the so-called ligaments (ligamenta lahy- rinthi canalicular U7n). Otolithic membrane C%lia Fig. 862.- — Floor of scala media, showing the organ of Corti, etc. Outtcnla membrani' Hair cells — L Sustentacular \^_ cells Epitlielium of -sC^ propria. Fig. S63. — Trans-section of the maigin of the maculi sacculi of a guinea-pig. X 325. (After KoUiker.) Structure. — The walls of the utricle, saccule, and membranous semicircular canals consist of three layers. The outer layer is a loose and flocculent structiu-e, apparently composed of ordi- . nary fibrous tissue, containing bloodvessels and pigment cells. The middle layer, thicker and more transparent, bears some resemblance to the hyaloid membrane, but it presents on its inter- nal siu-f ace, especially in the semicircular canals, numerous papilliform projections, and, on the THE INTERNAL EAR, OR LABYRINTH 1143 addition of acetic acid, presents an appearance of longitudinal fibrillation and elongated nuclei. The inner layer is formed of simple polygonal epithelial cells. In the macula; of the utricle and sncculc, and in the transverse septa of the ampuUse of the canals, the middle coat is thickened; the (■i)ith(liiim is columnar, is increased in height, and passes into the neuroepithelium. The neuroepithelium consists of supporting cells and hair cells. 1. The supporting cells are long and fusiform, and contain an oval nucleus. Their deep ends are attached to the membrana propria, while their free extremities are united to form a thin cuticle. The protoplasm contains yellowish pigment granules. 2. The hair cells are columnar, with bulged lower ends and free upper ends. The bulged lower ends, each of which contains a spherical nucleus, do not reach higher than the middle of the epithelial layer. Each free upjier end is surmounted by a long, tapering filament. These filaments constitute auditory hair, and they project into the cavity. Each filament is found to consist of many fine hairs. The filaments of the auditory nerve enter these parts, and, having pierced the outer and thickened middle layer, they lose their myelin sheaths, and their axones divide into three or four branches at the larger and deeper ends of the hair cells. These branches form a horizontal plexus {stratwrti plexifomie). Numerous small prismatic bodies termed statoUths, otoconia, or otoUths, and consisting of a mass of minute crystalline grains of carbonate of lime, held together in a gelatinous substance, are contained in the walls of the utricle and saccule opposite the distribution of the nerves. The membrane is called the otolith membrane. A calcareous material is also, according to Bowman, .sparingly scattered in the cells lining the ampullfe of the semicircular canals. The conical thickening in the ampulla corresponds to the otolith membrane. OCHLEAR NERVE ^L^' AND GANGLION Fig. S64. — Cochlea in transverse section. Observe especially the canal of the cochle branous labyrinth. (Testut. ) part of the mem- The membranous cochlea, ductus cochlearis, or scala media consists of a spirally arranged tube enclosed in the bony canal of the coclilea and lying along its outer wall. The osseous spiral lamina, as already stated, extends only part of the distance between the modiolus and the outer bony wall of the cochlea. A membrane, the basilar membrane {membrana basilaris) (Fig. 862), stretches from its free edge 1144 THE ORGANS OF SPECIAL SENSE NERVE-FIBRES PASSING OUT GANGLION SPIRAL BETWE EN TH E TWO LAYERS I SPIRALE FIBRES LAM N A SPI RALIS OSSEA to the outer wall of the cochlea, and completes the roof of the scala tympani. A second and more delicate membrane, the membrane of Reissner (memhraiia vestibularis [Reissneri]) (Fig. 862), extends from the thickened periosteum covering the lamina spiralis ossea, at an angle of about 45 degrees, to the outer wall of the cochlea, to which it is attached at some litde distance above the membrana basilaris. A canal is thus shut off between the scala tympani below and the scala vestibuli above; this is the membranous canal of the cochlea (ductus cochlearis or scala media) (Fig. 863). It is triangular on transverse section, its roof being formed by the membrane of Reissner, its outer wall by the periosteum which lines the bony canal, and its floor by the membrana basilaris, and the outer part of the lamina spiralis ossea, on the former of which is placed the organ of Corti. Reissner's membrane is thin and homogeneous, and is covered on its upper and under surfaces by a layer of epithelium. The periosteum, which forms the outer wall of the ductus cochlearis, is greatly thickened and altered in character; forming what is called the spiral liga- ment of the cochlea (ligamentum spirale cochleae) {Fig. 862). It projects in- ward below as a triangular promi- nence, the crista basilaris, which gives attachment to the outer edge of the membrana basilaris, and immediately above which is a concavity, the sulcus spiralis extemus (Fig. 862). The upper portion of the ligamentum spirale contains numerous capillary loops and small bloodvessels within the epithelium, and forms what is termed the stria vascularis. The stria is limited below by a prominence {prominentia spiralis), in which a bloodvessel {yas pronii- nens) is distinctly visible. The lamina spiralis ossea (Fig. 86.3) consists of two plates of bone extending outward; between these are the canals for the transmission of the filaments of the auditory nerve. On the upper plate of that part of the osseous spiral lamina which is outside Reissner's membrane the periosteum is thickened to form the limbus laminae spiralis, and this terminates externally in a concavity, the sulcus spiralis intemus, which presents, on section, the form of the letter C; the upper part of the letter, formed by the overhanging extremity of the limbus, is named the labium vestibulare ; the lower part, prolonged and tapering, is called the labium tympanicum, and is perforated by numerous foramina (foramina nervosa) for the passage of the component parts of the cochlear nerve. Externally, the labium tympanicum is continuous with the membrana basilaris. The upper surface of the labium vestibulare is intersected at right angles by a number of furrows, between which are numerous elevations; these present the appearance of teeth along the free margin of the labium, and have been named by Huschke the audi- tory teeth. The basilar membrane may be divided into two areas, inner and outer. The inner is thin, and is named the zona arcuata or zona tecta (Fig. 862) ; it supports the organ of Corti. The outer is thicker and striated, and is termed the zona pectinata. The under surface of the membrane is covered by a layer of vascular connective tissue. One of these vessels is somewhat larger than the rest, and is named the vas spirale (Fig. 866) ; it lies below Corti's tunnel. The organ of Corti^ (organon spirale [Cortii]) (Figs. 866 and 867) is situated upon the inner part of the membrana basilaris within the canal of the ductus T^G. 865. — Part of the cochlear nerve, highly magnified. (Henle.) 1 Corti's original paper is in the Zeitschrift f. Wissen. Zool., iii, 109. THE INTERNAL EAJR, OB LABYRINTH 1145 cochlearis and appears as a ridge {crista spiralis), winding spirally throughout the whole length of the ductus cochlearis. It is seen to be composed of a remarkable arrangement of cells, which may be likened to the keyboard of a piano. Of these cells, the central ones are rod-like bodies and are called the inner and outer rods or pillars of Corti. Their bases are expanded and placed on the basilar membrane, Memhiana iectona Outer hair cells Deiters Ovter rod. Basilar membrane. Fig. 866. — Section through the organ of Corti. Magnified. (G. Retzius.) Aeri'e fibres. at some little distance from each other, while their intermediate portions are inclined toward each other, so as to meet at their opposite extremities, and form a series of arches roofing over a minute tunnel, the canal or tunnel of Corti, be- tween them and the basilar membrane, which ascends spirally through the whole length of the cochlea. Fig. 867. — Organ of Corti. Diagr.imm:itic riew of a small portion. (Testut.) The inner rods (Fig. 866), some 6000 in number, are more numerous than the outer ones, and rest on the basilar membrane, close to the labium tympanicum; they project obliquely upward and outward, and terminate above in ex-panded extremities which resemble in shape the upper end of the ulna, with its sigmoid cavity, coronoid and olecranon processes. On the outer side of the rod, in the 1146 THE ORGANS OF SPECIAL SENSE angle formed between it and the basilar membrane, is a nucleated mass of proto- plasm; while on the inner side is a row of epithelial cells, the inner hair cells (Fig. 866), surmounted by a brush of fine, stiff, hair-like processes. On the inner side of these cells are two or three rows of columnar supporting cells, which are con- tinuous with the cubical cells lining the sulcus spiralis internus. The outer rods (Fig. 866) , numbering about 4000, also rest by broad foot-plates on the basilar membrane; they incline upward and inward, and their upper extrem- ity resembles the head and bill of a swan; the back of the head fitting into the concavity — the analogue of the sigmoid cavity — of one or more of the internal rods, and the bill projecting outward as a phalangeal process of the membrana reticu- laris, presently to be described. In the head of these outer rods is an oval portion, where the fibres of which the rod appears to be composed are deficient, and which stains more deeply with carmine than the rest of the rod. At the base of the rod, on its internal side — ■ that is to say, in the angle formed by the rod with the basilar membrane — is a similar protoplasmic mass to that found on the outer side of the base of the inner Fig. 868. — Longitudinal section of the cochlea, showing the relations of the scalse, the ganglion spirale, etc. 5.V". Scalavestibuli. 5.2*. Scala tympani. S.ilf. Scala media. L.»S. Ligamentum spirale. G'..S. Ganglion spirale. rod; these masses of protoplasm are probably the undifferentiated portions of the cells from which the rods are developed. External to the outer rod are three or four successive rows of epithelial cells, more elongated than those found on the internal side of the inner rod, but, like them, furnished with minute hairs or cilia. These are termed the outer hair cells, in contradistinction to the inner hair cells above referred to. There are about 12,000 outer hair cells, and about 3500 inner hair cells. The hair cells are somewhat oval in shape; their free extremities are on a level with the heads of Corti's rods, and from each some twenty fine cilia project and are arranged in the form of a crescent, the concavity of which opens inward. The deep ends of the cells are rounded and contain large nuclei; they reach only as far as the middle of Corti's rods, and are in contact with the rami- fications of the nerve filaments. Between the rows of the outer hair cells are rows of supporting cells, called the cells of Deiters; their expanded bases are planted on the basilar membrane, while their opposite ends present a clubbed extremity or phalangeal process. Immediately to the outer side of Deiters' cells are some THE INTERNAL EAR, OB LABYRINTH 1147 five or six rows of columnar cells, the supporting cells of Hensen. Their Ijases are narrow, while their upper parts are expanded and form a rounded elevation on the floor of the ductus cochlearis. The columnar cells lying outside Hensen's cells are termed the cells of Claudius. A space is seen between the outer rods of Corti and the adjacent hair cells; this is called the space of Nuel. The lamina reticuhris, or membrane of Kolliker, is a delicate framework perfo- rated by rounded holes. It extends from the inner rods of Corti to the external row of the outer hair cells, and is formed by several rows of "minute fiddle-shaped cuticular structures" called phalanges, between which are circular apertures containing the free ends of the hair cells. The innermost row of phalanges consists of the phalangeal processes of the outer rods of Corti; the outer rows are formed by the modified free ends of Deiters' cells. Covering over these structures, but not touching them, is the membrana tectoria or membrane of Corti (Figs. 862 and 866), which is attached to the vestilnilar sur- face of the lamina spiralis close to the attachment of the membrane of Reissner. It is thin near its inner margin, and overlies the auditory teeth of Huschke. Its outer half is thick, and along its lower edge, opposite the inner hair cells, is a clear band, named Hensen's stripe. Externally, the membrane becomes much thinner, and is attached to the outer row of Deiters' cells (Retzius). It is made up of multitudes of delicate fibres embedded in a transparent matrix of a soft, transparent collagenous character with marked adhesiveness (Hardesty). The osseous labyrinth is lined by an exceedingly thin fibroserous membrane, analogous to a periosteum, from its close adhesion to the inner surfaces of these cavities, and performing the office of a serous membrane by its free surface. It lines the vestibule, and from this cavity is continued into the semicircular canals and the scala vestibuli of the cochlea, and through the helicotrema into the scala tympani. A delicate tubular process is prolonged along the aqueduct of the vesti- bule to the inner surface of the dura. This membrane is continued across the fenestra ovalis and fenestra rotunda, and consequently has no communication with the lining membrane of the tympanum. Its attached surface is rough and fibrous, and closely adherent to the bone; its free surface is smooth and pale, covered with a layer of epithelium, and secretes a thin, limpid fluid, the perilymph. The scala media (ductus cochlearis) is closed above and below. The upper blind extremity is termed the lagena, and is attached to the cupola at the upper part of the helicotrema; the lower end is lodged in the recessus cochlearis of the vesti- bule. Near this blind extremity, the scala media receives the canalis reuniens of Hensen (Fig. 860), a very delicate canal, by which the ductus cochlearis is brought into continuity with the saccule. The auditory nerve (n. acusticiis), the special nerve of the senses of hearing and of equilibrium, divides, at the bottom of the internal auditory meatus, into two branches, the cochlear and vestibular. The vestibular nerve {n. vestibularis), the posterior of the two, presents, as it lies in the internal auditory meatus, a ganglion, the vestibular ganglion or the ganglion of Scarpa (ganglion vestibulare) ; the nerve divides into three branches which pass through minute openings at the upper and back part of the bottom of the meatus (area vestibularis posterior), and, entering the vestibule, are distributed to the utricle and to the ampulla of the external and superior semicircular canals. The nerve filaments enter the ampullary enlargements opposite the septum trans- versum, and arborize around the hair cells. In the utricle and saccule the nerve fibres pierce the membrana propria of the maculie, and end in arborizations around the hair cells. "The cochlear nerve (n. cochlearis) gives off the branch to the saccule, the fila- ments of which are transmitted from the internal auditory meatus through the foramina of the area vestibularis inferior, which lies at the lower and back part 1148 THE ORGANS OF SPECIAL SENSE of the floor of the meatus. It also gives off the branch for the ampulla of the pos- terior semicircular canal, which leaves the meatus through the foramen singnlare. The rest of the cochlear nerve divides into numerous filaments at the base of the modiolus; those for the basal and middle coils pass through the foramina in the tractus foraminosus, those for the apical coil through the canalis centralis, and the nerves bend outward to pass between the lamellae of the osseous spiral lamina. Occupying the spiral canal of the modiolus is the spiral ganglion, or ganglion of Corti (ganglion spirale), consisting of bipolar nerve cells, which really constitute the true cells of origin of this nerve, one pole being prolonged centrally to the brain and the other peripherally to the hair cells of Corti's organ. Reaching the outer edge of the osseous spiral lamina, the nerve fibres pass through the foram- ina in the labium tympanicum. Some of these fibres end by arborizing around the bases of the inner hair cells, while others pass between Corti's rods and across the tunnel, to terminate in a similar manner in relation to the outer hair cells. The arteries of the Iab\Tinth are the internal auditory, from the basilar, and the stylomas- toid, from the posterior auricular. The internal auditory divides at the bottom of the internal auditory meatus into two branches, cochlear and vestibular. The cochlear artery divides into numerous minute branches, which enter foramina in the tractus spiralis foraminosa and course in the lamina spiralis ossea to reach the membranous structures. The largest of the cochlear branches is in the canalis centralis. The vestibular branches accompany the nerves, and sup- ply the membranous structures in the vestibule and semicircular canals. Tno arteries go to each canal. The two vessels enter opposite extremities of the canal, and anastomose at the summit of the canal. The vestibular vessels form a minute capillary network in the substance of each membranous labyrinth. The veins of the vestibule and semicircular canals, the auditory veins, accompany the arteries, and receive those of the cochlea at the base of the modiolus, to form the internal auditory vein {vv. auditivae internae), which opens into the posterior part of the inferior petrosal sinus or into the lateral sinus. THE ORGANS OP TASTE (ORGANON GUSTUS). The peripheral organs of the sense of taste consist of certain flask-shaped groups of modified epithelial cells, termed taste buds (calyculi gusfatorii), situated on the tongue and adjacent parts. They occupy nests in the stratified epithelium W -?^*^f ''''^' ^:'^'.%s^ Fig. 869. — Section of part of the papilla foliata of a rabbit. (Magnified.) and are present in large numbers on the sides of the circumvallate papillae (Fig- 869), and to a less extent on their opposed walls. They are also found on the fungiform papillae over the back part and sides of the tongue, and in the general THE SKIN 1149 epithelial covering of the same areas. They are very plentiful over the fimbriae linguae, and are also present on the under aspect of the soft palate, uvula, and on the lingual surface of the epiglottis. Each taste bud is flask-like in shape, its broad base resting on the corium, and the neck opening by an orifice, the gustatory pore, between the cells of the epithe- lium. The bud is formed by two kinds of cells, supporting cells and gustatory cells. The supporting cells are mostly arranged like the staves of a cask, and form an outer envelope for the I)ud. Some, however, are found in the interior of the bud between the gustatory cells. The gustatory cells occupy the central portion of the bud; they are spindle-shaped, and each possesses a large spherical nucleus near the middle of the cell. The peripheral end of the cell terminates at the gustatory pore in a fine, hair-like filament, the gustatory hair. The central pro- cess passes toward the deep extremity of the bud, and there ends in a single or bifurcated varicose filament, which was formerly supposed to be continuous with the terminal fibril of a nerve; the investigations of Lenhossek and others would seem to prove, however, that this is not so, but that the nerve fibrils after losing their myelin sheaths enter the taste bud, and terminate in fine extremities between Guntatory knirs Taste pore Epithelium- Tunica propria — r^- FiG. 870. — Taste buds from the papilla foliata of a rabbit. X 850. (Szymonowicz.) the gustatory cells. Other nerve fibrils may be seen ramifying between the sup- sporting cells and terminating in fine extremities; these, however, are believed to be nerves of ordinary sensation, and not gustatory. "The latest researches have shown that dendrites of sensor neurones (sensor nerves) enter the taste buds and end free in telodendria. The latter surround the neuroepithelial, and, to some extent, the sustentacular cells, their relations depending on contact.'" Nerves of Taste. — The chorda tympani nerve is generally regarded as the nerve of taste for the anterior two-thirds of the tongue; the nerve for the posterior third is the glosso- pharyngeal. THE SKIN (INTEGUMENTUM COMMUNE). The skin covers the body surface and is continuous with the mucous membrane at the origin and termination of the alimentary canal and at the openings of other canals. The skin is a protective coat, a regulator of body temperature, contains multitudes of the terminations of sensor nerves, and is the seat of the organ 0/ ' Journ.il of Anatomy and Physiology, 1891. 1150 THE ORGANS OF SPECIAL SENSE touch (organon tactus). These nerve organs are connected with nerve fibres of temperature, pressure, and pain. Connected with the skin are sw'eat glands which have important excretory functions and sebaceous glands. From its superficial part come appendages, the hairs, and nails. The skin is elastic and varies in thickness from 0.5 mm. to 4 mm. (-gig- to \ inch). It is thinnest in the eyelids and prepuce, and thickest over the back of the neck, back of the shoulders, palms of the hands, and soles of the feet. Its color depends in part on the blood within it, and in part upon pigment. The deepest hue is about the anus, in the genital region, in the axillae, over the mammary glands, and in the parts exposed to air, light, and varied temperatures. The color varies with age, being pinkish in extreme youth and becoming yellow in old age. It varies with exposure and with climate, being deepest in those who brave all weathers and temperatures and in those who dwell beneath a tropical sun. It also varies with race, and this is so well recognized that races are classified by the color of the skin into the White, Yellow, Brown, and Black races. The color of the skin is also affected in certain dis- eases; being extremely pale in anemia, bi-own in Addison's disease, yellow in jaundice, etc. In most situations the skin is mov- able, but in some it is attached closely to underlying structures, and is con- sequently immovable on the scalp, the palms of the hands, the soles of the feet, and the outer portion of the pinna of the ear. The skin is fairly smooth, but close examination dis- closes multitudes of openings, creases, furrows, depressions, folds, and hairs. Hair follicles open upon the surface, and the ducts of sebaceous glands and of sweat glands perforate the skin. About the joints are folds of skin (retinacula cutis), and temporary folds or wrinkles are created by the contraction of superficial muscles. The /aciaZ wrinkles of advancing years are due to habitual expression and loss of skin elasticity. A dimple is a permanent pit or depression due to adhesion of the surface to parts beneath. The ridges and furrows on the palms, soles, and flexor aspects of the digits are permanent, and over the palmar surface of the digits they are arranged in definite forms which endure through life and are so distinctive that they have been utilized by police officials in determining the identity of individuals. These folds are due to the papillae of the skin being arranged in rows ; some of the papillae proliferate, and linear depressions occur in the horny layer (Philippson). Fig. 871 shows skin ridges (cristae cutis), skin furrows (sulci cutis), furrows opposite joints due to acts of flexion, and called flexure furrows, and longitudinal furrows. When the skin is punctured by a round awl it tends to split in a definite direc- tion, which direction varies with the region stabbed. These clefts are known as the cleavage lines of Langer (Figs. 872 and 873) , and depend upon the arrange- ment of the connective-tissue bundles of the corium. These connective-tissue bundles certainly influence the formation of folds and fiu'rows. In many portions of the body the cutaneous surface is divided by linear furrows into irregularly LONGITUD1NA R'^Vn'1''^'*>>VM' ''■^VW'Jt.'S'* ^- FURROWS Fig. 879. — The furrows ; id ridges of true skin on the pahnar .surface having been removed. (Toldt.) ; of the fingers, the epidermis axillse, scrotum, labia majora). This is due to pigment within the epithelial and connective-tissue cells of the papillary layer of the corium, and in the basal cells of the epidermis. There are few or none of these pigmented cells in the stratum corneum of one of the Caucasian race. "In negroes and other colored races the deep pigmentation is due to a similar distribution of the pigment granules in the entire epidermis; but even here the Fig. 880. — The distribution of the bloodvessels in the skin of the sole of the foot. (Spalteholz.J pigmentation decreases toward the surface, although the uppermost cells of the stratum corneum always contain some pigment. The nuclei of the cells are always free from coloring matter. The Cjuestion as to the origin of the pigment is as yet unsolved.'" 1 A Text-book of Histology. By A. A. Bohm and M. von DavidoS. Translated and edited by G. Carl Huber. 1156 THE ORGANS OF SPECIAL SENSE The arteries supplying the skin vary in number, and vary much in size, being largest in re- gions exposed to pressure, as the skin of the palms, soles, and buttocks. The arteries enter the skin from a network in the subcutaneous tissue, and by an anastomosis in the deepest part of the corium form a network {rete arteriosuni cutaneum). The vessels send branches to the fat and to the sweat glands. Branches from the network just described ascend and form a second net- work in the corium beneath the papillae. This is called the subpapillary network (rete arfe- riosum subpapillare). From this network fine capillary vessels pass into liic papiihe, forming, in the smaller papillae, a single capillary loop, but in the larger a more or less comoluted vessel. From this network branches go to the hair follicles and sebaceous glands. The blood from the papillae passes into a plexus (rete venosum) beneath the papillae. This commimicates x^ith another plexus between the corium and subcutaneous tissue. In some regions one or more retia are interposed between these two. The veins from the sweat glands, sebaceous glands, superficial fat, and hair follicles are received by the retia venosa. From the deepest rete veins pass to the subcutaneous tissue, and these veins enter the large subcutaneous veins. There are numerous lymphatics supplied to the skin which form two networks, superficial and deep, communicating with each other and with the lymphatics of the subcutaneous tissue by oblique branches. They originate in the cell spaces of the tissue. The nerves of the skin terminate partly in the epidermis (Fig. 867) and partly in the cutis vera (Fig. 876). The former are prolonged into the epidermis from a dense plexus in the su])er- ficial layer of the corium and terminate between the cells in bulbous extremities; or, according to some observers, in the deep epithelial cells themselves. The latter terminate in end bulbs, touch corpuscles, or Pacinian bodies (Figs. 590 and 866), in the manner already described (p. 815), and, in addition to these, a considerable number of fibrils are distributed to the hair follicles, which are said to entwine about the follicle in a circular manner. Other ner^-e fibres are supplied to the smooth muscle fibres {mm. arrectorcs •pilormri) of the hair follicles and to the muscle coat of the bloodvessels. These are probably amyelinic fibres. THE APPENDAGES OF THE SKIN. The appendages of the skin are the nails, the hairs, the sudoriferous and seba- ceous glands, and their ducts. The nails and hairs are peculiar modifications of the epidermis, consisting essentially of the same cellular structure as that tissue. Stratum a i of the nail gi oove St) atum cot Ileum. ^f< atum q} atiutosum. ( UIIUM Fig. SSI.' — Longitudinal section through human nail and its c Davidoff's Histology.) ,il groove (sulcus). (From Bohm and The Nails (ungues) (Figs. 881 and 884) are flattened, elastic structures of a horny te.xture, placed upon the dorsal surface of the terminal phalanges of the fingers and toes. Each nail is convex on its outer surface, concave within. Its chief mass, called the body {corpus unguis), lies upon the nail bed. The free edge is called the margo liber. Each lateral margin (margo lateralis), like the pro.ximal short edge of the nail (margo occultus), lies in a groove of the cutis, the ungual sulcus (sulcus matricis unguis). The ungual wall (vallum unguis) overlies the lateral and posterior edges. The nail is implanted by means of a portion, called the root (radix unguis), into a groove in the skin. The root is beneath the ungual wall and is composed of cells which have not j'et become horny. It is white in color. The nail has a very firm adhesion to the cutis vera, being accurately moulded THE APPEND A GES OF THE SKIN 11. -,7 upon the surface of the true skin, as the epidermis is in other parts. The part of the cutis beneath the body and root of the nail is called the matrix (matrix unguis), because it is the part from which the nail is produced. Correspondint; to the body of the nail, the matrix is thick, and raised into a series of longitudinal ridges (cristae viatricis unguis), which are very vascular, and the color is seen through the transparent tissue. Behind this, near the root of the nail, the papilla? are small, less vascular, and have no regular arrangement, and here the tissue Nn,l Stratum Malptqlm Nml V II ' '^i— ' rt _^^ Nml g7 u ^f mill III rnnieiiin. ^/i ittinii iiramihsuii}. Fig. 882. — Transverse section through hu lil and ifci sulcus. (From Btihm and Davidoff's Histology.) of the nail is somewhat more opaque; hence this portion is of a whiter color, and is called the lunula on account of its crescentic shape. The cuticle, as it passes forward on the dorsal surface of the finger or toe, is attached to the surface of the nail, a little in advance of the nail root; at the extremity of the finger it is connected with the under surface of the nail a little behind its free edge. The cuticle and the horny substance of the nail (both epi- dermic structures) are thus directly continuous with each other. The nails con- sist of a greatly thickened stratum lucidum, the stratum corneum forming merely OF FINGER : section through tiie nail nd tlie terminal portion of the ring finger, (Toldt.) the thin cuticular fold (eponychium) which overlaps the lunula. The cells have a laminated arrangement, and are essentially similar to those composing the epidermis. The deepest layer of cells, which lie in contact with the papillre of the matrix, are columnar in form and arranged perpendicularly to the surface; those which succeed them are of a rounded or polygonal form, the more superficial ones becoming broad, thin, and flattened, and so closely compacted as to make the limits of each cell very indistinct. It is by the successive growth of new cells at the root and under surface of the body of the nail that it advances forward and 1158 THE ORGANS OF SPECIAL SENSE maintains a due thickness, while, at the same time, the growth of the nail in the proper direction is secured. As these cells in their turn become displaced by the growth of new oneS; they assume a flattened form and finally become closely MATRIX OF NAIL FREE EDGE CONCEALED MARGIN Fig. 884. — The finger-nail com- pletely isolated, seen from the con- vex side. (Toldt.) Fig. 88.5. —The matrix of the nail or nail bed, with the nail fold and nail walls displayed by the removal of the epidermic portion of the nail or nail proper and the surrounding epidermis. (Toldt.) Fig. 886.— Matrix of the nail with partly opened mar- ginal groove of the nail bed, (Toldt.) AH PAPILLA Fig. 887.— a hair of the head still in the course of growth, with hair bulb in longitudinal section. (Toldt.) compacted together into a firm dense, horny texture. In chemical composition the nails resemble the upper layers of the epidermis, containing, however, a some- what larger proportion of carbon and sulphur (Mulder). THE APPENDAGES OF THE SKIN 1159 The Hairs (pili) (Figs. SSS and 889) are peculiar modifications of tlie epi- dermis, and consist essentially of the same structure as that membrane. They are found on nearly every part of the sin-face of the body, excepting the palms of the hands, soles of the feet, the nipples, the inner surface of the prepuce, and the glans penis. Hairs include hairs of the head (capilU); of the eyebrows (supcrcilia); of the beard (barha); of the ears (fr number. A fourth group, the interbronchial nodes, are found in angles of bifurcation of the larger bronchi in the lung parenchyma. Very early in life the peritracheobronchial nodes become dark or even black from the deposition of carbonaceous substance brought by the leuko- cytes from the bronchial tubes. This condition is called anthracosis. Surface Form.— In the middle line of the neck some of the cartilages of the larvnx can readily be distinguished. In the angle below the chin the hyoid bone can easily be distinguished, and a finger's breadth below it is the pomum Adami, the prominence between the upper borders of the two alae of the thyroid cartilage. About an inch below this, in the middle line, is a depres- sion corresponding to the cricothyroid space, in which the operation of laryngotomy is per- formed. This depression is bounded below by a prominent arch, the anterior ring of the cricoid cartilage, below which the trachea can be felt", though it is only in the emaciated adult that the separate rings can be distinguished. The lower part of the trachea is not easily observed, for as it descends in the neck, following the curvature of the vertebral column, it takes a deeper position, and is farther removed from the surface. The level of the vocal cords corresponds to the middle of the anterior margin Of the thyroid cartilage. With the laryngoscope, the following structures can be seen. The base of the tongue and the lingual surface of the epiglottis, with the glossoepiglottic ligaments; the superior aperture of 1180 THE ORGANS OF VOICE AND BESPIBATION the larynx, bounded on either side by the arytenoepiglottidean folds, in which may be seen two rounded eminences corresponding to the cornicular and cuneiform cartilages. Beneath these, the false and true vocal cords, with the ventricle between them. Still deeper, the cricoid car- tilage and s(jnie of the anterior parts of the rings of the trachea, and sometimes, in deep inspira- tion, the bifurcation of the trachea. Applied Anatomy. — Foreign bodies often find their way into the air passages. These may be large, soft substances, as a piece of meat, which may become lodged in the upper aperture of the larynx or in the rima glottidis, and cause speedy suffocation unless rapidly got rid of, or unless an opening is made into the air passages below, so as to enable the patient to breathe. Smaller bodies, frequently of a hard nature, such as cherry- or plum-stones, small pieces of bone, buttons, etc., may find their way through the rima glottidis into the trachea or bronchus, or may become lodged in the ventricle of the larynx. The dangers then depend not so much upon the mechanical obstruction as upon the spasm of the glottis which they excite from reflex irritation. When lodged in the ventricle of the larynx, they may produce very few symptoms beyond sudden loss of voice or alteration in the voice sounds, immediately following the inhalation of the foreign body. When, however, they are situated in the trachea, they are constantly striking against the vocal cords during expiratory efforts, and produce attacks of dyspnea from spasm of the glottis. When lodged in the bronchus, they .usually become fixed there, and, occluding the lumen of the tube, cause a loss of the respiratory murmur on the affected side, which is, as stated above, more often the right. Beneath the mucous membrane of the upper part of the air passages there is a considerable amount of submucous tissue which is liable to become much swollen from effusion in inflamma- tory affections, constituting the disease known as "edema of the glottis." This effusion does not extend below the level of the true vocal cords, on account of the fact that the mucous mem- brane is closely adherent to these structures, without the intervention of any submucous tissue. So that, in cases of this disease in which it is necessary to open the air passages to prevent suffo- cation, the operation of laryngotomy is sufficient. Chronic laryngitis is an inflammation of the mucous membrane of the larynx, which occurs in those who speak much in public, and is due to the dryness induced by the large amount of cold air drawn into the air passages during prolonged speaking, which incites increased activity in the mucous glands to keep the parts moist, and this eventually terminates in inflammation of these structures. . Ulceration of the larynx may occur from syphilis, either as a superficial ulceration, or from the softening of a gumma; from tuberculous disease (laryngeal phthisis), or from malignant disease (epithelioma). The air passages may be opened surgically in two different situations — through the cricothyroid membrane (laryngotomy), or in some part of the trachea (tracheotomy); and to these some sur- geons have added a third method — opening the cricothyroid membrane and dividing the car- tilage with the upper ring of the trachea (laryngotracheotomy). Laryngotomy is anatomically the more simple operation; it can readily be performed, and should be employed in those cases where the air passages require opening in an emergency for the relief of some sudden obstruction to respiration. The cricothyroid membrane is very super- ficial, being covered in the middle line only by the skin, superficial fascia, and the deep fascia. On each side of the middle line it is also covered by the Sternohyoid and Sternothyroid muscles, which diverge from each other at their upper parts, leaving a slight interval between them. On these muscles rest the anterior jugular veins. The only vessel of any importance in connec- tion with this operation is the cricothjToid artery, which crosses the cricothyroid membrane, and which may be wounded, but rarely gives rise to any trouble. The operation is performed thus: The head being thrown back and steadied by an assistant, the finger is passed over the front of the neck, and the cricothyroid depression felt for. A vertical incision is then made through the skin, in the middle line over this spot, and carried down through the fascia until the crico- thyroid membrane is exposed. A cross-cut is then made through the membrane, close to the upper border ol the cricoid cartilage, so as to avoid, if possible, the cricothyroid artery, and a tracheotomy tube is introduced. It has been recommended, as a' more rapid way of performing the operation, to make a transverse instead of a longitudinal cut, through both the superficial and deep structures, and thus to open at once the air passages. It will he seen, however, that in opening in this way the anterior jugular veins would be in danger of being wounded. Tracheotomy may be performed either above or below the isthmus of the thyroid body, or this structure may be divided and the trachea opened behind it. The isthmus of the thyroid gland usually crosses the second and third rings of the trachea; along its upper border is frequently to be found a large transverse communicating branch between the superior thwoid veins; and the isthmus itself is covered by a venous plexus formed between the thyroid veins of the opposite sides. Theoretically, therefore, it is advisable to avoid dividing this structure in opening the trachea. Above the isthmus the trachea is comparatively superficial, being covered by the skin, super- ficial fascia, deep fascia, Sternohyoid and Sternothyroid muscles, and a second layer of the deep THE PLEURA 1181 fascia, which, attached above to the lower border of the hyoid bone, descends beneath the muscles to the thyroid body, where it divides into two layers and encloses the istiiiuus. Below the isthmus the trachea lies much more deeply, and is covered by the Sternohyoid and the Sternothyroid muscles and a quantity of loose areolar tissue in which is a plexus of veins, some of them of large size; they converge to two trunks, the inferior thyroid veins, which descend on either side of the median line on the front of the trachea and open into the innominate vein. In the infant the thymus gland ascends a variable distance along the front of the trachea, and opposite the episternal notch the windpipe is crossed by the left innominate vein. Occasionally, also, in young subjects, the innominate artery crosses the tube obliquely above the level of the sternum. The thyroidea ima artery, when that vessel exists, passes from below upward along the front of the trachea. From these observations it must be evident that the trachea can be more readily opened above than below the isthmus of the thyroid body. Tracheotomy above the isthmus is performed thus: The patient should, if possible, be laid on his back on a table in a good light. A pillow is to be placed under the shoulders and the head thrown back and steadied by an assistant. The surgeon, standing on the right side of his patient, makes an incision from an inch and a half to two inches in length in the median line of the neck from the top of the cricoid cartilage. The incision must be made exactly in the middle line, so as to avoid the anterior jugular veins, and after the superficial structures have been divided the interval between the Sternohyoid muscles must be found, the raph^ divided, and the muscles drawn apart. The lower border of the cricoid cartilage must now be felt for, and the upper part of the trachea exposed from this point downward in the middle line. Bose has recommended that the layer of fascia in front of the trachea should be divided transversely at the level of the lower border of the cricoid cartilage, and, having been seized with a pair of for- ceps, pressed downward with the handle of the scalpel. By this means the isthmus of the thyroid gland is depressed, and is saved from all danger of being wounded, and the trachea is cleanly exposed. The trachea is now transfixed with a sharp hook and drawn forward in order to steady it, and is then opened by inserting the knife into it and dividing the two or three upper rincs from below upward. If the trachea is to be opened below the isthmus, the incision to expose it must be made from a little below the cricoid cartilage to the top of the sternum. In the child the trachea is smaller, more deeply placed, and more movable than in the adult. In fat or short-necked people, or in those in whom the muscles of the neck are prominently developed, the trachea is more deeply placed than in others. A portion of the larynx or the whole of it has been removed for malignant disease, laryngec- tomi/. Some surgeons" do preliminary tracheotomy, insert a Trendelenburg cannula to prevent the flow of blood downward into the lungs, and then remove the larynx. Other surgeons do not employ preliminary tracheotomy. Perier's method of laryngectomy is as follows: Make a vertical incision in tlie median line from the level of the hyoid bone to below the level of the cricoid cartilage. Make a transverse incision at each end cf the vertical incision. This makes an I-shaped wound. Separate the soft parts from the larynx and upper part of the trachea, and separate these two structures from the oesophagus. After arresting bleeding, divide the trachea below the cricoid cartilage, introduce a special cannula, complete the removal of the larynx, suture the opening of the trachea to the lower angle of the wound, and close the rest of the wound after securing drainage. In malignant disease of the larynx the associated lymph nodes must be removed. Partial laryngectomy, according to Sir F. Semon, is the removal of not less than one wing of the thyroid cartilage. Removal of a lesser piece of the thyroid or of a bit of the arytenoid or cricoid he considers with the operation of thyrotomy. THE PLEURiE (Figs. 889, 919). Each lung is invested by an exceedingly delicate serous membrane, the pleura, which encloses the organ as far as its root, and is then reflected on to the peri- cardium, thoracic wall, and Diaphragm. The portion of the serous membrane investing the surface of the lung and dipping into the fissures between its lobes is called the visceral layer of the pleura (pleura pulmonalis) (Fig. 907), wiiile that which lines the inner surface of the thorax is called the parietal layer of the pleura {-pleura parietalis) (Fig. 907), The space between these two layers is called the cavity of the pleura (cavum pleurae), and contains a very litde clear fluid. It must be borne in mind that in the healthy condition the two layers are in contact, and there is no real cavity. When the lung becomes collapsed a separation of it from the wall takes place and a cavity results. Each pleura is therefore a shut 1182 THE ORGANS OF VOICE AND BESPIBATION sac, one occupying the right, the other the left half of the thorax, and they do not communicate with each other. The two pleurae do not meet in the middle line Pleura Pulmonalis, a Costalis. Sympathetic Nave Thoracic Duct Fig 907 — A trans^ erse section of the thor-i-s. showing the relative position of the viscera and the reflections of the pleurEe. \ena izyqob Major. Vagus Ne> ves of the thorax, excepting anteriorly opposite the second and third pieces of the ster- num. The region left between them contains all the thoracic viscera excepting the lungs, and is named the mediastinum or interpleural septum. Fig. 908. — The dome of the pleura. (Poirier and Charpy.) Different portions of the parietal pleura have received special names which indicate their position; thus, that portion which lines the inner surfaces of the ribs THi: PLEURJE 1183 and Intercostal muscles is the costal pleura (pleura costalis); that which covers the convex surface of the Diaphragm is the diaphragmatic pleura [pleura diaplmuj- matica); that which rises in the neck, over the apex of tlie lung, is the cervical pleura (cupula pleurae); and that which is applied to the adjacent structures of the mediastinum is tiie mediastinal pleura [pleura mediastinalis). Reflections of the Pleurae (Fig. 907).— Commencing at the sternum, the pleura passes laterad, covers the inner surfaces of the ribs and costal cartilages, and Internal intercostal muscles, and at the back part of the thorax passes over the gangliated cord of the sympathetic and its branches, and is reflected upon the sides of the bodies of the vertebrae where it is separated by a narrow interval, the posterior mediastinum [cavum mediastinale poster ius), from the opposite pleura. From the vertebral column the pleura passes to the side of the pericardium, which it SCALENUS MINIMUS MUSCLE Fig. 909.— The supports of the pli aside to show the pleural reenforcementi d arteries have been cut and pulled covers to a slight extent; it then covers the back part of the root of the lung, from the lower border of which a triangular sheet descends vertically by the side of the posterior mediastinum to the Diaphragm, but is not attached thereto. This sheet is the posterior layer of a wide fold, known as the broad ligament of the lung (ligamentum pulmonale or ligamentum latum pulmonis). From the -posterior aspect of the lung root, the pleura may be traced over the convex surface of the lung, the apex, and base, and also into the fissures between the lobes, on to its inner surface and the front part of its root; it is continued from the lower margin of the root as the anterior layer of the broad ligament, and from this it is reflected on to the pericardium, and from it to the back of the sternum. Beloiv, it covers the upper surface of the Diaphragm, and extends, in front, as low as the costal cartilage of the seventh rib; at the side of the thorax, to the lower border of the tenth rib on the left side and to the upper border of the same rib on the right side; and hehiiid, it reaches as low as the twelftii rib, and sometimes even as low as the transverse process of the first lumbar vertebra. Above, its apex projects, through the superior aperture of the thorax into the neck, extending from one to two inches (2.5 to 5 cm.) above the anterior extremity of the first rib ; this portion of the sac is strengthened by a dome-like expansion of fascia (Sibson's fascia) (Fig. 909), attached in front to the inner border of the first rib, and behind to the ante- 1184 THE ORGANS OF VOICE AND RESPIRATION rior border of the transverse process of the seventh cervical vertebra. This is cov- ered and strengthened by a few spreading muscle fibres derived from the Scaleni. In the front of the thorax, where the parietal layer of the pleura is reflected backward to the pericardium, the two pleural sacs are nearly in contact for a short distance (Fig. 919). At the upper part of the thorax, behind the manubrium, they are not in contact, the point of reflection being represented by a line drawn from the sternoclavicular articulation to the midpoint of the junction of the manubrium with the body of the sternum. From this point the two pleurae descend in close con- tact to the level of the fourth costal cartilages, and the line of reflection on the riyht side is continued downward in nearly a straight line to the lower end of the gladi- olus, and then turns outward, while on the left side the line of reflection diverges slightly outward and is continued downward, close to the left border of the ster- num as far as the sixth costal cartilage. The inferior limit of the pleura is on a con- siderably lower level than the corresponding limit of the lung, but does not extend to the attachment of the Diaphragm, so that below the line of reflection of the pleura from the thoracic wall on to the Diaphragm the latter is in direct contact with the rib cartilages and the Internal intercostal muscles. In ordinary inspiration the thin margin of the base of the lung does not extend as low as the line of pleural reflection, with the result that the costal and diaphragmatic pleura are here in contact, the narrow slit between the two being termed HRENic the costophienic sinus {sinus ■phrenicocostalis) (Fig. 910). A similar condition exists behind the sternum and rib cartilages, where the anterior thin margin of the lung falls short of the line of pleural reflection, and where the slit-like cavity between the two layers of pleura ' forms what is sometimes called the costome- diastinal sinus {sinus costomediastinalis) . The line along which the ric/hf plevra is re- flected from the thoracic wall to the Diaphragm starts in front, immediately below the seventh costosternal joint, and runs downward and backward behind the seventh costal cartilage Fig. 910.— Section of the wall of the thorax, so as to cross the tenth rib in the mid-axillary showing the phrenicocostal sinus. (Poirier and ,. ,, ,.,.. , , , Charpy.) Imc, trom which it is prolonged to the spine of the twelfth thoracic vertebra. The reflection of the left pleura follows at first the ascending part of the sixth costal cartilage, and in the rest of its course is slightly higher than that of the right side. The free surface of the pleura is smooth, polished, and moistened by a serous fluid; its attached surface is intimately adherent to the surface of the lung, and to the pulmonary vessels as they emerge from the pericardium; it is also adherent to the upper surface of the Diaphragm; throughout the rest of its extent it is some- what thicker, and may be separated from the adjacent parts with extreme facility. The right pleural sac is shorter, wider, and reaches higher in the neck than the left. Ligamentum Latum Pulmonis. — From the above description it will be seen that the root of the lung is covered in front, above, and behind by the pleura, and that at its lower border the investing layers come into contact. Here they form a sort of . mesenteric fold, the ligamentum latum pulmonis (lig. pulmonale), which extends THE MEDIASTINUM, OR INTERPLEURAL SPACE 1185 as far as the Diaphragm (but is not attached thereto) between the pericardium and the lower part of the inner surface of the lung, having a free falciform border below, between the lung and the Diaphragm. It serves to retain the lower part of the lung in position (Figs. 913 and 914). Structure of the Pleura. — The pleura is composed of fibroelastic connective tissue, its free surface being covered with a single layer of flat endothelial cells. It is fastened to adjacent structures liy suliscrous fibroelastic tissue. The subserous tissue of the visceral pleura is con- tinuous with tlie fibroelastic tissue of the lung. Vessels and Nerves. — The arteries of the pleura are derived from the intercostal, the internal mammary, the musculophrenic, thymic, pericardiac, and bronchial arteries. Tlie veins cor- respond to the arteries. The lymphatics are very niunerous in the jileura and suliserous tissue. The lyni|)hatics of the visceral layer eraply inri) the superficial pulmonary trunks; the Ivm- lihatiis (if ihe costal pleura empty into the intercostal trunks; of the (lia|ihriii;i]ialic pleura, into the diaphragmatic trunks; of the mediastinal pleura, into the posterior mediastinal nodes. The nerves are derived from the phrenic and sympathetic (Luschka). Applied Anatomy. — In operations upon the kidncij it must be borne in mind that the pleura may sometimes extend below the level of the last rib, and may therefore be opened in these operations, especially when the last rib is removed, in order to give more room. It is best to keep the incision at least one inch below the last rib, enlarging the wound afterward, when the finger can be introduced as a guide. In wounds of the Diaphragm the pleura may be injured. In operations about the root of the neck, especially in the removal of lymph nodes and the ligation of the first part of the subclavian artery, the pleura may be injured. Punctured wounds of the root of the neck are apt to reach the pleura. Empyema is a surgical disease. In acute empyema the treatment is drainage. A portion of the fifth or sixth rib in the axillary line is removed by subperiosteal resection, the pleura is opened, and a tube is introduced. In chronic empyema the lung is contracted and adherent and cannot expand; hence drainage will not cure it. It is necessary to perform multiple rib resection in order to permit the thoracic wall to sink in and obliterate the cavity, which, as the lung is unable to expand, it cannot do. The necessary operation may be the one of either Estlander, Schede, or Fowler (p. 168). If a large wound admits suddenly a quantity of air into the pleura, dangerous or fatal pneumo- thorax arises, and the lung collapses. This is usually met during operations by using the Fell- O'Dwyer apparatus for artificial respiration, as advised by Matas.' This apparatus keeps the lung expanded, in spite of the entrance of air into the pleural sac. A surgeon can open the pleura widely without any fear of the lung collapsing if he operates in a Sauerbruch chamber. The pressure within this chamber is negative. The patient's head is outside of the chamber, his body is within it. The bronchioles are distended by the patient inhaling air at the ordinary pressure, but the exposed lung is subjected to negative pressure, hence the lung does not collapse in spite of a large wound in the pleura. In surgical pneumothorax the lung may be sutured to the thoracic wall, so as" to block the opening. Sometimes, in order to arrest dangerous pulmonary bleeding, a surgeon deliberately induces pneumothorax, in the hope that the collapse of the lung will arrest bleeding. When an abscess of the liver is posterior and on the dorsum, transpleural hepatotomi/ is per- formed. A portion of the tenth and eleventh ribs below the angle of the scapula is removed. As a rule, the pleura is found obliterated at this point. If it is opened, it is at once sutured or closed with gauze packing. The exposed Diaphragm is incised, and, as it is usually adherent to the liver, the abscess cavity is entered. If it is not adherent, the liver is exposed and the abscess sought for with an aspirating needle. Grocco's sign is the presence of a triangular area of paravertebral dulness above the level of the twelfth rib on the side opposite to a pleural effusion. The dulness is believed to be due to a displacement of the contents of the posterior mediastinum by the fluid. THE MEDIASTINUM, OR INTERPLEURAL SPACE. The mediastinum is the space left in the median portion of the thorax by the non- apposition of the two pleurte. In reality it is an "interpleural septum." It ex- tends from the sternum in front to the vertebral column behind, and contains all the thoracic viscera excepting the lungs. The mediastinum may be divided for purposes of description into two parts — an upper portion, above the upper \e\e\ ' Annals of Surgery, April, 1899. 7.5 1186 THE ORGANS OF VOICE AND BESPIBATION of the pericardium, which is named the superior mediastinum; and a lower portion, below the upper level of the pericardium. This lower portion is again subdivided into three — that part which contains the pericardium, its contents, and other structures below this plane: the middle mediastinum; that part which is in front of the pericardium, the anterior mediastinum; and that part which is behind the peri- cardium, the posterior mediastinimi. The superior mediastinum (Fig. 911) is that portion of the interpleural space which lies between the manubrium sterni in front and the upper thoracic vertebrae behind. It is bounded below by a plane passing backward from the junction of the manubrium and gladiolus sterni to the lower part of the body of the fourth thoracic vertebra, and laterally by the lungs and pleurae. It contains the origins of the Sternohyoid and Sternothyroid muscles and the lower ends of the Longus colli muscles; the arch of the aorta; the innominate, the thoracic portion of the left carotid and subclavian arteries ; the upper half of the superior vena cava and Left Innom- Left Carotid mate Vein. Artery. Vagus Nerve.-y^ Vertebral ///!' Artet y ■ -'^^^y heft Sublcavian Ariel y ^;^^ Internal Mammary Artery. y/2nd Eib. Fig. 911. — Transverse section through the second tho 3rd Bib ertebra (Braune.) the innominate veins, and the left superior intercostal vein; the vagus, cardiac, phrenic, and left recurrent laryngeal nerves ; the trachea, oesophagus, and thoracic duct; the remains of the thymus gland and some lymph nodes. The anterior mediastinum (Fig. 907) is bounded in front by the sternum, laterally by the pleurae, and behind by the pericardium. It is narrow above, but widens out a little below, and, owing to the oblique course taken by the left pleura, it is directed from above obliquely downward and to the left. Its anterior wall is formed by the left Triangularis sterni muscle and the fifth, sixth, and seventh left costal cartilages. It contains a quantity of loose areolar tissue, some lym- phatic vessels which ascend from the convex surface of the liver, two or three lymph nodes (anterior mediastinal glands), and the small mediastinal branches of the internal mammary artery. The middle mediastinum (Fig. 907) is the broadest part of the interpleural space. It contains the heart enclosed in the pericardium, the ascending aorta, the lower half of the superior vena cava, with the vena azygos major opening into THE MEDIASTINUM, OR INTERPLEURAL HI' ACE 1187 it, the bifurcation of the trachea and the two bronchi, the pulmonary artery divid- ing into its two branches and the right and left pulmonary veins, the phrenic nerves, and some broneiiial lymph nodes. The posterior mediastiniun (Figs. 907 and 912) is an irreguhir triangular space running parallel with the vertebral column; it is bounded in jront by the peri- FiG. 912. — The posterior mediastinum. cardium above, and by the posterior surface of the Diaphragm below, behind by the ^'ertebral column from the lower border of the fourth to the twelfth thoracic vertebra, and on either side by the pleura. It contains the descending thoracic aorta, the venae azygos major and minor, the vagus and splanchnic nerves, the oesophagus, the thoracic duct, and some lymph nodes. 1188 THE ORGANS OF VOICE AND BESPIBATION Applied Anatomy. — Primary tumors of the mediastinum are usually lymphomata or lympho- sarcomata arising from the thymus or from the bronchial or posterior mediastinal lymph nodes; sarcomata, dermoid cysts, and embryomata, occur more rarely. These tumors give rise to pain, deformity of the thorax, and symptoms of pressure on the various nerves, bloodvessels, air passages, lymphatics, and on the oesophagus, as these various structures pass through the thorax. They may produce physical signs very much like those of an aortic aneiu^ism, so that diagnosis between the two is often difficult. The prognosis is bad, life usually ending within a few months or a year of the onset of the symptoms. Inflammation of the mediastinum due to wounds, or to the spread of inflammation from ad- jacent parts {e. g., the oesophagus, the pericardium), is sometimes acute, leading to abscess formation. A more chronic form associated with adhesions and inflammation of the pericar- dium— the so-called chronic adhesive mediastinopericarditis — gives rise to obscure symptoms suggesting gradual heart failure, and leads to death slowly but surely. THE LUNGS (PULMONES) (Figs. 913, 914). The lungs are the essential organs of respiration; they are two in number, placed one on each side of the thorax, separated from each other by the b^art and other contents of the mediastinum. A heaUhy lung hangs free within the pleural cavity. It is suspended by the root and by the ligamentum pulmonale. In many Groove foi innominate aiteiy Groove for supet ior_ vena cava G) oove for vena azygos major Eparterial bronchus Hyparterial broyichus Pulmonary veins Groove for oesophagus Ligamentum latum pulmonis Fig. 913. — Mediastinal surface of right lung. cases examined the lung does not hang free, but, as a result of former pleurisy, an area of the pulmonary pleura is adherent to the parietal pleura. Each lung is conical in shape, and presents for an examination an apex, a base, three bor- ders, and three surfaces. The apex {apex pulmonis) is rounded, and extends into the root of the neck about an inch to two inches (2.5 to 5 cm.) above the level of the anterior end of the first rib. A furrow produced by the subclavian artery as it curves outward in front of the pleura runs upward and outward immediatelj' below the apex. The brachial plexus is in close proximity to this portion of the lung. The base [basis pulmonis) or diaphragmatic surface is broad, concave, and rests upon the convex surface of the Diaphragm, which separates the right lung from the upper surface of the right lobe of the liver and the left lung from the THE LUNGS 1189 upper surface of the left lobe of the liver, the fundus of the stomach, and the spleen. Since the Diaphragm extends higher on the right than on the left side, it follows that the concavity on the base of the right lung is deeper than that of the left. Laterally and behind, the base is bounded by a thin, sharp margin which projects for some distance into the costophrenic^ sinus of the pleura, between the lower ribs and the costal attachment of the Diaphragm. The base of the lung descends during inspiration and ascends during expiration; its rela- tion to the thoracic wall is indicated in Figs. 919 and 920. Grooiefni left mhclavinii artery Grooie for left innominate vein Pulmonary artery Pulmonary veins Incisura cardiaca Fig. 9U.— Mediastinal surface of left lung. Surfaces. — The external, costal, or thoracic surface (fades costalis) (Figs. 917 and 918) is smooth, convex, of considerable extent, and corresponds to the form of the cavity of the thorax, being deeper behind than in front. It is in contact with the costal pleura, and presents, in a hardened specimen, slight grooves corresponding to the overlying ribs. The inner or mediastinal surface (fades viediastinalis) (Figs. 913 and 914) is in contact with that portion of the pleura which forms the lateral boundary of the mediastinal space. It presents a deep concavity which accommodates the pericardial sac; this is larger and deeper on the left than on the right lung, on account of the heart projecting farther to the left than to the right of the mesal plane. Above and behind this concavity is a triangular depression named the hilum (kilm pulmonis), where the structures which form the root of the lung enter and leave the viscus. Oti the right lung (Fig. 915), immediately above the hilum, is an arched furrow which accommodates the vena azygos major, while running upward, and then arching outward some little distance below the apex, is a wide groo\-e for the supe- rior vena cava and right innominate vein ; and behind this, nearer the apex, is a sec- ond furrow for the innominate artery. x\long the back part of the inner surface is a vertical groove for the oesophagus; this groove becomes less distinct below, owing to the inclination of the lower part of the oesophagus to the left of the middle line. In front and to the right of the lower part of the oesophageal groove, the inner surface is applied to the pleural covering of the right and posterior aspects 1190 THE ORGANS OF VOICE AND RESPIRATION of the thoracic parts of the inferior vena cava; this vessel being accommodated in a deep concavitj'. On the left lung (Fig. 914), immediately above the hilum, is a well-marked curved furrow produced by the arch of the aorta, and running upward from this toward the apex is a groove accommodating the subclavian artery; a slight impres- sion in front of the latter and close to the margin of the lung lodges the left in- nominate vein. Behind the hilum and pericardial depression is a vertical furrow produced by the descending thoracic aorta, and in front of this, near the base of the lung, the lower part of the oesophagus causes a shallow depression. Fig. 915.— Front of the heart and lungs. Borders. — The posterior border (margo posterior) is broad and rounded, and is received into the deep concavity on either side of the vertebral column. It is much longer than the anterior border. The inferior border (margo inferior) is the sharp margin of the base separating the costal and diaphragmatic surfaces. It projects, below, into the upper part of the costophrenic sinus. The anterior border (margo anterior) is thin and sharp, overlaps the front of the pericardium, and is projected into the costomediastinal sinus of the pleura. The anterior border of the right lung is almost vertical; that of the left presents, below, an angular notch, the incisura cardiaca, into which the heart and pericardium are received. A projection from the upper lobe comes forward beneath the cardiac notch; it is called the lingula pulmonis. Fissures and Lobes of the Lung.— The left lung is divided into two lobes, an upper and a lower, by an oblique fissure (incisura interlobaris) , which extends from the outer to the inner surface of the lung both above and below the hilum. THE LUNGS 1191 As seen on the surface, this fissure commences on the inner aspect of the hnig at the upper and posterior part of the hihim, and runs backward and upward ANCE OF AZYGOS CH OF PUL- RY ARTERY Fig. 916. — Pulmonary veins, seen in a dorsal view of the heart and lun^. The lungs have been pulled away from the median line, and a part of the right lung has been cut away to display the air ducts and bloodvessels. (Testut.) to the posterior border, which it crosses about two and a half inches (6.5 cm.) be- low the apex. It then extends downward and forward over the outer surface and 1192 THE ORGANS OF VOICE AND RESPIRATION reaches the lower border a little behind its anterior inferior extremity, and its further course can be followed upward and backward across the inner surface as far as the lower part of the hilum. The upper lobe {lohus superior) lies above and in front of this fissure, and includes the apex, the anterior border, and a considerable part of the outer surface and the greater part of the inner surface of the lung. The lower lobe {lobus inferior), the larger of the two, is situated below and behind this fissure, and comprises almost the whole of the base, a large portion of the outer surface, and the greater part of the posterior border. The right lung is divided into three lobes, upper, middle, and lower, by an oblique and a horizontal fissure. The oblique fissure separates the lower from the middle Fig. 919. — Front view of thorax, showing relations of pleurae and lungs to the thoracic wall. The blue lines indicate the lines of the reflection of the pleurae; the red, the outlines of the lungs and their fissures. and upper lobes, and corresponds closely with the fissure of the left lung. Its direction is, however, more vertical, and it cuts the lower border about three inches from the anterior margin. The horizontal fissure separates the upper from the middle lobe. It begins in the oblique fissure near the posterior border of the lung and, running horizontally forward, cuts the anterior border at the level of of the sternal end of the fourth costal cartilage ; on the inner surface it may be traced backward to the hilum. The middle lobe (lobiis mediiis), the smallest of the lobes of the right lung, lies between the horizontal fissure and the lower part of the oblique fissure; it is wedge-shaped and includes the lower part of the anterior border and the anterior part of the base of the lung. The right lung is the larger and heavier; it is broader than the left, owing to THE LUNGS 1193 the inclination of the heart to the left side; it is also shorter by an inch, in consequence of the Diaphragm risuig higher on the right side to accommodate the liver. The Root of the Lung {radix jndnwnis) (Figs. 913 and 914). — A little above the middle of the inner surface of each lung, and nearer its posterior than its anterior Fig. 920. — Lateral view of thorax, showing relations of right pleura and lung to the thoracic wall. The blue line in- dicates the line of pleural reflection; the red lines, the outline of the lung and its fissures. border, is its root, by which the lung is connected to the heart and the trachea. The root is formed by the bronchial tube, the pulmonary artery, the pulmonary veins, the bronchial arteries and veins, the pulmonary plexus of nerves, lymphatics, bronchial lymph nodes, and areolar tissue, all of which are enclosed by a reflection of the pleura. The root of the right lung lies behind the superior vena cava and ascending portion of the aorta, and below the vena azygos major. The root of the left lung lies beneath the arch of the aorta and in front of the descending aorta; the phrenic nerve and the anterior pulmonary plexus lie in front of each, and the vagus and posterior pulmonary plexus behind each; below each is the broad pulmonary ligament. The chief structures composing the root of each lung are arranged in a similar manner from before backward on both sides — viz., the two pulmonary veins in front, the pulmonary artery in the middle, and the bronchus, together with the bronchial vessels, behind. From above downward, on the two sides, their arrangement differs, thus: 1194 THE ORGANS OF VOICE AND RESPIRATION On the right side their position is — bronchus, pulmonary artery, pulmonary veins; but on the left side their position is — pulmonary artery, bronchus, pulmo- nary veins. It should be noted that the entire right bronchus does not lie above the right pulmonary artery, but only its eparterial branch (see p. 1177), which passes to the upper lobe of the right lung; the divisions of the bronchus for the middle and lower lobes lie below the artery. Divisions of the Bronchi. — Just as the lungs differ from each other in the number of their lobes, so the bronchi differ in their mode of subdivision. The right bronchus gives off, about an inch from the bifurcation of the trachea, a branch for the upper lobe. This branch arises above the level of the pulmonary artery, and is therefore named the eparterial bronchus. All the other branch bronchi come off below the pulmonary artery, and consequently are termed hyparterial bronchi. The first of these is distributed to the middle lobe, and the main tube then passes downward and backward into the lower lobe, giving off in its course a series of large ventral and small dorsal branches. The ventral and dorsal branches arise alternately, and are usually eight in number — four of each kind. The branch to the middle lobe is regarded as the first of the ventral series. The left bronchus passes below the level of the pulmonary artery before it divides, and hence all its branches are hyparterial; it may therefore be looked upon as equivalent to that portion of the right bronchus which lies on the distal side of its eparterial branch. The first branch of the left bronchus arises about two inches from the bifurcation of the trachea, and is distributed to the upper lobe. The main stem then enters the lower lobe, where it divides into ventral and dorsal branches similar to those in the right lung. The branch to the upper lobe of the left lung is regarded as the first of the ventral series. The true weight of the human lungs as ascertained in the bodies of criminals executed by electricity, in which the mode of death is attended by a nearly bloodless condition of the lungs,, is 215 grams (7^ ounces) for the left lung and 240 grams (8i ounces) for the right lung (E. A. Spitzka, Amer. Jour, of Anat., iii, 1, p. v)- Ordinarily, with the vascular channels more or less filled with blood and serum, the two lungs together weigh about 42 ounces, the right lung being 2 ounces heavier than the left, but much variation is met with according to the amount of blood or serous fluid they may contain. The lungs are heavier in the male than in the female. The specific gravity of the lung tissue varies from 0..345 to 0.746. The color of the lungs at birth is a pinkish white; in adult life a dark slate-color, mottbd in patches; and as age advances this mottling assumes a black color. The coloring matter con- sists of granules of carbonaceous substance deposited in the areolar tissue near the surface of the organ. It increases in quantity as age advances, and is more abundant in males than in females. The posterior surface of the lung is usually darker than the anterior. The surface of the lung is smooth, shining, and marked out into numerous polyhedral spaces, indicating the lobules of the organ; the area of each of these spaces is crossed by numerous lighter lines. The substance of the lung is of a light, porous, spongy texture; it floatsin water and crepi- tates when handled, owing to the presence of air in the tissue; it is also highly elastic; hence the collapsed state of these organs when they are removed from the closed cavity of the thorax. The Fetal Lung. — After respiration has' been established, the lung fills the pleural cavity. In the stillborn fetus, as the lung has never been distended with air and has never received a large amount of blood, it is gathered into a small mass at the back of the thorax. It will sink in water and feels solid to the touch. Structure. — The structm-e of the lung is such that the blood brought by the pulmonary artery comes into close relation with the air which enters from the bronchioles. The blood gives materials to the air, and the air gives elements to the blood, and the process of respiration causes the dark blood brought from the heart by the pulmonary artery to retiu-n to the heart as red blood in the pulmonary veins. The lungs are composed of an external serous coat, a sub- serous areolar tissue, and the pulmonary substance or parenchyma. The serous coat is thin, transparent, and invests the entire organ as far as the root. It is composed of a layer of endothelial cells resting upon a thin layer of fibroelastic tissue, and is continuous with the subserous tissue. It is known as the pulmonary plem-a (p. 1181). THE LUNGS 1195 The subserous areolar tissue contains a large proportion of elastic fibres; it invests the entire surface of the lung, and extends inward between the lobules. The parenchyma is composed of lobules which, although closely connected by an interlobular areolar tissue, are quite distinct from one another. The lobules vary in size from 0.3 cm. to .3 cm. (5 inch to U inches); those on the surface are large, of pyramidal form, with the bases turned toward the surface; those in the interior are smaller and of variou.s forms. Each lobule is composed of one of the ramifications of a bronchiole (about 1 mm. in diameter) and its terminal air cells, and of the ramifications of the pulmonary and bronchial vessels, lym- phatics, and nerves, all of these structures being connected by fibroelastic tissue. The bronchus upon entering the lung divides like the ducts of a gland, the terminal tubules, about I mm. in diameter, constituting the bronchioles. Each bronchiole forms a lol^ule that is separated and closed from its neighbor. The bronchiole diminishes in (liamctcr \>< about 0..5 mm. and divides into several tubules (0.3 to 0.4 ram. in diameter), the respiratory bronchioles, upon the sides of which some minute depressions, alveoli, may be seen. Each respiratory bronchiole further subdivides into several alveolar ducts (0.2 mm; in diameter), along which alveoli are numerous. The alveolar ducts lead into individual dilated spaces, the alvei, air sacs, or infun- dibula (0.3 to 5 mm. in diameter), upon the sides of which are alveoli or saccules (0.0.5 to 0.1 mm. in diameter). The alveoli are partially separated from one another by low partitions or septa, of the same structure as the alveolar wall. Changes in Stracture of the Bronchus and Its Divisions.— Each main bronchus resembles the trachea in structure. Within the lung the bronchial tubes are circular in outline. As the bronchus divides and redivides monopodially, changes occur in the various coats. The mucous coat presents a corrugated appearance and the cartilage in the submucosa changes to a com- plete investing layer composed of a number of individual plates. With this change the smooth muscle tissue, internal to the cartilage, increases so as to form a complete layer. As the smaller tubes are approached the cartilage decreases in amount, while the muscle increases relatively. The mucous glands in mucosa disappear in those tubules of 1 mm. in diameter, while the car- tilage persists until a diameter of about 0.5 mm. is reached. Each bronchiole consists of a layer of simple columnar and goblet epithelial cells resting upon a basement membrane and a fibroelastic tunica propria; external to this is found a layer of smooth muscle tissue, and beyond this a layer of white fibrous tissue containing the main vessels and nerves of the tubules. The respiratory bronchiole is lined by simple ciliated cells, that gradually give way to nonciliated columnar and cuboidal cells, and lastly flattened epithelium (the respiratory epithelium). Some muscle tissue is still present, and the elastic tissue increases in quantity. The alveolar ducts are lined by simple epithelial plates resting upon a basement membrane supported by elastic tissue. At the end of this tubule the muscle tissue disappears. The air sacs are composed of the alveoli or saccules lined by respiratory epithelium that rests upon a basement membrane supported by a meshwork of elastic tissue containing the densest capillary plexus of the body. This elastic tissue allows the alveoli to increase from two to three times their ordinary diameters. Separating one alveolus from another is a low septum that has the same structure as the alveolar wall. Vessels of the Lungs. — The pulmonary artery (Figs. 915 and 916) conveys the venous blood to the lungs; it divides into branches which accompany the bronchial tubes, and terminates in a dense capillary network upon the walls of the air cells. In the lung the branches of the pulmonary artery are usually above and in front of a bronchial tube, the vein below. The pulmonary artei-ics are the nutrient vessels of the respiratory epithelium. The pulmonary capillaries form plexuses which lie immediately beneath the epithelium of the walls and septa of the air cells and of the alveoli. In the septa between the air cells the capillary network forms a single layer. The capillaries form a very minute network, the meshes of which are smaller than the vessels themselves;^ their walls are also exceedingly thin. The arteries of neighboring lobules are independent of one another, but the veins freely anastomose. The pulmonary veins commence in the pulmonary capillaries, the radicles coalescing into larger branches, wiiich run along through the substance of the lung, independently from the minute arteries and bronchi. After freely communicating with other branches they form large vessels, which ultimately come into relation with the arteries and bronchial tubes, and accom- pany them to the hilum of the organ. Finally, they open into the left auricle of the heart, con- veying oxygenated blood to be eventually distributed to all parts of the body by the aorta. The bronchial arteries supply blood for the nutrition of bronchial tubes and vessels of the lung. The thoracic aorta usually gives off two left bronchial arteries. The single right bron- chial artery usually arises from the first right aortic intercostal, but sometimes from the superior left bronchial artery, or from the aorta. In the root of the lung they are posterior to the bron- chus, they accompany the bronchial tubes, supply the bronchial tubes and surrounding inter- lobular tissue, and give branches to the walls of the larger pulmonary vessels, the oesophagus, pericardium, and bronchial lymph nodes. Those supplying the bronchial tubes form a capil- lary plexus in the muscular coat, from which branches are given oft" to form a second plexus in the mucous coat. This plexus anastomoses with branches of the pulmonary artery, and empties 1196 THE ORGANS OF VOICE AND RESPIRATION into the pulmonary vein. Others are distributed in the interlobular areolar tissue, and terminate partly in the deep, partly in the superficial, bronchial veins. Lastly, some ramify upon the surface of the lung beneath the pleura, where they form a capillary network. There may be but one bronchial artery; there may be three or four. The bronchial veins are not found in the walls of the very small bronchi. The small bronchial veins run along by the front and back of the medium sized and larger tubes, and form two trunks at the root of each lung. These vessels terminate on the right side in the vena azygos major, and on the left side in the superior intercostal or left upper azygos vein. Tracheal and posterior mediastinal veins open into the bronchial veins. The venous blood from the smaller tubes passes to the pulmonary veins. BRONCHIOLe -A pulmonary lobule, and Charpy.) Fig. 922.^ — The terminal bronchial tubes. The respiratory bronchiole and alveoli. (Poirier and Charpy.) The lymphatics begin in networks about the lobules and form networks about the bronchi and beneath the bronchial mucous membrane. The superficial collecting trunks arise about the lobules and beneath the pleura. According to Sappey, the superficial trunks from the upper lobe begin on the costal surface; one set passes around the anterior border, another set around the posterior border, and a third into the incisura interlobaris. The same observer says that the superficial trunks from the middle lobe unite with the trunks from the upper and lower lobes; and the superficial trunks from the lower lobe, like those of the upper lobe, are in three sets. One set passes around the posterior margin, one around the anterior margin, and one into the interlobar fissure. All of the superficial trunks convey lymph to the nodes of the hilum. Some of the deep collecting trunks begin by the side of the small bronchi; others course along by the pulmonary veins or pulmonary arteries. All of them pass to the nodes of the hilum. The nodes of the hilum are in communication with the peritracheobronchial nodes. Nerves. — The lungs are supplied from the anterior and posterior pulmonary plexuses, formed chiefly by branches from the sympathetic and vagus. The filaments from these plexuses accom- pany the bronchial tubes, and are lost upon them. Small ganglia are found upon these nerves. Surface Form. — The apex of the lung is situated in the neck, behind the interval between the two heads of origin of the Sternomastoid muscle. The height to which it rises above the clavicle varies very considerably, but is generally about one inch. It may, however, extend as much as an inch and a half or an inch and three-quarters, or, on the other hand, it may scarcely project above the level of this bone. In order to mark out the anterior margin of the lung, a line is to be drawn from the apex point, one inch above the level of the clavicle, and rather nearer the posterior than the anterior border of the Sternomastoid muscle, downward and inward across the sternoclavicular articulation and first piece of the sternum until it meets, or almost meets, its fellow of the other side opposite the articulation of the manubrium and gladiolus. From this point the two lines are to be drawn downward, one on either side of the mesal line and close to it, as far as the level of the articulation of the fourth costal cartilages to the sternum. From here the two lines diverge; the left is to be drawn at first passing outward with a slight inclina- tion downward, and then taking a bend downward with a slight inclination outward to the apex THE LUNGS 1107 of the heart, and thence to the sixth sternochondral articulation. The direction of the anterior border of this part of the left lung is denoted with sufficient accuracy by a curved line with its convexity directed upward and outward from the articulation of the fourth right costal cartilage of the sternum to the fifth intercostal space, an inch and a half l^elow and three-(|uartcrs of an inch internal to the left nipple in the male. The continuation of the anterior border of the right lung is marked by a prolongation of its line from the level of the fourth costal cartilages vertically downward as far as the sixth, when it slopes off along the line of the sixth costal cartilage to its articulation with the rib. The lower border of the lung is marked out by a slightly curved line with its convexity down- ward from the articulation of the sixth costal cartilage to its rib to the spinous process of the tenth thoracic vertebra. If vertical lines are drawn downward from the middle of the clavicle, from the deepest part of the axilla, and. from the apex of the scapula, while the arms are raised from the sides, they should intersect this convex line, the first at the sixth, the second at the eighth, and the third at the tenth rib. It will thus be seen that the pleura extends farther down than the lung, so that it may be wounded, and a wound may pass through its cavity into the Dia- phragm, and the abdominal viscera may be injured without the lung being involved. The posterior border of the lung is indicated by a line drawn from the level of the spinous process of the seventh cervical vertebra, doAvn either side of the vertebral column, correspond- ing to the costovertebral joints as low as the spinous process of the tenth thoracic vertebra. The trachea bifurcates opposite the spinous process of the fourth thoracic vertebra, and from this point the two bronchi are directed outward. "The position of the great fissure of the lungs may be indicated by a line drawn from the third thoracic spine obliquely downward in such a manner as to reach the sixth rib close to the mid- clavicular line. The interlobar fissure between the upper and middle lobes of the right lung corresponds to a line drawn from the apex of the axilla almost horizontally to the sternum, reaching the latter at about the level of the fourth costal cartilage" (Ehrendrath). Applied Anatomy. — The lungs may be wounded or torn in three ways: (1) By compression of the thorax, without any injury to the ribs. (2) By a fractured rib penetrating the lung. (3) By stabs, giuishot wounds, etc. The first form, where the lung is ruptured by external compression without any fracture of the ribs, is very rare, and usually occurs in young children, and affects the root of the lung — i. e., the most fixed part — and thus, implicating the great vessels, is frecjuently fatal. It would seem to be a most unusual injury, and the exact mode of its causation is difficult to understand. The probable explanation is that immediately before the compression is applied a deep inspira- tion is taken and the lungs are fully iriflated; owing then to spasm of the glottis at the moment of compression, the air is unable to escape from the lung, the lung is not able to recede, and consequently gives way. In the second variety, when the wojind in the lung is produced by the penetration of a broken rib, both the pleura costalis nnd the pleura pulmonalis must necessarily be injured, and conse- quently the air taken into the wounded air cells may find its way through these wounds into the cellular tissue of the parietes of the thorax. This it may do without collecting in the pleural cavity; the two layers of the pleura are so intimately in contact that the air may pass straight through from the wounded lung into the subcutaneous tissue. Emphysema constitutes, there- fore, an important sign of injury to the lung in cases of fracture of the ribs. Pneumothorax, or air in the pleural cavity, is much more likely to occur in injuries to the lung of the third variety; that is to say, from external wounds, from stabs and gunshot injuries, in which cases air passes either from the wound of the lung or from an external wound into the cavitv of the pleura during the respiratory movements. In these cases there is generally no emphysema of the subcutaneous tissue unless the external wound is small and valvular, so that the air drawn into the wound during inspiration is then forced into the cellular tissue during expiration because it cannot escape from the external wound. Occasionally in wounds of the parietes of the thorax no air finds its way into the cavity of the pleura, because the lung at the time of the accident protrudes through the wound and blocks the opening. This occurs where the wound is large, and constitutes a so-called hernia of the lung. True hernia of the lung occurs, though very rarely, after wounds of the thoracic wall, when the wound has healed and the cicatrix subse- quently yields from the pressure of the viscus behind. It forms a globular, elastic, crepitating swelling, which enlarges during expiratory efforts, falls during inspiration, and disappears on holding the breath. Wounds of the lung may produce dangerous or fatal hemorrharje into the pleural sac. In many cases the bleeding is spontaneously arrested; in others the surgeon must interfere to save life. In some cases air has been admitted by intercostal incision and the inser- tion of a tube, and pulmonary collapse has arrested bleeding. In other cases it is necessary to resect portions of several ribs, and stop bleeding by ligatures or suture ligatm'es. J. Chalmers Da Costa reports a case in which a furious secondary hemorrhage followed a gunshot wound. He resected several ribs, packed the plem-al cavity about the lung with sterile gauze, to oljtain a base for support, and then arrested the bleeding by packing iodoform gauze against the firmly supported lung. This patient recovered. 1198 THE ORGANS OF VOICE AND RESPIRATION Incision of the lung (pneumotomy) is performed for pulmonary abscess (either tuberculous or pyogenic), pulmonary gangrene, hydatid cysts, and bronchiectasis. In pulmonary abscess, locate the area by physical signs and the -r-rays, resect a portion of a rib over it, and note if the pleura is adherent. If it is adherent, continue the operation. If it is not adherent, insert stitches of catgut through the two layers of pleura and the superficial part of the lung, so as to encircle a considerable area, and then wait several days for adhesions to'form. Adhesions protect the pleura from infection, and, by keeping air from the pleural sac, prevent pneumothorax. ^Vhen ready to continue the operation, locate the abscess with an aspirating needle and syringe, open it with a cautery at a dull red heat, and drain by means of a tube. Pneumotom}' is very unsatisfactory in tuberculous cavities and bronchiectasis. In tubercu- losis, excision of the diseased area (pneumectomy) has been emploj'ed, but it is not to be advised. Operations upon the lungs can be most safely performed with the patient in a Sauerbruch chamber. The danger of collapse of the lung is thus eliminated. The routine methods of physical examinations — inspection, palpation, percussion, and aus- cultation— are nowhere more important than they are in the diagnosis of diseases of the lungs. It is essential, too, that in every case the two sides of the thorax should be compared with each other, and that the wide variations that may be met with under normal conditions in different persons and at different ages should be kept in mind when the thorax is being examined. On iivspection the thorax will be seen to be enlarged and barrel-shaped in emphysema, in which the volume of the lungs is increased by dilatation of their alveoli, or in an acute attack of asthma, or when a large pleural effusion or mediastinal tumor is present. The thoracic wall will be flattened or sunken, on the other hand, over an area of lung that has collapsed or become fibrosed, as often happens in chronic pulmonary tuberculosis. The respiratory movements of the thoracic wall will be lessened, or even absent, over a part or the whole of the affected side in such acute disorders as pleurisy, pneumonia, or pleural effusion, or in more chronic disease where the underlying lung is fibrosed, or is crushed to one side by a mediastinal tumor; and by the use of the .r-rays a corresponding loss of movement or displacement of the Diaphragm on the affected side can often be observed. Under normal conditions the intercostal spaces are a little depressed; but they may be obliterated or even bulging on that side when a large effusion or newgrowth fills up one of the pleural cavities. On palpation, the hand can be used to verify the eye's impressions as to the degree of move- ment on respiration of any part of the thoracic wall. The facility with which the vibrations produced by the voice are conducted from the larynx by the underlying lung to the hand (in the form of vocal fremitus) can also be tested. The vocal fremitus is commonly much increased over the consolidated area in pneumonia or in fibrosis of the lung, and much diminished over a pleural effusion when the lung is pushed up by the fluid toward the top of the pleural cavity. It is also diminished, but to a less extent, in emphysema, and in bronchitis when the bronchi are blocked by secretion. In bronchitis the bubbling of the secretion in the tubes can often be felt by a hand placed on the thoracic wall as the patient breathes; and in chronic pleurisy the friction of the two roughened pleural surfaces against each other can sometimes be felt in the same way. On percussion, the normal resonance of the pulmonary tissue is found to be increased in em- physema, and in pneumothorax this hyperresonance may be still further increased. The resonance is lessened in any condition causing collapse or solidification of the lung tissue, or when its place is taken by fluid (pleural efl^usion) or some solid growth (mediastinal tumor). Thus, dulness on percussion at the bases of the lungs is common in the hypostatic congestion of the bases seen in heart failure; dulness at the right base is often due to compression of the lung by enlargement of the liver; some dulness at the apex of a lung is frequently met with in tuber- culosis of that part, before the disease has progressed very far. Complete dulness over one side of the thorax, back and front alike, except at the apex, is common when a large pleural effusion has taken the lung's place. Von Koranyi, Grocco, and others, have dra\\n attention to a tri- angular patch of dulness along the vertebral column (the paravertebral triangle of dulness) on the unaffected side in pleural efl^usion; this triangle of dulness is said to be absent in other con- ditions causing loss of pulmonary resonance on percussion, and is due to shifting over of the contents of the posterior mediastinum toward the sound side. The apex of this triangle is in the middle line at the upper level of the fluid effusion; its base, some two to four inches in length, runs horizontally outward from the middle line at the level where the pulmonary resonance normally comes to an end. On auscultation of the lungs, both in health and disease, the variety of sounds to be heard is very great. It is impossible to give adequate consideration to them here, and for further infor- mation reference should be made to the text-books dealing with the subject. THE OEGANS OF DIGESTION. THE Apparatus for tlie Digestion of the Food (apparatus digesiorius) consists of the alimentary canal and of certain accessory organs. The alimentary canal is a musculomembranous tube, about thirty feet, or nine meters, in length, extending from the mouth to the anus, and Hned throughout the entire extent by mucous membrane. It has received difi'erent names in the various parts of its course; at its commencement, the mouth, we find provision made for the mechanical division of the food (mastication), and for its admixture with a fluid secreted by the salivary glands (insalivation); beyond this are the pharynx and the oesophagus, the organs which convey the food (deglutitioii) into that part of the alimentary canal, the stomach, in which the principal chemical changes occur, and in which the reduction and solution of the food take place in digestion ; in the small iijtestine the nutritive principles of the food are separated, by its admixture with the Ijile, pancreatic and intestinal fluids, from that portion which passes into the large intestine, most of which is expelled from the system through the rectum and anal canal. Alimentary Canal. Mouth. Pharynx. (Esophagus. Stomach. f Duodenum. Small intestine \ Jejunum. L Ileum. [ Cecum and appendix. Colon. Rectum. . Anal canal. Large intestine • Accessory Organs. Teeth. Tongue. f Parotid. Salivary glands ] Submaxillary. Sublingual. Liver. Pancreas. THE MOUTH, ORAL OR BUCCAL CAVITY (CAVUM ORIS). The mouth is placed at the commencement of the alimentary canal; it is a nearly oval-shaped cavity, in which the mastication and insalivation of the food take place (Figs. 923 and 924). The aperture of the mouth (rima oris) is bounded by the lips. The angle of the mouth (angulus oris) is formed on each side by the meeting of the upper and lower lips {commissura labiorum). Wien at rest with the lips in contact, the runa is a slighdy curved line. Every movement which the lips make alters the shape of the rima. When the mouth is closed the floor and roof are usually in contact and its sides are approximated to the dental arches. The mouth consists of two parts — an outer, smaller portion, the vestibule, and an inner, larger part, the cavity proper of the mouth. ai99) 1200 THE ORGANS OF DIGESTION The Lips (labia oris) are two fleshy folds which surround the orifice of the mouth formed externally by integument and internally by mucous membrane, between which are found the Orbicularis oris muscle (Fig. 292), the labial vessels, some nerves (Fig. 439), areolar tissue, and fat, and numerous small labial glands. The upper lip is called the labium superius; the lower lip is called the labium inferius. The inner surface of each lip is connected in the middle line to the gum of the corresponding jaw by a fold of mucous membrane, the frenulum {frenulum labii superioris and frenuluvi labii inferioris) , the upper being the larger of the two. The labial glands (glandulae labialis) (Fig. 439) are situated between the mucous membrane and the Orbicularis oris muscle around the orifice of the mouth. They are circular in form and of small size; their ducts open by minute orifices upon the surface of the mucous membrane. In structure they resemble the salivary glands. The vestibule {vestibulum oris) is a slit-like space, bounded in front and later- ally by the lips and cheeks; behind and internally by the gums and teeth. Above and below it is limited by the reflection of the mucous membrane from the lips and cheeks to the gum covering the upper and lower alveolar arch respectively. It re- ceives the secretion from the parotid, buc- cal, molar, and labial glands, and commu- nicates, when the jaws are closed, w;ith the cavum oris by an aperture on each side be- hind the wisdom teeth, and by narrow clefts between opposing teeth (interdental spaces). The Cheeks (buccae) form the sides of the face and are continuous in front with the lips. They are composed externally of integument, internally of mucous mem- brane, and between the two of a layer of muscle, besides a large quantity of fat, areolar tissue, vessels, nerves, and buccal glands. The Mucous Membrane. — The mucous mem- brane lining the cheek is reflected above and below upon the gums, where its color becomes lighter; it is continuous behind with the lining membrane of the soft palate. It is composed of stratified squa- mous epithelial cells that rest upon a basement membrane and papillated tunica propria that con- sists of fibroelastic tissue supporting the smaller vessels and nerves. Opposite the second molar tooth of the upper jaw is a papilla, the summit of which presents the aperture of the parotid duct {ductus parotideus [Stenonis\} (Fig. 958). The principal muscle of the cheek is the Buccinator, but mmierous other muscles enter into its formation — viz., the Zygomatic!, Risorius, and Platj'sma. The Buccal Glands {glandulae buccales). — The buccal glands are placed in the submucous tissue between the mucous membrane and Buccinator muscle; they are similar in structure to the labial glands, but smaller. Foiu- or five glands of larger size than the pre\'iously mentioned glands are placed beneath the mucous membrane in the neighborhood of the last molar tooth. They are called the molar glands {glandulae molares). Their ducts open into the mouth opposite the last molar tooth The fat pad of the cheek {corpus adiposum buccae) has been described on page 376. The Glims {gingivae) are composed of a dense fibrous tissue, closely connected to the periosteum of the alveolar processes and surrounding the necks of the teeth. Thev are covered bv smooth and vascular mucous membrane, which is remarkable SMALL INTESTINE ANJJS Fig. 923. — Diagram of the alimentary tube and its appendages. (Testut.) THE ilOUril, ORAL OB BUCCAL CAVITY 1201 for its limited sensibility. Around the necks of the teeth the fibroelastic portion presents numerous fine papilhe; from here it is reflected into each alveolus, where it is continuous with the periosteal membrane lining that cavity. The cavity of the mouth proper (camm oris propriiim) is bounded laterally and in front by the alveolar arches with their contained teeth; hrhind, it ('f)mmuni- cates with the pharynx by a constricted aperture termed the isthmus faucium. It is roofed, in by the hard and soft palate. The greater part of the floor is formed by the tongue, the remainder being completed by the reflection of the mucous membrane from the sides and under surface of the tongue to the gum lining the inner aspect of the mandible. It receives the secretion from the submaxillary, sublingual, and lingual glands. Floor of the Mouth. — If the tongue be lifted out of its resting-place, the true floor of the mouth, or sublingual region, may be examined. In the middle a fold Fig. 924. — Antpro-infc that che pharyngeal istbu of mucous membrane, the frenum linguae, extends from the under surface of the tongue to the floor. On each side of the frenum is a papilla , the caruncula sublingu- alis, on the summit of which is the small orifice of the submaxillary (^Yharton's) duct. Extending backward from these caruncles, between the tongue and the al- veolar arches on each side, is a carunculated fold, the plica sublingualis, ^^■hich becomas lost posteriorly. The carunculated elevations, of variable number, present the orifices of the sublingual ducts. Structure. — The mucous mevihranc lining the mouth is continuous with tlie integument at the free margin of the lips and with the mucous lining of the pharynx behind; it is of a rose- pink tinge during life, and very thick where it covers the hard parts bounding the cavity. It is covered by stratified squamous epithelium. In the subepithelial fibroelastic tissue are seen many small accessory salivary glands. 1202 THE ORGANS OF DIGESTION The Palate (palatum) forms the roof of the mouth; it consists of two portions: the hard palate, about two-thirds in front; the soft palate, about one-third behind. The hard palate {palatum durum) (Figs. 924 and 925) is bounded in front and at the sides by the upper alveolar arches and gums; behind, it is continuous with the soft palate. It is formed by the palate processes of the maxillae and the palate processes of the palate bones (Fig. 72). It is covered by a dense structure formed by the periosteum and mucous membrane of the mouth, which are inti- mately adherent, particularly to the front and sides, by means of a layer of fibrous DESCENDING PALATINE ARTERY the right side of the mucous membrane has been removed, membrane and the glandular layer. (Poirier and Charpy.) left side shows tissue. Along the middle hne is a linear ridge or raphe (raphe palati), which terminates anteriorly in a small papilla, the incisive papilla {papilla incisiva), corresponding with the inferior opening of the anterior palatine fossa. On either side and in front of the raphe the mucous membrane is thick, pale in color, and corrugated; these corrugations, which are composed of fibrous tissue, are the palatine^ rugae (plicae palatinae transversae) . In very young children the rugae are distinct and definite. In the aged they are indistinct. Behind, it is thin, smooth, and of a deeper color; it is covered with stratified squamous epithelium and the fibrous tissue beneath it contains many mucous glands, the palatine glands (glandulae palatinae). The palatine vessels and nerves lie in the fibrous tissue beneath the mucous membrane. The soft palate (palatum molle) (Figs. 924 and 925) is a movable slanting fold suspended from the posterior border of the hard palate, and forming an incomplete septum between the mouth and pharynx. It consists of a fold of mucous mem- ' Concerning the etymology O' palatal and palatii i footnote on page 109. THE MOUTH, ORAL OR BUCCAL CA V'lTY 1203 brane enclosing muscle fibres, an aponeurosis, vessels, nerves, lymphoid tissnc, and mucous glands. When occupying its usual position it is relaxed and pendent, and its oral surface is concave, continuous with the roof of the mouth, and marked by a median ridge or raphe, which indicates its original separation into two lateral halves. Its pharyngeal surface is convex, and continuous with the mucous mem- brane covering the floor of the posterior nares. Its anterior or upper border is attached to the posterior margin of the hard palate, and its sides are blende>d witli the pharynx. Its posterior or lower border is free. The posterior portion of the soft palate (velum palatiimm) terminates posteriorly and externally on eacii side in a free margin, the posterior arch of the palate, and bounds the isthmus of the pharynx. Hanging from the middle of its lower border is a small, cone-shaped, pen- dulous process, the uvula {uvula falatind). The uvula varies greatly in length in different individuals. It is composed of glands and connective tissue, contains a prolongation of the Azygos uvulre muscle and is covered with mucous membrane, and arching outward and downward from the base of the uvula on each side are two curved folds of mucous membrane, containing muscle fibres, called the arches or pillars of the soft palate or pillars of the fauces {anus 'palatini). The anterior pillar (arms glossopalatinus) (Fig. 924) on each side runs downward, outAA'ard, and forward to the side of the base of the tongue, and is formed by the projection of the Palatoglossus muscle, covered by mucous membrane. The posterior pillar (arcus pharyngopalatmus) (Fig. 924) is larger and projects farther inward than the anterior; it runs downward, outward, and backward to the sides of the pharynx, and is formed by the projection of the Palatopharyn- geus muscle, covered by mucous membrane. The anterior and posterior pillars are separated below by a triangular interval {tonsillar sinus), in which the tonsil is lodged. The aperture by which the mouth communicates with the pharynx is called the isthmus of the fauces {isthimis faucium) . It is boui'^ded, above, by the free margin of the soft palate; helow, by the back of the tongue; and on each side, by the pillars of the fauces and the tonsils. The aponeurosis of the soft palate is a thin but firm fibrous layer attached above to the pos- terior border of the hard palate, and becoming thinner toward the free margin of the soft palate. Laterally, it is continuous with the pharyngeal aponeurosis. It forms the framework of the anterior half of the soft ]ialate, and is joined by the tendons of the Tensor palati nuiscles. The muscles of the soft palate arc found in its posterior h:df, and arc six on cac-h side — the Levator palati, Tensor palati, Azygos uvulae, Palatoglossus, Palatopharyngeus, and Sal- ■pingopharyngeus (see p. 397). The following is the relative position of these structures in a dissection of the soft palate from the posterior or nasopharyngeal to the anterior or oral surface: Immediately beneath the jiharyngeal mucous membrane is a thin stratum of muscle tissue, the posterior fasciculus of the Palatopharyngeus muscle, joining with its fellow of the opposite side in the middle line. This posterior fasriculus is joined by the Salpingopharyngeus muscle. Beneath -this arc the Azygos uvulas and Salpingopharsmgeus muscles, consisting of two rounded fleshy fasciculi, placed side by side in the niciliau line of the soft jjalate. Next comes the apo- neurosis of the Levator palati, joining with the muscle ;)f tlie opposite side in the middle line. Fourthly, the anterior fasciculus of the Palatopharyngeus, thicker than the posterior, and sepa- rating the Levator palati from the next muscle, the Tensor palati. This muscle terminates in a tendon which, after winding around the hamular process of the internal pterygoid plate of the sphenoid bone, expands into a broad aponeurosis in the soft palate, anterior to the other muscles so far enumerated. Finally, we have a thin muscular stratum, the Palatoglossus muscle, placed in front of the aponeurosis of the Tensor palati, and separated from the oral mucous membrane by lymphoid tissue. The mucous membrane of the soft palate is thin, and covered with stratified squamous epi- thelium on both surfaces, excepting near the orifice of the Eustachian tube, where its epithelium is stratified and ciliated.' Beneath the mucous membrane on the oral siu-face of the soft palate ' According to Klein, the mucous membrane on tlie nasal surface of the soft palate in the fetus is covered through- out by columnar ciliated epithelium, which subsequentb' becomes squamous; and some anatomists state that it is covered with columnar ciliated epithelium, except at its free margin, throughout life. 1204 THE ORGANS OF DIGESTION is a considerable amount of lymphoid tissue. The palatine glands form a continuous layer on the pharyngeal surface and around the uvula. The arteries supplying the palate are the descending palatine branch of the internal maxil- lary artery (a. palatina descendens) , the ascending or palatine branch of the facial artery (a. palatina ascendens), and sometimes a palatine branch of the ascending pharyngeal. The ■veins terminate chiefly- in the pterygoid and tonsillar plexuses. The lymphatic vessels pass to the superior deep cervical nodes. The motor nerves are chiefly derived from the pharjoigeal plexus, the Tensor palati, however, receiving a special branch from the otic ganglion. The sensor nerves are derived from the de- scending palatine, nasopalatine, and from the glossopharyngeal. Development of the Mouth. — The mouth is developed partly from the stomodeum, the depression between the head end of the embryo and the pericardial area, and partly from the floor of the extreme end of the foregut. The floor of the stomodeum is the thin, buccopharyngeal membrane, formed by the apposition'of ectoderm and entoderm; this membrane wholly disap- pears after the second week of embryonic life, and a communication is established between the mouth and future pharynx. With the development of the face the nasal passages are separated from the mouth proper by the coalescence of the maxillary and palatal processes of the first visceral arch with the lateral nasal and globular proce.sses forming the maxilte and palate. The development of the teeth is described on page 1212. Applied Anatomy. — Cleft palate is by no means a rare congenital deformity, and may be partial or complete. Most of the cleft is in the middle line. It may be a mere cleft of the uvula, it may be limited to the soft palate, or it may involve the hard palate to but not include the alveolus'. It may pass through the alveolus, but if it does so it ceases to be median at this point, and follows the line of suture between the incisive bone and the maxilla (pp. 106 and 152). Complete cleft palate is likely to be accompanied by harelip. This cleft in the lip is not median, but is at the termination' of the palate cleft. If the cleft of_ a cleft palate runs along each side of the incisive bone, the bone is isolated from the maxilla and the cleft is Y-shaped. In such a case double harelip is present. The Teeth {denies).— ^he human subject is provided with two sets of teeth, which make their appearance at different periods of life. Those of the first set appear in childhood, and are called the temporary, decidu- ous, or milk teeth. Those of the second set are named permanent or succedaneous teeth. The temporary teeth are twenty in number — four incisors, two canines, and four molars in each jaw (Figs. 926 and 947). The permanent teeth are tliirty-two in number — four incisors (two central and two lateral), two canines, four bicuspids, and six molars in each jaw (Figs. 928 and 932). The dental formulae may be represented as follows: Temporary Teeth. Upper jaw . Molar. Canine. Incisor. .2 1 2 Lower jaw Incisor. Canine. Molar. 2 1 2 Total, 20. Permanent Teeth. Molar. Bicuspid. Canine. Incisor. Upper jaw .3 2 1 2 Incisor. Canine. Bicuspid. Molar 2 12 3 Total, 32. Lower jaw .3 2 1 2 General Characters (Fig. 933). — ^Each tooth consists of three portions — the crown or body (corona dentis), projecting above the gums; the root or fang {radix dentis), entirely concealed within the alveolus; and the neck (collum dentis), the constricted portion between the root and crown, covered by the gum. The roots of the teeth are firmly implanted within the sockets or alveoli of the jaws (alveoli dentalc^; (see pp. 104 and 117). These depressions are lined with periosteum, which is reflected on to the tooth at the apex of the root and covers 1 According to Klein, the mucous membrane on the nasal surface of the soft palate in the fetus is covered throughout by columnar ciliated epithelium, which subsequently becomes squamous; and some anatomists state that it is covered with columnar ciliated epithelium, except at its free margin, throughout hfe. THE MOUTH, ORAL OH BUCCAL CAVITY 1205 it as far as the neck. This is the root-, or pericemental membrane (periosteum alve- olare). At the margin of the alveoki.s the periosteian l)econies continuous with the fil)rous structure of the gums. Surfaces. — In consequence of the curve of the dental arch, such terms as anterior, posterior, internal, and external, as applied to the teeth, are misleading and con- fusing. Special terms are therefore applied to the different surfaces of a tootii: That which looks toward the lips and cheek is the labial or buccal surface (fades Fig. 026. — Deciduous teetli of left side. Labial view. Fig. 927. — Deciduous teeth. Lingual view. lahialis); that toward the tongue is the lingual surface { fades lingualis); that surface which is directed toward the mesal plane, supposing the teeth were arranged in a straight line outward from the central incisor, is known as the proximal surface, looks toward predecessor; while that directed away from the mesal plane is called the distal surface, looks toward successor. The surface which comes in contact with the teeth of the opposite jaw is the grinding, masticating, or occlusal surface (fades masticator ia^. Fig. 928. — Permanent teeth, right side. (Burehard.) The Temporary, Deciduous, or Milk Teeth (dentes decidui) (Figs. 926 and 927) are smaller, but resemble in form those of the permanent set. The neck is more marked, owing to the greater degree of convexity of the labial and lingual surfaces of the crown. The last of the two temporary molars is the largest of all the deciduous teeth, and is succeeded by the second bicuspid. The first upper molar has only three cusps — two labial, one lingual; the second upper molar has four cusps. The first lower molar has four cusps; the second lower molar has five. 1206 THE ORGANS OF DIGESTION The roots of the temporary molar teeth are smaller and more diverging than those of the permanent set, but in other respects bear a strong resemblance to them. Permanent Teeth {denies permanentes) (Fig. 928). — ^The incisors or cutting teeth {denies incisivi) are so named from their presenting a sharp cutting edge, adapted for incising the food. They are eight in number, and comprise the four front teeth in each jaw. The crown is directed vertically and is chisel-shaped, being bevelled at the expense of its lingual surface, so as to present a sharp horizontal cutting edge. Before being subjected to attrition this edge presents three small elevations. The labial surface is convex, smooth, and highly polished. The lingual surface is con- cave, and is marked by two marginal ridges extending from an encircling ridge at the neck to the angles of the cutting edge of the tooth. The ridge at the neck is termed the cingulum or basal ridge. The neck of the tooth is constricted. The root is long, single, conical, transversely flattened, thicker before than behind, and slightly grooved on either side in the longitudinal direction. The root may be curved. Fig. 929. — Right half of upper jaw (from below), with the corresponding teeth. The letters and numbers point to the classes of teeth and the numbers in classes. Fig. 930.— Right half of lower jaw. with the cor- responding teeth. The letter and numbers point to the various cusps or their modifications on the differ- ent teeth. (Burchard.) The incisors of the upper jaw are altogether larger and stronger than those of . the lower jaw, the central incisors being larger and flatter than the lateral incisors. They are directed obliquely downward and forward. The incisors of the lower jaw are smaller and flatter than the upper, and the elevations upon their lingual faces are not marked. The two central are smaller than the two lateral incisors, being the smallest of all the teeth. The roots of these teeth are flattened laterally. The Canine Teeth {denies canini) are four in number, two in the upper, two in the lower jaw — one being placed distal to each lateral incisor. They are larger and stronger than the incisors, especially in the roots, which are deeply implanted and each causes a well-marked prominence of the process at the place of inser- tion. The crown is large, of spear-head form, and its very convex labial surface is marked by three longitudinal ridges. The concave lingual surface is also marked by three ridges which unite at a basal ridge. The point or cusp is longer than in the other teeth, and is the point of division between a short proximal and a long distal cutting edge. These two edges form an obtuse angle with each other. TH?: MOUTH, ORAL OR BUCCAL CAVfTY ] 207 The root is single, oval, or elliptical on transverse section, and is lonf;er and more prominent than the roots of the incisors. The upper canines, popularly called the eye teeth, are larger and longer than the two lower, and in occlusion are distal to them to the extent of half the width of the crown. The lower canines, popularly called the stomach teeth, have the general form of the upper canines, but their lingual surfaces are much more flattened, owing to the absence of the elevations marking the upper teeth. Their roots are more flattened and may be bifid at their apices. The bicuspid teeth, or the premolars {dentes 'premolares) are eight in number, four in each jaw; they are placed distal to the canine teeth, two upon each side of the jaw. The crown is surmounted by two cusps, one buccal and one lingual, separated by a groove, the buccal being more prominent and larger than the lingual. The lower bicuspids are not truly bicuspid, the first having but a primitive lingual cusp, the second having the lingual cusp divided into two sections — /. e., it is usually tricuspid. The necks of the teeth are ovaX; the roots are single and later- ally compressed, that of the first upper bicuspid being frequently bifid. The first upper bicuspid is usually the largest of the series. The roots of the lower bicuspids are less compressed and more rounded. The Molar Teeth {dentes molares) are the largest and strongest teeth of the per- manent set, and are adapted by their forms for the crushing and grinding of the food. They are twelve in number, six in each jaw, three being placed posterior to each second bicuspid. The crowns are cuboidal in form, are convex bucally and lingually; they are flattened proximally and distally. They are formed by the fusion of three primi- tive cuspids in the upper and four in the lower. To these are added in the first and second upper molars a distolingual tubercle, and in the first and third molars of the lower jaw a distobuccal tubercle. The unions of the primitive forms are marked by sulci. The necks of these teeth are large and rhom- boidal in form. The roots of the upper molars are three in number — one large lingual or palatal root, and two smaller buccal roots. In the lower molars, two roots are found, a proximal and a distal, each of which is much flattened from before backward. The first molar teeth are the largest of the dental series; they have four cusps on the upper and five in the lower — three buccal and two lingual. The second molars are smaller; the crowns of the upper are compressed until the distolingual cusp is reduced. The crowns of the lower are almost rectangular, with a cusp at each angle. The third molars are called the wisdom teeth, or dentes sapientiae (denies serotini) , from their late eruption ; they have three cusps upon the upper and five upon the lower. The three roots of the upper are frequently fused together, forming a grooved cone, which is usually curved backward. The roots of the lower, two in number, are compressed together, and curve backward. Of the permanent teeth, all but the molars represent succedaneous teeth, that is, teeth that succeed those of the temporary set. The molars are primary teeth, as they possess no predecessors in the temporary set. Arrangement of the Teeth.i — The human teeth are arranged in two parabolic arches, the upper row or arch {amis dentalis sirperior) being larger, its teeth over- lapping the lower row or arch {arms dentalis inferior). The a^'erage distance between the centres of the condyles of the mandible is about four inches, which is also the distance from either of these points to the line of junction between the lower incisor teeth. Whether the jaw be large or small, the equilateral triangle 1 After Dr. W. G A. Bonwill. 1208 THE ORGANS OF DIGESTION indicated is included in it; the range of size is between three and one-half and four and one-half inches. Fig. 931. — View of teeth in situ, with the external plates of the alveolar processes removed. tCryer.) Owing to the smaller sizes of the lower incisors, the teeth of the mandible are each one-half a tooth in advance of its upper fellow, so that each tooth of the dental Fig. 932. — Front and side views of the teeth and jaws. (Cryer.) series has two antagonists, with the exception of the lower central incisors and upper third molars (Figs. 931 and 932). THE MOUTH, ORAL OR BUCCAL CAVITY 12U9 The grinding faces of the upper bicuspids and molars curve progressively upward and point outward, the first molar being at the lowest point of the curve, the third molar at the highest. The curve of the lower dental arch is the reverse, the first molar at its deepest part, the third molar at its extremity. The greater the depth to which the upper incisors overlap the lower, the more marked this curve and the more pointed are the cusps of the grinding teeth. The movement of the human mandible is forward and downward, the resultant of these directions being an oblique line, upon an average of 35 degrees from the horizontal plane.' When the mandible is advanced until the cutting edges of the in- cisors are in contact, the jaws are separated, but at the highest point of the lower arch its third molar advances, and meets and rests upon a high point, the second molar of the upper arch, and thus undue strain upon the incisors is obviated. In the lateral movements of the mandible but one side is in effective action at one time; the oblique positions of the cusps of the oppo- site teeth are such that when either side is in action the other is balanced at two or more points. I'ulp Cavity. Fig. 934. — Vertical section of a tooth in situ (15 diam- eters), c is placed in the pulp cavity, opposite the cervix, or neck of the tooth; the part above is the crown, that below is the root (fang). 1. Enamel with radial and concentric markings. 2. Dentin with tubules and incremental lines. 3. Cementum or crusta petrosa, ^\-ith bone corpuscles. 4. Perice- FlG. 933. — Vertical section of molar tooth. mental membrane. 5. Bono of mandible. There is an anatomical correspondence between the forms and arrangement of the teeth, the form of the condyle of the mandible, and the muscular arrange- ment. Individuals who have teeth with long cusps have the head of the bone much rounded from before backward, and have a preponderance of the direct over the oblique muscles of mastication, and vice versa; teeth with short or no cusps are associated with a flattened condyle and strong oblique muscles. Very great aberrations in the dental arrangement are frequently followed by accommodative changes in the condyles of the mandible. Structure of the Teeth.— A longitudinal section of a tooth will show the presence of a central chamber having the general form of the crown of the tooth, and called the pulp chamber or pulp cavity {camim dentis). The solid jiortion of the tooth exhibits three hard tissues: one, the 1 W. E. W.alker, Dental Cosmos, 1896. 1210 THE ORGANS OF DIGESTION proper dental substance, called dentin or ivory sheathed upon the exposed crown by a layer called the enamel, while the dentin of the root is enclosed in a distinct tissue, the cementum or crusta petrosa. Both enamel and cementum are thinnest at the neck and thickest upon their distal portions. The enamel {substantia adamantina) (Figs. 934, 935, and 938) is the hardest and most com- pact part of a tooth, and forms a thin crust over the e.xposed part of the crown, as far as the commencement of the root. It is thickest on the grinding surface of the crown until worn away by attrition, and becomes thinner toward the neck. It consists of a congeries of minute hex- agonal rods, columns, or prisms, known as enamel fibres or prisms (prismata adamantina) (Fig. 938). In general they lie parallel with one another, resting by one extremity upon the dentin, which presents a number of minute depressions for their reception, and forming the free surface of the crown by the other extremity. There are additional shorter (supplemental) prisms filling in the spaces between the long diverging prisms. There are occasional collections of prisms which run diagonally. The prisms are directed vertically on the summit of the crown, horizontally at the sides; they are about tttVu inch in diameter, and pursue a more or less wavy course. By reflected light radial striations are visible, best marked near the dentin. These are Schreger's lines and are due to the fact that the prisms take an undulatory course '/ Fig. 935. — Longitudinal ground section through the apex of a canine tooth from a three-and-a-half-year-( boy. The entrance of the dental canaliculi between the enamel prisms and the course taken by the latter i shown. X 135. (Szymonowicz.) and those of two layers may have opposite directions. Another series of lines, having a brown appearance from pigmentation, and denominated the parallel striae or brown striae of Betzius, or the colored lines, are seen on a section of the enamel. These lines are concentric, and cross the enamel rods. They are caused by the mode of enamel deposition. Inasmuch as the enamel columns, when near the dentin, cross each other and only become parallel farther away, a series of radial markings, light and dark alternately, is obtained (Fig. 934). The enamel prisms are themselves calcified and are fixed to each other by a very small amount of cement substance. Numerous minute interstices intervene between the enamel fibres near their dentinal surface. It is noted that some of the dentinal canals at the crown penetrate a certain distance between the rods of the enamel; this is considered pathological by some (Fig. 935). No nutritive canals exist in the cniunpl, except the very few dentinal canals which at the crown penetrate a short distance, mikI llicsc are found only in a small area. Chemical Composition. — According to Bibra, enamel consists of 96.5 per cent, of earthy matter and 3.5 per cent, of animal matter. The earthy matter consists of the phosphate and THE MOUTH, ORAL OR BUCCAL CAVITY 1211 the carbonate of calcium, with traces of fluoride of calcium, phosphate of magnesia ami other salts. ' The enamel of a recently erupted tooth is covered by a membrane, tiie thickness of which IS 20^0 mch It is known as enamel cuticle oi- Nasmyth's membrane (ciillnila deniia) It IS probably the remains of the enamel organ, though some consider it the contiruiation of the cementum. The dentin or ivory (substantia eburnca) (Fig. 937) forms the principal mass of the tooth. It represents modified bone, but' differs from the latter in that its cells are upon the siu^ace of the pulp and not In the substance of the dentin. The important parts are: dentinal tubules denlMKil shcntiis, matrix, and dentinal fibres. Till' dentinal tubules are minute canals which have a spiral course, more or less perpendicular to the pulp cavity, and extending from this cavity to the enamel or to the cementum. The diameter at the pulpal end is about ^niVs of an inch, and this diminishes as the tubules branch. The tubules usually end blindly near the enamel; some, however, terminate in the interglobular spaces or anastomose with other tubules. The dentinal tubules contain the dentinal fibres, which represent the pcriplK'iul prijfcsses of the odonto- blastic cells, and their branches follow the divisions of the tubules. The tubule branches are most numerous near the enamel or the cementum. Fig. 936. — Ground section through the root of a human pre- molar. D. Dentin. K. Cement corpuscles. O. Osteoblasts, Ep. Remains of Hertwig's epithelial sheath, 200 diameters. -A Interglobular spaces. (Rose.) Fig. 937. — From a ground section through the parts of a dentin, near the pulp, of a human canine tooth which lias been impregnated with pigment. The dental canaliculi are cut across and are joined together by side branches. X 400. The dentinal sheaths, or Netmiann's sheaths, are tubes of markedly resistant dentin sur- rounding and bounding the dentinal tnlinlcs. They branch and curve as do the tubules. Tlie matrix, or intertubular dentin, is less dense than that of the sheaths. It fills the spaces between the sheaths, and seems to be composed of lamellae that run parallel to the pulp chamber. Fibrils have been found in the matrix. Scattered in the matrix, and especially near the enamel, are numerous spaces filled with a gelatinous substance; these are the interglobular spaces (spatia interglobulares) , representing areas of incomplete calcification. Between the dentin and cementum the spaces are very numerous, but small; these constitute Tomes' granular layer. In a dry tooth a section of dentin often displays a series of lines — the incremental lines oi Salter — which are parallel with the laminae above mentioned. These lines are caused by two facts: (1) The imperfect calcification of the dentinal laminae immediately adjacent to the line. (2) The drying process, which reveals these defects in the calcification. These lines are wide or narrow according to the number of laminae involved, and along their coiu'se, in consequence of the imperfection in the calcifying process, little irregular cavities are left, which are the inter- globular spaces already referred to. They have received their name from the fact that they are smrounded by minute nodules or globules of dentin. Other curved lines may be seen ]>arallel to the surface. These are the concentric lines of Schreger, and are due to the optical effect of simultaneous ciu'vature of the dentinal tubules. 1212 THE ORGANS OF DIGESTION Chemical Composition. — According to Berzelius and Bibra, dentin consists of twenty-eight parts of animal and seventy-two of earthy matter. The animal matter is resolvable by boiling into gelatin. The earthy matter consists of phosphate and carbonate of calcium, with a trace of fluoride of calcium, phosphate of magnesia, and other salts. The cementum, or crusta petrosa (substantia ossea) (Fig. 934). is disposed as a thin layer on the roots and neck of a tooth, from the termination of the enamel as far as the apex of the root, where it is usually very thick. At the neck it overlies a slight margin of enamel. In structure and chemical composition it is true bone. It consists of a number of lamella; that are thicker near the apex than the neck of the tooth in young teeth. In older teeth there are addi- tional shorter supplemental lamellae at the apex. Between the lamellae are the lacunae and canaliculi, and it is claimed that in thick cementum even Haversian systems may be found. It is composed of about 66 per cent, organic matter and 34 per cent, inorganic matter. The teeth of the young usually contain Haversian systems in the thicker portions of the cementum. The neck of the tooth does not contain lacunje. Sharpey's fibres (p. 38) are very numerous. Some of the lacunae of the cementum receive dentinal tubes from the dentine. As age advances the cement increases in thickness, and gives rise to those bony growths, or exostoses, so common in the teeth of the aged; the pulp cavity becomes also partially filled by a hard substance intermediate in structure between dentin and bone (the osteodentin of Owen; the secondary dentin of Tomes). It is formed by the odontoblasts, the dental pulp lessening in volume. Fig. 938.' — Enamel prisms (350 diameters). A. Fragments and single fibres of the enamel isolated by the action of hydrochloric acid. B. Sm-face of a small fragment of enamel, showing the hexagonal ends of the fibres. The pulp ipulpa dentis) occupies the pulp cavity or chamber. This chamber communicates with the outside through a minute canal in the apex of each fang, called the root canal (canalis radicis dentis). The foramen at the apex is called the apical foramen (foramen apieis dentis). The pulp is a highly vascular and sensitive mass of mucous connective tissue connected with the nutrition and sensitiveness of the tooth. It consists of a network of delicate fibrils sup- porting spindle-shape, stellate, and spheroidal cells, and, lastly, the odontoblasts, which are arranged in a single row upon the surface of the pulp; each odontoblast is a cylindrical or flask- shaped cell possessing several processes, of which the peripheral becomes the dentinal fibre. The bloodvessels of the pulp break up into innumerable capillary loops which lie beneath the layer of odontoblasts. The nerve fibrils break up into numberless amyelinic filaments, which spread out beneath the odontoblasts, and probably send terminal filaments to the extreme periphery of the pulp outside the odontoblasts. The matrix cells and their processes are irregu- larly arranged in the body of the pulp, but in the canal portion the fibrillae are in the direction of the axis of the root. The peridental membrane (perieementum) is a vascular and sensitive fibrous tissue membrane that holds the tooth in place. Upon its internal surface it forms cementum, while upon its outer surface it forms the bone of the alveolar process of maxilla or mandible. It is thickest at the apical and gingival regions of the tooth and thin in the middle. Upon its inner surface are. seen cementoblasts, and upon its outer surface are found osteoblasts. The arteries are derived from the apical artery, and ultimately form a capillary plexus beneath the cemental and alveolar surfaces of the membrane. The venous channels converge at the apex to empty into the apical vein. Lymphatics are said to be absent. Development of the Teeth (Figs. 939 to 945). — The teeth are an evolution from the dermoid system, and not of the bony skeleton; they are developed from two of the blasto- THE MOUTH, ORAL OR BUCCAL CA VfTY 1213 dermic layers, the ectoderm and mesoderm. From the former the enamel is developed; from the latter the dentinal pulp, dentin, cementum, and peridental membrane. It is customary to view the development of the permanent and temporary teeth as separate studies. The earliest evidence of tooth formation in the human embryo is observed about the sixth week. The epithelium covering the embryonic jaws is seen to rise as a ridge along the summit of each jaw. This ridge is the maxillary rampart of Kblliker and Waldeyer. A transverse section through the jaw will show the clcwiiidii in lie due lo a liiii-ar and miilincd activity of the germinal epithelial layer; a corresponding c|iithclial growth is seen lo .sink as a liand into the mesodermal tissue beneath. This band is called the dental lamina (jr dental shelf. The local ■^. Enamel pidp Superficial cells of enamel organ ..Epithelium of oral cavity Basal layer Superficial cells of eitatnel organ 'Enamel pulp -Dentinal papilla Fic 939 — \nlage of the enamel germ con- nected ^ith the oral epithelium by the enamel ledge \ 110 Fig. 940.— First trace of the dentinal papilla. X 110. Epithelium of ~ — oral cavity s^ Basal layer Part of enamel ledge of a permanent tooth Enamel germ of ane)it toolh cl pulp Dentinal papilla Odontoblasts Enamel cells Fig. 941. — Advanced stage with larger papilla and differentiating enamel pulp. X 110. Fig. 942. — Budding from the enamel ledge of the anlage of tlie enamel germ, which later goes to form the enamel of a permanent tooth; at the periphery of the papilla the odontoblasts are be- ginning to differentiate. X 40. Figs. 939 to 942.— Four stage; 1 the development of a tooth in a sheep i (From Bohm and Davidoff.) iibryo (from the lower jaw) cell activity continues, and in its descent the band appears to meet with a resistance which causes a flattening of its extremity into a continuous lamina. From the outer or labial surface of the shelf epithelial buds are given off successively, ten in number, one for each temporary tooth; the earliest (central incisors) appear about the seventh to the eiijhth week. The growth of each bud continues, and each expands into a flask-like form, the walls covered by a layer of germinal cells, its interior composed of stellate cells. The bulb is now seen to flatten upon its deep surface, as though it had met with an outlined resistance from the mesodermal 1214 THE ORGANS OF DIGESTION tissue beneath. The mesoderm at the base of each enamel organ condenses, and seems to force the adjacent part of the enamel germ toward the apex of the organ, producing thus a sac- like structure, the enamel organ; the latter now consists of three layers, outer columnar layer, middle, stellate reticulum, and inner, enamel-forming cells, the membrana adamantina. The papilla-like mass of mesoderm that extends into the enamel organ is called the dental papilla. Dental furiow Remains of ' ' nech ' of enamel organ, or of the— common dental shelf Permanent special dental germ Meckel's cartilage. Fig. 943. — Vertical sestioa of the mandibl lute} nal enamel layer, 0) ada lantohlasts De ital sac »v» E lai lel palp Exte nal enamel layei Papiha early human fetus. (Magnified 25 diameters.) The mesoderm peripheraii to the enamel organ condenses to form a sheath called the dental sac or follicle. In the meantime the dental shelf becomes attenuated and tends to disappear, and bone is being deposited in the intervals around and between the teeth, so that the latter soon lie in a gutter of bone. The cells of the enamel organ now undergo a series of differentiations. The inner layer, arranged as columnar epithelium, are the enamel cells, or ameloblasts. The layer is called" the Dentine c. Fig. 944. — Section through tooth follicle ^— human canine seven and one-half months. A, Follicular wall. B. Outer epithelial coat. C. Stellate reticulum. Z>. Stratum inter- medium. E. .\meloblasts. F. Odontoblasts. G. Pulp. Fig. 945. — Diagram after Williams (Dental Cosmos, 1896), mode of enamel deposition. A. Blood supply to B, secreting papilla;. C Layer of ameloblasts containing enamel globules and droplets of calcoglobulin. D. Enamel globules deposited. E. Formed dentin. F. Forming dentin. G. Layer of odonto- blasts. H. Blood supply to odontoblastic layer. ameloblastic or enamel-forming layer (Figs. 944, 94.5, and 946). The cells of the outer wall remain cuboidal; the cells which lie between become much distended, and on account of their appearance when seen in section this portion of the organ is called the enamel jelly or the stellate reticulum. The layer of cells immediately contiguous to the ameloblasts forms a layer called the stratimi intermedium (Fig. 944, D). THE MOUTH, ORAL OR BUCCAL CAVITY 1215 The enclosed mesoblastic papilia (tlie fiittire dental pulp) has its peripheral cells, whieh are called odontoblasts, differentiated into columnar bodies disposed as a layer, each cell iKiving 8 large nucleus. The vascular supply of the pulp is now well marked. A section of a follicle at this period will exhibit the follicular wall springing from the base of the dental papilla and having a well-marked blood supply. The bony alveolar walls are well outlined, and e\idences of a periosteum appear (Figs. 943, 944, and 945). Development of Enamel (Fig. 945). — In point of time, the deposition of dentin actually begins before that of enamel, so that the first-formed layer of enamel is deposited against a layer of immature dentin, and is formed from within outward, so that the youngest enamel is ■upon the sm-face of the tooth . The enamel is built up of two distinct substances — globules of uniform size which are formed by the ameloblasts, and a cementing substance, probably an albuminate of calcium (caleoglobulin), the basis of all the calcified tissues. In the ends of the ameloblasts, next to the dentin, the secretion of caleoglobulin is deposited, and into the plastic mass the enamel globules are extruded, each globule remaining connected with the ameloblasts by plasmic strings, which also join the globules laterally.' The first deposit of enamel begins in the tips of the cusps, and is quickly followed by a disap- pearance of the stellate reticulum at that point; the stellate reticulum appears to atrophy, so that the vascular follicular wall is brought into direct apposition with the stratum intermedium, which becomes differentiated into a glandular (secreting) tissue which elaborates the calcic albuminous basis of the enamel. The secretion passes from the cells of the stratum intermedium through a membrane into the ameloblasts, where it is in part combined with the cellular globules, and irregular masses of it are extruded as cementing substance. The deposition continues until the enamel cap has its typical form. The deposition of the layers of globules is indicated by parallel lines transverse to the axes of the enamel rods. At the completion of amelification the ameloblasts are partially calcified and form the enamel cuticle or Nasmyth's membrane (cuticii/a deniis). Fig. 946.— Part of section of developing Formation of Dentin. — The layer of columnar tooth of young rat, showing the mode of 11 1 1-^1 .1 p .1 1 .1 J J. deposition of the dentin (highly magnified). cells bounding the periphery of the pulp, the OdontO- a. Outer layer of fully calcified dentin, b. blasts, are in apposition with the olexus of capillary Uncalcified matri.i with a few nodules of cal- 1 /T-<- ^ i/i\ T-t 1 11 • ,• I 11*1 careous matter, c. Odontoblasts with proc- vessels (I'lg. 946). iiach cell is a secreting body which esses extending into the dentin, d. Pulp. selects the material for dentin building. Against the The section is stained , p 111., I 7 T- -,i colors the uncalcifaed matrix, but not the cal- layer ot ameloblasts, the membrana ebons, covering the cified part. dental papilla, the odontoblasts deposit globules of the calcium albuminate, and receding as the deposits are made, leave one or more protoplasmic proc- esses in the calcic deposit. These are known as Tomes' or dentinal fibres. The process contin- ues until the normal dentin thickness is formed. The deposit is laid down in a scaffolding of finely fibrillated tissue, and begins about the sixteenth week. The layer of formative cells remains constant. The remains of the dentinal papilla constitute the pulp and lie in the pulp cavity (p. 1212). Formation of Cementum. — Aa the enamel organ continues to grow the dental follicle cov- ering atrophies, while that over the future root region continues to grow. Upon its dentinal surface the stellate cells constitute the cementoblasts. Upon its outer surface the stellate cells are osteoblasts that form the alveolar bone. The cementum of the tooth is not formed until the dentin has extended below the enamel cap, while the cementum of the apex is usually not completed until after the eruption of the tooth. Formation of Alveoli. — By the time the crowns of the teeth have formed, each is enclosed in a loeulus of bone which has developed around it and at some distance from it; the developing permanent tooth is contained in the same loeulus, but is later separated from the temporary tooth by a growth of bone. The alveolar process is not completed until after the eruption of the teeth. During eruption that portion of the process overlying the crown undergoes absorp- tion, and as soon as the immature tooth is erupted the alveolar process has developed about the root, whose formation is also completed after eruption. Development of the Permanent Teeth. — The permanent teeth as regards their develop- ment may be divided into two sets: (1) Those which replace the temporary teeth, and which, like them, are ten in number; these are the successional permanent teeth; and (2) those which have no temporary predecessors, but are superadded at the back of the dental series. These are three in number on either side in each jaw, and are termed the superadded permanent teeth. They are the three molars of the permanent set, the molars of the temporary set being replaced by the premolars or bicuspids of the permanent set. I J. L. Williams, Dental Cosmos, 1S06. 1216 THE ORGANS OF DIGESTION The Development of the Successional Permanent Teeth — the ten anterior ones in either jaw — will be first considered. The germs for these teeth are developed from the lingual side of the dental shelf, opposite to the corresponding temporary teeth. The germ for the central incisor appears at about the serenieenth week, and the others follow successively in order of their eruption. The deposition of enamel, dentin, and cementum occurs as in the temporary teeth. The sac of each permanent tooth is also connected with the fibrous tissue of the gum by a slender band of the gubemaculum, which passes to the margin of the jaw behind the corre- sponding milk tooth (see above). The Superadded Permanent Teeth — three on each side in each jaw — develop as primary teeth. The enamel germ for the first molar tooth appears during the sixteenth week from the end of the dental shelf. The enamel germ for the second molar tooth appears about the fourth month after birth from the neck of the enamel sac of the first molar tooth, while that for the third molar or wisdom tooth does not appear until the third year after birth, from the enamel sac of the second molar tooth. Eruption. — When the teeth are ready to erupt the bone between them and the gum is absorbed as well as that covering the labial surface of the crown, until one-half of the enamel is exposed. The bone covering the lingual surface is more slowly absorbed, as it protects the permanent tooth germ beneath. As a result of this process the tooth is exposed chiefly by the removal of the bone around the crown, and not by a growth upward of the tooth itself. In the replacement of the temporary teeth by the permanent set the roots of the temporary teeth are gradually absorbed until merely the enamel cap and contained dentin remain. The hold of the tooth upon the jaw is weakened so that it mav readilv be remox-ed or lost. Fig. 947.— The milk teeth in a child aged about four years. The permanent teeth are seen in their alveoli. (Cryer.) Calcification of the permanent teeth proceeds in the following order: First molar, soon after birth; the central incisor, lateral incisor, and canine, about six months after birth; the bicuspids, at the second year or later; second molar, end of second year; third molar, about the twelfth The Eruption of the Temporary Teeth commences at the seventh month, and is complete about the end of the second year. The periods for the eruption of the temporary set are (C. S. Tomes) : Lower central incisors 6 to 9 months. Upper incisors 8 to 10 ^^ Lower lateral incisors and first molars 1.5 to 21 Canines l^ ^° II « Second molars -0 to -4 THE TONGUE 1217 The Eruption of the Permanent Teeth takes place at the follo\\in<; periods, the teeth of the lower jaw preceding those of tlie upper by a short interval: 6i years, first molars. 10th year, second bicuspid. 7th year, two middle incisors. 11th to 12th year, canine. 8th year, two lateral incisors. 12th to 13th year, second molars. 9th year, first bicuspid. 17th to 21st year, third molars. THE TONGUE (LINGUA) (Fig. 948). The tongue is a very mobile muscular organ, undergoing changes in length and width at every contraction of its muscle. It is one of the organs of the special sense of taste, and is also an organ of speech, and assists in insalivation, masti- cation, and deglutition. It is situated in the floor of the mouth, in the interval between the two lateral portions of the body of the mandible, and when at rest is about three and one-half inches (8.75 cm.) in length. We describe the body, base, apex, dorsum, margin, and inferior surface. The body {corpus linguae) forms the great bulk of the organ and is composed of striated muscle. The base or root (radix linguae) is directed backward and connected with the hyoid bone by the Hyoglossi and Geniohyoglossi muscles and the hyoglossal mem- brane; with the epiglottis by three folds, glossoepiglottic folds, of raucous membrane; with the soft palate by means of the anterior pillars of the fauces; and with the pharynx by the Superior constrictor muscles and the mucous membrane. The apex or tip (apex linguae) is free, thin, and narrow, and is directed forward against the inner surface of the lower incisor teeth. The dorsum of the tongue {dorsum linguae) of a living person, when at rest, is markedly arched from before backward. On the dorsum is a median longitudinal raph^ {sulcus medianus linguae). This slight depression terminates posteriorly in the depression known as the foramen cecum (foramen caecum linguae [Morgagnii]), from which a shallow, V-shaped groove, the sulcus terminalis of His, runs outward and forward on each side to the lateral margin of the tongue. The part of the dorsum of the tongue in front of this groove, known as the anterior, apical, or oral part, forming about two-thirds of its upper surface, looks upward, is practically horizontal, and is rough and covered with papilla?; the posterior or basal third of the dorsum is vertical and looks backward, is smoother, and contains numerous muciparous glands and lymphoid nodules. The margin of the tongue (jnargo lateralis linguae) is free in front of the anterior arch of the palate. Just in front of the arch are several vertical folds, the folia linguae . The under or inferior surface {fades inferior linguae) of the tongue is connected with the mandible by the Geniohyoglossi muscles; from its sides the mucous mem- brane is reflected to the inner surface of the gums, and from its under surface on to the floor of the mouth, where, in the middle line, it is elevated into a distinct vertical fold, the frenum linguae (frenulum linguae). To each side of the frenum is a slight fold of the mucous membrane, the plica fimbriata, the free edge of which exhibits a series of fringe-like processes. The tip of the tongue, part of the under surface, its sides, and dorsum are free. Structure of the Tongue. — The tongue is partly invested by mucous membrane and a sub- mucous fibrous layoT surrounding the central muscle tissue. It consists of symmetrical halves, separated from each other, in the middle line, by an incomplete fibrous septum. Each half is composed of muscle fibres arranged in various directions (p. 393), containing many glands and much interposed fat, and supplied by vessels and nerves. The mucous membrane {tunica mucosa linguae) invests the entu-e e.xtent of the free surface of the tongue. On the dorsum it is thicker behind than in front, and is continuous with the 1218 THE ORGANS OF DIGESTION sheath of the muscles attached to it, through the submucous fibrous layer. On the under surface of the organ, where it is thin and smooth, it can be traced on each side of the frenum through the ducts of the submaxillary and the sublingual glands. As it passes over the borders of the organ it gradually assumes a papillary character. That covering the under surface of the organ is thin, smooth, and identical in structure with that lining the rest of the oral cavity. The mucous membrane covering the tongue behind the foramen cecum and sulcus terminalis is thick and freely movable over the subjacent parts. The mucosa consists of stratified squamous epithelial cells resting upon a basement mem- brane, and this upon a papillated tunica propria of fibroelastic tissue containing the capillary loops and nerves. Upon the apical two-thirds of the dorsum of the tongue the projections of the mucosa are seen, and these are the papillse. They vary in number, size, form., and location; they are the filiform papillae, fungiform papillae, and circumvallate papillae. EPIGLOTTIS IRCUM- VALLATE PAPILUC. Fig. 94S. — Upper surface of the tongue. The filiform or conical papillae {papillae filiformes) are small and scattered over the apical two-thirds (dorsum and margin) of the tongue, and are arranged in parallel lines that are directed outward and forward, especially posteriorly. Minute secondary papillae of a whitish color pro- ject from these filiform structures. The fvingiform papillae (papillae fungiformes) (Fig. 949) are scattered sparingly over the dorsum of the tongue, and are more numerous at the sides and apex. They are largjer in size but less numerous than the preceding, and are readily recognized by their large size and deep red color. Their bases are narrow and constricted, while the free ends are large and blunt; the whole papilla is above the general epithelial surface of the tongue. These papillae possess secondary papillee, and in their epithelium taste buds are at times seen. The circumvallate papillae (papillae vallatae) (Fig. 949) are of large size, but only eight to twelve in number. They are arranged like a letter V at the junction of the apical two-thirds and basal one-third of the dorsum, with the apex at the foramen cecum and the arms directed out- THE TONGUE 1219 ward and forward just in front of the sulcus terrainalis. These papillse are partially or wholly submerged, that is, lie in depressions. Each consists of a narrow base, attached at the bottom of the depression, while the remainder is surrounded by the vallum or ditch. Kach papilla is from jV to iV inch in width and possesses secondary papillfe. In the epithelium of the sides are found the taste buds. The foramen cecum, accordinj; to His, represents the remains of ilic cva<,'inatlon that formed the middle lobe of the thyroid body and the upper end of the supposed thyrnirlossal duct {ductus thi/roglossus). This may exist as a canal, at times e.xtending toward the hyuid bone. Filiform. Circnmvallate, Fig. 949. — Filiform papillse, Fig. 950. — Fungiform papillae, magni- Fig. 951. — Circumvallate papillae, mag- magnified, fied. ■ nified. Upon the posterior or basal one-third of the dorsum of the tongue papillse are not found. The surface is irregular, however, due to the presence of nodular collections of lymphoid tissue, that produce rounded elevations of the mucosa. Each nodule possesses a little pit or crypt, and collectively the follicles are termed the lin§rual tonsil {tonsilla lingiialis). Each crypt is lined by stratified sciuamous epithelial cells upon basement membrane and timica propria; in the latter are numerous solitary nodules arranged aroimd the pit, and each group is isolated from the neighboring collection. These groups constitute the hngual tun l1 Beneath the tunica propria of the mucosa is the muscle tissue of the tongue. This muscle tissue is of the voluntary striated variety and is divided into two sets of muscles — Intrinsic and Extrinsic (described on p. 393). Scattered throughout the tongue, but especially located in definite areas, are glands of a mucous and serous character. The mucous glands are found behind the circumvallate papillie and along the margins, and an especial group at the apex, called the apical glands or glands of Nuhn and Blandin (glnmlular liiir/uales anteriores of Nuhn and Blandin) (Fig. 953) Each gland is situated at the side of the frenulum and is covered by a fasciculus of muscle fibres derived from the Stylo- glossus and Inferior lingualis mu.scles. Each gland is from one-half inch to nearly an inch in length (1 to 2 cm.) and about one-third of an inch broad (S mm.). Each gland has from four to six ducts, which open on the under surface of the apex. The serous glands, or glands of von Ebner, occur in the basal part of the tongue, the ducts opening chiefly into the fossre around the circiuiivallate papillfe. Both mucous ami serous glaud.s resemble the other salivary gl.-imls in stniciure (p. 122(>). The Vessels of the Tongue. -The arteries of the tongue are derived from the lingual, the facial, and ascending pharyngeal. The veins of the tongue open into the internal jugular. The lingual artery (Fig, 0.5.5) on each side passes forward beneath the Kyoglossiis muscle and courses to the apex of the tongue, between the Genioglossus and the Inferior lingual mu.scles, about one-eighth of an inch from the surface. It divides into the ranine (Fig. 953) and sub- '; \\ !.>. Frc 0o2 — Circum-\ \lHte papilla? of tongue of rihbit snoring po-sition ot t iste goblets a. DuctofgUnd rl SeiousgHnd n Tai,te buds. / Prim ir\ s^pf i nd I second ir> septn. of papillp » Mvtlmited ner^e V Vubck hbres. (.stohr ) 1220 THE ORGANS OF DIGESTION lingual (Fig. 955). Near the apex a branch is given off from the ranine artery, which pene- trates the septum and joins a like branch from the other side. The dorsalis linguae is a branch of the lingual supplying the posterior part of the tongue, and rami from the tonsillar branch of the facial go to the same region. A network of capillary vessels is placed beneath the epithelium. The ranine veins lie to the side of the frenum underneath the mucous membrane. Each ranine vein runs backward, superficial to and upon the Hyoglossus muscle and near to the Lingual nerve, Sanine artery. Fig. 953. — Under surface of tongue, showing position and relations of gland of Blandin or Nuhn. (From a preparation in the Museum of the Royal College of Surgeons of England.) hypoglossal nerve. The venae comites of the lingual artery usually join the ranine vein, and the trunk opens into the internal jugular vein, but the vessels may open separately into the jugular vein (Fig. 496). The Lymphatic Vessels of the Tongue (Fig. 559). — The lymphatic vessels from the anterior half of the tongue pass to the submaxillary lymph nodes. Lymph vessels from the posterior half of the tongue are connected with satellite nodes on the Hyoglossus muscle and terminate in the deep cervical nodes. The last-named lymph vessel "accompanies the ranine vein. The lingual lymphatics arise from a network beneath the LONGITU VEBTICALIS. JALIS.— fe-^gg^i^, ' f ^^^\im-^>^ LINGU/E MUSCLE |3>^5^^ TRAHSVERSUS ^J^f^^^^&^Z^ — \ LINGU>E MUSCLE^ V, VjfyW^M^*?.' ' ~ INFERIOR LONCITUDINALIS MUSC '•^^. STYLOGLOSSUS afli MUSCLE SUBLINGUAL Fig. 954. — Frontal section through the body of the tongue of ; vborn babe. X 3. (Spalteholz.) epithelium. Across the anterior two-thirds of the tongue there is little or no lymphatic con- nection between the two sides; in the posterior one-third there is free connection, due to absence of septum here. THE TONGUE 1221 The Nerves of the Tongue (Fig. Ooo).— Tlie nerves of the tonRne are five in nnmhcr in each half — the lingual branch of the Inferior maxillary division of the trigeminal, whicli is distributed to the papillae at the fore part and sides of the tongue, and forms the nerve of ordinary sensibilitv for its anterior two-thirds; the chorda tsrmpani, which runs in the sheath of the lingual, is gen- erally regarded as the nerve of taste for the same area (p. 997); the lingual branch of the glosso- pharyngeal, ■whicii is disiiilnited to the mucous membrane at the ba.se and sides of the tongue, and to the |>a|)illae lircunnallatae, and which supplies both sensor and gustatory filaments to this region; the hypoglossal nerve, which is the motor nerve to the muscular substance of the tongue; and the internal laryngeal branch of the superior laryngeal, which sends some fine branches to the root near to the epiglottis. Sympathetic filaments also pass to the tongue from the nervi mollcs on the lingual and other arteries supplying it. Some of the nerves end free between the cells of epithelium; others terminate as end organs (Meissner's corpuscles and the end-bulbs of Krause), and in taste buds as sensor dendrites (p. 1149). Jntet nal lai ynqeal blanch of the superior laryngeal. -Under surface of tongue, showing the distribution of nerves to this organ, in the Museum of the Royal College of Surgeons of England.) (From a prei aration The Development of the Tongue (Figs. 956 and 957). — The tongue is developed in the floor of the pharynx. The rudiment of the anterior or buccal portion appears during the third week as a rounded elevation, immediately behind the ventral ends of the mandibular arches. This elevation is named the tuberculum impar (Figs. 956 and 957); it extends forward on the oral surface of the mandibular arch, and increases markedly in size by the development of a pair of lateral tongue elevations, which raise themselves from the inner surfaces of the mandibular arches, ancl, blending with the tuberculum impar, form the tip and greater portion of the buccal part of the tongue. These lateral growths correspond with similar structures which were de- scribed by E. Kallius in the development of the tongue of the lizard. From the ventral ends of the fourth arch there arises a second and larger elevation, in the centre of which is a median groove or furrow. This elevation is named the furcula (Fig. 956), and is at first separated from the 1222 THE ORGANS OF DIGESTION tuberculum impar by a depression, but later by a ridge formed by the forward growth and fusion of the ventral ends of the second and third arches. The posterior or pharyngeal part of the tongue is developed from this ridge, which extends forward in the form of a V, so as to embrace between its tv%'0 limbs the tuberculum impar (Figs. 956 and 957). At the apex of the V a pit- like invagination occurs, to form the middle thyroid rudiment, and this depression is represented in the adult by \he foramen, cecum of the tongue. In the adult the union of the anterior and pos- terior parts of the tongue is marked by a V-shaped depression (sulcus terminalis), the apex of which is at the foramen cecum, while the two limbs run outward and forward, parallel to, but a little behind, the circumvallate papillse. The prominent anterior part of the furcula forms the epiglottis; the furrow behind it is the entrance to the larynx; and the anterior parts of its lateral margins constitute the arytenoepiglottidean folds. Tnbermlum impar (papillary part of tongue) Posterior part of tongue. Mandibular arch. ■Hyoid arch. Entrance to larynx. Fig. 956. — The floor of the pharynx of a human embryo about twenty-three days old. X 30. (From His.) Applied Anatomy. — The diseases to which the tongue is liable are numerous, and its ap- plied anatomy is of importance, since any or all the structures of which it is composed — muscles, connective tissue, mucous membrane, glands, vessels, nerves, and lymphatics — may be the seat of morbid changes. It is not often the seat of congenital defects, though a few cases of vertical cleft have been recorded, and it is occasionally, though much more rarely than is commonly sup- posed, the seat of tongue-tie, from shortness of the frenum. There is, however, one condition which must be regarded as congenital, though not uncom- monly it does not exhibit the significant changes until a year or two after birth. This is an enlargement of the tongue which is due primarily to a dilatation of the lymph channels and a greatly increased development of the lymphatic tissue throughout the tongue (macroglossia) . This is often aggravated by inflammatory changes induced by injury or exposure, and the tongue may Papillary portion of tongue. Mandibular arch. Syoid arch. Foramen cxcum. Posterior part Third arch, of tongue. Fig. 957. — Floor of mouth of an embryo slightly older than that shown in Fig. 956. X 16. (From His.) assume enormous dimensions and hang out of the mouth, giving the child an imbecile expression. The treatment consists in excising a V-shaped portion and bringing the cut surfaces together with deeply placed silver sutures. Acute inflammation of the tongue (acute glossitis) may be caused by injury or the introduction of some septic or irritating matter, and it is attended by great swelling from infiltration of the connective tissue of the tongue; this connective tissue is present in considerable quantity. The great swelling renders the patient incapable of swal- lowing or speaking, and may seriously impede respiration. The condition may eventuate in THE SALIVARY GLANDS 1223 suppuration and the formation of an ai'iilc ah.^irxx. Chronic absce.is, which has been mistaken for cancer, may also occur in the sul)>t:iiiir df the tongue. The mucous membrane of the tongue ina\- hceonic chronically inflamed, and presents different appearances in different stages of the disease, to which the terms leukoplakia, ■psoriasis, and ichthyosis have been given. The tongue, being very vascular, is often the seat of nevoid growths, and these have a tendency to grow rapidly. The tongue is frequently the seat of ulceration, which may arise from many causes, as from the irritation of jagged teeth, dyspepsia, tuberculosis, syphilis, and cancer. Of these, the cancerous ulcer is the most important, and probably also the most common. The variety is the squamous epithelioma, which soon develops into an ulcer with an indurated base. It produces great pain which speedily extends to all parts supplied with sensation by the trigeminal nerve, especially to the region of the ear. The pain in these cases is conducted to the ear and temporal region by the lingual nerve, and from this nerve pain radiates to the other branches of the inferior ma.xii- lary nerve, especially the auriculotemporal. Possibly pain in the ear itself may be due to impli- cation of the fibres of the glossopharyngeal nerve, which by its tympanic branch reaches the tympanic plexus. Cancer of the tongue spreads through the organ very rapidly because of the almost constant muscular movements. Cancer of the tonejue may necessitate removal of a part or the whole of the organ, and many different methods have been adopted for its excision. The better method is by the scissors, usually known as Whitehead's method. The mouth is widely opened with a gag, the tongue is transfixed with a stout silk ligature, by which to hold and make traction on it and the reflection of mucous membrane from the tongue to the jaw, and the insertion of the Geniohyoglossi first divided with a pair of curved blunt scissors. The Palatoglossi are also divided. The tongue can now be pulled well out of the mouth. The base of the tongue is cut through by a series of short snips, each bleeding vessel being dealt with as soon as divided, until the situation of the ranine artery is reached. The remaining undivided portion of tissue is to be seized with a pair of Wells'_ forceps, the tongue removed, and the vessel secured. In the event of the ranine arterv being accidentally injured early in the operation, hemorrhage can be at once controlled by passing two fingers over the dorsum of the tongue as far as the epiglottis and dragging the root of the tongue forcibly forward. In cases where the disease is confined to one side of the anterior portion of the tongue this operation may be modified by splitting the tongue down tb^ centre and removing only the affected half. If the posterior portion of the tongue is attacked by cancer the entire tongue must be removed, even if but one side of the organ is apparently involved. The exchange of lymph between the halves of the posterior portion of the tongue makes it certain that the opposite half becomes involved soon after the origin of the disease. Whatever operation is performed for cancer of the tongue, the lymph nodes must be removed from both sides of the neck. This is to be done, even if but one side of the tongue is removed. Finally, where both sides of the floor of the mouth are involved in the disease, or where very free access is required on account of the extension backward of the disease to the pillars of the fauces and the tonsil, or where the mandible is involved, the operation recommended by Syme must be performed. This is done by an incision through the central line of the lip, across (he chin, and down as far as the hyoid bone. The mandible is sawed through at the symphysis, and the two halves of the bone forcibly separated from each other. The mucous membrane is sepa- rated from the bone, the Geniohyoglossi detached from the bone, and the Hyoglossi divided. The tongue is then drawn forward and removed close to its attachment to the hyoid bone. Ad- jacent lymph nodes can be removed, and if the bone is implicated in the disease, it can also' be removed by freeing it from the soft parts externally and internally, and making a second section with the saw beyond the diseased part. THE SALIVARY GLANDS (Fig. 95S) The principal salivary glands communicating with the mouth, and pouring their secretion into its cavity, are the parotid, submaxillary, and sublingual. The Parotid Gland (glcndida parotis) is the largest of the three salivary glands, varying in weight from half an ounce to an ounce. It lies upon the side of the face, immediately below and in front of the external ear. The main portion of the gland is superficial, somewhat flat and quadrilateral in form, and is placed between the ramus of the mandible in front and the mastoid process and Sternomastoid muscle behind, overlapping, however, botli boiuidaries. Above, it is limited by the zygoma; beloiv, it extends to about the level of a line joining the tip of the mas- 1224 THE ORGANS OF DIGESTION toid process to the angle of the mandible. The remainder of the gland is wedge- shaped, and extends deeply inward toward the pharyngeal wall. The gland is enclosed within a capsule continuous with the deep cervical fascia; the layer covering the outer surface is dense and closely adherent to the gland; a portion of the fascia, attached to the styloid process and the angle of the mandible, is thickened to form the stylomandibular ligament which intervenes between the parotid and submaxillary glands. The anterior surface of the gland is moulded on the posterior border of the ramus of the mandible with the attached Internal pterygoid and Masseter muscles, and advances forward between the two Pterygoid muscles and overlaps the Masseter. A part of the overlapping portion, immediately below the zygoma, is usually detached, and is named the socia parotidis {gl. paroiis accessoria). The outer or superficial surface, slightly lobulated, is covered by the integument, the superficial fascia containing the facial branches of the great auricular nerve and some small lymph nodes, and the fascia which forms the capsule of the gland. Pig. 958. — The salivary glands. (Note that the deep process of the submaxillary gland lies upon the deep surface of the Mylohyoid.) The inner or deep surface extends inward by means of two processes, one of which lies on the styloid process and the styloid group of muscles and projects under the mastoid process and Sternomastoid muscle; the other is situated in front of the styloid process and passes into the posterior part of the glenoid fossa behind the temporomandibular joint. The deep surface is in contact with the internal and external carotid arteries, the internal jugular vein, and the vagus and glassopharyngeal nerves. The anterior harder lies on the superficial surface of the Masseter; the j>osterior abuts on the external auditory canal and the mastoid process, and overlaps THE HA LIVA R Y GLA NDS 1 225 the anterior edge of the Sternomastoid. The superior border is in contact with the zygomatic arch, and the inferior overlaps the posterior belly of the Digastric. The inner border at the junction of the anterior and inner surfaces is in relation with the styloid process and styloid muscles, and is separated from the pharyngeal wall by some loose connective tissue. Structures within the Gland. — The external carotid arteri/ lies at first in contact with the deep surface, and then in the substance of the gland. The artery gives off its posterior auricular branch which emerges from the gland behind; it then divides into its terminal branches, the internal maxillary and superficial temporal; the former runs inward behind the neck of the mandible; the latter runs upward across the zygoma and gives off its transverse facial branch which emerges from the front of the gland. Superficial to the arteries are the temporal and internal maxillary veins, uniting to form the temporomaxillary vein; in the lower part of the gland this vein divides into anterior and posterior divisions. The anterior division emerges from the gland to join the facial vein; the posterior unites in the gland with the posterior auricular vein to form the external jugular vein (Fig. 495). On a still more superficial plane is the facial nerve, the branches of which emerge at the upper and anterior borders of the gland. Branches of the great auricular nerve pierce the gland to join the facial, and the auriculotemporal branch of the inferior maxillary nerve emerges from the upper part of the gland. Lymph nodes, known as the parotid nodes, are in and about the parotid gland, some Ijeing embedded in the outer surface of the parotid fascia, others being in the inner surface of the fascia, others in the gland itself, particularly along the temporomaxillary vein and external carotid artery (see p. 775). The Duct of the Parotid Gland, or Stenson's Duct (ductus jmrotideus [Ste7207iis]) (Fig. 958), is about two inches and a half (5 to 6 cm.) in length. It commences by numerous branches from the anterior part of the gland, crosses the Masseter muscle, and at its anterior border turns inward nearly at a right angle and passes into the substance of the Buccinator muscle, which it pierces; it then runs for a short distance obliquely forward between the Buccinator muscle, and the mucous membrane of the mouth, and opens upon the inner surface of the cheek by a small orifice, opposite the second upper molar tooth (Fig. 936). While crossing the Masseter it receives the duct of the socia parotidis. In this position it has the transverse facial artery above it and some branches of the facial nerve below it. The parotid duct is dense, it is of considerable thickness, and its canal is about the size of a crowquill; but at its orifice on the inner aspect of the cheek its lumen is greatly reduced in size. The duct corresponds to the middle third of a line drawn across the face from the lower margin of the external auditory meatus to midway between the red margin of the upper lip and the columella of the nose. Vessels and Nerves. — The arteries supplying the parotid gland are derived from the ex- ternal carotid, and from the branches given oflF by that vessel in or near its substance. The veins empty into the external jugular thi-ough some of its tributaries. The l3nmphatics terminate in the superficial cervical and the deep cervical nodes, passing in their course through two or three lymph nodes placed on the surface and in the substance of the parotid. The nerves are derived from the plexus of the sympathetic on the external carotid artery, the nervus inter- medius, the auriculotemporal, ami the great auricular nerves, ll is probable that the branch from the auriculotemporal nerve is ilcri\ed from the glossopharyngeal through the otic gan- glion. At all events, in some of the lower animals this has been proved experimentally to be the case. The Submaxillary Gland (glandula submaxillar is) (Fig. 958) is irregular in form and weighs about two drams (eight to ten grams). A considerable part of it is situated in the submaxillary triangle, reaching forward to the anterior belly of the Digastric and backward to the stylohyoid ligament which intervenes 1226 THE ORGANS OF DIGESTION between it and the parotid gland. Above, it extends under cover of the body of the mandible ; heloic, it usually overlaps the intermediate tendon of the Digastric and the insertion of the Stylohyoid, while from its deep surface a tongue-like deep process extends forward and inward above the Mylohyoid muscle. The deep surface is in relation with the Mylohyoid, Hyoglossus, Styloglossus, Stylohyoid, and posterior belly of the Digastric muscles; in contact with it are the mylohyoid nerve and the mylohyoid and submental vessels. The facial artery is embedded in a groove in the posterior border of the gland. The deep process of the gland extends forward and inward between the Mylo- hyoid below and externally, and the Hyoglossus and Styloglossus internally; above it is the lingual nerve; below it, the hypoglossal nerve and ranine vein. The duct of the submajcillary gland, or Wharton's duct (ductus sitbmaxiUaris [U'hartoni]), is about two inches (5 cm.) in length, and its wall is much thinner than that of the parotid duct. It begins by numerous branches from the deep portion of the gland which lies on the upper surface of the Mylohyoid muscle, and runs forward and inward between the Mylohyoid and the Hyoglos- sus and Geniohyoglossus muscles, then between the sublingual gland and the Geniohyoglossus muscle, and opens by a narrow orifice on the summit of a small papilla [caruncula sidilingvalu) at the side of the frenum linguae. On the Hyoglossus muscle it lies between the lingual and hypoglossal nerves, but at the anterior border of the muscle it is crossed by the lingual nerve. Vessels and Nerves. — The arteries supplying the submaxillary glands are branches of the facial and lingual. Its veins follow the course of the arteries. The lymphatics drain into the submaxillary lymph nodes. The nerves are derived from the submaxillary ganglion, through which it receives filaments from the chorda tympani and from the lingual branch of the inferior maxillary, sometimes from the mylohyoid branch of the inferior dental and from the S3mipa- 1:hetic. The Sublingual Gland (glandida sublingiuilis) (Fig. 958) is the smallest of the salivary glands. It is situated beneath the mucous membrane of the floor of the mouth, at the side of the frenum linguae, in contact with the inner surface of the mandible, close to the symphysis. It is narrow, flattened, in shape some- what like an almond, and weighs about a dram. It is in relation, above, with the mucous membrane; beloiv, with the Mylohyoid muscle; in front, with the mandible and its fellow of the opposite side; behind, with thd deep part of the submaxillary gland; and internally, with the Geniohyoglossus, from which it is separated by the lingual nerve and submaxillary duct. Its excretory ducts or ducts of Rivinus {ductus sublingualis minores) are from eight to twenty in number; some join the submaxillary duct, others open separately into the mouth, on the elevated crest of mucous membrane {plica sublingualis) caused by the projection of the gland on either side of the frenum linguse. One or more join to form a tube which opens into the submaxillary duct; this is called the duct of Bartholin {ductus sublingualis major). Vessels and Nerves. — The sublingual gland is supplied with blood from the sublingual and submental arteries. Its nerves are derived from the lingual. Structure of Salivary Glands (Fig. 959). — The salivary glands are compound tubulorace- mose or racemose glands, surrounded by a capsule of white fibrous connective tissue that divides the gland into numerous lobes and lobules. The tissue between the lobules supports blood- vessels, nerves, lymphatics, and ducts. Each lobule consists of the ramifications of a single duct, dividing frequently like the branches of a tree, the branches terminating in either rounded or tubular ends, the acini or alveoli, around which the capillaries are distributed. Each alveolus or acinus consists of a single layer of columnar or pyramidal epithelial cells resting upon a 6a.se- ment membrane, further supported by the fibroelastic fiinira propria, in which the capillaries and nerves are found. Within the lobide are found intralobular ducts that collect the secretion from the alveoli and empty it into the interlobular ducts between the lobules. The latter join, to ultimately form the excretory duct of the gland. The main or excretory duct of each gland consists of mucous, muscle, and fibrous coats. The mucous coat is composed of either simple columnar or stratified columnar epithelial cells THE FiALIVARY GLANDS 1227 that rest upon a basement membrane, and fibroelastic tunica [iropria. Tlie muscle coat consists of circularly arrancred smooth muscle tissue. The fibrous coat consists of fibrmlaslic tissue and serves to support the other coats. The salivary glands are mucous, serous, and mixed. The mucous glands secrete a thick viscid fluid and the cells of the acini stain lightly. The alveoli arc tubular in form and the cells large and of a columnar shape, cloudy to transparent, and may even he striated in appearance. At intervals peculiar, darkly staining crescent-shaped cells or cell groups arc seen lielwccn the above epithelium and the basement membrane; these are the demilunes of Heidenhain or crescents of Gianuzzi (Fig. 959), by some regarded as mucous cells in the resting stage, and by others as distinctly separate cells. These glands are the small unnamed glands of lips, cheek, pharynx, cesophagus, and tongue (especially the glands of Nuhn and Blandin). Serous glands are those that secrete a thin, watery fluid, anrl the cells of the acini stain darkly. The acini arc grape-like and the cells are somewhat pyramidal in form, smaller than mucous cells, and possess richly granular protoplasm. These glands are the parotid and many small unnamed glands in the tongue and lips. Mixed glands are those in which some of the alveoli are tubular (mucous) and others grape- like (serous), representing both of the above varieties in one capsule. Here belong the sub- lingual and submaxillary glands. The arteries enter the capsule and divide into branches that enter the interlobular tissues; from these vessels branches enter the lobules and form capillary plexuses around the alveoli in close proximity to the basement membrane. The veins return the blood in vessels parallel to the arteries. The nerves enter with the vessels and ultimately form plexuses in the interlobular and intra- lobular tissue, the latter sending filaments that end in relation to the epithelial cells and blood- vessels. In the submaxillary gland small ganglia are found in connection with the interlobular nerve plexus. Development of the Salivary Glands. — The salivary glands arise as diverticula from the epithelial lining of the mouth, and their rudiments appear in the following order — viz., the parotid during the fourth week, the submaxillary in the sixth week, and the sublingual during the ninth week (Hammar). ( lescent of Gianazsi. Urary duct. -A highly magnified section of the submaxillary gland of the dog, stained with carmine. (Koliiker.) Surface Form. — The orifice of the mouth is bounded by the lips, two thick, fleshy folds covered externally by integument and internally by mucous membrane, and consisting of muscles, vessels, nerves, areolar tissue, and numerous small glands. The size of the orifice of the mouth varies considerably in different individuals, but seems to bear a close relation to the size and prominence of the teeth. Its corners correspond pretty accurately to the outer border of the canine teeth. In the Ethiopian tribes the front teeth are large and inclined forward, the mouth is large; and this, combined with the thick and everted lips which appear to be associated with prominent teeth, gives to the negro's face much of the peculiarity by which it is characterized. The smaller teeth and the slighter prominence of the alveolar arch of the more highly civilized races render the orifice of the mouth much smaller, and thus a small mouth is an indication of intelligence, and is regarded as an evidence of the higher civilization of the individual. Upon looking into the mouth, the first thing we may note is the tongue, the upper surface of which will be seen occupying the floor of the cavity. This surface is convex, and is marked along the middle line by a raph^ which divides it into two symmetrical portions. The anterior two-thirds is rough and studded with papillae; the posterior third, smooth and tuberculated, contains numerous lymphoid structures which proiect from the surface. Upon raising the 1228 THE ORGANS OF DIGESTION tongue the mucous membrane which invests the upper surface may be traced covering the sides of the under surface, and then reflected over the luoor of the mouth on to the inner surface of the mandible, a part of which it covers. As it passes over the borders of the tongue it changes its character, becoming thin and smooth and losing the papillae which are to be seen on the upper surface. In the middle line the mucous membrane on the under surface of the tip of the tongue forms a distinct fold, the freiium. linguw, by which this organ is connected to the sym- physis of the mandible. Occasionally it is found that this frenum is rather shorter than natural, and, acting as a bridle, prevents the complete protrusion of the tongue. When this condition exists and an attempt is made to protrude the organ, the tip will be seen to remain buried in th^ floor of the mouth, and the dorsum of the tongue is rendered very convex, and more or lesp extruded from the mouth; at the same time a deep furrow will be noticed to appear in the middle line of the anterior part of the dorsum. Sometimes, a little external to the frenum, the ranine vein may be seen immediately beneath the mucous membrane. The corresponding artery, being more deeply placed, does not come into view, nor can its pulsation be felt with the fin- ger. On either side of the frenum, in the floor of the mouth, is an elevation or ridge, pro- duced by the projection of the sublingual gland, which hes immediately beneath the mucous membrane. And close to the attachment of the frenum to the tip of the tongue may be seen on either side the slit-like orifices oi the submaxillary duds, into which a fine probe may be passed without much difficulty. By everting the lips the smooth mucous membrane lining them may be examined, and may be traced from them on to the outer surface of the alveolar arch. In the middle line, both of the upper and lower lip, a small fold of mucous membrane passes from the lip to the bone, constituting the frena ; these are not so large as the frenum linguae. By pulling outward the angle of the mouth, the mucous membrane lining the cheeks can be seen, and on it may be perceived a little papilla which marks the position of the orifice of the parotid duct. The exact position of the orifice of the duct will be found to be opposite the second upper molar tooth. The introduction of a probe into this duct is attended with considerable difficulty. The teeth are the next objects which claim our attention upon looking into the mouth. These, are, as stated above, ten ia either jaw in the temporary set, and sixteen in the permanent set. The gums, in which they are implanted, are dense, firm, and vascular. At the back of the mouth is seen the isthmus of the fauces, or, as it is popularly called, "the throat;" this is the space between the pillars of the fauces on either side, and is the means by which the mouth communicates with the pharynx. Above, it is bounded by the soft palate, the anterior surface of which is concave and covered with mucous membrane, which is con- tinuous with that lining the roof of the mouth. Projecting downward from the middle of its lower border is a conical-shaped projection, the uvula. On either side of the isthmus of the fauces are the anterior and posterior pillars, formed by the Palatoglossus and Palatopharyngeus muscles, respectively, covered over by mucous membrane. Between the two pillars on either side is situated the tonsil. When the mouth is wide open a prominent tense fold of mucous membrane may be seen and felt, extending upward and backward from the position of the fang of the last molar tooth to the posterior part of the hard palate. This is caused by the pterygoma.xillanj ligament, which is attached by one extremity to the apex of the internal pterygoid plate, and by the other to the posterior extremity of the mylohyoid ridge of the lower jaw. It connects the Buccinator with the Superior constrictor of the pharynx. The fang of the last molar tooth indicates the position of the lingual nerve where it is easily accessible, and can with readiness be divided in cases of cancer of the tongue (see p. 993). On the inner side of the last molar tooth we can feel the hamular process of the internal pterygoid plate of the sphenoid bone, around which the tendon of the Tensor palati plays. The exact position of this process is of importance in per- forming the operation of staphylorrhaphy. About one-third of an inch (8 mm.) in front of the hamular process, and the same distance directly inward from the last molar tooth, is the situation of the opening of the posterior palatine canal, through which emerges the posterior or descend- ing palatine branch of the internal maxillary artery and one of the descending palatine nerves from Meckel's ganglion. The exact position of the opening on the subject may be ascertained by driving a needle through the tissues of the palate in this situation, when it will be at once felt to enter the canal. The artery emerging from the opening runs forward in a groove in the bone just internal to the alveolar border of the hard palate, and may be wounded in the operation for the cure of cleft palate. Under these circumstances the palatine canal may require plugging. By introducing the finger into the mouth the anterior border of the coronoid process of the mandible can be felt, and it is especially prominent when the jaw is dislocated. By throw- ing the head well back a considerable portion of the posterior wall of the pharynx may be seen through the isthmus faucium, and on introducing the finger the anterior surface of the bodies of the upper cervical vertebrae may be felt iminediately beneath the thin muscular stratum form- ing the wall of the pharynx. The finger can be hooked around the posterior border of the soft palate, and by turning it forward the posterior nares, separated by the septum, can be felt, or the presence of any adenoid or other growths in the nasopharynx can be ascertained. THE PHARYNX 1229 Applied Anatomy. — The duct of a salivary gland may be blocked by a ciilculii.i, and the condition is often productive of severe pain. A wound of the parotid duct or of the parotid gland may be followed liy a .wlitary fistula. The parotid recess is completely linefl Ijy fascia, except above. " Between the anterior edge of the styloid process and the posterior border of the External pterygoid muscle there is a gap in the fascia, through which the parotid space communicates with the connective tissue about the pharynx." This explains why there is frequently swelling of the parotid region in postpharyngeal abscess. A 'parotid abscess rarely bm'sts through the skin; it may pass into the temporal fossa, may enter the zygomatic fossa, may advance toward the mouth, pharynx, or neck. Because of the situa- tion of the gland, a parotid abscess may cause inflammation of the temporomandibular joint or periostitis of the bone about the canal, and may even burst into the external auditory canal (Treves). The facial nerve passes through the gland, and inflammation or tuberculosis of the gland may cause facial palsy. Some enlargements of the parotid region are due to inflammation of the parotid lymph nodes, and these nodes may become tuberculous. Mumps is characterized by acute inflammation of the parotid gland. Various tumors occur in the parotid (fibroma, sarcoma, carcinoma, enchondroma, etc.). Most parotid tumors contain more or less cartilage. Complete extirpation of the parotid gland surgically is certainly extremely difficult, and Treves and others maintain that it is impossible. THE PHARYNX (Figs. 964, 965). The pharynx is that part of the ahmentary canal which is placed behind, and communicates with the nose, mouth, and larynx. It is a musculomembranous tube, somewhat conical in form, with the base upward and the apex downward, extending from the under surface of the skull to the level of the cricoid cartilage in front and that of the sixth cervical vertebra behind. The cavity of the pharynx {camim -pharynqis) is about five inches in length, and broader in the transverse than in the antero-posterior diameter. Its greatest breadth is immediately below the base of the skull, where it projects on either side, behind the orifice of the Eustachian tube, as a recess termed the fossa of Rosen- miiller; its narrowest part is at its termination in the oesophagus. It is limited above by the body of the sphenoid as well as by the basilar process of the occipital; helow, it is continuous with the oesophagus; posteriorly, it is connected by loose are- olar tissue with the cervical portion of the vertebral column and the Longus colli and Rectus capitis anticus muscles ; this areolar tissue is contained in what is called the retropharyngeal space; anteriorly, it is incomplete, and is attached in succession to the Eustachian tube, the internal pterygoid plate, the pterygomandibular liga- ment, the posterior termination of the mylohyoid ridge of the mandible, the mucous membrane of the mouth, the base of the tongue, hyoid bone, the thy- roid and cricoid cartilages; laterally, it is connected to the styloid processes and their muscles, and is in contact with the common and internal carotid arteries, the internal jugular veins, and the glossopharyngeal, vagus, hypoglossal, and sympathetic nerves, and above with a small part of the Internal pterygoid muscles. Seven openings communicate with it — viz., the two posterior nares, the two Eustachian tubes, the mouth, larynx, and oesophagus. The cavity of the pharynx may be subdivided from above downward into three parts — nasal, oral, and laryngeal. The Nasal Part, or Nasopharynx {pars nasalis pharyngis) (Fig. 964), lies behind the nose and above the level of the soft palate; it differs from the two lower parts of the tube in that its cavity always remains patent. In front it communicates through the posterior nares (ehoanae) (Fig. 965) with the nasal fossa. On its lateral wall is the pharyngeal orifice of the Eustachian tube {p.stium pharyngeum tubae auditivae) (Figs. 960 and 961), somewhat triangular in shape and bounded behind by a firm prominence, the Eustachian cushion {torus tubarius), caused by 1230 THE ORGANS OF DIGESTION the inner extremity of the cartilage of the tube which elevates the mucous mem- brane (Fig. 961). At the pharyngeal end of the tube is a collection of lymphoid tissue called by Gerlach the tubal tonsil. The orifice is about one-third to one-half inch behind the inferior turbinated bone. A vertical fold of mucous membrane, the salpingopharsmgeal fold {-plica salpingopharyngea) (Fig. 961), stretches from the lower part of the cushion to the pharynx; it contains the Salpingopharyngeus muscle. A second and smaller fold, the salpingopalatine fold (plica salpingo palatina) (Fig. 949) , stretches from the upper part of the cushion to the palate. Behind the orifice of the Eustachian tube is a deep recess, the lateral recess or fossa of Rosenmiil- ler {recessus pJiaryngeus) (Fig. 961), which represents the remains of the upper part of the second inner branchial cleft. The posterior wall of the nasopharynx is directed upward and forward, and it meets the superior wall at an angle constituting the vault of the pharynx (fornix pharyngis) . On the posterior wall, above the level of the orifices of the Eustachian tubes, is a prominence, best marked in childhood, produced by a mass of lymphoid tissue which is known as the phar3mgeal tonsil (tonsilla pharyngea) (Fig. 960). In the pharyngeal vault, in the middle line, an irregular flask-shaped depression of the mucous membrane is sometimes seen extending up as far as the basilar process of the occipital bone. It is known as the pharyngeal bursa, a possible vestige of the pharyngeal tonsil. The floor of the nasopharynx is formed by the upper surface of the sloping soft palate; in front the floor is continuous with that of the nasal cavities, while behind it ends at the free margin of the soft palate, which bounds the isthmus of the phar3mx (isthmus pharyngonasalis). The Oral Part (pars oralis pharyngis) of the pharynx reaches from the under surface of the soft palate to about the level of the hyoid bone. It opens ante- riorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the two pillars of the fauces, is the tonsil. SALPINGO- NASAL FOLD EUSTACHIAN CUSHION -Pharyngeal tonsil in an adult. (Escat.) GEAL FOLD Fig. 961. — The posterior lateral cavity of the naso- pharynx. (Escat.) The Tonsils (tonsilla palatina) (Figs. 963 and 964) are two lymphoid bodies situated one on each side of the fauces, between the anterior and posterior pillars of the soft palate, corresponding in position externally to the angle of the mandible. They are usually of an oval form as viewed from their oral aspect, and vary con- siderably in size in different individuals. As seen in horizontal sections in hard- ened heads, the form of each tonsil is rather that of a Brazil nut, with antero- internal, lateral, and posterior surfaces, and an upjxr and a loiver pole} A recess, ' Cf. George Fetterolf'a article: "The Anatomy and Relations of the Tonsil i can Journal of the Medical Sciences, July, 1912. I the Hardened Body, THE PHARYNX 1231 the supratonsillar fossa {fossa supmtonsillaris) may be seen, directed upward, outward, and liackward above the tonsil, the recess being the remains of the second inner visceral cleft. The space below the tonsil, between the tongue in front and the posterior pillar behind, is called the tonsillar sinus. The tonsil is encased within a thin fibrous capsule over its lateral and posterior surfaces. An extension of the tonsillar capsule, inward and backward beyond the anterior pillar of the fauces, with its free surface covered by mucous membrane and partly coA'ering the antero-internal surface of the tonsil is called the plica triangularis. "Of its three sides the anterior is attached apparently to the anterior pillar, the posterior runs downward and backward over the tonsil, and the inferior either is inserted into the side of the tongue, or, in the case of a small tonsil'and a large fossa, fades away in the lower part of the tonsillar sinus. "^ The fibrous capsule covering the lateral and posterior surfaces of the tonsil lies in contact with the aponeurosis of the Superior constrictor muscle of the pharynx; external to this is a mass of areolar tissue with the ascending palatine arterj' and, more laterally, the Internal pterygoid muscle. The internal carotid artery lies behind and to the outer side of the tonsil, and nearly an inch (20 to 25 mm.) distant from it. The Palatoglossus courses along the anterior margin, while the Palatopharyngeus is in contact with the capsule investing the posterior surface of the tonsil. The free or antero-internal surface of the tonsil is directed toward the cavity of the oropharynx and presents from twelve to fifteen orifices, each leading into small recesses or crypts {fossulae tonsillares) . From the crypts numerous follicles branch out into the substance of the tonsil by means of very irregular channels. As indicated above, this surface of the tonsil is partially covered by the plica triangularis, which may be free or attached. Structure. — The tonsil is covered externally by a capsule of white fibrous tissue that separates it from the siurounding organs and tissues, and is continued into the plica triangularis. This capsule sends in trabeculae that divide the organ into irregular compartments. Within the compartments is the delicate framework and reticulum in the meshes of which are found dififuse lymphoid tissue and solitary nodules or follicles. The internal svu'face presents twelve to fifteen depressions or crypts that extend into the organ in the form of irregular, blindly ending, tortuous channels or follicles. The internal sitfface of the tonsils and the crypts and follicles are lined by stratified squamous cells, exhibiting in places marked degenerative changes, and in others leukocytes that are passing through the epithelial layer to the crypts. The arteries supplying the tonsil are all derived from branches of the external carotid. Accord- ing to the observations of J. Leslie Davis,' they usually enter the tonsil at what is commonly called the hilum, just behind and about a quarter of an inch from the margin of the anterior pillar, about midway between the upper and lower poles. Fetterolf^ enumerates: (1) an anterior tonsillar artery, a branch from the dorsalis linguae; (2) the superior tonsillar artery, from the descending palatine; (3) the posterior tonsillar artery, a branch of the ascending pharyngeal, and (4) three inferior tonsillar arteries, of which one is a branch of the dorsalis linguae, while the other two are offshoots from the tonsillar branches of the facial. The veins of the tonsil terminate in the tonsillar plexus on the lateral and posterior surfaces of the tonsil, and the tonsillar plexus joins the pharyngeal plexus which communicates with the pterygoid plexus of the internal jugular or the facial vein. While most of the veins leave at the hilum, there is usually a large vein com-sing downward along the posterior siu-face of the tonsil, to the outer side of the Palatopharyngeus. Surrounding each follicle is a close plexus of lymphatic vessels. From these plexuses the lymphatic vessels pass to the submaxillary lymph nodes below the angle of the mandible. From the submaxillary nodes lymph passes to the deep cervical nodes. The Nerves of the Tonsil. — A branch from the glossopharyngeal nerve by uniting with branches from the middle and posterior palatine branches from the sphenopalatine ganglion forms the tonsillar plexus. 1 G. Fetterolf, loc. cit. 2 "Tonsillectomy, Why, When, and How," etc., Pennsylvania Medical .lournal, November, 1911. 3 G. Fetterolf, loc. cit. 1232 THE ORGANS OF DIGESTION Development. — The tonsils are developed from the lower parts of the second inner visceral clefts, immediately behind the anterior pillars of the fauces. The entoderm wliich lines these Fig. 962. — Diagrams of horizontal sections of left tonsillar region, viewed from above, the upper one showing the attached form of plica and the lower one the free form: T, Tonsil; C, capsule; PT, pHca triangularis; M, M, mucous membrane; L, L, lacunae; AF, anterior tonsillar fossa; SC, superior constrictor; A, Palato-glossus; P, Palato-pharyn- geus; y, V, main veins of tonsillar plexus. (Fetterolf.) Fig. 963. — Actual shape of (left) tonsil, with arterial supply: 1, Mesa! aspect; 2, postero- lateral aspect; E, lateral surface; B, posterior surface; G, groove for Palato-pharyngeus; T, tonsil tissue; PT, plica triangularis; C, capsule; A A, anterior tonsillar artery; PA, posterior tonsillar artery; SA, superior tonsillar artery; I A, inferior tonsillar arteries. iFetterolf.) THE PHARYNX 1233 clefts grows in the form of a number of solid burls into the siirrounrling mesoderm. These buds become hollowed out by the degeneration and casting oH' of their central cells, and by this means the tonsillar crypts are formed. Lymphoid cells accumulate around the crypts, and become grouped to form the lymphoid follicles; the latter, however, are not well defined until after birth. Applied Anatomy. — ^The tonsils can be easily inspected by instructing the patient to throw the head back with mouth wide open, the tongue being depressed by a spatula or tongue depressor. The normal tonsil should not project inward beyond the plane of the anterior pillar of the fauces. When enlarged they make deglutition and respiration troublesome. The deafness which so often attends hypertrophy of the tonsil is not due to blocking of the Eustachian orifice by the tonsil, but is due to the attendant thickening of the mucous mem- brane lining the tube itself. The tonsils may be the seat of acute Inflammation, which may run on to suppuration, reciuiring evacuation of the pus. The incision into the tonsil should always be made from in front backward and inward. Another form of acute inflammation of the tonsil is follicular tonsillitis, due to the lodgment of micro-organisms in the tonsillar crypts. Tonsillectomy is the complete enucleation of the gland. In this operation, profuse bleeding may be avoided by the use of dis.sectors designed to keep to the outer surface of the capsule and by the use of the snare and tenaculum. Successful methods are those of Fetterolf and Davis,^ whereby enucleation is complete without inflicting damage upon surrounding structures, such as the faucial pillars, which, if injured, may cause discomfort and affect the voice, and also avoiding injiuy to the ascemting pharyngeal artery or one of the palatine arteries lying without the capsule of the tonsil. The tonsil may be the seat of malignant growth, either an epithelioma or a lymphosarcoma. The Laryngeal Part of the pharynx {fars laryugea fharyngis) i.s that division which lies behind the larynx; it is wide above where it is continuous with the oral portion, while below at the lower border of the cricoid cartilage it becomes continu- ous with the oesophagus. In front it presents the triangular aperture of the larynx, the base of which is directed forward and is formed by the epiglottis, while its lateral boundaries are constituted by the arytenoepiglottic folds. On either side of the laryngeal orifice is a recess, termed the sinus pyriformis (rccessus pyriformis) (Fig. 964); it is bounded internally by the arytenoepiglottic fold, externally by the thyroid cartilage and thyrohyoid membrane. In the anterior part of the sinus pyriformis is a fold (plica nervi laryngei), which passes downward and inward. Extending outward from the epiglottis on each side is a fold, the pharjmgoepiglottic fold {plica pharyngoepiglottica). This ascends in the lateral wall of the pliaiynx, nearly to the posterior arch of the fauces. Structure. —The pharynx i.s composed of mucous, fibrous, and muscular coats. The mucous coat {tunica mucosa) is continuous with thai liiiini;- ilic iMislarhian tubes, the nasal fo.ssje, the mouth, and the larynx. In the nasopharynx it is covered by stratified ciliated epithelium; in the buccal and laryngeal portions the epithelium is of the stratified squamous variety. In the tunica propria considerable difl^use lymphoid tissue, pharyngeal tonsil, and mucous glands (ghiudu/ar plinrtpir/eae) are found; the latter are especially numerous at the upper part of the |iharviix around the orifices of the Eustachian tubes. The pharyngeal aponeurosis or fibrous coat is situated between the mucous and the muscle layers, and consists of large bundles of white fibrous connective tissue. It is thick above, where the muscle fibres are wanting, and is firmly connected to the periosteum of the basilar process of the occipital and petrous portion of the temporal bones. As it descends it diminishes in thick- ness, and is gradually lost. It is strengthened posteriorly by a strong fibrous band, which is attached above to the pharyngeal spine on the under surface of the basilar portion of the occipital bone, and passes downward, forming a median raphe, which gives attachment to the Constrictor muscles of the pharynx. The muscular coat has been already described (pp. .394 to 397). The motor nerves are derived chiefly from the pharyngeal ])lexus; the Tensor palati, however, receives a special branch from the otic ganglion. The sensor filaments are derived from the descending palatine, nasopalatine, and from the glossopharyngeal nerve. ' G. Fetterolf, loc. cit. ^ J. Leslie Davis, loo. cit. 1234 THE ORGANS OF DIGESTION The Lymphatic Pharyngeal Ring. — This name was applied by Waldeyer to the lymphatic ■ structures gathered into a sort of ring about the pharynx. There are foiu- chief collections of this tissue on each side. The first is known as the lingual tonsil (p. 1219); the second as the palatal tonsil (p. 1230); the third as the pharyngeal tonsil (p. 1230); and the fourth as the tubal tonsil (pp. 112S, 1230). Development of the Pharjmx (Figs. 956, 957). — The pharynx develops from the cephalic portion of the foregut, flanked by the five branchial (visceral) arches, with four intervening bran- chial clefts (visceral pouches). These have become retrogressively modified in that they have GENIO- HYOGLOSSUS MUSCLE SOFT PALATE NASOPHARYNX ANTERIOR PALA- TINE ARCH POSTERIOR PALA- ARCH TONSIL CAVITY OF PHARYNX TONSILLAR SINUS EPIGLOTTIS EPIGLOTTIC FOLD CUNEIFORM CARTILAGE Fig. 964. — Sagittal median section of the head and neck. The head is thrown backward into complete extension, which explains the relations between the. lower jaw and the hyoid bone as seen in the figure. (Luschka.) lost their respiratory function (as gills), but recur in the development of each individual for the purpose of forming organs not entirely vestigial. Thus, the first or most cephalic branchial arch assists in the formation of the jaws, the malleus, incus, sphenomandibular ligament, and part of the external ear. The second arch forms the styloid process, lesser cornu of hyoid and the intervening stylohyoid ligament, the stapes, a part of the external ear, and a part of the posterior one-third of the tongue. From the third arch are formed the body and greater cornu of the hyoid bone, and part of the posterior one-third of the tongue. The foiu-th and fifth arches share in forming the thjToid cartilage. The inner furrows or clefts, lined by entoderm, contribute to the formation of important structures. Thus, the first inner furrow becomes the middle- ear cavity and Eustachian tube, the "closing membrane" persisting as the tympanic membrane THE PHARYNX 1235 separating the inner from the outer furrow, whioh becomes the external auditory meatus. The second inner furrow becomes the lateral recess of the pharynx, and its entodcrmal lining gives rise to the tonsil. From the third inner furrow are developed the thymus and the inferior parathyroid gland, while the fourth gives rise to the lateral lobes of the thyroid and the superior parathyroid glands. The isthmus of the thyroid is derived by a median ventral evagination of the entoderm arising between the tuberculum impar and the second visceral bar. Another median ventral evagination occiu-s at the level of the fourth visceral arch to form the respiratory apparatus. The tuberculum impar forms the papillary portion of the tongue. Applied Anatomy. — The internal carotid arteri/ is in close relation with the pharynx, so that its pulsations can be felt through the mouth. It has been occasionally wounded by sharp- pointed instruments introduced into the mouth and thrust through the wall of the pharynx. Fig. 965. — The anterior surface of the pharynx. (Sappey.) In aneurism of this vessel in the neck the tumor necessarily bulges into the pharynx, as this is the direction in which it meets with the least resistance, nothing lying between the vessel and the mucous membrane except the thin Constrictor muscle, whereas on the outer side there is the dense cervical fascia, the muscles descending from the styloid process, and the margin of the Sternomastoid muscle. The mucous membrane of the pharynx is very vascular, and is often the seat of infiammation, frequently of a septic character, and dangerous on account of its tendency to spread to the larynx. On account of the tissue which surrounds the pharyngeal wall being loose and lax, the inflam- mation is liable to spread through it far and wide, extending downward into the posterior medi- astinum along the oesophagus. Abscess may form in the connective tissue behind the pharynx, between it and the vertebral column, constituting what is known as retropharyngeal abscess. This is most commonly due to caries of the cervical vertebrfe, but may also be caused by sup- puration of a lymph node which is situated in this position opposite the axis, and which receives lymphatics from the nares, or by gumma or by acute pharyngitis. In these cases the pus may be easily evacuated by an incision, with a gtiarded bistoury, through the mouth, but, for aseptic 1236 THE ORGANS OF DIGESTION reasons, it is desirable that the abscess should be opened from the neck. In some instances this is perfectly easy; the abscess can be felt bulging at the side of the neck and merely requires an inci- sion for its relief; but this is not always so, and then an incision should be made along the posterior border of the Sternomastoid and the deep fascia should be divided. A director should now be inserted into the wound, the forefinger of the left hand being introduced into the mouth and pressm-e made upon the swelling. This acts as a guide, and the director is to be pushed onward until pus appears in the groove. A pair of sinus forceps are now inserted along the director and the opening into the cavity dilated. Foreign bodies not infrequently become lodged in the U mm pharynx and most usually at its termination at about the level of the cricoid cartilage, just beyond the reach of the finger, as the distance from the arch of the teeth to the commencement of the cssophagus is about six inches. Hypertrophy of the lymphoid tissue of the naso- pharynx produces groups of hypertrophic masses known as adenoids. A child with adenoids has a cough, and 19 mm when awake or asleep, breathes noisily and with the mouth open. The voice is muffled, the hearing is im- paired, the expression is vacant, the mind is dull, and the tonsils are enlarged. THE (ESOPHAGUS (Figs. 966, 967). The (esophagus, or gullet, is a musculomembra- nous canal, about nine or ten inches in length, extending from the pharynx to the stomach. It commences at the upper border of the cricoid cartilage, opposite the sixth cervical vertebra, descends along the front of the vertebral column through the posterior mediastinum, passes through the Diaphragm, and, entering the abdo- men, terminates at the cardiac orifice of the stomach, opposite the eleventh thoracic verte- bra, about an inch (2.5 cm.) to the left of the me- dian plane. The general direction of the oesopha- gus is vertical, but it presents two or three slight curves in its course. At its commencement it is placed in the median line, but it inclines to the left side as far as the root of the neck, gradually passes to the middle line again, and finally deviates to the left as it passes forward to the oesophageal opening of the Diaphragm (Jiiatus oesophageus). The oesophagus also presents antero-posterior flexures, corresponding to the curvature of the cervical and thoracic portions of the vertebral column. It is the narrowest part of the alimentary canal, being most con- tracted at its commencement, at about the level of the third thoracic vertebra, and at the point where it passes through the Diaphragm (Fig. 966). When empty, the oesophagus is contracted so that its anterior and posterior walls come in contact and the lumen is stellate on account of the longitudinal foldings of the inelastic mucous membrane loosely held by the submucosa. The calibre lS-14 mm L^O Fig. 966. — Contour of the CESophagus. On the left the distances of the co istric- tions from the incisor teeth are given in centimeters: on the right are given the diameters in millimeters. (Half natural size.) THE (ESOPHAGUS 1237 of the lumen varies between half an inch to an inch or more, dependintr upon the absence or presence of swallowed substances. The average distance from the upper incisor teeth to the beginning of the gullet is about six inches (15 cm.); the average distance from the incisor teeth to the cardiac opening of the stomach is fifteen or sixteen inches (40 cm.). The portion of the a\sophagus which is in the neck is called the cervical portion ipcn-s ccrvicalis); the portion in the thorax, the thoracic portion {pars thoracalis); and the portion which lies in the oesophageal groove of the liver, and therefore below the Diaphragm, is the abdom- inal portion. The abdominal portion of the oesopha- gus {pars ahdominalis) is not over half an inch in length, and is limited to the small portion of the anterior and left lateral surface observed when a stomach which is completely empty is drawn downward with considerable force. The abdominal portion of the oesophagus is covered by perito- Mirr""' PULMONARY OESOPHAGUS -DIAPHRAGM Fig. 968. — The relations of cesopha- FlG. 967. — Pleural cul-de-sac of the posterior mediastinum. Level gus, trachea, and aorta in an infant, of sixth thoracic vertebra. (Poirier and Charpy.) neum only on its ventral and left aspects. It is somewhat conical, with its base toward the stomach, and is known as the antrum, cardiacum. Relations. — The cervical portion of the oesophagus is in relation, in front, with the trachea, and at the lower part of the neck, where it projects to the left side, with the thjToid _ gland ; behind, \i rests upon the vej-tebral column and Longus colli muscles; on either side, it is in relation with the common carotid artery (especially the left, as it inclines to that side) and part of the lateral lobe of the thyroid gland; the recurrent laryngeal .nerves ascend between it and the trachea; to its left side is the thoracic duct. The thoracic portion of the cesophaguis is at first situated a litde to the left of the median line; it then passes behind the aortic arch, separated from it by the trachea, and descends in the posterior mediastinum, along the right .side of the aorta, then runs in front and a little to the left of the aorta, and enters the abdomen through the Diaphragm at the level of the tenth thoracic vertebra. Just before it passes through the Diaphragm it presents a distinct dilatation or bidb. It is in relation, in front, with the trachea, the left bronchus, the pericardium, and the Diaphragm; behind, it rests upon the vertebral column, the Longus colli muscles, the right intercostal arteries, the thoracic duct, and the vena azygos minor veins; and beloiv, near the Diaphragm, upon the 1238 THE ORGANS OF DIGESTION front of the aorta. On its lejt side, in the superior mediastinum, p.re the terminal part of the arch of the aorta, the left subclavian artery, the thoracic duct, and left pleiua, while running upward in the angle between it and the trachea is the left recurrent laryngeal nerve; below, it is in relation with the descending thoracic aorta. On its right side are the right pleura and the vena azygos major, which it overlaps. The vagus nerves descend in close contact with it, the right nerve passing down behind, and the left nerve in front of it; the two nerves uniting to form a plexus {plexus oesophageus s. gulae) aroimd the tube. In the lower part of the posterior mediastinum the thoracic duct lies to the right side of the oesophagus; higher up, it is placed behind it, and, crossing about the level of the fourth thoracic vertebra, is continued upward on its left side. LEFT PULMONARY ARTERY LEFT LUNG LEFT BR THORACIC DUCT VAGUS NERVE PLEURA AZYGOS VEI :::z:iM^ DIAPHRAGM 1 the cervical region and i (Poirier and Charpy.) the posterior mediastinum. Structure. — The cesophagus has four coats — an external or fibrous, a muscular, a sub- mucous, and an internal or mucous coat. The fibrous coat consists of white fibrous connective tissue tha,t supports the other coats and assists in connecting the oesophagus to the surrounding tissues or organs. The muscular coat (tutuca muscularis) is composed of two planes of considerable thickness, an external longitudinal and an internal circular. The longitudinal fibres are arranged, at the commencement of the tube, in three fasciculi — one in front, which is attached to the vertical ridge on the posterior surface of the cricoid car- tilage, and one at each side, which is continuous with the fibres of the Inferior constrictor of the pharynx; as they descend they blend together and form a uniform layer, which covers the outer surface of the tube. Accessory slips of muscle tissue pass between the oesophagus and the left pleura, where the latter covers the thoracic aorta, or the root of the left bronchus, or the back of the peri- cardium (Fig. 970). THE (ESOPHAGUS 1239 The circular fibres are continuous above with the Inferior constrictor of the pharynx; their direction is transverse at the upper and lower parts of the tube, but oblique in the intermediate part. Below, the circular fibres pass iiiiu ihc circular and oblique fibres of the stomach. The muscle fibres in the upper part "f ilic u-^cijihagus are of a red color, and consist chiefly of the striped variety, but below they con.si.^l for the must part of involuntary muscular fibres. The submucous coat {tela submucosd) connects loosely the mucous and muscular coats. The mucous coat (limica mucosa) is thick, of a reddish color above and pale below. It is disposed in longitudinal folds, which disappear on distention of the tube. Its surface is studded with minute papilla;, and is covered throughout with a thick layer of stratified pavement epi- thelium. Beneath the mucous membrane, between it and the submucous coat, is a layer of lonoiliidiiKilly arranged nonstriped muscle tissue. This is the muscularis mucosae {lamina muscularis mucosae). At the coinnieiiccincnt of the oesophagus it is absent, or only represented by a few scattered bundles; lower down it forms a considerable stratum. The oesophageal glands are small compound racemose glands of the mucous type; they are lodged in the submucous tissue and each opens upon the mucous surface by a long excretory duct. Vessels and Nerves. — The larger vessels are in the submucosa and send branches to the mucosa and muscularis. The arteries supplving the rjesophagus are derived from the inferior thyroid branch of the thyroid axis of the subclavian, from the descending thoracic aorta and the bronchial arte- ries, and from the gastric branch of the coeliac axis, and from the left inferior phrenic of the abdominal aorta. They have for the most part a longitudinal direction. The veins are gathered into a plexus on the outer surface of the oesopha- gus. This plexus receives the venous blood from the walls of the tube. From the lower portion of tlie plexus branches go to the coronary vein of the stomach. Higher up branches go to the azygos veins and thyroid veins. In this manner a communication is opened between the portal vein and the systemic veins. The lymphatics drain into the inferior deep cervical nodes and the nodes of the posterior mediastinum. The nerves are derived from the vagus and from the sympathetic; they form a plexus in which are groups of ganglion cells between the two layers of the muscular coat. From this fibres pass to supply the muscle, and others go to the submucous tissue to form a secondary plexus. It is usual to regard the plexus as consisting of two parts, an anterior oesophageal plexus, derived from the left vagus, and a posterior oesophageal plexus, derixed from the right vagus. These two plexuses are in the posterior mediasti- num ; they communicate with each other and contain sym- pathetic fibres. Applied Anatomy. — The relations of the oesophagus are of considerable practical interest to the surgeon,'as he is frequently required, in cases of stricture of this tube, to dilate the canal by a bougie, when it is of importance that the direction of the oesophagus and its relations to surrounding parts should be remembered. In cases of malignant disease of the oesophagus, where its tissues have become softened from infiltration of the morbid deposit, the greatest care is requisite in directing the bougie through the strictured part, as a false passage may easily be made, and the instrument may pass into the mediastinum, or into one or the other pleural cavity, or even into the pericardium. One should also remember that obstruction of the oesophagus, and consequent symptoms of stricture, are occasionally produced by aneurism of some part of the aorta pressing upon the tube. In such a case the passage of a bougie could only hasten the fatal issue. In passing a bougie the left forefinger should be introduced into the mouth and the epiglottis felt for, care being taken not to throw the head too far backward. The bougie is then to be passed beyond the finger until it touches the posterior wall of the pharynx. The patient is now asked to swallow, and at the moment of swallowing the bougie is passed gently down- , ward, all violence being carefully avoided. It occasionally happens that "a foreign body becomes impacted in the oesophagus and can neither be brought upward nor moved downward. When all ordinary means for its removal have failed, and the body is lodged above the lower one-third of the gullet, external wsopha- FlG. 970. — Accessory muscle slips between the CESophagus and pleura, and cesophagus and trachea. (From a preparation in the Museum of the Royal College of Surgeons of England.) 1240 THE ORGANS OF DIGESTION gotomy is performed. If the foreign body is lodged in the lower one-third of the gullet, the stomach is opened (gastrotomy) and the foreign body is extracted. If the foreign body is allowed to remain lodged in the oesophagus, extensive inflammation and ulceration may ensue. In one case the foreign body ultimately penetrated the intervertebral substance, and destroyed life by inflammation of the membranes and substance of the spinal cord. The operation of cesophagotomy is thus performed: The patient being placed upon his back, with the head and shoulders slightly elevated, an incision, aljout four inches in length, should be made on the left side of the trachea, from the thyroid cartilage downward, dividing the skin, Platysma, and deep fascia. The edges of the wound being separated, the Omohyoid muscle should, if necessary, be divided, and the fibres of the Sternohyoid and Sternothyroid muscles drawn inward; the sheath of the carotid vessels, being exposed, must be drawn outward, and retained in that position by retractors; the cesophagus will now be exposed, and should be divided over the foreign body, which can then be removed. Great care is necessary to avoid wounding the thyroid vessels, the thyroid gland, and the laryngeal nerves. The oesophagus may be obstructed not only by foreign bodies, but also by changes in its coats, producing siridure, or by pressure on it from without of new growths or aneurisms, etc. The different forms of stricture are: (1) the spasmodic, occurring in neurotic individuals, and intermittent in character, so that the dysphagia is not constant. Spasmodic stricture of the oesophagus sometimes occurs incases of cancer of the stomach and cancer of the liver; (2) fibrous, due to cicatrization after injuries, such as swallowing corrosive fluids or boiling water; and (3) maligtiant, usually epitheliomatous in its nature. Cancer is most common either at the upper end of the tube, opposite to the cricoid cartilage, or at its lower end at the cardiac orifice. Cicatricial stricture may be treated by gradual dilatation. If a stricture is impassable from above, the stomach may be opened, an instrument passed from below, and a string used to divide the stricture. The operation of (B.?o;:i/i090«fomi/ has occasionally been performed, but if any operative interference is undertaken for stricture, with the idea of forming an orifice for the introduction of food, it is better to perform gastrostomy. In malignant stricture, gastrostomy is the only operation to be thought of. THE ABDOMEN. The abdomen is that portion of the trunk which lies below the Diaphragm, and it contains the largest cavity in the body. It is of an oval form, the extremities of the oval being directed upward and downward; the upper one is formed by the under surface of the Diaphragm, the lower end is limited by the structures Male Type Fig. 971. — Schematic outlines of the abdomen. which clothe the inner surface of the bony pelvis, principally the Levatores ani and the Coccygei muscles on either side. These muscles are sometimes termed the Diaphragm of the pelvis. In order to facilitate description, it is artificially divided into two parts, an upper and larger part, the abdomen proper, and a lower and smaller part, the pelvis. The cavities of these divisions are not separated from each other, but the limit between them is marked by the brim of the true pelvis. The cavity is wider above than below, and measures more in the vertical than in the transverse diameter. The abdomen proper differs from the other great cavities of the body in being bounded for the most part by muscles and fascise, so that it can vary in capacity and shape according to the condition of the viscera which it contains; but, in THE ABD03IEN 1241 addition to this, the abdomen varies in form and extent with age and sex (Fig. 971). In the adult male, with moderate distention of the viscera, it is oval or barrel-shaped, but at the same time flattened from before backward. In the adult female, with a fully developed pelvis, it is conical with the apex above, and in young children it is conical with the apex below. Heart contoitr /-. Small intestine Peritoneum — Fig. 972. — Topography of thoracic and abdominal viscera. Boundaries.— The boundary between the thorax and abdomen is the Dia- phragm, which extends as a dome over the abdomen, so that the cavity extends high into the bony thorax, reaching on the right side, in the midclavicular line, to the upper border of the fifth rib; on the left side it falls below this level by about half an inch or more. The abdomen proper is bounded in front and at the sides by the lower ribs, the abdominal muscles, and the iliac fossa?; behind, by the vertebral column and the Psoas and Quadratus lumborum muscles; above, by the Diaphragm; below, by the plane of the inlet or brim of the pelvis. The muscles forming the boundaries of the cavity are lined upon their inner surface by a layer of fascia, differently named, according to the part which it covers. 1242 THE ORGANS OF DIGESTION The abdomen contains (Fig. 972) the greater part of the ahmentary canal ; some of the accessory organs to digestion — viz., the liver and pancreas; the spleen, the kidneys, and adrenals, or suprarenal capsules. Most of these structures, as well as the wall of the cavity in which they are contained, are covered by an extensive and complicated serous membrane, the peritoneum (Fig. 1004). The Apertures in the Walls of the Abdomen. — ^The apertures found in the walls of the abdomen, for the transmission of structures to or from it, are the umbilicus, for the transmission (in the fetus) of the umbilical vessels; the caval opening in the Diaphragm, for the transmission of the inferior vena cava; the aortic opening, for the passage of the aorta, vena azygos major, and thoracic duct; and the oesophageal opening, for the oesophagus and vagus nerves. Below, there are two apertures on each side , one for the passage of the femoral vessels, and the other for the transmission of the spermatic cord in the male, and the round ligament in the female. Limit i^iiiLsc^, Fig. 973. — The regions of the abdomen and their contents. Edges of costal Regions (Fig. 973). — For convenience of description of the viscera, as well as of reference to the morbid conditions of the contained parts, the abdomen is arti- ficially divided into nine regions by imaginary planes, two horizontal and two sagittal, passing through the cavity, the edges of the planes being indicated by lines drawn on the ventral surface of the body. Of the horizontal planes, the upper or infracostal is indicated by a line encircling the body at the level of the lowest points of the tenth costal cartilages, the lower by a line carried around the trunk at the level of the summits of the iliac crests. The lower plane closely corre- sponds to the intertubercular plane passing through the trunk at the level of the prominent and easily defined tubercle on the iliac crest about two inches behind THE ABDOMEN 1243 the anterior superior iliac spine. By means of these imaginary planes the abdomen is divided into three zones, which are named, from above downward, ■mbcostal, umbilical, and hypogastric zones. Each of these is furtlier sul)divided by two sagittal planes, which are indicated on the surface by lines drawn vertically through points half way between the anterior superior iliac spines and tlie symphysis pu\ns. The regions as outlined by the BNA Commission are shown in Fig. 974.' The middle region of the upper zone is called the epigastric, and the two lateral reo-ions, the right and left hypochondriac. The central region of the middle zone is the umbilical; and the two lateral regions, the right and left lumbar. The middle region of the lower zone is tlie hypogastric or pubic region; and the lateral regions are the right and left iliac or inguinal. REGIO INGUINAUIS- The pelvic cavity is that part of the abdominal cavity which lies below and behind a plane passing through the promontory of the sacrum, the iliopectineal lines and the pubic crests. It is bounded behind by the sacrum, coccyx, Pyriformis muscles, and the great sacrosciatic ligaments; in front and laterally by the pubes and ischia and Obturator internus muscles; above, it communicates with the cavity of the abdomen; beloiv, it is closed by the Leva tores ani and Coccygei muscles and the triangular ligament. The pelvic cavity contains the urinary bladder, the sigmoid colon, the rectum, a few coils of small intestine, and some of the generative organs. If the anterior abdominal wall is reflected in the form of four triangular flaps by means of vertical and transverse incisions — the former from the ensiform car- tilage to the symphysis pubis, the latter from flank to flank at the level of the umbilicus — the abdominal or peritoneal cavity is freely opened and the contained ^ Anatomists are far from agreed as to the best method of subdividing the abdooainal cavity, .\ddison (Jour- nal of Anatomy and Physiology, vols, xxxiv and xxxv), in a careful analysis of the abdominal viscera in forty subjects, adopts the following lines: (1) a median, from the symphysis pubis to the ensiform cartilage: C2) two lateral lines drawn vertically through a point midway between the anterior superior iliac spine and the sjTnphysis pubis: (3) an upper transverse line half way between the symphysis pubis and the suprasternal notch: and (4) a lower transverse line midway between the last and the upper border of the symphysis pubis. The upper transverse line corresponds with what he has termed the transpylonc plane, from the fact that in most cases this plane traverses the pylorus. 1244 THE ORGANS OF DIGESTION viscera are in part exposed. Above and to the right side is the liver, situated chiefly under the shelter of the right ribs and their cartilages, but extending across the middle line, and reaching for some distance below the level of the ensiform cartilage. To the left of the liver is the stomach, from the lower border of which an apron-like fold of peritoneum, the greater omentum, descends for a varying distance, and obscures, to a greater or less extent, the other viscera (Fig. 1002). Below it, however, some of the coils of the small intestine can generally be seen, while in the right and left iliac regions respectively the cecum and the sigmoid flexure of the colon are exposed. The bladder occupies the anterior part of the pelvis, and, if distended, will project above the symphysis pubis; the rectum lies in the concavity of the sacrum, but is usually obscured by the coils of the small intestine. The sigmoid colon lies between the rectum and the bladder. If the stomach is followed from left to right it will be found to be continuous with the first part of the small intestine, or duodenum, the point of continuity being marked by a thickened ring which indicates the position of the pyloric sphincter. The duodenum passes toward the under surface of the liver, and then, curving downward, is lost to sight. If, however, the great omentum be thrown upward over the thorax, the terminal part of the duodenum will be observed passing across the vertebral column toward the left side, where it becomes con- tinuous with the coils of the small intestine. These measure some twenty feet in length, and if followed downward will be seen to end in the right iliac fossa by opening into the cecum, the commencement of the large intestine. From the cecum the large intestine takes an arched course, passing at first upward on the right side, then across the middle line and downward on the left side, and forming respectively the ascending, transverse, and descending parts of the colon. In the left iliac region it assumes the form of a loop, the sigmoid flexure, then follows the curve of the sacrum and terminates in the rectum and anal canal. The spleen lies behind the stomach in the left hypochondriac region, and may be in part exposed by pulling the stomach over toward the right side. The glistening appearance of the deep surface of the abdominal wall and of the exposed viscera is due to the fact that the former is lined and the latter more or less completely covered by a serous membrane, the peritoneum. THE PERITONEUM (TUNICA SEROSA). The peritoneum is the largest serous membrane in the body, and consists, in the male, of a closed sac, a part of which is applied against the abdominal parietes, while the remainder is reflected more or less completely over the contained viscera. In the female the peritoneum is not a closed sac, since the free extremities of the Fallopian tubes open directly into the peritoneal cavity. The part which lines the parietes is named the parietal peritoneum; that which is reflected over the viscera, the visceral peritoneum. The free surface of the membrane is smooth, covered by a layer of flattened endothelium, and lubricated by a smafl quantity of serous fluid. Hence the viscera can glide freely against the wall of the cavity or upon one another with the least possible amount of friction. The attached surface is rough, being connected to the viscera and inner surface of the parietes by means of areolar tissue termed the subserous areolar tissue [tela subserosa). The parietal portion is loosely connected with the fascia lining the abdomen and pelvis, but more closely to the under surface of the Diaphragm and also in the middle line of the abdomen. The space between the parietal and visceral layers of the peritoneum is named the peritoneal cavity; but it must be remembered that under normal conditions this cavity is a potential one, since the parietal and visceral layers are in contact. THE PERITONEUM 1245 The peritoneal "cavity" is subdivided into a greater and a lesser cavity or sac, wliicii communicate through the foramen of Winslow {foramen, eplplolcwii). I'he greater sac is opened wiien tlie ventral abdominal wall is pierced; the lesser is situated behind tiie stomacli and adjoining structures, and may be regarded as a diverticulum of the greater sac. The disposition of the peritoneum as it is applied to the parietes and also reflected over the viscera contained in the abdominal cavity is best vndersfood after tracing the developmental (enibrijolorjic) history of the peritoneum and the alimentary tract. Development of the Peritoneum and Alimentary Tract/ — ^The segment- ing ovum, at an early stage, becomes a blastodermic vesicle with two layers of cells composing its wall, named, from without inward, ectoderm and ento- derm. The cavity of the vesicle is filled with the nutritive yolk {vitellus). Only a part of the ovum is destined to form the embryo, the remainder being used up in the formation of membranes and other appendages which are concerned in protection and nutrition; the ovum may, therefore, be divided into its embryonic area and extra-embryonic portion. In the embryonic area, in its caudal part, appears the transitory primitive streak and groove produced by an axial thickening of the ectoderm. From the head process of the primitive streak a third layer of cells, the mesoderm, extends in all directions between ectoderm and entoderm, ex- tending alongside the neural tube and notochord. The extension of the mesoderm takes place throughout the whole of the embryonic and extra-embryonic areas of the ovum except in certain regions. One such area, devoid of mesoderm, is seen Fig. 975. — Diagrammatic outline of a longitudinal vertical section of the chick on tte fourth day. ep. Ecto- derm, sm. Somatic mesoderm, hit. Entoderm, vm. Visceral mesoderm, af. Cephalic fold, vt- Caudal fold, am. Cavity of true amnion, ys. Yolk sac. i. Intestine, s. Foregut. a. Future anus, still closed, m. The mouth, me. The mesentery, al. The allantoic vesicle, pp. Space between inner and outer folds of amnion. (From Quain's Anatomy, Alien Thomson.) immediately cephalad of the neural tube. This is named the buccopharyngeal area, since it afterward forms the temporary septum between the primitive mouth and primitive pharynx. This membrane extends from the head to the peri- cardial area. A similar area devoid of mesoderm is seen immediately caudad of the embryonic area, and is named the cloacal membrane, since it afterward forms the temporary septum between the anal pit and the primitive hindgut. While the paraxial mesoderm extends along the neural tube and notochord and in all directions, its lateral portion splits into two concentric layers; the outer or somatic layer becomes applied to the ectoderm, and with it forms the somato- pleure or body wall; the inner or splanchnic layer adheres to the entoderm, and with it forms the splanchnopleure, from which the greater portion of the digestive tract is formed. The space created between the layers of the mesoderm is termed the coelom or body cavity. A portion of this space is later enclosed within the embryo, and is called the embryonic coelom, while the portion of the coelomic 1 In the preparation of this chapter the editor has consulted several original treatises, i ton's "Anatomy of the Human Peritoneum and Abdominal Cavity," 1903. atably G. S. Huntingr 1246 THE OB&ANS OF DIGESTION cavity left outside the embryo, the extra-embryonic coelom, envelops the vitelline or yolk sac. -Diagram of a longitudinal section of a bryo. Very early, (After Quain.) The relatively slow growth of the margin of the embryonic area and the relati-\'ely rapid growth of the axial parts soon come to form a ring of constriction between the embryo and the yolk sac, and a part of the latter — that is, a part of its splanch- * nopleural wall and part of the cavity — becomes enclosed within the embryo to form the primitive alimentary canal (Fig. 976). At the same time a part of the coelom becomes enclosed within the em- bryo by the relative approximation of the lateral, cephalic, and caudal folds, and the embryonic coelom cavity forms the rudiment of the pleural, pericardial, and peritoneal cavities. The abdominal cavity is separated from the other cavities by the septum transversum, the proton of the Diaphragm. The embryo grows more rapidly in length than in width, and its cephalic and caudal extremities are bent ventrad; the forward growth of the head tilts the areas situated cephalad so that the posi- tions of the buccopharyngeal and pericardial areas become reversed; the same inversion takes place with regard to the cloacal membrane. Figs. 977 and 978. — Early form of the alimentary canal. In Fig. 977 a front view, and in Fig. 978 an antero-posterior sec- tion are represented, a. Four pharyngeal or visceral pouches. h The pharynx, c, c. The commencing lungs, d. The stom- ach. /, /. The diverticula connected with the formation of the liver, g. The yolk sac, into which the middle intestinal groove opens. h. The hind gut. (From Kolliker, after Bischoff.) THE PERITONEUM 1247 The alimentary tube, now in its simplest form, is nearly straight and may he divided into three portions: (a) the foregid between the pericardium and noto- Bitccopharynqeal membrane Pharynx - Auditory pit Aortic bulb Cloacal dilataiwn- of hindgut Allantoic stall Umbilical vein lOplic vesicle. Stomach -+-- _Mid(jut and yolk ^Hindgut, illantois Umbilical aiteiy Fig. 979. — Human emoryo, about fifteen days old. Brain and heart represented from right side; alimentarji canal and yolk sac in mesal section. (After His.) chord; (b) the midgut, opening directly into the yolk sac; and (c) the hindgut, contained within the caudal fold. The passage between the midgut and the (Esophagus. V-shaped loop of hindgut.' Vitello-intestinal duct. Cloaca. Figs. 9S0 and 9S1. — Front (Esophagus, stages in the development of the alimentary canal. (His.) yolk sac is at first relatively wide, but it is subsequently narrowed and lengthened to become the tubular vitelline duct (to wholly disappear eventually). 1248 THE ORGANS OF DIGESTION In its course from the head to the tail the primitive alimentary canal is held to the body axis (notochord) by a broad mass of mesoderm, from which the common Bathke's pouch {pituitary invagination). Median rudiment of I thyroid gland. Mandibular arch. Notochord. Rathke's ~~ pouch {pituitary invagination). Omphalo- mesenteric duct. AUantois.-'\ Terminal portion of ~ hindgut. -Wolffian duct. Figs. 982 and 983. — Sketches in profile of two stages in the development of the human alimentary canal. Fig. 982, A X 30. Fig. 983. B X 20. (His.) mesentery of the gut is subsequently developed. The foregut^ is also held by a ventral mesentery, the thoracic portion of which becomes modified by the de- velopment of the heart and lungs, while the abdominal portion serves as a matrix for the developing liver, and ultimately becoming the falciform ligament and gastro- ' The junction of the foregut with the midgut is generally understood to be at the level of the orifice of the com- mon bile duct, or site of origin of the liver diverticulum. THE PEBITOJS-EUM 1249 hepatic omentum. The mesoderm lining the body cavity as well as the free surfaces of the mesenteries soon assumes the character of a serous membrane, and is then called the peritoneum. Topographically, this membrane may be sul)- divided into: (a) Parietal peritoneum, investing the inner surface of the abdominal cavity; (6) visceral peritoneiun, investing the alimentary tube and its derivatives; (c) mesenteric peritoneum, connecting the two former, as a suspensory support for the alimentary tract, and carrying the vessels and nerves to it. The pharynx, oesophagus, stomach, and part of the duodenimi are developed from the foregut; the descending and sigmoid parts of the colon, the rectum, and the tubular diverticulum of the allantois are developed from the hindgut; the midgut gives origin to the remainder of the alimentary tube. Point where J inteissa, the ovarian fossa, in which the ovary normally lies. 2. In the Lower Abdomen (Fig. 997). — Starting from the linea alba, below the level of the transverse colon, and tracing the continuity in a horizontal direction to the right, the peritoneum covers the inner surface of the abdominal wall almost as far as the outer border of the Quadratus lumborum; it encloses the cecum and appendix, and is reflected over the sides and aiiterior surface of the ascending colon; it may then be traced over the Psoas muscle and the inferior vena cava toward the middle line, whence it passes along the mesenteric vesiels to invest the small intestine, and back asain to the laro-e vessels in front of the vertebral 1258 THE ORGANS OF DIGESTION column, forming the mesentery, between the layers of which are contained the mesenteric bloodvessels, nerves, lacteals, and lymph nodes. It is then continued over the left Psoas muscle; it covers the sides and anterior surface of the descending colon, and, reaching the abdominal wall, is continued on it to the middle line. 3. In the Upper Abdomen (Fig. 998). — Above the transverse colon the peri- toneum can be traced, forming the greater and lesser sacs, and their communication through the foramen of Winslow can be demonstrated. Mesentery Aorta Mesocolon (imperject) Fig. 997. — Peritoneal reflection in transverse section of lumbar region below the tr; from above. Schematic. (Tillaux.) (a) Greater Sac. — Commencing on the posterior abdominal wall at the inferior vena cava, the membrane may be followed to the right over the front of the upper part of the right kidney on to the antero-lateral abdominal wall. From the middle of the anterior wall a backwardly directed fold encircles the impervious umbilical vein and forms the falciform ligament of the liver. Continuing to the left, the peritoneum lines the lateral abdominal wall and covers the outer part of the front of the left kidney, and is reflected to the posterior border of the hilus of the spleen as the posterior layer of the lienorenal ligament (Fig. 1001). It can then be traced over the surface of the spleen to the front of the hilus, and thence to the cardiac extremity of the stomach as the anterior layer of the gastrosplenic omentum. It covers the antero-superior surface of the stomach and first part of the duodenum and extends up from the lesser curvature of the stomach to the liver, the latter portion forming the anterior layer of the gastrohepatic omentum. (b) Lesser Sac. — On the posterior abdominal wall the peritoneum of the greater sac is continuous with that of the lesser sac in front of the inferior vena cava. Starting from here, the lesser sac maybe traced across the aorta and over the inner part of the front of the left kidney to the hilus of the spleen as the anterior layer of the lienorenal ligament. From the spleen it is reflected to the stomach as the posterior layer of the gastrosplenic omentum. It covers the postero-inferior surfaces of the stomach and commencement of the duodenum, and from the lesser curvature of the stomach extends upward to the liver as the posterior layer of the gastrohepatic omentum; the right margin of this layer is continuous around the hepatic artery, bile duct, and portal vein with the wall of the greater sac. The foramen of Winslow (foramen epiploicum) is the passage of communication THE PERITONEUM 1259 between the greater and lesser sacs. It is bounded in front by the free border of the gastrohepatic omentum, with the hepatic artery, common bile duct, and portal vein between its two layers; behind by the peritoneum covering the inferior vena cava; above by the peritoneum on the caudate lobe of the liver, and heloio by the peritoneum covering the commencement of the duodenum and the hepatic artery, the latter passing forward below the foramen before ascending between the two layers of the gastrohepatic omentum (Fig. 998). Lig. teres Common bite duct Inferior Vena Cava Fig. 998.^ — Transverse section of peritoneum above the transverse colon. The arrow points to the lesser sac and passes through the foramen of Winslow. The boundaries of the lesser sac will now be evident. It is bounded in front, from above downward, by the Spigelian lobe of the liver, the gastrohepatic omen- tum, the stomach, and the anterior two layers of the greater omentum; behind, it is limited, from below upward, by the two posterior layers of the greater omentum, the transverse colon, and the ascending layer of the transverse mesocolon, the upper surface of the pancreas, the left suprarenal gland, and the upper end of the left kidney. Laterally, the lesser sac extends from the foramen of Winslow to the spleen {recessus lienalis) (Fig. 1001), where it is limited by the lienorenal ligament and the gastrosplenic omentum. In the fetus the lesser sac reaches as far as the free margin of the great omentum, but in the adult its vertical extent is usually more limited, owing to adhesions between the layers of the omentum. It should be stated that during a consider- able part of fetal life the transverse colon is suspended from the posterior abdomi- nal wall by a mesentery of its own — the two posterior layers of the greater omen- tum passing, at this stage, in front of the colon (Fig. 990). This condition some- times persists throughout adult life, but, as a rule, adhesion occurs between the mesentery of the transverse colon and the posterior layer of the greater omentum, with the result that the colon appears to receive its peritoneal co\ering by the splitting of the two posterior layers of the latter fold. In the adult the lesser sac intervenes between the stomach and the structures on which that viscus lies, and performs, therefore, the functions of a serous bursa for the stomach. Numerous peritoneal folds extend between the various organs or connect them to the parietes. They serve to hold them in position, and, at the same time, 1260 THE ORGANS OF DIGESTION enclose the vessels and nerves proceeding to them. Some of these folds which connect certain viscera with the parietes are called ligaments, such as the ligaments of the liver and the false ligaments of the bladder. Others, which connect certain parts of the intestine with the abdominal wall, constitute the mesenteries; and lastly, those which proceed from the stomach to certain viscera in its neighborhood are called omenta. The ligaments, formed by folds of the peritoneum, include those of the liver, spleen, bladder, and uterus. They will be found described with their respective organs. The omenta are the lesser omentum, the greater omentum, and the gastrosplenic omentum. The lesser or gastrohepatic omentum (omentum minus) (Figs. 996 and 999) is the duplicature which extends between the transverse fissure of the liver and the right side of the abdominal portion of the oesophagus, the lesser curvature of the stomach, and the upper portion of the superior surface of the duodenum. Papillayy tubercle Cut edge of peritoneum Cut edge of pei itoneum Fig. 999. — Bursa omentalis, or lesser sac, opened from the front by an incision through the gastrocolic omen- tum. A probe passes through the foramen of Winslow and rests on the gastropancreatic fold. (Hecle.) The portion going to the oesophagus and stomach is called the hepatogastric ligament (/1,9a- mentum hepatogastricum) . The division of the ligament which goes to the oesophagus is strong and dense; the division which goes to the lesser curvature of the stomach is thin and relaxed. The portion of the lesser omentum which goes to the duodenum is continuous with the first- named portion. It is called the hepatoduodenal ligament (Hgamentinn hcpatoditodenale). The right margin of this ligament is free and concave. The hepatocolic Ugament (ligavientwn hepatocolicum is not invariably present. It is a fold of the hepatoduodenal ligament and runs from the posterior surface of the gall-bladder to the descending portion of the duodenum or possibly to the transverse colon. The lesser omentum is thin, and is continuous with the two layers which cover respectively the anterior and posterior surfaces of the stomach. ^Vhen the two layers reach the lesser curvature of the stomach, they join and ascend as the double THE PERITONEUM 1261 fold to the transverse or portal fissure of the liver; to the left of this fissure the double fold is attached to the bottom of the fissure for the ligamentum venosum, along which it is carried to the Diaphragm, where the two layers separate to embrace the end of the oesophagus. At the right border the two layers are continuous and form a free margin which constitutes the anterior boundary of the foramen of Winslow. Between the two layers, close to this free margin, are the hepatic artery, the com- mon bile duct, the portal vein, lymphatics, and the hepatic plexus of nerves (Fig. 1000) — all these structures being enclosed in loose areolar tissue which is continuous with Glisson's capsule. Between the layers where they are attached to the stomach lie the gastric artery and the pyloric branch of the hepatic artery. The greater or gastrocolic omentum {omentum majtis) (Figs. 996 and 1002) is the largest peritoneal fold. It consists of a double sheet of peritoneum, folded on itself so that it is made up of four layers. The two layers which descend from the stomach pass in front of the small intestines, sometimes as low down as the pelvis; they then turn upon themselves, and ascend again as far as the transverse colon, where they separate and enclose that part of the intestine. These separate layers may be easily demonstrated in the young subject, but in the adult they are morev CYSTIC DUCT FREE EDG OF LESSE OMENTU PANCREATIC DUCT IGHT GASTRO- PIPLOIC ARTERY SUPERIOR PANCREATICO' DUODENAL ARTERY Fig. 1000. — Structures between the layers of the lesser omentum. The liver has been raised up, and the anterior layer of the omentum removed. Semidiagrammatic. (Cunningham.) or less inseparably blended. The left border of the greater omentum is continuous with the gastrosplenic omentum; its right border extends only as far as the duo- denum. The greater omentum is usually thin, presents a cribriform appearance, and always contains some adipose tissue, which in fat persons accumulates in considerable quantity. Between its two anterior layers is the anastomosis between the right and left gastroepiploic arteries. In opening the abdomen the greater omentum is rarely found spread out evenly over the intestines. It often projects between intestinal coils, or is largely gathered in some one region, or is pushed in front of the stomach by distention of the colon. The gastrosplenic omentimi is the fold which connects the margins of the hilum of the spleen to the stomach, being continuous by its lower border with the greater omentum. It contains the vasa brevia. 1262 THE ORGANS OF DIGESTION RENAL SURFACE POUCH OF GREATER SAC LIENORENAL L'.GAWENT PHRENIC SURFACE GASTROSPLENIC OMENTUM POUCH OF GREATEP SAC GASTRIC S'iRFACE Fig. 1001.— Horizontal section through the stomach, pancreas, spleen, and the left kidney to show peritoneal reflec- tions at the hilum of the spleen. (G. S. H.) Fig. 1002. — The greater omentum as seen from the front. (Testut.) THE PERITONEUM 1263 mesocolon, and the mesentery of the vermiform appendix. In addition to these there are sometimes present an ascending and a descending mesocolon. The mesentery (mesenterium) (Figs. 1003 and 1004), is the broad, fan-shaped fold of peritoneum which connects the convolutions of the jejunum and ileum with ^Duodenum Soot of meseii ^ tery ^ t- Sigmoid Jiexin r Ceciim Fig. 1003. — Mesentery. Small intestine pushed upward to the right l,Tiilau\ ) the posterior wall of the abdomen. Its root (radix mesenterii), the part connected with the structures in front of the vertebral column, is narrow, about six inches in length, and directed obliquely from the left side of the second lumbar vertebra to the right iliac fossa (Fig. 1004). Its intestinal border is about twenty feet in length, and here the two layers separate so as to enclose the intestine and form its peritoneal coat. Its breadth, between its vertebral and intestinal border, is about eight inches. Its upper border is continuous with the under surface of the trans- verse mesocolon; its lower border, with the peritoneum covering the cecum and ascending colon. It serves to retain the small intestines in their position, and contains between its layers the mesenteric vessels and nerves, the lymphatic vessels, and mesenteric lymph nodes. These nodes number from 50 to 150. The mesentery is somewhat translucent, particularly at its upper part, but in stout individuals it becomes opaque on account of the fat deposited between its layers. In most cases the peritoneum covers only the front and sides of the ascending 1264 THE ORGANS OF DIGESTION and descending parts of the colon. Sometimes, however, these are surrounded by the serous membrane and attached to the posterior abdominal wall by an ascending mesocolon {mesocolon ascendens) and a descending mesocolon {mesocolon descendens) respectively. At the place where the transverse colon turns downward to form the descending colon, a fold of peritoneum is continued to the under surface of the Diaphragm opposite the tenth and eleventh ribs. This is the phrenocolic ligament {ligamenhim lihrenicocolicum) ; it passes below the spleen, and serves to support this organ, and therefore it has received the name of sustentaculum lienis. Peritoneum. Extraperitoneal t Diaphragmatic end of gastrohepatic omeittun Gastrophrenic ligament. 5 Bare surface for 2nd pan 5 Left lateral false liga- leaves the wall of the The transverse mesocolon {mesocolon transversum) (Fig. 1004) is a broad fold which connects the transverse colon to the posterior wall of the abdomen. It is formed by the two posterior layers of the greater omentum, which, after separating to surround the transverse colon, join behind it, and are continued backward to the vertebral column, where they diverge in front of the anterior border of the pancreas. This fold contains between its layers the vessels which supply the transverse colon. The sigmoid mesocolon {mesocolon sigmoidciim) (Fig. 1004) is the fold of peri- toneum which retains the sigmoid flexure in connection with the pelvic wall. Its line of attachment forms a V-shaped curve, the apex of the curve being placed THE PERITONEUM 1265 about the point of division of the left common iliac artery. The curve begins on the inner side of the left Psoas, and runs upward and backward to the apex, from \\hich it bends sharply downward and inward, and ends in the mesal ]5lane at the level of the third sacral segment. Between the two layers of this fold run the sigmoid and superior hemorrhoidal vessels. Fig. 1005. — Superior and inferior duodenal fossse. (Po »RTEHy ■ and Cliarpy.) The mesoappendix or mesentery of the vermiform appendix (mesenteriolmn pro- cessus vermiformis) (Fig. 1008) is a double fold of peritoneum derived from the left leaf of the mesentery. In the majority of cases it is triangular in shape and usually extends along the entire length of the appendix. Between its two layers lie the appendicular artery (Fig. 1055), a branch of the ileocolic artery, some connective tissue, and lymph vessels and nerves. The appendices epiploicae are small pouches of the peritoneum filled with fat .and situated along the colon and upper part of the rectum. They are chiefly appended to the transverse colon. Retroperitoneal Fossae. — In certain parts of the abdominal cavity there are recesses of peritoneum forming culs-de-sac or pouches, which are of surgical inter- est in connection with the possibility of the occurrence of retroperitoneal hernia. One of these is the lesser sac of the peritoneum (Figs. 996 and 998), which may be regarded as a recess of peritoneum through the foramen of Winslow, in which a hernia may take place, but there are several others, of smaller size, which require mention. These recesses, or fossse, may be divided into three groups — viz. : (1) the duodenal fossae; (2) pericecal fossae; and (3) the intersigmoid fossa. 1. Duodenal Folds and Fossse. — Moynihan has described no less than nine fossae as occurring in the neighborhood of the duodenum. Three of these are fairly constant. Five of the fossae are here considered: (a) The inferior duodenal fossa, or fossa of Treitz (Fig. 1005), is the most constant of all the peritoneal fossse in this region, being present in from 70 to 75 per cent, of cases. It is situated opposite the third lumbar vertebra on the left side of the ascending portion of the duodenum. Its opening is directed upward, and is boimded by a thin, sharp fold of peritoneum with a concave free upper margin, called the inferior duodenal fold {plica duodenomesocolica) . The tip of the index finger introduced into the fossa under the fold passes some little distance behind the ascending or fourth portion of the duodenum, (b) The superior duodenal fossa (Fig. 1005) is the next most constant pouch or recess, being present in from 40 to 50 per cent, of cases. It often coexists with the inferior one, and its orifice looks downward, in the oppo- site direction to the preceding fossa. It lies to the left of the ascending portion 1266 THE ORGANS OF DIGESTION of the duodenum. It is bounded by the free edge of the superior duodenal fold (plica duodenojejunalis), which presents a semihinar margin; to the right it is blended with the peritoneum covering the ascending duodenum, and to the left with the peritoneum covering the perirenal tissues. The fossa is bounded in front by the superior duodenal fold; behind by the second lumbar vertebra; to the right by the duodenum, (c) The duodenojejunal fossa or mesocolic fossa (recessus duodenojejunalis) is formed where the duodenojejunal angle enters the root of the transverse mesocolon. There are two forms: (1) a single fossa and (2) a double fossa. It can be seen by pulling the jejunum downward and to the right after the transverse colon has been pulled upward. It will appear as an almost circular opening, looking downward and to the right, and bounded by two free borders or folds of peritoneum, the duodenomesocolic ligaments. The opening DUODENUM- RIGHT DUODENO- MESOCOLrC LIGAMENT INFERIOR MESEN- TERIC ARTERY Fig. 1006. — Duodenojejunal fossa. (Poirier and Charpy.) admits the little finger into the fossa to the depth of from four-fifths to one and one- fifth inches, or 2 to 3 cm. The fossa is bounded above by the pancreas, to the right by the aorta, and to the left by the kidney; beneath is the left renal vein. The fossa exists in from 15 to 20 per cent, of cases, and has never yet been found in conjunction with any other form of duodenal fossa, (d) Paraduodenal fossa or the fossa of Landzert (recessus duodenojejunalis) is most distinct in the infant, and is to the left of the ascending portion of the duodenum. The fold of peri- toneum to its outer side and above is produced by the inferior mesenteric vein. Its lower limit is a fold called the mesentericomesocolic fold, (e) The retro- duodenal fossa (Fig. 996) was described in 1893 by Jonnesco. It is a peritoneal cul-de-sac, sometimes found behind the horizontal and ascending portions of the duodenum. 2. Pericecal Folds and Fossae. — There are at least three pouches or recesses to be found in the neighborhood of the cecum, which are termed pericecal fossae. (1) The ileocolic fossa or superior ileocecal {recessus ileocecalis superior) (Fig. 1007) is formed by a fold of peritoneum, the ileocolic fold, arching over the branch of the ileocolic artery which supplies the ileocolic junction. The fossa is a narrow THE PERITONEUM 1267 chink situated between the ileocolic fold in front, and the mesentery or the small intestine, the ileum, and a small portion of the cecimi behind. (2) The ileocecal or ileoappendicular fossa {recessiis ileocecalis inferior) (Fig. 1007) is situated behind the angle of junction of the ileum and cecum. It is formed by a fold of peri- toneum, the ileocecal fold (plica ileocecalis), or "bloodless fold" of Treves, the upper border of which is attached to the ileum, opposite its mesenteric attach- ment, while the lower border, passing over the ileocecal junction, joins the mesentery of the appendix, and sometimes the appendix itself; hence this fold is sometimes called the ileoappendicular fold. Between this fold and the mesen- tery of the vermiform appendix is the inferior ileocecal fossa. It is bounded above by the posterior surface of the ileum and the mesentery; in front and below by the ileocecal fold and behind by the upper part of the mesentery of the appendix. (3) The retrocecal or subcecal fossa {recessns retrocecalis) (Fig. 1008) is situated ^fcs& \% ^Epiploic appendages. /Ileocolic fold. Superior ileocecal recess. Inf(7ior ileocecal Jossa Cecal fold Retrocecal recess. Ileocecal fold. Fia. 1007.— The pericecal folds and foss: behind the cecum, which has to be raised to bring the fossa into view. It varies much in size and extent. In some cases it is sufficiently large to admit the index finger and extends upward behind the ascending colon in the direction of the kidney ; in others it is merely a shallow depression. It is bounded and formed by two folds: one, the external parietocolic fold, or the superior cecal fold, which is attached by one edge to the abdominal wall from the lower border of the kidney to the iliac fossa and by the other to the postero-external aspect of the colon; and the other, the inferior cecal or mesentericoparietal fold, which is in reality the insertion of the mesentery into the iliac fossa. In some instances the subcecal fossa is double. 3. The intersigmoid fossa {recessns intersigmoideus) is constant in the fetus and common during infancy, but disappears in a large percentage of cases as age advances. Upon drawing the sigmoid flexure upward, the left surface of the sig- moid mesocolon is exposed, and on it will be seen a funnel-shaped recess of the peritoneum, lying on the external iliac vessels, in the interspace between the Psoas and Iliacus muscles. This is the orifice leading to the fossa intersigmoidea, which lies behind the sigmoid mesocolon, and in front of the parietal peritoneum. The fossa varies in size; in some instances it is a mere dimple, whereas in others it will admit the whole of the index finger. 1268 THE ORGANS OF DIGESTION Any of these fossse may be the site of a retroperitoneal hernia. The pericecal fossae are of especial interest, because hernia of the vermiform appendix frequently takes place into one of them, and may there become strangulated. The presence of these pouches also explains the course which pus has been known to take in cases of perforation of the appendix, where it travels upward behind the ascend- ing colon as far as the Diaphragm.^ Applied Anatomy. — Study of the peritoneum by Robinson and others shows that absorption takes place more rapidly from the region of the Diaphragm, less rapidly but still very actively from the region of the small intestine, slowly from the pelvic region. Clinically we know that pelvic ILEO -APPENDICULAR MESO-APPENDIX Fig. 1008.— The retr. al fossa. The ileum and i '. drawn backward and upward. (Souligoux.) peritonitis is not nearly so dangerous as peritonitis in the small intestine or Diaphragm areas, and that peritonitis in the region of the Diapliragm is the most fatal form of the infection. After abdominal operations in infected cases, it is well to elevate the head of the bed (Fowler's position), so as to obtain the aid of gravity in draining septic fluids away from the dangerous region and toward the safer region.' In areas in which absorption is rapid, protective exudation is not apt to form. In areas in which absorption is slow, inflammatory exudation is apt to circumscribe the area and prevent diffusion. After an operation in a noninfected case, if salt solution has been left in the abdominal cavity because of shock or hemorrhage, raising the foot of the bed will aid rapid absorption of the fluid by favoring the natural current toward the Diaphragm and hurrying the fluid to a region in which absorption is rapid. Dr. John B. Murphy's plan of treating general peritonitis has proved remarkably successful. He does not remove the exudation of lymph which is seen upon the peritoneum. This exudation is conservative, blocks up lymph spaces, and lessens the absorption of dangerous toxins. He inserts a drainage tube into the peritoneal cavity above the pubes, puts the patient erect or semierect in bed (Fowler's position), and administers salt solution continuously by low pressure proctolysis. According to Murphy, the lymph circulation is reversed and the peritoneum becomes a secreting surface. Certain it is that the salt solution absorbed from the rectum reaches the peritoneal cavity in large amounts and flows out of the drainage tube. The greater omentum stores up fat, and, being movable, it is able to pass to diff'erent parts ot the peritoneal cavity. Dr. Robinson, in his work on the Peritoneum, describes its functions as follows: "The omentum is the great protector against peritoneal infectious invasions. It builds barriers of exudates to check infection. It is like a man-of-war, ready at a moment's notice to move to invaded parts. It circumscribes abscesses, it repairs visceral wounds, and prevents 1 On the anatomy of these fossae, see the Arris and Gale Lecturi 2 George R. Fowler, in Medical Record, April 14, 1900. i by Moynihan. 1899. THE PERITONEUM 1269 adhesions of mobile viscerca to the anterior abdominal wall. It resists infectious invasions by typical peritoneal exudates, and not by succumbing to absorbed sepsis. It is a director of peri- toneal fluids, a peritoneal drain." In abdominal wounds the greater omentum often protrudes. This structure frequently con- stitutes or is part of a hernia, and is almost invariably present in umbilical hernia. As a result of inflammation, it may become adherent to adjacent structures. Adhesions may be of service by matting together the intestines and circumscribing infections. They may be harmful by constricting the bowels and producing oljstruction. A portion of the omentum may become adherent to some other part and form a band, and under this band the gut may be caught and stranqidated. The omentum may adhere to and plug a perforation in a hollow viscus, and the surgeon may utilize it for the same purpose, or to cover a raw surface or overlie a suture line. The omentum may be in the sm-geon's way while operating. If it is, the patient is placed in the Trendelenburg position (pelvis elevated). Any tear or opening found by the surgeon in the greater omentum must be closed with sutures, because of the danger that intestine might enter and be caught in such an opening. A tumor cut off from its proper blood supply, for instance, an ovarian cyst with a twisted pedicle, may continue to receive nourishment from adherent omentum, and gangrene may thus be prevented. The lax character and sliiriing Icndency of the subserous tissue explains the occurrence of ■ptosis of the abdominal viscera and kiihieijs. The vast number of nerves in the peritoneum accounts for the profound shock which follows a wound, attends an intraperitoneal calamity, or which develops from infection. An infective process of any portion of the peritoneum produces pain and reflex symptoms (vomiting, ab- dominal rigidity, intestinal paresis, etc.). The parietal peritoneum is very sensitive to pain, but not to touch; hence, after injecting a local anesthetic and opening the abdomen, a fairly satisfactory exploration can be made with the finger. The intestine, the mesentery, the stomach, the anterior- margin of the liver, and the gall-bladder are insensitive, and may be cut or even burned without pain.i Viscera which obtain their inner- vation purely from visceral nerves are insensitive; those which receive branches from somatic nerves are sensitive (Lennander). The oblique origin of the mesentery causes this structure to form a sort of shelf. A hemor- rhage or extravasation into the abdomen, to the right of the mesentery, tends to flow into the right iliac fossa; one occurring on the left side flows into the pelvis. Monks shows how the mesentery can be utilized to determine the direction of an intestinal loop: "Now, let us suppose that the surgeon has between his fingers a loop of bowel, and wishes to determine its direction. He knows that one side of the loop is the left side of the intestine, and that the corresponding side of the mesentery, if closely followed down to the mesenteric root, will conduct him into the left fossa; he also knows that the other side of the bowel is its right side, and that the mesentery on that side will conduct him into the right fossa. Now, if his finger goes into the great fossa on the left side of the abdomen, after having closely fol- lowed the mesentery down to its root and arranged his loop to be parallel with that root, he then knows that the left and right sides of the intestine face to the left and right sides of the abdomen respectively, and that the end of the loop which points downward is the end nearest the ileo- cecal valve. He can determine the direction of the gut in a similar way in case his finger enters the right fossa. All this would seem very simple were it not for the twists in mesentery and intestine, which tend to mislead one. A little practice will usually enable one to recognize a twist in the mesentery. This should be untwisted by rotation of the gut, after which the direction is determined by another palpation of the mesenteric root."* The studies made of the arrangement and variations of the loops of the mesenteric vessels by Dr. Thomas Dwight'have been utilized and expanded by Dr. George H. Monks in laj'ing down rules for the determination of the exact portion of small intestine which may be in the surgeon's hand.* His views are as follows: "General Vascularity of the Mesentery near the Bowel. — Opposite the upper part of the bowel the mesenteric vessels are distinctly larger than opposite any other part of it. These vessels grow smaller and smaller as we pass downward until the lower third of the gut is reached, where they remain about the same size as far as the ileocecal valve. The arrangement of the mesenteric vessels has some features which iiiliinatcly concern the subject in hand, and which I shall describe with some detail. Diagranuiiaiically speaking, the main branches of the superior mesenteric artery unite with each other by means of loops, which are called for convenience 'primary loops;' in some parts of the tube, 'secondary loops,' and even, occasionally, 'tertiary loops,' are super- imposed upon these. From these loops little straight vessels — the vasa recta already referred to — run to the bowel, upon which they ramify, alternating, as a rule, as to the side of the intestine which they supply. The mesenteric veins are arranged in a manner somewhat similar to the arteries. ' Dr. K. E. L. Lennander, in Mittheilungen aus dem Grenzgebieten der Medicin und Chirurgie, Band x, Heft, 1, 2. 2 Intestinal Localization, by George H. Monks, Annals of Surgery, October, 1903. 3 Reports of tiie Meeting of American Anatomists, 1S97. ■* Annala of Surgery, 1903. 1270 THE ORGANS OF DIGESTION " The Loops of the Mesenteric FesseZs.— Opposite the upper part of the bowel there are only primary loops. Occasionally a secondary loop appears, but it is small and insignificant as com- pared with the primary loops, which are large and quite regular. As we proceed down the bowel, secondary loops become more numerous, larger, and approach nearer to the bowel than the primary loops in the upper part. As a rule, secondary loops become a prominent feature at about the fourth foot. As we continue farther downward, the secondary loops (and, possibly, tertiary loops) become still more numerous and the primary loops smaller, the loops all the time getting nearer and nearer to the gut. Opposite the lower part of the gut the loops generally lose their characteristic appearance, and are represented by a complicated network. "The Vasa Recta. — Opposite the upper part of the intestine the vasa recta are from three to five centimetres long, when the loop of small intestine to which they run is lifted up so as to put them gently on the stretch. They are straight, large, and regular, and rarely give off branches in the mesentery. In the lower third they are very short, being generally less than 1 cm. in length. Here they are less straight, smaller, less regular, and have frequent branches in the mesentery. " THE STOMACH (GASTER; VENTRICULUS) (Figs. 972, 1010). The stomach is one of the principal organs of digestion, and serves as a tem- porary receptacle for food. It is the most dilated part of the alimentary canal and is situated between the termination of the oesophagus (cardia) and the commencement of the small intestine. It lies more or less obliquely or horizontally in the epigastric, umbilical, and left hypochondriac regions of the abdomen, and occupies a recess or chamber called the stomach chamber (Fig. 999). When distended the viscus completely fills the space. \Yhen the stomach is empty it lies upon the floor of the chamber, and the portion it has vacated is occupied by the transverse colon, which ascends in front of the stomach and finally gets above it. The anterior and left wall of the stomach chamber is formed by the anterior abdominal wall and Diaphragm. The roof is formed by the under surface of the Diaphragm and the under surface of the left lobe of the li^'er. The floor is formed by the left suprarenal gland and the summit of the left kidney, the gastric surface of the spleen, the upper surface of the pancreas, the transverse mesocolon, and the colon. The shape and position of th^ stomach are so greatly modified by changes within itself and in the surrounding organs that no one form can be described as typical. The chief modifications are determined by (1) the amount of the stomach contents, (2) the stage which the digestive process has reached, (3) the degree of development or functional power of the gastric musculature, and (4) the con- dition of the adjacent intestines. When empty and contracted, as after a iith Thoracic V. -^ Z ~{\ ,' pcrlod of Tcst,^ thc stomach is sickle- or sausage-shaped, as shown in Fig. 1009. At an early stage of gastric digestion the stomach commonly consists of two seg- ^ ments — (a) a large globular portion on the fst Lumbar V. / / L \ ^^i^^^ gnd (6) a narrow tubular portion on the right, corresponding to the fundus and pyloric portions, and forming an angle with each other, the axis of the fundus Fig. 1009.— Form and topography of the stem- being directed dowuward and inward while S?aU^™terd';Sh''lnr:S?ufedl^j:^dur°" the pyloric portiou curvcs upward and to the right. The stomach presents two openings, two borders or curvatures, and two sur- faces. ; given by the immediate examination of the organ in situ in executed THE STOMACH nil Antrum cardiacum Pyloric vestibule Openings. — The opening by which the oesophagus communicates with the stomach is known as the cardiac orifice, and is situated at the level of the eleventh thoracic vertebra, nearly an inch from the midline, corresponding to the seventh left chondrosternal junction. The short intra-abdominal portion of the oesopha- gus (anfntm cardiacum) is conical in shape and curved sharply to the left, the base of the cone being continuous with the cardiac orifice of the stomach. The right mar- gin of the oesophagus is continuous with the lesser curvature of the stomach, while the left margin joins the greater curvature at an acute angle, the incisura cardiaca. The pyloric orifice communicates with the duodenum, and its position is indi- cated on the surface by a circular g^oo^•e, the duodenopyloric constriction. This orifice lies to the right of the middle line at the le^'el of the first lumbar -vertebra ; it may be from one to two inches to the right of the middle line, depending upon the degree of distention of the stomach. Its position on the ventral surface of the body would be indicated by a point in the transpyloric plane (see p. 1243) about one inch to the right of the middle line. Curvatures. — The lesser ciurature {cur- xatura reniricidi minor), extending be- sulcus intermediis tween the cardiac and pyloric orifices, forms the right or posterior border of the stomach. It descends as a continuation of the right margin of the oesophagus in front of the left crus of the Diaphragm, and then, turning to the right, it crosses the first lumbar vertebra and ends at the pylorus. Nearer its pyloric than its cardiac end is a well-marked notch, the incisura angularis, which varies somewhat in position with the state of distention of the viscus, it serves to separate the stomach into a right and left portion. The lesser curvature gives attachment to the two layers of the gastrohepatic omentum, and between these two layers are the gastric artery and the pyloric branch of the hepatic artery. It is from three to four inches (S-10 cm.) in length. The greater curvature {curvatura ventrictili major) is directed mainly forward and to the left, and is three or four times as long as the lesser curvature (twelve to sixteen inches, or 30 to 40 cm.); starting from the cardiac orifice at the incisura cardiaca it forms an arch backward, upward, and to the left; the highest point of the convexity is on a le\ el with the sixth left costal cartilage or tenth thoracic ^"ertebra. From this level it may be followed downward and forward with a slight convexity to the left as low as the cartilage of the ninth rib ; it then turns to the right to end at the pylorus. Directly opposite the incisura angularis of the lesser curvature the greater cur\"ature presents a dilatation, the pyloric vestibule or anirum, which is limited on the right by a slight groove, the sulcus intermedins; this sulcus is about an inch from the duodenopyloric constriction. The portion between the sulcus intermedins and the duodenopyloric constriction is termed the pyloric canal. At its commencement the greater curvature is covered by peritoneum con- tinuous 'sv'ith that covering the front of the organ. The left part of the curvature gives attachment to the gastrosplenic omentum, while to its anterior portion are attached the two anterior layers of the great omentum, separated from each other by the gastroepiploic vessels. Surfaces. — \\\\en the stomach is in the slightly dilated condition, its surfaces are directed more upward and downward respectively, but when the viscus is dis- tended they are directed more forward and backward. They may, therefore, be described as antero-superior and postero-inferior. 1272 THE ORGANS OF DIGESTION Antero-superior Surface. — The left half of this surface is in contact with the Dia- phragm, which separates it from the base of the left lung, the pericardium, the seventh, eighth, and ninth ribs, and intercostal spaces of the left side. The right half is in relation with the left and quadrate lobes of tlie liver and with the ventral ' abdominal wall. When the stomach is empty the transverse colon may be found lying on the front part of this surface. The whole surface is covered by peri- toneum. The Postero-inferior Surface {paries posterior) is in relation with the Diaphragm, the gastric surface of the spleen, the left suprarenal gland, the upper part of the front of the left kidney, the anterior surface of the pancreas, the splenic flexure of the colon, and the upper layer of the transverse mesocolon. These structures form a shallow concavity (^'stomach bed"), on which the stomach rests. The transverse mesocolon intervenes between the stomach and the duodenojejunal flexure and small intestine. The postero-inferior surface is covered with peri- toneum, except over a small area close to the cardiac orifice; this area is limited by the lines of attachment of the gastrophrenic ligament, and lies in contact with the Diaphragm and frequently with the upper portion of the left adrenal gland. Component Parts of the Stomach. — The stomach may be divided into a left portion or body and a right or pyloric portion or antrum by a plane passing through the incisura angularis and the left limit of the opposed dilatation (pyloric vestibule) on the greater curvature. The left portion of the body (corpus ventriculi) is known as the fundus, while that which is adjacent to the cardiac orifice is known as the cardiac antrum. The pyloric antrum is divided into a right part, the pyloric canal, and a left, the pyloric vestibule, by a plane passing through the sulcus intermedius at right angles to the axis of this portion (Fig. 1010). The size of the stomach varies considerably in diflFerent subjects. WTien mod- erately distended its greatest length, from the top of the fundus to the lowest part of the greater curvature, is from ten to twelve inches and its diameter at the widest part from four to five inches. The distance between the two orifices, when the stomach is in situ, is three to four inches, and the measurement from the anterior to the posterior wall three and one-half inches. Its weight, according to Clendinning, is about four ounces and a half, and its capacity in the adult male is five to eight pints. The stomach of a newborn child holds about one ounce. Alterations in Position, — There is no organ in the body the position and connections of which present such frequent aUerations as the stomach. When empty, it lies at the back part of the abdomen, some distance from the ventral abdominal wall, and is in the left hypochondriac region and the left portion of the epigastric region. Its fundus is directed upward and backward toward the Diaphragm. The long axis of the viscus is quite oblique. Its pyloric end is directed toward the right, covered in front by the left lobe of the liver, and on a level with the first lumbar vertebra. When empty and contracted the stomach assumes a more or less cyhndrical form, especially noticeable at its pyloric end, and resembles a piece of thick-walled intestine. When the stomach is distended, its surfaces become convex and the shape becomes pyriform, its long axis being downward, forward, and to the right. The greater curvature is elevated and carried forward, so that the anterior surface is turned more or less upward and the posterior surface downward, and the stomach is brought well against the anterior wall of the abdomen. Its fundus expands and rises considerably above the level of the cardiac orifice; in doing this the Diaplu'agm is forced upward, contracting the cavity of the thorax; hence the dyspnea complained of as inspiration is impeded. The apex of the heart is also tilted tipward; hence the oppression in this region and the palpitation experienced in extreme distention of the stomach. The left lobe of the liver is pushed toward the right. When the stomach becomes distended the change in the position of the pylorus may be considerable; it is shifted to the right as much as two inches from the median line, and lies under cover of the liver, near the neck of the gall- bladder. In consequence of the distention of the stomach the pyloric antrum bulges in front of the pylorus, concealing it from view, and causing it to undergo a rotation, so that its orifice is directed backward. When the stomach is greatly distended its lower border may enter the um- bilical and the left lumbar regions. During inspiration the stomach, is displaced downw-ard by the descent of the Diaphragm, and it is elevated by the pressure of the abdominal muscles during expiration. Pressure from witlwut, as from tight lacing, pushes the stomach down toward the pelvis. In fact, in the female, because of tight lacing, the body of the stomach may be to the left THE STOMA CH vm side of the vertebral column and nearly vertical in direction, the pyloric portion being sharply angled upward toward the pylorus, which lies underneath the liver.. Besides the anfjulation, the stomach may have a median constriction, and there may even be an hour-fjlaxn sttnitacli. In disease the position and connection of the stomach may be greatly changed, from the accumu- lation of fluid in the thoracic cavity or abdomen, or from alteration in size of any of the surround- ing viscera. Variations According to Age. — In an early period of development the stomach is vertical, and in the newborn child it is more vertical than later on in life, as owing to the large size of the liver it is pushed over more to the left side of the abdomen, and the whole of the anterior surface is covered by the left lobe of this organ. Interior of the Stomach. — When examined after death, the stomach i.s usually fixed at some temporary stage .of the digestive process. A common form is that shown in Fig. 1011. If the viscus be laid open by a section through the plane of its two curvatures, it is seen to consist of the two segments aheady described — viz., a large globular portion to the left, comprising the body and fundus, and the tubular pyloric portion to the right. The mucous membrane lining the interior is soft and velvety, red or reddish brown in the body and fundus, and of a pinkish tinge at the pyloric end. It is thrown into numerous folds or nigae, chiefly longi- tudinal in direction and most marked toward the pyloric end and along the greater curvature. To the left of the cardiac orifice is the incisura cardiaca; the projec- tion of this notch into the cavity of the stomach increases as the organ distends, and has been supposed to act as a valve preventing regurgitation into the oesopha- gus. In the pyloric portion are seen (a) the elevation corresponding to the incisura angularis, and (6) the circular projection from the duodenopyloric con- striction which forms the pyloric valve. The separation of the pyloric vestibule from the pyloric canal is scarcely indicated, but the manner in which the pylorus is invaginated into the duodenum is evident. The pyloric valve (vahnda jpylori) (Fig. 1013) is formed by a reduplication of the mucous membrane of the stomach, containing numerous circular fibres, which are aggregated into a thick circular ring, the Pyloric Sphincter (m. sphincter pylori) ; some of the deeper longitudinal fibres turn in and interlace with the circular fibres Pijloi as Pylonc canal. Fig. 1011. — Interior of the stomach. of the valve. The pylorus is normally kept closed by the action of this Sphincter muscle. During the early stage of digestion it remains closed, but after a time opens now and then, this relaxation becoming more frequent and the period of patency more prolonged as digestion advances. 1274 THE ORGANS OF DIGESTION Structure. — The wall of the stomach consists of four coats — serous, muscular, submucous, and mucous, together with vessels and nerves. The serous coat {tunica serosa) is derived from the peritoneum, and covers the entire surface of the organ, excepting along the greater and lesser curvatures, at the points of attachment of the greater and lesser omenta; here the two layers of peritoneum leave a small triangular space uncovered by peritoneum along which the nutrient vessels and nerves pass. On the posterior surface of the stomach, close to the cardiac orifice, there is also a small triangular ai'ea uncovered by peritoneum, where the organ is in contact with the under surface of the Diaphragm. The muscular coat {tunica viuscularis) (Figs. 1014 and 1015) is situated immediately beneath the serous covering, to which it is closely connected. It consists of three sets of smooth muscle tissue — longitudinal, circular, and oblique, from without inward, in the order named. The longitudinal fibres {stratum, longitudinale) are the most superficial, and are arranged in two sets. The first set consists of fibres continuous with the longitudinal fibres of the oesophagus; they radiate in a stellate manner from the cardiac orifice and are practically all lost before the pyloric portion is reached. The second set commences on the body of the stomach and passes to the right, its fibres becoming more closely collected as they approach the pylorus. Some of the more superficial fibres of this set pass on to the duodenum, but the deeper fibres dip in and interlace with ,the circular fibres of the pyloric valve Sphincter. The bundles of longitudinal lagrami Fig. 1012, view of the coats of the stom- ach, duodenum, and pylorus. The ridge is the pyloric valve, (Allan Thomson.) Fig. 1013. — The superficial muscular layer of the stomach. s'ed from above and in front. (Spalteholz.) muscle fibre on the upper and lower surfaces of the pylorus are particularly firm and distinct, and are called the pyloric ligaments {!ir/amcnta pylori). The circular fibres {stratum circulare) form a uniform layer throughout the whole extent of the stomach internal to the longitudinal fibres. They begin as tiny rings at the left extremity of THE STOMACH 1275 the fundus and pass over into larger and larger rings to encircle the entire organ. At the pylorus they are most abundant, and are aggregated into a circular ring or Sphincter, which projects into the cavity, and forms, with the fold of mucous membrane covering its surface, the pyloric valve (Fig. 1012). The circular fibre stratum is continuous with the circular layer of the oesophagus, the fibres being interlaced at the transition. The oblique fibres ( jibrae obliquae) arise at the left side of the cardia from the circular fibres of the cesophagus. The fibres pass down in the anterior and posterior walls, and almost reach the pylorus. Certain oblique muscular fibres encircle the fundus of the stomach in a series of rings. The submucous coat {tela submucosa) consist of loose areolar tissue, connecting the mucous and muscular coats. It supports the large bloodvessels previous to their distribution to the mucous membrane; hence it is sometimes called the vascular coat. Fig. lOH. — 1'he middle and deep muscular layer of the stomach, viewed from above and in front. (Spalteholz.) The mucous membrane (tunica mucosa) (Figs. 1015, 1016, 1017, and lOlS) is thick, its surface smooth, soft, and velvety. In the fresh state it is of a pinkish tinge at the pyloric end, and of a red or reddish-brown color over the rest of the surface. In infancy it is of a brighter hue, the vascular redness being more marked. It is thin at the cardiac extremity, but thicker toward the pylorus. During the contracted state of the organ it is thrown into numerous folds or rugae [plicae mucosae) (Figs. 1015 and 1016), which for the most part have a longitudinal du-ection, and are most marked toward the pyloric end of the stomach and along the greater curvature. These folds consist of mucous and submucous coats, and are entirely obliterated when the organ becomes fully distended. Structure of the Mucous Membrane. — When examined with a lens the inner surface of the mucous membrane presents a peculiiir lujncycomb appearance, from being covered with small shallow depressions, the gastric crypts or pits (foirokie gastricae) (Figs. 1015 and lOlS) of a poly- gonal or hexagonal form, \\hich vary from [J;] to ^hi of an inch in diameter, and are separated by slightly elevated ridges (plicae villosae). The pits in the cardiac and fundal portions of the stomach extend tlirough about one-sixth the thickness of the mucosa, while in the pj'loric end they extend through about one-half the mucous coat. In the bottom of the crypts are seen three to seven orifices of minute tubes, the gastric glands (Fig. 1018), which are placed per- 1276 THE ORGANS OF DIGESTION pendicularly side by side throughout the entire substance of the mucous membrane. The sur- face of the mucous membrane of the stomach is covered by a single layer of columnar epithe- lium and a few goblet cells; it lines the crypts, and also for a certain distance the mouths of the gastric glands; in the glands the character of the epithelium changes. This epithelium com- Gaatric Areas. Bugte. Fig. 1015. — Mucous membri of the atoraaou, from the pars pylo (Spalteholz.) viewed from the surface. X 5. Midges beticecn the alveoli. Gastric alveoli. Fig. 1016. — Mucous membrane of etomach, from the pars pylorica, \'iei from the surface. X 16. (Spalteholz.) mences very abruptly at the cardiac orifice, where the cell.i suddenly change in character from the stratified epithelium of the n'.sophagus. The Gastric Glands. — The gastric glands are of three kinds — the true gastric glands, the pyloric glands, and the cardiac glands. The true gastric glands (Fig. 1020) are called also the oxyntic glands, the fundus glands, and the peptic glands (iilu)uhdae gaslricae propriae). They are dis- tributed throughout the entire fundus and body, and may be found even at the pylorus. They are mainly of the simple tubular variety, and are lined by simple epithelial cells resting upon a delicate basement mem- brane supported by the tunica propria. The duct, or mouth, however, in these glands is shorter than in the other variety, sometimes not amounting to more than one-sixth of the whole length of the gland; it is lined throughout by columnar epithelium. ."Vt the point where the terminal tubes open into the mouth, and which is termed the neck, the epithelium alters, and consists of short columnar or polyhedral, granular cells, which almost fill the tube, so that the lumen becomes suddenly constricted, and is continued down as a very fine channel. They are known as the chief or the peptic or the central cells of the glands, and furnish pepsin. Between these cells and the basement memlirane are found other darker granular-looking cells, studded throughout the tubes at intervals, and giving it a beaded or varicose appearance. The fun- dus is the blind extremity of the gland, and here the chief cells predominate. These are known as the acid, parietal, or oxyntic cells. Some of the parietal THE STOMA CH 1277 cells empty directly into the lumen of the crland by secretory capillaries; others empty by a channel which divides into secretory capillaries. The parietal cells secrete the acid of the ^ lA. S^-^ --v-^ ^'kU V. w.. TWO MAMMILL/E L Figs. 1017 and 1018.— The mucous membrane of the stomach. Fig. 1017. Natural size. Fig. 1018. Magnified 25 diameters. In Fig. 1017 the rugae and the mamillated surfaces are shown In Fig 1018 the glind mouth'^ (foveolae gastricae), with the gland tubes leading from some of them, and the r dges separat ng the n ou h (p ae villosae) are seen. (Cunningham.) Fig. 1019.- Pyloric gland. Fig. 1020.— Peptic gastric gland. gastric juice. Between the glands the tunica propria consists of fibroelastic connective-tissue framework with lymphoid tissue and a rich capillary plexus. In places this latter tissue, especially in early life, is collected into little masses, which to a certain extent resemble the 1278 THE ORGANS OF DIGESTION PLEXUS BENEATH THE EPITHELIUM solitary nodules of the intestine, and are by some termed the lenticular follicles of the stom- ach. They are not, however, so distinctly circumscribed as the solitary follicles. The pyloric glands {glandulae pyloricae) (Fig. 1019) are the branched tubular glands, and secrete mucus and pepsin. They are placed most plentifullj^ about the pylorus, but between the fundus and pylorus, in the region known as the transitional or intermediate zone, both true gastric glands and pyloric glands are found. Each pyloric gland consists of two or three short tubes opening into a com- mon mouth or duct, the external orifice of which is situated at the bottom of a ervpt. The tubes are wavy, and are of about equal length with the duct. The tubes and duct are lined throughout with simple epithelium, the duct being lined by columnar cells continuous with the epithelium lining the surface of the mucous membrane of the stomach, the tubes with tall, broad, and pale-staining cells, which are finely granular. The pyloric glands branch more frequently, are more curved in direction, and open into deeper foveolae than the true gastric glands (Szymono- wicz). They contain only chief or peptic cells and do not possess parietal cells. These glands, at times, extend into the submucous coat. The cardiac glands are found about the oeso- phageal orifice. They resemble the glands of the oesophagus and are mucous in character. External to the tunica propria of the mucous membrane, and between it and the submucous coat, is a thin stratum of involuntary muscle tis- sue {muscularw mucosae), which in some parts consists only of a single longitudinal layer; in others, of two layers, an irmer circular, and an outer longitudinal. Vessels and Nerves. — The arteries supplying the stomach are the gastric, the pyloric. and the right gastroepiploic branch of the gastroduodenal, the left gastroepiploic and vasa brevia from the splenic. The gastric artery passes to the lesser curvature just below the cardia It gives off the oesophageal branch, and passes from left to right along the lesser curvature of the stomach beneath the peritoneum between the two layers of the lesser omentum and upon the wall of the stomach. It may in this course be a single vessel, or may divide into two branches. PLEXUS OF BLOODVESSELS IN SUBMUCOUS TISSUE Fig. 1021. — Terminations of the bloodvessels in the mucous membrane of the stomach. (Poirier and Charpy.) (Poirier and Charpy.) which run along each side of the lesser curvature (Fig. 1022). If there is a single artery, it gives off six or seven descending branches to the anterior wall and about the same number to the pos- terior wall of the stomach. It also gives branches to the lesser omentum. If two vascular arches form, one gives branches to the anterior wall of the stomach, the other to the posterior THE STOMACH 1279 wall, and both to the lesser omentum. The termination of the gastric anastomoses with the pyloric liranch or two rami of the pyloric branch of the hepatic artery. From each arch si.x or seven descending branches come off to the anterior and posterior walls of the stomach. The gastroduodenal artery is given off by the hepatic. From the gastroduodenal comes the right gMstrucpiploic. The left gastroepiploic comes from the splenic. The right gastroepiploic artery passes from right to left in the gastrocolic omentum below the greater curvature of the stomach. The left gastroepiploic artery iiasses forward in the gastrosplenic omentum to below the greater curvature of tlic .stomach, and pas.ses from left to right along that curvature in the greater omentum, and joins the right gastroepiploic artery. The gastroepiploic arteries are not upon but are distinctly below the stomach wall. From them numerous gastric branches are sent to the anterior and posterior walls of the stomach, and they anastomose with branches of the gastric and pyloric. Vasa brevia, four or five in number, arise from the splenic, pass forward in the gastrosplenic omentum, and supply the fundus. The arteries of the stomach lie first beneath the peritoneum, but soon enter the muscular coat, supply it, pierce it, ramify in the submucous coat, and are finally distributed to the mucous membrane. The arrangement of the vessels in the mucous membrane is somewhat peculiar (Fig. 1021). The arteries break up at the base of the gastric tubules into a plexus of fine capillaries which run upward between the tubules, anastomosing with each other, and ending in a plexus of larger capillaries, which surround the mouths of the tubes and also form hexagonal meshes around the crypts. The capillarv network about the glands gives origin to the veins. The various small veins unite and form a plexus in the submucous tissue (Fig. 1021). From this plexus come branches which pass through the muscular coat and terminate in the right gastroepiploic branch of the superior mesenteric, the left gastroepiploic branch of the splenic, the veins to the siilcnic which correspond to the vasa brevia arteries, and the gastric or coronary branch of the portal. The lymphatics (Figs. 570 and .571) arise in the mucous membrane and terminate in a net- work in the submucous tissue. From this network trunks arise which perforate the muscular coat in the regions of the curvatures and terminate in the seromuscular collecting trunks. The details of the lymphatic drainage of the stomach are given on page 792. The nerves of the stomach come from the right and left vagi and from the solar plexus of the sympathetic. The left \agus ])asses to the front of the stomach, and the right nerve passes to the back, and thev unite with the fibres of the sympathetic. The fibers thus formed are mostly amvelinic. Thev form Auerbach's plexus in the muscular coat between the circular and longi- tudinal fibres and Meissner's plexus in the submucous coat, the latter plexus being formed by fibres from the former. Auerbach's ])lexus supplies the muscular coat of the stomach, while fibres from Meissner's plexus ramify in the submucous coat and terminate in the muscularis mucosae and the mucous membrane, branches passing to the gastric glands and to just beneath the epithehum. (See nerve supply of small intestine, p. 1295). Relations of the Stomach. — The antero-superior surface is in relation with the left and quadrate lobes of the liver, the ventral abdominal parietes, and the costal portion of the Diaphragm. The postero-inferior surface is in relation with the lumbar portion of the Dia- phragm, the pancreas, and the transverse mesocolon, while the fundus may come into contact with the left kidney and suprarenal gland, the spleen, and splenic fiexure of the colon. The lesser curvature is directed toward the transverse fissure of the liver, while the greater curvature may be in contact with the transverse colon. Movements and Innervation of the Stomach, Movements. — It has apparently been demonstrated that the stomach "consists of two parts physiologically distinct."' The cardiac portion of the stomach is a food reservoir in which salivary digestion continues; the pyloric portion is the seat of active gastric digestion. Cannon affirms that there are no peristaltic waves in the cardiac portion, but that as the food passes from the pyloric portion into the intestines, tonic contraction of the muscles of the fundus squeezes the contents of the pyloric portion. Moritz, Levan, and Cannon assert that muscular activity is chiefly manifested in the pyloric portion. In this portion during digestion there is a succes- sion of peristaltic waves, which waves in the human being pass at the rate of three per minute (Moritz). Cannon points out that the efficiency of peristalsis in mixing the food depends upon the contraction of the pyloric sphincter. So long as the sphincter holds, each constric- tion ring coursing from the middle to the end of the stomach presses the food into a blind pouch; the tood, unable to escape through the pyloric opening, has as its only outlet the opening in the advancing ring. This is an admirable device for bringing the food under the influence of the glandular secretions of the pyloric region. For, as a constriction occurs, the secreting sur- face enclosed by the narrowed muscular ring is pressed close around the food within the ring. As the constriction advances it continually presses inward fresh glandular surfaces, and further- 1 Walter B. Cannon, . Medical News, May 20, 1905. 1280 THE ORGANS OF DIGESTION more, as the constriction advances, a thin stream of food is continuously forced back through the ring and thus past the moutlis of the glands. The old view that the pyloric sphincter only opens after several hours' continuance of the process of digestion, and that then the stomach empties at once, is incorrect. It is emptied in small amounts, which escape at frequent intervals because of the intermittent opening of the pylorus. When the pylorus is open a wave of peri- stalsis forces some of the material from the stomach into the duodenum (Cannon). Cannon is of the opinion that the pyloric sphincter is caused to relax by the presence of free hvdrochloric acid in the pyloric portion of the stomach. When the pylorus is open acid chyme passes into the duodenum, and acid in the duodenum causes the pylorus to close. The acid in the duodenum causes a flow of alkaline pancreatic juice and the acid is neutralized. "As the neutralizing proceeds, the stimulus closing the pylorus is weakened until the acid in the stomach again opens the sphincter."' Innervation. — The stomach, as previously shown, has nerve plexuses in its walls and is connected to the cerebrospinal and sympathetic systems. It is probable that gastric peristalsis is due to a local reflex from Auerbach's plexus (Magnus), the local reflex being inaugurated by local stimulation, which stimulation, in the words of Bayliss and Starling, "produces excitation above and inhibition below the excited spot."^ Reversed peristalsis cannot occur if "the reflex mechanism is intact" (Cannon). Cannon in the previously quoted article states that cutting the vagi or splanchnic nerves does not destroy the reflex mechanism of the pylorus, but, never- theless, it is markedly affected by the central nerve system. Surface Form (see p. 1241). — The cardiac orifice corresponds to the articulation of the seventh left costal cartilage with the sternum. The pyloric orifice of the empty stomach is about an inch to the right of the midline in the transpyloric line. According to Braune, when the stomach is distended, the pylorus moves considerably to the right, sometimes as much as three inches. The fundus of the stomach reaches, on the left side, as high as the level of the sixth costal car- tilatre of the left side, being a little below and behind the apex of the heart. The portion of the distended stomach which is in contact with the abdominal walls, and is therefore accessible for opening in the operations of gastrotomy and gastrostomy, is represented by a triangular space, the base of which is formed by a line drawn from the tip of the tenth costal cartilage on the left side to the tip of the ninth costal cartilage on the right, and the sides by two lines drawn from the extremity of the eighth costal cartilage on the left side to the end of the base line. What> is commonly termed the semilunar space of Traube is that portion of the stomach which is not covered by neighboring viscera. It is bounded above by the left lobe of the liver and the inferior margin of the left lung, posteriorly and to the left by the spleen; on percussion, this area is nor- mally tympanitic. Applied Anatomy. — Operations on the stomach are frequently performed, ulcers are excised, malignant growths are removed with the associated lymphatic involvement, the entire stomach may be removed for cancer, etc. By "gastrotomy" is meant an incision into the stomach for the removal of a foreign body, or the arrest of hemorrhage, or for exploration, the opening being immediately afterward closed — in contradistinction to "gastrostomy," the making of a more or less permanent fistulous opening. Gastrotomy is probably best performed by an incision in the linea alba, especially if the foreign body is large. The cut may reach from the ensiform car- tilage to the umbilicus. The incision may be made over the foreign body itself, where this can be felt, or by one of the incisions for gastrostomy, to be mentioned shortly. The peritoneal cavity is opened, and the point at which the stomach is to be incised decided upon. This portion is then brought out of the abdominal wound and sponges carefully packed around. The stomach is now opened by a transverse incision and the foreign body extracted. The wound in the stomach is then "closed by Lembert sutures — i. e., by sutures passed through the peritoneal, muscular, and submucous coats in such a way that the peritoneal surfaces on each side of the wound are brought into apposition. Gastrostomy was formerly done in two stages by the direct method. The first stage consisted in opening the abdomen, drawdng up the stomach into tht external wound, and fixing it there; and the second stage, performed from two to four days afterward, consisted in opening the stomach. The operation is now done by a valvular method. The following plan is known as the Ssabanejew-Frank operation. An incision is commenced opposite the eighth intercostal space, two inches to the left of the median line, and carried down- ward for three inches. By this incision the fibres of the Rectus muscle are exposed and these are separated from one another in the same line. The posterior layer of the sheath, the trans- versalis fascia, and the peritoneum are then divided, and the peritoneal cavity is opened. In- stead of the above incision, the curved incision of Fenger can be made at the margin of the left costal cartilages. The anterior wall of the stomach is now seized and drawn out of the wound and a silk suture passed through its submucous, muscular, and serous coats at the point selected for opening the viscus. This is held by an assistant so that a long conical diverticulum of the stomach protrudes from the external wound, and the parietal peritoneum and the posterior layer of the sheath of the Rectus are sutured to the base of the cone. A second incision is made through » Walter B. Cannon, Medical News, May 20, 1905. ^ Ibid. THE SMALL INTESTINE 1281 the skin, over the margin of the costal cartilage, above and a little to the outer side of the first incision. If Fenger's incision were used, the second incision should be above the margin of the cartilages. With a pair of dressing forceps a track is made under the skin through the subcu- taneous tissue from the one opening to the other and the diverticulum of the stomach is drawn along this track bv means of this suture inserted into it; so that its apex appears at the second opening. A small perforation is now made into the stomach through this protruding ape.x and its margin carefully and accurately sutured to the margin of the external wound. The remainder of this incision and the whole of the first incision are then closed in the ordinary way and the wound dressed. In cases of gastric ulcer, perforation sometimes takes place, and this was formerly rewarded as an almost fatal complication. In the present day, by opening the abdomen and closing the perforation, which is generally situated on the anterior surface of the stomach, a consider- able percentage of cases are cured, provided the operation is undertaken within twelve to fifteen hours after the perforation has taken place. The opening is best closed by bringing the peri- toneal surfaces on either side into apposition by means of Lembert sutures. Pylorectomy or excision of the pylorus is performed, particularly for early cancer, but is also done for cicatricial stricture and for ulcer. The mortality after operation for cancer was, until recently, very great, but of late years it has been notably reduced, though it is still much higher than that which follows operations for any non-malignant condition. In operating for cancer, bear in mind Cuneo's study of the lymphatics (p. 792). These observations indicate that the fundus and two-thirds of the greater curvature are free from lymphatic involvement in pyloric cancer.' In every operable case of cancer of the pylorus the entire lesser curvature must be removed up to the gastric artery (Mikulicz's point), and the greater curvature must be removed to the left of the involved lymph nodes (Hartmann's rule). Gastroenterostomy is an operation which establishes a fistulous communication between the stomach and jejunum. The operation is often called gastrojejunostomy. The opening may be made upon either the anterior or the posterior wall of the stomach, between the cardia and the seat of pyloric disease. The operation is employed for stricture of the pylorus (benign or malig- nant), and occasionally for ulcer of the stomach. Hypertrophy and spasm of the circumferential muscular coat of the pylorus coming on during the first few weeks of life, and somewhat erroneously described as congenital hyper- trophic stenosis of the pylorus, is a rare but serious disorder of infancy. It is characterized by abdominal pains and obstinate vomiting coming on after food has been given, and gastric peristalsis can be observed by inspection of the child's epigastrium after it has been fed and before vomiting has occurred. Progressive wasting for want of nourishment and death from exhaustion tend to ensue. Treatment should be by washing out the stomach, and the admin- istration at frequent intervals of small quantities of easily digested food. Surgical interference — pyloroplasty or pylorectomy — entailing a severe operation, gives less favorable result. Total gastrectomy is the removal of the entire stomach. It is only used for cancer. It was first performed by Conner, of Cincinnati. The first successful operation was done by Schlatter, of Zurich, in 1898. A number of successes have been reported. It is a justifiable operation onlv in a case in which almost the entire stomach is cancerous, in which the viscus is movable, in which there are no secondary deposits, and no irremovable diseased lymph nodes. Gastrogastrostomy is an operation employed in hour-glass stomach. In this operation an anastomosis is made between the pyloric and cardiac ends of the stomach. Gastroplication is the operation of suturing the stomach wall into folds or reefs, in order to lessen its size. It is employed in some cases of gastric dilatation. Gastroptosis is a condition in which the stomach is displaced downward. In some of these cases the greater curvature almost reaches the level of the symphysis pubis, and the lesser curva- ture is midway between the umbilicus and ensiform cartilage. The condition is usually associated with enteroptosis and movable kidney (nephroptosis). In this condition the gastrohepatic omen- tum is pulled upon and lengthened. The best operation for gastroptosis was devised by Beyea. He applies sutures so as to make folds in and thus shorten the stretched omentum. Thus' the stomach is elevated to its proper position, and its mobility is not lessened, as it is in other opera- tions which suture it to the abdominal wall. THE SMALL INTESTINE (INTESTINUM TENUE). The small intestine is a convoluted tube, extending from the pylorus to the ileocecal valve, where it terminates in the large intestine. It is about twenty feet ' Willium J. Mayo, .\nnals of Surgery, March, 1904. 81 1282 THE ORGANS OF DIGESTION (6 m.) in length,' and gradually diminishes in size from its commencement to its termination. It is contained in the central and lower part of the abdominal cavity, and is surrounded above and at the sides by the large intestine; a portion of it extends below the brim of the pelvis and lies in front of the rectum. It is in relation, in front, with the great omentum and abdominal parietes, and the greater part of it is connected to the vertebral column by a fold of peritoneum, the mesentery (p. 1263). The small intestine is divisible into three portions — the duodenum, the jejunum, and the ileum. The Duodenum (Figs. 1023, 1030). The duodenum has received its name from being about equal in length to the breadth of twelve fingers (ten inches). It is the shortest, the widest, and the most fixed part of the small intestine, and has no mesentery, being only partially in- vested by peritoneum. Somewhat more than the upper half of the duodenum is placed in the epigastric region; the remainder is in the umbilical region. Its course prevents a remarkable curve, somewhat of the shape of an incomplete circle, so that its termination is not far removed from its beginning. In the adult the course of the duodenum is as follows: Commencing at the pylorus it passes backward, upward, and to the right, beneath the quadrate lobe of the liver to the neck of the gall-bladder, varying slightly in direction according to the degree of distention of the stomach; it then takes a sharp curve and descends along the right margin of the head of the pancreas, for a variable distance, gener- ally to the level of the upper border of the body of the fourth lumbar vertebra. It now takes a second bend, and passes from right to left across the front of the vertebral column, having a slight inclination upward; and to the left side of the vertebral column it ascends for about an inch, and then terminates opposite the second lumbar vertebra in the jejunum. As it unites with the jejunum it turns abruptly forward, forming the duodenojejimal flexure. From the above descrip- tion it will be seen that the duodenum may be divided into four portions — superior, descending, transverse, and ascending. The first or superior portion {pars superior) (Figs. 1023 and 1024) is about two inches (5 cm.) in length. Beginning at the pylorus, it ends at the level of the neck of the gall-bladder. It is the most movable of the four portions. It is almost completely covered by peritoneum derived from the two layers of the lesser omen- tum, but a small part of its posterior surface near the neck of the gall-bladder and the inferior vena cava is uncovered (Fig. 1024). It is in such close relation with the gall-bladder that it is usually found to be stained by bile after death, especially on its anterior surface. It is in relation above and in front with the quadrate lobe of the liver, lying in a slight concavity, the impressio duodenalis, and the gall-bladder; behind, with the gastroduodenal artery, the common bile duct, and the portal vein; and below, with the head of the pancreas. The second or descending portion (pars descendens) (Figs. 1023 and 1025) is between three and four inches (7.5 to 10 cm.) in length, and extends from the neck of the gall-bladder on a level with the first lumbar vertebra along the right side of the vertebral column as low as the body of the fourth lumbar vertebra. It is crossed in its middle third by the transverse colon, the posterior surface of which is uncovered by peritoneum and is connected to the duodenum by a small quantity of connective tissue. The portions of the descending part of the duodenum above and below this interspace are named the supracolic and infracolic portions, and are * Treves states that m one hundred cases the average length of the small intestine in the adult male was 22 feet 6 inches, and in the adult female 23 feet 4 inches; but that it varies very much, the extremes in the male being 31 feet 10 inches in one case and 15 feet 6 inches in another, a difference of over 15 feet. He states that he has convinced himself that the length of the bowel is independent, in the adult, of age, height, and weight. THE DUODENUM 1283 covered in front by peritoneum (Fig. 1025). Tlie infracolic part is covered by the right leaf of the mesentery. Posteriorly the descending portion of the duodenum Trihntary to Hepatic artery, portal vein, and bile duct. Supra leual oupiiic! tira of Diaphragm. Gast} ic a}tei y Fig. 1023. — Relations of duodenum, pancreas, and spleen. (From a cast by Professor Birmingham.') The broken line represents the line of attachment of the transverse ] is not covered by peritoneum. It is in relation, in front, with the transverse colon, and above this with the right lobe of the liver, where it lies in the impressio duo- ^ In the subject from which the east was taken the left kidney i 1284 THE ORGANS OF DIGESTION denalis for the second part of the duodenum ; behind, with the inner part of the right kidney, to which it is connected by loose areolar tissue, the right renal vessels, and the inferior vena cava; at its inner side is the head of the pancreas and the common bile duct; to its outer side is the hepatic flexure of the colon. The common bile duct passes downward behind the first portion of the duodenum, descends to the Lesser omentum Hepatic Artery Portal Vein /■' ^ .'.-'Greater' t --'.-• Sac omentum Transverse Mesocolon E. A. S. Fig. 1024. — Diagram of cross-section of the first part of tile duodenum, to sliow its peritoneal rela- tions. (Gerrisli.) Fig. 1025. — Diagram of cross-section of the second part of the duodenum, to show its peritoneal rela- tions. (Gerrish.) inner side of the second portion, is joined by the pancreatic duct, and the two to- gether perforate the inner side of this portion of the intestine obliquely, and empty into the duodenum by a common opening or by two openings at the summit of a papilla, some three and a half or four inches (9 to 10 cm.) beyond the pylorus. .^J^il:::;--. Fig. 1026. — Diagram of the third jjart of the duodenum, to show its peritoneal relations. (Ger- rish.) Fig. 1027. — Diagram of the fourth part of the duode- num, to show its peritoneal relations. (Gerrish.) ' The relations of the second part of the duodenum to the right kidney present con- siderable variations. The third, preaortic, or transverse portion {pars horizonialis inferior) (Figs. 1023 and 1026) is from two to three inches in length. It commences at the right side of the upper border of the fourth lumbar vertebra and passes from right THE DUODENUM 1285 to left, with a slight indination upward, in front of the great vessels and crura of the Diaphragm, and ends in the fourth portion in front of or just to the left of the abdominal aorta. It is crossed by the superior mesenteric vessels and the mesentery. Its ventral surface is co\'ered by peritoneum, except near the middle line, where it is crossed by the superior mesenteric vessels (Fig. 1026). Its posterior surface rests upon the aorta, the inferior vena cava, and the crura of the Dia- phragm. Its upper surface is in relation with the head of the pancreas. The fourth or ascending portion of the duodenum (pars ascendens) (Figs. 1023 and 1027) is about an inch (2.5 cm.) long. It ascends on the left side of the vertebral column and aorta, as far as the level of the upper border of the second lumbar vertebra, where it turns abruptly forward to become the jejunum, forming the duodenojejunal flexure {flexura diiodenojejunalis) (Fig. 1028). It lies in front of the left Psoas muscle and left renal vessels, and is covered in front and partly at the sides by peritoneum, continuous with the left portion of the mesentery (Fig. 1027). The left side of the termination of the ascending portion is also covered by peritoneum, and in this region some of the duodenal fossae are found (p. 1265). DIAPHRAGM CCELIAC AXIS GANGLION OF CCELIAC PLEXUS SUPERIOR MESEA TERIC ARTERY SUSPENSORY MUSCLE OF DUODENUM CELLULAR MEMBRANE 3NNECTINGTHE PARTS 'FTHE DUODENALRING BEHIND THE PANCREAS Fia. 1028. — Suspensory muscle of the duodenu ■ muscle of Treitz, (Po and Charpy.) The first part of the duodenum, as stated above, is somewhat movable, but the rest is practically fixed and is bound down to neighboring viscera and the posterior abdominal wall by the peritoneum. In addition to this, the fourth part of the duodenum and the duodenojejunal flexure is further bound down and fixed by a structure called the Suspensory muscle of the duodenum or the suspensory ligament of Treitz {m. suspensorius duoden i) (Fig. 1 028) . This structui-e com niences in the connective tissue around the CQ?liac axis and left crus of the Diaphragm, and passes downward to be inserted into the superior border of the duodenojejunal curve and a part of the ascending duodenum, and from this it is continued into the mesentery. It possesses, according to Treitz, some few nonstriated muscle fibres mixed with the fibrous tissue, of which it is principally made up. It is of little importance as a muscle, but acts as a suspensory ligament. 1286 THE ORGANS OF DIGESTION Interior of the Duodenum (Fig. 1029).— The proximal part of the duodenum is comparatively smooth. Valvulae conniventes begin to appear in the distal half COMMON BILE DUCT Fig. 1029.— The interior of the duodenum. (Spalteholz.) Gastric artery Hepatic fiuct-^rr^—^^^ Cystic duct ^°- ^ ^^^- Hepatic artery- liigfd sjiprarenal, gland Pyloric orifice- HigfU gastro-epiploLC artery ' ""'¥^ ' ' '/111 ni^B' I K ' .l""" '" ' Spermatic veisels ^Spermatic vessels Ivjerior viesenteric artery Via. 1030.— The duodenum, its four parts marked a, 6, c, d. The Hver is hfted up; the greater part of the stomach is removed, broken hues indicating its former position. (Testut.) THE JEJUNUM AND ILEUM 1287 of the first portion, being at first trivial elevations irregularly placed. They become higher, regular, and more numerous farther on, and near the termination of the duodenum are strongly marked and closely placed transverse or spiral folds (Fig. 1029 and p. 1289). In the descending portion (Fig. 1029), to the side and rear, is a longitudinal fold {plica longitvdinalis duodeni), which is formed by the projection of the bile duct and pancreatic duct beneath the mucous membrane. The caruncula major of Santorini or the bile papilla is a projection in the lower part of the longitudinal fold. At the summit of this papilla the bile duct and pan- creatic duct empty into the duodenum. One inch above and half an inch or more in front of the bile papilla is a much smaller papilla, the caruncula minor of Santorini {papilla duodeni [Santoriai'\), on the summit of which the acces- sory pancreatic duct of Santorini opens when present. ANASTOMOSIS OF THE TWO PANCREATICO- DUODENAL ARTERIES Fig. 1031.' — The bloodvessels of the duodenum. (Poirier and Charpy.) Structure of the Duodenum.— (See Structure of the Small Intestine, p. 1289.) Vessels and Nerves. — The arteries (Fig. 1031) supplying the duodenum are the pyloric and pancreaticoduodenal branches of the hepatic, and the inferior pancreaticoduodenal branch of the superior mesenteric. The veins (Fig. 1031) correspond to the arteries. The superior duodenal vein passes into the superior mesenteric, and the inferior duodenal vein passes into the portal. The Ijrmphatics pass along with the pancreaticoduodenal arteries, lymph nodes being present here and there, and terminate in the nodes about the coeliac axis. The nerves are derived from the solar plexus. Applied Anatomy. — Ulcer oftlie duodenum is more common than used to be thought. The portion of the duodenum between the pylorus and the bile papilla is about four inches in length, and is called by the Mayo brothers the vestibule of the duodtnum. Here the acid gastric juice enters and may produce an ulcer. The portion of the duodenum beldvv the vestibule is not liable to ulcer, because it is protected by the alkaline bile and pancreatic juice. A duodenal ulcer may perforate a large duodenal vessel and cause death from hemorrhage, or may perforate the intestine and produce septic peritonitis. A perforated ulcer is treated by laparotomy and closure of the perforation. Occasionally ulceration of the duodenal glands (Curling's ulcer) may occur in cases of extensive burns of the skin, but is not a very common complication. The Jejunum and Ileum (Figs. 972, 1003). The remainder of the small intestine from the termination of the duodenum comprises the jejunum and ileum ; the former name being given to the upper two- fifths and the latter to the remaining three-fifths. Spalteholz and others call all of the small intestine below the duodenum the intestinum tenue mesenterial. There 1288 THE ORGANS OF DIGESTION is no morphological line of distinction between the jejunum and ileum, and the division is arbitrary; but at the same time it must be noted that the character of the intestine gradually undergoes a change from the commencement of the jeju- num to the termination of the ileum, so that a portion of the bowel taken from these two situations would present characteristics and marked differences. These are briefly as follows : Jejunum. Ileum. Calibre larger (1| inches). smaller (1 inch). Wall thicker, heavier. thinner, lighter. Color red, more vascular. pale, less vascular. Valvulae conniventes . . prominent. smaller and fewer. Lymphoid tissue .... diffuse and few nodules. diffuse and manj' Peyer's patches. Villi numerous, short, and broad, fewer, slender, filiform. Intestinal glands .... more numerous. less numerous. The Jejunum (intestinum jejununi). — The jejunum is wider, its diameter being about one inch and a half (3.75 cm.), and is thicker, more vascular, and of a deeper color than the ileum, so that a given length weighs more. Its valvulae conniventes are large and thickly set and its villi are larger than in the ileum. The patches of Peyer are almost absent in the upper part of the jejunum, and in the lower part are less frequently found than in the ileum, and are smaller and tend to assume a circular form. Brunner's glands are only found in the duodenum. By grasping the jejunum between the finger and thumb the valvulae conniventes can be felt through the walls of the gut; these being absent in the lower part of the ileum, it is possible in this way to distinguish the upper from the lower part of the small intestine. The Ileum (intestinum ilewni). — The ileum is narrower, its diameter being one inch (2.5 cm.) or a little more, and its coats are thinner and less vascular than those of the jejunum. It possesses but few valvulae conniventes, and they are small and disappear entirely toward its lower end, but Peyer's patches are larger and more numerous. The jejunum for the most part occupies the umbilical and left iliac regions, while the ileum occupies chiefly the umbilical, hypogastric, right iliac, and pelvic regions, and terminates in the right iliac fossa by opening into the inner side of the commencement of the large intestine. The jejunum and ileum are attached to the posterior abdominal wall by an extensive fold of peritoneum, the mesentery (p. 1263), which allows the freest motion, so that each coil can accommodate itself to changes in form and position. The mesentery is fan-shaped; its posterior border or root, about six inches (15 cm.) in length, is attached to the posterior abdominal wall from the left side of the body of the second lumbar vertebra to the right iliac fossa, crossing successively the third part of the duodenum, the aorta, the inferior vena cava, the right ureter, and the right Psoas muscle (Fig. 1004). Its breadth between its vertebral and intestinal borders is about eight inches (20 cm.) from its commencement to its termination at the intestine, and it is greater in the middle than at either end of the bowel. According to Lockwood, it tends to increase in length as age advances. Between the two layers of which it is composed are contained bloodvessels, nerves, lacteals, and lymph nodes, together with a variable amount of fat. Meckel's Diverticulum (diverticulum ilei). — ^This consists of a pouch which pro- jects from the lower part of the ileum in about 2 per cent, of subjects. Its average position is about three feet from the ileocolic junction, and its average length about two inches. Its calibre is generally the same as that of the ileum. Sometimes only a portion of the proximal end has a lumen and the balance of the structure is impervious and shrunk to a fibrous cord. In other cases the diverticulum is actually of greater diameter than the intestine. It usually is at a right angle to the intestine, but may take almost any direction. Its blind extremity may be unattached or may be connected with the abdominal wall or with some other THE JEJUNUM AND ILEUM 1289 portion of the intestine by a fibrous .band. It represents the remains of the vitelline or omphalomesenteric duct, the duct of communication between the umbilical vesicle and the alimentary canal in early fetal life. Structure of the Small Intestine, Including the Duodenum. — The wall of the small intestine is composed of four coats — serous, muscular, subm.ucous, and mucous. The Serous Coat {tunica serosa). — The relation of the jieritoneum to the duodenum has been described. The remaining portion of the small intestine is surrounded by the peritoneum, excepting along its attached or mesenteric border; here a space is left for the vessels and nerves to pass to the gut. The muscular coat {tunica muscularis) consists of two layers of fibres, an external or longi- tudinal layer and an internal or circular layer. The longitudinal fibres {stratum longitudinale) are thinly scattered over the surface of the intestine, and are more distinct along its free border. The circular fibres {stratum circulare) form a thick, uniform layer; they siuround the cylinder of the intestine in the greater part of its circumference, and are composed of smooth muscle cells of considerable length. The muscular coat is thicker at the upper than at the lower part of the small intestine. The submucous coat (fcla subinucosa) connects the mucous and muscular layers. It con- sists of loose, filamentous areolar tissue, which forms a bed for the subdivisions of the nutrient vessels, previous to their distribution to the mucous surface, also for the lymph channels and nerves. The submucous coat contains lymph nodules {noduli lymphatici). Each nodule is pyramidal or pear-shaped, and the apex lies in the mucous membrane and forms a rounded elevation. These rounded elevations mark the solitary follicles and Peyer's patches (Figs. 1033 and 1040), and nowise resemble villi. In the duodenum the submucous tissue contains the duo- denal glands. The submucous tissue is prolonged into the valvulae conniventes. It contains bloodvessels, Meissner's plexus of nerves, and lymph vessels. The mucous membrane {tunica mucosa) is thick and highly vascular at the upper part of the small intestine, but somewhat paler and thinner below. It consists of the following structures: next the areolar or submucous coat is a layer of unstriped muscle tissue, the muscularis mucosae; internal to this is a quantity of retiform tissue, enclosing in its meshes lymph corpuscles (diffuse lymphoid tissue), and in which the bloodvessels and nerves ramify. Lastly, a basement mem- brane, supporting a single layer of columnar epithelial and goblet cells. They are granular in appearance, and each possesses a clear, oval nucleus. At their superficial or unattached end they present a distinct layer of highly refracting material, the cuticiilar border, marked by vertical striae. The mucous membrane presents for examination the following structures contained within it or belonging to it: Valvulae conniventes. Villi. Intestinal glands. Lymphatic nodules i „ ,•' •' ^ j r n- i ■' '^ I reyer s or agmmated follicles. The valvulae conniventes or the valves of Kerkring {plicae circulares [Kerkringi]) (Fig. 1032) are large folds or valvular flaps projecting into the lumen of the bowel. They are composed of reduplications or folds of the mucous membrane, the two layers of the fold being bound together by submucous tissue; they contain no muscular fibres, and, unlike the folds in the stomach, they are permanent, and are not obliterated when the intestine is distended. The majority ex- tend transversely across the cylinder of the intestine for about one-half or two-thirds of its circumference, but some form complete circles, and others have a spiral direction; the latter usually extend a little more than once around the bowel, but occasionally two or three times. The larger folds are about one-third of an inch in depth at the broadest part; but the greater number are of smaller size. The larger and smaller folds alternate with each other. They are not found at the commence- ment of the duodenum, but begin to appear about one or two inches beyond the pylorus. „ ,.„„ •,, , ■ .. *i. T ,1 1 p , 1 !• • Fig. 1032. — Valvulae conniventes in the upper part In the lower part of the descending portion, of the small intestine. (Poirier and Charpy.) 1290 THE ORGANS OF DIGESTION LA ,,R Of LONCJtUI^WAl, J^tPf^fQ COUS C0A4 Fig. 1033. — Mucosa of small intestine in ideal vertical cross-section. (Testut, after Heitzmann.) 'C tic la) In del Tunica pyopi a / Lpitheliiim Blood capilla les^ _^ ■> " ^o « ^ 3 "=" H """'*' "'S ««^' >v * 1 -^ ~"^ \ Je ts of smooth I iscle cell t al lymph 6pace .4f « i.% s^ ^1 -ki C '^li.rarl^, _-l Fig. 1034. — Longitudinal section through the end of a villus from the small intestine of a cat. X 450. THE JEJUNUM AND ILEUM 1291 below the point where the bile and pancreatic ducts enter the intestine, they are very large and closely approximated. In the transverse portion of the duodenum and upper half of the jejunum they are large and numerous; and from this point, down to the middle of the ileum, they diminish considerably in size. In the lower part of the ileum they almost entirely disappear; hence the comparative thinness of this portion of the intestine as compared with the duodenum and jeju- num. The valvulae conniventes retard the passage of the food along the intestine, and afford a more extensive surface for absorption. The villi (villi intestinalis) (Figs. 1034 and 10.35) are minute, highly vascular processes, never larger than 1 millimeter, projecting from the mucous membrane of the small intestine throughout its whole extent, and giving to its surface a velvety appearance. They spring from the valvulae conniventes and also from the sjiaces between them. In shape, according to Rauber, they are short and leaf-shaped in the duodenum, tongue-shaj)ed in the jejunum, and filiform in the ileum. They are largest and most numerous in the duodenum and jejunum, and become fewer and smaller in the ileum. Kraus estimates their number in the upper part of the small intestine at from fifty to ninety in a sc[uare line; and in the lower part from forty to seventy, the total number for the whole length of the intestine being about four millions. F^ymph trunk. CapUiaries. Lymphatic plexus. testine. (Cadiat.) Structure of the Villi (Figs. 1034 and 1035).— The structure of the villi has been studied by many eminent anatomists. We shall here follow the description of Watney,' whose researches have a most important bearing on the physiology of that which is the peculiar function of this part of the intestine, the absorption of fat. The essential parts of a villus are the lacteal vessel, the bloodvessels, the epithelium, the basement membrane, and muscle and lymphoid tissues of the mucosa, these structures being supported and held together by retiform tissue. These structures are arranged in the following manner: Situated in the centre of the villus is a space, the lacteal, terminating near the summit in a blind extremity; running beside this vessel are unstriped muscle fibres; surrounding it is a meshwork of fibroelastic tissue supporting a plexus of capillary vessels and diffuse lymphoid tissue, the whole being enclosed by a basement membrane, and covered by simple columnar epithelium and goblet cells. Nerve fibres are con- tained within the villi; they form ramifications throughout the reticulum. The lacteals are in some cases double, and in some animals mult i pic. Situated in the axis of a villus, each commences by a dilated cecal extremity near to, but not quite at, the summit of the villus. The walls are composed of a single layer of endothelial cells, the interstitial substance between the cells being continuous with the reticulum of the matrix. The muscle fibres are derived from the muscularis mucosae, and are arranged in bundles around the lacteal vessel. 1 Phil. Trans., vol. clxv, part i 1292 THE ORGANS OF DIGESTION extending from the base to the summit of the villus, and giving off laterally individual muscle cells, which are enclosed by the reticulum, and by it are attached to the basement membrane. The bloodvessels form a plexus between the lacteal and the basement membrane, and are enclosed in the reticular tissue; in the interstices of the capillary plexus, which they form, are contained the cells of the villus. The intestinal glands, crypts or glands of Lieberkiihn (glandidae intestinales [Liebrkuhni]) (Figs.1036 and 1040), are found in considerable numbers over every part of the mucous membrane of the small intestine. They consist of minute simple tubular depressions of the mucous mem- brane, arranged perpendicularly to the surface, upon which they open by small circular aper- tures. They may be seen with the aid of a lens, their orifices appearing as minute dots seen at iDe base of the villi. Their walls are thin, consisting of a basement membrane lined by simple columnar epithelium and goblet cells, and are surrounded by capillary vessels. In the glands of the ileum and also to a certain extent those of the jejunum are seen some coarsely granular cells, the cells of Faneth. They seem to be cells of special secretion. The duodenal or Brimner's glands (glandulae duodenales [Brumieri]) are limited to the duode- num. They are small, branched, tubular glands in the submucous coat, and open upon the surface of the mucous membrane by minute excretory ducts. They are most numerous and largest near the pylorus. They resemble the pyloric glands in appearance, and are believed to be a direct continuation of those glands. The cells are clear and pale staining, and Stohr states that cells resembling parietal ceils are occasionally seen. d of Lieberkiihn in the (Paneth.) Fig. 1037. — Transverse section of crypts of Lieberkiihn. (Klein and Noble Smith.) The lymph nodules (noduli lymphaiici) are small pyriform structures. The bodies of the nodes are in the submucous coat; the apices are in the mucous membrane, which is thrown by them into rounded elevations. They are divided into solitary follicles and Peyer's patches. The solitary foUicles (noduli lymphatici solitarii) (Fig. 1033) are found scattered throughout the mucous and submucous coats of the small intestine and the large intestine. In the small intestine they are most numerous in the lower part of the ileum, upon and between the valvulae cormiventes. They are small, round, whitish bodies, from one-twenty-fourth of an inch to one- quarter of an inch (1 to 6 mm.) in diameter. Their free surface is free of villi, and each follicle is surrounded by the openings of the glands of Lieberkiihn. They are now recognized as lymph nodules. They consist of a dense interlacing retiform tissue closely packed with lymph corpuscles and permeated with an abundant capillary network. The interspaces of the retiform tissue are continuous with larger lymph spaces at the base of the nodule, through which they communicate with the lacteal system. Each consists of a lighter central area, the germinal centre, where the leukocytes are reproducing, and a peripheral darker zone, where the cells are more numerous and closely packed. Peyer's patches, the agminated foUicles, or the tonsillae intestinales {noduli lymphatici aggregati[Peyeri]) (Figs. 1038, 1039, and 1040) may be regarded as aggregations of solitary follicles, forming circular or oval patches from ten to sixty in number, and varying in length from half an inch to four inches (1.2.5 to 10 cm.). Thev are largest and most numerous in the ileum. In the lower part of the jejunum they are small, of a circular form, and few in number. They are occasionally seen in the duodenum. They are placed lengthwise in the intestine, and are situated in the portion of the tube most distant from the attachment of the mesentery. Each patch is formed of a group of the above-described solitary follicles covered with mucous membrane, and in almost every respect are similar in structure to them. They do not, however, as a rule. THE JEJUNUM AND ILEUM 1293 possess villi on their free surface nor glands. Each patch is surrounded by a circle of the crypts of Lieberkuhn. They are best marked in the young subject, becoming indistinct in middle age and sometimes altogether disappearing in advanced life. They are largely supplied with blood ^..■•Capillary uetwoyTc. Fig. 1038. — Transverse section through the equatorial plane of three of Peyer's follicles from the rabbit. Fig. 1039. — Free surface of a Peyer' patch. (After Quain.) vessels, which form an abundant plexus around each follicle and give off fine branches which permeate the lymphoid tissue in the interior of the follicle. The lacteal plexuses which are found throughout the small intestine are especially abundant around these patches: here they form rich plexuses with sinuses around the glands (Fig. 1024). In typhoid fever there is ulcera- tion of Peyer's patches. CHYLI FERGUS Fig. 1040. — Vertical section of a Peyer's patch with the lymphatic vessels injected. (Frey.) Vessels and Nerves. — The arteries {vasa intestini tenuis (are branches of the superior mesenteric (Fig. 470) and course within the mesentery, forming single, double, or even tertiary loops (Figs. 1041, 1042, 1043, 1044, 1045, and 1046). The terminal branches reach the intestine, and each branch divides into two, one going to each side of the intestine and passing transversely around it. At first they are directly beneath the peritoneum, but after a time they pass to the 1294 THE ORGANS OF DIGESTION submucosa and form a plexus, from which branches go to the mucous membrane Some of these enter the villi; others form plexuses about the glands of Lieberkuhn (Birmingham). The details of the arterial blood supply of the small intestines are given on page 663. Seventeen feet. Twenty feet. Figs. 1041, 1042, 104.3, 1044, 1045, 1046. — Diagrams showing the arrangement and variations of the loops of the mesentenc vessels for various segments of the small intestine of average length. Nearest the duodenum the mesenteric loops are primary, the rasa recta are long and regular in distribution, and the translucent spaces (lunettes) are extensive. Toward the ileocolic junction, secondare and tertiary loops are observed, the vessels are smaller and become obscured by numerous fat-tabs. (After ilonts.) (See p. 1269 for detailed description.) THE JEJUNUM AND ILEUM 1295 The veins correspond to the arteries, and the venous blood passes to the superior mesenteric vein, which, it will he remembered, unites with the splenic vein to form the portal vein. The mesenteric veins are devoid of valves. The lacteals are lymphatics (Figs. 1033 and 1040) which arise in the villi. Lymphatics also becin in sinuses at the base of the solitary follicles and in Peyer's patches. There is an extensive lymphatic jilexus in the submucous coat, another in the muscular coat, another under the peri- toneum. The submucous plexus is formed by lymphatics from the villi and mucous membrane. This plexus is joined by lymphatics from the bases of the solitary follicles, and the lymph passes oy vessels to larger vessels at the mesenteric border of the gut. The muscular lymphatics are placed between the two muscular layers. They form a plexus and communicate freely with the lymphatics from the mucous membrane, and empty themselves in the same manner into the commencement of the lacteal vessels at the attached border of the gut. The vessels from all sources of lymphatic supply pass up between the two layers of the mesentery, being connected with the mesenteric nodes (Fig. 572), and unite to form a trunk, the intestinal lymphatic txunk, which opens into the receptaculum chyli, or the vessels unite to form several trunks, which open separately into the receptaculum chyli. . 1047.— lleissn i plexi ( Ramon y Cajal.) The nerves of the small intestine (Fig. 1047) are derived from the coeUac plexus about the superior mesenteric artery. They pass along within the mesentery with the superior mesenteric artery and reach the intestine. They pass to the plexus of nerves and ganglia situated between the circular and longitudinal muscular fibres (Auerbach's plexus), from which the nerve branches are distriliuicd to the muscular coats of the intestine. From this plexus a secondary plexus is derived (Meissner's plexus). It is formed by branches which have perforated the cir- cular muscular fibres. This plexus lies in the submucous coat. It is also gangliated, and from it the ultimate fibres pass to the muscularis mucosae, to the villi, and to the mucous membrane. The nerves of the intestine are amyelinic, and some of the fibres are derived from the vagus. Applied Anatomy. — The applied anatomy of the small intestine, especially the surgical anatomy of the hernias, is given on page 1315. THE LARGE INTESTINE (INTESTINUM CRASSUM) (Figs. 977, 1078). The large intestine extends from the termination of the ileum to the anus. It is about five feet or more in length, being one-fifth of the whole extent of the intestinal canal. It is largest at its commencement at the cecum, and gradually 1296 THE ORGANS OF DIGESTION diminishes as far as the rectum, where there is a dilatation of considerable size just above the anal canal. It differs from the small intestine in its greater size, its more fixed position, its sacculated wall, and in possessing certain appendages to its external coat, the appendices epiploicae (Fig. 1048), little peritoneal pouches containing fat. ACCULATIONS PENDtCES EPIF MUSCULAR BAND Fig. 104S. — Large intestine. A piece of transverse colon from a child two years old. The three chief character- istics of the large intestine — sacculations, taenite, and appendices epiploicae — are shown. (Cunningham.) Further, the longitudinal muscle fibres of the large intestine do not form a con- tinuous layer around the gut, but are arranged in three longitudinal bands or taeniae {taeniae coli) (Fig. 104S). The large intestine, in its course, describes an arch which surrounds the convolutions of the small intestine. The segment of the intestinal tract where the small intestine joins the large is termed the ileocecal or ileocolic junction. The large intestine commences in the right inguinal region, in a dilated part, the cecum, together with a rudimentary structure, the appendix. It ascends through the right lumbar and right hypochondriac regions to the under surface of the liver; here it takes a bend to the left (hepatic flexure), and passes trans^'ersely across the abdomen on the confines of the epigastric and umbilical regions, to the left hypochondriac re- gion; it then bends again (splenic flexure), and descends through the left lumbar re- gion to the left iliac fossa, where it be- comes convoluted, and forms the sigmoid flexure; finally it enters the pelvis and descends along its posterior wall to the anus. The large intestine is divided into the cecum, colon, rectum, and anal canal. The Cecum. The cecum {iniesiinum cecum) (Figs. 1050 and 1051-1054), the commencement of the large intestine, is the large blind pouch situated below the ileocecal valve. Its blind end or fundus is directed downward, and its open end upward, communi- cating directly with the colon, of which this blind pouch appears to be the beginning or head, and hence the old name caput cecum coli was applied to it. Its size is variously estimated by different authors, but on an average it may be said to be two and one-half inches (6.25 cm.) in length and three (7.5 cm.) in breadth.* 1 In 435 careful autopsies, Robinson found the cecum and appendix congenitally absent in one case (St. Louis Courier of Medicine, October-December. 1902). Sometimes a very large, sometimes an exceedingly small, cecum is encountered. A large cecum maybe four inches in width, entirely surrounded by peritoneurn, and usually is excessively mobile. An adult cecum may be only one inch in width and one-half an inch in length, and it is usually devoid of mobility. THE CECUM 1297 It is situated in the right iliac fossa, above the outer half of Poupart's ligament; it rests on the Iliopsoas muscle, and lies immediately behind the abdominal wall. As a rule, it is entirely enveloped on all sides by peritoneum, but in a certain number of cases (6 per cent. , according to Berry) the peritoneal covering is not complete, so that a small portion of the upper end of the posterior surface is uncovered and connected to the iliac fossa by connective tissue. The cecum lies quite free in the abdominal cavity and is capable of a considerable amount of movement, so that it may become herniated down the right inguinal canal, and has occasion- ally been found in an inguinal hernia on the left side.' The cecum varies in shape, but, according to Treves, in man it may be classified under one of four types (Figs. 1051-1054). In early fetal life it is short, conical, and broad at the base, with its apex turned upward and inward toward the ileocecal junction. It then resembles the cecum of some of the monkey tribe, e. rn the two layers of the mesocolon; upward and to the inner side or upward and to the outer side of the cecum and colon. It may pass to the left under the ileum and mesentery, upward and to the left or downward and to the left into the true pelvis. It may pass directly downward under the cecum. It may pass to the right in front of or back of the cecum. It may occupy any one of the peri- cecal fossff (p. 1266), but most often enters the ileocecal fossa. When the cecum is mobile the appendix may be found almost anywhere within the abdomen. When the cecum is undescended, the appendix of course shares in the failure to descend, and may be below the gall-bladder or in front of the right kidney, and may pass in several directions — upward behind the cecum, to the left behind the ileum and mesentery; or downward and inward into the true pelvis. It varies from one- FlG, 1055. — Arteries of the cecum and of the appendix venniformis and of the terminal porti( (Poirier and Charpj'.) half an inch to nine inches in length (1.25 to 22.5 cm.) its average being about three inches (7.5 cm.). Its diameter is from one-eighth inch to one-quarter inch (3 to 6 mm.). The operating surgeon may occasionally fail to find an appendix buried in one of the cecal fossae, and may conclude that the diverticulum is absent. In rare instances the appendix has been found absent. It is retained in position by a fold of peritoneum derived from the left leaf of the mesentery, which forms a mesentery for it, and is called the mesoappendix (p. 1265 and Figs. 1007 and 1008). This fold, in the majority of cases, is more or less triangular in shape, and, as a rule, extends along the entire length of the tube. In color the healthy ap- pendix is yellowish-pink and is soft and smooth to the touch. The canal of the appendix is small and extends throughout the whole length of the organ. The walls of the healthy di\'erticulum are thick, and the diameter of the lumen is usually triv- ial as compared with the diameter of the appendix itself. The lumen of the ap- pendix communicates with the cecum by an orifice wliich is placed below and behind the ileocecal opening (Fig. 1060). It is sometimes guarded above and to the left side by a semilunar fold of mucous membrane, the valve of Gerlach (valvula processus vermiform is). The valve is inconstant, and is never perfect. It is stated that the lumen of the appendix tends to undergo obliteration in advanced age as an involution change in a supposedly functionless organ. The lumen rarely contains foreign bodies after death, but often contains fecal concretions. Certain it is that in 25 per cent, of necropsies upon adults or elderly persons the lumen is foimd to be partially or completely occluded. 1300 THE ORGANS OF DIGESTION Structure of the Appendix (Fig. 105S).— The coats of the appendix correspond to the coats of the bowel — serous, muscular (the outer layer of longitudinal, the inner of circular fibres), submucous, and mucous. The outer or serous coat forms a complete investment for the appendix except al^ RIGHT LATERAL -Ti^^ / PER/rn..^>^ LIGAMENT Hepatic aiteiy, I Common Oile duct. Fir,, loss.— Posterior and under surfaces of the liver. (Drawn from His' model.) The fossa or fissure for the gall-bladder (fossa vesicae felleae) is a shallow, oblong fossa, placed on the under surface of the right lobe, parallel with the longitudinal fissure. It extends from the anterior free margin of the liver, which is notched for its reception, to the right extremity of the transverse fissure. The fissure for the inferior vena cava (fossa venae cavae) (Fig. 1084) is a short, deep fissure, in some cases a complete canal, in consequence of the substance of the liver occasionally surrounding this vessel. It extends obliquely upward from the lobus caudatus, which separates it from the transverse fissure on the posterior surface of the liver, and is situated between the Spigelian lobe and the bare area of the liver. On slitting open the inferior vena cava the orifices of the hepatic veins will be seen opening into this vessel at its upper part, after perforating the floor of this fissure. Lobes. — ^The lobes of the liver, like the ligaments and fissures, are five in number — the right lobe, the left lobe, the lobus quadratus, the lobus Spigelii, and the lobus caudatus, the last three being merely parts of the right lobe. 1324 THE ORGANS OF DIGESTION The right lobe (lohiis hepatis dexter) (Figs. 1083 and 1084) is much larger than the left, the proportion between them being as six to one. It occupies the right hypochondrium, and is separated from the left lobe, on its upper and anterior sur- faces, by the falciform ligament; on its under and posterior surfaces by the longi- tudinal fissure; and in front by the umbilical notch. It is of a somewhat quadri- lateral form, its under and posterior surfaces being marked by three fissures — the transverse fissure, the fissure for the gall-bladder, and the fissure for the inferior vena cava, which separate its left part into three smaller lobes — the lobus Spigelii, lobus quadratus, and lobus caudatus. On it are seen, four shallow impressions — one in front, for the hepatic flexure of the colon; a second behind, for the right kidney; a third internal, between the last-named and the gall-bladder, for the second part of the duodenum; and a fourth on its posterior surface, for the suprarenal gland. The lobus quadratus (Figs. 1084 and 1085) is situated on the under surface of the right lobe, is bounded in front by the inferior margin of the liver; behind, by the transverse fissure; on the right, by the fissure of the gall-bladder; on the left, by the umbilical fissure. It is oblong in shape, its antero-posterior diameter being greater than its transverse. The lobus Spigelii Qob^ts caudatus \Spigelii\) (Figs. 1084 and 1085) is situated upon the posterior surface of the right lobe of the liver. It looks directly back- ward, and is nearly vertical in direction. It is bounded below by the transverse fissure, on the right by the fissure for the inferior vena cava, and on the left by the fissure for the ductus venosus. It is longer from above downward, and is somewhat concave in the transverse direction. Its lower end usually projects in the form of a rounded process, the tuber papillare (processus papiUaris). The lobus caudatus {processus caudatus) (Fig. 1084), or tailed lobe, is a small elevation of the hepatic substance extending obliquely outward, from the lower extremity of the Spigelian lobe to the under surface of the right lobe. It is situ- ated behind the transverse fissure, and separates the fissure for the gall-bladder from the commencement of the fissure for the inferior vena cava. The left lobe (lohis hepatis sinister) (Figs. 1083 and 1084) is smaller and more flattened than the right. It is situated in the epigastric and left hypochondriac regions. Its upper surface is slightly convex; its under surface is concave, and presents a shallow depression for the stomach, the gastric impression. This is situated in front of the groove for the oesophagus, and is separated from the lon- gitudinal fissure by the omental tuberosity, which lies against the small omentum and lesser curvature of the stomach. The posterior end of the left lobe frequently exhibits a flat projection, composed of connective tissue, and called the appendix fibrosus hepatis. In the adult, portions only of bile ducts are present in it. In the newborn it is a definite portion of secreting liver substance, which later under- goes connective-tissue transformation. Ligaments. — The liver is connected to the under surface of the Diaphragm and the anterior walls of the abdomen by five ligaments, four of which are peri- toneal folds; the fifth is round, fibrous cord, resulting from the occlusion of the umbilical vein. These ligaments are the falciform, two lateral, coronary, and round. It is also attached to the lesser curvature of the stomach by the gastro- hepatic or small omentum (p. 1260). The falciform ligament (ligameniuvi falciforvie hepatis) (Figs. 1086 and 1087) is a broad and thin antero-posterior peritoneal fold, falciform in shape, its base being directed downward and backward, its apex upward and backward. It is attached by one margin to the under surface of the Diaphragm, and the posterior surface of the sheath of the right Rectus muscle as low down as the umbilicus; by its hepatic margin it extends from the notch on the anterior margin of the liver, as far back as its posterior surface. It is composed of two layers of peritoneum closely united. Its free edge contains the round ligament of the liver. THE LIVER 1325 The coronary ligament {\u\mnenium. coronarium. hepatis) (Figs. 1083 and 1086) connects the posterior surface of the liver to the Diaphragm. It consists of tMo layers. The upper layer is formed by the reflection of the peritoneum from the upper margin of the bare area of the liver to the under surface of the Diaphragm, and is continuous with the right layer of the falciform ligament. The loner layer is reflected from the lower margin of the bare area on to the right kidney and suprarenal gland. RrGHT LATERAL / LIGAMENT Fig. 1086. — The peritoneal ligaments of the ii" (Schematic.) (Poirier and Charpy.) The lateral ligaments (Figs. 1083 and 1086) are two in number, and are called the right and left lateral ligaments. The right lateral ligament {ligaynentum triangulare de.rtrum) (Figs. 1083 and 1086) is in reality the right extremity of the coronary ligament. This ligament is triangular in form, runs from the liver to the Diaphragm, and is formed by the apposition of the upper and lower layers of the coronary ligament. The left lateral ligament {liganien- tum triangulare sinistrum) (Figs. 1083 and 1086) is a fold of some considerable size, which connects the posterior part of the upper sur- face of the left lobe to the Dia- phragm; its anterior layer \h con- tinuous with the left layer of the falciform ligament. The round ligament {ligamentmn teres hepatis) (Figs. 1085 and 1087) is a fibrous cord resulting from the occlusion of the fetal umbilical vein. It ascends from the umbilicus, in the free margin of the falciform ligament, to the notch in the ante- rior border of the liver, from which it may be traced along the umbilical fissure on the inferior surface of the liver; on the posterior surface it is continued upward as the impervious ductus venosus (Jig. venosiim) as far as the inferior vena cava. Support and Movability of the Liver. — The liver is movable within certain narrow limits. It moves with respiration. On inspiration it moves down with the Diaphragm to distinctly below the costal arch in the right midclavicular line. Its fixation to the under surface of the Diaphragm by means of Qonnective tissue gives it its strongest support. The surface relations of the liver are given on page 1334. Fig. 1087. — Diagram to show the relations of the falciform or suspensorj' and round ligaments to the liver and the ab- dominal wall. (Gerrish.) 1326 THE ORGANS OF DIGESTION Abnormalities of the Liver. — The liver may be divided into many lobules, and such lobu- lation is most evident on the parietal surface of the right lobe. Lobulation is probably a patho- logical change. Occasionally the right lobe is small and the left large. Accessory Livers are fragments of hepatic tissue or vestiges, which are entirely separated from the liver. They are seldom met with. When they do exist their most common situation is in the suspensory ligament, but they have been found in the great omentum, in the peritoneum, wall of the gall-bladder, and in other situations. They may be congenital or may be due to atrophy of the pedicle of an accessory lobe or of a pedunculated lobe. Tight lacing alters the shape and position of the liver (Fig. 10S8) It may flatten the dome and increase the length of the anterior surface, this change being especially obvious in the right lobe, and a costal groove may be formed by the pressure of a rib. "When the elongated right lobe passes over the right kidney, there is atrophy of the hepatic substance and thickening of the capsule, which is opaque and forms a hinge-like ligament between the main part of the right lolie above the constricted lower portion. This lobe is variously termed partial hepatoptosis, constriction lobe, or the sustentacular formation of the right lobe (Hertz). The constriction furrow is produced by the pressure of the corset in front and the resistance of the kidney behind. The constriction lobe tapers to a point, so that the shape of the liver, as seen from the front, is that of a right-angled triangle, with the ape.x downward."' Such a constriction lobe is known as Riedel's lobe. The left lobe may also project down, but not so markedly. Tight lacing may cause the entire organ Fig. loss. — Deformed female lii (Poirier and Charpy.) to occupy a level higher than normal. Such a liver is thick and excessively convey above and thin below, and reaches to or laps over the spleen. In severe cases the superior surface is thrown into antero-posterior creases or folds. Riedel's lobe (Fig. 1088) may be congenital, may be due to tight lacing, or may arise in cholelithiasis or cholecystitis from the traction of adhesions. Such a lobe comes off from the right lobe. It may be a tapering mass of liver tissue, it may have a thin pedicle of liver tissue, or its pedicle may be merely a double fold of peritoneum. The gall- bladder may lie upon its under surface, or may be placed to the left of it. Vessels. — The bloodvessels connected with the liver are the hepatic artery, the portal vein, and the hepatic veins. The hepatic artery and portal vein (Figs. 467, 468, 557, and 1089), accompanied by numerous lymphatics and nerves, ascend to the transverse fissure between the layers of the gastrohepatic omentum, and in front of the foramen of Winslow. The hepatic duct, lying in company with them, descends from the transverse fissure between the layers of the same omentum. The rela- tive position of the three structures in the lesser omentum (Fig. 1000) is as follows : The hepatic of the Liver. THE LIVER 1327 duct lies to the right, the hepatic artery to the left, and the portal ye.n behind and between 1 e other two They e iter the transverse fissure in the above-desxT.bcc order, but in tha fissure u Icr. --earnuZMncnt, the duct being in front, the artery in the middle, and the vein behind. T ' r . V he ^'in, and the duct divide into a right and left branch and several smaller branches and wi h n the or<.an the vessels from the three sources accompany each other and divide at the Fig. 1089.-Scheraatic section o£ the liver. The fibrous tunic is shown in black and the capsule of Glisson in rect same points; so each branch of the portal vein is accompanied by a branch o the hepatic artery and of the duct. They are enveloped in a loose areolar tissue, the capsule of Ghsson (Fig ^0S9) which accompanies the vessels in their course through the fortal canals in the interior of *The"hepatic veins (Fig. 471) convey the blood from the liver. They commence in the sub- st'ince of the liver, in the capillary terminations of the portal vein and hepatic artery; tiiese tributaries o-radually uniting, usually form three veins, which converge toward the posterior surface of the liver and open into the portion of the inferior vena cava situated in the groove a t e back part of this organ. Of these three veins, one from the right and another from the^ e lobe open obliquely intS the inferior vena cava, that from the middle of the organ and lobus Spigelii having a straight course. COMMON D' DUODENUM -The relations of the vessels as they pass into the transverse fissure of the liver. (Poirier and Charpy.; The hepatic veins have very little cellular investment; what there is binds their parietes closely to the walls of the canals through which they run; so that, on section of the organ, these'veins remain widely open and solitary (Fig. 1092), and may be easily d-tmgu^^d from the branches of the portal vein (Fig. 1093), which are more or less col apsed, and always ac- companied by an artery and duct; the hepatic veins are destitute of valves. 1328 THE ORGANS OF DIGESTION Structure. —The substance of the hver is composed of lobules held together by extremely fine areolar tissue, and of the ramifications of the portal vein, hepatic duct, hepatic artery, hepatic veins, lymphatics, and nerves, the whole being invested by a serous and fibrous coat. The serous coat {tunica serosa) is derived from the peritoneum, and invests the greater part of the surface of the organ. It is intimately adherent to the fibrous coat. The axeolar or fibrous coat (capsula fibrosa [Olissoni]) lies beneath the serous investment and covers the entire surface of the organ; it is called the capsule of Glisson; the latter term has also been retained for the heavy fibrous tissue, at the portal fissure, that envelops and accompanies the vessels into the liver. It is difficult of demonstration, excepting where the serous coat is deficient. The areolar tissue which surrounds and binds together the liver lobules is continuous with the areolar coat. The Lobules' (lobuli hepatis) (Fig. 1096).— The lobules form the chief mass of the hepatic substance; they may be seen either on the surface of the organ or by making a section through the gland. They are small granular bodies about the size of a millet seed, measuring from one- twentieth to one-tenth of an inch in diameter. In the human subject their outline is very irreg- ular, but in some of the lower animals (for example, the pig) they are well defined, and when divided transversely have a polygonal outline. If divided longitudinally they are more or less foliated or oblong. The bases of the lobules are clustered around the smallest radicles of the hepatic veins {sublobular veins), to which each is connected by means of a small branch which issues from the centre of the lobule {intralobular vein). The remaining part of the surface of each lobule is imperfectly isolated from the surrounding lobules by a thin stratum of areolar tissue in which are ducts and a plexus of vessels, the interlobular plexus (Figs. 1094 and 1095). In some animals, as the pig, the lobules are completely isolated from one another by this interlobular areolar tissue. If one of the sublobular veins be laid open, the bases of the lobules may be seen through the thin wall of the vein on which they rest, arranged in the form of a tesselated pavement, the centre of each polygonal space presenting a minute aperture, the mouth of an intralobular vein (Fig. 1092). Fig. 1091. — The hepatic cells at different stages of digestion. (Heidenhain.) Microscopic Appearance. — Each lobule is composed of irregular, anastomosing chains of cells, hepatic ceUs (Fig. 1091), surrounded by a dense capillary plexus, composed of vessels which penetrate from the circumference to the centre of the lobule, and terminate in a single straight central vein, which runs through its centre, to open at its base into one of the radicles of the hepatic vein. These structures are supported by a delicate meshwork of retiform connective tissue. Within the chains of the cells are the minute commencements of the bile ducts. There- fore, in the lobule we have all the essentials of a secreting gland; that is to say, (1) cells, by which the secretion is formed; (2) bloodvessels, in close relation with the cells, containing the blood from which the secretion is derived; and (3) ducts, by which the secretion, when formed, is carried away. Each of these structures will have to be further considered. 1. The hepatic cells are epithelial in nature and of more or less cuboidal or polygonal form. They vary in size from the xt/to to the yjyVff "f ^^ mch in diameter; they consist of a granular protoplasm without any cell wall, and contain one or sometimes two distinct nuclei. In the nu- cleus is a highly refracting nucleolus with granules. Embedded in the protoplasm are niunerous brownish particles, the coloring matter of the bile, oil globules, and glycogen granules in varying quantities. Secretory capillaries are to be found in the cells. The cells adhere together by their surfaces so as to form rows, which radiate from the centre to the circumference of the lobules. .\s stated above, they are the chief agents in the secretion of the bile. 2. The Bloodvessels. — The blood in the capillary plexus around the liver cells is brought to the liver principally by the portal vein, but also to a certain extent by the hepatic artery. For the sake of clearness the distribution of the blood derived from the hepatic artery may be con- sidered first. The hepatic artery, entering the liver at the transverse fissure with the portal vein and hepatic duct, ramifies with these vessels through the portal canals. It gives ofT vaginal branches which ^ According to Mall (Jour, of Anat., vol. v, No. 3), the lobule as here described is not his structural unit, refers to all the tissue surrounding each terminal branch of the portal vein. THE LIVER 1329 raniifv in the interlobular tissue, and appear to be destined chiefly for the nutrition of the coats of the large vessels, the ducts, and the investing membrane of the liver. It also gives nlf capsular branches which reach the surface of the organ, terminating in the fibrous coat in stellate ])lcxuscs. Finally, it gives off interlobular branches (rami artcriosi interlobulares) which form a plexus of capillaries {interlobular capi/lariix) on the outer side of each lobule, to supply its wall and the accompanying bile ducts. From this plexus some lobular branches enter the lobule and end in the capillary network between the cells. OHJices of intralohular i . 1092. — Longitudinal section of an hepatic vein. (After Kiernan.) Fig. 1093. — Longitudinal section of a small portal vein and canal. (After Kiernan.) Theportal vein also enters at the transverse fissure and runs through the portal canals, dividing into branches in its course, which finally break up into a plexus, the interlobular plexus, in the interlobular connective tissue. In their course these branches' receive the vaginal and capsular veins, corresponding to the vaginal and capsular branches of the hepatic artery (Fig. 1094). Thus it will be seen that all the blood carried to the liver by the portal vein and hepatic Intralobular Trunk of intralobular vein. Fig. 1094. — Horizontal section of injected liver (dog). artery, except perhaps that derived from the interlobular branches of the hepatic artery, directly or indirectly finds its way into the interlobular plexus. From this plexus the blood is carried into the lobule by fine branches which pierce its wall and then converge from the cu-cumference to the centre of the lobule, forming a number of converging vessels, intralobular capillaries, wliich are connected by transverse branches (Figs. 109.5 and 1096). In the interstices of the network S4 1330 THE ORGANS OF DIGESTION of vessels thus formed are situated, as before said, the liver cells; and here it is that the blood is brought into intimate connection with the liver cells and the bile is secreted. The endothelium of Fig. 1095. — Magnified section of a human liver, placed in preservative a few minutes after death (electro- cution). The sinusoidal endotlielium is seen closely applied to the hepatic epithelial cells. The cell elements of the blood in the sinusoids have been omitted, but in this as in other similarly obtained preparations numerous bell-shaped forms of red blood'cells were seen. ranch of portal vein. Small Hie dnct. y Branch of / hepatic artefy. '11 Small hile f'^'r duct. ', V. ~ Branch of • ' • hepatic artery. '>"■ Branch of. portal vein. Fig. 1096. — A lobule of human liver. (After Eauber-Kopsch.) the capillaries and the epithelial cells are closely adherent to each other, forming sinusoids. Arrived at the centre of a lobule, all these minute vessels empty themselves into one vein, of THE EXCRETORY APPARATUS OF THE LIVER 1331 considerable size, which runs down the eentre of the lobule from apex to base and is called the intralobular or central vein (rciid iiitrdldlnilnnx) (Fig. 1096). At the base of the lobule this vein opens direetly into the sublobular vein, with which the lobule is connected, and which, as before mentioned, is a radicle of the hepatic vein. The sublobular veins, uniting into larger and larger trunks, end at last in the hepatic veins, which do not receive any intralobular veins directly. Finally, the hepatic veins, as mentioned on page 751, converge to form three large trunks which open into the inferior vena cava, while that vessel is situated in the fissure appropriated to it at the back of the liver. The portal vein is the nutrient vessel of the parenchyma of the liver, while the hepatic artery nourishes the vessels, ducts, and interlobular connective tissue. 3. The Ducts. — Having shown how the blood is brought into intimate relation with the hepatic cells in order that the bile may be secreted, it remains now only to consider (he way in which the secretion, having been formed, is carried away. Several views have pre\aile(l as to the mode of origin of the hepatic ducts; it seems, however, to be clear that they eomnienee by little passages, which are formed between the cells and which have been termed intercellular biliary passages, bile capillaries, or bile canalicuU {ductus biliferi). These passages are merely little channels or spaces left between the contiguous surfaces of two cells or in the angle where three or more liver cells meet, and it seems doubtful whether there is any delicate membrane forming the wall of the channel. Heidenhain, however, thinks they have coats. The channels thus formed radiate to the circumference of the lobule, and empty into small interlobular ducts between the lobules. These- are lined by low epithelial cells supported by a basement mem- brane and a little fibrous tissue. The interlobular ducts pass into the portal canals, become enclosed in Glisson's capsule, and, accompanying the portal vein and hepatic artery (Fig. 1096), join with other ducts to form two main trunks, the right and left branches of the hepatic duct, which leave the liver at the transverse or portal fissure, and by their union form the hepatic duct. The larger interlobular ducts possess some circularly arranged smooth muscle tissue, while the main ducts possess three coats — mucous, muscular, and fibrous. The mucous coat consists of tall columnar epithelial cells, basement membrane, and tunica propria. The mus- cular coat consists of smooth muscle tissue circularly arranged. The fibrous coat consists of loose white fibrous tissue supporting the other coats. The lymphatics, in the substance of the liver (Fig. 569), commence in lymphatic spaces around the capillaries of the lobules; they accompany the vessels of the interlobular plexus, often enclosing and surrounding them. These unite and form larger vessels, which run in the portal canals, enclosed in Glisson's capsule, and emerge at the portal fissure to be distributed in the manner described. Other superficial lymphatics arise from the superficial lobules, pass under the peritoneum, and form a close plexus, where this membrane covers the liver. The first- named group of lymphatics gives origin to the deep collecting trunks, the second to the superficial collecting trunks. One group of deep collecting trunks accompanies the portal vein, there being fifteen to eighteen of them emerging from the transverse fissure. They empty into the lymph nodes of the hilum. Another group -accompanies the hepatic veins. There are five or six trunks which pass through the Diapfiragm and terminate in the lymph nodes about the inferior vena cava (intrathoracic nodes). The superficial trunks of the superior surface are divided into posterior, anterior, and superior trunks. Some of the posterior trunks terminate in the nodes about the coeliac axis, others in the nodes about the lower portion of the inferior vena cava in the thorax; others in the nodes about the abdominal portion of the oesophagus. The anterior trunks which are limited to the right lobe pass to the nodes of the hilum. The superior trunks ascend in the suspensory ligament. Some pass to the nodes about the inferior vena cava, just above the Diaphragm; others to the hepatic nodes. The balance unite to form a very large trunk, which passes through the Diaphragm and divides into branches which enter the nodes back of the base of the ensiform cartilage. The nerves of the liver are derived from the left vagus and sympathetic. The branches of the left vagus ascend from in front of the stomach within the lesser omentum. The sympathetic nerves pass along the hepatic artery, enter the liver at the transverse fissure, and accompany the vessels and ducts to the interlobular spaces. Here, according to Korolkow, the myelinic fibres are dis- tributed almost exclusively to the coats of the bloodvessels, while the amyelinic fibres enter the lobides and ramify between the cells. The Excretory Apparatus of the Liver. The excretory apparatus of the liver consi.st.s of (1) the hepatic duct, formed, as we have seen, by the junction of the two main ducts, which pass out of the liver at the transverse fissure; (2) the gall-bladder, which serves as a ^eser^■oir for the bile; (3) the cystic duct, or the duct of the gall-bladder; and (4) the common bile duct, formed by the junction of the hepatic and cystic ducts. 1332 THE ORGANS OF DIGESTION The Hepatic Duct (ductus hepaticus) (Figs. 1097 and 1098). — T-no main trunks of nearly equal size issue from the liver at the transverse fissure, one from the right, the other from the left lobe; these unite to form the hepatic duct, which then passes downward and to the right for about an inch and a half or two inches (3.75 to 5 cm.), between the layers of the lesser omentum, where it is joined at an acute angle by the cystic duct, and so forms the common bile duct (ductus communis choledochus) . The hepatic duct is accompanied by the hepatic artery and portal vein (Fig. 1090). The Gall-bladder {vesica fellea) (Figs. 1084 and 1097).— The gall-bladder is the reservoir for the bile; it is a conical or pear- shaped musculomembranous sac, lodged in a fossa on the under surface of the right lobe of the liver, and fixed in it by connective tissue, and extending from near the right extremity of the transverse fissure to the anterior border of the organ. It is from three to four inches (7.5 to 10 cm.) in length, one inch (2.5 cm.) , in breadth at its widest part, and holds from eight to ten drams (30 to 40 c.c). It is divided into a fundus, body, and neck. The fundus (fundus vesicae felleae), or broad ex- tremity, is directed downward, forward, and to the right, and projects beyond the anterior border of the liver; the body (corpus vesicae felleae) and neck (collum vesicae felleae) are directed upward and backward to the left.. The neck of the gall-bladder is on a slightly higher level than the lowest point of the gall- bladder; thus the weight of the bile is away from rather than toward the outlet. The upper surface of the gall-bladder is attached to the liver by connective tissue and vessels. The under surface is covered by peritoneum, which is reflected on to it from the surface of the liver. Occasionally the whole of the organ is invested by the serous membrane, and is then Fig. io97.-The^ ^'.'"''(st'iHehoil)''"'' '^"""' Connected "to the liver by a kind of mesentery. Relations. — Tiie body of the gall-bladder is in relation, hy its upper surface, with the hver, to which it is connected by areolar tissue and vessels; by its under surface, with the commence- ment of the transverse colon; and farther back, with the upper end of the descending portion of the duodenum or sometimes with the pyloric end of the stomach or the first portion of the duodenum. The fundus is completely invested by peritoneum; it is in relation, in front, with the abdominal parietes, immediately below the ninth costal cartilage; behind, with the trans- verse arch of the colon. The neck is narrow, and curves upon itself like the letter S; at its point of connection with the cystic duct it presents a well-marked constriction. When the gall-bladder is distended with bile or filled with calculi, the fundus may be felt through the abdominal parietes, especially in an emaciated subject; the relations of this sac will also serve to explain the occasional occurrence of abdominal biliary fistulse, through which biliary calculi may pass out, and of the passage of calculi from the gall-bladder into the stomach, duo- denum, or colon, which occasionally happens. Structure.— The gall-bladder consists of three coats— serofibrous, muscular, and mucous. The external or serofibrous coat (timica serosa vesicae felleae) consists of white fibrous tissue that surrounds the muscle coat; the fundus is completely covered by peritoneum, while the body and neck are covered on their under surfaces only. The muscular coat (tunica muscularis vesicae felleae) is a thin but strong la.Ter which forms GALL-.^ ay* »DDER' . S»,fU. THE EXCRETORY APPARATUS OF THE LIVER 1333 the framework of the sac, consisting of dense fibrous tissue which interlaces in all directions and is mixed with plain muscle fibres which are disposed chiefly in a longitudinal direction, a few running transversely. The internal or mucous coat {tunica mucosa vesicae felleae) is loosely connected with the fibrous portion of the preceding coat. It is generally tinged with a yellowish-brown color, and is everywhere elevated into minute rugae, by the union of which numerous meshes are formed, the depressed intervening spaces having a polygonal outline. The meshes are smaller at the fundus and neck, being most developed about the centre of the sac. Opposite the neck of the gall-bladder the mucous membrane projects inward in the form of oblique ridges or folds, forming a spiral valve (Fig. 1097). The mucous membrane is covered with columnar epithelium, and secretes an abundance of thick viscid mucus; it is continuous through the hepatic duct with the mucous membrane lining the ducts of the liver, and through the ductus communis choledochus with the mucous membrane of the duodenum. Mucous glands may be found in this coat, as well as diffuse lymphoid tissue and solitary follicles. The Cystic Duct (ductus cysticus). — The cystic duct, the smallest of the three biliary ducts, is about an inch and a half (3.75 cm.) in length. It passes obliquely downward and to the left from the neck of the gall-bladder, and joins the hepatic duct to form the common bile duct. It lies in the gastrohepatic omentum in front of the portal vein, the hepatic artery lying to its left side. The mucous membrane lining its interior is thrown into a series of crescentic folds, from five to twelve in number, similar to those found in the neck of the gall-bladder. They project into the duct in regular succession, and are directed obliquely around the tube, presenting much the appearance of a continuous spiral valve (yalvula spiralis [Heisteri]) (Fig. 1097). When the duct is distended, the spaces between the folds are dilated, so as to give to its exte- rior a twisted appearance. The common bile duct {ductus cJiole- PATic dochus) (Figs. 1097 and 1098), the largest ''^ of the three, is the common excretory duct of the liver and gall-bladder. It is about three inches in length, is of the diameter ;t of a goose-quill, and is formed by the junction of the cystic and hepatic ducts. It descends along the right border of the lesser omentum behind the first portion of the duodenum, in front of the portal vein, ""°'* and to the right of the hepatic artery (Fig. 1000); it then passes between the head of the pancreas and descending I'IG. 1098. — The biliary ducts. (Schematic.) (Poirier and Charpy.) Fig. 1099. — The sphincter of the common bile duct. (Poirier and Charpy.) portion of the duodenum, and, running for a short distance along the right side of the terminal part of the pancreatic duct, passes ^^^th it obliquely through the wall of the descending portion of the duodenum between the mucous and muscular 1334 THE ORGANS' OF DIGESTION coats in the submucous tissue for one-half to three-quarters of an inch (1.25 to 2 cm.). The two ducts usually unite just before opening into the duodenum (Figs. 1098 and 1099), but may remain independent throughout (in about 10 per cent, of individuals). The ampulla of Vater (Fig. 1098) is the conical cavity formed by the fusion of the two ducts, and is much larger than the opening on the bile papilla. It averages 9.3 mm. in length. The average diameter of the orifice is 2.5 mm. (Opie). The two ducts open by a common orifice if there is an ampulla, or by two separate orifices if there is no ampulla, upon the summit of a papilla, situated at the inner side of the descending portion of the duodenum, a little below its middle and about three or four inches (7.5 to 10 cm.) below the pylorus. Circular muscle fibres, continuous with the longitudinal fibres of the ducts, surround the termination of the two ducts in the ampulla. These fibres constitute the so-called sphincter of Oddi (Fig. 1099). Structure.— The coats of the large bihary ducts are an external or fibrous, a middle or mus- cular, and an internal or mucous. The fibrous coat is composed of strong fibroareolar tissue. The muscular coat consists chiefly of circularly arranged smooth muscle tissue. The mucous coat is continuous with the lining membrane of the hepatic ducts and gall-bladder, and also with that of the duodenum; and, like the mucous membrane of these structures, its epithelium is of the simple columnar variety. It is provided with numerous mucous glands, which are lobu- lated and open by minute orifices scattered irregularly in the larger ducts. It is questionable if the smallest biliary ducts, which lie in the interlobular spaces, have any coats. Heidenhain thinks they have a connective-tissue coat, in which are muscle cells arranged both circularly and longitudinally, and an epithelial layer, consisting of short columnar cells. Dimensions of the Bile Ducts. — The hepatic duct is about two inches (5 cm.) in length, and its lumen is one-sixth of an inch (4 mm.) in diameter. The cystic duct is about one and one- half inched (3.75 cm.) in length, and its lumen is one-twelfth of an inch (2 mm.) in diameter. The common duct is aibout three inches (7.5 cm.) in length, and its lumen is one-quarter of an inch (6 mm.) in diameter. The duodenal opening is smaller than the common duct. The ducts are capal^le of considerable distention, but the duodenal opening cannot be dilated (HjTtl). Bloodvessels, Lymphatics, and Nerves of the Gall-bladder and Bile Ducts. —The cystic artery (Fig. 4G7), a branch from the right division of the hepatic, supplies the gall-bladder and cystic duct with blood. It passes along the cystic duct, and on reaching the gall-bladder divides into an upper branch and a lower branch. The upper branch lies between the gall-bladder and the liver and sends branches to each. The lower branch is between the peritoneum and the wall of the gall-bladder. The cystic veins empty into the portal vein. The common duct receives branches from the superior pancreaticoduodenal artery. There is a submucous lymphatic network and a muscular lymphatic network. The lymphatics are much less numerous at the fundus of the gall-bladder than at the neck or in the extrahepatic ducts. The collecting trunks end in lymph nodes along the cystic and common ducts, and these glands are in communication with the duodenal lymphatics and the lymphatics from the head of the pancreas. The nerves of the gall-bladder and bile ducts come from the coeliac plexus of the sympathetic. The Bile (fel). — The bile is a reddish-brown or greenish fluid. It contains pigments (bili- rubin and biliverdin), fats and soaps, cholesterin, sodium salts of glycocholic and taurocholic acid, lecithin, and nucleoalbumin furnished by the mucous membrane. There are also present CO2; chlorides, carbonates, phosphates, and sulphates of the alkalies and of calcium, and iron. The aiiKiuiit iKjnnally secreted is from one pint to one and one-half pints in the twenty-four hours. Surface Relations. — The liver is situated in the right hypochondriac and the epigastric regions, and is moulded to the arch of the Diaphragm. In the greater part of its extent it lies under cover of the lower ribs and their cartilages, but in the epigastric region it comes in con tact with the abdominal wall, in the subcostal angle. The upper limit of the right lobe of the liver may be defined in the middle line by the junction of the mesosternum with the ensiform cartilage; on the right side the line must be carried upward as far as the fifth rib cartilage in the midclavicular line and then downward to reach the seventh rib at the side of the thorax. The upper limit of the left lobe may be defined by continuing this line to the left with an inclination downward to a point about 7 cm. to the left of the mesal plane on a level with the sixth left costal cartilage. The lower limit of the liver may be indicated by a line drawn half an inch below the lower border of the thorax on the right side as far as the ninth right costal cartilage, and thence obliquely upward across the subcostal angle to the eighth left costal cartilage. A slight curved line with its convexity to the left from this point — i. e., the eighth left costal cartilage — to the termination of the line indicating the upper limit will denote the left margin of the liver. The fundus of the gall-bladder approaches the surface behind the anterior extremity of the ninth costal cartilage, close to the outer margin of the right Rectus muscle. THE EXCRETORY APPARATUS OF THE LIVER 1335 It must be remembered that the liver is subject to considerable alterations in position, and the student should make himself acquainted with the different circumstances under which this occurs, as they are of importance in determining the existence of enlargement or other diseases of the organ. Its position varies according to the posture of the body. In the erect position in the adult male the edge of the liver projects about half an inch below the lower edge of the right costal car- tilages, and its anterior border can be often felt in this situation if the abdominal wall is thin. In the supine position the liver gravitates backward and recedes above the lower margin of the ribs, and cannot then be detected by the finger. In the prone position it falls forward, and can then generally be felt in a patient with loose and lax abdominal walls. Its position varies also with the ascent or descent of the Diaphragm. In a deep inspiration the liver descends below the ribs; in expiration it is raised behind them. Again, in emphysema, where the lungs are distended and the Diaphragm descends very low, the liver is pushed down; in some other dis- eases, as phthisis, where the Diaphragm is much arched, the liver rises very high up. Pressure from without, as in tight lacing, by compressing the lower part of the thorax, displaces the liver considerably, its anterior edge often extending as low as the crest of the ilium; and its convex surface is often at the same time deeply indented from the pressure of the ribs. Again, its posi- tion varies greatly according to the greater or less distention of the stomach and intestines. \\Tien the intestines are empty the liver descends in the abdomen, but when they are distended it is pushed upward. Its relations to surrounding organs may also be changed by the growth of tumors (ir liy (•(illcctions of fluid in the thoracic or abdominal cavities. Applied Anatomy. — Movable liver or hepatoptosis is a rare condition, in which the liver moves or can be moved from its normal position. It is due to lessened tone of the abdoininal muscles and relaxation of the liver supports. In movable liver the organ may be rotated on its vertical axis or on its transverse axis. Tongue-lLke lobes have been referred to. On account of its large size, its fixed position, and its friability, the liver is more frequently ruptured than any other of the abdominal viscera. The rupture may vary considerably in extent, from a slight scratch to an extensive laceration completely through its substance, dividing it into two parts. Some- times an internal rupture without laceration of the peritoneal covering takes place, and such injuries are most susceptible of repair; but small tears of the surface may also heal; when, how- ever, the laceration is extensive, death usually takes place from hemorrhage, on account of the fact that the hepatic veins are contained in rigid canals in the liver substance and are unable to contract, and are, moreover, unprovided with valves. The liver may also be torn by the end of a broken rib perforating the Diaphragm. The liver may be injured by stahs or other punc- tured vjounds, and when these are inflicted through the chest wall both pleural and peritoneal cavities may be opened up and both lung and liver be wounded. In cases of wound of the liver from the front, protrusion of a part of this viscus may take place, but can generally easily be replaced. In cases of laceration of the liver, when there is evidence that bleeding is going on, the abdomen must be opened, the laceration sought for, and the bleeding arrested. This may be done temporarily by introducing the forefinger into the foramen of Winslow and placing the thumb on the gastrohepatic omentum and compressing the hepatic artery and portal vein between the two. Any bleeding points can then be seen. Bleeding is, if possible, arrested by suture hgatures. The edges of a small laceration are simply brought together and sutured by means of a blunt, curved, round needle passed from one side of the wound to the other. "All sutures must be passed before any are tied, and this must be done with the greatest gentleness, as the liver substance is very friable. If suture fails the actual cautery may succeed. When the laceration is extensive, the liver is sutured to the abdominal wall to hold it firm when pressure is applied, and then the laceration is packed with a piece of iodoform gauze, the end of which is allowed to hang out of the external wound. Abscess of the liver is of not infrequent occurrence, and may open in many different ways on account of the relations of this viscus to other organs. Thus, it may burst into the lung, the pus being coughed up, or into the stomach, the pus perhaps being vomited; it may burst into the colon or into the duodenum, or, by perforating the Diaphragm, it mav empty itself into the pleural cavity. Frequently it makes its way forward, and points on the anterior abdominal wall, and finally it may burst into the peritoneal or pericardiac cavity. Abscesses of the liver require opening, and this must be done by an incision in the abdominal wall, in the thoracic wall, or in the lumlsar region, according to the direction in which the abscess is tracking. The incision through the abdominal wall is to be preferred when possible. The abdominal wall is incised over the swelling, and unless the peritoneum is adherent, gauze is packed all around the exposed liver surface and the abscess opened, if deeply seated, preferably by the thermo- cautery. Hydatid cysts are more often found in the liver than in any other of the viscera. The reason of this is not far to seek. The embryo of the egg of the tenia echinococcus being liberated in the stomach by the disintegration of its shell, bores its way through the gastric walls and usually enters a bloodvessel, and is carried by the blood stream to the hepatic capillaries, where its onward course is arrested, and where it undergoes development into the fully formed hydatid. Tumors of the liver have recently been subjected to surgical treatment by removal of a portion of the organ. The abdomen is opened and the diseased portion of liver exposed; the circula- 1336 THE ORGANS OF DIGESTION tion is controlled by compressing the portal vein and the hepatic artery in the gastrohepatic omentum and a wedge-shaped portion of liver containing the tumor removed; the divided vessels are ligated, and the cut siu-faces brought together and sutured in the manner directed on page 1333. When the gall-bladder or one of its main ducts is ruptured, which may occur independently of laceration of the liver, death usually occurs from peritonitis. If the symptoms have led to the performance of a laparotomy and a small rent is found, it should be sutured; if an extensive opening is found the gall-bladder should be removed. If the cystic duct is torn, its distal end must be closed and the gall-bladder removed. In rupture of either of the other ducts, simply provide for free drainage. The gall-bladder may become distended with bile in cases of obstruction of its duct or of the common bile duct, or it may become distended from a collection of gallstones within its interior, thus forming a large tumor. The swelling due to distention with bile is pear-shaped, and pro- jects downward and forward to the umbilicus. It moves with respiration, since it is attached to the liver. To relieve a patient of gallstones, the gall-bladder must be opened and the gallstones removed. The operation is performed by an incision two or three inches long in the right semi- lunar line, commencing at the costal margin. The peritoneal cavity is opened, and, the tumor having been found, gauze pads are packed around it to protect the peritoneal cavity, and it is aspirated. When the contained fluid has been evacuated the flaccid bladder is drawn out of the abdominal wound and its wall incised to the extent of an inch; any gallstones in the bladder are now removed and the interior of the sac sponged dry. If the case is one of obstruction of the duct, an attempt must be made to dislodge the stone by manipulation through the wall of the duct; or it may be crushed from without by the fingers or carefully padded forceps. If this does not succeed, the safest plan is to incise the duct, extract the stone, close the incision in the duct by fine sutures in two layers, and employ drainage. After all obstruction has been removed, four courses are open to the surgeon: (1) The wound in the gall-bladder may be at once sewed up, the organ returned into the abdominal cavity, and the external incision closed. (2) The edges of the incision in the gall-bladder may be sutured to the fascia of the external wound, and a fistulous communication established between the gall-bladder and the exterior; this fistulous opening usually closes in the course of a few weeks. (3) The gall-bladder may be connected with the intestinal canal, preferably the duodenum, by means of a lateral anastomosis; this is known as cholecystenterostomy. (4) The gall-bladder may be completely removed (cholecystectomy) . If a stone blocks the ampulla of Vater and if the common bile duct and the pancreatic duct empty into the diverticulum, it is evident that both ducts will be blocked. It has been demonstrated that in such a case the pressure urging the bile onward is sufficient to overcome the pressure in the pancreatic duct and drive bile into the ducts of the pancreas, the result, perhaps, being disastrous inflammation of the pancreas. Septic trouble arises more rapidly when a stone is blocked in the duct than when stones merely block the gall-bladder, because the first-named part is richer in lymphatics (Murphy). THE PANCREAS (Figs. 1100, 1102). Dissection. — -The pancreas may be exposed for dissection in three different ways: (1) By raising the liver, drawing down the stomach, and tearing through the gastrohepatic omentum and the ascending layer of the transverse mesocolon. (2) By raising the stomach, the arch of the colon, and greater omentum, and then dividing the inferior layer of the transverse mesocolon and raising its ascending layer. (3) By dividing the two layers of peritoneum, which descend from the greater curvature of the stomach to form the greater omentum; turning the stomach upward, and then cutting through the ascending layer of the transverse mesocolon (see Fig. 996). The pancreas is a compound racemose gland, analogous in its structure to the salivary glands, though softer and less compactly arranged than those organs. It is long and irregularly prismatic in shape, and of a reddish-white color. Its right extremity, being broad, is called the head, and is connected to the main portion of the organ, the body, by a slight constriction, the neck; while its left extremity gradually tapers to form the tail. It is situated transversely across the posterior wall of the abdomen, at the back of the epigastric and left hypochondriac regions. Its length varies from five to six inches (12.5 to 15 cm.), its breadth is an inch and a half (3.75 cm.), and its thickness from half an inch to an inch (1.25 to 2.5 cm.), being greater at its right extremity and along its upper border. Its weight varies from two to three and one-half ounces (60 to 100 grams). THE PANCREAS 1337 The head {caput pancreatis) (Fig. 1100) is flattened from before backward, and is lodged within the curve of the duodenum. The upper border is in contact with the first part of the duodenum, and its lower overlaps the third part; its right HEPATIC DUCT — Iflt, , CYSTIC DUCT — SW] SUPERIOR MESENTERIC VEIN Fig. 1100. — Position and relations of pancreas. p. MESENTERIC ARTERY. AREA FOR Fig. 1101. — The pancreas and duodenum from behind. (Drawn from His' model.) and left borders overlap in front, and insinuate themselves behind, the second and fourth parts of the duodenum respectively. The angle of junction of the lower and left lateral borders forms a prolongation, termed the processus uncinatus. In the groove between the duodenum and the right lateral and lower borders in 1338 THE ORGANS OF DIGESTION front are the anastomosing superior and inferior pancreaticoduodenal arteries; the common bile duct descends behind, along the right border, to its termination in the second part of the duodenum. The greater part of the right half of the anterior surface is in contact with the transverse colon, only areolar tissue intervening. From its upper part the neck originates, its right limit being marked by a groove for the gastroduodenal artery. The lower part of the right half, below the transverse colon, is covered by peri- toneum continuous with the inferior layer of the transverse mesocolon, and is in contact with the coils of the small in- testine. The superior mesenteric artery passes down in front of the left half across the uncinate process; the superior mesenteric vein runs upward along the right side of the artery, and, behind the neck of the pancreas, joins with the splenic vein to form the portal vein. The posterior surface is in relation with the inferior vena cava, the renal veins, the right crus of the Diaphragm, and the aorta. The neck springs from the right upper portion of the front of the head. It is about an inch (2.5 cm.) long, and is directed, at first, upward and forward, and then upward and to the left to join the body; it is somewhat flattened from above downward and backward. Its antero-superior surface supports the pylorus; its postero-inferior surface is in relation with the commencement of the portal vein; on the right it is grooved by the gastroduodenal artery. The body {corpus pancreatis) is somewhat prismatic in shape, and has three surfaces — anterior, posterior, and inferior. The anterior surface (fades anterior) is somewhat concave, and is directed for- ward and upward; it is covered by the postero-inferior surface of the stomach which rests upon it, the two organs being separated by the lesser sac of the peri- toneum. Where it joins the neck extremity there is a well-marked prominence, called the omental tuberosity (tuber omentale), which abuts against the posterior surface of the small omentum. The posterior surface (fades posterior) (Fig. 1101) is devoid of peritoneum, and is in contact with the aorta, the splenic vein, the left kidney and its vessels, the left suprarenal gland, the crura of the Diaphragm, and the origin of the superior mesenteric artery. The inferior surface (fades inferior) (Fig. 1101) is narrow on the right, but broader on the left, and is covered by peritoneum ; it lies upon the duodenojejunal flexure and on some coils of the jejunum; its left extremity rests on the splenic flexure of the colon. The superior border (margo superior) of the body is blunt and flat to the right; narrow and sharp to the left, near the tail. It commences to the right in the omental tuberosity, and is in relation with the coeliac axis, from which the hepatic artery courses to the right just above the gland, while the splenic branch runs toward the left in a groove along this border. The anterior border (margo anterior) separates the anterior from the inferior surface, and along this border the two layers of the transverse mesocolon diverge from each other; one passing upward over the anterior surface, the other back- ward over the inferior surface. The inferior border (margo inferior) separates the posterior from the inferior surface; the superior mesenteric vessels emerge under its right extremity. THE PANCREAS 13.39 Tlie tail (caiida paucreatis) is narrow; it extends to the left as far as the lower part of tlie gastric surface of the spleen, and it is in contact with the splenic flexure of the colon. Birmingham describes the body of the pancreas as projecting forward as a prominent ridge into the abdominal cavity and forming a sort of shelf on whicli the stomach lies. He says: "The portion of the pancreas to the left of the middle line has a very considerable antero-posterior thickness; as a result the anterior surface is of considerable extent, it looks strongly upward, and forms a large and important part of the shelf. As the pancreas extends to the left toward the spleen it crosses the upper part of the kidney, and is so moulded on to it that the top of the kidney forms an extension inward and backward of the upper surface of the pancreas and extends the bed in this direction. On the other hand, the extremity of the pancreas comes in contact with the spleen in such a way that the plane of its upper surface runs with little interruption upward and backward into the concave gastric surface of the spleen, which completes the bed behind and to RECTUS MUSCLE /th Costal Caihlane nil Costal Cai tilage. ,,'Sih Rib. Fig. 1103. — Transver; Abdominal Aorta. section through the middle of the first lumbar pancreas. (Braune.) 11th Rib. vertebra, showing the relations of the the left, and, running upward, forms a partial cap for the wide end of the stomach. The principal excretory duct of the pancreas, called the pancreatic duct or canal of Wirsung (duchi^ paiwreaticus [Wirsungi]) (Figs. 1100 and 1102), extends trans- versely from left to right through the substance of the pancreas. In order to expose it, the superficial portion of the gland must be removed. It commences by the junction of the small ducts of the lobules situated in the tail of the pancreas, and, running from left to right through the body, it constantly receives the ducts of the various lobules composing the gland. Considerably augmented in size, it reaches the neck, and, turning obliquely downward, backward, and to the right, it comes into relation with the common bile duct, lying to its left side; leaving the head of the gland, it passes very obliquely through the mucous and muscular coats of the duodenum, and usually terminates by an orifice common to it and the 1340 THE ORGANS OF DIGESTION common bile duct upon the summit of an elevated papilla, situated at the inner side of the descending portion of the duodenum, three or four inches (7.5 to 10 cm.) below the pylorus (Figs. 1098 and 1099). Sometimes the pancreatic duct and common bile duct open separately into the duodenum (Fig. 1029). Frequently there is an accessory duct, which is given off from the canal of Wirsung in the neck of the pancreas and passes horizontally to the right to open into the duodenum about an inch above the orifice of the main duct. This is known as the duct of Santorini {dudm pancreatic-m accessorius [Santorini]) (Fig. 1102). The pancreatic duct, near the duodenum, is about the size of an ordinary quill ; its walls are thin, consisting of three coats, an external fibrous, a middle muscular, and an internal mucous; the latter is smooth, and furnished near its termination with a few scattered follicles. Structure. — In structure, the pancreas resembles the salivary glands. It differs from them, however, in certain particulars, and is looser and softer in its texture. It is not enclosed in a distinct capsule, but is surrounded by areolar tissue, which dips into its interior, and connects the various lobules of which it is composed. Each lobule, like the lobules of the salivary glands, consists of one of the ultimate ramifications of the main duct, terminating in a number of cecal pouches or alveoli, which are mainly grape-like. The minute ducts connected with the alveoli are narrow and lined with flattened cells. The alveoli are almost completely filled with secreting cells, so that scarcely any lumen is visible. In the centre of the end-tubules flat cells are frequently found. They are continuations into the tubules of the duct epithelium. These cells are known as the centro-acinar cells of Langerhans. The true secreting cells which line the wall of the alveolus are very characteristic. They are pyramidal or rounded in shape and present two zones — an outer one clear and finely striated next the basement membrane, and an inner granular one next the lumen. The highly refracting granules are known as zsrmogen granules. During digestion the granules gradually disappear and the cells become clear. Dur- ing fasting the granular zone occupies more than one-half of the cell (Szymonowicz). In some secreting cells of the pancreas is a spherical mass, staining more easily than the rest of the cells; Interlobular duct. this is termed the paranucleus, and it is believed to be an extension from the nucleus. The con- nective tissue among the gland tubules and alveoli presents in certain parts collections of cells, which are termed interalveolar cell islets, or islands of Langerhans. Opie points out that they are most common in the splenic end of the pancreas. The cells of the islands are smaller and paler than the secretmg cells of tlie alveoli, and are arranged in layers with intervening spaces. Tlie islands are sharply demarcated from the alveoli, are much larger than the latter, and are THE PANCREAS 1341 very vnsciifiir. There are no duels in the ishxnds of Langerhans. Their function is to furnish the iiiliTHiil sccreliciii of ihe ]ian(rea.s. Bloodvessels, Lymphatics, and Nerves.— The arteries of the pancreas come from the superior pancreaticoduodenal branch of the gastroduodenal ; 1 he inferior pancreaticoduodenal branch of the superior mesenteric; the inferior pancreatic branch of the superior mesenteric; pancreatic branches of the hepatic and pancreatic branches of the splenic. In a fe« cases a large artery, the pancreatica magna, aceom))anies the pancreatic duel. In mcjst cases fiiere is no such vessel. The veins are the anterior pancreaticoduodenal branch of the superior mes- enteric; the posterior pancreaticoduodenal branch and olher pancreatic branches of the portal; and pancreatic branches of the splenic. The lymphatics arise in a network al)ont the lobules. Numerous collecting trunks jiass to the surface of the pancreas, anastomose with each other, and enter into nodes about the pancreas. The splenic nodes receive most of the trunks. Others are received by nodes along the aorta (Sappey), nodes at the origin of the superior mesenteric artery, and nodes along the pancreaticoduodenal vessels. The nerves eome from the coeliac, superior mesenteric, and splenic plexuses. The Pancreatic Juice. — The pancreatic juice is a clear, somewhat viscid alkaline liquid. Its speeifie gravity is about 1 .0.30. The solid matter consists chiefly of proteids, and amounts to about 10 per cent, of a sample of the juice. The juice contains a ferment which breaks up fat, a ferment which converts starch into sugar, and a fermeht which digests proteid material. Surface Form. — The pancreas lies in front of the second lumbar vertebra, and can some- times be felt, in emaciated subjects, when the stomach and colon are empty, by making deep' pressure in the middle line about three inches above the umbilicus. Applied Anatomy. — Of late years our knowledge of the structure, functions, and diseases of the pancreas has been notably increased, and surgeons have begun to operate for certain pan- creatic diseases. It is occasionally the seat of cancer, which usually affects the head or duodenal end, and therefore often speedily involves the common bile duct, leading to persistent jaundice. Cancer of the pancreas may be primary or secondary. Primary sarcoma is very unusual; sec- ondary sarcoma is more common, but cancer is far commoner than either form of sarcoma. Adenoma may also occur. Cases are on record of the successful removal of tumors of the pan- creas, but the operations are very dangerous, are extremely difficult, and are seldom attempted. The pancreas may be the seat of syphilitic or tuberculous disease. As a result of pancreatic injury, there may be effusion into the lesser peritoneal cavity. The lesser cavity becomes distended, and the fluid of this pseudocyst may contain pancreatic juice (.lordan Lloyd). True cysts of the pancreas are occasionally found. Pancreatic cysts may result from blocking of the duct, from epithelial proliferation, from traumatism and hemorrhage, or from hydatid disease. Con- genital cysts may occur, and cystic carcinoma is sometimes encountered. Cysts of the pancreas may present in the epigastric region above and to the right of the umbilicus. The fluid in these cysts contains some of the pancreatic secretion. A pancreatic cyst is best treated by opening the abdomen, suturing the cyst to the skin, opening the cyst, and providing for drainage. Com- plete extirpation of the cyst is invariably difficult and is usually impossible. It has been said that the pancreas is the only abdominal viscus which has never been found in a hernial protru- sion; but even this organ has been found, in company with otlier viscera, in rare cases of dia- phragmatic hernia. The pancreas has been known to become invaginated into the intestines and portions of the organ have sloughed off. In cases of excision of the pylorus great eare must be exercised to avoid wounding the pancreas, as the escape of the pancreatic fluid may be attended with serious and even with fatal results, peritonitis and fat necrosis, and gangrene being caused. Rupture of the pancreas as a solitary result of traumatism is very unusual, but is more common in violent injuries which rupture the liver and spleen as well. An injury which lacerates the pancreas and permits blood and pancreatic juice to flow into the lesser peritoneal cavity is usually rapidly fatal, but may not be. The foramen of Winslow may be occluded by inflammation, and a pseudocyst may form. In severe laceration of the pancreas alone it would be proper to open the abdomen, ligate bleeding vessels, suture the pancreas, and drain the lesser peritoneal cavity posteriorly. A gunshot wound of the pancreas requires posterior drainage. Every effort must be made in a pancreatic wound to rapidly get rid of pancreatic fluid by drainage from the wound area, as this fluid is extremely irritant and may cause gangrene. Inflammation of the pancreas is due to infection. Occasionally it seems to follow the entrance of bile into the pancreatic duct, because of plugging of the amjjulla with a calculus (Halsted, Opie). Hemorrhage into the pancreas is frequent in acute pancreatitis, and fat necrosis is com- mon in the fat of the naesentery, subperitoneal tissue, omentum, and other parts. Acute pan- creatitis may be recovered from if the abdomen is opened, the pancreas incised, and drainage employed. In chronic interstitial pancreatitis of the head of the pancreas the bile duct is apt to become blocked, and the disease is frequently mistaken for cancer. Cure may follow opening and drainage of the gall-bladder. Extensive fibrosis of the islands of Langerhans is one of the commonest lesions found post mortem in cases of diabetes meUitus. THE UEINOGENITAL OEGANS.' THE urinogenital organs (apparatus itrogenitalis) consist of (a) the urinary organs for the excretion of the urine, and (b) the genital organs which are concerned with the process of reproduction. THE URINARY ORGANS. The urinary organs comprise the kidneys, which secrete the urine; the ureters or ducts wliich convey it to the bladder, where it is for a time retained; and the urethra, through which it is discharged from the body. THE KIDNEYS (RENES) (Figs. 1105, 1107). The kidneys are situated in the posterior part of the abdomen, one on each side of the vertebral column, behind the peritoneum, and are surrounded by a mass of fat and loose areolar tissue. Their upper extremities are on a level with the upper border of the twelfth thoracic vertebra, the lower extremity on a level with the third lumbar vertebra. The right kidney is usually on a slightly lower level than the left, probably on account of the vicinity of the liver. In the female the kidneys are a little lower than in the male. The long axis of each kidney is directed from above downward and outward, the transverse axis from within backward and outward. Each kidney is about four and one-half inches (11.5 cm.) in length, two to two and one-half inches (5.5 cm.) in breadth, and about one and one-half inches (3.7 cm.) in thickness. The left is somewhat longer and narrower than the right. The weight of the kidney in the adult male varies from four and one-half ounces to six ounces (130 to 170 grams); in the adult female, from four ounces to five and one-half ounces (115 to 155 grams). The specific gravity is about 1.052. The kidney has a characteristic form, resembling that of a lima bean, and presents for examination two surfaces, two borders, and an upper and a lower extremity. The combined weight of the two kidneys in proportion to the body is about 1 to 240. Relations. — The anterior surface (fades anterior) of each kidney is convex, and looks for- ward and outward. Its relations to adjacent viscera differ so completely on the two sides that separate descriptions are necessary. (a) Anterior Surface of Right Kidney. — ^A narrow portion at the upper extremity is in relation with the suprarenal gland. Immediately below this a large area, involving about three-fourths of the surface, lies in the renal impression on the inferior surface of the liver, and a narrow but somewhat variable area near the inner liorder is in contact with the second part of the duodenum. The lower part of the anterior surface is in contact externally with the hepatic flexure of the 1 Usage has sanctioned the employment of urogenital as the equivalent of urinogenital, although the latter form only is philologically correct. (1343) 1344 THE URINOGENITAL ORGANS colon, and internally with the small intestine. The areas in relation with the liver and intestine are covered by peritoneum; the suprarenal, duodenal, and colic areas are devoid of peritoneum. licriplndilitin Great splanchnic nerve piercing chyh. (!) eat splanchnic lUlK pu't( Semilunar ganglion. Fig. 1105. — The relations of the viscera and large vessels of the abdomen. (Seen from behind, the last thoracic vertebra being well raised.) (6) Anterior Surface of Left Kidney. — ^A small area along the upper part of the inner border is in relation with the suprarenal gland, and close to the outer border is a narrow strip in contact with the renal impression on the spleen. A broad. THE KIDNEYS 1345 somewhat quadrilateral field, at)out the middle of the anterior surface, marks the site of contact with the body of the pancreas, on the deep surface of which are the splenic vessels. Above this is a small triangular portion, between the suprarenal and splenic areas, in contact with the postero-inferior surface of the stomach. Below the pancreatic area the outer part is in relation with the splenic flexure of the colon, the inner with the small intestine. The area in contact with the stomach is covered by the peritoneum of the lesser sac, while that in relation to the small intestine is covered by the peritoneum of the greater sac; behind the latter are some liranches of the left colic vessels. SUPERIOR MCSCI ARTERY INFERrOR MESENTERIC ARTERY Fig. 1106.— Poster! ■ abdominal wall, after removal of the peritoneum, showing kidneys, suprarena and great vessels. (Corning.) The Posterior Surface {fades posterior) (Fig. 1108).^ — ^The posterior surface of the kidney is flatter than the anterior and is directed backward and inward. It is entirely devoid of peritoneal covering, being embedded in areolar and fatty tissues. It lies upon the Diaphragm, the anterior layer of the lumbar aponeuro- sis, the external and internal arcuate ligaments, the Psoas andTransversalis muscles, one or two of the upper lumbar arteries, the last thoracic, iliohypogastric, and ilioinguinal nerves. The lumbocostal ligaments overlie the posterior surface of the kidney (Fig. 993). The right kidney rests upon the twelfth rib (Fig. 993), the left usually on the eleventh and twelfth ribs. The Diaphragm separates the 85 1346 THE URINOGENITAL ORGANS kidney from the pleura as the pleura dips down to form the phrenicocostal sinus (Fig. 910), but frequently the muscle fibres of the Diaphragm are defective or Fig. 1107. — Right kidney. Anterior ' Fig. 1108.— Left kidney. Posterior ' absent over a triangular area immediately above the external arcuate ligament, and when this is the. case the perirenal areolar tissue is in immediate apposition SUPRARENAL AREA Fig. 1109. — The anterior surfaces of the kidneys, showing areas of contact of neighboring viscera. with the diaphragmatic pleura. In the lower part of the posterior surface of the kidney is an impression produced by the Quadratus lumborum muscle and called THE KIDNEYS 1347 the impressio muscularis. A little internal to this a flattening, caused by the Psoas muscle, is often recognizable. Fig. 1110. — The posterior surfaces of the kidneys, showing areas of relation to the parietes. Fig. 1111 — Longitudinal section, showing the arrangement of the renal fascia. (After Gerota.) RARENAL FAT QUADRATUS LUM" SACROLUMBALIS BORUM MUSCUE GROUP Fig. 1112. — Transverse section, showing the relations of the renal fascia and the two layers of fat. (After Gerota.) Borders.— The external border {marcio lateralis) (Figs. 1107 and 1108) is convex, and is directed outward and backward, toward the posterolateral wall of the 1348 THE URINOOENITAL ORGANS abdomen. On the left side it is in contact, at its upper part, with the spleen (Fig. llOfi). The internal border {margo 7nedialis) (Figs. 1107 and 1108) is concave, and is directed forward, inward, and a little downward. It presents a deep longitudinal fissure, bounded by a prominent overhanging anterior and posterior lip. This fissure is named the hilum {hilus renalis) (Fig. 1108), and allows of the passage of the vessels, nerves, and ureter into and out of the kidney. At the hilum of the kidney the relative position of the main structures passing into and out of the kidney is as follows : The vein is in front, the artery in the middle, and the duct or ureter behind and toward the lower part (Fig. 1107). By a knowledge of these relations the student may distinguish between the right and left kidney. The kidney is to be laid on the table before the student on its posterior surface, with its lower extremity toward the observer — that is to say, with the ureter behind and beloio the other vessels; the hilum will then be directed to the side to which the kidney belongs. Frequently, however, the branches of both artery and vein are placed behind the ureter. Extremities. — The superior extremity {extremitas superior) (Figs. 1107 and 1108) is directed slightly inward as well as upward, being situated about 4 cm. from the mesal plane. It is thick, broad, bulky, and rounded, and is surmounted by the suprarenal gland (Fig. 1113), which covers also a small portion of the anterior surface. The inferior extremity {extremitas inferior) (Figs. 1107 and 1108), directed a little out- ward as well as downward, is smaller and thinner and usually more pointed than the superior. It is situated about 6 cm. from the mesal plane, and extends to within two inches (5 cm.) of the crest of the ilium. Fixation of the Kidney (Figs. 1111 and 1112). — The kidney and its vessels are em- bedded in a mass of fatty tissue termed the perirenal fat (capsida adiposa), which is thickest at the margins of the kidney and is prolonged through the hilum into the renal sinus. The kidney and the capsula adiposa are enclosed in a sheath of fibrous tissue continuous with the subperitoneal fascia, and named the fascia renalis. At the outer border of the kidney the fascia renalis splits into an anterior and a pos- terior layer. The anterior layer is carried in- ward in front of the kidney and its vessels, and is continuous over the aorta with the corre- sponding layer of the opposite side. The pos- terior layer extends inward behind the kidney and blends with the fascia on the Quadratus lumborum and Psoas muscles and through this fascia is attached to the vertebral column. At the upper margin of the suprarenal gland the two layers of the fascia renalis fuse, and imite with the fas- cia of the Diaphragm; below they remain separate, and are gradually lost in the subperitoneal fascia of the iliac fossa (Fig. 1 1 1 1 ) . The fascia renalis is connected to the fibrous capsule of the kidney by numerous trabeculse, which traverse the adipose capsule and are strongest near the lower end of the organ. The perirenal fat does not look like the fat in other regions, but is soft, delicate, and of a canary-yellow color. Behind the fascia renalis is a considerable quantity of fat which constitutes the Fig. 1113. — Vertical section of kidney. THE KIDNEYS 1349 WALL OF RENAL CALIX Fig. 1114. — Area cribrosa of renal papilla. (Toldt.) pararenal or Transversalis fat. The kidney is held in position throngh the at- tachments of the fascia renahs and by the apposition of the neighboriiis viscera. General Structure of the Kidney.— ^„e:a chibhosa The Uiilncy is invested by a capsule of interlacing bundles of fibrous connective tissue (tunica fibrosa), which forms a firm, smooth covering for the organ. The cap- sule can be easily stripped off, but in doing so, numerous fine processes of connective tissue and .small bloodvessels are torn through. Beneath this coat, a thin wido- meshed network of unstriped muscle fibres forms an incomplete covering. When the capsule is removed, the surface of the kidney is found to be smooth and even, and of a very deep red color. In infants, fissures extending for some depth may be seen on the surface of the organ, a remnant of the lobular construction of the gland (Fig. 1105). The kidney is dense in texture, but is easily lacerable by mechan- ical force. If a vertical section of the kidney be made from its convex to its concave border, and the loose tissue and fat removed from around the vessels and the excretory duct, it will be seen that the organ consists of a central cavity surrounded, except at the hilum, by the proper kidney substance (Fig. 1113). This central cavity is called the renal sinus (sinus renalis) and is SUPERIOR lined by a prolongation of the cap- sule, which is continued around the lips of the hilum. Through the hilum the bloodvessels of the kidney and its excretory duct pass, and therefore these structures, upon entering the kidney, are contained within the sinus. The excretory duct or ureter begins as a funnel-shaped sac, the pelvis of the ureter (pelvis ureter- iciis s. renalis). The pelvis begins at the renal papillfe in the form of a number of truncated cup-shaped infundibular divisions, the calices minores, into each of which usually one papilla projects. These minor calices vary from ten to twenty in number. Several minor calices unite to form larger divisions, the calices majores (Fig. 1115), which are usually two in number, though more may be present. These major calices unite to form the main compartment of the pelvis, which becomes narrowed below at the le\'el of the second lumbar ver- tebra to be continued as the ureter proper (Fig. 1115). The kidney substance or paren- chyma consists of very irregular tubules, the uriniferous tubules, which are supported by a frame- work of retiform connective tissue and surrounded by blood- and lymph vessels and nerves. It is readily divisible into an outer third, the cortex, about one-third to one-half of an inch (8 to 12 mm.) in thickness, and an inner two-thirds, the medulla, two-thirds to three-quarters of an inch (16 to 20 mm.) in thickness. Fig. 1115. — The right kidney with the pelvis of the ureter exposed, and showing dorsal branch of the renal artery, viewed from behind. (Spalteholz.) 1350 THE VRINOGENITAL ORGANS The cortex is reddish brown in color and soft and granular in consistence. It lies imme- diatel}- beneath the capsule, arches over the bases of the pyramids, and dips in between adjacent pyramids toward the renal sinus in the form of renal columns {columnae renales [Bertini]). If a section of the cortex be examined with a lens, it will be seen to consist of a series of liwhter colored, ray-like prolongations of straight tubules from the medulla, called the medullary rays {pars radiata). The darker colored intervening substance composing the remainder of the cortex, from the complexity of its structure, is called the labyrinth {pars convoluta), and contains the convoluted portions of the uriniferous tubules and the Malpighian corpuscles. The medul- lary rays gradually taper toward the circumference of the kidney, but do not reach the capsule. The meduUa consists of reddish, striated, conical masses, the medullary psrramids (pijramides renales [Malpighii]), the number of which, varying from ten to twinty, corrrsiionds to the number of lobes of which the organ is composed in the fetal state. The pyramids are composed of straight tubes which pass from the base to the apex. The sides of the pyramids are contiguous with the renal columns, while the apices, known as the renal papillae, project into the minor calices of the ureteral pelvis, each calix receiving one, two, or three papillae. Each papilla shows Fig. 1116. — A section through the cortex of an ape's kidney. beginning of the tubule, is shown. X 350. (Szymonowicz.) upon its apex a number (16 to 20) of minute orifices of the excretory ducts of the pyramid; this perforated area of the apex is called the area ciibrosa (Fig. 1114). The renal colimms (of Berlin) separate the pyramids from one another and consist of cortical masses extending toward the renal sinus. At the sinus ends they contain a considerable amount of white fibrous and adipose tissue. They serve as a passageway for the main bloodvessels, lymphatics, and nerves to and from the parenchyma of the organ. Minute Anatomy. — The uriniferous tubules {tiibuli renales) are in part very convoluted and in part straight and regular. They arise in the cortex, pass into the medulla, return to the cortex, and end at the area cribrosa of" the renal papilla. Each tubule starts at the glomerulus or renal corpuscle {Malpighian body), a small, round, reddish mass, which measurerT20 to 200 /i. "Elaclrorthese ITTrtrTJbdies is composed of two parts, a central glomerulus of vessels, called a Malpighian tuft and a membranous envelope, the Malpighian capsule, or capsule of Boumian, which is the small pouch-like commencement of a uriniferous tubule. The Malpighian tuft, or vascular glomerulus, is a network of convoluted capillary bloodvessels, held together by scanty connective tissue. This capillary network is derived from a small arterial twig, the afferent vessel, which pierces the wall of the capsule, generally at a point opposite to that at which the latter is connected with the tube; and the resulting vein, the efferent vessel. THE KIDNEYS 1351 that at which the latter Is connected with tlie tube; and the resulting arteriole, the efferent vessel, emerges from the capsule at the same point. The afferent vessel is usually the larger of the two (Fig. 1116). The Malpighian or Boivman's capsule, wliich surrounds the glomerulus, is formed of a hyaline membrane, supported by a small amount of connective tissue, which is continuous with the connective tissue of the tube. It is lined on its inner surface by a single layer of squam- ous epithelial cells, which ai-e reflected from the lining membrane to the glomerulus, at the point of entrance or exit of the afferent and efferent vessels. The whole surface of the glomerulus is co\-ered with a continuous layer of the same cells, which rests on a delicate supporting membrane (Fig. 1116). Thus, between the glomerulus and the capsule a space is left, forming a cavity lined by a continuous layer of squamous cells; this cavity varies in size according to the state of secretion and the amount of fluid present in it. In the fetus and young subject the cells are polyhedral or even columnar. At the junction of a tubule with the Malpighian capsule there is a somewhat constricted por- tion which is termed the neck (Fig. 1118). Beyond tliis the tubule becomes convoluted, and ])uiMi('s i\ considerable course in the cortical structiu-e, constituting the proximal or first convo- luted tubule (Figs. 1118 and 1121). After a time the convolutions disappear, and the tubule approaches the medullary portion of the kidney in a more or less spiral manner. This section of the tubule has been called the spiral tube of Schachowa. Throughout this portion of their course the tubuli uriniferi are contained entirely in the cortical structure, and present a fairly uniform calibre. They now enter the medullary portion, suddenly become much smaller, MEDULLAR MEDUL Fig. 1117.— Part of a section through the cortex of the kidney in the direction of the straight tubules. (Toldt.) quite straight in du-ection, and dip down for a variable depth into the pjTamids, constituting the descending hmb of Henle's loop. Bending on themselves, they form what is termed the loop of Henle, and re-ascending, they become suddenly enlarged and again spiral in direction, forming the ascending Umb of Henle's loop, and reenter the cortical structiu-e. In the cortex the tubule again becomes slightly convoluted, and is called the distal or second convoluted tubule (Fig. 1116). This terminates in a narrow arched collecting or junctional tubule, which enters the straight collecting tubule. Each straig'ht collecting tubule {iuhulus renalis recta) passes from the cortex into the medulla, receiving at various intervals in the cortical part of its course several arched collecting tubules. In the medullary pyramid, several straight collecting tubules unite to form from sixteen to twenty papillary or excretory ducts, which empty at the area cribrosa of the renal papilla. As they approach the papilla, their diameter gradually increases. It will be seen from the above description that there is a continous series of tubes from their commencement in the Malpighian bodies to their termination at the orifices on the apices of the pyramids of Malpighi, and that the urine, the excretion of which commences in Bowman's capsule, finds its way through these tubes into the calices of the ureter. Structure of the Uriniferous Tubule. — The uriniferous tubule consists throughout of 1352 THE UBINOGENITAL ORGANS a single layer of epithelial cells resting upon a basement membrane which is supported by a delicate meshwork of retiform connective tissue. The tissue contains the vessels, nerves, and lymphatics. The diameter of the tubule and the size of the cells vary in the different portions. The capsule of Bowman is lined with simple squamous cells, and the renal corpuscle has a diameter of 120 to 200 microns; the neck is lined by simple squaraous cells, and has a diameter of about 15 microns; the proximal convoluted and spiral tubules are lined with irregular columnar cells; the lumen of the tubule is irregular and the diameter averages about 40 microns; the descend- ing limb ofHenle's loop is lined with simple squa- mous cells, and the diameter is from 10 to 1.3 microns; the loop and ascending limb are lined with regular cuboidal cells, and the diameter averages from 23 to 28 microns; the distal con- voluted tubule is lined with irregular columnar cells, the lumen is irregular, and the diameter about 45 microns; the arched connecting tubule is lined with simple cuboidal cells, and the diameter is about 45 microns; the straight col- lecting tubule is lined by columnar cells, and the diameter increases from 45 to 75 microns; the papillary ducts are lined with tall columnar cells, and the diameter reaches 200 to 300 microns. The protoplasm of these cells is granular at the basal end, while the luminal end is striated. The parts of the kidney in which the various portions of the uriniferous tubules lie are as follows: Cortex. — In the labyrinth are found the renal corpuscles, the neck, and the proximal and distal convoluted tubules. In the medullary rays are found the upper ends of the descending and ascending limbs of Henle's loop, the arched collecting tubules, and the upper ends of the straight collecting tubules. Medulla. — Here are found the lower ends of the descending and ascending limbs of Henle's loop, the loop, the straight collecting tubules, and the papillarii ducts. The Renal Bloodvessels. — The kidney is plentifully supplied with blood by the renal artery Fig. 1118. — Diagram of three uriniferous tubules and tlieir relation to a collecting tubule. A. Of a tubule, the Malpighian corpuscle of which is situated • in the lowermost portion of the cortex. B. About the middle of tlie cortex. C. In the outer portion of the cortex, tii. Malpighian corpuscle, v. Vessel porta, n. Neck. p(:. Proximal convoluted portion. es. End segment, dl. Descending limb. al. As- cending limb of tile loop of Henle. dc. Distal convoluted portion. j. Junctional tubule. c. Collecting tubule. (Huber.) Fig. 1119. — Longitu- dinal section of Henle's descending Umb. a. Membrana propria, b. Epithelium. Fig. 1120. — Longitudiniil section of straight tube. a. Cylindrical or cubical epi- thelium, b. Membrana pro- pria. (Figs. 1107 and 1115); a large branch of the abdominal aorta given off at the level of the articular disk between the first and second lumbar vertebrje. The importance of the kidney as an excre- THE KIDNEYS 1353 tory organ is evidenced by the fact that the artery is three times as large as is necessary for the nutrition of an organ of the size of the kidney. Previously to entering tiie kidney, each artery divides into four or five branches, which are distributed to its substance. At the hilum these branches He between the renal vein and ureter, the vein lieing in front, the ureter behind. Each vessel gives off a small branch to the suprarenal glands, the ureter, and the surrounding tissue and nniscles. It has been pointed out by Hyrtl (p. 665) that the renal artery gives off a branch which Hivides and supplies the dorsal portion of the kidney and a larger branch which divides and sup- plies the ventral portion of the kidney. Between these two vascular systems is a nonvascular Interlobular riery and cein Fig. 1121. — Diagrammatic representation of the course of the uriniferous tubules (left) and the kidney vessels (right). The arteries are red. the veins blue; capsules of Bowman, convoluted tubules I order and loops of Henle are black; convoluted tubules II order and collecting tubules gray. I, II, III, IV. Four kidney lobules, a. Vas alTerens. e. Vas efferens. 1. Bowman's capsule. 2. Convoluted tubule I order. 3. Descending limb of loop of Henle. 4. .\scending limb of loop of Henle. 5. Convoluted tubule II order. 6, 7. (Collecting tubules. S. Papillary duct. (Szymonowicz.) zone, called by Robinson the exsanguinated renal zone of Hyrtl. It "is one-half inch dorsal to the external border of the kidney." Frequently there is a second renal artery, which is given off from the abdominal aorta at a lower leveh and supplies the lower portion of the 1354 THE UBINOGENITAL ORGANS '""X kidney. It is termed the accessory renal artery. Within the sinus the renal artery divides into foiu- or five branches, about tlxree-foiu'ths of the blood going to the anterior pyramids and the remainder to the posterior pyramids. Each extremity of the kidney is supplied by a branch which divides into anterior, middle, and posterior branches, which do not anastomose with each other. The branches of the renal arteries pass to the kidney substance between the pyramids and are known as interlobar arteries (arteriae interlohares rents) (Fig. 1117). At the junction of the cortical and medullary portions (the boundary zone) these vessels tiu-n and for a short distance piusue a course parallel to the kidney surface. There are thus formed a series of incomplete vascular arches across the bases of the pyramids, the arcuate arteries (arteriae arci- formes) (Figs. 1113 and 1121). From these arches two sets of vessels come. The vessels of one set go to the periphery and enter the cortex, the intralobular, or cortical arteries, those of the other set pass toward the sinus and enter the medulla. These last vessels are the arteriolae recti (Figs. 1117 and 1121). As the intralobular arteries pass toward the capsule they give off branches to each renal corpuscle, the vasa afEerentia or afferent arterioles. As the arteriole enters the corpuscle it divides into several branches, each of which forms a capillary plexus. The blood from each plexus is collected by a small branch which joins with its fellows to form the vas eflerens or efferent arteriole. These various plexuses constitute a glomerulus or Mal- pighian Tuft (Fig. 1116). On leaving the glomerulus the arteriole forms a capillary network around the adjacent portions of the imniferous tubule. The blood is collected by various channels and emptied into the intralobular vein, which starts in the venae stellatae, beneath the capsule, and empties its blood into the arcuate vein. The arteriolae rectae supply the medulla and are smaller in diameter than the intralobular arteries, and soon form a rich capillary plexus around the tubules of the medulla. The blood is collected by the venae rectae, which empty into the arcuate vein {vena arciformis) at the boun- dary zone. The blood is carried to the cohunns of Bertin, where it continues toward the sinus in the interlobular veins. In the sinus these veins unite to form the renal vein {vena renali^) (Fig. 1107). The nerves of the kidney, although small, are about fifteen in number. They have small ganglia developed upon them, and are derived from the renal plexus, which is formed by branches from the solar plexus, the lower and outer part of the semilunar ganglion and aortic plexus, and from the lesser and smallest splanchnic nerves. They communicate with the spermatic plexus, a circumstance which may explain the occurrence of pain in the testicle in affections of the kidney. So far as they have been traced, they seem to accompany the renal artery and its branches, and they have been traced to the epithelium, but their exact mode of termination is not known. The Lsrmphatics are described on page 796. Variations and Abnormalities. — Congenital absence of the kidney has licrii iil>served. Not unusually one kidney is con- siderably larger than the other; occasionally one is very large and the other is very small, from atrophy, the large organ having become large in response to a functional need, which causes it to compensate for the insufficiency of the small kidney. If a kidney is removed surgically, the other kidney enlarges. As previously stated, the kidneys of the fetus and of the young child show distinct fissures which make each organ lobulated (Fig. 1122). The aihilt kiiliicys frequently exhibit remains of these fissures. A horseshoe kidney is a condition in which the lower extremi- ties of the two kidneys are united by kidney structure, the bond of union crossing the middle line. The strip of kidney tissue which effects the junction may be slight, considerable, or extensive in amount. Sometimes the two kidneys are completely fused together into one large organ with two ureters. Surface Form. — The kidneys, being situated at the back part of the abdominal cavity and deeply situated, cannot be felt unless enlarged or misplaced. They are situated on the confines of the epigastric and umbilical regions internally, with the hypochondriac and lumbar regions externally. The left is somewhat higher than the right. According to Morris, the position of the kidney may be thus defined: Anteriorly: "(1) A horizontal line through the umbilicus is below the lower edge of each kidney. (2^ A vertical line carried upward to the costal arch from the middle of Poupart's ligament has one-third of the kidney to its outer side and two-thirds to its inner side — i. e., between this line and the median line of the body." In adopting these lines it must be borne in mind that the axes of the kidneys are not vertical, but oblicfue, and if con- tinued upward would meei aDout the ninth thoracic vertebra. Posteriorly: The upper end of the left kidney would be defined by a line drawn horizontally outward from the spinous process of the eleventh thoracic vertebra, and its lower end by a point two inches (5 cm.) above the iliac crest. Fig. 1122. — Peta! kidney, showing lobulation, (Testut.) THE KIDNEYS 1355 The right kichit-y would be half to three-quarters of an inch lower. Morris lays clown the fol- lowini' rules for indicating the position of the kidney on the posterior surface of the body: •'(1) A line parallel with, and one inch from, the vertebral column, between the lower edge of the tip of the spinous process of the eleventh thoracic vertebra and the lower edge of the spinous process of the third lumbar vertebra. (2) A line from the top of this first line outward at right angles to it for two and three-quarter inches. (3) A line from the lower end of the first trans- versely outward for two and three-c[uarter inches. (4) A line parallel to the first and connecting the outer extremities of the second and third lines just described." The hilum of the right kidney is two inches from the mesal plane; the hilum of the left one and one-half inches from the mesal plane. A line joining the two hili crosses the vertebral column op]50site the disk between the first and second lumbar vertebrae. Applied Anatomy. — Cases of congenital absence of a kidney, of atrophy of a kidney, and a liiir.s-islinr L-i:liini are of great importance, and must be duly taken into account when neph- rectum)- is c()nlein|)iated. A more common malformation is where the two kidneys are fused together. They may be only joined together at their lower ends by means of a thick mass of renal tissue, so as to form a horseshoe-shaped body, or they may be completely united, forming a disk-like kidney, from which two ureters descend into the bladder. These fused kidneys are generally situated in the middle line of the abdomen, but may be misplaced as well. One or both kidneys may be misplaced as a congenital condition, and remain fixed in this abnormal position. They are then very often misshapen. They may be situated higher or lower than normal or removed farther from the spine than usual or they may be displaced into the iliac fossa, over the sacroiliac joint, on to the promontory of the sacrum, or into the pelvis be- tw-een the rectum and bladder or by the side of the uterus. In these latter cases they may give rise to very serious trouble. The kidney may also be misplaced as a congenital condition, but may not be fixed. It is then known as a floating kidney. It is believed to be due to the fact that the kidney is completely enveloped by peritoneum, which then passes backward to the vertebral column as a double layer, forming a -mesonephron, which permits of movements taking place. The kidney may also be misplaced as an acquired condition; in these cases the kidney is mobile in the tissues by which it is surrounded, either moving in or moving with its fatty capsule. This condition is known as movable kidney {nephroptosis), and is more common in the female than in the male, and on the right than the left side. If a displaced kidney becomes fixed in an abnormal position, it is said to be dislocated. Movable kidney cannot be distinguished from floating kidney until the kidney is exposed by incision. Other malformations are the persist- ence of the fetal lobulation; the presence of two pelves or two ureters to the one kidney. In some rare instances a third kidney may be present. The kidney is embedded in a large quantity of loose fatty tissue, and is but partially covered by peritoneum; hence rupture of this organ is not nearly so serious an accident as rupture of the liver or spleen, since the extravasation of blood and urine which follows is, in the majority of cases, outside the peritoneal cavity. Occasionally the kidney may be bruised by blows in the loin or by being compressed between the lower ribs and the ilium when the body is violently bent forward. This is followed by a little transient hematuria, which, however, speedily passes off. Occasionally, when rupture involves the pelvis of the ureter or the commencement of the ureter, this duct may become blocked, and hydroiiephrosis follows. The loose cellular tissue around the kidney may be the seat of suppuration, constituting perinephritic abscess. This may be due to injury, to disease of the kidney itself, or to extension of inflammation, from neighboring parts. The abscess may burst into the pleura, causing empyema ; into the colon or bladder ; or may point externally in the groin or loin. Tumors of the kidney, of w-hich, perhaps, sarcoma in children is the most common, may be recognized by their position and fixity; by the resonant colon lying in front of it; by their not moving with respira- tion; and by their rounded outline, not presenting a notched anterior margin like the spleen, with which they are most likely to be confounded. The examination of the kidney should be bimanual; that is to say, one hand should be placed in the flank and firm pressure made forward, while the other hand is buried in the abdominal wall, over the situation of the organ. Manipulation of the kidney frequently produces a peculiar sickening sensation and some faintness. The kidney is frequently attacked surgically. It may be exposed and opened for exploration or the evacuation of pus {nephrotomy); it may be incised for the removal of stone {nephro- lithotomy); it may be sutured when wounded {nephrorrhaphy); it may be fixed in place by sutures {nephropexy) or gauze pads when movable or floating; or it may be removed {nephreo- tomy). The kidney may be exposed either by a lumbar or abdominal incision. The operation is best performed by' a lumbar incision, except in a case of very large tumor or of wandering kid- ney with a loose "mesonephron, on account of the advantages which it possesses of not opening the peritoneum and of aft'ording admirable drainage. It may be performed either by an olslique, a vertical, or a transverse incision. A common incision for exposing the kidney begins an inch below the twelfth rib, at the margin of the Erector spinae muscle, and passes obliquely down- 1356 THE VRINOQENITAL ORGANS ward and forward, exposing the anterior border of the Latissimus dorsi and the posterior border of the Internal oblique. The surgeon divides the posterior leaflet of the lumbar fascia, dra^s aside or incises the Quadratus lumborum, and cuts the anterior leaflet of the lumbar fascia and also the transversalis fascia. He opens the fatty capsule down to the kidney and strips it from the true capsule, bringing the kidney outside of the body for inspection. The vertical incision at the edge of the Erector spinae muscle is frequently used. A gridiron or muscle-splitting operation is used by some in order to avoid the division of nerves, vessels, and muscle fibres. The abdominal operation is best performed by an incision in the linea semilunaris on the side of the kidney to be removed, as recommended by Langenbuch; the kidney is then reached from the outer side of the colon, ascending or descending, as the case may be, and the vessels of the colon are not interfered with. If the incision were made in the linea alba, the kidney would be reached from the inner side of the colon, and the vessels running to supply the colon would necessarily be interfered with. The incision is made of varying length according to the size of the kidney, and commences just below the costal arch. The abdominal cavity is opened. The intestines are held aside, and the outer layer of the mesocolon incised, so that the fingers can be introduced behind the peritoneum and the renal vessels are sought for. These vessels are then to be ligated; if tied separately, care must be taken to ligate the artery first. The kidney must now be enucleated, and the vessels and the ureter divided, and the latter disinfected and tied, and, if it is thought necessary, stitched to the edge of the wound. THE URETERS (Figs. 1106, 1115). The ureters are the two tubes which convey, the urine from the kidneys into the bladder. Each ureter commences within the sinus of the corresponding kidney by a number of short cup-shaped branches, the minor caUces or infun- dibula, which unite either directly or indirectly to form a dilated pouch, the pelvis (Fig. 1115), from which the ureter, after passing through the hilum of the kidney, descends to the bladder. The minor caMces encircle the apices of the renal papillse; but inasmvich as one calix may include two or even more papillae, their number is generally less than the pyramids themselves. The minor calices vary in number from ten to twenty or more. These calices con- verge into two or three tubular di\'isions, the major calices, which by their junction form the pelvis or dilated portion of the ureter, which is situated be- hind the renal vessels and which lies partly within and partlj' outside the renal sinus. It is usually placed on a level with the spinous process of the first lumbar vertebra. The ureter proper is a cylindrical membranous tube, about ten to twelve inches (25 to 30 cm.) in length and about one-sixth inch (4 mm.) in diameter, directly continuous near the lower end of the kidney with the tapering extrem- ity of the pelvis. Its walls are from 1 to 2 mm. thick, and its calibre va- ries. It exhibits four main constrictions — (1) at its junction with its pelvis; (2) as it passes over the brim of the pelvis; (3) as it enters the bladder; (4) at its termination. Its course is obliquely downward and inward through the lumbar region {fars abdoniinalis) (Fig. 1106), into the cavity of the pelvis {pars ■pelvina) (Fig. 1124), where it passes downward, forward, and inward across that cavity to the base of the bladder, into which it then opens by a constricted orifice {orificium ureterw) (Fig. 1134), after having passed obliquely for nearly an inch between the vesical muscular and mucous coats (Fig. 1123). The lower part of the abdominal portion of the ureter exhibits a spindle-shaped dilatation. Relations (Fig. 1124). — The ahiominal -part lies behind the peritoneiun on the inner part of the Psoas muscle, and is crossed obliquely by the spermatic or ovarian vessels. It enters the pelvic cavity by crossing either the termination of the common, or the commencement of the external, iliac vessels. At its origin the right ureter is usually covered by the second part of the duodenum, and in its THE URETERS 1357 course downward lies to the right of the inferior vena cava and is crossed by the right colic artery, while near the pelvic brim it passes behind the lower part of the mesentery and the terminal part of the ileum. The left ureter is crossed by the left colic artery, and near the brim of the pelvis passes behind the sig- moid colon and its mesentery. The pelvic part runs at first downward on the lateral wall of the pelvic cavity under cover of the peritoneum, lying in front of the internal iliac vessels and on the inner side of the impervious part of the hypogastric artery and the obturator nerve and vessels. Opposite the lower part of the great sacrosciatic foramen it inclines inward behind the vas def- erens (which crosses to its inner side) and reaches the base of the bladder, where in the male it is situated in front of the up[)er end of the seminal vesicle and at a distance of about two inches from the opposite ureter. Finally, the ureters run obliquely for about three-quarters of an inch through the wall of the bladder and open by sht-like apertures into the " ca\-ity of that viscus_ at the lateral angles of the trigone. „eft°od oVentri;c?rf''thTurlterT^to When the bladder is distended the openings of the ureters are the bladder. (F. H. Gerrish.) about two inches apart, but when it is empty and contracted the distance between them is diminished by one-half. Owing to their oblique course through the coats of the bladder, their upper and lower walls become closely applied to each other when the viscus is distended, and, acting as a valve, prevent regurgitation of urine from the bladder. In the female, the ureter forms, as it lies in relation to the wall of the pelvis, the posterior boun- dary of a shallow depression named the ovarian fossa, in which the ovary is situated. It then rims inward and forward on the lateral aspect of the cervix of the uterus and of the upper part of the vagina to reach the base of the bladder. In this part of its course it is accompanied for RIGHT URET APPENDIX (drawn up under) il\^) Fig. H24 — The relations of the pelvic mesocolon with the wall the iliac sigmoid arteries, and the ureter (Poirier and Charp> ) nd superior hemorrhoidal about an inch by the uterine artery, which then crosses in front of the ureter and ascends between the two layers of the broad ligament. The ureter is distant about three-quarters of an inch from the lateral aspect of the neck of the uterus. The ureter is sometimes double, and the two tubes may remain distinct as far as the base of the bladder. On rare occasions they open separately into the bladder cavity. 1358 THE URINOGENITAL 0RGA2s^S Structure. — The ureter is composed of three coats — fibrous, muscular, and mucous. The fibrous coat (tunica adventitia) is the same throughout the entire length of the duct, being continuous at one end with the fibrous capsule of the kidney at the floor of the sinus, while at the other it is lost in the fibrous structure of the bladder. In the pelvis of the ureter the muscular coat (tunica muscularis) consists of tw-o layers, an internal longitudinal and an external circular; the longitudinal fibres become lost upon the sides of the papillae at the extremities of the calices; while the circular fibres become more prom- inent and resemble a small sphincter. In the ureter proper the muscle layers are very distinct, and are three in number — an external longitudinal (stratum externum), a middle circular (stratum medium), and an internal longitudinal layer (stratum internum). The external longi- tudinal layer is found more prominent in the lower half or lower third of the ureter. The mucous coat (tunica mucosa) is smooth, and presents a few longitudinal folds which be- come effaced by distention. It is continuous with the mucous membrane of the bladder below, while above it is prolonged over the papillie of the kidney. Its epithelium is of a peculiar char- acter, and resembles that found in the bladder. It is known by the name of transitional epi- thelium. It consists of several layers of cells, of which the innermost — that is to say, the cells in contact with the urine — are quadrilateral in shape, with concave margins on their outer surface, into which fit the rounded ends of the cells of the second layer. These, the intermediate cells, more or less resemble columnar epithelium, and are pear-shaped, w-ith a rounded internal ex- tremity, which fits into the concavity of the cells of the first layer, and a narrow external extremity which is wedged in between the cells of the third layer. The external or third layer consists of conical or oval cells varying in number in different parts, and presenting processes which extend down into the basement membrane. A few racemose glands are at times seen in the mucous coat. Vessels and Nerves. — The arteries supplying the ureter are branches from the renal, sper- matic, internal iliac, and inferior vesical. The nerves are derived from the inferior mesenteric, spermatic, and pelvic plexuses. Applied Anatomy. — Subcutaneous rupture of the ureter is not a common accident, but occa- sionally occurs from a sharp direct blow on the abdomen, as from the kick of a horse. The ureter may be either torn completely across, or only partially divided, and, as a rule, the peritoneum escapes injury. If torn completely across, the urine collects in the retroperitoneal tissues; if it is not completely divided, the lumen of the tube may become obstructed and hydronephrosis or pyonephrosis results. The ureter may be accidentally wounded in some abdominal operations; if this should happen, the divided ends must be sutured together, or, failing to accomplish this, the upper end must be implanted into the bladder or the intestine. Stones (calculi) not uncommonly become impacted in the ureter. This may occur at any part, but most commonly either at the point where the tube is crossing the pelvic brim or at the termination, where it is passing obliquely through the muscular wall of the bladder. In the former case, an incision with its centre opposite and one inch internal to the anterior superior spine of the ilium dividing all the structiu'es down to the peritoneum, enables the operator to reach the ureter by pushing the unopened peritoneum inward; the stone can then be felt in the ureter, the wall of which is incised, and the stone extracted, free drainage being provided for the escaping urine. ^Vhen the stone is impacted at the vesical end of the tube a preliminary incision into the bladder is required, and by scratching through the mucous membrane overlying it the calculus can then be removed. The diagnosis of ureteral calculus is sometimes made by an a;-ray examination. In identifying any shadows in the picture thus secured, caution must be exercised not to mistake similar shadows thrown by ■periureteral phleboliths in the pelvic veins as ureteral calculi.' THE URINARY BLADDER (VESICA URINARIA) (Figs. 1127, 1128). The urinary bladder is a musculomembranous sac situated in the pelvis, behind the pubes, and in front of the rectum in the male, the cervix uteri and vagina intervening between it and that intestine in the female. The shape, position, and relations of the bladder are greatly influenced by age, sex, and the degree of distention of the organ. During infancy it is conical in shape, and projects above the symphysis pubis into the hypogastric region. In the adxdt cadaver, when quite empty and collapsed (Figs. 1125 and 1126), it is cup-shaped, and on vertical median section its cavity, with the adjacent portion of the urethra, presents a Y-shaped cleft, the stem of the Y corresponding to the urethra. It is placed 1 Consult article by George O. Clark in Annals of Surgery, 1909. p. 913. THE URINARY BLADDER 1359 deeply in the pelvis, flattened from before backward, and reaches as high as the upper border of the symphysis pubis. When empty and contracted, and as seen immediately after death (as after electrocution) , the bladder is nearly spher- ical in shape. When slightly distended, it has a rounded form, and is still con- tained within the pelvic cavity (Fig. 1126), and when greatly distended (Figs. 1126 and 1182), it is ovoid in shape, rising into the abdominal cavity, and often extend- FlG. 1125. — The empty bladder. (Poirier and Charpy.) Fig. 1126.— Modifications of form of the bladder during distention. (Poirier and Charpy.) ing nearly as high as the umbilicus. It is larger in its vertical diameter than from side to side, and its long axis is directed from above obliquely downward and backward, in a line directed from some point between the symphysis pubis and umbilicus (according to its distention) to the end of the coccyx. The bladder, when distended, is slightly curved forward toward the anterior wall of the abdo- men, so as to be more convex behind than in front. When moderately distended, it measures about five and one-half inches (14 cm.) in the vertical di- ameter, four and one-half inches (12 cm.) across, and three inches (10 cm.) antero-posteriorly. In the female it is larger in the transverse than in the vertical diameter, and its capacity is said to be greater than in the male. The ordinary amount which it can contain with- out serious discomfort is about a pint. The bladder is divided for pur- poses of description into a superior, an antero-inferior, and two lateral surfaces, a base or fundus, and a summit or apex. Surfaces. — The superior or ab- dominal surface (Figs. 994 and 1106) is entirely free, and is invested throughout by peritoneum. It looks almost directly upward into the abdominal cavity, and extends in an antero-posterior direction from the apex to the base of the bladder. It is in relation with the small intestine and sometimes with the sig- moid flexure, and, in the female, with the uterus. On each side, in the male, a portion of the vas deferens is in contact with the hinder part of this surface, lying beneath the peritoneum. In the relaxed and empty condition of the blad- der a transverse fold of peritoneum {plica vesicalis transversa) is formed on this surface. Fig. 1127.— Mesal 1360 THE UBINOGENITAL ORGANS The antero-inferior or pubic surface (Figs. 337 and 1128) looks downward and forward. In the undistended condition it is uncovered by peritoneum, and is in relation with the Obturator internus muscle on each side, with the rectovesical fascia, and anterior true ligaments of the bladder. It is separated from the body of the pubis by a triangular interval, occupied by fatty tissue, the pubovesical space of Retzius. As the bladder ascends into the abdominal cavity during dis- tention the distance between its apex and the umbilicus is necessarily diminished, and the urachus (Figs. 994 and 1128) is thus relaxed; so that, instead of passing directly upward to the umbilicus, it descends first on the upper part of the anterior surface of the bladder, and then curving upward, ascends on the back of the abdominal wall. The peritoneum, which follows the urachus, thus comes to form a pouch of varying depth between the anterior surface of the viscus and the Prostatic plexxis of veins. Prepuce.- FiG. 112S. — Vertical section of bladder, penis, and urethra. abdominal wall (Fig. 337) . The pouch passes to the neighborhood of the internal abdominal rings. Thus, when the bladder is distended, the upper part of its anterior surface is in relation with the urachus and is covered by peritoneum. The lower part of its anterior surface, for a distance of about two inches above the symphysis pubis, is devoid of peritoneum, and is in contact with the abdominal wall. The lateral surfaces are invested behind and above by peritoneum, which extends as low as the level of the impervious hypogastric artery; below and in front of this, these surfaces are uncovered by peritoneum, and are separated from the Levatores ani muscles and the walls of the pelvis by a quantity of loose areolar tissue contain- ing fat. In front this surface is connected to the rectovesical fascia by a broad expansion on either side, the lateral true ligaments. The vas deferens crosses the THE URINARY BLADDER 1361 hinder part of the lateral surface obliquely, and passes between the ureter and the bladder. When the bladder is emjity the peritoneum descends on the pelvic wall as low as the lateral border of the bladder and enters a groove known as the paravesical fossa. The lateral surfaces, the pubic surface, and the abdominal surface together constitute the body of the bladder (corjms vesicae). The fundus or base {fundus vesicae) (Figs. 1128 and 1152) is directed downward and backward, and is partly covered by peritoneum. In the male the upper por- tion, to within about an inch and a half of the prostate, is covered by the recto- vesical pouch of peritoneum (Fig. 998). The lower part is in direct contact with the anterior wall of the second part of the rectum, the seminal vesicles, and the vasa deferentia (Figs. 1 128 and 1 135) . The ureters enter the bladder at the upper part of its base, about an inch and a half above the base of the prostate gland (Fig. 1128). The portion of the bladder in relation with the rectum corresponds to a tri- angular space, bounded helow, by the prostate gland; above, by the rectovesical fold of the peritoneum; and on each side, by the seminal vesicles and the vas de- ferens. It is separated from direct contact with the rectum by the rectovesical fascia. When the bladder is very full, the peritoneal fold is raised with it, and the distance between its reflection and the anus is about four inches; but this distance is much diminished when the bladder is empty and contracted. In the female, the base of the bladder is connected to the anterior aspect of the cervix uteri by areolar tissue, and is adherent to the anterior wall of the vagina (Fig. 996). Its upper surface is separated from the anterior surface of the body of the uterus by the uterovesical pouch of the peritoneum (Fig. 996). The so-called neck or cervix of the bladder {collum vesicae), the fixed portion of this viscus, is the point of commencement of the urethra; there is, however, no tapering part, which would constitute a true neck, but the bladder suddenly contracts to the opening of the urethra (Fig. 337). In the male it is surrounded by the prostate gland and its direction is oblique when the individual is in the erect posture (Figs. 337 and 1128). In the female its direction is obhquely downward and forward. The so-called neck is the most fixed portion of the bladder, and is located one inch (2.5 cm.) behind the junction of the inferior and middle thirds of the symphysis pubis; or two inches (5 cm.) behind and below the superior border of the symphysis. The sumniit or apex (vertex vesicae) is the portion of the bladder which when that organ is empty or nearly empty is nearest to the upper border of the symphysis. It is directed upward and forward. In a distended bladder the apex is well above the pubes in the abdominal cavity. The urachus or middle umbilical ligament (Ugamentum umbilicale medium) (Fig. 994) is the impervious remains of the tubular canal of the allantois, which existed in the embryo, and a portion of which expanded to form the bladder. It passes upward, from the apex of the bladder, between the transversalis fascia and peritoneum, to the umbilicus, becoming thinner as it ascends. It is composed of fibrous tissue, mixed with plain muscle fibres. ■ The urachus causes the formation of a peritoneal fold, the phca umbiUcalis media (Fig. V)94). On each side of it is placed a fibrous cord, the imperious portion of the hypogastric artery, which, passing upward from the side of the bladder, approaches the urachus above its summit. Over each cord is the fold known as the plica umbihcahs lateraUs (Fig. 994). In the infant, at birth, the urachus is occasionally found pervious, so diat the urine escapes at the umbilicus, and calculi have been found in its canal. Ligaments. — ^The bladder is retained in its place by ligaments, which are divided into true and false. The true ligaments are five in number — two anterior, two lateral, and the urachus. The false ligaments, also five in number, consist of folds of the peritoneum. 1362 THE URINOGENriAL ORGANS The two anterior true ligaments or puboprostatic ligaments (ligamenta pubo' prostaiica) extend from the back of the ossa pubis, one on each side of the sym- physis, to the front of the neck of the bladder, over the anterior surface of the prostate gland. The two lateral true ligaments, formed by expansions from the fascia lining the lateral wall of the pelvis, are broader and thinner than the preceding. They are attached to the lateral parts of the prostate gland and to the sides of the base of the bladder. The urachus or middle umbilical ligament is the fibromuscular cord already men- tioned, extending between the summit of the bladder and the umbilicus. The two posterior false ligaments pass forward, in the male, from the sides of the rectum (plicae rectovesicales) ; in the female, from the sides of the uterus {plicae vesicouterinae), to the posterior and lateral aspect of the bladder; they form in the male the lateral boundaries of the rectovesical pouch (excavatio rectovesicalis (Figs. 337 and 1067) ; in the female the peritoneum is reflected from the rectum to tlie upper part of the posterior vaginal wall, forming the rectovaginal pouch Fig. 1129.— Fibn longitudinal layer, Charpy . ) ! of the external (Poirier and Fig, 1130.— Fibres of the middle Fig. 1131.— Fibres of the inter- or circular layer. (Poirier and nal longitudinal \ayer. (Poirier Charpy.) and Charpy.) or pouch of Douglas (Fig. 1068). It is continued over the posterior surface and fundus of the uterus on to its anterior surface and then to the bladder, forming here a second but shallower pouch, the uterovesical pouch, bounded on either side by the uterovesical or posterior false ligaments of the bladder. The poste- rior false ligaments contain the impervious hypogastric arteries and the ureters, together with vessels and nerves. In the base of each fold is smooth muscle fibre, the Rectovesical muscle (m. rectovesicalis). The two lateral false ligaments are reflections of the peritoneum, from the iliac fossfe and lateral walls of the pelvis to the sides of the bladder. Each lateral false ligament (ligameutum umhilicale laterale) passes in front into the pUca umbilicalis lateralis over the corresponding hypogastric artery. The two lateral reflections of peritoneum are continuous in front of the apex of the bladder, at which point the peritoneum passes upon the urachus. The superior or anterior false ligament (plica umbilicus media; suspensory liga- ment) is the prominent fold of peritoneum extending from the summit of the bladder to the umbilicus. It is carried off from the bladder by the urachus. The THE VBINARY BLADDER 1363 peritoneal fold over each imper\ious hypogastric artery is called the plica umbili- calis lateralis (Fig. 994), and is the prolongation forward of the ligamentum nmbil- icale laterale. Besides the true and false ligaments, the bladder receives support from the fibrous tissue and unstriated muscle about the seminal vesicles, and ter- minations of the ureters and vasa deferentia. In the female the connection with the anterior vaginal wall supports the base of the bladder. In both sexes the most solidly fixed part of the bladder is about the internal orifice of the urethra. Structure. — The bladder is composed of tliree coats — fibrous, muscvilar, and mucous. Tlie fibrous coat (tunica fi})r(tsa) consists of white fibrous tissue, which supports the other coats. It is partially in\fsted by peritonevim. The muscular coat {tunica niuscularis) (Figs. 1129, 1130, and 1131) consists of three incom- pletely differentiated layers of unstriped muscular fibre — an external layer, composed of fibres having for the most part a longitudinal arrangement; a middle layer, in which the fibres are arranged, more or less, in a circular manner; and an internal layer, in which the fibres have a general longitudinal arrangement. The fibres of the external longitudinal layer (stratum externum) arise from the posterior sur- face of the body of the os pubis in both sexes (m. pubovesicalis), and in the male arise also from the adjacent part of the prostate gland and its capsule. They pass, in a more or less longitudinal manner, up the anterior surface of the bladder, over its apex, and then descend along its pos- terior surface to its base, where they become attached to the prostate in the male ami to ihe front of the vagina in the female. At the sides of the bladder the fibres are arranged iibii(|iicly and intersect one another. The external longitudinal layer has been named the Detrusor urinae muscle. The middle circular layers (stratum medium) are very thinly and irregularly scattered on the body of the organ, and, though to some extent placed transversely to the long axis of the bladder, are for the most part arranged obliquely. Toward the lower j)art of the bladder, around the neck and the commencement of the urethra, they are disposed in a thick circular layer, forming the sphincter vesicae, which is continuQus with the muscle fibres of the prostate gland. The internal longitudinal layer (stratum internum) is thin, and its fasciculi have a reticular arrangement, but with a tendency to assume for the most part a longitudinal direction. Two bands of oblique fibres, originating behind the orifices of the ureters, converge to the back part of the prostate gland, and are iusrrtnJ, by means of a (ibroiis process, into the so-called middle lobe of that organ. They are the muscles of the ureters, described by Sir C. Bell, who supposed that during the contraction of the bladder they served to retain the oblique direction of the ureters, and so prevent the reflux of the urine into them. Fig. 1132. — Superficial layer of the epitfielium of Fig. 1133. — Deep layers of epithelium of bladder, the bladder. Composed of polyhedral cells of vari- showing large club-shaped cells above, and smaller, ous sizes, each with one, two, or three nuclei. (Klein more spindle-shaped cells below, each with an oval and Noble Smith.) nucleus. (Klein and Noble Smith.) The mucous coat (tunica mucosa) is thin, smooth, and of a pale rosefolor. It is continuous above through the ureters with the lining membrane of the uriniferous tubes, and below with that of the urethra. Except at the trigone, it is connected very loosely to the muscular coat by a layer of areolar tissue, and is therefore thrown into folds or rugfe when the bladder is empty (Fig. 1135). The epitheliiim covering it is of the transitional variety, consisting of a superficial layer of polyhedral flattened cells, each with one, two, or three nuclei (Fig. 1132); beneath these is a stratum of large club-shaped cells with the narrow extremity of each cell du-ected downward and wedged in between smaller spindle-shaped cells, each with an oval nucleus (Fig. 1133). There are no true glands in the mucous membrane of the bladder, though certain mucous follicles 1364 THE VBINOGENITAL ORGANS which exist, especially near the neck of the bladder, have been regarded as such. The epithelial cells rest upon a basement membrane, beneath which is the fibroelastic tunica propria, which contains diffuse lymphoid tissue, and in which solitary nodules have been found. \ BIDGE FORMED BV INTERURETEHAL MUSCLE UVULA VESICAE Fig. 1134.— The interior of the bl wing the vesical trigone. (Poirier and Charpy.) The Interior of the Bladder. — Upon the inner surface of the bladder are seen the mucous membrane, orifices of the ureters, the trigone, and the commencement of the urethra. ~' -l4jj FIBRES W OR,F,CEOF CIRCULAR -TRIGONE TRANSVERSE RES OF LONGITUOINAl FIBRES OF TRIGONE Fig. 1135. — The internal surface of the bladder. (Poirier and Charpy.) The mucous membrane of the empty bladder is thrown into folds or ruga, except over the trigone, where it is firmly adherent to the muscular coat and is smooth (Figs. 1134 and 1135). The folds disappear when the bladder is distended. THE URINARY BLADDER 1365 The vesical trigone or the trigonum vesicae (Fig. 1135) Is a smooth, triangular surface, with the apex directed forward, situated at the base of the bladder, imme- diately behind the urethral orifice. It represents an equilateral triangle, the sides measuring about one inch in the empty bladder and increasing to about one and one-half inches in the distended bladder. It is paler in color than the rest of the interior, and never presents anj' rugae, even in the contracted condition of the organ, owing to the intimate adhesion of its mucous membrane to the subjacent tissue. It is bounded at each basal angle by the orifice of a ureter, and at its apex by the orifice of the urethra. Projecting from the lower and anterior part of the bladder, and reaching to the orifice of the urethra, is a slight elevation of mucous membrane, particularly prominent in old persons, called the uvula vesicae. Stretching from one ureteral opening to the other is a smooth, slightly curved ridge (torus interuretericus), the convexity of which is toward the urethra. It is produced by transverse muscle fibres beneath the mucous membrane. The outer prolongations of this ridge beyond the ureteral orifices are called the ureteral folds {plicae uretericae). They are formed by the ureters as they traverse the bladder wall. About the urethral orifice are slight radial folds of mucous membrane, which are continuous with the longitudinal folds of the prostatic urethra. The internal urethral orifice (orificium urethrae internum) is sickle-shaped and is surrounded by a circular prominence {annulus urethralis), which is most dis- tinct in the male. Vessels and Nerves. — The arteries (Fig. 472) supplying the bladder are the superior, middle, and inferior vesical in the male, with additional branches from the uterine and vaginal in the female. They are all derived from the anterior trunk of the internal iliac. The obturator and sciatic arteries also supply small visceral branches to the bladder. The veins form a com- pllraicd plexus around the neck, sides, and base of the bladder (Fig. 524). The veins communi- cate below with tlie plexus about the prostate and terminate in the internal iliac vein. The lymphatics are few in number; they form two plexuses, one in the muscular and another in the deep tissue of the mucous coat, and accompany the bloodvessels. The subepithelial portion of the mucous membrane of the bladder contains no lymphatics whatever (Sappey). The mus- cular tissue contains a few lymphatics. The subperitoneal tissues contain the usual number. The collecting trunks from the anterior surface terminate in the external iliac nodes. The trunks from the posterior surfa>:'e terminate in tlie internal iliac nodes, the hjrpogastric nodes, and the nodes in front of the sacral promontory. The nerves are derived from the pelvic plexus of the sympathetic and from the third and fourth sacral nerves ; the former supplying the upper part of the organ, the latter its base and neck. According to F. Darwin, the sympathetic fibres have ganglia connected with them, which send branches to the vessels and to the muscular coat. Surface Form. — The surface form of the bladder varies with its degree of distention and under other circumstances. In the young child it is represented by a conical figure, the apex of which, even when the viscus is empty, is situated in the hypogastric region, about an inch above the level of the symphysis pubis. In the adult, when the bladder is empty, its apex does not reach above the level of the upper border of the symphysis pubis, and the whole organ is situated in the pelvis; the neck, in the male, corresponding to a line drawn horizontally backward through the symphysis a little below its middle. As the bladder becomes distended, it gradually rises out of the pelvis into the abdomen, and forms a swelling in the hypogastric region, which is jierceptible to the hand as well as to percussion. In extreme distention it reaches into the umbili- cal region. Under these circumstances the lower part of its anterior surface, for a distance of about two inches above the symphysis pubis, is closely applied to the abdominal wall, without the intervention of peritoneum, so that it can be tapped by an opening in the middle line just above the symphysis pubis, without any fear of wounding the peritoneum. When the rectum is distended, the prostatic portion of 'the urethra is elongated and the bladder lifted out of the pelvis and the peritoneum pushed upward. Advantage is taken of this by some sur- geons in performing the operation of suprapubic oystotomy. The rectum is distended by a rubber bag, which is introduced into this cavity empty, and is then filled with ten or twelve ounces of water. If, now, the bladder is injected with about half a pint of some antiseptic fluid it will appear above the pubes plainly perceptible to the sight and touch. The peritoneum will be pushed out of the way, and an incision three inches lotig may be made in the hnea alba, from the symphysis pubis upward, without any great risk of wounding the peritoneum. Other 1366 THE UBINOGENITAL ORGANS surgeons object to the employment of this bag, as its use is not unattended with risk, since it causes pressure on the prostatic veins and hence produces congestion of the vessels over the bladder and a good deal of venous hemorrhage. When distended, the bladder can be felt in the male, from the rectum, behind the prostate, and fluctuation can be perceived by a bimanual examination, one finger being introduced into the rectum and the distended bladder being tapped on the front of the abdomen with the finger of the other hand. This portion of the bladder — that is, the portion felt in the rectum by the finger — is uncovered by peritoneum. Applied Anatomy. — A certain defect of development in which the bladder is implicated is known under the name of extroversion of the bladder. In this condition the lower part of the abdominal wall and the anterior wall of the bladder are wanting, so that the posterior surface of the bladder presents on the abdominal surface, and is pushed forward by the pressure of the viscera within the abdomen, forming a red, vascular protrusion, on which the openings of the ureters are visible. The penis, except the glans, is rudimentary, and is cleft on its dorsal sur- face, exposing the floor of the urethra — a condition known as epispadias. The pelvic bones are also arrested in development (see p. 220). The bladder may be ruptured by violence applied to the abdominal wall when the viscus is distended without injury to the bony pelvis, or it may be torn in case of fracture of the pelvis. The rupture may be either intraperitoneal or extraperitoneal, that is — may implicate the superior surface of the bladder in the former case, or one of the other surfaces in the latter. Rupture of the antero-inferior surface alone is, however, very rare. Until recently intraperitoneal rupture was uniformly fatal, but now abdominal section and suturing the rent with Lembert sutures often saves the patient. The sutures are inserted only through the peritoneal and muscular coats in such a way as to bring the serous surfaces at the margin of the wound into apposition, and one is also inserted just beyond each end of the wound. The bladder should be tested as to whether it is water-tight before closing the external incision. The muscular coat of the bladder undergoes hypertrophy in cases in which there is any per- sistent obstruction to the flow of urine. Under these circumstances the bundles of which the muscular coat consists become much increased in size, and, interlacing in all directions, give rise to what is known as \he fasciculated bladder. Between these bundles of muscle fibres the mucous membrane may bulge out, forming sacculi, constituting the sacculated bladdfr, and in these little pouches phosphatic concretions may collect, forming encysted calculi. The mucous membrane is very loose and lax, except over the trigone, to allow of the distention of the viscus. Various forms of tumors have been found springing from the wall of the bladder. The inno- cent tumors are the papilloma and the mucous polypus, arising from the mucous membrane; the fibrous tumor, from the deep mucous tissue; and the myoma, originating in the muscle tissue; and, very rarely, dermoid tumors, the exact origin of which it is difficult to explain. Of the malignant tumors, epitheliomata are the most common, but sarcomata are occasionally found in the bladders of children. Puncture of the bladder is performed above the pubes without wounding the peritoneum. Suprapubic cystotomy is considered above under the heading of Surface Form. This operation may be employed to permit of the removal of a calculus, and is then called suprapubic lithotomy. THE MALE URETHRA (URETHRA VIRILIS) (Figs. 1136, 1137). The urethra in the male extends from the neck of the bladder at the internal orifice of the urethra {orificmm urethrae internum) to the meatus urinarius, the external orifice of the urethra {orificium urethrae externum), at the end of the penis. The internal orifice has been described (p. 1363). The urethra presents a double curve in the flaccid state of the penis (Fig. 1128), but in the erect state of this organ it forms only a single curve, the concavitj^ of which is directed upAvard. It presents three important constrictions — (1) at the beginning, (2) in the mem- branous portion, (3) at the end. Its length varies from seA'en to eight inches (17 to 20 cm.); and it is divided into three portions, the prostatic, membranous, and spongy, the structure and relations of which are essentially different. Except during the passage of the urine or semen, the urethra is a mere transverse, T- shaped, or crescentic cleft or slit (Fig. 1137), with its upper and under surfaces in contact. At the meatus urinarius the slit is vertical, and in the prostatic portion somewhat arched (Fig. 1137). The prostatic portion (jmrs prostatica) (Figs. 1136 and 1171), the AA-idest part of the canal, is about an inch in length. It is between the internal orifice THE MALE URETHRA 1.367 of the urethra and the deep layer of the triangular ligament and lies within the pelvic cavity. It passes almost vertically through the prostate gland from its base to its apex, lying nearer its anterior than its posterior surface. The gland seeTus to completely surround this portion of the urethra (Fig. 1166), but the glandular substance proper does not (Fig. 1169). The gland is like a clasp open in front, and the open part of the clasp is closed by the prostatic muscle. The form of the canal is spindle-shaped, being wider in the middle than at either extremity, and narrowest below, where it joins the membranous portion. Except during the passage of fluid, the canal is in a collapsed state and is horseshoe-shaped on trans-section, the anterior M'all resting upon the posterior wall (Fig. 1137), and the mucous membrane exhibiting longi- tudinal folds. When distended, the largest portion of the prostatic urethra in the ca- daver has a diameter of about one-half inch (12 mm.). Upon the posterior wall or floor of the canal is a narrow longitudinal ridge, the verumontanum or caput gallinaginis (Figs. 1136 and 1171) {crista iirethralis), formed by an elevation of the mucous membrane and its subjacent tissue (Fig. 1170). It is about 16 mm. in length and about 3 mm. in height, and contains, according to Kobelt, muscle and erectile tissues. On either side of the verumontanum is a slightly depressed fossa, the prostatic sinus, the floor of which is perforated by numerous aper- tures, the orifices of the prostatic ducts (Figs. 1136 and 1171), from the lateral lobes of the glands; the ducts of the middle lobe open behind the verumontanum. At the forepart of the verumontanum, in the middle line, is a depression, the sinus pocularis {idriculus prostaticus) (Figs. 337 and 1171), upon the margins of which are the slit-like openings of the ejaculatory ducts (Fig. 1171). The sinus pocularis forms a cul-de-sac about a quarter of an inch in length, which runs upward and backward in the substance of the prostate into the so-called middle lobe; its prominent ante- rior wall partly forms the verumontanum. Its walls are composed of fibrous tissue, muscle fibres, and mucous membrane, and numerous small glands open on its inner surface. It has been called the uterus masculinus, because it is developed from the united lower ends of the atrophied JMiillerian ducts, and therefore is homologous with the uterus and vagina in the female. The membranous portion {fars memhranacea) (Figs. 1128 and 1136) lies between the two layers of the triangular ligament, and extends downward and for- ward between the apex of the prostate and the bulb of the corpus spongiosum. It is the narrowest part of the canal (excepting the meati), has a calibre of about one-third of an inch (8 mm.), and measures about half an inch (10 to 12 mm.) in length. Its anterior concave surface is placed about an inch below and behind Fossa name. rethra, laid open rface). (Testut.) 1368 THE UBINOGENITAL ORGANS the pubic arch, from which it is separated by the dorsal vessels and nerve of the penis, and some muscle fibres. Its posterior convex surface is separated from the rectum by a triangular mass of tissue which constitutes the perineal body. As it pierces the superficial layer of the triangular ligament the fibres around the opening are prolonged over the tube and fix the two structures firmly to each other. The membranous urethra is surrounded ,by cavernous tissue and by the Compres- sor urethrae muscle {in. sphincter urethrae membranaceae) (Fig. .338). On the floor of the membranous urethra is the anterior extremity of the verumontanum. Behind this part of the urethra, on each side of the middle a. .«■. line, are Cowper's glands (Figs. 334 and 1128). When the urethra is empty the mucous membrane of this part is thrown into longitudinal folds, which are obliterated by dis- tention. The penile or spongy portion (pars cavernosa) (Figs. 1136 and 1138) is the longest part of the urethra, and is contained in the corpus spongiosum. It is about six inches (15 cm.) in length, and extends from the termination of the membranous portion to the meatus urinarius. Its proximal end is fixed in position and unchangeable in direction. Its distal end is movable and changeable in direction. Com- mencing just below the triangular ligament it is first directed forward through the bulb; it then passes downward and for- ward, the turn beginning at the point of attachment of the suspensory ligament of the penis (Fig. 1128). The direction of the spongy portion of the urethra is changed by altera- tions in the position of the penis. When the canal is closed the anterior and posterior walls are in contact (roof and floor), except in the glans penis, where the lateral walls ,{«SI.. i^ MM Fig. 1137. — Cross-sec- tion of ihe male urethra at various distances from its free end, showing marked alterations of form. (Testut.) Fig. 1138.— The distal port on of the male urethra, laid open on its posterior (under) surface, showing the lacunte. (Testut.) come together. The calibre of the spongy urethra varies in different por- tions of the tube. It is narrow and of uniform size in the body of the penis, measuring about one-third of an inch (9 mm.) in diameter; it is dilated behind, within the bulb (13 to 14 mm.), and again anteriorly within the glans penis (12 to 14 mm.), where it forms the fossa navicularis (fossa navicularis urethrae). In the roof of the fossa navicularis there is a transverse fold of mucous membrane, THE MALE VB.ETHBA 1369 the valve of Guerin (valvtilae fossae navicularis), g'uarding a recess, the lacuna magna. The urethra opens anteriorly by the meatus urinarius. The bulbous portion is a name sometimes given to the posterior part of the spongy portion contained within the bulb. The meatus urinarius or external orifice of the urethra {orificiiim urethrae e.rtermnn) (Figs. 1136 and 113S) is the most contracted part of the urethra. Its calibre averages about 7 mm. It is a vertical slit (Fig. 1137), bounded on each side by a small lip or labium. The inner surface of the lining membrane of the urethra, especially on the floor of the spongy portion, presents the orifices of numerous mucous glands (Fig. 1138) situated in the subepithelial tissue, and named the glands of Littre (gla?uhilae urethrales). Besides these there are a number of little recesses or follicles, of varying sizes, called lacunae {lacunae urethrales). Their orifices are directed for- ward, so that they may easily intercept the point of a catheter in its passage along the canal. One of these lacunae, larger than the rest, is situated in the upper sur- face of the fossa navicularis, about half an inch from the orifice; it is called the lacuna magna (Fig. 1138). Into the bulbous portion are found opening the ducts of Cowper's glands. Structure. — ^The male urethra is composed of three coats — mucous, muscular, and fibrous. The mucous coat forms part of the urinogenital mucous membrane. It is continuous with the mucous membrane of the bladder, ureters, and kidneys; externally with the integument covering the glans penis; and is prolonged into the ducts of the glands which open into the urethra — viz., Cowper's glands and the prostate gland — into the vasa deferentia and the seminal vesicles through the ejaculatory ducts. The mucous membrane is arranged in longitudinal folds when the tube is empty. Small papillae are found upon it near the orifice, and its epithelial lining varies in the different divisions. The prostatic portion is lined by transitional cells, con- tinued from the bladder, the membranous portion by stratified columnar cells, and the penile portion, by simple columnar epithelium, except in the/oraa navicularis, where stratified squamous cells are found. The cells rest upon a basement membrane supported by the tunica propria, composed of fibroelasiic tissue. In the latter are found diffuse lymphoid tissue and racemose glands, the urethral glands (glands of Littre). The muscular layer is continuous with the muscle of the prostate and bladder, and lies external to the mucous coat. It is composed of nonstriated muscle arranged in an outer layer of circular fibres (stratum eirculare) and an inner layer of longitudinal fibres (stratum longitudinale). These layers are prominent in the prostatic urethra, less so in the membranous portion, and ultimately disappear in the spongy part. The longitmlinal fibres, when contracted, shorten the urethra and increase its diameter. The cii'cular fibres are in a state of tonic contraction and close the urethra, constituting, ap])arently, a real sphincter (ZeissI, Zuckerkandl). The so-called sphincter of the urethra, the Accelerator uiinae, is a voluntary muscle and is not the real sphincter. Out- side of the muscle layer of tl>e urethi-a is the tissue of the corpus spongiosum. The fibrous coat (tunica fibrosa) consists chiefly of white fibrous tissue supporting the pre- ceding coats. Applied Anatomy. — The urethra may be ruptured by the patient falling astride of any hard substance and striking his perineum, so that the urethra is crushed against the pubic arch. Bleeding will at once take place from the urethra, and this, together with the bruising in the perineum and the history of the accident, will at once point to the nature of the injury. Rupture of the urethra leads to extrava^sation of urine. In rupture back of the superior layer of the triangular ligament the urine usually follows the rectum and reaches the margin of the anus. Rupture of the membranous part liberates urine between the two layers of the triangular ligaipent, where it remains until a path of exit is made by suppuration or the surgeon's knife. In rupture superficial to the anterior layer of the ligament the urine passes into the scrotum and may mount up to the abdomen between the symphysis and the pubic spine, between which points the deep layer of the superficial fascia is not attached. It cannot pass to the thigh nor cross the midline, because the fascia is attached to the fascia lata and at the midline. The applied anatomy of the urethra is of considerable importance in connection with the passage of instruments into the bladder. Otis was the first to point out that the urethra is capable of great dilatation, so that, excepting through the external meatus, an instrument corre- sponding to 20 to 28 French gauge can usually be passed without damage. The orifice of the lu'etlira is not so dilatable, and therefore may require slitting, although the introduction of the Oberlander dilator, which is expanded after introduction, renders slitting of the meatus seldom necessary in cases of clu-onic gonorrhoea. A recognition of this dilatability caused Bige- 1370 THE VBINOGEXITAL ORGANS low to very considerably modify the operation of lithotrity and introduce that of litholaiiaxy. In passing a fine catheter, the point of the instrument after it has passed the lacuna magna should be kept as far as possible along the upper wall of the canal, as the point is otherwise verv liable to enter one of the lacunae. Stricture of the urethra is a disease of very common occurrence, and is generally situated in the spongy portion of the urethra, most commonly in the bulbous portion just in front of the membranous urethra, but in a very considerable number of cases in the penile part of the canal. Even in a normal urethra, and very markedly in an inflamed urethra, a bougie encounters resistance behind the bulb. This is usually supposed to be due to spasm of the Compressor urethrse muscle. In irrigation of the urethra by gravity fluid tends to block at the same point, especially if it is thrown in suddenly or forcibly. If a reservoir is raised seven and one-half feet from the floor, and if a patient sits on a chair or lies upon a bed, fluid can be readily made to pass by hydraulic pressure from the meatus to the bladder. Spasm may temporarily prevent the inflow, but the weight of the column of fluid soon tires out the muscle and causes it to relax. Relaxation is favored by having the patient take slow, deep breaths, and make efforts at urination (Valentine). Chronic gonorrhea is frequently kept up by persistent inflammation of the ducts and follicles in the mucous membrane. This condition is known as chronic glandular urethritis or para- urethritis. In these crypts and glands gonococci may remain when gonorrhea appears to have passed away, and from time to time reinfection of the urethra may arise from such a source. Median urethrotomy or perineal section is opening of the membranous urethra. Through such an opening the bladder can be drained and explored, and the operation is sometimes called median cystotomy. In lateral lithotomy the knife enters the membranous urethra and strikes the groove of the staff. Its edge is then turned toward the left ischial tuberosity and is carried along the groove into the bladder, dividing the membranous urethra, the prostatic urethra, the posterior layer of the triangular ligament, the Compressor urethrse muscle, anterior fibres of the Levator ani muscle and the left lobe of the prostate gland. THE FEMALE URETHRA (URETHRA MULIEBRIS). The female urethra is a narrow membranous canal, about an inch and a half in length, extending from the internal urethral orifice at the neck of the bladder to the meatus urinarius. It is placed behind the symphysis pubis, embedded in the anterior wall of the vagina, and its direction is obliquely downward and forward; its course is slightly curved and the concavity directed forward and upward. Ordinarily the wall is collapsed so that the lumen is of stellate outline; the urethra may be dilated to about a quarter of an inch (6 to 8 mm.); toward the bladder the calibre increases slightly. The urethra perforates both layers of the tri- angular ligament, and its external orifice is situated directly in front of the vaginal opening and about an inch behind the glans clitoridis. Structure. — The female urethra consists of three coats — mucous, muscular, and fibrous. The mucous coat (tunica mucosa^ is pale, continuous externally with that of the vulva, and internally with that of the bladder. It is thrown into longitudinal folds, one of which, placed along the floor of the canal, extends from the vesical trigone almost to the external orifice of the urethra. It is called the crest (crista urethralis). The outline of the urethra is stellate when collapsed, because of the formation of numerous longitudinal folds. It is lined by laminated epithelium, which becomes transitional near the bladder. Many mucous glands open into the urethra, and there are numerous lacunfe. On either side of the terminal portion of the urethra lie a group of mucous glands (glandulae paraurethrales), each lateral group opening into the vesti- bule by a common duct (ductus paraurethralis) at the side of the urinary meatus. These glands are regarded as being homologous with the prostate in the male. The mucous coat is lined by .stratified .irpiamous cells resting upon a basement membrane and by papillated tunica propria; the latter consists of fibroelastic tissue containing the smaller vessels, some lymphoid tissue, and a few racemose glands. In the deeper portion of the tunica propria the structure is very vascular, is of a spongy nature, and constitutes the erectile tissue. The muscular coat (tunica wuseularis) is continuous with that of the bladder; it extends the whole length of the tube, and consists of an internal layer of nonstriated longitudinal fibres (stratum longitudinale) and an external layer of nonstriated circular fibres (stratum, circulare). In addition to these, between the two layers of the triangular ligament, the female urethra is sur- rounded by the Compressor urethrse muscle, as in the male. THE TEfiTICLES AND THEIR COVERINGS 1371 The fibrous coat consists of \Yhite fibrous tissue which supports the other coats. The urethra, because it is not surrounded by dense resisting structures, as in the male, aduiite of creat dilatation, which enables the surgeon to remove with considerable facility calculi or other foreign bodies from the cavity of the bladder. Fig. 1139. — Mesal section through the pelv 5 of a woman, aged twenty-one years. (Corning.) Peritoneum in blue. THE MALE REPRODUCTIVE ORGANS. The male reproductive organs (ore/ana genitalia virilia) include the testes, the vasa deferentia, the seminal vesicles, the ejaculatory ducts, and the penis, together with the following accessory structures — viz., the prostate and Cowper's glands. THE TESTICLES (TESTES) AND THEIR COVERINGS (Figs. 1140, 1141). The testes are two glandular organs, which secrete the spermatozoa; they are situated in the scrotum, being suspended by the spermatic cords. At an early period of fetal life the testes are contained in the abdominal cavity, behind the peritoneum. Before birth they descend to the inguinal canal, along which they pass with the spermatic cord, and emerging at the external abdominal ring, they descend into the scrotum, becoming invested in their course by coverings derived 1372 THE VRINOGENITAL ORGANS from the serous, muscular, and fibrous layers of the abdominal parietes as well as by the scrotum proper. The coverings of the testis are the following: Skin ) o . bcrotum. Dartos Intercolumnar or External spermatic fascia. Cremasteric fascia. Infundibuliform or Internal spermatic fascia. Tunica vaginalis. ^IGUINAL CA CREMASTERIC AND FASC INTEHCO FASC 4LF OF SCF Fig. 1140.— The scrotum. On the left side the cavity of the tunica vaginalis has been opened; on the right side only the layers superficial to the Cremaster have been removed. (Testut.) The scrotum' (Figs. 1140 and 1141) is a cutaneous pouch which contains the testes and part of the spermatic cords. It is divided on its surface into two lateral portions by a median line or raphe (raphe scrofi), which is continued forward to the under surface of the penis and backward along the middle line of the perineum to the anus. Of these two lateral portions, the left is usually longer than the right, to correspond with the usual greater length of the left sper- matic cord. Its external aspect varies under different circumstances; thus, under the influence of warmth and in old and debilitated persons it becomes elongated and flaccid but under the influence of cold or sexual excitement and in the young . bag of leather or skin; through a blunder two of the letters in the word have become THE TESTICLES AND THEIR CO VEHINGS i;i7: and robust it is siiort, corrugated, and closely applied to the testes. The wrinkles in the scrotum are called rugae. The scrotum consists of two layers, the integument and the dartos. The integument is very thin, of a brownisli color, and generally thrown into folds or ruo-re. It is provided with sebaceous follicles, the secretion of which has a peculiar odor, and is beset with thinly scattered, crisp hairs, the roots of which may be seen through tlie skin. ACCESSORY SLIP OF ORIGIN OF CREMASTER MUSCLE RVE FILAMENTS SPERMATIC EXUS Fig. 1141. — The scrotum. The penis has been turned upward, and the anterior wall of the scrotum has been removed. On the right side, the spermatic cord, the jnfundibuliform fascia, and the Cremaster muscle are dis- played; on the left side, the infundibuliform fascia has been divided by a longitudinal incision passing along the front of the cord and the testicle, and a portion of the parietal layer of the tunica vaginalis has been removed to disjjlay the testicle and a portion of the head of "the epididymis, which are covered by the visceral layer of the tunica vaginalis. (Toldt.) The dartos {tunica dartos) (Figs. 1140 and 1142) is a thin layer of loose vascular tissue, containing smooth muscle tissue, but no fat; it forms the proper tunic of the scrotum, is continuous around the base of the scrotum, with the two layers of the superficial fascia of the groin and perineum, and sends inward a distinct mesal septum, the septum of the scrotum {septum scroti) (Fig. 1140), which dn'ides it into two cavities for the two testes, the septum extending between the raph^ and the under surface of the penis as far as its root. 1374 THE UBINOGENITAL ORGANS The dartos is closely united to the skin externally, but connected with the subjacent parts by delicate areolar tissue, upon which it glides with the greatest facility. The intercolumnar or external spermatic fascia (Fig. 1140) is a thin membrane de^i^'ed from the margin of the pillars of the external abdominal ring, during the descent of the testis in the fetus, which is prolonged downward around the surface of the cord and testis. It is separated from the dartos by loose areolar tissue, which allows of considerable moA'ement of the latter upon it, but is inti- mately connected with the succeeding layers. The cremasteric fascia {fascia cremasterica) (Figs. 1140 and 1141) consists of scattered bundles of muscle fibres, the Cremaster muscle (m. cremaster) (Figs. 1140 and 1141) derived from the lower border of the Internal oblique and collected within a continuous covering by intermediate areolar tissue. Shin - Dartos Intercolumnar fascia Cremasteric fascia InfundibiUiform fascia Parietal tunica vaginalis Visceral tunica vaginalis Tunica alimginea ~ Tunica vasevlosa A lobule of the testicle ^ A septum Mediastinum testi': Digital fossa Spermatic vein Epididymis Vas deferens Artery to vas Spei-matic artery Internal muscle tunic of Kolliker Fig. 1 142. — Transverse section through the left side of the scrotum and the left testis. The sac of the tunica vagi- nalis is represented in a distended condition. (Del^pine.) The infundibuliform fascia {tunica vaginalis communis [testis et funiculi sper- matid]) (Figs. 1140 and 1141) is a thin membranous layer, which loosely invests the surface of the cord. It is a continuation downward of the fascia transversalis. Beneath it is a quantity of loose connective tissue which connects this layer of fascia with the spermatic cord and posterior parts of the testicle. This connective tissue is continuous above with the subserous areolar tissue of the abdomen. These two layers, the infundibuliform fascia and the tissue beneath it, are known collectively as the fascia propria. The infundibuliform fascia completely encloses the testicle and epididymis and is fused witl^ the parietal lamina of the tunica vaginalis propria testis. 'The tunica vaginalis (tunica vaginalis propria testis) is described with the testis (p. 1.379). Vessels and Nerves. — The arteries supplying the coverings of the testis are the superficial and deep external pudic, from the femoral; the superficial perineal branch of the internal pudic; and the cremasteric branch from the deep epigastric. The veins follow the course of the corre- sponding arteries. The lymphatics terminate in the inguinal nodes. The nerves are the ilioinguinal and genital branch of the genitofemoral nerve and of the lumbar plexus, the tn-o superficial perineal branches of the internal pudic nerve, and the inferior pudendal branch of the small sciatic nerve. THE TESTICLES AND THEIR COVERINGS 1375 ANTERIOR GROUP OF VEINS The inguinal or spermatic canal {canalis ing^dnalis) (Figs. 330 and 1124) contains tlie spermatic cord in tlie male and the round ligament in the female. It is an ol)lique canal, about an inch and a half in lengdi, directed downward and in- ward and placed parallel with, and a little above, Poupart's ligament. It com- mences above at the internal or deep alidominal ring, which is the point where the cord enters the inguinal canal, and terminates below at the ex- ternal or superficial ring. It is bounded, in front, by the integument and superficial fascia, by the aponeurosis of the External oblique through- out its whole length, and by the Internal oblique for its outer third; behind, by the triangular fascia, the conjoined tendon of the Internal oblique and Trans versalis, transver- salis fascia, and the subperi- toneal fat and peritoneum; above, by the arched fibres of the Internal oblique and Transversalis; below, by the imion of the transversalis fascia with Poupart's ligament. FiQ. 1143.— The arteries of the testis : Charpy.) id the cord. (Poirier and TRANSVERSALIS DEEP EPIGASTRIC ARTERY SPERMATIC Fig. 1144. — The spermatic cord and the ligament of Cloquet. (Poirier and Charpy.) The spermatic cord (funicuhis spermaiicms) (Figs. 1140 and 1144) extends from the internal abdominal ring, where the structures of which it is composed 1376 THE URINOQEXITAL ORGANS converge, to the back part of the testicle. In the abdominal wall the cord passes obliquely along the inguinal canal, lying at first beneath the Internal oblique muscle and upon the fascia transversalis; but nearer the pubes it rests upon Poupart's ligament, having the aponeurosis of the External oblique in front of it and the conjoined tendon behind it. It then escapes at the external ring, and descends nearly vertically into the scrotum. The left cord is usually rather longer than the right, consequently the left testis generally hangs somewhat lower than its fellow. DEFERENS .SPERMATIC ^ CORD INTERNAL SAPHENOUS VEIN Fig, 1145.^ — The spermatic cord in the inguinal canal. (Poirier and Charpy.) Structure. — The spermatic cord contains the spermatic duct or vas deferens, the deferential artery and veins, the spermatic artery, the pampiniform plexus of veins, the spermatic plexus, and the deferential plexus of the symjiathetic nerve, lymphatics, and the cord-like remnant of the funicular process of peritoneiun called the ligament o£ Cloquet (Fig. 1144). All the above structures are held together by connective tissue. These structures are ensheathed by the infundibuliform process of the transversalis fascia (Fig. 1144 and p. 1374). This fascia is thin above and tliicker below, and encloses the testicle and epididymis, as well as the cord, being firmly adherent to the parietal layer of the vaginal tunic of the testicle and with the posterior por- tion of the testicle and epididymis. Upon this fascia are the fibres of the Cremaster muscle, which spring from the Internal oblique, and in this fascia are the cremasteric artery, the genital branch of the genitofemoral nerve, and external spermatic veins. This fascia is surrounded by the intercolumnar or spermatic fascia, which is distinct above, but not below. Vessels and Nerves of the Spermatic Cord. — The arteries (Figs. 1141 and 1J143) of the cord are the spermatic, from the aorta; the artery of the vas deferens, from the superior vesical; the cremasteric, from the deep epigastric. The spermatic artery {a. spermatica interna) arises from the abdominal aorta below the renal artery, descends l)y the Psoas muscle, crosses the ureter and external iliac vessels, meets the vas deferens at the internal abdominal ring, escapes from the abdomen at the internal or deep ab- dominal ring, and lying in front of the vas deferens accompanies the other constituents of the spermatic cord along the inguinal canal and through the external abdominal ring into the scrotum. It then descends to the testis, and, becoming tortuous, divides into several branches, two or three of which, the epididymal branches, accompany the vas deferens and supply the epididymis, anastomosing with the artery of the vas deferens and the cremasteric artery; others, the glandular branches, pierce the back of the tunica albuginea and supply the substance of the testis. The artery of the vas deferens (a. deferentialis), a branch of the superior vesical, is a long slender vessel which accompanies the vas deferens, ramifying upon the coats of that duct, and anastomosing with the spermatic artery and the cremasteric artery near the testis. THE TESTICLES AND THEIR COVERINGS J 377 The cremasteric artery {a. spermatica externa) is a branch of the deep epigastric artery. It accorapjinics the s|]erniiitic cord and supplies the Cremaster muscle and other coverings of the cord, aiiMstoiiinsiiii; with the spermatic and deferential arteries. The spermatic veins (Figs. 523 and 1146) emerge from the back of the testis and receive tributaries from the epididymis; they unite and form a convoluted plexus, the pampiniform plexus (plexus pampiniformis), which forms the chief mass of the cord; the ves.sels composing this plexus are very numerous, and ascend along the cord in front of the vas deferens; below the external or superficial abdominal ring they unite to form three or four veins, which pass along the inguinal canal, and, entering the abdomen through the internal or deep abdominal ring, coalesce to form two veins. These again unite to form a single vein, which opens on the right side into the inferior vciki cava at an acute angle, and on the left side into the left renal vein at a right angle. The lymphatic vessels of the scrotum terminate in the superficial inguinal nodes. The lym- phatics of the testicle join the lymphatics of the epididymis and of the visceral layer of the vaginal tunic of the testicle, and ascend in the spermatic cord. They reach the lumbar region along the spermatic bloodvessels and terminate in the lateral aortic nodes, and sometimes in the nodes in front of the aorta. The lymphatics of the seminal duct pass to the external iliac nodes. The nerves are the spermatic plexus from the sympathetic, joined by filaments from the pelvic plexus which accompany the artery of the vas deferens. Fig. 114G. — Spermatic veins. (Testut.) The testes (Figs. 1 141 and 1146) are suspended in the scrotum by the spermatic cords, the left testis hanging somewhat lower than its fellow. The average dimen- sions of this gland are from one and a half to two inches (4 cm.) in length, one inch (2.5 cm.) in breadth, and an inch and a quarter (3 cm.) in the antero-posterior diameter, and the weight varies from six to eight drams (25 to 30 grams) . It is of a grayish-white color, and of resilient consistency. Each gland is of an oval 87 1378 THE VRINOGENITAL ORGANS form, compressed laterally, and having an oblique position in the scrotum, the upper extremity {e.xtreviitus superior) being directed forward and a little outward, the lower extremity {extremitus inferior), backward and a little inward; the an- terior convex border looks forward and downward; the posterior or straight border {margo posterior), to which the cord is attached, backward and upward. The anterior border {margo anterior) and lateral surfaces {fades lateralis et fades medialis), as well as both extremities of the organ, are convex, free, smooth, and invested by the visceral layer of the tunica vaginalis. The posterior border, to which the cord is attached, receives only a partial investment from that mem- brane. To the inferior part of the posterior border is attached the gubemaculum testis (see p. 1424), which anchors the testis firmly to the scrotum. Lying upon the outer edge of this posterior border is a long, narrow, flattened body, named, from its relation to the testis, the epididymis (Figs. 1147 and 1148), which curves outward and backward. Spet maiic cord ■ll^Pi II of LO}d. Tunica rafjnialis, parietal lat/er. '\ Kon-pcdimcnlated hydatid. Digital foasa. Fig. 1147. — The left testis in situ, the tunica vagi- nalis having been laid open. ALBUGINEA Fig. 1148. — Frontal section of the testis and epi- didymis. (Poirier and Charpy. ) The epididymis consists of a central portion or body (corpus epididymidis); an upper enlarged extremity, the head or globus major {caput epididymidis); and a lower pointed extremity, the tail or globus minor {caiida epididymidis'). The globus major is directed inward and is intimately connected with the upper end of the testicle by means of its efferent ducts, and the globus minor is connected with its lower end by cellular tissue and a reflection of the tunica vaginalis. The globus minor bends suddenly and passes into the seminal duct, the direction of which is upward and backward. The outer surface and upper and lower ends of the epididymis are free and covered by serous membrane; the body is also com- pletely invested by it, excepting along its inner border, and between the body and the posterior part of the outer surface of the testis is a pouch or cul-de-sac, named the digital fossa (sinus epididymidis). Above this fossa is a fold of the tunica vaginalis, which is called the Ugamentum epididymidis superior, and below it is another fold, the Ugamentum epididymidis inferior. The epididymis is con- nected to the back of the testis by a fold of the serous membrane. Attached to the upper end of the testis, close to the globus major, is a small body; it is oblong in shape and has a broad base, and is called the sessile hydatid {appendix testis [Morgagni]) (Figs. 1140 and 1147). Attached to the globus major of the epi- THE TESTICLES AND THEIR CO VERINOS 1379 didymis is another small, pear-shaped body — the pedunculated hydatid {appendix epididymidis). These bodies are the remains of embryonic structures. When the testis is removed from the body, the position of the vas deferens, on the pos- terior surface of the testis and inner side of die epididymis, marks the side to which the eland has belonged. Structure of the Epididymis. — The epididymis is surrounded by a capsule of white fibrous tissue. The globus major consists of from ten to fifteen tubules, which are convoluted and lined by stratified ciliated epithelial cells. The body and globus minor are composed of the convolu- tions of a single tubule, which if straightened would measure upward of twenty feet. These parts are lined by stratified ciliated cells and continue as the vas deferens. The Tunics of the Testicle. — l''he testis is invested by two tunics — the tunica vaginalis and the tunica albuginea Tlie tunica vaginalis (tunica vaginalis propria testis) (Figs. 1147 and 11.50) is the serous covering of the testis and epididymis. It is a pouch of serous mem- brane, derived from the peritoneum (processus vaginalis peritonaei) during the descent of the testis in the fetus from the abdomen into the scrotum. After its descent that portion of the pouch which extends from the internal ring to near the upper part of the gland, the funicular process, becomes obliterated, the lower portion remaining as a shut sac, which invests the outer surface of the testis, and is re- flected to the internal surface of the scrotum; hence it may be described as consisting of a visceral and parietal portion. The visceral portion (lamina visceralis) of the timica vagi- nalis propria covers the outer surface of the testis, as well as the epididymis, connecting the latter to the testis by means of a distinct fold. From the posterior border of the gland it is reflected to the internal surface of the infundibuliform process of the transversalis fascia, and between the tunic and the fascia is a layer of unstriated muscle fibres, the Internal cremaster muscle (Fig. 1142). The parietal portion (lamina parietalis) of the tunica vaginalis propria is the reflected portion. It is far more extensive than the visceral portion, extending upward for some distance in front and on the inner side of the cord, and reaching below the testis. The inner surface of the tunica vaginalis is free, smooth, and covered by a layer of endothelial cells. The interval between the visceral and parietal layers of this membrane constitutes the cavity of the timica vaginalis and contains a small amount of serous fluid. The obliterated portion of the pouch may generally be seen as a fibrocellular thread, the ligament of Cloquet (rudimentum processus vaginalis) (Fig. 1144), lying in the loose areolar tissue around the spermatic cord; sometimes this may be traced as a distinct band from the upper end of the inguinal canal, where it is the arrange- 1380 THE URINOGENITAL ORGANS connected with the peritoneum, down to the tunica vaginalis; sometimes it gradu- ally becomes lost on the spermatic cord. Occasionally no trace of it can be de- tected. In some cases it happens that the pouch of peritoneum does not become obliterated, but the peritoneal cavity communicates with the tunica vaginalis. This may give rise to one of the varieties of oblique inguinal hernia or hydrocele; or in other cases the pouch may contract, but not become entirely obliterated; it then forms a minute canal leading from the peritoneum to the tunica vaginalis. The tunica albuginea (Figs. 1148 and 1149) is the fibrous covering of the testis. It is a dense fibrous membrane, of a bluish-white color, composed of bundles of white fibrous tissue, which interlace in every direction. Its outer surface is covered by the tunica vaginalis, except at the points of attachment of the epididy- mis to the testis, and along its posterior border, where the spermatic vessels enter the gland. It consists of two portions, the tunica fibrosa and the tunica vasculosa ; the former is the thicker of the two and contains few vessels, while the latter con- tains many small vessels. The tunica vasculosa sends septa into the organ which divide it into compartments. These septa converge and end at the mediastinum. This membrane surrounds the glandular structure of the testis, and at its posterior border forms a projection, triangular in shape and cellular in structure, which is reflected into the interior of the gland, forming an incomplete vertical septum, called the mediastinum testis. The mediastinum testis (corpus Highmori) (Figs. 1148 and 1149) extends from the upper, nearlv to the lower, extremity of the gland, and is wider above than below. From the front and sides of this septum numerous slender fibrous cords and imperfect septa — septv.la testis (Fig. 1149) — are given off, which radiate toward the surface of the organ, and are attached to the inner surface of the tunica albuginea. This scaffolding of connective tissue divides the parenchyma {'paren- chyma testis) of the organ into a number of incomplete spaces, which are somewhat cone-shaped, being broad at their bases at the surface of the gland, and becoming narrower as they converge to the mediastinum. The mediastinum supports the bloodvessels, lymphatics, and ducts of the testis in their passage to and from the substance of the gland, and contains numerous fine canals, into which open the very small tubules of the proper substance of the testis. Structure of the Testis (Fig. 1149).— The glandular structure of the testis consists of numerous lobules (lobuli testis). Their number, in a single testis, is estimated to be about 200. They differ in size according to their position, those in the middle of the gland being larger and longer. The lobules are pyramidal in shape, the base of each being directed toward the circum- ference of the organ, the apex toward the mediastinum. Each lobule is contained in one of the intervals between the fibrous cords and vascular processes which extend between the medias- tinum testis and the tunica albuginea, and consists of from one to three or more minute convo- luted tubes 2{ feet in length and 140 to 200 ft in diameter, the tubuli seminiferi contorti, which usually end blindly beneath the tunica albuginea. The contorted tubes unite at the apex of the lobules and form several straight tubes (tiihuli recti), which pass into the mediastinum testis and form the network known as the rate testis (Fig. 1149). The efferent ducts (ductuli effer- entes testis) (Fig. 1149), about twelve to fifteen in number, arise from the rete and continue into the globus major as the coni vasculosi. The total number of tubes is considered by Lauth to be about 840. The tubuli recti and rete testes are lined by simple squamous or cuboidal cells, while the vasa efferentia are lined by simple columnar cells which are either ciliated or non- ciliated. The convoluted tubules are pale in color in early life, but in old age they acquire a deep yellow tinge from containing much fatty matter. Each tube consists of a basement layer, formed of epithelial cells united edge to edge, outside of which are other layers of flattened cells arranged in interrupted laminse, which give to the tube an appearance of striation in cross- section. The cells of the outer layers gradually pass into the interstitial tissue. Within the base- ment membrane are epithelial cells arranged in several irregular layers, which are not always clearly separated, but which may be arranged in different groups that do not form clearly defined layers. The various groups cannot be seen in a single cross-section, but may be discerned in successive sections. Among these cells may be seen the spermia in different stages of develop- .raent. (1) Lining the basement membrane and forming the outer zone is a layer of cubical cells, spermatogonia, containing small nuclei and pyramidal cells, the columns of Sertoli. The THE TESTICLES AND THEIR CO VEBINGS 1381 nucleus of the former may be seen to be in the process of indirect division (karyokinesis), and in consequence of this daufj;li(or cells arc I'urmcd, which constilulc ihc second zone. (2) Within this first layer is to be seen a nuiiilicr cif lar;;cr cells wiili clear nuclei, arranged in two or three strata; these are the spermatocytes of the first order, or mother cells. Most of the cells are in a con- dition of karyokinctic division, and the cells which result from this division form those of the next layer, the spermatocytes of the second order, or daughter cells. (.3) The latter by division give rise to the spermids, which change into the spermia or spermatozoa. In addition to these three layers of cells, others are seen, which are termed the supporting cells, or cells of Sertoli. They are elongated and columnar, and project inward from the basement membrane toward the lumen of the tube. They give off numerous lateral branches, which form a reticulum for the support of the three groups of cells just described. As development of the spermia proceeds, the latter group themselves around the inner extremities of the supporting cells. The nuclear part of the spermid, which is partly embedded in the supporting cell, is differentiated to form the head of the spermium, while the cell protoplasm becomes lengthened out to form the middle piece and tail, the latter projecting into the lumen of the tube. Ultimately the heads are separated from the column of Sertoli and the spermia are set free. The process of spermatogenesis bears a close relation to that of matiffation of the ovum. The spermatocyte is equivalent to the immature ovum. It undergoes subdivision, and ulti- mately gives origin to fom' spermia, each of which contains, therefore, only one-fourth of the chromatin elements of the nucleus of the spermatocyte (see Ovum, p. 1400). EPIDIDYMIS Tig. 1150. — Vaginal tunics of the rigiit testicle. (Poir- ier and Charpy.) Fig. 1151. — Ligament of the scrotum or gube naculum testis. (Poirier and Charpy.) The tubules are enclosed in a delicate plexus of capillary vessels, and are held together by an intertubular connective tissue, which presents large interstitial spaces lined by endothelium, which are believed to be the rootlets of lymphatic vessels of the testis. In this interstitial tissue are groups of large granular cells, the interstitial cells. These contain pigment, fat, and crystal- loids, and are more numerous before and after sexual activity. The aberrant ducts of the epididymis (ductidi aberrantes) are tortuous and end in blind ex- tremities. The superior aberrant duct (ductus aberrans superior) is in the globus major and joins the rete testis. The inferior aberrant duct (ductus aberrans inferior) (Fig. 1149). is in the tail of the epididymis, and lakes origin from the duct of the epididymis or the seminal duct. It is a persi-stent canal of the Wiilffian body. It extends up the cord for two or three inches and terminates liy a blind exlrcniity, which is occasionally bifurcated. It may be as much as fourteen inches in length when uin'avellcv;irv and each enipiies into diirtner's duct at a right angle. Gartner's duct is a portion of the \\'(ilftian duet, which has jiersisted and is represented in the male by the canal of the epi- didymis. The tubules which join the duct are persistent mesonephric tubules and are the homologues of the vasa eiferentia and coni vasculosi of the testis, and probably also the aberrant ducts of the canal of the epididymis. The paroophoron is within the mesosalpinx, but is nearer to the uterus than is the epoophoron. It consists of several small tubules, which can be seen in an adult only by the aid of a pocket lens. They are visible to the naked eye in a child at birth. It represents the organ of Giraldes in the male and is derived from the mesonephros. Applied Anatomy. — An ovary may fail to descend and remain well above the pelvic brim; it may prolapse into Douglas' pouch; it may enter the sac of a hernia; it may inflame; a tumor or cyst may arise from it. A solid tumor of the ovary may be a fibroma, a sarcoma, or a carcinoma. "Cysts may originate in any part of the tuboovarian structure; as the cortical, medullary, or parenchymatous portions of the ovary; in the structure between the tube and ovary known as the Rosenmiiller organ or parovarian structures; and in the hydatid of JMorgagni." Cysts may be simple, proliferating, or dermoid; unilocular or multilocular. Glandular proliferous cysts, papillary proliferous cysts, dermoid cysts, and parovarian cysts may attain a large or even an enormous size. The operation for the removal of an ovarian cyst is one of the most successful of the major procedures of surgery. THE FALLOPIAN TUBE, OR OVIDUCT (TUBA UTERINA [FALLOPII]) (Figs. 1177, 1178). The Fallopian tubes or oviducts convey the ova from the ovaries to the cavity of the uterus. They are two in number, one on each side, situated in the upper margin of the broad hgament, extending from each superior angle of the uterus to the side of the pelvis. Each tube is about four inches (10 cm.) in length, and is described as consisting of three portions — (1 ) the isthmus {isthvius tuhae uterinae) (Fig. 1177), or inner constricted third; (2) the ampulla {ampulla tuhae. uterinae) (Fig. 1177), or outer dilated portion, which curves over the ovary; and (.3) the infundibulum (infimdibuhim tubae uterinae), the funnel-hke expansion of the tube, at the bottom of which is the abdominal orifice or pavilion (ostium abdominale tubae uterinae) (Fig. 1177). The abdominal orifice has a small diameter (2 mm. when relaxed to its full extent). The margin of the infundibulum is rendered irregular by the presence of numerous small processes, the fimbriae (fimbriae tubae). This end of the tube is called the fimbriated extremity (Fig. 1177), because of these processes. The surfaces of the fimbriae looking into the cavity of the infundibulum are covered with mucous membrane continuous with the tubal mucous membrane. The outer surfaces are covered with peritoneum. One of the fimbriae is attached to the ovary and is called the ovarian fimbria (fimbria ovarica) (Fig. 1177). The uterine opening (ostium uterinum tubae) is even smaller than the abdominal opening, and will admit only a small bristle. In connection with the fimbriae of the Fallopian tube or with the broad ligament close to them 1402 THE UBINOGENITAL ORGANS there are frequently one or more small pedunculated vesicles. These are termed the hydatids of Morgagni {appendices vesicidosi). The course pursued by the Fallopian tube has been given in its relations to the ovary on page 1398. Structure. — The Fallopian tube consists of three coats — serous, muscular, and mucous. The external or serous coat (tunica serosa) is peritoneal. Beneath this lies the tunica adventitia, composed of lax connective tissue. The middle or muscular coat (tunica muscularis) consists of an external longitudinal layer (stratum longitudinale), and an internal circular layer [stratum circulare) of smooth muscle fibres continuous with those of the uterus; near the uterine end of the tube an inner longitudinal la\'er is found. The internal or muocus coat (tunica mucosa) is continuous with the mucous lining of the uterus and, at the free extremity of the tube, with the peritoneum. It is thrown into branched longitudinal folds or villi (plicae iubariae), which in the outer, larger part of the tube or ampulla (plicae ampullare.s) are much more extensive than in the narrow canal of the isthmus (plicae isthmicae). The lining epithelium is simple ciliated. This form of epithelium is also found on the inner surface of the fimbriae, while on the outer or serous surfaces of these processes the epi- thelium gradually merges into the endothelium of the peritoneum. Fimbria ucarica. Fig. 1177. — Dissection of uterine appendages, L from behind. (Henle.) Vessels and Nerves. — The cliief artery of the tube is the tubal branch of the uterine artery (ramus tuharius) (Fig. 1185). It also receives branches from the ovarian (Fig. llSo). Some of the tubal veins empty into the uterine veins, some into the ovarian veins. The lymphatics (Fig. 1186) coming from the tube unite with the trunks coming from the uterus and ovary and terminate in the lateral aortic nodes. The nerves come from the same plexuses that send branches to the uterus and ovary. Applied Anatomy. — Extrauterine pregnancy most commonly occurs in the ampulla of the tube. The product of the conception may escape tlirough the ostium abdominale or the walls of the tube may rupture, a violent hemorrhage resulting. Pelvic peritonitis is a not uncommon sequence of tubal disease. Salpingitis is inflammation of the mucous coat of the tube — inter- stitial salpingitis of the middle coat; perisalpingitis of the peritoneal coat. If inflammation closes the uterine and the abdominal ends of the tube, mucus gathers and distends the tube (hydrosalpinx). If purulent matter gathers, the condition is known as pyosalpiivx. THE UTERUS, OR WOMB (Figs. 1178, 1181). The uterus is the organ of gestation, receiving the fecundated ovum in its cavity, retaining and supporting it during the development of the fetus, and becoming the principal agent in its expulsion at the time of parturition. It is a hollow THE UTERUS, OR WOMB 1403 muscular organ. The nonpregnant uterus is contained in the cavity of the pelvis between the bladder and the rectum (Figs. 1183 and 11S8). It is rarely placed exactly in the midline, but inclines to one side or the other, more often to the left than to the right. The walls of the organ are extremely thick. The uterus is movable as a whole, and the body of the uterus is movable upon the neck. Its position varies with the condition of adjacent parts, especially of the bladder and rectum. The cervix is more firmly fixed than the body and fundus, and hence the latter vary more in position than the former. Normally, in an erect indi- vidual, with the bladder and rectum empty, the external os is at the level of the upper surface pf the pubic symphysis (Fig. 1174) and in a frontal plane passing through the ischiatic spines. The long axis of the uterus is directed forward and upward (Fig. 1174) and is angled where the body and cervix join. Hence, nor- mally, with the bladder empty, the uterus is anieverted and anieflexed. When the bladder fills, the anteversion and anteflexion are almost aboli.shed. If the bladder is overdistended and the rectum is empty, the uterus is pushed strongly backward; so that its long axis corresponds to the long axis of the vagina; in other words, it is retroverted. MESOVARI MESOSALPINX TUBAL EXTREMITY OF OVAH^ FALLOPIAN OUND LIGAMENT F UTERUS POST. FORNIX OF VAGINA VAGINAL RTION OF RVIX Fig. 1178. — The uterus, the left Fallopian tube, and the left ovary in their connection with the broad ligament of the uterus, which has been fully unfolded. Seen from behind. From a virgin, aged nineteen jjears. (Toldt.) In the virgin state it is pear-shaped, flattened from before backward, and is retained in its position by the round and broad ligaments on each side, and projects into the upper end of the vagina below (Figs. 1178 and 1179). Its upper end, or base, is directed upward and forward; its lower end, or apex, downward and backward, in the line of the axis of the inlet of the pelvis. It therefore forms an angle of about 110 degrees with the vagina, since the direction of the vagina corresponds to the axis of the cavity and outlet of the pelvis. The nonpregnant adult uterus measures about three inches (7.5 cm.) in length, two inches (5 cm.) in breadth at its upper part, and nearly an inch (2.5 cm.) in thickness, and it weighs from an ounce to an ounce and a half (30 to 45 grams). It consists of two parts (Fig. 1178): (1) An upper and larger portion, consists ing of the body and fundus. This portion is flattened from before backward, (2) A lower, smaller, and cylindrical portion, the cervix. On the surface, about midway between the base and apex, a slight constriction, known as the isthmus uteri, and a corresponding narrowing of the uterine cavity, the internal os, serve to demarcate the two portions. 1404 THE UBINOQENITAL ORGANS The fundus {fundus uteri) (Fig. 1 178) is the upper broad extremity of the uterus. If a Hue is drawn from the uterine opening of one Fallopian tube to the other, the portion above the line is the fundus. The fundus is directly continuous with the body. The body of the uterus {corpus uteri) (Fig. 1178) gradually narrows from the fundus to the isthmus. In outline, when seen from in front or laehind, it resembles a triangle, the base being above and the apex being absent. The anterior surface {fades vesicales) is so slightly rounded as to appear flattened. It is covered by eXTCRNAL ORIFICE OF URETHRA RAVAGI^ PORTION CERVIX Fig. 1179, — The external genital organ of a virgin attached to the vagina, which has been isolated and opened, and a portion of the cervix uteri. (Toldt.) peritoneum (Fig. 1178), which becomes reflected from it at its isthmus to form the uterovesical pouch, which lies between the uterus and bladder (Fig. 1182). Its posterior surface is more rounded than the anterior, being convex transversely. It is covered by peritoneum throughout except along the attachments of the layers of the broad ligament (Fig. 1183), and is separated from the rectum by some convolutions of the small intestine (Fig. 1182). The peritoneum which THE UTERUS, OB WOMB 1405 covers the posterior surface forms most of the anterior wall of Douglas' cul-de-sac (Figs. 1181 and 1182, and p. 1407). Its lateral margins (Figs. 1178 and 1181) are slightly convex. At the upper angle the Fallopian tube joins the body of the uterus; immediately below this the round ligament is attached, and be- hind the latter is the attachment of the ligament of the ovary; behind both of Fig. 1180. — The parovarium. The mesoaalpinx is partly removed. (Poirier and Charpy.) these structures, and from the side of the womb the broad ligament passes. The division between the body and the cervix is indicated externally by the isthmus and by the reflection of the peritoneum from the anterior surface of the uterus on tp the bladder, and internally by a narrowing of the canal called the internal OS (Fig. 1181). The neck or cervix uteri (Figs. 1178 and 1181) is the lower constricted segment of the uterus; around its circumference is attached the upper end of the vagina (Figs. 1178 and 1182), which extends upward a greater distance behind than in front. The neck is spindle-shaped in the nulliparous and cylindrical in parous women. UTEnmc ORIFICE OF FALLOPIAN TUBE EPOOPHOHON UTEROVAGINAL VENOUS PLEXUS Fig. 1181.— The uterus and the right Fallopian tube opened from behind. (Toldt.) The supravaginal portion {poiiio S2ipravaginalis [cervicis]) (Figs. 1178 and 1182) is not covered by peritoneum in front; a pad of cellular tissue is interposed between it and the bladder. Behind, the peritoneum is ex-tended over it. The vaginal portion (portio vaginalis [cervicis]) (Figs. 1178 and 1182) is the lower end projecting into the vagina. It is circular or elliptical, the long axis of the 1406 THE imiNO GENITAL ORGANS CTAL PERITONEUM CTOVAGrNAL POUCH NTERIOR AND POS- TERIOR LAYERS OF ellipse being transversely placed. On its surface is a small aperture, the ex- ternal OS or OS uteri {orificium externum uteri) (Figs. 1178 and 1181), gener- ally linear in shape, but sometimes oval or almost circular. If a woman has borne children, the opening is trans- verse and the margins are irregular. The margin of the opening is, in the absence of parturition or di-sease, quite smooth. This aperture divides the vaginal portion of the cervix into two lips, an upper or posterior lip (labium posterius) and an anterior lip (labium anterius). On each side of the cervix and upper portion of the vagina there is a space containing bloodvessels and filled with loose cellular tissue. This loose tissue passes upward between the layers of the broad ligament, and is called parametrium. On each side of the cervix and three-quarters of an inch away is the terminal portion of the corresponding ureter. Fii lis- I he re \agina, fanow in^ thei grammatic (Te^tut \ IX uteri and tipper end of the relationb to the peritoneum. Dia- Fig. llS3._Douglas' pouch. (From a preparation in the Museum of the Royal College of Surgeons of England. Folds and Ligaments.— The ligaments of the uterus are eight in number. Some are simple folds of peritoneum; others contain connective tissue and muscle. The ligaments are as follows: one anterior, one posterior, two lateral or broad, ous ABRANC THE UTERUS, OR WOMB 1407 two sacrouterine — all these being formed of peritoneum — and, lastly, two round ligaments. The anterior ligament or the uterovesical fold is reflected on to the bladder from the front of the uterus, at the junction of the cervix and body. It forms the utero- vesical pouch {excavatio vesicoiderina) (Figs. 1182 and 1183). The posterior ligament or the rectovaginal fold passes from the posterior wall of the uterus over the upper fourth of the vagina, and thence on to the rectum and sacrum. It thus forms a pouch, called the rectovaginal pouch or Douglas' pouch (Figs. 1182 and 1183), the boundaries of which are, in front, the posterior wall of the uterus, the supra\'aginal portion of the cervix, and the upper fourth of the vagina; behind, the rectum and sacrum; above, the small intestine; and laterally, the folds of Douglas or rectouterine folds, which contain the sacrouterine ligaments. The broad ligament {ligamentwn latum uteri) (Figs. 1183 and 1184) is a peri- toneal fold which passes from each side of the uterus to the lateral wall of the pelvis as high as the external iliac vein. From this region comes the peritoneal fold called the suspensory ligament of the ovary (Fig. 1173). The two broad ligaments form a septum across the pelvis, which divides that cavity into two por- tions. In the anterior part are contained the bladder, urethra, and vagina; in the posterior part, the rectum. With the uterus normally placed the anterior surface of the broad ligament faces forward and downward, and the posterior surface faces upward and backward. The ligament is more nearly vertical at its pelvic attachment. The two layers of the broad ligament are mostly near to each ^-^Sn mesosalpinx other, to the side and below they separate and pass into the peritoneum of the lateral pehic wall, the bladder, and the rectum. Between the two layers of each broad liga- ment are contained (1) the Fallopian tube superiorly; (2) the round ligament; (3) the ovary and its ligament; (4) the parovarium or organ of Rosenmiiller, and the paroopho- ron; (5) loose connective tissue, which is called parametrium; (6) unstriped muscle tissue; and (7) bloodvessels and nerves. The Fallopian tube is in the free edge of the ^ i,q, -yu u j ,• * <• *w , \.. . , . ° . , Fig. 1184.— The broad ligament of the broad hgament, and is contained in a special uterus, wuh the mesovarium, the mesosai- n , I .... ,, 1 I , ,1 , V ,1 pinx, the ovary, and the Fallopian tube in lOlcl, which IS attached to the part or the transverse section. (Toldt.) ligament near the ovary, and is known by the name of the mesosalpinx (Figs. 1181 and 1184). If the mesosalpinx is spread out, it is seen to be roughly triangular; the base of the triangle is outward, the apex at the upper and outer angle of the uterus ; the upper boundary is the Fallo- pian tube, and the lower boundary is the ovary and its ligament. Between the two layers of the mesosalpinx are the parovarium and the paroophoron. Between the fimbriated extremity of the tube and the lower attachment of the broad ligament is a concave rounded margin, called the infundibulopelvic ligament (Fig. 1177). The mesovarium passes upward from the posterior surface of the broad liga- ment (Fig. 1184). Beneath the mesovarium is a larger and thicker portion of the broad ligament, called the mesometrium (Fig. 1184). The sacrouterine or rectouterine ligaments {plicae rectouterinae) are contained in the peritoneal folds of Douglas. They pass from the second and third segments of the sacrum, downward and forward on the lateral aspects of the rectum, to be attached one on each side of the uterus at the junction of the supravaginal cervix and the body, this point corresponding internally to the position of the os internum. 1408 THE URINOGENITAL ORGANS They contain fibrous tissue and unstriated muscle fibre. Muscle fibres from the uterine wall to the rectal wall constitute the Rectouterinus muscle {miisculus recto- uterinus). This muscle is part of the sacrouterine ligaments. A round ligament (ligamentiim teres uteri) (Figs. 1178 and 1183) is attached on each side of the uterus. The two ligaments are rounded cords between four and five inches in length, each situated between the layers of the broad ligament in front of and below the Fallopian tube. Commencing at the superior angle of the uterus, this ligament passes forward, upward, and outward through the internal abdominal ring, along the inguinal canal, to the labium majus, in which it becomes lost. The round ligament consists principally of muscle tissue pro- longed from the uterus; also of some fibrous and areolar tissue, besides bloodvessels and nerves, enclosed in a duplicature of peritoneum, which in the fetus is pro- longed in the form of a tubular process for a short distance into the inguinal canal. This process is called the canal of Nuck. It is generally obliterated in the adult, but sometimes remains pervioUs even in advanced life. It is analogous to the peritoneal pouch which precedes the descent of the testis. The cavity of the uterus (cavum uteri) (Fig. 1181) is small in comparison with the size of the organ, because of the great thickness of the wall. That portion of the cavity which corresponds to the body is triangular, flattened from before backward, so that its anterior and posterior walls are closely approximated, and having its base directed upward toward the fundus. At each superior angle is the minute orifice of the Fallopian tube. At the inferior angle of the uterine cavity is a small constricted opening, smaller and more nearly circular than the external os uteri, the internal os uteri (orificium internum uteri) (Fig. 1181), which leads into the cavity of the cervix. The cavity of the cervix (canalis cervicis uteri) (Fig. 1181) extends from the internal os uteri to the external os uteri. It is somewhat fusiform, flattened from before backward, broader at the middle than at either extremity, and communicates below with the vagina. The wall of the canal presents, anteriorly and posteriorly, a longitudinal column, from which proceed a number of small oblicjue columns, giving the appearance of branches from the stem of a tree; and hence the name uterine arbor vitae (plicae palmatae) applied to it. The longitudinal ridges are not exactly apposed, but fit against each other so as to close the cervical canal. These folds usually become very indistinct after the first labor.- The total length of the uterine cavity from the external os to the fundus is about two and a half inches. The Uterus at Different Ages.— The uterus of the fetus is in the abdominal cavity pro- jecting above the brim of the pelvis. The cervix is considerably larger than the body. At birth the cervix is larger relatively than in the adult ; there is no distinct internal os distinguishing the cavity of the body of the uterus from the cavity of the cervix. The arbor vitse is distinct and extends to the upper part of the cavity of the organ. The growth of the uterus is slow until puberty is almost reached, vi'hen for a time the growth is rapid. The growth of the uterine body causes the mucous membrane of this part to lose its folds, hence the arbor vitse disappears from the body. In a woman who has had children the uterine cavity is larger than in a woman who has never borne a child. In advanced years the uterine wall becomes paler and hard and rigid from atrophic fibrous changes. A more distinct constriction separates the body and cervix. The internal os frequently and the external os occasionally are obliterated in old age. Abnormalities. — Very rarely the uterine cavity is divided into two by a septum. Occasionally the condition known as bicomate uterus exists. In this condition each lateral angle is pro- longed into a horn or cornu. The uterus is formed by the union of the two ducts of Muller, and failure of fusion of these ducts makes a double uterus or a bicornate uterus. Changes at a Menstrual Period.— For several days before the menstrual flow begins the mucous membrane increases in thickness and vascularity and its surface is cast into folds. After these preparatory changes the superficial portions of the mucous membrane break down and are cast off, and bleeding begins. At the termination of menstruation the mucous membrane rapidly regenerates. At each menstrual period from four to five fluidounces of blood are dis- charged. The meaning of menstruation is uncertain. Pfliiger believes the wall of the uterus THE UTERUS, OB WOMB 1409 is made raw, so that if an impregnated ovum arrives it will adhere. Reichert believes that menstruation means that no impregnated ovum has arrived in the womb, and hence no bed is needed for one. Changes Induced by Pregnancy .^The muscle fibres hypertrophy enormously and be- come vastly longer and broader. There is a great increase in connective tissue, and new connective-tissue fibres pass between bundles of muscle. The peritoneal coat undergoes hyper- plasia. It remains closely adherent to the uterus, except over the lower segment, from which region it can be easily stripped. The bloodvessels become large and tortuous. The nerves are increased in length and new filaments form. The lymphatics undergo hypertrophy and hyper- plasia. The uterus becomes spherical, and after the fourth month ovoidal. Early in pregnancy the increase in weight causes the uterus to descend in the pelvis. After the third month it rises progressively, and during the ninth month the fundus reaches the epigastrium. "Before term (four weeks in primiparse, ten days or one week in multiparae) the fundus sinks again, as the presenting part and lower uterine segment become engaged in the pelvic cavity. This phenome- non is explained by contraction of the overstretched abdominal walls."' The womb is acutely antetlexed during the first three months of pregnancy. After this period, as the womb rises, the anteflexion is diminished, but some degree remains, because the abdominal walls are too lax to hold the organ straight. The uterus passes somewhat to the right side and undergoes a rota- tion on its longitudinal axis, so that the anterior surface looks front and to the right. These changes in position are caused by fecal distention of the sigmoid. The intestines are above and back of the uterus. During the first four months the cervix softens and enlarges somewhat. The length of the cervical canal is not altered during pregnancy, and the canal does not dilate until labor begins. During pregnancy the cervical glands secrete thick mucus, which coagulates and occludes the cervical canal; the round ligaments become stronger, and the layers of the broad ligaments are separated toward their inner portions by the enlarging womb. After parturition the uterus nearly regains its former size, usually weighing something over one and a half ounces; but its cavity is larger than in the virgin state, the external orifice is more marked, its edges present a fissured surface, its vessels are very tortuous, and its muscle layers are more defined. Structure. — The uterus is composed of three coats — an external or serous coat, a middle or muscular coat, and an internal or mucous coat. Tlie serous coat or perimetrium ilniiini .vrni.va) is derived from the peritoneum; it invests the fundus and the whole of the posterior surface of the uterus; but covers the anterior surface only as far as the junction of the body and cervix. In the lower fourth of the posterior surface the peritoneum, though covering the uterus, is not closely connected with it, being separated from it by a layer of loose cellular tissue and some large veins. At the lateral margins of the uterus the serous coat passes on to the broad ligaments. The serous coat adheres closely to the uterus, and it is very difficult to separate _it from the muscle. The muscular coat {tiinicn vuiscularis) (Fig. 1181) forms the chief bulk of the substance of the uterus. In the unimprcgnated -tate it is dense, firm, of a grayish color, and cuts almost like cartilage. It is thick opposite the middle of the body and fundus, and thin at the orifices of the Fallopian tubes. It consists of bundles of unstriped muscle tissue, disposed in layers, intermixed with areolar tissue, bloodvessels, lymphatic vessels, and nerves. The muscle tissue is disposed in three layers — external, middle, and internal. The external layer is placed beneath the peritoneum, disposed as a thin plane on the anterior and posterior surfaces. It consists of fibres which pass transversely across the fundus, and, con- verging at each superior angle of the uterus, are continued on the Fallopian tube, the round ligament, the ligament of the ovary; some passing at each side of the broad ligament, and others running backward from the cervix into the sacrouterine ligaments. The fibres of the external portion of the outer layer {stratum subserosum) are longitudinal. The fibres of the inner portion of the outer layer {stratum supravasculare) are partly circular and partly longitudinal. The middle layer of fibres {stratum vasculare), which is thickest, presents bundles of circular fibres closely connected with bloodvessels. In this layer are most of the large bloodvessels. The circular fibres about the internal os form a distinct sphincter. Those which surround the orifices of the Fallopian tubes are arranged in the form of two hollow cones, the apices of which surround the orifices of the Fallopian tubes, their bases intermingling with one another on the middle of the body of the uterus. The internal or deep layer {stratum mucosum) consists of longitudinal fibres. Some consider the deeper portion of the muscle tissue of the uterus to be the muscularis mucosae. But the deep portion of the muscle substance is continuous with the more superficial portion, and there is no submucous coat between the muscle and the mucous membrane. The deeper layer of muscle fibres of the uterus contains connective tissue and elastic fibres. The muscle tissue of the cervix contains more connective and elastic tissue than does the body of the uterus; hence, the cervix is harder and stiffer than the body. > A Text-book of Obstetrics. By Prof. Barton Cooke Hirst. 1410 THE UBINOGENITAL ORGANS The mucous membrane (tunica jiuicosa) (Fig. IISI) is thin, smooth, and closely adherent to the subjacent muscle tissue. It is continuous, through the fimbriated extremity of the Fallopian tubes, with the peritoneum, and through the os uteri with the lining of the vagina. In the body of the uterus it is smooth, soft, of a pale red color, lined with simple ciliated epi- thelium, and presents, when viewed with a lens, the orifices of numerous tubular glands arranged perpendicularly to the surface. It is not provided with any submucosa, but is intimately con- nected with the innermost layer of the muscular coat. In structure its tunica propria difi^ers from ordinary mucous membrane, consisting of an embryonic nucleated and highly cellular form of connective tissue, in which run numerous large lymphatics. In it are the tube-like uterine glands (glandidae iderinae), which are of small size in the unimpregnated uterus, but shortly after impregnation become enlarged and elongated, presenting a contorted or waved apjiearance toward their closed extremities, which reach into the muscularis, and may be single or bifid. The uterine glands consist of a delicate membrane, lined with epithelium, which becomes ciliated toward the orifices. In the cervix the mucous membrane is sharply differentiated from that of the uterine cavity. It is thrown into numerous oblique ridges, which diverge from an anterior and posterior longi- tudinal raphe, presenting an appearance which has received the name of arbor vitae {plicae Branches to tube. nal arteries. Fig, 1185.^ — The arteries of the internal reproductive organs of the female, seen from behind. (After Hyrtl.) pahnatae). In the upper two-thirds of the canal the mucous membrane is_ provided with numer- ous deep glands (glandidae cervicales uteri), which secrete a clear viscid alkaline mucus; and in addition, extending through the whole length of the canal, are a variable number of little cysts, presumably glands, which have become occluded and distended with retained secretion. They are called the ovules of Naboth. The mucous membrane covering the lower half of the cervical canal presents numerous papillae. The epithelium of the upper two-thirds is ciliated, but below this it loses its cilia, and close to the external os gradually changes to squamous epithelium. Vessels and Nerves (Fig. 11S5).— The arteries of the uterus are the uterine, from the inter- nal iliac, and the ovarian, from the aorta. They are remarkable for their tortuous course in the substance of the organ and for their frequent anastomoses. The uterine artery reaches the lower part of the uterus at the side and is prolonged as a large artery to the body and fundus, which ascends between the layers of the broad ligament. The uterine artery gives off a smaller branch, the cervical, which descends to supply the cervix and sends cervicovaginal branches to the vagina. The azygos arteries of the vagina come from the cervicovaginal reenforced by branches of the vaginal arteries (Fig. 1187). A median longitudinal vessel is formed in front and behind, which descends in the vaginal wall. The termination of the ovarian artery meets the termination of the uterine artery, and forms an anastomotic trunk from which branches are given off to THE UTERUS, OR WOMJS 1411 supply the uterus. Dr. Robinson, instead of describing the uterine and ovarian arteries as two vessels, describes them as parts of one vessel, the arteria uterina ovarica {\t. 673). The veins are of large size, and correspond with the arteries. In tlic iiii])rct;natcil ut(T\is these vessels form the uterine sinuses, consisting of the lining membrane of the \eins adhering to the walls of the canals channelled through the substance of the uterus. They terminate in the uterine plexuses, which empty into the internal iliac veins. The lymphatics (Fig. 1 186) are descrilied on page 797. The nerves come chiefly from the uterovaginal plexus, which continues into the hypo- gastric plexus and receives filaments from the third and fourth sacral nerves. The uterus also receives direct fibres from the hypogastric plexus and from the vesical plexus. VESSELS FROM NECK OF UTERUS TO LATERAL SACRAL NODE VESSELS FROM NECK OF UTERUS Fig. 1186. — The lymphatics of the internal organs of generation in the female. (Poirier and Charpy.) AppUed Anatomy. —Pftoic cellulitis {-parametritis) is inflammation of the pelvic cellular tissue. It is due to sepsis, and its usual antecedent is uterine sepsis. A laceration of the cervix may admit bacteria. An abscess may form. If it points in the vagina it should be incised through the vaginal wall. The uterus may require removal (hysterectomy) in cases of malignant disease or for fibroid tumors. Carcinoma is the most common form of malignant disease of the uterus, though cases of sarcoma do occur. Carcinoma may show itself either as a columnar carcinoma or as a squamous carcinoma, the former commencing either in the cervix or body of the uterus, the latter always commencing in the epithelial cells of the mucous membrane covering of the vaginal surface of the cervix. The columnar form may be treated in the early stage, before fixation has taken place, by removal of the uterus, either through the vagina or by means of abdominal section. The former operation is attended by the smaller death rate. Vaginal hysterectomji 1412 THE UBINOGENITAL ORGANS may be performed in any case in which the uterus or the uterus and tumor are not too large to be withdrawn through the vagina. It is difficult in this operation to deal with adhesions and other complications in the upper part of the pelvis, and for this reason many surgeons prefer the abdom- FimirinteA extremity of t (he /rw> Fallopian tube '^ I ugma, aiae Fig. 11S7. — The uterus and its appendages. Posterior ^-iew. The parts have been somewhat displaced from their proper position in the preparation of the specimen; thus, the right ovary has been raised aboA'e the Fal- lopian tube, and the fimbriated extremities of the tube have been turned upward and outward. (From a prepa- ration in the Museum of the Royal College of Surgeons of England.) inal operation. Vaginal hysterectomy is performed by placing the patient in the lithotomy posi- tion and introducing a large duckbill speculum into the vagina. The cervix is then seized with a volsellum and pulled down as far as possible and the mucous membrane of the vagina incised around the cervix as near to it as the disease will allow, especially in front, where the ureters are in danger of being wounded. A pair of dressing forceps are then pushed through into Douglas' pouch and opened sufficiently to allow of the introduction of the two forefingers, by means of which the opening is dilated laterally as far as the sacrouterine ligaments. A some- what similar proceeding is adopted in front, but here the bladder has to be separated from the anterior wall of the uterus for about an inch before the vesicouterine fold of peritoneum can be reached. This is done by carefully burrowing upward with a director and stripping the tissues from the anterior uterine wall. When the vesicouterine pouch has been opened and the opening dilated laterally, the uterus remains attached only •by the broad ligaments, in which are con- tained the vessels that supply the uterus. Before division of the ligaments these vessels have to be dealt with. The forefinger of the left hand is introduced into Douglas' pouch and an aneurism needle, armed with a long silk ligature, is inserted into the vesicouterine pouch, and is pushed through the broad liga- ment of one side about an inch above its lower level and at some distance from the uterus. One end of the ligature is now pulled through the anterior opening, and in this way we have the lowest inch of the broad ligament. in which is contained the uterine artery, enclosed in a ligature. This is tied tightly, and the operation is repeated on the other side. The broad ligament is then divided on either side, between the ligature and the uterus, to the extent to which it has been constricted. By traction on the volsellum which grasps the cervix, the uterus Fig. IISS. — Relations between uterus, ureter, and uterine artery. (Schematic.) THE VAGiy^A > 1413 can be pulled considerably farther down in the vagina, and a second inch of the broad ligament is treated in a similar way. This second ligature will embrace the pampiniform plexus of veins, and, when the broad ligament has been divided on either side, it will be found that a third liga- ture can be made to pass over the Fallopian tube and top of the broad ligament, after the uterus has been dragged down as far as ]Jossible. After the third ligature has been tied and the struc- ture between it and the uterus divided, this organ will be freed from all its connections and can be removed from the vagina. This canal is then sponged out and lightly dressed with gauze, no sutures being used. The gauze may be removed at the end of the second day. In squamous epithelioma, amputation of the cervix is done by some in those cases where the disease is recog- nized before it has invaded the walls of the vagina or the neighboring broad ligaments. The operation consists in removing a wedge-shaped piece of the uterus, including the cervix, through the vagina and attaching the cut surface of the stump to the anterior and posterior vaginal walb, so as to prevent retraction. In view, however, of the continuity of the lymphatic network of the cervix with the lymphatics of the body, the operation is insufficient and should be condemned. Complete abdominal hysterectomy is rarely necessary, except for malignant disease. In this opera- tion the entire uterus is removed. The preliminary introduction of bougies into the ureters as practised by Kelly and Clark enables the surgeon to readily recognize the situations of these tubes. After the abdomen has been opened the uterine vessels are secured and the broad ligaments divided in a similar manner to that employed in vaginal hysterectomy, except that the proceeding is commenced from above. When the first two ligatures have been tied and the broad ligament divided, it will be found that the uterus can be raised out of the pelvis. A transverse incision is now made through the peritoneum, where it is reflected from the anterior surface of the uterus on to the back of the bladder and the serous membrane peeled from the surface of the uterus until the vagina is reached. The anterior wall of this canal is cut across. The uterus is now turned forward and the peritoneum at the bottom of Douglas' pouch incised transversely, and the posterior wall of the vagina cut across until it meets the incision on the anterior wall. The uterus is now almost free, and is held only by the lower part of the broad ligament on either side, containing the uterine artery. A third ligature is made to encircle this, and, after having been tied, the structures are divided between the ligature and the uterus. The organ can now be removed. The vagina is plugged with gauze, and the external wound closed in the usual way. The vagina acts as a drain, and therefore the opening into it is usually left unsutured. In some cases of uterine fibroid the abdomen is opened and the tumor is removed, but the uterus is not taken away. This operation is called myomectomy. This operation is suited only to solitary subperitoneal or interstitial tumors (Penrose). The common operation for uterine fibroids is supravaginal amputation. The uterus is cut away and the cervical flaps are sutured. Before the technique of hysterectomy was perfected and before myomectomy was devised the favorite operation for uterine fibroids was sal pin (jo- oophorectomy, and by it a large majority of cases operated upon were cured. When it succeeds, a premature menopause is induced and the tumor shrinks. The operation is useless if a woman is past the menopause, and is likely to fail if the turnor is very soft or very large. THE VAGINA (Figs. 1174, 1192). The vagina {indvouterine canal) is a musculomembranous passage, which extends from the vulva to the uterus. It is situated in the cavity of the pelvis, behind the bladder and in front of the rectum. Its direction is curved upward and backward, at first in the line of the pelvic outlet, and afterward in that of the axis of the cavity of the pelvis. Its walls are ordinarily in contact, and its usual shape on transverse section is that of an H, the transverse limb being slighdy curved forward or backward, while the lateral limbs are somewhat convex toward the median line. Its length is about two and a half inches (6.25 cm.) along its anterior wall (paries anterior), and three and a half inches (8.75 cm.) along its posterior wall {paries posterior), and its wall is about 2 mm. thick. It is constricted at its commencement, and becomes dilated medially, and narrowed near its uterine extremity; it surrounds the vaginal portion of the cervix uteri, a short distance from the os, its attachment extending higher up on the posterior than on the anterior wall of the uterus (Fig. 1182). To the recess behind the cervix the term posterior fornix is applied, while the smaller recess in front is termed the anterior fornix. 1414 THE UBINOGENITAL ORGANS Relations (Figs. 1174 and 1192). — The upper part of the anterior wall of the vagina is in relation with the base of the bladder, being separated from that viscus by lax connective tissue. Lower down the middle line of the anterior wall and closely joined to it is the urethra. The upper part of the posterior wall, near the middle line, is covered for a quarter of an inch or more with peritoneum, which forms the anterior wall of the depths of the rectovaginal pouch of peritoneum or pouch of Douglas {excavatio rectoiiterina [Doriglasi]) (Fig. 11S2), between the uterus and vagina and the rectum. The portion of the posterior wall below the level of the pouch of Douglas is placed close to the rectum, a layer of pelvic fascia intervening. As the vaginal orifice is approached, the rectum and vagina separate, and interposed between them is a mass of fibro- fatty tissue called the peiineum or perineal body. Its sides are enclosed between the Levatores ani muscles. The lu-eter toward its termination (Fig. 1183) lies near the lateral wall of the vagina, passing at this point in a direction downward, inward, and slightly forward to reach the bladder. The vagina near its termination passes through the triangular hgament, and upon its sides are the bulbs of the vestibule, the glands of Bartholin, and the Bulbocavernous muscle. Structure. — The vagina consists of an internal mucous lining, a muscular coat, and a fibrous coat; between the first two is found a layer of erectile tissue. AFFERENTS TO EXTERNAL ILIAC NODES Fig. 1189. — The lymphatics of the vagina. Schematic. (Poirier and Charpy.) The mucous membrane (tunica mucosa) (Fig. 1179) is continuous above with that lining the uterus. Its inner surface presents, along the anterior and posterior walls, a longitudinal ridge or raph^, called the rugous columns of the vagina (colvmna ruganim anterior et posterior). The anterior column extends downward as far as the external orifice of the urethra, forming the carina urethralis vaginae. Numerous transverse ridges or rugse (rngae vaginales) extend out- ward from the raphe on either side. These rugse are separated by furrows of variable depth, giving to the mucous membrane the appearance of being studded over with conical projections or papillae; they are most numerous near the orifice of the vagina, especially in women before parturition. The epithelium covering the mucous ibembrane is of the stratified squamous variety. The subepithelial tissue is very loose and contains numerous large veins, which by their anastomoses form a plexus, together with smooth muscle fibres from the muscular coat; it is regarded by Gussenbauer as an erectile tissue. It contains a number of mucous crypts, but no true glands. The muscular coat {tunica muscularis) consists of two layers, an external longitudinal, which is far the stronger, and an internal circular layer. The longitudinal fibres are continuous with the superficial muscle fibres of the uterus. The strongest fasciculi are those attached to the recto- vesical fascia on each side. The two layers are not distinctly separable from each other, bu; THE EXTERNAL ORGANS 1415 are connected by oblique decussating fasciculi which pass from the one layer to the other. Above the triangular ligament the fibres are nonstriated; in the region of the ligament they show stria- tions. In addition to this, the vagina at its lower end is surrounded by a band of striped muscle tissue, the Sphincter vaginae (p, 445). Tile fibrous coat is composed of dense white fibrous connective tissue, which connects the vagina to (he surrounding organs. It contains a large plexus of bloodvessels. The erectile tissue consists of a layer of loose connective tissue situated between the mucous membrane and the muscular coat; embedded in it is a plexus of large veins, and numerous bundlt-s of unstripcd muscular fibres derived from the circular muscular layer. The arrange- ment of the veins is similar to that found in other erectile tissues. Bloodvessels, Nerves, and Lymphatics. — The arteries of the vagina are branches of the vesicovaginal artery, ihc vaginal branch of the uterine artery f|), 672) and branches of the internal pudic and middle hemorrhoidal. The veins form an alnuulant plexus around the wall of the vaginii and pass to ihc internal iliac veins. The lymphatics (Fig. 1189) arise from two communicating networks, one of which is beneath the mucous incniljrane, the other in the muscu- lar wall. There is a third network around the vaginal wall, from w hicli the collectors arise. The trunks from the upper third of the vagina pass to the external Uiac nodes; those from the middle third pass to the internal iliac nodes; those from the lower third terminate in the nodes at the promontory of the sacrum or in the lateral sacral nodes. The nerves come from the third and fourth sacral nerves and from the uterovaginal and vesical plexuses of the sympathetic. THE EXTERNAL ORGANS (PARTES GENITALES EXTERNAE MULIEBRES). The external reproductive organs in the female are the mens Veneris, the labia majora and minora, the vestibule, the clitoris, the vaginal bulb, and tiie glands of Bartholin. The term vulva {pudendum, midiebre), as generally appHed, includes all of these parts. In examining the structures entering into the formation of the vulva we find the homologues of most of the structures which make up the male genitals. Labia majora = Scrotum. Clitoris = Corpora cavernosa. Bulbus vestibuli = Corpus spongiosum. Vestibular glands = Bulbourethral glands (of Bartholin). (of Cowper). The mons Veneris (commissura lahiorum anterior) is the rounded eminence in front of the pubic symphysis formed by a collection of fatty tissue beneath the integument. It becomes covered with hair at the time of puberty. The labia majora (labia majora imdendi) (Figs. 1190 and 1191) are two promi- nent longitudinal cutaneous folds, narrow behind, but fuller and larger toward the mons Veneris, and bounding the pudendal slit {rima inidendi) or common urinogeni- tal opening. Each labium majus has two surfaces, an outer, which is covered by pigmented skin with numerous sebaceous glands and strong, crisp hairs, and an in- ner, which is smooth and moist and is continuous with the genitourinary mucous tract. In the subcutaneous areolofatty tissue of each labium majus the round ligament of the uterus ends. The labia are joined with each other anteriorly by the mons Veneris or anterior commissure. Posteriorly they appear to become lost in the neighboring integument, although sometimes connected by a slight transverse fold in front of the anus, the posterior commissvure (commissura labioriim -posterior), or posterior l)oundary of the vulvar orifice. The interval between the posterior commissure and the anus, about an inch in length, constitutes the obstetric perineum. Bloodvessels, Nerves, and Lymphatics.— The arteries of the labia majora are derived from the superficial external pudic arteries ami from iicriiual branches of the internal pudic arteries. Homologous with the scrotum, tlie nerve supply is ilcrivcil from branches of the ilioinguinal, internal pudic, and perineal branches of the small sciatic. The lymphatics drain into the superficial inguinal and internal iliac lymph nodes. 1416 THE URINOGENITAL ORGANS The labia minora, or nymphse {labia minora pvdendi) (.Figs. 1191, 1192), are two smaller, narrower longitudinal folds, with a delicate covering of modified skin, and usually hidden from view unless the labia majora are separated. They end posteriorly by gradually joining the labia majora, although in the young there is usually a transverse fold, the fourchette or frenulum (Jreimluvi labiorum fiidendi). Traced forward each labium minus divides into an outer and an inner portion or limb. The outer parts of" the two labia unite over the glans clitoridis to form the prepuce of the clitoris ipraeputium clitoridis) (Fig. 1191). The internal limbs unite at an acute angle beneath the glans clitoris and are attached to the under surface of the glans to form the frenulum clitoridis. The two labia minora are in contact, flanked by the labia majora, and are covered by modified skin, MONS VENERIS POSTERIOR COMMISSURE OF VULVA NTERIOR OMMISSUDE F VULVA 1190.^ — The female pudendum or A-ulva with the labia majora. (Toldt.) with numerous, sebaceous glands (glwidulae vestibidares minores), resembling the smooth, moist, pink-colored integument of the inner surface of the labia majora. The cleft between the labia minora is called the vestibule, the structures of which are seen only on separating the labia. The vestibule (vestibidum vaginae) (Figs. 1174 and 1191) is the cleft between the labia minora, between the glans clitoridis in front and the fourchette behind. On separating the labia minora the following structures in the vestibule are seen: (1) The external urethral orifice and the minute openings, one on each side, of the paraurethral ducts; (2) the vaginal orifice; and (3) the openings of the ducts of the vestibular glands (of Bartholin). The recess between the fourchette and the vaginal orifice is called the fossa navicularis. THE EXTERNAL ORGANS 1417 The external orifice of the urethra, or urinary meatus (orificimn 7irrthrac c.vicrnum) (Figs. 1191 and 1194), is situated immediately in front of tlie vaginal orifice and about an inch behind the glans clitoridis. The orifice usually presents the appearance of a vertical slit, and is surrounded by a prominent elevation of the mucous membrane. On each side of the urinary meatus there may sometimes be seen the minute orifice of the duct of the paraurethral glands, supposed to be the homologues of the prostate. vAON 5 VENERIS 1191. — The vulva. External female organs of generation. The vaginal opening is situated behind the urethral orifice, and its appearance varies with the condition of the hymen, a membranous fold which more or less closes the aperture in the virgin. The hymen varies much in shape. Its commonest form is that of a ring, gener- ally broadest posteriorly; sometimes it is represented by a .semilunar or crescentic fold, with its concave margin turned toward the pubes. A complete septum stretched across the lower part of the vaginal orifice is called an imperforate hymen. Occasionally the hymen is cribriform, or its free margin forms a mcmhrantnis fringe, or it may be entirely absent. It may persist after copulation, so that it cannot be considered as a test of virginity. After rupture of the hymen the small 1418 THE UBINOGENITAL ORGANS rounded nodular elevations known as the carunculae myrtiformes (canmculae hymenales) are found as the remains of the structure. The clitoris (Figs. 1191, 1192) is an erectile structure which is the morpho- logic homologue of the penis; unlike the penis, however, it is not traversed by the urethra. It is situated beneath the anterior commissure (or mons Veneris) and is partly hidden between the anterior extremities of the labia minora. It is com- posed of a body and two crura; the extremity of the body is surmounted by a small glans. -Sagittal section of the lower part of a female trunk, right segment. SM, INT. Small intestine. (Testut.) The body of the clitoris, composed of erectile tissue, is about an inch and a quarter in length (3 cm.), and is bent upon itself so that the angle opens downward. It tapers toward the glans, is enclosed by a dense fibrous coat, and is divided by an incomplete septum corporum cavemosorum into two semicylindrical corpora cavernosa clitoridis, homologous with the corpora cavernosa of the male. A sus- ■ pensory ligament passes from the pubic symphysis to the fibrous coat of the body of the clitoris. Each corpus cavernosum diverges from its fellow to form the eras clitoridis. Each crus is attached to the pubic arch (pubis and ischium) and is covered by the Ischiocavernosus muscle (in. erector clitoridis). THE EXTERNAL ORGANS 1419 The glans clitoridis is a minute mass of erectile tissue, surmounting tiie tapering apex of the Ijody of the chtoris. It is covered by a very sensitive epitheUum, and its erectile tissue, like that of the glans penis, is continuous with the erectile tissue CRESCENTIC FRINGED BILABIAL Bl PERFORATE CRIBRIFORM Fig. 1193. —Varieties of hymen. (Testut, after Rose.) SPHINCTER VAGINAE MUSCLE MUSCLE ORIFICE OF URETHRA TRANSVERSE PEHINEI MUSCLE j|;.^>fyi^=^ EXCRETORY Fig. H94. — The female external organs of generation dissected. (Spalteholz.) 1420 THE VRINOGENITAL ORGANS of the bulbus vestibuli, the homologue of the corpus spongiosum of the male. The praeputium clitoridis and the frenulum clitoridis have already been described (p. 1416) as divisions of the labia minora. Arteries and Nerves of the Clitoris. — The body and the crura of the clitoris derive their blood supply from the deep artery of the clitoris (arteria profunda clitoridis), a branch of the internal pudic artery. Another branch of this artery, the dorsal artery of the clitoris (arteria dorsiili.s clitoridis) supplies the glans. The nerve supply is derived from the dorsal nerve of the clitoris, from the internal pudic, and from the h3rpogastric sympathetic" plexus. The vaginal bulb (bulbus vestibuli) (Fig. 1194) may be regarded as the homo- logue of the bulb portions of the corpus spongiosum of the male. The principal morphological difference lies in the fact that the two halves are fused in the male, but remain separated in the female. The bulbus vestibuli consists of a mass of minute convoluted bloodvessels, of such plexiform arrangement as to be often called erectile tissue, arranged in two halves, one on either side of the vaginal and urethral orifices. Each half is thicker or more massive posteriorly, while anteriorly it is attenuated and joins its fellow of the opposite side to form the pars intermedia, continuous with the erectile tissue of the glans clitoridis. Each half of the bulbus vestibuli rests against the lateral wall of the vagina and lies superficial to the triangular ligament. Externally and inferiorly it is covered by the Bulbocaver- nosus muscle. Arteries and Nerves of the Bulbus Vestibuli. — The blood is supplied by the artery to the bulb (arteria hulbi vestibuli), a branch of the internal pudic artery. The nerve supply is by branches of the hypogastric sympathetic plexus. The Glands of "BdiXtho^ni^glandula vestibularis major [Bartholini]) (Fig. 1194). — On each side of the posterior part of the commencement of the vagina is a round or oblong body, of a reddisli-yellow color, and of the size of a horse-bean, analo- gous to Cowper's gland in the male. It is called the gland of Bartholin, the gland of Duvemey, the vulvovaginal gland, or the suburethral gland. Bartholin's gland lies partly in the inferior or anterior leaf of the triangular ligament. The pos- terior portion of the bulbus vestibuli and the Bulbocavernous muscle partly cover it. Each gland opens by means of a long single duct immediately external to the hymen, in the angle or groove betw^een it and the nympha (Fig. 1193). DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS. The permanent organs of the adult are preceded by a set of purely embryonic structures which, with the exception of their ducts, almost entirely disappear before birth. These embryonic structures, all developed from the intermediate cell mass of mesodermal tissue, are on either side; the pronephros, the mesonephros, the Wolffian (mesonephric) duct, and the Miillerian duct (oviduct). The pronephros disappears very early; the structural elements of the meso- nephros mostly atrophy, but in their place is developed the genital gland, in association with which the mesonephric duct remains as the duct of the male genital gland, the oviduct as that of the female. The pronephros is an early embryonic structure in all vertebrates. It develops at about the level of the heart by a proliferation of the mesodermal cells of the intermediate cell mass. In it appear (a) a longitudinal cord of cells, which later acquires a lumen to form the pronephric duct; (6) two transverse pronephric tubules develop as invaginations of the coelomic meso- thelium. Of these, the cephalic one acquires a lumen and opens into the coelomic cavity; the other remains a solid cord of cells. Neither tubule becomes connected with the pronephric duct. The pronephric duct remains to become the Wolffian duct of the next stage, while the tubules are represented, in the adult, by t'le hydatids at the fimbriated end of the Fallopian tube in the female, and by the stalked hydatid at the upper end of the testis in the male. The Mesoiiephros, Miillerian Duct, and Genital Gland. — On the inner side of the Wolffian duc't a series of tubules, the Wolffian tubules, are developed. Each tubule opens laterally into the duct, while its middle part is invaginated by a tuft of capillary bloodvessels to form a glom- DEVELOPMENT OF UBINARY AND GENERATIVE ORGANS 1421 erulus. These tubules increase in number, and collectively constitute the mesonephros or Wolffian body (Figs. 1195, 1196). At the beginning of the second month this body forms an elongated spindle-shaped structure, which projects into the ccelomic cavity at the side of the dor- sal mesentery, and reaches from the septum transversum cephalad to the fifth lumbar somite caudad. The Wolffian body persists and forms the permanent kidney in fishes and amphibians, Iffian duct. ^.MilUerJan duct. ( Stroma Genital J of ovary, ridge. | Pr' [^ ova. -Body wall. \]\\m\ ^^^s/ i Mesentery.- Fig. 1195. — Section of the urinogenital area of a chick embryo of the fourth day. (Waldeyer.) but in reptiles, birds, and mammals it is superseded by the metanephros, which forms the perma- nent kidney in these animals. The cephalic tubules of the Wolffian body become attached to the sexual eminence or genital ridge, from which the ovary in the female and the testicle in the male are developed. Diu-ing the development of the permanent kidneys the Wolffian bodies atrophj', and this process proceeds to a much greater extent in the female than in the male. Mullerian ducts. Fig. 1196.— Enlarged view from the front of the left Wolffian body before the establishment of the distinc- tion of sex. o. b, c. d. Tubular structure of the Wolf- fian body. e. Wolffian duct. /. Its upper extremity, ff. Its termination in x, the urinogenital sinus, h. The duct of Miiller. t. Its upper, funnel-shaped extremity. k. Its lower end, terminating in the urinogenital sinus. I. The mass of blastema for the reproductive organ, ovary, or testicle. (From Farre, after Kobelt.) Fig. 1197.— Urinogenital sinus of female ,uman embryo of eight and a half to nine i^eeks old. In the male, the Wolffian duct persists, and forms the tube of the epididymis, the vas deferens, and common ejaculatory duct, while the seminal vesicle arises as a lateral diverticulum from its caudal end. The cephalic Wolffian tubules form the rete testis, vasa efferentia, and coni vas- culosi of the testis; while the caudal tubules atrophy or are represented by the occasional vasa aberrantia of the globus minor and by the paradidymis. In the female, the Wolffian bodies and ducts atrophy. The remains of the Wolffian tubules are represented by the epobphoron and the paroophoron (p. 1407), while the cephalic portion of the Wolffian duct sometimes persists as the functionless duct of Gartner (Fig. IISI). 1422: THE UBINOGENITAL 0BGAN8 Fig. 1198. — Diagram of the primitive urinogenital organs in the embryo pre- vious to sexual distinction. 3. Ureter. 4. Urinary bladder. 5. Uraehus. cl. Cloaca, cp. Elevation which becomes clitoris or penis, i. Lower part of in- testine. Is. Fold of integument from which the labia majora or scrotum are formed, m, m. Right and left Miillerian ducts uniting and running with the WoIflHan ducts in gc, the genital cord. ot. The genital ridge from which either the ovary or testicle is formed, ug. Sinus urogenital!. TF. Left Wolffian body, w, w. Kight and left Wolffian ducts. Fig. 1199. — Diagram of the female type of sexual organs. c. Gland of Bartholin, and immediately above it the urethra. cc. Corpus cavernosum clitoridis. dG. Remains of the left Wolffian duct, such as give rise to the duct of Gartner, represented by dotted lines; that of the right side is marked w. f. The abdominal opening of the left Fallopian tube. g. Round liga- ment corresponding to gubernaculum. k. Situation of the hymen, i. Lower part of the intestine. /. Labium, n. Nympha. o. The left ovary. po. Parovarium (epoophoron of Waldeyer). sc. Vascular bulb or corpus spongiosum. u. Uterus. The Fallopian tube of the right side is marked m. v. Vulva, va. Vagina. W. Scattered remains of Wolffian tubes near it (paroophoron of Waldeyer). Fig. 1200. — Diagram of the male type of sexual organs. C. Cowper's gland of one side. cp. Corpora cav- ernosa penis cut short, e. Caput epi- didymis, g. The gubernaculum. i. Lower part of the intestine, ni. Miil- lerian duct, the upper part of which remains as the hydatid of Morgagni; the lower part, represented by a dotted line descending to the prostatic vesicle, constitutes the occasionally existing cornu and tube of the uterus mascu- iinus. pr. The prostate gland. $. Scrotum. sp. Corpus spongiosum urethrae. t. Testicle in the place of its original formation. t'. Together with the dotted lines above, indicates the direction in which the testicle and epididymis descend from the abdomen into the scrotum. vd. Vas deferens. vh. Vas aberrans. 7'S. The vesicula seminalis. TF. Scattered remains of the Wolffian body, constituting the organ of Giraldes, or the paradidymis of Waldeyer. Figs. 119S to 1200. — Diagrams to show the development of the male and female generative organs from ; ent type. (Allen Thomson.) DEVELOPMENT OF URINARY AND GENERATIVE ORGANS 1423 Wolffian body Milllermn duct Wolffian duct The Miillerian Ducts. — Shortly after the formation of the Wolffian ducts a second pair of ducts is developed. These are named the Miillerian ducts. Each arises on the outer aspect of the corresponding Wolffian body as a tubular invagination of the cells lining the coelom (Fig. 1194). The orifice of the invagination remains patent, and undergoes enlargement and modi- fication to form the abdominal ostium of the Fallopian tube. The ducts pass caudad on the outer aspects of the Wolffian bodies, but toward the posterior end of the embryo they cross to the inner side of the Wolffian ducts, and thus come to lie side by side between and behind the latter — the four ducts forming what is termed the (jcnital cord (Fig. 1197). Ultimately, the Miillerian ducts open into the ventral part of the cloaca between the orifices of the Wolffian ducts, and terminate on an elevation named the Mullerian eminence (Fig. 1197). In the male the Mullerian ducts atrophy, but traces of their cephalic ends are represented by the sessile hydatids of the epididymis, while their terminal fused portions form the uterus mascu- linus or sinus pocularis in the floor of the prostatic portion of the uretlira (Fig. 1200). In the female, the Mullerian ducts persist and undergo further development. The portions which lie in the genital cord fuse to form the uterus and vagina; the parts cephalad of this cord re- main separate, and each forms the correspond- ing Fallopian tube — the abdominal ostium of which is developed from the anterior extremity of the original tubular invagination from the ca?lom (Fig. 1199), The fusion of the Muller- ian ducts begins in the third month, and the septum formed by their fused mesal walls disappears from below upward, and thus the cavities of the vagina and uterus are produced. About the fifth month an annuMr constriction marks the position of the neck of the uterus, and after the si.xth month the walls of the uterus begin to thicken. The development of the vagina in the manner just described would necessitate the growth of a septum between it and the urethra; but Wood-.Jones maintains that no such septum exists, and that "the vagina is, for a great part of fetal life, a solid rod, and not an open canal at all." He says: "Early in the history of the embryo the Mullerian ducts open into the urogenital sinus at its upper part; late in its history they open at the hind-end of the vagina, and for 'a considerable interval they have no open- j,^^ I201.-Transverse section of human embryo of ing at all — the old one being losi and the new eight and a half to nine weeks old. (From model by one not yet formed. No septal division is K^ibel.) employed in this change; but as the hindgut, when its cloacal opening is lost, reestabhshes communication with the exterior by a new downgrowth, so the Miillerian ducts, when their cloacal opening becomes obliterated, tunnel a new passage to the hind end." Genital Gland. — The first appearance of the genital gland is essentially the same in the two sexes, and consists in a thickening of the epithelial layer which lines the jieritoneal or body cavity on the inner side of the Wolffian ridge. Beneath the thickened epithelium an increase in the mesoderm takes place, forming a distinct projection. This is termed the (jcnital ridge (Fig. 1135), and from it the testis in the male and the ovary in the female are developed. At first the Wolf- fian body and genital ridge are suspended by a common mesentery, but as the embryo grows the genital ridge gradually becomes pinched off from the Wolffian body, with which it is at first con- tinuous, though it still remains connected to the remnant of this body by a fold of peritoneum, the mesorchium or mesovarium (Fig. 1201). About the seventh week the distinction of sex in the genital ridge begins to be perceptible. The ovary, thus formed from the genital ridge, consists of a central part of connective tissue covered by a layer of epithelium, the germinal epithelium. Between the cells of the germinal epithelium a number of larger cells, the primitive ova, are found, and these are carried into the subjacent sti'oma by bud-like ingrowths of the germinal epithelium, the cells of which surround the primitive ova; in this manner the primitive Graafian follicles are formed. The rest of the ger- minal epithelium on the surface of the ovary forms the permanent epithelial covering of this organ (Fig. 1202). According to Beard, the primitive ova are early set apart during the segmen- tation of the ovum and migrate into the germinal ridge. Waldeyer taught, and for many years his views have been accepted, that the primitive germ ci;lls are derived from the "germinal epithelium" covering the genital ridge. Beard,' on the 1 Journal of Anatomy and Physiology, vol. x.>Lxviii, -^Svinal ™''''- Spinal ganglion, Nolochord. ■Sympathetic ganglion. Inferior vena cava. ■Common iliac criery. Ureter. Mesovarium. ^Intestine. Bladder. *f- - Umbilical artery. 1424 THE URINOGENITAL ORGANS other hand, maintains that in the skate they are not derived from this epithehum, but arc probably formed during the later stages of cell cleavage, before there is any trace of an embiyo; and a similar view was advanced by Nussbaum as to their origin in amphibia. Beard says: "At the close of segmentation many of the future germ cells lie in the segmentation cavity just beneath the site of the future embryo, and there is no doubt they subsequently wander into it." The germ cells, "after they enter the resting phase, are sharply marked off from the cells of the em- bryo by entire absence of mitoses among them." They can be further recognized by their irregular form and amoeboid processes, and by the fact that their cytoplasm has no affinity for ordinary stains, but assumes a brownish tinge when treated by osmic acid. The path along which they travel into the embryo is a very definite one — viz., "from the yolk sac upward between the splanchopleure and gut in the hinder portion of the embryo." This pathway, named by Beard the germinal path, "leads them directly to the position which they ought finally to take up in the 'germinal ridge.' " A considerable number apparently never reach their proper desti- nation, since "vagrant germ cells are found in all sorts of places, but more particularly on the mesentery." Some of these may possibly find their way into the germinal ridge; some probably undergo atrophy, while others may persist and become the seat of dermoid tumors. Ovarian tube of epithelium. Blood-v Graafian follicle. — Germinal epithelium. Primitive ova. -Cell nest. Fig. 1202. — Section of the ovary of i vborn child. (Waldeye The testis is developed in a very similar way to the ovary. Like the ovary, in its earliest stages it consists of a central mass of connective tissue covered by germinal epithelium, among which larger cells, the primitive sperm cells, are seen. These are carried into the subjacent stroma by tubes of germinal epithelium, which form the lining of the seminiferous tubules, while the primitive sperm cells form the spermatogonia. The seminiferous tubules become connected with outgrowths from the Wolffian body, which, as before mentioned, form the rete testis and vasa efFerentia. Descent of the Testes. — The testes, at an early period of fetal life, are placed at the back part of the abdominal cavity, behind the peritoneum and a little below the kidneys; their anterior surfaces and sides are invested by peritoneum. About the third month of intrauterine life a peculiar structure, the gubemaculum testis, makes its appearance. This is at first a slender band, extending from that part of the skin of the groin which afterward forms the scrotum through the inguinal canal to the body and epididymis of the testis, and is then continued upward in front of the kidney toward the Diaphragm. As development advances, the peritoneum cover- ing the testis encloses it and forms a mesentery, the mesorchium, which encloses also the guber- naculum and forms two folds, one above the testis and the other below it. The one above the testis is the plica vascularis, and contains ultimately the spermatic vessels; the one below, the plica gubernatrix, contains the lower part of the gubernaculum, which has now grown into a thick cord; it terminates below at the internal ring in a tube of peritoneum, the processus vagi- nalis, which protrudes itself down the inguinal canal. The lower part of the gubernaculum by the fifth month has become a thick cord, while the upper part has disappeared. The lower part can now be seen to consist of a central core of unstriped muscle fibre, and outside this of a firm layer of striped elements, connected, Ijehind the peritoneum, with the abdominal wall. As the scrotum develops, the main portion of the lower end of the gubernaculum is carried with the skin to which it is attached to the bottom of this pouch; other bands are carried to the inner side of the thigh and to the perineum. The fold of peritoneum, constituting the processus vaginalis, projects itself downward into the inguinal canal, and emerges at the external abdominal ring, DEVELOPMENT OF URINARY AND GENERATIVE ORGANS 1425 pushing before it a part of the Internal oblique and the aponeurosis of the External oblique, which form, respectively, the Cremaster muscle and the external spermatic fascia. It forms a gradually elongating pouch or cul-de-sac, which eventually reaches the bottom of the scrotum, and behind this the testis is drawn by the growth of the body of the fetus, for the gubernaculum does not grow commensiu'ately with the growth of other parts, and therefore the testis, being attached by the gubernaculum to the bottom of the scrotum, is prevented from rising as the body grows, and is drawn first into the inguinal canal and eventually into the scrotum. It seems cer- tain also that the gubernacular cord becomes shortened as development proceeds, and this assists in causing the testis to reach the bottom of the scrotum. By the eighth month the testis has reached the scrotum, preceded by the lengthened pouch of peritoneum, the processus vaginalis, which communicates by its upper extremity with the peritoneal cavity. Just before birth the upper part of the pouch usually becomes closed, and this obliteration extends gradually down- ward to within a short distance of the testis. The process of peritoneum surrounding the testis is now entirely cut off from the general peritoneal cavity and constitutes the tunica vaginalis.^ In the female there is also a gubernaculum, which effects a considerable change in the position of the ovary, though not so extensive a change as in that of the testis in the male. The guber- naculum in the female, as it lies on either side in contact with the fundus of the uterus, contracts adhesions to this organ, and thus the ovary is prevented from descending below this level. The UmbllnnI < o, d MSllerian duct Kidney dU ei tn iihim. Fig. 1203.— Tail end of human embryo of twenty- Fig. 1204.— Tail end of human embryo of thirty- five to twenty-nine days old. (From model by two to thirty-three days old. (From model by Keibel.) Keibel.) upper part of the gubernaculum, i. e., the part between the ovary and the uterus, becomes ulti- mately the rounded ligament of ihe ovary, while the lower part, i. e., the part between the attach- ment of the cord to the uterus and its termination in the labium majus, ultimately forms the round ligament of the uterus. A pouch of peritoneum accompanies it along the inguinal canal, analogous to the processus vaginalis in the male; it is called the canal of Nuck. In rare cases the guber- naculum may fail to contract adhesions to the uterus, and then the ovary descends through the inguinal canal into the labium majus, extending down the canal of Nuck, and under these circumstances its position resembles that of the testis in the male. The Metanepnros or Permanent Kidney. — The rudiments of the permanent kidneys make their appearance about the end of tiie first or beginning of the second month. Each arises as a diverticulum from the hind end of the Wolffian duct, close to where the latter opens into the cloaca (Figs. 1203, 1204). This diverticulum grows cephalad into the posterior part of the intermediate cell mass, where its blind or cephalic extremity becomes dilated and subsequently divides into several buds, which form the rudiments of the pelvis and calices of the lu-eter. By fiu'ther subdivisions it gives rise to the collecting tubules of the kidney The secretory tubules are developed from condensations of the nephrogenic tissue. At first these are spher- ical masses of cells which become hollowed, forming the renal vehicles. These become elon- gated and S-shaped; one end of the S-shaped tube becomes continuous with the lumen of a renal diverticular branch, the other end becomes cup-shaped and then spherical, being invagi. nated by a tuft of capillaries derived from the renal artery to form a glomerulus. The inter- vening portions of the tube become convoluted and looped to form the uriniferous tubule. The mesoderm around the subdivisions of the diverticulum becomes condensed to form the connec- tive tissue and vessels of the kidney. The diverticulum is elongated to form the ureter, the posterior extremity of which opens at first into the hind end of the Wolffian duct; after the sixth week it separates from the Wolffian duct, and opens independently, into the part of the I The obliteration of the process of peritoneum which accompanies the < process, is often incomplete. )rd, and is hence called the fu 1426 THE UBINOGENITAL ORGANS Ureter, Wolffian duct MiWei lan duct Bladder Symphysis pvt)^''^^^ cloaca which ultimately becomes the bladder (Fig. 1205). The manner in which this separation is brought about is not fully known.' The secretory tubules of the kidney become arranged into pyramidal masses or lobules, and the lobulated condition of the kidneys exists for some time after birth, while traces of it may be found even in the adult. The kidney of the ox and many other animals remains lobulated throughout life. The Urethra. — In the female the lu-ethra is formed from the upper part of the urinogenital sinus — viz., that part which lies above the openings of the Wolffian and INIiillerian ducts. The portion of the sinus below these openings becomes gradually shortened, and it is ultimately opened out to form the vestibule, and in this manner the lu-ethra and vagina come to open separately on the surface. Wood-Jones regards the female uretlira as "the cloacal remnant in its simplest form," and points out that "it does not remain tubular throughout fetal life, but is for a time obliterated more or less completely by the proliferation of the vaginal bulbs." Developmentally considered, the male urethra consists of two parts — (1) the prostatic and membranous portions, which are derived from the iffinogenital sinus, and correspond to the whole of the female urethra; (2) the penile portion, which is formed by the fusion of the inner genital folds. The prostate gland originally consists of two separate portions, each of which arises as a series of diverticular buds from the epithelial lining of the urinogenital sinus, between the third and fourth months. These buds become tubular, and form the glandular substance of the two lobes, which ultimately meet and fuse behind the uretlira and also extend on to its ventral aspect. The third or middle lobe is formed as an extension of the lateral lobes between the common ejaculatory ducts and the blad- der. Skene's ducts in the female urethra are regarded as the homologues of the pros- tatic glands. The glands of Coicper in the male, and of Bartholin in the female, also arise as diverticula from the epithelial lining of the (Urogenital sinus. The Urinary Bladder. — The trigone of the bladder is formed from the upper part of the urinogenital sinus; the remainder of the viscus is developed from the part of the cloaca which lies above the sinus (Fig. 1204). The bladder is at first tubular in shape, its canal being continuous with that of the allan- tois, but after the second month its cavity expands to form a sac, from the summit of which the tube of the allantois extends to the umbilicus; this tube undergoes obliteration to form the fibrous cord of the urachus. In some cases the allantoic canal remains patent, and urine may escape by it at the umbilicus. If the urethra be looked upon as the remnant of the cloaca, then the bladder, with the exception of the trigone, must be regarded as being developed by a dilatation of the proximal part of the allantois. The external organs of generation (Fig. 1206), like the internal, pass during development through an indifferent stage in which there is no distinction of sex. It is therefore necessary to describe this stage, and then follow the development of the female and male organs, respectively. The cloacal membrane, which is composed of ectoderm and entoderm, originally extends from the umbilicus to the tail. The mesoderm around the cloacal chamber gradually extends between the layers of the membrane, stopping short, however, around the margins of the entodermal cloaca, so that the bilaminar cloacal membrane is limited to this part. About the fifth week a prominence, the genital tubercle, arises in front of the cloacal membrane, while at the sides the edges of the mesoderm are elevated to form the lahioscrotal or outer genital folds. Along the under surface of the genital tubercle the ectoderm is thickened, and at the apex of the tubercle projects forward as an epithelial horn. In this ectodermal thickening a longitudinal Glans perns lietlua. Vertebral culuinn. Fig. 1205. — Tail end of human embryo, from eight and a half to nine weelis old. (From model by Keibel.) 1 The separation of the uterus from the Wolffian duct may be brought about by the absorption of the hinder end of the latter into the genitourinary chamber, and by the growth of the wall of this chamber between the openings. Robinson (Proceedings of the Anatomical Society of Great Britain and Ireland, May, 1903, p. 63) states, regarding an embryo of about seven weeks, that ' 'from the posterior or lower opening of the WolflBan duct a grooved ridge, the Wolffian ledge, runs caudally on the wall of the genitourinary chamber and gradually disappears at the junction of the Wolflian angle with the body of the chamber. The lateral margins of the groove are continuous anteriorly with the lateral margins of the Wolffian duct, and apparently fuse together to form the ventral wall of the lower part of the duct. . . . Obviously, if the lateral margins of the groove were to fuse from before backward, the aperture of the Wolffian duct would be carried farther backward in the chamber, and its distance from the opening of the ureter increased." DEVELOPMENT OF URINARY AND GENERATIVE ORGANS 1427 groove, the genital groove, appears, and into its lips the mesoderm extends to form the inner genital folds. After the ruptiu-e of the cloaca! membrane this groove becomes continuous with the urogenital sinus. With the formation of these parts the indifferertt stage of the external genital organs is reached. In the female this stage is largely retained; the lower part of the urinogenital sinus persists as the vestibule, the genital tubercle forms the clitoris, the labioscrotal folds the labia majora, and the inner genital folds the labia minora. Heal cord, nilal tubercle. 1 . L ^ Genital tubercle. A V Labioscrotal fold. 1 } Inner oenital fold* Genital groove. Labioscrotal fold. Inner genital fold. Genital f^roove. Perineum. J J T' -Glans clitoridis. -Labioscrofal fold. -Inner genital fold, "Genital groove. j! ,wniia,v\v\\.xw-^^^ 1/ Raphe. Vaginal orifice. s- -Stages in the development of the external sexual orsan; the Ecker-Ziegler models.) the male and female In the male the changes are greater on account of the development of the penile portion of the urethra. The genital tubercle enlarges to form the corpora cavernosa and glans penis. The lips of the inner genital folds meet and fuse from behind forward to form the penile urethra, the bulb, and the corpus spongiosum. The part of the urethral groove on the glans penis is closed independently, and the last part of the urethral tube to be completed is that at the junction of the glans and body of the penis. If the lips of the groove fail to close, the condition known as hi/pospadias results. The labioscrotal folds meet and unite in the middle line to form the scrotum, their line of union being indicated by the median raph^. 1428 THE URINOGENITAL ORGANS The prepuce is formed by the growth of a sohd plate of ectoderm into the superficial part of the genital tubercle; on coronal section this plate presents the shape of a horseshoe. By the breaking-down of its more centrally situated cells this plate is split into two lamellae and a cutaneous fold, the prepuce/ is liberated and forms a hood over the glans. "Adherent prepuce is not an adhesion really, but a hindered central desquamation" (Berry Hart, op. cit.). The homologies of the different parts of the sexual organs may be stated in tabular form as follows: Indifferent Stage. Male. Female, Genital Ridge. Testis (secretory portion). Ovary. Wolffian body. Rete testis, vasa efferentia, coni vasculosi, paradidymis. Epoophoron or organ of Rosen- miiller. Paroophoron. AYolffian duct . Canal of epididymis, vas deferens, common ejaculatory duct. Sem- inal vesicle. Hydatid of Morgagni. (Duct of Gartner.) Miillerian ducts . Sessile hydatids of epididymis. Uterus masculinus. Fallopian tubes, uterus, vagina. Genital tubercle . Corpora cavernosa and glans penis. Prostatic and membranous parts of urethra. Clitoris. Urethra. Vestibule. Urinogenital sinus Inner genital folds Penile urethra, bulb, and corpus spongiosum. Labia minora. Labioscrotal folds Scrotum. Labia majora. THE MAMMARY GLAND (MAIMMA) (Figs. 1208, 1210). The breasts, mammary glands or mammae, secrete the milk, and are accessory glands to the organs of reproduction. They develop fully in the female, but usually remain rudimentary in the male. There are two of these glands, and they are situated in the superficial fascia of the anterior portion of the thorax. Description of a Well-developed Breast. — ^Each gland appears as a hemispher- ical body projecting from the front of the thorax beneath the skin and lying over a portion of the Pectoralis major muscle and a smaller portion of the Serratus magnus muscle. The hemispherical projection extends usually from the margin of the sternum to the axilla and from the level of the second rib to the level of the sixth rib, or from the third rib to the seventh rib, but this does not represent the real size of the gland. The gland is much larger than this, being rendered so by tails or prolongations of breast tissue, which will be described later (p. 1430). The nipple {papilla mammae) (Figs. 1207 and 1210) projects from a little below and to the median side of the summit of the hemisphere at or above the level of the fifth rib, and is covered with thin skin. The right nipple may not exactly correspond in situation and direction to the left nipple. The nipple varies considerably in height and shape. In the virgin it is usually cylindrical and is directed forward and slightly upward and outward. The apex of the 1 Spicer (Journal of Anatomy and Physiology, vol. xliii, 1909) describes the prepuce as arising in the form of an annular hood of niesoblastic. tissue which proceeds forward wiihin the substance of the surrounding epithe- lium. ^ ','The main portion of this hood springs from mesoblastic tissue considerably posterior to the cervix glandis, is in the form of a crescentic swelling, or collar, and this creeps forward, burrowing always in the epithelial layers, bridging over the groove of the cervix which is filled with epidermal cells, and finally overlaps the body of the glans. This hood is the prepuce." ' 'The epidermis covering the glans thuis becomes divided into two layers — an outer, which forms the super- ficial covering of the prepuce, and an inner, which remains as a more or less solid layer between the prepuce and the glans until after birth. From it is differentiated a basal layer of cubical or cylindrical epithelium to line the inner aspect of the prepuce, and another to cover the surface of the glans, while central desquamation ensues later and prepares the way for a movable prepuce." THE MAMAfARY GLAND 1429 nipple is rendered rough by fissures (Fig. 1207), it exhibits a depression in which are the openings of the milk ducts (Fig. 1209), and its circumference is thrown into concentric ridges (Fig. 1209). The nipple is surrounded by a darker circular wrinkled area, the areola (areola, mammae) (Figs. 1207 and 1208), which contains sweat glands and on which are twelve or fifteen small rounded elevations. These ele\'ations are caused by cutaneous sebaceous glands which in structure represent a transition between sebaceous and mammary glands. They are probably rudimentary portions of the mammary gland and are known as the glands of Montgomery {glandulae areolares) (Fig. 1209). The color of the nipple and areola varies with the complexion of the individual. In brunettes it is darker than in blondes. The usual color of the nipple in a young woman is rosy pink, the areola being of a darker shade. During the early months of pregnancy the nipple and areola become dark brown in color, the areola becomes larger in circumference, and the glands of Montgomery increase in size (Fig. 1210). The nipple contains nonstriated muscle, and mechanical irritation or sexual excitement makes it stiff and erect. The skin covering the breast is clear, soft, and delicate, and sub- cutaneous veins are often visible. The skin of the nipple and areola is particularly delicate. Lactiferous duct. Lobnh unravelled 1 mpulla. [ ni nil m tounectwe iiasne. Fig. 1207. — Dissection of the lower half of the female breast during the period of lactation. (From Luschka.) Variations in the Mammae. — Before puberty the glands are small, are of the infantile type, grow slowly, and differ but slightly from the male organs. The nipple is small, flat, and pale. At puberty the increase in the size of the breast is rapid and considerable, due to growth of gland tissue and of subcutaneous fat. In the young virgin the breasts are of hemispherical form and of firm con- sistency. During pregnancy the breasts enlarge greatly and remain very large throughout lactation. This enlargement is due to new gland tissue and increased vascularity. Numerous blue veins are visible in the skin, the areola darkens, and the glands of Montgomery enlarge (Fig. 1210). After the termination of lactation the breasts diminish in size. They do not become as small as the virgin breast, are apt to lose their hemispherical outlines, and become soft and 1430 THE URINOGENITAL ORGANS flabby. They droop as flaccid pendulous masses, the subcutaneous fat is largely gone, and the oudines of the lobular breast tissue can be seen and felt. The nipple is long and hangs down like a teat. At the menopause the breast usually shrinks. In some cases, however, it actually increases in size. In such a case, although the gland atrophies, there is an extensive deposit of fat. In old age the glands undergo atrophy and largely disappear, the skin is flabby and thrown into wrinkles, and the breasts contain very little glandular structure, and are hard from the presence of fibrous tissue. The nipples become pigmented and corru- gated. Women vary greatly in the development of the breasts. In some women they are large, firm, and well proportioned; in others they are small, flat, or atrophy occurs in the course of certain bodily diseases, as in phthisis, and in certain mental diseases, as melancholia. If the ovaries are ill-developed the breasts remain flat and small. The outline and direction of the breast and also of the nipple may be altered by corsets. The left mamma is usually somewhat larger than the right. One gland or both glands may be entirely absent, the nipple being also absent. One or both glands may be absent, one or both nipples being present. When there is only one nipple, it is apt to be the left. The term polsrmazia {mammae accessonde muliebris) means the presence of supernumerary breasts, with or without nipples. Polythelia means the presence of supernu- merary nipples, the associated glandular structure being rudimentary. There may be one, two, or several supernumerary breasts, and when more than one exists, are usually asymmetrical. If one is functionally active, it enlarges during pregnancy and furnishes milk. Supernumerary mammfe may secrete milk or may be without function. The most common situation is on the part of the chest below and to the inner side of the normally placed gland. They may also exist in the axilla, the abdomen, the groin, the back and the thigh. Many cases of supposed supernumerary glands have been really instances in which moles, warts, or sebaceous cysts have been mistaken for nipples, but some cases are undoubted. Prolongations of Mammary Tissue. — As previously stated, the outlines of the breast are not regular, but here and there tails, prolongations, or cusps come off from and are true portions of the gland. Two or even more prolongations pass to the edge of the sternum ; others pass toward the axilla, the clavicle, and the origin of the External oblique muscle from the ribs. Underneath the mammary gland prolongations of mammary tissue penetrate the pectoral fascia (Heidenhain). If one of the glandular cusps is of considerable size it is called an outlying lobule. Structure of Mammary Gland and Nipple (Figs. 1207 and 1208).— The glands of the breast (corpus mammae) rest by a smooth posterior surface upon the loose pectoral fascia, which fastens the breast to the muscle beneath, but so loosely that the breast is movable. The mamma consists of gland tissue; of fibrous tissue, connecting its lobes, of fatty tissue in the intervals between the lobes, of retinacula, and of skin. The gland tissue, when freed from fibrous tissue and fat, is of a pale reddish color, firm in texture, generally globular in form, with prolongations here and there, flattened from before backward, thicker in the centre than at the circumference, and presenting several inequalities on its surface, especially in front. On the anterior surface there are many irregular elevated processes with deep spaces between them. From the summits of the elevations connective-tissue strands {redinacula cutis) pass to the true skin. The glandular structure consists of numerous glands divided into lobes (/o6i mammae), and these are composed of lobules {lobuli mammae), connected by areolar tissue, which contains the bloodvessels and ducts. The smallest lobules consist of a cluster of rounded alveoli (Fig. 1207), which open into the smallest branches of the excretory ducts; these ducts, uniting, form larger ducts, which terminate in single canals. Each canal is called a lactiferous, galactophorous, or mammillary duct {ductus lactiferus) (Fig. 1207). The alveoli are tubular in form and are lined by low columnar epithelial cells which rest upon a basement membrane.' Each glandular area possesses one lactiferous duct. This passes to the apex of the lobe and then into the nipple. The lactif- erous ducts are white and cord-like, and contrast with the yellowish-red tissue of the gland itself. The number of excretory ducts varies from fifteen to twenty, each representing an individual gland. They converge toward the areola, beneath which each duct possesses a spindle-shaped 1 According to Lacroix and Benda, there is a thin layer of noDstriated muscle between the basement mem- brane and the secreting cell. THE MAMMARY GLAND 14-Sl dilatation, the ampulla (sinus lactiferans) (Fig. 1207). The ampullse serve as reservoirs for the milk. At the base of the nipple the ducts become contracted and pursue a straight course to its summit, perforating it by separate orifices considerably narrower than the ducts themselves. Each orifice (poms lactiferus) is the orifice of a tube which drains an individual gland. The ducts are composed of areolar tissue, with longitudinal and transverse elastic fibres and some muscle tissue derived from that of the nipple; their mucous lining is continuous, at the point of the nipple, with the integument. The epithelium of the mammary gland difi^ers according ,to the state of activity of the organ. In the gland of a woman who is not pregnant or nursing the alveoli are very small, few in number, solid, and filled with a mass of granular polyhe- dral cells. During pregnancy the alveoli increase in number and enlarge and the cells undergo rapid multiplication. At the commencement of lactation the cells in the centre of an alveolus undergo fatty degeneration, and are eliminated in the first milk as colostrum corpuscles. The peripheral cells of the alveolus remain, and form a single layer of granular, short columnar cells lining the limiting membrana propria. The single nucleus of each cell divides and forms two. Fig. 120S. — Right breast in sagittal section, inner surface of outer segment. (Testut.) In the protoplasm, especially in the end of the cells toward the alveolus, drops of fat appear and the nucleus toward this end of the cell also becomes fatty. The end of the cell toward the alveolus breaks down, and the liberated material constitutes " the albuuiinous ingredients of the milk, while the drops of fat become the milk globules. The portion of the cell which remains forms new cytoplasm, and the same process is repeated over and over again. The cells also secrete water and the salts which are found in the milk."' After lactation a number of the alveoli atrophy and disappear, while the remainder become much reduced in size. The gland then consists mainly of adipose and fibrous tissues. Tiie fibrous tissue (Fig. 1208) invests the entire surface of the breast, and sends down septa between its lobes, which serve to hold them together. The fatty tissue (Figs. 1207 and 1208) siurounds the surface of the gland and occupies the intervals between its lobes. It usually exists in considerable abundance, and determines the form and size of the gland. There is no fat immediately beneath the areola and nipple. ' Human Physiology. By Joseph Howard Raymond. 1432 THE URINOGENTTAL ORGANS Vessels and Nerves. — The arteries supplying the mammary gland are derived from the perforating branches of the iatemal mammary, the long thoracic branches of the axUlary, and branches from the intercostals. The veins describe an anastomotic circle around the base of the nipple, called by Haller the circulus venosus. From this large branches transmit the blood to the circumference of the gland and end in the axillary and internal mammary veins. The lymphatics of the mammary gland (Fig. 562) and mammary region have been previously described (pp. 782 and 797). The nerves are derived from the fourth, fifth, and sixth inter- costal nerves, and sympathetic filaments from the thoracic cord pass to the breast along the branches of the intercostal nerves. Applied Anatomy. — Occasionally the mammary gland undergoes enormous hypertrophy. This may occur in any age, even in the virgin. The physiological enlargement of puberty may become excessive or the physiological enlargement of pregnancy and lactation may continue and increase after the termination of lactation. The chief elements in lie enlargement are fat and connective tissue, and it is doubtful if there is extensive reproduction of glandular tissue. Abscess of the breciM may occur at any age, but is most common by far in nursing women. The portals are opened to infection by a crack in the nipple and bacteria are carried inward by the lymph vessels. In some cases the pus gathers beneath the skin (supramanmiary abscess), in others in the breast tissue {intramammary abscess). In rare cases pus gathers beneath the breast (retromammary abscess). In intramammary abscess the pus burrows through the fibrous septa or fascia and forms numerous channels, and such a channel is constricted in hour-glass shape at the point where it passes through fascia or a fibrous septum. AREOLA — LARGE 5EBACEOU: GLANDS CONCENTRIC Fig. 1209.^ — Nipple and areola of a virgin, (Testut.) Fig. 1210. — Nipple and areolae of a preg- nant woman. (Testut.) In every patient suffering from abscess the nipple should be examined for a sore or crack, and the area when found should be treated antiseptically. A supramammary abscess should be opened by an incision radiating from the nipple. • In intramammary abscess follow the advice of Sheild: Open the abscess by an incision radi- ating from the nipple, insert the index finger, and when possible pass it to the bottom of the abscess and carry the tip from the depths of the abscess to as near the surface as possible. At this point make a counter opening. The finger breaks down septa which cause constriction and thus converts the tracking sinuses into one large cavity.' Drain by tubes. A retromammary abscess is opened by an incision, following the outline of the breast at the thoracomammary junction, the finger being pushed through the incision and up under the gland. Tuberculosis of the breast may occur, and if it does, cold abscess is apt to form. The best treatment is removal of the gland and the associated lymph nodes. Chronic mastitis is a condition of mammary fibrosis, most common in neurotic single women, and apt to be associated with ovarian or uterine disease. Malignant dermatitis or Paget's disease of the nipple is a chronic condition consisting of epi- thelial proliferation, induration, desquamation, and ulceration, and it is apt to be followed by epithelioma. Chancre of the nipple is occasionally met with. Secondary and tertiary syphilitic lesions are seen upon the skin of the breast, the nipple, and the areola. Cysts and tumors are common in the breast. There may be cystic degeneration of the gland m women near the menopause (involution cysts); a lacteal cyst; a hydatid cyst; an adenoma ^ Diseases of the Breast. By A. Marmaduke Sheild. THE MAMMARY GLAND 1433 may become cystic. The nipple may suffer from epithelioma, myoma, myxoma, angioma, papil- loma, or fibroma. The innocent tumors of the breast are fibroadenoma, cystic adenoma, myxoma, and angioma. The skin of the breast may suffer from any form of growth or cyst which could arise from the skin of another ])art. Malignant tumors of the glandular structure are ten times as frequent as innocent tumors. Sdraima is rare; carcinoma is very common. Carcinoma of the breast has occupicii much of the attention of surgeons during recent years. The old operation was uniformly followed by recurrence. The modern radical operation has been evolved from the studies of Moore, the younger Gross, Heidenhain, Stiles, Banks, Halsted, and others. The modern operation always removes at least the skin and subcutaneous tissue over the hemispherical portion of the breast, the outlying lobules of the breast, the ]5ectoral fascia, and the sternal portion of the great Pectoral muscle, the lymphatic tracts from the breast, the lymphatic nodes and cellular tissue from the axilla, and from beneath the Latissimus dorsi muscle. The pectoral fascia and the sternal portion of the great Pectoral muscle must come away in every case, because breast tissue may pass through the fascia. The entire breast must be re- moved, because even in a recent case the entire breast is regarded as infected. The clavicular portion of the great Pectoral muscle is anatomically distinct from the sternal portion and its removal is not imperative. Some operators remove the lesser Pectoral muscle. To leave it is of no value to the arm, and it frequently causes an annoying rigid band anterior to the axilla. To take it away gives ready access to the axillary vessels at a desirable point above. The sheath of the axillary vein should be removed with the nodes and cellular tissue of the axilla. The nodes receiving lymph from the cancerous area must be removed, of course. In view of the fact that in an undetermined percentage of cases a lymph tract passes direct to the subclavian nodes, it is evident that these nodes may become infected by this route instead of, as is more usual, secondarily to axillary infection; hence it seems wiser in every case to remove the cellular tissue and nodes from the subclavian triangle. All of these structures should be removed as one piece, in order to avoid cutting across lymph tracts and flooding the wound with carcinoma cells which might adhere, grow, and reproduce cancer. Halsted's operation is the method adopted by most surgeons. The wound cannot be com- pletely closed, and the raw spot is covered at once or later with Thiersch's skin grafts. (For surgical considerations regarding the lymphatics in mammary carcinoma see page 804). The male breast (mamma virilis) is a small, flat structure, consisting chiefly of connective tissue, but containing some branched tubules. Under normal circumstances it remains permanently of the infantile type. It possesses a nipple which is much smaller than that of the female breast, and which usually lies over the fourth intercostal space, but may lie over the fourth or fifth rib. The nipples of the two sides are rarely placed quite symmetrically. Accessory glands and accessory nipples are as common among males as females. The male breast may exhibit some evidence of temporary functional activity at birth and at puberty. Cases have been recorded of actual lactation by the male breast. Applied Anatomy. — The male breasts may undergo enormous hypertrophy (gynecomazia). In these cases the penis is often small and the testicles may be atrophied. The breasts may be absent in the male. Disease of the male breast is not nearly so frequent as disease of the female breast. The organ may be the seat of syphilis, tuberculosis, acute or chronic mastitis, abscess or tumor. A number of cases of cancer of the male breast have been recorded. THE DUCTLESS GLANDS. THERE are certain organs, in various situations, which are very similar to secreting glands, but differ from them in one essential feature — viz., they do not possess any ducts by which their secretion is discharged. These organs are known as the ductless glands. They are capable of internal secretion — that is to say, of forming, from materials brought to them by the blood, substances which have a certain influence upon the nutritive and other changes going on in the body. This secretion is carried into the blood stream, either directly by the veins or indirectly through the medium of the lymphatics. These glands include the thyroid and the parathyroids, the thymus, the spleen, the suprarenal glands, and the small carotid, coccygeal, and parasympathetic bodies, which will be described in this section. They also include the lymph and hemolymph nodes (or glands) which have already been described on pages 76S to 802 ; and the epiphysis (pineal gland) and hypophysis (pituitary) described with the brain on pages 906 and 909. Certain isolated cell masses in the pancreas, the testicle, and ovary, apparently engaged in internal secretion, are described with those organs. THE THYROID GLAND OR BODY (GLANDULA THYREOIDEA) (Fig. 1211). The thyroid gland is a highly vascular organ, situated at the front and sides of the neck, and extending upward upon each side of the larynx; it consists of two lateral lobes connected across the middle line by a narrow transverse portion, the isthmus. The weight of the gland is somewhat variable, but is usually about one ounce. It is somewhat heavier in the female, in whom it becomes enlarged during men- struation and pregnancy. The lateral lobes are conical in shape, the apex of each being directed upward and outward as far as the junction of the middle with the lower third of the thy- roid cartilage; the base looks downward, and is on a level with the fifth or sixth tracheal ring. Each lobe is about two inches (5 cm.) in length, its greatest width is about one inch and a quarter (3 cm.), and its thickness about three-quarters (2 cm.) of an inch. The summit of the lateral lobe is not unusually pointed and reaches to the level of the oblique line upon the ala of the thyroid cartilage or even higher. The right lobe is, as a rule, somewhat larger than the left. The lower portion of the gland, when the head is extended, is about one inch above the upper margin of the sternum; when the head is flexed, it is at the level of the upper border of the sternum or even below and behind it. The external or superficial surface is convex, and covered by the skin, the super- ficial fascia, the deep fascia, the Sternomastoid, the anterior belly of the Omo- hyoid, the Sternohyoid, and Sternothyroid muscles, and beneath the last-named muscles by the pretracheal layer of the deep fascia, which forms a capsule for the gland (Fig. 297). The deep or internal surface is moulded over the underlying structures — \\z., the thyroid and cricoid cartilages, the trachea, the Inferior constrictor and pos- 14.35 1436 THE DUCTLESS GLANDS terior part of the Cricothyroid muscles, the oesophagus (particularly on the left side of the neck), the superior and inferior thyroid arteries, and the recurrent laryngeal nerves. The deep surface of each lobe is fixed by bands of fibrous tissue passing from the capsule of the isthmus and lateral lobes to the sides of the cricoid cartilage and the posterior fascia of the trachea. These bands are called the lateral or suspensory ligaments. Because of this fixation to the larynx and trachea by the capsule and fT^ J by the lateral ligaments, the thyroid gland R m moves with the trachea and ascends during the act of swallowing. The recurrent laryn- geal nerve on each side is in contact with the outer and posterior surface of the sus- pensory ligament. The anterior border is thin, and inclines obliquely from above downward and inward toward the middle line of the neck, while the posterior border is thick and overlaps the com- mon carotid artery. The isthmus (isthmus cjlaudidae thyroidea) connects the lower two-thirds of the two lat- eral lobes; it measures about half an inch in breadth and the same in depth, and usually covers the second and third rings of the trachea, but sometimes also the first and fourth rings. Its situation and size present, however, many variations, a point of importance in the oper- ation of tracheotomy. In the middle line of the neck it is covered by the skin and fascia, and close to the middle line, on either side, by the Sternohyoid muscle. Across its upper border run branches of the superior thyroid artery and vein; at its lower border is a branch of the inferior thyroid veins. Some- times the isthmus is altogether wanting. The third, pyramidal or middle lobe frequently Fig. 12H. -The thyroid gland. (Spaitehoiz.) arises from the upper part of the isthmus, or from the adjacent portion of either lobe, but most commonly from the left lobe, and ascends in front of the thyroid cartilage in the direction of the middle of the hyoid bone. It may reach the bone or may not reach it. If it reaches the bone it is attached to it. If it does not reach the bone, fibrous tissue, which often contains muscle, is prolonged from the tip of the pyramid to the back of the bone or to the thyrohyoid membrane. The pyramid is occasionally quite detached, or divided into two or more parts. A few muscle bands, derived from the Thyrohyoid muscles, are occasionally found attached, above, to the body of the hyoid bone, and below to the isthmus of the gland or its pyramidal process. These form a muscle, which was named by Soemmerring the Levator glandulae thyreoideae. Accessory Thjrroids {glandulae thyreoideae accessoriae). — ^Frequently small isolated masses of thyroid tissue exist. They are found particularly about the lateral lobes of the thyroid gland in the sides of the neck or just above the hyoid bone, and are called accessory thyroids. Structure of the Thyroid (Fig. 1212).— The thyroid body is invested by a capsule of con- nective tissue which projects into its substance as a framework and imperfectly divides it into THE THYROID GLAND OR BODY 1437 masses of irregular form and size, known as lobes and lobules. More slender septa separate the secretory alveoli from one another. While the anterior portion of the capsule is thin and easily torn, the posterior portion is thick and dense. When the organ is cut into, it is of a brownish-red color, and is seen to be made up of a number of closed vesicles or alveoli con- taining a yellow glairy fluid and separated from each other by intermediate connective tissue. It is a compound tubular gland, each lobule of which consists of a number of short closed tubules or alveoli, which are surrounded by the interstitial reticulum. According to Baber, who has published some important observations on the minute structure of the thyroid, the vesicles of the thyroid of the adult animal are generally closed cavities; but in some young animals (e. g., young dogs) the vesicles are more or less tubular and branched. This appearance he supposes to be due to the mode of growth of the gland, and merely indicating that an increase in the number of vesicles is taking place. Each vesicle is lined by a single layer of cuboidal epithelial cells which rest upon a delicate basement membrane. Between the tubules exists a delicate reticulum. The vesicles are of various sizes and shapes, and contain as a normal product a viscid, homogeneous, semifluid, slightly yellowish material which frequently contains red corpuscles in various stages of disintegration and deeolorization, the yellow tinge being probably due to the hemoglobin, which is thus set free from the colored corpuscles. This normal product is known as colloid material, and it is secreted by the epithelium. What part if any the Li/n il U eisel Wall of gland le^ cle -om a transverse section of the thyroid of a dog. Semi- tlatic. (Baber.) colloid plays in the formation of the internal secretion of the gland is not known. It is quite possible that the colloid corresponds to the external secretion of glands with ducts and that the true internal secretion passes directly into the capillaries which form a network about the alveoli (Szymonowicz), or passes into the lymphatics. In the thyroid gland of the dog, Baber has found large round cells, parenchymatous cells, each provided with a single oval-shaped nucleus, which migrate into the interior of the gland vesicles. Between the thyroid vesicles in the human being are collections of round cells. They are, in reality, miniature immature vesicles, and are much more numerous in youth than in old age. The capillary bloodvessels form a dense plexus in the connective tissue around the vesicles, between the epithelium of the vesicles and the endothelium of the lymph spaces, which latter surround a greater or smaller part of the circumference of the vesicles. These lymph spaces empty themselves into lymphatic vessels which run in the interlobular connective tissue, not uncommonly surrounding the arteries which they accompany, and communicate with a network in the capsule of the gland. Small glands may be connected with this network. Baber has found in the lymphatics of the thyroid a viscid material which is morphologically identical with the normal constituent of the vesicle. Vessels and Nerves.— The arteries (Figs. 444 and 499; see also p. 592) supplying the thy- roid are the superior thjrroid from the external carotid, and the inferior thjrroid from the thyroid axis of the first ])art of the subclavian. Sometimes there is an atlditional vessel, the thjrroidea media or ima, usually arising from the innominate artery, but sometimes from the arch of the aorta or the common carotid. It ascends upon the front of the trachea. The superior thjToid 1438 THE DUCTLESS GLANDS artery reaches the summit of the upper horn of the gland, and usually at this point gives off a vessel which courses down the posterior surface of the gland. The main trunk passes down- ward and inward at the junction of the inner and anterior border of the upper horn, giving branches to adjacent srructiu'es and sending branches over the anterior siu^ace of the th^Toid gland. It reaches the isthmus and crosses the isthmus at its upper border to anastomose with the artery from the other side. The inferior th\Toid artery, which is usually larger than the supe- rior, after it has passed posterior to the sheath of the carotid and the sympathetic nerve, reaches the posterior surface of the gland. At this point branches are given off; some pass into the hilum ; the others go to the posterior surface of the gland. The relation of the artery to the recurrent laryngeal nerve is very important to the sm-geon. "Usually the main trunk of the artery passes behind the nerve; sometimes the artery breaks up before reaching the nerve; in this case one or more of the branches may pass in front of it. Aluch less commonly the main trunk or all its branches will be found to lie in front of the nerve."' If the th_\Toidea ima is present it goes to the lower part of the gland. The larger branches of the th\Toid arteries are beneath the capsule and upon the sm-face of the gland; smaller branches pass to the interior of the gland (Berri-). The arteries are remarkable for their large size and frequent anastomoses. The thjrroid veins (Figs. 49S and 499; see also p. 715J form a plexus upon the surface of the gland and beneath the capsule. Here and there veins pass through the capsule and go to adja- cent venous trunks. Berry, accepting Kocher"s description, notes the following veins: The superior thyroid vein runs with the superior th^Toid artery and passes to the internal jugular vein. A transverse vein of the upper border of the isthmus joins the two superior thvToid veins. A single vein, the middle thyroid, sometimes emerges from the side of the gland and passes to the internal jugular. Usually, however, instead of this single vein there are two veins, the supe- rior and inferior a;Ccessory tiyroids. The superior accessory thyroid emerges from the outer side of the upper horn, below the apex, and passes to the internal jugular. The inferior accessory thyroid emerges from the posterior and inferior portion of the gland and passes to the internal jugular. The veins from the lower border of the gland vary greatly. A vein passes vertically down on each side in front of the trachea from the isthmus and from the inner side of the inferior horn. It is called by Kocher the thyroidea ima. The vein of the left side passes to the left innominate; the vein of the right side passes to the right innominate or left innominate. As Berry points out, the vein of one side may be small or may be absent, or the two veins may unite and form one vein which enters the left innominate. An inferior thyroid vein is often present. It is of small size, emergen at the inferior and external part of the gland, and passes to the corresponding innominate vein." The Ismiphatics are numerous and of large size. Collecting trunks arise from a network within the capsule. Some trunks ascend from the upper margin of the isthmus and reach the node in front of the larynx; others ascend along the superior th}Toid artery and reach the nodes at the bifurcation of the carotid. Descending trunks from the lower margin of the isthmus reach the nodes in front of the trachea; trunks from the side of the gland descend to the nodes about the recurrent laryngeal nerve.' The nerves of the thjToid are amyelinic and are derived from the middle and inferior ganglia of the sympathetic. They reach the gland by following the thjToid arteries.^ Applied Anatomy. — The th\Toid gland may be congenitally absent, and when it is the indi- vidual suffers from the worst form of crdinixm. One lobe may be congenitally absent, but this will provoke no trouble unless the other lobe undergoes atrophy. Complete removal of the th\Toid and parath\Toids will produce operative myxedema (cachexia sfrumipriva), unless accessory th\Toids enlarge and perform the functions of the thvToid. The th\Toid gland may be congenitally enlarged. The gland tends to atrophy in old age. It is atrophied in m_\-xedema and cretinism. Some forms of th^Toid enlargement are called goitre. ^Vhen all parts of the gland enlarge the condition is known as parenchymatous goitre. Adenomatous goitre consists of an adenoma or of adenomata. In cystic goitre there are one or more cysts due to cystic degeneration of adenomata or to fusion of adjacent tubules. A pulsating goitre is one which receives impulses from the carotid pulsations. In a fibroid goitre there is increase of interstitial connective tissue. A goitre which passes back of the sternum is known as substernal or intrathoracic. A goitre may extend back of the trachea or back of the oesophagus. Exophthalmic goitre, Graves' disease or Basedow's disease, is a remarkable disease. Its three chief symptoms are enlargement of the th^Toid, or goitre; prominence of the eyeballs, or exoph- thalmos (see p. 372); and very rapid pulse, or tachycardia. Dyspnea, tremor, and various other symptoms are usually found. The th\Toid gland may be the seat of a carcinoma or sarcoma {mahgnant goitre), syphilitic or tuberculous disease, ordinary inflammation, suppuration, or 1 Diseases of the Th\Toid Gland. By James Berr>'. - Ibid. ^ The LjTuphatics. By Poirier, Cun^o, and Delamere. Translated and edited bv Cecil H. Leaf. ' D. A. Rhinehart: Amer. Jour, of .Anat., vol. xiii, Mav 15, 1912. THE PARATHYROID GLANDS 1439 hydatid disease. For the relief of ordinary goitre various methods have been employed. Tap- ping, injection of astringents, simple incision, and the seton are obsolete. Ligation of the thy- roid arteries is rarely performed as a curative measure. The superior and inferior thyroids of one side have been tied in some cases; all four thyroids in other cases. Jaboulay has. performed exothyropcxy. In this operation the gland is dislocated from its bed, brought out of the vvfound, and left exposed, in hope that it will atrophy. Diviidon. of the isthmus is occasionally practised to relieve dyspnea. The operation some- times succeeds, but often fails. Extirpation of one-half or two-thirds of the gland is a very successful operation. Removal of the entire gland will be followed by operative myxedema. Removal or injury of the parathyroids causes tetany. In extirpating a lobe of the thyroid by the method until recently in vogue, great care must be taken to avoid tearing the capsules, as if this happens the gland tissue bleeds profusely. The thyroid arteries should be ligated on the diseased side before an attempt is made to remove the mass, and in ligating the inferior thyroid the position of the recurrent laryngeal nerve must be borne in mind, so as not to include it in the ligature. In order to preserve the parathyroids from injury, C. H. Mayo recommends that after the vessels entering and leaving the thyroid have been double clamped and divided, the entire lobe should be elevated, the capsule split along the side of the gland and pushed back with gauze, and the gland lifted and removed without disturbing the posterior portion of the capsule. As pointed out before, the posterior portion of the capsule is so thick and strong that it is easier to leave it in situ than to bring it out of the wound with the gland. A cystic or solid tumor of the thyroid may be removed by iiiiraglandular enucleation. If opera- tion becomes necessary in exophthalmic goitre, partial extirjiation is usually preferred. Bilateral extirpation of the cervical ganglia of the sympathetic (syiiipafhcrtoiny or Jonnesco's operation) has been practised by some surgeons for exophthalmic goitre. The value of the procedure is uncertain. THE PARATHYROID GLANDS (Fig. 1213). The parathyroid glands are small, brownish-red bodies, situated near the thy- roid gland, but differing from it in structure, being composed of masses of cells arranged in a more or less reticular fashion with numerous intervening bloodvessels. They measure on an average about a quarter of an inch (6 mm.) in length, and from an eighth to a sixth of an inch (3 to 4 mm.) in breadth, and usually present the appearance of flat oval disks. They are classified according to their position into superior and inferior. The supe- rior, usually two in number, are the more con- stant in position, and are situated, one on either side, at the level of the lower border of the cricoid cartilage, behind the junction of the pharynx and oesophagus, and in front of the prevertebral fascia. The inferior, also usually two in number, may be applied to the lower edge of the lateral lobe, or may be placed at some little distance below the thyroid body, or may be found in relation with one of the inferior thyroid veins. Although there are usually four parathyroids, there may be but three, or there may be six or even eight. Parathyroid tissue may exist within the thyroid gland even when the superior parathyroids are present. Acces- sory parathyroids may be found over a wide area. Rogers and Fergusson found one in the middle of the posterior portion of the pharynx. Ogle found a gland in the thorax which was partly parathyroid. Fig. 1213. -The position of the thyroid glands (Zuckerkandl.) 1440 THE DVCrLESS GLANDS Structure. — The structure of the parathyroids is different frora that of the thyroid. They are composed of groups of epithehal ceils arranged in a chain-Iilie fasliion with numerous inter- vening capillaries. There is a certain type of cell, but the form varies. These variations result from changes due to episodes of rest and activity (Verebely). MacCallum's studies seem to lead to the same conclusion. Thomson' states that he finds only one type of cell in the infant gland, and that in the adult there is primarily but one type of cell, the other cells noted being modifications of the principal cell due to degeneration or hyperfunction. There is much lym- phoid tissue in the interstitial connective tissue. The capillaries are of the sinusoidal variety. The nerves of the parathyroids are derived from the sympathetic system. Each parathyroid gland is supplied by a parathyroid artery. The inferior parathyroid artery is always a branch of the inferior thyroid artery or of the anastomosing channel between the superior and inferior thyroid arteries of one side (Geist). The superior parathyroid artery may be a branch of the superior thyroid (Poole), but it is usually a branch of the inferior thyroid or of the anasto- mosing channel. Ginsburg' has shown that each of the glands has an accessory blood supply, by anastomotic channels from the opposite side. Embryology. — The parathyroids develop chronologically in advance of the thyroid. They are derived from the third and fourth branchial clefts of each side. An independent accessory parathyroid may develop from the fifth cleft (Getzowa, Michand). Some have regarded the para- thyroids as embryonic portions of the thyroid, but, as MacCallum says, " there is no histological proof that parathyroid tissue can ever become converted into thyroid tissue." Most observers regard the parathyroids as distinct glands possessed of a special function. Certain it is, as Gley ' and others have shown, removal of the parathyroids from herbivora, leaving the thyroid intact, is followed by spasms, tetany, etc., just as complete thyroidectomy is followed by such symptoms in carnivora. Applied Anatomy. — Surgeons have become convinced that removal of the parathyroids in man causes tetany, and that damage to them may produce serious symptoms. Because of this danger most surgeons now prefer to remove a goitre from within the capsule of the thyroid gland, after the plan of the Mayos, and thus avoiding the parathyroids. THE THYMUS GLAND (Fig. 1214). The thymus gland is a temporary organ, attaining its full size at the end of the second year, when it ceases to grow and remains practically stationary until puberty, at which period it rapidly degenerates. It does not entirely disappear, Trachea Thyroid veins Right vagus Superior vena cava Ihi/ioid body I eft common carotid artery. .Left ijitet nal jugular vein. Left subclavian vessels. Fig. 1214. — The thymus gland of a full-time fetus exposed in situ, for the shrunken and degenerated mass, even later in life, maintains a likeness to the original form and retains within its substance small portions of thymus tissue (Waldeyer). If examined when its growth is most active, it will be found to con- ' Internal Secretions. By William Hanna Thomson. New York Medical Journal, November 19, 1904. ^ University of Pennsylvania Medical Bulletin, January, 1908. ^ American Journal of the Medical Sciences, 1907, n. s., cxxxiv, p. 562. THE THYMUS GLAND 1441 sist of two lateral lobes placed in close contact along the middle line, situated partly in the superior mediastinum, partly in the neck, and extending from the level of the fourth costal cartilage upward as high as the lower border of the thy- roid gland. It is covered by the sternum and by the origins of the Sternohyoid and Sternothyroid muscles. Belotv, it rests upon the pericardium, being separated from the arch of the aorta and great vessels by a layer of fascia. In the neck it lies on the front and sides of the trachea, behind the Sternohyoid and Sterno- thyroid muscles. The two lobes generally differ in size; they are occasionally united so as to form a single mass, and are sometimes separated by an intermediate lobe. The thymus is of a pinkish-gray color, is soft, and is lobulated on its sur- faces. It is about two inches (5 cm.) in length, one and a half inches (3.75 cm.) in breadth below, and about a quarter of an inch (6 mm.) in thickness. At birth it weighs about half an ounce. '^^■IM' -i - Fig. 1215. — A lobule of the thymus of a child, as seen under low power. C. Cortex, c. Concentric corpuscles within medulla, b. Bloodvessels, tr. Tra- beculse. (Schiifer.) Fig. 1216.— Elements of the thymus. ;■, 300. a. Lymph corpuscles, b. Concentric corpuscle. (Schiifer, after Cadiot.) Structure (Figs. 1195 and 1197). — Each lateral lobe is composed of numerous lobules held together by deHcate areolar tissue, the entire gland being enclosed in an investing capsule of a similar but denser structure. The primary lobules vary in size from a pin's head to a small pea, and are made up of a number of small nodules which are irregular in shape and are more or less fused together, especially toward the interior of the gland. Each lobule consists of a cortical and medullary portion, which differ in many essential particulars from each other. The cortical portion is mainly composed of dense lymphoid tissue, consisting chiefly of lympho- cytes and hyaline cells supported by a delicate reticulum. In addition to this reticulum, of which traces only are found in the medullary portion, there is also a network of finely branched cells which is continuous with a similar network in the medullary portion. This network forms an adventitia to the bloodvessels. The medullary portion consists of difiEuse Isrmphoid tissue (granular cells) and concentric corpuscles (cnriui.-^cles of Hassal). The granular cells are rounded or flask-shaped masses attached (often by fibrillated extremities) to bloodvessels and to newly formed connective tissue. The concentric corpuscles are composed of a central mass consisting of one or more granular cells, and of a capsule which is formed of concentrically arranged epithelioid cells which seem to be continuous with the branched cells forming the net- work mentioned above. Each lobule is surrounded by a capillary plexus from which vessels pass into the interior and radiate from the periphery toward the centre, and form a second zone just within the margin of the medullary portion. In the centre of the medulla there are ver}' few vessels, and they are of minute size. Watney has made the important observation that hemoglobin is found in the thymus either in cysts or in cells situated near to or forming part of the concentric corpuscles; This hemo- globin varies from granules to masses exactly resembling colored blood corpuscles, oval in the bird, reptile, and fish; circular in all mammals except in the camel. Dr. Watney has also dis- covered in the lymph issuing from the thymus similar cells to those found in the gland, and, like them, containing hemoglobin either in the form of granules or masses. From these facts 1442 THE DUCTLESS GLANDS he arrives at the physiological conclusion that the thymus is one source of the colored blood eor|5uscles. Vessels and. Nerves. — The arteries supplying the thymus are derived from the interna] mammary and from the superior and inferior thyroid. The veins terminate in the two innom- inate veins, and in the internal mammary and the thyroid veins. The Ijrmphatics are of large size, arise in the substance of the gland, and are said to terminate in the internal jugular vein. The nerves are exceedingly minute; they are derived from the vagus and sympathetic. Branches from the descendens hjrpoglossi and phrenic reach the investing capsule, but do not penetrate into the substance of the gland. Fig, 1217. — Minute structure of the thymus gland. Lobule of injected thymus from a calf, four days old, slightly diagrammatic, magnified about 50 diameters. The large vessels are disposed in two rings, one of which surrounds the lobule, the other lies just within the margin of the medulla, A and B. From thymus of camel, ex- amined without addition of any reagent. Magnified about 400 diameters. A. Large, colorless cells containing small oval masses of hemoglobin. Similar cells are found in the Ijonph nodes, spleen, and medulla of bone. B. Colored blood corpuscles, (Watney.) Applied. Anatomy. — Sudden death — "thymus death" — with heart failure, and with or without acute respiratory embarrassment, has been recorded in a number of infants and children in whom the thymus was enlarged, and the lymphatic tissues throughout the body showed general hypertrophy, but who showed no other evidence of disease. Such deaths have often occurred during the administration of anesthetics. Primary tumors of the thymus are rare forms of mediastinal newgrowth, and are usually dermoids or lymphosarcomas. THE SPLEEN (LIEN) (Figs. 1218, 1219). The spleen is situated principally in the posterior portion of the left hypoclion- driac region, its upper and inner extremity e.xtending into the epigastric region; it hes between the fundus of the stomach and the Diaphragm. It is obliquely placed, its long axis following the obliquity of the tenth rib. If the abdomen is THE SPLEEN 1443 opened a spleen of ordinary size is not visible from tlie front, as it is placed between the left kidney, Diaphragm, and stomach. It moves with the respiratory OMENTUM Fig. 121S. — The spleen. Internal or visceral .surfact I'li;. 1219. — The splei Diapuragmatic surface. movements and with the movements of the stomach. It is the largest of the so- called ductless glands, and varies greatly in size. Usually it measures some five 1444 THE DUCTLESS GLANDS inches in length. It is of an oblong, flattened, tetrahedral form, soft, of very friable consistence, highly vascular, and of a dark-purplish color. Relations. — The external or phrenic surface (fades diphragmatica) is convex, smooth, and is directed upward, backward, and to the left, except at its upper end, where it is directed snghtly inward. It is in relation with the under surface of the Diaphragm, which separates it from the nhith, tenth, and eleventh ribs of the left side, and the intervening lower border of the left lung and pleura. The internal surface is concave, and divided by a ridge into an anterior or gastric, and a posterior or renal portion. The gastric surface (fades gastrica), which is directed forward and inward, is broad and concave, and is in contact with the posterior wall of the fundus of the stomach; and below this with the tail of the pancreas. It presents near its inner border a long fissure, termed the hiltun (hilus lienis), in which are several irregular apertures, for the entrance and exit of vessels and nerves. The renal surface (fades renalis) is directed inward and downward. It is somewhat flattened, is considerably narrower than the gastric surface, and is in relation with the upper part of the outer surface of the left kidney and occasionally with the left suprarenal gland. The upper end of the spleen (extremitas superior) is directed inward, toward the vertebral column, where it lies on a level with the eleventh thoracic vertebra, within one and one-half to two inches of the midline. The lower end (extremitas inferior), sometimes termed the basal surface, is flat, triangular in shape, and rests upon the splenic flexure of the colon and the phrenocolic ligament, and is generally in contact with the tail of the pancreas. The anterior loorder (margo anterior) is free, sharp, and thin, and is often notched, especially below; it sepa- rates the phrenic surface from the gastric surface. The posterior border (margo posterior), more rounded and blunter than the anterior, separates the renal from the phrenic surface; it corresponds to the lower border of the eleventh rib and lies between the Diaphragm and left kidney. The internal border, or intermediate margin, is the ridge which separates the renal and gastric portions of the internal surface. The spleen, with the exception of its hilum, is completely invested with peritoneum, which is firmly adherent to the capsule of the organ. Two folds of peritoneal tissue — the lienorenal Ugament and the gastrosplenic omentum — serve to hold the organ in position. The lienorenal ligament (Figs. 998 and 1001) is derived from the layers of the peritoneum forming the greater and lesser sacs where they come into contact between the left kidney and the spleen. Between these two layers the splenic vessels pass. The gastrosplenic omentum (ligamentum gastro- lienale) is also formed of two layers, derived from the greater and lesser sacs, respectively, where they meet between the spleen and the fundus of the stomach (Fig. 1001). Between these two layers run the vasa brevia and the left gastroepiploic branches of the splenic artery and vein. The spleen is also supported by the phrenocolic Ugament (see p. 1263). The size and weight of the spleen are liable to extreme variations at different periods of life in different individuals, and in the same individual under different conditions. In the adult, in whom it attains its greatest size, it is usually about five inches (12 cm.) in length, tliree inches (7.5 cm.) in breadth, and an inch or an inch and a cjuarter (3 cm.) in thickness, and weighs about six and one-half ounces (195 gm.) At birth its weight, in proportion to the entire body, is almost equal to what is observed in the adult, being as 1 to 350; while in the adult it varies from 1 to 320 to 1 to 400. In old age the organ not only decreases in weight, but decreases considerably in proportion to the entire body, being as 1 to 700. The size of the spleen is increased during and after digestion, and varies considerably according to the state of nutrition of the body, being large in well-fed, and small in starved animals. In intermittent and other fevers it becomes much enlarged, weighing occasionally from eighteen to twenty pounds. Frequently in the neighborhood of the spleen, and especially in the gastrosplenic and great omenta, small nodules of splenic tissue may be found, either isolated, or connected to the spleen by thin bands of splenic tissue. Every such nodule is known as a supernumerary or accessory spleen (lien accessorius). Accessory spleens vary in size from that of a pea to that of a plum. Support and Mobility of the Spleen. — The spleen is normally movable within certain narrow limits. It moves with respiration and with the stomach movements. It is supported by ligaments (p. 1258). An unduly mobile spleen is called a movable spleen. In order that a spleen shall become unduly movable, the ligaments must stretch, and this stretching is often effected when the organ is greatly enlarged, but even an apparently normal spleen may become movable. Movable spleen is usually associated with movable left kidney. Structure. — The spleen is invested by a capsule consisting of an external serous and an internal fibromuscular layer. The external or serous layer (tunica serosa) is derived from the peritoneum ; it is thin, smooth, and in the hiunan subject is intimately adherent to the fibromuscular layer. It invests the entire organ, except at the places of its reflection on to the stomach and Diaphragm and at the hilura. THE SPLEEN 1445 The flbromuscular layer (tunica albuginca) forms the framework of the spleen. It is com- posed of white fibrous connective tissue containing smooth muscle cells and elastic fibres, and it invests the organ as a capsule, and at the hilum is reflected inward upon the vessels in the form of sheaths. From these sheaths, as well as from the inner surface of the flbromuscular layer. numerous small fibrous bands, trabeculae (trabecidae lienis) (Figs. 1220 and 1221). are given oft' in all directions; these uniting with the bands from the vessel sheaths constitute the frame- work of the spleen. This framework resembles a sponge-like material, consisting of a number of small spaces or areolae. The spaces of the areolee contain the lymphoid material known as splenic pulp (pulpa lienis). Fig. 1221. — Transverse section of the hu Within the capsule is the parenchjona, consisting of the splenic pulp and splenic ( Malpighian) corpuscles. The splenic pulp is dark reddish brown in color and consists of a delicate niinihim, ujion the fibres of which arc seen stellate connective-tissue cells. In the meshes of the reticulum are diffuse lymphoid tissue, erythrocytes, ervthroblasts, disintegrating erythrocytes, pigment granules, branched cells, and certain large polynuclear elements, splenic cells. The lymphoid tissue consists of leukocytes, mainly lymphocytes, and hyaline cells scattered throughout the reticulum. The erythrocytes are on their way to or from the blood current; the erythroblasts 1446 THE DUCTLESS GLANDS are newly formed red blood cells that have as yet not lost their nuclei. The disintegrating red cells are useless cells that by their disintegration contribute the coloring matters to the bile. The branched cells are large, flattened, stellate elements, the processes of which seem to anas- tomose to assist in forming the reticular substance, and also seem to connect with the endo- thelial cells of the capillaries. The splenic cells are large polynuclear elements possessing the power of ameboid movements. They often contain pigment granules and red cells in their protoplasm, thus indicating phagocyiosin. The trabeculse are continuations of the capsule, and consist of white iibrous connective tissue and smooth muscle tissue. The splenic (Malpighian) corpuscles are dense, spherical or cylindrical collections of lym- phoid tissue (solitary nodules) surrouiiding an arteriole. Each corpuscle shows a lighter genninal centre and a darker peripheral zone where the leukocytes are more numerous and more closely packed. Each corpuscle usually exhibits an excentrically placed arteriole, as the lymphoid tissue is collected in the adventitial sheath of the vessel. These bodies are visible to the naked eye, and appear as whitish dots. Bloodvessels of the Spleen.' — The splenic artery enters the hilum and divides into branches that follow the trabeculse. Of these, some quickly pass to the pulp, while others follow the trabecule to their smallest divisions. The external coats of these arterioles, at first consisting of ordinary connective tissue, undergo a transformation, becoming much thickened and converted into lymphoid tissue. The spleen is divided into circulatory lobules about 1 mm. in diameter, each of which is divided into histological units, one for each terminal vessel, or ampulla. These terminal vessels are large endothelial channels surrounded by lymphoid tissue, called the ellip- soidal sheath. These terminal ampullae are porous and continue as veins, that collect the blood and empty it into the splenic vein at the hilum. I esse; undergoing lymphoid change. ssel continuous jfe>v with processes of Jl supporting cells. Supporting cell. Fig. 1222.- Section of spleen, showing the termination of the small bloodvessels. The spleen is subject to rhythmical contractions, one per minute; during a contraction the organ is reduced about 18 per cent, in volume. These contractions are produced by the con- tractions of the smooth muscle tissue in the capsule and trabeculse of the pulp. When the cardiac impulse sends the blood into the arterial channels the blood passes through the porous walls of the ampulla into the pulp. When the rhythmical contractions occur the blood is forced into the veins through the pores of the ampullae, and at the same time the arteries are closed. The lymphatics originate in two ways — {. e. from the sheath of the arteries and in the trabeculfe. The former trunks are the deep collecting trunks, and accompany the blood- vessels; the latter pass to the superficial Ijrmphatic plexus, which may be seen on the surface of the organ. Lymphatic channels do not exist in the pulp. The deep trunks at the hilum number from five to ten, and terminate in the splenic nodes. The superficial trunks also pass to the hilum and terminate in the .splenic nodes. The nerves are derived from the splenic plexus, which is a part of or connected with the solar plexus. The nerves enter the spleen with the vessels. Surface Form. — The spleen is situated under cover of the lower ribs of the left side, being separated from them by the Diaphragm, and above by a small portion of the lower margin of the left lung and pleura. Its position corresponds to the ninth, tenth, and eleventh ribs. It is placed very obliquely. " It is oblique in two directions — viz., from above downward and outward, and also from above downward and forward" (Cunningham). "Its highest and lowest points are on a level respectively with the ninth thoracic and first lumbar spines; its inner end is dis- 'F. P. Mall, Amer. .Jour, of .\nat., 1903, vol. ii. No. 3. THE SUPRARENAL GLANDS, OR ADRENAL CAPSULES 1447 tant about an inch and a half from the median plane of the body, and its outer end about reaches the niidaxillary line" (Quain). Applied Anatomy. — Injury of the spleen is less common than that of the liver, on account of its protected situation and connections. It may be ruptured by direct or indirect violence, torn by a broken rib, or injured by a punctured or gunshot wound. When the organ is enlai'ged the chance of rupture is increased. The great risk is hemorrhage, owing to the extreme vascu- larity of the organ, and the absence of a proper system of capillaries. The injurv is not, how- ever, necessarily fatal, and this would appear to be due in a great measure to the contractile power of its capsule, which narrows the wound and thus antagonizes the escape of blood. In cases in which the symptoms suggest such an injury and indicate danger to life, laparatomy must be performed; and if the hemorrhage cannot be arrested by ordinary surgical methods the spleen must be removed. The spleen may become displaced, producing great pain from stretch- ing of the vessels and nerves, and this dislocation may render necessary removal of the organ. The spleen may become enormously enlarged in certain diseased conditions, such as ague, leu- kemia, syphilis, valvular disease of the heart, or without any obtainable history of previous disease. It may also become enlarged in lymphadenoma as a part of a general blood disease. In these cases the mass may fill the abdomen and extend into the pelvis, and may be mistaken for ovarian or uterine disease. The spleen is sometimes the seat of cystic tumors, especially hydatids, and of abscess. These cases require treatment by incision and drainage; and in abscess great care must be taken if there are no adhesions between the spleen and abdominal cavity, to prevent the escape of any of the pus into the peritoneal cavity. If possible, the operation should be performed in two stages. Sarcoma and carcinoma are occasionally found in the spleen, but very rarely as a primary disease. In movable spleen, if the organ is normal, follow the advice of Rvdvgier and loosen the parietal peritoneum to make a pocket, place the spleen in the pocket, and pass sutures through the parietal peritoneum and splenic ligaments. A movable diseased spleen should be removed. Extirpation of the spleen has been performed for wounds or injuries, floating spleen, simjjle hypertrophy, and leukemic enlargement; but in the latter case the operation is now regarded as unjustifiable, as it is practically certain to terminate fatally. The incision is best made in the left semilunar line: the spleen is isolated from its surroundings, and the pedicle transfixed and ligated in two portions, before the tumor is turned out of the abdominal cavity, if this is possible, so as to avoid any traction on the pedicle, which may cause tearing of the splenic vein and which inevitably induces grave shock. In applying the ligatures the surgeon must not include the tail of the pancreas, and in lifting out the organ care must be taken to avoid rupturing the capsule. THE SUPRARENAL GLANDS, OR ADRENAL CAPSULES (GLANDULAE SUPRARENALIS) (Figs. 122.3, 1224). The suprarenal glands are two small flattened bodies, of a yellowish color, situated at the back part of the abdomen, behind the peritoneum, and immedi- ately above and in front of the upper extremity of each kidney ; hence their name. The right one (Fig. 122.3) is somewhat triangular in shape, bearing a resemblance to a cocked hat; the left (Fig. 1224) is more semilunar, usually larger and placed at a higher level than the right. They vary in size in different indi\iduals, being sometimes so small as to be scarcely detected; their usual size is from an inch and a quarter to nearly two inches (3 to 5 cm.) in length, rather less in width, and one-quarter of an inch (6 mm.) in thickness. Their average weight is from one to one and one-half drams (6 grams) each. Relations. — The relations of the suprarenal glands differ on the two sides of the body. The right suprarenal (Fig. 1223) is situated behind the inferior vena cava and the right lobe of the liver, and in front of the Diaphragm and the upper end of the right kidney. It is roughly triangular in shape, and its base, directed downward, is in contact with the inner and anterior aspects of the upper end of the right kidney. It presents two surfaces for examination, an anterior and a posterior. The anterior surface (fades anterior) presents two areas, separated by a furrow, the hilum (hilus gla7idulae suprarenalis) ; one area, occupying about one-third of the 1448 THE DUCTLESS GLANDS whole surface, is situated above and internally; it is depressed, uncovered by peritoneum, and is in contact in front with the posterior surface of the right lobe of the liver, and along its inner border with the inferior vena cava; the remain- ing area is elevated, and is divided into a nonperitoneal portion, in contact with the hepatic flexure of the duodenum, and a portion covered by peritoneum forming the hepatorenal fold. The posterior surface [fades 'posterior) is divided into an upper and a lower part by a curved ridge; the upper, slighdy concave, rests upon the Diaphragm; the lower, or base (basis glandulae suprarenalis) is concave, and is in contact with the upper end and the adjacent part of the anterior surface of the kidney. The left suprarenal (Fig. 1224), slighdy larger than the right, is crescentic in shape, its concavity being adapted to the inner border of the upper extremity of the left kidney. It presents an inner border which is convex, and an outer which is concave; its upper border is narrow; and its lower rounded. Its anterior •^* HILUM-^Srf*' SB ^r li» SUPRARENftl r V ARTERY 1 SUPRARENAl- PRARENAL (IBFTJI «■ ARTERY VEIN HI G. 1223.— The right s (Spaltehol luprarenal gland. z.) Fig. 1224. — The left suprarenal gland. (Spalteholz.) surface presents two areas — an upper one, covered by the peritoneum forming the lesser sac, which separates it from the cardiac end of the stomach and to a small extent from the superior extremity of the spleen; and a lower one, which is in contact with the pancreas and splenic artery, and is, therefore, not covered by the peritoneum. A hilum is present, as in the right suprarenal. Its posterior surface presents a vertical ridge, which divides it into two areas. The ridge lies in the sulcus between the kidney and crus of the Diaphragm, while the area on either side of it lies on these parts respectively; the outer area, which is thin, rest- ing on the kidney, and the inner and smaller area resting on the left crus of the Diaphragm. The surface of the suprarenal gland is surrounded by areolar tissue containing much fat, and closely invested by a thin fibrous coat, which is difficult to remove, on account of numerous fibrous processes and vessels which enter the organ through the furrows on its anterior surface and base. Accessory suprarenal glands (glandulae suprarenales accessoriae) are often to be found in the connective tissue around the suprarenals. The smaller of these, on section, show a uniform surface, but in some of the larger a distinct medulla can be made out. Structure (Fig. 1225). — On making a perpendicular section, the suprarenal gland is seen to consist of two substances — surrounded by a capsule — the external or cortical and the internal or medullary. The former, which constitutes the chief part of the organ, is of a deep- THE SUPRARENAL GLANDS, OR ADRENAL CAPSULES 1449 yellow color. The medullary substance is soft, pulpy, and of a dark-brown color. In the centre is often seen a space, not natural, but formed after death by the disintegration of the medullary substance. The capsule consists of white fibrous connective tissue in which some smooth muscle tissue is seen. From the capsule and vessel sheaths the framework of the organ is derived. The cortical portion consists of epithelial cells arranged in three zones. The zona glomer- ulosa — the outermost — consists of oval or round cell groups surrounded by capillary plexuses and reticulum. The cells are polyhedral in .sluipc \\iili clear nuclei; the protoplasm is granular and contains many fat globules. The zona fasciculata — or middle zone — consists of columns of ejiithelial cells (usually two cells wide) supported by reticulum containing bloodvessels and lym- phatics. These cells resemble the above, but the nuclei are in the peripheral portion of the cells. The zona reticularis, the innermost of the three, consists of anastomosing columns or chains of cells. Tliese cells are smaller than the preceding, are distinct in outline, and possess a granular and pigmented protoplasm. 'MeduUary vein. 3 i. CJ:-<^ F G 1'25 — Sect on of human up a enal gl nd Rada h ) The medullary portion {substantia medullaris) (Fig. 1225). is usually separated from the cortex by a layer of large smooth cells. Beneath this layer the epithelial cells are arranged in irregular groups and chains, surrounded by reticulum and capillaries. The cells are small and their outlines are indistinct. They color deeply with chromium salts, and are called chromaffin ciUn. Many sympathetic nerve cells are present. Vessels and Nerves. — The numerous arteries which enter the suprarenal bodies from the sources mentioned below form plexuses in the capsule and penetrate the cortical part of the gland, where they break up into capillaries in the fibrous septa, and these converge to the very numerous thin-walled veins of the medullary portion. These veins usually empty directly into the large central veins. The medullary vessels are derived from the cortical vessels, and pass to the medulla without branching to form plexuses of capillaries around the cells. The veins in this region converge to form from two to four central veins, which unite to become the suprarenal vein, which in tm-n emerges as a single vessel from the centre of the gland. The arteries supplying the suprarenal glands are three in number and of large size; they are derived from the aorta, the phrenic, and the renal; they subdivide into numerous minute branches previous to entering the substance of the gland. The suprarenal vein returns the blood from the medullary venous plexus, and receives several branches from the cortical substance; it emerges from the hilum and opens on the right side into the inferior vena cava, on the left side into the renal vein. The lymphatics form several collections which are about the beginning of the suprarenal vein. They terminate in the noiles at the corresponding sid'e of the aorta. The nerves arc myelinated and amyelinated, are exceedingly numerous, and are derived from the solar and renal plexuses, and, according to Bergmann, from the phrenic and vsigus nerves. They enter the lower and inner part of the gland. A plexus in the gland sends branches into the cortex, where plexuses are formed around the vessels. Branches are also sent to the medulla, where rich plexuses are formed around the cells and vessels. Many sym- pathetic ganglia are seen there. 1450 THE DUCTLESS GLANDS THE CAROTID GLANDS, OR CAROTID BODIES (GLOMUS CAROTICUM). The carotid bodies, two in number, are situated one on either side of the neck, behind the common carotid artery at its point of bifurcation into the internal and external carotid trunks. They are reddish brown in color and oval in shape, the long diameter measuring about one-fifth of an inch (5 mm.) Each is invested by a fibrous capsule and consists of spherical or irregular masses of cells — the masses being more or less isolated from each other by septa which extend inward from the capsule. A network of large capillaries from tlie carotid artery ramifies among the cell masses, together with numerous sympathetic nerve fibres. The cells are polyhedral in shape, and each contains a large nucleus embedded in finely granular protoplasm which is stained yellow by chromic salts. Applied Anatomy. — Tumors may arise in this structure. Such a tumor is apt to be above the level of the upper margin of the thyroid cartilage, and in most cases it moves with each arterial beat. THE COCCYGEAL GLAND OR BODY, OR LUSOHKA'S GLAND (GLOMUS COCCYGEUM). Lying near the tip of the coccyx in a small tendinous interval formed by the union of the Levator ani muscles and just above the coccygeal attachment of the Sphincter ani is a small conglobate body about as large as a millet seed, first described by Luschka, and named by him the coccygeal gland. Its most obvious connections are with the middle sacral artery. Structure. — It consists of a congeries of small arteries with little aneurismal dilatations derived from the middle sacral and freely communicating with each other. The gland is sur- rounded by a capsule of white fibrous connective tissue which sends in septa to form the frame- work of the organ and to divide it into spaces which contain groups of polyhedral cells. Each cell contains a large round or oval nucleus, the protoplasm surrounding which is clear and is not stained by chromic salts.' Nerves pass into this little body from the sympathetic, but their mode of termination is unknown. Macalister believes the glomerulus of the vessels "con- sists of the condensed and convoluted metameric dorsal arteries of the caudal segments em- bedded in tissue which is possibly a small persisting fragment of the neurenteric canal." THE PARASYMPATHETIC BODIES (ORGANA PARASYMPATHETICA ; PARAGANGLIA LUMBALE). The parasympathetic bodies were discovered in 1901 by Zuckerkandl. They are from one to four in number, situated retroperitoneally, ventrad of the abdominal aorta at the level of the third and fourth lumbar vertebrae. Each parasympathetic body is from 6 to 10 mm. in length and from 2 to 4 mm. in width, and is surrounded by a capsule of fibrous tissue. In the meshes of the reticulum are found groups of polyhedral or cuboidal epithelial cells, closely packed and of the chromaiEn type. These bodies are usually supplied by fine arterial twigs from the aorta. They are best developed in the fetus and in infancy, apparently being absent in the adult. 1 Consult J. W. T. Walker, "Ueber die menschliche Steissdriise," Arck. f . mikr. Anat. u. Entwickgesch., 1904- INDEX Abdomen, 1240 boundaries of, 1241 • fascite of, 424 triangular, 425, 428 lymphatic vessels of, 789, 790 lymphatics of, 787 muscles of, 423 regions of, 1242 veins of, 739 walls of, apertures in, 1242 Abdominal aorta, 657 applied anatomy of, 658 surface marking of, 657 aortic plexus of nerves, 1076 furrow, 439 ring, 426, 436, 437 xascera, lymphatic vessels of, 792 Abdominothoracic arch, 166 Abducent nerve, 993 applied anatomy of, 994 nucleus, 883 Abduction, 267 Abductor hallucis muscle, 538 indicis muscle, 494 minimi digiti muscle, foot, 539 surface form of, 544 hand, 493 pollicis longus muscle, 485 muscle, 489 Aberrant ganglion, 1014 Accelerator urinae muscle, 443 Accessory cephalic vein, 731 ganglion, 1014 ligament. 275 liver, 1326 obturator nerve, 1049 olivary nuclei, 873 posterior palatine canals, 110, 128 pudic artery, 675 suprarenal glands, 1448 thyroid gland, 1436 veins, 717 Acervus cerebri, 906 Acetabulum, 213 fossa, of, 213 transverse ligament of, 325 Acid cells, 1276 Acoustic nerve, 1000 applied anatomy of, 1001 nuclei, 881 Acromial angle, 177 artery, 638 bursa, 303 nerve, 1022 region, muscles of, 462 Acromioclavicular articulation, 297 applied anatomy of, 299 surface form of, 299 ligaments, 297 Acromion, 175 angle, 177 process, 175 Acromiothoracic artery, 638 Adduction, 267 Adductor brevis muscle, 514 canal, 685 longus muscle, 513 Adductor longus muscle, applied anatomy of, 515 surface form of, 543 magnus muscle, 514 applied anatomy of, 515 surface form of, 543 minimus muscle, 514 obliquus hallucis muscle, 541 pollicis muscle, 492 transversus hallucis muscle, 541 polHcis muscle, 492 surface form of, 497 tubercle, 225 Aditus laryngis, 1169 Adminiculum linae albae, 428 Adrenal capsule, 1447 Aequator leniis, 1107 Afferent lymphatic vessels, 768 root of spinal cord, 823 Agger nasi, 1082 Agminated follicles, 1292 Air sacs, 1195 sinus, frontal, 79 Ala cinerea, 866 lobuli centralis cerebelli, 886 nasi, 1079 sacralis, 61 Alae of ethmoid, 96 magna, 92 parvae, 93 of sphenoid, 92 of vomer, 114, 138 Alar cartilage. 1080 thoracic artery, 639 Alcock's canal, 450, 675 Alimentary canal, 1199 tract, development of, 1245 Alisphenoids, 95 Alveolar artery, 601 index of skull, 147 point of skull, 146 process of maxilla;, 104 Alveoli dentales, 104, 117, 1204 of lungs, 1195 Alveus, 929, 942 Ameloblasts, 1214 Amphiarthrosis, 264, 266 Ampulla ductus deferentis, 1383 lacrimalis, 1116 of Fallopian tube, 1401 of lacrimal canal, 1116 of rectum, 1308 tubae uierinae, 1401 of vas deferens, 1383 of Vater, 1334 Ampullae Tuembranaceae, 1142 ossea, 1137 Ampullar nerve, 1001 Amygdala, 887, 948 Amygdaline fissure, 924 nucleus, 948 Amygdaloid tubercle, 939, 948 Anal canal, 1309 fascia, 446, 454 oriBce, 1309 pockets, 1310 valves, 1310 Anastomosis of arteries, 572 circumpatellar, 696 between portal and systemic veins, 754 Anastomosis, crucial, 678, 690 of veins, 706 Anastomotic vein of Trolard, 720 Anastomotica magna of brachial, 643 of femoral, 691 Anatomical neck of humerus, 178 Anconeus muscle, 482 surface form of, 496 Andersch, ganglion of, 1002 Angiology, definition of, 34 Angle, acromial, 177 filtration, 1105 of jaw, lis lateral, inferior, 60 of Ludwig, 157, 166 nasal, 100 of pubis, 212 of ribs, 163 Rolandic, 918 sacrovertebral, 58 subcostal, 156 subscapular, 172 Angular gyre, 923 processes, 77, 135 vein, 710 Angulu^ costae, 163 frontalis, 76 inferior, 176 infra^ternalis, 156 iridis, 1105 lateralis, 176 Ludovici, 157, 166 mandibulae, 118 mastoideus, 76 medialis, 176 occipitalis, 76 oris, 1199 sphenoidalis, 76 Anfde bone, 244 Ankle-joint, 342 applied anatomy of, 346 surface form of, 346 Anlage of cerebellum, 855 Annuli fibrosi, 562 Annulus femoralis, 428, 503, 685 fibrosus, 270, 558 dexter, 558 sinister, 560 inguinalis abdominis, 437 subcutaneous, 426 cru^ inferius, 427 superius, 427 ovalis, 557 tendineus communis, 370 tympanicus, 1123 urethralis, 1365 Anococcygeal body, 1309 nerves, 1062 raph6, 451, 453 Ansa ceniicalis, 1024 hypoglossi, 1024 lenticularis, 905, 9.51 peduncularis, 905, 951 subclavii [Vieussenii], 1069 Antecubital fossa, 641 lymph nodes, 781 Antihelix of ear, 1120 Antitragicus muscles, 1121 Antitragus of ear, 1120 Antrum cardiacum, 1237, 1271 ( 14.-,! ! 1452 Antrum of Highmore, 101, 103 mastoid, 83 opening of, 1126 iy?npanicum, 1126 Anus, 1309 lymphatic vessels of, 794 Aorta, 57.5 abdominal, 657 abdominalis, 657 arch of, 579 applied anatomy of, 580 development of, 761 ascendens, 576 ascending, 576 descending, 653 dorsal, 762 primitive, 755 surf-line of, 580 thoracalis, 653 rami mediastinales, 654 pericardiaci, 654 thoracic, 653 transverse, 579 ventral, 761 Aortenspindel, 580 Aortic arches, 761 bulb, 757, 759 isthinus, 762 lymph nodes, 788 opening of diaphragm, 419 septum, 759, 760 spindle, 762 stem, primitive, 757, 759 valve, 560 Aorticorenal ganglion, 1073 Apertura externa aquaeducti canaliculi cochleae, 86 lateralis [ventriculi quarii\, 867, 969 ■ medialis [ventriculi quarti], 867, 969 pelvis [minoris] inferior, 217 superior, 215 pyriformis, 135, 138, 1081 scalae vestibuli cochlece, 1137 sinus sphenoidalis, 91, 95 superior canaliculi tympanici. 84 thoracis inferior, 156 superior, 155 Apex capituli fibulae, 236 linguae, 1217 nasi, 1079 OSS. sacri, 61 patellae, 231 prostatae, 1391 pulmonis, 1188 Apical foramen, 1212 glands, 1219 Aponeuroses, 360 epicranial, 363 of external obUque, 425 gluteal, 516 of internal oblique, 428 lumbar, 409 palatal, 397 pharyngeal, 395 of soft palate, 1203 suprahyoid, 389 vertebral, 404, 408 Aponeurosis palmaris, 488 plantaris, 537 Aponeurotic fascia, 361 Apophysis of bone, 37 Apparatus digestorius, 1199 lacrimalis,^ 1115 respiratorius, 1163 Appendices epiploicae, 1265, 1296, 1309 vesiculosi, 1402 Appendicular artery, 664 lymph nodes, 791 planes of body, 34 INDKX Appendix, ensiform, 159 epididymidis, 1379 testis [Morgagni], 1378 ventriculi, 1171 vermiform, 1298 xiphoid, 159 , . , Applied anatomy of abdommal aorta, 658 of abducent nerve, 994 of acoustic nerve, 1001 of acromiocla^acular articu- lation, 299 of adductor longus muscle, 515 magnus muscle, 515 of ankle-joint, 346 of anterior tibial artery, 697 of arch of aorta, 580 of articulations of elbow- joint, 309 of hip-joint, 329 of phalanges of foot, 256 of shoulder-joint, 304 of tarsus, 351 of vertebral column, 278 of wrist-joint, 315 of ascending pharyngeal artery, 597 of auditory canal, 1124 of axilla, 634 of axillary artery, 637 veins, 732 of azygos veins, 737 of bladder, 1366 of bone, 46 of bones of foot, 256 of brachial artery, 641 plexus of nerves, 1039 of carotid glands, 14.50 of carpal bones, 205 of cavernous sinuses, 724 of cervical fascia, 384 ganglion, 1069 lymph nodes, 780 of choroid, 1110 of clavicle, 172 of colon, 1306 of common carotid artery, 586 iliac arteries, 669 of conjunctiva, 1118 of cornea, 1109 of coronary artery, 578 of costal cartilages, 167 of crystalUne lens, 1111 of deep epigastric artery, 681 definition of, 33 of deltoid muscle, 463 of descending palatine ar- tery, 602 of dorsalis pedis artery, 699 of duodenum, 1287 of emissary veins, 727 of external abdominal ring, 427 carotid artery, 588 iliac artery, 680 of eyelids, 1118 of facial artery, 595 nerve, 999 , veins, 711 of femoral artery, 687 of femur, 229 of fibula, 239 of glossopharyngeal nerve, 1003 of hamstring muscles, 525 of heart, 568 of hemorrhoidal plexus of veins, 745 of humerus, 184 of hyoid bone, 154 of hypoglossal nerve, 1012 of ilio tibial band, 508 Applied anatomy of inferior ealcaneoscaphoid liga- ment, 349 vena cava, 748 of innominate artery, 582 of intercostal arteries, 657 of internal ealcaneoscaphoid ligament, 349 carotid artery, 608_ iliac artery, 671, 679 jugular vein, 717 of intestines, 1295, 1314 of iris, 1110 of kidneys, 1355 of knee-joint, 338 of lacrimal gland, 1118 sac, 1119 of lateral sinus, 724 of hver, 1335 of lumbar plexus of nerves, 1062 of lymph nodes of lower extremity, 786 of upper extremity,_7S4 of lymphatic vessels, 770 of diaphragm, 799 of stomach, 793 of male breast, 1433 urethra, 1369 of mammary gland,^ 1432 of mediastinum, 1188 of middle meningeal artery, 600 of mouth, 1204 of muscles, 359 of back, 416 of cranial region, 365 of femoral region, 512, 515 of leg. 535 of lower extremity, 544 of orbital region, 371 of palatal region, 399 of radioulnar region, 478, 485 of tongue, 394 of upper extremity, 497 of nasal duct, 1119 of nose, 1084 of oculomotor nerve, 977 of oesophagus, 1239 of olfactory nerve, 974 of optic nerve, 975 of ovaries, 1401 of palmar fascia, 489 of pancreas, 1341 of parathyroid glands, 1440 of patella, 231 of pelvis, 220 of penis, 1390 of pericardium, 550 of peritoneum, 1268 of pharynx, 1235 of phrenic nerve, 1025 of plantar arch, 704 of pleurae, 1185 of pophteal artery, 693 of portal veins, 754 of posterior tibial artery, 701 of pronator teres muscle, 473 of prostate gland, 1395 of psoas magnus musclej__505 of pulmonary artery, 575 veins, 708 of pyloric artery, 662 of quadriceps extensor muscle, 512 of radial artery, 646 of radius, 192 of rectus femoris muscle, 512 of retina, 1111 of ribs, 167 of salivary glands, 1229 • of saphenous veins, 741 of scapula, 178 INDEX 1453 Applied anatomy of sclera, 1110 of scrotum, 1382 of seminal vesicles, 1385 of serratus magnus muscle, 461 of skull, 149 of spermatic veins, 750 of spinal accessory nerve, 1009 arteries, 621 cord, 842 pia, 846 of spleen, 1447 of sternoclavicular articula- tion, 297 of sternomastoid muscle, 386 of sternum, 167 of stomach, 1280 of subclavian artery, 627 of superficial palmar arch, 652 of superior mesenteric lymph nodes, 791 radioulnar articulation, 311 thyroid artery, 590 of synovial membranes of wrist, 487 of temporal artery, 598 of temporomandibular ar- ticulation, 281 of testes, 1383 of thoracic aorta, 654 duct, 774 of thorax, 167 of thymus gland, 1442 of thyroid gland, 1438 of tibia, 239 of tongue, 1222 of tonsil, 1233 of trachea, 1180 of tracheobronchial lymph nodes, 802 of triceps muscles, 471 of trigeminal nerve, 991 of trochlear nerve, 978 of tympanum, 1135 of ulna, 192 of ulnar artery, 649 of ureters, 1358 of uterus, 1411 of vaginal artery, 673 of vagus nerve, 1008 of vermiform appendix, 1302 of vertebral artery, 620 column, 68 Aquaeductus cochleae, 86, 131, 1140 Fallopii, 85 vestibuli, 86, 128, 1137 Aqueduct of midbrain, 896 Aqueous chamber, 1105 humor, 1105 Arachnoid of brain, 968 ■villi of, 970 spinal, 844 Arachnoidea encephali, 968 spinalis, 844 Arbor vitae cerebelli, 886 Arboriform nerve cells, 808 Arch, abdominothoracic, 166 of aorta, 579 of atlas, 50, 51 axillary, 407 crural, 684 femoral, 436 nasal, of veins, 710 palmar, 645, 652 plantar, 704 pubic, 217 supraorbital, 77 tarsal, 612 Arches, aortic, 761 Arcuate fibres, 873 of medulla oblongata, 863 Arcuate ligaments, 419 Arcus aortae, 579 cartilaoinis cricoideae, 1165 dentalis inferior, 1207 superior, 1207 glossopalatiniis, 1203 lumbocostalis lateralis, 419 medialis, 419 palatini, 1203 pharyng'opalalinus, 1203 planiaris, 704 rami perforantes anteriores, 704 posteriores, 704 pubis, 217 superciliares, 77, 79 tarseus inferior, 612 superior, 612 iendineus, 449, 450 venosi digitales, 728, 729 venosus dorsalis pedis, 739 plantaris, 741 vertebrae, 48 volaris profundus, 645 superficialis, 652 Area acustica, 866 cribrosa, 85 media, 85 superior, 85 plumiformis, 873 ■vestibularis inferior, 1147 posterior, 1147 Areola mammae, 1429 of mammary gland, 1429 Areolar tissue, subcutaneous, 1154 Arm, bones of, 178 fascia of, 461, 467 muscles of, 461, 467 Arnold, bundle of, 957 nerve of, 1005 ponticulus of, 863 Arrectores pilorum, 1161 Arteria aheolaris inferior, 601 rainus ^nylohyoideus, 601 superior posterior, 601 angularis, 594 anonyma, 582 appendicularis, 664 arcuata, 699 auditiva interna, 622 auricularis posterior, 596 ramus auricularis, 596 mastoideus, 596 profunda, 600 axillaris, 635 rami pectorales, 638 ramus acromialis, 638 clavicularis, 638 deltoideus, 638 basilaris, 622 rami ad pontem, 622 brachialis, 640 buccinatoria, 601 bulbi urethrae, 675 vestibuli, 1420 canalis pterygoidei, 602 carQ^is communis, 583 dextra, 583 sinistra, 583 externa, 588 interna, 606 ramus caroticotympanicus, 609 centralis retinae, 613, 1090, 1105 cerebelli inferior anterior, 622 posterior, 621 superior, 622 cerebri anterior, 614 media, 616 posterior, 622 cenicalis ascendens, 629 profunda, 633 chorioidea, 617 Arteria ciliares, 613 circumflexa femoris lateralis, 690 medialis, 690 ramus acetabuli, 690 profundus, 690 superficialis, 690 humeri anterior, 639 posterior, 639 ilium profunda, 682 superficialis, 689 scapulae, 639 coeliaca, 659 colica dextra, 664 media, 664 sinistra, 666 coUateralis ulnaris inferior, 643 superior, 643 comes nervi phrenici, 1024 comitans nervi ischiadici, 677 communicans anterior, 615 posterior, 617 coronoria [cordis] dextra, 578 sinistra, 578 cystica, 661 deferentalis, 1376 dorsalis clitoridis, 676, 1420 hallucis, 700 nasi, 612 pedis, 698 penis, 676 epigastrica inferior, 680 ramus pubicus, 681 superficialis, 689 superior, 633 ethmoidalis anterior, 611 posterior, 611 femoralis, 683 frontalis, 612 gastrica dextra, 661 sinistra, 660 roTni oesophagei, 661 gastroduodenalis, 661 gastroepiploica dextra, 661 rami epiploici, 661 sinistra, 662 {7e7iu inferior lateralis, 695 medialis, 695 media, 695 superior lateralis, 695 . medialis, 694 suprema, 691 ramus musculoarticularis, 691 saphenus, 691 glutaea inferior, 677 superior, 678 ramus inferior, 678 superior, 678 hemorrhoidalis inferior, 675 media, 672 superior, 667 hepatica, 661 hypogastrica, 669 ileocolica, 664 iliaca externa, 679 iliolumbalis, 678 ramus iliacus, 678 lumbalis, 678 spinalis, 678 infraorbitalis, 602 interossea communis, 650 dorsales, 650 recurrens, 651 volaris, 650 labialis inferior, 593 superior, 594 lacrimalis, 610 laryngea superior, 590 lienalis, 661 rami pancreatica, 662 ligamenti teretis uteri, 680 lingualis, 590 ramus hyoidews, 591 dorsalis linguae, 591 1454 INDEX Arteria magna, 575 hallucis, 700 malleolaris anterior posterior medialis, 703 ■mammaria interna, 631 rami intercostales, 632 perforantes, 632 stemales, 632 masseterica, 601 maxillaris externa, 592 rami glandulares, 593 ramus tonsillaris, 593 interna, 598 mediana, 650 Tneningea anterior, 609 media, 600 posterior, 597 mentalis, 601 ■mesenlerica inferior, 666 superior, 663 musculophrenica, 632 nutrida fibulae, 702 humeri, 643 iifoiae, 702 ramus communicoTis, 703 ohturatoria, 673 ramus anterior, 674 iliacus, 673 posterior, 674 pvhieus, 673 vesicalis, 673 occipitalis, 595 ramt muscidares, 595 occipitales, 596 ramus auricularis, 596 descendens, 596 meningeus, 596 7nastoideu3, 596 ophthalmica, 610 ovaricae, 665 palatina ascendens, 593, 1204 descendens, 602, 1204 pancreaticoduodenalis inferior, 663 superior, 661 perforans prima, 691 secunda, 691 tertia, 691 pericardiacophrenica, 632 perinei, 675 peronaea, 701 ramus calcaneus lateralis, 702 comir.unicans, 702 perforans, 702 pharyngea ascendens, 597 rami pharyngei, 597 plantaris lateralis, 703 medialis, 703 ramus superficialis, 703 poplitea, 691 princeps cervicis, 596 hallucis, 700 poinds, 647 profunda brachii, 641 rami musculares, 644 clitoridis, 676, 1420 femoris, 689 ram/as ascendens, 690 descendens, 690 linguae, 591 penis, 676 pudenda externa profunda, 689 superficialis, 689 interna, 674 pulmonalis, 574 ramus dexter, 575 sinister, 575 radialis, 644 rami musculares, 646 perforantes, 648 ramus carpeiis dorsalis, 647 volaris, 647 volaris superficialis, 647 Arteria recurrens radialis, 646 tibialis anterior, 698 posterior, 698 recurrentes ulnaris anterior, 650 posterior, 650 sacralis lateralis, 678 rami spinales, 678 sigmoideae, 667 spermatica externa, 680, 1377 interna, 665, 1376 sphenopalatina, 602 spinalis anterior, 621 posterior, 621 sternocJeidomastoidea, 595 siylomastoidea, 596 subdavia, 623 sublingualis, 591 submentalis, 593 subscapularis, 639 supraorbitalis, 610 suprarenalis inferior, 665 media, 662 larsea lateralis, 699 temporalis media, 598 profunda anterior, 601 posterior, 601 superficialis, 597 rami auriculares anierio- res, 598 ramus frontalis, 598 parietalis, 598 thoracalis lateralis, 638 suprema, 638 thyreoidea ima, 582 inferior, 629 rami oesophagi, 629 tracheales, 629 superior, 589 rami glandulares, 590 ramus anterior, 589 cricnthyroideus, 590 hyoideus, 590 posterior, 589 siernocleidonvistoideus, 590 tibialis anterior, 696 posterior, 700 transversa colli, 630 ramus ascendens, 630 descendens, 630 faciei, 598 scapulae, 629 ram.us acromialis, 630 tympanica anterior, 600 inferior, 597 superior, 600 ulnaris, 648 rami musculares, 651 ramus carpeus dorsalis, 651 volaris, 651 volaris profundu^s, 651 urethralis, 676 uterina, 672 ramus ovarii, 672 vaginalis, 672 vertebralis, 619 rami spinales, 620 ramu^ meningeus, 621 vesiculis inferior, 672 medialis, 672 superior, 671 volaris indicts radialis, 647 zygomaticoorbitalis, 598 Arteriae alveolares superiores an- teriores, 602 arciformes, 1354 bronchiales, 654 ciliares anteriores, 613 posteriores breves, 613 longae, 613 digitales dorsales, 647, 699 plantares, 704 volar es communes, 652 propriae, 652 gastricae breves, 662 Arteriae ileae, 663 iliacae communes, 668 intercostales, 655 rami cutanei laferales, 656 musculares, 656 ramus posterior, 655 interlobares rents, 1354 inlestinales, 663 jejunales, 663 lumbales, 662 ramus dorsalis, 663 spinalis, 663 mediastinales anteriores, 632 metacarpeae dorsales, 647 volares, 648 metatarseae dorsales, 699 plantares, 704 oesophageae, 654 palpebrales laterales, 610 mediates, 612 phrenicae inferiores, 658 rami suprarenales supe- rior, 659 receptaculi, 609 renales, 665 surales, 694 tunica adventitia, 573 inlima, 573 media, 573 Arterial sheath, 574 Arteriolae recti, 1354 Arterioles, 547 precapillary, 573 Artery or Arteries, 572 acromial, 638 acromiothoracic, 638 of ala, 574 alveolar, 601 anastomosis of, 572 around elbow-joint, 644 circumpatellar, 696 crucial, 678, 690 anastomotica magna of bra- chial, 643, 644 of femoral, 691 angular, 592, 594 of ankle-joint, 345 antero-lateral ganglionic, 617 antero-median ganglionic, 614 aorta, 57,5 abdominal, 657 arch of, 579 ascending, 576 descending, 653 thoracic, 653 appendicular, 664 articular, 694, 695 of auditorj^ canal, 1123 internal, 622 auricular, 596 anterior, 598 deep, 600 posterior, 596 axiUary, 635 azygos, articular, 695 of vagina, 672 basilar, 622 of bile ducts, 1336 of bladder, 1365 brachial, 640 bracliiocephalic, 582 of brain, 617 bronchial, 582, 654 buccal. 601 of bulb, 675 bulbar, 622 calcaneal, 702, 703 capsular, 662 carotid, common, 583 external, 588 internal, 609 of cecum, 664, 1300 central ganglionic system of, 618 of retina, 613 INDEX 1455 Artery or Arteries, cerebellar, 621, 622 cerebral, anterior, 614 hemorrhage, 617 middle, 616 posterior, 622 cervical, 629, 630 cervicouterine, 672 cervicovaginal, 672 choroid, 617, 622, 1099 ciliary, 613 circle of Willis, 617 circumflex, 639, 690 circumpatellar, anastomosis of, 696 clavicular, 638 of clitoris, 1420 coats of, 573 coccygeal, 677 cceliac, 659 colic, 664, 666 communicating, anterior, 614, 650 of dorsalis pedis, 700 of peroneal, 702 posterior, 617 of cornea, 1092 coronary, 578, 660 of corpus cavernosum, 676 cortical system of, 619 cranial, from occipital, 596 cremasteric, 680 cricothyroid, 590 cystic, 661 dental, 601, 602 ^ development of, 761 digital, 652 collateral, 652 plantar, 704 ulnar, 652 dorsal, of penis, 676 dorsalis hallueis, 700 indicis, 647 hnguae, 591 nasi, 613 pedis, 698 polhcis, 647 scapulse, 639 of duodenum, 1287 dural, from ascending pharyn- geal, 597 from occipital, 596 of elbow-joint, 308 epigastric, deep, 680 superficial, 689 superior, 633 ethmoidal, 611 facial, 592 transverse, 598 of Fallopian tube, 1402 femoral, 683, 689 fibular, 698 frontal. 598, 612. 615, 617 of gall-ljladder, 1335 ganglionic, 614, 617, 618 gastric, 660 gastroduodenal, 661 gastroepiploic, 661 glandular, 593 of globe of eye, 1108 gluteal, 678 of head, 583 of heart, 565 hemorrhoidal, 672, 675 hepatic, 661 of hip-joint, 327 histology of, 573 humeral, 63S hypogastric, 570, 669, 763 imperious, 671 ileal, 664 ileocecal, 664 ileocolic, 664 iliac, common, 668 deep circumflex, 682 Artery or Arteries, iliac, external, 679 internal, 669 superficial circumflex, 689 iliolumbar, 678 infrahyoid, 590 infraorbital, 602 infrascapular, 639 innominate, 582 inosculation of, 572 intercostal, 632, 655 interosseous, foot, 699, 700 hand, 647, 64S recurrent, 651 ulnar, 650 of iris, 1099 of Iddneys, 1352 of knee-joint, 337 of labia majora, 1415 labial coronary, 593, 594 lacrimal, 610 of large intestines, 1310 laryngeal, 590, 629, 1174 lateralis nasi, 594 lenticulostriate, 617 lingual, 590, 591, 601 of liver, 1326 of lower extremity, 682 lumbar, 662 lymphatics of, 574 malar, 610 malleolar, 698, 703 mammary, 631, 638 masseteric, 601 mastoid, from occipital, 596 from posterior auricular, 596 maxillary, 598 mediastinal, 632, 654 medidural, 600 medullary, 619 of membrana tympani, 1131 meningeal, anterior, 609 from ascending pharyngeal, 597 from occipital, 596 middle, 600 posterior, 597, 621 small, 600 mental, 601 mesenteric, 663, 666 metatarsal, 699 musculophrenic, 632 mylohyoid, 601 nasal, 612, 613 nasopalatine, 602 of neck, 583 nerves of, 574 of nose, 1081 nutrient, of fibula, 702 of humerus, 643 of tibia, 702 obturator, 673 occipital, 595, 623 oesophageal, 629, 654, 1239 ophthalmic, 610 orbital, 598 ovarian, 665, 1401 palatine, 596, 597, 602, 1204 palpebral, 610, 612 pancreatic, 662, 1341 pancreaticoduodenal, 661, 663 parietal, 617 of parotid gland, 1225 par\ddural, 600 of penis, 1389 perforating, 690 of foot, 704 fourth, 689 of hand, 648 pericardiac, 632, 654 perineal, 675 perirenal, 665 peroneal, 701, 702 petrosal, 600 pharyngeal, 597 Artery or Arteries, phrenic, 658 of pia of brain, 972 of spinal cord, 846 of pinna of ear, 1121 plantar, 700, 703 of pleura;, 1185 pontile, 622 popliteal, 691 postdural, 597 postero-median ganglionic, 617 prevertebral, 597 princeps hallueis, 700 polhcis, 647 profunda femoris, 689 inferior, 643 superior, 642 of ulnar, 651 of prostate gland, 1395 pterygoid, 601 pterygopalatine, 602 pubic, 681 pudic, accessory, 675 external, 689 internal, 674, 676 pulmonary, 574 pyloric, 661 radial, 644 carpal, 647 radialis indicis, 647 ranine, 591 recurrent, radial, 646 tibial, 698 ulnar, 650 renal, 665 sacral, 669, 678 of salivary glands, 1227 scapular, 630 sciatic, 677 of seminal vesicles, 1385 of septum, 594, 602 of shoulder-joint, 303 sigmoid, 667 of skin, 1156 of small intestine, 1293 spermatic, 665, 1376 spinal, 620, 621 splenic, 661, 1446, 1449 splenopalatine, 602 sternal, 632 sternomastoid, 590, 595 of stomach, 1278 stylomastoid of posterior au- ricular, 596 subclavian, 623 sublingual, 591 submaxillary, 593, 1226 submental, 593 subpleural, mediastinal plexus of, 632 subscapular, 630, 639 superficialis volae, 647 supra-acromial, 6.30 suprahyoid, 591 supraorbital, 610 suprarenal, 662 suprascapular, 629 suprasternal, 629, 630 sural, 694 tarsal, 699 temporal, 600, 617 anterior, 598, 623 deep, 601 middle, 598 posterior, 598, 623 superficial, 597 of temporomandibular articu- lation, 281 terminal, definition of, 573 thoracic, 638, 639 thymic, 582, 1442 thyroid axis, 628 inferior, 629 superior, 589 thyroidea ima, 582 tibial, 696, 700 1456 INDEX Artery or Arteries, of tongue, 1219 tonsillar, 593, 1231 tracheal, 629, 1179 of trunk, 653 tympanic, 609 anterior, 600 from ascending pharyngeal, 597 superior, 600 ulnar, 648, 651 umbilical, 570 of upper extremity, 623 ureteral, 665, 1358 urethral, 676 uterine, 672, 1410 vaginal, 672, 1415 bulb, 1420 of vas deferens, 671 vasa brevia, 662 intestini tenuis, 663 of vermiform appendix, 1300 vertebral, 619, 628 vesical, 671, 672 Vidian, 602, 609 of voluntary muscles, 356 of wrist-joint, 315 Arthrodia, 264, 265, 266 Articular arteries, 694, 695 cartilage, 260 disks, 260 triangular, 312 eminence of zygomatic process of temporal bone, 81 facet of clavicle, 171 fibrocartilage, 260 lamella of bone, 259 meniscus, 280 nerve corpuscles, 817 processes of atlas, 51 surfaces of axis, 52 of sacrum, 60 synovial membrane, 261 ArticulatioacromioclavicularisfiQ? atlantoepislTophica, 273 atlantooccipitalis, 275 calcaneocuboidea, 347 carpometacarpeae pollicis, 317 coxae, 322 citbiti, 306 cuboideonavicularis, 350 genu, 331 humeri, 301 intercarpea, 315 mandihidaris, 279 radiocarpea, 314 radioulnaris, 310 distalis, 312 sacroiliaca, 290 stemoclavicularis, 295 talocalcanea, 347 talocruralis, 342 tarsi transversa [Choparti], 349 iibiofibularis, 340 Ariiculationes capitulorum, 282 carpometacarpeae, 317, 318 costotransversariae, 284 costovertehrales, 282 digitorum manus, 321 pedis, 354 interchondrales, 288 intermetacarpeae, 319 intermetatarseae, 352 intertarseae, 347 metacarpophalangeae, 320 metatarsopkalangeae, 353 ossiculorum auditus, 1133 stemocostales, 286 tarsometatarseae, 351 Articulations, 259 acromiocla^dcular, 297 of astragalus with scaphoid, 349 of atlas with axis, 273 with occipital bone, 275 of axis mth occipital bone, 277 biaxial, 264, 265 Articulations, calcaneo-astragal- oid, 347 calcaneocuboid, 347 calcaneoscaphoid, 348 carpometacarpal, 318 of carpus, 315 of cartilages of ribs with each other, 288 costocentral, 282, 285 costosternal, 286 costotransverse, 284, 285 costovertebral, 2S2 of cuneiform bones with each other, 350 of elbow-joint, 306 of external cuneiform bone with cuboid, 351 of hip-joint, 322 immovable, 263 intercuneiform, 350 interneural, 271 of knee-joint, 331 of lower extremity, 322 mediotarsal, 349 metacarpophalangeal, 320 of metatarsal bones with each other, 352 metatarsophalangeal, 353 mixed, 264 movable, 264 of ossicles of tympanum, 1133 of pelvis, 290 of phalanges of foot, 354 of hand, 321 polyaxial, 264 of pubic bones, 294 radiocarpal, 314 radioulnar, 310 of ribs with their cartilages, 288 with vertebrae, 282 sacroihac, 290 of sacrum and coccyx, 292 and ilium, 290 of scaphoid with cuboid, 350 with cuneiform, 349 of scapula, 299 scapulocla"\acular, 297 of shoulder-joint, 301 sternoclavicular, 295 of sternum, 288 tarsometatarsal, 351 of tarsus, 347 temporomandibular, 133, 279 tibiofibular, 340 tibiotarsal, 342 transverse tarsal, 349 of trunk, 268 of upper extremity, 295 of vertebral column, 268 with cranium, 275 with pelvis, 289 of wrist-joint, 314 Aryepiglottic muscles, 1173 Arytenoepiglottic fold, 1167, 1170 Arytenoid cartilage, 1166 Arytenoideus muscles, 1172 Ascending aorta, 576 colon, 1303 mesacolon, 1264 Association nerve fibers, 954 Asterion, 133, 146 Astragaloscaphoid ligament, 349 Astragalus, 244 articulation of calcaneus and, 347 of scaphoid mth, 349 Astrocytes, 818 Atlanto-axial ligaments, 274 Atlanto-odontoid joint, 274 Atlas, 50 accessory ligament of, 275 articulation of, -with axis, 273 with occipital bone, 275 Atlas, development of, 63 transverse ligament of. 274 Atrium, 1125 dextrum, 554 maxillary, orifice of, 141 meatus medii, 141 nasi, 1082 of nasal meatus, 141 sinistrum, 559 Attic, 1125 Attollens aurem muscle, 366 Attrahens aurem muscle, 366 Auditory artery, internal, 622 canal, 1122 applied anatomy of, 1124 arteries of, 1123 cartilaginous portion of, 1122 lymphatics of, 1123 nerves of, 1123 osseous portion of, 1122 skin of, 1123 veins of, 1123 hair, 1143 meatus, 1122 external, 88, 133, 1122 lymphatic vessels of, 777 internal, 85, 128 nerve, 1000 nuclei, 881 teeth, 1144 vesicles, 142 Auerbach's plexus of nerves, 1279 Aula, 908 Aulix, 908 Auricles of ear, 1119 of heart, fibres of, 562 left, 559 right, 554 primitive, 757 Atiricula, 1119 dextra, 554 sinistra, 559 Auricular appendix, 554, 559 artery, 596, 598, 600 canal, 757 fissure, 131 IjTnph nodes, 774 nerve, anterior, 988 from vagus, 1005 great, 1020 posterior, 997 point of skull, 146 region, muscles of, 365 systole, 565 vein, 712 Auriculotemporal nerves, 988 Auriculoventricular bundle of His, 564 opening, 557, 559 Auris interna, 1136 Avalanche conduction of Ramon y Cajal, 815 Axes of pehas, 218 Axial planes of body, 34 Axilla, 633 applied anatomy of, 634 dissection of, 455 ligaments of, 456 Axillary arch, 407 artery, 635 applied anatomy of, 637 fascia, 456, 633 lymph nodes, 782 sheath, 636 veins, 731 applied anatomj- of, 732 Axis, 52 articulation of, with occipital bone, 277 coeliac, 659 of crystalline lens, 1107 development of, 64 optic, 1088 sagittal, 1088 INDEX 1457 .Vxis, thyroid, 628 vi.su ill, loss Axia Icntis, 1107 oinica, loss pdms, 218 ■ Axis-cvliiider process, 807, 811 Axones.'SlO amyelinic, S12 myelinic, 811 of spinal cord, myelinization of, S40 Azygos arteries of vagina, 672 articular arterj', 695 uvulae muscle, 398 veins, 736 applied anatomy of, 737 Back, fascia of, 404 muscles of, 403 applied anatomy of, 416 fifth layer, 413 first layer, 404 fourth layer, 410 second layer, 407 surface form of, 416 third layer, 408 Baillarger, fibre band of, 953 Ball-and-socket joint, 264 Band of Vicq d'Azyr, 932 Barha, 1159 Bartholin, duct of, 1226 glands of, 1420 Basihyal, 153 Basilar artery, 622 groove, 73 of pons, 864 membrane, 1143 process, 71 sinus, 727 suture, 122 vein, 720 Basilic vein, 730 Basion, 131, 146 Basis cochleae, 1138 cordis, 551 glandulae suprarenalis, 1448 mandibulae, 117 modioli, 1138 nasi, 1079 ossa metacarpalia, 201 metatarsalia, 250 sacri, 61 patellae, 231 phalangis, 204 prostatae, 1391 pulmonis, 1188 Basisvlvian fissure, 917 Basket cells, 892 Basophiles, 40 Bechterew, fibre band of, 953 Bell, respiratory nerve of, exter- nal, 1029 internal, 1024 Bertin, ligament of, 323 Biaxial articulations, 264 Biceps brachii muscles, 469 femoris muscle, 522 applied anatomy of, 525 bursa of, 524 surface form of, 543 flexor cubiti muscle, 469 muscle, 469 surface form of, 495 Bichat, fissure of, 940 Bicipital fascia, 469, 730 groove, 180 tuberosity, 191 Bicornate uterus, 1408 Bicuspid teeth, 1207 valve, 561 Bifurcatio tracheae, 1175 Bigelow, ligament of, 324 92 Bile, 1334 duct, 1333 arteries of, 1334 lymphatics of, 796, 1334 nerves of, 1334 veins of, 1334 papilla, 1287 Bipolar nerve cells, SOS, 1102 "Bird's nest" of cerebellum, 888 Biventer cervicis muscles, 413 Biventral lobes, 887 muscle, 358 Bladder, 1358 applied anatomy of, 1366 arteries of, 1365 cervix of, 1361 development of, 1426 interior of, 1364 ligaments of, 1361 true, 1362 lymphatics of, 796, 1365 mucous membrane of, 1364 nerves of, 1365 rugae of, 1364 surface form of, 1365 trigone of, 1365 veins of, 1365 Blind spot, 1101 Blood cells, 40 circulation of, 547 islands, 755 Blood-vascular system, 547 development of, 755 Bloodvessels of bone, 40 of nerves, 813 BNA, definition of, 33 Bochdalek, ganglion of, 984 Bodies, carotid, 1450 Nissl, 809 parasympathetic, 1450 quadrigeminal, 894 tigroid, 809 Body, ciliary, 1094 coccygeal, 1450 geniculate, external, 905 internal, 895 lateral, 910 of Luys, 905 pineal, 906 pituitary, 909 thyroid, 1435 vitreous, 1105 ! Bone or Bones, acetabulum, 213 i ankle, 244 apophysis of, 37 appUed anatomy of, 46 of arm, 178 astragalus, 244 atlas, 50 axis, 52 bloodvessels of, 40 breast, 157 calcaneus, 239 calcification of, 44 calf, 236 cambium layer of, 46 canaliculi of, 39 cancellous, 40 carpus, 195 of cerebral cranium, 70 chemical composition of, 41 of chest, 154 clavicle, 169 coccyx, 61 colhir, 169 compact, 38 covering, 142 of cranium, 70 cuboid, 245 cuneiform, of foot, 247 of hand, 197 dense, 38 dermal, 142 destroyers, 44 diaphysis of, 35 Bone or Bones, of elbow, 185 cndosteuni of, 39 epactal, 144 ei)ii)hyses of, 35 epiptcric, 144 ethmoid, 96 extremities of, 35 of face, 99 femur, 221 fibers of, 38 fibula, 236 flat, 36 of foot, 239 of forearm, 185 formers, 44 frontal, 76 growth of, 42 of hand, 194 lower row, 198 upper row, 196 heel, 239 liip, 207 humerus, 178 hvoid, 153 ilium, 207 interparietal, 74 irregular, 36 ischium, 210 knee-cap, 230 lacrimal, 106 lesser, 107 lacuna of, 39, 259 lamellce of, 39 articular, 259 of leg, 230 lingual, 153 long, 35 of lower extremity, 207 jaw, 115 lymphatics of, 41 malar, 107 mandible, 115 marrow of, 40 maxillte, 100 medullary canal of, 35 metacarpus, 201 metatarsal, 249 nasal, 99 navicular, of foot, 246 of hand, 196 nerves of, 41 occipital, 70 OS calcis, 239 coxae, 207 innominatum, 207 magnum, 199 pubis, 207, 212 trigonum, 245 osseous tissue of, 38 ossification of, 42 palate, 109 parietal, 74 patella, 230 of pelvis, 215 periosteum of, 38 phalanges of foot, 252 of hand, 204 pisiform, 198 premaxillary, 105 proliferation of, 44 pubis, 212 radius, 190 ribs, 161 rider's, 229, 360, 515 sacrum, 58 scaphoid, of foot, 246 of hand, 196 scapula, 172 semilunar, 197 sesamoid, 257 shaft of, 35 shin, 231 short, 36 shoulder blade, 172 girdle, 169 1458 INDEX Bone or Bones, of skull, 69 sphenoid, S9 spine, 48 sternum, 157 supernumerary, 144 sutural, 144 tarsus, 239 temporal, 80 thigh, 220 of thorax, 154 tibia, 231 trapezium, 198 trapezoid, 199 turbinated, 113, 139 ulna, 185 unciform, 200 of upper extremity, 168 jaw, 100 vascularization of, 45 vertebrse, 48 cervical, 49 coccygeal, 58 lumbar, 56 sacral, 58 thoracic, 53 vomer, 114 wedge, 247 Wormian, 144 Bony semicircular canals, 1137 Born, ostium primum of, 759 secundum of, 759 Bowman, capsule of, 1350, 1351 membrane of, 1091 Brachia conjunctiva, 891 Bracliial artery, 640 applied anatomy of, 641 surface marking of, 641 fascia, 467 plexus of nerves, 1026 applied anatomy of, 1039 veins, 731 . Brachialis anticus muscle, 469 surface form of, 496 Brachiocephalic artery, 582 veins, 733 Brachioradialis muscle, 479 surface form of, 496 Brachium quadrigeminuTn infe- rius, 895 superius, 895 Brachy cephalic cranium, 146 Brain, 846 adult human, 860 arachnoid of, 968 ■idlli of, 970 areas of, 959 arteries of, 617 cerebellum, 884 development of, 850 dimensions of, 849 dura of, 964 fourth ventricle of, 864 hind, 861 isthmus, 860 (note) laminse of, 855 localization of function of, 959 medulla oblongata, 861 meninges of, 964 nuclei of, 857 Pacchionian bodies of, 970 pia of, 972 pons, 864 structure of, plan of, 858 topography of, 847 tube, development of, 852 flexures of, 855 vesicle, primary, 851 weight of, 849 zones of, 855 Breast bone, 157 female, 1428 male, 1433 Bregma, 76, 123, 146 Bregmatic fontanelle, 143 Brim of pelvis, 215 Broad ligament of lung, 1183 of uterus, 1407 Broca's cap, 917 diagonal band, 928 Bronchi, 1175 left, 1177 right, 1176 Bronchial artery, 582, 654 veins, 737 Bronchioles, respiratory, 1195 Bronchiomediastinal lymph nodes, 801 Bronchus dexter, 1176 ramus hronchialis eparteria- lis, 1177 hyparterialis, 1177 sinister, 1177 Bruce and Campbell, intermedio- lateral tract of, 839 Bruch, membrane of, 1093 Bruns, falciform margin of, 508 Bryant's triangle, 329 Buccae, 1200 Buccal artery, 601 cavitv, 1199 glands, 1200 lymph nodes, 776 nerve, 987, 998 region, muscles of, 374 Buccinator muscle, 375 nerve, 987 Buccopharyngeal fascia, 377, 394 Bulb, aortic, 759 artery of, 675 of corpora cavernosa, 1386 of internal jugular vein, 714 occipital, 939 olfactory, 927 urethral, 1386 Bulbar arteries, 622 Bulboid corpuscles, 817 Bulbous aortae, 576 Bulbus cordis, 757, 759 cornu posterioris, 939 oculi, 1086 olfactorius, 927 jnli, 1159 urethrae, 1386 vena jugularis inferior, 714 superior, 714 vestibuli, 1420 Bulla ethmoidalis, 1082 Burdach, column of, 827 Bursa or BursEe, about knee-joint, 336 of biceps femoris muscle, 524 deep infrapatellar, 336 of elbow-joint, 308 gluteofemoral, 327 of gluteus maximus muscle, 516 medius muscle, 517 of greater trochanter, 327 of hand, 487 of hip-joint, 327 iliopectineal, 327 infrapatellar, deep, 336 infraspinatus, 303 ischiogluteal, 327 of knee-joint, 336 obturator, 327, 518 olecranon, 308 patellar, deep, 512 prepatellar, 336, 512 of pjTiformis muscle, 517 of quadriceps femoris muscle, 521 of shoulder-joint, 303 subacromial, 303, 462 subcutaneous acromial, 303 tibial, 336 trochanteric, 327 subdeltoid, ,303, 462 Bursa or Burste, subscapular, 303 subtendinous iliac, 327 suprapatellar, 336, 511 synovial, subcutaneous, 262 subtendinous, 262 thecal, 262 of tendo Achillis, 530 • tensoris veil palati, 397 of tibialis anticus muscle, 526 of wrist, 487 Bursa or Bursae, anserina, 513, 524 hicipitogastrocnemialis, 524 bicipitoradialis, 308 glutaeofemorales, 327, 516 iliaca subtendinea, 327, .504 iliopectinea, 327, 504 infrapatellaris profunda, 336, 512 intermetacarpophalangeae, 487 intratendinea olecrani, 308 ischiadica musculus ghdaei maximi, 327, 516 mucosae subcutaneae, 262 subtendineae, 262 tnuscidi poplitei, 337 m.usculus bicipitis femoris in- ferior, 524 infraspinati, 465 obiuratorii interni, 327, 518 peciinei, 513 pisiformis, 517 recti femoris, 510 sartorii propria, 509 sternohyoidei, 1167 subscapularis, 464 tensoris veli palati, 397 teretis majoris, 466 praepatellaris subcutanea, 336, 506, 512 subfacialis, 336 svhtendinea, 336 sternohyoidii, 387 suhacromialis, 462 subcutanea calcanea, 530 digitorum dorsales, 487 epicondyli humeri lateralis, 308 medialis, 308 olecrani, 308 prominentiae laryngeae, 1164 tuberositatis tibiae, 336 subdeltoidea, 462 subtendinea musculus tibialis anterioris, 526 olecrani, 308 suprapatellaris, 336, 511 tendinis calcanei, 530 trochanterica musculus glutaei maximi, 516 medii anterior, 517 posterior, 517 minimi, 517 subcutanea, 327, 506 Bursal synovial membrane, 262 Cacuminal lobes, 886 Cajal, nerve cells of, 1102 Calcaneal arteries, 702, 703 nerves, 1057 Calcaneo-astragaloid articula- tion, 347 ligaments, 347 Calcaneocuboid articulation, 347 ligamients, 348 Calcaneoscaphoid articulation, 348 ligaments, 348 Calcaneus, 239 articulation of astragalus and, 347 of scaphoid and, 348 INDEX 1459 Calcaneus, articulation with cu- boid, 347 Calcar, 939 avis, 939 femorale, 227 Calcarine fissure, 919 Calf bono, 536 Calices majores, 1349 minor es, 1349 of ureters, 1356 Callosal eminence, 939 gyre. 920, 921 Calyculi gualaiorii, 1148 Catncra oculi anterior, 1105 posterior, 1105 Camper, fascia of, 424 Canal or Canals, adductor, 685 Alcock's, 450, 675 alimentary, 1199 anal, 1309 auditory, 1122 auricular, 757 carotid, 131 of Corti, 1145 crural, 684 dental, 102, 117 diploic, 718 ethmoidal, 79, 98 for Eustachian tube, 1127 femoral, 503, 684 Haversian, 39 of Huguier, 84, 88, 997, 1126 Hunter's, 511, 515, 685 hyaloid, 1106 incisor, 105 infraorbital, 102, 136 inguinal, 437, 1375 lacrimal, 1116 malar, 108 medullary, of bone, 35 membranous, of cochlea, 1144 for nasal duct, orifice of, 141 nasopalatine, 114 of Nuck, 1408 nutrient, of fibula, 237 of metacarpal bones, 201 of radius, 191 of ulna, 189 obturator, 517 palatine, anterior, 139 posterior, 102, 110, 134 accessory, 1 10, 128 palatomaxillary, 102 of Petit, 1106 pterygoid, 130 pterygopalatine, 92, 130, 134 pyloric, 1272 sacral, 61 of Schlemm, 1092 semicircular, bony, 1137 membranous, 1142 spermatic, 437, 1375 of spinal cord, central, 831 for tensor tympani, 1127 of vermiform appendix, 1299 vertebral, 49, 67 Vidian, 93, 130, 134 Volkmann's, 39 of Wirsung, 1339 Canales diploid [Brescheli\, 718 palatini, 110 semicirculares ossei, 1137 lateralis, ,1138 posterior, 1137 superior, 1137 Canaliculi of bone, 39 caroticotympanici, 86 Canaliculus chordae tympani, 88, 1126 innominatum, 92, 127, 1135 tympanicus, 87, 1125 Canalis adductorius [Hunteri], 511, 515, 685 centralis cochleae, 85 medullae spinalis, 831 Canalis ccrviris uteri, 1408 COIIillllni,l,„x. 71 ethiii,n,hilr .inlrrias, 98 /«/,v/. /•,«,s-, '.IS faeiaUs, S5 femoralis, 503, 684 hyaloideus, 1106 hypoglossi, 71 inguinalis, 437, 1375 iayr'.nialis, 104 mandihulae, 117 niuscidotid}arius, 87 nasolacrivialis, 102 ohturatorius, 517 pteryfjoideus, 93 pterygopalatirtus, 110 radicis dentis, 1212 reuniens of Hensen, 1142 sacralis, 61 spiralis cochleae, 1140 modioli, 1139 vertebralis, 49 Cancellous bone, 40 Canine eminence, 101 fossa, 101, 135 teeth, 1206 Canthi of eyelids, 1113 Capillaries, 547, 573 Capilli. 1159 Capitellum, 182 Capitulum costae, 162 fibulae, 236 humeri, 182 mallei, 1131 mandihulae, 118 ossa yneiacarpalia, 201 metata.rsalia, 250 radii, 190 stapedis, 1133 ulnae, 189 Capsula adiposa, 1348 articularis cricoarytaenoidea, 1168 extrema, 948 lentis, 1107. Capsulae articulares. See Indi- vidual joints. Capsular artery, 662 ligaments. See Individual joints. Capsule, adrenal, 1447 of Bowman, 1350, 1351 of crystalline lens, 1107 external, 951 internal, 948 Malpighian, 13.50, 1351 of Ti5non, 371, 1086 Caput cecum coli, 1297 epididymidis, 1378 femoris, 221 gallinaginis, 1367 gelatinosa Rolandi, 830 humeri, 178 obliguum musculus adductoris hallucis, 541 panereatis, 1337 transversuirt musculus adducto- ris hallucis, 541 Cardiac cycle, 565 ganglion of Wrisberg, 1072 glands, 1278 muscle fibers, 355, 357 muscles, 355 nerves, cervical, 1007 inferior, 1069 superior, 1068 thoracic, 1007 orifice, 1271 plexus of nerves, 1072 revolution, 565 veins, 708 anterior, 556 Carina urcthralis vaginae, 1414 Caroticotympanic nerve, 1066 Carotid arteries, common, 583 applied anatomy of, 586 left, 583 right, 583 surface marking of, 586 external, 588 applied anatomy of, .588 surface marking of 588 internal, 606 applied anatomy of, 608 cavernous portion of, 608 cerebral portion of, 60S cervical portion of, 607 petrous portion of, 607 bodies, 1450 canal, 131 , foramen, 84, 86 ganglion, 1066 glands, 586, 1450 groove, 126 nerve, 1003 plexus of, 1069 sheath, 383 triangle, 388, 603, 604 Carpal arch, 647 artery, radial, 647 ulnar, 651 bones, 195 applied anatomy of. 205 common characters of, 196 surface form of, 205 meniscus, 317 Carpometacarpal articulations, 317 Carpus, 195 articulations of, 315 Ugaments of, 315 Cartilage, 259 alar, lesser, 1080 articular, 260 arytenoid, 1166 costal, 165 cricoid, 1165 cuneiform, 1166 elastic, 261 epiphyseal, 44 hyaline, 260 intrathyroid, 1165 of Jacobson, 1080, 1083 of larynx, 1163 matrix, 260 Meckel's, 118 of nose, 1079 parachordal, 141 of pinna of ear, 1120 of Santorini, 1166 sesamoid, 1080 thyroid, 1163 of trachea, 1177 vomerine, 1080 of Wrisberg, 1166 Cartilagincs alares mitwres, 1080 arytenoideae, 1166 basis, 1166 crista arcuata, 1166 fm>ea oblonga, 1166 triangularis, 1166 processus muscularis, 1166 voealis, 1166 corniculatae, 1166 cuneiformes, 1166 laryngis, 1163 nasi, 1079 Cartilaginous ear capsules, 141 Cartilago alaris major, 1079 cru^ laterale, 1070 mediate, 1079 auriculae, 1120 costalis, 165 cricoidea, 1165 epiglottica, 1167 nasi lateralis, 1079 septi nasi, 1080 thyreoidea, 1163 triticea, 1168 1460 INDEX Cartilago tubae auditivae, 1128 lamina lateralis, 1128 medialis, 1128 ■vomeronasalis, 1080 Caruncula lacrimalis, 1115 sublingualis, 1201, 1226 Carunculae hymenales, 1418 myrtiformes, 1418 Cauda epididymidis, 1378 equina, 823, 845 helicis, 1120 pancreatis, 1339 Caudate lobe of liver, 1324 nucleus, 937, 946 Caudatum, 854, 937, 946 Cavernous groove, 91 nerves, 1077 plexus of, 1066 sinuses, 724 Cavitas glenoi'dalis, 176 Cavity or Cavities, cotyloid, 213 glenoid, 176 of heart, 553 of mouth, 138 nasal, 138 of pelvis, 216 pulp, 1212 sigmoid, of radius, 192 of ulna, 187 of thorax, 157 tjTiipanic, 1125 Cavum ariiculare, 294 \genu], 336 conchae, 1120 dentis, 1209 epidurale, 843 laryngis, 1169 mediastinale posterius, 1183 nasi, 138, 1081 regio olfactoria, 1082 respiratoria, 1082 oris, 1199 proprium, 1201 pharyngis, 1229 pleurae, 1181 septi pellucidi, 913, 945 subarachnoideale, 845, 969 thoracis, 154, 157 tympani, 1125 paries carotica, 1127 jugularis, 1125 labyrinthica, 1126 mastoidea, 1126 tegmentalis, 1125 irfen', 1408 Cecal arteries, 664, 1300 fold, 1267 Cecum, 1296 arteries of, 664, 1300 interior of, 1298 lymphatics of, 1300 miicous membrane of, 1300 veins of, 1300 Cell or Cells, acid, 1276 air, mastoid, 1127 basket, 892 centro-acinar, of Langerhans, 1340 of Claudius, 1147 commissural, of cord, 841 of Deiters, 1146 enamel, 1214 ependymal, 818 ethmoidal, 79, 97, 98, 141 ganglion, 807 of Golgi, 952 gustatory, 1149 hair, 1143 ' outer, 1146 of Hensen, 1147 interstitial, 1399 islets, interalveolar, 1340 of lateral ventricles, 936 lutein, 1400 of Martinotti, 952, 953 Cell or Cells, mastoid, S3 nerve, arboriform, 80S bipolar, 808, 1102 of cerebral cortex, 952 ciliated ependymal, 806 germinal, 806 gUa, 818 Golgi, 808 multipolar, 808 of spinal cord, 832 stellate, 808 unipolar, 808 oxyntic, 1276 parenchymatous, 1437 parietal, 1276 polymorphous, 952 Purkinjean, 892 pyramidal, 952 splenic, 1445 Cellulae eihmoidales, 97 mastoideae, 83, 1123 Cementum of teeth, 1212 Centripetal nerve fiber, 810 Centro-acinar cells of Langer- hans, 1340 Centrum semiovale, 932 lendineum, [diaphragma], 419 Cephalic fixture of brain, 855 index of skull, 146 vein, 730 accessory, 731 Ceratohyals, 154 Cerebellar artery, anterior in- ferior, 622 posterior inferior, 621 superior, 622 hemispheres, S85 tract of spinal cord, 838 veins, 720 Cerebello-olivary fibers, 873 Cerebellospinal tract of cord, 839 Cerebellum, 884 anlage of, 855 "bird's nest" of, 888 cortex of, microscopic appear- ance of, 892 fibers of, 891 fissures of, 885 flocculus of, 888 peduncles of, 888 folia of, 884 frenulum of, 891 furrowed band of, 888 gray masses of, 888 lingula of, 886 lobes of, 885 nuclei of, 888 peduncles of, 889 peduncular sulcus of, 885 postramus of, 888 preramus of, 888 proton of, 855 ramus of, 888 vermis of, 885 weight of, 883 worm of, 885 Cerebral artery, anterior, 614 middle, 616 posterior, 622 cortex, 932 nerve cells of, 952 fibres of, 952 cranium, bones of, 70 fibre systems, summarj^ of, 954 fissures, 915 gyres, 915 hemispheres. 912 configuration of, 914 gray masses in, 946 hemorrhage, arterv of, 617 lobes, 916 veins, 719 Cerebrospinal fluid, 845, 970 tract, ventral, 840 Cerebrum, 912 Cerumen, 1123 Cervical arteries, 629, 630 cardiac nerve, 1007 curve of vertebral column, 66 enlargement of spinal cord, 823 fascia, applied anatomy of, 384 flexure of brain, 855 ganglion, 1066, 1069 lymph nodes, 777, 779 nerves, di\'ision of, 1016 nucleus of spinal cord, 833 pleura, 1183 plexus of nerves, 1018, 1020 applied anatomy of, 1026 rib, 53, 64 veins, 717, 718 vertebrae, 49 seventh, 53 Cer^^calis ascendens muscle, 412 Cer\icofacial nerve, 996 Cervicouterine artery, 672 Cervicovaginal artery, 672 Cervix uteri, 1405 portio supravaginalis, 1405 vaginalis, 1405 Chassaignac's tubercle, 68 Check ligaments, 1087 Cheeks, 1200 Chemoprosope skull, 146 Chest, 154. See Thorax. Chiasma opticum, 974 Choanae, 138, 1081, 1229 Chondrin, 260 Chondroblasts, 259 Chondroglossus muscle, 392, 393 Chondrosternal ligaments, 286, 287 Chondroxiphoid ligaments, 288 Chorda obliqua, 311 tympani, 877, 882, 997 Chordae tendineae, 558, 561 Willisii, 721 Chorioidea, 1093 Choroid, 1093 applied anatomy of, 1110 artery of, 617, 1099 fissure, 940 nerves of, 1099 plexuses of fourth ventricle, 867 of lateral ventricles, 940 of third ventricle, 940 vein, 720 Chromatophiles, 809 Chyle, 767 Chyliferous vessels, 767 Cilia, 1113, 1159 Ciliary arteries, 613 body, 1094 ganglion, 982 glands, 1162 ligament, 1096 " muscle, 1095 nerves, 981, 982 processes, 1094 Ciliated ependymal nerve cells, 806 Cinerea, 819 Cingulum, 955, 1206 Circle of Willis, 617, 618 Circular sinus, 726 Circulation of blood, 547 fetal, 568 placental, 755, 756 pulmonary, 548 systemic, 548 umbilical, 756 vitelline, 755 Circulus arteriosus, 617 iridis major, 1099 minor, 1099 tonsillaris, 1003 Circumanal glands, 1162 Circumduction, 267 Circumference of pehfis, 215, 217 INDEX 1461 Circumfereniia articularis, 191 Circumferential lamella of bone, 39 Circumflex arteries, 639, 690 iliac vein, 742 nerve, 1030 Circuminsular fissure, 925 CirciiiiipaliHai imastomosis, 696 Cish ni.i l.n^.ilis. 969 c-'nl„li,,ni,'hillnns, 969 L..DU, 77U, 772 interpeduncularis, 970 ponlis, 969 Cisternae subarachnoidales, 969 Clarke's column, 830, 833 Claudius, cells of, 1147 Claustrum, 948, 954 Clam, 863 Clavicle, 169 applied anatomy of, 172 surface form of, 171 Clavicula, 169 Clavicular artery, 638 facet, 157 nerve, 1022 Clavipectoral fascia, 456, 459 Cleavage lines of Langer, 1150 Cleft palate, 151 Clinoid processes, 90, 94, 126 Clitoris, 1418 arteries of, 1420 frenulum of, 1416 nerves of, 1420 prepuce of, 1416 Clival lobes, 886 Clivus, 73, 90 Cloquet, ligament of, 1376, 1379 lymph nodes of, 786 septum crurale of, 504 Club foot, 256 Coaptation, 267 Coccygeal artery, 677 body, 1450 ganglion, 1072 gland, 1450 ligament, 843, 845 nerves, 1019 divisions of, 1051 plexus of, 1062 vertebra, 58 Coccygeus muscle, 453 Coccyx, 61 Cochlea, 1138 bony canal of, 1138, 1140 membranous canal of, 1144 Cochlear nerve nuclei, 881 Coelileariform process, 1127 Coeliac artery, 659 axis, 659 plexus of nerves, 1008, 1073 Coeliolympha, 970 Coelom, 1245 Cohnheim's fields, 356 Colic arteries, 664, 666 impression of liver, 1321 lymph nodes, 791 olexus of nerves, 1076 Co'llar bone, 169 Collateral circulation, definition of, 573 eminence, 938 CoUes, fascia of, 424, 441 fracture, 193 passive motion after, 268 CoUieuli inferiores [corpora quad- rigemini], 894 superiores [corpora, quadrigem- ini], 894 Colliculus nervi opHci, 1101 Collum anatomicum, 178 chirurgicum, 178 costae, 162 dentis, 1204 femoris, 221 Collum mallei, 1131 viandibulae, 118 radii, 191 scapulae, 176 tali, 245 vesicae, 1361 felleae, 1332 Colon, 1303 applied anatomy of, 1306 aseendens, 1303 descende^is, 130.5 hepatic flexure of, 1303 mucous membrane of, 1310 sigmoid flexure of, 1300 sigmoideum, 1306 splenic flexure of, 1303 transversum, 1303 Colostrum corpuscles, 1431 Column of Burdaeh, 827, 835 Clarke's, 830, 833 of Goll, 827, 835 of Sertoli, 1380 of spinal cord, 826 Columna rugarum anterior, 1414 posterior, 1414 vertebralis, 48, 66 Columnae carneae, 558, 561 renales [Bertini], 1350 pars convoluta, 1350 radiata, 1350 Comes nervi iscliiadiei artery, 677 mediana artery, 650 phrenici artery, 632 Comma tract of Schultze, 835 Commissura anterior alba, 840 cinerea [grisea], 830 inferior [Gitddeni], 895 labiorum, 1199 anterior, 1415 posterior, 1415 maxima, 933 palpebrarum lateralis, 1113 medialis, 1113 ventralis alba, 830 Commissural cells of cord, 841 Commissure, anterior, 946 of Gudden, 895 habenular, 906 hippocampal, 944 middle, ?03 posterior, 906 of spinal cord, gray, 830, 831, white, 834 Communicantes hypoglossi ^ nerve, 1023 Communicating artery, anterior, 614, 650 of dorsalis pedis, 700 of peroneal, 702 posterior, 617 of tibia, 703 peroneal nerve, 1059 Complexus muscle, 412 Compressor narium minor mus- cle, 372 urethrae muscle, 448 Concentric corpuscles, 1441 lamella of bone, 39 Concha auriculae, 1120 nasalis inferior, 113 media, 98 superior, 98 Conchae sphenoidales, 91, 95 Conductor sonorus, 866 Condylar foramen, 71, 127, 128, 132 fossa, 132 Condyle, external, 182 internal, 182 Condyles of liones. See Bones. Condyloid joint, 264, 265 process of mandible, 118 ConAylus lateralis femoris, 225 tibiae, 233 Condylus medialis fem.oris, 225 tibiae, 233 occipitalis, 71 Confluence of sinuses, 72, 724 I ( 'niijhu „» .sinuum, 72, 724 ( 'u]i|iil;:i1 ligaments, 271 r„i:j:,,,aln, 215 Conjugate diameter of pelvis, 215 Conjunctiva, 1114 applied anatomy of, 1118 fornices of, 1115 glands of, 1115 nerves of, 1115 Conoid ligament, 298 tulierelo, 169 Constriction lobe of liver, 1326 Constrictions of Ranvier, 811 Constrictor isthmi faueium mus- cle, 391 (note) muscles, 394, 395 urethrae muscle, 448 Contralateral tract cells of cord, 841 Conus arteriosus, 557, 574 elasticus, 1168 medullaris, 823 Cooper, ligament of, 428, 456 Cor, 551 fades diaphragmatica, 552 sternocostalis, 551 margo acutua, 552 obtusus, 552 sulci longitudinales, 553 sulcus coronarius, 553 longitudinalis anterior, 553 posterior, 553 Coracoaeromial ligament, 299 Coracobrachialis muscle, 468 surface form of, 495 Coracoclavicular ligament, 298 Coracohumeral ligament, 302 Coracoid process, 176 Cord, gangliated, 1066 spermatic, 437, 1375 spinal. See Spinal cord. Corium of skin, 1153 stratum papillare, 1153 reticular e, 1154 Cornea, 1090 applied anatorav of, 1109 arteries of, 1092 dissection of, 1092 nerves of, 1092 Corneal corpuscle, 1091 spaces, 1091 Corniculum laryngis, 1166 Cornu ammonis, 929 Cornua coccygea, 62 of coccyx, 62 of lateral ventricles, 936 majora ossei hyoidei, 154 minora ossei hyoidei, 154 sacral, 59 of spinal cord, 830 Cornucommissural tract, g37 Corona ciliaris, 1094 dentis, 1204 glandis, 1388 radiata, 905, 949 Coronal planes of body, 34 suture, 76, 121 Coronary arteries, 578. 660 ligament of knee-joint, 336 plexus of nerves, 1073, 1076 sinus, 555, 708 valve, 555, 708 veins. 709 Coronoid fossa, 182 process of mandible, 118 Corpora albicaniia, 907 Arantii, 561 cavernosa, 1386 bulb of, 1386 clitoridis, 1418 penis, 1386 1462 INDEX Corpora mammillaria, 847 guadrigemina, 894, 897 Corpus adiposum biiccae, 376, 1200 albicans, 1400 Arantii, 559 callosum, 912, 933 development of, 934 genu of, 934 peduncle of, 928 rostrum of, 934 splenium of, 934 tapetuni of, 938 cavernosun;!, artery of, 676 urethrae, 13S6 ciliare, 1094 costae, 163 epididymidis, 1378 femoris, 224 fibulae, 236 geniculatum laterale, 904, 905 hemorrhagicum, 1400 Highmori, 1380 humeri, ISO hypothalamicus, 905 incudis, 1132 linguae, 1217 luteum, 1400 mammae, 1430 mandibulae, 115 maxillare, 101 ■medullare, 888 OS sphenoidale, 90 ossa metacarpalia, 201 metatarsalia, 250 ossei hyoidei, 153 ossi's ischii, 210 pubis, 212 pancreaiis, 1338 phalangii, 204 resiiformc, 864, 889 spongiosum, 1386 sterni, 157 striatum, 946 fe'biae, 234 ulnae, 187 unguis, 1156 Mteri, 1404 fades vesicles, 1404 ventriculi, 1272 vertebrae, 48 vesicae, 1361 felleae, 1332 vitreum, 1105 Corpuscles, articular, 817 bulboid, 817 colostrum, 1431 concentric, 1441 corneal, 1091 genital, 817 of Hassal, 1441 Herbst's, 816 ■ lamellated, 816 Malpighian, 1445 Pacinian, 816 renal, 1350 splenic, 1445 tactile, 816 touch, of Meissner and Wagner, 816 Vater's, 816 Corpuscula bulboidea, 817 lamellosa, 816 nervorum articularia, 817 genitalia, 817 tactus, 816 Corrugator cutis ani muscle, 453 supercilii muscle, 367 Cortex, cerebral. 932 of kidneys, 1349 Corti, canal of, 1145 ganglion of, 1148 Corti, ganglion of, spirale of, 1139 membrane of, 1147 organ of, 1144 rods of, 1145 Cortical arterial system, 619 Corticopontile tract, 900 Corticothalamic fibers, 905 Costae, 161 spuriae, 161 verae, 161 Costal cartilages, 165 pleura, 1183 process, 50 Costoaxillary veins, 732 Costocentral articulations, 285 Costoclavicular ligament, 296 Costocoracoid ligament, 460 membrane, 459 Costomediastinal sinus, 1184 Costophrenic sinus, 1184 Costosternal articulations, 286 Costotransverse articulations, 284 ligaments, 284, 285 foramen, 50 Costovertebral articulations, 282 ligament, 282 Cotyloid cavity, 213 ligament, 325 notch, 213 Cowper's glands, 1396 development of, 1426 Cranial branches of occipital artery, 596 fossa, 138 indices, 146 nerves, 972 periosteum, 364 region, fascia of, 363 muscles of, 362 applied anatomy of, 365 Craniocerebral topography, 962 Craniology, 144 Cranium, articulations of verte- bral column with, 275 bones of, 70 brachycephalic, 146 cerebrate, 70 dolichocephalic, 146 muscles of, 362 membranous, primordial, 141 Cremaster muscle, 430 Cremasteric arteries, 680 fascia, 430, 1374 Crescentic lobes of cerebellum, 886 Crest, ethmoidal, 91 falciform, 85 frontal, 78, 124 of ilium, 210 incisor, 105 of lacrimal bone, 137 nasal, 105, 110^ neural, 805 obturator, 213 occipital, 70, 72, 132 of pubis, 212 supramastoid, 81 temporal, 74 of tibia, 234 turbinated, 102, 104, 110 Cribriform fascia, 506, 508 lamina, 1090 plate of ethmoid, 96 Cricoarytenoid ligaments, 1169 muscles, 1172 Cricoid cartilage, 1165 Cricothyroid artery, 590 membrane, 1165, 1168 muscles, 1172 Cricotracheal ligaments, 1168 Crista anterior corpus fibulae, 237 , tibiae, 234 \basilaris, 1144 T Crista colli costae, 162 conchalis, 102, 110 ethTnoidalis, 104, 110 fenestrae cochleae, 1126 frontalis, 78 iliaca, 210 infratemporalis, 92 interossea, 189 corpus fibulae, 237 radii, 191 tibiae, 234 intertrochanterica, 224 lacrimalis posterior, 107 lateralis corpus fibulae, 237 mallei, 1131 medialis corpus fibidae, 237 nasalis, 105, 110 obturatoria, 213 occipitalis externa, 70 interna, 72 sacralis media, 59 sphenoidalis, 91 spiralis, 1145 supraventricularis, 557 terminalis [His], 758 atrii dextri, 554, 551, 557 transversa, 85 ureihralis, 1370 vesiibidi, 1137 Cristae cutis, 1150 matricis unguis, 1157 sacrales articulares, 59 laterales, 60 Cristi gaUi, 96, 124 Crucial anastomosis, 678, 690 ligaments, 333 ridge, 71 Cruciform ligament, 275 Crura anlhelicis, 1120 cerebri, 847, 895 of diaphragm, 419 of ear, 1120 fornicis, 944 of penis, 1386 Crural arch, 684 canal, 684 cisterna, 969 nerve, 1049 ring, 428, 685 sheath, 683 Crureus muscle, 511 surface form of, 543 Crus clitoridis, 1418 kelicis, 1120 Crusta of midbrain, 900 petrosa, 1212 Cruveilheir, glenoid ligament of, 321 Crypts of Lieberkiihn, 1292 of Morgagni, 1310 of tonsils, 1231 Crystalline lens, 1106 applied anatomy of, 1111 Cuboid bone, 245 articulation of calcaneus with, 347 of scaphoid with, 350 Culrainal lobes, 886 Cuneal fissure, 924 Cuneate columns of spinal cord, 826 Cuneiform bones, articulation of scaphoid with, 349 of foot, 247, 248 of hand, 197 cartilage, 1166 Cupola, 1140 Cupula. 1138, 1140 pleurae, 1183 Curvatura ventriculi major, 1271 minor, 1271 Cusps of mitral valve, 561 Cutaneous nerve, external, 1045 femoral, 1055 from external popliteal, 1059 INDEX 1463 Cutaneous nei-ve, gluteal, 1055 internal, 1032, 1050 lesser, 1034 lateral, 1045 middle, 1050 perforating, 1060 perineal, 1055 postfemoral, 1054 Cuticle of skin, 1151 Cuiicula dentis, 1211 pili. 1161 Cutis vera, 1153 Cuvirr, duct of, S.W, 764 Cijmba conchav, 1120 Cystic artery, 661 duct, 1333 lymph nodes, 790 plexus of nerves, 1076 vein, 754 Dacryon, 137, 146 Dartos of scrotum, 1373 Darwin, tubercle of, 1120 Deciduous t«eth, 1205 Decussaiio pyramidiim, 863, 869 Decussation of lemnisei, 870 of pyramids of medulla ob- longata, 869 Deglutition, muscles of, 397, 399 Deiters' cells, 1146 nucleus, 839 Deltoid impression, 180, 181 ligament, 343 muscle, 462 applied anatomy of, 463 surface form of, 495 tubercle, 169 Demours, membrane of, 1091 Dendraxones, 811 Dendrites, 804, 809 Dense bone, 38 'Dental arteries, 601, 602 canal, anterior, 102 inferior. 117 posterior, 102 follicle, 1214 lamina, 1213 nerves, 984, 989 papilla, 1214 sac, 1214 shelf, 1213 Dentate fascia, 930 gyre, 930 gray substance of, 953 ligament, 846 Dentatofasciolar groove, 930 Denies, 1204 canini, 1206 deddui, 1205 fades labialis, 1205 lingualis, 1205 masticatoria, 1205 incisivi, 1206 molarcs, 1207 permanentes, 1206 premolares, 1207 serotini, 1207 Dentin, intertubular, 1211 of teeth, 1211 Dentinal fibres, 1211 sheaths, 1211 tubules, 1211 Depression, infrasternal. 166 Pacchionian, 74 pterygoid, 118 trigeminal, 84 Depressor alae nasi muscle, 372 anguli oris muscle, 374 labii inferioris muscle, 374 Dermal bones, 142 Dermis, 1153 Descemet, membrane of, 1091 Descendens hvpoglossi nerve, 1014 Descending aorta, 653 colon, 1305 mesocolon, 1264 Detrusor urinee muscle, 1363 Development of alimentary tract, 1245 aortic arches, 761 arteries, 761 atlas, 63 axis, 64 bladder, 1426 blood-vascular system, 755 brain, 850 carpal bones, 206 clavicle, 171 coccyx, 65 common iliac veins, 764 corpus callosum, 934 Cowper's glands, 1426 dorsal aorta, 762 ductus venosus, 764 ethmoid bone, 99 femur, 228 fibula, 238 frontal bone, 80 generative organs, 1420 heart, 755, 760 humerus, 183 hyoid bone, 154 ilium, 214 inferior vena cava, 765 ischium, 214 island of Reil, 917 jugular veins, 764 lacrimal bone, 107 lymphatic vessels, 769 malar bone, 109 mandible, 118 maxilliE, 105 metacarpal bones. 206 metatarsal bones, 254 mouth, 1204 nerve system, 804 tissue, 806 occipital bone, 73 OS innominatum, 214 palate bone, 112 parathyroid glands, 1440 parietal bone, 76 veins, 764 patella, 231 peritoneum, 1245 phalanges of foot, 254 of hand, 207 pharynx, 1234 portal veins, 764 prostate gland, 1426 pubis, 214 radius, 192 ribs, 165 sacrum, 65 salivary glands, 1227 scapula, 176 skeletal muscles, 361 skull, 141 sphenoid bone. 95 spinal cord, 827 sternum, 159 sylvian cleft, 917 tarsal bones, 254 teetli, 1212 temporal bone, 88 tibia, 235 tongue. 1221 tonsil, 1232 turbinated bone, 114 ulna, 190 urethra, 1426 urinary organs, 1420 valves of heart, 760 veins, 763 ventral aorta, 761 vertebrse, 63 Diii-InpiiicMt of vomer, 115 I)i:m..iK,l fissures, 920 l),n,n,i'r niiliqua pclvis niinoHs, 21G transverse pelvis minoris, 215 Diameters of pelvis, 215, 216 Diaphragm, 418 crura of, 419 ligaments of, 419 lymphatic vessels of, 799 openings of, 419, 421 of pelvis, 1240 • Diaphragma, 418 scllae, 967 iirogenitale, 446 Diaphragmatic lymph nodes, 798 pleura, 1183 Diaphysis of bone, 35 Diaplexus, 940 Diarthrosis, 264, 266 Diastole, ventricular, 565 Diaxonic neurones, 810 Dieneephalon, 902 Digastric fossa, 82, 117, 131 muscle, 388 nerve from facial, 998 Digital arteries of foot, 704 of hand, 652 fossa, 223, 1376 veins, dorsal, 728, 739 plantar, 741 Dilator naris muscles, 372 Diploe, 36 veins of, 718 Diploic canals, 718 Discus arlicularis, 280, 296, 298, 312 proligerus, 1400 Disks, articular, 260 interpubic, 294 optic, 1100 Dissection of axilla, 455 of ciliary body, 1093 of cornea, 1092 of costocoracoid membrane, 459 of deep layer of muscles of forearm, 476 of inferior mesenteric artery, 666 of internal oblique muscle, 428 of left auricle of heart, 559 ventricle of heart, 560 of meninges of brain, 964 of muscles of abdomen, 423 of anterior femoral region, 505 humeral region, 467 scapular region, 463 tibiofibular region, 525 of arm, 461 of auricular region, 366 of back, 404, 407, 408, 410, 413 of buccal region, 374 of cranial region, 362 of fibular region, 534 of forearm, 471 of gluteal region, 515, 516 of hand, 486 of infrahyoid region, 386 of internal femoral region, 512 of larynx, 1172 of lingual region, 391 of mandibular region, 374 of orbital region, 368 of palatal region, 397 of palpebral region, 366 of pectoral region, 455 of pharyngeal region, 394 of plantar region, 538, 539 of posterior femoral region, 522 1464 INDEX Dissection of muscles of posterior scapular region, 464 tibiofibular region, 528 of pterygomandibular re- gion, 379 of radial region, 479 of shoulder, 461 of superficial cervical region, 381 of suprahyoid region, 388 of mylohyoid muscle, 390 of pancreas, 1336 of pectoralis muscles, 459 of popliteal space, 691 of rectus abdominis muscle, 433 of right auricle of heart, 555 ventricle of heart, 557 of spinal cord, 842 of superior mesenteric artery, 663 of temporal nmscle, 378 of transversalis muscle, 432 Distobuccal tubercle, 1207 Distolingual tubercle, 1207 Diverticulum ilei, 1288 Meckel's, 1288 Dobies' line, 356 Dolichocephalic cranium, 146 Dolichofacial skull, 146 Dorsal artery of penis, 676, 1463 nerve of penis, 1061 region of foot, fascia of, 537 muscle of, 537 ^ root of spinal cord, S23 veins of penis, 746 Dorsales poUicis arteries, 647 Dorsalis hallucis artery, 700 indicis artery, 647 linguae artery, 591 nasi artery, 613 pedis artery, 698 applied anatomy of, 699 surface marking of, 699 scapulae artery, 639 Dorso-epitrochlearis muscle, 407 Dorsolateral fissure of medulla oblongata, 862 of spinal cord, 825 spinocerebellar tract of cord, 838 Dorsomediales Sakralfeld [Ober- steiner], 836 Dorsomedian fissure of medulla oblongata, 862 Dorsoparamedian fissure of spinal cord, 826 furrow of medulla oblongata, 863 Dorsum ilii, 207 linguae, 1217 nasi, 1079 sellae, 90, 126 Douglas, pouch of, 1256, 1362, 1407 semilunar fold of, 430 Drum of ear, 1124 Duct of Bartholin, 1226 bile, 1333 of Cuvier, 550, 764 cystic, 1333 ejaculatory, 1385 excretory, 1385 galactophorous, 1430 Gartner's, 1401 hepatic, 1332 interlobular, 1226 intralobular, 1226 lactiferous, 1430 lymphatic, right, 773 mammillary, 1430 Miillerian, 1423 nasal, 1117 canal for orifice of, 141 Duct, pancreatic, 1339 parotid, 1200 gland, 1225 pronephric, 1420 of Rivinus, 2261 of Santorini, 1340 seminal, 1383 Stenson's, 1225 of submaxillary gland, 1226 thoracic, 771 thyroglossal, 1219 Wharton's, 1226 Ductless glands, 1435 Ductuli aberrantes, 1381 efferentes testis, 1380 Ductus aberrans inferior, 1381 superior, 1381 arteriosus, 569, 575 cochlearis, 1144 coledochus, 1333 cysticus, 1333 deferens, 1383 stratum externum, 1384 internum, 1384 medium, 1384 tunica adventitia, 1384 mucosa, 1384 niuscularis, 1384 ejaculaforii, 1385 endolymphaticus, 86, 1137, 1141 excretorius, 1385 hepaticus, 1332 lacrimalis inferior, 1116 superior, 1116 lactiferus, 1430 lymphaticus dexter, 773 nasolacrimalis, 1117 pancreaticus [Wirsunoi\, 1339 accessorius, 1339 paraurethralis, 1370 parotideus [Stenonis], 1200, 1225 reuniens [Henseni], 1142 semicirculares, 1142 sublingualis major, 1226 minores, 1226 snhmaxillaris [Whartoni\, 1226 sudoriferus, 1162 thoracic-US, 771 thyroglossus, 1219 -oenosus, 764 Duodenal fossae, 1265 glands, 1289 impression of liver, 1321 Duodenojejunal flexure, 1282, 1285 fossaj, 1265 Duodenomesocolic ligaments, 1265 Duodenopylorio constriction, 1270 Duodenum, 1282 applied anatomy of, 1287 arteries of, 1287 interior of, 1286 lymphatic vessels of, 793, 1287 nerves of, 1287 pars ascendens, 1285 descendens, 1282 horizontalis inferior, 1284 superior, 1282 suspensory muscle of, 1285 Dura of brain, 964 arteries of, 967 nerves of, 968 veins of, 967 m.ater encephali, 964 spinalis, 843 of spinal cord, 843 Dural artery, 596, 597 nerves, 983, 1005, 1011 veins, 719 Duverney, glands of, 1420 E Ear, 1119 antihelix of, 1120 fossa of, 1120 antitragus of, 1120 auditory canal, 1122 meatus, 1122 auricula of, 1119 capsules, cartilaginous, 141 cochlea of, 1138 crura of, 1120 drum of, 1124 external, 1119 helix of, 1119 incus of, 1132 internal, 1136 labyrinth of, 1136 malleus of, 1131 membrana tvnipani, 1128 middle, 1124 modiolus of, 1138 pinna of, 1119 saccule of, 1141 semicircular canals of, bonv. 1137 membranous, 1142 stapes of, 1133 tragus of, 1120 tympanum, 1124 utricle of, 1140 vestibule of, 1136 Ectal arcuate fibres of medulla oblongata, 863 Efferent root of spinal cord, 823 Eighth nerve, 1000 Ejaculatory ducts, 1385 Elastic cartilage, ^61 lamina, 573 tissue, vellow, 261 Elbow, bend of, 641 bones of, 185 joint, anastomosis of arteries around, 644 articulation of, 306 applied anatomy of, 309 surface form of, 309 bursas of, 308 Eleventh nerve, 1009 thoracic vertebra, 55 Elliptical recess, 1137 Embryology, definition of, 33 Eminence, callosal, 939 canine, 101 collateral, 938 frontal, 76 hypothenar, 486 iliopectineal, 210, 213 of Jacobson, 1083 olivary, 90 parietal, 74 thenar, 486 Eminentia abducentis, 866, 994 arcuata, 84 articularis, 81, 131 conchae, 1120 fossae triangularis, 1120 iliopectinea, 210, 213 intercondyloidea, 233 m,edialis, 866 pyramidalis. 1127 teres, 866, 994 Emissaria, 727 Emissarium condyloideum, 727 mastoideum, 727 occipitale, 727 parietale, 727 Emmissary speech tract, 957 veins, 727 Enamel cells, 1214 jeUy, 1214 of teeth, 1210 Enarthrosis, 264, 265, 266 Encephalocele, 149 Encephalon, 846 INDEX 1465 End-bulbs of Krause, 813, 817 Endocardial cushions, 758 Endocardium, 562 Endognathion, 106 Endolympli, 1140 Endomysium, 355 Endoneurium, 812 Endoskeleton, 35 Endosteum of bone, 39 Endothelium camerae anlerioris, 1092 Ensiform appendix, 159 Entocinerea, 829 Eosinophiles, 40 Epactal bones, 145 Eparterial branch bronchus, 1177 Ependymal cells, 818 EpicarcHum, 549, 565 Epicondylus lateralis, 182, 226 medians, 182, 226 Epicranial aponeurosis, 363 Epidermis, 1151 siratuTTi corneum, 1151 germinativum [Malphigii] , 1152 Epididymis, 1378 Epidural space, 843 Epigastric artery, deep, 680 applied anatomy of, 681 superficial, 689 superior, 633 vein, 742 Epiglottis, 1167 Epdmysium. 355 Epineurium, 812 Epiotic portion of temporal bone, 88 Epiphyseal cartilage, 44 recess, 906 Epiphyses of bone, 35 Epiphysis, 906 Epipteric bone, 145 Episternal centres, 160 Epistropheus, 52 Episylvian ramus, 917 Epithalamus, 907 Epithelium corneae, 1091 germinal, 1399 lends, 1108 respiratory, 1195 Epitrochlear lymph nodes, 782 Epitympanic recess, 1125 Eponychium, 1157 Epoophoron, 1401 Erector clitoridis muscle, 446 penis muscle, 444 spinae aponeurosis, 410 muscle, 410 surface form of, 416 Erythroblasts, 40, 755 Ethmoid bone, 96 Ethmoidal arteries, 611 canals, 79, 98 cells, 79, 97, 98, 139 crest, 91 foramen, structures trans- mitted by, 125, 137 infundibulum, 99 notch, 79 process, 114 spine, 90, 12.5 Eustachian cushion, 1229 tube, 1127 canal for, 1127 valve, 555 Excavatio papillae nerni optici, 1101 reclouterina [Douolasi], 1256, 1414 rectovesicalis, 1255, 1362 vesicouterina, 1256, 1407 Excitoglandular neurones, 804 Excitomotor neurones, 804 Excretory apparatus" of liver, 1331 duct, 1385 Exognathion, 106 Exoskeleton, 35 Expression, muscles of, 380 Exsanguinated renal zone of Hyrtl, 665 Extensor brevis digitorum muscle, 537 poUicis muscle, 483 carpi radialis brevior muscle, 479 longior muscle, 479 ulnaris muscle, 482 coccygis muscle, 414 communis digitorum muscle, 480 indicis muscle, 484 longus digitorum muscle, 527 surface form of, 544 pollicis muscle, 484 minimi digiti muscle, 481 ossis metacarpi pollicis muscle, 482 proprius hallucis muscle, 527 surface form of, 544 Extracranial lymphatics, 774 Extravertebral veins, 737 Extremitas acromialis, 171 sternalis, 171 Extrinsic ligaments of larynx, 1167 muscles of tongue, 393 Eye, 1086 appendages of, 1112 aqueous humor of, 1105 choroid, 1093 ciliary body, 1094 cornea of, 1090 crystalline lens of, 1106 globe of, arteries of, 1108 lymphatics of, 1109 nerves of, 1 109 veins of, 1109 iris, 1096 refracting media of, 1105 retina of, 1100 sclera of, 1090 suspensory ligament of, 1087 tunics of, 1089 vitreous body of, 1105 EyebaU, 1086 fascia of, 371 Eyebrows, 1112 Eyelashes, 1113 Eyelids, 1112 applied anatomy of, 1118 canthi of, 1113 structure of, 1113 surface form of, 1117 F Face, bones of, 69, 99 exterior of, veins of, 710 lymph nodes of, 777 Ij^mphatic vessels of, 777 muscles of, 362 surface form of, 380 Facet, acromial, of clavicle, 171 articular, of clavicle, 171 costal, 171 Facial artery, 592 applied anatomy of, 595 transverse, 598 nerve, 994 applied anatomy of, 999 nucleus, 882 suture, transverse, 121 vein, 710 applied anatomy of, 711 common, 710 deep, 712 Facial vein, transverse, 712 Fades anterior, 101 corpus fibulae, 237 lateralis, 181 medialis, 181 articularis acromialis, 171 anterior, 52 calcanei anterior, 242, 245 media, 242, 245 posterior, 239, 245 carpea, 192 cuboidea, 243 fibularis, 233 inferior, 51, 235 malleoli, 238 navicularis, 245 patellae, 230 posterior, 52 sternalis, 171 superior, 52, 233 tuberculi costae, 162 auricularis, 60, 210 cerebralis, 74, 78, 79, 92 convexa cerebri, 914 costalis, 172 diaphragmatica cordis, 552 dorsalis, 59, 172, 189 corpus radii, 191 frontalis, 76 infralemporalis, 101 lateralis corpus fibulae, 237 radii, 191 tibiae, 234 lunata, 213 malaris, 107 malleolaris lateralis, 245 medialis, 245 maxillaris. 111 medialis, 189 cerebri, 914 corpus fibulae, 237 tibiae, 234 nasalis, 102, 109, 110 orbitalis, 79, 102, 108 palatina, 109 parielalis, 74 patellaris, 225 pelvina, 58 posterior, 181 corpus fibulae, 237 tibiae, 234 sternocostalis cordis, 551 temporalis, 107 ureihralis, 1388 volaris, 189 corpus radii, 191 Falciform crest, 85 ligament, 1320, 1324 margin of Bruns, 508 process of fascia lata, 508 of sacrosciatic ligament, 291 Falcula, 967 Fallopian tube, 1401 ampulla of, 1401 applied anatomy of, 1402 arteries of, 1402 fimbria of, 1401 infundibulum of, 1401 isthmus of, 1401 lymphatic vessels of, 797, 1402 nerves of, 1402 pa^dliou of, 1401 structure of, 1402 veins of, 1402 False pelvis, 215 suture, 264 Falx cerebelli, 967 cerebri, 914, 966 Fascia or Fascise, 355, 360 of abdomen, 424, 428 anal, 446, 450 antebrachial, 471 aponeurotic, 361 of arm, 461, 467 14G6 INDEX Paseia or Fascise, axillary, 456, 633 of back, 404 bicipital, 469, 730 brachial, 467 buccopharyngeal, 377, 394 of Camper, 424 cervical, 382, 383 clavipectoral, 459 of CoUes, 425, 441 covering quadratus lumborum, 439 of cranial region, 363 cremasteric, 430, 1374 cribriform, 506, 508 deep, 361 dentate, 930 endopelvina, 450 of eyeball, 371 of foot, 536 dorsal region, 537 of forearm, 471 of hand, 486 of hip, 515 iliac, 592 infraspinatus, 464 infundibuliform, 436, 1374 intercolumnar, 427, 1374 intercostal, 417 ischiorectal, 446 of leg, 525 of lower extremity, 501 lumbar, 409 masseteric, 377 of neck, 380 nuchse, 406 obturator, 448 orbital, 371 palmar, 488 parotid, 377 pectoral, 456 pelvic, 448 of pelvic outlet, 440 plantar, 537 pretracheal, 384 prevertebral, 384 propria, 1374 of pyriformis, 448 rectovesical, 1361 renal, 1348 of Scarpa, 424 of shoulder, 461 Sibson's, 1183 spermatic, 427, 437, 1374 subscapular, 463 superficial, 360 supraspinatus, 464 temporal, 378 of thigh, 506 of thoracic region, 455, 456 of thorax, 416 triangular, 425, 428 of trunk, 403 of upper extremity, 454 Fascia or Fasciae, antibrachii, 471 axillaris, 456, 633 brachii, 467 buccopharyngea, 377, 394 bulbi [Tenoni], 1086 colli, 382 coracoclavicularis, 459 cremasterica, 430, 1374 cribrosa, 506 cruris, 503 diaphragmaiis urogenitalis in- ferior, 446 superior, 449 dorsalis pedis, 537 iliaca, 502 inferior diaphragmaiis pelvis, 454 infraspinata, 464 lata, 506 parotideomasseterica, 377 ■praeoertebralis, 384 Fascia or Fasciae, subscapularis, 463 supraspinata, 464 temporalis, 378 transversalis, 436 Fasciculus albicantiothalami, 905 anterolateralis superficialis [Gowersi], 838 * atrioventricularis, 564 cerebellospinalis, 838 cerebrospinalis anterior, 839. lateralis, 838 cunealus [Burdachi\, 835 gracilis [Golli], 835 intermedins of Lowenthal and Bechterew, 839 lateralis proprius, 839 longitudinalis inferior, 955 superior, 955 marginalis, 835 pedunculomammillaris, 907 perpendicular, 955 rectus, 955 retroflexus, 898, 906 ihalamomammillaris, 905, 907 uncinafus, 955 Fasciola cinerea, 930 Fat collagen, 42 »> Fauces, isthmus of, 1203 pillars of, 1203 Female breast, 1428 reproductive organs, 1397 urethra, 1370 Femoral arches, 427, 436 artery, 683 applied anatomy of, 687 deep, 689 surface marking of, 687 canal, 503, 684 fossa, 1315 hernia, 1317 ligament, 508 nerves, cutaneous, 1055 region, anterior, muscles of, 505 applied anatomy of, 512 internal, muscles of, 512 applied anatomy of, 515 posterior, muscles of, 522 ring, 428, 685 sheath, 503, 683 spur, 227 vein, 742 Femur, 221 applied anatomy of, 229 condyles of, 225 distal extremity of, 225 linea aspera, 224 quadrati, 224 popliteal surface of, 224 proximal extremity of, 221 ridges of, 224 shaft of, 224 spiral line of, 224 surface form of, 228 trochanters of, 222 trochlea of, 225 tubercle of, 224 tuberosities of, 226 Fenestra cochleae, 1126 ovalis, 1126, 1137 rotunda, 85, 1126, 1140 vestibuli, 85, 1126, 1137 Fenestrated membrane of Henle, 573 Fetal circulation, 570 left superior vena cava, 550 lungs, 1194 Fetus, hypogastric artery in, 670 pelvis in, 219 vascular system in, peculi- arities of, 568 Fibrae arcuatae, 1091 externae, 863, 864 Fibrae arcuatae internae, 864 cerebello-olivares, 873 intercrurales, 427 lentis, 1107 Fibres, arcuate, 873 of medulla oblongata, 863 of auricles of heart. 562 cerebello-olivary, 873 of cerebellum, 891 corticothalamic, 905 dentinal, 1211 frontothalamic, 950 intercolumnar, of external abdominal ring, 427 muscle, cardiac, 355 plain, 355 unstriped, 355 nerve, centripetal, 810 of cerebral cortex, 952 glia, 818 of spinal cord, 832, 834 olivocerebellar, 873 osteogenetic, 42 Purkinje's, 357, 565 Remak's, 812 striatothalamic, 950 thalamocortical, 905 thalamofrontal, 950 thalamostriate, 950 tracts of midbrain, 900 in pars dorsalis pontis, 876 in tegmentum of midbrain, 898^ of ventricles of heart, 563 Fibrillae, 356 peripheral, 816 terminal, 816 Fibrocartilages, 259, 260 articular, 260 circumferential, 261 connecting, 261 intervertebral, 269 semilunar, 334, 335 Fibrocartilagines interoerlebrales, 269 Fibroelastic tissue, subendothe- lial, 573 Fibrous pericardium, 548 sheaths of flexor tendons, 539 Fibula, 236 applied anatomy of, 239 nutrient artery of, 702 canal of, 237 foramen of, 237 surface form of, 238 Fibular artery, 698 region, muscles of, 534 Fifth lumbar vertebra, 57 - nerve, 978 ventricle, 934, 945 Fila olfactoria, 927 radicularia, 1013 Filaments, temporomalar, 109 Filtration angle, 1105 Filum durae spinalis, 843, 845 externuTn, 825 internum, 825 terminale, 825 Fimbria, 929, 930, 943 ovarica, 1401 tubae, 1401 First nerve, 973 thoracic vertebra, 54 Fissura antitragohelicina, 1 120 calcarina, 919 cerebri lateralis [Sylvii], 916 collateralis, 924 ectorhinalis, 924 inflexa, 920 longitudinalis cerebri, 847, 914 mediana anterior [medullae ob- longatae], 861 [medullae spinalis] , 825 , ' T [medulla oblongata] , INDEX 1467 Fii^snm urripilaUs, 91S url.,l.:hs ,„hi;,.i; 134 p„r:M„n,.,l:,l, 1123 IP I, r,,.,!,,!,... 122 p,lruii/„ii"",ir„ laiaseri], 1126 I,(,>lii,iiKili>, '.f2i rliiiii.':i, :ar, SI,h,„.,„rr,i„l„IU, 122 »;./,.„. .,„/,.;n-/. 122 <™„.s,,,.s» r,/t/»-i, 847 iymjiiinninn^ituidea, 87 vestibuli, 1137, 1140 Fissure or Fissures, amygdaline, 924 antitragohelicina, 1120 auricular, 131 basisylvian, 917 of Bichat, 940 calcarine, 919 central, 918 of cerebellum, 885 cerebral, 915 choroid, 940 cireuminsular, 917, 925 collateral, 924 cuneal, 924 diagonal, 920 of frontal lobe, 919 Glaserian, 88, 1126 inflected, 920 interlobar, 916 intermedial, 923 ' intraprecuneal, 924 of liver, 1322 of lungs, 1190 medifrontal, 919 meditemporal, 924 of medulla oblongata, 861 occipital, 918, 924 olfactory, 920 orbital, 93 orbitofrontal, 919 paracentral, 920 paramesal, 919 parietal, 923 petrosphenoidal, 122 petrotympanic, 88, 1126 postcalcarine, 919 postcentral, 923 postinsular, 925 postrhinal, 925 precentral, 919 ■ precuneal, 923 preinsula, 925 pterygomaxillary, 134 radiate, 920 rhinica, 925 of Rolando, 918 rostral, 920 of Santorini, 1122 sphenoidal, 93, 126, 134 sphenomaxillary, 109, 134, 137 of spinal cord, 825 sternal, 161 subcentral, 923 subfrontal, 919 subrostral, 920 subtemporal, 924 supercentral, 919 superfrontal, 919 sylvian, 916 of temporal lobe, 924 of tragus of car, 1121 transinsular, 925 transorbital, 921 transparietal, 923 transprecentral, 920 transtemporal, 924 tympanomastoid, 87 Fixation muscles, 359 Flat bones, 36 Flechsig, nucleus semilunaris of, 905 oval bundle of, 836 Flexor accessorius muscle, 539 Flexor brevis digitorum muscle, 538 surface form of, 544 haUucis muscle, 541 minimi digiti muscle, foot, 541 hand, 494 poUicis muscle, 490, 492 (note) carpi radialis muscle, 473 surface form of, 496 ulnaris muscle, 474 surface form of, 496 longus digitorum muscle, 533 hallucis muscle, 532 poUicis muscle, 476 profundus digitorum muscle, 476 sublimis digitorum muscle, 475 surface form of, 496 tendons, fibrous sheaths, of, 539 at wrist, synovial mem- branes of, 486 Flexura coli dextra, 1303 sinistra, 1303 duodenojejunalis, 1285 Flexures of brain tube, 855 of colon, 1303 hepatic, 1296, 1303 sigmoid, 1296, 1303 Floating ribs, 161 Floccular fossa, 86, 128 Flocculi secundarii, 888 Flocculus of cerebellum, 888 peduncles of, 888 Flood's ligament, 302 Floor of fourth ventricle of brain, 865 Flumina pilorum, 1159 Folia, 884 linguae, 1217 Folium vermis, 886 Follicles, agminated, 1292 solitary, 1292 Folliculus pili, 1159 Fontana, spaces of, 1092, 1097 Fontanelles, 143 anterior, 76, 142 bregmatie, 143 lateral, 144 posterior, 76, 143 Foot, arch of, longitudinal, 254 transverse, 255 arteries of, 699, 703 bones of, 239 applied anatomy of, 256 surface form of, 255 club, 256 construction of, as a whole, 254 fascia of, 536 flat, 255 muscles of, 536 phalanges of, 252 articulations of, 354 veins of, 739, 741 Foramen, apical, 1212 caroticum externum, 86 internum, 84 carotid, 84, 86 cecum, 7S, 96. 124, 862, 1217 condylar, 71, 127. 12S, 132 costot^ans^'er^e, 50 ethmoidal. 137 of Husclike, 89 incisor, 105 infraorbital, 101, 136 intervertebral, 49 jugular, 71, 131 of Key and Retzius, 845, 969 of Langer, 783 of Luschka, 867, 969 of Majendie, 845, 867, 969 Foramen, malar, 107, 136 of mandible, 117 mastoid, 82, 128, 133 mental, 116, 136 of Monro, 936 nasal, 99 nutrient, of clavicle, 170 of fibula, 237 of metacarpal bones, 201 of radius, 191 . of tibia, 234 of ulna, 189 obturator, 213 olfactory, 138, 139 optic, 90, 94, 126 palatine, 121 parietal, 74 pterygospinous, 383 sacral, 59 sacrosciatic, great, 211, 292 lesser, 211, 292 of Scarpa, 105, 128 sphenopalatine, 112, 134, 138, 140 spinal, 49 of Stenson, 105, 128 sternal, 159, 161 stylomastoid, 87, 131 supracondyloid, 181 (note) supraorbital, 135 supratrochlear, 182 temporomalar, 109 thyroid, 213 transverse, 50 vertebral, 49 vertebrarterial, 50 Vesalii, 92, 127 of Win.slow, 1259 Foramen apicis dentis, 1212 caecum linguae [Morgagnii\, 1217 cecum, 78, 96, 124, 862, 1217 diaphragmatis sellae, 967 epiploicum, 1245, 1258 ethmoidale anterius, 79 posterius, 79 infraorhitale, 101 ischiadicum majus, 211, 292 minus, 211, 292 jugulare, 127 lacerum, 127 anterius, 93, 126 medium., 127, 131 pOsteriv^, 71, 73, 127 magnum, 71, 127, 131 mandihulare, 117 mastoideum., 82 mentale, 116 obturalum, 213 occipitale magnum, 71 opticum, 90 ovale, 92, 127, 131, 557, 759 parietale, 74 rotundum, 92, 127, 134 singulare, 85, 1148 sphenopalatinum, 112 spinosum, 92, 127, 131 stylomastoideuni, 87 transversarium, 50 venae cavae, 421 verlehrnU, 49 zygomnlii-iilrmpnrak; 108 Fornmuin ,,h,nlu,-;,i. 102 intern rlrhr.il in. Is, 49 sacraliii anicriosa, 59 posteriosa, 60 venarum minimarum [Thebesii], 555 Forearm, bones of, 185 fascia of, 471 muscles of. 471 Forebrain, 902 development of, 852 structure of, 902 1468 INDEX Forebrain, thalami of, 902 Foregut, 1247 Formalio reticularis, 872, 897 alba, 872 grisea, 872 Fornices conjunctivae, 1115 Fornicolumns, 954 Fornix, 913, 942 body of, 942 periphericus, 959 pharyngis, 1230 pillars of, 943, 944 Fossa of acetabulum, 213 antecubital, 641 of antihelix of ear, 1120 canine, 101, 136 condylar, 131 coronoid, 182 cranial, 138 digastric, 82, 117, 131 digital, 223, 1376 duodenal, 1265 duodenojejunal, 1266 femoral, 1315 floccular, 86, 128 glenoid, 87, 137 hyaloidea, 1105 hypophyseos, 90, 909 iliac, 209 ileoappendicular, 1267 ileocecal, 1267 iliocolic, 1266 incisive, 101, 135 incisor, 116 incudis, 1127 infraspinous, 172 inguinal, 1315 intersigmoid, 1267 ischiorectal, 454 jugular, 86, 87 lacrimal, 79 of Landzert, 1266 mesocolic, 1266 nasal, 138, 1081 occipital, 128 olecranon, 182 orbital, 138 palatine, 105, 128 paraduodenal, 1266 pararectal, 1256 paravesical, 1361 pericecal, 1266 pterygoid, 94, 109 radial, 182 retroduodenal, 1266 retroperitoneal, 1265 rhomboidal, 865 of Rosenmiiller, 1230 scaphoid, 94, 130, 1120 sigmoid, 82 of skull, anterior, 123 inferior occipital, 128 middle, 125 posterior, 127 sphenomaxillary, 109, 134 subcecal, 1267 sublingual, 117 submaxillary, 117 subscapular, 172 supraspinous, 172 supratonsUlar, 1231 temporal, 92, 134 of Treitz, 1265 trochanteric, 223 trochlear, 79 vesicalis, 1321 zygomatic, 92, 101, 130, 134 Fossa acetabuli, 213 cdnina, 101 coronoidea, 182 cranii anterior, 123 media, 125 posterior, 127 dinastrica, 117 Fossa ductus venosi, 1323 glandulae lacrimalis, 79 iliaca, 209 infraspinata, 172 infratemporalis, 133 intercondyloidea, 225 anterior, 233 posterior, 233 ischiorectalis, 454 jugularis, 86, 87 longitudinalis sinistra, 1322 mandibularis, 87 mastoidea, 82 navicularis, 1368, 1416 urethrae, 1368 olecrani, 182 ovalis, 508, 557 margo falciformis, 508 ovarii, 1398 pterygopalatina, 134 radialis, 182 rhomboidea, 865 sacci lacrimalis, 107 scaphoidea, 94 subarcuata, 86 subscapularis, 172 supraspinMa, 172 supratonsillaris, 1231 temporalis, 92, 134 triangularis [auriculae], 1120 trochanterica, 223 venae cavae, 1323 umbilicalis, 1321 vesicae felleae, 1321 Fossae frenuli, 1389 Fossulae tonsillares, 1231 Fountain decussation, 900 Fourchette, 1416 Fourth nerve, 977 ventricle of brain, 864 Fovea articularis superior, 51 capitis femoris, 221 capituli radii, 190 centralis, 1100, 1104 costalis inferior, 53 superior, 53 transversalis, 54 dentis, 50 hemieUiptica, 1137 inferior, 866 inguinalis lateralis, 1315 Tnedialis, 1315 supravesicalis, 1315 mediana, 866 pterygoidea, 118 sublingualis, 117 submaxillaris, 117 superior, 866 trigemini, 866 trochlearis, 79 Foveola grannlaris [Pacchioni\, 970 Foveolae gastricae, 1275 granulares [Pacchio7ii\, 74 Frankfort, horizontal line of, 146 Frenulum of cerebellum, 891 clitoridis, 1416 of clitoris, 1416 Giacomini, 930 of ileocecal valve, 1301 labii inferioris, 1200 superioris, 1200 labiorum pudendi, 1416 linguae, 1217 of penis, 1389 praeputii, 1389 valvulae, 895 coli, 1301 Frenum linguae, 1201, 1217 Frontal air sinus, 79 artery, 598, 612 anterior internal, 615 ascending, 617 inferior external, 617 internal, 615 Frontal artery, middle internal, 615 posterior internal, 615 bone, 76 crest, 78, 124 diploic vein, 718 eminence, 76 lobe, 919 fissures of, 919 gyre of, 921 nerve, 980 planes of body, 34 process of malar bone, 108 suture, 121 vein, 710 Frontalis muscle, 363 Frontoethmoidal suture, 122 Frontolacrimal suture, 122 Frontomalar suture, 121 Frontomaxillary suture, 122 Frontoparietal operculum, 917 suture, 121 Frontopontile tract, 900, 950,. 957 Frontosphenoidal suture, 121 Frontothalamic fibers, 950 Fundiform ligament of Retzius, 536 Fundus folliculi pili, 1159 glands, 1276 tympani, 1125 uteri, 1404' vesicae, 1361 felleae, 1332 Funicular process, 1379 Funiculi niedullae sjnnalis, 826 Funiculus anterior, 827 cuneaius, 827, 835, 863 gracilis, 827, 835, 863 lateralis, 817, 835, 864 [Rolandi], 872 separans, 866 spermaticus, 437, 1375 Furcula, 1221 Fusiform muscles, 358 G Galactophoeotjs duct, 1430 Galea aponcurotica, 363 Galen, veins of, 720, 943 Gall-bladder, 1332 arteries of, 1334 lymphatic vessels of, 795, 1334 nerves of, 1334 veins of, 1334 Ganglia aberrantia, 1014 coeliaca, 1073 trunci sympathici, 1063 Gangliated cord, 1066 cervicocephalic, 1066 lumbar, 1071 thoracic, 1070 Ganglion, aberrant, 1014 accessory, 1014 of Andersch, 1002 aorticorenal, 1073 of Bochdalek, 984 cardiac, of Wrisberg, 1072 carotid, 1066 cell, 807 cervical, 1066, 1069 ciliary, 982 coccygeal, 1072 of Corti, 1148^ Gasserian, 978 geniculate, 996 inferior, 1002 interpeduncular, 906 jugular, 1002 lenticular, 982 Meckel's, 984 ophthalmic, 982 INDEX 1469 Ganslion, otic, 989 petrous, 1002 phrenic, 1074 of Scarpa, 1000, 1147 semilunar, 978, 1073 of Sonimering, 896 sphenopalatine, 982, 984, 986 spinal, 1016 spiral, 1000, 1148 of Corti, 1139 submaxillary, 990 superior, 1002 of Valentin, 984 vestibular, 1000 Ganylion cardiacum [WrisberOil, 1072 cervicale inferius, 1069 viedium, 1069 supcrius, 1066 ciliarc, 982 radix brevis ganglii ciliaris, 982 longa ganglii ciliaris, 981, 982 sympathetica ganglii cilia- ris, 982 coccijgcum impar, 1063, 1072 gcnicuH, 996 habenulae, 906 Jugulare, 1005 itiesentericuin superius, 1076 nodosum, 880, 1005 oticum, 989 ramus anastomoticus cum n. auriculotemporali, 990 pcirosum, 880 phrenicum, 1074 semilunare [Gasseri], 978 sphenopalatinum, 984 ratni nasales posterioris in- feriores, 986 superiores, 986 spirale, 1148 cochleae, 1139 splanchnicimi, 1071 submaxillare, 990 rami coniynunicanies cum. n. linguali, 990 submaxillares, 990 superius, 880 vestibulare, 1147 Ganglionic arteries, 614, 617, 618 Gartner's duct, 1401 Gasserian ganglion, 978 Gaster, 1270 Gastric artery, 660 crypts, 1275 glands, 1276 impression of liver, 1321 lymph nodes, 790 nerve, 1007 pits, 1275 plexus of nerves, 1076 veins, 753 Gastrocnemius muscle, 528 surface form of, 544 Gastrocolic omentum, 1254, 1261 Gastroduodenal artery, 661 plexus of nerves, 1076 Gastroepiploic arteries, 661 lymph nodes, 790 plexus of nerves, 1076 A'eins, 753 Gastrohepatic omentum, 1254, 1260 Gastrosplenic omentum, 1261 Gelaiinosa centralis, 829, 831 Rolandi, 829, 833 Gemellus inferior muscle, 520 superior muscle, 520 Gcmmules, 810 Generative organs, development of, 1420 Genial tubercles, 117 Geniculate body, external, 905 internal, 895 lateral, 910 ganglion, 996 tract, 950 Geniculum n. facialis, 996 Geniohyoglossus muscle, 391 Geniohyoid muscle, 390 Genital corpuscles, 817 gland, 1423 ridge, 1423 Genitals, external, lymphatic vessels of, 790 Gennari, fiber band of, 953 Genu corporis callosi, 934 facialis internum, 882 Gerlach, valve of, 1299 Germinal centre, 1292 epithelium, 1399 nerve cells, 806 spot, 1400 vesicle, 1400 Gianuzzi, crescents of, 1227 Gimbernat's ligament, 426, 428 Gingivae, 1200 Ginglymus, 264, 265 Girald(5s, organ of, 1384 Glabella, 77, 134, 146 Gladiolus, 159 Glands, apical, 1219 of Bartholin, 1420 buccal, 1200 cardiac, 1278 carotid, 586, 1450 ciliary, 1162 circumanal, 1162 coccygeal, 1450 of conjunctiva, 1115 Cowper's, 1396 ductless, 1435 duodenal, 1289 of Duverney, 1420 fundus, 1276 gastric, 1276 genital, 1423 intestinal, 1292 labial, 1200 lacrimal, 1115 of larynx, 1174 of Lieberkiihn, 1292 of Littr^, 1369 Luschka's, 1450 lymphatic. See Lymph nodes. mammary, 1428 Meibomian, 1114 molar, 1200 of Moll, 1113 of Montgomery, 1429 of Nuhn and Blandin, 1219 oesophageal, 1239 oxyntic, 1276 palatine, 1202 parathyroid, 1439 parotid, 1223 peptic, 1276 prostate, 1391 pyloric, 1278 salivary, 1223 sebaceous, 1113, 1161 serous, 1219 sublingual. 1226 submaxillary, 1225 suburethral, 1420 sudoriferous, 1161 suprarenal, 1447 sweat, 1161 tarsal, 1114 thymus, 1440 thyroid, 1435 of trachea, 1178 trachoma, 1115 of von Ebner, 1219 Glands, vulvovaginal, 1420 Glandula lacrimalis, 1115 inferior, 1116 superior, 1116 parotis, 1223 accessoria, 1224 sublingualis, 1226 submaxillaris, 1225 thyreoidea, 1435 accessoriae, 1436 vestibularis major [BarthoKni\, 1420 Glandulae areolares, 1429 buccales, 1200 bulbourethralis, 1396 ceruminosae, 1123 cervicales uteri, 1410 ciliares [Molh'\, 1113, 1162 circumanales, 1162, 1309 duodenales [Brunneri], 1292 gastricae propriae, 1276 inlestinales [LieberkUhni\, 1292 labialis, 1200 linguales anieriores, 1219 tnolares, 1200 mucosae [Krausei], 1115 olfactoriae, 1085 palatinae, 1202 paraurethrales, 1370 pharyngeae, 1233 praeputii, 1389 pyloricae, 1278 sebaceae, 1113, 1161 sudoriferae, 1161 suprarenaies accessoriae, 1448 fades anterior, 1447 posterior, 1448 suprarenalis, 1447 tar sales [Meibomi\, 1114 tracheales, 1178 Tysonii odoriferae, 1389 urethrales, 1369 uterinae, 1410 vestibulares minores, 1416 Glandular artery, 593 Glans clitoridis, 1419 penis, 1387 Glaserian fissure, 88, 1126 Glenohumeral ligament, .302 Glenoid fossa, 87, 131 ligament, 176, 303 of Cruveilheir, 321 surface of scapula, 176 GHa cells, 818 fibers, 818 Ghding joints, 264 Gliosa centralis, 829 cornualis, 829, 833, 870 Globus pallidus, 948 Glomus carotic.um, 1450 coccygeum, 1450 Glossoepiglottic fold, 1167 Glossopharyngeal nerve, 1001 applied anatomy of, 1003 nucleus, 880 Gluteal aponeurosis, 516 artery, 678 nerves, 1054, 1055 region, muscles of, 515 ridge, 224 veins, 743 Gluteofemoral bursse, 327 Gluteus maximus muscle, 515 bursse of, 516, 517 surface form of, 543 medius muscle, 516 surface form of, 543 Gnathic index of skull, 147 Golgi, cells of, 808, 952 organs of, 817 Goll, column of, 827, 835 Gomphosis, 264 Gonion, 146 Gower's, tract of, 838 Graafian folhcles, 1399 1470 INDEX Gracile column of spinal cord, 826 lobes, 887 Gracilis muscle, 512 bursa of, 513 surface form of, 543 Granulationes arachnoidales [Pac- chioni], 721, 970 Gray commissure of spinal cord, 830 masses of cerebellum, 888 substance of spinal cord, 829 Grooves, auriculoventricular, 553 basilar, 73 of pons, 864 bicipital, 180 carotid, 126 cavernous, 91 dentatofasciolar, 930 infraorbital, 102, 136 interauricular, 553 interventricular, 553 lacrimal, 102, 104, 107, 137, 138 musculospiral, 180 mylohyoidean, 117 nasopalatine, 114 obturator, 211, 213, 214 occipital, 82, 131 oesophageal, 421 optic, 90, 126 peroneal, 246 popliteal, 226 pterygopalatine, 110, 111 pyramido-olivary, 863 sacral, 60 of spinal cord, 825 subclavian, 171 subcostal, 163 ulnar, 182 vertebral, 67 Growth of bone, 42 Guhernaculum testis, 1378 Gudden, infracommissure of, 895 tractus peduncularis transver- sus, 895 Guerin, valve of, 1369 Gullet, 1236 Gums, 1200 Gustatory areas of brain, 960 cells, 1149 hair, 1149 path, 1003 Gyre, angular, 923 callosal, 920, 921 cerebral, 915 dentate, 930 hippocampal, 925 marginal, 923 medifrontal, 921 meditemporal, 924 mesorbital, 920, 922 olfactory, 928 paracentral, '921 paraoccipital, 923 parietal, 923 postcentral, 923 postparietal, 923 precentral, 921 preinsular, 926 subcalcarine, 925 subcallosal, 928 subcollateral, 925 subfrontal, 921 subtemporal, 925 superfrontal, 920, 921 supertemporal, 924 transtemporal, 924 uncinate, 925 Gyri Andreae Retzii, 930 Gyrus ambiens, 928 angularis, 923 breves insulae, 926 centralis anterior, 921 posterior, 923 Gyrus dentatus, 929 epicallosus, 930 fasciolaris, 930 fornicatus, 921 frontalis inferior, 921 medius, 921 superior, 921 fusiformis, 925 hippocampi, 925 lingualis, 925 longus insulae, 915 occipitotemporalis, 925 rectus, 922 semiluTmris, 928 supracallosus, 931 supramarginalis, 923 temporalis inferior, 925 medius, 925 superior, 925 Habenulah commissure, 906 Hairs, 1159 auditory, 1143 bulb, 1159 cells, '1143 outer, 1146 follicle, 1159 fundus of, 1159 gustatory, 1149 papilla, 1159 root of, 1159 sheaths of, 1160 streams, 1159 whirlpools, 1159 Hallucis, etymology of, 525 Hamstring muscles, 522 applied anatomy of, 525 Hamular process, 94, 107, 130 Hamulus, 1140 lacrimalis, 107 laminae spiralis, 1140 ossis hamati, 200 pterygoideus, 94 Hand, arteries of, 647 bones of, 194 lower row, 198 upper row. 196 bursce of, 487 fasciae of, 486 ligaments of, 315 muscles of, 486 phalanges of, 204 articulations of, 321 veins of, plexus of, 729 superficial, 728 Hard palate, 1202 Harelip, 151 Hasner, valve of, 1117 Hassal, corpuscles of, 1441 Haversian canal, 39 lamella of bone, 39 Head, arteries of, 583 lymph nodes of, 774 muscles of, surface form of, 380 veins of, 710 Heart, 551 apex of, 551 applied anatomy of, 565 arteries of, 565 auricles of, fibers of, 562 left, 559 right, 554 base of, 551 beat, myogenic theory of, 566 neurogenic theory of, 566 cavities of, 553 capacity of, 561 component parts of, 553 development of, 755, 760 endocardium', 562 Heart, grooves of, auriculoven- tricular, 553 interauricular, 553 interventricular, 553 infundibulum of, 557 left, 553 lymphatic vessels of, 5C5, 802 margins of, 552 muscular fibers of, 562 myocardium, 562 nerves of, 565 position of, 551 pulmonary, 553 right, 553 rudiments of, 755 size of, 552 surface form of, 567 surfaces of, 551 systemic, 553 valves of, action of, 565 development of, 760 veins of, 565 ventricles of, fibers of, 563 left, 560 right, 557 weight of, 552 Hebenula, 906 Heel bone, 239 Heidenhain, demilunes of, 1227 Helicis major muscle, 1121 minor muscle, 1121 Helicolrema, 1138, 1140 Hehx of ear, 1119 Helweg, olivospinal tract of, 8391 Hemicerebra, 847 Hemiseptum, 934 Hemisphaeria bulbi urethrae, 1387 Hemispheres, cerebral, 912 Hemolymph nodes, 768 Hemorrhoidal artery, inferior, 675 middle, 672 superior, 667 nerve, inferior, 1061 plexus of nerves, 1077 veins, 744, 753 plexus of, 745 Henle, fenestrated memljrane of, 573 layer of nerve fiber of, 1103, 1160 ligament of, 433 loop of, 1351 sheath of, 812 spine of, 81 Hensen, canalis reuniens of, 1142, 1147 cells of, 1147 membrane of, 356 stripe of, 1147 Hepar, 1319 capsula fibrosa [Glissoni], 132S fades inferior, 1321 posterior, 1321 superior, 1320 impressio cardiaca, 1320 colica, 1321 duodenalis, 1321 gastrica, 1321 oesophagea, 1322 pylorica, 1321 renalis, 1321 suprarenalis, 1322 ■margo inferioris, 1322 tunica serosa, 1328 Hepatic artery, 660 duct, 1332 flexure of colon, 1296 lymph nodes, 790 plexus of nerves, 1076 veins, 751 Hepatocolic ligaments, 1260 Hepatoduodenal ligaments, 1260 Hepatogastric ligaments, 1260 Herbst's corpuscles, 816 INDEX 1471 Hernia, 1315 femoral, 1317 inguinal, 1315 Hesselbach, ligament of, 433 triangle of, 437, 1315 Hey, ligament of, 508 Hiatus aorticus diaphragma, 419 canalalis facialis, 84 Fallopii, 84 maxillaris, 102, 103 oesophageiis, 1236 diaphragma, 421 sacralis, 59, 01 semilunaris, 1081 tentorial, 847 Highmore, antrum of, 101, 103 Hilura of kidneys, 1348 of nucleus dentatus, 888 of suprarenal glands, 1448 Hilus alandulae suprarenahs, 1448 lienis, 1444 nuclei dentati, 888 pulmonis, 1189 renalis, 1348 Hindbrain, 861 development of, 855 structure of, 861 Hindgut, 1247 Hinge-joint, 264, 205 Hip bone, 207 fasciEe of, 515 -joint, arteries of, 327 articulations of, 322 applied anatomy of, 329 surface form of, 329 bursEB of, 327 movements of, 328_ muscles of, 326, 515 nerves of, 327 synovial membrane of, 326 Hippocampal commissure, 944 gyre, 925 Hippocampus, 942 gray substance of, 953 Hirci, 1159 His, auriculoventricular bundle of, 564 crista terminalis of, 758 spina vestibuli of, 758 sulcus terminalis of, 1217 Histology, definition of, 33 Homolateral tract cells of cord, 841 Homologies of sexual organs, 1428 Horner's muscle, 367 Horns of spinal cord, 830 Horny layer of skin, 1151 Horseshoe kidney, 1354 Houston's valves, 1310 Howship's foveolEe, 39 Huguier, canal of, 88, 997, 1126 Humeral artery, 638 ligament, 303 lymph nodes, 782 region, muscles of, 467, 470 Humerus, 178 applied anatomy of, 184 development of, 183 head of, 178 neck of, anatomical, 178 surgical, 178 shaft of, 180 surface form of, 184 tuberosities of, 180 Humor aqueus, 1105 vitreus, 1105 Hunter's canal, 511, 515, 685 Huschke, foramen of, 89 Huxley's layer, 1160 Hyaline cartilage, 260 Hyaloid canal, 1106 membrane, 1106 Hydatids of Morgagni, 1402 Hydatids, pedunculated, 1379 sessile, 1378 Hydrenccphalocele, 149 Hymen, 1417 imperforate, 1417 Hyoepiglottic ligaments, 1167 Hyoglossus muscle, 391 Hyoid bone, 153 applied anatomy of, 154 development of, 154 elevators of, 388 surface form of, 154 Hyparterial branch bronchus, 1177 Hypogastric arteries, 570, 669 763 in fetus, 670 impervious, 671 lymph nodes, 787 plexus of nerves, 1077 vein, 743 Hypoglossal nerve, 1010 applied anatomy of, 1012 nucleus, 878 Hypophysis, 909 Hyposylvian ramus, 917 Hypothalamic tegmental sub- stance, 905 Hypothalamus, structure of, 908 Hypothenar eminence, 486 Hyrtl, exsanguinated renal zone of, 665 Ileal artery, 664 lymph nodes, 791 Ileoappendicular fold, 1267 fossa, 1267 Ileocecal arteries, 664 fossa, 1207 junction, 1296 valve, 1301 Ileocolic fold, 1266 fossa, 1266 junction, 1296 lymph nodes, 791 plexus of nerves, 1076 Ileum, 1288 Iliac arteries, common, 668 applied anatomy of, 669 surface marking of, 669 deep circumflex, 682 ' external, 079 applied anatomy of, 680 surface marking of, 680 internal, 069 applied anatomy of, 671 679 surface marking of, 679 superficial circumflex, 689 bursa, subtendinous, 327 fascia, 502 fossa, 209 furrow, 219, 439 lymph nodes, 787, 788 region, muscles of, 502 veins, common, 747 development of, 704 deep circumflex, 742 external, 742 internal, 743 Iliacus muscle, 504 Iliococcygeus muscles, 452 Iliocolic arteries, 004 Iliocostalis muscle, 410 Iliofemoral ligament, 323 Iliolumbar artery, 078 ligament, 290 veins, 748 Iliopectineal bursa, 327 eminence, 210, 213 ligament, 503 hne, 209, 212 Iliopsoas muscle, 504 (note) Iliosacralis muscles, 452 Iliotibial band, 507 applied anatomy of, 508 Iliotrochanteric ligament, 324 Ilium, 207 crest of, 210 curved lines of, 207, 208 spinous processes of, 210 lips of, 210 intermediate space of, 210 Impervious hypogastric artery, 671 Impressio Irigemini, 84, 85 Impression, deltoid, 180, 181 rhomboid, 171 Incisive fossa, 101, 135 papilla, 1202 Incisor canal, 105 crest, 105 foramina, 105 fossa, 116 Incistira acetabuli, 213 cardiaca, 1190 cerebelli posterior, 884 clavicularis, 157 costalis I, 157 //, 159 VII, 159 ethmoidalis, 79 frontalis, 77 interlobaris, 1190 intertragica, 1120 ischiadica, minor, 211 jugularis, 71, 157 lacrimalis, 102 mandibulae, 118 mastoidea, 82 poplitea, 233 radialis, 187 scapiilae, 175 semilunaris, 187 sphenopalatine, 112 supraorbitalis, 77 tentorii, 893 terminalis auris, 1120 thyreoidea superior, 1164 tympanica [Rivini], 1125 ulnaris, 192 umbilicalis, 1322 vertebralis inferior, 49 superior, 49 resicae felleae, 1322, 1323 Incisurae cartilaginis meatus acustici externi [Santorinil, 1122 Incisures of Sohmidt-Lanter- mann, 811 Incus, 1132 crus breve, 1133 longum, 1133 processus lenlicularis, 1133 Indices, cranial, 140 Indusium. 930, 931, 934 Inflected fissures, 920 Infraclavicular lymph nodes, 782, 783 nerve, 1029 Infracommissure of Gudden, 895, 910 Infracostales muscles, 417 Infraglenoid tubercle, 175 Infrahyoid artery, 590 region, muscles of, 380 Infraorbital artery, 002 canal, 102. 136 foramen, 101, 130 groove, 102 nerve, 982 (note), 998 plexus of nerves, 984, 998 Infrapatellar bursa, 336 I pad, 336 \ Infraseapular arteries, 639' I Infraspinatus bursa, 303 fascia, 464 muscle, 465 I Infraspinous fossa, 172 1472 INDEX Infrasternal depression, 166 Infratioehlear nerve, 981 Infundibula of lungs, 1195 of ureters, 1356 Infundibuliform fascia, 436, 437, 1374 Infundibulopelvic ligament, 1407 Infundibulum, 141, 760, 909 ethmoidal, 99 elhmoidale, 99 of Fallopian tube, 1401 of heart, 557 iuher uterinae, 1401 Inguinal canal, 437, 1375 fossae, 1315 hernia, 1315 lymph nodes, 785 Inion, 146 Inlet of pelvis, 215 of thorax, 155 Innervation of intestines, 1313 of stomach, 1280 Innominate artery, 582 veins 733 Inosculation of arteries, 572 Inscriptiones tendineae, 433 Insula, 925 Integument of nose, 1081 of scrotum, 1373 Integumentum commune, 1149 Interalveolar cell islets, 1340 Interauricular groove, 553 septum, 559 Interbronchial lymph nodes, 801, 1179 Intercalatum of midbrain, 897 Intercavernous sinuses, 726 Intercellular lymph spaces, 767 substance of bone, 39 luterchondral ligaments, 288 Interclavicular ligament, 296 Intercolumnar fascia, 427, 1374 fibers of external abdominal . ring, 427 Intercondyloid notch, 225 Intercostal arteries, 655 anterior, 632 applied anatomy of, 657 superior, 633 fascia, 417 lymph nodes, 798 lymphatic vessels, 799 muscles, 417 nerves, 1040 applied anatomy of, 1043 space, 155 veins, 735, 736 Intercostobrachial nerve, 1042 Intercostohumeral nerves, 1042 Intercuneiform articulations, 350 Interdigital veins, 739 Interglobular spaces, 1211 Interlobar fissures, 916 Interlobular duets, 1226 Intermaxillary suture, 135 Intermedial fissures, 923 Intermediate lamella of bone, 39 space of ilium, 210 Intermediolateral tract of Bruce and Campbell, 839 Intermiiscular septum of arm, 467 of thigh, 507, 508 Internasal suture, 135 Interneural articulations, 271 Interossei muscles, foot, 541 hand, 494 surface form of, 497 Interosseous arteries, foot, 699, 700 hand, 647, 650 recurrent artery, 651 veins, 729 Interpalpebral slit, 1112 Interparietal bone, 74 Interparietal suture, 121 Interpeduncular gangUon, 906 nucleus, 898 Interpleural space, 1185 Interpubic disk, 294 Intersigmoid fossa, 1268 Interspinales muscle, 414 Interspinous ligament, 272 Intersternal ligaments, 288 Interstitial cells, 1399 lamella of bone, 39 Intertransversales laterales mus- cle, 414 mediales muscle, 414 Intertransverse ligaments, 272, 293 Intertrochanteric line, 224 Intertubular dentin, 1211 Interventricular grooves, 553 septum, 557, 561 Intervertebral fibrocartilage, 269 foramina, 49 notches, 49 substance, structure of, 270 veins, 738 Intestinal glands, 1292 lymphatic trunks, 772 plexus of nerves, 1076 Intestines, applied anatomy of, 1314 innervations of, 1313 large, 1295 arteries of, 1310 lymphatic vessels of, 794, 1312 nerves of, 1312 veins of, 1312 movements of, 1312 relations of, 1250 small, 1281 applied anatomy of, 1314 arteries of, 1293 lymphatic vessels of, 793, 1295 mucous membrane of, 1289 nerves of, 1295 veins of, 1295 vilU of, 1291 structure of, 1291 surface form of, 1313 Intestinum cecum, 1296 crCLSsum, 1295 ileum, 1288 jejunum, 1288 rectum, 1306 pars analis recti, 1309 tenue, 1281 mesenteriale, 1287 plicae circular es [Kerkri?igi], 1289 tela submucosa, 1289 tunica mucosa, 1289 muscularis, 1289 stratum circulare, 1289 longitudinale, 1289 serosa, 1289 Intra-articular ligament, 283 Intracartilaginous ossification, 42 Intracranial lymphatics, 774 Intraiugular process, 73 Intralobular ducts, 1226 veins, 751 Intramembranous ossification, 42 Intraparietal sulcus of Turner, 922 Intraprecuneal fissure, 924 Intrathyroid cartilage, 1165 Intravertebral veins, 738 Intrinsic ligaments of larynx, 1168 muscles of tongue, 393 Intumescentia cervicalis, 823 ganglioformis, 996 lumbalis, 823 Involuntary muscles, 355, 357 Iris, 1096 applied anatomy of, 1110 arteries of, 1099 epithelium of, pigmented, 1099 muscle fibers of, 1099 nerves of, 1099 stroma of, 1098 structure of, 1098 Irregular bones, 36 Ischiobulbosus muscle, 444 Ischiocapsular ligament, 323 Ischiogluteal bursa, 327 Ischiorectal fascia, 446 fossa, 454 region, muscles of, 453 Ischium, 210 obturator groove of, 211 ramus of, 212 spine of, 211 tuberosity of, 211 Islands of Langerhans, 1340 of Reil, 925 development of, 917 Isthmus aortae, 580 cartilaginis auris, 1121 of Fallopian tube, 1401 of fauces, 1201, 1203 faucium, 1201, 1203 glandulae thyroidea, 1436 gyri hippocampi, 925 pharyngonasalis, 1230 of pharynx, 1230 rhombencephali, 855 tubae audilivae, 1128 uterinae, 1401 Iter chordae, 1126 Ivory of teeth, 1211 Jacob's membrane, 1103 Jacobson, cartilage of, 1080, 1083 eminence of, 1083 nerves of, 1002 Jaw, angle of, 118 lower, bones of, 115 upper, bones of, 100 Jejunum, 1288 Joints. See Articulations. Jugular foramen, 71, 131 fossa, 86 ganglion, 1002 lymph nodes, 778 process, 71, 131 sinus, 713 tubercle, 73 veins, 713 development of, 764 Keekeing, valves of, 1289 Key and Retzius, foramen of, 845, 969 Kidneys, 1343 abnormalities of, 1354 applied anatomy of, 1355 arteries of, 1352 columns of, 1349 convolutions of, 1351 cortex of, 1349 fixation of, 1348 glomerulus of, 1350 hilum of, 1348 horsehsoe, 1349 labyrinth of, 1349 lymphatic vessels of, 796, 1354 medulla of, 1349 minute anatomy of, 1350 nerves of, 1354 parenchyma of, 1349 INDEX 1473 liidncys, permanent, 1425 relations of, 1343 structure of, 1349 substance, 1349 surface form of, 1354 tubules of, 1351 ^'eins of, 1354 Kneecap, 230 Knee-joint, applied anatomy of, 338 arteries of, 337 hursce of, 336 lijiaments of, 331 nio\'enients of, 337 ner\-es of, 337 structiu'es around, 337 surface form of, 338 synovial memlirane of, 336 Krause, end-bulbs of, 813, 817 membrane of, 356 Kiihne, muscle spindles of, 817 Labia majora, 1415 minora, 1416 pudendi, 1416 oris, 1200 Labial artery, 593 coronarv arteries, 594 glands, 1200 nerves, 984 Labium externum cristi iliaca, 210 qUnoidale, 303, 325 inferius, 1200 internum crista iliaca, 210 lalerale [linea aspera], 224 mediate [linea aspero\, 224 superius, 1200 tympanicutn, 1144 vestibulare, 1144 Labyrinth of ear, 1136 membranous, 1140 structure of, 1142 osseous, 1136 of ethmoid, 97 of kidneys, 1349 LabyrinthuJi ethmoidalis, 97 membranaceus, 1140 osseus, 1136 Lacertus fibrosus, 469 Lachrymal. See Lacrimal. Lacrimal apparatus, 1115 artery, 610 bone, 106 crests of, 137 lesser, 107 canal, 104, 107, 1116 ampulla of, 1116 fossa, 79 gland, 1115 applied anatomy of, 11 IS groove, 102, 104, 137, 138 nerve, 980 notch, 102 papilla, 1113, 1116 process, 114 sac, 1116 applied anatomy of, 1119 sulcus, 107 tubercle, 104 Lacteals. 767 Lactiferous duct, 1430 Lacuna of bone, 39, 259 magna, 1369 musculorum, 503 vasorum. 503 Lacunae, 39 laterales, 721 urethrales, 1369 Lacus lacrimalis, 1113, 1115 Lagena, 1 147 Lambda, 76, 123, 146 Lambdoid suture, 73, 76, 121 j 93 Lamella of bone, 39 Lamellated corpu.scles, 816 Lamina basalis, 1093 of brain, 885 cartilaginis cricoideae, 1165 choriocapillaris, 1093 cribriform, 1090 cribrosa, 85 sclerae, 1090 elaslica anterior, 1091 posterior, 1091 fibrocartilaginea interpubica, 294 fusca, 1090 horizontal, of ethmoid, 96 lateralis processus pterygoidei, 94 Tnedialis processus pterygoidei, 94 medullaris interna, 905 papyracea, 98 periclaustral, 948 perpendicularis, 97 reticular, 1147 reticularis, 1147 rostralis, 913 spiralis ossea, 1138, 1140, 1144 secundaria, 1137, 1140 suprachoroidea, 1093, terminalis, 847, 908, 909 vasculosa, 1093 Landzert, fossa of, 1266 Langer, cleavage lines of, 1150 foramen of, 783 Langerhans. centro-acinar cells of, 1340 islands of, 1340 Lanugo, 1159 Laryngeal artery, inferior, 629 superior, 590 nerve, 1078 inferior, 1007 recurrent, 1007 superior, 1006 sinus, 1170 veins, 735 Larynx, 1163 arteries of, 1174 cartilages of, 1163 glands of, 1174 interior of, 1169 ligaments of, 1167 movements of, 1169 mucous membrane of, 1174 muscles of, 1172 nerves of, 1174 veins of, 1174 ventricles of, 1170 Lateralis nasi artery, 594 Latissimus dorsi muscle, 406 surface form of, 416 Leg, bones of, 230 fasciae of, 525 muscles of, 525 applied anatomy of, 535 Lemnisci, decussation of, 870 Lemniscus lateralis, 876 medialis, 876 Lens crystallina, 1106 crystalHne, 1106 ligament of, suspensory, 1106 Lenticula, 854, 947 Lenticular ganglion, 982 nucleiis, 947 Lenticulostriate arteries, 617 Leptoprosope skull, 146 Lesser's triangle, 591, 1012 Leukocytes, 40 Levator anguli oris muscle, 373 scapulae muscle, 407 surface form of, 416 ani muscle, 450 costarum muscle, 417 glandulae thyroideae muscle, 1436 Levator labii superioris alaoque nasi muscle, 372 muscle, 373 menti mu.scle, 374 palati muscle, 397 palpebrae superioris muscle, 369 prostatae muscle, 452 Lieberkiihn, crypts of, 1292 glands of, 1292 Lien, 1442 exiremitas inferior, 1444 superior, 1444 fades diaphrdgmatica, 1444 gastrica, 1444 renalis, 1444 margo anterior, 1444 posterior, 1444 tunica albuginea, 1445 serosa, 1444 Ligamenta accessoria plantaria, 354 alaria, 277, 336 basium ossis metacarp. dorsa- Ha, 319 interossea, 319 volaria, 319 metatars. dorsalia, 352 interossea, 352 plantaria, 352 brevia, 476 carpometacarpeae dorsalis, SIS volaria, 318 collatcralia, 321 articulationes digitorum pe- dis, 354 metatarsophalangeae, 354 columnae vertebralis, 268 cruciata genu, 333 cuneometatarsea interossea, 352 intercarpea dorsalia, 315, 316, 317 interossea, 315, 316 volaria, 315, 316 intercostalia externa, 288 interna, 288 intercruralia, 271 intercuneiformia dorsalia, 350 interossea, 3.50 plantaria, 350 interspinalia, 272 intertransversariu, 272 Inbyrinthi canaliculorum, 1142 lata uteri, 1256 longa, 476 navicnlaricuneiformia dorsalia, 350 plantaria, 350 puboprostatica, 1362, 1393 pylori, 1274 sacroiliaca anteriora, 290 subflava, 271 tarsometatarsea dorsalia, 352 plantaria, 352 Ligamenti auricularia [Valsal- vae], 1121 Ligamentous action of muscles, 267 Ligaments, 259, 261 accessory. 275 acromioclavicular, 297 annular, anterior, 486, 536 external, 537 internal, 536 posterior, 487 of radius, 310 arcuate, 419 astragaloscaphoid, 349 atlanto-axial, 274 of axilla, suspensory, 456 of Bertin, 323 of Bigelow, 324 of bladder, 1361 true, 450 broad, 11S3, 1407 1474 INDEX Ligaments, calcaneo-astragaloid, 347 calcaneocuboid, 348 calcaneoscaphoid, 348 cat>sular. See Individual joints, of carpus, 315 check, 1087 chondrosternal, 286, 287 chondroxiphoid, 288 ciliary, 1096 of Cloquet, 1376, 1379 coccygeal, 843, 845 common, anterior, 268 posterior, 269 conjugal, 271 conoid, 298 of Cooper, 428 coracoaeromial, 299 coracoclavicular, 298 coracohumeral, 302 coronary, of knee-joint, 336 eostocla-sdcular, 296 costocoracoid, 460 costotransverse, 284, 285 costovertebral, 282 cotyloid, 325 cricoarytenoid , 1 1 69 cricotracheal, 1168 crucial, 333 cruciform, 275 deltoid, 343 dentate, 846 of diaphragm, 419 duodenomesocolic, 1266 falciform, 1320, 1324 femoral, 50S of fingers, 319 Flood's, 302 fundiform, of Retzius, 536 Gimbernat's, 426, 428 glenohumeral, 302 ^ glenoid, 176, 303 of Cruveilheir, 321 of hand, 315 of Henle. 433 hepatocolic, 1260 hepatoduodenal, 1260 hepatogastric, 1260 of Hesselbach, 433 of Hey, 508 of hip, 322 hyoepiglottic, 1167, 1168 iliofemoral, 323 iliolumbar, 290 iliopectineal, 503 iliotrochanteric, 324 of incus, 1133 infundibulopeh-ic, 1407 interchondral, 288 intercla"\'icular, 296 interosseous. See Individual joints, interspinous, 272 iutersternal, 288, 289 intertransverse, 272, 293 intra-articular, 283 ischiocapsular, 323 of knee-joint, 331 lateral. See Individual joints, of liver, 1324 lumbosacral, 289, 1345 malleus, 1133 oblique, 311 obturator, 295 occipito-atlantal, 275, 276 oecipito-axial, 277 odontoid, 277, 278 orbicular, 310 of patella, 331 phrenocolic, 1305 of pinna of ear, 1121 Poupart's, 426, 427 pterygomandibular, 376, 383 pterygospinous, 383 Ligaments, pubic, 294 pubofemoral, 323 puboprostatic, 450 pyloric, 1274 radioulnar, 312 rhomboid, 296 round, 437 sacrococcygeal, 293 sacroiliac, 290 sacrosciatic, 291, 292 sacrouterine, 1407 of scapula, 299, 300, 301 Schlemm's, 302 spinal, 268 spinoglenoid, 301 of stapes, 1133 stellate, 282 sternoclavicular, 296 sternocostal, 286 stylohyoid, 389 stylomandibular, 280, 382 superficial transverse, of fin- gers, 489 suprascapular, .300 supraspinous, 272 suspensory, of Ijladder, 1362 of Cooper, 456 of eve, 1087 of lens, 1106 of penis, 424 of Treitz, 1285 sutural, 121, 259 syno^dal, 262 tarsal, 366 thjToarytenoid, 1170 thyroepiglottic, 1167, 1169 thyrohyoid, 1167 tibiotarsal, 343 transverse','of acetabulum, 325, 326 of atlas, 274 humeral, 303 of knee-joint, 336 metatarsal, 353 pelvic, 446 trapezoid, 298 triangular, deep layer of, 449 in female, 446 in male, 446 true, of bladder, 450 umbilical, 1361 uterosacral, 1407 of uterus, 1406 of vertebral bodies, 268 volar, 315 of Winslow, 332 of Wrisberg, 336 of wTist-joint, 314 Y, 324 of Zinn, 370 LigameTUum acromioclamculare, 297 annulare baseos stapedius, 1133 radii, 310 apicis dentis, 278 arcuatum externum, 439 pubis, 294 arteriosum, 570, 575 auriculare anterius, 1121 posterius, 1121 superiu^, 1121 bifurcatum, 348 calcaneocuhoideum dorsale, 348 plantare, 348 calcaneofibulare, 344 calcaneonavicular'e plantare, 348 calcaneotibiale, 343 capituli costae interarticulare, 283 radiatum, 282 capitulorum- ossis metacarpa- liuTTi transversum, 320 carpi dorsale, 487 fasciculi transversi, 489 transversum, 486 Ligamentum collaterale carpi radi- ate, 314 ulnare, 314 fihulare, 333 radiate, 308 tibiale, 332 ulnare, 307 colli costae, 284 conoideum, 298 coracoacromiale, 299 coracoclavicularc, 298 coracohuinerale, 302 coronarium hepatis, 1325 costoclamculare, 296 costotransDersarium anterius, 284 posterius, 285 costoxiphoideum anterius, 288 cricoaryteTioideum posterius, 1168 cricothyrqideum medium, 1168 cricotracheale, 1168 cruciatum anterius, 333 atlantis, 275 cruris, 536 posterius, 333 cuboideona\aculare dorsale, 350 plantare, 350 cuneocuboideum dorsale, 351 interosseum, 350, 351 plantare, 351 deltoideum, 343 denticulatum, 821, S45, 846, 1013 epididytnidis inferior, 1378 superior, 1378 falciforme hepatis, 1253, 1324 gastrolienale, 1444 hepatocolicum, 1260 hepatodv^denale, 1260 hepatogastricum, 1260 hyoepigloiticum, 1168 kyotkyreoideum laterale, 1167 medium, 1167 iliofemorale, 323 iliolunibale, 290 incudis posterius, 1133 superius, 1133 inguinale, 427 rejlexum, 428 inter clavicular e, 296 iiiterfoveolare, 433 ischiocapsulare, 323 laciniatum, 536 lacunare, 428 laterale externum breve seu posticum, 333 latum pulmonis, 1184 uteri, 1407 longitudinale anterius, 268 posterius, 269 mallei anterius, 1133 laterale, 1153 sup^ius, 1153 malleoli lateralis anterius, 341 posteriu^s, 342 mucosum, 336 nuchae, 272, 406 ossiculorum auditus, 1133 palpebrale mediate, 367, 1114 patellae, 331 pectinatum iridis, 1092, 1096 phrenicocolicum, 1264 pisohamatum, 316 pisometacarpeum, 316 plantare Ionium, 348 popliteum obliquum, 332 pubicum superius, 294 pubocapsulare, 323 pulmonale, 1184 radiocarpeum dorsale, 314 volare, 314 sacrococcygeum anterius, 293 posterius, 293 INDEX 1475 Ligamentum sacrococcygeum pos- tcrius profundum, 293 supcrficiale, 293 sacroiliacum posterius, 290 breve, 290 longum, 290 sacrosjnnosufn, 292 sacrotuberosum, 291 splienomanflibidare, 279 spirale cochleae, 1144 sternoclavipularc, 296 sternocosiale inlerariiculare, 287 radiatum, 286 siernopericardica, 548 siylohyoideus, 389 stylomandibulare, 280 supraspincde, 272 suspensorium penis, 13SS talocalcaneum anterius, Si? interosseum, 347 laterale, 347 mediale, 347 posterius, 347 talofibulare anterius, 344 posterius, 344 ialotibiale anterius, 343 posterius, 343 temporomandibulare, 279 teres, 324, 752, 764 femoris, 324 hepatis, 1325 Mteri, 437, 1408 thyreoepiglotticum , 1169 tibionaviculare, 343 transversum acetabuli, 326 atlantis, 274 cruris, 536 genu, 336 pelvis, 446 scapulae inferius, 301 superius, 300 trapezoideum, 298 triangulare dextruni, 1325 sinistrum, 1325 unibilicale laterale, 671, 1362 medium, 1361 vaginale, 321 jieraa ca»ae sinistrae, 550 venosum, 752, 1325 Light stimuli, path of, 1104 Limbic lobe, 929 lAmhus fossae ovalis [Vieussenii\, 557 laminae spiralis, 1144 tnembranae iympanae, 1130 Limen insulae, 925 nasi, 1082 Line, iliopectineal, 209 intertrochanteric, 224 spiral, of femur, 224 iinea aibo, 426, 435, 439 arcuata, 209, 212 aspera, 224 glutaea anterior, 207 inferior, 208 posterior, 207 intercondyloidea, 226 intermedia crista iliaca, 210 intertrochanterica, 224 mylohyoidea, 117 nuchae inferior, 70 superior, 70 suprema, 70 obliqua, 117, 1164 pectineal 224 poplitea, 234 quadrati, 224 semicircularis, 430, 435 semilunaris, 439 of abdomen, 436 splendens, 845 temporalis inferior, 74 superior, 74 transversae, 439 m'sus, 1088 Lineae musculares, 172 semilunares, 436 transversae, 58 Lingua, 1217 fades inferior, 1217 margo lateralis, 1217 tunica mucosa, 1217 Lingual arteries, 590, 591, 601, 1219 bone, 153 lymph nodes, 776 muscles, 393 nerves, 988 from glossopharyngeal, 1003 region, muscles of, 391 septum, 393 tonsil, 1219 veins, 715 Lingula, 91, 117, 867, 886 cerehelli, SS6 mandibulae, 117 pulmonic, 1190 sphrnoidalis, 91 Lips, 1200 Liquor cerebrospinalis, 970 folliculi, 1400 Littr(5, glands of, 1369 Liver, 1319 abnormalities of, 1326 accessory, 1326 applied anatomy of, 1335 arteries of, 1326 colic impression of, 1321 constriction lobe of, 1326 duodenal impression of, 1321 excretory apparatus of, 1331 fissures of, 1322 gastric impression of, 1321 Egaments of, 1324 ligamentum venosum of, 764 lobes of, 1323 lobules of, 1328 lymphatic vessels of, 794, 1331 movability of, 1325 nerves of, 1331 omental tuberosity of, 1321 renal impression of, 1321 Riedel's lobe of, 1326 structure of, 1328 support of, 1325 suprarenal impression of, 1322 surface relations of, 1334 surfaces of, 1320 veins of, 1327 Lobe or Lobes, biventral, 887 cacuminal, 886 central, 886 of cerebellum, 885 cerebral, 915 clival, 886 crescentic, 886 culminal, 886 frontal, 919 gracile, 887 limbic, 929 of lungs, 1190 nodular, 888 occipital, 924 olfactory, 926 parietal, 922 pyramidal, 887 quadrate, 886 semilunar, 887 temporal, 924 tuberal, 887 uvular, 887 Lobi m,ammae, 1430 Lobules of liver, 1328 of lungs, 1195 Lobuli hepatis, 1328 mamm.ae, 1430 testis, 1380 Lobulus auriculae, 1120 biventer cerebelU, 887 centralis cerebclli, 886 Lobulus paracentralis, 921 parieialis inferior, 923 superior, 923 semilunaris inferior {cerebelli\, 887 Lobus caudatus [Spigelii], 1324 frontalis, 921 hepatis dexter, 1324 sinister, 1324 occipitalis, 924 olfactorius, 926 parietalis, 922 temporalis, 924 Lockwood, tendon of, 370 Locus caeruleus, 866 Longissimus dorsi muscle, 412 Longitudinal fasciculus, 955 - vertebral veins, 738 zones of brain, 855 Longus colli muscle, 401 Lowenthal and Bechterew, fas- ciculus intermedins of, fS39 tract of cord, 840 Lower, tubercle of, 557 Ludwig, angle of, 157, 166 Lumbar aponeurosis, 409 arteries, 662 curve of vertebral column, 66 enlargement of spinal cord, 823 fascia, 409 lymph nodes, 788 lymphatic trunks, 772 nerves, 1019 divisions of, 1018, 1044 plexus of nerves, 1044 applied anatomy of, 1062 portion of gangliated cord, 1071 puncture, 68 veins, 749 ascending, 736, 749 vertebrae, 56 fifth, 57 Lumbosacral ligament. 289. 1345 plexus of nerves, 1044 Lumbricales muscle, foot, 540 hand, 493 Lungs, 1188 alveoli of, 1195 applied anatomy of, 1197 arteries of, 1195 borders of, 1190 broad Ugamcnt of, 1183 color of, 1194 fetal, 1194 fis.sures of, 1190 infundibula of, 1195 lobes of, 1190 lobules of, 1195 lymphatic vessels of, 802, 1196 nerves of, 1196 parenchvma of, 1195 root of, 1193 saccules of, 1195 septa of, 1195 structure of, 1194 substance of, 1194 surface form of, 1196 surfaces of, 1189 veins of, 1195 weight of, 1194 Lunula, 1157 of nails, 1157 Lunulae valvularum sem iluna- rium, 559, 561 Luschka, foramen of, 867, 969 gland of, 1450 Lutein cells, 1400 Luys, body of, 905 centrum medium of, 905 Lymph, 767 nodes, antecubital, 781 aortic, 788 appendicular, 791 auricular, posterior, 774 1476 INDEX Lymph nodes, axillary, 782 bronchiomediastinal, 801 buccal, 776 cervical, 777, 779 of Cloquet, 786 colic, 791 cystic, 790 definition of, 768 diaphragmatic, 798 epitrochlear, 782 of face, 774, 776 gastric, 790 gastroepiploic, 790 of head, 774 hepatic, 790 humeral, 782 hypogastric, 787 ileal, 791 ileocolic, 791 ihac, 787, 788 infraclavicular, 782, 783 inguinal, 785, 786 interbronchial, 801, 1179 intercostal, 798 jugular, 778 Ungual, 776 of lower extremity, 784 lumbar, 788 mammary, 798 mandibular, 776 mastoid, 774 maxillary, 776 mediastinal, SCO mesenteric, 790, 791 mesocolic, 791 middle, of Stahr, 778 of neck, 774, 777 obturator, 787 , occipital, 774 pancreaticoduodenale, 793 paracardial, 790 parietal, 787, 798 parotid, 774 pectoral, 782 peritracheobronehial, 1179 popliteal, 784 preaortic, 789 preauricular, 774 prelaryngeal, 779 pretracheal, 779 retroaortic, 789 retropharyngeal, 776 retropyloric, 790 of RosenniiiUer, 786 sacral, 788 splenic, 790 subclavian, 783 submaxillary, 778 submental, 779 subparotid, 776 subpyloric, 790 subscapular, 783 substernomastoid, 779 supracla'vicular, 779 suprahj'oid, 779 supratrochlear, 782 of thorax, 798 tibial, 784 of trachea, 1179 tracheobronchial, 800 of upper extremitj^ 781, 782 visceral, 790, 800 sinuses, 768 spaces, 767 periscleral, 1086 perivascular, 707 suprascleral, 1086 -vascular system, 547 Lymphatic or Lymphatics, 767 applied anatomy of, 770 duct, right, 773 extracranial, 774 glands. See Lymph nodes, intracranial, 774 origin of, 769 Lymphatic or Ljonphatics, pas- sages of eyeball, 1109 pharyngeal ring, 1234 sacs, primary, 770 structure of, 769 terminations of, 769 trunks, intestinal, 772 lumbar, 772 vessels of abdomen, 787, 789, 790 of abdominal viscera, 792 afferent, 768 of anus, 794 of arteries, 574 of auditory meatus, exter- nal, 777 of bladder, 796 of bone, 41 of cecum, 1300 of common bile-duct, 796 development of, 769 of diaphragm, 799 of duodenum, 793 efferent, 768 of external genitals, 790 of face, 774, 777 of Fallopian tube, 797 of gall-bladder, 795 of head, 774 of heart, 802 intercostal, 799 of intestine, large, 794 small, 793 of kidney, 796 of labia majora, 1415 of liver, 794 of lower extremity, 786, 787 of lungs, 802 ■ of mammary gland, 798 of membrana tympani, 1131 of mouth, 777 of muscles of neck, 780 of nasal fossae, 777 of neck, 774, 780 of nose, 1081 of oesophagus, 802 of ovaries, 797 of pancreas, 796 of parotid gland, 1225 of pelvic viscera, 792 of pelvis, 789, 790 of penis, 1390 j of perineum, 790 of pinna, 777 of pleura, 802 of prostate, 796 of rectum, 794 of reproductive organs, 796 of scalp, 776 of seminal vesicles, 797 of skin, 1156 of spermatic cord, 1377 of spleen, 796, 1446 of stomach, 792, 1279 of submaxillary gland, 1226 of suprarenal glands, 796, 1449 of testes, 796 of thoracic viscera, 802 wall, 798 of thorax, 798 of thymus gland, 802 of thyroid gland, 1438 of tongue, 777 of tonsil, 1231 of upper extremity, 783, 784 of ureter, 796 of urethra, 796 of urinary organs, 796 of uterus, 797 of vagina, 797 of vas deferens, 797 of vermiform appendix, 1300 Lymphoglandulae, 768 auriculares anteriores, 775 Lymphoglandulae auriculares pos- ieriores, 774 axillares, 782 bronchiales, 801, 1179 cervicales profundae, 779 inferiores, 779 superficiales, 777 superiores, 779 coeliacae, 795 faciales profundae, 776 gastricae inferiores,, 790 superiores, 790 hepaticae, 790 hypogastricae, 787 inguinales, 785 intercostales, 798 linguales, 776 lumbales, 788 mediastinales anteriores, 800 posteriores, 800 mesentericae, 790 occipitales, 774 pancreaticolienales, 790 parotideae, 774 pectorales, 782 popliteae, 784 suhinguinales, 785 profundae, 786 suhniaxillares, 778 tibialis anterior, 784 tracheales, 801, 1179 M McBdrney's point, 1298, 1313 Macewen's suprameatal triangle, 81, 151 Macula acustica sacculi, 1141 lutea, 1100, 1104 utriculi, 1141 Majendie, foramen of, 845, 867, 969 Malar arteries, 610 bone, 107 canal, 108 foramen, 107, 136 nerve, 998 of superior maxillary, 983 process of maxillae, 101, 104 Male breast, 1433 reproductive organs, 1371 urethra, 1366 Malleolar arteries, 698, 703 folds, 1130 sulcus, 238 Malleolus, external, 237 internal, 235 lateralis, 237 Tnedialis, 235 Malleus, 1131 ligaments of, 1133 processus anterior [Foliii, 1132 lateralis, 1132 Malpighian body, 1350 capsule, 1350 corpuscles, 1445 layer of skin, 1152 tuft, 1350 Mamma virilis, 1433 Mammae accessoridae muliebris, 1430 Mammary artery, external, 638 internal, 631 gland, 1428 applied anatomy of, 1432 areola of, 1429 arteries of, 1432 lymphatic vessels of, 798, 1432 nerves of, 1432 prolongation of, 1430 variations in, 1429 veins of, 1432 lymph nodes, internal, 798 INDEX 1477 Mammary veins, 734 Mammillary duct, 1430 Mandible, 115 changes produced in, by age, 119 condyle of, 118 condyloid process of, 118 coronoid process of, 118 depressors of, 388 olilique line of, 117 perpendicular portions of, 117 side views of, at different periods of life, 119 symphysis of, 115 MntuHbuln, 115 Mandiliular lymph nodes, 776 nerve, 987 from facial, 998 region, muscles of, 374 Manubrium mallei, 1131 stemi, 157 Marclii's tract of cord, 839 Margin of orbit, 101 Marginal cusp of mitral valve, 561 gyre, 923 tract of spinal cord, 836 veins, 709 MarQO acutus, 552 axillaris, 175 ciliaris, 1096 dorsalis corpus radii, 191 ulnae, 187 frontalis, 76 infraorhitalis, 101, 137 loTubdoideus, 73 lateralis, 180 ma^toideus, 73 mcdialis, 180 corpus tibiae, 234 nasi, 1079 obiiisus, 552 occipitalis, 76 pupillaris, 1097 sagittalis, 76 squamosus, 76 supraorbitalis, 77, 137 vertebralis, 175 volaris corpus radii, 191 ulnae, 187 Marrow, bone, 40 cells, 40 Marshall, oblique vein of, 550, 709 vestigial fold of, 550 Martinotti, cells of, 952, 963 Massae laterales, 51 Masseter muscle, 377 surface form of, 380 Masseteric artery, 601 fascia, 377 nerve, 987 Mastoid air cells, 1127 antrum, 83 • artery, 596 bone, sigmoid fossa of, 82 cells, 83 foramen, 82, 128, 133 lymph nodes, 774 portion of temporal bone, 82 process of temporal bone, 82 Masto-occipital suture, 73, 122 Mastoparietal suture, 122 Matrix of nails, 1157 unguis, 1157 Maxilla;, 100 alveolar process of, 104 malar process of, 104 nasal process of, 104 palatal process of, 104 Maxillary artery, 59S atrium, orifice of, 141 hiatus, 102 IjTiiph nodes, 776 Maxillary nerve, 982, 9S7 process of palate bone. 111 of turbinated bone, 114 region, muscles of, 373 sinus, 101, 103 tuljerosity, 102 vein, 712 Meatus acuslicus externus, 1122 carlilagineus, 1122 osseous, 1122 pars externa, 1122 interna, 1122 media, 1122 interjius, 85 auditory, 1122 external, 88, 133 internal, 85, 128 nasi inferior, 1082 medius, 1082 superior, 1082 of nose, 98, 110 atrium of, 141 urinarius, 1369 Meckel's cartilage, 118 diverticulum, 1289 ganglion, 984 Median nerves, 1034 veins, 730 Mediastinal arteries, 632, 654 lymph nodes, 800 pleura, 1183 plexus, subpleural, 632 Mediastinum, 1185 applied anatomy of, 1188 testis [corpus Highmoi'i], 1380 Medicommissure, 903 Medicornu, 938 Medidural artery, 600 Medifrontal fissures, 919 gyre, 921 Mediotarsal articulation, 349 Medipedunculi, 890 Meditemporal fissure, 924 gyre, 924 Medulla of kidneys, 1349 oblongata, 861 areas of, 862 fissures of, 861 funiculus of, 863 olive of, 863 pyramids of, 863, 869 restis of, 864 tuberculum cinereum of, 864 veins of, 721 ossium rubra, 40 spinalis, 820 Medullary arteries, 619 body, 888 canal of bone, 35 cavity, formation of, 45 pyramids, 1349 rays, 1349 sheath of Schwann, 811 velum, inferior, 884, 891 posterior, 888 superior, 884, 891 Medullated axis-cyhnder proc- esses, 811 Megacephalic skiUls, 145 Meibomian glands, ill4 Meissner and Wagner, touch corpuscles of, 816 Meissner's plexus of nerves, 1279 Membrana adamantina, 12l4 atlantooccipitalis anterior, 275 posterior, 276 basilaris, 1138, 1143 cricothyroidea, 1165 flaccida of Shrapnell, 1130 hyaloidea, 1105 hyothyreoidea, 1167 interossea antebrachii, 312 cruris, 341 mucosa nasi, 1083 nictitans, lil5 Membrana obluratoria, 517 stapedis, 1133 pupillaris, 1100 sacciformis, 318 slerni, 286 tectoria, 277, 1147 tympani, 87, 1122, 1128 artei'ies of, 1131 lymphatics of, 1131 nerves of, 1131 secundaria, 1126, 1140 stratum circulare, 1131 mucos'um, 1130 radiatum, 1131 veiris of, 1131 vestibularis [Reissneri], 1144 Membrane, basilar, 1143 Bowman's, 1091 of brain, 964 of Bruch, 1093 of Corti, 1147 costocoracoid, 459 cricothyroid, 1165, 1168 of Demours, 1091 of Descemet, 1091 of Henle, fenestrated, 573 of Hensen, 356 hyaloid, 1106 intercostal, 417 of KoUiker, 1147 of Krause, 356 Nasmyth's, 1211 otolith, 1143 peridental, 1212 of Reissner, 1144 of Ruysch, 1093 Schneiderian, 1083 serous, of diaphragm, 421 of spinal cord, 842 - sutural, 263 synovial, 259, 261 thyrohyoid, 1164, 1167 tympanic, 1128 vitelhne, 1400 Membranous canal of cochlea, 1144 labyrinth of ear, 1140 primordial cranium, 141 semicircular canals, 1142 Meningeal artery, 596, 597 anterior, 609 middle, 600 posterior, 597, 621 small, 600 nerve, 983 from hypoglossal, 1011 from internal maxillary, 987 from vagus, 1005 veins, 719 Meninges of brain, 964 encephali, 964 Meningocele, 149 Meningorachidian veins, 843 Menisci, 334 articidares, 260 Meniscofemoral joint, 338 Meniscotibial joint, 338 Meniscus lateralis, 335 niedialis, 334 Mental artery, 601 foramen li6, 136 point of skull, 146 process, 116, 135 tubercles, ll6 Mesal plane of skull, 146 Mesencephalic root nuclei, 884 Mesencephalon, 893 Mesenteric arteries, 663, 666 lymph nodes, 790 peritoneum, 1249 plexus of nerves, 1076 veins, 753 Mesentericomesocolic fold, 1266 Mesentericoparietal fold, 1267 1478 INDEX Mesenteriolum processus vermi- formis, 1265 Mesenterium, 1263 Mesentery, 1263 of vermiform appendix, 1265 Masoappendix, 1265, 1299 Mesocele, 897 Mesocephalic skull, 145 Mesooolic band, 1310 fossae, 1266 lymph nodes, 791 Mesocolon, ascending, 1264 descending, 1264 sigmoid, 1264 transverse, 1264 Mesocolon ascendens, 1264 descendens, 1264 sigmoideum, 1264 transversum, 1264 Mesogastrium, 1249 Mesognathion, 106 Mesometrium, 1407 Meson planes of body, 34 Mesonephros, 1420 Mesorbital gyre, 920, 922 Mesorchium, 1423 Mesosigmoid, 1306 Mesosteruum, 157 Mesovariuin, 139S, 1407, 1423 Metacarpal bones, 201 of index finger, 202 of little finger, 203 of middle finger, 203 nutrient canal of, 201 foramen of, 201 peculiar characters of, 202 of ring finger, 203 of thumb, 202 spaces, 202 Metacarpophalangeal articula- tions, 320 surface form of, 321 Metacarpus, 201 Metanephros, 1425 Metapore, 845, 867, 969 Metasternum, 157 Metatarsal artery; 699 articulation, synovial mem- brane in, 353 ; bones, 249 articulations of, 252, 352 common characters of, 250 fifth, 252 first, 250 fourth, 251 peculiar characters of, 250 second, 251 third, 251 ligament, transverse, 353 veins, 741 Metatarsophalangeal articula- tions, 353 Metopic suture, 121 Meynert, fasciculus retroflexus of, 906 Microcephalic skulls, 145 Midbrain, 893 aqueduct of, S97 central aqueduct gray, 897 crusta of, 900 development of, 855 fiber tracts of, 899, 900 gray masses in, summary of, 900 intercalatum of, 897 pes of, 900 structure of, 894, 896 substantia nigra of, 897 tegmentum of, 89^6 Midgut, 1247 Milk teeth, 1205 Mitral orifice, 560 valve, 561 Mixed articulation, 264 Moderator band, 558 Modiolus, 1138, 1139 Molar glands, 1200 teeth, 1207 Moll, glands of, 1113 Monakow's tract of cord, 839 Monaxonic neurones, 810 Monro, foramen of, 936 Mons Veneris, 1415 Montgomery, glands of, 1429 Monticulus cercbelli, 885 Morgagni, crypts of, 1310 hydatids of, 1402 sinus of, 395 valves of, 1310 Moss fibers of Ramon y Cajal, 893 Motor area of brain, 959 end plates, 816 neurones, 804 root of spinal cord, 823 Mouth, 1199 angle of, 1199 aperture of, 1199 applied anatomy of, 1204 cavity of, 138, 1201 development of, 1204 floor of, 1201 lymphatic vessels of, 777 structure of, 1201 vestibule of, 1200 Movable articulations, 264 Mucous membrane of bladder, 1364 of cecum, 1310 of cheeks, 1200 of colon, 1310 of larynx, 1174 of nasal fossae, 1083 of nose, 1081 of small intestine, 1289 of soft palate, 1203 of stomach, 1275 of tongue, 1217 of trachea, 1178 of tympanum, 1134 of uterus, 1410 of vagina, 1414 Miiller, muscle of, 371 nerve fibers of, 1104 ring muscle of, 1096 Miillerian duct, 1423 Multifidus spinae muscle, 413 Multipenniforni muscle, 358 Multipolar nerve cells, 808 Muscle or Muscles, 355 of abdomen, anterio-lateral, 423 posterior, 439 abductor hallucis, 538 indicis, 494 minimi digiti, foot, 539 hand, 493 polUcis, 489 longus, 485 accelerator urinae, 443 of acromial region, 462 adductor brevis, 514 longus, 513 magnus, 514 minimus, 514 obliquus hallucis, 541 poUicis, 492 transversus hallucis, 541 poUicis, 492 anconeus, 482 anomalous, 361 antitragicus, 1121 applied anatomy of, 359 of arm, 461, 467 arrectores pilorum, 1161 of articulations of elbow-joint 308 of shoulder-joint, 303 aryepiglottic, 1173 ■ arytenoideus, 1172 Muscle or Muscles, attachment of, 357 attoUens aurem, 366 attrahans aurem, 366 of auricular region, 365 azygos uvulae, 398 of back, 403 biceps, 469 femoris, 522 flexor cubiti, 469 biventer cervices, 413 biventral, 358 brachialis anticus, 469 brachioradialis, 479 of buccal region, 374 buccinator, 375 cardiac, 355 cervicalis ascendens, 412 chondroglossus, 393 ciliary, 1095 coccygeus, 453 complexus, 412 compressor bulbi, 444 hemisphaerium bulbi, 444 naris, 372 narium minor. 372 urethrae, 448 constrictor, inferior, 394 middle, 395 radicis penis, 444 superior, 395 urethrae, 448 coracobrachialis, 468 ccrrugator cutis ani, 453 supercilii, 367 of cranial region, 362 of cranium, 362 cremaster, 430 cricoarytenoid, 1172 cricothyroid, 1172 crureus, 511 of deglutition, 397 deltoid, 462 depressor alae nasi, 372 anguU oris, 374 labii inferioris, 374 detrusor urinae, 1363 development of, 361 of diaphragm, 418 digastric, 388 dilator naris, anterior, 372 posterior, 372 of dorsal region, 537 erector clitoridis, 446 penis, 444 spinae, 410 of expression, 380 extensor brevis digitorum, 537 polUcis, 483 carpi radialis brevior, 479 longior, 479 ulnaris, 482 coccj'gis, 414 communis digitorum, 480 indicis, 484 longtis digitorum, 527 poUicis, 484 minimi digiti, 481 ossis metacarpi poUicis, 482 proprius hallucis, 527 of face, 362 of femoral region, anterior, 505 internal, 512 posterior, 522 fibers, 355 of fibular region, 534 fixation, 359 flexor accessorius, 539 brevis digitorum, 538 hallucis, 541 minimi digiti, foot, 541 hand, 493 poUicis, 490, 492 (note) carpi radialis, 473 ulnaris, 474 INDEX 1479 Muscle or Muscles, flexor longus digitorum, 533 hallucis, 532 pollicis, 476 profundus digitorum, 476 sublimis digitorum, 475 of foot, 536 ■ of forearm, 471 form of, 357 frontalis, 364 fusiform, 358 gastrocnemius, 528 geraelli, 520 geniohyoglossus, 391 geniohyoid, 390 of gluteal region, 515 gluteus maximus, 515 medius, 516 minimus, 517 gracilis, 512 hamstring, 522 of hand, 486 hclicis major, 1121 minor, 1121 of hip, 515 Horner's, 367 of humeral region, 467, 470 hyoglossus, 391 of iliac region, 502 iliacus, 504 iliococcygeus, 452 iliocostalis, 410 iliopsoas, 504 (note) iliosacralis, 452 incisivus, 375 inferior oblique, 370 infracostales, 417 of infrahyoid region, 386 infraspinatus, 465 insertion of, definition of, 359 intercostal, 417 interossei, foot, 541 of hand, 494 interspinales, 414 intertransversales, 414 involuntary, 355 nonstriated, bloodvessels of, 357 nerves of, 357 ischiobulbosus, 444 of ischiorectal region, 453 of larynx, 1172 latissimus dorsi, 406 of leg, 525 levator anguli oris, 373 scapulae, 407 ani, 450 glandulae thyroideae, 1436 labii superioris, 373 alaeque nasi, 372 menti, 374 palati, 397 palpebrae superioris, 369 penis, 444 prostatae, 452 levatores costarum, 417 ligamentous action of, 367 of lingual region, 391 lingualis, 393 longissimus dorsi, 412 longus colli, 401 of lower extremity, 501 lumbricales, foot, 540 hand, 493 of mandibular region, 374 masseter, 377 of maxillary region, 373 Miiller's, 371 nuiltifidus spinae, 413 multipennate, 358 mylohyoid, 389 of nasal region, 372 nasolabialis, 375 of neck, 380 of nose, 1081 oblique. l_'l exUTiial, 4:14 internal, 428 obliquus auriculae, 1121 inferior, 415 superior, 415 obturator externus, 521 internus, 518 occipitalis, 363 occipitofrontalis, 363 omohyoid, 388 opponens minimi digiti, foot, 541 hand, 493 pollicis, 490 orbicular, 358 orbicularis oris, 374 palpebrarum, 366 orbital, 368, 371 origin of, definition of, 359 of palatal region, 397 palatoglossus, 398 palatopharyngeus, 398 of palmar region, 493 palmaris brevis, 492 longus, 474 of palpebral region, 366 papillary, 558 pectineus, 513 pectoralis major, 456 minor, 460 of pelvic outlet, 440 penniform, 358 of perineum in female, 445 in male, 442 peronelis brevis, 535 longus, 534 tertius, 527 of pharyngeal region, 394 of pinna of ear, 1121 of plantar region, 537 plantaris, 530 platysraa, 381 popliteus, 531 pronator quadratus, 478 teres, 472 psoas magnus, 504 parvus, 504 pterygoid, 379, 380 of pterygomandibular region, 379 pubocavernosus, 444 pubococcygeus, 452 puboreotalis, 452 pyramidalis, 435 nasi, 372 pyriformis, 517 quadratus femoris, 520 lumborum, 439 menti, 374 quadriceps extensor, 509 quadrilateral, 358 of radi.al region, 479, 489 of radioulnar region, 472, 480 recti, 370 rectoeoecygeal, 1311 rectouterinus, 1408 rectOA'esieal, 1362 rectus abdominis, 433 capitis anticus, 400 lateralis, 400 posticus, 414 femoris, 510 retrahens aurera, 366 rhomboideus, 407 ring, of Muller, 1096 risorius, 377 rotatores spinae, 413 salpingopharyngeus, 399 sartorius, 508 scalenus anticus, 401 medius, 401 posticus, 402 Muscle or Muscles of scapular region, 463, 464 semimembranosus, 524 semispinalis colli, 413 dorsi, 413 semitendinosus, 524 serratus magnus, 461 posticus, 408 of shoulder, 461 skeletal, 355 of soft palate, 1203 soleus, 529 spinalis colli, 412 dorsi, 412 sphincter, 358 ani, 453, 454 recti, 452 urethrae memliranaceae, 448 vaginae, 445 spindle, 357 spindles of Kuhne, 817 splenius capitis, 409 colli, 409 stapedius, 1134 sternalis, 459 sternohyoid, 386 sternomastoid, 385 sternothyroid, 387 striated, 355 striations of, cross, 356 longitudinal, 356 striped, 355 styloglossus, 392 stylohyoid, 389 stylopharyngeus, 396 subanconeus, 471 subclavixis, 460 subcrureus, 512 subsoapvilaris, 464 substance, 356 of superficial cervical region, 381 superior oblique, 370 supinator [brevis], 482 longus, 479 of suprahyoid region, 388 supraspinales, 414 supraspinatus, 464 suspensory, of duodenum, 1285 synergic, 359 tarsal, 369, 370 temporal, 378 of temporomandibular region, 377 tensor fasciae femoris, 508 palati, 397 tarsi, 367 teres major, 466 minor, 466 of thigh, 505 of thoracic region, 455, 461 of thorax, 416 thyroarytenoid, 1173 thyroepiglotticus, 1173 thyrohyoid, 387 tibialis anticus, 526 posticus, 533 of tibiofibular region, anterior, 525 posterior, 528 of tongue, 393 traehealis, of Todd and Bow- man, 1178 trachelomasfoid, 412 tragicus, 1121 transversalis, 432 capitis, 412 (note) cervicis, 412 transverse perineal, 442, 44.5 transversus auriculae, 1121 perinei profundus, 448 trapezius, 404 triangular, 358 triangularis sterni, 417 triceps, 470 1480 INDEX Muscle or Muscles, triceps ex- tensor cubiti, 470 ot trunk, 403 of tympanum, 1134 ot ulnar region, 492 unstriped, 355 of upper extremity, 454 of ureters, 1363 variable, 361 vastus externus, 510 internus, 511 vegetative, 355 of vertebral region, 400, 401 voluntary, 355 arteries of, 356 nerves of, 357 veins of, 357 zygomaticus major, 373 minor, 373 Musculi airectores pilorum, 1161 intercoslales externi, 417 interni, 417 interossei, 493 dorsales, 494 volares, 494 interspinales, 414 intertraTisversarii, 414 laxator tympani major et mi- nor, 1134 levatores costarum, 417 lumbricales, 493 papillares, 558, 561 pectinati, 554, 557, 559 rotatores, 413 subcoslales, 417 supraspinalcs, 414 Musculocutaneous nerve, 1060 Musculophrenic artery, 632 Musculospiral groove, 180 nerve, 1037 Musoulus abductor digili quinti, 492, 539 brevis, 493 hallucis, 538 pollidis brevis, 489 longus, 482 accessorius, 410 adductur brevis, 514 longiis, 613 magThUS, 514 mininiuc, 514 poUicis, 490 transvernus pollicis, 492 anconaeus, 482 antitragicuj, 1121 articularis genu, 512 auricularis anterior, 366 posteriori', 366 superior, 366 arytenoideas obliquus, 1172 iransversus, 1173 biceps brachii, 469 caput breve, 469 Imifjum, 469 femoris, 522 capwj fereae, 523 longum, 522 bipennatus, 358 biventer cerncis; 413 brachialis, 469 brachiorddialis, 479 buccinator, 375 bulbocavernosus, 443, 445, 675 caninus, 373 capitis posterior major, 414 Tninor, 414 chondroglossus, 392 ciliaris, 1095 fibrae circiilares, 1096 meridianales, 1095 coccygeiis, 453 compressor bulbi, 444 hemisphaerium bulbi, 444 constrictor isthi faucium, 391 (note) Musculus constrictor pharyngis inferior, 394 medius, 395 superior, 395 radicis penis, 444 coracobra-chialis, 468 cremaster, 430, 1374 cricoarytenoideus lateralis, 1172 posterior, 1172 cricotkyreoideus, 1172 deltoideus, 462 depressor septi, 372 digastricus, 388 dilatator pupillae, 1099 epicranius, 363 erector clitoridis, 1418 extensor carpi radialis brevis, 479 longus, 479 digiti quinti proprius, 481 digitorum brevis, 537 communis, 480 longus, 527 hallucis longus, 527 indicis proprius, 484 pollicis brevis, 483 longus, 484 flexor carpi radialis, 473 ulnaris, 474 caput humerale, 474 ulnare, 474 digiti quinti brevis, 541 digitorum brevis, 538 longus, 533 profundus, 476 sublimis, 475 caput humerale, 475 radiate, 475 ulnare, 475 pollicis brevis, 490 longus, 476 frontalis, 363 gastrocnemius, 528 caput laterale, 528 mediale, 528 gemellus inferior, 520 superior, 520 genioglossus, 391 geniohyoideus, 390 glossopalatinus, 398 glutaeus maximus, 515 medius, 516 minimus, 517 gracilis, 512 hallucis longus, 532 helicis major, 1121 m.inor, 1121 hyoglossus, 391 iliacus, 504 iliococcygeus, 452 iliocostalis ceroids, 412 dorst, 410 lumborum, 410 iliosacralis, 452 incisivus inferior, 375 superior, 375 infraspinatus, 465 interossei, 541 dorsales, 541 plantar es, 542 ischiobulbosus, 444 ischiocavernosus, 444, 446, 675 latissimus dorsi, 406 levator scapulae, 407 jicH palatini, 397 longissimus cdpitis, 412 cervicis, 412 dorsi, 412 longitudinalis inferior, 393 superior, 393 longus capitis, 400 coiZi, 401 lumbricales, 540 masseter, 377 mentalis, 374 Musculus multifidus, 413 mylohyoideus, 389 nasalis, 372 nasolabialis, 375 obliquus auriculae, 1121 capitis inferior, 415 superior, 415 externus abdominis, 424 internus abdominis, 428 ocuZi inferior, 370 superior, 370 obturator externus, 521 internus, 518 occipitalis, 363 omohyoideus, 388 opponens digiti quinti, 493 pollicis, 490 orbicularis oculi, 366 oris, 374 orbitale, 371 ossiculorum auditus, 1134 palmaris brevis, 492 longus, 474 pectineus, 513 pecioralis major, 456 minor, 460 peronaeus brevis, 535 longus, 534 tertiv^, 527 pharyngopalatinus, 398 piriformis, 517 plantaris, 530 platysma, 381 popliteus, 531 procerus, 372 pronator quadratus, 478 ieres, 472 caput humerale, 472 ulnare, 472 psoas major, 504 mino)-, 504 pterygoideus externus, 379 internus, 380 ptibocajjerraostts, 444 pubococcygeus, 452 puborectalis, 452 pubovesicalis, 1363 pyramidalis, 435 quadratus femoris, 520 Zo&ii inferioris, 374 lumborum, 439 plantae, 539 quadriceps femoris, 509 rectococcygeus, 1310 rectouterinus, 1408 rectovesicalis, 1362 rectus abdominis, 433 capitis anterior, 400 lateralis, 400 femoris, 510 rhomboideu^ major, 407 minor, 407 risorius, 377 sacrospinalis, 410 salpingopharyngeus, 399 sartorius, 508 scalenus anterior, 401 medius, 401 posterior, 402 semimembranosis, 524 semispinalis capitis, 412 cervicis, 413 dorsi, 413 semitendinosus, 524 serratus anterior, 461 posterior inferior, 408 superior, 408 solcus, 529 sphincter ani externus, 453 internus, 454 papillae, 1099 pylori, 1273 recti, 452 urethrae membranacea, 448, 1368 INDEX 1481 Musculus spinalis ccrmcis, 412 dorsi, 412 splenius capitis, 409 ceroids, 409 sta,pedius, 1134 sternoclcidomastoideus, 385 sternohyoideus, 386 slernothyreoideus, 387 styloglossus, 392 stylohyoidcus, 389 slylopharyngeus, 396 suhclavius, 460 subscapularis, 464 supinator, 482 supraspinatus, 464 suspensoriiis duodenum, 1285 temporalis, 378 tensor fasciae laiae, 508 iieZi palatini, 397 ieres major, 466 minor, 466 thyreoarytenoideus , 1173 thyreoepiglotticus, 1173 Ihyreohyoideus, 387 tibialis anterior, 526 posterior, 533 transversalis capitis, 412 (note). transversus ahdomiriis, 432 auriculae, 1121 linguae, 393 menti, 374 (note) perinei superficialis, 442, 445 thoracis, 417 trapezius, 405 triangularis, 374 triceps brachii, 470 caput laterale, 470 longum, 470 mediate, 470 unipennatus, 358 uvulae, 398 vastus intermedius, 511 lateralis, 510 medialis, 511 verticalis liTi/juae, 393 vocalis, 1173 zygomaticus, 373 Myelencephalon, 861 Myelin sheath, 811 Myelocele, 831 Myelocytes, 40 Mylohyoid artery, 601 muscle, 389 nerves, 989 ridge, 117 Mylohyoidean groove, 117 Myocardium, 562 Myogenic theory of heart beat, 566 Myology, definition of, 34 N Nails, 1156 lunula of, 1157 matrix of, 1157 Nares, 1081 anterior, 1081 posterior, 138, 1081 Nasal angle, 100 aperture, anterior, 138 arch of veins, 710 artery, 612 transverse, 613 bones, 99 cavity, 138 crest, 105, 110 duct, 1117 ■ applied anatomy of, 1119 canal for orifice of, 141 foramen, 99 fossa;, 1081' arteries of, 1085 inner wall of, 1083 Nasal fossae, lymphatic vessels of, 777, 1085 mucous membrane of, 1083 nerves of, 1085 outer wall of, 1082 veins of, 1085 index of skull, 146 meatus, atrium of, 141 inferior, 141 middle, 140 superior, 139 nerve, 980, 984 process of maxillas, 104 region, muscles of, 372 sinus, septum of, 139 slit, 139 spine, 79 anterior, 135, 139 posterior, 129, 139 surface of maxillae, 102 Nasion, 134, 146 Nasmyth's membrane, 1211 Nasofrontal suture, 122 vein, 725 Nasomaxillary suture, 135 Nasopalatine arterj', 602 canal, 114 groove, 114 nerve, 986 Nasopharynx, 1229 Nasus externus, 1079 Navicular bone, foot, 246 hand, 196 Neck, arteries of, 583 fascia of, 380 lymphatics of, 774 muscles of, 380 lymphatic vessels of, 780 surface form of, 402 sldn of, lymphatic vessels of, 780 triangles of, 385, 602 veins of, 710, 713 N^laton's line, 229, 329 Nerve or Nerves, 812 abducent, 993 acoustic, 1000 acromial, 1022 ampullar, 1001 of ankle-joint, 345 anococcygeal, 1062 Arnold's, 1005 of arteries, 574 articular, from external pop- liteal, 1059 from great sciatic, 1055 from internal popliteal, 1057 from posterior tibial, 1057 from ulnar, 1036 of articulations of elbow-joint, 308 of shoulder-joint, 303 auditory, 1000 of auditory canal, 1123 auricvilar, anterior, 988 from vagus, 1005 great, 1020 posterior, 997 auriculotemporal, 988 beginnings, peripheral, 815 of bile ducts, 1334 of bladder, 1365 bloodvessels of, 813 of bone, 41 buccal, 987, 998 buccinator, 987 calcaneal, 1057 cardiac, cervical, 1007 great, 1069 inferior, 1069 middle, 1069 superior, 1068 thoracic, 1007 of cardiac muscle, 357 caroticotympanic, 1066 Nerve or Nerves, carotid, 1003 cavernous, 1077 cell, bipolar, 1102 body, 807 arboriform, SOS bipolar, 808 central endoplastic por- tion, 809 Golgi, 808 peripheral exoi:)lastic portion, 809 multipolar, 808 stellate, 808 unipolar, 808 of cerebral cortex, 952 ciliated ependymal, 806 germinal, 806 glia, 818 nidi, S12 nuclei, 812 of spinal cord, 832 cervical, 1021 cervicofacial, 998 chemical composition of, 819 chorda tympani, 997 of choroid, 1099 ciliary, 981, 982 circumflex, 1030 clavicular, 1022 of clitoris, 1420 coccygeal, 1019 cochlear, 1000 communicans tibialis, 1057 communicantes hypoglossi, 1023 of conjunctiva, 1115 of cornea, 1092 corpuscles, 816, 817 cranial, 972 crural, anterior, 1049 cutaneous, of abdomen, 1043 external, 1047 femoral, 1055 from external popliteal, 1059 from musculospinal, 1038 gluteal, 1055 internal, 1032, 1050 lesser, 1034 lateral, 1047 middle, 1050 palmar, 1036 perforating, 1060 perineal, 1055 postfemoral, 1054 dental, 984, 989 descendens hypoglossi, 1011 digastric, from facial, 998 digital dorsal, 1060 dorsal, of clitoris, 1061 of penis, 1061 of duodenum, 12S7 of dura of brain, 968 dural, 983 from hypoglossal. 1041 from vagus, 1005 eighth, 1000 eleventh, 1009 facial, 994 of Fallopian tube, 1402 femoral, 1049 fibers, 812 association, 954 centripetal, 810 of cerebral cortex, 952 commissural, 955 glia, 818 projection, 956 radiating, 1104 of spinal cord, 832, 834 supporting, of Miiller, 1104 sympathetic, 812 vasomotor, 813 fifth, 978 first, 973 fourth, 977 14S IXDEX Keire or Xerves, frontal, 9S0 of gall-bladder, 13.3-4 gauglion of, of Andersch, 1002 aorticorenal, 1073 of Bochdalek. 9S4 cardiac, of Wrisberg, 1072 carotid, 1066 cer\-ical, 1069 ciliary, 9S2 coccygeal, 1072 Gasserian. 978 geniculate. 996 inipar. 1072 inferior, 1002, 1005 jugular, 1002, 1005 lenticular, 9S2 Meckel's. 984 ophthalmic, 982 otic. 989 petrous. 1002 of Scarpa. 1000 semilunar, 978, 1073 sphenopalatine, 982, 984, 986 spiral, 1000 submasillarj-, 990 superior, 1002 of Valentin, 984 vestibular, 1000 gastric, 1007 genitocrural. 1047 genitofemoral. 1047 gingival, 95>4 glossopharj-ngeal, 1001 gluteal, 1054 granules. 1103 of heart, 565 hemorrhoidal, inferior, 1061 of hip-joint. 327 h\-pogastric, 1046 h\-poglossal, 1010 ffiae, 1046 iliohj-pogasmc. 1045 ilioinguinal, 1046 infraclaricular. 1029 infraorbital. 982 (note), 998 infratrochlear, 981 intercostal. 1040 intercostobrachial, 1042 intercostohunieral, 1042 interosseous, anterior, 1036 volar. 1036 of involuntar\" striated muscle, 357 of iris, 1099 Jacobson's, 1002 of kidneys, 1354 of knee-joint, 337 of labia majora, 1415 labial, 984 lacrimal, 980 of large intestine, 1312 larj-ngeal. 1068 inferior, 1007 recurrent, 1007 superior, 1006 of larj-ns, 1174 lingual, 988 from elossophar\Tigeal, 1003 of liver. 1-331 lumbar, 1020 lumboinguinal, 1047 of lungs. 1196 malar, 998 of superior mavillary, 983 from facial, 998 of mammarj- gland, 1432 mandibular. 987 from facial. 998 masseteric. 9s>< maxillarj-. inferior, 987 superior. 982 median, 1034 of membranan tjTnpani, 1131 meningeal. 9S3 Nerve or Nerves, meningeal, from hjTxiglossal, 1011 from inferior maxfUarj-, 987 from vagus, 1005 muscular, of brachial plexus, 1028 from glossopharjiigeal, 1003 from great sciatic, 1055 from hj-poglossal, 1012 from internal plantar, 1059 popliteal, 1057 from median, 1035 from musculospinal, 1037 from posterior tibial, 1057 from ulnar, 10-36 musculocutaneous. 1031, 1060 musculospiral, 1037 mylohyoid, 989 nasal, 980, 984 fossiB. 1085 nasopalatine, 986 ninth, 1001 of nose, 1081 obturator, 104* accessory". 1049 occioital. great, 1017 small. 1020 third, 1017 oculomotor, 976 of oesophagus, 1239 olfactorj-. 973 ophthalmic, 979 optic, 974 orbital, 983 origin of, 814 of ovaries, 1-401 palatine, 986 palpebral, 984 of pancreas, 1-341 papiUse, 1154 parotid. 988 of parotid glands, 1225 patellar, 1051 of penis, 1390 pericranial. 9b0 perineal, 1061 peroneal, 1057, 1059 petrosal, 98-5 deep, 1066 superficial, 989, 996 phar\-ngeal. 986, 1003, 1006, 1068 phrenic. 1024 of pia of brain, 970 plantar, 1057, 1058 of pleura, 1185 plexus of abdominal aortic, 1076 Auerbach's, 1279 brachial, 1026 cardiac. 1072 carotid. 1066 cavernous, 1066 cervical. 1018. 1020 coccygeal. 1062 coeliac. 1008, 1073 coUc, 1076 coronar\-. 1073, 1076 cvstic, 1076 gastric, 1076 gastroduodenal, 1076 gastroepiploic, 1076 hemorrhoidal, 1077 hepatic, 1076 hj-pogastric. 1077 ileocolic, 1076 infraorbital, 984, 998 intestinal. 1076 lumbar, 1044 lumbosacral. 1044 ileissner's. 1280 mesenteric, 1076 oesophageal. 1007, 1073, 1075 ovarian, 1076 Nerve or Nerves, plextis, pan- creatic, 1076 pancreaticoduodenal, 1076 patellar, 1051 peh-ic, 1077 pharj-ngeal, 1003, 1006 phrenic, 1074 prostatic. 1077 pudendal, 1060 pulmonarj-, 1073 posterior, 1005 pvloric. 1076 renal, 1008^ 1075 sacral- 1053 sigmoid, 1076 solar, 1073 spermatic. 1076 splenic, 1008, 1076 suprarenal. 1074 thjToid, 1069 tjTnpanic, 1002 uterine. 1077 vaginal- 1077 vertebraUs^ 1069 vesical, 10 1 7 pnevunogastric, 1003 pophteal, 1055, 1059 of prostate eland, 1395 pterj-goid, 987, 988 pterj-gopalatine, 986 pudendal, 1055 pudic. 1061 pulmonary, 1007 radial. 1038 recurrent. 987 respirator^-, of Bell, 1024, 1029 sacral, 1019 of salivary' glands, 1226 saphenous. 1056, 1057 scapular, posterior, 1029 sciatic, 1054, 1055 scrotal, long. 1055 second, 974 of seminal vesicles, 1385 seventh, 994 sheath of. 812 sixth, 993 of skin, 1156 of small intestine, 1295 spermatic, 1047 sphenoidal, 990 sphenopalatine, 983 spinal, 1012 accessorj-, 1009 spindles. 817 splanchnic. 1071 of spleen. 1446, 1449 sternal. 1022 of stomach, 1279 structure of, 812 stj-lohyoid, 998 subcutaneus malae, 983 of submaxillary gland, 1226 subscapular. 1030 supracla^-icular, 1022 supraorbital. 980 suprascapular, 1029 supratrochlear, 980 system, 803 central, 819 development of, 804 structure of, 80/ supporting tissue elements of, 818 sympathetic. 1063 tarsal, 1059 of taste, 1149 temporal, from facial, 998 from internal maxillary, 987 from superior masHlarj-, 983 temporofacial, 998 temporomalar, 983 of temporomandibular articu- lation, 281 tenth, 1003 INDEX 1483 Nerve or Nerves, termination of, «17 third, 976 thoracic, 1018 anterior, 1030 long, 1029 posterior, 1029 thoraeicolumlsar, 1043 thoracoabdominal intercostal, 1043 of thymus gland, 1440 thyrohyoid, 1011 thyroid, 1069' of thyroid gland, 1438 tibial, 1055 anterior, 1059 posterior, 1057 tissue, development of, 800 of tongue, 1221 of tonsil, 1231 tonsillar, 1003 tract, cerebellospinal, 838 Lowenthal's, 840 ventral cerebrospinal, 840 Monakow's, 839 prepvramidal, 839 tirifacial, 978 trigeminal, 978 trochlear, 977 twelfth, 1010 tympanic, from facial, 997 from glossopharyngeal, 1002 of tympanum, 1135 ulnar, 1036 of ureters, 1358 of uterus, 1411 utricular, 1000 utriculoampullar, 1000 of vagina, 1415 of vaginal bulb, 1420 vagus, 1003 vestibular, 1000 Vidian, 985, 1066 of voluntary muscles, 357 of > Wrisberg, 1034 of wrist-joint, 315 Nirm anococcygei, 1062 miriculares anteriores, 988 rami parotidei, 988 temporales superficiales, 9SS carotid externi, 1068 ■cavernosi penis ininores, 1077 ■cerebrales, 972 ciliares breves, 982 longi, 981 cluniwm. inferiores [latcrales], 1055 ■digitales dorsales hallucis later- alis, 1060 pedis, 1060 plantares communes, 1057 proprii, 1058 wlares communes, 1035 proprii, 1035 ■digiti secundi medialis, 1060 intercostales, 1041 rami anteriores, 1042 cutanei laterales, 1042 musculares, 1042 posteriores, 1042 labiales anteriores, 1047 posteriores, 1061 nervorum, '813 palatini, 986 palatinus anterior, 986 medius, 986 posterior, 986 scrotales anteriores, 1047 posteriores, 1061 sphenopalatini, 983 spinales, 1012 radix anterior, 1013 posterior, 1013 rami anteriores, 1015 Nervi spinales rami posteriores, 1014 rainus communicans, 1015 meninocus, 1014 sutjscapiilfireii, 1030 supraclavicularcs, 1022 anteriores, 1022 nicdii, 1022 posteriores, 1022 temporalis profundi, 987 ihoracales anteriores, 1030 Nervus abducens, 993 accessorius, 1009 ramus externus, 1009 internus, 1009 acusiicus, 1000, 1147 radix cochlearis, 1000 vestibularis, 1000 aheolaris inferior, 989 auricularis magnus, 1020 posterior, 997 ramus occipitalis, 998 auriculotemporalis, 988 rami anastomotica cum n. faciali, 988 axillaris, 1030 buccinatorius, 987 canalis pterygnidei, 985 cardiacu-s inferior, 1069 medius, 1069 superior, 1068 caroticotyinpanicus inferior, 1003 superior, 1003 caroticus internus, 1066 cavernous penis major, 1077 cochlearis, 1147 CMtanetts antebrachii dorsalis, 1038 lateralis, 1031 Tnedialis, 1032 hrachii lateralis, 1030 medialis, 1034 posterior, 1038 coZii, 1021 rami inferiores, 1021 ramus superior, 1021 dorsalis intermedius, 1060 medialis, 1060 femoris lateralis, 1047 posterior, 1054 rami perineales, 1055 SMrac lateralis, 1059 ramus anastomoticus pe- ronaeus, 1059 medialis, 1057 ramus anastoinoticus pe- ronaefiLS, 1057 dorsalis clitoridis, 1061 penis, 1061 scapulae, 1029 facialis, 994 gewM internum, 994 rami buccales, 998 temporales, 998 zygomatici, 998 ramus coiZi, 999 digastricus, 998 marginalis mandibulae, 998 stylohyoideus, 998 femoralis, 1049 frontalis, 980 genitofemoralis, 1047 glossopharyngeus, 1001 ganglion inferius, 1002 superius, 1002 glutaeus inferior, 1054 superior, 1054 hemorrhoidalis inferior, 1061 hyoglossus, 1010 rami linguales, 1012 ramus descendens, 1011 thyreohyoideus, 1011 iliohypogastricus, 1045 Nervus iliohypogastricus rami musculares, 1045 ramus cutaneus anterior, 1046 lateralis, 1046 ilioinguinalis. 1046 rami musculares, 1046 infratrochlearis, 981 intercostalis I, 1040 ramus cutaneus anterior, 1041 intercostobrachialis, 1042 intermedius, 877, 882, 955, 995 interosseus [antebrachii] dor- salis, 1039 DoZoris, 1035 , ischiadicus, 1055 rami arliculares, 1055 musculares, 1055 jugularis, 1068 lacrimalis, 980 laryngeus superior, 1006 ramus externus, 1006 internus, 1006 lingualis, 988 lumboinguinalis, 1047 mandibularis, 987 maxillaris, 982 rami alvcolares superiores posteriores, 984 ra»ni gingivales supe- riores, 984 lahialis superiores, 984 nasales inierni, 984 palpebrales inferiores, 984 ramus alveolaris superior anteriores, 984 medius, 984 meatus auditorii externi, 988 ramus membranae tym- pani, 988 mediamts, 1034 rami musculares, 1035 ramus cutaneus palmaris n. mcdiani, 1035 meninqeus medius, 983 menialis, 989 mtisculocutaneus, 1031 mylohyoideus, 989 rami deniales inferiores, 989 gingivales inferiores, 989 nasociliaris, 980 rami nasales laterales, 981 mediales, 981 nasopalatimis, 986 obfuratorius, 1047 accessorius, 1049 ramus anterior, 1049 cutaneus, 1049 posterior, 1049 occipitalis major, 1017 minor, 1020 tertius, 1017 oculomotorius, 976 ra(ii.i; hreois ganglii ciliaris, 977 ramus inferior, 976 superior, 976 olfactorius, 97.3 ophthalmicus, 979 opticus, 974 perinei, 1061 peronaeus communis, 1059 rami arliculares, 1059 profundus, 1059 rami m2isculares, 1059 super ficialis, 1060 petrosus profundus, 985, 1135 super ficialis. 1135 major, 985 phrenicv^, 1024 plantaris lateralis, 1058 ramus profundiis, 1059 superficialis, 1058 1484 INDEX Nenus plantaris medialis, 1057 pterygoideus externus, 988 internus, 987 pudendus, 1061 radialis, 1037 Tami musculares, 1037 ramus superficialis, 1038 nn. digitali 1039 recurrens, 1007 ra?ni cardiaci inferiores, 1007 superiores, 1007 saphenus, 1050 ramus infrapatellaris, 1051 spermaticus externus, 1047 spinosu^, 987 splanchnicus imus, 1071 , mujor, 1071 minor, 1071 stapedius, 997 subclavius, 1029 subscapularis, 1029 supraorbitalis, 980 supratrochlearis, 980 temporalis profundus anterior, 987 posterior, 987 thoracalis longus, 1029 thoracodorsalis, 1030 tibialis, 1055 rami articulares, 1057 m,usculares, 1057 calcanei laterales, 1057 mediales, 1057 ramtts articularis ad articula- tionem talocruralem, 1057 trigeminus, 978 irochlearis, 977 tyTnpanicus, 1002, 1125, 1135 romi linguales, 1003 pharyngei, 1003 tonsillares, 1003 ramus stylopharyngetis, 1003 ulnaris, 1036 rami Tnusculares, 1036 ramus cutaneus palmaris, 1036 dorsalis manus, 1036 nn. digitales dorsales, 1036 profundus, 1037 superficialis, 1037 Bogtis, 1003 rami coeliaci, 1008 gastrici, 1007 hepatica, 1008 lienales, 1008 oesophagei, 1007 renales, lOOS ramus aurieularis, 1005 meningewi, 1005 pharyngeus, 1006 vestibularis, 1147 zygomaticus, 983 ramus zygomaticofacialis, 983 zygomaticotemporalis, 983 Neumann's sheaths, 1211 Neural crest, 805 segments, 851 Neuraxone, 807 Neurilemma, 811 nucleus of, 812 Neuroblasts, 806 Neuroeentral suture, 63 Neuroepithelium, 1143 Neurofibrils, 809 Neurogenic theory of heart beat, 566 Neuroglia, 806, 818 Neurology, definition of, 34 Neuromeres, 851 Neuromuscular spindles, 817 Neurones, 803, 807 centripetal, peripheral nerve beginnings of, 816 Neurones, diaxonic, 810 excitoglandular, 804 excitomotor, 804 monaxonic, 810 motor, 804 polyaxonic, 810 sensor, 804 theory of, 818 varied forms of, 807 Neurotendinous spindles, 817 iVicZi, 832 Nidus avis, 888 habenulae, 906 laryngoi, 879 pharyngei, 879, 881 Ninth nerve, 1001 thoracic vertebra, 54 Nipple, 1428 Nissl bodies, 809 Nodes, hemolymph, 768 lymph, 768 Parrot's, 151 of Ranvier, 811 of Tawara, 564 Noduli lymphatici aggregati [Pey- cri], 1292 solitarii, 1292 Nodulus, 888 valvulae semilunaris [Arantii] 559, 561 vermis, 888 Norma basalis, 128 frontalis, 134 lateralis. 132 verticalis, 123 Nose, 1079 apphed anatomy of, 1085 arteries of, 1081 cartilage of, 1079 framework of, liony, 1079 cartilaginous, 1079 integument of, 1081 lymphatics of, 1081 meatus of, 110 mucous membrane of, 1081 muscles of, 1081 nerves of, 1081 septum of, 138 artery of, 602 cartilage of, 1080 veins of, 1081 Nostrils, 1081 Notch, cotyloid, 213 ethmoidal, 79 intercondyloid, 225 intervertebral, 49 lacrimal, 102 popliteal, 233 preoccipital, 914 presternal, 157, 166, 171 pterygoid, 94 of Rivinus, 1130 sacrosciatic, 210, 211 sigmoid, 118 sphenopalatine, 112 supraorbital, 77, 135 suprascapular, 175 suprasternal, 403 Nuck, canal of, 1408 Nuclei, 832 of abducent nerve, 883 of acoustic nerve, 881 of auditory nerve, 881 of brain, 857 of cerebellum, 888 of cochlear nerve, 881 of facial nerve, 882 of glossopharyngeal nerve, 880 of hypoglossal nerve, 878 of oculomotor nerve, 901 olivarii accessorii, 873 dorsalis, 873 medialis, 873 ■ of olive, 873 Nuclei radicis ascendentis nervi trigemini, 883 of solitary tract, 880 of spinal accessory nerve, 879 cord, cervical, 833 Deiters', 839 sacral, 833 of tegmentum, 897 of trigeminal nerve, 883 of trochlear nerve, 901 of vagus nerve, 880 of vestibular nerve, 881 Nucleus arabiguus, 881 amygdaline, 948 anterius, 905 thalami, 905 arcuatus, 873 caudate, 937, 946 • caudatus, 946 dentatus, 888 dorsalis [Clarkii], 830, 833 emboliformis, 889 funiculi cuneati, 863 gracilis, 863 teretis, 873 globosus, 889 globulus, 889 glossopharyngci, 880 hypoglossi, 1010 incertus, 876 intercalatus, 873 interpeduncular, 898 lateralis, 873, 905 thalami, 905 lenticular, 947 lentis, 1107 magnocellularis, 881 medialis, 905 mesencepalic root, 884 olivarius inferior, 873 superior, 876 olivary, 873 postremus, 873 pulposus, 270 red, 898 salivatorius, 882 semilunaris [Flechsigi], 905 tegmenti, 898 tractus solitarii, 882 vagi, 880 Nuel, space of, 1147 Nuhn and Blandin, glands of, 1219 Nutrient arterv of brachial, 643 of filjula, 702 of tibia, 702 canal of fil:»ula, 237 of metacarpal bones, 201 of radius, 191 of ulna, 189 foramen of fibula, 237 of metacarpal bones, 201 of radius, 191 of tibia, 234 of ulna, 189 Nymphae, 1416 Obelion, 123, 146 Obex [ventriguli] guarti, 867 Oblique diameter of pelvis, 216 foramen of mandible, 117 inguinal hernia, 1315 ligament, 311 line of clavicle, 169 of mandible, 117 of radius, 191 of tibia, 234 of trapezium. 199 muscles, ascending, 428 descending, 424 external, 424 INDEX 1485 0))li<|ii(' iiiiisclis, internal, 428 s:i.'niili;,r li-allicnt, 290 siiiii^ of |ii rirnrdium, 549 vein of .M:ii>li;i,ll, 550, 709 ■Ohlicpnis :iiirirul:ii' muscles, 1121 inlriior niusrlc, 415 siii.crior niusclo, 415 Olilongatii, 861 Obstetric perineum, 1415 Obturator artery, 673 liur^a, 327 cimal, 517 civst. 1213 pxternus muscle, 521 fascia, 44S foramen, 213 groove, 211, 213, 214 intornus muscle, 51S l^ursa of, 51S ligament, 295 membrane, 517 nerve, accessory, 1049 vein, 744 Occipital artery, 595 bcfne, 70 articulation of atlas with, 275 of axis with, 277 bulb, 939 crest, external, 70, 132 internal, 72, 128 diploic vein, 719 fissure, 918 fossa, inferior, 128 groove, 82, 131 lobe, 924 fissures of, 924 gray substance of, 953 lymph nodes, 774 nerves, 1017, 1020 point of skull, 146 protuberance, 70, 72, 132 sinus, 723 triangle, 388, 605 vein, 713 Occipitalis muscle, 363 Occipito-atlantal ligaments, 275 Occipito-axial ligament, 277 Occ'iiiitofn>iit;iIis muscle, 363 Occi|ntiJiiir,iiitt'phalic tract, 957 Ocri|>itoi,:nii'lal suture, 121 Occipitupuiitile tracts, 950 Oculomotor uerve, 976 Odontoblasts, 1212, 1215 Odontoid ligaments, 277, 278 CEsophageal arteries, 629, 654 glands, 1239 groove, 421 opening of diaphragm, 421 plexus of nerves, 1005 (Esophagus, 1236 applied anatomy of, 1239 arteries of, 1239 Ixmiina macularis mucosae, 1239 lymphatic vessels of, 802, 1239 nerves of, 1239 pars abdotninalis, 1237 ceroicalis, 1237 thoracalis, 1237 relations of, 1237 tela submucosa, 1239 tunica mucosa, 1239 mu^cularis, 1238 veins of, 735, 1239 Olecranon, 185 bursa, .308 fossa, 182 Olfactory areas of brain, 960 bulb, 927 gray substance of, 953 fissure, 920 foramina, 138 gyre, 928 lobe, 926 Olfactory nerve, 973 applied anatomy of, 974 pathways, 958 tract, 927 tubercle, 928, 973 Oliva, 863 Olivary body, 863 eminence, 90 fasciculus, 900 nucleus, accessory, 873 inferior, 873 superior, 876 process, 126 Olive of medulla oblongata, 863 Olivocerebellar fibers, 873 Olivospinal tract of Helweg, 839 Omental band, 1310 tuberosity of liver, 1321 Omentum, gastrocolic, 1254, 1260 gastrohepatic, 1254, 1260 gastrosplenic, 1261 greater, 1251, 1261 lesser, 1253, 1260 niajus, 1261 viiiius, 1260 Omohyoid muscle, 388 surface form of, 403 Opcrcuhim, 917 Ophryon, 146 Ophthalmic artery, 610 ganglion, 982 nerve, 979 veins, 725 Opisthion, 132, 146 Opisthotic portion of temporal bone, 88 Opponens minimi digiti muscle, foot, 541 hand, 493 poUicis muscles, 490 Optic-acoustic reflex path, 898 Optic axis, 1088 chiasm, 910, 974 cup, 1101 disk, 1100 foramen, 90, 126 groove, 90, 126 nerves, 974 papilla, 1101 radiation, 905 tract and its central connec- tions, 909 vesicles, 852 Oraserrata, 1100, 1104 Oral cavity, 1199 Orbicular ligament, 310 muscle, 358 Orbicularis oris muscle, 374 palpebrarum muscle, 366 surface form of, 380 Orbiculus ciliaris, 1094 Orbit, 136 fascia of, 371 margin of, 101 Orbita, 136 Orbital artery, 598 fascia, 371 fossa, 138 index of skull, 146 muscle, 371 sheaths of, 371 nerve, 983 •operculum, 917 plates, 79 portion of frontal bone, 79 process of malar bone, 108 of palate bone, 112 region, muscles of, 368 applied anatomv of, 371 septum, 368, 1112 sinus, 112 veins, 712 wings of sphenoid bone, 93 Orbitofrontal fissures, 919 OrbitoiKil|,i'l,nil sulcus, 1112 Orbitos|,lMii,,i,|s, 'J.-, Organ • ,f ' niii. nil of digusUuu, ll'J'J of Girald(3s, 1384 of Golgi, 817 reproductive, female, 1397 male, 1371 of respiration, 1163 of Rosenmiiller, 1401 of taste, 1148 of touch, 1150 urinary, 1343 urogenit.al, 1343 of voice, 1163 Organa genitalia muliebria, 1397 virilia, 1371 oculi nrcrssnnV,, 1112 ■pamx/i/iiiHillnlirn, 1450 Oraanon n'lrliliis, 1119 (Justus, 1148 olfactm, 1079 spirale [Cortii], 1144 tactus, 1150 vomeronasale, 1083 Orifice of canal for nasal duct, 141 of maxillary atrium, 141 mitral, 560 tricuspid, 556 Orificium externum uteri, 1406 labium anterius, 1406 posterius, 1406 internum uteri, 1408 ureteris, 1356 urethrae externum, 1366, 1369, 1417 internum, 1365, 1366 Os acetabuli, 213, 214 calcis, 239 capitatum, 199 centrale, 206 coceygis, 61 cordis, 562 coxae, 207 cuboideum, 245 cuneiforme primum, 247 secundum, 248 tertium, 248 external, 1406 frontale, 76 hamatum, 200 hyoideum, 153 ilium, 207 incae, 74 incisivum, 105 innominatum, 207 internal, 1405 ischii, 210 lacrimale, 106 magnum, 199 metacarpale, I, 202 //, 202 III, 202 IV, 203 V, 203 metatarsale, I, 250 //, 251 III, 251 IV, 251 y, 252 multanguluni majus, 198 mitnis, 199 7\avicidirc manus, 196 pedis, 246 occipitale, 70 palatinurn, 109 parietalc, 74 pisiforme, 198 planum, 98 pidns, 212 sacrum, 58 sphenoidale, 89 temporale, 80 1486 INDEX Os trigonuni, 245 triquetrum, 197 uteri, 1406 Osborn, supracommissure of, 906 Ossa carpi, 95 faciei, 99 metacarpalia, 201 metatarsalia, 249 nasalia, 99 sesamoidea, 257 tarsi, 2.39 triquetra, 144 unguis, 106 Ossein, 42 Osseous labyrinth of ear, 1136 tissue of bone, 38 Ossicles of tympanum, 1131 articulations of, 1133 movements of, 1134 Ossicula auditus, 1131 Ossification of bone, 42 centre of, 44 intracartilaginous, 42 intramenibranous, 42 Osteoblasts, 39, 40, 44 Osteogenetic fibers, 42 Osteology, definition of, 34 Ostium ahdominale tubae uterinae, 1401 arteriosum, 560 •pulmonis, 558 pharyngeum tubae auditivae, 1229 primum of Born, 759 secundum of Born, 759 uterinum tubae, 1401 venosum dextriim, 556 ventriculi dextri, 557 sinistri, 559, 560 Otic ganglion, 989 vesicles, 141 Otoconia, 1143 Otoliths, 1141, 1143 membrane, 1143 Outlet of pelvis, 217 Oval bundle of Flechsig, 836 Ovaria, 1397 discus proligerus, 1400 liquor folliculi, 1399 theca folliculi, 1399 tunica albuginea, 1399 zona granulosa, 1399 pellucida, 1400 radiata, 1400 Ovarian plexus of nerves, 1076 Ovaries, 1397 applied anatomy of, 1401 arteries of, 665, 1401 cortex of, 1399 descent of, 1398 at different ages, 1399 fimbrise of, 1401 hilum of, 1400 lymphatic vessels of, 797, 1401 medulla of, 1400 nerves of, 1401 suspensory ligament of, 1398 veins of, 751, 1401 Ovarium, 139S Oviduct, 1401 Ovoid depression of femur, 221 Ovulation, 1400 Ovules of Naboth, 1410 Owen, osteodentin of, 1212 Oxyntic cells, 1276 glands, 1276 Pacchionian bodies of brain, 970 depressions, 74 Pacinian corpuscles, 816 Pad, sucking, 376 Palatal aponeurosis, 397 Palatal process of maxilloe, 102, 104 region, muscles of, 397 applied anatomy of, 399 Palate, 1202 arteries, 1204 bone, 109 cleft, 151 Palatine artery, 597 ascending, 593 descending, 602 applied anatomy of, 602 canal, anterior, 138, 139 , posterior, 102, 110, 111, 134 accessory, 110, 128 foramen, posterior, 128 fossa, anterior, 128 glands, 1202 nerves, 986 ruga;, 1202 spine, 110 Palatoglossus muscle, 398 Palatomaxillary canal, 102 Palatopharyngeus muscle, 398 Palatum, 1202 durum, 1202 ' molle, 1202 Pallidum, 948 Palmar arch, deep, 645 superficial, 652 applied anatomy of, 652 surface marking of, 652 cutaneous nerve, 1036, 1037, 1039 fascia, 488 interossei muscles, 494 interosseous arteries, 648 plexus of veins, 729 region, muscles of, 493 veins, 731 Palmaris brevis muscle, 492 surface form of, 497 longus muscle, 474 surface form of, 496 Palpebrae, 1112 Palpebral arteries, 610, 612 nerves, 984 region, muscles of, 366 Pancreas, 1336 applied anatomy of, 1341 arteries of, 662, 1341 fades anterior, 1338 inferior, 13.38 posterior, 1338 lymphatic vessels of, 796, 1341 margo anterior, 1338 inferior, 1338 superior, 1338 nerves of, 1341 surface form of, 1341 veins of, 753, 1341 Pancreatic duct, 1340 juice, 1341 magna, 662 plexus of nerves, 1076 Pancreaticoduodenal arteries, 661, 663 lymph nodes, 793 plexus of nerves, 1076 veins, 753 Panniculus adiposus, 360, 1154 Papilla, bile, 1287 duodeni [Santorini], 1287 incisiva, 1202 lacrimal, 1113 mammae, 1428 pili, 1159 renal, 1349 Papillae filiformes, 1218 fungiformes, 1218 lacrimalis, 1116 of tongue, 1218 mllatae, 1218 Papillary layer of skin, 1153 muscles, 558 Paracardial lymph nodes, 700 Paracentral fissure, 920 gyre, 921 Parachordal cartilages, 141 Paradidymis, 1384 Paraduodenal fossa, 1266 Paramesal fissures, 919 Parametrium, 1406, 1407 Paranucleus, 1341 Paraoccipital fissure, 923 Paraplexus, 940, 971 Pararectal fossa, 1256 Parasinoidal spaces, 721 Parasympathetic bodies, 1450 Parathyroid glands, 1439 applied anatomy of, 1440- development of, 1440 Paravesical fossa, 1361 Paraxones, 811 Parenchyma of kidneys, 1349 of lungs, 1195 of .spleen, 1445 of testes, 1380 Parenchymatous cells, 1437 Parietal artery, ascending, 817 bone, 74 cells, 1276^ eminence, 74 foramen, 74 fissure, 923 lobe, 922 fissures of, 922 gyres of, 923 lymph nodes, 787, 798 peritoneum, 1244 veins, development of, 764 Parietocolic fold, 1267 Parietotemporal artery, 617 Parolfactory area, 928 sulcus, anterior, 928 Paroophoron, 1401 Parotid duct, 1200 fascia, 377 glands, 1223 arteries of, 1225 duct of, 1225 lymphatics of, 1225 nerves of, 1225 veins of, 1225 lymph-nodes, 774, 1225 nerves, 988 Parovarium, 1401 Parrot's nodes, 151 Pars basilaris, 71 pontis, 874 calcaneocuboid ea ligamenti bi- furcati, 348 ca Icaneonavicularis ligamenti bifurcati, 348 ciliaris retinae, 1100 diaphragmatica fasciae pelvis, 454 dorsalis pontis, 864 fiber tracts in. 876 iridica retinae, 1098, 1099, 1100 lacrimalis musculus orbicularis oculi, 367 Tnetencephalica [tnedullae ob~ longatae], 864 orbitalis musculus orbicularis oculi, 366 palpebralis musculus orbicula- ris oculi, 366 tympanica, 87 Partes genitales externae mulie- bres, 1415 petrosa et mastoidea, 81 Parumbilical veins, 754 Parvidural artery, 600 Patella, 230 applied anatomy of, 231 ligaments of, 331 surface form of, 231 Patellar bursa, 512 INDEX 1487 Patellar plexus of nerves, 1051 Pavilion of Fallopian tube, 1401 Peetineus muscle, 513 Pectoral fascia, 456 lymph nodes, 782 region, dissection of, 455 Pectoralis major muscle, 456 surface form of, 495 minor muscle, 460 surface form of, 495 muscles, dissection of, 459 Peculiar ribs, 163 thoracic vertebra, 54 Peduncle of cerebellum, 889 of corpus callosum, 928 Peduncular sulcus of cerebel- lum, 885 Pedunculated hydatid, 1379 Pelvic colon, 1306 curve of vertebral column, 66 fascia, 448 ligament, transverse, 446 outlet, fascice of, 440, muscles of, 440 plexuses of nerves, 1077 viscera, lymphatic vessels of, 792 Pelvis, 215 applied anatomy of, 220 articulations of, 290 vertebral column with, 289 axes of, 218 brim of, 215 cavity of, 216 axis of, 218 circumference of, 215, 217 diameters of, 215, 217 diaphragm of, 1240 difference between male and female, 218 false, 216 in fetus, 219 inlet of, 215 axis of, 218 plane of, 218 lymphatics of, 787, 789, 790 major, 215 minor, 215 outlet of, 217 axis of, 218 position of, 217 surface form of, 219 true, 215 of ureter, 1349, 1356 uretericus s. renalis, 1349 veins of, 739 white line of, 449 Penis, 1386 applied anatomy of, 1390 arteries of, 1389 dorsal, 676 dorsum of, 1388 frenulum of, 1389 lymphatics of, 1390 nerves of, 1390 dorsal, 1061 prepuce of, 1388 suspensory ligament of, 1388 tunica albuginea, 1386 urethral surface of, 1388 veins of, 1390 dorsal, 746 Penniform muscle, 358 Peptic glands, 1276 Perforated space, anterior, 928 posterior, 898 Perforating arteries of foot, 704 of thigh, 690 cutaneous nerve, 1060 Pericardium, 54S applied anatomv of, 550 arteries of, 550, 632, 654 fibrous, 548 nerves of, 550 serous, 549 Pericardium, sinus of, 550 vestigial fold of, 550 Pericecal fossa, 1266 Pericellular lymph spaces, 767 Perichondrium, 44, 259 Perichoroidal space, 1090 Periclaustral lamina, 948 Pericranial nerves, 980 Peridental membrane, 1212 Perilymph, 1136 space, 1136 Perimedullary lamella of bone, 39 Perimetrium, 1409 Perimysium, 355 Perineal arteries, 675 body, 1309 fascia, 446 muscle, superficial transverse, 442, 445 nerves, 1061 cutaneous, 1055 Perineum, central tendinous point of, 442 in female, muscles of, 445 lymphatic vessels of, 790 in male, muscles of, 442 Perineural lymph spaces, 767 Perineurium, 812 Periosteal lamella of bone, 39 Periosteum alveolare, 1205 of bone, 38, 44 cranial, 364 Peripheral axone of an afferent neurone, 807 fibrilL-E, 816 lamella of bone, 39 nerve beginnings, 815 Perirenal arteries, 665 fat, 1348 Periscleral lymph spaces, 1086 Peritoneal cavity, 1244 Peritoneum, 1244 apphed anatomy of, 1268 development of, 1245 mesenteric, 1249 parietal, 1244 rectovesical fold of, 1361 pouch of, 1361 uterovesical pouch of, 1361 visceral, 1244 Peritracheobronchial lymph nodes, 1179 Perivascular Ivmph spaces, 707, 767 Perivitelline space, 1400 Peroneal arteries, 701, 702 groove, 246 nerve, 1059 spine, 242 Peroneus brevis muscle, 535 surface form of, 544 longus muscle, 534 surface form of, 544 tertius muscle, 527 surface form of, 544 Perpendicular plate of palate bone, 110 portions of mandible, 117 Pes anserinus, 996 hippocampi, 942 leonis, 942 of midbrain, 900 Petrolus epiglottidis, 1167 Petromastoid portion of tem- poral bone, 82 Petro-occipital suture, 73, 122, 127 Petrosal artery, 600 nerves, 985 deep, 1066 superficial, 989, 996 process, 90 sinus, 715, 726 Petrosphenoidal fissure, 122 suture, 131 Petrosquamous sinus, 723 suture, 84 Petrotympanic fissure, 88, 1126 Petrous ganglion, 1002 portion of temporal bone, 83 Peyer's patches, 1293 Phalanges digilorum manus, 204 pedis, 252 of foot, 252 applied anatomj* of, 256 articulations of, 354 surface form of, 354 , of hand, 204 applied anatomy of, 206 articulations of, 321 development of, 207 surface form of, 205 ungual, 205 Phalanx prima digilorum pedis, 252 secuTida digitoruni pedis, 253 ieriia digilorum- pedis, 253 Pharyngeal aponeurosis, 395 artery, ascending, 597 nerve, 986, 1003, 1006, 1068 plexus of nerves, 1003, 1006 of veins, 715 region, muscles of, 394 ring, lymphatic, 1234 spine, 71, 131 tonsil, 1230 veins, 715 Pharyngoepiglottic fold, 1233 Pharynx, 1229 applied anatomy of, 1235 development of, 1234 isthmus of, 1230 pars laryngea, 1233 nasalis, 1229 omlis, 1230 tunica rmicosa, 1233 Philtrum, 375 Phrenic arteries, 658 ganglion, 1074 nerve, 1024 applied anatomy of, 1025 plexus of nerves, 1074 veins, 734, 751 Phrenicocostal sinus, 1346 Phrenocolic ligament, 1305 Pia of brain, 971 arteries of, 972 nerves of, 972 veins of, 972 mater encephali, 971 spinalis^ 845 of spinal cord, 845 applied anatomy of, 846 arteries of, 846 Pigmentation of skin, 1155 Pili, 1159 Pillars of external al^dominal ring, 427 Pineal body, 906 Pinna of ear, 1119 arteries of, 1121 cartilage of, 1120 integument of, 1120 ligaments of, 1121 lymphatics of, 777, 1122 muscles of, 1121 veins of, 1121 Pisiform bone, 198 Pisometacarpal ligament. 316 Piso-uncinate ligament, 316 Pit of stomach, 166 Pituitary body, 909 Pivot-joint, 264, 265 Placental circulation, 755 Planes of body. 34 Plantar arch, 704 arteries, 703 surface marking of. 704 metatarsal veins, 741 nerves, 1057, 1058 1488 INDEX Plantar region, fascia of, 537 muscles of, 538 veins, 741 Plantaris muscle, 530 Planum popUteum, 224 sternale, 159 Plate, cribriform, of ethmoid, 96 horizontal, of palate bone, 109 perpendicular, of palate bone, 110 pterygoid, 94 tympanic, 131 vertical, of ethmoid, 97 of palate bone, 110 Platysma muscle, 381 surface form of, 402 Pleura costalis, 1183 diaphragmatica, 1183 Tnediastinalis, 1183 parietalis, 1181 pulmonalis, 1181 Pleuras, 1181 applied anatomy of, 1185 arteries of, 1185 cavity of, 1181 cervical, 1183 costal, 1183 diaphragmatic, 1183 lymphatic vessels of, 802, 1185 mediastinal, 1183 nerves of, 1185 reflections of, 1183 veins of, 1185 Plexus of arteries, subpleural me- diastinal, 632 ^ choroid, of fourth ventricle, 867 of lateral ventricles, 940 of third ventricle, 940 of nerves, abdominal aortic, 1076 brachial, 1026 cardiac, 1072 carotid, 1066 cavernous, 1066 cer-sdcal, 1018, 1020 coccygeal, 1062 cceliac, 1008, 1073 colic, 1076 coronary, 1073, 1076 cystic, 1076 gastric, 1076 gastroduodenal, 1076 gastroepiploic, 1076 hemorrhoidal, 1077 hepatic, 1008, 1076 hypogastric, 1077 ileocolic, 1076 infraorbital, 984, 998 intestinal, 1076 lumbar, 1044 lumbosacral, 1044 mesenteric, 1074 03sophageal, 1005, 1007, 1073 ovarian, 1076 pancreatic, 1076 pancreaticoduodenal, 1076 patellar, 1051 pelvic, 1077 pharyngeal, 1003, 1006 phrenic, 1074 prostatic, 1077 pudendal, 1060 p»lmonarv, 1073 posterior, 1005, 1007 pyloric, 1076 renal, 106S, 1075 sacral, 1053 sigmoid, 1076 solar, 1076 spermatic, 1076 splenic, 1008, 1076 suprarenal. 1074 thjToid. 1069 tympanic, 1002 Plexus of nerves, uterine, 1077 vaginal, 1077 vesical, 1077 of veins of foot, 739 of hand, 729 hemorrhoidal, 745 palmar, 729 pampiniformis, 750 pharyngeal, 715 pterygoid, 712 spermatic, 750 on thyroid body, 734 uterine, 747 vaginal, 747 vertebral, 737 vesical, 745 vesicoprostatic, 745 Plexus aorticus ahdominalis, 1072, 1076 arteriae ovaricae, 1076 basilaris, 727 brachialis, 1026 fasciculus lateralis, 1028 medialis, 102S posterior, 1028 pars infraclavicularis, 1028 supraclavicularis, 1027 rami musculares, 1028 cardiacus, 1072 caroticus externus, 1069 internus, 1066 cavernosus, 1066 concharum, 1084 cervicalis, 1020 ■ chorioideus ventriculi lateralis, 971 quarti, 972 tertii, 971 coccygeus, 1062 coeliacus, 1073 coronarius anterior, 1073 posterior, 1073 dentalis inferior, 989 superior, 984 gastricus superior, 1076 gulae, 1004, 1238 haeynorrhoidalis inferior, 1077 hepaticus, 1076 hypogastricus, 1072, 1077 lienalis, 1076 lumhalis, 1044 lujnbosacralis, 1044 rami anterior es, 1044 mesentericus inferior, 1076 superior, 1076 oesophageus, 1238 pampiniformis, 750 pharyngeus, 1006 ' ' phrenicus, 1074 prosiaiicus, 1077 pudendus, 1060 pulmonalis anterior, 1007 posterior. 1004, 1005, 1007 ra??ii bronchiales anteriores, 1007 posteriores, 1007 , 1075 sacralis, 1053 spermaticiis, 1076 suprarenalis, 1074 ' sympathici, 1063 thyroideus, 1069 tynipanicus, 1002 [Jacobsoni], 1135 uterovaginalis, 1077 venosi pampiniformis, 1377 pterygoideus, 712 thyreoideus impar, 734 vertebrales, 717 anteriores, 737 externi, 737 interni, 738, 843 posteriores, 737 venosus caroticus internus, 714, 727 Plexus verlebralis, 1069 vesiculis, 1077 Plica aryepiglottica, 1166 duodenojejunalis, 1266 duodenomesocolica, 1265 fimhriata, 1217 ileocecalis, 1267 lacrimalis [Hasneri], 1177 longiiudinalis duodeni, 1287 - nervi laryngei, 1233 pharyngoepiglotlica , 1233 salpingopalatina, 1230 salpingopharyngea, 1230 semilunaris conjunctivae, 1115 sublingualis, 1201, 1226 synovialis patellaris, 336 triangularis, 1231 umhilicalis, 1361 lateralis, 1361, 1363 rnedia, 1361, 1362 vesicalis transversa, 1256, 1359 Plicae alares, 336 palatinae transversae, 1202 palmatae, 1408, 1410 rectouterinae, 1407 rectovesicales, 1255, 1362 semilunares coli, 1298, 1310 uretericae, 1365 ventriculares, 1170 vesicouterinae, 1362 vocales, 1170 Pneumogastric nerve, 1003 Polus anterior lentis, 1107 posterior lentis, 1107 Polyaxonic neurones, 810 Polymazia, 1430 Polymorphous cells, 952 Polynuclear cells, 40 Polythelia, 1430 Pomum Adami, 1164 Pons, 864 basilar surface of, 864 tegmental part of, 876 tract, inter-radicular, 864 varolii, 864 veins of, 720 Ponticulus of Arnold, 863 Pontile arteries, 622 flexure of brain, 855 Pophteal artery, 691 applied anatomy of, 693 surface marking of, 693 groove, 226 lymph nodes, 784 nerves, 1055, 1059 notch, 233 space, 691 boundaries of, 692 contents of, 692 position of contained parts, 692 vein, 742 Popliteus muscle, 531 Porta, 853 hepatis, 1323 Portal vein, 751 applied anatomy of, 754 development of, 764 Porus lactiferus, 1431 opticus, 1090, 1100 sudorifervs, 1162 Postbrachium, 895 Postcalcarine fissure, 919 Postcapillary veins, 706 Postcardiual veins, 764 Posteava, 748 Postcentral fissures, 923 gyre, 923 Postcisterna, 969 Postcornu, 939 Postdural artery, 597 Postfemoral cutaneous nerve, 1054 Postforceps, 933 Postgemina, 897 INDEX 1489 Postgenieulum, 895 Postglenoid process, 81 Posthypophysis, 909 Postinsula, 925 Postoblongata of Wilder, 861 Postoperouluin, 917 Postorbital linil.us, 922 PosdKirii'lnl u-vrr, 923 Pos(prdiuiculii>, SS9 Postperfoiatuiii, 817, 898. Postpontile recess, 862 Postramus of cerebellum, 888 Postrhinal fissure, 925 Postvermis, 885 Poupart's ligament, 426, 427 Praeputium, 1388 diioridis, 1416, 1420 Preaortic lymph nodes, 789 Preauricular lymph nodes, 775 Prebrachium, 895 Precapillary arteriole, 573 Precardinal veins, 764 Precava, 735 Precentral fissures, '919 gyre, 921 Precommissure, 946 Precornu, 936 Precuneal fissures, 923 Precuneus, 924 Preforceps, 933 Pregemina, 894, 897 Pregeniculum, 904 Prehypophysis, 909 Preinsula, 925 fissure, 925 Preinsular gyres, 926 Prelaryngeal lymph nodes, 779 Premaxillary bones, 105 centre, 106 Preoblongata, 864 Preoccipital notch, 914 Preoperculum, 917 Prepatellar bursa, 336, 512 Prepedunculi, 891 Preperforatum, 847, 928 Prepuce of clitoris, 1416 of penis, 1388 Prepyramidal tract of cord, 839 Preramus of cerebellum, 888 Presternal notch, 157, 166, 171 Presternum, 157 Presylvian ramus, 917 Pretracheal fascia, 384 lymph nodes, 779 Prevermis, 885 Prevertebral artery, 597 fascia, 384 Primitive sheath of Schwann, 811 Princeps hallucis artery, 700 poUicis artery, 647 Prismata adamantina, 1210 Process or Processes, acromion, 175 alveolar, of maxillEe, 104 angular, 77, 78, 135 of atlas, 51 of axis, 52 axis cylinder, 807 mediillated, 811 nonmeduUated, 812 basilar, 71 of calcaneus, 242 ciharv, 1094 chnoid, 90, 94, 126 cochleariform, 1127 condyloid, of mandilile, 118 coracoid, 176 coronoid, of mandible, 118 costal, 50 ethmoidal, 114 falciform, 508 frontal, of malar, 108 funicular, 1379 94 Process or Processes, hamular, 94, 107, 130 intrajugular, 73 jugular, 71, 131 lacrimal, 114 malar, 101, 104 mastoid, of temporal bone, 82, 133 maxillary. 111, 114 mental, 116, 135 nasal, of maxiUse, 104 olivary, 126 orbital, of malar, 108 of palate bone, 112 palatal, of maxillae, 102, 104 petrosal, 99 postglenoid, 81 pterygoid, of sphenoid bone, 94 sphenoidal, 1080 of palate bone, 112 turbinated, 91, 95 spinous, of ilium, 210 stylohyal, 89 styloid, 88, 131 of fibula, 236 of radius, 192 of ulna, 189 supracondylar, 181 (note) . transverse, 71 turbinated, middle, 98, 139 sphenoidal, 138 superior, 98 tympanohyal, 88 unciform, 200 of ethmoid, 98 vaginal, of sphenoid, 92, 94, 95 zygomatic, of malar, 109 of temporal bone, 81 Processus accessorius, 57 aheolaris, 104 articularis inferior, 49 superior, 49 caudatus, 1324 ciliares, 1094 clinoidei medii, 90 posterior, 90 clinoirieus anterior, 94 condyloideus, 118 coracoideus, 176 coronoideus, 118, 185 costarius, 57 durae matris encephali, 966 ethmoidalis concha nasalis in- ferior, 114 falciformis ligamentum sacrotu- berosum, 291 frontalis, 104 frontosphenoidalis, 108 inferior tegm-enti tympani, 88 intrajugularis, 71, 73 jugularis, 71 lacrimalis concha nasalis in- ferior, 114 lateralis tuberis calcanei, 242 mammillaris, 57 mastoideus, 82 maxilla? is. 111 concha nasalis inferior, 114 medialis tuberis calcanei, 242 orbitalis, 112 palatinus, 102, 104 papillaris, 1324 posterior tali, 245 pterygoidei, 94 pyramidalis, 111 sphenoidalis, 112 septi cartilaginei, 1080 spinosus, 49 slyloideus, 189, 192 OS metacarpale III, 203 temporalis, 109 trochlearis, 242 tubarius, 94, 1138 U7icinatus, 98, 1337 Processus vaginalis ' peritonaei, 1379 processus pterygoidei, 95 vermiformis, 1298 xiphoideus, 157 zygomaticus, 104 Profunda arteries, 642, 643, 651, 689 Prominentia canalis facialis, 1126 laryngea, 1164 spiralis, 1144 styloideae, 1125 Promontorium, 58, 1126 Promontory of sacrum, 58 of temporal bone, 85 of tympanum, 1126 Pronator quadratus muscle, 478 teres, 472 aiDplied anatomy of, 473 surface form of, 496 Pronephric duct, 1420 tubules, 1420 Pronephros, 1420 Pro-otic portion of temporal bone, 88 Prosencephalon, 902 Prtfsiaia, 1391 fades anterior, 1393 posterior, 1391 Prostate gland, 1391 applied anatomy of, 1395 arteries of, 1395 development of, 1426 lymphatics of, 796, 1395 nerves of, 1395 veins of, 1395 Prostatic ducts, orifice of, 1367 plexus of nerves, 1077 sinus, 1367 Pcosthion, 146 Proton of cerebellum, 855 Protuberance, occipital, 70, 72, 131 Protuberantia nientalis, 116 occipitalis externa, 70 interna., 72 Prussak, pouch of, 1134 Psalterium, 944 Pseudocele, 934, 945 Psoas magnus muscle, 504 applied anatomy of, 505 parvus muscle 504 Pterion, 76, 133, 146 ossicle, 80, 144 Pteriotic portion of temporal bone, 88 Pterygoid artery, 601 canal, 130 depression, 118 fossa, 94, 109 muscles, 379, 380 nerves, 987, 988 notch, 94 plates, 94 plexus of veins, 712 processes of sphenoid bone, 94 ridge, 92, 132 tubercle, 95 Pterygomandibular ligament, 376 region, muscles of. 379 Pterygomaxillary fissure, 134 Pterygopalatine artery, 602 canal, 92, 1.30, 134 groove, 110, 111 nerve, 986 Pterygospinous foramen, 383 hgament, 382 Pubes, 1159 Pubic arch, 217 artery, 681 bones, articulation of, 294 ligaments, 294 vein, 743 Pubis, 212 1490 INDEX Pubis, angle of, 212 body of, 212 crest of, 212 ramus of, 213, 214 spine of, 212 Pubococcygeus muscles, 452 Pubofemoral ligament, 323 Puboprostatic ligament, 450 Puborectalis muscles, 452 Pubovesical space of Retzius, 1360 Pudendal nerve, inferior, 1055 plexus of nerves, 1060 Pudendum muliebre, 1415 Pudic artery, accessory, 675 external, 6S9 internal, 674, 676 nerves, 1061 veins, internal, 744 Pulmonary artery, 574 applied anatomy of, 575 left, 575 opening of, 557 right, 575 circulation, 548 heart, 553 nerves, 1007 plexus of nerves, 1005, 1007, 1073 sinuses of Valsalva, 559, 561 valve, 559 veins, 559, 707 applied anatomy of, 708 Pulmones, 1188 fades costalis, 1189 mediasiinalis, 1189 lobiis inferior, 1192 medium, 1192 superior, 1192 marge anterior, 1190 inferior, 1190 posterior, 1190 Pulp cavity, 1212 chamber, 1212 Palpa dentis, 1212 lienis, 1445 Pulvinar, 904, 910 Puv^ta lacrimalia, 1116 Punctum lacrimale, 1113, 1116 Pupil of eve, 1096 Pupilla, 1096 Pupillary margin, 1097 Purldnje fibers, 357, 565 Purkinjean cells, 892 Putamen, 948 Pyloric artery, 661 applied anatomy of, 662 canal, 1272 glands, 1278 ligaments, 1274 orifice, 1271 plexus of nerves, 1076 sphincter, 1273 valve, 1273 vein, 754 vestibule, 1272 Pj'ramid of medulla oblongata, 863 of vestibule of ear, 1137 Pyramidal cells, 952 lobes, 887 tract of brain, 900 of cord, crossed, S3S direct, 839 PjTamidalis muscle, 435 nasi muscle, 372 surface form of, 380 Pyramides [medullae oblongatae], 863 renales [Malpighii], 1350 Pyramido-olivary groove, 863 Pyramis veslibuli, 1137 Pyriformis muscle, 517 bursa of, 517 fascia of, 448 Q Quadrate lobes of brain, 886 of liver, 1324 Quadratus femoris muscle, 520 bursa of, 521 lumborum muscle, 439 fascia covering, 439 menti muscle, 374 tubercle of, 224 (note) Quadriceps extensor muscle, 509 applied anatomy of, 512 surface form of, 543 tendons of, 512 Quadrigeminal bodies, 894, 897 Quadrilateral muscles, 358 Quiet respiration, 423 R Radial artery, 644 applied anatomy of, 646 surface marking of, 646 carpal arteries. 647 fossa, 182 nerve, 1038 recurrent artery, 646 region, muscles of, 479, 489 veins, 730 Radialis indicis artery, 647 Radiate fissures, 920 Radiatio callosi, 933 Radii lentis, 1107 Radiocarpal articulation, 314 Radioulnar articulation, 310 inferior, 312 middle, 311 superior, 310 applied anatomj' of, 311 surface form of, 311 surface form of, 314 synovial membrane of, 313 ligaments, 312 region, anterior, muscles of, 472 applied anatomj' of, 478 posterior, muscles of, 480 applied anatomy of, 485 Radius, 190 applied anatomy of, 192 oblique line of, 191 shaft of, 191 sigmoid cavity of, 192 , surface form of, 192 Radix arcus vertebrae, 48 dentis, 1204 linguae, 1217 mesenterii, 1263 nasi, 1079 penis, 1388 pili, 1159 puhnonis, 1193 unguis, 1156 Rami calcanei mediales, 703 perforantes anteriores [arcus plantaris], 704 posteriores [arcus plantaris], 704 [venae mammariae internae], 734 sternales [venae mammariae in- ternae, 734 Ramus carpens dorsalis [arteria radialis], 647 of cerebellum, 888 communieans [arteria nulricia tibiae], 703 episyhdan, 917 hjTJOsylvian, 917 inferior ossis ischii, 212 pubis, 213 of ischium, 212 of mandible, 117 plantaris profundus, 700 Ramus, presylvian, 917 of pubis, 212, 213 subsylvian, 917 superficialis [arteria plantaris medialis], 703 superior ossis pubis, 212 Ranine artery, 591 vein, 715 Ranvier, constrictions of, 811 nodes of, 811 Raphe, 872 palati, 1202 palpebralis lateralis, 367, 1114 ■pterygomandihularis, 376 scroti, 1372 Receptaculum chyli, 771, 772 Recess, elliptical, 1137 epitympanic, 1125 spheno-ethmoidal, 140 spherical, 1137 Recessus duodenojejunalis, 1266 epitympanicus, 1125 ileocecalis inferior, 1267 superior, 1266 intersigmoideus, 1267 lienalis, 1259 membranae iympani anterior, 1134 posterior, 1134 superior, 1134 nasopalaiinus, 1083 pharyngeals, 1230 pinealis, 906 pyriformis, 1163, 1233 retrocecalis, 1267 sacciformis, 308, 313 sphenoethmoidalis, 140, 1082 suprapinealis, 908 utriculi, 1140 Rectal valves, 1310 Recti muscles, 370 Rectococcygeal muscles, 1310 Rectouterinus muscle, 1408 Rectovaginal fold, 1407 pouch, 1256, 1362, 1407 Rectovesical fascia, 1361 fold of peritoneum, 1256, 1361 muscle, 1362 pouch of peiitoneum, 1255, 1361, 1362 Rectum, 1306 ampulla of, 1308 lymphatic vessels of, 794 relations of, 1308 Rectus abdominis muscle, "433 surface form of, 439 capitis anticus major muscle, 400 minor muscle, 400 lateralis muscle, 400 posticus major muscle, 414 minor muscle, 414 femoris muscle, 510 applied anatomy of, 512 surface form of, 543 sheath, 434 Recurrent artery, radial, 646 tibial, 698 ' ulnar, 650 Red nucleus, 898 Reil, island of, 925 Reissner, membrane of, 1144 Remak's fibers, 812 Renal arteries, 665 columns, 1349 corpuscles, 1350 fascia, 1348 impression of liver, 1321 papillse, 1349 plexus of nerves, 1008, 1075 sinus, 1349 veins, 751 zone of Hyrtl, exsanguinated, 665, 1353 Renes, 1343 INDEX H'Jl Rcncs cxtrcmilnx inferior, Ki-18 .s»;j..r/-»-, Ki-lS fiinrs aiilrrinr, lS4:i /loslrriur. V.Ur:, iiiiprr.sKni iiiiixi-ularis, 1347 n,nni„ lnl.n,l,s. 1347 nn,r„lli.-:. I.MS /»/Kta ,/;6njsa, 1349 Reproductive organs, female, 1397 male, 1371 Kesiiiration, forced, 423 mechanism of, 422 organs of, 1163 quiet, 423 Respiratory bronchiole?, 1195 cpitheUum, 1195 nerves of Bell, 1024, 1029 Restir,,rm IhhIv, S73 ;fr,sY/x, S(iL'. MU Rch' artf rinsiini rutaiiciiin, 1156 siihpapiUarr, 1156 vcnoswn, 1156 canalis hypofjlossi, 727 carpi dorsalc [ay-teria radialis], 647 [arteria ulnaris], 651 volar e [arteria radialis], 647 foraminis ovalis, 727 testis, 1380 venosum. dorsale ijianus, 729 pedis cutaneum, 739 plantare cutaneum, 739 Retia mirabilia, 573 Reticular formation of spinal cord, 830 laver of skin, 1154 Retina, 1100 applied anatomy of, 1111 central artery of, 613 layers of, 1101 nerve fibers of, 1101 supporting framework of, 1104 yellow spot of, 1100 Relinneula cutis. 1150, 1430 Retinaculum of capsular liga- ment of hip, 322 musculi peronaeorum inferius, 537 superius, 537 patellae laterale, 331, 510 mediate,, 331, 511 Retrahens aurem muscle, 366 Retroaortic lymph nodes, 789 Retrocecal fo^sa, 1267 Retroduodonal fossa, 1266 Retroperitoneal fossae, 1265 Retropharyngeal lymph nodes, 776 space, 384, 1229 Retrorectal space, 1308 Retzius, brown stria of, 1210 fundiform ligament of, 536 pubovesical space of, 1360 Rliinencephalon. 926 Rhodopsin, 1100 Rhombencephalon, 861 Rhomboid impression, 171 ligament, 296 Rhomboidal fossa, 865 Rhomboideus major muscle, 407 surface form of, 416 minor muscle, 407 surface form of, 416 Ribs, 161 applied anatomy of, 167 articulations of, with vertebras, 282 cer'\'ical, 53, 64, 167 common characters of, 162 false, 161 floating, 161 peculiar, 163 true, 161 tubercle of, 162 Ribs, verd'hral, 161 veil.hn.rl Iial, 161 vri1,l.rn^l,rn;,l, 161 Ridel', lol.r (,l liver, 1320 Rider's hone, 229 Ridge, crucial, 71 gluteal, 224 mylohyoid, 117 pterygoid, 92, 132 superciliary, 77, 79, 134 supracondylar, 180 supraorbital, 135 temporal, of frontal bone, 78 of parietal boue, 74 trapezoid, 109 Rima ijlottidis, 1171 pars inlercartilaginea, 1171 interniemhranacea, 1171 oris. 1199 palprebranwi, 1112 pudcndi, 1415 Ring muscle of Mi'iller, 1090 Ripa, 903 Risorius muscle, 377 Rivinus, duct of, 1220 notch of, 1130 Rivus lacrinialis, 1113 Rods of Corti, 1145 Rolaudic angle, 918 Rolando, fissure of, 918 Rosenmiiller, fossa of, 1229 lymph nodes of, 780 organ of, 1401 Rostral fissure, 920 Rostrum corporis callosi, 934 of corpus callosum, 934 of sphenoid, 92 spheiioidalis, 92 Rotary joint, 205 Rotation in joints, 267 Rotatores spinae muscle, 413 Rubrospinal tract of cord, 839 Rubrum, 898 Rudiniontal third trochanter, 224 Rudimcntum processus vaginalis, 1379 Rugae vaginales, 1414 Ruysch, membrane of, 1093 Sac, lacrimal, 1116 Saccule, 1141 laryngeal, 1171 of lungs, 1195 Sacculi, 1310 Sacculus, 1141 Saccus lacrimalis, 1116 Sacral arteries, 669, 678 canal, 61 cornua, 59 foramina, 59 groove, 60 Ivmph nodes, 788 nerves, 1019 divisions of, 1019, 1051 nucleus of spinal cord, 833 plexus of ner\-es, 1053 veins, 744, 748 vertebra, 58 Sacrococcygeal ligaments, 293 Sacrogenital folds, 1257 Sacroiliac artieidation, 290 surface form of, 290 ligaments, 290 Sacrosciatic foramen, 292 great, 211 lesser, 211 ligaments, 291, 292 notch, 210, 211 Sacrouterine ligaments, 1407 Sacrovertebral angle, 58 Sacrum, 58 Sacrum, .-dii of, 01 articiiliilionsof, 01, 290. 292 dilTirii between mule unci rcmale, 01 promontory of, 58 variations in, 01 Saddle-joint, 204, 265 Sagittal axis, 108H planes of body, 34 sinus, 74, 124, 721 sulcus, 72, 78 .suture, 121 Salivary glands, 1223 applied anatomy of, 1229 artcrie-s of, 1227 developnwnl of, 1227 nerves „f, 1227 surface form of, 1227 veins of, 1227 Salpingopalatine fold, 12.30 Salpingopharyngeal fold, 1230 Sal|)ingopharyngeus muscle, 399 .Sanlorini, cartilage of, 1100 caruncula of, 1287 duct of, 1340 fissures of, 1122 Saphenous nerves, 1050, 1057 opening, .TOS veins. 740, 741 Sarcolemma, 356 Sarcomere, ."^56 Sarcoplasm, 356 Sarcostj'le, 356 Sarcous elements of muscle, 350 Sartorius muscle, 508 surface form of, 543 Scala tympani, 1140 vcstibuH, 1140 Scalenus anticus nuiscle, 401 mcdius niiisclr, 101 posticus ITlU^clr. 402 Scalp, l\'nij»hatic \'eesels of, 776 skin of, 363 Scapha, 1120 Scaphoid, articulation of astraga- lus with, 340 of ealcanre- and, 348 witli cuLoid, 350 with cuneiform, 349 bone of foot, 240 of hand, 196 fossa, 94, 130, 1120 Scapula, 172 applied anatomy of, 178 head of, 176 ligaments of, 299 neck of, 176 anatomical, 178 siu'gical, 17l-niv, 1245 Soiiii -iiiL', ■jaii!J:Uon of, 896 Space, cijidural, 843 of Fontana, 1097 intercostal, 155 intornvdintc, of ilium, 210 illlrv|.lrur:il, 1185 lli.Uir,iip:il, 202 of Xu.'l, U 17 perilymph, 1136 popliteal, 691 retropharyngeal, 384 semilunar, of Traube, 1280 subarachnoid, 845 subdural, 845 suprasternal, 383 Spaiia arwuli iridis [Fonlanae], 1092, 1097 interolobtilares, 1211 interossea metacarpi, 202 zonularia, 1106 Spatium intercostale, i^o perichoroideale, 1090 suprasternale, 383 Speech tract, emissary, 957 Spermatic arteries, 665, 1376 canal, 437, 1375 cord, 437, 1375 arteries of, 1376 lymphatics of, 1377 nerves of, 1377 veins of, 1377 fascia, external, 427, 1374 internal. 437 nerve, 1047 plexus of nerves, 1076 of veins, 750 veins, 750 Spermatocytes, 1381 Spermatogonia, 1380 Spermatozoa, 1381 Spermia, 1381 Sphenoetlimoidal recess, 140 Sphenofrontal suture, 122 Sphenoid bone, 89 rostrum of, 92, 130 Sphenoidal fissure, 93, 126, 134 foramen, structures transmit- ted by, 126 nerves, 990 process, 1080 of palate bone, 112 sinuses, 91, 139 spine, 92 turbinated processes, 91, 95, 138 Sphenomaxillary fissure, 109, 134, 137 fossa, 109, 134 Sphenopalatine foramen, 112, 134, 138, 139 ganglion, 982, 984, 986 nerve, 983 notch, 112 Sphenoparietal sinuses, 725 suture, 122 Spherical recess, 1137 Sphincter ani muscles, 453, 454 muscle, 35S Sphincter, ii.\lr\-. fiS7 intpriiiil iliiir aiir-rv, 679 plantar -M^^-rv-.. 704 popliteal artery, 693 posterior tibial artery, 701 radial artery, 646 Surface marking of subclavian artery, 626 of superficial palmar arch, 652 of trigeminal nerve, 990 of ulnar artery, 649 relations of liver, 1.334 Surf-line of aorta, 580 Surgical anatomy. See Applied anatomy, neck of humerus, 178 Suspensory ligament of axilla, 456 of chtoris, 1418 of Cooper, 456 of eye, 1087 of lens, 1106 of liver, 1325 of malleus, 1133 of mamma, 456 of ovaries, 1398 of penis, 138.8 of Treitz, 1285 muscle of duodenum, 1285 Sustentaculmn lienis, 1264 tali, 242 Sutura, 263 coronalis, 121 dentata, 264 frontalis, 121 frontoethmoidalis, 122 frontolacrinialis, 122 frontomaxillaris, 122 hxirmonia, 264 intermaxillaris, 135 internasalis, 135 lambdoidea, 121 limbosa, 264 nasofrontalis, 122 nasoniaxillaris, 135 occipito7nastoid-ea, 122 parietomastoidea, 122 sagitlalis, 121 serrata, 264 sphenofrontalis, 121 spherwparietalis, 122 sphenosquamosa, 122 squamosa, 264 vera, 264 zygomaticofrontalis, 121 Sutural bones, 144 ligament, 121, 259 membrane, 263 Sutures, 121 basilar, 122 coronal, 76, 121 false, 264 frontal, 121 fronto-ethmoidal, 122 frontolacrimal, 122 frontomalar, 121 frontomaxillary, 122 frontoparietal, 121 frontosphonoidal, 121 intermaxillary-, 135 internasal, 135 interparietal, 121 lambdoid, 73, 76, 121 lateral, 121 mastn-neeipiliil, 73, 122 nasotronlal. 122 nasomaxillar.i,-. 135 neuroeentrali 63 obliteration of, 144 occipitoparietal, 121 petro-occipital. 73 petrosphenoidal, 131 petrosquamous, S4 sagittal, 76, 121 sphenofrontal, 122 sphenoparietal, 122 squamoparietal, 122 squamosphenoidal, 122 Sutures, transverse, 122, 139 facial, 121 true, 264 zygomaticofrontal, 122 Sweat glands, 1161 Sylvian fissure and its rami, 916 development of, 917 veins, 720 Sympathetic nerve sy.stem, 1063 Symphysis of mandible, 115 ossiuni pubis, 294 sacrococcygea, 292 Synarthrosis, 263, 266 Synchondrosis, 264 sphenooccipitalls, 122 sternalis, 157 Syndesmology, definition of, 34 Syndesmosis tibiofihularis, 341 Syndosmo-odontoid joint, 274 Synergic muscles, 359 Synovia, 261 Synovial burss, subcutaneous, 262 subtendinous, 262 thecal, 262 ligaments, 262 membrane, 259, 261 of acromioclavicular articu- lation, 298 of ankle-joint, 345 articular, 261 of articulations of carpus, 317 of elbow-joint, 308 of shoulder-joint, 303 bursal, 262 of calcaneo-astragaloid ar- ticul.ation, 347 of calcaneocuboid articula- tion, 348 of carpometacarpal articula- tions, 318 of costocentral articulations, 283 of costosternal articulations, 288 of flexor tendons at wrist, 486 of hip-joint, 326 of inferior tibiofibular artic- ulation, 342 of knee-joint, 336 in metatarsal joint, 353 of radioulnar articulations, 313 of sternoclavicular articula- tion, 296 of superior tibiofibular artic- ulation, 341 in tarsal joint, 353 of tarsometatarsal articula- tion, 352 of temporomandibular ar- ticulation, 280 vaginal, 262 pads, 262 .sheath, 262 villi, 262 Systemic circulation, 548 veins, 708 Systole, auricular, 565 ventricular, 565 TABLE.S of skull, 36 Tactile corpuscles, 816 Taenia coli, 1310 libera, 1310 mesocolica, 1310 omentalis, 1310 pontis, 895 semicircularis, 937, 938 thalami, 903 INDEX 1497 Taeniae cnli, 1296 Talus, 244 Tapetum of corpus callosum, 933, 938 Tarsal arch, inferior, 612 superior, 612 artery, 699 articulations, syno^^al mem- brane in, 353 transverse, 349 bones, development of, 254 glands, 1114 ligaments, 366 muscles, 369, 370 nerve, 1059 plates, 1113 Tarsometatarsal articulations, 351 synovial membrane of, 352 Tarsus, 239 articulations of, 347 Taste buds, 1149 nerves of, 1149 organs of, 1148 Tawara, node of, 564 Tectospinal tract, 900 Teeth, 1204 auditory, 1144 bicuspid, 1207 calcification of, 1216 canine, 1206 cementum of, 1212 chemical composition of, 1210 deciduous, 1205 dentin of, 1211 development of, 1212 eruption of, 1216 enamel of, 1210 ivory of, 1211 milk, 1205 molar, 1207 permanent, 1206 premolar, 1207 stomach, 1207 structure of, 1209 temporary, 1205 Tegvien tyynpani, 84, 1125 Tegmental part of pons, 876 tract, 900 Tennunliim, S96, 897 of midbrain, 897 fiber tracts in, 898 nucleus of, 898 Tela choroidea, 867, 971 superior, 940 ventriculi quarli, 865, 867, 972 tertii, 971 subcutanea, 1154 Telencephalon, 902 pars optica hypothalami of, 908 Telodendria, 811, 815 Temporal arteries, 597, 598, 600, 601, 617 bone, 80 crest, 74 diploic veins, 718 fascia, 378 fossa, 92, 132 lobe, 924 fissures of, 924 gyres of, 924 muscle, 378 surface form of, 380 nerve from facial, 998 from internal maxillary, 987 from superior maxillary, 983 ridge of frontal bone, 78 of parietal bone, 74 veins, 712 wings of sphenoid, 92 Temporofacial nerve, 996 Temporomalar filaments, 109 foramen, 109 Temporomalar nerve, 983 Temporomandibular articula- tion, 133, 279 applied anatomy of, 281 surface form of, 281 synovial membrane of, 280 region, muscles of, 377 Tempbromaxiilary vein, 712 Tcmporopontile tract, 900, 950, 957 Tcmh, 360 Achillis, 530 l^ursa of, 530 crilcancua [ArhilKs], 530 ocuh, 366, 367 Tendons, 360 of diaphragm, 419 flexor, fibrous sheaths of, 539 at wrist, synovial mem- branes of, 486 of Lockwood, 370 of quadriceps extensor muscle, 512 of triceps muscle, 470 of Zinn, 370 Tenon's capsule, 371 Tensor fasciae femoris muscle, 508 surface form of, 543 palati muscle, 397 tarsi muscle, 367 tympani, canal for, 1127 Tenth nerve, 1003 thoracic verteljra, 54 Tentorial liiatus, 847 sinus, 732 Tentorium cerebelli, 966 Teres major muscle, 466 surface form of, 495 minor muscle, 466 Terma, 847, 908, 909 Terminal arteries, 573, 618 fibrilla;, 816 Testes, 1371, 1377. ,See also Testicle, applied anatomy of, 1383 descent of, 1424 efferent ducts of, 1380 extremiius inferior, 1378 superior, 1378 fades lateralis, 1378 Tnedialis, 1378 lymphatic vessels of, 796 margo anterior, 1378 posterior, 1378 parenchyma of, 1380 structure of, 1380 tunica albiiginea, 1380 dartos, 1373 fibrosa, 13S0 vaginalis communis, 1374 propria, 1374, 1379 lamina parietalis, 1379 visceralis, 1379 vascvlosa, 1380 Testicle, 1371 coverings of, 1372 tunics of, 1379 Thalamencephalon, 902 Thalami, 902 Thalaraofrontal fibers, 950 Thalamostriate fibers, 950 Thebesius, valve of, 555, 70S veins of, 709 Theca folliculi, 1399 Thecal synovial bursa, 262 Thenar eminence, 486 Thigh, fascia of. 505 muscles of, 505 Third nerve, 976 occipital nerve, 1017 ventricle, 907 Thoracic aorta. 653 applied anatomy of, 654 arteries, 638, 639 Thoracic cardiac ner\'C 1007 curve of vertcl)rul co!\itnii, flO duct, 771 applied anatomy of, 771 tributaries of, 772 nerve, 1018 anterior, 1030 divi.sions of, lOlK, 10 10 long, 1029 posterior, 1029 portion of gangliatcd cord, 1070 region, fasciie of, 455 muscles of, 455, 401 vein, long, 732 vertebra.', 53 \-i3ccra, lymphatic vessels of, 802 wall, lymphatic vessels of, 798 Thoracicoepigastric vein, 732 Thoracicolunibar nerves, 1043 Thoracoabdominal intercostal nerves, 1043 Thorax, 154 applied anatomy of, 167 fascia; of, 416 inlet of, 155 l.vmph nodes of, 798 muscles of, 416 surface form of, 166 veins of, 727 Thymic artery, 582, 1442 Thymus gland, 1440 applied anatomy of, 1442 arteries of, 1442 lymphatic vessels of, S02, 1442 nerves of, 1442 veins of, 1442 Thyroarytenoid ligaments, 1170 muscles, 1173 Thyroepiglottic ligaments, 1167, 1169 ThjToepiglotticus muscle, 1173 Thvroglossal duct, 1219 Thyrohyals, 154 Thyrohyoid ligaments, 1167 membrane, 1164, 1167 muscle, 387 nerve, 1011 Thyroid artery, inferior, 629 .superior, 589 axis, 628 body, 1435 plexus of veins on. 734 cartilage, 11G3 foramen, 213 gland, 1435 acces.sory, 1436 applied anatomy of, 1438 arteries of, 1437 lymphatics of, 1438 nerves of, 1438 structure of, 1436 veins of, 1438 nerve, 1069 plexus of, 1069 vein, inferior, 734 middle, 716 superior, 715 ThjToidea ima artcr.v, 582 vein. 735 Tibia, 231 crest of, 234 internal malleolus of. 235 nutrient artery of, 702 foranu'U of, 234 obliriue line of, 234 poi>litcal notch of. 233 spine of, 233 structure of, 235 surface form of, 236 tubercle of, 233 Tibial artery, anterior, 696 1-1!)8 INDEX itcry, anterior, applied ;iii!ifoniy of, 697 ■.■iirn-iit, BOS irfarr ni:ii-kiu«of, 097 :i|.|'li'-ii :ii]:itoniy of, 701 ri'ciirrciit, 69S surface marking of, 701 bursa, subcutaneous, 330 Ivnipb tir.'Ic. 7S4 M,-n.-, 111,-1,-,. lll.-,7, 1059 TibLili- :inii-u- muscle, 526 \,m>-A ..r. 520 surface form of, 544 Ijosticus muscle, 533 surface form of, 544 Tibiofibular articulations, 340, 3U rejriou, nmscles of, 525, 528 Tiliiotarsal articulation, 342 ligaments, 343 Tifiroid bodies, 809 Tissue, fibroelastic, subendo- thelial, 573 spaces, 767 subarachnoid, 845 Todd and Bowman, trachealis muscle of, 1178 Tomes, graniilar layer of, 1211 socondarv dentin of, 1212 Tongue, 1217 applied anatomy of, 1222 arteries of, 1219 ■development of, 1221 lymphatic vessels of, 777, 1220 mucous membrane of, 1217 muscles of, 393 nerves of, 1221 papilla' of, 1218 veins of, 1219 Tonsilla, 887 ccrehelli, 887 intestinalis, 1292 linfliudls, 1219 palatina, 1230 pharyiiffea, 1230 Tonsillar artery, 593 nerve, 1003 Tonsils. 1230 applied anatomy of, 1233 arteries of, 1231 development of, 1232 lingual, 1219 lymphatics of, 1231 nerves of, 1231 pharyngeal, 1230 tubal, 1128 veins of, 1231 Topographic anatomy, defini- tion of, 33 Topographv, craniocerebral, 962 Torculnr, 72, 12S Hrn.phili, 7_'-l Tvru:i i,il,nir rubrospinalis, 898 solitarius, 880 spinotectalis, 838 spiralis foraminosus, 85, 1139 thalamicus, 838 tectospinalis, 840 Tragi, 1159 Tragicus muscles, 1121 Tragus, 1120 Transinsula fissure, 925 Transorbital fissure, 921 Transparietal fissure, 924 Transprecentral fissures, 920 Transtemporal fissure, 924 gyre, 924 gray substance of, 953 Transversalis capitis muscles, 412 cervicis muscle, 412 fascia, 436 muscle, 432 Transverse aorta, 579 colon, 1303 mesocolon, 1264, 1304 Transversus auriculae muscles, 1121 perinei profundus, 448 sulcus antihelicis, 1121 Trapezium, 876 bone, 198 Trapezius muscle, 404 surface form of, 416 Trapezoid bone, 199 ligament, 298 ridge, 169 Treitz, fossse of, 1265 suspensory ligament of, 1285 Triangle, carotid, 388, 603, 604 of election, 604 He.sselbach's, 437 Lessor's, 591, 1012 of necessitv, 603 of neck, 386, 602, 603, 605 occipital, 388, 605 Petit, 407, 426 Scarpa's, 509, 685 subclavian, 388, 605 submaxillary, 604 suboccipital, 415, 620 suprahyoid, 605 Triangle, suprameatal, 81 Triangular articular disk, 312 fascia, 425, 428 ligament in female, 446, in male, 446 muscles, 358 Triangularis sterni muscle, 417 Triceps extensor cubiti muscle, 470 muscle, 470 applied anatomy of, 471 surface form of, 496 tendon of, 470 Tricuspid orifice, 557 valve, 558 Trifacial nerve, 978 Trigeminal depression, 84 nerve, 978 applied anatomy of, 991 nucleus of, 883 surface marking of, 990 Trigone of bladder, 1367 Trigonum collatcrale, 938 feniorale, 685 fihrosuyn, 562 habenulae, 903, 906 hypoglossi, 866 lumbale, 426 olfactorium, 928, 973 vagi, 866 ventriculi, 938 vesicae, 1365 Trineural fasciculus, 880 Trochanter, greater, 222 bursa of, 327 lesser, 223 major, 222 minor, 223 rudimental third, 224 tertius, 224 Trochanteric bursa, 327 fossa, 223 Trochlea, 182 of femur, 225 humeri, 182 phalangis, 205 of superior oblique muscle, 370 tali, 245 Trochlear fossa, 79 nerve, 977 nucleus, 901 Trochoid, 264, 265 Troeltsch, recesses of, 1134 Trolard, anastomotic vein of, 720 True pelvis, 215 skin, 1153 suture, 264 Trunci lumbales, 772, 789 Truncus corporis callosi, 933 costocervicalis, 633 intestinalis, 772, 789 jugularis, 780 lumbosacralis, 1044 subclavius, 783 sympatheticus, 1066 pars cepholica, 1066 cervicalif-, 1066 sympathici, 1066 thyreocervicalis, 628 Trunk, arteries of, 653 articulations of, 268 fasciae of, 403 muscles of, 403 Tuba audiliva [Eustachii], 1127 pars cartilaginea, 1127 ossea, 1127 interna [Fallopii], 1401 stratwn circulare, 1402 longitudinale, 1402 t^mica mucosa,^ 1402 plicae ampullares, 1402 isthmicae, 1402 tubariae, 1402 muscularis, 1402 serosa, 1402 INDEX \V.)\) TuImI tonsil, 1128 Tube, Eustacliian, 1127 Tuber caicunci, 243 cinereum, 847, 908 frontale, 76 ischiacHcum, 211 innxUhir,. 102 o,t„„i,il,. \:;-l\, 1338 l>" :,l„h TuhL:riil luljfs, 887 Tubercle, adductor, 225 amygdaloid, 939, 948 of calcaneus, 242 Chassaignae's, 68 conoid, 169 of Darwin, 1120 deltoid, 169 distobuccal, 1207 distolingual, 1207 of femur, 224 genial, 117 of ilium, 210 infraglenoid, 175 jugular, 73 lacrimal, 104 of Lower, 557 mental, 116 olfactory, 928, 973 pterygoid, 95 of quadratus, 224 (note) supraglenoid, 176 of tibia, 233 of ulna, 187 zygomatic, 81 Tubercula menlalia, 116 Tuberculum ncusticum, 866, 881 anteriuf!, 50, 904 Ihalai,,;. 904 ,n,r,r:il,n {Dnrwini], 1120 ,;//,./>.(„/, Mil costac, 102 epiglotticum, 1167 inlercondyloideum lateralc, 233 Ttiediale, 233 iniervenosum [Loioeri], 557 jugulare, 73 ma jus, 180 minus, 180 obturatorium anterius, 214 posterius, 214 ossis multanouli majoris, 199 navicidaris, 196 papillare, 1322 phanjii'jcnm, 71 posterius, 51 pubicum, 212 scaleni, 163 sellae, 90 ihyroideum inferius, 1164 superius, 1164 vestibularis, 866 Tuberositas coracoidea, 169 costae II, 165 costalis, 171 deltoidea, 181 glutaea, 224 iliaca, 210 infraglenoidalis, 175 ossis cuboidei, 246 metaiarsalis I, 251 F, 252^ navicularis, 247 radii, 191 sabralis, 60 supraglenoidalis, 176 iiftiac, 233 ulnae, 187 unguiculnris, 205 Tuberosity, bicipital, 191 of femur, 226 of humerus, 180 of ischium, 211 maxillary, 102 of palate bone. 111, 128 of ribs, 162 Tuberosity of scaphoid bono of foot, 247 of tibia, 233 Tuhuirs, pinncphric, 1420 Tu/.k// ,-..7,, i:;mi ,■/.//,.•. ///..,■//, IUSO Tui.i,':! all.iiL'iiir:!. i:;mi l„,ti„l,n,r,n„. lilt (il.l IMS Uncinate (jvre, 925 C/ncu.f, 929 Ungual phalanKcs, 205 Ungues, 1150 margo latcritlis, 1 1 50 lihcr. 1150 ^//>>, 1 1: SOK 357 .„■»/,, Ul.s'.l intima, 573 mucosa lympani, 1134 p/ica incudis, 1134 malleolaris anterior 1134 posterior, 1134 stapedis, 1134 serosa, 1244 /cia sufescrasrt, 1244 vaginalis, 1379 vasculosa, 1380 ocuK, 1092 Tunics of eye, 1089 of testicle, 1379 Turbinated bone, 113 crests, 102, 104, 110 process, middle, 98, 139 sphenoidal, 91, 95, 139 superior, 98 Tiirck's bundle, 957 Turner, intraparietal sulcus of, 922 Twelfth nerve, 1010 thoracic vertebrte, 55 Tympanic arteries, 597, 600, 609 cavity, 1125 membrane, 87, 1128 nerve from facial, 997 from glossopharyngeal, 1002 plate, 131 plexus of nerves, 1002 portion of temporal bone, 87 sulcus, 87, 1122, 1130 TjTiipanohyal process, 88 Tympanum, 1124 appHed anatomy of, 1135 arteries of, 1135 floor of, 1125 mucous membrane of, 1134 muscles of, 1134 nerves of, 1135 ossicles of, 1131 promontory of, 1126 roof of, 1125 veins of, 1135 wall of, anterior, 1127 inner, 1126 outer, 1125 posterior, 1126 Ulna, 185 applied anatomy of, 192 surface form of, 192 Ulnar artery, 648 carpal arteries, 651 groove, 182 nerve, 1036 recurrent arteries, 650 region, muscles of, 492 veins, 729 Umbilical arteries, 570 circulation, 756 ligament, 1361 vein, 764 Umbilicus, 435 Umbo membranae hjmpanae, lldU Unciform hone, 200 process, 200 of ethmoid, 98 I Uncinate fasciculus, 955 Ul. n, - , Uli-lri I n.ii UnslriiH.I mil , Urachns, 1301) Ureteral folds, 1365 orifice, 1305 Ureters, 1356 applied anatomy of, 1358 arteries of, 1358 calices of, 1356 ■ infundibula of, 1356 lymphatic vessels of, 796 muscles of, 1363 nerves of, 1358 pars ahdomiiudis, 1356 petvina, 1356 pelvis of. 1349, 1356 rclalinii.^ ..f. i:'..")(j sirnlu,,, ,xh .„„,„. 1358 tunicii adrcnlilia, 1358 mucosa, 1358 muscularis, 1358 Urethra, arteries of, 676 development of, 1426 female, 1370 lymphatic vessels of, 796 male, 1366 applied ana'tomy of, 1369 bulbous portion, 1369 membranous portion, 1367 penile portion. 1368 prostatic portion, 1366 spongy portion,. 1368 muliebris, 1370 stralum circulare, 1370 lo7igitudinale, 1370 tunica mucosa, 1370 muscularis, 1370 orifice of, 1369 virilis, 1366 pars cavernosa, 1368 metnbranacca, 1367 prostatica, 1366 stratum circidarc, 1369 longitudinale, 1369 tunica fibrosa, 1369 Urethral bulb, 1386 Urinary bladder, 1358 meatus, 1417 organs, 1343 development of, 1420 Ivmphatic vessels of, 796 Uriniferous tubules, structure of, 1.351 Urinogenital organs, 1343 Uterine arbor vitae, 14(28 plexus of nerves, 1077 plrxu-^rs nf veins. 747 Uten«i.r;-I liu:,iiients. 1107 Utonivi-iriil fi.lil. 1407 pourh, IJ.Ml. 1:502. 1 104. 1407 Uterus, 1402 _ abnormalities of, 1408 applied anatomy of. 1411 arteries of. 672, 1410 bieornate, 1408 changes in, at menstrual period, 1408 by pregnancy, 1409 at different ages, 140S folds of, 1406 ligaments of. 1406 l,\-mphatic vessels of, 797. Mil masculinus , 1367 mucous membrane of, 1410 nerves of, 1411 Irmica viucosa, 1410 1500 uterus lunica muscularis, 1409 stratum mucosum, 1409 subserosum, 1409 supravasculare, 1409 vasculare, 1409 serosa, 1409 veins of, 747, 141 1 Utricle, 1140 Utricular nerve, 1000 Utriculoampullar nerves, 1000 Utriculus, 1140 prostat'icus, 1367 Uvea, 1098 UviUa, 1203 palatina, 1203 vermis, 887 vesieae, 1365 Uvular lobes, 887 Vagina, 1413 arteries of, 672, 1415 applied anatomy of, 673 lymphatic vessels of, 797, 1415 mucosa intertubercularis, 303 tendinis, 262 mucous membrane of, 1414 musculus recti abdominis, 434 nerves of, 1415 'paries anterior, 1413 posterior, 1413 relations of, 1414 rugous columns of, 1414 tunica mucosa, 1414 muscularis, 1414 veins of, 747, 1415 vestibule of, 1416 Vaginal bulb, 1420 arteries of, 1420 nerves of, 1420 plexus of nerves, 1077 of veins, 747 process of sphenoid, 92, 94 syno'i'ial membrane, 262 Vagus nerve, 1003 applied anatomy of, 1008 nucleus, 880 Valentin, ganglion of, 984 Vallecula, 884, 1167 syhdi, 917 Valleculae, 1167 Vallum unguis, 1156 Valsalva, sinuses of, 576 pulmonary, 559, 561 Valve, anal, 1310 aortic, 561 bicuspid, 561 coronary, 555, 708 Eustachian, 555 of Gerlach, 1299 of Guerin, 1369 of Hasner, 1117 of heart, action of, 565 development of, 760 Houston's, 1310 ileocecal, 1.301 of Kerkring. 1289 mitral, 561 of Morgagni, 1310 pulmonary, 559 pyloric, 1273 rectal, 1310 of Thebesius, 555, 708 tricuspid, 558 venous, 758 of Vieussens, 891 Valvula, 884, 891 bicuspidalis, 561 cuspis anterior, 561 posterior, 561 pylori, 1273 spiralis [Heisteri], 1333 tricuspidalis, 558 cuspis anterior, 558 iNi>i:x Valvula tricuspidalis cuspis medi- alis, 558 posterior, 558 venae cavae inferioris [Eu^- tachii], 556 Valvulae conniventes, 1289 fossa navicularis, 1369 semilunares aortae, 561 arteria pulmonalis, 559 sinus coronarii [Thehesii], 556 Valvuli coli, 1301 labium inferius, 1301 superius, 1301 Vas deferens, 1383 ampulla of, 1383 arteries of, 671 lymphatic vessels of, 797 efferens, 768 Vasa aberrantia, 641 afferentia, 768 brevia arteries, 662 intestini tenuis, 663, 1293 Vascular papillse, 1154 system, changes in, at birth, 571 in fetus, peculiarities of, 568 Vascularization of bone, 45 Vasomotor nerve fibers, 813 Vastus externus muscle, 510 surface form of, 543 internus muscle, 510 surface form of, 543 Vater, ampulla of, 1334 corpuscles of, 816 Vegetative muscle, 355 Vein or Veins, 705 of abdomen, 739 accessory cephalic, 731 adventitia of, 706 anastomosis of, 706 between portal and sys- temic, 754 anastomotic, posterior, 720 of Trolard, 720 angular, 710 of auditory canal, 1123 auricular, 712 axillary, 731 azygos, 736 basilar, 720 I basilic, 730 of bile ducts, 1334 of bladder, 1365 of bodies of vertebrte, 738 brachial, 731 brachiocephalic, 733 bronchial, 737 cardiac, 708 anterior, 556 of cecum, 1300 cephalic, 730, 731 cerebellar, 720 cerebral, 719 cervical, 717 choroid, 720 companion, 731 coronary, 709 costoaxillarj', 732 cystic, 754 definition of, 548 development of, 763 digital, 728, 739, 741 of diploe, 718 dorsal, of penis, 746 of dura of brain, 967 dural, 719 emissary, 727 epigastric, 742 extravertebral, 737 of face, exterior of, 710 facial, 710, 712 of Fallopian tube, 1402 femoral, 742 of fingers, superficial, 728 of foot, 739, 741 frontal, 710 Vein or Veins, of Galen, 720, 942 of gall-bladder, 1334 gastric, 753 gastroepiploic, 753 of globe of eye, 1109 gluteal, 743 of hand, 728 of head, 710 of heart, 565 hemorrhoidal, 744 hepatic, 751 histology of, 706 iliac, 742, 743, 747 iliolumbar, 748 innominate, 733 intercostal, 735, 736 interdigital, 739 interosseous, 731, 739 intervertebral, 738 intima of, 706 intralobular, 751 intravertebral, 738 jugular, 713, 714 of kidneys, 1354 of large intestine, 1312 laryngeal, 735 of larynx, 1174 of left ventricle, 709 lingual, 715 of Uver, 1328 of lower extremity, 739, 741 lumbar, 749 ascending, 736, 749 of mammary gland, 734, 1432: marginal, 709 maxillary, 712 media of, 706 median, 721, 730 of medulla oblongata, -721 membrana tympani, 1131 meningeal, 719 meningorachidian, 843 mesenteric, 753 metatarsal, 741 nasal arch of, 710 . fossa;, 1085 nasofrontal, 725 of neck, 710, 713 of nose, 1081 oblique, of Marshall, 550, 709' obturator, 744 occipital, 713 oesophageal, 735, 1239 ophthalmic, 725 orbital, 712 ovarian, 751, 1401 palmar, 731 pancreatic, 753, 1341 pancreaticoduodenal, 753 parietal, development of, 764 of parotid gland, 1225 parumbilical, 754 of pelvis, 739 of penis, 1390 pharyngeal, 715 phrenic, 734, 751 of pia of brain, 972 of pinna of ear, 1121 plantar, 741 of pleura, 1185 plexus of, of toot, 739 of hand, 729 hemorrhoidal, 745 palmar, 729 pharj'ngeal, 715 pterygoid, 712 spermatic, 750 on thyroid body, 734 uterine, 747 vaginal, 747 vesical, 745 vesicoprostatic, 745 vertebral, 737 of pons, 720 popliteal, 742 INDEX loOl II • r ^'-ins, portal, 751 .„ - , ; i llhlVV, 706 ,..- . i.linni. 764 po-.;'-.a, 74S prtCLirdinal, 764 pronava, 735 of prostate gland, 1395 puliie, 743 I)iulic, 744 piJnionary, 559, 707 pyloric, 754 radial, 730, 731 ranine, 715 renal, 751 sacral, 744, 748 of salivary glands, 1227 saphenous, 740, 741 sciatic, 744 of seminal vesicles, 1385 of skin, 11.56 of small intestine, 1295 spermatic, 750 ■spinal, external, 845 of spinal cord, 739 splenic, 752, 1446, 1449 of stomach, 1279 striate, inferior,_720 subcardinal, 765 suV'cerebellar, 720 subclavian, 732 sul'lobular, 751 of submaxillary gland, 1226 supracardinal,^ 765 supraorbital, 710 suprarenal, 751 sural, 742 sylvian, 720 systemic, 708 temporal, 712 temporomaxillary, 712 of Thebesius, 709 thoracic, long, 732 thoracicocpigastric, 732 of thorax, 727 of thymus gland, 1442 thyroid accessory, 717 inferior. 734 gland, 1438 , ! middle, 716 _ superior, 715 thvroidea ima, 735 tibial, 742 of tongue, 1220 of tonsil, 1231 tracheal, 735, 1179_ of tvmpanum, 1135 ulnar, 729 umbilical, 752, 764 of upper extremity, 727, 728, 731 uterine, 747, 1411 vaginal, 747, 1415 _ vena capitis lateralis, 766 cava, inferior, 748 applied anatomy of, 748 development of, 765 ^ opening for, in dia- phragm, 421 superior, 735 of vermiform appendix, 1300 vertebral, 717, 737 of voluntary muscles, 357 Vdlecula nrehelli, 884 Vnlum, 884 inlerposilum, 884, 903, 934, 940, 971 medullare anterius, 865 postcrius, 866, 888 pnlatinum. 1203 Vena anonyma dexfra, 733 simstm, 734 amformis. 1354 widitivae iniernae, 1148 aurioularis posterior, 712 axillaris, 731 Vena nzyoos, 736 .■,7;< o/;»7(.v lalrnili',, 766 ^ cava inferior, 555, 748 sinistra, 550 superior, 555, 735 cephalica, 730 acc-ess&ria, 731 cerebri magna, 720 cervicalis profunda, 713, 718 choroidea, 720 circumflexa ilium profunda, 742 colica dextrae, 753 media, 753 cordis magna, 709 media, 709 parva, 709 coronaria ventriculi, 753 corporis striati, 720 cystica, 754 dipl- id frontalis, 718 OLyipitulis, 719 temporalis anterior, 718 posterior, 718, 719 epigastrica inferior, 742 facialis anterior, 710 communis, 710 posterior, 712 femoralis, 742 frontalis, 710 gastroepiplmca dextra, 753 sinistra, 753 hemiazygos, 736 accessoria, 737 hcmorrhoidalis media, 744 superior, 753 hypogastrica, 743 iliaca communis dextra, 748 sinistra, 748 externa, 742 intercostalis suprema dextra, 735 sinister, 7.35 jugularis anterior, 713 externa, 713 internxt, 714 posterior, 713 laryngea inferior, 735 linealis, 752 lumbalis ascendens, 736, 737, 749 magna Galeni, 720 maxillaris interna,^ 712 mediana basilica, 730 cephalica, 730 cubiti, 730 mesenterica inferior, 753 superior, 753 nasofrontalis, 710, 725 obliqua atriisinistri [Marshallil 550, 709 obturatoria, 744 occipitalis, 713 ophthalmica inferior, 726 superior, 725 popliiea, 742 portae, 751 . . . - posterior ventriculi simstri, 709 profunda femoris, 742 radialis, 730 renalis, 1354 sacrdlis media, 748 saphena magna, 740 parva, 741 subclavia, 732 supraorbitalis, 710 thoracalis lateralis, 732 thoracoepigastrica, 732 thyreoidea ima, 735 superioris, 715 vertebralis, 717 Fenac anonymac, 733 auditivae internae, 723, 72b to^st'Ziis [iJoscntAaZi], 720 Venae basis vertebrae, 48 brachiales, 731 bronehiales anteriores, 737 postcriares, 737 cerebelli inferiores, 720 supcriores, 720 cerebri, 719 inferiores, 720 internae, 720 media, 720 superiores, 719 comites, 697, 707, 731 cordis, 708 anteriores, 709 minimae, 709 costoaxillares, 732 digiiales communes pedis, 739 dorsales propriae, 728 pedis dorsalis, 739 plantares, 741 volares propriae, 729 gastricae breves, 753 glutaeae inferiores, 744 superiores, 743 hemorrhoidales inferiores, 744 hepaticae, 751 iliolutnbales, 748 intercapitulares, 729, 739 intercostalis, 736 intervertebrales, 737, 738 iniestinales, 753 lingu/xles, 715 lumbales, 749 mammariae internae, 734 rami perforanles, 734 sternales, 734 meningeae, 719 metacarpeae dorsales, 729 metqtarseae dorsales pedis, 741 • plantares, 7il minimae cordis, 555, 559 oesophageae, 735 ovariacae, 751 pancreaticae, 753 pancreaticoduodenales, 753 parumbilicales, 754 pharyngeae, 715 phrenicae inferiores, 751 pulmonales, 707 rectae, 1354 renales, 751 revehentes, 764 sacrales laterales, 744 saphena parva, 1054 sifimoideae, 753 spermaticae, 750 spinales, 739 extemne, 845 suprarenales, 751 ^ thyreoideae inferiores, 734 tibialis anteriores, 742 posteriores, 742 tracheales, 735 uterinae, 747 rorticosae, 725, 1090, 1093 Venous arches of fingers, 728 mesocardium, 549 valves, 758 yenfer anterior 7nuscidus digas- tricu^, 389 inferior musculus omohyoideus, 388 , J. , . posterior musculus d^gastncus, 388 , . , superior musculus omohyoid- eus, 388 Ventral aorta, 761 cerebrospinal tract._840 column of cord, 827 ground bundle of, 840 fissure of medulla oblongata, 861 of spinal cord. 825 horn of spinal cord, 834 lamina of brain, 855 1502 Ventral root of spinal cord, 823 spinal artery, 621 Ventrales Hinderstrangsbundel [Striimpell], 837 Ventricle of brain, Bfth, 934, 945 fourth, 864 choroid plexus of, 867 floor of, 865^ furrows of, 866 roof of, 866 of heart, fibers of, 563 left, 560 right, 557 of larynx, 1170 lateral, 936 left, vein of, 709 primitive, 757 third, 907 Ventricular diastole, 565 septum, 759 systole, 565 VentriciXlus, 1270 dexter, 557 larynqis [Morrjagnii], 1170 lateralis, 936 cornu anterius, 936 inferius, 938 pars centralis, 936 fronioparietalis, 937 paries posterior, 1272 plicae mucosae, 1275 villosae, 1275 quartus, S64 sinister, 560 tela suhmucosa, 1275 tertius, 907 tunica mucosa, 1275 muscularis, 1274 fibrae ohliquae, 1275 stratum circulare, 1274 longitudinale, 1274 serosa, 1274 Ventrolateral fissure of medulla oblongata, 862 Ventromedian fissure of medulla oblongata, 861 Ventroparamedian fissure of spinal cord, 826 Venules, 547, 706 Verga's ventricle, 944 Vermiform appendix, 1298 applied anatomy of, 1302 arteries of, 1300 canal of, 1299 lymphatics of, 1300 mesentery of, 1265 veins of, 1300 Vermis, 885 Verrucae gyri hippocampi, 925 Verumontanum, 1367 Vertebra, 48 cervical, 49 atlas of, 50 axis of, 52 seventh, 53 lumbar, 56 structure of, 62 thoracic, 53 Vertebrae cervicales, 49 coccyjeae, 61 lumbales, 56 prominens, 50, 53, 67 thoracales, 53 Vertebral aponeurosis, 404, 408 artery, 619, 628 applied anatomy of, 620 bodies, ligaments of, 268 canal, 49, 67 column, 48 applied anatomy of, 68 articulations of, 268 applied anatomy of, 278 "with cranium, 275 with pelvis, 289 with ribs, 282 Vertebral column, movements of, 272 surface form of, 67 as a whole, 66 foramen, 49 groove, 67 region, muscles of, 400 ribs, 161 ^ veins, 737 . Vertebrarterial foramen, .30 Vertebrochondral ribs, 161 Vertebrosternal ribs, 161 Vertex of skull, 123 vesicae, 1361 Vesica fellea, 1332 tunica mucosa, 1333 muscularis, 1332 serosa, 1332 urimiria, 1358 stratum externum, 1363 internum, 1363 mciKun, 1363 tunica fibrosa, 1363 mucosa, 1363 tnuscularis, 1363 Vesical arteries, 671, 672 plexus of nerves, 1077 of veins, 745 Vesicles, auditory, 141 optic, 852 otic, 141 Vesicoprostatic plexus of veins, 745 Vesiculae seminales, 1384 tunica adventitia, 1385 vfiucpsa, 1385 Tnuscularis, 1385 Vestibular ganglion, 1000 nerve, 1000 nuclei, 881 Vestibule of ear, 1136 of vagina, 1416 Vestibulospinal tracts of cord, 839, 840 Vestibulum, 1136 macula crihrosa inferior, 1138 media, 1137 superior, 1137 nasi, 1082 oris, 1200 recessus cochlearis, 1137 ellipticus, 1137 sphaericus, 1137 vaginae, 1416 Vestigial fold of Marshall, 550 Vibrissae, 1159 Vicq d' Azvr, bundle of, 905 Vidian artery, 602, 609 canal, 93, 130, 134 nerve, 985, 1066 Vieussens, valve of, 891 Villi intestinales, 1291 of small intestine, 1291 Vincula accessoria tendinum, 476 lingulae cerebclli, 886 iendineae, 476 Visceral lymph nodes, 790, 799 peritoneum, 1244 veins, 763 Visual axis, 1088 purple, 1100 Vitelline circulation, 755 membrane, 1400 veins, 763 Vitellus, 755 Vitreous body, 1105 humor, 1105 table of skull, 36 Vocal cords, 1170 Voice, organs of, 1163 Volar interosseous nerve, 1036 hgament, 319 Volkmann's canals, 39 Voluntary muscles 355 Vomer, 114 Vomer, alae of, 114, 13s Vomerine cartilage, 108 ) Vou Ebner, glands of, 1219 ^^ortices pilorum, 1159 Vulvovaginal glands, 1420 ■ W Wedge bones, 247 Weight of brain, 849 of spinal cord, 821 Wernekink's commissuc, 899 Wliarton's duct, 1225 White blood cells, 40 commissure of spinal cord, 834 line of pelvis, 449 .' ■ substance of spinal cord, 833, 841 Wilder, postoblongata of, SOI- Willis, circle of, 617, 61s Winslow, foramen of, 1258 1" .striiiir liu'ament of. 332 Wirsuii". .im-il of, 1.339 . Wol.ttiun I i"lv, 1421 Womb, 14U2 Worm of cerebellum, 885 Wormian bones, 144 Wrisberg, cardiac gariL'ii'.n "' 1072 cartilage of, 1166 ligament of, 336 , nerves of, 1034 _ I pars intermedia of, 995 Wrist, articulations of, 314 i applied anatomy of, 31a| bursse of, 487 v flexor tendons at, synqviai men"il>ranes of, 4S6 > -joint, arteries of, 315 ^ nerves of, 315 surface form of, 315 syno\ial membrane of, 315 ligaments of, 314 . > ■ Xiphoid appendix, 159 Y-LIGAMENT, 324 Yellow elastic tissue, 2t.l spot of retina, 1100 ZiNN, ligament of, 370 ' zonule of, 1106 i Zona arcuata, 1144 J fasciculata, 1449 . J glomerulosa, 1449 • : granulosa, 1399 orbicularis, 322 pectinata, 1144 pellucida, 1400 radiata, 1400 reticularis, 1449 tecta, 1144 Zone of brain, 855 cornu commissurale [Mariel^ 837 _ . exsanguinated renal, <>< Wyrtt 665 Zonula ciliaris, 1106 Zonule of Zinn, 1106 Zygapophyses, 49 Zygoma, 80 Zygomatic fossa, 92, 1^ >.l . 133 process of malar bone, lO'.i of temporal bone, 80 tubercle, 81 j Zygomaticofrontal sutui|B, "'22. Zygomaticus muscles. 37|( Zymogen granules, 1340 J COLUMBIA UNIVERSITY This book is due on the date indicated below, or uL the expiration of a definite period after the date of borrowing, as provided by the rules of the Library or by special ar- rangement with the Librarian in charge. • DATE BORROWED DATE DUE DATE BORROWED DATE DUE m ■- .^■. 'APR 1 J 1944 H^'ir : '40 4AN 3 1 1i m OCT 1 2 19^ G£fc& ^ <■ ^^ i4S ywyj y o Oa;-' "2 0 W '"''^' 1^ 5 j< 4§j ^AY 2 194' MAY 2 9 IS 41 -■^ yUK 27 ^' 4t 1^: . ^:i44 1 p^ ^: ^ .iA : "-• >- ^ >--. . %d., V ;: '^'t ii 0 ■:a@lb' y V,o.. J 'in® f ^^ ^^' ii m 1 c2e(e3s>Mso 1!1N 2 2 1954