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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(<d
bone and about one and a half inches (-3.75 cm.) behind it. This fossa is deeply
concave in front, convex behind, traversed by grooves which lodge branches of
the deep temporal arteries, and filled by the Temporal muscle.
The Mastoid Portion. — The mastoid portion of the side of the skull is bounded
in front by the anterior root of the zygoma; above, by a line which runs from the
posterior root of the zygoma to the end of the mastoparietal suture; behind and
below by the masto-occipital suture. It is formed by the mastoid and part of the
squamous and petrous portions of the temporal bone; its surface is convex and
rough for the attachment of muscles, and presents, from behind forward, the
mastoid foramen, the mastoid process, the external auditory meatus surrounded by
External auditory meatus
Tympanicplate
Spheno-inii.ciUary fissure
Infra- temporal crest
Pterygo-inaxillary fissure
Hamidar process
Styloid process
Glenoid cavity
Zygomatic process (cut)
External pterygoid plate
Fig. 100. — Left zygomatic fossa.
the tympanic plate, and, most anteriorly, the temporomandibular articulation. The
point where the posterior inferior angle of the parietal meets the occipital and
mastoid portion of the temporal is named the asterion.
The Zygomatic Fossa {fossa infratemporaUs). — The zygomatic fossa is an irregu-
larly shaped cavity, situated below and on the inner side of the zygoma ; bounded in
front by the zygomatic surface of the maxilla and the ridge which descends from its
134 SPECIAL ANATOjMY OF THE SKELETON
malar process; behind, by the posterior border of the external pterygoid plate and
the emiiientia articularis; above, by the pterygoid ridge on the outer surface of the
greater wing of the sphenoid and the under part of the squamous portion of the
temporal ; below, by the alveolar border of the maxilla ; internally, by the external
pterygoid plate; and externally, by the zygomatic arch and ramus of the mandible
(Fig. 100). It contains the lower part of the Temporal, the External and Internal
pterygoid muscles, the internal maxillary artery and vein, and inferior maxillary
nerve and their branches. In its roof are seen the foramen ovale and the foramen
spinosum; on its anterior wall open the posterior dental canals. At its upper and
inner part may be observed the sphenomaxillary and pterygomaxillary fissures.
The sphenomaxillary fissure {fissura orbitalis inferior), horizontal in direction,
opens into the outer and back part of the orbit. It is formed above bj' the lower
border of the orbital surface of the greater wing of the sphenoid; below, by the
external border of the orbital surface of the maxilla and a small part of the palate
bone; externally, by a small part of the malar bone;^ internally, it joins at right
angles with the pterygomaxillary fissure. This fissure permits the orbit to com-
municate with three fossae — the temporal, zygomatic, and sphenomaxillary fossae;
it transmits the superior maxillary nerve and its orbital branch, the infraorbital
vessels, and ascending branches from the sphenopalatine or Meckel's ganglion.
The pterygomaxillary fissure is vertical, and descends at right angles from the
inner extremity of the preceding; it is a V-shaped interval formed by the diver-
gence of the maxilla from the pterygoid process of the sphenoid. It serves
to connect the sphenomaxillary fossa with the zygomatic fossa, and transmits
the internal maxillary artery.
The Sphenomaxillary Fossa (fossa pterygopalatina). — ^The sphenomaxillary fossa
is a small, triangular space situated at the angle of junction of the sphenomaxillary
and pterygomaxillary fissures, and placed beneath the apex of the orbit. It is formed
above by the under surface of the body of the sphenoid and by the orbital process of
the palate bone; in front, by the maxilla; behind, by the anterior surface of the base
of the pterygoid process and lower part of the anterior surface of the greater wing of
the sphenoid ; internally, by the vertical plate of the palate. This fossa has three
fissures terminating in it — the sphenoidal, sphenomaxillary, and pterygomaxillary;
it communicates with the orbit by the sphenomaxillary fissure; with the nasal
fossae by the sphenopalatine foramen, and with the zygomatic fossa by the pterygo-
maxillary fissure. It also communicates with the cavity of the cranium, and has
opening into it five foramina. Of these, there are three on the posterior wall —
the foramen rotimdum above; below and internal to this, the Vidian canal; and
still more inferiorly and internally, the pterygopalatine canal. On the inner wall
is the sphenopalatine foramen, by which the sphenomaxillary communicates with
the nasal fossa; and below is the superior orifice of the posterior palatine canal,
besides occasionally the orifices of the accessory posterior palatine canals. The
fossa contains the superior maxillary nerve and Meckel's ganglion, and the termi-
nation of the internal maxillary artery.
The Anterior Region of the Skull (norma frontalis). — The norma frontalis
forms the face, is of an oval fo*'m, presents an irregular surface, and is excavated
for the reception of two of the organs of sense, the eyes and the nose. It is bounded
above by the glabella and margins of the orbit; below, by the prominence of the
chin; on each side by the malar bone and interior margin of the ramus of the man-
dible. In the median line are seen from above downward the glabella, and diverg-
ing from it are the superciliary ridges, which indicate the situation of the frontal
sinuses and support the eyebrow. Below the glabella is the frontonasal suture,
the mid-point of which is termed the nasion, and below this is the arch of the nose,
1 Occasionally the maxilla and the sphenoid articulate with each other at the anterior extremity of this fissure:
the malar is then excluded from entering into its formation.
THE SKULL AS A WHOLE
135
formed by the nasal bones, and the nasal processes of the maxillae. The nasal
arch is convex from side to side, concave from above downward, presenting in the
median line the intemasal suture (sutura inter nasalis), formed between the nasai
bones, laterally, on either side, the nasomaxillary suture {sutura nasomaxillaris),
formed between the nasal bone and the nasal process of the maxilla. Below the
nose is seen the opening of the apertura pyriformis, which is heart-shaped, with
the narrow end upward, and presents laterally the thin, sharp margins serving
for the attachment of the lateral cartilages of the nose, and in the middle line
below a prominent process, the anterior nasal spine, bounded by two deep notches.
Below this is the intermaxillary suture {sutura intermaxillaris), and on each side
of it the incisive fossa. Beneath this fossa are the alveolar processes of the maxilla
and mandible, containing the incisor teeth, and at the lower part of the median
line the symphysis of the chin, the mental process, with its two mental tubercles,
separated by a median groove, and the incisive fossa of the mandible.
On each side, proceeding from above downward, is the supraorbital ridge,
terminating externally in the external angular process at its junction with the malar,
and internally in the internal angular process; toward the inner third of this ridge
is the supraorbital notch or foramen, for the passage of the supraorbital vessels
Fig. 101. — Anterior aspect of the skull.
and nerve. Beneath the supraorbital ridge is the opening of the orbit, bounded
externally by the orbital ridge of the malar bone; below, by the orbital ridge
formed by the malar and maxilla; internally, by the nasal process of the maxilla
136
SPECIAL ANATOMY OF THE SKELETON
and the internal angular process of the frontal bone. On the outer side of the
orbit is the quadrilateral outer surfact; of the malar bone, perforated by one or
two small malar foramina. Below the inferior margin of the orbit is the infra-
orbital foramen, the termination of the infraorbital canal, and beneath this the
canine fossa, which gives attachment to the Levator anguli oris ; still lower are the
alveolar processes, containing the teeth of the upper and lower jaws. Beneath the
alveolar arch of the mandible is the mental foramen, for the passage of the mental
\Groove for
facial artery
Fig. 102. — Anterolateral region of the skull.
vessels and nerve, the external oblique line, and at the lower border of the bone,
at the point of junction of the body with the ramus, a shallow groove for the
passage of the facial artery.
The Orbits. — The orbits (Fig. 102) are two quadrilateral pyramidal cavities, situ-
ated at the upper and anterior part of the face, their bases being directed forward
and outward, and their apices backward and inward, so that the axes of the two, if
continued backward, would meet over the body of the sphenoid bone. Each orbit
(orbita) is formed of seven bones — the frontal, sphenoid, ethmoid, maxilla, malar,
lacrimal, and palate; but three of these, the frontal, ethmoid, and sphenoid,
enter into the formation of both orbits, so that the two cavities are formed of
eleven bones only. Each cavity presents for examination a roof, a floor, an inner
and an outer wall, four angles, a base, and an apex.
THE SKULL AS A WHOLE 137
The roof {paries superior) is concave, directed downward and slightly forward,
and formed m front by the orbital plate of the frontal; behind, by the lesser wing
of the sphenoid. This surface presents internally the depression for the carti-
laginous pulley of the Superior oblique muscle; externally, the depression for the
lacrimal gland; and posteriorly, the suture connecting the frontal and lesser wing
of the sphenoid.
The floor (paries inferior) is directed upward and outward, and is of less extent
than the roof; it is formed chiefly by the orbital surface of the maxilla; in front, to
a small extent, by the orbital process of the malar, and behind, by the superior
surface of the orbital process of the palate. This surface presents at its anterior
and internal part, just external to the lacrimal groove, a depression for the attach-
ment of the Inferior oblique muscle; externally, the suture between the malar
and the maxilla; near its middle, the infraorbital groove; and posteriorly, the suture
between the maxilla and palate bone.
The inner or medial wall (paries medialis) is flattened, nearly vertical, and formed
from before backward by the nasal process of the maxilla, the lacrimal, os planum
of the ethmoid, and a small part of the body of the sphenoid. This surface pre-
sents the lacrimal groove and crests of the lacrimal bone, and the sutures connect-
ing the lacrimal with the maxilla, the ethmoid with the lacrimal in front, and the
ethmoid with the sphenoid behind.
The outer or lateral wall (paries lateralis) is directed forward and inward, and
is formed m front by the orbital process of the malar bone; behind, bv the orljital
surface of the greater wing of the sphenoid. On it are seen the orifices of one or
two malar canals, and the suttn-e connecting the sphenoid and malar bones.
Of the angles, the superior external is formed by the junction of the upper
and outer walls; it presents from before backward, the suture connecting the
frontal with the malar in front and with the greater wing of the sphenoid behind;
quite posteriorly is the foramen lacerum anterius, or sphenoidal fissure, which
transmits 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. The
superior internal is formed by the junction of the upper and inner wall, and pre-
sents the suture connecting the frontal bone with the lacrimal in front and with
the ethmoid behind. The point of junction of the anterior border of the lacri-
mal with the frontal has been named the dacryon. This angle presents two fora-
mina, the anterior and posterior ethmoidal foramina, the former transmitting the
anterior ethmoidal vessels and nasal nerve, the latter the posterior ethmoidal vessels.
The inferior external, formed by the junction of the outer wall and floor, pre-
sents the sphenomaxillary fissure, which transmits the superior maxillary nerve and
its orbital branches, the infraorbital vessels, and the ascending branches from the
sphenopalatine or Meckel's ganglion. The inferior internal is formed by the
union of the lacrimal bone and the os planum of the ethmoid with the maxilla
and palate bone.
The circumference or base of the orbit, quadrilateral in form, is bounded above
(margo supraorbitalis) by the supraorbital ridge; below (margo infraorbital is),
by the anterior border of the orbital plate of the malar and maxilla; externally,
by the external angular process of the frontal and malar bones ; internally, by the
internal angular process of the frontal and the nasal process of the maxilla. The
circumference is marked by three sutures, the frontomaxillary internally, the
frontomalar externally, and the malomaxillary below; it contributes to the forma-
tion of the lacrimal groove, and presents, above, the supraorbital notch (or fora-
men), for the passage of the supraorbital vessels and nerve.
138 SPECIAL ANA TOMY OF THE SKELETON
The apex is situated at the back of the orbit and corresponds to the optic
foramen,' a short circular canal which transmits the optic nerve and ophthalmic
artery. It will thus be seen that there are nme openings communicating with
each orbit — viz., the optic foramen, sphenoidal fissure, sphenomaxillary fissure,
supraorbital foramen, infraorbital canal, anterior and posterior ethmoidal for-
amina, malar foramina, and the canal for the nasal duct.
The Nasal Cavity. — The nasal cavities {camim nasi), or nasal fossae (Figs. 81 and
103), are two large, irregular cavities situated on either side of the middle line
of the face, extending from the base of the cranium to the roof of the mouth,
and separated from each other by a thin vertical septum, the septum of the nose,
formed by the perpendicular plate of the ethmoid and by the vomer. Each
cavity communicates by a large aperture, the anterior nasal aperture {apertura
pyriformis),^ with the front of the face, and by the two posterior nares (choance)
LACRIMAL CANAL PALATE BONE
Fig. 103.— Nasal cavity, right lateral wall, from the left. (Spalteholz.)
with the nasopharynx behind. These fosste are much narrower above than
below, and in the middle than at the anterior or posterior openings; their depth,
which is considerable, is much greater in the middle than at either extremity.
The nasal fossse are surrounded by four other fossae — above is the cranial fossa;
laterally, the orbital fossae; and below, the cavity of the mouth. Each nasal fossa
communicates with four sinuses — the frontal above, the sphenoidal behind, and
the maxillary and ethmoidal on the outer wall. Each fossa also communicates
with four cavities — with the orbit by the lacrimal groove, with the mouth by the
anterior palatine canal, with the cranium by the olfactory foramina, and with the
sphenomaxillary fossa by the sphenopalatine foramen; and they occasionally
iQuain, Testut, and others give the apex of the orbit aa corresponding with the inner end of the sphenoidal
fiaaure. It seems better, however, to adopt the statement in the text, since the muscles of the eyeball take origin
around the optic foramen, and diverge from it to the globe of the eye.
2 In the skull freed of soft parts the anterior nasal cavities open in front by the apertura pyriformis. In the
skull with the soft parts in place they open by the anterior nares.
THE SKULL AS A WHOLE 139
communicate with each other by an aperture in the septum. The bones entering
into their formation are fourteen in number — three of the cerebral cranium, the
frontal sphenoid, and ethmoid, and ail the bones of the face, excepting the malar
and mandible. Each cavity is bounded by a roof, a floor, an inner and an outer
wall.
The upper wall, or roof, is long, narrow, and horizontal in its centre, but slopes
downward at its anterior and posterior extremities ; it is formed in front by the
nasal bones and nasal spine of the frontal, which are directed downward and
forward; in the middle, by the cribriform plate of the ethmoid, which is hori-
zontal ; and behind, by the anterior and under surface of the body of the sphenoid
and sphenoidal turbinated process, the ala of the vomer and the sphenoidal process
of the palate bone, which are directed downward and backward. This surface
presents, from before backward, the internal aspect of the nasal bones ; on their outer
side, the suture formed between the nasal bone and the nasal process of the maxilla;
on their inner side, the elevated crest which receives the nasal spine of the frontal
and the perpendicular plate of the ethmoid, and articulates with its fellow of the
opposite side; while the surface of the bones is perforated by a few small vascular
apertin-es, and presents the longitudinal groove for the nasal nerve; farther back
is the transverse suture, connecting the frontal with the nasal in front, and the
ethmoid behind, the olfactory foramina and nasal slit on the under surface of the
criiiriform plate, and the suture lietween it and the sphenoid behind; quite pos-
teriorly are seen the sphenoidal turbinated process, the orifice of the sphenoidal
sinus, and the articulation of the ala of the vomer with the under surface of the
body of the sphenoid.
The floor (Fig. 103) is flattened from before backward, concave from side to
side, and wider in the middle than at either extremity. It is formed in front
by the palatal process of the maxilla ; behind, by the horizontal plate of the palate
bone. This surface presents, from before backward, the anterior nasal spine;
behind this, the upper orifices of the anterior palatine canal; the elevated crest
which articulates with the vomer; and behind, the suture between the palate
and maxilla, and the posterior nasal spine.
The inner or medial wall, or septum (septum nasi osseum) (Fig. 105), is a thin
vertical partition which separates the nasal fossse from each other. It is formed,
in front, by the crest of the nasal bones and nasal spine of the frontal ; in the
middle, by the perpendicular plate of the ethmoid and ethmoidal crest of the
sphenoid; behind, by the vomer and rostrum of the sphenoid; below, by the crests
of the maxillae and palate bones. It presents, in front, a large, triangular notch,
which receives the septal cartilage of the nose; and behind, the grooved edge of the
vomer. Its surface is marked by numerous canals for vessels and nerves, and
the groove for the nasopalatine nerve, and is traversed by sutures connecting
the bones of which it is formed.
The outer or lateral wall (Figs. 81 and 103) is formed, in front, by the nasal
process of the maxilla and lacrimal bones ; in the middle, by the ethmoid and inner
surface of the body of the maxilla and turbinated bone; behind, by the vertical
plate of the palate bone; and the internal pterygoid plate of the sphenoid. Upon
this outer wall are two marked projections of bone (Fig. 81). One is known
as the turbinated bone and the other as the middle turbinated process. The supe-
rior turbinated process appears as a less distinct bony projection. This surface
presents three irregular longitudinal passages, termed the superior, middle, and
inferior meatuses of the nose (Fig. 104). The superior meatus, the smallest of
the three, is situated at the upper and back part of each nasal fossa, occupying
the posterior.third of the outer wall. It is situated between the superior and mid-
dle turbinated processes, and has opening into it two foramina, the sphenopalatine
foramen at the back of its outer wall, and the posterior ethmoidal cells at the front
140
SPECIAL ANATOMY OF THE SKELETON
part of the outer wall. The sphenoidal sinus opens into a recess (recesstw spheno-
ethmoidalis) , which is situated above and behind the superior turbinated process.
The middle meatus is situated external to the middle turbinated process, between
TRUM OF-iJ
STLE PASSED THRG
NDIBULUM FROM
TAL SINUS TO
LE MEATUS
OBE PASSED
THROUGH LACRI-
L CANAL
NTAL CANAL
ASAL CANAL
Fig. 104. — Coronal section through the frontal sinus and nasal fossa. (Poirier and Charpy.)
Crest of nasal bone.
Nasal spine of
frontal boi
Space for triangula)
cartilage of ieptiini
» . " Ci est of palate bone.
Crest of maxilla.
Fig. 105. — Inner wall of nasal fossEe, or septum of i
THE SKULL AS A WHOLE
141
it and the turbinated bone, and extends from the anterior end of the turbinated
to the sphenopalatine foramen of the outer wall of the nasal fossa. Anteriorly
it terminates in a depression, the atrium of the nasal meatus {atrium meatiw medii).
The middle meatus presents in front the orifice of the infundibulimi, by which
the middle meatus communicates with the anterior ethmoidal cells, and through
these with the frontal sinuses. The posterior ethmoidal cells also open into
this meatus, while at the centre of the outer wall is the orifice of the maxillary
antrum which varies somewhat as to its exact position in different skulls. The
inferior meatus, the largest of the three, is the space between the turbinated bone
and the floor of the nasal fossa. It extends along the entire length of the outer
wall of the nose, is broader in front than behind, and presents anteriorly the lower
orifice of the canal for the nasal duct.
Pituitary
fossa
Mesoderm of base
of skull
Development of the Skull. — Up to a cei-tain stage the development of the skull corresponds
with that of the vertebral column; but it is modified later in association with the expansion of
the brain vesicles, the formation of the organs of smell, sight, and hearing, and the development
of the mouth and pharynx.
The notochord extends as far forward in the
base of the future skull as the anterior end of the
mid-brain, and becomes partly surrounded by
mesoderm (Fig. 106). The posterior part of this
mesodermal investment corresponds with the
future basiocciput, and shows a subdivision into
four segments, which are separated by the roots
of the hypoglossal nerve. The mesoderm then
extends over the brain vesicles, and thus the entire
brain is enclosed by a mesodermal investment,
which is termed the membranous primordial cra-
nium. From the inner layer of this the bones of
the skull and the membranes of the brain are de-
veloped; from the outer layer the muscles, blood-
vessels, true skin, and subcutaneous tissues of the
scalp. In the shark and dog-fish this ineinbnin-
ous cranium undergoes complete chondrifi( ation,
and forms the cartilaginous skull, or rliondro-
cranium, of these animals. In mammals, on the
other hand, the process of chondrification is
limited to the base of the skull — the roof and
sides being covered in by membrane. Thus,
the bones of the base of the skull are preceded
by cartilage, those of the roof and sides by membrane. The posterior part of the base of the
skull is developed around the notochord, and exhibits a segmented condition analogous to
that of the vertebral column, while the anterior part arises in front of the notochord and shows
no regular segmentation. The base of the skull may therefore be divided into (a) o chordal or
vertebral, and (6) a prechordal or prevertebral portion.
In the lower vertebrates two pairs of cartilages are developed, viz., a pair of parachordal
cartilages, one on either side of the notochord; and a pair of prechordal cartilages, the trabeculae
cranii, in front of the notochord (Figs. 107 and 108). The parachordal cartilages (Fig. 108) unite
to form a cartilaginous plate, from which the cartilaginous part of the occipital bone and the basi-
sphenoid are developed. On the lateral aspect of the parachordal cartilages the otic or auditory
■vesicles are situated, and the mesoderm enclosing them is soon converted into cartilage, forming
the cartilaginous ear capsules. These cartilaginous ear capsules, which are of an oval shape,
fuse with the lateral aspects of the basilar plate, and from them arise the petromastoid portions
of the temporal bones. The trabeculae cranii (Fig. 107) are two curved bars of cartilage which
embrace the pituitary body; their posterior ends soon unite with the basilar plate, while their
anterior ends join to form the ethmoidal plate, which extends forward between the forebrain and
the olfactory pits. Later, the trabecula; meet and fuse below the pituitary body, forming the
floor of the pituitary fossa, and so cutting off the anterior lobe of the pituitary body from the stoma-
todeum. The mesal part of the ethmoidal plate forms the bony and cartilaginous parts of the
nasal septum. From the lateral margins of the trabeculae cranii three processes grow out on
either side. The anterior forms the lateral mass of the ethmoid and the alar cartilages of the
nose; the middle gives rise to the lesser wing of the sphenoid, while from the posterior the greater
wing and external pterygoid plate of the sphenoid are developed (Figs. 109 and 110). The bones
Anterior arch of atlas
Notochord
Body of axis
Third cervical
vertebra
Fig, 106. — Sagittal section of cephalic end of
notochord. (Furness).
142
SPECIAL ANATOMY OF THE SKELETON
of the vault are of membranous formation, and are termed dermal or covering hones. They are
partly developed from the mesoderm of the primordial cranium, and partly from that which
lies outside the entoderm of the foregut. They comprise the upper part of the tabular por-
tion of the occipital (interparietal), the squamous temporals and tympanic plates, the panetals,
Situation of olfactory pit Ethmoid plate
and nasal Olfactory organ
K sp.ptu
Pituitary fossa
Extension around
olfactory organ
Foramina for
olfactory nerves
— Eyehall
-- Pituitary fossa
Figs. 107 and 108. — Diagrams of the cartilaginous cranium. (Wiedersheim.)
Meckel's cartilage
Malleus
Incus
Int. aud. meat
JugutXar f '>*>■' >*''' ■
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^<?'"g I^ss oblique than the lower. The extent of
'"X ~f/ oblic{uity reaches its maximum at the ninth ril), and
'^•^^ gradualty7recTeases~from that rib to the twelfth. The
ribs are situated one below the other in such a
^'^-^fdeT^rferioraipeJt.*"'"" manner that spaces are left between them. Each
' Sometimes the eighth rib cartilage articulates with the sternum; this condition occurs more frequently on the
■ight than on the left side.
11
162
SPECIAL ANATOMY OF THE SKELETON
space is called an intercostal space (spatium intercostale). The length of these
spaces corresponds to the length of the ribs and their cartilages; their breadth
is greater in front than behind, and between the upper than between the lower
ribs. The ribs increase in length from the first to the seventh, when they again
diminish to the twelfth. In breadth they decrease from above downward; in the
upper ten the greatest breadth is at the sternal extremity.
Common Characters of the Ribs. — A rib from the middle of the series
should be taken in order to study the common characters of the ril)s (Figs. 129
and 130). Each rib presents two extremities, a posterior or vertebral, an anterior
or sternal, and an intervening portion — the body or shaft.
Posterior Extremity. — The posterior or vertebral extremity presents for examina-
tion a head, neck, and tuberosity.
The head (capituhim costae) (Fig. 130) is marked by a kidney-shaped artic-
ular surface, divided by a horizontal ridge (crista capituli) into two facets for
Demifacet for vertebra
Interariicular crest
',C^^''%J>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
st<Tnal cxtreraity. The primary centre for the shaft appears very early, before that of any
other bone, at about the fifth or sixth week of fetal life. The secondary centre for the sternal
end makes its appearance about the fifteenth to the twentieth year, and unites with the rest of
the bone about the twenty-fifth year.
Articulations. — With the sternum, scapula, by intra-articular fibrocartilaginous disks, and
with tiie cartilage of the first rib.
Attachment of Muscles. — To six — the Sternomastoid, Trapezius, Pectoralis major,
Deltoid, Subclavius, and Sternohyoid.
Surface Form. — The clavicle can be felt throughout its entire length, even in persons who
are very fat. Commencing at the inner end, the enlarged sternal extremity, where the bone
projects above the upper margin of the sternum, can be felt, forming with the sternum and the
rounded tendon of the Sternomastoid a V-shaped notch, the presternal notch. Passing out-
ward, the shaft of the bone can be felt immediately under the skin, with its convexity forward
in the inner two-thirds, the surface partially obscured above and below^ by the attachments of
the Sternomastoid and Pectoralis major muscles. In the outer third it forms a gentle curve
backward, and terminates at the outer end in a somewhat enlarged extremity which articulates
with the acromial process of the scapula. The direction of the clavicle is almost, if not quite,
horizontal when the arm is lying quietly by the side, though in well-developed subjects it may
172 SPECIAL ANATOMY OF THE SKELETON
incline a little upward at its outer end. Its direction is, however, very changeable, altering with
the varying movements of the shoulder-joint.
Applied Anatomy. — The clavicle is the most he(\\iexit\y fractured of any single bone in the
body. This is due to the fact that it is much exposed to violence, and is the only bony connec-
tion between the upper limb and the trunk. The bone, moreover, is slender, and is very super-
ficial. The bone may be broken by direct or indirect violence or by muscular action. The most
common cause is, however, from indirect violence, and the bone then gives way at the junction
of the fi.xed outer one-third with the movable inner two-thirds of the bone. This is the weakest
and most slender part of the bone. The fracture is generally oblique, and the displacement
of the outer fragments is inward, away from the surface of the body; hence, compound fracture
of the clavicle is of rare occurrence. The inner fragment, as a rule, is little displaced. Beneath
the bone the main vessels of the upper limb and the great nerve cords of the brachial plexus
lie on the first rib, and are liable to be wounded in fracture, especially in fracture from direct
violence, when the force of the blow drives the broken ends inward. Fortunately, the Subclavius
muscle is interposed between these structures and the clavicle, and this often protects them
from injury.
The clavicle is not uncommonly the seat of sarcomatous tumors, rendering the operation
of excision of the entire bone necessary. This operation is best performed by exposing the
bone freely, disarticulating at the acromial end, and turning it inward. The removal of
the outer part is comparatively easy, but resection of the inner part is fraught with difficulty,
the main danger being the risk of wounding the great veins which are in relation with its •
under surface.
The Scapula, or Shoulder Blade.
The scapula forms the back part of the shoulder girdle. It is a large flat bone,
triangular in shape, situated at the posterior aspect and side of the thorax, between
the second and seventh or sometimes the eighth rib, its internal border or base
being about an inch from and nearly but not quite parallel with the spinous pro-
cesses of the vertebrse, so that it is rather closer to them above than below. It
presents for examination two surfaces, three borders, and three angles.
Surfaces. — The anterior or ventral surface (fades costalis) (Fig. 138) presents
a broad concavity, the subscapular fossa (fossa subscapular is). It is marked, in
the inner two-thirds, by several oblique ridges (lineae musculares), which pass
outward and upward; the outer third is smooth. The oblique ridges give origin
to the tendinous intersections, and the surfaces between them to the fleshy fibres,
of the Subscapularis muscle. The outer third of the fossa is smooth, is covered
by, but does not afford attachment to, the fibres of this muscle. This surface is
separated from the internal border by a smooth, triangular margin at the supe-
rior and inferior angles, and in the interval between these by a narrow edge which
is often deficient. This marginal surface aft'ords attachment throughout its entire
extent to the Serratus magnus muscle. The subscapular fossa presents a trans-
verse depression at its upper part, where the bone appears to be bent on itself,
forming a considerable angle, called the subscapular angle, thus giving greater
strength to the body of the bone from its arched form, while the summit of the
arch serves to support the spine and acromion process. It is in this situation
that the fossa is deepest, so that the thickest part of the Subscapularis muscle
lies in a line perpendicular to the plane of the glenoid cavity, and must conse-
quently operate most effectively on the head of the humerus, which is contained
in that cavity.
The posterior or dorsal surface (fades dorsal is) (Fig. 139) is arched from above
downward, alternately concave and convex from side to side. It is subdivided
unequally into two parts by the spine; the portion above the spine is called the
supraspinous fossa, and that below it the infraspinous fossa.
The supraspinous fossa (fossa supraspinata), the smaller of the two, is concave,
smooth, and broader at the vertebral than at the humeral extremity. It affords
attachment by its inner two-thirds to the Supraspinatus muscle.
The infraspinous fossa (fossa infraspinata) is much larger than the preceding;
THE SCAPULA,' OR SHOULDER BLADE
173
toward its vertebral margin a shallow concavity is seen at its upper part; its centre
presents a prominent convexity, while toward the axillary border is a deep groove
which runs from the upper toward the lower part. The inner two-thirds of this
surface affords origin to the Infraspinatus muscle; the outer third is only covered
by it, without giving attachment to its fibres. This surface is separated" from the
axillary border by an elevated ridge, which runs from the lower margin of the glenoid
Coraco-aCTora ial
ligament
Fig. 138. — Left scapula. Anterior surface or venter.
cavity downward and backward to the internal border, about an inch above the
inferior angle. The ridge serves for the attachment of a strong aponeurosis which
separates the Infraspinatus from the two Teres muscles. The surface of bone
between this line and the axillary border is narrow in the upper two-thirds of its
extent, and traversed near its centre by a groove for the passage of the dorsalis
scapulae vessels; it affords origin to the Teres minor muscle. Its lower third
174
SPECIAL ANATOMY OF THE SKELETON
presents a broader, somewhat triangular surface, which gives origin to the Teres
major, and over which the I>atissimus 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-
TH1<J FOOT
249
ward. It occupies the centre of the front row of the tarsus, between the middle
cuneiform internally, the cuboid externally, the scaphoid behind, and the third
metatarsal in front. It is distinguished from the internal cuneiform bone by its
more regular wedge-like shape and by the absence of the kidney-shaped articular
surface; from the middle cuneiform, by the absence of the L-shaped facet, and
by the two articular facets which are present on both its inner and outer surfaces.
It has six surfaces for examination.
The anterior surface, triangular in form, articulates with the third metatarsal
bone. The posterior surface articulates with the most external facet of the scaphoid,
and is rough below for the attachment of ligamentous fibres. The internal
surface presents two articular facets, separated by a rough depression; the anterior
one, sometimes divided into two, articulates with the outer side of the base of
the second metatarsal bone; the posterior one skirts the posterior border and articu-
lates with the middle cuneiform; the rough depression between the two gives
attachment to an interosseous ligament. The external surface also presents two
articular facets, separated by a rough nonarticular surface; the anterior facet,
situated at the superior angle of the bone, is small, and articulates with the inner
side of the base of the fourth metatarsal ; the posterior and larger one articulates
with the cuboid; the rough, nonarticular surface serves for the attachment of
For scaphoid For tniddle-cuneiforin
For Uh
metatarsal' For cuhoid
Fig. 200. — The left external cuneiform. A. Postero-internal
Antero-external view.
an interosseous ligament. The three facets for articulation with the three meta-
tarsal bones are continuous with one another, and covered by a prolongation of
the same cartilage; the facets for articulation with the middle cuneiform and
scaphoid are also continuous, but that for articulation with the cuboid is usually
separate. The dorsal surface is of an oblong square form, its posterior external
angle being prolonged backward. The plantar surface is an obtuse rounded
margin, and serves for the attachment of ligaments and a part of the tendon of
the Tibialis posticus, and for part of the fibres of origin of the Flexor brevis hallucis.
To ascertain to which side the bone belongs, hold it with the broad dorsal surface upward,
the prolonged edge backward; the separate articular facet for the cuboid will point to the proper
side.
Articulations. — With dx bones — the scaphoid, middle cuneiform, cuboid, and second, third,
and fourth metatarsal bones.
Attachment of Muscles. — To two— ]>3,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<j;ular fibres which descend from the anterior surface of the
sacrum to the front of the coccyx, becoming blended with the periosteum. It
is a continuation of tiie anterior common ligament.
The posterior sacrococcygeal ligament [ligameufum sacmcoccygeum poaferim)
(Fig. 241) is divided into two portions, tiie deep and the superficial. Tlie deep
portion (Ikjamcidum sacrococcygcum posterius profuiidum), which is a continua-
tion of the posterior common ligament, is a flat band of a pearly tint, which arises
from the margin of the lower orifice of the sacral canal, and descends to be inserted
into the posterior surface of the coccyx. This ligament completes the lower
and back part of the sacral canal. Its superficial fibres are much longer than
the more deeply seated. This ligament is in relation, behind, with the Gluteus
maximus. The superficial portion (ligamentum sacrococcygeiivi posferius super-
ficiale) is composed of longitudinal fibrous bands which extend from the lower
portion of the middle sacral ridge to the posterior surface of the coccyx and
closes partly the sacral hiatus, and of fibrous bands which extend from the sacral
cornua to the coccygeal cornua. A portion of this ligament corresponds to the
ligamenta subflava and the balance to the capsular ligament.
EX OF SACRUM
LATERAL SACBO-
CCYGEAL LIGAMENT
PERFICIAL PORTION OF POST
CROCOCCYGEAL LIGAMENT
EF PORTION OF POSTERIOR
SACROCOCCYGEAL LIGAMENT
Fig. 241. — Ligaments between the
and the coccyx. (Spalteholz.)
A lateral sacrococcygeal or intertransverse ligament (Fig. 241) connects the
trans\'erse process of the coccyx to the lower lateral angle of the sacrum on each
side.
A fibrocartilage or articular disk is interposed between the contiguous surfaces
of the sacrum and coccyx; it diti'ers from that interposed between the bodies of
the vertebrae in being thinner, and its central part firmer in texture. It is some-
what thicker in front and behind than at the sides. Occasionally, a synovial
membrane is found and the coccyx is freely movable. This is especially the case
during pregnancy.
The different segments of the coccjnc are connected by an extension downward
of the anterior and posterior sacrococcygeal ligaments, a thin annular articular
disk being interposed between each of the bones. In the adult male all the
pieces become ossified, but in the female this does not commonly occur until a
later period of life. The separate segments of the coccyx are first united, and at
a more advanced age the joint between the sacrum and coccyx is obliterated.
294
THE ARTICULATIONS, OB JOINTS
Movements.— The movements which take place between the sacrum and coccyx, and between
the different pieces of the latter bone, are forward and backward, and are very limited. Their
extent increases during pregnancy.
Interpubic dish
Cavity at uppe
and back pa} t
4 Articulation of the Pubic Bones (Symphysis Ossioi Pubis)
(Figs. 238, 242).
The articulation between the pubic bones is an amphiarthrodial joint, formed
by the apposition of the two oval articular surfaces of the pubic bones. The
ligaments of this articulation are the
Anterior Pubic. Superior Pubic.
Posterior Pubic. Inferior Pubic.
Interpubic Disk.
The anterior pubic Ugament (Fig. 238) consists of several superimposed layers
which pass across the front of the articulation. The superficial fibres pass ob-
liquely from one bone to the other.
Hyaline cartiiaiie coveHnri bone. decussating and forming an interlace-
ment with the fibres of the aponeurosis
of the External oblique and the tendon
of the Rectus abdominalis muscles.
The deep fibres pass transversely
across the symphysis, and are blended
with the interpubic disk.
The posterior pubic ligament consists
of a few thin, scattered fibres which
unite the two pubic bones posteriorly.
The superior pubic ligament Qiga-
mentum pubicum superhis) (Fig. 238)
is a band of fibres which connects
the two pubic bones superiorly.
The inferior pubic or subpubic
ligament Qigamentum arciiatit m pubis)
(Fig. 238) is a thick, triangular arch
of ligamentous fibres, connecting the
two pubic bones below and forming the upper boundary of the pubic arch.
Above, it is blended with the articular disk; laterally it is united with the descend-
ing rami of the pubis. Its fibres are closely connected and have an arched
direction. Its lower margin is separated from the triangular ligament of the
perineum by a gap, through which runs the dorsal vein of the penis.
The interpubic disk (lamina fibrocartilaginea interpubica) (Fig. 242) consists
of a disk of fibrocartilage connecting the surfaces of the pubic bones in front.
Each of the two surfaces is covered by a thin layer of hyaline cartilage whicli is
firmly connected to the bone by a series of nipple-like processes which accurately
fit within corresponding depressions on the osseous surfaces. These apposed
cartilaginous surfaces are connected by an intermediate stratum of fibrous
tissue and fibrocartilage which varies in thickness in different subjects. It
often contains a cavity (cavwrn articulare) in its centre, probably formed by
the softening and absorption of the fibrocartilage, since it rarely appears before
the tenth year of life, and is not lined by synovial membrane. It is larger in the
female than in the male. It is most frequently limited to the upper and back
Fig. 242. — Vertical section of the symphysis pubi>
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
<iluteus medius, the Pyriformis, Obturator externus and internus, Gemellus superior and inferior,
Quadratus femoris, Iliacus, Gluteus maximus, the three Adductors, the Pectineus, and the
Sartorius.
Surface Form. — A line drawn from the anterior superior spinous process of the ilium to
the most prominent part of the tuberosity of the ischium (Nelaton's line) runs through the
centre of the acetabulum, and would, therefore, indicate the level of the hip-joint; or, in other
words, the upper border of the great trochanter, which lies on Nekton's line, is on a level with
the centre of the hip-joint.
Applied Anatomy. — Inflammation of hursoB about the hip-joint gives rise to confusing
symptoms, and is not uncoriimonly mistaken for hip-joint disease.
Great sacrosciat
Small sacrosctatic
ligament
' J Anterior superior
spine
.Great trochanter
of femur.
Fig. 264. — Nelaton's line and Bryant's triangle.
In dislocation of the hip "the head of the thigh bone may rest at any point around its socket"
(Bryant); but whatever position the head ultimately assumes, the primary displacement is
generally downward and inward, the capsule giving way at its weakest — that is, its lower and
inner — part. The situation that the head of the bone subsequently assumes is determined
by the degree of flexion or extension, and of outward ov inward rotation of the thigh at the
moment of luxation, influenced, no doubt, by the iliofemoral ligament, which is not easily rup-
tured. When, for instance, the head is forced backward, this ligament forms a fixed axis, around
which the head of the bone rotates, and the head is thus driven on to the dorsum of the ilium.
The iliofemoral ligament also influences the position of the thigh in the various dislocations:
in the dislocations backward it is tense, and produces inversion of the limb; in the dislocation
on to the pubes it is relaxed, and therefore allows the External rotators to evert the thigh; while
in the thyroid dislocation it is tense and produces flexion.
330 THE ABTICULA TIONS, OB JOINTS
. The iliofemoral ligament is rarely torn in dislocations of the hip, and this fact is taken advan-
tao-e of by the surgeon in reducing these dislocations by manipulation. It is made to act as
a fulcrum to a lever of which the long arm is the shaft of the femur, and the short arm the
neck of the bone.
The hip-joint is rarely the seat of acute synovitis from injury, on account of its deep position
and its thick covering of soft parts. Acute inflammation may, and does, frequently occur as
the result of constitutional conditions, as rheumatism, pyemia, etc. When, in these cases,
effusion takes place, and the joint becomes distended with fluid, the swelling is not very easy
to detect on account of the thickness of the capsule and the depth of the articulation. It is
principally to be found on the front of the joint, just internal to the iliofemoral ligament; or
behind, at the lower and back part. In these two places the capsule is thinner than elsewhere.
Disease of the hip-joint is much more frequently of a chronic character and is usually, of tuber-
culous origin. It begins either in the bones or in the synovial membrane, more frequently in the
former, and probably, in most cases, in the growing, highly vascular tissue in the neighborhood
of the epiphyseal cartilage. In this respect it differs very materially from the tuberculous arthritis
of the knee, where the disease often commences in the synovial membrane.
In chronic hip disease the affected limb assumes an altered position, the cause of which it
is important to understand. In the early stage of a typical case the limb is flexed, abducted,
and rotated outward. In this position all the ligaments of the joint are relaxed — the front of
the capsule by flexion; the outer band of the iliofemoral ligament by abduction; and the inner
band of this ligament and the back of the capsule by rotation outward. It is, therefore, the
position of the greatest ease. The condition is not quite obvious at first upon examining a
patient. If the patient is laid in the supine position, the affected limb will be found to be ex-
tended and parallel with the other. But it will be found that the pelvis is tilted downward on
the diseased side and the limb apparently longer than its fellow, and that the lumbar portion of
the vertebral column is arched forward (lordosis). If now the thigh is abducted and flexed, the tilt-
ino- downward and the arching forward of the pelvis disappears. The condition is thus explained.
A limb which is flexed and abducted is obviously useless for progression, and, to overcome the
difficulty, the patient depresses the affected side of his pelvis in order to produce parallelism
of his limbs, and at the same time rotates his pelvis on its transverse horizontal axis, so as to
direct the limb downward instead of forward. In the latter stages of the disease the limb becomes
flexed, adducted, and inverted. The position probably depends upon the muscular action,
at all events as regards the adduction. The Adductor muscles are supplied by the obturator
nerve, which also largely supplies the joint. These muscles are therefore thrown into reflex
a?tion by the irritation of the peripheral terminations of this nerve in the inflamed articulation.
Osteoarthritis is not uncommon in the hip-joint, and it is said to be more common in the male
than in the female, in whom the knee-joint is more frequently affected. It is a disease of middle
age or more advanced period of life.
Congenital dislocation is more commonly met with in the hip-joint than in any other articula-
tion. The displacement usually takes place on to the dorsum ilii. It gives rise to extreme
lordosis, and a waddling gait is noticed as soon as the child commences to walk.
Excision of the hip may be required for disease or for injury, especially for gunshot wound.
It may be performed either by an anterior or an external incision. The former one entails
less interference with important structures, especially muscles, than the posterior one, but .
permits of less efficient drainage. In the operation in front the surgeon makes an incision
three or four inches in length, starting immediately below and external to the anterior superior
spinous process of the ilium, downward and inward between the Sartorius and Tensor fasciae
femoris, to the neck of the bone, dividing the capsule at its upper part. A narrow-bladed saw
now divides the neck of the femur, and the head of the bone is extracted with sequestrum forceps.
All diseased tissue is carefully removed with a sharp spoon or scissors, and the cavity thoroughly
flushed with a hot aseptic fluid.
The external method consists in making an incision three or four inches long, commencing
midway between the top of the great trochanter and the anterior superior spine, and ending
over the shaft, just below the trochanter. The muscles are detached from the great trochanter,
and the capsule opened freely. The head and neck are freed from the soft parts and the bone
sawed through just below the top of the trochanter with a narrow saw. The head of the bone is
then levered out of the acetabulum. In both operations, if the acetabulum is eroded, it must be
freely gouged.
THE KNEE-JOINT 331
II. The Knee-joint (Articulatio Genu).
The knee-joint was formerly described as a ginglymus or hinge-joint, but is
really of a much more complicated character. It must be regarded as consist-
ing of three articulations in one — one between each condyle of the femur and the
corresponding tuberosity of the tibia, which are condyloid joints, and one between
the patella and the femur, which is partly arthroidal, but not completely so, since
the articular surfaces are not mutually adapted to each other, so that the movement
is not a simple gliding one. This view of the construction of the knee-joint
receives confirmation from the study of the articulation in some of the lower
mammals, where three synovial membranes are sometimes found, corresponding
to these three subdivisions, either entirely distinct or only connected by small
communications. This view is further rendered probable by the existence of
the two crucial ligaments within the joint, which must be regarded as the external
and internal lateral ligaments of the inner and outer joints respectively. The
existence of the ligamentum mucosum would further indicate a tendency to sepa-
ration of the synovial cavity into two minor sacs, one corresponding to each joint.
The bones entering into the formation of the knee-joint are the condyles of the
femur above, the head of the tibia beloiv, and the patella in front. The bones are
connected by ligaments, some of which are placed on the exterior of the joint,
while others occupy its interior.
External Ligaments. Interior Ligaments.
Capsular. Anterior, or External Crucial.
Anterior, or Ligamentum Patellae. Posterior, or Internal Crucial.
Posterior. Two Semilunar Fibrocartilages.
Internal Lateral. Transverse.
Two External Lateral. Coronary.
The capsular ligament (capsula articularis) (Fig. 265) consists of an exceedingly
thin, but strong, fibrous membrane, which is strengthened in almost its entire
extent by heavy bands which are inseparably connected with it. In front it blends
with and forms part of the lateral patellar ligaments and fills in the interval
between the anterior and lateral ligaments of the joints, with which latter structures
it is closely connected. It is deficient above the joint and beneath the tendon of
the Quadriceps extensor. Behind, it is formed chiefly of vertical fibres, which
arise above from the condyles and intercondyloid notch of the femur, and is con-
nected below with the back part of the head of the tibia, being closely united
with the origins of the Gastrocnemius, Plantaris, and Popliteus muscles. It
passes in front of, but is inseparably connected with, the posterior ligament.
The anterior ligament, or ligamentimi patellae (Figs. 265, 269, and 270), is the
central portion of the common tendon of the Extensor muscles of the thigh, which
is continued from the patella to the tubercle of the tibia, supplying the place of
an anterior ligament. It is a strong, flat, ligamentous band about three inches in
length, attached, above, to the apex of the patella and to the rough depression on
its posterior surface; below, to the lower part of the tubercle of the tibia, its super-
ficial fibres being continuous over the front of the patella with those of the tendon
of the Quadriceps extensor. The lateral portions of the tendon of the Extensor
muscles in conjunction with the fascia lata pass down on either side of the patella,
and are attached to the tibia on either side of the tubercle; these are termed
lateral patellar ligaments (retinaculum patellae mediale et laterale), and merge
into the capsule. The posterior surface of the ligamentum patellae is separated.
332
THE ARTICULATIONS, OB, JOINTS
above, from the synovial membrane by a fold of fat; beloiv, it is separated from
the head of the tibia by a synovial bursa.
The posterior ligament {ligamentum popliteum ohliquum) (Fig. 266) is a broad,
flat, fibrous band, formed of fasciculi separated from one another by apertures
for the passage of vessels and nerves. It is attached, above, to the upper margin
of the intercondyloid notch of the femur, and, below, to the posterior margin of
the head of the tibia. Superficial to the main part of the ligament and forming
a portion of it is a strong fasciculus derived from the tendon of the Semimembra-
nosus; it passes from the back part of the inner tuberosity of the tibia obliquely
upward and outward to the back part of the outer condyle of the femur and blends
with the posterior ligament. This expansion from the tendon of the Semimem-
FiG 265 — Right knee joint Anterior
Fig. 266. — Right knee-joint. Posterior ■
branosus muscle is called the posterior ligament of Winslow. The posterior liga-
ment forms part of the floor of the popliteal space, and the popliteal artery rests
upon it.
The internal lateral ligament {ligamentum collaterale tibiale) (Figs. 265 and
266) is a broad, flat, membranous band, thicker behind than in front, and situated
nearer to the back than the front of the joint. It is attached, above, to the inner
tuberosity of the femur; below, to the inner tuberosity and inner surface of the
shaft of the tibia to the extent of about two inches. It is crossed, at its lower
part, by the tendons of the Sartorius, Gracilis, and Semitendinosus muscles, a
synovial bursa being interposed. Its deef surface covers the anterior portion of
the tendon of the Semimembranosus, with which it is connected by a few fibres,
and the inferior internal articular vessels and nerve; it is intimately adherent
to the internal semilunar fibrocartiiage.
THE KNEE-JOINT
333
Femur.
The external lateral or long external lateral ligament (Ugamentum collaierale
fibidare) (Figs. 266 and 270) is a .strong, rounded, fibrous cord situated nearer
to the back than the front of the joint. It is attached, above, to the back part
of the outer tuberosity of the femur; below,
to the outer part of the head of the fibula.
Its outer surface is covered by the tendon
of the Biceps femoris, which divides at its
insertion into two parts, separated by the
ligament. The ligament has, passing be-
neath it, the tendon of the Popliteus muscle
and the inferior external articular vessels
and nerve.
The short external lateral ligament
(ligamentum laterale externum breve seu
posticum) (Fig. 266) is not a constant
structure. It is an accessory bundle of
fibres placed behind and parallel with the
preceding, attached, above, to the lower
and back part of the outer tuberosity of the
femur; below, to the summit of the styloid
process of the fibula. This ligament is in-
timately connected with the capsular liga-
ment, and has, passing beneath it, the
tendon of the Popliteus muscle and the
inferior external articular vessels and nerve.
The crucial ligaments (ligamenta cru-
ciata genu) (Figs. 267 and 268) are two
interosseous ligaments of considerable
strength situated in the interior of the joint,
nearer its posterior than its anterior part.
They are called crucial because they cross
each other somewhat like the lines of the
letter X; and have received the names anterior crucial and posterior crucial, from
the position of their attachment to the tibia.
The anterior or external crucial ligament {ligamentum cruciatum anterhis) (Fig.
267) is attached to the depression in front of the spine of the tibia, being blended
with the anterior extremity
of the external semilunar
fibrocartilage, and, passing
obliquely upward, backward,
and outward, is inserted into
the inner and back part of
the outer condyle of the
femur.
The posterior or internal
crucial ligament {ligamen-
tum cruciatum posterius) is
stronger, but shorter and
less oblique in its direction
than the anterior. It is at-
tached to the back part of
the depression behind the
spine of the tibia, to the popliteal notch, and to the posterior extremity of the
external semilunar fibrocartilage; and passes upward, forward, and inward, to
Showing interior
Fig. 268.— Head of tibi
milunir oirtil iges
Right side.
334
THE ARTICULATIONS, OR JOINTS
be inserted into the outer and fore part of the Inner condyle of the femur. It is
in relation, in front, with the anterior crucial ligament; behind, with the capsular
ligament.
The semilunar fibrocartilages (menisci) (Figs. 267 and 268) are two crescentic
lamellfe which serve to deepen the surface of the head of the tibia, for articula-
tion with the condyles of the femur. The circumference of each cartilage is thick,
convex, and attached to the inside of the capsule of the knee; the inner border
PATELLAR BURSA
TUBEROSITY
.t.-l'^'fiy" "^,1.%* J.'^tVtJ'HV'' 1 O'' TIBIA
^ . ' v/ -'. &* * V * -e a » -^ V S
Fig. 269. — Right knee-ioint Sagittal section through the external condyle of the femur. Mesal half oi
section, from the lateral side. The knee is slightly flexed; the joint surfaces have been pulled a little apart.
<Spalteholz.)
is thin, concave, and free. Their upper surfaces are concave, and in relation
with the condyles of the femur; their lower surfaces are flat, and rest upon the
head of the tibia. Each cartilage covers nearly the outer two-thirds of the
corresponding articular surface of the tibia, leaving the inner third uncovered;
both surfaces are smooth and invested by synovial membrane.
The internal semilunar fibrocartilage {tiieniscus medialis) is nearly semicir-
cular in form, a little elongated from before backward, and broader behind than
THi: KNEE-JOINT
335
in front; its anterior extremity, thin and pointed, is attached to a depression on the
anterior margin of the head of the tibia, in front of the anterior crucial Hgament;
its posterior extremity is attached to the depression behind the spine, between
the attachments of the external cartilage and the posterior crucial ligaments.
The external semilunar fibrocartilage {meniscus lateralis) forms nearly an entire
circle, covering a larger portion of the articular surface than the internal one.
J OF QUAD-
RICEPS EXTENSOR
FEMORIS
13MG EXTE
LATERAL.
LIGAMENT
REPATELLAR
TERNAL SEMI-
NAR FIBRO-
RTiLAGE
FiQ. 270.— Eight knee-joint, from the lateral surface. The joint cavity and several bursffi have been injectea
with a stiffening medium and then dissected out. (Spalteholz.)
It is grooved on its outer side for the tendon of the Popliteus muscle. Its ex-
tremities, at their insertion, are interposed between the two extremities of the
internal cartilage; the anterior extremity is attached in front of the spine of the
tibia to the outer side of, and behind, the anterior crucial ligament, with which
it blends; the posterior extremity is attached behind the spine of the tibia, in
front of the posterior extremity of the internal cartilage. Just before its insertion
336 THE ARTICULATIONS, OH JOINTS
posteriorly it gives off a strong fasciculus, tlie ligament of Wrisberg, which passes
obliquely upward and outward, to be inserted into the inner condyle of the femur,
close to the attachment of the posterior crucial ligament. Occasionally a small
fasciculus is given off which passes forward to be inserted into the back part
of the anterior crucial ligament. The external cartilage gives oft' from its anterior
convex margin a fasciculus which forms the transverse ligament.
The transverse ligament (ligamentum transversum genu) (Fig. 268) is a
band of fibres which passes transversely from the anterior convex margin of the
external cartilage to the anterior convex margin of the internal cartilage; its
thickness varies considerably in different subjects, and it is sometimes absent
altogether.
The coronary ligaments are merely portions of the capsular ligament, which
connect the circumference of each of the semilunar fibrocartilages with the margin
of the head of the tibia.
Ssmovial Membrane (Figs. 269 and 270). — The synovial membrane encloses the articular
cavity {cavum ariiculare) of the knee-joint. It is the largest and most extensive synovial mem-
brane in the body. Commencing above the upper border of the patella, it forms, on the lower
part of the front of the shaft of the femur, a short cul-de-sac beneath the Quadriceps extensor
tendon of the thigh; this communicates, by an orifice of variable size, with a synovial bursa inter-
posed between the tendon and the front of the femur (bursa suprapateUaris). On each side of the
patella the synovial membrane extends beneath the aponeurosis of the Vasti muscles, and more
especially beneath that of the Vastus internus. Below the patella it is separated from the anterior
ligament by the anterior part of the capsule and a considerable quantity of adipose tissue, known
as the infrapatellar pad (Fig. 269), In this situation the synovial membrane sends off a tri-
angular prolongation, containing a few ligamentous fibres, which extends from the anterior
part of the joint below the patella to the front of the intercondyloid notch. This fold has been
termed the ligamentum mucosmn (plica synovialis patellaris). It also sends off two fringe-
like folds, called the ligamenta alalia (;plicae alares) (Fig. 269). which extend from the sides of
the ligamentum mucosum, upward and laterally between the patella and femiir. On either
side of the joint it passes downward from the femur, lining the capsule to its point of attach-
ment to the semilunar cartilages; it may then be traced over the upper surfaces of these
cartilages to their free borders, and from thence along their under surfaces to the tibia.
At the back part of the external one it forms a cul-de-sac between the groove on its surface
and the tendon of the Popliteus; it surrounds the crucial ligaments and lines the inner surface
of the ligaments which enclose the joint. The pouch of synovial membrane between the Quad-
riceps extensor tendon and the front of the femur is supported, during the movements of the
knee, by a small muscle, the Subcrureus, which is inserted into the upper part of the capsular
ligament.
The folds of synovial membrane and the fatty processes contained in them act, as it seems,
mainly as a padding to fill up interspaces and obviate concussions. Sometimes the bursa beneath
the Quadriceps extensor is completely shut off from the rest of the synovial cavity, thus forming
a closed sac between the Quadriceps and the lower part of the front of the femur; sometimes it
communicates with the synovial cavity by a minute aperture; usually the two cavities are incom-
pletely separated by a synovial fold.
Bursae. — The burste about the knee-joint are the following: In front there are four bursse; one
is interposed between the patella and the skin. It is known as the prepatellar bursa (bursa
praepaiellaris subcutanea); another, of small size, between the upper part of the tuberosity of
the tibia and the ligamentum patellae is called the deep infrapatellar bursa (bursa infrapatellaris
profunda); and a third between the lower part of the tuberosity of the tibia and the skin, the
subcutaneous tibial bursa (bursa subcutanea tuberositatis tibiae). A fourth bursa exists in front,
the suprapatellar biu:sa (bursa suprapateUaris). It lies between the anterior surface of the
lower end of the femur and the posterior surface of the Quadriceps femoris. Spalteholz says that
the suprapatellar bursa is closely connected with the Quadriceps tendon and is usually incom-
pletely shut off from the cavity of the joint.^ Occasionally there is a bursa between the ex-
pansion of the fascia lata and the Quadriceps and the patella (bursa praepafellaris suhfascialis),
and sometimes one between the tendon of the Quadriceps and the anterior surface of the patella
(bursa praepatellaris subtendinea) . On the outer side there are four bursEe: (1 ) One (which some-
times communicates with the joint) beneath the outer head of the Gastrocnemius; (2) one above
the external lateral ligament between it and the tendon of the Biceps femoris; (3) one beneath the
1 Sualteholz's Hand .\tlas of Human Anatomy. Translated by Lewellys F. Barker.
THE KNEE JOINT 337
external lateral ligament between it and the tendon of the Popliteus (this is sometimes only an
(■xpansion from the next bursa); (4) one beneath the tendon of the Popliteus {bursa mu.icuK
poplitri) between it and the condyle of the femur, which is almost always an extension from the
synovial membrane of the joint. On the inner side there are five bursa- : (1) One beneath the
inner head of the Gastrocnemius, which sends a prolongation between the tendons of the Gastroc-
nemius and Semimembranosus; this bursa often communicates with the joint; (2) one above
the internal lateral ligament between it and the tendons of the Sartorius, Gracilis, and Semi-
tendinosus; (3) one beneath the internal lateral ligament between it and the tendon of the
Semimembranosus; this is sometimes only an expansion from the next bursa; (4) one beneath
the tendon of the Semimembranosus, between it and the head of the tibia; (5) sometimes there
is a bursa between the tendons of the Semimemltranosus and of the Semitendinosus.
Structures around the Joint. —In front and at the sides, the Quadriceps extensor; on the
oitier sidr, the tendons of the Biceps fo-moris and (he Popliteus and the external popliteal nerve;
on the inner side, the Sartorius, Gracilis, Semitendinosus, and Semimembranosus; behind, an
expansion from the tendon of the Semimembranosus, the popliteal vessels, and the internal
popliteal nerve, the Popliteus, the Plantaris, and the inner and outer heads of the Gastrocnemius,
some lymph nodes, and fat.
The arteries supplying the joint are derived from the anastomotica magna branch of the
femoral, articular branches of the (lopliteal, anterior and posterior recurrent branches of the
anterior tibial, and a descending branch fniin (lie external circumflex of the profunda.
The nerves are derived from the oliturator, femoral, and external and internal pojiliteal.
Movements. — The knee-joint permits of movements of /?f.vion and extension, and, in certain
positions, of slicjht rotation inward and outward. The movement of flexion and extension does
not, however, take place in a simple, finger-like manner, as in other joints, but is a complicated
movement, consisting of a certain amount of gliding and rotation; so that the same part of one
articular surface is not always applied to the same part of the other articular surface, and the
axis of motion is not a fixed one. If the joint is examined while in a condition of extreme flexion,
the posterior part of the articular surfaces of the tibia will be found to be in contact with the
posterior rounded extremities of the condyles of the femur; and if a simple hinge-like movement
•were to take place, the axis, around which the revolving movement of the tibia occurs, would be
in the back part of the condyle. If the leg is now brought forward into a position of semiflexion,
the upper surface of the tibia will be seen to glide over the condyles of the femur, so that the '
middle part of the articular facets are in contact, and the axis of
rotation must therefore have shifted forward to nearer the centre
of the condyles. If the leg is now brought into the extended posi-
tion, a still further gliding takes place and a further shifting for-
ward of the axis of rotation. This is not, however, a simple
movement, but is accompanied by a certain amount of rotation
outward around a vertical axis drawn through the centre of the
head of the tibia. This rotation is due to the greater length of
the internal condyle, and to the fact that the anterior portion
of its articular surface is inclined obliquely outward. In conse-
■quence of this it will be seen that toward the close of the move-
ment of extension — that is to say, just before complete extension
is effected — the tibia glides obliquely upward and outward over • ^'°' f '^ ~7lh^ °'^ hJ"' ''t'fl""
this oblique surface on the inner condvle, and the leg is therefore showing diagrammatically the
■necessarily rotated outward. In flexion of the joint the converse fn'^"igere'S'''posTt'ions'''c/'''the
of these movements takes place; thetiViia glides back^vard around knee,
the end of the femur, and at the commencement of the move-
ment the tibia is directed downward and inward along the oblique curve of the inner condyle,
thus causing an inward rotation to the leg.
During flexion and extension the patella moves on the lower end of the femur, but this
movement is not a simple gliding one; for if the articular surface of this bone is examined, it
will be found to present on each side of the central vertical ridge two less marked transverse
Tidges, which divide the surface, except a small portion along the inner border, which is cut off
by a slight vertical ridge into six facets (Fig. 271), and therefore does not present a uniform
■curved surface as would be the case if a simple gliding movement took place. These six facets —
three on each side of the median vertical ridge — correspond to and denote the parts of the bone,
respectively, in contact with the- condvles of the femur during flexion, semiflexion, and extension.
In flexion only the upper facets on the patella are in contact with the trochlea of the femur; the
lower two-thirds of the bone rests upon the infrapatellar pad which occupies the space between
the femur and tibia. In the semiflexed position of the joint the middle facets on the patella rest
upon the most prominent portion of the trochlea, and thus afford greater leverage to the Quad-
riceps by increasing its distance from the centre of motion. In complete extension the patella
is drawn up, so that only the lower facets are in contact with the trochlea. The narrow strip
338 THE ARTICULATIONS, OB JOINTS
along the inner border is in contact with the outer aspect of the internal condyle when the leg
is fully flexed at the knee-joint. As in the elbow, so it is in the knee — the axis of rotation in
flexion and extension is not precisely at right angles to the axis of the Vjone, but during flexion
there is a certain amount of alteration of plane; so that, whereas in flexion the femur and tibia
are in the same plane, in extension the one bone forms an angle of about 10 degrees with the
other. There is, however, this difference between the two extremities: that in the upper, during
extension, the humeri are parallel and the bones of the forearm diverge; in the lower, the femora
converge below and the tibis are parallel.
In addition to the slight rotation during flexion and extension, the tibia enjoys an independent
rotation on the condyles of the femur in certain positions of the joint. This movement takes
place between the articular menisci and the tibia, whereas the movement of flexion and extension
takes place between the articular menisci and the femur. So that the knee may be said to consist
of two joints, separated by the menisci — an upper, meniscofemoral, in which flexion and extension
take place; and a lower, meniscotibial, allowing of a certain amount of rotation. This latter
movement can only take place in the semiflexed position of the limb, W'hen all the ligaments are
relaxed.
Durinu iJexion the ligamentum patellae is put upon the stretch, as is also the posterior crucial
lii'ament in extreme flexion. The other ligaments are all relaxed by flexion of the joint, though
the relaxation of the anterior crucial ligament is very trifling. During life flexion is checked
by the contact of the leg with the thigh. In the act of extending the leg upon the thigh the liga-
mentum patellae is tightened by the Quadriceps extensor; but when the leg is fully extended, as
in the erect posture, the ligament becomes relaxed, so as to allow free lateral movement to the
'latella, which then rests on the front of the lower end of the femur. The other ligaments, with
the exception of the posterior crucial, which is partly relaxed, are all on the stretch. When the
limb has been brought into a straight line, extension is checked mainly by the tension of all the
ligaments except the posterior crucial and the ligamentum patellae. The movements of rotation
of which the knee is capable are permitted in the semiflexed condition by the partial relaxation
of both crucial ligaments, as well as of the lateral hgaments. Rotation inward appears to be
limited bv the tension of the anterior crucial ligament, and by the interlocking of the two liga-
ments; but rotation outward does not appear to be checked by either crucial ligament, since
they uncross during the execution of this movement, but it is checked by the lateral ligaments,
especially the internal. The main function of the crucial ligaments is to act as a direct bond
of union between the tibia and femur, preventing the former bone from being carried too far back-
ward or forward. Thus, the anterior crucial ligament prevents the tibia being cari'ied too far
forward by the Extensor tendons, and the posterior crucial checks too great movement back-
ward by the Flexors. They also assist the lateral ligaments in resisting any lateral bending of the
joint. The semilunar cartilages are intended, evidently, to adapt to a certain extent the surface
of the tibia to the shape of the femur, in order to fill intervals which would otherwise occur in the
changing of joint position and to interrupt jars which otherwise would be so frequently trans-
mitted up the limb through jumping or falling on the feet. These cartilages also contribute to
the varieties of motion — flexion, extension, and rotation — as explained above. The patella is a
treat defence to the knee-joint from any injury inflicted in front, and it distributes upon a large
and tolerably even surface during kneeling the pressure which would otherwise fall upon the
prominent ridges of the condyles; it also affords leverage to the Quadriceps extensor muscle when
it acts upon the tibia ; and Mr. Ward has pointed out' how this leverage varies in the various
positions of the joint, so that the action of the muscles produces velocity at the expense of force
in the commencement of extension, and, on the contrary, at the close of extension tends to
diminish velocity, and therefore the shock to the ligaments at the moment tension of the struc-
tures takes place.
Extension of the leg on the thigh is performed by the Quadriceps extensor; /p.Tio» by the Ham-
string muscles, assisted by the Gracilis and Sartorius, and, indirectly, by the Gastrocnemius,
Popliteus, and Plantaris; rotation outward, by the Biceps femoris; and rotation inward by the
Popliteus, Semitendinosus, and, to a slight extent, the Semimembranosus, the Sartorius, and the
Gracilis.
Surface Form. — The interval between the two bones enteriiig into the formation of the knee-
joint can always easily be felt. If the limb is extended, it is situated on a slightly higher level
than the apex of the patella; but if the limb is slightly flexed, a knife carried horizontally back-
ward immediately below the apex of the patella would pass directly into the joint. When the
knee-joint is distended with fluid, the outline of the synovial membrane at the front of the knee
may be fairly well mapped out.
Applied Anatomy. — The bursce about the knee are frequently the seat of inflammation.
Enlargement of the prepatellar bursa constitutes housemaid's knee. The bursa beneath the
1 Human Osteology, p. 40.=;.
THE KNEE-JOINT 339
Semimembranosus may enlarge greatly. It communicates with the knee-joint and can frequently
be made to disappear by pressure when the knee is flexed. Treves points out that enlargement
of the bursa between the Biceps tendon and the external lateral ligament causes great pain
because the peroneal nerve crosses the sac'
From a consideration of the construction of the knee-joint it would at first sight appear to be
one of the least secure of any of the joints in the body. It is formed between the two longest
liones, and therefore the amount of leverage which can be brought to bear upon it is very con-
siderable; the articular surfaces are but ill adapted to each other, and the range and varietv of
motion which it enjoys is great. All these circumstances tend to render the articulation very
insecure; but, nevertheless, on account of the very powerful ligaments which bind the bones
together, the joint is one of the strongest in the body, and dislocation from traumatism is of very
rare occurrence. When, on the other hand, the ligaments have been softened or destroyed
by disease, partial displacement is very liable to occur, and is frequently brought about by the
mere action of the muscles displacing the articular surfaces from each other. The tibia may
be dislocated in any direction from the femur — forward, backward, im\'ard, or outward; or a
combination of two of these dislocations may occur — that is, the tibia may be dislocated for-
ward and laterally, or backward and laterally, and any of these dislocations may be complete
or incomplete. As a rule, however, the antero-posterior dislocations are complete, the lateral
ones incomplete.
One or other of the semilunar cartilages may become displaced and nipped between the femur
and tibia. The accident is produced by a twist of the leg when the knee is flexed, and is accom-
panied by a sudden pain and fixation of the knee in a flexed position. The cartilage may be
displaced either inward or outward; that is to say, either inward toward the tibial spine, so
that the cartilage becomes lodged in the intercondyloid notch; or outward, so that the cartilage
projects beyond the margin of the articular surface. Acute synovitis, the result of traumatism
or exposure to cold, is very common in the knee, on account of its superficial position. When
distended with fluid, the swelling shows itself above and at the sides of the patella, reaching
about an inch or more above the trochlear surface of the femur, and extending a little higher
under the Vastus internus than the Vastus externus. Occasionally the swelling may extend
two inches or more. At the sides of the patella the swelling extends lower at the inner side
than it does on the outer side. The lower level of the synovial membrane is just above the level
of the upper part of the head of the fibula. In the middle line it covers the upper third of the
ligamentum patellae, being separated from it, however, by the capsule and a pad of fat. Chronic
si/n.ovitis principally shows itself in the form of pulpy degeneration of the synovial membrane,
the result of tuberculous arthritis. The reasons why tuberculous disease of the knee so often
commences in the synovial membrane appear to be the complex and extensive nature of this
sac; the extensive vascular supply to it; and the fact that injuries are generally dift'used and
applied to the front of the joint rather than to the ends of the bone. Syphilis not infrequently
attacks the knee-joint. In the hereditary form of the disease the attack is usually symmetrical —
both joints are involved. They become filled with synovial effusion and cure is very difficult.
In acquired syphilis gummatous infiltration of the synovial membrane may take place. The
knee is one of the joints most commonly affected with osteoarthritis, and is said to be more
frequently the seat of this disease in women than in men. The occurrence of the so-called loose
cartilage is almost confined to the knee, though loose cartilages are occasionally met with in the
elbow, and, rarely, in some other joints. Many of them occur in cases of osteoarthritis, in which
calcareous or cartilaginous material is formed in one of the synovial fringes and constitutes the
foreign body, and may or may not become detached, in the former case only meriting the usual
term, "loose" cartilage. In other cases they have their origin in the exudation of inflammatory
lymph, and possibly, in some rare instances, a portion of the articular cartilage or one of the
semilunar cartilages becomes detached and constitutes the foreign bodv.
Genu valgum, or knock-knee, is a common deformity of childhood, in which, owing to changes
in and about the joint, the angle between the outer border of the tibia and femur is diminished,
so that as the patient stands the two internal condyles of the femora are in contact, but the two
internal malleoli of the tibiae are more or less widely separated from each other. When, howe\'er,
the knees are flexed to a right angle, the two legs are practically parallel with each other. At
the commencement of the disease there is a yielding of the internal lateral ligainent and other
fibrous structures on the inner side of the joint; as a result of this there is a constant undue
pressure of the outer tuberosity of the tibia against the outer condyle of the femur. This extra
pressure causes arrest of growth, and, possibly, wasting of the outer condyle, and a consequent
tendency for the tibia to become separated from the internal condyle. To prevent this the
internal condyle becomes depressed; probably, as was first pointed out bv Mikulicz, bv an
increased growth of the lower end of the diaphysis on its inner side, so that the line of the
epiphysis becomes oblique instead of transverse to the axis of the bone, with a direction down-
1 .Applied Anatomy.
340
THE ARTICULATIONS, OB JOINTS
ward and inward. It is often said that the deformity is produced by undue length of the inner
condyle, but in reality the condyle grows as the deformity progresses.
Excision of the knee-joint is most frequently required for tuberculous disease of this articulation,
but is also practised in cases of disorganization of the knee after rheumatic fever, pyemia, etc.,
in osteoarthritis, and in ankylosis. It is also occasionally called for in cases of injury, gun-
shot or otherwise. The operation is best performed either by a horseshoe incision, starting from
one condyle, descending as low as the tubercle of the tibia, where it crosses the leg, and is then
carried upward to the other condyle; or by
a transverse incision across the patella.
In this latter incision the patella is either
removed or sawed across, and the halves
subsequently sutured together. The bones
having been cleared, and in those cases
where the operation is performed for
tuberculous disease all pulpy tissue hav-
ing been carefully removed, the section
of the femur is first made. This should
never include, in children, more than, at
the most, two-thirds of the articular sur-
face, otherwise the epiphyseal cartilage
will be involved, with disastrous results
as regards the growth of the limb. After-
ward a thin slice should be removed from
the upper end of the tibia, not more than
half an inch. If any diseased tissue still
appears to be left in the bones, it should
be removed with the gouge rather than
by making a further section of the bones.
III. The Tibiofibular Articulation
(Articulatio Tibiofibularis) .
The articulations between the
tibia and fibula are effected by
ligaments which connect both ex-
tremities, as well as the shafts of
the bones. It may, consequently, be
subdivided into three articulations:
(1) The superior tibiofibular articu-
lation. (2) The middle tibiofibular
ligament or interosseous membrane.
(3) The inferior tibiofibular articu-
lation.
1. The Superior Tibiofibular-
Articulation (Articulatio
Tibiofibularis).
This articulation is an arthrodial
joint. The contiguous surfaces of
the bones present two flat, oval
facets covered with cartilage, and
are interconnected by the following
ligaments :
272. — Ligaments of the right ieg, from i
(Spalteholz.)
Capsular.
Anterior Superior Tibiofibular.
Posterior Superior Tibiofibular.
THE TIBIOFIBULAR ARTICULATION 341
The capsular ligament (capsula ariicularis) consists of a membranous bag
which surrounds the articulation, being attached around the margins of the
articular facets on the tibia and fibula, and is much thicker in front than behind.
The anterior superior ligament (Fig. 272) consists of two or three broad and
fiat bands which pass obliquely upward and inward from the front of the head
of the fibula to the front of the outer tuberosity of the tibia.
The posterior superior ligament ( Fig. 265) is a single thick and broad band
which passes upward and inward from the back part of the head of the fibula
to the back part of the outer tuberosity of the tibia. It is covered by the
tendon of the Popliteus muscle.
Synovial Membrane. — A synovial membrane lines this articulation, which at its upper and
back part is occasionally continuous with that of the knee-joint.
2. The Middle Tibiofibular Ligament or Interosseous Membrane
(Membrana Interossea Cruris) (Fig. 272).
An interosseous membrane extends between the contiguous margins of the
tibia and fibula and separates the muscles on the front from those on the back
of the leg. It consists of a thin, aponeurotic lamina composed of oblique fibres
which for the most part pass downward and outward between the interosseous
ridges on the two bones; some few fibres, however, pass in the opposite direction,
downward and inward. It is broader above than below. Its upper margin
does not quite reach the superior tibiofibular joint, but presents a free concave
border, above which is a large, oval aperture for the passage of the anterior tibial
vessels forward to the anterior aspect of the leg. At its lower part is an opening
for the passage of the anterior peroneal vessels. It is continuous below with
the inferior interosseous ligament, and is perforated in numerous places for the
passage of small vessels. It is in relation, in front, with the Tibialis anticus.
Extensor longus digitorum, Extensor proprius halhicis, Peroneus tertius, and
the anterior tibial vessels and nerve; behind, with the Tibialis posticus and
Flexor longus hallucis.
3. The Inferior Tibiofibular Articulation (Syndesmosis Tibiofibularis)
(Figs. 274, 275).
This articulation is formed by the rough, convex siu'face of the inner side of
the lower end of the fibula, connected with a concave rough surface on the outer
side of the tibia. Below, to the extent of about one-sixth of an inch, these sur-
faces are smooth, and covered with cartilage, which is continuous with that of
the ankle-joint. The ligaments of this joint are:
Anterior Inferior Tibiofibular. Transverse or Inferior.
Posterior Inferior Tibiofibular. Inferior Interosseous.
The anterior inferior ligament (Ugamentum malleoli lateralis anierius) (Figs.
272 and 276) is a flat, triangular band of fibres, broader below than above, which
extends obliquely downward and outward, between the adjacent margins of the
tibia and fibula, on the front aspect of the articulation. It is in relation, in front,
with the Peroneus tertius, the aponeurosis of the leg, and the integument, behind,
with the inferior interosseous ligament; and lies in contact with the cartilage
covering the astragalus.
342
THE ARTICULATIONS, OB JOINTS
The posterior inferior ligament (ligamentum malleoli lateralis posterius) (Fig.
276), smaller than the preceding, is disposed in a similar manner on the posterior
surface of the articulation.
The inferior transverse ligament lies under cover of the posterior ligament,
and is a strong, thick band of yellowish fibres which passes transversely across
the back of the joint, from the external malleolus to the posterior border of
the articular surface of the tibia, almost as far as its malleolar process. This
ligament projects below the margin of the bones, and forms part of the articulating
surface for the astragalus.
The inferior interosseous ligament (Fig. 274) consists of numerous short, strong,
fibrous bands which pass between the contiguous rough surfaces of the tibia and
fibula, and constitute the chief bond of union between the bones. This ligament
is continuous above with the interosseous membrane.
Synovial Membrane. — The synovial membrane lining the articular surface is derived from
that of the ankle-joint (Fig. 274).
Movements. — The movement permitted in these articulations is limited to a very slight
gliding of the articular surfaces one upon another.
IV. The Tibiotarsal Articulation, or Ankle-joint (Articulatio Talocruralis)
(Figs. 273, 274).
The ankle is a ginglymus or hinge-joint. The bones entering into its forma-
tion are the lower extremity of the tibia and its malleolus and the external malleolus
of the fibula, which forms a mortise (Fig. 272) to receive the upper convex surface
Tarsometatarsal
articulations X
Tarsal articulations.
Fig. 273. — Ankle-joint: tarsal and tarsometatarsal articulations. Internal view. Right
of the astragalus and its two lateral facets. The bony surfaces are covered by
hyaline cartilage and interconnected by a capsule (capsida articularis), which in
places forms thickened bands constituting the following ligaments:
Anterior.
Posterior.
Internal I^ateral.
External Lateral.
THE TIBIOTAIU^AL ARTICULATION
343
The anterior tibibtarsal ligament (ligameiiium taloUbiale anterius) is a broad,
thin, niemhraiious layer, attaelied, above, to the anterior margin of the lower
extremity of the tibia; beUnv, to the margin of the astragalus, in front of its
articular surface. It is in relation, in front, with the Extensor tendons of the
toes, with the tendons of the Tibialis anticus and Peroneus tertius, and the
anterior tiliial vessels and nerve; behind, it lies in contact with the synovial
membrane.
The posterior tibiotarsal ligament (ligamentum talotihiale posierius) is very
thin, and consists principally of transverse fibres. It is attached, above, to the
margin of the articular surface of the tibia, blending with the inferior transverse
tibiofibular ligament; below, to the astragalus, behind its trochlear surface,
externally, where it blends with the inferior transverse tibiofibular ligament, it is
thickest.
The internal lateral or deltoid ligament {liyamentitm deltoidev7n) (Figs. 274
and 275) consists of a superficial and a deep set of fibres; the superficial set consti-
ADIPOSE PAD
TER08SE0US CAL-
INEO-ASTRAGALOID
LIGAMENT
FLEXOR LONGUS
DIGITORUM
FLEXOR LONGUS
TIBIAL VESSELS
Fig. 274. — Coronal section through the ankle-joint and the calcaneo-aatragaloid articulation. (Poirier and
Charpy.)
tute a strong, flat, triangular band, which is attached, above, to the apex and to
the anterior and posterior borders of the inner malleolus. The most anterior
fibres pass forward to be inserted into the scaphoid bone {lig. calcaneotibiale) and
the inferior calcaneoscaphoid ligament {lig. tibionavicidare) , the middle descend
almost perpendicularlj' to be inserted into the sustentaculum tali of the calcaneus
{lig. calcaneotibiale) ; and the posterior fibres pass backward and outward to be
attached to the inner side of the astragalus (Zigr. taloiibiale posteriiis). The deep
set is attached, above, to the notch of the inner malleolus, and, below, to the
inner side of the astragalus. This ligament is covered by the tendons of the
Tibialis posticus and Flexor longus digitorum. muscles.
The external lateral ligament (Figs. 275 and 276) consist of three distinctly
specialized fasciculi of the capsule, taking dift'erent directions and separated
by distinct intervals; for which reason it is divided by some anatomists into
three distinct ligaments, and so described.'
^ Humphry, On the Skeleton, p. 559.
344
THE ARTICULATIONS, OR JOINTS
The anterior fasciculus (ligamentum talofihulare anterius); the shortest of the
three, passes from the anterior margin of the external malleolus forward and
inward to the astragalus, in front of its external articular facet.
INTERNAL
INTEROSSEOUS
LIGAMENT
TARSO-
METATARSAL
»HTICULATIONS
ASTRAGALO-
SCAPHOID
ARTICULATION
RLE-JOINT
MIDDLE EASCICULUS
,OF THE EXTERNAL
LATERAL LIGAMENT
Fig. 275. — Joints of the right foot, from the back of the foot. (Spalteholz.)
The posterior fasciculus (ligamentum talofibvlare posterms), the most deeply
seated, passes inward from the depression at the inner and back part of the
external malleolus to the prominent external tubercle on the posterior surface of
the astragalus. Its fibres are almost horizontal in direction.
The middle fasciculus {ligamentum calcaneofibulare) (Figs. 275 and 276), the
longest of the three, is a narrow, rounded cord passing from the apex, of the
THE TIIilOTARSAL ARTICULATION
345
external malleolus downward and slightly backward to the peroneal spine on the
outer surface of the calcaneus. It is covered by the tendons of the Peroneus
longus and brevis.
Synovial Membrane. — The synovial membrane (Fig. 272) invests the inner surface of the
ligaments, and sends a duplicature upward between the lower extremities of the tibia and fibula
for a short distance.
Relations. — The tendons, vessels, and nerves in connection with the joint are, in front, from
within outward, the Tibialis anticus. Extensor proprius hallucis, anterior tibial vessels and
nerve, Extensor longus digitorum, and Peroneus tertius; behind, from within outward, the
Tibialis posticus. Flexor longus digitorum, posterior tibial vessels and nerve, Flexor longus
hallucis; and in the groove behind the external malleolus, the tendons of the Peroneus longus
and brevis.
The arteries supplying the joint are derived from the malleolar branches of the anterior
tibial and the peroneal.
The nerves are derived from the anterior and posterior tibial.
Inferior tibiofibular articulation.
Fig, 27G. — Ankle-joint: tarsal and tarsometatarsal articulations. External ■
Right side.
Movements. — The movements of the joint are those of flexion and extension. Flexion con-
sists in the apjiroximation of the dorsum of the foot to the front of the leg, while in extension
the heel is drawn up and the toes pointed downward. The malleoli tightly embrace the astragalus
in all positions of the joint, so that any slight degree of lateral movement which may exist is •
simply due to stretching of the inferior tibiofibular ligaments and slight bending of the shaft of
the filDula. Of the ligaments, the internal is of very great strength — so much so that it usually
resists a force which fractures the process of bone to which it is attached. Its middle portion,
together with the middle fasciculus of the external lateral ligament, binds the bones of the leg
firmly to the foot and resists displacement in every direction. Its anterior and posterior fibres
limit extension and flexion of the foot, respectively, and the anterior fibres also limit abduction.
The posterior portion of the external lateral ligament, assists the middle portion in resisting the
displacement of the foot backward, and deepens the cavity for the reception of the astragalus. The
anterior fasciculus is a security against the displacement of the foot forward, and limits extension
of the joint. The movements of inversion and eversion of the foot, together with the minute
changes in form by which it is applied to the ground or takes hold of an object in climbing, etc.,
are mainly effected in the tarsal joints, the one which enjoys the greatest amount of motion
being that between the astragalus and ("ilcanciis behind and the scaphoid and cuboid in front.
This is often called the transverse or mediotarsal joint, and it can, with the subordinate joints
of the tarsus, replace the ankle-joint in a great measure when the latter has become anky-
losed.
346
THE ARTICULATIONS, OB JOINTS
Extension of the tarsal bones upon the tibia and fibula is produced by theGast; ),?neinius
Soleus, Plantaris, Tibialis posticus, Peroneus longus and brevis, Flexor longus digitcium, and
Flexor longus hallucis; flexion, by the Tibialis anticus, Peroneus tertius. Extensor longus
dio-itorum, and Extensor proprius hallucis' (Fig. 268); inversion, in the extended position, is
produced by the Tibialis anticus and posticus; and eversion by the Peronei.
Surface Form. — The line of the ankle-joint may be indicated by a transverse line drawn
across the front of the lower part of the leg, about half an inch above the level of the tip of the
internal malleolus.
Applied Anatomy. — Displacement of the trochlear surface of the astragalus from the tibio-
fibular mortise is not of common occurrence, as the ankle-joint is a very strong and powerful
articulation, and great force is required to produce dislocation. Nevertheless, dislocation does
occasionallv occur, both in antero-posterior and a lateral direction. In the latter, which is the
most common, fracture is a necessary accompaniment of the injury. The dislocation in these
cases is somewhat peculiar, and is not a displacement in a horizontally lateral direction, such as
usually occurs in lateral dislocations of ginglymoid joints, but the astragalus undergoes a partial
rotation around an antero-posterior axis drawn through its own centre, so that the superior
surface, instead of being directed upward, is inclined more or less inward or outward accordinji
to the variety of the displacement.
Fig. 277. — Section of the right foot near its inner border, dividing the tibia, astragalas, calcaneus, scaphoid
internal cuneiform, and first metatarsal bone, and the first phalanx of the great toe. (After Braune.)
The ankle-joint is more frequently sprained than any other joint in the body, and this may-
lead to acute synovitis. In these cases, when the synovial sac is distended with fluid, the bulging
appears principally in the front of the joint, beneath the anterior tendons, and on either side,
between the Tibialis anticus and the internal lateral ligament on the inner side, and between the
Peroneus tertius and the external lateral ligament on the outer side. In addition to this, bulging
frequently occurs posteriorly, and a fluctuating swelling may be detected on either side of the
tendo Achillis.
Chronic synovitis may result from frequent sprains, and when once this joint has been sprained
it is more liable to a recurrence of the injury than it was before; chronic synovitis ma}' be tuber-
culous in its origin, the disease usually commencing in the astragalus and extending to the joint,
though it may commence as a synovitis, the result probably of some slight strain in a tuber-
culous subject.
Excision of the ankle-joint is not often performed for two' reasons. In the first place, disease
of the articulation, for which this operation is indicated, is frequently associated with disease of
the tarsal bones, which prevents its performance; and, secondly, the foot after excision is fre-
quently of very little use; far less, in fact, than after a Syme's amputation, which is often, there-
fore, a preferable operation in these cases.
'The student must bear m mmd that the Extensor Irngus digitorum and Extensor proprius hallucis are
■extm^ors of the toes, but flexors of the ankle, and that tne Flexor longus digitorum and Flexor longus hallucis
Jlre flexors of the toes, but extensors of the ankle.
THE ARTICULATIONS OF THE TAliNVS 347
V. The Articulations of the Tarsus (Articulationes Intertarseae)
(Figs. 275, 276).
1. The Articulu^tion of the Calcaneus and Astragalus (Articulatio
Talocalcanea) (Fig. 275).
The articulations between the calcaneus and astragalus are two in number —
anterior and posterior. They are arthrodial joints. The bones are connected
by a capsule (capsula articularis) , which is at certain points accentuated into
definite ligaments. There are five ligaments in this articulation:
External Calcaneo-astragaloid. Anterior Calcaneo-astragaloid.
Internal Calcaneo-astragaloid. Posterior Calcaneo-astragaloid.
Interosseous.
The external calcaneo-astragaloid ligament {ligamenhtm talocalcaneiim laterale)
(Fig. 276) is a short, strong, fasciculus passing from the outer surface of the
astragalus, immediately beneath its external malleolar facet, to the outer surface
of the calcaneus. It is placed in front of the middle fasciculus of the external
lateral ligament of the ankle-joint, with the fibres of which it is parallel.
The internal calcaneo-astragaloid ligament (lir/amentmn talocalcaneum mediale)
is a band of fibres connecting the internal tubercle of the back of the astragalus
with the back of the sustentaculum tali. Its fibres blend with those of the inferior
calcaneoscaphoid ligament.
The anterior calcaneo-astragaloid ligament (ligamenium talocalcaneum. an-
terius) passes from the front and outer surface of the neck of the astragalus to
the superior surface of the calcaneus.
The posterior calcaneo-astragaloid ligament {licjamentum. talocalcaneum jms-
terius) connects the external tubercle of the astragalus with the upper and inner
part of the calcaneus; it is a short band, the fibres of which radiate from their
narrow attachment to the astragalus.
The interosseus ligament {ligamentuvi talocalcaneuvi interosseuvi) (Fig. 279)
forms the chief bond of union between the bones. It consists of numerous
vertical and oblique fibres attached by one extremity to the groove between
the articulating facets on the under surface of the astragalus; by the other to
a corresponding depression on the upper surface of the calcaneus. It is very
thick and strong, being at least an inch in breadth from side to side, and serves
to unite the calcaneus and astragalus solidly together.
Sjmovial Membrane. — The synovial membranes (Fig. 279) are two in number, one for the
posterior calcaneo-astragaloid articulation, a second for the anterior calcaneo-astragaloid joint.
The latter synovial membrane is continued forward between the contiguous surfaces of the
astragalus and scaphoid bones.
Movements. — ^The movements permitted between the astragalus and calcaneus are limited to
a gliding of the one bone on the other in a du-ection from before backward, and from side to side.
2. The Articulation of the Calcaneus with the Cuboid (Articulatio
Calcaneocuboidea) (Fig. 275).
In this joint the articular capsule {capsula articularis) is strengthened at certain
points by definite ligaments.
The ligaments connecting the calcaneus with the cuboid are four in number:
Superior Calcaneocuboid. rj, , pi , f Long Calcaneocuboid.
The Internal Calcaneocuboid. ^° ^^ \ Short Calcaneocuboid.
348 THE ARTICULATIONS, OR JOINTS
The superior calcaneocuboid ligament (ligamentum cahaneocuhoideuvi dorsale)
(Fig. 276) is a broad portion of the capsule which passes between the contiguous
surfaces of the calcaneus and cuboid on the dorsal surface of the joint.
The internal calcaneocuboid or the interosseous ligament (fjars calcaneo-
cuboidea ligamenti bifurcati) is a short but thick and strong band of fibres arising
from the calcaneus, in the deep hollow which intervenes between it and the astrag-
alus, and closely blended, at its origin, with the superior calcaneoscaphoid liga-
ment. These two ligaments are often regarded as a single bifurcated ligament
(ligamentum bifurcatiim). The internal calcaneocuboid ligament is inserted into
the inner side of the cuboid bone. This ligament forms one of the chief bonds
of union between the first and second rows of the tarsus.
The long calcaneocuboid or long plantar or superficial long plantar ligament
(ligamentum plantare longum) (Fig. 278), the more superficial of the two plantar
ligaments, is the longest of all the ligaments of the tarsus; it is attached to the
under surface of the calcaneus, from near the tuberosities, as far forward as the
anterior tubercle; its fibres pass forward to be attached to the ridge on the under
surface of the cuboid bone, the more superficial fibres being continued onward
to the bases of the second, third, and fourth metatarsal bones. This ligament
crosses the groove on the under surface of the cuboid bone, converting it into a
canal for the passage of the tendon of the Peroneus longus.
The short calcaneocuboid or short plantar ligament (ligamentum calcaneo-
cuhoideum lolantare) (Fig. 278) lies nearer the bones than the preceding, from which
it is separated by a little areolar tissue. It is exceedingly broad, about an inch
in length, and extends from the tubercle and the depression in front of it, on the
fore part of the under surface of the calcaneus, to the inferior surface of the cuboid
bone behind the peroneal groove.
Synovial Membrane (Fig. 279). — The synovial membrane in this joint is distinct. It Hnes
the inner surface of the ligaments.
Movements. — The movements permitted between the calcaneus and cuboid are limited to a
slight gliding upon each other.
3. The Ligaments Connecting the Calcaneus ant) Scaphoid.
Though these two bones do not, as a rule, directly articulate, they are con-
nected by two ligaments:
Superior or External Calcaneoscaphoid.
Inferior or Internal Calcaneoscaphoid.
The superior or external calcaneoscaphoid ligament (pars calcaneonavicuhris
ligamenti bifurcati) arises, as already mentioned, with the internal calcaneocuboid
in the deep hollow between the astragalus and calcaneus, constituting a part of
the ligamentum bifurcatum; it passes forward from the upper surface of the ante-
rior extremity of ]the calcaneus to the outer side of the scaphoid bone. These
two ligaments resemble the letter Y, being blended together behind, but separated
in front.
The inferior or internal calcaneoscaphoid ligament (ligamentum calca7ieonavicu-
lare plantare) (Fig. 278) is by far the larger and stronger of the two ligaments be-
tween these bones; it is a broad and thick band of fibres, which passes forward
and inw^ard from the anterior margin of the sustentaculum tali of the calcaneus
to the under surface of the scaphoid bone. This ligament not only serves to
connect the calcaneus and scaphoid, but supports the head of the astragalus,
forming part of the articular cavity in which it is received. The upper surface
THE ARTICULATIONS OF THE TARSUS
349
presents a fibrocartilaginous facet, lined with the synovial membrane continued
from the anterior calcaneo-astragaloid articulation, upon which a portion of the
head of the astragalus rests. Its under surface is in contact with the tendon of the
Tibialis posticus muscle, its inner border is blended with the fore part of the deltoid
ligament, thus completing the socket for the head of the astragalus.
Applied Anatomy. — ^The inferior calcaneoscaphoid ligament, by supporting the head of the
astragakis, is principally concerned in maintaining the arch of the foot, and wlien it yields the
liead of the astragalus is pressed downward, inward, and forward by the weight of the body, and
the foot become flattened, expanded, and turned
outward, constituting the condition known as fiat-
foot. This ligament contains a considerable amount
of elastic tissue, so as to give elasticity to the arch
and spring to the foot; hence, it is sometimes called
the " spring" ligament. It is supported, on its under
surface, by the tendon of the Tibialis posticus, which
spreads out at its insertion into a number of fascic-
uli which are attached to most of the tarsal and
metatarsal bones; this prevents undue stretching of
the ligament, and is a protection against the occur-
rence of flat-foot.
4. The Articulation of the Astragalus
WITH the Scaphoid Bone ( Articulatio
Talonavicularis) (Fig. 275).
This is an arthrodial joint, the rounded
head of the astragalus being received into
the concavity formed by the posterior sur-
face of the scaphoid, the anterior articulating
surface of the calcaneus, and the upper sur-
face of the inferior calcaneoscaphoid liga-
ment, which fills up the triangular interval
between these bones. The only ligament of
this joint is the superior astragaloscaphoid
Fig. 273). It is a broad band, which passes
obliquely forward from the neck of the
astragalus to the superior surface of the
scaphoid bone. It is thin, and weak in
texture, and covered by the Extensor ten-
dons. The inferior calcaneoscaphoid liga-
ment supplies the place of an inferior
astragaloscaphoid ligament.
Synovial Membrane (Fig. 279), — The synovial membrane which lines the joint is continued
forward frc^m the anterior calcaneo-astragaloid articulation.
Movements. — This articulation permits of considerable mobility, but its feebleness is such
as to allow occasionally of dislocation of the otlu'i- bones of the tarsus from the astragalus.
The transverse tarsal or mediotarsal joint {(irlirn/iiiln tarsi transversa [Choparti]) (Figs. 275
and 280) is formed by the articulation of the os calcis with the cuboid, and by the articulation
of the astragalus with the scaphoid. The movement which takes place in this joint is more
extensive than that in the other tarsal joints, and consists of a sort of rotation by means of
which the sole, of the foot may be slightly flexed and extended or carried inward (inverted) and
outward (everted).
5. The Articulation of the Scaphoid with the Cuneiform Bones
(Articulatio Cuneonavicularis) (Fig. 275).
The scaphoid is connected to the three cuneiform bones by
Dorsal and Plantar Ligaments.
350 THE ARTICULATIONS, OR JOINTS
The dorsal ligaments Qigamenta navicidaricuneiformia dorsalia) (Figs. 273 and
275) are small, longitudinal bands of fibrous tissue arranged as three bundles,
one to each of the cuneiform bones. That bundle of fibres which connects the
scaphoid with the internal cuneiform is continued around the inner side of the
articulation to be continuous with the plantar ligament which connects these
two bones.
The plantar ligaments Qigamenta Jiavicularicimeiformia plantaria) (Fig. 278)
have a similar arrangement to those on the dorsum. They are strengthened by
processes given off from the tendon of the Tibialis posticus.
Synovial Membrane (Fig. 279). — The synovial membrane of these joints is part of the
great tarsal synovial membrane.
Movements. — The movements permitted between the scaphoid and cuneiform bones are
limited to a slight gliding upon each other.
6. The Articulation of the Scaphoid with the Cuboid (Articulatio
cuboideonavicularis) .
The scaphoid bone is connected with the cuboid by
Dorsal, Plantar, and Interosseous Ligaments.
The dorsal ligament {ligamentum cuhoideonaviculare dorsale) (Fig. 276) con-
sists of a band of fibrous tissue which passes obliquely forward and outward
from the scaphoid to the cuboid bone.
The plantar ligament {Jigamentum cuhoideonaviculare plantare) consists of a
band of fibrous tissue which passes nearly transversely between these two bones.
The interosseous ligament (Figs. 275 and 279) consists of strong transverse
fibres which pass between the rough nonarticular portions of the lateral sur-
faces of these two bones.
Synovial Membrane (Fig. 279). — The synovial membrane of this joint is part of the great
tarsal synovial membrane.
Movements. — The movements permitted between the scaphoid and cuboid bones are
limited to a slight gliding upon each other.
7. The Articulations of the Cuneiform Bones with Each Other or
THE Intercuneiform Articul.a.tions (Fig. 275).
These bones are connected by
Dorsal, Plantar, and Interosseous Ligaments.
The dorsal ligaments {ligamenta intercuneiformia dorsalia) consist of two bands
of fibrous tissue which pass transversely, one connecting the internal with the
middle cuneiform, and the other connecting the middle with the external cunei-
form.
The plantar ligaments (Ugaynenta intercuneiformia plantaria) have a similar
arrangement to those on the dorsum. They are strengthened by the processes
given off from the tendon of the Tibialis posticus.
The interosseous ligaments {ligamenta intercuneiformia interossea) consist of
strong transverse fibres which pass between the rough nonarticular portions of
the lateral surfaces of the first and second and the second and third cuneiform
bones. The outer portion of the third cunieiform is attached to the cuboid h^
the ligamentum cuneocuboideum interosseum (page 351).
THE TARSOMETATARSAL ARTICULATIONS 351
Synovial Membrane (Fig. 279). — The synovial membrane of these joints is part of the great
tarsal synovial membrane.
Movements. — The movements permitted between the cuneiform bones are limited to a slight
gliding upon each other.
8. The Articulation of the External Cuneiform Bone with the
Cuboid (Fig. 275).
These bones are connected by
Dorsal, Plantar, and Interosseous Ligaments.
The dorsal ligament (llgamentum cuneocuboideum dorsale) (Fig. 276) consists
of a band of fibrous tissue which passes transversely between these two bones.
The plantar ligament {ligamentum cuneocuboideum plantare) has a similar
arrangement. It is strengthened by a process given ofp from the tendon of the
Tibialis posticus.
The interosseous ligament (ligamentum cuneocuboideum interosseum) (Fig.
275) consists of strong transverse fibres which pass between the rough non-
articular portions of the lateral surfaces of the adjacent sides of these two bones.
Synovial Membrane (Fig. 279). — The synovial membrane of this joint is part of the great
tarsal synovial membrane.
Movements. — The movements permitted between the external cuneiform and cuboid are
limited to a slight gliding upon each other.
Nerve Supply. — All the joints of the tarsus are supplied by the anterior tibial nerve.
Applied Anatomy. — In spite of the great strength of the ligaments which hold the tarsal
bones together, dislocation at some of the tarsal joints occasionally occurs; these bones, on account
of their spongy character, are, as the result of direct violence, more frequently broken than dis-
located. When dislocation does occur, it is most commonly in connection with the astragalus;
for not only may this. bone be dislocated from the tibia and fibula at the ankle-joint, but the
other bones may be dislocated from it, the trochlear surface of the bone remaining in situ in the
tibiofibular mortise. This constitutes what is known as the suhastragaloid dislocation. Or,
again, the astragalus may be dislocated from all its connections — from the tibia and fibula
above, the os calcis below, and the scaphoid in front — and may even undergo a rotation, either
on a vertical or horizontal axis. In the former case the long axis of the bone becoming directed
across the joint, so that the head faces the articular surface on one or other malleolus; or, in the
latter, the lateral surfaces becoming directed upward and downward, so that the trochlear sur-
face faces to one or the other side. Finally, dislocation may occur at the mediotarsal joint, the
anterior tarsal bones being luxated from the astragalus and calcaneum. The other tarsal bones
are also, occasionally, though rarely, dislocated from their connections.
Pes planus or flat-foot is a condition in which there is abduction, eversion, and loss of both
the longitudinal and the transverse arch. The head of the astragalus passes downward and
inward; the anterior portion of the foot is turned outward and the inner side of the foot is
lengthened and broadened. Deformity is increased when standing. In severe cases the
patient walks on the inner side of the foot. The condition is due to weakness of the Tibialis
posticus muscle, with a consequent yielding of the tarsal ligaments. Abduction is permitted
by yielding of the internal lateral and calcaneo-astragaloid ligaments. Yielding of the inferior
calcaneo-scaphoid ligament permits the head of the astragalus to pass downward and forward,
and the entire arch falls.
VI. The Tarsometatarsal Articulations (Articulationes Tarsometatarseae)
(Figs. 275, 276).
These are arthrodial joints. The bones entering into their formation are four
tarsal bones — viz., the internal, middle, and external cuneiform and the cuboid —
which articulate with the metatarsal bones of the fi^'e toes. The metatarsal
bone of the great toe articulates with the internal cuneiform; that of the second
is deeply wedged in between the internal and external cuneiform, rests against
the middle cuneiform, and is the most strongh' articulated of all the metatarsal
352 THE ARTICULATIONS, OB JOINTS
bones; the third metatarsal articulates with the extremity of the external cunei-
form; the fourth, with the cuboid and external cuneiform; and the fifth, with
the cuboid. The articular surfaces are covered by hyaline cartilage, lined with
syno^'ial membrane, and interconnected by capsules and by the following liga-
ments :
Dorsal. Plantar. Interosseous.
The dorsal ligaments (ligamenta. tarsometatarsea dorsalia) consist of strong,
flat, fibrous bands, which connect the tarsal with the metatarsal bones. The
first metatarsal is connected to the internal cuneiform by a single broad, thin,
fibrous band; the second has three dorsal ligaments, one from each cuneiform
bone; the third has one from the external cuneiform; the fourth has two, one
from the external cuneiform and one from the cuboid; and the fifth, one from
the cuboid.
The plantar ligaments {Ugavienta tarsometatarsea flantaria) consist of longi-
tudinal and oblique fibrous laands connecting the tarsal and metatarsal bones,
but disposed with less regularity than on the dorsal surface. Those for the first
and second metatarsal are the most strongly marked; the second and third
metatarsal receive strong fibrous bands which pass obliquely across from the
internal cuneiform; the plantar ligaments of the fourth and fifth metatarsal
consist of a few scanty fibres derived from the cuboid.
The interosseous ligaments {ligamenta cuneometatarsea interossea) are three
in number— internal, middle, and external. The internal one is the strongest
of the three, and passes from the outer extremity of the internal cuneiform to
the adjacent angle of the second metatarsal. The middle one, less strong than
the preceding, connects the external cuneiform with the adjacent angle of the
second metatarsal. The external interosseous ligament connects the outer angle
of the external cuneiform with the adjacent side of the third metatarsal.
Synovial Membrane (Fig. 279). — The synovial membrane between the internal cuneiform
bone and the first metatarsal bone is a distinct sac. The synovial membrane between the middle
and external cuneiform behind, and the second and third metatarsal bones in front, is part of the
great tarsal synovial membrane. Two prolongations are sent forward from it — one between
the adjacent sides of the second and third metatarsal bones, and one between the third and
fourth metatarsal bones. The synovial membrane between the cuboid and the fourth and
fifth metatarsal bones is a distinct sac. From it a prolongation is sent forward between the fourth
and fifth metatarsal bones.
Movements. — The movements permitted between the tarsal and metatarsal bones are
limited to a slight gliding upon each other.
VII. The Articulations of the Metatarsal Bones with Each Other
(Articulationes Intermetatarseae) (Figs. 275, 276).
The base of the first metatarsal bone is not connected with the second meta-
tarsal bone by any ligaments; in this respect it resembles the thumb.
The bases of the four outer metatarsal bones are connected by dorsal, plantar,
and interosseous ligaments.
The dorsal ligaments (ligamenta hasium [oss. mefatars.] dorsalia) consist of
bands of fibrous tissue which pass transversely between the adjacent metatarsal
bones.
The plantar ligaments (ligamenta basium [oss. metatars.] plantaria) have a
similar arrangement to those on the dorsum.
The interosseous ligaments (ligamenta basium [oss. metatars.] interossea) con-
sist of strong transverse fibres which pass between the rough nonarticular portions
of the lateral surfaces.
THE METATARSOPHALANGEAL ABTLCTJLATIONS
353
Synovial Membrane. — The synovial membrane between the second and third and the third
and fourth metatarsal bones is part of the great tarsal synovial membrane. The synovial mem-
brane between the fourth and fifth metatarsal bones is a prolongation of the synovial membrane
of the cubometatarsal joint (Fig. 279).
Movements.- -The movement permitted in the tarsal ends of the metatarsal bones is limited
to a sliijht i/liiliini of the articular surfaces upon one another.
The Synovial Membranes in the Tarsal and Metatarsal Joints. — The synovial mem-
branes (Fig. 279) found in the articulations of the tarsus and metatarsus are six in number —
one for the posterior calcaneo-astragaloid articulation; a second for the anterior calcaneo-astrag-
aloid and astragaloscaphoid articulations; a third for the calcaneocuboid articulation; and a
fourth for the articulations of the scaphoid with the three cuneiform, the three cuneiform
with each other, the external cuneiform with the cuboid, and the middle and external cunei-
form with the bases of the second and third metatarsal bones, and the lateral surfaces of the
Becond, third, and fourth metatarsal bones with each other. The Jiffh synovial membrane is
found in the articulation of the internal cuneiform with the metatarsal bone of the great toe; and
tiere is a sixth for the articulation of the cuboid with the fourth and f5fth metatarsal bones. A
small synovial membrane is sometimes found between the contiguous surfaces of the scaphoid
and cuboid bones.
Nerve Supply. — The nerves supplying the tarsometatarsal joints are derived from the
anterior tibial.
Fig. 279. — Oblique section of the articuhtions of tarsus and metatarsus Showing the six s\ no\ lal membranes.
The digital extremities .'f all the metatarsal bones are connected by the transverse
metatarsal ligament.
The transverse metatarsal ligament is a narrow fibrous band which passes
transversely across the anterior extremities of all the metatarsal bones, con-
necting them. It is blended aiiieriorhj with the plantar (glenoid) ligament of
each metatarsophalangeal articulation. To its posterior border is connected
the fascia covering the Interossei muscles. Its inferior surface is concave where
the Flexor tendons pass over it. Above it the tendons of the Interossei muscles
pass to their insertion. It differs from the transverse metacarpal ligament in
that it connects the metatarsal bone of the great toe with the rest of the meta-
tarsal bones.
Vin. The Metatarsophalangeal Articulations (Articulationes Metatarso-
phalangeae) .
The metatarsophalangeal articulations are of the condyloid variety, formed by
the reception of the rounded heads of the metatarsal bones into shallow cavities
in the extremities of the first phalanges. Each joint has a capsule and certain
other ligaments. These ligaments are :
Plantar.
Two Lateral.
354 THE ARTICULATIONS, OB JOINTS
The plantar ligaments (ligamenta accessoria flantaria) are thick, dense, fibrous
structures. Eacii is placed on the plantar surface of the joint in the interval
between the lateral ligaments, to which it is connected. The plantar ligaments
are loosely united to the metatarsal bones, but very firmly to the bases of the
first phalanges. The plantar surface of each is intimately blended with the
transverse metatarsal ligament, and, except in the great toe, presents a groove
for the passage of the Flexor tendons, the sheath surrounding which is connected
to each side of the groove. The plantar ligament of the great toe contains two
large sesamoid bones. By their deep surface they form part of the articular sur-
face for the head of the metatarsal bone, and are lined with synovial membrane.
The lateral ligaments (ligamenta collateralia) 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 metatarsal bone; and, by the other, to
the contiguous extremity of the phalanx.
The place of a dorsal ligament is supplied by the Extensor tendon over the
back of the joint.
Movements. — The movements permitted in the metatarsophalangeal articulations are flexion,
• extension, abduction, and adduction.
IX. The Articulations of the Phalanges (Articulationes Digitorum Pedis).
The articulations of the phalanges are ginglymoid joints. Besides the cap-
. sular the ligaments are :
Plantar. Two Lateral Qigamenta collateralia).
The arrangement of these ligaments is similar to those in the metatarsophalan-
geal articulations; the Extensor tendon supplies the place of a dorsal ligament.
Movements. — The only movements permitted in the phalangeal joints are flexion and exten-
-sion; 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
bv the pkntar and lateral ligaments.
Surface Form. — The principal joints which it is necessary to distinguish, with regard to the
surgery of the foot, are the intertarsal and the tarsometatarsal. The joint between the astragalus
and the scaphoid is best found by means of the tubercle of the scaphoid, for the line of the joint
is immediately behind this process. If the foot is grasped and forcibly extended, a rounded
prominence, the head of the astragalus, will appear on the inner side of the dorsum in front
of the ankle-joint, and if a knife is carried downward, just in front of this prominence and behind
the line of the scaphoid tubercle, it will enter the astragaloscaphoid joint. The calcaneocuboid
joint is situated midway between the external malleolus and the prominent end of the fifth
metatarsal bone. The plane of the joint is in the same line as that of the astragaloscaphoid.
The position of the joint between the fifth metatarsal bone and the cuboid is easily found by
the projection of the fifth metatarsal bone, which is the guide to it. The direction of the line
of the joint is very oblique, so that, if continued onward, it would pass through the head of the
first metatarsal bone. The joint between the fourth metatarsal bone and the cuboid and external
cuneiform is the direct continuation inward of the previous joint, but its plane is less oblique; it
would be represented by a line drawn from the outer side of the articulation to the middle of the
first metatarsal bone. The plane of the joint between the third metatarsal bone and the external
cuneiform is almost transverse. It would be represented by a line drawn from the outer side
of the joint to the base of the first metatarsal bone. The tarsometatarsal articulation of the great
toe corresponds to a groove which can be felt by making firm pressure on the inner side of the
foot one inch in front of the tubercle on the scaphoid bone; and the joint between the second
metatarsal bone and the middle cuneiform is to be found on the dorsum of the foot, half
an inch behind the level of the tarsometatarsal joint of the great toe. The line of the joints
between the metatarsal bones and the first phalanges is about an inch behind the webs of the
' corresponding toes.
Applied Anatomy.— This is considered on p. 256.
THE MUSCLES AND FASCM/
MYOLOGY is the branch of anatomy which treats of the muscles. The
muscles are formed of bundles of reddish fibres, endowed notably with the
property of contractility in the direction of the long axes of the muscle cells.
Contractions of muscle fibres induce motion. The two principal kinds of muscle
tissue found in the body are the more highly differentiated, or voluntary, and
the less highly differentiated, or involuntary. The former of these, from the char-
acteristic appearances which its fibres exhibit under the microscope, is known as
striated, or striped muscle. As most striped muscles are capable of being put into
action and controlled by the will, they are generally called "voluntary" muscles.
The fibres of involuntary muscle do not present any cross-striped appearance, and
■are not under the control of the will; such muscles are known as unstriated, un-
striped or vegetative. The muscle fibres of the heart differ in certain particulars
from both these groups, and they are therefore separately described as cardiac
muscle fibres.
Thus, it will be seen that there are three varieties of muscle tissue: (1) Trans-
versely striated fibres, which are for the most part voluntary and under the control
■of the will. This variety of muscle is also called skeletal. (2) Transversely
striated muscle fibres, which are not under the control of the will — i. e., the
cardiac muscles. The cardiac muscle occupies a mid-position in the scale be-
tween the cells of involuntary and the striated fibres of voluntary muscle. (3)
Plain or unstriped muscle fibres, which are involuntary, and are controlled by
.a different part of the nerve system from that which controls the activity of the
voluntary muscles. Such are the muscular walls of the stomach and intestine,
of the uterus and bladder, of the bloodvessels, of certain canals and ducts, etc.
The statement that striated muscle is always voluntary, and that nonstriated
muscle is always involuntary, cannot be accepted as invariably and inevitably
true. There are animals in which some voluntary muscle is free from distinct
striation, while the Diaphragm, made up of striated muscle fibres, is not wholly
under the control of the will.
Although the voluntary striated muscle tissue alone is concerned in the skeletal
musculature, all three varieties of muscle tissue will be described here. The
skeletal muscles act upon the bones, and thus produce movement. The primitive
contractile elements of a muscle are the fibres. Fibres are gathered into groups
known as primary bundles or fasciculi, and the fasciculi are aggregated into masses
called secondary bundles. In coarse muscles the fasciculi are of considerable
size; in fine muscles they are of trivial size. Fasciculi may be long or short,
.and the length does not depend on the length of the muscle.
Structure of Striated Muscle. — Each muscle is surrounded by a sheath of fibrous tissue
called the epimysium; this sends in septa which surround the secondary bundles; these in
turn send in the perimysium which surrounds each muscle fasciculus. The fibres of each
* The Muscles and Fascite are described conjointly, in order that the student may consider the arrangement
of the latter in his dissection of the former. It is rare for the student of anatomy in this coiintry to dissect
the fasciiE separately: and it is for this reason, as well as from the close connection that exists between the
muscles and their investing sheaths, that they are considered together. Some general observations are first
made on the histology and anatomy of the nauscles and fasciie, the special description being given in connection
with the different regions.
(355)
356
THE MUSCLES AND FASCIJE
fasciculus are separated by a delicate meshwork of fibroelastic tissue, the endcmysium, which
supports the small vessels and nerves.
Structure of the Muscle Fibre. — A muscle fibre is a long cylindrical cell varying from
less than one to fi\'e inches (2.5 to 12.5 cm.) in length. It is surrounded by a delicate sheath
called the sarcolemma, within which lie the nuclei and muscle substance. The muscle sub-
stance consists of two elements — the fibrillae, or contractile portion of the fibre, and the sarco-
plasm, or undifferentiated portion. The fibrillae are arranged parallel to one another and are
separated by the sarcoplasm; and as the former respond well to the protoplasmic stains, and the
latter practically not at all, the alternation of such stained and unstained stripes produces the
\tropiC Mjcr— ijHiiH If r(<ittJ(»*!/
fi i" fiiHiiivi!.;.'
Primitive jibril
\Mxmi\i
se line of Briicke
Fig. 280. — Two human muscle fibres.
X .350. In the one the bundle of fibrilte
(6) is torn, and the sarcolemma (a) is
seen as an empty tube.
; (fiij xitiuiiiii'X
'.'tiiiifuiiiiiiitji;
i ii\ i i 1 a Hi f /'lifiij
; (iiiiiiijj'^f'jtJj.'ifJ y
jMfiJtntTij'ifiin]'! —
' .(iiJtini iiiijiji'i
ituTiuTiJsii'}}'!
fiisiKriHi''!!!? r^ , ,
lljliiill i f HilljL-^'""'""^^ membrane
^iliiiisjinjiyi'- '' "^
Fig. 281, — A bit of a cross-striated muscle of a frog, show-
ing the nucleus and the ease of its division both transversely
and longitudinally. X 650. (Szymonowicz and MacCallum.)
longitudinal striaiions so typical of the appearance of a longitudinal section of muscle under
the microscope. • In a cross-section the fibrillae are arranged more or less in groups called
Cohnheim's fields.
The fibrillar, or sarcostyle, are not unbroken threads, but all are interrupted at intervals into
short segments called sarcous elements. As a result of this segmentation a fibre exhibits alter-
nating transverse dark and light bands (cross-striations). If a muscle fibre be examined under
high magnification, a light line is seen traversing each
dark band (anisotropic) ; this is the membrane of Hensen.
The light band (isotropic) is traversed by a dark line,
Dobie's line, or the memjorane of Krause, that divides
the band into two parts, the lateral disks. A sarcomere
is that part of a fibril between two membranes of
Krause, and consists of a sarcous element and a lateral
disk at each end of the sarcous element.
The nuclei are numerous and are situated peripherally,
i. e., just beneath the sarcolemma. They are narrow
and elongated in form, and respond readily to the usual
stains. Branched fibres are occasionally seen in the
tongue. There are two kinds of fibres, red and wltite;
the former are rich in sarcoplasm and the nuclei are
deeply placed and are intermediate in development be-
tween myoplasm and the white fibres. The w/iife fibres are poor in sarcoplasm and predominate
in human muscles. The Trapezius muscle contains both red and white fibres.
The arteries of voluntary muscles are numerous. They pierce the epimysium, pass along
the septa from the epimysium, and divide into small branches, which enter between the
Fig. 2S2. — Section of a muscle fibre,
showing areas of Cohnheim. Three nuclei
are seen lying close to the sarcolemma.
(Schafer.)
FOBBI AND ATTACHMENT OF MUSCLES
357
m
fasciculi. These small branches pass into capillaries which run parallel to the fibres. At
intervals dilatable connections {ampullce) are established between the capillaries, and it is into
these that during contractions of the muscle the blood passes to relieve the tension in the longi-
tudinal capillaries.
Veins accompany the arteries, and even the smaller ones possess valves (Spalteholz) .
The nerve endings in voluntary nuiscle comprise both motor and sen.sor varieties. A motor
nerve iiirrccs the ciiiinysiuiri and breaks up into numerous branches to form an interfascicular
plexus in I lie pciimysiuni. From this ]ilexus nerve fibrils arise, and usually one nerve fibril passes
to each muscle fibre. The nerve fibril pierces the sarcolemma, the neurilemma, and myelinic
sheath disappearing before the nerve fibril reaches the muscle fibre, and probably being lost
by fusing with the sarcolemma. The naked axone beneath
the sarcolemma of a fibre continues to the surface of the mms: , r, - , ■ --, .,_ ,.„„^
muscle fibre and undergoes arborization to form an end organ.
Ai-ound the end organ is a quantity of grantilar saix Jiilasm,
which, with the nerve and organ, constitutes a sole plate.
A sensor nerve takes origin from a muscle spindle, \\ Inch
consists of a. bundle of encapsulated muscle fibres about sensor
nerve twigs.
Involuntary striated or cardiac muscle is found in the
heart and is not under the control of the will. Each fibre is
a short cylinder varying from 1 00 ,« to 200 /i in length and
of about 25 /j. to 40 fi in diameter. The striations are both
longitudinal and transverse, but the latter are usually not
distinct. Each fibre is surrounded by a delicate membrane.
The cells give off narrow processes of branches which con-
nect with each other, thus forming "a reticulum of muscle
fibres. The meshes of this reticulum are occupied by areolar
tissue in which the vascular and nerve supply of the tissue
is situated."
Usually a single, large, oval nucleus occupies the centre of
the cell and is surrounded by an area of clear and undiffer-
entiated protoplasm in which fibrilloe do not exist. Pigment
granules are seen in this undifferentiated protoplasm.
Purkinje fibres are peculiar muscle fibres found in the
heart, and will be described with that organ.
The nerves are both sympathetic and cerebrospinal.
Involimtaiy non-striated or smooth muscle is not under the control of the will. It is found
in the alimentary tract from the middle third of the oesophagus down, in gland ducts, trachea,
bronchi, bronchial tubes, in the urinogenital system, bloodvessels and lymph vessels, etc. It is
found arranged in layers that encircle the organs longitudinally, transversely, and sometimes
in an interlaced manner.
-'J
Fig. 283. ■ — Anastomosing muscle
fibres of the heart, seen in a longitu-
dinal section. On the right the limits
of the separate cells with their nuclei
are e.\hibited somewhat diagrammat-
ically.
Intercellular
bridges'
Fig. 284. — Longitudinal section in the smooth muscle of a dog's large intestine, to show especially intercellular
bridges. X 530. (Szymonowicz and IMacCallum.)
Each fibre is short and spindle-shaped, varying from 25 /i to 200 fi in length and from 5 /j.
to 7 /i in diameter. In the gravid uterus they are much larger in both dimensions. Occa-
sionally, longitudinal striations are seen, and then the fibrillse so formed are coarse and periph-
erally located. Each fibre contains a single slender nucleus which is centrally located. Branched
fibres are occasionally seen in the aorta and in the bladder.
The bloodvessels form a raeshwork between the fibres.
The nerves are from the sympathetic system, though Kuntz has recently shown that in some
organs, at least, the nerves are originally derived from the vagus.
Form and Attachment of Muscles. — The muscles are connected with the bones,
cartilages, liaaments, and skin, either directly or through the intervention of
358 THE MUSCLES AND FASCIA
fibrous structures called tendons or aponeuroses. Where a muscle is attached
to bone or cartilage, the fibres terminate in blunt extremities upon the periosteum
or perichondrium, and do not come into direct relation with the osseous or carti-
laginous tissue. Where muscles are connected with the skin, they either lie as
a flattened layer beneath it, or are connected with its areolar tissue by larger or
smaller bundles of fibres, as in the muscles of the face. The origin of a muscle
is its head (caput), while the intermediate portion is called the belly, or venter.
The muscles vary extremely in their form. In the limbs they are of consider-
able length, especially the more superficial ones, the deep ones being generally
broad; they surround the bones and form an important protection to the various
joints. In the trunk they are broad, flattened, and expanded, forming the parietes^
of the cavities which they enclose; hence the reason of the terms lotig, broad,
short, etc., used in the description of a muscle.
There is a considerable variation in the arrangement of the fibres of certain
muscles with reference to the tendons to which they are attached. In some, the
fibres are parallel and run directly from their origin to their insertion; these are
quadrilateral muscles, such as the Thyrohyoid. A modification of these is found
in the fusiform muscles in which the muscle tapers at each end; in their action,
however, they resemble the quadrilateral muscles.
Secondly, in other muscles the fibres are con-
vergent; arising by a broad origin, they converge
to a narrow or pointed insertion. This arrange-
ment of fibres is found in the triangular muscles —
e. (J., the Temporal. In some muscles, which
otherwise would belong to the quadrilateral or
triangular type, the origin and insertion are not in
the same plane, but the plane of the line of origin
intersects that of their insertion; such is the case
in the Pectineus muscle. Thirdly, in some muscles
the fibres are oblique and converge, like the
plumes of a pen, to one side of a tendon, which
runs the entire length of the muscle. Such a
muscle is penniform Qn. unipennatus), as the
„„„,,,. ti,. T^, •■ Peronei. A modification of these muscles is found
Fig. 285.— Diagram of the Deltoid, an . , , t t m i i
example of a multipennate muscle. m tllOSC CaSCS Wliere obliqUC nbrCS COllVCrge tO DOth
sides of a central tendon which runs down the
middle of the muscle ; these are called bipenniform (??i. bipennaius), and an example is
afforded in the Rectus femoris. Multipennate muscles are those in which the muscle
fibres alternate with a series of tendinous bands, as in the Deltoid. Biventral
muscles occur, such as the Digastric, while the Rectus abdominis shows subdivision
into four or more sections by intervening inscriptiones tendineae. Certain muscles
do not act in a direct manner, for they or their tendons pass around a bony pro-
jection or through a septal pulley (trochlea). Finally, we have muscles in which
the fibres are arranged in curved bundles in one or more planes, as in an orbicular
muscle and in that variety of orbicular muscle called a sphincter muscle. The
arrangement of the muscle fibres is of considerable importance in respect to their
relative strength and range of movement. Those muscles in which the fibres are
long and few in number have great range, but diminished strength; where, on
the other hand, the fibres are short and more numerous, there is great power,,
but lessened range.
Muscles differ much in size; the Gastrocnemius forms the chief bulk of the
back of the leg; the Sartorius is very long; the Stapedius, a small muscle of the
internal ear, weighs about a grain, and its fibres are not more than 4 mm. in
length.
FOBM AND ATTACHMENT OF MUSCLES 359
The names applied to the various muscles have been derived (1) from their
situation, as the Tibialis, Radialis, Ulnaris, Peroneus; (2) from their direction, as
the Rectus abdominis, Obliquus capitis. Transversal is; (3) from their uses, as
Flexors, Extensors, Abductors, I^evators, Compressors, etc. ; (4) from their shape,
as the Deltoid, Trapezius, Rhomboideus, Digastric; (5) from the v.umber of their
divisions, as the Biceps, the Triceps; (6) from their points of attachment, as the
Sternomastoid, Sternohyoid, Sternothyroid.
In the description of a muscle the term origin is meant to imply its more fixed
or central attachment, and the term insertion, the movable point to which the
force of the muscle is directed; but the origin is absolutely fixed in only a very
small number of muscles, such as those of the face, which are attached by one
extremity to the bone and by the movable integument; the greater number of
muscles can be made to act from either extremity.
In the dissection of the muscles, the student should pay especial attention to
the exact origin, insertion, and actions of each, and its more important relations
with surrounding parts. While accurate knowledge of the points of attachment of
the muscles is of great importance in the determination of their actions, it is not to
be regarded as conclusive. The action of a muscle deduced from its attachments,
or even by pulling on it in the dead subject is not necessarily its action in the
living. By pulling, for example, on the Brachioradialis in the cadaver the hand
may be slightly supinated' when in the prone position and slightly pronated when
in the supine position, but there is no evidence that these actions are performed
by the muscle during life. It is impossible for an individual to throw into action
any one muscle; in other words, movements, not muscles, are represented in the
central nerve system. To carry out a movement a definite combination of muscle?
is called into play, and the individual has no power either to leave out a muscle
from this combination, or to add one to it. One muscle (or more) of the combina-
tion is the chief moving force: when this muscle passes over more than one joint
other muscles (sjmergic muscles) come into play to inhibit the movements not
required; a third set of muscles (fixation muscles) fix the limb — /. e., in the case
of the limb movements — and also prevent disturbances of the equilibrium of
the body generally. As an example, the movement of the closing of the fist
may be considered: (11 The prime movers are the Flexores digitorum, Flexor
longus pollicis, and the small muscles of the thumb; (2) the synergic muscles are
the Extensores carpi, which prevent flexion of the wrist; while (3) the fixation
muscles are the Biceps and Triceps, which steady the elbow and shoulder. A
further point which must be borne in mind in considering the actions of muscles
is that in certain positions a movement can be efl^ected by gravity, and in such a
case the muscles acting are the antagonists of those which might be supposed
to be in action. Thus, in flexing the trunk when no resistance is interposed the
Erectores spinae contract to regulate the action of gravity, and the Recti abdominis
are relaxed.^
Applied Anatomy. — By a consideration of the 'action of the muscles the surgeon is able to
explain the causes of displacement in various forms of fracture, and the causes \yhich produce
distortion in various deformities, and, consequently, to adopt appropriate treatment in each
case. The relations, also, of some of the muscles, especially those in immediate apposition
with the larger bloodvessels, and the surface-markings they produce, should be carefully remem-
bered, as they form useful guides in the application of ligatures to those vessels.
Degeneration of muscle tissue is important clinically, and is met with in two main conditions.
In one, the degeneration is myopathic, or primary in the muscles themselves; in the other it
is neuropathic, or secondary to some lesion of the nerve system — a hemorrhage into the brain,
1 Hence the old name Supinator longus, dow supplanted by Brachioradialis.
- Consult in this connection the Croonian Lectures (190.3) on " Muscular Movements and Their Representation in
the Central Nervous System," by Charles E. Beevor, M.D.
360 THE MUSCLES AND FASCIA
for example, or injury or inflammation of some part of the spinal cord or peripheral nerves.
In either case more or less paralysis and atrophy of the affected muscles result. When the
degeneration begins primarily in the muscles, however, it often happens that though the muscle
fibres waste away, their place is taken by fibrous and fatty tissue to such an extent that the
affected muscles increase in volume, and actually appear to hypertrophy.
Ossification of muscle tissue as a result of repeated strain or injury is not infrequent. It is
oftenest found about the tendon of the Adductor longus and Vastus internus in horsemen, or in
the Pectoralis major and Deltoid of soldiers. It may take the form of exostoses firmly fixed to
the bone — e. g.^ "rider's bones" on the femm- (pages 229 and 51.5) — or of layers or spicules of
bone lying in the muscles of their fasciae and tendons. Busse states that these bony deposits
are preceded by a hemorrhagic myositis due to injury, the effused blood organizing and being
finally converted into bone. In the rarer disease, progressive myositis ossifi,cans, there is an
unexplained tendency for practically any of the voluntary muscles to become converted into
solid and brittle bony masses which are completely rigid.
Tendons are white, glistening, fibrous cords, varying in length and thickness,
sometimes round, sometimes flattened, of considerable strength, and devoid of
elasticity. They consist almost entirely of dense, white fibrous tissue, the fibrils
of which run in an undulating parallel course and are firmly united together.
They are very sparingly supplied with bloodvessels, the smaller tendons present-
ing not a trace of them in their interior. Nerves supplying tendons have special
modifications of their terminals, termed neurotendinous spindles or organs of
Golgi (p. 817).
Aponeuroses are fllattened or ribbon-shaped tendons, of a pearly-white color,
iridescent, glistening, and similar in structure to the tendons; the thicker ones are
only sparingly supplied with bloodvessels.
The tendons and aponeuroses are connected, on the one hand, with the muscles,
and, on the other hand, with movable structures, as the bones, cartilages, liga-
ments, fibrous membranes (for instance, the sclera). Where the muscle fibres
are in a direct line with those of the tendon or aponeurosis, the two are directly
continuous, the muscle fibre being distinguishable from that of the tendon only
by its striation and increase of muscle nuclei. But where the muscle fibres join
the tendon or aponeurosis at an oblicjue angle the former terminate, according
to KoUiker, in rounded extremities, which are received into corresponding de-
pressions on the surface of the latter, the connective tissue between the fibres
being continuous with that of the tendon. The latter mode of attachment occurs
in all the penniform and bipenniform muscles, and in those muscles the tendons
of which commence in a membranous form, as the Gastrocnemius and Soleus.
The fasciae are fibroareolar or aponeurotic laminte of variable thickness and
strength, found in all regions of the body, investing the softer and more delicate
organs. The fascise have been subdivided, from the situation in which they are
found, into two groups, superficial and deep.
The superficial fascia (pannicidus adiposus) is found immediately beneath the
integument over almost the entire surface of the body. It connects the skin
with the deep or aponeurotic fascia, and consists of fibroareolar tissue, containing
in its meshes pellicles of fat, in varying quantity. The superficial fascia varies
in thickness in different parts of the' body : in the groin it is so thick as to be
capable of being subdivided into several laminae. Beneath the fatty layer of
the superficial fascia, which is immediately subcutaneous, there is generally
another layer of the same structure, comparatively devoid of adipose tissue,
in which the trunks of the subcutaneous vessels and nerves are found, as the
superficial epigastric vessels in the abdominal region, the radial and ulnar veins
in the forearm, the saphenous veins in the leg and thigh, and the superficial
lymph nodes. Certain cutaneous muscles also are situated in the superficial
fascia, as the Platysma in the neck, and the Orbicularis palpebrarum around
the eyelids. This fascia is most distinct at the lower part of the abdomen, the
scrotum, perineum, and extremities; it is very thin in those regions where mus-
APONEUROSES' 361
cle fibres are inserted into the integument, as on the side of the neck, the face,
and around the margin of the anus. It is very dense in the scalp, in the mammae,
the palms of the hands and soles of the feet, forming a fibrofatty layer which
binds the integument firmly to the subjacent structure.
The superficial fascia connects the skin to the subjacent parts, facilitates the
movement of the skin, serves as a soft medium for the passage of vessels and nerves
to the integument, and retains the warmth of the body, since the fat contained in
its areoliie is a poor conductor of heat.
The deep or aponeurotic fascia, is a dense, inelastic, unyielding fibrous mem-
brane, forming sheaths for the muscles and afl^ording them broad surfaces for
attachment. It consists of shining tendinous fibres, placed parallel to one
another, and connected by other fibres disposed in a rectilinear manner. It is
usually exposed on the removal of the superficial fascia, forming a strong in-
vestment,which not only binds down collectively the muscles in each region, but
gives a separate sheath to each, as well as to the vessels and nerves. The fascia
are thick in unprotected situations, as on the outer side of a limb, and thinner on
the inner side. The deep fascise assist the muscles in their action by the degree
of tension and pressure they make upon their surface; and in certain situations
this is increased and regulated by muscular action; as, for instance, by the Tensor
fasciae femoris and Gluteus maximus in the thigh, by the Biceps in the upper
and lower extremities, and Palmaris longus in the hand. In the limbs the fasciae
not only invest the entire limb, but give off septa which separate the various
muscles, and are deeply attached to the periosteum; these prolongations of fasciae
are usually spoken of as intermuscular septa.
Bevelopment of the Skeletal Musculature. — The voluntary muscles are developed from
the myotomes of the mesodermal somites. Portions of the myotomes retain their position along
the body axis in segmental order, such as the short muscles of the vertebral column. Others
migrate into the body wall, where again they may retain their segmental relation (intercostal
muscles), or may fuse with adjacent segments to form Qat muscles such as those in the abdom-
inal wall. In the limbs, portions of myotomes wander into the limb buds and there undergo
fusions and alterations in form to produce the limb muscles, thus losing their segmental char-
acter, but retaining the appropriate segmental nerve supplies. Some of the limb muscles expand
and migrate secondarily toward the dorsimesal line (e. g., Trapezius, Latissimus) or toward
the ventromesal line (e. g., Pectoralis major). Again, muscles may migrate cephalad (e. g.,
the facial muscles derived from the hyoid arch) or caudad (e. g., Serratus magnus). In all
cases the muscles carry with them the segmental nerves of the myotomes from which they were
derived; the most striking example is the Diaphragm which is derived from the third, fourth,
and fifth cervical myotomes, and is supplied by the phrenic nerves, which spring from the
third, fourth, and fifth cervical nerves. Some of the derivatives of the myotomes degenerate
and are converted into ai^oneuroses (e. g., epicranial aponeurosis) or into ligaments {c. g., great
sacrosciatic ligament and external lateral ligament of the knee).
Various disturbances of development characterize what are known as variable or anomalous
muscles. Such muscles may be wanting, or excessively developed in the way of accessory
portions or with atypic attachments. The resemblance which such muscles in the human subject
bear to certain muscles in lower animals has been regarded by some anatomists as an expression
of atavistic reversion.'
The muscles and fasciae may be arranged according to the general division
of the body, into those of the cranium, face, and neck; those of the trunk; those of
the upper "extremity or pectoral limb; and those of the lower extremity or pelvic
limb.
■ See. however, Huntington, American Journal of Anatomy, 1902-03, vol. ii, p. 157.
362
THE MUSCLES AND FASCIA
MUSCLES AND FASCI-ffi OF THE CRANIUM AND FACE.
The muscles of the cranium and face consist of ten groups, arranged according
to the region in which they are situated:
6. Maxillary Region.
7. Mandibular Region.
8. Buccal Region.
9'. Temporomandibular Region.
10. Pterygomandibular Region.
1. Cranial Region.
Auricular Region.
Palpebral Region.
Orbital Region.
Nasal Region.
The muscles contained in each of these groups are the following:
1. Cranial Region. 6. Maxillary Region.
Occipitofrontalis. Levator labii superioris.
2. Auricular Region.
Attrahens aurem.
Attollens aurem.
Retrahens aurem.
3. Palpebral Region.
Orbicularis palpebrarum.
Corrugator supercilii.
Tensor tarsi.
4. Orbital Region.
Levator palpebrae.
Rectus superior.
Rectus inferior.
Rectus internus.
Rectus externus.
Obliquus oculi superior.
Obliquus oculi inferior.
5. Nasal Region.
Pyramidalis nasi.
Levator labii superioris alaeque
nasi.
Dilatator naris posterior.
Dilatator naris anterior.
Compressor nasi.
Compressor narium minor.
. Depressor alae nasi.
Levator anguli oris.
Zygomaticus major.
Zygomaticus minor.
7. Mandibular Region.
Levator menti.
Depressor labii inferioris.
Depressor anguli oris.
8. Buccal Region.
Buccinator.
Risorius.
Orbicularis oris.
9. Temporomandibular Region,
Masseter.
Temporal.
10. Pterygomandibular Region.
Pterygoideus externus.
Pterygoideus internus.
1. The Cranial Region.
Occipitofrontalis.
Dissection (Fig. 286).— The head being shaved, and a block placed beneath the back of
the neck, make a vertical incision through the skin, commencing at the root of the nose in front,
THE CRANIAL BEGION
363
and terminating behind at the occipital protuberance; make a second incision in a horizontal
direction along the forehead and around the side of the head, from the anterior to the posterior
extremity of the preceding. Raise the skin in front, from the subjacent mus.?le, from below
upward; this must be done with extreme care, removing the integument from the outer surface
of the vessels and the nerves which lie immediately beneath the skin.
The Skin of the Scalp. — This is thicker than in any other part of the body. It is intimately
adherent to llii- Nupcrficial fascia, which attaches it firmly to the underlying aponeurosis and
muscle. ^lovcnicuts of (lie mascle move the skin. The hair follicles are very closely set together,
and extend throughout the whole thickness of the skin. It also contains a number of sebaceous
glands.
Fig. 2SG. — Dissection of the head, face, and neck.
The superficial fascia in the cranial region is a firm, dense, fibrofatty layer,
intimately adherent to the integument, and to the Oceipitofrontalis and its tendi-
nous aponeurosis; it is continuous, behind, with the superficial fascia at the back
part of the neck; and, laterally, is continued over the temporal fascia. It contains
between its layers the superficial vessels and nerved and much fat.
The Oceipitofrontalis {m. epicranius) (Fig. 287) is a broad musculofibrous
layer, which covers the whole of one side of the vertex of the skull, from the occiput
to the eyebrow. It consists of two muscle slips, separated by an intervening
tendinous aponeurosis. The occipital portion {m. occipitalis) is thin, quadri-
lateral in form, and about an inch and a half in length; it arises from the outer
two-thirds of the superior curved line of the occipital bone, and from the mastoid
portion of the temporal bone. Its fibres of origin are tendinous, but they are
soon succeeded by muscle fibres, and ascend in a parallel direction to terminate
in a tendinous aponeurosis. The frontal portion {m. frontalis) is thin, of a quadri-
lateral form, and intimately adherent to the superficial fascia. It is broader,
its fibres are longer, and their structures paler than the occipital portion. It has
no bony attachments. Its medial fibres are continuous with those of the
Pyramidalis nasi. Its middle fibres become blended with the Corrugator super-
cilii and Orbicularis palpebrarum; and the outer fibres are also blended with the
latter muscle over the external angular process. From these attachments the
fibres are directed upward, and join the aponeurosis in front of the coronal suture.
The inner margins of the frontal portions of the two muscles are joined together
for some distance above the root of the nose; but between the occipital portions
there is a considerable, though variable, interval, which is occupied by the apon-
eurosis.
The epicranial aponeurosis (c/alea aponeurotica) covers the upper part of the vertex
of the skull, being continuous across the middle line with the aponeurosis of the
364
THE MUSCLES AND FASCIjE
opposite muscle. Behind, it is attached, in the interval between the occipital
origins, to the occipital protuberance and highest curved lines of the occipital
bone; in front, it forms a short and narrow prolongation between the frontal por-
tions'; and on each side it gives origin to the Attollens and Attrahens aurem muscles.
This aponeurosis is closely connected to the integument by the firm, dense,
fibrofatty layer which forms the superficial fascia; it is connected with the pen-
Fig. 287. — Muscles of the head, face, and neck.
cranium (cranial periosteum) by loose cellular tissue, which allows of a consider-
able degree of movement of the integument. It is continuous with the temporal
fascia below the temporal ridge, and it is in reality the representative of the deep
fascia.
Nerves. — The frontal portion of the OccipitofrontaHs is supplied by the temporal branches
of the facial nerve; its occipital portion by the posterior auricular branch of the facial.
THE A URICULAB BEG ION
365
Actions. — The frontal portion of the muscle raises the eyebrows and the skin over the root of
the nose, and at the same time draws the scalp forward, throwing the integument of the forehead
into transverse wrinkles. The posterior portion draws the scalp backward. By bringing alter-
nately into action the frontal and occipital portions the entire scalp may be moved forward and
backward. In the ordinary action of the muscles, the eyebrows are elevated, and at the same
time the aponeurosis is fixed by the posterior portion, thus giving to the face the expression of
surprise; if the action is more exaggerated, the eyebrows are still further raised, and the .skin
of the forehead thrown into transverse wrinkles, as in the expression of fright or horror.
Applied Anatomy. — The skull is covered by the scalp (Fig. 288). This consists, from without
inward, of live layers: (1) Skin; (2) subcutaneous fat; (3) the Occipitofrontalis mu.scle and apo-
neurosis; (4) a layer of connective tissue beneath the Occipitofrontalis aponeurosis (subaponeu-
rotic tissue) ; (.5) the pericranium. The subcutaneous tissue is composed of bands of fibrous
tissue enclosing spaces filled with fat. The fibrous character of this tissue greatly limits discolor-
ation and swelling when inflammation occurs. The edges of a wound which does not involve the
aponeurosis or muscle do not retract, hence the wound does not gape. The bloodvessels run prac-
tically in the skin, and as they lie in very dense tissue and are adherent to it, wounds bleed profusely,
the arteries being unable freely to contract and retract. It is very difficult or impossible to pick
up with forceps a vessel in the skin of the scalp, and bleeding must be arrested by suture liga-
tures or by the stitches which close the wound. Sebaceous glands in the skin of the scalp may
develop into sebaceous cysts (wens). If a wound involves the muscle or aponeurosis, it gapes
widely, the greatest amount of gaping being observed in transverse wounds. The subaponeu-
RICRANIUM
Fig. 2SS. — The scalp. Sagittal section. (Schematic.) (Poirier and Charpy.)
rotic tissue space between the aponeiu-osis and the pericranium is called by Treves the danger-
ous area of the scalp. It contains a layer of connective tissue, and suppuration in this tissue
spreads widely. An abscess in the dangerous area should be opened above the superior curved
line of the occipital bone, above the eyebrow or above the zygoma. In a wound or contusion
superficial to the aponeurosis but little blood can be effused in the tissue because its fibrous
structure prevents it, and abscesses do not tend to spread widely. Between the aponeurosis
and the pericranium a great amount of blood can be effused. An effusion of blood beneath
the pericranium is called a cephalhematoma. Such a condition may occur from pressure during
birth. An extravasation beneath the pericranium is limited to the surface of one bone. The
pericranium is tightly attached to the sutures, but adheres lightly to the surface of the bone,
and abscess beneath the pericranium is restricted to the surface of one bone.
2. The Auricular Region (Fig. 287).
Attrahens aiirem.
Attollens aurem.
Retrahens aurem.
These three small muscles are placed immediately beneath the skin, around the
external ear. In man, in whom the external ear is almost immovable, they are
366 THE MUSCLES AND FASCIA
rudimentary. They are the homologues of large and important muscles in some
of the mammalia.
Dissection. — This requires considerable care, and should be performed in the following
manner: To expose the AttoUens aurem, draw the pinna, or broad part of the ear, downward,
when a tense band will be felt beneath the skin, passing from the side of the head to the upper
part of the concha; by dividing the skin over this band in a direction from below upward, and
then reflecting it on each side, the muscle is exposed. To bring into view the Attrahens aurem,
draw the helix backward by means of a hook, when the muscle will be made tense, and may be
exposed in a similar manner to the preceding. To expose the Retrahens aurem, draw the pinna
forward, when the muscle, being made tense, may be felt beneath the skin at its insertion into
the back part of the concha, and may be exposed in the same manner as the other muscles.
The Attrahens aurem {m. auricularis anterior), the smallest of the three,
is thin, fan-shaped, and its fibres pale and indistinct; they arise from the lateral
edge of the aponeurosis of the Occipitofrontalis, and converge to be inserted
into a projection of the front of the helix.
The AttoUens aurem (jn. auricularis superior), the largest of the three, is
thin and fan-shaped; its fibres arise from the aponeurosis of the Occipitofrontalis
and converge to be inserted by a thin, flattened tendon into the upper part of the
cranial surface of the pinna.
The Retrahens aurem (m. auricularis posterior) consists of two or three
fleshv fasciculi, which arise from the mastoid portion of the temporal bone by
short aponeurotic fibres. They are inserted into the lower part of the cranial
surface of the concha.
Nerves. — The Attrahens and AttoUens aurem are supplied by the temporal branch of the
facial ; the Retrahens aurem is supplied by the posterior auricular branch of the same nerve.
Actions. — In man, these muscles possess very little action: the Attrahens aiu:em draws the
pinna forward and upward; the .^ttolens aurem slightly raises it; and the Retrahens aurem
draws it backward.
3. The Palpebral Region (Fig. 287).
Orbicularis palpebrarum. Levator palpebrae.
Corrugator supercilii. Tensor tarsi.
Dissection (Fig. 286). — In order to expose the muscles of the face, continue the longitudinal
incision made in the dissection of the Occipitofrontalis down the median line of the face to the
tip of the nose, and from this point onward to the upper lip; and carry another incision along the
margin of the lip to the angle of the mouth, and transversely across the face to the angle of the
mandible. Then make an incision in front of the external ear, from the angle of the mandible
upward; to join the transverse incision made in exposing the Occipitofrontalis. These incisions
include a square-shaped flap, which =hould be removed in the direction marked in the figure,
with care, as the muscles at some points are intimately adherent to the integument.
The Orbicularis palpebrarum (m. orbicularis oculi) is a sphincter muscle, which
surrounds the circumference of the orbit and eyelids. It arises from the internal
angular process of the frontal bone, from the frontal process of the maxilla in
front of the lacrimal groove for the nasal duct, and from the anterior surface
and borders of a short tendon, the tendo oculi, or internal tarsal ligament, placed
at the inner angle of the orbit. From this origin the fibres are directed outward,
forming a broad, thin, and flat layer, which covers the e}-elids, surrounds the
circumference of the orbit, and spreads out over the temple and downward on the
cheek. The internal or palpebral portion (pars palpebral is) of the Orbicularis is
thin and pale; it arises from the bifurcation of the tendo oculi, and forms a series
of concentric curves, which are on the outer side of the eyelids inserted into
the external tarsal ligament. The external or orbital portion {^pars orbitalis) is
thicker and of a reddish color; its fibres are well developed, and form complete
THE PALPEBRAL REGION 3G7
ellipses. The upper fibres of tiiis portion blend with the Occipitofrontalis and
Corrugator supercilij.
Relations. — By its superficial surface, with the integument. By its deep surface, above, -with
the Occipitofrontalis and Corrugator superciHi, with which it is intimately blended, and with
the supraorbital vessels and nerve; below, it covers the lacrimal sac, and the origin of the Levator
labii superioris alaeque nasi, the Levator labii superioris, and the Zygomaticus minor muscles.
Internally, it is occasionally blended with the Pyramidalis nasi. Externally, it lies on the tem-
poral fascia. On the eyelids it is separated from the conjunctiva by the Levator paipebrae,
the tarsal ligaments, the tarsal plates, and the Meibomian glands.
The tendo ocuii or internal tarsal ligament {ligamentum palpebrale mediale) is a
short tendon, about one-si.\th of an inch in length and half as much in breadth,
attached to the frontal process of the maxilla in front of the lacrimal groove.
Crossing the lacrimal sac, it divides into two parts, each division being attached
to the inner extremity of the corresponding tarsal plate. As the tendon crosses
the lacrimal sac, a strong aponeurotic lamina is given ofi" from the posterior surface,
which expands over the sac, and is attached to the ridge on the lacrimal bone.
This is the reflected aponeurosis of the tendo oculi.
The external tarsal ligament (raphe palpebralis lateralis) is a much weaker struc-
ture than the tendo oculi. It is attached to the margin of the frontal process of
the malar bone, and passes inward to the outer commissure of the eyelid, where
it divides into two slips, which are attached to the margins of the two tarsal plates.
Use of Tendo Oculi. — Besides giving attachment to part of the Orbicularis
palpebrarum and to the tarsal plates, it serves to suck the tears into the lacrimal
sac, by its attachment to the sac. Thus, each time the eyelids are closed, the
tendo oculi becomes tightened, through the action of the Orbicularis, and draws
the wall of the lacrimal sac outward and forward, so that the tears are sucked along
the lacrimal canals into it.
The Corrugator supercilii (Figs. 287 and 289) is a small, narrow, pyramidal
muscle, placed at the inner extremity of the eyebrow, beneath the Occipito-
frontalis and Orbicularis palpebrarum muscles. It arises from the inner extrem-
ity of the superciliary ridge, from whence its fibres pass upward and outward
between the palpebral and orbital portions of the Orbicularis palpebrarum,
and are inserted into the deep surface of the skin, opposite the middle of the
orbital arch.
Relations. — By its superficial surface with the Occipitofrontalis and Orbicularis palpebrarum
muscles; by its deep surface, with the frontal bone and supratrochlear nerve.
The Tensor tarsi or Horner's muscle (pars lacrimalis m. orhindaris ocidi)
(Fig. 289) is a small thin muscle about a quarter of an inch in breadth and
half an inch in length, situated at the inner side of the orbit, behind the tendo
oculi and lacrimal sac. It arises from the crest and adjacent part of the orbital
surface of the lacrimal bone, and, passing across the lacrimal sac, divides into two
slips, which coverthe lacrimal canals and are inserted into the tarsal plates internal
to the puncta lacrimalia. Its fibres appear to be continuous with those of the
palpebral portion of the Orbicularis palpebrarum; it is occasionally very indis-
tinct.
Nerves. — The Orbicularis palpebrarum, Corrugator supercilii, and Tensor tarsi are supplied
by the facial nerve.
Actions. — The Orbicularis palpebrarum is the sphincter muscle of the eyelids. The palpebral
portion acts involuntarily, closing the lids gently, as in sleep, or in blinking; the orbicular por-
tion is subject to the will, ^^^len the entire muscle is brought into action, the skin of the fore-
head, temple, and cheek is drawn inward toward the inner angle of the orbit, and the eyelids
are firmly closed as in photophobia. When the skin of the forehead, temple, and cheek is thus
drawn inward by the action of the muscle it is thrown into folds, especially radiating from the
368
THE MUSCLEiS AND FASCIA
outer ano-le of the eyelids, which give rise in old age to the so-called "crow's feet." The Levator
palpebrae is the dii-ect antagonist of this muscle; it raises the upper eyelid and exposes the globe
of the eye. The Corrugator supercilii draws the eyebrow downward and inward, producing the
vertical wrinkles of the forehead. It is the "frowning" muscle, and may be regarded as the
principal agent in the expression of suiTering. The Tensor tarsi draws the eyelids inward and
compresses the eyelids and the extremities of the lacrimal canals against the surface of the globe
of the eye; thus placing the canals in the most favorable situation for receiving the tears. It
serves, also, to compress the lacrimal sac.
FRONTAL SrNUS
4f TENSOR
nighmore:
ORBITAL portion OF
ORBICULARIS PALPEBRARUM
Fig. 289. — The three portions of the Orbicularis palpebrarum muscle, and the relation of this muscle to the
Corrugator supercilii muscle, seen from behind. (Left side.) (Toldt.)
4. The Orbital Region (Fig. 291).
Levator palpebrae superioris. Rectus internus.
Rectus superior. Rectus externus.
Rectus inferior. Obliquus oculi superior.
Obliquus oculi inferior.
Dissection. — To open the cavity of the orbit, remove the skullcap and brain ; then saw through
the frontal bone at the inner extremity of the supraorbital ridge, and externally at its junction
with the malar. Break in pieces the thin roof of the orbit by a few slight blows of the hammer,
and take it away; drive forward the superciliary portion of the frontal bone by a smart stroke,
but do not remove it, as that would destroy the pulley of the Obliquus superior. When the
fragments are cleared away, the periosteum of the orbit will be exposed; this being removed,
together with the fat which fills the cavity of the orbit, the several muscles of this region can
be examined. The dissection will be facilitated by distending the globe of the eye. In order
to effect this, puncture the optic nerve near the eyeball with a curved needle, and push the needle
onward into the globe; insert the point of a blowpipe through this aperture, and force a little
air into the cavity of the eyeball; then apply a ligature around the nerve so as to prevent the air
escaping. The globe being now drawn forward, the muscles will be put upon the stretch.
Orbital Septum. — Subjacent to the Orbicularis palpebrarum a dense fascial
sheet supports the tarsal plates and serves as a septum (septum orbitale), which
is attached to the orbital margin. It is perforated by the small vessels and
THE ORBITAL REGION
369
nerves which supply the integument of the eyeUds. The tarsal ligaments pre-
viously descrilied are reen forcing bands of this fascial septum.
The Levator palpebrae superioris is thin, flat, and triangular in shape. It
arises from the under surface of the lesser wing of the sphenoid, above and in
front of the optic foramen, from which it is separated by the origin of the Superior
Tendon of Obliquus siipt;}'i
OrWal plate of frontal hone
Let}alor palpehrce supu torts
Jiecli^s sitpet lot
Optic nerve
Rectus inferior
Roof of antrum of High
Obliquus inferior
Ot hicularis palpebrarum
Superior tarsal plate
Upper eyelid
Lower eyelid
Iitferior tarsal plate
Orbicularis palpebrarum
Fig. 290. — Sagittal section of left orbital cavity.
rectus (Fig. 292). At its origin it is narrow and tendinous, but soon becomes
broad and fleshy, and terminates anteriorly in a wide aponeurosis, which splits
into three lamellse. The superficial lamella blends with the superior palpebral
ligament, and is prolonged forward above the superior tarsal plate to the palpebral
part of the Orbicularis palpebrarum and to the deep surface of the skin of the
of the right orbit.
upper eyelid. The middle lamella, largely made up of unstriped muscle fibres
(superior tarsal muscle), is inserted into the upper margin of the superior tarsal
plate, while the deepest lamella blends with an expansion from the sheath of
the Superior rectus muscle and with it is attached to the superior forni.x of the
conjunctiva (Fig. 290).
370 THE MUSCLES AND FASCIA
Relations.— By its orbital surface, with the frontal nerve and supraorbital artery, the peri-
osteum of the orbit and lacrimal gland; and, in the lid, with the inner surface of the tarsal liga-
ment; bv its ocular surface, with the Superior rectus, and, in the lid, with the conjunctiva. A
small branch of the oculomotor nerve enters its under surface.
The four Recti (Fig. 292) arise from a fibrous ring {annulus tendineus comvninis)
[Zinn] which surrounds the upper, inner, and lower margins of the optic foramen
and encircles the optic nerve. Two specialized parts of this ring may be made out :
(1) A lower, ligament of Ziim, which gives origin to the Inferior rectus, part of the
Internal rectus, and the lower head of the External rectus; and (2) an ujjper,
the tendon of Lockwood, which gives origin to the Superior rectus, the rest of the
Internal rectus, and the upper head of the External rectus.
Each of the four Recti passes forward in the position implied by its name, to
be inserted by a tendinous expansion into the sclera, about a quarter of an inch
from the margin of the cornea. Between the two heads of the External rectus
is a narrow interval, through which pass the
two divisions of the oculomotor nerve, the nasal
Reciu,s,.p<Tior brauch of the ophthalmic division of the tri-
^wsuperiorJ j — geminal nerve, the abducent nerve, and the
Superior oblique} I '<s^*%s^^ ophthalmic vein. Of the four Recti, the
Internal rectus is the broadest, the External
the longest, and the Superior the thinnest and
narrowest. Beyond the insertion of the Inferior
rectus a thin layer of non-striated muscle
fibres (inferior tarsal muscle) continues into
the lower eyelid to be inserted into the inferior
tarsal plate.
Fig. 292. — The relative position and attach- rpi £!„„,-_;„■« ...l^K^iin / IT T
ment of the muscles o£ the left eyebaU. i he bUpePlOr ODliqUe (?«.. obhquVS OCUU
superior) is a fusiform muscle placed at the
upper and inner side of the orbit, internal to the Levator palpebrae. It arises a
little above the inner margin of the optic foramen (Fig. 292), and, passing forward
to the inner angle of the orbit, terminates in a rounded tendon, which plays in a
fibrocartilaginous ring or pulley, the trochlea, attached to the trochlear fossa near
the internal angular process of the frontal bone. The contiguous surfaces of the
tendon and ring are covered with a delicate synovial membrane and are enclosed
in a thin fibrous investment. The tendon is reflected backward, outward, and
downward beneath the Superior rectus to the outer part of the globe of the eye,
and is inserted into the sclera, behind the equator of the eyeball, the insertion of
the muscle lying between the Superior and External recti.
Relations. — By its orbital surface, with the periosteum covering the roof of the orbit and the
trochlear nerve; the tendon, where it lies on the globe of the eye, is covered by the Superior
rectus; by-its ocular surface, with the nasal nerve, ethmoidal arteries, and the upper border of the
Internal rectus.
The Inferior oblique (m. ohliquus ocuU inferior) is a thin, narrow muscle placed
near the anterior margin of the orbit. It arises from a depression on the orbital
plate of the maxilla, external to the lacrimal groove (Fig. 291). Passing outward,
backward, and upward between the Inferior rectus and the floor of the orbit,
and then between the eyeball and the External rectus, it is inserted into the outer
part of the sclera between the Inferior and External recti, near to, but somewhat
behind, the tendon of insertion of the Superior oblique.
Relations. — By its ocular surface, with the globe of the eye and with the Inferior rectus; by
its orbital surface, with the periosteum covering the floor of the orbit, and with the External
rectus. Its borders look forward and backward; the posterior one receives a branch of the
oculomotor nerve.
THE ORBITAL REGION 371
The orbital muscle, or Miiller's muscle (muscttlvs orbitale), which spans the
sphenomaxillary fissure and infraorbital groove, is composed of nonstriated
fibres, and is a rudimentary structure continuous with the periosteum of the
orbit.i
Nerves. — The Levator palpebrae, Inferior oblique, and all the Recti excepting the External
are supplied by the oculomotor nerve; the Superior oblique, by the trochlear; the External
rectus, by the abducent.
Actions. — The Levator palpebrae raises the upper eyelid, and is the direct antagonist of the
Orbicularis palpebrarum. The four Recti muscles are attached in such a manner to the globe
of the eye that, acting singly, they will turn its corneal surface either upward, downward, inward,
or outward, as expressed by their names. The movement produced by the Superior or Inferior
rectus is not quite a simple one, for, inasmuch as they pass obliquely outward and forward to the
eyeball, the elevation or depression of the cornea must be accompanied by a certain deviation
inward, with a slight amount of rotation. These latter movements are corrected by the Oblique
muscles, the Inferior oblique correcting the deviation inward of the Superior rectus, and the
Superior oblique that of the Inferior rectus. The contraction of the External and Internal
recti, on the other hand, produces a purely horizontal movement. If any two contiguous Recti
of one eye act together, they carry the globe of the eye in the diagonal of these directions —
viz., upward and inward, upward and outward, downward and inward, or downward and out-
ward. The movement of circumduction, as in looking around a room, is performed by the alter-
nate action of the four Recti. The Oblique muscles rotate the eyeball on its antero-posterior axis,
this kind of movement being required for the correct viewing of an object when the head is moved
laterally, as from shoulder to shoalder, in order that the picture may fall in all respects on the
same part of the retina of either eye. Sometimes the corresponding Recti and sometimes the
opposite ones of the two eyes act together ; for instance, the two Superior and Inferior recti carry
both ej'eballs upward and downward, respectively. In looking toward the right, the right Exter-
nal and left Internal recti act together, the reverse being the case in looking toward the left. In
turning both eyes toward the middle line, as in directing our vision toward an object less than
twenty feet distant, the two Internal recti act together.
Fascise of the Orbit. — The connective tissue of the orbit is in various places condensed into
thin membranous layers, which may be conveniently described as (1) the orbital fascia; (2) the
sheaths of the muscles; and (3) the fascia of the eyeball.
1. The Orbital Fascia. — This forms the periosteum of the orbit. It is loosely connected to
the bones, from whirh it can be readily separated. Beliind, it is connected with the dura by
processes which pass through the optic foramen and sphenoidal fissure, and with the sheath of
the optic nerve. In front it is connected with the periosteum at the margin of the orbit, and
sends off a process which assists in forming the palpebral fascia or orbital septum. From its
internal surface two processes are given off — one to enclose the lacrimal gland, the other to
hold the pulley of the Superior oblique muscle in position.
2. The Sheaths of the Muscles. — The sheaths of the muscles give off expansions to the
margins of the orbit which limit the action of the muscles.
3. The Fascia of the Eyeball. — Tenon's capsule — surrounds the posterior two-thirds of the
eyeball; it will l>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-
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—
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
<J »*-— -_^,o.j)TR.t.sfl ts »/(/ the fractured portion downward and forward; and the
'J ,1^^^^ '°"/\/l ll V^ displacement may easily be discovered by tracing the
yA „ --r^ ^^/ //Mm V''' I'"'^ margin of the clavicle outward, when the fragment
/^ r~\ri.>-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..."... ></ saphenous vein, and several smaller vessels.
\ I m \ f^'noralherma, q^^^ ^f ^y^^^^ ^^^ j^^^^.^^ ^j^^ superficial, is
continuous above with the superficial fascia of
the abdomen. Internally it is continuous with
the superficial fascia of the perineum. The
deep layer of the superficial fascia is a very thin
fibrous layer, best marked on the inner side of
the long saphenous vein and below Poupart's
ligament. It is placed beneath the subcuta-
neous vessels and nerves and upon the surface
of the fascia lata. It is intimately adherent to
the fascia lata a little below Poupart's ligament.
It covers the saphenous opening (Fig. 378)
in the fascia lata, being closely united to the
margins of the opening, and is connected to
the sheath of the femoral vessels. The portion
of the fascia covering this aperture is perfo-
rated by the internal saphenous vein and by
numerous bloodvessels and lymphatic vessels;
hence, it has been termed the cribriform fascia
(fascia cribrosa). The cribriform fascia adheres
closely both to the superficial fascia and to the
fascia lata, so that it is described by some anato-
mists as part of the fascia lata, but is usually
considered (as in this work) as belonging to the
superficial fascia. It is not until the cribriform
fascia has been cleared away that the saphenous
opening is seen, so that this opening does not
in ordinary cases exist naturally, but is the
result of dissection. A large subcutaneous bursa {bursa praepatellaris subcutanea)
is found in the superficial fascia over the patella, and another (bursa trochanterica
subcutanea) in the superficial fascia over the great trochanter.
The Deep Fascia, or Fascia Lata (Fig. 378).— The deep fascia of the thigh is
exposed on the removal of the superficial fascia, and is named, from its great
extent, the fascia lata; it forms a uniform investment for the whole of this region
of the limb, but varies in thickness in different parts; thus, it is thicker in the upper
and outer part of the thigh, where it receives a fibrous expansion from the Gluteus
maximus muscle, and where the Tensor fasciae femoris is inserted between its
layers; it is very thin behind, and at the upper and inner part where it covers
the Adductor muscles, and again becomes stronger around the knee, receiving
'3. Front of leg.
4- Dorsum of foot.
THE ANTERIOR FEMORAL REGION
507
fibrous expansions from tlie tendons of the Biceps femoris externally, from the
Sartorius internally, and from the Quadriceps extensor in front. The fascia lata
is attached above, and behind, to the back of the sacrum and coccyx; externally,
to the crest of the ilium; in front, to Poupart's ligament and to the body of the os
pubis; and internoUy, to the descending ramus of the os pubis, to the ramus and
tuberosity of the is< hium, and to the lower border of the great sacrosciatic ligament.
From its attachment to the crest of the ilium it passes down over the Gluteus
medius muscle to (he upper border of the Gluteus maximus, where it splits into
two layers, one passing superficial to and the other beneath this muscle. At the
lower border of the muscle the two layers reunite. Externally the fascia lata
receives the greater part of the tendon of insertion of the Gluteus maximus, and
becomes proportionately thickened. The portion of the fascia lata arising from
the front part of the crest of the ilium, corresponding to the origin of the Tensor
EXTERNAL
'ABDOMINAI
RJNG
Fig. 378.— Right external aljdonmi 1 rint. tii i iphe
fasciae femoris, passes down the outer side of the thigh as two layers, one super-
ficial to and the other beneath this muscle. These layers at the lower end of the
muscle become blended into a thick and strong band, having first received the
insertion of the muscle. This band is continued downward, under the name of
the iliotibial band (tradus iliotibialis [Maissidt.i]), to be inserted into the external
tuberosity of the tibia. Below, the fascia lata is attached to all the prominent
points around the knee-joint — viz., the condyles of the femur, tuberosities of
the tibia, and head of the fibula. On each side of the patella it is strengthened
by transverse fibres given off from the lower part of the Vasti muscles, which are
attached to and support this bone. Of these, the outer fibres are the stronger,
and are continuous with the iliotibial band. From the deep surface of the fascia
lata are given off two strong intermuscular septa, which are attached to the whole
length of the linea aspera and its prolongations above and below; the external
508 THE MUSCLES AND FASCIA
intermuscular septum (septum iidermusculare laterale) is the stronger. It extends
from the insertion of the Gluteus maximus to the outer condyle, separates the
Vastus externus in front from the short head of the Biceps femoris behind, and
gives partial origin to these muscles; the internal intermuscular septum (septum
intermusculare mediale), the thinner of the two, separates the Vastus internus
from the Adductor and Pectineus muscles. Besides these there are numerous
smaller septa, separating the individual muscles and enclosing each in a distinct
sheath. At the upper and inner part of the thigh, a little below Poupart's ligament,
a large, oval-shaped aperture is observed; it transmits the internal saphenous vein
and other smaller vessels, and is termed the saphenous opening (fossa ovalis)
(Fig. 378). This opening is covered by a. portion of the deep layer of the super-
ficial fascia, the cribriform fascia. In order more correctly to consider the mode
of formation of this aperture, the fascia lata in this part of the thigh is described
as consisting of two portions — an iliac portion and a pubic portion.
The iliac portion is all that part of the fascia lata on the outer side of the saphe-
nous opening. It is attached, externally, to the crest of the ilium and its anterior
superior spine, to the whole length of Poupart's ligament as far internally as the
spine of the os pubis, and to the iliopectineal line in conjunction with Gimbernat's
ligament. From the spine of the os pubis it is reflected downward and outward,
forming an arched margin, the falciform process or the falciform margin of Bums
(inargo falciformis). This margin overlies and is adherent to the superficial
layer of the sheath of the femoral vessels; to its edge is attached the cribriform
fascia; and, below, it is continuous with the pubic portion of the fascia lata. The
femoral ligament, or the ligament of Hey, is the point at which the falciform process
joins the base of Gimbernat's ligament.
The pubic portion is situated at the inner side of the saphenous opening; at the
lower margin of this aperture it is continuous with the iliac portion. Traced
upward, the pubic portion covers the surface of the Pectineus, Adductor longus,
and Gracilis muscles, and, passing behind the sheath of the femoral vessels, to
which it is closely united, is continuous with the sheath of the Psoas and Iliacus
muscles, and is attached above to the iliopectineal line, where it becomes continu-
ous with the iliac fascia. From this description it may be observed that the iliac
portion of the fascia lata passes superficial to the femoral vessels, and the pubic
portion behind them, so that an apparent aperture exists between the two, through
which the internal saphenous joins the femoral vein.
Applied Anatomy. — The iliotihial hand at a point between the crest of the ihum and the
great trochanter is so tense that it is impossible to sink the fingers deeply in this region. Dr.
Allis points out that in fracture of the neck of the femur the great trochanter mounts toward
the iliac crest, the iliotibial band relaxes, and the fingers can be sunk deeply into the space
between the great trochanter and the iliac crest. Shortening is thus indicated. This is known
as Allis' sign. A Psoas abscess usually points at the termination of the Psoas muscle, but the
tuberculous pus may be directed down the thigli beneath the fascia lata, and it may reach the
popliteal space or may go even lower.
The Tensor fasciae femoris (m. tensor fasciae lafae) (Fig. 379) arises from the
anterior part of the outer lip of the crest of the ilium, from the outer surface of
the anterior superior spine, and part of the outer border of the notch below it,
between the Gluteus medius and Sartorius, and from the surface of the fascia
covering the Gluteus medius. It is inserted between two layers of the fascia lata,
about one-fourth down the outer side of the thigh. From the point of insertion
the fascia is continued downward to the external tuberosity of the tibia as a thick-
ened band, the iliotibial band.
The Sartorius (m. sartorius) (Fig. 379), the longest muscle in the body, is flat,
narrow, and ribbon-like; it arises by tendinous fibres from the anterior superior
THE ANTERIOR FEMORAL REGION
509
spine of the ilium and the upper half of the
notch below it, passes obliquely across the
upper and anterior part of the thigh, from
the outer to the inner side of the limb, then
descends vertically, as far as the inner side of
the knee, passing behind the inner condyle of
the femur, and terminates in a tendon which,
curving oblicjuely forward, expands into a
broad aponeurosis, to be inserted in front of
the Gracilis and Semitendinosus, into the
upper part of the inner surface of the shaft
of the tibia, nearly as far forward as the crest.
The upper part of the tendon is curved back-
ward over the upper edge of the tendon of the
Gracilis in order to be inserted behind it (Fig.
185). An ofl'set is derived from the upper mar-
gin of the aponeurosis, which blends with the
fibrous capsule of the knee-joint, and another,
gi-ven off from its lower border, blends with
the fascia on the inner side of the leg.
Relations. — By its swperficial surface, with the
fascia lata; by its deep surface, with the Rectus
femoris, Iliacus, Vastus internus, femoral nerve, sheath
of the femoral vessels, Adductor longus. Gracilis,
Semitendinosus, long saphenous nerve, and internal
lateral ligament of the knee-joint. Frequently there
is a bursa (bursa m. sariorii propria) between the
tendon of the Sartorius and the tendons of the Gra-
cilis and Semimembranosus.
The relations of this muscle to the femoral artery
should be carefully examined, as it constitutes the
chief guide in tying the vessel. In the upper third of
the thigh it forms the outer side of a triangular space,
Scarpa's triangle (trigonum femorale), the inner side
of which is formed by the inner border of the Adductor
longus, and the base, which is turned upward, by
Poupart's ligament; the femoral artery passes per-
pendicularly through the middle of this space from
its base to its apex. In the middle third of the thigh
the femoral artery lies first along the inner border,
and then behind the Sartorius.
The Quadriceps extensor (m. quadriceps
femoris) (Fig. 381) includes the four remaining
muscles on the front of the thigh. It is the
great Extensor muscle of the leg, forming a
large fleshy mass which covers the front and
sides of the femur, being united below into
a single tendon; attached to the patella, and
above subdivided into separate portions,
which have received distinct names. Of
these, one occupying the middle of the thigh,
connected above with the ilium, is called the
Rectus femoris, from its straight course. The
other divisions lie in immediate connection
with the shaft of the femur, which they cover
from the trochanters to the condyles. The
-Muscles of the ihac
femoral region.
510
THE MUSCLES AND FASCIJE
PSOAS MAGNUS
PyRIFORMia
PECTINEU8
fiATOR
portion on the outer side of the femur is termed the Vastus externus ; that cover-
ing the inner side, the Vastus internus; and that covering the front of the femur,
the Criireus.
The Rectus femoris {m. rectus femoris) is situated in the middle of the anterior
region of the thigh ; it is fusiform in shape, and its superficial fibres are arranged
in a bipenniform manner, the deep fibres running straight down to the deep apon-
eurosis. It arises by two tendons — one, the anterior or straight, from the anterior
inferior spine of the ilium ; the other, the posterior or reflected tendon, from a groove
above the brim of the acetabulum; the two unite at an acute angle and spread
into an aponeurosis, which is prolonged
downward on the anterior surface of the
muscle and from which the muscle fibres
arise. '^ The muscle terminates in a broad
and thick aponeurosis, which occupies the
lower two-thirds of its posterior surface,
and, gradually becoming narrowed into a
flattened tendon, is inserted into the patella
in common with the Vasti and Crureus.
Between the tendon of origin and the ace-
tabulum there is often a bursa (bursa m.
recti femoris).
The Vastus externus (m. vastus lateralis)
is the largest division of the Quadriceps
extensor. It arises by a broad aponeuro-
sis, which is attached to the upper half
of the anterior intertrochanteric line, to
the anterior and inferior borders of the
root of the great trochanter, to the outer
lip of the gluteal ridge, and to the upper
half of the outer lip of the linea aspera;
this aponeurosis covers the upper three-
fourths of the muscle, and from its inner
surface many fibres take origin. A few
additional fibres arise from the tendon of
the Gluteus maximus, and from the ex-
ternal intermuscular septum between the
Vastus externus and short head of the
Biceps. The fibres form a large fleshy
mass, which is attached to a strong apon-
eurosis, placed on the under surface of the
muscle at its lower part; this becomes nar-
rowed and thickened into a flat tendon,
which is inserted into the outer border of
the patella, blending with the Quadriceps
extensor tendon, and giving an expansion
to the capsule of the knee-joint. Some of the fibres run down by the side of the
patella to the condyle of the tibia, and are called the retinaculum patellae laterale.
The Vastus internus and Crureus appear to be inseparably united, but when the
Rectus femoris has been reflected, a narrow interval will be observed extending
upward from the inner border of the patella between the two muscles. Here
they can be separated, and the separation should be continued upward as far
Fig. 380. — Diagram showing the attachments of
the mu.scle3 of the thigh. Anterior aspect. Origins,
red; insertions, blue.
1 Mr. W. R. WiUiams, in an interesting paper in the Journ. of Anat. and Phys., vol. xiii, p. 204, points out that
the refiected tendon is the real origin of the muscle, and is alone present in early fetal life. The direct tendon is
merely an accessory band of condensed fascia. The paper will well repay perusal, though in some particulars the
description in the text is more generally accurate.
THE ANTERIOR FE310RAL REGION
511
as the lower part of the anterior intertrochanteric Hne, where, however, the two
muscles are frequently continuous.
The Vastus internus (m. vastus medialis) arises from the lower half of the
anterior intertrochanteric line, the inner lip of the linea aspera, the upper part
of the internal supracondylar line, the tendon of the Adductor magnus, and
FEMORAL ARTERV -eMORAL NERVE
BRANCHES OF
OBTURATOR NERVE
Fic, 381.— Tri
section of the thigh below the lesser troch.inter. The femoral artery, vein, and nerve are
seen in Hunter's canal. (After Braune.)
the internal intermuscular septum. Its fibres are directed downward and for-
ward, and are chiefly attached to an aponeurosis which lies on the deep surface of
the muscle and is inserted into the inner border of the patella and the Quadriceps
extensor tendon, an expansion being sent to the capsule of the knee-joint. Some
of the fibres run down by the side of the patella to the condyle of the tibia and
are called the retinaculum patellae mediale.
The Crureus (m. vastus iittermediiis) arises from the front and outer aspect of
the shaft of the femur in its upper two-thirds and from the lower part of the external
intermuscular septum. Its fibres end in a superficial aponeurosis, which forms
the deep part of the Quadriceps extensor tendon.
Relations. — The inner edge of the Crureus is in contact with the anterior edfje of the Vastus
internus, but when separated from each other, as directed above, the latter muscle is seen merely
to overlap the inner aspect of the femoral shaft without taking any fibres of origin from it. The
Vastus internus is partly covered by the Rectus femoris and Sartorius, but where these separate
Bear the knee it becomes superficial, and produces a well-marked prominence above the inner
aspect of the knee. In the middle third of the thigh it forms the outer wall of Hunter's canal
(canalis adductorius [Hunteri]) (Fig. 381), which contains the femoral vessels and the long saph-
enous nerve; the roof of the canal is formed by a strong fascia which e.xtends from the Vastus
internus to the Adductores longus and magnus. The Crureus is almost completely hidden by
the Rectus femoris and Vastus extc-nus. The deep surface of the two muscles is in relation
with the femur and Subcrureus muscles. A synovial bursa {bursa suprapatellaris) is situated
between the femur and the portion of the Quadriceps extensor tendon above the patella; in
the adult it communicates with the synovial cavity of the knee-joint.
512 THE MUSCLES AND FASCIA
The tendons of the different portions of the Quadriceps extensor unite at the lower part of
the thigh, so as to form a single strong tendon, which is inserted into the upper part of the patella;
some few fibres pass over it to blend with the ligamentum patellae. Strictly speaking, the
patella may be regarded as a sesamoid bone, developed in the tendon of the Quadriceps; and
the ligamentum patellae, which is continued from the lower part of the patella to the tuberosity
of the tibia, as the proper tendon of insertion of the muscle. A synovial bursa, the deep patellar
bursa {bursa infrapatetlaris profunda), is interposed between the tendon and the upper part
of the tubercle of the tibia; and another, the prepatellar bursa (bursa praepaiellaris subndavca),
is placed over the patella itself. This latter bursa often becomes enlarged, constituting "house-
maid's knee."
The Subcrureus {m. articularis genu) is a small muscle, usually distinct from
the Crureus, but occasionally blended with it, which arises from the anterior
surface of the lower part of the shaft of the femur, and is inserted into the upper
part of the cul-de-sac of the capsular ligament, which projects upward beneath
the Quadriceps for a variable distance. It sometimes consists of several separate
muscle bundles.
Nerves. — The Tensor fasciae femoris is supplied by the fourth and fifth lumbar and first
sacral nerves through the superior gluteal nerve; the other muscles of this region, by the second,
third, and fourth lumbar nerves, through branches of the femoral.
Actions. — The Tensor fasciae femoris is a tensor of the fascia lata; continuing its action, the.
oblique direction of its fibres enables it to abduct and to rotate the thigh inward. In the erect
posture, acting from below, it will serve to steady the pelvis upon the head of the femur, and by
means of the iliotibial band it steadies the condyles of the femur on the articular surfaces of the^
tibia, and assists the Gluteus maximus in supporting the knee in the extended position. The Sar-
torius flexes the leg upon the thigh, and, continuing to act, flexes the thigh upon the pelvis; it next,
rotates the thigh outward. When the knee is bent the Sartorius assists the Semitendinosus,,
Semimem.branosus, and Popliteus in rotating the tibia inward. Taking its fixed point from the
leg, it flexes the pelvis upon the thigh, and, if one muscle acts, assists in rotating the pelvis.
The Quadriceps extensor extends the leg upon the thigh. The Rectus muscle assists the Psoas
and Iliacus in supporting the pelvis and trunk upon the femur. It also assists in flexing the
thigh on the pelvis, or if the thigh is fixed it will flex the pelvis. The Vastus internus draws the
patella inward as well as upward.
Applied Anatomy. — A few fibres of the Rectus femoris muscle are liable to be ruptured from
severe strain. This accident is especially liable to occur during the games of football and base-
ball. The patient experiences a sudden pain in the part, as if he had been struck, and the
Rectus muscle stands out and is felt ro be tense and rigid. The accident is often followed by
considerable swelling from inflammatory effusion. Occasionally the Quadriceps extensor may
be torn away from its insertion into the patella, or the tendon of the Quadriceps may be rup-
tured about an inch above the bone. This accident is caused in the same manner that fracture
of the patella by muscular action is produced — viz., by a violent muscular effort to prevent
falling while the knee is in a position of semiflexion. A distinct gap can be felt above the
patella, and, owing to the retraction of the muscle fibre's, union may fail to take place. Sudden
and powerful contraction of the Quadriceps extensor femoris is the usual cause of transverse-
fracture of the patella.
2. The Internal Femoral Region.
Gracilis. Adductor longus.
Pectineus. Adductor brevis.
Adductor magnus.
Dissection. — These muscles are at once exposed by removing the fascia from the fore part
and inner side of the thigh. The limb should be abducted, so as to render the muscles tense and
easier of dissection.
The Gracilis (???. gracilis) (Figs. 379 and 384) is the most superficial muscle
on the inner side of the thigh. It is thin and flattened, broad abo^•e, narrowing
and tapering below. It arises by a thin aponeurosis from the posterior half of the
margin of the symphysis and the anterior half of the pubic arch. The fibres pass
vertically downward, and terminate in a rounded tendon which passes behind the
raidyle of the femur, and, curving around the inner tuberosity of the tibia.
THE INTERNAL FEMORAL REGION
513
becomes flattened, and is inserted into the upper part of the inner surface of the
shaft of the tibia, below the tuberosity. A few of the fibres of the lower part of
the tendon are prolonged into the deep
fascia of the leg. The tendon of this
muscle is situated immediately above that
of the Semitendinosus, and its upper edge is
overlapped by the tendon of the Sartorius,
with which it is in part blended. As it
passes across the internal lateral ligament
of the knee-joint it is separated from it by
a synovial bursa {bursa anserbia) common to
it and tiie Semitendinosus muscle.
Relations. — By its superficial surface, with the
fascia lata and the Sartorius below; the internal
saphenous vein crosses it obliquely near its lower
part, lying superficial to the fascia lata; the internal
saphenous nerve emerges between its tendon and
that of the Sartorius; by its deep surface, with the
Adductor brevis and the Adductor magnus and
the internal lateral ligament of the knee-joint.
The Pectineus (m. pedineiis) (Fig. 379)
is a flat, quadrangular muscle, situated at
the anterior part of the upper and inner
aspect of the thigh. It arises from the ilio-
pectineal line, and to a slight extent from
the surface of the bone in front of it between
the pectineal eminence and spine of the os
pubis, and from the fascia covering the
anterior surface of the muscle; the fibres
pass downward, backward, and outward, to
be inserted into a rough line leading from
the lesser trochanter to the linea aspera.
Relations. — By its superficial surface, with the
pubic portion of the fascia lata, which separates it
from the femoral vessels and internal saphenous
vein; by its deep surface, with the capsular liga-
ment of the hip-joint, the Adductor brevis and
Obturator externus muscles, the obturator vessels
and nerve being mterposed; by its outer border,
with the Psoas, a cellular interval separating them,
through which pass the internal circumflex vessels;
by its inner border, with the margin of the Adductor
longus. There is usually a bursa {bursa m. peciinei)
between the Pectineus and the tendon of the Psoas
and Iliacus.
The Adductor longus (m, adductor longus)
(Figs. 379 and 382), the most superficial
of the three Adductors, is a flat triangular
muscle lying on the same plane as the
Pectineus. It arises, by a flat narrow ten-
don, from the front of the os pubis, at the
angle of junction of the crest with the inner
border; and soon expands into a broad fleshy belly, which, passing downward,
backward, and outward, is inserted, by an aponeurosis, into the linea aspera,
33
514 THE MUSCLES AND FASCIA
between the Vastus internus and the Adductor magnus, with both of which it is
usually blended.
Relations. — By its superficial surface, with the fascia lata, the Sartorius, and, near its inser-
tion, with the femoral artery and vein; by its deep surface, with the Adductores brevis and
magnus, the anterior brandies of the obturator nerve, and with the profunda artery and vein
near its insertion; by its outer border, with the Pectineus; by its inner border, with the Gracilis.
The Pectineus and Adductor longus should now be divided near their origin, and turned
downward, when the Adductor brevis and Obturator externus will be exposed.
The Adductor brevis (m. adductor brevis) (Fig. 382) is situated immediately
behind the two preceding muscles. It is somewhat triangular in form, and arises
by a narrow origin from the outer surface of the body and descending ramus of
the OS pubis, between the Gracilis and Obturator externus. Its fibres passing
backward, outward, and downward, are inserted, by an aponeurosis, into the
lower part of the line leading from the lesser trochanter to the linea aspera, and
the upper part of the same line, immediately behind the Pectineus and upper
part of the Adductor longus.
Relations. — By its superficial surface, with the Pectineus, Adductor longus, profunda fem-
oris artery, and anterior branches of the obturator nerve; by its deep surface, with the Adductor
magnus and posterior branch of the obturator nerve; by its outer border, with the internal cir-
cumflex artery, the Obturator externus, and conjoined tendon of the Psoas and Iliacus; by its
in7ier border, with the GraciUs and Adductor magnus. This muscle is pierced, near its insertion,
by the second or by the first and second perforating branches of the profunda femoris artery.
The Adductor brevis should now be cut away near its origin, and turned outward, when the
entire extent of the Adductor magnus will be exposed.
The Adductor magnus (m., adductor magnus) (Fig. 382) is a large, triangular
muscle forming a septum between the muscles on the inner and those on the back
of the thigh. It arises from a small part of the descending ramus of the os pubis,
from the ramus of the ischium, and from the outer margin of the inferior part of
the tuberosity of the ischium. Those fibres which arise from the ramus of the
OS pubis are very short, horizontal in direction, and are inserted into the rough
line leading from the great trochanter to the linea aspera, internal to the Gluteus
maximus. They are considered by some a distinct muscle and called the Adductor
minimus. The fibres taking origin from the ramus of the ischium are directed
downward and outward with different degrees of obliquity, to be inserted, by means
of a broad aponeurosis, into the linea aspera and the upper part of its internal
prolongation below. The internal portion of the muscle, consisting principally
of those fibres which arise from the tuberosity of the ischium, forms a thick
fleshy mass consisting of coarse bundles which descend almost vertically, and
terminate about the lower third of the thigh in a rounded tendon, which is inserted
into the Adductor tubercle on the inner condyle of the femur, and is connected
by a fibrous expansion to the line leading upward from the tubercle to the linea
aspera. Between the two portions of the muscle an interval is left, tendinous
in front and fleshy behind, for the passage of the femoral vessels from Hunter's
canal into the popliteal space. The external portion of the muscle at its attachment
to the femur presents three or four osseoaponeurotic openings, formed by tendi-
nous arches attached to the bone, from which muscle fibres arise. The three
superior of these apertures are for the three perforating arteries, and the fourth,
when it exists, is for the terminal branch of the profunda.
Relations. — By its superficial surface, with the Pectineus, Adductor brevis, Adductor longus,
and the femoral and profunda vessels and obturator nerve; by its deep surface, with the great
sciatic nerve, the Gluteus maximus, Biceps femoris, Semitendinosus, and Semimembranosus.
By its superior or shortest border it lies parallel to the Quadratus femoris, the internal circumflex
THE GLUTEAL REGION 515
artery passing between them; by its internal or longer border, with the Gracilis, Sartorius, and
fascia lata; by its external or attached border it is inserted into the femur behind the Adductor
brevis and Adductor longus, which separate it from the Vastus internus, and in front of the
Gluteus maxinius and short head of the Biceps femoris, which separate it from the Vastus externus.
Nerves. — The three Adductor muscles and the Gracilis are supplied by the third and fourth
lumbar nerves through the obturator nerve; the Adductor magnus receiving an additional
branch from the sacral plexus through the great sciatic. The Pectineus is supplied by the
second, third, and fourth lumbar nerves through the femoral, and by the accessory obturator,
from the third lumbar, when it exists. Occasionally it receives a branch from the obturator
nerve.'
Actions, — The Pectineus and three Adductors adduct the thigh powerfully; they are espe-
cially used in horseback riding, the flanks of the horse being grasped between the knees by the
actions of these muscles. In consequence of the obliquity of their insertion into the linea aspera
they rotate the thigh outward, assisting the external Rotators, and when the limb has been
abducted they draw it inward, carrying the thigh across that of the opposite side. The Pec-
tineus and Adductor brevis and longus assist the Psoas and Iliacus in flexing the thigh upon the
pelvis. In progression, also, all these muscles assist in drawing forward the hinder limb. The
Gracilis assists the Sartorius in fle.xing the leg; it is also an adductor of the thigh. If the lower
extremities are fixed, these muscles may take their fixed point from below and act upon the pelvis,
serving ti) maintain the body in an erect posture, or, if their action is continued, to flex the pelvis
forward upim the femui'.
Hunter's Canal (canalh adductorius {Hunteri^ extends from the apex of Scarpa's triangle to
the opening in the Adductor magnus muscle. The antero-internal boundary or roof of Hunter's
canal is the Sartorius and the aponeurotic expansion from the Adductors to the Vastus internus.
It is bounded externally by the Vastus internus. The Adductor longus and magnus constitute
its floor or the 'posterointernal boundary. The canal contains the femoral artery, femoral vein,
the long saphenous nerve, and the nerve to the Vastus internus.
Applied Anatomy. — The Adductor longus is liable to be severely strained in those who ride
much on horseback, or its tendons to be ruptured by suddenly gripping the saddle. Occasionally,
especially in cowboys and cavalry soldiers, the tendon of insertion of the Adductor magnus
may become ossified, constituting the rider's bone (pp. 229, 360).
III. MUSCLES AND FASCLffl OF THE HIP.
3. The Gluteal Region (Figs. 384, 385).
Gluteus maximus. Obturator internus.
Gluteus medius. Gemellus superior.
Gluteus minimus. Gemellus inferior.
Pyriformis. Quadratus femoris.
Obturator externus.
Dissection (Fig. 383). — The subject should be turned on its face, a block placed beneath
the pelvis to make. the buttocks tense, and the limbs allowed to hang over the end of the table,
with the foot inverted and the thigh abducted. Make an incision through the integument along
the crest of the ilium to the middle of the sacrum, and thence downward to the tip of the coccyx,
and carry a second incision from that point obliquely downward and outward to the outer side
of the thigh, four inches below the great trochanter. The portion of integument included between
these incisions is to be removed in the direction shown in the figure.
The Gluteus maximus (m. glutaeus maximus) (Fig. 384), the most superficial
muscle in the gluteal region, is a very broad and thick, fleshy mass of a quadri-
lateral shape, which forms the prominence of the buttock. Its large size is one
of the most characteristic points in the muscular system of man, connected as it
is with the power he has of maintaining the trunk in the erect posture. In structure
the muscle is remarkably coarse, being made up of muscle fasciculi lying parallel
1 Professor Paterson describes the Pectineus as consisting of two incompletely separated strata, of which
the outer or dorsal stratum, which is constant, is supplied by the femoral nerve, or in its absence by the acces-
sory obturator, with which it is intimately related: while the inner or ventral strattmi, when present, is supplied
by the obturator nerv;. — Journ. of Anat. and Phys., vol. xxvi, p. 43.
516
THE 3irSCLES AND FASCIJE
to one another, and collected into large bundles, separated by deep cellular
intervals. It arises from the superior curved line of the ilium, and the portion
of bone, including the crest, immediately above and behind it; from the posterior
surface of the lower part of the sacrum, the side of the coccyx, the aponeurosis
of the Erector spinae muscle, the great sacrosciatic ligament, and the fascia cover-
ing the Gluteus medius. The fibres are directed oblicjuely downward and outward ;
those forming the upper and large portion of the muscle, together with the super-
ficial fibres of the lower portion, terminate in a thick tendinous lamina, which
passes across the great trochanter and is inserted into the fascia lata covering the
duter side of the thigh; the deeper fibres of
the lower portion of the muscles are inserted
into the rough line leading from the great
trochanter to the linea aspera between the
Vastus externus and Adductor magnus.
1. Dissection of
gluteal region. Relations.— By its superficial surface, with a thin
fascia, which separates it from the subcutaneous
tissue; by its deep surface, from above downward,
with the iHum, sacrum, coccyx, and great sacrosciatic
ligament, part of the Gluteus medius, Pyriformis,
Gemelli, Obturator internus, Quadratus femoris, the
tuberosity of the ischium, great trochanter, the origin
of the Biceps femoris, Semitendinosus, Semimem-
branosus, and Adductor magnus muscles. The
superficial part of the gluteal artery reaches the deep
surface of the muscle by passing between the Pyrifor-
mis and the Gluteus medius; the sciatic and internal
pudic vessels and nerves and muscular branches from
the sacral plexus issue from the pelvis below the
Pyriformis. The first perforating artery and the
terminal branches of the internal circumflex artery
are also found under cover of the muscle. Its upper
border is thin, and connected with the Gluteus medius
by the fascia lata. Its lower border is free and promi-
nent.
Several sjmovial bursffi are found in relation with
this muscle. One of these (bursa trochanterica m.
glutaei maxirai), of large size, and generally multiloc-
ular, separates it from the great trochanter. A second
(bursa iscliiadica m. glutaei ma-xiini), often wanting, is
situated on the tuberosity of the ischium. A third
bursa is found between the tendon of this muscle and
the Vastus externus. Two or three small bursse
(bursae glutaeofemorales) are placed between the ten-
don of the muscle and that of the Vastus externus.
Dissection. — Divide the Gluteus maximus near its.
origin by a vertical incision carried from its upper to
its lower border; a cellular interval will be exposed,
separating it from the Gluteus medius and External
rotator muscles beneath. The upper portion of the muscle is to be altogether detached, and
the lower portion turned outward; the loose areolar tissue filling up the interspace between
the trochanter major and tuberosity of the ischium being removed, the parts aheady enumerated
as exposed by the removal of this muscle will be seen.
3 Is. Back of thigh.
S. Popliteal apace.
4- / 4- Back of leg.
5. Sole of foot.
The Gluteus medius (m. glutaeus medius) (Fig. 384) is a broad, thick, radiating
muscle, situated on the outer surface of the pelvis. Its posterior third is covered
by the Gluteus maximus; its anterior two-thirds by the fascia lata, which separates
it from the integument. It arises from the outer surface of the ilium, between
the superior and middle curved lines, and from the outer lip of that portion, of
the crest which is between them; it also arises from the dense fascia, the gluteal
aponeurosis, covering its outer surface. The fibres converge to a strong flattened
THE GLUTEAL REGION 517
tendon which is inserted into the oblic|ue line which traverses the outer surface
of the great trochanter.
Relations. — By its superficial surf aee, with, the Gluteus maximus behind, the Tensor fasciae
femoris and deep fascia in front; by its deep surface, with the Gluteus minimus and the gluteal
vessels and superior gluteal nerve. Its anterior border is blended with the Gluteus minimus.
Its posterior border lies parallel to the Pyriformis, the gluteal vessels intervening.
A synovial bursa (bursa trochanterica m. glutaei medii anterior) separates the tendon of the
muscle frnni the summit of the great trochanter. There is freq^uently a bursa {bursa trochan-
terica m. ijliitaci mi'dii posterior) between the tendons of the Gluteus medius and Pyriformis.
This muscle should now be divided near its insertion and turned upward, when the Gluteus
minimus will be exposed.
The Gluteus minimus (m. glutaeus minimus) (Fig. 384), the smallest of the
three Glutei, is placed immediately beneath the preceding. It is fan-shaped,
arising from the outer surface of the ilium, between the middle and inferior
curved lines, and behind, from the margin of the great sciatic notch; the fibres
converge to the deep surface of a radiated aponeurosis, which, terminating in
a tendon, is inserted into an impression on the anterior border of the great
trochanter.
Relations. — By its superficial surface, with the Gluteus medius and the gluteal vessels and
superior gluteal nerve; by its deep surface, with the ilium, the reflected tendon of the Rectus
femoris, and the capsular ligament of the hip-joint. Its anterior margin is blended with the
Gluteus medius; its posterior margin is in contact and sometimes joined with the tendon of
the PjTiformis. There is a synovial bursa (bursa trochanterica m. glutaei minimi) between the
tendon of the Gluteus minimus and the great trochanter.
The Pyriformis {m. piriformis) (Figs. 384 and 385) is a fiat muscle, pyramidal
in shape, lying almost parallel with the posterior margin of the Gluteus medius.
It is situated partly within the pelvis at its posterior part and partly at the back of
the hip-joint. It arises from the front of the sacrum by three fleshy digitations
attached to the portions of bone between the first, second, third, and fourth
anterior sacral foramina, and also from the grooves leading from the foramina;
a few fibres also arise from the margin of the great sacrosciatic foramen and from
the anterior surface of the great sacrosciatic ligament. The muscle passes out
of the pelvis through the great sacrosciatic foramen, the upper part of which it
fills, and is inserted by a rounded tendon into the inner side of the upper border
of the great trochanter, behind, but often partly blended with, the tendon of the
Obturator intemus and Gemelli muscles.
Relations. — By its deep surface, unthin the pelvis, with the rectum (especially on the left
side), the sacral plexus of nerves, and the branches of the internal iliac vessels; external to the
pelvis, with the posterior surface of the ischium and the capsular ligament of the hip-joint) by
its superficial surface, within the pelvis, with the sacrum, and external to it, with the Gluteus
maximus; by its upper border, with the Gluteus medius, from which it is separated by the gluteal
vessels and superior gluteal nerve; by its lower border, with the Gemellus superior and Coccygeus,
the sciatic vessels and ner\es, the internal pudic vessels and nerve, and muscular branches from
the sacral jilcxus, pussiiii; from the pelvis in the interval between the two muscles.
The Obttirator Membrane (membrana obturaioria) (Fig. 240) is a thin layer of interlacing
fibres which closes almost completely the obturator foramen. It is attached, externally, to
the margin of the foramen; internally, to the posterior surface of the ischiopubic ramus, below
and internal to the margin of the foramen. It presents at its upper and outer parts a small
canal, obturator canal (canalis obturatorius) for the passage of the obturator vessels and nerve.
Both obturator muscles are connected with this membrane.
There is usually a bursa (bursa m. piriformis) between the tendon of the Pyriformis and the
ilium.
Dissection. — The next muscle, as well as the origin of the Pyriformis, can only be seen when
the pelvis is divided and the viscera removed.
518
THE MVSCLES AND FASCIA
Inner Hamstring
teTidons.
Fig. 3S4.— Muscles of the hip and thigh.
The Obturator intemus (m.
obturator intemus (Figs. 384
and 385), like the preceding
muscle, is situated partly within
the cavity of the pelvis, and
partly at the back of the hip-
joint. It arises from the inner
surface of the anterior and ex-
ternal wall of the pelvis, where
it surrounds the greater part
of the obturator foramen, being
attached to the descending ramus
of the OS pubis and the ramus of
the ischium, and at the side to
the inner surface of the innomi-
nate bone below and behind
the pelvic brim, reaching from
the upper part of the great
sacrosciatic foramen above and
behind to the obturator fora-
men below and in front. It
also arises from the inner surface
of the obturator membrane ex-
cept at its posterior part, from
the tendinous arch which com-
pletes the canal for the passage
of the obturator vessels and nerve
and to a slight extent from the
obturator layer of the pelvic
fascia, which covers it. The
fibres converge rapidly, and are
directed backward and down-
ward, and terminate in four or
five tendinous bands, which are
found on its deep surface; these
bands are reflected at a right
angle over the inner surface of
the tuberosity of the ischium,
which is grooved for their recep-
tion; the groove is covered by
cartilage, and lined with a syno-
vial bursa (bursa m. obturatoris
iuterni). The muscle leaves the
pelvis by the lesser sacrosciatic
foramen; and the tendinous
bands unite into a single flat-
tened tendon, which passes hori-
zontally outward, and, after
receiving the attachment of the
Gemelli, is inserted into the fore
part of the inner surface of the
great trochanter in front of the
Obturator externus.
THE GLUTEAL REGION
519
In ordri- to (lls|iliiy llic peculiar a|>|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, a<nd
with the mental branch of the inferior dental artery.
38
594
THE VASCULAR 8YSTEMS
The inferior labial coronary (Figs. 438 and 439) is derived from the facial artery,
near the angle of the mouth; it passes upward and inward beneath the Depressor
anguli oris, and, penetrating the Orbicularis oris muscle, runs in a tortuous course
along the edge of the lower lip between this muscle and the mucous membrane,
anastomoses with the artery of the opposite side. This artery supplies the labial
glands, the mucous membrane, and muscles of the lower lip, and anastomoses
with the inferior labial from the facial and the mental branch of the inferior
dental artery.
The superior labial coronary (a. labialis superior) (Figs. 438 and 439) is larger and
more tortuous in its course than the preceding. It follows the same course along
the edge of the upper lip, lying between the mucous membrane and the Orbicu-
laris oris, and anastomoses with the artery of the opposite side. It supplies the
tissues of the upper lip, and gives off in its course two or three vessels which ascend
to the nose. One, named the inferior artery of the septum, ramifies on the septum
of the nostrils as far as the point of the nose; another, the artery of the ala, supplies
the ala of the nose.
The lateralis nasi is derived from the facial, as that vessel is ascending along
the side of the nose ; it supplies the ala and dorsum of the nose, anastomosing with
its fellow, the nasal branch of the ophthalmic, the inferior artery of the septum,
the artery of the ala, and the infraorbital.
Fig. 439.- — The labial coronary arteries, the glands of the lips,
posterior surface after removal of the mucous m(
serves of the right side seen from the
(Poirier and Charpy.)
The angular artery (a. annularis) is the termination of the trunk of the facial;
it ascends to the inner angle of the orbit, embedded in the fibres of the Levator
Jabii superioris alaeque nasi, and accompanied by a large vein, the angular vein;
it distributes some branches on the cheek which anastomose with the infraorbital.
After supplying the lacrimal sac and Orbicularis palpebrarum muscle, the angular
artery terminates by anastomosing with the nasal branch of the ophthalmic artery.
The muscular branches are distributed to the Internal pterygoid and Stylohyoid
in the neck, and to the Masseter and Buccinator on the face.
The anastomoses of the facial artery are very numerous, not only with the
vessel of the opposite side, but, in the neck, with the sublingual branch of the lingual;
with the ascending pharyngeal; and with the posterior palatine, a branch of the
internal maxillary, by its ascending palatine and tonsillar branches; on the face,
with the mental branch of the inferior dental as it emerges from the mental foramen,
with the transverse facial, a branch of the temporal; with the infraorbital, a branch
of the internal maxillary, and with the nasal branch of the ophthalmic.
Peculiarities, — The facial artery not infrequently arises by a common trunk with the lingual.
This vessel is also subject to some variations in its size and in the extent to which it supplies
the face. It occasionally terminates as the submental, and not infrequently supplies the face
THE EXTERNAL CAROTID ARTERY
595
only ns liioh as tlie niiffle of the mouth or nose. The deficiency is then supplied by enlargement
of one of ilic lu'l^'hhorini^ arteries.
Applied Anatomy.— The passage of the facial artery over the body of the mandible would
appear to afl'ord a favorable position for the application of pressure in case of hemorrhage from the
lips, the result either of an accidental wound or during an operation; but its application is useless,
e.xcept for a very short time, on account of the free communication of this vessel with its fellow
and with numerous branches from different sources. In a wound invohmg the lip it is better
to seize the part between the fingers, and evert it, when the bleeding vessel may be at once secured
with pressure forceps. In order to prevent hemorrhage in cases of removal "of diseased growths
from the part, the lip should be compressed on each side between the fingers and thumb or by
a pair of specially devised clamp forceps, while the surgeon excises the diseased part. In order
to stop hemorrhage where the lip has been divided in an operation, it is necessary, in uniting
the edges of the wound, to pass the sutures through the cut edges from the skin almost as deep
as the mucous surface; by these means not only are the cut surfaces more neatly and securely
adapted to each other, but the possibility of hemorrhage is prevented by including in the suture
the divided artery. If the suture is, on the contrary,
passed through merely the cutaneous portion of the wound,
hemorrhage occurs into the cavity of the mouth. Lastly,
the relation of the angular artery to the lacrimal sac should
be observed, and it will be seen that, as the vessel passes up
along the inner margin of the orbit, it ascends on the
nasal side. In operating iov fistula lacrimalis the sac should
always be opened on its outer side, in order that this vessel
may be avoided.
4. The occipital artery (a. occipitalis) (Figs.
435 and 440) arises from the posterior part of the
external carotid, opposite the facial, near the lower
margin of the Digastric muscle.
Relations. — At its origin it is covered by the posterior
belly of the Digastric muscle and the Stylohyoid muscle,
and the hypoglossal nerve winds around it from behind
forward; higher up, it passes across the internal carotid
artej-y, the internal jugular vein, and the vagus and spinal
accessory nerves; it then ascends to the interval between the
transverse process of the atlas and the mastoid process of
the temporal bone, and passes horizontally backward in the
occipital groove on the mastoid portion of the temporal,
being covered by the Sternumastoid, Splenius, Trachelo-
mastoid, and Digastric muscles, and resting upon the
Rectus lateraHs, the Superior oblique, and Complexus
muscles; it then changes its course and passes vertically
upward, pierces the fascia which connects the cranial
attachment of the Trapezius with the Sternomastoid, and
ascends in a tortuous course over the occiput, as high as the vertex, where it divides into
numerous branches. It is accompanied in the latter part of its course by the great occipital
nerve, and occasionally by a cutaneous filament from the suboccipital nerve.
Branches. — ^The branches given off from this vessel are:
Muscular. Meningeal or diiral.
Sternomastoid. Mastoid.
Auricular. Arteria princeps cervicis.
Cranial branches.
The muscular branches (rami musculares) supply the Digastric, Stylohyoid,
Splenius, and Trachelomastoid muscles.
The sternomastoid fa. steriiocleidomastoidea) is a large and constant branch,
generally arising from the artery close to its commencement, but sometimes spring-
ing directly from the external carotid. It first passes downward and backT\-ard
over the hypoglossal nerve, and enters the substance of the muscle in company
with the spinal accessory nerve.
Fig. 440. — The loop of the hypo-
glossal nerve and the branches of the
external carotid artery.
596 THE VASCULAR SYSTEMS
The auricular branch {ramus auricularis) supplies the back part of the concha.
It frequently gives off a branch, which enters the skull through the mastoid foramen
and supplies the dura, the diploe, and the mastoid cells.
The meningeal or dural branch {ramus meningeus) ascends with the internal
juo'ular vein, and enters the skull through the foramen lacerum posterius, or
through the anterior condylar foramen, to supply the dura in the posterior fossa.
The mastoid branch {ramus mastoideus) is a small vessel, by no means constant.
It passes into the skull through the mastoid foramen and is distributed upon the
dura of the posterior fossa.
The arteria princeps cervicis {ravmis descendens), the largest branch of the
occipital, descends along the back part of the neck and divides into a superficial
and a deep branch. The superficial branch runs beneath the Splenius, giving off
branches which perforate that muscle to supply the Trapezius, and then anasto-
mose with the superficial cervical artery, a branch of the transversalis colli; the
deep branch passes beneath the Complexus between it and the Semispinalis colli,
and anastomoses with branches from the vertebral and with the deep cervical
artery, a branch of either the superior intercostal or the subclavian. The
anastomosis between these vessels helps to establish the collateral circulation
after ligation of the carotid or subclavian artery.
The cranial branches {rami occipitales) of the occipital artery are distributed upon
the occiput ; they are very tortuous^ and lie between the integument and Occipito-
frontalis, anastomosing with the artery of the opposite side, the posterior auricular
and temporal arteries. They supply the back part of the Occipitofrontalis muscle,
the integument, and pericranium.
5. The posterior auricular artery {a. auricidarls 'posterior') (Figs. 436 and 438)
is a small vessel which arises from the external carotid, above the Digastric and
Stylohyoid muscles, opposite the apex of the styloid process. It ascends, under
cover of the parotid gland, on the styloid process of the temporal bone, to the
groove between the cartilage of the ear and the mastoid process, immediately
above which it divides into its two terminal branches, the auricular and mastoid.
Just before arriving at the mastoid process, this artery is crossed by the facial
nerve, and has beneath it the spinal accessory nerve.
Branches. — Besides several small branches to the Digastric, Stylohyoid, and
Sternomastoid muscles and to the parotid gland, this vessel gives ofi' three branches :
Stylomastoid. Auricular. Mastoid.
The stylomastoid branch {a. stylomastoidea) enters the stylomastoid foramen,
and supplies the tympanum, mastoid cells, and semicircular canals. In the young
subject a branch from this vessel forms, with the tympanic branch from the in-
ternal maxillary, a vascular circle, which surrounds the tympanic membrane,
and from which delicate vessels ramify on that membrane. It anastomoses with
the petrosal branch of the middle meningeal artery by a twig, which enters the
hiatus Fallopii.
The auricular branch {ramus auricidaris), one of the terminal branches, ascends
behind the ear, beneath the Retrahens aurem muscle, and is distributed to the back
part of the cartilage of the ear, upon which it ramifies minutely, some branches
curving around the margin of the fibrocartilage, others perforating it, to supply
its anterior surface. It anastomoses with the posterior branch and also with the
anterior auricular branches of the superficial temporal.
The mastoid branch {ramus mastoideus) passes backward, over the Sternomastoid
muscle, to the scalp above and behind the ear. It supplies the posterior belly of
the Occipitofrontalis muscles and the scalp in this situation. It anastomoses
with the occipital artery.
THE EXTERNAL CAROTID ARTERY 597
6. The ascending pharyngeal artery {n. ■pharyngea ascendens) (Figs. 435 and
436), the smallest branch of the external carotid, is a long, slender vessel, deeply
seated in the neck, beneath the other branches of the external carotid and the
Stylopharyngeus muscle. It arises from the back part of the external carotid, near
the commencement of that vessel, and ascends vertically between the internal
carotid and the side of the pharynx, to the under surface of the base of the skull,
lying on the Rectus capitis anticus major muscle.
Branches. — Its branches may be subdivided as follows:
Prevertebral. Palatine.
Pharyngeal. Tympanic.
Meningeal or dural.
The prevertebral branches are numerous small vessels which supply the Recti
capitis antici and Longus colli muscles, the sympathetic, hypoglossal, and vagus
nerves, and the lymph nodes. They anastomose with the ascending cervical
artery, a branch of the inferior thyroid.
The pharyngeal branches (rami pharyiigei) are three or four in number. Two
of these descend to supply the Middle and Inferior constrictors and the Stylo-
pharyngeus, ramifying in the substance of the muscles and in the submucous
tissue of the mucous membrane lining them.
The palatine branch varies in size, and may take the place of the ascending
palatine branch of the facial artery, when that vessel is small. It passes inward
upon the Superior constrictor, and sends ramifications to the soft palate and tonsil,
and supplies a branch to the Eustachian tube.
The tympanic branch (a. tym-panica inferior) is a small artery which passes
through a minute foramen in the petrous portion of the temporal bone, in com-
pany with the tympanic branch of the glossopharyngeal nerve to supply the inner
wall of the tympanum and anastomose with the other tympanic arteries.
The meningeal or dural branches consist of several small vessels, which pass
through foramina in the base of the skull, to supply the dura. One, the posterior
meningeal or postdural (a. meningea posterior), enters the cranium through the
foramen lacerum posterius; a second passes through the foramen lacerum medium;
and occasionally a third through the anterior condylar foramen.
Applied Anatomy. — The ascending pharyngeal artery has been -nounded from the throat,
as in the case in which the stem of a tobacco-pipe was driven into the vessel, causing fatal hemor-
rhage. After removal of the tonsil there is sometimes severe bleeding. This is almost never
due to wounding of the internal carotid artery, as the latter vessel, if normally placed, is too
far away to be damaged. The bleeding comes from the branches of the ascending pharyngeal,
tonsillar, or ascending palatine arteries.
7. The superficial temporal artery (a. temporalis superficialis) (Figs. 435 and
438) , the smaller of the two terminal branches of the external carotid, appears, from
its direction, to be the continuation of that vessel. It commences in the substance
of the parotid gland, behind the neck of the mandible, and crosses over the posterior
root of the zygoma, passes beneath the Attrahens aurem muscle, lying on the tem-
poral fascia, and divides, about two inches above the zygomatic arch, into two
branches, an anterior and a posterior. This vessel is accompanied by the auriculo-
temporal nerve.
Relations. — The superficial temporary artery, as it crosses the zygoma, is covered by the
Attrahens aurem muscle, and by a dense fascia given off from the parotid gland; it is crossed
bv the temporofacial division of the facial nerve and one or two veins, and is accompanied by
the auriculotemporal nerve, which lies behind it.
698 THE VASCULAR SYSTEMS
Besides some twigs to the parotid gland, the articulation of the mandible, and
the Masseter muscle, its branches are:
Transverse facial. Anterior auricular.
Middle temporal. Anterior temporal.
Orbital. Posterior temporal.
The transverse facial branch (a. transversa faciei) is given off from the tem-
poral before that vessel quits the parotid gland; running forward through its
substance, it passes transversely across the face, between the parotid duct and
the lower border of the zygoma, and divides on the side of the face into numerous
branches, which supply the parotid gland, the Masseter muscle, and the integu-
ment, anastomosing with the facial, masseteric, and infraorbital arteries. This
vessel rests on the Masseter, and is accompanied by one or two branches of the
facial nerve. It is sometimes a branch of the external carotid.
The middle temporal artery (a. temporalis media) arises immediately above
the zygomatic arch, and, perforating the temporal fascia, gives branches to the
Temporal muscle, anastomosing with the deep temporal branches of the internal
maxillary. It occasionally gives off an orbital branch, which runs along the upper
border of the zygoma, between the two layers of the temporal fascia, to the outer
angle of the orbit. This branch, which may arise directly from the superficial
temporal artery, supplies the Orbicularis palpebrarum, and anastomoses with
the lacrimal and palpebral branches of the ophthalmic artery.
The orbital artery (a. zijgomaticoorbitalis) comes off from the temporal just
above the zygoma and is distributed to the upper orbital margin.
The anterior auricular branches (rami aurimdares anteriores) are distributed to
the anterior portion of the pinna, the lobule, and part of the external meatus,
anastomosing with branches of the posterior auricular.
The anterior temporal runs tortuously upward and forward, to the forehead,
supplying the muscles, integument, and pericranium in this region, and anasto-
moses with the supraorbital and frontal arteries. The terminal portion of the
anterior branch is called the frontal artery (ramus frontalis).
The posterior temporal, larger than the anterior, curves upward and backward
along the side of the head, lying superficial to the temporal fascia, and inosculates
with its fellow of the opposite side, and with the posterior auricular and occipital
arteries. The terminal portion of the posterior branch is named the parietal
artery (ramus parietalis).
Applied Anatomy. — The temporal artery, as it crosses the zygoma, Hes immediately beneath
the skin, and its pulsations may be readily felt during the administration of an anesthetic, or
under circumstances where the radial pulse is not available; or it may be easily compressed
against the bone in order to check bleeding from the temporal region of the scalp. When a flap
is raised from this part of the head, as in the operation of trephining, the incision should be
shaped like a horseshoe, with its convexity upward, so that the flap shall contain the temporal
artery which insures a sufficient supply of blood. The same principle is applied, as far as
possible, in making incisions to raise flaps in other parts of the scalp.
8. The internal maxillary artery (a. maxillaris interna) (Figs. 441 and 442),
the larger of the two terminal branches of the external carotid, arises behind the
neck of the mandible, and is at first embedded in the substance of the parotid gland;
it passes inward between the ramus of the mandible and the internal lateral liga-
ment, and then upon the outer surface of the External pterygoid muscle to the
sphenomaxillary fossa to supply the deep structures of the face. For convenience
of description it is divided into three portions — a maxillary, a pterygoid, and a
sphenomaxillary.
The first or maxillary portion passes horizontally forward and inward, between
the ramus of the mandible and the internal lateral ligament, where it lies parallel
THE EXTERNAL CAROTID ARTERY
599
to and a little below the auriculotemporal nerve; it crosses the inferior dental nerve,
and lies along the lower border of the External pterygoid muscle.
The second or pterygoid portion runs obliquely forward and upward under co\er
of the ramus of the mandible, on the outer (very frequently on the inner) surface of
the External pterygoid muscle; it then passes between the two heads of origin
of this muscle and enters the sphenomaxillary fossa.
^Buccal
r dental ^ \\ Internal pterygoid
Fig. 442. — Plan of the branches of the internal maxillary artery.
The third or sphenomaxillary portion lies in relation with Meckel's ganglion.
The branches of this vessel may be divided into three groups, corresponding
with its three divisions.
Branches of the maxillary portion (Fig. 442) :
Anterior tympanic. Middle meningeal or Medidural.
Deep auricular. Small meningeal or Parvidural.
Inferior dental.
600 THE VASCULAR SYSTEMS
The anterior tympanic branch (a. tyvifanica anterior) passes upward behind
the articulation of the mandible, enters the tympanum through the Glaserian
fissure, and ramifies upon the membrana tympani, forming a vascular circle
around the membrane with the stylomastoid artery, and anastomosing with the
Vidian and the tympanic branch from the internal carotid.
The deep auricular branch (a. auricularis 'profunda) often arises in common
with the preceding. It ascends in the substance of the parotid gland, behind the
temporomaxillary articulation, pierces the cartilaginous or bony wall of the external
auditory meatus, and supplies its cuticular lining and the outer surface of the
tympanic membrane. It gi^•es a branch to the temporomandibular joint.
The middle meningeal or medidural branch (a. meningea media) is the largest
of the branches which supply the dura. It ascends between the internal lateral
ligament and the neck of the mandible, and passes vertically upward between
the two roots of the auriculotemporal nerve to the foramen spinosum of the sphe-
noid bone, through which it enters the cranium; it then runs upward and forward
in a groove on the greater wing of the sphenoid bone and divides into two branches,
anterior and posterior. The anterior branch, the larger, crosses the greater wing
of the sphenoid, and reaches the groove, or canal, in the antero-inferior angle of
the parietal bone, and then divider into two branches which spread out between the
dura and internal surface of the cranium, some passing upward as far as the ver-
tex, and others backward to the occipital region. The posterior branch crosses the
squamous portion of the temporal, and on the inner surface of the parietal bone
divides into branches which supply the posterior part of the dura and cranium.
The branches of this vessel are distributed pardy to the dura, but chiefly to the
bones; they anastomose with the arteries of the opposite side, and with the anterior
and posterior meningeal arteries.
The middle meningeal on entering the cranium gives off the following collateral branches:
(1) Numerous small vessels to the Gasserian ganglion, and to the dura in this situation. (2)
A branch, the petrosal branch (ramiin prtrnsiis superficialis), which enters the hiatus Fallopii,
supplies the facial nerve, and anaslomoscs with the stylomastoid branch of the posterior auricular
artery. (3) A minute superior tympanic branch (a. tyvifamca superior), which runs in the
canai for the Tensor tympani muscle, and supplies this muscle and the lining membrane of the
canal. (4) Orbital branches, which pass through the sphenoidal fissure, or through separate
canals in the greater wing of the sphenoid to anastomose with the lacrimal or other branches of
the ophthalmic artery. (5) Temporal or anastomotic branches, which pass through the fora-
mina in the greater wing of the sphenoid bone and anastomose in the temporal fossa with the
deep temporal arteries.
Applied Anatomy. — The middle meningeal is an artery of considerable surgical importance,
as it may be injured in fractures of the temporal region of the skull. The vessel may be ruptured
by traumatism, even though the skull escape fracture. Rupture of the middle meningeal artery
will be followed by considerable hemorrhage between the bone and dura, which may cause
compression of the brain and require the operation of trephining for its relief. This artery
crosses the anterior inferior angle of the parietal bone at a point 1 i inches (3.75 cm.) behind
the external angular process of the frontal bone, and If inches (4.-5 cm.) above the zygoma.
From this point the anterior branch passes upward and slightly backward to the sagittal suture,
lying about \ inch (12 mm.) to f inch (18 mm.) behind the coronal suture. The posterior
branch passes upward and backward over the squamous portion of the temporal bone. In
order to expose the artery as it lies in the groove in the parietal bone, a semilunar incision, with
its convexity upward, should be made, commencing an inch behind the external angular process,
and carried backward for two inches. The structures cut through are: (1) Skin; (2) superficial
fascia, with branches of the superficial temporal vessels and nerves; (3) the fascia continued
down from the aponeurosis of the Occipitofrontalis; (4) the two layers of the temporal fascia;
(.5) the Temporal muscle; (6) the deep temporal vessels; (7) the pericranium. The bone is
trephined, the clot removed, and the vessel secured by ligatures, suture ligatures, or gauze
packing.
The small meningeal or parvidural branch {ramus meningeus accessorius) is some-
times derived from the preceding. It enters the skull through the foramen
ovale, and supplies the Gasserian ganglion and dura.
THE EXTERNAL CABOTJD ARTERY 601
The inferior dental branch (a. alveolaris inferior) descends with the inferior dental
nerve to the foramen on the inner side of the ramus of the mandible. It runs
along the dental canal in the substance of the bone, accompanied by the nerve,
and opposite the first bicuspid tooth divides into two branches, the incisor and
mental; the incisor branch is continued forward beneath the incisor teeth as far as
the symphysis, where it anastomoses with the artery of the opposite side; the
mental branch (o. mentalis) escapes with the nerve at the mental foramen, supplies
the structures composing the chin, and anastomoses with the submental, inferior
labial, and inferior coronary arteries. Near its origin the inferior dental artery gives
off a lingual branch, which descends with the lingual nerve and supplies the mucous
membrane of the mouth. As the inferior dental artery enters the foramen it gives
off a mylohyoid branch (ramus mylohyoideus), which runs in the mylohyoid groove,
and ramifies on the under surface of the Mylohyoid muscle. The inferior dental
artery and its incisor branches during their course through the substance of the
bone give off a few twigs which are lost in the cancellous tissue, and a series of
branches which correspond in number to the roots of the teeth; these enter the
minute apertures at the extremities of the fangs and supply the pulp of the teeth.
Branches of the pterygoid portion (Fig. 442):
Deep temporal. Masseteric.
Pterygoid. Buccal.
These branches are distributed, as their names imply, to the muscles in the
maxillary region.
The deep temporal branches, two in number, anterior (a. temporalis frofunda
anterior) and posterior (a. temporalis profunda posterior), each occupy that part
of the temporal fossa indicated by its name. Ascending between the Temporal
muscle and pericranium, they supply the muscle and anastomose with the middle
temporal artery. The anterior branch communicates with the lacrimal artery
by means of small branches which perforate the malar bone and greater wing of
the sphenoid.
The pterygoid branches (rami pteri/goidei), irregular in their number and origin,
supply the Pterygoid muscles.
The masseteric (a. masseterica) is a small branch which passes outward, above
the sigmoid notch of the mandible, to the deep surface of the Masseter muscle.
It supplies that muscle, and anastomoses with the masseteric branches of the facial
and with the transverse facial artery.
The buccal (a. buccinator ia) is a small branch which runs obliquely forward
lietween the Internal pterygoid and the ramus of the mandible, to the outer surface
of the Buccinator, to which it is distributed, anastomosing with branches of the
facial artery.
Branches of the sphenomaxillary portion (Fig. 442) :
Alveolar or Posterior dental. Vidian.
Infraorbital. Pterygopalatine.
Descending palatine. Naso- or sphenopalatine.
The alveolar or posterior dental branch (a. alveolaris superior posterior) is given
off from the internal maxillary in conjunction with the infraorbital, and just as
the trunk of the vessel is passing into the sphenomaxillary fossa. "Descending
upon the tuberosity of the maxilla, it divides into niunerous branches, some of which
enter the posterior dental canals, to supply the upper molar and bicuspid teeth
and the lining of the antrum, while others are continued forward on the alveola^
process to supply the gums.
602 THE VASCULAR SYSTEMS
The infraorbital (a. infraorbiiaiis) appears, from its direction, to be the con-
tinuation of the trunk of the internal maxillary, but often it arises from that vessel
in conjunction with the preceding branch. It runs along the infraorbital canal
with the superior maxillary nerve, and emerges upon the face at the infraorbital
foramen, beneath the Levator labii superioris muscle. While in the canal, it
gives off (a) branches which ascend into the orbit, and assist in supplying the
Inferior rectus and Inferior oblique muscles and the lacrimal gland, and (b) the
anterior dental branches (aa. alveolares siiperiores anteriores), which descend through
the anterior dental canals in the bone to supply the mucous membrane of the
antrum and the front teeth of the maxilla. On the face, some branches pass
upward to the inner angle of the orbit and the lacrimal sac, anastomosing with
the angular branch of the facial artery; others run inward toward the nose, anas-
tomosing with the nasal branch of the ophthalmic; and others descend beneath the
Levator labii superioris muscle, and anastomose with the transverse facial and
buccal arteries.
The four remaining branches arise from that portion of the internal maxillary
which is contained in the sphenomaxillary fossa.
The descending palatine (a. palatum desceiidens) descends through the posterior
palatine canal with the anterior palatine branch of the sphenopalatine (Meckel's)
ganglion, and, emerging from the posterior palatine foramen, runs forward in a
groove on the inner side of the alveolar border of the hard palate to the anterior
palatine canal, where the terminal branch of the artery passes upward through the
incisive canal (foramen of Stenson) to anastomose with the nasopalatine artery.
Branches are distributed to the gums, the mucous membrane of the hard palate,
and the palatine glands. In the palatine canal it gives off branches which descend
in the accessory palatine canals to supply the soft palate and tonsil, anastomosing
with the ascending palatine artery.
Applied Anatomy. — The position of the descending palatine artery on the hard palate
should be borne in mind in performing an operation for the closure of a cleft in tlie hard palate,
as the vessel is in danger of being wounded, and may give rise to formidable hemorrhage. In
case it should be wounded it may be necessary to plug the posterior palatine canal in order to
arrest the bleeding.
The Vidian branch (a. canalis pierygoidei) passes backward along the Vidian
canal with the Vidian nerve. It is distributed to the upper part of the pharynx
and Eustachian tube, sending a small branch into the tympanum, which anasto-
moses with the other tympanic arteries.
The pterygopalatine, a very small branch, runs backward through the pterygo-
palatine canal with the pharyngeal nerve, and is distributed to the upper part of
the pharynx and Eustachian tube.
The naso- or sphenopalatine (a. sphenopalatina) passes through the spheno-
palatine foramen into the cavity of the nose, at the back part of the superior meatus,
and divides into several branches. One, the nasopalatine, or artery of the septum,
courses obliquely downward and forward along the septum nasi, supplies the
mucous membrane, and anastomoses in front with the terminal branch of the de-
scending palatine; the other branches, two or three in number, are distributed to
the lateral wall of the nose, the antrum, and to the ethmoidal and sphenoidal cells.
THE TRIANGLES OF THE NECK (Fig. 443).
The student having considered the relative anatomy of the large arteries of the
neck and their branches, and the relations they bear to the veins and nerves, should
now examine these structures collectively, as they present themselves in certain
THE TRIANGLE8 OF THE NECK
603
regions of the neck, in each of which important operations are constantly being
performed.
The side of the neclc presents a somewhat quadrilateral outline, limited, above,
by the lower border of the body of the mandible, and an imaginary line extending
from the angle of the mandible to the mastoid process; heloiv, by the prominent
upper border of the clavicle; in front, by the median line of the neck; behind, by
the anterior margin of the Trapezius muscle. This space is subdivided into two
large triangles by the Sternomastoid muscle, which passes obliquely across the
neck, from the sternum and clavicle below to the mastoid process above. The
triangular space in front of this muscle is called the anterior triangle; and that
behind it, the posterior triangle.
Suprahyoid triangh
Submaxillary triangle. V
A
Superior carotid
triangle
Occipital triangle.
Subclavian triamiJr.
Fig. 443.— Tlie triangleb of tl
The anterior triangle is bounded, in front, by a line extending from the symphy-
sis menti to the sternum; behind, by the anterior margin of the Sternomastoid; its
base, directed upward, is formed by the lower border of the body of the mandible
and a line extending from the angle of the mandible to the mastoid process; its
apex is below, at the sternum. This space is subdivided into four smaller tri-
angles by the Digastric muscle above and the anterior belly of the Omohyoid below.
These smaller triangles are named from below upward, the inferior carotid, the
superior carotid, the submaxillary, and the suprahyoid triangles.
The inferior carotid triangle, or the triangle of necessity, is bounded, in front, by
the median line of the neck; behind, by the anterior margin of the Sternomastoid;
above, by the anterior belly of the Omohyoid; and is covered by the integument,
superficial fascia, Platysma, and deep fascia, ramifying between which are some
of the descending branches of the superficial cervical plexus. Beneath these
superficial structures are the Sternohyoid and Sternothyroid muscles, which,
together with the anterior margin of the Sternomastoid, conceal the lower part of
the common carotid artery.^ The floor of this triangle is formed by the Longus
1 Therefore, the common carotid artery and internal jugular vein are not, strictly speaking, contained in this
triangle, since they are covered by the Sternomastoid muscle; that is to say, lie behind the anterior bordei
of that muscle, which forms the posterior border of the triangle. But, as they lie very close to the structures
which are really contained in the triangle, and whose position it is essential to remember in operating on this
part of the artery, it has seemed expedient to study the relations of all these parts together.
604 THE VAtiCULAB SYSTEMS
colli muscle below and by the Scalenus anticus muscle above, between which
muscles the vertebral artery and vein will be found passing into the foramen of
the transverse process of the sixth cervical vertebra. A small portion of the origin
of the Rectus capitis anticus major may also be seen on the floor of the space.
The common carotid artery is enclosed within its sheath, together with the
internal jugular vein and vagus nerve; the vein lying on the outer side of the
artery on the right side of the neck, but overlapping it below on the left side;
the nerve lying between the artery and vein, on a plane posterior to both. In
front of the sheath are a few filaments descending from the loop of communication
between the descendens and communicans hypoglossi; behind the sheath are seen
the inferior thyroid artery, the recurrent laryngeal nerve, and the sympathetic
cord'; and on its inner side, the trachea, the thyroid gland — much more prominent
in the female than in the male — and the lower part of the larynx. By cutting into
the upper part of this space and slightly displacing the Sternomastoid muscle
the common carotid artery may be tied below the Omohyoid muscle.
The superior carotid triangle, or the triangle of election, is bounded, behind, by
the Sternomastoid; below, by the anterior belly of the Omohyoid; and above,
by the posterior belly of the Digastric muscle. It is covered by the integument,
superficial fascia, Platysma, and deep fascia, ramifying between which are branches
of the facial and superficial cervical nerves. Its floor is formed by parts of the
Thyrohyoid and Hyoglossus muscles, and the Inferior and INIiddle constrictor
muscles of the pharynx. This space, when dissected, is seen to contain ^he upper
part of the common carotid artery, which bifurcates opposite the upper border
of the thyroid cartilage into the external and internal carotid. These vessels are
occasionally somewhat concealed from view by the anterior margin of the Sterno-
mastoid muscle, which overlaps them. The external and internal carotid lie
side by side, the external being the more anterior of the two. The following
branches of the external carotid are also met with in this space, the superior thyroid
running forward and downward, the lingual directly forward, the facial forward
and upward, the occipital backward, and the ascending pharyngeal directly up-
ward on the inner side of the internal carotid. The veins met with are the internal
jugular, which lies on the outer side of the common and internal carotid arteries,
and veins corresponding to the above-mentioned branches of the external carotid
— viz., the superior thyroid, the lingual, facial, ascending pharyngeal, and some-
times the occipital, all of which accompany their corresponding arteries and ter-
minate in the internal jugular.- The nerves in this space are the following: In
front of the sheath of the common carotid is the descendens hypoglossi. The hypo-
glossal nerve crosses both the internal and external carotids above, curving around
the occipital artery at its origin. Within the sheath, between the artery and vein,
and behind both, is the vagus nerve; behind the sheath, the sympathetic cord.
On the outer side of the vessels the spinal accessory nerve runs for a short dis-
tance before it pierces the Sternomastoid muscle; and on the inner side of the
external carotid, just below the hyoid bone, may be seen the internal branch of
the superior laryngeal nerve; and, still more inferiorly, the external branch of the
same nerve. The uppef part of the larynx and lower part of the pharynx are
also found in the front part of this space.
The submaxillary triangle corresponds to the part of the neck immediately beneath
the body of the mandible. It is bounded, above, by the lower border of the body of
the mandible and a line drawn from its angle to the mastoid process ; below, by the
posterior belly of the Digastric muscle and the Stylohyoid muscle; in front, by the
anterior belly of the Digastric. It is covered by the integument, superficial fascia,
Platysma, and deep fascia, ramifying between which are branches of the facial
and ascending filaments of the superficial cervical nerves. Its floor is formed
by the Mylohyoid and Hyoglossus muscles. This space contains, in front, the
THE TRIANGLES OF THE NECK 605
submaxillary gland, superficial to which is the facial vein, while embedded in it are
the facial artery, and its glandular branches; beneath this gland, <m the surface of
the Mylohyoid muscle, are the submental artery and the mylohyoid artery and
nerve. The posterior part of this triangle is separated from the anterior part
by the stylomaxillary ligament; it contains the external carotid artery, ascending
deeply in the substance of the parotid gland; this vessel here lies in front of, and
superficial to, the internal carotid, being crossed by the facial nerve, and gives ofi' in
its course the posterior auricular, temporal, and internal maxillary branches; more
deeply are the internal carotid artery, the internal jugular vein, and the vagus
nerve, separated from the external carotid by the Styloglossus and Stylopharyn-
geus muscles and the glossopharyngeal nerve/
The suprahyoid triangle is limited behind by the anterior belly of the Digastric,
m front by the middle line of the neck between the symphysis menti and the hyoid
bone, helo'w by the body of the hyoid bone; its floor is formed by the Mylohyoid.
It contains one or two lymph nodes and some small veins; the latter unite to
form the anterior jugular vein.
The posterior triangle is bounded, in front, by the Sternomastoid muscle;*
hehind, by the anterior margin of the Trapezius; its base corresponds to the middle
third of the clavicle; its apex, to the occiput. The space is crossed, about an inch
above the clavicle, by the posterior belly of the Omohyoid, which divides it un-
equally into two, an upper or occipital and a lower or subclavian triangle.
The occipital triangle, the larger division of the posterior triangle, is bounded,
in front, by the Sternomastoid; behind, by the Trapezius; beloiv, by the Omo-
hyoid. Its floor is formed from above downward by the Splenius, Levator anguli
scapulae, and the Middle and Posterior scaleni muscles. It is covered by the
integument, the Platysma below, the superficial and deep fascine; the spinal
accessory nerve is directed obliquely across the space from the Sternomastoid,
which it pierces, to the under surface of the Trapezius; below, the descending
branches of the cervical plexus and the transversalis colli artery and vein cross
the space. A chain of lymph nodes is also found running along the posterior
border of the Sternomastoid, from the mastoid process to the root of the neck.
The subclavian triangle, the smaller of the two posterior triangles, is bounded,
above, by the posterior belly of the Omohyoid; below, by the clavicle, its base,
directed forward, being formed by the Sternomastoid. The size of the subclavian
triangle varies according to the extent of attachment of the clavicular portion of the
Sternomastoid and Trapezius muscles, and also according to the height at which
the Omohyoid crosses the neck above the clavicle. Its height also varies much
according to the position of the arm, being much diminished by raising the limb,
on account of the ascent of the clavicle, and increased by drawing the arm down-
ward, when that bone is depressed. This space is covered by the integument,
the Platysma, the superficial and deep fascite, and crossed by the descending
branches of the cervical plexus. Just above the level of the clavicle the third
portion of the subclavian artery curves outward and downward from the outer
margin of the Scalenus anticus, across the first rib, to the axilla. Sometimes this
vessel rises as high as an inch and a half above the clavicle, or to any point inter-
mediate between this and its usual level. Occasionally it passes in front of the
Scalenus anticus or pierces the fibres of that muscle. The subclavian vein lies
behind the clavicle, and is usually not seen in this space; but it occasionally rises
as high up as the artery, and has even been seen to pass with that vessel behind
the Scalenus anticus. The brachial plexus of nerves lies above the artery, and
in close contact with it. Passing transversely behind the clavicle are the supra-
' The remark made about the carotid triangle applies also to this one. The structures enumerated OS con-
tained in its posterior part lie, strictly speaking, beneath the. muscles which form the posterior boundary of
the triangle: but as it is very important to bear in mind their close relation to the parotid gland, aU these parts
are spoken of together.
606
THE VASCULAR SYSTEMS
scapular vessels, and traversing its upper angle in the same direction, the trans-
versalis colli artery and vein. The external jugular vein runs vertically downward
behind the posterior border of the Sternomastoid muscle, to terminate in the
subclavian vein; it receives the transverse cervical and suprascapular veins, which
occasionally form a plexus in front of the artery, and a small vein which crosses
the clavicle from the cephalic. The small nerve to the Subclavius muscle also
crosses this triangle about its middle. A lymph node is also found in the space.
Its floor is formed by the first rib with the first digitation of the Serratus magnus.
1st Aortic Iflte'''^"'
Fig. 444. — The internal carotid and vertebral arteries. Right side.
The Internal Carotid Artery (A. Carotis Interna).
The internal carotid artery supplies the anterior part of the brain, the eye and
its appendages, and sends branches to the forehead and nose. Its size in the
THE INTERNAL CAROTID ARTERY 607
adult is equal to that of the external carotid, though in the child it is larger than
that vessel. It is remarkable for the number of curvatures that it presents ii\
different parts of its course. It occasionally has one or two flexures near the base
of the skull, while in its passage through the carotid canal and along the side of
the body of the sphenoid bone it describes a double curve which resembles some-
what the letter S.
In considering the course and relations of this vessel it may be conveniently
divided into four portions — the cervical, petrous, cavernous, and cerebral portions.
Cervical Portion. — ^This portion of the internal carotid commences at the
bifurcation of the common carotid, opposite the upper border of the thyroid
cartilage, and runs perpendicularly upward, in front of the transverse processes
of the upper three cervical vertebra, to the carotid canal in the petrous portion
of the temporal bone. It is comparatively superficial at its commencement,
where it is contained in the superior carotid triangle, and lies behind and to the
outer side of the external carotid, overlapped by the Sternomastoid and covered
by the deep fascia, Platysma, and integument; it then passes beneath the parotid
gland, being crossed by the hypoglossal nerve, the Digastric and Stylohyoid muscles,
and the occipital and posterior auricular arteries. Higher up, it is separated from
the external carotid by the Styloglossus and Stylopharyngeus muscles, the tip of
the styloid process and the stylohyoid ligament, the glossopharyngeal nerve, and
pharyngeal branch of the vagus.
Relations. — It is in relation, behind, with the Rectus capitis anticus major, the superior
cervical ganglion of the sympathetic, and superior laryngeal nerve; externally, with the internal
jugular vein and vagus nerve, the nerve lying on a plane posterior to the artery; internally,
with the pharynx, tonsil, the superior laryngeal nerve, and ascending pharyngeal artery. At
the base of the skull the glossopharyngeal, vagus, spinal accessory, and hypoglossal nerves lie.
between the artery and the internal jugular vein.
Plan of the Relations of the Internal Carotid Artery in the Neck.
In front.
Skin, superficial and deep fascia.
Platysma.
Sternomastoid.
Occipital and posterior auricular arteries.
Hypoglossal nerve.
Parotid gland.
Styloglossus and Stylopharyngeus muscles.
Glossopharyngeal nerve.
Pharyngeal branch of the vagus.
ExternalUj. / ~X Internally.
Internal jugular vein. / internal \ Pharynx.
TT ■ Carotid o ' ■ i i
Vagus nerve. \ Artery. / buperior laryngeal nerve.
Ascending pharyngeal artery.
Tonsil.
Behind.
Rectus capitis anticus major.
Sympathetic.
Superior laryngeal nerve.
Petrous Portion. — When the internal carotid artery enters the canal in the
petrous portion of the temporal bone, it first ascends a short distance, then curves
forward and inward, and again ascends as it leaves the canal to enter the cavity of
608 THE VASCULAR SYSTEMS
the skull between the lingiila and petrosal process. In this canal the artery lies
at first below and in front of the cochlea and tympanum; behind and internal to
the canals for the Eustachian tube and Tensor tympani ; from the tympanum it is
separated by a thin, bony lamella. Farther forward it is separated from the
Gasserian ganglion by a thin plate of bone, which forms the floor of the fossa for
the ganglion and the roof of the horizontal portion of the canal. Frequently this
bony plate is more or less deficient, and then the ganglion is separated from the
artery by a fibrous membrane. The artery is separated from the bony wall of
the carotid canal by a prolongation of the dura, and is surrounded by a number of
small veins and by filaments of the carotid plexus, derived from the ascending-
branch of the superior cervical ganglion of the sympathetic.
Cavernous Portion. — The internal carotid artery in this part of its course i;i
situated between the layers of the dura forming the cavernous sinus, but is covered
by the lining membrane of the sinus. It at first ascends to the posterior clinoid
process, then passes forward by the side of the body of the sphenoid bone, and
again curves upward on the inner side of the anterior clinoid process, and perfor-
ates the dura forming the roof of the sinus. In this part of its course it is sur-
rounded by filaments of the sympathetic nerve, and has in relation with it ex-
ternally the abducent nerve.
Cerebral Portion. — Having perforated the dura, on the inner side of the anterior
clinoid process, the internal carotid passes between the optic and oculomotor
nerves to the anterior perforated substance at the inner extremity of the sylvian
fissure, where it gives oft' its terminal or cerebral branches. This portion of the
artery has the optic nerve on its inner side, and the oculomotor nerve externally.
Peculiarities. — The length of the internal carotid varies according to the length of the neck,
and also according to the point of bifurcation of the common carotid. Its origin sometimes
takes place from the arch of the aorta; in such rare instances this vessel has been found to be
placed nearer the middle line of the neck than the external carotid, as far up^vard as the larynx,
when the latter vessel crossed the internal carotid. The course of the vessel, instead of being
straight, may be very tortuous. A few instances are recorded in which this vessel was altogether
absent; in one of these the common carotid passed up the neck, and gave off the usual branches
of the external carotid, the cranial portion of the internal carotid being replated by two branches
of the internal maxillary, which entered the skull through the foramen rotundum and the foramen
ovale and joined to form a single vessel.
Applied Anatomy. — The cervical part of the internal carotid is very rarely wounded. ^Ir.
Cripps, in an interesting paper in the Medico-Chirurgical Transactions, compares the rareness
of a wound of the internal carotid with one of the external carotid or its branches. It is, however,
sometimes injured by a stah or gunshot wound in the neck, or even occasionally by a siah from
within the mouth, as when a person receives a thrust from the end of a parasol or falls down
with a tobacco-pipe in his mouth. It used to be believed that the internal carotid was occa-
sionally wounded in the removal of the tonsil. Such an accident cannot happen if the artery is
normally placed. The severe and sometimes fatal hemorrhage which has followed this oper-
ation in a few instances probably had as its source enlarged branches of the ascending pharyn-
geal, tonsillar, or ascending palatine arteries. Recently, however. Dr. Gwilym G. Davis, of
Philadelphia, demonstrated a specimen in which the internal carotid could have been wounded
by incision of the tonsil. The indications for ligation are wounds, when the vessel should be
exposed by a careful dissection and tied above and below the bleeding point; and aneurism,
which if non-traumatic may be treated by ligation of the common carotid, but if traumatic in
origin by exposing the sac and tying the vessel above and below. The incision for ligation of
the cervical portion of the internal carotid should be made along the anterior border of the
Sternomastoid, from the angle of the mandible to the upper border of the thyroid cartilage. The
superficial structures being divided and the Sternomastoid defined and drawn outward, the
cellular tissue must be carefully separated and the posterior belly of the Digastric muscle and
the hypoglossal nerve sought for as guides to the vessel. 'When the artery is found the external
carotid should be drawn inward and the Digastric muscles upward, and the aneurism needle
passed from without inward.
Obstruction of the internal carotid by embolism or thrombosis may give rise to symptoms of
cerebral anemia and softening if the collateral circulation is ill-developed. The patient sufFers
from giddiness, with failure of mental powers, and convulsions, coma, or hemiplegia on the
opposite side of the body, may be observed.
THE INTERNAL CAROTID ARTERY
609
The branches given off from the internal carotid artery are:
„ , „ r. • f Tympanic (internal or deep).
From the Petrous Portion I -^^idJan
( Arteriae Receptaculi.
From the Cavernous Portion -^ AjitenoLAIeningeal.
( O^hthalniic.
I' Anterior Cerebral.
„ , ,^ , , Ti ,• J ^liddle Cerebral.
From the Cerebral Portion < Pogtg^Tc^Uumicating.
t Anterior Choroid or Prechoroid.
The cervical portion of the internal carotid gives off no branches.
1. The tympanic (ramus caroticotym-panicus) is a small branch from the petrous
portion, which enters the cavity of the tympanum through a minute foramen in
the carotid canal, and anastomoses with the tympanic branch of the internal
maxillary, and with the stylomastoid artery.
Nasal. Palpebral.
Supraorbital.
Anterior ethmoidal
Posterior ethmoidal
Temporal branches
of lacrimal,
nitety of letina.
L icrimal
Ophthalmic
Internal carotid.
Fig. 445. — The ophthalmic artery and its branches, the roof of the orbit having been removed.
2. The Vidian is a small, inconstant branch which passes through the Vidian
canal and anastomoses with the Vidian branch of the internal maxillary artery.
3. The arteriae receptaculi are numerous small vessels, derived from the inter-
nal carotid in the cavernous sinus; they supply the hypophysis (pituitary body),
the Gasserian ganglion, and the walls of the cavernous and inferior petrosal
sinuses. Some of these branches anastomose with branches of the middle
meningeal.
4. The anterior meningeal (o. vieningea anterior) is a small branch which
passes over the lesser wing of the sphenoid to supply the dura of the anterior
39
610 THE VASCULAR SYSTEMS
fossa; it anastomoses with the diiral branch from the posterior ethmoidal
artery.
5. The ophthalmic artery (a. ophthalmica) arises from the internal carotid,
just as that vessel is emerging from the cavernous sinus, on the inner side of the
anterior clinoid process, and enters the orbit through the optic foramen, below and
on the outer side of the optic nerve. It then passes over the nerve to the inner wall
of the orbit and thence horizontally forward, beneath the lower border of the
Superior oblique muscle, to a point behind the internal angular process of the
frontal bone, where it divides into two terminal branches, the frontal and nasal
branches. As the artery crosses the optic nerve it is accompanied by the nasal
nerve, and is separated from the frontal nerve by the Rectus superior and Levator
palpebrae superioris muscles.
Branches. — The branches of this vessel may be divided into an orbital group,
which are distributed to the orbit and surrounding parts, and an ocular group,
which supply the muscles and globe of the eye:
Orbital Group.
Ocular Group.
Lacrimal.
Short ciliary.
Supraorbital.
Long ciliary.
Posterior ethmoidal.
Anterior ciliary.
Anterior ethmoidal.
Central artery of the retina,
Internal palpebral.
Muscular.
Frontal.
Nasal.
The lacrimal (a. lacrimalis) is one of the largest branches derived from the
ophthalmic, arising close to the optic foramen; not infrequently it is given off from
the ophthalmic artery before it enters the orbit. It accompanies the lacrimal
nerve along the upper border of the External rectus muscle, and is distributed to
the lacrimal gland. Its terminal branches, escaping from the gland, are distributed
to the eyelids and conjunctiva; of those supplying the eyelids, two are of consider-
able size and are named the external palpebral {aa. palpebrales laterales) ; they run
inward in the upper and lower lids respectively, and anastomose with the internal
palpebral arteries, forming an arterial circle in this situation. The lacrimal artery
gives off one or two malar branches, one of which passes through a foramen in
the malar bone, to reach the temporal fossa, and anastomoses with the deep tem-
poral arteries; the other appears on the cheek through the malar foramen, and
anastomoses with the transverse facial. A recurrent branch passes backward
through the sphenoidal fissure to the dura, and anastomoses with a branch of
the middle meningeal artery.
Peculiarities. — The lacrimal artery is sometimes derived from one of the anterior branches
of the middle meningeal artery.
The supraorbital artery {a. supraorbitalis) arises from the ophthalmic as thai .
vessel is crossing over the optic nerve. Ascending so as to arise above all the muscles
of the orbit, it passes forward, with the supraorbital nerve, between the periosteum
and Levator palpebrae muscle; and, passing through the supraorbital foramen,
divides into a superficial and deep branch, which supply the integument, the
muscles, and the pericranium of the forehead, anastomosing with the frontal, the
anterior branch of the temporal, and the supraorbital artery of the opposite side.
This artery in the orbit supplies the Superior rectus and the Levator palpebrae
muscles, and sends a branch inward, across the pulley of the Superior oblique
muscle, to supply the parts at the inner canthus. At the supraorbital foramen
it frequently transmits a branch to the diploe.
THE INTERNAL CAROTID ARTERY
611
The ethmoidal branches are two in number — posterior (a. cthmoidalis posterior')'
and anterior (a. cthmoidalis anterior). The posterior ethmoidal artery, which is
the smaller, passes through the posterior ethmoidal foramen, supplies the posterior
ethmoidal cells, and, entering the cranium, gives off a meningeal or dural branch,
FiQ. 446. — The arteries of the base of the brain. The right half of the cerebellum and pons have been
removed. N. B. — It will be noticed that the two anterior cerebral arteries have been drawn at a considerable
distance from each other; this makes the anterior communicating artery appear very much longer than it
really is.
which supplies the adjacent dura; and nasal branches which descend into the
nose through apertures in the cribriform plate, anastomosing with branches of the
sphenopalatine. The anterior ethmoidal artery accompanies the nasal nerve through
the anterior ethmoidal foramen, supplies the anterior ethmoidal cells and frontal
612
THE VASCULAR SYSTEMS
■ sinuses, and, entering the cranium, gives off a dural branch which supplies the
adjacent dura; and nasal branches, which descend into the nose, through the slit
by the side of the crista galli, and, running along the groove on the under surface
of the nasal bone, supply the skin of the nose.
The internal palpebral arteries (aa. palpebrales mediales), two in number, supe-
rior and inferior, arise from the ophthalmic, opposite the pulley of the Superior
oblique muscle; they leave the orbit to encircle the eyelids near their free margin,
formino- a superior tarsal arch (arcus tarseus superior) and an inferior tarsal arch
(arcm tarseus inferior), which lie between the Orbicularis muscle and the tarsal
plates. The superior palpebral anastomoses, at the outer angle of the orbit, with
the orbital branch of the temporal artery, and with the upper of the two external
palpebral branches from the lacrimal artery; the inferior palpebral anastomoses,
Fig. 447. — Vascular area of the upper surface of the cerebrum. I. The part supplied by the external and
inferior frontal artery. II. The part supplied by the ascending frontal. III. The part suppUed by the ascending
parietal. IV. The part supphed by the sphenoparietal artery. (After Buret.)
at the outer angle of the orbit, with the lower of the two external palpebral branches
from the lacrimal and with the transverse facial artery, and at the inner side of the
lid with a branch from the angular artery. From this last anastomosis a branch
passes to the nasal duct, ramifying in its mucous membrane, as far as the inferior
meatus.
The frontal artery (a. frontalis), one of the terminal branches of the ophthalmic,
leaves the orbit at its inner angle with the supratrochlear ner\'e, and, ascending
on the forehead, supplies the integument, muscles, and pericranium, anastomosing
with the supraorbital artery and with the frontal artery of the opposite side.
The nasal artery (a. dorsalis iiasi), the other terminal branch of the ophthalmic,
emerges from the orbit above the tendo oculi, and, after giving a branch to the
upper part of the lacrimal sac, divides into two branches, one of which crosses
THE INTERNAL CAROTID ARTERY
613
the root of the nose, the transverse nasal, and anastomoses with the angular artery;
the other, the dorsalis nasi, runs along the dorsum of the nose, supplies its outer
surface, and anastomoses with the artery of the opposite side and with the lateral
nasal branch of the facial.
The ciliary arteries (o. ciUarcs) are divisible into three groups — the short, long,
and anterior. The short ciliary arteries (aa. ciliares posieriores breves), from sLx
to twelve in number, arise from the ophthalmic or some of its branches ; they sur-
round the optic nerve as they pass forward 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 long ciliary arteries (aa. ciliares posteriores longae),
two in number, pierce the posterior part of the sclera at some little distance from
the optic nerve, and run forward, along each side of the eyeball, between the
sclera and choroid, to the ciliary muscle, where they divide into two branches;
these form an arterial circle, the circulus major, around the circumference of the
iris, from which numerous radiating branches pass forward, in its substance, to
its pupillary aperture, where they form a second arterial circle, the circulus minor.
Cnilrnl Fisnire
Fig. 448. — Vascular area of the internal surface of the cerebrum. I. The part supplied by the anterior
internal frontal. II. The part supplied by the middle internal frontal. III. The part supplied by the posterior
internal frontal. IV. The part supplied by the posterior temporal. V. The part supplied by the occipital, both
terminal branches of the posterior cerebral. (After Duret.)
The anterior ciliary arteries {aa. ciliares anteriores) are derived from the muscular
branches (see below) ; they pass to the front of the eyeball in company with the
tendons of the Recti muscles, form a vascular zone beneath the conjunctiva, and
then pierce the sclera a short distance from the cornea and terminate in the circu-
lus major of the iris.
The central artery of the retina {arteria centralis retinae) is the first and one of the
smallest branches of the ophthalmic artery. It runs for a short distance within
the dural sheath of the optic nerve, but about half an inch behind the eyeball it
pierces the optic nerve obliquely, and runs forward in the centre of its substance,
and enters the globe of the eye through the porus opticus. Its mode of distribu-
tion will be described in the section on the anatomy of the eye.
The muscular branches {rami musculares), two in number, superior and inferior,
frequently spring from a common trunk. The superior, the smaller, often want-
ing, supplies the Levator palpebrae, Superior rectus, and Superior oblique. The
inferior, more constant in its existence, passes forward between the optic nerve and
the Inferior rectus muscle, and is distributed to the External, Internal, and Inferior
recti, and Inferior oblique. This vessel gives off most of the anterior ciliary
614
THE VASCULAR SYSTEMS
arteries. Additional muscular branches are given off from the lacrimal and supra-
orbital arteries or from the ophthalmic itself.
(For the Circulus or Circle of Willis, the posterior cerebral artery, and rhe
bloodvessels of the cerebellum, see page 617.)
The anterior cerebral (a. cerebri anterior) arises from the internal carotid
at the inner extremity of the sylvian fissure. It passes forward and inward
across the anterior perforated substance, above the optic nerve, to the commence-
ment of the intercerebral fissure. Here it comes into close relationship with
the anterior cerebral artery of the opposite side, and the two vessels are con-
nected by a short anastomosing trunk, about two lines, \ inch (4 mm.) in length,
the anterior communicating artery. From this point the two vessels run side by
side in the intercerebral fissure, curve around the genu of the corpus callosum,
and, turning backward, continue along its upper surface to its posterior part,
where they terminate by anastomosing with the posterior cerebral arteries.
Fig. 449. — Vascular area of the inferior surface of the cerebrum. I. The part supplied by the anterior tem-
poral from the posterior cerebral artery. II. The part supplied by the posterior temporal" from the posterior
cerebral artery. III. The part supplied by the occipital from the posterior cerebral artery. (After Duret.)
Branches. — In their course the anterior cerebral arteries give off the following
branches:
Antero-median ganglionic.
Inferior internal frontal.
Anterior internal frontal.
Aliddle internal frontal.
Posterior internal frontal
The antero-median ganglionic are a group of small arteries which arise at the
commencement of the anterior cerebral artery; they pierce the anterior perforated
THE INTERNAL CAROTID ARTERY
615
substance and lamina terminalis, and supply the rostrum of the corpus callosum,
the septum lucidum, and the head of the caudate nucleus.
The inferior internal frontal branches, two or three in number, are distributed
to the orbital surface of the frontal lobe, where they supply the olfactory lobe,
gyrus rectus, and internal orbital (mesorbital) convolution.
The anterior internal frontal supply a part of the mesal surface of the prefrontal
region, and send branches over the edge of the hemisphere to the superfrontal
and medifrontal gyre and upper part of the precentral gyre.
The middle internal frontal supplies the corpus callosum, the callosal gyre, the
ANTEf^lOR CHOR
3LANDOF REIL-t _^//yl ( / /
X. C.«,CUU,T. r/
INT. GENICULATE ^--^a^ / )l
BODY ^"v-ir y
MIDDLE CORN
OF LATERE
VENTRICLE
Fig. 4.50. — The anterior cerebral and choroid arteries. (Spalteholz.)
mesal surface of the superfrontal convolution, and the dorsal part of the pre-
central gyre.
The posterior internal frontal supplies the precuneus and adjacent outer sur-
face of the hemisphere.
The anterior communicating artery {a. communicans anterior, a. praecommuni-
cans) is a short branch, about 4 mm. in length, but of moderate size, connecting
the two anterior cerebral arteries across the intercerebral fissure. Sometimes
this vessel is wanting, the two arteries joining to form a single trunk, which
afterward divides. Or the vessel may be wholly or partially divided into two;
616
THE VASCULAR SYSTEMS
frequently it is longer and smaller than usual. It gives off some of the antero-
median ganglionic group of vessels, which are, however, principally derived from
the anterior cerebral.
PERCALLOSAL
INTERNAL POSTERIOR POSTERIOR
CAROTID COMMUNICATING CEREBRAL
ARTERY ARTERY ARTERY
Fig. 451. — The arteries of the medial surface of the right cerebral hemisphere. (Spalteholz.)
The middle cerebral artery (a. cerebri media) (Fig. 452), the largest branch of
the internal carotid, passes obliquely outward along the sylvian fissure, and
divides on the surface of the insula into its terminal branches.
Fig. 452. — The distribution of the middle cerebral artery. The trunk of the middle cerebral artery Ues i
depths of the sylvian cleft. (After Charcot.)
Branches. — The branches of the middle cerebral arterv are:
Antero-lateral ganglionic.
Inferior external frontal.
Ascending frontal.
Ascending parietal.
Parietotemporal .
Temporal.
THE ARTERIES OF THE BRAIN 617
The antero-lateral ganglionic branches, a group of small arteries which arise at
the commencement of the middle cerebral artery, are arranged in two sets; one,
the internal striate, passes upward through the inner segment of the lenticular
nucleus, and supplies it, the caudate nucleus, and the internal capsule; the other,
the external striate, ascends through the outer segment of the lenticular nucleus,
and supplies the caudate nucleus and the thalamus. One artery of this group
(also called lenticulostriate artery) is of larger size than the rest, and is of special
importance, as being the artery in the brain most frequently ruptured; it has been
termed by Charcot the artery of cerebral hemorrhage. It passes up between the
lenticular nucleus and the external capsule, and ultimately ends in the caudate
nucleus.
The inferior external frontal supplies the subfrontal convolution (Broca's convolu-
tion) and the outer part of the orbital surface of the frontal lobe.
Tile ascending frontal supplies the precentral gyre.
The ascending parietal is distributed to the postcentral convolution and the
lower part of the superior parietal convolution.
The parietotemporal supplies the supramarginal and angular gyres, the super-
temporal, and part of the meditemporal gyre.
The temporal branches, two or three in number, are distributed to the outer
surface of the temporal lobe.
The posterior communicating artery (a. communicans posterior) runs backward
from the internal carotid, and anastomoses with the posterior cerebral, a branch
of the basilar. This artery varies considerably in size, being sometimes small,
and occasionally so large that the posterior cerebral may be considered as aris-
ing from the internal carotid rather than from the basilar. It is frequently larger
on one side than on the other. From the posterior half of this vessel are given
off a number of small branches, the postero-median ganglionic branches, which,
with similar vessels from the posterior cerebral, pierce the posterior perforated
substance and supply-^the internal surfaces of the thalami and the walls of the
third ventricle.
The choroid artery (a. chorioidea) is a small but constant branch which arises
from the back part of the internal carotid, near the posterior communicating
artery. Passing backward and outward between the temporal lobe and the crus,
it enters the descending horn of the lateral ventricle through the choroidal fis-
sure and ends in the choroid plexus. It is distributed to the hippocampus,
fimbria, velum interpositum, and choroid plexus.
THE ARTERIES OF THE BRAIN.
Investigations show that the mode of distribution of the vessels of the brain has
an important bearing upon a considerable number of the anatomical lesions of
which this part of the nerve system may be the seat; it is therefore important to
consider a little more in detail the manner in which the cerebral vessels are
distributed.
The cerebral arteries are derived from the internal carotid and the vertebral,
which at the base of the brain form a remarkable anastomosis known as the circle
of Willis (circulus arteriosus) (Fig. 453). It is formed in front by the anterior
cerebral arteries, branches of the internal carotid, which are connected by the ante-
rior communicating; behind by the two posterior cerebrals, branches of the basilar,
which are connected on each side to the internal carotid by the posterior communi-
cating (Fig. 446). The parts of the brain included within this arterial circle
are the lamina terminalis, the chiasm or commissure of the optic nerves, the tuber
cinereum, the corpora albicantia, and the posterior perforated substance. This
arrangement of the vessels of the circle is not invariable; according to Windle, it
618
THE VASCULAR SYSTEMS
is maintained in little more than half the recorded cases. In the other cases
there are different variations.
The three trunks which together supply each cerebral hemisphere arise from
the circle of Willis. From its anterior part proceed the two anterior cerebrals,
from its antero-lateral part the middle cerebrals, and from its posterior part the
posterior cerebrals. Each of these principal arteries gives origin to two ^'e^y dif-
ferent systems of secondary vessels. One of these systems has been named the
central ganglionic system, and the vessels belonging to it supply the central ganglia
of the brain; the other has been named the cortical arterial system, and its vessels
ramify in the pia and supply the cortex and subjacent medullary substance. These
two systems, although they have a common origin, do not communicate at any
point of their peripheral distribution, and are entirely independent of each other,
representing terminal arteries. Though some of the arteries of the cortical system
approach, at their terminations, the regions supplied by the central ganglionic
system, no communication between the two sets of vessels takes place, and there
is between the parts supplied by the two systems a borderland of diminished
nutritive activity. In the brains of old people softening is especially apt to occur
in this ill-nourished territory.
Anterior cerebral-
Middle cerebral
Anterior choroit
Posterior communicating-
Posterior cerebral-
Anterior cojnmunicating
Superior cerebellar-
Basilar
Anterior inferior cerebellar-
Interior auditory
Posterior inferior cerebellar
Vertebral
E. A. S.
Posterior spinal' "Anterior spinal
Fig. 453. — Diagram of the arteries at the base of the brain, including the circle of Willis. I. Antero-median
group of ganglionic branches. II. Poatero-median group. III. Right and left antero-lateral group. IV. Right
and left postero-Iateral group.
The Central Ganglionic System. — All the vessels belonging to this system
are given off from the circle of Willis or from the vessels immediately after their
origin from it, so that if a circle is drawn at a distance of about an inch from the
circle of Willis, it will include the origin of all the arteries belonging to this system
(Fig. 453). The vessels of this system form four principal groups: (I) The antero-
median group, derived from the anterior cerebrals and anterior communicating;
(II) the postero-median group, from the posterior cerebrals and posterior communi-
cating; (III) the right and left antero-lateral group, from the middle cerebrals;
and (IV) the right and left postero-Iateral group, from the posterior cerebrals, after
they have wound around the crura. The vessels belonging to this system are larger
than those of the cortical sj'stem, and are what Cohnheim has termed terminal
arteries — that is to say, vessels which from their origin to their termination neither
THE VERTEBRAL ARTERY
619
supply nor receive any anastomotic branches, so that by one of the small vessels
only a limited area of the central ganglia can be injected; and the injection cannot
be driven beyond the area of the part supplied by the particular vessel which is
the subject of the exjieriment.
The Cortical Arterial System. — The vessels forming this system are the ter-
minal branches of the anterior, middle, and posterior cerebral arteries, descriljed
above. These vessels divide and ramify in the substance of the pia, and give off
nutrient arteries which penetrate the cortex perpendicularly. These nutrient ves-
sels are divisible into two classes — the long and short. The long — or, as they are
sometimes called, the medullary — arteries pass through the gray substance to pene-
trate the centrum ovale to the depth of about an inch and a half, without intercom-
municating otherwise than by very fine capillaries, and thus constitute so many
Fig. 454. — Distribution of the cortical arteries. 1. Medullary arteries, 1'. Group of medullary arteries in
the sulcus between two adjacent convolutions, 1", Arteries situated among the short association fibres. 2, 2,
Cortical arteries, a. Capillary network with fairly wide meshes, situated beneath the pia. h. Network with
more compact, polygonal meshes, situated in the cortex, c. Transitional network, with wider meshes, d.
Capillary network in the white substance, (,\fter Charcot.)
independent small systems. The short vessels are confined to the cortex, where
they form with the long vessels a compact network in the middle zone of the gray
substance, the outer and inner zones being sparingly supplied with blood (Fig, 454),
The vessels of the cortical arterial system are not so strictly terminal as those of
the central ganglionic system, but they approach this type very closely, so that
injection of one area from the vessel of another area, though it may be possible,
is frequently very difficult, and is only effected through vessels of small caliber.
As a result of this, obstruction of one of the main branches or its divisions may have
the effect of producing softening in a very limited area of the cortex.
The Vertebral Artery (A. Vertebralis).
The vertebral artery (a. vertebralis) (Figs, 444 and 455) is generally the first and
largest branch of the subclavian; in rare instances it springs independently from
the arch of the aorta. It arises from the upper and back part of the first portion
of the vessel, and, passing upward, enters the foramen in the transverse process of
620 THE VASCULAR SYSTEMS
the sixth cervical vertebra/ and ascends through the foramina in the transverse
processes of all the vertebrae above this. Above the upper border of the axis it
inclines outward and upward to the foramen in the transverse process of the atlas,
through which it passes; it then winds backward behind its articular process,
runs in a deep groove on the upper surface of the posterior arch of this bone (Fig.
16), and, passing beneath the posterior occipito-atlantal ligament (Figs. 224 and
227), pierces the dura and arachnoid, and enters the skull through the foramen
magnum. It then passes forward and upward, inclining from the lateral aspect
to the front of the medulla oblongata. It unites in the middle line with the vessel
of the opposite side at the lower border of the pons to form the basilar artery
(Fig. 426).
Relations. — At its origin it is situated behind the internal jugular and vertebral veins, and
is crossed by the inferior thyroid artery; it lies between the Longus colli and Scalenus anticus
muscles, having the thoracic duct in front of it on the left side. It rests on the transverse process
of the seventh cervical vertebra and the sympathetic cord. Within the foramina formed by
the transverse processes of the vertebrfe it is accompanied by a plexus of nerves from the inferior
cervical ganglion of the sympathetic, and is surrounded by a dense plexus of veins which unite
to form the vertebral vein at the lower part of the neck. It is situated in front of the cervical
nerves, as they issue from the intervertebral foramina. While winding around the articular
process of the atlas, it is contained in the suboccipital triangle — a triangular space formed by
the Rectus capitis posticus major, the Obliquus capitis superior and the Obliquus capitis
inferior muscles. The suboccipital nerve here lies between the artery and the posterior arch of
the atlas. Within the skull, as the artery winds around the oblongata, it is placed between the
hypoglossal nerve and the anterior root of the suboccipital nerve, beneath the first digitation of
the ligamentum denticulatum, and finally ascends between the basilar process of the occipital
bone and the anterior surface of the medulla oblongata.
Applied Anatomy. — The vertebral artery has been tied in several instances. (1) For wounds
or traumatic aneurism; (2) after ligation of the innominate, either immediately to prevent hem-
orrhage, or later on to arrest bleeding where it has occurred at the seat of ligation. The oper-
ation of ligation of the vertebral is performed by making an incision along the posterior border
of the Sternomastoid muscle, just above the clavicle. The muscle is pulled to the inner side,
and the anterior tubercle of the transverse process of the sixth cervical vertebra is sought for.
A deep layer of fascia being now divided, the interval between the Scalenus anticus and the
Longus colli muscles just below their attachment to the tubercle is defined, and the artery and
vein are found in the interspace. The vein is to be drawn to the outer side, and the aneurism
needle is passed from without inward. Drs. Ramskill and Bright have pointed out that severe
pain at the back of the head may be symptomatic of disease of the vertebral artery just before
it enters the skull. This is explained by the close connection of the artery with the suboccipital
nerve in the groove on the posterior arch of the atlas. Disease of the same artery has been also
said to affect speech, from pressure on the hypoglossal nerve where it is in relation with the
vessel, leading to paratysis of the muscles of the tongue.
Branches. — These may be divided into two sets — those given off in the neck
and those within the cranium.
Cervical Branches. Cranial Branches.
Spinal rami, or Lateral spinal. Posterior meningeal.
Muscular. Anterior spinal, or Ventral spinal.
Posterior spinal, or Dorsal spinal.
Posterior inferior cerebellar.
Bulbar.
The spinal branches (rami spinales) enter the vertebral canal through the inter-
vertebral foramina and divide into two branches. Of these, one passes along the
roots of the nerves to supply the spinal cord and its membranes, anastomosing
with the other arteries of the spinal cord; the other divides into an ascending and
^ ^ The vertebral artery sometimes enters the foramen in the transverse process of the fifth vertebra. Dr.
Smyth, who tied this artery in the living STibject, found it, in one of his dissections, passing into the forameD
in the seventh vertebra.
THE VERTEBRAL ARTERY 621
a descending branch, which unite with similar branches from the artery above
and below, so that two hxteral anastomotic chains are formed on the posterior
surface of the vertebrEe near the attachment of the pedicles. From these anasto-
motic chains branches are given off to supply the periosteum and the bodies of the
vertebrte, and to communicate with similar branches from the opposite side; from
these communicating branches small branches are given off which join similar
branches above and below, so that a central anastomotic chain is formed on the
posterior surface of the bodies of the vertebrae.
Muscular branches are given off to the deep muscles of the neck, where the ver-
tebral artery curves around the articular process of the atlas. They anastomose
with the occipital and with the ascending and deep cervical arteries.
The posterior meningeal (ramus meningeus) is a small branch given off from
the vertebral opposite the foramen magnum. It ramifies between the bone and
dura in the cerebellar fossa^, and supplies the falx cerebelli. It is frequently repre-
sented by two small branches.
The anterior or ventral spinal (a. spinalis anterior) is a small .branch which
rises near the termination of the vertebral, and, descending ventrad of the
medulla oblongata, unites with its fellow on the opposite side at about the
level of the foramen magnum. One of these \'essels is usually larger than the
other, but occasionally they are about ecjual in size. The single trunk thus formed
descends on the front of the spinal cord, and is reinforced by a succession of small
branches which enter the vertebral canal through the intervertebral foramina;
these branches are derived from the vertel^ral artery and the ascending cervical
branch of the inferior thyroid artery in the neck; from the intercostal in the
thoracic region; and from the lumbar, iliolumbar, and lateral sacral arteries in
the lower part of the vertebral column. They unite, by means of ascending and
descending branches, to form a single terminal artery, which extends as far as
the lower part of the spinal cord. This vessel is placed in the pia along the
anterior median fissure; it supplies that membrane and the substance of the cord,
and sends oft' branches at its lower part to be distributed to the cauda equina,
and ends on the central fibrous prolongation of the cord.
The posterior or dorsal spinal (a. spinalis posterior) arises from the vertebral
at the side of the medulla oblongata; passing backward to the dorsal aspect
of the spinal cord, it descends on each side, lying behind the dorsal roots of the
spinal nerves, and is reinforced by a succession of small branches which enter
the vertebral canal through the intervertebral foramina, and by which it is con-
tinued to the lower part of the cord and to the cauda equina. Branches from
the posterior spinal arteries form a free anastomosis around the dorsal roots
of the spinal nerves, and communicate, by means of very tortuous transverse
branches, with the vessel of the opposite side. Close to its origin each gives off
an ascending branch, which terminates at the side of the fourth ventricle.
Applied Anatomy. — Bleeding into the spinal membranes or into the substance of the spinal
cord itself is not common, but may occur from injuries received at birth when labor is imduly
prolonged or instruments are used. It is also met with in chronic insanity, and in tetanus and
strychnine poisoning.
The posterior inferior cerebellar artery (a. cerebelli inferior posterior) (Fig. 446),
the largest branch of the vertebral, winds backward around the upper part
of the medulla oblongata, passing between the origin of the vagus and spinal
accessory nerves, over the restiform body to the under surface of the cerebel-
lum, where it divides into two branches — an internal, which is continued back-
ward to the notch between the two hemispheres of the cerebellum; and an ex-
ternal, which supplies the under surface of the cerebellum as far as its outer
622 THE VASCULAR SYSTEMS
border, where it anastomoses with the anterior inferior cerebellar and the supe-
rior cerebellar branches of the basilar artery. Branches from this artery supply
the choroid plexus of the fourth ventricle.
The bulbar arteries comprise several minute vessels which spring from the
vertebral and its branches and are distributed to the medulla oblongata.
The basilar artery (a. hasilaris) (Fig. 446), so named from its position at the base
of the skull, is a single trunk formed by the junction of the two vertebral arteries;
it extends from the posterior to the anterior border of the pons, lying in the median
pontile groove, under cover of the arachnoid. It ends by dividing into the two
posterior cerebral arteries.
Branches. — Its branches on either side are the following:
Transverse. Anterior inferior cerebellar.
Internal auditory. Superior cerebellar.
Posterior cerebral.
The transverse or pontile branches {rami ad ponteni^ are a number of small vessels
which come off at right angles on either side of the basilar artery and supply the
pons and adjacent parts of the brain.
The internal auditory (a. auditiva interna), a long slender branch, arises from
near the middle of the artery; it accompanies the corresponding auditory nerve
into the internal auditory meatus and is distributed to the internal ear.
The anterior inferior cerebellar artery (a. cerebelli inferior anterior) passes back-
ward to be distributed to the anterior part of the under surface of the cerebellum,
anastomosing with the posterior inferior cerebellar branch of the vertebral.
The superior cerebellar artery (a. cerebelli superior) arises near the termination
of the basilar. It passes outward, immediately behind the oculomotor nerve,
which separates it from the posterior cerebral artery, winds around the crus, close
to the trochlear nerve, and, arriving at the upper surface of the cerebellum,
divides into branches which ramify in the pia and, reaching the circumference of
the cerebellum, anastomose with the branches of the inferior cerebellar artery.
Several branches are given to the epiphysis, the superior medullary velum, and
the velum interpositum.
The posterior cerebral artery (a. cerebri posterior) (Figs. 446 and 453) is larger
than the preceding, from which it is separated near its origin by the oculomotor
nerve. Passing outward, parallel to the superior cerebellar artery, and receiving
the posterior communicating from the internal carotid, it winds around the crus,
and passes to the under surface of the temporal lobe of the cerebrum, and divides
up into branches for the supply of the temporal and occipital lobes.
The branches of the posterior cerebral artery are:
( Postero-median ganglionic. ( Anterior temporal.
Ganglionic -^ Posterior choroid. Cortical < Posterior temporal,
t Postero-lateral ganglionic. ( Occipital.
Ganglionic. — The postero-median ganglionic branches (Fig. 453) are a group of
small arteries which arise at the commencement of the posterior cerebral artery;
these, with similar branches from the posterior communicating, pierce the posterioT
perforated substance, and supply the internal surfaces of the thalamus and the
wails of the third ventricle. The posterior choroid enters the interior of the brain
beneath the splenium of the corpus callosum, and supplies the velum interpositum
and the choroid plexus. The postero-lateral ganglionic branches are a group of
small arteries which arise from the posterior cerebral artery, after it has turned
around the crus; they supply a considerable portion of the thalamus.
THE SUBCLA VIAJST ARTERY 623
Cortical. — The cortical branches are the anterior temporal branches, to the basal
surface of the anterior portion of the temporal lobe; the posterior temporal branches,
to the external surface of the occipital lobe and the subtemporal convolution;
and the occipital branches, to the mesal and lateral surfaces of the occipital lobe.
ARTERIES OF THE UPPER EXTREMITY.
The artery which supplies the upper extremity continues as a single trunk
from its commencement down to t4ie elbow, but different portions of it have
received different names according to the region through which it passes. That
part of the vessel which extends from its origin to the outer border of the first
rib is termed the subclavian artery; beyond this point to the lower border of the
axilla it is termed the axillary artery; and from the lower margin of the axillary
space to the bend of the elbow it is termed the brachial artery; here the single trunk
terminates by dividing into two branches, the radial and ulnar.
THE SUBCLAVIAN ARTERY (A. SUBCLAVIA) (Fig. 456).
On the right side the subclavian artery arises from the innominate artery opposite
the right sternoclavicular articulation; on the left side it arises from the arch
of the aorta. The two vessels, therefore, in the first part of their course, differ
in length, direction, and relation with neighboring structures.
In order to facilitate the description of these vessels, more especially from a
surgical point of view, each subclavian artery has been divided into three parts.
The first portion, on the right side, passes
upward and outward from the origin of the f)
vessel to the inner border of the Scalenus .//
anticus. On the left side it ascends nearly /<^^~~^
vertically, to gain the inner border of that /^/
muscle. The second part passes outward, Clgj^^.,-- Ih M
behind the Scalenus anticus; and the third "^^^^grt^N/^ l|) ^
part passes from the outer margin of that ^;ir?iS^^---~^l=/~-J~/ \ \
muscle, beneath the clavicle, to the outer ^^^jand / /g^^^^^\\ \
border of the fii-st rib, where it' becomes the /'^*^'°tLi^^^VTi~~^ '^^ \
axillary artery. The first portion of these <^i^*/-^^P- ■■' ) || l\ fX °* \
two vessels differs so much in its course and ^^"'^ ■■'" J/^ %\ \ \
in its relations with neighboring parts '^^ yj \ ,j
that it will be described separatelv. The
second and third parts are alike on "the two ^"'- ^^^-^'j^ubdal^ln^Se*'.' °' *' "^^^
sides.
First Part of the Right Subclavian Artery (Fig. 4.56).— The first part of the
right subclavian artery arises from the innominate artery, opposite the upper
part of the right sternoclavicular articulation, and passes upward and outward
to the inner margin of the Scalenus anticus muscle (Fig. 456). It ascends a little
above the clavicle, the extent to which it does so varying in different cases.
Relations. — It is covered, iti front, by the integument, superficial fascia, Platysma, deep
fascia, the clavicular origin of the Sternomastoid, the Sternohyoid, and the Sternoth}Toid muscles,
and another layer of deep fascia. It is crossed by the internal jugular and vertebral veins,
and by the vagus nerve and the cardiac branches of the vagus and sympathetic nerves. A loop
of the sympathetic nerve itself also crosses the artery, forming a ring (misa suhdavia) around
the vessel. The anterior jugular vein passes outward in front of the artery, but is not in contact
with it, being separated from it by the Sternohyoid and Sternothyroid muscles. Below and
behind the artery is the pleura; behind is the gangliated cord of the sympathetic, the Longus colli
muscle and the first thoracic vertebra. The right recurrent laryngeal nerve winds aroimd the
lower and back part of the vessel.
624
THE VASCULAR SYSTEMS
PJnentc nerve Ve>tehal 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<! Suprascapular.
(Transverse cervical.
On the left side all four branches generally arise from the first portion of the
vessel, but on the right side the superior intercostal usually arises from the second
portion of the vessel. On both sides of the body the first three branches arise close
together at the inner margin of the Scalenus anticus; in the majority of cases a
free interval of from half an inch to an inch exists between the commencement
of the artery and the origin of the nearest branch. The vertebral artery
arises from the upper and posterior part of the subclavian artery, the internal
mammary from the lower part of the artery; the thyroid axis from in front and
the superior intercostal from behind.
The vertebral artery, the first branch of the subclavian, is distributed entirely
to the head and neck, chiefly supplying the posterior portion of the brain. It
has been described on pages 619 to 623.
The thyroid axis (iruncus thyreocervicalis) (Figs. 435 and 458) is a short thick
trunk which arises from the fore part of the first portion of the subclavian artery.
THE SUBCLA VIAN ARTERY 629
close to the inner border of the Scalenus anticus muscle, and divides, almost
immediately after its origin, into three branches — the inferior thyroid, supra-
scapular, and transverse cervical.
The inferior thyroid artery (a. thyreoidea inferior) (Fig. 4.35) passes upward, in
front of the vertebral artery and Longus colli muscle; then turns inward behind the
sheath of the common carotid artery and internal jugular vein, and also behind
the sympathetic cord, the middle cervical ganglion resting upon the vessel, and,
reaching the lower border of the lateral lobe of the thyroid gland, it divides into
two branches, which supply the postero-inferior parts of the gland, and anasto-
mose with the superior thyroid and with the corresponding artery of the opposite
side. The recurrent laryngeal nerve passes upward, generally behind, but occa-
sionally in front of, the artery. Its branches are :
Inferior laryngeal. OEsophageal.
Tracheal. Ascending cervical.
Muscular.
The inferior larjmgeal branch (a. laryngea inferior) ascends upon the trachea
to the back part of the larynx, in company with the recurrent laryngeal nerve,
and supplies the muscles and mucous membrane of this part, anastomosing with
the inferior laryngeal branch from the opposite side and with the laryngeal branch
from the superior thyroid artery.
The tracheal branches (rami tracheales) are distributed upon the trachea, anasto-
mosing below with the bronchial arteries.
The oesophageal branches (rami oesophagei) are distributed to the oesophagus,
and anastomose with the oesophageal branches of the aorta.
The ascending cervical (a. cervicalis ascendens) is a small branch which arises
from the inferior thyroid just where that vessel is passing behind the common
carotid artery, and runs up on the anterior tubercles of the transverse processes
of the cervical vertebrtie in the interval between the Scalenus anticus and Rectus
capitis anticus major muscles. It gives branches to the muscles of the neck,
which anastomose with branches of the vertebral, and sends one or two branches
into the vertebral canal through the intervertebral foramina to be distributed to
the spinal cord and its membranes, and to the bodies of the vertebrae in the same
manner as the lateral spinal branches from the vertebral. It anastomoses with
the ascending pharyngeal and occipital arteries.
The muscular branches supply the Depressors of the hyoid bone, the Longus
colli, the Scalenus anticus, and the Inferior constrictor of the pharynx. One
of the muscular. branches passes between the transverse processes of the fourth
and fifth cervical vertebrae and reaches the deep muscles of the neck. It is called
the ramus profundus.
The suprascapular artery (a. transversa scapulae) (Figs. 4.35 and 457) passes
at first downward and outward across the Scalenus anticus and phrenic nerve,
being covered by the Sternomastoid; it then crosses the subclavian artery and the
cords of the brachial plexus, and runs outward, behind and parallel with the
clavicle and Subclavius muscle, and beneath the posterior belly of the Omohyoid,
to the superior border of the scapula, where it passes over the transverse ligament
of the scapula, which separates it from the suprascapular nerve, and reaches the
supraspinous fossa. In this situation it lies close to the bone, and ramifies be-
tween it and the Supraspinatus muscle, to which it supplies branches. It then
passes downward behind the neck of the scapula, to reach the infraspinous fossa,
where it anastomoses with the dorsalis scapulae branch of the subscapular artery
and branches of the posterior scapular arteries. Besides distributing branches
to the Sternomastoid, Subclavius, and neighboring muscles, it gives off a supra-
630
THE VASCULAR SYSTEMS
sternal branch, which crosses over the sternal end of the clavicle to the skin of the
upper part of the thorax; and a supra-acromial branch {ramus acromialls), which
piercing the Trapezius muscle, supplies the skin over the acromion, anastomosing
with a branch of the acromiothoracic artery. A small subscapular branch is given
off as the artery passes over the transverse ligament of the scapula; it descends into
the subscapular fossa, ramifies beneath the Subscapular muscle, and anastomoses
with the posterior and subscapular arteries. The suprascapular artery also sends
branches to the acromioclavicular and shoulder-joints, and a nutrient artery to
the clavicle.
Posterior scapular.
Suprascapular.
rminaiion of
suhscapular.
Fig. 457. — The scapular and circumflex arteries.
The transverse cervical artery (a. transversa colli) (Fig. 435), larger than the
suprascapular, passes transversely outward, across the upper part of the sub-
clavian triangle, to the anterior margin of the Trapezius muscle, beneath which
it divides into two branches, the superficial cervical and the posterior scapular.
In its passage across the neck it crosses in front of the phrenic nerve, Scaleni
muscles, and the brachial plexus, between the divisions of which it sometimes
passes, and is covered by the Platysma, Sternomastoid, Omohyoid, and Trapezius
muscles.
The superficial cervical (ramus ascendens) ascends beneath the anterior margin
of the Trapezius, distributing branches to it and to the neighboring muscles and
lymph nodes in the neck, and anastomosing with the superficial branch of the
arteria princeps cervicis.
The posterior scapular (ramus descendens) (Fig. 435) passes beneath the Levator
anguli scapulae muscle to the superior angle of the scapula, and then descends
along the posterior border of that bone as far as the inferior angle. In its course
it is covered by the Rhomboid muscles, supplying them and the Latissimus dorsi
and Trapezius, and anastomosing with the suprascapular and subscapular arteries,
and with the posterior branches of some of the intercostal arteries.
PecuUarities. — The superficial cervical frequently arises as a separate branch from the thy-
roid axis; and the posterior scapular, from the third, more rarely from the second, part of the
subclavian.
THE SUBCLA VIAN ARTERY
631
The internal mammary artery (a. mammaria interna) (Fig. 458) arises from
the under surface of the first portion of the subclavian artery, opposite the thyroid
Scalenus
anticus.
iiiterio} uitei costal
branches
Musculo-
pli7'emc ^AaW
Fig. 458.— The internal iiuimma
■External
iliac.
iteiy and its branches.
axis. It descends behind the cartilages of the upper six ribs at a distance of
about half an inch from the margin of the sternum; and at the level of the sixth
intercostal space divides into the musculophrenic and superior epigastric arteries.
632 THE VASCULAR 8YSTEM8
Relations. — At its origin it is cohered by the internal jugular and subclavian veins, and as
it enters the thorax is crossed from without inward by the phrenic nerve, and then passes for-
ward close to the outer side of the innominate vein. In the upper part of the thorax it lies behind
the costal cartilages and Internal intercostal muscles, and is crossed by the terminations of the
upper six intercostal nerves. Behind it lies upon the pleura, as far as the third costal cartilage;
below this level upon the Triangularis sterni muscle. It is accompanied by two venae comites;
these unite into a single vein, which passes to the inner side of the artery and ends in the corre-
sponding innominate vein.
Branches. — The branches of the internal mammary are:
■Comes nervi phrenici. Anterior intercostal.
Mediastinal. Perforating.
Pericardiac. Musculophrenic.
Sternal. Superior epigastric.
The comes nervi phrenici (a. pericardiacophrenica^ is a long slender branch
which accompanies the phrenic nerve, between the pleura and pericardium, to
the Diaphragm to which it is distributed; it anastomoses with the other phrenic
branches from the internal mammary and with phrenic branches of the abdominal
aorta.
The mediastinal branches (aa. mediastinales anteriores) are small vessels which
are distributed to the areolar tissue and lymph nodes in the anterior medias-
tinum and to the remains of the thymus gland.
The pericardiac branches supply the upper part of the anterior surface of the
pericardium, the lower part receiving branches from the musculophrenic artery.
The sternal branches (rami sternales) are distributed to the Triangularis sterni
and to the posterior surface of the sternum.
The mediastinal, pericardiac, and sternal branches, together with some twigs
from the comes nervi phrenici, anastomose with branches from the intercostal and
bronchial arteries, and form a minute plexijs beneath the pleura, which has been
named by Turner the subpleural mediastinal plexus.
The anterior intercostal arteries (rami intercostales) supply the five or six upper
intercostal spaces. The branch corresponding to each space soon divides into
two, or the two branches may come off separately from the parent trunk. The
small vessels pass outward in the intercostal spaces, one, the larger, lying near
the lower margin of the rib above, and the other, the smaller, near the upper
margin of the rib below, and anastomose with the intercostal arteries from the
aorta. They are at first situated between the pleura and the Internal intercostal
muscles, and then between the Internal and External intercostal muscles. They
supply the Intercostal muscles, and, by branches which perforate the External
intercostal muscle, reach the Pectoral muscles and the mammary gland.
The perforating arteries (rami perforantes) correspond to the five or six upper
intercostal spaces. They ari.se from the internal mammary, pass forward through
the intercostal spaces, and, curving outward, supply the Pectoralis major and the
integument. Those which correspond to the second, third, and fourth spaces are
distributed to the mammary gland. In females, during lactation, these branches
are of large size.
The musculophrenic artery (a. muscidophreiiica) is directed obliquely down-
ward and outward, behind the cartilages of the false ribs, perforating the Dia-
phragm at the eighth or ninth rib, and terminating, considerably reduced in size,
opposite the last intercostal space. It gives off anterior intercostal arteries to
each of the intercostal spaces across which it passes; these diminish in size as the
spaces decrease in length, and are distributed in a manner precisely similar to
THE AXILLA 633
the anterior intercostals from the internal mammary. The musculophrenic also
gives branches to the lower part of the pericardium, and others which run back-
ward to the Diaphragm and downward to the Abdominal muscles.
The superior epigastric (a. epicjasirica superior) continues in the original direc-
tion of the internal mammary; it descends through the cellular interval between
the costal and sternal attachments of the Diaphragm, and enters the sheath of the
Rectus abdominis muscle, at first lying behind the muscle, and then perforating
it and supplying it, and anastomosing with the deep epigastric artery from the
external ihac. Some branches perforate the sheath of the Rectus and supply the
muscles of the abdomen and the integument, and a small branch, which passes
inward upon the side of the ensiforUi appendix, anastomoses in front of that
cartilage with the superior epigastric artery of the opposite side. It also gives
some twigs to the Diaphragm, while from the artery of the right side small branches
extend into the falciform ligament of the liver and anastomose with the hepatic
artery.
The superior intercostal (truncus costocervicaUs) (Figs. 444 and 464) arises from
the upper and back part of the subclavian artery, behind the Scalenus anticus mus-
cle on the right side and to the inner side of that muscle on the left side. Passing
backward, it gives off the deep cervical branch, and then descends behind the
pleura in front of the necks of the first two ribs, and anastomoses with the first
aortic intercostal. As it crosses the neck of the first rib it lies to the inner side
of the anterior division of the first thoracic ner^'e and to the outer side of the first
thoracic ganglion of the sympathetic cord.
In the first intercostal space it gives off a branch which is distributed in a manner
similar to the distribution of the aortic intercostals. The branch for the second
intercostal space usually joins with one from the highest aortic intercostal. Each
intercostal gives off a branch to the posterior spinal muscles, and a small branch
which passes through the corresponding intervertebral foramen to the spinal cord
and its membranes.
The deep cervical branch (a. ccrvicalis profunda) arises, in most cases, from
the superior intercostal, and is analogous to the posterior branch of an aortic
intercostal artery; occasionally it arises as a separate branch from the subclavian
artery. Passing backward, above the eighth cervical nerve and between the
transverse process of the seventh cervical vertebra and the first rib, it runs up the
back part of the neck, between the Complexus and Semispinalis colli muscles,
as high as the axis vertebra, supplying these and adjacent muscles, and anasto-
mosing with the deep branch of the arteria princeps cervicis of the occipital,
and with Ijranches which pass outward from the vertebral. It gives off a special
branch which enters the vertebral canal through the intervertebral foramen
between the seventh cervical and first thoracic vertebrae.
THE AXILLA.
The axilla or armpit is a pyramidal space, situated between the upper and lateral
part of the thorax and the inner side of the arm.
Boundaries. — Its apex, which is directed upward toward the root of the neck,
corresponds to the interval between the first rib, the upper edge of the scapula,
and the clavicle, through which the axillary vessels, the brachial plexus of ner\es,
and the long thoracic nerve pass. This interval is the cervico-axillary passage.
The base, directed downward, is formed by the integument and a thick layer of
fascia, the axillary fascia (fascia axillaris) (Fig. 346), extending between the lo\\-er
border of the Pectoralis major in front and the lower border of the Latissimus
634 THE VASCULAR SYSTEMS
dorsi behind (page 406). The axilla is broad internally at the thorax, but narrow
and pointed externally at the arm. The anterior wall is formed by the Pectoralis
major and minor muscles, the former covering the whole of the anterior wall of
the axilla, the latter covering only its central part, the costocoracoid membrane,
the clavicle, and the Subclavius muscle. The posterior boundary, which extends
somewhat lower than the anterior, is formed by the Subscapularis above, the Teres
major and Latissimus dorsi below. On the inner side are the first four ribs with
their corresponding Intercostal muscles, and part of the Serratus magnus. On
the outer side, where the anterior and posterior boundaries converge, the space is
narrow, and bounded by the humerus, the Coracobrachialis and Biceps muscles.
Contents. — It contains the axillary vessels, and the brachial plexus of nerves,
with their branches, some branches of the intercostal nerves, and a large number
of lymph nodes, all connected by a quantity of fat and loose areolar tissue.
Position of the Contents. — The axillary artery and vein, with the brachial plexus
of nerves, extend obliquely along the outer boundary of the axilla, from its apex
to its base, and are placed much nearer the anterior than the posterior wall, the
vein lying to the inner or thoracic side of the artery and partially concealing
it. At the fore part of the axilla, in contact with the Pectoral muscles, and along
the anterior margin are the thoracic branches of the axillary artei-y, and along
the lower margin of the Pectoralis minor the long thoracic artery extends to the
side of the thorax. At the back part, in contact with the lower margin of the Sub-
scapularis muscle, are the subscapular vessels and nerves; winding around the
outer border of this muscle is the dorsalis scapulae artery and veins ; and, close
to the neck of the humerus, the posterior circumflex vessels and the circumflex
nerve are seen curving backward to the shoulder.
Along the inner or thoracic side no vessel of any importance exists, the upper
part of the space being crossed merely by a few small branches from the superior
thoracic artery. There are some important nerves, however, in this situation —
viz., the long thoracic nerve, descending on the surface of the Serratus magnus,
to which it is distributed ; and perforating the upper and anterior part of this wall,
the intercostohumeral nerve or nerves, passing across the axilla to the inner side
of the arm.
The cavity of the axilla is filled by a quantity of loose areolar tissue and a large
number of small arteries and veins, all of which are, however, of inconsiderable
size, and numerous lymph nodes, the position and arrangement of which are
described on a subsequent page.
Applied Anatomy. — The axilla is a space of considerable surgical importance. It trans-
mits the large vessels and nerves to the upper extremity, and these may be the seat of injury or
disease; it contains numerous lymph nodes \Yhich may require removal when diseased; in
it is a quantity of loose connective and adipose tissue which may be readily infiltrated with blood
or pus. The axilla may be the seat of rapidly growing tumors. Moreover, it is covered at its
base by thin skin, largely supplied with sebaceous and sweat glands, which is frequently the
seat of small cutaneous abscesses and bcrils, and of eruptions due to irritation.
In suppuration in the axilla the arrangement of the fascife plays a very important part in the
direction which the pus takes. As described on p. 456, the costocoracoid membrane, after
covering in the space between the clavicle and the upper border of the Pectoralis minor, splits
to enclose this muscle, and, reblending at its lower border, becomes incorporated with the axillary
fascia at the anterior fold of the axilla. Suppuration may take place either superficial to or
beneath tnis layer of fascia; that is, either between the Pectorals or beneath the Pectoralis minor;
in the former case the pus would point either at the anterior border of the axillary fold or in
the groove between the Deltoid and the Pectoralis major; in the latter instance, the pus would
have a tendency to surround the vessels and nerves and ascend into the neck, that being the direc-
tion in which there is least resistance. Its progress toward the skin is prevented by the axillary
fascia; its progress backward, by the Serratus magnus; forward, by the costocoracoid fascia;
inward, by the wall of the thorax; and outward, by the upper limb. The pus in these cases,
THE AXILLARY ARTERY
635
after extending into the neck, has been known to spread through the suiicrior ojjcning of the
thorax into the mediastinum.
In opening an axillary abscess the knife should be entered in the floor of the axilla, midway
between the anterior and posterior margins and near the thoracic side of the space. It is well
to use a director and dressing forceps after an incision has been made through the skin and fascia
in the manner directed by the late Mr. Hilton.
The relations of the vessels and nerves in the several parts of the axilla are important, for it is
the universal plan to remove the nodes from the axilla in operating for cancer of {he breast.
Fig. 459. — The axillary artery
The Axillary Artery (A. Axillaris) (Fig. 459).
The axillary artery, the continuation of the suljclavian, commences at the
outer border of the first rib, and terminates at the lower border of the tendon
of the Teres major muscle, where it talces the name of brachial. Its direction
varies with the position of the limb; when the arm lies by the side of the thorax,
the vessel forms a gentle curve, the convexity being upward and outward; when
the arm is directed at right angles with the trimk, the vessel is nearly straight;
and when the arm is elevated still higher, the arteries describe a curve the con-
cavity of which is directed upward. At its commencement the artery is very deeply
'situated, but near its termination it is superficial, being covered only by the skin
and fascia. The description of the relations of this vessel is facilitated by its
division into three portions, the first portion being above, the second portion be-
hind, and the third below the Pectoralis minor.
Relations. — The first portion of the axillary artery is in relation, in front, with the clavicular
portion of the Pectoralis major, the costocoracoid membrane, the external anterior thoracic nerve,
and the acromiothoracic and cephalic veins; behind, with the first intercostal space, the corre-
636 THE VASCULAR SYSTEMS
spending Intercostal muscle, the first and second digitations of the Serratus magnus, and the
Long thoracic nerve; on its outer side, with the brachial plexus, from which it is separated by
a little areolar tissue; on its inner or thoracic side, with the axillary vein, which overlaps the
artery. It is enclosed, together with the axillary vein and the brachial plexus, in a fibrous
sheath — the axillary sheath — continuous above with the cervical fascia.
Relations of the First Portion of the Axillary Artery.
In front.
Pectoralis major.
Costocoracoid membrane.
External anterior thoracic nerve.
Acromiothoracic and cephalic veins.
Outer side. I Axillary \ ■ Inner side.
Artery. 1
Brachial plexus. I i^"^' portion. / Axillary vein.
Behind. "(B?
First Intercostal space and Intercostal muscle.
First and Second digitations of Serratus magnus.
Long thoracic and internal anterior thoracic nerves.
The second portion is covered, in front, by the Pectoralis major and minor muscles; behind
it is the posterior cord of the brachial plexus and some areolar tissue which intervenes between
it and the Subscapularis; on the inner side is the axillary vein, separated from the artery by the
inner cord of the brachial plexus and the internal anterior thoracic nerve; on the outer side is
the outer cord of the brachial plexus. The brachial plexus of nerves thus surrounds the artery
on three sides, and separates it from direct contact with the vein and adjacent muscles.
Relations of the Second Portion of the Axillary Artery.
In front.
Pectoralis major and minor.
Outer side.
Inner side.
Axillary vein.
Outer cord of brachial plexus. \ porUon. J • Inner cord of brachial plexus.
Internal anterior thoracic nerve.
Behind.
Subscapularis.
Posterior cord of brachial plexus.
The third portion of the axillary artery extends from the lower border of the Pectoralis
minor to the lower border of the tendon of the Teres major. It is in relation, infroni, with
the lower part of the Pectoralis major above, being covered only by the integument and fascia
below; behind, with the lower part of the Subscapularis and the tendons of the Latissimus dorsi
and Teres major; on its outer side, with the Coracobrachialis; on its inner or thoracic side, with
the axillary vein. The nerves of the brachial plexus bear the following relation to the artery
in this part of its course; on the outer side is the median nerve and the musculocutaneous for a
short distance; on the inner side, the ulnar nerve (between the vein and artery) and the lesser
internal cutaneous nerve (to the inner side of the vein); m front are the inner head of the median
and the internal cutaneous nerve, and behind, the musculospiral and circumflex, the latter
extending only as far as the lower border of the Subscapularis muscle.
THE AXILLAE V ARTERY 637
Relations of the Third Portion of the Axillary Artery.
In front.
Integument and fascia.
Pectoralis major.
Inner head of median nerve.
Internal cutaneous nerve.
Outer side. /^ \^ Inner side.
Coracobrachialis. i Artery^ | Ulnar nerve.
Median nerve. I Third portion. / Axillary vein.
Musculocutaneous nerve. V / Lesser internal cutaneous nerve.
Behind.
Subscapularis.
Tendons of Latissimus dorsi and Teres major.
Musculospiral and circumflex nerves.
Peculiarities. — The axillary artery, in about one case out of every ten, gives off a large
branch, which forms either one of the arteries of the forearm or a large muscular trunk. In the
first set of cases this artery is most frequently the radial (1 in 3.3), sometimes the ulnar (1 in 72)
and, very rarely, the interosseous (1 in 506). In the second set of cases the trunk has been
found to give origin to the subscapular, circumflex, and profunda arteries of the arm. Some-
times only one of the circumflex, or one of the profunda arteries, arises from the trunk. In
these cases the brachial plexus surrounded the trunk of the branches and not the main vessel.
Suriace Marking. — The course of the axillary artery may be marked out by raising the
arm to a right angle with the body and drawing a line from the middle of the clavicle to the
point where the tendon of the Pectoralis major crosses the prominence caused by the Coraco-
brachialis as it emerges from under cover of the anterior fold of the axilla. The third portion
of the artery can be felt pulsating beneath the skin and fascia, at the junction of the anterior
with the middle third of the space between the anterior and posterior folds of the axilla, close to
the inner border of the Coracobrachialis muscle.
Applied Anatomy. — Compression of the vessel may be required in the removal of tumors
or in amputation of the upper part of the arm; and the only situation in which this can be efi'ect-
ually made is in the lower part of its course; by pressing on it in this situation from within
outward against the humerus the circulation may be effectually arrested.
With the exception of the popliteal, the axillary artery is perhaps more frequently lacerated
than any other artery in the body by violent movements of the extremity, especially in those
cases where its coats are diseased. It has occasionally been ruptured in attempts to reduce old
dislocations of the shoulder-joint. This accident is most likely to occur during the preliminary
breaking down of adhesions, in consequence of the artery having become fixed to the capsule
of the joint. Aneurism of the axillary artery is of frequent occurrence, a large percentage of
the cases being traumatic in their origin, due to the violence to which the vessel is exposed in
the varied, extensive, and often violent movements of the limb.
The application of a ligature to the axillary artery may be required in cases of aneurism of
the upper part of the brachial or as a distal operation for aneurism of the subclavian ; and there
are only t(vo situations in which the vessel can be secured — viz., in the first and in the third
parts of its course; for the axillary artery at its central part is so deeply seated, and, at the same
time, so closely surrounded with large nerve trunks, that the application of a ligature to it in
that situation would be almost impracticable.
In the third part of its course the operation is most simple, and may be performed in the
following manner: The patient being placed on a bed and the arm separated from the side, with
the hand supinated, an incision about two inches in length is made through the integument
forming the floor of the axilla, the cut being a little nearer to the anterior than the posterior
fold of the axilla. After carefully dissecting through the areolar tissue and fascia, the median
nerve and axillary vein are exposed; the former having been displaced to the outer and the
latter to the inner side of the arm, the elbow being at the same time bent, so as to relax the
structures and facilitate their separation, the ligature may be passed around the artery from the
ulnar to the radial side.
This portion of the artery is occasionally crossed by a muscular slip, the axillary arch, derived
from the Latissimus dorsi, which may mislead the surgeon during an operation. The occasional
existence of this muscle fasciculus was spoken of in the description of the muscles. It may
easily be recognized by the transverse direction of its fibres.
638 THE VASCULAR SYSTEMS
The first portion of the axillary artery may be tied in cases of aneurism encroaching so far
upward that a ligature cannot be applied in the lower part of its course. Notwithstanding that
this operation has been performed in some few cases, and with success, its performance is attended
with much difficulty and danger. The student will remark that in this situation it would be
necessary to divide a thick muscle, and, after incising the costocoracoid membrane, the artery
would be exposed at the bottom of a more or less deep space, with the cephalic and axillary
veins in such relation with it as must render the application of a ligature to this part of the vessel
particularly hazardous. Under such circumstances it is an easier, and at the same time more
advisable, operation to tie the subclavian artery in the third part of its course.
The vessel in the first part of its course can best be secured through a curved incision the
convexity of which is downward. This incision passes from a point half an inch external to
the sternoclavicular joint to a point half an inch internal to the coracoid process. The limb
is to be well abducted and the head inclined to the opposite side, and this incision is carried
through the superficial structures, care being taken to avoid the cephalic vein at the outer
angle of the incision. The clavicular origin of the Pectoralis major is then divided in the whole
extent of the wound. The arm is now to be brought to the side, and the upper edge of the
Pectoralis minor defined and drawn downward. The costocoracoid membrane is to be care-
fully divided close to the coracoid process, and the axillary sheath exposed; this is to be opened
with especial care, on account of the vein overlapping the artery. The needle should be passed
from below, so as to avoid wounding the vein.
In a case of wound of the vessel the general practice of cutting down upon and tying it above
and below the wounded point should be adopted in all cases.
Branches. — The branches of the axillary artery are:
V. /? J J f Superior thoracic. j^ , , f Long thoracic.
r rom first pari i » • ^.i ■ ^ fom second part i . i ^i
•' ^ (^Acromiothoracic. ^ [Alar thoracic.
{Subscapular.
Posterior circumflex.
Anterior circumflex.
The superior thoracic (a. thoracalis suprema^ is a small artery which arises
from the axillary separately or by a common trunk with the acromiothoracic.
Running forward and inward along the upper border of the Pectoralis minor, it
passes between it and the Pectoralis major to the side of the thorax. It supplies
these muscles and the parietes of the thorax, anastomosing with the internal mam-
mary and intercostal arteries.
The acromiothoracic (a. thoracoacromialis) is a short trunk which arises
from the fore part of the axillary artery, its origin being generally overlapped
by the upper edge of the Pectoralis minor. Projecting forward to the upper
border of the Pectoralis minor, it divides into four sets of branches — ^thoracic,
acromial, descending, and clavicular.
The thoracic branches (rami pectorales), two or three in number, are distributed
to the Serratus magnus and Pectoral muscles, anastomosing with the intercostal
branches of the internal mammary.
The acromial branch (ramus acromialis) is directed outward toward the acro-
mion, supplying the Deltoid muscle, and anastomosing, on the surface of the
acromion, with the suprascapular and posterior circumflex arteries.
The descending or humeral branch (ramus delioideus) runs in the space between
the Pectoralis major and Deltoid, in the same groove as the cephalic vein, and
supplies both muscles.
The clavicular branch (ramus clavicularis), which is very small, runs upward
to the Subclavius muscle.
The long thoracic or the external mammary (a. thoracalis lateralis) -passes
downward and inward along the lower border of the Pectoralis minor to the side
of the thorax, supplying the Serratus magnus, the Pectoral muscles, and mammary
gland, and sending branches across the axilla to the axillary nodes and Sub-
scapularis; it anastomoses with the interiml mammary and intercostal arteries.
THE AXILLARY ARTERY
639
The alar thoracic is a small branch which supplies the nodes and areolar
tissue of the axilla. Its place is frequently supplied by branches from some of
the other thoracic arteries.
The subscapular (a. siibscapidaris), the largest branch of the axillary artery,
arises opposite the lower border of the Subscapularis muscle, and passes down-
ward and backward along its lower margin to the inferior angle of the scapula,
where it anastomoses with the long thoracic and intercostal arteries and with the
posterior scapular branch of the trans-
verse cervical, and terminates by sup-
plying branches to the muscles in the
neighborhood. About an inch and a
half from its origin it gives off a large
branch, the dorsalis scapulae.
The dorsalis scapulae (a. circumflexa
scapulae) is generally larger than the
continuation of the subscapular. It
curves around the axillary border of the
scapula, leaving the axilla through the
space between the Teres minor above,
the Teres major below, and the long
head of the Triceps externally (Fig.
457), and enters the infraspinous fossa
by passing under cover of the Teres
minor, where it anastomoses with the
posterior scapular and suprascapular
arteries. In its course it gives off two
branches: one (infrascapular) enters the
subscapular fossa beneath the Subscap-
ularis, which it supplies, anastomosing
with the posterior scapular and supra-
scapular arteries; the other is continued
along the axillary border of the scapula,
between the Teres major and minor,
and, at the dorsal surface of the inferior
angle of the bone, anastomoses with the
posterior scapular. In addition to these,
small branches are distributed to the
back part of the Deltoid muscle and the
long head of the Triceps, anastomosing
witli an ascending branch of the superior
profunda of the brachial.
The circumflex arteries wind around
the surgical neck of the himierus. The
posterior circumflex (a. circumflexa hum-
eri posterior) (Fig. 457), the larger of
the two, arises from the back part of the
axillary opposite the lower border of
the Subscapularis muscle, and, passing backward with the circumflex veins and
nerve through the quadrangular space bounded by the Teres major and minor, the
scapular head of the Triceps and the humerus, winds around the neck of that bone
and is distributed to the Deltoid muscle and shoulder-joint, anastomosing with the
anterior circumflex and acromial thoracic arteries, and with the superior profunda
branch of the brachial artery. The anterior circumflex (a. circumflexa humeri ante-
rior) (Figs. 457 and 459), considerably smaller than the preceding, arises nearly
Anastonotica
magna.
The bnchial artery
640 THE VASCULAR SYSTE3IS
opposite that vessel from the outer side of the axillary artery. It passes horizon-
tally outward beneath the Coracobrachialis and short head of the Biceps lying
upon the fore part of the neck of the humerus, and, on reaching the bicipital
groove, gives ofT an ascending branch which passes upward along the groove
to supply the head of the bone and the shoulder-joint. The trunk of the vessel
is then continued outward beneath the Deltoid, which it supplies, and anasto-
moses with the posterior circumflex artery.
The Brachial Artery (A, BrachiaUs) (Fig. 460).
The brachial artery (a. brachialis) commences at the lower margin of the tendon
of the Teres major, and, passing down the inner and anterior aspect of the arm,
terminates about half an inch below the bend of the elbow, where it divides into
the radial and ulnar arteries. At first the brachial artery lies internal to the humerus,
but as it passes down the arm it gradually gets in front of the bone, and at the bend
of the elbow it lies midway between the two condyles.
Relations . — This artery is superficial throughout its entire extent, being covered, in front,
by the integument, the superficial and deep fasciae; the bicipital fascia separates it opposite the
elbow from the median basilic vein; the median nerve crosseg it at its middle; behind, it is
separated from the long head of the Triceps by the musculospiral nerve and superior profunda
artery. It then lies upon the inner head of the Triceps, next upon the insertion of the Coraco-
brachialis, and lastly on the Brachialis anticus. By its outer side, it is in relation with the
commencement of the median nerve and the Coracobrachialis and Biceps muscles, the two
muscles overlapping the artery to a considerable extent. By its iiiner side, its upper half is in
relation with the internal cutaneous and ulnar nerves, its lower lialf with the median nerve.
The basilic vein lies on the inner side of the artery, but is separated from it in the lower part
of the arm by the deep fascia. The brachial artery is accompanied by two venae comites,
which lie in close contact with the artery, being connected at intervals by short transverse
communicating branches.
Plan of the Relations of the Brachial Artery.
In front.
Integument and fasciae.
Bicipital fascia, median basilic vein.
Median nerve (in middle portion).
Overlapped by Coracobrachialis and Biceps.
Outer side. \ /^ ^\ Inner side.
Median nerve (above). j Brachial j Internal cutaneous and ulnar nerves.
Coracobrachialis. \ ' '"^^' / Median nerve (below).
Biceps. ^^ y Basilic vein
Behind.
Triceps (long and inner heads).
Musculospiral nerve.
Superior profunda artery.
Coracobrachialis.
Brachialis anticus.
A^^ATOMY OF THE BEND OF THE ELBOW G41
THE ANATOMY OF THE BEND OF THE ELBOW (ANTECUBITAL
FOSSA).
At the bend of the elbow the brachial artery sinks deeply into a triangular inter-
val, the antecubital fossa, the base of \\hich is directed upward, and may be repre-
sented by a line connecting the two condyles of the humerus; the sides are bounded,
externally, by the inner edge of the Brachioradialis; inteniallij, by the outer "mar-
gin of the Pronator teres; its floor is formed by the Brachialis anticus and Supi-
nator [brevis]. This space contains the brachial artery with its accompanying
veins, the radial and ulnar arteries, the median and musculospiral nerves, and the
tendon of the Biceps. The brachial artery occupies the middle line of this space,
and divides opposite the neck of the radius into the radial and ulnar arteries; it is
covered, in. front, by the integument, the superficial fascia, and the median basilic
vein, the vein being separated from direct contact with the artery by the bicipital
fascia. Behind, it lies on the Brachialis anticus, which separates it from the
elbow-joint. The median nerve Ires on the inner side of the artery, close to it
above, but separated from it below by the coronoid origin of the Pronator teres.
The tendon of the Biceps lies to the outer side of the space, and the musculospiral
nerve still more externally, situated upon the Supinator [brevis] and partly con-
cealed by the Brachioradialis.
Peculiarities of the Brachial Artery as Regards its Course. — The brachial artery, accom-
panied bv the median nerve, may leave die inner border of the Biceps and descend toward the
inner condyle of the humerus, where it usually cui\es around a prominence of bone, the supra-
condylar process. From this process, in most subjects, a fibrous arch is thrown over the artery.
The vessel then inclines outward, beneath or thi-ough the substance of the Pronator teres
muscle, to the bend of the elbow. The variation bears considerable homology to the normal
condition of the artery in some of the carnivora; it has been referred to in the description of the
humerus (page 181).
As Regards its Division. — Occasionally, the artery is divided for a short distance at its upper
part into two trunks which are united above and below. A similar peculiarity occurs in the
main vessel of the lower limb.
The vessels concerned in the high division of the brachial artery are three — viz., radial, ulnar,
and interosseous. Most frequently the radial is given off high up, the other limb of the bifurca-
tion consisting of the ulnar and interosseous. In some instances the ulnar arises from the
brachial above the ordinary level, and the radial and interosseous form the other limb of the
division; and occasionally the interosseous arises high up.
Sometimes long slender vessels, vasa aberrantia, connect the brachial or axillary arteries
with one of the arteries of the forearm or a branch from them. These vessels usually join the
radial.
Varieties in Muscular Relations.' — The brachial artery is occasionally concealed in some
part of its course by muscular or tendinous slips derived from the Coracobrachialis, Biceps,
Brachialis anticus, and Pronator teres muscles.
Surface Marking. — The direction of the brachial artery is marked by a line drawn along
the inner edge of the Biceps from the junction of the anterior and middle thirds of the axillary
outlet to the middle of the front of the elbow-joint.
Applied Anatomy.— Compression of the brachial artery is required in cases of amputation
and some other operations in the arm and forearm; and it will be observed that it may be efi'ected
in almost any part of the course of the artery. If pressure is made in the upper part of the
limb, it should be directed from within outward, and if in the lower part, from before backward,
as the arterv lies on the inner side of the humerus above an<l in front of the humerus below.
The most favorable situation is about the middle of the arm, where it lies on the tendon of the
Coracobrachialis on the inner flat side of the humerus.
The application of a ligature to the brachial artery may be required in case of wound of the
vessel and in some cases of wound of the palmar arch. It is also sometimes necessary in cases
of aneurism of the brachial, the radial, ulnar, or interosseous arteries. The artery may be
secured in any part of its course. The chief guides in determining its position are the sur-
face markings produced by the inner margin of the Coracobrachialis and Biceps, the known
' See Struther's Anatomical and Physiological Observations.
642 THE VASCULAR SYSTEMS
course of the vessel, and its pulsation, which should be carefully felt for before any operation is
performed, as the vessel occasionally deviates from its usual position in the arm. In whatever
situation the operation is performed, great care is necessary, on account of the extreme thinness
of the parts covering the artery and the intimate connection which the vessel has throughout its
whole coiu-se with important nerves and veins. Sometimes a thin layer of muscle fibre is
met with concealing the artery; if such is the case, it must be cut across in order to expose the
vessel.
In the upper third of the arm the artery may be exposed in the following manner: The patient
being placed supine upon a table, the affected limb should be raised from the side and the hand
supinated. An incision about two inches in length should be made on the inner side of the
Coracobrachialis muscle, and the subjacent fascia cautiously divided, so as to avoid wounding
the internal cutaneous nerv-e or basilic vein, which sometimes runs on the surface of the artery
as high as the axillary. The fascia having been divided, it should be remembered that the ulnar
and mternal cutaneous nerves lie on the inner side of the artery, the median on the outer side,
the latter nerve being occasionally superficial to the artery in this situation, and that the venae
comites are also in relation with the vessel, one on either side. These being carefully separated,
the aneurism needle should be passed around the artery from the inner to the outer side.
In the case of a high division, the two arteries are usually placed side by s'de; and if they
are exposed in an operation, the surgeon should endeavor to ascertain, by alternately pressing
on each vessel, which of the two communicates with the wound or aneurism, when a ligature
may be applied accordingly; or if pulsation or hemorrhage ceases only when both vessels are
compressed, both vessels may be tied, as it may be concluded that the two communicate above
the seat of disease or are reunited.
It should also be remembered that two arteries may be present in the arm in a case of high
division, and that one of these may be found along the inner intermuscular septum^ in a line
toward the inner condyle of the humerus, or in the usual position of the brachial, but deeply
placed beneath the common trunk; a knowledge of these facts w'ill suggest the precautions
necessary in every case, and indicate the measures to be adopted when anomalies are met with.
In the middle of the arm the brachial artery may be exposed by making an incision along
the inner margin of the Biceps muscle. The forearm being bent so as to relax the muscle, it
should be drawn slightly aside, and, the fascia being carefully divided, the median nerve will be
exposed lying upon the artery (sometimes beneath) ; this being drawn inward and the muscle
outward, the artery should be separated from its accompanying veins and secured. In this
situation the inferior profunda may be mistaken for the main trunk, especially if enlarged, from
the collateral circulation having become established; this may be avoided by directing the
incision externally toward the Biceps, rather than inward or backward toward the Triceps.
The lower part of tlw brachial artery is of interest from a surgical point of view, on account of the
relation which it bears to the veins most commonly opened in venesection. Of these vessels,
the median basilic is the largest and most prominent, and, consecjuently, the one usually selected
for the operation. It should be remembered that this vein runs parallel with the brachial
artery, from which it is separated by the bicipital fascia, and that care should be taken in opening
the vein not to carry the incision too deeply, so as to endanger the artery.
Collateral Circulation. — After the application of a ligature to the brachial artery in the
upper third of the arm, the circulation is carried on by branches from the circumflex and sub-
scapular arteries, anastomosing with ascending branches from the superior profunda. If the
brachial is tied below the origin of the profunda arteries, the circulation is maintained by the
branches of the profundse, anastomosing with the recurrent radial, ulnar, and interosseous
arteries.
Branches. — ^The branches of the brachial artery are:
Superior profunda. Inferior profunda.
Nutrient. Anastomotica magna.
Muscular.
The superior profunda artery (a. profunda brachii) arises from the inner ana
back part of the brachial, just below the lower border of the Teres major, and
passes backward to the interval between the outer and inner heads of the Triceps
muscle; accompanied by the musculospiral nerve it winds around the back part of
the shaft of the humerus in the spiral groove, between the outer head of the Triceps
and the bone, to the outer side of the humerus, where it reaches the external inter-
muscular septum and divides into two terminal branches. One of these pierces
the external intermuscular septum^ and descends, in company with the musculo-
AJSTATOMY OF THE BEND OF THE ELBOW
643
SadiaX recurrent.
spiral nerve, to the space between the Brachialis anticus and Brachioradialis,
where it anastomoses with the recurrent branch of the radial artery; while the
other, much the larger of the two,
descends along the back of the exter-
nal intermuscular septum to the back
of the elbow-joint, where it anasto-
moses with the posterior interosseous
recurrent, and across the back of the
humerus with the posterior ulnar re-
current, the anastomotica magna, and
inferior profunda (Fig. 464). The
superior profunda supplies the Tri-
ceps muscle and gives off a nutrient
artery which enters the bone at the
upper end of the musculospiral
groove. Near its commencement it
sends off a branch which passes up-
ward between the external and long
heads of the Triceps muscle to anas-
tomose with the posterior circumflex
artery, and, while in the groove, a
small branch which accompanies
a branch of the musculospiral nerve
through the substance of the Tri-
ceps muscle and ends in the Anco-
neus below the outer condyle of the
humerus.
The nutrient artery {a. nutricia
humeri) of the shaft of the humerus
arises from the brachial, about the
middle of the arm. Passing down-
ward it enters the nutrient canal of
that bone near the insertion of the
Coracobrachialis mucle.
The inferior profunda (a. collat-
eralis ulnaris superior), of small size,
arises from the brachial, a little below ^"■P'>-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 longitu<linal liircclion. Each endothelial cell is shaped
like a lance-head and has serrated borders. The middle coat consists of a longitudinal layer
lAL ARTERY
VERTEBRAL VEJN
THORACrc DUCT
Fig. 654. — The bend of the thoracic duct at its termination in the subclavian vein. (Poirier and Charpy.)
of white connective tissue with elastic fibres, external to which are several laminae of muscle
tissue, the fibres of which are for the most part disposed transversely, but some are oblique or
longitudinal. The muscle fibres are intermixed with elastic fibres. The external coat is
composed of areolar tissue, with elastic fibres and isolated fasciculi of nonstriated muscle fibres.
The Right Lymphatic Duct (Ductus Lymphaticus Dexter) (Figs. 552, 555).
The right lymphatic duct, about half an inch in length, courses along the inner
border of the Scalenus anticus at the root of the neck and terminates in the right
Fig. 555. — Terminal collecting trunks of the right side : a. Jugular trunk 6. Subclavian trunk, c. Broncho-
mediastinal trunk, d. Right lymphatic trunk, e. Node of the internal mammary chain, f. Node of the deep
■cervical chain. (Poirier and Charpy.)
subclavian vein at its angle of junction with the right internal jugular vein. The
orifice of the right lymphatic duct is guarded by two semilunar valves, which
prevent the passage of venous blood into the duct.
Tributaries. — It receives the lymph from the right side of the head and neck
through the right jugular trunk; from the right upper extremity through the right
subclavian trunk; from the right side of the thorax, the right lung, and right side
of the heart, and from part of the convex surface of the liver, through the right
bronchomediastiiial trunk. These three collecting trunks frecjuently open sepa-
rately in the angle of union of the two veins.
774 THE VASCULAR SYSTEMS
Applied Anatomy. — Blockage of the thoracic duct by mature specimens of the minute
parasitic worm Microfilaria nodurna gives rise to stasis of the chyle, and to its passage in various
abnormal directions on its course past the obstruction. The neighboring abdominal, renal,
and pelvic lymphatics become enlarged, varicose, and tortuous, and chyle may make its way
into the urine (chyluria), the tunica vaginalis (chylocele), the abdominal cavity {chylous ascites),
or the pleural cavity (chylous pleural effusion), in consequence of rupture of some of these
distended lymphatic vessels.
The thoracic duct may be secondarily infected in intestinal or pulmonary tuberculosis, and
may contain either miUary tubercles, caseating tuberculous masses, or even tuberculous ulcers.
It is often the seat of secondary carcinomatous deposits in cases of cancer of some abdominal
viscus, becoming infihrated throughout until it becomes a stiff moniliform rod as thick as a
pencil, with multiple stenoses and dilatations of its lumen; in such cases the left supraclavicular
nodes often become infected and enlarged, while the lungs remain entirely free from secondary
growths.
LYMPHATICS OF THE HEAD, FACE, AND NECK.
Intracranial lymphatics have not been demonstrated. It is probable, but not
yet conclusively demonstrated, that the perivascular spaces around the cerebral
arteries are the beginning of a cerebral lymph system, and that these perivascular
lymph channels pass out of the cranium with the arteries and the internal jugular
veins and terminate in the superior deep cervical nodes. It is also probable
that lymph spaces surround the dural bloodvessels and terminate in the superior
deep cervical and the internal maxillary nodes. The lymphatics of the nasal
fossEe can be injected from the subdural and subarachnoid spaces.
The extracranial lymphatics are divided into superficial and deep, and the two
systems freely communicate. All of these vessels run into nodes about the
head and neck. The superficial lymphatics take origin in the subcutaneous
tissue and superficial muscles. The deep vessels arise in the orbit, mouth, nose,
pharynx, oesophagus, tongue, larynx, and the muscular, ligamentous, and osseous
structures.
The Lymph Nodes of the Head and Face.
The lymphatic nodes of the head and face are as follows:
1. The Occipital.
2. The Posterior Auricular.
3. The Parotid and Subparotid.
4. The Facial.
5. The Internal Maxillary.
6. The Lingual.
7. The Retropharyngeal.
The occipital nodes (lymphoglandulae occipitales) (Fig. 556), one to three
in number, are situated upon the occipital insertion of the Complexus muscle,
at the lateral border of the Trapezius, and beneath the deep fascia. Their
afferents drain the occipital region of the scalp, while their efferents pass to the
upper deep cervical nodes.
The posterior auricular or mastoid nodes (lymphoglandulae auriculares
posteriores (Fig. 556), usually two in numl>er, 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<J
Dimensions. — The sagittal or occipitofrontal diameter of the wliite male adult
brain averages 16 to 17 cm. (6.4 to 6.8 inches), the maxinuim width in the
parietal region averages 13 to 14 cm. (5.2 to 5.(5 inches), while the maximum height
is about 12.5 cm. (5 inches). The dimensions of the female brain are usually
somewhat less. The brains of dolichocephalic individuals are naturally longer
and narrower than those of brachycephalic, and other differences in size and
shape are found in conformity with the cranial configuration and other factors.
Weight of the Brain. — ^The average weight of the brain in the adult male is 1400
grams (49.5 ounces avoirdupois); that of the female, 1250 grams (44 ounces
avoirdupois). Among 1500 brains of males the brain weights ranged from 960
grams to over 1900 grams; the great majority of this series ranged from 1250
grams to 1500 grams. The average weight in the newborn is 400 grams (14.1
ounces avoirdupois) in the male and .380 grams (13.4 ounces avoirdupois) in the
female. The weight is doubled at the end of the first, and trebled at the end of the
fourth or fifth year, the female brain growing less rapidly than the male brain.
Brain growth generally ceases in the eighteenth or twentieth year, earlier' in the
female than the male. After the sixtieth year the brain loses weight, at first
slowly, but more rapidly in advanced senescence. Other factors, besides age and
sex, which influence brain weight are stature, body weight, cranial form, and race.
Persons of large stature average heavier brains than those of short stature in abso-
lute figures, but not relatively. Brachycephalic persons average heavier brains
than the dolichocephalic. A most profound influence upon brain weight appears
to be exerted by racial differences. Representatives of the white race have heavier
brains than those of the other races, although data are not sufficient to make a
positive statement. Thus, the few Eskimo brains that have been secured so far
are notable for their size and weight. The following table gives approximately
accurate averages based upon greater or less numbers of brain weights:
I Males.
Females.
C Germans
1425
1260
Bohemians
1420
1290
Scots
1420
1260
'WTiite race
Swedes
Russians
1415
1.395
1260
1260
English
1380
1255
Italians
1375
1240
1360
1365
1250
Japanese .
1215
Chinese .
1360
Negroes (var
ous races) ' .
1390-1200
1330
1250
Australians
.
1185
The intellectual status is in some way reflected in the mass and weight of the
brain. The average brain weight of 100 men eminent in the professions, arts,
and sciences, with an average age of sixty- two years, was 1470 grams (nearly
52 ounces avoirdupois), exceeding the average weight of the ordinary population
of about the same age by more than 100 grams (nearly 4 ounces avoirdupois).
A further analysis shows that the brains of men devoted to the higher intellectual
occupations, such as the mathematical sciences, involving the most complex
mechanisms of the mind, those of men who have devised original lines of research,
and those of forceful character are among the heaviest of all.^
' A Study of the Brains of Six En
Qt Scientists and Scholars, etc.," Trans. An
850
THE NERVE SYSTEM
The brains of the microcephalic idiots are far under the minimal size necessary
for mental integrity, which is about 1000 grams (35 ounces avoirdupois) in the
male and 900 grams (31.7 ounces avoirdupois) in the female. Certain idiotic
individuals possess brains of normal size or even abnormally large brains, but
structural defects underlie these forms of idiocy.
The whale, porpoise, dolphin, and elephant possess larger brains than man,
but relative to the size and weight of the body the human brain is proportionately
larger.
The Development of the Brain and the Usual Classifications of its Sub-
divisions.— The cephalic region of the embryonic neural plate is characterized,
as already pointed out (p. 804), by a rapid process of expansion and intensity of
growth energy which seems to indicate the higher functional potentiality of what
is to become the brain. The fusion of the margins of the neural plate, proceeding
rapidly cephalad and caudad from about the cervical region, soon effects the
complete closing in of the brain portion of the neural tube and its complete separa-
tion from the overlying ectoderm. For a brief period prior to the completion of
the tube formation there exists a minute opening affording communication be-
tween the interior of the neural tube and the surrounding amniotic cavity; this
temporary passage is called the neuropore (Fig. 620), and is morphologically
the cephalic end of the tube. Its adult position is probably in the hypophyseal
THE BRAIN OR ENCEPHALON
851
The simple brain tube expands very early in intrauterine life in a sac-like
manner, with the formation of three dilatations or pouches — the primary brain
vesicles — demarcated by two constrictions.' The vesicles are designated respec-
tively the
Fore-brain (Prosencephalon). Mid-brain (Mesencephalon).
Hind-brain (Rhombencephalon or Metencephalon).
NEUROPORE -\
l_2 IFORE.-BRAJN
Fio. 620. — Brain tube of embryo salamander, sagittal section,
showing neural segmentation (neuromeres): F.l.~lll. Fore-brain
neuronieres. M. l.-II. Mid-brain neuromeres. H. I.-VI. Hind-
brain neuromeres. (Adapted from Kupffer.)
i-PROTOVERTEBRA I.
Fig, 621.— Brain tube of chick (25j^
hours), showing partly closed brain
tube with eleven folds or neuromeres.
(After C. Hill.)
This classification has been
found acceptable from every com-
parative standpoint in brain mor-
phology, but attempts have been
made to establish a further seg-
mentation into definite anatomical
divisions regarding which opinions
and usages differ widely and have
proved to be a hindrance, rather
than an aid to the homologization
of brain structures in the vertebrate
series. The difficulties in formu-
lating a satisfactory schema of the
segmental divisions of the brain
will be overcome, perhaps, only
by distinguishing the neuromeres
or neural segments conforming to.
the general segmental plan of the
vertebrate body. The existence
of a neuromerism that is akin to the metamerism or serial segmentation of the
body, or to the branchiomerism characterizing the arrangement of the branchial
arches, is indicated in several ways, but thus far only the earliest embryonic
Middle peduncle
Injtrior peduncle
Medulla oblongata
Fig. 622.— Sche
! showing the connection of the several
parts of the brain.
' The constriction between mid- and hind-brain has been called thi
he regards it as coordinate with the other segments recognized by h
a definitive segmental value tha
prosencephaii.
Ihvms rhomhencephali by Prof. His, and
>.>...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<i,
CENTRAL FISSURE
Fig. 717. — The projection tracts joining the cortex with lower nerve centres. Sagittal section showing the
arrangements of tracts in the internal capsule- A. Tract from the frontal lobe to the frontal half of the capsule,
thence in part to the optic thalamus, A-, and in part to the pons, and thus to the cerebellar hemisphere of the
opposite side. B. Motor tract from the precentral convolution to the facial nucleus in the pons and to the
spinal cord. C. Sensor tract from dorsal columns of the cord, through the dorsal part of the medulla oblon-
gata, pons, crus, and capsule to the parietal lobe. Z>. 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 ....<! Anterior or ventral pulmonary.
I Posterior or dorsal pulmonary.
'^ CEsophageal.
In the abdomen .... Gastric.
The Meningeal or Dural Branch (ramus meningeus) is a recurrent filament
given off from the ganglion of the root on the jugular foramen. It passes back-
ward, and is distributed to the dura lining the posterior fossa of the base of the
skull.
The Auricular Branch or Arnold's Nerve (ramus aurimdaris) (Fig. 750) arises
from the ganglion of the root, and is joined soon after its origin by a filament
from the petrous ganglion of the glossopharyngeal; it passes outward behind the
jugular vein, and enters a small canal on the outer wall of the jugular fossa.
Traversing the substance of the temporal bone, it crosses the facial canal or
aquaeductus Fallopii about 4 mm. (^ inch) above its termination at the stylo-
mastoid foramen; here it gives off an ascending branch, which joins the facial.
The continuation of the nerve reaches the surface by passing through the auricular
fissure between the mastoid process and the external auditory meatus, and divides
1006
THE NERVE SYSTEM
into tw'o branches, one of which communicates with the posterior auricular nerve,
while the other suppHes the integument at the back part of the pinna and the
posterior part of the external auditory meatus.
The Pharyngeal Branch (ramus pharyiigeus), the principal motor nerve of the
pharynx, arises from the upper part of the ganglion of the trunk of the vagus.
It consists principally of filaments from the vagal accessory portion of the spinal
accessory nerve; it passes across the internal carotid artery to the upper border
of the ^Middle constrictor of the pharynx, where it divides into numerous filaments
which join with those from the glossopharyngeal the superior laryngeal (its
external branch), and sympathetic, to form the pharyngeal plexus (plexus pharyii-
geus), from which branches are distributed to the muscles and mucous membrane
of the pharynx and the muscles of the soft palate, except the Tensor palati. From
the pharyngeal plexus a minute filament is given off, which descends and joins
the hypoglossal nerve as it winds around the occipital artery.
to external auditory
me'Xijus and back
Fig. 750.— Plan of Arnold's nerve. (W. Keiller.)
Fig. 751. — Relations of vagus and recurrent laryn-
geal nerves to the great vessels: (W. Keilier.)
The Superior Laryngeal Nerve (;;. laryugeus superior) (Figs. 748 and 749) is
larger than the preceding, and arises from the middle of the ganglion of the
trunk of the vagus. In its course it receives a branch from the superior cervical
ganglion of the sympathetic. It descends by the side of the pharynx behind the
internal carotid artery, where it divides into two branches, the external and internal
Laryngeal.
The external laryngeal branch (ramus externus) (Fig. 749) the smaller, descends
by the side of the larynx, beneath the Sternothyroid, to supply the Cricothyroid
muscle. It gives branches to the pharyngeal plexus and the Inferior constrictor,
and communicates with the superior cardiac nerve, behind the common carotid.
The internal laryngeal branch (ramus intermis) descends to the opening in the
thyrohyoid membrane, through which it passes with the superior laryngeal artery,
and is distributed to the mucous membrane of the larynx. A small branch com-
municates with the recurrent laryngeal nerve. The branches to the mucous
membrane are distributed, some in front to the epiglottis, the base of the tongue,
and the epiglottidean glands; while others pass backward, in the arytenoepi-
glottidean fold, to supply the mucous membrane surrounding the superior orifice
of the larynx, as well as the membrane which lines the cavity of the larynx as
low down as the vocal cord. The filament which joins with the recurrent laryn-
THE TENTH, VAGUS, OB PNEUMOGASTBIC NERVE 1007
geal descends beneath the mucous membrane on the inner surface of the thyroid
cartilage, where the two nerves become imited.
The Inferior or Recurrent Laryngeal Branch of the Vagus (n. recvrrens) Figs.
749 and 751), so called from its reflected course, is the motor nerve of the lar-
ynx. It arises, on the right side, in front of the subclavian artery; winds from
before backward around that vessel, and ascends oblkiuely to the side of the trachea
behind the common carotid artery, and either in front of or behind the inferior
thyroid artery. On the left side it arises in front of the arch of the aorta, and
winds from before backward around the aorta at the point where the impervious
ductus arteriosus is attached, and then ascends to the side of the trachea. The
nerve on each side ascends in the groove between the trachea and oesophagus,
and, passing under the lower border of the Inferior constrictor muscle, enters the
larynx behind the articulation of the inferior cornu of the thyroid cartilage with
the cricoid, being distributed to all the muscles of the larynx except the Crico-
thyroid. It communicates with the superior laryngeal nerve and gives off a
few filaments to the mucous membrane of the lower part of the larynx.
The recurrent laryngeal, as it winds around the subclavian artery and aorta,
gives off several cardiac filaments, which unite with the cardiac branches from
the vagus and sympathetic. As it ascends in the neck it gives off oesophageal
branches, more numerous on the left than on the right side, which supply the
mucous membrane and muscular coat of the oesophagus; tracheal branches to
the mucous membrane and muscular fibres of the trachea; and some pharyngeal
filaments to the Inferior constrictor of the pharynx.
The Cervical Cardiac Branches (rami cardiaci superiores), two or three in number,
arise from the vagus, at the upper and lower parts of the neck.
The superior branches are small, and communicate with the cardiac branches
of the sympathetic. They can be traced to the great or deep cardiac plexus.
The inferior branches, one on each side, arise at the lower part of the neck,
just above the first rib. That from the right vagus passes ventrad or by the
side of the innominate artery, and communicates with one of the cardiac nerves
proceeding to the great or deep cardiac plexus; that from the left runs across the
left side of the arch of the aorta and joins the superficial cardiac plexus.
The Thoracic Cardiac Branches (rami cardiaci inferiores), on the right side,
arise from the trunk of the vagus as it lies by the side of the trachea, and from its
recurrent laryngeal branch, but on the left side from the recurrent nerve only;
passing inward, they terminate in the deep cardiac plexus.
The Anterior or Ventral Pulmonary Branches, two or three in number, and of
small size, are distributed on the anterior aspect of the root of the lungs. They
join with filaments from the sympathetic, and form the anterior pulmonary plexus
(plexus pulmonalis anterior).
The Posterior or Dorsal Pulmonary Branches, more numerous and larger than
the anterior, are distributed on the posterior aspect of the root of the lung; they
are joined by filaments from the third and fourth (sometimes also from the first
and second) thoracic ganglia of the sympathetic, and form the posterior pulmonary
plexus (plexus pulmonalis posterior). Branches from both plexuses accompany
the ramifications of the bronchi through the substance of the lungs (rami hronchiales
anteriores and rami hronchiales posteriores).
The (Esophageal Branches (rami oesophagei) are given ofT from the vagus both
above and below the pulmonary branches. The lower are more numerous and
larger than the upper. They form, together with branches from the opposite
nerve, the (esophageal plexus. From this plexus branches are distributed to the
back of the pericardium.
The Gastric Branches (rami gastrici) (Fig. 749) are the terminal filaments of
the vagus nerve. The nerve on the right side is distributed to the posterior
1008 THE NER VE SYSTEM
surface of the stomach. The right vagus sends branches to the coeliac plexus
{rami coeliaci), to the splenic plexus (rami lienales), and to the renal plexus {rami
renales). The nerve on the left side is distributed over the anterior surface of
the stomach and along the lesser curvature. They unite with branches of the
right nerve and with the sympathetic, some filaments {rami hepatica) passing
through the lesser omentum to the hepatic plexus.'
Applied Anatomy. — It is a well-recognized fact that disease or injury of the vagus may induce
serious symptoms. Bruising may cause such symptoms; so may injury of the nerve by a stab,
a bullet, or during surgical operations. Either accidental ligation or crushing with clamp for-
ceps is particularly dangerous. Michaux accidentally ligated the vagus, and the patient became
Qomatose and ceased to breathe, but was restored on removing the ligature. Tillmanns, while
removing a cancer, accidentally caught and crushed a portion of the nerve in a clamp, and both
pulse and respiration ceased. The clamp was removed, the patient was restored with difficulty,
and the nerve was sutured. Recovery followed. It thus becomes evident that division of the
vagus on one side is not, as was so long taught, a necessarily fatal accident; in fact, it is sometimes
undertaken deliberately in removing tumors adherent to the nerve. Division of a nerve which
has been long compressed is probably not so dangerous as division of a healthy nerve, as in the
former case the opposite vagus has probably assumed some of its colleague's duties. A number
of cases of deliberate division have been reported. Twenty-three cases are referred to in the
system of surgery by von Bergmann and Mikulicz, and in twelve the patients died, but in none
of the deaths was the removal of the vagus the apparent cause of the fatality. Three American
cases are notable: One was operated upon by Dr. W. Joseph Hearn, one by Dr. Melvin Franklin,
and one by Dr. J. Chalmers Da Costa. All three recovered, and not one presented any serious
disturbance, although each had hoarseness and weakness of voice.
One would assume that after division of the vagus below the superior laryngeal nerve and
above the recurrent laryngeal nerve (the region usually attacked) there would be paralysis
of all the muscles of one side of the larynx, except the Cricothyroid, and widespread aberration
evinced by disturbances of the heart, stomach, and lungs. As a matter of fact, this has not been
the case. It might be and probably would be the case, were a healthy nerve divided; but the
surgeon who deliberately divides the nerve does so during the removal of a tumor which has long
made pressure. In most cases there is no change in the pulse or respiration. In some cases
dysphagia and pneumonia arise, but they may be due to other causes than vagus-nerve injury
(the formidable nature and the duration of the operation — the ligation of vessels of large size —
the age of the subject).
Larj'ngeal symptoms, to a greater or less degree, are always noted. The difference in the
degree of the palsy is explainable when we recall Exner's statement that the muscles supplied
by the recurrent laryngeal also receive some innervation from the superior laryngeal. In fact.
Mills points out that a portion of the recurrent laryngeal has been resected without completely
paralyzing the muscles supposed to be supplied solely by the recurrent laryngeal. The laryngeal
symptoms result from unilateral laryngeal paralysis, in which there is paralysis of the muscles
which open the glottis. The voice may be lost or may be hoarse. Usually, after a time, this is,
to a great extent, compensated for by the opposite vocal cord, although the voice may always
remain weak, and the patient will tire easily on talking. If both vagi were to be divided death
would ensue.
The laryngeal nerves are of considerable importance in considering some of the morbid con-
ditions of the larynx. When the peripheral terminations of the superior laryngeal nerve are
irritated by some foreign body passing over them, refle.r spasm of the glottis is the result. When
the trunk of the same nerve is pressed upon by, for instance, a goitre or an aneurism of the upper
part of the carotid, we have a peculiar, dry, brassy cough. When the nerve is paralyzed we
have anesthesia of the mucus membrane of the larynx, so that foreign bodies can readily enter-
the cavity, and, in consequence of its supplying the Cricothyroid muscle, the vocal cords cannot
be made tense, and the voice is deep and hoarse. Paralysis of the superior laryngeal nerves
may be the result of bulbar paralysis, may be a sequel to diphtheria, when both nerves are
usually involved, or it may, though less commonly, be caused by the pressure of tumors or
aneurisms, when the paralysis is generally unilateral. Irritation of the inferior laryngeal nerves
produces spasm of the muscles of the larynx. When both the recurrent nerves are paralyzed
the vocal cords are motionless in the so-called cadaveric position — that is to say, in the position
in which they are found in ordinary tranquil respiration — neither closed as in phonation, nor
open as in deep inspiratory effort. When one recurrent nerve is paralyzed, the cord of the same
side is motionless, while the opposite cord crosses the middle line to accommodate itself to the
affected one; hence phonation is present, but the voice is altered and weak in timbre. The recur-
rent laryngeal nerves may be paralyzed in bulbar paralysis or after diphtheria, when the paralysis
usually affects both sides; or they may be affected by the pressure of aneurisms of the aorta.
THE ELEVENTH OR SPINAL ACCESSORY NERVE 100!)
innominate or subclavian arteries; by mediastinal tumors; by bronchocele; or by cancer of the
upper part of the oesophagus, when the paralysis is often unilateral.- .The nerve may he acci-
dentally divided during the operation for goitre.
THE ELEVENTH OR SPINAL ACCESSORY NERVE (N. ACCESSORIUS)
(Figs. 748, 749).
The eleventh or spinal accessory nerve consists of two parts, one the accessory
part to the vagus, and the other the spinal portion.
The bulbar or vagal accessory part (ramus interims) is the smaller of the two.
It is accessory to the vagus. Its superficial origin (Fig. 748) is by four or five
delicate filaments from the side of the medulla oblongata, below the roots of the
vagus. Its dee-p origin, is described in detail on page 879. It passes outward
to the jugular foramen, where it interchanges fibres with the spinal portion or
becomes united to it for a short distance; it is also connected, in the foramen,
with the upper ganglion of the vagus by one or two filaments. It then passes
through the foramen (Fig. 749), and becoming again separated from the spinal
portion it is continued over the surface of the ganglion of the trunk of the vagus,
being adherent to its surface, and is distributed principally to the pharyngeal
and superior laryngeal branches of the vagus. Through the pharyngeal branch
it probably supplies the Azygos uvulae and Levator palati muscles (see p. 399).
Some few filaments from it are continued into the trunk of the vagus below the
ganglion, to be distributed with the recurrent laryngeal nerve to supply most
of the laryngeal muscles and probably also with the cardiac nerves.
The spinal portion (ramus externus) is firm in texture. Its superficial origin
(Fig. 748) is by several filaments or rootlets from the lateral tract of the cord,
as low down as the sixth cervical nerve. Its deep origin (Fig. 650) may be traced
to the intermediolateral tract of the gray substance of the cord. The rootlets
of origin join and form a trunk which ascends in the subdural space between the
ligamentum denticulatum and the anterior roots of the spinal nerves, enters the
skull through the foramen magnum, and is then directed outward to the jugular
foramen, through which it passes, lying in the same sheath as the vagus, but
separated from it by a fold of the arachnoid. In the jugular foramen it receives
one or two filaments from the vagal accessory portion. At its exit from the jugular
foramen it passes backward, either in front of or behind the internal jugular vein,
and descends obliquely behind the Digastric and Stylohyoid muscles to the upper
part of the Sternomastoid muscle. It pierces that muscle, and passes obliquely
across the posterior triangle, to terminate in the deep surface of the Trapezius
muscle. During its passage through the Sternomastoid muscle it gives several
branches to the muscle, and joins in its substance with branches from the second
cervical. In the posterior triangle it joins with the second and third cervical
nerves, while beneath the Trapezius it forms a sort of plexus with the third and
fourth cervical nerves, and from this plexus fibres are distributed to the muscle.
Applied Anatomy. — Division of the external branch of the spinal accessory nerve causes
paralysis of the Sternomastoid and Trapezius muscles; not absolute paralysis, for these muscles
also receive nerves from the cervical plexus. In cases of spaismodic torticollis in which all pal-
liative treatment has failed, division or excision of a portion of the external branch of the spinal
accessory nerve has been suggested by Keen.' This may be done either along the anterior or
posterior border of the Sternomastoid muscle. The former operation is performed by making
an incision from the apex of the mastoid process, three inches in length, along the anterior border
of the Sternomastoid muscle. The anterior border of the muscle is defined and pulled back-
ward, so as to stretch the nerve, which is then to be sought for beneath the Digastric muscle,
about two inches below the apex of the mastoid process. The other operation consists in
making an incision along the posterior border of the muscle, so that the centre of the incision cor-
responds to the middle of this border of the muscle. The superficial structures having been
1010
THE NERVE SYSTEM
divided and the border of the muscle defined, the nerve is to be sought for as it emerges from
the muscle to cross the occipital triangle. When found, it is to be traced upward through the
muscle, and a portion of it is excised above the point where it gives off its branches to the Sterno-
mastoid. In this operation one of the descending branches of the superficial cervical plexus is
liable to be mistaken for the nerve.
THE TWELFTH OR HYPOGLOSSAL NERVE (N. HYPOGLOSSUS)
(Figs. 752, 753).
The twelfth or hypoglossal nerve is the motor nerve of the tongue. Its super-
ficial origin is by several filaments, from ten to fifteen in number, from the groove
between the pyramidal and olivary bodies of the medulla oblongata, in a continuous
line with the ventral roots of the spinal nerves. Its deep origin can be traced to a
nucleus of gray substance (nucleus hi/poglossi) in the floor of the fourth ventricle,
described on page 878.
To Dura mater
Trunk of Vagus
" To Sternohyoid
To Sternothyroid
To Posterior Belly oj Omohyoid
Fig. 752. — Plan of the hypoglossal nerve.
The filaments of this nerve are collected into two bundles, which perforate the
dura separately, opposite the anterior condylar foramen, and unite together
after their passage through it. In those cases in which the anterior condylar
or hypoglossal foramen in the occipital bone is double, these two portions of the
nerve are separated by the small piece of bone which divides the foramen. The
nerve descends almost vertically to a point corresponding with the angle of the
mandible. It is at first deeply seated beneath the internal carotid artery and internal
jugular vein, and is intimately connected witli the vagus nerve (Fig. 753); it then
THE TWELFTH OR HYPOGLOSSAL NERVE 1011
passes forward between the vein and artery, and lower down in the neck becomes
superficial below the Digastric muscle. The nerve then loops around the occipital
artery, and crosses the external carotid and its lingual branch below the tendon
of the Digastric muscle. It passes beneath the tendon of the Digastric, the
Stylohyoid, and the Mylohyoid muscles, lying between the last-named muscle
and the Hyoglossus (Fig. 753), and communicates at the anterior border of the-
Hyoglossus with the lingual nerve (Fig. 752); it is then continued forward in the
fibres of the Geniohyoglossus muscle as far as the tip of "the tongue, distributing
branches to its muscle substance.
Branches of Communication (Fig. 752). — The branches of communication are
with the —
JS. First and second cervical nerves.
Sympathetic. Lingual.
The communication with the vagus takes place close to the exit of the nerve
from the skull, numerous filaments passing between the hypoglossal and the gan-
glion of the trunk of the vagus through the mass of connective tissue which unites
the two nerves. It also communicates with the pharyngeal plexus by a minute
filament as it winds around the occipital artery.
The communication with the sympathetic takes place opposite the atlas by
branches derived from the superior cervical ganglion, and in the same situation
the nerve is joined by filaments derived from the loop connecting the first two
cervical nerves.
The communication with the lingual nerve takes place near the anterior border
of the Hyoglossus muscle by numerous filaments which ascend upon it.
Branches of Distribution (Fig. 752). — ^The branches of distribution are:
Meningeal or Dural. Thyrohyoid.
Descendens hypoglossi. Muscular.
Of these branches, the descendens hypoglossi and the branches to the Infra-
hyoid muscles are not actually derived from the hypoglossal nerve, but, as is
shown in Fig. 752, are branches from the loop formation (better called avsa
cervicalis) of the first with the second and third cervical nerves. A part of the
loop, commonly called the descendens hypoglossi, is enclosed, for a short distance,
in the sheath which invests the hypoglossal nerve.
Meningeal or Dural Branches (Fig. 752). — As the hypoglossal nerve passes
through the anterior condylar foramen it gives off, according to Luschka, several
filaments to the dura in the posterior fossa of the base of the skull.
The Descendens Cervicalis or Descendens Hypoglossi {ramus descendens) (Figs.
752 and 753) is a long slender branch, which leaves the hypoglossal where it tiu-ns
around the occipital artery. It consists mainly of fibres which pass along the
sheath of the hypoglossal nerve from the first and second ce^^•ical nerves in the
above-mentioned communication. It descends in front of or within the sheath of
the common carotid artery, giving ofi^ a branch to the anterior belly of the Omo-
hyoid, and then joins the communicating branches from the second and third
cervical nerves, just below the middle of the neck, to form a loop, the ansa cer-
vicalis (hypoglossi) . From the convexity of this loop branches pass to supply the
Sternohyoid, Sternothyroid, and the posterior belly of the Omohyoid.
The Thyrohyoid Branch {ramus thyreohyoidevs) (Fig. 752) is a small branch
arising from the hypoglossal near the posterior border of the Hyoglossus; it
passes obliquely across the great cornu of the hyoid bone and supplies the Thyro-
hyoid muscle.
1012
THE NERVE SYSTEM
The Muscular Branches (Fig. 752) are distributed to the Styloglossus, Hyo-
glossus, Geniohyoid, and Geniohyoglossus muscles and to the Chondroglossus,
when present. At the under surface of the tongue numerous slender branches
{rami linguales) pass upward into the substance of the organ to supply its In-
trinsic muscles.
Applied Anatomy. — A wound in the submaxillary region may injure the hypoglossal nerve
and result in motor paralysis of the corresponding half of the tongue. The hypoglossal nerve is
an important guide in the operation of ligation of the lingual artery (see p. 591). It runs for-
vfard on the Hyoglossus muscle just above the great cornu of the hyoid bone, and forms the
upper boundary of the triangular space (Lesser's triangle) in which the artery is to be sought for
by cutting through the fibres of the Hyoglossus muscle.
THE SPINAL NERVES (NERVI SPINALES).
The spinal nerves spring from the spinal cord, and are transmitted through
the intervertebral foramina on either side of the spinal column. There are
thirty-one pairs of spinal nerves, which are arranged in the following groups,
corresponding to the region of the vertebral column through which they pass :
Cervical 8 pairs.
Thoracic 12 "
Lumbar 5 "
Sacral 5 "
Coccygeal ............. 1 pair.
THE SPINAL NEBVES
1013
POSTERrOR
NERVE ,
ROOTS )
( ANTERIOR
It will be observed that each group of nerves corresponds in number with the
vertebrae in that region, except the cervical and coccygeal. Sometimes there is no
thirty-first pair. Occasionally below the thirty-first pair there may be one or
even two filamentous pairs which do not pass out of the vertebral canal.
P^ach spinal nerve arises by two roots, an anterior, ventral, or motor root and a
posterior, dorsal, or sensor root, the latter being distinguished by a ganglion termed
the spinal ganglion.
The Anterior or Ventral Root (radix anterior). — The superficial origin is from
the antero-lateral columns of the cord, corresponding to the situation of the
anterior cornu of gray substance. Each root is composed of from four to eight
filaments.
The deep origin can be traced from cells in the gray substance of the anterior
cornu of the same as well as of the opposite side. The majority of the axones
arise from the various groups of cells in the anterior cornu of the same side,
while others arise from the large cells
of the anterior cornu of the opposite
side, the axones passing across the
median plane in the anterior white
commissure. The axone bundles, after
leaving the gray substance, penetrate
horizontally through the longitudinal
bundles of the antero-lateral column
to emerge as described above.
The Posterior or Dorsal Root (radix
posterior). — The superficial origin is by
filaments (fila radicularia), from the
postero-lateral fissure of the cord. The
real origin of these fibres is from the
nerve cells in the posterior root gan-
glion, from which they can be traced
into the cord in two main bundles,
the course of which has already been
studied (p. 835). The posterior or
dorsal root of the first cervical nerve is
exceptional in that it is smaller than
the anterior; it is occasionally wanting.
Within the vertebral canal the nerve
roots are separated from each other by
\he lig amentum denticidatum^Fig. 755).
In the cervical region the spinal portion
of the spinal accessory nerve separates
the roots.
The spinal ganglia are collections of
nerve cells on the posterior root of each
of the spinal nerves. Each ganglion is oval in shape and of a reddish color;
and its size bears a proportion to that of the nerve root upon which it is situated; it
is bifid internally where it is joined by the two bundles of the posterior nerve root.
The ganglia are usually placed in the intervertebral foramina, ectad of the point
where the nerves perforate the dura. There are, however, exceptions to this
rule. Thus, the ganglia upon the first and second cervical nerves lie on the neural
arches of the atlas and axis respectively; those of the sacral nerves are placed
within the vertebral canal; and that on the coccygeal nerve, also in the canal,
is situated at some distance from the apparent origin of the posterior root.
I — n>
_ 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
*, /^ <S ^AV im >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<IDGES OF SKIN
INTERRUPTED BY
LONGITUDINAL"^'
FURROWS
Fig. S71. — The furroTvs and ridges of the surface of
the skin from the palm or surface of the middle finger.
(Toldt.)
THE SKIN
1151
shaped areas (Fig. 874). The skin consists of two layers: a superficial layer,
the epidermis, and a deep layer, the corium or dermis.
Tlie Cuticle, Scarf Skin, or Epidermis (Figs. 875 and 876) is composed of
layers of epithelium and is derived from the ectoderm. The epithelium is strati-
FlG. 872. — Anterior surface.
Fig. S73. — Posterior surface.
The general course of the connective-tissue bundles of the corium. determined by the direction assumed by the
linear clefts made in the skin when it is punctured by a round awl. (Langer.)
Red, and is devoid of bloodvessels. Two layers can be readily made out, the
superficial or homy layer and the deeper or Malpighian layer.
Tlie homy layer (stratum corneum) is formed by several layers of non-nucleated
scaly cells. The cells consist of keratin. The surface cells of the horny layers
1152
THE ORGANS OF SPECIAL SENSE
are being constantly rubbed off, and are being replaced by cells from the Mal-
pighian layer, which are converted into keratin as they approach the surface.
The Malpighian layer (stratum Malpighii) of the epidermis is divided into
f&ur layers, named, from without inward, the stratum lucidum, the stratum granu-
losum, the stratum mucosum, and the stratum germinativum.
S=^ w .^
^<!"
r
fff
Fig. 874. — The furrows of the skin and the areas which these furrows delimit, reproduced from an impression ot
the dorsal surface of the wrist. (Toldt.)
The stratum lucidum is the most superficial part of the Malpighian layer. It
consists of several layers of flat cells, the nuclei of which are beginning to disappear.
The cells contain eleidin granules. In regions where the epidermis is thin the
stratum lucidum is absent.
The stratum granulosum consists of several layers of nucleated flat cells, con-
taining keratohyaline granules. These granules are probably formed from the
disintegrating nucleus, and in the stratum lucidum are converted into eleidin,
an intermediate substance in the formation of keratin. It is best developed in the
sole and palms.
FURROWS OF SKIN
RIDGES OF SKIN
ERMIS^
TOOCH CORPUSCLE^
STRATUM CORNEUM
STRATUM LUCIDUM
RETE MUCOSUM
f STRATUM PA
^STRATUM RETI
kPILLARE I
ICULARE (.
BODY OF
SUDORIFEROUS
GLAND
Fig. 875. — Vertical section through the skin ot the finger-tip. The layers of the epidermis and of the
The subcutaneous areolar tissue- The sudoriferous or sweat-gland. (Toldt.)
The mucous layer or the stratum mucosum consists of numerous layers of nucle-
ated, polygonal, spine-shaped cells known as prickle cells or finger cells. Between
the cells of the stratum mucosum are spaces containing pigment granules and
leukocytes. Processes from the prickle cells join adjacent cells. This layer
contains numerous connective-tissue fibres arranged in a network, and known as
epidermic fibrils.
The stratum cylindricum or stratum germinativum is composed of cylindrical
or prickle cells, the points of which are directed downward. Fine fibrils pass up
THE SKIN 1153
from the coriiim between the cells, and there is cement substance as well between
them.
The Corium, Cutis Vera, Dennis, or True Skin (Figs. 876 and 880) is a con-
nective-tissue structure which arises from the mesoderm. It consists especially
of connective tissue and elastic fibres; it contributes elasticity to the skin, and is
the seat of the sense organs. The corium is composed of two layers, the papillary
and the reticular.
Duct of _'^'
sweat ' ' ~ '
Adipose tiss
Fig. 876. — Diagrammatic sectional view of the skin. (Magnified.)
The superficial or papillary layer or corpus papillare of the corium (stratum papil-
lare) lies just beneath the epidermis, contains the papilla?, and is composed of a
network of fine bundles of fibrous tissue. The papilla; are composed of fine
strands of connective tissue and elastic tissue. They project from the corium
beneath the epidermis and enter into depressions of the epidermis. They vary
greatly in size, averaging y^ of an inch in height and ^to" ^^^ ^^ '""^'^ '" width
at the base. In the face, especially in the eyelids, they are insignificant. On the
glans penis, the palms of the hands, and the soles of the feet, and in the nipples,
they are large. In the palmar surfaces of the hands and fingers and the plantar
surfaces of the feet and toes they produce permanent ridges (Fig. 879). A ridge
is composed of two or more rows of papilh?, and the ducts of sweat glands emerge
73
1154
THE ORGANS OF SPECIAL SENSE
between rows of papilUe, and open on the curved surface ridges (Fig. 875). Most
of the papillae contain loops of capillaries, and are called vascular papillae. Some
contain nerve terminations, and are called nerve papilla. Between the papillary
stratum lucidttm
Stratum grannJosum
Stratum niucosum
Malpiqhii
Stratum ger-minativum
- Nerve Jiirila,
Fig. 877. — Section of epide:
layer of the cerium and the epidermis is a very thin and structureless membrane
called the basal membrane.
The deep or reticular layer (stratum reticulare) rests upon the subcutaneous
tissue. It passes superficially into the papillary layer, and at most places into
the subcutaneous tissue without a sharp
«HRECTOR HAIR liuc of differentiation. At some places,
PILl MUSCLE FOLLICLE CORIUM EPIDERMIS r. • • i -ill
tor mstance m the nipple, the deep
layer of the corium rests upon a layer
of muscle tissue. In the face this
muscle tissue is striated and sends pro-
longations to the papillary layer; in the
nipple and scrotum it is nonstriated.
The reticular layer is composed of bun-
dles of white fibrous tissue, arranged
in a network. In the meshes of the
network are fat, bloodvessels, lymphat-
ics, sebaceous glands, sweat glands,
and hair follicles.
The subcutaneous areolar tissue, or
tela subcutanea (panniculus adiposiis),
connects the skin to the parts beneath;
it is composed of bundles of connective
tissue which cross repeatedly and form
spaces. In almost all regions the spaces contain fat, but in the scrotum, exter-
nal ear, penis, and eyelid they do not contain fat. When the connective-tissue
fibres of the panniculus adiposus are long and nearly parallel to the skin surface.
Fig. 878. — Vertical section through the skin of the
trunk in the region of the arch of the ribs. One
of the small hairs is seen in longitudinal section.
(Toldt.)
THE SKIN
1155
the skin becomes wrinkled; when they are short and nearly at riglit angles to the
surface, the skin cannot wrinkle.
Pigmentation of the Skin. — As previously stated, in certain regions the skin of the
white race is brown because of pigmentation (areoUie, nipples, around the anus,
PAPILLjE o
^■S>'^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<if/i); of the nostrils (vihri.ssir); the eyelashes
(cilia); hairs of the axilla (Jilrci); of (he pubes (ptibes); and the small hairs of the
skin or woolly hairs [lanugo). They \ai-y much in length, thickness, and color
in different parts of the body and in different races of mankind. In some parts,
as in the skin of the eyelids, they are so short as not to project beyond the follicles
containing them; in others, as upon the scalp, they are of considerable length;
again, in other parts, as the eyelashes, the hairs of the pubic region, and the whis-
kers and beard, they are remarkalile for their thickness. Straight hairs are stronger
EPIDERMIS
CORIUM -
HAIR FOLLICLE
ROOT
Fig. 888. — Vertical section through the skin of the head. The hairs of the head in longitudinal section. (Toldt.)
than curly hairs, and present on transverse section a cylindrical or oval oudine;
curly hairs, on the other hand, are flattened. The hairs are usually oblique to
the surface from which they arise (Fig. 888). Their direction depends upon the
region from which they spring, being fairly regular in certain regions. Thus-
are formed hair streams {flumina pilcrum) and hair whirlpools (vortices pilorum).
A hair consists of the root, the part implanted in the skin; the shaft, the portion
projecting from its surface; and the point.
The root of the hair (radix pili) presents at its extremity a bulbous enlargement,
the hair bulb (hulhus pili) (Fig. 887), which is whiter in color and softer in texture
than the shaft, and is lodged in a follicular involution of the epidermis called the
hair follicle (folliculus pili) (Fig. 878). ^M:ien the hair is of considerable length
the follicle extends into the subcutaneous cellular tissue. The hair follicle com-
mences on the surface of the skin with a funnel-shaped opening, and passes inward
in an oblique or curved direction — the latter in curly hair — to become dilated at
its deep extremity or fundus (fundus folliculi pili), whei'e it corresponds with the
bulbous condition of the hair which it contains. It has opening into it, near its
free extremity, the orifices of the ducts of one or more sebaceous glands (Figs.
887 and 888). At the bottom of each hair follicle is a small, conical, vascular
eminence or papilla, the hair papilla (papilla pili) (Figs. 887 and 888), similar
in every respect to the papillae found upon the surface of the corium; it is continu-
ous with the dermic layer of the follicle, is highly vascular, and is probably supplied
1160
THE ORGANS OF SPECIAL SENSE
with nerve fibrils. In structure the hair folUcle consists of two root sheaths — an
outer or dermic, and an inner or epidermic (Figs. 887 and 889).
The outer or dermic root sheath is formed mainly of fibrous tissue; it is continuous
with the corium, is highly vascular, and is supplied by numerous minute nerve
filaments. It consists of three layers. The most internal, the cuticular lining
of the follicle, consists of a hyaline basement membrane, the hyaline layer, having
a glassy, transparent appearance, which is well marked in the larger hair follicles,
but is not very distinct in the follicles of minute hairs. It is continuous with the
basement membrane of the surface of the corium. External to this is the inner
fibrous layer, a compact layer of fibres and spindle-shaped cells arranged circularly
around the follicle. This layer extends from the bottom of the follicle as high as
the entrance of the ducts of the sebaceous glands. Externally is the outer fibrous
layer, a thick layer of connective tissue, arranged in longitudinal bundles, forming
a more open texture and corresponding to the reticular part of the corium. In this
are contained the bloodvessels and nerves.
ROOT SHEATH
ROOT SHEATH
The inner or epidermic layer is closely adherent to the root of the hair, so that
when the hair is plucked from its follicle this layer most commonly adheres to it
and forms what is called the root sheath. It consists of two strata, named respec-
tively the outer and inner root sheaths; the former of these corresponds with the
Malpighian layer of the epidermis, and resembles it in the rounded form and
soft character of its cells; at the bottom of the hair follicles these cells become
continuous with those of the root of the hair. The inner root sheath consists of
a delicate cuticle next the hair, composed of a thin layer of imbricated scales having
a downward direction, so that they fit accurately over the upwardly directed
imbricated scales of the hair itself; then of one or two layers of horny, flattened
nucleated cells, known as Huxley's layer; and finally of a single layer of horny
oblong cells without visible nuclei, called Henle's layer.
The hair follicle contains the root of the hair, which terniinates in a bulbous
extremity, and is excavated so as to exactly fit the papilla from which it grows.
The bulb is composed of polyhedral epithelial cells, which as they pass upward
into the root of the hair become elongated and spindle-shaped, except some in
the centre, which remain polyhedral Some of these latter cells contain pigment
granules, which give rise to the color of the hair. It occasionally happens that
these pigment granules completely fill the cells of the medullary substance in
the centre of the bulb, which gives rise to the dark tract of pigment often found,
of greater or less length, in the axis of the hair.
THE APPENDAGES OE THE SKIN 1161
Tlie shaft of the hair (scapiis pili) (Fig. 887) consists of a central pitli or medulla,
the fibrous part of the hair, and the true cuticle externally. The medulla (■itih-
stantia meduUaris pili) occupies the centre of the shaft and ceases toward the
point of the hair. It is usually wanting in the fine hairs covering the surface of
the body, and commonly in those of the head. It is found in the shafts of all thick
hairs and in the deeper parts of the root of most hairs. It is more opaque and
deeper colored when ^■iewed by transmitted light than the fibrous part; but when
viewed by reflected light it is white. It is composed of rows of polyhedral cells,
\\hich contain granules of eleidin and frequently air spaces. The cortical substance
of the hair {substantia corticalis pili) constitutes the chief part of the shaft; its
cells are elongated and unite to form flattened fusiform cells. Between the cells
are found minute spaces which contain either pigment granules in dark hair or
minute air spaces in white hair. In addition to this there is also a diffused pig-
ment contained in the cells. The cells which form the outer hair membrane or
true cuticle icuticula pili) consist of a single layer which surrounds those of the
cortical part; they are converted into thin, flat scales, having an imbricated ar-
rangement.
Connected with the hair follicles are minute bundles of involuntarj' muscle
fibres, termed Arrectores pilonun {mm. arrectores pilorum) (Figs. 878 and 887).
They arise from the superficial layer of the corium, and are inserted into the outer
surface of the hair follicle, below the entrance of the duct of the sebaceous gland.
They are placed on the side toward which the hair slopes, and by their action
elevate the hair.^ When the hair is elevated a depression forms over the seat of
origin of the muscle, and the parts about the hair are elevated. This condition
is known as goose skin. It is probable that the contraction of these muscles aids
in emptying sebaceous glands.
Bloodvessels and Nerves (Fig. 878). — ^A hair follicle possesses a rich network of capillaries
about the hyaline membrane, and capillary loops pass to the papilla. We have little knowledge
as to nerve terminations of the human hair.
The Sebaceous Glands (glandulae sebaceae) are small, sacculated, glandular
organs, lodged in the substance of the corium. They are found in most parts of
the skin, but are especially abundant in the scalp and face ; they are also very numer-
ous around the apertures of the anus, nose, mouth, and external ear, but are want-
ing in the palms of the hands and soles of the feet. Each gland consists of a
single duct, more or less capacious, which terminates in a cluster of small secreting
pouches or saccules. The sacculi connected with each duct vary in number,
as a rule, from two to five, but in some instances may be as many as twenty.
They are composed of a transparent, colorless membrane, enclosing a number
of epithelial cells. Those of the outer or marginal layer are small and polyhedral,
and are continuous with the lining cells of the duct. The remainder of the sac
is filled with larger cells, containing fat, except in the centre, where the cells have
become broken up, leaving a cavity containing their debris and a mass of fatty
matter, which constitutes the sebaceous secretion. The orifices of the ducts
open most frequently into the hair follicles, but occasionally upon the general
surface, as in the labia minora and the free margins of the lips. On the nose
and face the glands are of large size, distinctly lobulated, and often become much
enlarged from the accumulation of pent-up secretion. The largest sebaceous
glands are those found in the eyelids — the ^Meibomian glands.
The Sudoriferous or Sweat Glands {glandulae sudoriferae) (Figs. 878 and 888)
are the organs by which a large portion of the aqueous and gaseous materials
' Arthur Thomson suggests that the contraction of these muscles on follicles which contain weak, fiat hairs will
tend to produce a permanent curve in the follicle, and this curve will be impressed on the hair which is moulded
within it, so that the hair, on emerging through the skin, will be curled. Curved hair follicles are characteristic of
the scalp of the Bushman.
1162 THE ORGANS OF SPECIAL SENSE
is excreted by the skin. They are found in almost every part of this structure,
being absent on the red border of the lips, the glans penis, and inner surface of
the prepuce. On the eyelids they are somewhat modified, and are called ciliary
glands (glandulae ciliares [MoUi]); about the anus they are extremely large, and
are called circumanal glands {glandulae circumanales). The sweat glands are
situated in small pits below the under surface of the coriiun, or, more frequently,
in the subcutaneous areolar tissue, surrounded by a quantity of adipose tissue.
They are small, lobular, reddish bodies, consisting of a single convoluted tube,
from which the efferent duct (ductus sudoriferus) proceeds outward through the
corium and cuticle, becomes somewhat dilated at its extremity, and opens on the
surface of the cuticle by an oblique valve-like aperture (porus siidoriferus). The
duct, as it passes through the epidermis, presents a spiral arrangement, being
twisted like a corkscrew, in those parts where the epidermis is thick; where,
however, the epidermis is thin, the spiral arrangement does not exist. In the
superficial layers of the corium the duct is straight, but in the deeper layers it is
convoluted or even twisted. The spiral course of these ducts is especially distinct
in the thick cuticle of the palm of the hand and sole of the foot. The size of the
glands varies. They are especially large in those regions where the flow of perspi-
ration is copious, as in the axillfe, whei'e they form a thin, mamillated layer of a
reddish color, which corresponds exactly to the situation of the hair in this region;
they are large also in the groin. Their number varies. They are most numerous
on the palm of the hand, presenting, according to Krause, 2800 orifices on a square
inch of the integument, and are rather less numerous on the sole of the foot. In
both of these situations the orifices of the ducts are exceedingly regular, and open
on the curved surface ridges. In other situations they are more irregularly
scattered, but the number in a given extent of surface presents a fairly uniform
average. In the neck and back they are least numerous, their number amounting
to 417 on the square inch (Krause). Their total number is estimated by the same
writer at 2,381,248, and supposing the aperture of each gland to represent a surface
of -g^ of an inch in diameter, he calculates that the whole of these glands would
present an evaporating surface of about eight square inches. Each gland consists
of a single tube intricately convoluted, terminating at one end by a blind extremity,
and opening at the other end upon the surface of the skin. The wall of the duct
is thick, the lumen seldom exceeding one-third of the diameter of the tubes. The
tube, both in the gland and where it forms the excretory duct, consists of two
layers (except in the epidermis, where the epithelium of this layer forms the wall)
— an outer, formed by fine areolar tissue, and an inner layer of epithelium. The
external coat is thin, continuous with the superficial layer of the corium, and extends
only as high as the surface of the corium. The epithelial lining in the distal
part of the coiled tube consists of a single layer of cubical cells, supported on a
basement membrane. Between the epithelium and the fibrocellular coat lies a
layer of longitudinally or obliquely arranged involuntary muscle fibres, the con-
traction of which aid in the expulsion of the sweat. In the proximal part there
are two or more layers of polyhedral cells lined on the internal surface (next the
lumen of the tube) by a delicate membrane devoid of muscle fibres. The contents
of the smaller sweat glands is quite fluid; but in the larger glands the contents
are semifluid and opaque, and contain a number of colored granules and cells
which appear analogous to epithelial cells.
The bloodvessels are branches from the subcutaneous vessels and the arterial plexus of the
deep part of the corium. Numerous amyelinic nerve fibres lie upon the membrana propria of a
sweat gland. From them fibrils pass inward and terminate by end bulbs upon the cells of the gland.
THE ORGANS OF VOICE AND EESPIEATION.
THE respiratory organs (apparattis respiratorius) consist of the larynx, or organ of
voice, the trachea, bronchi, lungs, and pleurae.
THE LARYNX.
The larynx, or organ of voice, is placed at the upper part of the air passage.
It is situated between the trachea and base of the tongue, at the upper and fore
part of the neck, where it forms a considerable projection in the middle line.
On either side of it lie the great vessels of the neck; behind, it forms part of the
boundary of the pharynx, and is covered by the mucous membrane lining that
cavity. Its vertical extent corresponds to the fourth, fifth, and sixth cervical ver-
tebrae, but it is placed somewhat higher in the female and also during child-
hood.
According to Sappey, the average measurements of the adult larynx are as
follows :
In males. In females.
Vertical diameter 44 mm. 36 mm.
Transverse diameter 43 " 41 "
Antero-posterior diameter 36 " 26 "
Circumference 136 " 112 "
Until puberty there is no marked difTerence between the larynx of the male and that of the
female. In the latter its fiu-ther increase in size is only slight, whereas in the former the increase
is great; all the cartilages are enlarged, and the thyroid becomes prominent as the pomum Adami
in the middle line of the neck, while the length of the glottis is nearly doubled.
The larynx is broad above, where it presents the form of a triangular box,
flattened behind and at the sides, and bounded in front by a prominent vertical
ridge. Below, it is narrow and cylindrical. It is composed of cartilages, which
are connected by ligaments and moved by numerous muscles. It is lined by
mucous membrane, which is continuous above with that lining the pharynx and
below with that of the trachea. On each side internal to the thyroid cartilage
a small recess, the recessus pyriformis, extends forward from the cavity of the
pharynx (p. 1231).
The Cartilages of the Larynx {cartilagines laryncjis) are nine in number, three
single and three pairs:
Thyroid. Two Arytenoid.
Cricoid. Two Cornicula Laryngis.
Epiglottis. Two Cuneiform.
The Thyroid Cartilage (cartilago thijroidea) (Figs. 891 and 892) is the largest
cartilage of the larynx. It consists of two lateral lamellee or alae, united at an acute
angle in front, forming a vertical projection in the midline, which is prominent
(1163)
1164
THE ORGANS OF VOICE AND BESPIBATION
above and called the pomum Adami {prominentia laryngea). This prominence
is subcutaneous, is more distinct in the male than in the female, and is often
separated from the integument by a bursa, the bursa subcutanea prominentiae
laryngeae. The anterior borders of the alse of the thyroid cartilage which are
continuous below are separated above by a V-shaped notch, the thyroid notch
{incisura thyroidea superior). The posterior borders are free, rounded, and
somewhat thickened, and are extended in the form of superior and inferior
cornua.
The Older surface of each ala (Fig. 891) presents an oblique ridge {linea obliqua),
which passes downward and forward from a tubercle situated near the root of the
superior cornu, the superior tubercle (tuberculum. thyroideum superitis), to a small
tubercle near the anterior part of the lower border, the inferior tubercle (tuberculum
thyroideum' inferius). This ridge gives attachment to the Sternothyroid and Thyro-
hyoid muscles, and the portion of cartilage included between it and the posterior
border gives attachment to part of the Inferior constrictor muscle.
ASCENDtNa
Fig. 890. — Sagittal section of a man twenty
(After W. Braune.)
of the thjToid and
The inner surface (Fig. 892) of each ala is smooth, slightly concave, and covered
by the mucous membrane of the outer wall of the sinus pyriformis above and
behind; but in front, in the receding angle formed by the junction of the alse,
are attached the epiglottis, the true and false vocal cords, the Thyroarj'tenoid
and Thyroepiglottidean muscles, and the thyroepiglottidean ligament.
The upper border (Fig. 891) is sinuously curved, being concave at its posterior
part, then rising into a convex outline in front; it gives attachment throughout
its whole extent to the thyrohyoid membrane.
The lower border (Fig. 892) is nearly straight in front, but behind, close to the
cornu, it is concave, the two parts being separated by the inferior tubercle. A
small part of it, in and near the median line, is connected to the cricoid cartilage by
THE LARYNX
1165
the middle portion of the cricothyroid membrane (membrcma cricothyroidca) ; and, on
either side, by the Cricothyroid muscle.
The posterior borders (Fig. 892) are thick and rounded, and eacli terminates
above, in a superior comu (cornu superius), and below, in an inferior comu {cornu
inferius). The two superior cornua are long and narrow, directed upward, l^ack-
ward, and inward, and terminate in conical extremities, which give attachment
to the lateral thyrohyoid ligaments. The two inferior cornua are short and thick;
they pass downward, with a slight
inclination forward and inward,
and each presents on its inner sur-
face a small oval articular facet for
articulation with the side of the
cricoid cartilage (Fig. 891). The
posterior border receives the in-
sertion of the Stylopharyngeus and
Palatopharyngeus muscles on each
side.
Daring infancy the alte of the thyroid
cartilage are joined to each other by a
narrow, lozenge-shaped strip, named the
intrathyroid cartilage. This strip ex-
tends from the upper to the lower border
of the thyroid cartilage in the middle
line, and is distinguished from the al;e
by being more transparent and more
flexible.
Epiglott
Thyroid.
Cuneiform cartilage.
Arytenoid.
PiMerior
iiiiface.
The Cricoid Cartilage {cartilago
cricoidea) (Figs. 891 and, 892) is so
called from its resemblance to a
signet ring {^f)cxo(;, a ring). It is
smaller, but thicker and stronger
than the thyroid cartilage, and
forms the lower and back part of
the cavity of the larynx. It is hya-
line cartilage, and consists of two
parts — a quadrate portion, situated
behind, and a narrow ring, or arch,
one-fourth or one-fifth the depth
of the posterior part, situated in
front. The posterior scjuare por-
tion rapidly narrows at the sides of
the cartilage, at the expense of the
upper border, into the anterior
portion.
Its posterior portion, or lamina
(lamina cartilaginis cricoideae), is very deep and broad, and measures from above
downward about an inch (2.5 cm.); it presents, on its posterior surface, in the
middle line, a vertical ridge for the attachment of the longitudinal fibres of the
oesophagus, and on either side a broad depression for the Cricoarytenoideus
posticus muscle.
Its anterior portion, or arcus {arcus cartilaginis cricoideae), is narrow and convex,
and measures vertically about one-fourth or one-fifth of an inch (6 to 5 mm.);
it affords attachment externally in front and at the sides to the Cricothyroid
muscles, and, behind, to part of the Inferior constrictor.
Cricoid.
Articula r facet for
arytoioid cartilage.
A rlicular facet for
inferior cornu of
thyroid cartilage.
Fig. 892. — The cartilages of the laryi
1166 THE ORGANS OF VOICE AND BESPIBA TION
At the junction of the posterior quadrate portion with the rest of the cartilage
is a small round articular eminence, for articulation with the inferior cornu of the
thyroid cartilage.
The lower border of the cricoid cartilage is horizontal, and connected to the
uppermost ring of the trachea by fibrous membrane (Figs. 891 and 892).
Its upper border is directed obliquely upward and backward, owing to the great
depth of the posterior surface. It gives attachment, in front, to the middle
portion of the cricothyroid membrane ; at the sides, to the lateral portion^ of the
same membrane and to the lateral Cricoarytenoid muscle ; hehind, it presents, in
the middle, a shallow notch, and on each side of this is a smooth, oval surface,
directed upward and outward, for articulation with the base of an arytenoid
cartilage.
The inner surface of the cricoid cartilage is smooth, and covered by mucous
membrane.
The Arytenoid Cartilages {cartilagines arytenaideae) (Fig. 892) are two in number,
and situated at the upper border of the cricoid cartilage, at the back of the larynx
in the interval between the posterior borders of the alffi of the thyroid cartilages.
Each cartilage is in form a three-sided pyramid, and presents for examination
three surfaces, a base, and an apex.
The posterior surface is triangular, smooth, concave, and gives attachment to
the transverse portion of the Arytenoid muscle.
The antero-extemal surface is somewhat convex and rough. It presents, near
its apex, a small elevation, the colliculus; from this a ridge (crista arcuata) passes
backward and then forward and downward into a sharp-pointed process, the
vocal process. This ridge separates a deep depression above, the fovea triangularis,
from a broader and shallower depression below, the fovea oblonga. A short dis-
tance above the base a small tubercle on the anterior border gives origin to the
ligament of the false vocal cord, the superior thyroarytenoid ligament. To the
outer part of the ridge, as well as the surface above and below, is attached the
Thyroarytenoid muscle.
The internal surface is narrow, smooth, and flattened, and forms the lateral
boundary of the respiratory part of the glottis.
The base (basis) of each cartilage is broad, and presents a concave smooth
surface, for articulation with the cricoid cartilage. Two of its angles require
special mention: The external angle, which is short, rounded, and prominent,
projects backm'ard and outward, and is termed the muscular process (processus
muscularis), from receiving the insertion of the Posterior and Lateral crico-
arytenoid muscles. The anterior angle, also prominent, but more pointed, pro-
jects horizontally forward, and gives attachment to the inferior thyroarytenoid
ligament, the supporting ligament of the true vocal cord. This angle is called
the vocal process (processus vocalis).
The apex of each cartilage is pointed, curved backward and inward, and sur-
mounted by a small conical, cartilaginous nodule, the comiculum laryngis, articu-
lated with or united to the arytenoid cartilage.
The Comicula Laryngis or Cartilages of Santorini (cartilagines corniculatae) (Figs.
892 and 898) are two small conical nodules, consisting of yellow elastic cartilage,
which articulate with the summits of the arytenoid cartilages and serve to pro-
long them backward and inward. They are situated in the posterior parts of the
arytenoepiglottic folds, and are sometimes united to the arytenoid cartilages.
The Cuneiform Cartilages or Cartilages of Wrisberg (cartilagines cuneiformes)
(Figs. 892 and 897) are two small, elongated pieces of yellow elastic cartilage,
placed one on each side, in the arytenoepiglottic fold (plica aryepiglottica) (Fig.
897), where they give rise to small whitish elevations on the inner surface of the
mucous membrane, jtist in front of the arytenoid cartilages.
THE LARYNX 1167
The Epiglottis {cartilaqo epiqlottlca) (Figs. 892 and 893) is a thin, flexible lamella
of fibrocartilage, of a yellowish color, shaped like a leaf, and projecting behind the
tongue in front of the superior opening of the larynx. The projecting extremity is
broad and rounded; its attached part or apex (pctiolus epigloUidis) is long, narrow,
and connected to the receding angle between the two ahe of the thyroid cartilage,
just below the median notch, by a ligamentous band, the thyroepiglottic ligament
(Fig. 894). The lower part of its anterior surface is connected to the upper Ijorder
of the body of the hyoid bone by an elastic ligamentous band, the hyoepiglottic
ligament.
Its anterior or lingual surface is curved forward, toward the tongue, and covered
at its upper, free part by mucous membrane, which is reflected on to the sides and
base of the organ, forming a median and two lateral folds, the glossoepiglottic
folds (Fig. 897); the lateral folds are partly attached to the wall of the pharynx.
The depressions between the epiglottis and base of the tongue on each side of the
median fold are named the valleculae. The lower part of the anterior surface of
the epiglottis lies behind the hyoid bone, the thyrohyoid membrane, and upper
part of the thyroid cartilage, but is separated from these structures by a mass of
fatty tissue.
Its posterior or laryngeal surface is smooth, concave from side to side, concavo-
convex from above downward; its lower part projects backward as an elevation,
the tubercle or cushion (iuberculwn epiglotticum) (Fig. 893). When the mucous
membrane is removed, the surface of the cartilage is seen to be indented by
a number of small pits, in which mucous glands are lodged. To its sides the
arytenoepiglottic folds are attached (Fig. 897).
Structure. — The cornicula laryngis and cuneiform cartilages, the epiglottis, and the apices
of the arytenoids at first consist of hyaline cartilage, but later elastic fibres grow in from the
perichondrium, and eventually they are converted into yellow fibrocartilage; they show little
tendency to calcification. The thyroid, cricoid, and the greater part of the arytenoids consist
of hyaline cartilage, and become more or less ossified as age advances. Ossification commences
aljout the twenty-fifth year in the thyroid cartilage, somewhat later in the cricoid and aryte-
noids; by the sixty-fifth year these cartilages may be completely converted into bone.
Ligaments. — ^The ligaments of the larynx are extrinsic — i. e., those connecting
the thyroid cartilage and epiglottis with the hyoid bone, and the cricoid cartilage
with the trachea; and i)iiriusic, those which connect the several cartilages of the
larynx to each other.
Extrinsic Ligaments. — ^The ligaments connecting the thyroid cartilage with the
hyoid bone are foin- in number — the thyrohyoid membrane, the two lateral
thyrohyoid ligaments, and the hyoepiglottic ligament.
The Thyrohyoid Membrane (membraiia hyothyreoidea) (Fig. 894) is a broad,
fibroelastic, membranous layer, attached below to the upper border of the thyroid
cartilage, and above to the upper margin of the posterior surface of the body and
greater cornua of the hyoid bone, thus passing behind the posterior surface of
the hyoid, and being separated from it by a synovial bursa (bursa m. sternohyoidei),
which facilitates the upward movement of the larynx during deglutition. It
is thicker in the middle line dian at either side. This thickening is due to elastic
Hbres, and constitutes the middle thyrohyoid ligament (ligamentum hyothyreoidcum
medium). On each side the posterior extremity of the membrane is thickened
by elastic fibres, constituting the lateral thyrohyoid ligament (ligamenium hyothy-
reoidemn laterale). The thyrohyoid membrane is pierced on each side by the supe-
rior laryngeal vessels and the internal branch of the superior laryngeal nerve. The
anterior surface of the thyrohyoid membrane is in relation with the Thyrohyoid,
Sternohyoid, and Omohyoid muscles and with the body of the hyoid bone. The
two lateral ligaments are rounded, elastic cords, which pass between the superior
1168
THE ORGANS OF VOICE AND RESPIRATION
EPIGLOTTIDEUS
cornua of the thyroid cartilage and the extremities of the greater cornua of the
hyoid bone. A small cartilaginous nodule (cartilago iriiicea), sometimes bony,
is frequently found in each.
The ligament connecting the epiglottis with the hyoid bone is the hyoejnglqtiic.
In addition to this extrinsic ligament, the epiglottis is connected to the tongue by
the three glossoepiglottic folds of mucous membrane, which may also be considered
as extrinsic ligaments of the epiglottis. The hyoepiglottic ligament {ligameutmn
hyoepiglotticum) is an elastic band, which extends from the anterior surface of
the epiglottis, near its apex, to the upper border of the body of the hyoid bone.
The cricotracheal ligament (ligameiitum cricotracheale) connects the cricoid
cartilage with the first ring of the trachea. It resembles the fibrous membrane
which connects the cartilaginous rings of the trachea.
Intrinsic Ligaments. — ^The ligaments connecting the thyroid cartilage to the
cricoid are three in number — the cricothyroid membrane and the two capsular
ligaments.
The Cricothyroid Membrane (conus elasticus) (Figs. 891 and 901) is composed
mainly of yellow elastic tissue. It consists of three parts, a central triangular
portion and two lateral portions. The central part (ligamentum cricothyreoideiim
mediuvi) is thick aiid strong,
narrow above and broaden-
ing out below. It connects
the contiguous margins of the
thyroid and cricoid cartilages.
It is convex, concealed on
each side by the Cricothyroid
muscle, but subcutaneous in
the middle line; it is crossed
horizontally by a small anas-
tomotic arterial arch, formed
by the junction of the two
cricothyroid arteries. The
lateral portions are thinner
and lie close under the mucous
membrane of the larynx.
They extend from the superior
border of the cricoid cartilage
to the inferior margin of the
true vocal cords with which
they are continuous. These
cords may therefore be re-
garded as the free borders of
the lateral portions of the
cricothyroid membrane; they
extend from the vocal processes of the arytenoid cartilages to the receding
angle of the thyroid cartilage near its centre. The lateral portions are lined
internally by mucous membrane, and are separated from the thyroid cartilage
by the Cricoarytenoideus lateralis and Thyroarytenoideus muscles.
A capsular ligament, strengthened posteriorly by a well-marked fibrous band,
encloses the articulation of the inferior cornu of the thyroid with the cricoid
cartilage on each side. The articulation is lined by synovial membrane.
Each arytenoid ' cartilage is connected to the cricoid by a capsular ligament
(capsula articularis cricoarytaenoidea) and a posterior cricoarytenoid ligament
(ligamentum cricoarytenoideum posterius). The capsular ligament is thin and
loose, and is attached to the margin of the articular surfaces, and lined by synovial
-Coronal section of lary
(Testut.)
THE LARYNX
1169
membrane. The posterior cricoarjrtenoid ligament extends from the cricoid to
the inner and back part of the base of the arytenoid cartilage.
The thyroepiglottic ligament (ligmnentum thyreoepigloHlcum) (Fig. 894) is a
long, .slender elastic cord which connects the apex of the epiglottis with the internal
surface of the receding angle of the thyroid cartilage, immediately beneath the
^nedian notch, above the attachments of the false and true vocal cords.
Movements. — The articulation between the inferior cornu of the thyroid and the cricoid
cartilage on either side is a diarthroidal one, and permits of rotary and gliding movements.
The rotary movement is one in which the inferior cornua of the thyroid cartilage rotate upon
the cricoid cartilage around an axis passing transversely through both joints. The gliding
movement consists in a limited shifting of the cricoid on the thyroid in different directions.
The articulation between the arytenoid cartilages and the cricoid is also a diarthrodial one,
and permits of two varieties of movement — one a rotation of the arytenoid on a vertical axis,
whereby the vocal process is moved outward or inward and the opening of the rima glottidis
increased or diminished; the other is a gliding movement and allows the arytenoid cartilages
to approach or recede from each other; from the direction and slope of the articular surfaces
outward gliding is accompanied by a forward and downward movement. The two movements
of gliding and rotation are associated, the gliding inward being connected with inward rota-
tion, and the gliding outward with outward rotation. The posterior cricoarytenoid ligaments
limit the forward movement of the arytenoid cartilages on the cricoid.
Interior of the Larynx (Figs. 893, 894, and 897).— The cavity of the larynx
(cavum laryngis) extends from the superior aperture of the larynx to the lower
border of the cricoid cartilage. It is divided into two parts by the projection
inward of the true vocal
cords, between which is
a narrow triangular fis-
siu'e or chink, the rima
glottidis. The portion
of the cavity of the
larynx above the true
vocal cords, sometimes
called the vestibule
(vestibulum laryngis), is
wide and triangular in
shape, its base or an-
terior wall presenting,
however, about its centre
the backward projection
of the cushion of the
epiglottis. It contains
the false vocal cords
(plicae veniriculares),
and between these and
the true vocal cords are
the ventricles of the
larynx. The portion
below the true vocal
cords is at first of an
elliptical form, but lower
down it widens out, assumes a circular form, and is continuous with the tube of
the trachea.
The Superior Aperture of the Lar3mx (aditus laryngis) (Figs. 893 and 897) is
a triangular or cordiform opening, wide in front, narrow behind, and sloping
obliquely downward and backward. It is bounded, in front, by the epiglottis;
behind, by the apices of the arytenoid cartilages and the cornicula laryngis; and
74
Fig. S94. — Sagittal section of larynx, right half. (Testut.)
1170
THE OBGAWS OF VOICE AND BESPIBA TION
laterally, by a fold of mucous membrane, enclosing ligamentous and muscle
fibres, stretched between the side of the epiglottis and the apex of the arytenoid
cartilage; this is the arytenoepiglottic fold (Figs. 894 and 897), on the margin of
which the cuneiform cartilage forms a more or less distinct whitish prominence.
The superior or false vocal cords {plicae ventriculares) (Figs. 893 and 894), so
called because they are not directly concerned in the production of the voice,
are two thick folds of mucous membrane, each enclosing a very narrow band of
connective tissue, the so-called superior thyroarjrtenoid ligament. This is attached
in front to the angle of the thyroid cartilage immediately below the attachment
of the epiglottis, and behind to the antero-external surface of the arytenoid carti-
lage. The lower border of this ligament, enclosed in mucous membrane, forms a
free crescentic margin, which constitutes the upper boundary of the ventricle
of the larynx.
Fig. 895. — Muscles of larynx, front '\
thyroids and right Thyrohyoid hav
(Testut.)
Fig 896 — Muscles of larynx, from behind
(Testut.)
The inferior or true vocal cords {plicae vocales) (Figs. 893 and 894), so called
from their being concerned in the production of sound, are two strong bands
named the inferior thyroarytenoid ligaments. Each ligament consists of a band
of yellow elastic tissue, attached in front to the depression between the alse of the
thyroid cartilage, and behind to the vocal process at the base of the arytenoid.
Its lower border is continuous with the thin lateral part of the cricothyroid mem-
brane. Its upper border forms the lower boundary of the ventricle of the larynx.
Externally, the Thyroarytenoideus muscle lies parallel with it. It is covered
internally by mucous membrane, which is extremely pale, thin, and closely ad-
herent to its surface. The node-like attachment of the ligament to the thyroid
cartilage appears as a yellow spot {macula flava) ; the vocal process also shines
through the mucosa as a yellowish spot.
The ventricle of the larynx or laryngeal sinus {ventriculus laryngis [Morgagnii])
(Figs. 893 and 894) is an oblong fossa, situated between the superior and inferior
vocal cords on each side, and extending nearly their entire length. This fossa is
bounded, above, by the free crescentic edge of the false vocal cord; below, bj- the
straight margin of the true vocal cord ; externally, by the mucous membrane cover-
THE LARYNX
1171
ing the corresponding Thyroarytenoideus muscle. The anterior part of the ven-
tricle leads up by a narrow opening into a cecal pouch of mucous membrane of
variable size, called the laryngeal saccule.
The larjTHgeal saccule [appoidix vcntricidi) (Fig. 893), or laryngeal pouch, is
a membranous sac, placed between the superior vocal cord and the inner surface
of the thyroid cartilage, occasionally extending as far as its upper border or even
higher; it is conical in form, and curved slightly backward. On the surface
of its mucous membrane are the openings of si.xty or seventy mucous glands,
which are lodged in the submucous areolar tissue. This sac is enclo.sed in a
fibrous capsule, continuous below with the superior thyroarytenoid ligament;
its laryngeal surface is covered by a few delicate muscle fasciculi wliich arise
from the apex of the arytenoid cartilages and Ijecome lost in the fold of mucous
membrane extending between the arytenoid cartilage and the side of the epiglottis
{they were named by Hilton the compressor sacculi laryngis); while its exterior
is covered by the Thyroarytenoideus and Thyroepiglottideus muscles. These
muscles compress the laryngeal saccule, and express the secretion it contains upon
the vocal cords to lubricate their surfaces. The saccule assists in imparting
resonance to the voice.
APEX OF SUP. HORN OF
-^1.
CORNICULUM
FORM
CARTILAGE
RYTENO EPIGLOT-
TIDIAN FOLD
PEX OF GREAT
ORN OF HYOID
Fig. 897.— Larynx,
SLOTTIDIAN FO
wed from abo
The Rima Glottidis (Figs. 893 and 897) is the elongated fissure or chink between
the true vocal cords in front, and between the bases and vocal processes of the
arytenoid cartilages behind. It is therefore frequently subdivided into an anterior,
interligamentous or vocal portion, the glottis vocaUs (pars intermenibrauacea),
and a posterior, intercartilaginous or respiratory portion, the glottis respiratoria
(pars infercartilaginea). Posteriorly it is limited by the mucous membrane passing
between the arytenoid cartilages. The vocal portion averages about three-
fifths of the length of the entire aperture. It is the narrowest part of the cavity
of the larynx, and its level corresponds to the bases of the arytenoid cartilages.
Its length, in the male, measures rather less than an inch (23 mm.); in the female
it is shorter (16 to 20 mm.). The width and shape of the rima glottidis vary
with the movements of the vocal cords and arytenoid cartilages during respiration
and phonation. In the condition of rest — /. e., when those structures are unin-
fluenced by muscular action, as in quiet respiration, the glottis vocalis is triangular,
with its apex in front and its base behind, the latter being represented by a line
1172 THE ORGANS OF VOICE AND RESPIRATION
about 8 mm. {\ inch) long, connecting the anterior extremities of the vocal
processes, while the inner surfaces of the arytenoids are parallel to each other,
and hence the glottis respiratoria is rectangular. During extreme adduction
of the cords, as in the emission of a high note, the glottis vocalis is reduced to a
linear slit by the apposition of the cords, while the glottis respiratoria is triangular,
its apex corresponding to the anterior extremities of the vocal processes of the
arytenoids, which are approximated by the inward rotation of the cartilages.
Conversely in extreme abduction of the cords, as in forced inspiration, the aryte-
noids and their vocal processes are rotated outward, and the glottis respiratoria
is triangular in shape, but with its apex directed backward. In this condition
the entire glottis is somewhat lozenge-shaped, the sides of the glottis vocalis
diverging from before backward, those of the glottis respiratoria diverging from
behind forward, the widest part of the aperture corresponding with the attachment
of the cords to the vocal processes.
Muscles of the Larynx. — The extrinsic muscles are those which pass between
the larynx and parts around — these have been described on pages 387 to 389,
The intrinsic muscles, confined entirely to the larynx, are:
Cricothyroideus. Cricoarytenoideus lateralis.
Cricoarytenoideus posticus. Arytenoideus.
Thyroarytenoideus,
The Arytenoideus is a single muscle, the other four are paired.
Dissection. — In order to expose the Lateral cricothyroid and Thyroarvtenoid muscles
the thyroid cartilage of one side must be removed. Begin by taking away the Cricothyroid
muscle, then dividing the lateral thyrohyoid ligament, disarticulate the inferior cornu of the
thyroid cartilage from the cricoid cartilage, then carefully cut through the thyroid cartilage a-
short distance from its union with its twin.
The Cricothyroid (??i. cricothyreoideus) (Figs. 898 and 899) is triangular in form,,
and situated at the fore part and side of the cricoid cartilage. It arises from the
front and lateral part of the cricoid cartilage; its fibres diverge, passing obliquely
upward and outward to be inserted into the lower border of the thyroid cartilage
and into the anterior border of the lower cornu. The inner borders of these
two muscles are separated in the middle line by a triangular interval occupied
by the central part of the cricothyroid membrane.
The Posterior Cricoarytenoid {in. cricoarytaenoideus posterior) (Figs. 898 and 899)
arises from the broad depression occupying each lateral half of the posterior
surface of the cricoid cartilage; its fibres pass upward and outward, converging
to be inserted into the outer angle (muscular process) of the base of the arytenoid
cartilage. The upper fibres are nearly horizontal, the middle oblique, and the
lower almost vertical.
The Lateral Cricoarytenoid (m. cricoarytaenoideus lateralis) (Figs. 898 and 899),
a paired muscle, is smaller than the preceding, and of an oblong form. It arises-
from the upper border of the side of the cricoid cartilage, and, passing obliquely
upward and backward, is inserted into the muscular process of the arytenoid
cartilage in front of the posterior Cricoarytenoid muscle. The deep surface
is applied to the cricothyroid membrane, its external or superficial surface is
subjacent to the thyroid cartilage.
The Arytenoideus (Figs. 898 and 899) is a single muscle filling up the posterior
concave surface of the arytenoid cartilages. It arises from the posterior surface
and outer border of one arytenoid cartilage, and is inserted into the corre-
sponding parts of the opposite cartilage. It consists of three planes of fibres,
two oblique and one transverse. The oblique fibres {vi. arytenoideus obliqmis)^
THE LARYNX
1173
the most superficial, form two fasciculi, which pass from the base of one cartilage
to the apex of the opposite one, and which, therefore, cross each other like the
limbs of the letter X. The transverse fibres (m. arijtaenoideus transversus), the
deepest and most numerous, pass transversely across between the two cartilages.
A few of the oblique fibres are continued around the outer margin of the cartilage,
and blend with the Thyroarytenoid in the arytenoepiglottic fold, and are called
the Aryepiglotticus muscle.
The Thj^oarytenoid (m. thyroanjtenokleus) (Figs. S9S and 899), a paired muscle,
is broad and flat. It lies parallel with the outer side of the true vocal cord. It
arises in front from the lower half of the receding angle of the thyroid cartilage,
and from the cricothyroid membrane. Its fibres pass backward and outward, to
be inserted into the base and antero-external surface of the arytenoid cartilage.
This muscle consists of two fasciculi.' The inner portion (?w. vocalis) is a tri-
angular band which is inserted into the
vocal process of the arytenoid cartilage,
and into the adjacent portion of its antero-
external surface; it lies parallel with the
true vocal cord, to which it is adherent.
This fasciculus on its deeper surface
Articular facet for
inferior corntt of
thyroid cartilage.
Fig. 89S.— Muscles of larynx. Side view,
of thyroid cartilage removed.
Right ala
seen from above.
gives off some fibres which are attached to the true vocal cord. These are called
the Aryvocalis (Ludwig). The outer portion (m. thyreoarytenoideus), the thinner,
is inserted into the antero-external surface and outer border of the arytenoid
cartilage above the preceding fibres ; it lies on the outer side of the laryngeal saccule,
immediately beneath the mucous membrane.
A considerable number of the fibres of the Thyroarytenoideus are prolonged
into the arytenoepiglottic fold, where some of them become lost, while others
are continued forward to the margin of the epiglottis. They have received a
distinctive name, Thyroepiglotticus (m. thyreoepiglotticus), and are sometimes
described as a separate muscle.
' Henle describes these two portio
thyroarytenoids.
separate muscles, under the names of the External and Internal
1174 THE ORGANS OF VOICE AND BESPIBATION
Actions. — In considering the action of the muscles of the larynx, they may be conveniently
divided into two groups — viz.: (1) Those which open and close the glottis. (2) Those which
regulate the degree of tension of the vocal cords.
1. The muscles which open the glottis are the two Posterior cricoarytenoids; and those
which close it are the Arytenoideus and the two Lateral cricoarytenoids.
2. The muscles which regulate the tension of the vocal cords are the two Cricothyroids, which
render tense and elongate them, and the two Thyroarytenoids, which relax and shorten them.
The Posterior cricoarytenoids separate the chordae vocales, and consequently open the glottis,
by rotating the arytenoid cartilages outward around a vertical axis passing through the crico-
arytenoid joints, so that their vocal processes and the vocal cords attached to them become widely
separated.
The Lateral cricoarytenoids close the glottis by rotating the arytenoid cartilages inward so
as to approximate their vocal processes.
The Arytenoideus muscle approximates the arytenoid cartilages, and thus closes the opening
of the glottis, especially at its back part.
The Cricothyroid muscles produce tension and elongation of the vocal cords. This is effected
as follows: the thyroid cartilage is fixed by its Extrinsic muscles; then the Cricothyroid muscles,
when they act, draw upward the front of the cricoid cartilage, and so depress the posterior por-
tion, which carries with it the arytenoid cartilages, and thus elongate the vocal cords.
The Thyroarytenoid muscles, consisting of two parts having different attachments and dif-
ferent directions, are rather complicated as regards their action. Their main use is to draw
the arytenoid cartilages forward toward the thyroid, and thus shorten and relax the vocal cords.
But, owing to the connection of the inner portion with the vocal cord, this part, if acting sepa-
rately, is supposed to modify its elasticity and tension, and the outer portion, being inserted
into the outer part of the anterior surface of the arytenoid cartilage, may rotate it inward, and
thus narrow the rima glottidis by bringing the two cords together.
The manner in which the superior aperture of the larynx is closed during deglutition is referred
to on page 399.
The mucous membrane of the larsmx is continuous above with that lining the mouth and
pharynx, and it is prolonged through the trachea and bronchi into the lungs. It lines the pos-
terior surface and the anterior part of the upper surface of the epiglottis, to which it is closely
adherent. In the rest of the larynx, above the true vocal cords, it is lax and rests upon a con-
siderable submucous layer. The mucous membrane, with the submucous coat, ligamentous
and muscular fibres, forms the arytenoepiglottic folds, which folds are the lateral boundaries
of the superior aperture of the larynx. It lines the whole of the cavity of the larynx, forms
by its reduplication the chief part of the superior or false vocal cord, and, from the ventricle,
is continued into the laryngeal saccule. It is then refiected over the true vocal cords, where it
is thin and very intimately adherent; covers the inner surface of the cricothyroid membrane
and cricoid cartilage; and is ultimately continuous with the lining membrane of the trachea.
The fore part of the anterior surface and the upper half of the posterior surface of the epiglottis,
the upper part of the arytenoepiglottic folds, and the true vocal cords are covered by stratified
squamous epithelium; the rest of the laryngeal mucous membrane is covered by stratified ciliated
cells.
The mucous membrane above the rima glottidis is extremely sensitive, and during life the
lightest touch of a foreign body produces cough.
Glands. — The mucous membrane of the larynx is furnished with numerous muciparous
glands, the orifices of which are found in nearly every part; they are very numerous upon the
epiglottis, being lodged in little pits in its substance; they are also found in large numbers along
the posterior margin of the arytenoepiglottic fold, in front of the arytenoid cartilages, where
they are termed the arytenoid glands. They exist also in large numbers upon the inner surface
of the laryngeal saccule. None are found on the surface of the true vocal cords.
Vessels and Nerves. — The arteries of the larynx (Fig. 900) are the laryngeal branches
derived from the superior and inferior thyroid. The superior laryngeal artery from the
superior thyroid accompanies the internal branch of the superior laryngeal nerve; the inferior
laryngeal artery from the inferior thjrroid courses along with the recurrent laryngeal nerve.
The veins accompany the arteries; those accompanying the superior laryngeal artery join the
superior thyroid vein, which opens into the internal jugular vein; while those accompanying
the inferior laryngeal artery join the inferior thyroid vein, which opens into the innominate
vein. The Ijrmphatics consist of two sets, superior and inferior. The superior accompany the
superior laryngeal artery, pierce the thjTohyoid membrane, and terminate in the nodes situated
at the bifurcation of the carotid artery. Of the inferior lymphatics, some pass through the
cricothyroid membrane to terminate in a node lying in front of that membrane or in front of
the upper part of the trachea, while others pass to the deep cervical nodes and to the nodes
along the inferior thyroid artery.
The nerves are derived from the internal and external laryngeal branches of the superior
laryngeal nerve, from the inferior or recurrent laryngeal, and from the sjmipathetic. The
THE TRACHEA AND BRONCHI
1175
internal laryngeal nerve is almost entirely sensor, but some motor filaments are said to be carried
by it to the Arytenoideus muscle. It divides into a branch which is distributed to both surfaces
of the epiglottis, a second to the arytenoepiglottic folds, and a third, the largest, which sup])iies
the mucous membrane over the back of the larynx and communicates with the recurrent laryn-
geal. The external laryngeal branch sujiplies the Cricothyroid muscle. The recurrent laryn-
geal passes upward under the lower border of the Inferior constrictor, and enters the larynx
between the cricoid and thyroid cartilages. It supplies all the muscles of the larynx except the
Cricothyroid and part of the Arytenoideus. The sensor branches of the laryngeal nerves form
subepithelial plexuses, from which fibres ascend to end between the cells covering the mucous
membrane. Sympathetic filaments accompany all of the laryngeal nerves.
Over the posterior surface of the epiglottis, in the arytenoepiglottidean folds, and less regu-
larly in some other parts, taste buds, similar to those in the tongue, are found.
Fig. 900.— The origin and distribution of the arteries of the larynx. (Luschka.)
THE TRACHEA AND BRONCHI (Fig. 901).
The trachea, or windpipe, is a cartilaginous, membranous, elastic, cylindrical
tube, flattened posteriorly, which extends from the lower part of the laryixs, on a
level with the sixth cervical vertebra, to opposite the body or upper border of the
fifth thoracic vertebra, where it divides (bifurcatio tracheae) into two stem bronchi,
one for each lung. The trachea is nearly, but not quite, cylindrical, being flattened
posteriorly (Fig. 903). The largest diameter of the tube is at the middle; from this
point the diameter diminishes toward the bronchi and toward the laryngeal end.
The trachea measures about four inches and a half (U cm.) in length; its diameter,
in the cadaver, from side to side is from three-c|uarters of an inch to an inch
(19 to 25 mm.), being always greater in the male than in the female. Its calibre
is not quite uniform throughout; the middle third is somewhat w-ider than the
rest of the tube, while just below, before its bifurcation, the trachea is slighdy
diminished in diameter where it is in relation with the arch of the aorta. In the
living subject, owing to the muscle tone of the wall, the transverse diameter is
12.5 mm. (0.5 inch); the antero-posterior, 11 mm. (0.44 inch).
Relations. — The anterior surface of the trachea is convex, and covered in the neck, from
above downward, by the isthmus of the thyroid gland, the inferior thyroid veins, the arteria
thvroidea ima (when that vessel exists), the Sternohyoid and SternothjToid muscles, the cervical
1176
THE ORGANS OF VOICE AND RESPIRATION
fascia, and, more superficially, by the anastomosing branches between the anterior jugular veins;
in the thorax it is covered from before backward by the first piece of the sternum, the remains
of the thymus gland, the left innominate vein, the arch of the aorta, the innominate and left com-
mon carotid arteries, and the deep cardiac plexus. Posteriorly, it is in relation with the oesoph-
agus; laterally, in the neck, it is in relation with the common carotid arteries, the lateral lobes
of the thyroid gland, the inferior thyroid arteries, and recurrent laryngeal nerves; and, in the
thorax, it lies in the upper part of the interpleural space (superior viedia.itinuvi), and is in relation
on the right with the pleura and right vagus, and near the root of the neck with the innominate
artery; on its left side are the recurrent laryngeal nerve, the aortic arch, the left common carotid
and subclavian arteries.
PIGLOTTIS
THYROID
Fig. 901. — Front \-iew of cartilages of larynx, the trachea and bronchi.
The Right Bronchus (bronchus dexter) (Fig. 901), wider, shorter, and more
vertical in direction than the left, is about an inch in length (2.5 cm.), and enters
the hihim of the right lung opposite the fifth thoracic vertebra. It forms an angle
THE TEA CHE A AND BRONCHI
in?
to the median plane of about 25 degrees. The vena azygos major arches
over it from behind; and the right pulmonary artery lies below and then in front
of it. About one inch from its commencement it gi^•es off a branch to the
upper lobe of the right lung. This is termed the eparterial branch bronchus
(ramus bronchialis eparferialis), because it is given off above the right pulmonary
artery. The bronchus now passes below the
artery, is known as the hyparterial branch bron-
chus (ramus bronchialis hyparterialis), and
divides into two branches for the middle and
lower lobes.
The Left Bronchus (bronchus sinister') (Fig.
901) is smaller and longer than the right, being
nearly two inches in length. It forms an angle
to the median plane of about 46 degrees. It is
slightly curved and enters the root of the left
lung, opposite the sixth thoracic vertebra, about
an inch lower than the right bronchus. It
passes beneath the arch of the aorta, crosses in
front of the oesophagus, the thoracic duct, and
the descending aorta, and has the left pul-
Left
Fig. 903. — Transverse section of the trachea, just
bifurcation, with a bird's-eye view of the inteiior, sh(
carina tracheae.
monary artery lying at first above, and then behind it. The left bronchus has
no branch corresponding to the eparterial branch of the right bronchus in the
sense that it is given off above the pulmonary artery. The first hyparterial branch
bronchus of the left side is the morphological equivalent of the right eparterial
branch bronchus, as shown by Huntington.^
The further subdivision of the bronchi will be considered with the anatomy
of the lung.
If a transverse section of the trachea is made a short distance above its point
of bifurcation, and a bird's-eye view taken of its interior (Fig. 90.3), the septum
(carina tracheae) placed at the bottom of the trachea and separating the two bron-
chi will be seen to occupy the left of the median line, and the right bronchus appears
to be a more direct continuation than the left, so that any solid body dropping into
the trachea would naturally be directed toward the right bronchus. This tend-
ency is aided by the larger size of the right tube as compared with its fellow. This
fact serves to explain why a foreign body in the trachea more frequently falls into
the right bronchus than into the left.-
Structure of the Trachea. — The trachea is composed of incomplete cartilaginous rings,
fibrous membrane, muscle fibres, mucous membrane, and glands.
The Cartilages \ary from si.xteen to twenty in number; each forms an incomplete ring, which
siuTOunds about two-thirds of the cylinder of the trachea, being imperfect behind, where the
' The Eparterial Bronchial System of the Mammalia, Annals N. Y. Acad. Sci., 1898.
2 Reigel asserts that the entrance of a foreign body into the left bronchus is by no means so infrequent as is gener-
ally supposed. See also Med.-Chir. Transactions, vol. Ixxi, p. 121.
1178
THE ORGANS OF VOICE AND RESPIRATION
tube is completed by muscle and fibrous tissue. The cartilages are placed horizontally above each
other, separated by narrow intervals bridged by fibroelastic tissue. They measure about J of
an inch in depth, and ^V of an inch in thickness, tapering at their posterior ends. Their outer
sm-faces are flattened, but internally they are convex, from being thicker in the middle than at
the margins. Two or more of the cartilages often unite, partially or completely, and are some-
times bifurcated at their extremities. They are highly elastic, but sometimes become calcified
in advanced life. In the right bronchus the cartilages vary in number from six to eight; in the
left, from nine to twelve. They are shorter and narrower than those of the trachea. The
peculiar cartilages of the trachea are the first and the last.
The first cartilage is broader than the rest, and sometimes divided at one end; it is con-
nected by fibrous membrane with the lower border of the cricoid cartilage, with which or with
the succeeding cartilage it is sometimes blended.
The last cartilage is thick and broad in the middle, in consequence of its lower border being
prolonged into a triangular hook-shaped process which curves downward and backward between
the two bronchi. It terminates on each side in an imperfect ring which encloses the com-
mencement of the bronchi. The cartilage above the last is often somewhat broader than the
rest at its centre.
Ventral view. Dorsal v
js. 904 and 905. — Radiographs of trachea and bronchi filled with fusible metal.
(After J. A. Blake.)
The Fibrous Membrane. — The cartilages are enclosed in a fibroelastic membrane which
forms a double layer, one layer, the thicker of the two, passing over the outer surface of the
ring, the other over the inner surface; at the upper and lower margins of the cartilages these two
layers blend together to form a single membrane, which intervenes between the rings. They
are thus, as it were, embedded in the membrane. In the space behind, between the extremities
of the rings, the membrane forms a single distinct layer.
The muscle fibres are disposed in two layers, longitudinal and transverse.
The longitudinal fibres are external, and consist merely of a few scattered longitudinal bundles
of fibres.
The transverse fibres, the Trachealis muscle of Todd and Bowman, foriii a thin internal
layer which extends transversely lietween the ends of the cartilages and the intervals between
them, thus extending the entu-e length of the posterior part of the trachea. The muscle fibres
are of the unstriped variety.
The mucous membrane is continuous above with that of the larynx, and below with that of
the bronchi. Microscopically, it consists of stratified ciliated epithelial cells, among which a
number of goblet cells are seen; the basal cells are often branched and rest upon the basement
membrane, beneath which is a layer of fibroelastic tissue containing diffuse lymphoid tissue.
The tunica propria blends with the next coat, the submucosa, and here are found the cartilage
rings and a number of mucous glands, the tracheal glands.
The tracheal glands (glnudiilae tracheales) are found in great abundance at the posterior part
of the trachea. Thev are racemose glands, and consist of a basement membrane lined by col-
umnar mucus-secreting cells. They are situated at the back of the trachea, outside the layer
of muscle tissue, between it and the outer fibrous layer. Their excretory ducts pierce the
THE TRACHEA AND BRONCHI
1179
muscle and inner fibrous layers, and pass through the submucous and mucous layers to open
on the surface of the mucous membrane. Some glands of smaller size are also found at the
sides of the trachea, between the layers of fibrous tissue connecting the rings, and others imme-
diately beneath the mucous coat. The secretion from these glands serves to lubricate the inner
surface of the trachea.
Vessels and Nerves. — The trachea is supplied with blood by the inferior thyroid arteries.
The veins terminate in the thyroid venous plexus. The nerves are derived from the vagus and
its recurrent branches and from the sympathetic.
Lymph Nodes. — The trachea is surrounded by lax connective tissue which contains nu-
merous lymph nodes, known as the peritracheobronchial nodes. They are divided into four
groups (Barely). A group to the right side, in the angle between the trachea and right bronchus
and ascending to the region of the subclavian vessels. A group to the left side, in the ancrje
formed by the trachea and left bronchus, and ascending to about the arch of the aorta and the
recurrent laryngeal nerve. The two groups just described are usually called tracheal nodes
[lymphoglandulae trachcale.i). A third group is in the angle formed by the bifurcation of the
trachea. These constitute the bronchial nodes {lym,phoglandvlae hronchiales), ten or twelve in
MPH NODES
Fig. 906. — The tracheobronchial and interbronchial lymph nodes, seen from in front. The dotted lymph nodes
and lymph vessels are not visible from in front: d', d-. First and second dorsal branch bronchi. !)', v^. First and
second ventral branch bronchi. (Sukiennikow. >
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 intei<tinal
' loops cross
each other.
Mesocolon.
Large intes-
tine.
Small inieS'
tine.
Figs. 9S4 and 985. — Illustrating two stages in the development of the human alimentary canal and its mesentery.
The arrow indicates the entrance to the bursa omentalis. (Hertwig.j
The upper part of the foregut becomes dilated in the form of branchial pouches
to form the pharynx; the succeeding part remains tubular' and with the descent
of the stomach becomes elongated to form the oesophagus. About the fifth week
a fusiform dilatation, the future stomach, makes its appearance. The stomach,
together with a succeeding part of the duodenum, has a ventral mesentery, called
the ventral mesogastrium, in addition to its dorsal attachment, the dorsal meso-
gastrium. In the base of the dorsal mesogastrium courses the aorta which sup-
plies a series of branches, embedded in the mesoderm, to the alimentary tube.
The stomach undergoes a further dilatation, and its two curvatures can be recog-
nized, the greater directed dorsad and the lesser ventrad, while its two surfaces
look to the right and left respectively. The midgut undergoes great elongation
and forms a loop which projects downward and forward; from the arch of the loop
the vitelline duct passes to the umbilicus. For a time a part of the loop extends
beyond the abdominal cavity into the umbilical cord, but is withdrawn into the
cavity by the end of the third month.
About the sixth week a lateral diverticulum makes its appearance on the caudal
part of the loop a short distance from the vitelline duct, and indicates the future
cecum and appendix. The part of the loop on the distal side of the cecal diver-
ticulum increases in diameter and forms the future ascending and transverse
portions of the large intestine. The cecal diverticulum shares only partially in
this increase in calibre, its pendant portion remaining rudimentary and forming
the appendix.
The stomach and intestine, with their mesenteries, undergo changes of position
determined by several growth factors, such as the elongation of the intestine, and
1 The epithelium of the cesophagus and certain other portions of the gut increases so greatly in thickness by active
proliferation of the cells that the lumen is nearly or wholly closed during the second month, to be restored about one
jnonth later (Congenital stenosis).
1250
THE ORGANS OF DIGESTION
the development of such organs as the liver, pancreas, and spleen. Such devel-
opmental changes, with subsequent displacements, adhesions, and absorptions,
serve to form all the mesenteries, omenta, and peritoneal folds of the adult, so
that, while in the primitive condition the intestinal tube is suspended by a dorsal
mesentery and freely movable, certain portions of it become later, by secondary
adhesion, firmly connected with the parietes (retroperitoneal) or with other por-
tions of the tract.
Rotation of Stomach and Intestine. — ^The stomach rotates so that its greater
(dorsal) curvature with the attached dorsal mesogastrium is carried downward
and to the left, so that the right surface of the stomach is now directed backw'ard
and the left surface forward (ventrad) — a change in position which explains
why the left vagus nerve is found on the front of the
stomach and the right vagus on the back of it. As the
stomach rotates, the dorsal mesogastrium is necessarily
elongated; this elongation is, however, augmented in
further development, so that a large pouch, the bursa
omentalis or lesser sac is formed. The entrance to this
pouch constitutes the future foramen of Winsloiv.
The duodenum, developed from that part of the tube
which immediately succeeds the stomach, undergoes
S" pt tm ti ansi ersiim.
Fig. 987.— Final disposition
of the intestines and their vas-
cular relations, A. .\orta. H,
Hepatic artery. 5. Splenic ar-
tery. M , Col. Branches of supe-
rior mesenteric artery, vi, m'.
Branches of inferior mesenteric
artery. (Jonnesco.)
Intcsth
y -shaped loop,
Mesente
little elongation. It is at first suspended by a mesentery (mesoduodenum) and
projects forward in the form of a loop. The loop is subsequently displaced
backward by the transverse colon, so that the right surface of the mesoduodenum
is swung back, and, adhering to the parietal peritoneum pardy in front of the
right kidney, is obliterated; in this way the duodenum, together with the pancreas
which has invaded the dorsal mesoduodenum, become retroperitoneal. It is
further fixed in position by the liver and pancreas which arise as diverticula from
it. The liver, developing between the layers of the ventral mesogastrium, comes
to occupy the upper right portion of the abdominal cavity, and thus reduces the
entrance to the omental bursa to the small foramen of Winslow.
The remainder of the alimentary canal becomes elongated, and as a consequence
the tube becomes complexly coiled on itself, and this elongation demands a
corresponding increase in the width of the intestinal attachment of the mesentery,
which becomes folded.
Rotation of the Intestine. — At an early stage the small and large intestines are
attached to the dorsal wall of the abdomen by a common mesentery, the coils
THE PERITONEUM
1251
of the small intestine falling to the right, while the large intestine lies on the left
side.^
The gut now becomes rotated upon itself, so that the large intestine is carried
over in front of the small intestine, and the cecum is placed immediately below
the liver; about the sixth month the cecum descends into the right iliac fossa,^
and the large intestine now forms an arch consisting of the ascending, transverse,
and descending portions of the colon — the transverse portion crossing in front of
the duodenum and lying just below the greater curvature of the stomach ; within
this arch the coils of the small intestine are disposed (Figs. 984 and 985). The
intestine in its rotation twists the mesentery in a funnel-shaped manner, so that
Fig. 988. — Torsion of the umbilical loop.
Initial position. (Jonnesco.)
Fig. 989.— Torsion of the umbilical loop.
Acquired position. (Jonnesco.)
the original right leaf of the mesentery of the small intestine has become the left,
and vice versa. The mesentery of the small intestine assumes the oblique attach-
ment characteristic of its adult conditions. All divisions of the large intestine
are at first freely movable, being suspended by a free mesocolon; but subsequently
the ascending and descending portions become fixed retroperitoneal structures
in consequence of adhesion of the opposed surfaces of the ascending and descending
mesocolons and of the dorsal parietal peritoneum. Occasionally the descending
mesocolon, more rarely the ascending, persists so that the bowel is more or less
movable in these divisions. The sigmoid colon usually remains mo^'able through-
out life.
The omental bursa, which at first reaches only as far as the greater curvature
of the stomach, grows downward as a double-layered, pouch-like fold, the interior
layer derived from the right leaf of the primitive mesogastrimn, its exterior layer
from the left leaf. This omental sac or greater omentum extends downward as an
apron-like fold in front of the transverse colon and the coils of the small intestine.
The anterior layer of the transverse mesocolon is at first quite distinct from the
1 Sometimes this condition persists throughout life, and it is then found that the duodenum does not cross from
the right to the left side of the vertebral column, but lies entirely on the right side of the mesal plane, where it is
continued into the jejunum; the arteries to the small intestine (rami intestini tenuis) also arise from the right instead
of the left aide of the superior mesenteric artery.
2 Sometimes the downward progress of the cecum is arrested, so that in the adult it may be found lying imme-
diately below the liver instead of m the right iliac region.
5252
THE ORGANS OF DIGESTION
Diaphragm
Greater curvature
Anterior lamella of greater omentum .
Posterior lamella of greater omentum
2Ya7isverse colon
Greater omentum
'se mesocolon
Duodenum
Small intestine
Fig. 990. — Illustrating the development of the bursa omentaHs, cavity of the greater omentum or lesser sac.
Fetal stage. * Lesser sac. (Hertwig.)
Stomach
Greater curvature
Posterior lamella of greater omentum
Transverse colon
Greater omentuv.
Lesser omentum
Pancreas
Part of omentum enclosing pane
Transverse mesocolon
Duodenum
Small intestine
Fig. 991- — Development of bursa omentalis. Infantile stage. Greater omentum covers the intestines and ha
fused with the transverse mesocolon. Pancreas is free from peritoneum posteriorly. (Hertwig.)
^ I Bursa omentalis.
Border of the
Dorsal
mesogastrium-
2- Duodenum.
Greater omentum.
Transverse colon.
Fig. 992. — Schematic figure of the bursa omentalis. etc. Human embryo of eight weeks. (Kollmann.l
THE PERITONEVM
1253
posterior layer of the bursa omentalis, but ultimately the two l)leiK], and hence the
greater omentum appears as if attached to the transverse colon (Figs. 990, 991,
and 992).
The lesser omentum is formed by a thinning of the mesoderm (jf the ventral
mesogastrium which attaches the stomach and part of the duodenum to the ventral
abdominal wall. By the subsequent growth of the liver this leaf is divided into
two parts — viz., the falciform and coronary ligaments between the liver and the
abdominal wall and Diaphragm; and the lesser or gastrohepatic omentum, be-
tween the liver and the stomach.
Ventral mesofjasti u(
Fig, 093. — Abdominal part of al
uperior mesenteric
artery.
Mesentery.
mesenteric artery.
r:iTi:il ;iiid its attachment to the primitive or common mesentery.
il.iiu (jf six weelcs. (Kollmann.)
Vertical Disposition of the Greater Sac (Fig. 995). — It is convenient to trace the
greater sac from the back of, the abdominal wall at the level of the umbilicus.
On following the parietal peritoneum upward from this level it is seen to be
reflected around a fibrous cord, the ligamentum teres or impervious umbilical vein
(Figs. 998 and 1087), which reaches from the umbilicus to tlie under surface of
the liver. This reflection forms a somewhat triangular fold, the falciform or
suspensory ligament of the liver (ligamentum falciforme hepatis), attaching the
upper and anterior surfaces of the liver to the Diaphragm and abdominal wall.
With the exception of the line of attachment of this ligament the peritoneum
covers the whole of the under surface of the anterior part of the Diaphragm and
is continued from it on to the upper surface of the right lobe of the liver as the
superior layer of the coronary ligament, and on to the upper surface of the left
lobe as the superior layer of the left lateral ligament of the liver. Covering the
upper and anterior surfaces of tiie liver it is continued around i^" sharp margin
on to its under surface, where it presents the following relations: (a) It covers
the under surface of the right lobe and is reflected from the back part of this to
the upper extremity of the right kidney, forming in this situation die inferior
layer of the coronary ligament; from the kidney it is carried downward to the tluo-
denum and hepatic flexure of the colon and inward to the inferior vena cava.
1254
THE ORGANS OF DIGESTION
where it is continuous with the posterior wall of the lesser sac. Between the two
layers of the coronary ligament" there is a triangular surface of the liver which
is devoid of peritoneal covering; this is named the bare area of the liver, and is
attached to the Diaphragm by areolar tissue. Toward the right margin of the
liver the two layers of the coronary ligament gradually approach each other, and
ultimately fuse to form a small triangular fold connecting the right lobe of the
liver to the Diaphragm, and named the right lateral ligament of the liver. The
Intel lud iiKimiicu
OTll
^upenoi ^et,ital
ai te) y
(Idle mgutiial,
fossa
Fig, 994. — Posterior view of the anterior abdominal wall in its lower half. The peritoneum is in place,
and the various cords are shining through. (After Joessel.)
apex of the triangular bare area corresponds to the point of meeting of the two
layers of the coronary ligament, its base with the fossa of the inferior vena cava.
(b) It covers the lower surface of the quadrate lobe, the under and lateral surfaces
of the gall-bladder, and the under surface of the posterior border of the left lobe;
it is then reflected from the upper surface of the liver to the Diaphragm as the
inferior layer of the left lateral ligament, and from the transverse fissure and
the fissure for the ligamentum venosum to the lesser curvature of the stomach as
the anterior layer of the gastrohepatic, or lesser omentum. If this layer of the lesser
omentum be followed to the right it will be found to turn around the hepatic
artery, bile duct, and portal vein and become continuous with the anterior wall of
the lesser sac, forming a free folded edge of peritoneum.
Traced downward it covers the antero-superior surface of the stomach and the
commencement of the duodenum, and is carried down from the greater curvature
of the stomach into a large free fold, the gastrocolic or greater omentum (Figs. 996
and 1002). Reaching the free edge of this fold, it is reflected upward to cover
the under and posterior surfaces of the transverse colon, and thence to the pos-
THE PERITONEUM
1 255
terior abdominal wall as the inferior layer of the transverse mesocolon fFif;. 995).
It reaches the abdominal wall at the upper border of the tliird part of the duo-
denum, and is then carried down on the superior mesenteric v-essels to the small
intestine as the anterior layer of the mesentery. It encircles the intestine, and
Fig. 995. — Diagram showing the vertical disposition of the peritoneum. Lesser sac in red; greater
subsequently may be traced, as the posterior layer of the mesentery, upward and
backward to the abdominal wall. From this it sweeps down o^'er the aorta into
the pelvis, where it invests the sigmoid colon, its reduplication forming; the sigmoid
mesocolon (Fig. 1004). Leaving first the sides and then the front of the rectum,
it is reflected on to the base of the bladder, and, after covering the upper surface
of that viscus, is carried along the urachus and impervious hypogastric arteries
to the back of the abdominal wall, from which a start was made.
Between the rectum and the bladder the peritoneum forms, in the male, a pouch,
the rectovesical pouch (excavatio rectovesicalis), bounded on the sides by two
crescentic or semilunar folds (plicae rectovesicales), which pass from the posterior
surface of the bladder to the sides of the rectum; the bottom of this pouch is about
on a \e\e\ with the middle of the seminal vesicles — /. e., three inches or so from
the orifice of the anus. When the bladder is distended the peritoneum is carried
up with the expanded viscus, so that a considerable part of the anterior surface
of the latter lies directlv against the abdominal wall without the intervention of
1256 THE ORGANS OF DIGESTION
the peritoneal membrane. When the bladder is empty the peritoneum forms
a transverse fold over its upper surface (plica vesicalis transversa).
In the female the peritoneum is reflected from the rectum to the upper part
of the posterior vaginal wall, forming the rectovaginal pouch or pouch of Douglas
(excavatio rectouterina) (Fig. 996) . It is continued over the posterior surface
and fundus of the uterus on to its anterior surface, which it covers as far as
the junction of the body and cervix uteri, forming here a second but shallower
depression, the uterovesical pouch (excavatio vesicouferina). It is also reflected
from the sides of the uterus to the lateral wall of the pelvis on each side as two
expanded folds, the broad ligaments of the uterus (ligamenta lata uteri), in the
free margin of each of which is the Fallopian tube.
Vertical Disposition of the Lesser Sac (Fig. 995). — A start may be made in this
case on the posterior abdominal wall above the pancreas. From this region
the peritoneum may be followed upward on to the inferior surface of the Dia-
phragm, and thence on to the Spigelian and caudate lobes of the liver to the fissure
for the ligamentum venosum and the transverse fissure; this cul-de-sac is the Spige-
lian recess. Traced laterally, it is continuous over the inferior vena cava with the
posterior wall of the greater sac. From the liver it is carried downward to the
lesser curvature of the stomach as the posterior layer of the gastrohepatic omentum,
and is continuous on the right, around the hepatic artery, bile duct, and portal vein,
with the greater sac. The posterior layer of the gastrohepatic omentum is carried
down to the greater curvature of the stomach as a covering for the postero-inferior
surface of this viscus, and from the greater curvature is continued downward
as the deep layer of the greater or gastrocolic omentum. From the free margin
of this fold it is reflected upward on itself to the anterior and superior surfaces of
the transverse colon and thence as the superior layer of the transverse mesocolon
to the upper border of the third part of the duodenum, from which it may be
followed over the front of the pancreas to the level at which a start was made.
It will be seen that the loop formed by the wall of the lesser sac below the transverse
colon follows, and is closely applied to, the deep surface of that formed by the
greater sac, and that the greater omentum or large fold of peritoneum which hangs
in front of the small intestine therefore consists of four layers, two anterior and
two posterior, separated by the potential cavity of the lesser sac though inseparably
blended, as a rule, in the adult.
Horizontal Disposition of the Peritoneum. — Below the transverse colon the
arrangement is extremely simple, as it includes only the greater sac (Fig. 997) ;
above the level of the transverse colon it is more complicated on account of the
existence of the two sacs. Below the transverse colon it may be considered in
in three regions — ^viz., in the pelvis and in the abdomen proper, upper and lower
portions.
1. 7/1 the Pelvis. — ^The peritoneum here follows closely the surfaces of the pelvic
viscera and the irregularities of the pelvic walls and presents important differences
in the two sexes: (a) In the male it encircles the sigmoid flexure, from which
it is reflected to the posterior wall as a fold, the sigmoid mesocolon. It then
leaves the sides and, finally, the front of the rectum, and is continued to the bladder;
on either side of the rectum it forms a fossa, the pararectal fossa, which varies in
size with the distention of the rectum. In front of the rectum the peritoneum
forms the rectovesical pouch, which is limited laterally by peritoneal folds extending
from the sides of the bladder to the rectum and sacrum. These folds are known
from their position as the rectovesical or sacrogenital folds. The peritoneum of
the anterior pelvic wall covers the superior surface of the bladder, and on either
side of this viscus forms a depression, termed the paravesical fossa, and limited
externally by the fold of peritoneum covering the vas deferens. The size of this
fossa is dependent on the state of distention of the bladder; when the bladder is
empty, a variable fold of peritoneum, the plica vesicalis transversa, divides the
THE PERITONEUM
1257
fossa into two portions. On the peritoneum between the paravesical and para-
rectal fossffi the only elevations are those produced by the ureters and the internal
iliac vessels. (6) In the female, pararectal and paravesical fosstB similar to those
in the male are present; the outer limit of the paravesical fossa is the peritoneum
investing the round ligament of the uterus. The rectovesical pouch is, however,
LESSER SSC
-FORAMEN OF
WINSLOW
WITH ARROW
PASSED
Fig. 996. — Diagrammatic mesal section of the female body, to show the peritoneum on vertical tracing.^ The
greater sac of the peritoneum is black and is represented as being much larger than in nature; the lesser sac is very
darkly shaded; the peritoneum on section is shown as a white line, and a white arrow is passed through the fora
men of Winslow from the greater into the lesser sac. (Cunningham.)
divided by the uterus and vagina into a small anterior uterovesical and a large,
deep, posterior rectovaginal pouch or pouch of Douglas. The sacrogenital folds
form the margins of the latter, and are continued on to the back of the uterus to
form a transverse fold, the torus uterinus. The broad ligaments extend from the
sides of the uterus to the lateral walls of the pelvis ; they contain in their free margins
the Fallopian tubes, and on their posterior surface the ovaries attached by the
mesovaria. Below, the broad ligaments are continuous witn the peritoneum on
the lateral walls of the pelvis. On the lateral pelvic wall behind the attachment
of the broad ligament, in the angle between the elevations produced by tlie
diverging internal and external iliac vessels, is a slight if>ssa, 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. </., j\Ian-
gabey monkey. As the fetus grows the
cecum increases in length more than in
breadth, so that it forms a longer tube than
in the primitive form and without the broad
base, but with the same inclination inward
of the apex toward the ileocecal junction.
This form is seen in others of the monkey
tribe, e. g., the spider monkey. As develop-
ment goes on, the lower part of the tube
ceases to grow and the upper part becomes
greatly increased, so that at birth there is a
narrow tube, the vermiform appendix, hang-
ing from a conical projection, the cecum.
This is the infantile form, and as it persists
throughout life, in about 2 per cent, of cases
it is regarded by Treves as the first of his
four types- of human ceca. The cecum is
conical and the appendix rises from its
apex. The three longitudinal bands start
from the appendix and are equidistant
from each other. In the second type, the
conical cecum has become quadrate by the
growing out of a saccule on either side of the
anterior longitudinal band. These saccules
are of equal size, and the appendix arises from between them instead of from the
apex of a cone. This t}'pe is found in about 3 per cent, of cases. The third type
is the normal type of man. Here the two saccules, which in the second type were
uniform, have grown at unequal rates, the right with greater rapidity than the left.
In consequence of this an apparently new apex has been formed by the growing
downward of the right saccule, and the original apex, with the appendix attached,
is pushed over to the left toward the ileocecal junction. The three longitudinal
bands still start from the base of the appendix, but they are now no longer equi-
distant from one another, because the right saccule has grown between the anterior
and postero-external bands, pushing them over to the left. This type occurs in
about 90 per cent, of cases. The fourth type is merely an exaggerated condition
of the third; the right saccule is still larger, and at the same time the left saccule
has been atrophied, so that the original apex of the cecum, with the appendix,
is close to the ileocecal junction, and the anterior band courses inward to the
same situation. This type is present in about 4 per cent, of cases.
Fig. 1050.— The ^
show the ileocecal ■
Tnd colon laid open to
^ In 310 adult males, Robinson found 8 per cent, with undescended cecum and appendix. Nondescent was
found in less than 4 per cent, of females, A partly descended cecum usually lies upon the right kidney.
1298
THE ORGANS OF DIGESTION
The Interior of the Cecum. — Corresponding to the surface sacculations are seen
the pouch-Hke depressions (haustra) bounded by the semilunar folds (plicae semi-
lunares coli) (Fig. 1050), corresponding to the surface constrictions which mark
off the saccules. The interior of the cecum is continued into the colon above,
and the orifice of the ileum and of the appendix open into it. These orifices,
guarded respectively by the ileocecal valve and by the valve of Gerlach, are
described on pages 1299 and 1301.
Pericecal Folds and Fossae. — See page 1266, and Figs. 1007 and 1008.
Ttpe III. Type II.
90%
Ttpe I (Treves).
Figs. 1051 to 105-1. — The four t\-pes of cecum.
The Vermiform Appendix {process7is vermiformis) (Figs. 1056 and 1062). — The
vermiform appendix is found only in man, the higher apes, and the wombat,
although in certain rodents a somewhat similar arrangement exists. In carnivo-
rous animals the cecum is very slightly developed; in herbivorous animals (with
a simple stomach) it is, as a rule, extremely large. It has been suggested that the
vermiform process in man is the degenerated remains of the herbivorous cecum,
which has been replaced by the carnivorous form. The vermiform appendix is
a long, narrow, worm-shaped, musculomembranous tube, which starts from what
was originally the apex of the cecum. After development has advanced the vermi-
form appendix comes off, as a rule, from the inner side of the posterior wall of the
cecum, below and behind the termination of the ileum. This origin usually cor-
responds to McBumey's point on the abdominal wall, two to three inches from the
anterior superior iliac spine on a line from this process to the umbilicus, and which
is the usual seat of the greatest tenderness in appendicitis. The origin of the
THE CECUM
1299
appendix varies with the type of cecum present. These variations are shown in
Figs. 1051-1054. The movable portion of the appendix may be met with in dif-
ferent situations. It may pass upward and in front of the cecum and colon,
upward and behind the cecum, and even behind the colon betwe>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<jni;; the narrow line of attachment of its
mesentery in its pi-oximal two-thirds or more.
The longitudinal muscle layer is thin and irregularly distrib-
uted, and in certain regions may be exceedingly thin or actually
absent, so that the peritoneal and submucous coats are contiguous
over small areas.
The circular muscle layer is a much thicker layer than the
preceding, and at the blind extremity forms a dome-like col-
lection of interlacing fibres. Both layers have openings at in-
tervals for the passage of bloodvessels.
The submucous coat varies greatly in thickness. It contains
bloodvessels, nerves, and lymphatics, and a large number of
lymphoid follicles (.300 to 400) and, at times, adipose tissue.
The mucous membrane (Fig. 10.56) is lined by columnar
epithelium and contains numerous solitary lymph follicles, glands
of Lieberkiihn (about 25,000), surrounded by diffuse lymphoid
tissue, bloodvessels, lymphatics, and nerves.
The muscularis mucosae may be absent, may be scanty, or
may be distinct. The lymphoid foUicles are visible to the naked
eye (Fig. 1056). Some of them are in the submucosa, some of
them chiefly in the mucosa, the bases of the latter, however, being
in the submucosa.
The ajteries of the cecum and appendix are derived from the
ileocolic branch of the superior mesenteric artery. Close to the
ileocecal junction the ileocolic artery gives off anterior and pos-
terior ileocecal branches to the terminal part of the ileum and
beginning of the large intestine. The terminal branches to the
cecum are called anterior and 'posterior cecal arteries. The appendix is supplied by the
appendicular artery, a branch of the posterior ileocecal artery (see p. 664).
The veins of the appendix are numerous, thin walled, and large. Veins from the submucous
plexus pass through the muscular gaps and enter the subperitoneal plexus. Veins from the sub-
peritoneal plexus pass into the veins in the mesoappendix which correspond to but do not really
Fig. 1056.— The internal sur-
face of the vermiforin appendix,
(Bonamy and Broca.)
ILEOCOLIC ARTERY
POSTERIOR
ILEOCECAL
ARTERY
AND VEIN
Fig. 1057. — Arteries and veins of the cecum and vermiform appendix seen from behind. (Poirier and Charpy.)
accom]5any the arteries (Lockwood). Most of the veins of the mesoappendix pass to the pos-
terior ileocecal vein, though some pass directly to the cecal vein. These veins are radicles of
the portal system.
The lymphatics of the cecum and appendix are described on page 794.
THE CECUM
1301
The Ileocecal Valve (valvuli coli) (Figs. 1060 and 1061). — The lower end of the
ileum terminates by opening into the inner and back part of the large intestine,
at the point of junction of the cecum with the colon. The opening is guarded
by a valve, consisting of two semilunar segments, an upper or colic segment {labium
s-uperius) and a lower or cecal segment {labium iiiferius), which project into the
EPITHELIUM
MUSCULAR LAYER
Fig. 1058. — Transverse section of the vermiform appendix of i
lumen of the large intestine. The upper one, nearly horizontal in direction, is
attached by its convex border to tlie point of junction of the ileum with the colon;
the lower segment, which is more concave and longer, is attached to the point of
junction of the ileum with the cecum. At each end of the aperture the two segments
ANTERIOR
LYMPHATICS
OF CECUM
Fig. 1039. — Lymph.itica of tlie cecum and appendix, anterior view. (Poirier and Charpy.)
of the valve coalesce, and are continued as a narrow membranous ridge around
the canal for a short distance. Each ridge is known as the frenulum of the valve
(frenulum valvulae coli). The left or anterior part of the aperture is rounded;
the right or posterior is narrow and pointed. In the formation of the valve the
termination of the small intestine invaginates for a short distance into the lumen
1302
THE ORGANS OF DIGESTION
of the large intestine (Fig. 1061), the invaginated portion of the wall of the small
intestine uniting with a corresponding portion of the wall of the large intestine.
Each segment of the valve is formed by a reduplication of the mucous membrane
and of the circular muscle fibres of the intestine, the longitudinal fibres and peri-
toneum being continued uninterruptedly
across the one portion of the intestine to
the other.
The surface of each segment of the
valve directed toward the ileum possesses
villi, and presents the characteristic
structure of the mucous membrane of the
ORIFICE O
Fig. lOGO. — Ileocecal valve of the circula
(Poirier.)
Fig, 1061. — Vertical section througli the cecum and
ileocecal valve. (Gegenbaur.)
small intestine; while that turned toward the large intestine is destitute of villi,
and marked with the orifices of the numerous tubular glands peculiar to the mucous
membrane of the large intestine. ' These differences in structure continue as far
as the free margins of the
valve. ^^Tien the cecum is
distended it is supposed that
the margins of the opening
are approximated so as to
pr€;vent reflux into the ileum.
It is known, however, that a
very large enema which dis-
tends the cecum and colon
may in part enter the ileum,
being driven there by waves
of reversed peristalsis. The
valve resists, but a certain
amount of pressure over-
comes it. Some believe that
the so-called ileocecal valve
is not a valve, but a distinct
sphincter. This has been
demonstrated to be true in
cats and dogs, but lacks dem-
onstration in man (p. 1.313).
AppUed Anatomy. — The vermiform appendix is very liable to become inflamed, the condi-
tion being known as appendicitis. The condition may be set up by a catarrhal inflammation
arising in the appendix or derived from the colon. It may remain catarrhal and then subside.
It may become purulent or may be purulent from the beginning. Anything which lessens vital
LONG MUSCU-
LAR FIBRES
FROM ILEUM
Fig. 1062.^ — Cecum and
•ermiform appendix; ileum cut through.
(Sappey.)
THE COLON
1.303
resistance makes the appendix a read.y prey to bacteria. Among causes which lessen resistance
are fecal concretions, twists of tlie mesoappendix cutting off the lilood supply, bruises inflicted
by the Psoas muscle (Byron Robinson), blocking of tlie outlet of the apjiendix by catarrhal
exudate, concretions, proliferated lymphoid tissue, or adhesions. Appendicitis may arise by the
appendix becoming twisted, owing to
the shortness of its mesentery, in con-
sequence of distention of the cecum.
As the result of inflammation, its
blood supply, which is mainly through
one large artery running in the meso-
appendix, becomes interfered with.
Again, in rarer cases, the inflamma-
tion is set up by the impaction of a
solid mass of feces or a foreign body
in the appendix. The inflammation
may result in ulceration and perforation,
or in gangrene of the appendix the ap-
pendix may be blocked and full of pus,
or abscess may form outside of it (appen-
dicular abscrss). These conditions re-
quire prompt operative interference,
and in cases of recurrent attacks of
appendicitis it is advisable to remove
this diverticulum between the attacks.
The cecum and appendix may be
implicated in cases of strangulated
hernia, giving rise to serious symptoms
of obstruction. An obstruction in the
distal part of the large bowel causes distention, particularly of the cecum, which sometimes
assumes enormous dimensions, and has been known to rupture, causing fatal peritonitis.
Fig. 1063. — Ileocecal valve. ( Sappey.)
The Colon.
The colon is divided into four parts — the ascending, transverse, and descending
colon and the sigmoid flexure.
The ascending colon {colon ascendens) is smaller than the cecum, with which
it is continuous. It passes upward, from its commencement at the cecum, oppo-
site the ileocecal valve, to the under surface of the right lobe of the liver, on the
right of the gall-bladder, where it is lodged in a shallow depression on the liver,
the impressio colica; here it bends abruptly forward and inward to the left, forming
the hepatic flexure (flexura coli dextra). It is retained in contact with the pos-
terior wall of the abdomen by the peritoneum, which covers its anterior surface
and sides, its posterior surface being connected by loose areolar tissue with the
Quadratus lumborum muscle, and with the front of the lower and outer part
of the right kidney (Fig. 1064). Sometimes the peritoneum almost completely
invests it, and forms a distinct but short mesocolon' (p. 1251). It is in relation,
in front, with the convolutions of the ileum and the abdominal parietes.
The transverse colon {colmi transversum) (Fig. 999), the longest and most
movable part of the large intestine, passes transversely from the right hypo-
chondriac region across the abdomen, within the confines of the epigastric and
umbilical zones, into the left hypochondriac region, where it ciir\-es downward
beneath the lower end of the spleen, forming the splenic flexure {flexiira coli
sinistra). In its course the transverse colon describes an arch, the concavity of
1 Treves states that after a careful examination of one hundred subjects, he found that in fifty-two there was
neither an ascending nor a descending mesocolon. In twenty-two there was a descendmg mesocolon, but no
trace of a corresponding fold on the other side. In fourteen subjects there was a mesocolon to both the ascend-
ing and the descending segments of the bowel; while in the remaining twelve there wa^ an ascending mesocolon,
but no corresponding fold on the left side. It follows, therefore, that in performing lumbar colostomy a meso-
colon may be expected on the left side in 36 per cent, of all cases, and on the right in 26 per cent. (The Anatomy
of the Intestinal Canal and Peritoneum in Man, 1885, p. 55.)
1304
THE OBGAXS OF DIGESTION
which is directed backward toward the vertebral column and a little upward.
It is almost completely invested by peritoneum, and connected to the posterior
Fig 1064 — Diagram of the relations of the large mtestme and kidnej s from behind
abdominal wall by a large and vade duplicature of that membrane, the transverse
mesocolon (Fig. 1013). The transverse colon is in relation, by its upper surface,
■with the hver and gall-bladder, the greater curvature of the stomach, and the lower
THE COLON
] :105
DESCENDING COLON
end of the spleen; by its under surface, with the small intestines; by its anterior
surface, with the anterior layers of the greater omentum and the abdominal
parietes; its posterior surface on the right side
is in relation with the second portion of the duo-
denum, and on the left side is in contact with
some of the con\'oIutions of the jejunum and
ileum.
The splenic flexure is in relation with the lower
end of the spleen and the tail of the pancreas. It
lies at a higher level than, and on a plane posterior
to, the hepatic flexure, and is attached to the Dia-
phragm opposite the tenth and eleventh ribs, by
a peritoneal fold, the phrenocolic ligament (see
p. 1264).
The descending colon {colon descendens) passes
downward through the left hypochondriac and
lumbar regions along the outer border of the left
kidney. At the lower end of the kidney it turns
. 1066. — Sigmoid colon and rectum, front vie
of the sigmoid colon. The small intestine i
'. The broken lines indicate the situation of the concealed part
drawn away, and the anus is turned forward. (Testut.)
inward toward the outer border of the Psoas muscle, along which it descends to
the crest of dae ilium, where it terminates in the sigmoid flexure. It is retained
1306 THE ORGANS OF DIGESTION
in position by the peritoneum, which covers its anterior surface and sides, its
posterior surface being connected by areolar tissue with the outer border of
the left kidney, and the Quadratus lumborum muscle (Fig. 1004). It is smaller
in calibre and more deeply placed than the ascending colon, and is more fre-
quently covered with peritoneum on its posterior surface than the ascending
colon (Treves).
The sigmoid flexure, pelvic colon, or sigmoid colon {colon sicjmoideum) (Figs.
1065 and 1066) is the narrowest part of the colon; it is situated in the left iliac fossa,
commencing from the termination of the descending colon, at the margin of the
crest of the ilium, and then forming a loop, which varies in length and position,
and which terminates in the rectum at the level of the attachment of the mesen-
tery upon the front of the third sacral vertebra. It passes downward about
two inches (5 cm.) parallel to the outer border of the Psoas muscle, then taking a
transverse direction enters the cavity of the pelvis, crosses this cavity from left to
right and a little upward to the lower margin of the right iliac fossa; thence it
passes downward, backward, and inward along the anterior surface of the sacrum
to its junction with the rectum. It is surrounded by the peritoneum and is
attached to the posterior abdominal wall by the mesosigmoid. "When the sigmoid
is lifted upward and to the right and the mesosigmoid is put slightly on the stretch
the intersigmoid fossa (p. 1267) is brought into view. When the sigmoid flexure
is empty most of it falls into the rectovesical or rectovaginal space (Fig. 1066).
When distended it mounts up into the abdomen, reaching to or even above the
umbilicus. The sigmoid flexure is in relation in front with the small intestine
and abdominal parietes. The sigmoid mesocolon is attached to a line running
downward and inward from the crest of the ilium, across the left Psoas muscle,
left external iliac artery and vein, left spermatic or ovarian vessels, and the left
ureter (Fig. 1004).
Applied Anatomy. — The diameter of the large intestine gradually diminishes from the
cecum, which has the greatest diameter of any part of the bowel, to the point of junction of the
sigmoid flexure with the rectum, at or a little below which point stricture most commonly occurs
and diminishes in frequency as" one proceeds upward to the cecum. When distended by some
obstruction low down, the outline of the large intestine can be defined throughout nearly the
whole of its course — all, in fact, except the hepatic and splenic flexures, which are more deeply
placed; the distention is most obvious in the two flanks and on the front of the abdomen just
above the umbilicus. The cecum, however, is that portion of the bowel which is, of all, most
distended (see p. 1297). The hepatic flexure and the right extremity of the transverse colon are
in close relationship with the liver, and abscess of this viscus sometimes bursts into the gut in this
situation. The gall-bladder may become adherent to the colon, and gallstones may find their
way through into the gut, where they may become impacted or may be discharged per anum.
The mobihty of the sigmoid flexure renders it more liable to become the seat of a volvulus or
twist than any other part of the intestine. It generally occurs in patients who have been the
subjects of habitual constipation, and in whom, therefore, the mesosigmoid is elongated. The
gut at this part being loaded with feces, from its weight falls over the gut below, and so gives
rise to the twist.
The Rectum (Intestinum Rectum) (Figs. 1067, 1068).
The rectum is continuous with the sigmoid flexure, while below it ends in the
anal canal. From its origin at the level of the third sacral vertebra it passes
downward, lying in the sacrococcygeal curve, and extends for about an inch (2.5
cm.) in front of, and a little below, the tip of the coccyx, as far as the apex of
the prostate gland. It then bends sharply backward to continue as the anal canal.
It therefore presents two antero-posterior curves. An upper, with its convexity
backward, is due to the conformation of the sacrococcygeal column. The lower
one has its convexity forward, and is angular. Two lateral curves are also
described — the one to the right, opposite the junction of the third and fourth sacral
TIIl^ RECTUM
1307
I GLAND
L TRANSVERSA
Fig. 1067.— Sagittal section in tVie median line of the male pelvis. Rectum distended. (Poirier and Charpy.)
BECTAL FOLD
Fig. 106S.— Jlcdian sagittal section of the female pelvis. Rectum distended. (Luschka.)
1308
THE ORGANS OF DIGESTION
vertebrae; the other to the left, opposite the sacrococcygeal articulation. They
are, however, of little importance.
The adult rectum measures about five inches (12.5 cm.) in length, and at its
commencement its calibre is similar to that of the sigmoid flexure, but near its
termination it is dilated to form the rectal ampulla. The rectum has no saccu-
lations comparable to those of the colon, but a sacculated condition, due to the
presence in its interior of valves (shortly to be described), is sometimes seen.
The peritoneum is related to the upper two-thirds of the rectum, covering at
first its front and sides, but lower down its front only; from the latter it is reflected
on to the seminal vesicles in the male and the posterior vaginal wall in the female,
forming the vesico-uterine cul-de-sac of Douglas.
The level at which the peritoneum leaves the anterior wall of the rectum to be
reflected on to the viscus in front of it is of considerable importance from a surgical
point of view, in connection with removal of the lower part of the rectum. It is
.higher in the male than in the female. In
the former the height of the rectovesical
pouch is about three inches (7.5 cm.) ; that is
to say, the height to which an ordinary index
finger can reach from the anus. In the
female the height of the rectovaginal pouch
is about two and a quarter inches (5.2
cm.) from the anal orifice. The rectum
is surrounded by a dense tube of fascia de-
rived from the fascia endopehina , but fused
behind with the fascia covering the sacrum
and coccyx. The fascial tube is loosely
attached to the rectal wall by areolar tissue
in order to allow the viscus to distend.
Fig. 1069. — Diagram of rectum, showing Hous-
ton's valves in the interior. (Cunningham.)
Relations of the Rectum. — The upper part
of the rectum is in relation, hehind, with the
superior hemorrhoidal vessels, the left PjTiformis
muscle, and left sacral plexus of nerves, which
separate it from the anterior surfaces of the sacral vertebra; in its lower part it lies directly
on the sacrum, coccyx, and Levatores ani, a dense fascia alone intervening; in front, it is sep-
arated above, in the male, from the posterior surface of the bladder; in the female, from the
posterior surface of the uterus and its appendages by some convolutions of the small intestine
(Fig. 1068). To the sides below the peritoneal reflections, the rectum is sm'rounded by cellular
tissue in wliich on each side lie the lateral sacral artery and the bifurcated hypogastric plexus of
RECTAL VALVES
Fig. 1070. Fig. 1071. Fig. 1072.
Figs. 1070-1072. — The anal canal and lower part of the rectum in the fetus. Fig. 1070. Aged four to five months.
Pig. 1071. Six months. Fig. 1072. Nine months. In each the anal canal is distinctly marked off from the rectum
proper; the columns of Morgagni and the rectal valves are distinct. (Cunningham.)
the sympathetic. This portion of the rectum is separated from the sacrum and coccyx by an
interval, the retrorectal space, which is filled with cellular tissue. The lower or prostatic portion
in the male is in relation anteriorly with the triangular portion of the base of the bladder, the
seminal vesicles, vasa deferentia, and, more anteriorly, with the prostate gland; in the female,
with the posterior wall of the vagina.
THE RECTUM
1309
The Anal Canal {pars analis recti) (Figs. 1070-1073).— The anal canal is
the terminal portion of the large intestine. It begins at the level of the apex of
the prostate, is directed downward and backward, and ends at the anus. It forms
an ano-le with the lower part of the rectum and measures an inch to an inch and
a half''(2.5 to 3.75 cm.) in length. It has no peritoneal covering, but is invested
b\ the Internal sphincter, supported by the Levatores ani muscles, and surrounded
at its termination by the External sphincter; in the empty condition it presents
the appearance of a longitudinal slit. Behind is a mass of muscle and fibrous
tissue, the anococcygeal body; in front of it, in the male, are the membranous por-
tion and bulb of the urethra, and the base of the triangular ligament, and in the
female it is separated from the lower end of the vagina by a mass of muscle and
fibrous tissue, named the perineal body.
PART OF H
LEVATOR ANI (
INTERNAL
SPHINCIER"
ANALCANALC hi ,^
ANAL VALVES
Fig. 1073. — The interior of the anal canal and lower part of the rectum, showing the columns of Morgagni and
the anal valves between their lower ends. The columns were more numerous in the specimen than usual.
(Cunningham.)
The Anal Orifice or Anus is the external opening of the anal canal, formed
by pigmented skin containing numerous sebaceous and sudoriparous glands
glaudulae circumanales) and furnished with hairs. "i-VTiile the anus is closed,
the skin around it is thrown into radial folds by the contraction of the External
sphincter.
Structure of Large Intestine.— The large intestine has four coats— serous, muscular, sub-
mucous, and mucous. The serous coat is derived from the peritoneum, and invests the different
portions of tiie large intestine to a variable extent. The cecum is completely covered by the
serous membrane, except in a small percentage of cases (5 or 6 per cent.), where a small portion
of the upper end of the posterior surface is uncovered. The ascending and descending colon
are usually covered only in front and at the sides; a variable amount of the posterior surface
is uncovered.' The transverse colon is almost completely invested, the parts corresponding to
the attachment of the great omentum and transverse mesocolon being alone excepted. The
sigmoid flexure is completely surrounded, except along the line to which the sigmoid mesocolon
is attached. The upper two-thirds of the rectum is covered in front and laterally by the peri-
toneum, but not posteriorly, between the two posterior folds of peritoneum, the so-called meso-
rectiim; later it is covered only on its anterior surface; and the lower portion is entirely devoid
of any serous covering. In the course of the colon the peritoneal coat is thrown into a number of
small pouches filled with fat, called appendices epiploicae. They are chiefly appended to the
transverse colon, and are particularly numerous along the anterior band.
The muscular coat consists of an external longitudinal and an internal circular layer of smooth
muscle tissue.
The longitudinal fibres do not form a uniform layer over the whole surface of the large intes-
tine. In the cecum and colon they are especially collected into three flat longitudinal bands
1 See footnote, page 1303.
];310 THE ORGANS OF DIGESTION
or taeniae {taenicB coli) (Figs. 104S and 1049), each being about half an inch (12 mm.) in width,
and named, respectively, the mesocolic, omental, and free longitudinal bands or tseniee. These
bands commence at the base of the vermiform appendix, which structure is surrounded bv a
uniform layer of longitudinal muscular fibres. The bands pass from the base of the appendix
to the rectum. At this point they broaden, fuse, and surround the rectum. On the ascending,
descending, and sigmoid colon the mesocolic band {taenia mesocolica) is posterior and internal;
the omental band {taenia omentalis) is posterior and external; the free band {taenia libera) is
anterior. On the transverse colon the taenia Ubera is inferior; the taenia mesocolica is poste-
rior; the taenia omentalis is anterior and superior. These bands are one-sixth shorter than the
other coats of the intestine to which they are applied, and serve to produce the sacculi (Fig.
1049), which are characteristic of the cecum and colon; accordingly, when they are dissected off,
the tube can be lengthened, and its sacculated character becomes lost. There are three rows of
the sacculations separated from each other by the longitudinal bands. These pouches are also
subdivided by transverse furrows which correspond to concave folds of mucous membrane,
called semilunar folds {plicae semilunares coli). In the sigmoid flexure the longitudinal fibres
become more scattered, and around the rectum they spread out and form a layer which com-
pletely encircles this portion of the gut, but is thicker on tlie anterior and posterior surfaces than
on the lateral surfaces. In addition to the muscular fibres of the bowels, two bands of smooth
muscle fibres arise from the second and third coccygeal vertebrae, and pass downward and for-
ward to blend with the longitudinal muscle tissue on the posterior wall of the anal canal. They
are known as the rectococcygeal muscles {m. rectococcygeus).
The circular fibres form a thin layer over the cecum and colon, being especially accumulated
in the intervals between the sacculi. In the rectum the circular fibres constitute a thick layer,
and in the anal canal they become numerous and constitute the Internal sphincter.
The submucous coat {tela submucosa) connects the muscular and mucous layers closely
together. Solitary follicles are quite numerous here.
The mucous membrane, in the cecum and colon, is pale, smooth, destitute of villi, and raised
into numerous crescentic folds which correspond to the intervals between the sacculi. In the
rectum it is thicker, of a darker color, more vascular, and connected loosely to the muscular
coat, as in the oesophagus. It consists of simple columnar and goblet cells resting upon a base-
ment membrane, beneath which is seen the tunica propria, which contains the capillaries and a
considerable amount of diffuse lymphoid tissue. Externally, is seen the muscularis mucosae.
Simple tubular glands, lined chiefly by goblet cells, are present. They are much broader than
those of the small intestine.
Wlien the lower part of the rectum is contracted, its mucous membrane is thrown into a num-
ber of folds, which are longitudinal in direction and are effaced by the distention of the gut.
Besides these, are certain permanent horizontal folds, of a semilunar shape, known as the rectal
or Houston's valves (Figs. 1070 to 1072). They are usually three in number; sometimes a fourth
is found, and occasionally only two are present.' One is situated near the commencement of the
rectum, on the right side; a second extends inward from the left side opposite the middle of the
sacrum; a third, the largest and most constant, projects backward from the forepart of the
rectum, opposite the base of the bladder. When a fourth is present, it is situated nearly an inch
(2. .5 cm.) above the anus on the left and posterior wall of the tube. These folds are about half
an inch (12 mm.) in width and contain some of the circular fibres of the gut. In the empty
state of the intestine they overlap each other so effectually that they render the introduction of
a bougie or the finger somewhat difficult, and their use seems to be "to support the weight of
fecal matter, and prevent its urging toward the anus, where its presence always excites a sensa-
tion demanding its discharge."
The lumen of the anal canal presents, in its upper half, a number of vertical folds, produced
by an infolding of the mucous membrane and some of the muscle tissue. They ai-e known as
the columns of Morgagni or anal columns (columnae rectales [Morgagni]) (Figs. 1073 and 1074).
There are from five to ten of these folds, each of which is about half an inch long. They are
most prominent when the Sphincter contracts. The outer angle of each column below passes
into a semilunar valve. The grooves between the columns are shallow above and deeper below,
and end in the anal valves. The valves of Morgagni or anal valves (Figs. 1073 and 1074)
are folds wliich stretch from the base of one column to another, and form the anal pockets
or crypts of Morgagni {ximix rectales). Just below the anal valves is the junction of the mucous
memljrane of the anal canal with the skin; this is indicated by the so-called white line of Hilton
or anocutaneous line of Hermann (Fig. 1074).
Vessels and Nerves of the Large Intestine. — The arteries (see also p. 664) supplying the
large intestine give off large branches, which ramify between the muscular coats supplying them,
and, after dividing into small vessels in the submucous tissue, pass to the mucous membrane.
The cecum, the appendix, and the ileocecal valve are supplied by the branches from the anasto-
motic loops between the right coUc and ileocolic branches of the superior mesenteric artery
^ Dublin Hospital Reports, vol. v, p. 163.
THE RECTUM
1311
(Fig. 1075). The ascending colon is supplied by the right colic, and the transverse colon by
the middle colic branch of the superior mesenteric. The descending colon is supi^lied by the
^^\.Ly. \\%;^^^
LULAH TISSUE
Fig. 1074. — Inner wall ot the lower end of the rectum and anus. On the right the mucous membrane has
been removed to show the dilatation of the veins and how they pass through the muscular wall to anastomose
with the external hemorrhoidal plexus. (Luschka.)
Fig. 1075. — The arterial blood supply of the anterior (ventral) surface of the cecum and appendix: .4. Ileo-
colic artery. B. Cecal appendicular artery. D. Anterior cecal artery. F and G. Appendicular artery. Note
that the cecal and appendicular arteries anastomose by fine capillaries, both ventrally and dorsally. C. Iliac
artery. 1. Right colon. 2. External sac cuius of cecum (to right of taenium coli). 3. Appendix. 4. Iliac
muscle. 5. Psoas muscle, (Robinson.)
1312
THE ORGANS OF DIGESTION
left colic branch of the inferior mesenteric, and the sigmoid flexure by the sigmoid branches
of the inferior mesenteric. The rectum (Fig. 1076) is supplied mainly bj- the superior hemor-
rhoidal branch of the inferior mesenteric, but also at its lower end by the middle hemorrhoidal
from the internal Uiac, and the
inferior hemorhoidal from the
internal pudic artery. The
superior hemorrhoidal, the con-
tinuation of the inferior mesen?
teric, divides into two branches,
which run down either side of the
rectum to within about five inches
(12.5 cm.) of the anus; they here
split up into about six branches,
which pierce the muscular coat
and descend between it and the
mucous membrane in a longitu-
dinal direction, parallel with each
other as far as the Internal
sphincter, where they anastomose
with the other hemorrhoidal arte-
ries and form a series of loops
around the anus. The veins of
the large intestine correspond to
the arteries and join the superior
and inferior mesenteric veins
which join the portal vein. The
veins of the rectum (Fig. 1076)
commence in a plexus of vessels
which surrounds the lower ex-
tremity of the intestinal canal.
In the vessels forming this
plexus are small saccular dilata-
tions just within the margin of
the anus (Figs. 1074 and 1076);
from it about six vessels of con-
siderable size are given off.
These ascend between the mus-
cular' and mucous coat for about
five inches (12.5 cm.), running
parallel to each other; they then
pierce the muscular coat, and,
by their union, form a single
trunk, the superior hemorrhoidal
vein, which empties into the
inferior mesenteric tributary of
the portal vein. This arrange-
ment is termed the hemorrhoidal
plexus (Fig. 523); it communi-
cates with the tributaries of the
middle and inferior hemorrhoidal
veins at its commencement, and thus a communication is established between the systemic
and portal circulations. The inferior hemorrhoidal veins empty into the internal pudic
veins, and the middle hemorrhoidal veins empty into the internal iliac veins.
The lymphatics of the large intestine are described on page 794.
The nerves are derived from the sympathetic plexuses around the branches of the superior
and inferior mesenteric arteries. They are distributed in a similar way to those found in the
small intestine. The spinal centre for the nerves of the anus and rectum is situated in the first
and second sacral segments of the spinal cord.
Fig. 1076. — The bloodvessels of the rectum and anus, showing the
distribution and anastomosis on the posterior surface near the termi-
nation of the gut. (Poirier and Charpy.)
Movements and Innervation of the Intestines.
Movements. — As the small intestine is devoid of any sphincter arrangement, peristalsis cannot
mix the food as it does in the pyloric portion of the stomach. The process by which the food is
mixed with the secretions and is brought against the intestinal wall for absorption is called by
Cannon "rhythmic segmentation." Rhythmic motions "mix the food and expose it to the
MOVEMENTS AND INNERVATION OE THE INTESTINES V.Mi
Gland of Lieierkuhn
A//^B
~!l2^^i0!SiM^^iS^^&l^^^<h SoUtary gland
mucosa without advancing it apprcriativdij along the canal."' In this process constrictions occur
in the circular fibres, with the result that a collection of stationary food is divided into a number
of segments. In the middle of each segment constrictions appear and the earlier constrictions
relax. Then the latter constrictions relax and the earlier reappear, and so on until the food is
thoroughly mixed with digestive secretions. Finally, the food is driven on by peristalsis, coming
again to rest, and being again subjected to "rhythmic segmentation." Cannon says that in the
duodenum "rhythmic segmentation" lasts for several minutes, but in other parts of the intestine
it may continue for half an hour or more, the food which is being subjected to it scarcely moving
aloncr the canal. It is probable that in man there are from seven to eight segmentations per
minute in a given area. It is also probable that there is a sphincter action at the ileocecal opening.
Cannon divides the large intestine into two parts — a distal part, in which the material is hard
and lumpy and is "advanced by rings of tonic contraction," and a proximal part, in which the
material is soft. In this part " the common movements are waves of constriction running back-
ward toward the cecum." The resistance of
the valve or sphincter enables reversed peri-
stalsis or antiperistalsis to mix the food.
When more food enters from the small intes-
tine, antiperistalsis ceases, tonic contraction of
the cecum and proximal portion of the colon
occurs, some of the food is merged into the
transverse colon, and antiperistalsis again
begins to act on what remains. The above
facts have been observed in animals and are
probably true in man.
Innervation. — The vagus fibres of the
small intestine seem to excite contraction of
the circular fibres after a brief preliminary
period of inhibition.^ Some observers main-
tain that the splanchnic fibres are inhibitory,
but others claim that they are also motor.
The local reflex of the small intestine is in
Auerbach's plexus. Cannon quotes Bayliss
and Starling to the effect that the pelvic visceral
nerves to the large intestine, "arising like
the vagus from the central nerve system, are
augmentary nerves, whereas the supply from
the sympathetic system is purely inhibitory
in its action." It is further contended that
the pelvic visceral nerves are distributed to
the distal colon only. "The region of anti- _ .„ , .
..T'j ^^1, s • --„i Fig. 1077. — Transverse section of wall of large intestine.
peristalsis does not, tneretore, receive motor
imjiulses from the pelvic nerves."
Surface Form.— The coils of the small intestine occupy the front of the abdomen below the
transverse colon, and are covered more or less completely by the great omentum. For the most
part the coils of the jejunum occupy the left side of the abdominal cavity— i. e., the left lumbar
and inguinal regions and the left half of the umbilical region— while the coils of the ileum are
situated to the right, in the right lumbar and inguinal regions, in the right half of the umbilical
region, and also in the hypogastric region. The cecum is situated in the right inguinal region.
Its position varies slightly, but the mid-point of a line drawn from the anterior superior spinous
process of the ilium to the symphysis pubis will about mark the middle of its lower border. It is
comparatively superficial. " From it the ascending colon passes upward through the right lumbar
and hypochondriac regions, and becomes more deeply situated as it ascends to the hepatic flexure,
which is deeply placed under cover of the liver. The transverse colon crosses the belly trans-
versely on the confines of the umbilical and epigastric regions, its lower border being on a level
slightly above the umbilicus, its upper border just below the greater curvature of the stomach.
The splenic flexure of the colon is situated behind the stomach in the left hypochondrium, and
is on a higher level than the hepatic flexure. The descending colon is deeply seated, passing
down through the left hvpochondriac and lumbar regions to the sigmoid flexure, which is situ-
ated in the left inguinal' region, and which can be felt in thin persons, with relaxed abdominal
walls, rolling under the fingers when empty, and when distended forming a distinct bulge. The
usual position of the base of the vermiform appendix is indicated by a point on the cutaneous
surface two to three inches (.5-7.5 cm.) from the anterior superior spinous process of the ilium, on-
a line drawn from tliis process to the umbilicus. This is known as McBumey's point. Another
mode of defining the position of the base of the appendix is to draw a line between the anterior
superior spines of the ilia and marking the point where this line intersects the right semilunar
line.
tudinal muscle
jlbres
' Medical Newa, May 20. 1905.
2 Bayliss and Starling, Journal of Physiology, 1899.
1314 THE ORGANS OF DIGESTION
Upon introducing the finger into the rectum, the membranous portion of the urethra can
be felt, if an instrument has been introduced into the bladder, exactly in the middle line; behind
and above this the prostate gland can be recognized by its shape and hardness and any enlarge-
ment detected; above the prostate the fluctuating wall of the bladder when full can be felt,
and if thought desirable it can be tapped in this situation; on either side and behind the prostate
the seminal vesicles can be readily felt, especially if enlarged by tuberculous disease. Behind,
the coccyx is to be felt, and on the mucous membrane one or two of Houston's folds. The
ischiorectal fossae can be explored on either side, with a view to ascertaining the presence of
deep-seated collections of pus. Finally, it will be noted that the finger is firmly gripped by the
sphincter for about an inch (2.5 cm.) up the bowel.
Applied Anatomy. — The small intestine is much exposed to injury, but, in consequence
of its elasticity and the ease with which one fold glides over another, it is not so frequently rup-
tured as would otherwise be the case. Any part of the small intestine may be ruptured, but
probably the most common situation is the transverse duodenum, on account of its being more
fixed than other portions of the bowel, and because it is situated in front of the bodies of the
vertebrae, so that if this portion of the intestine is struck a sharp blow, as from the kick of a
horse, it is unable to glide out of the way, but is compressed against the bone and lacerated.
Wounds of the intestine sometimes occur. If the wound is a small puncture, under, it is said,
eie-quarter of an inch (6 mm.) in length, there may be no extravasation of the contents of the
bowel. The mucous membrane becomes everted and perhaps plugs the little opening. The
bowels, therefore, may be punctured with a fine capillary trocar, in cases of excessive distention
of the intestine with gas," without much danger of extravasation. A longitudinal wound gapes
mOre than a transverse wound, owing to the greater thickness of the circular muscular coat. In
closing a wound of the intestine, use Lembert's inversion sutures, which bring the peritoneal
surfaces in contact. Halsted showed that these sutures must include the tough submucous
coat. The portions of intestine which lie in the pelvis are inflamed in pelvic peritonitis and
become embedded in adhesions. The portions of intestine which may be present are the termi-
nation of the ileum, the portion of small intestine with the largest mesentery (Treves), the rectum,
and the pelvic colon. The small intestine, and most frequently the ileum, may become strangu-
lated by internal bands, or through apertures, normal or abnormal. The bands may be formed in
several different ways: they may be old peritoneal adhesions from previous attacks of peritonitis;
or adherent omentum from the same cause; or the band may be formed by Meckel's diverticulum,
which has contracted adhesions at its distal extremity; or the band may be the result of the
abnormal attachment of some normal structure, as the adhesion of two appendices epiploicae,
or an adherent vermiform appendix or Fallopian tube. Intussusception or invagination of the
small intestine may take place in any part of the jejunum and ileum, but the most frequent situa-
ation is at the ileocecal valve, the valve forming the apex of the entering tube. This form may
attain great size, and it is not uncommon in these cases to find the valve projecting from the anus.
Stricture, the impaction of foreign bodies, and twisting of the gut (volvulus) may lead to intestinal
obstruction. Volvulus is most common in the sigmoid flexure. Meckel's diverticulum may
itself become twisted and strangulated.
Resection of a portion of the intestine may be required in cases of gangrene of the bowel; in
cases of intussusception; for the removal of a newgrowth in the bowel; in dealing with artificial
anus; and in cases of rupture. The operation is termed enterectomy, and is performed as follows:
The abdomen having been opened and the amount of bowel requiring removal having been deter-
mined upon, the gut must be clamped on either side of this portion in order to prevent the escape
of any of the contents of the bowel during the operation. The portion of bowel is then separated
above and below by means of scissors. If the portion removed is small, it may be simply removed
from the mesentery at its attachment and the bleeding vessels tied ; but if it is large, it will be
necessary to remove also a triangular piece of the mesentery, and having secured the vessels,
suture the cut edges of this structure together. The surgeon then proceeds to unite the cut
ends of the bowel. He may do it by the operation termed end-to-end ana^tomosk. There
are many ways of doing this, which may be divided into two classes — one, where the anastomosis
is made by means of some mechanical appliance, such as Murphy's button, or one of
the forms of decalcified bone bobbins; and the other, where the operation is performed by
simply suturing the ends of the bowel in such a manner that the peritoneum covering the free
divided ends of the bowel is brought into contact, so that speedy union may ensue.
In some cases after resection each open end of the gut is closed, the side of the terminal portion
is sutured to the side of the initial portion, a fistula is made in each, and the suturing is com-
pleted so as to cause the two flstulse to correspond. A permanent side-to-side opening is thus
made. Lateral anastomosis without resection may be practised between two pieces of intestine,
-in order to side-track an intervening portion, which is the seat of malignant disease or of an
artificial anus. Complete exclusion of a portion of intestine is performed for irremovable tumors
or persistent fecal fistulse of the large intestine. The intestine is cut through above and below
the diseased area and the ends of the healthy gut are united to each other, or the larger end is
closed, an opening is made into the side of the larger end and the smaller end is implanted in it
MOVEMENTS AND INNERVATION OF THE INTESTINES 1315
{lateral implantation). The two ends of the excluded portion are fastened to the skin and are
left open.
In ascites resultinfi from cirrhosis of the hver, benefit occasionally follows the performance of
Talma's operation [rpijdiiprxii). The abdomen is' ojjened and the omentum is sutured to the
anterior abdominal wall or in the abdominal wound, in the hope of establishing a more free
communication between the portal and systemic circulations, thus lowering portal pressure.
Hernia. — The two chief sites at which e.xternal hernia may take place are the inguinal region
and the crural canal. The description of the inguinal canal and its relations will be found on
pages 437 to 439 and that of the crural canal on pages 503 and 684. Some points in regard
to the disposition of the peritoneum in these regions may, however, be recapitulated here.
Between the upper margin of the front of the pelvis and the umbilicus, the peritoneum,
when viewed from behind, will be seen to be raised into fine folds with intervening depressions,
by more or less prominent bands which converge to the umbilicus. The urachus, situated in
the middle line, is covered by a fold of peritoneum known as the plica urachi. On either side of
this a fold of peritoneum around the impervious hypogastric artery forms the plica hypogastrica.
To either side of these three cords is the deep epigastric artery covered by the plica epigastrica.
Between these raised folds are depressions constituting the so-called fossae. The most internal,
between the plica urachi and plica hypogastrica, is known as the internal inguinal fossa {fovea
supravesicalis). The middle one is situated between the plica hyjiogastrica and plica epigas-
trica, and is termed the middle inguinal fossa {fovea iinjiiiiintix iiinliiilix). The external one is
external to the plica epigastrica and is known as the external inguinal fossa {fovea inguinalis
lateralis). Occasionally the deep epigastric artery corresponds in position to the impervious
hypogastric artery, and then there is but one fold on each side of the middle line. In the usual
position of the parts the floor of the external inguinal fossa corresponds to the internal abdominal
ring, and into this fossa an oblique inguinal hernia descends. To the inner side of the plica
epigastrica are the two internal fossae, and through either of these a direct hernia may descend.
The whole of the space between the deep cpii^astric artery, the margin of the Rectus and Pou-
part's ligament, is known as Hesselbach's triangle. Below the level of Poupart's ligament
is a small depression corresponding to ihe jiosiiion of the crural ring. It is known as the femoral
fossa, and into it a femoral hernia descends.
Inguinal Hernia. — Inguinal hernia is that form of protrusion which makes its way through
the abdomen in the inguinal region. There are two principal varieties of it — external or oblique,
and internal or direct.
In oblique inguinal hernia the intestine escapes from the abdominal cavity at the internal ring,
pushing before it a pouch of peritoneum which forms the hernial sac. As it enters the inguinal
canal it receives an investment from the extraperitoneal tissue and is enclosed in the infun-
dibuliform fascia. In passing along the inguinal canal it displaces upward the arched fibres
of the Transversalis and Internal oblique, and receives a covering of Cremaster muscle and
cremasteric fascia. It then passes along the front of the spermatic cord and escapes frCm the
inguinal canal at the external ring, becoming invested by intercolumnar fascia. Lastly, it
descends into the scrotum, receiving coverings from the superficial fascia and the integument.
The seat of stricture in oblique inguinal hernia is at either the external or internal abdominal
ring; most frequently in the latter situation. If it is situated at the external ring, the division of
a few fibres at one point of the circumference is all that is necessary for the replacement of the
hernia. If at the internal ring, it is necessary to divide the aponeurosis of the External oblique
so as to lay open the inguinal canal; in dividing the aponeurosis the incision should be directed
parallel to Poupart's ligament, and the constriction at the internal ring should then be divided
directly upward.
When the intestine passes along the inguinal canal and escapes from the external ring into the
scrotum, it is called complete oblique inguinal or scrotal hernia. If the intestine does not escape
from the external ring, but is retained in the inguinal canal, it is called incomplete inguinal
hernia or bubonocele. In each of these cases the coverings which invest it will depend upon
the extent to which it descends in the inguinal canal.
There are some other varieties of oblique inguinal hernia (Figs. 1078 to 1082) depending
upon congenital defects in the processus vaginalis, the pouch of peritoneum which precedes
the descent of the testis. Normally this pouch is closed before birth, closure commencing at
two points — viz., at the internal abdominal ring and at the top of the epididymis, and gradually
extending until the whole of the intervening portion is converted into a fibrous cord. From
failure in the completion of this process, variations in the relation of the hernial protrusion to
the testis and tunica vaginalis are produced; these constitute distinct varieties of inguinal
hernia — viz., congenital, infantile, encysted, and hernia of the funicular process.
Where the processus vaginalis remains patent throughout, the cavity of the tunica vaginalis
communicates directly with that of the peritoneum. The intestine det":ends along this pouch
into the cavity of the tunica vaginalis which constitutes the sac of the hernia, and the gut lies in
contact with the testis. Though this form of hernia is termed congenital, the term does not imply
that the hernia existed at birth, but merely that a condition is present which may allow of the
1316
THE ORGANS OF DIGESTION
descent of the hernia at any moment. As a matter of fact, congenital hernise frequently do not
appear until adult life.
Where the processus vaginalis is occluded at the internal ring only and remains patent through-
out the rest of its extent, two varieties of oblique inguinal hernia may be produced — viz., infantile
Fig, 1078. — Commoii scrotal hernia.
Fig, 1079. — Congenital hernia
Fig. 10S2, — Hernia into the funicular process.
Figs. 1078 to 1082. — Varieties of oblique inguinal hernia.
and encysted hernite. In the infantile form (Fig. 1080) the bowel pressing upon the septum and
the peritoneum in its immediate neighborhood causes it to yield and form a sac which descends
behind the tunica vaginalis; so that in front of the bowel there are three layers of peritoneum.
MOVEMENTS AND INNERVATION OF THE INTESTINES 1317
the two layers of the tunica vaginalis and its own sac. In the encysted form (Fig. 1060) pressure
at the occkided spot causes the septum to yield and form a sac which projects into the tunica
vaoinalis, forming thus a sac within a sac, so that in front of the bowel there are two layers of
peritoneum, one from the tunica vaginalis and one from its own sac.
Where the processus vaginalis is occluded at the lower point only, i. e., just above the testis,
the intestine descends into the pouch of peritoneum as far as the testis, but is prevented from
enterincf the sac of the tunica vaginalis by the septum which has formed between it and the
pouch. "^ This is Icnown as hernia into the funicular jrrocess; it resembles the congenital form
e.Kcejjt that instead of envelo|)ing the testis it lies above it.
In direct inguinal hernia the protrusion makes its way through some part of Hesselbach's
triangle, either through {a) the outer part, where only extraperitoneal tissue and transversalis
fascia intervene between the peritoneum and the aponeurosis of the External oblique; or through
(i) the conjoined tendon which stretches across the inner two-thirds of the triangle between the
artery and the middle line. In the former the hernial protrusion escapes from the abdomen on
the outer side of the conjoined tendon, pushes before it the peritoneum, extraperitoneal tissue,
and transversalis fascia, and enters the inguinal canal. It passes along nearly the whole length
of the canal and finally emerges from the external ring, receiving an investment from the inter-
columnar fascia. The coverings of this form of hernia are similar to those of the oblique form,
except that a portion derived from the general layer of transversalis fascia replaces the infun-
dibuliform fascia.
In the second form, which is the more frequent, the hernia is either forced through the fibres
of the conjoined tendon, or the tendon is gradually distended in front of it so as to form a com-
plete investment for it. The intestine then enters the lower end of the inguinal canal, escapes at
the external ring lying on the inner side of the cord, and receives additional coverings from the
external spermatic fascia, the superficial fascia, and the integument. The coverings of this form,
therefore, differ from those of the oblique form in that the conjoined tendon is substituted for the
cremaster, and the infundibuliform fascia is replaced by a portion of the general layer of the
transversalis fascia.
The seat of stricture in both varieties of direct hernia is usually found either at the neck of the
sac or at the external ring. In that form which perforates the conjoined tendon it not infre-
quently occurs at the edges of the fissure through which the gut passes. In all cases of inguinal
hernia', whether direct or oblique, it is proper to divide the stricture directly upward; by cutting
in this direction the incision is made parallel to the deep epigastric artery — external to it in the
oblique variety, internal to it in the direct form of hernia; all chance of wounding the vessel is
thus avoided. Direct inguinal hernia is of much less frequent occurrence than the oblique, and
is found more often in men than in women. The main differences in position between it and
the oblique form are: (o) it is placed over the pubis and not in the course of the inguinal canal;
(&) the deep epigastric artery runs on the outer or iliac side of the neck of the sac; and (c) the
spermatic cord lies along its external and posterior sides, not directly behind it, as in oblique
inguinal hernia.
Femoral Hernia. — In femoral hernia the protrusion of the intestine takes place through
the crural ring. As already described (p. 503), this ring is closed by the septum crurale, a
partition of modified extraperitoneal tissue; it is, therefore, a weak spot in the abdominal wall,
and especially in the female, where the ring is larger and where profound changes are produced
in the tissues of the abdomen by pregnancy. Femoral hernia is, therefore, more common in
women than in men.
When a portion of intestine is forced through the femoral ring it carries before it a pouch of
peritoneum which forms the hernial sac. It receives an investment from the extraperitoneal
tissue or septum crurale and descends along the femoral canal, or inner compartment of the
sheath of the femoral vessels, as far as the saphenous opening ; at this point it changes its course,
being prevented from extending farther down the sheath on account of the narrowing of the
latter, and its close contact with the vessels, and also from the close attachment of the superficial
fascia and femoral sheath to the lower part of the circumference of the saphenous opening.
The tumor is consequently directed forward, pushing before it the cribriform fascia, and then
curves upward over Poupart's ligament and the lower part of the External oblique, being covered
by the superficial fascia and integument. While the hernia is contained in the femoral canal it is
usually of small size owing to the resisting nature of the surrounding parts, but when it escapes
from the saphenous opening into the loose areolar tissue of the groin it becomes considerably
enlarged. The direction taken by a femoral hernia in its descent is at first downward, then for-
ward and upward; in the application of taxis for the reduction of a femoral hernia, therefore,
pressure should be directed in the reverse order.
The coverings of a femoral hernia, from within outward, are peritoneum, septum crurale,
femoral sheath, cribriform fascia, superficial fascia, and integument. Sir Astley Cooper has
described an investment for femoral hernia under the name of fascia propria, lying immediately
external to the peritoneal sac but frequently separated from it by some adipose tissue. Surgi-
cally it is important to remember the frequent existence of this layer on account of the ease with
1318 THE ORGANS OF DIGESTION
which an inexperienced operator may mistake the fascia for the peritoneal sac and the contained
fat for omentum, as there is often a great excess of subperitoneal fatty tissue enclosed in the
"fascia propria." In many cases it resembles a fatty tumor, but on further dissection the true
hernial sac will be found in the centre of the mass of fat. The fascia propria is merely modified
extraperitoneal tissue which has been thickened to form a membranous sheet by the pressure of
the hernia.
When the intestine descends along the femoral canal only as far as the saphenous opening the
condition is known as incomplete femoral hernia. The small size of the protrusion in this form
of hernia, on account of the firm and resisting nature of the canal in which it is contained, ren-
ders it an exceedingly dangerous variety of the disease from the extreme difficulty of detecting
the existence of the swelling, especially in corpulent subjects. The coverings of an incomplete
femoral hernia would be, from without inward, integument, superficial fascia, superior falciform
process of fascia lata, femoral sheath, septum crurale, and peritoneum.
The seat of stricture of a femoral hernia varies ; it may be in the peritoneum at the neck of the
hernial sac; in the greater number of cases it is at the point of junction of the superior falciform
process with the free edge of Gimbernat's ligament; or it may be at the margin of the saphenous
opening. The stricture should in every case be divided in a direction upward and inward for a
distance of about one-sixth to one-quarter of an inch. All vessels or other structures of impor-
tance in relation to the neck of the sac will thus be avoided.
The spine of the pubis forms an important landmark in serving to differentiate the inguinal
from the femoral variety of hernia. The inguinal protrusion is above and to the inner side of
the spine, while the femoral is below and to its outer side.
By the term internal hernia, we mean hernia into the foramen of Winslow, into the retro-
duodenal fossa, into the retrocecal fossa, or into the intersigmoid fossa. Such a hernia produces
the symptoms of acute strangulation of the intestine.
In typhoid fever there is ulceration of Peyer's patches. One of these ulcers may perforate.
The only chance for life is immediate laparotomy and closure of the perforation. This saves
one-fifth, or possibly one-third, of the cases. The incision is made to expose the lower ileum, as
in the vast majority of cases the perforation is in this portion of the gut.
The surgical anatomy of the rectum is of considerable importance. There may be congenital
malformation due to arrested or imperfect development. Thus, there may be no invagination of
the ectoderm, and consequently a complete absence of the anus; or the hind gut may be imper-
fectly developed, and there may be an absence of the rectum, though the anus is developed;
or the invagination of the ectoderm may not communicate with the termination of the hind guf
from want of solution of continuity in the septum which in early fetal life exists between the
two. The mucous membrane is thick and but loosely connected to the muscular coat beneath
and thus favors prolapse, especially in children. The vessels of the rectum are arranged as
mentioned above, longitudinally, and are contained in the loose cellular tissue between the
mucous and muscular coats, and receive no support from surrounding tissues, and this favors
varicosity. Moreover, the veins, after running upward in a longitudinal direction for about five
inches in the submucous tissue, pierce the muscular coats, and are liable to become constricted
at this point by the contraction of the muscular wall of the gut. In addition to this there are no
valves in the superior hemorrhoidal veins, and the vessels of the rectum are placed in a dependent
position, and are liable to be pressed upon and obstructed by hardened feces. The anatomical
arrangement, therefore, of the hemorrhoidal vessels explains the great tendency to the occurrence
of piles. The presence of the Sphincter ani is of surgical importance, since it is the constant
contraction of this muscle which prevents an ischiorectal abscess from healing and tends to
cause a fistula. Also, the reflex contraction of this muscle is the cause of the severe pain com-
plained of in fissure of the anus. The relations of the peritoneum to the rectum are of impor-
tance in connection with the operation of removal of the lower end of the rectum for malignant
disease. The membrane gradually leaves the rectum as it descends into the pelvis ; first leaving
its posterior surface, then the sides, and then the anterior surface, to become refiected in the
male on to the posterior wall of the bladder, forming the rectovesical pouch, and in the female
on to the posterior wall of the vagina, forming Douglas' pouch. The rectovesical pouch of
peritoneum extends to within three inches (7.5 cm.) from the anus, so that it is not desirable
to remove more than two and a half inches (6.25 cm.) of the entire circumference of the bowel, for
fear of the risk of opening the peritoneum. When, however, the disease is confined to the poste-
rior surface of the rectum, or extends farther in this direction, a greater amount of the posterior
wall of the gut may be removed, as the peritoneum does not extend on this surface to a lower
level than five inches from the margin of the anus. The rectovaginal or Douglas' pouch in the
female extends somewhat lower than the rectovesical pouch of the male, and therefore it is
advisable to remove a less length of the tube in this sex. Of recent years, however, much more
extensive operations have been done for the removal of cancer of the rectum, and in these the
peritoneal cavity has necessarily been opened. If, in these cases, the opening is plugged with
iodoform gauze until the operation is completed, and then the edges of the wound in the peri-
toneum are accurately brought together with sutures, no evil result appears to follow. For cases
THE LIVER 1319
of cancer of the rectum which are too low to be reached by abdominal section, and too high to be
removed by the ordinary operation from below, Kraske has devised an operation which goes by
his name. The patient is placed on his right side and an incision is made from the second sacral
spine to the anus. The soft parts are now separated from the back of the left side of the sacrum
as far as its left margin, and the greater and lesser sacrosciatic ligaments are divided. A portion
of the lateral mass of the sacrum, commencing on the left border at the level of the third poste-
rior sacral foramen, and running downward and inward through the fourth foramen to the cornu,
is now cut away with a chisel. The left side of the wound being now forcibly drawn outward,
the whole of the rectum is brought into view, and the diseased portion can be removed, leaving
the anal portions of the gut, if healthy. The two divided ends of the gut can perhaps then be
approximated and sutured together. Kraske's operation is in many cases preceded by the per-
formance of iliac colostomy. In cancer high up in the rectum removal of the growth through
the abdomen is sometimes practised, the divided lower end of the rectum being sutured to the
divided upper end (Weir's operation).
The colon frequently reciuires opening in cases of intestinal obstruction, and by some sur-
geons this operation is performed in cases of cancer of the rectum, as soon as the disease is recog-
nized, in the hope that the rate of growth may be retarded by removing the irritation produced
by the passage of fecal matter over the diseased surface. The operation of colostomy may be
performed either in the inguinal or lumbar region; but inguinal colostomy (Maydl's operation)
has at the present day superseded the lumbar operation. The main reason for preferring this
operation is that a spur-shaped process of the mesocolon can be formed, which prevents any fecal
matter finding its way past the artificial anus and becoming lodged on the diseased structures
below. The sigmoid flexure being surrounded by peritoneum, a coil can be drawn out of the
wound, and when it is opened transversely a spur is formed, and this prevents any fecal matter
finding its way from the gut above the opening into that below. The operation is performed
by making an incision two or three inches in length from a point one inch internal to the anterior
superior spinous process of the ilium, parallel to Poupart's ligament. The various layers of
abdominal muscles are cut through, and the peritoneum opened and sewed to the external
skin. The sigmoid flexure is now sought for, and pulled out of the wound and fixed by pushing
a glass bar through a slit in the mesocolon. The two parts of the loop are sutured together.
The intestine is now sutured to the parietal peritoneum. The wound is dressed, and either
immediately or between the second to the fourth day, according to the requirements of the case,
the protruded coil of intestine is opened. It is opened transversely with the Paquelin cautery.
The loose connective tissue around the rectum is occasionally the site of an abscess, the active
focus of which, however, may be located elsewhere. This form of abscess may be described as
the superior pelvic rectal; it is placed above the pelvic diaphragm, but beneath the peritoneum.
The acute variety is generally due to ulceration or perforation of the bowel (possibly produced by
a foreign body) above the level of the attachment of the Levator ani. The abscess may also occur
above a stricture (simple or malignant) of the rectum; occasionally it arises from suppuration
around the prostate, and more rarely follows abscess of the seminal vesicles. Chronic abscesses
also appear in the same region either from caries of the anterior surface of the sacrum or from
caseation of the presacral lymph nodes, while in other cases an abscess finds its way down into
the pelvis from disease of the anterior surfaces of the bodies of the lumbar vertebral.
THE LIVER (HEPAR) (Figs. 1083, 1084).
The liver is the largest gland in the body and is situated in the upper and
right part of the abdominal cavity, occupying almost the whole of the right hypo-
chondrium, the greater part of the epigastrium, and not uncommonly extending
into the left hypochondrium as far as the midclavicular line. In the male it weighs
from fifty to sixty ounces; in the feinale, from forty to fifty. It is relatively
much larger in the fetus than in the adult, constituting, in the former, about one-
eighteenth, and in the latter, about one-thirty-sixth of the entire body weight.
Its greatest transverse measurement is from eight to nine inches (20 to 22 cm.).
Vertically, near its lateral or right surface, it measures about six or seven inches
(15 to IS cm.), while its greatest antero-posterior diameter is on a level with the
upper end of the right kidney and is from four to five inches (10 to 12 cm.). Op-
posite the vertebral column its measurement from before backward is reduced
to about three inches (7.5 cm.). Its consistence is that of a soft solid; it is, how-
ever, friable and easily lacerated; its color is a dark reddish brown, and its
specific gravity is 1.05.
1320
THE ORGAKS OF DIGESTION
To obtain a correct idea of its shape, it must be hardened in situ, and it will
then be seen to present the appearance of a wedge, the base of which is directed
to the right and the thin edge toward the left. Symington describes its shape as
that "of a right-angled triangular prism with the right angles rounded off."
Surfaces. — The liver possesses five surfaces — viz., a superior, inferior, anterior,
posterior, and a right lateral surface. A sharp, well-defined margin divides the
inferior from the anterior and lateral surfaces, but the other surfaces are separated
from one another by thick, rounded borders. The superior and anterior surfaces
are separated from each other by a thick rounded border, and are attached to the
Diaphragm and anterior abdominal wall by a triangular or falciform fold of peri-
toneum, the suspensory or falciform ligament, in the free margin of which is a rounded
cord, the ligamentum teres or impervious umbilical vein. The line of attachment
of the falciform ligament divides the liver into two unequal parts, termed the
right and left lobes, the right being much the larger. The inferior and posterior
surfaces are divided into five lobes by five fissures, which are arranged in the form
T LATERAL
Fig. 1083.— The liver. Upper surface. (Drawn from His' model.)
of the letter H. The left limb of the H marks on these surfaces the division of
the liver into right and left lobes; it is known as the longitudinal fissure, and con-
sists of two parts — viz., the umbilical fissure in front and the fissure for the ductus
venosus behind. The right limb of the H is formed in front by the fissure or
fossa for the gall-bladder, and behind by the fissure for the inferior vena cava ; these
two fissures are separated from one another by a band of liver substance, termed
the caudate lobe. The bar connecting the two limbs of the H is the transverse
or portal fissure; in front of it is the quadrate lobe, behind it is the Spigelia)i lobe.
The superior surface (fades superior) (Fig. 1083) comprises a part of both
loljes, and, as a whole, is convex, and fits under the vault of the Diaphragm; its
central part, however, presents a shallow depression, the cardiac depression (im-
pressiocardiaca), which corresponds with the position of the heart on the upper
surfaces of the Diaphragm. It is separated from the anterior, posterior, and lateral
surfaces by thick, rounded borders. Its left extremity is continued into the under
surface by a prominent sharp margin. Except along the lines of attachment
of the falciform ligament this surface is completely covered by peritoneum.
The anterior surface is large, triangular in shape, and comprises also a part of
both right and left lobes. It is directed forward, and the greater part of it is in
THE LIVER 1321
contact with the Diaphragm, which separates it on the right from the sixth to
the tenth ribs and their cartilages, and on the left from the seventh and eighth
costal cartilages. In the middle line it lies behind the ensiform cartilage, and in
the angle between the diverging rib cartilages of opposite sides the anterior sur-
face is in contact with the abdominal wall. It is separated from the inferior
surface by a sharp margin, and from the superior and lateral surfaces by thick
rounded borders. It is completely covered by peritoneum except along the line
of attachment of the falciform ligament.
The lateral or right surface (Figs. 1083 and 1084) is convex from before back-
ward and slightly so from above downward. It is directed toward the right side,
forming the base of the wedge, and lies against the lateral portion of the Dia-
phragm, which separates it from the lower part of the right pleura and lung, outside
which are the right costal arches from the seventh to the eleventh inclusive. .
The inferior or visceral surface {fades inferior) (Figs. 1084 and 1085) is uneven,
concave, directed downward, backward, and to the left, and is in relation with the
stomach and duodenum, the hepatic flexure of the colon, and the right kidney
and suprarenal glands. The surface is divided by a longitudinal fissure into a right
and a left lobe, and is almost completely invested by peritoneum; the only parts
where this covering is absent are where the gall-bladder is attached to the liver
and at the transverse fissure, where the two layers of the lesser omentum are sepa-
rated from each other by the bloodvessels and duct of the viscus. The under
surface of the left lobe presents to the right and near the centre a rounded emi-
nence, the omental tuberosity (tuber omentale) (Fig. 1084), which is in contact with
the lesser omentum. It is surrounded by a broad depression, the gastric surface
or impression {impressio gasf.rica), with which the stomach is in contact. Between
the gall-liladder and the left lobe is the quadrate lobe. The quadrate lobe is
bounded to the left by the umbilical fissure or the fissure for the umbilical vein (fossa
venae umbiUcalis), which is the anterior portion of the longitudinal fissure and
lodges the round ligament. The under surface of the right lobe is divided into two
unequal portions by a fossa, which lodges the gall-bladder and is called the fossa
vesicalis [fossa vesicae felleae). The portion to the left, the smaller of the two,
is the quadrate lobe, and is in relation with the pyloric end of the stomach (impressio
pylorica) and the first portion of the duodenum. The portion of the under sur-
face of the right lobe to the right of the fossa vesicalis presents two shallow concave
impressions, one situated behind the other, the two being separated by a" ridge.
The anterior of these two impressions, the colic impression (impressio colica),
is produced by the hepatic flexure of the colon ; the posterior, the renal impression
(impressio reualis), is occupied by the 'upper end of the right kidney and lower part
of the suprarenal gland (Fig. 1084). To the inner side of the renal impression is a
third and slightly marked impression, lying between it and the neck of the gall-
bladder. This is caused by the second portion of the duodenum, and is known
as the duodenal impression (impressio duodenalis). Just in front of the inferior
vena cava is a narrow strip of liver tissue, the caudate lobe, which connects the
right inferior angle of the Spigelian lobe to the under surface of the right lobe.
It forms the upper boundary of the foramen of Winslow.
The posterior surface (fades posterior) (Fig. 1085) is rounded and broad behind
the right lobe, but narrow on the left. Over a large part of its extent it is not
covered by peritoneum; this uncovered area (Fig. 1084) is about three inches (7.5
cm.) broad, and is in direct contact with the Diaphragm, being united to it by
areolar tissue. It is marked off from the upper surface by the line of reflection of
the upper or anterior layer of the coronary ligament and from the under surface
of the liver by the line of reflection of the lower layer of the coronary ligament
(Fig. 1086). The central part of the posterior surface presents a deep concavity
which is moulded on the vertebral column and crura of the Diaphragm. To the
1322
THE ORGANS OF DIGESTION
right of this the inferior vena cava is lodged in an indentation in the hver substance,
lying between the uncovered area and the Spigelian lobe. Close to the right of
this indentation and immediately above the renal impression is a small triangular
depressed area, the suprarenal impression {impressio siqyrarenalis) (Fig. 1084),
the greater part of which is devoid of peritoneum; it lodges the right suprarenal
gland, which is inserted between the liver and Diaphragm. To the left of the
fossa for the inferior vena cava is the Spigelian lobe, which lies between the fissure
for the inferior vena cava and the fissure for the ductus venosus. Below and in
front it projects and forms part of the posterior boundary of the transverse fissure.
Here, to the right, it is connected with the under surface of the right lobe of the
liver by the caudate lobe, and to the left it presents a tubercle, the tuberculum
papillare (Fig. 1084). It is opposite the tenth and eleventh thoracic vertebrse,
and rests upon the aorta and crura of the Diaphragm, being covered by the peri-
toneum of the lesser sac. On the posterior surface to the left of the Spigelian
lobe is a groove, the oesophageal groove (impressio oesophagea) ,^ indicating the
position of the abdominal portion of the oesophagus (Fig. 1084).
Umbilical jisstire. li i li nt
1084. — The liver. Posterior and inferior surfaces.
from His' model.)
The inferior border or margin (margo inferioris) is thin and sharp, and marked
opposite the attachment of the falciform ligament by a deep notch, the umbilical
notch (incisura umbilicalis), and opposite the cartilage of the ninth rib by a second
notch for the fundus of the gall-bladder (incisura vesicae felleae). In adult males
this border generally corresponds with the lower margin of the thorax in the right
midclavicular line; but in women and children it usually projects below the ribs.
The left extremity of the inferior margin of the liver is thin and flattened from
above downward.
Fissures. — ^Five fissures are seen upon the under and posterior surfaces of the
liver, which serve to divide it into its five lobes. They are: the umbilical fissure,
the fissure for the ductus venosus (forming together the longitudinal fissure), the
transverse fissiu'e, the fissure for the gall-bladder, and the fissure for the inferior
vena cava.
The longitudinal fissure (fossa longitvdinalis sinistra) is a deep groove, which
extends from the notch on the anterior margin of the liver to the upper border of
the posterior surface of the organ. It separates the right and left lobes, the
transverse fissure (Fig. 1084) joins it, at right angles, and divides it into two parts.
The anterior part, or umbilical fissure (fossa venae imibilicalis), lodges the umbilical
THE LIVER
1323
vein in the fetus, and its remains {ligamentum teres) in the adult; it h'ts between
the quadrate lobe and the left lobe of the liver, and is often partially bridged
over by a prolongation of the liepatic substance, the pons hepatis. The posterior
part or fissure for the ductus venosus {fossa ductus veiiosi.) lies Ijetween the left
lobe and the Spigelian lobe; it lodges in the fetus the ductus venosus, and in the
adult a slender fibrous cord (lig. venosum) the impervious remains of that vessel.
The transverse or portal fissure (porta hepatis) (Fig. 1084) is a short but deep
fissure, about two inches (5 cm.) in length, extending transversely across the under
surface of the left portion of the right lobe, nearer to its posterior surface than
its anterior border. It joins, nearly at right angles, with the longitudinal fissure,
and separates the quadrate lol^e in front from the caudate and Spigelian lobes
behind. By the older anatomists this fissure was considered the gateway (porta)
of the liver; hence the large vein which enters at this fissure was called the portal
vein (Fig. 1085). Besides this vein, the fissure transmits the hepatic artery and
nerves, and the hepatic duct and lymphatics. At their entrance into the fissure,
the hepatic duct lies in front and to the right, the hepatic artery to the left, and
the portal vein behind and between the duct and artery.
iV'snn'haqeal qroove. Portal vein. Suprarenal impreasmn.
^';Ar(5^£RED"~§P>^ 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'avellc<l. Its structure is similar to that of the vas deferens.
The descent of the testis will be described on page 1424.
The Semen. — The semen is the viscid, whitish, or opalescent fluid, of alkahne
reaction and characteristic odor, which is secreted by the testes, prostate, seminal
vesicles, and Cowper's glands. It contains water artd about IS per cent, of solid
matter, chiefly consisting of proteids, salts, and nitrogenous substances. The
semen serves to convey and maintain the vitality of the spermia in their course
along the seminal passages.
The Spermatozoa, or Spermia, are present in enormous numbers in the seminal
fluid. Each consists of a head, neck, body, and tail.
1382
THE UBINOGENITAL ORGANS
■ The head is oval, but flattened so that when viewed in profile it is pear-shaped.
Its anterior part is covered by a layer of modified tissue called the head-cap or
'perforator.
The neck and body together form a cylindric or rod-like segment, the neck
containing the two centrosomes. From the posterior centrosome proceeds the
axial filament, which in the body of the spermium is encircled by a spiral thread.
The tail is about four limes the combined length of the head and body, and
consists of the axial filament surrounded by a delicate sheath of protoplasm.
The terminal portion of the tail is named the end piece, and consists of the axial
filament only.
Bv virtue of their tails, which act as propellers, the spermia, in the fresh con-
dition, are capable of free movement, and if placed in favorable surroundings
(e. g., in the female passages) may retain their vitality forseveral days.
w-
Middle
' piece
' Main pit
Middle _
piece
■of
the
tail
Applied Anatomy. — The scrotum forms an admirable
covering for the protection of the testicle. This body, lying
suspended and loose in the cavity of the scrotum, and sur-
rounded by a serous membrane, is capable of great mobility,
and can therefore easily slip about within the scrotum, and
thus avoid injuries from blows or squeezes. The skin of the
scrotum is very elastic and capable of great distention, and
on account of the looseness and amount of subcutaneous
tissue, the scrotum becomes greatly enlarged in cases of
edema, to which this part is especially hable on account of
its dependent position. The scrotum is frequently the seat
of epithelioma; this is no doubt due to the rugse on its surface,
which favor the lodgement of dirt, and this, causing irritation,
is the exciting cause of the disease. Cancer was especially
common in chimney-sweeps from the lodgement of soot.
The scrotum is also the part most frequently' affected by
elephantiasis.
On account of the looseness of the subcutaneous tissue
considerable extravasations of blood may take place from very
slight injuries. It is therefore generally recommended never
to apply leeches to the scrotum, since they may lead to
considerable ecchytnosis, but rather to puncture one or more
of the superficial veins of the scrotum in cases where local
bloodletting from this part is judged to be desirable. The
muscle tissue in the dartos causes contraction and consider-
able diminution in the size of a wound of the scrotum, as
after the operation of castration, and is of assistance in keep-
ing the edges together and covering the exposed parts.
Abnormalities in the formation and in the descent of the testes may occur. The testis may
fail to be developed, or it may be fully developed and the vas deferens may be undeveloped in
whole or in part; or, again, both testes and vas deferens may be fully developed, but the duct may
not become connected to the gland. The testis may fail in its descent (cryptorchismus) or it may
descend into some abnormal position (ectopia testis). Thus, it may be retained in the position
where it was primarily developed, below the kidney; or it may descend to the internal abdominal
ring, but fail to pass through this opening; it may be retained in the inguinal canal, which is,
perhaps, the most common position; or it may pass through the external abdominal ring and
remain just outside it, failing to pass to the bottom of the scrotum. On the other hand, it may
get into some abnormal position; it may pass the scrotum and reach the perineum, or it may
fail to enter the inguinal canal, and may find its way through the femoral ring into the crural
canal, and present itself on the thigh at the saphenous opening. Ectopia testis is due to the
absence, overdevelopment, or malposition of some portion of the gubernaculum. There is still
a third class of cases of abnormality in the position of the testis, where the organ has descended in
due course into the scrotum, but is malplaced. The most common form of this is where the testis
is inverted; that is to say, the organ is rotated, so that the epididymis is connected to the front of
the scrotum, and the body, surrounded by the tunica vaginalis, is directed backward. In these
cases the vas deferens is to be felt in the front of the cord. The condition is of importance in
connection with hydrocele and hematocele, and the position of the testis should always be care-
fully ascertained before performing any operation for these affections. Again, more rarely, the
testis may be reversed. This is a condition in which the top of the testis, indicated by the globus
-End pie
Fig. 1152. — Spermium of man. A1
the left a surface view is shown;
at the right a lateral view. X 1200
(Szymonowicz, after Retzius.)
THE VA8 DEFERENS 1383
major of the epididymis, is at the bottom of the scrotum, and the vas deferens comes ofT from the
summit of the organ.
The testis may require removal for malitfnani, disease, tuberculous disease, cystic disease, in
cases of large hernia testis, and in some instances of incom-pletely descended or misplaced testes.
The operation of castration is a comparatively simple one. An incision is made into the cavity
of the tunica vaginalis from the external ring to the bottom of the scrotuni. The coverings are
shelled off the organ, and the mesorchium, stretching between the back of the testis and the
scrotum, divided. The cord is then isolated, and an aneurism needle, armed with a double
ligature, passed under it, as high as is thought necessary, and the cord tied in two places, and
divided between the ligatures. Sometimes, in cases of malignant disease, it is desirable to
open the inguinal canal arid tie the cord as near the internal abdominal ring as possible.
A collection of serous fluid in the sac of the vaginal tunic of the testicle is known as an ordinary
or testicular hydrocele. In congenital hydrocele a communication remains between the tunica
vaginalis testis and the peritoneal cavity. This communication should have closed during
development. In infantile hydrocele the tunica vaginalis and part of the funicular process are
distended with fluid, but the funicular process is closed above and the cavity of the hydrocele
does not communicate with the peritoneal cavitj'. In encysted hydrocele of the cord the funicular
process is closed above and below, but between these points is not obliterated. In funicular
hydrocele the funicular process is closed below and open above. Congenital hydrocele can
usually be cured by the application of a truss. This obliterates the upper end of the funicular
process, and the obliteration once begun may proceed to completion. If it does not, the condi-
tion has become an infantile hydrocele. An infantile hydrocele can usually be cured bj' multiple
puncture or tapping. The same is true of encysted hydrocele of the cord. In hydrocele of the
funicular process a truss should be worn for a time and the fluid then evacuated by ta|)ping.
In ordinary testicular hydrocele incise and pack, or incise and suture the cut edge of the parietal
layer of the tunic to the skin, or extirpate the parietal layer of the tunic. A successful method
is that of Longuet. He makes an incision, pulls out the testis, and allows all the coats except the
skin to fall behind and make a sheath for the cord. These coats are held behind by one catgut
suture. A bed is made for the testis beneath the skin toward the septum of the scrotum. The
testicle is rotated on its long axis, and placed in the bed, and the skin is sutured above it. This
operation is known as cvtraserous transposition. If a portion of bowel enters an open vaginal
process the condition is congenital hernia.
In infantile hernia the funicular process is closed above but not below, and the hernia descends
in a special sac back of the vaginal tunic. If the hernia pushes down on the vaginal process and
causes it to double on itself the condition is encysted infantile hernia.
THE VAS DEFERENS (DUCTUS DEFERENS) (Figs. 1145, 1153).
The vas deferens, or seminal duct, the excretory duct of the testis, is the con-
tinuation of the epididymis. Commencing at the lower part of tlie globus minor,
it ascends along the posterior border of the testis and inner side of the epididymis,
and along the back pa'rt of the spermatic cord, through the inguinal canal to
the internal or deep abdominal ring. From the ring it curves around the outer
side of the deep epigastric artery, and ascends for about an inch in front of the
external iliac artery. It is next directed backward and slightly downward, and,
crossing the external iliac vessels obliquely, enters the pelvic cavity, where it lies
between the peritoneal membrane and the lateral wall of the pelvis, and passes
on the inner side of the impervious hypogastric artery and the obtm-ator ner\'e
and vessels. It then crosses in front of the ureter, and, reaching the inner side
of this tube, bends at an acute angle, and runs inward and sliglitly forward
between the base of the bladder and the upper end of the seminal ^•esicle. Reach-
ing the inner side of the seminal vesicle, it is directed downward and inward
in contact with this structure and gradually approaches the vas of the opposite
side. Here the vas deferens lies between the base of the bladder and the rectinn,
where it is enclosed, together with the seminal vesicle, in a sheath derived from the
rectovesical fascia.
At the base of the bladder it becomes enlarged and sacculated, forming the
ampulla (ampulla ductus deferentis) (Fig. 1153), and tlien, becoming narrowed
at the base of the prostate, it is joined by tiie duct of the seminal vesicle to form
1384
THE URINOGENITAL ORGANS
the ejaculatory duct (Fig. 1154). The vas deferens offers a hard and cord-hke
sensation to the fingers; it is about two feet in length if unravelled, of cylindrical
form, and about 3 mm. in diameter. Its walls are dense, measuring 0.7 mm.,
and its canal is extremely small, measuring about 0.5 mm.
Structure. — The vas deferens consists of three coats: (1) An external or areolar coat {tunica
adrentitia). (2) A muscular coat {tunica muscularis), which in the greater part of the tube
consists of three layers of unstriped muscle tissue, an inner layer of thin longitudinal fibres
{stratum internum), a thick middle layer of circular fibres {stratum medium), and a thick external
layer of longitudinal fibres {stratum externum). (3) An internal or mucous coat {tunica mucosa),
which is pale, and arranged in longitudinal folds; its epithelial cells are chiefl)' of the stratified
columnar variety of which the superficial layer is ciliated.
Organ of Giraldes (paradidymis). — ^This term is applied to a small body of
rounded shape in the lower end of the spermatic cord, in front of the bloodvessels.
It consists of a small collection of minute vesicles and a small collection of con-
voluted tubules. These tubes are lined with columnar ciliated epithelium, and
probably represent the remains of a part of the Wolffian body.
MUSCULAR
THE SEMINAL VESICLES (VESICULAE SEMINALES) (Figs. 1152, 1153).
The seminal vesicles are two convoluted membranous pouches placed between
the base of the bladder and the rectum, serving as reservoirs for the spermia, and
secreting a fluid to be added to the secretion of the testes. Each sac is some-
what pyramidal in form, the
broad end being directed
backward and the narrow
end forward toward the
prostate. It measures about
two and a half inches
(6.25 cm.) in length, about
10 mm. in breadth, and 4 to
6 mm. in thickness. They
vary, however, in size, not
only in different individ-
uals, but also in the same
individual on the two sides.
The anterior surface is in
contact with the base of
the bladder, extending from
near the termination of
the ureters to the base of
the prostate gland. The
posterior surface rests upon
the rectum, from which it
is separated by the recto-
vesical fascia. Their upper
extremities diverge from
each other. Their lower
extremities are pointed, and
converge toward the base
of the prostate gland, where each joins with the corresponding vas deferens to
form the ejaculatory duct. Along the inner margin of each vesicle runs the
ampulla of the vas deferens. The inner border of the vesicle and the correspond-
FiG. 1153. — The urinary bladder, distended, with surrounding
structures, viewed from behind. (Spalteholz.l
THE EJACULATOBV DUCTS
1385
in" vas deferens form the lateral boundaries of a triangular space, limited behind
by the rectovesical peritoneal fold; the portion of the l)ladder included in this space
rests on the rectum.
Each vesicle consists of a single tube, coiled upon itself and giving oft' several
irregular cecal diverticula (Fig. 1154), the separate coils, as well as the diverticula,
beino- connected by fibrous tissue. Wien uncoiled this tube is about the diameter
of a quill, and varies in length from four to six inches (10 to 15 cm.); it terminates
above in a cul-de-sac; its lower extremity becomes constricted into a narrow
straight duct, the excretory duct (ductus excretorius) (Fig. 1154), which joins with
the corresponding vas deferens to form the ejaculatory duct.
VERUMONTANUM
URETHRA
IlG, 1154. — The ejaculatory ducts viewed from in front and above. (Spalteholz.)
Structure. — The semina! vesicles are composed of three coats — an external or fibrous
{tunica adve.ntitia) ; a middle or muscular coat (tunica muscularis), which is thinner than in the
seminal duct, and is arranged in two layers, an outer, longitudinal, and an inner, circular; an
internal or mucous coat (tunica mucosa), which is usually thrown into waves or folds, and which
is pale, of a whitish-brown color, and of a delicate reticular structure, like that seen in the gall-
bladder. The epithelium is of the columnar variety, and, in the diverticula, goblet cells are
present, the secretion of which increases the bulk of the seminal fluid.
Vessels and Nerves. — The arteries supplying the seminal vesicles are derived from the
middle and inferior vesical and middle hemorrhoidal. The veins and lymphatics accompany
the arteries. The lymphatics anastomose on the surface of the vesicle. The trunks from this
network anastomose with the lymphatics of the bladder and prostate, and pass to the external
and internal iUac nodes. The nerves are derived from the pelvic plexus.
Applied Anatomy. — The seminal vesicles are often the seat of an extension of the diseaSS"
in cases of tiil)rrruIosis of the testis, and should always be examined through the rectum before
coming to a decision with regard to castration in this affection. The vesicles have been deliber-
ately extirpated for local tuberculosis. In gonorrhea the seminal vesicles may become acutely
inflamed {acute seminal vesiculitis). Chronic seminal vesiculitis may follow the acute form or
may arise insidously during gonorrhea.
THE EJACULATORY DUCTS (DUCTUS EJACULATORII) (Fig. 1154).
The eiaculatory ducts are two in number, one on each side. Each duct is formed
by the junction of the duct of the seminal vesicle with the vas deferens. Each duct
is about three-quarters of an inch (2 cm.) in length; it commences at the base of
the prostate, and runs forward and downward between the middle and lateral
1386 THE URINOGENITAL ORGANS
lobes of that gland, and along the side of the sinus pocularis, to terminate by a
separate slit-like orifice close to the margins of the sinus. The ducts diminish
in size and also converge toward their terminations.
Structure. — The coats of the ejaculatory ducts are extremely thin. They are an outer
fibrous layer, which is almost entirely lost after the entrance of the duct into the prostate;
a layer of muscle fibres, consisting of an oider thin circular and an inner longitudinal layer; and
the mucous membrane, lined by simple columnar epithelial cells.
THE PENIS (Figs. 1155, 1156).
The penis is a pendulous organ suspended from the front andsides of the pubic
arch and containing the greater part of the urethra. In the flaccid condition
it is cylindrical in shape, but when erect assumes the form of a triangular prism
with rounded sides, one side of the prism forming the dorsum. It is composed of
three cylindrical masses of erectile tissue bound together by fibrous tissue and
covered with skin. Two of the masses are lateral, and are known as the corpora
cavernosa; the third is median, and is termed the corpus spongiosum (Figs. 1155
and 1163).
The two corpora cavernosa (corpora cavernosa penis) (Figs. 1155 and 1156)
form the greater part of the body of the penis. They consist of two fibrous
cylindrical tubes, placed side by side, and intimately connected along the median
line for their anterior three-fourths, while at their back part they separate from
each other to form the crura penis, which are two strong tapering fibrous processes
or roots firmly connected to the rami of the os pubis and ischium (Figs. 1155 and
1156). Each cms commences by a blunt-pointed process in front of the tuberosity
of the ischium, and before its junction with its fellow to form the body of the penis
it presents a slight enlargement, named by Kobelt the bulb of the corpus cavemosum.
Just beyond this point they become constricted, and retain an ecjual diameter
to their anterior extremity, where they form a single rounded end (digital pro-
cess) which is received into a fossa in the base of the glans penis (Fig. 1155).
A median groove on the upper surface lodges the dorsal arteries, nerves, and veins
of the penis (Figs. 1161 and 116.3), and the groove on the under surface receives
the corpus spongiosum (Fig. 1155).
The corpora cavernosa are surrounded by a strong fibrous envelope (hmica
albuginea^ consisting of superficial and deep fibres. The superficial fibres are
longitudinal in direction, being common to the two corpora cavernosa, and in-
vesting them in a common covering; the other, deep, circular in direction, and
being proper to each corpus cavernosum. The internal circular fibres of the two
corpora cavernosa form, by their junction in the mesal plane, an incomplete
partition or septum (septum penis) between the two bodies. This is thick and
complete behind, but in front it is incomplete, and consists of a number of vertical
bands, which are arranged like the teeth of a comb. It is therefore named the
septum pectiniforme. These bands extend between the dorsal and the urethral
surface of the corpora cavernosa. The fibrous investment of the corpora cavernosa
is extremely dense, of considerable thickness, and consists of bundles of shining
white fibres, with an admixture of well-developed elastic fibres, so that it is
possessed of great elasticity.
The corpus spongiosum (corpus cavernosum urethrae) (Figs. 1155 and 1156)
contains the urethra, and is situated in the groove on the under surface of the
corpora cavernosa penis. Behind, it is expanded to form the urethral bulb (bidhus
urethrae) and lies in apposition with the superficial layer of the triangular ligament,
from which it receives a fibrous investment. The urethra enters the bulb nearer
to the upper than to the lower surface. On the latter there is a depressed
THE PKNLS
1387
median raphe (sulcus bulbi), from wliich a thin fibrous septum projects into the
substance of the bulb and divides it imperfectly into two lateral lobes or hemi-
spheres {liemisphaeria bulbi urethrae).
Tiie portion of the corpus spongiosum '^"o^ure'thra
in front of the bulb lies in a groove on
the under surface of the conjoined corpora
cavernosa. It is cylindrical in form and
tapers slightly from behind forward. Its
anterior extremity is expanded in the
form of an obtuse cone, flattened from
above downward. This expansion, termed
URETHRA
'j- — The penis, with the pubic bone:
from before and below. (Toldt.)
Fig. 1156. — The penis, with the urethra, Cowper's
glands, the prostate gland, and the seminal vesicles
seen from below and behind. (Toldt.)
the glans penis, is moulded on the rounded ends of the corpora cavernosa, extending
farther on their upper than on their lower surfaces. At the summit of the glans
1388
THE URINOGENJTAL OBGAXS
is the vertical, slit-like urethral orifice or meatus. The circumference of the base
of the glans forms a rounded projecting border, the corona glandis, overhanging
a deep sulcus (sulcus retrocjlandularis), behind which is the neck of the penis
(collum fenis).
For descriptive purposes it is convenient to divide the penis into three parts —
the root, the body, and the extremity.
The root (radix penis) of the penis is triradiate in form, consisting of the di-
verging crura, one on either side, and the mesal bulb of the corpus spongiosum.
Each crus is covered by the Erector penis muscle, v^'hile the bulb is surrounded
by the Accelerator urinse muscle. The root of the penis lies in the perineum
between the superficial layer of the triangular ligament and the fascia of Colles.
In addition to being attached to the pubic rami and to the triangular ligament,
the root is bound to the front of the symphysis pubis by the suspensory ligament
(lig. suspensorium penis). The upper fibres of this ligament pass downward from
the lower end of the linea alba, and the lower fibres from the symphysis pubis;
together they form a strong, fibrous band which extends to the upper surface of
the root, where it splits into two fasciculi and blends with the fascial sheath of
the orffan.
.-MEDIAN GROOVE
Fig. 11.58.— Glans penis, under surface. (Testut.)
The body of the penis (corpus penis) extends from the root to the ends of the
corpora cavernosa between the root and extremity. In the flaccid condition
of the organ it is cylindrical, but when erect it has a triangular prismatic form
with rounded angles, the broadest side being turned upward, and called the dorsum
penis. The lower surface of the body of the penis is called the urethral surface
(fades urethralis). The body is covered by integument, and contains in its
interior a large portion of the urethra.
The extremity is formed by the glans penis, the expanded anterior (distal) end
of the corpus spongiosum. It is separated from the body by the constricted neck,
which is surmounted by the corona glandis.
The integument covering the penis is remarkable for its thinness, its dark color,
its looseness of connection with the deeper parts of the organ, and for the absence
of adipose tissue. At the root of the penis the integument is continuous with
that upon the pubes, scrotum, and perineum. At the neck of the glans it leaves
the surface and becomes . folded upon itself to form the prepuce (praeputium)
(Fig. 1161). The internal layer of the prepuce is directly continuous, along the
line of the neck, with the integument over the glans. Immediatelv behind the
THE PENIS
1389
urinary meatus it forms a small, secondary reduplication, attached along the
bottom of a depressed median raphe, which extends from the meatus to the neck;
this fold is termed the frenulum {frenulum praefutii). The integument covering
the glans is continuous with the urethral mucous membrane at the meatus; it is
devoid of hairs, but projecting from its free surface are a number of small,
Fig. 1159. — a. Capillary network. Fk
b. Cavernous spaces.
Figs. 1159 and 1160. — From the peripheral portion of the corpus
(Copied from Langer.)
Connection of the arterial twigs (a) wit
penis under a low magnifying powe
LACUNA MAGNA
highly sensitive papillfe. In the retroglandular sulcus numerous small glands, the
glandulae Tysonii odoriferae (glandidae praeputii) have been described. They
secrete a sebaceous material of very peculiar odor, called smegma praepufii, which
probably contains casein, and readily undergoes decomposition.
The prepuce covers a variable amount of the glans and is separated from it
by a potential sac — the preputial sac — which presents two shallow recesses {fossae
frenuli), one on either side of the frenuluni.
Structure.— From the internal meatus
surface of the fibrous envelope of
the corpora cavernosa, as well as
from the sides of the septum, are
given off a number of band.s or
cords which cross the interior of
each crus in all directions, subdi-
viding it into a number of separate
compartments, and giving the entire
structure a spongy appearance.
These bands and cords are called
trabeculae corporum cavemosum,
and consist of white fibrous tissue,
elastic fibres, and smooth muscle
tissue. In them are continued
numerous arteries and nerves.
The component fibres of which
the trabecula; are composed are
larger and stronger around the
circumference than at the centre of
the corpora cavernosa; they are
also thicker behind than in front.
The interspaces, on the contrary,
are larger at the centre than at the
circumference their long diameter
being directed tninsversely; they
are largcsl aiikTinrly. They are
called cavernous spaces and are occupied by blood during erection, and are lined by a layer of
flattened endothelial cells (Fig. 1159).
The arteries bringing the blood to these spaces are the arteries of the corpora cavernosa
and branches from the dorsal artery of the penis, which perforate the fibrous capsule, along
the upper surface, especially near the fore part of the organ.
CAVERNOSUM
I sagittnl sectic
(Testut.)
1390
THE URINOGENITAL ORGANS
On entering the cavernous structure the arteries divide into branches which are supported and
enclosed by the trabecule. Some of these terminate in a capillary network, the branches of
which open directly into the cavernous spaces (Fig. 1160); others assume a tendril-like ajjpear-
ance, and form convoluted and somewhat dilated vessels, which were named by Muller helicine
arteries (arteriae helicinae). They project into the spaces, and from them are given off small
capillary branches to supply the trabecular structure. They are bound down in the spaces by
fine fibrous processes, and are more abundant in the back part of the corpora cavernosa.
Fig. 1162. — Diagram of the arteries of the penis. (Testut.)
The blood from the cavernous spaces is returned by a series of vessels, some of which emerge
in considerable numbers from the base of the glans penis and converge on the dorsum of the
organ to form the deep dorsal vein; others pass out on the upper surface of the corpora cavernosa
and join the dorsal vein; some emerge from the under surface of the corpora cavernosa,
and, receiving branches from the corpus spongiosum, wind around the sides of the penis to ter-
minate in the dorsal vein; but the greater number pass out at the root of the penis and join the
prostatic plexus.
The fibrous envelope of the corpus spongiosum is thinner, whiter in color, and more elastic
than that of the corpora cavernosa. The trabecule are more delicate, more nearly uniform in
size, and the meshes between them smaller than in the corpora cavernosa, their long diameter,
for the most part, corresponding with that of the penis. The external envelope or outer coat of
the corpus spongiosum is formed partly
of unstriped muscle tissue, and a layer
of the same tissue immediately surrounds
the canal of the urethra. The corpus
spongiosum receives its blood through the
bulbourethral branch of the internal pudic
artery.
The lymphatics of the skin of the penis
terminate in the inguinal nodes. The
lymphatics of the penile 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
pass to the internal iliac nodes.
The nerves are derived from the in-
ternal pudic nerve and the pelvic plexus.
On the glans and bulb some filaments of
the cutaneous nerves have Pacinian bodies connected with them, and, according to Krause,
many of them terminate in peculiar end-bulbs (see p. 817).
Applied Anatomy. — It is occasionally necessary to remove a penis for malignant disease.
Usually, removal of the antescrotal portion is all that is necessary, but sometimes it is requisite
to remove the whole organ from its attachment to the rami of the ossa pubis and ischia. The
former operation is performed either by cutting off the whole of the anterior part of the penis
with one sweep of the knife, or, what is better, cutting through the corpora cavernosa from the
dorsum, and (^hen separating the corpus spongiosum from them, dividing it at a level nearer the
glans penis. The mucous membrane of the urethra is then slit up, and the edges of the flap
attached to the external skin, in order to prevent contraction of the orifice, which would other-
SULBOCAVERNOUS ARTERY/
— ANTERIOR BRANCH ( "RET
CORPUS
SPONGIOSUM
THE PROSTATE
1391
wise take place. The vessels which re(|uire ligation are the two dorsal arteries of the jjenis, ihu
arteries of the corpora cavernosa, and the artery of the septum. VVhen the entire organ requires
removal the patient is placed in the lithotomy position, and an incision is made through the
skin and subcutaneous tissue around the root of the penis, and carried down the median line of
the scrotum as far as the perineum. The two halves of the scrotum are then separated from
each other, and a catheter having been introduced into the bladder as a guide, the spongy ])or-
tion of the urethra below the triangular ligament is separated from the corjiora cavernosa and
divided, the catluicr hiiving been with-
drawn just behind the l)ulb. The sus-
pensory ligament is now severed, and the
crura separated from the bone with a
periosteum scraper, and the whole penis
removed. The membranous portion of
the urethra, which has not been removed,
is now to be attached to the skin at the
posterior extremity of the incision in the
perineum. The remainder of the wound
is to be brought together, free drainage
being provided for.
THE PROSTATE GLAND (PROS-
TATA) (Figs. 1153, 1156,
1166).
The prostate gland is a structure
accessory to the true generative
organs and secretes a viscid, opal-
escent secretion in which spermia
will live and which furnishes a
medium "in which they maintain
the motile activity necessary to
carry them to their destination.
It is a pale, firm, partly glandular
and partly muscular body, which is
placed immediately belov the neck
of the bladder and about the com-
mencement of the urethra.
It is situated in the pelvic cavity below the lower part of the symphysis pubis,
above the deep layer of the triangular ligament, and in front of the rectum, through
which it may be distinctly felt, especially when enlarged. It is about the size
of a horse chestnut and somewhat conical in shape, and presents for examination
a base, an apex, an anterior, a posterior, and two lateral surfaces.
The base (basis prostatae) is directed upward, and is applied to the under
surface of the bladder. The greater part of this surface is directly continuous
with the bladder wall; the urethra penetrates it nearer to its anterior than to its
posterior border.
The apex (apex prostatae) is directed downward and rests upon the deep layer
of the triangular ligament. The apex is fixed, except for the slight mobility of
the triangular ligament; the rest of the gland is somewhat movable.
Surfaces. — The posterior surface (fades posterior) is flattened from side to side
and convex from above downward; it rests on the rectum, and is distant about
an inch and a half from the anus. Near its upper border there is a depression
through which the two common ejaculatory ducts enter the prostate. Tliis de-
pression serves to divide the posterior surface into a lower larger and upper smaller
part. The upper smaller part constitutes the so-called "middle lobe" of the pros-
tale and intervenes between the ejaculatory ducts and the urethra; it varies greatly
SUPERFICIAL DORSAL VEIN
EXTERNAL PUDIC VEIN
.— OBTURATOR VEIN
Fig, 11G4.— Veins of the penis. (Testut.)
1392
THE URINOQENITAL ORGANS
in size and in some subjects is destitute of glandular tissue. The lower larger
portion sometimes presents a shallow median furrow which imperfectly separates
it into a right and a left lateral lobe ; these form the main mass of the gland and are
BULBO-
CAVERNOSU
MUSCLE
Fig, 1165. — Male pelvic organs seen from right side. Bladder and rectum distended; relations of peritoneum
to the bladder and rectum shown in blue. The arrow points to the rectovesical pouch. (Corning.)
DEFERENS
PROSTATE
Fig. 1166. — Prostate -with seminal vesicles and seminal duets, viewed from in front and above. (Spalteholz.)
THE PROSTA TE
i;593
directly continuous with each otlier behind the urethra. In front of tiie urethra
tliey are connected by a band which is named tiie anterior commissure; tliis consists
of the same tissues as tiie capsule and is devoid of glandular suljstance.
The anterior surface (fades anterior) measures about one inch (2.5 cm.) from
above downward, l)ut is narrow and convex from side to side. It is placed
about three-fourths of an inch behind the pubic symphysis, from which it is .sepa-
rated by a plexus of veins and a quantity of loo.se fat. It is connected to die pubic
hone on either side by the puboprostatic ligaments. The urethra emerges from this
surface a little above and in front of tlie apex of the gland.
The lateral surfaces are prominent, and are covered by the anterior portions of
the Leva tores ani muscles, which are, however, separated from the gland by a
plexus of veins.
PERITONEUM
EJACULATORY
CAVERNOSUM
Fig. 1167. — Diagrammatic representation of the male organs of reproduction and their i
the urethra. Lateral view. (Toldt.)
ilations to the bladder and
The prostate measures about an inch and a half (3.75 cm.) transversely at the
base, three-quarters of an inch (1.8 cm.) in its antero-posterior diameter, and an
inch and a quarter (3 cm.) in its vertical diameter. Its weight is about four and
a half drams (18 grams). It is held in position by the anterior ligaments of the
bladder {Ugamenta jmboprostatica) ; by the deep layer of the triangular ligament,
which invests the commencement of the membranous portion of the urethra and
prostate gland; and by the anterior portions of the Levatores ani muscles, which
pass backward from the os pubis and embrace the sides of the prostate. These
portions of the Levatores ani, from the support they afford to the prostate, are
named the Levatores prostatae.
The prostate gland is perforated by the urethra and the ejaculatory ducts.
The urethra usually lies along the junction of its anterior with its middle third.
The ejaculatory ducts pass obliquely downward and forward through the posterior
part of the prostate, and open into the prostatic portion of the urethra.
Structure. — The prostate is immediately enveloped by a thin but firm musculofibrous capsule,
distinct from the prostatic fascia derived from the rectovesical fascia, and separated from it by
a plexus of veins. The capsule is firmly adherent to the prostate and is structurally continuous
with the stroma of the gland, being composed of the same tissues — viz., smooth muscle and
fibrous tissue. The prostatic fascia, distinct and dense, does not cover the apex and at the
1394
THE UBINOGENITAL ORGANS
attachment of the base to the under surface of the bladder. The substance of the prostate is of
a pale, reddish-gray color, of great densitj', and not easily torn. It consists of glandular sub-
stance and muscle tissue.
The muscle tissue, according to KoUiker, constitutes the proper stroma of the prostate, the
connective tissue being very scanty, and simply forming thin trabeculse between the muscle fibres,
in which the vessels and nerves of the gland ramify. The muscle tissue is arranged as follows:
Immediately beneath the fibrous capsule is a dense layer, which forms an investing sheath for
the gland; secondly, around the urethra, as it lies in the prostate, is another dense layer of cir-
cular fibres, continuous above with the internal layer of the muscle coat of the bladder, and heloic
blending with the fibres surrounding the membrcinous portion of the urethra. Between these
LEFT COMMON
Fig. 116S. — Sagittal section of the lower part of a male trunk, the right segment. (Testut.)
two layers strong bands of muscle tissue, which decussate freely, form meshes in which the
glandular structure of the organ is embedded. In that part of the gland which is situated in
front of the urethra the muscle tissue is especially dense, and there is here little or no gland tissue;
while in that part which is behind the urethra the muscle tissue presents a wide-meshed structure,
which is densest at the base of the gland — that is, near the bladder — and becomes looser and
more sponge-like toward the ape.x of the organ.
The glandular substance is composed of lobules containing numerous branched tubular
glands opening into elongated canals, which join to form from twelve to twenty small excretory
ducts. The glands are held together by areolar tissue, supported by prolongations from the
fibrous capsule and muscle stroma, and enclosed in a delicate capillary plexus. The epithelium
which lines the canals and the terminal tubules is of the columnar variety. The prostatic ducts
THE PROSTATE
1395
open into the floor of the prostutii- portion of the urethra, and are lined by two layers of epithe-
liviiii, the inner layer consisiinfj; of ((jluniiiar and the outer of small eubical cells.
Vessels and liferves.— Tiie arteries .supplyino; the prostate are derived from the internal
pudic, inferior vesical, and middle hemorrhoidal. Branches of the vessels enter the gland in
the septa between the lobules and send off
minute branches to the lobules (Walker). The =,=„.=T.x,r
veins form a plexus around the sides and base
of the gland between the layers of the fascial
sheath; they receive in front the dorsal vein of
the penis, and terminate in the internal Uiac
vein. The lymphatics of the prostate are de-
scribed on ]5age 796. The nerves are derived
from the pelvic plexus.
Applied Anatomy, — The relation of the
■prostate to the rectum should be noted; by means
of the finger introduced into the rectum the
surgeon detects enlargement or other disease of
the prostate; he can fee! the apex of the gland,
which is the guide to Cock's operation for stric-
tm-e; he is enabled also by the same means to
direct the point of a catheter when its introduc-
tion is attended with difficulty either from injury or disease of the membranous or prostatic portions
of the urethra. When the finger is introduced into the bowel the surgeon may, in some cases, espe-
cially in boys, learn the position, as well as the size and weight, of a calculus in the bladder. In
the operation for the removal of a calculus, if, as is not infrequently the case, the stone should be ,
lodged behind an enlarged prostate, it may be displaced from its position by pressing upward the
base of the bladder from the rectum. The prostate gland is occasionally the seat of suppuration,
Fir. 1169.— Section of the prostate. (.Jarjavay.)
Fig. 1170 — Transverse section of normal prostate through the middle of the verumontanum, from a subject
aged nineteen years; a. Longitudinal section of ducts leading from the lobules of the prostatic glands. 6.
Verumontanum. c. Sinus pocularis. d. Urethra, c. Ejaculatory ducts, f. Arteries, veins, and venous
sinuses in sheath of prostate, ff. Nerve trunks in sheath, h. Point of origin of fibromuscular bands encircling
urethra, i. Zone of striated voluntary muscle on superior surface. (Drawn with Edinger projection appa-
ratus.) (Taylor.)
either due to injury, gonorrhea, or tuberculous disease. The gland is enveloped in a dense un-
yielding capsule, which determines the course of an abscess, and also explains the great pain which
is present in acute inflammation. The abscess most frequently bursts into the urethra, the direc-
tion in which there is least resistance, but may occasionally burst into the rectum, or more rarely
in the perineum. In advanced life the prostate often becomes considerably enlarged, and may
project into the bladder so as to impede the passage of the urine. According to Dr. Messer's
1396
THE UBINOGENITAL ORGANS
researches, conducted at Greenwich Hospital, it would seem that such obstruction exists in 20
per cent, of all men over sixty years of age. The prostate may be enlarged by the growth of
innocent tumors, adenomata, fibromata, myomata, and myofibromata. The entire gland may
be hypertrophied. A tumor may be encapsulated, but often is surrounded by an area of hyper-
plasia of prostatic tissues, and usually the area of hyperplasia is much more extensive than the
tumor. A tumor may be beneath the mucous membrane, deep in the gland, or beneath the
sheath. The growth called the third lobe is submucous. In some cases the enlargement affects
principally the lateral lobes, which may undergo considerable enlargement without causing much
inconvenience. In other cases it would seem that the nodule forms the so-called middle lobe,
and even a small enlargement of this character may act injuriously, by forming a sort of valve
over the urethral orifice, preventing the passage of the urine, and the more the patient strains,
the more completely will it block the opening into the urethra. In consequence of the enlarge-
ment of the prostate a pouch is formed at the base of the bladder behind the projection, in which
urine collects and cannot be entirely expelled. The urine becomes decomposed and ammoniacal,
and leads to cystitis. If the prostate enlarges the urethra is lengthened, often dilated, altered in
shape, or distorted.
The relation of the enlarged prostate to the neck of the bladder is greatly altered from the
relation of the normal prostate. Normally, it is extravesical; when enlarged it may encapsule
"the neck of the bladder in a cuff -like manner, extending several inches upward on its wall,"
and often it protrudes "into the vesical cavity, carrying on its surface the mucosa vesicae." In
many cases of prostatic enlargement the gland should be removed (prostatectomy). One method
is enucleation through a suprapubic incision; another method is enucleation through a perineal
incision; another method is carried out by both incisions (the combined method).
In elderly individuals the gland tubules may form round, indurated, and sometimes calcified
masses, about 1 mm. in diameter, and called prostatic stones.
A RIDGE OF
MUCOSA
ULBOUS
RETHRA
Fig. 1171. — Proximal portion of the urethra, laid open by a median, anterior cut. (Testut.)
COWPER'S GLANDS (GLANDULAE BULBOURETHRALES) (Fig. 1171).
Cowper's glands are two small, rounded, and somewhat lobulated bodies of
a yellow color, about the size of peas, placed behnid the fore part of the mem-
branous portion of the urethra, between the two layers of the triangular ligament.
THE OVARIES
1397
They lie close above the bulb, and are enclosed by the transverse fibres of the
Compressor iirethrae muscle. Their existence is said to be constant; they gradu-
ally diminish in size as age advances.
The excretory duct of each gland, nearly an inch in length, passes obliquely
forward beneath the mucous membrane, and opens by a minute orifice on the
floor of the bulbous portion of the urethra.
Structure. — Each gland consists of several lobules held together by a fibrous investment.
Each lobule consists of a number of acini lined by columnar epithelial cells, opening into one
duct, which, joining with the ducts of other lobules outside the gland, form the single excretory
duct.
THE FEMALE REPRODUCTIVE ORGANS.
The female reproductive organs (organa genitalia muliebria) consist of an internal
and an external group. The internal organs are situated within the pelvis, and
consist of the ovaries, the Fallopian tubes or oviducts, the uterus, and the vagina.
The external organs are placed superficial to the triangular ligament of the urethra
and below and in front of the pubic arch. They comprise the mons veneris,
the labia majora et minora, the clitoris, the bulbi vestibuli, and the glands of
Bartholin.
THE OVARIES (OVARIA) (Figs. 1172, 1177).
The ovaries are homologous with the testes in the male. They are two nodular,
oval-shaped bodies of an elongated form, situated one on either side of the uterus,
in the posterior layer of the broad ligament behind and below the Fallopian tube.
f
' ^ Ligament of ovary.
Fallopian tube.
Hound ligament
of uterifi.
Fig. 1172. — Female pelvis and its contents, seen from above and in front.
The ovaries are of a grayish-pink color, and present either a smooth or a puckered,
inieven surface. They are each about an inch and a half (3.75 cm.) in length
three-quarters of an inch (2 cm.) in width, and about a third of an inch (8 mm.)
thick, and weigh from one to two drams (4 to 8 grams).
1398
TFIE UBINOGENITAL ORGANS
Each ovary {ovarium) presents an outer and an inner surface, an upper and
a lower extremity, and an anterior and a posterior border. It lies in a shallow
depression, named the fossa ovarii, on the lateral wall of the pelvis; this fossa is
bounded above by the external iliac vessels, in front by the impervious hypogastric
artery, and behind by the ureter. The exact position of the ovary has been the
subject of considerable difference of opinion, and the description here given
applies to the nulliparous woman. The ovary becomes displaced during the
first pregnancy and probably never again returns to its original position.
In the erect posture the long axis of the ovary is nearly vertical. The uffer
or tubal extremity is near the external iliac vein; to it is attached the ovarian
fimbria of the Fallopian tube and a fold of peritoneum, the suspensory ligament
of the ovary, which is directed upward over the iliac vessels and contains the
ovarian vessels. The lower or uterine end is directed toward the pelvic floor; it
Fig. 1173. — Female pehic organs t« sztu, seen from above (Bardeleben.)
is usually narrower than the upper end and is attached to the lateral angle of the
uterus, immediately behind the Fallopian tube, by a rounded cord termed the
ligament of the ovary, which lies within the broad ligament and contains some non-
striated muscle fibres. The outer surface is in contact with the parietal peritoneum
which lines the fossa ovarii, the inner surface is to a large extent covered by the
fimbriated extremity of the Fallopian tube. The anterior or straight border is
directed toward the impervious hypogastric artery, and is attached to the back
of the broad ligament by a short fold named the mesovarium. Between the two
layers of this fold the bloodvessels and nerves pass to enter the hilum of the
ovary. The posterior or convex border is free and is directed toward the ureter.
The Fallopian tube arches over the ovary, running upward in relation to its anterior
border, then curving over its upper or tubal pole, and finally passing downward
on its posterior border and inner surface.
The Descent of the Ovary is described on page 1425.
THE OVARIES
1399
The Ovary at Different Ages. — The ovary of childhood is smooth and even. The scars
of many ruptured Graafian follicles cause this surface of the ovary to become pitted, puckered,
fibrous, and uneven in old age. The surface of the ovary is grayish red in color. The corpus
luteum of a nonpregnant woman slowly degenerates and disappears. The corpus luteum of
an impregnated woman enlarges during pregnancy.
Fig. 1174. — Diagrammatic representation of the female reproductive organs and their relations to the bladder and
urethra, lateral view. (Toldt.)
Structure (Figs. 1175, 1176, and 1184). — The ovary consists of the cortex and medulla,
in the former of which are founi) the Graafian follicles and theu- remains and the hilum of the
ovary. The cortex consists of stroma and
Graafian follicles. Peripherally, the stroma
is condensed to form a capsule, the tunica
albuginea, which is covered by a layer of
cuboidal epithelial cells called the germinal
epithelium, and is often referred to as the
serous covering of the organ. These cells
are sharply marked off by a whitish line,
at the hilum of the ovary, from the endo-
thelium of the peritoneum. The stroma
consists of a delicate white fibrous tissue
meshwork, containing many small blood-
vessels and groups of large polygonal epi-
thelial cells called interstitial ceils.
In the stroma are foimd the Graafian
follicles (Fig. 1175) and their remains.
The follicles are of different sizes; the
smallest are beneath the tunica a;lbuginea,
the medium-sized follicles are found toward
the medulla, while the largest extend from
the innermost part of the cortex and beyond
its ordinary limit, thus causing the nodular
appearance of the surface of the ovary. A
large follicle consists of a sheath of stroma called the theca foUiculi, the inner portion of which
is quite vascular. Lining the theca are several layers of granular cells, the zona granulosa.
The greater part of the follicle is devoid of cells, but contains a licjuid, the liquor foUiculi, and the
Fig. 1175. — Section of the ovary: 1. Outer covering.
1'. Attached border. 2. Central stroma. 3. Peripheral
stroma. 4. Bloodvessels. 5. Graafian follicles in their
earliest stage. 6, 7, 8. More advanced follicles. 9. An
almost mature follicle. 9'. Follicle from which the ovum
has escaped. 10. Corpus luteum. (.\fter Schron.)
1400
THE UBINOGENITAL ORGANS
space occupied by this is termed the antrum. At one point the zona granulosa forms a mass
which projects into the antrum; this mass, the discus proligerus, contains the ovum and its
membrane. Beneath the granular cells of the discus is a layer of radially placed tall columnar
cells, the corona radiata, within which lies a broad clear membrane, the zona pellucida, or zona
radiata. Between the zona pellucida and the ovum, which lies within it, is said to exist a narrow
space, the perivitelline space.
The ovum consists of an outer membrane, the vitelline membrane, internal to which is the
protoplasm or vitellus. Embedded in the latter is a large, pale-staining, eccentrically placed
nucleus, the germinal vesicle, which contains a large, deeply staining nucleolus, or germinal
spot. Although the ovum is usually described as a typic cell, the matured ovum, since it does
not contain a centrosome, cannot be so designated.
When a follicle enlarges it ruptures and the ovum usually escapes into the oviduct. This
process constitutes ovulation. When the ovum escapes, the vessels of the follicle rupture and fill
the antrum with blood and form thus the corpus hemorrhagicum. As this becomes organized, the
hemoglobin is absorbed and this body becomes yellowish, due to the presence of a great number
of large yellow ekments, the lutein cells, and thus the corpus luteum is formed. If pregnancy
{fibre
Tkecn
follkuir
3Iemhrana^
granulosa
Fig. 1176. — Section through a Graafian foUicle from an ape's ovary. X 90. (Szymonowicz.)
supervenes, this body persists almost the entire period of gestation; if the ovum is not
impregnated, the corpus luteum soon becomes contracted and whitish, and forms the corpus
albicans.
The medulla consists of a loose network of coarse bundles of white fibrous tissue, which sup-
ports many large bloodvessels; here are also seen smooth muscle tissue and interstitial cells.
The hiliim is a scar-like depression at which the medulla comes to the surface; here the vessels,
nerves, and lymphatics enter and emerge.
Each ovum, before it can be fertilized, must undergo maturation. In this process the oocyte
undergoes two divisions, resulting in four cells, each of which contains one-fourth the amount
of chromatin in the form of one-half the number of chromosomes. Three of these, the polar
bodies, are small and unimportant and disappear. The fourth is the large matured ovum.
The development and maturation of the Graafian vesicles and ova continue uninterruptedly
from puberty to the end of the fruitful period of woman's life, while their formation commences
before birth. Before puberty the ovaries are small, the Graafian vesicles contained in them are
disposed in a comparatively thick layer in the cortical substance; here they present the appear-
ance of a large number of minute closed vesicles, constituting the early condition of the Graafian
vesicles; many, however, never attain full development, but shrink and disappear. At puberty
the ovaries enlarge and become more vascular, the Graafian vesicles are developed in greater
abundance, and their ova are capable of fecundation.
THE FALLOPIAN TUBE, OR OVIDUCT 1401
Vessels and Nerves. — The arteries of the ovaries (Figs. 118.5 and 1187) are the ovarian
from the aorta, corresponding to the spermatic arteries in the male. The ovarian artery on each
side enters the pelvis in the fold of broad ligament known as the suspensory ligament of the ovary
and enters the attached border, or hilum, of the ovary. The ovarian vessels anastomose about
the hilum with branches of the uterine artery. The veins follow the course of the arteries;
they form a plexus near the ovary, the pampiniform plexus, corresponding to a like structure
near tlie testis of the male. The lymphatics (Pis- llSd) terminate in the nodes to the corre-
sponding side of tiie aorta, and tiiey anasloniosi- in their cdurse with trunks from the uterine
fundus and oviduct. The nerves come from the ovarian plexus, which is a continuation of the
renal plexus along the ovarian artery, anti from the aortic plexus.
The epobphoron, parovarium or organ of Rosenmiiller (Figs. 1177, 1180, and 1181) is placed
in the meso.salpinx, between the ovary and tube. It consists of a number of epithelial-lined
closed tubes. This structure can be readily seen if the mesosalpinx is stretched and held in
front of the light. One of these tubes runs parallel to the Fallopian tube, and is called Gartner's
duct {(hictiis cpuopjinri Iniii/itiiilhtalis). A number of tubes (duduli trarwversi) ascend from near
the (>v;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, 17<S
spine of, 174
surface form of, 177
Scapular artery, posterior, 030
nerve, posterior, 1029
region, muscles of, anterior,
463
posterior, 464
Scapuloclavicular articulation,
297
Scopus pili, 1161
Scarf skin, 1151
Scarpa, fascia of, 424
foramina of. 105, 128
givnglion of, 1000. 1147
triangle of, 509, 085
Schachowa. spiral tube of. 1351
Sehindvlesis, 264
Schlcmm. canal of. 1092
ligament of, 302
Schmidt-Lantcrmanii, incisures
of, 811
Sehneiderian membrane. 1083
Schreger. concentric lines of. 1211
Schultze. comma tract of, 835
Schwann, .sheaths of, Sll
Sciatic artery, 677
1492
INDEX
Sciatic nerves, 1054
veins, 744
Sclera, 1090
applied anatomy of, 1110
Scleral sulcus, lOSS
Scrobiculus cordis, 166
Scrotal nerve, 1055
Scrotum, 1372
applied anatomy of, 1382
dartos of, 1373
integument of, 1373
septum of, 1373
Sebaceous glands, 1113, 1161
Second nerve, 974
Sella turcica, 90, 126
Semen, 1381
Semicanalis niiisculus iensoris
tympani, 1127
tubae audiiivae, 1127
Semicircular canals, bony, 1137
membranous, 1142
Semilunar bone, 197
fibrocartilages, 334, 335
fold of Douglas, 430
ganglion, 978, 1073
hiatus, 730
lobe, inferior, 887
Semimembranosus muscle, 524
surface form of, 544
Seminal duct, 1383
vesicles, 1384
applied anatomy of, 1385
arteries of, 1385
lymphatics of, 797, 1385
nerves of, 1385
veins of, 1385
Semispinalis colli muscle, 413
dorsi muscle, 413
Semitendinous muscle, 524
surface form of, 543
Sensor area of l^rain, 960
neurones, 804
root of spinal cord, 823
Septa of lungs, 1195
Septomarginal tract of cord, 837
Septum, aortic, 759, 760
dorsal, fenestrated, 845
interauricular, 559
interventricular, 557, 561
lingual, 393
of nasal sinus, 139
nasi osseum, 139
of nose, 138
artery of, 602
orbital," 368, 1112
pectiniforme, 1386
of scrotum, 1373
secundimi, 759
spurium. 758
ventricular, 759
Septum atriorum, 559
canalis muscidotvbarii, 1127
corporum caveniosorum, 1418
femorale [Cloqucti], 504
inferius, 759
intermedium, 759
iniermusculare laterale, 508
mediale, 508
linguae, 393
lucidum, 934, 945
menibranaceum ventriculorum,
561
mobile nasi. 1079
musculare ventriculorum, 561
orbitale, 1112
pelluciduin, 913, 945
penis, 1386
prlmum, 759
scroti, 1373
sinuum frontalium, 79
sphenoidalium, 91
ventriculorum. 557, 561
Serous membranes of diaphragm,
421
pericardium, 549
Serratus magnus muscle, 461
applied anatomy of, 461
surface form of, 495
posticus muscles, 408
surface form of, 416
Sertoh, columns of, 1380
Sesamoid bones. 257
cartilage, lOSO
Sessile hydatid, 1378
Seventh nerve, 994
Sharpey's fibers, 38
Sheath, axillary, 636
crural, 683
femoral, 683
of Henle, 812
myelin, 811
of nerves, 812
of orhiital muscle, 371
rectus, 434
of Schwann, 811
Sliin bone, 231
Shoulder blade, 172
fascia of, 461
girdle, 169
-joint, articulations of, 301
applied anatomy of, 304
arteries of, 303
bursae of, 303
muscles of, 303
nerves of, 303
surface form of, 304
synovial membrane of, 303
muscles of, 461
Shrapnell, membrana flaccida of,
1130
Sibson's fascia, 1183
Sigmoid arteries, 667
cavity of radius, 192
of ulna, 187
flexure, 1297
fossa, 82
mesocolon, 1264
notch, 118
plexus of nerves, 1076
sinus, 723
Sinus or Sinuses, 707
of aorta, great, 576
basilar, 727
cavernous, 723
circular, 726
confluence of, 723
coronary, 555, 708
costomediastinal, 1184
costophrenic, 1184
definition of, 77 (note)
of dura, 721
epididymis, 1378
ethmoidal, 99
facialis, 721
frontal air, 79
intercavernous, 726
of internal jugular vein, 714
jugular, 713
laryngeal, 1170
lateral, 722
lymph, 768
maxillary, 101, 103
of Morgagni. 395
occipital, 723
orbital, 112
of pericardium, 550
petrosal, 715, 726
petrosquamous, 723
phrenicocostal, 1346
prostatic, 1367
pvriformis, 1233
renal, 1349
sagittal, inferior, 721
superior. 74, 124, 721
sigmoid. 723
sphenoidal. 91, 139
sphenoparietal, 725
straiglit, 722
tentorial. 722
terminaUs, 831
Sinus or Sinuses, of Valsalva, 576
pulmonary, 559, 561
venosus, 554, 757
venous, 707
Sinus or Sinuses, cavernosus, 724
circularis, 726
coronarius, 55.5, 708
cost07nediastinalis, 1184
durae m.atris, 721
epididymidis, 1378
frontalis, 79
intercavernosus anterior, 726
posterior, 726
lactiferans, 1431
maxillaris, 103
occipitalis, 723
petrosus inferior, 726
superior, 726, 966
phrenicocostalis, 1184
pocularis, 1367
rectales, 1310
rectus, 722, 966
renalis, 1349
sagittalis inferior, 721, 966
superior, 721, 966
sphenoidales, 91
spkenoparietalis, 725
tarsi, 239
tentorii, 722
transversus, 722, 727, 966
. pericardii, 550
venarum, 554
venosus sclerae, 1092
vcrtebrales longitttdinales, 738
Sinusoids, 573, 751, 763
Sixth nerve, 993
Skeletal muscles, 355
Skin, 1149
appendages of, 1156
arteries of, 1156
of auditory canal, 1123
bloodvessels of, 1161
coriimi of, 1153
cuticle of, 1151
folds of, 1150
furrows, 1150
lymphatics of, 1156
nerves of, 1156, 1161
pigmentation of, 1155
ridges, 1150
of scalp, 363
scarf, 1151
true, 1153
veins of, 1156
SkuU, anterior region of, 134
applied anatomy of, 149
base of, 123
bones of. 69
brachyfacial, 146
chemoprosope, 146
development of, 141
differences in, due to age, 143
to sex, 144
dolichofacial, 146
fossa of, anterior, 123
condylar, 131
digastric, 131
floccular, 128
glenoid, 131
inferior occipital, 128
middle, 125'
posterior, 127
scaphoid, 130
sphenomaxillary, 134
temporal, 132
zygomatic, 130, 133
index of, 146, 147
lateral regions of, 132
leptoprosope, 146
measurements of, 146
megacephalic, 145
mesal plane of, 146
mesocephalic, 145
microcephalic, 145
surface form of, 147
INDEX
\\\r.i
Skull, sutures of, 121
obliteration of, 144
tables of, 36
vertex of, 123
Smegma praepulii, 1389
Socia parotidis, 1224
Soft palate, 1202
aponeurosis of, 1203
mucous membrane of, 1203
muscles of, 1203
piUars of, 1203
Solar plexus of nerves, 1073
Sole plate, 357
Soleus muscle, 529
surface foi-m of, 544
Solit:.n- r'.llirl,.^ 1292
SoiiKil.M>l-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.\l<irii', 1273
linihrn, ill. nihiflitacCaC, 448
vaKinai' iiui.s.-lc, 445
Spigelian loljc of liver, 1324
recess, 1256
Spina annularis, 92
bifida, 68
helicis, 1120
iliaca anterior inferior, 210
superior, 210
posterior inferior, 210
superior, 210
ischiadica, 211
nasalis anterior, 105
posterior, 110
scapiilnc, 174
vestibuli of His, 758
Spinae inentalcs, 117
Spinal accessory nerve, 1009
nucleus of, 879
arteries, 620, 621
Ijulh, 8G1
column. 48
cord, 820
applied anatomy of, 842
arachnoid of, 844
axones of, myelinization of,
840
central canal of, 831
ligament of, 845
columns of, 826
dorsal, ground bundle of,
837
lateral, ground bundle of,
839
ventral, ground bundle of,
840
commissure of, gray, 831
white, 834
conus, 823
cornua of, 8.30
development of, 827
dura of, 843
enlargements of, 823
filum, 825
fissures, 825
grooves of, 825
horns of, 8.30
membranes of, 842
morphology of, 822, 829
nerve cells of, 832
fibers of, 832, 834
nucleus of, 834
pia of, 845
reticula of. 830
roots of, 823
substance of, gray, 829, 840
■whjte, 833, 841
tracts of,_834
veins of, 739
weight of, 821
foramen, 49
ganglia, 1013
nerves, 1012
connections of sympathetic
with, 1064
divisions of, 1014, 1019
points of emergence of, 1014
roots of, 1013
veins, external, 845
Spinalis colh muscle, 412
dor.si muscle, 412
Spindles, muscle, of Kiihne, 817
neuromuscular, 817
neurotendinous, 817
Spine, 48
ethmoidal, 90, 125
of helix of car, 1120
of Henle, 81
of ischium, 211
nasal, 79
anterior, 105, 135, 139
posterior. 129, 139
palatine, 110
Spine, peroneal, 242
pharyiigeul, 71, 131
of pubis, 212
of Bcajiula, 174
sphenoidal, 92
of tibia. 233
Spinoglenoid ligament, 301
Wpinome.sencephalic tract of cord,
838
Spinothalamic tract of cord, 838
Si)inous processes of ilium, 210
Spiral ganglion, 1000
line of fenuir, 224
tube of Schacliowa, 1351
Splanchnic ncr\'es, 1071
Splanchnology, definition of, 34
Splanchnopleure, 1245
Spleen, 1442
applied anatomy of, 1447
arteries of, 1446, 1449
lymphatic vessels of, 706, 1446,
1449
mobility of, 1444
nerves of, 1446, 1449
parenchyma of, 1445
relations of, 1444
supports of, 1444
surface form of, 1446
trabecuUe of, 1445
veins of, 752, 1446, 1449
Splenial crntrc, 119
Splenic arterv, 661
cells, 1445
corpuscles, 1445
lymph nodes, 790
plexus of nerves, 1008, 1076
pulp, 1445
Splcnium corporis cnllosi, 934
of corpus callosum, 934
Splenius capitis muscle, 409
colli muscle, 409
surface form of, 416
dorsi muscle, surface form of,
416
Spongioblasts, 806
Squamoparietal suture, 122
Sciuamosphenoidal suture, 122
Squamous portion of temporal
bone, 80
temporalis, SO
Stahr, middle lymph node of, 778
Stapedius muscles, 1 134
Stapes, 1133
crura of, 1133
cms anterins, 1133
posferiu-s, 1133
head of, 1133
ligament of, 1133
neck of, 1133
Statoliths, 1143
Stellate ligament, 282
ner\'e cells, 808 ...^
Stenson, duct of, 1225
foramina of, 105. 128
Stephanion, 133, 146
Sternal arteries, 632
fissure, 161
foramen, 1.59, 161
furrow, 166
nor\-e, 1022
Sternoclavicular articulation, 295
applied anatomy of, 297
surface form of. 297
syno\-ial membranes of. 296
ligaments. 296
Sternocostal ligaiiienl. 2S6
Sternohyoid muscle. 3sC
Sternoniastoid arter.v, 590, 595
muscle, 385
applied anatomy of, 386
surface form of. 402
Sternothyroid nuiscles, 387
Sternum, 157
applied anatomy of, 167
articulations of, 161, 288
1494
INDEX
Sternum, ensiforra appendix of,
159
gladiolus of, 159
ligaments of, 2SS, 289
manubrium of, 157
xiphoid appendix of, 159
Stomach, 1270
alterations in position of, 1272
applied anatomy of, 12S0
arteries of, 1278
rliamber, 1270
component parts of, 1272
curvatures of, 1271
fundus of, 1270
innervation of, 1280
interior of, 1273
l.\'mphatic vessels of, 792, 1279
movements of, 1279
mucous membrane of, 1275
nerves of, 1279
openings of, 1271
pit of. 166
relations of, 1279
rugEe, 1273
surface form of, 1280
surfaces of, 1271
teeth, 1207
veins of, 1279
Stomata, 573, 767
Straight sinus, 722
Stratum cinereum, 897
lemni-sci, 897
opticum. 897, 898
reticulatuni, 904
zoTialc, 897
Stria nuUleolaris, 1130
medxdlaris, 903, 906
thnlami, 958
termiualis, 903
vascularis, 1144
Striae acusticae, 865, 866
Lancisii, 934
lougitudinales, 928
mfdullares, 865
obliquae, 866
Striate veins, 720
Striated muscles, 355, 357
involuntarj'. ner\'es of, 357
structure of, 355
Striatothalamie fibers, 950
Striped muscle-. 355
Stroma irirlis, 1098
of iris, 109S
Structure of arachnoid of brain,
g70
of bile duct, 1334
of bladder, 1363
of bone, 38
of cartilages of larj^ns, 1167
of cerebellum, 888
of cerebral cortex, 951
hemispheres, 912, 931
of choroid, 1093
of ciliarj' processes, 1095
of clavicle, 171
of coccygeal gland, 1450
of coccv-x, 63
of cornea, 1091
of Cowper's glands, 1397
of crystalline lens. 1106 '
of duodenum. 1289
of dura of brain, 967
of spinal cord, 844
of ejaculatory ducts, 1386
of epidid%Tnis. 1379
of eyelids, 1113
of Fallopian tube, 1402
of female urethra, 1370
of femur. 226
of forebrain, 902
of frontal bone. SO
of gall-bladder, 1332
of heart, 562
of hindbrain, S61
of humerus, 182
Structure of invertebral sub-
stance, 270
iris, 1098
kidneys, 1349
lacrimal gland, 1116
sac, 1117
large intestine, 1309
liver, 1328
lungs, 1194
lymphatics, 769
male urethra, 1369
mammary gland, 1430
medulla oblongata, 867
Meibomian glands, 1114
membrana tjTnpani, 1130
membranous labjTinth,
1142
midbrain, 894, 896
mouth, 1201
mucous membrane of nasal
fossa!, 1084
muscle fiber, 356
nerve system, 807
nerves, 812
nipple, 1430
nose, 1079
occipital bone, 73
oesophagus, 1238
OS innominatum, 214
ovaries, 1399
pancreas, 1340
parath^Toid glands, 1440
parotid gland, 1225
pars dorsalis pontis, 874
patella, 231
penis, 1389
pharjTix, 1231
pineal body, 906
pinna of ear. 1120
pituitary body, 909
pleura, 1185
pons, 874
prostate gland, 1393
radius, 192
retina, 1101
ribs, 165
sacrum, 63
salivarj- glands, 1226
scapula, 176
sclera, 1090
seminal vesicles, 1385
small intestine, 1289
spermatic cord, 1376
spinal arachnoid, 845
cord, 822. 829
ners-es, 1014
pia. 846
of spleen, 1444
of sternum. 159
of stomach. 1274
of striated muscle. 355
of stiprarenal glands. 1448
of tarsal glands, 1114
of teeth, 1209
of temporal bone, 88
of testes, 1380
of thalamus. 905
of thoracic duct. 773
of th'VTnus dand, 1441
of th^Toid gland, 1436
of tibia, 235
of tongue, 1217
of tonsils. 1231
of trachea. 1177
of ulna. 190
of uriniferous tubules, 1351
of uterus, 1409
of vagina. 1414
of vas deferens. 1384
of vermiform appendix, 1300
of vertebrae. 62
of villi of small intestine, 1291
Styloglossus muscle, 392
St.vlohyal process, 89
Stylohyoid ligament, 389
Stylohyoid muscle, 389
ners-e, 998
Styloid process of fibula, 236
of radius, 192
of ulna, 189
Stylomandibular Ugament, 280
382
Stylomastoid artery, 596
foramen, 87, 131
Stylopharyngeus muscle, 396
! Subacromial bursa, 303
Subanconeus muscle, 471
Subarachnoid cisterna, 969
space, 845, 969
tissue, 845
Subarachnoidean areolar tissue,
968
Subarcuate fossa, 86
Subcalcarine gyve, 925
Subcapsrdar Ijinph sinus, 768
Subcardinal veins, 765
Subcecal fossa, 1267
Subcentral fissures, 923
Subcerebellar veins, 720
Subclainan arterj', 623
applied anatomj- of, 627
left, 625
right, 623
surface marking of, 626
groove, 171
hrniph nodes. 783
triangle, 388, 605
vein, 732
Subcla^-ius muscle, 460
SuljcoUateral gj-re, 925
Subcoracoid centre, 177
Subcostal angle, 156
groove, 463
Subcutaneous acromial bursa,
303
areolar tissue, 1154
malae ner\'e, 983
svno^-ial bursae, 262
tibial bursa, 336
trochanteric bursa, 327
Subdeltoid bursa, 303, 462
Subdural space, 845
Subendothelial fibroelastic tis-
sue, 573
Subfrontal fissures, 919
gj^e, 921
Sublingual artery, 591
fossa, 117
gland, 1226
Sublobular veins, 751
Submaxillary artery, 593
fossa, 117
ganglion. 990
gland, 1225
arteries of, 1226
duct of, 1226
Ij-mphatics of, 1226
neries of. 1226
veins of, 1226
hTiiph nodes, 778
triangle, 604
Submental artery, 593
l^■mph nodes, 779
Subnasal point of skull, 146
Suboccipital triangle, 415, 620
Suboperculum, 917 .
Subparotid IjTnph nodes, 776
Subpleural mediastinal plexus,
632
Subpubic ligament, 294
Subpyloric Ij-mph nodes, 790
Subrostral fissure, 920
Subscapular angle, 172
artery, 630, 639
bursa, 303
fascia, 463
fossa, 172
Kmiph nodes, 783
nerv'e, 1030
Subscapularis muscle, 464
INDEX
1495
Sitlisliuilin ndinnnnlina, 1210
nll.n ,„,,l,i/l„ spinuUs, 81'J, S33
inh, mil
,un,,a. IL'II
,/,/-, //„„x„ |/,'„/„«f/,-|, 829
Uns.a rnilnilis, N-'.l
i,„,l„ll„ ,.,„„„/, .s, 819
),H,/„llnri« pill, 11111
nidra, S97
ossea, 1212
perforata posterior, 847
reticularis alba, 925
spongiosa, 3S
Substernomastoid lymph nodes,
779
Subsylvian ramus, 917
Subtemporal fissure, 924
gyre, 925
Subtendinous iliac bursa, 327
synovial bursse, 262
Sulxirethral glands, 1420
Sucldng pad, 376
Sudoriferous glands, 1161
Sulci cutis, 1150
longitudinales, 553
orbilales, 921
Sulcomarginal tract of cord, 840
Sulcus, intraparietal, of Turner,
922
lacrimal, 107
lunatus, 924
of Monro, 908
orbitopalpebral, 1112
parolfactory, 928
peduncular, of cerebellum, 885
sagittal, 72, 78
scleral, 1088
tympanic, 87, 1122, 1130
Sulcus antihclicus transversus,
1121
arteria occipitalis, 82
arteriae vertebralis, 51
basilaris [pontis], 864
bulbi, 1387
calcanei, 239
caroticus, 91
centralis [Rolandi], 918
chiasmatis, 90
circularis [Reili\, 917
coronarius 553
costae, 163
frontalis inferior, 919
superior, 919
horizontalis cerebelli, 885
infraorbitalis, 102
intermedius anterior [medullae
spinalis], 826
posterior [medullae spinalis],
826
interparietalis, 922
intertubercularis, 180
lacrimalis, 107
lateralis anterior [medullae ob~
longatae], 862
mesencephali, 894
posterior [medullae ob-
longatae], 862
[medidlae spinalis], 825
limitans [fossae rhomboideac],
866
longitudinalis anterior, 553
m. flexoris halluds longi, 245
m. peronei longi, 246
malleolaris, 235, 238
matricis unguis, 1156
mediaretts linguae, 1217
posterior [medullae spinalis],
825
■mylohyoideus, 117
meri'i oculomotorii, 894, 897
radialis, 180
ulnaris, 182
Sulcus obturatorius, 213, 214,
1)20
piiriilfaclorius anterior, 928
posterior, 928
praci'cntralis, 919
superior, 91!)
pminontorii, 1126
pliruiiopnlnlinuH, 92, 95, 110
T<1riiiiliiiidiil(irix. 1388
sdipllnliy., IJ., 78
sc/rrac, 11188
spiralis, 1144
e.rternus, 1144
iutcmus, 1144
sutniamae, 163
/«;/, 245
tiinporulis inferior, 924
vicdius, 924
superior, 924
terminalis, 554
rt?fw (/f.r/ci, 554
(,-' ■ - ' , 1128
/v, , , . -7, 1122, 1130
Sui.uivLiiUal li.-,.,urcs, 919
Supcrcilia, 1112, 1159
Superciliary ridge, 77, 79, 134
Superfrontal fissures, 919
gyre, 921
Supernumerary bones, 144
Supinator [brevis] muscle, 482
longus muscle, 479
Supra-acromial artery, 6.30
Supracardinal veins, 765
Supraclavicular lymph nodes,
779
nerve, 1022
Supracommissure of Osborn,
906
Supracondvlar process, 181 (note)
ridge, 180
Supracondyloid foramen, 181
(note)
Suprahyoid aponeurosis, 389
artery, 591
lymph nodes, 779
region, muscles of, 388
triangle, 605
-'upramastoid crest, 81
.■^uprameatal triangle of Mac-
Ewan, 81, 151
Supraorbital arch, 77
artery, 610
foramen, 135
nerve, 980
notch, 77, 135
ridge, 135
vein, 710
Suprapatellar bursa, 336
Suprarenal artery, 662
glands, 1446
accessory, 1448
hilum of, 1447
lymphatic vessels of, 796
impression of liver, 1322
plexus of nerves, 1074
veins, 751
Suprascapular artery, 629
ligament, 300
nerve, 1029
notch, 175
Suprascleral lymph spaces, 1086
Supraspinales muscle, 414
Supraspinatus fascia, 464
muscle, 464
Supraspinous fossa, 172
ligament, 272
Suprasternal artery, 629
notch, 403
space, 3 S3
Supratonsillar fossa, 1231
Supratrochlear foramen, 182
lymph nodes, 782
nervp, 980
Sural artery, 694
Sural veins, 742
Surface form of abductor huIluciH
muscle, 544
minimi diKiti muscle, 544
of ueromiocluvicular articu-
lation, 299
of adductor longus muscle,
543
maitnus muscle, M'.i
transversus liollicis mus-
cle, 497
of anconeus muscle, 490
of ankle-joint, 340
of articulations of elbow-
joint, 309
of hip-joint, 329
of phalanges of foot. 3.54
of shoulder-joint, 304
of biceps fcmoris muscle,
543
muscle, 495
of bladder, 1365
of bones of foot, 255
of lirachialis anticus muscle,
4UU
of IjrachioradiaUs muscle,
496
of carpal bones, 205
of clavicle, 171
of coracobrachialis muscle,
495
of crureus muscle, 543
of deltoid muscle, 495
of digastric muscle, 403
of erector spinae muscle,
416
of extensor brevis digitorum
muscle, 544
longus digitorum muscle,
544
proprius hallucis muscle,
544
of external oblique muscle,
439
of eyeUds, 1117
of femur, 228
of fibula, 238
of flexor brevis digitorum
muscle, .544
carpi radialis muscle, 496
ulnaris muscle, 496
sublimis digitorum mus-
cle, 496
of foot, 255
of gastrocnemius muscle,
544
of gluteus maximus muscle,
543
medius muscle, 543
of gracilis muscle, 543
of heart, 567
of humerus, 184
of hyoid bone, 154
of interossei muscle, 497
of intestines, 1313
of kidneys, 1354
of knee-joint, 338
of latissimus ■ dorsi nnisclc,
416
of levator anguli scapulae
nuisclc. 416
of lumbricalcs muscle. 497
of lungs, 1196
of niassetcr muscle, 380
of metacarpal bonci. 20,5
of metacarpophalanceal ar-
ticulations. 321
of muscles of face, 380
of head, 380
of lower extremity, 543
of neck, 402
of upper extremity, 495
of omohyoid muscle, 403
of orliicularis palpebrarum
muscle, 380
14!)(j
INDEX
Surface form of piilinaris hrevis
muscle, 497
longus niusclc. 49G
' pancreas, 1341
patella, 231
pcetoralis muscles, 405
pelvis, 219
peroneus nmscles, 544
phalanges, 205
' platysma nmsele, 402
pronator teres muscle,
496
pyramidalis nasi muscle,
380
ciuadriceps extensor mus-
cle, 543
radioulnar articulation,
314
radius, 192
rectus alidorainis muscle,
439
femoris muscle, 543
rhomboideus muscles, 416
sacroiliac articulation, 290
salivary glands, 1227
sartorius muscle, 543
scapula, 177
semimembranous muscle,
544
semitendinous muscle,
543
serratus magnus muscle,
495
posticus muscles, 416
skull, 147
soleus muscle, 544
spleen, 1446
splenius colli muscle, 416
dorsi muscle, 416
sternocalvicular articu-
lation, 297
steruomastoid muscle,
402
stomach, 1281
subcrureus muscle, 543
superior radioulnar artic-
ulation, 311
temporal muscle, 380
temporomandibular ar-
ticulation, 281
tensor fasciae femori?
muscle, 543
teres major muscle, 495
thorax, 166
tibia, 236
tibialis muscles, 544
trachea, 1179
trachelomastoid muscle,
416
trapezius muscle, 416
triceps muscle, 496
ulna, 190
vastus externus muscle,
. 543
internus muscle, 543
vertebral column, 67
wrist-joint, 315
:ing of abdominal aorta,
657
anterior tibial artery, 697
axillary artery, 637
brachial artery, 641
common carotid artery,
586
iliac arteries, 669
dorsalis pedis artery, 699
external carotid artery,
588
iliac artery, 680
femoral artf>r\-. 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<l,rinis, 1365
tiilmriiix. lL'2il
utcrinus, 1257
Touch . corpuscles of Meissner
and Wagner, 816
organ of, 11,50
Triihecidrie carneae, 558
corporum cavernosutn, 1389
nrmii, 141
lirnis, 1445
of spleen, 1445
Trails cerebri. 933
Trachea, 1175
applied anatomy of, 1180
arteries of, 629, 1179
cartilages of, 1177
glands of. 1178
lynipli nodes of, 1179
mucous menjlirane of, 1178
relations of, 1175
surface form of, 1179
veins of, 735, 1179
Tracheal lymph nodes, 1179
Trachealis nmscle of Todd and
Bowman, 1178
Trafhcluniastoid muscle, 412
surface form of, 416
Trarheubronchial lymph nodes,
801
Trachoma glands, 1115
Tract, ascending, 957
cells of spinal cord, 841
corticopontile, 900
descending, 956
frontopontile, 900, 951, 957
geniculate, 9.50
nerve, cerebrospinal, 838
Lowenthal's, 840
ventral cerebrospinal, 840
Marchi's, 839
Monakow's, 839
prepyramidal, 839
occipitomesencephalic, 957
occipitopontile, 950
olfactory, 927
pyramidal, 900
solitary, nucleus of, 880
speech, emissary, 957
of spinal cord, 834
tectospinal, 900
tegmental, 900
temporopontile, 900, 950, 957
Tractus cervicolumbalis, 836
iliotibialis [Maissiati], 507
olfaciorius, 927
peduncularis transversus, 895
poniocerebellares, 890 >
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
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